A fundamental study of oil release mechanism in soap and non-soap thickened greases

- The morphology of thickener particles were measured using light scattering.
- Calcium sulfonate (CS) and Li-X thickeners were spheres and rods respectively.
- Bleed of CS shows a non-linear dependency with oil content unlike other greases.
- A model was proposed relating grease bleed to the thickener microstructure.
- Increase in bleed of CS was related to structural opening of spherical thickeners.

The oil bleed behavior of lithium complex, calcium sulfonate and polyurea thickened greases have been studied. Results were interpreted within a model where the grease thickener is treated as particles suspended in a matrix of oil. There is a region surrounding the thickener particles, called the effective media, which is assumed to have completely immobilized the oil. Bleed is assumed to occur from the viscous flow of the unbound oil in a porous structure made of the effective media. Dynamic/Static light scattering (DLS/SLS) techniques were used to assess the geometry of the thickener particles. In the light of this model different bleed behaviors of the greases were explained, relating them to the geometry of the thickener particles.

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