A study of the electrorheological effect of gamma-Fe2O3/polyacrylate composite particles

gamma-Fe2O3/polyacrylate composite particles were synthesized through inver sed emulsion polymerization. The particles were then dispersed in silicone oil forming the electrorheological fluid. The effects chemical constitution of the particles, including the content of gamma-Fe2O3, the crosslinking a gent N,N'-methylene-bis acrylamide (MBAM) and the comomoner maleic anhydrid e (MA) on the shear stress of the fluid were investigated under direct and alternating electrical fields respectively. The influence of the emulsifyin g agent concentration during the particle preparation on the electrorheolog ical (ER) effect of the fluid was studied. The results show that the ER eff ects are different under direct and alternating electrical fields. The ER e ffects of the gamma-Fe2O3/lithium polyacrylate particles at some gamma-Fe2O 3 contents are stronger than that of the lithium polyacrylate especially un der alternating fields. The contents of the crosslinking agent MBAM, the co monomer MA and the emulsifying agent cetyltrimethyl ammonium bromide influe nce the ER effects and the morphology of the composite particles. (C) 1999 John Wiley & Sons, Ltd.