Structural evolution of biodegradable polyglycolide fibers under stress-temperature coupled field and its impact on properties

The properties of polyglycolide (PGA) fibers used as surgical sutures depend on their aggregated state structure. The study investigated the relationship between the structural evolution and macroscopic properties of PGA fibers with low-crystallinity under coupled stress-temperature fields by conducting in-situ WAXD/SAXS, DSC and SEM measurements. The WAXD and SAXS results indicated that the structural evolution during the lowtemperature stretching stage primarily relied on stress-induced amorphous molecular chain orientation and the formation of small crystals. The DSC results confirmed that uniaxial stretching enhanced the orientation of amorphous molecular chains, leading to cold crystallization of PGA fibers at lower temperatures. During the heating stretching stage at temperatures of 60-90 degrees C, numerous crystals were generated through a lamellar insertion mechanism and underwent lateral growth. This is reflected by the crystallinity, crystal orientation, and crystallite sizes increased significantly, while the long period decreased rapidly. The high-temperature stretching stage resulted in fragmentation and recrystallization of lamellar crystals, forming fibrous crystals. Stretching at 110 degrees C exhibited higher Iq2/Iq1 values than other temperatures, which means that 110 degrees C is more favorable for the formation of fibrous crystals. Additionally, PGA fibers stretched at 150 degrees C exhibited the highest crystallinity and crystal orientation, which led to a 440 % increase in tensile strength. Its resistance to degradation has also been significantly improved compared to the original fibers.