Sequential Dual-Curing-Accessed Epoxy/Benzoxazine Interpenetrating Networks for High-Performance and Degradable Carbon Fiber Composites

Composites composed of epoxy resin and carbon fiber prepared by prepreg-based processing are appealing for demanding structural applications due to their exceptional mechanical properties. Nevertheless, the one-part nature and nondegradability of common partially cured epoxy resins render prepregs prone to undesired premature curing, thus entailing functional failure. Here, we report a sequential dual-curing strategy to fabricate resins with epoxy/benzoxazine interpenetrating networks. At low temperature, the epoxy monomer reacts with Jeffamine to form a flexible network featuring ester bonds. Upon heating to higher temperatures, the benzoxazine monomers undergo ring-opening polymerization to generate a rigid network within the preformed flexible matrix, forming a synergistic interpenetrating architecture. This stepwise approach not only prevents premature cross-interference but also generates a synergistic interpenetrated morphology with high mechanical properties and thermal stability ( T g of 270 °C, flexural strength of 120 MPa, flexural modulus of 4.7 GPa). This strategy is compatible with prepreg processing, allowing impregnated carbon fibers to remain stable at room temperature for more than 30 days after the single curing and subsequently be converted into high-performance composites during the dual curing stage (flexural strength of 408 MPa, flexural modulus 59 GPa, and interlaminar shear strength of 34 MPa). Furthermore, the embedded ester bonds enable chemical degradation of the matrix under acidic conditions, allowing efficient recovery of carbon fibers. This strategy will inspire the development of practical applications of interpenetrating polymer networks.