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A biodegradable blend foaming material of poly (butylene adipate-co-terephthalate) (PBAT)/poly (propylene carbonate) (PPC) was successfully prepared by chemical foaming agent and screw extrusion method. First, PBAT was modified by bis(tert-butyl dioxy isopropyl) benzene (BIBP) for chain extension, and then the extended PBAT (E-PBAT) was foamed with PPC using a twin (single) screw extruder. By analyzing the properties of the blends, we found that Young's modulus increased from 58.8 MPa of E-PBAT to 244.7 MPa of E-PBAT/PPC50/50. The viscosity of the polymer has a critical influence on the formation of cells. Compared with neat PBAT (N-PBAT), the viscosity of E-PBAT increased by 3396 Pa/s and E-PBAT/PPC 50/50 increased by 8836 Pa/s. Meanwhile, the dynamic mechanical analysis (DMA) results showed that the storage modulus (E') at room temperature increased from 538 MPa to 1650 MPa. The various phase morphologies (“sea-island”, “quasi-co-continuous” and “co-continuous”) and crystallinity of the blends affected the spread velocity of gas and further affected the foaming morphology in E-PBAT/PPC foam. Therefore, through the analysis of phase morphology and foaming mechanism, we concluded that the E-PBAT/PPC70/30 component has both excellent strength and the best foaming performance.

Poly (butylene adipate-co-terephthalate) (PBAT)/thermoplastic starch (TPS) films with additives (maleic anhydride (MA) and titanate coupling agent (TC)) were prepared. The thermal, mechanical, morphological, hydrophobic and biodegradable properties of the films were tested. With the addition of MA and TC, the compatibility and dispersibility of the composite demonstrate enormous improvement, which enhanced the mechanical properties of the films. The tensile strengths of PBAT/TPS films increased from 13.1 to 26.7 MPa in the machine direction (MD) and from 8.3 to 17.2 MPa in the transverse direction (TD). The Young’s modulus increased from 101.5 to 155.6 MPa in MD and from 84.3 to 120.7 MPa in TD. Meanwhile, the biodegradation test showed that the PBAT/TPS films had a higher aging resistance in the presence of MA/TC. These findings gave PBAT/TPS films great applications for designing and manufacturing biodegradation package in life.

Biodegradable poly(propylene carbonate) (PPC)/epoxidized soybean oil (ESO) blends with different component ratios were prepared by melt blending to improve the performance of PPC. The phase morphology, thermal properties, rheological properties and mechanical properties of the blends were investigated in detail. SEM examination revealed good interfacial adhesion between PPC matrix and ESO. According to DSC and DMA, as the content of ESO increased, the glass transition temperature of the PPC component increased, indicating that there was a strong interfacial interaction between the PPC matrix and ESO. The interfacial interaction may be caused by ring-opening reaction between the hydroxyl end groups of PPC and the epoxy groups of ESO, which restricted the chain movement of PPC matrix. The disappearance of the epoxy groups in FTIR indicated that the interfacial interaction between the two phases was due to the ring-opening reaction between PPC and ESO. With the addition of ESO, the thermal stabilities were enhanced. With the increasing ESO content, the modulus gradually decreased. However, the strength at yield, the strength at break and the elongation at break were increased for the PPC/ESO blends, suggesting that the enhancement of the strength and toughness of PPC was achieved by the incorporation of ESO. The rheological measurement revealed that the complex viscosity, storage modulus and loss modulus of PPC were increased with the increasing ESO content at low frequency, which indicated that the addition of ESO enhanced the melt strength of PPC instead of plasticizing PPC.

Polylactide (PLA), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)), and poly(butylene adipate-co-terephthalate) (PBAT) ternary blends were prepared by extrusion blending. The biodegradable PLA/P(3HB-co-4HB)/PBAT films were successfully obtained by using blown films technique. Excellent stiffness-toughness balance was achieved for 55/10/35 PLA/P(3HB-co-4HB)/PBAT film. The tensile strength reached 33.0 MPa (MD) and 23.5 MPa (TD), the elongation at break exceeded 130 %, and tear strength exceeded 110 kN/m. The Young’s modulus as low as about 1800 MPa also met packaging applications. SEM observations revealed rough and long ligaments, indicating that the tear specimens were broken yieldingly. The addition of PBAT elastomers was the main reason for the improved toughness of the film. From DMA and SEM analysis, it was demonstrated that PLA, P(3HB-co-4HB), and PBAT were partially compatible. With increasing P(3HB-co-4HB) content, the melt and cold crystallization of PLA was promoted. The enzymatic degradation experiments indicated that the films had good biodegradability. These findings gave important implications for designing and manufacturing biodegradation package of high biological carbon content.

We successfully prepared butyl rubber (IIR)/polypropylene (PP) thermoplastic vulcanizate (IIR/PP-TPV) for shock-absorption devices by dynamic vulcanization (DV) using octyl-phenolic resin as a vulcanizing agent and studied the morphological evolution and properties during DV. We found that the damping temperature region of the IIR/PP-TPV broadened with the disappearance of the glass transition temperature (Tg) in the PP phase, which is ascribed to the improvement of compatibility between the IIR and PP with increasing DV time. As DV progresses, the size of the dispersed IIR particles and the PP crystalline phase decreases, leading to the formation of a sea–island morphology. After four cycles of recycling, the retention rates of tensile strength and elongation at break of the IIR/PP-TPV reached 88% and 86%, respectively. The size of the IIR cross-linking particles in the IIR/PP-TPV becomes larger after melt recombination, and the continuous PP phase provides excellent recyclability. Significantly, the prepared IIR/PP-TPV exhibits excellent recyclability, high elasticity, and good damping property.

In order to obtain the unique properties of graphene-based composites, to realize homogeneous dispersion of graphene throughout the polymer matrix remains the key challenge. In this work, edge-oxidized graphene/polypropylene (EOGr/PP) composites with well-dispersed EOGr in PP matrix, synchronously exhibiting high electrical conductivity and thermal property, were simply fabricated for the first time using a novel strategy by in situ artificial PP latex preparation in the presence of EOGr based on solution-emulsification technique. The good dispersion state of EOGr in the PP matrix was demonstrated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). A blue shift in Raman G peak of the EOGr nanosheets was observed in the EOGr/PP composites, indicating the strong interactions between the EOGr nanosheets and the PP matrix. The onset crystallization and crystallization peak temperatures increased as the EOGr loading increases due to its good nucleating ability. An improved thermal stability of EOGr/PP composites was observed as evaluated by TGA. The EOGr/PP composites showed an insulator-to-conductor percolation transition in between that of 1 and 2 wt% EOGr content. Such strategy provides a very effective pathway to fabricate high-performance nonpolar polymer/graphene composites with excellent dispersion state of graphene.

Poly( l -lactic acid) (PLLA) sheets with dramatic improvement of mechanical properties, especially toughness, were obtained by uniaxial pre-stretching around Tg. It was found that a network structure consisting of cohesional entanglements was formed during the usual compression molding process, leading to the brittleness of PLLA, and the destruction of the network structure due to disentanglement after pre-stretching, leading to the toughness of PLLA. The network structure could not be destroyed when pre-stretching ratio (PSR) was in the elastic deformation region I and strain softening region II (PSR

In this research, boron nitride (BN) acting as both nucleating agent and thermally conductive filler was melt-mixed with poly(3-hydroxybutyrate) (PHB). It was assumed that the introduction of BN not only formed thermally conductive pathways to increase the thermal conductivity of PHB, but also reduced the interfacial thermal resistance due to the interaction between BN and PHB. The assumption was confirmed by density test, morphological observation, and rheological tests. Besides, the introduction of BN improved the thermal stability of PHB, as well. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3,4HB) was introduced as a comparison with PHB to illustrate the effect of crystallinity on the thermal conductivity of PHB/BN composites. According to the DSC tests, BN was proved to be a good nucleating agent for both PHB and P3,4HB. As the wide-angle X-ray diffraction analysis results showed that the crystal structure of PHB/BN and P3,4HB/BN composites was the same, the reason that the thermal conductivity of PHB/BN composites was higher than that of P3,4HB/BN composites at all BN levels was mainly because of the difference of the degree of crystallinity.

The BiFeO3 was used to intumescent flame retardant (IFR) polypropylene (PP) composites as a synergist. The limiting oxygen index (LOI) and UL-94 tests indicated that there is an optimum synergistic concentration of BiFeO3 in the PP/IFR composites. Thermogravimetric analysis (TG) results of flame retardant PP showed that the moderate of BiFeO3 can reduce the decomposition rate of sample at high temperatures. TG of APP/PER/BiFeO3 showed that BiFeO3 main affects the third mass loss stage of APP/PER. So the morphology and composition of the char residue of APP/PER/BiFeO3 composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and laser Raman spectroscopy (LRS). An appropriate amount of BiFeO3 can react with APP/PER forming BiOP and FeOP bond, and so more P elements was involved in a crosslinking reaction to form more stable char residue, which can effectively increase the flame retardant properties of PP. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Acetylated maltodextrins (AMDs) were synthesized. It was found that maltodextrin (MD) was easily acetylated to form AMDs with high degree of substitution (DS). The DS of the prepared AMDs was much higher than that of acetylated corn starches (ACSs) obtained under the same reaction conditions. The differential scanning calorimetry (DSC) measurements clearly highlighted that AMD underwent a glass transition at about 109°C. Moreover, AMD possessed higher thermal stability than MD. The AMD with DS 2.13 (AMD2.13) was melt-blended with poly(butylene adipate-co-terephthalate) (PBAT) to fabricate novel PBAT/AMD polymer blends. Rheological measurements indicated that AMD2.13 had a plasticizing effect on PBAT. Moreover, scanning electron microscopy (SEM) measurements indicated good interfacial adhesion between PBAT and AMD2.13. The onset temperature of non-isothermal melt crystallization of PBAT increased from 81.95 to 92.19°C due to the favorable heterogeneous nucleation effect. Mechanical tests showed that the yield strength of the PBAT/AMD blends was enhanced.

We reveal a convenient and feasible processing technique to blow polylactide (PLA) film with excellent tensile toughness, which was: PLA granules were isothermally crystallized and then were blown at a temperature lower than the complete melting temperature. The initial crystalline state of PLA granules was changed by adjusting isothermal crystallization temperature, which was a key point to influence the condensed structures and mechanical properties of films. The results showed that a lower annealing temperature was beneficial for tension toughness of films. When the temperature was set at 90 °C, the elongation at break of film reached 114% and 127% along transverse direction (TD) and machine direction (MD), respectively. The mechanical performances of films were related with their condensed structures. The residual crystals effectively induced tensile crystallization and mesophase during blow molding. Crystals, acting as physical linked points, increased the stress transfer. Cohesive entanglement was an important factor causing PLA film embrittlement, which was suppressed by mesophase.

Poly(lactic acid) with 2%, 4%, and 12% d -isomer content were selected to investigate the influence of stereoregularity on mechanical properties of uniaxially pre-stretched PLAs (ps-PLAs). The mobility of molecular chains was activated by pre-stretching because the network structures composed of cohesional entanglements were destroyed, leading to a brittle-ductile transition. The elongation at break increased to 145%, 175% and 190% at pre-stretching ratio of 0.5 for ps-PLA2, ps-PLA4 and ps-PLA12, respectively. The network structures of cohesional entanglements were easier destroyed in PLAs with more d -isomer due to the stereoregularity defects, leading to higher elongation at break. Then the elongation at break decreased with increasing pre-stretching ratio owing to the development of mesophase which might initiate crazing. The more d -isomer the less strain-induced mesophase resulting from the more active chain relaxation, and then the slower decrease of elongation at break. In addition, the modulus and strength of ps-PLAs were all increased with increasing pre-stretching ratio.

The microporous poly( l -lactic acid) (PLLA) materials were prepared by uniaxial stretching PLLA/20 wt% silica (SiO2) composites. The SiO2 fillers with particle size of 15 nm, 200 nm, 500 nm, 1 μm, 2 μm, and 5 μm were selected to investigate the effect of particle size of fillers on the microstructures and physical properties of the microporous PLLA materials. Micropores were formed due to the debonding at the interface between PLLA and SiO2. The composites with SiO2 particle size of 15 nm, 200 nm, 500 nm, 1 μm, 2 μm, and 5 μm began to debond at 1.4, 1.0, 1.0, 1.0, 0.9, and 0.7, respectively. With the increase of SiO2 particle size, the micropore diameter was enlarged at the same stretching ratio, while the particle number of SiO2 was decreased, however, the porosity was still increased. The mechanical properties, thermal insulation properties, and water vapor permeation properties of microporous PLLA samples were all improved compared with that of undrawn PLLA.

In this work, a specific polylactide (PLA) 4032D was melt-mixed with a new toughener: butyl acrylate (BA), ethyl acrylate (EA) and glycidyl methacrylate (GMA) copolymer (BA-EA-GMA). DMA tests showed that PLA/BA-EA-GMA blends were partially miscible. The degree of crystallinity of PLA increased while the cold crystallization temperature shifted to higher temperatures with increasing BA-EA-GMA content. The SEM micrographs showed that PLA/BA-EA-GMA blends had a good dispersion and this phenomenon was in good agreement with their higher impact strength. The result showed that the adding of BA-EA-GMA has enhanced the flexibility of PLA/BA-EA-GMA blends as compared with pure PLA. The impact strength was changed from 3.4 kJ/m2 for pure PLA to 29.6 kJ/m2 for 80/20 PLA/BA-EA-GMA blend.

Polylactide (pla) was first plasticized with polydiethylene glycol adipate (pdega). then the plasticized pla was further blended with acrylic impact modifier (acr) using a twin-screw extruder. finally, the extruded samples were blown using the blown thin film technique. both pdega and acr significantly affected the physical properties of the films. the results indicated that elongation at break and the tear strength of the films were significantly improved. the cavitation and large plastic deformation observed in films subjected to the tear test were the important energy-dissipation process, which led to a torn pla film. moreover, the pla/pdega/acr blown films had excellent optical properties. acr could act as a tear resistance modifier for pla blown films. these findings contribute new knowledge to the additives area and give important implications for designing and manufacturing polymer packaging materials. (c) 2013 society of chemical industry

Biodegradable polymer composites based on poly(-caprolactone) (PCL) and poly(lactic acid) (PLA) fibers were prepared by melt compounding. The effects of PLA fibers on the crystallization, mechanical properties, and enzymatic degradation of PCL composites were investigated. The addition of PLA fibers enhanced the crystallization of PCL due to the heterogeneous nucleation effect of fibers. However, the final crystallinity of the PCL in the composites was little changed in the presence of PLA fibers. With the addition of PLA fibers, significant improvement in storage modulus (E) of PCL in the composites was achieved. A significant increase in E was 173% for the composites as compared to that of the neat PCL at 20 degrees C. With the increase in PLA fibers content, the PCL composites showed decreased elongation and strength at break; however, the tensile yield strength and modulus were increased significantly, indicating that PCL was obviously reinforced by adding PLA fibers. Although the PLA fibers retarded the enzymatic degradation of PCL, it was possible to be completely degraded without much degradation time for PCL blending with suitable amounts of PLA fibers. POLYM. COMPOS., 34:1745-1752, 2013. (c) 2013 Society of Plastics Engineers

Biodegradable poly(epsilon-caprolactone) (PCL)/silica nanocomposites containing 1-9 wt% silica nanoparticles were prepared by melt compounding in this work. The rheology, mechanical properties, and biodegradation were investigated. PCL/silica nanocomposite shows a high percolation threshold, which is between 7 and 9 wt%. Once percolation network structure forms, the long-range motion of PCL chains is highly restrained. From the results of mechanical tests, the tensile strength, modulus, and yield strength of the nanocomposites are enhanced by the incorporation of silica nanoparticles. Moreover, it is interesting to find that the biodegradation rates have been enhanced obviously in the PCL/silica nanocomposites than in neat PCL, which may be of great use for the practical application of PCL. POLYM. COMPOS., 34:1620-1628, 2013. (c) 2013 Society of Plastics Engineers

A new flame retardant poly (1, 2-propanediol 2-carboxyethyl phenyl phosphinate) (PCPP) was synthesized with 2-carboxyethyl phenylphosphinic acid (CEPPA) and 1, 2-propanediol (PD). The structure of PCPP has been studied by FTIR and C-13 NMR spectra. A series of poly (lactic acid) (PLA) blends were prepared by direct melt compounding with PCPP as flame retardant and plasticizer. And it was proved to be an effective flame retardant for the PLA as evidenced by increasing limiting oxygen index (LOI) value, which increasing from 19.7 for pristine PLA to 28.2 for the PLA with 10 wt% PCPP. Additionally, the introduction of PCPP also amended the theological and mechanical properties of the PLA. When the content of PCPP in the composites was up to 15 wt%, the flame retardant and the mechanical properties were improved simultaneously. (C) 2013 Elsevier Ltd. All rights reserved.

A phosphorus-containing polyester, poly (ethylene diglycol phenylphosphinate) (PEDPP) was synthesized from phenylphosphonic dichloride and ethylene diglycol. The structure of PEDPP has been determined by Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance and matrix assisted laser desorption ionization-time of flight-mass spectrometer. A series of polylactide (PLA) blends with various content of PEDPP as flame retardant was prepared by direct melt compounding; the PLA/PEDPP blend is partially miscible. PEDPP is an effective flame retardant for PLA. The limiting oxygen index values increased from 19.7% for pure PLA to 29.0% for the blend containing 10wt% PEDPP. Thermogravimetric analysis-FTIR analysis indicated that the PEDPP affected the pyrolytic decomposition process of PLA, which is established by the change of the pyrolytic decomposition rate and the gross mass of gaseous fuel formation. The pyrolytic decomposition activation energies of PLA and PLA/10%PEDPP were estimated via FlynnWallOzawa method. Copyright (c) 2013 John Wiley & Sons, Ltd.

Melt blending of poly(lactic acid) (PLA) and ethylene/methyl acrylate/glycidyl methacrylate terpolymer (EGA) containing relatively high-concentration epoxide groups (8 wt%) was performed to improve the toughness and crystallization of PLA. The results of nonisothermal and isothermal crystallization investigation showed that the addition of EGA accelerated the crystallization rate and increased the final crystallinity of PLA in the blends. Significant enhancement in toughness and flexibility of PLA were achieved by the incorporation of the EGA elastomer. When 20 wt% EGA added, the impact strength increased from 3.0 kJ m(-2) of neat PLA to 59.8 kJ m(-2) and the elongation at break increased from 4.9 to 232.0%. The failure mode changed from brittle fracture of neat PLA to ductile fracture of the blend. (c) 2013 Society of Plastics Engineers

In this study, cross-linked poly(propylene carbonate) (PPC) was prepared using polyaryl polymethylene isocyanate (PAPI) as a cross-linking agent. The gel content, thermal behaviors, mechanical and rheological properties of the cross-linked PPC were investigated. FTIR results showed that the chemical reactions took place between PPC and PAPI and the interactions demonstrated that PPC may be cross-linked with the PAPI. The results of gel content revealed that PPC was partially cross-linked with the PAPI. The cross-linked PPC showed higher glass transition temperature and decomposition temperature compared with pure PPC. Accordingly, the melt flow index gradually decreased and complex viscosity increased with increasing PAPI content. Moreover, the mechanical properties proved also to be enhanced as evidenced by tensile tests. The introduction of small amount of cross-linkable moiety provides an efficient and convenient method to improve the properties of PPC and extend its application area.

Biodegradable poly(epsilon-caprolactone) (PCL)/silica nanocomposites at various silica loadings were prepared via direct melt compounding method in this work. Scanning electron microscopy observation indicated that when the silica content was < 3 wt%, the nanoparticles dispersed evenly in the PCL matrix and exhibited only aggregates with particle size of less than 100 nm. The results of nonisothermal melt crystallization showed that the crystallization peak temperature was higher in the nanocomposites than in neat PCL; moreover, the overall crystallization rate was faster in the nanocomposites than in neat PCL during isothermal melt crystallization. Both nonisothermal and isothermal melt crystallization studies suggested that the crystallization of PCL was enhanced by the presence of silica and influenced by the silica loading. The effect of silica on the crystallization behavior was twofold: the presence of silica may provide heterogeneous nucleation sites for the PCL crystallization while the aggregates of silica may restrict crystal growth of PCL. However, the crystal structure of PCL remained almost unchanged despite the presence of silica in the nanocomposites. POLYM. COMPOS., 2013. (c) 2012 Society of Plastics Engineers

Biosourced poly(lactic acid) (PLA) blends with different content of poly(ethylene oxide-b-amide-12) (PEBA) were prepared by melt compounding. The miscibility, phase structure, crystallization behavior, mechanical properties, and toughening mechanism were investigated. The blend was an immiscible system with the PEBA domains evenly dispersed in the PLA matrix. The PEBA component suppressed the nonisothermal melt crystallization of PLA. With the addition of PEBA, marked improvement in toughness of PLA was achieved. The maximum for elongation at break and impact strength of the blend reached the level of 346% and 60.5 kJ/m2, respectively. The phase morphology evolution in the PLA/PEBA blends after tensile and impact tests was investigated, and the corresponding toughening mechanism was discussed. It was found that the PLA matrix demonstrates obvious shear yielding in the blend during the tensile and impact tests, which induced energy dissipation and therefore lead to improvement in toughness of the PLA/PEBA blends. POLYM. COMPOS., 2013. (c) 2012 Society of Plastics Engineers

Silica-filled polylactide (PLA) nanocomposites were prepared by melt compounding. The oscillatory rheological properties and biodegradation behavior were then investigated. As the silica loadings reach up to 5 wt%, percolated silica network structures form. For the percolated PLA/silica nanocomposites sample (the silica content was >5 wt%), the modulus enhances with an increase of temperature evidently. Moreover, it is interesting to find that the biodegradation rates have been enhanced obviously in the PLA/silica nanocomposites than in neat PLA. The erosion mechanism of neat PLA and the PLA/silica nanocomposites was further discussed. POLYM. COMPOS., 2012. (c) 2012 Society of Plastics Engineers

The effect of crystallization on the microstructure and mechanical properties of a poly[(ethylene oxide)-block-(amide-12)] (PEBA)-toughened poly(lactic acid) (PLA) blend was investigated. Annealing was used to govern the crystallization microstructure and hence the mechanical properties of the blend. Crystallization resulted in the morphology of the PLA component altering from a continuous amorphous phase to continuous crystalline phase. Moreover, as the crystallization of PLA proceeded, the degree of crystallinity, spherulite size and lamellar thickness increased, and the interlamellar and interspherulitic connections became weaker. These led to the large plastic deformation in the matrix during tension being suppressed, and cracks appeared easily under tensile load, which was favorable to fracture for the blend during tension and so a small elongation at break was obtained. However, the elongation at break for all the annealed specimens was higher than that for neat amorphous PLA, suggesting that PEBA still showed a toughening effect for PLA under annealing. (C) 2012 Society of Chemical Industry

Brittle polylactide (PLA) was toughened by introducing 5–25 wt % of methyl methacrylate–butadiene–styrene (MBS) copolymer. PLA/MBS blends were characterized by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), dynamic rheometer, mechanical testing, scanning electron microscopy, and transmission electron microscope. From the result of DSC, MBS could act as an effective heterogeneous nucleation agent for PLA and significantly improved the degree of crystallinity of PLA. DMA results showed a single high temperature peak of Tg between that of pure PLA and that of the shell composition of the MBS, which suggested that PLA and the shell of MBS were compatible. With an increase of MBS content, the tensile strength of the blends decreased; however, the elongation at break and impact strength increased significantly which indicated the toughening effects of the MBS on PLA. It was found that the PLA matrix showed large plastic deformation (shear yielding) in the blend subjected the impact tests, which was an important energy-dissipation process and led to a toughened polymer blend. MBS could act as impact modifier of PLA. Rheological investigation demonstrated that there was a significantly dependence of viscosity on composition. When the MBS content increased, the viscosity began to increase. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Biodegradable polymer blends based on biosourced polymers, namely polylactide (PLA) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)), were prepared by melt compounding. The effects of P(3HB-co-4HB) on the miscibility, phase morphology, thermal behavior, mechanical properties, and biodegradability of PLA/P(3HB-co-4HB) blends were investigated. The blend was an immiscible system with the P(3HB-co-4HB) domains evenly dispersed in the PLA matrix. However, the Tg of P(3HB-co-4HB) component in the blends decreased compared with neat P(3HB-co-4HB), which might be attributed to that the presence of the phase interface between PLA and P(3HB-co-4HB) resulted in enhanced chain mobility near interface. The addition of P(3HB-co-4HB) enhanced the cold crystallization of PLA in the blends due to the nucleation enhancement of PLA caused by the enhanced chain mobility near the phase interface between PLA and P(3HB-co-4HB) in the immiscible blends. With the increase in P(3HB-co-4HB) content, the blends showed decreased tensile strength and modulus; however, the elongation at beak was increased significantly, indicating that the inherent brittlement of PLA was improved by adding P(3HB-co-4HB). The interesting aspect was that the biodegradability of PLA is significantly enhanced after blends preparation. POLYM. COMPOS., 2012. (C) 2012 Society of Plastics Engineers

Biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)]/silica nanocomposites were prepared by melt compounding. The effects of silica on the morphology, crystallization, thermal stability, mechanical properties, and biodegradability of P(3HB-co-4HB) were investigated. The nanoparticles showed a fine and homogeneous dispersion in the P(3HB-co-4HB) matrix for silica contents below 5 wt%, whereas some aggregates were detected with further increasing silica content. The addition of silica enhanced the crystallization of P(3HB-co-4HB) in the nanocomposites due to the heterogeneous nucleation effect of silica. However, the crystal structure of P(3HB-co-4HB) was not modified in the presence of silica. The thermal stability of P(3HB-co-4HB) was enhanced by the incorporation of silica. Silica was an effective reinforcing agent for P(3HB-co-4HB), and the modulus and tensile strength of the nanocomposites increased, whereas the elongation at break decreased with increasing silica loading. The exciting aspect of this work was that the rate of enzymatic degradation of P(3HB-co-4HB) was enhanced significantly after nanocomposites preparation. POLYM. ENG. SCI., 2012. (C) 2011 Society of Plastics Engineers

Melt blending of poly(lactic acid) (PLA) and poly(epichlorohydrin-co-ethylene oxide) copolymers (ECO) was performed to improve the toughness and crystallization of PLA. Thermal and scanning electron microscopy analysis indicated that PLA and ECO were not thermodynamically miscible but compatible to some extent. The addition of a small amount of ECO accelerated the crystallization rate and increased the final crystallinity of PLA in the blends. Significant enhancement in toughness and flexibility of PLA were achieved by the incorporation of the ECO elastomer. When 20 wt% ECO added, the impact strength increased from 5 kJ/m(2) of neat PLA to 63.9 kJ/m(2), and the elongation at break increased from 5% to above 160%. The failure mode changed from brittle fracture of neat PLA to ductile fracture of the blend. Rheological measurement showed that the melt elasticity and viscosity of the blend increased with the concentration of ECO. POLYM. ENG. SCI., 51:2370-2380, 2011. (C) 2011 Society of Plastics Engineers

Poly(L-lactide) (PLLA) was prepared via melt blending and nucleated using three layered metal phosphonates, i.e. zinc phenylphosphonate (PPZn), calcium phenylphosphonate (PPCa) and barium phenylphosphonate (PPBa). The morphology, crystallization and enzymatic hydrolysis of PLLA nucleated using PPZn, PPCa and PPBa were investigated. The results of both wide-angle X-ray diffraction and transmission electron microscopy observations show that the layers of PPZn, PPCa or PPBa are barely exfoliated or intercalated by PLLA chains in the melt-blending process. PPZn, PPCa and PPBa serve as effective nucleating agents, accelerating both non-isothermal and isothermal crystallization and enzymatic hydrolysis of PLLA. An interesting aspect is that the nucleating ability of PLLA incorporating PPZn, PPCa and PPBa decreases in the order PPZn > PPCa > PPBa, whereas the enzymatic hydrolysis of PLLA incorporating PPZn, PPCa and PPBa decreases in the reverse order, which is due to the different dispersion and interfacial interactions of PPZn, PPCa and PPBa throughout the PLLA matrix. Copyright © 2010 Society of Chemical Industry

The performance and radiation-induced cross-linking of polycaprolactone (PCL) in the presence of vinyltrimethoxysilane (VTMS) have been investigated. Radiation-induced cross-linking of PCL in the presence of VTMS followed the Charlesby–Pinner equation, and VTMS promoted the radiation-induced cross-linking of PCL. As the concentration of VTMS increased, the gelation dose and the ratio of degradation to cross-linking (p0/q0) decreased and the efficiency of radiation-induced cross-linking increased. Differential scanning calorimetry analyses showed differences between the first and second scans. Glass-transition temperature (Tg) and mechanical properties of the polymers increased. Radiation-induced cross-linking of PCL in the presence of VTMS was found to retard hydrolytic degradation greatly. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Biodegradable poly(L-lactide) (PLA)/silica (SiO(2)) nanocomposites were prepared by melt compounding to investigate the effect of spherical nanofillers on the thermal stability of PLA. The nanocomposites displayed improved thermal stability both under nitrogen and in air. The stabilization mechanism was attributed mainly to the barrier effect of the network formed, which was demonstrated by the improved barrier properties and rheological performance. The dispersion of nanofiller and matrix-nanoparticle interactions were investigated to evaluate the dependence of the network on SiO(2) loadings. Fourier transform infrared spectroscopy and thermogravimetric analysis indicated that hydroxyl groups on SiO(2) surfaces and PLA chain-ends reacted during melt processing. The resulting grafted SiO(2) and entangled PLA chains formed a dense network, which hindered the diffusion of oxygen and volatile decomposition products. Furthermore, the improvement in thermal stability resulted from the restraining effect on the mobility of active hydroxyl end-groups, so that some related thermal decomposition reactions were inhibited, which was confirmed from gel permeation chromatography measurements. (C) 2010 Society of Chemical Industry

Porous poly( l -lactic acid) (PLLA) sheets were prepared by uniaxial stretching PLLA sheets containing starch filler. Here, the starch filler content, stretching ratio, stretching rate and stretching temperature are important factors to influence the structure of the porous PLLA sheets, therefore, they have been investigated in detail. The pore size distribution and tortuosity were characterized by Mercury Intrusion Porosimetry. The results revealed that the porosity and pore size enlarged with the increase of the starch filler content and stretching ratio, while shrank with the rise of stretching temperature. On the other hand, the pore structure almost had no changes with the stretching rate ranging between 5 and 40 mm/min. In order to test and verify that the porous PLLA sheet was suitable for the tissue engineering, the starch particles were removed by selective enzymatic degradation and its in vitro biocompatibility to osteoblast-like MC3T3-E1 cells was investigated.

The thermal degradation behavior of the blend based on polylactide (PLA) and poly(1,2-propanediol 2-carboxyethyl phenyl phosphinate) (PCPP) was investigated by the thermogravimetric analysis (TGA). Thermal degradation activation energies (E-a) of neat PLA and PLA/15% PCPP blend were calculated via the Flynn-Wall-Ozawa method. The E-a of the blends increased with the addition of PCPP increasing when the conversion was higher than 10%. In addition, the appropriate conversion models for the thermal degradation process of PLA and PLA/15% PCPP were studied via the Criado method. At the same time, the main gaseous decomposition products of PLA and its blend were identified by TGA/infrared spectrometry (TGA-FTIR) analysis. And it revealed that the PCPP improved the flame-retardant property of PLA via altering the release of the flammable gas and nonflammable gas. Moreover, the PCPP improved the flame-retardant property of PLA by inhibiting exothermic oxidation reactions in the combustion, which was further proved by pyrolysis-gas chromatography-mass spectrometry analysis. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40480.

Biodegradable hyperbranched poly(ester amide) (HBP) was used as a compatibilizer to modify PLA/SiO2 nanocomposites for the first time. The ternary composites displayed dramatically improved mechanical properties including excellent toughness and fairly high stiffness. TEM images revealed that an encapsulation structure was formed by HBP surrounding SiO2 nanopartides, and their surfaces became flocculent due to the migration process of silica. The linear viscoelastic behavior of the nanocomposites measured by parallel plate rheometer indicated that strong interface adhesion existed between PLA matrix and silica nanofiller after incorporating of HBP. The compatibilization effect of HBP and the enhanced mobility of nanoparticles contributed to the improved mechanical properties.

Silica nanoparticles and poly(butylene succinate) (PBS) nanocomposites were prepared by a melt-blending process. The influence of silica nanoparticles on the nonisothermal crystallization behavior, crystal structure, and mechanical properties of the PBS/silica nanocomposites was investigated. The crystallization peak temperature of the PBS/silica nanocomposites was higher than that of neat PBS at various cooling rates. The half-time of crystallization decreased with increasing silica loading; this indicated the nucleating role of silica nanoparticles. The nonisothermal crystallization data were analyzed by the Ozawa, Avrami, and Mo methods. The validity of kinetics models on the nonisothermal crystallization process of the PBS/silica nanocomposites is discussed. The approach developed by Mo successfully described the nonisothermal crystallization process of the PBS and its nanocomposites. A study of the nucleation activity revealed that the silica nanoparticles had a good nucleation effect on PBS. The crystallization activation energy calculated by Kissinger's method increased with increasing silica content. The modulus and yield strength were enhanced with the addition of silica nanoparticles into the PBS matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010