Evolution of structure of highly crystalline poly(glycolide-co-lactide) under varying hot stretching rates

Abstract

With the sustained global focus on sustainable development, the utilization of biodegradable polymers as alternatives to traditional plastics has emerged as a significant research topic. Among them, poly(glycolide-co-lactide) (P(GA-co-LA)) has garnered widespread attention in practical applications due to its exceptional biocompatibility and biodegradability. In this study, in-situ synchrotron radiation wide-angle X-ray diffraction (WAXD)/small-angle X-ray scattering (SAXS) techniques were employed to investigate the structural evolution of highly crystalline eutectic P(GA-co-LA) during hot stretching at strain rates ranging from 0.04·min⁻¹ to 4.00·min⁻¹. The research results indicate that the structural evolution primarily encompasses crystal slip, fragmentation, and recrystallization processes, as well as stress-induced formation of new crystals. In the early stage of stretching, as the strain rate decreases, the phenomenon of crystal slip diminishes, effectively inhibiting crystal fragmentation. During the intermediate stage, low-rate stretching leads to a higher degree of order in the molecular chain structure due to the enhanced exclusion effect of LA units. In the later stage of stretching, low-rate stretching conditions are more conducive to the growth of new lamellar crystals and the formation of highly oriented crystals. The crystallite size continues to decrease, and the structural arrangement of P(GA-co-LA) tends to become more regular. It is difficult for LA units to incorporate into the newly formed crystals, thereby enhancing the crystallinity and orientation of P(GA-co-LA). Low-rate stretching further promotes the perfection and evolution of the lamellar structure, facilitating the transition from lamellar crystals to highly oriented fibrous crystals. This reduces the probability of LA units incorporating into the lattice, thus enhancing the regularity of the overall crystal structure.