The University of Pennsylvania and ExxonMobil have discovered how lubricant additives work at a molecular level.
The research will help the testing of new anti-wear additives because of its ability to pinpoint the level of stress at which they begin to break down and form tribofilms.
Anti-wear additive zinc dialkyldithiophosphate, or ZDDP, was accidentally discovered to have anti-rust properties in the 1940s as well as increasing the anti-wear properties of motor oil.
While historic analysis has shown that ZDDP breaks down and becomes a "tribofilm" (a thin, solid layer that adheres to the surfaces in contact protecting them from further wear), the way the breakdown occurs has remained unclear.
Using a nanoscale approach to 'tribochemistry' and specialist microscopy, the researchers observed the behaviour of ZDDP-infused oil on a moving metal object.
"The combination of friction and mechanical pressure enhances the probability of chemical reactions by reducing the energy needed to break or form bonds," states Robert Carpick, Penn's chair of the Department of Mechanical Engineering and Applied Mechanics.
"In this case, it helps break down the ZDDP molecules and also helps them react to form the tribofilm on the surface. And when the pressure drops, the film growth stops as needed."
The research findings have created potential to design even smarter engine oils and improve fuel economy.
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