Abstract
Isotropic polydimethylsiloxane (PDMS)-based magnetorheological elastomers (MREs) filled with various contents of graphene oxide (GO) additive were fabricated by the solution blending-casting method in this work. The morphologies of the produced MREs were characterized, and the results indicate that the uniform distribution of GO sheets and carbonyl iron particles (CIPs) becomes difficult with the increase of GO content. The steady-state and dynamic shear properties of the MREs under different magnetic field strengths were evaluated using parallel plate rheometer. It was found that the physical stiffness effect of GO sheets leads to the increase of the zero-field shear modulus with increasing GO content under both the steady-state and dynamic shear loads. The chemical crosslinking density of PDMS matrix decreases with the GO content due to the strong physical crosslinking between GO and the PDMS matrix. Thus, the MREs filled with higher GO content exhibit more fluid-like behavior. Under the dynamic shear load, the absolute MR effect increases with the GO content due to the increased flexibility of the PDMS matrix and the dynamic self-stiffening effect occurring in the physical crosslinking interfaces around GO sheets. The highest relative MR effect was achieved by the MREs filled with 0.1 wt.% GO sheets. Then, the relative MR effect decreases with the further increase of GO content due to the improved zero-field modulus and the increased agglomerations of GO and CIPs. This study shows that the addition of GO sheets is a possible way to prepare new MREs with high MR effect, while simultaneously possessing high zero-field stiffness and load bearing capability.
Highlights
Since the magnetic particles are locked in the polymeric matrix, the sedimentation and leakage problems associated with their liquid-state analog, i.e., magnetorheological fluid (MRF), are overcome
The results reveal that the addition of COOH-MWCNT helps to improve the initial modulus, magneto-induced modulus and damping of magnetorheological elastomers (MREs), and these viscoelastic properties begin to decrease at a COOH-MWCNT content higher than 1.0 wt.%
In the fracture surface of MRE-5, the graphene oxide (GO) aggregations and micro-fissures caused by pulling out of GO sheets become more serious. These results indicate that the restack of the exfoliated GO sheets happens in the GO/PDMS pre-polymer solution during the stirring and THF evaporation processes, and it increases with the increase of GO content due to the high hydrophilicity of GO [42,43,44]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Found that the addition of graphite particles in PDMS-based MREs results in an increment of the absolute MR effect but a decrement of the relative MR effect due to the increased zero-field mechanical properties. As one of the most important derivatives of graphene, GO has abundant functional groups, such as hydroxyl, carboxyl and epoxy, which make GO uniquely amphiphilic and result in the uniform distribution of GO sheets in different polymeric matrices These functional groups facilitate the good interaction between the polymer matrix and GO sheets, leading to the physical reinforcement and the improvement of the mechanical, thermal and electromagnetic properties of polymer matrix nanocomposites [35,36,37,38,39,40,41]. The steady-state shear stress–strain curves and the dynamic rheological behavior of the GO-filled MREs under different magnetic field strengths were tested by using a parallel plate rheometer, and the influence of GO content and the plausible mechanisms were considered
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