Proceedings of the Royal Society of London A Mathematical and Physical Sciences · 1966 · 117 citations · 1 references
EngineeringMaterials EngineeringMaterials ScienceRheologySurface ScienceThin FilmsLubricant AdditivesLubricant PropertiesLubricant RheologyLubrication EngineeringLubrication SystemsViscous FlowAdditive Effects On RheologyLubricantsLubricating MaterialsLubrication MechanismsLubricityOil LubricationSurface Active AdditivesSurface Active Molecules
The Langmuir isotherm explains lubrication failure that can cause surface seizure. The study investigates how surface‑active additives affect lubrication in a slow‑running four‑ball machine. Pure paraffin lubricants with long‑chain acids, amines, or alcohols were used, and the effect was interpreted through adsorption thermodynamics, extending the theory to describe mineral oil lubrication. Oil film properties and scuffing load peaked when additive and carrier chain lengths matched, a result confirmed by surface viscosity measurements and supporting the role of long‑range forces.
The paper sets out to study the influence of surface active compounds on lubrication of a slow running four ball machine first noted by Beeck, Givens, Smith & Williams (1940). The lubricants are pure paraffins, mainly hexadecane, and the additives long chain acids, amines and alcohols. It was found that the oil film was markedly influenced by the additive and a sharp peak in the curve of scuffing load against chain length was found when the additive and the carrier were of the same chain length and shape. The surface viscosities were measured by a falling plate viscometer and the same peak was found when complete matching of the chain length occurred. These results lend support to the existence of long range forces. The Langmuir isotherm gives an explanation of the failure of lubrication, which leads to the seizure of the surfaces. This explanation is in terms of the heat of adsorption and of the standard change of entropy of adsorption of the polar compound onto the surface. A reasonable extension of the theory allows the lubricating characteristics of mineral oils to be described.
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