Hydrophobic metal particles for magnetorheological composition
OwnerVardarajan R. Iyengar, Robert Thomas Foisterinventors
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Abstract
Hydrophobic metal particles that are useful as the magnetizable particles in magnetorheological fluids and magnetorheological elastomers are provided. Hydrophilic metal particles, such as carbonyl iron particles, are made hydrophobic by reacting a surface hydroxyl on the solid metal particle with a reactive surfactant. Particles are coated with the reactive surfactant to cover at least about 90% of the surface of the particles and then washed with a low viscosity synthetic hydrocarbon to remove any excess surfactant. The particles are stabilized against oxidation and irreversible coagulation during further processing, and formulation and use in magnetorheological fluids and elastomers.
Claims15
A hydrophobic metal powder for use in magnetorheological fluids and magnetorheological elastomers comprising a plurality of solid metal particles selected from iron or iron alloys and a surfactant comprising at least one hydroxyl, carbonyl, or amine group and including at least one pendant hydrophobic alkyl group adsorbed to at least about 90% of the surface area of said metal particles.
A magnetorheological composition of a fluid or elastomer comprising,
- a. a hydrophobic carbonyl iron powder comprising a plurality of particles having an ethoxylated amine surfactant adsorbed to at least about 90% of the surface area of said particles,
- b. a polyalphaolefin carrier fluid, and
- c. a fumed silica thixotrope,
- wherein the amount of said non-adsorbed surfactant in the magnetorheological composition is less than about 2% by weight of said composition.
A process for producing hydrophobic metal particles for use in magnetorheological fluids and magnetorheological elastomers comprising, treating hydrophilic solid metal particles of iron or iron alloys having surface hydroxyl groups with a surfactant comprising at least one hydroxyl, carbonyl, or amine group and including at least one pendant hydrophobic alkyl group until said surfactant has been adsorbed onto at least about 90% of the surface area of said particles, and washing at least about 95% by weight of the unreacted surfactant from said particles using a low viscosity synthetic hydrocarbon.
Dependencies are inferred from the claim text.