This paper deals with the thermal degradation of silicone rubber that is used on the cover of polymeric insulators. To carry out this research three samples were previously aged at different temperatures and a fourth one was kept at room temperature. Afterwards, a study was done by means of a tensile test on the silicone rubber. The tensile properties were evaluated by means of the graphs obtained from the tensile-strain, where the straight part of the graphs corresponds to the elastic modulus of the material, called modulus of elasticity.86653657