Compositions – Electrically conductive or emissive compositions – Elemental carbon containing
Patent
1998-02-13
1999-04-27
Kopec, Mark
Compositions
Electrically conductive or emissive compositions
Elemental carbon containing
H01B 124
Patent
active
058978135
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
The invention relates to the field of the manufacture of electrically conductive paint materials on the basis of synthetic polymer binders, and may be used in various fields of technology for the production of electrically conductive film coatings on dielectric backings with a large area of heat-emitting surface, primarily for the production of elastic electrically conductive film coatings with a working temperature of the heat-emitting surface of up to 120.degree. C.
PRIOR ART
There is a known electrically conductive paint (FR, 2662703) on the basis of a polymer film-forming binder, the composition of which includes a solvent for polymer binder and a fine-disperse electrically conductive filler in the form of a mixture of silver (60-75 wt. % of the components) and graphite (0.5-10 wt. % of the components).
The film of electrically conductive paint coating on the basis of the known paint, after drying out, has a cubic resistance of the order of 10.sup.3 to 10.sup.6 ohms.times.cm. The high specific resistance of the paint coating film is explained by the fact that, in spite of the high percentage content of silver (which in the pure form has a specific resistance of the order of 1.49.times.10.sup.-6 ohms.times.cm), it is virtually impossible in this paint coating to ensure direct dense contact of the fine-disperse silver particles with each other, since these particles, in the process of the dispersion of the components in the preparation of the paint, become coated with the polymer binder.
Because of this, contact of adjacent particles of silver in the electrically conductive paint film coating produced takes place mainly through a layer of binder material.
The presence of particles of graphite in the known composition of electrically conductive paint facilitates a certain reduction in the specific resistance of the paint coating film, since the fine-disperse particles of graphite, possessing a high degree of porosity, are capable of adsorbing the binder, thus ensuring dense direct contact of the surfaces of the adjacent particles of graphite.
However, where the composition of the known electrically conductive paint includes particles of silver, the dimensions of which are greater than those of the pores of the graphite material, during the dispersion process the graphite pores will be filled with particles of metal (silver).
As a result of this, there will not be dense contact between all the graphite particles present in the paint coating film.
Taking account of the fact that the total content of graphite particles is small in proportion to the content of silver particles, the specific resistance of the paint coating film will be determined mainly by the specific resistance of the film-forming binder, which is several orders higher than that of the graphite and silver.
Calculations show that when a paint coating film of electrically conductive paint of the known composition is applied to a specimen in the form of a dielectric backing in the shape of a square of an area of one square meter, for a thickness of coating film equal to 25 .mu.m, when voltage of 220 V is applied to the corresponding sectors of the coating film (on condition that the specific cubic resistance of the coating film is 10.sup.3 ohms.times.cm), power of about 2 W will be produced on this specimen.
Comparing this power with the power, for instance, of a standard domestic oil radiator (which is 800-1200 W) for the same area of heat-emitting surface, the conclusion can be drawn that the known electrically conductive paint is inapplicable for use in producing heat-emitting electrically conductive surfaces of heating devices and systems.
This is due to the high specific cubic resistance (10.sup.3 -10.sup.6 ohms.times.cm) of the paint coating film based on electrically conductive paint of the known composition.
Furthermore, the electrically conductive paint of the known composition is very expensive, which limits its field of application.
There is a known electrically conductive polymer composition (WO, application
REFERENCES:
patent: 4578286 (1986-03-01), Vasta
Platonov Jury Mikhailovich
Titomir Alexandr Kozmovich
Kopec Mark
Mirson
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