Impact of ultraviolet irradiation on space charge dynamics and surface properties of epoxy micro-nano composites

Epoxy micro-nano composites reinforced with silica micro filler and ion trapping nanoparticles were subjected to ultraviolet (UV) radiation for a period of 240 and 480 hours respectively. The average value of absolute space charge density increases whereas mean life time of charge decay decreases with UV ageing time. The surface potential decay characteristics of UV irradiated specimens were modelled with a double exponential function and it is noticed that the initial surface potential marginally decreases and decay rate increases with exposure to UV radiation. The increase in carrier mobility of the epoxy specimens is correlated with the increase in the density of shallow traps with UV irradiation, that occur because of the radiation induced structural degradation. The surface properties such as mean surface roughness and surface hardness tend to deteriorate after exposure to UV radiation.