Overcoming and Quantifying ‘Wall Slip’ in Measurements Made on a Rotational Rheometer
Application Note Jul 19, 2016
Malvern Instruments Limited
When making shear rheological measurements on structured liquids, in particular suspensions, emulsions or foams there is a high probability that the measurement maybe affected by a phenomenon known as 'wall slip'. Wall slip generally results from a local depletion of the dispersed phase near the geometry walls, effectively forming a lubrication layer at the surface. As a consequence bulk rheological properties are no longer being accurately measured leading to an underestimation of the true viscosity. A similar effect can be observed when measuring solid like materials where there is insufficient friction between the sample and the wall to support the applied stress.