Friction Modifier Additives

Abstract

The need for energy efficiency is leading to the growing use of additives that reduce friction in thin film boundary and mixed lubrication conditions. Several classes of such friction modifier additive exist, the main ones being organic friction modifiers, functionalised polymers, soluble organo-molybdenum additives and dispersed nanoparticles. All work in different ways. This paper reviews these four main types of lubricant friction modifier additive and outlines their history, research and the mechanisms by which they are currently believed to function. Aspects of their behaviour that are still not yet fully understood are highlighted.

Advances in nonequilibrium molecular dynamics simulations of lubricants and additives

“…Despite this, classical MD simulations have given unique insights into the behaviour of a range of lubricant additives including detergents [207,208], dispersants [209,210], viscosity modifiers [91,92,211], anti-wear additives [212][213][214][215], and corrosion inhibitors [216][217][218]. The most widely studied class of lubricant additives with MD are friction modifiers [219], which are a wellsuited application of confined NEMD simulations.…”

“…The need for greater energy efficiency to reduce energy consumption has led to a shift toward lowerviscosity lubricants, which means that an increasing number of engineering components operate under boundary lubrication conditions [219]. As a result, lubricant additives that reduce friction and wear under boundary conditions (i.e., friction modifiers) are of increasing importance [219].…”

“…As a result, lubricant additives that reduce friction and wear under boundary conditions (i.e., friction modifiers) are of increasing importance [219]. Several classes of friction modifier additives exist, the main ones being organic friction modifiers (OFMs), functionalised polymers, organo-molybdenum additives and dispersed nanoparticles [219].…”

“…Several classes of friction modifier additives exist, the main ones being organic friction modifiers (OFMs), functionalised polymers, organo-molybdenum additives and dispersed nanoparticles [219]. An overview of the experimental advances on friction modifier additives is given by in 2015 by Spikes [219]. Sections 3.1 and 3.2 will focus on classical MD simulations of OFMs and nanoparticle friction modifiers respectively, and a brief discussion of "reactive" MD simulations of other additives is given in Section 4.1.…”

“…Their main friction reduction mechanism involves the adsorption of the polar head group to metal, ceramic, or carbon-based surfaces, with strong, cumulative van der Waals forces between proximal nonpolar tails leading to the formation of incompressible monolayers that prevent contact between solid surfaces to reduce adhesion and friction [220]. Many different head and tail groups have been tested in the literature, as discussed elsewhere [219].…”