WO2021203656A1 - Lightweight and highly conductive coating, preparation method therefor, and use thereof - Google Patents

Abstract

Disclosed is a highly conductive coating, which is composed of conductive microspheres and a polymer adhesive, wherein the volume ratio of the conductive microspheres to the polymer adhesive is 1:2 to 2:1, and the conductive microsphere is a conductive microsphere plated with silver or copper. The highly conductive coating can has a density that is as close as possible to that of a carbon fiber reinforced composite material, without adding extra weight to the composite material product. In addition, the coating has a surface resistivity as low as 0.01 Ω/square, such that the conductivity is not less than that of a conductive coating of a copper powder filler. Lightning strikes can be prevented and the interference of static electricity on electromagnetic waves can be eliminated. The highly conductive coating can be used in a surface coating of a composite material of a plane, a high-speed train, an unmanned aerial vehicle, a wind turbine blade or a car made of the composite material, and effectively solves the problem that existing commercial conductive coatings are not very suitable for such product coatings.

Description

Lightweight high-conductivity paint and preparation method and application thereof

Technical field

[0001] The invention relates to the field of polymer materials, in particular to a high-conductivity paint that can be used for the surface coating of composite materials on aircraft, high-speed trains, unmanned aerial vehicles, wind turbine blades, and automobiles made of composite materials, and preparation thereof Methods and applications.

Background technique

[0002] Fiber-reinforced composite materials have the advantages of high strength, light weight, corrosion resistance, etc., such as glass fiber, basalt fiber, special polymer fiber, carbon fiber, etc., are widely used in the manufacture of composite materials, and are widely used in airplanes, high-speed trains, and automobiles. , Mechanical structure and other fields. Especially for some weight-sensitive applications, such as aircraft, unmanned aerial vehicles and other aircraft, the light weight characteristics make composite materials show special advantages. Such as carbon fiber reinforced composite materials ( CFRC ) Has a density of 1.5 — 1.8g/cm ³, the density of the corresponding aluminum alloy is up to 2.7 g/cm ³. This makes CFRC It is increasingly used in the manufacture of new generation aircraft to reduce the weight of the airframe, thereby achieving the goal of saving fuel. With the increase in fuel prices that can be expected and the requirement to reduce carbon emissions, the application of more composite materials in transportation has become a development trend.

[0003] However, compared with metal materials, resin-based fiber-reinforced composite materials have a significant feature that is electrical insulation. Traditional aluminum alloy has good conductivity, and its conductivity is ~3.6 X 10 7 S/m . Carbon fiber composite materials have the best conductivity among fiber composite materials, but they are still very low. For example, the epoxy resin composite material increased by carbon fiber, its conductivity is ~1.38 X 10 3 S/m . The low electrical conductivity makes its application in the aircraft body face the risk of lightning and electric shock, causing damage to the aircraft body, and even crashes. In addition, poor conductors can accumulate static electricity, which can interfere with electromagnetic waves and affect communication and navigation. Electric sparks generated by electrostatic discharge can cause a series of safety hazards such as fires. This makes how to design the airframe and increase the electrical conductivity of the airframe in the application of carbon fiber composite materials in aircraft manufacturing has become an important topic. Especially for the risk of lightning strikes, when using carbon fiber composite materials, it is necessary to design a body that can conduct a large amount of current. It is estimated that FAA Certified commercial aircraft will be struck by lightning twice a year. In major lightning incidents, the aircraft must have conduction 200000 ampere / Milliseconds or more Ability. If there is no proper current conduction path, it will cause mechanical damage, thermal decomposition of materials, and damage to electronic components. In addition, corona, light flow, and current related to lightning strikes will continue to exist before and after lightning strikes.

[0004] During the flight, it can cause the accumulation of static electricity and produce electromagnetic effects, such as communication and navigation. Static electricity can come from particles in the air, such as the impact of rain and snow on the body (that is, friction-generating electricity), or the flow of liquid and fuel. In addition to the impact of static electricity on electronic equipment, it can generate sparks in severe cases and cause fire or explosion hazards.

[0005] At present, aircraft using carbon fiber composite materials usually add copper or aluminum mesh to the surface of the composite material to increase conductivity. This technology can disperse the current from the surface of the aircraft body without going deep into the aircraft body, effectively coping with lightning or static electricity to the aircraft. Damage and communication interference. But the density of copper is as high as 8.96 g/cm ³, the metal mesh will increase the weight of the composite material layer a lot, which will greatly reduce the light weight of the carbon fiber composite material. For this reason, the use of metal mesh in composite materials is also limited to some key parts, such as parts that are susceptible to lightning strikes or electromagnetic waves. Even so, a substantial increase in the overall weight of the body is inevitable. In addition, since the metal mesh is embedded in the composite material, once damage occurs, the integral parts of the composite material must be replaced. The repair cost and time will be huge.

[0006] A more effective way to avoid the effects of lightning and static electricity is to apply a conductive coating on the surface of the body. Because the coating is on the surface, when a lightning strikes, the surface coating may be damaged, and when repairing, only the coating needs to be replaced without replacing the whole part. The cost and time of repair can be greatly reduced.

[0007] The current commercial conductive coatings are usually silver powder or copper powder filled epoxy resin, acrylic resin, phenolic resin, polyimide resin, silicone resin, or polyurethane resin and other coatings. Metal powder filled epoxy resin coatings are generally in 0.05 It can reach about 0.1 Ω / Square low resistivity. But the content of metal powder needs to be greater than 50% Volume ratio, in this way, the density of the coating will be as high as about 5g/cm ³, this will cause the total weight of the aircraft to increase a lot. On the other hand, the lightweight effect of composite materials will be greatly affected. In addition, the high metal powder filling ratio will lead to the deterioration of the adhesion and mechanical properties of the coating. This may cause the coating to not meet the minimum requirements for aviation flight. Therefore, the existing commercial conductive coatings are not very suitable for aircraft coatings.

Summary of the invention

[0008] In view of the above-mentioned shortcomings and deficiencies in the prior art, the purpose of the present invention is to provide a conductive coating that can provide sufficiently high conductivity, and has relatively low density and sufficiently high adhesion and mechanical strength, and to provide The preparation method of the conductive coating.

[0009] Specifically, the inventor provides the following technical solutions:

First of all, the inventor provides a light-weight high-conductivity paint, which is composed of conductive microspheres and a polymer binder, where the ratio of conductive microspheres to polymer binder is the volume ratio 1:2 to 2:1 , The preferred range can be in 0.7/1-1/0.7 Between, but not limited to the range listed; the conductive microspheres are silver- or copper-plated conductive microspheres made by the following steps, namely, polymer microspheres→polyamine surface modification→microsphere surface carrier Catalyst activation→electroless plating surface plating metal thin layer→barrel plating metal thick layer.

[0010] Ideal conductive coatings need to provide sufficiently high conductivity, relatively low density, and sufficiently high adhesion and mechanical strength. Such ideal conductive coatings have always been the goal pursued by scientists from various countries engaged in research in this area. The present invention provides a solution for preparing this ideal conductive coating. Firstly, make a uniform micron-sized polymer microsphere with suitable functional groups on the surface of the microsphere; after further processing the surface of the microsphere, the microsphere becomes an activated base ball that can be electrolessly plated; activated base ball After electroless plating or / After electro-barrel plating, it is plated with a layer of copper or silver plating with a suitable thickness to form conductive microspheres-polymer microspheres with copper or silver plated on the surface with uniform particle distribution. Then, the conductive microspheres are mixed with polymer resins such as epoxy resin, polyacrylic resin, phenol resin, polyimide resin, silicone resin, polyurethane resin, etc., in an appropriate ratio, and then they can be made into lightweight and highly conductive coating.

[0011] Generally choose the diameter 3-10 Micron polymer microspheres are used as the base ball, and the surface of the base ball is plated 100 ~ 300 The nano metal layer is made into conductive microspheres. Example: The density of the polymer base ball is 1.05 g/cm ³ to 5 Micron plating 200 Take nano-copper plating as an example, the density of conductive microspheres after plating is 2.68 g/cm ³. When the volume ratio of conductive microspheres and resin is 1:1 After being mixed and formulated into conductive paint, the density of the paint is 1.85 ~ 2.0 g/cm ³. The conductive paint made by this can achieve the same conductivity as the resin paint filled with copper powder, but the density is only that of the resin paint filled with copper powder. 40% about. Therefore, the lightweight high-conductivity coating of the present invention can be as close as possible to carbon fiber reinforced composite materials ( CFRC ) Without increasing the additional weight of application products such as airplanes.

[0012] Preferably, the polymer microspheres in the present invention are copolymerized polymers with a high degree of cross-linking, and the copolymer composition includes divinylbenzene, styrene, chloromethylstyrene, (meth)acrylate or maleic anhydride. The body is aggregated. The conductive base ball is composed of a copolymer polymer with a high degree of cross-linking, and the degree of cross-linking is greater than 20% , The ideal degree of crosslinking is 50% above. The copolymer contains active functional groups such as benzyl chloride, styryl, (meth)acrylic acid, and maleic anhydride. Other monomers of copolymerized polymer microspheres can be monomers with inactive functional groups such as divinylbenzene and styrene. The active groups on the microspheres can react with polyamines to form polyamine-modified microspheres and polyamine compounds. It is a linear or branched polyamine, which can be ethylenediamine, propylenediamine, diethyltriamine, triethyltetramine, tetraethylpentamine, tri( 2- Aminoethyl) amine and low molecular weight polyethylene imine ( PEI ), etc., triamines or polyamine compounds above triamines are more desirable.

[0013] More preferably, the divinylbenzene content of the polymer microspheres of the present invention is within 20% ~ 90% between.

[0014] Preferably, the polymer binder in the present invention includes, but is not limited to, epoxy resin, acrylic resin, phenol resin, polyimide resin, silicone resin, or polyurethane resin.

[0015] The particle size of the polymer microspheres before metallization in the present invention is 1 Micron~ 10 Micrometers, preferably, the particle size is in 3 Micron~ 8 Micron, the most preferred, choose the particle size in 4 Micron~ 6 Micrometers. Coefficient of variation of particle size distribution is less than 20% , As a preference, the coefficient of variation of particle size distribution is less than 10% , Most preferably, the coefficient of variation of particle size distribution is less than 4% .

[0016] Preferably, the plating thickness of the silver or copper-plated conductive microspheres in the present invention is 20 Nano~ 500 Nano.

[0017] The present invention also provides a method for preparing the above-mentioned light-weight high-conductivity paint, which includes the following steps:

(1) Preparation of conductive microspheres plated with silver or copper:

(1.1) Polyamine surface modification

The polymer microspheres are first chemically modified into polyamine-modified sphere surfaces. The copolymer composition includes microspheres polymerized from divinylbenzene, styrene, chloromethylstyrene, (meth)acrylate, and maleic anhydride monomers, which have functional groups that can react with polyamine molecules. The microspheres containing benzyl chloride groups react with polyamines for the following reactions. The reaction can be carried out in multiple steps to achieve the surface of the amine-modified microspheres. Benzyl chloride can react with amines and can react with secondary amines. The density depends on the density of benzyl chloride on the surface of the microspheres. The high density of amine groups is more beneficial to the next step of electroless metal plating.

To

[0018] Containing styrene-based microspheres, first react with concentrated sulfuric acid, and then react with excess polyamine to carry out the following series of multi-step reactions:

To

The microspheres obtained by polymerization of (meth)acrylate and inactive functional group monomers can be hydrolyzed to convert the (meth)acrylate groups on the surface of the microspheres into (meth)acrylic groups, and then react with polyamine molecules , The formation of (meth) allylamine salt. Amine salt can form more stable (meth)acrylamide after high temperature treatment.

[0019] Maleic anhydride functionalized microspheres can directly react with polyamine molecules. After maleic anhydride reacts with polyamine molecules, after high temperature treatment, stable maleimide is formed, and the microspheres are modified to polyamine surface.

[0020] In the reaction between the polyamine and the functional groups on the surface of the microspheres, the reaction between the (meth)acrylic group and the polyamine molecule is an acid-base reaction, and the other is a nucleophilic reaction. The solvent of the reaction has a key effect on the speed of the reaction. . In the present invention, considering the relatively low polarity of the unmodified microspheres, organic solvents or mixed organic solvents are selected as the solvent, so that even if the microspheres can be wetted, the nucleophilic reaction can be promoted. Organic solvents can be non-quality molecules with high dipole moments such as DMF , DMSO , Acetonitrile, the reaction is carried out under heating and reflux to promote the rapid progress of the reaction, so that the surface of the microspheres is covered with the maximum amount of polyamine molecules. In addition, the amine propionate salt can form a more stable amide bond under heating, which makes the subsequent metal plating bond more firmly on the surface of the microspheres. Since the surface modification reaction of the microspheres is carried out in organic solvents and high temperatures, the microspheres must have high stability to the organic solvent, otherwise the microspheres may be dissolved or swelled, which will completely destroy the morphology of the microspheres. For microspheres with high stability in organic solvents, a sufficiently high degree of cross-linking must be required. If the degree of cross-linking is higher than 20% .

[0021] Polyamine modified microspheres must be able to react with the solvent that is DMF , DMSO , Acetonitrile miscible low-boiling solvent is washed several times, and filtered to remove DMF , DMSO And excess polyamine molecules. The low boiling point solvent can be methanol, ethanol, acetone, etc. After the cleaned microspheres are vacuum dried, they can be used for the subsequent surface activation reaction. Any residual solvents such as DMF , DMSO And unreacted polyamine molecules may cause defects in the metal coating.

[0022] The surface polarity of the polyamine-modified microspheres will be greatly changed than the original microspheres, and the microspheres have very good hydrophilicity. The microspheres can be easily dispersed in an aqueous medium, which also shows that the microspheres have high surface energy, which makes the subsequent surface activation and metal plating of the microspheres easier. The present invention uses Tianshu microsphere products with high functional group density on the one hand, and on the other hand, based on the high crosslinking degree of the microsphere itself, it can perform high-temperature modification reactions. Makes the density of amine groups on the surface of the microspheres reach the highest possible level. The amine groups are combined in the form of covalent bonds in the microspheres, which is stable and firm. The subsequent metal coating has very strong adhesion to the surface of the microspheres. This brings great convenience to the construction of conductive coatings and conductive coatings, and can greatly avoid problems such as peeling of the metal coating and microspheres due to shearing forces in the construction of conductive coatings and conductive coatings. Layer quality provides a reliable guarantee.

[0023] (1.2) The surface support of the microspheres is activated on the catalyst

The supported catalyst on the surface of the microspheres is activated. The polyamine-modified microspheres interact with platinum, palladium, and tin salts, and the salts are reduced to platinum, palladium, tin or mixed metal-coated activated base spheres by a reducing agent.

[0024] The polyamine-modified microspheres are activated through a common electroless plating surface activation step. The activation step is also called the catalytic step. That is, the catalyst particles are attached to the surface of the microspheres. The catalyst particles are usually tin, platinum, palladium or a mixture of them, such as tin / palladium . Catalyst particles usually start with these metal salts, and after reduction, they form nano-sized metal particles, which firmly adhere to the surface of the microspheres. The reason for the firm adhesion is the high polarity of the microspheres given by the amine groups on the surface of the microspheres ( High surface energy ) . In addition, catalyst metal ions and amine groups can form complexes. A large number of catalyst metal ions are attached to the surface of the microspheres. When interacting with the reducing agent, these metal ions are reduced to metal nanoparticles and attached to the microspheres in situ. surface.

[0025] The solution of activated polyamine modified microspheres is usually composed of palladium, platinum, tin sulfate or hydrochloride, and the activation reaction is carried out in water, protic organic solvents such as methanol, ethanol or their solvents, so the activation solution is also With the same solvent formulation. In view of the low solubility of this kind of salt or the characteristics of easy hydrolysis and precipitation, the activation solution is usually added with ammonia water to make it into an ammonia salt complex. pH Stable activation solution at low value.

[0026] After the activation solution is mixed with the polyamine-modified microspheres, the amine on the surface of the microspheres as a complexing agent will participate in the reaction to replace the ammonia in the ammonia salt complex, so that the ammonia salt complex is bound to the surface of the microspheres. This reaction is conducive to more concentration of the catalyst on the surface of the microspheres. After the activation solution is mixed with the polyamine-modified microspheres, an appropriate reducing agent, such as dimethylamine borane ( DMAB ), at the appropriate temperature (below 100 ℃), the reducing agent can make metal salt ions such as Pd(II) It is reduced to nano-metal palladium, and is firmly bonded to the surface of the microspheres.

[0027] (1.3) Electroless metal plating thin layer

The coating thickness of the silver or copper-plated conductive microspheres is 20 Nano~ 500 Nano.

[0028] The microspheres with metal nanoparticles are activated base balls, and the activated base balls can be well infiltrated in the water-based electroless plating solution. The activated base ball can be plated with metals such as copper, silver, nickel, gold, etc. by using common electroless plating solutions. The metal nanoparticles attached to the microspheres are the catalyst activation points for subsequent electroless plating. The metal plating first nucleates at these points and develops a metal plating layer. The quality of the metal coating, such as mechanical strength, adhesion between the metal coating and the base ball, surface coverage, smoothness, etc., is related to the size and density of the metal nanoparticles on the activated base ball. Small and densely distributed metal nanoparticles can produce high-quality metal coatings, while larger and sparsely distributed metal nanoparticles may cause defects in the metal coating, or even fail to obtain a complete metal coating. Generally speaking, metal nanoparticles are 10 Nanometer or less is better, with 4 Nano or so is most suitable. The denser the distribution density of metal nanoparticles, the better. In the present invention, high-functional modified starting microspheres and high degree of cross-linking enable it to withstand relatively severe amination reaction conditions, so that microspheres with high metal nanoparticle density can be obtained. The activated base ball of the present invention has very good hydrophilicity, and in the process of further electroless copper and silver plating, it is not necessary to add the wetting agent required for the electroless plating of the conventional plastic surface. The wetting agent is usually a surfactant, which is easy to be adsorbed on the surface of the microspheres, and affects the deposition of metal on the surface of the microspheres, thereby causing coating defects. The coating on the microspheres of the present invention strongly adheres to the surface of the microspheres and can form a defect-free surface coating.

[0029] The activated base ball can be plated with a relatively thin metal plating layer by a common electroless plating method, that is, one-time plating, so that the microspheres have preliminary conductivity. Thin initial coating, usually 10-20 Nano. Electroless plating can be carried out under elevated temperature conditions to increase the metal deposition rate. The electroless plating layer is copper or silver.

[0030] (1.4) Electroless metal plating or electric barrel plating metal thick layer

The electroless plating method can also obtain the required thick coating at one time, and the thick coating is usually 200-500 Nano. However, it is difficult to control the precise coating thickness with electroless plating. For applications that do not require strict coating thickness, one-time electroless plating can be used. Otherwise, the electro-barrel plating can be used to thicken the coating.

[0031] The thickness of the coating layer is further increased by the electrochemical barrel plating method. Thin-layer coated microspheres with preliminary conductive properties can be thickened by ordinary electroplating methods, that is, secondary plating. The specific method of electroplating adopts the barrel plating method in which the object to be plated does not need to be fixed and connected to the electrode. Thicker plating layer is usually up to 180-500 Nano, according to the needs of conductivity, can increase or decrease the thickness of the coating. Considering that the thickness of the plating layer changes, it will greatly affect the density of the conductive microspheres. The increase of the plating layer increases the conductivity, but the density of the microspheres also increases significantly. Therefore, conductivity and microsphere density must be comprehensively balanced with reference to practical conditions.

[0032] The thickness of the plating layer can be calculated theoretically and obtained from the weight gain of the microspheres after plating. The weight gain of the microspheres can be estimated from the plating time and current intensity, or it can be finally weighed. by 5 Take micron microspheres as an example, the density of microspheres before plating is 1.05g/cm ³, the first electroless plating 20 After nano copper, the density increased to 1.237 g/cm ³. After the second electroplating, if the copper plating layer of the microspheres is increased to 200 Nano, the density of microspheres increases to 2.68 g/cm ³. If one kilogram 5 Micron microspheres, copper-plated for the first time and thickened 20 Nano, the total weight of the microspheres increases to 1.21kg . After secondary copper plating and thickening 200 Nano, the total weight of the microspheres increases to 3.22Kg . On the contrary, the thickness of the plating layer is estimated based on the weight gain of the microspheres, thereby determining the plating time.

[0033] The table below is one kilogram 5 The relationship between the weight of micron microspheres after two copper and silver plating and the particle size of the microspheres:

To

(2) Preparation of light-weight high-conductivity paint:

In the present invention, the conductive microspheres and the polymer binder are mixed to form a lightweight conductive coating. The ratio of conductive microspheres to the polymer binder is a key indicator of the conductive coating. If the ratio of conductive microspheres is too low, the conductive coating will become conductive. The performance drops drastically, and it is not even conductive. If the proportion of conductive microspheres is too high, the specific gravity of the conductive coating will be too high, and the effect of the conductive coating when applied to vehicles or aircrafts that require lightweight is greatly reduced. In addition, an excessively high proportion of conductive microspheres will also cause damage to the mechanical strength of the coating. The ratio of conductive microspheres to binder is about 1:1 In the case of conductive coatings, the conductivity, density and mechanical properties of the coating are more balanced. Among them, for applications with different performance requirements, the ratio can be selected, and the more applicable range can be in 0.7/1-1/0.7 between. With epoxy resin and 5 Micron /0.2 Take the micron copper coating as an example. The following table shows the relationship between the paint density and the surface conductivity of the conductive coating.

To

[0034] Where the surface conductivity values are from carbon fiber / The coating thickness of epoxy resin composite is 0.05 Measured in mm conductive coating.

[0035] The present invention also provides the application of the above-mentioned light-weight high-conductivity paint on the conductive coating of non-conducting fiber composite material. It can protect the application products from lightning strikes or electromagnetic wave interference.

[0036] Preferably, in the present invention, the lightweight conductive coating is used for the coating of composite materials on airplanes, high-speed trains, unmanned aerial vehicles, wind turbine blades or automobiles.

[0037] Compared with the prior art, the advantages of the present invention are:

1 , The present invention is as close as possible to the carbon fiber reinforced composite material ( CFRC ) Without increasing the additional weight of the aircraft; while the surface resistivity is as low as 0.01 Ω / Square, the conductivity is not lower than the conductive paint of copper powder filler.

[0038] 2 , Compared with ordinary conductive paint, the coating has higher mechanical strength. It is suitable for applications where the strength and durability of the coating are strict, such as airplane wings, high-speed trains, and wind power blades. Because ordinary conductive coatings usually have about 50% The volume ratio of conductive fillers (such as silver powder, copper powder), due to the irregular shape of the filler particles and high specific gravity, is easy to aggregate and adhere to each other, so that the binder cannot be mixed between the particles, so that the particles around the particles cannot fully contact the binder. This leads to a decrease in the strength of the bonding layer. Therefore, the strength can only be ensured by reducing conductive fillers and giving up certain conductive properties. The high-strength, high-uniformity conductive microspheres of the present invention will not be deformed due to mutual extrusion even in the case of a high proportion. Due to its uniformity and spherical characteristics, it is ensured that the microspheres can always be filled with enough adhesive to maintain a strong bonding layer strength. And the higher the ratio, the strength of the bonding layer will not decrease.

[0039] 3 The lightweight high-conductivity coating provided by the present invention is used as a conductive coating for non-conductive fiber composite materials. The conductive coating can be used for aircraft, high-speed trains, unmanned aerial vehicles, wind turbine blades, and automobiles made of composite materials. The surface coating of the composite material on the surface to prevent lightning strikes and eliminate the interference of static electricity on electromagnetic waves.

Detailed ways

[0040] In the following, the content of the present invention will be explained in more detail with reference to the embodiments. It should be noted that the following embodiments are only representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the following embodiments, and many variations are possible. All modifications directly derived or associated with the content disclosed in the present invention should be regarded as the protection scope of the present invention.

[0041] In the present invention, unless otherwise specified, all parts and percentages are weight units, and all equipment and raw materials can be purchased from the market or commonly used in the industry. The methods in the following examples, unless otherwise specified, are all conventional methods in the art.

[0042] Example 1

( 1 ) Polyamine surface modification

by 25% Chloromethyl styrene and 75% Divinylbenzene copolymer 5 Micron microspheres are starting microspheres (the microspheres are provided by Taizhou Tianshu New Material Technology Co., Ltd. TS005CI Microspheres, the coefficient of variation of the particle size distribution of the microspheres is 2.8% ).

[0043] will 20g of TS005CL with 2.5g Of three ( 2- Aminoethyl) amine is added to the 250ml of DMF of 500ml Round bottom flask. Under electromagnetic stirring, heat the solution to 105 ℃, the reaction continues 5 Hour. After cooling, filter and rinse thoroughly with deionized water. By vacuum 100 Dry the polyamine-modified microspheres at ℃ for two hours. The microspheres were analyzed by infrared spectroscopy, and the benzyl chloride groups on the surface of the microspheres were completely converted into amine groups.

[0044] (2) The surface support of the microspheres is activated on the catalyst

will 20g Polyamine modified by the above polyamine surface modification reaction TS005CL Microspheres are added to the containing 1000ml Distilled 5000ml Round bottom flask. Under electromagnetic stirring, heat the solution to 60 ℃, add 1000ml 0.05% (NH)2PdCl4 Solution. The response continues 30 minute. After cooling, filter and rinse thoroughly with deionized water.

[0045] Add the above-mentioned palladium salt-loaded microspheres containing 1000ml Distilled 5000ml Round bottom flask. Under electromagnetic stirring, heat the solution to 60 ℃, add 2000ml 10% Dimethylamine borane ( DMAB ), the response continues 20 minute. After cooling, filter and rinse thoroughly with deionized water. Obtain palladium activated microspheres.

[0046] (3) Electroless plating surface copper plating thin layer

will 20g The palladium activated microspheres obtained by the above reaction were added to the containing 1000ml Thin electroless plating Copper liquid 5000ml Round bottom flask. Under electromagnetic stirring, heat the solution to 50 ℃. The response continues 40 minute. After cooling, filter and rinse thoroughly with deionized water. have to 24g Thin-layer copper-plated microspheres, copper coating is about 20 Nano. To

Thin electroless plating The composition of the copper liquid is : 4 g Copper sulfate, 25 g Sodium tartrate, 10g Formaldehyde and 0.1 g Thiourea, pH Value is 12 .

[0047] (4) Barrel plated metal thick layer

Will be obtained according to the above thin plating method 500 g The thin copper-plated microspheres are added to a four-liter small barrel plating device with a rotation speed of 20/ minute, 100 Abe current, electrolysis 9 Hour. have to 1.5 k g Thick copper-plated microspheres. Copper plating approximately 190 Nano. The copper plating solution is a commercially available common plating solution.

[0048] (5) Preparation of light-weight high-conductivity paint

Combine the conductive microspheres prepared above with epoxy resin in accordance with 0.8 : 1 The volume ratio is mixed to make a lightweight conductive paint. The preparation method adopts the method commonly used in the art, and will not be repeated.

[0049] After testing, carbon fiber / The coating thickness of epoxy resin composite is 0.05 Mm conductive coating, surface conductivity (Ω / Square) is 0.15 , Paint density ( g/cm3 )for 1.86 .

[0050] Example 2

Other steps are the same as in the embodiment 1 , The difference is:

( 1 ) Polyamine surface modification

by 65% Divinylbenzene polymerization 4.5 Micron microspheres are the starting microspheres (numbered TS0045-Y The microspheres are provided by Taizhou Tianshu New Material Technology Co., Ltd. The coefficient of variation of the particle size distribution of the microspheres is 3.0% ).

[0051] will 50g TS0045-Y Microspheres are added containing 500 Acetonitrile 1000ml In a round bottom flask, slowly add dropwise 3ml 98% Concentrated sulfuric acid, electromagnetic stirring at room temperature 5 Hour. Add slowly 10ml The molecular weight is 800 Of anhydrous polyethyleneimine ( PEI ). After the addition is complete, the temperature is slowly raised to the reflux of acetonitrile. Continue the reaction for three hours. After cooling, filter and rinse thoroughly with deionized water. By vacuum 100 Dry the polyamine-modified microspheres at ℃ for two hours. The microspheres were analyzed by infrared spectroscopy, and the styryl groups on the surface of the microspheres were completely converted into amine groups.

[0052] (3) Electroless plating surface copper plating thin layer and thick layer copper plating

will 20g Palladium activated microspheres 1000ml Thick electroless plating Copper liquid 5000ml Round bottom flask. Under electromagnetic stirring, heat the solution to 50 ℃. The response continues 5 Hour. After cooling, filter and rinse thoroughly with deionized water. have to 64 g Thick-layer copper-plated microspheres, copper coating is about 200 Nano.

[0053] Thick electroless plating The composition of the copper liquid is : 100 g Copper sulfate, 480 g Sodium tartrate, 200 g Formaldehyde and 2.0 g Thiourea, pH Value is 12 .

[0054] (5) Preparation of light-weight high-conductivity paint

Combine the conductive microspheres prepared above with epoxy resin in accordance with 1.1: 1 The volume ratio is mixed to make a lightweight conductive paint. The preparation method adopts the method commonly used in the art, and will not be repeated.

[0055] After testing, carbon fiber / The coating thickness of epoxy resin composite is 0.05 Mm conductive coating, surface conductivity (Ω / Square) is 0.008 , Paint density ( g/cm3 )for 2.05 .

[0056] Example 3

Other steps are the same as in the embodiment 1 , The difference is:

( 1 ) Polyamine surface modification

by 25% Maleic anhydride and 75% Divinylbenzene copolymer 3.05 Micron microspheres are the starting microspheres (numbered TS00305-AN The microspheres are provided by Taizhou Tianshu New Material Technology Co., Ltd. The coefficient of variation of the particle size distribution of the microspheres is 5.5% ).

[0057] will 50g TS00305-AN Microspheres are added containing 500 Acetonitrile 1000ml In a round bottom flask, slowly add dropwise 5 g The temperature of the triethyltetraamine is slowly heated to the reflux of acetonitrile. Continue the reaction for three hours. After cooling, filter and rinse thoroughly with deionized water. By vacuum 100 Dry for two hours at °C. Then under nitrogen, heat to 205 ℃ for two hours. Polyamine modified microspheres. The microspheres were analyzed by infrared spectroscopy, and the maleic anhydride groups on the surface of the microspheres were completely converted into amine groups and maleamide.

[0058] (5) Preparation of light-weight high-conductivity paint

Combine the conductive microspheres prepared above with epoxy resin in accordance with 0.9 : 1 The volume ratio is mixed to make a lightweight conductive paint. The preparation method adopts the method commonly used in the art, and will not be repeated.

After testing, the coating thickness of the carbon fiber/ epoxy resin composite material is 0.05 mm conductive coating, the surface conductivity (Ω / square) is 0.045 , and the coating density ( g/cm3 ) is 1.98 .

Claims (8)

1. A light-weight high-conductivity paint, which is composed of conductive microspheres and a polymer binder, and is characterized in that: the ratio of conductive microspheres to polymer binder is 1:2 to 2:1 by volume; Conductive microspheres are silver- or copper-plated conductive microspheres produced through the following steps, namely, polymer microspheres → polyamine surface modification → microsphere surface support is activated on the catalyst → electroless plating surface metal coating → barrel metal plating Thick layer.
2. The light-weight high-conductivity coating of claim 1, wherein the polymer microspheres are copolymerized polymers with a high degree of cross-linking, the degree of cross-linking is greater than 20%, and the copolymer composition includes two Vinylbenzene, styrene, chloromethylstyrene, (meth)acrylate or maleic anhydride monomers are polymerized.
3. The light-weight high-conductivity coating of claim 1, wherein the polymer binder comprises epoxy resin, acrylic resin, phenol resin, polyimide resin, silicone resin or polyurethane Resin.
4. The light-weight high-conductivity coating of claim 1, wherein the particle size of the polymer microspheres before metallization is 1 micron-10 microns, and the coefficient of variation of particle size distribution is 1%- Between 20%.
5. The light-weight high-conductivity paint according to claim 1, wherein the coating thickness of the silver or copper-plated conductive microspheres is 20 nanometers to 500 nanometers.
6. The method for preparing a light-weight high-conductivity coating according to claim 1, characterized in that it comprises the following steps:

   (1) Preparation of conductive microspheres plated with silver or copper:

   (1.1) Polyamine surface modification, polymer microspheres with functional groups that can react with polyamine molecules react with polyamines to achieve amine modification on the surface of the microspheres. Polyamine molecules come from ethylenediamine, propylenediamine, and diethyl Triamine, triethyltetraamine, tetraethylpentamine, tris(2-aminoethyl)amine and low molecular weight polyethyleneimine (PEI),

   (1.2) The support catalyst on the surface of the microspheres is activated, and the polyamine-modified microspheres interact with platinum, palladium, and tin salts, and the salts are reduced to platinum, palladium, tin or mixed metal-coated activated base spheres by a reducing agent.

   (1.3) The electroless plating surface is plated with a thin metal layer, and the initial plating thickness of the silver or copper-plated conductive microspheres is 10 nanometers to 20 nanometers,

   (1.4) Electroless metal plating or electric barrel plating metal thick layer, the plating thickness of the silver or copper-plated conductive microspheres is 200 nanometers to 500 nanometers,

   (2) Preparation of light-weight and high-conductivity paint. Conductive microspheres and polymer binder are mixed to make light-weight conductive paint. The ratio of conductive microspheres to polymer binder is 1:2 to 2:1 by volume.
7. An application of the light-weight high-conductivity coating as claimed in claim 1 on the conductive coating of a non-conductive fiber composite material.
8. The application according to claim 7, wherein the lightweight conductive coating is used for coating of composite materials on airplanes, high-speed trains, unmanned aerial vehicles, wind turbine blades or automobiles.