Abstract:

Multi-arm polylactide(MA-PLA) was melt-blended with commercial polylactide(PLLA) to improve its crystallinity. MA-PLA was prepared by the ring-opening polymerization of L-lactide using multi-hydroxy-terminated polyester as initiator. The DSC curve during the 2nd heating shows an apparent cold crystallization peak(41.5 J/g) and a melting peak(42.5 J/g) for MA-PLA, which could not be observed for commercial PLLA 3051D and indicated a better crystallinity of MA-PLA than that of 3051D. The L-lactic acid unit content in MA-PLA was 97% and was higher than that in 3051D(91%). After blending with 6% MA-PLA, the blend showed an obvious cold crystallization peak and a melting peak. Polarized optical microscopy(POM) observation revealed a faster nucleation rate and an earlystage spherulite growth rate in the blend than those in neat 3051D. The isothermal crystallization gave a half crystallization time of 53.6 min for neat 3051D and 31.7 min for the blend. In addition, the Avrami indexes(n) are 2.25 and 2.60 for 3051D and the blend respectively. The improvement in crystallinity was ascribed to the heterophase nucleation effect caused by the multi-arm polylactide.

Key words: Multi-arm polylactide, Crystallization, Spherulites, Nucleation