Enhancing carbon fibre recovery through optimised thermal recycling: Kinetic analysis and operational parameter investigation

Abstract

Thermal recycling is an attractive method for recovering carbon fibre from carbon fibre-reinforced polymer (CFRP) composite waste. The main drawbacks of the thermal recycling approach are its high operational cost resulting from significant energy requirements and the risk of fibre surface damage caused by overheating. In this research, we will establish an optimal heating temperature and operating parameters (such as atmosphere, heating rates and isothermal dwelling time) through an analysis of the kinetic behaviour of CFRP thermal degradation to obtain clean and undamaged recycled fibres, while minimising energy requirements. The results show that a higher conversion fraction can be reached by applying a lower nitrogen flow rate, moderate heating rate and cap temperature of 425 °C. To ensure the complete removal of any residual matrix and pyrolytic carbon, and to obtain clean recycled carbon fibres, an additional recycling step is employed. In this case, oxidation is conducted with a 45-min isothermal period following pyrolysis. Using the proposed method, it was possible to retain 87.6 % of the fibre's tensile modulus and 80.3 % of its strength after the recycling process. The outcomes of this research will contribute to production of high-grade recycled carbon fibres with controlled mechanical performance and physical characteristics.