Sustainable epigallocatechin gallate-based polycarbonate vitrimers with flame-retardant and antioxidant properties for closed-loop recyclable carbon fiber composites

Sustainable polycarbonate (PC) vitrimers were synthesized through a green one-step reaction between biomass-derived epigallocatechin gallate (EGCG) and bis(6-membered cyclic carbonate) (BCC). These EGCG-based networks exhibit exceptional mechanical properties, flame retardancy, antioxidant capacity, self-healing ability and reprocessability. EGCG content significantly affects the performance of the resulting networks. As the EGCG content increases, the mechanical properties, stress relaxation, flame retardancy, antioxidant capacity were improved. The increased EGCG content enhances crosslinking density, resulting in superior flame retardancy with a UL-94 V-0 rating and limiting oxygen index (LOI) of 28.1 %. The dynamic network structure enables efficient stress relaxation, retaining over 80 % of mechanical properties after three reprocessing cycles. Additionally, the material exhibits thermal self-healing efficiency of 90 % through transcarbonation-driven network rearrangement. Additionally, EGCG-based carbon-fiber composites achieved close loop recycling, addressing environmental concerns while maintaining high performance. Present strategy simultaneously enhances recyclability, fire safety, and sustainability, offering a circular economy-aligned solution for polymers used in electronics, automotive, and aerospace applications.