Polylactide fibers with enhanced hydrolytic and thermal stability via complete stereo-complexation of poly(l-lactide) with high molecular weight of 600000 and lower-molecular-weight poly(d-lactide)

Abstract

One-hundred percent stereo-complexation in poly(l-lactide) (PLLA)/poly(d-lactide) (PDLA) fibers with non-equivalent molecular weights could be achieved via thermal treatment. Stereo-complexed polylactide (sc-PLA) fibers exhibited excellent hydrolysis resistance and thermal resistance. Till now, preparation of sc-PLA fibers with satisfactory qualities required both PLLA and PDLA with equivalently high molecular weights. Moreover, the high-molecular-weight PDLAs are expensive, restricting industrial-scale production and applications of sc-PLA products. In this study, equal-weight mixtures of low-molecular-weight PDLA (L-PDLA) and high-molecular-weight PLLA (H-PLLA) were melt spun into sc-PLA fibers and then completely stereo-complexed via thermal treatment. The hydrolysis resistance of L3/D1 fibers [PLLA (Mv = 3.0 × 105)/PDLA (Mv = 1.0 × 105)] was similar to that of L3/D3 fibers [PLLA (Mv = 3.0 × 105)/PDLA (Mv = 3.2 × 105)], but much higher than that of L3 fibers [PLLA (Mv = 3.0 × 105)]. Melting temperature and softening temperature of L3/D1 fibers (223 and 126 °C) were also similar to those of L3/D3 fibers (224 and 131 °C), but higher than that of L3 fibers (172 and 72 °C). Utilizing H-PLLA and L-PDLA to prepare sc-PLA fibers with excellent performance is conducive to the wide industrial application of sc-PLA.