Dielectric Properties of Electrorheological Fluids Containing Zeolite Particles

(Received 13 June 1994, revised 29 November 1994, accepted 22 February 1995)

Abstract
Relationships between electrorheological (ER) effects and dielectric properties of suspensions are investigated from measurements of ER and dielectric properties of suspensions containing particles of type A zeolite such as 3A, 4A and 5A. In each suspension containing zeolite 3A or 4A particles, the ER effect is recognized, i.e., an increase in the apparent viscosity is observed when an electric field is applied, and the dielectric property is characterized by a dielectric dispersion in audio frequency region. On the other hand, the suspension containing zeolite 5A particles does not show a distinct ER effect and has a low dielectric constant without dielectric dispersion above 1 Hz. These results indicate that relaxation time of the induced polarization is associated with the ER effect; for the appearance of the ER effect the relaxation time should be shorter than a characteristic time. It is suggested that the characteristic time is associated with an angular velocity of rotating particles under a steady shear flow and also that the relaxation time of the polarization is mainly determined by the electric conductivity of the particle.