Zero-waste closed-loop recycling of carbon fiber reinforced vitrimer-based polymer composites with a long-extended prepreg shelf life

Abstract

Despite significant advances in recyclable carbon fiber reinforced polymer (CFRP) composites, the successful integration of high-performance vitrimer polymers into the CFRP composite industry faces two major challenges. The first hurdle is establishing a viable closed-loop recycling system, where both the polymer matrix and carbon fibers can be entirely reused without any loss in mechanical performance. The second challenge lies in integrating vitrimer polymers into CFRP prepregs while maintaining their high-performance characteristics. In this study, a vitrimer polymer was synthesized from the reaction of a vanillin-derived trialdehyde monomer and poly (propylene glycol) amine-terminated ether (PPGTA) curing agent, forming a highly fire-resistant crosslinked Schiff base polymer network with dynamic imine bonds. The resulting vitrimer exhibited high mechanical properties, including a tensile strength of 48.5 MPa, Young’s modulus of 1.83 GPa, And 10% elongation at break, which are within the range of automotive-grade epoxy resins. In the developed zero-waste recycling process, both the polymer matrix and carbon fibers were fully reclaimed through depolymerization in an excess amount of PPGTA curing agent solution, followed by re-polymerization to fully close the loop for CFRP composite fabrication. The recycled Schiff base polymer demonstrated mechanical properties nearly identical to the original, with > 98% retention of tensile strength and modulus, ensuring effective and true closed-loop recycling with zero waste. Moreover, the dry Schiff base vitrimer-based CFRP prepregs Maintained their mechanical properties even after 3 months of storage at room temperature, showing only a 1.8% decrease in tensile strength And a 0.9% reduction in modulus, eliminating the need for cold storage and simplifying logistics.