ON THE CONDUCTIVITY MODEL FOR THE ELECTRORHEOLOGICAL EFFECT

A model is presented for the electric current and attractive force between two slightly conducting spherical particles in a nonpolar liquid. The model includes the nonlinear conductivity of the liquid but does not require that the zone between the particles be divided into two distinct regions, nor is there a need to assume an equipotential condition at the particle surface. Further, the model gives the pertinent properties as a function of the separation of the particles. Numerical values are presented for the properties as a function of the conductivity ratio of the particles to the host oil (silicone oil), the electric field, and the separation of the particles. It is shown that good accord exists between the predicted yield stress and that measured on a suspension of zeolite particles in silicone oil. Some accord also occurs for the current density. Illustrated is the importance of the electrical conductivity parameter E(c) of the host oil on ER response. Empirical equations for the shear modulus and static yield stress are given in the Appendix. (C) 1995 Society of Rheology.