Steady shear viscosity measurements of viscoelastic fluids with the falling needle viscometer

Abstract

Previous measurements by other investigators of the purely viscous properties of viscoelastic fluids using the falling ball viscometer have been shown to yield anomalous results. These occur because the ball falling through the viscoelastic fluid creates a stress field which requires up to one hour to relax to its stress free state before another ball can be dropped. This is experimentally inconvenient. To further investigate this effect for a variety of viscometers, time interval measurements were made on a viscoelastic fluid (AP-273 Separan) using falling ball, falling needle and rotating cylinder viscometers. Although the falling ball measurements showed considerable time interval effects, the falling needle and rotating cylinder measurements did not. Thus the falling needle and rotating cylinder viscometers can be used to conveniently measure the steady shear viscosity of viscoelastic fluids.