X-ray photoelectron spectroscopic studies of carbon fiber surfaces. 24. Interfacial interactions between polyimide resin and electrochemically oxidized PAN-based carbon fibers

The interfacial interaction between PAN-based IM7 carbon fibers and Avimid K3B, a thermoplastic polyimide resin was investigated using core and valence band X-ray photoelectron spectroscopy (XPS). The extent of interaction between the fiber and the matrix material has a significant effect on the strength of the ultimate composite. The fibers were treated to remove the surface treatment applied to the fibers by the manufacturer by resistive heating in a vacuum. The interaction of the detreated fiber, subjected to subsequent electrochemical treatment, with the resin was compared to the interaction of the commercially surface-treated fiber with the resin. Better interaction between the fiber and matrix was found in the case of the electrochemically surface-treated fiber than with a commercially surface-treated fiber, emphasizing the importance of tailoring the surface treatment to the matrix chemistry. Based on chemical shifts seen in the core region and differences in the valence band region, a reaction scheme is suggested for the possible interaction between the fiber and the resin.