Effect of dielectric property of hydrous dispersoid on electrorheology

The effect of the dielectric property was investigated of titania and microcrystalline cellulose particles dispersed in a silicon oil on Electrorheology(ER). A commom understanding of the mechanism of ER is the electrical interaction by the interfacial polarization of dispersed particles. Block et al. reported the relaxation frequency of ER fluids, i. e. the rate of polarization, was very important to have an appreciable ER effect. We found that the free water on the cellulose and the titania particles dispersed in the silicon oil, which is respectively dehydrated below the temperature of ca 110 and 300 degree centigrade, was necessary for an appreciable ER effect. The relation was measured between the water content and the dielectric properties such as dielectric constant epsilon' and dielectric loss factor epsilon '', as the water adsorbed on the particles was estimated to alter the dielectric properties of the ER fluid Both the dielectric constant and the relaxation Frequency, which is defined by the applied frequency for a peak of the dielectric loss factor, increased with the increase of the water content. The relation was discussed between the ER effect and the dielectric properties.