Novel Testing System for Evaluating the Thermal Stability of Polyol Ester Lubricants

Abstract

This paper reports the development of a novel testing system for evaluating the thermal stability of polyol ester lubricants. The thermal degradation of three pentaerythritol tetrapelargonate based lubricants in the temperature range of 180−220 °C was studied using the developed comprehensive system. The system includes (1) a high-temperature quartz crystal microbalance for the real-time, in situ measurement of the solid residual deposition on metal surfaces and the viscosity change of thermally stressed liquid phase; (2) an on-line gas chromatograph for monitoring the volatiles generation in real time; and (3) an off-line gel permeation chromatograph for determining the molecular weight distribution of the liquid-phase products. The results indicate that the strategy can provide an integrated picture of the thermal stability of lubricants by providing quantitative, real-time, in situ information on gas-, liquid-, and solid-phase products during the thermal decomposition of the lubricants.