Isothermal Crystallization Kinetics of Polylactic Acid Toughened with an Impact Modifier

Isothermal crystallization kinetics and morphology of polylactic acid (PLA) and PLA/impact modifier (IM) blends were studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The DSC data obtained were evaluated using the Avrami equation. The crystallization half-time (t(1/2)) of PLA in the blends was lower than in pure PLA suggesting that the addition of IM facilitated crystallization of PLA in the blends. At high IM content (>= 5 wt %), the crystallization rate (1/t(1/2)) of PLA decreased with increasing IM content. This suggests that the addition of IM not only facilities PLA to crystallize but also might act as hindrance to crystallization reducing the growth rate of PLA spherulites in the blends. The 1/t(1/2) values of the blends decreased with increasing crystallization temperature (Tc) (>= 110 degrees C) probably due high mobility of PLA chain segments that limits the number of primary nuclei formed and prevents the growth of PLA spherulites.