Thermal Analyses of Electrically Aged Silicone

Abstract

In this work we are interested in the silicone material used for the coating of the insulator systems, confronted with the external pollution aggression. In this context, we investigate the electrical aging phenomenon of Silicone coated insulators. Accelerated testing under alternating 50 Hz homogeneous electrical field, were conducted on both polluted and clean silicone. A wet pollution is used, of conductivities σ = 0.2 mS and σ = 5 mS. Then, the samples were chemically analyzed using TGA, DTG, DTA and DSC before and after aging caused by a series of surface breakdown. The analyses thermograms give, respectively, the evolution of the mass loss rate, the mass loss speed, the heat flux gradient and the glass transition temperature, in addition to the different degradation temperatures of the material. The thermal stability of the silicone before and after aging is thus determined. It should be noted that the value of the glass transition temperature Tg is significantly affected as well in the case of clean condition aging as under wet pollution aging of the silicone surface.