Surface treatment of carbon fibers by an electrolytic potential method

An electrolytic potential method has been employed for surface treatment of high-strength medium-modulus carbon fibers (CF). The effect of current intensity on the chemical composition on the surface, wettability of the CF, and the interlayer shear strength (ILSS) was investigated using XPS, dynamic contact angle measurements and ILSS tests. Analysis of the results before and after treatment of CF using the electrolytic potential method showed a deviation of the linear relationship between current and voltage intensity during surface treatment. This indicates the occurrence of oxidation reactions on the surface of CF. With increasing current intensity, the oxygen content and the O/C ratio on the surface of CF increased and the carbon content decreased. The main functional groups on the surface of CF were C-OH and O-C=O, and their amount increased markedly for current intensities above 0.3 A. The dynamic contact angle of CF decreased from 90.2° to 62.4° after treatment at 0.5 A, and the wettability of CF significantly improved after treatment, with an increase in surface activity. The ILSS values of epoxy resin and the CF after treatment at current intensities of 0.3 A and 0.5 A and were 90.35 MPa and 99.41 MPa, respectively, which are 42% and 56% higher than the values for untreated CF. A slight increase in the tensile strength of the treated CF was observed after electrolytic potential treatment.