The structural attributes and degradation mechanisms are reviewed for Fomblin Z®, Demnum , and space applications such as in satellites [4]. The backbone of the molecule contains only single bonds which allow free rotation of the backbone atoms producing a fluid with excellent viscosity characteristics. The high temperature oxidative stability is partly due to their high molecular weight and the shielding effect the highly electro-negative fluorine atoms have on protecting the carbon/oxygen backbone [5]. Comparing hydrocarbon chemistry in oxidative environments, hydrocarbons have the tendency to form water and OH radicals via a free radical process. This situation does not apply to perfluorinated compounds due to the resistance of the C-F bond to the attack by free radicals and the thermodynamic instability of OF 2 and OF species [6,7]. This renders PFPAEs JOURNAL OF SYNTHETIC LUBRICATION
Polyol-ester lubricants have been used and developed for aviation gas turbine engines for many decades. The newest MIL-PRF-23699 lubricant class, called enhanced ester (EE), provides the best combination of thermal stability, load carrying capability, boundary lubrication and compatibility with fluoroelastomer O-rings. Two candidate EE Class formulations and one high thermal stability class formulation conforming to MIL-PRF-23699G were evaluated for oil degradation with up to 3000 h of bearing operation. Lubricant degradation was studied using VIM VAR M50 bearings with M50 and silicon nitride balls under two operating conditions using two bearing test rigs. Oil degradation in terms of oxidation time, total acid number and viscosity was studied as a function of time with varying results for the three lubricants.
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