Rubber composition and rubber product

A rubber composition comprising:

• an EDPM polymer of 100 parts by mass;
• a carbon black of 66 to 93 parts by mass;
• an electrical insulating filler of 87 to 145 parts by mass;
• a softener of 31 to 76 parts by mass;
• and
• a sulfur-based vulcanizing agent and vulcanization accelerator so that a total sulfur content thereof is 1.2 to 1.8 parts by mass,
• wherein 10 or more % by mass of the electrical insulating filler is constituted as amorphous or spindle-shaped filler, and
• wherein an obtained vulcanized product is satisfied with the following Equations (1) and (2):
• volume resistivity≧1.0×106 Ω·cm (1)
• (M30<100° C.>/M30<23° C.>−1)×100≧−15% (2)
• where M30<23° C.> is a tensile stress at elongation of 30% as measured by a tensile test at a room temperature;
• and
• M30<100° C.> is a tensile stress at elongation of 30% as measured by a tensile test at 100° C.