DTA Study on Oxidation of Lithium Soap Grease

Abstract

The phase behavior of lithium soap/hydrocarbon oil and lithium soap/synthetic oil greases has been investigated using DTA. The change in the shape and size of soap micelle in the grease was examined with an electron microscope. It has been found that the phase behavior and the shape and size of the soap micelles in the grease are greatly affected by the oxidation stability of the base oil used. For the lithium stearate/squalane grease, the phase transition temperature and the L/D value of the fibers formed by the soap micelles decreased with the oxidation time. However those of the grease prepared with pentaerythritol tetraoctanoate which was stable for oxidation were hardly affected. These facts may be rcduced to a small amount of the polar compounds produced by the oxidation of a base oil.