Mechanisms of electrorheology: the effect of the dielectric property

The effect of the dielectric properties of electrorheological fluids on electrorheology was investigated in DC electric fields by using both hydrous and anhydrous electrorheological fluids. The relaxation frequency, which is defined by a local maximum of the dielectric loss factor of an electrorheological fluid, was in the range from 100-10(5) Ha whenever the electrorheological fluid had a large electrorheological effect. This effect increased with increasing difference between the dielectric constants (Delta epsilon') below and above the relaxation frequency both for hydrous and anhydrous electrorheological fluids, when the relaxation frequency was in the range 100-10(5) Hz. For the electrorheological fluid containing microcrystalline cellulose, the change of the rheology curve, namely the shear rate versus si?ear stress((gamma) over dot versus tau) curve, with increasing adsorbed water content could be interpreted in terms of the relation between the shear rate and the polarization rate. The mechanism of electrorheology could also explain the effect of the current density on the ER effect.