Solvothermal degradation and reuse of carbon fiber reinforced boron phenolic resin composites

Recycling of carbon fibers via solvothermal degradation of carbon fiber reinforced boron phenolic resin composites (CF/BPR) was investigated in this paper. The solvothermal degradation reaction was performed in a teflon-lined autoclave of 50 ml capacity between 225 °C and 280 °C for 1–4 h using 1-propanol, water and acetone as solvents. KOH was chosen as additives to accelerate the degradation process. The effect of the concentration of KOH, reaction time and temperature on the degradation ratio (Dr) of the resin was studied. The Dr was as high as 98.3% and there existed few resins on the surface of the recycled carbon fibers. Surface and microstructural properties of both the virgin and recycled carbon fibers were characterized by SEM, FT-IR, XPS, contact angle measurement, XRD and Raman spectra. FT-IR and GC-MS were utilized to determine the structure of the degradation products and identify the compositions of them. Finally, a four-step solvothermal degradation mechanism is proposed to explain how the degradation reaction occurred. Besides, recycled carbon fibers reinforced boron phenolic resin composites (RFs/BPR) were prepared. The mechanical tests showed that RFs/BPR had superior flexural strength than that of virgin ones due to better interfaces as revealed by SEM images of fracture surfaces.