Influence of base oil polarity and thickener type on visco-elastic properties. Investigations with strain sweep rheometry at +25℃ and +80℃

摘要

This paper reports about experiments with a modern high resolution viscosimeter where model greases were tested at +25℃ and +80℃. The aim was to study the influence of base oil polarity on visco-elastic properties of greases. As thickening systems Lithium-12-hydroxystearate, diurea and highly dispersed silica were selected and each combined with PAO, PAO/mineral oil, ester and polyglycol. The experiments showed that there are significant differences in visco-elastic behaviour and yield point detectable. If the yield point is considered as the ability of grease to seal a lubrication area from the environment or to flow into a lubricating gap it becomes obvious that the common layout according to NLGI classes is not sufficient when it comes to greases with different base oil types or thickeners.