A moisture- and heat-resistant graphene conductive coating and its preparation method

Abstract

This invention discloses a moisture- and heat-resistant graphene conductive coating and its preparation method. The moisture- and heat-resistant graphene conductive coating has a multi-layered composite structure. It comprises layers of slurry consisting of graphene mixed with auxiliary conductive materials, organic additives, and resin binders or solvents in progressively decreasing mass fractions. The conductive layer, conductive transition layer, and protective layer are sequentially prepared using methods such as planar coating, screen printing, and air spraying. The synergistic effect of the multi-dimensional conductive media in each layer of this invention achieves excellent conductivity. Furthermore, thanks to the multi-layered structural design and the selection of a resin with excellent thermal stability, the conductive coating exhibits excellent moisture- and heat resistance. The preparation method provided by this invention is simple and easy to implement, with low production costs. Its unique moisture- and heat resistance allows for the application of the conductive coating in marine environments.

Description

Technical Field

[0001] This invention belongs to the field of conductive coating materials technology, specifically relating to a moisture- and heat-resistant graphene conductive coating and its preparation method. Background Technology

[0002] Conductive coatings are coating materials obtained by dispersing conductive materials in a binder to form conductive ink and then coating them. They typically possess excellent conductivity and can be used as printed conductive dots or conductive circuits. Conductive inks can be divided into metal-based conductive inks and carbon-based conductive inks. The former includes gold-based, silver-based, and copper-based inks, with metal conductive media as the main component; the latter uses carbon materials as the main conductive medium. Generally, coatings made from metal-based conductive inks have excellent conductivity, but these coatings are prone to oxidation in humid and hot environments, leading to a significant reduction in conductivity. Coatings made from carbon-based conductive inks have relatively weak conductivity, but they can also experience cracking and other failure behaviors at high temperatures, greatly limiting the application of this type of coating in humid and hot marine environments, such as in offshore power equipment or seabed exploration equipment.

[0003] Graphene possesses characteristics such as high carrier mobility at room temperature and large specific surface area. Therefore, as a new generation of conductive medium, graphene has been rapidly applied to the field of conductive inks. For example, Chinese patent CN114958074A discloses a graphene conductive ink and its preparation method. This method involves coating nano-copper materials with graphene, and then grinding and dispersing them with organosilicon resin, hydroxyl acrylic resin, and dispersants to obtain a high-performance graphene conductive ink. Patent application CN114213902A discloses an aqueous graphene conductive ink for batteries, its preparation method, and its application. This method involves uniformly mixing graphene with acrylic resin and conductive slurry to obtain a two-dimensional sheet-like structure layer by layer, forming a dense conductive network. The conductive coating prepared based on this conductive ink also exhibits excellent conductivity. Although the above-disclosed graphene conductive ink preparation methods can obtain conductive coatings with a certain degree of conductivity, the binder in the coating components will exhibit melting and decomposition failure behaviors in humid and hot environments, and graphene will also undergo oxidation in light-exposed and oxygen-rich environments, leading to a decrease in conductivity. Therefore, preparing conductive coatings with humid and hot resistance is of great significance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a moisture- and heat-resistant graphene conductive coating and its preparation method, thereby solving the problems mentioned in the background art.

[0005] One of the technical solutions adopted by this invention to solve its technical problem is: a method for preparing a moisture- and heat-resistant graphene conductive coating, comprising the following steps:

[0006] (1) Prepare the slurry for the conductive layer, conductive transition layer, and protective layer: where,

[0007] The conductive layer slurry composition by mass fraction includes: 1-10% graphene, 1%-10% auxiliary conductive material, 5%-20% organic additives, 4%-30% resin binder, and 30%-89% solvent;

[0008] The conductive transition layer slurry composition by mass fraction includes: 0.5-5% graphene, 1%-15% organic additives, 1%-20% resin binder, and 60%-97.5% solvent;

[0009] The protective layer slurry composition includes, by mass fraction: 0.1%–1% graphene, 0.1%–15% resin binder, and 84%–99.8% solvent;

[0010] Furthermore, the mass concentration of graphene in the slurry of the conductive layer, conductive transition layer, and protective layer decreases sequentially.

[0011] (2) Preparation of conductive layer: The conductive layer slurry is coated onto the surface of the substrate and cured to obtain the conductive layer;

[0012] (3) Preparation of conductive transition layer: The conductive transition layer slurry is sprayed onto the surface of the conductive layer by air spraying and cured to obtain the conductive transition layer;

[0013] (4) Preparation of protective layer: The protective layer slurry is sprayed onto the surface of the conductive transition layer by air spraying and cured to obtain the protective layer; the final coating of the composite structure of conductive layer, conductive transition layer and protective layer is the moisture-heat resistant graphene conductive coating.

[0014] In this invention, the graphene has 1 to 10 layers and a sheet diameter of 1 to 10 μm.

[0015] In this invention, the auxiliary conductive material includes one or both of ultrafine carbon powder and carbon nanotubes; wherein the diameter of the ultrafine carbon powder is 20-100 nm; and the length of the carbon nanotube is 1-100 μm and the diameter is 5-30 nm.

[0016] In this invention, the organic additives include one or more of dispersants, wetting agents, and defoamers.

[0017] In this invention, the resin adhesive includes one or more of bisphenol A type epoxy resin, waterborne epoxy resin emulsion, waterborne acrylic resin, waterborne chloroacetic acid resin and phenolic resin.

[0018] In this invention, the solvent includes one or more of anhydrous ethanol, isopropanol, ethylene glycol, and ultrapure water.

[0019] In this invention, the slurry prepared in step (1) is dispersed and then stirred and defoamed before use. The dispersion treatment is mechanical grinding or high-frequency ultrasonic dispersion. The grinding time is 1 to 12 hours, the ultrasonic time is 30 to 60 minutes, and the ultrasonic treatment is stopped for 1 to 3 seconds every 2 to 6 seconds.

[0020] In this invention, the coating method of the conductive layer paste in step (2) is either flat squeegee coating or screen printing. The distance between the blade of the squeegee and the substrate is 0.3 to 1.5 mm, and the coating speed is 20 to 100 mm / s. The screen printing is done with a plastic screen with a mesh count of 80 to 200. The squeegee is a rubber squeegee, and the printing angle formed between the squeegee and the screen surface is 30 to 60°. The number of printing times is 1 to 15.

[0021] In this invention, in steps (3) and (4), the nozzle diameter for air spraying is 0.3 to 4 mm.

[0022] In this invention, the curing method is drying curing, the curing temperature is 100-160℃, and the curing time is 1-12h.

[0023] The second technical solution adopted by this invention to solve its technical problem is: providing a heat-resistant graphene conductive coating, prepared by the above-mentioned method. The heat-resistant graphene conductive coating has a conductive layer, a conductive transition layer, and a protective layer sequentially disposed on the surface of a substrate; wherein the thickness of the conductive layer is 25–200 μm, the thickness of the conductive transition layer is 5–10 μm, and the thickness of the protective layer is 1–3 μm, and the mass fraction of graphene in the conductive layer, conductive transition layer, and protective layer decreases sequentially.

[0024] Compared with the prior art, this technical solution has the following advantages:

[0025] 1. The moisture- and heat-resistant graphene conductive coating of this invention comprises a three-layer composite structure. The conductive layer is designed with two-dimensional material graphene, one-dimensional material carbon nanotubes, and zero-dimensional material ultrafine carbon powder. Through the synergistic cooperation of conductive media of different dimensions, a three-dimensional conductive network is built, achieving excellent conductivity. The conductive transition layer and the protective layer can effectively prevent the influence of the humid and hot environment on the underlying conductive layer. In addition, the conductive media used are all carbon-based conductive media, and the binder used is a high-temperature stable binder, ensuring the stability of the coating's conductivity under humid and hot conditions.

[0026] 2. In the multilayer composite structure of the present invention, a high-concentration conductive layer serves as a functional layer, and the graphene content is then designed to decrease in a gradient manner. The conductive transition layer ensures the continuity of the conductive path, and the protective layer prevents performance degradation caused by the oxidation of graphene, which is the main conductive medium, under humid and hot conditions.

[0027] 3. The preparation method of this invention is simple. The conductive transition layer and the protective layer are prepared by air spraying. While achieving extremely low thickness of the two layers, the coating and protective properties are guaranteed. Finally, the coating conductivity and resistance to damp heat are balanced: the sheet resistance of the coating is 25.9Ω / sq. After boiling in water at 60℃ for 30-60 minutes or baking in an oven at 100℃ for 1 hour, the sheet resistance of the coating does not change significantly.

[0028] 4. The heat-resistant graphene conductive coating of this invention has good application prospects in hot and humid marine environments. Attached Figure Description

[0029] Figure 1 This is a macroscopic morphology image of the heat-resistant graphene conductive coating prepared in Example 1;

[0030] Figure 2 This is a SEM image of the surface of the heat-resistant graphene conductive coating prepared in Example 1. Detailed Implementation

[0031] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of the moisture- and heat-resistant graphene conductive coating, its preparation method, and its application, is provided but should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1

[0033] This embodiment discloses a method for preparing a moisture- and heat-resistant graphene conductive coating, comprising the following steps:

[0034] (1) By mass fraction, add 51% isopropanol, 25.5% ultrapure water, 10% dispersant, 2% wetting agent, 1% defoamer (the dispersant, wetting agent and defoamer are all from Guangzhou Houhuan Chemical Additives Co., Ltd.), 1.5% graphene (sheet diameter 10μm, number of layers 3, Yaotian New Materials Technology Co., Ltd.), 1.5% ultrafine carbon powder (diameter 20nm, Yaotian New Materials Technology Co., Ltd.), 1.5% multi-walled carbon nanotubes (length 15-30μm, diameter 5-15nm, Yaotian New Materials Technology Co., Ltd.), and 6% bisphenol A type epoxy resin (Hunan Tuochuang Polymer New Materials Co., Ltd.) to a beaker to obtain a high-concentration graphene slurry, which is used as a conductive layer slurry.

[0035] The obtained conductive layer slurry was spread out and coated with a scraper. The distance between the scraper blade and the substrate was 0.5 mm, and the scraping speed was 45 mm / s. After coating, the coating was placed in an oven at 150°C for 2 hours to obtain the conductive layer (i.e., the bottom layer). The actual thickness of the conductive layer coating was 54 μm.

[0036] (2) By mass fraction, add 59.3% isopropanol, 29.7% ultrapure water, 5% dispersant (Guangzhou Houhuan Chemical Additives Co., Ltd.), 1.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), 2% bisphenol A type epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.), and 2.5% phenolic resin (Henan Jinrun New Materials Co., Ltd.) to a beaker to obtain a medium-concentration graphene slurry. Use the obtained medium-concentration graphene slurry as a conductive transition layer slurry.

[0037] The conductive transition layer slurry was sprayed onto the surface of the conductive layer using an air spraying process with a nozzle orifice diameter of 1.3 mm. After spraying, the coating was placed in an oven at 150°C for 2 hours to dry, thus obtaining the conductive transition layer (i.e., the intermediate layer). The actual thickness of the conductive transition layer was 7 μm.

[0038] (3) Add 89.5% anhydrous ethanol, 0.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), and 10% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.) to a beaker by mass fraction to obtain a low-concentration graphene slurry. Use the obtained low-concentration graphene slurry as a protective layer slurry.

[0039] The protective layer slurry was sprayed onto the surface of the conductive transition layer using an air spraying process with a nozzle orifice diameter of 0.5 mm. After spraying, the coating was placed in an oven at 150°C for 2 hours to dry, thus obtaining the protective layer (i.e., the surface layer). The actual thickness of the protective layer was 1 μm.

[0040] The resulting multi-layered coating is a moisture- and heat-resistant graphene conductive coating, with a measured total thickness of 62 μm. The sheet resistance of the graphene conductive coating was measured to be 36.3 Ω / sq using a four-probe resistor. After boiling in water at 60°C for 30–60 minutes using the water boiling test, the sheet resistance was measured to be 36.6 Ω / sq. The sheet resistance did not change significantly after the water boiling test, demonstrating excellent moisture and heat resistance.

[0041] Example 2

[0042] The difference between Example 2 and Example 1 is as follows:

[0043] (1) By mass fraction, add 46% isopropanol, 23% ultrapure water, 7% dispersant, 2% wetting agent, 1% defoamer (the dispersant, wetting agent and defoamer are all from Guangzhou Houhuan Chemical Additives Co., Ltd.), 2.8% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), 3.5% ultrafine carbon powder (20nm diameter, Yaotian New Materials Technology Co., Ltd.), and 0.7% multi-walled carbon nanotubes (15-30μm length, 5-15nm diameter, Yaotian) to a beaker. A high-concentration graphene slurry was obtained by mixing 5.4% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.) and 8.6% phenolic resin (Henan Jinrun New Materials Co., Ltd.). The obtained high-concentration graphene slurry was spread and coated with a doctor blade at a distance of 0.5 mm from the substrate and a coating speed of 45 mm / s. After coating, the coating was placed in an oven at 150°C for 2 hours to dry, thus obtaining the bottom layer of a moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the bottom layer of the coating was 58 μm.

[0044] (2) By mass fraction, 59.3% isopropanol, 29.7% ultrapure water, 5% dispersant (Guangzhou Houhuan Chemical Additives Co., Ltd.), 1.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), 2% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.), and 2.5% phenolic resin (Henan Jinrun New Materials Co., Ltd.) were added to a beaker to obtain a medium-concentration graphene slurry. The medium-concentration graphene slurry was then sprayed with air using a nozzle with an orifice diameter of 1.3mm. After spraying, the coating was placed in an oven and dried at 150℃ for 2h to obtain the intermediate layer of the moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the intermediate layer was 5μm.

[0045] (3) By mass fraction, 89.5% anhydrous ethanol, 0.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), and 10% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.) were added to a beaker to obtain a low-concentration graphene slurry. The obtained low-concentration graphene slurry was sprayed with air using a nozzle orifice diameter of 0.5mm. After spraying, the coating was placed in an oven at 150℃ for 2h to obtain the surface layer of a moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the coating surface layer was 1μm.

[0046] The resulting multi-layered coating is a moisture-heat resistant graphene conductive coating, with a measured total thickness of 64 μm. The sheet resistance of the graphene conductive coating was measured to be 25.9 Ω / sq using a four-probe resistor. After boiling in water at 60°C for 30–60 minutes using the water boiling test, the sheet resistance remained at 25.9 Ω / sq, demonstrating excellent moisture-heat resistance.

[0047] Example 3

[0048] The difference between Example 3 and Example 1 is as follows:

[0049] (1) By mass fraction, add 54.7% isopropanol, 27.3% ultrapure water, 10% dispersant, 1.8% wetting agent, 0.2% defoamer (dispersant, wetting agent and defoamer are all from Guangzhou Houhuan Chemical Additives Co., Ltd.), 1.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), 1.5% multi-walled carbon nanotubes (15-30μm length, 5-15nm diameter, Yaotian New Materials Technology Co., Ltd.), and 2.6% bisphenol A epoxy resin (Guangdong) to a beaker. A high-concentration graphene slurry was obtained by mixing 0.2% water-based acrylic resin emulsion (Guangzhou Houhuan Chemical Additives Co., Ltd.) and 0.2% water-based chloroacetic acid resin (Guangzhou Houhuan Chemical Additives Co., Ltd.). The obtained high-concentration graphene slurry was spread and coated with a doctor blade at a distance of 0.5 mm from the substrate and a coating speed of 45 mm / s. After coating, the coating was placed in an oven at 150°C for 2 hours to obtain the bottom layer of a moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the bottom layer of the coating was 33 μm.

[0050] (2) By mass fraction, 59.3% isopropanol, 29.7% ultrapure water, 5% dispersant (Guangzhou Houhuan Chemical Additives Co., Ltd.), 1.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), 2% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.), and 2.5% phenolic resin (Henan Jinrun New Materials Co., Ltd.) were added to a beaker to obtain a medium-concentration graphene slurry. The medium-concentration graphene slurry was then sprayed with air using a nozzle with an orifice diameter of 1.3mm. After spraying, the coating was placed in an oven and dried at 150℃ for 2h to obtain the intermediate layer of the moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the intermediate layer was 9μm.

[0051] (3) By mass fraction, 89.5% anhydrous ethanol, 0.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), and 10% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.) were added to a beaker to obtain a low-concentration graphene slurry. The obtained low-concentration graphene slurry was sprayed with air using a nozzle orifice diameter of 0.5mm. After spraying, the coating was placed in an oven at 150℃ for 2h to obtain the surface layer of a moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the coating surface layer was 1μm.

[0052] The resulting multi-layered coating is a moisture-heat resistant graphene conductive coating, with a measured total thickness of 43 μm. The sheet resistance of the graphene conductive coating was measured to be 30.2 Ω / sq using a four-probe resistor. After boiling in water at 60°C for 30–60 minutes using the water boiling test, the sheet resistance remained at 30.2 Ω / sq, demonstrating excellent moisture-heat resistance.

[0053] Example 4

[0054] The difference between Example 4 and Example 1 is as follows:

[0055] (1) By mass fraction, add 52% isopropanol, 26% ultrapure water, 7% dispersant, 2% wetting agent, 1% defoamer (dispersant, wetting agent and defoamer are all from Guangzhou Houhuan Chemical Additives Co., Ltd.), 1.6% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), 2% ultrafine carbon powder (20nm diameter, Yaotian New Materials Technology Co., Ltd.), and 0.4% multi-walled carbon nanotubes (15-30μm length, 5-15nm diameter, Yaotian New Materials Technology Co., Ltd.) to a beaker. A high-concentration graphene slurry was obtained by mixing 3% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.) and 5% phenolic resin (Henan Jinrun New Materials Co., Ltd.). The obtained high-concentration graphene slurry was spread and coated with a doctor blade at a distance of 0.5 mm from the substrate and a coating speed of 45 mm / s. After coating, the coating was placed in an oven at 150°C for 2 hours to obtain the bottom layer of a moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the bottom layer of the coating was 45 μm.

[0056] (2) By mass fraction, 59.3% isopropanol, 29.7% ultrapure water, 5% dispersant (Guangzhou Houhuan Chemical Additives Co., Ltd.), 1.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), 2% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.), and 2.5% phenolic resin (Henan Jinrun New Materials Co., Ltd.) were added to a beaker to obtain a medium-concentration graphene slurry. The medium-concentration graphene slurry was then sprayed with air using a nozzle with an orifice diameter of 1.3mm. After spraying, the coating was placed in an oven and dried at 150℃ for 2h to obtain the intermediate layer of the moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the intermediate layer was 7μm.

[0057] (3) By mass fraction, 89.5% anhydrous ethanol, 0.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), and 10% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.) were added to a beaker to obtain a low-concentration graphene slurry. The obtained low-concentration graphene slurry was sprayed with air using a nozzle orifice diameter of 0.5mm. After spraying, the coating was placed in an oven at 150℃ for 2h to obtain the surface layer of a moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the coating surface layer was 1μm.

[0058] The resulting multi-layered coating is a moisture-heat resistant graphene conductive coating, with a measured total thickness of 53 μm. The sheet resistance of the graphene conductive coating was measured to be 34.1 Ω / sq using a four-probe resistance meter. After boiling in water at 60°C for 30–60 minutes using the water boiling test, its sheet resistance was measured to be 34.0 Ω / sq. The sheet resistance of the coating did not change significantly after the water boiling test, demonstrating excellent moisture-heat resistance.

[0059] Example 5

[0060] The difference between Example 5 and Example 1 is as follows:

[0061] (1) By mass fraction, add 42.7% isopropanol, 21.3% ultrapure water, 7% dispersant, 2% wetting agent, 1% defoamer (dispersant, wetting agent and defoamer are all from Guangzhou Houhuan Chemical Additives Co., Ltd.), 4% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), 8% ultrafine carbon powder (20nm diameter, Yaotian New Materials Technology Co., Ltd.), 1% multi-walled carbon nanotubes (15-30μm length, 5-15nm diameter, Yaotian New Materials Technology Co., Ltd.), and 5.8% [other components] to a beaker. Bisphenol A type epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.) and 7.2% phenolic resin (Henan Jinrun New Materials Co., Ltd.) were used to obtain a high-concentration graphene slurry. The obtained high-concentration graphene slurry was screen printed using a plastic screen with a mesh count of 200 mesh and a rubber squeegee. The printing angle between the squeegee and the screen surface was 45°, and the printing was performed 3 times. After coating, the coating was placed in an oven at 150°C for 2 hours to obtain the bottom layer of a moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the bottom layer of the coating was 21 μm.

[0062] (2) By mass fraction, 59.3% isopropanol, 29.7% ultrapure water, 5% dispersant (Guangzhou Houhuan Chemical Additives Co., Ltd.), 1.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), 2% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.), and 2.5% phenolic resin (Henan Jinrun New Materials Co., Ltd.) were added to a beaker to obtain a medium-concentration graphene slurry. The medium-concentration graphene slurry was then sprayed with air using a nozzle with an orifice diameter of 1.3mm. After spraying, the coating was placed in an oven and dried at 150℃ for 2h to obtain the intermediate layer of the moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the intermediate layer was 5μm.

[0063] (3) By mass fraction, 89.5% anhydrous ethanol, 0.5% graphene (3μm diameter, 3 layers, Kaina Graphene Technology Co., Ltd.), and 10% bisphenol A epoxy resin (Guangzhou Tongshang Yunhua Co., Ltd.) were added to a beaker to obtain a low-concentration graphene slurry. The obtained low-concentration graphene slurry was sprayed with air using a nozzle orifice diameter of 0.5mm. After spraying, the coating was placed in an oven at 150℃ for 2h to obtain the surface layer of a moisture-resistant and heat-resistant graphene conductive coating. The actual thickness of the coating surface layer was 1μm.

[0064] The resulting multi-layered coating is a moisture- and heat-resistant graphene conductive coating, with a measured total thickness of 27 μm. The sheet resistance of the graphene conductive coating was measured to be 77.2 Ω / sq using a four-probe resistor. After boiling in water at 60°C for 30–60 minutes using the water boiling test, the sheet resistance was measured to be 77.4 Ω / sq. The sheet resistance did not change significantly after the water boiling test, demonstrating excellent moisture and heat resistance.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a moisture- and heat-resistant graphene conductive coating, characterized in that: Includes the following steps: (1) Prepare the slurry for the conductive layer, conductive transition layer, and protective layer: where, The conductive layer slurry composition by mass fraction includes: 1-10% graphene, 1%-10% auxiliary conductive material, 5%-20% organic additives, 4%-30% resin binder, and 30%-89% solvent; The conductive transition layer slurry composition by mass fraction includes: 0.5-5% graphene, 1%-15% organic additives, 1%-20% resin binder, and 60%-97.5% solvent; The protective layer slurry composition includes, by mass fraction: 0.1%–1% graphene, 0.1%–15% resin binder, and 84%–99.8% solvent; Furthermore, the mass concentration of graphene in the slurry of the conductive layer, conductive transition layer, and protective layer decreases sequentially. (2) Preparation of conductive layer: The conductive layer slurry is coated onto the surface of the substrate and cured to obtain the conductive layer; (3) Preparation of conductive transition layer: The conductive transition layer slurry is sprayed onto the surface of the conductive layer by air spraying and cured to obtain the conductive transition layer; (4) Preparation of protective layer: The protective layer slurry is sprayed onto the surface of the conductive transition layer by air spraying and cured to obtain the protective layer; the final coating of the composite structure of conductive layer, conductive transition layer and protective layer is the moisture-heat resistant graphene conductive coating.

2. The method for preparing a moisture- and heat-resistant graphene conductive coating according to claim 1, characterized in that: The graphene has 1 to 10 layers and a sheet diameter of 1 to 10 μm.

3. The method for preparing a moisture- and heat-resistant graphene conductive coating according to claim 1, characterized in that: The auxiliary conductive material includes one or both of ultrafine carbon powder and carbon nanotubes; wherein the diameter of the ultrafine carbon powder is 20-100 nm; and the length of the carbon nanotube is 1-100 μm and the diameter is 5-30 nm.

4. The method for preparing a moisture- and heat-resistant graphene conductive coating according to claim 1, characterized in that: The organic additives include one or more of dispersants, wetting agents, and defoamers.

5. The method for preparing a moisture- and heat-resistant graphene conductive coating according to claim 1, characterized in that: The resin adhesive includes one or more of bisphenol A type epoxy resin, waterborne epoxy resin emulsion, waterborne acrylic resin, waterborne chloroacetic acid resin, and phenolic resin.

6. The method for preparing a moisture- and heat-resistant graphene conductive coating according to claim 1, characterized in that: The solvents include one or more of anhydrous ethanol, isopropanol, ethylene glycol, and ultrapure water.

7. The method for preparing a moisture- and heat-resistant graphene conductive coating according to claim 1, characterized in that: The slurry prepared in step (1) is dispersed and then stirred and degassed before use. The dispersion method is mechanical grinding dispersion or high-frequency ultrasonic dispersion. The grinding time is 1 to 12 hours, the ultrasonic time is 30 to 60 minutes, and the ultrasonic treatment is stopped for 1 to 3 seconds every 2 to 6 seconds.

8. The method for preparing a moisture- and heat-resistant graphene conductive coating according to claim 1, characterized in that: Step (2) The conductive layer paste is coated by flat squeegee or screen printing. The distance between the blade of the squeegee and the substrate is 0.3 to 1.5 mm, and the squeegee speed is 20 to 100 mm / s. The screen printing is done with a plastic screen with a mesh count of 80 to 200. The screen squeegee is a rubber squeegee. The printing angle formed between the squeegee and the screen surface is 30 to 60°, and the number of printing times is 1 to 15.

9. The method for preparing a moisture- and heat-resistant graphene conductive coating according to claim 1, characterized in that: In steps (3) and (4), the nozzle diameter for air spraying is 0.3 to 4 mm.

10. The method for preparing a moisture- and heat-resistant graphene conductive coating according to claim 1, characterized in that: The curing method is drying curing, the curing temperature is 100~160℃, and the curing time is 1~12h.

11. A moisture- and heat-resistant graphene conductive coating, characterized in that: It is prepared by the method described in any one of claims 1 to 10.

12. The moisture- and heat-resistant graphene conductive coating according to claim 11, characterized in that: A conductive layer, a conductive transition layer, and a protective layer are sequentially disposed on the surface of a substrate; wherein the thickness of the conductive layer is 25-200 μm, the thickness of the conductive transition layer is 5-10 μm, the thickness of the protective layer is 1-3 μm, and the mass fraction of graphene in the conductive layer, the conductive transition layer, and the protective layer decreases sequentially.

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