Effect of Plasma Treatment Condition on Mechanical and Chemical Properties of Carbon Fibers

Improving interfacial bonding between carbon fibers recovered from used carbon composites can reduce costs and address environmental concerns surrounding landfill of carbon composite materials. This study investigated the mechanical and chemical characteristics of carbon fibers exposed to different plasma treatment times in an argon and oxygen atmosphere. After plasma treatment for 1 min, there was no difference in the tensile and morphological properties of commercial carbon fibers and plasma-treated carbon fibers. However, oxygen penetrated into the carbon fiber with the oxygen atoms close to each other, resulting in increase in lactone groups that were not observed in commercial carbon fibers, while the hydroxyl and carbonyl groups were removed in the form of CO and CO₂ and thus decreased in number. In addition, the polar surface energy of the carbon fibers markedly increased after the plasma treatment as compared to that of the commercial carbon fibers. After plasma treatment for 3 min, carbon fiber surface damage was observed, and tensile properties were greatly reduced. In addition, lactone, hydroxyl, and carbonyl groups on the carbon fiber surface decreased due to the exposure of C-C and C = C.