Electrorheological effect in suspension composed of starch powder and silicone oil

Measurements of the electrorheological (ER) effect, a rheological change in duced by an application of an electric field, are made on the ER suspension s composed of potato starch powder and silicone oil. When an electric field of a few kV mm(-1) is applied, there appears an increase in the viscosity, which is characterized by a rapid increase of the viscosity, followed by a slow increase having a relaxation time longer than a few minutes, As a pos sible mechanism, the chain and the columnar structure formations are sugges ted to be associated with the rapid and the slow components, respectively. It is also found that there appears a memory effect; if the electric field is turned off for a short period, the shear stress slowly induced by the el ectric field recovers its value instantaneously. (C) 1999 Academic Press.