Behavior of ER Fluids based on Three Variants of a Liquid Crystalline Polysiloxane

Abstract

ER fluids of three types, composed of liquid crystalline polymethylsiloxanes (LCSs) differing in the range of polysiloxane chain length and mesogenic group content diluted by polydimethylsiloxanes (DMSs) with or without phenyl groups, were prepared and the ER effect of each was investigated in terms of its temperature dependence and rise time. Type A fluid exhibited an ER effect with a short rise time but a strong temperature dependence. The ER effect of the Type B fluid showed little temperature dependence but a comparatively long rise time. The Type C fluid exhibited a short rise time, comparable to that of Type A, and a temperature independence similar to that of Type B. For all three types, the decay time of the ER effect was long. Investigation of the decay time for the Type A fluid showed that it was affected particularly by shear rate and DMS dilution ratio and also by temperature and DMS viscosity, and indicated that deformation by shear stress was necessary for a return of the fluid to its original non viscous structure.