An Evaluation of Insulative Property of Polluted Silicone Rubber by Non-Contact Surface Resistivity Measurement

In order to observe the insulation property of polluted silicone rubber (SiR), surface resistivity was measured by a non-contact method using a surface potential probe with a corona charger. The polluted layer was formed on the SiR surface by non-soluble powders (Tonoko) with Non-Soluble Deposit Density (NSDD) ranging from 0.62 to 4.71mg/cm2. The surface resistivity decreased with NSDD, reaching less than 1013Ω/sq just after pollution. It then increased over time due to the exudation of low molecular weight components in SiR. The elapsed time after pollution is significantly important to the recovery of hydrophobic property of the polluted SiR. After spraying deionized water or artificial seawater on the polluted SiR and drying, surface resistivity was measured. The timing of water spraying affected resistivity due to differences in hydrophobic recovery. The surface resistivity of deionized water spray sample with 24 hours after pollution was higher than that with just after pollution by two or three order magnitude. When artificial seawater was sprayed on the polluted layer, the surface resistivity after dried condition was significantly decreased due to tidal dissolution and didn't recover even after a subsequent time lapse.