Full Recovery of Polyimide Wastes Into High-Value Products Through Break and Reconstruction of Imide Ring.

Polyimide (PI) is a promising engineering plastic but difficult to recycle due to its aromatic heterocyclic structures, especially for thermosetting PI. Herein, an ingenious cascade pathway for high-value and full recovery of thermosetting PI under mild conditions is presented. Specifically, the imide ring is first broken through aminolysis to degrade PI and is reconstructed under following hydrolysis to achieve excellent thermal stability in subsequent products. When recycling thermoplastic PI, the yield of 91% and 82% appears in diamines and polyhydroxylated compounds, respectively. As focusing on the recovery of thermosetting PI, aside from the efficient recovery of diamines, the crosslinked component is converted into hyperbranched flame retardant carbonizers for preparing copolyester, and it correspondingly achieves good flame retardant effect with an addition of merely 4 wt.%. The success of this work capitalizes on the unique structure and properties of the raw material, stimulating innovative pathways in the field of thermoset waste recovery and new material design.