Enhanced rheological, crystallization, mechanical, and heat resistance performance of poly(L-lactide)/basalt fibers composites via in situ formation of stereocomplex polylactide crystals

Due to its favorable mechanical strength, transparency, and biocompatibility, polylactic acid (PLA) has considerable potential as a biodegradable material. Nevertheless, developing high-performance PLA composites through environmentally friendly and cost-effective methods remains a significant challenge. In this study, the composites comprising poly(L-lactide) (PLLA), basalt fibers (BFs), and poly(D-lactide) (PDLA) are prepared through facile melt blending. The in situ formed stereocomplex polylactide (SC-PLA) crystals improve the crystallization ability and rheological behavior of PLLA/BF/PDLA composites. Upon adding 5 wt% PDLA, BFs are nicely dispersed in PLLA matrix because of increased shear intensity. The synergistic effect of BFs and SC-PLA crystals enhances the mechanical, thermomechanical, and heat resistance properties of PLLA. In particular, PLLA/BF/10%PDLA composites exhibit a Vicat Softening Temperature (VST) of 155.5°C, increasing by approximately 100°C over neat PLLA. Annealing treatment increases the Young's modulus, thermomechanical properties, and VST of samples while reducing their tensile strength. Interestingly, the tensile strength of the annealed PLLA/BF/10%PDLA composites is 50.2 MPa, twice that of the annealed neat PLLA due to the introduction of SC-PLA crystals. Simultaneously improving the rheological, mechanical, and heat resistance performance of PLLA opens possibilities for expanding its potential applications in the industrial field.