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

The Influence of Molecular Architecture on the Macroscopic Lubrication Properties of the Brush-Like Co-polyelectrolyte Poly(L-lysine)- g -poly(ethylene glycol) (PLL- g -PEG) Adsorbed on Oxide Surfaces

The co-polymer poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG) has been investigated as a potential biomimetic boundary-lubrication additive for aqueous lubrication systems. In this work, the influence of the co-polymer's architecture on its tribological performance has been investigated. The architectural parameters investigated comprise side-chain (PEG) length, Lys/PEG grafting ratio and backbone chain (PLL) length. The tribological approaches applied in this work include ultra-thin-film interferometry, the mini-traction machine (MTM), and pin-on-disk tribometry. Both an increase in the molecular weight of the PEG side chains and a reduction in the grafting ratio result in an improvement in the lubricating properties of aqueous PLL-g-PEG solution at low speeds. MTM measurements show that an increase in the molecular weight of the PLL backbone results in an increase of the coefficient of frictio

The influence of molecular architecture on the macroscopic lubrication properties of the brush-like co-polyelectrolyte poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG) adsorbed on oxide surfaces

ISSN:1023-8883ISSN:1573-271

Boundary Lubrication of Oxide Surfaces by Poly(L-lysine)- g -poly(ethylene glycol) (PLL- g -PEG) in Aqueous Media

In this work, we have explored the application of poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG) as an additive to improve the lubricating properties of water for metal-oxide-based tribo-systems. The adsorption behavior of the polymer onto both silicon oxide and iron oxide has been characterized by optical waveguide lightmode spectroscopy (OWLS). Several tribological approaches, including ultra-thin-film interferometry, the mini traction machine (MTM), and pin-on-disk tribometry, have been employed to characterize the frictional properties of the oxide tribo-systems in various contact regimes. The polymer appears to form a protective layer on the tribological interface in aqueous buffer solution and improves both the load-carrying and boundary-layer-lubrication properties of wate