Efficient degradation of epoxy resin and recovery of carbon fibers from CFREP in mix-solvent system

Abstract

Recycling of carbon fiber reinforced epoxy resin (CFREP) is challenging due to its thermosetting property, in which amine-cured one shows more difficulty due to the hard C–O bond or C–N bond breaking via simple solvolysis. Here, a mix-solvent system with low concentrated catalyst is developed for chemical recycling carbon fiber (CF) reinforced dicyandiamide (DICY) cured CFREP, where the portion of tetrahydrofuran (THF), H₂O and ZnCl₂ is 8.1:0.9:0.5. The strong swelling ability of THF facilitates the incorporation of H₂O and ZnCl₂ into the covalent matrix, resulting in the removal of as high as 99.0% epoxy resin (EP) polymers after 5 h at 230 °C. The system can be reused three times and is scalable. The degraded product is the oligomers containing N and the unit of bisphenol A, which can be further hydrogenated to (alkyl)cyclohexane, a constituent of jet fuel. The recovered CFs still maintain their structure and a tensile strength of 87%.

Keywords

Carbon fiber reinforced epoxy resin / recovery / mix-solvent / low-concentrated catalyst / swelling effect

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