A double-layer polyurethane acrylic superhydrophobic coating and its preparation method

Abstract

This invention discloses a double-layer polyurethane-acrylic superhydrophobic coating and its preparation method, relating to the field of hydrophobic materials technology. The method includes: preparing a polyurethane-acrylic-2 mixed solution; screen-printing the polyurethane-acrylic-2 mixed solution onto a substrate, followed by xenon lamp curing to obtain a polyurethane-acrylic-2 bonding layer; modifying P25 nano-titanium dioxide particles to obtain modified P25 nano-titanium dioxide particles; preparing a polyurethane-acrylic-6 superhydrophobic coating reagent; and screen-printing the polyurethane-acrylic-6 superhydrophobic coating reagent onto the polyurethane-acrylic-2 bonding layer, followed by xenon lamp curing to obtain a double-layer polyurethane-acrylic superhydrophobic coating. The superhydrophobic coating prepared by this invention exhibits strong adhesion, durability, and corrosion resistance, making it suitable for large-scale production and application in the coatings industry.

Description

Technical Field

[0001] This invention relates to a double-layer polyurethane acrylic superhydrophobic coating and its preparation method, belonging to the field of hydrophobic materials technology. Background Technology

[0002] Superhydrophobicity is a phenomenon frequently observed in nature and has been a subject of extensive research for decades, with applications in various fields. However, the large-scale preparation and application of artificial superhydrophobic coatings remains a significant challenge due to the unresolved issues regarding adhesion and corrosion resistance.

[0003] To achieve large-scale production and application, the fabrication of superhydrophobic coatings generally involves two approaches: first, constructing micro / nanostructures on the substrate surface using low surface energy materials to impart surface roughness; and second, directly treating the substrate surface to achieve roughness. To this end, numerous methods have been developed to prepare multifunctional surfaces with excellent hydrophobicity, such as sol-gel technology, electrospinning, dip coating, and deposition techniques. One common method involves co-depositing colloidal nanomaterials with low-energy-transfer molecules. While this method can achieve enhanced bonding between the substrate and the coating, the complex fabrication process prevents the large-scale production of superhydrophobic coatings. Therefore, we need to explore simpler coating fabrication processes to make industrial production possible. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a double-layer polyurethane acrylic superhydrophobic coating and its preparation method. The prepared superhydrophobic coating has strong adhesion, durability and corrosion resistance, and is suitable for large-scale production and application in the coating field.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a double-layer polyurethane acrylic superhydrophobic coating, comprising:

[0007] Preparation of polyurethane acrylate-2 mixed solution: Polyurethane acrylate-2 and acrylic resin were dispersed in isobornyl acrylate, and γ-glycidoxypropyltrimethoxysilane and cyclohexanediol were added to obtain polyurethane acrylate-2 mixed solution.

[0008] A polyurethane-acrylic-2 mixed solution was screen-printed onto a substrate and cured under a xenon lamp to obtain a polyurethane-acrylic-2 bonding layer.

[0009] P25 nano-titanium dioxide particles were modified to obtain modified P25 nano-titanium dioxide particles.

[0010] Preparation of polyurethane acrylate-6 superhydrophobic coating reagent: Modified P25 nano titanium dioxide powder was dispersed in a silane coupling agent, and polyurethane acrylate-6, epoxy acrylate and aliphatic polyurethane acrylate were added to obtain polyurethane acrylate-6 superhydrophobic coating reagent.

[0011] A polyurethane acrylate-6 superhydrophobic coating agent was screen-printed onto a polyurethane acrylate-2 bonding layer and cured under a xenon lamp to obtain a double-layer polyurethane acrylate superhydrophobic coating.

[0012] Furthermore, the mass ratio of the acrylic resin to isoborneol acrylate is 2-4:1; the acrylic resin includes methyl acrylate, ethyl acrylate and n-butyl acrylate; the mass ratio of γ-glycidoxypropyltrimethoxysilane to cyclohexanediol is 3-4:10.

[0013] Furthermore, a photoinitiator a is added to the preparation of the polyurethane acrylic-2 mixed solution. The photoinitiator a includes ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-carboxy-2-methyl-1-phenyl-1-propanone, benzophenone, and methyl benzoylformate.

[0014] The reagent for preparing the polyurethane acrylate-6 superhydrophobic coating also includes a photoinitiator b and a surfactant. The photoinitiator b includes ethyl 2,4,6-trimethylbenzoylphenylphosphonate and diphenyl ketone, and the surfactant is perfluorodecyltriethoxysilane.

[0015] Furthermore, the mass ratio of ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-carboxy-2-methyl-1-phenyl-1-propanone, benzophenone, and methyl benzoylformate in the photoinitiator a is 1:2:2:1~2.

[0016] The mass ratio of ethyl 2,4,6-trimethylbenzoylphenylphosphonate to diphenyldione in photoinitiator b is 5~7:1.

[0017] Furthermore, the preparation of the polyurethane acrylate-2 mixed solution and the preparation of the polyurethane acrylate-6 superhydrophobic coating reagent were both carried out under ultrasonic vibration conditions.

[0018] Furthermore, during the preparation of the polyurethane acrylic-2 bonding layer, the mesh size of the screen printing is 150, the xenon lamp light source power is 280~400W, and the illumination time is 15~60s.

[0019] In the preparation process of the polyurethane acrylic superhydrophobic coating, the screen printing mesh size is 100 mesh, the xenon lamp light source power is 280~400W, and the illumination time is 45~90s.

[0020] Furthermore, the P25 nano-titanium dioxide particles were modified to obtain modified P25 nano-titanium dioxide particles, including:

[0021] γ-methacryloxypropyltrimethoxysilane was dissolved in anhydrous ethanol, heated, and then P25 nano-titanium dioxide particles were added and stirred to obtain an emulsion.

[0022] Modified P25 nano-titanium dioxide particles were obtained by centrifuging, washing, drying, and grinding the emulsion.

[0023] Furthermore, the mass ratio of γ-methacryloxypropyltrimethoxysilane to anhydrous ethanol is 0.5~1.5:100; the mass ratio of P25 nano-titanium dioxide particles to γ-methacryloxypropyltrimethoxysilane is 5~8:1; the heating temperature is 65~75℃, and the heating time is 1~2h.

[0024] The centrifugation speed is 5000~7000 r / min, and the centrifugation time is 4~6 min; the washing uses an ethanol solution with a water to ethanol volume ratio of 1:1~1.5, and the washing is performed 3 times; the drying temperature is 120℃, and the drying time is 1.5~2.5 h.

[0025] Furthermore, the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane, and its mass ratio with the modified P25 nano-titanium dioxide particles is 1.5~2.5:1.

[0026] The mass ratio of the modified P25 nano-titanium dioxide particles to polyurethane acrylate-6, epoxy acrylate, and aliphatic polyurethane acrylate is 4.8~5.5:1.

[0027] Secondly, the present invention provides a double-layer polyurethane acrylic superhydrophobic coating, which is prepared by the preparation method of the double-layer polyurethane acrylic superhydrophobic coating described in any one of the above claims.

[0028] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0029] This invention improves the stability of the superhydrophobic coating by simultaneously introducing acrylic resins with different properties, increasing the adhesion between the material and the coating. Furthermore, the modified P25 nano-titanium dioxide and the surfactant perfluorodecyltriethoxysilane reduce the surface energy of the coating, improving its durability. The preparation method uses screen printing and UV curing to prepare the superhydrophobic coating, simplifying the production steps.

[0030] The superhydrophobic coating prepared by this invention has strong adhesion, durability and corrosion resistance. It maintains its adhesion to the substrate in repeated friction and wear tests and tape tests, and even exhibits long-lasting adhesion to the substrate under boiling water conditions. It is suitable for large-scale production and application in the coatings industry. Attached Figure Description

[0031] Figure 1 This is a comparative schematic diagram of P25 nano-titanium dioxide particles and modified P25 nano-titanium dioxide particles in Example 1 of the present invention, wherein (a) is a SEM schematic diagram of P25 nano-titanium dioxide particles; (b) is a SEM schematic diagram of modified P25 nano-titanium dioxide particles; (c) is a TEM schematic diagram of P25 nano-titanium dioxide particles; and (d) is a TEM schematic diagram of modified P25 nano-titanium dioxide particles.

[0032] Figure 2 This is a schematic diagram of the infrared spectra of P25 nano-titanium dioxide before and after modification in Example 1 of the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of the double-layer polyurethane acrylic superhydrophobic coating in Embodiment 1 of the present invention, wherein (a)~(b) are SEM schematic diagrams of the double-layer polyurethane acrylic superhydrophobic coating; (c)~(f) are schematic diagrams of the elemental distribution of the double-layer polyurethane acrylic superhydrophobic coating; and (g) is a schematic diagram of the AFM rough structure of the double-layer polyurethane acrylic superhydrophobic coating.

[0034] Figure 4 The diagram below shows the hydrophobic performance test of the double-layer polyurethane acrylic superhydrophobic coating in Example 1 of the present invention. (a) is a diagram showing the addition of different droplets to the double-layer polyurethane acrylic superhydrophobic coating; (b) is a diagram showing the addition of water droplets after the double-layer polyurethane acrylic superhydrophobic coating is applied to the surface of an aluminum sheet; (c) is a diagram showing the addition of water droplets after the double-layer polyurethane acrylic superhydrophobic coating is applied to the surface of a ceramic; (d) is a diagram showing the addition of water droplets after the double-layer polyurethane acrylic superhydrophobic coating is applied to the surface of wood; and (e) to (h) are diagrams showing the hydrophobic behavior test of the double-layer polyurethane acrylic superhydrophobic coating.

[0035] Figure 5 The diagram shows the self-cleaning performance test of the double-layer polyurethane acrylic superhydrophobic coating in Example 1. (a) to (c) are self-cleaning diagrams of ordinary glass; (d) to (f) are self-cleaning diagrams of the double-layer polyurethane acrylic superhydrophobic coating after sand is adhered to it and water droplets are used; (g) to (i) are self-cleaning diagrams of the double-layer polyurethane acrylic superhydrophobic coating after methyl orange solution is adhered to it.

[0036] Figure 6The diagrams show the adhesion performance tests of the polyurethane acrylic-2 bonding layer and the double-layer polyurethane acrylic superhydrophobic coating in Example 1. (a) is a structural diagram of the polyurethane acrylic-2 bonding layer after boiling in water for one hour; (b) is a schematic diagram of the polyurethane acrylic-2 bonding layer after a cross-cut adhesion test; (c) is a schematic diagram of the polyurethane acrylic-2 bonding layer after a cross-cut adhesion test using adhesive tape; (d) is a structural diagram of the double-layer polyurethane acrylic superhydrophobic coating after boiling in water for two hours; (e) is a schematic diagram of the double-layer polyurethane acrylic superhydrophobic coating after a cross-cut adhesion test; and (f) is a schematic diagram of the double-layer polyurethane acrylic superhydrophobic coating after a cross-cut adhesion test using adhesive tape.

[0037] Figure 7 This is a schematic diagram of the structure of the polyurethane acrylic-6 superhydrophobic coating in Example 2 after boiling in water for 15 minutes;

[0038] Figure 8 This is a schematic diagram of the adhesion performance test of the double-layer polyurethane acrylic superhydrophobic coating in Example 1, where (a) to (c) are schematic diagrams of the 5H hardness of the double-layer polyurethane acrylic superhydrophobic coating; (d) to (f) are schematic diagrams of the 6H hardness of the double-layer polyurethane acrylic superhydrophobic coating; and (g) to (i) are schematic diagrams of the 7H hardness of the double-layer polyurethane acrylic superhydrophobic coating.

[0039] Figure 9 The diagram below shows the durability test results of the double-layer polyurethane acrylic superhydrophobic coating in Example 1. (a) shows the contact angle of the double-layer polyurethane acrylic superhydrophobic coating after different number of tape peels; (b) shows the contact angle of the double-layer polyurethane acrylic superhydrophobic coating under different friction cycles; (c) shows the contact angle of the double-layer polyurethane acrylic superhydrophobic coating after immersion in 3.5wt% NaCl solution for different times; and (d) shows the contact angle of the double-layer polyurethane acrylic superhydrophobic coating in solutions with different pH values.

[0040] Figure 10 This is a schematic diagram of the corrosion resistance test of the double-layer polyurethane acrylic superhydrophobic coating in Example 1, wherein (a) is a Tafel diagram of the ordinary iron sheet and the coated iron sheet (double-layer superhydrophobic PUAcoating); (b) is a schematic diagram of the equivalent circuit model fitted to the EIS data of the ordinary iron sheet; (c) is a schematic diagram of the equivalent circuit model fitted to the EIS data of the coated iron sheet; and (d) is a Bode diagram of the ordinary iron sheet and the iron sheet coated with the double-layer polyurethane acrylic superhydrophobic coating. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0042] Example 1:

[0043] This invention provides a method for preparing a double-layer polyurethane acrylic superhydrophobic coating, comprising:

[0044] S1. Preparation of polyurethane-acrylic acid-2 mixed solution:

[0045] Prepare 6g of polypropylene resin. Specifically, the 6g of polypropylene resin includes 3g of polyurethane acrylate-2 (PUA-2), 1g of methyl acrylate (MA), 1g of ethyl acrylate (EA), and 1g of n-butyl acrylate (n-BA).

[0046] A polymer precursor solution was prepared by dissolving and dispersing 6g of polypropylene resin in 2g of isobornyl acrylate (IBOA) and then sonicating for 5 minutes.

[0047] Adding 0.4 g of γ-glycidyl etheroxypropyltrimethoxysilane and 0.8 g of cyclohexanediol to the polymer precursor solution yields a transparent viscous liquid.

[0048] Under ultrasonic oscillation conditions, a photoinitiator was continuously added dropwise. Specifically, the photoinitiator consisted of 0.1 g of ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L), 0.2 g of 2-carboxy-2-methyl-1-phenyl-1-propanone (HMPP), 0.2 g of methyl benzoylformate (MBF), and 0.1 g of benzophenone, resulting in a polyurethane acrylic-2 mixed solution.

[0049] S2. The polyurethane acrylic-2 mixed solution is screen-printed onto a 25.4 mm × 76.2 mm glass slide using a 150-mesh screen and cured with a xenon lamp (300 W, 30 seconds) to obtain the polyurethane acrylic-2 bonding layer.

[0050] S3. Modification of P25 nano-titanium dioxide particles:

[0051] 0.5g of γ-methacryloxypropyltrimethoxysilane (silane coupling agent KH-570) was dissolved in 50g of anhydrous ethanol and heated and stirred at 70℃ for 1.5h. Then, 3g of P25 nano titanium dioxide particles were added and stirred for 3h to form a white emulsion.

[0052] The emulsion was centrifuged, washed three times with water and anhydrous ethanol in a 1:1 volume ratio, and dried at 120°C for 2 hours to obtain modified P25 nano-titanium dioxide particles.

[0053] S4. Preparation of a double-layer polyurethane-acrylic superhydrophobic coating:

[0054] Under ultrasonic oscillation conditions, 1.5 g of modified P25 nano-titanium dioxide particles were dispersed in 0.3 g of γ-methacryloyloxypropyltrimethoxysilane, and 0.2 g of polyurethane acrylate-6 (PUA-6), 0.05 g of epoxy acrylate (EPAR), 0.2 g of aliphatic polyurethane acrylate-4 (PUA-4), a photoinitiator, and a surfactant were added. The photoinitiator consisted of 0.05 g of ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L) and 0.05 g of benzophenone (BAPO), and the surfactant was 0.3 g of perfluorodecyltriethoxysilane (PFDTES), thus obtaining a polyurethane acrylate-6 superhydrophobic coating reagent.

[0055] S5. The polyurethane acrylic-6 superhydrophobic coating agent is screen-printed onto the polyurethane acrylic-2 bonding layer through a 100-mesh screen and cured with a xenon lamp (300 W, 1 minute of light exposure) to obtain a double-layer polyurethane acrylic superhydrophobic coating. Example

[0056] This embodiment provides a method for preparing a double-layer polyurethane acrylic superhydrophobic coating, including:

[0057] S1. Modification of P25 nano-titanium dioxide particles:

[0058] 0.5g of γ-methacryloxypropyltrimethoxysilane (silane coupling agent KH-570) was dissolved in 50g of anhydrous ethanol and heated and stirred at 70℃ for 1.5h. Then, 3g of P25 nano titanium dioxide particles were added and stirred for 3h to form a white emulsion.

[0059] The emulsion was centrifuged, washed three times with water and anhydrous ethanol in a 1:1 volume ratio, and dried at 120°C for 2 hours to obtain modified P25 nano-titanium dioxide particles.

[0060] S2. Preparation of polyurethane acrylic-6 superhydrophobic coating:

[0061] Under ultrasonic oscillation conditions, 1.5 g of modified P25 nano-titanium dioxide particles were dispersed in 0.3 g of γ-methacryloyloxypropyltrimethoxysilane, and 0.2 g of polyurethane acrylate-6 (PUA-6), 0.05 g of epoxy acrylate (EPAR), 0.2 g of aliphatic polyurethane acrylate-4 (PUA-4), a photoinitiator, and a surfactant were added. The photoinitiator consisted of 0.05 g of ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L) and 0.05 g of benzophenone (BAPO), and the surfactant was 0.3 g of perfluorodecyltriethoxysilane (PFDTES), resulting in a polyurethane acrylate-6 superhydrophobic coating.

[0062] The hydrophobic coatings and modified P25 nano-titanium dioxide particles prepared in Examples 1 and 2 are tested and analyzed below.

[0063] First, the P25 nano-titanium dioxide particles obtained in Example 1 and the modified P25 nano-titanium dioxide particles were tested by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results are as follows: Figure 1 As shown, from Figure 1 As can be seen from (b) and (d), the modified P25 nano-titanium dioxide particles are easily dispersed and have a spherical structure.

[0064] Infrared spectroscopy was performed on P25 nano-titanium dioxide particles and modified P25 nano-titanium dioxide particles, such as... Figure 2 As shown, P25 represents P25 nano-titanium dioxide particles, M-P25 represents modified P25 nano-titanium dioxide particles, and 2925 and 1710 cm⁻¹ are also mentioned. -1 The presence of -CH2 and C=O functional groups indicates that γ-methacryloyloxypropyltrimethoxysilane (silane coupling agent KH-570) has successfully modified P25 nano-titanium dioxide particles, transforming the hydrophilic P25 nano-titanium dioxide particles into hydrophobic P25 nano-titanium dioxide particles.

[0065] Secondly, the bilayer polyurethane-acrylic superhydrophobic coating prepared in Example 1 was tested by scanning electron microscopy (SEM), such as... Figure 3 (a) and Figure 3 As shown in (b), the double-layer polyurethane acrylic superhydrophobic coating prepared in Example 1 has a spherical three-dimensional microstructure with obvious hierarchical structure. Figure 3 (c) to (f) are schematic diagrams of the elemental distribution of the double-layer polyurethane-acrylic superhydrophobic coating. It can be seen that the double-layer polyurethane-acrylic superhydrophobic coating is uniformly prepared. Figure 3 (g) is a schematic diagram of the AFM rough structure of the double-layer polyurethane acrylic superhydrophobic coating. The roughness of the coating was measured to be Ra = 86.2 nm.

[0066] Different water droplets were added to the surface of the double-layer polyurethane acrylic superhydrophobic coating of Example 1, namely milk, iced tea, room temperature tea, water, and coffee. Figure 4 (a) It can be seen that different water droplets can all bulge on the coating surface, indicating that the double-layer polyurethane acrylic superhydrophobic coating has a hydrophobic effect.

[0067] A double-layer polyurethane-acrylic superhydrophobic coating was applied to the surface of different substrates, and water droplets were then dropped onto the surface of the double-layer polyurethane-acrylic superhydrophobic coating. Figure 4 As shown in (b) to (d), Figure 4 (b) is an aluminum sheet. Figure 4 (c) is ceramic. Figure 4 (d) represents wood. It can be seen that no matter what kind of substrate the double-layer polyurethane acrylic superhydrophobic coating is prepared on, water droplets can protrude on the surface of the coating, indicating that the double-layer polyurethane acrylic superhydrophobic coating is hydrophobic when prepared on different types of substrates. Figure 4 (e)~(h) are schematic diagrams of the hydrophobic behavior test of the double-layer polyurethane acrylic superhydrophobic coating. When water droplets fall on the coating surface, the water droplets bounce off the coating surface due to the extremely low surface tension of the coating surface, indicating that the coating has good superhydrophobic properties.

[0068] Next, a self-cleaning test was conducted on the double-layer polyurethane acrylic superhydrophobic coating prepared in Example 1, using ordinary glass as a comparison. Figure 5 As shown in (a) to (c), ordinary glass surfaces do not have a self-cleaning effect; water droplets cannot remove sand and dirt from the glass surface. Figure 5 (d) to (f) are schematic diagrams illustrating the self-cleaning properties of sand adhered to a double-layer polyurethane acrylic superhydrophobic coating. It can be seen that the sand can roll under the influence of water droplets, leaving no dirt residue on the coating surface. Figure 5 (g) to (i) are schematic diagrams of the self-cleaning of the double-layer polyurethane acrylic superhydrophobic coating with methyl orange solution. The methyl orange solution can also slide off the coating surface without leaving any dirt marks. In summary, this shows that the double-layer polyurethane acrylic superhydrophobic coating has good self-cleaning performance.

[0069] Then, the adhesion of the polyurethane acrylic-2 bonding layer and the double-layer polyurethane acrylic superhydrophobic coating prepared in Example 1 was tested, and the test results are as follows: Figure 6 As shown, Figure 6 (a) is an image of the polyurethane acrylic-2 bonding layer after boiling in water for one hour. Figure 6 (d) is a picture of the double-layer polyurethane acrylic superhydrophobic coating after boiling for two hours. As can be seen from the picture, the polyurethane acrylic-2 bonding layer and the double-layer polyurethane acrylic superhydrophobic coating did not fall off the surface of the glass substrate.

[0070] Cross-cut adhesion and tape peel tests were performed on the polyurethane acrylic-2 bonding layer and the double-layer polyurethane acrylic superhydrophobic coating, such as... Figure 6 (b) Figure 6 As shown in (c), there were no signs of the polyurethane acrylate-2 bonding layer peeling off the surface of the 3M tape. The polyurethane acrylate-2 bonding layer remained well adhered to the glass substrate, indicating good adhesion between the polyurethane acrylate-2 bonding layer and the glass substrate. Figure 6 (e) Figure 6 As shown in (f), there were no traces of the double-layer polyurethane acrylic superhydrophobic coating peeling off on the surface of the 3M tape. The double-layer polyurethane acrylic superhydrophobic coating was still well attached to the glass substrate, which indicates that the double-layer polyurethane acrylic superhydrophobic coating has good adhesion to the glass substrate.

[0071] Figure 7 The image shows the polyurethane acrylic-6 superhydrophobic coating prepared in Example 2 after boiling in water for 15 minutes. It can be seen that the coating has peeled off from the substrate surface, has poor adhesion, and its performance is unqualified.

[0072] like Figure 8 As shown in the figure, the hardness of the double-layer polyurethane acrylic superhydrophobic coating is 6H, which indicates that the polyurethane acrylic-2 bonding layer has a good bridging effect and can enhance the adhesion between the coating and the substrate. The polyurethane acrylic superhydrophobic coating also has good adhesion.

[0073] Next, the durability performance of the double-layer polyurethane-acrylic superhydrophobic coating prepared in Example 1 was tested, and the test results are as follows: Figure 9 As shown in (a) to (b), the coating retains its superhydrophobic properties even after undergoing multiple physical damage cycles, such as 60 cycles of tape peeling or 80 cycles of friction. Figure 9 As shown in (c) to (d), whether soaked in 3.5wt% NaCl salt water for one hour or in solutions with different pH values, the superhydrophobic coating can still maintain good superhydrophobicity, and the contact angle CA is still >150°.

[0074] Finally, the corrosion resistance performance of the double-layer polyurethane acrylic superhydrophobic coating prepared in Example 1 was tested, and the test results are as follows: Figure 10 As shown, Figure 10(a) is a schematic diagram of Tafel testing for ordinary iron sheet and coated iron sheet (double-layer superhydrophobic PUA coating). The coating has a large anodic slope and a small cathodic slope, indicating that the circuit density changes slowly with the increase of the cathodic branch potential. This is also consistent with Table 1, which shows the Tafel data parameters for the double-layer polyurethane acrylic superhydrophobic coating, as follows:

[0075] Table 1: Tafel data parameters for the double-layer polyurethane acrylic superhydrophobic coating.

[0076]

[0077] As can be seen from the data in Table 1, the i of the coated iron sheet corr 2.200×10 -7 A cm −2 The i is far lower than that of ordinary iron sheets corr This indicates that the coating can effectively reduce the probability and severity of corrosion.

[0078] For a standard iron sheet, its EIS spectrum reveals a concave semicircle at high frequencies, representing the charge transfer resistance at the electrode / electrolyte interface. Therefore, an equivalent circuit model is used for fitting, consisting of a modified Randles circuit. Where R... s R represents the resistance of the solution. ct The charge transfer resistance at the electrode / electrolyte interface, CPE (phase constant element), is used to simulate the behavior of non-ideal capacitors, such as... Figure 10 As shown in (b) to (c), these are schematic diagrams of equivalent circuit models for fitting the impedance data of ordinary iron sheets and iron sheets coated with a double-layer polyurethane acrylic superhydrophobic coating, respectively. The fitting results are shown in Table 2.

[0079] Table 2: EIS data fitting results for ordinary iron sheets and coated iron sheets

[0080]

[0081] As shown in Table 2, the polyurethane-acrylic superhydrophobic coating has a larger capacitor circuit diameter compared to the iron sheet, indicating an increased charge transfer resistance. This is attributed to the presence of a protective layer at the metal-solution interface. The R0 of the coated iron sheet... f and R ct All are higher than ordinary iron sheets, and the CPE of coated iron sheets is higher. dl Three orders of magnitude lower than ordinary iron sheets, with a higher R ct and lower CPE dl This indicates that the polyurethane acrylic superhydrophobic coating has good anti-corrosion properties.

[0082] Combination Figure 10 (d) shows a Bode diagram of a plain iron sheet and a coated iron sheet. Compared to the plain iron sheet, the coated iron sheet exhibits higher impedance at all frequencies. Furthermore, the Z-value of the coating at 0.01 Hz is 1.02 × 10⁻⁶. 5 Ω cm -2 It is 10 times that of ordinary iron sheet. 3 The Bode modulus at a low frequency of 0.01 Hz (|Z|) is [times]. 0.01 It has been reported as an indicator of corrosion inhibition capability. Polyurethane acrylic superhydrophobic coatings exhibit high |Z|. 0.01 The value proves that it has good resistance to corrosion and oxidation-reduction reactions.

[0083] Based on the above test results, the following conclusions can be drawn: This invention provides a simple superhydrophobic coating with excellent physical and chemical properties through screen printing and UV curing. The prepared double-layer polyurethane-acrylic superhydrophobic coating has a contact angle greater than 150º, exhibiting excellent hydrophobic properties. When sand and dye are applied to the surface of the polyurethane-acrylic superhydrophobic coating, the coating surface is self-cleaning. After heating in boiling water for 2 hours, the polyurethane-acrylic superhydrophobic coating remains firmly adhered to the substrate surface. Furthermore, the coating did not detach after cross-section and tape peeling tests. Moreover, the coating retains its hydrophobicity after several sandpaper rubbings. In addition, even in a strong electrolyte environment, the polyurethane-acrylic superhydrophobic coating maintains good superhydrophobicity, and its excellent corrosion resistance better protects the substrate.

[0084] Therefore, the double-layer polyurethane acrylic superhydrophobic coating prepared by this invention exhibits excellent self-cleaning properties, adhesion, durability, and corrosion resistance. This provides great potential for large-scale production applications.

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a double-layer polyurethane acrylic superhydrophobic coating, characterized in that, include: Preparation of a bifunctional polyurethane acrylate mixed solution: The bifunctional polyurethane acrylate and acrylic resin are dispersed in isobornyl acrylate, and γ-glycidoxypropyltrimethoxysilane and cyclohexanediol are added to obtain the bifunctional polyurethane acrylate mixed solution. The acrylic resin includes methyl acrylate, ethyl acrylate and n-butyl acrylate. A bifunctional polyurethane acrylate mixture was screen-printed onto a substrate and cured under a xenon lamp to obtain a bifunctional polyurethane acrylate bonding layer. P25 nano-titanium dioxide particles were modified to obtain modified P25 nano-titanium dioxide particles. Preparation of a superhydrophobic coating reagent for polyhexafunctional polyurethane acrylate: Modified P25 nano-titanium dioxide powder is dispersed in a silane coupling agent, and then a hexafunctional polyurethane acrylate, epoxy acrylic acid, aliphatic polyurethane acrylic acid, photoinitiator b, and surfactant are added to obtain a superhydrophobic coating reagent for polyurethane acrylate. The photoinitiator b includes ethyl 2,4,6-trimethylbenzoylphenylphosphonate and diphenyl ketone, and the surfactant is perfluorodecyltriethoxysilane. A hexafunctional polyurethane acrylate superhydrophobic coating agent was screen-printed onto a two-functional polyurethane acrylate bonding layer, and then cured under a xenon lamp to obtain a double-layer polyurethane acrylate superhydrophobic coating.

2. The method for preparing the double-layer polyurethane acrylic superhydrophobic coating according to claim 1, characterized in that, The mass ratio of the acrylic resin to isobornyl acrylate is 2-4:1; the acrylic resin includes methyl acrylate, ethyl acrylate and n-butyl acrylate; the mass ratio of γ-glycidoxypropyltrimethoxysilane to cyclohexanediol is 3-4:

10.

3. The method for preparing a double-layer polyurethane acrylic superhydrophobic coating according to claim 1, characterized in that, The photoinitiator a is also added to the preparation of the bifunctional polyurethane acrylate mixed solution. The photoinitiator a includes ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-carboxy-2-methyl-1-phenyl-1-propanone, benzophenone and methyl benzoylformate.

4. The method for preparing the double-layer polyurethane acrylic superhydrophobic coating according to claim 3, characterized in that, The mass ratio of ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-carboxy-2-methyl-1-phenyl-1-propanone, benzophenone and methyl benzoate in photoinitiator a is 1:2:2:1~2. The mass ratio of ethyl 2,4,6-trimethylbenzoylphenylphosphonate to diphenyldione in photoinitiator b is 5~7:

1.

5. The method for preparing a double-layer polyurethane acrylic superhydrophobic coating according to claim 1, characterized in that, The preparation of the bifunctional polyurethane acrylate mixed solution and the preparation of the hexafunctional polyurethane acrylate superhydrophobic coating reagent were both carried out under ultrasonic vibration conditions.

6. The method for preparing a double-layer polyurethane acrylic superhydrophobic coating according to claim 1, characterized in that, During the preparation of the bifunctional polyurethane acrylate bonding layer, the screen printing mesh size is 150 mesh, the xenon lamp light source power is 280~400W, and the illumination time is 15~60s. In the preparation process of the polyurethane acrylic superhydrophobic coating, the screen printing mesh size is 100 mesh, the xenon lamp light source power is 280~400W, and the illumination time is 45~90s.

7. The method for preparing a double-layer polyurethane acrylic superhydrophobic coating according to claim 1, characterized in that, Modified P25 nano-titanium dioxide particles were obtained by modifying them, including: γ-methacryloxypropyltrimethoxysilane was dissolved in anhydrous ethanol, heated, and then P25 nano-titanium dioxide particles were added and stirred to obtain an emulsion. Modified P25 nano-titanium dioxide particles were obtained by centrifuging, washing and drying the emulsion.

8. The method for preparing a double-layer polyurethane acrylic superhydrophobic coating according to claim 7, characterized in that, The mass ratio of γ-methacryloxypropyltrimethoxysilane to anhydrous ethanol is 0.5~1.5:100; the mass ratio of P25 nano-titanium dioxide particles to γ-methacryloxypropyltrimethoxysilane is 5~8:1; the heating temperature is 65~75℃, and the heating time is 1~2h. The centrifugation speed is 5000~7000 r / min, and the centrifugation time is 4~6 min; the washing uses an ethanol solution with a water to ethanol volume ratio of 1:1~1.5, and the washing is performed 3 times; the drying temperature is 120℃, and the drying time is 1.5~2.5 h.

9. The method for preparing a double-layer polyurethane acrylic superhydrophobic coating according to claim 1, characterized in that, The silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane, and its mass ratio to the modified P25 nano-titanium dioxide particles is 1.5~2.5:1; The mass ratio of the modified P25 nano-titanium dioxide particles to the hexafunctional polyurethane acrylate, epoxy acrylic acid, and aliphatic polyurethane acrylate is 4.8~5.5:

1.

10. A double-layer polyurethane acrylic superhydrophobic coating, characterized in that, It is prepared by the method described in any one of claims 1 to 9 for preparing a double-layer polyurethane acrylic superhydrophobic coating.

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