A millimeter wave radar signal enhancement coating and a method of making the same

Abstract

The application provides a millimeter wave radar signal enhancement coating and a preparation method thereof. The millimeter wave radar signal enhancement coating comprises the following substances in parts by mass: 30 parts of a water-based acrylic emulsion; 10-14 parts of floating aluminum silver paste; 8-12 parts of modified inorganic filler; 2.8-3.2 parts of modified polyacrylate; 50-55 parts of water; 0.6-1 part of an anticorrosive agent; 0.12-0.16 parts of a leveling agent; and 0.06-0.1 part of a defoaming agent. The modified inorganic filler is an inorganic filler with polyoxyethylene chain segments and ketone imine-terminated primary amino sites coupled on the surface. The modified polyacrylate is a polyacrylate grafted with fluorine-containing chain segments, epoxy-containing chain segments and hydroxyl-containing chain segments. The millimeter wave radar signal enhancement coating is applied to low traffic facilities.

Description

Technical Field

[0001] This application relates to the field of functional coatings technology, specifically to a millimeter-wave radar signal enhancement coating and its preparation method. Background Technology

[0002] With the development of intelligent transportation and autonomous driving technologies, millimeter-wave radar signals are widely used in vehicle environmental perception and driver assistance systems due to their advantages such as all-weather operation, high precision, and anti-interference capabilities.

[0003] However, the surfaces of low-lying traffic facilities such as traffic cones, guardrails, and traffic barriers have weak millimeter-wave reflection capabilities, resulting in insufficient radar echo signals and low recognition rates in complex environments, which affects system judgment and response.

[0004] To improve the ability of millimeter-wave radar signals to identify low-rise transportation facilities, various methods have been proposed, such as covering the surface of low-rise transportation facilities with metal plates or foils, spraying electromagnetic reflective coatings containing metal powder or conductive fillers, using high dielectric constant filler coatings, or designing reflector arrays with special geometries. These methods have improved millimeter-wave reflection performance to some extent, but still have the following shortcomings:

[0005] Metallic coatings: Although they have high reflectivity, they are prone to oxidation and corrosion, have poor adhesion, and are complex and costly to install.

[0006] Conductive filler coatings: Aluminum powder, silver powder or carbon materials are prone to agglomeration, have poor dispersibility, insufficient weather resistance, and rapid performance degradation during long-term use;

[0007] High dielectric filler coating: mainly enhances scattering rather than specular reflection, with limited reflection efficiency;

[0008] Special geometric reflector arrays are complex to manufacture, costly, sensitive to installation angles, and have poor adaptability.

[0009] Therefore, there is an urgent need to develop a millimeter-wave radar signal enhancement coating that has excellent millimeter-wave radar signal reflection enhancement effect, strong weather resistance and good adhesion, so as to improve the recognition accuracy and safety of intelligent transportation systems. Summary of the Invention

[0010] This invention provides a millimeter-wave radar signal enhancement coating and its preparation method, aiming to solve the problems of insufficient millimeter-wave radar signal reflection enhancement effect, poor coating weather resistance, and poor adhesion of existing millimeter-wave radar signal reflective coatings.

[0011] In a first aspect, this application provides a millimeter-wave radar signal enhancement coating, comprising, by weight parts: 30 parts of water-based acrylic emulsion; 10-14 parts of floating aluminum silver paste; 8-12 parts of modified inorganic filler; 2.8-3.2 parts of modified polyacrylate; 50-55 parts of water; 0.6-1 parts of corrosion inhibitor; 0.12-0.16 parts of leveling agent; and 0.06-0.1 parts of defoamer; wherein the modified inorganic filler is an inorganic filler whose surface is simultaneously coupled with polyoxyethylene segments and ketimine-terminated primary amino sites; and the modified polyacrylate is a polyacrylate simultaneously grafted with fluorinated segments, epoxy segments, and hydroxyl segments.

[0012] According to this application, in the early stage of film formation of the millimeter-wave radar signal enhancement coating, the fluorinated segments of the modified polyacrylate drive the hydrophobic flake aluminum particles in the floating aluminum silver paste to migrate to the coating surface formed by the millimeter-wave radar signal enhancement coating through hydrophobic interaction. Meanwhile, the primary amino groups on the surface of the modified inorganic filler are chemically inert in the early stage of film formation after being capped by ketimine, and do not generate a driving force for migration to the surface. In the middle and late stages of film formation, as small molecule ketones are more volatile than water, the hydrolysis of ketimine proceeds in the forward direction. The released active primary amine groups can undergo ring-opening addition reactions with the epoxy segments in the modified polyacrylate. At this time, the coating matrix has initially formed a film. The huge viscous resistance prevents the reflective structure of the flake aluminum particles on the surface from being reversed due to the chemical crosslinking in the later stage of film formation, thus achieving a synergistic enhancement of millimeter-wave radar signal reflection effect, poor coating weather resistance, and adhesion.

[0013] Specifically, in the early stage of coating film formation, due to the extremely high electronegativity and small atomic radius of fluorine, the carbon-fluorine bonds have extremely high bond energy and extremely low polarizability. Although the fluorine-containing segments are randomly distributed on the modified polyacrylate backbone, the extremely low surface tension of the fluorine-carbon bonds drives the fluorine-containing segments in the modified polyacrylate to spontaneously undergo conformational rearrangement and directional migration to the gas-liquid interface, resulting in excellent hydrophobicity of the surface layer. Furthermore, due to the hydrophobic effect of the fluorine-containing segments of the modified polyacrylic acid, strong physical adsorption or hydrophobic affinity can be generated with the hydrophobically treated sheet-like aluminum particles in the floating aluminum silver paste. Utilizing the kinetic induction effect generated by the spontaneous surface enrichment of fluorine-containing segments, the hydrophobic affinity between the fluorine-containing segments generates a significant traction force on the sheet-like aluminum particles, thereby overcoming the viscosity resistance of the matrix and driving the sheet-like aluminum particles to complete directional rearrangement.

[0014] As the film-forming process enters the middle and late stages, the water and cosolvents in the system begin to evaporate in large quantities. Due to the higher evaporation rate of small molecule ketones compared to water, their rapid decrease in concentration forcibly disrupts the hydrolysis equilibrium of the ketimine, driving the reaction to proceed efficiently in the direction of releasing active primary amine groups. The highly active primary amine groups released in situ rapidly capture the epoxy groups in the modified polyacrylate segments and undergo ring-opening addition reactions. At this point, the modified polyacrylic acid epoxy segments form a stable covalent bond with the aqueous acrylic emulsion matrix during the coating formation process. The coating matrix has entered the gelation stage, and the resulting viscous resistance ensures that the sheet-like aluminum particle reflective structure, which has completed directional rearrangement on the surface and is in a thermodynamically stable state, will not shift in the interior of the coating due to the shrinkage force generated by the later chemical crosslinking. This achieves a synergistic enhancement of millimeter-wave radar signal reflection effect, poor coating weather resistance, and adhesion.

[0015] In some embodiments, the modified inorganic filler includes the following preparation steps:

[0016] Inorganic filler, aminosilane coupling agent, polyethylene glycol trimethoxysilylpropyl ether, and lower fatty alcohols are dispersed in an acetate-sodium acetate buffer solution with a pH of 4.5-5.5. The silanols obtained by hydrolyzing the aminosilane coupling agent and polyethylene glycol trimethoxysilylpropyl ether undergo a condensation reaction with the hydroxyl groups on the surface of the inorganic filler under acidic conditions to obtain silane coupling modified inorganic filler.

[0017] The silane-coupled modified inorganic filler is dispersed in a ketone solvent, so that the primary amino groups on the surface of the silane-coupled modified inorganic filler are converted into ketimine structures, thereby obtaining the modified inorganic filler.

[0018] The aminosilane coupling agent includes γ-aminopropyltriethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane; the inorganic filler includes at least one of barium sulfate, titanium dioxide, silicon dioxide, talc, and mica; the lower fatty alcohol includes at least one of ethanol, propanol, and isopropanol; and the ketone solvent includes at least one of 4-methyl-2-pentanone and 3-methyl-2-butanone.

[0019] Through the above embodiments, in an acetate-sodium acetate buffer solution system with a pH of 4.5-5.5, the silanol groups generated after hydrolysis of aminosilane coupling agent and polyethylene glycol trimethoxysilylpropyl ether can undergo a condensation reaction with the hydroxyl groups on the surface of inorganic fillers under acidic conditions, so that the aminosilane coupling agent and polyethylene glycol trimethoxysilylpropyl ether are covalently grafted onto the surface of inorganic fillers. By converting the primary amino group into a ketimine structure to temporarily end the primary amino group, the modified inorganic filler remains chemically inert in the early stage of film formation. The strong steric hindrance effect provided by the polyoxyethylene segments improves the dispersion stability and wettability of the modified inorganic filler in the matrix.

[0020] Furthermore, the modified inorganic filler includes the following preparation steps:

[0021] 100 parts of inorganic filler, 0.5-0.8 parts of aminosilane coupling agent, 0.4-0.6 parts of polyethylene glycol trimethoxysilyl propyl ether, and 40-60 parts of lower fatty alcohol are dispersed in 200-300 parts of acetate-sodium acetate buffer solution with pH 4.5-5.5. The mixture is stirred at 400-600 rpm for 1-2 hours at 25-35℃, and then allowed to stand for aging for 1-2 hours to obtain silane coupling modified inorganic filler.

[0022] The silane-coupled modified inorganic filler was dispersed in 150-400 parts of ketone solvent and refluxed at 95-120℃ with stirring at 300-500 rpm for 3-5 hours to obtain the modified inorganic filler.

[0023] Through the above embodiments, under acidic conditions of acetate-sodium acetate buffer, the aminosilane coupling agent and polyethylene glycol trimethoxysilylpropyl ether undergo controlled hydrolysis and condense with the hydroxyl groups on the surface of the inorganic filler to form a relatively stable and dense coupling layer; static aging further improves the bonding strength; subsequently, reflux reaction in ketone solvent causes almost all the primary amino groups introduced by the aminosilane coupling agent to be converted into ketimine structures, which are chemically balanced and inhibited from hydrolyzing under sealed conditions.

[0024] In some embodiments, the inorganic filler has an average particle size of 1.5-3.5µm.

[0025] By controlling the average particle size of the inorganic filler to 1.5-3.5µm through the above embodiments, it is beneficial for the aminosilane coupling agent and polyethylene glycol trimethoxysilylpropyl ether to be fully grafted on its surface; and it avoids the mechanical obstruction of the migration of the plate-like aluminum particles caused by the modified inorganic filler prepared with an excessively large average particle size, and also avoids the increase in system viscosity caused by an excessively small average particle size. As a result, the modified inorganic filler prepared exhibits better dispersion stability and anti-agglomeration performance in the aqueous acrylic emulsion matrix.

[0026] In some embodiments, the floating aluminum silver paste has an average particle size of 12-15µm, a floatability ≥90%, a non-volatile content of 65-75%, and a hiding power ≥28000cm. 2 / g; the water-based acrylic emulsion has a solid content of 38-42%, a viscosity of 40-60 mPa·s, a pH value of 6.5-7.5, and a hydroxyl content of about 1-2%; the corrosion inhibitor includes at least one of zinc phosphate, zinc 2-ethylhexanoate, benzotriazole, and methylbenzotriazole; the leveling agent includes at least one of polyether modified silicone oil and polyoxypropylene ethylene glycerol ether; the defoamer is silicone oil.

[0027] Through the above implementation scheme, the floating aluminum silver paste can form a continuous and parallel-oriented metal reflective layer on the coating surface; the water-based acrylic emulsion has high film density, excellent water resistance and good polar functional group distribution; the corrosion inhibitor can build a protective layer and inhibit the aluminum powder oxidation and hydrogen evolution reaction induced by water vapor penetration; the leveling agent optimizes the coating spread and rheological matching; the defoamer effectively inhibits the generation of bubbles during the construction and curing stages, avoiding micropore and pinhole defects.

[0028] In some embodiments, the modified polyacrylate is prepared by the following method:

[0029] Epoxy acrylate monomers, fluorinated acrylate monomers, hydroxyl acrylate monomers, and a free radical initiator are dispersed in an organic solvent to allow the three unsaturated monomers to undergo a free radical copolymerization reaction, thereby obtaining modified polyacrylate.

[0030] The epoxy acrylate monomer includes at least one of glycidyl methacrylate and glycidyl acrylate; the fluorinated acrylate monomer includes at least one of trifluoroethyl methacrylate and 2,2,2-trifluoroethyl acrylate; the hydroxyl acrylate monomer includes at least one of hydroxyethyl methacrylate and hydroxypropyl methacrylate; the free radical initiator includes at least one of azobisisobutyronitrile and benzoyl peroxide; and the organic solvent includes at least one of toluene, xylene, ethyl acetate, and acetone.

[0031] Through the above implementation scheme, the copolymerization of epoxy acrylate monomers, fluorinated acrylate monomers, and hydroxyl acrylate monomers is initiated in an organic solvent by a free radical initiator. This allows epoxy groups, short-chain fluorinated side chains, and hydroxyl side chains to be introduced more uniformly into the same polymer backbone. Based on the characteristics of free radical polymerization—rapid chain growth rate and wide monomer compatibility—the three types of functional groups can achieve relatively stable coexistence in the polymer chain segments, avoiding structural segregation caused by differences in reactivity. This results in an amphiphilic grafted polymer backbone with both polar groups and hydrophobic fluorinated segments. Furthermore, the selected organic solvent can effectively dissolve the three types of monomers and provide a suitable free radical diffusion environment, making the polymerization process more uniform and controllable.

[0032] Furthermore, the modified polyacrylate is prepared by the following method:

[0033] Under nitrogen protection, 50 parts of epoxy acrylate monomer, 30-40 parts of fluorinated acrylate monomer, 15-25 parts of hydroxyl acrylate monomer, and 0.6-1 parts of free radical initiator are dispersed in 150-250 parts of organic solvent and stirred at 300-500 rpm for 4-6 hours at 70-80℃ to obtain modified polyacrylate.

[0034] The above implementation scheme can improve the conversion rate of the three unsaturated monomers while ensuring the stable generation of free radicals, so that the three unsaturated monomers can achieve more complete and more uniform copolymerization and embedding in the formed modified polyacrylate.

[0035] Secondly, this application provides a method for preparing a millimeter-wave radar signal enhancement coating, comprising the following preparation steps:

[0036] Provide raw materials for the millimeter-wave radar signal enhancement coating according to any embodiment of the first aspect;

[0037] The raw materials are mixed to obtain a millimeter-wave radar signal enhancement coating.

[0038] Through the above-described implementation methods, the scientific selection and proportioning of raw materials ensure that each functional raw material can play its full role in subsequent steps, laying the foundation for the preparation of millimeter-wave radar signal enhancement coatings; the desired millimeter-wave radar signal enhancement coating is obtained by mixing the raw materials.

[0039] Furthermore, the preparation method of the millimeter-wave radar signal enhancement coating includes the following preparation steps:

[0040] S1: Provide raw materials for the millimeter-wave radar signal enhancement coating according to any embodiment of the first aspect;

[0041] S2: Mix 30-35 parts of water and water-based acrylic emulsion, stir at 300-500 rpm for 5-10 minutes at 20-30℃, then add modified inorganic filler, disperse at 1000-1500 rpm for 20-30 minutes, then add defoamer and leveling agent, stir at 300-500 rpm for 5-10 minutes to obtain grinding base material;

[0042] S3: Mix the floating aluminum silver paste, 5-8 parts of water, and the grinding base material, and stir at 200-300 rpm for 2-3 minutes at 20-30℃. Then add the modified polyacrylate and stir at 300-500 rpm for 10-15 minutes. Then add the corrosion inhibitor and stir at 300-500 rpm for 5-10 minutes. Finally, add the remaining water and continue stirring for 3-5 minutes. After degassing and filtration, the millimeter-wave radar signal enhancement coating is obtained.

[0043] The above implementation scheme can effectively ensure the uniformity of the obtained millimeter-wave radar signal enhancement coating system and smooth construction.

[0044] Thirdly, a low-profile transportation facility, according to this application, provides a coating formed by curing a millimeter-wave radar signal enhancement coating prepared according to the millimeter-wave radar signal enhancement coating of the first aspect or the method described in the second aspect.

[0045] Compared with the prior art, the beneficial effects of this application are at least as follows:

[0046] In the early stage of film formation of the millimeter-wave radar signal enhancement coating, the modified polyacrylate causes the flake-like aluminum particles to migrate and accumulate on the coating surface during film formation, forming a relatively continuous millimeter-wave radar signal reflection layer. In the middle and late stages of film formation, the differential volatilization of moisture and small molecule ketones and the positive in-situ hydrolysis of ketimine promote the rapid ring-opening addition reaction between the highly active primary amines released by the modified inorganic filler and the epoxy groups in the matrix. At this time, because the modified polyacrylic acid epoxy segments form a stable covalent bond with the waterborne acrylic emulsion matrix during the coating formation process, the coating matrix has entered the gelation stage, ensuring the stability of the millimeter-wave radar signal reflection layer and improving the weather resistance of the coating. Detailed Implementation

[0047] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0050] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0051] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0052] The floating aluminum silver paste used is TFW412 type floating aluminum silver paste from Shanghai Yantai Industrial Co., Ltd.

[0053] The waterborne acrylic emulsion used is Bayhydrol® A 2846 from Covestro Polymers (China) Co., Ltd.

[0054] Barium sulfate, average particle size: 2μm;

[0055] Polyethylene glycol trimethoxysilylpropyl ether, CAS No. 98358-37-3, number average molecular weight 600;

[0056] Silicone oil, CAS No. 63148-62-9, number average molecular weight 2000;

[0057] The polyether-modified silicone oil was selected from BYK-333 by BYK Chemicals;

[0058] Polyoxypropylene ethylene glycerol ether, model Pluronic® F-68.

[0059] Preparation Example 1

[0060] Preparation of modified inorganic fillers:

[0061] 100 parts of barium sulfate, 0.6 parts of γ-aminopropyltriethoxysilane, 0.5 parts of polyethylene glycol trimethoxysilyl ether, and 50 parts of isopropanol were dispersed in 260 parts of an acetate-sodium acetate buffer solution with a pH of 5.0. The mixture was stirred at 500 rpm for 2 hours at 25°C, then allowed to stand for aging for 1 hour. After centrifugation at 4000 rpm for 12 minutes, the supernatant was discarded. The mixture was washed twice with 300 parts of isopropanol and twice with 500 parts of water. After drying at 75°C to constant weight, the silane-coupled modified inorganic filler was obtained.

[0062] 80 parts of silane-coupled modified inorganic filler were dispersed in 250 parts of 4-methyl-2-pentanone and refluxed at 120℃ with stirring at 400 rpm for 3-5 h. After cooling to room temperature, the mixture was allowed to stand for 30 min and centrifuged at 5000 rpm for 15 min. The ketone mother liquor containing water and byproducts was discarded. The precipitate was then washed twice with 200 parts of anhydrous ethanol and centrifuged. It was then vacuum dried at 45℃ to constant weight and obtained by air-flow fractionation as modified inorganic filler with an average particle size of 2 μm.

[0063] Comparative Preparation Example 1

[0064] Preparation of silane-coupled modified inorganic fillers:

[0065] 100 parts of barium sulfate, 0.6 parts of γ-aminopropyltriethoxysilane, 0.5 parts of polyethylene glycol trimethoxysilyl ether, and 50 parts of isopropanol were dispersed in 260 parts of an acetate-sodium acetate buffer solution at pH 5.0. The mixture was stirred at 500 rpm for 2 hours at 25°C, then allowed to stand for aging for 1 hour. After centrifugation at 4000 rpm for 12 minutes, the supernatant was discarded. The mixture was washed twice with 300 parts of isopropanol and then twice with 500 parts of water. After drying at 75°C to constant weight, the silane-coupled modified inorganic filler was obtained.

[0066] Preparation Example 2

[0067] Preparation of modified polyacrylate:

[0068] Under nitrogen protection, 50 parts glycidyl methacrylate, 35 parts trifluoroethyl methacrylate, 20 parts hydroxyethyl methacrylate, and 0.75 parts azobisisobutyronitrile were dispersed in 220 parts toluene. The mixture was stirred at 400 rpm for 6 h at 75 °C. The mixture was then vacuum distilled at -0.095 MPa at 50 °C until solid precipitates. 400 parts of 0 °C ice-cold methanol were added and the mixture was stirred at 200 rpm for 1 h. After centrifugation at 4000 rpm for 12 min, the supernatant was discarded. The mixture was washed twice with 300 parts of 0 °C ice-cold methanol and dried under vacuum at 45 °C to constant weight to obtain modified polyacrylate.

[0069] Comparative Preparation Example 2

[0070] Preparation of epoxy-free modified polyacrylates:

[0071] The preparation method is largely the same as in Example 2, except that 50 parts of glycidyl methacrylate in step P1 are replaced with 31.8 parts of trifluoroethyl methacrylate and 18.2 parts of hydroxyethyl methacrylate.

[0072] Comparative preparation example 3

[0073] Preparation of fluorine-free modified polyacrylates:

[0074] The preparation method is largely the same as in Example 2, except that the 35 parts of trifluoroethyl methacrylate in step P1 are replaced with 25 parts of glycidyl methacrylate and 10 parts of hydroxyethyl methacrylate.

[0075] Example 1

[0076] Preparation of a millimeter-wave radar signal enhancement coating:

[0077] S1: Provides 12 parts floating aluminum silver paste; 30 parts aqueous acrylic emulsion; 10 parts modified inorganic filler from Preparation Example 1; corrosion inhibitor: 0.8 parts benzotriazole; leveling agent: 0.14 parts polyether modified silicone oil; defoamer: 0.07 parts silicone oil; 3 parts modified polyacrylate from Preparation Example 2; 52 parts water;

[0078] S2: Mix 32 parts of water and waterborne acrylic emulsion, stir at 400 rpm for 8 minutes at 25°C, then add modified inorganic filler, disperse at 1200 rpm for 28 minutes, then add silicone oil and polyether modified silicone oil, stir at 400 rpm for 8 minutes to obtain grinding base material.

[0079] S3: Mix the floating aluminum silver paste and 8 parts water and add it to the grinding base. Stir at 300 rpm for 2 minutes at 25°C. Then add the modified polyacrylate and stir at 400 rpm for 13 minutes. Then add the corrosion inhibitor and stir at 400 rpm for 10 minutes. Finally, add 12 parts water and continue stirring for 3 minutes. Let stand for 60 minutes to degas. After filtering through a 200-mesh filter, the millimeter-wave radar signal enhancement coating is obtained.

[0080] Comparative Example 1

[0081] Similar to Example 1, except that the 10 parts of modified inorganic filler in step S2 are replaced with 10 parts of silane coupling modified inorganic filler from Comparative Preparation Example 1.

[0082] Comparative Example 2

[0083] Similar to Example 1, except that the 3 parts of modified polyacrylate in step S3 were replaced with 3 parts of modified polyacrylate without epoxy groups in Comparative Preparation Example 2.

[0084] Comparative Example 3

[0085] The process is largely the same as in Example 1, except that the 3 parts of modified polyacrylate in step S3 are replaced with 3 parts of fluorine-free modified polyacrylate from Comparative Preparation Example 3.

[0086] Comparative Example 4

[0087] Similar to Example 1, except that the 3 parts of modified polyacrylate in step S3 are replaced with 2 parts of fluorine-free modified polyacrylate and 1 part of trifluoroethyl methacrylate from Comparative Preparation Example 3.

[0088] Test section

[0089] A standard PP cone was selected as the substrate. After corona treatment, its surface tension was required to reach 40 mN / m. Then, a 0.6 mm thick layer of millimeter-wave radar signal enhancement coatings from each embodiment and comparative example was applied using a wire bar coater and allowed to dry and cure. The following tests were then conducted:

[0090] Millimeter-wave radar signal enhancement test:

[0091] Place them in front of a 77GHz millimeter-wave radar signal system, with the radar installed at a height of 1m and the beam pointing horizontally. Place the test sample at a distance of 30m and a yaw angle of 10°. Collect 200 frames of radar data, record the relative amplitude A (dB) of the target's peak echo and take the average value (with the uncoated sample as the 0dB reference).

[0092] Weather resistance test:

[0093] Salt spray resistance test: After undergoing the same salt spray treatment as GB / T 10125-2021, a millimeter-wave radar signal enhancement test was conducted.

[0094] The test results are shown in Table 1:

[0095] Table 1

[0096]

[0097] As shown in Table 1, the millimeter-wave radar signal enhancement test and weather resistance test of Example 1 are both better than those of the comparative example. This may be because the filler used in Comparative Example 1 is a silane-coupled modified inorganic filler. The primary amino groups on its surface have not been treated with ketimine end-capping and have high chemical activity. In the early stage of film formation, they crosslink prematurely with the epoxy groups in the modified polyacrylate, which leads to a sharp increase in the viscosity of the system in the early stage of water evaporation, thus hindering the directional rearrangement and surface enrichment of the sheet-like aluminum particles driven by fluorine-containing segments.

[0098] The modified polyacrylate without epoxy groups used in Comparative Example 2 lacks chemical reaction sites of epoxy segments, resulting in insufficient interfacial bonding between the coating and the substrate, reduced weather resistance and structural stability, and the coating is prone to defects during film formation and performance degradation in environments such as salt spray.

[0099] The fluorine-free modified polyacrylate used in Comparative Example 3 lacks the driving force of fluorine segments on the flake aluminum particles in the floating aluminum silver paste, resulting in insufficient coating ability to modulate the reflection of millimeter-wave radar signals; at the same time, due to the lack of hydrophobicity imparted by fluorine groups, the coating is more prone to water absorption and defects.

[0100] In Comparative Example 4, although fluorinated acrylate monomers were introduced during the feeding process, the fluorinated acrylates did not embed into the polymer backbone through free radical polymerization, but existed in the form of small molecules. As a result, the fluorinated groups were prone to uneven distribution and aggregation during the coating formation process, and their ability to migrate and accumulate on the coating surface was limited, which resulted in insufficient coating ability to control the reflection of millimeter-wave radar signals.

[0101] In addition, in Example 1, the adhesion test was conducted in accordance with GB / T 9286-2021, and the adhesion reached level 0.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A millimeter-wave radar signal enhancement coating, characterized in that, The product comprises the following components by weight: 30 parts aqueous acrylic emulsion; 10-14 parts floating aluminum silver paste; and 8-12 parts modified inorganic filler. 2.8-3.2 parts modified polyacrylate; 50-55 parts water; 0.6-1 part corrosion inhibitor; 0.12-0.16 parts leveling agent; 0.06-0.1 parts defoamer; The modified inorganic filler is an inorganic filler with polyoxyethylene segments and ketimine-terminated primary amino sites simultaneously coupled on its surface, and includes the following preparation steps: Inorganic filler, aminosilane coupling agent, polyethylene glycol trimethoxysilylpropyl ether, and lower fatty alcohols are dispersed in an acetate-sodium acetate buffer solution with a pH of 4.5-5.

5. The silanols obtained by hydrolyzing the aminosilane coupling agent and polyethylene glycol trimethoxysilylpropyl ether undergo a condensation reaction with the hydroxyl groups on the surface of the inorganic filler under acidic conditions to obtain silane coupling modified inorganic filler. The silane-coupled modified inorganic filler is dispersed in a ketone solvent, so that the primary amino groups on the surface of the silane-coupled modified inorganic filler are converted into ketimine structures, thereby obtaining the modified inorganic filler. The aminosilane coupling agent includes γ-aminopropyltriethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane; the inorganic filler includes at least one of barium sulfate, titanium dioxide, silica, talc, and mica; the lower fatty alcohol includes at least one of ethanol, propanol, and isopropanol; and the ketone solvent includes at least one of 4-methyl-2-pentanone and 3-methyl-2-butanone. The modified polyacrylate is prepared by the following method: Epoxy acrylate monomers, fluorinated acrylate monomers, hydroxyl acrylate monomers, and a free radical initiator are dispersed in an organic solvent to allow the three unsaturated monomers to undergo a free radical copolymerization reaction, thereby obtaining modified polyacrylate. The epoxy acrylate monomer includes at least one of glycidyl methacrylate and glycidyl acrylate; the fluorinated acrylate monomer includes at least one of trifluoroethyl methacrylate and 2,2,2-trifluoroethyl acrylate; the hydroxyl acrylate monomer includes at least one of hydroxyethyl methacrylate and hydroxypropyl methacrylate; the free radical initiator includes at least one of azobisisobutyronitrile and benzoyl peroxide; and the organic solvent includes at least one of toluene, xylene, ethyl acetate, and acetone.

2. The millimeter-wave radar signal enhancement coating according to claim 1, characterized in that, The preparation method of the modified inorganic filler includes the following steps: 100 parts of inorganic filler, 0.5-0.8 parts of aminosilane coupling agent, 0.4-0.6 parts of polyethylene glycol trimethoxysilyl propyl ether, and 40-60 parts of lower fatty alcohol are dispersed in 200-300 parts of acetate-sodium acetate buffer solution with pH 4.5-5.

5. The mixture is stirred at 400-600 rpm for 1-2 hours at 25-35℃, and then allowed to stand for aging for 1-2 hours to obtain silane coupling modified inorganic filler. The silane-coupled modified inorganic filler was dispersed in 150-400 parts of ketone solvent and refluxed at 95-120℃ with stirring at 300-500 rpm for 3-5 hours to obtain the modified inorganic filler.

3. The millimeter-wave radar signal enhancement coating according to claim 1 or 2, characterized in that, The average particle size of the inorganic filler is 1.5-3.5 mm. m.

4. The millimeter-wave radar signal enhancement coating according to claim 1, characterized in that: 1) The average particle size of the floating aluminum silver paste is 12-15 mm. m, buoyancy value ≥90%, non-volatile content 65-75%, hiding power ≥28000 cm 2 / g; 2) The aqueous acrylic emulsion has a solid content of 38-42%, a viscosity of 40-60 mPa·s, a pH value of 6.5-7.5, and a hydroxyl content of 1-2%. 3) The corrosion inhibitor includes at least one of zinc phosphate, zinc 2-ethylhexanoate, benzotriazole, and methylbenzotriazole; 4) The leveling agent includes at least one of polyether-modified silicone oil and polyoxypropylene ethylene glycerol ether; 5) The defoamer is silicone oil.

5. The millimeter-wave radar signal enhancement coating according to claim 1, characterized in that, The modified polyacrylate is prepared by the following method: Under nitrogen protection, 50 parts of epoxy acrylate monomer, 30-40 parts of fluorinated acrylate monomer, 15-25 parts of hydroxyl acrylate monomer, and 0.6-1 parts of free radical initiator are dispersed in 180-220 parts of organic solvent and stirred at 300-500 rpm for 4-6 hours at 70-80℃ to obtain modified polyacrylate.

6. A method for preparing a millimeter-wave radar signal enhancement coating, characterized in that, The preparation steps include the following: Provide raw materials for the millimeter-wave radar signal enhancement coating according to any one of claims 1-5; The raw materials are mixed to obtain a millimeter-wave radar signal enhancement coating.

7. The method according to claim 6, characterized in that, The preparation steps include the following: S1: Providing raw materials for the millimeter-wave radar signal enhancement coating according to any one of the embodiments of claims 1-5; S2: Mix 30-35 parts of water and water-based acrylic emulsion, stir at 300-500 rpm for 5-10 minutes at 20-30℃, then add modified inorganic filler, disperse at 1000-1500 rpm for 20-30 minutes, then add defoamer and leveling agent, stir at 300-500 rpm for 5-10 minutes to obtain grinding base material; S3: Mix the floating aluminum silver paste, 5-8 parts of water, and the grinding base material, and stir at 200-300 rpm for 2-3 minutes at 20-30℃. Then add the modified polyacrylate and stir at 300-500 rpm for 10-15 minutes. Then add the corrosion inhibitor and stir at 300-500 rpm for 5-10 minutes. Finally, add the remaining water and continue stirring for 3-5 minutes. After degassing and filtration, the millimeter-wave radar signal enhancement coating is obtained.

8. A low-profile transportation facility, characterized in that, The coating includes the millimeter-wave radar signal enhancement coating according to any one of claims 1-5 or the millimeter-wave radar signal enhancement coating prepared by the method according to claim 6 or 7, which is cured to form a coating.

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