The damping behavior of magnetorheological gel based on polyurethane matrix

As a kind of new MR material, Magnetorheological Gel (MRG) can be considered to be the intermediate system between the MR fluids (MRF) and MR elastomers (MRE). And damping performance plays a significant role in its application system (especially in the vibration and noise control). However, the damping mechanism and source of MRG have not been investigated comprehensively. In this study, several samples of MRGs with different iron particle contents (0, 20, 40, 60, and 80 wt%) were prepared. The nonmagnetic damping (without magnetic field) and magneto‐induced damping (with several constant magnetic fields) of MRG were systematically studied by using an advanced commercial rheometer under oscillatory shear modes. The influence of time history, strain amplitude and frequency in the zero‐field and several constant magnetic fields on the nonmagnetic damping and magneto‐induced damping of MRG was also systematically studied. The experimental results show that, just the opposite to MRE, the loss factor of MRG decrease with the increase of carbonyl iron powder particles (CIP) content. The reasons are known through theoretical analysis combined with microstructure observation that the polyurethane molecular chain will become shorter with the increase of CIP content is a very important factor, and the formation and thickening of the chain structure of CIP is the reason for the loss factor of MRG decline with the magnetic field. POLYM. COMPOS., 38:1248–1258, 2017. © 2015 Society of Plastics Engineers