A durable superhydrophobic coating and its preparation method

Abstract

This invention relates to a durable superhydrophobic coating and its preparation method. The coating is obtained by preparing a three-dimensional polymer skeleton with a cross-linked / hyper-cross-linked network through a thermal evaporation method. This invention produces a superhydrophobic coating with superior mechanical abrasion resistance and high-pressure water impact resistance, providing an effective and low-cost new strategy for the preparation of high-durability superhydrophobic coatings, which can promote the practical application of superhydrophobic coatings in fields such as construction and transportation.

Description

Technical Field

[0001] This invention belongs to the field of superhydrophobic coatings, and specifically relates to a durable superhydrophobic coating and its preparation method. Background Technology

[0002] Superhydrophobic coatings have been widely used in construction, microfluidics, de-icing, corrosion protection, and fairings over the past few decades. Currently, methods for obtaining superhydrophobic surfaces include etching, CVD, and low surface energy material modification. However, superhydrophobic coatings prepared by these methods generally suffer from poor durability. To address this issue, many scholars have proposed their own methods. Among them, constructing superhydrophobic coatings by combining superhydrophobic inorganic components with polymer components that have excellent adhesion is considered one of the effective strategies to solve the problem of poor coating durability.

[0003] Patent CN201510280756, "A Transparent Wear-Resistant Superhydrophobic Coating and Its Preparation Method and Coating Process", introduces a method for preparing a transparent wear-resistant superhydrophobic coating. The obtained superhydrophobic coating can maintain its superhydrophobic properties after friction. However, the solvents used in the preparation process are highly toxic solutions such as acetone and xylene, which do not meet environmental protection requirements, and the construction process is complicated.

[0004] Patent CN104418509A, “A method for preparing a wear-resistant and superhydrophobic coating”, prepares a wear-resistant and superhydrophobic antireflective coating in the visible and near-infrared light regions. However, the preparation process uses ammonia water and requires a high-temperature calcination process, which is relatively complex and not energy-efficient or environmentally friendly.

[0005] Therefore, it is necessary to find a new superhydrophobic coating and its preparation process. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a durable superhydrophobic coating and its preparation method, which provides an effective and low-cost new strategy for the preparation of high-durability superhydrophobic coatings, and can promote the practical application of superhydrophobic coatings in fields such as construction and transportation.

[0007] The present invention provides a durable superhydrophobic coating, which is obtained by preparing a three-dimensional polymer skeleton with a cross-linked / hyper-cross-linked network by a thermal evaporation method.

[0008] Preferably, the polymer is one or more of polycarbonate (PC), polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP), and polyethylene (PE).

[0009] The coating has a large number of micropores and a thickness of 100-200 μm.

[0010] The coating of this invention achieves superhydrophobicity and can withstand more than 400 bidirectional friction cycles or water impacts for more than 20 hours. During the preparation process, the coating forms a 3D network framework structure capable of accommodating superhydrophobic nanoparticles. The crosslinking agent allows for control of the coating structure by changing conditions such as temperature during the bonding process. Furthermore, introducing polymer molecular chains into crosslinking bridges forms a hypercrosslinked structure that strengthens the polymer network framework, resulting in a robust bonding force.

[0011] This invention also provides two methods for preparing durable superhydrophobic coatings, comprising the following steps:

[0012] (1) Prepare polymer nanoparticles with a particle size controlled between 400-500 nm;

[0013] (2) By thermal evaporation of crosslinking agent, polymer nanoparticles and superhydrophobic nanoparticles are constructed to form a three-dimensional polymer network framework;

[0014] (3) The three-dimensional polymer network skeleton is formed into a durable superhydrophobic coating by thermal evaporation of the crosslinking agent and secondary hypercrosslinking.

[0015] or,

[0016] (1) Prepare polymer nanoparticles with a particle size controlled between 400-500 nm;

[0017] (2) A superhydrophobic coating was prepared by blending polymer nanoparticles and superhydrophobic nanoparticles and spraying, followed by hot pressing;

[0018] (3) The superhydrophobic coating obtained by hot pressing is subjected to hot steaming of a crosslinking agent to obtain a superhydrophobic coating that has undergone hot pressing and hot crosslinking treatment;

[0019] (4) The superhydrophobic coating after hot pressing and thermal crosslinking is formed by hot steaming of the crosslinking agent and secondary super crosslinking.

[0020] The superhydrophobic nanoparticles are one or more of the following: fluorinated chain silica (FC-SiO2), zinc sulfide fluoride (F-ZnS), magnesium fluoride (MgF2), calcium fluoride (CaF2), barium fluoride (BaF2), sodium fluoride (NaF), lithium fluoride (LiF), and silicon (Si).

[0021] The crosslinking agent is one or more of divinylbenzene (DVB), carbon tetrachloride (CCl4), dicumyl peroxide (DCP), benzoyl peroxide (BPO), diethylenetriamine (DTA), ethyl methacrylate (EMA), and maleic anhydride (MA).

[0022] The mass ratio of the polymer nanoparticles to the superhydrophobic nanoparticles is 2-4:1; the amount of the crosslinking agent added is 120-300 mL / m² of the sample surface. 2 .

[0023] The polymer nanoparticles and superhydrophobic nanoparticles are spherical, needle-shaped, rod-shaped, or chain-shaped.

[0024] The steaming temperature is 50-80℃, and the steaming time is 10-30 minutes.

[0025] The hot pressing process parameters are as follows: the roller pressure is set to 1-2 kPa, the rolling speed is set to 2-5 cm / s, and the hot roller temperature is set to 150-200℃.

[0026] This invention utilizes thermal evaporation to prepare a three-dimensional polymer framework with a crosslinked / hypercrosslinked network, thereby constructing a highly durable superhydrophobic coating. The prepared superhydrophobic coating comprises a loose structure formed by the stacking of polymer microspheres. Based on the dissolution of polymer microspheres by the crosslinking agent and the ease with which the crosslinking agent self-polymerizes to form a crosslinked network, thermal evaporation of the crosslinking agent initiates self-polymerization to form a crosslinked network. This network interweaves with the linear polymer molecular chains to form an interpenetrating polymer crosslinked network. Combined with the dissolution and bonding mechanism of the crosslinking agent on the polymer microspheres, a highly stable polymer framework structure is obtained. Subsequently, another crosslinking agent is thermally evaporated to hypercrosslink the linear polymer molecular chains in the framework, introducing -CO- crosslinking bridges into the molecular chains, thereby forming a polymer hypercrosslinked network. This further enhances the stability of the polymer framework, ultimately achieving the preparation of a highly durable superhydrophobic coating.

[0027] The features of this invention are:

[0028] (1) Based on the properties of crosslinking agent to dissolve polymer and easy self-polymerization and crosslinking, a polymer skeleton of "polymer physical bonding + molecular chain interpenetrating crosslinking network" was constructed by crosslinking agent thermal evaporation technology. The thermal evaporation preparation process was explored, and combined with hot pressing process, a superhydrophobic coating with good mechanical friction resistance and high pressure water impact resistance was prepared.

[0029] (2) Based on the Friedel-Crafts hypercrosslinking reaction mechanism, a two-stage thermal evaporation process is employed. First, a three-dimensional polymer network framework is constructed by thermal evaporation of a crosslinking agent. Then, a thermally evaporated hypercrosslinking agent is used to hypercrosslink the linear polymer molecular chains, introducing -CO- crosslinking bridges into the linear polymer molecular chains in the polymer framework, thereby forming a hypercrosslinked network and enhancing the stability of the polymer framework. For example, using carbon tetrachloride (CCl4) as a crosslinking agent and anhydrous aluminum chloride (AlCl3) as an initiator, the thermal evaporation hypercrosslinking process was explored. Combined with hot pressing, a superhydrophobic coating with superior mechanical abrasion resistance and high-pressure water impact resistance was prepared.

[0030] Beneficial effects

[0031] (1) The present invention uses physical bonding of similar dissolves to weave the polymer long chain containing superhydrophobic nanoparticles and the self-polymerized crosslinking agent chain to form an entangled fabric-like structure. Then, a -CO- crosslinking bridge is introduced through chemical crosslinking to form a super-crosslinked structure between the two long chains. The superhydrophobic nanoparticles are partially encapsulated in the polymer and partially exposed on the coating surface to form a micro-nano rough structure, so that the coating has excellent superhydrophobic properties.

[0032] (2) The coating of the present invention has a large number of micropores and the thickness is controlled between 100-200μm. The small molecules of crosslinking agent can enter the interior of the coating to form a self-similar structure from top to bottom. The surface after friction is similar to the original surface structure, which can ensure continuous superhydrophobic performance and improve the durability of the coating accordingly.

[0033] (3) The present invention prepares a superhydrophobic coating with better mechanical abrasion resistance and high-pressure water impact resistance. After 420 cycles of linear wear at 6 kPa pressure, it still maintains superhydrophobic properties. After being impacted by water flow at 25 kPa pressure for 22 hours, the surface superhydrophobic properties do not decrease significantly and the surface structure is not damaged. This provides an effective and low-cost new strategy for the preparation of high-durability superhydrophobic coatings, which can promote the practical application of superhydrophobic coatings in fields such as construction and transportation. Attached Figure Description

[0034] Figure 1 The superhydrophobic properties (a) and contact angle (b, before friction) of the secondary supercrosslinked durable superhydrophobic coating after hot pressing in Example 2 are shown.

[0035] Figure 2 The surface SEM image of the secondary hypercrosslinked durable superhydrophobic coating after hot pressing in Example 2. Detailed Implementation

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] Example 1

[0038] (1) Preparation of polystyrene (PS) nanospheres

[0039] Spherical PS nanoparticles with a particle size of 400–500 nm were prepared by a conventional hydrothermal synthesis method. Under N2 protection, using anhydrous ethanol as solvent and styrene as raw material, potassium persulfate (KPS) solution was added, and spherical PS nanoparticles with a particle size of 400–500 nm were synthesized under mechanical stirring.

[0040] (2) Preparation of ultra-durable superhydrophobic coating by thermal crosslinking method

[0041] The specific process is as follows: Place the aluminum sheet (200 mm × 40 mm × 0.1 mm) in acetone and immerse it for 20 minutes to remove the oily dirt on the surface of the aluminum sheet. Then, clean the immersed aluminum sheet with deionized water and anhydrous ethanol respectively and put it in a 65℃ oven to dry for later use.

[0042] The prepared PS nanospheres were ultrasonically mixed with fluorinated chain silica (FC-SiO2) for 2 h to form a homogeneous solution with a PS to FC-SiO2 mass ratio of 3:1. 30 mL of this solution was placed in a spray gun with a pressure of 0.8 MPa. The spray gun was positioned 20 cm from the aluminum sheet, and sprayed evenly in both vertical and horizontal directions at a speed of 10 cm / s. During spraying, the coating should be kept semi-wet to ensure a smooth surface for subsequent hydrophobicity testing. The sprayed aluminum sheet was then cut to dimensions of 100 mm × 40 mm × 0.1 mm for later use.

[0043] The prepared superhydrophobic coating was subjected to thermal evaporation: The prepared aluminum sheet was placed in the center of a glass container. To ensure that the coating was fully enveloped by divinylbenzene (DVB) vapor, the glass container should not be too large, just slightly larger than the sample. 0.5 mL of DVB was added. After the oil bath was heated to 75°C, the container was sealed and placed in the oil bath for thermal evaporation for 20 minutes to obtain the thermally evaporated PS coating. At this point, the coating had a contact angle of 160° and a roll-off angle of 2°. The coating could withstand more than 70 cycles of bidirectional friction while still maintaining its superhydrophobic properties, with a contact angle of 150° and a roll-off angle of 4°.

[0044] (3) Preparation of ultra-durable superhydrophobic coatings by secondary hypercrosslinking method

[0045] The specific preparation process is as follows: (1) Place 6 mL of CCl4 and 0.3 g of AlCl3 in a three-necked flask, heat to 75°C, and magnetically stir for 20 min at a stirring rate of 350 r / min to obtain a CCl4 / AlCl3 mixed solution; (2) Place the prepared thermally evaporated PS coating in a sealed glass container, preheat it in an oil bath at 75°C for 2 min, and then place 0.85 mL of the prepared CCl4 / AlCl3 mixed solution in it to perform a second thermal evaporation of the coating to obtain an ultra-durable superhydrophobic coating. At this time, after 340 bidirectional friction cycles, the contact angle of the coating is 151° and the roll-off angle is 7°, still exhibiting superhydrophobic properties.

[0046] Example 2

[0047] (1) Preparation of polystyrene (PS) nanospheres

[0048] Spherical PS nanoparticles with a particle size of 400–500 nm were prepared by a conventional hydrothermal synthesis method. Under N2 protection, using anhydrous ethanol as solvent and styrene as raw material, potassium persulfate (KPS) solution was added, and spherical PS nanoparticles with a particle size of 400–500 nm were synthesized under mechanical stirring.

[0049] (2) Preparation of ultra-durable superhydrophobic coatings after hot pressing and thermal cross-linking treatment

[0050] First, a superhydrophobic coating was prepared by spraying a mixture of PS nanospheres and fluorinated chain silica (FC-SiO2) at a mass ratio of 3:1. Then, hot pressing was performed with the roller pressure set to 1 kPa, the rolling speed to 3 cm / s, and the hot roller temperature to 180℃. Finally, 0.5 mL of DVB was added to the hot-pressed coating. After the oil bath temperature reached 75℃, the container was sealed and placed in the oil bath for hot steaming for 20 minutes, ultimately obtaining a superhydrophobic coating that underwent hot-pressing and thermal cross-linking treatment. At this point, after 200 cycles of bidirectional friction, the coating's contact angle was 153° and its roll-off angle was 3°, still exhibiting superhydrophobic properties.

[0051] (3) Preparation of ultra-durable superhydrophobic coatings by hot-pressing followed by secondary hypercrosslinking

[0052] The specific preparation process is as follows: (1) Place 6 mL of CCl4 and 0.3 g of AlCl3 in a three-necked flask, heat to 75°C, and magnetically stir for 20 min at a stirring rate of 350 r / min to obtain a CCl4 / AlCl3 mixed solution; (2) Place the prepared superhydrophobic coating after hot pressing and thermal crosslinking treatment in a sealed glass container, preheat in an oil bath at 75°C for 2 min, and then place 0.85 mL of the prepared CCl4 / AlCl3 mixed solution in it to perform a second thermal evaporation on the coating to obtain an ultra-durable superhydrophobic coating. At this time, the contact angle of the coating can reach 159.3° and the roll-off angle is 2°. After 400 cycles of bidirectional friction, the contact angle of the coating is 150° and the roll-off angle is 7°, still exhibiting superhydrophobic properties.

Claims

1. A method for preparing a highly durable superhydrophobic coating with a self-similar structure, comprising the following steps: (1) Prepare polymer nanoparticles with a particle size controlled between 400-500 nm; the polymer nanoparticles are one or more of polycarbonate, polystyrene, polyvinyl chloride, polypropylene, and polyethylene; (2) A superhydrophobic coating is prepared by blending polymer nanoparticles with superhydrophobic nanoparticles and spraying, followed by hot pressing; the superhydrophobic nanoparticles are one or more of fluorinated chain silica, fluorinated zinc sulfide, magnesium fluoride, calcium fluoride, barium fluoride, sodium fluoride, lithium fluoride, and silicon. (3) The superhydrophobic coating obtained by hot pressing is subjected to hot steaming of the first crosslinking agent to obtain a superhydrophobic coating that has undergone hot crosslinking treatment after hot pressing; The first crosslinking agent is divinylbenzene; (4) The superhydrophobic coating after hot pressing and heat cross-linking is formed by heat steaming with the second cross-linking agent and then super-cross-linking. The second cross-linking agent is carbon tetrachloride.

2. The preparation method according to claim 1, characterized in that: The mass ratio of polymer nanoparticles to superhydrophobic nanoparticles in step (2) is 2-4:

1.

3. The preparation method according to claim 1, characterized in that: The polymer nanoparticles and superhydrophobic nanoparticles in step (2) are spherical, needle-shaped, rod-shaped, or chain-shaped.

4. The preparation method according to claim 1, characterized in that: The hot pressing process parameters in step (2) are as follows: the roller pressing pressure is set to 1-2 kPa, the rolling speed is set to 2-5 cm / s, and the hot roller temperature is set to 150-200℃.

5. The preparation method according to claim 1, characterized in that: The amount of the first and second crosslinking agents added is 120-300 mL / m² of the sample surface. 2 .

6. The preparation method according to claim 1, characterized in that: The steaming temperature in steps (3) and (4) is 50-80℃ and the steaming time is 10-30min.

7. A highly durable superhydrophobic coating with a self-similar structure obtained by the preparation method as described in claim 1, characterized in that: The coating is obtained by preparing a three-dimensional polymer skeleton with a cross-linked / hyper-cross-linked network through a thermal evaporation method.

8. The durable superhydrophobic coating according to claim 7, characterized in that: The coating has a large number of micropores and a thickness of 100-200 μm.

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