Influência da cera de carnasúba do desempenho de revestimento de silicone aplicados no isolamento externo.

Abstract

In this work the influence of carnauba wax on the composition of silicone coatings applied to outdoor insulation in high voltage systems was investigated. The composites were contained of vulcanizable silicone rubber at room temperature added with different concentrations of alumina trihydrate and carnauba wax. The morphology and filler distribution in the composites were analyzed by SEM. The chemical structure of carnauba wax and RTV-SIR coatings was characterized by the infrared spectrum of absorption. The effects of polarization and resistance to electrical rupture were analyzed from measurements of dielectric constant and dielectric strength. Accelerated aging tests were performed through the exposure to UV radiation and application of electrical stresses as a function of time. The dielectric supportability of insulators coated with the investigated compositions was evaluated through the application of successive disruptive discharges with different levels of pollution. The state of isolation after the test was determined from leakage current measurements. The resistance to the electrical tracking and erosion phenomena was evaluated for composite samples. The length of the tracking, the eroded mass and leakage current measurements were used as parameters of the analysis. The effects caused by exposure of composite samples to UV radiation were evaluated by variations in hydrophobicity and FTIR spectrum. From the results, it was verified that the exposure to ultraviolet radiation causes a reduction in the contact angle values for samples of the investigated material. Samples containing carnauba wax at mass concentrations up to 10% showed good dielectric supportability in pollution conditions, low leakage current values in fog tests realized after the application of disruptive discharges and resistance to electrical tracking and erosion. The best performances were obtained for the compositions filled carnauba wax and alumina trihydrate compositions at concentrations of 5% and 20%, respectively.