Effects of nucleation and stereocomplex formation of poly(lactic acid)

The effects of poly(d-lactide) (PDLA), nanoclay, talc, and stereocomplex formation were investigated in blends where these materials were added as a minor phase in a major phase of poly(l-lactide) (PLLA). Blends containing 2% PDLA, nanoclay, or talc as nucleants were prepared via melt blending and showed a strong increase in the crystallization rate as revealed by isothermal and nonisothermal crystallization measurements. The blending of 2% PDLA with PLLA led to the highest crystallization rate. Moreover, a stereocomplex formation was observed in a PLLA/PDLA blend (50:50). Wide-angle X-ray diffraction and differential scanning calorimetry verified that complete stereocomplex crystallites that do not form homocrystallites can be achieved. Compared with pure PLLA, the stereocomplex had a higher melting temperature and a higher crystallization temperature, by more than 50°C and 25°C, respectively.