Closed-loop recycling and degradation of guaiacol-based epoxy resin and its carbon fiber reinforced composites with S-S exchangeable bonds

The waste and desertion of petroleum-based epoxy resins have attracted increasing concerns on the damage and pollution to the environment because they are difficult to reprocess and reuse after curing. Once broken or injured, the recovery or degradation of composites is a tough challenge owing to their permanently cross-linked networks. In this paper, a novel guaiacol-based epoxy resin (BGF-EP) was prepared from renewable resources instead of conventional petroleum-based bisphenol A, curing with 4-aminophenyl disulfide (AFD). The epoxy vitrimer BGF-EP-AFD had appreciable thermal stability (Tg:143 °C, Td5%:295 °C), sufficient mechanical properties (tensile strength:55.54 MPa, elongation at break:12.23%) and stress relax from 300 min at 130 °C to 27.5 s at 200 °C. And the vitrimer could be reprocessed into a complete film. More excitingly, an efficient strategy was proposed to dissolve the cured resin and recycle its carbon fiber reinforced composites in a closed loop in an appropriate mixing solution (50%DMF/50%β-ME) at room temperature. The recovered carbon fibers are not altered and remain intact for the next utilization as confirmed by SEM. This work contributes the development of guaiacol-based renewable functional materials and provides a feasible and economical way to recycle and reprocess the carbon fiber reinforced epoxy composites.