The main function of an insulator is to insulate the current carrying
conductors from each other and from the ground, which requires
materials with very low dielectric constant. For rubber, the dielectric
constant increases with temperature due to change in intra and inter
molecular interactions. Therefore it is necessary to modify rubber to
thermally more stable by adding some ingredients or dynamic
vulcanization. The variation of dielectric constants of pure components
and the blends of NR/CS as a function of frequency is shown in
Fig. 5.