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. © 2013 Society of Chemical Industry
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 Flynn–Wall–Ozawa method. Copyright © 2013 John Wiley & Sons, Ltd.
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. © 2012 Society of Plastics Engineers
Polylactide (PLA) was melt blended with poly(butylene carbonate) (PBC) in an effort to improve the toughness of the PLA without compromising its biodegradability and biocompatibility. The miscibility, morphology, thermal behavior, and mechanical properties of the blends were investigated. The blend was an immiscible two-phase system with PBC uniformly dispersed within the PLA matrix. Because of the interfacial function, the incorporation of PBC accelerated the crystallization rate of PLA. By the incorporation of PBC, a polylatide-based material with high stiffness and toughness was achieved. Even at 10% of PBC, high elongation at break of 139% was obtained, while the tensile strength remained as high as 50.7 MPa. The Pukanszky model gave credit to modest interfacial adhesion between PLA and PBC although PLA/PBC is an immscible blend. The plastic deformation, occurring via debonding process, is an important energy-dissipation process and leads to a toughened, biodegradable polymer blend. The important point is that the toughening mechanism requires only modest level of adhesion between particles and the polymer. The molecular mobility is a crucial factor for yield stress and plastic flow. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
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. © 2012 Society of Chemical Industry
Polylactide (PLA) was melt blended with poly(1,2-propylene glycol adipate) (PPA) in a Thermo-Haake mixer. Thermal, mechanical, and rheological properties of the blends were investigated by means of differential scanning calorimetry, dynamic mechanical analysis, tensile test, and small amplitude oscillatory shear rheometry. PPA lowered the glass transition temperature and increased the ability of PLA to cold crystallization. With the increase in PPA content (5–25 wt%), the blends showed decreased tensile strength and Young's modulus; however, impact strength and elongation-at-break along were dramatically increased due to the plastic deformation. Morphological results of PLA/PPA blends showed that PPA was good compatible with PLA. The plasticization effect of PPA was also manifested by the lowering of dynamic storage modulus and viscosity in the melt state of the blends compared with neat PLA. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
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. © 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. © 2012 Society of Plastics Engineers
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
In this study, carbon black (CB) was used to control the conductivity and the compatibility of immiscible poly(butylene succinate)/polylactide (PBS/PLA) blend. It is shown that most of the CB particles are selectively dispersed in the matrix PBS phase because of the viscosity ratio of the blend components. The increasing viscosity of PBS phase prevents the coalescence of the dispersed PLA domain during the melt mixing. The domain sizes of PLA are refined when compared with that of blank PBS/PLA blend. The ternary composite shows an onset of the electrical conductivity at low filler loadings (1.5 wt %), which is attributed to a percolation of CB in the insulating matrix polymer. Moreover, the composites exhibited remarkable improvement of rheological properties in the melt state when compared with that of blank PBS/PLA blend. According to the van Gurp-Palmen plot, the rheological percolation threshold for ternary systems is lower than 1.5 wt %. Furthermore, the ternary composites present improved mechanical properties and thermal stability even at very low loading levels of the CB. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
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. © 2011 Society of Plastics Engineers
Biodegradable poly(L-lactide) (PLA)/silica (SiO2) 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 SiO2 loadings. Fourier transform infrared spectroscopy and thermogravimetric analysis indicated that hydroxyl groups on SiO2 surfaces and PLA chain-ends reacted during melt processing. The resulting grafted SiO2 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. Copyright © 2010 Society of Chemical Industry
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/m2 of neat PLA to 63.9 kJ/m2, 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., 2011. © 2011 Society of Plastics Engineers.
In this article, biodegradable poly(ε-caprolactone)/layered silicate nanocomposites were prepared and characterized. The dispersion state of modified clay in PCL matrix and its effect on thermal, rheological and mechanical properties of PCL were studied. The PCL/clay nanocomposites were then foamed using chemical foaming method. Cellular parameters such as mean cell size, cell wall thickness and cell densities of nanocomposite foams with different clay loading were collected. Effect of layered silicate on the structure and mechanical properties of PCL foams were evaluated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Biodegradable poly(ε-caprolactone) (PCL)/calcium carbonate (CaCO3) nanocomposites were prepared and characterized. Effect of CaCO3 on thermal and mechanical properties of PCL matrix was studied. Results showed that CaCO3 acts as a crystallization nucleating agent and introduction of CaCO3 leads to improved mechanical properties of the PCL matrix. PCL/CaCO3 nanocomposite foams were prepared using chemical foaming method. Cellular parameters such as mean cell size, cell wall thickness, and cell density were collected. The cellular structure of nanocomposite foams changes with different CaCO3 loading. Mean cell size achieved the minimum value at 5 wt% CaCO3 loading, and cell wall thickness increased with CaCO3 content. The changes in cellular structure and improvement of mechanical properties also enhanced the mechanical properties of PCL/CaCO3 nanocomposite foams. Compressive moduli of PCL/CaCO3 nanocomposite foams with similar density increased with increasing CaCO3 loading. POLYM. COMPOS., 31:1653–1661, 2010. © 2009 Society of Plastics Engineers
Poly(L-lactide) (PLA)/silica (SiO2) nanocomposites containing 1, 3, 5, 7, and 10 wt % SiO2 nanoparticles were prepared by melt compounding in a Haake mixer. The phase morphology, thermomechanical properties, and optical transparency were investigated and compared to those of neat PLA. Scanning electron microscopy results show that the SiO2 nanoparticles were uniformly distributed in the PLA matrix for filler contents below 5 wt %, whereas some aggregates were detected with further increasing filler concentration. Differential scanning calorimetry analysis revealed that the addition of SiO2 nanoparticles not only remarkably accelerated the crystallization speed but also largely improved the crystallinity of PLA. An initial increase followed by a decrease with higher filler loadings for the storage modulus and glass-transition temperature were observed according to dynamic mechanical analysis results. Hydrogen bonding interaction involving CO of PLA with SiOH of SiO2 was evidenced by Fourier transform infrared analysis for the first time. From the mechanical tests, we found that the tensile strength and modulus values of the nanocomposites were greatly enhanced by the incorporation of inorganic SiO2 nanoparticles, and the elongation at break and impact strength were slightly improved. The optical transparency of the nanocomposites was excellent, and it seemed independent of the SiO2 concentration; this was mainly attributed to the closed refractive indices between the PLA matrix and nanofillers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Biodegradable poly(ε-caprolactone) (PCL) foams with a series of controlled structures were prepared by using chemical foaming method. The cell morphology was detected by scanning electron microscope (SEM). The compressive behavior of the foams was investigated by uniaxial compression test. The effect of density and structural parameters on the foam compressive behavior was analyzed. It was found that the relative compressive modulus has a power law relationship with relative density. Increasing of both the cell wall thickness and the cell density lead to higher compressive modulus of the foam; however, the cell size has no distinct effect on compressive behavior. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Poly(ε-caprolactone) (PCL), a saturated polyester, derived from ring-opening polymerization of ε-caprolactone, was chemically crosslinked with various amounts of benzoyl peroxide (BPO) by a two-step method by first evenly dispersing the BPO into the PCL matrix and then crosslinking at elevated temperature. The gel fraction increased with an increase in BPO content. The modified Charlesby–Pinner equation was used to calculate the ratio of chain scission and crosslinking. The results showed that both scission and crosslinking occurred, and that crosslinking predominated over scission. The number-average molecular weight between the crosslinks determined by the rubber elasticity theory using the hot set test showed a decrease with increasing BPO content. The melting temperature and crystallinity decreased with an increase in BPO content, and the crystallization temperature increased after crosslinking. Dynamic mechanical analysis results showed a decrease in the glass transition temperature as a result of chemical crosslinking of PCL. This was explained by the observed reduction in crystallinity and the increase in free volume due to restrictions in chain packing. Moreover, Young's modulus and elongation at break generally decreased with an increase in BPO content, but the tensile strength first increased with BPO content up to 1.0 wt%, reached a maximum, and then decreased. Copyright © 2007 Society of Chemical Industry
Poly(ϵ-caprolactone) was crosslinked by γ radiation in the presence of triallyl isocyanurate. The influence of γ-radiation crosslinking on the thermal and mechanical properties of poly(ϵ-caprolactone)/triallyl isocyanurate was investigated. Differential scanning calorimetry analyses showed differences between the first and second scans. Dynamic mechanical analysis showed an increase in the glass-transition temperature as a result of the radiation crosslinking of poly(ϵ-caprolactone). Thermogravimetric analysis showed that γ-radiation crosslinking slightly improved the thermal stability of poly(ϵ-caprolactone). The γ radiation also strongly influenced the mechanical properties. At room temperature, crosslinking by radiation did not have a significant influence on the Young's modulus and yield stress of poly(ϵ-caprolactone). However, the tensile strength at break and the elongation at break generally decreased with an increase in the crosslinking level. When the temperature was increased above the melting point, the tensile strength at break, elongation at break, and Young's modulus of poly(ϵ-caprolactone) were also reduced with an increase in the crosslinking level. The yield stress disappeared as a result of the disappearance of the crystallites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2676–2681, 2007
In order to modify poly [(3-hydroxybutyrate)-co-(3-hydroxyvalerate)] (PHBV), the crosslinking of this copolymer was carried out at 160 °C using dicumyl peroxide (DCP) as the initiator. The torque of the PHBV melt showed an abrupt upturn when DCP was added. Appropriate values for the gel fraction and crosslink density were obtained when the DCP content was up to 1 wt% of the PHBV. According to the NMR spectroscopic data, the location of the free radical reaction was determined to be at the tertiary carbons in the PHBV chains. The melting point, crystallization temperature and crystallinity of PHBV decreased significantly with increasing DCP content. The effect of crosslinking on the melt viscosity of PHBV was confirmed as being positive. Moreover, the mechanical properties of PHBV were improved by curing with DCP. When 1 wt% DCP was used, the ultimate elongation of PHBV increased from 4 to 11 %. A preliminary biodegradation study confirmed the total biodegradability of crosslinked PHBV. Copyright © 2004 Society of Chemical Industry
Blends of synthetic poly(propylene carbonate) (PPC) with a natural bacterial copolymer of 3-hydroxybutyrate with 3-hydroxyvalerate (PHBV) containing 8 mol % 3-hydroxyvalerate units were prepared with a simple casting procedure. PPC was thermally stabilized by end-capping before use. The miscibility, morphology, and crystallization behavior of the blends were investigated by differential scanning calorimetry, polarized optical microscopy, wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS). PHBV/PPC blends showed weak miscibility in the melt, but the miscibility was very low. The effect of PPC on the crystallization of PHBV was evident. The addition of PPC decreased the rate of spherulite growth of PHBV, and with increasing PPC content in the PHBV/PPC blends, the PHBV spherulites became more and more open. However, the crystalline structure of PHBV did not change with increasing PPC in the PHBV/PPC blends, as shown from WAXD analysis. The long period obtained from SAXS showed a small increase with the addition of PPC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4054–4060, 2003
The thermal decomposition mechanism of maleated poly(3-hydroxybutyrate) (PHB) was investigated by FTIR and 1H NMR. The results of experiments showed that the random chain scission of maleated PHB obeyed the six-membered ring ester decomposition process. The thermal decomposition behavior of PHB and maleated PHB with different graft degree were studied by thermogravimetry (TGA) using various heating-up rates. The thermal stability of maleated PHB was evidently better than that of PHB. With increase in graft degree, the thermal decomposition temperature of maleated PHB gradually increased and then declined. Activation energy Ea as a kinetic parameter of thermal decomposition was estimated by the Flynn-Wall-Ozawa and Kissinger methods, respectively. It could be seen that approximately equal values of activation energy were obtained by both methods. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1789–1796, 2002; DOI 10.1002/app.10463
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