A study of structure and property changes of biodegradable polyglycolide and poly(glycolide-co-lactide) fibers during processing and in vitro degradation

Structure and properties of bioabsorbable polyglycolide (PGA) and poly(glycolide-co-lactide) (PGA-co-PLA) fibers were investigated during several industrial processing stages and in vitro degradation by means of wide-angle X-ray diffraction (WAXD), dynamic mechanical analysis (DMA) and mechanical property tests. In the orientation stage, the PGA fibers were found to have higher degrees of crystallinity than corresponding PGA-co-PLA samples produced under similar conditions. In the hot-stretching and post-annealing stages, after fibers were braided, PGA samples were found to gain more crystallinity and higher T_g than PGA-co-PLA samples. The higher crystallinity in PGA fibers resulted in a slower rate of degradation. DMA results showed that a great deal of internal stress that was built during orientation and hot-stretching stages was released in the post-annealing stage for all PGA and PGA-co-PLA samples. During earlier stages of in vitro degradation, both PGA and PGA-co-PLA samples exhibited the typical cleavage-induced crystallization mechanism. The heat shrinkage in the glass transition area was found to disappear after 6-8 days of degradation for all PGA and PGA-co-PLA samples, indicating the amorphous portions of the polymers lost orientation after a short period in the buffer solution, most likely due to relaxation of the cleaved chains.