Magnetic dispersions of ferrite particles with high magnetic energy product in flexible highly saturated nitrile rubber and methods of producing the same

摘要

A flexible magnetic blend composition is pro­vided which is comprised of high energy ferrite magnetic particles in a flexible high temperature resistant and oil resistant polymer binder. The binder system is preferably a highly saturated nitrile rubber (HSN) or a polymer alloy of the same in which a HSN is the major polymer containing alloying polymers and/or additives which are compatible with processing, subsequent electron beam curing, and final product performance. The system binder is highly loaded usually from 55 to 65 volume percent with the high energy ferrite particles, i.e, barium and/or strontium ferrite particles, which can produce bonded magnets with a maximum energy product of at least 1.0 megagauss-oersteds, a remenance, Br, of at least 2000 gauss, a coercive force, H_c, of at least 1800 oersteds, and an intrinsic coercivity, H_ci, of at least 2000 oersteds. The process for production of this system involves the binder system and ferrite particles being mixed, the ferrite particles oriented in a preferred direction during processing, then formed into a final geometry before being cured by high voltage electron beam radiation, preferably in excess of 3,000,000 electron volts. The electron beam curing in the solid state fixes dimensional stability, magnetic properties, oil, solvent, and chemical resistance of the part even when exposed to subsequent hostile temperature environments of 125^oC or higher. Any off geometry parts or trim produced in the process prior to radiation curing can be recycled through processing several times without fear of premature cure.