Preparation method of wear-resistant nanocomposite super-hydrophobic coating

Abstract

The application is a preparation method of a wear-resistant nano-composite super-hydrophobic coating. The method uses polysilsesquioxane (PSQ) precursor as the only stabilizer, and styrene and tridecafluoro octyl acrylate (TFOA) as the comonomer, and successfully prepares hybrid organic silicon super-hydrophobic nanoparticles (HHP) through a soap-free emulsion polymerization method; then, the HHP is blended with the adhesive layer, and finally, a super-hydrophobic coating with a hierarchical structure of the hybrid organic silicon super-hydrophobic nanoparticles (HHP) and the adhesive layer is obtained. The application can make the coating maintain the super-hydrophobic property in the wear process by relying on the increase of roughness caused by friction and the exposure and migration of the F element in the HHP, and solves the problem that the nanoparticles are easy to fall off in the spraying process.

Description

Technical Field

[0001] This invention belongs to the field of coating preparation technology, specifically relating to a method for preparing a wear-resistant nanocomposite superhydrophobic coating. Background Technology

[0002] Superhydrophobic materials, due to their strong water repellency, hold immense promise for applications in self-cleaning, oil-water separation, antifouling, waterproofing, and anti-icing. The superhydrophobic coating is primarily determined by its rough structure and surface chemical composition. The incorporation of nanoparticles is typically used to enhance coating roughness, while fluorocarbons are often used as typical low surface energy materials. Despite significant progress in the research of artificial superhydrophobic coatings, their practical applications still face many limitations. It is well known that superhydrophobic coatings obtained through spraying are susceptible to physical damage due to the fragility of their micro / nano surface structures, severely shortening their lifespan and limiting their wide range of applications.

[0003] Compared to traditional spherical nanoparticles, hierarchical nanoparticles are more advantageous for superhydrophobic coating applications due to their unique morphology. However, many current methods for preparing hierarchical nanoparticles, such as template-assisted synthesis and self-templating methods, have many inherent drawbacks. Wang et al. successfully synthesized needle-like silica nanoparticles using CTAB surfactant as a template via single-micelle epitaxy, but subsequent applications required the removal of CTAB with acetone (Acs Central Science, 2017, 3, 839-846). In addition to the template consumption and waste issues mentioned above, the removal of some templates also requires time-consuming and environmentally polluting high-temperature calcination or chemical dissolution steps. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of current technologies by providing a method for preparing a wear-resistant nanocomposite superhydrophobic coating. This method uses polysilsesquioxane (PSQ) precursor as the sole stabilizer and styrene (St) and tridecafluorooctyl acrylate (TFOA) as comonomers to successfully prepare hybrid organosilicon superhydrophobic nanoparticles (HHP) via soap-free emulsion polymerization. Then, the HHP is blended with a binder layer to finally obtain a superhydrophobic coating composed of hybrid organosilicon superhydrophobic nanoparticles (HHP) with a hierarchical structure and a binder layer. This invention allows the coating to maintain its superhydrophobic properties during wear by relying on the increased roughness caused by friction and the exposure and migration of fluorine (F) elements in the HHP, thus solving the problem of nanoparticles easily detaching during spraying.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a wear-resistant nanocomposite superhydrophobic coating, the method comprising:

[0007] First, St, compound A, initiator, and PSQ precursor are added to a reactor and ultrasonically dispersed at 30–80 Hz for 2–15 min to obtain dispersion A. Then, dispersion A is added to hydrochloric acid. The mixture is then stirred at 200–350 rpm at room temperature for 30–90 min. Ammonia is then added to adjust the pH of the system to 9–13. After stirring for another 30–90 min, the stirring speed is adjusted to 50–180 rpm, and the temperature is raised to 50–70 °C under a nitrogen atmosphere. The reaction is continued for 1–6 h to obtain HHP.

[0008] The mass ratio of St to compound A to initiator to PSQ precursor is 0.65–1.17: 0.13–0.65: 0.0065–0.0117: 0.65–5.2; 0.5–5.0 g of PSQ precursor is added to every 30–80 mL of hydrochloric acid.

[0009] Compound A is one or more of fluorinated acrylates containing double bonds;

[0010] The PSQ precursor is one or more of siloxanes;

[0011] The hydrochloric acid has a pH value of 2 to 5;

[0012] The dispersion A is added to the hydrochloric acid over a period of 3 to 15 minutes.

[0013] The second step is to blend HHP with the adhesive layer material and disperse it with ultrasound for 20-90 minutes to obtain emulsion A.

[0014] In the second step, the mass ratio of HHP to the adhesive layer is 0.2 to 0.5:1.

[0015] The adhesive layer material is a coating; specifically, the coating is a water-based polyurethane emulsion, a styrene-acrylic emulsion, a water-based epoxy emulsion, or a water-based acrylic emulsion.

[0016] The third step involves directly dripping emulsion A onto the substrate to form a coating thickness of 40–60 μm. After drying at 20–60 °C for 24–72 h, a wear-resistant nanocomposite superhydrophobic coating is obtained.

[0017] The compound A is one of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, tridecylfluorooctyl methacrylate, perfluoroalkylpropyl acrylate, 1H,1H-perfluoron-octyl acrylate, perfluorooctylpropyl acrylate, 3-perfluorooctyl-2-hydroxypropyl acrylate, 3,3,4,4,5,5,6,6,7,8,8,8-dodecano-7-(trifluoromethyl)octyl acrylate, and 2-(perfluorooctyl)ethyl methacrylate;

[0018] The initiator is a water-soluble initiator or an oil-soluble initiator; specifically, it is azobisisobutyronitrile (AIBN) or potassium persulfate (KPS).

[0019] The PSQ precursor is one of methyltriethoxysiloxane (MTES), methacryloxytrimethoxysilane (MPS), γ-methacryloxypropyltrimethoxysilane (KH-570), vinyltrimethoxysilane (A171), vinyl-tris(2-,methoxyethoxy)silane (KH-172), γ-aminopropyltriethoxysilane (KH-550), and γ-glycidoxypropyltrimethoxysilane (KH-560).

[0020] The adhesive layer mentioned in the second step is one of waterborne polyurethane emulsion, styrene-acrylic emulsion, waterborne epoxy emulsion, and waterborne acrylic emulsion.

[0021] The substrate mentioned in the third step is one of glass sheet, tinplate, leather, or steel plate.

[0022] The essential features of this invention are:

[0023] First, this invention designs a high surface roughness and low surface energy HHP. Using polysilsesquioxane (PSQ) precursor as the sole stabilizer and styrene (St) and tridecafluorooctyl acrylate (TFOA) as comonomers, HHP was successfully prepared via soap-free emulsion polymerization. This method avoids the problems of using small-molecule emulsifiers and template waste in the aforementioned hierarchical nanoparticle preparation methods.

[0024] Then, the HHP was blended with the binder layer to obtain the composite coating. The blending method gives the coating a uniform overall structure, which is beneficial for constructing a homogeneous structure. This allows the coating to maintain its superhydrophobic properties during wear by relying on the increased roughness caused by friction and the exposure and migration of the fluorine element in the HHP, thus solving the problem of nanoparticles easily falling off during the spraying process.

[0025] The beneficial effects of this invention are as follows:

[0026] Firstly, it pioneers a novel method for preparing hierarchical nanoparticles. It uses amphiphilic siloxane oligomers (PSQ) generated by the hydrolysis and condensation of methyltriethoxysilane as the sole stabilizer, anchoring them onto the surface of a soft template composed of styrene and tridecafluorooctyl acrylate comonomer droplets to form a mesoporous PSQ shell. The resulting nanoparticles are then obtained through confined polymerization of the comonomers within the shell. This method avoids the use of small-molecule emulsifiers and the problems associated with template waste.

[0027] Secondly, a wear-resistant nanocomposite superhydrophobic coating was constructed. This was achieved by blending hierarchical HHP nanoparticles with a binder layer. This method allows the coating to maintain its superhydrophobic properties during wear by relying on the increased roughness caused by friction and the exposure and migration of fluorine (F) elements in the HHP. The coating can withstand 40 wear cycles without losing its superhydrophobicity, and the fluorine content increased from 1.55% before wear to 17.46% after wear. This method solves the problem of nanoparticles easily detaching during spraying. Attached Figure Description

[0028] Figure 1 The image shows a SEM image of HHP from Example 1.

[0029] Figure 2 Image showing the water contact angle of HHP in Example 1;

[0030] Figure 3 These are SEM images of the pure WPU coating and the WPU-HHP coating in Example 2; wherein, Figure 3 A is a SEM image of a pure WPU coating; Figure 3 B is a SEM image of the WPU-HHP coating;

[0031] Figure 4 Images showing the water contact angles of the pure WPU coating and the WPU-HHP coating in Example 2; wherein, Figure 4 Image A shows the water contact angle of a pure WPU coating. Figure 4 Image B shows the water contact angle of the WPU-HHP coating.

[0032] Figure 5 This is a graph showing the change of water contact angle with wear cycle during wear of the pure WPU coating and the WPU-HHP coating in Example 2;

[0033] Figure 6 The image shows a SEM image of the WPU-HHP coating after wear in Example 2.

[0034] Figure 7 XPS images of the WPU-HHP coating before and after wear in Example 2; Detailed Implementation

[0035] Example 1:

[0036] The specific steps for preparing an HHP are as follows:

[0037] 60 mL of hydrochloric acid aqueous solution with a pH of 3 was measured using a graduated cylinder and added to a four-necked round-bottom flask. 0.9 g of St, 0.4 g of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, 0.0091 g of initiator (AIBN), and 2.6 g of MTES were weighed into centrifuge tubes and ultrasonically dispersed at 60 Hz for 15 min to obtain dispersion A. Then, dispersion A was injected into the above hydrochloric acid aqueous solution using a syringe pump within 3 min. The above system was stirred at 300 rpm for 90 min at room temperature, and then a certain amount of ammonia water (37%) was added to bring the pH of the system to 11. After stirring for another 90 min, the stirring speed was adjusted to 50 rpm, and the temperature was raised to 60 °C under a nitrogen atmosphere. The reaction was continued for 4 h to obtain HHP emulsion.

[0038] The surface morphology of HHP was characterized using a Nano 450 scanning electron microscope from FEI Corporation, USA. The results are as follows: Figure 1 As shown. The water contact angle (WCA) of the HHP-coated particle film was tested, and the results are as follows. Figure 2 As shown, HHP has a WCA of 170.1°, indicating superhydrophobicity.

[0039] Example 2:

[0040] The specific steps for preparing a wear-resistant nanocomposite superhydrophobic coating are as follows:

[0041] 5g of the HHP emulsion prepared in Example 1 was mixed with 10g of aqueous polyurethane emulsion (14%) under ultrasonic dispersion at 60Hz for 60min, and then dropped onto a glass slide (2x5 cm). 2 A 40 μm thick coating was applied to the surface and dried at 40 °C for 24 h to obtain a wear-resistant nanocomposite superhydrophobic coating (WPU-HHP).

[0042] The results are as follows Figure 3 As shown, the roughness of the WPU-HHP coating is greater than that of the WPU coating, and the combination... Figure 4 The water contact angle photographs show that the addition of HHP effectively improves the hydrophobicity of the coating. Weight abrasion tests were conducted on the WPU-HHP coating and the WPU coating. The coated glass plate was placed under 600-grit sandpaper and subjected to a 200g load, then pushed back and forth horizontally, 5cm each time. Two back-and-forth movements constituted one cycle, and the WCA of the coating was measured every five cycles. The results are as follows... Figure 5 As shown, with the increase of wear cycles, the WCA of the WPU-HHP coating shows a trend of first increasing and then decreasing. The WCA reaches a maximum of 160.1° at 30 wear cycles, but the WCA of the WPU coating only increases slightly after wear. Figure 6The results show that one of the reasons for the significant increase in WCA of the WPU-HHP coating after wear is that the previously encapsulated HHP is exposed with the help of wear, thus increasing the surface roughness of the WPU-HHP coating. XPS tests were performed on the WPU-HHP coating before and after wear, and the results are as follows: Figure 7 As shown, the fluorine content increased from 1.55% before wear to 17.46% after wear, indicating that the second reason for the increase in WCA after wear is the exposure and migration of F in HHP.

[0043] Example 3:

[0044] The specific steps for preparing a wear-resistant nanocomposite superhydrophobic coating are as follows:

[0045] 5g of the HHP emulsion prepared in Example 1 was mixed with 12g of styrene-acrylic emulsion (15%) and ultrasonically dispersed at 50Hz for 50min. Then, it was dropped onto a glass slide (2x5 cm). 2 A 40 μm thick coating was applied to the surface and dried at 40 °C for 24 h to obtain a wear-resistant nanocomposite superhydrophobic coating (WPU-HHP).

[0046] The prepared nanocomposite superhydrophobic coating exhibits excellent wear resistance, similar to that of Example 2.

[0047] Example 4:

[0048] The specific steps for preparing a wear-resistant nanocomposite superhydrophobic coating are as follows:

[0049] 6g of the HHP emulsion prepared in Example 1 was mixed with 14g (14%) of aqueous acrylic emulsion under ultrasonic dispersion at 60Hz for 70min, and then dropped onto a glass slide (2x5 cm). 2 A 50 μm thick coating was applied to the surface and dried at 50 °C for 24 h to obtain a wear-resistant nanocomposite superhydrophobic coating (WPU-HHP).

[0050] The prepared nanocomposite superhydrophobic coating exhibits excellent wear resistance, similar to that of Example 2.

[0051] Example 5:

[0052] The specific steps for preparing an HHP are as follows:

[0053] 40 mL of hydrochloric acid aqueous solution with a pH of 4 was measured using a graduated cylinder and added to a four-necked round-bottom flask. 0.9 g of St, 0.5 g of 2-(perfluorooctyl)ethyl methacrylate, 0.0098 g of initiator (KPS), and 2.2 g of MPS were weighed into centrifuge tubes and ultrasonically dispersed at 60 Hz for 15 min to obtain dispersion A. Then, dispersion A was injected into an acidic aqueous solution using a syringe pump within 5 min. The above system was stirred at 220 rpm for 70 min at room temperature, and then a certain amount of ammonia (37%) was added to bring the pH of the system to 10. After stirring for another 60 min, the stirring speed was adjusted to 70 rpm, and the temperature was raised to 65 °C under a nitrogen atmosphere. The reaction was continued for 3 h to obtain HHP emulsion.

[0054] The obtained particle structure is similar to that of Example 1.

[0055] Example 6:

[0056] The specific steps for preparing an HHP are as follows:

[0057] 40 mL of hydrochloric acid aqueous solution with a pH of 5 was measured using a graduated cylinder and added to a four-necked round-bottom flask. 1.2 g of St, 0.6 g of perfluorooctylpropyl acrylate, 0.0099 g of initiator (KPS), and 2.8 g of KH-550 were weighed into centrifuge tubes and ultrasonically dispersed at 60 Hz for 15 min to obtain dispersion A. Then, dispersion A was injected into an acidic aqueous solution using a syringe pump over 7 min. The above system was stirred at 250 rpm for 70 min at room temperature, and then a certain amount of ammonia (37%) was added to bring the pH of the system to 10. After stirring for another 80 min, the stirring speed was adjusted to 70 rpm, and the temperature was raised to 70 °C under a nitrogen atmosphere. The reaction was continued for 3 h to obtain HHP emulsion.

[0058] The obtained particle structure is similar to that of Example 1.

[0059] Example 7:

[0060] The specific steps for preparing a wear-resistant nanocomposite superhydrophobic coating are as follows:

[0061] 6g of the HHP emulsion prepared in Example 5 was mixed with 14g of aqueous acrylic emulsion (15%) under ultrasonic dispersion at 60Hz for 70min, and then dropped onto tinplate (2x5 cm). 2 A 50 μm thick coating was applied to the surface and dried at 50 °C for 48 h to obtain a wear-resistant nanocomposite superhydrophobic coating (WPU-HHP).

[0062] The prepared nanocomposite superhydrophobic coating exhibits excellent wear resistance, similar to that of Example 2.

[0063] Example 8:

[0064] The specific steps for preparing a wear-resistant nanocomposite superhydrophobic coating are as follows:

[0065] 4g of the HHP emulsion prepared in Example 6 was mixed with 10g of aqueous epoxy emulsion (12%) and ultrasonically dispersed at 60Hz for 70min. The mixture was then dropped onto leather (2x5 cm). 2 A 50 μm thick coating was applied to the surface and dried at 50 °C for 24 h to obtain a wear-resistant nanocomposite superhydrophobic coating (WPU-HHP).

[0066] The prepared nanocomposite superhydrophobic coating exhibits excellent wear resistance, similar to that of Example 2.

[0067] In summary, this invention uses amphiphilic siloxane oligomers (PSQ) generated by the hydrolysis and condensation of methyltriethoxysilane as the sole stabilizer, anchoring them onto the surface of a soft template composed of styrene and tridecafluorooctyl acrylate comonomer droplets to form a mesoporous PSQ shell. Hierarchical nanoparticles (HHP) are then obtained through the confined polymerization of the comonomers within the shell. This method avoids the use of small-molecule emulsifiers and the problem of template waste. Subsequently, we constructed a wear-resistant nanocomposite superhydrophobic coating, obtained by blending the hierarchical nanoparticles (HHP) with a binder layer. The addition of HHP significantly improves the hydrophobicity of the coating and extends its lifespan. This is attributed to the physical damage contributing to increased surface roughness and the exposure and migration of fluorine (F) elements in HHP, while also solving the problem of nanoparticles easily detaching during spraying.

[0068] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing a wear-resistant nanocomposite superhydrophobic coating, characterized in that the method comprises the following steps: First, St, compound A, initiator, and PSQ precursor are added to a reactor and ultrasonically dispersed at 30-80 Hz for 2-15 min to obtain dispersion A. Then, dispersion A is added to hydrochloric acid. The mixture is then stirred at 200-350 rpm at room temperature for 30-90 min. Ammonia is then added to bring the pH of the system to 9-13. After stirring for another 30-90 min, the stirring speed is adjusted to 50-180 rpm, and the temperature is raised to 50-70 °C under a nitrogen atmosphere. The reaction is continued for 1-6 h to obtain HHP. in, The mass ratio of St:compound A:initiator:PSQ precursor is 0.65~1.17:0.13~0.65:0.0065~0.0117:0.65~5.2; 0.5~5.0 g of PSQ precursor is added to every 30~80 mL of hydrochloric acid. Compound A is one or more of fluorinated acrylates containing double bonds; The PSQ precursor is one or more of siloxanes; The second step is to blend HHP with the adhesive layer material and disperse it with ultrasound for 20-90 min to obtain emulsion A. The mass ratio of HHP to adhesive layer material is 0.2~0.5:1; the adhesive layer material is one of waterborne polyurethane emulsion, waterborne epoxy emulsion, and waterborne acrylic emulsion. The third step involves coating emulsion A onto the substrate with a thickness of 40-60 μm and drying it at 20 ℃-60 ℃ for 24-72 h to obtain a wear-resistant nanocomposite superhydrophobic coating.

2. The method for preparing the wear-resistant nanocomposite superhydrophobic coating as described in claim 1, characterized in that compound A is one of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecylfluorooctyl acrylate, tridecylfluorooctyl methacrylate, 1H,1H-perfluoro-n-octyl acrylate, perfluorooctylpropyl acrylate, 3-perfluorooctyl-2-hydroxypropyl acrylate, 3,3,4,4,5,5,6,6,7,8,8,8-dodecano-7-(trifluoromethyl)octyl acrylate, and 2-(perfluorooctyl)ethyl methacrylate.

3. The method for preparing the wear-resistant nanocomposite superhydrophobic coating as described in claim 1, characterized in that the initiator is a water-soluble initiator or an oil-soluble initiator; specifically, it is azobisisobutyronitrile (AIBN) or potassium persulfate (KPS).

4. The method for preparing the wear-resistant nanocomposite superhydrophobic coating as described in claim 1, characterized in that: The PSQ precursor is one of methyltriethoxysilane (MTES), methacryloxytrimethoxysilane (MPS), γ-methacryloxypropyltrimethoxysilane (KH-570), vinyltrimethoxysilane (A171), vinyl-tris(2-,methoxyethoxy)silane (KH-172), γ-aminopropyltriethoxysilane (KH-550), and γ-glycidoxypropyltrimethoxysilane (KH-560).

5. The method for preparing the wear-resistant nanocomposite superhydrophobic coating as described in claim 1, characterized in that the pH value of the hydrochloric acid is 2-5; and the dispersion A is added to the hydrochloric acid at a time of 3-15 minutes.

6. The method for preparing the wear-resistant nanocomposite superhydrophobic coating as described in claim 1, characterized in that the substrate in the third step is one of glass sheet, tinplate, leather, and steel plate.

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