subject: Electromagnetic Shielding Coatings [print this page] Electromagnetic shielding coating is made of synthetic resin, conductive filler, solvent. The existing electromagnetic shield coating is based on conductive coating, the conductive coating material added in electrically conductive filler is typically gold, silver, copper, nickel and other metal powder and carbon black, graphite and other non-metallic powder. Gold dusts conductive is the highest, with good chemical stability, but it is expensive, so the use has been limited. Silver conductivity is also very good, the price is lower than gold, although easily precipitate, have plastic "migration" phenomenon, but they are more commonly used. The performance of copper, nickel is similar with silver, the price is much lower than silver, but easily oxidized, conductive is instability, with plastic poor durability. Carbon black, graphite powder as a conductive filler dispersion, the price is low, but poor electrical conductivity, it is ideal to use as electromagnetic shielding materials.
Earliest silver conductive paint is used as electromagnetic shielding material appeared in the 1960s, characterized by stable, good shielding effect, but its cost is too high; nickel-based coatings affordable, good shielding effect, the antioxidant capacity than copper, and thus become the Europe and the United States and other countries electromagnetic shielding coatings mainstream; conductivity of copper-based paints, but poor oxidation resistance. But with the anti-oxidation technology development in recent years, the development and application of copper-based paint is gradually increasing. Since the volume resistivity of the copper is smaller than nickel, therefore when the coating thickness is the same, and the surface resistivity of the copper-based paint is lower than the nickel-based coating.
Conductive coating of graphite and carbon black, need to use high electrical conductivity and high-structured carbon black as filler to make the volume resistance below 10 cm, a minimum of up to l0-2 cm. Due to the relatively poor conductivity of carbon-based coatings, used as electromagnetic shielding material effect than other metal filler worse. Carbon based paint has good environmental resistance, low density, and low price.
Currently, the key researches on electromagnetic shielding metallic conductive coating lies in how to solve the settlement problem better in the oxidation resistance of copper and nickel powder and paint filler metal during storage. In addition, a potentially important trends in the field is the development of waterborne coatings, in this regard there have been many excellent performance formulations with metallic nickel as a filler, because this metal within a large range of pH values have excellent corrosion resistance. Electromagnetic shielding coating resistivity is between 10-2-10-3 ohm, development direction is light-colored, water-based, wide effective band and multi-spectral mask.
Electric coating is mixed with organic and inorganic liquid coating, its mechanism is: first spread silver and nickel of the metal cast on the inorganic surface, make it become the conductive filler, and then dispersed into this filler by thermalafter hardening of the resin to make the filler can heat, this heat conductive filler and a combination of both of the heat-hardening resin Coated, constitutes the base frame of the electric coating on this base frame, and then pass on the electricity became full electric paint. The electrothermal coating can be applied to various objects such as metals, plastics, ceramics, glass, siding above. Its advantages are: coated at room temperature just need 20 minutes to completely dry, less power consumption, such as use electric heating equipment paint coated per square meter can save power more than doubled. Because it will produce far-infrared radiation, up to 90% of the surface radiation heat, high thermal efficiency, easy to use, only need to pass on electrical appliances or equipment can be effective.
