Dual dynamic bonds induced reversibly cross-linked carbon fiber-reinforced epoxy composites with anti-flammability, self-healing capacity and recyclability

Traditional carbon fiber-reinforced epoxy composites face problems such as high flammability, irreversible damage, and solid waste treatment. To overcome these problems, furan-derived epoxy vitrimers were synthesized by introducing dual ester and Diels-Alder dynamic bonds into crosslinked networks. By tuning the ratios of hardeners (DOPO-MA and glutaric anhydride), a series of furan-derived epoxy vitrimers (PDMP-DGFA-D₀G₁, PDMP-DGFA-D₁G₂, PDMP-DGFA-D₁G_1.5 and PDMP-DGFA-D₁G₁) were prepared. Furthermore, the optimized formulation (PDMP-DGFA-D₁G₂) was selected as the resin matrix to impregnate the carbon fibers, and PDMP-DGFA-D₀G₁ without flame retardant elements was used as the control sample. Carbon fiber-reinforced epoxy composites (PDMP-DGFA-D₀G₁/CF and PDMP-DGFA-D₁G₂/CF) based on dual dynamic bonds were prepared. Compared with PDMP-DGFA-D₀G₁/CF, PDMP-DGFA-D₁G₂/CF reached the UL-94 V-0 classification, with the LOI increasing from 35.5% to 43.5%. The tensile strength and impact strength of PDMP-DGFA-D₁G₂/CF were 407.74 MPa and 96.3 kJ/m², respectively. PDMP-DGFA-D₁G₂/CF had good recyclability, and the surface morphology and chemical structure of the recycled carbon fibers were essentially unchanged, indicating the non-destructive recycling of the carbon fibers. This work not only effectively addresses the difficult balance between high-performance and closed-loop recycling in traditional thermosetting composites but also significantly improves resource utilization efficiency.