Formulation, rheology and thermal aging of polymer greases—Part II: Influence of the co-thickener content

• Four polymer thickened greases of different formulation were tested.
• Rheological tests were performed on fresh and thermally aged greases.
• Thermal aging analyzed through IR spectroscopy, oil-bleed rate and viscosity changes.
• Influence of the co-thickener/elastomer content analyzed.

In the first part of this work, the effect of the thickener content on the rheological behavior of polymer greases was investigated. The aim of this part II is to show the correlation between these greases’ rheology and its formulation, regarding the co-thickener content.Even though the greases were formulated with the same base oil, the co-thickener content and nature clearly influence the bleed-oil viscosity and the greases’ mechanical stability, allowing us to control the oil bleeding rate. Therefore, analyzing the rheology of these polymer greases, this study aims to bring some light on the base oil vs bleed-oil viscosity approach at high shear rate and the effect on the properties of the active lubricant in the EHD contact.