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-healingandrecycling performance are highly relevant to sustainable development.Disposal of plastic wastes generated during DCPN reprocessing stillfaces serious challenges and deserves to be explored. Herein, high-performancepolyacylsemicarbazide (PASC) with DCPNs exhibiting excellent self-healingand recycling properties are synthesized by the reaction of sebacicdihydrazide with isophorone diisocyanate and hexamethylene diisocyanatetrimer. Upcycling of the PASC waste generated after four-time reprocessingis achieved by adding epoxy monomers and amine curing reagents, followedby a thermal treatment. The optimized epoxy resin exhibits a tensilestrength of 101 MPa, Young's modulus of 2.73 GPa, elongationat break of 8.67%, toughness of 7.13 MJ & BULL;m(-3), T (g) of 140 & DEG;C, and T (d) of 250 & DEG;C, which overall surpass those of the originalDCPNs, demonstrating excellent upcycling performance. The recycledresin waste from the carbon fiber-reinforced DCPNs can be upcycledusing the same strategy. The upcycled epoxy resin and recycled fibercan be re-employed to prepare high-performance composites with robustmechanical properties. Given the low cost and commercial availabilityof the monomers, successful upcycling of PASC wastes not only reducesenvironmental pollution, but also enables possible industrializationand contributes to the circular economy. Upcycling of the plastic wastes generatedfrom multiplereprocessing of polyacylsemicarbazide is achieved by adding epoxymonomers and amine curing reagents followed by thermal treatment.