Shear-induced particle rotation and its effect on electrorheological and dielectric properties in cellulose suspension.

Electrorheological (ER) and dielectric properties under high electric fields were measured simultaneously on hydroxypropylcellulose suspension. When measuring these properties as a function of frequency of the electric field, we found a positive peak in each spectrum of the ER effect and the first-order dielectric permittivity while a negative one in the spectrum of the third-order dielectric permittivity with these peak frequencies nearly equal to (shear rate)/4pi . Referring to the well-known results for the particle rotation in the sheared suspension, it is suggested that the observed peaks are due to shear-induced particle rotation and the rotation occurs even under high electric field. On the basis of these results, effects of the particle rotation on the ER and the dielectric properties are discussed.