Effect of molecular stereoregularity on the transcrystallinization properties of poly(l-lactide)/basalt fiber composites.

A comparative study on interfacial crystallization of poly(l-lactic acid) (PLLA) with different stereoregularity (PLLA2003D 96.0%, PLLA4032D 98.5%, and PLLA290 99.2%) surrounding macroscopic basalt fibers (BF) has been carried out in polymer composites. The effect of stereoregularity on the interface crystallization was systemically studied by microstructure. From polarized optical microscopy (POM) analysis, it was found that the transcrystallinity of PLLA was influenced by temperature. Moreover, stereoregularity significantly affects the crystallization kinetics. It was also found that increased molecular mobility providing faster orientation with high stereoregularity and low molecular weight. It might be the reason for the observation that the PLLA290 samples crystallized more rapidly than the PLLA4032D samples. Appropriate molecular stereoregularity exhibits a clear increase in extensional stress that is directly correlated with the crystalline orientation of the crystallization samples. The mechanism of formation of transcrystallinity underwent the process of "a mismatch in thermal expansion coefficients" with the extensional stress.