CN111234657A

CN111234657A - Light high-conductivity coating and preparation method and application thereof

Info

Publication number: CN111234657A
Application number: CN202010261989.7A
Authority: CN
Inventors: 张竟; 郑国栋; 郑争
Original assignee: Taizhou Tianshu New Material Technology Co Ltd
Current assignee: Taizhou Tianshu New Material Technology Co Ltd
Priority date: 2020-04-05
Filing date: 2020-04-05
Publication date: 2020-06-05
Also published as: WO2021203656A1

Abstract

The invention relates to the field of high polymer materials, in particular to a high-conductivity coating, which consists of conductive microspheres and a high polymer adhesive, wherein: the volume ratio of the conductive microspheres to the polymer binder is 1:2 to 2:1, and the conductive microspheres are silver-plated or copper-plated conductive microspheres. The invention can approach the density of the carbon fiber reinforced composite material to the maximum extent without increasing the extra weight of the composite material product; the surface resistivity is as low as 0.01 omega/square, the conductivity is not lower than that of the conductive coating with copper powder filler, and the conductive coating can prevent lightning strike and eliminate the interference of static electricity on electromagnetic wave. The invention can be used for the surface coating of composite materials on airplanes, high-speed trains, unmanned planes, wind driven generator blades and automobiles which are made of the composite materials, and effectively solves the problem that the existing commercial conductive coating is not very suitable for the coating of the products.

Description

Light high-conductivity coating and preparation method and application thereof

Technical Field

The invention relates to the field of high polymer materials, in particular to a high-conductivity coating for a surface coating of a composite material on an airplane, a high-speed train, an unmanned aerial vehicle, a wind driven generator blade and an automobile which are made of the composite material, and a preparation method and application thereof.

Background

The fiber reinforced composite material has the advantages of high strength, light weight, corrosion resistance and the like, such as glass fiber, basalt fiber, special polymer fiber, carbon fiber and the like, is widely applied to manufacturing composite materials, and is generally adopted in the fields of airplanes, high-speed trains, automobiles, mechanical structures and the like. In particular, for some weight-sensitive applications, such as aircrafts like airplanes and unmanned planes, the light weight characteristic enables the composite material to show special advantages. For example, Carbon Fiber Reinforced Composite (CFRC) has a density of 1.5-1.8 g/cm in thin-walled carbon fiber, and the corresponding aluminum alloy has a density of 2.7 g/cm in thin-walled carbon fiber according to thin-walled carbon fiber. This has led to the increased adoption of CFRC for new generation aircraft manufacturing to reduce airframe weight for fuel economy purposes. With the expected increase in fuel prices and the demand for lower carbon emissions, the use of more composite materials in transportation is a growing trend.

However, resin-based fiber-reinforced composites have a significant feature of electrical insulation as compared to metallic materials. The traditional aluminum alloy has good conductivity, and the conductivity of the traditional aluminum alloy is 3.6 multiplied by 10⁷And (5) S/m. Carbon fiber composites are the best conductive, but still very low, of fiber composites. Such as carbon fiber reinforced epoxy resin composites having a conductivity of 1.38 x 10³And (5) S/m. The low conductivity makes the application of the conductive material in the airplane body face the risk of damage of the airplane body caused by lightning electric shock, even crash accidents. In addition, the bad conductors can cause static electricity to gather and interfere with electromagnetic waves, which affects communication and navigation. The electric spark generated by the electrostatic discharge can cause a series of potential safety hazards such as fire hazard. Therefore, how to design the airframe in the aircraft manufacturing by applying the carbon fiber composite material and increase the electrical conductivity of the airframe becomes an important subject. Especially with regard to the risk of lightning strikes, in the use of carbon fiber composite materials, bodies must be designed which are capable of conducting a sufficiently large amount of current. It is estimated that FAA certified commercial aircraft will be struck twice a year by lightning and that in the event of a large lightning strike, the aircraft must have the ability to conduct more than 200000 amps/millisecond. Without proper current conduction paths, mechanical damage, material thermal decomposition, and electronic component damage can result. Also associated with lightning strikes, e.g. coronaOptical flow, electrical current will exist continuously before and after a lightning strike.

During flight, static electricity can accumulate to generate electromagnetic influence, such as communication and navigation. Static electricity can originate from airborne particles, such as the impact of rain and snow on the body (i.e., triboelectric charging), or the flow of liquids and fuels. In addition to the effects of static electricity on electronic equipment, in severe cases, sparks can be generated, causing fire or explosion hazards.

At present, the aircraft using the carbon fiber composite material is usually added with copper or aluminum mesh on the surface layer of the composite material to increase the conductivity, and the technology can disperse the current from the surface of the aircraft body without going deep into the aircraft body, thereby effectively dealing with the damage of thunder or static electricity to the aircraft and the communication interference. However, when the density of copper is as high as 8.96 g/cm for carrying out the high-speed thin-wall carbon fiber composite material, the weight of the composite material layer is increased greatly due to the metal mesh, and the advantage of light weight of the carbon fiber composite material is greatly reduced. For this reason, the use of metal mesh in composite materials is limited to critical areas, such as those susceptible to lightning strikes or to electromagnetic interference. Even so, the overall weight of the body is inevitably increased. Furthermore, since the metal mesh is embedded in the composite material, once damage occurs, the integral parts of the composite material must be replaced. The cost and time for repair will be enormous.

A method for effectively avoiding the influence of lightning strike and static electricity is to coat a conductive coating on the surface of a machine body. Because the coating is on the surface, the surface coating may be damaged during a lightning strike, and only the coating needs to be replaced again without replacing the entire component during repair. The cost and time of repair can be greatly reduced.

The conductive coatings that are now commercially available are typically silver or copper powder filled epoxy, acrylic, phenolic, polyimide, silicone, or urethane coatings. Metal powder filled epoxy coatings typically achieve a low resistivity of about 0.1 omega/square at 0.05 mm thickness. However, the content of metal powder needs to be more than 50% by volume, so that the density of the coating is as high as about 5g/cm during thin strip production, which leads to a considerable increase in the total weight of the aircraft. On the other hand, the lightweight effect of the composite material is greatly affected. In addition, high metal powder fill ratios can result in impaired adhesion and mechanical properties of the coating. This may result in the coating not meeting minimum specification requirements for aviation flight. Thus, the current commercial conductive coatings are not well suited for aircraft coatings.

Disclosure of Invention

In view of the above-mentioned drawbacks and disadvantages of the prior art, an object of the present invention is to provide an electrically conductive coating material capable of giving a sufficiently high electrical conductivity, and having a relatively low density and a sufficiently high adhesion and mechanical strength, and a method for preparing the same.

Specifically, the inventors provide the following technical solutions:

firstly, the inventor provides a light high-conductivity coating, which consists of conductive microspheres and a high-molecular adhesive, wherein: the ratio of the conductive microspheres to the polymer binder is 1:2 to 2:1 by volume, and the preferred range can be between 0.7/1 and 1/0.7, but is not limited to the listed range; the conductive microsphere is a silver or copper plated conductive microsphere prepared by the following steps of polymer microsphere → polyamine surface modification → microsphere surface carrier activation → chemical plating surface metal thin layer → barrel plating metal thick layer.

The ideal conductive coating needs to give sufficiently high conductivity, relatively low density and sufficiently high adhesion and mechanical strength, and such ideal conductive coatings have been the goal of much research by many scientists. The invention herein provides a solution for preparing such ideal conductive coatings. Firstly, preparing a uniform micron-sized polymer microsphere, wherein the surface of the microsphere has proper functional groups; further processing the surface of the microsphere to make the microsphere become an activated base sphere which can be chemically plated; after the activated base ball is plated with a layer of copper or silver plating layer with proper thickness after chemical plating or/and electric barrel plating, the conductive microsphere-the polymer microsphere with evenly distributed particles and copper or silver plated on the surface is formed. And then mixing the conductive microspheres with high polymer resins such as epoxy resin, polyacrylic resin, phenolic resin, polyimide resin, organic silicon resin, polyurethane resin and the like in a proper proportion to prepare the light high-conductivity coating.

Generally, polymer microspheres with the diameter of 3-10 microns are selected as base spheres, and 100-300 nanometer metal layers are plated on the surfaces of the base spheres to prepare the conductive microspheres. Examples are: the density of the polymer-based spheres was obtained by thin-wall chemical vapor deposition, such as by thin-wall chemical vapor deposition, and then thin-wall chemical vapor deposition, such as by thin-wall chemical vapor deposition, or by thin-wall chemical vapor deposition. And after the conductive microspheres and the resin are mixed according to the volume ratio of 1:1 to prepare the conductive coating, carrying out thin film forming on the conductive coating according to the density of 1.85-2.0 g/cm. The conductive coating prepared by the method can reach the conductivity equivalent to that of a copper powder filled resin coating, and the density is only about 40 percent of that of the copper powder filled resin coating. Therefore, the lightweight, highly conductive coating of the present invention can maximally approach the density of Carbon Fiber Reinforced Composites (CFRC) without adding additional weight to application products such as aircraft.

Preferably, the polymer microspheres in the invention are copolymerized polymers with high crosslinking degree, and the copolymer composition comprises divinylbenzene, styrene, chloromethylstyrene, (meth) acrylate or maleic anhydride monomers. The conductive base ball is composed of high-crosslinking degree copolymerized macromolecules, the crosslinking degree is more than 20%, and the ideal crosslinking degree is more than 50%. The copolymer polymer contains active functional groups such as a benzyl chloride group, a styryl group, a (methyl) acrylic group, a maleic anhydride group, and the like. The other monomer of the copolymerized polymer microsphere may be a monomer having an inactive functional group such as divinylbenzene, styrene, etc., the active group on the microsphere may be chemically reacted with a polyamine to form a polyamine-modified microsphere, the polyamine compound may be a linear or branched polyamine, and may be ethylenediamine, propylenediamine, diethyltriamine, triethyltetramine, tetraethylpentamine, tris (2-aminoethyl) amine, low molecular weight Polyethyleneimine (PEI), etc., and a polyamine compound of triamine or more is more preferable.

More preferably, the divinylbenzene content of the polymeric microspheres of the present invention is between 20% and 90%.

Preferably, the polymer binder in the present invention includes, but is not limited to, epoxy resin, acrylic resin, phenolic resin, polyimide resin, silicone resin, polyurethane resin, or the like.

The particle size of the polymer microsphere before metal plating is 1-10 microns, preferably 3-8 microns, most preferably 4-6 microns. The coefficient of variation of the particle size distribution is less than 20%, preferably less than 10%, and most preferably less than 4%.

Preferably, the plating thickness of the conductive silver or copper-plated microspheres in the present invention is 20 nm to 500 nm.

The invention also provides a preparation method of the light high-conductivity coating, which comprises the following steps:

(1) preparing silver or copper-plated conductive microspheres:

(1.1) polyamine surface modification

The polymer microsphere is chemically modified to be a polyamine-modified sphere surface. The copolymer comprises divinylbenzene, styrene, chloromethyl styrene, (methyl) acrylate and maleic anhydride monomers which are polymerized into microspheres which have functional groups capable of reacting with polyamine molecules. Reacting the microsphere containing benzyl chloride groups with polyamine, wherein the reaction can be carried out in multiple steps to achieve the microsphere surface modified by amino groups, the benzyl chloride can react with amine and secondary amine, and the modification density depends on the density of the benzyl chloride on the microsphere surface. The high amine group density is more beneficial to the next step of electroless plating.

Styrene-based microspheres are reacted with concentrated sulfuric acid and then with excess polyamine alkane to perform the following series of multi-step reactions:

the microspheres obtained by polymerizing (methyl) acrylate with non-active functional group monomers can be hydrolyzed to convert the (methyl) acrylate groups on the surfaces of the microspheres into (methyl) acrylic groups, and then the (methyl) acrylic groups are reacted with polyamine molecules to form (methyl) acrylamide salts. After the amine salt is treated at high temperature, more stable (meth) acrylamide can be formed.

The maleic anhydride functionalized microspheres can directly react with polyamine molecules, and after the maleic anhydride reacts with the polyamine molecules, stable maleimide is formed through high-temperature treatment, and the microspheres are modified to be polyamine surfaces.

In the reaction between polyamine and the functional group on the surface of the microsphere, except that the reaction between (methyl) acrylic acid group and polyamine molecule is acid-base reaction, other reaction is nucleophilic reaction, and the solvent of the reaction has a bond function on the reaction speed. In the invention, the relatively low polarity of the unmodified microsphere is considered, and the solvent is selected from an organic solvent or a mixed organic solvent, so that the microsphere can be wetted and nucleophilic reaction can be promoted. The organic solvent may be a non-polar high dipole moment molecule such as DMF, DMSO, acetonitrile, and the reaction is carried out under reflux with heating to promote the reaction to proceed rapidly and to cover the surface of the microspheres with a maximum amount of polyamine molecules. In addition, the amine propionate can form more stable amido bond under heating, so that the subsequent metal coating is combined on the surface of the microsphere more firmly. Because the microsphere surface modification reaction is carried out in an organic solvent and at a high temperature, the microspheres must have higher stability to the organic solvent, otherwise the microspheres may be dissolved or swelled, and the morphology of the microspheres is completely destroyed. For microspheres with high stability in organic solvents, a sufficiently high degree of crosslinking is necessary. Such as a degree of crosslinking above 20%.

Polyamine modified microspheres must be washed several times with a low boiling solvent that is miscible with the reaction solvent, i.e., DMF, DMSO, acetonitrile, and filtered to remove DMF, DMSO and excess polyamine molecules. The low boiling point solvent can be methanol, ethanol, acetone, etc., the washed microspheres can be used for the subsequent surface activation reaction after vacuum drying, and any residual solvent such as DMF, DMSO and unreacted polyamine molecular molecules can cause the defects of the metal coating.

The polarity of the surface of the polyamine modified microsphere is greatly changed compared with that of the original microsphere, and the microsphere has good hydrophilicity. The microspheres can be easily dispersed in an aqueous medium, which simultaneously indicates that the microspheres have high surface energy, so that the microspheres are easier to be subjected to subsequent surface activation and metal plating. The invention uses high functional group density Tianshu microsphere product, and can carry out high temperature modification reaction based on high crosslinking degree of microsphere. So that the density of the amine groups on the surface of the microsphere reaches the highest possible degree. The amido groups are combined in the microspheres in a covalent bond mode, and the stability and firmness are realized. The adhesion force between the metal coating and the microsphere surface obtained subsequently is very strong. The method brings great convenience to the construction of preparing the conductive coating and the conductive coating, can greatly avoid the problems of stripping a metal coating from the microspheres and the like due to shearing force in the construction of preparing the conductive coating and the conductive coating, and finally provides reliable guarantee for the coating quality.

(1.2) activation of microsphere surface Carrier in catalyst

Activating the microsphere surface carrier catalyst. The polyamine modified microspheres react with platinum, palladium and tin salts, and the salts are reduced into platinum, palladium, tin or mixed metal-coated activated base spheres by a reducing agent.

The polyamine-modified microspheres are subjected to a conventional electroless surface activation step to activate the microspheres. The activation step is also referred to as the catalysis step. I.e., catalyst particles, typically tin, platinum, palladium, or mixtures thereof, such as tin/palladium, are attached to the surface of the microspheres. The catalyst particles are usually formed by reducing salts of these metals as starting reactants to form nanosized metal particles, which are firmly attached to the surface of the microspheres. The reason for the strong attachment is the high polarity (i.e., high surface energy) imparted to the microspheres by the amine groups on the microsphere surface. In addition, the catalyst metal ions and amine groups can generate complexes, a large amount of catalyst metal ions are attached to the surface of the microsphere, and when the catalyst metal ions act with a reducing agent, the metal ions are reduced into metal nano particles and are attached to the surface of the microsphere in situ.

The solution of the activated polyamine-modified microspheres is usually composed of a sulfate or hydrochloride salt of palladium, platinum, tin, and the activation reaction is carried out in water, a protic organic solvent such as methanol, ethanol, or a solvent thereof, so that the activation solution is formulated in the same solvent. In view of the low solubility of such salts or the tendency to hydrolyze and precipitate, ammonia is usually added to the activation solution to form an ammonia salt complex, thereby producing an activation solution that is stable at the pH required for the reaction.

After the activating solution is mixed with the microsphere modified by polyamine, amine on the surface of the microsphere is taken as a complexing agent to participate in a reaction to replace ammonia in the ammonia salt complex, so that the ammonia salt complex is bonded to the surface of the microsphere, and the reaction is favorable for concentrating a catalyst on the surface of the microsphere. After the activating solution is mixed with the polyamine modified microsphere, a proper reducing agent, such as dimethylamine borane (DMAB), is added, and the reducing agent can reduce metal salt ions, such as Pd (II), into nano metal palladium at a proper temperature (lower than 100 ℃) so as to be firmly bonded on the surface of the microsphere.

(1.3) electroless plating of a thin layer of metal

The thickness of the plating layer of the silver or copper plated conductive microsphere is 20 to 500 nanometers.

The microspheres attached with the metal nano particles are activated base spheres, and the activated base spheres can be well soaked in the water-based chemical plating solution. The activated base sphere can be used for producing metal plating by the action of common chemical plating solution, such as copper, silver, nickel, gold and other metals, and the metal nano particles attached to the microspheres are the catalyst activation points of the subsequent chemical plating. The metal plating first nucleates at these points and develops a metal coating. The quality of the metal plating layer, such as mechanical strength, adhesion of the metal plating layer to the base sphere, surface coverage, finish, etc., is related to the size and density of the metal nanoparticles on the activated base sphere. The fine and densely distributed metal nano particles can produce a high-quality metal coating, and the larger and sparsely distributed metal nano particles can cause the defects of the metal coating and even can not obtain a complete metal coating. Generally, the metal nanoparticles are preferably 10 nm or less, and most preferably about 4 nm. And the denser the metal nanoparticles distribution density, the better. The invention adopts the initial microsphere modified by high functionality and high crosslinking degree, so that the initial microsphere can bear relatively violent amination reaction conditions, and the microsphere with high metal nano-particle density can be obtained. The activated base ball has very good hydrophilicity, and does not need to add wetting agents required by the conventional plastic surface chemical plating in the further chemical copper plating, silver plating and other processes. The wetting agent is usually a surfactant, and is easily adsorbed on the surface of the microsphere, so that the deposition of metal on the surface of the microsphere is influenced, and coating defects are generated. The coating on the microsphere is very strongly bonded on the surface of the microsphere, so that a defect-free surface coating can be formed.

The activated base spheres can be plated with a relatively thin metal plating layer by a common chemical plating method, namely, one-step plating, so that the microspheres have primary conductivity. A thin initial coating, typically 10-20 nm. The electroless plating can be carried out at elevated temperature to increase the metal deposition rate, the electroless plating being copper or silver.

(1.4) electroless plating of a thick layer of metal or electrobarrel plating of a thick layer of metal

The chemical plating method can also obtain the required thick plating layer at one time, and the thick plating layer is usually 200-500 nm. However, the precise coating thickness is difficult to control by chemical plating, and for the application with relaxed coating thickness requirement, one-time chemical plating can be adopted. Otherwise, the electro-barrel plating thickened coating can be adopted.

Further increases the thickness of the plating layer by an electrochemical barrel plating method. The thin layer plating microsphere with primary conductive performance can be thickened by a common electroplating method, namely secondary plating. The specific method of electroplating adopts a barrel plating method that the object to be plated does not need to be fixedly connected with an electrode. The thickness of the plated layer can be increased or decreased according to the requirement of conductivity, which can usually reach 180-500 nm. Considering that the change of the thickness of the plating layer can greatly affect the density of the conductive microspheres, the plating layer increases the conductivity, but the density of the microspheres is obviously increased. Therefore, the conductivity and microsphere density must be balanced in a comprehensive manner for practical reference.

The thickness of the plating layer can be obtained from the weight gain of the plated microspheres through theoretical calculation. The weight gain of the microspheres can be estimated from the electroplating time and the current intensity, and can also be obtained by final weighing. Taking 5 micron microspheres as an example, the density of the microspheres before plating is 1.05g/cm and the density is increased to 1.237 g/cm for carrying out thin film fruit-bearing thin. After the second electroplating, the density of the microspheres is increased to 2.68 g/cm for carrying out the flash evaporation when the copper plating layer of the microspheres is increased to 200 nm. If one kilogram of 5 micron microspheres were first plated with copper and thickened by 20 nanometers, the total weight of the microspheres increased to 1.21 kg. After secondary copper plating and thickening of 200 nm, the total weight of the microspheres is increased to 3.22 Kg. And on the contrary, the thickness of the plating layer is estimated according to the weight increase of the microspheres, so that the electroplating time is determined.

The following table shows the relationship between the weight of one kg of 5 μm microspheres plated with copper twice and the silver weight and the particle size of the microspheres:

(2) preparing a light high-conductivity coating:

in the invention, the conductive microspheres and the high molecular binder are mixed to prepare the light conductive coating, the ratio of the conductive microspheres to the high molecular binder is a key index of the conductive coating, and the conductivity of the conductive coating is severely reduced even the conductive coating is not conductive due to too low ratio of the conductive microspheres. And if the proportion of the conductive microspheres is too high, the specific gravity of the conductive coating is too high, so that the effect of applying the conductive coating to the vehicle or aircraft needing light weight is greatly reduced. In addition, the mechanical strength of the coating is also damaged due to the excessively high proportion of the conductive microspheres, and the conductivity, the density and the mechanical property of the coating of the conductive coating are balanced under the condition that the volume ratio of the conductive microspheres to the binder is about 1: 1. Wherein, the proportion of the applications with different performance requirements can be selected, and the range of the application can be between 0.7/1 and 1/0.7. Taking epoxy and 5 micron/0.2 micron copper plating as examples, the following table shows the relationship between the paint density and the surface conductivity of the conductive coating.

Wherein the surface conductivity value is measured from a conductive coating layer of the carbon fiber/epoxy resin composite material with a coating thickness of 0.05 mm.

The invention also provides application of the light high-conductivity coating on a conductive coating of a non-conductive fiber composite material. The application product can be protected from lightning strikes or electromagnetic waves.

Preferably, in the invention, the light conductive coating is used for coating composite materials on airplanes, high-speed trains, unmanned planes, wind driven generator blades or automobiles.

Compared with the prior art, the invention has the advantages that:

1. the present invention maximizes the density of the Carbon Fiber Reinforced Composite (CFRC) without adding additional weight to the aircraft; and the surface resistivity is as low as 0.01 omega/square, and the conductivity is not lower than that of the copper powder filler.

2. Compared with the common conductive coating, the coating has high mechanical strength. The coating is suitable for application places with strict coating strength and durability, such as airplane wings, high-speed trains, wind power generation blades and the like. Since a general conductive coating material usually contains about 50% by volume of a conductive filler (e.g., silver powder or copper powder), since the filler particles are irregular in shape and high in specific gravity, and are easily aggregated and attached to each other, the binder cannot be mixed between the particles, the periphery of the particles cannot sufficiently contact with the binder, and the strength in the binder layer is reduced. Therefore, the strength can only be ensured by reducing the conductive filler and giving up certain conductive performance. The conductive microspheres with high strength and high uniformity particles of the invention can not deform due to mutual extrusion even under the condition of high mixture ratio. Because of its uniform and spherical characteristics, it is ensured that the microspheres are always filled with sufficient binder to maintain strong bond line strength. And the adhesive strength is not reduced when the proportion is higher.

3. The light high-conductivity paint provided by the invention is used as a conductive coating of a non-conductive fiber composite material, and can be used for surface coatings of composite materials on airplanes, high-speed trains, unmanned aerial vehicles, wind driven generator blades and automobiles manufactured by the composite materials so as to prevent lightning and eliminate the interference of static electricity on electromagnetic waves.

Detailed Description

The present invention will be described in more detail with reference to examples. It should be noted that the following examples are merely 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 which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

In the invention, all parts and percentages are weight units, and all equipment, raw materials and the like can be purchased from the market or are commonly used in the industry, if not specified. The methods in the following examples are conventional in the art unless otherwise specified.

Example 1

(1) Polyamine surface modification

5-micron microspheres copolymerized by 25% of chloromethyl styrene and 75% of divinylbenzene are taken as initial microspheres (the microspheres are TS005CI microspheres provided by Taizhou Tianshu new material science and technology Co., Ltd., and the coefficient of variation of the particle size distribution of the microspheres is 2.8%).

20g of TS005CL and 2.5g of tris (2-aminoethyl) amine were added to a 500ml round-bottom flask containing 250ml of DMF. The solution was heated to 105 ℃ with magnetic stirring and the reaction was continued for 5 hours. After cooling, the mixture was filtered and thoroughly washed with deionized water. Drying for two hours at 100 ℃ in vacuum to obtain the polyamine modified microspheres. And (4) analyzing the microspheres by infrared spectroscopy, wherein benzyl chloride groups on the surfaces of the microspheres are completely converted into amino groups.

(2) Activation of microsphere surface carrier in catalyst

20g of polyamine-modified TS005CL microspheres obtained by the above polyamine surface modification reaction were added to a 5000ml round-bottomed flask containing 1000ml of distilled water. The solution was heated to 60 ℃ with electromagnetic stirring, and 1000ml of 0.05% (NH) were added₂PdCl₄And (3) solution. The reaction was continued for 30 minutes. After cooling, the mixture was filtered and thoroughly washed with deionized water.

The above microspheres loaded with palladium salt were added to a 5000ml round bottom flask containing 1000ml distilled water. The solution was heated to 60 ℃ with magnetic stirring, 2000ml of 10% dimethylamine borane (DMAB) was added and the reaction was continued for 20 minutes. After cooling, the mixture was filtered and thoroughly washed with deionized water. Obtaining the palladium activated microspheres.

(3) Copper-plated thin layer on chemical plating surface

20g of the palladium-activated microsphere microspheres obtained by the above reaction were added to a 5000ml round bottom flask containing 1000ml of a thin electroless copper plating solution. The solution was heated to 50 ℃ with magnetic stirring. The reaction was continued for 40 minutes. After cooling, the mixture was filtered and thoroughly washed with deionized water. 24g of thin-layer copper-plated microspheres are obtained, and the copper plating layer is about 20 nanometers.

The chemical copper plating solution for thin plating consists of 4g of copper sulfate, 25 g of sodium tartrate, 10g of formaldehyde and 0.1 g of thiourea, and the pH value is 12.

(4) Barrel plating of thick metal layer

500 g of the thin copper plating microspheres obtained by the thin plating method is added into a four-liter small barrel plating device, the rotating speed is 20/minute, the current is 100 ampere times, and electrolysis is carried out for 9 hours. 1.5 k g thick layers of copper-plated microspheres were obtained. The copper plating is about 190 nm. The copper plating solution is a common electroplating solution sold in the market.

(5) Preparation of light high-conductivity coating

Mixing the prepared conductive microspheres with epoxy resin according to the weight ratio of 0.8: 1 volume ratio to prepare the light conductive coating. The preparation method adopts a general method in the field and is not described in detail.

The detection shows that the carbon fiber/epoxy resin composite material is coated with a conductive coating layer with the thickness of 0.05 mm, the surface conductivity (omega/square) is 0.15, and the coating density (g/cm)³) Is 1.86.

Example 2

The other steps are the same as example 1, except that:

(1) polyamine surface modification

65% divinylbenzene polymerized 4.5 micron microspheres were used as the starting microspheres (TS 0045-Y microsphere number provided by Techno Tianshu New Material science and technology Co., Ltd., Taizhou, particle size distribution variation coefficient of the microspheres was 3.0%).

50g of TS0045-Y microspheres are added into a 1000ml round-bottom flask containing 500 acetonitrile, 3ml of 98% concentrated sulfuric acid is slowly dropped, and the mixture is electromagnetically stirred for 5 hours at room temperature. 10ml of anhydrous Polyethyleneimine (PEI) having a molecular weight of 800 were then slowly added dropwise. After the addition was completed, the temperature was slowly raised to acetonitrile reflux. The reaction was continued for three hours. After cooling, the mixture was filtered and thoroughly washed with deionized water. Drying for two hours at 100 ℃ in vacuum to obtain the polyamine modified microspheres. The infrared spectrum analysis of the microsphere shows that the styryl group on the surface of the microsphere is completely converted into amino group.

(3) Chemical plating surface copper-plated thin layer and thick layer copper-plated

20g of palladium activated microsphere microspheres were added to a 5000ml round bottom flask containing 1000ml of thick electroless copper plating solution. The solution was heated to 50 ℃ with magnetic stirring. The reaction was continued for 5 hours. After cooling, the mixture was filtered and thoroughly washed with deionized water. 64 g of thick-layer copper-plated microspheres were obtained, the copper plating being about 200 nm.

The thick chemical copper plating solution consists of 100 g of copper sulfate, 480 g of sodium tartrate, 200 g of formaldehyde and 2.0 g of thiourea, and the pH value is 12.

(5) Preparation of light high-conductivity coating

And mixing the prepared conductive microspheres with epoxy resin according to the volume ratio of 1.1: 1 to prepare the light conductive coating. The preparation method adopts a general method in the field and is not described in detail.

Through detection, the carbon fiber/epoxy resin composite material is coated with a conductive coating layer with the thickness of 0.05 mm, the surface conductivity (omega/square) is 0.008, and the coating density (g/cm)³) Was 2.05.

Example 3

The other steps are the same as example 1, except that:

(1) polyamine surface modification

The 3.05 micron microsphere copolymerized by 25 percent of maleic anhydride and 75 percent of divinylbenzene is taken as AN initial microsphere (the microsphere with the serial number of TS00305-AN is provided by Techno material science and technology Limited of Tend, Taizhou, and the coefficient of variation of the particle size distribution of the microsphere is 5.5 percent).

50g of TS00305-AN microspheres are added into a 1000ml round-bottom flask containing 500 acetonitrile, 5g of triethyltetramine is slowly dropped, and the temperature is slowly raised until the acetonitrile is refluxed. The reaction was continued for three hours. After cooling, the mixture was filtered and thoroughly washed with deionized water. Dried for two hours at 100 ℃ under vacuum. Then, the mixture was heated to 205 ℃ for two hours under nitrogen. Polyamine modified microspheres. The microsphere is analyzed by infrared spectroscopy, and the maleic anhydride group on the surface of the microsphere is completely converted into an amino group and maleic amide.

(5) Preparation of light high-conductivity coating

Mixing the prepared conductive microspheres with epoxy resin according to the weight ratio of 0.9: 1 volume ratio to prepare the light conductive coating. The preparation method adopts a general method in the field and is not described in detail.

The detection proves that the carbon fiber/epoxy resin composite material is coated with a conductive coating layer with the thickness of 0.05 mm, the surface conductivity (omega/square) is 0.045, and the coating density (g/cm)³) Is 1.98.

Claims

1. A light high-conductivity coating is composed of conductive microspheres and a high-molecular adhesive, and is characterized in that: the volume ratio of the conductive microspheres to the polymer binder is 1:2 to 2: 1; the conductive microsphere is a silver or copper plated conductive microsphere prepared by the following steps of polymer microsphere → polyamine surface modification → microsphere surface carrier activation → chemical plating surface metal thin layer → barrel plating metal thick layer.

2. The light-weight high-conductivity coating according to claim 1, wherein the polymer microspheres are high-crosslinking degree copolymer polymers, the crosslinking degree is more than 20%, and the copolymer composition comprises divinylbenzene, styrene, chloromethylstyrene, (meth) acrylate or maleic anhydride monomers.

3. The lightweight high-conductivity coating according to claim 1, wherein the polymer binder comprises epoxy resin, acrylic resin, phenolic resin, polyimide resin, silicone resin, or polyurethane resin.

4. The light weight high conductivity paint as claimed in claim 1, wherein the particle size of the polymer microsphere before plating metal is 1-10 microns, and the variation coefficient of the particle size distribution is 1-20%.

5. The light weight high conductivity paint according to claim 1, wherein the plating thickness of the silver or copper plated conductive microspheres is 20 nm to 500 nm.

6. The method for preparing the light-weight high-conductivity coating according to claim 1, comprising the following steps:

(1) preparing silver or copper-plated conductive microspheres:

(1.1) polyamine surface modification, reacting polymer microspheres with functional groups capable of reacting with polyamine molecules with polyamine to obtain amino modified microsphere surfaces, wherein the polyamine molecules are selected from ethylenediamine, propylenediamine, diethyltriamine, triethyltetramine, tetraethylpentamine, tri (2-aminoethyl) amine and low molecular weight Polyethyleneimine (PEI),

(1.2) activating a carrier catalyst on the surface of the microsphere, reacting the polyamine modified microsphere with platinum, palladium and tin salts, reducing the salts into platinum, palladium, tin or mixed metal-coated activated base spheres by using a reducing agent,

(1.3) chemically plating a metal thin layer on the surface, wherein the initial plating thickness of the conductive microspheres plated with silver or copper is 10-20 nanometers,

(1.4) chemically plating a metal thick layer or electrically plating a metal thick layer in a rolling way, wherein the plating thickness of the conductive microspheres plated with silver or copper is 200-500 nanometers,

(2) preparing the light high-conductivity coating, mixing the conductive microspheres with a high-molecular binder to prepare the light conductive coating, wherein the volume ratio of the conductive microspheres to the high-molecular binder is 1:2 to 2: 1.

7. Use of the lightweight highly conductive coating according to claim 1 in the conductive coating of non-conductive fibre composites.

8. Use according to claim 7, wherein the lightweight conductive coating is used for coating composite materials on aircraft, high speed trains, drones, wind turbine blades or automobiles.