Simple and Mild Method for the Recycling of Carbon-Fiber-Reinforced Bismaleimide Resin Composite Waste

Recycling of high-performance carbon-fiber-reinforced polymer (CFRP) composite waste has been significantly challenging due to its insoluble and infusible thermosetting matrix. In this study, a simple and efficient strategy for the closed-loop recycling of a commercial bismaleimide (BMI)-based composite was described. The mild conditions utilized for the decomposition of CFRP composites circumvented the severe conditions required for the recycling of traditional composites. The BMI resin polymer was successfully degraded and removed from the composite within 5 h at a reaction temperature of 160 °C and ambient pressure, which was achieved using only monoethanolamine (MEA) solvent without any catalyst. During the reaction, the C–N and C–C bonds in the cross-linked structure were broken, and the polymer was completely transformed to oligomers containing amine and hydroxyl groups. Then, the clean carbon fibers (CFs) were recycled with a strength retention of ∼94% and a modulus retention of ∼97%. The solvent used during recycling was recovered with a recovery efficiency of ∼85%. In addition, the degraded BMI resin was facilely reclaimed from the degraded liquid products by distillation. The degraded BMI resin was reused to fabricate a new resin material with good mechanical properties. In this study, a novel recycling paradigm for a waste BMI-based composite is provided, which is conducive to minimizing environmental contaminations and alleviating the consumption of highly valuable CF resources.