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Polylactide (PLA) composites with various talc content were prepared by melt extrusion. The thermal, dynamic mechanical, tensile and flexural properties, and fracture surface morphologies of neat PLA and PLA/talc composites were investigated and compared. The results showed that talc had significant nucleation effect and the cold crystallization temperature of PLA decreased with talc concentration. The thermal degradation and heat distortion temperature of PLA were slightly enhanced by compounding with talc. Talc showed significant reinforcing and toughening effects on PLA, the tensile strength, flexural strength and modulus increased with talc content ranging from 0 to 24.3 wt %. The results of tensile test showed that the elongation at break increased with talc content up to 18.1 wt % with obvious changes in fracture behavior, changing from brittle to ductile, when talc content increased to 24.3%, samples failed in a brittle manner with low elongation at break. The fracture surface morphologies showed that the talc layers were partially delaminated, aligned along the flow direction, and uniformly dispersed in the PLA matrix. The results obtained by SEM and FTIR confirmed that the interfacial adhesion between talc and PLA matrix was good. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

The nonisothermal crystallization behaviors of poly(lactic acid) (PLA) under ambient N2 and compressed CO2 (5−50 bar) at cooling rates of 0.2−2.0 °C/min were carefully studied using high-pressure differential scanning calorimetry. The presence of compressed CO2 postponed the crystallization peak to a lower temperature region while effectively reducing the half-crystallization time and enhancing the crystallinity of the PLA specimen. On the basis of these findings, a new foaming strategy was proposed and utilized to fabricate PLA foams using the ordinary unmodified PLA. The upper and lower temperature limits of this foaming strategy were 105 and 90 °C, which were determined by the melt strength and crystallization behavior of the unmodified PLA specimen, respectively. In this temperature range, PLA foams with interconnected structures, porosity of 67.9−91.4%, and expansion ratio of 15−30 times are controllably produced. The obtained PLA foams have widely distributed average bubble size of 80−270 μm and CO2 enhanced crystallinity of 32−38%.

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