Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE 150 N1 base oil (lowest thickener content, 10.5 wt%). Chart 1. Thickener Content Required for Different Greases, wt%
For the other thickeners in Chart 1, the amounts of thickener do not always follow the same order as for Li 12-HSA. The pattern of increasing thickener content does not hold, it varies with aniline indicating that the oil to thickener interaction depends on the type and chemistry of the thickener.
Chart 2. Aniline Point vs Thickener Content
For all thickener types, with the exception for the calcium sulfonate grease, the use of a naphthenic ISO VG 150 base oil reduced the amount of thickener required to formulate an NLGI Grade 2 grease. For the Li 12-HSA greases, the amount of thickener can be reduced by 25 to 30% when a naphthenic base oil is used instead of a paraffinic base oil, either a Group I or II. For the Li complex greases, the decrease in the amount of thickener was 7 to 9%. For the Al complex greases, the decrease was 40 to 50%, and for the clay greases it was 20 to 30%. For the Ca sulfonate greases, the ISO VG 460 naphthenic required slightly less thickener than the ISO VG 150 naphthenic. The decrease in the amount of thickener, compared to the paraffinic base oils, was up to 20%.
Solvency Aromatic hydrocarbons exhibit the lowest aniline points and paraffins have the highest. The lower the
36 LUBE MAGAZINE NO.144 APRIL 2018
In general, the higher the solvency of the base oil, the lower the required thickener content. The Ca sulfonate grease behaves differently with respect to the solvency of the base oils. Of the parameters tested, none correlated to the required calcium sulfonate thickener content.
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aniline point, the higher or stronger the solvency of the base oil. Chart 2 plots the relationship between the aniline point of the base oil and thickener content to generate an NLGI Grade 2 grease using various thickeners. The R-squared values ranged from 0.65 to 0.97 for all thickeners except for the Ca sulfonate (R-squared = 0.09). This demonstrates the importance of the solvency of the base oil in minimizing the thickener content required to produce the target NLGI grade grease.
Chart 3. Viscosity Index vs Thickener Content
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