Measuring Low Viscosities and High Shear Rates with a Rotational Rheometer in a Thin-gap Parallel-disk Configuration

Abstract

We modify a commercial rheometer so that the disks are aligned perpendicular to the axis of rotation with a precision in parallelism of about 1 μm independent of the rheometer reading. This leads to decrease the zero-gap error by a factor of 25 and more. It enables samples to be studied at gap widths well below the absolute error of commercial rheometers. At gap widths of 20 μm, the modification allows the measurement range to be extended to shear rates up to 105 s-1 enabling to measure low viscosities such as that of solvents or water and of dilute polymer solutions. The measurements are restricted mainly by the torque resolution at low shear rates and by inertia at high shear rates.

Keywords

• thin-gap rheometry
• parallel-disk configuration
• low viscous liquids
• high shear rates
• polymer solutions