ABSTRACT
In 1919, it was found that the addition of oleic acid to mineral oils improved the latters’ friction and wear performance to equal that of natural oils [1]. ˜is sparked considerable research and in the early 1920s, Langmuir, Hardy, and others showed that the property of oiliness could be produced by monolayers of long-chain surfactants adsorbed or reacted on solid surfaces. In 1922, Hardy and Doubleday coined the word “boundary lubrication” to describe this eµect [2]. Nowadays, the superiority of natural
20.1 Origins of Boundary Lubrication.................................................20-1 20.2 Stribeck Curves and Boundary Lubrication ...............................20-2 20.3 Solid-Like and Viscous-Like Boundary Films ...........................20-3
20.5 Film Replenishment .......................................................................20-6 20.6 Types of Boundary Film ................................................................20-7
20.7 Friction Control by Boundary Films .........................................20-11 20.8 Wear Control by Boundary Films ..............................................20-12 20.9 Correlation between Friction and Wear Properties of
Boundary Films.............................................................................20-13 20.10 Strength of Boundary Films ........................................................20-13 20.11 Prediction of Boundary Lubrication Performance .................20-14 References ..................................................................................................20-15
oils in terms of boundary lubrication is considered to be due to their partial decomposition to form long-chain surfactants, either carboxylic acids or partial esters, that act as “natural” friction modiŸers.
