THE EFFECT OF BLENDING PARTICLES WITH DIFFERENT CONDUCTIVITY ON ELECTRORHEOLOGICAL PROPERTIES

We have carried out a set of experiments using anhydrous carbonaceous particles to determine the effect on the electrorheological properties of blending particles of different conductivities. We find that there is a significant dip in the shear stress under an electric field as t he concentration of higher conductivity particles is increased, showin g that uniformity of the electrical properties among the particles is a most important factor in achieving optimum electrorheological fluid (ERF) performance. We explain this behavior by a simple model based on the strength of particle-particle interactions. Measurements of the d ielectric permittivity show that the cr parameter of the Cole-Cole exp ression provides an excellent way to express the degree of uniformity in the electrical properties. This gives a convenient method to evalua te the potential performance of an ERF. (C) 1996 Society of Rheology.