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DME lubricity and viscosity

A combination of experimental and theoretical (Molecular Dynamics Calculations) calculations has improved our understanding of the processes involved in the region of boundary lubrication. For simple molecules, the influence of molecular structure has been shown, and a new lubrication region called "Quasi-Boundary lubrication has been proposed. In this region, continuum properties, such as viscosity are not meaningful.

This study represents the first time that the fundamental processes leading to wear and friction have been studied in detail with molecular dynamics, and results correlated with experimental lubricity testing.

It has been shown that a primary property influencing the lubricity is the number of atoms per unit surface area present in the final molecular layers of lubricant squeezed out from between the lubricated surfaces. It has also been shown that long chain type molecules have better lubricity properties than their branched isomers.

Though viscosity is not the property that best describes lubricity considerations (boundary lubrication), this is not to say that viscosity is insignificant, as it is important in many other situations. Since few studies of lubrication have been performed with high vapour pressure liquids, additional viscosity measurements have been made with these fluids to supplement previous DME results.

These results are significant in future studies of lubrication with low viscosity substances in particular, but also with other lubricants where boundary lubrication is encountered. Through an understanding of the basic processes involved, future developments in lubricity improving additives and surface materials and treatments can be based on fundamental principles instead of conjecture. This may make it possible to develop more effective solutions to boundary type lubrication, not only with DME but also with a large number of other lubricants in other physical situations.

Work in progress is underway for more complicated molecular structures, such as branched chain molecules and molecules with dipole moments. The results of the work are routinely and promptly presented in relevant scientific journals and technical conferences.

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