SOME FACTORS AFFECTING ELECTRORHEOLOGICAL PROPERTIES OF ANHYDROUS SUSPENSIONS CONTAINING POLYANILINE PARTICLES

Abstract

Some factors, such as the final pH value of the ammonia solution used to dedope the polyaniline (PAn) particles, water adsorbed by the PAn particles, coupling agent used to couple the surface of the particles with the insulating medium and different types of electric fields, affecting the electrorheological (ER) properties of the ER fluid containing PAn particles and the dependence of leak current density on temperature and on electric field voltage were studied. The results showed that the PAn particles dedoped with dilute ammonia water at a final pH value of 8–9 showed the maximum value of static yield stress of about 9 kPa with volume fraction of the particles at 0.25 in chlorinated paraffin oil under a DC electric field of 2.8 kV/mm. Addition of a small amount of silane coupling agent is beneficial to the ER properties. The ER fluid containing PAn particles exhibits ER properties in the absence of water, though a small amount of water enhances both yield stress and leak current density, yet the efficiency is lowered. The ER fluid showed lower yield stress and higher leak current density under AC electric field than under DC electric field. The dependence of leak current density on temperature and on electric field voltage obeys the Arrhenius equation and exponential equation, respectively. With increasing final pH value of the dilute ammonia water used to dedope the PAn particles, the activation energy increases, whereas the exponent in the exponential equation decreases.