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In this study, an environmental friendly poly(butylene succinate-co-adipate) (PBSA)/ poly(lactic acid) (PLA) blend was prepared with 1,4-bis(tert-butyl peroxy isopropyl) benzene (BIPB) as a reactive compatibilizer. Rheological analysis and gel permeation chromatography analysis showed that the addition of BIPB increased the melt strength and molecular weight of PBSA/PLA blends by reacting with PBSA and PLA during the melt-blending process. The morphology of the cryo-fractured surfaces of PBSA/PLA/BIPB blends showed that adding BIPB could significantly enhance the compatibility between PBSA and PLA. Moreover, the tensile tests showed that adding BIPB could improve the tensile strength, Young's modulus and breaking strain of PBSA/PLA blends. Furthermore, the effect of isothermal treatment on PBSA/PLA/BIPB blends was also studied. WAXD and DSC curves showed that the isothermal treatment could obviously increase the crystallinity of PLA and then increase the heat deflection temperatures of PBSA/PLA/BIPB blends. In addition, adding PLA could significantly improve the hydrolytic properties of PBSA/PLA/BIPB blends.

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.

The poly(lactic acid) (PLA) composites with the silane coupling agent treated basalt fiber (SBF) and basalt fiber powder (SBFP) were prepared. The crystalline morphology, mechanical properties, and heat resistance of PLA/SBF/SBFP composites were investigated. The results indicated that SBF or SBFP not only acted as heterogeneous nucleating agents for PLA crystallization but also improved the mechanical properties and heat resistance of PLA. Morphological analyses showed that SBFP could play nucleating role to reduce the spherulites size of PLA, and SBF could restrict the mobility of PLA chains and construct interface crystallization for PLA during isothermal crystallization process. The composites with higher SBF loading, the “Transcrystalline-network” built in the composites significantly improved the heat resistance properties of PLA. Due to the synergistic effect of SBF and SBFP, the PLA/SBF/SBFP composites showed high heat deformation temperature (HDT), especially after isothermal crystallization, the HDT increased to 150.5 °C for the PLA/SBF/SBFP 50/10/40 composite, much higher (about 190%) than that of pure PLA (71.7 °C).

A series of poly(lactic acid) (PLA), poly(butylene adipate-co-terephthalate) (PBAT) and glycidyl methacrylate-grafted poly(ethylene octene) (GPOE) blends and films with different GPOE content were prepared by melt blending and blowing film technique. The effect of GPOE on the rheological behavior, melt strength, crystallization behavior, crystallization morphology, miscibility, mechanical property, phase morphology, thermal stability and water vapor permeability were studied. The addition of GPOE improved melt rheological properties. Results of DSC showed that addition of GPOE encouraged the mobility of PLA molecular chains and enhanced crystalline ability. POM observations revealed that the addition of GPOE made the density of spherulite nucleation increase and the size of crystalline particles decrease. From DMA and SEM analysis, it was demonstrated that PLA/PBAT blend was an immiscible system and GPOE in the blend could improve compatibility between PLA and PBAT. Results of mechanical test showed that the PLA/PBAT/GPOE blends and films obtained had excellent mechanical properties. The elongation at break of 50/30/20 w/w/w PLA/PBAT/GPOE blend (477%) was higher by about 2.2 times than that of 70/30/0 w/w/w PLA/PBAT/GPOE blend (220%). The tensile strength of all the PLA/PBAT/GPOE blends exceeded 31 MPa. The tensile strength reached 32.9 MPa (MD) and 22.5 MPa (TD), the elongation at break exceeded 210% and tear strength exceeded 140 kN/m for 50/30/20 w/w/w PLA/PBAT/GPOE film. With increasing GPOE content, thermal stability and water vapor barrier property also improved.

Heat resistance poly(lactic acid) PLA/ethylene butyl methacrylate glycidyl methacrylate terpolymer (GEBMA)/talc composites were fabricated by melt mixing. Talc is a high aspect ratio filler that has the potential to substantially enhance the heat resistance of crystalline polymer composites. The heat resistance of PLA/GEBMA/talc composite was remarkably enhanced by incorporating a small amount of talc. GEBMA has been introduced as a compatibilizer to improve the interphase balance between the constituent PLA matrix and talc. GEBMA coated on the surface of talc and lead to closely contact with PLA during the melting process. Well-dispersed talc composites were obtained, as observed by scanning electron microscopy. The polarized optical microscopy and thermal analysis results showed that the talc acted as a heterogeneous nucleating agent promoted the crystallization of the PLA (increased the crystallization rate and reduce the crystal size). However, the high content talc affects the mechanical properties of the composites, the tensile strength and impact strength decreased. Besides, the weakened chemical reaction was found between PLA and GEBMA during melt blending. Therefore, the PLA/GEBMA/talc composites have good heat resistance properties.

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.

In the work, the poly(lactic acid) (PLA)/poly (ethylene-butylacrylate-glycidyl methacrylate) (PTW) blends were prepared by melt compounding. PTW as a toughening agent for PLA, the PLA/PTW blends had good compatibility due to the chemical reaction between the epoxy groups of PTW and the end group of PLA during the blending process. With increasing PTW content from 0 to 20%, the impact strength of PLA/PTW blends was enhanced from 4.6 to 54.1 kJ/m2 and the elongation at break was increased from 5.6% to 270%. The scanning electron microscopy (SEM) images of the impact fracture surfaces showed a large amount of cavities and plastic deformation, which caused by the elastomer and the interfacial adhesion enhanced through the interaction of the terminal functional groups. That was the reason that the toughness of PLA was increased. Finally, proteinase K-catalyzed degradation tests shown that the addition of PTW was beneficial to the biodegradation of PLA and reduced environmental pollution.

Polylactide (PLA), as a biodegradable packing material, has attracted plenty of attention. However, some problems still limit the application of PLA in packing industry such as the inherent brittleness and low crack propagation resistance. In order to overcome these challenges, we blended PLA with a reactive toughening agent (Ethylene-Acrylic ester-Glycidyl methacrylate terpolymer) during extrusion and film processing. The glycidyl methacrylate groups in toughening agent offered some sites to react with COOH and OH groups of PLA thus leaded to a great interfacial compatibility. The proper compatibility was the premise of adjusting the phase structure of blend and film based on different processing methods. The blend had a sea-island structure after melting extrusion and heat pressed technologies while film formed annular layer structure after film blowing. The structure determined properties. Both the toughness and melt strength of blends had been improved. Moreover, it was interesting to found that tear strength of film with 10% toughening agent dramatically increased to 197.8 KN/m and 137.7 KN/m in the transverse direction (TD) and in the machine direction (MD), respectively. Besides, the elongation at break of film could reach 242.2% in MD. This work exhibited that phase morphology was significant for mechanical performances.

Polylactide (PLA), methyl methacrylate-butadiene-styrene copolymer (MBS), and poly(propylene carbonate) polyurethane (PPCU) were blended and subjected to blown film process. The rheological, mechanical, morphological, thermal, and crystalline properties of the PLA/MBS/PPCU ternary blends and the mechanical properties of the resulting films were studied. Results of mechanical test showed that PPCU and MBS could synergistically toughen PLA. The impact strength of 50/10/40 PLA/MBS/PPCU blend (74.7 kJ/m2) was about 7.5 times higher than that of the neat PLA (10.8 kJ/m2), and the elongation at break of 50/10/40 PLA/MBS/PPCU blend (276.5%) was higher by about 45 times that of PLA (6.2%). The tear strength of PLA/MBS/PPCU films was 20 kN/m higher than that of PLA, and the elongation at break (MD/TD) of 50/10/40 PLA/MBS/PPCU films was 271.1%/222.3%, whereas that of PLA was only 2.7%/3.0%. POM observations displayed that the density of spherulite nucleation increased and the size of crystalline particles decreased with the addition of MBS. With increasing PPCU content from 5% to 20%, the density of spherulite nucleation increased and the size of crystalline particles decreased continuously, but the nucleation density of spherulites was slightly lowered with increasing PPCU content from 30% to 40%. The PLA/MBS/PPCU films exhibited excellent mechanical properties, which expanded the application range of these biodegradable films.

Poly(L-lactic acid) (PLLA) blends with excellent low-temperature toughness and strength were prepared by melt compounding with acrylic ester based impact resistance agent (AEIR). The morphology, thermal properties, mechanical properties and biodegradability of the blends were investigated. Morphology observations revealed the blend was immiscible but had good compatibility with the dispersed phase size of about 200–300 nm. With the addition of AEIR, dramatic improvement in toughness of PLLA was achieved in a wide temperature range, especially at low temperatures the tensile strength was effectively remained. For the blend with 20 wt% AEIR, the tensile strength, elongation at break and impact strength were 51.6 MPa, 72% and 77.1 KJ/m2 at −20 °C, respectively, much greater than that reported. The calculated Tg of AEIR was lower than the test temperatures, and the brittle-tough transition occurred. The PLLA matrix demonstrated obvious shear yielding which induced energy dissipation and therefore lead to excellent toughness of the blends. Moreover, the biodegradation of PLLA was enhanced after blends preparation.

Frequent oil spillages and industrial discard of many organic solvents have created severe environmental and ecological problems. Therefore, it is imperative to find effective absorbent materials with high performance. Simultaneously, a green process of preparing such absorbent materials should be developed. Herein we present a facile approach to prepare open-cell polypropylene (PP)/starch blend foams with low density by twin-screw extrusion using water as a physical blowing agent and starch as an effective water carrier. The cell diameter of the prepared PP/starch blend foams was controlled by using different nucleating agents and changing the die geometry. Foams with mean cell diameter in the range of 0.4–4.5 mm and open-cell content larger than 90% were successfully obtained. Moreover, a remarkable improvement of hydrophobicity of the foams was obtained when decreasing the cell diameters. Consequently, the water contact angle and oil recovery efficiency were increased up to 142.2° and 98.4%, respectively, when the mean cell diameter was reduced to 0.4 mm. These characteristics make this foam a promising candidate absorbent material for use in oil-spill cleanup.

Biodegradable polymer composites based on poly(ɛ-caprolactone) (PCL) and poly(lactic acid) (PLA) fibers with diameters of 18, 26, 180 μm were prepared by melt compounding. The PLA fiber content in the composites was constant at 20% by weight. The effects of fibers with different diameters on the physical properties and enzymatic degradation of PCL were investigated. The morphological analysis indicated good interfacial adhesion between PCL and PLA fiber, which was beneficial to improve the physical properties of PCL. With increasing PLA fiber diameter, the complex viscosity and modulus of PCL were significantly increased, especially at low frequencies, indicating that the hindered effect of the fiber on the mobility of the PCL molecular chains was more obvious when PLA fiber diameter was thicker. However, as for the mechanical properties, the reinforcement was more obvious to PCL with the smaller PLA fiber diameter. This was because increasing efficient load transfer may be appeared due to the larger surface area and better interface bonding force of the fiber with thinner diameters. The enzymatic degradation of PCL was accelerated with the addition of large PLA fiber diameter of 26 and 180 μm, and hardly changed with the small PLA fiber diameter of 18 μm.

Poly(1,2-propylene glycol adipate) (PPA) was used as an environmentally friendly plasticizer in flexible poly(vinyl chloride) (PVC). Thermal, mechanical, and rheological properties of the PVC/PPA blends were characterized by differential scanning calorimetry, dynamic mechanical analysis, tensile test, scanning electron microscopy and small amplitude oscillatory shear rheometry. The results showed that PPA lowered the glass transition temperature of PVC. The introduction of PPA could decrease tensile strength and Young’s modulus of the PVC/PPA blends; however, elongationat-break was dramatically increased due to the plastic deformation. The plasticization effect of PPA was also manifested by the decrease of dynamic storage modulus and viscosity in the melt state of the blends. The results indicated that PPA had a good plasticizing effect on PVC.

Fully biodegradable polymer blends based on biosourced polymers, namely poly(L-lactide) (PLLA) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) are prepared by melt compounding. The enzymatic degradation and porous morphology of PLLA/P(3HB-co-4HB) blends are investigated in detail. The lipase from Pseudomonas mendocina reveals preferred enzymatic degradation of P(3HB-co-4HB) but insignificant attack to PLLA in the blends. At the same time, proteinase K can degrade PLLA, but cannot degrade P(3HB-co-4HB). On account of the surface erosion mechanisms, the enzymatic degradation rates of both the P(3HB-co-4HB) and PLLA in the blends are improved because of the presence of the other component to increase the specific surface area. The results of the 1H NMR and GPC indicate that there is no more intermediate products formed during the enzymatic degradation of the PLLA and P(3HB-co-4HB). Due to the specificity of the degradation enzymes, selective enzymatic degradation is adopted to degrade and remove one component from the blends, and various porous morphologies are acquired.

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.

In this study, acrylate (ACR) copolymer was used to toughen polylactide (PLA). Dynamic mechanical analysis and differential scanning calorimetry results showed that PLA was partially miscible with ACR. Isothermal crystalline behavior indicated that the incorporation of ACR significantly prevented the crystallization of PLA. The transmission electron micrograph showed that ACR was uniformly dispersed in PLA matrix. The mechanical properties of PLA could be improved by the addition of ACR. The analysis of yield stress indicated mild interfacial adhesion between PLA and ACR. Scanning electron micrograph of PLA/ACR blends revealed that the major toughening mechanism was matrix shear yield and plastic flow. Complex viscosity values of PLA/ACR blends were remarkably improved with the incorporation of ACR. Moreover, the van Gurp–Palmen plot, the rheological percolation threshold for the blends was lower than 15 wt%. The incorporation of ACR decreased the absorption coefficient (α), which was caused decreasing transmittance of PLA. POLYM. ENG. SCI., 55:386–396, 2015. © 2014 Society of Plastics Engineers

Highly enhanced compatibilization of biosourced and biodegradable polylactide (PLA) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) blends were successfully prepared by reactive melt compounding. Large shifts towards each other in terms of glass transition temperatures, a considerable reduction in the dispersed phase particle size and a significant increase in the interfacial adhesion between the PLA and P(3HB-co-4HB) phases were observed after compatibilization. In addition, chain branches occurred during the branching reaction decreased the crystallization ability of PLA, while crosslinks formed in the crosslinking reaction enhanced the crystallization ability of PLA on a large scale. Moreover, the blends exhibited a remarkable improvement of rheological properties of melt state when compared with that of blank PLA/P(3HB-co-4HB) blends. Upon increasing the content of the crosslinking agent, dicumyl peroxide (DCP), the blends showed increased yield tensile strength, modulus, and elongation at break. However, when DCP cooperated with triallyl isocyanurate (TAIC), the elongation at break decreased because the crosslinking network limited the mobility of the polymer chains to deform under a tensile load. Most notably, two typical and different kinds of growth of stress–strain curves were observed, and for the first time we demonstrated the toughening mechanism behind it in detail. Furthermore, SEM images of the fracture surfaces of the blends confirmed the toughening mechanism and that plastic deformation of the matrix and a debonding process were the two important ways of induced energy dissipation leading to toughened blends.

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

poly(l-lactide) (plla)/poly(d-lactide) (pdla)/clay nanocomposites are prepared via simple melt blending method at pdla loadings from 5 to 20 wt%. formation of the stereocomplex crystals in the nanocomposites is confirmed by differential scanning calorimetry and wide-angle x-ray diffraction (waxd). the internal structure of the nanocomposites has been established by using waxd and transmission electron microscope analyses. the dispersion of clay in the plla/pdla/clay nanocomposites can be improved as a result of increased intensity of shear during melt blending. the overall crystallization rates are faster in the plla/pdla/clay nanocomposites than in plla/clay nanocomposite and increase with an increase in the pdla loading up to 10 wt%; however, the crystallization mechanism and crystal structure of these nanocomposites remain unchanged despite the presence of pdla. the storage modulus has been apparently improved in the plla/pdla/clay nanocomposites with respect to plla/clay nanocomposite. moreover, it is found that the hydrolytic degradation rates have been enhanced obviously in the plla/pdla/clay nanocomposites than in plla/clay nanocomposite. polym. eng. sci., 54:914-924, 2014. (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

Glycidyl methacrylate-functionalized methyl methacrylate–butadiene (MB-g-GMA) copolymers were prepared via an emulsion polymerization process. These functionalized copolymers were blended with polylactide (PLA). Dynamic mechanical analysis and differential scanning calorimetry results showed that the addition of MB-g-GMA did not result in a marked change in the glass transition temperature of PLA. With an increase of MB-g-GMA content, the tensile strength of the blends decreased; however, the elongation at break and impact strength increased significantly. From scanning electron micrographs, there was large plastic deformation (shear yielding) in blends subjected to impact tests, which was an important energy-dissipation process and led to a toughened polymer. Rheological investigation demonstrated that there was a significant dependence of viscosity on composition. When the MB-g-GMA content increased, the viscosity began to increase. © 2013 Society of Chemical Industry

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

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

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

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

BACKGROUND: Poly(butylene adipate-co-terephthalate) (PBAT) has attracted wide interest as a biodegradable polymer. However, its use is restricted in certain applications due to its low melting point.RESULTS: PBAT was treated using gamma-radiation. The radiation features were analyzed using Soxhlet extraction, and the ratio of chain scission and crosslinking and gelation dose were determined using the classical Charlesby-Pinner equation. The results showed that PBAT is a radiation-crosslinkable polymer. The degree of crosslinking increased with increasing radiation dose; the relation between sol fraction and dose followed the Charlesby-Pinner equation. Differential scanning calorimetry analyses showed that the melting temperature (T-m) and the heat of fusion (Delta H-m) of PBAT exhibited almost no change in the first scan. The second scan, however, showed a decrease in T-m and Delta H-m. The glass transition temperature of irradiated PBAT increased with increasing radiation dose.

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.

Correction for ‘Toughening mechanism behind intriguing stress–strain curves in tensile tests of highly enhanced compatibilization of biodegradable poly(lactic acid)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blends’ by Yijie Bian et al., RSC Adv., 2014, 4, 41722–41733.

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

A series of branched/crosslinked poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] with changing gel fractions were obtained by adding small amounts of crosslinking agents dicumyl peroxide (DCP) and triallyl isocyanurate (TAIC). The thermal and rheological properties of the samples were investigated. The chain branches formed by adding a certain amount of DCP bring in not only excess free volume which enhanced the cold crystallization ability but also defective crystals which decreased the melting temperature. Additionally, the rheological properties of branched samples were improved compared with those of neat P(3HB-co-4HB). The most intriguing result was the crystallization behavior of crosslinked P(3HB-co-4HB). The crosslinks, acting as favorable nucleation sites, can enhance the crystallization nucleation rate markedly. However, too many crosslinks could impede the transportation of macromolecular chain segments during the crystallization, resulting in a decreased crystallization rate, and the final crystallinity of crosslinked P(3HB-co-4HB) was independent of the degree of crosslinking. Furthermore, due to the formation of a gel network, crosslinked biodegradable P(3HB-co-4HB) exhibited remarkable improvement in rheological properties than branched samples, extending its processing methods, like foaming and film blowing. Accordingly, the practical applications of this biosourced and biocompatible polymer can be widely achieved.