Thickeners impart the pasty, non-flowing nature of greases. While it does not normally contribute to friction reduction activities, or lubrication, (the base oil and additive perform these functions), it nonetheless provides important characteristics to the grease that aid over-all performance. Thickeners can impact the following,
1.) Consistency, where stiffer greases are more adherent to surfaces, and where softer greases are more pumpable
2.) Water-resistance / Steam-resistance
3.) Temperature performance (dropping-points and/or low-temperature behavior)
4.) Acid and Alkali resistance
5.) Corrosion Protection
6.) Grease stability
Simple soaps are frequently used as thickeners, and for higher performance requirements, complex soaps are utilized. The table below provides an over-view of how a soap-type affects grease performance.
In some cases, non-soap, or inorganic thickeners may also be used, especially in applications at higher temperature. Some non-soap thickeners would include bentonite (clay), polyurea, silica and polytetrafluoroethylene (PTFE).