Crystallization Kinetics and Morphology of Poly(Lactic Acid)/Ethylene Acrylate Copolymer Blends

Abstract

Isothermal crystallization kinetics and morphology of Poly (lactic acid) (PLA) and PLA/ethylene acrylate copolymer (EAC) blends were studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM) at various temperatures (95–125°C). The DSC data obtained was analyzed using the Avrami equation. The crystallization rate was found to depend on the crystallization temperature (Tc) and EAC content. At a given Tc, the crystallization rate value was greater in the blends than in PLA suggesting that the presence of EAC enhanced crystallization of PLA. Based on the DSC analysis the crystallization rate was maximum when PLA blend with 1 wt.% EAC was isothermally crystallized at 103°C. The presence of EAC did not significantly change in the spherulitic growth rate (G) of PLA. Analysis of the growth rates using the Lauritzen-Hoffman theory showed that a regime II to regime III transition was present for all PLA/EAC blends and that this transition occurred at temperature of 100°C. The fold surface energy values of PLA/EAC blends were lower than that of PLA indicating that PLA chains can readily fold onto the crystal nucleus surface after the incorporation of EAC.