A Curing Agent for Facile Fabrication of Intrinsically Flame-Retardant Epoxy Vitrimers with Catalyst-Free Mixed Carboxylate/Phosphonate Transesterification

Epoxy vitrimers combine the advantages of thermosetting and thermoplastic materials, making them an ideal alternative to traditional thermosetting resins. However, the fabrication of high-performance flame-retardant epoxy vitrimers remains a challenge. In this study, utilizing (2-carboxyethyl)phenylphosphinic acid (CEPPA) as a curing agent, we facilely fabricated a dual-dynamic epoxy vitrimer incorporating carboxylate esters and phosphonate esters (CEEP). Compared to traditional epoxy resin (DDEP), the epoxy vitrimer exhibited tensile strength comparable to traditional epoxy resins and significantly outperformed in terms of Young's modulus. In comparison to carboxylate ester epoxy vitrimer (PAEP), CEEP demonstrated improved solvent resistance and the ability for recycling without the need for a catalyst. Additionally, CEEP exhibited outstanding flame retardancy, achieving a V-0 rating in UL-94 testing, with a remarkable 66.9% reduction in peak heat release rate (PHRR) and a significant 34.5% decrease in total heat release (THR) in cone calorimetry test compared to DDEP. The work offers a promising way for the facile fabrication of high-performance flame-retardant epoxy vitrimers.