ELECTRORHEOLOGICAL PROPERTIES OF SEMICONDUCTING POLYMER-BASED SUSPENSIONS

A new type of semiconducting polymer (oxidized polyacrylonitrile)- based electrorheological (ER) suspension is described which shows reasonable ER effects, especially at high temperatures. Rheological properties, such as yield stress, transient stresses, flow curve, dynamic modulus as functions of electric field, particle concentration, water content and temperature, are measured with a modified Rheometrics mechanical spectrometer. The characteristic ER responses in various deformation histories are found to be described approximately by a rate insensitive stress, which can be yield stress, steady shear stress, the recovery stress after cessation of flow, or the product of dynamic modulus and strain amplitude. This stress is dominated only by the electrically induced interparticle forces. These results can be well explained using a spanned strands model.