The electrorheological (ER) properties were studied with ternary suspensions containing solid and liquid dispersoids in silicone oil (DMS). The solid dispersoid used was polyether/montmorillonite nanocomposite particles in which polyether molecules were intercalated between the layers of montmorillonite. The liquid dispersoid was urethane-modified polyether prepared from 4,4′-diphenylmethane diisocyanate (MDI) and poly(propylene glycol) (PPG). The steady shear viscosity and dynamic viscoelasticity were measured with a rotating parallel disc rheometer equipped with ER measurement system. The binary and ternary mixtures of these solid and liquid dispersoids with DMS, i.e. composite particle/DMS suspension, polyether/DMS liquid blend, and ternary blend containing both dispersoids, showed an increase of viscosity in response to an electric field (positive ER effect). The ER effect of a ternary suspension containing the particles and polyether liquids was larger than those of binary suspension or blend with one of these dispersoids. The ER effect was found to be improved by combination of the solid and liquid dispersoids, although the recovery time of viscosity after removing the electric field became rather longer, which would be due to the partly irreversible macroscopic aggregation of the dispersoids.
