# US 7,608,197 B2 · Magnetorheological elastomers and use thereof

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- Number: US 7,608,197 B2
- Document ID: US7608197B2
- Status: Granted
- Kind: B2
- Application number: 11/574,397
- Filed: 2005-08-25
- Published: 2008-12-25
- Granted: 2009-10-27
- Earliest claimed: 2004-08-27
- Assignees: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
- Inventors: Holger Böse; Rene Röder
- Web page: https://patentgrep.com/patent/US7608197B2

## CPC

- H01F 1/447: {characterised by magnetoviscosity, e.g. magnetorheological, magnetothixotropic, magnetodilatant liquids (electrorheological fluids C10M171/001)}
- F16F 1/361: {comprising magneto-rheological elastomers [MR], (magneto-rheological fluid dampers F16F9/535)}
- H01F 1/375: Flexible bodies
- H01F 1/28: dispersed or suspended in a bonding agent
- Y10T 428/2982: Particulate matter [e.g., sphere, flake, etc.]
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- F16F: SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The present invention relates to magnetorheological elastomers comprising at least one non-magnetizable elastomeric carrier medium and magnetizable particles contained therein and also to the use thereof. In the case of MREs of this type, the mechanical properties, such as the rigidity modulus, can be changed reversibly by an applied magnetic field.

## Claims

### Claim 1

A magnetorheological elastomer comprising at least one non-magnetisable elastomeric carrier medium and magnetisable particles contained therein, wherein the at least one elastomeric carrier medium is an elastomer selected from silicone and polyurethane which has a rigidity modulus<250 kPa measured at 10 Hz and a deformation of 1%.

### Claim 2 (depends on 1)

A magnetorheological material according to claim 1, wherein the magnetisable particles are soft magnetic materials.

### Claim 3 (depends on 2)

A magnetorheological elastomer according to claim 2, wherein the magnetisable particles are soft magnetic metallic materials.

### Claim 4 (depends on 2)

A magnetorheological elastomer according to claim 2, wherein the magnetisable particles are soft magnetic oxide ceramic materials.

### Claim 5 (depends on 1)

A magnetorheological elastomer according to claim 1, wherein the magnetisable particles are mixed ferrites.

### Claim 6 (depends on 1)

A magnetorheological elastomer according to claim 1, wherein the magnetisable particles are selected from iron carbide, iron nitride, alloys of vanadium, tungsten, copper and manganese and mixtures thereof.

### Claim 7 (depends on 1)

A magnetorheological elastomer according to claim 1, wherein the average particle size of the magnetisable particles is between 5 nm and 10 mm.

### Claim 8 (depends on 1)

A magnetorheological elastomer according to claim 1, wherein the magnetisable particles have a bimodal size distribution.

### Claim 9 (depends on 1)

A magnetorheological elastomer according to claim 1, wherein the magnetisable particles have an anisotropic distribution in the elastomer matrix.

### Claim 10 (depends on 1)

A magnetorheological elastomer according to claim 1, wherein the magnetisable particles have an isotropic distribution in the elastomer matrix.

### Claim 11 (depends on 1)

A magnetorheological elastomer according to claim 1, further containing additives selected from dispersion agents, antioxidants, defoamers, softeners friction-reducing agents, and a combination thereof.

### Claim 12 (depends on 1)

A magnetorheological material claim 1, wherein
the magnetisable particles are present in an amount between 5 and 70% by volume;
the elastomeric carrier medium is present in an amount between 20 and 95% by volume;
the additives are present in an amount up to 20% by mass (relative to the magnetisable solid materials).

### Claim 13 (depends on 1)

A magnetorheological material according to claim 1, wherein:
the magnetisable particles are present in an amount between 10 and 60% by volume;
the elastomeric carrier medium is present in an amount between 30 and 90% by volume; and
the additives are present in an amount between 0.01 and 15 (relative to the magnetisable solid materials).

### Claim 14 (depends on 3)

A magnetorheological material according to claim 3, wherein the soft magnetic metallic materials are selected from iron, cobalt, nickel, alloys thereof, magnetic steel, iron-silicon, and a mixture thereof.

### Claim 15 (depends on 4)

A magnetorheological material according to claim 4, wherein the soft magnetic oxide-ceramic material is selected from garnets, perovskites and cubic ferrites of the general formula
MO.Fe2O3
with one or more metals from the group M=Mn, Fe, Co, Ni, Cu, Zn, Ti, Cd or magnesium and mixtures thereof.

### Claim 16 (depends on 5)

A magnetorheological material according to claim 5, wherein the mixed ferrite is selected from MnZn-, NiZn-, NiCo-, NiCuCo-, NiMg-, CuMg-ferrites and mixtures thereof.

### Claim 17 (depends on 7)

A magnetorheological material according to claim 7, wherein the average particle size of the magnetisable particles is between 10 nm and 1 mm.