Super-hydrophobic high-thermal-conductivity composite coating, and preparation method and application thereof

Abstract

The present application relates to a kind of super-hydrophobic high thermal conductivity composite coating and its preparation method and application, the super-hydrophobic high thermal conductivity composite coating is formed by super-hydrophobic high thermal conductivity composite coating, the super-hydrophobic high thermal conductivity composite coating includes the following components by mass fraction: ethanol solution 60~80 parts, dispersing agent 3~5 parts, adhesion agent 3~5 parts, dimethyl silicone oil 0.3~0.5 parts, polytetrafluoroethylene micro powder 8~10 parts, silicon dioxide 1~2 parts, graphene 0.8~1.2 parts, silicon carbide 2~3 parts, hardening wear-resistant agent 1.2~1.5 parts and polytetrafluoroethylene emulsion 4~6 parts.The super-hydrophobic high thermal conductivity composite coating in the present application has stable super-hydrophobic characteristics and excellent thermal conductivity performance, has excellent wear resistance and mechanical stability, is suitable for acid and alkali and other harsh environments, is suitable for the place of promoting condensation heat transfer strengthening, especially suitable for steam-liquid / gas heat exchanger and other heat exchange places.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coating coating materials, and particularly relates to a super-hydrophobic high-thermal-conductivity composite coating as well as a preparation method and application thereof. BACKGROUND

[0002] A large amount of waste steam is generated in the aerobic fermentation process of organic solid waste. This waste heat source has the characteristics of low grade (50-70℃) and long production cycle (7-30 days). At present, using an external heat exchanger to capture the heat energy in the fermentation steam is the most effective and convenient fermentation heat recovery method. However, fermentation steam is different from industrial waste steam such as boiler steam. It is low and unstable in temperature and belongs to saturated wet hot air. The presence of non-condensable gas can seriously affect the condensation heat transfer performance. The above problems make it more difficult to recover the fermentation waste heat. The key to optimizing the fermentation waste heat recovery process lies in reducing heat loss and improving the heat transfer performance inside the heat exchanger to maximize the recovery of fermentation heat energy. For heat loss, optimization process and enhanced equipment insulation can be used, while for the improvement of heat transfer performance, the key lies in strengthening the condensation heat transfer process of fermentation steam in the heat exchanger.

[0003] For the condensation heat transfer inside the heat exchanger, most of the heat and mass transfer is in the form of film condensation. Under the same supercooling degree, the heat transfer performance of dropwise condensation is one order of magnitude higher than that of film condensation. Therefore, promoting the occurrence of dropwise condensation can effectively improve the condensation heat transfer performance. By hydrophobic modification of the surface of the heat exchange sheet, film condensation can be converted into dropwise condensation. The commonly used method for hydrophobic modification of the surface of the metal heat exchange sheet is to attach a hydrophobic polymer material to the surface of the heat exchange sheet to form a super-hydrophobic coating with self-cleaning and other characteristics. The super-hydrophobic structure enables the water droplets formed by condensation inside the heat exchanger to quickly detach from the heat exchange surface, thereby promoting the generation of new water droplets, i.e. promoting the process of steam condensation and heat release.

[0004] However, the condensation heat transfer performance is not significantly improved after the surface modification of the metal heat exchange sheet, because the thermal conductivity of the polymer material is low, and the thermal conductivity of most metals is 100 times or even 1000 times that of the polymer. This leads to a significant decrease in the overall thermal conductivity after the combination of the coating and the heat exchange sheet substrate, thereby inhibiting the condensation heat transfer performance.

[0005] In addition, a small amount of ammonia gas and particulate matter is carried in the fermentation steam, which causes the condensed droplets to have a certain alkalinity. Therefore, it is necessary to improve the alkali corrosion resistance and chemical stability of the super-hydrophobic coating. At the same time, the presence of particulate matter and convective heat transfer will continuously wear the coating, so the coating still needs to have good wear resistance and mechanical stability.

[0006] At present, there are many methods for preparing super-hydrophobic coating, but most of the preparation and modification processes are complex, and the cost is high, which is difficult to realize batch production and large-scale promotion. Therefore, it is particularly important to develop a low-cost, simple and easy-to-operate high-thermal-conductivity super-hydrophobic coating preparation method. SUMMARY

[0007] In order to solve one or more technical problems existing in the prior art, the present application aims to provide a super-hydrophobic high-thermal-conductivity composite coating and a preparation method and application thereof. The super-hydrophobic high-thermal-conductivity composite coating has stable super-hydrophobic properties and excellent thermal conductivity, has excellent wear resistance and mechanical stability, is suitable for use in harsh environments such as acid and alkali, and is suitable for use in places to promote condensation heat transfer strengthening, especially in heat exchange places such as vapor-liquid / gas heat exchangers.

[0008] In a first aspect, the present application provides a super-hydrophobic high-thermal-conductivity composite coating formed from a super-hydrophobic high-thermal-conductivity composite coating material, wherein the super-hydrophobic high-thermal-conductivity composite coating material comprises the following components in mass fraction: 60-80 parts of an ethanol solution, 3-5 parts of a dispersing agent, 3-5 parts of a adhesion agent, 0.3-0.5 parts of dimethyl silicone oil, 8-10 parts of polytetrafluoroethylene micro powder, 1-2 parts of silicon dioxide, 0.8-1.2 parts of graphene, 2-3 parts of silicon carbide, 1.2-1.5 parts of a hardening and wear-resistant agent, and 4-6 parts of a polytetrafluoroethylene emulsion.

[0009] Preferably, the ethanol solution is an ethanol aqueous solution, and the volume percentage of ethanol in the ethanol aqueous solution is 80-90%; and / or the solid content of the polytetrafluoroethylene emulsion is 40-60%.

[0010] Preferably, the dispersing agent is a sodium salt of polycarboxylic acid dispersing agent; the adhesion agent is a modified silane polymer; the silicon dioxide is silicon dioxide modified by silane coupling agent KH-550; the graphene is few-layer graphene or single-layer graphene, preferably, the carbon content in the graphene is not less than 98wt%; and / or the hardening and wear-resistant agent is a modified organic silicon complex nano silicon solution.

[0011] Preferably, the particle size of the polytetrafluoroethylene micro powder is not more than 1 μm; the particle size of the silicon dioxide is not more than 20 nm; the particle size D50 of the graphene is not more than 12 μm; and / or the particle size of the silicon carbide is not more than 1 μm.

[0012] In a second aspect, the present application provides a preparation method of the super-hydrophobic high-thermal-conductivity composite coating described in the first aspect, and the method comprises the following steps:

[0013] (1) adding a dispersing agent, an adhesion agent and dimethyl silicone oil into an ethanol solution and stirring uniformly to obtain solution A;

[0014] (2) adding polytetrafluoroethylene micro powder, silicon dioxide, graphene and silicon carbide into solution A and uniformly ultrasonic dispersing to obtain solution B;

[0015] (3) adding hardening and wear-resistant agent and polytetrafluoroethylene emulsion into solution B and uniformly ultrasonic dispersing, and then filtering through a mesh screen of more than 100 meshes to obtain the super-hydrophobic high-thermal-conductivity composite coating;

[0016] (4) pretreating the substrate, then spraying the super-hydrophobic high-thermal-conductivity composite coating on the substrate, and then baking to obtain the super-hydrophobic high-thermal-conductivity composite coating on the substrate.

[0017] Preferably, in step (2) and / or step (3), the ultrasonic dispersing time is 15-30 min, preferably 20 min.

[0018] Preferably, the spraying is carried out under the condition that the pressure is 0.2-0.4 MPa, and the distance between the spray gun and the substrate is 100-250 mm during spraying.

[0019] Preferably, the baking is first carried out at 250-280℃ for 10-20 min, and then carried out at 360-400℃ for 10-30 min; and / or the temperature rising rate for rising the temperature to the baking temperature is 5-10℃ / min.

[0020] In a third aspect, the present application provides the super-hydrophobic high-thermal-conductivity composite coating prepared by the preparation method described in the second aspect of the present application; preferably, the water contact angle of the super-hydrophobic high-thermal-conductivity composite coating is above 159°, the thermal conductivity coefficient is 18.4 W / (m·K), the adhesion is 0 or 1 grade, and the pencil hardness is above 3H; preferably, the water contact angle of the super-hydrophobic high-thermal-conductivity composite coating after abrasion and peeling tests is above 157°, and the water contact angle after acid and alkali corrosion tests for 24 h under the condition that the pH is in the range of 3-11 is above 154°.

[0021] In a fourth aspect, the present application provides the application of the super-hydrophobic high-thermal-conductivity composite coating described in the first aspect of the present application or the super-hydrophobic high-thermal-conductivity composite coating prepared by the preparation method described in the second aspect of the present application in strengthening condensation heat transfer.

[0022] Compared with the prior art, the present application has at least the following beneficial effects:

[0023] (1) The super-hydrophobic high-thermal-conductivity composite coating in the application is mainly provided with super-hydrophobicity by the combined action of four components of silicon dioxide, graphene, dimethyl silicone oil and polytetrafluoroethylene, and is constructed with a high-roughness and low-surface-energy surface structure, and it is found that the surface structure with high roughness and low surface energy is also conducive to improving the super-hydrophobicity of the coating; the high-thermal-conductivity of the super-hydrophobic high-thermal-conductivity composite coating in the application is mainly provided by the combined action of three components of graphene, silicon carbide and silicon dioxide, and the three solid fillers with different dimensions are uniformly dispersed in the coating to form an interlaced thermal-conductivity network, which is conducive to improving the thermal-conductivity of the coating; the excellent wear resistance and bonding strength of the super-hydrophobic high-thermal-conductivity composite coating in the application are mainly strengthened by the combined action of the adhesion agent, silicon carbide and the hardening and wear-resistant agent, and in particular, the adhesion agent and the hardening and wear-resistant agent are synergistically combined to connect the inorganic filler, the metal substrate and the organic resin (polytetrafluoroethylene component) through cross-linking, thereby effectively improving the adhesion and / or hardness of the coating.

[0024] (2) In the preparation of the super-hydrophobic high-thermal-conductivity composite coating, the super-hydrophobic high-thermal-conductivity composite coating can be obtained by a blending method, and then the super-hydrophobic high-thermal-conductivity composite coating is formed by spraying and baking, the water contact angle of the super-hydrophobic high-thermal-conductivity composite coating in the application is above 159°, and the rolling angle is less than 4°, after the coating is coated on a 2.5mm thick stainless steel plate, the overall thermal conductivity of the coating can be preferably above 18.4W / (m·K), which is higher than that of the stainless steel substrate; and the super-hydrophobic high-thermal-conductivity composite coating in the application has excellent adhesion (adhesion) (GB / T9286-1998 standard, 0 or 1 level) and hardness (pencil hardness above 3H); after the wear and peeling test, the water contact angle changes little (the water contact angle can still be maintained above 157°), and after the acid and alkali corrosion test for 1 day, the super-hydrophobicity (the water contact angle can still be maintained above 154°) is still maintained in the range of pH=3-11.

[0025] (3) The raw materials used in the super-hydrophobic high-thermal-conductivity composite coating and the super-hydrophobic high-thermal-conductivity composite coating in the application are low in cost and can be purchased on the market, and the raw material cost of the small-scale preparation of the finished coating in the laboratory is not higher than 265 yuan / kg. The preparation process of the super-hydrophobic high-thermal-conductivity coating in the application is simple and easy, which is a simple blending method, and the coating can be prepared by spraying and baking without special instruments and equipment. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is the AFM graph of the super-hydrophobic high-thermal-conductivity composite coating obtained in Example 1 of the application;

[0027] Figure 2 is the AFM graph of the coating obtained in Comparative Example 1 of the application;

[0028] Figure 3is a performance test result curve of the super-hydrophobic high-thermal-conductivity composite coating obtained by the embodiment 1 of the present application; Figure 3 In the figure, (a) corresponds to the abrasion test result curve; (b) corresponds to the peeling test result curve; (c) corresponds to the water impact test result curve; (d) corresponds to the acid and alkali corrosion test result curve. DETAILED DESCRIPTION

[0029] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0030] The present application provides, in a first aspect, a super-hydrophobic high-thermal-conductivity composite coating, which is formed from a super-hydrophobic high-thermal-conductivity composite coating material, the super-hydrophobic high-thermal-conductivity composite coating material comprising the following components in mass fractions:

[0031] ethanol solution 60-80 parts (for example 60, 65, 70, 75 or 80 parts), dispersant 3-5 parts (for example 3, 3.5, 4, 4.5 or 5 parts), adhesion agent 3-5 parts (for example 3, 3.5, 4, 4.5 or 5 parts), dimethyl silicone oil 0.3-0.5 parts (for example 0.3, 0.4 or 0.5 parts), polytetrafluoroethylene micro powder 8-10 parts (for example 8, 9 or 10 parts), silicon dioxide 1-2 parts (for example 1, 1.2, 1.5, 1.8 or 2 parts), graphene 0.8-1.2 parts (for example 0.8, 0.9, 1, 1.1 or 1.2 parts), silicon carbide 2-3 parts (for example 2, 2.2, 2.5, 2.8 or 3 parts), hardening and wear-resistant agent 1.2-1.5 parts (for example 1.2, 1.3, 1.4 or 1.5 parts) and polytetrafluoroethylene emulsion 4-6 parts (for example 4, 4.5, 5, 5.5 or 6 parts); in the present application, “parts” all refer to “mass parts”, in specific examples and comparative examples, the unit of mass parts may, for example, be unified as “g” or “kg” and the like weight units; in the present application, for example, after the super-hydrophobic high-thermal-conductivity composite coating is sprayed and then baked, a super-hydrophobic high-thermal-conductivity composite coating is prepared, and a high-thermal-conductivity super-hydrophobic coating is quickly constructed; the baking is first baking at 250-280°C (for example 250°C, 260°C, 270°C or 280°C) for 10-20 min (for example 10, 15 or 20 min), and then baking at 360-400°C (for example 360°C, 370°C, 380°C, 390°C or 400°C) for 10-30 min (for example 10, 15, 20, 25 or 30 min); the temperature rising rate for rising to the baking temperature is 5-10°C / min (for example 5, 6, 7, 8 or 9°C / min).

[0032] The present application finds that the performance of the super-hydrophobic high-thermal-conductivity composite coating formed can be effectively improved by using a staged baking method (baking at 250-280 DEG C for 10-20 min + baking at 360-400 DEG C for 10-30 min) after spraying the super-hydrophobic high-thermal-conductivity composite coating, because the staged baking used in the present application helps to gradually remove the solvent and moisture in the coating, reduces the formation of bubbles or pores, and can promote the uniform solidification of the coating and the discharge of bubbles, thereby forming a more dense coating structure, which helps to improve the super-hydrophobic performance and hardness of the surface, etc. In addition, during the low-temperature stage baking, the coating can better bond with the surface of the substrate, and then during the high-temperature stage baking, cross-linking or solidification is carried out, which can enhance the adhesion of the coating. The super-hydrophobicity of the super-hydrophobic high-thermal-conductivity composite coating in the present application is mainly provided by the combined action of the four components of silicon dioxide, graphene, dimethyl silicone oil and polytetrafluoroethylene, but it is also inseparable from the high-roughness and low-surface-energy surface structure jointly constructed by other components. The present application finds that the high-roughness and low-surface-energy surface structure is also conducive to improving the super-hydrophobic performance of the coating. The high-thermal-conductivity of the super-hydrophobic high-thermal-conductivity composite coating in the present application is mainly provided by the combined action of the three components of graphene, silicon carbide and silicon dioxide. The three different dimensional solid fillers are uniformly dispersed in the coating to form an interlaced thermal conduction network, which is conducive to improving the thermal conductivity performance of the coating, but it is also inseparable from the influence of other components on the formed thermal conduction network structure. The excellent wear resistance and adhesion strength of the super-hydrophobic high-thermal-conductivity composite coating in the present application are mainly strengthened by the combined action of the adhesion agent, silicon carbide and the hardening and wear-resistant agent. In particular, the adhesion agent and the hardening and wear-resistant agent synergistically act to connect the inorganic filler, the metal substrate and the organic resin (polytetrafluoroethylene component) through cross-linking, effectively improving the adhesion and / or hardness of the coating, but other components also affect the cross-linking. The present application finds that the content of each component contained in the super-hydrophobic high-thermal-conductivity composite coating needs to be controlled to be appropriate. If the content of each component is not appropriate, it will adversely affect the super-hydrophobicity, thermal conductivity performance, wear resistance, mechanical stability and / or adhesion of the coating, etc. For example, excessive hardening and wear-resistant agent will significantly affect the hydrophobicity of the coating, excessive dimethyl silicone oil will significantly reduce the hardness and adhesion of the coating, and excessive graphene or silicon carbide powder will also increase the porosity of the coating, affecting the density and thus the overall performance of the coating.

[0033] The super-hydrophobic high-thermal-conductivity composite coating in the present application has stable super-hydrophobic properties and excellent thermal conductivity performance, has excellent wear resistance and mechanical stability, is suitable for use in harsh environments such as acid and alkali, is suitable for use in places that promote condensation heat transfer strengthening, and is especially suitable for use in heat exchange places such as vapor-liquid / gas heat exchangers. The super-hydrophobic high-thermal-conductivity composite coating in the present application can be used as a super-hydrophobic high-thermal-conductivity durable coating (super-hydrophobic high-thermal-conductivity composite coating) for strengthening condensation heat transfer.

[0034] According to some preferred embodiments, the ethanol solution is an ethanol aqueous solution containing 80-90% (e.g. 80%, 85% or 90%) of ethanol by volume, and in the present application, the ethanol aqueous solution contains part of water, which can make the adhesion agent hydrolyze; and / or the solid content of the polytetrafluoroethylene emulsion is 40-60%; the present application does not make specific limitations on the polytetrafluoroethylene emulsion, and a commercially available product can be used.

[0035] According to some preferred embodiments, the dispersant is a polycarboxylic acid sodium salt dispersant; the present application does not make specific limitations on the polycarboxylic acid sodium salt dispersant, and for example, a commercially available product can be used; in some specific embodiments, the polycarboxylic acid sodium salt dispersant is for example polycarboxylic acid sodium salt dispersant SN-DISPERSANT 5040; the adhesion agent is a modified silane polymer; in the present application, the adhesion agent is an adhesion promoter, and the main component is a modified silane polymer; in some specific embodiments, the adhesion agent can be for example adhesion agent SRE-6015W, and the main component is a modified silane polymer; the silicon dioxide is silicon dioxide modified by silane coupling agent KH-550, and the use of silicon dioxide modified by silane coupling agent KH-550 in the present application is beneficial to improve the hydrophobicity of the coating, and if unmodified silicon dioxide is used, the hydrophobicity of the coating will be affected; the present application does not make specific limitations on the silicon dioxide modified by silane coupling agent KH-550, and a commercially available product or silicon dioxide modified by silane coupling agent KH-550 obtained by a prior method can be used; in some specific embodiments, the silicon dioxide is for example silicon dioxide modified by silane coupling agent KH-550, and the model number is ZD-SiO2-Z22; the silicon dioxide with the model number ZD-SiO2-Z22 can be purchased from Jinan Zhiding Welding Material Co., Ltd., and the particle size is preferably 20 nm, and the specific surface area is preferably 230 m 2 / g; the graphene is few-layer graphene or single-layer graphene, preferably single-layer graphene, and preferably the carbon content in the graphene is not less than 98wt%; and / or the hardening and wear-resistant agent is a modified organic silicon complex nano-silicon solution; the present application does not have special requirements for the hardening and wear-resistant agent, and a commercially available product can be used; in the present application, preferably, the hardening and wear-resistant agent is hardening and wear-resistant agent SRE-5250, and in the present application, the mass percentage of silicon dioxide (SiO2) in the hardening and wear-resistant agent SRE-5250 is 35%.

[0036] According to some preferred embodiments, the particle size of the polytetrafluoroethylene micro-powder is not more than 1 μm; the particle size of the silicon dioxide is not more than 20 nm; the particle size D50 of the graphene is not more than 12 μm; and / or the particle size of the silicon carbide is not more than 1 μm.

[0037] The present application provides, in a second aspect, a method for preparing the super-hydrophobic high-thermal-conductivity composite coating described in the first aspect of the present application, the method comprising the following steps:

[0038] (1) adding a dispersing agent, an adhesion agent and dimethyl silicone oil in an ethanol solution and stirring uniformly to obtain solution A;

[0039] (2) adding polytetrafluoroethylene micro-powder, silicon dioxide, graphene and silicon carbide in solution A and ultrasonically dispersing uniformly to obtain solution B;

[0040] (3) adding a hardening and wear-resistant agent and a polytetrafluoroethylene emulsion in solution B and ultrasonically dispersing uniformly, and then filtering through a mesh screen with a mesh size of more than 100 meshes to obtain a super-hydrophobic high-thermal-conductivity composite coating; in the present application, the mesh screen is for example a stainless steel mesh screen;

[0041] (4) pretreating a substrate, then spraying the super-hydrophobic high-thermal-conductivity composite coating on the substrate, and then baking to obtain a super-hydrophobic high-thermal-conductivity composite coating on the substrate; in the present application, the substrate is for example a stainless steel and / or copper substrate; the pretreatment is for example cleaning, drying and preheating the substrate; in the present application, the preheating is for example preheating at 80-100℃ for 5-10 min.

[0042] In the preparation of the super-hydrophobic high-thermal-conductivity composite coating, the super-hydrophobic high-thermal-conductivity composite coating can be first obtained by a blending method, and then the super-hydrophobic high-thermal-conductivity composite coating can be formed by a spraying+baking method. The super-hydrophobic high-thermal-conductivity composite coating in the present application has a water contact angle of more than 159° and a rolling angle of less than 4°. After the coating is applied on a 2.5 mm thick stainless steel plate, the overall thermal conductivity can reach more than 18.4 W / (m·K), which is higher than that of the stainless steel substrate. Furthermore, the super-hydrophobic high-thermal-conductivity composite coating in the present application has excellent adhesion (adhesive force) (GB / T9286-1998 standard, 0 or 1 level) and hardness (pencil hardness of more than 3H). After wear and tear and peeling tests, the water contact angle changes little (the water contact angle can still remain above 157°), and after acid and alkali corrosion tests for 1 day, the super-hydrophobicity is still maintained (the water contact angle can still remain above 154°) in the pH=3-11 range. The raw materials for the super-hydrophobic high-thermal-conductivity composite coating and the super-hydrophobic high-thermal-conductivity composite coating in the present application are inexpensive and commercially available. The raw material cost for small-scale preparation of the finished coating in the laboratory is not higher than 265 yuan / kg. The preparation process of the super-hydrophobic high-thermal-conductivity coating in the present application is simple and easy to operate, and the coating can be prepared by a simple spraying+baking method without the need for special instruments and equipment.

[0043] According to some preferred embodiments, in step (2) and / or step (3), the time for ultrasonic dispersion is 15-30 min (e.g. 15, 20, 25 or 30 min), preferably 20 min; in the present application, the ultrasonic dispersion is performed, for example, by using an ultrasonic cleaner.

[0044] According to some preferred embodiments, the spraying is performed under a pressure (air pressure) of 0.2-0.4 MPa (e.g. 0.2, 0.3 or 0.4 MPa), and the distance between the spray gun and the substrate is 100-250 mm (e.g. 100, 120, 150, 180, 200, 220 or 250 mm) during spraying; in the present application, it is preferred to perform the spraying under an air pressure of 0.2-0.4 MPa, which can ensure uniform distribution of the paint and effective coverage on the surface of the substrate, and is helpful to form a uniform coating layer, avoiding sagging or omission, and a higher air pressure can better atomize the paint, making the particles smaller, thereby improving the adhesion of the coating layer, and can improve the spraying efficiency, reduce the waste of paint and save material cost.

[0045] According to some preferred embodiments, the baking is performed by first baking at 250-280 °C (e.g. 250 °C, 260 °C, 270 °C or 280 °C) for 10-20 min (e.g. 10, 15 or 20 min), and then baking at 360-400 °C (e.g. 360 °C, 370 °C, 380 °C, 390 °C or 400 °C) for 10-30 min (e.g. 10, 15, 20, 25 or 30 min); and / or the heating rate for heating to the baking temperature is 5-10 °C / min (e.g. 5, 6, 7, 8 or 9 °C / min); it is found in the present application that the use of the staged baking method (10-20 min at 250-280 °C + 10-30 min at 360-400 °C) after spraying the super-hydrophobic high-thermal-conductivity composite paint can effectively improve the performance of the formed super-hydrophobic high-thermal-conductivity composite coating, because the use of the staged baking method in the present application can help to gradually remove the solvent and moisture in the coating, reduce the formation of bubbles or pores, promote the uniform solidification of the coating and the discharge of bubbles, thereby forming a more dense coating structure, which is helpful to improve the super-hydrophobic performance and hardness of the surface, etc. In addition, the coating can better combine with the surface of the substrate during the low-temperature stage baking, and the subsequent cross-linking or solidification during the high-temperature stage baking can enhance the adhesion of the coating.

[0046] According to some specific embodiments, the preparation of the super-hydrophobic high-thermal-conductivity composite coating is as follows:

[0047] ①In 60-80 parts of an ethanol aqueous solution with an ethanol volume percentage of 80-90%, 3-5 parts of a dispersant (polycarboxylic acid sodium salt dispersant SN-DISPERSANT 5040), 3-5 parts of an adhesion agent (adhesion agent SRE-6015W) and 0.3-0.5 parts of dimethyl silicone oil (dimethyl silicone oil PMX-200) are added, and stirred uniformly to obtain solution A.

[0048] ②In the solution A obtained in step ①, 8-10 parts of polytetrafluoroethylene powder, 1-2 parts of silicon dioxide, 0.8-1.2 parts of graphene and 2-3 parts of silicon carbide are added, and then dispersed for 20 min by an ultrasonic cleaner to obtain solution B; wherein the particle size of the polytetrafluoroethylene powder is preferably not more than 1 μm; the silicon dioxide is silicon dioxide modified by silane coupling agent KH-550, with a model number of ZD-SiO2-Z22, and the particle size is preferably not more than 20 nm; the graphene is few-layer graphene or single-layer graphene, and preferably single-layer graphene, the carbon content of the single-layer graphene is not less than 98%, and the particle size D50 is preferably not more than 12 μm; the particle size of the silicon carbide is preferably not more than 1 μm.

[0049] ③In the solution B obtained in step ②, 1.2-1.5 parts of a hardening and wear-resistant agent (hardening and wear-resistant agent SRE-5250, containing 35 wt% of SiO2 as an effective component) and 5 parts of polytetrafluoroethylene emulsion are added while stirring, and then dispersed for 20 min by an ultrasonic cleaner, and filtered through a stainless steel mesh with a mesh size of more than 100, to obtain a super-hydrophobic and high-thermal-conductivity composite coating; wherein the solid content of the polytetrafluoroethylene emulsion is 40-60%.

[0050] ④After polishing, cleaning, drying and preheating a stainless steel plate and / or a copper plate substrate, the substrate is sprayed by a spray gun at a distance of 100-250 mm from the substrate, and perpendicular to the surface of the substrate, under the condition of an air pressure of 0.2-0.4 MPa; and then baked in an oven, with a temperature rising rate of 5-10 ℃ / min: first, the temperature is raised to 260 ℃ at a temperature rising rate of 5-10 ℃ / min, and baked at a constant temperature for 10-20 min; then, the temperature is raised to 380 ℃ at a temperature rising rate of 5-10 ℃ / min, and baked at a constant temperature for 10-30 min; and finally, naturally cooled to room temperature, to obtain a super-hydrophobic and high-thermal-conductivity composite coating on the substrate.

[0051] In a third aspect, the application provides a super-hydrophobic and high-thermal-conductivity composite coating prepared by the preparation method described in the second aspect of the application.

[0052] According to some preferred embodiments, the super-hydrophobic high-thermal-conductivity composite coating has a water contact angle of above 159°, a thermal conductivity of 18.4 W / (m·K), an adhesion of 0 or 1 grade, and a pencil hardness of above 3H; preferably, the super-hydrophobic high-thermal-conductivity composite coating has a water contact angle of above 157° after abrasion and peeling tests, and a water contact angle of above 154° after 24h acid-base corrosion tests with pH ranging from 3 to 11.

[0053] The present application provides, in a fourth aspect, use of the super-hydrophobic high-thermal-conductivity composite coating described in the first aspect of the present application or prepared by the method described in the second aspect of the present application in strengthening condensation heat transfer.

[0054] The present application will be further described below by way of examples, but the scope of protection of the present application is not limited to these examples.

[0055] Example 1

[0056] ①In 70 parts of an ethanol aqueous solution with a volume percentage of 85% ethanol, 3 parts of a dispersant (polycarboxylic acid sodium salt dispersant SN-DISPERSANT 5040), 5 parts of an adhesion agent (adhesion agent SRE-6015W), and 0.5 parts of dimethyl silicone oil (dimethyl silicone oil PMX-200) were added and stirred uniformly to obtain solution A.

[0057] ②In the solution A obtained in step ①, 10 parts of polytetrafluoroethylene micro powder, 1.5 parts of silicon dioxide, 1.2 parts of graphene, and 3 parts of silicon carbide were added and dispersed for 20 min by an ultrasonic cleaning instrument to obtain solution B; wherein the particle size of the polytetrafluoroethylene micro powder was 1 μm; the silicon dioxide was silicon dioxide of type ZD-SiO2-Z22 modified by silane coupling agent KH-550, with a particle size of 20 nm; the graphene was single-layer graphene, with a carbon content of 98 wt% and a particle size D50 of 12 μm; the silicon carbide had a particle size of 1 μm.

[0058] ③In the solution B obtained in step ②, 1.5 parts of a hardening and wear-resistant agent (hardening and wear-resistant agent SRE-5250 containing 35 wt% of SiO2 as an effective ingredient) and 5 parts of polytetrafluoroethylene emulsion were added while stirring, and then dispersed for 20 min by an ultrasonic cleaning instrument and filtered through a 100-mesh stainless steel screen to obtain a super-hydrophobic high-thermal-conductivity composite coating; wherein the polytetrafluoroethylene emulsion had a solid content of 60%.

[0059] (4) 0.4 mm-thick stainless steel plate was used as a substrate, and the stainless steel plate was polished, washed, dried and preheated, and then the super-hydrophobic high-thermal-conductivity composite coating obtained in step (3) was sprayed vertically to the surface of the plate at a distance of 180 mm from the substrate under the condition of air pressure of 0.3 MPa, and then baked in an oven, with the temperature increasing rate set to 5°C / min: first, the temperature was increased to 260°C at a rate of 5°C / min, and then kept constant for 15 min, and then the temperature was increased to 380°C at a rate of 5°C / min, and then kept constant for 25 min, and finally naturally cooled to room temperature, to obtain a super-hydrophobic high-thermal-conductivity composite coating on the substrate.

[0060] Examples 2-19

[0061] Examples 2-19 are basically the same as Example 1, except that some components in the adopted formula are different from those in Example 1, and the specific differences are shown in Table 1.

[0062] Table 1

[0063]

[0064]

[0065] Comparative Example 1

[0066] This comparative example provides a commercial polytetrafluoroethylene emulsion as a coating, and a coating is formed by the same method as step (4) in Example 1; wherein the solid content of the polytetrafluoroethylene emulsion is 60%.

[0067] Comparative Example 2

[0068] Comparative Example 2 is basically the same as Example 1, except that:

[0069] (4) 0.4 mm-thick stainless steel plate was used as a substrate, and the stainless steel plate was polished, washed, dried and preheated, and then the super-hydrophobic high-thermal-conductivity composite coating obtained in step (3) was sprayed vertically to the surface of the plate at a distance of 180 mm from the substrate under the condition of air pressure of 0.3 MPa, and then baked in an oven, with the temperature increasing rate set to 5°C / min: first, the temperature was increased to 260°C at a rate of 5°C / min, and then kept constant for 15 min, and then the temperature was increased to 380°C at a rate of 5°C / min, and then kept constant for 25 min, and finally naturally cooled to room temperature, to obtain a super-hydrophobic high-thermal-conductivity composite coating on the substrate.

[0070] Comparative Example 3

[0071] Comparative Example 3 is basically the same as Example 1, except that:

[0072] (4) taking a stainless steel plate with a thickness of 0.4 mm as a substrate, polishing the stainless steel plate, cleaning, drying and preheating, and then spraying the super-hydrophobic high-thermal-conductivity composite coating obtained in step (3) on the stainless steel plate at a distance of 180 mm from the substrate and perpendicular to the surface of the plate under the condition of an air pressure of 0.3 MPa; then baking and shaping in an oven, setting the temperature increasing rate at 5 ℃ / min, increasing the temperature at a rate of 5 ℃ / min to 380 ℃, and then baking at a constant temperature for 40 min, and finally naturally cooling to room temperature, so as to obtain a composite coating on the substrate.

[0073] The present application tests the performance of the coating obtained in each embodiment and each proportion, and the test results are shown in Table 2; wherein the water contact angle is the average value of 3-5 measurements; the thermal conductivity is the thermal conductivity of the coating in each embodiment or each proportion, which is measured by a laser thermal conductivity instrument and sprayed on a 2.5 mm thick stainless steel plate by the same method as step (4) in embodiment 1; the pencil hardness is measured according to the standard GB / T 6739-2022; and the adhesion grade is measured according to the standard GB / T9286-1998.

[0074] Table 2

[0075]

[0076]

[0077] The present application performs AFM characterization on the super-hydrophobic high-thermal-conductivity composite coating obtained in embodiment 1 and the coating obtained in comparative example 1, and the AFM results are shown in Figure 1 and Figure 2 respectively; it is shown from the AFM characterization results that the roughness Ra of the coating in comparative example 1 is 55 nm, and the roughness Ra of the super-hydrophobic high-thermal-conductivity composite coating in embodiment 1 is 119.6 nm; this indicates that the super-hydrophobic high-thermal-conductivity composite coating in the present application has excellent super-hydrophobicity after doping, which also benefits from the higher roughness of the coating itself after doping.

[0078] The present application also tests the mechanical stability and chemical stability of the super-hydrophobic high-thermal-conductivity composite coating in embodiment 1, and the test method is as follows:

[0079] 1. abrasion test: place the sandpaper with a particle size of 800 on the coated sample with the face downward, then place a 150 g weight on the overlapping part of the sandpaper and the sample, so that the sample test area and the sandpaper are in close contact. Move the sample back and forth in a certain direction for 10 cm, then rotate 90° and move the same distance; this process represents an abrasion cycle, and the water contact angle of the sample is recorded once every 20 cycles, and the abrasion test result curve is shown in Figure 3 (a).

[0080] 2. Peeling test: The peeling of the coated sample was performed using a strong adhesive tape (3M 600-1PK model, adhesion force up to (10±1) N / 25mm), and a 1.0 kg weight was placed to ensure complete adhesion of the tape. The water contact angle change of the sample was recorded after each 30 peeling cycles as a period, and the peeling test result curve was measured as shown in Figure 3 (b).

[0081] 3. Water impact test: The coated sample was fixed on a surface inclined at 45°, and water droplets were continuously dropped from a height of 50 cm at a speed of 20 mL / min. The wettability (water contact angle) change of the sample was recorded every 30 min as a period, and the water impact test result curve was measured as shown in Figure 3 (c).

[0082] 4. Chemical stability test: The surface of the coating was corroded by HCl solution / NaOH solution with pH=1-13 for 24 h, and the water contact angle of the coating after corrosion was tested. The acid-base corrosion test result curve was measured as shown in Figure 3 (d), wherein the result corresponding to pH=7 is the result measured by corroding the surface of the coating with a 3.5wt% NaCl aqueous solution for 24 h.

[0083] From the results of Figure 3 , it can be seen that the contact angle of the coating can be maintained above 151.5° after the stability test; among them, the mechanical stability is more excellent, and the water contact angle change is small (the water contact angle can still be maintained above 157°) after the abrasion and peeling test; the water impact resistance of the coating is relatively poor, but the super-hydrophobic structure can still be maintained during the test; in the alkali corrosion resistance test, after the acid-base corrosion test for 1 day (24 h), it still has super-hydrophobicity (the water contact angle can still be maintained above 154°) in the range of pH=3-11, but due to the doping of silica, graphene and other substances in the coating, the coating density decreases slightly, and the surface hydrophobic structure may be damaged after long-term strong alkali (pH not less than 13, corrosion time greater than 24 h) corrosion.

[0084] The part of the present application not described in detail is the technology known to those skilled in the art.

[0085] Finally, it should be pointed out that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A superhydrophobic and highly thermally conductive composite coating, characterized in that: The superhydrophobic and high thermal conductivity composite coating is formed from a superhydrophobic and high thermal conductivity composite coating, which contains the following components in parts by mass: The mixture contains 60-80 parts ethanol solution, 3-5 parts dispersant, 3-5 parts adhesion agent, 0.3-0.5 parts dimethyl silicone oil, 8-10 parts polytetrafluoroethylene micro powder, 1-2 parts silicon dioxide, 0.8-1.2 parts graphene, 2-3 parts silicon carbide, 1.2-1.5 parts hardening and wear-resistant agent, and 4-6 parts polytetrafluoroethylene emulsion. The silica is silica modified with silane coupling agent KH-550; the adhesion agent is adhesion agent SRE-6015W; and the hardening and wear-resistant agent is hardening and wear-resistant agent SRE-5250.

2. The superhydrophobic and high thermal conductivity composite coating according to claim 1, characterized in that: The ethanol solution is an aqueous ethanol solution, and the volume percentage of ethanol in the aqueous ethanol solution is 80-90%; and / or The solid content of the polytetrafluoroethylene emulsion is 40% to 60%.

3. The superhydrophobic and high thermal conductivity composite coating according to claim 1, characterized in that: The dispersant is a sodium polycarboxylate dispersant; The graphene is few-layer graphene or single-layer graphene, and the carbon content in the graphene is not less than 98 wt%.

4. The superhydrophobic and high thermal conductivity composite coating according to claim 1, characterized in that: The particle size of the polytetrafluoroethylene micro powder does not exceed 1 μm; The particle size of the silica is no more than 20 nm; The particle size D50 of the graphene does not exceed 12 μm; The particle size of the silicon carbide is no more than 1 μm.

5. The method for preparing the superhydrophobic and high thermal conductivity composite coating according to any one of claims 1 to 4, characterized in that, The method includes the following steps: (1) Add dispersant, adhesive and dimethyl silicone oil to ethanol solution and stir until homogeneous to obtain solution A; (2) Add polytetrafluoroethylene micro powder, silicon dioxide, graphene and silicon carbide to solution A and disperse them evenly by ultrasonication to obtain solution B; (3) Add hardening and wear-resistant agent and polytetrafluoroethylene emulsion to solution B and disperse them evenly by ultrasonication. Then filter through a sieve with a mesh size of 100 or higher to obtain a superhydrophobic and high thermal conductivity composite coating. (4) The substrate is pretreated, and then the superhydrophobic and high thermal conductivity composite coating is sprayed onto the substrate and then baked to obtain a superhydrophobic and high thermal conductivity composite coating on the substrate. The baking is first baked at 250~280℃ for 10~20min, and then baked at 360~400℃ for 10~30min. The heating rate to the baking temperature is 5~10℃ / min.

6. The preparation method according to claim 5, characterized in that: In step (2) and / or step (3), the ultrasonic dispersion time is 15 to 30 minutes.

7. The preparation method according to claim 6, characterized in that: In step (2) and / or step (3), the ultrasonic dispersion time is 20 min.

8. The preparation method according to claim 5, characterized in that: The spraying is carried out under a pressure of 0.2~0.4MPa, and the distance between the spray gun and the substrate is 100~250mm.

9. The superhydrophobic and high thermal conductivity composite coating prepared by any one of claims 5 to 8, characterized in that: The superhydrophobic and high thermal conductivity composite coating has a water contact angle of over 159°, a thermal conductivity of 18.4 W / (m·K), an adhesion grade of 0 or 1, and a pencil hardness of over 3H. The superhydrophobic and high thermal conductivity composite coating has a water contact angle of over 157° after wear and peel tests, and a water contact angle of over 154° after a 24-hour acid-base corrosion test with a pH range of 3 to 11.

10. The application of the superhydrophobic and high thermal conductivity composite coating according to any one of claims 1 to 4 or the superhydrophobic and high thermal conductivity composite coating prepared by any one of claims 5 to 8 in enhancing condensation heat transfer.

Images