Eco-friendly recovery of pure and long carbon fibres from aged epoxy matrix composites by H2O2 as an oxidant

In this study, we focused on the chemical recovery of carbon fibres from epoxy matrix composite wastes. First, we laminated and cured composite panels from carbon fibre-reinforced prepregs (CFRP) and then aged them under controlled circumstances to simulate their lifespan. Fibre recovery was then carried out by hydrogen peroxide (H2O2) at 6 bar and between 60 and 150 degrees C. We chose this material because it results in a rapid, cost-efficient, and environmentally friendly process. Besides, we expected it would allow the removal of the polymer matrix without fragmenting the fibres. We aimed to investigate the matrix decomposition in H2O2, the purity of the obtained fibres and the retention of their mechanical properties. The purity and the structure of the obtained carbon fibres were then characterised by using scanning electronic microscopy (SEM), X-ray diffraction (XRD), thermogravimetry (TGA), infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS). We found that H2O2 was effective in recovering carbon fibres, especially at 150 degrees C. The mechanical results showed that the retention of the modulus was complete, while the tensile strength and elongation at break decreased by 35% due to microstructural damages. The fibres still have better properties than glass or basalt fibres; therefore, good-quality composites can be made using them.