Magnetorheological polymer gels

Details Magnetorheological polymer gels Magnetorheological polymer gels

2001-02-20

2003-03-04

Koslow, C. Melissa (Department: 1755)

Compositions

Magnetic

With wax, bitumen, resin, or gum

C252S062530, C252S062520

Reexamination Certificate

active

06527972

ABSTRACT:

BACKGROUND OF THE INVENTION
Magnetorheological fluids (MRFs) are commercially available magnetic fluids which are currently used for a variety of applications. These include use in automotive parts: engine mounts, shock absorbers, and seat dampers [Phule, Pradeep P., and John M. Ginder, eds., “The Materials Science of Field-Responsive Fluids”
MRS Bulletin,
19-21, August 1998; Ginder, John M., “Behavior of Magnetorheological Fluids”
MRS Bulletin,
26-29, August 1998; Ginder, E. M. and Davis, C. S., “Shear Stresses in Magnetorheological Fluids: Role of Magnetic Saturation,”
Appl. Phys. Lett.
65 3410-3412, Dec. 26, 1994; Ashour, Osama, and Craig A. Rogers, “Magnetorheological Fluids: Materials Characterization and Devices.”
J Int. Mat. Sys. Struct.
7: 123-130, March 1996]. Other applications cover a range from exercise equipment to aspherical optical lens polishing. In the area of vibration control and damping, earthquake resistant structures are built that utilize these fluids using semi-active control [Phule, Pradeep P., and Ginder, John M., eds., “The Materials Science of Field-Responsive Fluids”
MRS Bulletin,
19-21, August 1998; Ginder, John M. “Behavior of Magnetorheological Fluids”
MRS Bulletin,
26-29, August 1998; Ashour, Osama, and Craig A. Rogers. “Magnetorheological Fluids: Materials Characterization and Devices.”
J. Int. Mat. Sys. Struct.
7 123-130, March 1996; Tang, X., X. J. Wang, W. H. Li, and P. Q. Zhang. “Testing and Modeling of an MR Damper in the Squeeze Flow Mode”].
MRFs excel in these applications because their rheological properties are controlled over several orders of magnitude. Without an applied magnetic field, the typical MRF acts like a Newtonian fluid [Ginder, John M., “Behavior of Magnetorheological Fluids”
MRS Bulletin,
26-29, August 1998; Dang, Anh, Liling Ooi, Janine Fales, and Pieter Stroeve, “Stress Measurements of Magnetorheological Fluids in Tubes.”
Ind. Eng. Chem. Res.
39:2269-2274, 2000]. When a field is applied, a dipole moment is induced in the particles in the MRF. This causes the particles to align “head-to-tail” and form chains of particles. Thus, these particles form structures parallel to the magnetic field [Ginder, John M., “Behavior of Magnetorheological Fluids”
MRS Bulletin,
26-29, August 1998]. The MRF becomes a weak viscoelastic solid when the chain or column structures form. As a result, the rheological properties of the materials change. As the magnetic field increases, the material exhibits a rapid and nearly reversible increase in yield stress. Because of the change in material properties under the influence of a magnetic field, the MRF properties are controlled and therefore provide a new means of controlling electromechanical devices. [Phule, Pradeep P., and John M. Ginder, eds. “The Materials Science of Field-Responsive Fluids”
MRS Bulletin,
19-21, August 1998; Jolly, Mark R., Jonathan W. Bender, and J. David Carlson “Properties and Applications of Commercial Magnetorheological Fluids”
SPIE
5
th
Int. Symposium on Smart Structures and Materials
San Diego, Calif., Mar. 15, 1998.]
While MRFs may be similar to ferrofluids, they also have important differences. They are composed of three components like ferrofluids; thus, they have a carrier fluid, magnetic particles, and additives [Raj, K. B. Moskowitz, and R. Casciari “Advances in Ferrofluid Technology” J. Magn. Magn. Mat. 149 174-180, 1995]. However, the particles used in ferrofluids are superparamagnetic iron oxide nanoparticles (~5-10 nm). [Phule, Pradeep P., and John M. Ginder, eds., “The Materials Science of Field-Responsive Fluids”
MRS Bulletin,
19-21, August 1998; Raj, K. B. Moskowitz, and R. Casciari “Advances in Ferrofluid Technology”
J. Magn. Magn. Mat.
149 174-180, 1995]. As a result, they do not exhibit a shear yield stress like MRFs while under an applied magnetic field. [Phule, Pradeep P., and John M. Ginder, eds. “The Materials Science of Field-Responsive Fluids”
MRS Bulletin,
19-21, August 1998; Ashour, Osama, and Craig A. Rogers, “Magnetorheological Fluids: Materials Characterization and Devices.”
J. Int. Mat. Sys. Struct.
7 123-130, March 1996.] This is due to a reduced tendency to form chains under a magnetic field. Thus, while viscosity changes can be observed, they are small. [Ashour, Osama, and Craig A. Rogers, “Magnetorheological Fluids: Materials Characterization and Devices.”
J. Int. Mat. Sys. Struct.
7 123-130, March 1996; Odenbach, Stefan, Thomas Rylewicz, and Michael Heyen. “A Rheometer Dedicated for the Investigation of Viscoelastic Effects in Commercial Magnetic Fields.”
J. Magn. Magn. Mat.
201 155-158 1999.] The applications, as a result, are much different. In addition to being used in seals, the ferrofluids have applications in stepper motors and sensors. [Raj, K. B. Moskowitz, and R. Casciari “Advances in Ferrofluid Technology”
J. Magn. Magn. Mat.
149 174-180, 1995.]
For an MRF, magnetic particles, such as iron, can be suspended in a fluid. Under a magnetic field, these particles form chains [Phule, Pradeep P., and John M. Ginder, eds., “The Materials Science of Field-Responsive Fluids”
MRS Bulletin,
19-21, August 1998; Phule, Pradeep P., “Synthesis of Novel Magnetorheological Fluids”
MRS Bulletin,
23-25, August 1998; Huang, Jiun-Yan and Pik-Yin Lai, “Formation and Polarization of Dipolar Chains”
Physica A
281 105-111, 2000] that significantly increase the yield stress of the material. The carrier fluid acts as the medium for other components. Suspended in the medium are the magnetic particles that form chains when a magnetic field is applied. Finally, additives are used to provide stability to the mixture, corrosion control, lubrication, anti-oxidants, pH shifters, dyes and pigments, salts, and deacidifiers. [Phule, Pradeep P. and John M. Ginder, eds. “The Materials Science of Field-Responsive Fluids”
MRS Bulletin,
19-21, August 1998; Dang, Anh, Liling Ooi, Janine Fales, and Pieter Stroeve. “Stress Measurements of Magnetorheological Fluids in Tubes.”
Ind. Eng. Chem. Res.
39 2269-2274, 2000; Phule, Pradeep P. “Synthesis of Novel Magnetorheological Fluids”
MRS Bulletin,
23-25, August 1998; A. Fuchs, F. Gordaninejad, C D. Blattman, and G. Hamann. “Magneto-rheological Polymeric Gel Materials.” Provisional U.S. Patent, February 2000.]
Typically, the carrier medium is a silicone oil or hydrocarbon fluid. [Phule, Pradeep P., and John M. Ginder, eds. “The Materials Science of Field-Responsive Fluids”
MRS Bulletin,
19-21, August 1998; Dang, Anh, Liling Ooi, Janine Fales, and Pieter Stroeve. “Stress Measurements of Magnetorheological Fluids in Tubes.”
Ind. Eng. Chem. Res.
39 2269-2274, 2000.] This is because it exhibits many of the properties that are desirable in MRF. Ideally, the fluid should be thermally stable, have a high boiling point, be nonreactive (especially with the dispersed material) and be nontoxic. Also, the fluid should contribute to the stability of the mixture, but at the same time enable the redispersibility of the magnetic particles. The temperature dependence of the medium's viscosity is also very important, and is in fact the dominating factor in the operating range of the MRF. For the stability of the MRF, the carrier fluid should be noncorrosive and nonreactive with the magnetic particles and other ingredients. Finally, the fluid should not cause sealing problems in the device in which it will be used. [Ginder, John M., “Behavior of Magnetorheological Fluids”
MRS Bulletin,
26-29, August 1998; Phule, Pradeep P. “Synthesis of Novel Magnetorheological Fluids”
MRS Bulletin,
23-25, August 1998.]
The dispersed phase of an MRF usually is a soft magnetic material like iron particles of 1-10 um size [Phule, Pradeep P. and John M. Ginder, eds., “The Materials Science of Field-Responsive Fluids”
MRS Bulletin,
19-21; August 1998.] Several important factors must be considered in the choice of the dispersed phase. First, the volu

Affiliated with

Also associated with

Rating

Magnetorheological polymer gels does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Magnetorheological polymer gels, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetorheological polymer gels will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3010382