Effects of Soap Fiber Structure on Boundary Lubrication of Lithium Soap Greases

Abstract

This paper describes the influence of fiber length of lithium-soap thickener of greases on friction under boundary lubrication conditions. Ball-on-disk sliding tests were conducted with lithium soap greases with polyol ester as the base oil. The tests revealed that the greases had a lower friction coefficient than that for the base oil. The grease with a long soap fiber structure had a lower friction coefficient than that for the grease with a short soap fiber structure. The tests with only soap fibers showed that the soap fibers had better lubricity than the base oil under the boundary conditions tested, but there was little difference in the lubricity of the longer fibers and the shorter fibers. The partial coat tests revealed that the grease with longer soap fibers was easily entrained into the contact. It was concluded that this entrainment capability of the grease led to favorable lubrication to maintain low friction coefficient.

Keywords

• grease
• thickener
• fiber
• friction
• boundary lubrication