Characterization of Stereocomplex Polylactide/Nanoclay Nanocomposites

Abstract Poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA)/nanoclay nanocomposites with nanoclay contents ranging from 1% to 8% w/w were prepared by melt blending using an internal mixer. Wide-angle X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results confirmed that complete stereocomplex polylactide (PLA) crystallites without any homocrystallites were produced when equal amounts of PLLA and PLDA were mixed. The nanoclay in the stereocomplex polylactide nanocomposites acted as a nucleating agent that significantly enhanced stereocomplex crystallization, resulting in smaller and finer spherulites. Compared to neat PLLA, the melting temperature of the stereocomplex polylactide and its nanocomposites was about 55°C higher. The crystallization temperature of the stereocomplex nanocomposites was also 16°C and 55°C higher than that of the stereocomplex PLA and neat PLLA, respectively. These significant increases in transition temperatures improved the thermal stability of the stereocomplex nanocomposites compared to regular polylactide, which was confirmed by thermogravimetric analysis (TGA). The TGA results also showed that increasing nanoclay content increased the thermal stability of the stereocomplex nanocomposites. Finally, XRD and transmission electron microscopy showed an intercalation nanoclay basal spacing of 3.22 nm in the stereocomplex nanocomposites; a slight increase from the 1.86 nm basal spacing in the as-received nanoclay.