Influence of Distribution Anisotropy and Particle Shape on Magnetorheological Properties of Magnetoactive Elastomers

Viscoelastic properties of magnetoactive elastomers with spherical and plate-shaped filler have been studied. Four series of samples based on silicone elastomer and carbonyl iron microparticles have been prepared. A series of samples with a concentration of magnetic filler from 30 to 60 wt % which differed in the shape of filler particles (spherical and platelike) and in their distribution in the polymer matrix (isotropic and anisotropic). The magnetorheological properties of the obtained magnetoactive elastomers have been examined by dynamic mechanical analysis. Storage modulus values for samples of different compositions are in the range of 10–100 kPa. It has been shown that anisotropic materials are stiffer than the isotropic counterparts and demonstrate a higher magnetorheological effect: the increase in the elastic modulus of an anisotropic sample with the maximum filler content exceeds an order of magnitude in a magnetic field of 1 T. At the same filler concentrations, materials based on platelike iron are stiffer than those based on spherical iron. At low magnetic filler concentrations, the use of platelike iron makes it possible to achieve a higher magnetic response of the material; at high filler concentrations, the increase in the elastic modulus is greater for samples based on spherical particles. The anisotropic materials exhibit a more pronounced Payne effect.