Abstract
C4F7N (fluorinated nitrile) has been introduced as a remarkable substitute gas for the greenhouse gas SF6 (sulfur hexafluoride) which is used in gas-insulated equipment (GIE). Intensive investigations about the compatibility between C4F7N and materials used in GIE are required to decide their long-term behavior. In this paper, the interaction mechanism between EPDM, used as a sealing ring in GIE, and C4F7N-CO2 was explored. The composition and morphology properties of EPDM were first revealed based on scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that EPDM rubber is incompatible with the C4F7N-CO2 gas mixture at temperatures higher than 70 °C. There exist chemical reactions between EPDM and C4F7N, resulting in the generation of gaseous byproducts including C3F6, CF3H, and C2F5H and corrosion of EPDM. DFT calculation also shows that the interaction between C4F7N and EPDM could cause the dissociation of C4F7N. Relevant results provide important guidance for the engineering application of the C4F7N gas mixture.