Behavior of High Temperature Lubricants in a Pressure Differential Scanning Calorimeter

Abstract

The effects of pressure and diffusion restriction on pressurized differential scanning calorimetry (PDSC) data were investigated for several classes of high temperature lubricants, including polyphenylethers, polyphenylthioethers, cyclophosphazenes and perfluoroalkylethers. Unlike conventional lubricants, such as mineral oils and synthetics like ester-based lubricants, appreciable oxidation only occurs when both diffusion restriction and high pressure exist. This was shown to be due to a reduction in the rate of weight loss of the lubricant and, although not shown, is also probably due to oxygen saturation of the liquid phase. The onset of the exotherm and the onset of extreme degradation for these lubricants correlated for polyphenylethers and polyphenylthioethers but not for the cyclophosphazene. Perfluoroalkylethers display very small exotherms which are very likely due to their unusually high stability and scissioning degradation mechanism.

Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

KEY WORDS:

• Lubricant Analytical Techniques
• Thermogravimetric Analysis (TGA)
• Lubricant Degradation/Stability
• Adverse Environments Tribology
• High Temperatures
• Polyethers

Notes

Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998