Synergistic modification of carbon fiber by electrochemical oxidation and sizing treatment and its effect on the mechanical properties of carbon fiber reinforced composites

In this article, The CF surface was modified by the synergistic modification of electrochemical oxidation and sizing treatment. Firstly, the electrochemical oxidation was carried out using fatty alcohol polyoxyethylene ether phosphate (AEOPK) as the electrolyte. The content of active groups on the modified CF surface increased by 235%. However, the strength of CF monofilament decreased due to the etching. Then, the electrochemically oxidized CFs were sized with the phosphate modified epoxy resin (PAEK). The etched defects on CF surface caused by the electrochemical oxidation were repaired by sizing agent molecules according to the AFM results. Furthermore, the spreadability of PAEK emulsion on the CF surface, the content of CF surface groups and the interaction of CFRC were characterized by using the monofilament contact angle, XPS and Raman spectroscopy. The results suggested that the synergistic modification could improve the CF surface activity, facilitate the spreading of PAEK on the CF surface, and increase the interaction between the CFs and the resin matrix. There were 20.3 and 22.6% enhancement in the breaking strength and elongation of CF monofilament. In addition, the interlaminar shear strength (ILSS) of CFRC prepared with synergistically modified CFs was increased from 12.81 to 33.04 MPa. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48028.