Hydrophobicity of organic insulating materials

The contact angle and the time for a water film to be formed on a surface are measured to investigate the hydrophobicity of UV (ultraviolet) irradiated materials. Ethylene propylene rubber and silicone rubber, both commonly used for graphic organic insulators, were adopted as specimens. For comparison, polyethylene and polymethylmethacrylate were also tested. The correlation between UV irradiation time and the time to the formation of a water film under fog is shown. It is found that the contact angle is closely related to the formation of a conductive film on a surface. It is concluded that the measurement of the contact angle seems to be an effective method to evaluate the hydrophobicity of materials in spite of its simplicity.<>