Uniform Dispersion of Carbonyl Iron Particles in Bulk Magnetorheological Flexible Foam

Abstract

Magnetorheological (MR) foams are smart materials which their rheological properties can be manipulated by stimulation of the external magnetic field. However, these materials suffer from low homogeneity of magnetic particles in MR foams. This paper seeks to remedy this issue by using flexible polyurethane foam. Two types of foams were fabricated, one without magnetic particles which refer as polyurethane (PU) foam and the other with 55 wt% magnetic particles of carbonyl iron (CIPs), known as MR foam. Magnetic properties of both foams were characterised using vibrating sample magnetometer (VSM). Concurrently, the MR foam was characterised at three different positions; top, middle and bottom in order to validate the distribution of CIPs. VSM analysis shows that the PU foam exhibited diamagnetic material while MR foam exhibit superparamagnetic material. The most important relevant finding is that the magnetic saturation of MR foam are 68.512, 70.367 and 68.879 Am²/kg at top, middle and bottom position respectively. Moreover, the standard deviation for all positions was only 1.990 Am²/kg indicating that the distributions of CIPs in the MR foam are uniform. Similar findings are also observed for the coercivity, remanence and permeability of MR foam with standard deviation of 0.029 × 10⁻³ kA/m, 0.009 and 0.041 × 10⁻² Am²/kg, respectively for all positions. The result is believed to be significant in contributing high performance of MR foam with uniform magnetic properties for various products and applications.