Flame-retardant epoxy vitrimers with high strength and high-Tg for recyclable carbon fiber-reinforced composites

Epoxy vitrimers are attractive as matrices for recyclable carbon fiber-reinforced composites (CFRC) but are usually limited by the relatively low glass transition temperature (Tg), low strength, and flammability. Herein, we developed high-strength, high-Tg, and flame-retardant epoxy vitrimers based on dynamic imine bonds and reactive flame-retardant agents 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its derivative TZ. We obtained high performance and fire-safe CFRC with remarkable mechanical properties (tensile strength: 679 MPa, tensile modulus: 5.8 GPa) and excellent flame retardance (LOI: 35.0%, UL94: V-0 ranking) by using the vitrimer as a matrix. In addition, we achieved non-destructive recycling of the carbon fiber through deconstruction of the vitrimer network by using the dynamic nature of the imine bonds. We believe that this study could provide hints for future works in terms of high-performance, fire-safe, and recyclable CFRCs.