Surface resistance of PVC in the presence of salt-fog

Polymer materials are increasingly being used in a wide range of applications in outdoor and indoor insulation. The aging of polymeric insulation is influenced by the presence of moisture and contamination which gradually change the property of the surface from being hydrophobic into hydrophilic. The modified surface then permits the development of dry band arcing that leads to flashover. It has been suggested that measurements of the surface resistance of insulators in situ might offer a convenient method to characterize its electrical property and thus its performance under operating conditions. In the present paper the surface resistance and the contact angle of polyvinyl chloride (PVC) rod specimens are measured in the presence of salt fog. The dependence of the surface resistance on such parameters as the duration of the wetting, the applied electric stress, the length of the specimen rod and on the time subsequent to die removal from the fog chamber is reported. The contact angle is also measured and is correlated with the surface resistance. The diffusion coefficient of the saline solution into the PVC is determined