The high pressure rheology of polymer-oil solutions

We present perhaps the most comprehensive work on the high-pressure shear-thinning of polymer-blended mineral oil. Three solutions of commercial polymer VI improver in mineral oil are characterized for the effect of pressure and shear rate on viscosity. We show that the film thinning measured in concentrated contact can be explained by ordinary shear-thinning of the power-law type. We present extended high-pressure flow curves for a model polybutene-mineral oil blend that has been previously studied and show the possibility of two shear-thinning transitions; one for the polymer and one for the base oil. Solutions of well-characterized, narrow distribution polyisobutylene in squalane were prepared. The high-pressure mixing rule was determined and Carreau parameters were extracted from flow curves and compared to existing models for calculating characteristic times from molecular weight and concentration.