Load enhancement and friction reduction effects by polymer-thickened oils lubricating externally sliding cylinders

Apparatus is described in which a jet of oil is projected into the narrow gap between two cylinders, one of which rotates. The axes of the cylinders are parallel. By measuring the normal force on the fixed cylinder and the tangential force on the rotating one, it is possible to measure load factor and coefficient of friction for different lubricants.Two oils containing an olefin copolymer additive are tested, the load factor and coefficient of friction being compared with that of a Newtonian oil of similar viscosity at temperatures of 24°C, 40°C and 55°C.It is found that the load factor is increased by some 50 per cent for polymer-thickned oils, and the coefficient of friction reduced by 10–25 per cent, compared with the values obtained for the Newtonian oil. The latter values are found to be in good agreement with theory, thus providing a sound basis for the tests. The elastic properties of the polymer-thickened oils are measured and shown to be consistent with the degree of load enhancement obtained.The data provide basic evidence of the improved load bearing and frictional characteristics of polymer-thickened oils.