Cold crystallization and postmelting crystallization of PLA plasticized by compressed carbon dioxide

Abstract

AbstractThe cold crystallization at temperature Tcc (melting > Tcc > glass transition) and the postmelting crystallization of polylactic acid plasticized by compressed carbon dioxide (CO2) were studied using a high‐pressure differential scanning calorimeter. The kinetics of the two kinds of crystallization were evaluated by the Avrami equation as a function of pressure at certain temperatures. The effects of using talc as a nucleation agent on the two types of crystallization under pressure were also investigated. The results show that compressed CO2 increased the mobility of the polymer chains in solid state, resulting in an increased rate of cold crystallization. The decreased rate of postmelting crystallization was mainly in the nucleation‐controlled region, which indicates that the number of nuclei was decreased by the compressed CO2. The growth rate of the two crystallization types followed the Avrami equation, but the kinetics of each depended upon temperature and pressure. The inclusion of talc accelerated postmelting crystallization but had little effect on cold crystallization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2630–2636, 2008