Comparison of silicone rubbers for high voltage insulation: Influence of vulcanization methods

Silicone rubbers from two manufacturers were compared, each in a series of six different vulcanization techniques. Hot-air vulcanization and in-mold vulcanization for rubbers cured with peroxide or addition reaction catalysts were included in each series. Rheological, mechanical and electrical properties were measured. Some differences due to curing method are discussed; however, these were small compared to other types of formulation differences, such as choice of fillers. A slight reduction in mechanical properties was measured when hot-air vulcanization was compared with the molded method. Addition cured silicone rubbers exhibited lower water absorption and slightly faster hydrophobicity recovery than peroxide cured ones. Dielectric properties were not affected by different curing techniques, provided complete curing was obtained. Excellent properties can be obtained with any of the vulcanization techniques studied if properly formulated