Electrorheology of suspension of sulfonated styrene-co-divinylbenzene particles - Approach based on the dielectric properties of the suspension

Effects of particle concentration, water content and temperature on the electrorheology of suspensions of highly sulfonated styrene-co-divinylbenzene (SSD) particles in a silicone oil were investigated. The induced shear stress was measured with a modified rotary rheometer. The electrorheology of the suspension was largely affected by the particle concentration, the water content and the measurement temperature. The induced shear stress for the particle concentration of 40 wt % was about twice as large as that of 20 wt %. The induced shear stress for the water content of 4 wt % was about twice as large as that of 2 wt %. The induced shear stress for the temperature of 80 degrees C was about 15 times as large as that of 20 degrees C. Dielectric properties were measured to elucidate the mechanism of electrorheology. In order for an ER fluid to have a large ER effect, relaxation frequency of the ER fluid should be between 100 and 10(5) Hz and the difference of the dielectric constant below and above the relaxation frequency (Delta epsilon') must be large, which we refer to as the dielectric property mechanism. The relation between measured ER effect and dielectric property mechanism was discussed.