Isothermal crystallization of poly(L-lactide) and poly(butylene adipate) crystalline/crystalline blends

The isothermal crystallization kinetics, morphology and melting behavior of poly(L-lactide) and poly(butylene adipate) (PLLA/PBA) crystalline/crystalline blends were studied in the high- and low-temperature regions using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). In the high-temperature region, the PLLA crystallized faster, and the blends had lower equilibrium melting temperatures than neat PLLA due to the high-mobility PBA chain. In the low-temperature region, the PBA crystallization rate was lower in the blends. Additionally, the polymorphic structures and crystallization morphologies of PBA were influenced by PLLA greatly. The PBA in the blends formed alpha and beta crystal structures, whereas neat PBA only formed alpha crystal structures. POM indicated that the neat PBA formed Maltese-cross spherulites across the studied temperature range. However, banded spherulites formed in the blend at 32 and 34 degrees C.