The crystallization and miscibility of poly(L-lactide)/poly(DL-lactide) blends

Poly (L-lactide)/poly(DL-lactide) (PLLA/PDLLA) blends were prepared by co-solution precipitation. They were molded into phi 3.2 mm rods by a method of fibrillated compression. The crystallization and miscibility of the blends were studied using differential scanning calorimetry(DSC) The results showed that the PLLA component can crystallize in the process of co-solution precipitation. The melting temperature (T-m) and crystallinity (X-c) of PLLA component are identical with those of the pure PLLA until the content of PDLLA in the blends up to 30%; however, they are decreased obviously for the blend containing 50% PDLLA. The T-m and X-c of the PLLA component in the rods scattered significantly and this may be attributed to their inconsistency in preparation. It was found that two glass transitions corresponding respectively to PDLLA and PLLA occurred in DSC heating scannings of the blends. This may indicate that PDLLA and the non-crystalline PLLA in the blends are immiscible.