Dynamic dielectric response of electrorheological fluids in drag flow

摘要

We have determined the response time of dilute electrorheological fluids (ER)in drag flow from the dynamic dielectric response. On the basis of a kineticrate equation a new formula was derived to approximate the experimentaltime-dependent dielectric permittivity during the temporal evolution of themicrostructure. The dielectric response time was compared to the standardrheological response time extracted from the time-dependent shear stress, and agood agreement was obtained. We found that the dielectric method is moresensitive to detect any transient during the chain formation process. Theexperimental saturation value of the dielectric permittivity corresponding tothe equilibrium microstructure was estimated on the basis of formulas derivedfrom the Clausius-Mossotti equation.