Influence of clay-based additive on sedimentation stability of magnetorheological fluid

Abstract Sedimentation stability is one of the most important features of magnetorheological (MR) fluids. Clay-based additives are known for improving the stability of the MR fluids. This article describes the dependency of the clay-based additive concentration on the sedimentation stability and the rheological properties of MR fluids in non activated state (without magnetic field). The sedimentation was measured for two different base oil viscosities, two different carbonyl iron particle sizes, and additive concentration between 2 and 6 wt%. The measurements showed that the sedimentation rate exponentially decreases with the additive concentration, while the yield stress is rising. The measurements of rheological properties also showed the dependency of rheological properties of MR fluid with a clay-based additive on loading history. The influence of carrier fluid viscosity or particle size has a minor effect on the sedimentation in comparison with the clay-based additive. The addition of 6 wt% slows down the sedimentation by more than 3000 times compared to MR fluid without additives. The MR fluid with 4.85% of clay-based additive achieves slightly better sedimentation stability than commercial MR fluid LORD MRF122.