A long-lasting and durable super-hydrophobic nano-gradient composite coating and its preparation method

Abstract

The present invention relates to the field of material surface engineering technology, especially a kind of long-acting firm super-hydrophobic nano gradient composite coating and preparation method thereof, now propose following scheme, it includes S1:Modified super-hydrophobic coating is obtained using resin modified super-hydrophobic nano coating;S2:By bonding coating spraying on contact object surface, solidify and form semi-solidified bonding bottom layer;S3:Modified super-hydrophobic coating is sprayed on the surface of semi-solidified bonding bottom layer, after being cured, form the first coating layer, spray PDMS curing agent solution on the surface of the first coating layer and solidify, obtain semi-solidified layer;S4:Modified super-hydrophobic coating is sprayed on the surface of semi-solidified layer, after being cured, form the second coating layer, spray PDMS curing agent solution on the surface of the second coating layer and solidify, obtain super-hydrophobic nano composite coating;Or repeat S4 step at least once to obtain super-hydrophobic nano composite coating.Preparation technology of the present invention is simple, and the coating prepared has robustness, super-hydrophobicity, chemical durability and long-acting property.

Description

Technical Field

[0001] The present invention relates to the field of material surface engineering, and in particular to a long-lasting and robust super-hydrophobic nano-gradient composite coating and a preparation method thereof. Background Art

[0002] Inspired by the "lotus effect," superhydrophobic coatings with biomimetic micro-nanostructures and low-surface-energy materials have been developed and are attracting significant attention from researchers. These coatings boast static contact angles greater than 150° and rolling angles less than 10°. They also offer excellent properties such as water repellency, antifouling, dustproofing, drag reduction, corrosion resistance, and frost and icing resistance. They are widely used in applications such as corrosion and bioadhesion protection for engineering equipment, corrosion resistance and drag reduction for ships, mildew and dust resistance for wood and building materials, water and dust protection for glass, and frost and icing protection for air conditioners and refrigerators.

[0003] In recent years, super-hydrophobic coating is obtained by carrying out super-hydrophobic modification to inorganic nanoparticles, and the super-hydrophobic coating prepared by spraying method has excellent performance, and its preparation technology is simple, preparation efficiency is high, and application range is wide. However, super-hydrophobic coating has poor adhesion, and the bonding force between inorganic nanoparticles in coating is weak, causing coating to be in application process, and its surface micro-nano structure is easily destroyed, thus losing super-hydrophobic performance. Therefore, how to prepare long-acting firm super-hydrophobic coating with more simple and efficient method is extremely critical. For this reason, the present invention proposes a kind of long-acting firm super-hydrophobic nano gradient composite coating and preparation method thereof. Summary of the Invention

[0004] In order to overcome the defects and shortcomings of the existing technology, the present invention proposes a long-lasting and robust super-hydrophobic nano-gradient composite coating and a preparation method thereof, aiming at the problems of poor long-term effectiveness, robustness and chemical durability of super-hydrophobic coatings under harsh service environments.

[0005] The present invention adopts bottom surface composite technology to pre-set bonding bottom layer to improve the adhesion of coating, and improves the binding force between inorganic nanoparticles and the adhesion of coating by resin modification of super hydrophobic coating, thereby further improving the stability of super hydrophobic coating. By designing a multi-layer gradient structure of the coating, a high-strength adhesive (E-7 glue) is applied to the surface of the contact object as a base layer to improve the bonding strength between the super-hydrophobic nano-coating and the contact object. The hydrophobic nano-coating is modified by resin, and the bonding strength of the chemical bond formed between the resin and the high-strength adhesive (E-7 glue) and the appropriate content ratio of the resin and the hydrophobic nano-coating are utilized to improve the bonding strength between the nano-particles (silicon dioxide and silicon micropowder) and between the nano-particles and the bonding bottom layer, as well as the super-hydrophobic performance. At the same time, PDMS, which has hydrophobicity, alkali resistance and high bonding strength, is sprayed on the surface of the super-hydrophobic nano-coating layer in multiple passes as a transition layer and cured. The PDMS transition layer acts as a connected whole. On the one hand, strong hydrogen bonds are formed between PDMS and silica, and on the other hand, PDMS is cross-linked and cured with the high-strength adhesive (E-7 glue), firmly fastening the super-hydrophobic nano-coating layer to the bonding bottom layer, thereby further improving the robustness, hydrophobicity, chemical durability and long-term effectiveness of the coating.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a method for preparing a long-lasting and durable super-hydrophobic nano-gradient composite coating, comprising the following steps:

[0008] S1: Modified super-hydrophobic coating is obtained by modifying super-hydrophobic nano-coating with resin:

[0009] Add nano-silicon dioxide, nano-silicon powder and low surface energy material to anhydrous ethanol, and ultrasonically disperse for 20-60 minutes. Preferably, the ultrasonic power is set to 130-400w and the ultrasonic time interval is 5s to obtain a super-hydrophobic nano-coating;

[0010] The resin is added to anhydrous ethanol and ultrasonically dispersed for 10-30 minutes to obtain a clear solution. The super-hydrophobic nano coating and the clear solution are mixed and stirred for 5-25 minutes at a stirring rate of 100-400 r / min to obtain a modified super-hydrophobic coating.

[0011] S2: Spray the bonding coating onto the cleaned surface of the contact object and cure it at 80-120°C for 3-15 minutes to form a semi-cured bonding base layer;

[0012] S3: spraying the modified super-hydrophobic coating onto the surface of the semi-cured bonding base layer in multiple passes, curing at room temperature for 5 minutes to form a first coating layer, spraying a PDMS-curing agent solution on the surface of the first coating layer and curing at a curing temperature of 120° C. for 5 minutes to obtain a semi-cured layer;

[0013] S4: spraying a modified super-hydrophobic coating on the surface of the semi-cured layer, curing it at room temperature for 5 minutes, forming a second coating layer after curing, spraying a PDMS-curing agent solution on the surface of the second coating layer and curing it, curing it at 100-120°C for 1-2 hours or at room temperature for 1-7 days to obtain a super-hydrophobic nanocomposite coating.

[0014] In some embodiments, step S4 is repeated 1-4 times to obtain a super-hydrophobic nanocomposite coating.

[0015] In some embodiments, the ratio of the super-hydrophobic nano-coating and the resin in the modified super-hydrophobic coating in S4 is greater than the ratio of the super-hydrophobic nano-coating and the resin in the modified super-hydrophobic coating in S3.

[0016] In some embodiments, the particle size ratio of the nano-silicon dioxide to the nano-silicon powder is 1:(4-40), the particle size range of the nano-silicon dioxide is 15-50 nm, and the particle size range of the nano-silicon powder is 200-600 nm.

[0017] In some embodiments, the low surface energy substance includes at least one of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 1H,1H,2H,2H-heptadecafluorodecyltriethoxysilane;

[0018] The mass ratio of the nano-silicon dioxide and nano-silicon powder: the low surface energy substance: the anhydrous ethanol is 1: (0.07-0.22): (6.67-11.1);

[0019] When the mass of the nano-silicon dioxide and the nano-silicon powder is 12 g, the mass ratio of the nano-silicon dioxide to the nano-silicon powder is 1:(0.33-3).

[0020] In some embodiments, the preparation process of the PDMS-curing agent solution includes: adding PDMS and curing agent into tetrahydrofuran and ultrasonically dispersing them to obtain a PDMS-curing agent solution, wherein the mass ratio of PDMS:curing agent:tetrahydrofuran is 1:0.1:(5-25).

[0021] In some embodiments, the resin includes at least one of a two-component epoxy resin, a special epoxy resin, a high-temperature resistant epoxy resin, a wrapped epoxy resin, a low-molecular-weight 650-polyamide resin, a high-purity epoxy resin, or a silicone resin, and the mass ratio of the resin to anhydrous ethanol is 1:(1-6), and the mass ratio of the clear solution to the super-hydrophobic nanocoating is 1:(1-8).

[0022] In some embodiments, the spraying process parameters are: spraying air pressure 0.3-0.7 MPa, spraying distance 15-20 mm;

[0023] The contact object includes a rigid matrix / soft matrix, the rigid matrix includes metal, wood, polymer hard objects, concrete and ceramic products, and the soft matrix includes polymer soft objects.

[0024] In some embodiments, the bonding coating includes a mixed liquid obtained by ultrasonically dispersing E-7 glue and acetone for 10-30 minutes.

[0025] In some embodiments, the mass ratio of E-7 glue to acetone is 1:(0.5-3).

[0026] The second aspect of the present invention provides a long-lasting and robust super-hydrophobic nano-gradient composite coating prepared according to the above preparation method.

[0027] Beneficial effects of the present invention:

[0028] 1. The present invention selects nano-silicon dioxide and nano-silicon micropowder as main hydrophobic material components, optimizes super-hydrophobic nano-coating by designing the content ratio, mass ratio and particle size ratio of nano-silicon dioxide and nano-silicon micropowder, and simultaneously modifies the two in a mixed solution. Nano-scale silicon dioxide particles and nano-silicon micropowder have the same main element composition, and the two can be bonded to form a fixed distribution phase, so that after being modified by resin, they can be evenly distributed and have super-hydrophobic properties. Moreover, since they can form a fixed distribution phase, complicated mixing process is avoided, and the process production process is simplified;

[0029] 2. The present invention utilizes resin to modify nano-silicon dioxide and nano-silicon powder. The chemical bonding between the resin and silicon dioxide provides bonding force between the nano-particles and between the coating and the bonding bottom layer, and the bonding bottom layer improves the adhesion of the coating.

[0030] 3. The present invention uses a bottom composite technology to pre-place a high-strength adhesive (E-7 glue) to bond the bottom layer, and sprays a super-hydrophobic nano-coating to prepare the coating. While improving the roughness, the high-strength adhesive (E-7 glue) is combined with the bottom layer to achieve super-hydrophobic properties. The coating surface is resistant to various liquids such as beverages, milk, ink, muddy water, sewage, etc., and has stain resistance and self-cleaning functions;

[0031] 4. The long-lasting and strong super-hydrophobic nano-gradient composite coating prepared by the present invention uses PDMS, which is hydrophobic, alkali-resistant and has high bonding strength, as a transition layer. The strong hydrogen bonding between PDMS and silica and the cross-linking and curing with the high-strength adhesive further improve the super-hydrophobicity, strength, chemical durability and long-term effectiveness of the coating. The adhesion of the paint film tested using the cross-hatch method was grade 0, and the pencil hardness of the coating was 2H; the micro-nanostructure of the coating surface was strong, the Cassie-Baxter state of water droplets on the coating surface was more stable, the static contact angle of water droplets reached 176.1°, and the contact angle hysteresis was 0.9°; after immersion in solutions with different pH values ​​for 24 hours, the contact angle of the coating was significantly higher than 150°, and after immersion in a pH = 7 aqueous solution and a 3.5wt% NaCl solution for 30 days, the coating still showed a superhydrophobic state; after 70 cycles of tape stripping, the contact angle of the coating surface was still higher than 150°, and the coating could still maintain superhydrophobic properties when abraded 400 cm on 600-mesh sandpaper under a load of 500g; at the same time, after the coating was placed in a natural environment for one year, there was no obvious change on the coating surface and it still had superhydrophobic properties.

[0032] 5. The long-lasting and robust super-hydrophobic nano-gradient composite coating substrate prepared by the present invention has a wide range of applications. It can be sprayed or brushed on metal materials, inorganic materials such as ceramics, concrete and cement, and hard or soft substrates such as polymers. The coating has good bonding strength and can be prepared on a large area on non-planar complex structure substrates. The required equipment and process are simple, efficient, low-cost, and suitable for on-site construction. In addition, the coating can be used for corrosion and anti-biological adhesion on the outer surfaces of engineering equipment components, corrosion resistance and drag reduction on ship surfaces, mildew and dust prevention of wood and building materials, and various occasions such as the outer surfaces of various industrial parts and the inner walls of pipelines that require anti-fouling, dust prevention, and corrosion resistance.

[0033] The present invention can prepare super-hydrophobic coatings on a large area on various complex structure substrates with simple process, high efficiency, suitability for on-site construction and low cost. The prepared super-hydrophobic nanocomposite coating not only has excellent super-hydrophobic properties, but also has excellent chemical stability, mechanical stability and thermal stability, thereby improving the long-term effectiveness and robustness of the super-hydrophobic nanocomposite coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 (a)-(h) are contact angle diagrams of super-hydrophobic nanocomposite coatings prepared in Examples 1-3 and Comparative Examples 1-5, respectively;

[0035] Figure 2 The scanning electron microscope morphology images of the super-hydrophobic nanocomposite coating prepared in Example 3 at different magnifications are shown;

[0036] Figure 3The contact angle and contact angle hysteresis diagram of the super-hydrophobic nanocomposite coating prepared in Example 3 after tape stripping for different times;

[0037] Figure 4 The contact angle and contact angle hysteresis diagram of the super-hydrophobic nanocomposite coating prepared in Example 3 after being abraded at different times;

[0038] Figure 5 The contact angle and contact angle hysteresis diagram of the super-hydrophobic nanocomposite coating prepared in Example 3 after being immersed in a pH = 1-14 solution for 24 hours;

[0039] Figure 6 The contact angles and contact angle hysteresis diagrams of the super-hydrophobic nanocomposite coating prepared in Example 3 after being immersed in acid solutions with pH = 1, base solutions with pH = 13, and neutral solutions with pH = 7 for different times;

[0040] Figure 7 This is a graph showing the anti-fouling and self-cleaning test results of the super-hydrophobic nanocomposite coating prepared in Example 3 tested according to the method of Test Example 6. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0042] Unless otherwise specified, the experimental materials and reagents used in the following examples are all currently available and commercially available. Where specific techniques or conditions are not specified in the examples, they can be carried out according to conventional techniques or conditions disclosed in the art.

[0043] In the following embodiments, spraying is adopted, and the process parameters of spraying are set as follows: spraying air pressure 0.7 MPa, spraying distance 20 mm.

[0044] Example 1 (step S4 is not repeated)

[0045] A method for preparing a long-lasting and durable super-hydrophobic nano-gradient composite coating comprises the following steps:

[0046] S1: 6 g of nano-silica with a particle size of 30 nm, 6 g of nano-silicon powder with a particle size of 300-400 nm, and 1.5 g of 1H,1H,2H,2H-perfluorooctyltriethoxysilane were added to 100 g of anhydrous ethanol, and ultrasonically dispersed for 60 minutes at a power of 400 W and a time interval of 5 seconds to obtain a uniformly dispersed super-hydrophobic nano-coating;

[0047] 5 g of high-purity epoxy resin and 5 g of low-molecular-weight 650-polyamide resin were added to 10 g of anhydrous ethanol and ultrasonically dispersed for 30 minutes to obtain a clear solution;

[0048] 5 g of the super-hydrophobic nano-coating was mixed with 10 g of the clear solution, and mechanically stirred for 25 minutes at a rate of 400 r / min to obtain a first modified super-hydrophobic coating.

[0049] S2: 15 g of E-7 glue was added to 12 g of acetone and ultrasonically dispersed for 30 minutes to obtain a uniform adhesive coating;

[0050] 5 g of bonding coating was evenly sprayed on the clean steel plate surface to form a uniform bonding layer, and cured at 120° C. for 10 minutes to form a semi-cured bonding base layer.

[0051] S3: 5 g of the first modified super-hydrophobic coating prepared in S1 was evenly sprayed on the semi-cured bonding base layer and cured at room temperature of 25° C. for 5 minutes to form a first coating layer;

[0052] 10 g of PDMS and 1 g of curing agent (PDMS (Sylgard 184)) were added to 5 g of tetrahydrofuran and ultrasonically dispersed for 30 minutes to obtain a first PDMS-curing agent solution;

[0053] 5 g of the first PDMS-curing agent solution was sprayed on the surface of the first coating layer and cured at 120° C. for 5 minutes to obtain a first semi-cured layer.

[0054] S4: 10 g of the super-hydrophobic nano-coating obtained in S1 was mixed with 5 g of the clarified solution obtained in S1, and mechanically stirred for 25 minutes at a rate of 400 r / min to obtain a second modified super-hydrophobic nano-coating; then, 5 g of the second modified super-hydrophobic nano-coating was uniformly sprayed on the surface of the first semi-cured layer in multiple passes, and cured at room temperature of 25° C. for 5 minutes to form a second coating layer;

[0055] 10 g of PDMS and 1 g of curing agent (PDMS (Sylgard 184)) were added to 15 g of tetrahydrofuran and ultrasonically dispersed for 30 minutes to obtain a second PDMS-curing agent solution. 5 g of the second PDMS-curing agent solution was sprayed on the surface of the second coating layer and cured at 120° C. for 5 minutes to obtain a second semi-cured layer.

[0056] Heating and curing stage: curing at 120°C for 1.5 hours to obtain a long-lasting and durable super-hydrophobic nano-gradient composite coating.

[0057] Example 2 (repeat step S4 once)

[0058] A method for preparing a long-lasting and durable super-hydrophobic nano-gradient composite coating comprises the following steps:

[0059] Steps S1-S4 are the same as those in Example 1, with the addition of step S5;

[0060] S5: Repeat step S4 once: 20 g of the super-hydrophobic nano-coating obtained in S1 was mixed with 5 g of the clear solution obtained in S1, and mechanically stirred for 25 minutes at a rate of 400 r / min to obtain a third modified super-hydrophobic nano-coating;

[0061] 5 g of the third modified super-hydrophobic nano coating was evenly sprayed on the surface of the second semi-cured layer in multiple passes and cured at room temperature for 5 minutes to obtain a third coating layer;

[0062] 10 g of PDMS and 1 g of curing agent (PDMS (Sylgard 184)) were added to 25 g of tetrahydrofuran and ultrasonically dispersed for 30 minutes to obtain a third PDMS-curing agent solution. 5 g of the third PDMS-curing agent solution was sprayed on the surface of the third coating layer and cured.

[0063] Heating and curing stage: curing at 120°C for 1.5 hours to obtain a long-lasting and durable super-hydrophobic nano-gradient composite coating.

[0064] Example 3 (repeat step S4 twice)

[0065] A method for preparing a long-lasting and durable super-hydrophobic nano-gradient composite coating comprises the following steps:

[0066] Steps S1-S4 are the same as those in Example 1, with the addition of steps S5 and S6;

[0067] S5: Repeat step S4 once, which is the same as step S5 in Example 2, and cure at 120° C. for 5 minutes to obtain a third semi-cured layer;

[0068] S6: Repeat step S4 once: 20 g of the super-hydrophobic nano-coating obtained in S1 was mixed with 5 g of the clear solution obtained in S1, and mechanically stirred for 25 minutes at a rate of 400 r / min to obtain a fourth modified super-hydrophobic nano-coating;

[0069] 5 g of the fourth modified super-hydrophobic nano coating was evenly sprayed on the surface of the third semi-cured layer in multiple passes and cured at room temperature for 5 minutes to obtain a fourth coating layer;

[0070] 10 g of PDMS and 1 g of curing agent (PDMS (Sylgard 184)) were added to 25 g of tetrahydrofuran and ultrasonically dispersed for 30 minutes to obtain a fourth PDMS-curing agent solution. 5 g of the fourth PDMS-curing agent solution was sprayed on the surface of the fourth coating layer and cured.

[0071] Heating and curing stage: curing at 120°C for 1.5 hours to obtain a long-lasting and durable super-hydrophobic nano-gradient composite coating.

[0072] Comparative Example 1 (Compared with Example 1, gradient spraying was not performed to verify the effect of the prepared composite coating)

[0073] Steps S1-S3 are the same as those in Example 1;

[0074] Heating and curing stage: curing at 120°C for 1.5 hours to obtain a super-hydrophobic nanocomposite coating.

[0075] Comparative Example 2 (Compared with Example 1, the raw material of the super-hydrophobic nano-coating is only nano-silicon dioxide, verifying the effect of the prepared composite coating)

[0076] The difference between step S1 and step S1 of Example 1 is that 12 g of nano-silica and 1.5 g of 1H,1H,2H,2H-perfluorooctyltriethoxysilane are added to 100 g of anhydrous ethanol, and ultrasonically dispersed for 60 minutes at a power of 400 W and a time interval of 5 seconds to obtain a uniformly dispersed super-hydrophobic nano-coating;

[0077] The other steps of S1 and S2, S3, and S4 are the same as those of S1 and S2, S3, and S4 in Example 1;

[0078] Heating and curing stage: curing at 120°C for 1.5 hours to obtain a super-hydrophobic nano-gradient composite coating.

[0079] Comparative Example 3 (Compared with Example 1, the raw material of the super-hydrophobic nano coating is only nano-silicon powder, verifying the effect of the prepared composite coating)

[0080] The difference between step S1 and step S1 of Example 1 is that 12 g of nano-silicon powder and 1.5 g of 1H,1H,2H,2H-perfluorooctyltriethoxysilane are added to 100 g of anhydrous ethanol, and ultrasonic crushing and dispersion are performed for 60 minutes, with the ultrasonic setting power being 400 W and the ultrasonic time interval being 5 s, to obtain a uniformly dispersed super-hydrophobic nano-coating;

[0081] The other steps of S1 and S2, S3, and S4 are the same as those of S1 and S2, S3, and S4 in Example 1;

[0082] Heating and curing stage: curing at 120°C for 1.5 hours to obtain a super-hydrophobic nano-gradient composite coating.

[0083] Comparative Example 4 (Compared with Comparative Example 1, the same amount of PDMS-curing agent solution as that of Comparative Example 1 was used together with E-7 glue as the bonding base layer to verify the effect of the prepared composite coating)

[0084] Step S1 is the same as that of Comparative Example 1;

[0085] S2: Add 15 g of E-7 glue to 12 g of acetone and ultrasonically disperse for 30 minutes to obtain a mixed solution;

[0086] 10 g of PDMS and 1 g of curing agent (PDMS (Sylgard 184)) were added to 5 g of tetrahydrofuran and ultrasonically dispersed for 30 minutes to obtain a PDMS-curing agent solution;

[0087] The PDMS-curing agent solution and the mixed solution are mixed evenly to obtain a bonding coating;

[0088] S3: 5 g of the bonding coating was evenly sprayed on the clean steel plate surface to form a uniform bonding layer, and cured at 120° C. for 10 minutes to form a semi-cured bonding base layer.

[0089] S4: 5 g of the first modified super-hydrophobic coating prepared in S1 was evenly sprayed on the semi-cured bonding base layer and cured at room temperature of 25° C. for 5 minutes to form a first coating layer;

[0090] Heating and curing stage: curing at 120°C for 1.5 hours to obtain a super-hydrophobic nanocomposite coating.

[0091] Comparative Example 5 (Compared with Example 1, the super-hydrophobic nano-coating was not modified with resin to verify the effect of the prepared composite coating)

[0092] S1: 6 g of nano-silica with a particle size of 30 nm, 6 g of nano-silicon powder with a particle size of 300-400 nm, and 1.5 g of 1H,1H,2H,2H-perfluorooctyltriethoxysilane were added to 100 g of anhydrous ethanol, and ultrasonically dispersed for 60 minutes at a power of 400 W and a time interval of 5 seconds to obtain a uniformly dispersed super-hydrophobic nano-coating;

[0093] S2: 15 g of E-7 glue was added to 12 g of acetone and ultrasonically dispersed for 30 minutes to obtain a uniform adhesive coating;

[0094] 5 g of bonding coating was evenly sprayed on the clean steel plate surface to form a uniform bonding layer, and cured at 120° C. for 10 minutes to form a semi-cured bonding base layer.

[0095] S3: 5 g of the super-hydrophobic coating prepared in S1 was evenly sprayed on the semi-cured adhesive base layer and cured at room temperature of 25° C. for 5 minutes to form a first coating layer;

[0096] 10 g of PDMS and 1 g of curing agent (PDMS (Sylgard 184)) were added to 5 g of tetrahydrofuran and ultrasonically dispersed for 30 minutes to obtain a first PDMS-curing agent solution;

[0097] 5 g of the first PDMS-curing agent solution was sprayed on the surface of the first coating layer and cured at 120° C. for 5 minutes to obtain a first semi-cured layer.

[0098] S4: 5 g of super-hydrophobic nano-coating is evenly sprayed on the surface of the first semi-cured layer in multiple passes, and cured at room temperature of 25° C. for 5 minutes to form a second coating layer;

[0099] 10 g of PDMS and 1 g of curing agent (PDMS (Sylgard 184)) were added to 15 g of tetrahydrofuran and ultrasonically dispersed for 30 minutes to obtain a second PDMS-curing agent solution. 5 g of the second PDMS-curing agent solution was sprayed on the surface of the second coating layer and cured at 120° C. for 5 minutes to obtain a second semi-cured layer.

[0100] Heating and curing stage: curing at 120°C for 1.5 hours to obtain a super-hydrophobic nano-gradient composite coating.

[0101] Test example

[0102] The super-hydrophobic nanocomposite coatings prepared in Examples 1-3 and Comparative Examples 1-5 were tested according to the following test method:

[0103] 1. Contact angle test: The contact angle (CA) and contact angle hysteresis (CAH) of the coating surface were measured using a drop shape analyzer DSA30. The water droplet size was 10 μL. The contact angle and contact angle hysteresis were measured at five different locations on each coating surface, and the average value was taken.

[0104] 2. Surface morphology test: The morphology of the prepared samples was observed using a scanning electron microscope.

[0105] 3. Chemical durability test: Hydrochloric acid (HCl) and deionized water were used to prepare a corrosive aqueous solution with a pH of 1-6, and sodium hydroxide (NaOH) and deionized water were used to prepare a corrosive aqueous solution with a pH of 8-14. The coating was immersed in the corrosive solutions with different pH values ​​and in a 3.5wt% NaCl solution (pH = 7) for 24 hours. The coating was then removed and dried for a period of time, and the CA and CAH of the coating surface were measured using a 10μL water droplet. The coating was immersed in pH = 1, 7, 13 solutions and a 3.5wt% NaCl solution (pH = 7) for different periods of time, then removed and dried, and the CA and CAH of the coating surface were measured using a 10μL water droplet.

[0106] 4. Mechanical durability test: This includes a sandpaper abrasion test and an ultrasonic test. The superhydrophobic surface of the coating sample was placed face-down against a horizontal 600-grit sandpaper. A 500g weight was then placed on the back of the coating sample. A steel ruler was used to push the coating back and forth along a straight line at a constant speed, each movement distance being 10cm. One round trip constituted one cycle. After every five cycles, a 10μL water droplet was used to measure the surface CA and CAH of the coating.

[0107] 5. Coating Adhesion Test: Stick a special 3M test tape to the surface of the super-hydrophobic coating, then place a 1kg weight on the tape and keep it there for 5 minutes. Remove the weight and peel off the tape. One peeling cycle is considered one cycle. Use a 10μL water droplet to measure the CA and CAH of the coating surface.

[0108] 6. Antifouling and Self-Cleaning Test: Hold the coating with tweezers and place it in a beaker of muddy water. Let it sit for a while, then remove it and observe whether there is any residual sewage on the coating surface. Place the coating in a glass petri dish at a certain angle (<10°). Sprinkle soil, chalk dust, gravel and other contaminants on the coating surface. Drip deionized water from above the coating to observe whether the contaminants on the coating surface are completely removed.

[0109] Table 1: Contact angle test results of super-hydrophobic nanocomposite coatings prepared in Examples 1-3 and Comparative Examples 1-5

[0110]

[0111] As can be seen from Table 1, the contact angles and contact angle hysteresis of the coatings obtained in Examples 1-3 are not much different. The static contact angle of the water droplet is as high as 176.1°, and the contact angle hysteresis is 0.9°. The water droplet is spherical on the coating surface. Figure 1 (ac) As shown. The contact angle of the coating prepared in Comparative Example 1 is 168.1°. Figure 1As shown in (d), the contact angle hysteresis increases slightly. Comparative Examples 2 and 3 are coatings prepared from a single raw material. The contact angles of the coatings are only 150, 1° and 152.5°, and the contact angle hysteresis is as high as 12.8° and 9.4°. The water droplets on the coating surface are oblate spherical, as shown in Figure 1 Compared with Comparative Example 1, the contact angle of Comparative Example 4 is reduced to 164.1°, as shown in (e) and (f). Figure 1 As shown in (g), the contact angle hysteresis increases to 5.7°. The direct mixing of the PDMS-curing agent solution and the E-7 adhesive coating affects the bonding effect, which reduces the contact angle of the coating. The contact angle of the coating prepared in Comparative Example 5 without resin modification is 157.9°, and the contact angle hysteresis is 6.2°. Figure 1 Table 2: Contact angle test results of the super-hydrophobic nanocomposite coatings prepared in Examples 1-3 and Comparative Examples 1-5 after immersion in 3.5 wt% NaCl solution for 24 hours

[0112]

[0113] As can be seen from Table 2, after immersion in a 3.5 wt% NaCl solution for 24 hours, the contact angles and contact angle hysteresis of Examples 1-3 decreased slightly, with the static water droplet contact angle remaining as high as 175.8° and the contact angle hysteresis remaining at 0.9°. However, the contact angles of Comparative Examples 1-5 decreased significantly, with the contact angles of Comparative Examples 1 and 4 exceeding 150°, indicating that the coating surfaces still retained superhydrophobic properties, while Comparative Examples 2, 3, and 4 had lost their superhydrophobic properties.

[0114] Table 3: Contact angle test results of super-hydrophobic nanocomposite coatings prepared in Examples 1-3 and Comparative Examples 1-5 after 5 cycles of wear

[0115]

[0116] As can be seen in Table 3, after five abrasion cycles, i.e., at an abrasion distance of 100 cm, the contact angles and contact angle hysteresis of Examples 1-3 decreased slightly, with static water droplet contact angles greater than 168.0° and contact angle hysteresis less than 2.5°. Compared to Examples 1-3, the contact angles of Comparative Examples 1-5 decreased significantly. Comparative Examples 1 and 4 still maintained superhydrophobicity, with contact angles greater than 150°. However, the contact angles of Comparative Examples 2, 3, and 5 were less than 150°, indicating that the coating surfaces had lost their superhydrophobicity.

[0117] Figure 2(a) and (b) are microscopic morphologies of the coating surface prepared in Example 3. The surface of the steel substrate is evenly covered with micro-nano-sized protrusions, which are composed of resin-bonded nanoparticles. The surface of the protrusions is evenly covered with nano-silicon powder and nano-silicon dioxide. The roughness of the coating surface is large, and the Cassie-Baxter state of water droplets on the coating surface is more stable. In addition, no bonding bottom layer was found on the coating surface. The use of modified super-hydrophobic nano-coatings and high-temperature curing can effectively improve the adhesion, chemical stability and mechanical stability of the coating. According to GBT 6739-2022, the adhesion of the coating is level 0; after 50 cycles of the tape stripping test, the contact angle of the coating is still higher than 150°, as shown in FIG. Figure 3 As shown, it shows that the coating surface can still maintain a certain hydrophobicity.

[0118] Figure 4 The contact angle test results of the coating prepared in Example 3 after the wear test. Figure 4 It can be seen that after 20 cycles of wear, the contact angle of the coating is 153.8°. Observing the morphology of the coating after the wear test, the coating surface is still white, indicating that the chemical bond between the modified super-hydrophobic nano-coating and the high-strength adhesive improves the bonding strength between the nanoparticles and between the nanoparticles and the bonding base layer. In addition, the PDMS transition layer, as a connected whole, forms a strong hydrogen bond with silica on the one hand, and cross-links and solidifies with the E-7 glue on the other hand, so that the coating can maintain a certain super-hydrophobicity before being completely worn out, and the mechanical stability of the coating has been stably and effectively improved.

[0119] The coating prepared in Example 3 was immersed in solutions with different pH values ​​for 24 hours and then the contact angle test was performed. Figure 5 , the coating surface still maintains superhydrophobic properties, with a contact angle greater than 150°, a contact angle hysteresis less than 10°, and it is observed that the coating surface is not wetted.

[0120] The coating prepared in Example 3 was immersed in solutions with pH values ​​of 1, 7, and 13 for different periods of time, and its contact angle was measured. The results are shown in FIG. Figure 6 As shown in the figure, after immersion in a solution with a pH of 7 for 30 days, the contact angle of the coating surface is still 150.9°, the contact angle hysteresis is 9.5°, and the coating surface still maintains superhydrophobic properties; after immersion in solutions with pH of 1 and 13 for 4 days, the contact angles of the coating surface are 150.6° and 150.3°, respectively, and the contact angle hysteresis is 9.3° and 9.5°, respectively.

[0121] Furthermore, after continuous immersion in a 3.5wt% saline solution for 30 days, the coating prepared in Example 3 showed no wetting. Even after one year in a natural environment, the coating remained superhydrophobic. These experimental results demonstrate that the coating can resist corrosion from corrosive ions for extended periods in harsh environments, including acidic, alkaline, neutral, and saline solutions, demonstrating excellent chemical durability.

[0122] Depend on Figure 7 It can be seen that after the coating was immersed in muddy water and red ink for 5 minutes, no muddy water remained on the coating surface. In addition, the rolling water droplets can easily carry away the chalk dust on the coating surface. These results show that the coating has excellent self-cleaning and anti-fouling properties, and the coating surface is resistant to muddy water, sewage, ink and other liquids.

[0123] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a long-lasting and robust super-hydrophobic nano-gradient composite coating, characterized in that: The steps include: S1: Modifying a super-hydrophobic nano-coating by resin to obtain a modified super-hydrophobic coating; S2: Spray the bonding coating onto the surface of the contact object and solidify it to form a semi-cured bonding base layer; S3: spraying the modified super-hydrophobic coating on the surface of the semi-cured bonding base layer to form a first coating layer after curing, spraying a PDMS-curing agent solution on the surface of the first coating layer and curing it to obtain a semi-cured layer; S4: spraying a modified super-hydrophobic coating on the surface of the semi-cured layer to form a second coating layer after curing, spraying a PDMS-curing agent solution on the surface of the second coating layer and curing it to obtain a super-hydrophobic nano-composite coating; optionally, repeating step S4 at least once to obtain a super-hydrophobic nano-composite coating; The ratio of the super-hydrophobic nano-coating and the resin in the modified super-hydrophobic coating in S4 is greater than the ratio of the super-hydrophobic nano-coating and the resin in the modified super-hydrophobic coating in S3.

2. The method for preparing a long-lasting and robust super-hydrophobic nano-gradient composite coating according to claim 1, wherein The preparation process of the super-hydrophobic nano coating comprises: adding nano-silicon dioxide, nano-silicon powder and low surface energy material into anhydrous ethanol, and performing ultrasonic crushing and dispersion to obtain the super-hydrophobic nano coating.

3. The method for preparing a long-lasting and robust super-hydrophobic nano-gradient composite coating according to claim 2, wherein: The preparation process of the modified super-hydrophobic coating comprises: adding resin into anhydrous ethanol, performing ultrasonic dispersion to obtain a clear solution, and mixing the super-hydrophobic nano coating with the clear solution to obtain the modified super-hydrophobic coating.

4. The method for preparing a long-lasting and robust super-hydrophobic nano-gradient composite coating according to claim 3, wherein: The preparation process of the PDMS-curing agent solution includes: adding PDMS and a curing agent into tetrahydrofuran and ultrasonically dispersing the mixture to obtain the PDMS-curing agent solution, wherein the mass ratio of the PDMS:curing agent:tetrahydrofuran is 1:0.1:(5-25).

5. The method for preparing a long-lasting and robust super-hydrophobic nano-gradient composite coating according to claim 4, wherein: The particle size ratio of the nano-silicon dioxide to the nano-silicon powder is 1:(4-40), the particle size range of the nano-silicon dioxide is 15-50 nm, and the particle size range of the nano-silicon powder is 200-600 nm.

6. The method for preparing a long-lasting and robust super-hydrophobic nano-gradient composite coating according to claim 5, wherein: The low surface energy substance includes at least one of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 1H,1H,2H,2H-heptadecafluorodecyltriethoxysilane; The mass ratio of the nano-silicon dioxide and nano-silicon powder: low surface energy material: anhydrous ethanol is 1: (0.07-0.22): (6.67-11.1); The mass of the nano-silicon dioxide and nano-silicon powder is 12 g, and the mass ratio of the nano-silicon dioxide to the nano-silicon powder is 1:(0.33-3).

7. The method for preparing a long-lasting and robust super-hydrophobic nano-gradient composite coating according to claim 6, wherein: The resin is selected from at least one of a two-component epoxy resin, a low molecular weight 650-polyamide resin or a silicone resin, the mass ratio of the resin to anhydrous ethanol is 1:(1-6), and the mass ratio of the clear solution to the super-hydrophobic nano coating is 1:(1-8).

8. The method for preparing a long-lasting and robust super-hydrophobic nano-gradient composite coating according to claim 1, wherein: The spraying process parameters are: spraying air pressure 0.3-0.7MPa, spraying distance 15-20mm; The contact object is a rigid matrix or a soft matrix. The rigid matrix includes metal, wood, polymer hard objects, concrete and ceramic products, and the soft matrix includes polymer soft objects.

9. The method for preparing a long-lasting and robust super-hydrophobic nano-gradient composite coating according to claim 8, wherein: The bonding coating comprises a mixed liquid obtained by ultrasonically dispersing E-7 glue and acetone; In S2, the bonding coating is sprayed on the surface of the contact object and cured at 80-120° C. for 3-15 minutes to form a semi-cured bonding base layer; In the S3, the modified super-hydrophobic coating is sprayed on the surface of the semi-cured bonding bottom layer through multiple passes, and cured at room temperature for 5 minutes to form a first coating layer. The PDMS-curing agent solution is sprayed on the surface of the first coating layer and cured at a curing temperature of 120° C. for 5 minutes to obtain a semi-cured layer; In the S4, a modified super-hydrophobic coating is sprayed on the surface of the semi-cured layer and cured at room temperature for 5 minutes. After curing, a second coating layer is formed. A PDMS-curing agent solution is sprayed on the surface of the second coating layer and cured. The solution is cured at 100-120° C. for 1-2 hours or at room temperature for 1-7 days to obtain a super-hydrophobic nanocomposite coating.

10. A long-lasting and robust super-hydrophobic nano-gradient composite coating prepared by the preparation method according to any one of claims 1 to 9.

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