Life‐Cycle‐Integrated Molecular Design of Hindered Phenylene Biacetal Epoxies for Practical Recyclable Composite Applications

Abstract

ABSTRACT Carbon‐fiber reinforced polymer (CFRP) composites are central to lightweight wind‐energy infrastructure but suffer from poor end‐of‐life circularity due to permanent epoxy thermoset matrices. Here we present a life‐cycle‐integrated molecular design strategy for circular epoxy resins based on a hindered phenylene biacetal architecture, overcoming the longstanding industrial trade‐offs between scalable synthesis, processability, high in‐service performance, chemical recyclability, and long‐term stability. The resins are prepared through one‐pot scalable synthesis (≥200 g), producing liquid monomers compatible with vacuum‐assisted resin infusion molding (VARI) with processing windows exceeding 60 min at 55°C. The resulting networks exhibit strong thermal–mechanical properties ( T g = 119°C–136°C, tensile strength ≥72 MPa) and significantly improved impact resistance (+83% vs. commercial bisphenol A epoxy), together with excellent durability, including negligible creep at 180°C and stable properties after prolonged hygrothermal aging (60°C/90% RH, 32 days). Dormant dynamic acetal linkages enable weak‐acid‐triggered deconstruction at room temperature, allowing 100% nondestructive carbon‐fiber recovery and >80% recovery of high‐purity monomeric precursors. Artificial‐intelligence‐assisted life‐cycle assessment indicates a 45%–56% reduction in cradle‐to‐grave CO 2 emissions compared with conventional CFRP disposal, with a total resource reutilization/upcycling rate exceeding 92%. This platform provides a practical pathway toward circular structural composites for net‐zero infrastructure.