Abstract
We investigated properties of lubricants confined between mica surfaces using resonance shear measurement (RSM) which can monitor the rheological and tribological properties of the lubricants as a function of the surface separation distance (D) as well as the normal load (L). The formulations of the five lubricants investigated were; oil A (mineral oil + viscosity modifier (VM) + Antiwear additive + Metallic detergent + Ashless dispersant + Anti-oxidant + Foam inhibitor), oil B (oil A + Molybdenum dithiocarbamate (MoDTC)), oil-C (oil A + Glycerol monooleate (GMO)), oil D (mineral oil + viscosity modifier (VM)), and oil E (mineral oil only). The oil E showed the friction coefficient (µ) of 0.45 at the normal load (L) below 2.0 mN. The oil D, which contained VM, showed significant decrease in the µ value to 0.19. In the case of oil A, B, C, the thickness of lubricant layers became significantly thicker than those of oil E and D, however, the no clear reduction in the µ value compared with oil D was observed. These results have demonstrated that the RSM can evaluate the contribution of the each component on the lubrication in order to optimize their properties and performance.
