Electrorheology of Non-aqueous Suspensions

Abstract

An excellent electrorheological (ER) suspension is invented with composite particles consisting of polymer core and inorganic shell. When the composite particles are subjected to jetstream agitation, the ER effects are strikingly enhanced. Since the ER effects can be attributed to the shell layers on the polymer particles, the surface of inorganic particles must be barely exposed to the surrounding oil. The importance of surface conditions is demonstrated by a scaling analysis. The creep curves at low stresses for suspensions in electric fields are composed of instantaneous elastic and retarded elastic regions. But the suspensions show no elastic recovery after the removal of stresses. The creep and recovery behavior is purely plastic. The dipole-dipole interactions cause chainlike structures of particles. The development of Bingham yield stress can be derived from the ideal chain model in which the particles all align into chains of single-particle width and equal spacing. However, the model cannot predict the solidlike deformation without recovery. The thick column formed by several chains may be responsible for purely plastic responses. The particle concentrations in column are increased in nonuniform electric fields. Since the increase in particle concentration of column lead to high yield stresses, the ER performance of suspension as an overall response can be improved by the electrode design.