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.