Degradable Carbon Fiber-Reinforced Epoxy Resin Composites Based on Dynamic Benzyl Ether Bonds

Epoxy-based carbon fiber composites have been increasingly applied in aerospace, transportation, sports goods, electronic fields, etc. The recycling and reuse of epoxy composite becomes an environmental issue and remains a challenge due to the permanent cross-linked network structure of epoxy. Developing epoxy resins with covalent adaptive network structures by incorporation of dynamic covalent bonds provides an opportunity to overcome this challenge. In this study, we develop a kind of novel epoxy monomer containing a dynamic benzyl ether bond, which further reacts with commercial amine-curing reagents to obtain epoxy thermosets. The dynamic epoxy thermosets can degrade at 190 degree celsius in benzyl alcohol under the catalysis of aluminum chloride within 3 h, which is ascribed to the dynamic bond-exchange reaction between benzyl ether bond and benzyl alcohol. The optimized epoxy thermoset exhibits a glass transition temperature of 167 degree celsius, a tensile strength of 91.8 MPa, and Young's modulus of 2.2 GPa. Furthermore, based on the epoxy resin containing a benzyl ether bond, the carbon fiber-reinforced composites are fabricated by applying a solvent-free hand lay-up process. The as-fabricated composite possesses a tensile strength of 725 MPa and Young's modulus of 27 GPa. Notably, the interlaminar shear strength reaches similar to 62 MPa, which is similar to 19% higher than that of the control sample made using the conventional bisphenol A epoxy resin. The degradability of the epoxy matrix realizes the nondestructive recovery of the carbon fibers from the composite wastes.