Volumetric Properties and Viscosity of PIBs and PIB-Based Dispersants in a Mineral Oil

Abstract In this study we report on the influence of poly(isobutylene) (PIB) and PIB-based dispersants on the high pressure thermodynamic properties and the viscosity of a mineral base oil used in passenger vehicle transmission fluids. Density was measured over a pressure range from 10 to 35 MPa at isotherms of 298, 323, 348, 373, and 398 K using a high pressure variable-volume view cell. The density data were then correlated with the Sanchez-Lacombe Equation of State from which the thermodynamic properties of isothermal compressibility, isobaric expansively and internal pressure were derived. Viscosity was measured over a pressure range from 10 to 45 MPa at 298, 323, 248, and 373 K using a uniquely designed high pressure rotational viscometer. Viscosity data were then correlated with density according to the free volume and density-scaling formalisms to provide further insights into molecular packing and interactions.