Parameters characterizing the kinetics of the nonisothermal crystallization of thermoplastic starch/poly(lactic acid) composites as determined by differential scanning calorimetry

摘要

To guide the use of thermoplastic starch (TPS)/poly(lactic acid) (PLA) composites, the nonisothermal crystallization kinetics of pure PLA and TPS/PLA composites were investigated with differential scanning calorimetry (DSC) at three different cooling rates. The results indicate that the TPS/PLA composites showed different crystallizations because of their different contents and different cooling rates. TPS, as a nucleating agent, improved the crystallinity of the PLA and constrained the mobility of the PLA chains. Three theoretical models, namely, the Avrami, Ozawa, and Mo models, were used to describe the process of nonisothermal crystallization. The Avrami analysis modified by Jeziorny and the Mo method was successful in describing the nonisothermal crystallization process of the pure PLA and the TPS/PLA composites. However, the Ozawa analysis could not give an adequate description. Kinetic parameters such as the Avrami exponent, kinetic crystallization rate constant, relative degree of crystallinity, and crystallization enthalpy, among others, were determined at various scanning rates.