The nonlinear behavior of surfactant-activated electrorheological suspensions

Abstract

The nonlinear electrorheological (ER) behavior of nonionic surfactant-activated ER suspensions is investigated. The influence of three nonionic surfactants (Brij(R)30, GMO, and GTO) on the electrorheological (ER) response of various alumina/silicone oil suspensions shows similar behavior. The prevalent feature common to all formulations is that the yield stress, tau(0), initially increases with surfactant concentration, passes through a maximum, then decreases with surfactant concentration. The nonlinear behavior observed at large surfactant concentrations (i.e., tau(0) approximate to E-n, where n<2) arises from field-induced phase separation of a surfactant-rich phase as opposed to field-dependent conductivity of a homogeneous continuous phase.