Research On Degradation And Kinetics Of CFRP In Supercritical Fluids

Carbon Fiber Reinforced Plastics (CFRP) are used in a wide range of applications in industries such as aerospace, automotive and renewable energy, due to their interesting combination of properties:strength, durability, high strength-to-weight ratios and resistance. But the high price of carbon fiber limits the widespread use of CFRP. Scrap and defective products generated in its production process, the destroyed structures in usage and the end-of-life materials contains a large number of high-performance carbon fiber material. Thus, recovery and recycling of waste CFRP is the key to achieving a wide range of its applications.Home-made CFRP was taken as the research object, and its decomposition was studied based on developed device. The main research contents in this paper is as follows.(1) The decomposition of CFRP under supercritical CO2was studied. The effect of supercritical CO2with different alcohols was also studied. The results showed that the decomposition of CFRP with supercritical CO2was not obvious. The synergy of supercritical CO2and alcohols can decompose CFRP effectively. The study also found a positive correlation between heat preservation time, reaction temperature, content of alcohols and resin degradation rate. The pressure has little effect on the resin degradation rate. Acid catalysts and the addition of H2O2can improve resin degradation rate significantly.(2) The decomposition of CFRP under supercritical alcohols (methanol, ethanol, n-propanol, n-butanol) was studied. Using a combination of single fiber tensile test and weibull analysis method, the mechanical properties of recycled carbon fibers were characterized. Using Scanning Electron Microscopy (SEM), Atomic Force Microscope (AFM) and X-ray photoelectron spectroscopy (XPS) characterization methods, the microstructure and surface chemical composition change of reclaimed carbon fiber were characterized. The results showed that degradation ability of solvents: methanol<ethanol<n-propanol<n-butanol. Under the condition that the temperature was360℃, the heat preservation time was60min and the amount of solvent was350mL, the average tensile strength of the fibers recycled by supercritical n-propanol and n-butanol were about98%than that of the virgin fibres. The results from the SEM and AFM measurements showed that the fibres were clean and no cracks or defects were found.(3) The degradation kinetics of CFRP under supercritical alcohols were studied. The kinetics model of degradation reaction was established, Based on the degradation experiments of CFRP under different supercritical conditions of temperature and time, and considering the best fitting and condition fitting, the order of reaction was determined as n=2, the effective reaction rate coefficient k was calculated, and the supercritical reaction activation energy E and the advanced factor ko were calculated, and the degradation kinetics equation of supercritical alcohols were derived.