Enhancement of the rheological properties of magnetorheological elastomer via polystyrene‐grafted carbonyl iron particles

Abstract

In this work, carbonyl iron particles (CIP) was grafted with polystyrene coating on its surface via polymerization method, and the coated-CIPs were then embedded into a silicone rubber with the ratio of 70:30 of CIP to silicone rubber in order to enhance the rheological properties of magnetorheological elastomer (MRE) in terms of lower initial storage modulus and higher MR effect. By using field emission scanning electron microscopy (FESEM) that is equipped with the energy dispersive X-ray spectroscopy for elemental analysis, it was observed that elements of C, N, O, Si, Fe, Br, Cu, and Sn were detected, confirming that the coating layer has been successfully developed on the CIP.Additionally, the investigation of the rheological characteristics was conducted at 25 C with three different sweep conditions using rheometer MCR 302.Firstly the strain amplitude was swept from 0.001% to 10% strain with 1 Hz frequency. Then, the frequency was varied from 1 Hz to 100 Hz under 0.01% strain at an applied current of 0-5 A. Lastly, the current was swept from 0 to 5 A under 0.01% strain amplitude and 1 Hz excitation frequency. It was discovered that the storage modulus of the polystyrene-coated CIP MRE is lower than that of uncoated-CIP MRE in all three sweep profiles. Advantageously, the magnetorheological (MR) effect of the coated-CIP MRE sample is higher than that of the uncoated-CIP MRE by 28.04%. Moreover, it was found that the coated-CIP MRE exhibited higher damping behavior with more than 0.14 loss factor than 0.12 loss factor of the uncoated sample. The dimensional stability of polystyrene coating on the CIP was an attributing factor to this enhanced damping behavior of the coated-CIP MRE. Thus, it became clear that the polystyrene-coated CIP embedment in MRE is more desirable than that of MRE with uncoated CIP.

Magnetorheological Elastomer Films with Controlled Anisotropic Alignment of Polystyrene-Modified Fe3O4 Nanoplates

“…Among the various magnetic particles, magnetite (Fe 3 O 4 ) nanoparticles are considered favorable magnetic fillers for rubbers owing to their high initial permeability, high saturation magnetization, and low coercivity. − However, unmodified Fe 3 O 4 nanoparticles always show poor dispersion stability in rubbers, resulting in deterioration of the chemical properties and mechanical properties. , To improve the agglomeration and dispersion stability of Fe 3 O 4 nanoparticles, one of the most effective ways is to utilize polymers to modify the surface of Fe 3 O 4 nanoparticles via surface-initiated atom transfer radical polymerization (SI-ATRP). − One available polymer is polystyrene (PS), which can improve the dispersion stability and functionality of Fe 3 O 4 nanoparticles . In addition, PS chains also have good compatibility with rubber matrices, such as styrene–butadiene rubber and nitrile-butadiene rubber, leading to a remarkable improvement in the mechanical properties of MRE composites. , Surface modification of Fe 3 O 4 nanoparticles with PS chains also helps avoid the introduction of compatibilizers such as zinc dimethacrylate (ZDMA), which reduces the chemical stability to acids and bases . Hence, incorporating PS-modified Fe 3 O 4 nanoparticles into rubbers such as polybutadiene to obtain stimuli-responsive functional rubbers with toughness is of interest.…”