Preparation method of super-hydrophobic composite coating with long-acting anti-corrosion and self-cleaning functions

Abstract

The application discloses a preparation method of a super-hydrophobic composite coating with long-term corrosion prevention and self-cleaning functions, which comprises the following steps: preparing Pickering emulsion by using a water phase containing nano particles and an oil phase with photo-curing characteristics, then performing photo-curing treatment under ultraviolet lamp irradiation, and then performing washing and drying to obtain Pickering micro-sphere particles; dissolving bis-aminopropyl terminated polydimethylsiloxane and isophorone diisocyanate in an organic solvent, adding a mixed chain extender, and synthesizing polyurea modified polydimethylsiloxane adhesive; preparing super-hydrophobic coating suspension by using the polyurea modified polydimethylsiloxane adhesive and the Pickering micro-sphere particles, and then performing brushing or spraying by using the super-hydrophobic coating suspension to obtain the super-hydrophobic composite coating. The polyurea modified polydimethylsiloxane adhesive and the Pickering micro-sphere particles are used to prepare the super-hydrophobic coating with micro-nano composite structure, and the super-hydrophobic coating has excellent hydrophobic performance, mechanical strength and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of superhydrophobic materials technology, specifically to a method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions. Background Technology

[0002] Superhydrophobicity is often accompanied by a very large water contact angle (>150°) and a very small roll-off angle (<10°). The wetting properties of superhydrophobic surfaces originate from the material's low surface free energy and abundant micro- and nano-level roughness. Relying on these unique properties, superhydrophobic surfaces have shown great application potential and development prospects in fields such as self-cleaning, oil-water separation, anti-fogging, anti-corrosion, and anti-icing.

[0003] However, due to the low surface energy and micro / nano roughness required to construct superhydrophobic surfaces, existing superhydrophobic surfaces often face several problems: First, the extensive use of fluorine-containing compounds to reduce the surface free energy of materials not only significantly increases usage costs but also endangers environmental safety and human health; second, the complex steps required to construct the composite roughness of the surface are cumbersome; finally, the fragile mechanical stability brought about by micro / nano roughness means that most superhydrophobic surfaces, once they lose surface roughness due to mechanical damage, often lose their superhydrophobic properties, and this ability is difficult to replenish and recover; in addition, the construction of micro / nano roughness usually relies on phase separation, resulting in poor coating density and limited physical barrier effect against corrosive media. Therefore, developing an environmentally friendly, fluorine-free superhydrophobic surface that can achieve long-term corrosion resistance is particularly important. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions. The method utilizes an adhesive and Pickering microspheres to prepare a dense and continuous superhydrophobic coating with a micro-nano composite structure.

[0005] The technical solution adopted in this invention is as follows: A method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions includes the following steps: (1) A Pickering emulsion was prepared by using an aqueous phase containing nanoparticles and an oil phase with photocuring properties, and then photocured by ultraviolet light to obtain a Pickering microsphere suspension. (2) The Pickering microsphere suspension obtained in step (1) was washed with water and centrifuged to obtain a paste, which was then freeze-dried to obtain Pickering microsphere particles. (3) Dissolve diaminopropyl-terminated polydimethylsiloxane and isophorone diisocyanate in an organic solvent and add a mixed chain extender to synthesize polyurea-modified polydimethylsiloxane adhesive. (4) Use the polyurea-modified polydimethylsiloxane adhesive obtained in step (3) and the Pickering microspheres obtained in step (2) to prepare a superhydrophobic coating suspension, and then use the superhydrophobic coating suspension to brush or spray to obtain a superhydrophobic composite coating.

[0006] Further, in step (1), the aqueous phase is a mixture of nanoparticles, water, and surfactant. The nanoparticles are at least one of silica particles, carbon nanotubes, polysaccharides, titanium dioxide, and starch, and the particle size of the nanoparticles is 10-20 nm. The surfactant is at least one of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, FS-48, FS-61, polyvinyl alcohol, and alkylphenol polyoxyethylene ether. In step (1), the concentration of nanoparticles in the aqueous phase is 0.1-5 wt%, and the concentration of surfactant is 0.01-5 wt%.

[0007] Further, in step (1), the oil phase is a mixture of a photocurable oil phase substance, a photocurable crosslinking agent, and a photoinitiator, and the photocurable crosslinking agent is at least one of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and polyvinyl cinnamate, and the photoinitiator is at least one of 2-hydroxy-2-methylphenylacetone, 1-hydroxycyclohexylphenyl ketone, and diphenyl ketone.

[0008] Furthermore, hydrophobic nanofillers are added to the oil phase in step (1). The hydrophobic nanofillers are at least one of hydrophobic silica particles, hydrophobic titanium dioxide particles, and hydrophobic iron oxide particles, and the particle size of the hydrophobic nanofillers is 15~60nm.

[0009] Furthermore, in step (1), the mass ratio of the photocurable oil phase substance, the photocurable crosslinking agent, and the photoinitiator in the oil phase is 4~6:4~6:1, and the concentration of the hydrophobic nanofiller in the oil phase is 0~10wt%.

[0010] Further, the photocurable oil phase substance in step (1) is at least one of methacryloyloxy modified silicone oil, vinyl-terminated polydimethylsiloxane, ethyl 2-dimethacrylate, octadecenoic acid, and trimethylpropane triacrylate, wherein the preparation process of methacryloyloxy modified silicone oil is as follows: Weigh out polydimethylsiloxane, 3-methylpropenylpropylmethyldimethylsiloxane, dibutyltin dilaurate, and deionized water in a mass ratio of 20~30:2~5:0.1~1:1, and stir and mix at room temperature for 10~20 hours. Then, remove the residual water in the mixture by vacuum distillation at 40~80℃ to obtain methacryloyloxy modified silicone oil, which is stored at room temperature away from light for later use.

[0011] Further, in step (3), the molar ratio of diaminopropyl-terminated polydimethylsiloxane to isophorone diisocyanate is 1:1~3; The chain extender mixed in step (3) includes isophorone diamine and polyetheramine, and the molar ratio of isophorone diamine to polyetheramine is 0.5~2:1; The total molar amount of the chain extender mixed in step (3) is 0.1 to 0.5 of the total molar amount of diaminopropyl-terminated polydimethylsiloxane and isophorone diisocyanate.

[0012] Furthermore, the polyurea-modified polydimethylsiloxane adhesive in step (3) is synthesized using a two-step method: (31) Dissolve diaminopropyl-terminated polydimethylsiloxane and isophorone diisocyanate in an organic solvent, and then react at 50~80℃ for 2~5h to generate isocyanate-terminated prepolymer; (32) Add a mixed chain extender to the prepolymer and then continue the reaction at 50~80℃ for 2~5h. After the reaction is completed, evaporate the organic solvent to obtain polyurea modified polydimethylsiloxane adhesive.

[0013] Furthermore, the preparation process of the superhydrophobic composite coating in step (4) is specifically as follows: (41) Dissolve the polyurea-modified polydimethylsiloxane adhesive in an organic solvent to form an adhesive solution, then add Pickering microspheres to the adhesive solution and stir to mix evenly to obtain a superhydrophobic coating suspension. (42) Apply or spray the superhydrophobic coating suspension onto the surface of a dry and clean substrate, and obtain a superhydrophobic composite coating after drying.

[0014] Furthermore, in step (3), the concentration of the adhesive solution is 5-15 wt%, and the mass ratio of Pickering microspheres to the adhesive solution is 1:3-6.

[0015] The beneficial effects of this invention are as follows: (1) This invention proposes a method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions. A superhydrophobic coating with micro-nano composite structure is prepared by using an adhesive and Pickering microsphere particles. Its roughness reaches 25 μm and the contact angle is above 160°. It has excellent hydrophobic properties for a variety of common liquids and good repulsion ability for common liquid pollutants, that is, it has self-cleaning function. (2) The present invention modifies the adhesive and synthesizes a polyurea-modified polydimethylsiloxane with "soft and hard segment combination" through targeted design. It not only has excellent mechanical strength and low surface energy, but also the adhesive is an organosilicon binder and the Pickering microspheres are organosilicon microspheres. The two have good interfacial compatibility and the microspheres can be uniformly dispersed in the binder, thereby forming a superhydrophobic coating with a dense, continuous morphology and a micro-nano structure on the surface. It gets rid of the dependence on phase separation structure, and the dense and continuous structure also makes the coating have excellent mechanical strength and corrosion resistance. (3) In the preparation of Pickering microspheres, the present invention also adds hydrophobic nanofillers to the oil phase. The hydrophobic nanofillers agglomerate inside the Pickering microspheres, which enhances the mechanical properties of the Pickering microspheres and provides better mechanical performance support for the application of the coating in complex stress environments. In addition, when the coating is worn, the hydrophobic nanofillers filled inside the microspheres will be gradually exposed and reconstructed to achieve automatic compensation of superhydrophobic properties. (4) The superhydrophobic coating prepared by the present invention is fluorine-free and environmentally friendly. Attached Figure Description

[0016] To clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The images show the microstructure of the PMC@U-PDMS coating prepared in Example 1 and the U-PDMS coating prepared in Comparative Example 1, where a is the SEM image of the PMC@U-PDMS coating, b is the LSM image of the PMC@U-PDMS coating, and c is the LSM image of the U-PDMS coating. Figure 2 This is a SEM image of the PMC@U-PDMS coating after wear in Embodiment 1 of the present invention; Figure 3 The mechanical durability test results of the PMC@U-PDMS coating prepared in Example 1 of the present invention are shown, where a represents water impact resistance, b represents Taber wear resistance, c represents bending resistance, d represents sand impact resistance, e represents reciprocating wear resistance, and f represents tape peeling resistance. Figure 4The Nyquist curves of the PMC@U-PDMS coating prepared in Example 1 of the present invention, i.e. the U-PDMS coating prepared in Comparative Example 1, are shown. In this figure, a is the Nyquist curve of the U-PDMS surface and the PMC@U-PDMS surface, and b is the Nyquist curve of the PMC@U-PDMS surface at different times. Figure 5 The images show the microstructure of the PMC particles prepared in Example 1 and the n-PMC particles prepared in Example 2 of this invention. In the images, a is an SEM image of the PMC particles prepared in Example 1, b is an SEM image of the cross-section of the PMC particles prepared in Example 1, and c is an SEM image of the cross-section of the n-PMC particles prepared in Example 2. Figure 6 The stress-strain curves of U-PDMS adhesives with different hard segment contents prepared in Examples 1 and 2 and Comparative Example 2 of this invention are shown. Figure 7 SEM images of pure U-PDMS coatings prepared with U-PDMS adhesives of different hard segment contents prepared in Examples 1 and 2 and Comparative Example 2 of the present invention, wherein a is H20S80, b is H40S60, c is H50S50, and d is H60S40. Figure 8 The surface energy test results are for U-PDMS adhesives with different hard segment contents prepared in Examples 1 and 2 and Comparative Example 2 of this invention. Detailed Implementation

[0018] This invention provides a method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] The present invention will now be described in detail with reference to the accompanying drawings.

[0020] Example 1 This embodiment provides a superhydrophobic composite coating with long-lasting anti-corrosion properties, and the preparation steps are as follows: (1) Preparation of Pickering microspheres Preparation of the aqueous phase: Silica with a particle size of 15 nm and deionized water were mixed at a mass ratio of 1:198. Then, hexadecyltrimethylammonium bromide was added to assist dispersion. The concentration of hexadecyltrimethylammonium bromide added to the aqueous phase was 0.1 wt%. The mixture was then ultrasonically dispersed for 10 min to ensure that the aqueous phase was uniformly mixed. Preparation of the oil phase: First, polydimethylsiloxane (PDMS), 3-methacryloylpropylmethyldimethylsiloxane (KH-571), dibutyltin dilaurate (DBTDL), and deionized water were weighed in a mass ratio of 22:3.6:0.34:1 and stirred at 800 rpm for 12 h at room temperature. Then, the mixture was subjected to vacuum distillation at 60 °C for 12 h to remove residual water from the system, finally obtaining a photocurable methacryloyloxy modified silicone oil, denoted as MA-PDMS. Then, MA-PDMS, 1,6-hexanediol diacrylate, and 2-hydroxy-2-methylphenylacetone were weighed in a mass ratio of 5:5:0.9, and KH-570 grafted silica (hydrophobic silica) with a particle size of 50 nm was added, with the amount of KH-570 grafted silica added to the oil phase being 5 wt%. The mixture was ultrasonically dispersed for 10 min until the oil phase did not separate into layers. Preparation of Pickering microsphere suspension: The oil phase and aqueous phase were mixed at a volume ratio of 1:13 and ultrasonically dispersed for 10 min until no large oil phase liquid agglomerates were present in the emulsion, thus obtaining a Pickering emulsion with oil phase droplets uniformly dispersed in water and nanoparticles encapsulating the oil phase droplets. Subsequently, the Pickering emulsion was stirred at 600 rpm and placed under a UV light source for 10 min for in-situ crosslinking and curing, resulting in a Pickering microsphere suspension, denoted as PMC suspension. Extraction of Pickering microspheres: The PMC suspension was washed with deionized water and centrifuged three times to obtain a water-containing PMC paste, which was then frozen in a refrigerator. After being completely frozen, the water was removed in a freeze dryer to finally obtain Pickering microspheres, denoted as PMC particles. (2) Preparation of polyurea-modified polydimethylsiloxane adhesive 1 mmol of diaminopropyl-terminated polydimethylsiloxane with a molecular weight of 2500 and 2 mmol of isophorone diisocyanate (IPDI) were dissolved in tetrahydrofuran and reacted at 60 °C for 3 hours to generate a prepolymer with terminal isocyanate groups (-NCO). Subsequently, a mixed chain extender with a total molar amount of 1 mmol was added to the prepolymer, wherein the isophorone diamine (IPDA) and polyetheramine with a molecular weight of 600 were in a molar ratio of 6:4 (PEA). The reaction was continued at 60 °C for 3 hours. After the reaction was completed, the solvent was evaporated to obtain the product, a polyurea-modified polydimethylsiloxane adhesive, denoted as U-PDMS adhesive. (3) Preparation of superhydrophobic composite coating Preparation of PMC@U-PDMS suspension: U-PDMS was dissolved in a mixed solvent of 30wt% butyl acetate and 70wt% tetrahydrofuran to form a 10wt% transparent and free-flowing solution, denoted as U-PDMS solution; PMC particles and U-PDMS solution were mixed at a mass ratio of 1:5 and stirred at 1500rpm for 3h to ensure uniform mixing to obtain PMC@U-PDMS suspension; Substrate pretreatment: First, the substrate is cut into appropriate sizes, then immersed in anhydrous ethanol and cleaned in a 40kHz ultrasonic bath for 30 minutes to remove organic contaminants attached to the surface; then it is transferred to n-hexane for further ultrasonic cleaning for 10 minutes to further purify the substrate surface, and finally the substrate is placed to dry at room temperature. Preparation of PMC@U-PDMS superhydrophobic composite coating: The prepared PMC@U-PDMS suspension was added to a spray gun, with the nozzle of the spray gun approximately 15 cm away from the surface of the substrate to be coated. The suspension was slowly and evenly sprayed at a rate of 15 g / m³. 2 The coating is sprayed onto the surface of the substrate, and the substrate with the coating is then placed in an oven at 80°C and dried for 1 hour to obtain the PMC@U-PDMS superhydrophobic composite coating.

[0021] A static water contact angle test was performed on the superhydrophobic coating of this embodiment, and the water contact angle was found to be 161.6°.

[0022] Example 2 This embodiment provides a superhydrophobic composite coating with long-lasting anti-corrosion properties. The difference between this embodiment and Example 1 is that in this embodiment, when preparing Pickering microspheres, the amount of KH-570 grafted silica added to the oil phase is 0wt% and 10wt%, respectively. The PMC particles prepared without the addition of KH-570 grafted silica are denoted as n-PMC particles, and the corresponding coating is denoted as n-PMC@U-PDMS coating.

[0023] Static water contact angle tests were conducted on the superhydrophobic coating of this embodiment. When the amount of KH-570 grafted silica added was 10wt%, the water contact angle was 162.5°. When the amount of KH-570 grafted silica added was 0wt%, the water contact angle was 162.1°.

[0024] Example 3 This embodiment provides a superhydrophobic composite coating with long-lasting anti-corrosion properties. The difference between this embodiment and Example 1 is that in the preparation of polyurea-modified polydimethylsiloxane adhesive, the molar ratios of isophorone diamine (IPDA) and polyetheramine (PEA) with a molecular weight of 600 in the mixed chain extender are 5:5 and 4:6, respectively.

[0025] The superhydrophobic coating of this embodiment was subjected to a static water contact angle test. When the molar ratio of IPDA to PEA was 5:5, the water contact angle was 159.3°; when the molar ratio of IPDA to PEA was 4:6, the water contact angle was 160.5°.

[0026] Example 4 This embodiment provides a superhydrophobic composite coating with long-lasting anti-corrosion properties. The difference between this embodiment and Example 1 is that the mass ratio of PMC particles to U-PDMS solution is 1:3.75 when preparing the PMC@U-PDMS superhydrophobic composite coating.

[0027] A static water contact angle test was performed on the superhydrophobic coating of this embodiment, and the water contact angle was found to be 161.8°.

[0028] Example 5 This embodiment provides a superhydrophobic composite coating with long-lasting anti-corrosion properties. The difference between this embodiment and Example 1 is that, in the preparation of Pickering microspheres, the mass ratio of silica to deionized water in the aqueous phase is 1:100, the concentration of surfactant is 1wt%, the mass ratio of MA-PDMS, 1,6-hexanediol diacrylate, and 2-hydroxy-2-methylphenylacetone in the oil phase is 4:5:1, the amount of KH-570 grafted silica added in the oil phase is 5wt%, and the volume ratio of the oil phase to the aqueous phase is 1:20.

[0029] A static water contact angle test was performed on the superhydrophobic coating of this embodiment, and the water contact angle was found to be 158.6°.

[0030] Example 6 This embodiment provides a superhydrophobic composite coating with long-lasting anti-corrosion properties. The difference between this embodiment and Example 1 is that the concentration of the U-PDMS solution is 15wt% when preparing the superhydrophobic composite coating.

[0031] A static water contact angle test was performed on the superhydrophobic coating of this embodiment, and the water contact angle was found to be 160.3°.

[0032] Comparative Example 1 This comparative example provides a method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions. The difference between this method and Example 1 is that no PMC particles were added when preparing the PMC@U-PDMS superhydrophobic composite coating in this comparative example, i.e., a pure U-PDMS coating was prepared.

[0033] A static water contact angle test was conducted on the superhydrophobic coating of this comparative example, and the water contact angle was found to be 110.5°.

[0034] Comparative Example 2 This comparative example provides a method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions. The difference between this method and Example 1 is that in the preparation of polyurea-modified polydimethylsiloxane adhesive, the molar ratios of isophorone diamine (IPDA) and polyetheramine (PEA) with a molecular weight of 600 in the mixed chain extender are 2:8 and 8:2, respectively.

[0035] Static water contact angle tests were conducted on the superhydrophobic coating of this comparative example. When the molar ratio of IPDA to PEA was 2:8, the water contact angle was 158.3°; when the molar ratio of IPDA to PEA was 8:2, the water contact angle was 160.5°.

[0036] The coatings, PMC particles, or U-PDMS adhesives prepared in the above embodiments and comparative examples were tested for microstructure, mechanical properties, and hydrophobicity to characterize the various properties of the coatings.

[0037] The superhydrophobic composite coating prepared in Example 1 above was subjected to the following tests: (1) Surface morphology and microstructure of superhydrophobic coating To observe the surface microstructure of the PMC@U-PDMS composite coating prepared in Example 1 and the distribution of PMC particles in the U-PDMS matrix, the surface morphology of the coating was characterized using scanning electron microscopy. The results are as follows: Figure 1 As shown in Figure a, the low-magnification SEM image reveals that the coating surface is uniform, dense, and defect-free. PMC particles are evenly distributed within the U-PDMS matrix, with no obvious particle agglomeration. Furthermore, upon further magnification, the coating surface exhibits a typical micro-nano composite rough structure. Micrometer-sized PMC particles are partially embedded in the U-PDMS matrix and partially exposed on the coating surface, forming uniform micrometer-sized protrusions. The spacing between these protrusions is moderate, which is beneficial for trapping air layers.

[0038] To quantitatively evaluate the surface roughness of the PMC@U-PDMS composite coating prepared in Example 1 and its difference from that of the pure U-PDMS coating, the three-dimensional morphology of the two coatings was characterized using laser confocal microscopy. The results are as follows: Figure 1As shown in figures b and c, the surface morphology of the PMC@U-PDMS coating prepared in Example 1 exhibits significant undulations. Areas with strong light and dark contrasts correspond to protrusions formed by PMC particles and depressions formed by interparticle gaps. Furthermore, densely distributed micron-sized particle protrusions are clearly visible in the three-dimensional morphology image. These protrusions have a relatively uniform height distribution, forming a micron-sized rough structure that is beneficial for trapping air layers. In contrast, the pure U-PDMS coating surface exhibits an extremely smooth morphology with minimal differences in undulation height, resulting in an overall smooth and uniform surface. Image analysis software calculations show that the arithmetic mean height Sa of the PMC@U-PDMS coating prepared in Example 1 is 25.2 μm, while the arithmetic mean height Sa of the pure U-PDMS coating is only 0.57 μm.

[0039] In addition, the PMC@U-PDMS coating prepared in Example 1 was subjected to mechanical wear treatment, and the surface morphology of the worn coating was characterized by scanning electron microscopy. The results are as follows. Figure 2 As shown in the figure, it can be clearly observed that, compared to before wear, a large number of nanospheres appeared on the coating surface after wear. These nanospheres, with a size of approximately 200-500 nm, are densely distributed in the wear area. These nanospheres originate from KH-570 grafted nano-silica filling the PMC particles. During the wear process, the PMC particles break under external pressure exceeding their mechanical limits, exposing and releasing the stored nanofillers to the wear surface, forming new nanoscale rough structures. These newly formed nanospheres themselves possess hydrophobic properties, effectively compensating for the micro-nano structure loss caused by wear, allowing the coating to maintain its superhydrophobic properties even after damage.

[0040] (2) Static and dynamic superhydrophobic properties of superhydrophobic coating To evaluate the static wetting properties of the PMC@U-PDMS composite coating prepared in Example 1 and its ability to repel common liquid contaminants, a video optical contact angle meter was used to measure the static water contact angle of the coating, and the optical phenomena when the coating was immersed in water were observed. The repulsion behavior of the coating against various complex liquids, including tea, cola, juice, milk, and mud, was also investigated. Tests showed that water droplets on the PMC@U-PDMS coating surface exhibited a near-perfect spherical shape, with a static water contact angle as high as 161.6°, demonstrating typical Cassie-Baxter superhydrophobic properties. Furthermore, when the coating sample was completely immersed in water, its surface exhibited a significant silver mirror effect, meaning the entire coating surface was enveloped by a bright silver film, reflecting light like a mirror. In addition, the coating's ability to repel complex liquids was further tested. Tea, cola, juice, milk, and mud were dropped onto the coating surface. All these test droplets maintained a complete spherical shape on the coating surface, without spreading or wetting. This indicates that the PMC@U-PDMS composite coating is superhydrophobic to a variety of common liquids and has a good ability to repel common liquid contaminants, that is, it has a self-cleaning function.

[0041] Simultaneously, the dynamic hydrophobic properties of the PMC@U-PDMS composite coating prepared in Example 1 were tested. The coating sample was placed on an inclined stage, and the tilt angle was slowly increased. The critical angle at which a 10 μL water droplet began to roll was recorded. The test showed that the sliding angle of the water droplet on the coating surface was approximately 3°. When the sample stage was tilted to this small angle, the water droplet rolled off the PMC@U-PDMS coating surface quickly, leaving no water residue. Furthermore, a syringe equipped with a flat-tipped needle was used to spray deionized water onto the coating surface at an incident angle of approximately 45°. High-speed photography revealed that the water flow did not spread or wet the coating surface upon contact, but rather bounced off at a reflection angle of approximately 15°, exhibiting a reflection behavior similar to an elastomer collision.

[0042] The above static and dynamic superhydrophobic performance test results show that the PMC@U-PDMS coating not only has an extremely high static contact angle, but also exhibits excellent dynamic water repellency, enabling the coating to resist water wetting in practical applications and possess self-cleaning, anti-icing and anti-fouling capabilities.

[0043] (3) Mechanical durability of superhydrophobic coating To comprehensively evaluate the mechanical durability of the PMC@U-PDMS coating prepared in Example 1 under practical application scenarios, the wear resistance, impact resistance, interfacial bonding strength, and flexibility of the PMC@U-PDMS superhydrophobic coating prepared in Example 1 were systematically characterized through water impact, reciprocating sandpaper abrasion, abrasive impact, tape peeling, Taber abrasion, and repeated bending tests. Figure 3As shown, the PMC@U-PDMS coating withstood a 420s water shock test (the sample was placed at a 45° angle under a faucet, the distance between the faucet and the sample was adjusted to 15cm, and deionized water was used at a flow rate of 10...). The following tests were conducted: continuous impact on the coating surface at a flow rate of m / s; 370 Taber abrasion cycles (using CS-10 grinding wheels according to ASTM-D4060, rotating abrasion under a load of 125g, with the turntable speed set at 60rpm); 300 repeated bending cycles (bending the coating sample on the thermoplastic polyurethane elastomer (TPU) film at a bending angle of 180°); 1200g abrasive impact (fixing the coating sample at a 45° angle on the sample stage, using 100-300μm abrasive grains, falling freely from 50cm above the sample surface); 68m abrasive paper reciprocating abrasion (applying a 100g weight above the sample as a load, pushing the sample in a reciprocating linear motion on the abrasive paper surface at a speed of 10cm / s, with a single stroke distance of 10cm); and 120 tape peeling cycles (ASTM-D4060). The D3359 standard (tape peel test method) proves that the PMC@U-PDMS coating has excellent mechanical stability, not only good wear resistance and impact resistance, but also good adhesion and matching flexibility between the coating and the substrate.

[0044] (4) Corrosion resistance of superhydrophobic coating The corrosion resistance of the PMC@U-PDMS composite coating prepared in Example 1 and the pure U-PDMS coating prepared in Comparative Example 1 to steel sheets was characterized by EIS testing. Figure 4 As shown. Generally speaking, the diameter of the Nyquist curve is directly proportional to the corrosion resistance; the larger the diameter of the Nyquist curve, the stronger the corrosion resistance. From... Figure 4 As shown in Figure a, the Q345 steel substrate electrode coated with PMC@U-PDMS exhibits the greatest corrosion resistance and the largest semi-circular diameter, clearly demonstrating that this surface is an effective barrier preventing direct contact between the underlying metal and the corrosive medium. Furthermore, from... Figure 4 As shown in Figure b, time-gradient EIS testing of the PMC@U-PDMS coated steel substrate revealed that although the capacitance arc diameter decreased with increasing immersion time, after immersion in a 3.5 wt.% NaCl solution for 7 days, the capacitance arc diameter of the PMC@U-PDMS coated substrate remained significantly larger than that of the pure U-PDMS surface, maintaining a high level of corrosion resistance. Furthermore, corrosion resistance can be assessed using Bode impedance. Corrosion at the metal-coating interface resonates in the low-frequency range; therefore, the low-frequency impedance modulus (|Z|=0.01Hz) can be considered a semi-quantitative indicator of corrosion resistance. Figure 4As shown in Figure c, even after one week of corrosion in a 3.5 wt.% NaCl solution, the low-frequency impedance modulus of the substrate coated with PMC@U-PDMS is still more than 6 orders of magnitude higher than that of the original Q345 substrate, indicating that the surface still has excellent corrosion resistance and can still provide long-term protection for the substrate.

[0045] Through the above tests, the PMC@U-PDMS superhydrophobic composite coating prepared in Example 1 has good superhydrophobic properties, self-cleaning properties, mechanical durability and long-term corrosion resistance.

[0046] The PMC@U-PDMS superhydrophobic composite coating prepared in Example 1 above is mainly composed of PMC particles and U-PDMS adhesive. The performance of PMC particles and U-PDMS adhesive was further tested and analyzed.

[0047] The PMC particles prepared in Examples 1 and 2 above with different amounts of hydrophobic silica were tested as follows: (1) Superhydrophobic properties of PMC particles The wettability of the PMC particles prepared in Example 1 and the n-PMC particles prepared in Example 2 was characterized by a monolayer powder method (PMC particles were fixed in a monolayer on the surface of an adhesive tape, with a dense glass slide as the substrate, so that when a droplet fell, the liquid only contacted the surface of the particles and could not penetrate inward along the gaps between the particles). Tests showed that the static water contact angle of PMC with different amounts of hydrophobic silica reached approximately 165°, all exhibiting extremely strong hydrophobic properties and demonstrating excellent superhydrophobic characteristics.

[0048] (2) Microstructure of PMC particles To observe the microstructure of the PMC particles prepared in Example 1, the surface morphology of the PMC particles was characterized using scanning electron microscopy. The results are as follows: Figure 5 As shown in Figure a, the low-magnification SEM image clearly shows that the PMC particles exhibit a regular spherical outline with a relatively concentrated particle size distribution. The main microspheres are concentrated between 3 and 5 μm in size. Further magnification reveals that the surface of these micron-sized microspheres is not smooth, but rather densely covered with a large number of nanoscale particles, forming a typical "raspberry-like" micro-nano composite structure. These nanoscale microspheres are approximately 100-300 nm in size, uniformly covering the surface of the micron-based spheres. The adjacent nanoparticles and the nanoparticles are tightly bound together, with no obvious detachment or aggregation. This structural feature results in a rich surface roughness, with the micron-sized spheres providing the basic contour undulations, while the nanoscale protrusions further increase the specific surface area and geometric complexity.

[0049] In addition, the cross-sections of the PMC particles prepared in Example 1 and the n-PMC particles prepared in Example 2 were subjected to microscopic examination, as shown below. Figure 5 As shown in b and c. From Figure 5 As clearly observed in Figure b, a large number of aggregated particles with a size of several hundred nanometers are uniformly distributed within the PMC particles. These aggregated particles are mainly concentrated between 200 and 500 nm in size, exhibiting an approximately spherical or irregular blocky morphology, tightly embedded within the polymer matrix. Figure 5 As shown in image c, the internal cross-section of the n-PMC particles without hydrophobic filler exhibits a smooth characteristic, with only a few granular protrusions or agglomerates. The smooth and flat cross-section is typical of the brittle fracture morphology of pure polymer materials. A comparison of the two SEM images confirms that hydrophobic nano-silica filler was successfully incorporated into the PMC. This filler effectively compensates for the micro / nano-structure loss caused by wear, allowing the coating to maintain its superhydrophobic properties even after damage.

[0050] To demonstrate the superhydrophobic replenishment effect of the hydrophobic nano-silica filler on the worn coating, the PMC@U-PDMS coatings prepared in Examples 1 and 2, and the n-PMC@U-PDMS coating prepared in Example 2, were subjected to the same degree of wear treatment, and the static water contact angle after wear was measured. The contact angle of the PMC@U-PDMS coating prepared in Example 1 before wear was 161.6°, and the contact angle after wear was 162.5°; the contact angle of the PMC@U-PDMS coating prepared in Example 2 before wear was 162.2°, and the contact angle after wear was 162.5°; the contact angle of the n-PMC@U-PDMS coating prepared in Example 2 before wear was 162.1°, and the contact angle after wear was 160.2°. That is, the water contact angle of the coating with hydrophobic nano-silica filler increased slightly after wear, while the water contact angle of the coating without hydrophobic nano-silica filler decreased slightly after wear. This phenomenon is attributed to the fact that the interior of n-PMC particles is a pure polymer matrix, lacking available nano-hydrophobic particles. During the wear process, after the micro-nano structure of the coating surface is destroyed, the exposed interior of the particles has a smooth polymer cross-section, which cannot provide effective nano-roughness, resulting in irreversible loss of hydrophobic properties.

[0051] (3) Mechanical properties of PMC particles To investigate the mechanical properties of PMC particles at the microscale, nanoindentation technology was used to characterize the mechanical properties of the PMC particles prepared in Example 1 and the n-PMC particles without hydrophobic nano silica prepared in Example 2. The unloading curves were analyzed by the Oliver-Pharr method, and the nanoindentation hardness and elastic modulus of the two types of particles were calculated.

[0052] The hardness test results show that the nanoindentation hardness value of PMC particles is 0.10±0.01 GPa, while that of n-PMC particles is 0.09±0.02 GPa, both values ​​being close to 0.10 GPa. The elastic modulus test results show that the elastic modulus of PMC particles is 2.28±0.15 GPa, while that of n-PMC particles is only 1.30±0.12 GPa, representing an improvement of approximately 75% for PMC compared to n-PMC. In summary, PMC particles achieve a significant improvement in elastic modulus while maintaining a hardness comparable to n-PMC. This optimization of mechanical properties—consistent hardness but enhanced rigidity—provides superior mechanical performance support for coatings containing these particles in complex stress environments.

[0053] The performance of U-PDMS adhesives with different hard segment contents prepared in Examples 1, 3, and Comparative Example 2 was tested as follows: (1) Mechanical properties of U-PDMS adhesive U-PDMS adhesives with different hard segment contents prepared in Examples 1 and 2, and Comparative Example 2 were made into dumbbell-shaped specimens for tensile testing to obtain stress-strain curves and corresponding mechanical parameters, such as... Figure 6 As shown, H20S80 corresponds to a molar ratio of isophorone diamine to polyetheramine of 2:8, H40S60 corresponds to a molar ratio of isophorone diamine to polyetheramine of 4:6, H50S50 corresponds to a molar ratio of isophorone diamine to polyetheramine of 5:5, H60S40 corresponds to a molar ratio of isophorone diamine to polyetheramine of 6:4, and H80S20 corresponds to a molar ratio of isophorone diamine to polyetheramine of 8:2. Figure 6As can be seen, the tensile strength continuously increases with the increase of the proportion of hard segments. The tensile strength of H40S60 rises to 13.1 MPa, while the elongation at break drops to 36%. The tensile strength of H50S50 reaches 16.0 MPa, and the elongation at break is 27%. At this point, the proportion of hard segments and soft segments is close to equilibrium, and the material has both high strength and moderate toughness. When the proportion of hard segments continues to increase to H60S40, the tensile strength reaches the maximum value of 17.5 MPa among the series of samples, and the elongation at break further decreases to 24%. When the proportion of hard segments is too high, such as H80S20, the tensile strength drops to 10.2 MPa, and the elongation at break is only 19%. This indicates that excessive hard segments lead to increased brittleness of the material, and excessively aggregated hard segment micro-regions may form inside, which are prone to stress concentration points under stress and cause early fracture. Furthermore, linear regression analysis was performed on the initial stage of the stress-strain curves to obtain the elastic modulus of samples with different hard-soft segment ratios. The calculated elastic modulus was: 119.7 MPa for H20S80, 163.4 MPa for H40S60, 248.1 MPa for H50S50, 269.3 MPa for H60S40, and 174.0 MPa for H80S20. It is evident that the mechanical properties of U-PDMS samples with different hard segments exhibit relatively large differences.

[0054] (2) Film-forming properties of U-PDMS adhesive To observe the surface microstructure and film quality of the U-PDMS adhesive, scanning electron microscopy was used to characterize pure U-PDMS coating samples prepared with U-PDMS adhesives of different hard segment contents prepared in Examples 1, 2, and 2, and Comparative Example 2. The results are as follows: Figure 7 As shown in the SEM images at different magnifications, all U-PDMS samples exhibited a uniform and dense surface, without any defects such as microcracks, pores, or macroscopic phase separation. Even in the H60S40 and H80S20 samples with higher hard segment content, the surface remained smooth and uniform, without micro-cracks or interfacial peeling caused by excessive hard segment aggregation. This indicates that U-PDMS possesses good leveling and structural stability during film formation, enabling the formation of continuous and complete polymer films.

[0055] (3) Surface energy of U-PDMS adhesive The surface free energy of U-PDMS was calculated using the Owens two-liquid method. The results are as follows: Figure 8 As shown. From Figure 8 It can be seen that the surface energy of U-PDMS with different hard segment contents remains between 27 and 37 mJ·m. -2 Within this range, it belongs to the typical low surface energy range. Among them, H40S60 has the lowest surface energy, at 27.05 mJ·m⁻². -2The H50S50 has the highest surface energy, at 36.31 mJ·m. -2 The surface energy of H60S40 is moderate, at 32.24 mJ·m⁻. 2 Furthermore, the static water contact angle of pure adhesive coatings prepared with U-PDMS of different hard segment contents all reached about 110~115°, which shows a certain degree of hydrophobicity.

[0056] (4) Adhesion strength of U-PDMS adhesive According to ASTM D3359 (tape peel test), cross-cut adhesion tests were conducted on U-PDMS coatings with different hard-to-soft ratios (H40S60, H50S50, H60S40). The tests showed that after tape peeling, the edges of the crossed areas were smooth and intact, with no peeling or detachment observed in any of the squares. The coating surface within the cross-cut areas was flat, without peeling, cracking, or flaking along the edges of the scratches. Based on the grading rules of ASTM D3359, the adhesion grade of the U-PDMS coating was determined to be 5B, the highest grade in the standard, indicating excellent interfacial bonding strength between the coating and the glass substrate.

[0057] Analysis of the performance of PMC particles and U-PDMS adhesive reveals that the PMC@U-PDMS superhydrophobic coating primarily relies on the micro-nano structure of PMC particles to provide surface roughness, while U-PDMS mainly provides adhesive strength and film-forming ability. Simultaneously, the rough structure of PMC particles and the low surface energy of U-PDMS synergistically endow the PMC@U-PDMS surface with extremely low liquid adhesion and the ability to trap air layers, giving the coating superhydrophobic properties. Furthermore, the synergistic effect of hard segment reinforcement and soft segment toughening of the U-PDMS adhesive results in higher mechanical strength, superior toughness, and a denser cross-linked network, thus endowing the coating with excellent mechanical properties and structural density. This enhances the coating's physical barrier effect against corrosive media, enabling it to meet the requirements for long-term corrosion protection in marine engineering, chemical corrosion prevention, and other scenarios.

[0058] It should be noted that any parts not mentioned in this invention can be achieved by using or referencing existing technologies.

[0059] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions, characterized in that, Including the following steps: (1) Pickering emulsion was prepared by using an aqueous phase containing nanoparticles and an oil phase with photocuring properties, and then photocured by irradiation with ultraviolet light. After washing and drying, Pickering microspheres were obtained. (2) Diaminopropyl-terminated polydimethylsiloxane and isophorone diisocyanate were dissolved in an organic solvent and mixed chain extender was added to synthesize polyurea-modified polydimethylsiloxane adhesive. (3) Use the polyurea-modified polydimethylsiloxane adhesive obtained in step (2) and the Pickering microspheres obtained in step (1) to prepare a superhydrophobic coating suspension, and then use the superhydrophobic coating suspension to brush or spray to obtain a superhydrophobic composite coating.

2. The method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions according to claim 1, characterized in that, In step (1), the aqueous phase is a mixture of nanoparticles, water, and surfactant. The nanoparticles are at least one of silica particles, carbon nanotubes, polysaccharides, titanium dioxide, and starch, and the particle size of the nanoparticles is 10~30nm. The surfactant is at least one of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, FS-48, FS-61, polyvinyl alcohol, and alkylphenol polyoxyethylene ether. In step (1), the oil phase is a mixture of a photocurable oil phase substance, a photocurable crosslinking agent, and a photoinitiator. The photocurable crosslinking agent is at least one of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and polyvinyl cinnamate, and the photoinitiator is at least one of 2-hydroxy-2-methylphenylacetone, 1-hydroxycyclohexylphenyl ketone, and diphenyl ketone.

3. The method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions according to claim 2, characterized in that, The volume ratio of the oil phase to the water phase in step (1) is 1:10~30; In step (1), the concentration of nanoparticles in the aqueous phase is 0.1~5wt%, and the concentration of surfactant is 0.01~5wt%. In step (1), the mass ratio of the photocurable oil phase substance, the photocurable crosslinking agent, and the photoinitiator in the oil phase is 4~6:4~6:

1.

4. The method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions according to claim 2, characterized in that, The oil phase in step (1) also contains hydrophobic nanofillers with a particle size of 15~60nm.

5. The method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions according to claim 4, characterized in that, The concentration of hydrophobic nanofiller in the oil phase of step (1) is 0~10wt%.

6. The method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions according to claim 4, characterized in that, The photocurable oil phase substance in step (1) is at least one of the following: methacryloxy-modified silicone oil, vinyl-terminated polydimethylsiloxane, ethyl 2-dimethacrylate, octadecenoic acid, and trimethylpropane triacrylate. The preparation process of the methacryloxy-modified silicone oil is as follows: Weigh out polydimethylsiloxane, 3-methylpropenylpropylmethyldimethylsiloxane, dibutyltin dilaurate, and deionized water in a mass ratio of 20~30:2~5:0.1~1:1, and stir and mix at room temperature for 10~20 hours. Then, remove the residual water in the mixture by vacuum distillation at 40~80℃ to obtain methacryloyloxy modified silicone oil, which is stored at room temperature away from light for later use.

7. The method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions according to claim 1, characterized in that, In step (2), the molar ratio of diaminopropyl-terminated polydimethylsiloxane to isophorone diisocyanate is 1:1~3. The chain extender mixed in step (2) includes isophorone diamine and polyetheramine, and the molar ratio of isophorone diamine to polyetheramine is 0.5~2:1; In step (2), the total molar amount of the mixed chain extender is 0.1 to 0.5 of the total molar amount of diaminopropyl-terminated polydimethylsiloxane and isophorone diisocyanate.

8. The method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions according to claim 1, characterized in that, The polyurea-modified polydimethylsiloxane adhesive in step (3) is synthesized using a two-step method: (31) Dissolve diaminopropyl-terminated polydimethylsiloxane and isophorone diisocyanate in an organic solvent, and then react at 50~80℃ for 2~5h to generate isocyanate-terminated prepolymer; (32) Add a mixed chain extender to the prepolymer and then continue the reaction at 50~80℃ for 2~5h. After the reaction is completed, evaporate the organic solvent to obtain polyurea modified polydimethylsiloxane adhesive.

9. The method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions according to claim 1, characterized in that, The preparation process of the superhydrophobic composite coating in step (3) is as follows: Polyurea-modified polydimethylsiloxane adhesive was dissolved in an organic solvent to form an adhesive solution. Pickering microspheres were then added to the adhesive solution and stirred until homogeneous to obtain a superhydrophobic coating suspension. A superhydrophobic coating suspension is brushed or sprayed onto a dry and clean substrate surface, and after drying, a superhydrophobic composite coating is obtained.

10. The method for preparing a superhydrophobic composite coating with long-lasting anti-corrosion and self-cleaning functions according to claim 9, characterized in that, In step (3), the concentration of the adhesive solution is 5-15 wt%, and the mass ratio of Pickering microspheres to the adhesive solution is 1:3-6.

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