In-situ formed nanoscale Fe⁰ for fenton-like oxidation of thermosetting unsaturated polyester resin composites: Nondestructively recycle carbon fiber

Thermosetting unsaturated polyester resin (UPR) composites were found widespread industrial applications. However, the numerous stable carbon-carbon bonds in cross-linked networks made them intractable for degradation, causing the large-scale composite wastes. Here a nanoscale Fe⁰ catalyst in-situ forming strategy was exploited to nondestructively recycle carbon fiber (CF) from UPR composites via Fenton-like reaction. The nano-Fe⁰ catalyst employed in this strategy activated H₂O₂ for removing UPR, featuring mild conditions and efficient degradation ability. Aiming at facile growth of the catalyst, a porous UPR was achieved by the hydrolysis of alkalic system. The nanoscale Fe⁰ catalyst was subsequently formed in-situ on the surface of hydrolyzed resin by borohydride reduction. Benefiting from fast mass transfer, the in-situ grown nano-Fe⁰ showed more efficient degradation ability than added nano-Fe⁰ or Fe²⁺ catalyst during Fenton-like reaction. The experiments indicated that hydrolyzed resin could be degraded more than 90% within 80 min, 80 °C. GC-MS, FT-IR analysis and Density functional theory (DFT) calculation were conducted to explained the fracture processes of carbon skeleton in hydrolyzed resin. Especially, a remarkable recovery process of CF from composites was observed, with a 100 percent elimination of resin. The recycled CF cloth exhibited a 99% strength retention and maintained the textile structure, microtopography, chemical structure, resulting in the nondestructive reclaim of CF. This in-situ formed nanoscale Fe⁰ catalytic degradation strategy may provide a promising practical application for nondestructively recycle CF from UPR composites.