Rheological Characterization of Yield-Stress Fluids with Brookfield Viscometer

This paper analyzes various techniques to use viscometers equipped with vane spindles to characterize rheological properties of yield stress fluids. Specifically, application of Brookfield viscometers to this end is discussed. A wide selection of toothpastes and lotions were tested. It is shown that a simple method based on apparent shear rate and stress, commonly referred to as a representative viscosity method, works well for moderately non-Newtonian samples but may significantly underestimate viscosity for samples with a more pronounced yield stress behavior. To get more accurate data an integral equation relating torque to angular velocity needs to be solved which can be easily done numerically to get a good agreement between the data collected on an inexpensive viscometer and the data from high-end rheometers.