Comparative study of single-step and two-step thermal recycling for near 100% carbon fiber recovery from T800 CFRP waste

The study presents a comprehensive analysis of the high-temperature pyrolysis process of CFRP, along with a comparative analysis between single-step and two-step methods during thermal recycling. Before thermal recycling through a customized muffle furnace, optimized pyrolysis process parameters were determined using thermogravimetric analysis (TGA), optical microscopy, scanning electron microscopy (SEM), and EDS to evaluate degradation characteristics and surface morphology of reclaimed carbon fibers (CFs). The results show near 100% recyclability of CFs through a single-step and two-step in 1.25 h and 2 h, respectively, achieving more than 81% tensile strength and 83% modulus. The optimized parameters in the single-step process are heating CFRP waste at 25°C/min till 490°C under an air atmosphere. CFRP is first pyrolyzed under argon and nitrogen atmospheres at 650°C separately, followed by oxidation under air atmosphere until 490°C using a two-step method. Analysis of surface morphology shows a slight improvement in the quality of reclaimed CFs with two-step E1 than that of two-step E2 and single-step E3 . During thermal recycling, the influence of isothermal time on CFRP under air atmosphere is highly significant. The findings emphasize the critical impact of heating ranges, temperature limits, and atmosphere, providing insights into the thermal recycling process to reclaim CFs for remanufacturing advanced composite materials.