Magnetic stimuli-response properties of polyurethane-based magnetorheological soluble gel

Abstract

Magnetorheological (MR) gels are one of the categories of magnetic smart materials, whose mechanical properties change significantly in the presence of a magnetic field. In the paper, considering the significant effect of PU matrix content on the rheological response of MR materials, PU-based MR soluble gel (MRSG) with the carbonyl iron powder (CIP) weight fraction of 40%, 60% and 80% were developed. The magnetic stimuli-response properties were systematically tested (both under rotational and oscillatory shear) and the impacts of the CIPs concentration and magnetic field were comprehensive analyzed. It was found that the prepared MRSG samples exhibit a soft magnetic characteristic; The huge differences in MR properties of MRSG samples (for example, the dynamic yield stress MRSR with 80 wt% of CIPs (MRSG-80) is above twice orders of magnitude larger than that of MRSG with 60 wt% of CIPs (MRSG-60) under applied current at 4A) shows a high dynamic yield stress (49.4694 kPa). Movements of CIPs in the presence of a magnetic flux density were analyzed, which is of great significance to interpret the rheological behavior of MR gel from microstructure and to further understand the rheological mechanism. The maximum magneto-induced storage modulus is 3179.83 kPa obtained by MRSG-80 under applied current at 4A; the relative MR effect of MRSG-60 reaches as high as 11917% with suitable initial storage modulus of 17.41. This kind of MRSG shows a much higher MR performance than the previously reported MR elastomer (MRE). In addition, linear viscoelastic (LVE) range increased gradually with the increase of applied current and mass content of CIPs.