Abstract:

Stereocomplex poly(lactic acid) (sc-PLA) could form inthe mixture of poly(L-lactide) (L-lactide) (PLLA) and poly(D-lactiole) (PDLA) at a mass ratio of 1:1. In this paper, the thermal properties, crystallization kinetics and spherulites morphologies of the miztures with different molecular weights (0.6×10⁴ -1.2×105, homopolymers) were studied. All the homopolymers were prepared from L-LA or D-LA by melt comdensation. Compared to cerrespinding homopolymers, sc-PLA formed by solution blending of PLLA show much better crystallinity and higher melt temperature. The crystallization kinetics of the mixtures were investigated by DSC cooling scan at the rates of 5, 10, 20, adn 30°C/min. The results showed that the sampoes with higher molecular weight, possess faster rates of crystallization, which should be ascribed to the better ability of stereocomplexation between the enantiometric chain segments prior to occurrence of mixtures were investigated on polarizing microscope. Cracks formed in the samoles with lower molecular weight. The temperature-dependant reversibility of cracks might be resulted from the inner stress due to too fast cooling rates.

Key words: stereocomplexed poly(lactic acid), thermal property, crystallization kinetics, cracked spherulite