Electric breakdown of gases and vapors of chloro-fluoro-hydrocarbons

In the past decade fluorine chemistry has advanced very rapidly and many completely fluorinated compounds have become available. These compounds, termed perfluorocarbons, were generally much more stable and inert than chlorocarbons, or chloro-fluorocarbons. Many of these high molecular weight perfluorocarbons are reported(1) to have unusually high dielectric strength whereas the lowest molecular weight perfluorocarbons have relatively low dielectric strength(2,3). The investigation reported in this paper was undertaken to obtain information on the variation of dielectric strength as the hydrogen in a hydrocarbon is replaced by the halogens (Cl and F). These results are reported for both low and higher molecular weight compounds. The high dielectric strength of halogen containing compounds has been attributed to the electronegativity of these elements. Fluorine is the most electronegative of all elements, and it might, therefore be expected that fluorine containing compounds should show higher dielectric strength than other electronegative gases and vapors. It has been shown to be true for SF₆, and other fluorine containing gases and vapors(1). However, exceptions will be found in lower molecular weight compounds.