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

The electro-rheological (ER) behaviour of suspensions in silicone oil of ph osphoric ester cellulose particles (average particle size 17.77 mu m) was i nvestigated at room temperature with electric fields up to 2.5kV mm(-1) wit h the aim of developing anhydrous ER suspensions applicable over a wide tem perature range. Anhydrous ER suspensions dispersing cellulose particles whi ch were treated by phosphoric ester reaction of 2 mol phosphoric acid and 4 mol urea were measured; not only were the electrical characteristics such a s dielectric constant, current density and electrical conductivity studied but also the rheological properties on the electric fields and volume fract ion of dispersing particles. Anhydrous ER suspensions dispersing phosphoric ester cellulose particles showed very low current density, conductivity an d 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 quad ratic dependence on electric fields. (C) 2000 Society of Chemical Industry.