​Twenty percent of worldwide CO₂ emissions comes from road and marine transport. Inside the engines of these vehicles, friction can cause both energy loss and damage over time. Organic Friction Modifiers (OFMs) are surface-active molecules (surfactants) that are included in engine oil formulations to reduce friction by approximately 3%.

Improving this friction reduction could lead to improvements in fuel economy with a resulting decrease in global CO₂ emissions by up to 50 Mt each year, almost as much as the total emissions from UK power stations. To reach this target, businesses need to understand how lubricant additives work at the molecular level, enabling better molecules to be designed and synthesised on short time scales.

Professor Pete Dowding from the speciality chemicals company Infineum and colleagues Oliver Delamore, Elizabeth Mould and Colin Willis, in collaboration with a team from the University of Cambridge led by Professor Alex Routh, worked with Sandy Armstrong and Becky Welbourn from ISIS to build and commission a unique piece of equipment to do just this. Their beamline tribometer enables them to do neutron reflectometry of a sample under conditions that replicate those inside an engine.

Neutron reflectometry is particularly well suited to these investigations because of to the unique interaction of neutrons with the hydrogen atoms present in the oil and surfactant. To interpret the results, they worked with a group of scientists from the University of Edinburgh led by Professor Phil Camp, who performed molecular-dynamics simulations to complement the experiments.

Through this collaborative partnership between academia, central facilities and industry, Professor Dowding and the team developed the capability to visualise the molecular-scale processes responsible for friction and wear and predict friction coefficients.

An improvement in friction reduction will result in lower environmental impacts of transport and other sectors through the design of new molecules. Infineum is now carrying out engine tests to determine whether the molecular behaviour seen at ISIS translates to real-world conditions.

Using the new tribometer, they have been able to understand the behaviour of lubricant additives for lots of different types of system. This includes those relevant to biofuels, where they found that changing the additives can potentially lead to up to a 7% improvement in fuel efficiency. The equipment could also be used in other industries, for example investigating joint lubrication in medical applications.

Further planned studies include focusing on the surface-adsorbed layer. Understanding this layer, in terms of molecular-scale mechanisms, could open up new approaches to friction reduction, new product development, and further CO₂ emission reductions.

For more information, read the ISIS science highlight about the development of the tribometer.