Degradation in Mechanical and Dielectric Properties of Silicone Rubber under Severe Aging Conditions

Silicone rubber (SiR), which meets the specifications of insulators in electric cables for use in nuclear power plants (NPPs), was degraded under various aging conditions. The samples were then examined by measuring mid-infrared absorption, elongation at break (EAB), and complex permittivity. As a result, it has become clear that cross-linked structures with siloxane bonds are formed under all the conditions. This degrades the mechanical properties, but the dielectric loss becomes lower. It has also become clear that measurements of EAB and complex permittivity are useful to monitor the aging status of SiR.