Image analysis of hydrophobicity of polymer insulators by observing at microscopic area

Hydrophobicity of polymeric insulating material surfaces such as silicone rubber (SIR) and ethylene propylene diene monomer rubber (EPDM) insulator was studied by using image data analysis of the sample surface. Using a very high-speed microscope CCD camcorder, we digitized the hydrophobic surface image under the spraying of a mist of water. The size of the observed image area is only about 2 mm², the effect of aging in water and its recovery in air on the hydrophobicity of specimens was measured by the surface images of water droplets on the sample surface. Using this microscopic image, we can determine the hydrophobicity class (STRI´s HC level) without the effect of gravity or inclination of the surface to the formation of water droplets on the surface. Image data analysis can calculate the image indexes such as size and shape factor of the droplets. They are also helpful to define the hydrophobicity class more accurately