Influence of the Electric Field on the Electrorheological Behaviour of Crystalline Cellulose Suspensions in Silicone Oils

This work deals with electrorheological (ER) behaviour of moist crystalline cellulose dispersed in silicone oils of different viscosities (0.1, 0.35 and 1.0 Pa.s) in DC and 50 Hz AC electric fields. The experiments were performed on a parallel-plate viscometer with various width of the gap. In the AC field the intensity of the ER effect was lower and the rheological behaviour of suspensions was in accordance with the Bingham law. In the DC field, on the other hand, the flow curves were rather complex. Higher viscosity of the continuous phase limited reorganization of the ER structure in the flow field; hence, the ER effect intensity was lower. The plot of relative viscosity, η/ηc, vs. the Mason number, Mn, provided a common line, which supports an idea of a pronounced influence of the ratio of viscous and polarization forces as the main factor controlling electrorheological properties of the system.