Hydrophobicity recovery in silicone insulators: a closer look at testing

Silicone polymer-based high voltage insulators enjoy an inherent advantage in their rapid return to a hydrophobic surface after electrical discharge. This work describes a close scrutiny of the factors that influence the level of surface breakdown (corona discharge time, intensity, distance of application) as well as the subsequent evaluation of the recovery (contact angle measurement technique, operator). Six sigma tools were used to identify the factors influencing test results. A reproducibility and repeatability study identified the contribution of the equipment and operator to the test results. By controlling key instrument and test method parameters, it was possible to develop a novel analysis model to predict the time to return to hydrophobic behavior that is useful in formulation development testing.