The oxidation of carbon fibers through K2S2O8/AgNO3 system that preserves fiber tensile strength

Carbon fiber reinforced composite materials can be enhanced by introducing oxygen-containing groups on the surface of the reinforcing fibers to improve the interface bonding strength between carbon fibers and polymer matrix. While the addition of oxygen-containing groups has been shown to effectively increase the interfacial interaction between fibers and matrix, the treatments tend to consume the carbon fiber tensile strength. In this work, the surface of carbon fibers is oxidized by a chemical oxidation method which employs a strong oxidant of K2S2O8 and a catalyst of AgNO3 to effectively creating carboxyl and hydroxy functionalized surface and the reaction is shown that it can preserve the tensile strength and morphology of the carbon fibers. The surface oxidation is investigated by X-ray photoelectron spectroscopy, which shows that the relative surface coverage by oxygen atoms is increased from an initial 4.49% up to a maximum of 14.11% while the results of single fiber tensile strength tests demonstrate that the reaction did not lead to any obvious decrease in the fiber tensile strength. After oxidation, the interfacial shear strength (IFSS) improved from 59.52 to 96.73 MPa, with a increase of 62.5%.