Hygrothermal Degradation Behavior and Structural Evolution of Electrospun Poly(ethylene terephthalate) Fiber Mats

Growing environmental concerns over plastic waste have recently spurred interest in degradable polymers. Among these, polyesters are considered promising candidates due to the hydrolyzable nature of their ester linkages. While the degradation behavior of aliphatic polyesters, known for their relatively high degradability, has been extensively studied with a focus on aggregation structures, our understanding of aromatic polyesters, which exhibit much lower degradability, remains limited. In this study, we investigated the time-dependent degradation behavior of electrospun poly(ethylene terephthalate) (PET) fiber mats exposed to a hygrothermal environment at 403 K and 85% relative humidity. Initially, the weight of the PET fiber mats remained nearly constant, followed by a marked decrease upon longer exposure. Scanning electron microscopy revealed progressive surface roughening, along with the formation of holes and cracks in the fibers. Structural analysis using attenuated-total-reflection Fourier transform infrared spectroscopy and X-ray diffraction analysis indicated that in the early stages, hydrolysis-induced chain scission promoted crystallization. In contrast, during later stages, extensive hydrolysis led to depolymerization of the PET chains into monomeric species, resulting in marked weight loss. These findings provide new insights into the degradation mechanism of aromatic polyesters and may inform the design and development of degradable aromatic polyester-based materials and devices.