Effects of corrosion rate of the magnetic particles on the field-dependent material characteristics of silicone based magnetorheological elastomers

Carbonyl iron particles (CIPs) embedded in magnetorheological elastomers (MREs) as magnetic filler play a dominant candidate that can affect resultant properties of MREs including the field-dependent viscoelasticity. In this work, the effects of corrosion rate on the rheological properties of MREs are experimentally investigated. The CIPs undergo an accelerated corrosion test in diluted hydrochloric (HCl) acid at various concentrations, particularly at 0.5, 1.0 and 1.5 vol.% for 30 min immersion time, individually. Four samples of CIPs, including the non-corroded one are prepared, and their morphological characterization are observed via field emission scanning electron microscope (FESEM), that equipped with energy dispersive x-ray spectroscopy (EDS) for elemental compositions. In addition, x-ray diffraction (XRD) is used to identify the crystalline phase structure of the samples. In order to examine the corrosion rate of each sample, weight-loss method is used by pressing the CIPs into pellet shape and being immersed in the respective concentrations of HCl. It is shown that the corrosion rate of CIPs is increased with the increasing of HCl concentration in which higher weight loss of the measured pallet CIPs is observed. Meanwhile, the field-dependent rheological properties of MREs are investigated via rheometer to analyze the change in dynamic modulus of MREs such as storage modulus, loss factor and absolute MR effect. These experimental results indicate that MRE samples with higher corrosion rate of CIP exhibit lower storage modulus, loss factor and MR effect, as this subsequently would deteriorate the performance of MRE. Therefore, it is identified that the purity of CIP plays the most important contribution towards the field-dependent viscoelastic properties of MRE for a long period use of the material.