Hygroscopic properties of pollutants on silicone rubber surface

Silicone rubber when contaminated by dust has the ability to transfer the hydrophobicity through pollutants. Water on the polluted silicone rubber forms separate droplets. It is a unique advantage of this material. However, the pollution layer on silicone rubber absorbs moisture at high air humidity similar to the pollutants on the glass surface. Under high timidity conditions the surface conductivity on heavy polluted (ESDD and DDD in the range of 0,1 mg/cm2 ) silicone insulators increases to the value in the range a few uS. This leads to dry band formation, arcing and possible surface erosion. The surface conductivity on the silicone rubber contaminated a week earlier by NaCl without bentonite is very small, in the range of 0,1 uS. The surface conductivity of 6 uS was measured on similarly polluted porcelain sample. The pure sea salt pollution is not dangerous for silicone insulators