Compatibility and Interaction Mechanism between the C 4 F 7 N/CO 2 /O 2 Gas Mixture and FKM and NBR.

The C 4 F 7 N/CO 2 /O 2 gas mixture received a great deal of attention for its potential use in eco-friendly gas-insulated equipment (GIE). The evaluation of the compatibility between C 4 F 7 N/CO 2 /O 2 and sealing rubber is necessary and significant considering the high working pressure (0.14-0.6 MPa) of GIE. Herein, we explored the compatibility between C 4 F 7 N/CO 2 /O 2 and fluororubber (FKM) and nitrile butadiene rubber (NBR) for the first time by analyzing the gas components, rubber morphology, elemental composition, and mechanical properties. The interaction mechanism of the gas-rubber interface was further investigated based on the density functional theory. We found that C 4 F 7 N/CO 2 /O 2 is compatible with FKM and NBR at 85 °C, while the surface morphology changed at 100 °C, with white granular and agglomerated lumps appearing on FKM and multi-layer flakes being generated on NBR. The accumulation of the fluorine element occurred, and the compressive mechanical properties of NBR deteriorated after the gas-solid rubber interaction. Overall, the compatibility between FKM and C 4 F 7 N/CO 2 /O 2 is superior, which could be employed as the sealing material for C 4 F 7 N-based GIE.