Recycling of Carbon Fiber Reinforced Polymers in Subcritical Water with Acetic Acid Amendment

Abstract

A novel single-stage solvolysis process is proposed for recycling carbon fibers from an unknown epoxy-based composite material using 50 wt % acetic acid under subcritical conditions. The process yields 100 % recovery efficiency for fibers in less than 30 min when operating at 300 °C. Qualitative analysis of the fibers using SEM and EDS analysis reveals that the recovered fibers are completely free of epoxy, and the fiber surface does not show any damage. SEM images and gravimetric measurements of the composite at lower temperatures and low residence times also reveal an initial swelling of the CFRP samples, suggesting a two-step process, i.e., the initial swelling of the composite matrix followed by chemical decomposition of the polymer. FTIR and GC-MS analyses confirm epoxy decomposition and formation of aromatic compounds, phenolic derivatives, and high molecular weight compounds.