Time–temperature superposition of silicone rubber embedded with irregular-shaped magnetic particles under different magnetic fields

The present work reports an investigation of the thermomechanical dynamic viscoelastic properties of a magnetorheological (MR) elastomer embedded with electrolytic iron particles (EIP, 40% wt, irregular shapes) in a silicone matrix. Unlike conventional MREs produced from spherical carbonyl iron particles, irregular flake-shaped EIPs offer greater particle-particle interactions and enhanced field sensitivity. The temperature rise from 30 to 70 °C significantly influences the matrix properties, altering the magnetic field-induced changes in the modulus as particle orientation with the field improves and friction between the particles and the matrix decreases. The thermomechanical dynamic viscoelastic properties of the present MRE confirm these interactions, along with the effects of strain amplitude (0.01 to 10%), frequency rate (0.1-40 Hz), and applied magnetic field strength (0.016 to 640 mT). The increase in temperature from 30 to 70 °C shows an overall 12.5% decrease in G' while there is a 67% increase in G" for silicone rubber. In MRE40, there is an 18.9% reduction in the storage modulus and a 4% increase in the loss modulus. This variation indicates that the high aspect ratio of the iron particles initially provides higher stiffness, but above a certain temperature, thermal energy overcomes it, leading to a higher rate of decrease of G' with temperature. Additionally, the time-temperature superposition (TTS) master curve is established for the present MRE. The damping behavior also varies with both temperature and field intensity, demonstrating the material's dual sensitivity. This work introduces a novel method for creating thermally adjustable MREs using flake-shaped magnetic fillers, which could enhance vibration control isolation pads used to minimize thrust force, operating under varying temperature conditions.