阅读说明：本技术 一种轻质碳基电磁屏蔽涂料及其制备方法 (Light carbon-based electromagnetic shielding coating and preparation method thereof ) 是由 罗振涛 王才良 何惊华 王浩继 龙昌 丁铁伢 刘柳 韦芳 于 2021-08-30 设计创作，主要内容包括：本发明提供了一种轻质碳基电磁屏蔽涂料及其制备方法,包括如下重量百分比的组分：电磁屏蔽填料：10%-25%,电磁屏蔽填料分散剂：2%-5%,聚氨酯改性环氧树脂：28%-40%,固化剂：4%-8%,稀料：25%-35%,助剂：2%-5%；其中电磁屏蔽填料包括三维石墨烯和镀镍碳纳米管中的一种或两种。本发明在碳基电磁屏蔽涂料的基础上,引入金属Ni,构筑Ni/C多元复合电磁屏蔽填料,达到保持金属系电磁屏蔽涂料较高的屏蔽效能且能够降低涂层密度的目的。此外,在Ni/C多元复合电磁屏蔽填料中引入三维石墨烯,进一步降低了涂层的面密度,而且借助三维石墨烯的分散作用,促进了镀镍碳纳米管在树脂体系中的均匀分散,显著提升了其导电性和涂层的电磁屏蔽性能。(The invention provides a light carbon-based electromagnetic shielding coating and a preparation method thereof, wherein the light carbon-based electromagnetic shielding coating comprises the following components in percentage by weight: electromagnetic shielding filler: 10% -25%, electromagnetic shielding filler dispersant: 2% -5%, polyurethane modified epoxy resin: 28% -40%, curing agent: 4% -8%, diluent: 25% -35%, auxiliary agent: 2% -5%; the electromagnetic shielding filler comprises one or two of three-dimensional graphene and nickel-plated carbon nanotubes. On the basis of the carbon-based electromagnetic shielding coating, the invention introduces metal Ni to construct Ni/C multi-element composite electromagnetic shielding filler, thereby achieving the purposes of keeping higher shielding efficiency of the metal electromagnetic shielding coating and reducing the density of the coating. In addition, the three-dimensional graphene is introduced into the Ni/C multi-element composite electromagnetic shielding filler, so that the surface density of the coating is further reduced, the uniform dispersion of the nickel-plated carbon nano tube in a resin system is promoted by virtue of the dispersion effect of the three-dimensional graphene, and the conductivity and the electromagnetic shielding performance of the coating are remarkably improved.)

1. The light carbon-based electromagnetic shielding coating is characterized by comprising the following components in percentage by weight: electromagnetic shielding filler: 10% -25%, electromagnetic shielding filler dispersant: 2% -5%, polyurethane modified epoxy resin: 28% -40%, curing agent: 4% -8%, diluent: 25% -35%, auxiliary agent: 2% -5%; the electromagnetic shielding filler comprises one or two of three-dimensional graphene and nickel-plated carbon nanotubes.

2. The lightweight carbon-based electromagnetic shielding paint according to claim 1, wherein: the electromagnetic shielding filler dispersing agent is one or more of DS-172, AKN-2076, SY-2076 and AD 8301.

3. The lightweight carbon-based electromagnetic shielding paint according to claim 1, wherein: the polyurethane modified epoxy resin comprises one or more of EPU-301, EPU-303 and EPU-133L.

4. The lightweight carbon-based electromagnetic shielding paint according to claim 1, wherein: the curing agent comprises one or more of T-31, MH-112 and NX-2040.

5. The lightweight carbon-based electromagnetic shielding paint according to claim 1, wherein: the thin material comprises one or more of butyl acetate, cyclohexanone, ethyl acetate and xylene.

6. The lightweight carbon-based electromagnetic shielding paint according to claim 1, wherein: the auxiliary agent comprises a leveling agent and an antifoaming agent.

7. The light carbon-based electromagnetic shielding coating as claimed in any one of claims 1 to 6, wherein the three-dimensional graphene is prepared from graphene by a sol-gel method, and the preparation steps are as follows:

1) graphene pretreatment: in N₂Carrying out heat treatment on the graphene at the temperature of more than 800 ℃ for 15-25 min under protection;

2) preparing three-dimensional graphene hydrogel: adding water into the pretreated graphene to prepare a solution, then adding vitamin C into the solution, continuously stirring the solution uniformly after dissolving, performing ultrasonic dispersion, and reacting the prepared solution in an oven at the temperature of 60-80 ℃ for 3-4 hours to obtain three-dimensional graphene hydrogel;

3) preparing three-dimensional graphene: freezing the three-dimensional graphene hydrogel washed by distilled water, then putting the three-dimensional graphene hydrogel into a freeze dryer for freeze drying, and finally freeze dryingSubjecting the graphene aerogel to Ar at 1150-1250 DEG C₂And carrying out heat treatment in the atmosphere for more than 2 hours to obtain the three-dimensional graphene.

8. The light-weight carbon-based electromagnetic shielding coating as claimed in any one of claims 1 to 6, wherein the nickel-plated carbon nanotube is obtained by plating metal nickel on the outer wall of the carbon nanotube by a chemical plating process, and the preparation steps are as follows:

1) pretreating the carbon nano tube: in N₂Placing the carbon nano tube above 800 ℃ for heat treatment for 15-25 min under protection;

2) surface sensitization and activation of the carbon nano tube: putting the pretreated carbon nano tube into a mixed solution composed of stannous chloride and dilute hydrochloric acid, stirring for sensitization, filtering the carbon nano tube, washing with deionized water, and then putting the carbon nano tube into a mixed solution composed of palladium chloride and dilute hydrochloric acid, stirring for activation treatment;

3) nickel plating of the carbon nano tube: and (3) putting the sensitized and activated carbon nano tube into a nickel sulfate and sodium hydrogen phosphate solution at 70-90 ℃ for chemical nickel plating, continuously dropwise adding ammonia water to control the pH value of the solution to be 7.8 +/-0.2, filtering, washing and drying to obtain the nickel-plated carbon nano tube.

9. The preparation method of the lightweight carbon-based electromagnetic shielding coating of any one of claims 1 to 8, characterized by comprising the following steps:

s1, dissolving the polyurethane modified epoxy resin subjected to drying treatment by using a thinner, then adding the electromagnetic shielding filler, the electromagnetic shielding filler dispersing agent and the auxiliary agent while stirring, and dispersing uniformly to obtain an electromagnetic shielding filler dispersing solution; if the electromagnetic shielding fillers are multiple, respectively preparing electromagnetic shielding filler dispersion liquid;

s2, mixing the electromagnetic shielding filler dispersion liquid uniformly, adding a curing agent, and stirring uniformly to obtain the light carbon-based electromagnetic shielding coating.

10. The preparation method of the lightweight carbon-based electromagnetic shielding coating according to claim 9, wherein: when the raw materials in the S1 are mixed to prepare the electromagnetic shielding filler dispersion liquid, the dispersion liquid is dispersed for 15 to 20 minutes at the stirring speed of 500-600r/min, and in the S2, the stirring time is 20 to 30 minutes after the curing agent is added.

Technical Field

The invention belongs to the technical field of materials, and relates to an electromagnetic shielding coating, in particular to a light carbon-based electromagnetic shielding coating and a preparation method thereof.

Background

The rapid development of electronic information technology has led to a rapid increase in the number of various wireless communication devices and a significant increase in the frequency of use of electronic devices. They also generate a large amount of electromagnetic radiation while bringing convenience to the production and life of people. At present, electromagnetic radiation is listed as a fourth pollution source by the world health organization, and not only can irreversibly affect human health, but also can cause interference to normal operation of electronic equipment. The electromagnetic environment which is getting worse and worse is attracting wide attention of all countries, and the preparation of electromagnetic shielding materials with excellent performance is very important in both civil and military fields.

The electromagnetic interference means that electromagnetic signals emitted by the electronic and electrical equipment in operation disturb the normal operation of other surrounding electrical equipment and cause certain radiation damage to surrounding organisms. Electromagnetic shielding (EMI) refers to the situation where, in order to avoid electromagnetic interference and ensure good electromagnetic compatibility among electronic devices, certain conductive or magnetic materials are used to limit the electromagnetic wave energy in a specific space or control the electromagnetic radiation amount within a certain specified range, so as to ensure that electronic devices have a certain ability to resist external electromagnetic interference and do not radiate electromagnetic wave energy too much.

The traditional electromagnetic shielding material is mainly a metal sheet or a metal cover made of copper, iron and the like, and the metal material can concentrate magnetic flux on the surface of the material so as to prevent the transmission of electromagnetic waves. However, these materials have a large mass, are prone to corrosion, have a limited range of adjustment of shielding effectiveness, and their use temperature is often limited by the curie temperature, and cannot be used in high temperature environments. In addition, the shielding mechanism of the metal material is mainly reflection, and the electromagnetic wave pollution is not eliminated. Therefore, it is necessary to prepare a novel material with light weight, thin thickness, good environmental tolerance, excellent mechanical properties, and electromagnetic shielding properties and wave absorption properties.

At present, more and more researches are focused on the research of polymer-based electromagnetic shielding composite materials and electromagnetic shielding coatings. The polymer matrix material has little loss and reflection to electromagnetic wave, and the purpose of shielding electromagnetic wave is achieved by filling conductive filler in the polymer matrix material. The commonly used conductive fillers are of three types, one is a metal filler, a metal fiber or a metal nanoparticle; one is a conductive polymer; the other is a carbon-based filler. In contrast, carbon-based fillers are the most widely used, studied the most, and developed the fastest class of conductive fillers to date.

Common carbon shielding and wave absorbing fillers include carbon black, carbon fibers, carbon nanotubes, graphene, and the like. The graphene serving as a constituent unit of various carbon materials has the characteristics of small density, high electron mobility, good heat conduction and electric conductivity, excellent corrosion resistance and high temperature resistance, good mechanical properties and the like, and is widely researched and applied in various fields of wave absorption, electromagnetic shielding, heat conduction, electric conduction, energy storage and the like. However, after the graphene is filled in the resin to reach a certain concentration, van der waals force existing in the sheet layer enables the graphene to be easily agglomerated and stacked, so that the specific surface area of the graphene is greatly reduced, and the electromagnetic shielding performance of the coating is greatly influenced. Therefore, how to solve the agglomeration of graphene in the resin matrix becomes a great challenge for the development of the carbon-based electromagnetic shielding coating.

Disclosure of Invention

The invention provides a light carbon-based electromagnetic shielding coating and a preparation method thereof, which can solve the technical problems of large thickness, high density, poor temperature resistance and corrosion resistance, low shielding effectiveness and the like of the conventional electromagnetic shielding material.

The invention adopts the technical scheme that the light carbon-based electromagnetic shielding coating comprises the following components in percentage by weight: electromagnetic shielding filler: 10% -25%, electromagnetic shielding filler dispersant: 2% -5%, polyurethane modified epoxy resin: 28% -40%, curing agent: 4% -8%, diluent: 25% -35%, auxiliary agent: 2% -5%; the electromagnetic shielding filler comprises one or two of three-dimensional graphene and nickel-plated carbon nanotubes.

Further, the electromagnetic shielding filler dispersing agent is one or more of DS-172, AKN-2076, SY-2076 and AD 8301.

Further, the polyurethane modified epoxy resin comprises one or more of EPU-301, EPU-303 and EPU-133L.

Further, the curing agent comprises one or more of T-31, MH-112 and NX-2040.

Further, the thin material comprises one or more of butyl acetate, cyclohexanone, ethyl acetate and xylene.

Further, the auxiliary agent comprises a leveling agent and an antifoaming agent.

Further, the three-dimensional graphene is prepared by taking graphene as a raw material by a sol-gel method, and the preparation steps are as follows:

1) graphene pretreatment: in N₂Carrying out heat treatment on the graphene at the temperature of more than 800 ℃ for 15-25 min under protection;

2) preparing three-dimensional graphene hydrogel: adding water into the pretreated graphene to prepare a solution, then adding vitamin C into the solution, continuously stirring the solution uniformly after dissolving, performing ultrasonic dispersion, and reacting the prepared solution in an oven at the temperature of 60-80 ℃ for 3-4 hours to obtain three-dimensional graphene hydrogel;

3) preparing three-dimensional graphene: freezing the three-dimensional graphene hydrogel washed by distilled water, then putting the three-dimensional graphene hydrogel into a freeze dryer for freeze drying, and finally putting the freeze-dried graphene aerogel into Ar at 1150-1250 DEG C₂And carrying out heat treatment in the atmosphere for more than 2 hours to obtain the three-dimensional graphene.

Further, the nickel-plated carbon nanotube is obtained by plating metal nickel on the outer wall of the carbon nanotube by adopting a chemical plating process, and the preparation steps are as follows:

1) pretreating the carbon nano tube: in N₂Placing the carbon nano tube above 800 ℃ for heat treatment for 15-25 min under protection;

2) surface sensitization and activation of the carbon nano tube: putting the pretreated carbon nano tube into a mixed solution composed of stannous chloride and dilute hydrochloric acid, stirring for sensitization, filtering the carbon nano tube, washing with deionized water, and then putting the carbon nano tube into a mixed solution composed of palladium chloride and dilute hydrochloric acid, stirring for activation treatment;

3) nickel plating of the carbon nano tube: and (3) putting the sensitized and activated carbon nano tube into a nickel sulfate and sodium hydrogen phosphate solution at 70-90 ℃ for chemical nickel plating, continuously dropwise adding ammonia water to control the pH value of the solution to be 7.8 +/-0.2, filtering, washing and drying to obtain the nickel-plated carbon nano tube.

The invention also relates to a preparation method of the light carbon-based electromagnetic shielding coating, which comprises the following steps:

s1, dissolving the polyurethane modified epoxy resin subjected to drying treatment by using a thinner, then adding the electromagnetic shielding filler, the electromagnetic shielding filler dispersing agent and the auxiliary agent while stirring, and dispersing uniformly to obtain an electromagnetic shielding filler dispersing solution; if the electromagnetic shielding fillers are multiple, respectively preparing electromagnetic shielding filler dispersion liquid;

s2, mixing the electromagnetic shielding filler dispersion liquid uniformly, adding a curing agent, and stirring uniformly to obtain the light carbon-based electromagnetic shielding coating.

Furthermore, when the raw materials in S1 are mixed to prepare the electromagnetic shielding filler dispersion liquid, the raw materials are dispersed for 15 to 20 minutes at the stirring speed of 500-600r/min, and the stirring time is 20 to 30 minutes after the curing agent is added in S2.

The invention has the following beneficial effects:

1. on the basis of the carbon-based electromagnetic shielding coating, the invention introduces metal Ni to construct Ni/C multi-element composite electromagnetic shielding filler, thereby achieving the purposes of keeping higher shielding efficiency of the metal electromagnetic shielding coating and reducing the density of the coating. In addition, the three-dimensional graphene is introduced into the Ni/C multi-element composite electromagnetic shielding filler, so that the surface density of the coating is further reduced, the uniform dispersion of the nickel-plated carbon nano tube in a resin system is promoted by virtue of the dispersion effect of the three-dimensional graphene, efficient electromagnetic transmission double network channels are formed in a resin matrix, and the conductivity and the electromagnetic shielding performance of the coating are remarkably improved.

2. When the three-dimensional graphene is prepared, the three-dimensional graphene is subjected to heat treatment, so that the content of organic groups on the surface of the graphene is reduced, the conductivity is improved, and the surface activation degree of the graphene is improved; then, the three-dimensional graphene is prepared by a sol-gel method, so that the technical problem that the two-dimensional graphene is seriously agglomerated due to van der Waals force is solved, and the electromagnetic shielding performance of the coating is improved.

3. The invention adopts the chemical plating process to successfully plate the metallic nickel on the outer wall of the carbon nano tube, so that the carbon nano tube has certain orientation in the dispersing and spraying processes, and the electrical property of the coating is improved.

4. The light carbon-based electromagnetic shielding coating prepared by the invention has the advantage of high shielding efficiency of a metal electromagnetic shielding coating, and has the characteristics of light weight and strong environment resistance of the carbon-based electromagnetic shielding coating. When the thickness of the coating is 0.05mm, the surface density is less than 50g/m²And the electromagnetic shielding effectiveness (8 GHz-12 GHz) exceeds 80dB, so that the requirements of commercial electromagnetic shielding materials are far met. The electromagnetic shielding coating is suitable for the civil field and the military field, can effectively improve the electromagnetic protection capability of weaponry, reduce the electromagnetic radiation of modern intelligent household appliances, and realize the wide application of the shielding coating in the aspects of military equipment, intelligent household appliances and the like.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention.

Example 1: a light carbon-based electromagnetic shielding coating comprises the following raw materials in percentage by weight:

electromagnetic shielding filler: 15% of electromagnetic shielding filler dispersing agent: 4%, polyurethane modified epoxy resin: 35% of curing agent: 6%, thinner 35%, and auxiliary agent: 5 percent.

Specifically, in the embodiment, the electromagnetic shielding filler is three-dimensional graphene and nickel-plated carbon nanotubes, wherein the three-dimensional graphene accounts for 10%, the nickel-plated carbon nanotubes accounts for 5%, the electromagnetic shielding filler dispersant is AD8301, the polyurethane modified epoxy resin is EPU-301, the curing agent is NX-2040 and MH-112, the NX-2040 accounts for 4%, the MH-112 accounts for 2%, the diluent is a mixed solvent of xylene, cyclohexanone and butyl acetate with a ratio of 3:3:1, the auxiliary agent includes two leveling agents and an antifoaming agent, the leveling agent is DN-2867, and the antifoaming agent is BYK-410.

Based on the same inventive concept, the embodiment of the invention also provides a preparation method of the light carbon-based electromagnetic shielding coating, which comprises the following steps:

s1: graphene pretreatment: in N₂And under protection, placing the graphene in a heating box at 800 ℃ for heat treatment for 20 minutes, reducing the content of organic groups on the surface of the graphene, improving the conductivity and improving the surface activation degree of the graphene.

S2, preparing the three-dimensional graphene hydrogel: adding water into the pretreated graphene to prepare a solution of 5g/L, adding vitamin C into the solution, continuously stirring the solution for 60 minutes after dissolving the vitamin C, and then ultrasonically dispersing the solution for 30 minutes at the temperature of 40 ℃. And (3) putting the dispersed solution into an oven at 70 ℃ for reaction for 3 hours to obtain the three-dimensional graphene hydrogel.

S3, preparing three-dimensional graphene: freezing the three-dimensional graphene hydrogel washed by distilled water for 12 hours, then putting the three-dimensional graphene hydrogel into a freeze dryer for freeze drying, and finally putting the freeze-dried graphene aerogel into Ar at 1200 DEG C₂And carrying out heat treatment for 2 hours in the atmosphere to obtain the three-dimensional graphene.

S4, preparing a three-dimensional graphene dispersion liquid: dissolving part of EPU-301 polyurethane modified epoxy resin subjected to drying treatment in xylene, cyclohexanone and butyl acetate according to the ratio of 3:3:1, adjusting a proper stirring speed, adding the prepared three-dimensional graphene, part of AD8301 type electromagnetic shielding filler dispersing agent, part of DN-2867 type flatting agent and BYK-410 type defoaming agent auxiliary agent while stirring, and continuously dispersing for 20 minutes at a fixed stirring speed after the addition is finished to obtain the three-dimensional graphene dispersion liquid.

S5, pretreatment of the carbon nano tube: in N₂Placing the carbon nano-tube under the protection of 800Heat treatment in a heating box at 20 ℃ for 20 minutes.

S6, surface sensitization and activation of the carbon nano tube: putting the pretreated carbon nano tube into stannous chloride (SnCl)₂·2H₂O) and dilute hydrochloric acid (HCl) were slowly stirred for 15 minutes to sensitize. Filtering carbon nanotube, washing with deionized water, and adding palladium chloride (PdCl)₂) The mixture solution was slowly stirred for 20 minutes with dilute hydrochloric acid to carry out the activation treatment.

S7, carbon nanotube nickel plating: putting the carbon nano tube after the sensitization and activation treatment into nickel sulfate (NiSO) at the temperature of 80 DEG C₄·6H₂O) and sodium hydrogen phosphate (NaH)₂PO₂·H₂Chemical nickel plating is carried out in O) solution, and ammonia water (NH) is continuously dropped₃·H₂O) controlling the pH value of the solution to be 8.0, filtering, washing and drying to obtain the nickel-plated carbon nano tube.

S8, preparing a nickel-plated carbon nanotube dispersion liquid: dissolving part of EPU-301 polyurethane modified epoxy resin subjected to drying treatment in xylene, cyclohexanone and butyl acetate according to the ratio of 3:3:1, adjusting a proper stirring speed, adding the prepared nickel-plated carbon nano tube, part of AD8301 type electromagnetic shielding filler dispersing agent, part of DN-2867 type flatting agent and BYK-410 type defoaming agent auxiliary agent while stirring, and continuously dispersing for 20 minutes at a fixed stirring speed after the addition is finished to obtain the nickel-plated carbon nano tube alkene dispersion liquid.

S9, preparing electromagnetic shielding paint: and mixing and stirring the uniformly dispersed three-dimensional graphene dispersion liquid and the nickel-plated carbon nanotube dispersion liquid, adding NX-2040 type and MH-112 type curing agents in proportion, and finally stirring for 15 minutes to obtain the light carbon-based electromagnetic shielding coating prepared by the invention.

Embodiment 2 a light carbon-based electromagnetic shielding coating comprises the following raw materials by weight:

electromagnetic shielding filler: 20% of electromagnetic shielding filler dispersing agent: 3% of polyurethane modified epoxy resin: 34% of a curing agent: 6%, thinner 33%, auxiliary agent: 4 percent.

In the embodiment of the application, the electromagnetic shielding filler is three-dimensional graphene and nickel-plated carbon nanotubes, wherein the three-dimensional graphene accounts for 5%, the nickel-plated carbon nanotubes accounts for 15%, the electromagnetic shielding filler dispersing agent is SY-2076, the polyurethane modified epoxy resin accounts for EPU-301, the curing agent is NX-2040 and MH-112, the NX-2040 accounts for 4%, the MH-112 accounts for 2%, the thinner accounts for a mixed solvent of xylene, cyclohexanone and butyl acetate with a ratio of 4:1:1, the auxiliary agent comprises two types of a leveling agent and an antifoaming agent, the leveling agent is BYK-333, and the antifoaming agent is BYK-410.

Based on the same inventive concept, the embodiment also provides a preparation method of the light carbon-based electromagnetic shielding coating, which comprises the following steps:

s1: graphene pretreatment: in N₂And under protection, placing the graphene in a 820 ℃ heating box for heat treatment for 15 minutes, reducing the content of organic groups on the surface of the graphene, improving the conductivity and improving the surface activation degree of the graphene.

S2, preparing the three-dimensional graphene hydrogel: preparing the pretreated graphene into a solution of 5g/L, adding vitamin C into the solution, continuously stirring for 50 minutes after dissolving, and then ultrasonically dispersing for 30 minutes at 35 ℃. And (3) putting the dispersed solution into an oven at 80 ℃ for reaction for 3.5 hours to obtain the three-dimensional graphene hydrogel.

S3, preparing three-dimensional graphene: freezing the three-dimensional graphene hydrogel washed by distilled water for 12 hours, then putting the three-dimensional graphene hydrogel into a freeze dryer for freeze drying, and finally putting the freeze-dried graphene aerogel into Ar at 1150 DEG C₂And carrying out heat treatment for 2.5 hours in the atmosphere to obtain the three-dimensional graphene.

S4, preparing a three-dimensional graphene dispersion liquid: dissolving a part of dried EPU-301 type polyurethane modified epoxy resin into a thin material composed of dimethylbenzene, cyclohexanone and butyl acetate according to a ratio of 4:1:1, adjusting a proper stirring speed, adding the prepared three-dimensional graphene, a part of SY-2076 type electromagnetic shielding filler dispersing agent, a part of BYK-333 type flatting agent, a BYK-410 type defoaming agent and other auxiliary agents while stirring, and continuously dispersing for 20 minutes at a fixed stirring speed after the addition is finished to obtain the three-dimensional graphene dispersion liquid.

S5 carbon nanotube pre-treatmentAnd (3) treatment: in N₂The carbon nano tube is placed in a heating box at 800 ℃ for heat treatment for 20 minutes under protection.

S6, surface sensitization and activation of the carbon nano tube: putting the pretreated carbon nano tube into stannous chloride (SnCl)₂·2H₂O) and dilute hydrochloric acid (HCl) for 20 minutes to sensitize. Filtering carbon nanotube, washing with deionized water, and adding palladium chloride (PdCl)₂) The mixture was slowly stirred for 15 minutes with dilute hydrochloric acid to carry out the activation treatment.

S7, carbon nanotube nickel plating: putting the sensitized and activated carbon nano tube into nickel sulfate (NiSO) at 85 DEG C₄·6H₂O) and sodium hydrogen phosphate (NaH)₂PO₂·H₂Chemical nickel plating is carried out in O) solution, and ammonia water (NH) is continuously dropped₃·H₂O) controlling the pH value of the solution to be 8.2, filtering, washing and drying to obtain the nickel-plated carbon nano tube.

S8, preparing a nickel-plated carbon nanotube dispersion liquid: dissolving part of the dried EPU-301 polyurethane modified epoxy resin into a thin material composed of dimethylbenzene, cyclohexanone and butyl acetate according to the ratio of 4:1:1, adjusting a proper stirring speed, adding the prepared nickel-plated carbon nano tube, part of SY-2076 type electromagnetic shielding filler dispersing agent, part of BYK-333 type flatting agent, BYK-410 type defoaming agent and other auxiliary agents while stirring, and continuously dispersing for 20 minutes at a fixed stirring speed after the addition is finished to obtain the nickel-plated carbon nano tube alkene dispersing solution.

S9, preparing electromagnetic shielding paint: and mixing and stirring the uniformly dispersed three-dimensional graphene dispersion liquid and the nickel-plated carbon nanotube dispersion liquid, adding NX-2040 type and MH-112 type curing agents in proportion, and finally stirring for 15 minutes to obtain the light carbon-based electromagnetic shielding coating prepared by the invention.

Embodiment 3 a light carbon-based electromagnetic shielding coating comprises the following raw materials by weight:

electromagnetic shielding filler: 25% of electromagnetic shielding filler dispersing agent: 4%, polyurethane modified epoxy resin: 28% of curing agent: 4%, thinner 35%, and auxiliary agent: 4 percent.

In the embodiment of the application, the electromagnetic shielding filler is three-dimensional graphene and nickel-plated carbon nanotubes, wherein the three-dimensional graphene accounts for 10%, the nickel-plated carbon nanotubes accounts for 15%, the electromagnetic shielding filler dispersing agent is SY-2076, the polyurethane modified epoxy resin is EPU-133L, the curing agent is NX-2040 and MH-112, the NX-2040 accounts for 2%, the MH-112 accounts for 2%, the thinner is a mixed solvent of xylene, cyclohexanone and butyl acetate with the proportion of 3:3:1, the auxiliary agent comprises two of a leveling agent and an antifoaming agent, the leveling agent is BYK-333, and the antifoaming agent is BYK-410.

The embodiment of the application also provides a preparation method of the light carbon-based electromagnetic shielding coating, which comprises the following steps:

s1: graphene pretreatment: in N₂And under protection, placing the graphene in a heating box at 800 ℃ for heat treatment for 20 minutes, reducing the content of organic groups on the surface of the graphene, improving the conductivity and improving the surface activation degree of the graphene.

S2, preparing the three-dimensional graphene hydrogel: preparing the pretreated graphene into a solution of 5g/L, adding vitamin C into the solution, continuously stirring the solution for 60 minutes after dissolving the vitamin C, and then ultrasonically dispersing the solution for 30 minutes at the temperature of 40 ℃. And (3) putting the dispersed solution into an oven at 70 ℃ for reaction for 3.5 hours to obtain the three-dimensional graphene hydrogel.

S3, preparing three-dimensional graphene: freezing the three-dimensional graphene hydrogel washed by distilled water for 12 hours, then putting the three-dimensional graphene hydrogel into a freeze dryer for freeze drying, and finally putting the freeze-dried graphene aerogel into Ar at 1200 DEG C₂And carrying out heat treatment for 2 hours in the atmosphere to obtain the three-dimensional graphene.

S4, preparing a three-dimensional graphene dispersion liquid: dissolving part of EPU-133L type polyurethane modified epoxy resin subjected to drying treatment in xylene, cyclohexanone and butyl acetate according to the proportion of 3:3:1, adjusting a proper stirring speed, adding the prepared three-dimensional graphene, part of SY-2076 type electromagnetic shielding filler dispersing agent, part of BYK-333 type flatting agent, BYK-410 type defoaming agent and other auxiliaries while stirring, and continuously dispersing for 20 minutes at a fixed stirring speed after the addition is finished to obtain the three-dimensional graphene dispersion liquid.

S5, pretreatment of the carbon nano tube: in N₂The carbon nano tube is placed in a heating box at 800 ℃ for heat treatment for 20 minutes under protection.

S6, surface sensitization and activation of the carbon nano tube: putting the pretreated carbon nano tube into stannous chloride (SnCl)₂·2H₂O) and dilute hydrochloric acid (HCl) were slowly stirred for 15 minutes to sensitize. Filtering carbon nanotube, washing with deionized water, and adding palladium chloride (PdCl)₂) The mixture solution was slowly stirred for 20 minutes with dilute hydrochloric acid to carry out the activation treatment.

S7, carbon nanotube nickel plating: putting the carbon nano tube after the sensitization and activation treatment into nickel sulfate (NiSO) at the temperature of 80 DEG C₄·6H₂O) and sodium hydrogen phosphate (NaH)₂PO₂·H₂Chemical nickel plating is carried out in O) solution, and ammonia water (NH) is continuously dropped₃·H₂O) controlling the pH value of the solution to be 8.0, filtering, washing and drying to obtain the nickel-plated carbon nano tube.

S8, preparing a nickel-plated carbon nanotube dispersion liquid: dissolving part of EPU-133L type polyurethane modified epoxy resin subjected to drying treatment in xylene, cyclohexanone and butyl acetate according to the proportion of 3:3:1, adjusting a proper stirring speed, adding the prepared nickel-plated carbon nano tube, part of SY-2076 type electromagnetic shielding filler dispersing agent, part of BYK-333 type flatting agent, BYK-410 type defoaming agent and other auxiliary agents while stirring, and continuously dispersing for 20 minutes at a fixed stirring speed after the addition is finished to obtain the nickel-plated carbon nano tube alkene dispersion liquid.

S9, preparing electromagnetic shielding paint: and mixing and stirring the uniformly dispersed three-dimensional graphene dispersion liquid and the nickel-plated carbon nanotube dispersion liquid, adding NX-2040 type and MH-112 type curing agents in proportion, and finally stirring for 15 minutes to obtain the light carbon-based electromagnetic shielding coating prepared by the invention.

Comparative example 1

A light carbon-based electromagnetic shielding coating comprises the following raw materials in percentage by weight:

electromagnetic shielding filler: 10% of electromagnetic shielding filler dispersing agent: 4%, polyurethane modified epoxy resin: 40% and a curing agent: 8% of diluent: 33% and auxiliary agent: 5 percent.

In the embodiment, the electromagnetic shielding filler is three-dimensional graphene, the dispersing agent of the electromagnetic shielding filler is DS-172, the polyurethane modified epoxy resin is EPU-301, the curing agent is NX-2040, the thinner is a mixed solvent of xylene and cyclohexanone in a ratio of 4:3, the auxiliary agent comprises a leveling agent and an antifoaming agent, wherein the leveling agent is DN-2867, and the antifoaming agent is BYK-410.

The embodiment of the application also provides a preparation method of the light carbon-based electromagnetic shielding coating, which comprises the following steps:

s1: graphene pretreatment: in N₂And under protection, placing the graphene in a heating box at 800 ℃ for heat treatment for 20 minutes, reducing the content of organic groups on the surface of the graphene, improving the conductivity and improving the surface activation degree of the graphene.

S2, preparing the three-dimensional graphene hydrogel: preparing the pretreated graphene into a solution of 5g/L, adding vitamin C into the solution, continuously stirring the solution for 60 minutes after dissolving the vitamin C, and then ultrasonically dispersing the solution for 30 minutes at the temperature of 40 ℃. And (3) putting the dispersed solution into an oven at 70 ℃ for reaction for 3 hours to obtain the three-dimensional graphene hydrogel.

S3, preparing three-dimensional graphene: freezing the three-dimensional graphene hydrogel washed by distilled water for 12 hours, then putting the three-dimensional graphene hydrogel into a freeze dryer for freeze drying, and finally putting the freeze-dried graphene aerogel into Ar at 1200 DEG C₂And carrying out heat treatment for 2 hours in the atmosphere to obtain the three-dimensional graphene.

S4, preparing a three-dimensional graphene dispersion liquid: dissolving the dried EPU-301 type polyurethane modified epoxy resin into a thin material composed of dimethylbenzene and cyclohexanone according to a ratio of 4:3, adjusting a proper stirring speed, adding the prepared three-dimensional graphene, the DS-172 type electromagnetic shielding filler dispersing agent, the DN-2867 type flatting agent, the BYK-410 type defoaming agent and other auxiliaries while stirring, and continuously dispersing for 20 minutes at a fixed stirring speed after the addition is finished to obtain the three-dimensional graphene dispersion liquid.

S5, preparing electromagnetic shielding paint: adding an NX-2040 type curing agent into the uniformly dispersed three-dimensional graphene dispersion liquid, and stirring for 15 minutes to obtain the light carbon-based electromagnetic shielding coating prepared by the invention.

Comparative example 2

A light carbon-based electromagnetic shielding coating comprises the following raw materials in percentage by weight:

electromagnetic shielding filler: 15% of electromagnetic shielding filler dispersing agent: 3% of polyurethane modified epoxy resin: 40% and a curing agent: 8% of diluent: 30% and auxiliary agent: 4 percent.

In the embodiment, the electromagnetic shielding filler is a nickel-plated carbon nanotube, the dispersing agent of the electromagnetic shielding filler is DS-172, the polyurethane modified epoxy resin is EPU-303, the curing agent is NX-2040, the thinner is a mixed solvent of xylene, cyclohexanone and butyl acetate with the proportion of 3:3:1, the auxiliary agent comprises a leveling agent and an antifoaming agent, wherein the leveling agent is BYK-333, and the antifoaming agent is BYK-410.

The embodiment also provides a preparation method of the light carbon-based electromagnetic shielding coating, which comprises the following steps:

s1, pretreatment of the carbon nano tube: in N₂The carbon nano tube is placed in a heating box at 800 ℃ for heat treatment for 20 minutes under protection.

S2, surface sensitization and activation of the carbon nano tube: putting the pretreated carbon nano tube into stannous chloride (SnCl)₂·2H₂O) and dilute hydrochloric acid (HCl) were slowly stirred for 15 minutes to sensitize. Filtering carbon nanotube, washing with deionized water, and adding palladium chloride (PdCl)₂) The mixture solution was slowly stirred for 20 minutes with dilute hydrochloric acid to carry out the activation treatment.

S3, carbon nanotube nickel plating: putting the carbon nano tube after the sensitization and activation treatment into nickel sulfate (NiSO) at the temperature of 80 DEG C₄·6H₂O) and sodium hydrogen phosphate (NaH)₂PO₂·H₂Chemical nickel plating is carried out in O) solution, and ammonia water (NH) is continuously dropped₃·H₂O) controlling the pH value of the solution to be 7.8, filtering, washing and drying to obtain the nickel-plated carbon nano tube.

S4, preparing a nickel-plated carbon nanotube dispersion liquid: dissolving the dried EPU-303 type polyurethane modified epoxy resin in xylene, cyclohexanone and butyl acetate according to the proportion of 3:3:1, adjusting a proper stirring speed, adding the prepared nickel-plated carbon nano tube, the DS-172 type electromagnetic shielding filler dispersing agent, the BYK-333 type leveling agent, the BYK-410 type defoaming agent and other auxiliary agents while stirring, and continuously dispersing for 20 minutes at a fixed stirring speed after the addition is finished to obtain the nickel-plated carbon nano tube alkene dispersion liquid.

S5, preparing electromagnetic shielding paint: adding NX-2040 type curing agent into the uniformly dispersed nickel-plated carbon nanotube dispersion liquid, and stirring for 15 minutes to obtain the light carbon-based electromagnetic shielding coating prepared by the invention.

The light multi-element electromagnetic shielding coatings prepared in examples 1 to 3 and comparative examples 1 to 2 were tested for thickness, areal density, shielding effectiveness, conductivity, and other properties, and the results are shown in table 1 below. The test methods used in examples 1-3 and comparative examples 1-2 were as follows:

(1) coating surface density test mode:

weighing the substrate plate mass, denoted M₁And the area is marked as S, after the wave-absorbing coating is sprayed and cured on the substrate board, the weighing mass is marked as M₂The surface density of the wave-absorbing coating is calculated according to the following formula.

(2) Coating shielding effectiveness test mode:

and testing the shielding effectiveness of the coating by adopting a NA7500 type vector network analyzer according to the test standard of ASTM D4935-10.

(3) Coating conductivity test mode:

after the sample is placed at room temperature for a period of time, the conductivity of the coating is tested by a four-probe method, the distance between four probes is 1mm, the test is carried out for 6 times in parallel, and the average value is taken.

TABLE 1 results of performance tests of barrier coatings prepared in different examples and comparative examples

As can be seen from table 1 above, the lightweight carbon-based electromagnetic shielding coating prepared by the present invention has very low areal density, and at the same time, has excellent shielding effectiveness and conductivity. When the thickness of the coating is 0.05mm, the surface density of the coating is less than 50 g.m^-2The electromagnetic shielding effectiveness of 8 GHz-12 GHz can reach more than 80dB, and the electric conductivity is close to 20S/cm. In contrast, the introduction of the metal layer greatly improves the conductivity of the carbon-based material, and as can be seen from comparative example 1 and comparative example 2, the conductivity of the nickel-plated carbon nanotube is significantly better than that of the three-dimensional graphene. The three-dimensional graphene is introduced into the nickel-plated carbon nanotube dispersion liquid, so that on one hand, the uniform dispersion of the nickel-plated carbon nanotube in a resin system is promoted by virtue of the dispersion effect of the three-dimensional graphene, and the three-dimensional graphene and the resin matrix form an efficient electromagnetic transmission dual network channel, so that the conductivity of the nickel-plated carbon nanotube and the electromagnetic shielding performance of a coating are remarkably improved. In addition, the specific surface area of the material is effectively increased by the porous structure of the three-dimensional graphene, and the transmission distance of electromagnetic waves is increased when the electromagnetic waves are continuously reflected on the hole wall when being transmitted in the three-dimensional directional holes, so that the electromagnetic wave energy is subjected to multiple reflections in an electromagnetic field and is finally lost in the form of heat energy. It can be seen from comparison of example 3, comparative example 1 and comparative example 2 that the addition of three-dimensional graphene to the nickel-plated carbon nanotubes significantly improves the conductivity and shielding effectiveness of the coating. On the other hand, the density of the three-dimensional graphene is extremely low, and the addition of the three-dimensional graphene can greatly reduce the surface density of the coating, so that the development requirement of light weight of the electromagnetic shielding material is met.