On the evolution of oil-separation properties of lubricating greases under shear degradation
Femke Hogenberk, Jude A. Osara, Dirk van den Ende, Piet M. Lugt
Abstract
The bleed rate of a grease may change over time due to degradation of the thickener microstructure and a decrease in oil content, as oil is released from the grease. In this work, the bleed properties—quantified by the permeability—of five types of lubricating greases are studied. Controlled shear ageing is performed using a grease worker. It is shown that the bleed rate does not change significantly in a grease worker at room temperature, as opposed to changes in rheology and microstructure. This is explained using a permeability model. It is shown, via a comparison with rolling bearings results, that ageing grease in a grease worker is too mild to yield significant changes in the permeability of lubricating greases.