Preparation method of'microstructure-liquid-like surface 'underwater drag-reduction, noise-reduction and antifouling multifunctional composite coating

Abstract

The invention relates to a preparation method of a'microstructure-liquid-like surface 'underwater drag-reduction, noise-reduction and antifouling multifunctional composite coating, and belongs to the field of underwater equipment. The multifunctional composite coating provided by the invention comprises an anti-drag microstructure arranged on the surface of a substrate and a liquid-like surface arranged on the surface of the anti-drag microstructure, and the liquid-like surface retains the original morphology of the anti-drag microstructure. According to the micro-structure, the distance between the wall face and a turbulent vortex can be increased, the frequency and strength of a flow vortex pair can be restrained, and resistance reduction is achieved; and on the liquid-like surface, resistance reduction can be achieved by enabling fluid to generate wall face slippage and reducing the speed gradient of the fluid on the boundary. The two mechanisms of action are different but do not interfere with each other, and a better drag reduction effect can be achieved through the synergistic effect. Meanwhile, the composite coating can achieve the noise reduction effect by reducing the turbulence intensity of the wall face. In addition, the liquid-like surface can resist adhesion of marine organisms, the integrity of the microstructure is guaranteed, and therefore the long-term drag reduction effect is achieved.

Description

Technical Field

[0001] The invention belongs to the field of underwater equipment, and in particular relates to a method for preparing a "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and anti-fouling multifunctional composite coating. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Long range, high speed and strong stealth are important technical indicators of modern naval equipment such as submarines and ships. The seawater resistance encountered by naval equipment during navigation mainly includes friction resistance, viscous resistance and wave-making resistance, among which friction resistance has the most significant impact on naval equipment. When naval equipment is traveling at medium and low speeds, the friction resistance it encounters accounts for 70-80% of the total resistance; when traveling at high speeds, the friction resistance it encounters accounts for 40% of the total resistance. At the same time, the increase in friction will directly increase the hydrodynamic noise, seriously reducing the stealth and self-detection capabilities of naval equipment. Therefore, reducing friction resistance to improve the navigation speed, endurance and stealth of naval equipment is an effective method.

[0004] During the voyage, non-biological substances such as proteins and polysaccharides and various marine organisms such as bacteria, algae, mussels, and barnacles will attach to the surface of naval equipment, resulting in marine biofouling. Marine biofouling attached to naval equipment will significantly increase its navigation resistance, reduce its navigation speed and stealth. In addition, marine organisms will produce acidic metabolites such as sulfides and sulfates, which will accelerate the corrosion of the hull, thereby shortening the service life of naval equipment and reducing its comprehensive combat capability.

[0005] Currently, constructing microstructured surfaces is the most commonly used drag reduction strategy. However, microstructures are easily damaged by biofouling, thus losing their drag reduction effect. In addition, the action mechanism of microstructures is single, so the drag reduction effect is limited.

[0006] Patent 202310784088.X discloses a microstructure of a drag-reducing functional surface, which combines a micro-nano structure with a hydrophobic coating into a super-hydrophobic coating, and achieves drag reduction by reducing the contact between the fluid and the substrate surface, but its anti-fouling and drag-reducing effect still needs to be improved. At the same time, the stability of the super-hydrophobic surface is very poor, especially in an underwater environment where bubbles cannot exist stably, and it is necessary to continuously electrolyze seawater to generate new bubbles, which consumes a lot of extra energy. In addition, the use of chlorine generated in the process of electrolyzing seawater for anti-fouling is a method of biological extermination, which will cause marine pollution.

[0007] Patent 202311341481.8 discloses a bionic drag reduction method using microgrooves and viscoelastic fluid coatings, in which the viscoelastic fluid reduces drag by reducing the wall turbulence intensity by absorbing flow field energy through polymer chains. However, the viscoelastic fluid coating contains water-soluble polymer molecules, which will slowly dissolve in water. Therefore, when the polymer molecules dissolve, many pores will appear in the viscoelastic fluid coating, and the morphology of the microstructure will also be destroyed, which will not only lose the original drag reduction effect, but also increase the resistance.

[0008] Liquid-like surface is a new type of polymer brush coating material with dynamic interface properties. It is prepared by covalently grafting highly flexible polymer molecules with extremely low glass transition temperature on the solid surface. The glass transition temperature of these polymer molecules is usually below -100°C, which makes the grafted molecular chains have highly dynamic characteristics of fluids and can rotate and move freely. Therefore, they are often used in the field of anti-fouling. However, there are basically no reports on the application of liquid-like surfaces in the field of fluid drag reduction. Summary of the invention

[0009] In order to solve the above problems, the present invention provides a "microstructure-liquid-like surface" underwater drag reduction and antifouling composite coating preparation strategy. The present invention innovatively applies the liquid-like surface to the field of fluid drag reduction, and the proposed composite coating can achieve better drag reduction effect through the synergistic effect of the microstructure and the liquid-like surface. In addition, the composite coating has a good antifouling effect, can effectively resist the adhesion of marine organisms, maintain the integrity of the microstructure, and achieve a long-term drag reduction effect.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] The first aspect of the present invention provides a "microstructure-liquid-like surface" underwater drag reduction, noise reduction, anti-fouling multifunctional composite coating, comprising:

[0012] A microstructure disposed on the surface of a substrate;

[0013] a liquid-like surface disposed on the surface of the microstructure;

[0014] The liquid-like surface retains the original morphology of the microstructure, and the material of the liquid-like surface is a high molecular polymer with a main chain of CO bonds and Si-O bonds.

[0015] Liquid-like surfaces can make various polar and non-polar liquids exhibit low adhesion and easy sliding properties, and therefore also have good drag reduction effects. The present invention grafts a high molecular polymer with highly dynamic fluid properties onto the substrate surface to form a liquid-like surface, and innovatively uses the liquid-like surface in the field of fluid drag reduction.

[0016] In some embodiments, the height of the microstructure is 50 to 1000 μm;

[0017] In some embodiments, the thickness of the liquid-like surface is 10-200 nm. The liquid-like surface can achieve drag reduction by causing the fluid to generate wall slip and reducing the velocity gradient of the fluid on the boundary.

[0018] In some embodiments, the drag reduction microstructure includes but is not limited to common microstructures such as protrusions, pits, grooves, rectangular or triangular ribs, etc. The microstructure can achieve drag reduction by increasing the distance between the wall and the turbulent vortex and suppressing the frequency and intensity of the streamwise vortex pairs.

[0019] In some embodiments, the liquid-like surface is made of polydimethylsiloxane or perfluoropolyether.

[0020] The second aspect of the present invention provides a method for preparing a "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and anti-fouling multifunctional composite coating, comprising:

[0021] A microstructured surface is prepared on a substrate;

[0022] A liquid-like surface is prepared on the surface of the microstructure, that is,

[0023] Wherein, the material of the liquid-like surface is a high molecular polymer of CO bonds and Si-O bonds.

[0024] In some embodiments, the preparation method of the microstructure includes 3D printing, laser processing, mechanical processing or photo-stereolithography and corresponding template processing methods.

[0025] In some embodiments, the method for preparing the liquid-like surface comprises polycondensation of siloxane monomers and direct grafting of long-chain polymers.

[0026] In some embodiments, the method for preparing a liquid-like surface by polycondensation of siloxane monomers comprises:

[0027] Introducing active hydroxyl groups on the substrate surface by plasma treatment or piranha solution treatment;

[0028] For siloxanes without halogenated (mainly chlorine and bromine) groups, condensation polymerization is carried out in solution under acid and base catalysis to form a liquid-like surface;

[0029] For siloxanes containing halogenated groups, liquid-like surfaces are constructed by solution polymerization under acid or base catalysis, or by chemical vapor deposition.

[0030] In some embodiments, the polymerization temperature is 10-100°C.

[0031] In some embodiments, the method for preparing a liquid-like surface by direct grafting of a long-chain polymer comprises the following steps:

[0032] Functional groups capable of being used for long-chain polymer grafting are introduced on the substrate surface, including at least one of carboxyl, epoxy, and carbon-carbon double bonds; then, under ultraviolet light or heating conditions, the long-chain polymer is grafted onto the substrate surface to form a liquid-like surface.

[0033] The third aspect of the present invention provides the application of the above-mentioned "microstructure-liquid-like surface" underwater drag reduction, noise reduction and anti-fouling multifunctional composite coating in the field of underwater drag reduction and anti-fouling.

[0034] The microstructure in the present invention can achieve drag reduction by increasing the distance between the wall and the turbulent vortex and suppressing the frequency and intensity of the streamwise vortex pairs. The liquid-like surface can achieve drag reduction by causing the fluid to slip on the wall and reducing the velocity gradient of the fluid on the boundary. The two have different action mechanisms but do not interfere with each other. Therefore, the present invention couples the microstructure with the liquid-like surface to form a "microstructure-liquid-like surface composite coating". The two drag-reducing coatings work synergistically to achieve better drag reduction effects. At the same time, the composite coating can reduce the hydrodynamic noise of the fluid by reducing the turbulence intensity near the wall, thereby achieving a noise reduction effect. In addition, the liquid-like surface has a good anti-fouling effect and can resist the adhesion of marine organic matter and microorganisms, thereby ensuring the integrity of the microstructure and achieving a long-term drag reduction effect.

[0035] Beneficial effects of the present invention

[0036] (1) The present invention innovatively applies liquid-like surfaces to the field of fluid drag reduction. The microstructure and liquid-like surface in the proposed composite coating have different action mechanisms but do not interfere with each other. Therefore, the formed "microstructure-liquid-like surface" composite coating can achieve better drag reduction effect through multiple action mechanisms. In addition, the composite coating provided by the present invention has a good anti-fouling effect, so it can resist the adhesion of marine organisms, maintain the integrity of the microstructure, and achieve a long-term drag reduction effect.

[0037] (2) The "microstructure-liquid-like surface" synergistic drag reduction strategy of the present invention includes increasing the distance between the wall and the turbulent vortex through the microstructure, suppressing the frequency and intensity of the streamwise vortex pairs and the liquid-like surface to cause the fluid to slip on the wall, and reducing the velocity gradient of the fluid on the boundary. Multiple drag reduction mechanisms work together to achieve better drag reduction effects.

[0038] (3) Different from the existing drag reduction strategies, the microstructure surface in the present invention achieves drag reduction by changing the state and distribution of the flow field; the liquid-like surface reduces drag by causing the fluid to slip on the surface and reducing the velocity gradient of the fluid near the wall. The two drag reduction strategies combined in the present invention have different mechanisms of action and can work synergistically to achieve better drag reduction effects, so the drag reduction effect is better. At the same time, the composite coating of the present invention has an anti-fouling effect, which can ensure that the microstructure is not fouled, thereby achieving a long-term drag reduction effect.

[0039] (4) The preparation method of the present invention is simple, practical and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0041] Figure 1 Schematic diagram of the synergistic drag reduction mechanism of the "microstructure-liquid-like surface" composite coating;

[0042] Figure 2 Schematic diagram of processing raised microtexture by laser processing template method in Example 1;

[0043] Figure 3 This is a comparison chart of the drag reduction effects of the substrate, microstructure surface, liquid-like surface and the "microstructure-liquid-like surface" composite coating in Experimental Example 1.

[0044] Figure 4 This is a comparison chart of the anti-fouling effects of the substrate, microstructure surface, liquid-like surface and the "microstructure-liquid-like surface" composite coating in Experimental Example 2. DETAILED DESCRIPTION

[0045] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0046] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0047] Example 1

[0048] like Figure 2 As shown, the raised microstructure surface is processed by laser processing template method: In this embodiment, the microstructure template is processed by laser processing technology, and then the microstructure surface is processed by polydimethylsiloxane (PDMS). Specifically:

[0049] Using nano-laser processing equipment, a micro-textured array is processed on an opaque metal (such as aluminum alloy, stainless steel, titanium alloy, etc.) or plastic (acrylic, Teflon, etc.), and the height of the microstructure is changed by changing the number of processing times and the pulse width, thereby completing the processing of the microstructure template. The laser processing substrate used in this embodiment is a black acrylic sheet. The micro-textured template is immersed in octadecyltriethoxysilane for hydrophobic treatment to facilitate the subsequent demolding of PDMS. Then, the A and B components of PDMS are mixed in a ratio of 10:1, poured into the micro-structured template, and then evacuated with a vacuum pump to remove bubbles in the PDMS. Afterwards, the micro-structured template with PDMS is heated at a temperature of 80°C for 1 hour, and the PDMS micro-structured surface is obtained after demolding, and a sample with micro-texture is obtained.

[0050] Example 2

[0051] Preparation of liquid-like surface on the microstructure surface prepared in Example 1 by polycondensation: In this example, a "grafting-from" method is used, dimethyl dimethoxysiloxane is used as a monomer, and polycondensation is carried out under acid catalysis to form a liquid-like surface. Specifically:

[0052] First, the PDMS is treated with plasma treatment technology, and the effect of plasma treatment is controlled by changing process parameters such as power, gas composition, and treatment time. The power used in this embodiment is 70W, the gas composition is air atmosphere, and the treatment time is 5 minutes. Then, a reaction solution is prepared, and isopropanol, dimethyldimethoxysilane and sulfuric acid (mass concentration is 96% to 98%) are mixed and stirred evenly in a volume ratio of 100:10:1, and placed at room temperature for 30 minutes. After that, the above reaction solution is dripped onto the surface of the plasma-treated PDMS microstructure, so that the reaction solution is evenly spread on the PDMS surface, and hydrolyzed and condensed at room temperature for 30 minutes, thereby forming a liquid-like surface on the PDMS surface. Finally, it is washed with isopropanol, anhydrous ethanol and deionized water in turn to remove the loosely adsorbed polymer to obtain a "microstructure-liquid-like surface" composite coating.

[0053] Example 3

[0054] The method of Example 2 was used to prepare a liquid-like surface on a smooth sample to obtain a smooth sample with a liquid-like surface.

[0055] Experimental Example 1

[0056] The smooth sample, the sample with microtexture, the smooth sample with liquid-like surface, and the sample with "microtexture-liquid-like surface" composite coating were named PDMS, Peak, Liquid, and Peak-Liquid, respectively.

[0057] A high-precision rheometer is used to test the drag reduction effect of different surfaces to verify the improvement effect of the drag reduction performance of the composite coating. The substrate materials used in this comparative example are all PDMS. The specific method is: respectively stick a smooth sample, a sample with a micro-texture, a smooth sample with a liquid-like surface, and a sample with a "micro-texture-liquid-like surface" composite coating to the bottom of the container facing the rheometer turntable, and the distance between the sample and the rheometer turntable is 2mm. Then, increase the speed of the turntable from 0 to 1500 rpm, and maintain the speed of 1500 rpm for a period of time, and test the torque applied to the turntable during this process. The drag reduction rate is obtained by comparing samples with different surfaces with smooth samples.

[0058] Experimental Example 2

[0059] The antibacterial effect of different surfaces was tested by antibacterial adhesion experiment to verify the antifouling effect of the composite coating. The specific method was as follows: smooth samples, samples with micro-textures, smooth samples with liquid-like surfaces, and samples with "micro-texture-liquid-like surface" composite coatings were immersed in bacterial culture solution (colony forming units were 1×10 8 ), after incubation for a period of time, the sample surface was rinsed with deionized water to remove loosely adsorbed bacteria. The sample was then ultrasonically rinsed with deionized water to obtain the bacteria adsorbed on the sample, and the bacterial desorption solution was applied to the agar plate and cultured for 12 hours. Finally, the antifouling performance of different samples was evaluated by the number of colonies on the corresponding agar plate.

[0060] Depend on Figure 3 It can be seen that the "microstructure-liquid-like surface" composite coating has a better drag reduction effect than the single microstructure surface and liquid-like surface;

[0061] Depend on Figure 4 It can be seen that the "microstructure-liquid-like surface" composite coating has a better anti-fouling effect than a single microstructure surface. Therefore, it can effectively prevent marine fouling, maintain the integrity of the microstructure, and achieve a long-term drag reduction effect.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and anti-fouling multifunctional composite coating, characterized in that: include: A drag reducing microstructure disposed on the surface of the substrate; a liquid-like surface disposed on the surface of the drag-reducing microstructure; The liquid-like surface retains the original morphology of the drag-reducing microstructure, and the material of the liquid-like surface is a high molecular polymer with a main chain of CO bonds and Si-O bonds.

2. The "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and anti-fouling multifunctional composite coating as claimed in claim 1, characterized in that: The height of the drag reduction microstructure is 50 to 1000 μm; Alternatively, the liquid-like surface has a thickness of 10 to 200 nm.

3. The "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and anti-fouling multifunctional composite coating as claimed in claim 1, characterized in that: The drag reduction microstructure is a protrusion, a pit, a groove, or a rectangular or triangular rib.

4. The "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and anti-fouling multifunctional composite coating as claimed in claim 1, characterized in that: The material of the liquid-like surface is polydimethylsiloxane or perfluoropolyether.

5. A method for preparing a "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and anti-fouling multifunctional composite coating, characterized in that: include: A microstructured surface is prepared on a substrate; A liquid-like surface is prepared on the surface of the microstructure, that is, Wherein, the material of the liquid-like surface is a high molecular polymer of CO bonds and Si-O bonds.

6. The method for preparing the "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and antifouling multifunctional composite coating according to claim 5, characterized in that: The preparation method of the microstructure includes 3D printing, laser processing, mechanical processing or photocuring molding and corresponding template processing methods.

7. The method for preparing the "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and antifouling multifunctional composite coating according to claim 5, characterized in that: The preparation method of the liquid-like surface includes polycondensation of siloxane monomers and direct grafting of long-chain polymers.

8. The method for preparing the "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and antifouling multifunctional composite coating as claimed in claim 5, characterized in that: The method for preparing a liquid-like surface by polycondensation of siloxane monomers comprises: Introducing active hydroxyl groups on the substrate surface by plasma treatment or piranha solution treatment; For siloxanes without halogenated groups, condensation polymerization is carried out in solution under acid or base catalysis to form a liquid-like surface; For siloxanes containing halogenated groups, liquid-like surfaces are constructed by solution polymerization under acid or base catalysis, or by chemical vapor deposition. Alternatively, the polymerization temperature is 10-100°C.

9. The method for preparing the "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and antifouling multifunctional composite coating as claimed in claim 5, characterized in that: The method for preparing a liquid-like surface by direct grafting of a long-chain polymer comprises the following steps: Functional groups capable of being used for long-chain polymer grafting are introduced on the substrate surface, including at least one of carboxyl, epoxy, and carbon-carbon double bonds; then, under ultraviolet light or heating conditions, the long-chain polymer is grafted onto the substrate surface to form a liquid-like surface.

10. Application of the "microstructure-liquid-like surface" underwater drag reduction, noise reduction, and anti-fouling multifunctional composite coating described in claims 1-4 in the field of underwater drag reduction and anti-fouling.

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