Compatibility and Interaction Mechanism between the C4F7N/CO2/ O2 Gas Mixture and FKM and NBR

The C4F7N/CO2/O2 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 C4F7N/CO2/O2 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 C4F7N/CO2/O2 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 C4F7N/CO2/ O2 is compatible with FKM and NBR at 85 degrees C, while the surface morphology changed at 100 degrees 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 C4F7N/CO2/O2 is superior, which could be employed as the sealing material for C4F7N-based GIE.