Imine-Containing Thermosetting Epoxy Resin and Closed-Loop Recycling of Carbon Fiber Reinforced Composites

Thermosetting epoxy materials find extensive applications across diverse fields, but their irreversible chemical cross-linked networks lead to severe resource depletion. To address this problem, current closed-loop recycling approaches frequently rely on high-temperature/high-pressure conditions and a long recycling reaction time, demonstrating low efficiency and economic viability. In this work, a high-performance recyclable epoxy resin (EP-VAN-DDMX) was prepared through the strategy of designing cross-linked networks to lock molecular structures and leveraging the excellent dynamic properties of dynamic bonds. In the locked state, EP-VAN-DDMX exhibited excellent tensile properties (tensile strength and Young’s modulus of 94.68 MPa and 2.34 GPa, respectively), thermal stability (Td5% at 333.75 °C), and solvent resistance. Through the excellent exchange mechanism of dynamic imine bonds, these epoxy resins were effectively reprocessed via heat treatment or rapid room-temperature hydrolysis (with a recycling efficiency close to 100%), thereby achieving versatile recycling. Based on its excellent recycling property, it could serve as a high-performance matrix material for fabricating carbon fiber reinforced composites (CFRCs). The depolymerization process of composite materials proceeded rapidly at room temperature without affecting the performance of carbon fibers (CFs), and recycled CFRCs still maintained their original performance. This study established a methodology for fabricating high-performance thermosetting epoxy resins while enabling their implementation in closed-loop recyclable CFRCs.