Polyethylene surface super-hydrophobic coating as well as preparation method and application thereof

Abstract

The invention provides a polyethylene surface super-hydrophobic coating as well as a preparation method and application thereof, and belongs to the technical field of hydrophobic materials. A coating with the following three-layer structure is formed on polyethylene with an active hydroxyl surface, a TiO2 bottom layer, a KH560 middle layer and a SiO2 surface layer are sequentially arranged on the polyethylene surface, the TiO2 bottom layer is formed by a TiO2 precursor solution, and the TiO2 precursor solution is formed by a reaction of a TiCl4 hydrochloric acid solution and hydrogen peroxide; the KH560 intermediate layer is formed by a hydrolyzed KH560 solution; the SiO2 surface layer is formed by a mixed solution of hydrophilic SiO2 and hydrophobic SiO2, a certain mass ratio of the SiO2 mixed solution is met, the prepared polyethylene surface super-hydrophobic coating has excellent mechanical stability, a coated polyethylene substrate shows excellent self-cleaning, wear-resistant and super-hydrophobic performance, and the polyethylene surface super-hydrophobic coating has excellent self-cleaning, wear-resistant and super-hydrophobic properties. The method is suitable for the fields of plastic pipeline antifouling self-cleaning, acid and alkali corrosion resistance and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrophobic materials, and more specifically, to a polyethylene surface super-hydrophobic coating and a preparation method and application thereof. Background Art

[0002] Superhydrophobic surfaces have shown broad application potential in many fields due to their unique properties, such as self-cleaning, anti-fouling, and anti-corrosion. Superhydrophobic surfaces refer to surfaces with a static water contact angle greater than 150° and a rolling angle less than 10°.

[0003] Traditional methods for preparing super-hydrophobic surfaces include chemical vapor deposition, sol-gel method, electrochemical deposition, spray coating, dip coating, etc. Although these methods can prepare surfaces with super-hydrophobic properties, they often have problems such as high cost, complex process, and difficulty in large-scale preparation. In addition, the durability, wear resistance and stability of these coatings are also key factors that limit their practical applications.

[0004] The preparation of super-hydrophobic coatings on the surface of polyethylene (PE) substrates usually requires increasing the surface roughness by introducing micro-nano structures and reducing the surface energy by chemical modification. However, the prior art often faces the following challenges when preparing super-hydrophobic coatings on polyethylene surfaces: many existing methods use expensive equipment and complex processes, which limit the possibility of large-scale production; the coatings are easily worn in actual use, resulting in a decrease in super-hydrophobic performance; the performance stability of some coatings in extreme environments (such as high temperature, acid-base environment) is insufficient; the bonding force between the coating and the polyethylene substrate is insufficient, affecting the durability of the coating.

[0005] The prior art discloses a The invention relates to a super hydrophobic composite coating and a preparation method and application thereof, belonging to the technical field of hydrophobic materials. Titanium dioxide and hydrophobic silicon dioxide nanoparticles are used as nanomaterials, ethyl orthosilicate is introduced as a silicon source precursor, and ( Titanium dioxide and hydrophobic silica are modified by aminopropyl) triethoxysilane and hexadecyltrimethoxysilane. However, hexadecyltrimethoxysilane, i.e., long-chain (C≥12) alkylsiloxane, is used for modification. Long-chain siloxane is prone to self-crosslinking during the solution preparation process, loses reaction sites, and cannot react well with the substrate. The degree of modification of silica is insufficient, and the surface roughness needs to be improved. The mechanical stability of the coating is poor, and the wear resistance of the corresponding substrate material after coating is poor.

[0006] Therefore, the present invention proposes a polyethylene surface super-hydrophobic coating with excellent mechanical stability, which has important research significance and application value. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art, the primary purpose of the present invention is to provide a polyethylene surface super-hydrophobic coating, the prepared polyethylene surface super-hydrophobic coating has excellent mechanical stability, and the coated polyethylene substrate exhibits excellent self-cleaning, wear-resistant and super-hydrophobic properties.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned super-hydrophobic coating on the polyethylene surface.

[0009] Another object of the present invention is to provide another method for preparing the above-mentioned super-hydrophobic coating on the surface of polyethylene.

[0010] Another object of the present invention is to provide an application of the above-mentioned super-hydrophobic coating on the polyethylene surface.

[0011] To achieve the above object, the present invention adopts the following technical solutions:

[0012] The present invention protects a polyethylene surface super-hydrophobic coating, and forms a coating having the following three-layer structure on the polyethylene having an active hydroxyl surface:

[0013] From the polyethylene surface, there are TiO2 bottom layer, KH560 middle layer and SiO2 surface layer;

[0014] The TiO2 bottom layer is formed by a TiO2 precursor solution, which is formed by the reaction of a TiCl4 hydrochloric acid solution and hydrogen peroxide; the KH560 middle layer is formed by a hydrolyzed KH560 solution; and the SiO2 surface layer is formed by a mixed solution of hydrophilic SiO2 and hydrophobic SiO2.

[0015] The mass ratio of hydrophilic SiO2 to hydrophobic SiO2 in the mixed solution is 1-6:1-6;

[0016] The hydrophobic SiO2 is modified by short-chain siloxane with carbon atoms ≤ 6.

[0017] A large number of active hydroxyl groups exist on the rough structure of TiO2 produced by the present invention, and chemical reactions are easy to occur.

[0018] The present invention uses hydrolyzed KH560. A large number of active hydroxyl groups are generated at both ends of KH560 after hydrolysis. Due to the ring-opening effect of octadecylamine, KH560 is cross-linked to form a regular three-dimensional network, which wraps and fixes hydrophilic and hydrophobic silica particles, and reacts with the rough structure of TiO2 to form a multi-level rough microstructure, thereby improving the durability of the coating.

[0019] The polyethylene surface super-hydrophobic coating of the present invention has a three-layer structure, TiO2 and SiO2 are connected by new covalent bonds through KH560, and the prepared coating also has covalent bonds with the polyethylene substrate, thereby achieving close connection between the coatings and between the coatings and the substrate, so that the super-hydrophobic coating after drying obtains excellent mechanical stability, and the polyethylene substrate after coating exhibits excellent self-cleaning, antibacterial, and acid and alkali corrosion resistance properties.

[0020] The hydrophobic SiO2 of the present invention is obtained by modifying a short-chain siloxane having a carbon number of ≤6, because a long-chain (C≥12) alkylsiloxane is used for modification, and the long-chain siloxane is easy to self-crosslink in the process of configuring the solution, loses the reaction site, cannot react well with the substrate, and cannot fully modify the silicon dioxide. And the hydrophilic and hydrophobic silicon dioxide are compounded, and the hydrophobic SiO2 provides a low surface energy for the coating, and the hydrophilic SiO2 increases the roughness of the coating, and when the ratio is too high, the coating roughness is insufficient, and when it is too low, the coating surface energy is too high, and at an appropriate ratio, the roughness and surface energy can be adapted to each other, and the super-hydrophobic effect is achieved.

[0021] Preferably, the method for producing the polyethylene having an active hydroxyl surface is selected from one of the following two methods:

[0022] (1) UVO technology: Use UVO machine to treat polyethylene to generate a large number of active hydroxyl groups; or

[0023] (2) Immerse polyethylene in a mixed solution of concentrated sulfuric acid and hydrogen peroxide.

[0024] Specifically, (1) UVO technology: placing polyethylene in a UVO machine for 20 minutes to generate a large number of active hydroxyl groups; or

[0025] (2) Immerse the polyethylene in a mixed solution of concentrated sulfuric acid and hydrogen peroxide, wherein the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 1:2 to 4.

[0026] Specifically, the concentration of the concentrated sulfuric acid is 95-98%; the concentration of the hydrogen peroxide is 28-32%.

[0027] Further preferably, the polyethylene having an active hydroxyl surface is produced by UVO technology.

[0028] Preferably, the method for preparing the TiO2 precursor solution comprises the following steps:

[0029] Add TiCl4 and hydrochloric acid solution to water at 0-10°C, adjust pH to 6-10, and mix well. Add the filtered solid to hydrogen peroxide solution and mix well to obtain a TiO2 precursor solution.

[0030] Specifically, the method for preparing the TiO2 precursor solution comprises the following steps:

[0031] Add TiCl4 acid solution (0.09M, 20wt% HCl) to water at 0-10°C, adjust pH to 6-10, and stir for 24-48h. Add the filtered solid to hydrogen peroxide solution, stir for 8-10 hours, and a TiO2 precursor solution can be obtained. The dilution volume ratio of the TiCl4 acid solution is 1:10-13, and the solute to solvent volume ratio of the hydrogen peroxide solution is 1:3-5.

[0032] Preferably, the method for preparing the hydrolyzed KH560 solution comprises the following steps:

[0033] Mix water, ethanol and KH560 evenly, add octadecylamine and react for 1 to 3 hours; the mass ratio of water, ethanol, KH560 and octadecylamine is 16:80 to 85:5:1.

[0034] Hydrophilic SiO2 is a silicon dioxide material with hydrophilic groups, which can be stably dispersed in the water phase. SiO2 itself is hydrophilic. The hydrophilic SiO2 prepared by the following method has better hydrophilicity.

[0035] Preferably, the preparation method of the hydrophilic SiO2 comprises the following steps:

[0036] Mix water, sodium hydroxide, ethanol and tetraethyl orthosilicate, and react them at 40°C to 50°C in an inert gas atmosphere for 6 to 10 hours to obtain SiO2; wherein the volume ratio of water: ammonium hydroxide: ethanol: tetraethyl orthosilicate is 1:1.5 to 1.7:20:1.

[0037] More preferably, the inert gas atmosphere in the method for preparing the hydrophilic SiO2 is argon.

[0038] Preferably, the mixed solution of hydrophilic SiO2 and hydrophobic SiO2 is a mixture of 50 mg SiO2 dissolved in 5 mL ethanol.

[0039] Preferably, the preparation method of the hydrophobic SiO2 is: SiO2, ethanol, ammonia water, and short-chain siloxane are mixed and stirred for two to three hours, and the modified SiO2 is obtained by filtering and washing with ethanol, wherein the mass ratio of SiO2, ethanol, ammonia water, and short-chain siloxane is 1:100:10:7-9.

[0040] Preferably, the short-chain siloxane is selected from at least one of methyltriethoxysilane, ethyltriethoxysilane or propyltriethoxysilane.

[0041] The present invention provides a method for preparing a super hydrophobic coating on a polyethylene surface, comprising the following steps:

[0042] S1. Bottom layer: A large number of active hydroxyl groups are generated on the surface of polyethylene to form a TiO2 nano-rough structure, which is cured at high temperature to form a bottom layer;

[0043] S2. Intermediate layer: The hydrolyzed KH560 solution is coated on the bottom layer and cured at high temperature to form an intermediate layer;

[0044] S3. Surface layer: A mixture of hydrophilic SiO2 and hydrophobic SiO2 is coated on the surface of the middle layer and cured at high temperature.

[0045] Preferably, the method for preparing the TiO2 nano-rough structure comprises the following steps:

[0046] The TiO2 precursor solution is formed on the polyethylene surface by at least one of immersion method, spin coating method or spray coating method.

[0047] Preferably, the coating method is selected from at least one of spin coating, spray coating or immersion coating.

[0048] Preferably, the high temperature curing temperature is 80°C to 120°C.

[0049] The present invention also protects another method for preparing a super hydrophobic coating on a polyethylene surface, comprising the following steps:

[0050] A TiO2 precursor solution, a hydrolyzed KH560 solution, and a mixed solution of hydrophilic SiO2 and hydrophobic SiO2 are placed in three hoppers respectively, and three-layer co-extruded to obtain a three-layer co-extruded film, which is coated on a polyethylene surface with an active hydroxyl surface and cured at 120°C; wherein the mass ratio of the TiO2 precursor solution, the hydrolyzed KH560 solution, the hydrophilic SiO2 and the hydrophobic SiO2 mixed solution is 1:1:1-2.

[0051] The application of the above-mentioned polyethylene surface super-hydrophobic coating in the preparation of anti-fouling and self-cleaning plastic pipes is also within the protection scope of the present invention.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] The invention provides a polyethylene surface super-hydrophobic coating, which has a three-layer structure and comprises a TiO2 precursor solution, a hydrolyzed KH560 solution, and a mixed solution of hydrophilic SiO2 and hydrophobic SiO2. The super-hydrophobic coating has excellent mechanical stability after drying, and the polyethylene substrate after coating exhibits excellent self-cleaning, wear-resistant and super-hydrophobic properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0055] Figure 1 The water contact angle of the super-hydrophobic coating spin-coated on the polyethylene surface in Example 1 of the present invention;

[0056] Figure 2 The water contact angle of the super-hydrophobic coating spin-coated on the polyethylene surface in Example 2 of the present invention;

[0057] Figure 3 The water contact angle of the super-hydrophobic coating spin-coated on the polyethylene surface in Example 3 of the present invention;

[0058] Figure 4 The water contact angle of the super-hydrophobic coating spin-coated on the polyethylene surface in Example 4 of the present invention;

[0059] Figure 5 The water contact angle of the super hydrophobic coating spin-coated on the polyethylene surface in Example 5 of the present invention;

[0060] Figure 6 The water contact angle of the super-hydrophobic coating spin-coated on the polyethylene surface in Example 6 of the present invention;

[0061] Figure 7 The water contact angle of the super hydrophobic coating spin-coated on the polyethylene surface in Example 8 of the present invention;

[0062] Figure 8 The water contact angle of the super hydrophobic coating spin-coated on the polyethylene surface of Comparative Example 1 of the present invention;

[0063] Fig. 9 The water contact angle of the super hydrophobic coating spin-coated on the polyethylene surface of Comparative Example 2 of the present invention;

[0064] Fig.10 The water contact angle of the super hydrophobic coating spin-coated on the polyethylene surface of Comparative Example 3 of the present invention;

[0065] Fig.11 The water contact angle of the super hydrophobic coating spin-coated on the polyethylene surface of Comparative Example 4 of the present invention;

[0066] Fig.12 The water contact angle of the super hydrophobic coating spin-coated on the polyethylene surface of Comparative Example 5 of the present invention;

[0067] Fig.13 The water contact angle of the super hydrophobic coating spin-coated on the polyethylene surface in Comparative Example 6 of the present invention;

[0068] Fig.14 This is the TEM surface morphology of the super-hydrophobic coating spin-coated on the polyethylene surface in Example 1 of the present invention;

[0069] Fig.15 The TEM surface morphology of the super-hydrophobic coating spin-coated on the polyethylene surface in Example 2 of the present invention;

[0070] Fig.16 This is the TEM surface morphology of the super-hydrophobic coating spin-coated on the polyethylene surface of Example 3 of the present invention;

[0071] Fig.17 The TEM surface morphology of the super-hydrophobic coating spin-coated on the polyethylene surface in Example 4 of the present invention;

[0072] Fig.18 This is the TEM surface morphology of the super-hydrophobic coating spin-coated on the polyethylene surface in Example 5 of the present invention;

[0073] Fig.19 This is a self-cleaning performance test of the super-hydrophobic coating spin-coated on the polyethylene surface of Example 1 of the present invention. DETAILED DESCRIPTION

[0074] In order to more clearly and completely describe the technical solution of the present invention, the present invention is further described in detail by specific examples below. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention. Various changes can be made within the scope of the present invention. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0075] This embodiment provides a series of methods for preparing super-hydrophobic coatings on polyethylene surfaces, and the components are shown in Table 1.

[0076] Table 1 Raw material components of Examples 1 to 9

[0077]

[0078]

[0079] This comparative example provides a series of methods for preparing super-hydrophobic coatings on polyethylene surfaces, and the components are shown in Table 2.

[0080] Table 2 Raw material components of comparative examples 1 to 7

[0081]

[0082] Example 1 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0083] 27.03mL hydrochloric acid was added to 22.30mL deionized water to prepare an acid solution, and then 0.49mL TiCl4 liquid was added to the acid solution to prepare 50mL TiCl4 solution (0.09M, 0.2wt% HCl). Under a temperature of 5°C, 36mL TiCl4 solution was dissolved in a 1000mL single-mouth bottle containing 300mL deionized water under strong magnetic stirring. After 30 minutes, an ammonia solution was added dropwise to adjust the pH value to 7, and the mixture was stirred vigorously for 24 hours. A fine white precipitate was obtained by filtration, and the mixture was washed with deionized water for several times. The presence of chloride ions was detected with a silver nitrate solution. Finally, the obtained precipitate was dissolved in 80mL deionized water at room temperature, and 28mL H2O2 was added dropwise to the mixture and stirred for 4 hours to form a transparent light yellow TiO2 precursor aqueous solution.

[0084] The PVC film was treated in a UVO machine for 20 min, then immersed in a TiO2 solution for 15 s, and the excess solvent was dried in an oven at 90 °C.

[0085] 10 mL of deionized water and 3 mL of KH560 were added to 50 mL of ethanol, sealed with plastic wrap, stirred, and ultrasonically dispersed for 30 min, and then 0.6 g of octadecylamine (ODA) was added to the uniformly dispersed solution. Finally, the mixture was stirred and ultrasonically dispersed for 2 h to form a hydrolyzed KH560 intermediate connection layer solution, and the PVC film with TiO2 deposited was spin-coated with the hydrolyzed KH560 solution and cured and dried at 90 ° C. The entire process, including spin coating and drying, was repeated 3 times.

[0086] Mix 9mL of deionized water, 14.4mL of ammonia solution, and 180mL of ethanol at 40°C, and stir. Quickly add 9mL of tetraethyl orthosilicate, and react in an argon atmosphere for 8 hours. Finally, centrifuge the mixture to obtain SiO2 particles, wash them two to three times with ethanol, and dry them at high temperature to obtain hydrophilic SiO2. Pour 0.5g of SiO2 into a single-mouth bottle, add 50mL of anhydrous ethanol and 5mL of ammonia solution, stir evenly at 25°C, slowly drip 3.8mL of methyltriethoxysilane, stir for 2h, centrifuge to obtain solid particles, and wash them three times with ethanol, and dry them at high temperature to obtain hydrophobic SiO2.

[0087] 25 mg of hydrophilic SiO2 and 25 mg of hydrophobic SiO2 were added to 10 ml of ethanol solution, ultrasonicated for 30 minutes, and the solution was spin-coated onto the above substrate and cured and dried at 120°C.

[0088] Example 2 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0089] The scheme is the same as Example 1, except that 17 mg of hydrophilic SiO2 and 34 mg of hydrophobic SiO2 are added to 10 mL of ethanol solution, ultrasonicated for 30 minutes, the solution is spin-coated onto the above substrate, and cured and dried at 120°C.

[0090] Example 3 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0091] The scheme is the same as Example 1, except that 50 mg of hydrophilic SiO2 is added to 10 mL of ethanol solution, ultrasonicated for 30 minutes, the solution is spin-coated onto the above substrate, and cured at high temperature.

[0092] Example 4 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0093] The scheme is the same as Example 1, except that: 34 mg of hydrophilic SiO2 and 17 mg of hydrophobic SiO2 are added to 10 mL of ethanol solution, ultrasonicated for 30 minutes, the solution is spin-coated onto the above substrate, and cured and dried at 120°C.

[0094] Example 5 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0095] The scheme is the same as Example 1, except that: 50 mg of hydrophobic SiO2 is added to 10 mL of ethanol solution, ultrasonicated for 30 minutes, the solution is spin-coated onto the above substrate, and cured and dried at 120°C.

[0096] Example 6 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0097] The scheme is the same as Example 1, except that: 0.5 g of SiO2 is poured into a single-mouth bottle, 50 mL of anhydrous ethanol and 5 mL of ammonia water are added, and after stirring evenly at 25°C, 3.8 mL of ethyltriethoxysilane is slowly dripped in, stirred for 2 h, and solid particles are obtained by centrifugation, and washed three times with ethanol, and dried at high temperature to obtain hydrophobic SiO2.

[0098] 50 mg of hydrophobic SiO2 was added to 10 mL of ethanol solution, ultrasonicated for 30 minutes, and the solution was spin-coated onto the above substrate and cured and dried at 120°C.

[0099] Example 7 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0100] The scheme is the same as Example 1, except that the mass ratio of hydrophilic SiO2 to hydrophobic SiO2 is 6:1.

[0101] Example 8 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0102] The scheme is the same as Example 1, except that butyltriethoxysilane is used to modify the hydrophobic SiO2.

[0103] Example 9 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0104] 27.03mL hydrochloric acid was added to 22.30mL deionized water to prepare an acid solution, and then 0.49mL TiCl4 liquid was added to the acid solution to prepare 50mL TiCl4 solution (0.09M, 0.2wt% HCl). Under a temperature of 5°C, 36mL TiCl4 solution was dissolved in a 1000mL single-mouth bottle containing 300mL deionized water under strong magnetic stirring. After 30 minutes, an ammonia solution was added dropwise to adjust the pH value to 7, and the mixture was stirred vigorously for 24 hours. A fine white precipitate was obtained by filtration, and the mixture was washed with deionized water for several times. The presence of chloride ions was detected with a silver nitrate solution. Finally, the obtained precipitate was dissolved in 80mL deionized water at room temperature, and 28mL H2O2 was added dropwise to the mixture and stirred for 4 hours to form a transparent light yellow TiO2 precursor aqueous solution.

[0105] The PVC film was treated in a UVO machine for 20 min, then immersed in a TiO2 solution for 15 s, and the excess solvent was dried in an oven at 90 °C.

[0106] The TiO2 precursor solution, the hydrolyzed KH560 solution, the hydrophilic SiO2 and the hydrophobic SiO2 mixed solution are placed in three hoppers respectively, and three layers are co-extruded to obtain a three-layer co-extruded film, which is coated on polyethylene treated by a UVO machine, and the treatment method is the same as that of Example 1, and cured at 120°C; wherein the mass ratio of the TiO2 precursor solution, the hydrolyzed KH560 solution, the hydrophilic SiO2 and the hydrophobic SiO2 mixed solution is 1:1:1.5. The co-extrusion forming process includes an extrusion device of a screw extruder and a die head, the screw speed is 40rpm, and the temperature of the three hoppers is room temperature.

[0107] Comparative Example 1 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0108] The scheme is the same as Example 1, except that the topmost layer of silicon dioxide is not spin-coated, and there is only a TiO2 rough structure and a KH560 middle layer.

[0109] Comparative Example 2 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0110] The scheme is the same as Example 1, except that the TiO2 rough structure is not spin-coated.

[0111] Comparative Example 3: A super-hydrophobic coating on polyethylene surface and its preparation method and application

[0112] The scheme is the same as Example 1, except that the KH560 intermediate layer is not spin-coated.

[0113] Comparative Example 4: A super-hydrophobic coating on polyethylene surface and its preparation method and application

[0114] The scheme is the same as Example 1, except that a long-chain modifier having a carbon number greater than 6 is used to treat the hydrophobic SiO2.

[0115] Comparative Example 5: A super-hydrophobic coating on polyethylene surface and its preparation method and application

[0116] The scheme is the same as Example 1, except that the mass ratio of hydrophilic SiO2 to hydrophobic SiO2 is 0.5:7.

[0117] Comparative Example 6 A super hydrophobic coating on polyethylene surface and its preparation method and application

[0118] The scheme is the same as Example 1, except that the mass ratio of hydrophilic SiO2 to hydrophobic SiO2 is 7:0.5.

[0119] 2. Experimental results

[0120] Test indicators:

[0121] (1) Contact angle test: The coating prepared by the present invention is subjected to a contact angle test according to the test method of standard GB / T 30447-2013;

[0122] (2)TEM surface morphology;

[0123] (3) Self-cleaning test: self-cleaning performance of the prepared coating to different powder liquids (coffee powder, alkaline solution);

[0124] (4) Wear resistance test: The coating was placed face down on sandpaper (800 Cw), a 150 g weight was placed, and the hydrophobic angle of the coating was measured after each 25 cm movement, and the cycle was repeated multiple times.

[0125] 1. Contact angle test

[0126] Table 2 Performance parameters of Examples 1 to 9 and Comparative Examples 1 to 6

[0127]

[0128] like Figure 1 As shown, the contact angle of the coating prepared in Example 1 is 155.58°. Figure 2 As shown in , the contact angle of the prepared coating is 153.97°; Figure 3 As shown, the contact angle of the prepared coating is 150.00°; Figure 4 As shown, the contact angle of the prepared coating is 150.24°; Figure 5As shown, the contact angle of the prepared coating is 151.88°; Figure 6 As shown, the contact angle of the prepared coating is 151.32°; Figure 7 As shown, the contact angle of the prepared coating is 152.38°. The contact angle test proves that the coatings prepared in Examples 1 to 9 have super-hydrophobic properties.

[0129] like Figure 8 As shown, the contact angle of the prepared coating is 119.23°, proving that the combination of KH560 and TiO2 can prepare a coating with a certain hydrophobicity, but the contact angle is far less than that of the coating prepared in the embodiment. The main reason is that KH560 will produce a large number of hydrophilic active hydroxyl groups after hydrolysis.

[0130] like Figures 1 to 7 It can be seen that the contact angle of the hydrophobic coating made by adjusting the ratio of hydrophilic and hydrophobic SiO2 is greater than 150°. Hydrophobic SiO2 provides low surface energy for the coating, and hydrophilic SiO2 increases the roughness of the coating. When the ratio is too high, the coating roughness will be insufficient, and when it is too low, the coating surface energy will be too high. When the hydrophilic and hydrophobic ratio is moderate, that is, 3:3, the coating can show the best super hydrophobicity.

[0131] 2.TEM surface morphology

[0132] like Figures 14 to 18 It can be observed that the surface has a nano-scale rough structure, which proves that Examples 1 to 5 successfully prepared micro-nano rough structures that meet the requirements of super-hydrophobic coatings. From the 50,000 times magnified image, it can be seen that the hydrophilic SiO2 has active hydroxyl groups on the surface and is easy to agglomerate into larger particles, such as Figure 1 As shown. When the ratio of hydrophilic and hydrophobic SiO2 is appropriate, that is, hydrophilic SiO2: hydrophobic SiO2 = 1:1, the surface morphology is uniform and rough, showing super hydrophobic properties. When the hydrophobic SiO2 content is too high, methyltrimethoxysilane and the active groups that are not cross-linked with SiO2 will react with each other, so that the rough structure of silica is obscured, and the change in contact angle can also illustrate this problem.

[0133] 3. Self-cleaning test

[0134] Sprinkle coffee powder on the super-hydrophobic coating and rinse with water. It can be seen that there is almost no coffee powder left in the area rinsed with water; alkaline droplets on the coating can be completely absorbed by the pH test paper, indicating that the coating has a certain self-cleaning property ( Fig.19 ).

[0135] 4. Wear resistance test

[0136] Under the pressure of a 150g weight, after the coating moves 200cm, the contact angle does not change significantly, and the hydrophobicity of the coating is not seriously damaged, and it still maintains superhydrophobicity, indicating that the prepared coating has good wear resistance.

[0137] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A super hydrophobic coating on a polyethylene surface, characterized in that: A coating having the following three-layer structure is formed on polyethylene having an active hydroxyl surface: From the polyethylene surface, there are TiO2 bottom layer, KH560 middle layer and SiO2 surface layer; The TiO2 bottom layer is formed by a TiO2 precursor solution, which is formed by the reaction of a TiCl4 hydrochloric acid solution and hydrogen peroxide; the KH560 middle layer is formed by a hydrolyzed KH560 solution; and the SiO2 surface layer is formed by a mixed solution of hydrophilic SiO2 and hydrophobic SiO2. The mass ratio of hydrophilic SiO2 to hydrophobic SiO2 in the mixed solution is 1-6:1-6; The hydrophobic SiO2 is modified by short-chain siloxane with carbon atoms ≤ 6.

2. The polyethylene surface super-hydrophobic coating according to claim 1, characterized in that, The method for producing the polyethylene having an active hydroxyl surface is selected from one of the following two methods: (1) UVO technology: Use UVO machine to treat polyethylene to generate a large number of active hydroxyl groups; or (2) Immerse polyethylene in a mixed solution of concentrated sulfuric acid and hydrogen peroxide.

3. The polyethylene surface super-hydrophobic coating according to claim 1, characterized in that, The preparation method of the TiO2 precursor solution comprises the following steps: Add TiCl4 and hydrochloric acid solution to water at 0-10°C, adjust pH to 6-10, and mix well. Add the filtered solid to hydrogen peroxide solution and mix well to obtain a TiO2 precursor solution.

4. The polyethylene surface super-hydrophobic coating according to claim 1, characterized in that, The preparation method of the hydrolyzed KH560 solution comprises the following steps: Mix water, ethanol and KH560 evenly, add octadecylamine and react for 1 to 3 hours; the mass ratio of water, ethanol, KH560 and octadecylamine is 16:80 to 85:5:

1.

5. The polyethylene surface super-hydrophobic coating according to claim 1, characterized in that, The preparation method of the hydrophilic SiO2 comprises the following steps: Mix water, sodium hydroxide, ethanol and tetraethyl orthosilicate, and react them at 40°C to 50°C in an inert gas atmosphere for 6 to 10 hours to obtain SiO2; wherein the volume ratio of water: ammonium hydroxide: ethanol: tetraethyl orthosilicate is 1:1.5 to 1.7:20:

1.

6. The polyethylene surface super-hydrophobic coating according to claim 1, characterized in that, The short-chain siloxane is selected from at least one of methyltriethoxysilane, ethyltriethoxysilane and propyltriethoxysilane.

7. The method for preparing the polyethylene surface super-hydrophobic coating according to claim 1, characterized in that, The following steps are involved: S1. Bottom layer: A large number of active hydroxyl groups are generated on the surface of polyethylene to form a TiO2 nano-rough structure, which is cured at high temperature to form a bottom layer; S2. Intermediate layer: The hydrolyzed KH560 solution is coated on the bottom layer and cured at high temperature to form an intermediate layer; S3. Surface layer: A mixture of hydrophilic SiO2 and hydrophobic SiO2 is coated on the surface of the middle layer and cured at high temperature.

8. The preparation method according to claim 7, characterized in that: The preparation method of the TiO2 nano-rough structure comprises the following steps: The TiO2 precursor solution is formed on the polyethylene surface by at least one of immersion, spin coating or spray coating.

9. The method for preparing the polyethylene surface super-hydrophobic coating according to claim 1, characterized in that, The following steps are involved: A TiO2 precursor solution, a hydrolyzed KH560 solution, and a mixed solution of hydrophilic SiO2 and hydrophobic SiO2 are placed in three hoppers respectively, and three-layer co-extruded to obtain a three-layer co-extruded film, which is coated on a polyethylene surface with an active hydroxyl surface and cured at 120°C; wherein the mass ratio of the TiO2 precursor solution, the hydrolyzed KH560 solution, the hydrophilic SiO2 and the hydrophobic SiO2 mixed solution is 1:1:1-2.

10. Use of the polyethylene surface super-hydrophobic coating according to any one of claims 1 to 6 in the preparation of anti-fouling and self-cleaning plastic pipes.

Images