Reprocessable and Closed-Loop Recyclable Bio-Based Cross-Linked Polyimide Composites Towards Regeneration

With the global surge in polymeric material consumption, the exploitation of sustainable thermosetting composites with high mechanical performance, superior tribological properties and recyclability is urgently demanded. In this study, we synthesized a bio-based cross-linked polyimide (Bio-PI x ) via Schiff base reaction, and the prepared materials exhibit high thermomechanical properties, with a tensile strength of approximately 105.6 MPa and a Young's modulus of about 3.5 GPa. Moreover, it possesses recyclability, as evidenced by a monomer recovery rate of up to 90% under mild conditions through the cleavage and recombination of imine bonds (–CN–). Furthermore, reduced graphene oxide (rGO) was selected as a solid lubricant to fabricate rGO-reinforced Bio-PI x (rGO@Bio-PI x ) composites. Results demonstrated that compared with pure Bio-PI x , the rGO@Bio-PI x composites not only maintained favorable mechanical stability but also exhibited significantly enhanced tribological properties with a 65.6% and 55.5% reduction in friction coefficient (COF) and volume wear rate ( W ), respectively. More importantly, rGO@Bio-PI x can be depolymerized into monomers at room temperature, achieving a 95% recovery rate for rGO. Notably, the rGO@Bio-PI x composite material can be reconstructed without requiring catalysts, and the recycled rGO@Bio-PI x (R-rGO@Bio-PI x ) retained its superior performance, demonstrating renewable lubricating property. This approach presents a promising pathway for developing high-performance thermoset polyimide composites for sustainable multifunctional applications. Highlights The bio-based cross-linked polyimide films exhibit excellent comprehensive performance and reprocessability. 90% monomer recovery is achieved under mild conditions via imine bond rearrangement. Composites show superior tribological properties and closed-loop recyclability.