Surface degradation properties of ultraviolet treated epoxy/glass fiber

In order to analyze the degradation process of epoxy/glass fiber in outdoor conditions, FRP laminate was exposed to different wavelengths of ultraviolet (UV) rays and evaluated by comparing contact angle, surface resistivity, surface potential decay, and XPS. As irradiation energy increased, the surface properties deteriorated remarkably at the region of 300 nm. But the measured values within 400 to 440 nm showed a slightly abnormal increase compared with the untreated FRP laminate. Also, the results of XPS confirmed that a great deal of oxygen groups appeared on the spot which showed the maximum decrease of surface properties, particularly the existence of ether groups on the surface of the discoloured spot. It was concluded that the surface degradation of UV-treated epoxy composites is dominated by the abrupt increase of ester and carboxyl groups as hydrocarbon chains are oxidized. This degradation process occurs continuously through the reorientation of oxygen groups by thermodynamic reaction and the formation of an electric double layer by electrostatic force