Reversibly Cross‐Linked Plastics Meet Carbon Fibers: Closed‐Loop Recyclable Composites with Enhanced Mechanical Strength and Stability

Abstract

Abstract Efficient recycling of carbon fiber‐reinforced polymer composites (CFRCs) into their original monomers and carbon fibers (CFs) in a non‐destructive manner remains a significant challenge. In this study, high‐performance, closed‐loop recyclable aromatic polyamide (APAD) plastics are synthesized via polycondensation of aromatic amines and aromatic aldehydes through dynamic imine bonds. Due to their fully aromatic structure as well as interchain hydrogen bonds and π–π interactions, APAD plastics exhibit a tensile strength of ≈78.3 MPa, a glass transition temperature ( T g ) of ≈200.4 °C, and excellent chemical resistance. The APAD plastics can be depolymerized in a mixture of polar organic solvents and acids at ambient temperature, enabling high‐purity recovery of monomers through their precipitation in selective solvents. Water‐resistant CF/APAD composites are fabricated through complexation of APAD plastics with CF cloths. These composites exhibit mechanical properties comparable to those of CF/epoxy thermoset composites and superior thermal stability. The mild depolymerization conditions for APAD plastics enable the efficient disintegration of CF/APAD composites. Therefore, non‐destructive recovery of CFs and monomers can be realized. The recovered CF cloths and monomers can be used to re‐manufacture the original CF/APAD composites. This study presents an effective method for the closed‐loop recycling of CFRCs, offering significant environmental and economic benefits.