Thermal oxidative studies of poly(hexafluoropropene oxide) fluids

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 (550°F), was found to be due to the presence of ∼3% of thermooxidatively unstable chains believed to be hydrogen terminated; treatment at 650°F in oxygen volatilized these chains by unzipping. The resultant fluid was unaffected by oxygen at 650°F and by M‐50 and Ti(4Al, 4Mn) alloys at 600°F in oxidizing atmospheres. M‐50 alloy catalyzed the degradation of the hydrogen‐terminated chains below and at 600°F, but after completion of this process did not affect the remainder of the fluid at these temperatures. At 650°F 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 hydrogen‐terminated chains, degraded poly(hexafluoropropene oxide) fluids at 550°F by chain scissions.