Development of an innovative hybrid thermo-chemical recycling method for CFRP waste recovery

Abstract

Disposal of carbon fibre reinforced polymer (CFRP) waste in landfill is a significant environmental issue. Cost-benefit and life cycle assessments have demonstrated that pyrolysis and chemical recycling are among the most effective waste treatment strategies. This paper presents the development of a novel low-temperature pyrolysis combined with solvolysis pre-treatment as an effective recycling method for CFRP composite wastes. In this research, the process parameters were meticulously determined to ensure the simultaneous achievement of increased material utilisation and energy efficiency. The kinetic analysis results demonstrate that the pre-treated CFRP, unlike its untreated counterparts, displays an additional preliminary reaction stage, facilitating a higher level of breakdown at lower temperatures. Moreover, solvolysis pre-treatment increased retention of the fibres' mechanical properties by reducing the heat consumption during recycling. With a proper pre-treatment prior to thermal deterioration, the strength of the recycled fibres was preserved at up to 90.53% of their virgin state, which is 10.21% higher than the strength of recycled fibres recovered via thermal degradation only. To demonstrate the practicality of this research, a commercial bike's fork and airplane scraps made of CFRP composites were successfully recycled using the hybrid approach developed in this research. The results validate the effects of chemical pre-treatment and also demonstrate the efficacy of coating removal on the mechanical characteristics of carbon fibres recovered from various types of CFRP for real-world applications.