Network Regulation Strategy for High-Performance and Recyclable Biobased Epoxy Vitrimers and Efficient Recycling of Carbon Fiber-Reinforced Composites

Abstract

Balancing mechanical strength and dynamic adaptability remains a critical challenge for biobased epoxy vitrimers, which often suffer from compromised strength upon incorporating dynamic covalent bonds. Herein, a network regulation strategy is proposed to address this limitation through the rational design of cross-linking architecture in imine-based epoxy resins. A bioderived aromatic epoxy monomer (VTEP) was synthesized from vanillin and tyramine, followed by curing with diamine agents of varied structures to systematically tune network stiffness and cross-link density. Among the resulting systems, the epoxy vitrimer cured with m-xylylenediamine (VTEP/MXDA) possesses a high effective cross-link density of 2394 mol m–3 and exhibits a favorable combination of high mechanical strength (tensile strength, Young’s modulus, and elongation at break are 83.56 MPa, 2.35 GPa, and 9.68%, respectively), elevated glass transition temperature (172 °C), and appreciable dynamic behavior. The enhanced performance is attributed to the incorporation of rigid aromatic segments, which reinforce network integrity while preserving the exchangeable imine linkages. As a result, the VTEP/MXDA vitrimer demonstrates rapid stress relaxation, self-healing capability, and reprocessability. In contrast to conventional methods that rely on strong acids for imine bond hydrolysis, the vitrimer can achieve efficient degradation in a 2 M acetic acid solution under mild conditions, facilitating the recovery of carbon fibers with well-preserved morphology and mechanical properties from the corresponding carbon fiber-reinforced polymer composites. This work provides a feasible strategy for developing biobased epoxy resins with superior mechanical strength as well as favorable dynamic properties and offers insights into the design of recyclable carbon fiber-reinforced polymer composites.