A military stealth coating and its preparation method

Abstract

The present invention relates to a military stealth coating and a preparation method thereof, belonging to the technical field of coatings. Aiming at the problems of existing stealth coatings for clothing or tents, such as insufficient response to multiple detection means, poor chemical stability, and short service life, the present invention designs a stealth coating. The coating adopts modified Fe3O4@ZIF-8, manganese aluminum boron MAB phase ceramic material, carbon nanotubes, nano zinc oxide, nano titanium dioxide, isoamyl p-methoxycinnamate, and other ingredients, which are used in combination in specific proportions. The coating can simultaneously meet the stealth requirements of multiple detection means such as radar, infrared, and laser, and has good chemical stability, which can effectively extend the service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a military stealth coating and a preparation method thereof. Background Art

[0002] Traditional military combat environments are relatively monotonous, and the military's need for equipment concealment primarily focuses on visual camouflage. However, with the rapid advancement of modern detection technologies, such as radar, infrared, and multispectral detection, simple visual camouflage alone is no longer sufficient for battlefield needs. Enemies can easily detect troops through radar reflections, infrared radiation emitted by objects, and characteristic differences across different spectrums. Consequently, stealth coatings for military clothing and tents have emerged, designed to comprehensively counter multiple detection methods and ensure the concealment of military operations.

[0003] To protect against radar invisibility, stealth coatings used on military clothing and tents must effectively absorb or scatter radar waves. Materials with unique electromagnetic properties, such as conductive polymers, metal micropowders, and ceramics, are often added to the coating. Conductive polymers, thanks to their unique conjugated structure, interact with radar waves, converting electromagnetic energy into heat and dissipating it. Metal micropowders, through their inherent conductivity and magnetism, reflect and scatter radar waves, interfering with radar detection. These materials, combined in specific proportions and microstructures, provide stealth coatings with excellent absorption properties within radar frequencies, effectively reducing the echo signal strength of clothing and tents on radar screens, making it difficult for enemy radar to detect the target.

[0004] For infrared detection, stealth coatings achieve stealth by adjusting the coating's infrared emissivity. Infrared detection equipment primarily identifies targets by detecting differences in infrared radiation emitted by objects. Stealth coatings for military clothing and tents utilize materials with low infrared emissivity, such as metal oxides doped with specific elements. These materials can reduce the intensity of infrared radiation emitted from the equipment's surface, making it similar to the infrared signature of the surrounding environment, making it difficult for infrared detection equipment to distinguish. Furthermore, some coatings have thermal management capabilities, effectively regulating the temperature distribution on the equipment's surface. This prevents heat generated by personnel activity or equipment operation from forming noticeable hot spots on clothing and tent surfaces, further enhancing infrared stealth performance.

[0005] Early stealth coating technology had numerous limitations, including a single function that only responded to a specific detection method; a short service life and susceptibility to failure in harsh field environments; and a complex coating process and high costs. With the continuous advancement of materials science and nanotechnology, new stealth coatings are constantly emerging. The application of nanomaterials has brought a qualitative leap forward in stealth coatings. Nanoscale particles possess unique surface and quantum size effects that can significantly enhance the performance of coatings. For example, adding nanoscale carbon nanotubes, graphene, and other materials to coatings not only enhances the coating's ability to absorb electromagnetic waves across different wavelengths, achieving broadband stealth, but also improves the coating's wear resistance and chemical stability, extending the lifespan of clothing and tents.

[0006] Although stealth coatings for military clothing or tents have made some progress, they still have the following problems and defects:

[0007] (1) Insufficient response to multiple detection methods: It is difficult to simultaneously meet the stealth requirements of multiple detection methods such as radar, infrared, and laser, and it is often difficult to focus on one while neglecting another.

[0008] (2) Some special materials used in stealth coatings have poor chemical stability and are prone to react with oxygen, moisture, etc. in the air, reducing stealth performance and possibly affecting the service life of clothing or tents.

[0009] Therefore, it is necessary to continuously improve coating technology to overcome various usage defects and ensure stealth safety and service life. Summary of the Invention

[0010] To address the problems of existing stealth coatings for clothing or tents, such as insufficient response to multiple detection methods, poor chemical stability, and a short service life, the present invention provides a military stealth coating and its preparation method. The coating utilizes modified Fe3O4@ZIF-8, manganese aluminum boron (MAB) phase ceramic material, carbon nanotubes, nano-zinc oxide, nano-titanium dioxide, isoamyl p-methoxycinnamate, and other ingredients, combined in specific proportions. This coating can simultaneously meet the stealth requirements of multiple detection methods, including radar, infrared, and laser, while also exhibiting excellent chemical stability and effectively extending its service life. The specific technical solution is as follows:

[0011] A military stealth coating, comprising the following raw materials in parts by weight: 4 to 6 parts of modified Fe3O4@ZIF-8, 12 to 15 parts of manganese aluminum boron (MAB) phase ceramic material, 6 to 8 parts of carbon nanotubes, 2 to 3 parts of nano zinc oxide, 2 to 3 parts of nano titanium dioxide, 2 to 3 parts of isoamyl p-methoxycinnamate, 3 to 4 parts of silane coupling agent KH-560, 50 to 60 parts of polyurethane resin, 1 to 1.5 parts of polycarboxylate dispersant, 6 to 8 parts of isocyanate crosslinking agent, 0.5 to 1 part of acetylene glycol wetting agent, 0.2 to 0.5 parts of organosilicon defoaming agent, 3 to 5 parts of phosphate plasticizer, and 35 to 45 parts of solvent;

[0012] The modified Fe3O4@ZIF-8 is Fe3O4@ZIF-8 surface-modified with aminopropyltriethoxysilane.

[0013] In the above-mentioned coating, the preparation method of the modified Fe3O4@ZIF-8 comprises the following steps: according to the mass ratio of Fe3O4@ZIF-8:aminopropyltriethoxysilane=100:(2-5), Fe3O4@ZIF-8 is ultrasonically dispersed in toluene with a mass of 6 to 8 times that of Fe3O4@ZIF-8 at 40kHz to 60kHz until uniform, then aminopropyltriethoxysilane is added, and the mixture is stirred at 60°C to 80°C at a speed of 200r / min to 400r / min under nitrogen protection. The mixture should be centrifuged at a speed of 8000r / min to 10000r / min for 15min to 25min for 3h to 5h, the supernatant was discarded, and the precipitate was washed 1 to 2 times with toluene 1.8 times to 2.5 times the mass of the precipitate, and then washed 2 to 3 times with ethanol 1.8 times to 2.5 times the mass of the precipitate. After that, it was dried in a vacuum drying oven at 55℃ to 65℃ for 12h to 15h and broken up to obtain Fe3O4@ZIF-8 surface-modified with aminopropyltriethoxysilane, i.e., modified Fe3O4@ZIF-8.

[0014] In the above-mentioned preparation method of modified Fe3O4@ZIF-8, the particle size range of the Fe3O4@ZIF-8 is 150nm to 400nm.

[0015] In the above coating, the solvent includes the following raw materials in parts by mass: 40 to 50 parts of deionized water, 20 to 40 parts of propylene glycol methyl ether, 10 to 30 parts of propylene glycol methyl ether acetate and 10 to 25 parts of dipropylene glycol dimethyl ether.

[0016] In the above coating, the sheet diameter of the manganese aluminum boron (MAB) phase ceramic material ranges from 5 μm to 50 μm.

[0017] In the above coating, the particle size of the carbon nanotubes is less than 30 nm.

[0018] In the above coating, the particle size of the nano zinc oxide is below 30 nm.

[0019] In the above coating, the particle size of the nano titanium dioxide is below 50 nm.

[0020] The preparation method of the above-mentioned military stealth coating comprises the following steps:

[0021] S1: premixing carbon nanotubes, nano zinc oxide and nano titanium dioxide by air flow according to their mass fractions to obtain mixture A; adding a polycarboxylate dispersant to a solvent, stirring and mixing at a speed of 600 r / min to 800 r / min for 5 min to 10 min, then adding mixture A, stirring and mixing at a speed of 600 r / min to 800 r / min for 20 min to 40 min, then ultrasonically dispersing at 40 kHz to 60 kHz for 15 min to 25 min, then adding manganese aluminum boron MAB phase ceramic material and modified Fe3O4@ZIF-8, stirring and mixing at a speed of 300 r / min to 500 r / min for 20 min to 30 min to obtain mixture B;

[0022] S2: Add mixture B, silane coupling agent KH-560, isoamyl p-methoxycinnamate, isocyanate crosslinker, acetylene glycol wetting agent, silicone defoamer, and phosphate plasticizer to the polyurethane resin in sequence while stirring at a speed of 200 r / min to 300 r / min, and continue stirring at a speed of 200 r / min to 300 r / min for 20 min to 40 min; filter through a sieve to obtain a coating.

[0023] In S2 of the above preparation method, the mesh size of the sieve is 200-250 meshes.

[0024] The present invention provides a military stealth coating and a preparation method thereof, which have the following beneficial effects:

[0025] 1. The coating of this invention incorporates modified Fe3O4@ZIF-8. Fe3O4 is inherently magnetic and can absorb radar waves through magnetic loss. ZIF-8 has a large specific surface area and a porous structure, causing radar waves to be reflected and scattered multiple times within its pores, attenuating electromagnetic waves and creating a synergistic magnetic-dielectric absorption effect. After modification, aminopropyltriethoxysilane alters the surface properties of the material, allowing for better integration with other components and a more uniform structure, enhancing radar absorption and scattering. The infrared absorption properties of Fe3O4 and the low thermal conductivity of ZIF-8 reduce infrared radiation, while the nanostructure of Fe3O4 modulates thermal radiation to reduce infrared signatures. The modification improves compatibility with the substrate, resulting in a more uniform distribution, more effectively blocking heat transfer and reducing the intensity of target infrared radiation. The porous ZIF-8 and magnetic Fe3O4 both scatter and absorb laser light. The modification increases surface active sites, causing multiple scattering and absorption of laser light within the material, reducing laser reflectivity. Aminopropyltriethoxysilane forms a protective film on the surface of Fe₃O₄@ZIF-8, isolating it from corrosive substances, reducing its contact with air and moisture, and improving its chemical stability. Its excellent chemical stability and excellent integration with other components ensure the material maintains stable performance in various environments, resisting shedding and decomposition, and extending its service life.

[0026] Second, the coating of this invention incorporates a manganese aluminum boron (MAB) phase ceramic material with a unique crystal structure and electromagnetic properties. This material modulates electromagnetic parameters such as the dielectric constant to better match the electromagnetic properties of free space, reducing radar reflection and achieving superior absorption in certain frequency bands. The high electrical conductivity of the MAB phase ceramic can induce eddy current losses, and its layered structure enhances the electromagnetic absorption bandwidth through interfacial polarization. It has a low infrared emissivity, which reduces its own infrared radiation. It also modulates the thermal conductivity of the material to a certain extent, achieving a more uniform temperature distribution on the target surface and reducing the probability of infrared detection. It has a certain ability to absorb and scatter laser light. Its crystal structure and chemical bond vibrations interact with laser energy, converting it into other forms of energy dissipation. MAB phase ceramic materials have high chemical bond energy and a stable structure, making them less reactive to chemicals such as acids and bases, and capable of maintaining their performance in complex chemical environments. Thanks to their high hardness, wear resistance, and chemical stability, they resist environmental erosion and wear over long-term use, maintaining their stealth properties and extending the coating's service life.

[0027] Third, the coating of this invention incorporates isoamyl p-methoxycinnamate, which has a specific molecular structure and functional groups that absorb infrared light of a specific wavelength. It synergizes with other ingredients to address certain deficiencies in performance and homogeneity, thereby synergistically improving the overall effectiveness of the other materials. Isoamyl p-methoxycinnamate absorbs ultraviolet light, reducing its damage to other coating components and improving the coating's light stability. It prevents aging, discoloration, and cracking due to long-term light exposure, helping to maintain the appearance and performance stability of the stealth coating. This substance possesses certain organic properties that help improve the coating's film-forming properties, allowing it to form a more uniform, smooth film on the surface. This, to a certain extent, helps reduce optical scattering from the film surface and contributes to the overall performance of the stealth coating. It can also regulate the coating's surface tension, allowing the coating to spread and adhere better to the surface, improving the adhesion between the coating and the coated object, and ensuring that the stealth coating firmly adheres to the target surface and maintains its long-term performance.

[0028] The combined effects of modified Fe3O4@ZIF-8 and isoamyl p-methoxycinnamate: Modified Fe3O4@ZIF-8 absorbs and scatters radar waves, while isoamyl p-methoxycinnamate modulates the electromagnetic properties of the coating surface. The combination of the two optimizes the coating's surface electromagnetic parameters, enhancing radar absorption and scattering. Modified Fe3O4@ZIF-8 blocks heat, while isoamyl p-methoxycinnamate absorbs specific infrared light. The synergistic effect enhances infrared absorption and heat insulation, reducing infrared radiation. Modified Fe3O4@ZIF-8 scatters and absorbs laser light, while isoamyl p-methoxycinnamate improves the coating's surface optical properties, ensuring more efficient laser scattering and absorption both on and within the coating, reducing laser reflection. The protective film of the modified Fe3O4@ZIF-8 and the low surface energy of isoamyl p-methoxycinnamate work together to reduce contact between the coating and foreign matter, improving chemical stability. This multifaceted synergy improves stealth performance, mitigates performance degradation due to environmental influences, and extends service life.

[0029] Advantages of modified Fe₃O₄@ZIF-8 over unmodified Fe₃O₄@ZIF-8: The modified Fe₃O₄@ZIF-8 provides a tighter bond with other components and more uniform dispersion within the coating, improving overall performance. Its enhanced chemical stability makes it less susceptible to corrosion and degradation in harsh environments, maintaining its stealth properties. In terms of radar, infrared, and laser stealth, the altered surface properties and improved synergy with other components enable more effective absorption and scattering of waves in the corresponding bands, resulting in superior stealth.

[0030] Sixth, the preparation method of the present invention employs a step-by-step mixing process, enabling the components to be thoroughly mixed and dispersed at different stages. For example, premixing the carbon nanotubes and other ingredients before gradually mixing them with the other ingredients results in a more uniform dispersion than direct blending. This step-by-step process allows the polycarboxylate dispersant to be fully dispersed in the solvent before mixing with the other ingredients. This facilitates the dispersant's effectiveness and allows more time for the components to interact physically and chemically. For example, silane coupling agents can achieve better coupling effects. The resulting coating has a more stable structure and excellent performance reproducibility, minimizing performance fluctuations caused by uneven mixing and incomplete reactions.

[0031] 7. Carbon nanotubes, with their high conductivity and unique structure, regulate electromagnetic parameters to absorb radar waves. Their excellent thermal conductivity aids in heat dissipation and regulates infrared radiation, enhancing the coating's mechanical properties and extending its service life. Nano-zinc oxide and nano-titanium dioxide absorb and scatter ultraviolet light, enhancing chemical stability. They also absorb and scatter infrared light to some extent, aiding infrared stealth, and improving the coating's surface properties and weather resistance. Polyurethane resin is a film-forming substance that provides excellent adhesion and flexibility, forming a continuous and stable coating, ensuring the effectiveness of other components and extending its service life. Isocyanate crosslinkers react with polyurethane resin to form a crosslinked structure, increasing the coating's hardness, strength, and chemical stability, extending its service life. Alkyne diol wetting agents are used to reduce the coating's surface tension, enabling the coating to better wet the substrate, improving adhesion, and enhancing film quality. Phosphate plasticizers are used to increase the coating's flexibility and plasticity, reducing its brittleness and extending its service life. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to specific implementation cases, but the present invention is not limited to these embodiments.

[0033] Example 1

[0034] A military stealth coating comprises the following raw materials in parts by mass: 5 parts of modified Fe3O4@ZIF-8, 13 parts of manganese aluminum boron (MAB) phase ceramic material, 7 parts of carbon nanotubes, 2.5 parts of nano zinc oxide, 2.5 parts of nano titanium dioxide, 2.5 parts of isoamyl p-methoxycinnamate, 3.5 parts of silane coupling agent KH-560, 55 parts of polyurethane resin, 1.2 parts of polycarboxylate dispersant, 7 parts of isocyanate crosslinking agent, 0.8 parts of acetylene glycol wetting agent, 0.3 parts of organosilicon defoaming agent, 4 parts of phosphate plasticizer, and 40 parts of solvent; the solvent comprises the following raw materials in parts by mass: 45 parts of deionized water, 30 parts of propylene glycol methyl ether, 20 parts of propylene glycol methyl ether acetate, and 18 parts of dipropylene glycol dimethyl ether.

[0035] Among them, the preparation method of modified Fe3O4@ZIF-8 includes the following steps: according to the mass ratio of Fe3O4@ZIF-8:aminopropyltriethoxysilane = 100:3.5, Fe3O4@ZIF-8 is ultrasonically dispersed in toluene with a mass of 7 times that of Fe3O4@ZIF-8 at 50kHz until uniform, then aminopropyltriethoxysilane is added, and under nitrogen protection, the reaction is stirred at 300r / min at 70°C for 4h, centrifuged at 9000r / min for 20min, the supernatant is discarded, and the precipitate is washed once with toluene 2.2 times the mass of the precipitate, and then washed twice with ethanol 2.2 times the mass of the precipitate, and then dried in a vacuum drying oven at 60°C for 14h and broken up to obtain Fe3O4@ZIF-8 surface modified with aminopropyltriethoxysilane, that is, modified Fe3O4@ZIF-8.

[0036] The preparation method of the above-mentioned military stealth coating comprises the following steps:

[0037] S1: pre-mixing carbon nanotubes, nano-zinc oxide and nano-titanium dioxide by air flow according to their mass fractions to obtain mixture A; adding a polycarboxylate dispersant to a solvent, stirring and mixing at a speed of 700 r / min for 8 minutes, then adding mixture A, stirring and mixing at a speed of 700 r / min for 30 minutes, then ultrasonically dispersing at 50 kHz for 20 minutes, then adding manganese aluminum boron MAB phase ceramic material and modified Fe3O4@ZIF-8, stirring and mixing at a speed of 400 r / min for 25 minutes to obtain mixture B;

[0038] S2: Under stirring at a speed of 250 r / min, add mixture B, silane coupling agent KH-560, isoamyl p-methoxycinnamate, isocyanate crosslinker, acetylene glycol wetting agent, silicone defoamer, and phosphate plasticizer to the polyurethane resin in sequence, and continue stirring at a speed of 250 r / min for 30 min; filter through a 200-mesh sieve to obtain a coating.

[0039] Example 2

[0040] A military stealth coating comprises the following raw materials in parts by mass: 4 parts of modified Fe3O4@ZIF-8, 12 parts of manganese aluminum boron (MAB) phase ceramic material, 6 parts of carbon nanotubes, 2 parts of nano zinc oxide, 2 parts of nano titanium dioxide, 2 parts of isoamyl p-methoxycinnamate, 3 parts of silane coupling agent KH-560, 50 parts of polyurethane resin, 1 part of polycarboxylate dispersant, 6 parts of isocyanate crosslinking agent, 0.5 parts of acetylene glycol wetting agent, 0.2 parts of organosilicon defoaming agent, 3 parts of phosphate plasticizer, and 35 parts of solvent; the solvent comprises the following raw materials in parts by mass: 40 parts of deionized water, 20 parts of propylene glycol methyl ether, 10 parts of propylene glycol methyl ether acetate, and 10 parts of dipropylene glycol dimethyl ether.

[0041] Among them, the preparation method of modified Fe3O4@ZIF-8 includes the following steps: according to the mass ratio of Fe3O4@ZIF-8:aminopropyltriethoxysilane = 100:2, Fe3O4@ZIF-8 is ultrasonically dispersed in toluene with a mass of 6 times that of Fe3O4@ZIF-8 at 40kHz until uniform, then aminopropyltriethoxysilane is added, and under nitrogen protection, the reaction is stirred at 200r / min at 60°C for 3h, centrifuged at 8000r / min for 15min, the supernatant is discarded, and the precipitate is washed once with toluene with a mass of 1.8 times that of the precipitate, and then washed twice with ethanol with a mass of 1.8 times that of the precipitate, and then dried in a vacuum drying oven at 55°C for 12h and broken up to obtain Fe3O4@ZIF-8 surface modified with aminopropyltriethoxysilane, that is, modified Fe3O4@ZIF-8.

[0042] The preparation method of the above-mentioned military stealth coating comprises the following steps:

[0043] S1: pre-mix carbon nanotubes, nano-zinc oxide, and nano-titanium dioxide by air flow according to their mass fractions to obtain mixture A; add a polycarboxylate dispersant to a solvent, stir and mix at a speed of 600 r / min for 5 minutes, then add mixture A, stir and mix at a speed of 600 r / min for 20 minutes, then ultrasonically disperse at 40 kHz for 15 minutes, then add manganese aluminum boron MAB phase ceramic material and modified Fe3O4@ZIF-8, stir and mix at a speed of 300 r / min for 20 minutes to obtain mixture B;

[0044] S2: Under stirring at 200 r / min, add mixture B, silane coupling agent KH-560, isoamyl p-methoxycinnamate, isocyanate crosslinker, acetylene glycol wetting agent, silicone defoamer, and phosphate plasticizer to the polyurethane resin in sequence, and continue stirring at 200 r / min for 20 minutes; filter through a 200-mesh sieve to obtain a coating.

[0045] Example 3

[0046] A military stealth coating comprises the following raw materials in parts by mass: 4 parts of modified Fe3O4@ZIF-8, 15 parts of manganese aluminum boron (MAB) phase ceramic material, 6 parts of carbon nanotubes, 3 parts of nano zinc oxide, 2 parts of nano titanium dioxide, 3 parts of isoamyl p-methoxycinnamate, 3 parts of silane coupling agent KH-560, 60 parts of polyurethane resin, 1 part of polycarboxylate dispersant, 8 parts of isocyanate crosslinking agent, 0.5 parts of acetylene glycol wetting agent, 0.5 parts of organosilicon defoaming agent, 3 parts of phosphate plasticizer, and 42 parts of solvent; the solvent comprises the following raw materials in parts by mass: 40 parts of deionized water, 40 parts of propylene glycol methyl ether, 10 parts of propylene glycol methyl ether acetate, and 25 parts of dipropylene glycol dimethyl ether.

[0047] Among them, the preparation method of modified Fe3O4@ZIF-8 includes the following steps: according to the mass ratio of Fe3O4@ZI F-8:aminopropyltriethoxysilane = 100:2.5, Fe3O4@ZIF-8 is ultrasonically dispersed in toluene with a mass of 8 times that of Fe3O4@ZIF-8 at 45kHz until uniform, then aminopropyltriethoxysilane is added, and under nitrogen protection, the reaction is stirred at 400r / min at 60°C for 3h, centrifuged at 10000r / min for 15min, the supernatant is discarded, and the precipitate is washed once with toluene 2.5 times the mass of the precipitate, and then washed twice with ethanol 2.5 times the mass of the precipitate, and then dried in a vacuum drying oven at 65°C for 12h and broken up to obtain Fe3O4@ZIF-8 surface modified with aminopropyltriethoxysilane, that is, modified Fe3O4@ZIF-8.

[0048] The preparation method of the above-mentioned military stealth coating comprises the following steps:

[0049] S1: pre-mix carbon nanotubes, nano-zinc oxide, and nano-titanium dioxide by air flow according to their mass fractions to obtain mixture A; add a polycarboxylate dispersant to a solvent, stir and mix at a speed of 600 r / min for 10 min, then add mixture A, stir and mix at a speed of 600 r / min for 20 min, then ultrasonically disperse at 60 kHz for 15 min, then add manganese aluminum boron MAB phase ceramic material and modified Fe3O4@ZIF-8, stir and mix at a speed of 500 r / min for 20 min to obtain mixture B;

[0050] S2: Under stirring at a speed of 200 r / min, add mixture B, silane coupling agent KH-560, isoamyl p-methoxycinnamate, isocyanate crosslinker, acetylene glycol wetting agent, silicone defoamer, and phosphate plasticizer to the polyurethane resin in sequence, and continue stirring at a speed of 200 r / min for 40 minutes; filter through a 200-mesh sieve to obtain a coating.

[0051] Example 4

[0052] A military stealth coating comprises the following raw materials in parts by mass: 6 parts of modified Fe3O4@ZIF-8, 15 parts of manganese aluminum boron (MAB) phase ceramic material, 8 parts of carbon nanotubes, 3 parts of nano zinc oxide, 3 parts of nano titanium dioxide, 3 parts of isoamyl p-methoxycinnamate, 4 parts of silane coupling agent KH-560, 60 parts of polyurethane resin, 1.5 parts of polycarboxylate dispersant, 8 parts of isocyanate crosslinking agent, 1 part of acetylene glycol wetting agent, 0.5 parts of organosilicon defoaming agent, 5 parts of phosphate plasticizer, and 45 parts of solvent; the solvent comprises the following raw materials in parts by mass: 50 parts of deionized water, 40 parts of propylene glycol methyl ether, 30 parts of propylene glycol methyl ether acetate, and 25 parts of dipropylene glycol dimethyl ether.

[0053] Among them, the preparation method of modified Fe3O4@ZIF-8 includes the following steps: according to the mass ratio of Fe3O4@ZIF-8:aminopropyltriethoxysilane = 100:5, Fe3O4@ZIF-8 is ultrasonically dispersed in toluene with a mass of 8 times that of Fe3O4@ZIF-8 at 60kHz until uniform, then aminopropyltriethoxysilane is added, and under nitrogen protection, the reaction is stirred at 400r / min at 80°C for 5h, centrifuged at 10000r / min for 25min, the supernatant is discarded, and the precipitate is washed twice with toluene with a mass of 2.5 times that of the precipitate, and then washed three times with ethanol with a mass of 2.5 times that of the precipitate, and then dried in a vacuum drying oven at 65°C for 15h and broken up to obtain Fe3O4@ZIF-8 surface modified with aminopropyltriethoxysilane, that is, modified Fe3O4@ZIF-8.

[0054] The preparation method of the above-mentioned military stealth coating comprises the following steps:

[0055] S1: pre-mixing carbon nanotubes, nano-zinc oxide and nano-titanium dioxide by air flow according to their mass fractions to obtain mixture A; adding a polycarboxylate dispersant to a solvent, stirring and mixing at a speed of 800 r / min for 10 min, then adding mixture A, stirring and mixing at a speed of 800 r / min for 40 min, then ultrasonically dispersing at 60 kHz for 25 min, then adding manganese aluminum boron MAB phase ceramic material and modified Fe3O4@ZIF-8, stirring and mixing at a speed of 500 r / min for 30 min to obtain mixture B;

[0056] S2: Under stirring at 300 r / min, add mixture B, silane coupling agent KH-560, isoamyl p-methoxycinnamate, isocyanate crosslinker, acetylene glycol wetting agent, silicone defoamer, and phosphate plasticizer to the polyurethane resin in sequence, and continue stirring at 300 r / min for 40 min; filter through a 250-mesh sieve to obtain a coating.

[0057] Example 5

[0058] A military stealth coating comprises the following raw materials in parts by mass: 6 parts of modified Fe3O4@ZIF-8, 12 parts of manganese aluminum boron (MAB) phase ceramic material, 8 parts of carbon nanotubes, 2 parts of nano zinc oxide, 3 parts of nano titanium dioxide, 2 parts of isoamyl p-methoxycinnamate, 4 parts of silane coupling agent KH-560, 50 parts of polyurethane resin, 1.5 parts of polycarboxylate dispersant, 6 parts of isocyanate crosslinking agent, 1 part of acetylene glycol wetting agent, 0.2 parts of organosilicon defoaming agent, 5 parts of phosphate plasticizer, and 38 parts of solvent; the solvent comprises the following raw materials in parts by mass: 50 parts of deionized water, 20 parts of propylene glycol methyl ether, 30 parts of propylene glycol methyl ether acetate, and 10 parts of dipropylene glycol dimethyl ether.

[0059] Among them, the preparation method of modified Fe3O4@ZIF-8 includes the following steps: according to the mass ratio of Fe3O4@ZIF-8:aminopropyltriethoxysilane = 100:4.5, Fe3O4@ZIF-8 is ultrasonically dispersed in toluene with a mass of 6 times that of Fe3O4@ZIF-8 at 55kHz until uniform, then aminopropyltriethoxysilane is added, and under nitrogen protection, the reaction is stirred at 200r / min at 80°C for 5h, centrifuged at 8000r / min for 25min, the supernatant is discarded, and the precipitate is washed twice with toluene with a mass of 1.8 times that of the precipitate, and then washed three times with ethanol with a mass of 1.8 times that of the precipitate, and then dried in a vacuum drying oven at 55°C for 15h and broken up to obtain Fe3O4@ZIF-8 surface-modified with aminopropyltriethoxysilane, that is, modified Fe3O4@ZIF-8.

[0060] The preparation method of the above-mentioned military stealth coating comprises the following steps:

[0061] S1: pre-mixing carbon nanotubes, nano-zinc oxide and nano-titanium dioxide by air flow according to their mass fractions to obtain mixture A; adding a polycarboxylate dispersant to a solvent, stirring and mixing at a speed of 800 r / min for 5 minutes, then adding mixture A, stirring and mixing at a speed of 800 r / min for 40 minutes, then ultrasonically dispersing at 40 kHz for 25 minutes, then adding manganese aluminum boron MAB phase ceramic material and modified Fe3O4@ZIF-8, stirring and mixing at a speed of 300 r / min for 30 minutes to obtain mixture B;

[0062] S2: Under stirring at 300 r / min, add mixture B, silane coupling agent KH-560, isoamyl p-methoxycinnamate, isocyanate crosslinker, acetylene glycol wetting agent, silicone defoamer, and phosphate plasticizer to the polyurethane resin in sequence, and continue stirring at 300 r / min for 20 min; filter through a 250-mesh sieve to obtain a coating.

[0063] In the above embodiments, the particle size of Fe3O4@ZIF-8 ranges from 150 nm to 400 nm. The flake diameter of the manganese aluminum boron MA B-phase ceramic material ranges from 5 μm to 50 μm. The particle size of the carbon nanotubes ranges from 30 nm to 30 nm. The particle size of the nano-zinc oxide ranges from 30 nm to 30 nm. The particle size of the nano-titanium dioxide ranges from 50 nm to 50 nm.

[0064] In the above examples, the raw materials are as follows: Fe3O4@ZIF-8 is sourced from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., with the product number XFF58. Manganese aluminum boron MAB phase ceramic material is sourced from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., and Mn2AlB2 manganese aluminum boron MAB phase ceramic material is sourced from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., with the product number XFK49. Isoamyl p-methoxycinnamate is sourced from Shanghai Aoji Chemical Co., Ltd. Silane coupling agent KH-560 (propyltrimethoxysilane) is sourced from Dongguan Kangjin New Materials Technology Co., Ltd. Polyurethane resin is sourced from Dongguan Yibao Resin Co., Ltd., with the product number BY-40. Polycarboxylate dispersant is sourced from Shandong Yousuo Chemical Technology Co., Ltd., with the product number 5040. Isocyanate crosslinker is sourced from Shanghai Youen Chemical Co., Ltd., with the product number 074. Alkyne diol wetting agent is sourced from Anhui Yuanchen New Materials Technology Co., Ltd., with the product number YC-3003. Silicone defoamer is sourced from Guangdong Yuanfeng New Materials Co., Ltd., and Dow Corning AFE-3168 silicone defoamer is sourced from Dow Corning. Phosphate ester plasticizers, including tricresyl phosphate (TCP), were sourced from Shanghai Zhenzhun Biotechnology Co., Ltd. Aminopropyl triethoxysilane, model KH-550, was sourced from Dongguan Kangjin New Materials Technology Co., Ltd. Propylene glycol methyl ether (PM) was sourced from Shandong Mingcheng New Materials Co., Ltd. Propylene glycol methyl ether acetate (PMA) was sourced from Zhongrun (Shandong) New Materials Co., Ltd. Dipropylene glycol dimethyl ether (DMM) was sourced from Guangzhou Changhong Chemical Technology Co., Ltd.

[0065] Comparative Example 1

[0066] No modified Fe3O4@ZIF-8 was added to the coating; other parameters and methods were the same as in Example 1.

[0067] Comparative Example 2

[0068] In the coating, the modified Fe3O4@ZIF-8 was replaced by Fe3O4@ZIF-8; other parameters and methods were the same as in Example 1.

[0069] Comparative Example 3

[0070] In the coating, the manganese aluminum boron MAB phase ceramic material is replaced by alumina ceramic; other parameters and methods are the same as in Example 1.

[0071] Comparative Example 4

[0072] No isoamyl p-methoxycinnamate was added to the coating; the mass fraction of isoamyl p-methoxycinnamate was replaced by a solvent; other parameters and methods were the same as in Example 1.

[0073] Comparative Example 5

[0074] In the coating, modified Fe3O4@ZIF-8 was replaced by Fe3O4@ZIF-8; isoamyl p-methoxycinnamate was not added; the mass fraction of isoamyl p-methoxycinnamate was replaced by a solvent; other parameters and methods were the same as in Example 1.

[0075] Comparative Example 6

[0076] The preparation method is to directly blend all raw materials to obtain the coating without preparing the mixed material B in advance; other parameters and methods are the same as those in Example 1.

[0077] The coatings prepared in the above embodiments and comparative examples were tested for their performance.

[0078] The coating was applied to a tent fabric (polyester fabric) with a thickness of 0.5 mm to prepare a test sample.

[0079] 1. Radar Stealth Performance Test: Coated tent fabric was carefully cut into 1.5m x 1.5m square samples, ensuring neat edges. The samples were fixed flat on a high-strength test stand using a clamp to ensure they were wrinkle-free and motionless during testing. A high-performance vector network analyzer (VNA) was used, with a transmit frequency range of 0.3GHz to 20GHz and a frequency sweep step of 0.05GHz to obtain more accurate RCS data. The transmit power was set to 15dBm to ensure signal strength sufficient for effective detection without damaging the sample. The transmitting and receiving antennas were located on either side of a turntable, at a 45° angle to the sample, with each antenna 5m from the sample. The turntable rotated at a constant speed of 1° / s to simulate radar detection of a target at different angles. During rotation, the VNA recorded the RCS values of the sample at different frequencies and angles in real time. To ensure data accuracy, each sample was tested three times, and the average value was used as the radar stealth performance indicator for that sample. The test results are shown in Table 1 below.

[0080] 2. Infrared stealth performance test: Place the sample in a constant temperature and humidity environment at a temperature of 25°C and a relative humidity of 50% for 2 hours to allow the sample to fully reach a thermal equilibrium state and eliminate the influence of environmental factors on the test results. Use an infrared thermal imager to shoot at a distance of 1m from the sample, and ensure that the thermal imager lens is vertically aligned with the center of the sample. The resolution of the thermal imager is set to 640×480, which can clearly capture subtle temperature differences on the surface of the sample. Emissivity measurement: Use a Fourier transform infrared spectrometer to measure the infrared emissivity of the sample in the 8μm-14μm band. Set the number of scans to 64 times. The resolution is set to 2cm -1 , which can accurately distinguish the changes in the sample's emissivity within this band. Each sample was measured at three different locations, and the average value was taken as the sample's infrared emissivity indicator. The test results are shown in Table 1 below.

[0081] 3. Laser stealth performance test: Fix the sample on an electric bracket with precise angle adjustment to ensure that the position of the sample is stable during the test and the angle can be easily adjusted. A pulsed laser with a wavelength of 1.06μm is used as the light source, which is a common laser detection wavelength. The transmission power is set to 10W, the pulse width is 10ns, and the repetition frequency is 10Hz to simulate a real laser detection scene. The receiving device is located 1m in front of the sample and is equipped with a high-precision photodetector that can accurately receive the reflected laser signal. Adjust the angle between the laser and the sample to 30° and measure the reflectivity of the sample to the laser. Each sample is measured 5 times, and the average value of the 5 measurements is taken as the laser reflectivity index of the sample. The test results are shown in Table 1 below.

[0082] 4. Chemical Stability Test: Samples were placed in a climate chamber, simulating a high-temperature, high-humidity environment at 60°C and 90% relative humidity for 1000 hours, simulating the long-term use of tents in tropical, humid regions. After 1000 hours, the samples were removed and performance retested. Using the same radar, infrared, and laser stealth performance test equipment, the stealth performance values of the samples were measured, compared to the initial values, and the performance degradation rate was calculated. The average of the radar, infrared, and laser stealth performance degradation rates was used to assess the impact of chemical stability on stealth performance. The test results are shown in Table 1 below.

[0083] 5. Service life test: Install the sample on the wear tester and set the friction pressure to 500g to simulate the friction force in actual use. The friction frequency is 100 times / minute to accelerate the wear rate. At the same time, simulate ultraviolet radiation with a power of 100W / m 2 A UV lamp was placed 30 cm from the sample to simulate outdoor sunlight. A rainwater spray rate of 1 L / min was set to simulate a rainy environment. Sample Inspection: The test was stopped every 50 hours and the sample surface was carefully inspected. When the average stealth performance decreased by more than 30%, the test time at that point was recorded as the sample's service life. The test results are shown in Table 1 below.

[0084] Table 1 Test results

[0085]

[0086] The above results demonstrate that Examples 1 to 5 possess a complete and optimized formulation system, with significant synergistic stealth effects from their respective components. The interaction between the components forms a stable chemical structure, providing strong resistance to environmental corrosion and a low percentage of stealth performance degradation after 1000 hours.

[0087] In Comparative Example 1, the modified Fe₃O₄@ZIF-8 was omitted, resulting in a significant loss of radar stealth performance. Infrared and laser stealth were also severely impacted by the lack of this component's modulating effect on overall electromagnetic properties. In simulated environments, the lack of this component's stabilizing effect resulted in poor overall coating performance and inability to effectively resist wear and environmental erosion.

[0088] In Comparative Example 2, unmodified Fe₃O₄@ZIF-8 was substituted, resulting in inferior performance compared to the Example. The unmodified material exhibited poor synergy with the other components, failing to fully utilize its radar absorption and electromagnetic properties. Radar, infrared, and laser stealth performance was reduced. Chemical stability was also compromised, and the unmodified material exhibited poor environmental stability. The overall performance degradation of the coating made it more susceptible to failure in accelerated aging tests.

[0089] In Comparative Example 3, alumina ceramics were used to replace manganese aluminum boron MAB phase ceramic materials. Due to the different electromagnetic and infrared properties of the two, the stealth performance was deteriorated. The absorption and scattering properties of alumina ceramics are not as good as those of manganese aluminum boron MAB phase ceramic materials, and the average radar RCS is 0.9m. 2 , infrared emissivity is 0.45, and laser reflectivity is 0.35. Chemical stability is also affected. The bonding strength and synergy between alumina ceramics and other components are not as good as those of manganese aluminum boron MAB phase ceramic materials. Because of the change in material properties, the overall wear resistance and weather resistance of the coating are affected.

[0090] In Comparative Example 4, without the addition of isoamyl p-methoxycinnamate, stealth performance declined. This ingredient contributes to multi-band stealth, and its absence affects the coating's ability to absorb and scatter electromagnetic waves across different bands. This ingredient also has a synergistic effect on the coating's chemical stability and durability.

[0091] In Comparative Example 5, there are problems of unmodified Fe3O4@ZIF-8 and lack of isoamyl p-methoxycinnamate, and the stealth performance and chemical stability are worse.

[0092] In Comparative Example 6, direct blending without pre-preparation of Mixture B resulted in uneven dispersion of the ingredients, which affected the adhesion of the coating to the fabric and the synergistic effect of the ingredients. This compromised chemical stability, indicating that the uneven composition reduced the coating's resistance to environmental corrosion. This uneven dispersion also made the coating more susceptible to coating detachment and performance degradation during accelerated aging testing.

Claims

1. A military stealth coating, characterized in that: The coating comprises the following raw materials in parts by weight: 4 to 6 parts of modified Fe3O4@ZIF-8, 12 to 15 parts of manganese aluminum boron MAB phase ceramic material, 6 to 8 parts of carbon nanotubes, 2 to 3 parts of nano zinc oxide, 2 to 3 parts of nano titanium dioxide, 2 to 3 parts of isoamyl p-methoxycinnamate, 3 to 4 parts of silane coupling agent KH-560, 50 to 60 parts of polyurethane resin, 1 to 1.5 parts of polycarboxylate dispersant and 6 to 8 parts of isocyanate crosslinking agent, 0.5 to 1 part of acetylene glycol wetting agent, 0.2 to 0.5 parts of silicone defoaming agent, 3 to 5 parts of phosphate plasticizer and 35 to 45 parts of solvent; The modified Fe3O4@ZIF-8 is Fe3O4@ZIF-8 surface-modified with aminopropyltriethoxysilane; The preparation method of the coating comprises the following steps: S1: premixing carbon nanotubes, nano zinc oxide and nano titanium dioxide by air flow according to their mass fractions to obtain mixture A; adding a polycarboxylate dispersant to a solvent, stirring and mixing at a speed of 600 r / min to 800 r / min for 5 min to 10 min, then adding mixture A, stirring and mixing at a speed of 600 r / min to 800 r / min for 20 min to 40 min, then ultrasonically dispersing at 40 kHz to 60 kHz for 15 min to 25 min, then adding manganese aluminum boron MAB phase ceramic material and modified Fe3O4@ZIF-8, stirring and mixing at a speed of 300 r / min to 500 r / min for 20 min to 30 min to obtain mixture B; S2: Add mixture B, silane coupling agent KH-560, isoamyl p-methoxycinnamate, isocyanate crosslinker, acetylene glycol wetting agent, silicone defoamer, and phosphate plasticizer to the polyurethane resin in sequence while stirring at a speed of 200 r / min to 300 r / min, and continue stirring at a speed of 200 r / min to 300 r / min for 20 min to 40 min; filter through a sieve to obtain a coating.

2. A military stealth coating according to claim 1, characterized in that: The preparation method of the modified Fe3O4@ZIF-8 comprises the following steps: according to the mass ratio of Fe3O4@ZIF-8:aminopropyltriethoxysilane=100:(2-5), Fe3O4@ZIF-8 is ultrasonically dispersed in toluene with a mass of 6 to 8 times that of Fe3O4@ZIF-8 at 40 kHz to 60 kHz until uniform, then aminopropyltriethoxysilane is added, and the reaction is stirred at 60°C to 80°C and a speed of 200 rpm to 400 rpm under nitrogen protection for 3 hours. The mixture was centrifuged at 8000 rpm to 10000 rpm for 15 to 25 min, the supernatant was discarded, and the precipitate was washed once or twice with toluene (1.8 to 2.5 times the mass of the precipitate), and then washed twice or three times with ethanol (1.8 to 2.5 times the mass of the precipitate), and then dried in a vacuum drying oven at 55 to 65 ° C for 12 to 15 h and broken up to obtain Fe3O4@ZIF-8 surface-modified with aminopropyltriethoxysilane, i.e., modified Fe3O4@ZIF-8.

3. A military stealth coating according to claim 2, characterized in that: The particle size of the Fe3O4@ZIF-8 is in the range of 150nm to 400nm.

4. The military stealth coating according to claim 1, characterized in that: The solvent comprises the following raw materials in parts by mass: 40 to 50 parts of deionized water, 20 to 40 parts of propylene glycol methyl ether, 10 to 30 parts of propylene glycol methyl ether acetate and 10 to 25 parts of dipropylene glycol dimethyl ether.

5. The military stealth coating according to claim 1, characterized in that: The sheet diameter of the manganese aluminum boron (MAB) phase ceramic material ranges from 5 μm to 50 μm.

6. The military stealth coating according to claim 1, characterized in that: The particle size of the carbon nanotubes is less than 30 nm.

7. The military stealth coating according to claim 1, characterized in that: The particle size range of the nano zinc oxide is below 30 nm.

8. The military stealth coating according to claim 1, characterized in that: The particle size range of the nano titanium dioxide is below 50 nm.

9. A method for preparing a military stealth coating, for preparing a military stealth coating according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: S1: premixing carbon nanotubes, nano zinc oxide and nano titanium dioxide by air flow according to their mass fractions to obtain mixture A; adding a polycarboxylate dispersant to a solvent, stirring and mixing at a speed of 600 r / min to 800 r / min for 5 min to 10 min, then adding mixture A, stirring and mixing at a speed of 600 r / min to 800 r / min for 20 min to 40 min, then ultrasonically dispersing at 40 kHz to 60 kHz for 15 min to 25 min, then adding manganese aluminum boron MAB phase ceramic material and modified Fe3O4@ZIF-8, stirring and mixing at a speed of 300 r / min to 500 r / min for 20 min to 30 min to obtain mixture B; S2: Add mixture B, silane coupling agent KH-560, isoamyl p-methoxycinnamate, isocyanate crosslinker, acetylene glycol wetting agent, silicone defoamer, and phosphate plasticizer to the polyurethane resin in sequence while stirring at a speed of 200 r / min to 300 r / min, and continue stirring at a speed of 200 r / min to 300 r / min for 20 min to 40 min; filter through a sieve to obtain a coating.

10. The method for preparing a military stealth coating according to claim 9, characterized in that: In S2, the mesh size of the sieve is 200-250 meshes.

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