Friction Modifier Additives
Friction modifier additives are being fuelled by the growing interest in reducing friction in lubricated machine components, to thereby increase the energy efficiency of machines. One important way to minimize friction is to employ suitable additives to reduce friction in thin-film boundary lubrication conditions.
Accordingly, there are currently three main types of friction modifier additive,
- Oil-soluble organomolybdenum
- Functionalized polymers.
In common practice, a single such additive is generally employed in a formulated lubricant, but it is of interest to explore whether combinations of two additives may prove beneficial.
In this study, the performance of eight commercial friction modifier additives spanning all three main types was first measured in three quite different friction tests. The aim was to identify the contact conditions under which each additive was most effective.
Additive solutions in both a base oil and a formulated engine oil were investigated. In general, functionalised polymers were most beneficial in sliding–rolling contacts, while oil-soluble organomolybdenum friction modifiers worked best in severe, reciprocating sliding conditions. However, all friction modifier additive response was strongly affected by the other additives present in formulated engine oils.
The friction performance of combinations of friction modifier additives was then explored. When two different additives were combined in solution, several possible outcomes were observed.
The most common was for one of the additives to predominate, to give friction that was characteristic of that additive alone, while in some cases friction lay between the values produced by either additive on its own.
In a few cases, the additives behaved antagonistically so that the combination gave higher friction than either additive by itself.
In other cases, true synergy was observed, where a combination of two additives produced lower friction in a given test than either individual component at the same overall concentration.
Another, and possibly more important synergy could also occur, however, when a pair of Friction Modifiers worked more effectively than either individual additive over the range of test conditions present in different friction tests.
This study suggests that optimal combinations of Friction Modifiers may provide a means of reducing boundary friction and thus increasing the efficiency of machines, especially if the latter contains a range of lubricated machine components that operate with different types of tribological contacts.
Cited and Adapted from:
Guegan, J., Southby, M. & Spikes, H. Friction Modifier Additives, Synergies and Antagonisms. Tribol Lett 67, 83 (2019). https://doi.org/10.1007/s11249-019-1198-z
Our Friction Modifier Additives
NanoClear304 is a synthetic additive containing nanoparticles for oils and lubricants of different grades and viscosities, including mineral, semi-synthetic and synthetic oils. NanoClear304 reduces friction & wear. Please go to our Products Page for more information.