Characterisation of cohesion, adhesion, and tackiness of lubricating greases using approach–retraction experiments

Greases are widely used in machinery and automotive components to protect components from frictional and wear losses. As a result, interaction properties like adhesion to the substrate, cohesion or consistency, and tackiness become crucial factors and often dictate their performance. All these properties are related to microstructural aspects of grease like thickener network, wetting agents, and additives. The aim of this paper is to use approach–retraction experiments for qualitative/quantitative determination of the above mentioned properties and also understand the influence of grease constituents on these properties. It was found that among all the grease constituents, the thickener in particular dictates the cohesiveness and tackiness of a grease with less influence on the adhesion. The effect of thickener on the lubricating properties of the greases was not clear, which supports the notion that oil in the grease provides the lubrication and thickener to be a carrier. The data on cohesiveness/consistency obtained from this approach–retraction experimental method correlate with the traditional cone penetration tests thus validating this methodology.

► Novel characterisation technique for viscoelastic materials.
► Studying structure-property relationship in greases.
► Role of thickener unveiled for the first time through quantitative measurements.
► Electrostatic attraction of polarised particles and implications on tribological properties.