{"id":0,"sentence":"Kim et al., 2006b), has conduced to confused interpretations about biodegradation mechanisms. To compensate for this problem, it is necessary to explain the different phenomena involved in biodegradation (i. e. biodeterioration, biofragmentation and assimilation).","label":"BIODEGRAD_PROP"}
{"id":1,"sentence":"A similar type of physical damage in the hydrolytically degraded PBS and PLA samples has been observed by Kanemura et al. 33 and Deroin é et al.","label":"BIODEGRAD_POLY"}
{"id":2,"sentence":"At pH 1 and 9, the overall observations were similar to those made for hydrolysis in distilled water, namely, a rapid initial molecular weight decrease and an induction period in terms of weight loss.","label":"BIODEGRAD_PROP"}
{"id":3,"sentence":"As expected, the kinetic constants showed a progressive increase with temperature. The kinetic constant increased by a factor of 2. 5 when the temperature was increased by 10 °C.","label":"BIODEGRAD_PROP"}
{"id":4,"sentence":"This can be observed from Figure 9. The cracks and pores set in much earlier than at pH 7. 4, implying that degradation was accelerated to the harsher conditions.","label":"BIODEGRAD_PROP"}
{"id":5,"sentence":"The synthesis of lactic acid into high−molecular−weight PLA can follow two different routes of polymerization, as depicted in Fig. 1.Lactic acid is condensation polymerized to yield a low−molecular−weight, brittle, glassy polymer,","label":"POLY_STRUC"}
{"id":6,"sentence":"Figure 1 Open in figure viewer PowerPoint Residual weight (%) of the PCL‐b‐PEG copolymer films after degradation at pH 7. 4 and pH 9. 5.","label":"BIODEGRAD_PROP"}
{"id":7,"sentence":"Eq. 5 corresponds to the initial viscosity increase which can be attributed to a post−polymerization due to a initial presence of reactive chain ends or, eventually, non−reacted monomer. s10 refers to the initial concentration of these reactive species.","label":"RHEOLOGICAL_PROP"}
{"id":8,"sentence":"Mass spectroscopy was used to determine the nature of the water soluble products of degradation. At pH 7. 4, a variety of oligomers with different numbers of repeating units were present whereas the harsher degradation conditions at pH 9.","label":"BIODEGRAD_PROP"}
{"id":9,"sentence":"the degradation process can occur during the manufacturing process, when the polymer is exposed to high levels of energy (heat) and mechanical stress (shear).","label":"BIODEGRAD_PROP"}
{"id":10,"sentence":"Table XIV. Effect of Processing on Molecular Weight of Injection−Mold−Grade Cargill – Dow PDLLA (3. 6 % D−Isomer Content)","label":"POLY_STRUC"}
{"id":11,"sentence":"We have conducted a quantum mechanics \/ molecular mechanics molecular dynamics (QM \/ MM MD) study of the hydrolysis of a model compound of PCL by the thermophilic esterase from the hyper−thermophilic archaeon AfEST.","label":"BIODEGRAD_PROP"}
{"id":12,"sentence":"Δ Hi \/ Wi, where Δ Hi is the area of the endothermic peak for the PEG or PCL segment read from the DSC curves and Wi is the weight fraction of the corresponding segment.","label":"BIODEGRAD_POLY"}
{"id":13,"sentence":"19 The increased flexural strength is probably due to the increased crystallinity of the samples after being exposed to elevated temperature. 40 However, it is important to note that the PBS and PBS \/ PBAT blend samples became more brittle after 30 days conditioning and leading to premature failure during flexural test, as shown in Figure 7.","label":"MECHANICAL_PROP"}
{"id":14,"sentence":"The block copolymers produced in this study showed superior properties over previously reported random copolymers of similar compositions. (28) Block copolymer P3HP−b−29 % P4HB was revealed with a higher yield strength of 20.","label":"POLY_STRUC"}
{"id":15,"sentence":"The enthalpies of crystallization and melting were a maximum at a 5 % starch content, and they decreased as the starch content increased above 5 %. It was suggested that at a high starch level,","label":"POLY_STRUC"}
{"id":16,"sentence":"A NMR study was employed to identify differences among the block, random copolymer and blend of P3HP and P4HB. In random copolymer P (3HP−co−4HB),","label":"BIODEGRAD_POLY"}
{"id":17,"sentence":"and PBS \/ PBAT impact strength decreased up to 6 days of conditioning. Over the hydrolysis time, the samples had rough surfaces and corrosive holes in the SEM micrographs.","label":"POLY_STRUC"}
{"id":18,"sentence":"While factors such as temperature, degradation media, and mechanical stimulus have an influence on the degradation of PLA, the degree of crystallinity may also be a factor of pronounced importance 26.","label":"BIODEGRAD_PROP"}
{"id":19,"sentence":"Figure 3 Open in figure viewer PowerPoint Hydrolysis reaction of PBAT. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary. com.]","label":"BIODEGRAD_PROP"}
{"id":20,"sentence":"Witt et al. [19] reported that copolyesters of PET, poly (propylene terephthalate) (PPT), and PBT with adipic acid and sebacic acid degraded in a compost simulation test at 60 °C up to a terephthalic acid content of about 50 % (in moles).","label":"BIODEGRAD_POLY"}
{"id":21,"sentence":"and PP increased with the decreasing of temperature from room temperature to−18. C. The effect of decreasing temperature was not observed on elongation. It was appeared from the results obtained for FTIR and DSC measurements that PLA and PBAT were immiscible, separating into two phases.","label":"BIODEGRAD_POLY"}
{"id":22,"sentence":"Second, the weight loss occurred much more rapidly. For example, it took only 3 days to reach 80 % weight loss of the aPLA. For cPLA, similar weight loss occurred in around 5 days.","label":"BIODEGRAD_PROP"}
{"id":23,"sentence":"The ratio of growth rates of the 0.4 % to 6. 6 % meso concentration was more than 340.This behavior is a manifestation of the reduction in equilibrium melting temperature with meso concentration.","label":"POLY_STRUC"}
{"id":24,"sentence":"the soft aliphatic domain (BA) and the amorphous region are more susceptible to hydrolysis and biodegradation than the rigid aromatic domain (BT) and the crystalline region.","label":"BIODEGRAD_PROP"}
{"id":25,"sentence":"Biodegradation was greatest at 46 °C for the of three polymers studied. PHB and PHB−V showed similar biodegradation at both temperatures. The crystallinity and melting temperature of the polymers were determined by thermal analysis.","label":"BIODEGRAD_PROP"}
{"id":26,"sentence":"which was smaller than 1, confirming that this sample was a random copolymer of P (3HP−co−3HB). In a blend of P3HP and P4HB, where no cross−correlation with the monomers of 3HP and 4HB is expected, their F4HB * 3HP and F3HP * 4HB were equal to 0, its D value could not be calculated.","label":"BIODEGRAD_POLY"}
{"id":27,"sentence":"1 Materials The polylactides used in this study were supplied by Purac Biochem (The Netherlands). Poly (e−caprolactone) (PCL) was provided by Solvay (Chesire, UK).","label":"BIODEGRAD_POLY"}
{"id":28,"sentence":"By contrast, the cPLA surfaces after a 10‐day exposure to neutral media, shown in Figure 4 (d), exhibited a significantly different behavior.","label":"BIODEGRAD_POLY"}
{"id":29,"sentence":"On the whole, lowering the temperature from room temperature down to−18. C significantly resulted in the increase of UTS. Like the case of elastic modulus,","label":"MECHANICAL_PROP"}
{"id":30,"sentence":"the other is that most of the vibration bands, except for the CH2 rocking band, overlap seriously with the amorphous bands. Interestingly, as shown in Figure 3, for all the three crystal forms,","label":"POLY_STRUC"}
{"id":31,"sentence":"Table 4. Kinetic Constant of the Pseudo‐First‐Order Model for PLA Hydrolysis at Various pHs and 70 °C PLA grade aPLA cPLA pH 1 5. 4 9 12 1 5. 4 9 12 k1 × 102 (days−1) 68. 2 72. 2 65. 6 98. 9 44. 7 50.4 44. 2 49.","label":"BIODEGRAD_POLY"}
{"id":32,"sentence":"The morphological study showed significantly improved interfacial adhesion for compatibilized blends, and this was supported by FTIR analysis and a rheological study. Impact strengths, thermal stabilities,","label":"MECHANICAL_PROP"}
{"id":33,"sentence":"For example, for aPLA, we found that the E \/ R factors were 388. 4 and 358. 7 K for the first and second kinetic stages, respectively, whereas Lyu et al.","label":"BIODEGRAD_POLY"}
{"id":34,"sentence":"This study proposed a new block copolymer based microstructure within E. coli. Thus, by controlling the cofeeding module of BDO and PDO block copolymers P3HP−b−P4HB were biosynthesized.","label":"POLY_STRUC"}
{"id":35,"sentence":"The cracks could be attributed to the increasing crystallinity of the PCL segment (substantiated by DSC results above), causing the films to become more brittle.","label":"POLY_STRUC"}
{"id":36,"sentence":"which is assigned to the CH3 deformation and known to be suitable as internal standard for PLA. PLA was shown to be slightly sensitive to thermo−mechanical degradation.","label":"BIODEGRAD_POLY"}
{"id":37,"sentence":"Thermal properties were studied using DSC and molecular weights were studied using GPC. Abbreviations are as follows : Tg, glass transition temperature ; Tm, melting temperature ;","label":"POLY_STRUC"}
{"id":38,"sentence":"Hydroxyl−terminated PLA can be synthesized by the condensation of lactic acid in the presence of a small amount of multifunctional hydroxyl compounds such as 2−butene−1, 4−diol, glycerol,","label":"BIODEGRAD_POLY"}
{"id":39,"sentence":"When the molecular weight was decreased further to about 4. 0 kg \/ mol, the melting enthalpy increased to about 70 J \/ g. This was a very high value for cPLA because upon slow cooling or annealing under dry conditions (i. e., without hydrolysis),","label":"POLY_STRUC"}
{"id":40,"sentence":"The k1 values, for both aPLA and cPLA, at four pH values are summarized in Table 4. For pH values of 1, 9, 5. 4,","label":"BIODEGRAD_POLY"}
{"id":41,"sentence":"Finally, the molecular weight change was easily correlated with the melt viscosity measurements. The power law relation was found to be in agreement with the expected behavior for linear polymers above their critical entanglement molecular weight.","label":"POLY_STRUC"}
{"id":42,"sentence":"The augmentation of derived biodegradability tests, developed by different research groups (Pagga et al., 2001, Rizzarelli et al., 2004, Wang et al., 2004,","label":"BIODEGRAD_PROP"}
{"id":43,"sentence":"the monomeric and oligomeric degradation products formed can migrate from the polymer matrix resulting in an observed weight loss. To derive a model that accurately and simply describes the degradation of PLA, each component of the process must be examined to determine the rate limiting step.","label":"BIODEGRAD_PROP"}
{"id":44,"sentence":"46 The increased crystallinity (χ c) further accounts for the enhanced modulus as well as stiffness. The crystallization temperature (Tc) of the PBS and PBS \/ PBAT significantly reduced after 30 days of conditioning.","label":"BIODEGRAD_POLY"}
{"id":45,"sentence":"However, as noted in Table 1, the CH2 bending and rocking bands of the all−trans P3HP chains, which are singlet (i. e., 1427 and 801 cm−1) for the β−form, split into 1434 and 1427 cm−1,","label":"BIODEGRAD_POLY"}
{"id":46,"sentence":"With the concentration of PLA in the blends from 30 % upward, Eb dropped to the lowest values for PLA \/ PBAT mixture in this experiment, approximately 13 % (Fig. 3).","label":"BIODEGRAD_POLY"}
{"id":47,"sentence":"The small amount of weight loss observed after 60 days of aging is likely due to water absorbed in the fibers before aging that was liberated due to the lack of humidity in the nitrogen purged vials.","label":"BIODEGRAD_PROP"}
{"id":48,"sentence":"which is available at wileyonlinelibrary. com.] Kinetic Analysis The molecular weight data (Mn) versus the hydrolysis time in aqueous media for each temperature were analyzed.","label":"POLY_STRUC"}
{"id":49,"sentence":"The degradation profile of such a polymer is important in assessing its potential as a biomaterial, particularly in the determination of suitable in‐vivo applications. 1 For example,","label":"BIODEGRAD_PROP"}
{"id":50,"sentence":"The stress and strain at the yield point are the yield stress, σ eng and yield strain, ε eng of polymer materials. Somehow, the stress−strain curve might not display a conventional yield point, for which the yield stress, σ eng associated with yield strain, ε eng can be obtained by applying the procedure as reported by Brooks et al. [14, 36].","label":"MECHANICAL_PROP"}
{"id":51,"sentence":"the ester and water concentrations are constant and the kinetics can be reduced to pseudo‐zero‐order kinetics13, 15 : (2) where k is the rate constant, t is the time and Mn and ρ are the number‐average molecular weight and polymer density, respectively.","label":"POLY_STRUC"}
{"id":52,"sentence":"which is known as autocatalytic bulk erosion. In this case, degradation occurs faster in the bulk of the sample than in the outer layer. 8, 9 The kinetics of PLA hydrolysis has been described and studied by many authors. 10−13 The PLA ester bonds are randomly hydrolyzed by water molecules according to the following reaction ; this results in carboxylic and hydroxyl end groups : (1)","label":"BIODEGRAD_PROP"}
{"id":53,"sentence":"and poly [(R)‐3‐hydroxybutyrate] (PHB) because of their potential biomedical applications. 2−15 In addition to their classical uses as sutures and drug delivery systems, new applications including selectively biodegradable vascular grafts, noninvasive surgical procedures, prevention of postsurgical adhesions and scaffolds in tissue engineering have been created. 16−23 PCL is a substantially hydrophobic, semicrystalline aliphatic synthetic polyester which degrades to a naturally occurring metabolite, 6‐hydroxyhexanoic acid.","label":"BIODEGRAD_POLY"}
{"id":54,"sentence":"and PBS \/ PBAT and 180 °C for PP. In the literature, the durability of polymers, polymer blends, and their composites was studied at different accelerated environmental conditions, 21−23 in vehicle and in‐field conditions. 13, 14 Furthermore, long‐term durability of the polymeric material has been studied in the presence of Xenon light, UV light, metal halide,","label":"BIODEGRAD_PROP"}
{"id":55,"sentence":"a) Mn, b) Mw. Similar behavior was observed for average number molecular weight, that decreased from 23612 to 7398 and 11799 g \/ mol for PLA and PLA with stabilizer, respectively.","label":"POLY_STRUC"}
{"id":56,"sentence":"The degree of crystallinity was calculated from the measured heats of fusion and cold crystallization, Δ Hf and Δ Hcc, respectively, relative to an estimated 93 J g−1 for a 100 % crystalline PLA,","label":"POLY_STRUC"}
{"id":57,"sentence":"The development of different microbial species, in a specific order, increases the biodeterioration facilitating in this way the production of simple molecules. Moreover, according to Warscheid and Braams (2000),","label":"BIODEGRAD_PROP"}
{"id":58,"sentence":"In this case, the ratio of cohesive energy of BA to BT (EBA \/ EBT) of PBAT film with fBA \/ fBT of 0.59 \/ 0.","label":"BIODEGRAD_POLY"}
{"id":59,"sentence":"the entanglement density decreased in the polymers it led to a reduction in the toughness of the resultant materials. Apparently, PBAT is more ductile and less crystalline than PBS due to the higher degree of chain entanglements.","label":"POLY_STRUC"}
{"id":60,"sentence":"Figure 5 Open in figure viewer PowerPoint Calculated PDI for PLA32 (▪, •, ▴) and PLA118 (□, ○, Δ) fibers aged at 40, 60,","label":"BIODEGRAD_POLY"}
{"id":61,"sentence":"which are environment−friendly sustainable elastomers. In this paper, the thermal stability, viscoelastic property and mechanical property for these triblock copolymers are investigated due to their application purpose and the effect of formation of PLA crystals on their mechanical property is particularly concerned with because the end blocks of these triblock copolymers are crystallizable when prepared by solvent−casting after their synthesis.","label":"MECHANICAL_PROP"}
{"id":62,"sentence":"The composites were then injection molded into standard specimens for thermal and micro−morphological characterizations. 2. 3. Characterization The flow properties of the PLA \/ PPG composites were investigated by a capillary rheometer (Rheologic 5000,","label":"RHEOLOGICAL_PROP"}
{"id":63,"sentence":"Figure 5 Open in figure viewer PowerPoint Tensile strength of PP, PBS, PBAT, and PBS \/ PBAT as a function of exposure time at 50 °C with 90 % RH. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":64,"sentence":"the strengths of the total MDDI for the polymorphic phases rank as δ > γ ≈ β. At present, it is safe to conclude that the molecular mobility ranks as δ ≪ γ ≪ β.","label":"POLY_STRUC"}
{"id":65,"sentence":"He calculated the Avrami exponent, n, as well as the rate constant, k, and presented the data. His work was fairly comprehensive, and this publication should be investigated prior to any crystallization kinetics studies.","label":"POLY_STRUC"}
{"id":66,"sentence":"and poly (butyl succinate) or (PBS) [1−5]. These bioplastics are biodegradable in nature. Among bioplastics, PLA offers the highest tensile strength and being available at considerably low cost. PLA appears to be a high potential candidate to replace polypropylene (PP).","label":"BIODEGRAD_POLY"}
{"id":67,"sentence":"The biodegradability of the compatibilized PLA \/ PCL 70 \/ 30 blend was more than twice that of PLA (50 % vs. 22 %) after composting for 45 days.","label":"BIODEGRAD_POLY"}
{"id":68,"sentence":"Data were acquired from the first heating run because the intention is to verify the crystalline properties of the film at various time intervals of degradation. The crystallinity of the PCL segment in the copolymer film increased overall.","label":"POLY_STRUC"}
{"id":69,"sentence":"The first stage was characterized by a fast molecular weight decrease, the appearance of a dual‐peak molecular weight distribution, and also a stable PLA sample weight.","label":"BIODEGRAD_PROP"}
{"id":70,"sentence":"The original PLA discs and those subjected to hydrolysis for 8, 16, and 24 h at 60 and 70 °C were characterized. The measurements were carried out in dynamic small‐amplitude oscillatory shear mode with a stress‐controlled Anton Paar MCR 502 rheometer at 180 °C with 25‐mm parallel‐plate geometry.","label":"RHEOLOGICAL_PROP"}
{"id":71,"sentence":"(19) Furthermore, other carboxylesterases were found to promote PCL depolymerization. (22) Comparison of the AfEST−active site with other esterases \/ lipases with the known structure also shows that AfEST has a large combined volume of the active−site pockets (Figure S3).","label":"BIODEGRAD_POLY"}
{"id":72,"sentence":"and heptamers. Mass Spectroscopy Results for the Water‐Soluble Degradation Products at pH 7. 4 Chemical structure Calculated molecular weight Observed molecular weight 246 245. 5 284 283. 7 360 359. 5 474 473. 7 588 587. 7 702 701.5 816 815.","label":"POLY_STRUC"}
{"id":73,"sentence":"and PY is PBAT in yard compost. Fig. 3. Evolution of CO2 gas from respiration of manure, food, or yard composts as function of time ; values of 2, 430 and 8, 080 mg indicate the window of recommended compost according to ASTM D5338 standard,","label":"BIODEGRAD_POLY"}
{"id":74,"sentence":"11 s 1⁄4 2. : ð 3 Þ Mw Mw0 Fig. 4. Decomposition of the degradation curve in three different mechanisms 3. 4. 1 Kinetics of PCL Degradation Previous studies on PCL thermal degradation (Persenaire et al., 2001 ;","label":"BIODEGRAD_PROP"}
{"id":75,"sentence":"Table V summarizes the work of Vasanthakumari and Pennings [84]. Urbanovici et al. [108] obtained isothermal DSC crystallization data for poly (lactic acid).","label":"POLY_STRUC"}
{"id":76,"sentence":"the maximum melting enthalpy for this material was around 45 J \/ g. Figure 6 Open in figure viewer PowerPoint Differential scanning calorimetry thermograms of the samples hydrolyzed in neutral media at 70 °C : (a) aPLA and (b) cPLA.","label":"BIODEGRAD_POLY"}
{"id":77,"sentence":"The degradation rate increases with a decreasing PPG MW and the degradation rate of PLA \/ PPG−200 is the fastest. Figure 5. Rate of relative decrease of the temperature−adjusted torque (rate of degradation) in the interval from 15 to 20 minutes for the neat PLA and PLA \/ PPG composites.","label":"BIODEGRAD_POLY"}
{"id":78,"sentence":"Mw \/ Mn Tg (°C) Tm (°C) 4032D (cPLA) 2 106, 000 168, 000 1.58 61 166 8302D (aPLA) 10 88, 000 146, 500 1.66 59 — Hydrolysis The hydrolysis experiments were carried out in 50 mL centrifugal tubes containing 30 mL of hydrolysis media for a predetermined duration and at various temperatures.","label":"POLY_STRUC"}
{"id":79,"sentence":"Most studies on polymer biodegradation describe the thermal evolution by using the differential scanning calorimeter that gives the glass transition temperature (Tg), cold crystallisation temperature (Tcc)","label":"POLY_STRUC"}
{"id":80,"sentence":"On the other hand, 3−hydroxypropionate (3HP) is a platform chemical for production of poly (3−hydroxypropionate) (P3HP), 1, 3 propanediol, acrylic acid,","label":"BIODEGRAD_POLY"}
{"id":81,"sentence":"Melt−rheological properties were investigated on a HAKKE rotational rheometer RS6000 using a plate diameter of 25 mm and a gap less than 1 mm. Dynamic frequency sweep tests over a frequency range from 0.","label":"RHEOLOGICAL_PROP"}
{"id":82,"sentence":"Table XXIII shows what Kim reported [133]. Park et al [123] reported the thermal properties of poly (L−lactic acid) \/ cornstarch and six−armed star PLA \/ cornstarch composites.","label":"BIODEGRAD_POLY"}
{"id":83,"sentence":"With the addition of the compatibilizers, the interfacial phase of PLA and PBAT became indistinct and the size of the PBAT dispersed phase decreased as shown in Fig. 4 (B)−(F).","label":"BIODEGRAD_POLY"}
{"id":84,"sentence":"It was found that there was no transesterification at temperatures less than 150 °C, which yields polymers with narrow molecular weight distribution [73]. This “ living ” polymerization is characterized by the linear dependence of the number average molecular weight on the monomer−to−initiator molar ratio and conversion.","label":"POLY_STRUC"}
{"id":85,"sentence":"For immiscibility blends, the cole−cole plot often yields two arcs, which are distributed according to two different relaxation mechanisms corresponding to two different phases [34], [35].","label":"RHEOLOGICAL_PROP"}
{"id":86,"sentence":"However, molecular weight distribution is independent to zero shear viscosity (η o). Generally, the η o is obtained from extrapolation of the shear viscosity at lower shear rate (Newtonian region),","label":"RHEOLOGICAL_PROP"}
{"id":87,"sentence":"These PLA crystals surely can improve the network strength of the previously existing network of PLA glassy hard phase domains of the end blocks for these ABA−type thermoplastic elastomers [25].","label":"POLY_STRUC"}
{"id":88,"sentence":"the molecular weight decrease of PLA when exposed to the melting temperature, shear and oxygen. Fig. 7. Variation of PLA melting temperature (Tm) with average molecular weight for neat and processed materials ;","label":"POLY_STRUC"}
{"id":89,"sentence":"Despite its low melting point, PCL showed a very wide thermal stability and hence it is a very suitable polymer for melt blending with a variety of polymers, even those having high thermal transitions, using melt processing methods.","label":"BIODEGRAD_POLY"}
{"id":90,"sentence":"Various esterification−promoting adjuvents and chain−extending agents have been reported that can be used to increase the molecular weight of the PLA condensation products [14].","label":"POLY_STRUC"}
{"id":91,"sentence":"Table IX. Comparison of Physicochemical Properties of Poly (Lactic Acid) PLA (ZnO catalyst) PLA (SnCl2H2O catalyst) Properties Acid value 46 57 Hydroxyl value (%) 2. 004 0.","label":"BIODEGRAD_POLY"}
{"id":92,"sentence":"The fracture surface was sputter coated with gold prior to imaging. 2. 4. Methodology 2. 4. 1.Determination of the Polymer Non−Newtonian Index Polymers are viscoelastic and can be oriented by a shear force in a viscous flow state so polymer melts have non−Newtonian fluid properties [31].","label":"RHEOLOGICAL_PROP"}
{"id":93,"sentence":"The spectrum (Figure 2 (c)) of the separated substance from the uncompatibilized blend was similar to that of the pure PLA (Figure 2 (a))","label":"BIODEGRAD_POLY"}
{"id":94,"sentence":"Fig. 7. FTIR absorbance spectra in the wavenumber range of 3800 – 2750 cm−1 of PBAT film in (a) phosphate buffer solution, (b) vermiculite, (c) manure compost, (d) food compost,","label":"BIODEGRAD_POLY"}
{"id":95,"sentence":"G′ and G′′ gradually decreased by increasing the compatibilizers in the blends in accordance with η ∗. As shown in Fig. 7 (B),","label":"RHEOLOGICAL_PROP"}
{"id":96,"sentence":"WAXD patterns were collected with 30 min. The software xPolar was applied to calibrate the WAXD data. Thus, the correlation field splitting could be excluded, but the intramolecular splitting,","label":"POLY_STRUC"}
{"id":97,"sentence":"5 g \/ 10 min (measured at 190 °C at a load of 2. 16 kg) was purchased from NatureWorks LLC, and PCL (TONE−787) of the melt flow index 0.","label":"BIODEGRAD_POLY"}
{"id":98,"sentence":"All samples presented typical sea−island morphologies, where minor phase−separated PBAT particles were dispersed in the PLA matrix. Fig. 4 (A) shows that the sample without compatibilizer had an obvious interface between the PBAT particles and PLA matrix, indicating poor interfacial adhesion between PLA and PBAT.","label":"BIODEGRAD_POLY"}
{"id":99,"sentence":"Water will continue to diffuse into the polymer until the specimen is saturated after which time the water concentration remains relatively constant. When the degradation has proceeded to a significant degree,","label":"POLY_STRUC"}
{"id":100,"sentence":"Each kind of microbial flora developing successively into the materials contributes to the chemical biodeterioration. Succinic acid, adipic acid, lactic acid and others, as well as, butanediol are released by abiotic and \/ or biotic hydrolysis of several polymers (e. g.","label":"BIODEGRAD_PROP"}
{"id":101,"sentence":"In recent years, bio−based or biodegradable polymers have attracted considerable interest from researchers because these compounds are environmentally friendly and renewable [1], [2], [3].","label":"BIODEGRAD_POLY"}
{"id":102,"sentence":"55 These studies suggest that the formed irregular surface morphology is ascribed to the dissolution of the oligomers during hydrolysis process. 55 It can be seen that the SEM image (Figure 17) of the PBS showed significant erosion pits and large eroded regions compared with PBAT and PBS \/ PBAT.","label":"BIODEGRAD_POLY"}
{"id":103,"sentence":"Process Mol. wt. method Mn (g \/ mol) Mw (g \/ mol) Before injection molding Before injection molding After injection molding Before twin−screw extrusion After twin−screw extrusion Gel permeation chromatography Dilute solution viscometry Dilute solution viscometry Dilute solution viscometry Dilute solution viscometry 98, 000 Mv 5 164, 737 Mv 5 195, 333 Mv 5 164, 737 Mv 5 173, 729 203, 000 Note :","label":"POLY_STRUC"}
{"id":104,"sentence":"Fig. S2 demonstrates that the storage moduli, E′ at 25 °C for PLA−b−PI−b−PLA triblock copolymers drop obviously from 291 to 4 MPa with increasing molecular mass of PI midblock, indicating their mechanical property can be manipulated as demanded and desired.","label":"MECHANICAL_PROP"}
{"id":105,"sentence":"(41) Before the mechanical property studies, all PHA samples were maintained at the room temperature for two weeks to allow stable crystallization. It can also produce random copolymers of P (3HP−co−4HB) when PHA synthase was expressed.","label":"BIODEGRAD_POLY"}
{"id":106,"sentence":"and poly (3−hydroxybutyrate) have attracted much interest because of their desirable properties of biocompatibility and biodegradability. (2) PCL is a bioresorbable polymer with a slow hydrolytic degradation rate (2 – 3 years)","label":"POLY_STRUC"}
{"id":107,"sentence":"Calculation of the compositions for all films was done by using the integration ratio of resonances at 3. 64 ppm for PEG and 4. 06 ppm for PCL.","label":"BIODEGRAD_POLY"}
{"id":108,"sentence":"This is much lower than that at pH 7. 4 (14, 300 g \/ mol). The basic environment accelerated the cleavage of the ester bonds and also led to a greater number of bonds being cleaved, leading to lower molecular weights in a shorter time.","label":"BIODEGRAD_PROP"}
{"id":109,"sentence":"The McNeill and Leiper work supports that radical reaction just occurs at temperatures above 270 °C, leading to a decrease in molecular weight. Scheme 2.","label":"POLY_STRUC"}
{"id":110,"sentence":"The analysis of the residual monomers and released fragments is realised by the same techniques mentioned previously (i. e. Microbial development depends on the constitution and the properties of polymer materials.","label":"BIODEGRAD_PROP"}
{"id":111,"sentence":"As in the above study, we could not adjust the PDO \/ BDO concentration for the block copolymer formation. Here, we had selected BDO as the first substrate and PDO as the second one for block copolymerization.","label":"POLY_STRUC"}
{"id":112,"sentence":"The cofeeding module of structurally related carbon supplements in the form of 1, 4−butanediol (BDO) and 1, 3−propanediol (PDO) was utilized to biosynthesize block copolymer.","label":"POLY_STRUC"}
{"id":113,"sentence":"Samples of less than 300, 000 g \/ mole developed 30 – 50 % crystallinity. Addition of 1 % calcium lactate, by weight, increased the rate of crystallization of a 90 \/ 10 L \/ D isomeric ratio in PLA to the point where no crystallization exotherm was observed during heating of a polymer sample that had been quenched from the melt during injection molding.","label":"POLY_STRUC"}
{"id":114,"sentence":"Crystallinity was calculated from melting enthalpies. Reference values of 205. 0 and 139. 5 J \/ g for completely crystallized PEG and PCL were used, respectively.","label":"POLY_STRUC"}
{"id":115,"sentence":"and \/ or (200), and (203) \/ (113) reflection planes for α−form PLA crystals [26]. The apparent crystallinity values for the four crystallized solvent−cast samples are 20.9, 19. 7, 14.","label":"POLY_STRUC"}
{"id":116,"sentence":"which is available at wileyonlinelibrary. com.] Among the mechanical properties, impact energy is more sensitive to the environmental exposure. Table 1 shows the impact strength of PBS, PBAT, PBS \/ PBAT,","label":"BIODEGRAD_POLY"}
{"id":117,"sentence":"Dynamic thermomechanical analysis (DMA) was conducted from−90 to 140 °C in a tensile mode on a DMA Q800 spectrometer (TA Instruments) with a frequency of 10 Hz, an amplitude of 30 μm and a heating rate of 5 °C \/ min.","label":"MECHANICAL_PROP"}
{"id":118,"sentence":"(21−23) P4HB was approved as a biodegradable suture. (24, 25) Various attempts had been made to produce P (3HB−co−4HB) from glucose as a sole carbon source in E. coli to bring down its production cost for its wide scale applications.","label":"BIODEGRAD_POLY"}
{"id":119,"sentence":"34 ppm (d) and 1.67 – 1.69 ppm (g), respectively. First, in the PBT segment, 4. 38 – 4.","label":"BIODEGRAD_POLY"}
{"id":120,"sentence":"Figure 5 (a, b) shows the bulk surface after 3 days of hydrolysis in alkaline media and after 20 days in neutral media, respectively.","label":"BIODEGRAD_PROP"}
{"id":121,"sentence":"Residence times were as little as 1 minute under a blanket of nitrogen. Because condensation of water was observed on the inside of the vials containing these samples after they were removed from the oven, it is believed that they did not hold their seal and that the samples were exposed to some level of humidity during the final 30 days of exposure.","label":"BIODEGRAD_PROP"}
{"id":122,"sentence":"The Tg of PLA and PBAT gradually shifted to each other with increasing compatibilizer content. The results confirmed that the tri−block copolymer compatibilizers in the blends really modified the miscibility of PLA and PBAT.","label":"BIODEGRAD_POLY"}
{"id":123,"sentence":"Numerous dilute−solution viscosity experiments were performed on poly (lactic acid). Publications regarding poly (lactic acid) usually report a viscosity−average molecular weight.","label":"BIODEGRAD_POLY"}
{"id":124,"sentence":"Pure PLA and PCL exhibited a long Newtonian viscosity plateau region and uncompatibilized PLA \/ PCL (90 \/ 10) and (70 \/ 30) blends showed weak shear thinning behavior.","label":"BIODEGRAD_POLY"}
{"id":125,"sentence":"This finding has good agreement with a previous study. 52 According to Kfoury et al. 54 the percentage of crystallinity, size of crystallites, and spherulite morphology have great influence on the impact strength.","label":"POLY_STRUC"}
{"id":126,"sentence":"Newtonian viscosity (go) and critical frequency for deviation Table 4. Newtonian viscosity (go) and critical frequency for deviation from newtonian behavior (xo)","label":"RHEOLOGICAL_PROP"}
{"id":127,"sentence":"It can be clearly seen that all the E′ curves show two obvious storage modulus dropping steps, all the E′′ curves show accordingly the two obvious peaks,","label":"MECHANICAL_PROP"}
{"id":128,"sentence":"0 J \/ g) [17] and wt % B900 is the weight percentage of the incorporated stabilizer. The number (Mn) and weight average (Mw) molar mass and polydispersity index (PDI) were measured by GPC.","label":"POLY_STRUC"}
{"id":129,"sentence":"The abiotic hydrolysis is performed in acidic (HCl and H2SO4) or alkaline (NaOH) media (Yu et al., 2005, Jung et al., 2006).","label":"BIODEGRAD_PROP"}
{"id":130,"sentence":"and polyanhydrides (G ö pferich and Tessmar, 2002) ; and bulk erosion for PLA and PLGA (Siepmann and G ö pferich, 2001).","label":"BIODEGRAD_POLY"}
{"id":131,"sentence":"16 However, it is very important to understand the durability behaviors of the PBS, PBAT, and PBS \/ PBAT blend in order to diversify as well as in predicting their applications.","label":"BIODEGRAD_POLY"}
{"id":132,"sentence":"The elongation between the blocks of the PLA \/ PBAT blends with 5 % HPB compatibilizer was seven times more than that of the pristine blends. The experimental results established that tri−block copolymers improved the interfacial interaction and the miscibility between PLA and PBAT.","label":"BIODEGRAD_POLY"}
{"id":133,"sentence":"20 Because of the early interest in PLA for biomedical applications, a large number of publications have covered the hydrolysis of PLA at normal body temperature. One of the difficulties of such experiments is its long duration because hydrolysis at 37 °C can take from many weeks8, 21 to 3 years.","label":"BIODEGRAD_PROP"}
{"id":134,"sentence":"The cross‐head movement speeds of 14 mm \/ min for flexural test and 50 mm \/ min for tensile test were used as recommended by the respective standards.","label":"MECHANICAL_PROP"}
{"id":135,"sentence":"Subsequently, the samples were kept at close to crystallization temperature (90 °C) and the spherulite growth was recorded using a Nikon camera. Morphological Analysis The specimens were prepared by sputtering gold particles in order to avoid electrical charging during examination.","label":"POLY_STRUC"}
{"id":136,"sentence":"In this regard, PLA−PBAT−PLA tri−block copolymer was previously used to improve the miscibility of PLA and PBAT. Sun [26] found that tri−block copolymers with a low molecular weight acted as carriers for high−molecular−weight tri−block copolymers to compatibilize PLA and PBAT,","label":"BIODEGRAD_POLY"}
{"id":137,"sentence":"This could be due to the improved crystallinity by molecular weight reduction during the exposure time. The increased crystallinity was consistent with observed spherulite morphology. The zero shear viscosity of the 6 days exposed samples was lower compared to corresponding unexposed samples.","label":"BIODEGRAD_PROP"}
{"id":138,"sentence":"For example, the water uptake was nearly zero during the induction stage, and this closely followed the weight loss curve during the second hydrolysis regime. The higher weight loss of aPLA was also reflected in a greater water uptake.","label":"BIODEGRAD_PROP"}
{"id":139,"sentence":"and PLA) because of its inherent non‐biodegradability character. To the best of our knowledge, there have not been many studies available in literature on the durability of PBS, PBAT,","label":"BIODEGRAD_POLY"}
{"id":140,"sentence":"Another variable used to monitor the hydrolysis process shown in Figure 2 was the water uptake. The water uptake provided another measure of the polymer morphology. The weight loss by bulk erosion increased the porosity of the polymer matrix.","label":"BIODEGRAD_PROP"}
{"id":141,"sentence":"Molecular Characterizations Molecular weight of the copolymers and their degradation products were determined by gel permeation chromatography (GPC). Transition temperatures were taken as peak maxima. RESULTS AND DISCUSSION Residual Mass Analysis of PCL‐b‐PEG Copolymer Film The residual mass of the PCL‐b‐PEG copolymer showed an overall decreasing trend over the entire period of degradation at both pHs.","label":"BIODEGRAD_PROP"}
{"id":142,"sentence":"Abstract The biodegradation of poly (ɛ−caprolactone) (PCL), poly−β−(hydroxybutyrate) (PHB), and poly−β−(hydroxybutyrate−co−β−valerate) (PHB−V) was assessed based on the mass retention when the polymers were incubated in soil compost at 46 and 24 °C.","label":"BIODEGRAD_POLY"}
{"id":143,"sentence":"This may be due to the hydrolysis product of PBS or PBAT accelerating the molecular weight reduction of the PBS \/ PBAT blend. After 6 days of exposure to heat (50 °C)","label":"BIODEGRAD_POLY"}
{"id":144,"sentence":"Fig. 1.FTIR peaks height ratio of PLA degradation characteristic bands. Fig. 2. FTIR spectra of PLA obtained before and after a) 25 min of processing and b) 120 h thermo−oxidative conditions.","label":"BIODEGRAD_PROP"}
{"id":145,"sentence":"The mechanical properties of these composites were in close agreement to similar composites compounded at USDA−ARSNCAUR. Table XXII summarizes the mechanical properties research by Kim.","label":"MECHANICAL_PROP"}
{"id":146,"sentence":"which would result in the formation of — COOH groups on the polymer chain ends. This cleavage will decrease the number of ester linkages and increase the number of carboxyl end−groups, resulting in an increase in the melting temperature of PLA on degradation [117].","label":"POLY_STRUC"}
{"id":147,"sentence":"and yard compost (33. 9 ± 1.5 %), respectively (Fig. 2). The biodegradation of cellulose also shows a similar pattern, highest biodegradation in manure compost, followed by food and yard compost.","label":"BIODEGRAD_PROP"}
{"id":148,"sentence":"C for PLA, PBAT and PP, respectively. The formulations of PLA \/ PBAT blends were given in Table 1.The blends were mixed using an extruder at 165.","label":"BIODEGRAD_POLY"}
{"id":149,"sentence":"and Wdry : (6) Molecular Weight Characterization The molecular weight characterization was performed for the original and hydrolyzed PLA discs via gel permeation chromatography with an Agilent 1100 high‐performance liquid chromatography series instrument equipped with Agilent ResiPore columns and a refractive‐index detector.","label":"POLY_STRUC"}
{"id":150,"sentence":"This phenomenon can reduce the initial crystallinity of PLA. Lezak et al. [19] plasticized PLA \/ flax fiber composite by PPG, which reduced the cold crystallization temperature of PLA and improved the crystallinity of the composite.","label":"BIODEGRAD_POLY"}
{"id":151,"sentence":"The results indicate that the mass reduction of PLLA starts around 270 °C ; however, the initiation of mass reduction in PCL is observed at a higher temperature, 300 °C.","label":"BIODEGRAD_PROP"}
{"id":152,"sentence":"The major disadvantage of this model is that it operates under the assumption that no oligomers or monomers leave the system and therefore there is no observable mass loss 24.","label":"BIODEGRAD_PROP"}
{"id":153,"sentence":"The PLA melt was characterized as a pseudoplastic, non−Newtonian fluid. Power−law equations were used to describe the behavior of the PLA melts [120] (Table XIX).","label":"BIODEGRAD_POLY"}
{"id":154,"sentence":"Therefore, much of the research associated with hydrolytic PLA degradation has been aimed at degradation in aqueous or biological media, typically at 37 °C and pH 7.4 4−7.","label":"BIODEGRAD_PROP"}
{"id":155,"sentence":"In addition, the torque values of the PLA \/ PPG composites were significantly lower than those of the neat PLA. The PLA \/ PPG composites had a lower melt viscosity and better melt flow properties,","label":"BIODEGRAD_POLY"}
{"id":156,"sentence":"Δ H0 PHB 0 146, 000 J \/ kg, and Δ H0 PHB−V 0 146, 000 J \/ kg. The Δ H0 for PHB−V was assumed to be the same as that for PHB [22].","label":"BIODEGRAD_POLY"}
{"id":157,"sentence":"and temperature ; n is the non−Newtonian index ; Mw is the weight average MW of the polymer. RM is used to indicate the relative rate of the change of the Mw per unit processing time at a certain temperature.","label":"POLY_STRUC"}
{"id":158,"sentence":"The required mechanical property can be controlled through the component composition adjustment [3, 4]. Polylactide (PLA) is a typical biocompatible and biodegradable linear aliphatic polyester with high mechanical strength and modulus [11].","label":"MECHANICAL_PROP"}
{"id":159,"sentence":"Mixed Isomer Crystallization Kinetics Data for Poly (Lactic Acid) Sample % meso−lactide % D−isomer content Gmax (mm \/ min) A 0 0.4 4.","label":"POLY_STRUC"}
{"id":160,"sentence":"Figure 3 Open in figure viewer PowerPoint The observed melting temperature (Tm) for PLA32 (▪, •, ▴) and PLA118 (□, ○,","label":"POLY_STRUC"}
{"id":161,"sentence":"2 Materials and methods 2. 1.Materials PBAT (Ecoflex F Blend 1200) was purchased from BASF Company. PLA (grade 2003D) was purchased from Nature Work Company. PP (grade 1102k) was purchased from Global Connections Company.","label":"BIODEGRAD_POLY"}
{"id":162,"sentence":"the crystallinity of both PLA32 and PLA118 increased significantly from 11 % and 8 % to 41 % and 42 %, respectively. The crystallinity of both PLA32 and PLA118 remained roughly the same between 1 and 7 days.","label":"BIODEGRAD_POLY"}
{"id":163,"sentence":"Each sample was measured twice, indicating an experimental error of 0.5 °C. The melting temperature (Tm) and melting enthalpy () were determined from the second heating curves.","label":"POLY_STRUC"}
{"id":164,"sentence":"and 80 °C. The experiment duration was not sufficient for obtaining the half‐life of cPLA. Nevertheless, the weight loss of cPLA showed a very similar behavior at all temperatures.","label":"BIODEGRAD_POLY"}
{"id":165,"sentence":"Fifty milligrams of PBAT disks were dissolved in 5 mL of deuterated chloroform (δ 0 7. 24 ppm) from Cambridge Isotope Laboratories Inc. (Andover,","label":"BIODEGRAD_POLY"}
{"id":166,"sentence":"and molecular weight reduction. The hydrolysis test was performed using an FDA migration cell consisting of a 40 ml glass amber, a screw cap with a hole,","label":"BIODEGRAD_PROP"}
{"id":167,"sentence":"The degradation mechanisms and molecular weight change of PLA over time have been reported previously for 130‐μm thick films at elevated temperature and humidity 12, 13 ; however, there is a lack of information about the degradation characteristics for fibers.","label":"BIODEGRAD_PROP"}
{"id":168,"sentence":"Effective compatibilizers for PLA \/ PBAT blends were developed by synthesizing two types of PLA−PBAT−PLA tri−block copolymers (LPB and HPB) by solution polymerization.","label":"BIODEGRAD_POLY"}
{"id":169,"sentence":"the β−form crystal does not show any splitting of vibration at all, which again confirms the poor packing of β−form. On the other hand, it is reasonable to attribute the spectral difference of the β−and γ−from to their different packing efficiency, since the PHP chains adopt the similar conformation, i. e.,","label":"POLY_STRUC"}
{"id":170,"sentence":"Among the existing work of PPG plasticized PLA, researchers paid more attention to the mechanical and crystallization properties of the plasticized PLA. However, investigations on the degradation of PLA during processing as a function of PPG MW and content have been rarely reported.","label":"BIODEGRAD_POLY"}
{"id":171,"sentence":"and the addition of compatibilizers, LPB or HPB, simultaneously leads to significant improvements in elongation at the break point. The blends with only 1 % LPB and HPB compatibilizers show elongation at break values of 40.9 % and 41.8 %, respectively, nearly twice as high as that of the pristine blends.","label":"MECHANICAL_PROP"}
{"id":172,"sentence":"On the other hand, when the chain conformation varies from the all−trans conformation of the β−and γ−forms to the 21−helix one of the δ−form, β CH2 becomes gauche to the ester oxygen across the C (═ O)−CH2 bond, while keep trans to α CH2 across the O−C (═ O) bond.","label":"POLY_STRUC"}
{"id":173,"sentence":"at low temperatures. As to provide an alternative to synthetic plastics for eco−friendly food packaging industry, the impact resistance of PLA need to be enhanced [1, 3].","label":"BIODEGRAD_POLY"}
{"id":174,"sentence":"Ratto et al., 1999). Studies on the biodegradation of bacterial polymers show that microorganisms secrete extracellular depolymerases. The first discovery on the hydrolytic cleavage of a microbial polymer by specific enzymes was made on poly (hydroxybutyrate) (PHB).","label":"BIODEGRAD_POLY"}
{"id":175,"sentence":"Fig. 4. Anionic ring−opening polymerization mechanism for PLA. An extensive study of various anionic initiators for lactide polymerization was conducted. This deprotonation causes inconsistent polymerization, racemization,","label":"BIODEGRAD_POLY"}
{"id":176,"sentence":"Two tri−block copolymers with PLA blocks with different chain lengths were synthesized : a low molecular weight tri−block copolymer with short−chain PLA blocks (LPB) and a high molecular weight tri−block copolymer with long−chain PLA blocks (HPB).","label":"POLY_STRUC"}
{"id":177,"sentence":"The latter can easily suffer homolytic cleavage of the O – O bond, forming new free radicals that provoke chain scission or crosslinking. Scheme 3. Hydroperoxide formation and decomposition during the thermo−oxidation of PLA.","label":"BIODEGRAD_PROP"}
{"id":178,"sentence":"Figure 5 Open in figure viewer PowerPoint SEM micrographs of the cPLA fracture surfaces before and after hydrolysis at 70 °C : (a) after 3 days in an alkaline medium and (b) after 20 days in a neutral medium.","label":"BIODEGRAD_POLY"}
{"id":179,"sentence":"This may be the reason that the Tm of the blends decreased with the addition of compatibilizers, as shown by the DSC data in Table 3. Although the samples with HPB compatibilizers had lower Tm than the LPB samples,","label":"POLY_STRUC"}
{"id":180,"sentence":"The blends were melt blended in a Brabender twin−crew extruder and the dogbone tensile bars were compression molded. Kim [133] indicated that the starch granules were incompatible with the PLLA matrix, based on scanning electron microscopy (SEM) micrographs.","label":"BIODEGRAD_POLY"}
{"id":181,"sentence":"and PBS \/ PBAT Blend Before and After 6 Days Conditioned at 50 °C with 90 % RH Samples Zero shear viscosity (Pa s) Viscosity ratio (η 1 \/ η 2)","label":"RHEOLOGICAL_PROP"}
{"id":182,"sentence":"Fungi protect themselves against free radicals by the production of low molecular weight molecules that have a high affinity for these radicals. If the mechanism of formation of free radicals is not well known, on the contrary,","label":"POLY_STRUC"}
{"id":183,"sentence":"In this study, observed impact strength had good agreement with the spherulite morphology and crystallinity. Figure 16 Open in figure viewer PowerPoint Polarized optical micrographs of PBS, PBAT,","label":"BIODEGRAD_POLY"}
{"id":184,"sentence":"Naturally, assimilated molecules may be the result of previous (bio) deterioration and \/ or (bio) fragmentation. Assimilation is generally estimated by standardised respirometric methods (ISO 14852, 1485,","label":"BIODEGRAD_PROP"}
{"id":185,"sentence":"70 Optical Polarizing Microscopy Figure 16 shows the spherulite morphology of PBS, PBAT, and PBS \/ PBAT before and after 30 days of exposure to raised humidity and temperature.","label":"BIODEGRAD_POLY"}
{"id":186,"sentence":"Gel permeation chromatography used a THF \/ methylene chloride mixture as a solvent. A possible explanation for the increase in the viscosity−average molecular weight of the injection−mold−grade PDLLA is that during processing (i. e., extrusion and injection molding) there was polymer chain entanglement,","label":"POLY_STRUC"}
{"id":187,"sentence":"which can also be derived from biobased succinic acid. PBS has many desirable properties including good toughness and melt processability. The mechanical properties of the PBS fall between polyolefins with a wide processing window. 1, 2 In addition,","label":"BIODEGRAD_POLY"}
{"id":188,"sentence":"Mw \/ Mn 0 2. 48 ; P3HP70k, Mn 0 7. 0 × 104, Mw \/ Mn 0 2. 03), which are synthesized by the ring opening polymerization of propiolactone, were kindly supplied by Tokuyama Co.","label":"POLY_STRUC"}
{"id":189,"sentence":"New Castle, Del., USA) was used to determine changes in crystallinity of PBAT due to biodegradation in different compost media via changes in the heat of fusion.","label":"POLY_STRUC"}
{"id":190,"sentence":"Despite the fact that Mn decreased to approximately 5 % of its original value and 12 % of the sample weight was lost, no cavities were found on the sample surface.","label":"BIODEGRAD_PROP"}
{"id":191,"sentence":"The thermal properties of P3HP−b−P4HB were compared with block copolymers PHB−b−PHVHHp, P3HB−b−P4HB, and PHB−b−PHHx from previous studies.","label":"BIODEGRAD_POLY"}
{"id":192,"sentence":"the reader is referred to the Web version of this article.) Fig. 6 displays the nominal stress−strain curves for each pair of PLA−b−PI−b−PLA triblock copolymers,","label":"MECHANICAL_PROP"}
{"id":193,"sentence":"The fact that during the first 15 days only slight change in molecular weight distributions (MWD) was observed indicates that, initially, the hydrolytic main chain scission favored the chain ends because of the increased free volume associated with them.","label":"BIODEGRAD_PROP"}
{"id":194,"sentence":"The assignments of the specific triad−monomer sequence for random copolymer P (3HP−co−4HB) were similar with that of the previous studies.","label":"POLY_STRUC"}
{"id":195,"sentence":"The literature reports numerous Mark – Houwink equations for poly (lactic acid). The Mark – Houwink constants are a function of the type of poly (lactic acid) used,","label":"BIODEGRAD_POLY"}
{"id":196,"sentence":"The normalized complex viscosities of pure PLA and PCL decreased to 0.62 and 0.83, respectively, after 30 min indicating PCL was more stable than PLA during melt processing.","label":"BIODEGRAD_POLY"}
{"id":197,"sentence":"As indicated in the figure, the degradation rates of PLA \/ PPG−800 and PLA \/ PPG−1000 are close to that of the neat PLA.","label":"BIODEGRAD_POLY"}
{"id":198,"sentence":"and, when done by the active chain end, termination, which thereby limits the molecular weights. Sipos et al. [48] reported that the use of 18−crown−6 ether complexes will yield higher molecular weights with narrow distributions, (PDI 0 1.1 – 1.2), but they slow the rate and give lower overall conversions.","label":"POLY_STRUC"}
{"id":199,"sentence":"The molecular weights of the PDLLA prior to and after injection molding, as determined by SEC−MALLS, were statistically insignificant. Molecular weight studies, on the general−purpose, as well as the injection−mold−grade, PDLLA, using dilute−solution viscosity, were performed at USDA−ARS−NCAUR in Peoria,","label":"POLY_STRUC"}
{"id":200,"sentence":"Biodegradable and compostable polymers have gained attention from industries, consumers, and governments as a potential way to reduce municipal solid waste since they can be recycled or energy recovered through composting into soil amendment products [1].","label":"POLY_STRUC"}
{"id":201,"sentence":"Figure 9 Open in figure viewer PowerPoint Tensile modulus of PP, PBS, PBAT, and PBS \/ PBAT as a function of exposure time at 50 °C with 90 % RH. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":202,"sentence":"Much emphasis has been placed on synthesizing and modifying biodegradable polymers such as poly (ε‐caprolactone) (PCL), poly (lactic acid) (PLA),","label":"BIODEGRAD_POLY"}
{"id":203,"sentence":"This PHA microstructure characterization demonstrated that the monomer sequence structures of the putative block copolymers were indeed a block copolymer P3HP−b−P4HB. Additional evidence of the block copolymer were obtained from a Bernoullian model (eq 1) describing the diad−dependent carbonyl resonances in the 13C NMR spectrum of the putative block copolymer P3HP−b−P4HB and random copolymer P (4HB−co−3HP).","label":"POLY_STRUC"}
{"id":204,"sentence":"Annealing crystallizable PLA copolymers to induce crystallinity often produced two melting peaks [100]. This is what was observed at the USDA−NCAUR (Peoria, IL) with PDLLA in injection−molded starch \/ PDLLA \/ adipic PHEE blends.","label":"BIODEGRAD_POLY"}
{"id":205,"sentence":"On the other hand, PEG crystallinity was not detected at all, even at the beginning of degradation and a possible reason is that its original composition was too low relative to the PCL composition and hence its crystallization was totally hampered.","label":"POLY_STRUC"}
{"id":206,"sentence":"Polymers Tg1 (oC) Tg2 (oC) Tm1 (oC) Tm2 (oC) PBAT−33. 8−122. 9−PLA10−36. 2 55. 3 126. 3 148. 6 PLA20−34. 9 55. 5 128. 0 148. 1 PLA30−36. 3 55. 6 128. 3 147. 5 PLA40−34. 0 55. 7 128. 6 147. 6 PLA−56. 1−152.","label":"BIODEGRAD_POLY"}
{"id":207,"sentence":"0017 d−1), hydrolysis in buffer solution (0.0192 ± 0.0011 d−1) and in vermiculite (0.0216 ± 0.","label":"BIODEGRAD_PROP"}
{"id":208,"sentence":"or in more aggressive media relevant to a chemical recycling process requiring accelerated hydrolysis. The hydrolysis in aqueous media of semicrystalline and amorphous PLA grades was studied between 60 and 80 °C and at pH values between 1 and 12.","label":"BIODEGRAD_PROP"}
{"id":209,"sentence":"The results are listed in Table X. The wide variance in the oriented properties is due to the degree of orientation and stereochemical composition of various poly (lactic acid) samples.","label":"BIODEGRAD_POLY"}
{"id":210,"sentence":"Moreover, except PBAT, all the samples exhibit brittle failure with increasing conditioning time. Table 1.Notched Izod Impact Strength of the Samples Before and After Conditioned at 50 °C with 90 % RH Samples Before conditioning After 6 days conditioning After 12 days conditioning After 24 days conditioning After 30 days conditioning PBS 24. 80 ± 6. 55 12. 54 ± 6. 20 13. 19 ± 1.91 12. 90 ± 1.003 12. 41 ± 1.07 PBAT Non‐break (210.55 ± 10.37)","label":"BIODEGRAD_POLY"}
{"id":211,"sentence":"Our findings have good agreement with previous studies. 14 According to these studies, the chain scission leads to reduced entanglement density and tie molecules of the semi crystalline polymers.","label":"BIODEGRAD_PROP"}
{"id":212,"sentence":"the mechanical properties of PBS and PBAT were significantly affected with increasing conditioning time. The PBS, PBAT, and PBS \/ PBAT showed an increase in modulus as well as a decrease in tensile strength and elongation at break with increased exposure time.","label":"BIODEGRAD_POLY"}
{"id":213,"sentence":"Jendrossek, 1998), enzyme fragmenting the poly (caprolactone). According to the microbial species, low molecular weight fragments can be metabolised or not.","label":"POLY_STRUC"}
{"id":214,"sentence":"The reaction starts with a nucleophilic attack performed by the oxygen atom of Ser160 on the PCL model compound and leading to the formation of INT−1,","label":"BIODEGRAD_POLY"}
{"id":215,"sentence":"Melting enthalpy (Δ Hm) of the sample was calculated by measuring the area under the melting peak while crystallization enthalpy (Δ Hc) was the measured area under the crystallization peak.","label":"POLY_STRUC"}
{"id":216,"sentence":"and (70 \/ 30) blends. The SEM images of uncompatibilized blends (Figures 1 (a) and 1 (c)) showed voids between the dispersion phase (PCL)","label":"BIODEGRAD_POLY"}
{"id":217,"sentence":"Tensile properties of PLA \/ PBAT blends and PLA fibre−reinforced PBAT composite","label":"BIODEGRAD_POLY"}
{"id":218,"sentence":"This pointed to the major difference in the erosion mechanism and the fact that essentially in alkaline conditions, the surface and bulk erosion proceeded simultaneously, whereas in neutral and acid media, it was mainly the bulk erosion mechanism that was responsible for the weight loss.","label":"BIODEGRAD_PROP"}
{"id":219,"sentence":"Hydrolysis of poly (α‐hydroxy esters), including PLA, has traditionally been modeled using the first order kinetic scheme of Eq. 1 where [COOH], [ester],","label":"BIODEGRAD_PROP"}
{"id":220,"sentence":"Eq. 3. Following day 7, the first order model consistently overestimated the Mn of both PLA32 and PLA118. For the samples degraded at 80 °C,","label":"BIODEGRAD_POLY"}
{"id":221,"sentence":"In order to incorporate more widespread semicrystalline biodegradable polymers in durable applications, including automotives and electronics, the performance of the polymers must be maintained throughout their life time.","label":"POLY_STRUC"}
{"id":222,"sentence":"For designing some other sustainable di−or tri−block copolymers with monomers from bioresources, our facile mild synthesis strategy might be better to consider about.","label":"POLY_STRUC"}
{"id":223,"sentence":"which increases the entanglement density between the compatibilizer and blends. In addition, the long−chain HPB copolymer may be the more effective compatibilizer for PLA and PBAT.","label":"BIODEGRAD_POLY"}
{"id":224,"sentence":"A total of 5 g \/ L of BDO was added as the first precursor for P4HB block synthesis. In another case, when BDO was almost exhausted after 28 h of cultivation, PDO was then added as the second precursor, leading to formation of a copolymer consisting of 37 mol % 4HB and 63 mol % 3HP (Table 1).","label":"BIODEGRAD_POLY"}
{"id":225,"sentence":"the mechanical and thermal properties of the PBS depend on the degree of crystallinity and the spherulite morphology. 3 Degradability of the PBS has been widely studied under different environmental conditions. 4−8 These studies claimed that the PBS is susceptible to hydrolysis in the presence of moisture \/ water.","label":"BIODEGRAD_POLY"}
{"id":226,"sentence":"The nonlinear decrease in the Young's modulus with increasing PI midblock molecular mass indicates that this mechanical parameter is more correlated with the glassy and \/ or crystallized hard phase domains in the network.","label":"MECHANICAL_PROP"}
{"id":227,"sentence":"Finally, research conducted on starch – PLA composites is introduced. KEY WORDS : Poly (lactic acid) ; synthesis ; crystallization kinetics ; viscosity ; composites. INTRODUCTION Poly (lactic acid) (PLA) belongs to the family of aliphatic polyesters commonly made from a−hydroxy acids,","label":"BIODEGRAD_POLY"}
{"id":228,"sentence":"Overall, the mechanical property of these triblock copolymers covers a wide range, inferring that the synthesis of these samples can be well manipulated according to certain application demands.","label":"MECHANICAL_PROP"}
{"id":229,"sentence":"For samples degraded at 40 °C, one model was not clearly better than the other. The R2 values for those fits were low because the molecular weight did not begin to decrease until after day 7 of degradation.","label":"BIODEGRAD_PROP"}
{"id":230,"sentence":"Analysis of the molecular weight profile during the course of degradation revealed that random chain scission of the ester bonds in PCL predominates at the initial induction phase of polymer degradation.","label":"BIODEGRAD_PROP"}
{"id":231,"sentence":"Reed and Gilding [18] examined the effect of temperature (25 – 50 °C) on the degradation of PGA sutures and observed that high temperatures markedly increased degradation.","label":"BIODEGRAD_PROP"}
{"id":232,"sentence":"The initial structure was modeled from AfEST crystal structure pdb code 1JJI. (8) Hydrogen atoms were added according to the protonation states of the residues taking in account a medium with pH 7 (the enzyme has optimal activity for pH 6. 5 – 7. 5).","label":"POLY_STRUC"}
{"id":233,"sentence":"Supporting Information). The cPLA crystallized quickly during hydrolysis ; a melting enthalpy of 25 J \/ g was reached (Mw ≈ 92 kg \/ mol) in just a few hours after the samples were immersed in the hydrolysis media.","label":"BIODEGRAD_PROP"}
{"id":234,"sentence":"The micrographs are depicted in Figure 7. Films at Week 1 and 3 of degradation appeared smooth and largely similar to the one at Week 0, implying that degradation has not set in or is largely insignificant.","label":"BIODEGRAD_PROP"}
{"id":235,"sentence":"The stabilizer effect was evaluated based on molecular weight analysis, therefore the intrinsic viscosity was measured at different times during processing (Fig. 5). Since this method has higher sensibility to chain scission than FTIR, it was possible to observe that the intrinsic viscosity of neat PLA decreased linearly (around 50 %) with processing time, due to the synergetic effect of shear, temperature and oxygen.","label":"RHEOLOGICAL_PROP"}
{"id":236,"sentence":"At molecular weights below the critical entanglement molecular weight, the polymer viscosity was proportional to Mw. For molecular weights above the critical entanglement molecular weight, the polymer viscosity is known to obey a power law relation, with the viscosity increasing proportionally to, where n is an exponent reported to be approximately 3.","label":"POLY_STRUC"}
{"id":237,"sentence":"the starch aggregated, the particle sizes of starch aggregation became larger, and consequently, the large starch particles prevented crystal growth. As the starch content increased,","label":"POLY_STRUC"}
{"id":238,"sentence":"To hinder the further oxidation and thermal degradation of PLA, experiments were done under a nitrogen atmosphere. Scanning Electron Microscopy (SEM) Micrographs SEM micrographs of the hydrolyzed sample surfaces were carried out to better understand the erosion mechanism.","label":"BIODEGRAD_PROP"}
{"id":239,"sentence":"Several studies have been performed on PLA thermal degradation [12], [13], [13] [a], [13] [b].","label":"BIODEGRAD_POLY"}
{"id":240,"sentence":"4 for linear polymers. 29 Elastic relaxation of the polymer will also be affected in the same way with the relaxation time increasing with Mw. The plateau viscosity is presented as a function of Mw for aPLA and cPLA in Figure 8.","label":"POLY_STRUC"}
{"id":241,"sentence":"Mechanical degradation can take place due to compression, tension and \/ or shear forces. So, thermoplastic films can undergo several mechanical degradations under field conditions (e. g. low−tunnel films, mulches, etc.) (Briassoulis, 2004,","label":"BIODEGRAD_PROP"}
{"id":242,"sentence":"To quantify the loss of volatiles from the PLA32 and PLA118 samples, the total mass of the samples before and after aging were compared. The percentage mass loss of the samples exposed to 40, 60,","label":"BIODEGRAD_PROP"}
{"id":243,"sentence":"which was verified by wide−angle X−ray diffraction technique (WAXD). The thermal behavior and mechanical property of PLA−b−PI−b−PLA triblock copolymers were examined by thermogravimetric analysis (TGA), dynamic thermomechanical analysis (DMA),","label":"MECHANICAL_PROP"}
{"id":244,"sentence":"Arrhenius Relationship In this study, it was assumed that hydrolysis was the primary mechanism of degradation for the samples and that the temperature dependence of the rate followed Arrhenius'law as where k 0 rate constant ;","label":"BIODEGRAD_PROP"}
{"id":245,"sentence":"and chain scission (Norrish II). Norrish II reaction has been recently described during photodegradation of PLA (poly [lactic acid]) and PCL (poly [caprolactone]) (Tsuji et al., 2006).","label":"BIODEGRAD_POLY"}
{"id":246,"sentence":"Variations of torque during the terminal stage of the processing could be attributed to the combined effect of melting temperature and the matrix MW change. The torque value is thus only related to the MW of the polymer.","label":"POLY_STRUC"}
{"id":247,"sentence":"Marten et al., 2005, Bikiaris et al., 2006, Marqu é s−Calvo et al., 2006). The estimation of hydrolysis is determined by the appropriated techniques cited above.","label":"BIODEGRAD_PROP"}
{"id":248,"sentence":"1H‐NMR, DSC, FTIR, XRD, and SEM. A faster rate of degradation took place at pH 9. 5 than at pH 7. 4.","label":"BIODEGRAD_PROP"}
{"id":249,"sentence":"or composite materials as MaterBi ® (tm ≈ 64 °C) exhibit melting temperatures near to environmental conditions. Biodegradable polymers such as l−PLA, PCL, PBA (poly [butylene adipate])","label":"BIODEGRAD_POLY"}
{"id":250,"sentence":"30 For both PBS and PBS \/ PBAT, no change was observed in the melting temperature (∼115 °C) after 30 days of exposure time.","label":"BIODEGRAD_POLY"}
{"id":251,"sentence":"5 resulted in the formation of dimers. As these oligomers can be found in the natural metabolites in the body, the degradation fragments are not expected to be toxic to humans.","label":"BIODEGRAD_PROP"}
{"id":252,"sentence":"and a polymer erosion period (mass loss) as reported by Lee et al. 34 For a complete degradation study, these three phases should be monitored together with the examination of both the short‐term and long‐term degradation behavior of the polymer.","label":"BIODEGRAD_PROP"}
{"id":253,"sentence":"Scanning electron microscopy revealed good adhesion of the starch granules to the PLA matrix up to 5 % starch content. In the case of the star−PLA \/ cornstarch composites,","label":"BIODEGRAD_POLY"}
{"id":254,"sentence":"The thermal stability of the PLA \/ PPG composites was investigated using a synchronous thermal analyzer (Jupiter STA 449F3, Netzsch, Selb, Germany) under a nitrogen atmosphere.","label":"MECHANICAL_PROP"}
{"id":255,"sentence":"To compare quantitatively the decaying behaviors of crystalline bands, we introduced here the normalized intensity (Hs), which is defined as (Ht−H ∞) \/ (H0−H ∞),","label":"POLY_STRUC"}
{"id":256,"sentence":"The small molecular chains have potential to rearrange into the crystalline region which is called chemi‐crystallization. This behavior has been observed in most of the semicrystalline aliphatic biodegradable polymers including PBS.","label":"POLY_STRUC"}
{"id":257,"sentence":"An in vitro study of AfEST hydrolysis of PNP hexanoate indicates a barrier of 15. 5 kcal \/ mol, which is expected to be higher than the hydrolysis of PCL because of the aromatic moiety of this substrate.","label":"BIODEGRAD_PROP"}
{"id":258,"sentence":"The molecular weights and PDIs were derived from a calibration curve based on narrow polystyrene standards. 1H NMR analyses were performed for initial PLA, PLA after 25 min of processing and after 120 h of thermo−oxidative.","label":"POLY_STRUC"}
{"id":259,"sentence":"The mass spectrum is presented in Supporting Information Figures S2 and S3. The PCL segment of the copolymer has been cleaved into a variety of products comprising different number of mer units, including : dimers, dimers coupled with K + ion (due to presence of KCl in the buffer solution), trimers, tetramers, pentamers, hexamers,","label":"BIODEGRAD_POLY"}
{"id":260,"sentence":"Both PLA32 and PLA118 were aged at 40 and 60 °C under nitrogen purge. The degradation of the fibers was evaluated based on changes in the total weight, crystallinity, and molecular weight of the samples.","label":"BIODEGRAD_POLY"}
{"id":261,"sentence":"Similarly, at τ 0 20 s, which is almost five times of the medium T1C (2. 1−5. 2s), the resonance line should arise only from the crystalline phase.","label":"POLY_STRUC"}
{"id":262,"sentence":"With considering possible differences in the magnetic dipole−dipole interaction among three crystal forms, the molecular mobilities of crystalline phases were estimated by the values of 13C spin−lattice relaxation time to rank as δ ≪ γ ≪ β.","label":"POLY_STRUC"}
{"id":263,"sentence":"03 Å, Table S2). AfEST has been extensively characterized in the synthesis of PCL. (17, 20, 21) It was found that the enzyme can accommodate PCL at its active site, however,","label":"BIODEGRAD_POLY"}
{"id":264,"sentence":"Fig. 2. Temperature dependences of (a) storage modulus, E′, (b) loss modulus, E′′, and (c) loss tangent, tan δ for solvent−cast PLA−b−PI−b−PLA triblock copolymers.","label":"MECHANICAL_PROP"}
{"id":265,"sentence":"the rate and extent of crystallization also depend on the presence or absence of nucleating agents as well as the time−at−temperature above Tg [100].","label":"POLY_STRUC"}
{"id":266,"sentence":"and catalytic abilities to use and to transform a variety of nutrients cannot be anticipated. Thermo−oxidative exposure of the samples was carried out in an oven under air at 140 °C for 120 h.","label":"BIODEGRAD_PROP"}
{"id":267,"sentence":"Before molding, the materials were dried in a vacuum oven at 40 °C for 24 h. Subsequently, the dried PLA pellets were compression‐molded at 200 °C in the form of 25 mm diameter disk samples with an approximately 2 mm thickness and an approximate weight of 1.","label":"BIODEGRAD_POLY"}
{"id":268,"sentence":"Thermal Analysis DSC measurements were conducted on the fiber samples after the specified degradation time and the calculated percent crystallinities are shown in Fig. 2. For the fibers degraded under nitrogen purge, shown in Fig.","label":"BIODEGRAD_PROP"}
{"id":269,"sentence":"0009 and−0.0280 +−0.0006 ml \/ g, at a wavelength of 632. 8 nm in benzene, were determined by a Wyatt DSP differential refractometer (Santa Barbara, CA) for general−purpose and injection−mold grades of PDLLA, respectively.","label":"BIODEGRAD_POLY"}
{"id":270,"sentence":"Table 5. Yield stress, σ eng, yield strain, ε eng, and strain−hardening modulus, G for (a) solvent−cast and (b) melt−quenched PLA−b−PI−b−PLA triblock copolymers.","label":"MECHANICAL_PROP"}
{"id":271,"sentence":"Table XVI. Effect of Temperature on the Molecular Weight of 90 \/ 10 Copolymers [100] PLA Copolymer [100] Initial molecular weight Mw after 30 min at 160 °C Mw after 30 min at 190 °C 151, 000 (Mn) 102, 000 84, 000 255, 000 (Mw) 160, 000 104, 000 285, 000 (Mz) 204, 000 142, 000 470, 000 (Mn) 354, 000 228, 000 562, 000 (Mw) 362, 000 223, 000 950, 000 (Mz) 650, 000 390, 000 Bigg [100] had shown tables, graphs,","label":"POLY_STRUC"}
{"id":272,"sentence":"In this equation ecomp and e0 are the elongation to break of the composite and the matrix, respectively. The Nicolais – Narkis equation is as follows : scomp 0 s0 [1−1.21 (ff) 1 \/ 3] (19)","label":"MECHANICAL_PROP"}
{"id":273,"sentence":"and thus change the frequency (16) and absorption (18) of crystalline bands, or even split them. (11, 16a, 16b)","label":"POLY_STRUC"}
{"id":274,"sentence":"The spheres in bright green color represent PLA hard domains. PI chains are marked by purple color and PLA chains by oliver color. Crystallized PLA hard domains with Tm, PLA are shown in (a)","label":"BIODEGRAD_POLY"}
{"id":275,"sentence":"which causes the Tg of PLA to increase. As shown in Fig. 2, the melting temperatures (Tm) of the macro−initiator, LPB,","label":"POLY_STRUC"}
{"id":276,"sentence":"and \/ or melting temperature (Tm), (Weiland et al., 1995, Ratto et al., 1999, Hakkarainen et al., 2000,","label":"POLY_STRUC"}
{"id":277,"sentence":"An autocatalytic mechanism was assumed in neutral and acidic media to describe the hydrolysis kinetics. The measured molecular weight decrease over time was successfully described by a two‐stage exponential model. © 2016 Wiley Periodicals,","label":"BIODEGRAD_PROP"}
{"id":278,"sentence":"This observation corroborated with the modulus improvements. Thermogravimetric analysis (TGA) measurements were carried out from 30 to 700 °C with a heating rate of 10 °C \/ min using a Discovery TA 5500 (TA Instruments) under nitrogen atmosphere.","label":"MECHANICAL_PROP"}
{"id":279,"sentence":"These unique properties were combined through the development of a new molecular microstructure in P3HP−b−P4HB block copolymer. The stress – strain measurements of chloroform−extracted solvent cast films were determined.","label":"BIODEGRAD_POLY"}
{"id":280,"sentence":"In contrast to PCL, the results of PLLA reveal linear degradation kinetics. Since the PLLA used in this work is of very high purity (less than 0.01 % of residual solvent and less than 0.1 % residual monomer)","label":"BIODEGRAD_POLY"}
{"id":281,"sentence":"The apparent equilibrium monomer concentration is in direct proportion to the degree or percent of amorphous phase in the polymer [62]. The addition of hydroxylic or carboxylic impurities has also been shown to greatly affect the polymerization rate.","label":"POLY_STRUC"}
{"id":282,"sentence":"Biodegradability studies were performed as per ISO 14855 under aerobic controlled composting conditions [20, 25]. Biodegradability was defined as the percentage of carbon from test materials mineralized to carbon dioxide during composting.","label":"BIODEGRAD_PROP"}
{"id":283,"sentence":"Changes in Tg, Tcc, and Tm of PLA after adding PPG indicate interactions between the PLA chains and the PPG chains. Figure 8. Differential scanning calorimetry (DSC) thermograms of the neat PLA and PLA \/ PPG composites.","label":"BIODEGRAD_POLY"}
{"id":284,"sentence":"The melting and glass transition temperatures of a polymer are examples of thermal transitions. These transitions up to complete pyrolysis (Table 1) using GC – MS have been observed by Kim et al.","label":"POLY_STRUC"}
{"id":285,"sentence":"Effect of Processing Conditions on the Mechanical Properties of PLA Copolymers [100] Copolymer Ratio, Tensile strength, Young ’ s modulus, Elongation (L \/ D,","label":"MECHANICAL_PROP"}
{"id":286,"sentence":"The same pattern of molecular weight reduction for the PBAT samples in the phosphate buffer solution and vermiculite media are observed in Fig. 4a and b, indicating the same hydrolysis process for these two environments.","label":"BIODEGRAD_PROP"}
{"id":287,"sentence":"the Mw and Mn values for the PLA32 sample were 1400 and 690 Da. For PLA118, the Mw and Mn values were 1500 and 730 Da.","label":"POLY_STRUC"}
{"id":288,"sentence":"Figure 3 Open in figure viewer PowerPoint Plot of the natural logarithm of the fractional ester bonds remaining versus degradation time for the degradation occurring at pH 7.","label":"BIODEGRAD_PROP"}
{"id":289,"sentence":"Mass Loss Measurements Samples were weighed before being exposed to the prescribed conditions to determine the initial weight of each sample, Mi.","label":"BIODEGRAD_PROP"}
{"id":290,"sentence":"DSC has its limitations when used to study PCL‐b‐PEG based copolymers because of the proximity of melting temperatures for the PEG and PCL homopolymers (especially when their molecular weights are similar), hence making it difficult to ascribe the melting endotherms to the particular component of this copolymer.","label":"BIODEGRAD_POLY"}
{"id":291,"sentence":"2 The temperature dependence of hydrolysis kinetics in aqueous media has been modeled with the Vogel – Tammann – Fulcher equation [cf. eq. (4)].","label":"BIODEGRAD_PROP"}
{"id":292,"sentence":"Table 3. Thermal properties of blends with different amounts of compatibilizers. The thermal properties were investigated in more detail by also studying other parameters using DSC.","label":"MECHANICAL_PROP"}
{"id":293,"sentence":"The thermoplastic elastomers are applicable mainly depending on their mechanical property, which can be enhanced by the incorporated polymer crystals [17, 24, 25].","label":"MECHANICAL_PROP"}
{"id":294,"sentence":"or cellulose are semi−crystalline polymers, they possess amorphous and crystalline regions (Wyart, 2007). Structural changes take place at their glass transition temperature (Tg) (e. g. 50 °C for l−PLA, 25 °C for PBT (poly [butylene terephtalate]), 5 °C for PHB,−10 to−45 °C for PBS (poly [butylene succinate])),","label":"BIODEGRAD_POLY"}
{"id":295,"sentence":"Specific gravity Glass−Transition Type of PDLLA strength elongation temp. (°C) d General purpose 5 % 67 6 1.15 11.3 6 0.40 914 6 37. 7 1.25b 55 Injection mold grade 3. 6 % 72. 356 6 0.832 11.346 6 1.254 1279. 907 6 109. 05 1.27c 55 a ASTM method D−638. b MSDS. c ASTM method D−792. d DSC at 10 °C per minute.","label":"POLY_STRUC"}
{"id":296,"sentence":"To assess the direct effect of hydrolysis on the thermal properties of PLA, only the first heating scan was considered. Rheological Characterization The relationship between the molecular weight and the viscoelastic properties of the hydrolyzed PLA samples was investigated through rheological characterization.","label":"RHEOLOGICAL_PROP"}
{"id":297,"sentence":"The normalized number average (Fig. 4B) and weight average (Fig. 4A) molecular weights of both the PLA32 and PLA118 samples aged at 100 % RH are shown in Fig.","label":"POLY_STRUC"}
{"id":298,"sentence":"Unless stated otherwise, the samples were fully amorphous at the start of the hydrolysis process. For the data at 60 °C, however, we compared the evolution observed for cPLA that was fully crystallized (i. e., annealed) before hydrolysis to the behavior of the amorphous sample (i. e., quenched).","label":"POLY_STRUC"}
{"id":299,"sentence":"and 80 °C. With respect to the total weight loss, changes in crystallinity, melting temperature and molecular weight, there was no significant difference observed between the two diameters of fiber tested at any of the temperatures.","label":"BIODEGRAD_PROP"}
{"id":300,"sentence":"Mn was reduced from 53, 200 Da before degradation to 1700 Da after 30 days, and reduced further to 690 Da after 90 days of degradation.","label":"BIODEGRAD_PROP"}
{"id":301,"sentence":"By contrast, in the highly alkaline media, it was shown that PLA hydrolysis occurred mainly through a surface‐erosion mechanism. In this case, the alkaline medium reacted directly with the sample surface ; this led to little or no induction period in terms of weight loss and to an observable sample size reduction.","label":"BIODEGRAD_PROP"}
{"id":302,"sentence":"Our previous FTIR results also indicated that the δ−form P3HP, as similar to the crystalline P3HB, adopts the 21−helix conformation, (5c) but at that time no any information is available on its packing.","label":"POLY_STRUC"}
{"id":303,"sentence":"Because an exponential relation was expected, the data were plotted in the log‐normal scale. According to this figure, a shift in the kinetic rate was observed during the PLA hydrolysis.","label":"BIODEGRAD_PROP"}
{"id":304,"sentence":"The packing and dynamics of the β -, γ -, and δ−forms of poly (3−hydroxypropionate) (P3HP), which represents the basic skeleton of bacterial poly (3−hydroxyalkanoate) s, were investigated by the variable−temperature FTIR and 13C solid−state NMR measurements (SNMR).","label":"BIODEGRAD_POLY"}
{"id":305,"sentence":"the long term durability of polylactide (PLA) samples has been studied by few researchers. 13, 14, 20 These studies showed that the mechanical performance of the PLA was significantly affected after exposure to elevated temperature and moisture levels.","label":"BIODEGRAD_POLY"}
{"id":306,"sentence":"Indeed, the failure of this predication occurs not only for P3HP, but also for P3HB, (23a) polypivalolactone (PPL) (23b) and possibly other P3HAs built on P3HP skeleton.","label":"BIODEGRAD_POLY"}
{"id":307,"sentence":"Morphologies of Blends The morphologies of PLA \/ PCL blends compatibilized or not by electron−beam treatment in the presence of GMA were compared. Figure 1 shows the SEM images of cryofractured surfaces of compatibilized and uncompatibilized PLA \/ PCL (90 \/ 10)","label":"BIODEGRAD_POLY"}
{"id":308,"sentence":"On the other hand, PCL merely lost monomer units of insignificant weight from ester bond cleavage. Thus, the compositional changes in PEG and PCL were expected.","label":"BIODEGRAD_POLY"}
{"id":309,"sentence":"It may seem counter−intuitive but PCL, which has a lower melting temperature (Tm 0 60 °C), shows significantly higher thermal stability than PLLA (Tm 0 180 °C).","label":"POLY_STRUC"}
{"id":310,"sentence":"As reported in Table 2, the crystallinity of the PBS increased from 58. 62 % to 73. 43 % after 30 days exposed to 50 C with 90 % RH.","label":"POLY_STRUC"}
{"id":311,"sentence":"which is available at wileyonlinelibrary. com.] Table 2. DSC Results for PBS, PBAT, and Their Blend Before and After 30 Days Conditioned at 50 °C with 90 % RH Samples Tm (°C)","label":"BIODEGRAD_POLY"}
{"id":312,"sentence":"The biodeterioration of thermoplastic polymers could proceed by two different mechanisms, i. e., bulk and surface erosion (Von Burkersroda et al., 2002,","label":"BIODEGRAD_PROP"}
{"id":313,"sentence":"Analysis of the molecular weight profile during the course of degradation revealed that random chain scission of the ester bonds in PCL predominates at the initial induction phase of polymer degradation.","label":"BIODEGRAD_PROP"}
{"id":314,"sentence":"3 Results and Discussion 3. 1 Calorimetry DSC experiments were conducted in order to determine the Tg and Tm of both PCL and PLLA (Table 2). PCL shows a low Tg at. 60 °C, hence it shows a rubbery behavior at room temperature,","label":"POLY_STRUC"}
{"id":315,"sentence":"which is available at wileyonlinelibrary. com.] Figure 6 Open in figure viewer PowerPoint Flexural strength of PP, PBS, PBAT, and PBS \/ PBAT as a function of exposure time at 50 °C with 90 % RH. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":316,"sentence":"To overcome these shortcomings of PLA, we considered blending it with poly (ε−caprolactone) (PCL), which is a soft biodegradable polymer.","label":"BIODEGRAD_POLY"}
{"id":317,"sentence":"and foaming, which require high melt viscosity and elasticity. 3. 4. Thermal Stability Investigation It is well known that thermal degradation reaction occurs during the melt processing of polymers and that this affects their final properties and those of their blends [2].","label":"RHEOLOGICAL_PROP"}
{"id":318,"sentence":"which consists of a short−chain microstructure of P3HP polymer chain restoring its ultrahigh strength and P4HB capturing its elasticity forming a thermoplastic elastomeric polymer. This polymer can be useful in the field of chemical industry, medicinal applications, plastic industry,","label":"POLY_STRUC"}
{"id":319,"sentence":"Adding this stabilizer, B900, is expected to minimize the molecular weight decrease during processing. Fig. 4 depicts the evolution of carbonyl groups of PLA and PLA + B900 with processing time.","label":"BIODEGRAD_POLY"}
{"id":320,"sentence":"Consequently, the BA unit was more vulnerable to hydrolysis and biodegradation. During biodegradation, increases in PBAT crystallinity were observed, which indicated that the amorphous regions biodegraded faster than the crystalline regions.","label":"BIODEGRAD_PROP"}
{"id":321,"sentence":"Concomitantly, the pH inside pores is modified by the degradation products, which normally have some acid – base characteristics (G ö pferich, 1996).","label":"BIODEGRAD_PROP"}
{"id":322,"sentence":"which is seven times more than the blends without compatibilizers. The reason might be that the presence of the tri−block copolymers decreases the interfacial tension of PLA and PBAT,","label":"BIODEGRAD_POLY"}
{"id":323,"sentence":"The peak at 755 cm21 can be assigned to the crystalline phase, while the peak at 869 cm21 can be assigned to the amorphous phase. The ultraviolet spectrum of poly (lactic acid) is presented in the literature.","label":"POLY_STRUC"}
{"id":324,"sentence":"(38) About 1.0 g of original samples was dissolved in chloroform and ethanol was added dropwise to this solution until the PHA was precipitated at room temperature.","label":"BIODEGRAD_POLY"}
{"id":325,"sentence":"Overall, PPG can effectively reduce the melt viscosity of PLA, especially at low MW. The values of n for the PLA and PLA \/ PPG composites at different shear rates are listed in Table 1.","label":"BIODEGRAD_POLY"}
{"id":326,"sentence":"In the phosphate buffer solution, the pattern of decreased fBA and increased fBT continued until the reverse pattern occurred (increased fBA and decreased fBT), which suggested that at this point the BT domains started undergoing hydrolysis.","label":"BIODEGRAD_PROP"}
{"id":327,"sentence":"Fig. 2 shows typical thermograms of the macro−initiator and tri−block copolymers. The curve of HO−PBAT−OH reveals that the glass transition temperature (Tg) is at−27. 84 °C.","label":"POLY_STRUC"}
{"id":328,"sentence":"Scheme 1.Proposed degradation mechanisms of PLA by hydrolysis. Consequently, to have a clear picture of the degradation extension, the intrinsic viscosity and crystallinity were assessed,","label":"BIODEGRAD_PROP"}
{"id":329,"sentence":"Zhang et al. showed that the crystal structures formed during the degradation process may display a lower regularity and smaller domain size compared to those formed by annealing 26.","label":"POLY_STRUC"}
{"id":330,"sentence":"In the late stages of hydrolysis, that is, after the 20th day, once again, a narrow monomodal molecular weight distribution with a polydispersity index close to 1 appeared.","label":"POLY_STRUC"}
{"id":331,"sentence":"In Figure 7 are shown the wavenumbers of CH2 bending doublet (1434 and 1427 cm−1) and those of CH2 rocking doublet (806, 801 cm−1) as functions of temperature for the γ−form.","label":"POLY_STRUC"}
{"id":332,"sentence":"Non‐break (193. 16 ± 35. 47) PBS \/ PBAT Non‐break (226. 77 ± 43. 95) 56. 22 ± 4. 24 52. 24 ± 14. 24 11.36 ± 1.92 13. 04 ± 2.","label":"BIODEGRAD_POLY"}
{"id":333,"sentence":"In this study, two commercial polylactide (PLA) grades with different d‐lactate contents were subjected to hydrolysis in neutral, acidic, and alkaline aqueous media at temperatures above the glass transition.","label":"BIODEGRAD_POLY"}
{"id":334,"sentence":"Characterization Morphological analysis was carried out by scanning electron microscopy (SEM, Hitachi model s−4200, Japan) on cryofractured surfaces of blends. Rheological properties were measured using a rotational rheometer (Physica MCR 30 ;","label":"RHEOLOGICAL_PROP"}
{"id":335,"sentence":"The thermal properties of blends with different amounts of compatibilizers were characterized by DSC. The glass transition temperature (Tg) is well known to be an effective parameter to assess the miscibility of blends.","label":"POLY_STRUC"}
{"id":336,"sentence":"which is available at wileyonlinelibrary. com.] Figure 12 Open in figure viewer PowerPoint DSC cooling curves for PBS, PBAT, and PBS \/ PBAT before and after exposed to 50 °C with 90 % RH for 30 days. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":337,"sentence":"1 Introduction Thermal degradation of polymers is usually not a concern during their service life unless the material is directly exposed to the sun or elevated temperatures. However,","label":"BIODEGRAD_PROP"}
{"id":338,"sentence":"In addition to microbial activity, hydrolysis has a substantial influence on biodegradation and biodegradation rates of biodegradable polyesters such as PBAT, since hydrolysis is one of the initial processes of biodegradation [7], [23], [24], [25].","label":"BIODEGRAD_PROP"}
{"id":339,"sentence":"A similar trend has been reported in the literature for PP, 41 high density polyethylene (HDPE), 42 and PHBV. 37 After conditioning, PBS showed lower elongation than PP during the entire exposure time.","label":"BIODEGRAD_POLY"}
{"id":340,"sentence":"and may be fully automated (Oxitop ®). This technique is also used to estimate the evolution of carbon dioxide, but in most cases, FTIR is preferred (Itavaara and Vikman, 1995,","label":"BIODEGRAD_PROP"}
{"id":341,"sentence":"and humidity (90 % RH). On the other hand, they have noticed that the PC \/ ABS blend did not show any significant changes in the flexural strength up to 30 days conditioning because of the resistance to the hydrolysis.","label":"MECHANICAL_PROP"}
{"id":342,"sentence":"The adhesion forces between PLA and starch may be due to polar interactions between the two phases and hydrogen bonding between the carbonyl group of PLA and the hydroxyl group of starch.","label":"BIODEGRAD_POLY"}
{"id":343,"sentence":"Mw, weight average molecular weight ; Mn, number average molecular weight ; and PDI, polydispersity index. P4HB has a high elasticity and P3HP possesses an ultrahigh strength.","label":"POLY_STRUC"}
{"id":344,"sentence":"and an injection temperature of 165 °C for PHB and PHB−V, and 100 °C for PCL. Thermal analyses of PCL, PHB,","label":"BIODEGRAD_POLY"}
{"id":345,"sentence":"and HPB tri−block copolymers are 135. 59 °C, 124. 59 °C, and 124. 06 °C, respectively. The results suggested that these different lengths of PLA and PBAT blocks in the tri−block chains acted as impurities to disturb the crystallization of the block chains and finally reduce the Tm of the tri−block copolymers [28].","label":"POLY_STRUC"}
{"id":346,"sentence":"As mentioned before, PBS and PBAT are susceptible to the moisture. Therefore, it can be expected that the moisture can easily hydrolyze the PBS and PBAT at 90 % RH and it leads to a decrease in the molecular weight as well as viscosity.","label":"BIODEGRAD_POLY"}
{"id":347,"sentence":"the period in the aqueous media enabled the full crystallization of the sample. The melting peak also shifted to a lower temperature when the hydrolysis experiment proceeded but at a lower rate than for the aPLA.","label":"POLY_STRUC"}
{"id":348,"sentence":"Obviously, the CH2 bending and rocking doublet of the γ−form were further split by cooling, which is as similar as what occurs for the all−trans PE chains in the orthorhombic crystal, (11)","label":"POLY_STRUC"}
{"id":349,"sentence":"Similar to the observation at pH 9. 5, a porous networked structure was also discovered at the edges of the film under close scrutiny ; enforcing the suggestion that degradation occurred via the edges inwards.","label":"BIODEGRAD_PROP"}
{"id":350,"sentence":"PBAT is an aliphatic aromatic copolyester produced from petroleum based resources and certified as compostable by the Biodegradable Products Institute (BPI) according to the ASTM D6400 specification [3].","label":"POLY_STRUC"}
{"id":351,"sentence":"As can be seen from Equation (9), the ratio of the torque to the viscosity at the same temperature and shear rate is equal. The results indicate that the viscosity was continuously lowered when the MW of PPG was lowered.","label":"RHEOLOGICAL_PROP"}
{"id":352,"sentence":"Fig. 6. Nominal stress−strain curves for each pair of PLA−b−PI−b−PLA triblock copolymers (solvent−cast and melt−quenched).","label":"MECHANICAL_PROP"}
{"id":353,"sentence":"For PLLA, thermal decomposition began at 310 °C and was completed by 400 °C. For the PLLA \/ cornstarch composite, the onset of decomposition was at 220 °C – 230 °C, with most of the decomposition occurring between 280 °C and 340 °C.","label":"BIODEGRAD_POLY"}
{"id":354,"sentence":"Fig. 3, Fig. 4). The elevated temperature increased the rate of degradation probably by favoring the nonenzymatic hydrolysis of ester bonds, as suggested by Reed and Gilding [18].","label":"BIODEGRAD_PROP"}
{"id":355,"sentence":"To understand the relationship between the enzymatic degradation and solid structure of PHAs at a molecular level is obviously very helpful for us to design the novel biodegradable PHAs.","label":"BIODEGRAD_PROP"}
{"id":356,"sentence":"which reflect the change of the chain packing, were monitored during cooling, and further compared among the three crystal forms. Second, the heating−induced spectral alterations of two all−trans crystals were also in situ monitored,","label":"POLY_STRUC"}
{"id":357,"sentence":"and (c) 80 °C. Unfilled symbols indicate aPLA, and filled symbols indicate cPLA. At 60 °C (in dashed green),","label":"BIODEGRAD_POLY"}
{"id":358,"sentence":"The aim of the present work was to investigate the effect of fiber diameter on the degradation characteristics of PLA fibers exposed to elevated temperature corresponding to less, comparable, and greater than the Tg of ∼60 °C (40, 60, and 80 °C) and varied humidity (0 and 100 % RH).","label":"POLY_STRUC"}
{"id":359,"sentence":"Intern. Polymer Processing XXII (2007) 5. Carl Hanser Verlag, Munich A. Lopez Arraiza et al. : Rheological Behavior and Modeling of Thermal Degradation 2 Materials and Techniques 2.","label":"RHEOLOGICAL_PROP"}
{"id":360,"sentence":"Glass transition temperature (Tg) and melt temperature (Tm) of PLLA and PCL c 2007 Carl Hanser Verlag, Munich, Germany www. polymer−process. com Not for use in internet or intranet sites.","label":"POLY_STRUC"}
{"id":361,"sentence":"(18, 19) The synthesis of PCL catalyzed by AfEST was previously described. The existing forms, free and immobilized, allow the formation of polymeric chains with molecular mass (Mn) values between 900 and 1340 g \/ mol and monomer conversion ratios between 72 and 99 % at 80 °C.","label":"POLY_STRUC"}
{"id":362,"sentence":"Table XXI is a table from the literature [128] for poly (D, L−lactic acid). The value of the solubility parameter is most likely closer to that reported in the aforementioned tables.","label":"BIODEGRAD_POLY"}
{"id":363,"sentence":"Poly (lactic acid), contrary to what is reported in the literature, is insoluble in acetonitrile. Crystalline PLA is soluble in chlorinated solvents and benzene at elevated temperatures.","label":"BIODEGRAD_POLY"}
{"id":364,"sentence":"A mild synthesis method has just been applied to prepare a series of PLA−b−PI−b−PLA triblock copolymers, which has just been reported in our recent paper [3].","label":"BIODEGRAD_POLY"}
{"id":365,"sentence":"at 10 to 50 reciprocal seconds. The weight−average molecular weights (Mw) of these PLA grades, determined by gel permeation chromatography (GPC), are about 100, 000 for injection molding to about 300, 000 for cast−extruded film grades.","label":"POLY_STRUC"}
{"id":366,"sentence":"the shear rate, the type of melt processing, and the amount of work put into the polymer [5]. Table XIX. Power−Law Equations for Poly (D, L−Lactic Acid) Temperature Table XX.","label":"RHEOLOGICAL_PROP"}
{"id":367,"sentence":"and biomedical materials as alternatives to commodity plastics. (1) These polymers, in particular, poly (butylene succinate), poly (ε−caprolactone) — PCL, poly (lactic acid),","label":"BIODEGRAD_POLY"}
{"id":368,"sentence":"Either the change in amorphous‐crystal surface energy or a decreased in the lamellar thickness was responsible for the Tm decrease of a polyester after exposure to elevated temperature and humidity.","label":"POLY_STRUC"}
{"id":369,"sentence":"5 than at pH 7. 4. The initial stage of degradation was predominated by random chain scission of the ester bonds in PCL. There was also an insignificant mass loss of the films observed.","label":"BIODEGRAD_PROP"}
{"id":370,"sentence":"The mechanical properties of P (3HP−b−P4HB) were superior as compared to previously biosynthesized block copolymers. The tension strength and elongation at break of P (3HP−b−P4HB) in this study, were significantly increased as compared to other block copolymers, such as PHB−b−PHVHHp, P3HB−b−P4HB,","label":"BIODEGRAD_POLY"}
{"id":371,"sentence":"O (1 \/ k). Additionally, two models for the degradation were compared. For the obtained data, both models provided a reasonable fit of the molecular weight data.","label":"BIODEGRAD_PROP"}
{"id":372,"sentence":"Figure 9 Open in figure viewer PowerPoint SEM micrographs of block copolymer films at various stages of degradation at pH 9. 5. Figure 10 Open in figure viewer PowerPoint Schematic illustration of degradation process of the copolymer. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_PROP"}
{"id":373,"sentence":"and compatibilized (d) PLA \/ PCL (70 \/ 30) blends. 3. 2. FTIR Analysis The FTIR analysis was performed to support the results of the morphology study, that is, to provide evidence of increased compatibility due to cross−copolymerization by electron−beam irradiation.","label":"BIODEGRAD_POLY"}
{"id":374,"sentence":"and their homopolymers. The present work aimed at microbial synthesis and characterization of P3HP−b−P4HB for possibility to generate new materials with better properties. PHA content and composition were analyzed by gas chromatography (GC ; GC−2014,","label":"BIODEGRAD_POLY"}
{"id":375,"sentence":"This can be due to chain oxidation caused by the synergetic effect of temperature and oxygen, provoking cleavage of the long chains into shorter ones via the degradation mechanisms (hydrolysis, random chain−scission, trans−esterification, β−scission...) together with a significant increase of carboxyl end groups [10].","label":"BIODEGRAD_PROP"}
{"id":376,"sentence":"The lateral crystal sizes are in the range of 13 – 15 nm, which do not change much with molecular mass of PI midblock. This result is related to the confined crystal growth for PLA end blocks in their microphase separated domains.","label":"POLY_STRUC"}
{"id":377,"sentence":"The cold crystallization temperatures of the PLA \/ PPG composites decreased with a decreasing PPG MW, while the glass transition temperature and melting point remained almost unchanged.","label":"POLY_STRUC"}
{"id":378,"sentence":"This may be attributed to the hydrolysis products of PBS accelerating the degradation of PBAT in the PBS \/ PBAT blend. The differential scanning calorimetry results suggested that the crystallinity of the samples increased after being exposed to elevated temperature and humidity.","label":"BIODEGRAD_PROP"}
{"id":379,"sentence":"45 The notched Izod impact strength of PBS, PBAT, PBS \/ PBAT blend, and PP samples after conditioning for 18 days is explained elsewhere. 19 With increased exposure time (from 6 to 30 days),","label":"BIODEGRAD_POLY"}
{"id":380,"sentence":"and the degradation degree of the composite materials increased as the MW of PPG was decreased. Poly (lactic acid) (PLA) [6, 7, 8] is a typical aliphatic polyester,","label":"BIODEGRAD_POLY"}
{"id":381,"sentence":"The obtained yield point for each stress−strain curve marked by an orange solid circle is shown in Fig. 6. At large strains the strain−hardening modulus,","label":"MECHANICAL_PROP"}
{"id":382,"sentence":"When the weight‐average molecular weight (Mw) was decreased to 2. 8 kg \/ mol, one single Tm was found (121 °C),","label":"POLY_STRUC"}
{"id":383,"sentence":"For example, Carrasco et al. determine the chemical structure, crystallinity, thermal stability and mechanical properties of PLA after processed by injection moulding [9].","label":"POLY_STRUC"}
{"id":384,"sentence":"For specimens maintained at 100 % RH, ∼30 mg samples of PLA fiber were placed into separate uncovered vials. The vessel containing the sample vials was housed in an oven maintained at 40, 60, or 80 °C for the prescribed degradation time. ","label":"BIODEGRAD_POLY"}
{"id":385,"sentence":"which are slightly lower than that for PI10k (Tonset 0 345. 3 °C), but much higher than that for PLA−CTA (Tonset 0 279. 1 °C).","label":"BIODEGRAD_POLY"}
{"id":386,"sentence":"which was deduced from the well−known invariant expression. (20a) Here, ρ c and ρ a are the mass densities of the crystalline and amorphous phases, κ is the ratio of the electron density to the mass density,","label":"POLY_STRUC"}
{"id":387,"sentence":"When the molecular weights of the copolymers are compared at Week 20, the PCL‐b‐PEG copolymer degraded to 9, 900 g \/ mol at pH 9. 5.","label":"POLY_STRUC"}
{"id":388,"sentence":"The samples degraded at 80 °C showed a rapid increase in the crystallinity for both diameters tested. The percent crystallinity for both samples peaked between 5 and 6 days at ∼73 and 72 % for the PLA32 and PLA118 samples.","label":"POLY_STRUC"}
{"id":389,"sentence":"They have noticed a reduction in the mechanical performance of PLA and PLA \/ PC blend with increasing conditioning time. Therefore, the author concludes that the PLA accelerated the degradation of PC in the PLA \/ PC blend under these conditions.","label":"BIODEGRAD_POLY"}
{"id":390,"sentence":"and PP (around 7−13 %), indicating its highly flexible nature. The addition of PLA to PLA \/ PBAT blends gradually degraded the value of Eb, the flexibility.","label":"BIODEGRAD_POLY"}
{"id":391,"sentence":"RAFT polymerization was then used by taking PLA−CTA as the chain transfer agent, PI, isoprene as the monomer, and DTBP, di−tert−butyl peroxide as the initiator.","label":"BIODEGRAD_POLY"}
{"id":392,"sentence":"This phenomenon may be attributed to the hydrolysis product of PBS accelerating the degradation of PBAT in the PBS \/ PBAT blend. 31 Changes in Mechanical Properties Mechanical properties are the main indicators in order to evaluate the durability of the polymeric materials.","label":"BIODEGRAD_PROP"}
{"id":393,"sentence":"Because of the obvious degradation of PLA \/ PPG−200, the change of the viscosity caused by degradation is not negligible. Therefore, the torque of the materials should be higher before degradation and lower after degradation.","label":"BIODEGRAD_PROP"}
{"id":394,"sentence":"The hard segments form physical reversible cross−linking points by virtue of the interchain force, providing strength and hardness. On the other hand, the soft segments contribute to toughness and elasticity of TPEs [2].","label":"MECHANICAL_PROP"}
{"id":395,"sentence":"The degradation of thick, melt‐processed samples in contrast to solution cast films is also addressed. The examination of thick samples enabled differentiation between the surface and bulk erosion trough microscopic examination of the samples.","label":"BIODEGRAD_PROP"}
{"id":396,"sentence":"According to the literature, 50 the weight average molecular weight (M) is directly proportional to the viscosity of the polymer melt at a zero shear rate.","label":"RHEOLOGICAL_PROP"}
{"id":397,"sentence":"the contribution from the amorphous phase should be almost zero. That is, only the resonances of the crystalline phase and the phase with the medium T1C could be observed.","label":"POLY_STRUC"}
{"id":398,"sentence":"PLA pellets were first dried at 60 °C with a nitrogen purge for 12 h until they contained less than 50 ppm moisture.","label":"BIODEGRAD_POLY"}
{"id":399,"sentence":"The increase in crystallinity eventually increased the modulus of the conditioned samples. The enhanced crystallinity was further confirmed by polarizing optical microscopy analysis. Moreover, the hydrolysis of the polyesters was evaluated by scanning electron microscopy, rheology,","label":"POLY_STRUC"}
{"id":400,"sentence":"and 3. 0 %, and 6 % for meso−containing polymer, respectively [105]. Kolstad [103] studied the crystallization kinetics of poly (L−co−meso−lactide) and found that the crystallization half time increased approximately 40 % for every 1 wt % increase in the meso−lactide.","label":"POLY_STRUC"}
{"id":401,"sentence":"30 The possible hydrolytic degradation of PBS and PBAT under elevated humidity and temperature is depicted in Figures 2 and 3, respectively. The chain scission is frequently terminated by carboxylic acid end groups13, 30, 31 and hydroxyl end groups.","label":"BIODEGRAD_PROP"}
{"id":402,"sentence":"The decrease in residual mass could be due to the leaching of cleaved hydrophilic PEG‐rich segments into the degradation medium. However, the decrease is very gradual showing a mass loss of only about 6 % after 20 weeks of degradation (Figure 1).","label":"BIODEGRAD_PROP"}
{"id":403,"sentence":"Sun et al. [134] reported the mechanical properties of poly (L−lactic acid) \/ starch composites. The reported molecular weight of the PLLA was 120, 000 g \/ mole.","label":"BIODEGRAD_POLY"}
{"id":404,"sentence":"Poly (4−hydroxybutyrate) (P4HB) is a highly elastic polymer, whereas poly (3−hydroxypropionate) (P3HP) is a polymer with enormous tensile strength.","label":"BIODEGRAD_POLY"}
{"id":405,"sentence":"and brittleness, which limits its potential applications. Furthermore, although PLA is biodegradable, it degrades at a relatively low rate, and this leaves cope for improvement for industrial composting solid waste treatment.","label":"MECHANICAL_PROP"}
{"id":406,"sentence":"During processing, PLA was plasticized by PPG with different MWs. And the effect of the PPG MW on the melt fluidity of the mixed system was investigated by capillary rheometer.","label":"BIODEGRAD_POLY"}
{"id":407,"sentence":"Nowadays, society is more motivated to use biodegradable plastics, not only as a way to solve the disposal problem of plastics in landfills, but also as a valid alternative to replace conventional polymers [2], [3].","label":"BIODEGRAD_PROP"}
{"id":408,"sentence":"All the samples were stretched with a 50 mm \/ min stretching rate at room temperature. Dynamic analysis (DMA) was performed on a Mettler DMA \/ SDTA861e instrument.","label":"MECHANICAL_PROP"}
{"id":409,"sentence":"This same concept can be used to synthesize an all−carboxyl−terminated PLA by the condensation reaction in the presence of multifunctional carboxylic acids such as maleic, succinic, adipic,","label":"BIODEGRAD_POLY"}
{"id":410,"sentence":"and a melting transition centered at 60 °C. The Tg of PLLA appears at 60 °C hence it is a glassy polymer at room temperature ; melting is observed around 180 °C.","label":"POLY_STRUC"}
{"id":411,"sentence":"These differences in Tg and Tm for PCL and PLLA indicate that viscosity properties and processing temperatures for their conventional thermoplastic processes (injection, extrusion, etc.) should be expected to be very different.","label":"POLY_STRUC"}
{"id":412,"sentence":"and it was suggested that as the amorphous regions are degraded, the crystalline regions can be ultimately degraded. (23) Consequently, thermophilic enzymes able to operate at higher temperatures than Tg of many types of polyesters are good candidates for protein engineering and can help solving the plastic pollution problems that we are currently facing.","label":"POLY_STRUC"}
{"id":413,"sentence":"which lacks the regular packing but hold the long−range order along the chains. With considering the possible differences in the magnetic dipole−dipole interaction among the three crystal forms,","label":"POLY_STRUC"}
{"id":414,"sentence":"In addition to crystallinity data, the melting temperature, Tm, was determined for each sample and can be seen in Fig. 3. For the samples degraded under nitrogen purge,","label":"POLY_STRUC"}
{"id":415,"sentence":"Furthermore, rapidly growing biodegradable packaging applications have pointed out the importance of investigating the hydrolysis process at an industrial compost temperature of about 55 – 60 °C.","label":"BIODEGRAD_PROP"}
{"id":416,"sentence":"The three kinetic models described earlier were able to describe the hydrolysis behavior, but for simplicity, pseudo‐first‐order kinetics were assumed [cf. eq.","label":"BIODEGRAD_PROP"}
{"id":417,"sentence":"Table XIX summarizes the power−law equations for PLA melt viscosity [120]. Melt flow index data of poly (lactic acid) can be found in the literature [31].","label":"BIODEGRAD_POLY"}
{"id":418,"sentence":"Figure 2 Open in figure viewer PowerPoint The calculated percent crystallinity for PLA32 (▪, •, ▴) and PLA118 (□, ○, Δ) fibers aged at 40, 60,","label":"BIODEGRAD_POLY"}
{"id":419,"sentence":"The d‐lactate content is known to drastically reduce the crystalline content of PLA, 28 and therefore, the effect of d‐lactate may be indirect, through its effect on the crystalline level of the starting material.","label":"POLY_STRUC"}
{"id":420,"sentence":"the vibration bands were then classified into the crystalline bands (from crystalline phase) and amorphous ones (from amorphous phase). The crystalline bands, which reflect the packing and conformation of each crystal form, were then assigned to the characteristic bands of the δ -, γ -, or β−forms.","label":"POLY_STRUC"}
{"id":421,"sentence":"Sample means were compared using the Tukey ’ s test when significant difference (p < 0.05) was found. 3 Results and discussion 3. 1 Tensile properties of polymer blends and polymer composite Other than neat PBAT and neat PLA, for comparison purpose, PP sample was also tested along with the samples of PLA \/ PBAT blends and PLA (fiber) \/ PBAT composite.","label":"BIODEGRAD_POLY"}
{"id":422,"sentence":"5 μm, as shown in Fig. 4 (H). Furthermore, the gap between PBAT and PLA disappeared, and most of the particles were wrapped in PLA resin.","label":"BIODEGRAD_POLY"}
{"id":423,"sentence":"0 rad \/ s and a strain of 2 % [24]. The mechanical properties of pure PLA and blends were determined using a tensile tester (Instron 4464 ;","label":"MECHANICAL_PROP"}
{"id":424,"sentence":"Illinois. Extrusion and injection molding resulted in a molecular weight reduction (Tables XIII and XIV). The PDLLA was dissolved in tetrahydrofuran, and the viscosity studies were carried out at 31.15 °Cina Ubbelohde viscometer.","label":"POLY_STRUC"}
{"id":425,"sentence":"In PBS, the band at 917 cm−1 was corresponding to the C OH bending vibration of the carboxylic acid groups. The peak at 1045 cm−1 was attributed to the O C C stretching vibration and the peak in the range 1151 cm−1 was due to the C O C groups in the ester linkage of PBS.","label":"BIODEGRAD_POLY"}
{"id":426,"sentence":"5 rad \/ s. Changes in the complex viscosities of pure PLA and PCL and of all blends as a function of angular frequency are shown in Figure 5.","label":"BIODEGRAD_POLY"}
{"id":427,"sentence":"Young ’ s modulus, elongation at break, and impact strength of blends were increased by reactive compatibilization. Recently, exposure of polymer blends to high−energy radiation at room temperature has also been introduced to improve PLA \/ PCL compatibility [15 – 18].","label":"MECHANICAL_PROP"}
{"id":428,"sentence":"The initial degradation of PLA \/ PPG composites during melt processing was monitored in real time. The results indicate that PPG can significantly reduce the melt viscosity of PLA \/ PPG composites, leading to obvious pseudoplastic fluid behavior.","label":"BIODEGRAD_POLY"}
{"id":429,"sentence":"There was however no clear evidence of interaction between PLA and PBAT in the blends. 3. 3 Glass transition and melting temperatures DSC thermogram of PLA \/ PBAT blends generally showed two Tg ’ s and two Tm ’ s corresponding to those for PLA and PBAT.","label":"BIODEGRAD_POLY"}
{"id":430,"sentence":"24 g \/ cm3 and a weight average MW (Mw) of 112, 000 g \/ mol. The PLA resin was dried in an oven at 80 °C for 10 h before use. PPG was supplied by Guangzhou Runhong Chemical Co.,","label":"POLY_STRUC"}
{"id":431,"sentence":"Hydrolysis in Neutral Media : Temperature Effect Temperature accelerates the hydrolysis of PLA. To evaluate this effect, hydrolysis in aqueous media was carried out at 60, 70,","label":"BIODEGRAD_PROP"}
{"id":432,"sentence":"Poly−β−(hydroxybutyrate−co−β−valerate) (PHB – V) is a copolymer of PHB containing random segments of hydroxyvalerate. PHB−V was the first polyalcanoate to be commercially explored,","label":"BIODEGRAD_POLY"}
{"id":433,"sentence":"08 II 130 20 1.40 g + C tF III 220110 0 tC g + F IV 22020 1.52 tC tF t 0 trans ; g 0 gauche In addition to the dependence on the molecular weight and the L−concentration,","label":"POLY_STRUC"}
{"id":434,"sentence":"Proikakis et al., 2006). Consequently, the abiotic degradation must not be neglected. Herein, we describe the different degrees of the biodegradation process : biodeterioration, biofragmentation and assimilation including the abiotic involvement.","label":"BIODEGRAD_PROP"}
{"id":435,"sentence":"However, comparing the resonance line observed at τ 0 2 s with that at τ 0 20 s, we can not detect any difference in the line shape and chemical shift for both the α CH2 and β CH2 resonances of all the three samples, indicating that the P3HP chains with the medium T1C adopt the conformation similar to the crystalline ones and thus are attributable to the mobile crystalline phase or interphase.","label":"POLY_STRUC"}
{"id":436,"sentence":"and PP after being exposure to 18 days of elevated humidity and heat. 19 However, after 30 days of conditioning, the tensile strength of the PBS and PBS \/ PBAT blend exhibited extreme degradation in contrast to PBAT.","label":"BIODEGRAD_POLY"}
{"id":437,"sentence":"The conventional CPT1 pulse sequence (14) was applied to monitor the spin−lattice relaxation of the semicrystalline P3HP, and the 13C spin−lattice relaxation time (T1C) were further estimated by the experiential exponential model.","label":"POLY_STRUC"}
{"id":438,"sentence":"The properties of PBAT can be compared with that of low density polyethylene with regards to its tensile properties. Nowadays, PBS and PBAT are widely used for many applications because of their inherent properties in addition to biodegradability.","label":"BIODEGRAD_POLY"}
{"id":439,"sentence":"5 rad \/ s, respectively. These rheological results provide additional evidence of enhanced compatibility due to electron−beam−induced cross−copolymerization between PLA and PCL [21].","label":"BIODEGRAD_POLY"}
{"id":440,"sentence":"and poly (ɛ−caprolactone) (PCL), have been developed [9]. Poly (ɛ−caprolactone) (PCL), a linear polyester with high crystallinity, a low melting point,","label":"BIODEGRAD_POLY"}
{"id":441,"sentence":"and their blends at elevated temperature and humidity. Considering the above, in the present study, our attention was to investigate the durability of PBS, PBAT, and PBS \/ PBAT blend at an elevated temperature and humidity level.","label":"BIODEGRAD_PROP"}
{"id":442,"sentence":"Kim et al., 2006b, Tsuji et al., 2006), elongation at break by a mechanical tester (Tserki et al., 2006), elongation percentage and elasticity by dynamic mechanical thermal analysis (Domenek et al., 2004).","label":"MECHANICAL_PROP"}
{"id":443,"sentence":"Under such assumptions, the above equation can be integrated to yield Eq. 2 where [ester] (t) is the concentration of ester bonds in the polymer matrix as a function of degradation time and [ester] o is the initial concentration of ester bonds in the polymer matrix 18.","label":"POLY_STRUC"}
{"id":444,"sentence":"8 times higher (51.9 J \/ m) than that of pure PLA, whereas that of the uncompatibilized PLA \/ PCL (70 \/ 30) blend (31.","label":"BIODEGRAD_POLY"}
{"id":445,"sentence":"The intermolecular coupling was demonstrated to be poorly related to the temperature dependence of crystalline band intensities. (18) However, the packing efficiency of crystal decides the amplitudes of low frequency modes,","label":"POLY_STRUC"}
{"id":446,"sentence":"5 Table IV. Mass Spectroscopy Results for the Water‐Soluble Degradation Products at pH 9. 5 Chemical structure Calculated molecular weight Observed molecular weight 284 283. 8 474 473.","label":"POLY_STRUC"}
{"id":447,"sentence":"4 and 12 at 70 °C is presented in Figure 1 (other media are shown in the Supporting Information). Regardless of the PLA grade,","label":"BIODEGRAD_POLY"}
{"id":448,"sentence":"Shirahase et al., 2006 ; Sivalingam et al., 2003, 2004a, 2004c, 2004d) have leaded to divergent interpretations. The chain scission kinetics of PCL, as modeled in this work, is shown in Fig. 4.","label":"BIODEGRAD_PROP"}
{"id":449,"sentence":"In general, Tg value of the amorphous phase in semicrystalline polymers depends on the degree of crystallinity. 46 Initially, the PBS and PBAT had Tg values of−17 °C and−20 °C, respectively.","label":"POLY_STRUC"}
{"id":450,"sentence":"On both curves of LPB and HPB, there are two inflection points that are assigned to the Tg of PBAT and PLA chains. The Tg of PBAT shifts to higher temperature with increasing chain length of the PLA blocks,","label":"BIODEGRAD_POLY"}
{"id":451,"sentence":"Experimental 2. 1.Materials PLA (Ingeo TM Biopolymer, 2003D) was supplied by NatureWorks LLC (Minnetonka, MN), with a density of 1.","label":"BIODEGRAD_POLY"}
{"id":452,"sentence":"and carbon arc lamps by many researchers. 24, 25 However, in order to model the PBS, PBAT, and PBS \/ PBAT blend for automotive interior applications ; all the moulded samples were conditioned under simulated temperature (50 °C)","label":"BIODEGRAD_POLY"}
{"id":453,"sentence":"the trans, in both crystal forms. In parts a and b of Figure 8 are shown the time−resolved FTIR spectra for the melting of the β−form sample and that of the γ−form sample, respectively.","label":"POLY_STRUC"}
{"id":454,"sentence":"and yard compost environments having different microbial activities. The highest biodegradation rate was found in manure compost, which had the highest CO2 emissions and lowest C \/ N ratio.","label":"BIODEGRAD_PROP"}
{"id":455,"sentence":"0254 m were placed in the cells separated in between by glass beads. The weight average molecular weight reduction of the samples was determined by dissolving the PBAT sample in tetrahydrofuran (THF),","label":"BIODEGRAD_PROP"}
{"id":456,"sentence":"which was detected only in the low molecular weight P3HP samples. (5a, 5c) Previously, we have investigated the conformation of β -, γ -, and δ−forms with using FTIR measurement.","label":"POLY_STRUC"}
{"id":457,"sentence":"Fig. 4. Biodegradation of PHB−V based on mass retention. The pH increased slightly during aging in all soils, indicating the activity of microorganisms,","label":"BIODEGRAD_PROP"}
{"id":458,"sentence":"We aim to predict the plasticization of polylactic acid (PLA) using polypropylene glycol (PPG) with different MWs. The rheological properties of the PLA \/ PPG composites containing PPG with different MWs were systematically studied by capillary rheometry and torque rheometry.","label":"BIODEGRAD_POLY"}
{"id":459,"sentence":"10 for PLLA in which a carbon−oxygen bond is broken giving an acid and an unsaturated ester. 4 Conclusions This paper presents a comprehensive study of melt rheology of poly (e−caprolactone) and poly (L−lactide) in the range of their usual processing temperature window.","label":"BIODEGRAD_POLY"}
{"id":460,"sentence":"Figure 9 Initial tensile moduli of pure PLA, compatibilized PLA \/ PCL blends, and uncompatibilized PLA \/ PCL blends. 3. 6. Biodegradability The ASTM defines “ biodegradable ” as being “ capable of undergoing decomposition into carbon dioxide, methane, water, inorganic compounds,","label":"BIODEGRAD_POLY"}
{"id":461,"sentence":"The intrusion of water initiates the hydrolysis of the polymer, leading to the creation of oligomers and monomers. Progressive degradation changes the microstructure of the matrix due to the formation of pores, then oligomers and monomers are released.","label":"BIODEGRAD_PROP"}
{"id":462,"sentence":"Figure 15 Open in figure viewer PowerPoint Shear viscosity curves for PBS, PBAT and PBS \/ PBAT before and after 6 days exposed to 50 °C with a RH of 90 %. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":463,"sentence":"which make the whole cooling process need only 15−17 min. In view of the reasons shown above, the blue−shift of P3HP crystalline bands in the fingerprint region is also quite attributable to the enhanced intermolecular interaction at lower temperatures.","label":"POLY_STRUC"}
{"id":464,"sentence":"The PI matrix contains the hard PLA domains, which are physical cross−linking points, providing the sufficient storage moduli at ambient temperature for these triblock copolymers. PLA end blocks can form α−form crystals as confirmed by wide−angle X−ray diffraction, when the triblock copolymers are prepared by solvent−casting,","label":"POLY_STRUC"}
{"id":465,"sentence":"PLA is degraded by simple hydrolysis of the ester bond and does not require the presence of enzymes to catalyze this hydrolysis. The rate of degrada−tion is dependent on the size and shape of the article,","label":"BIODEGRAD_PROP"}
{"id":466,"sentence":"Compared with 13C NMR splitting fingerprints of the block copolymer P3HP−b−P4HB and mixture of block P3HP−b−P4HB, P3HP, and P4HB (Figure 5),","label":"BIODEGRAD_POLY"}
{"id":467,"sentence":"Though preparing PAL (fiber) \/ PBAT composite could be challenging, some mechanical properties might be positively improved making it suitable for using as food packaging material.","label":"BIODEGRAD_POLY"}
{"id":468,"sentence":"Tg and Tm of PLA were slightly changed by the addition of PBAT. The results accorded to the shifting of the FTIR spectrum. Fig. 4.","label":"POLY_STRUC"}
{"id":469,"sentence":"Figure 13 Open in figure viewer PowerPoint Storage modulus of PBS, PBAT, and PBS \/ PBAT before and after exposed to 50 °C with 90 % RH for 30 days. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":470,"sentence":"and uncompatibilized PLA \/ PCL (70 \/ 30) (□) blends at 190 °C. 3. 5. Mechanical Properties Figure 8 presents the impact strengths of pure PLA and PLA \/ PCL blends as determined by the notched Izod impact test.","label":"BIODEGRAD_POLY"}
{"id":471,"sentence":"Initial time lags (time required for the hydrolysis of polymer into diffusible oligomers before the onset polymer mass loss or microbial utilization) of pure PLA and PCL were approximately 14 and 2 days, respectively [20].","label":"BIODEGRAD_PROP"}
{"id":472,"sentence":"PPG can be used to reduce the melt viscosity of PLA, and the PLA \/ PPG composites exhibited an obvious pseudoplastic fluid behavior. The lower the MW of PPG,","label":"BIODEGRAD_POLY"}
{"id":473,"sentence":"Figure 2 FTIR spectra (3200 – 650 cm−1) of pure PLA (a), pure PCL (b), and the separated substances from uncompatibilized (c)","label":"BIODEGRAD_POLY"}
{"id":474,"sentence":"Table 2. Thermal stability parameters acquired from TGA curves for PLA−CTA, PI10k and PLA−b−PI−b−PLA triblock copolymers.","label":"BIODEGRAD_POLY"}
{"id":475,"sentence":"Figure 3. Torque (a) and temperature (b) versus time when processing the neat PLA and PLA \/ PPG composites. The temperature−adjusted torque is calculated using Equation (7)","label":"BIODEGRAD_POLY"}
{"id":476,"sentence":"In order to avoid degradation of the samples during the experiments, all the samples were vacuum dried at 80 °C for 4 h before performing the experiments.","label":"BIODEGRAD_PROP"}
{"id":477,"sentence":"This is possibly due to the partial aromatic structure of PBAT. On the contrary, the FTIR spectra of PBS \/ PBAT showed a remarkable decrease in the characteristic peak intensity.","label":"BIODEGRAD_POLY"}
{"id":478,"sentence":"The study was carried out on thin films synthesized solely of ll‐lactide, and they showed a similar molecular weight evolution but slower weight loss with highly crystalline samples.","label":"BIODEGRAD_PROP"}
{"id":479,"sentence":"These results have implications for deployment of biodegradable polymers in commercial composting environments. Biodegradation of biodegradable polyesters such as PBAT was strongly influenced by the total microbial activity of the exposure environments,","label":"POLY_STRUC"}
{"id":480,"sentence":"The PLA phase became discontinuous when the starch content increased to > 0 60 %, and at 80 % starch, the starch granules were not covered by the PLA phase.","label":"BIODEGRAD_POLY"}
{"id":481,"sentence":"The polymer is shortened by the hydrolysis of the resulting lactide. The intramolecular degradation occurs by a random alkaline attack on the carbon of the ester group, followed by the hydrolysis of the ester link.","label":"BIODEGRAD_PROP"}
{"id":482,"sentence":"The fracture surface of the neat PLA shows an obvious brittle fracture morphology, but the PLA \/ PPG composites show a ductile fracture morphology. Figure 10.","label":"BIODEGRAD_POLY"}
{"id":483,"sentence":"the tensile strength of PBS, PBAT, and PBS \/ PBAT blend was reduced by 40 %, 39 %, and 11 %, respectively. The reduced tensile strength may be attributed to the combined effect of hydrolytic degradation and molecular weight reduction after being exposed to the raised humidity and temperature.","label":"BIODEGRAD_POLY"}
{"id":484,"sentence":"Minho). Melting endotherms (upon heating in a differential scanning calorimeter) in excess of 70 J \/ g were attained. The reaction coordinates used in RC to INT−1 and INT−1 to EAM were the distance between the PCL2 (Ca) – Ser160 (Ob),","label":"POLY_STRUC"}
{"id":485,"sentence":"It was observed that, all the samples showed Newtonian and non‐Newtonian flow behavior at lower and higher frequencies, respectively. The 6 days conditioned samples exhibit a slight decrease in the shear viscosity compared with the before conditioned samples.","label":"RHEOLOGICAL_PROP"}
{"id":486,"sentence":"and consist of two chains. (6) On the basis of a careful investigation on the single crystal of the γ−form, the γ−form unit cell was found to have dimensions of a 0 0.","label":"POLY_STRUC"}
{"id":487,"sentence":"which likely indicates that the γ−form is more difficult to be compressed, and is packed more efficiently. In addition, with comparing Figure 4b with Figure 4c,","label":"POLY_STRUC"}
{"id":488,"sentence":"Thermal stability represents an important property of thermoplastic elastomeric materials for industrial applications. Fig. 1 shows the TGA and derivative TGA curves of PLA−CTA, PI10k and solvent−cast PLA−b−PI−b−PLA triblock copolymers.","label":"BIODEGRAD_POLY"}
{"id":489,"sentence":"3 J \/ g) 8 and PBAT (114 J \/ g). 26 Δ Hm is the measured enthalpy of melting. The PBS cystallinity in the PBS \/ PBAT blend was calculated as follows : (3) where wf is the weight fraction of the PBAT in the PBS \/ PBAT blend.","label":"BIODEGRAD_POLY"}
{"id":490,"sentence":"The impact energy of the PBS and PP decreased for the first 6 days of conditioning. This reduction is probably due to the inadequate degree of entanglement between amorphous and crystalline phase after exposed to 50 °C and 90 % RH.","label":"BIODEGRAD_POLY"}
{"id":491,"sentence":"Compost with appropriate C \/ N ratio and CO2 emission may not directly be a suitable testing media, due to lower total biodegradation of cellulose positive controls and different enzymatic specificity of microorganisms in composts.","label":"BIODEGRAD_PROP"}
{"id":492,"sentence":"at a given temperature of 170 °C with the torque obtained by the torque rheological test. Figure 4 demonstrates the relationship of the temperature−adjusted torque versus time in the interval of 15 to 20 minutes of processing time of the PLA and PLA \/ PPG composites.","label":"BIODEGRAD_POLY"}
{"id":493,"sentence":"These equations are as follows : Q 0 m \/ r (15) where Q 0 volumetric flow rate (m3 \/ sec) m 0 mass flow rate (kg \/ sec) r 0 density of the PLA melt (kg \/ m3) r 0 1.1452 \/ 1 + 0.0074 (Tmelt−150) (16)","label":"BIODEGRAD_POLY"}
{"id":494,"sentence":"However, PLA \/ PC blend exhibits superior flexural strength than neat PLA during the entire conditioning period. Another study by Kim and Kim17 showed that polypropylene (PP) has a more hydrolytic resistant behaviour than biodegradable polymers (PBS, PBAT,","label":"BIODEGRAD_POLY"}
{"id":495,"sentence":"Mn is the number average molecular weight of the polymer, and DP is the degree of polymerization. Upon substitution and rearrangement, Eq. 3 can be obtained that relates Mn to the degradation time, where Mo is the monomer molecular weight and Mn (0) is the initial molecular weight of the sample.","label":"POLY_STRUC"}
{"id":496,"sentence":"The L (+) isomer is produced in humans and other mammals, whereas both the D (-)−and L (+)−enantiomers are produced in bacterial systems.","label":"BIODEGRAD_POLY"}
{"id":497,"sentence":"Crystallization Kinetics Data for Poly (Lactic Acid) Sample number Mv 3 1025 Tg (°C) log G0 G0 (mm \/ min) Kg 3 1025 sse 3 106 (J2 \/ m4)","label":"POLY_STRUC"}
{"id":498,"sentence":"Interestingly, the normalized complex viscosities of compatibilized blends were higher than 1.A similar result for the normalized complex viscosity of a compatibilized blend was reported by Al−Itry et al. [2].","label":"RHEOLOGICAL_PROP"}
{"id":499,"sentence":"The wide temperature range (− 20 to 60 °C) for the plateaus of both storage and loss moduli of the triblock copolymers endows their potential applications as appropriate elastomers with sufficient moduli in varied temperature environments.","label":"MECHANICAL_PROP"}
{"id":500,"sentence":"Separation of Blends For FTIR analysis, compatibilized and uncompatibilized PLA \/ PCL (70 \/ 30) blends were separated into components using N, N−dimethyl formamide (DMF),","label":"BIODEGRAD_POLY"}
{"id":501,"sentence":"The most used analytical technique to separate oligomers with different molecular weight is the GPC, also called size exclusion chromatography (SEC) (Ratto et al., 1999,","label":"POLY_STRUC"}
{"id":502,"sentence":"Table 3. 1H NMR data for PLA samples. However, there are some differences in the signal intensities and in proton area ratio (CH3 \/ CH) for the samples processed,","label":"BIODEGRAD_POLY"}
{"id":503,"sentence":"These were selected because they differed widely in d‐isomer content. PLA 4032D had around 2 % d‐lactate and could crystallize upon cooling, whereas 8302D comprises a larger amount of d‐lactate, about 10 %,","label":"POLY_STRUC"}
{"id":504,"sentence":"Inc. J. Appl. Polym. Sci., 2013The in‐vitro hydrolytic behavior of diblock copolymer films consisting of poly (ε‐caprolactone) (PCL)","label":"BIODEGRAD_POLY"}
{"id":505,"sentence":"Studies found that more than 5 % of PBAT is phase−separated in PLA resin, thus it is necessary to explore an effective compatibilizer to improve the interaction between PLA and PBAT [21], [22].","label":"BIODEGRAD_POLY"}
{"id":506,"sentence":"Tg, to the number−average molecular weight as follows : Tg 0 Tg `−K \/ Mn (13) where Tg ` 0 | Tg at infinite molecular weight K 0 a constant representing the excess free volume of the end−groups of the polymer chains Jamshidi [3] reported the values as follows :","label":"POLY_STRUC"}
{"id":507,"sentence":"At a given temperature and shear rate, viscosity η is proportional to the high power of the weight average MW of the polymer matrix, Mw [35].","label":"RHEOLOGICAL_PROP"}
{"id":508,"sentence":"The second route of producing PLA is to collect, purify, and ring−open polymerize (ROP) lactide to yield high−weight−average molecular weight (Mw > 100, 000) PLA.","label":"BIODEGRAD_POLY"}
{"id":509,"sentence":"Experimental results of the mechanical properties, obtained on two different grades of poly (lactic acid) supplied by Cargill, are presented in Table XII. The literature reports density values for poly (L−lactic acid) [112].","label":"BIODEGRAD_POLY"}
{"id":510,"sentence":"and compatibilized these PLA \/ PCL blends by electron−beam irradiation in the presence of a reactive agent to overcome drawbacks of PLA. To produce compatibilized blends, mixtures of the PLA \/ PCL \/ reactive agent were prepared using a twin−screw extruder and exposed to electron−beam radiation at room temperature.","label":"BIODEGRAD_POLY"}
{"id":511,"sentence":"and the molecular weight continued to decrease but at a lower rate. During the induction period, the molecular weight dropped dramatically from 100 kg \/ mol to the 10 – 20 kg \/ mol range.","label":"POLY_STRUC"}
{"id":512,"sentence":"For each isothermal crystallization temperature, they presented the Avrami parameters as well as the enthalpy of crystallization. The Avrami equation can be stated as follows :−ln (1−a) 0 Ztn 0 (kt) n ; k 0 Z−n Avrami equation Table V.","label":"POLY_STRUC"}
{"id":513,"sentence":"and other environments such as soil burial [10]. Biodegradability of these biodegradable polymers in composting conditions and soil burial conditions is affected by both biotic and abiotic factors of the environment, such as temperature, moisture, pH, bio−surfactant and enzymes ;","label":"BIODEGRAD_PROP"}
{"id":514,"sentence":"The intrinsic viscosity (η) of all samples (initial and degraded) was determined using an Ubbelohde capillary viscometer, with 5 mg \/ mL solutions in chloroform at 25. 0 ± 0.5 °C and according to equation (3) [16] : (3) where η r is the relative viscosity and c is polymer solution concentration.","label":"RHEOLOGICAL_PROP"}
{"id":515,"sentence":"Furthermore, the dissolution of PEG segments could resulted in the formation of pores in the film as observed from the SEM micrographs. The products mentioned arose from iterative ester bond scission of the PCL chain.","label":"BIODEGRAD_PROP"}
{"id":516,"sentence":"and PBS \/ PBAT before and after 30 days exposed to 50 °C with 90 % RH. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":517,"sentence":"Ishii et al. [21], and Nakajima−Kambe et al. [22]. Fig. 2. Mineralization of PBAT and cellulose positive control in three different composts, where CM is mineralization of cellulose in manure compost, PM is PBAT in manure compost, CF is cellulose in food compost, PF is PBAT in food compost CY is cellulose in yard compost,","label":"BIODEGRAD_POLY"}
{"id":518,"sentence":"Hydrolysis Experiments Copolymer films were prepared by solvent casting from a 10 wt % chloroform solution. The resultant films were dried in vacuo at 50 °C for 2 days, cut into discs (diameter, 8 mm : thickness, 80 μm)","label":"BIODEGRAD_PROP"}
{"id":519,"sentence":"Table 1.n values for the neat PLA and PLA \/ PPG composites at various shear rates. 3. 2. Torque Rheological Properties and Degradation of the PLA and PLA \/ PPG Composites The curves of torque and temperature versus time for the neat PLA at different processing temperatures are shown in Figure 2.","label":"BIODEGRAD_POLY"}
{"id":520,"sentence":"25 g cm−3. PLA pellets were dried in a vacuum oven at 60 °C for 12 h before use to prevent hydrolysis since this polymer is very hygroscopic.","label":"BIODEGRAD_POLY"}
{"id":521,"sentence":"This was validated by the residual mass results, the decreasing PEG weight composition from 1H NMR analysis and also the data obtained from mass spectroscopy. In particular, mass spectroscopy results revealed that the products formed initially comprised a larger number of mer units before eventually degrading into dimeric products.","label":"BIODEGRAD_PROP"}
{"id":522,"sentence":"The intensity and size of the cracks rose as degradation progressed. As shown in Figure 8, a porous network was formed at the edge of the film (Week 20), indicating that degradation most probably transpired via the edges inwards to the rest of the film.","label":"BIODEGRAD_PROP"}
{"id":523,"sentence":"Furthermore, in order to undergo cocrystallization, the cohesive energies of the two comonomers should be relatively comparable so that the comonomer with greater cohesive energy does not get separated and form crystal lattices of only one copolymer.","label":"POLY_STRUC"}
{"id":524,"sentence":"In addition, this phenomenon may be due to induced crystallization from low molecular weight polymer chains that occurs during conditioning. 13 Therefore, low molecular weight polymer chains are often favored to the crystallinity enhancement.","label":"POLY_STRUC"}
{"id":525,"sentence":"The change in Z * over time given at a constant temperature indicates the change in MW caused by cross−linking, chain extension or degradation of the polymer during processing.,","label":"POLY_STRUC"}
{"id":526,"sentence":"In the present study, we first determined the optimum radiation dose required to compatibilize PLA \/ PCL blends and then investigated the storage moduli and complex viscosities of the compatibilized blends prepared at optimum dosage.","label":"RHEOLOGICAL_PROP"}
{"id":527,"sentence":"and extrusion, the polymer must possess adequate thermal stability to prevent degradation and maintain molecular weight and properties. PLA undergoes thermal degradation at temperatures above 200 °C (392 °F) [3] by hydrolysis, lactide reformation, oxidative main chain scission,","label":"BIODEGRAD_PROP"}
{"id":528,"sentence":"Only the aPLA at pH 12 showed a remarkable acceleration. The hydrolysis rate of aPLA was around 1.4 times faster than those at the other pH values.","label":"BIODEGRAD_POLY"}
{"id":529,"sentence":"This confirmed that the alkaline media favored the hydrolysis, as pointed out earlier. The results were dramatically different at pH 12. First, weight loss started immediately without any induction stage and was carried out in parallel to the molecular weight reduction.","label":"BIODEGRAD_PROP"}
{"id":530,"sentence":"and rheological properties of PLA \/ PCL blends were improved by compatibilization, and the biodegradabilities of compatibilized PLA \/ PCL blends were greater than that of pure PLA. 1.","label":"BIODEGRAD_POLY"}
{"id":531,"sentence":"When B900 was added, the PLA crystallinity increase is less noticeable, corroborating the results discussed before. Fig. 6. DSC curves of neat PLA and PLA reprocessed at 180 °C in the presence and absence of B900 :","label":"BIODEGRAD_POLY"}
{"id":532,"sentence":"Analysis of fractions according to 13C NMR spectrum confirmed that D value of the putative block polymer P4HB−b−P3HP was 46. 69 (F3HP * 3HP 0 0.6963, F4HB * 4HB 0 0.1934, F4HB * 3HP 0 0.0677, F3HP * 4HB 0 0.0426),","label":"POLY_STRUC"}
{"id":533,"sentence":"Data was collected during the second heating run. (39) Chemical structures of PHA were analyzed by NMR spectrometer. The PHA samples were dissolved in deuterated chloroform (CDCl3).","label":"BIODEGRAD_POLY"}
{"id":534,"sentence":"The selected temperature range was based on the glass transition temperature and melting temperature of the samples. Rheological Properties Rheological properties were obtained in an Anton Paar Rheometer MCR302.","label":"RHEOLOGICAL_PROP"}
{"id":535,"sentence":"2 Kinetics of PLLA Degradation Fig. 8 shows the reduction of PLLA relative viscosity (g \/ g0) with time at 200 °C, 220 °C, 230 °C, 240 °C and 250 °C.","label":"BIODEGRAD_PROP"}
{"id":536,"sentence":"Earlier, Hoogsteen et al. [99] showed that the b−form of poly (L−lactic acid) has an orthorhombic unit cell (containing 6 chains) containing a 31 (3 A rise \/ 1 monomeric unit) polymeric helix.","label":"BIODEGRAD_POLY"}
{"id":537,"sentence":"The molecular weights of the PLLA and the star−shaped PLA were 367, 000 and 61, 000 g \/ mole, respectively. Tables XXIV and XXV summarize the thermal analysis (differential scanning calorimetry) study by Park [123].","label":"BIODEGRAD_POLY"}
{"id":538,"sentence":"They had characterized the physicochemical properties of the poly (lactic acid) synthesized by each of the aforementioned catalyst systems. The mechanical properties of poly (lactic acid) were studied.","label":"BIODEGRAD_POLY"}
{"id":539,"sentence":"Finally, we give a perspective to use the natural labelling of stable isotopes in the environment, by means of a new methodology based on the isotopic fractionation to validate assimilation by microorganisms.","label":"BIODEGRAD_PROP"}
{"id":540,"sentence":"Neither model takes into consideration the considerable weight loss observed in the samples as they degrade at elevated temperatures. When compared to calculated rate constants in the literature, values from both models were consistent with those obtained at similar temperatures 24, 29, 30.","label":"BIODEGRAD_PROP"}
{"id":541,"sentence":"The tensile and impact strength test specimens were prepared by injection molding (Nissei 35−oz, Japan) at a cylinder temperature of 200 °C and mold temperature of 40 °C.","label":"MECHANICAL_PROP"}
{"id":542,"sentence":"The biodegradation rates of aliphatic aromatic polyester under different compost environments was measured and compared with hydrolysis in buffer solution and in vermiculite as an example of an abiotic compost−like material.","label":"BIODEGRAD_PROP"}
{"id":543,"sentence":"and biodegradability of PLA. Morphological, rheological, and mechanical properties of compatibilized PLA \/ PCL blends were measured and compared with those of uncompatibilized blends. In addition,","label":"BIODEGRAD_PROP"}
{"id":544,"sentence":"13C NMR, GPC, and DSC measurements. Compared to the short chains of the PLA blocks (LPB) in the copolymers, HPB was a more effective compatibilizer for two immiscible blends because the long chains achieve enhanced interpenetration of the relevant homopolymers.","label":"BIODEGRAD_POLY"}
{"id":545,"sentence":"Thus, two different methods were used ; in the first, PLA films prepared by compression moulding were exposed to temperature and oxygen and, in the second, PLA pellets were processed in an internal mixer and samples were collected after different mixing times.","label":"BIODEGRAD_POLY"}
{"id":546,"sentence":"and 80 °C. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary. com.] Rheology – Molecular Weight Relationship The rheological behavior of the polymer melt was strongly affected by the molecular weight.","label":"RHEOLOGICAL_PROP"}
{"id":547,"sentence":"A power law relation was observed, as expected. Regardless of the hydrolysis conditions, the data fell on a single curve. The power law exponent (n) was 3. 95.","label":"BIODEGRAD_PROP"}
{"id":548,"sentence":"In comparison to the random copolymers P (3HP−co−25 % 4HB) and P (3HP−co−38 % 4HB), each having only one Tg of−31.","label":"POLY_STRUC"}
{"id":549,"sentence":"The number of PLLA chain scissions, according to Saito ’ s equation, is shown in Fig. 9. It is remarkable to observe that the degradation accelerated considerably as the temperature increased above 230 °C.","label":"BIODEGRAD_PROP"}
{"id":550,"sentence":"33 A plethora of methods have been used to probe the degradation mechanism of biodegradable polymers as mentioned in the literature. Examples include the examination of the physical mass loss of the films,","label":"BIODEGRAD_PROP"}
{"id":551,"sentence":"The semicrystalline PLA samples were intentionally molded into amorphous disks through rapid cooling. The semicrystalline PLA rapidly developed its crystalline structure during the hydrolysis experiments, as expected, because the hydrolysis was carried out above the PLA Tg.","label":"POLY_STRUC"}
{"id":552,"sentence":"Therefore, reduction of the carbonyl absorbance (1710 cm−1) also results from hydrolysis. Only slight reductions in carbonyl groups were observed in the PBAT samples hydrolyzed in phosphate buffer (Fig. 7f)","label":"BIODEGRAD_PROP"}
{"id":553,"sentence":"For the same concentration of PLA (40 %) in PLA−PBAT mixture, PLAF exhibited higher values of E and UTS than that of PLA \/ PBAT blends.","label":"BIODEGRAD_POLY"}
{"id":554,"sentence":"The Young ’ s modulus of block copolymers also showed significant improvements : P3HP−b−29 % P4HB had a Young ’ s modulus of 177.","label":"MECHANICAL_PROP"}
{"id":555,"sentence":"The remaining material will then show a more uniform polydispersity. The two kinetic models discussed in Modeling Hydrolytic Degradation section were used to obtain rate‐constant values for the hydrolysis of PLA32 and PLA118 at each of the temperatures studied.","label":"BIODEGRAD_PROP"}
{"id":556,"sentence":"Young ’ s modulus, and elongation at break were increased by compatibilization. For the reactive compatibilized PLA \/ PCL blends, Semba et al. and Wang et al. [5, 6] reported that the biodegradability and mechanical properties such as tensile strength,","label":"MECHANICAL_PROP"}
{"id":557,"sentence":"71 a Tg obtained from tan δ peaks. In a semi‐crystalline polymer, initially the amorphous regions are more susceptible for hydrolysis. 6 From the DSC analysis, it was clearly observed that the Δ Hm and Δ Hc of the PBS, PBAT and PBS \/ PBAT increased after 30 days of conditioning, indicating that degradation mainly occurred in the amorphous regions.","label":"POLY_STRUC"}
{"id":558,"sentence":"The crystallization of aPLA was unexpected because this material did not develop a crystalline structure before hydrolysis, even after annealing for several days. In this situation, however,","label":"POLY_STRUC"}
{"id":559,"sentence":"In contrast to elastic modulus and the ultimate tensile strength, the decrease of temperature from room temperature to−18. C did not significantly affect the elongation at break.","label":"MECHANICAL_PROP"}
{"id":560,"sentence":"and (C), respectively. The storage modulus represented the elastic character of the blends or the energy stored in the deformation, and the loss modulus is related to the energy dissipated in the flow or the viscous character.","label":"RHEOLOGICAL_PROP"}
{"id":561,"sentence":"The PLA−PBAT−PLA tri−block copolymers were recovered in the form of a white powder. Before melt−blending, commercial PLA and PBAT were dried in a vacuum oven for 12 h at 50 °C. PLA \/ PBAT blends at a fixed ratio (70 \/ 30, w \/ w) were prepared by melt blending in the presence of various amounts (i. e., from 0 to 1 %, 3 %,","label":"BIODEGRAD_POLY"}
{"id":562,"sentence":"These morphological results indicate that interfacial adhesion between the PLA matrix and the PCL dispersion was substantially enhanced by electron−beam treatment, presumably caused by electron−beam initiated cross−copolymerization between PLA and PCL at PLA \/ PCL interfaces [21, 26].","label":"BIODEGRAD_POLY"}
{"id":563,"sentence":"Introduction Poly lactic acid (PLA) is an important bio−based and biodegradable polymer of high tensile strength and modulus, which now can be found in various industrial items,","label":"BIODEGRAD_POLY"}
{"id":564,"sentence":"The higher degradation in manure compost than food and yard compost can be attributed to greater microbial activity in the manure compost. CO2 production from yard compost during the first 10 days was just 4. 3 % below the recommended value, while those from manure and food compost were within the recommended range.","label":"BIODEGRAD_PROP"}
{"id":565,"sentence":"at−47. 03 and−16. 15 °C, almost the same as homopolymers P4HB and P3HB with Tg of−47 and−17. 85 °C, respectively.","label":"POLY_STRUC"}
{"id":566,"sentence":"and PLA118 (□, ○, Δ) fibers aged at 40, 60, and 80 °C at 100 % RH. 95 % confidence intervals are indicated with bars.","label":"BIODEGRAD_POLY"}
{"id":567,"sentence":"The subscript 0 indicates the initial values before hydrolysis. Early studies have shown that the hydrolysis of polyester is autocatalyzed by the carboxylic end groups. 14, 15 Because ρ does not change significantly in the early stages of hydrolysis,","label":"BIODEGRAD_PROP"}
{"id":568,"sentence":"L−lactide), which melts at 126 – 127 °C [1, 29]. Fig. 3. Cationic ring−opening polymerization mechanism for PLA.","label":"BIODEGRAD_POLY"}
{"id":569,"sentence":"PLA, obtained from renewable resources, is the most widely used biodegradable polymer in the world and the quantities produced start to answer industrial demands at competitive prices [3], [5].","label":"BIODEGRAD_POLY"}
{"id":570,"sentence":"At these temperatures, unzipping and chain scission reactions leading to loss of as well as thermal degradations, are known to occur. Consequently, PLA homopolymers have a very narrow processing window.","label":"BIODEGRAD_PROP"}
{"id":571,"sentence":"The average melting temperature during this time frame was 167 °C for both samples. After 30 days of degradation, the melting temperatures of PLA32 and PLA118 were observed to be 146 and 149 °C, respectively.","label":"POLY_STRUC"}
{"id":572,"sentence":"Thermal, NMR, fractionation, and mechanical characterizations confirmed the resulting polymer as a block copolymer of P3HP−b−P4HB. Two block copolymers were formed from this study, including the P3HP−b−29 % P4HB and P3HP−b−37 % P4HB, they showed superior properties over random copolymers P (3HP−co−4HB).","label":"BIODEGRAD_POLY"}
{"id":573,"sentence":"and 1000 g \/ mol). PLA and PPG were dried in an oven at 80 °C for 10 h, melt blended at 170 °C with a torque rheometer (Rheo Drive 7,","label":"BIODEGRAD_POLY"}
{"id":574,"sentence":"which illustrates that the droplet−matrix morphology changes to a co−continuous morphology in the internal structures. The results show that the tri−block copolymers in the PLA \/ PBAT blends act as compatibilizer that interferes with the coalescence of PBAT particles.","label":"BIODEGRAD_POLY"}
{"id":575,"sentence":"It is noteworthy that the elongations at break of the blends with 5 % LPB and HPB compatibilizers are as high as 124. 5 % and 165. 8 %, respectively,","label":"MECHANICAL_PROP"}
{"id":576,"sentence":"For non−Newtonian fluids, the relationship between shear stress, shear rate, and flow index n (non−Newtonian index) is expressed by Equations (1)","label":"RHEOLOGICAL_PROP"}
{"id":577,"sentence":"Degradation at pH 7. 4 was carried out for 20 weeks for the copolymers. For degradation at pH 9. 5, the PCL‐b‐PEG copolymers were tested for 20 weeks.","label":"BIODEGRAD_PROP"}
{"id":578,"sentence":"Antheunis et al. also proposed a more rigorous degradation model that describes the concentration of all polymer chains present during the degradation based on the initial concentrations of chain lengths 25.","label":"BIODEGRAD_PROP"}
{"id":579,"sentence":"the densities of the δ−and β−forms were further estimated : ρ c δ 0 1.394 g \/ cm3, and ρ c β 0 1.","label":"POLY_STRUC"}
{"id":580,"sentence":"C \/ N ratio and CO2 production, specification of compost type and the current recommended parameters may not be sufficient as a guideline for testing because of the lack of consistency of microbial composition among different composts and within the same compost [20].","label":"BIODEGRAD_PROP"}
{"id":581,"sentence":"Dynamic thermomechanical analysis discloses two separate glass transitions associated with sufficiently high storage moduli due to their typical phase−separated morphology with the glass transition temperature of hard glassy phase domains higher than ambient temperature.","label":"POLY_STRUC"}
{"id":582,"sentence":"Since the first isolation of poly (3−hydroxybutyrate) (P3HB) from bacteria, a number of hydroxyalkanoate (HA) units have been found to be constituents of carbon−and energy−storing inclusions in a wide variety of microorganisms.","label":"BIODEGRAD_POLY"}
{"id":583,"sentence":"Table 6 shows the different fitting constants for the s 0.Kt) so (1.e curve. Being as PCL is a polyester, a similar degradation mechanism is proposed in Fig.","label":"BIODEGRAD_POLY"}
{"id":584,"sentence":"46 ppm (b) and 1.66 ppm (e) were assigned to the outer and inner methylene protons, respectively. Second, in the PBA segment, 4. 11 – 4.","label":"BIODEGRAD_POLY"}
{"id":585,"sentence":"Figure 6. Rate of relative decrease of Mw (rate of degradation) in the interval from 15 to 20 minutes for the neat PLA and PLA \/ PPG composites.","label":"BIODEGRAD_PROP"}
{"id":586,"sentence":"The possible presence of extracellular enzymes in manure and food composts may facilitate the hydrolytic reaction since greater molecular weight reduction rates were observed in these composts. 1H NMR and thermal analysis revealed that, while PBAT is a semi−crystalline copolyester with cocrystallization of BT and BA dimers,","label":"BIODEGRAD_POLY"}
{"id":587,"sentence":"(5d) However, the fundamental issue why the polymorphic P3HPs differ in the enzymatic degradability still remains open for debate. A further investigation on the packing and dynamics of polymorphic P3HPs is expected to be helpful for us to understand the unique P3HP biodegradation.","label":"BIODEGRAD_PROP"}
{"id":588,"sentence":"Determined by Differential Scanning Calorimetry Tcrystal Tmelt Starch content (wt %) Tg (°C) 7 The relative mechanical properties of the PLA \/ cornstarch composites were studied using the Nielsen and Nicolais – Narkis equations.","label":"MECHANICAL_PROP"}
{"id":589,"sentence":"Since fibers of PLLA have a higher refractive index in the negative birefringence present appears to be due to the fact that molecular chains are oriented in the direction otherorthogonal to the radius of the spherulites,","label":"BIODEGRAD_POLY"}
{"id":590,"sentence":"Here, too, SEC data are used for the calibration. 3. 4 Modeling of Thermal Degradation Rheological curves were recorded at various temperatures. Ea \/ RT).","label":"BIODEGRAD_PROP"}
{"id":591,"sentence":"On the other hand, poly (ethylene glycol) (PEG) is a biocompatible and hydrophilic polyether that has been widely used in biomedical research and applications. 2, 5 Through copolymerization, hydrophilic segments of hydrophilic PEG can be incorporated with PCL.","label":"BIODEGRAD_POLY"}
{"id":592,"sentence":"The weight loss was directly related to visual observation of the thickness and diameter reduction of the samples ; this suggested a surface‐erosion mechanism. As the temperature increased,","label":"BIODEGRAD_PROP"}
{"id":593,"sentence":"This outcome, together with the decreasing molecular weight and the insignificant physical mass loss of the copolymer films implies that much of the chains were merely broken up into smaller segments without the formation of water‐soluble products leaching into the buffer solution.","label":"BIODEGRAD_PROP"}
{"id":594,"sentence":"The modulus and tensile strengths were greatest for PLA polymers with a viscosity−average molecular weight above 55, 000 g \/ mole [110]. The impact strength and Vicat softening temperature increased with crystallinity and molecular weight [110].","label":"MECHANICAL_PROP"}
{"id":595,"sentence":"or food composts as a function of time. Dashed lines are the fitted curves to represent the increasing trend of heat of fusion. Based on the structure of PBAT (Fig. 1), several functional groups, such as hydroxyl (OH)","label":"POLY_STRUC"}
{"id":596,"sentence":"the post−polymerization and the random chain scission due to the presence of structural irregularities appearing in PCL degradation is not observed in PLLA. Hence, the degradation mechanism is limited to a depolymerization (Eq. 7).","label":"BIODEGRAD_PROP"}
{"id":597,"sentence":"and High Amylose Cornstarch (HACS) [133] Tensile strength Elongation at break Modulus Impact strength Polymer (MPa) (%) (GPa) Toughness (kg−f \/ cm) PLLA 60.00 3. 1 2. 5 0.93 125.","label":"MECHANICAL_PROP"}
{"id":598,"sentence":"The formation of block copolymers was proved by NMR analysis and DSC tests. A NMR study showed that block copolymers consist of polymer chains of P3HP and P4HB covalently linked together,","label":"POLY_STRUC"}
{"id":599,"sentence":"Fig. 2 shows the viscosity curves of PCL vs. frequency at 100 °C, 140 °C, 160 °C and 180 °C.","label":"RHEOLOGICAL_PROP"}
{"id":600,"sentence":"In addition, the mode of chain scission was determined using the method proposed by Shih. 35, 36 The number of ester bonds in the PCL segment was calculated based on eq.","label":"BIODEGRAD_PROP"}
{"id":601,"sentence":"The thermal properties of the PLA \/ PPG composites were characterized by a differential scanning calorimetry (DSC Q20, TA Instruments, New Castle, DE, USA) under a nitrogen atmosphere.","label":"MECHANICAL_PROP"}
{"id":602,"sentence":"In fact, complex viscosities of compatibilized PLA \/ PCL (90 \/ 10) and (70 \/ 30) blends were 18 and 11 times higher than that of pure PLA at 0.","label":"BIODEGRAD_POLY"}
{"id":603,"sentence":"This is in agreement with FTIR results, which showed more PLA chain scission during processing than during thermo−oxidative. While the decrease in viscosity caused by thermo−mechanical degradation was due to high temperature, oxygen and shear during melt mixing, during thermo−oxidative exposure, chain scission occurred by the synergetic effect of temperature and oxygen, resulting in oxidative degradation.","label":"BIODEGRAD_PROP"}
{"id":604,"sentence":"(2006a) and Bikiaris et al. (2007), they have shown that the thermal degradation of aliphatic polyesters is a mechanism of α or β hydrogen bond scission.","label":"BIODEGRAD_PROP"}
{"id":605,"sentence":"This polymer contained mixture of homopolymers P3HP and P4HB and block P3HP−b−P4HB, as analyzed by NMR. This phenomenon could be attributed due to a weaker synthase activity for the conversion of 4−hydroxybutanoyl−CoA to P4HB, during the late exponential growth phase or stationary phase.","label":"BIODEGRAD_POLY"}
{"id":606,"sentence":"Thus, the development of biodegradable polymers from renewable resources has been motivated by problems associated to the persistence of plastic in the environment, dwindling petroleum resources, shortage of landfill space and emission of toxic gases during incineration [1].","label":"BIODEGRAD_PROP"}
{"id":607,"sentence":"On the other hand, after 30 days of hydrolysis test, the PBS, PBAT, and PBS \/ PBAT blend showed deep holes, cavities as well as eroded regions.","label":"BIODEGRAD_POLY"}
{"id":608,"sentence":"Similar results were obtained using Al (OiPr) 3 in the bulk of 100 °C, and using proton NMR it was found that all chains contained isopropoxy ester end−groups and molecular weights corresponding to the number of alkoxide groups [73].","label":"POLY_STRUC"}
{"id":609,"sentence":"Microorganisms in composts and their enzymes responsible for the hydrolytic degradation can be identified in order to solve this issue. Table 1.Rate constants (k) calculated from reduced molecular number of biodegradation of PBAT films in manure, yard,","label":"BIODEGRAD_PROP"}
{"id":610,"sentence":"and Week 20 (6. 5 %). Compared against degradation at pH 7. 4 (1.7 % in the same time period), accelerated degradation occurring at a higher pH can once again be verified.","label":"BIODEGRAD_PROP"}
{"id":611,"sentence":"which suggested the presence of a different molecular environment. Therefore, the main objective of this work was to investigate the role of temperature, shear and oxygen on PLA degradation.","label":"BIODEGRAD_PROP"}
{"id":612,"sentence":"Their result indicated that PPG modified the mechanical properties of the resultant composites by altering the crystallinity of PLA. PPGs are viscous liquids in the MW range of 150 – 4000 g \/ mol.","label":"BIODEGRAD_POLY"}
{"id":613,"sentence":"Polymer Processing XXII (2007) 5 A. Lopez Arraiza et al. : Rheological Behavior and Modeling of Thermal Degradation tion curve of PET, for comparison.","label":"RHEOLOGICAL_PROP"}
{"id":614,"sentence":"the PLA \/ PBAT blends without compatibilizer clearly showed a shoulder and terminal zone at low frequency, which was attributed to droplet relaxation. The phenomenon is likely to be caused by the decreased droplet size of the dispersed phase with the addition of compatibilizers, in accordance with the results shown in Fig. 4.","label":"BIODEGRAD_POLY"}
{"id":615,"sentence":"(28, 43) Based on Bernoullian statistics, the random copolymer P (3HP−co−4HB) can be described by the molar fraction of 3HP as stated below including parameter of F3HP * 3HP, F3HP * 4HB, F4HB * 3HP,","label":"POLY_STRUC"}
{"id":616,"sentence":"the presence of slime increases the accumulation of atmospheric pollutants, this accumulation favour the development of microorganisms and accelerate the biodeterioration (Zanardini et al., 2000).","label":"BIODEGRAD_PROP"}
{"id":617,"sentence":"Representative tables of d−spacings of the b−structure of PLLA, discrete energy minima of PLLA chains, and standard bond lengths and angles used in conformational energy calculations are presented in Tables I to III [99].","label":"BIODEGRAD_POLY"}
{"id":618,"sentence":"and their blend. It can be seen that the PBS had higher storage modulus than PBAT and PBS \/ PBAT. Similar occurrence has been observed in the tensile and flexural modulus.","label":"BIODEGRAD_POLY"}
{"id":619,"sentence":"Most biodegradable polymers belong to thermoplastics (e. g. poly (lactic acid), poly (hydroxyalkanoate), poly (vinyl alcohol)) or plants polymers (e. g. cellulose and starch).","label":"BIODEGRAD_POLY"}
{"id":620,"sentence":"Accordingly, the increase in molecular mass of PI midblock further enhances thermal stability of the triblock copolymers (Figs. S1a and d). Similar thermal stability enhancement has been reported in other triblock copolymers, for examples, poly (ethylene oxide)−b−poly [(R)−3−hydroxy butyrate]−b−poly (ethylene oxide) (PEO−b−PHB−b−PEO) [27]","label":"POLY_STRUC"}
{"id":621,"sentence":"Biodeterioration. Biofragmentation. ssimilation. Tensile tests (strength, elongation at break) are used to investigate mechanical changes during the degradation (ISO 527−3, 1995, ASTM D 882, 2002).","label":"BIODEGRAD_PROP"}
{"id":622,"sentence":"Fig. 9. Mole fraction of BA and BT content of hydrolyzed PBAT films in phosphate buffer or in vermiculite at 58 °C as a function of logarithmic reduction of molecular number (Mn).","label":"BIODEGRAD_POLY"}
{"id":623,"sentence":"However, in nature, biotic and abiotic factors act synergistically to decompose organic matter. Polymeric materials that are exposed to outdoor conditions (i. e. weather, ageing and burying) can undergo transformations (mechanical, light, thermal,","label":"POLY_STRUC"}
{"id":624,"sentence":"Several lipases (EC 3. 1.1.3) and some carboxylesterases (EC 3. 1.1.1) are active on aliphatic polyesters and thus can be employed in their synthesis or hydrolysis.","label":"POLY_STRUC"}
{"id":625,"sentence":"Harris and Lee13 found that the PLA and PLA \/ PC blend underwent severe flexural strength reduction because of the hydrolytic degradation under the exposed elevated temperature (70 °C)","label":"BIODEGRAD_POLY"}
{"id":626,"sentence":"According to ASTM D5338, sources of inocula used in biodegradation tests for biodegradable polymers are composts [6]. The authors have previously studied the biodegradation of biodegradable polyesters, such as poly (lactic acid) and PBAT, in various composting [2], [8], [9]","label":"POLY_STRUC"}
{"id":627,"sentence":"It has been reported that the a−structure has a melting point of 185 °C, versus 175 °C for the b−structure, suggesting that the a−structure is more stable than the b−structure [99].","label":"POLY_STRUC"}
{"id":628,"sentence":"Previously, the FTIR measurement was frequently used to investigate the conformation of polymers. (10) However, only a few FTIR results, possibly just those of polyethylene, (11) are available on the chain packing of polymers.","label":"POLY_STRUC"}
{"id":629,"sentence":"The aim of this review is to emphasise the importance of measure as well as possible, the last stage of the biodegradation, in order to certify the integration of new materials into the biogeochemical cycles.","label":"BIODEGRAD_PROP"}
{"id":630,"sentence":"(1) Fig. 3. Rheological behavior of PLLA at different temperatures, under inert atmosphere c 2007 Carl Hanser Verlag, Munich, Germany www. polymer−process. com Not for use in internet or intranet sites.","label":"RHEOLOGICAL_PROP"}
{"id":631,"sentence":"This synthesis method took PLA−CTA as a macroinitiator and applied RAFT polymerization, a reversible addition−fragmentation chain transfer. A ring−opening polymerization (ROP) method was first used to prepare PLA−CTA, taking PMHD, 1, 4−phenylenebis (methylene) bis (2−hydroxyethyl) dicarbonotrithioate functioning as the key bifunctional initiator.","label":"BIODEGRAD_POLY"}
{"id":632,"sentence":"For the measurements at low temperature, sample specimens were infused in liquid nitrogen for 10 min before testing. The elastic modulus (E), elongation at break (Eb)","label":"MECHANICAL_PROP"}
{"id":633,"sentence":"After “ C3−labelling ”, any other nutrient assimilation leads to an isotopic modification of the developing microbial biomass. Applying this procedure to the biodegradation of industrial materials, a change of the isotopic content confirms unquestionably the assimilation of the polymeric material used as substrate (Lucas, 2007).","label":"BIODEGRAD_PROP"}
{"id":634,"sentence":"Fig. 2. Lactide ring formation. The azeotropic condensation polymerization is a method to obtain high−molecular−weight polymer without the use of chain extenders or adjuvents.","label":"POLY_STRUC"}
{"id":635,"sentence":"3 nm, (6c) and it is about 3 times that between the bonded couple. In this case, the strengths of the total MDDI for the three polymorphic crystals are comparable,","label":"POLY_STRUC"}
{"id":636,"sentence":"These cyclic catalysts, due to the coordination \/ insertion mechanism, form high−molecular−weight PLA macrocycles with little racemization when polymerized in bulk at 120 °C.","label":"BIODEGRAD_POLY"}
{"id":637,"sentence":"The crystallization of these samples can be detected by using wide−angle X−ray diffraction (WAXD) technique. Fig. 3 shows the WAXD curves for the solvent−cast and melt−quenched PLA−b−PI−b−PLA triblock copolymers.","label":"POLY_STRUC"}
{"id":638,"sentence":"Complex viscosity of the uncompatibilized PLA \/ PCL (70 \/ 30) blend lays between those of pure PLA and PCL due to lack of compatibility, whereas that of the uncompatibilized PLA \/ PCL (90 \/ 10) blend was higher than pure PLA below an angular frequency 1 rad \/ s due to the effect of hydrogen bonding, as mentioned above.","label":"BIODEGRAD_POLY"}
{"id":639,"sentence":"In the last years, an exponential increase of the environmental problems associated with plastics has stimulated a new interest in aliphatic polyesters for several applications such as degradable materials in packaging, disposables,","label":"POLY_STRUC"}
{"id":640,"sentence":"29 Due to the moisture absorption, it can be expected that the PBS and PBAT can undergo hydrolytic degradation at elevated temperature and humidity. Normally, higher moisture absorption of polyesters causes undesirable losses in mechanical performances. 13, 30 Figure 1 Open in figure viewer PowerPoint Moisture absorption curves as a function of conditioning time. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_PROP"}
{"id":641,"sentence":"DSC thermograms should indicate an increase of the crystalline region of the polymer as a function of time as samples are subjected to hydrolysis and \/ or biodegradation.","label":"BIODEGRAD_PROP"}
{"id":642,"sentence":"Shimadzu, Japan). PHA was extracted from lyophilized cells using boiling chloroform treatment for 4 h. The PHA dissolved in the supernatant thus obtained was precipitated with 10 times ice cold ethanol.","label":"BIODEGRAD_POLY"}
{"id":643,"sentence":"5 resulted in the formation of dimers. From the results, it can be proposed that a more complete understanding of the degradation behavior of the PCL‐b‐PEG copolymer can be monitored using a combination of physiological and accelerated hydrolytic degradation conditions. © 2012 Wiley Periodicals,","label":"BIODEGRAD_PROP"}
{"id":644,"sentence":"L)−PLA 56 140 80 \/ 20 (L \/ D, L)−PLA 56 (125) a a Melting point achieved by strain crystallization.","label":"BIODEGRAD_POLY"}
{"id":645,"sentence":"19 and−20.20 °C and−45. 19 and−21.58 °C, respectively, corresponding to the glass transition temperature values of P4HB and P3HP block polymer chains, respectively (Figure 6,","label":"BIODEGRAD_POLY"}
{"id":646,"sentence":"which has been found to be a general feature for spherulites. After carrying out crystallization experiments using the DSC, they suggested that poly (L−lactic acid) crystallinity might not exceed 60 %.","label":"BIODEGRAD_POLY"}
{"id":647,"sentence":"Following degradation, the samples were removed from the humidity chamber and dried in vacuo with desiccant for 48 h at 50 °C.","label":"BIODEGRAD_PROP"}
{"id":648,"sentence":"which is available at wileyonlinelibrary. com.] The molecular weight reduction is permanent damage caused by hydrolysis of the ester functionalities on the polyesters backbone. Phua and coworkers8 have studied the molecular weight of hydrolytically degraded PBS samples.","label":"BIODEGRAD_PROP"}
{"id":649,"sentence":"The rapid decreases in Mn and Mw continued through day 30 of degradation. Between 30 and 90 days, however, the degradation rate slowed significantly. For PLA32,","label":"BIODEGRAD_PROP"}
{"id":650,"sentence":"at long residence times in the rheometer. In fact, viscosity measurements begin at high frequency, and the time spent at a given frequency increases when frequency decreases.","label":"RHEOLOGICAL_PROP"}
{"id":651,"sentence":"The increased crystallinity also confirmed that the amorphous regions are more susceptible to biodegradation than the crystalline regions as reported by Mochizuki and Hirami [33], Hakkarainen et al. [34],","label":"POLY_STRUC"}
{"id":652,"sentence":"and structural changes determined by DSC, FTIR, and 1H NMR were used as indicators of the biodegradation and hydrolysis rates. Poly (butylene adipate−co−terephthalate), PBAT, film biodegraded at distinctive rates in manure, food,","label":"BIODEGRAD_PROP"}
{"id":653,"sentence":"the impact energies of both PBS and PP were not significantly affected. In contrast, the impact energy of the PBAT remains unchanged up to 30 days of conditioning at elevated temperature and humidity.","label":"BIODEGRAD_POLY"}
{"id":654,"sentence":"Five measurements were performed and averaged to obtain the solution viscosity of each sample. Thermal properties were determined in a Perkin−Elmer DSC Diamond under nitrogen.","label":"RHEOLOGICAL_PROP"}
{"id":655,"sentence":"However, modulus values between those of pure PLA and PCL at higher frequencies indicate that hydrogen bonding forces were negligible compared with dynamic shear force portion required for deformation [30].","label":"BIODEGRAD_POLY"}
{"id":656,"sentence":"The k value from PBAT biodegradation in manure compost was the highest (0.0593 ± 0.0025 d−1) and those from biodegradation in yard compost (0.0237 ± 0.","label":"BIODEGRAD_PROP"}
{"id":657,"sentence":"and zinc yielding the purest polymers. It was found that the most effective catalysts with respect to yield, molecular weight, and racemization were tin (II) oxide or octoate, lead (II) oxide, antimony octoate,","label":"POLY_STRUC"}
{"id":658,"sentence":"and the Tm values at 129. 9. C and 147. 9. C, respectively for PBAT and PLA phases. Given in Table 3 are additional data for Tg and Tm values obtained for PLA \/ PBAT blends.","label":"POLY_STRUC"}
{"id":659,"sentence":"Figure 11 Open in figure viewer PowerPoint DSC heating cycles for PBS, PBAT, and PBS \/ PBAT before and after exposed to 50 °C with 90 % RH for 30 days. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":660,"sentence":"Therefore, after sufficient time for diffusion within the sample, both the surface and bulk erosion contributed to hydrolysis. This was confirmed by SEM micrographs performed on PLA sample surfaces.","label":"BIODEGRAD_PROP"}
{"id":661,"sentence":"Fig. 1.DSC curves for PCL, PHB, and PHB−V. Table 1.Melting temperature and crystallinity of PCL, PHB, and PHB−V The DSC curve for PHB (Fig. 1) had a short shoulder at low temperature,","label":"BIODEGRAD_POLY"}
{"id":662,"sentence":"The impact strength of pure PLA was relatively low (28. 8 J \/ m) due to its brittleness [31]. The impact strength of uncompatibilized PLA \/ PCL (90 \/ 10) blend was 1.","label":"MECHANICAL_PROP"}
{"id":663,"sentence":"(2) The number average molecular weight of PLA has been previously shown to be directly related to the scission of the polymer chains 21.As described by Zhu et al. 22,","label":"POLY_STRUC"}
{"id":664,"sentence":"At predetermined time intervals the test tubes were removed from the water bath and the film samples were separated from the buffer solution. Mt was obtained after lyophilization of the samples at 50 °C for 1 week.","label":"POLY_STRUC"}
{"id":665,"sentence":"We envisioned that more perfect crystals were unaffected by hydrolysis but that as amorphous chain segments got cleaved, the crystals progressively reorganized into smaller crystals and lower Tm crystals.","label":"POLY_STRUC"}
{"id":666,"sentence":"This is expected since the degradation in the temperature range of 40 – 80 °C is driven by hydrolysis, which would be minimal under a nitrogen purge.","label":"BIODEGRAD_PROP"}
{"id":667,"sentence":"which is consistent with the trend shown in Figure 5. But the Mw of the plasticized PLA after adding the PPG with different MWs does not change as significantly as the torque.","label":"POLY_STRUC"}
{"id":668,"sentence":"PLA degradation was assessed by viscosity, 1H Nuclear magnetic resonance spectroscopy (1H NMR), infrared spectroscopy (FTIR), gel permeation chromatography (GPC)","label":"BIODEGRAD_PROP"}
{"id":669,"sentence":"Typical stress−strain curves of the specimens are shown in Fig. 3. The pristine blends show a brittle fracture phenomenon similar to PLA. Fig. 3.","label":"MECHANICAL_PROP"}
{"id":670,"sentence":"Equation (5) is the formula describing the interaction of a certain viscosity of a melt with a certain geometry of the mixing cavity, where the shape of the mixing roll is approximately cylindrical and the radius is Ri, k is the ratio of Ri to the cylindrical cavity radius Rb ; VF is the volume of the mixing chamber ; is the melt viscosity at low shear rates (Newtonian fluid) ; is the characteristic time of the melt,","label":"RHEOLOGICAL_PROP"}
{"id":671,"sentence":"An increase in OH groups (3350 cm−1) in all the samples was observed, and was more prominent in the compost samples than in phosphate buffer and vermiculite (Fig. 7a – e).","label":"BIODEGRAD_PROP"}
{"id":672,"sentence":"and tensile strength (UTS) were obtained from a stress−strain curve. 2. 4 Fourier transform infrared spectroscopy (FTIR) FTIR measurements were carried out at room temperature using the IRPrestige−21 (Shimadzu) spectrometer in attenuated total reflectance (ATR) mode.","label":"MECHANICAL_PROP"}
{"id":673,"sentence":"Universidade S ã o Francisco, for use of their thermal analysis equipment. Abstract The biodegradation and hydrolysis rates of an aliphatic aromatic copolyester were measured in manure, food,","label":"BIODEGRAD_PROP"}
{"id":674,"sentence":"It can be seen that the PP absorbed a very small amount (0.011 % ± % 0.004 %) of moisture and the moisture absorption curve has reached a typical Fickian behavior.","label":"BIODEGRAD_PROP"}
{"id":675,"sentence":"or in vermiculite, or from biodegradation in manure, yard, or food composts as a function of time ; the regression are performed using 1st order reaction.","label":"BIODEGRAD_PROP"}
{"id":676,"sentence":"While in surface erosion, matter is lost but there is not change in the molecular weight of polymers of the matrix. Some authors describe erosion mechanisms of polymers : surface erosion for aliphatic – aromatic copolyesters (Muller, 2006), PHB (Tsuji and Suzuyoshi, 2002)","label":"POLY_STRUC"}
{"id":677,"sentence":"Aliphatic \/ aromatic polyesters, such as polylactic acid (PLA), polyhydroxybutyrate (PHB), polycaprolactone (PCL) and poly (butylene adipate terephthalate) (PBAT) are among the most popular biodegradable polymers [4].","label":"BIODEGRAD_POLY"}
{"id":678,"sentence":"From the results, it can be proposed that a more complete understanding of the degradation behavior of the PCL‐b‐PEG copolymer can be monitored using a combination of physiological and accelerated hydrolytic degradation conditions.","label":"BIODEGRAD_PROP"}
{"id":679,"sentence":"and Fourier transform infrared spectroscopy analysis. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42189. INTRODUCTION During the past decade, biodegradable polymers and their blends have gained great attention in wide range of applications due to their low environmental footprint.","label":"BIODEGRAD_PROP"}
{"id":680,"sentence":"Alcamo, 1998). It consists in measuring the consumption of oxygen or the evolution of carbon dioxide (Pagga, 1997). The unique proof that a polymer is consumed by microorganisms is the release of carbon dioxide.","label":"BIODEGRAD_PROP"}
{"id":681,"sentence":"All the samples exhibited a decrease in η ∗ with an increase in frequency because the blends were pseudoplastic liquids and presented shear−thinning tendency. Moreover, further increasing the tri−block copolymer content gradually reduced the η ∗ of the samples.","label":"RHEOLOGICAL_PROP"}
{"id":682,"sentence":"The composites were melt blended in a Haake twin−screw extruder, and dogbone tensile bars were compression molded. The relative mechanical properties of the PLLA \/ starch composites were studied using the Nielsen and Nicolais – Narkis equations.","label":"MECHANICAL_PROP"}
{"id":683,"sentence":"Kalb and Pennings [85] dissolved PLLA crystals in p−xylene and studied their dissolution temperature as a function of crystallization temperature, Tc, using differential scanning calorimetry.","label":"POLY_STRUC"}
{"id":684,"sentence":"The spectrum of pure PLA (Figure 2 (a)) showed absorption bands corresponding to C 0 O stretching vibration at 1745 cm−1, CH3 stretching at 2994 and 2947 cm−1, asymmetric bending absorption of CH3 at 1453 cm−1,","label":"BIODEGRAD_POLY"}
{"id":685,"sentence":"The cast P3HP70k samples were then melted at 130 °C to erase the residual thermal history, and then quenched to 0 and 70 °C directly to melt−crystallize, respectively,","label":"POLY_STRUC"}
{"id":686,"sentence":"A Literature Review of Poly (Lactic Acid) Donald Garlotta1 A literature review is presented regarding the synthesis, and physicochemical, chemical, and mechanical properties of poly (lactic acid) (PLA).","label":"BIODEGRAD_POLY"}
{"id":687,"sentence":"and PBS \/ PBAT before and after 30 days conditioned at 50 °C and 90 % RH. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":688,"sentence":"This behavior could be explained by observation of the weight loss trend. At the beginning, the induction stage took place, and no weight loss occurred.","label":"BIODEGRAD_PROP"}
{"id":689,"sentence":"which considered as weight average molecular weight. 51 This relationship can be explained as follows : 50 (4) where K and M are the material constant and molecular weight, respectively.","label":"POLY_STRUC"}
{"id":690,"sentence":"which can obviously enhance the mechanical property of the triblock copolymers, with respect to the Young's modulus, yield stress, ultimate tensile strength, and strain−hardening modulus, with slight reduction in elongation at break and yield strain.","label":"MECHANICAL_PROP"}
{"id":691,"sentence":"and compared with each other to further reveal the evolution of chain conformation and \/ or packing during melting. Finally, the solid structure and chain mobility of the β -, γ -, and δ−forms were investigated by the solid state 13C NMR measurement.","label":"POLY_STRUC"}
{"id":692,"sentence":"Fig. S1b) as compared with neat PLA (Tmax, 1 0 337. 4 °C) apparently due to homogenous dispersion of PLA domains in the PI matrix [3, 26], noting that PI shows much higher thermal stability with higher Tmax, 2 and Tmax, 3 values (Figs. S1b, c, d).","label":"BIODEGRAD_POLY"}
{"id":693,"sentence":"The wheat starch had shown a slightly better adhesion to the PLLA than did the cornstarch, but the adhesion was still poor. The average granular size of wheat starch was greater than that of cornstarch, so the contact surface area at the interface between PLA and wheat starch would be larger than that between PLA and cornstarch.","label":"BIODEGRAD_POLY"}
{"id":694,"sentence":"This loss indicated that PHB−V was easily hydrolyzed, probably because the presence of tertiary carbons favored the stabilization of the carbonic ion in the hydrolysis mechanism.","label":"BIODEGRAD_PROP"}
{"id":695,"sentence":"and 806 and 801 cm−1 for the γ−form, respectively. On the other hand, as the δ−form P3HPs adopt the 21−helix conformation, as shown in Figure 1,","label":"BIODEGRAD_POLY"}
{"id":696,"sentence":"Meanwhile, Figure 3 reveals that the temperature of the PLA and PLA \/ PPG composites increased to 170 °C after 4 minutes, while the torque of the PLA and PLA \/ PPG composites decreased slightly, indicating that the composites were well melted under the fixed conditions.","label":"BIODEGRAD_POLY"}
{"id":697,"sentence":"Materials and Methods 2. 1.Materials PLA (NatureWorks ® PLA Polymer 4032D) of density 1.24 g \/ cm3 and a melt flow index of 6.","label":"BIODEGRAD_POLY"}
{"id":698,"sentence":"(17, 20, 21) Here, we have studied the catalytic mechanism for PCL hydrolysis and were able to characterize in detail all intermediates involved in polyester hydrolysis by this enzyme.","label":"BIODEGRAD_PROP"}
{"id":699,"sentence":"It can catalyze the hydrolysis of a broad range of esters, including p−nitrophenyl esters, vinyl esters, and triacylglycerols with a short chain, which exhibit the highest activity toward p−nitrophenyl hexanoate among the p−nitrophenyl esters tested.","label":"BIODEGRAD_PROP"}
{"id":700,"sentence":"and showed characteristic PLA bands, such as C 0 O stretching vibration at 1745 cm−1 and CH3 stretching at 2994 and 2947 cm−1.","label":"BIODEGRAD_POLY"}
{"id":701,"sentence":"Furthermore, we suggest the technical estimation adapted to each level of biodegradation. Sometimes, these abiotic parameters are useful either as a synergistic factor, or to initiate the biodegradation process (Jakubowicz et al., 2006).","label":"BIODEGRAD_PROP"}
{"id":702,"sentence":"both the chain packing (intermolecular interaction) and the conformation (intramolecular interaction) contribute the molecular mobility. However, when two polymorphic phases with different conformations, e. g.,","label":"POLY_STRUC"}
{"id":703,"sentence":"Under cooling, most of IR bands in the 1500−750 cm−1 region were noted to be distinctively blueshifted and enhanced, which should reflect the increased intermolecular interaction and depend on the chain packing of each crystal form.","label":"POLY_STRUC"}
{"id":704,"sentence":"The objective of this study was to further improve our understanding of the degradation kinetics at elevated temperature. In particular, this study focused on commercial PLA (with d‐content limiting crystallization) rather than on pure PLA.","label":"BIODEGRAD_POLY"}
{"id":705,"sentence":"Figure 6 Open in figure viewer PowerPoint XRD spectra of copolymer films after degradation at (a) pH 7. 4 and (b) pH 9. 5.","label":"BIODEGRAD_PROP"}
{"id":706,"sentence":"Table 3. DSC data for the neat PLA and PLA \/ PPG composites. The TGA results (Figure 9) show that the PLA \/ PPG composites barely lost weight during the processing temperature range (150 – 180 °C), indicating that the composites at this temperature range have a good thermal stability.","label":"BIODEGRAD_POLY"}
{"id":707,"sentence":"Degradation Conditions For fibers of both diameters, samples were prepared and exposed to either 100 % relative humidity (RH) or nitrogen purge.","label":"BIODEGRAD_PROP"}
{"id":708,"sentence":"Unfortunately, the disadvantages of poor toughness and low elongation at break limit their application range [12]. Therefore, it is usually necessary to improve toughness of PLA in practical applications [13, 14].","label":"MECHANICAL_PROP"}
{"id":709,"sentence":"However, for polyesters with higher melting points, the degree of crystallinity is a major limiting factor for hydrolysis. Nevertheless, the amorphous region will contain polymer chains that can access the active site,","label":"POLY_STRUC"}
{"id":710,"sentence":"and the effect of processing conditions on the mechanical properties of PLA (Table XVII). Some of the graphs shown are dynamic modulus versus temperature, viscosity versus shear rate,","label":"MECHANICAL_PROP"}
{"id":711,"sentence":"Poly (lactic acid) produced by condensation polymerization has five characteristic peaks at 169. 27, 169. 31, 169. 42, 169. 49,","label":"BIODEGRAD_POLY"}
{"id":712,"sentence":"which is consistent with the capillary rheological test results. Figure 2. Torque (a) and temperature (b) versus time when processing the neat PLA at different chamber wall temperatures.","label":"RHEOLOGICAL_PROP"}
{"id":713,"sentence":"The thermal degradation in unstabilized PLLA was very rapid at temperatures above 230 °C and increased with long residence times. However, the high thermal stability of PCL allowed the exposition of the polymer to higher levels of energy without degradation.","label":"BIODEGRAD_PROP"}
{"id":714,"sentence":"and in vermiculite (Fig. 7g). However, PBAT samples in manure (Fig. 7h), food (Fig. 7i), and yard composts (Fig. 7j) manure showed greater reduction in carbonyl groups possibly due to synergistic effects of enzymatic degradation.","label":"BIODEGRAD_PROP"}
{"id":715,"sentence":"the two models fit the data comparably based on the R2 values calculated for each diameter and model. The autocatalytic model underestimated the molecular weight after 4 days and the first order kinetic model overestimated the molecular weight between days 3 and 7.","label":"POLY_STRUC"}
{"id":716,"sentence":"Thermal analyses were also done on the samples in order to assess whether there was any correlation between the polymer crystallinity and biodegradation. Poly (ɛ−caprolactone) (PCL) was supplied as pellets by Union Chemical Carbide (P−767) (Cubat ã o, SP,","label":"POLY_STRUC"}
{"id":717,"sentence":"the large‐scale production of PLA from renewable resources has enabled its use in high‐volume food‐packaging and textile applications. 1, 2 PLA is subject to hydrolysis and biodegradation.","label":"BIODEGRAD_POLY"}
{"id":718,"sentence":"Figure 5 Open in figure viewer PowerPoint FTIR spectra of degradation products after hydrolysis at pH 7. 4 (a) copolymer film and (b) water soluble products.","label":"BIODEGRAD_PROP"}
{"id":719,"sentence":"4 Mv 0.73 (Shindler et al., 1982)]. Special care was used in handling all samples to exclude moisture in order to avoid hydrolytic degradation.","label":"BIODEGRAD_PROP"}
{"id":720,"sentence":"When the molecular weight was decreased to about 4. 0 kg \/ mol, Tm reached 145 °C. The enthalpy development and Tm changes were independent of the pH of the media (Figure S3,","label":"POLY_STRUC"}
{"id":721,"sentence":"and thermal stability. In addition, the biodegradability of PLA was also increased by blending of PCL. It is believed these enhancements substantially increase the utilities of PLA \/ PCL blends.","label":"BIODEGRAD_POLY"}
{"id":722,"sentence":"or poly (ethylene terephthalate). In this paper the thermal degradation of poly (e−caprolactone) (PCL) and poly (L−lactide) (PLLA) melts was investigated by rheometry and thermogravimetry under different temperatures and inert atmosphere.","label":"BIODEGRAD_POLY"}
{"id":723,"sentence":"The greater the cornstarch content in the composite, the lower the thermal degradation onset temperature [133]. Kim [133] reported water immersion data for PLLA and PLLA \/ cornstarch composites.","label":"BIODEGRAD_POLY"}
{"id":724,"sentence":"Bacterial block copolymerization of PHA polymers adds new physical properties by introducing polymer microstructure in biological PHA systems. (30) Here, different blocks of polymers covalently link within a polymer chain.","label":"BIODEGRAD_POLY"}
{"id":725,"sentence":"Chloroform was used as an eluent at a flow rate of 1 mL min−1.Nine polystyrene standards of narrow molecular weight distribution (Polysciences ; weight‐average molecular weight ∼436 – 990, 500 Da) were used for the calibration.","label":"POLY_STRUC"}
{"id":726,"sentence":"The L−PLA has a narrow window of processing, (12 °C), whereas a 90 \/ 10 L−to D−copolymer has a much wider range of processing (40 °C) due to its lower melting temperature.","label":"BIODEGRAD_POLY"}
{"id":727,"sentence":"Suprakas et al., 2003) or natural fibres (Placketta et al., 2003 ; Ruseckaite and Jimenez, 2003). Studies related to hydrolysis (Dwan et al., 2003 ;","label":"BIODEGRAD_PROP"}
{"id":728,"sentence":"The evolution of melt viscosity of PLLA with time, different temperatures Fig. 9. Number of chain scissions versus time in PLLA, different temperatures T (°C) 200 220 230 240 250 so (mol \/ kg)","label":"RHEOLOGICAL_PROP"}
{"id":729,"sentence":"Conclusions The degradation of the PLA \/ PPG composites containing different MW PPG during real processing was monitored by the changing trend of viscosity, which appears to be an effective and simple approach for studying the degree of degradation during PLA processing.","label":"BIODEGRAD_POLY"}
{"id":730,"sentence":"8 Contrary, the crystallization temperature of PBAT was shifted to higher temperature. This is probably due to the nucleation effect which is caused by oligomers. 48 Dynamic Mechanical Analysis Figure 13 shows the temperature dependence dynamic modulus of PBS, PBAT,","label":"BIODEGRAD_POLY"}
{"id":731,"sentence":"Fig. 5. Effect of stabilizer on PLA crystallinity (graph bars) and intrinsic viscosity (graph lines) along processing time. DSC heating curves obtained after erasing thermal history (i. e. 2nd heating) are shown in Fig. 6,","label":"POLY_STRUC"}
{"id":732,"sentence":"Based on the results presented above, shear has a crucial role in PLA degradation mechanisms during processing. Fig. 3. PLA crystallinity and intrinsic viscosity after processing and exposure to thermal−oxidative conditions.","label":"BIODEGRAD_POLY"}
{"id":733,"sentence":"and chain propagation by deacylation by the terminal alcohol of a growing PCL chain. Although chain initiation is necessary for ROP, 6−HCA and water are competitive nucleophiles to the growing PCL chain.","label":"BIODEGRAD_POLY"}
{"id":734,"sentence":"The confined crystal growth of PLA in the PLA−riched domains was reported in our recent work [26]. The crystallinity value increases modestly with decreasing PI midblock molecular mass, however,","label":"POLY_STRUC"}
{"id":735,"sentence":"An analogous approach is presented by Doi 16. Typical diffusivities of species within PLA are on the order of 10−8−10−9 cm2 s−1 17.","label":"BIODEGRAD_POLY"}
{"id":736,"sentence":"(22) For all the three crystal forms, the α CH2 shows the T1C value slightly larger than that for the β CH2. Furthermore, the solid−state 13C spin−lattice relaxation time of the crystalline phase was noted to depend on the crystalline structure, that is,","label":"POLY_STRUC"}
{"id":737,"sentence":"which is due to the formation of α−form PLA crystals [31, 32]. Note that the two major crystalline peaks locating at 2 θ of 16. 8 °and 19. 2 °respectively correspond to the (110)","label":"POLY_STRUC"}
{"id":738,"sentence":"Typical DSC thermogram of polymer blend sample : treatment PLA40 4 Conclusions Elastic modulus of PLA \/ PBAT blends could be improved when the concentration of PLA was at least 40 % (by volume).","label":"BIODEGRAD_POLY"}
{"id":739,"sentence":"The hydrolysis temperature (TH) can be classified into three ranges : TH < Tg, Tg ≤ TH < Tm, and TH > Tm (where Tm is the melting temperature).","label":"POLY_STRUC"}
{"id":740,"sentence":"Not for electronic distribution. Material RS % RM % α deg [g] dl \/ g Mv g \/ mol PLLA PCL < 0.01.< 0.1.. 158. 4. 4. 4 1.4 2. 25 · 105 1.28 · 105 Table 1.","label":"BIODEGRAD_POLY"}
{"id":741,"sentence":"RM can be derived from Equations (8) – (10), approximately : (11) 3. Results and Discussion 3. 1.Capillary Rheological Properties The logarithmic curves of the apparent viscosity as a function of shear rate and the logarithmic curves of the shear stress σ as a function of shear rate for the PLA and PLA \/ PPG composites are shown in Figure 1.","label":"RHEOLOGICAL_PROP"}
{"id":742,"sentence":"Crystallization of the amorphous, but thermally crystallizable, PLA copolymers (various L−to D−content) by annealing could be initiated at temperatures between 75 °C and the melting point.","label":"POLY_STRUC"}
{"id":743,"sentence":"As the annealing time increased, so did the crystalllinity of the PDLLA in the starch \/ PDLLA \/ adipic PHEE blends. Bigg [100] also investigated the effects of molecular weight and nucleating agents on the crystallinity of PDLLA.","label":"POLY_STRUC"}
{"id":744,"sentence":"Inc. J. Appl. Polym. Sci., 2013 INTRODUCTION Biodegradable polymers break down into simpler monomeric or oligomeric components owing to the presence of cleavable chemical bonds present within the polymer backbone.","label":"BIODEGRAD_PROP"}
{"id":745,"sentence":"1H‐NMR, DSC, FTIR, XRD, and SEM. A faster rate of degradation took place at pH 9. 5 than at pH 7. 4.","label":"BIODEGRAD_PROP"}
{"id":746,"sentence":"5 allows for the prediction of the long‐term hydrolytic degradation behavior of the copolymers within a shorter time frame. Initially, the copolymer entered an induction period whereby very insignificant mass loss was observed.","label":"BIODEGRAD_PROP"}
{"id":747,"sentence":"Graphical abstract Download : Download high−res image (370KB) Download : Download full−size imageThermoplastic elastomers (TPEs) are generally block copolymers composed of at least two types of blocks, referred to as hard segments and soft segments [1].","label":"POLY_STRUC"}
{"id":748,"sentence":"and (d) cPLA at pH 12. [Color figure can be viewed in the online issue, which is available at wiley onlinelibrary. com.]","label":"BIODEGRAD_POLY"}
{"id":749,"sentence":"Wide−angle X−ray diffraction technique (WAXD) demonstrates that the end blocks crystallize and eventually PLA α−form crystals form. The variable mechanical property of triblock copolymers can be obviously enhanced by controlling crystallization of the end blocks, with the crystallized PLA domains replacing the glassy amorphous PLA domains, facilitating development of sustainable green elastomers with sufficient applicable mechanical property.","label":"POLY_STRUC"}
{"id":750,"sentence":"The PLA−b−PI−b−PLA triblock copolymers show sufficient thermal stability for application purpose as biodegradable thermoplastic elastomers. Dynamic mechanical analysis discloses obvious microphase separation with the PLA end blocks forming hard glassy domains and the PI midblock forming the soft rubbery matrix.","label":"BIODEGRAD_POLY"}
{"id":751,"sentence":"(5)] of the samples before and after 6 days of conditioning. After 6 days conditioning, a significant reduction in molecular weight and viscosity were observed for all the samples.","label":"BIODEGRAD_PROP"}
{"id":752,"sentence":"A new series of lactide polymerization catalysts has been developed that gives rapid living polymerizations with low−molecular−weight distributions [77 – 82]. They report room−temperature lactide polymerizations that achieve full conversion after 15 minutes using a 417 : 1 molar catalyst ratio (lactide : catalyst)","label":"POLY_STRUC"}
{"id":753,"sentence":"A large number of studies have shown that the introduction of soft blocks can effectively improve the toughness of PLA, especially the synthesis of ABA triblock copolymers [3, [15], [16], [17]].","label":"MECHANICAL_PROP"}
{"id":754,"sentence":"For the random copolymer P (3HP−co−4HB), all the carbon resonances were split into diad, triad, or quadrupled, reflecting the sensitivity of the carbon nuclei to different chemical microenvironments of 3HP and 4HB comonomer sequences (Figure 3B).","label":"POLY_STRUC"}
{"id":755,"sentence":"The same monomodal \/ bimodal transitions were found when PLA was subjected to pHs of 1 and 9, but the duration of the experiments was not long enough to reach the narrow monomodal regimes (Figure S1 in the Supporting Information).","label":"BIODEGRAD_POLY"}
{"id":756,"sentence":"The greater loss of PEG at this pH suggests that the degradation at pH 9. 5 occurs more preferentially near the PEG site. Yet in spite of this,","label":"BIODEGRAD_PROP"}
{"id":757,"sentence":"53 In addition, the PBS had a less amount of nucleation sites than PBAT because of the severe molecular weight reduction by hydrolytic degradation. This phenomenon was consistent with observed crystallization temperature by the DSC analysis.","label":"BIODEGRAD_POLY"}
{"id":758,"sentence":"040 week−1 observed in the first 9 weeks meant that the rate of cleavage was faster initially because there were more ester bonds remaining, leading to a greater probability of attack by the water molecules.","label":"BIODEGRAD_PROP"}
{"id":759,"sentence":"Abou−Zeid et al. [39], and Muller et al. [40]. Esterase (hydrolase) enzymes are lipase type and enzymatic degradation rates can be dictated mainly by the mobility of the chain, i. e. the length of aromatic domains not the length of aliphatic counterparts [24], [33], [41], [42], [43], [44].","label":"POLY_STRUC"}
{"id":760,"sentence":"15 These drawbacks could be overcome by blending or alloying polymers while tailoring the material's overall performance and cost. 14 With this regard, we have extensively studied the PBS \/ PBAT blend in our previous research.","label":"BIODEGRAD_POLY"}
{"id":761,"sentence":"It is well known that it is often possible to use the cole−cole plot (imaginary viscosity (η ’ ’) versus real viscosity (η′)) to characterize the two−phase structure of blends.","label":"RHEOLOGICAL_PROP"}
{"id":762,"sentence":"1 g. Table 1.Molecular Characteristics of the PLAs before Hydrolysis PLA grade d‐Lactate (%) Mn (g \/ mol) Mw (g \/ mol)","label":"POLY_STRUC"}
{"id":763,"sentence":"Tokyo, Japan). To prepare thin films for IR measurements, we sandwiched a very small amount of P3HP between two BaF2 windows, and slide the upper one smoothly to reduce the film thickness.","label":"BIODEGRAD_POLY"}
{"id":764,"sentence":"Preparation of PLA \/ PPG Composites The PLA \/ PPG composites were prepared by adding 5 phr PPG with various MWs (200, 400, 600, 800,","label":"BIODEGRAD_POLY"}
{"id":765,"sentence":"and relatively poor biodegradability) of PLA. PLA \/ PCL blends were compatibilized by electron−beam irradiation in the presence of GMA. Morphology study showed that compatibilization diminished PCL (dispersed phase) particle sizes in blends and markedly reduced voids at PLA \/ PCL interface.","label":"BIODEGRAD_POLY"}
{"id":766,"sentence":"Fang and Hanna [120] presented two equations that related density of the PLA melt to the volumetric flow rate and the PLA melt temperature, Tmelt.","label":"BIODEGRAD_POLY"}
{"id":767,"sentence":"The value of k is typically between 10−3 and 10−9 1 \/ s. The diffusion timescale (in seconds) is therefore at least several orders of magnitude shorter than the reaction timescale, suggesting that the process of PLA hydrolysis is reaction limited rather than diffusion limited 18.","label":"BIODEGRAD_PROP"}
{"id":768,"sentence":"and 5 %) of tri−block copolymer LPB or HPB. The tensile tests were carried out by employing an Instron−5699 tester according to ASTM D638.","label":"POLY_STRUC"}
{"id":769,"sentence":"They are considered as one of the main causes of biodeterioration (Warscheid and Braams, 2000). Chemical biodeterioration may also be the result of oxidation processes.","label":"BIODEGRAD_PROP"}
{"id":770,"sentence":"The composition of PEG decreased very gradually as hydrolysis advanced while the opposite was true for PCL. PEG composition fell because the breakage of an ester bond near or at the PEG segment will result in dissolution in the buffer solution since PEG is water soluble.","label":"BIODEGRAD_POLY"}
{"id":771,"sentence":"or the development of microbial biomass (e. g. macroscopic and microscopic observations). A microbial assimilation of molecules from a C3 plant generates a “ C3−labelled ” biomass.","label":"BIODEGRAD_PROP"}
{"id":772,"sentence":"at different temperatures for PCL melts from newtonian behavior (xo) at different temperatures for PLLA melts Intern. Polymer Processing XXII (2007) 5 A.","label":"BIODEGRAD_POLY"}
{"id":773,"sentence":"In this work, in order to further weaken the possible contribution of the intramolecular coupling, all P3HP samples were cooled at a rather fast rate, i. e., 10 °C \/ min,","label":"POLY_STRUC"}
{"id":774,"sentence":"which is available at wileyonlinelibrary. com.] A similar analysis was carried out for the films which were degraded at pH 9. 5. Surface deterioration is evident with significant pores and cracks appearing at Week 1 and the porosity and extent of these cracks increased as the hydrolysis period lengthened.","label":"BIODEGRAD_PROP"}
{"id":775,"sentence":"which possibly reflected the lower amount of low molecular weight polymer. Although this polymer had higher crystallinity values, the biodegradation test revealed a considerable loss of PHB−V, similar to that of PHB.","label":"POLY_STRUC"}
{"id":776,"sentence":"The melting enthalpy before hydrolysis for the annealed cPLA was about 45 J \/ g. Figure 2 Open in figure viewer PowerPoint (•) Mn, (◼) weight loss (Wloss),","label":"POLY_STRUC"}
{"id":777,"sentence":"In contrast, MDDI with the intermolecularly coupled protons varies with the packing of chains. For the γ−form, the internuclear distance between the closest intermolecular couple is about 0.","label":"POLY_STRUC"}
{"id":778,"sentence":"As previous authors noted, Lyu et al. noted that the rapid molecular weight decreased under aggressive conditions, and a certain induction time before sample weight loss occurred.","label":"BIODEGRAD_PROP"}
{"id":779,"sentence":"It is one of the few polymers in which the stereochemical structure can easily be modified by polymerizing a con−trolled mixture of the L−or D−isomers to yield high−molecular−weight amorphous or crystalline polymers that can be used for food contact and are generally recognized as safe (GRAS) [2].","label":"POLY_STRUC"}
{"id":780,"sentence":"This behavior is due to the hydrolysis of the PLA chains being reaction controlled with the diffusion timescale, O (R2 \/ D), being many orders of magnitude faster than the reaction timescale,","label":"BIODEGRAD_PROP"}
{"id":781,"sentence":"As PLA is degraded, changes in the mechanical properties, thermal properties, molecular weight, and mass of the samples have been observed 6, 8−11.","label":"BIODEGRAD_PROP"}
{"id":782,"sentence":"This model was able to accurately describe the total molecular weight distribution and reasonably predicted mass loss trends, but required the solution of multiple coupled differential equations.","label":"POLY_STRUC"}
{"id":783,"sentence":"FTIR Analysis of PCL‐b‐PEG Copolymer Film Fourier transform infra‐red spectroscopy was used to probe the functional group changes in the copolymer as the degradation proceeded.","label":"BIODEGRAD_POLY"}
{"id":784,"sentence":"The Tg values of PBS, PBAT, and PBS \/ PBAT blends are summarized in Table 2. The position of each tan δ peak is affected slightly after conditioning at 50 °C with 90 % RH.","label":"BIODEGRAD_POLY"}
{"id":785,"sentence":"9 However, Tm of PBAT phase in the blends slightly increased with increasing PLA as Tg of PLA phase in the blends were slightly decreased by the increase of PBAT according to the results obtained by Zhao et al. [5],","label":"POLY_STRUC"}
{"id":786,"sentence":"L−lactide to create amorphous or semicrystallline polymers. They found that the glass transition temperature wasn ’ t greatly affected by the stereochemical makeup or the range of molecular weights tested.","label":"POLY_STRUC"}
{"id":787,"sentence":"Comparison of Physical Properties of Poly (D, L−Lactic Acid) Supplied by Cargill Percent of D−isomer Ultimate tensilea (MPa) Percenta Young ’ S modulus (MPa)","label":"MECHANICAL_PROP"}
{"id":788,"sentence":"After 1 day of hydrolysis in the alkaline media, cavities already appeared on the surface, as shown in Figure 4 (b). These cavities could have been associated with the 7 % weight loss already attained at this point.","label":"BIODEGRAD_PROP"}
{"id":789,"sentence":"Two types of PLA resins (amorphous and semicrystalline) at 150 °C and 170 °C, and at various shear rates (30, 50, 70, 90, 110, 130,","label":"BIODEGRAD_POLY"}
{"id":790,"sentence":"23 The Vogel – Tammann – Fulcher equation describes the effect of the temperature on the rate of hydrolysis above Tg11 : (4) where k0 and E are the characteristic Vogel – Fulcher – Tammann parameters,","label":"BIODEGRAD_PROP"}
{"id":791,"sentence":"Under Tg (glassy state), the formation of spherulites may take place, generating inter−spherulitic cracks and the brittleness of the thermoplastics polymers (El−Hadi et al., 2002).","label":"POLY_STRUC"}
{"id":792,"sentence":"Both diameters exhibited similar total weight loss, crystallinity, and molecular weight loss profiles under each set of degradation conditions. Two models for the change in molecular weight were compared :","label":"BIODEGRAD_PROP"}
{"id":793,"sentence":"and (70 \/ 30) were 2. 9 and 3. 1 times higher, respectively, than that of pure PLA. Figure 8 Impact strengths of pure PLA, compatibilized PLA \/ PCL blends,","label":"BIODEGRAD_POLY"}
{"id":794,"sentence":"and PP to increase significantly ; but did not affect the elongation. Results from FTIR and DSC measurements suggested that PLA and PBAT were immiscible.","label":"BIODEGRAD_POLY"}
{"id":795,"sentence":"The relative higher Tg values as obtained from DMA measurements than from DSC measurements illustrate the different measurement mechanisms for the same sample system, which is consistent with other reports [30].","label":"POLY_STRUC"}
{"id":796,"sentence":"In addition, the sample with 5 % compatibilizer exhibited the smallest Δ Tg (Tg gap between PLA and PBAT). The Δ Tg of the HPB−5 % sample is 82. 7 °C, a decrease of 11.79 °C compared to the pristine blends.","label":"POLY_STRUC"}
{"id":797,"sentence":"However, as is the case for most polymer blends, PLA and PCL are immiscible and incompatible, and considerable efforts have been made to enhance compatibility between these two polymers to achieve acceptable PLA \/ PCL blends.","label":"BIODEGRAD_POLY"}
{"id":798,"sentence":"Thus, by adjusting the schedule of cofeeding of precursors, the block polymer P3HP−b−P4HB was synthesized from the recombinant E. coli. The detailed NMR analysis and physical and mechanical characterization of the two block copolymers were described below.","label":"BIODEGRAD_POLY"}
{"id":799,"sentence":"Treatment formulations and code name of polymer blend \/ composite samples. Treatments PLA : PBAT ratio (by volume) Code name 1 100 : 0 PLA 2 40 : 60 PLA40 3 30 : 70 PLA30 4 20 : 80 PLA20 5 10 : 90 PLA10 6 0 : 100 PBAT 7 40 (fiber) : 60 PLAF 2. 3 Tensile property measurements The measurements for tensile properties at room temperature were performed according to ISO 527 : 1996 using a computerized tensile testing machine model QC−536M1 (COMETECH).","label":"BIODEGRAD_POLY"}
{"id":800,"sentence":"At day 7 of degradation, the PLA118 sample began to show a further increase in crystallinity, which continued through 30 days of aging at which point the crystallinity was 64 %.","label":"BIODEGRAD_PROP"}
{"id":801,"sentence":"Injection molding PLA resulted in a molecular weight decrease of 14 – 40 % [110]. Independent studies by DOW Chemical found that injection molding the general purpose Cargill PDLLA didn ’ t result in a molecular weight decrease, as determined by size exclusion chromatography \/ multi−angle light scattering (SEC−MALLS) (Table XIII).","label":"POLY_STRUC"}
{"id":802,"sentence":"which lacks the regular packing but hold the long−range order along chains, rather than directly to the random coil. Actually, the IR results are not the only evidence available to support the efficient packing of the δ−and γ−forms.","label":"POLY_STRUC"}
{"id":803,"sentence":"and heat of fusion \/ unit volume, DHf were determined for poly (L−lactic acid). The following equation was used in conjunction with Table IV :","label":"BIODEGRAD_POLY"}
{"id":804,"sentence":"The finding suggests that for the same concentration of PLA in PLA−PBAT mixture, said 40 %, preparing PLA in the form of fiber yields the higher elastic modulus than melting and blending with PBAT. treatment PLA40.","label":"BIODEGRAD_POLY"}
{"id":805,"sentence":"Within the crystalline regions, there exist a polymorphism of crystals that can influence the biodegradation (Zhao and Gan, 2006). For instance, PBA contain two forms of crystals, α and β, a temperature above 32 °C favours the α−form, a temperature below 27 °C favours the β−form and between 27 °C and 32 °C, α and β crystals are mixed (Zhao et al., 2007). α crystals show a faster hydrolysis by the action of lipase from Pseudomonas sp.","label":"POLY_STRUC"}
{"id":806,"sentence":"At this stage, no weight loss had occurred. A low melting enthalpy value of 3. 8 J \/ g was achieved, with two melting peaks appearing at 122 and 133 °C.","label":"BIODEGRAD_PROP"}
{"id":807,"sentence":"Screw speed and take up speed were 18. 6 rpm and 0.033 m \/ s. First, film samples were analyzed for carbon content and composts for carbon to nitrogen ratio using a PerkinElmer CHN analyzer (Waltham,","label":"RHEOLOGICAL_PROP"}
{"id":808,"sentence":"the kinetics can be described by (3) where T is the temperature. The kinetic models represented by eqs. (2) and (3) have been used to describe the hydrolysis of bioresorbable polyesters through the plotting of either 1 \/ Mn or ln (Mn) as a function of time.","label":"BIODEGRAD_PROP"}
{"id":809,"sentence":"Obviously, whichever conformation the P3HP chain adopts, α CH2 is always trans to its γ−neighboring groups, i. e., carbonyl and β CH2, across, respectively,","label":"BIODEGRAD_POLY"}
{"id":810,"sentence":"and a sealing PTFE \/ silicon septum [17]. For each cell, fourteen circular PBAT disks of 38. 1 ± 5. 1 μm thickness with a diameter of 0.","label":"BIODEGRAD_POLY"}
{"id":811,"sentence":"and even higher than that of PP (around 288−640 MPa). The modulus of neat PBAT, PLA10, PLA20 and PLA30 were not significant different.","label":"BIODEGRAD_POLY"}
{"id":812,"sentence":"which was not observed from previously reported random copolymers. The molecular weights of block copolymers were comparably higher to homopolymers, blend polymers, and random copolymers.","label":"POLY_STRUC"}
{"id":813,"sentence":"Crystallization Half Time (Minutes) Data for Polylactide [103] 0 % meso 3 % meso 6 % meso Temperature (°C) Mn 5 Table VIII.","label":"BIODEGRAD_POLY"}
{"id":814,"sentence":"the voids were more easily observed and were larger than in the case of the PLLA \/ cornstarch composites [123]. Table XXIV. Thermal Properties of Poly (Star−Lactic Acid) \/ Cornstarch Composites,","label":"BIODEGRAD_POLY"}
{"id":815,"sentence":"Average number of PBT, PBA, and PLA units (NPBT, NPBA and NPLA) in the macro−initiator and tri−block copolymers estimated by 1H NMR.","label":"BIODEGRAD_POLY"}
{"id":816,"sentence":"The second model that was investigated was the simplified autocatalytic model proposed by Antheunis et al. as shown in Eq. 4 24. Both equations were fit to the Mn data obtained for the PLA32 and PLA118 samples degraded at 40, 60, and 80 °C.","label":"BIODEGRAD_POLY"}
{"id":817,"sentence":"A related study from Signori et al. reported that biodegradable thermoplastics were particularly susceptible to the thermal and thermal oxidative degradation during processing, as evidenced by a reduced MW and deteriorated properties after processing [20, 21, 22, 23, 24, 25].","label":"POLY_STRUC"}
{"id":818,"sentence":"The mechanical properties of these composites were in close agreement to similar composites compounded at USDA−ARS−NCAUR. Table XXVI is a summary of the mechanical properties of the composites [134].","label":"MECHANICAL_PROP"}
{"id":819,"sentence":"Kinetic Parameters of the Autocatalytic Model for PLA Hydrolysis in Aqueous Media PLA grade Temperature (°C) k1 × 102 (days−1) k2 × 102 (days−1)","label":"BIODEGRAD_PROP"}
{"id":820,"sentence":"Consequently, more water could enter these pores, and in turn, this promoted autocatalysis and weight loss. Interestingly, the water‐uptake behavior was always closely linked to the weight loss.","label":"BIODEGRAD_PROP"}
{"id":821,"sentence":"Sigma Aldrich, St. Louis, Mo., USA) as positive control ; or compost with 6 g of PBAT film cut into 1 cm × 1 cm pieces.","label":"BIODEGRAD_POLY"}
{"id":822,"sentence":"(8) Also, blending of various polymers can help improve various properties of a material. (9) PHA are produced as intracellular inclusion bodies that can be degraded by PHA depolymerases (PhaZ) to generate various monomers.","label":"BIODEGRAD_POLY"}
{"id":823,"sentence":"More specifically, the tensile and flexural modulus of PP and PBS was improved by ca. 200 MPa after 30 days conditioning period. This could be related to the increased crystallinity and subsequently increase in modulus. 45, 46 A number of researchers have observed a similar tendency in the modulus after exposure to different weathering conditions. 12, 37, 42 These studies were concluded that the modulus improvement of the conditioned samples is associated with structural relaxation, increase in crystallinity, crystal perfection,","label":"BIODEGRAD_PROP"}
{"id":824,"sentence":"Fig. 1b shows the derivative TGA curves of these samples, revealing existence of three mass loss peaks during thermal degradation in the range from 300 to 500 °C for the triblock copolymers.","label":"POLY_STRUC"}
{"id":825,"sentence":"The addition of lactic impurities (i. e., water, lactic acid) does not significantly affect the polymerization rate, only the final molecular weight [58, 62].","label":"POLY_STRUC"}
{"id":826,"sentence":"and hydrophilicity \/ hydrophobicity [13], and hence have more capability to biodegrade certain polymers. For example, the fungi Aspergillus niger and Aspergillus flavus, present in soil and crops, residue respectively, produce enzymes that more easily digest aliphatic polyesters derived from 6 – 12 carbon di−acid monomers than those produced from other monomers [14].","label":"BIODEGRAD_PROP"}
{"id":827,"sentence":"All of the polymers studied showed a smaller mass retention in soil compost at 46 °C compared to room temperature, indicating greater degradation at 46 °C (Fig. 2,","label":"BIODEGRAD_PROP"}
{"id":828,"sentence":"The extraction of low‐molecular‐weight species leads to a weight loss in the polymer sample, a phenomenon known as erosion. Depending on the ratio between the diffusion rate and the hydrolysis rate, three erosion mechanisms may arise : surface erosion, bulk erosion,","label":"BIODEGRAD_PROP"}
{"id":829,"sentence":"From these results, it can be concluded that blending PCL with PLA and electron−beam compatibilization in the presence of GMA reduced the brittleness of PLA and enhanced the storage modulus, melt viscosity,","label":"BIODEGRAD_POLY"}
{"id":830,"sentence":"The fracture surface for the alkaline media sample was smooth because most of the weight loss occurred from the surface rather than from the bulk of the sample.","label":"BIODEGRAD_PROP"}
{"id":831,"sentence":"They found that the crystalline structure almost disappears, 1H and 13C NMR confirmed that the chemical composition of PLA did not change, but the amount of methyl groups increased,","label":"POLY_STRUC"}
{"id":832,"sentence":"They had shown that when L−lactide is polymerized below the polymer crystalline melting temperature, crystalline domains form that exclude both monomer and catalyst. This constant enrichment of the amorphous phase leads to increased concentrations of catalyst,","label":"POLY_STRUC"}
{"id":833,"sentence":"454 Å 3, which is of considerable size compared with other esterases \/ lipases with the known structure that are capable to hydrolyze different aliphatic and semi−aromatic polyesters (Table S1).","label":"BIODEGRAD_PROP"}
{"id":834,"sentence":"which was calculated from 50 mg \/ g and 150 mg \/ g volatile solid of composts. While the previous biodegradation results indicated that samples in the manure compost environment degraded faster than in the other two composts, it did not determine whether there were differences in the biodegradation and \/ or hydrolysis rates in these different compost environments.","label":"BIODEGRAD_PROP"}
{"id":835,"sentence":"The initial degradation of the PLA \/ PPG composites during melt processing was estimated in real time. At the same time, the thermal properties and the micro−morphology of the PLA \/ PPG composites plasticized by different MWs of PPG were systematically investigated. 2.","label":"BIODEGRAD_POLY"}
{"id":836,"sentence":"The main route of hydrolytic degradation occurs through cleavage of ester linkages and leads to lower molecular weight compounds. Solely aromatic polyesters are resistant to biological degradation.","label":"BIODEGRAD_PROP"}
{"id":837,"sentence":"This phenomenon was attributed to the induced crystallization from low molecular weight polymer chains that occurred during hydrolysis. Therefore, low molecular weight polymer chains are often favored to the crystallinity enhancement.","label":"POLY_STRUC"}
{"id":838,"sentence":"From another viewpoint, crystallization of hard segments of triblock copolymers can significantly affect their crystallization kinetics [22], phase domain morphology [23, 24],","label":"POLY_STRUC"}
{"id":839,"sentence":"The addition of 5 % HPB improved the elongation of samples by seven times compared to pristine blends. Moreover, the interaction and miscibility at the interface between PLA and PBAT were improved by the addition of compatibilizers.","label":"BIODEGRAD_POLY"}
{"id":840,"sentence":"It is known that shorter chains have higher mobility and can reorganize easily leading to an increase of crystallinity degree. Chain scission occurrence is confirmed by the higher degree of crystallinity and lower intrinsic viscosity of the processed samples.","label":"POLY_STRUC"}
{"id":841,"sentence":"the compositional changes in either the PEG or PCL segment were not accentuated which may again be explained by the hydrophobic nature of the copolymer composition used in this project.","label":"POLY_STRUC"}
{"id":842,"sentence":"It can be observed that the tensile strength of PBS, PBAT, and PBS \/ PBAT blend decreased significantly with increasing hydrolysis time. For example, after 12 days exposure time,","label":"BIODEGRAD_POLY"}
{"id":843,"sentence":"In these experiments, the surface reaction was initiated as soon as the sample was placed in the media ; this led to immediate weight loss. It should be noted that some internal cavitation, related to bulk erosion, seemed to occur as well ; this was evidenced by the water‐uptake increase after an induction of 1 and 3 days for aPLA and cPLA, respectively.","label":"BIODEGRAD_PROP"}
{"id":844,"sentence":"90 Differential Scanning Calorimetry After exposing the polymers to raised humidity and temperature, it is expected that the spherulitic growth rates, lamellar thickness, and crystal interphase are modified due to the free energy changes in the crystals formation.","label":"POLY_STRUC"}
{"id":845,"sentence":"5 to 12 % for the fibers degraded at 40 °C (represented by open squares) and 16 % for fibers degraded at 60 °C (represented by open circles).","label":"BIODEGRAD_PROP"}
{"id":846,"sentence":"He also found that the polymer lost its ability to crystallize when the minor isomer content exceeded 15 % [103], which is in good agreement with Fischer [94].","label":"POLY_STRUC"}
{"id":847,"sentence":"As shown in Table 1, the higher the shear rate, the lower the n value of the PLA and PLA \/ PPG composites and the more pronounced non−Newtonian fluid behavior. PLA has the lowest n value at the same shear rate,","label":"RHEOLOGICAL_PROP"}
{"id":848,"sentence":"Most initial uses for PLA were focused on high‐value‐added biomedical applications such as sutures, stents, and drug delivery systems because of PLA's high initial cost 1−3.","label":"BIODEGRAD_PROP"}
{"id":849,"sentence":"All data were expressed as average value ± SD representing three parallel experiments : M, mixture of P3HP, P4HB and block P3HP−b−P4HB ;","label":"BIODEGRAD_POLY"}
{"id":850,"sentence":"Note that PLA−PI106k−PLA is a sample with very low crystallinity (Fig. 3, Fig. 4), while all the others crystallize when prepared from solvent casting, demonstrating that the crystals formed in these samples can function as stronger fillers to enhance the tensile strength during deformation [35].","label":"POLY_STRUC"}
{"id":851,"sentence":"Third, the about linear decrease in the strain−hardening modulus with increasing PI midblock molecular mass is more or less close to that for the ultimate tensile strength (Fig. 7c).","label":"MECHANICAL_PROP"}
{"id":852,"sentence":"PBAT is a statistical random copolymer consisting of soft butylene adipate (BA) sections and hard butylene terephthalate (BT) sections (Fig. 1).","label":"BIODEGRAD_POLY"}
{"id":853,"sentence":"the total decay curve for all three samples could not to be fitted well by single or two exponential components. In particular, the T1C value of the δ−form is noted to be near three times of that of the β−form.","label":"BIODEGRAD_PROP"}
{"id":854,"sentence":"The curves of the logarithm of the complex viscosity (η ∗) versus the logarithm of sweep frequencies for PLA and PBAT blends with different amounts of compatibilizers are shown in Fig. 7 (A).","label":"RHEOLOGICAL_PROP"}
{"id":855,"sentence":"Thus, new molecules with low molecular weight are produced. Fig. 2. PLA hydrolysis in alkaline conditions. The hydrolysis of the ester group allows the release of a lactic acid molecule leading to the decrease of the degree of polymerisation of the PLA.","label":"BIODEGRAD_PROP"}
{"id":856,"sentence":"(16, 17) As a PHA monomer, (18−20) 4−hydroxybutyrate (4HB) provides its homopolymer poly (4−hydroxybutyrate) (P4HB) with the highest elasticity (elongation to break) among all known PHA.","label":"BIODEGRAD_POLY"}
{"id":857,"sentence":"The condensation polymerization is the least−expensive route, but it is difficult in a solvent−free system to obtain high molecular weights, and therefore the use of coupling agents or esterification−promoting adjuvants is required, adding cost and complexity [14 – 28].","label":"POLY_STRUC"}
{"id":858,"sentence":"PLA hydrolysis is highly temperature dependent. 12, 17, 19 Hydrolysis is very slow at room temperature under dry conditions. Therefore, most studies have investigated hydrolysis under humid or aqueous conditions and at temperatures near or above the glass‐transition temperature (Tg), where macromolecular chains acquire greater mobility.","label":"BIODEGRAD_PROP"}
{"id":859,"sentence":"In addition, very few studies have examined polymer biodegradation. Several synthetic polymers with biodegradable properties, such as the aliphatic polyesters poly−β−(hydroxybutyrate) (PHB), poly−β−(hydroxybutyrate−co−β−valerate) (PHB−V), poly (lactic acid) (PLA),","label":"BIODEGRAD_POLY"}
{"id":860,"sentence":"The final thickness of the PBAT film was 38. 1 ± 5. 1 μm (1.5 ± 0.2 mil). An in−house built direct measurement respirometric system (DMR) connected to a CO2 infrared gas analyzer was used to determine the biodegradation of the PBAT films in compost.","label":"BIODEGRAD_POLY"}
{"id":861,"sentence":"Therefore, relating the biodegradation rate to general compost composition and \/ or other factors may overlook the specific families of microorganisms present in the compost that may be more or less successful than others at biodegrading the aliphatic aromatic polyester.","label":"BIODEGRAD_PROP"}
{"id":862,"sentence":"Like the products of Norrish reactions, peroxyl radicals resulting of the oxidative degradation can lead to crosslinking reactions and \/ or chain scissions. Hydrolysis is another way by which polymers can undergo chemical degradation (Muller et al., 1998,","label":"BIODEGRAD_PROP"}
{"id":863,"sentence":"In addition, each biodegradation stage must be associated with the adapted estimation technique. For instance, abiotic degradation and biodeterioration are mainly associated to physical tests (e. g. thermal transitions and tensile changes).","label":"BIODEGRAD_PROP"}
{"id":864,"sentence":"S. southwest in the summertime). METHODS Materials and Sample Preparation PLA pellets, supplied by NatureWorks (NatureWorks 6202D), were used to produce PLA fibers of two diameters : 32 μm (PLA32) and 118 μm (PLA118). ","label":"BIODEGRAD_POLY"}
{"id":865,"sentence":"Rasmussen et al., 2004). The biodegradation is a natural complex phenomenon. Nevertheless, biodegradability tests are necessary to estimate the environmental impact of industrial materials and to find solutions to avoid the disturbing accumulation of polymers.","label":"BIODEGRAD_PROP"}
{"id":866,"sentence":"and DSC thermograms of the various PLA samples investigated. Some of the tables shown are Tg and Tm of PLA (Table XV), effect of temperature on the molecular weight of PLA (Table XVI),","label":"BIODEGRAD_POLY"}
{"id":867,"sentence":"From the data of experiments carried out at pH 7. 4, the short‐term degradation process could be elucidated while accelerated degradation at pH 9.","label":"BIODEGRAD_PROP"}
{"id":868,"sentence":"On the contrary, the introduction of PI midblock modestly improves the chain segmental mobility of PLA end blocks, and the improvement becomes more effective when PI midblock length increases.","label":"POLY_STRUC"}
{"id":869,"sentence":"However, the two preexistent CH2 vibration doublets, i. e., 1434 and 1427 cm−1 and 806 and 801 cm−1, which were tentatively assigned to the intermolecular interaction induced splitting, (5b) were found to be enhanced by cooling.","label":"POLY_STRUC"}
{"id":870,"sentence":"Walsh, 2001). Microorganisms involved in biodeterioration are very diverse and belong to bacteria, protozoa, algae, fungi and lichenaceae groups (Wallstr ö m et al., 2005).","label":"BIODEGRAD_PROP"}
{"id":871,"sentence":"and 80 °C. The evolution of the molecular weight, weight loss, and water uptake are presented in Figure 2 for aPLA and cPLA, respectively.","label":"BIODEGRAD_PROP"}
{"id":872,"sentence":"The block copolymers had two glass transition temperatures (Tg) and two melting temperatures (Tm). In comparison to the homopolymers P3HP and P4HB, incorporation of block microstructure resulted in the lowering of Tm, block copolymers were revealed with higher Young ’ s modulus, yield strengths,","label":"POLY_STRUC"}
{"id":873,"sentence":"In the case of the star−PLA \/ cornstarch composite, both the crystallization and the melting temperatures were the lowest at a starch content of 5 wt % and shifted to higher temperatures as the starch content exceeded 5 %.","label":"POLY_STRUC"}
{"id":874,"sentence":"This step is called biodeterioration (Eggins and Oxley, 2001, Walsh, 2001).−Microorganisms secrete catalytic agents (i. e. enzymes and free radicals) able to cleave polymeric molecules reducing progressively their molecular weight.","label":"BIODEGRAD_PROP"}
{"id":875,"sentence":"Figure 7 Open in figure viewer PowerPoint (a) Enthalpy of fusion (Δ Hf) and (b) Tm as a function of Mn of the neutral media at 60, 70,","label":"POLY_STRUC"}
{"id":876,"sentence":"and thus, the amount of interfacial hydrogen bonding force had been increased. Figure 4 Storage modulus curves (measured at 190 °C) of pure PLA (▲), pure PCL (△), compatibilized PLA \/ PCL (90 \/ 10) (○), uncompatibilized PLA \/ PCL (90 \/ 10) (○), compatibilized PLA \/ PCL (70 \/ 30) (■),","label":"BIODEGRAD_POLY"}
{"id":877,"sentence":"and was, therefore, fully amorphous under normal conditions. Hereafter, the crystalline and amorphous grades are called cPLA and aPLA, respectively. The main molecular characteristics of these grades are summarized in Table 1.","label":"POLY_STRUC"}
{"id":878,"sentence":"which is available at wileyonlinelibrary. com.] Morphological Analysis To investigate the hydrolysis caused by moisture and temperature, SEM analysis was carried out before and after 30 days conditioned samples.","label":"BIODEGRAD_PROP"}
{"id":879,"sentence":"and uncompatibilized PLA \/ PCL (70 \/ 30) (□) blends. In contrast to uncompatibilized blends, the storage moduli of all compatibilized blends were higher than those of pure PLA and PCL over the entire frequency range tested, indicating that compatibility of the PLA \/ PCL blend has been increased by electron−beam irradiation.","label":"BIODEGRAD_POLY"}
{"id":880,"sentence":"Selecting the processing time of 15 to 20 minutes ensures that PLA and PPG were fully melted and uniformly mixed by that time, so the reduction of torque over time at adjusted temperature for the PLA and PLA \/ PPG composites was caused by degradation during processing.","label":"BIODEGRAD_POLY"}
{"id":881,"sentence":"By the comparison, the spectral features of each crystalline phase could be easily distinguished from those of the amorphous phase. With combining our previous in situ IR results on the crystallization and melting of the polymorphic samples, (5a−5c)","label":"POLY_STRUC"}
{"id":882,"sentence":"Moreover, the storage moduli of compatibilized PLA \/ PCL (90 \/ 10) and (70 \/ 30) blends were about 900 and 640 times higher, respectively, than those of pure PLA at an angular frequency of 0.","label":"BIODEGRAD_POLY"}
{"id":883,"sentence":"D -, or L−lactide [1]. Marega et al. [98] showed that the a−form of poly (Llactic acid) has a pseudo−orthorhombic unit cell containing 2 103 (10 A °rise \/ 3 monomeric units) polymeric helices.","label":"BIODEGRAD_POLY"}
{"id":884,"sentence":"and 80 °C and nitrogen purge (A) and 100 % RH (B) for PLA32 (▪, •, ▴) and PLA118 (□, ○,","label":"BIODEGRAD_POLY"}
{"id":885,"sentence":"Δ). As shown in Fig. 1A, overall, the fibers exposed to nitrogen purge exhibited little statistically relevant changes in weight during the 90‐day period.","label":"BIODEGRAD_PROP"}
{"id":886,"sentence":"Hydrolysis in Acid and Alkaline Media : pH Effect Figure 3 summarizes the molecular weight decrease (Mn), weight loss, and water uptake during the hydrolysis of aPLA and cPLA at 70 °C in more aggressive acid and alkaline media at pH 1 and 12 (see Figure S2 in the Supporting Information for the data at pH 9).","label":"BIODEGRAD_PROP"}
{"id":887,"sentence":"the solvent−cast and melt−quenched ones. It can be clearly seen that the tensile strength values of each PLA−b−PI−b−PLA triblock copolymer are much higher for the solvent−cast samples than for the melt−quenched samples except for PLA−PI106k−PLA.","label":"BIODEGRAD_POLY"}
{"id":888,"sentence":"Table 2. Samples identification. 1H NMR spectra of initial and degraded PLA samples were recorded on a Bruker Avance III 400 MHz spectrometer using deuterated chloroform as solvent and tetramethylsilane as internal standard.","label":"BIODEGRAD_POLY"}
{"id":889,"sentence":"the PBS and PBAT primarily can undergo hydrolytic degradation through cleavage of ester linkages on the polymer backbone. In addition, the hydrolysis reaction may occur in the form of depolymerization process and random chain scission mechanism.","label":"BIODEGRAD_PROP"}
{"id":890,"sentence":"It has been shown that the molecular weight is directly controlled by the amount of hydroxyl impurities and is independent of carboxylic acid impurities and catalyst concentration [54 – 62].","label":"POLY_STRUC"}
{"id":891,"sentence":"Normally, the crystal with one single chain in one unit cell can not give the correlation filed splitting. (11f, 12b) Therefore, the δ−form should contain at least and most probably two chains in one unit cell.","label":"POLY_STRUC"}
{"id":892,"sentence":"04 MPa in comparison to random copolymer P (3HP−co−25 % P4HB) with only 1.70 MPa. Block copolymer P3HP−b−37 % P4HB had a yield strength of 7.","label":"POLY_STRUC"}
{"id":893,"sentence":"Both polymers presented similar thermal degradation mechanisms involving the scission of the carbon−oxygen bond, yet in PCL also a post−polymerization contribution was observed.","label":"BIODEGRAD_PROP"}
{"id":894,"sentence":"Abstract We have reported a mild synthesis of triblock copolymers, polylactide−block−polyisoprene−block−polylactide (termed as PLA−b−PI−b−PLA),","label":"BIODEGRAD_POLY"}
{"id":895,"sentence":"Therefore, PBAT maintains its elongation up to 12 days conditioning even after extensive chain scission occurred. Interestingly, the PBS \/ PBAT blend has higher elongation than PBS and PP up to 12 days due to the PBAT chain entanglements.","label":"BIODEGRAD_POLY"}
{"id":896,"sentence":"The authors thank PHB do Brasil and Union Carbide for supplying the raw materials and the Laborat ó rio de Caracteriza ç ã o de Materiais (LCAM),","label":"BIODEGRAD_POLY"}
{"id":897,"sentence":"Tensile mechanical properties were studied on AI7000S universal testing machine (Gotech Testing Machines Corporation, China) at room temperature at a speed of 50 mm \/ min. PHA films prepared by solvent evaporation were cut into dumbbell shaped with a width of 10 mm and a thickness of about 100 μm.","label":"MECHANICAL_PROP"}
{"id":898,"sentence":"They mentioned the Hoffman – Weeks equation that relates Tm to Tc). The equation is as follows : Tm 0 Tm °(1−1 \/ 2b) + Td \/ 2b where b is a constant depending on the edge free−surface energy.","label":"POLY_STRUC"}
{"id":899,"sentence":"The non−Newtonian index n, viscosity η, and Mw have the following approximate relationship : (10) where the constants k1 and k2 depend on mixer geometry, material properties, processing conditions,","label":"RHEOLOGICAL_PROP"}
{"id":900,"sentence":"Degradation at pH 7. 4 mimics physiological conditions while accelerated degradation at a higher pH (more hydroxyl ions resulting in faster hydrolysis) would enable the prediction of the long‐term behavior.","label":"BIODEGRAD_PROP"}
{"id":901,"sentence":"SEM micrographs of the PBS, PBAT, and their blend are depicted in Figure 17. Before exposure to hydrolysis environment, a smooth surface morphology was observed for all the samples.","label":"BIODEGRAD_POLY"}
{"id":902,"sentence":"Thus, the structural changes caused by thermo−mechanical and thermo−oxidative treatments were established by comparing the FTIR peaks height ratios of PLA, Fig. 1.","label":"BIODEGRAD_POLY"}
{"id":903,"sentence":"and the tight molecular packings of the γ−and δ−forms were then well established independently of the IR results. In Figure 10 are shown the CP \/ MAS 13C NMR spectra of the β -, γ -, and δ−form samples.","label":"POLY_STRUC"}
{"id":904,"sentence":"Unfortunately, the melting point depression is accompanied by a significant decrease in crystallinity and crystallization rates [4]. High−molecular−weight poly (lactic acid) is a colorless, glossy, stiff thermoplastic polymer with properties similar to polystyrene.","label":"POLY_STRUC"}
{"id":905,"sentence":"As shown in Figure 4, the storage moduli of uncompatibilized PLA \/ PCL (90 \/ 10) and (70 \/ 30) blends lay between those of pure PLA and PCL over the frequency ranges of 20−500 rad \/ s and 7−500 rad \/ s, respectively, but were higher than pure PLA and PCL below 20 rad \/ s (PLA \/ PCL (90 \/ 10) blend)","label":"BIODEGRAD_POLY"}
{"id":906,"sentence":"In this case, the torque decreases along with the degradation of polymer during processing. Therefore, characterization of the torque of a polymer by rheological methods can be used to study the changes in MW because of the degradation.","label":"BIODEGRAD_PROP"}
{"id":907,"sentence":"This enables the modulation of hydrophilicity and changes the degradation behavior of the copolymer matrix. Recently, there have been many papers which utilize PEG and PCL block copolymers for different biomedical directed applications, such as micelles, nanoparticles,","label":"BIODEGRAD_PROP"}
{"id":908,"sentence":"Reasonably, the longest T1C is ascribed to the restricted local motion in the well ordered crystalline phase, and the shortest one should be associated with the fast motion in the amorphous phase.","label":"POLY_STRUC"}
{"id":909,"sentence":"There was a two phase decrease in the molecular weight of the copolymers. For pH 7. 4, the decrease in molecular weight was greater for the first 9 weeks as compared with the later weeks of degradation.","label":"POLY_STRUC"}
{"id":910,"sentence":"which is available at wileyonlinelibrary. com.] Rheological Properties Figure 15 represents the shear viscosity of the samples before and after 6 days of conditioning at the elevated temperature and humidity.","label":"RHEOLOGICAL_PROP"}
{"id":911,"sentence":"Because the aPLA contained a higher fraction of d‐lactate units, which acted as crystal defects, the crystalline lamellae were smaller and less stable. In the case of cPLA,","label":"BIODEGRAD_POLY"}
{"id":912,"sentence":"During the first 7 days of degradation at 100 % RH, there was no significant change in the melting temperature of either the PLA32 or the PLA118 samples degraded at 60 °C.","label":"BIODEGRAD_PROP"}
{"id":913,"sentence":"However, in the PBAT samples hydrolyzed in phosphate buffer, an increase in the OH group was only observed during the first week, since compounds with OH terminal groups may dissolve in the phosphate buffer due to the greater polarity of this solution compared to the PBAT matrix.","label":"BIODEGRAD_POLY"}
{"id":914,"sentence":"(28) In our present work, variation in cofeeding mode of precursors during the cultivation of E. coli, for the first time, resulted in accumulation of block copolymers P3HP−b−P4HB (Table 1).","label":"POLY_STRUC"}
{"id":915,"sentence":"Random chain scission of the ester bond linkages in PCL resulted in a decrease in molecular weight. The SEM micrographs showed that water penetrated through the film edges inwards, similar to the literatures. 10, 15 The polymer erosion stage involved the leaching of the PEG segments and other water soluble oligomeric degradation products into the degradation medium, hence causing a loss in mass.","label":"BIODEGRAD_PROP"}
{"id":916,"sentence":"Perego et al. reported specific optical rotation [a] values of−157 to−160 °for PLLA [110]. The solubility parameter of PLA is reported in the literature [127, 128].","label":"BIODEGRAD_POLY"}
{"id":917,"sentence":"(28) The blend polymer, which is a physical mixture of two homopolymers of 75 mol % P3HP and 25 mol % P4HB, showed two glass transition temperatures (Tg)","label":"POLY_STRUC"}
{"id":918,"sentence":"and Tm. Except in a very alkaline medium (pH 12), the hydrolysis process of PLA proceeded in two stages through a bulk erosion mechanism.","label":"BIODEGRAD_PROP"}
{"id":919,"sentence":"Interestingly, after 30 days of conditioning, the storage modulus of PBS, PBAT, and their blend samples was found to increase slightly. This is because the samples become stiffer, as evidenced by the increase in crystallinity after conditioning at elevated temperature and humidity.","label":"RHEOLOGICAL_PROP"}
{"id":920,"sentence":"From some previous studies, (45−47) random copolymers should have a D value near 1 ; the D value for a block copolymer should be much larger than 1, while that of an alternating copolymer should be smaller than 1.","label":"POLY_STRUC"}
{"id":921,"sentence":"This comonomer sequence was similar to random copolymer P (3HB−co−3HHx) (35) or PHBV. (44) Compared with the 13C NMR spectrum of random copolymer P (3HP−co−4HB),","label":"BIODEGRAD_POLY"}
{"id":922,"sentence":"and the melting enthalpy, were characterized through nonisothermal analyses with a TA Instruments Q2000 differential scanning calorimeter. Samples cut from the dried hydrolyzed and original PLA molded discs were heated from 10 to 200 °C at a rate of 20 °C \/ min under a nitrogen gas flow.","label":"BIODEGRAD_POLY"}
{"id":923,"sentence":"Compared with 13C NMR splitting fingerprints of the block copolymer P3HP−b−P4HB and random copolymer P (3HP−co−4HB) (Figure 4),","label":"POLY_STRUC"}
{"id":924,"sentence":"This is possibly due to the accelerated degradation of PBS with the increased time at elevated temperature and humidity. 15 Our finding had good agreement with the recent study by Kim and Kim.","label":"BIODEGRAD_PROP"}
{"id":925,"sentence":"Thermoplastics from polyolefins are not biodegradable, even if some of them have prooxidant additives making them photo and \/ or thermodegradable, the assimilation of oligomers or monomers by microorganims is not yet totally proved.","label":"BIODEGRAD_PROP"}
{"id":926,"sentence":"and 5. 58 × 105 in number−average molecular weights) with a low polydispersity (Sigma−Aldrich, Germany) were used to prepare a calibration curve.","label":"POLY_STRUC"}
{"id":927,"sentence":"The cold crystallization temperature (Tc) and enthalpy (Δ Hc) of the blends without compatibilizers were 104. 59 °C and 17. 28 J \/ g, respectively.","label":"POLY_STRUC"}
{"id":928,"sentence":"It can be considered that the time between exhaustion of first substrate and addition of second substrate in the medium must be minimum for block copolymerization. Because block copolymer synthesis is a complex process and does not happen on every polymer chain, neither does it occur in the late growth phase due to reduced PHA synthase activities.","label":"POLY_STRUC"}
{"id":929,"sentence":"Also, as for distilled water experiments, the amorphous aPLA showed a faster weight loss than the semicrystalline cPLA. Finally, the good match between the absorbed water and weight loss was maintained.","label":"POLY_STRUC"}
{"id":930,"sentence":"In contrast, when the weight loss began, the molecular weight was already reduced by almost 85 %. This led to a reduction in the ester link concentration and a decrease in the autocatalytic effect,","label":"BIODEGRAD_PROP"}
{"id":931,"sentence":"Two samples of putative P3HP−b−29 mol % P4HB and P3HP−b−37 mol % P4HB from the NMR analysis were proved to be diblock copolymers of P3HP and P4HB.","label":"BIODEGRAD_POLY"}
{"id":932,"sentence":"These decreases corresponded to a loss in molecular weight caused by thermal degradation in the rheometer. Furthermore, the normalized complex viscosities of uncompatibilized PLA \/ PCL (90 \/ 10)","label":"BIODEGRAD_PROP"}
{"id":933,"sentence":"Briassoulis, 2006, Briassoulis, 2007). Frequently, at the macroscopic level, damages are not visible immediately (Duval, 2004), but at the molecular level degradation could started.","label":"BIODEGRAD_PROP"}
{"id":934,"sentence":"As shown in Figure 4, parts a and b, most of crystalline bands of the γ−form are blue−shifted less than the corresponding ones of the β−form,","label":"POLY_STRUC"}
{"id":935,"sentence":"(17, 42) Therefore, in the above case after 72 h of cultivation, only P3HP homopolymer was synthesized, whereas P4HB polymer was not accumulated when BDO was added after 28 h and beyond (Table 1).","label":"BIODEGRAD_POLY"}
{"id":936,"sentence":"and gels for drug or gene delivery or as tissue engineering scaffolds. 24−30 It is therefore, increasingly important that there is a thorough degradation study done of this material.","label":"BIODEGRAD_PROP"}
{"id":937,"sentence":"EXPERIMENTAL Materials and Methods The copolymer films of PCL‐b‐PEG (Mn 0 20, 650 ; PEG (Mn) 0 2890) used in the experiment were purchased directly from Sigma‐Aldrich.","label":"BIODEGRAD_POLY"}
{"id":938,"sentence":"which is due to the much low crystallization rate of PLA−b−PI−b−PLA triblock copolymers during the quenching process. On the contrary, for the solvent−cast PLA−b−PI−b−PLA triblock copolymers the WAXD curves display two major diffraction peaks except for PLA−PI106k−PLA sample,","label":"BIODEGRAD_POLY"}
{"id":939,"sentence":"They can interact with low molecular weight molecules (Call and M ü cke, 1997, Zapanta and Tien, 1997, Hammel et al., 2002,","label":"POLY_STRUC"}
{"id":940,"sentence":"Fig. 2. Biodegradation of PCL based on mass retention. Degradation of the polymers at room temperature (24 °C) was relatively slow, with losses of 51 % and 56 % for PHB and PHB−V, respectively, after 321 days of aging.","label":"BIODEGRAD_PROP"}
{"id":941,"sentence":"which is commonly used to describe the fluidity of a polymer in a viscous flow state. (1) (2) 2. 4. 2.","label":"RHEOLOGICAL_PROP"}
{"id":942,"sentence":"FTIR analysis provided supporting evidence of an interfacial reaction between PLA and PCL. Furthermore, the storage modulus and complex viscosity of the compatibilized PLA \/ PCL (90 \/ 10) blend were about 900 and 18 times higher, respectively, than those of pure PLA at an angular frequency of 0.","label":"BIODEGRAD_POLY"}
{"id":943,"sentence":"Because the crystalline domains are less permeable to water penetration and degree of crystallinity increased significantly by day 30 for samples degraded at 60 °C and by day 3 for the 80 °C samples,","label":"POLY_STRUC"}
{"id":944,"sentence":"Peak Band Assignments for PLA Infrared Spectra [109, 122, 123] Fang and Hanna [120] studied the rheological properties of amorphous and semicrystalline poly (lactic acid) using a tube rheometer on an extruder.","label":"BIODEGRAD_POLY"}
{"id":945,"sentence":"The Mark – Houwink equation that was used is as follows : [h] 0 5. 50 3 10−4 Mv0.639 The viscosimetric studies revealed that there was a 21.85 % and 41.00 % molecular weight decrease when the PDLLA was injection molded and extruded, respectively (Table XIII).","label":"RHEOLOGICAL_PROP"}
{"id":946,"sentence":"or food composts or hydrolysis in phosphate buffer solution or in vermiculite. The preference of biodegradation and hydrolysis of amorphous polymeric regions in semi−crystalline biodegradable polymers is well established [28].","label":"BIODEGRAD_PROP"}
{"id":947,"sentence":"This dichotomy between durable and biodegradable polymers is not obvious. The designed materials must be resistant during their use and must have biodegradable properties at the end of their useful life.","label":"BIODEGRAD_PROP"}
{"id":948,"sentence":"Table 3 lists the glass transition temperatures of PI midblock (Tg1) and PLA end blocks (Tg2) and the storage modulus, E′ at 25 °C for PLA−b−PI−b−PLA triblock copolymers.","label":"BIODEGRAD_POLY"}
{"id":949,"sentence":"This excludes the possibility of chain transfer (CT) reaction where chain transfer agents lower the molecular weights by increasing the rate of chain termination (Figure 7).","label":"POLY_STRUC"}
{"id":950,"sentence":"This kind of materials of industrial interest and low environmental impact is not within the aim of this review due to a minor biodegradability. Technological innovations designed for the production of polymers for short duration (e. g. disposable packages, agricultural mulches, horticultural pots, etc.) (Bastioli, 1998,","label":"BIODEGRAD_PROP"}
{"id":951,"sentence":"17 After 30 days hydrolysis of PBS, a remarkable decrease of C O C and C O absorption intensity was observed. These reductions in absorption intensity were due to lowering of the molecular weight and deterioration of the chemical structure by hydrolysis after being exposed to moisture and heat. 8, 18, 34 Figure 4 Open in figure viewer PowerPoint FTIR spectra of PBS, PBAT,","label":"BIODEGRAD_PROP"}
{"id":952,"sentence":"The thermal and mechanical behaviors of block copolymers P3HP−b−29 % P4HB and P3HP−b−37 % P4HB and blend polymer were investigated using the differential scanning calorimetry (DSC).","label":"POLY_STRUC"}
{"id":953,"sentence":"the CH2 stretching at 2942 and 2864 cm−1, and C−O and C−C (crystal phase) stretching absorption at 1293 cm−1 [27].","label":"POLY_STRUC"}
{"id":954,"sentence":"the satellite peak of the sample S3 (Figure 4 B), which indicated cross interaction between 3HP and 4HB in the changing point, was very small and hard to observe compared with the block copolymer P3HP−b−P4HB (Figure 4 A).","label":"POLY_STRUC"}
{"id":955,"sentence":"The diversified mobilities of three polymorphic crystalline phases, which is the key to crystalline−structure dependent biodegradability of P3HP, were discussed with considering the packing and conformation.","label":"POLY_STRUC"}
{"id":956,"sentence":"Kim [133] reported the results of thermal degradation of PLLA and PLLA \/ starch composites, determined by thermogravimetric analysis (TGA).","label":"BIODEGRAD_POLY"}
{"id":957,"sentence":"the width of the crystallization peaks became narrower, and the maximum crystallization temperatures shifted to lower temperatures. These results were indicative of an increase in crystallization rate.","label":"POLY_STRUC"}
{"id":958,"sentence":"It is well‐known that the amorphous regions are more susceptible to degradation than crystalline regions in a semicrystalline polymer. This can be explained by the rate of moisture penetration being higher in the amorphous regions than in the crystalline regions.","label":"POLY_STRUC"}
{"id":959,"sentence":"These conditions are of interest if PLA is to be subjected to aggressive environments in an accelerated test for screening PLA formulations or from a fundamental perspective to illustrate the shift from a bulk erosion mechanism to a surface‐erosion mechanism as the medium becomes more aggressive.","label":"BIODEGRAD_PROP"}
{"id":960,"sentence":"Based on this principle, the degradation rate of materials under certain processing conditions can be further evaluated [27, 28, 29, 30]. The work presented herein focuses on the modification of PLA ’ s brittleness and degradation.","label":"BIODEGRAD_PROP"}
{"id":961,"sentence":"The block copolymer is a special class of polymer that suddenly changed from sequential 3HP monomer to another 4HB monomer (Figure 1A), while random copolymers maintain a static constant average composition along the polymer chain (Figure 1B), yet a blend of two homopolymers does not have a chemical conjugation between two monomers 3HP and 4HB (Figure 1C).","label":"POLY_STRUC"}
{"id":962,"sentence":"and crystalline−phase specific adsorption of enzyme. (3) Recently, the relationships between the enzymatic degradation of PHAs and some solid−state properties and structures, e. g., crystallinity (2, 3)","label":"POLY_STRUC"}
{"id":963,"sentence":"Lactide is obtained by the depolymerization of low−molecular−weight PLA under reduced pressure to give a mixture of L−lactide, D−lactide,","label":"POLY_STRUC"}
{"id":964,"sentence":"the HPB compatibilizer exhibited a greater tendency to reduce the Δ Tg of samples. Fig. 6. DMA curves (A) and Tg (B) of blends with different amounts of compatibilizers.","label":"POLY_STRUC"}
{"id":965,"sentence":"The onset decomposition temperature, Tonset defined as the temperature with a 5 % mass loss on the TGA curve. The maximum decomposition temperature, Tmax determined from the peak on derivative TGA curve, with Tmax, 1 standing for that of PLA end block,","label":"POLY_STRUC"}
{"id":966,"sentence":"Several soil decomposers, particularly brown−rot fungi, are able to produce H2O2 (Green III and Highley, 1997) that is an oxidative molecule very reactive allowing the enzymatic biodegradation of cellulose molecules.","label":"BIODEGRAD_PROP"}
{"id":967,"sentence":"In detail, with the conformation changing from all−trans to 21−helix, for P3HB only an upfield shift less than 1 ppm was observed, (23a) while for PPL even a downfield shift of ∼1.","label":"BIODEGRAD_POLY"}
{"id":968,"sentence":"the rate of controlled drug release depends primarily on the degradation rate of the encapsulating polymer as the drug is released only upon breakdown of the polymer matrix.","label":"BIODEGRAD_PROP"}
{"id":969,"sentence":"For this purpose, we prepared compatibilized PLA \/ PCL (90 \/ 10) blends irradiated at various doses (5−200 kGy) in the presence of GMA and then measured their complex viscosities in the angular frequency range 0.5 – 100 rad \/ s.","label":"BIODEGRAD_POLY"}
{"id":970,"sentence":"As for PLA, these samples were processed during different time (from 5 to 25 min) and removed. Sample identification is presented in Table 2.","label":"BIODEGRAD_POLY"}
{"id":971,"sentence":"It is worth noting that polyisoprene (PI), because of its low Tg value, has been investigated to serve as the toughener of some brittle polymers [4, 16, 18].","label":"POLY_STRUC"}
{"id":972,"sentence":"(d) Product formation can also be used as an indicator of biodeterioration. For instance the production of glucose can be followed to assert the degradation of polymeric materials containing cellulose (Aburto et al., 1999).","label":"BIODEGRAD_PROP"}
{"id":973,"sentence":"(c) Internal biodeterioration can be evaluated by change of rheological properties (Van de Velde and Kiekens, 2002). Tensile strength is measured with a tensile tester (Ratto et al., 1999,","label":"BIODEGRAD_PROP"}
{"id":974,"sentence":"and THF. This is due to the acceptable difference in refractive index values between PLA (1.44) and HFIP (1.275).","label":"BIODEGRAD_POLY"}
{"id":975,"sentence":"A similar deceasing trend for residual mass was observed for degradation at pH 9. 5, with the residual mass at about 90 % at the end of Week 20.","label":"BIODEGRAD_PROP"}
{"id":976,"sentence":"Most of the IR bands in the 1500−750 cm−1 region of the β -, γ -, and δ−forms were found to be distinctively blueshifted and enhanced by cooling to−100 °C,","label":"POLY_STRUC"}
{"id":977,"sentence":"Note : The PDLLA supplied by Cargill is insoluble in sequencer−grade ethyl acetate. The rheological properties of PLA, especially the shear viscosity, have important effects on thermal processes, such as injection molding, extrusion, film blowing, sheet forming, fiber spinning,","label":"BIODEGRAD_POLY"}
{"id":978,"sentence":"and a refractive index detector (RI−150, Thermo Spectra System U. S. A.). Original putative P3HP−b−P4HB samples were fractionated with chloroform \/ ethanol mixed solvent at ambient temperature.","label":"BIODEGRAD_POLY"}
{"id":979,"sentence":"However, the storage modulus of all the samples gradually decreased with increasing temperature. This is attributed to the enhanced polymer chain mobility with increasing temperatures. 16 As reported by Van der wal et al.","label":"RHEOLOGICAL_PROP"}
{"id":980,"sentence":"and thermal stability (Abe et al., 2004a, 2004b ; Sivalingam et al., 2003 ; Soedergard et Naesman, 1994 ; Persenaire et al., 2001) of PCL and PLLA have been well reported in the literature.","label":"BIODEGRAD_POLY"}
{"id":981,"sentence":"The viscosity curves of PLLA can be converted in terms of molar mass assuming that at its maximum value the viscosity−frequency curve is close to the Newtonian plateau, therefore the maximum values of viscosity are used in the power law as above for PCL (Table 4).","label":"RHEOLOGICAL_PROP"}
{"id":982,"sentence":"the molecular weight decrease of the polymers, surface degradation studies, NMR spectroscopic studies, and the isolation and analysis of degradation products. 11 The degradation pathway of a polymer occurs in three phases consisting of an incubation period (water uptake), an induction period (molecular weight decrease)","label":"BIODEGRAD_PROP"}
{"id":983,"sentence":"To further prove the polymers to be a block copolymer type, solvent−fractionation method was employed to separate imaginable existence of homopolymer P3HP and P4HB, or random copolymer P (3HP−co−4HB).","label":"POLY_STRUC"}
{"id":984,"sentence":"The extent of crystallinity is not mentioned for the samples in Table 11.On annealing, the impact resistance increased due to the crosslinking effects of the crystalline domains, while the tensile strength increased, presumably due to the stereoregularity of the chain [1, 110].","label":"POLY_STRUC"}
{"id":985,"sentence":"The results for hydrolysis at pH 9. 5 were similar to that at pH 7. 4 in that the molecular weights decreased as the period of degradation increased.","label":"BIODEGRAD_PROP"}
{"id":986,"sentence":"Tsuji et al. [126] measured the optical rotation of poly (D−lactic acid) and poly (L−lactic acid). The values of 156 °and−153 °were in good agreement to the reported values of 150 °and−150 °for PDLA and PLLA, respectively [126].","label":"BIODEGRAD_POLY"}
{"id":987,"sentence":"Following day 7, the PDI decreased to 2. 5. The crystallinity of the samples is likely contributing to this phenomenon. As the amorphous regions are further degraded,","label":"POLY_STRUC"}
{"id":988,"sentence":"Fig. 5 shows the curves of chain scission of PCL at 100 °C, 140 °C, 160 °C and 180 °C in function of time obtained by means of the experimental rheological data and Saito ’ s equa−Fig. 5.","label":"BIODEGRAD_PROP"}
{"id":989,"sentence":"(15) According to this model, polymers with high melting points such as polyethylene terephthalate (PET) would not be able to undergo biodegradation. Nevertheless, since then, several enzymes were discovered that are able to degrade PET.","label":"BIODEGRAD_POLY"}
{"id":990,"sentence":"Moreover, Fig. 5 also shows that, as the intrinsic viscosity decreases, the crystallinity increases. As expected, B900 stabilizes PLA, minimizing its degradation with processing time.","label":"RHEOLOGICAL_PROP"}
{"id":991,"sentence":"Germany) under a nitrogen atmosphere, at a heating rate of 10 °C \/ min. PCL was first heated from room temperature to 80 °C to eliminate the thermal history of the samples,","label":"BIODEGRAD_POLY"}
{"id":992,"sentence":"The chain scission process was modeled to explain the phenomenon. The analysis suggests that PLLA is degraded by an unzipping depolymerization process from the hydroxyl end of the polymer chains.","label":"BIODEGRAD_PROP"}
{"id":993,"sentence":"at × 2000, (b) at × 10, 000.SEM Analysis of PCL‐b‐PEG Copolymer Film Visual examination of the surface morphology of the degraded copolymer films at various time points was done using SEM.","label":"BIODEGRAD_POLY"}
{"id":994,"sentence":"the degradation of these films were characterized at various time intervals by mass loss measurements, molecular weight, compositional and crystallinity changes. A faster rate of degradation took place at pH 9.","label":"BIODEGRAD_PROP"}
{"id":995,"sentence":"1 with the assumption that the concentration of water was approximately constant throughout the degradation process. The hydrolysis rate equation can be rewritten in terms of the number of carboxylic acid end groups generated during the hydrolysis,","label":"BIODEGRAD_PROP"}
{"id":996,"sentence":"and tension strengths much better than the previously reported random copolymers of similar compositions. Block copolymerization of P3HP and P4HB adds a new vision on PHA polymerization by generation of new polymers with superior properties.","label":"BIODEGRAD_POLY"}
{"id":997,"sentence":"The apparent viscosity and shear stress of the PLA \/ PPG composites decrease with a decreasing PPG MW. The lower the MW of PPG, the lower the melt viscosity of the PLA \/ PPG composites and the better fluidity.","label":"RHEOLOGICAL_PROP"}
{"id":998,"sentence":"Figure 4 Open in figure viewer PowerPoint Normalized weight average (A) and number average (B) molecular weight profiles for PLA32 (▪, •, ▴)","label":"POLY_STRUC"}
{"id":999,"sentence":"Interestingly, they proposed a time – temperature superposition scheme to predict the temperature effects. Among the large body of work from the group of Tsuji et al., 19 the effect of the crystallinity on the degradation of PLA at elevated temperatures was also investigated.","label":"RHEOLOGICAL_PROP"}
{"id":1000,"sentence":"and polyethylene (PE) [5]. SYNTHESIS OF POLY (LACTIC ACID) The basic building block for PLA is lactic acid, which was first isolated in 1780 from sour milk by the Swedish chemist Scheele and first produced commer cially in 1881 [1].","label":"BIODEGRAD_POLY"}
{"id":1001,"sentence":"and crystal thickness, (4) were well revealed. However, the crystalline structure (conformation and packing), which also possibly play an important role in the enzymatic degradation, as the degradation occurs through the hydrolysis of the main chain ester linkages, has not received the attention it deserves so far.","label":"POLY_STRUC"}
{"id":1002,"sentence":"and the n value of PLA \/ PPG−200 composite is close to a Newtonian fluid (n 0 1) when the shear rate is lower than 100 s−1.","label":"RHEOLOGICAL_PROP"}
{"id":1003,"sentence":"1 Alcohol Note : PCL : polycaprolactone ; PEG400 : poly (ethylene glycol). composites remained almost unchanged, but the crystallization characteristics were influenced. In the case of the PLLA \/ cornstarch composite,","label":"POLY_STRUC"}
{"id":1004,"sentence":"Lowering the temperature from room temperature down to−18. C caused the increase of elastic. These could be clearly seen in treatments PLA, PLAF and PP. 3. 1.2 Ultimate tensile strength It could be seen from Fig. 2. that the obtained values of ultimate tensile (UTS) strength of samples were of similar trend with that of the elastic modulus.","label":"MECHANICAL_PROP"}
{"id":1005,"sentence":"and 80 °C under nitrogen purge (A) and at 100 % RH (B). 95 % confidence intervals are indicated with bars. Figure 2B shows the percent crystallinity calculated for the samples degraded at 100 % RH for up to 30 days.","label":"POLY_STRUC"}
{"id":1006,"sentence":"Ester vibration peak in PLA shifted from 864 to 872 cm−1.Data obtained for PLA40 showed the up−shift of C−O symmetric stretching vibration from 1265 to 1269 cm−1, also reported elsewhere [7].","label":"BIODEGRAD_POLY"}
{"id":1007,"sentence":"(17) On the contrary, random chain initiation is quite common during the bacterial PHA polymerization process. (32, 33) Therefore, it could be concluded from the above experiments that the timing of substrate addition must be controlled to allow formation of the block copolymers.","label":"BIODEGRAD_POLY"}
{"id":1008,"sentence":"Mass Spectroscopy Analysis of Water Soluble Products After Hydrolysis Mass spectrum of the water soluble products for Week 20 was obtained and the results are shown in Tables III and IV.","label":"BIODEGRAD_PROP"}
{"id":1009,"sentence":"and 169. 569 ppm. Infrared spectroscopy data of poly (lactic acid) is presented in the literature, and the data is presented in Table XX [121, 122].","label":"BIODEGRAD_POLY"}
{"id":1010,"sentence":"Poly−β−(hydroxybutyrate−co−β−valerate) (PHB−V) was also supplied in powder form by Copersucar and had a weight average molecular weight (Mw) of 150, 000 with 0.09 % nitrogen and 0.27 % ash (both w \/ w).","label":"BIODEGRAD_POLY"}
{"id":1011,"sentence":"This study aimed to biosynthesize a block copolymer consisting of soft P4HB block with a strong P3HP block to gain unique and excellent material properties. A recombinant Escherichia coli strain that produces homopolymers of P3HP and P4HB was employed for the block copolymer synthesis.","label":"BIODEGRAD_POLY"}
{"id":1012,"sentence":"and that the long chain of the PLA blocks played a key role in improving the miscibility. Moreover, Kim [27] also found that the chain length of PS−b−PI copolymers played different roles to compatibilize PS \/ PI blends.","label":"BIODEGRAD_POLY"}
{"id":1013,"sentence":"and poly (butylene adipate−co−terephthalate) (PBAT) [10], [11], [12]. Even though some of these polymers can be processed into highly efficient materials with extensive applications, it remains difficult to satisfy the requirements of all the applications with a single polyester.","label":"BIODEGRAD_POLY"}
{"id":1014,"sentence":"Thus, the chain length of block copolymers is known to influence the compatibilization of blends in different ways. This prompted us to investigate the effect of the chain length of PLA−PBAT−PLA tri−block copolymers on the compatibilization of PLA \/ PBAT blends.","label":"POLY_STRUC"}
{"id":1015,"sentence":"which is available at wileyonlinelibrary. com.] Figure 10 Open in figure viewer PowerPoint Flexural modulus of PP, PBS, PBAT, and PBS \/ PBAT as a function of exposure time at 50 °C with 90 % RH. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":1016,"sentence":"and narrower molecular weight distributions when compared to SnO2 [69]. Aluminum alkoxides are another catalyst system that proceeds through the coordination \/ insertion mechanism, and are reported to give controllable molecular weights with narrow distributions [70, 71].","label":"POLY_STRUC"}
{"id":1017,"sentence":"PLA has a degradation time in the environment on the order of six months to two years, which compares to 500 to 1000 years for conventional plastics such as polystyrene (PS)","label":"BIODEGRAD_POLY"}
{"id":1018,"sentence":"A typical 1H‐NMR spectrum for PCL‐b‐PEG copolymer dissolved in CDCl3 (Week 1 sample) is shown in Supporting Information Figure S1 with the appropriate assignment of peaks corresponding to the respective proton signals from either PEG or PCL.","label":"BIODEGRAD_POLY"}
{"id":1019,"sentence":"However, there are still several limitations for utilizing PLA as an ideal sustainable polymer material with respect to its mechanical properties. PLA is a rigid and brittle polymer at room temperature.","label":"BIODEGRAD_POLY"}
{"id":1020,"sentence":"The first heating cycle was considered in order to measure sample crystallinity before and after conditioning. The percentage crystallinity of the PBS and PBAT was calculated by using the following formula : (2) where Δ Hm100 is the theoretical enthalpy of melting for 100 % crystalline PBS (110.","label":"POLY_STRUC"}
{"id":1021,"sentence":"A measured spherulitic growth rate has been determined, at 125 °C, to be 4. 0, 2. 0, and 0.8 mm \/ min for pure PLLA,","label":"BIODEGRAD_POLY"}
{"id":1022,"sentence":"The initial degradation took place at a rate of 0.212 week−1, this value dropped to 0.0028 week−1 beyond 4 weeks.","label":"BIODEGRAD_PROP"}
{"id":1023,"sentence":"Hydrolytic random chain scission at ester linkages reduces the size of polyester chains into the size range that microorganisms can bio−assimilate. As the hydrolysis proceeds, while the MWD of the hydrolyzed samples becomes narrower, main chain scission starts to occur at the middle of the chains, indicated by the significant shift of MWD towards lower molecular weight.","label":"BIODEGRAD_PROP"}
{"id":1024,"sentence":"and compatibilized (d) PLA \/ PCL (70 \/ 30) blends. 3. 3. Rheological Properties Dynamic rheological properties of polymers and their blends are highly dependent on polymer molecular eight and blend structure and compatibility [2, 7, 10, 28].","label":"RHEOLOGICAL_PROP"}
{"id":1025,"sentence":"First, the P3HP18k and P3HP70k samples were cast at 25 °C under controlled volatilization from the 10 mg \/ mL chloroform solution to prepare the cast δ−form and γ−form samples, respectively.","label":"POLY_STRUC"}
{"id":1026,"sentence":"Howard, 2002, Szostak−Kotowa, 2004, Shah et al., 2008). Enzymes involved in biodeterioration require the presence of cofactors (i. e. cations present into the material matrix and coenzymes synthesised by microorganisms) for the breakdown of specific bonds (Pelmont, 2005).","label":"BIODEGRAD_PROP"}
{"id":1027,"sentence":"Ibrahim et al. reported that addition of more than 70 % of PBAT deteriorated the properties of the PVC \/ PBAT blends [9]. It could be also seen that PLAF showed a higher modulus (around 213−501 MPa) as compared to that of PLA40.","label":"BIODEGRAD_POLY"}
{"id":1028,"sentence":"The chains in the amorphous region are more susceptible to initial hydrolysis because water can more easily penetrate these regions. Because of the preferential degradation of the amorphous portion of the polymer, there is simply a larger percentage of crystalline material left behind.","label":"POLY_STRUC"}
{"id":1029,"sentence":"This can be related to the plasticization effect by the diffused moisture, which induces an increase in the amorphous chain mobility. 30 A similar type of negative Tg shift was observed in the PLA films20 and PET composites30 after exposure to elevated temperature and humidity.","label":"BIODEGRAD_PROP"}
{"id":1030,"sentence":"In PBS \/ PBAT blend, a single Tg (− 19 °C) was observed. This is due to the fact that Tg values of both neat PBS and PBAT were very close to each other and thus Tg may be overlapping in the PBS \/ PBAT blend.","label":"BIODEGRAD_POLY"}
{"id":1031,"sentence":"the lower the melt viscosity of the resultant PLA \/ PPG composites. The addition of PPG leads to the degradation of PLA during processing, and the degradation of the PLA \/ PPG composites was more obvious when the MW of PPG was less than 400 g \/ mol. MATEC Web of Conferences 192, 03014 (2018) https : \/ \/ doi. org \/ 10.1051 \/ matecconf \/ 201819203014 ICEAST 2018 c The Authors, published by EDP Sciences.","label":"BIODEGRAD_POLY"}
{"id":1032,"sentence":"A, PLA pellet ; B, PLA – 5 min ; C, PLA – 25 min ; D, PLA + B900 – 5 min and E, PLA + B900 – 25 min.","label":"BIODEGRAD_POLY"}
{"id":1033,"sentence":"The average spherulite radius was 120 mm and 140 mm for pure star−PLA and PLLA, respectively [123]. This suggested that starch may play a role as a nucleating agent for PLA.","label":"BIODEGRAD_POLY"}
{"id":1034,"sentence":"which were caused by water dilution and the extraction of low‐molecular‐weight lactic acid oligomers. It should be noted that once the oligomers were removed by dissolution in the media,","label":"BIODEGRAD_PROP"}
{"id":1035,"sentence":"Triplicates were prepared for each period of degradation for both pH settings to minimize the effects of random errors. Lyophilization was carried out for the buffer solution component which contained the water soluble degradation products.","label":"BIODEGRAD_PROP"}
{"id":1036,"sentence":"Furthermore, even small amounts of compatibilizer could significantly reduce the Δ Tg of the components, similar to the DSC results. As shown in Fig. 6 (B), compared to the blends with LPB compatibilizer,","label":"POLY_STRUC"}
{"id":1037,"sentence":"and Kijchavengkul et al. [9] in various biodegradable polymers. Fig. 6. Increased heat of fusion (areas under melting peak in DSC thermogram) of PBAT films incubated in manure, yard,","label":"POLY_STRUC"}
{"id":1038,"sentence":"which slightly increase due to degradation, indicating that chain scission has occurred during processing. This ratio has a theoretical value of 3 and it must remain constant if degradation takes place due to ester linkage scission, hydrolysis or radical degradation, among others.","label":"BIODEGRAD_PROP"}
{"id":1039,"sentence":"The rates of weight loss in soil at room temperature were significantly lower than in compost, and no chemical hydrolysis was observed over a 3−month period [20].","label":"BIODEGRAD_PROP"}
{"id":1040,"sentence":"This indicated that starch acted as a nucleating agent for the star−PLA, enhancing its crystallinity. The overall influence of the starch addition on star−PLA was larger than that of L−PLA \/ starch composites [123].","label":"BIODEGRAD_POLY"}
{"id":1041,"sentence":"Table 1 summarizes the melting temperatures and the crystallinity of the three polymers. The melting temperatures agreed with values in the literature [9], [22]. PHB showed the highest crystallinity and PCL the lowest.","label":"POLY_STRUC"}
{"id":1042,"sentence":"Both tensile and flexural modulus of the PP, PBS, and PBS \/ PBAT gradually increased with increasing conditioning time, whereas PBAT remains constant throughout the entire conditioning period.","label":"BIODEGRAD_POLY"}
{"id":1043,"sentence":"This step is called assimilation. The term “ biodegradation ” indicates the predominance of biological activity in this phenomenon. Several studies about biodegradation of some polymers show that the abiotic degradation precedes microbial assimilation (Kister et al., 2000,","label":"BIODEGRAD_PROP"}
{"id":1044,"sentence":"This step is called assimilation. The combined action of microbial communities, other decomposer organisms or \/ and abiotic factors fragment the biodegradable materials into tiny fractions.","label":"BIODEGRAD_PROP"}
{"id":1045,"sentence":"7 Table 6. Fitting constants for PLLA chain scission process Fig. 10.Mechanism of thermal degradation of PLLA Intern. Polymer Processing XXII (2007) 5 tion.","label":"BIODEGRAD_PROP"}
{"id":1046,"sentence":"the low molecular weight (Mw) of the obtained polyesters shows that hydrolysis competes with the synthesis depending on the amount of water available in the active site.","label":"POLY_STRUC"}
{"id":1047,"sentence":"Dynamic Mechanical Analysis DMA analysis was performed using TA Instrument (DMA Q800), The United States. The experiments were conducted from−60 °C to 100 °C.","label":"MECHANICAL_PROP"}
{"id":1048,"sentence":"Zapanta and Tien, 1997, Hofrichter, 2002, Otsuka et al., 2003). Some materials considered as recalcitrant polymers (e. g. polyurethane, polyvinylchloride and polyamide) are nevertheless subject to microbial biodeterioration (Shimao, 2001,","label":"BIODEGRAD_PROP"}
{"id":1049,"sentence":"and had voids at interfaces between the PLA matrix and the PCL particles, which result in local stress concentration in a broader region, and this caused more rapid fracture progress [32].","label":"BIODEGRAD_POLY"}
{"id":1050,"sentence":"A porous structure was illustrated by the fact that in this stage, the sample was able to absorb a significant amount of water into its interconnected pore network.","label":"POLY_STRUC"}
{"id":1051,"sentence":"Paris, France Rheological Behavior and Modeling of Thermal Degradation of Poly (e−Caprolactone) and Poly (L−Lactide) Growing environmental concerns have led to the development of alternative biodegradable polymers with properties comparable to the conventional poly (ethylene), poly (propylene)","label":"BIODEGRAD_PROP"}
{"id":1052,"sentence":"Nucleation Parameters from Isothermal and Nonisothermal Kinetic Analysis for PLLA Parameter Isothermal Nonisothermal Kg 2. 44 * 105 2. 69 * 105 sse 3106 (J2 \/ m4) 753. 0 830.","label":"BIODEGRAD_POLY"}
{"id":1053,"sentence":"In the absence of increased interfacial adhesion, the storage moduli of PLA \/ PCL blends would be expected to lie between the values of the pure PLA and PCL.","label":"BIODEGRAD_POLY"}
{"id":1054,"sentence":"Polymer Processing XXII (2007) 5 View publication stats View publication statsView publication stats The work presented herein focuses on simulating the compounding process via a torque rheometer, as well as the relationship between the melt viscosity and the polymer molecular weight (MW).","label":"RHEOLOGICAL_PROP"}
{"id":1055,"sentence":"Mass., USA). Total biodegradation of PBAT film at 45 days in manure compost was the highest (67. 3 ± 2. 8 %), followed by those in food compost (44. 9 ± 2. 6 %)","label":"BIODEGRAD_PROP"}
{"id":1056,"sentence":"However, their difference in chain packing is still not clearly understood yet. It is of our interests to compare the packing−states of the two polymorphs with the similar conformation.","label":"POLY_STRUC"}
{"id":1057,"sentence":"(33−35) The block copolymers P3HP−b−P4HB produced in this study had the lowest melting temperatures (Tm) over previously synthesized block copolymers, thus, this material could be more useful for various PHA applications.","label":"POLY_STRUC"}
{"id":1058,"sentence":"PLA−b−PI−b−PLA triblock copolymers exhibit obviously enhanced thermal stability with higher Tmax, 1 values (≥ 358. 5 °C,","label":"BIODEGRAD_POLY"}
{"id":1059,"sentence":"The difference in the chain mobility shown here could reasonably explain the biodegradation behavior of three P3HP crystal forms, as was reported elsewhere. (5d) Of course,","label":"POLY_STRUC"}
{"id":1060,"sentence":"Table XI lists the effects of stereochemistry and crystallinity on the mechanical properties of amorphous L−PLA, annealed L−PLA, and amorphous D, L−PLA [1, 110].","label":"BIODEGRAD_POLY"}
{"id":1061,"sentence":"As long as we know, the only method to prove the assimilation in complex media is the use of a radiolabelled polymer to perform 14CO2 respirometry (Reid et al., 2001,","label":"BIODEGRAD_PROP"}
{"id":1062,"sentence":"However, only a careful study of rheological behavior and thermal stability of these melts will provide information for processing PLLA \/ PCL blends in proper conditions (Aoyagi et al., 2002 ;","label":"RHEOLOGICAL_PROP"}
{"id":1063,"sentence":"At all temperatures, no weight loss occurred initially during the period that we refer to as the induction period. After this period, the weight loss followed an S‐shaped curve,","label":"BIODEGRAD_PROP"}
{"id":1064,"sentence":"the degradation rate increased, too, and the transitions between monomodal and bimodal distributions shifted to earlier stages of hydrolysis. The bimodal distribution has been repeatedly associated with heterogeneous degradation when autocatalytic bulk erosion is present.","label":"BIODEGRAD_PROP"}
{"id":1065,"sentence":"Highlights • The mechanical property of PLA−b−PI−b−PLA triblock copolymers is obviously enhanced by crystallization of the PLA blocks. • Sufficient thermal stability for broad applications is confirmed for PLA−b−PI−b−PLA triblock copolymers. • PLA phase domains become stronger when PLA crystals replace the amorphous glassy PLA.","label":"BIODEGRAD_POLY"}
{"id":1066,"sentence":"The cPLA did not achieve any crystallinity upon molding because it was rapidly cooled from the melt state. It was, nonetheless, crystallizable, and its heating thermograms exhibited a glass transition (∼61 °C) ; this was followed by a broad exothermic peak due to cold crystallization,","label":"POLY_STRUC"}
{"id":1067,"sentence":"the increased crystallinity could be a contributing factor to the slowing hydrolysis rate. The PDI for the fibers was calculated based on the obtained molecular weight data and is shown in Fig. 5.","label":"POLY_STRUC"}
{"id":1068,"sentence":"the rate of which increases with temperature. Most experiments in vitro have been done at 37 °C. Hyon et al. [17] found that PLA100 fibers remained intact for 6 months at 37 °C in phosphate−buffered saline, pH 7. 4, whereas a 50 % weight loss was detected after 30 h at 100 °C.","label":"BIODEGRAD_PROP"}
{"id":1069,"sentence":"This suggests that the molecular weight of the exposed sample is reduced as a result of hydrolytic degradation. Interestingly, it was found that the impact strength of the PBAT was not affected significantly over the entire exposure time, whereas for PP, PBS,","label":"BIODEGRAD_POLY"}
{"id":1070,"sentence":"Biofragmentation is mainly concerned by enzymes that belong to oxidoreductases and hydrolases. These polymers are, in some industrial composites, co−extruded with polyesters to increase the biodegradability (Chandra and Rustgi, 1998,","label":"BIODEGRAD_PROP"}
{"id":1071,"sentence":"The diad or triad monomer sequences in microstructures of PHA copolymer were differentiated based on the carbon resonances intensities topology by 13C NMR technology. (34, 35, 43)","label":"BIODEGRAD_POLY"}
{"id":1072,"sentence":"2 Thermogravimetry Fig. 1 shows the weight loss profile of PCL and PLLA at a heating rate of 10 °C \/ min. It is also shown the thermal degrada−Material Property Tg °C Tm °C PLLA 60 180 PCL. 60 60 Table 2.","label":"BIODEGRAD_POLY"}
{"id":1073,"sentence":"The samples degraded at 40 °C and 100 % RH showed very little change in the crystallinity until day 6 when the crystallinity began to increase. After 30 days of degradation,","label":"BIODEGRAD_PROP"}
{"id":1074,"sentence":"The ability to control the stereochemical architecture allows precise control over the speed and degree of crystallinity, the mechanical properties, and the processing temperatures of the material.","label":"POLY_STRUC"}
{"id":1075,"sentence":"which is due to the stretching of COO of the ester bonds found in PCL. 11 Figure 6 (b) shows the spectra obtained from the water soluble degradation products.","label":"BIODEGRAD_POLY"}
{"id":1076,"sentence":"and (70 \/ 30) blends were higher than that of pure PLA due to the blending of PCL. Figure 6 Evolution of versus time of pure PLA (▲), pure PCL (△), uncompatibilized PLA \/ PCL (90 \/ 10) (○),","label":"BIODEGRAD_POLY"}
{"id":1077,"sentence":"and β is the coefficient indicating the viscosity sensitivity of the melt to temperature. The non−Newtonian index n is negligible because of the temperature. (4) (5)","label":"RHEOLOGICAL_PROP"}
{"id":1078,"sentence":"which, of course, does not support that the δ−form was much compressed at low temperatures. Indeed, the compact packings of the γ−and δ−forms were evidenced more directly by the temperature−enhanced splitting of vibration band, as discussed later.","label":"POLY_STRUC"}
{"id":1079,"sentence":"A more detailed table of IR and Raman spectroscopy frequencies can be found in the literature for semicrystalline and amorphous PLLA [124, 125]. Younes and Cohn [121] reported two bands that are related to the crystalline and the amorphous phase of PLA.","label":"POLY_STRUC"}
{"id":1080,"sentence":"Dynamic frequency sweep testing was performed at a strain of 2 % in the angular frequency range 0.5 to 500 rad \/ s. Dynamic time sweep testing was also used to examine the thermal stabilities of blends at an angular frequency of 1.","label":"RHEOLOGICAL_PROP"}
{"id":1081,"sentence":"the Molecular Weight Distribution Computer Analysis (MWDCA), based on the ISO 4582 test. Table 1.(Bio) degradability tests summary Abiotic degradation.","label":"BIODEGRAD_PROP"}
{"id":1082,"sentence":"and PBT), these free radicals favour the thermochemical degradability of these plastics. Chemical transformation is the other most important parameter in the abiotic degradation. The oxidative degradation depends on the polymer structure (e. g. unsaturated links and branched chains) (Duval, 2004).","label":"BIODEGRAD_PROP"}
{"id":1083,"sentence":"and PHB−b−PHHx (Table 3). (33−35) These results clearly demonstrated that the incorporation of block microstructure helps to attain superior thermal and mechanical properties for PHA.","label":"BIODEGRAD_POLY"}
{"id":1084,"sentence":"Li et al. have studied the hydrolytic degradation of multiblock copolymers comprising PEG and PCL segments under physiological and alkaline conditions. 31, 32 The degradation of PCLs in acidic and basic media have also been studied by Kim et al.","label":"BIODEGRAD_PROP"}
{"id":1085,"sentence":"5 were determined by GPC. The molecular weight of PCL‐b‐PEG dropped steadily from Week 1 through to Week 20 (Figure 2).","label":"POLY_STRUC"}
{"id":1086,"sentence":"This information was important because it confirmed that erosion did occur within the core of the sample through nonhomogeneous hydrolysis and the creation of autocatalytic pockets, which led to the creation of an interconnected porosity.","label":"BIODEGRAD_PROP"}
{"id":1087,"sentence":"Fig. 5 shows changes in number average molecular weight (Mn) of PBAT films from biodegradation in the three different compost environments, as well as from hydrolysis in pH 8.","label":"BIODEGRAD_PROP"}
{"id":1088,"sentence":"(4, 5) Based on monomer carbon chain length, PHA are divided into two subclasses : PHA with monomers consisting of C3 – C5 chain length are known as short chain length (scl) PHA,","label":"BIODEGRAD_POLY"}
{"id":1089,"sentence":"Unfilled symbols indicate aPLA, and filled symbols indicate cPLA. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary. com.]","label":"BIODEGRAD_POLY"}
{"id":1090,"sentence":"Therefore, hydrolysis was examined at much higher temperatures and under more extreme pH conditions than what can be found in life‐science‐oriented studies. EXPERIMENTAL Materials and Sample Preparation Two commercial grades (4032D and 8302D) of PLA (NatureWorks LLC) were used.","label":"BIODEGRAD_PROP"}
{"id":1091,"sentence":"A summary of the research is described as follows. The PLA was obtained from Cargill. Both samples had a number−average molecular weight of 88, 000 g \/ mole.","label":"BIODEGRAD_POLY"}
{"id":1092,"sentence":"There was also an insignificant mass loss of the films observed. Mass spectroscopy was used to determine the nature of the water soluble products of degradation. At pH 7. 4, a variety of oligomers with different numbers of repeating units were present whereas the harsher degradation conditions at pH 9.","label":"BIODEGRAD_PROP"}
{"id":1093,"sentence":"0 found by Cooper‐White and Mackay. 32 Figure 8 Open in figure viewer PowerPoint Viscosity (η 0) as a function of the molecular weight for the hydrolyzed PLA samples. [Color figure can be viewed in the online issue,","label":"RHEOLOGICAL_PROP"}
{"id":1094,"sentence":"Usually, polymers with strong polar functionality such as carbonyl (> C O) groups and amine groups are able to absorb moisture by hydrogen bonds. 27 Therefore, it is expected that the polyesters can absorb more moisture than the relatively non‐polar polymers such as PP.","label":"BIODEGRAD_PROP"}
{"id":1095,"sentence":"the β -, the γ -, and the δ−form P3HP samples were prepared by casting of low or high molecular weight sample and subsequent melt−crystallization under the appropriate thermal condition.","label":"POLY_STRUC"}
{"id":1096,"sentence":"Fig. 1.Synthesis methods for high−molecular−weight PLA [1, 29]. Commercial fermentation is usually conducted in a batch process,","label":"POLY_STRUC"}
{"id":1097,"sentence":"6 to 2. 6 [29], which theoretically cannot crystallize [30], [31], [32], the lower melting temperature of PBAT (130 °C) than polybutylene terephthalate (PBT) (230 °C) is evidence that cocrystallization in PBAT can occur since the soft BA sections can adjust their chain conformation to that of the rigid BT units.","label":"BIODEGRAD_POLY"}
{"id":1098,"sentence":"Mark – Houwink Constants for Poly (Lactic Acid) in Selected Solvents (K 5 dl \/ g) 1.PLLA 0.73 [h] 5 5. 45 3 1024 Mv 25 °C in chloroform [96, 110] 2. PDLLA 0.77 [h] 5 2. 21 3 1024 Mv 258 C in chloroform [96, 110] 3. PDLLA 0.82 [h] 5 1.29 3 1025 Mv 25 °C in chloroform [97] 4.","label":"BIODEGRAD_POLY"}
{"id":1099,"sentence":"which was monitored by CO2 emissions or C \/ N ratio. PBAT degraded more and faster in manure compost than in yard or food waste composts. The ester group in the aliphatic BA unit was more susceptible to hydrolysis than that in the aromatic BT unit.","label":"BIODEGRAD_POLY"}
{"id":1100,"sentence":"The amorphous PLA is soluble in most organic solvents such as tetrahydrofuran (THF), chlorinated solvents, benzene, acetonitrile, and dioxane [1].","label":"POLY_STRUC"}
{"id":1101,"sentence":"and [water] are the concentrations of carboxyl end groups, ester, and water in the polymer matrix 19, 20.It is assumed that the rate constant, k, is dependent only on temperature.","label":"POLY_STRUC"}
{"id":1102,"sentence":"5 k and its PDI, polydispersity index is 1.3. Table 1.Characteristics of PLA−b−PI−b−PLA triblock copolymers.","label":"POLY_STRUC"}
{"id":1103,"sentence":"The micrograph from the sample hydrolyzed in the neutral media showed a very irregular surface topology, and more interestingly, it clearly showed hexagonal patterns that were left by spherulitic structures.","label":"BIODEGRAD_PROP"}
{"id":1104,"sentence":"the depression of the relaxation should result from the alteration of the crystalline structure rather than that of the crystal thickness. Reasonably, the solid−state 13C spin−lattice relaxation time for the P3HP crystal form is coherently related not only to the molecular motions but also to the strength of the relaxation ways enrolled in.","label":"POLY_STRUC"}
{"id":1105,"sentence":"and PBS \/ PBAT were significantly affected after conditioning. However, the flexural and tensile modulus of the PP, PBS, and PBS \/ PBAT were slightly improved after exposure to heat and humidity.","label":"BIODEGRAD_POLY"}
{"id":1106,"sentence":"Finally, among the three polyesters studied, the non−biodegradable PET (Tm 0 265 °C) shows the highest stability against thermal degradation. The degradation behavior under isothermal conditions revealed that the mass of PCL remained constant for two hours at temperatures ranging from 100 to 250 °C.","label":"BIODEGRAD_PROP"}
{"id":1107,"sentence":"Three bands were related to PLA degradation : CO stretching (around 1750 cm−1) and C – O stretch (1185 and 1090 cm−1) [2], [19].","label":"BIODEGRAD_PROP"}
{"id":1108,"sentence":"The Tm of P3HP block segment in P3HP−b−37 % P4HB, was further lowered to 66. 80 °C (Figure 6, Table 2).","label":"BIODEGRAD_POLY"}
{"id":1109,"sentence":"These volatiles, such as low molecular weight oligomers and monomers formed during the degradation process, are able to diffuse through the polymer matrix and leave the fibers at temperatures above Tg 12.","label":"POLY_STRUC"}
{"id":1110,"sentence":"Again, even the nucleated polymer could be quenched rapidly enough to inhibit crystal formation [100]. Table III. Standard Bond Lengths and Bond Angles Used in the Conformational Energy Calculations Angle,","label":"POLY_STRUC"}
{"id":1111,"sentence":"In this work, we further conducted a study on the effect of crystallization on the enhancement of mechanical property for the prepared PLA−b−PI−b−PLA copolymers.","label":"POLY_STRUC"}
{"id":1112,"sentence":"Monomer structures may be determined by NMR (Marten et al., 2005, Zhao et al., 2005), functional chemical changes are easily detected by FTIR (Nagai et al., 2005,","label":"POLY_STRUC"}
{"id":1113,"sentence":"Mn0, p0 and Mw0 refer to the initial state. The activation energy of the process is Ea 0 214. 210, 21 J \/ mol.","label":"BIODEGRAD_PROP"}
{"id":1114,"sentence":"Samples of PHB, PHB−V, and PCL were weighed and buried, in triplicate, in soil compost at 46 ± 3 °C, and at room temperature (24 °C).","label":"BIODEGRAD_POLY"}
{"id":1115,"sentence":"which values are smaller at lower temperatures. Hence, thermogravimetric analysis (TGA) was performed to reveal the thermal behavior of the synthesized samples. As shown in Figure 2b, no new splitting of vibration could be detected for the γ−form during cooling.","label":"BIODEGRAD_PROP"}
{"id":1116,"sentence":"the modulus of the uncompatibilized PLA \/ PCL (70 \/ 30) blend was higher than that of the uncompatibilized PLA \/ PCL (90 \/ 10) blend despite a higher PCL content, presumably because total interfacial area had been increased,","label":"BIODEGRAD_POLY"}
{"id":1117,"sentence":"Unimodal GPC profiles of the films were obtained. This increase was much faster at pH 9. 5 than for pH 7. 4. This corroborates well with the results for DSC.","label":"MECHANICAL_PROP"}
{"id":1118,"sentence":"The improvement of modulus could only be seen when PLA concentration in the blend was increased to 40 % (treatment PLA40). The results indicated poor interfacial adhesion between PBAT and PLA that led to the phase separation of PLA \/ PBAT blend.","label":"BIODEGRAD_POLY"}
{"id":1119,"sentence":"These two polymer samples were analyzed by NMR, which confirmed them to be a block copolymer of P3HP−b−P4HB. The analysis of this sample by NMR spectrometry indicated that it was the mixture of little amount of block P3HP−b−P4HB with homopolymers of P3HP and P4HB.","label":"BIODEGRAD_POLY"}
{"id":1120,"sentence":"The continued crystallization as well as the decrease in the melting temperature exhibited by both the PLA32 and PLA118 samples at 60 and 80 °C can be attributed to several phenomena that are likely occurring during the degradation of the fibers.","label":"POLY_STRUC"}
{"id":1121,"sentence":"There was an improvement of elastic modulus (E) for PLA \/ PBAT blends when PLA was 40 %. There was no significant difference of ultimate tensile strength (UTS) among the blends.","label":"MECHANICAL_PROP"}
{"id":1122,"sentence":"and humidity (90 %), the molecular weight reduction occurred in the following order PBS \/ PBAT > PBAT > PBS, as shown in Table 3.","label":"BIODEGRAD_POLY"}
{"id":1123,"sentence":"A ç ú car e Á lcool do Estado de S ã o Paulo, S ã o Paulo, SP, Brazil). The polymer had a weight average molecular weight (Mw) of 250, 000 and contained 0.2 % nitrogen and 0.66 % ash (both w \/ w).","label":"POLY_STRUC"}
{"id":1124,"sentence":"and φ is the volume crystallinity. The experimental invariant (Qexp) and volume crystallnity were calculated, respectively, by integrating the slit−smeared scattering data (20a) (not shown ; which are similar to those reported previously (5d)),","label":"POLY_STRUC"}
{"id":1125,"sentence":"This pure stereocomplex has a melting point of 230 °C and mechanical properties greater than either pure polymer [86 – 93]. Using lower−molecular−weight PLA, it has been reported that ultimate tensile strengths were 50 MPa for the 1 : 1 stereocomplex versus 31 MPa for pure L−PLA [86, 87].","label":"POLY_STRUC"}
{"id":1126,"sentence":"Figure 4. Temperature−adjusted torque versus time in the interval from 15 to 20 minutes of the neat PLA and PLA \/ PPG composites. The corresponding data calculated by Equations (8) to (11) are presented in Figure 5,","label":"BIODEGRAD_POLY"}
{"id":1127,"sentence":"Crystallinity was calculated from melting enthalpies. Reference values of 205. 0 and 139. 5 J \/ g for completely crystallized PEG and PCL were used, respectively. XRD Analysis of PCL‐b‐PEG Copolymer Film XRD analysis was used to support and validate the data obtained from DSC.","label":"POLY_STRUC"}
{"id":1128,"sentence":"which was sustained for the first week of degradation. This weight gain was likely due to absorbed water that was not able to be removed during the post‐aging drying process described in Mass Loss Measurements section.","label":"BIODEGRAD_PROP"}
{"id":1129,"sentence":"This is in contrast to the results achieved for pH 7. 4, and is because the harsher degradation conditions at pH 9. 5 has resulted in accelerated cleavage of the ester bonds to leave only dimers.","label":"BIODEGRAD_PROP"}
{"id":1130,"sentence":"and T 0 temperature, K. RESULTS AND DISCUSSION Total Mass Loss For the case of PLA fibers exposed to elevated temperature and humidity, a loss of total mass can be attributed to volatile material being released from the samples during aging.","label":"BIODEGRAD_PROP"}
{"id":1131,"sentence":"36 and 0.54 MPa, respectively. Though the block copolymers showed some reduction in elongation to break but were still higher in comparison to their homopolymers P3HP and P4HB.","label":"POLY_STRUC"}
{"id":1132,"sentence":"and (e) yard compost ; absorbance spectra in the wavenumber range of 1800 – 1650 cm−1 of PBAT film in (f) phosphate buffer solution, (g) vermiculite, (h) manure compost, (i) food compost,","label":"BIODEGRAD_POLY"}
{"id":1133,"sentence":"Four different power−law equations and 14 different Mark – Houwink equations are presented for PLA. Nuclear magnetic resonance, UV – VIS, and FTIR spectroscopy of PLA are briefly discussed.","label":"BIODEGRAD_POLY"}
{"id":1134,"sentence":"In Table 1 were summarized the characteristic bands of the δ -, γ -, and β−forms with the trial assignments. As the β−form and γ−form P3HPs both adopt the all−trans conformation, it is reasonable that the two crystal forms have a high similarity in the fingerprint IR absorption.","label":"POLY_STRUC"}
{"id":1135,"sentence":"the anisotropic polymer crystals, due to the vibrational anharmonicity, undergo lateral contract \/ expansion. Namely, decreasing \/ increasing temperature enhances \/ weakens the intermolecular interaction,","label":"POLY_STRUC"}
{"id":1136,"sentence":"PLA exhibited the highest value of ultimate tensile strength (UTS), around 52−67 MPa. The addition of PLA, up to 40 %, to PLA \/ PBAT blends did not affect the UTS.","label":"BIODEGRAD_POLY"}
{"id":1137,"sentence":"4 shows the changes in crystallinity and lateral crystal size [(110) \/ (200)] obtained from the WAXD curves with molecular mass of PI midblock for solvent−cast PLA−b−PI−b−PLA triblock copolymers.","label":"POLY_STRUC"}
{"id":1138,"sentence":"For example, PLA \/ PBAT blends are highly promising materials on account of the considerable mechanical strength conferred by PLA and the extreme toughness contributed by PBAT [16], [17], [18], [19], [20].","label":"BIODEGRAD_POLY"}
{"id":1139,"sentence":"Table 3. Glass transition temperatures (Tg1, Tg2) and storage modulus (E′) at 25 °C obtained from DMA measurements for PLA−b−PI−b−PLA triblock copolymers.","label":"MECHANICAL_PROP"}
{"id":1140,"sentence":"The crystallinity degree (χ c) was obtained using equation (4) : (4) where and are, respectively, the experimental melting enthalpy and the cold crystallization enthalpy obtained for the samples, is the melting enthalpy of the 100 % PLA (93.","label":"POLY_STRUC"}
{"id":1141,"sentence":"This work mainly involved the in situ FTIR observation of polymorphic P3HP crystals during cooling and heating. First, the concomitant wavenumber shift, intensity enhancement, and splitting of vibration band, (12, 13)","label":"POLY_STRUC"}
{"id":1142,"sentence":"(Tsukuba, Japan). Both P3HP samples were purified from chloroform solution by precipitation in heptane. With referring to our previous works, (5a−5c)","label":"BIODEGRAD_POLY"}
{"id":1143,"sentence":"145 kg \/ m3 and a weight average molecular weight (Mw) of 50, 000.Poly−β−(hydroxybutyrate) (PHB) was supplied as a powder by Copersucar (Cooperativa de Produtores de Cana,","label":"POLY_STRUC"}
{"id":1144,"sentence":"As expected, this behavior should be due to the molecular weight reduction by random chain scission after being exposed to elevated temperature and humidity. The molecular weight changes can be correlated with shear viscosity of the sample at low shear rate.","label":"BIODEGRAD_PROP"}
{"id":1145,"sentence":"Based on the rate constants obtained for each model, the activation energy for PLA degradation was calculated (26.3 kcal mol−1 for the first order model and 22.4 kcal mol−1 for the autocatalytic model).","label":"BIODEGRAD_PROP"}
{"id":1146,"sentence":"The unit cell dimensions are as follows : a 0 10.7 A, b 0 6. 126 A, and c 0 28. 939 A, with the diameter distribution of the crystallites ranging fom 390 to 440 A.","label":"POLY_STRUC"}
{"id":1147,"sentence":"which is available at wileyonlinelibrary. com.] Figure 8 represents the elongation at break of the samples with respect to exposure time. Except PBAT, all the samples showed drastic reduction in the elongation at break from early exposure time.","label":"MECHANICAL_PROP"}
{"id":1148,"sentence":"The stabilizer (B900, 0.2 wt %) was pre−mixed with the PLA pellets and then added together to the batch mixer chamber.","label":"BIODEGRAD_POLY"}
{"id":1149,"sentence":"There was no correlation between the extent of biodegradation and the crystallinity of the polymers since PHB, which had higher crystallinity than PHB−V, and PCL showed almost the same biodegradation as PHB−V during the period of monitoring.","label":"BIODEGRAD_POLY"}
{"id":1150,"sentence":"As the degradation proceeds further, the remaining crystalline regions are also susceptible to degradation, and the thickness of the crystalline regions decreases, leading to a reduction of the melting temperature 6.","label":"POLY_STRUC"}
{"id":1151,"sentence":"RESULTS AND DISCUSSION Molecular Weight Distribution Evolution Hydrolysis decreases the molecular weight and alters the molecular weight distribution of PLA. The evolution over time of the molecular weight distribution of PLA in aqueous media at pH 5.","label":"BIODEGRAD_PROP"}
{"id":1152,"sentence":"Although hydrolytic degradation studies for the PEG‐PCL copolymer have been carried out by a few groups, these were neither detailed nor comprehensive enough for the assessment of its suitability as a biomaterial. 17, 18 Therefore, this article attempts to gain a better and more complete understanding of the degradation process of this copolymer by conducting the hydrolysis experiments at different pH values.","label":"BIODEGRAD_PROP"}
{"id":1153,"sentence":"However, the crystallinity level that could be attained during the hydrolysis was much higher than that typically attained in crystallization from the melt state. We assessed this by heating the PLA samples in a differential scanning calorimeter.","label":"POLY_STRUC"}
{"id":1154,"sentence":"and have been concerned for many years. Up to date, a considerable body of knowledge on the enzymatic degradation of PHAs has been accumulated. Indeed, for a given PHA,","label":"BIODEGRAD_PROP"}
{"id":1155,"sentence":"The moisture absorption was proportional to the starch content of the composite. Finally, Kim [133] reported tensile and thermal properties of PLLA \/ starch \/ plasticizer composite films.","label":"MECHANICAL_PROP"}
{"id":1156,"sentence":"Because PLA hydrolysis involves the cleavage of ester groups, the presence of hydronium and hydroxide ions catalyzes the reaction. 20, 25 The high concentration of hydroxide ions in alkaline media strongly accelerates the hydrolysis process.","label":"BIODEGRAD_PROP"}
{"id":1157,"sentence":"To reduce or minimize the shear \/ temperature effect during processing, a stabilizer (B900) was added to PLA. PLA is sensitive to radical and nonradical degradation and, as it was presented above, shear imposed during melting and mixing process enhances degradation.","label":"BIODEGRAD_POLY"}
{"id":1158,"sentence":"This plot holds well for polymers of high molecular weight. The Tm and DHm values obtained were 184 °C and 3. 5 kcal \/ mol, respectively, for PLLA [3].","label":"POLY_STRUC"}
{"id":1159,"sentence":"the extended period under which the material was annealed over its Tg ; the high water content, which could have plasticized the material ; and the molecular weight loss, all contributed to reduce the dynamic barrier to crystallization.","label":"BIODEGRAD_PROP"}
{"id":1160,"sentence":"This is possibly due to the increased crystallinity after being exposed to the hydrolysis environment. Figure 17 Open in figure viewer PowerPoint SEM micrographs of PBS, PBAT,","label":"BIODEGRAD_PROP"}
{"id":1161,"sentence":"and by polymer characteristics, such as chain flexibility, crystallinity, regularity and heterogeneity, functional groups, and molecular weight [7], [11], [12].","label":"POLY_STRUC"}
{"id":1162,"sentence":"the hydrolysis reaction can be described by a second‐order kinetics model. 14 It is also assumed that at least in the early stages of hydrolysis,","label":"BIODEGRAD_PROP"}
{"id":1163,"sentence":"Most biodegradable polymers belong to thermoplastics (e. g. poly (lactic acid), poly (hydroxyalkanoate), poly (vinyl alcohol)) or plants polymers (e. g. cellulose and starch).","label":"BIODEGRAD_POLY"}
{"id":1164,"sentence":"PDO was added at the beginning of bacterial cultivation for P3HP production. After approximately 24 h of cell growth, when PDO was almost exhausted (in trace amount from HPLC examination), 10 g \/ L of BDO was added as the precursor,","label":"BIODEGRAD_POLY"}
{"id":1165,"sentence":"and a polydispersity of 1.15 [77 – 79]. Some examples of rare earth catalysts that were investigated were yttrium tris (N, N−dimethylaminoethoxide), yttrium tris (methyllactate), samarium tris (N,","label":"POLY_STRUC"}
{"id":1166,"sentence":"Perego et al. [110] studied the effects of molecular weight and crystallinity on the mechanical properties of PLA by polymerizing pure L−lactide and D,","label":"POLY_STRUC"}
{"id":1167,"sentence":"The lactide method was the only method of producing pure, high−molecular−weight PLA until Mitsui Toatsu Chemicals recently commercialized a process wherein lactic acid and catalyst are azeotropically dehydrated in a refluxing, high−boiling, aprotic solvent under reduced pressures to obtain PLA with weight−average molecular weights greater than 300, 000 [10 – 13].","label":"POLY_STRUC"}
{"id":1168,"sentence":"and compatibilized PLA \/ PCL (90 \/ 10) (•) and (70 \/ 30) (■) blends. 4. Conclusions In this work, PCL was blended into PLA at the loading of 10 or 30 % by weight to try to overcome the limitations (brittleness, low melt viscosity, thermal stability,","label":"BIODEGRAD_POLY"}
{"id":1169,"sentence":"and thermogravimetric analysis (TGA). Since UV radiation produces polymer fragments, the molecular weight of the released fragments are revealed by gel permeation chromatography (GPC).","label":"POLY_STRUC"}
{"id":1170,"sentence":"These block copolymers were revealed to have high molecular weights without serious aging problems in comparison to other PHA random copolymers. (31, 32) So far, only four following diblock copolymers were reported to be biosynthesized including PHB−b−PHBV, (32) PHB−b−PHVHHp, (33) P3HB−b−P4HB, (34)","label":"POLY_STRUC"}
{"id":1171,"sentence":"Tsuji et al., 2006). Crystallinity is determined by X−ray diffraction (Ki and Park, 2001, Abd El−Rehim et al., 2004,","label":"POLY_STRUC"}
{"id":1172,"sentence":"Biodegradation is considered to take place throughout three stages : biodeterioration, biofragmentation and assimilation, without neglect the participation of abiotic factors. However, most of the techniques used by researchers in this area are inadequate to provide evidence of the final stage : assimilation.","label":"BIODEGRAD_PROP"}
{"id":1173,"sentence":"Note that nitrogen was purged into the hot stage for preventing from possible sample degradation or cross−linking. It has a classical α \/ β hydrolase fold and a cap domain and displays a dimer arrangement.","label":"POLY_STRUC"}
{"id":1174,"sentence":"the β−form (β (IC0)) and the γ−form (γ (IC70)) crystalline phase. When the cast P3HP18k sample is melted at a low temperature, i. e., 110 °C,","label":"POLY_STRUC"}
{"id":1175,"sentence":"As determined by a life cycle inventory [4], PBAT, as well as other biodegradable polyesters, has the greatest environmental benefits when it is recovered through recycling or composting.","label":"BIODEGRAD_POLY"}
{"id":1176,"sentence":"Therefore, PLA is still an underperforming biopolymer for long‐term durable applications such as automotive parts. In addition, Harris and Lee13 have studied the hydrolytic degradation of PLA and a PLA \/ polycarbonate (PC) blend exposed to elevated temperature and humidity for 28 days.","label":"BIODEGRAD_POLY"}
{"id":1177,"sentence":"and uncompatibilized PLA \/ PCL blends. Figure 9 shows the tensile moduli of pure PLA and compatibilized and uncompatibilized PLA \/ PCL blends. For uncompatibilized blends, tensile moduli decreased as PCL content increased and were lower than that of pure PLA, whereas compatibilized blends had tensile moduli similar to that of pure PLA due to increased compatibility.","label":"BIODEGRAD_POLY"}
{"id":1178,"sentence":"Three samples were taken and dried at the end of each hydrolysis step. Thermal Characterization The thermal properties of PLA samples, such as Tg, Tm,","label":"MECHANICAL_PROP"}
{"id":1179,"sentence":"27 However, autocatalytic bulk erosion was reported even in the absence of bimodal distribution. 21 Figure 1 Open in figure viewer PowerPoint Molecular weight distribution (Mass fraction W for constant molar mass increments log M) of PLA hydrolyzed at 70 °C for (a) aPLA at pH 5. 4, (b) cPLA at pH 5. 4, (c) aPLA at pH 12,","label":"BIODEGRAD_POLY"}
{"id":1180,"sentence":"The blocky feature in the polymer added higher Young ’ s modulus, yield strength, and tensile strength. This block copolymer is a new study in PHA polymer area,","label":"MECHANICAL_PROP"}
{"id":1181,"sentence":"Figure 1 SEM images of cryofractured surfaces of uncompatibilized (a) and compatibilized (b) PLA \/ PCL (90 \/ 10) blends and uncompatibilized (c)","label":"BIODEGRAD_POLY"}
{"id":1182,"sentence":"Kim et al. [133] reported the mechanical properties of poly (L−lactic acid) \/ starch composites. The number and weight−average molecular weights of the PLLA were 190, 000 and 360, 000 g \/ mole, respectively.","label":"BIODEGRAD_POLY"}
{"id":1183,"sentence":"Melt−blended specimens with various amounts of LPB and HPB compatibilizers were prepared to investigate the influence of the copolymer compatibilizers on the mechanical properties of melting blends.","label":"MECHANICAL_PROP"}
{"id":1184,"sentence":"A statistical analysis and measurements of domains containing no fewer than 50 particles showed that the average size of the PBAT domains was reduced from ∼1.5 μm to ∼0.","label":"BIODEGRAD_POLY"}
{"id":1185,"sentence":"and (i) yard compost. Hydrolytic main chain scission at multiple locations in the polymer chain produces smaller molecules or oligomers, which can easily permeate out of the polymer matrix.","label":"BIODEGRAD_PROP"}
{"id":1186,"sentence":"The structure of the tri−block copolymers could be adjusted by varying the feeding ratios of the monomer and macro−initiator, and the polymers were characterized by 1H NMR,","label":"POLY_STRUC"}
{"id":1187,"sentence":"Secondly, the yield stress displays a nonlinear decrease with increasing PI midblock molecular mass, similar to the changing trend for the Young's modulus (Fig. 7a).","label":"MECHANICAL_PROP"}
{"id":1188,"sentence":"In terms of chemical structure, poly (3−hydroxyalkanoate) s (P3HAs), one family of the most famous PHAs, can be looked as produced by substituting β CH2 protons of P3HP with alkane groups, i. e., they all share the 3HP skeleton.","label":"BIODEGRAD_POLY"}
{"id":1189,"sentence":"The samples held at 80 °C showed a similar trend in molecular‐weight reduction to those aged at 60 °C, but at a much faster rate.","label":"BIODEGRAD_PROP"}
{"id":1190,"sentence":"the biodegradabilities of compatibilized PLA \/ PCL (90 \/ 10) and (70 \/ 30) blends were determined under specific composting conditions [20]. 2.","label":"BIODEGRAD_PROP"}
{"id":1191,"sentence":"As a result, molecular weight reduction occurs with the formation of lactide monomer and oligomers [10]. From the production point of view, these changes in PLA are undesired, not only because the material's melt viscosity and elasticity decrease, but also the processing equipment can be damaged due to the volatile lactide formation [3].","label":"RHEOLOGICAL_PROP"}
{"id":1192,"sentence":"Stabilized PLA samples were prepared by adding 0.2 % (w \/ w) [2] of B900, and its properties are indicated in Table 1.","label":"BIODEGRAD_POLY"}
{"id":1193,"sentence":"Gravimetric measures are frequently used, but loss of weight is often insignificant, so, they are associated to the techniques described above. Table 2. (Bio) degradability estimation : analytical techniques Differential scanning calorimetry (DSC) is used to study the thermal transitions of polymers.","label":"BIODEGRAD_PROP"}
{"id":1194,"sentence":"Mechanism for Complete Hydrolytic Degradation of PEG‐PCL Copolymers The SEM micrographs, in conjunction with other data obtained offered a good avenue to propose a degradation mechanism for the copolymer film.","label":"BIODEGRAD_PROP"}
{"id":1195,"sentence":"which also arise from tight chain packing, were found to decay faster than the conformation−sensitive backbone stretching in the melting. This asynchronization change indicates that the melting of the γ−form should pass through one mesophase,","label":"POLY_STRUC"}
{"id":1196,"sentence":"Instron, USA), and impact strengths were measured using an impact tester (Model 43 – 76 ; TMI Test Machines Inc., USA).","label":"MECHANICAL_PROP"}
{"id":1197,"sentence":"A schematic illustration of the possible degradation process based on the experimental results is shown in Figure 10.CONCLUSIONS The in‐vitro hydrolytic behavior of diblock copolymer films consisting of poly (ε‐caprolactone) (PCL)","label":"BIODEGRAD_PROP"}
{"id":1198,"sentence":"Fig. 1.Elastic modulus (E) of neat PLA, neat PBAT, neat PP, PLA \/ PBAT blends, and PLA fiber \/ PBAT composite.","label":"BIODEGRAD_POLY"}
{"id":1199,"sentence":"The slow decrease in residual mass implied that the bulk copolymer film is hydrolytically stable under physiological conditions for up to 20 weeks. A possible reason for this is that the hydrophilic PEG segment responsible for attracting the hydroxyl groups causing hydrolysis is present in only less than 15 wt % (molecular weight of 2890 out of 20, 650) of the total composition.","label":"BIODEGRAD_PROP"}
{"id":1200,"sentence":"Runt et al. [97] presented crystallization kinetics data for copolymers of poly (L−lactide−co−meso−lactide). At a crystallization temperature of 117 °C, a copolymer of 0.4 % D−content crystallized 60 times faster than a copolymer of 6. 6 % D−content.","label":"POLY_STRUC"}
{"id":1201,"sentence":"The peaks in the range of 700 – 900 cm−1 were attributed to benzene substitutes. 35 After 30 days of exposure to moisture and heat, there is no significant change observed in the FTIR spectra of PBAT.","label":"BIODEGRAD_POLY"}
{"id":1202,"sentence":"Although there have been studies that have evaluated the effect of different parameters on PLA hydrolysis, few of them have combined multiple effects simultaneously. Accordingly, the general context of this study was to investigate PLA hydrolysis and PLA crystallinity development at a higher temperature relevant to industrial composting (> 55 °C and high humidity)","label":"BIODEGRAD_PROP"}
{"id":1203,"sentence":"the enzymatic erosion rate does not only depend on the primary structure but also on the solid structure, due to both the amorphous phase preferential degradation (2)","label":"POLY_STRUC"}
{"id":1204,"sentence":"The tensile tests were performed until the conditioned samples broke at the grip region as a consequence of embrittlement. After 30 days, conditioned PBS samples became more fragile and would rupture during handling.","label":"MECHANICAL_PROP"}
{"id":1205,"sentence":"the tri−block copolymer with long−chain PLA blocks (HPB) achieved more effective compatibilization of PLA and PBAT because the long chains interpenetrate better to the relevant homopolymers and increased the entanglement density.","label":"POLY_STRUC"}
{"id":1206,"sentence":"Table 1.B900 properties. PLA pellets were pressed into thin films at 200 °C under 30 ton for 60 s. PLA was processed in a batch mixer (HAAKE Rheomix 600 OS ; volume 69 cm [3]) equipped with two rotors running in a counter−rotating way.","label":"BIODEGRAD_POLY"}
{"id":1207,"sentence":"which indicate that anisotropic polymer crystals undergo a large change in lateral area (e. g., about 6 % for PE from + 60 to−180 °C (15e)), but keep almost constant along chains (e. g., smaller than 0.25 % for PE from + 60 to−180 °C (15e)).","label":"POLY_STRUC"}
{"id":1208,"sentence":"and poly (styrene−b−soybean oil acrylate−b−styrene) (PS−b−PSBA−b−PS) and poly (styrene−b−soybean oil methacrylate−b−styrene) (PS−b−PSBMA−b−PS) triblock copolymers [28].","label":"POLY_STRUC"}
{"id":1209,"sentence":"Determination of Polymer Degradation Rate by TORQUE Rheometry By using a torque rheometer, the torque Z, the chamber temperature T, and the work W during the mixing process can be directly obtained by setting the temperature T0,","label":"RHEOLOGICAL_PROP"}
{"id":1210,"sentence":"PBAT is a linear random copolyester consisting of two types of dimer. Fig. 1.Chemical structure of poly (butylene adipate−co−terephthalate) or PBAT.","label":"BIODEGRAD_POLY"}
{"id":1211,"sentence":"Theglass−transition, crystallization, and melt temperatures of the PLLA were 60 °C, 125. 2 °C, and 172 °C, respectively [134].","label":"POLY_STRUC"}
{"id":1212,"sentence":"This can be due to chain scission leading to shorter molecular chains and reorganization of amorphous domains into crystalline ones, indicating an increase on molecular flexibility and mobility [9], [22].","label":"POLY_STRUC"}
{"id":1213,"sentence":"which is related to temperature−shear combination during processing. Moreover, it was shown that the presence of B900 minimizes the PLA degradation during consecutive processing cycles, preventing chain scission.","label":"BIODEGRAD_PROP"}
{"id":1214,"sentence":"It has also been observed that a 1 : 1 mixture of pure poly (L−lactide) with pure poly (D−lactide) will yield an insoluble gel formed by the stereocomplexation (racemic crystallite) of the two polymers during crystallization or polymerization.","label":"BIODEGRAD_POLY"}
{"id":1215,"sentence":"The enzymatic hydrolyzability of PLA \/ PCL blend compatibilized by the addition of PLLA−CL decreased with increasing PLLA−CL content ; however, tensile strength,","label":"BIODEGRAD_POLY"}
{"id":1216,"sentence":"Antheunis et al. 24 proposed a similar model for the degradation of PLA that takes into consideration the autocatalytic behavior observed by others. They began their analysis with Eq.","label":"BIODEGRAD_PROP"}
{"id":1217,"sentence":"which is available at wileyonlinelibrary. com.] Figure 14 shows the tan δ (loss factor) curves with respect to temperatures. In fact, the peak temperature of the tan δ represents the glass transition temperature (Tg).","label":"POLY_STRUC"}
{"id":1218,"sentence":"To ensure the greatest hydrolysis progress, the maximum duration of the hydrolysis was set accordingly to 50, 30, and 15 days, respectively. To investigate the effect of pH, additional experiments were carried out in acidic and alkaline conditions at pH values of 1, 9,","label":"BIODEGRAD_PROP"}
{"id":1219,"sentence":"The about linear decrease in ultimate tensile strength with increasing molecular mass of PI midblock indicates that this mechanical parameter is more correlated with soft PI matrix in the network in these samples.","label":"MECHANICAL_PROP"}
{"id":1220,"sentence":"the molecular weight distribution shifted to lower molecular weights and transformed into a bimodal distribution at the intermediate hydrolysis time. For example, for pH 5. 4,","label":"BIODEGRAD_PROP"}
{"id":1221,"sentence":"Since the increase of the PLA hydroxyl band after processing is not significant, it seems that degradation occurs mainly by chain scission. Therefore, the presence of moisture results in molecular weight reduction, following the mechanism proposed by Racha Al−Itry (Scheme 1) [10].","label":"BIODEGRAD_PROP"}
{"id":1222,"sentence":"Apparent viscosity versus shear rate curves, (b) shear stress versus shear rate curves. Figure 1a indicates that the apparent viscosity of the PLA and PLA \/ PPG composites decreases with an increasing shear rate from 50 to 3000 s−1.","label":"RHEOLOGICAL_PROP"}
{"id":1223,"sentence":"It has been found that high−molecular−weight PLA is easily polymerized in the presence of tin, zinc, aluminum, and other heavy metal catalysts, with tin (II)","label":"POLY_STRUC"}
{"id":1224,"sentence":"These observed double endothermic peaks are attributed to the different crystal lamella thickness formation. 8 In addition, the Tm of PBAT shifted to low temperature after 30 days conditioning.","label":"POLY_STRUC"}
{"id":1225,"sentence":"The relative mechanical properties showed that some adhesion existed between PLA and the starch granules, but the adhesion was poor. An increase in the starch content resulted in a reduction of tensile strength and elongation of the composites.","label":"MECHANICAL_PROP"}
{"id":1226,"sentence":"The addition of compatibilizers to the PLA \/ PBAT blends results in the droplet relaxation arc appearing incomplete ; in other words, a tail appears on the right side,","label":"BIODEGRAD_POLY"}
{"id":1227,"sentence":"In general, the mechanical properties of semicrystalline polymers are dependent on their molecular weight, crystal size, and percentage of crystallinity. 36 The tensile strength of PBS and PP showed slight enhancement after 6 days of exposure to 50 °C and 90 % RH.","label":"POLY_STRUC"}
{"id":1228,"sentence":"and yard compost environments and in phosphate buffer solution (pH 0 8. 0) and vermiculite at 58 °C. Mineralization, molecular weight reduction,","label":"BIODEGRAD_PROP"}
{"id":1229,"sentence":"They were compared with random copolymers P (3HP−co−25 % 4HB) and P (3HP−co−38 % 4HB) and homopolymers of P3HP and P4HB from previous studies.","label":"BIODEGRAD_POLY"}
{"id":1230,"sentence":"According to manufacturer information, the density and melt flow index of the PP‐1350N are 0.9 g \/ cm3 and 55 g \/ 10 min, respectively.","label":"RHEOLOGICAL_PROP"}
{"id":1231,"sentence":"In other words, after the induction stage, the weight loss began rapidly and followed a characteristic S‐shaped curve. Surprisingly for cPLA, the prior annealing of the samples did not lead to an increased hydrolytic stability.","label":"BIODEGRAD_PROP"}
{"id":1232,"sentence":"After 50 days of immersion, PLLA picked up 1 % moisture, whereas the PLLA \/ cornstarch composites picked up 6 to 8 % moisture, by weight, depending on the composite.","label":"BIODEGRAD_POLY"}
{"id":1233,"sentence":"Longer annealing times are required to produce the more perfect, higher−melting crystals. This is a result of first melting the less perfect, lower−melting crystals and then reforming them into higher−melting, more perfect crystals.","label":"POLY_STRUC"}
{"id":1234,"sentence":"Deterioration is a superficial degradation that modifies mechanical, physical and chemical properties of a given material. The biodeterioration is mainly the result of the activity of microorganisms growing on the surface or \/ and inside a given material (Hueck, 2001,","label":"BIODEGRAD_PROP"}
{"id":1235,"sentence":"The intrinsic viscosity of the PCL was obtained in tetrahydrofuran at 30 °C and the corresponding viscous molecular weight was calculated according to [g 0 1.395 · 10.","label":"RHEOLOGICAL_PROP"}
{"id":1236,"sentence":"3 Enthalpy change during melting determined in the DSC second heating run. Δ Hm) Δ Hi \/ Wi, where Δ Hi is the area of the endothermic peak for the PEG or PCL segment read from the DSC curves and Wi is the weight fraction of the corresponding segment.","label":"BIODEGRAD_POLY"}
{"id":1237,"sentence":"Figure 2 presents the FTIR spectra (3200 – 650 cm−1) of pure PLA, pure PCL, and the separated substances from uncompatibilized and compatibilized PLA \/ PCL (70 \/ 30) blends.","label":"BIODEGRAD_POLY"}
{"id":1238,"sentence":"From solubility studies done at the USDA−ARS−NCAUR, the poly (lactic acid) supplied by Cargill was soluble in benzene, chloroform, 1, 4−dioxane,","label":"BIODEGRAD_POLY"}
{"id":1239,"sentence":"which include polyglycolic acid or polymandelic acid, and are considered biodegradable and compostable. PLA is a thermoplastic, high−strength, high−modulus polymer that can be made from annually renewable resources to yield articles for use in either the industrial packaging field or the biocompatible \/ bioabsorbable medical device market.","label":"MECHANICAL_PROP"}
{"id":1240,"sentence":"From 7 days onward, the mass loss increased significantly at a rate of approximately 0.5 % daily. After 90 days, the PLA32 and PLA118 samples both showed an average mass loss of 50 %.","label":"BIODEGRAD_POLY"}
{"id":1241,"sentence":"Poly (butylene adipate−co−terephthalate) or (PBAT) is biodegradable random copolymer which is flexible. By incorporating with PLA, the PBAT is expected to help improve the flexibility of the polymer blend \/ composite.","label":"BIODEGRAD_POLY"}
{"id":1242,"sentence":"This effect may involve a direct action on mechanism of the hydrolysis or an indirect action by enhancing the activity of thermophylic microorganisms. Although PHB had a higher crystallinity than PHB−V and PCL, temperature was a more important factor in the biodegradation of the polymers than crystallinity.","label":"BIODEGRAD_POLY"}
{"id":1243,"sentence":"and bismuth octoate. The alkali metal carboxylates, such as sodium and calcium, were similar to the carbonates [40]. Previous research has led to the wide use of tin compounds, namely tin (II) bis−2−ethylhexanoic acid (tin or stannous octoate) as a catalyst in PLA synthesis.","label":"BIODEGRAD_POLY"}
{"id":1244,"sentence":"and 5. 09 ppm, respectively, and the results are presented in Table 1.The molar ratios of the BT and BA segments in the macro−initiator and tri−block copolymers was 1 : 1 in accordance with the feed molar ratio of TPA and AA.","label":"POLY_STRUC"}
{"id":1245,"sentence":"Also, the crystalline carbonyl vibration of PLA, 1755 cm−1, cannot clearly be identified in the spectrum (Fig. 2a), however the appearance of the hydroxyl band (3400 cm−1) indicates occurrence of hydrolysis degradation.","label":"POLY_STRUC"}
{"id":1246,"sentence":"Subsequently, the trials were performed for two hours under Newtonian frequency to determine the viscosity evolution under nitrogen atmosphere. The experiments were performed in a nitrogen atmosphere since extrusion and injection can be considered as almost anaerobic processes.","label":"RHEOLOGICAL_PROP"}
{"id":1247,"sentence":"Moreover, the melting temperature (Tm) decreased and enthalpy (Δ Hm) increased by increasing the tri−block copolymer content of the blends. The DMA curves of the PLA \/ PBAT compatibilized by tri−block copolymers are shown in Fig. 6 (A).","label":"POLY_STRUC"}
{"id":1248,"sentence":"and this leads to surface erosion. 6 If water diffusion is faster than degradation, a uniform weight loss is observed, and this is referred to as bulk erosion.","label":"BIODEGRAD_PROP"}
{"id":1249,"sentence":"Together with the insignificant physical mass loss results in the preceding section, it can be deduced that the copolymer films were at the induction phase of degradation undergoing random chain scission.","label":"BIODEGRAD_PROP"}
{"id":1250,"sentence":"Polyhydroxyalkanoates (PHA) are sustainable bioplastics produced by bacteria with biodegradability and biocompatibility. (1−3) PHA have shown their versatile thermal and mechanical properties due to their rich monomer structure variation.","label":"BIODEGRAD_POLY"}
{"id":1251,"sentence":"and differential scanning calorimetry (DSC). Commercial PLA grade (3251D) was supplied by NatureWorks LLC (USA) and according to Csikos et al. [14] it contains less than 2 % D isomer and its density is 1.","label":"BIODEGRAD_POLY"}
{"id":1252,"sentence":"A first order model and an autocatalytic model. For the obtained data, both models provided a reasonable fit of the molecular weight data.","label":"POLY_STRUC"}
{"id":1253,"sentence":"The molecular weights and the amounts of plasticizer govern the usable melt viscosities required for melt processing [5]. As previously mentioned, PLA undergoes thermal degradation at temperatures above 200 °C (3928F).","label":"POLY_STRUC"}
{"id":1254,"sentence":"and their blend was monotonically increased with increasing exposure time up to 34 days. After 34 days exposure, the PBS showed a maximum moisture absorption (1.11 % ± 0.002 %) followed by PBS \/ PBAT (1.05 % ± % 0.01 %)","label":"BIODEGRAD_POLY"}
{"id":1255,"sentence":"At present, the complexity of biodegradation is better understood and cannot be easily summarised (Grima, 2002, Belal, 2003). The biodegradation of polymeric materials includes several steps and the process can stop at each stage (Pelmont, 1995) (Fig. 1)−The combined action of microbial communities, other decomposer organisms or \/ and abiotic factors fragment the biodegradable materials into tiny fractions.","label":"BIODEGRAD_PROP"}
{"id":1256,"sentence":"the vibration frequency shift for the δ−form, when the same vibration modes were compared, was found to be even smaller than that for the γ−form,","label":"POLY_STRUC"}
{"id":1257,"sentence":"Similarly, the PLA32 sample showed an increasing percent crystallinity beginning at day 14 and continuing through day 30.After 30 days of degradation, the PLA32 samples exhibited 71 % crystallinity.","label":"BIODEGRAD_POLY"}
{"id":1258,"sentence":"The activation energies obtained were close to other values reported in the literature for PLA hydrolysis. The ability to manufacture polymer based products from renewable resources is becoming increasingly important as people become more sensitive to the use of fossil fuels for such applications.","label":"BIODEGRAD_PROP"}
{"id":1259,"sentence":"Ndimethyl−aminoethoxide), and lanthanum tris (2, 2, 6, 6−tetramethylheptanedionate) [77 – 82]. EXPERIMENTAL RESULTS AND DISCUSSION OF POLY (LACTIC ACID) The mechanical properties and crystallization behavior of PLA is very dependent on the molecular weight and stereochemical makeup of the backbone.","label":"BIODEGRAD_POLY"}
{"id":1260,"sentence":"and PBS \/ PBAT samples was examined after exposure to elevated temperature and humidity. As a result of chain scission through the hydrolysis mechanism, the elongation at break and tensile strength of the PBS, PBAT,","label":"BIODEGRAD_POLY"}
{"id":1261,"sentence":"The density of amorphous PLLA is 1.248 g \/ ml. The density for crystalline PLLA is 1.290 g \/ ml. Table VII.","label":"BIODEGRAD_POLY"}
{"id":1262,"sentence":"The degradation behavior of PLA depends largely on the molecular weight, crystallinity, geometry, and surrounding environment (temperature, moisture, pH, presence of micro‐organisms, etc.).","label":"POLY_STRUC"}
{"id":1263,"sentence":"Some extracellular enzymes, in particular the peroxidases, are able to couple the oxidation of cations and the catalytic degradation of hydrocarbons (Enoki et al., 1997,","label":"BIODEGRAD_PROP"}
{"id":1264,"sentence":"The hydrolytic degradation of the polymer matrix is affected by the amount of crystallinity in the samples. It has been shown that highly crystalline PLA will take months, sometimes years, to hydrolyze fully to lactic acid, whereas an amorphous sample is degraded in weeks.","label":"POLY_STRUC"}
{"id":1265,"sentence":"380 g \/ cm3. Thus, the present results indicate that the densities of the δ−and γ−forms are larger than that of the β−form,","label":"POLY_STRUC"}
{"id":1266,"sentence":"Initially, the PBAT film had a fBA \/ fBT ratio of 0.59 \/ 0.41, but as the hydrolysis proceeded and reduction of Mn was observed,","label":"BIODEGRAD_PROP"}
{"id":1267,"sentence":"the complete renewal of the hydrolysis media was done as soon as the pH level was varied by 0.5 units. The acidic hydrolysis media was not renewed because its pH level did not change significantly.","label":"BIODEGRAD_PROP"}
{"id":1268,"sentence":"The addition of talc reduced the 110 °C half time from 180 sec to 25 sec for pure poly (L−lactide) and from 420 to 60 sec for a 3 % meso containing polymer.","label":"BIODEGRAD_POLY"}
{"id":1269,"sentence":"and Tmax, 2 and Tmax, 3 for that of PI midblock. Dynamic mechanical analysis (DMA) was used to synchronously characterize both the thermal behavior and mechanical property with an oscillatory stress applied to the triblock copolymers in a wide temperature range.","label":"MECHANICAL_PROP"}
{"id":1270,"sentence":"Schyichuk et al., 2001). In abiotic degradation, the action of light radiation is one of the most important parameters. The Norrish reactions express photodegradation that transform the polymers by photoionisation (Norrish I)","label":"BIODEGRAD_PROP"}
{"id":1271,"sentence":"The multiformity in conformation and packing obviously make P3HP an ideal substrate to explore the possible dependence of enzymatic degradability on the crystalline structure. Moreover, as all P3HAs hold the significant similarity in chemical and crystalline structures,","label":"BIODEGRAD_POLY"}
{"id":1272,"sentence":"Pepic et al., 2008). In the case of bulk erosion, fragments are lost from the entire polymer mass and the molecular weight changes due to bond cleavage.","label":"BIODEGRAD_PROP"}
{"id":1273,"sentence":"Fig. 1.(a) TGA and (b) derivative TGA curves for PLA−CTA, PI10k and solvent−cast PLA−b−PI−b−PLA triblock copolymers measured at a heating rate of 10 oC \/ min under nitrogen atmosphere.","label":"BIODEGRAD_POLY"}
{"id":1274,"sentence":"Park [123] reported a decrease in the crystallization temperature with an increase in the starch content. The lowest PLLA crystallinities occurred at 60 % cornstarch and 50 % wheat starch [134].","label":"POLY_STRUC"}
{"id":1275,"sentence":"Tsuji et al., 2006). Crystallinity is determined by X−ray diffraction (Ki and Park, 2001, Abd El−Rehim et al., 2004,","label":"POLY_STRUC"}
{"id":1276,"sentence":"Generally, the environmental temperature is lower than the melting point of thermoplastic polymers. However, some thermoplastic polymers as PCL (tm ≈ 60 °C)","label":"POLY_STRUC"}
{"id":1277,"sentence":"The shear viscosity values of the samples both before and after conditioning were measured at 140 °C from 300 to 0.01 rad \/ s. RESULTS AND DISCUSSION Moisture Absorption Moisture absorption of all the samples was investigated as a function of exposure time.","label":"BIODEGRAD_PROP"}
{"id":1278,"sentence":"6 kg \/ mol. The behavior of cPLA was slightly different because only one Tm value was found for all Mw values. Before hydrolysis, cPLA showed a Tm value of 166 °C, but no crystallinity was initially present, as evidenced by the fact that the melting enthalpy was equal to the crystallization exotherm.","label":"POLY_STRUC"}
{"id":1279,"sentence":"Tsuji and Ikada, 2000, Yi et al., 2004). Hydrolysis is dependent on parameters as water activity, temperature, pH and time.","label":"BIODEGRAD_PROP"}
{"id":1280,"sentence":"The samples degraded at 60 °C showed an increase in the PDI up to 4. 0 at day 7. This increase in PDI can be attributed to the favored degradation in the amorphous regions of the samples.","label":"BIODEGRAD_PROP"}
{"id":1281,"sentence":"2 FTIR absorption characteristics FTIR absorption peaks for the neat PLA, PBAT and PLA \/ PBAT blends are given in Table 2. For PLA, the peak at around 752 cm−1 associated with the rocking vibration of α−methyl ; peak at around 864 cm−1 associated with the ester (O−CH−CH3) ; the peak at around 1042 cm−1, 1080 cm−1 and 1180 cm−1 associated Fig. 3.","label":"BIODEGRAD_POLY"}
{"id":1282,"sentence":"and used for the degradation experiments. After placing the films (≈ 20 mg) into test‐tubes, 10 mL of degradation buffer solution at either pH 7.","label":"BIODEGRAD_PROP"}
{"id":1283,"sentence":"Both glass transition and melting temperatures, Tg and Tm, were recorded. 2. 3 Thermogravimetry (TGA) The thermal degradation behavior was investigated in the thermogravimetric analyzer NETZSCH TG 209 under non−isothermal and isothermal conditions in a nitrogen flow environment.","label":"POLY_STRUC"}
{"id":1284,"sentence":"These FTIR results support that electron−beam−initiated cross−copolymerization had occurred in the presence of GMA at the PLA \/ PCL interface [21].","label":"BIODEGRAD_POLY"}
{"id":1285,"sentence":"4 N \/ A Elongation at break (%) 3. 1 – 5. 8 15 – 160 Rockwell hardness 82 – 88 82 – 88 Specific gravity (g \/ cm3) 1.25 1.25 Glass transition temperature (°C) 57 – 60 57 – 60 a Results depend on degree of orientation and isomer content.","label":"MECHANICAL_PROP"}
{"id":1286,"sentence":"This was associated with different degradation processes (mainly chain scission) that took place under the two conditions. Given the PLA robustness to endure reprocessing, it was possible to conclude that the primary and secondary antioxidant (B900) had a synergetic effect on PLA stability.","label":"BIODEGRAD_PROP"}
{"id":1287,"sentence":"17 Usually, the hydrolytic degradation and biodegradability of the polymers mainly depend on the easily hydrolysable ester functionality in the polymer backbone. In the present study, PP did not show any significant reduction in the tensile strength up to 30 days conditioning,","label":"BIODEGRAD_PROP"}
{"id":1288,"sentence":"However, after 6 days of exposure ; PBAT as well as PBS \/ PBAT blend showed a slight reduction in tensile strength. This could be due to the plasticization effect of hydrolytically degraded amorphous region in the PBAT.","label":"BIODEGRAD_POLY"}
{"id":1289,"sentence":"Eq. 6 corresponds to chain scissions attributed to initially present structural irregularities along the backbone, of which the initial concentration is s20.Eq. 7 corresponds to random chain scissions occurring in regular portions of the polymer chains, mainly in crystalline zones, being s30 the initial monomer concentration. k1, k2 and k3 are first order rate constants obeying the Arrhenius law.","label":"BIODEGRAD_PROP"}
{"id":1290,"sentence":"PCL had the lowest crystallinity and PHB the highest. There was no correlation between crystallinity and the extend of polymer biodegradation. Biodegradation can be studied using several approaches that range from direct incubation in an environment with an undefined biocenosis, to testing in highly defined synthetic media with selected cultures [1].","label":"BIODEGRAD_POLY"}
{"id":1291,"sentence":"the MATEC Web of Conferences 192, 03014 (2018) https : \/ \/ doi. org \/ 10.1051 \/ matecconf \/ 201819203014 ICEAST 2018 3 finding could be clearly seen in treatments PLA, PLAF and PP. 3. 1.3 Elongation at break PBAT showed a distinctively high value of elongation at break (Eb), around 477−458 %, as compared to that of PLA (around 8−12 %)","label":"BIODEGRAD_POLY"}
{"id":1292,"sentence":"The intrinsic viscosity decreased around 27 % up to 5 min, which could be attributed to non−radical reactions (Scheme 1), since the stabilizer cannot prevent its occurrence.","label":"RHEOLOGICAL_PROP"}
{"id":1293,"sentence":"Examples are polylactide (PLA) [4], [5], poly (butylene succinate) (PBS) [6], [7], poly (caprolactone) (PCL) [8], [9],","label":"BIODEGRAD_POLY"}
{"id":1294,"sentence":"The PP, PBS, and PBS \/ PBAT blend showed a drastic decrease in the percent elongation after 6 days conditioning. Therefore, it is clear that the toughness is more sensitive than the strength after being exposed to raised humidity and temperature.","label":"BIODEGRAD_POLY"}
{"id":1295,"sentence":"This change in crystallization process from rapidly forming, lower−melting crystals to more slowly reforming, higher−melting crystals occurred gradually as the annealing temperature progressed from 100 °C to 140 °C [100].","label":"POLY_STRUC"}
{"id":1296,"sentence":"This resulted from the melt‐recrystallization of PBS while heating. 47 However, after 30 days exposure, PBS and PBS \/ PBAT samples displayed a bimodal melting peak, as shown in Figure 11.","label":"BIODEGRAD_POLY"}
{"id":1297,"sentence":"Thermo Fisher Scientific, Karlsruhe, Germany). The trend of the melt torque of the PLA \/ PPG composites as a function of processing time and temperature was investigated.","label":"RHEOLOGICAL_PROP"}
{"id":1298,"sentence":"01 to 100 Hz were conducted and 5 % of strain was chosen. Because the molecular weight of the segmental structure of the compatibilizer can be expected to greatly affect its performance when blending, accurate quantitative synthesis of the compatibilizer is critical.","label":"POLY_STRUC"}
{"id":1299,"sentence":"Variations such as block and star copolymers of D−and L−lactide show this same stereocomplexation [1]. Table I. Calculated and Observed d Spacings (A) ofthe b Structure of Poly (L−Lactide) with the Orthorhombic Unit Cell ;","label":"BIODEGRAD_POLY"}
{"id":1300,"sentence":"32 MPa, respectively, whereas random copolymers P (3HP−co−25 % P4HB) and P (3HP−co−38 % P4HB) had 6.","label":"BIODEGRAD_POLY"}
{"id":1301,"sentence":"More importantly, the long term degradation would result in the formation of water soluble products. By knowing the composition of the water soluble degradation products, it is hoped that this would enable researchers to predict the toxicity and biocompatibility of these products which are often found at the final stages of degradation.","label":"BIODEGRAD_PROP"}
{"id":1302,"sentence":"A solvent−casting method was used to prepare the solvent−cast PLA−b−PI−b−PLA films. THF was used to dissolve PLA−b−PI−b−PLA triblock copolymers.","label":"BIODEGRAD_POLY"}
{"id":1303,"sentence":"L. jensenii, or L. acidophilus yield the D−isomer or mixtures of both [1]. Actually, the analytical techniques used to estimate the thermodegradation are very similar to those that are used for the estimation of photodegradation (i. e. tensile tests, TGA, GPC, FTIR, NMR and GC – MS) (Bikiaris et al., 1997a,","label":"MECHANICAL_PROP"}
{"id":1304,"sentence":"Aiming to answer all the issues referred above, the packing and dynamics of the β−form, γ−form, and δ−form crystals were investigated.","label":"POLY_STRUC"}
{"id":1305,"sentence":"5 μm to 0.5 μm. Abstract Polylactide−poly (butylene adipate−co−terephthalate)−polylactide tri−block copolymers incorporating PLA blocks (LPB and HPB) with different chain lengths were synthesized as compatibilizers for PLA \/ PBAT blends.","label":"BIODEGRAD_POLY"}
{"id":1306,"sentence":"22 Consequently, it has become important to develop accelerated hydrolytic tests at higher temperatures17, 19, 21 that can help to predict the behavior of resorbable devices in biomedical applications.","label":"BIODEGRAD_PROP"}
{"id":1307,"sentence":"Figure 7 Evolution of versus time for compatibilized PLA \/ PCL (90 \/ 10) (○), uncompatibilized PLA \/ PCL (90 \/ 10) (○), compatibilized PLA \/ PCL (70 \/ 30) (■),","label":"BIODEGRAD_POLY"}
{"id":1308,"sentence":"The rheological analysis of polymer melts allows one to translate the viscosity in terms of weight average molar mass using the well known power law, go 0 KMw 3. 4, provided that the Newtonian plateau (at which the viscosity is go) is observed and calibration is made by means of Steric Exclusion Chromatography (SEC).","label":"RHEOLOGICAL_PROP"}
{"id":1309,"sentence":"This model would be best suited for describing the degradation of PLA at the beginning of the degradation process when the concentration of acid groups is initially very low.","label":"BIODEGRAD_PROP"}
{"id":1310,"sentence":"The self−condensation of lactic acid results in a low−molecular−weight product with an equimolar concentration of hydroxyl and carboxyl end−groups. To increase the molecular weight, chain−coupling agents must be added,","label":"POLY_STRUC"}
{"id":1311,"sentence":"Fig. 3A, there was little statistically observable change in the melting temperature with degradation time and no multimodal DSC patterns that would influence Tm. The average Tm for both fibers was 168 °C.","label":"POLY_STRUC"}
{"id":1312,"sentence":"and poly (ethylene glycol) (PEG) was studied at pH 7. 4 and pH 9. 5 at 37 °C. By a combination of techniques,","label":"BIODEGRAD_POLY"}
{"id":1313,"sentence":"which should reflect the increased intermolecular interaction and depend on the chain packing. These splittings were found to be drastically enhanced by cooling and could be attributed to the correlation field splitting, indicating the tight chain packing of the δ−and γ−form.","label":"POLY_STRUC"}
{"id":1314,"sentence":"Thermo Fisher Scientific, Karlsruhe, Germany), and then pulverized. The pellets of the PLA \/ PPG composites were dried in an oven at 80 °C for 10 h before the capillary rheological and thermal characterizations.","label":"BIODEGRAD_POLY"}
{"id":1315,"sentence":"and food (36. 0 ± 1.7) composts were well within the recommended C \/ N range of 10 to 40.Therefore, this confirms that microbial activity of the compost and the C \/ N ratio play a significant role in the total biodegradation of biodegradable plastics as inferred by Ishii and Takii [20],","label":"BIODEGRAD_PROP"}
{"id":1316,"sentence":"On comparing the all−trans with 21−helix P3HP chains, it is found that β CH2 of the former is eclipsed by the oxygen of its γ−neighboring carbonyl, while that of the latter is not.","label":"POLY_STRUC"}
{"id":1317,"sentence":"which is made by a microbial fermentation product, lactic acid. Being non−toxic, completely biodegradable, highly transparent, strong, and stiff, PLA is one of the ideal materials to replace traditional plastics to alleviate environmental issues.","label":"BIODEGRAD_PROP"}
{"id":1318,"sentence":"Table XV. Primary Transition Temperatures of Selected PLA Glass transition Melting Temperature, Copolymer ratio temp. (°C) (°C) 100 \/ 0 (L \/ D,","label":"BIODEGRAD_POLY"}
{"id":1319,"sentence":"33 Generally, the hydrolytic degradation of the biodegradable polymers is higher in the amorphous regions than crystalline regions under high humidity. 39 A similar type of observation has been made in PBS, PBAT, PBS \/ PBAT,","label":"POLY_STRUC"}
{"id":1320,"sentence":"A Waters Breeze gel permeation chromatography system with a Waters Styragel HR5E column interfaced with a differential refractometer was used to obtain the number average molecular weight, Mn,","label":"POLY_STRUC"}
{"id":1321,"sentence":"Figure 6 and Figure 7 and Table 2. The relative reduction ratio of the temperature−adjusted torque can be used to indicate the rate of degradation during processing.","label":"BIODEGRAD_PROP"}
{"id":1322,"sentence":"The influence of moisture and heat on the mechanical properties was measured by tensile and flexural properties as well as impact strength. The mechanical properties of neat PBS, PBAT, PBS \/ PBAT blend,","label":"MECHANICAL_PROP"}
{"id":1323,"sentence":"11 found an intermediate value of 379 K for the hydrolysis of amorphous PLA over a temperature range from 37 to 90 °C. Table 3. Vogel – Tammann – Fulcher Equation Parameters for PLA Hydrolysis in Aqueous Media (E \/ R) 1 (K) k01 (days−1)","label":"BIODEGRAD_PROP"}
{"id":1324,"sentence":"the low‐molecular‐weight portion of the distribution was automatically subtracted. In addition to the actual molecular weight reduction by hydrolysis, this effect artificially reduced the kinetics because we could no longer account for the lower Mw species.","label":"POLY_STRUC"}
{"id":1325,"sentence":"4 N \/ A Tensile modulus (psi 3 103, MPa) 500 – 580, 3447 – 4000 564 – 600, 3889 – 4137 Notched izod impact (ft−lb \/ in.) 0.3 – 0.","label":"MECHANICAL_PROP"}
{"id":1326,"sentence":"This type of phenomenon is commonly found in the polymers when exposed to a degradation environment. 52, 53 Interestingly, the amount of spherulite formation was higher in the samples with a lower percentage of crystallinity.","label":"BIODEGRAD_PROP"}
{"id":1327,"sentence":"and 1 (d)). In addition, the diameters of dispersed PCL particles were smaller in compatibilized blends, which were attributed to reduced interfacial tension difference between the two phases.","label":"BIODEGRAD_POLY"}
{"id":1328,"sentence":"Besides presenting interesting qualities, such as good processability and good mechanical properties, it is suitable for many applications and also has low environmental impact, as shown in Life Cycle Analysis [6], [6] [a], [6] [b].","label":"MECHANICAL_PROP"}
{"id":1329,"sentence":"The growth of the crystals occurred along four planes. For single crystals prepared from p−xylene at 90 °C, the thickess of the lamellae was 12 nm,","label":"POLY_STRUC"}
{"id":1330,"sentence":"Apparently, all WAXD curves for melt−quenched PLA−b−PI−b−PLA triblock copolymers only display a singular peak for each, representing the amorphous halo for non−crystallized samples,","label":"BIODEGRAD_POLY"}
{"id":1331,"sentence":"As a thermoplastic polyester derived from natural resources such as corn starch and cane sugar, poly (lactic acid) (PLA) is gaining popularity in the medical, packaging, and textile industries because of its renewable feed stock and its ability to degrade under a variety of conditions.","label":"BIODEGRAD_POLY"}
{"id":1332,"sentence":"Since relatively few studies have appeared in the open literature concerning PCL and PLLA thermal stability based on rheological studies, this paper presents a comprehensive study of the thermal degradation of PCL and PLLA based on rheological experiments at different temperatures, including the modeling of their chain scission process.","label":"BIODEGRAD_POLY"}
{"id":1333,"sentence":"Ceast, Torino, Italy) at 170 °C with a shear rate of 50 – 3000 s−1.The melt flow properties of the PLA \/ PPG composites during processing were investigated by a torque rheometer (Rheo Drive 7,","label":"RHEOLOGICAL_PROP"}
{"id":1334,"sentence":"Mv : molecu−Fig. 1.Weight loss profile of PLLA, PCL and PET at a heating rate of lar weight (viscometric) 10 °C \/ min 390 Intern.","label":"BIODEGRAD_POLY"}
{"id":1335,"sentence":"In this review, we describe the different stages of biodegradation and we state several techniques used by some authors working in this domain. Validate assimilation (including mineralisation) is an important aspect to guarantee the real biodegradability of items of consumption (in particular friendly environmental new materials).","label":"BIODEGRAD_PROP"}
{"id":1336,"sentence":"Crystallization Half Time (Minutes) Data for Polylactide with 6 wt % Talc [103] Temperature (°C) 0wt % meso (Mn 0 123 K) 3wt % meso (Mn 0 105 K) 6wt % meso (Mn 0 122 K) 9wt % meso (Mn 0 81 K)","label":"POLY_STRUC"}
{"id":1337,"sentence":"and weight average molecular weight, Mw, of the PLA samples before and after degradation. PLA samples were dissolved in chloroform (Burdick & Jackson, HPLC grade) to achieve a nominal concentration of 1 mg mL−1.","label":"POLY_STRUC"}
{"id":1338,"sentence":"These authors reported that increasing the temperature favored the degradation of poly (glycolic acid) (PGA) sutures over the range of 25 to 50 °C.","label":"BIODEGRAD_PROP"}
{"id":1339,"sentence":"Previous studies have shown that the activation energy for polyester hydrolysis is greatly effected by increasing the degradation temperature from below to above Tg. Activation energies obtained by Agrawal et al. above Tg were nearly half of the activation energies obtained for samples degraded below Tg 32.","label":"BIODEGRAD_PROP"}
{"id":1340,"sentence":"Table XXVI. Mechanical Properties of Composites Containing Cornstarch and Wheat Starch with Various Blending Ratios Composite Tensile strength (MPa) Elongation at break (%) Modulus (GPa) PLLA 61 6 1.07 6. 33 6 0.33 1.204 6 0.","label":"MECHANICAL_PROP"}
{"id":1341,"sentence":"the loss tangent change of PLA end blocks as reflected by DMA is extensive and global, thus, it is much sensitive to the consecutive PI midblock length.","label":"MECHANICAL_PROP"}
{"id":1342,"sentence":"Also discussed are the effects of processing on PLA. Crystallization and crystallization kinetics of PLA are also investigated. Solution and melt rheology of PLA is also discussed.","label":"BIODEGRAD_POLY"}
{"id":1343,"sentence":"The addition of poly (L−lactide−co−caprolactone) (PLLA−CL) as a polymeric compatibilizer [3, 4] is one of the common ways to increase compatibility of the PLA \/ PCL blend [3, 4].","label":"BIODEGRAD_POLY"}
{"id":1344,"sentence":"Table 2 lists the corresponding thermal stability parameters as obtained from the TGA curves. As shown in Fig. 1a and Fig. S1 (in the Supplementary Material),","label":"MECHANICAL_PROP"}
{"id":1345,"sentence":"Annealed L−PLA L−PLA D, L−PLA Tensile strength (MPa) 59 66 44 Elongation at break (%) 7. 0 4. 0 5. 4 Modulus of elasticity (MPa) 3750 4150 3900 Yield strength (MPa) 70 70 53 Flexural strength (MPa) 106 119 88 Unnotched izod impact (J \/ m) 195 350 150 Notched izod impact (J \/ m) 26 66 18 Rockwell hardness 88 88 76 Heat deflection temperature (°C) 55 61 50 Vicat penetration (°C) 59 165 52 Table XII.","label":"MECHANICAL_PROP"}
{"id":1346,"sentence":"C and 20 rpm, and were subjected to compression moulding at 165. C and 1 MPa for 5 min. The treatment PLAF was prepared so that PLA remained in a form of fiber. PLA was first melted using an extruder at 170.","label":"BIODEGRAD_POLY"}
{"id":1347,"sentence":"There exist normalised tests to estimate the biodeterioration by the colonisation of microorganisms on Petri dishes (ASTM G21−70, 1980, ASTM G22−76, 1996, ISO 846, 1997, NF X41 – 514, 1981, NF X41−513, 1961, ISO 11266, 1126,","label":"BIODEGRAD_PROP"}
{"id":1348,"sentence":"14 Softening range, (°C) 125 – 135 °C 125 – 135 °C Table X. Comparison of Physical Properties of High−Molecular−Weight PLA [5, 62, 111]","label":"POLY_STRUC"}
{"id":1349,"sentence":"Fig. 7 indicates excellent relationship between the melting temperature and average molecular weight of PLA. An increase on processing time led to a decrease in average number molecular weight and, consequently, on Tm.","label":"POLY_STRUC"}
{"id":1350,"sentence":"It is important to develop new comparative tests to estimate their biodegradability. Actually, it seems to have confusion in the interpretation of biodegradation, biofragmentation and biodeterioration.","label":"BIODEGRAD_PROP"}
{"id":1351,"sentence":"or meso−lactide. Figure 2 demonstrates the synthesis of PLA from the lactide ring. The D−lactide and L−lactide enantiomers can form a 1 : 1 racemic stereocomplex (D,","label":"BIODEGRAD_POLY"}
{"id":1352,"sentence":"and 7 rad \/ s (PLA \/ PCL (70 \/ 30) blend), respectively (arrows in Figure 4). This increase in the storage moduli of uncompatibilized blends might be caused by hydrogen bonding interaction between ester carbonyls and hydroxyls of PCL and PLA at the interface [30].","label":"BIODEGRAD_POLY"}
{"id":1353,"sentence":"Results showed that Es decreased over the degradation period (Supporting Information Table A11). The rate of decrease of the ester bonds will follow a pseudo‐first‐order rate kinetics as described by eq.","label":"BIODEGRAD_PROP"}
{"id":1354,"sentence":"The crystallinity was reported to be 3. 9 %. The following equation was used to calculate the percentage crystallinity of PLLA in the blends [134] :","label":"POLY_STRUC"}
{"id":1355,"sentence":"0021 d−1) are among the lowest. The reduction of Mn of PBAT from biodegradation in yard compost was not different from those from hydrolysis due to the low microbial activity of yard compost, as indicated by poor CO2 emissions and a too high C \/ N ratio.","label":"BIODEGRAD_PROP"}
{"id":1356,"sentence":"and compatibilized PLA \/ PCL (90 \/ 10) blends irradiated at 5 kGy (◇), 10 kGy (◆), 20 kGy (•), 50 kGy (□), 100 kGy (■),","label":"BIODEGRAD_POLY"}
{"id":1357,"sentence":"at 40 %, preparing PLA in the form of fiber yields the higher UTS value than melting and blending with PBAT. treatment PLA40.The UTS value of PLAF was close to that of PP, but statistically significantly lowers.","label":"BIODEGRAD_POLY"}
{"id":1358,"sentence":"The degradation of amorphous and semicrystalline PLA grades (i. e., grades differing in optical purity) was investigated. The degradation of the amorphous grade was found to be slightly faster than that of the crystallizable PLA grade, but the two materials exhibited very similar responses to changes in the media acidity and media temperature.","label":"POLY_STRUC"}
{"id":1359,"sentence":"As shown in Figure 1 (c), the uncompatibilized PLA \/ PCL (70 \/ 30) blend had much larger PCL particles than the PLA \/ PCL (90 \/ 10) blend (Figure 1 (a))","label":"BIODEGRAD_POLY"}
{"id":1360,"sentence":"Weight Loss Measurement Samples removed from the hydrolysis media were wiped dry and weighed to determine the wet weight. The weight of the dried samples (Wdry) was then measured,","label":"BIODEGRAD_PROP"}
{"id":1361,"sentence":"From the above results, it can be seen that the network of glassy PLA domains and that of PLA crystals both involve in producing the final mechanical properties.","label":"BIODEGRAD_POLY"}
{"id":1362,"sentence":"Modeling Hydrolytic Degradation Hydrolytic degradation of PLA is a multi‐step process. When PLA is exposed to an aqueous environment, water will begin to diffuse into the amorphous portions of the polymer and begin to react with the ester linkages.","label":"BIODEGRAD_PROP"}
{"id":1363,"sentence":"The reduction of Mn from biodegradation in compost and hydrolysis in both media follows a first order reaction, where the rate constants (k) can be obtained from the slopes as shown in Table 1.","label":"BIODEGRAD_PROP"}
{"id":1364,"sentence":"In biodegradation of PBAT in manure, yard, and food composts, increased heat of fusion (Δ Hf) from DSC thermograms was observed in all three composts as biodegradation proceeded (Fig 6), indicating increased crystallinity as a result of the amorphous regions being degraded first.","label":"BIODEGRAD_PROP"}
{"id":1365,"sentence":"Not for electronic distribution. The number of chain scissions was calculated as follows : s 1⁄4 1 Mn. 1 Mn0.. 1⁄4 p Mw. p0 Mw0.. ; ð 2 Þ where Mn is the number average molar mass and p the polydispersity index.","label":"POLY_STRUC"}
{"id":1366,"sentence":"Crystallinity Data for the Copolymer Films After Undergoing Hydrolysis at pH 9. 5 Enthalpy change during melting determined in the DSC second heating run. Δ Hm)","label":"POLY_STRUC"}
{"id":1367,"sentence":"Kim et al., 2006b) (Table 2). CO2, ethanol, lactate, acetate and butanediol) (Regnault, 1990, Brock and Madigan, 1991,","label":"BIODEGRAD_PROP"}
{"id":1368,"sentence":"In addition, Lindstr ö m et al., 2004a, Lindstr ö m et al., 2004b have measured the biodeterioration of PBA and PBS by the quantification of the production of adipic acid, succinic acid and 1, 4−butanediol.","label":"BIODEGRAD_POLY"}
{"id":1369,"sentence":"This finding indicated that a long chain in the tri−block copolymers was more effective to compatibilize PLA and PBAT. Fig. 5. DSC curves of blends with different amounts of compatibilizers.","label":"POLY_STRUC"}
{"id":1370,"sentence":"The reaction mechanism of PLA thermo−degradation was explained by McNeill and Leiper [21] who assumed that, under these conditions, the main reaction is non−radical with intramolecular trans−esterification, depending on the point in the polymer backbone where this reaction occurs.","label":"BIODEGRAD_POLY"}
{"id":1371,"sentence":"the onset decomposition temperature, Tonset for PLA−b−PI−b−PLA triblock copolymers increases from 324. 3 to 329. 3 °C with increasing molecular mass of PI midblock,","label":"POLY_STRUC"}
{"id":1372,"sentence":"The two block copolymers P3HP−b−29 % P4HB and P3HP−b−37 % P4HB had tension strengths of 44. 71 and 25.","label":"BIODEGRAD_POLY"}
{"id":1373,"sentence":"Ea 0 energy of activation R 0 gas constant T 0 polymerization temperature in Kelvin DH 0 enthalpy of polymerization DS 0 entropy of polymerization The rates of chain growth vary greatly in a polymerization catalyzed with tin octoate and depend not only on impurities but also on the formation of crystalline phases during polymerization.","label":"POLY_STRUC"}
{"id":1374,"sentence":"Before conditioning ; all the samples showed a single melting temperature (Tm). In the heating cycles (Figure 11), a small exothermic peak was also observed for PBS and PBS \/ PBAT prior to melting peak.","label":"BIODEGRAD_POLY"}
{"id":1375,"sentence":"The different percentages of the lactide isomers formed depends on the lactic acid isomer feedstock, temperature, and catalyst [1]. The polymerization proceeds via triflate ester end−groups instead of free carbenium ions,","label":"BIODEGRAD_POLY"}
{"id":1376,"sentence":"Heating rate (°C \/ min) b 4 1.2 5 1.3 8 1.4 The Hoffman – Weeks equation can be alternatively written as [97] where lc is the lamella thickness.","label":"POLY_STRUC"}
{"id":1377,"sentence":"21 MPa, significantly higher than P (3HP−co−38 % P4HB) having a Young ’ s modulus of only 4. 40 MPa.","label":"BIODEGRAD_POLY"}
{"id":1378,"sentence":"which are 3. 07 ± 0.58 Å away from each other in the reactants, occurs concomitantly with the formation of the C – O bond between Ser160 and the PCL model compound (1.14 ± 0.","label":"BIODEGRAD_POLY"}
{"id":1379,"sentence":"It can be also seen that the crystallinity of PLA domains can also obviously enhance the ultimate tensile strength apparently due to the formation of crystal network in the samples.","label":"POLY_STRUC"}
{"id":1380,"sentence":"4 and 9. 5. On the basis of the above analysis, it can be concluded that degradation occurred via random hydrolytic ester cleavage along the PCL segments.","label":"BIODEGRAD_PROP"}
{"id":1381,"sentence":"This is corresponding to the higher rate of hydrolytic degradation of PBS after conditioning for 30 days under the simulated environment. 8 In addition, an irregular fractured surface was observed in the 30 days conditioned PBS sample.","label":"BIODEGRAD_PROP"}
{"id":1382,"sentence":"and the parameters calculated from those are depicted in Table 4. As can be seen, the processed PLA samples exhibit a decrease in the melting temperature (Tm), an increase in the melting enthalpy and, consequently, an increase in crystallinity.","label":"POLY_STRUC"}
{"id":1383,"sentence":"Following the designated degradation time, the samples were dried and re‐weighed to obtain the weight of remaining material, Md. The percentage of mass loss was then calculated as Mass loss % 0 100 x (Mi – Md) \/ Mi.","label":"BIODEGRAD_PROP"}
{"id":1384,"sentence":"Tables XIII and XIV summarize the molecular weights of general−purpose and injection−mold−grade PDLLA prior to and after processing. Table XI. Effects of Stereochemistry and Crystalllinity on Mechanical Properties [1, 110]","label":"POLY_STRUC"}
{"id":1385,"sentence":"The molecular weights and polydispersity indexes (PDI) were measured by GPC. Table 1 lists the number average molecular weight (Mn) and weight average molecular weight (Mw) of the macro−initiator as 17.","label":"POLY_STRUC"}
{"id":1386,"sentence":"which, for the most part, is unusable for any applications unless external coupling agents are used to increase the molecular weight of the polymer. The molecular weight of this condensation polymer is low due to the viscous polymer melt,","label":"POLY_STRUC"}
{"id":1387,"sentence":"the mechanism of cellulose degradation by free radicals has been described by Hammel et al. (2002). A polymer is considered as fragmented when low molecular weight molecules are found within the media.","label":"BIODEGRAD_PROP"}
{"id":1388,"sentence":"and uncompatibilized PLA \/ PCL (70 \/ 30) (□) blends at 190 °C. For compatibilized blends, however, complex viscosities were much higher than those of pure PLA or pure PCL and showed strong shear thinning behavior over the whole frequency range.","label":"BIODEGRAD_POLY"}
{"id":1389,"sentence":"at early stages of hydrolysis, that is, up to 3 days, a monomodal distribution was observed. This was gradually transformed into a bimodal distribution between the 5th and 10th day of hydrolysis.","label":"BIODEGRAD_PROP"}
{"id":1390,"sentence":"Our most recent work found that the enzymatic degradability of P3HP quite depends on the crystalline structure. (5d) The enzymatic degradation rate of the δ−form was almost 1 order of magnitude smaller than that of the fastest degraded β−form.","label":"BIODEGRAD_PROP"}
{"id":1391,"sentence":"There was also an insignificant mass loss of the films observed. Mass spectroscopy was used to determine the nature of the water soluble products of degradation. At pH 7. 4, a variety of oligomers with different numbers of repeating units were present whereas the harsher degradation conditions at pH 9.","label":"BIODEGRAD_PROP"}
{"id":1392,"sentence":"and good biocompatibility, can be molded by injection and extrusion or blended with other polymers [14], [15]. PCL is inherently biodegradable in soil and is more resistant to hydrolysis than other aliphatic polyesters, thus minimizing the premature loss of properties [16].","label":"BIODEGRAD_PROP"}
{"id":1393,"sentence":"and \/ or (200)), the lateral crystal sizes (by the Scherrer equation) can be calculated [33, 34]. Fig.","label":"POLY_STRUC"}
{"id":1394,"sentence":"Therefore, this indicates that the ester groups in the soft aliphatic BA section are more susceptible to hydrolysis, consequently making the BA sections more susceptible to biodegradation than the hard aromatic BT sections, as previously suggested by Kasuya et al. [23],","label":"BIODEGRAD_PROP"}
{"id":1395,"sentence":"Figure 1.Neat polylactic acid (PLA) and polylactic acid \/ polypropylene glycol (PLA \/ PPG) composites capillary rheology test results : (a)","label":"BIODEGRAD_POLY"}
{"id":1396,"sentence":"Table 4. DSC parameters for the thermal transitions observed to PLA and PLA + B900.To investigate the effect of B900 more deeply, size exclusion chromatography tests were performed and correlated with Tm.","label":"BIODEGRAD_POLY"}
{"id":1397,"sentence":"and F4HB * 4HB (FX * Y represents the molar fraction of XY sequence) : (1) To determine whether a polymer is a random copolymer or not, a parameter D is defined as following : (2)","label":"POLY_STRUC"}
{"id":1398,"sentence":"which was attributed to the enhanced intermolecular interaction at a lower temperature. (16a) In particular, the blue−shift of the CH2 rocking was found to linearly correlated to lateral dimensions of PE unit cell, due to its high sensitivity to intermolecular interactions.","label":"POLY_STRUC"}
{"id":1399,"sentence":"32 A similar type of hydrolytic degradation mechanism was proposed for PLA, 13 PBS, 8, 33 and poly (ethylene terephthalate) (PET).","label":"BIODEGRAD_POLY"}
{"id":1400,"sentence":"Since, in the present work, there was no CH2 protons signal in 1H NMR, this mechanism, if present, must be secondary or of minor importance during the thermal degradation.","label":"BIODEGRAD_PROP"}
{"id":1401,"sentence":"Polymer Processing XXII (2007) 5 A. Lopez Arraiza et al. : Rheological Behavior and Modeling of Thermal Degradation c 2007 Carl Hanser Verlag, Munich,","label":"RHEOLOGICAL_PROP"}
{"id":1402,"sentence":"The n ® p * transition characteristic of undegraded PLA occurs at 287 nm, whereas on degradation there is a blue shift, and the absorption band occurs at 280 nm, suggesting that the carbonyl carbon−oxygen bond cleavage is more efficient than other cleavages,","label":"BIODEGRAD_POLY"}
{"id":1403,"sentence":"The UTS values of these treatments were in a range of approximately 9 to 14 MPa. It was also found that, for the same concentration of PLA in PLA−PBAT mixture,","label":"MECHANICAL_PROP"}
{"id":1404,"sentence":"773 nm, b 0 0.448 nm, and c 0 0.477 nm, (6b) which, however, can not well explain the diffractions of the β−form crystal observed a little earlier.","label":"POLY_STRUC"}
{"id":1405,"sentence":"Before the hydrolysis, all samples were in the amorphous state. For aPLA, the first sign of crystallization appeared when Mn was reduced to approximately 40, 000 g \/ mol.","label":"POLY_STRUC"}
{"id":1406,"sentence":"Figure 7 Open in figure viewer PowerPoint SEM micrographs of block copolymer films at various stages of degradation at pH 7. 4 Figure 8 Open in figure viewer PowerPoint Degradation via edges of copolymer film after 20 weeks of degradation at pH 7. 4 ; (a)","label":"BIODEGRAD_PROP"}
{"id":1407,"sentence":"The spectra of the samples at various degradation weeks can be found in Figure 5 (a). The original undegraded PCL‐b‐PEG film exhibited a peak at 1722 cm−1,","label":"BIODEGRAD_PROP"}
{"id":1408,"sentence":"Table 3 summarizes the values of the Newtonian viscosity and critical frequency of PCL melts at temperatures ranging from 100 °C to 180 °C. This is not the case, however, for PLLA.","label":"BIODEGRAD_POLY"}
{"id":1409,"sentence":"Exceptionally, the compatibilized blend irradiated at 200 kGy had lower complex viscosity than uncompatibilized PLA \/ PCL blend in the high−frequency range due to decreased molecular weight and increased molecular weight distribution,","label":"POLY_STRUC"}
{"id":1410,"sentence":"Recently, we described a new method for assessing biodegradation by measuring the surface roughness [2], a technique commonly used in mechanical engineering. Although various methods for evaluating biodegradation have been described [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], few of them have been used to examine the effects at high temperatures.","label":"BIODEGRAD_PROP"}
{"id":1411,"sentence":"Chemoorganotrophic microorganisms use organic substrates as carbon, energy and electron sources (Alcamo, 1998, Pelmont, 2005). Some chemolithotrophic bacteria and some fungi can uptake iron and \/ or manganese cations from the matrix by oxidation reactions.","label":"POLY_STRUC"}
{"id":1412,"sentence":"and [COOH] o 0 ρ \/ Mn (0), respectively. The density of the fibers, ρ, was assumed to be 1240 g L−1 and the molecular weight of the monomer unit,","label":"POLY_STRUC"}
{"id":1413,"sentence":"21 A, and c 0 9. 0 A [99]. For the crystals grown in toluene at 55 °C, the lamellae were lozenge shaped and had a thickness of 10 nm.","label":"POLY_STRUC"}
{"id":1414,"sentence":"In addition, high interfacial adhesion between continuous and dispersed phases can induce morphological stability by acting as a morphological network structure and thus increase blend moduli as is observed for cross−linked polymers.","label":"POLY_STRUC"}
{"id":1415,"sentence":"and tp is the shift time between the two stages. Figure 9 Open in figure viewer PowerPoint Mn data versus the PLA hydrolysis time at 70 °C in neutral media : aPLA and cPLA. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":1416,"sentence":"Elongation of PLA \/ PBAT blends rapidly decreased upon the addition of PLA to the blends. The values of E and UTS for PLA \/ PBAT blends and composite, neat PLA,","label":"BIODEGRAD_POLY"}
{"id":1417,"sentence":"03 MPa, which was higher as compared to 14. 50 MPa of P (3HP−co−25 % P4HB), while P3HP−b−37 % P4HB had Young ’ s modulus of 113.","label":"BIODEGRAD_POLY"}
{"id":1418,"sentence":"The decrease in molecular weight was greater for the first 4 weeks as compared with the later weeks of degradation. Figure 2 shows that the decrease in molecular weight was enhanced under a higher pH, particularly in the earlier time intervals.","label":"BIODEGRAD_PROP"}
{"id":1419,"sentence":"The 0‐day result was for the molded sample before any contact with the aqueous media. As expected, the aPLA exhibited a clear glass transition around 57 °C and no trace of any cold crystallization or melting at higher temperatures.","label":"POLY_STRUC"}
{"id":1420,"sentence":"Tuan – Fuoss viscometer 12. PDLLA 0.64 [h] 5 6. 06 3 1024 Mv 25 °C in chloroform [118] 13. PLLA 0.72 [h] 5 5. 72 3 1024 Mv 30 °C in Benzene [118] 14. PDLLA 0.78 [h] 5 1.58 3 1024 Mn 25 °C in ethyl acetate [119] 15. PDLLA 0.73 [h] 5 1.63 3 1024 Mw 25 °C in ethyl acetate [119]","label":"BIODEGRAD_POLY"}
{"id":1421,"sentence":"Relative molecular weight (M1 \/ M2) Before (η 1) After (η 2) PBS 621.51 198. 54 3. 13 1.40 PBAT 2004. 7 411.9 4. 86 1.59 PBS \/ PBAT 1897. 1 318. 74 5. 95 1.","label":"BIODEGRAD_POLY"}
{"id":1422,"sentence":"and is produced from nonfossil renewable resources by fermentation of polysaccharide [1]. However, PLA has some drawbacks, which include low melt viscosity, low thermal stability,","label":"BIODEGRAD_POLY"}
{"id":1423,"sentence":"Table 2). The blend polymer had two melting temperatures (Tm) of 57. 14 and 78. 10 °C, almost the same as that of homopolymers P3HP and P4HB with respective values of 61 and 78 °C, indicated that the blending did not change the melting temperatures of homopolymers.","label":"POLY_STRUC"}
{"id":1424,"sentence":"Due to their faster relaxation dynamics than their counter parts ’, we thus attribute them to the noncrystalline phases, while their counterparts to the crystalline phases.","label":"POLY_STRUC"}
{"id":1425,"sentence":"Figure 3 Open in figure viewer PowerPoint (•) Mn, (◼) weight loss (Wloss), and (▴) water uptake (Wuptake) during PLA hydrolysis at 70 °C in different media at pH (a) 1 and (b) 12.","label":"BIODEGRAD_PROP"}
{"id":1426,"sentence":"The molecular weights of both PLA32 and PLA118 had been reduced by 99 %, and there was little difference between 32 and 118 μm fibers beyond 30 days of degradation time at 60 and 80 °C.","label":"BIODEGRAD_POLY"}
{"id":1427,"sentence":"and random copolymer P (3HP−co−4HB) in the putative block copolymer. However, we cannot rule out some minor amounts of random P (3HP−co−4HB) existing as a transit state between two blocks P3HP and P4HB, although this was too weak to be detectable by NMR.","label":"BIODEGRAD_POLY"}
{"id":1428,"sentence":"75 ppm methylene protons disappeared from the spectra of LPB and HPB and new proton signals attributable to PLA appeared at 5. 09 ppm (j,−CH (CH3) -)","label":"BIODEGRAD_POLY"}
{"id":1429,"sentence":"which led to an increase in the hydrodynamic volume, intrinsic viscosity, and, hence, the molecular weight of the polymer. The refractive index increment, dn \/ dc, of poly (lactic acid) has been reported in the literature.","label":"RHEOLOGICAL_PROP"}
{"id":1430,"sentence":"Additionally, as the amorphous phase of the fibers degrades, the newly formed short PLA chains have an increased mobility and can more readily rearrange to form new crystals 6, 26, 27.","label":"POLY_STRUC"}
{"id":1431,"sentence":"PHB is a natural aliphatic polyester that belongs to the polyhydroxyalkanoates that are produced and accumulated intracellularly by various microorganisms [9]. PHB has been used in small disposable products and in packing materials.","label":"BIODEGRAD_POLY"}
{"id":1432,"sentence":"(16b) Most recently, the temperature dependence of the CH2 stretching for main chain of alkanethiol was found to be mainly attributed to intermolecular interactions rather than intramolecular ones by combining the isotope dilution and temperature variation results.","label":"POLY_STRUC"}
{"id":1433,"sentence":"and the results are shown in Fig. 3. A significant level of molecular degradation occurred, either when PLA was processed in the batch mixer or exposed to thermo−oxidative environment.","label":"BIODEGRAD_PROP"}
{"id":1434,"sentence":"and 80 °C at 100 % RH. Table 1.Rate‐constant values obtained using Eqs. 3 and 4 for PLA32 and PLA118 samples degraded at 40, 60,","label":"BIODEGRAD_POLY"}
{"id":1435,"sentence":"The partially miscible components displayed two Tg transitions on the DSC curves and shifted towards each other. As shown in Fig. 5 and Table 3, the Tg of PLA and PBAT in the blends gradually shifted to each other with the addition of compatibilizers, suggesting that the tri−block copolymers can act as compatibilizers to improve the miscibility of PLA and PBAT [32].","label":"BIODEGRAD_POLY"}
{"id":1436,"sentence":"8 kg \/ mol to 34. 1 kg \/ mol and Mw ranging from 46. 5 kg \/ mol to 59. 8 kg \/ mol to be obtained with PDI from 1.","label":"POLY_STRUC"}
{"id":1437,"sentence":"Table 2. Tensile strength and elongation at break of blends with different amounts of compatibilizers. Images of the cryo−fractured surfaces of the pristine PLA \/ PBAT blends and samples using tri−block copolymers as the compatibilizers are shown in Fig. 4.","label":"MECHANICAL_PROP"}
{"id":1438,"sentence":"Table XIII. Effect of Processing on Molecular Weight of General−Purpose Cargill – Dow PDLLA (5 % D−Isomer Content) Process Mol. wt. method Mn (g \/ mol)","label":"POLY_STRUC"}
{"id":1439,"sentence":"Despite the fact that PBAT is a statistical random copolymer with a degree of randomness (r) of 0.97 to 1.02 and average block length of 1.","label":"POLY_STRUC"}
{"id":1440,"sentence":"31 Figure 8 Open in figure viewer PowerPoint Percentage elongation of PP, PBS, PBAT, and PBS \/ PBAT as a function of exposure time at 50 °C with 90 % RH. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":1441,"sentence":"Biodegradation was monitored every 15 days for approximately 10 months by measuring the mass retention. The DSC curves for PCL, PHB, and PHB−V are shown in Fig. 1.","label":"BIODEGRAD_POLY"}
{"id":1442,"sentence":"Li et al., 1996 ; Shirahase et al., 2006 ; Sivalingam et al., 2004d), enzyme degradation (Sivalingam et al., 2004d),","label":"BIODEGRAD_PROP"}
{"id":1443,"sentence":"This is mainly due to its solubility in many lactones, low toxicity, FDA approval, high catalytic activity, and ability to give high−molecular−weight polymers with low racemization [36, 50, 51].","label":"POLY_STRUC"}
{"id":1444,"sentence":"Lower Tm values were typically associated with less perfect crystal structures and to thinner crystalline lamellar thicknesses. The same behavior was found for samples hydrolyzed at 60 and at 80 °C.","label":"POLY_STRUC"}
{"id":1445,"sentence":"Of the polymers studied, PHB−V showed the best biodegradation at room temperature (Fig. 2, Fig. 3, Fig. 4).","label":"BIODEGRAD_POLY"}
{"id":1446,"sentence":"which was followed by a small endothermic melting peak centered at 165 °C. The melting enthalpy (area under the peak) was similar to the crystallization enthalpy ; this indicated that the cPLA was initially fully amorphous.","label":"POLY_STRUC"}
{"id":1447,"sentence":"The assimilation is the unique event in which there is a real integration of atoms from fragments of polymeric materials inside microbial cells. Assimilation allows microorganisms to growth and to reproduce while consuming nutrient substrate (e. g. polymeric materials) from the environment.","label":"BIODEGRAD_PROP"}
{"id":1448,"sentence":"Scheme 1.Reaction route for PLA−PBAT−PLA tri−block copolymers. The PLA−PBAT−PLA tri−block copolymers were synthesized by the ring−opening polymerization (ROP) of lactide in methylbenzene solution using HO−PBAT−OH as the macro−initiator and Sn (Oct) 2 as the catalyst.","label":"BIODEGRAD_POLY"}
{"id":1449,"sentence":"Tetramethylsilane (TMS) was used as an internal chemical shift standard. (40) Molecular weights of the PHA samples were studied on a size exclusion chromatography (SEC) equipped with a refractive index detector (RID−10A, SHIMADZU,","label":"POLY_STRUC"}
{"id":1450,"sentence":"Following day 14, decreases in both Mn and Mw were observed. At day 60, the molecular weights of both PLA32 and PLA118 were reduced by 50 %.","label":"BIODEGRAD_POLY"}
{"id":1451,"sentence":"The hydrolytic degradation of PBS, PBAT and their blend was further confirmed by FTIR analysis. Figure 4 shows FTIR spectrum of PBS, PBAT and PBS \/ PBAT before and after 30 days of being exposed to elevated humidity and temperature.","label":"BIODEGRAD_POLY"}
{"id":1452,"sentence":"Fig. 5 schematically illustrates the simplified microstructures for solvent−cast and melt−quenched PLA−b−PI−b−PLA triblock copolymers. In the solvent−cast samples, PLA crystals in lamellar format fill up the PLA hard phase domains, while in the melt−quenched ones, PLA hard phase domains remain in the amorphous state.","label":"BIODEGRAD_POLY"}
{"id":1453,"sentence":"4 as a function of degradation time. For the samples held at 40 °C, the molecular weight of the samples remained unchanged for the first 14 days of degradation.","label":"BIODEGRAD_PROP"}
{"id":1454,"sentence":"The authors found that the molecular weight reduction was higher with an increasing conditioning period. Table 3 reports the zero shear viscosity, viscosity ratio and relative molecular weight [calculated from eq.","label":"RHEOLOGICAL_PROP"}
{"id":1455,"sentence":"the number−average molecular mass of PI midblock ; for instance, PLA−PI106k−PLA indicates that PI midblock has Mn of 106 k. The Mn of PLA−CTA is 26.","label":"POLY_STRUC"}
{"id":1456,"sentence":"Figure 1 shows the moisture absorption curves in percent of the PP, PBS, PBAT, and PBS \/ PBAT blend up to 34 days. Generally, more or less ; all the polymers tend to absorb moisture in a humid atmosphere.","label":"BIODEGRAD_POLY"}
{"id":1457,"sentence":"In terms of the time required to reach a weight loss of 50 % of aPLA, it was around 23, 8, and 5 days at 60, 70,","label":"BIODEGRAD_PROP"}
{"id":1458,"sentence":"Annealing at higher temperatures, (i. e., 135 °C) didn ’ t produce complete crystallization. Annealing at temperatures close to the melting point produced only those crystals with the highest melting point.","label":"POLY_STRUC"}
{"id":1459,"sentence":"the biodegradation the polymers can be relatively quick. According to Chandra and Rustgi [16], temperature is a critical factor and plays an important role in polymer degradation,","label":"BIODEGRAD_PROP"}
{"id":1460,"sentence":"When the strain was grown in the presence of 1, 4−butanediol (BDO) as a 4HB precursor, P4HB block was formed. Sequential supplementation of 1, 3−propanediol (PDO) as a 3HP precursor allowed the strain to produce P3HP block.","label":"BIODEGRAD_POLY"}
{"id":1461,"sentence":"Figure 4 shows the micrographs of the cPLA surface before and after hydrolysis under alkaline and neutral media at 70 °C. Figure 4 (a) shows the surface before hydrolysis.","label":"BIODEGRAD_PROP"}
{"id":1462,"sentence":"which is a very sensitive−albeit comparative−way to measure the rate of degradation under processing using Equation (8) : (8) The measurements were performed in an internal mixer operated at constant rotor speed ; torque Z is directly proportional to melt viscosity η during the last processing stage (melt processing) [34], as expressed in Equation (9) : (9)","label":"BIODEGRAD_PROP"}
{"id":1463,"sentence":"The rheological behavior of PCL as observed here is typically pseudoplastic, with a well developed Newtonian zone that extends up to Fig. 2. Rheological behavior of PCL at different temperatures, under inert atmosphere a certain critical value of frequency from which the viscosity is observed to reduce.","label":"RHEOLOGICAL_PROP"}
{"id":1464,"sentence":"The compositional changes in the PEG and PCL segments after hydrolysis at pH 9. 5 can be observed from Table III. PEG composition fell 7. 5 % between Week 0 (14 %)","label":"BIODEGRAD_POLY"}
{"id":1465,"sentence":"Chandra and Rustgi, 1998, L ö rcks, 1998, Lunt, 1998, Averous and Le Digabel, 2006) must have the intention of fast biodegradability.","label":"BIODEGRAD_PROP"}
{"id":1466,"sentence":"The tensile properties of PLA \/ PBAT blends, PLA fibre reinforced PBAT composite (PLAF)","label":"BIODEGRAD_POLY"}
{"id":1467,"sentence":"The hydrolytic degradation of the polyesters was examined by using various analytical techniques. MATERIALS AND METHODOLOGY Materials For this study, commercially available PBAT pellets were supplied by Zhejiang Hangzhou Xinfu Pharmaceutical Co.,","label":"BIODEGRAD_PROP"}
{"id":1468,"sentence":"Because they are readily degraded, the molecular weight of the polymers in the amorphous regions will decrease much faster than those of the crystalline regions resulting in an increase in the PDI.","label":"POLY_STRUC"}
{"id":1469,"sentence":"G with increasing PI midblock molecular mass for solvent−cast and melt−quenched PLA−b−PI−b−PLA triblock copolymers. With a successful synthesis of PLA−b−PI−b−PLA triblock copolymers through ROP, ring−opening polymerization and RAFT, reversible addition−fragmentation chain transfer polymerization, we further demonstrate in this work that the mechanical property of these triblock copolymers can be obviously enhanced through control of crystallization of PLA end blocks for their broad potential applications.","label":"POLY_STRUC"}
{"id":1470,"sentence":"Thus, the thermal stability of polymers is important for long−term melt processing, such as that required for extrusion processes. To investigate thermal stabilities of pure PLA and PCL,","label":"MECHANICAL_PROP"}
{"id":1471,"sentence":"Structural deterioration of the film began only from about Week 7 onwards and some pores (where PEG‐rich segments could have broken off and dissolved in the buffer solution)","label":"BIODEGRAD_PROP"}
{"id":1472,"sentence":"The most probable explanation was that amorphous regions located between the spherulites were preferentially hydrolyzed. This clearly indicated than in the neutral media, the hydrolysis proceeded more or less uniformly in the bulk of the material.","label":"BIODEGRAD_PROP"}
{"id":1473,"sentence":"17 Figure 6 indicates the presence of crystalline PCL throughout 14 weeks of degradation at pH 7. 4 whereas the peak corresponding to crystalline PEG is not observed.","label":"BIODEGRAD_POLY"}
{"id":1474,"sentence":"Spinu et al. [4] showed one peak at 173. 75 ppm for an L \/ D−PLA “ as polymerized ” stereocomplex and an L,","label":"BIODEGRAD_POLY"}
{"id":1475,"sentence":"This was done for the rate constants obtained using each of the degradation models discussed in the previous section for completeness. The activation energy, Ea, was estimated to be 26.","label":"BIODEGRAD_PROP"}
{"id":1476,"sentence":"The results suggested that PLA \/ PBAT blends were immiscible [2, 4]. Table 3. The thermal properties of neat PLA, neat PBAT and PLA \/ PBAT blends.","label":"BIODEGRAD_POLY"}
{"id":1477,"sentence":"and humidity (90 %) it may be used for 10 year durable applications. 14 The biodegradable polymers are sensitive to hydrolysis under high temperature and humidity and thus limit their durability as well as long‐term performance under these conditions.","label":"BIODEGRAD_PROP"}
{"id":1478,"sentence":"One of the main disadvantages of PLA is its thermal instability, reported since 1985, as a complex process [7], [7] [a], [7] [b].","label":"BIODEGRAD_POLY"}
{"id":1479,"sentence":"the molecular mobilities of the crystalline phase could be estimated by the values of T1C to rank as δ ≪ γ ≪ β. See discussions, stats,","label":"POLY_STRUC"}
{"id":1480,"sentence":"The crystallinity degree may be estimated by X−ray diffraction. Thermal properties as glass transition, cold crystallisation and \/ or melting point are estimated by differential scanning calorimetry (DSC)","label":"POLY_STRUC"}
{"id":1481,"sentence":"The mechanical property was governed by interlamellar separation and \/ or interlamellar slip during PLA crystallization [25]. Recently, our group realized the synthesis of ABA triblock copolymers, polylactide−b−polyisoprene−b−polylactide (PLA−b−PI−b−PLA) by a mild preparation method [3].","label":"POLY_STRUC"}
{"id":1482,"sentence":"and (▴) water uptake (Wuptake) during PLA hydrolysis at pH 5. 4 at different temperatures : (a) 60, (b) 70,","label":"POLY_STRUC"}
{"id":1483,"sentence":"This result indicates that the chain segmental mobility of PI midblock can be severely restricted by PLA end blocks and the restriction becomes relatively weaker with decreasing PLA mass content, namely, increasing PI midblock length.","label":"BIODEGRAD_POLY"}
{"id":1484,"sentence":"The crystalline P3HP is known to have multiformity in conformation (21 helix and all−trans). (5, 6) Therefore, it is not amazing at all to note all P3HAs take on the similar 21 helix and \/ or all−trans conformation when crystallized, as well simulated by the conformational calculation and validated by many experiments.","label":"POLY_STRUC"}
{"id":1485,"sentence":"Krzan et al., 2006) (Table 1). Few biodegradability tests using complex media (e. g. soils, compost and sand) give information to assert assimilation of molecules from polymers by microbial cells.","label":"BIODEGRAD_PROP"}
{"id":1486,"sentence":"Similar trends were also observed for hydrolysis taking place at 60 and 80 °C. The behavior for aPLA at pH 12 was somehow different. The sample volume varied appreciably during hydrolysis.","label":"BIODEGRAD_PROP"}
{"id":1487,"sentence":"The lower the MW of PPG, the lower the viscosity of the PLA \/ PPG composite. The addition of PPG was favorable for the degradation of PLA during processing,","label":"BIODEGRAD_POLY"}
{"id":1488,"sentence":"and various other PHA applications. The function of the slime matrix is to protect microorganisms against unfavourable conditions (e. g. desiccation and UV radiations).","label":"POLY_STRUC"}
{"id":1489,"sentence":"and (d) after 10 days in a neutral medium. Crystallization Hydrolysis in aqueous media resulted in some changes in the PLA crystallinity. Figure 6 presents the differential scanning calorimetry heating thermograms obtained from aPLA and cPLA after being subjected to an increasing number of days in distilled water at 70 °C.","label":"POLY_STRUC"}
{"id":1490,"sentence":"The addition of free carboxylic acids, however, has an inhibitory effect on the polymerization rate but does not affect the final molecular weight. They increase the rate of polymerization in proportion to their concentration and also directly control the final molecular weight.","label":"POLY_STRUC"}
{"id":1491,"sentence":"Frequency sweep tests (x 0 100 to 0.01 rad \/ s) with a 1 % strain amplitude in nitrogen atmosphere were carried out at each measurement temperature in order to find the Newtonian frequency (xo).","label":"RHEOLOGICAL_PROP"}
{"id":1492,"sentence":"16 After 30 days conditioning, Tg of the PBS increased from−16. 72 °C to−14. 24 °C. This slight change can be attributed to the enhanced crystallinity, as corroborated by DSC result.","label":"POLY_STRUC"}
{"id":1493,"sentence":"and viscosity versus weight−average molecular weight of PLA. Jamshidi et al. presented Fox – Flory plots [3] of PLLA and PDLLA. The Fox – Flory equation relates the glass−transition temperature,","label":"BIODEGRAD_POLY"}
{"id":1494,"sentence":"The latter was expected to be the key for us to understand the unique enzymatic degradation of the polymorphic P3HPs. Two P3HP samples (P3HP18k, Mn 0 1.8 × 104,","label":"BIODEGRAD_POLY"}
{"id":1495,"sentence":"(28) The relative peak intensities obtained from 13C NMR were interpreted in terms of comonomer sequence distributions. The carbonyl carbon resonances [3HP (1), 4HB (1)] at 170 – 173 ppm were resolved into four peaks individually, arising from different quadruple sequences of 4HB and 3HP.","label":"POLY_STRUC"}
{"id":1496,"sentence":"which were caused by chain scission. Based on these results, we chose 20 kGy as the optimum dosage for preparing compatibilized PLA \/ PCL blends. Figure 3 Complex viscosities (measured at 190 °C) of pure PLA (▲), pure PCL (△), uncompatibilized PLA \/ PCL (90 \/ 10) (○),","label":"BIODEGRAD_POLY"}
{"id":1497,"sentence":"and uncompatibilized PLA \/ PCL (70 \/ 30) (□) blends at 190 °C. To observe the effect of compatibilization on the thermal stability of blends, we also normalized complex viscosities of compatibilized PLA \/ PCL (90 \/ 10)","label":"BIODEGRAD_POLY"}
{"id":1498,"sentence":"The PLA32 and PLA118 samples degraded at 80 °C showed a steady decrease in the melting temperature beginning after 1 day of aging. The melting temperatures observed at day 14 were ∼134 °C for both PLA32 and PLA118.","label":"BIODEGRAD_POLY"}
{"id":1499,"sentence":"When the resonance line is registered at τ 0 2 s, which is almost five times of the T1C (0.21−0.43 s) of the amorphous phase,","label":"POLY_STRUC"}
{"id":1500,"sentence":"The changes in the composition are shown in Figure 4. Figure 4 Open in figure viewer PowerPoint Composition of PCL in the films after degradation at pH 7. 4 and 9. 5.","label":"BIODEGRAD_POLY"}
{"id":1501,"sentence":"(12) Enzymatic hydrolysis is the major factor on the degradation of PCL in compost and sea water. (13) The biodegradability of polyesters depends on the chemical and physical properties of the polymer, particularly on the degree of crystallinity.","label":"BIODEGRAD_PROP"}
{"id":1502,"sentence":"The normalized intensities of the selected bands for the β−and γ−forms were plotted as functions of temperature in Figure 9, parts a and b, respectively.","label":"POLY_STRUC"}
{"id":1503,"sentence":"7 The dimer coupled with K + ion was the main product ascertained in the water soluble products of hydrolysis at higher pH, with a small amount of tetramer.","label":"BIODEGRAD_PROP"}
{"id":1504,"sentence":"and 200 kGy (╋). Figure 4 shows changes in the storage moduli of pure PLA, pure PCL, uncompatibilized blends, and blends compatibilized by electron−beam irradiation at 20 kGy.","label":"BIODEGRAD_POLY"}
{"id":1505,"sentence":"As expected, and taking into account the experimental error, for PLA, the trend line associated with the peak height ratio of carbonyl group has a positive slope, indicating chain scission and oxidation occurred to some extent.","label":"BIODEGRAD_POLY"}
{"id":1506,"sentence":"Interestingly, the flexural strength of PBS, PBS \/ PBAT blend, and PP were increased 13 %, 15 %, and 15 %, respectively, with increasing exposure time up to 6 days.","label":"BIODEGRAD_POLY"}
{"id":1507,"sentence":"Oxidation of PLA didn ’ t occur to a measurable extent during thermal degradation. The degradation process was complicated by the action of more than just molecular weight degradation.","label":"BIODEGRAD_PROP"}
{"id":1508,"sentence":"This might be the reason why tri−block copolymers at the interface emulsified the two immiscible phases, increasing the interfacial adhesion as a result. Compared to the short−chain compatibilizers,","label":"POLY_STRUC"}
{"id":1509,"sentence":"While for PLA the average molecular weight decreases from 54834 to 19979 g \/ mol, for PLA with B900 the value reaches 33096 g \/ mol. The presence of B900 minimize, as expected,","label":"BIODEGRAD_POLY"}
{"id":1510,"sentence":"Molecular Weight Analysis of PCL‐b‐PEG Copolymer Film The changes in molecular weight (Mn) of the PCL‐b‐PEG films at various periods of degradation at pH 7. 4 and pH 9.","label":"POLY_STRUC"}
{"id":1511,"sentence":"Reactions at higher temperatures can promote higher chain flexibility at the amorphous regions of polymers. An example is the esterase from the hyperthermophilic archaeon Archaeoglobus fulgidus (AfEST) that has broad substrate specificity and high stability.","label":"POLY_STRUC"}
{"id":1512,"sentence":"This step is called biodeterioration (Eggins and Oxley, 2001, Walsh, 2001). Microorganisms secrete catalytic agents (i. e. enzymes and free radicals) able to cleave polymeric molecules reducing progressively their molecular weight.","label":"BIODEGRAD_PROP"}
{"id":1513,"sentence":"Furthermore, the weight loss and water absorption were not fully correlated at pH 12 as the weight loss proceeded much more rapidly than the water uptake. This observation, combined with the readily visible sample size reduction over the course of the hydrolysis experiment, suggested that in the highly alkaline media, although bulk erosion was always present, surface erosion played a dominant role.","label":"BIODEGRAD_PROP"}
{"id":1514,"sentence":"The difference between corn and wheat starch might be caused by the difference in starch granule shape and size as well as size distribution. Abstract Within the frame of the sustainable development, new materials are being conceived in order to increase their biodegradability properties.","label":"BIODEGRAD_PROP"}
{"id":1515,"sentence":"The biodegradation of PLA is a two‐step process that includes an abiotic hydrolysis of the polymer matrix into oligomers and an assimilation of oligomers by microorganisms and their transformation into carbon dioxide and water. 3, 4 Abiotic hydrolysis is often considered as the limiting step of PLA degradation.","label":"BIODEGRAD_PROP"}
{"id":1516,"sentence":"The Mw were significantly increased from 24 to 48 h of bacterial cultivation. Thus, it could be confirmed that P3HP−b−P4HB was a living polymerization due to significant increase in Mw during the culture time course of E. coli S17−1.","label":"POLY_STRUC"}
{"id":1517,"sentence":"the complex viscosity of the compatibilized PLA \/ PCL blend increased on increasing dosage to 20 kGy. However, blend complex viscosity decreased when the radiation dose was increased over 20 kGy,","label":"RHEOLOGICAL_PROP"}
{"id":1518,"sentence":"and of PLA \/ PCL blends, oscillatory complex viscosities were measured as a function of time at a strain of 2 % and an angular frequency of 1 rad \/ s at 190 °C.","label":"BIODEGRAD_POLY"}
{"id":1519,"sentence":"For a semicrystalline homopolymer, which volume is fully filled with ideal lamellar stacks, the density difference between the crystalline and amorphous phases could be related to the SAXS invariant (Q) by (1)","label":"POLY_STRUC"}
{"id":1520,"sentence":"D−PLA random copolymer from racemic lactide having six peaks. These peaks are at 169. 136, 169. 301, 169. 342, 169. 400, 169. 548,","label":"BIODEGRAD_POLY"}
{"id":1521,"sentence":"This induction period also coincided with the monomodal molecular weight distribution mentioned previously. The induction time was strongly decreased as a function of the temperature, and it was also dependent on the PLA grade.","label":"POLY_STRUC"}
{"id":1522,"sentence":"In this way, the variable−temperature FTIR could be used as a probe of intermolecular force for polymorphic P3HP crystals. In Figure 2 are shown the time−resolved FTIR spectra in the fingerprint region for the β−form, γ−form, and δ−form samples registered during cooling at 10 °C \/ min.","label":"POLY_STRUC"}
{"id":1523,"sentence":"The samples were previously dried and used in the experiments in as received pellet form. Table 1 shows the values of the residual monomer content, the specific rotation in chloroform at 20 °C and the intrinsic viscosity in chloroform at 30 °C of polylactides, according to the supplier.","label":"RHEOLOGICAL_PROP"}
{"id":1524,"sentence":"The primary difference is the appearance of the carboxylic acid peak at Week 6 as compared with Week 7 for pH 7. 4. In all, the two sets of FTIR results confirm that hydrolytic degradation of the PCL‐b‐PEG copolymer occurs through cleavage of the ester bonds in the PCL segment.","label":"BIODEGRAD_PROP"}
{"id":1525,"sentence":"When held at 60 °C, both PLA32 and PLA118 showed an immediate decrease in Mn and Mw indicating that chain cleavage occurred readily at that temperature and 100 % RH.","label":"BIODEGRAD_POLY"}
{"id":1526,"sentence":"Mechanical factors are not predominant during biodegradation process, but mechanical damages can activate it or accelerate it (Briassoulis, 2005). In other cases, photosensitive molecular structures are added intentionally (i. e. by simple addition or copolymerisation) into the polymer framework to induce a macromolecular degradation by light (e. g. prooxidants agents that can be activated depending on the light intensity and time exposure) (Kounty et al., 2006,","label":"BIODEGRAD_PROP"}
{"id":1527,"sentence":"The DSC was calibrated using an Indium reference. The values of the glass transition temperature, Tg, and the melting temperature, Tm, were recorded for each sample.","label":"POLY_STRUC"}
{"id":1528,"sentence":"the residual δ−nuclei lead to the predominant growth of the δ−form, and the melt−crystallized δ−form sample (δ (IC70)) was obtained.","label":"POLY_STRUC"}
{"id":1529,"sentence":"The autocatalytic model, Eq. 4, was able to better capture the degradation characteristics for the fibers degraded at 60 °C compared to the first order kinetic model,","label":"BIODEGRAD_PROP"}
{"id":1530,"sentence":"Table 4. The mechanical properties for (a) solvent−cast and (b) melt−quenched PLA−b−PI−b−PLA triblock copolymers.","label":"MECHANICAL_PROP"}
{"id":1531,"sentence":"the concentration of ester bonds in the sample can be expressed as [ester] 0 ρ (DP – 1) \/ Mn, where ρ is the polymer density,","label":"POLY_STRUC"}
{"id":1532,"sentence":"For example, this period corresponded to 5, 3, and 1 days for aPLA and 10, 3 – 5, and 2 days for cPLA at 60, 70,","label":"BIODEGRAD_POLY"}
{"id":1533,"sentence":"For these applications it is sometimes desirable to modify the mechanical properties and the degradation behavior of PLLA and PCL following different strategies : blending with other polymers for example poly (D−lactide) (PDLA), poly (ethylenevinyl acetate) (EVA), poly (glycolide) (PGA) and poly [(R)−3hydroxybutyrate] (PHB) (Aoyagi et al., 2002 ;","label":"BIODEGRAD_POLY"}
{"id":1534,"sentence":"Figure 6 shows the rate of relative decrease of Mw (rate of degradation) in the interval from 15 to 20 minutes for the neat PLA and PLA \/ PPG composites,","label":"BIODEGRAD_PROP"}
{"id":1535,"sentence":"A sample of 400, 000 g \/ mole showed no crystallization exotherm or melting endotherm. He also found that the addition of 6 %, by weight, of talc as a nucleating agent increased the nucleation density greatly, reducing the crystallization half times.","label":"POLY_STRUC"}
{"id":1536,"sentence":"77 to 0.69 to 1.44 and 1.60, respectively, and impact strengths of these compatibilized blends were 2. 9−and 3. 1−fold higher, respectively, than that of pure PLA.","label":"MECHANICAL_PROP"}
{"id":1537,"sentence":"which is due to the non‐polar as well as its hydrophobicity type of characteristic. Figure 6 demonstrates the flexural strength of the PBS, PBAT, PBS \/ PBAT,","label":"BIODEGRAD_POLY"}
{"id":1538,"sentence":"Ltd. (Guangzhou, China), with MWs of 200, 400, 600, 800, and 1000 g \/ mol. 2. 2.","label":"POLY_STRUC"}
{"id":1539,"sentence":"Thermal Properties The DSC thermograms of the neat PLA and PLA \/ PPG composites are shown in Figure 8, and the corresponding glass transition temperatures (Tg), cold crystallization temperatures (Tcc),","label":"POLY_STRUC"}
{"id":1540,"sentence":"Kalb and Pennings [85] had grown PLLA crystals in various solvents. Growing PLLA crystals in toluene and p−xylene (0.08 wt %) yielded large lamellar single crystals.","label":"POLY_STRUC"}
{"id":1541,"sentence":"The Tc of samples decreased and Δ Hc increased gradually with the addition of compatibilizers, which indicated that compatibilizers acted as nucleating agents for the PLA component in the blends and increased the degree of crystallinity in the blends.","label":"POLY_STRUC"}
{"id":1542,"sentence":"and possibly arise from the splitting of vibration. Since decreasing temperature enhances the intermolecular interaction, and then the correlation field splitting, their true origination is possibly available if one in situ monitors the separation of splitting bands during cooling.","label":"POLY_STRUC"}
{"id":1543,"sentence":"The similarity of results for 32 and 118 mm fibers indicated experimentally that the degradation was not diffusion controlled. The chromatographs for both diameters at each temperature tested showed monomodal peaks indicative of homogeneous degradation 9.","label":"BIODEGRAD_PROP"}
{"id":1544,"sentence":"Typical stress−strain curves of blends with different amounts of compatibilizers. The tensile strength and elongation at break are presented in Table 2. The elongation at break of PLA \/ PBAT blends without compatibilizer is only 21.8 %,","label":"MECHANICAL_PROP"}
{"id":1545,"sentence":"In this study, relative molecular weight (M1 \/ M2) of the samples before and after conditioning can be calculated by using following equation : (5) where η 1 and η 2 are the Zero shear viscosity of the samples before and after conditioning.","label":"POLY_STRUC"}
{"id":1546,"sentence":"and 80 °C, respectively. In the second stage, the weight loss began abruptly. During this period, the molecular weight decrease rate progressively slowed down ; this was most likely due to the decrease in the ester link concentration and the loss of the autocatalysis effect.","label":"BIODEGRAD_PROP"}
{"id":1547,"sentence":"Molecular weights and polydispersity indexes (PDI) were measured by GPC. The chemical structure and weight contents of the macro−initiators, LPB and HPB were characterized by 1H NMR and 13C NMR, as shown in Fig. 1.","label":"POLY_STRUC"}
{"id":1548,"sentence":"which is available at wileyonlinelibrary. com.] Figure 7 Open in figure viewer PowerPoint Testing failure mode of PBS, PBAT, PBS \/ PBAT, and PP after 30 days exposed to 50 °C with 90 % RH. [Color figure can be viewed in the online issue,","label":"BIODEGRAD_POLY"}
{"id":1549,"sentence":"and melting points (Tm) are reported in Table 3. After being plasticized by PPG, the Tg of the PLA \/ PPG composites decreased by ca. 10 °C and two obvious melting peaks appeared.","label":"POLY_STRUC"}
{"id":1550,"sentence":"The two kinetic constants at the three temperatures were used to calculate the parameters of the Vogel – Tammann – Fulcher equation, and these are presented in Table 3.","label":"BIODEGRAD_PROP"}
{"id":1551,"sentence":"The viscometric molecular weight was calculated according to a Mark−Houwink type equation for polylactide, [g 0 5. 45 · 10.4 Mv 0.73 (Schindler and Harper, 1979)].","label":"POLY_STRUC"}
{"id":1552,"sentence":"After this initial period, the weight loss increased rapidly, whereas the molecular weight decreased slowly. Additionally, in alkaline media, hydrolysis occurred mainly through a surface‐erosion process ; this resulted in a simultaneous molecular weight decrease and weight loss without a noticeable induction period.","label":"BIODEGRAD_PROP"}
{"id":1553,"sentence":"(17) This enzyme has been well characterized with concern to the crystal structure, catalytic mechanism, and substrate specificity. The catalytic triad Ser160 – His285 – Asp255 is located between the α \/ β hydrolase fold and the cap.","label":"POLY_STRUC"}
{"id":1554,"sentence":"and its contribution to the relaxation should reflect the molecular motion. Similarly, MDDI with β−neighboring protons on the same chain has no dependence on the crystalline structure too.","label":"POLY_STRUC"}
{"id":1555,"sentence":"the solvent used, and the temperature of the solution. Table XVIII presents dilute−solution viscosity data for various poly (lactic acid) polymers. Table XVII.","label":"RHEOLOGICAL_PROP"}
{"id":1556,"sentence":"The downfield shoulder of the α CH2 resonance and the upfield shoulder of the β CH2 resonance are attributed to the amorphous phase due to their faster relaxation dynamics than their counterparts ’ as shown later.","label":"POLY_STRUC"}
{"id":1557,"sentence":"The following is the supplementary data to this article : Download : Download Word document (78KB) Supplementary Material. Supplementary Material. AbstractAbstract In this study, we blended poly (ε−caprolactone) (PCL) into poly (lactic acid) (PLA)","label":"BIODEGRAD_POLY"}
{"id":1558,"sentence":"Crystallinity Changes in PCL‐b‐PEG Copolymer Film DSC analysis was used to monitor the changes in crystallinity of the PEG and PCL segments as the degradation period increases.","label":"BIODEGRAD_POLY"}
{"id":1559,"sentence":"They do not crystallize and have a low glass transition temperature ranging from−60 to−75 °C [17]. Ke et al. [18] found that PPG and PLA had poor compatibility, showing inert dilution.","label":"POLY_STRUC"}
{"id":1560,"sentence":"5 resulted in the formation of dimers. From the results, it can be proposed that a more complete understanding of the degradation behavior of the PCL‐b‐PEG copolymer can be monitored using a combination of physiological and accelerated hydrolytic degradation conditions. © 2012 Wiley Periodicals,","label":"BIODEGRAD_PROP"}
{"id":1561,"sentence":"the IR spectra of the δ−form in the fingerprint region is completely different from those of the β−and γ−forms, and most of them could be explained reasonably by the 21−helix conformation (5c) except for the triplet (1021, 1011 and 998 cm−1)","label":"BIODEGRAD_POLY"}
{"id":1562,"sentence":"Assuming p ~ p0 ~ 2 and negligible crosslinking in both polymers, the number of chain scissions was calculated according to Saito ’ s equation (Saito, 1972).","label":"BIODEGRAD_PROP"}
{"id":1563,"sentence":"The second stage was characterized by a slower molecular weight change, which was accompanied by a gradual sample weight loss, because of the dissolution of low‐molecular‐weight PLA oligomers into the aqueous media.","label":"BIODEGRAD_PROP"}
{"id":1564,"sentence":"and inter−or intramolecular transesterification reactions. PLA degradation is dependent on time, temperature, low−molecular−weight impurities, and catalyst concentration [3].","label":"BIODEGRAD_PROP"}
{"id":1565,"sentence":"The percentage numbers in the random and block copolymers are molar percentage numbers. The blend sample consisted of P3HP (75 %) and P4HB (25 %).","label":"BIODEGRAD_POLY"}
{"id":1566,"sentence":"(5−9) In the present work, the polymorphic P3HP crystals are further found to have different packing efficiencies even when adopting the same conformation.","label":"POLY_STRUC"}
{"id":1567,"sentence":"As reflected in tan δ curves of Fig. 2c, the two glass transition temperatures for PI midblock and PLA end blocks for PLA−b−PI−b−PLA triblock copolymers show consistently left shifting trends with increasing molecular mass of PI midblock.","label":"BIODEGRAD_POLY"}
{"id":1568,"sentence":"10 The PBAT exhibits good thermal and mechanical properties with a terephthalic acid concentration above 35 mol %. 11 At the same time, PBAT possesses good biodegradability with an aromatic moiety concentration below 55 mol %.","label":"BIODEGRAD_POLY"}
{"id":1569,"sentence":"According to the sensitivity of the melt viscosity to the MW of the polymer, the relationship between the torque change and the MW drop was established by the data characterized by a torque rheometer [27].","label":"RHEOLOGICAL_PROP"}
{"id":1570,"sentence":"The degradation effects are accumulated at low frequencies (longer residence times) and this is why an apparent maximum in viscosity is observed in the rheological curves of PLLA ; PCL does not show this unusual behavior because of its higher thermal stability compared to PLLA and hence its behavior is current Newtonian.","label":"RHEOLOGICAL_PROP"}
{"id":1571,"sentence":"40 MPa much better than the random copolymer P (3HP−co−38 % P4HB) with only 0.92 MPa. The maximum tension strengths of block copolymers were higher in comparison to random copolymers.","label":"POLY_STRUC"}
{"id":1572,"sentence":"Hereby, we present a molecular dynamics (MD) and quantum mechanics \/ molecular mechanics MD study of the hydrolysis of a model of polycaprolactone, one of the most widely used biomaterials, by the thermophilic esterase from the archaeon Archaeoglobus fulgidus.","label":"BIODEGRAD_PROP"}
{"id":1573,"sentence":"and the amount of GMA content was fixed to 3 parts per hundred parts of resin (phr) based on the total mass of PLA and PCL. PLA, PCL,","label":"BIODEGRAD_POLY"}
{"id":1574,"sentence":"The biodegradabilities of compatibilized PLA \/ PCL (90 \/ 10) and (70 \/ 30) were increased to 41 and 50 %, respectively, and initial time lags were 12 and 7 days, respectively.","label":"BIODEGRAD_PROP"}
{"id":1575,"sentence":"and PBS \/ PBAT blend was assessed by exposure to 50 °C and 90 % relative humidity for a duration of up to 30 days. Due to the easy hydrolysis of esters,","label":"BIODEGRAD_POLY"}
{"id":1576,"sentence":"and these will preferentially react with either the hydroxyl or carboxyl group, which leads to different kinetic reaction rates of coupling. The condensed PLA can be modified to produce either all hydroxyl or all carboxyl groups.","label":"BIODEGRAD_POLY"}
{"id":1577,"sentence":"It was shown by several groups that the rate of degradation of various devices was dependent on the size 9, 14. Grizzi et al. showed that for plates, microspheres, beads,","label":"BIODEGRAD_PROP"}
{"id":1578,"sentence":"Hereafter, we are giving attention to the meaning of polymer biodegradation. Earlier, biodegradation was defined as a decomposition of substances by the action of microorganisms.","label":"BIODEGRAD_PROP"}
{"id":1579,"sentence":"This is likely due to the elevated temperature. Above Tg, the polymer chains have more mobility and the newly formed low molecular weight material can more readily diffuse out of the samples or become part of the crystalline regions.","label":"POLY_STRUC"}
{"id":1580,"sentence":"and Qexp δ \/ Qexp β 0 1.55) and the volume crystallinities (φ β 0 0.57, φ γ 0 0.53,","label":"POLY_STRUC"}
{"id":1581,"sentence":"which are even much higher than the Tg2 values [26]. Fig. 5. Schematic illustration of the microstructures for (a) solvent−cast and (b) melt−quenched PLA−b−PI−b−PLA triblock copolymers.","label":"BIODEGRAD_POLY"}
{"id":1582,"sentence":"The molecular weight of the samples dropped rapidly during the first 3 days of degradation at which point the degradation rate slowed. After 30 days of degradation,","label":"BIODEGRAD_PROP"}
{"id":1583,"sentence":"(1) The bacterial poly (hydroxyalkanoate) s (PHAs), together with chemically synthesized ones, are widely recognized as one class of the most important biodegradable polymers to solve the waste disposal challenge,","label":"BIODEGRAD_POLY"}
{"id":1584,"sentence":"and 30 days continuous conditioning at 50 °C and 90 % relative humidity (RH). Mechanical Properties Tensile and flexural tests were performed in an Instron Universal Testing Machine (Model 3382) according to ASTM D638 and D790, respectively.","label":"MECHANICAL_PROP"}
{"id":1585,"sentence":"The fibers exposed to 80 °C and 100 % RH exhibited a weight loss of ∼2 % daily through day 30.The average weight loss at day 30 was 69 and 65 % for PLA32 and PLA118 samples, respectively.","label":"BIODEGRAD_PROP"}
{"id":1586,"sentence":"A series of PLA−b−PI−b−PLA triblock copolymers were synthesized by increasing the chemical composition of the midblock of PI. Melt−quenching aimed to eliminate the effect of crystallization,","label":"BIODEGRAD_POLY"}
{"id":1587,"sentence":"Elongation at break (Eb) of of neat PLA, neat PBAT, neat PP, PLA \/ PBAT blends, and PLA fiber \/ PBAT composite. with the stretching vibration of C−O−C ; the peak at 1381 cm−1 associated with the CH symmetric bending vibration ; the peak at around 1450 cm−1 associated with the CH3 antisymmetric ; the peak at 1748 cm−1 associated with the carbonyl C 0 O stretching vibration ;","label":"BIODEGRAD_POLY"}
{"id":1588,"sentence":"Electron−Beam Irradiation The pellets of PLA \/ PCL \/ GMA mixtures were irradiated using a commercial electron−beam accelerator (ELV−0.5, BINP,","label":"BIODEGRAD_POLY"}
{"id":1589,"sentence":"Note that the differential scanning calorimetry (DSC) measurement shows a similar trend, but with a much less significant change for Tg2 of PLA end blocks [26], inferring that the chain segmental mobility change of PLA end blocks as reflected by DSC is local and regional, thus, it is less sensitive to the PI midblock length ; whereas,","label":"BIODEGRAD_POLY"}
{"id":1590,"sentence":"The film obtained at the end of Week 20 was also much more brittle than that in previous weeks, proving the enhanced crystallinity of the PCL segments in the copolymer film.","label":"POLY_STRUC"}
{"id":1591,"sentence":"1 Introduction Non−biodegradable plastics have posed an environment concern worldwide. The degree of concern has been raised along with the development in urbanization. [1−8]","label":"POLY_STRUC"}
{"id":1592,"sentence":"(4) : (4) where k is the pseudo‐first‐order‐rate constant. The extent of cleavage of ester bonds was discovered to be dependent on the total number of ester bonds in the polymer chain.","label":"BIODEGRAD_PROP"}
{"id":1593,"sentence":"and (70 \/ 30) blends. The biodegradabilities of pure PLA and PCL were 22 and 65 %, respectively, after the same period (Figure 10).","label":"BIODEGRAD_POLY"}
{"id":1594,"sentence":"The IR evidence measured during heating further reveal that the melting of the tightly packed γ−form would pass through some mesophase, which lacks the regular packing but hold the long−range order along the chains.","label":"POLY_STRUC"}
{"id":1595,"sentence":"XRD is a highly sensitive instrumental method capable of showing the presence of crystalline phases in materials such as polymers more conclusively. Crystalline PCL have peaks at around 2 θ 0 21.7 °and 24. 0 °while crystalline PEG will have peaks at around 2 θ 0 19. 4 °and 23. 7 °.","label":"BIODEGRAD_POLY"}
{"id":1596,"sentence":"08 A for all reflections in the spot pattern. The electron diffraction results suggest that the molecular chains were oriented in the direction orthogonal to the basal plane of the crystal and that the unit cell is hexagonal, having dimensions of a 0 b 0 5.","label":"POLY_STRUC"}
{"id":1597,"sentence":"which lead to higher polymerization rates. The apparent equilibrium monomer concentration is reduced in the total system due to lower percentage of amorphous (which holds the equilibrium monomer concentration and catalyst) to crystalline phases.","label":"POLY_STRUC"}
{"id":1598,"sentence":"However, C 0 O stretching vibration of PCL at 1723 cm−1 and CH2 stretching at 2864 cm−1 were absent. These results indicate the absence of an interfacial reaction between PLA and PCL.","label":"BIODEGRAD_POLY"}
{"id":1599,"sentence":"Additionally, Figure 5 presents SEM micrographs taken on the fracture surfaces in the bulk of the hydrolyzed sample in alkaline and neutral media at 70 °C.","label":"BIODEGRAD_PROP"}
{"id":1600,"sentence":"However, this rate was not sufficient to justify the total weight loss in 5 days ; this supported the assumption that in the strongly alkaline media, degradation proceeded mainly by a surface‐erosion mechanism.","label":"BIODEGRAD_PROP"}
{"id":1601,"sentence":"The crystallinity data for the various degradation periods can be found in Tables I and II. Table I. Crystallinity Data for the Copolymer Films After Undergoing Hydrolysis at pH 7.","label":"POLY_STRUC"}
{"id":1602,"sentence":"(3) in the Introduction]. Figure 9 presents the molecular weight as a function of the hydrolysis time for PLA hydrolyzed in distilled water at 70 °C.","label":"POLY_STRUC"}
{"id":1603,"sentence":"the mobility and the volume of the polymeric chains are modified. Above Tg (rubbery state), the desorganisation of chains facilitate the accessibility to chemical and biological degradations (Iovino et al., 2008).","label":"POLY_STRUC"}
{"id":1604,"sentence":"the impact strength of PBS \/ PBAT changed from a ductile to brittle fracture with increasing conditioning time, as shown in Figure 7. This could be due to the accelerated degradation of PBS with the increased exposure time.","label":"MECHANICAL_PROP"}
{"id":1605,"sentence":"All the FTIR results indicate that the γ−form has a stronger intermolecular interaction than the β−form, although both adopt the all−trans conformation.","label":"POLY_STRUC"}
{"id":1606,"sentence":"and the growth of the crystals occurred along six planes. Electron diffraction patterns on the single crystals suggested that the crystal lattice spacing was 5. 17 +−0.","label":"POLY_STRUC"}
{"id":1607,"sentence":"26 However, degradation in alkaline media proceeds via surface erosion rather than by a bulk erosion mechanism as in neutral media. 26 Most of the literature cited previously has been concerned with the degradation of PLA at low temperatures of around 37 °C because of the interest for PLA in biomedical applications.","label":"BIODEGRAD_PROP"}
{"id":1608,"sentence":"and blend of PBS \/ PBAT (60 \/ 40 wt %) were extruded in a Leistritz extruder with a screw speed of 100 rpm. The extrusion and injection molding process was carried out with a processing temperature of 140 °C for PBS, PBAT,","label":"BIODEGRAD_POLY"}
{"id":1609,"sentence":"and author profiles for this publication at : https : \/ \/ www. researchgate. net \/ publication \/ 286692227 Rheological Behavior and Modeling of Thermal Degradation of Poly (ε−Caprolactone) and Poly (L−Lactide) Article in International Polymer Processing Journal of the Polymer Processing Society · November 2007 DOI : 10.3139 \/ 217.","label":"BIODEGRAD_POLY"}
{"id":1610,"sentence":"The thermodynamics of polymerization of D, L−lactide and its polymer have been estimated by using adiabatic and isothermal calorimetry to measure the heat capacities and enthalpies of combustion.","label":"BIODEGRAD_POLY"}
{"id":1611,"sentence":"De Jong et al. (2001) observed PLA depolymerisation by a progressive release of dimers in alkaline conditions (Fig. 2). The end−chain degradation may be explained by an intramolecular transesterification.","label":"BIODEGRAD_POLY"}