Using a capillary viscometry technique, the high-shear-rate behavior of two polymer additives
(an ethylene−propylene block copolymer and a radial hydrogenated styrene−isoprene copolymer)
in a hydrocarbon-based oil solution has been investigated. At mass concentrations of up to 2.0%
for the styrene−isoprene copolymer and 1.5% for the ethylene−propylene additive, the viscosity
was measured over a range of shear rates from 104 to 106 s-1. To correct for the effects of viscous
heating and pressure changes, a numerical correction procedure is used which reduces the
experimental results to viscosity data at a common reference temperature and pressure for
comparison. Over the range of shear rates examined, the styrene−isoprene solutions exhibited
typical shear-thinning behavior, becoming more dramatic at higher polymer concentrations. In
addition to shear thinning at the higher shear rates, a shear-thickening region was observed in
the more concentrated ethylene−propylene solutions. As the polymer concentration increased,
the degree of shear thickening was shown to be more severe and the critical region was observed
at lower shear rates.