Anti electromagnetic interference shielding coating.Commonly known as: conductive paint.Conductive paint is a kind of paint with good conductivity, which uses copper, silver and other composite particles as conductive particles.
Chinese name
Anti electromagnetic interference shielding coating
Conductive coatingIt is a special type that has developed rapidly with modern science and technologyFunctional coatingIt has a history of about half a century.In 1948, the United States announced the preparation of silver and epoxy resinConductive adhesiveThis is the first published conductive coating.China also began to research and apply conductive coatings in the 1950s.In recent decades, conductive coatings have been applied in many military and civil industrial fields such as electronics, electrical appliances, aviation, chemical industry, printing, etc.Accordingly, the theoretical research of conductive coatings has also developed rapidly, and promoted the maturity and perfection of application technology.
function
Conductive paint is to add conductive metal powder to specific resin raw materials to makesprayOf paint coating, formed after dryingfilmIt can conduct electricity and shield electromagnetic interference.
Shielding is the metal isolation between two space areas to control the induction and radiation of electric field, magnetic field and electromagnetic wave from one area to another.Specifically, shielding is used to surround interference sources of components, circuits, assemblies, cables or the whole system to prevent interference electromagnetic fields from spreading outward;Enclose the receiving circuit, equipment or system with a shield to prevent them from being affected by external electromagnetic fields.
type
Classification according to application characteristics:
Classification according to application materials:
Eigentype
EigentypeConductive coatingIt refers to the intrinsic typeConductive polymerConductive coating made of film-forming material.Conductive polymerThe preparation methods for conductive coatings mostly focus on the direct use of conductive polymers as film forming resins, the mixed use of conductive polymers with other resins, and the use of conductive polymer materials as conductive fillers, among which the most typical ones arepolyaniline 、Polypyrrole、pth 、polyquinoline Etc. is an active research field.Intrinsic conductive coatings are mainly used in anti-corrosion and anti-static coatings, wave absorbing coatingselectromagnetic shielding Coatings, etc., many kinds of polyaniline antistatic have been developed in ChinaAnticorrosive coating。
Dopant type
Doped conductive coating refers to the conductive coatingPolymerAdd conductive materials on the basis of, and use the conductive effect of conductive materials to achieve the coatingconductivityAbove 10-12S/m.It not only has the conductive function, but also has many excellent characteristics of polymer. It can adjust the electrical and mechanical properties of the coating according to the use needs in a large range, and has low cost and simple operation, so it is widely used.Dopant typeConductive coatingIt is composed of high molecular polymer, conductive filler, solvent and additives.Commonly used conductive fillers include metal fillers, carbon fillersmetallic oxideSeries fillers, composite fillers, new nano conductive fillers, etc.
(1) Carbon conductive coating
Carbon conductive coating is one of the most widely usedFunctional coatingIt has the advantages of low cost, light weight, high structure, non-toxic and harmless.The conductive fillers used as carbon conductive coatings mainly includegraphite、Graphite fibre、carbon fibreHigh temperatureCalcined Petroleum Coke , variouscarbon blackas well assilicon carbideEtc.Especially carbon black fillingConductive polymerHas been widely used becauseConductive carbon blackThe utility model has the advantages of low price, small density, difficult sedimentation, strong corrosion resistance, etc., but the conductivity is relatively poor;At the same time, because the surface contains a lot ofPolar groupIt is difficult to disperse and flocculate. One of the most simple and effective solutions is to adddispersantReduce the attraction and cohesion between carbon black particles, so that they can be evenly and stably dispersed in the matrix.Carbon systemConductive coatingIt is usually composed of conductive fillers, matrix resins, additives and solvents, which are mechanically mixed and coated on nonConductorA special curing film is formed on the surface of the substrate to produce conductive effect.
Graphite is a highly conductive layered material, which is used as conductive filler andConductive polymerThe polymer matrix composites with excellent electrical conductivity can be prepared by the composite.graphiteWith its good conductivity, low price and simple operation process, the coating has an irreplaceable position in the coating of the inside and outside of the color tube glass shell.In order to make the coating have good conductivity, it is necessary to prepare high-purity ultra fine graphite through deep processing to meet the needs.
With the development of nanotechnology, conductive polymer materials made from graphite nanomaterials and matrix composites are increasingly emerging;expanded graphite As a new conductive filler, it hasConductivityGood, low friction loss, low pollution and other advantages. Moreover, the addition of expanded graphite can greatly improve the conductivity of polymer materials and reduce their conductivity filtration valueAntistatic coatingandConductive polymerComposite materials have important application value.
(3) Metal conductive paint
Metal systemConductive coatingThe conductivity depends on the type, quantityMetal fibreAnd the type and quantity of metal powder, and the shape of filler.Metal series fillers mainly includeSilver powder、Nickel powderandcopper powderEtc., including silver powderchemical stabilityGood, excellent anti-corrosion performance, high conductivity, it is a conductive filler that was developed and applied earlier.However, due to the high price of silver powder, it is mostly used in the military field, and less used in the civilian field.
Nickel powder is widely used because of its good chemical stability, effective anti electromagnetic interference performance and moderate price.Copper powder has low price and is similar to silverConductivityThe disadvantage is that copper is easy to be oxidized and its conductivity is unstable, but after special surface treatment, stable copper base can be obtainedConductive coatingWith the improvement of anti oxidation technology of copper powder, the research of copper based conductive coatings will receive further attention.
Nanotubes have greatAspect ratioAnd excellent electrical properties. Adding it to the polymer as a reinforcing phase can greatly improve the mechanical properties and photoelectric properties of the polymer, so it can be used to prepare functional propertiesCarbon nanotubes/PolymerConductive coating, applied in many fields.Nanotube conductive material and film forming material are almost the sameOrder of magnitudeThe particle size of the nano tube conductive coating penetrates each other without obvious interface, so the anti-corrosion performance of the nano tube conductive coating is better than that of ordinaryAnticorrosive coatingGood performance.
Because of its excellent electrical properties and light color, metal oxides can better supplement the poor corrosion resistance of metal conductive pigments and carbon conductive pigmentsDecorative performancePoor and other shortcomings.Common composite fillers include glass beads, copper powder andMica powderSilver coated and carbon black coatedNickel powderAnd so on.Metal oxide conductive pigments are mainly dopedTin oxide、zinc oxide, 2Antimony oxideAmong them, SnO2, as the representative, is valued for its low density, good stability in the air, light color and transparent coating.
working principle
Conductive paint passingspray、Brush coatingThe fully insulated non-metal or non-conductive surface has the same characteristics of absorbing, conducting and attenuating electromagnetic waves as metal, thus playing the role of shielding electromagnetic wave interference.The appearance of conductive paint effectively solves the problem of electrical connection on non-metallic surfaces.
Conductive paint isElectroplated silverAnti electromagnetic wave interference paint made of particles, single component, labor saving, time-saving, convenient, good adhesion, flat, strong cohesion, no loose particles, can be used for mobile phones, calculators, precision instruments and other inner walls with metal and composite materials as the base materialSpraying materials。After drying and curing, the performance of the paint layer is stable, and the coating on the surface of the workpiece is fine and smooth. It has excellent conductivity as pure silver conductive paint, and the fine conductive particles ensureElectronic componentsSecurity of.
In order to ensure the adhesion between the paint and the base surface, under normal circumstances, conductive paint is only recommended to be used in PC, ABS, etcNon metallic materialsIf it is used on the surface that is not commonly used, it may need primer to be used together.[1]
give an example
Announce
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Copper conductive paint
The following specific types of products are widely used: those added with silver metal powder are called silver conductive paint; those added with silver metal powder are called silver conductive paintcopper powderIs called copper conductive paint; addNickel powderAmong them, copper conductive paint is the most widely used, because it is much cheaper than silver conductive paint, and its conductivity is much better than nickel conductive paint. See the following for specific indicators:
Theoretical coverage rate: 8-12m2/kg (paint film thickness=20micron)
technical parameter
Conductive effect: ≤ 0.025 ohm/square centimeter (paint film thickness is not less than 20 microns) Application conductive parameter: 1 ohm/20 microns film thickness/distance 10cm Recommended film thickness: 20-25 microns (ASTM D4138-94)
Drying conditions
The drying time of the meter is 15 minutes, and the drying time is 65 ± 5 ℃/30 ± 10 minutes
Storage/shelf life
Store in a ventilated and dry indoor environment.6 months/25 ℃ (original)
Theoretical coverage rate: 12m2/kg (paint film thickness=13micron）
technical parameter
Conductive effect: ≤ 0.015 ohm/square centimeter (paint film thickness is not less than 13 microns) Conductive parameters for application: 1 ohm/15 microns film thickness/distance 10cm Recommended film thickness: 15 microns (ASTM D4138-94)
Use materials
ABS、HIPS、PS、PC、Hardware and other materials (if there are special materials, the company will prepare applicable conductive paint for customers) Thinner: ethanol/tap water（Boiling water）Oil opening ratio: 1:0.5 (weight ratio)
Theoretical coverage rate: 6-8m2/kg (paint film thickness=25micron）
technical parameter
Conductive effect: ≤ 0.25 ohm/square centimeter (paint film thickness is not less than 25 microns) Application conductive parameter: 2 ohm/25 microns film thickness/distance 10cm Recommended film thickness: 25-30 microns (ASTM D4138-94)
Test conditions
When measuring, the sprayed film must be completely cooled and dried.It should be displayed digitallyA multimeterMeasurement (generally, the gear of the multimeter should be adjusted to<200 Ω). The measured result should be the conductive value of the paint film after removing the resistance of the multimeter itself and the wire (i.e. the base mark).
Use materials
ABS, HIPS, PS, PC and other plastic parts (if there are special materials, the company will prepare applicable conductive paint for customers) Thinner: matchingBoiling water(boiling oil water) boiling ratio: 1:0.5 (weight ratio)
Before use, the paint shall be fully stirred in the paint tank before use.Nickel metal particles are evenly dispersed after stirring,sprayComing outfilmTo achieve conductivity.After the paint is diluted, it is better to mix it frequently for at least 5min to achieve the best conductive effect after coating;Diluted products should be used up as soon as possible to avoid long-term storage, because it is easy to precipitate after dilution, but it still does not affect the use characteristics after mixing.Protective measures: during use, ensure that the working environment is well ventilated, avoid long-term direct contact or inhalation, and do not pour paint into the water channel or sewer to pollute the environment.
Storage/shelf life
Sealed storage in ventilated and dryindoor environment 。6 months/25 ℃ (original).[2]
