Thermal stability of R$218$ $(\mathrm{C}_3\mathrm{F}_8)$ and R$31$-$10$ $(\mathrm{C}_4\mathrm{F}_{10})$ under heat exposure

The results of study of the thermal decomposition of fluorocarbons under constant and cyclic heating are presented. Studies are carried out in the temperature range of $500$–$670^{\circ}$C. For continuous heating, the exposure time was $4$ h; up to $10^6$ cycles were carried out under cyclic heating. The composition of fluorocarbons before and after each test series is compared using mass spectrometric analysis. As a result, the temperatures of the beginning of thermal decomposition of fluorocarbons upon heating in direct contact with the construction materials are determined. In addition, the development of the corrosive effect of the fluoride ion on structural materials upon thermal decomposition of fluorocarbons is revealed based on mass spectrometric analysis. The temperatures of the beginning of deep corrosion of construction materials are determined by the presence of the peak of $\mathrm{SiF}^+_3$ ion in the mass spectrum.