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The thermal mechanical properties and morphological changes of modified poly(lactic acid) (PLA) and polycarbonate (PC) polymer blends based on the equal weight fraction of each component were investigated. Several blend samples were prepared by melt processing with a twin screw extruder using both poly(butylene succinate-co-lactate) (PBSL) and epoxy (EP) as compatibilizers for the PLA/PC binary system. Differential scanning calorimetry (DSC) of PLA/PBSL and PC/PBSL binary blends showed that individual components were immiscible. Scanning electron microscopy (SEM) analysis of these blends revealed the domain size of PBSL was $ 0.5-1 lm in PLA/PBSL blend, and reduced to around 0.1 lm in PC/PBSL blend. The notched Izod impact strength (IS) of PLA/PC/PBSL ternary blends increased with PBSL content up to 10 phr PBSL due to enhanced interfacial interaction and proper domain size of the dispersed phase on the basis of DMA, DSC, and SEM analysis. The heat deflection temperature (HDT) showed a maximum at 5 phr PBSL, and it dropped with increasing PBSL content which is a ductile polymer. However, the HDT of PLA/PC/EP ternary blends increased considerably with 10 phr EP due to rigid interphase formation, and it increased further with 1 phr quaternary amine catalyst, however, the IS dropped nearly the same as that of unmodified PLA/PC blend. To take advantage of the two compatibilizers, PBSL and EP were added to the PLA/PC blend at 10 phr each plus 1 phr catalyst and both IS and HDT were improved significantly over unmodified PLA/PC pair.

The tensile strength and thermal stability of polylactide (PLA) were significantly improved through chemical crosslinking. However, it became much more rigid and brittle. To obtain a material with good thermal stability and enhanced ability to plastic deformation, chemical crosslinked PLA with 0.5 wt % triallyl isocyanurate and 0.5 wt % dicumyl peroxide was blended with different contents of dioctyl phthalate (DOP). The advantage of using DOP is that it does not crystallize, has low glass transition temperature, and is miscible with PLA. The morphology and the thermal and mechanical properties of the crosslinked PLA and the blends of crosslinked PLA with various contents of DOP were investigated by means of scanning electron microscope, differential scanning calorimetry, tensile test, and dynamic mechanical analysis. The rheological properties of samples were also explored by using a capillary rheometer. The results showed that the DOP was an effective plasticizer for the chemical crosslinked PLA, resulting in a significantly decreased Tg, lower yield stress, and improved elongation at break. The plasticization effect was enhanced by adding higher DOP content. In addition, the DOP enhanced the crystallinity of crosslinked PLA, and all the crosslinked samples showed better heat stability than neat PLA. The apparent viscosity of the blends decreased with the increase of DOP content and a phase separation occurred when the content of DOP exceeded 12.5 wt %. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1136–1145, 2009

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