Abstract: The static electrorheological properties of suspensions containing doped polyaniline(PAn) particles,pretreated with alkaline agent,in insulating oil No.2 under direct current high electric field were studied as functions of dielectric constants, conductivity(σ),volume fraction of the particles as well as applied electric field strength.The results showed that the PAn particles of the same a pretreated by ammonia water possessed higher dielectricconstants than those pretreated by aqueous NaOH, In the former case yield stress of the sus-pension increased nonlinearly with dipolar coefficient square when a of PAn was low enough,i.e.σ≤1.0×10^-7S/cm, while in the latter case a maximum yield stress occurred.As a re-sult anhydrous suspensions with high electrorheological activity can be obtained using PAnparticles pretreated with alkaline agent to a certain pH value.

Key words: electrorheological fluid, polyaniline, suspension, conductivity, dielectric constant