Tough Epoxy Networks With Dynamic Acylhydrazone Bonds for Recyclable Carbon Fiber‐Reinforced Composites

Carbon fiber-reinforced composites (CFRCs) that are based on thermosetting epoxy resins are widely used. However, they are difficult to recycle, thereby posing environmental challenges. Although incorporating reversible dynamic bonds into epoxy networks enables the recycling of CFRCs, achieving strong mechanical properties, reprocessability, and efficient degradation ability under mild conditions remains challenging. In this study, robust epoxy networks were developed using dynamic acylhydrazone bonds to recycle CFRCs. A novel acylhydrazone-containing diamine curing agent was synthesized and used to cure epoxy resin, resulting in an epoxy with excellent chemical and solvent resistance. Synergistic hydrogen bonding and C═N exchange enabled a tensile strength of up to 106.9 MPa, retaining > 75 MPa after three reprocessing cycles. Under mildly acidic conditions, C═N cleavage enabled the efficient recovery of intact carbon fibers comparable to that of virgin fibers, and the degraded matrix could be reused as an adhesive. This study presents a sustainable approach that combines high strength, reprocessability, degradability, and recyclability in high-performance epoxy networks and CFRCs systems.