Coating of polyaniline with an insulating polymer to improve the power efficiency of electrorheological fluids

Currents drawn under high fields often present practical limitations to ele ctrorheological (ER) fluids usefulness. For heavy-duty applications where l arge torques have to be transmitted, the power consumption of a ER fluid ca n be considerable, and for such uses a current density of similar to 100 mu A cm(-2) is often taken as a practical upper limit. This investigation was conducted into designing a fluid which has little extraneous conductance a nd therefore would demand less current. Selected semi-conducting polymers provide effective substrates for ER fluid s. Such. polymers are soft insoluble powdery materials with densities simil ar to dispersing agents used in ER formulations. Polyaniline is a semi-cond ucting polymer and can be used as an effective ER substrate in its emeraldi ne base form. In order to provide an effective ER fluid which requires less current polyaniline was coated with an insulating polymer. The conditions for coating was established for lauryl and methyl methacrylate. Results fro m static yield measurements indicate that ER fluids containing coated polya niline required less current than uncoated polyaniline ie 0.5 mu A cm(-2). The generic type of coating was also found to be important.