A biomimetic fish scale composite coating with lubrication and drag reduction properties and its preparation method

Abstract

This invention discloses a biomimetic fish scale composite coating with lubrication and drag reduction properties and its preparation method. The method includes the following steps: (1) mixing deionized water, Tween 80, dimethyl silicone oil, and isophorone diisocyanate, emulsifying them in an ice-water bath to form an emulsion; heating, adding ethylenediamine to the emulsion under nitrogen atmosphere, and obtaining polyurea microcapsules through a polyurea synthesis reaction; (2) mixing hydroxyl-terminated trifluoropropylmethyl polysiloxane, isophorone diisocyanate, dibutyltin dilaurate, and polyurea microcapsules evenly, coating them onto a substrate, vacuuming to semi-solidification at room temperature, then spraying a silica acetone solution, continuing to cure, and immersing in dimethyl silicone oil after complete curing to obtain the biomimetic fish scale composite coating with lubrication and drag reduction properties. The composite coating obtained by this invention has excellent anti-corrosion and color-changing properties. At the same time, the composite coating also has good lubrication and drag reduction properties and can be used as a drag reduction material for ships.

Description

Technical Field

[0001] This invention belongs to the field of biomimetic lubrication and drag reduction, and relates to a biomimetic fish scale composite coating with lubrication and drag reduction properties and its preparation method. Background Technology

[0002] During ship navigation, energy loss due to fluid resistance accounts for approximately 60%-70% of total energy consumption. Developing efficient drag reduction technologies is crucial for lowering transportation costs and reducing carbon emissions. Traditional drag reduction methods (such as air drag reduction and polymer additives) are limited by high energy consumption and poor environmental compatibility. Bio-inspired surface engineering technologies, however, have become a research hotspot due to their sustainability and adaptability. Among these, the microgroove structure of shark skin has been widely imitated, achieving drag reduction by suppressing turbulence. However, under complex flow conditions, rigid microstructures are prone to performance degradation due to boundary layer instability. In recent years, biological surfaces with multi-scale dynamic regulation mechanisms (such as fish scale-mucus synergistic systems) have shown more universal drag reduction potential.

[0003] The scales of crucian carp achieve efficient dissipation of water flow shear force through the synergistic effect of a specially arranged elastic matrix and surface mucus secretion. This multi-scale dynamic adjustment mechanism provides a unique perspective for the design of novel drag-reducing coatings. Existing biomimetic drag-reducing coatings mostly focus on a single physical structure or chemical lubrication strategy, making it difficult to achieve both simultaneously. For example, superhydrophobic coatings rely on an air film to maintain low drag, but are prone to failure due to air film rupture at high flow rates; while lubricant injection into the surface can reduce friction, it faces the bottleneck of rapid lubricant loss. To address these challenges, this invention, based on the biomimetic crucian carp scales, proposes a design concept of a multi-level synergistic mechanism of "elastic matrix-surface microstructure-mucus lubrication," and prepares a biomimetic fish scale composite coating system. The design and preparation of a novel drag-reducing composite coating with multi-scale dynamic adjustment is of great significance for ship navigation. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a biomimetic fish scale composite coating with lubrication and drag reduction properties, and its preparation method.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for preparing a biomimetic fish scale composite coating with lubrication and drag reduction properties includes the following steps:

[0007] (1) Deionized water, Tween 80, dimethyl silicone oil (DMPS) and isophorone diisocyanate (IPDI) are mixed and emulsified in an ice-water bath to form an emulsion; heated and ethylenediamine (EDA) is added to the emulsion under nitrogen atmosphere to obtain polyurea microcapsules (PUOMC) through polyurea synthesis reaction.

[0008] (2) After the hydroxyl-terminated trifluoropropylmethyl polysiloxane (HFPMOS), isophorone diisocyanate, dibutyltin dilaurate (DBTL) and polyurea microcapsules are mixed evenly, they are coated on the substrate and vacuumed at room temperature until semi-solidified. Then, a silica acetone solution is sprayed on and cured. After complete curing, the coating is immersed in dimethyl silicone oil to obtain the biomimetic fish scale composite coating (MCPU) with lubrication and drag reduction properties.

[0009] Furthermore, in step (1), the emulsification time is 10~30 min, preferably 15 min; and the heating temperature is 50℃.

[0010] Furthermore, in step (1), the molar ratio of isophorone diisocyanate to ethylenediamine is 1:1. The isocyanate groups of isophorone diisocyanate react with the amino groups of ethylenediamine in a 1:1 ratio to form urea bonds, thereby forming polyurea microcapsules. Dimethyl silicone oil is added to allow for better encapsulation.

[0011] Furthermore, in step (1), the polyurea synthesis reaction time is 1 to 7 hours. The polyurea microcapsules formed at different polymerization times are in different states. At 7 hours, the polyurea microcapsules are fully formed.

[0012] Furthermore, in step (2), the molar ratio of the hydroxyl-terminated trifluoropropylmethyl polysiloxane and isophorone diisocyanate is approximately 1:1, allowing the isocyanate groups and hydroxyl groups to react in a 1:1 ratio, thereby forming a polyurethane substrate.

[0013] Furthermore, in step (2), the mass ratio of the hydroxyl-terminated trifluoropropylmethyl polysiloxane to the polyurea microcapsules is 200:1.

[0014] Furthermore, in step (2), the substrate is an aluminum plate that has been treated with a sandblasting process.

[0015] Furthermore, in step (2), the semi-solidification time is 7 h. At this time, the substrate is not completely solidified, and the sprayed silica nanoparticles can form a special coffee ring structure.

[0016] Furthermore, in step (2), the concentration of the silica acetone solution is 3 wt%; the spraying pressure is 35~45 kg, preferably 40 kg / cm. 2 The time is 3 seconds. Using this pressure for spraying can form a coffee ring structure similar to the surface structure of fish scales.

[0017] Furthermore, by mixing evenly in step (2), adding a trace amount of dye can change the color of the composite coating to suit the application scenarios in the marine environment.

[0018] A biomimetic fish scale composite coating with lubrication and drag reduction properties was prepared using the method described above.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The present invention relates to a biomimetic fish scale composite coating with lubrication and drag reduction properties. This coating utilizes the reaction between the isocyanate groups of isophorone diisocyanate and the amino groups of ethylenediamine to encapsulate dimethyl silicone oil, forming polyurea microcapsules. The isocyanate groups of isophorone diisocyanate react with the hydroxyl groups of hydroxyl-terminated trifluoropropylmethyl polysiloxane to form a polyurethane substrate. This polyurethane substrate possesses a better elastic modulus than the fish scale surface. During semi-curing, silica nanoparticles are sprayed to form a coffee ring structure, mimicking the special structure of the fish scale surface. After curing, the coating is impregnated with silicone oil, mimicking the mucus on the fish scale surface. The fluorinated hydroxyl-terminated trifluoropropylmethyl polysiloxane reduces surface energy. The prepared composite coating biomimeticly mimics the special structure and mucus of the fish scale surface, achieving multi-level synergistic drag reduction through "elastic matrix - surface microstructure - mucus lubrication".

[0021] The biomimetic fish scale composite coating with lubrication and drag reduction properties prepared by this invention achieves multi-level synergistic biomimicry through the "elastic matrix-surface microstructure-viscous lubrication" strategy. It exhibits excellent drag reduction effect in small boat experiments. At the same time, the coating has good anti-corrosion properties and color-changing properties. Attached Figure Description

[0022] Figure 1 The following are schematic diagrams of the preparation process of (a) polyurea microcapsules, (b) biomimetic fish scale composite coating, (c) polyurea microcapsule formation mechanism, and (d) biomimetic fish scale composite coating formation mechanism in the embodiments of the present invention.

[0023] Figure 2 The images shown in the figures are (a) optical images of the emulsion during the preparation of polyurea microcapsules at 100x magnification in the embodiments of the present invention (i) emulsion reaction 0 h, ii) reaction 1 h, iii) reaction 4 h, iv) reaction 7 h, v) reaction 10 h); and (b) emulsion images at 250x magnification (i) emulsion reaction 0 h, ii) reaction 1 h, iii) reaction 4 h, iv) reaction 7 h, v) reaction 10 h).

[0024] Figure 3 The images shown are scanning electron microscope images of dried fish scales (a) ×35, (b) ×200, (c) ×8000 in the embodiments of the present invention; and scanning electron microscope images of biomimetic fish scale composite coatings without silicone oil impregnation (d) ×35, (e) ×350, (f) ×8000.

[0025] Figure 4The following figures illustrate the variation of nano-indentation modulus with indentation depth in embodiments of the present invention: (a) the surface of dried and cleaned fish scales, and (b) the biomimetic fish scale composite coating.

[0026] Figure 5 This is a comparison chart of the drag reduction rates of crucian carp mucus and dimethyl silicone oil in an embodiment of the present invention.

[0027] Figure 6 The images show the polarization curves of the aluminum plate after sandblasting and the biomimetic fish scale composite coating, as well as the intersection point diagram obtained by extrapolation in this embodiment of the invention.

[0028] Figure 7 This is a color change diagram of the biomimetic fish scale composite coating after adding a trace amount of ink in an embodiment of the present invention.

[0029] Figure 8 The images shown are: (a) a schematic diagram of the drag reduction device for a small boat in the embodiments of the present invention; (b) an image of a small boat with a biomimetic fish scale composite coating reaching the destination; (c) an image of a small boat without a coating reaching the destination; and (d) bottom images of the small boats with and without a biomimetic fish scale composite coating. Detailed Implementation

[0030] The technical solution of the present invention will be further described clearly and in detail below with reference to the accompanying drawings and specific examples. Example 1

[0031] 1) Mix 135 ml of deionized water and 0.675 g of Tween 80 thoroughly and add them to a 250 ml three-necked flask. Mix 3.32 g of dimethyl silicone oil and 9.98 g of isophorone diisocyanate thoroughly and add them dropwise to the three-necked flask. Emulsify the mixture in an ice-water bath at 700 rpm for 15 min to form an emulsion. Heat the emulsion to 50°C in an oil bath, turn on nitrogen gas, and add 2.7 g of ethylenediamine solution dropwise. Polymerize for 1 h to obtain polyurea microcapsules.

[0032] 2) Mix 3 g of hydroxyl-terminated trifluoropropylmethyl polysiloxane, 1 g of isophorone diisocyanate, 0.015 g of dibutyltin dilaurate, and 0.015 g of polyurea microcapsules evenly. Apply the evenly mixed solution to the surface of an aluminum plate treated with sandblasting. Vacuum the plate at room temperature for 7 h until it is semi-solidified. Spray a 3wt% silica acetone solution with a spray gun for 3 s and continue curing for 17 h. After complete curing, immerse the plate in dimethyl silicone oil to obtain a biomimetic fish scale composite coating.

[0033] The polyurea microcapsules prepared in this embodiment have a weak outer shell that is prone to collapse. This is because isophorone diisocyanate and ethylenediamine begin to form a polymer shell with a low degree of cross-linking. Example 2

[0034] 1) Mix 135 ml of deionized water and 0.675 g of Tween 80 thoroughly and add them to a 250 ml three-necked flask. Mix 3.32 g of dimethyl silicone oil and 9.98 g of isophorone diisocyanate thoroughly and add them dropwise to the three-necked flask. Emulsify the mixture in an ice-water bath at 700 rpm for 15 min to form an emulsion. Heat the emulsion to 50°C in an oil bath, turn on nitrogen gas, and add 2.7 g of ethylenediamine solution dropwise. The polymerization reaction is carried out for 4 h to obtain polyurea microcapsules.

[0035] 2) Mix 3 g of hydroxyl-terminated trifluoropropylmethyl polysiloxane, 1 g of isophorone diisocyanate, 0.015 g of dibutyltin dilaurate, and 0.015 g of polyurea microcapsules evenly. Apply the evenly mixed solution to the surface of an aluminum plate treated with sandblasting. Vacuum the plate at room temperature for 7 h until it is semi-solidified. Spray a 3wt% silica acetone solution with a spray gun for 3 s and continue curing for 17 h. After complete curing, immerse the plate in dimethyl silicone oil to obtain a biomimetic fish scale composite coating.

[0036] The polyurea microcapsules prepared in this embodiment have a higher degree of cross-linking of the polymer shell and a more stable shell layer. Example 3

[0037] 1) Mix 135 ml of deionized water and 0.675 g of Tween 80 thoroughly and add the mixture to a 250 ml three-necked flask. Mix 3.32 g of dimethyl silicone oil and 9.98 g of isophorone diisocyanate thoroughly and add the mixture dropwise to the three-necked flask. Emulsify the mixture at 700 rpm for 15 min in an ice-water bath to form an emulsion. Heat the emulsion to 50°C in an oil bath, turn on nitrogen gas, and add 2.7 g of ethylenediamine solution dropwise. The polymerization reaction is carried out for 7 h to obtain polyurea microcapsules.

[0038] 2) Mix 3 g of hydroxyl-terminated trifluoropropylmethyl polysiloxane, 1 g of isophorone diisocyanate, 0.015 g of dibutyltin dilaurate, and 0.015 g of polyurea microcapsules evenly. Apply the evenly mixed solution to the surface of an aluminum plate treated with sandblasting. Vacuum the plate at room temperature for 7 h until it is semi-solidified. Spray a 3wt% silica acetone solution with a spray gun for 3 s and continue curing for 17 h. After complete curing, immerse the plate in dimethyl silicone oil to obtain a biomimetic fish scale composite coating.

[0039] The polyurea microcapsules prepared in this example have stable shells and increased quantity.

[0040] The preparation process and mechanism of the biomimetic fish scale composite coating with lubrication and drag reduction properties in this invention are as follows: Figure 1 As shown, the preparation process of polyurea microcapsules is as follows: Figure 1 As shown in (a), the chemical reactions involved are as follows: Figure 1 As shown in (c), the isocyanate groups of isophorone diisocyanate react with the amino groups of ethylenediamine to form polyurea, thereby encapsulating dimethyl silicone oil to form polyurea microcapsules. The preparation process of the biomimetic fish scale composite coating is as follows: Figure 1 As shown in (b), the chemical reactions involved are as follows: Figure 1 As shown in (d), the isocyanate group of isophorone diisocyanate reacts with the hydroxyl group of hydroxyl-terminated trifluoropropylmethyl polysiloxane to form a polyurethane substrate, which is then sprayed with silica nanoparticles and impregnated with dimethyl silicone oil to form a biomimetic fish scale composite coating.

[0041] Polyurea microcapsules consist of dimethyl silicone oil as the core material, a polyurea network formed by isophorone diisocyanate and ethylenediamine as the wall material, dimethyl silicone oil as the oil phase, and Tween 80 as a nonionic surfactant to reduce the interfacial tension between oil and water. Figure 2 As shown in (a) i and (b) i, a large number of stable spherical emulsion droplets are formed, such as Figure 2 As shown in Tables (a) and (b) (ii), after 1 h of polymerization at 50°C, the spherical emulsion collapsed. This is because isophorone diisocyanate and ethylenediamine began to form a polymer shell, but due to the low degree of crosslinking of the polymer shell, the shell layer was weak, leading to collapse. As the polymerization time increased to 4 h, the degree of crosslinking of the polymer shell increased, and the shell layer became stable. Figure 2 In (a) and (b) of the reaction, a large number of stable spherical microcapsules are formed after 7 hours of reaction. Figure 2 (a) iv, Figure 2 In (b) and (iv), the number of spherical microcapsules increases after 10 h of reaction, at which point the microcapsules are fully formed. Figure 2 (a) v, Figure 2 (b) (v)

[0042] like Figure 3 As shown in Figure a, the scales of a dried crucian carp have a micro-protrusion structure of 100-200 μm on their surface, as... Figure 3 As shown in (b), the magnified view reveals that the micro-protrusions are arc-shaped, as... Figure 3 As shown in (c), further magnification reveals even smaller micro- and nano-structures on the micro-protrusion structure. These unique micro- and nano-structures on the fish scale surface guide water flow in a specific direction, maintaining laminar flow and slowing the transition from laminar to turbulent flow. When water flows over these micro- and nano-structures on the fish scale surface, it enhances water adhesion, preventing premature separation from the fish's surface, delaying boundary layer separation, and reducing drag. Figure 3As shown in (d), a coffee ring structure resembling micro-protrusions similar to fish scales is distributed on the surface of the biomimetic fish scale composite coating that has not been impregnated with dimethyl silicone oil. The coffee rings have a diameter of 100-200 μm, similar in size to the micro-protrusions on the fish scale surface. The coffee rings are formed because the polyurethane substrate is not fully cured after 7 hours of curing. At this time, silica nanoparticles are sprayed using a spray gun, and the high pressure impacts the polyurethane substrate to form the coffee ring structure. Since the polyurethane substrate has already cured to a certain extent, its fluidity is insufficient for leveling, ultimately forming the coffee ring structure. Further magnification of the coffee ring structure reveals that the outer side of the coffee rings also has an arc-shaped structure. Figure 3 In the middle (e), the internal structure of the coffee ring is further magnified, revealing micro-nano structures similar to those on the micro-protrusions of fish scales. Figure 3 (f)). The prepared biomimetic fish scale polymer coating exhibits a microstructure similar to that of dried and cleaned fish scales, with a distribution of micro-protrusions and a micro / nano structure. Figure 4 As shown in (a), the average modulus of fish scales in the depth range of 800-900 nm is 2.7803 GPa, as... Figure 4 As shown in (b), the average elastic modulus of the biomimetic fish scale composite coating is 0.2401 GPa in the depth range of 800-900 nm, indicating that the biomimetic fish scale composite coating has excellent elastomer properties. It can dissipate energy by undergoing small deformations with water flow pressure, thereby reducing drag. Figure 5 The figure shows the friction coefficients of crucian carp mucus and dimethyl silicone oil on aluminum alloy, stainless steel, and epoxy resin surfaces. The drag reduction rates of crucian carp mucus and dimethyl silicone oil on aluminum alloy are 63.0% and 70.2%, respectively; on stainless steel, they are 65.9% and 62.0%, respectively; and on epoxy resin, they are 70.6% and 67.8%, respectively. Dimethyl silicone oil has a similar drag reduction effect to crucian carp mucus, and the use of dimethyl silicone oil mimics the mucus on the surface of crucian carp. The Tafel polarization curves of the biomimetic fish scale composite coating and the aluminum plate after sandblasting are shown in the figure. Figure 6 As shown, the self-corrosion current density (Icorr), corrosion potential (Ecorr), and protection efficiency (Icorr) obtained by polarization curve extrapolation are... The biomimetic fish scale composite coating provides 99.9987% protection for aluminum plates treated with sandblasting, demonstrating excellent protective capabilities. corr The rate of reactive corrosion, I corr A larger value indicates a faster corrosion rate; the biomimetic fish scale composite coating has a higher I value. corr 10 -9.9212 The aluminum plate after sandblasting process corr 10 -5.0371 I of biomimetic fish scale composite coating corr Less than 4 orders of magnitude smaller than BSAL, E corrE reflects the thermodynamic stability and corrosion tendency of a material in a specific environment. corr A larger value indicates that the material is more likely to be in a stable state in the environment; the biomimetic fish scale composite coating has an E value of [missing information]. corr Larger than aluminum plates treated with sandblasting. This demonstrates the excellent corrosion resistance of the biomimetic fish scale composite coating. The color of the biomimetic fish scale composite coating can be changed with a small amount of ink. Figure 7 The coating is made in a highly visible color to facilitate ship identification and rescue, and in a color similar to the marine environment to reduce the probability of submarines and other vessels being detected by the naked eye or optical equipment, thus increasing the practical value of the coating. Figure 8 (a) shows a schematic diagram of the drag reduction test. The speeds of ship models coated with a biomimetic fish-scale composite coating and those without the coating were measured to investigate the drag reduction rate of the biomimetic fish-scale composite coating. To ensure the models travel in a straight line, the boats were connected to a steel wire guide rail by ropes. The deeper the draft, the larger the surface area of ​​the hull submerged in water (wet surface area), increasing the frictional resistance (viscous resistance) with the water, which leads to a decrease in speed. Before the test, the weights of the ship models with and without the biomimetic fish-scale composite coating were kept consistent. The bottom surfaces of the ship models with and without the biomimetic fish-scale composite coating are shown in the diagram. Figure 8 As shown in (d), since the power of the ship models with and without the biomimetic fish scale composite coating is the same, the difference in sailing speed is due to the drag reduction effect of the biomimetic fish scale composite coating. Figure 8 Image (b) shows the biomimetic fish-scale composite coated ship model reaching its destination after 11.57 seconds of sailing. At this point, the uncoated ship model is still sailing. Figure 8 Image (c) shows the uncoated ship model reaching its destination at 14.01 s. The ship model with the biomimetic fish scale composite coating traveled at a speed of 0.432 m / s, while the uncoated model traveled at 0.357 m / s, resulting in a drag reduction rate of 17.4%.

[0043] The above description is merely a preferred embodiment of the present invention. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for preparing a bionic fish scale composite coating with lubrication drag reduction performance, characterized in that, The method comprises the following steps: (1) mixing deionized water, Tween 80, dimethyl silicone oil and isophorone diisocyanate, and emulsifying to form an emulsion in an ice water bath; heating, and adding ethylenediamine into the emulsion under a nitrogen environment to prepare polyurea microcapsules through a polyurea synthesis reaction, wherein the polyurea microcapsule synthesis reaction time is 7-10 hours; (2) uniformly mixing hydroxyl-terminated trifluoropropylmethyl polysiloxane, isophorone diisocyanate, dibutyltin dilaurate and the polyurea microcapsules, coating on a substrate, vacuumizing at room temperature until semi-solidification, then spraying a silicon dioxide acetone solution, continuing to solidify, and then immersing in dimethyl silicone oil to obtain the bionic fish scale composite coating with lubricating and drag-reducing properties.

2. A method for preparing a bionic fish scale composite coating with lubrication drag reduction performance according to claim 1, characterized in that, In step (1), the emulsification time is 10-30 min; and the heating temperature is 45-55℃.

3. The method of claim 1, wherein the method is characterized by: In step (1), the molar ratio of isophorone diisocyanate to ethylenediamine is 1:

1.

4. The method of claim 1, wherein the method is characterized by: In step (2), the molar ratio of hydroxyl-terminated trifluoropropylmethyl polysiloxane to isophorone diisocyanate is 1:

1.

5. The method of preparing bionic fish scale composite coating with lubrication drag reduction performance according to claim 1, characterized in that, In step (2), the mass ratio of hydroxyl-terminated trifluoropropylmethyl polysiloxane to polyurea microcapsules is 200:

1.

6. The method of preparing bionic fish-scale composite coating with lubrication drag reduction performance according to claim 1, characterized in that, In step (2), the substrate is an aluminum plate treated by a sand blasting process; and the semi-solidification time is 6.5-7.5 h.

7. The method of claim 1, wherein the method further comprises the step of: 5 applying a lubricant to the surface of the fish scale-like structure. In the uniform mixing process in step (2), a trace amount of a dyeing agent is added to change the color of the composite coating.

8. The method of claim 1, wherein the method further comprises the step of: 8-1) applying a lubricant to the surface of the substrate. In step (2), the concentration of the silica acetone solution is 3 wt%; the spraying pressure is 35-45 kg / cm 2 , and the time is 3 s.

9. A biomimetic fish scale composite coating having lubrication drag reducing properties, characterized in that, The bionic fish scale composite coating with lubricating and drag-reducing properties is prepared by the method of any one of claims 1-8.

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