Impact of weather conditions and formulations on LMW silicone fluid content in RTV silicone rubber coatings

The presence of sufficient amount of low molecular weight (LMW) silicone fluid in RTV silicone rubber coating is a critical factor in the recovery of the hydrophobicity. In this paper, the effects of wind and water on LMW silicone fluid content in RTV coating are reported. The wind was found to have no effect on the LMW content in RTV coating for up to 20 months in a continuous wind at a speed of 7.45±0.2 km/h at 23±3°C. LMW silicone fluid was found to dissolve slightly in water after 12 months of immersion in a saline wafer of 70 μS/cm at 23±3°C. Alumina trihydrate (ATH), added to RTV to impart resistance to tracking and erosion, also displaced silicone rubber and reduced the available LMW fluid in the coating. The dependence of the content of LMW silicone fluid in RTV on the concentration of ATH was determined. The contact angle was measured to determine the hydrophobicity of the surface of the coating. The hydrophobicity was found to remain unchanged despite long exposure to wind and water and was also independent of the filler concentration in the range 50-150 pph