Electro-rheological properties of anhydrous ER suspensions based on phosphoric ester cellulose particles

Abstract

The electro-rheological (ER) behaviour of suspensions in silicone oil of phosphoric ester cellulose particles (average particle size 17.77 mu m) was investigated at room temperature with electric fields up to 2.5kV mm(-1) with the aim of developing anhydrous ER suspensions applicable over a wide temperature range. Anhydrous ER suspensions dispersing cellulose particles which were treated by phosphoric ester reaction of 2 mol phosphoric acid and 4mol urea were measured; not only were the electrical characteristics such as dielectric constant, current density and electrical conductivity studied but also the rheological properties on the electric fields and volume fraction of dispersing particles. Anhydrous ER suspensions dispersing phosphoric ester cellulose particles showed very low current density, conductivity and very high performance of ER effect (tau(A)/tau(0) approximate to 1030) on the 2.5 kV mm(-1) electric field, and the yield stress (tau(y)) had a quadratic dependence on electric fields. (C) 2000 Society of Chemical Industry.