Study on oxidation behavior during process of recycling carbon fibers from CFRP by pyrolysis

The study utilized a pyrolysis method to recycle carbon fibers from carbon fiber reinforced polymer (CFRP), followed by oxidation to remove pyrolysis carbon. The obtained recycled carbon fibers had good mechanical properties, and the tensile strength could reach 96.2% of the virgin carbon fibers under the optimal process conditions. The recycled carbon fibers displayed similar chemical structure and graphitization degree as the virgin carbon fibers, and showed better wettability with epoxy resin. In addition, density functional theory (DFT) calculations were also employed to analyze the mechanism of pyrolysis carbon oxidation removal. The results showed that the adsorption energy of oxygen on pyrolytic carbon and the reaction activation energy were lower than those of carbon fibers, indicating that pyrolytic carbon was more easily oxidized than carbon fibers. This allowed pyrolytic carbon to be removed by oxidation at relatively low temperatures and preserved the integrity of carbon fibers, thus ensuring that the carbon fibers also maintained excellent mechanical properties after recycling. This study helps to reveal the oxidation mechanism of resin pyrolysis carbon, providing technical support for efficient and clean recycling of carbon fibers.