Viscoelastic properties of electro-rheological fluids containing ion-conductive polyurethane particles under electric field

A non-hydrous electro-rheological fluid (ERF) containing polyurethane (PU) particles with electrolytes and automotive dampers utilizing it have been developed. In this study, we investigated the influence of electrolytes and particle properties on ER effect (yield stress) leading to improving the ER effect of non-hydrous ERFs. As a result, yield stress was increased by the inclusion of electrolytes to PU particles and decreased by increasing the glass transition point (Tg) of PU. The inclusion of electrolyte in particles doubled the yield stress of ERF at 5 kV mm⁻¹. The change in Tg of PU particles from −26.3 °C to −15.3 °C resulted in a decrease in yield stress by 0.7 times at 5 kV mm⁻¹. According to a theoretical model for calculating the ER effect and experimental data, the ionic conductivity associated with the electrolyte addition and the Tg change contributed to the dielectric constant of the PU particles, which affected the ER effect. This result provides important knowledge for deriving material compositions that can further improve the ER effect.