A white coating with super-hydrophobic-molecular adsorption-thermal control functions and a preparation method thereof

Abstract

The application discloses a white coating with super-hydrophobic-molecular adsorption-thermal control functions and a preparation method thereof, and belongs to the field of special functional coating. The application aims to solve the problems of adsorption capacity decrease caused by the combination of adsorption coating and water molecules and poor combination in a humid environment. The coating is modified by mixing gamma-methacryloxypropyl trimethoxysilane, tetraethyl orthosilicate and hydroxyl-terminated polydimethylsiloxane with a silica sol coating and a zeolite molecular sieve, so that the interface organic-inorganic coupling effect is realized, and the coating can selectively adsorb organic pollutants; the super-hydrophobic performance of the coating is good due to the rough micro-nano structure of the surface and the water repelling effect of the organic groups; in addition, the hierarchical layered three-dimensional pore space structure has a good radiation cooling effect, and is beneficial to enhancing the heat dissipation capacity of the coating in spacecraft thermal control. The application has a very wide application prospect in the fields of air purification, sewage treatment, pollution protection, aerospace and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of special functional coating, and particularly relates to a white coating with super-hydrophobicity-molecular adsorption-thermal control functions and a preparation method thereof. The present application has very wide application prospects in the fields of air purification, sewage treatment, pollution protection, aerospace, etc. BACKGROUND

[0002] As one of the most important tools for exploring space, the working state of a spacecraft will directly affect the smooth progress of a flight mission. When a spacecraft operates in a high-vacuum environment, organic small-molecule pollutants such as siloxane, acid ester and carbon hydrogen released by non-metallic materials used by the spacecraft will condense and deposit on the surfaces of various optical systems and thermal control systems, affecting the full play of their functions and even leading to failure. In addition, these organic molecule pollutants will also deposit in a manned cabin or a vacuum chamber, affecting the health of astronauts and the performance of sensitive components. With the development of spacecraft towards high performance, high reliability and long life, high precision and sensitivity of effective payloads are required, and corresponding means are urgently needed to solve the problem of on-orbit molecular pollution.

[0003] At present, using porous materials to adsorb organic molecule pollutants is a simple, convenient and low-cost effective method. Zeolite molecular sieve contains rich micropores, has a large specific surface area, selective adsorption and a certain catalytic activity due to a large number of acid sites, and has been widely used in the field of on-orbit pollutant control of spacecraft. However, the existing molecular pollution adsorbers with zeolite molecular sieve as functional materials have the disadvantages of large weight and size, inflexible installation position and insufficient absorption area, which cannot well meet the design requirements of spacecraft. Molecular pollution adsorption coating can collect pollutants in real time in space, reduce the possibility of on-orbit pollution, and thus improve the performance and life of the spacecraft. Therefore, it is of great significance to provide a preparation method of a molecular adsorption coating for spacecraft.

[0004] Although the molecular adsorption coating has incomparable advantages, it still faces a major challenge in practical application, i.e. the influence of water on its adsorption capacity. One of the main reasons is that the zeolite surface and the inside of the pore contain a large number of oxygen-containing functional groups and metal ion sites, which show high affinity to water molecules. Water molecules and pollutants compete for adsorption sites on the molecular adsorption, resulting in a decrease in the adsorption capacity of the target pollutants. In a humid environment, the strong combination of water molecules and zeolite molecular sieve adsorption coating will cause a decrease in the adhesion of the coating to the substrate, and problems such as cracking and falling off. Therefore, it is of great significance to develop a molecular adsorption thermal control coating with super-hydrophobicity. SUMMARY

[0005] The present application aims to solve the problem of adsorption capacity reduction caused by the combination of adsorption coating and water molecules, and the problem of poor binding force in a humid environment, thereby providing a white coating with super-hydrophobic-molecular adsorption-thermal control functions, which can stably combine in a humid environment, selectively adsorb space molecular pollutants, and enhance the heat dissipation capacity in spacecraft thermal control.

[0006] The present application provides a white coating with super-hydrophobic-molecular adsorption-thermal control functions, which is modified by mixing silica sol coating and zeolite molecular sieve, realizes the coupling effect of organic-inorganic interface, and can selectively adsorb organic pollutants. The coating can be directly applied to the inner surface of various precision equipment such as spacecraft by spraying method.

[0007] In order to achieve the above technical problems, the present application adopts the following technical solutions:

[0008] 1. The present application aims to provide a white coating with super-hydrophobic-molecular adsorption-thermal control functions and a preparation method thereof, characterized in that the method is realized by the following steps:

[0009] Step 1, vacuum programmed temperature heating pretreatment of molecular sieve powder to remove water vapor and CO2;

[0010] Step 2, a certain amount of gamma-methacryloxypropyl trimethoxysilane, tetraethyl orthosilicate, and hydroxyl-terminated polydimethylsiloxane are mixed with anhydrous ethanol to prepare modified silica sol coating;

[0011] Step 3, mixing the molecular sieve powder treated in step 1, hydrophobic modifier, and modified silica sol prepared in step 2, and stirring to form a spraying slurry;

[0012] Step 4, spraying the slurry obtained in step 3 on the surface of the sandblasted substrate to solidify and obtain the multifunctional white coating.

[0013] Further limited, in step 1, the vacuum pressure is ≤10 -5 pa.

[0014] Further limited, the maximum temperature is ≤500℃, and the heating time at each temperature is 3h-20h.

[0015] Further limited, in step 2, the mass concentration of hydroxyl-terminated polydimethylsiloxane is 5%-50%.

[0016] Further limited, the ratio of gamma-methacryloxypropyl trimethoxysilane / tetraethyl orthosilicate / ethanol in step 2 can be adjusted according to actual needs.

[0017] Further specifying step 2, a certain proportion of γ-methacryloxypropyltrimethoxysilane, tetraethyl orthosilicate, and anhydrous ethanol are placed in a magnetically stirred reactor; the mixture is slowly heated to 70°C, and then an acidic catalyst is slowly added dropwise to the mixture until the pH of the mixture is 3.5, and the mixture is continuously stirred for 5 hours; then hydroxyl-terminated polydimethylsiloxane is added, and stirring is continued for 4 hours; after the composite sol is cooled to room temperature, it is allowed to stand for 2 hours.

[0018] To be further specified, the acidic catalyst is hydrochloric acid, acetic acid, or sulfuric acid.

[0019] Further, in step 3, the stirring time is greater than 3 hours and the stirring rate is greater than 400 r / min.

[0020] Further specifying, in step 3, the hydrophobic modifier is one or a combination of more of the following: trimethoxymethylsiloxane, trimethoxyethylsiloxane, trimethoxybutylsiloxane, and trimethoxyphenylsiloxane.

[0021] Further specifying, in step 4, the matrix is ​​a metal matrix, a resin matrix, or an organic-inorganic composite matrix.

[0022] Further specifying, in step 4, the liquid delivery pressure is 0.4Mpa-1.0Mpa, the moving speed of the spray gun is 50m / s-200m / s, and the spray distance is 10cm-40cm.

[0023] Further specifying, in step 4, the coating thickness is 100μm-300μm.

[0024] Further, in step 4, the natural air drying time at room temperature is greater than or equal to 8 hours, and the maximum temperature for programmed heating and curing does not exceed 150°C.

[0025] This invention achieves integrated superhydrophobicity, thermal control, and molecular adsorption functions without blocking the original zeolite pore structure. Through modification, this invention enables the coating to exhibit strong adhesion in humid environments and preferential selective adsorption of molecular contaminants.

[0026] Compared with existing adsorbent materials, this invention's coating simultaneously possesses multiple functions including adsorption, thermal control, and superhydrophobicity, enabling strong binding in humid environments and preferential selective adsorption of molecular pollutants. This invention offers the following advantages:

[0027] This invention utilizes a white coating with a rough micro / nano structure and organic groups to repel water, resulting in excellent superhydrophobic properties.

[0028] The white coating of the present invention, which has superhydrophobic-molecular adsorption-thermal control functions, can selectively and preferentially adsorb spatial molecular organic pollutants and exclude water molecules in a humid environment, and has a high pollutant adsorption capacity.

[0029] The white coating of the present invention, which has superhydrophobic-molecular adsorption-thermal control functions, has a hierarchical layered three-dimensional porous spatial structure, which has a good radiative cooling effect and is beneficial to enhancing its heat dissipation capacity in spacecraft thermal control.

[0030] To further understand the features and technical content of this invention, please refer to the following detailed description and accompanying drawings. However, the accompanying drawings are for reference and illustration only and are not intended to limit the invention. Attached Figure Description

[0031] Figure 1 This is a SEM image of the white coating with superhydrophobic-molecular adsorption-thermal control functions prepared by the method in Example 1;

[0032] Figure 2 The nitrogen isotherm adsorption-desorption curve of the white coating with superhydrophobic-molecular adsorption-thermal control function prepared by the method of Example 1;

[0033] Figure 3 These are the UV-Vis spectrophotometer test results of the white coating with superhydrophobic-molecular adsorption-thermal control functions prepared by the method in Example 1;

[0034] Figure 4 The Fourier transform infrared absorption spectrum test results are of the white coating with superhydrophobic-molecular adsorption-thermal control function prepared by the method in Example 1.

[0035] Figure 5 The hydrophobic angle test results are for the white coating with superhydrophobic-molecular adsorption-thermal control functions prepared by the method in Example 1.

[0036] Figure 6 These are photos of the white coating with superhydrophobic-molecular adsorption-thermal control functions prepared by the method in Example 1 before and after a hot-cold alternation experiment. Detailed Implementation

[0037] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0038] The following examples are provided to better illustrate the present invention. However, the present invention is not limited to the specific embodiments described.

[0039] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, while not limiting the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0040] Example 1: The white coating with superhydrophobic-molecular adsorption-thermal control functions in this example is achieved through the following steps.

[0041] (1) Zeolite vacuum temperature program heating pretreatment

[0042] The graded porous FAU type zeolite molecular sieve powder is subjected to vacuum heating and drying degassing treatment to remove excess water vapor and CO2 from the zeolite, preventing it from affecting the formation of the coating slurry. The specific operation procedure is as follows: the graded porous zeolite molecular sieve powder is placed in a tube furnace, and a vacuum is drawn until the pressure reaches 10. -5 Pa; then, a segmented heating program was adopted, heating to 100℃ within 1 hour and holding for 4 hours; heating to 200℃ within 1 hour and holding for 4 hours; heating to 300℃ within 1 hour and holding for 4 hours, maintaining a vacuum state during the process, and naturally cooling to room temperature to complete the pretreatment.

[0043] (2) Preparation of modified silica sol coating

[0044] A certain proportion of γ-methacryloxypropyltrimethoxysilane, tetraethyl orthosilicate, and anhydrous ethanol were placed in a magnetically stirred reactor. The mixture was slowly heated to 70°C, and then an acidic catalyst (concentrated hydrochloric acid with a mass concentration of 36.5%) was slowly added dropwise to the mixture until the pH of the mixture was 3.5, and the mixture was stirred continuously for 5 hours. Then, 30 wt% of hydroxyl-terminated polydimethylsiloxane was added, and the mixture was stirred for another 4 hours. After the composite sol was cooled to room temperature, it was allowed to stand for 2 hours.

[0045] In step (2), the mass ratio of γ-methacryloxypropyltrimethoxysilane, tetraethyl orthosilicate and anhydrous ethanol is 1:1:4.

[0046] (3) Preparation of spray coating slurry

[0047] Under stirring conditions, vacuum-degassed zeolite is slowly and uniformly introduced into the composite modified silica sol at a constant stirring rate. The addition of zeolite alters the viscosity of the mixture; therefore, introducing it too quickly may lead to agglomeration. It is essential to ensure the zeolite is completely dissolved in the coating. After adding the zeolite, mechanical stirring continues for 5 hours. Then, 2% (by mass) of trimethoxyethylsiloxane is added, and stirring continues for another 5 hours to obtain the functional coating required for the spray coating process.

[0048] (4) Apply the slurry to the substrate surface by spraying.

[0049] In this embodiment, an aluminum alloy sheet is used as the substrate. After surface roughening by sandblasting, it is ultrasonically cleaned with anhydrous ethanol for 10 minutes. Following cleaning, the surface is wiped clean with a lint-free cloth soaked in anhydrous ethanol. The slurry for spraying is added to the reservoir of the ultrasonic-assisted thermal spraying device. The cavitation effect of the ultrasound promotes further uniform mixing of the slurry, and the coating is then sprayed onto the aluminum alloy substrate surface. Spraying conditions: nozzle diameter 2.5 mm, liquid delivery pressure 0.8 MPa, spray gun moving speed 100 cm / s, spray distance 25 cm. To prevent cracking due to poor coating adhesion, a multi-coating method is used, with a 10-minute interval between each coat.

[0050] (5) White coating curing and molding

[0051] The obtained graded FAU zeolite adsorption coating was left to air dry naturally at room temperature in a fume hood for 10 hours. Then, it was placed in a vacuum oven for programmed temperature rise curing to ensure a strong bond between the adsorption coating and the substrate and to prevent the coating from cracking. The specific temperature rise conditions were: initially heated to 50°C and held for 6 hours, then heated to 110°C and held for 3 hours, and finally heated to 150°C and held for 1 hour. This yielded a multifunctional 13X zeolite coating with hydrophobic, molecular adsorption, and thermal control properties.

[0052] The scanning electron microscope test results of the white coating with superhydrophobic-molecular adsorption-thermal control functions obtained in this embodiment are as follows: Figure 1 As shown, the coating has a rough and porous surface structure. The pore structure of the zeolite coating is not blocked after modification, which is conducive to the adsorption of spatial molecular pollutants.

[0053] The nitrogen isothermal adsorption-desorption curve test results of the white coating with superhydrophobic-molecular adsorption-thermal control functions obtained in this embodiment are shown in the figure below. Figure 2 As shown, its specific surface area, calculated using the BET method, is 587.3 m². 2 / g, a large specific surface area is beneficial for adsorbing space pollutant molecules.

[0054] The UV-Vis spectrometry test results of the white coating with superhydrophobic-molecular adsorption-thermal control functions obtained in this embodiment are as follows: Figure 3 As shown, the calculated average solar absorptivity in the wavelength range of 200–2500 nm is 12.8%, which meets the performance requirements of thermal control coatings for high-performance, high-reliability spacecraft.

[0055] The Fourier transform infrared absorption spectrum test of the white coating with superhydrophobic-molecular adsorption-thermal control functions obtained in this embodiment is as follows: Figure 4As shown, calculations show that the coating has an average emissivity of 94.3% in the wavelength range of 2–16 μm. The 8–13 μm wavelength range is also known as the atmospheric infrared transparency window (LWIR). This band is almost transparent to infrared radiation, allowing infrared radiation from the ground below this window to directly penetrate the atmosphere and radiate heat into outer space. Calculations show that the white coating exhibits a considerably high infrared emissivity within the LWIR window, which is highly beneficial for heat dissipation and achieves a temperature control effect.

[0056] The water contact angle test results of the white coating with superhydrophobic-molecular adsorption-thermal control functions obtained in this embodiment are as follows: Figure 5 As shown in the figure, its hydrophobic angle is 147°, indicating good hydrophobic properties.

[0057] The white coating with superhydrophobic-molecular adsorption-thermal control functions obtained in this embodiment was subjected to a thermal cycling test. The coating was placed in a vacuum high and low temperature tester for a thermal alternation test at -200 to 200°C. Figure 6 The comparison shows that the coating after the test did not show any cracking or powdering on the substrate and still has excellent interfacial adhesion.

[0058] The white coating material obtained in Example 1 and dioctyl phthalate, a typical molecular pollutant, were placed in a vacuum molecular pollution test system, with the heating stage temperature set to 80°C. Adsorption experiments were conducted on the heating stage, with samples taken every hour and weighed using a precision balance. The adsorption amount was calculated by determining the difference in weight before and after weighing. The results are shown in the table below:

[0059] Table 1 Adsorption test results of the white coating

[0060] Adsorption time Adsorption capacity (mg / cm 2 ) 1h 1.0975 2h 1.5689 3h 2.1753 4h 2.6968 5h 3.0652 6h 3.1898

[0061] As shown in Table 1, the white coating exhibits a strong adsorption capacity for spatial molecular pollutants, reaching near saturation after 6 hours with an adsorption capacity of 3.1898 mg / cm³. 2 .

[0062] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, while not limiting the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

Claims

1. A method for preparing a white coating that combines superhydrophobicity, molecular adsorption, and thermal control functions, characterized in that, The method is implemented through the following steps: Step 1: Vacuum programmed heating pretreatment of zeolite molecular sieve powder to remove water vapor and CO2; Step 2: Prepare a modified silica sol coating by mixing a certain amount of γ-methacryloxypropyltrimethoxysilane, tetraethyl orthosilicate, hydroxyl-terminated polydimethylsiloxane, and anhydrous ethanol. Step 3: Mix the zeolite molecular sieve powder treated in Step 1, the hydrophobic modifier, and the modified silica sol prepared in Step 2, and stir to form a spraying slurry. Step 4: Spray the slurry obtained in step 3 onto the sandblasted substrate surface and cure it to obtain the white coating that combines superhydrophobic, molecular adsorption and thermal control functions.

2. The method according to claim 1, characterized in that, In step 1, the vacuum pressure is ≤10. -5 pa.

3. The method according to claim 1, characterized in that, In step 1, the maximum temperature is ≤500℃, and the heating time for each temperature is 3h-20h.

4. The method according to claim 1, characterized in that, In step 2, the mass concentration of hydroxyl-terminated polydimethylsiloxane is 5%-50%.

5. The method according to claim 1, characterized in that, In step 3, the stirring time is greater than 3 hours and the stirring rate is greater than 400 r / min.

6. The method according to claim 1, characterized in that, In step 3, the hydrophobic modifier is one or a combination of more of the following: trimethoxymethylsiloxane, trimethoxyethylsiloxane, trimethoxybutylsiloxane, and trimethoxyphenylsiloxane.

7. The method according to claim 1, characterized in that, In step 4, the substrate is a metal substrate, a resin substrate, or an organic-inorganic composite material substrate.

8. The method according to claim 3, characterized in that, In step 4, the liquid delivery pressure is 0.4 MPa-1.0 MPa, the moving speed of the spray gun is 50 m / s-200 m / s, and the spray distance is 10 cm-40 cm.

9. The method according to claim 1, characterized in that, In step 4, the coating thickness is 100μm-300μm.

10. The method according to claim 1, characterized in that, In step 4, the natural air drying time at room temperature is greater than or equal to 8 hours, and the maximum temperature for programmed heating and curing is no more than 150℃.

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