Compositions – Electrically conductive or emissive compositions – Free metal containing
Patent
1992-01-06
1994-06-21
Group, Karl
Compositions
Electrically conductive or emissive compositions
Free metal containing
427130, H01B 102
Patent
active
053226410
DESCRIPTION:
BRIEF SUMMARY
This invention relates to inorganic materials which incorporate metallic material and which have desirable magnetic properties, to methods of making such filled materials, and to applications of the filled material, including their use as fillers in plastics and in ceramics.
Although principally concerned with the magnetic properties of materials, the present invention also envisages the production of desirable electrical properties in addition to the production of desirable magnetic properties. It will be appreciated by those skilled in the art that modification of a material's magnetic properties means that its electronic characteristics will also be modified, and vice versa.
Considering firstly plastics materials:
Plastics material formed of organic polymers have an enormous number of applications and commonly contain inorganic mineral fillers to modify their mechanical properties. Most plastics materials are excellent electrical insulators and are non-magnetic.
In some situations it is desirable to modify the magnetic or electrical properties of the plastics material. For example it may be desired to reduce the electrical resistance of a plastics article in order to render it anti-static, that is to allow accumulated static electric charge on its surface to be discharged through the article. It may also be desired to reduce the electric resistance sufficiently to enable the plastics material to act as a shield for electromagnetic radiation. The latter feature is becoming more and more important given the proliferation of electrical equipment in homes, offices and factories, which has led to a large increase in stray radiation of a wide range of frequencies which can disturb electronic data processing equipment, including computers. There is also a need to protect electronic data processing equipment, including computers, from unauthorised access via electronic eaves-dropping.
In a number of important applications it is also necessary to provide plastics articles with particular magnetic properties, for example in timing-motor rotors, magnetic indicators, and beam focusing devices for television receivers. Existing articles of this type generally comprise bodies of magnetic material encased in the plastics material. It is desirable to provide plastics materials themselves with the desired magnetic properties.
In order to increase the electrical conductivity of plastics materials and/or provide the material with significant magnetic properties it is known to apply to the material or an article formed therefrom a metal coating. Such a coating may be applied by a number of methods such as by the use of a conductive paint, flame or arc spraying, electrodeless plating and vacuum metallising or cathode sputtering. All these processes require treatment of the plastics article after it has been formed into shape, generally by moulding, and so are expensive in both labour and equipment. There are also dangers in surface treatments which involve high temperatures and chemical treatment, or the use of solvents, as these may attack the plastics material. Some of these methods are also limited by geometrical considerations, for example a metallic paint may not penetrate recessed areas of the surface. Such finishes are also liable to degrade by flaking, chipping, peeling and corrosion.
Another approach is to provide a core of electrically conducting or magnetic material within the plastics body, for example by forming a sandwich of a metal foil between two plastics layers. Such a sandwich is expensive as it cannot easily be produced in a single operation.
It is also possible to render plastics materials magnetic or electrically more conductive by incorporating into the material fillers which are themselves magnetic or conductive electrically. However known fillers have serious disadvantages. For example, non-porous spherical glass particles coated with a metal may be added to the material, but a very high content of these particles is required, seriously affecting the mechanical properties of the plastics material an
REFERENCES:
patent: 4201831 (1980-05-01), Slusarczuk et al.
patent: 4874433 (1989-10-01), Kiss et al.
Dul'nev, G. N. et al, "Method for calculating the thermal conductivity of porous granular materials with a metallic fillet in diferent media.," Thermodynamics, vol. 105, p. 447, (1986).
Nakao, Yukimichi et al, "Manufacture of metal-plated inorganic particles.," Chemical Abstracts, vol. 107, p. 146, (Sep. 12, 1987).
Okaniwa, Hiroshi et al, "Electrically conductive plastic composites.," Chemical Abstracts, vol. 80, p. 40, (Dec. 20, 1973).
Dyer Alan
Edwards Peter P.
Evans Kenneth A.
Kirkland Angus I.
Shiel Leslie E.
Alcan International Limited
Group Karl
Wright Alan
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