Thermal Decomposition Kinetics of Polyol Ester Lubricants

Abstract

Synthetic lubricants are widely used for applications that require high thermal and oxidative stability. In order to facilitate new designs and applications for these fluids, we are measuring a suite of thermophysical and transport properties for lubricant base fluids and mixtures. As part of the property measurements, here, we report the global thermal decomposition kinetics of four polyol ester lubricant base oils, in addition to a fully qualified (MIL-PRF-23699) formulation. The fluids were heated in stainless steel ampule reactors and the extent of decomposition was measured by gas chromatography coupled with flame ionization detection (GC-FID), from which pseudo-first-order rate constants were derived. The rate constants for decomposition ranged from 1 × 10 –8 s –1 at 500 K to 2 × 10 –4 s –1 at 675 K. Arrhenius parameters across this temperature regime are also reported. Other techniques for chemical characterization applied in this work include gas chromatography with mass spectrometry (GC-MS), nuclear magnetic resonance (NMR) spectroscopy, and Karl Fischer titration.