Electrorheological characterization of polyaniline dispersions

Suspensions of polyaniline in silicone oil have been investigated as potential candidates for dry-base electrorheological (ER) fluid systems. Polyaniline was synthesized by a chemical oxidation of aniline in an acidic media. Its optimum conductivity (in the semiconductive range) for ER purposes was achieved by adjusting the pH of an aqueous solution containing polyaniline particles. ER experiments were conducted with a Haake rheometer for steady shear experiments to investigate the effects of imposed electric fields, the polymerization temperature (molecular weight), and the dispersing oil on ER performance. ER properties of polyaniline suspensions were found to be improved by increasing both the imposed electric field and the polymerization temperature of the used polymer. Suspensions using kerosene also show greater ER effect than that using silicone oil because of the smaller dielectric constant of kerosene than that of silicone oil. A scaling law is introduced to analyse the ER data. (C) 1997 Elsevier Science Ltd. All rights reserved.