Rheologically Stable Calcium Sulfonate Grease – A Case Study That Leads to Novel Calcium Sulfonate and Polyurea Grease Blends Liwen Wei, President and CTO Novitas Chem Solutions, LLC Houston, TX USA Abstract A novel class of Rheologically Stable Calcium Sulfonate Grease (abbreviated as RSCG) is being developed as a viable and cost competitive option to replace lithium grease. It combines the merits of overbased calcium sulfonate grease and polyurea grease and offers enhanced load carrying performance and structural stability. 1. Introduction As automakers race to bring new models of electric vehicle (EV) to the marketplace, the grease industry is looking for options to replace lithium�based greases, which could be threatened should the demand outpace the supply in the foreseeable future. According to the NLGI 2017 Global Production Survey, lithium-based greases (shaded in yellow, Table 1) comprised 74% of the total grease market share. Calcium greases, including calcium sulfonate and calcium complex greases, (shaded in green) as well as polyurea greases (shaded in blue) are the two thickener types favored as lithium grease replacements [1-3].
Table 1 - 2017 NLGI Production Survey
Yet, each type of grease has its unique characteristics, challenges, and limitations. For instance, overbased calcium sulfonate grease (OBCSG) has gained popularity due to its inherent extreme pressure (EP) performance. Nevertheless, the thickener structure of OBCSG is spherical in shape as opposed to the fiber-like structures in lithium, lithium complex, and polyurea greases. This difference in thickener structure was noted in an AFM study (Figure 1 [4]) of entrapped thickener in rolling contacts undergoing elastohydrodynamic lubrication (EHL) under fully flooded conditions at medium speeds. - 20 NLGI Spokesman | VOLUME 84, NUMBER 2 | May/June 2020
