Surface studies of corona-treated silicone rubber high-voltage insulation

XPS (X-ray photoelectron spectroscopy) and microscopy studies of the brittle layer that is produced have established that corona exposure forms a wettable silica-like layer on the surface of most polydimethylsiloxane (PDMS) elastomers. This is consistent with similar effects from oxygen and inert gas plasma treatment. Such a layer cannot readily reorient between hydrophilic and hydrophobic states at the surface, suggesting that diffusion of low molecular weight PDMS components is an important mechanism of hydrophobic recovery. The recovery is followed by water contact changes which show differences between conventional peroxide-cured and platinum-cured silicone elastomeric materials. These latter materials recover more slowly. XPS chemical shift data also indicate interesting oxidation differences in silicon and carbon in the surface of these two classes of elastomers