Study of the degradation of two candidate diffusion-pump oils, Krytox and Fomblin. Final report

Activation energies were determined for decomposition of Fomblin HVAC 18/8 and Krytox 143AY oils (two perfluorinated polyethers) (respectively 60.6 kcal/mole and 55.6 kcal/mole) in the temperature range of 325/sup 0/ to 405/sup 0/C in a monel vessel. At any temperature in this range, Fomblin decomposes 30 +- 10 times faster than Krytox. The estimated decomposition in 10 years at 250/sup 0/C is 0.14% for Fomblin and 0.009% for Krytox. Effects of 304 ss and aluminum were determined. Although differences in the fluorine NMR spectrum of different batches of Krytox are observed, there are no significant changes detected between aged and unaged oils of the same batch. HF does not react with Krytox at 405/sup 0/C. Krytox can be chromatographed in spite of its high average molecular weight (3600 amu). GCMS showed that each smaller peak contained C/sub 2/F/sub 4/H-groups while the larger peaks contained only C/sub 2/F/sub 5/-groups. Hydrogen NMR on Krytox showed the C/sub 2/F/sub 4/H- to be CF/sub 3/CHF-groups. Chromatography of Fomblin gave a single broad envelope without resolved peaks.