Surface hydrophobicity of polymers used for outdoor insulation

The results of a study on silicone rubber and ethylene propylene diene monomer (EPDM) polymers are presented. The study was done to understand the mechanisms involved in the loss and subsequent recovery of surface hydrophobicity due to dry-band arcing and to investigate various experimental techniques which could be used for characterizing surface hydrophobicity. The materials are subjected to dry-band arcing in a log chamber. Several techniques such as measurement of contact angle, determining surface composition using electron spectroscopy for chemical analysis (ESCA), and measuring crossover voltage (COV) using a scanning electron microscope are examined. The experimental results and theoretical calculations demonstrate that the mobile species in the polymer are responsible for the surface hydrophobicity. In terms of repeatability and simplicity of measurement, the COV determination appears to be the most suitable technique for hydrophobicity studies