The temperature dependence of the conductivity of silicone oil and related electrorheology of suspensions containing zeolite particles

The effect of temperature (22-160 degrees C) on the conductivity of silicone oil was determined employing three heating-cooling schedules. In all cases the conductivity was super-ohmic with a good fit to the equation based on Onsager's dissociation theory, namely sigma(f) = sigma(f)(0){(1-A) + Aexp[(E/E-c)(1/2)]} where o(f)(0) is the conductivity at low electric field and A and E-c are constants which define the field-enhanced ionic dissociation. The parameters sigma(f)(0), A and E-c varied with temperature; however, the major effect of the heating-cooling schedules was on the parameter A. An analysis of the dissociation process gave that the valence of the conducting ions was in the range 1-2. The observed anomalous effect of temperature on the conductivity of the silicone oil was attributed to the gain and toss of water which occurred during a given heating-cooling schedule. We found good agreement between the measured anomalous temperature dependence of the yield stress (in dc field) of a zeolite-silicone oil suspension and that predicted by the conduction model when the variation of the conductivity of the oil with temperature was taken into account.