Dynamical behaviors of polylactide crystallization

In this paper, we presented a detailed investigation on the dielectric relaxation behavior of amorphous PLLA, and analyzed the evolution of segmental relaxation dynamic during the isothermal cold- and melt-crystallization process of PLLA at different temperatures. The amorphous PLLA exhibits a segmental relaxation process and a dielectric normal relaxation process at the temperature from the glass transition temperature to the melting point of PLLA. For both melt- and cold-crystallized PLLA, it was found that the relaxation strength of the segmental relaxation process increases with temperature. A significant increase of α breadth and decrement of intensity with increasing crystallization temperature could be detected. The obtained results indicate the segmental dynamics of PLLA were not determined by crystallinity but by the degree of supercooling. The change trends of segmental evolution during the cold isothermal crystallization process are different from that during the melt isothermal crystallization process. The maximum loss frequency of segmental relaxation process of PLLA shifts to the lower frequency range continually during the cold crystallization, but it keeps almost unchanged during the melt crystallization process.