Chichester, C., "Development of High Service Temperature Fluids," SAE Technical Paper 2016-01-0484, 2016, doi:10.4271/2016-01-0484.
Silicone fluids are known to have high Viscosity Indices (VI), and high Oxidation Onset Temperatures (OOT). Silicone VI and OOT characteristics make these fluids appealing for use as lubricants in high temperature applications, and where lubricant longevity is desired. Despite thermal and oxidative benefits, silicones lubricants have a reputation as being poor lubricants in metal-to-metal applications, and are typically only selected for use in plastic applications. Most industrial knowledge about silicone lubricants is based on characteristics of PolyDiMethyl Siloxanes (PDMS), in which case, lubricity limitations do exists. However, there are other silicone based lubricating fluid technologies, that have been commercially available for decades, that far exceed known lubricity performance of PDMS, and in some ways can rival traditional synthetic hydrocarbon. Phenyl-Methyl Silicones (PMS), Fluoro Silicones (FS), and Alkyl-Methyl Silicones (AMS) can offer great performance, at high temperatures, due to the high VI and OOT, for which silicones are known, and their molecular structures enable improved lubricity as compared to PDMS, giving these unique silicones combinatory benefits of thermal and oxidative stability, and lubricity even in metal-to-metal applications. This paper will discuss and compare different silicone-based fluids, as well as some comparison to polyalphaolefins, perfluoropolyethers, and other common synthetic lubricant technologies. Basic molecular structures will be reviewed, and comparative test data will be shared including SRV (Schwingungs-Reibungs und Verschleisstest) data, 4-Ball wear scar data, Viscosity Index, and Differential Scanning Calorimetry (DSC),. Following data sharing, a few potential high temperature applications ideas will be presented.