The place of dielectric spectroscopy in probing electrorheology

The measurement of the dielectric spectra of PAnQR based ER fluids under sh ear and electric fields is discussed and results presented. Data in which e ither but not both shear or electric fields are present are submitted to an alysis in terms of known theories. For flow alone, that analysis provides i nformation on the attenuation of polarization by the uniform shear fields w hilst the polarization of quiescent fluids by electric fields may lead to e stimates of particles packing within the columns. Permittivity data when bo th fields are acting is presented, but in the absence of suitable theory, n ot modelled quantitatively. Empirical correlations are discussed and the co nclusion drawn that fibrillation is readily suppressed by even moderate she ar rates, although long range dipolar forces still persist to high shear ra tes. The de conductance of these fluids have also been measured. This together w ith permittivity data under ER fluid working conditions has importance in e stablishing the electrical parameters for any ER fluid.