Abstract
Elucidation of mechanisms operative in thermal oxidative degradation of hexafluoropropene oxide derived polyethers and the effect of metals on these processes are reported. Thermal oxidative instability of a commercial fluid, at moderate temperatures (550ยฐF), was found to be due to the presence of โผ3% of thermooxidatively unstable chains believed to be hydrogen terminated; treatment at 650ยฐF in oxygen volatilized these chains by unzipping. The resultant fluid was unaffected by oxygen at 650ยฐF and by Mโ50 and Ti(4Al, 4Mn) alloys at 600ยฐF in oxidizing atmospheres. Mโ50 alloy catalyzed the degradation of the hydrogenโterminated chains below and at 600ยฐF, but after completion of this process did not affect the remainder of the fluid at these temperatures. At 650ยฐF a chain scission process promoted by the metals constituting the alloy, or their oxides or fluorides, came into play. Ti(4Al, 4Mn) alloy in the presence of CF~3~COF and COF~2~ species, formed via decomposition of the hydrogenโterminated chains, degraded poly(hexafluoropropene oxide) fluids at 550ยฐF by chain scissions.