Thermal Characteristics of Sulfur Hexafluoride

Abstract

Thermal decomposition of sulfur hexafluoride SF₆(gas), which is important for the preparation of electrical equipments, has been investigated. SF₆ was heated with various metal pieces in a stainless steel vessel at 250°C to confirm that the thermal decomposition product was SO₂ (Table 1). The amount of SO₂ depended on the kind of metal (Table 2). When SF₆ and silicon steel plate were heated at 150, 200, and 250°C, the amount of SO₂varied with temperature and moisture in a vessel (Fig.1). X-Ray microanalyzer showed the formation of fluoride and sulfide on a surface of steel heated in SF₆, whereas that of sulfide only on a surface of copper (Figs.2, 3). The amounts of fluoride ion on a surface of silicon steel and on an inner surface of a test vessel, heated with.SF₆ at 150, 200, and 250°C, increased with increasing temperature (Table 3). Silicone resin laminates, heated in SF₆ at 250°C, changed mechanical and electrical characteristics (Table 4). Benzene was detected in SF₆ which was heated with silicone resin laminates (Fig.4) and infrared spectra of acetone, extracts from these laminates, indicated that phenyl group was removed from polymethylphenylsiloxane (Fig.5). HF, produced by the thermal decomposition of SF₆, would take part in this reaction.