Isothermal crystallization kinetics of thermoplastic starch/poly(lactic acid) composites

The thermoplastic starch/poly(lactic acid) (TPS/PLA) composites were prepared using PLA melt blending with glycerol plasticized-starch. A systematic study of the isothermal crystallization kinetics of TPS/PLA composites was performed by differential scanning calorimetry (DSC) at different crystallization temperatures (Tc). The analysis based on the Avrami theory, which was applied to describe the process of isothermal crystallization, indicated that the spherulite growth rate, overall crystallization rate, and activation energy (ΔEa) of TPS/PLA composites were remarkably affected by the incorporation of TPS. TPS acts as a nucleating agent, improving the crystallinity of PLA in the composites. Furthermore, according to Lauritzen–Hoffman kinetic theory, the fold surface free energy (σe) of PLA blends is found to be higher than that of neat PLA, leading to a higher work of chain folding (q) and is ascribed to a general constraint of the PLA chain mobility in the composite melt due to the presence of TPS.