A visible and near-infrared coating and its preparation method

Abstract

This application relates to the field of camouflage coatings, specifically disclosing a visible-near-infrared coating and its preparation method. The visible-near-infrared coating comprises component A and component B, which are stored separately and mixed in a weight ratio of (6-8):1 when used. Component A contains the following raw materials in parts by weight: 40-60 parts fluorocarbon resin; 15-25 parts additives; 25-35 parts powder; 4-6 parts polyvinyl alcohol; 2-4 parts polyamide; 0.1-0.3 parts hydroxypropyl methylcellulose; and 20-30 parts solvent. Component B contains the following raw materials in parts by weight: 70-90 parts isocyanate curing agent; and 10-15 parts diluent. The preparation method is as follows: the fluorocarbon resin, solvent, polyvinyl alcohol, and polyamide are mixed evenly, then the additives, powder, and hydroxypropyl methylcellulose are added and mixed evenly to obtain component A; the isocyanate curing agent and diluent are mixed evenly to obtain component B. The visible-near-infrared coating of this application exhibits excellent anti-corrosion properties, and the coating can maintain a long service life.

Description

Technical Field

[0001] This application relates to the field of camouflage coating technology, and more specifically, to a visible and near-infrared coating and its preparation method. Background Technology

[0002] Camouflage coatings are applied to the surface of targets to alter their spectral characteristics, achieving a "same color and spectrum" between the target and the background in the optical band, thus blending the target into the background and concealing it. In modern warfare, this coating has proven highly effective in countering low-light night vision, visible light, and near-infrared reconnaissance, photographic, and multispectral imaging reconnaissance. It is increasingly widely used in defense facilities, various types of technical weapons, and can also be extensively applied to the camouflage of positions.

[0003] Visible-near-infrared (VNIIR) coatings are a special type of coating that achieves stealth effects within the near-infrared spectrum. Near-infrared light refers to light with wavelengths between 700 and 2500 nanometers, a range that falls between visible and infrared light. Visible-near-infrared coatings primarily achieve stealth by absorbing or reflecting near-infrared light. Absorption occurs through certain components of the coating that absorb near-infrared light, while reflection occurs through certain components that reflect near-infrared light. The main components of visible-near-infrared coatings include polymer resins, solvents, silica, and titanium dioxide.

[0004] Regarding the aforementioned technologies, the inventors believe that during actual use, the surface of visible and near-infrared coatings will inevitably be contaminated by dust, sand, and other factors. Regardless of the cause of the surface contamination, it can significantly increase the emissivity of the coating, thereby deteriorating the thermal infrared stealth properties of the coating, resulting in a shorter service life and the need for frequent repairs.

[0005] Therefore, there is an urgent need to propose a solution to address the aforementioned technical problems. Summary of the Invention

[0006] In order to improve the corrosion resistance of visible and near-infrared coatings and extend the service life of the coating, this application provides a visible and near-infrared coating and its preparation method.

[0007] In a first aspect, this application provides a visible-near-infrared coating, which adopts the following technical solution:

[0008] A visible-to-near-infrared coating comprises component A and component B, which are stored separately and mixed in a weight ratio of (6-8):1 when used. Component A contains the following raw materials in parts by weight:

[0009] 40-60 parts of fluorocarbon resin;

[0010] 15-25 parts of auxiliary agent;

[0011] 25-35 parts powder;

[0012] 4-6 parts of polyvinyl alcohol;

[0013] 2-4 parts of polyamide;

[0014] Hydroxypropyl methylcellulose 0.1-0.3 parts;

[0015] Solvent 20-30 parts;

[0016] Component B comprises the following raw materials in parts by weight:

[0017] 70-90 parts of isocyanate curing agent;

[0018] 10-15 parts diluent.

[0019] By adopting the above technical solution, fluorocarbon resin, with a strong CF bond as its backbone, has better heat resistance, chemical resistance, cold resistance, low-temperature flexibility, weather resistance and electrical properties compared with other resins. When used as the main component of visible and near-infrared coatings, it can maintain long-term durability in harsh environments. Meanwhile, in visible and near-infrared coatings, polyamide can improve the surface hardness and wear resistance of the coating; polyvinyl alcohol can tightly bind the various raw materials and form a coating with excellent adhesion; hydroxypropyl methylcellulose can improve the structural strength and durability of the coating. When polyamide, polyvinyl alcohol, and hydroxypropyl methylcellulose are compounded in visible and near-infrared coatings, the hydrogen bonds in the polyvinyl alcohol molecular chain are broken by hydroxypropyl methylcellulose, and then the strong hydrogen bonds between polyamide and polyvinyl alcohol are used to bind them together. This combination, along with the effect on the fluorocarbon resin system, can bring about excellent compound synergistic effects. This makes the visible and near-infrared coating exhibit strong resistance to corrosion when affected by pollution sources such as dust and sand, and the emissivity of the coating does not easily increase rapidly. Thus, the coating can maintain a longer service life, and the overall application effect of the visible and near-infrared coating is significantly improved.

[0020] Preferably, the raw material of component A further contains 7-9 parts by weight of modified carbon fiber, which is prepared by the following steps:

[0021] S1. Remove the carbon fiber raw material, soak it in a roughening solution, wash it with water and dry it to obtain pretreated carbon fiber.

[0022] S2. Tetraethoxysilane is added to anhydrous ethanol and stirred until homogeneous. Then, deionized water and acid catalyst are added, and the mixture is heated and stirred under reflux. N,N-dimethylformamide is then added and stirred to obtain silica sol. The pretreated carbon fibers are then impregnated in the silica sol, stretched, and calcined. After cooling, the modified carbon fibers are obtained.

[0023] By employing the above technical solution, the carbon fiber raw material is roughened, making its surface uneven and significantly increasing its specific surface area, resulting in pretreated carbon fiber. Then, a silica sol is prepared and used to impregnate the pretreated carbon fiber. After pulling and baking, a tightly bonded functional layer is formed on the carbon fiber surface, resulting in modified carbon fiber. Applying modified carbon fiber to visible and near-infrared coatings not only leverages the advantages of carbon fiber, improving electromagnetic shielding performance, but also utilizes its own surface functional layer to form an anti-corrosion protective network within the visible and near-infrared coating, significantly improving the coating's anti-corrosion performance and thus extending its service life.

[0024] Preferably, in step S1, the roughening solution is composed of nitric acid, hydrogen peroxide and water in a volume ratio of (0.8-1.2):(0.8-1.2):1, and the soaking time is 10-15 min.

[0025] By adopting the above technical solution, selecting the above roughening liquid, and controlling the above soaking time, the surface of the pretreated carbon fiber can be made to have a more uniform and moderately deep unevenness, and is more suitable for subsequent bonding of functional layers, thereby obtaining modified carbon fiber with better quality, and the final visible and near-infrared coating has better quality.

[0026] Preferably, in step S2, the molar ratio of hydrogen ions in tetraethoxysilane, anhydrous ethanol, water, and acid catalyst is 1:(6.2-6.5):(3.5-4.0):(0.08-0.09).

[0027] By adopting the above technical solution, the silica sol obtained by the above raw material ratio has a moderate viscosity, which makes it easier to adhere stably to the surface of the pretreated carbon fiber after the pretreated carbon fiber is pulled. At the same time, the solid content and particle size of the silica sol are also suitable for the uneven structure of the surface of the pretreated carbon fiber. Moreover, the functional layer formed after subsequent operations is more dense and stable, and can be tightly combined with the pretreated carbon fiber, thereby obtaining modified carbon fiber with better quality and enabling the modified carbon fiber to exert excellent and stable effects after application.

[0028] Preferably, in step S2, after the pretreated carbon fiber is impregnated with silica sol, the lifting speed is 10-16 cm / min.

[0029] By adopting the above technical solution and selecting the above-mentioned pulling speed, a uniformly distributed and smooth coating film can be formed on the surface of the pretreated fiber, thereby forming a high-quality functional layer after subsequent calcination. If the pulling speed is too fast, the coating film will be too thin, and the functional layer formed after calcination will not be able to completely cover the pretreated carbon fiber; if the pulling speed is too slow, the coating film will be too thick, and local cracks will easily occur on the surface of the structural layer after calcination. Therefore, the selection of the above-mentioned pulling speed is beneficial to obtaining modified carbon fibers with stable and excellent quality.

[0030] Preferably, in step S2, during the roasting process, the temperature is first increased to 200-220℃ at 0.4-0.6℃ / min, and then increased to 580-600℃ at 0.8-1.0℃ / min to complete the roasting.

[0031] By adopting the above technical solution, due to the uneven surface of the pretreated fiber, the surface coating formed after impregnation with silica sol and lifting also has differences in thickness. During the calcination process, it is necessary to pay close attention to the influence of temperature changes on the stress changes of various parts of the coating. The above temperature and corresponding temperature control can keep the coating relatively stable during the formation of the functional layer, making it less likely to cause cracking of the functional layer. As a result, the modified carbon fiber obtained has excellent quality, and after application, a high-quality visible and near-infrared coating can be obtained.

[0032] Preferably, the additives comprise the following components: pigments, dispersants, leveling agents, antioxidants, and film-forming aids.

[0033] By adopting the above technical solutions, the above-mentioned additives are all suitable for the preparation of visible and near-infrared coatings. After the raw materials of each component are mixed evenly, they can exert their own functions and make the resulting visible and near-infrared coatings have excellent construction performance.

[0034] Preferably, the powder is a combination of one or more of aluminum powder, zinc powder, copper powder, nickel powder and monocrystalline silicon.

[0035] By adopting the above technical solutions, the above-mentioned powders can be applied to visible and near-infrared coatings and can stably perform their functions, with a prominent effect in reducing emissivity, resulting in visible and near-infrared coatings of better quality.

[0036] Preferably, the powder is flake aluminum powder with a thickness of 0.5-1.5 μm and an average diameter of 20-50 μm.

[0037] By adopting the above technical solution and selecting the above-specified flaky aluminum powder as the powder material, it not only has a low infrared emissivity, but is also easily protected by the anti-corrosion protective net formed by modified carbon fiber, thereby enabling the visible and near-infrared coatings to maintain high stability during application.

[0038] Secondly, this application provides a method for preparing a visible-near-infrared coating, which adopts the following technical solution: A method for preparing a visible-near-infrared coating includes the following steps:

[0039] (1) Prepare raw materials containing fluorocarbon resin, additives, powder, polyvinyl alcohol, polyamide, hydroxypropyl methylcellulose, solvent, isocyanate curing agent and diluent according to the formula;

[0040] (2) Mix the fluorocarbon resin, solvent, polyvinyl alcohol and polyamide in step (1) evenly, then add the additives, powder and hydroxypropyl methylcellulose, mix evenly to obtain component A; mix the isocyanate curing agent and diluent in step (1) evenly to obtain component B;

[0041] (3) Mix components A and B from step (2) evenly during use to obtain a visible light near-infrared coating.

[0042] By adopting the above technical solution, the above preparation method is simple to operate, and the obtained components A and B can be stored separately. When applying, they can be mixed in proportion to obtain visible light and near-infrared coatings, which is more convenient to use.

[0043] In summary, this application has the following beneficial effects:

[0044] 1. Because this application uses a compound of polyamide, polyvinyl alcohol and hydroxypropyl methylcellulose, the visible and near-infrared coating exhibits strong anti-corrosion performance when affected by pollution sources such as dust and sand, and the service life of the coating is greatly improved.

[0045] 2. In this application, modified carbon fiber is applied to visible and near-infrared coatings. By forming an anti-corrosion protective network in the coating of visible and near-infrared coatings with modified carbon fiber, the anti-corrosion performance of visible and near-infrared coatings can be significantly improved, thereby enabling the coating to maintain a longer service life. Detailed Implementation

[0046] The present application will be further described in detail below with reference to the embodiments.

[0047] Unless otherwise specified, all raw materials used in the preparation examples and embodiments of this application are commercially available.

[0048] The fluorocarbon resin was purchased from Weideyu CF-803 fluorocarbon coating resin.

[0049] Polyvinyl alcohol was purchased from Wanwei Polyvinyl Alcohol 1788;

[0050] The polyamide was purchased from 651 polyamide resin, CAS number 63428-84-2;

[0051] The solvent is a mixture of ethyl acetate, hexafluoroisopropanol and ethylene glycol in a weight ratio of 1:1:1;

[0052] The isocyanate curing agent was purchased from Wanhua PM200.

[0053] The diluent was purchased from Dow Dipropylene Glycol Dimethyl Ether (DMM) diluent;

[0054] The carbon fiber has a diameter of 10 μm and a length of 2 mm;

[0055] The acid catalyst is sulfuric acid.

[0056] Preparation examples of raw materials and / or intermediates

[0057] Preparation Example 1

[0058] A modified carbon fiber is prepared by the following steps:

[0059] S1. Remove the carbon fiber raw material, soak it in a roughening solution, wash it with water and dry it to obtain pretreated carbon fiber.

[0060] S2. Tetraethoxysilane is added to anhydrous ethanol and stirred until homogeneous. Then, deionized water and acid catalyst are added, and the mixture is heated and stirred under reflux. N,N-dimethylformamide is then added and stirred to obtain silica sol. The pretreated carbon fibers are then impregnated in the silica sol, stretched, and calcined. After cooling, the modified carbon fibers are obtained.

[0061] Note: In the above operations, in step S1, the roughening solution is composed of nitric acid, hydrogen peroxide, and water in a volume ratio of 1:1:1, and the soaking time is 12.5 min. In step S2, the molar ratio of hydrogen ions in tetraethoxysilane, anhydrous ethanol, water, and acid catalyst is 1:6.35:3.75:0.085; after the pretreated carbon fibers are impregnated in silica sol, the pulling speed is 13 cm / min; during the calcination process, the temperature is first increased to 210℃ at 0.5℃ / min, and then increased to 590℃ at 0.9℃ / min to complete the calcination.

[0062] Preparation Example 2

[0063] A modified carbon fiber, which differs from Preparation Example 1 in that, in step S1, the roughening solution is composed of nitric acid, hydrogen peroxide and water in a volume ratio of 0.8:0.8:1.

[0064] Preparation Example 3

[0065] A modified carbon fiber, which differs from Preparation Example 1 in that, in step S1, the roughening solution is composed of nitric acid, hydrogen peroxide and water in a volume ratio of 1.2:1.2:1.

[0066] Preparation Example 4

[0067] A modified carbon fiber differs from Preparation Example 1 in that, in step S2, the molar ratio of hydrogen ions in tetraethoxysilane, anhydrous ethanol, water, and acid catalyst is 1:6.2:3.5:0.08.

[0068] Preparation Example 5

[0069] A modified carbon fiber differs from Preparation Example 1 in that, in step S2, the molar ratio of hydrogen ions in tetraethoxysilane, anhydrous ethanol, water, and acid catalyst is 1:6.5:4.0:0.09.

[0070] Preparation Example 6

[0071] A modified carbon fiber, which differs from Preparation Example 1, is pulled at a speed of 10 cm / min after the pretreated carbon fiber has been impregnated with silica sol in step S2.

[0072] Preparation Example 7

[0073] A modified carbon fiber, which differs from Preparation Example 1, is pulled at a speed of 16 cm / min after the pretreated carbon fiber has been impregnated with silica sol in step S2.

[0074] Preparation Example 8

[0075] A modified carbon fiber, which differs from Preparation Example 1, is characterized in that, in step S2, after the pretreated carbon fiber is impregnated with silica sol, the pulling speed is 9 cm / min.

[0076] Preparation Example 9

[0077] A modified carbon fiber, which differs from Preparation Example 1, is characterized in that, in step S2, after the pretreated carbon fiber is impregnated with silica sol, the pulling speed is 17 cm / min.

[0078] Preparation Example 10

[0079] A modified carbon fiber differs from preparation example 1 in that, in step S2, during the calcination process, the temperature is first increased to 200°C at 0.4°C / min, and then increased to 580°C at 0.8°C / min to complete the calcination.

[0080] Preparation Example 11

[0081] A modified carbon fiber differs from preparation example 1 in that, in step S2, during the calcination process, the temperature is first increased to 220°C at 0.6°C / min, and then increased to 600°C at 1.0°C / min to complete the calcination.

[0082] Preparation Example 12

[0083] A modified carbon fiber differs from preparation example 1 in that, in step S2, the calcination process is completed by increasing the temperature to 590°C at a rate of 0.5°C / min.

[0084] Preparation Example 13

[0085] A modified carbon fiber differs from preparation example 1 in that, in step S2, the calcination process is completed by increasing the temperature to 590°C at a rate of 0.9°C / min.

[0086] Example

[0087] Example 1

[0088] A visible-to-near-infrared coating comprises component A and component B, which are stored separately and mixed in a weight ratio of (6-8):1 when used. The raw materials of components A and B and their corresponding weights are shown in Table 1, and the preparation steps are as follows:

[0089] (1) Prepare raw materials containing fluorocarbon resin, additives, powder, polyvinyl alcohol, polyamide, hydroxypropyl methylcellulose, solvent, isocyanate curing agent and diluent according to the formula;

[0090] (2) Mix the fluorocarbon resin, solvent, polyvinyl alcohol and polyamide in step (1) evenly, then add the additives, powder and hydroxypropyl methylcellulose, mix evenly to obtain component A; mix the isocyanate curing agent and diluent in step (1) evenly to obtain component B;

[0091] (3) Mix components A and B from step (2) evenly during use to obtain a visible light near-infrared coating.

[0092] Note: In the above operation, the additives include the following components: pigment, dispersant, leveling agent, antioxidant, and film-forming aid; the pigment is the original Huntsman ALTIRIS 800 infrared reflective pigment for reflective heat insulation coatings, which is rutile titanium dioxide, accounting for 86% of the total weight of the additives; the dispersant is Dispex Ultra PX 4290, accounting for 5% of the total weight of the additives; the leveling agent is TEGO 4100, accounting for 2.5% of the total weight of the additives; the antioxidant is BASF antioxidant 1330, accounting for 5% of the total weight of the additives; and the film-forming aid is Dow DALPAD 292, accounting for 1.5% of the total weight of the additives.

[0093] The powder is flake aluminum powder with a thickness of 1μm and an average diameter of 35μm.

[0094] Example 2-3

[0095] A visible light near-infrared coating differs from Example 1 in that the raw materials and corresponding weights of components A and B are shown in Table 1.

[0096] Table 1. Raw materials of components A and B in Examples 1-3 and their weight parts (kg / part)

[0097]

[0098] Example 4

[0099] A visible light near-infrared coating differs from Example 1 in that the powder is flake aluminum powder with a thickness of 0.5 μm and an average diameter of 20 μm.

[0100] Example 5

[0101] A visible light near-infrared coating differs from Example 1 in that the powder is flake aluminum powder with a thickness of 1.5 μm and an average diameter of 50 μm.

[0102] Example 6

[0103] A visible light near-infrared coating differs from Example 1 in that the powder is flake aluminum powder with a thickness of 0.4 μm and an average diameter of 15 μm.

[0104] Example 7

[0105] A visible light near-infrared coating differs from Example 1 in that the powder is flake aluminum powder with a thickness of 1.6 μm and an average diameter of 55 μm.

[0106] Example 8

[0107] A visible-to-near-infrared coating differs from Example 1 in that 8 parts by weight of modified carbon fiber are added to the raw materials of component A. The modified carbon fiber is used together with additives, powder and hydroxypropyl methylcellulose, and the modified carbon fiber is obtained in Preparation Example 1.

[0108] Example 9

[0109] A visible-to-near-infrared coating differs from Example 8 in that the modified carbon fiber is added in 7 parts by weight.

[0110] Example 10

[0111] A visible-to-near-infrared coating differs from Example 8 in that the modified carbon fiber is added in 9 parts by weight.

[0112] Example 11

[0113] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber is obtained in Preparation Example 2.

[0114] Example 12

[0115] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber is obtained in Preparation Example 3.

[0116] Example 13

[0117] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber is obtained in Preparation Example 4.

[0118] Example 14

[0119] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber is obtained in Preparation Example 5.

[0120] Example 15

[0121] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber is obtained in Preparation Example 6.

[0122] Example 16

[0123] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber was obtained in Preparation Example 7.

[0124] Example 17

[0125] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber is obtained in Preparation Example 8.

[0126] Example 18

[0127] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber was obtained in Preparation Example 9.

[0128] Example 19

[0129] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber is obtained in Preparation Example 10.

[0130] Example 20

[0131] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber was obtained in Preparation Example 11.

[0132] Example 21

[0133] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber was obtained in Preparation Example 12.

[0134] Example 22

[0135] A visible-to-near-infrared coating, which differs from Example 8 in that the modified carbon fiber was obtained in Preparation Example 13.

[0136] Example 23

[0137] A visible light near-infrared coating differs from Example 8 in that modified carbon fiber and other materials are replaced with fiber raw materials.

[0138] Comparative Example

[0139] Comparative Example 1

[0140] A visible-to-near-infrared coating, which differs from Example 1 in that the raw material of component A does not contain polyamide and hydroxypropyl methylcellulose.

[0141] Comparative Example 2

[0142] A visible light near-infrared coating, which differs from Example 1 in that the raw material of component A does not contain polyamide and polyvinyl alcohol.

[0143] Comparative Example 3

[0144] A visible light near-infrared coating, which differs from Example 1 in that the raw material of component A does not contain polyvinyl alcohol and hydroxypropyl methylcellulose.

[0145] Comparative Example 4

[0146] A visible-to-near-infrared coating, which differs from Example 1 in that the raw material of component A does not contain polyamide.

[0147] Comparative Example 5

[0148] A visible-to-near-infrared coating, which differs from Example 1 in that the raw material of component A does not contain polyvinyl alcohol.

[0149] Comparative Example 6

[0150] A visible-to-near-infrared coating, which differs from Example 1 in that the raw material of component A does not contain hydroxypropyl methylcellulose.

[0151] Comparative Example 7

[0152] A visible-to-near-infrared coating, which differs from Example 1 in that the raw material of component A does not contain polyamide, polyvinyl alcohol and hydroxypropyl methylcellulose.

[0153] Performance testing test samples: The visible light and near-infrared coatings obtained in Examples 1-23 were used as test samples 1-23, and the visible light and near-infrared coatings obtained in Comparative Examples 1-7 were used as control samples 1-7.

[0154] Test Method: Test samples 1-23 and control samples 1-7 were coated with a 10-micron layer according to the requirements of standard GJB 5023.2-2003 "Materials and Coatings - Test Methods - Part 2 - Emissivity", and the corresponding emissivity was obtained. Each sample was measured three times, and the average value was recorded as the initial emissivity. The coatings of the above samples were then placed sequentially in an IPX56 dust test chamber, with the dust concentration controlled at 1500 mg / m³. 3 The dust particle size was ≤50 micrometers, the wind speed was 15m / s, the temperature was 35℃, and the relative humidity was 45%. After continuous sand blowing for 48 hours, the emissivity of the coating was measured using the same method. The average value of each sample was recorded as the emissivity after erosion. Then, the increase in emissivity of each sample was calculated. The increase in emissivity = (emissivity after erosion - initial emissivity) / initial emissivity, and the corresponding data are recorded in Table 2 below.

[0155] Table 2 Test results of test samples 1-23 and control samples 1-7

[0156]

[0157]

[0158] As can be seen from Examples 1-3 and Comparative Examples 1-7, and Table 2, the use of a compound of polyamide, polyvinyl alcohol, and hydroxypropyl methylcellulose can give the visible and near-infrared coating excellent resistance to sand and dust erosion, with a significantly lower increase in emissivity measured in the experiment, thus significantly improving the service life of the coating. Meanwhile, if only one or two of polyamide, polyvinyl alcohol, and hydroxypropyl methylcellulose are used, although the coating's erosion resistance can be improved, the improvement effect is limited and far less than that of the compound of all three. Therefore, the compound of polyamide, polyvinyl alcohol, and hydroxypropyl methylcellulose can bring about a more significant effect in this application.

[0159] Combining Examples 1 and 4-7 with Table 2, it can be seen that flake aluminum powder with a thickness of 0.5-1.5μm and an average diameter of 20-50μm can make the final visible and near-infrared coating exhibit relatively stable resistance to sand and dust erosion. However, when the powder size is lower or higher than the above range, the emissivity increases, indicating that the coating's resistance to sand and dust erosion is lost. Therefore, the size of the powder has a significant impact on the coating structure and the performance of its function.

[0160] Combining Examples 8-10 and Example 1 with Table 2, it can be seen that applying modified carbon fiber to visible and near-infrared coatings significantly improves the corrosion resistance of these coatings, while the increase in emissivity obtained in the tests is significantly lower. Furthermore, combining Example 23 with Table 2, it can be seen that although carbon fiber can also improve the resistance to sand and dust erosion in visible and near-infrared coatings, the effect is far less superior than that of modified carbon fiber. This indicates that modified carbon fiber forms a more effective anti-erosion protective network within the coating of visible and near-infrared coatings.

[0161] Based on Examples 8 and 11-12 and Table 2, it can be seen that in step S1, the roughening solution is composed of nitric acid, hydrogen peroxide, and water in a volume ratio of (0.8-1.2):(0.8-1.2):1, and the soaking time is 10-15 min. Both of these conditions can result in the final visible-near-infrared coating exhibiting good resistance to sand and dust erosion. Furthermore, based on Examples 13-14 and Table 2, it can be seen that in step S2, the molar ratio of hydrogen ions in tetraethoxysilane, anhydrous ethanol, water, and the acid catalyst is 1:(6.2-6.5):(3.5-4.0):(0.08-0.09), which can also result in the final visible-near-infrared coating exhibiting good resistance to sand and dust erosion.

[0162] Combining Examples 8 and 15-18 with Table 2, it can be seen that in step S2, after the pretreated carbon fiber is impregnated with silica sol, a pulling speed of 10-16 cm / min can improve the resistance of the modified carbon fiber to sand and dust erosion in the visible and near-infrared coating. However, when the pulling speed is lower or higher than the above range, the emissivity measured in the experiment increases significantly, indicating that the quality of the modified carbon fiber has decreased.

[0163] Combining Examples 8 and 19-22 with Table 2, it can be seen that in step S2, during the calcination process, the temperature is first increased to 200-220℃ at 0.4-0.6℃ / min, and then increased to 580-600℃ at 0.8-1.0℃ / min; both of these measures can ensure that the modified carbon fiber obtained has excellent and stable application effects. If the temperature control operation is changed, the emissivity measured in the experiment increases significantly, indicating that the calcination process is particularly important for obtaining high-quality modified carbon fiber.

[0164] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A visible-near-infrared coating, characterized in that, It consists of component A and component B, which are stored separately and mixed in a weight ratio of (6-8):1 when used. Component A contains the following parts by weight of raw materials: 40-60 parts of fluorocarbon resin; 15-25 parts of auxiliary agent; 25-35 parts powder; 4-6 parts of polyvinyl alcohol; 2-4 parts of polyamide; Hydroxypropyl methylcellulose 0.1-0.3 parts; Solvent 20-30 parts; Component B comprises the following raw materials in parts by weight: 70-90 parts of isocyanate curing agent; 10-15 parts diluent; The raw material of component A also contains 7-9 parts by weight of modified carbon fiber, which is prepared by the following steps: S1. Take carbon fiber raw material, soak it in roughening solution, wash it with water and dry it to obtain pretreated carbon fiber. S2. Tetraethoxysilane is added to anhydrous ethanol and stirred until homogeneous. Then, deionized water and acid catalyst are added, and the mixture is heated and stirred under reflux. N,N-dimethylformamide is then added and stirred to obtain silica sol. The pretreated carbon fibers are then impregnated in the silica sol, stretched, and calcined. After cooling, the modified carbon fibers are obtained. In step S1, the roughening solution is composed of nitric acid, hydrogen peroxide and water in a volume ratio of (0.8-1.2):(0.8-1.2):1, and the soaking time is 10-15 min; In step S2, after the pretreated carbon fiber is impregnated with silica sol, the pulling speed is 10-16 cm / min; during the calcination process, the temperature is first raised to 200-220℃ at 0.4-0.6℃ / min, and then raised to 580-600℃ at 0.8-1.0℃ / min to complete the calcination.

2. The visible and near-infrared coating according to claim 1, characterized in that: The additives comprise the following components: pigments, dispersants, leveling agents, antioxidants, and film-forming aids.

3. The visible and near-infrared coating according to claim 1, characterized in that: The powder is a combination of one or more of aluminum powder, zinc powder, copper powder, nickel powder and monocrystalline silicon.

4. The visible and near-infrared coating according to claim 3, characterized in that: The powder is flake aluminum powder with a thickness of 0.5-1.5 μm and an average diameter of 20-50 μm.

5. The method for preparing the visible and near-infrared coating according to claim 1, characterized in that: Includes the following steps: (1) Prepare raw materials containing fluorocarbon resin, additives, powder, polyvinyl alcohol, polyamide, hydroxypropyl methylcellulose, solvent, isocyanate curing agent, diluent and modified carbon fiber according to the formula; (2) Mix the fluorocarbon resin, solvent, polyvinyl alcohol and polyamide in step (1) evenly, then add the additives, powder, hydroxypropyl methylcellulose and modified carbon fiber, mix evenly to obtain component A; mix the isocyanate curing agent and diluent in step (1) evenly to obtain component B; (3) Mix components A and B in step (2) evenly during use to obtain a visible light near-infrared coating.

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