Chemically Recyclable Polyurea Thermosets: Reversible β-Amino Ester Networks Enable Undamaged Aramid Fiber Recovery...

Traditional thermoset-based aramid fiber-reinforced composites (AFRCs) possess ultrahigh specific strength and puncture resistance but face intractable recycling issues due to their permanent cross-links, leading to waste accumulation and underutilization of aramid fibers (AFs). Although dynamic covalent chemistry-based thermosets offer a sustainable alternative, balancing their mechanical performance with recyclability and realizing upcycling remains a bottleneck. Herein, we design a chemically recyclable polyurea thermoset (PUA-PBAE_x) based on reversible β-amino ester networks, which achieves high mechanical strength (∼74.4 MPa for PUA-PBAE_1.5) and good thermal stability. The PUA-PBAE_x can serve as an ideal matrix for AFRCs (PUA-PBAE_x/AF-y), delivering exceptional puncture resistance and specific strength. Notably, the PUA-PBAE_x/AF-y composite can be fully depolymerized under mild acidic conditions, enabling the full recovery of intact AFs and conversion of the degraded linear polyurea into a high-performance reusable adhesive with robust adhesion (∼13.8 MPa) to multiple substrates. This work provides a circular economy strategy for next-generation AFRCs that integrates high mechanical performance, closed-loop recycling, and upcycling capabilities.