Carbon Fiber-Reinforced Dynamic Covalent Polymer Networks Containing Acylsemicarbazide Bonds: Toward High-Performance Composites with Excellent Self-Healing and Upcycling Performance

Dynamic covalent polymer networks (DCPNs) with self-healing and recycling performance are highly relevant to sustainable development. Disposal of plastic wastes generated during DCPN reprocessing still faces serious challenges and deserves to be explored. Herein, high-performance polyacylsemicarbazide (PASC) with DCPNs exhibiting excellent self-healing and recycling properties are synthesized by the reaction of sebacic dihydrazide with isophorone diisocyanate and hexamethylene diisocyanate trimer. Upcycling of the PASC waste generated after four-time reprocessing is achieved by adding epoxy monomers and amine curing reagents, followed by a thermal treatment. The optimized epoxy resin exhibits a tensile strength of 101 MPa, Young's modulus of 2.73 GPa, elongation at break of 8.67%, toughness of 7.13 MJ·m–3, Tg of 140 °C, and Td of 250 °C, which overall surpass those of the original DCPNs, demonstrating excellent upcycling performance. The recycled resin waste from the carbon fiber-reinforced DCPNs can be upcycled using the same strategy. The upcycled epoxy resin and recycled fiber can be re-employed to prepare high-performance composites with robust mechanical properties. Given the low cost and commercial availability of the monomers, successful upcycling of PASC wastes not only reduces environmental pollution, but also enables possible industrialization and contributes to the circular economy.