Recycling of carbon fiber-reinforced epoxy resin composite via a novel acetic acid swelling technology

Compared with thermal or chemical recycling, the mechanical recycling of the carbon fiber-reinforced polymer (CFRP) is simpler, more economical, and produces less environmental pollution. However, the recycled products of mechanical recycling are only fillers or short fibers with poor reinforcing properties. In this study, acetic acid was used to achieve the full swelling and slight degradation of cured epoxy resin (CEP) in CFRP. The stiff CFRP became soft in the acetic acid medium at 140 °C, and it delaminated into soft single CFRP layers at 160 °C-220 °C within 1 h. Thus, the swollen CFRP can be easily cut into long strips, large thin slices, or other customized shapes. The length and strength of the carbon fibers were preserved well during the reusing process. The shear and delamination products exhibited excellent reinforcing properties, and they can be prepared into new CFRP products through hot pressing. The flexural strength of a newly prepared CFRP board can reach 47%–89% that of the original CFRP board. The swelling and degradation characteristics and mechanism of CEP in acetic acid were also investigated in this study. Thus, this work provides a novel method for recycling thermosetting composites.