Waste-free recycling of multifunctional epoxy resins and carbon fiber composites enabled by dynamic aminal bonds

Abstract

As one of the most widely used thermosetting resins, epoxy resins have extensive applications in composite materials. Growing environmental concerns and the need for resource optimization have brought increased attention to the degradation and recycling of these composites. In this study, a hardener incorporating aminal bonds was synthesized using 3-methylaminopropylamine, which contains both primary and secondary amine groups. Subsequently, a series of epoxy resins was prepared, accompanied by the development of a sustainable and efficient strategy for their recycling. Among these, EP-H4 resin undergoes rapid degradation in amines at 80 °C within 2 h via the dynamic exchange of aminal bonds, demonstrating shape-memory, self-healing and reprocessability properties. Compared to traditional epoxy resins, EP-H4 exhibits comparable thermal and mechanical properties. A composite material was fabricated using EP-H4 and CF fabrics, and the CF fabrics achieved non-destructive recycling at 80 °C for 4 h. The degradation products can be directly utilized as curing agents for epoxy resins. HMB can be readily synthesized, recycled, reused, and the whole process is entirely waste-free.