Conductivity effect of UV-c radiation on solid insulators

Due to global environmental changes out-door insulators are nowadays exposed to significantly higher UV radiation compared to the corresponding levels of the past. In this work, the resulting dc I-V characteristics during material exposure to UV-c excitation have been investigated for the steady state, and transient response following radiation cut-off. The examined materials were phenolic resins (bakelite and pertinax), polyethylene (PE), poly(vinyl chloride) (PVC), poly(tetrafluoroethylene) (PTFE), and poly(methyl methacrylate) (PMMA). Measuring processes were identical for comparison purposes. The samples had uniform field, gold electrodes, and were cleaned in a vacuum. According to the experimental results, only the phenolic resins did not exhibit significant radiation induced currents. Radiation induced conductivity (RIG) was recorded for all other materials. However, their transient profiles following the illumination cut-off were vastly different; some materials, exhibit negative current polarities over extended period. Possible excitation mechanisms, as well as, physical and chemical relaxation processes are discussed.