Image analysis of hydrophobicity and dielectric property of polymer insulating material

Hydrophobicity of polymeric insulating material surface such as silicone rubber insulator was studied by using image data analysis of the sample surface. Hydrophobicity of polymer was evaluated by the motion of water droplets on the sample surface under AC high field application. The vibration image of the water droplets was taken by CCD camcorder. The video image was divided into each image frame and the image indices such as size and shape factor of the droplets were evaluated for each image frame. Then, the time variation of the image indices of sample surface during high electric field application was evaluated, where electric field deformed the droplets. The motion of the water droplet was also determined by measuring the dielectric property of silicone rubber surface using a pair of inter-digital electrodes. The motion of water droplets was detected by using unbalance operation of current comparator type Capacitance Bridge system. The changes in dielectric loss current and capacitive current by the deformation of the water droplets were measured for every one cycle of the applied AC field. To compare these results the degradation of hydrophobicity of polymer insulator is defined more accurately.