Upcycling Recycled Epoxy-Based Vitrimer for Enhancing Toughness of Poly(ethylene terephthalate)

This article reports a potential high-value reuse pathway for a depolymerized vitrimer matrix from abandoned composites. A series of polyethylene terephthalate (PET)-based copolymers containing various amounts of added vitrimer as the toughness modifier were synthesized by melt polymerization. The thermal, mechanical, and crystallization behaviors of the synthesized copolymers were determined, indicating all samples presented excellent thermal stability at Td-5% above 390 °C. The differential scanning calorimetry and wide-angle X-ray scattering diffraction results demonstrated that the copolymers maintained the crystallization characteristics of normal PET, while a slight reduction in the crystallizability was observed upon the incorporation of the vitrimer. Moreover, the mechanical behaviors of the copolymers were investigated systematically. Surprisingly, a significant increment was observed in the elongation rate from 11.1 to 804.2% when the added vitrimer content increased from 0 to 0.25 wt%, and this trend decreased slightly as the vitrimer content increased further. Impact strength examinations revealed twofold enhancement as the vitrimer concentration increased from 0 to 0.25 wt%, with further improvement as the content was increased. The shore D hardness test illustrated that all samples showed comparable values at around 80, suggesting that introducing the vitrimer does not decrease the hardness of the PET-based copolymers.