EFFECT OF THE DISPERSION MEDIUM VISCOSITY ON THE ELECTRORHEOLOGICAL BEHAVIOR OF HALLOYSITE SUSPENSIONS IN POLYDIMETHYLSILOXANE

The electrorheological behavior of halloysite suspensions in polydimethylsiloxane with kinematic viscosities of 50, 100, and 400 cSt was studied. The filler concentration was 4 and 8 wt%. The suspensions under study are electrorheological fluids. All samples revealed viscoelastic properties under electric field and the yield stress values significantly increased. The rheological behavior of suspensions are changed due to the extended columnar structures formation from the filler particles along with the electric field. In present study, the dependence of the electrorheological effect intensity on the electric field strength, concentration of the filler and the viscosity of the dispersion medium was obtained. It was shown that the values of the yield stress increase with electric field strength and filler concentration. The values of the yield stress are independent on the viscosity of the dispersion medium at a fixed concentration and electric field in the framework of experimental accuracy. The sedimentation stability of the suspensions was evaluated as well. The sedimentation rate of halloysite particles was lower in suspensions based on more viscous oils, which in rough estimation correlates with the Stokes equation. The level of the final sedimentation ratio, i.e. the height of the colloidal phase to the total height of the liquid, depends on the concentration of the filler. Thus, the higher the particles concentration, the higher the sedimentation ratio. The non-monotonic dependence of the relative efficiency of the suspensions on the viscosity dispersion medium for 8 wt% suspensions was revealed. It was shown that a combination of three parameters, namely the dispersion medium viscosity, the filler concentration and the electric field strength, makes it possible to obtain electrorheological fluids with specified, predictable properties.