Cyclic ketal bridged bisepoxides: enabling the design of degradable epoxy-amine thermosets for carbon fiber composite applications

Abstract

A series of degradable epoxy-amine thermosets was developed using novel cyclic-ketal based bisepoxide monomers and a commercially available diamine. By tailoring the design of the ketal bridge, we fabricated thermosets that undergo complete degradation with tunable degradation profiles in low pH conditions while maintaining stability in mildly acidic to basic pH conditions. The thermomechanical and mechanical properties of these degradable thermosets were comparable to a non-degradable commercial variant, offering similar or superior performance. We further demonstrated the application of these degradable thermosets in the construction of carbon-fiber reinforced polymer (CFRP) composites. Using aqueous conditions, the polymer matrix could be fully degraded in low pH conditions, enabling the recovery of pristine carbon fibers. This work showcases the potential of cyclic-ketal based thermosets in achieving a delicate balance between robust performance in practical composite applications and efficient end-of-use recovery strategies. The successful recovery and reuse of high-quality carbon fibers from CFRPs not only contribute to resource sustainability but also offer economic advantages by potentially reducing material costs and waste.