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This research work has concerned a study on thermomechanical and crystallization properties of poly(lactic acid) (PLA) composites containing three different types of additives; namely: kenaf fiber (20 pph), Cloisite30B nanoclay (5 pph), and hexagonal boron nitrile (h-BN; 5 pph). The composites were prepared using a twin screw extruder before molding. Crystallization behaviors of the various composites were also examined using a differential scanning calorimetry. By adding the additives, tensile modulus of the polymer composites increased, whereas their tensile strength and elongation values decreased as compared to those of the neat PLA. Heat distortion temperature (HDT) values of the materials slightly increased, for about 3-5 C. However, after annealing at 100 C, HDT values of the fabricated PLA composites rapidly increased with annealing time before reaching a plateau after 10 min. The HDT values of above 120 C were achieved when 20 pph kenaf fiber was used as an additive. The above results were in a good agreement with DSC thermograms of the composites, indicating that percentage crystallinity of the materials increased on annealing and crystallization rate of the PLA/kenaf system was the highest.

This study has concerned preparation of polylactic acid grafted with maleated thermoplastic starch (PLA-g-MTPS) and a study on compatibilizing efficacy of the above copolymers in PLA/thermoplastic starch (TPS) blends. The PLA-g-MTPS copolymers were prepared by two-step reaction. First, maleated thermoplastic starch (MTPS) was prepared by reacting cassava starch with glycerol and maleic anhydride (MA). Second, the MTPS was grafted onto PLA molecules using peroxide as an initiator. Chemical structures of the products were characterized by using Fourier transform infrared spectroscopy and 1 H-NMR techniques, whereas the acid numbers of the copolymers were determined by titration. Thermal characteristic of the copolymer was also characterized by using dynamic mechanical thermal analysis. In total, 5 wt % of the graft copolymer was blended with PLA and TPS in a twin screw extruder. Mechanical, rheological, and morpho-logical properties of the blends were evaluated via tensile test, melt flow index test, and scanning electron microscopy, respectively. It was found that mechanical properties of the blends depended on starch content and type of the PLA-g-MTPS. When the PLA-g-MTPS was prepared at low amount (0.25 pph) of peroxide, the mechanical properties of the blend was improved remarkably as compared to those of the normal blend and/or the blend containing different compatibilizers. Compatibilizing efficacy of the above copolymers became more obvious when the thermoplastic starch (TPS) blending ratio was increased. The above results were ascribed in the light of change in the viscosity and morphology of the blends. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 126: E388-E395, 2012

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This research work has concerned a study on relationship between structure and properties of maleated thermoplastic starch (MTPS)/plasticized poly(lactic acid) (PLA) blend. The aim of this work is to investigate the effects of blending time, temperature, and blend ratio on mechanical, rheological, and thermal properties of the blend. The MTPS was prepared by mixing the cassava starch with glycerol and maleic anhydride (MA). Chemical structure of the modified starch was characterized by using a FTIR technique, whereas the degree of substitution was determined by using a titration technique. After that, the MTPS prepared by 2.5 pph of MA was further used for blending with triacetin-plasticized PLA under various conditions. Mechanical, thermal, and rheological properties of the blends were evaluated by using a tensile test, dynamic mechanical thermal analysis, and melt flow index (MFI) test, respectively. It was found that tensile strength and modulus of the MTPS/PLA blend increased with the starch content, blending temperature, and time, at the expense of their toughness and elongation values. The MFI values also increased with the above factors, suggesting some chain scission of the polymers during blending. SEM images of the various blends, however, revealed that the blend became more homogeneous if the temperature was increased. The above effect was discussed in the light of transesterification. Last, it was found that mechanical properties of the PLA/MTPS blend were more superior to those of the normal PLA/TPS blends.

Proton exchange membranes for a direct methanol fuel cell were prepared by blending poly(vinylidene fluoride) [PVDF] with sulfonated poly(etheretherketone) [SPEEK]. The effects of PVDF content on methanol permeability in the blend membranes were investigated by using a diffusion cell and gas chromatography technique. The thermal resistance and proton conductivity of the membranes were also determined by using a thermal gravimetric analysis (TGA) and an impedance analysis technique, respectively. It was found that methanol permeability in the blend membranes decreased with PVDF content at the expense of proton conductivity. The methanol permeability values of the blend membranes are much lower than that of Nafion 115, whereas proton conductivities of the membranes are comparable to that of Nafion. The thermal stability of these blend membranes are above 2508C which is sufficiently high for use in DMFC.

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This work concerns a study on the effects of fiber types and content of cellulose nanofiber on mechanical, thermal, and optical properties polyvinyl alcohol (PVA) composites. Two different types of cellulose nanofibers, which are nanofibrillated cellulose (NFC) and bacterial cellulose (BC), were prepared under various mechanical treatment times and then incorporated into the PVA prior to the fabrication of composite films. It was found that tensile modulus of the PVA film increased with nanofibers content at the expense of its percentage elongation value. DSC thermograms indicate that percentage crystallinity of PVA increased after adding 2-4 wt% of the fibers. This contributed to the better mechanical properties of the composites. Tensile toughness values of the PVA/BC nanocomposite films were also superior to those of the PVA/NFC system containing the same fiber loading. SEM images of the composite films reveal that tensile fractured surface of PVA/BC experienced more ductile deformation than the PVA/NFC analogue. The above discrepancies were discussed in the light of differences between the two types of fibers in terms of diameter and their intrinsic properties. Lastly, percentage total visible light transmittance values of the PVA composite films were greater than 90%, regardless of the fiber type and content.