The Viscous Behavior of Polymer Modified Lubricating Oils Over a Broad Range of Temperature and Shear Rate

Abstract

A high-shear capillary viscometer was used to determine the viscosity of mineral oil lubricants containing an olefin copolymer up to shear rates of a million reciprocal seconds. Comprehensive measurements were conducted for a range of polymer concentrations from 1–3 wt percent polymer and a temperature range of 38–120° C. The experimental technique utilizes a theoretical analysis procedure to handle the complications associated with viscous heating, the influence of pressure on the viscosity, and the excess pressure drop which occur at the entrance and exit of the capillary. The viscosity of the polymer solutions is determined over the complete range of shear rate starting from the lower Newtonian limit, through the shear-thinning region, and finally, the Newtonian behavior at high shear rates. It is shown that the standard ASTM plot for viscosity-temperature behavior can be used to correlate the viscous behavior for a given polymer concentration over this broad range of shear rates and shear stresses.