Effect of plasticizer poly(ethylene glycol) on the crystallization properties of stereocomplex-type poly (lactide acid)

Abstract

The effects of the plasticizer poly(ethylene glycol) (PEG) on crystallization properties of equimolar poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA) blends were investigated. Formation of the stereocomplex-type poly(lactide acid) (sc-PLA) crystallites was confirmed by Wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) analyses. Sc-PLA crystallites without any homochiral poly(lactide acid) (hc-PLA) formed, as the result of the incorporation of the plasticizer PEG (more than or equal to 10%(wt)) at a processing temperature (240 °C). Moreover, when the M W of PEG reached 1 000 g · mol–1, the crystallizability of stereocomplex crystallites was the best. Isothermal crystallization kinetics further revealed that PEG could accelerate the crystallization rate of sc-PLA, with the optimum crystallization kinetic parameters being obtained at 10% (wt) PEG. Several crystallization kinetics equations were applied to describe the effect of PEG on the crystallization behavior of sc-PLA. The influence of PEG on the spherocrystal morphologies of sc-PLA was also investigated using polarized optical microscopy.