Ethylene propylene diene monomer（EPDM） is a commonly-used sealing material in SF

6

gas-insulated equipment. If eco-friendly insulating gas C

3

F

7

CN is applied instead of SF

6

without changing the sealing material of the equipment

the compatibility of C

3

F

7

CN and EPDM should be confirmed to ensure the long-term safety and stability of the gas-insulated equipment. Therefore

the compatibility test between C

3

F

7

CN and EPDM was performed by using the thermal acceleration meth

od. After the test

the stress and strain properties of the rubber specimens were tested. The changes in solid and gas compositions were analyzed by FTIR

SEM-EDS

and GC-MS. It is found that the tensile stress and strain properties are seriously degraded

and the elongation at break is reduced to less than 50% of the initial value.The multi-layered sections and cracks appear on the surface

and the crystals of inorganic additives precipitate. The damage of the rubber seriously decreases the mechanical properties. The fluorine content on the rubber surface is significantly increased

and the characteristic peak of the fluorocarbon group appears in the infrared spectrum. The gas component contains decomposition products such as CO

2

C

3

F

6

hydrocarbons

and fluoroalkanes. Additives in this particular EPDM formulation such as CaCO

3

may be sufficiently basic enough to cause decomposition of C

3

F

7

CN

which is one of the reasons for the incompatibility between EPDM and C

3

F

7

CN. This factor should be taken into account when designing and manufacturing sealing materials for gas-insulated equipment.