Chemically Recyclable Carbon Fiber Reinforced Polymer Composites with Ultrafast Degradation Rate via an Epoxy Monomer Bearing Four Acetal Groups

Abstract Epoxy resins represent a cornerstone of high‐performance materials due to their outstanding thermal and mechanical properties. However, the irreversible covalently crosslinked architecture of conventional epoxy thermosets poses significant challenges for chemical recycling and circular utilization. Herein, acid‐activatable rigid spiro diacetal and acetal are incorporated into one epoxy monomer by fully exploiting both the hydroxyl and aldehyde functionalities of vanillin. This design combines excellent mechanical performance with controllable depolymerization of the cured epoxy resin network, allowing full recovery of vanillin, pentaerythritol, and defined polyols for direct monomer regeneration and upcycling into high‐resilience polyurethanes. The optimized resins cured with 1,3‐Bis(aminomethyl)benzene (MXDA), affording a tensile strength of 126.4 MPa, a Young's modulus of 2.9 GPa, can be fully degraded in 0.1 M HCl for 69 min at 50 °C or 110 min at room temperature. Furthermore, carbon fiber reinforced polymer (CFRP) composite fabricated from the degradable epoxy monomer is fully recyclable without fiber damaging, enabling sustainable and circular life cycles for advanced composite materials. This work offers a versatile and scalable strategy for designing high‐performance thermosetting systems with integrated degradability and full material circularity.