The phase behavior of polymer solutions and composites is a complex issue and is of both technological and fundamental interest. For a better understanding of the microstructure formation in magnetorheological (MR) elastomers, x-ray micro-computed tomography (XμCT) investigations were carried out. Magnetorheological elastomers with 5% mass content of iron powder were prepared under different magnetic field strengths between 1 and 220 kA m−1. Through quantitative analysis, valuable information was obtained regarding the number, size and frequency distribution of column structures in MR elastomers, as well as the magnetic field required to force structure formation.

The behavior of magnetic particles inside elastomeric matrices is a complex issue and can be influenced in many ways, e.g. by applying a magnetic field or external mechanical stimuli. It is of fundamental interest for theoretical descriptions and technological applications to study processes like structure formation of these particles in a magnetic field. For a better understanding of the microstructure and the motion of particles in magnetorheological elastomers (MRE), x-ray micro-computed tomography (Xμ-CT) investigations were carried out. A MRE with a quantity of 2 wt.% of iron powder and an isotropic allocation of the particles inside the matrix was prepared. By means of quantitative analysis with image processing software, information regarding the geometrical properties of the particles and their individual motion under the influence of a magnetic field was obtained. Therefore a set of three tomograms -a reference taken without magnetic field, a second tomogram in presence of an applied field and third one again taken at B = 0 mT-has been taken and compared. It is shown that the combination of Xμ-CT and digital image processing provides a tool for a quantitative analysis of single particle motion in a MRE forced by external stimuli.

The physical properties of magnetorheological elastomers (MRE) are a complex issue and can be influenced and controlled in many ways, e.g. by applying a magnetic field, by external mechanical stimuli, or by an electric potential. In general, the response of MRE materials to these stimuli is crucially dependent on the distribution of the magnetic particles inside the elastomer. Specific knowledge of the interactions between particles or particle clusters is of high relevance for understanding the macroscopic rheological properties and provides an important input for theoretical calculations. In order to gain a better insight into the correlation between the macroscopic effects and microstructure and to generate a database for theoretical analysis, x-ray micro-computed tomography (X-μCT) investigations as a base for a statistical analysis of the particle configurations were carried out. Different MREs with quantities of 2–15 wt% (0.27–2.3 vol%) of iron powder and different allocations of the particles inside the matrix were prepared. The X-μCT results were edited by an image processing software regarding the geometrical properties of the particles with and without the influence of an external magnetic field. Pair correlation functions for the positions of the particles inside the elastomer were calculated to statistically characterize the distributions of the particles in the samples.

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The initial magnetic response of magnetic elastomers can be explained by irreversible polymer matrix deformations under first external field application.