An underwater coating having a bubble trapping and maintaining function and a method for preparing the same

Abstract

The present application relates to underwater drag reduction technology field, specifically, relate to a kind of underwater coating with bubble trapping and maintaining function and its preparation method.The underwater coating includes polymer adhesive layer, and composite on the adhesive layer fiber composite layer;Fiber composite layer is made of micro-nano fiber and porous material loaded thereon by interlacing, form meso-micro multi-level pore network structure.The present application prepares coating by semi-solid spraying process, so that adhesive layer and fiber composite layer form strong and tough interface of physical interpenetration and chemical bonding combination.The present application actively traps micro-bubbles by capillary effect of inter-fiber channel, uses air-liquid-solid three-phase line locking bubble in porous material inner channel, actively traps and long-acting stable maintenance to micro-bubble are realized, break through the limitation of traditional super-hydrophobic coating to rely on passive air storage, gas film has recoverability, and coating durability is strong, preparation process is simple, applicable to a variety of underwater drag reduction scene.

Description

Technical Field

[0001] This invention relates to the field of underwater drag reduction technology, and more specifically, to an underwater coating with bubble trapping and maintenance functions and its preparation method. Background Technology

[0002] During navigation, the significant frictional resistance generated between the surface of an underwater vehicle and the water restricts its speed, range, and maneuverability. Constructing and maintaining a stable bubble (air film) on the surface of the vehicle, thus converting the solid-liquid contact into an air-liquid contact, is the most promising technical approach to reduce frictional resistance.

[0003] Currently, the main methods for generating bubble layers include compressed air injection and surface water electrolysis. However, the microbubbles generated are all affected by their own buoyancy, high-speed water flow shear force, and spontaneous diffusion of gas into the water in the underwater dynamic environment, making it easy for them to escape from the surface of the vehicle and difficult to achieve long-term, stable residence.

[0004] To prolong the residence time of bubbles on a surface, existing technologies generally employ a combination of a bubble generator and a conventional or superhydrophobic coating. Existing patent CN116588239A discloses a microstructure for drag reduction on an underwater vehicle and its forming method, which prolongs the residence time of bubbles on the component surface by coating a hydrophobic layer around an electrolytic microbubble generator component. Existing patent CN118833334A discloses an underwater vehicle drag reduction system, which sprays a superhydrophobic coating onto the outer periphery of a compressed air ventilation cavity to seal a drag-reducing gas film layer underwater. Existing patent CN116516370A discloses a gas film layer drag reduction device based on porous wettable electrodes, which impregnates the outer periphery of a porous electrode array with a superhydrophobic coating to facilitate the adsorption of bubbles generated by the electrodes and the formation of a continuous gas film.

[0005] Conventional or superhydrophobic coatings, due to their micro-nano rough structures and low surface energy, can capture and trap a portion of air at the solid-liquid interface, forming a Cassie-Baxter composite interface state, thus exhibiting excellent hydrophobicity and a certain bubble retention capacity. However, their bubble retention mechanism is essentially passive, relying entirely on the air pre-trapped by the coating's micro-nano structure during preparation or initial wetting. Once this limited "initial gas stockpile" is depleted by external water flow shear, pressure fluctuations, or long-term diffusion, the liquid will completely wet the coating's microstructure, causing the interface state to irreversibly transform from the Cassie state to the Wenzel state. At this point, the coating changes from superhydrophobic to hydrophilic, losing its ability to retain subsequently generated or injected bubbles, and the drag reduction effect subsequently diminishes sharply or even fails completely.

[0006] Therefore, there is an urgent need in this field for an underwater coating preparation technology that can overcome the limitations of the Cassie-Baxter model and possess the capabilities for active microbubble capture and long-term stable residence. This has significant engineering value and practical implications for improving the speed and range of underwater vehicles, reducing navigation energy consumption, and promoting the upgrading and development of marine engineering equipment technology. Summary of the Invention

[0007] In view of this, the present invention aims to propose an underwater coating with bubble trapping and maintenance functions and its preparation method, so as to solve the problems of existing superhydrophobic coatings relying on Cassie structures to passively trap air, the easy loss of the gas film and its irreversible transformation into a hydrophilic state, and existing active air supply technologies relying on complex hardware systems and the coating itself not having bubble management capabilities.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0009] This invention discloses an underwater coating with bubble trapping and maintenance functions, the underwater coating comprising:

[0010] A polymer adhesive layer and a fiber composite layer, wherein the fiber composite layer is laminated on the polymer adhesive layer;

[0011] The fiber composite layer consists of a three-dimensional porous framework composed of interwoven micro and nanofibers. The porous material is loaded and fixed on the surface of the micro and nanofibers and / or in the pores of the three-dimensional porous framework, so that the fiber channels formed by the interwoven micro and nanofibers are interconnected with the internal channels of the porous material itself, forming a multi-level pore network.

[0012] The underwater coating is configured to actively capture microbubbles through fiber channels and lock the captured microbubbles through the internal channels and fiber channels of the porous material, thereby achieving active capture and long-term stable maintenance of microbubbles.

[0013] This invention integrates and spreads dispersed microbubbles into a continuous and stable gas film by constructing a special multi-level porous network structure of fiber composite layer, which significantly improves the residence stability of gas film in underwater dynamic environment and realizes the dual function of underwater coating for active capture and stable locking of microbubbles.

[0014] The present invention also discloses a preparation method for preparing the above-mentioned underwater coating, comprising the following steps:

[0015] S1: Form a polymer adhesive layer on the surface of the substrate and allow the polymer adhesive layer to reach a semi-cured state;

[0016] S2: A mixture containing micro / nanofibers and porous materials is applied to a polymer adhesive layer in a semi-cured state to form a fiber composite layer;

[0017] S3: After the polymer adhesive layer and the fiber composite layer are fully cured, an underwater coating is formed. During the full curing process, the polymer adhesive layer and the fiber composite layer are bonded together through physical interpenetration and interfacial chemical bonding. The thickness of the polymer adhesive layer is 50~500μm, and the thickness of the fiber composite layer is 20~200μm.

[0018] The preparation method of this invention, through a process design of "semi-curing + secondary application," achieves a strong and tough bond between the polymer adhesive layer and the fiber composite layer, significantly improving the coating's resistance to water erosion and its long-term durability. Specifically, the semi-curing process design achieves a dual bonding mechanism between the polymer adhesive layer and the fiber composite layer, enabling the underwater coating of this invention to maintain structural integrity over a long period in high-speed underwater water flow environments, ensuring the sustained stability of its drag-reduction function.

[0019] Optionally, the size of the pores in the porous material is 0.1~100μm; the size of the pores is 1~2000μm; and the porous material is in the shape of spheres, rods, or crystalline particles.

[0020] Particulate porous materials can be loaded in a highly dispersed manner within a network framework composed of micro- and nanofibers, maximizing the exposure of their internal pore structures and thus providing more gas-liquid-solid three-phase locking sites. Simultaneously, this loading method ensures close contact between the porous material and the fiber channels, allowing bubbles trapped by the fiber channels to be quickly locked by neighboring porous materials, forming an efficient "capture-lock" synergistic mechanism.

[0021] Optionally, the micro / nanofiber is at least one of polyurethane, polyvinylidene fluoride and polyvinyl alcohol, and the fiber diameter is 0.05~1000μm.

[0022] The aforementioned micro and nanofibers can form a continuous and stable three-dimensional porous framework on the substrate surface through interweaving, providing ample loading sites for porous materials. Simultaneously, these fiber materials contain active functional groups on their surface, enabling them to undergo interfacial chemical bonding with the polymer adhesive layer during curing, forming a strong and tough interface combining physical interpenetration and chemical bonding, significantly improving the overall structural strength of the coating.

[0023] Optionally, the porous material is at least one of metal-organic framework materials, molecular sieves, and porous silica.

[0024] The aforementioned porous materials all possess a regular and interconnected internal pore structure, providing a high-density gas-liquid-solid three-phase curve and exhibiting excellent microbubble trapping ability. Simultaneously, these materials possess good chemical stability and mechanical strength, enabling them to maintain structural integrity in underwater environments for extended periods without failing due to water erosion or flow, thus ensuring the durability of the coating's bubble-holding function.

[0025] Optionally, in step S2, the mixture is a suspension applied by a spraying process; and the mass ratio of micro / nanofibers to porous materials in the suspension is 1:(5~10).

[0026] By pre-dispersing micro / nanofibers and porous materials in a solvent to form a uniform suspension, and then applying it through a spraying process, it is possible to ensure the uniform distribution of porous materials in the fiber network and avoid uneven functional layer structure caused by agglomeration.

[0027] Optionally, the polymer adhesive layer is prepared from at least one of polyurethane, epoxy resin, silicone resin, polytetrafluoroethylene, polyvinylidene fluoride, and polyimide.

[0028] The materials used in the polymer adhesive layer all have excellent water resistance and good adhesion to the substrate. They can maintain structural stability in long-term underwater immersion environments and will not hydrolyze, swell, or peel off from the substrate, providing a reliable anchoring foundation for the coating.

[0029] The present invention also discloses an underwater drag reduction device, which includes the above-mentioned underwater coating, and the underwater coating can be prepared by the above-mentioned preparation method.

[0030] The underwater drag reduction device of the present invention includes underwater vehicles, ships, torpedoes, underwater robots, etc. The underwater coating can be applied to the surface of the middle section of the underwater drag reduction device, the outer peripheral surface of the compressed air ventilation cavity, or the inner and outer sides of the groove structure where the electrolytic gas generation electrode array is located, thereby achieving efficient collection and maintenance of microbubbles from different sources.

[0031] Compared with existing technologies, the underwater coating with bubble trapping and maintenance functions and its preparation method described in this invention have the following advantages:

[0032] (1) The underwater coating disclosed in this invention can play the role of actively capturing and maintaining the spread of bubbles. Through fiber interpenetration and multi-scale channels of porous materials, based on capillary effect and gas-liquid-solid interface separation principle, it continuously captures newly generated microbubbles and integrates them into the surface bubble film in an orderly manner, ensuring the stability and recoverability of drag-reducing gas film layer, breaking through the dependence of existing superhydrophobic coating Cassie structure on the initial amount of trapped gas and the irreversibility of underwater hydrophilic / hydrophobic transformation.

[0033] (2) The underwater coating disclosed in this invention is prepared by a semi-curing spraying process. The fiber composite layer is partially embedded in the polymer bonding layer, forming a strong and tough interface that combines physical interpenetration and chemical bonding. It can effectively resist water flow shearing and scouring, and ensure the durability of the coating in navigation.

[0034] (3) The underwater coating preparation method disclosed in this invention is simple in process, easy to apply, and suitable for coating large areas and complex curved surfaces. Moreover, the underwater coating of this invention itself is an independent functional surface and can be integrated with various drag reduction devices such as electrolytic microbubble generators or compressed air injection systems. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0036] Figure 1 This is a scanning electron microscope image of the superhydrophobic coating described in Comparative Example 1 of the present invention;

[0037] Figure 2 This is a test diagram of the drag reduction performance of the superhydrophobic coating described in Comparative Example 1 of the present invention;

[0038] Figure 3 This is a scanning electron microscope image of the fiber composite layer described in Embodiment 1 of the present invention;

[0039] Figure 4 For the present invention Figure 3 Enlarged view of section A;

[0040] Figure 5 This is a test diagram of the drag reduction performance of the fiber composite layer described in Embodiment 1 of the present invention;

[0041] Figure 6 This is a test diagram of the drag reduction performance of the fiber composite layer described in Embodiment 2 of the present invention.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1. Fiber composite layer; 2. Micro / nanofiber; 3. Porous material; 4. Fiber channels. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0045] Example 1

[0046] This embodiment is a preferred implementation of the underwater coating with bubble trapping and maintenance functions described in this invention. The specific preparation and performance testing process is as follows:

[0047] 1 Sample Preparation

[0048] A polycarbonate cylinder with a diameter of 200mm and a height of 300mm was selected as the substrate and then sanded and cleaned with solvent before use.

[0049] S1: Preparation of the polymer adhesive layer and fiber composite layer 1. Fluorine-modified silicone resin was used as the matrix resin for the polymer adhesive layer to prepare an adhesive layer spraying liquid. An air spraying process was used to uniformly coat the adhesive layer spraying liquid onto the pretreated substrate surface, ultimately forming a continuous wet adhesive layer film with a thickness of approximately 50 μm on the substrate surface. The wet adhesive layer film was then allowed to reach a semi-cured state. Micro / nanofibers 2 were prepared using polyvinylidene fluoride fiber as the main raw material via electrospinning; porous molecular sieves 3 were selected as the porous material, possessing continuous interconnected internal channels.

[0050] S2: Molecular sieves and polyvinylidene fluoride fibers are dispersed in acetone solvent at a mass ratio of 5:1 to prepare a uniform and stable suspension. The suspension is then uniformly sprayed onto the surface of the semi-cured adhesive layer obtained in step S1 using an air spraying process to form fiber composite layer 1 with a thickness of 40 μm.

[0051] S3: Coating curing and molding. During the curing process, the semi-cured polymer adhesive layer and the bottom of the fiber composite layer 1 undergo deep physical interpenetration. At the same time, the active isocyanate groups in the resin undergo interfacial chemical bonding with the functional groups on the surface of the polyvinylidene fluoride fiber, making the polymer adhesive layer and the fiber composite layer 1 tightly bonded together.

[0052] Specifically, in step S1, the polymer adhesive layer material exhibits suitable viscosity and reactivity on its surface in the incompletely cured state. Polyurethane contains active isocyanate groups, epoxy resin contains epoxy groups, and silicone resin contains silanol groups. These functional groups can chemically react with the hydroxyl and carboxyl groups on the surface of the micro / nanofiber 2 to form covalent bonds, significantly improving the interlayer bonding strength. The semi-cured state in step S1 refers to the state where the surface of the polymer adhesive layer loses its fluidity but retains internal viscosity, and the active functional groups in its material retain their reactivity. This semi-cured state can be controlled by adjusting the curing temperature, curing time, or the amount of curing agent. In the suspension preparation process of step S2, the solvent is selected from acetone, xylene, ethanol, water, or mixtures thereof. The specific selection needs to consider the solubility of the micro / nanofiber 2 and the dispersion stability of the porous material 3. The parameters of the spraying process can be adaptively adjusted according to the underwater coating thickness and structural density. During the coating curing process in step S3, the application of the fiber composite layer 1 in the semi-cured state allows the micro- and nanofibers 2 to be partially embedded in the polymer adhesive layer, forming a physically interpenetrating structure. At the same time, the active functional groups in the polymer adhesive layer can undergo interfacial chemical bonding with the functional groups on the fiber surface, ultimately resulting in a sample with an underwater coating that has bubble trapping and maintenance functions.

[0053] More specifically, the micro / nanofiber 2 can be prepared using techniques known in the field, such as electrospinning, meltblown spinning, and template method.

[0054] It should be noted that the mass ratio of micro / nanofiber 2 to porous material 3 is controlled at 1:(5~10). This ensures that, while the micro / nanofiber 2 forms a continuous and stable multi-level pore network, a sufficient amount of porous material 3 is provided to load on the fiber surface and in the gaps. If the proportion of porous material 3 is too low, the density of the gas-liquid-solid three-phase lines will be insufficient, reducing the ability to trap bubbles, and the bubbles will easily escape under the action of buoyancy or shear force. If the proportion of porous material 3 is too high, it may overfill the fiber pores 4, resulting in a decrease in the effective porosity of the multi-level pore network, a weakening of the capillary effect, and impaired bubble trapping efficiency.

[0055] 2. Structural characterization and performance testing

[0056] like Figure 3 , Figure 4 As shown, the coating prepared in this embodiment was characterized by scanning electron microscopy. The image clearly shows that the fiber composite layer 1 is composed of interwoven polyvinylidene fluoride fibers forming a continuous three-dimensional porous framework. In this embodiment, the interwoven fibers form fiber channels 4 with a diameter of 1-10 μm. Porous material 3 (molecular sieve) particles are uniformly loaded on the surface and in the gaps between the micro / nano fibers 2, and their own internal channels (0.5-1 μm) together with the fiber channels 4 form a mesoscopic-microscopic hierarchical pore network structure.

[0057] It should be noted that the size of the fiber channels 4 directly affects the strength of the capillary effect and the efficiency of bubble trapping, while the size of the internal channels of the porous material 3 also has a significant impact on the bubble locking capability. Therefore, the dimensions of the fiber channels 4 and the internal channels need to be optimized according to the actual application scenario, but the size range of the fiber channels 4 is usually 1~2000μm, and the size range of the internal channels is usually 0.1~100μm. Moreover, the size matching relationship between the fiber channels 4 and the internal channels is equally important. Only when they are in a similar order of magnitude can the trapped bubbles be smoothly transferred from the fiber channels 4 to the internal channels, forming an efficient "trapping-locking" synergistic mechanism. In addition, the loading and distribution uniformity of the porous material 3 in the multi-level channel network also affect the overall efficiency of bubble locking. Too low a loading or uneven distribution may lead to insufficient locking capability in some areas.

[0058] The drag reduction performance of the samples in this embodiment was tested according to GB / T7791-2014 "Test Method for Drag Reduction Performance of Antifouling Coatings". An electrolytic seawater electrode was installed at the bottom of the cylindrical sample, and a 3.5wt% sodium chloride aqueous solution was used to simulate a real seawater environment. The electrolytic current was kept constant during the test. Rotational speed gradients of 300, 400, 500, 900, 1000, and 1200 rpm were set, and drag data at each speed was recorded. Simultaneously, drag data of an uncoated blank polycarbonate cylindrical sample of the same specification was tested. The drag reduction rate of the superhydrophobic coating at different speeds was calculated based on the difference between the two values, and the final result is as follows: Figure 5 The curve showing the change in drag reduction performance is shown.

[0059] 3. Test Results and Analysis

[0060] Test results show that the coating prepared in this embodiment achieves a drag reduction rate of 11% at a low rotation speed of 300 rpm, significantly better than the conventional superhydrophobic coating in Comparative Example 1. As the rotation speed increases, the drag reduction rate only shows a slow decreasing trend, maintaining a stable drag reduction rate of approximately 9% at 900 rpm, without the sharp decline observed in Comparative Example 1. This indicates that the coating prepared in this embodiment can effectively capture and seal the bubble layer, thereby maintaining the drag reduction effect of electrolytic bubbles.

[0061] Example 2

[0062] This embodiment is another preferred implementation of the underwater coating with bubble trapping and maintenance functions described in this invention. The specific preparation and performance testing process is as follows:

[0063] 1 Sample Preparation

[0064] In this embodiment, polycarbonate cylinders of the same specifications and batch as in Example 1 are used as the substrate, and the same surface pretreatment process as in Example 1 is adopted to ensure that the surface condition of the substrate is consistent with that of Example 1.

[0065] S1: Preparation of the polymer adhesive layer and fiber composite layer 1. Polyurethane resin was selected as the base resin for the adhesive layer, and an adhesive layer spraying liquid was prepared. An air spraying process was used to uniformly coat the adhesive layer spraying liquid onto the pretreated substrate surface, ultimately forming a continuous wet adhesive layer film with a thickness of approximately 60 μm on the substrate surface. The wet adhesive layer film was then allowed to reach a semi-cured state. Micro / nano fibers 2 were prepared using a template method with polyvinyl alcohol as the main raw material; porous silica prepared by the template method was selected as the porous material 3.

[0066] S2: Molecular sieves and polyvinylidene fluoride fibers are dispersed in xylene solvent at a mass ratio of 10:1 to prepare a uniform and stable suspension. The suspension is then uniformly sprayed onto the surface of the semi-cured adhesive layer obtained in step S1 using an air spraying process to form fiber composite layer 1 with a thickness of 50 μm.

[0067] S3: The coating is cured and formed, and the steps are the same as in Example 1.

[0068] 2. Structural characterization and performance testing

[0069] like Figure 3 , Figure 4 As shown, the coating prepared in this embodiment was characterized by scanning electron microscopy. The image clearly shows that the fiber composite layer 1 is composed of interwoven polyvinyl alcohol fibers forming a continuous three-dimensional porous framework. In this embodiment, the interwoven fibers form fiber channels 4 of 1-5 μm. Porous material 3 (porous silica) particles are uniformly loaded on the surface and in the gaps between the micro / nano fibers 2, and their own internal channels (5 μm) together with the fiber channels 4 form a mesoscopic-microscopic hierarchical pore network structure.

[0070] The drag reduction performance of the sample in this embodiment was tested. The test method, test equipment and test conditions were the same as in Example 1. The final drag reduction performance change curve is shown below. Figure 6 As shown.

[0071] 3. Test Results and Analysis

[0072] Test results show that the coating prepared in this embodiment also exhibits excellent drag reduction effect and working condition stability. At a low rotational speed of 300 rpm, the drag reduction rate of the coating can reach more than 12%; as the rotational speed increases, the drag reduction rate only shows a slow decreasing trend, and at a rotational speed of 900 rpm, it can still maintain a stable drag reduction rate of about 7%, which is far better than the conventional superhydrophobic coating of Comparative Example 1. This indicates that the coating prepared in this embodiment can effectively capture and seal the bubble layer, thereby maintaining the drag reduction effect of electrolytic bubbles.

[0073] Comparative Example 1

[0074] This comparative example provides a superhydrophobic coating prepared using a conventional spraying process, and the performance of the prepared coating is tested.

[0075] 1 Sample Preparation

[0076] This comparative example uses polycarbonate cylinders of the same specifications and batch as in Example 1 as the substrate, and adopts the same surface pretreatment process as in Example 1 to ensure that the surface condition of the substrate is consistent with that of Example 1.

[0077] A commercially available silicone-fluorine superhydrophobic coating system was selected, and a uniform superhydrophobic coating spray solution was prepared according to the coating instructions. The spray solution was uniformly sprayed onto the pretreated substrate surface using an air spraying process. After spraying, the sample was placed in a dust-free environment at room temperature and 50% relative humidity to allow the surface coating to cure, resulting in a control sample with a conventional superhydrophobic coating. The total dry film thickness was approximately 100 μm, and its microstructure was as follows. Figure 1 As shown.

[0078] 2 Performance Testing

[0079] The drag reduction performance of the control sample prepared in this comparative example was tested. The test methods, equipment, and conditions were the same as in Example 1. The final drag reduction performance change curve is shown below. Figure 2 As shown.

[0080] 3. Test Results and Analysis

[0081] Test results show that the conventional superhydrophobic coating in this comparative example only has a certain drag reduction effect under low speed conditions. At the initial speed of 300 rpm, the drag reduction rate of the coating can reach up to about 8%. However, as the speed continues to increase, the drag reduction rate of the coating shows a sharp downward trend. When the speed exceeds 900 rpm, the drag reduction rate drops sharply to below 2%. This indicates that the conventional superhydrophobic coating in this comparative example has difficulty maintaining bubble retention on the coating surface under high shear rotation conditions, resulting in a rapid decay of the drag reduction effect.

[0082] The underwater coating prepared by this invention can actively capture and maintain bubbles. This is because when the fiber channels 4 of the three-dimensional porous network formed by the interlacing of micro and nanofibers 2 in the fiber composite layer 1 are immersed in water, they form a meniscus and generate capillary negative pressure. Without relying on the air pre-sealed in the coating, it can actively draw in and capture the diffused microbubbles in the water, thus achieving active bubble management. At the same time, the channels of the porous material 3 loaded on the fibers can form a high-density gas-liquid-solid three-phase line with the captured bubbles. The low-energy state at the three-phase line firmly locks the bubbles, preventing them from escaping due to buoyancy and water flow shear. Finally, under the synergistic effect of the two types of channels, the bubbles gather, merge, and spread along the fiber network to form a continuous and stable gas film covering the coating surface.

[0083] In summary, the underwater coating provided by this invention, through the capillary "air-absorbing" effect of the multi-scale pores of the fiber composite layer 1 and the "air-locking" effect of the high-density gas-liquid-solid three-phase lines in the porous material 3, endows the coating with autonomous bubble management capabilities. This enables dynamic replenishment and autonomous recovery of the underwater drag-reducing gas film layer, maintaining a stable drag-reduction effect even under complex conditions of high flow rate and high shear. Furthermore, the semi-curing spraying process achieves a strong bond between the coating and the substrate, combining excellent durability with adaptability for large-area engineering coating.

[0084] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An underwater coating with bubble trapping and maintenance functions, characterized in that, The underwater coating includes: A polymer adhesive layer and a fiber composite layer (1), wherein the fiber composite layer (1) is laminated onto the polymer adhesive layer; The fiber composite layer (1) is composed of interwoven micro-nano fibers (2) forming a three-dimensional porous framework. The porous material (3) is loaded and fixed on the surface of the micro-nano fibers (2) and / or in the pores of the three-dimensional porous framework, so that the fiber channels (4) formed by the interwoven micro-nano fibers (2) are interconnected with the internal channels of the porous material (3) to form a multi-level pore network. The underwater coating is configured to actively capture microbubbles through the fiber channels (4) and lock the captured microbubbles through the inner channels of the porous material (3) and the fiber channels (4), thereby achieving active capture and long-term stable maintenance of microbubbles.

2. A preparation method for preparing the underwater coating as described in claim 1, characterized in that, Includes the following steps: S1: A polymer adhesive layer is formed on the surface of the substrate, and the polymer adhesive layer is brought to a semi-cured state; S2: Apply the mixture containing the micro / nanofibers (2) and the porous material (3) to the polymer adhesive layer in a semi-cured state to form the fiber composite layer (1). S3: The underwater coating is formed after the polymer adhesive layer and the fiber composite layer (1) are completely cured. During the complete curing process, the polymer adhesive layer and the fiber composite layer (1) are physically interpenetrated and chemically bonded together. The thickness of the polymer adhesive layer is 50~500μm and the thickness of the fiber composite layer is 20~200μm.

3. The preparation method according to claim 2, characterized in that, The size of the pores in the porous material (3) is 0.1~100μm; the size of the fiber pores (4) is 1~2000μm; and the porous material (3) is spherical, rod-shaped or crystalline granular, etc.

4. The preparation method according to claim 3, characterized in that, The micro / nanofiber (2) is at least one of polyurethane, polyvinylidene fluoride and polyvinyl alcohol, and has a diameter of 0.05~1000μm.

5. The preparation method according to claim 2, characterized in that, The porous material (3) is at least one of metal-organic framework materials, molecular sieves and porous silica.

6. The preparation method according to claim 2, characterized in that, In step S2, the mixture is a suspension, which is applied by a spraying process; and in the suspension, the mass ratio of the micro-nano fibers (2) to the porous material (3) is 1:(5~10).

7. The preparation method according to claim 2, characterized in that, The polymer adhesive layer is made of at least one of polyurethane, epoxy resin, silicone resin, polytetrafluoroethylene, polyvinylidene fluoride, and polyimide.

8. An underwater drag reduction device, characterized in that, The underwater drag reduction device includes the underwater coating as described in claim 1, wherein the underwater coating can be prepared by the preparation method described in any one of claims 2 to 7.

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