양극산화 및 플라즈마 표면처리법을 이용한 탄소섬유의 표면특성 변화연구

Abstract

The surface treatment of carbon fibers is known to be one of the key unit processes constituting their manufacturing stream process. Carbon fibers are treated to enhance their mechanical interfacial properties in their composite applications by modifying the physicochemical properties on their surfaces. In this study, carbon fibers were surface-treated by contacting with atmospheric plasma and anodizing electrolyte solution media, respectively. The influence of anodic oxidation was investigated on the mechanical interfacial properties of carbon fiber-reinforced epoxy composites. The property changes of carbon fiber surfaces were studied by measuring contact angles and electrokinetic potential, observing microscopic images and analyzing XPS and FT-IR spectroscopy. The mechanical interfacial properties of the resulting composites were measured and compared in terms of interlamiar shear strength, critical stress intensity factor and critical strain release rate. It was shown that the functional groups containing oxygen over the carbon fiber surfaces greatly affect the surface energetic of fibers and the mechanical interfacial properties, e.g., the ILSS values of the resulting composites. Contact angle measurements, based on the wicking rate of test liquid, exhibited that anodic oxidation leads to an increase of the surface free energy in the fibers, mainly of its specific or polar component. By considering surface energetic, the surface wetting was thought to play an important role in increasing the degree of adhesion at fiber-matrix interface of the composites. Atmospheric plasma was applied to the carbon fibers by supplying the mixed gas of helium and oxygen into the plasma zone. The effects of the plasma treatment on the surface energetic of the fibers were experimentally investigated with respect to the process variables of gas flow ratio, power intensity and exposing time, respectively. The plasma treatment showed its strong capability of developing new reactive groups on the surface, and they can contribute to form intermolecular bonding and to enhance the surface wettability in a hydrophilic polymer matrix.