A closed-loop recycling process for carbon fiber reinforced vinyl ester resin composite

Carbon fiber reinforced thermosetting polymer composites have been widely used in industrial fields, such as wind blades, aerospace and automobiles. However, it is extremely hard to degrade their waste due to the insoluble and infusible crosslinked networks. A solvothermal method is proposed to degrade carbon fiber reinforced vinyl ester resin composite (CF/VER) in this paper. The degradation reaction was conducted in a teflonlined autoclave at 160 degrees C to 240 degrees C for 60 min to 180 min using isopropanol and acetone as solvents. NaOH or KOH were added to efficiently accelerate degradation process. Degradation ratio up to 99.96% was achieved. Furthermore, a multi-step degradation mechanism was put forward based on FT-IR and GC/MS analysis of degradation products. SEM, FT-IR, and XPS analysis of recycled carbon fibers (RFs) revealed that resin was nearly completely removed. Furthermore, contact angle measurement showed surface wettability of RFs was enhanced. XRD and Raman spectra further verified microstructure of RFs was not damaged drastically. Besides, reusing of degradation products and RFs was explored. Epoxy resin cured with degradation products exhibited excellent performances. Meanwhile, flexural strength tests and SEM images of fracture surfaces showed RFs reinforced epoxy resin composites had superior mechanical strength due to stronger interfaces between fibers and resin. Therefore, an efficient and closed-loop recycling process demonstrated in this manuscript provides a new pathway for degradation and reuse of CF/VER.