Improved heat resistance properties of poly(l-lactide)/basalt fiber biocomposites with high crystallinity under forming hybrid-crystalline morphology.

In this work, the heat resistance and thermomechanical properties of biodegradable poly(l‑lactide) (PLLA) was improved greatly by using short basalt fibers (SBF). The heat deformation temperature (HDT) of PLLA/SBF composites was markedly improved from 62.5 to158.8 °C when its crystallinity was increased from 44.3% to 67.7% after appropriate thermal treatment. Fibers reinforcement and interface crystalline morphology were the two important reasons for the change of in heat deformation and storage modulus of PLLA before and after crystallization. Polarized optical microscopy (POM) demonstrated that the transcrystalline and shish-kebab were successfully induced by SBF, and the "crystalline-network" structure was formed in the composites after isothermal treatment. The PLLA/SBF composites with the formation of interface crystalline had a significantly higher overall heat resistance compared with the common PLLA. As the scanning electron microscope (SEM) analysis, the low values of impact strength might be due to the presence of large spherulites cracks and weak interfacial adhesion.