Evolutions of surface characteristics and electrical properties of the fluorinated epoxy resin during ultraviolet irradiation

Abstract

The photoinduced evolutions of surface physicochemical characteristics and electrical properties of the fluorinated epoxy resin have been investigated. Cured epoxy resin sheets were surface fluorinated in a laboratory vessel using a F2/N2 mixture with 12.5% F2 by volume at 0.1 MPa and 95 °C for 30 min. The fluorinated epoxy sample together with the unfluorinated (original) one for a comparison were exposed to ultraviolet (UV) radiation with wavelengths of 320 to 390 nm. During UV exposure, the evolution of surface physicochemical characteristics was investigated by attenuated total reflectance Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray energy dispersive spectroscopy, and the sessile drop technique. The corresponding evolution of surface electrical properties was evaluated by measurements of surface potential decay and surface conductivity. These results have shown that the crosslinking reaction rather than photodegradation occurred for the fluorinated sample, compared to a continuous degradation of the original sample during the UV exposure. These results also indicate that surface conduction and its sensitivity to humidity increased very significantly with UV exposure time for the original sample, while the opposite changes in surface conduction and its moisture sensitivity with the exposure time were found for the fluorinated sample. A relationship between the evolutions of surface electrical properties and surface physicochemical characteristics has been established.