Magneto-elastic coupling as a key to microstructural response of magnetic elastomers with flake-like particles

Using the combination of experiment and molecular dynamics simulations, we investigate structural transformations in magnetic elastomers with NdFeB flake-like particles, caused by applied moderate magnetic fields. We explain why and...

Magnetorheological Response for Magnetic Elastomers Containing Carbonyl Iron Particles Coated with Poly(methyl methacrylate)

The magnetorheological response for magnetic elastomers containing carbonyl iron (CI) particles with a diameter of 6.7 μm coated with poly(methyl methacrylate) (PMMA) was investigated to estimate the diameter of secondary particles from the amplitude of magnetorheological response. Fourier-transformed infrared spectroscopy revealed that the CI particles were coated with PMMA, and the thickness of the PMMA layer was determined to be 71 nm by density measurement. The change in the storage modulus for magnetic elastomers decreased by coating and it was scaled by the number density of CI particles as ΔG~N2.8. The diameter of secondary particle of CI particles coated with PMMA was calculated to be 8.4 μm. SEM images revealed that the CI particles coated with PMMA aggregated in the polyurethane matrix.

Hybrid magnetic elastomers prepared on the basis of a SIEL-grade resin and their magnetic and rheological properties

Hybrid magnetic elastomers (HMEs) belong to a novel type of magnetocontrollable elastic materials capable of demonstrating extensive variations of their parameters under the influence of magnetic fields. Like all cognate materials, HMEs are based on deformable polymer filled with a mixed or modified powder. The complex of properties possessed by the composite is a reflection of interactions occurring between the polymer matrix and the particles also participating in interactions among themselves. For example, introduction of magnetically hard components into the formula results in the origination of a number of significantly different behavioral features entirely unknown to magnetorheological composites of the classic type. Optical observation of samples based on magnetically hard filler gave the opportunity to establish that initial magnetization imparts magnetic moments to initially unmagnetized grains, as a result of which chain-like structures continue to be a feature of the material even after external field removal. In addition, applying a reverse field causes them to turn into the polymer as they rearrange into new ring-like structures. Exploration of the relationship between the rheological properties and magnetic field conducted on a rheometer using vibrational mechanical analysis showed an increase of the relative elastic modulus by more than two orders of magnitude or by 3.8 MPa, whereas the loss factor exhibited steady growth with the field up to a value of 0.7 being significantly higher than that demonstrated by elastomers with no magnetically hard particles. At the same time, measuring the electroconductivity of elastomers filled with a nickel-electroplated carbonyl iron powder made it possible to observe that such composites demonstrated an increase of variation of the resistivity of the composite influenced by magnetic field in comparison to elastomers containing untreated iron particles. The studies conducted indicate that this material exhibits both magnetorheological and magnetoresistive effect and does indeed have the potential for use in various types of devices.

Field-structured magnetic elastomers based on thermoplastic polyurethane for fused filament fabrication

The utilization of ‘smart’ materials with adaptable properties or characteristics are a widespread research issue, offering potential for tailored solutions, weight reduction or added value of products through integrated functionality. Therefore, field controlled hybrid materials such as magnetorheological (MR) elastomers or electrorheological (ER) fluids are particularly valuable and within the focus of science and research. At the same time, additive manufacturing has had a strong influence on production processes over the past decade. Today a 3D printer can be found across all disciplines in almost every company, research institution and even in many private households. The Fused Filament Fabrication (FFF) process is especially popular due to its low cost and simplicity. Within this work, a new approach for the generation of field-structured magnetic elastomers using the FFF process and a correspondingly developed prototype print head for implementation are presented and discussed. With its unique research landscape Dresden offers excellent conditions for the development of innovative processes and composite materials in the field of generative manufacture. In the ‘Dresden Concept’ network, experts from various disciplines collaborate and investigate the entire spectrum starting from biological materials, through lightweight fibre reinforced polymer composites, to high-temperature ceramics. This article is part of the theme issue ‘Patterns in soft and biological matters’.