Organic Friction Modifiers (OFMs) are surface-active molecules (surfactants) that are included in engine oil formulations to reduce friction between mechanical engine components that come into contact with one another. For more information on surfactants and their structure, see our explainer article.
It is commonly accepted that OFMs work by forming a layer between the metallic engine components and the engine oil. However, there is no unified theory which relates the structure of the layer to the resultant friction.
The forces present inside an engine are also likely to disrupt the structure, and therefore the behaviour, of the surfactant layer. To be able to investigate the layer formation, an experiment would need to effectively recreate the conditions inside an engine, whilst also allowing measurement of the surfaces.
Through the ISIS Collaborative Research and Development (ICRD) programme, researchers from Infineum have worked with staff from ISIS and Diamond Light Source to develop a new tribometer: an experimental setup that enables neutron and X-ray reflectometry of a sample under conditions that replicate those inside an engine. Neutron reflectometry is particularly well suited to these investigations due to the unique interaction of neutrons with the hydrogen atoms present in the oil and surfactant.
“Curiosity drives science," comments Infineum Principal Scientist Pete Dowding. “Having a mindset which challenges and questions how things work."
“We've channelled curiosity while working with the University of Cambridge, ISIS and Diamond to not only determine how molecules behave, but also how we can make use of them to reduce friction."
Their study, published in Scientific Reports, uses the new tribometer to study the industrial OFM glycerol monooleate (GMO) dispersed in dodecane. Experiments carried out on the Inter beamline at ISIS, FIGARO at the Institut Laue-Langevin and I07 at Diamond Light Source demonstrated its success in measuring the behaviour of interfaces under these harsh conditions.
The interface between dodecane and iron oxide was characterised using the new sample cell both with and without the addition of GMO under two different shear rates. They found that a layer of GMO that formed at the interface, but was not affected by shear force. The layer that was formed was also thicker than a simple monolayer.
“This facilitates molecular-level design of new products which is only possible with the advanced methods available at ISIS and Diamond," Pete concludes.
The ongoing collaboration between ISIS and Infineum has also led to the joint recruitment of a postdoctoral researcher. This researcher will continue to develop sample environments to perform in-situ, real-time studies of additive systems and establish structure-performance relationships.
The full paper can be found online at DOI: 10.1038/s41598-021-89189-1
This story also appeared on the Infineum news pages.