A method of making a durable superhydrophobic microstructure coating

Abstract

The application belongs to the technical field of functional material microstructure regulation, and relates to a method for preparing durable super-hydrophobic microstructure coating, the model construction method comprising the following steps: using phase change of hydrophobic micro-wax powder, coating silanized hydrophobic nanoparticles by combining melting and annealing processes, and then adding high-strength film-forming materials to obtain durable super-hydrophobic coating. A new type of super-hydrophobic structure is obtained by applying a hierarchical curing process to realize the transformation of surface morphology. The application designs a 'lotus-honeycomb' transformation model, and adopts a super-hydrophobic material scheme prepared by adopting a strategy of protecting first and releasing later to the nanoparticles, so that the new type of microstructure is further improved in durability while retaining high hydrophobicity. A plurality of combined materials with similar properties can be selected to prepare coating, and the coating is suitable for curing and forming on surfaces of various substrates. Meanwhile, the coating has advantages of high barrier property and high mechanical strength. The model can widen the design and preparation ideas of the durable super-hydrophobic structure, and provide new inspiration for the design and preparation of new type of high-performance durable super-hydrophobic materials.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, specifically relating to a method for preparing a durable superhydrophobic microstructure coating. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Currently, the fabrication of superhydrophobic materials primarily employs methods such as phase separation, etching, spraying / coating, electrical discharge machining, template methods, electroplating, biomimetic methods, and sol-gel methods to construct the required microstructures from top to bottom or vice versa. In most applications, coating materials have the widest applicability and are relatively easy to prepare. However, while pursuing functional applications, the durability of the coating is a key technology for evaluating material performance. Particularly in the fabrication of superhydrophobic materials, achieving stable adhesion between hydrophobic particles and the matrix while exposing more hydrophobic, rough microstructures presents a significant technical challenge. Summary of the Invention

[0004] This invention provides a method for preparing durable superhydrophobic microstructure coatings based on existing phase separation and spraying / coating techniques. The invention creatively constructs a "lotus seedpod-honeycomb" hierarchical curing transformation model, employing a protection-then-release strategy to build the durable superhydrophobic coating structure. The coating can be prepared using a variety of materials with similar properties and is suitable for curing on various substrate surfaces, while also possessing advantages such as high barrier properties and high mechanical strength.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A first aspect of the present invention provides a method for preparing a durable superhydrophobic microstructure coating, comprising:

[0007] Hydrophobic microwax powder is added to an organic solution and melted, then silanized hydrophobic nanoparticles are added and mixed evenly to obtain a mixture. Before destroying the crystal nuclei of the hydrophobic microwax powder, the mixture is annealed to allow the hydrophobic microwax powder to recrystallize, resulting in a homogeneous coating of hydrophobic microwax powder coated with hydrophobic nanoparticles.

[0008] A film-forming material is added to the homogeneous coating of hydrophobic microwax powder coated with hydrophobic nanoparticles and mixed evenly to obtain a superhydrophobic coating.

[0009] The superhydrophobic coating is applied to a substrate and cured to obtain a durable superhydrophobic microstructure coating.

[0010] This invention utilizes the phase change of hydrophobic microwax powder to coat silanized hydrophobic nanoparticles through a combination of melting and annealing processes, and then adds high-strength film-forming materials to obtain a superhydrophobic coating.

[0011] In some embodiments, the hydrophobic microwax powder is selected from at least one of natural wax, mineral wax, and synthetic wax;

[0012] Preferably, the natural wax is selected from at least one of beeswax powder, palm wax powder, candelilla wax powder, and soybean wax powder;

[0013] Preferably, the mineral wax is selected from at least one of montana wax powder and paraffin wax powder;

[0014] Preferably, the synthetic wax is selected from at least one of Fischer-Tropsch wax powder and polyethylene wax powder.

[0015] In some embodiments, the melting point of the hydrophobic microwax powder is higher than the curing temperature of the film-forming material;

[0016] In some embodiments, the particle size of the hydrophobic microwax powder is 5-30 μm.

[0017] In some embodiments, the silanized hydrophobic nanoparticles are selected from at least one of hydrophobic nano-silica, hydrophobic nano-diatomaceous earth, hydrophobic titanium dioxide, and hydrophobic nano-cellulose.

[0018] In some embodiments, the particle size of the silanized hydrophobic nanoparticles is 5-50 nm.

[0019] In some embodiments, the amount of hydrophobic microwax powder added is 5%-20% of the organic solvent;

[0020] In some embodiments, the amount of hydrophobic nanoparticles added is 15%-25% of the hydrophobic microwax powder.

[0021] In some embodiments, the organic solvent is ethanol;

[0022] In some embodiments, the annealing is performed in a cold water bath at 15-25°C.

[0023] More specifically, the melting and annealing process involves rapidly heating ethanol to near the melting point of the hydrophobic microwax powder, adding the hydrophobic microwax powder with low-speed stirring, then silanizing the hydrophobic nanoparticles, mixing and stirring until the hydrophobic microwax powder crystal nuclei are removed, and then rapidly placing it in a 15-25°C cold water bath for annealing and stirring to allow the hydrophobic microwax powder to recrystallize.

[0024] In some embodiments, the film-forming material is selected from at least one of epoxy resin, polyacrylic resin, and thermosetting polyurethane resin, and the amount of the film-forming material added is 10%-18% of the hydrophobic microwax powder.

[0025] Alternatively, the film-forming material is selected from at least one of epoxy acrylate resin, polyurethane acrylate resin, and polyester acrylate resin UV-curable resin, and the amount of film-forming material added is 15%-20% of the hydrophobic microwax powder.

[0026] A second aspect of the present invention provides a durable superhydrophobic microstructure coating prepared by the above method.

[0027] A third aspect of the present invention provides a method for curing a durable superhydrophobic microstructure coating, comprising:

[0028] The superhydrophobic coating prepared by the above method is coated on the substrate and cured in stages to obtain a durable superhydrophobic microstructure coating.

[0029] The specific steps of the graded curing include: first curing at a temperature higher than that of the film-forming material for 3-10 minutes, and then curing at a temperature higher than that of the hydrophobic microwax powder for 20-30 minutes;

[0030] Alternatively, add a UV photoinitiator, first select the most suitable wavelength of UV light for the corresponding resin to cure completely, and then cure for 20-30 minutes at a temperature higher than the melting temperature of the hydrophobic microwax powder.

[0031] This invention employs a graded curing process to achieve a transformation in surface morphology, resulting in a novel superhydrophobic structure.

[0032] In some embodiments, the coating process is selected from at least one of dip coating, dip coating, and spray coating, to ensure a high-density and uniform distribution of wax particles. Subsequently, the mixture is allowed to stand at room temperature, allowing the ethanol to evaporate and the film-forming material to settle.

[0033] Beneficial effects of the present invention

[0034] As shown in Figure (3), the “lotus seedpod-honeycomb” hierarchical solidification transformation model constructed in this invention adopts a strategy of protecting nanoparticles before releasing them, which is the key to achieving durable superhydrophobicity.

[0035] 1. Due to the non-polar similarity between silanized hydrophobic nanoparticles and hydrophobic microwax powder, as shown in Figure (2), the microemulsion state of the outer layer of micron-sized wax powder after short-term heat treatment in heated ethanol adsorbs the silanized hydrophobic nanoparticles onto the surface of the wax particles. Subsequent cold water bath annealing causes the microemulsion wax layer to recrystallize, firmly encapsulating the hydrophobic nanoparticles in the wax matrix. During this process, the core structure of the wax particles remains unchanged, and some hydrophobic nanoparticles can act as stabilizers, resulting in a stable homogeneous state in the ethanol solvent system. This constitutes the "lotus" in the "lotus seedpod" model. Since the strength of the recrystallized wax itself and its adhesion strength to the hydrophobic nanoparticles are not ideal, a small amount of high-strength film-forming material is added to assist in strengthening, resulting in a hydrophobic coating.

[0036] 2. After the hydrophobic coating is applied to the substrate surface, the high-strength film-forming material settles after being left to stand at room temperature. The high-strength film-forming material, originally covering the raised hydrophobic micro-wax powder, settles to the bottom, forming the "lotus seedpod" in the model. With thermosetting or UV curing of the high-strength film-forming material, a stable lotus seedpod structure is formed, with the high-strength film-forming material forming a network of grooves as the base and the wax-coated hydrophobic nanoparticles forming the raised structures. At this point, the coating reaches its highest hydrophobic performance, but its durability is significantly insufficient. Further high-temperature curing causes the hydrophobic micro-wax powder to completely melt and settle into the matrix layer, releasing the hydrophobic nanoparticles and transforming the "lotus seedpod" model into an embedded "honeycomb" model.

[0037] 3. The present invention employs a scheme of hydrophobic nanoparticles coated with hydrophobic microwax powder, which effectively highlights the hydrophobic properties of the nanoparticles. As shown in Figure (4), based on the mechanical stability of the high-strength film-forming material, the designed embedded "honeycomb" structure effectively improves the durability of the hydrophobic nanoparticles. Even if the surface structure is damaged, the hydrophobic nanoparticles embedded in the "honeycomb" can still achieve high hydrophobicity. The cured wax that sinks into the matrix forms a dense layer, which improves the barrier properties of the coating material.

[0038] 4. The superhydrophobic microstructure transformation model provided by this invention has a simple process, can be used to prepare coatings from a variety of combined materials with similar properties, and is applicable to curing on various substrate surfaces. It provides a new approach for preparing durable superhydrophobic coatings and has significant guiding significance for the preparation of high-performance coating microstructure materials. Attached Figure Description

[0039] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0040] Figure 1 This is a schematic diagram of the process flow for the new model of the durable superhydrophobic microstructure coating of the present invention.

[0041] Figure 2 This is a schematic diagram of a model of a novel durable superhydrophobic microstructure coating of the present invention, which involves hydrophobic microwax powder coating silanized hydrophobic nanoparticles.

[0042] Figure 3 This is a schematic diagram of the "lotus seedpod-honeycomb" graded curing transformation model of the new model of durable superhydrophobic microstructure coating of the present invention.

[0043] Figure 4 This is a scanning electron microscope image of the molded structure of the new model of durable superhydrophobic microstructure coating in Embodiment 1 of the present invention. Detailed Implementation

[0044] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0045] In a specific embodiment, the hydrophobic microwax powder of the present invention can be beeswax powder, palm wax powder, candelilla wax powder, soybean wax powder, etc., from natural waxes; montan wax powder, paraffin wax powder, etc., from mineral waxes; Fischer-Tropsch wax powder, etc., from synthetic waxes. The surface layer of the hydrophobic microwax powder is melted by heating in an appropriate ethanol environment. Then, silanized hydrophobic nanoparticles, such as hydrophobic nano-silica, hydrophobic nano-diatomaceous earth, hydrophobic titanium dioxide, hydrophobic nano-cellulose, etc., are added. Through polar adsorption, low-speed stirring, cold water bath annealing, phase transformation, and recrystallization, a homogeneous coating of hydrophobic microwax powder coated with hydrophobic nanoparticles is obtained. High-strength film-forming materials, including epoxy resin, polyacrylic resin, polyurethane thermosetting materials, etc., or epoxy acrylic resin, polyurethane acrylic resin, polyester acrylic resin, etc., UV curing materials, etc., are then added to obtain the hydrophobic coating. The hydrophobic microwax powder has a particle size of 5-30 μm and is added at 8%-20% of the ethanol content. The silanized hydrophobic nanoparticles have a particle size of 5-50 nm and are added at 10%-20% of the hydrophobic microwax powder content. Low-speed stirring is selected at 300-500 r / min, and the cold water bath annealing temperature is selected at 15-25℃. The high-strength film-forming material is added at 10%-20% of the hydrophobic microwax powder content. Dip coating, curtain coating, and spray coating processes are used to ensure a high-density and uniform distribution of the hydrophobic microwax powder on the substrate surface. Then, allow it to stand at room temperature to allow the ethanol to evaporate and the film-forming material to settle. For thermosetting film-forming materials, first cure at a low temperature slightly higher than the curing temperature of the high-strength film-forming material for 3-10 min, then cure at a high temperature higher than the melting temperature of the hydrophobic microwax powder for 20-30 min. Alternatively, for UV-curable film-forming materials, add a UV photoinitiator, first select the most suitable wavelength of UV light for the corresponding resin to cure completely, and then cure at a high temperature for 20-30 minutes above the melting temperature of the hydrophobic micro wax powder to obtain a durable superhydrophobic coating material.

[0046] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0047] In the following examples, the preparation methods of hydrophobic nano-silica, hydrophobic titanium dioxide, and hydrophobic nano-diatomaceous earth are as follows: 3g of nano-silica, hydrophobic titanium dioxide, or nano-diatomaceous earth are stirred and reacted at 60°C for 12h in a system of 100mL ethanol, 10mL deionized water, 5mL ammonia water, and 5mL hexadecyltrimethoxysilane, and then freeze-dried under vacuum at -30°C for 10h to obtain the final product.

[0048] Example 1

[0049] Reference Figure 1The specific steps for preparing a durable, superhydrophobic coating that is thermosetting and cured from palm wax powder / hydrophobic silica / water-based polyacrylic resin are as follows:

[0050] (1) Heat 100ml of ethanol to 80℃, turn off the heating switch, control the stirring speed at 300r / min and add 8g of palm wax powder. After 20s, add 4g of hydrophobic nano silica and continue stirring for 30s. Then quickly cool and stir in a 25℃ cold water bath to obtain a homogeneous coating of hydrophobic micro wax powder coated with hydrophobic nanoparticles.

[0051] (2) 10g of waterborne polyacrylic resin was added to ethanol and stirred at a high speed of 2000r / min to obtain a 10wt% waterborne polyacrylic resin dilution. 20g of the waterborne polyacrylic resin dilution was added to the above homogeneous coating and stirred at a low speed of 500r / min to obtain a durable superhydrophobic coating.

[0052] (3) Apply the hydrophobic coating to the substrate surface and let it stand at room temperature. The ethanol will evaporate and the film-forming material will settle. First, cure the water-based polyacrylic resin at a low temperature of 60℃ for 10 minutes, and then melt and cure the palm wax at a high temperature of 100℃ for 10 minutes to obtain the final product.

[0053] Example 2

[0054] Reference Figure 2 The specific steps for preparing a durable superhydrophobic coating of paraffin powder / hydrophobic titanium dioxide / polyurethane thermosetting are as follows:

[0055] (1) Heat 100ml of ethanol to 60℃, turn off the heating switch, control the stirring speed at 300r / min and add 8g of brown paraffin powder. After 20s, add 3g of hydrophobic titanium dioxide and continue stirring for 30s. Then quickly cool and stir in a 20℃ cold water bath to obtain a homogeneous coating of hydrophobic micro wax powder coated with hydrophobic nanoparticles.

[0056] (2) 10g of waterborne polyurethane was added to ethanol and stirred at a high speed of 2000r / min to obtain a 10wt% waterborne polyurethane dilution. 20g of the waterborne polyurethane dilution was added to the above homogeneous coating and stirred at a low speed of 500r / min to obtain a durable superhydrophobic coating.

[0057] (3) Apply the hydrophobic coating to the substrate surface and let it stand at room temperature. The ethanol will evaporate and the film-forming material will settle. First, cure the waterborne polyurethane at a low temperature of 50°C for 10 minutes, and then melt and cure the paraffin at a high temperature of 100°C for 10 minutes to obtain the final product.

[0058] Example 3

[0059] Reference Figure 1 The specific steps for preparing a durable, superhydrophobic coating using Fischer-Tropsch wax powder / hydrophobic nano-diatomaceous earth / waterborne epoxy acrylic resin UV curing are as follows:

[0060] (1) Heat 100ml of ethanol to 90℃, turn off the heating switch, control the stirring speed at 300r / min and add 8g of Fischer-Tropsch wax powder. After 20s, add 4g of hydrophobic nano diatomaceous earth, continue stirring for 20s, and then quickly cool and stir in a 25℃ cold water bath to obtain a homogeneous coating of hydrophobic micro wax powder coated with hydrophobic nanoparticles.

[0061] (2) 10g of waterborne epoxy acrylate resin was added to ethanol and stirred at a high speed of 2000r / min to obtain a 10wt% waterborne epoxy acrylate resin dilution. 20g of the waterborne epoxy acrylate resin dilution was added to the above homogeneous coating and stirred at a low speed of 500r / min to obtain a durable superhydrophobic coating.

[0062] (3) Apply the hydrophobic coating with added UV photoinitiator to the substrate surface, let it stand at room temperature, allow the ethanol to evaporate, and allow the film-forming material to settle. First, select a wide-range wavelength UV light to cure completely, and then melt and cure Fischer-Tropsch wax at 100℃ for 10 min to obtain the final product.

[0063] Example 4

[0064] Reference Figure 1 The specific steps for preparing a durable, superhydrophobic coating that is UV-cured from polyethylene wax powder / hydrophobic nano-silica / waterborne polyurethane acrylic resin are as follows:

[0065] (1) Heat 100ml of ethanol to 85℃, turn off the heating switch, control the stirring speed at 300r / min and add 7g of polyethylene wax powder. After 20s, add 3g of hydrophobic nano diatomaceous earth, continue stirring for 30s, and then quickly cool and stir in a 20℃ cold water bath to obtain a homogeneous coating of hydrophobic micro wax powder coated with hydrophobic nanoparticles.

[0066] (2) 12g of waterborne polyurethane acrylic resin was added to ethanol and stirred at a high speed of 2000r / min to obtain a 10wt% waterborne polyurethane acrylic resin dilution. 20g of the waterborne polyurethane acrylic resin dilution was added to the above homogeneous coating and stirred at a low speed of 500r / min to obtain a durable superhydrophobic coating.

[0067] (3) Apply the hydrophobic coating with added UV photoinitiator to the substrate surface, let it stand at room temperature, allow the ethanol to evaporate, and allow the film-forming material to settle. First, select a wide-range wavelength UV light to cure completely, and then melt and cure the polyethylene wax at 105℃ for 10 minutes to obtain the final product.

[0068] Comparative Example 1

[0069] The difference from Example 1 is that no palm wax powder was added.

[0070] Comparative Example 2

[0071] The difference from Example 1 is that step (2) is omitted.

[0072] Performance testing

[0073] The relevant performance of the new model of durable superhydrophobic microstructure coating prepared by Examples 1 to 4 of the present invention was tested.

[0074] Contact angle (CA) and sliding angle (SA) tests: The contact angle measurement method for nanofilms is adopted according to GB / T 30447-2013; Abrasion resistance and hydrophobicity test: The contact angle is measured after 20 and 50 cycles of cyclic abrasion using a 500g weight.

[0075] Table 1 Performance of durable superhydrophobic material examples

[0076] Sample number CA(θ°) SA(θ°) 20 times CA(θ°) 50 times CA(θ°) Example 1 162.4 4.2 158.7 156.3 Example 2 160.3 6.7 156.9 154.3 Example 3 157.7 8.8 154.1 150.6 Example 4 158.4 7.3 155.6 153.5 Comparative Example 1 103.5 21.5 94.2 92.1 Comparative Example 2 159.3 12.5 131.7 109.3

[0077] As can be seen from the comparison of Example 1 and Comparative Examples 1 and 2, the "lotus seedpod-honeycomb" graded curing transformation model constructed in this invention can significantly improve the wear resistance and hydrophobicity of the coating.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a durable superhydrophobic microstructure coating, characterized in that, include: Hydrophobic microwax powder is added to an organic solvent to melt it, and then silanized hydrophobic nanoparticles are added and mixed evenly to obtain a mixture. Before destroying the crystal nuclei of the hydrophobic microwax powder, the mixture is annealed to allow the hydrophobic microwax powder to recrystallize, resulting in a homogeneous coating of hydrophobic microwax powder coated with hydrophobic nanoparticles. A film-forming material is added to the homogeneous coating of hydrophobic microwax powder coated with hydrophobic nanoparticles and mixed evenly to obtain a superhydrophobic coating. The superhydrophobic coating is applied to a substrate and cured in stages to obtain a durable superhydrophobic microstructure coating. The specific steps of the graded curing include: first curing at a temperature higher than that of the film-forming material for 3-10 minutes, and then curing at a temperature higher than that of the hydrophobic microwax powder for 20-30 minutes; Alternatively, add a UV photoinitiator, first select the most suitable wavelength of UV light for the corresponding resin to cure completely, and then cure for 20-30 minutes at a temperature higher than the melting temperature of the hydrophobic microwax powder.

2. The method for preparing a durable superhydrophobic microstructure coating as described in claim 1, characterized in that, The hydrophobic microwax powder is selected from at least one of natural wax, mineral wax, and synthetic wax.

3. The method for preparing a durable superhydrophobic microstructure coating as described in claim 2, characterized in that, The natural wax is selected from at least one of beeswax powder, palm wax powder, candelilla wax powder, and soybean wax powder; Alternatively, the mineral wax is selected from at least one of montana wax powder and paraffin wax powder; Alternatively, the synthetic wax may be selected from at least one of Fischer-Tropsch wax powder and polyethylene wax powder.

4. The method for preparing a durable superhydrophobic microstructure coating as described in claim 1, characterized in that, The melting point of the hydrophobic microwax powder is higher than the curing temperature of the film-forming material; Alternatively, the particle size of the hydrophobic microwax powder is 5-30 μm.

5. The method for preparing a durable superhydrophobic microstructure coating as described in claim 1, characterized in that, The silanized hydrophobic nanoparticles are selected from at least one of hydrophobic nano-silica, hydrophobic nano-diatomaceous earth, hydrophobic titanium dioxide, and hydrophobic nano-cellulose. Alternatively, the particle size of the silanized hydrophobic nanoparticles is 5-50 nm.

6. The method for preparing a durable superhydrophobic microstructure coating as described in claim 1, characterized in that, The amount of hydrophobic microwax powder added is 5%-20% of the organic solvent; Alternatively, the amount of hydrophobic nanoparticles added is 15%-25% of the hydrophobic microwax powder.

7. The method for preparing a durable superhydrophobic microstructure coating as described in claim 1, characterized in that, The organic solvent is ethanol; Alternatively, the annealing is performed in a cold water bath at 15-25°C.

8. The method for preparing a durable superhydrophobic microstructure coating as described in claim 1, characterized in that, The film-forming material is selected from at least one of epoxy resin, polyacrylic resin, and thermosetting polyurethane resin, and the amount of the film-forming material added is 10%-18% of the hydrophobic micro wax powder. Alternatively, the film-forming material is selected from at least one of epoxy acrylic resin, polyurethane acrylic resin, and polyester acrylic resin UV-curable resin, and the amount of film-forming material added is 15%-20% of the hydrophobic micro wax powder.

9. The method for preparing a durable superhydrophobic microstructure coating as described in claim 1, characterized in that, The coating process is selected from at least one of dip coating, curtain coating, and spray coating.

10. A durable superhydrophobic microstructure coating prepared by the method of any one of claims 1-9.

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