Chemical recycling of carbon fibre composites using alcohols under subcritical and supercritical conditions

Chemical recycling of carbon fibre reinforced composites (CFRCs) has been investigated using subcritical and supercritical alcohols as reactive-extraction media. The epoxy resin that joins the fibres is degraded during the process, producing fibres that retain 85–99% of the strength of the virgin fibres. Methanol, ethanol, 1-propanol and acetone were employed as solvent-reagents to conduct experiments in batch and semi-continuous-type reactors at temperatures ranged from 200 to 450 °C. The impact of flow rate and the addition of alkali catalysts (i.e. NaOH, KOH and CsOH from 0.016 to 0.50 M), was also investigated. Experiments performed in the semi-continuous flow system enhanced the mass transfer steps and reduced temperature requirements, thus eliminations of resin of 98 wt.% were achieved using at 350 °C and 1.1 kg-alcohol/kg-fibre/min and, at the same solvent flowrate at 275 °C using 0.02 mol/L of KOH 96.5 wt.% was obtained.