Relationship between the response of microscopic and magnetic properties with highly uniform dispersion of carbonyl iron particles in magnetorheological polyurethane foam

Magnetorheological (MR) foam, which is comprised of magnetic particles inside the matrix phase, is capable of changing its physical and rheological properties corresponding to the applied magnetic field. However, the performance of this material seems unsatisfactory due to the nonuniform distribution of magnetic particles throughout the composite area resulting in uneven magnetic properties. Since uniform magnetic properties are significant regarding MR foam, in situ fabrication using a polyvinyl chloride mould can be used to achieve the targetted improvement. MR foam was prepared with various amounts of carbonyl iron particles (CIPs), 0, 35, 45 and 55 wt%, and investigated at three different positions (top, middle and bottom parts) with a vibration sample magnetometer. The results showed that the hysteresis loop at all CIP concentrations of 35, 45 and 55 wt% exhibited superparamagnetic properties with magnetic saturation. The M _s of the top, middle and bottom positions were almost the same with a small standard deviation below 2 Am² kg^–1. Moreover, it is observed that the effect of porosity results in the enhancement of the magnetic saturation and remanence values. These results reveal the promising uniform magnetic properties of MR foam, which can benefit the industry by helping produce a consistent MR foam. (paper)