Fluorine-free monolithic superhydrophobic coating material, preparation method and application thereof

Abstract

The application belongs to the technical field of super-hydrophobic materials, and particularly relates to a fluorine-free integral super-hydrophobic coating material, a preparation method and application thereof. The fluorine-free porous integral super-hydrophobic coating prepared by a non-solvent phase separation process has low surface energy, high wear resistance and integral super-hydrophobicity. The micro-rough structure exists not only on the surface of the coating, but also in the internal multi-porous structure of the material. The new surface exposed after the coating is worn also has a micro-rough structure, which makes the coating have good mechanical stability of super-hydrophobicity, solves the durability problem of the super-hydrophobic coating in an abrasive environment, and is suitable for special engineering structure protection, metal mechanical corrosion prevention and oil-water separation and many other fields.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of super-hydrophobic materials, and particularly relates to a fluorine-free integral super-hydrophobic coating material and a preparation method and application thereof. BACKGROUND

[0002] Super-hydrophobic materials have very broad application prospects in many fields such as building protection, metal corrosion prevention, fiber fabric waterproofing, oil-water separation, pipeline transportation, etc. Taking building protection as an example, super-hydrophobic coating can effectively resist the erosion of water-soluble harmful ions into the internal structure of the engineering structure, and can also ensure the cleanliness and non-pollution of the surface of the engineering structure to a certain extent. Marine structures such as coastal wharfs and offshore wind turbines are in a high-humidity and high-salt-pollution service environment all year round, and therefore require super-hydrophobic coating for protection.

[0003] Super-hydrophobicity refers to the contact angle and rolling angle between the surface of a material and water being greater than 150° and less than 10°, respectively. The super-hydrophobicity of a material is mainly derived from two characteristics: one is the low surface energy of the material, and the other is the micron or nanometer level rough structure of the material surface. According to the Cassie-Baxter theory, the above two characteristics not only reduce the solid-liquid interfacial force, but also help to capture and store gas on the material surface, thereby further reducing the attraction between the solid and the liquid. The realization of the low surface energy of the material often requires the introduction of functional groups with low surface energy such as fluorine atoms, long alkyl chains, and benzene rings. There are many methods for constructing the rough structure of the material, including soaking, spraying, chemical vapor deposition, template method, chemical etching, plasma etching, electrospinning, and electrodeposition, etc.

[0004] At present, scholars have also mostly started from the above two points to improve the super-hydrophobic effect of the coating. For example, patent CN116769344B discloses a fluorinated graphene / SiO2 / fluorosilane composite material and a preparation method thereof, which mainly introduces SiO2 loaded with fluorinated graphene into resin coating to reduce the surface energy of the resin material. The coating can play the functions of long-acting antifouling and self-cleaning on the surface of different types of insulating substrates. Patent CN118325467B discloses a preparation method of a super-hydrophobic silicone rubber coating, which uses the low surface energy characteristics of silicone rubber in combination with the solvent phase separation method to prepare a super-hydrophobic coating with a micro-rough structure. The contact angle of the coating with water is greater than 150°, and the rolling angle is less than 8°, which has important application prospects in the fields of waterproofing, anti-pollution, and anti-icing, etc.

[0005] However, the existing super-hydrophobic coatings generally have defects such as large amount of fluorides and poor mechanical stability. In particular, the mechanical stability, the existing super-hydrophobic coating materials and preparation processes are difficult to achieve stable protection in long-term abrasive environments, such as marine service environments. SUMMARY

[0006] The object of this invention is to provide a kind of fluorine-free overall super-hydrophobic coating material and its preparation method and application.The overall super-hydrophobic coating material, fluorine-free and with strong mechanical stability, compared with traditional super-hydrophobic coating, the greatest advantage is that micro-rough structure is not only present in coating surface, and material interior is multi-microporous structure.Therefore, there is also micro-rough structure in the new surface exposed after coating is worn, which makes coating possess good super-hydrophobic mechanical stability, solves the durability problem of super-hydrophobic coating in abrasive environment.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] In the first aspect, the present invention provides a fluorine-free integral super-hydrophobic coating material, comprising an epoxy resin bonding layer and a super-hydrophobic polydimethylsiloxane surface layer loaded on its surface; the epoxy resin bonding layer is composed of an epoxy resin main agent, an epoxy resin curing agent and acetone; the super-hydrophobic polydimethylsiloxane surface layer is composed of a PDMS main agent, a PDMS curing agent, polyethylene powder and an aqueous solvent.

[0009] In some other embodiments, the epoxy resin main agent is one or more of bisphenol A epoxy resin E12, E20, E44, E51, bisphenol F epoxy resin NPEF-170, NPEF-187 or 4,5-epoxytetrahydrophthalic acid diglycidyl ester;

[0010] Alternatively, the epoxy resin curing agent is one or more of polyetheramine curing agent D230, T403, D400, D2000, FL1000, polyamide curing agent 650, 651, T31 modified amine curing agent, ethylenediamine curing agent or xylenediamine curing agent.

[0011] In some other embodiments, the mass ratio of the epoxy resin main agent to the epoxy resin curing agent is (2.5-3.5):1; the mass ratio of the epoxy resin main agent to acetone is (1-1.8):1.

[0012] In some other embodiments, the PDMS main agent and the PDMS curing agent are one or more of Dow Corning SYLGARD 184 and its supporting curing agent, Dow Corning SYLGARD 182 and its supporting curing agent, or Momentive RTV615 and its supporting curing agent;

[0013] Alternatively, the aqueous phase solvent is a solvent composed of ethanol and water;

[0014] Alternatively, the particle size of the polyethylene powder is 5 to 7 μm, and the number average molecular weight of the polyethylene powder is 50,000 to 80,000.

[0015] In some other embodiments, the mass ratio of the PDMS main agent to the PDMS curing agent is 10:(0.8~1.5); the mass ratio of the polyethylene powder to the PDMS main agent is (1~3):5; the mass ratio of the ethanol to water is (0.15~0.25):1; and the mass ratio of the PDMS main agent to the aqueous solvent is 1:(0.6~1.2).

[0016] In a second aspect, the present invention provides a method for preparing the fluorine-free integral super-hydrophobic coating material according to the first aspect, comprising the following steps:

[0017] (1) polyethylene powder, PDMS main agent, and PDMS curing agent are mixed to prepare a mixed powder, and then an aqueous phase solvent prepared by mixing water and ethanol is added dropwise to the mixed powder to prepare a water-in-oil silicone oil emulsion;

[0018] (2) mixing acetone, an epoxy resin main agent, and an epoxy curing agent to prepare an epoxy resin adhesive; spraying the epoxy resin adhesive on the surface of the substrate and pre-curing it to form an epoxy resin adhesive layer;

[0019] (3) Applying the water-in-oil silicone oil emulsion on the surface of the epoxy resin bonding layer, and forming a super-hydrophobic polydimethylsiloxane surface layer after vacuum defoaming, curing and drying; and polishing the super-hydrophobic polydimethylsiloxane surface layer to form a fluorine-free overall super-hydrophobic coating material.

[0020] In some other embodiments, in step (2), the compressed air pressure used for spraying is 0.15-0.35 MPa, the diameter of the airbrush is 0.3 mm, and the distance between the nozzle and the substrate is 4-6 cm;

[0021] Alternatively, the pre-curing step is: curing at 20-28° C. for 6-10 hours.

[0022] In some other embodiments, in step (3), the vacuum defoaming is: defoaming for 10 to 20 minutes at room temperature under an air pressure of -0.09 to -0.05 MPa;

[0023] Alternatively, the curing step is: curing at 55-70° C. for 4-8 hours;

[0024] Alternatively, the drying step is: drying at 100-115° C. for 12-24 hours.

[0025] In some other embodiments, in step (3), the polishing is performed using 300-1000 grit sandpaper at a pressure of 15-25 kPa;

[0026] Alternatively, the thickness of the fluorine-free overall super-hydrophobic coating material is 0.5 to 2 mm.

[0027] In a third aspect, the present invention provides an application of the fluorine-free integral super-hydrophobic coating material described in the first aspect in special engineering structure protection, metal mechanical corrosion protection or oil-water separation.

[0028] Beneficial effects of the present invention:

[0029] (1) The fluorine-free overall super-hydrophobic coating material prepared by the present invention has the advantages of overall super-hydrophobicity, high wear resistance, and no fluorine. Its water contact angle is greater than 153° and the rolling angle is less than 7.8°. After polishing with sandpaper, the contact angle of the fluorine-free overall super-hydrophobic coating material is still greater than 150°, and the super-hydrophobicity does not decline.

[0030] (2) The present invention utilizes the immiscible nature of oil and water to prepare a water-in-oil silicone oil emulsion using a simple mechanical stirring process. The water-in-oil silicone oil emulsion is composed of a PDMS main agent, a curing agent, polyethylene powder, and an ethanol / water solvent. The surface energy of PDMS and polyethylene is very low. After mixing with the ethanol / water solvent and stirring, the water phase microbubbles are evenly distributed within the oil phase, forming a water-in-oil silicone oil emulsion. Furthermore, the density of the polyethylene powder and the ethanol / water solution is very close to that of PDMS, which is the key to ensuring the uniform distribution of various substances within the emulsion. The emulsion can be prepared using only a simple physical process, is fluoride-free, has a uniform texture, and is relatively stable, making it convenient for subsequent coating and use.

[0031] (3) In the present invention, the epoxy resin adhesive is first sprayed onto the substrate surface and pre-cured for a period of time before the water-in-oil silicone oil emulsion is applied. The abundant hydroxyl groups in the epoxy resin can undergo hydrolysis and condensation reactions with the siloxane groups in the PDMS, ensuring that the cured super-hydrophobic silicone layer can adhere firmly.

[0032] (4) The present invention creatively adopts a non-solvent phase separation process to obtain a fluorine-free porous overall super-hydrophobic coating; the cured super-hydrophobic coating simultaneously has low surface energy (PDMS and polyethylene have low surface energy), high wear resistance (polyethylene improves hardness), and overall super-hydrophobicity (the uniformly distributed micropores inside provide a micro-rough structure for the new interface that appears after abrasion); especially after being severely worn, the coating still has a stable super-hydrophobic effect. It has excellent application effects in many fields such as special engineering structure protection, metal machinery anti-corrosion, and oil-water separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0034] Figure 1Schematic diagram of the process for preparing a fluorine-free integral super-hydrophobic coating material by using a non-solvent phase separation process in an embodiment of the present invention; wherein, (1) spraying, (2) pre-curing, (3) stirring, (4) dripping an aqueous phase, (5) applying an oil-in-water silicone oil emulsion, (6) curing, (7) phase separation, and (8) polishing the surface; ① substrate, ② epoxy resin adhesive, ③ epoxy adhesive layer after pre-curing, ④ polyethylene powder, ⑤ PDMS main agent and curing agent, ⑥ ethanol / water solvent (aqueous phase), ⑦ oil phase, ⑧ oil-in-water silicone oil emulsion, ⑨ cured oil-in-water composite PDMS, ⑩ porous PDMS;

[0035] Figure 2 This is a diagram of the internal microporous structure of the fluorine-free integral superhydrophobic coating material in an embodiment of the present invention; wherein, the circular marks are polyethylene micro-nanoparticles, and the square marks are the pore structure in PDMS. DETAILED DESCRIPTION

[0036] The present invention provides a fluorine-free overall super-hydrophobic coating material and a preparation method thereof, the process diagram of which is as follows Figure 1 As shown, wherein, (1) spraying, (2) pre-curing, (3) stirring, (4) dripping water phase, (5) coating oil-in-water silicone oil emulsion, (6) curing, (7) phase separation, (8) surface polishing; ① substrate, ② epoxy resin adhesive, ③ pre-cured epoxy adhesive layer, ④ polyethylene powder, ⑤ PDMS main agent and curing agent, ⑥ ethanol / water solvent (aqueous phase), ⑦ oil phase, ⑧ oil-in-water silicone oil emulsion, ⑨ cured oil-in-water composite PDMS, ⑩ porous PDMS. Specifically including the following steps:

[0037] Step 1: Mix the PDMS main agent and the matching curing agent in proportion, and stir mechanically at room temperature at a speed of 500 rpm for 5 minutes; add polyethylene micro-nano powder, and stir mechanically at room temperature at a speed of 700-1200 rpm for 10-20 minutes to obtain a silicone oil phase; prepare an aqueous phase solvent composed of ethanol and water in proportion, and slowly add it to the oil phase at a drop rate of 30-40 mL / hr. During this process, stir continuously at a speed of 600-1000 rpm. After the addition is completed, continue stirring at room temperature for 30 minutes to obtain a uniform oil-in-water silicone oil emulsion.

[0038] Step 2: Mix acetone and water-based epoxy resin and stir until evenly combined. Then add epoxy curing agent and continue stirring until evenly combined to obtain the coating adhesive. Spray the coating adhesive evenly onto the substrate surface and pre-cure for 8 hours.

[0039] Step 3: After evenly applying the water-in-oil silicone oil emulsion on the surface of the bonding layer, perform vacuum defoaming treatment at room temperature; after defoaming, cure at 55-70°C, and then dry the internal aqueous phase at 100-115°C to obtain porous PDMS; finally, slightly polish the cured coating surface with 300-1000 mesh sandpaper to obtain SHC-PDMS.

[0040] The technical solution of the present invention is further described below with reference to specific embodiments.

[0041] The present invention has no particular limitation on the source of the reagents, and commercially available products known to those skilled in the art may be used.

[0042] Example 1

[0043] A method for preparing a fluorine-free overall super-hydrophobic coating material comprises the following steps:

[0044] Step 1: Mix 10 parts of Dow Corning SYLGARD 184 base and 1 part of the matching curing agent, and stir mechanically at room temperature at 500 rpm for 5 minutes; add 6 parts of polyethylene powder (particle size 6.5 μm, number average molecular weight 60,000) and stir mechanically at room temperature at 1000 rpm for 10 minutes to obtain a silicone oil phase; mix 1.4 parts of ethanol and 8.6 parts of deionized water to form an aqueous phase solvent, and slowly add it dropwise to the oil phase at a drop rate of 30 mL / hr. During this process, stir continuously at 700 rpm. After the addition is completed, continue stirring at room temperature for 30 minutes to obtain a uniform water-in-oil silicone oil emulsion.

[0045] Step 2: Mix 5 parts acetone and 5 parts water-based epoxy resin (bisphenol A epoxy resin E12) and stir until evenly combined. Then, add 1.7 parts D230 curing agent and continue stirring until evenly combined to obtain a coating adhesive. Spray the coating adhesive evenly onto the substrate surface (using compressed air pressure of 0.2 MPa, a 0.3 mm airbrush diameter, and a distance of 5 cm between the nozzle and the substrate). Pre-curing is then performed at room temperature for 8 hours.

[0046] Step 3: After evenly applying the water-in-oil silicone oil emulsion on the surface of the bonding layer, perform vacuum defoaming treatment at room temperature (defoaming for 10 minutes at an air pressure of -0.05 MPa); after defoaming, cure at 60°C for 4 hours, and then dry at 105°C for 24 hours to obtain a porous PDMS coating; finally, slightly polish the cured coating surface with 800-grit sandpaper to obtain SHC-PDMS.

[0047] Figure 2 The internal microporous structure diagram of the fluorine-free integral super-hydrophobic coating material in Example 1 of the present invention; wherein the circular marks are polyethylene micro-nanoparticles and the square marks are the pore structures in PDMS. Figure 2It can be seen that the micro-roughness of the coating material exists not only on the surface of the coating, but also in the microporous structure within the material. Therefore, the new surface exposed after the coating is worn also has the micro-roughness, which makes the coating have good super-hydrophobic mechanical stability and solves the durability problem of super-hydrophobic coating in abrasive environments.

[0048] Example 2

[0049] A method for preparing a fluorine-free overall super-hydrophobic coating material comprises the following steps:

[0050] Step 1: Mix 10 parts of Dow Corning SYLGARD 182 base and 1 part of the matching curing agent, and stir mechanically at 500 rpm at room temperature for 5 minutes; add 4 parts of polyethylene powder (particle size 5 μm, number average molecular weight 80,000) and stir mechanically at 1000 rpm at room temperature for 10 minutes to obtain a silicone oil phase; mix 1.3 parts of ethanol and 6.7 parts of deionized water to form an aqueous phase, and slowly add it dropwise to the oil phase at a rate of 30 mL / hr. During this process, stir continuously at 700 rpm. After the addition is completed, continue stirring at room temperature for 30 minutes to obtain a uniform water-in-oil silicone oil emulsion.

[0051] Step 2: Mix 5 parts acetone diluent and 8 parts water-based epoxy resin (bisphenol F epoxy resin NPEF-170) and stir until evenly combined. Then, add 3 parts T31 curing agent and continue stirring until evenly combined to obtain a coating adhesive. Spray the coating adhesive evenly onto the substrate surface (using compressed air pressure of 0.2 MPa, a 0.3 mm airbrush diameter, and a distance of 4 cm between the nozzle and the substrate). Pre-curing is then performed at room temperature for 8 hours.

[0052] Step 3: After evenly applying the water-in-oil silicone oil emulsion on the surface of the bonding layer, perform vacuum defoaming treatment at room temperature (defoaming for 15 minutes at an air pressure of -0.09 MPa); after defoaming, cure at 60°C for 8 hours, and then dry at 105°C for 24 hours to obtain a porous PDMS coating; finally, slightly polish the cured coating surface with 800-grit sandpaper to obtain SHC-PDMS.

[0053] Example 3

[0054] A method for preparing a fluorine-free overall super-hydrophobic coating material comprises the following steps:

[0055] Step 1: Mix 10 parts of Dow Corning SYLGARD 184 base and 1 part of curing agent, and stir mechanically at 500 rpm at room temperature for 5 minutes; add 6 parts of polyethylene powder (particle size 7 μm, number average molecular weight 70,000) and stir mechanically at 1000 rpm at room temperature for 10 minutes to obtain a silicone oil phase; mix 1.7 parts of ethanol and 10.3 parts of deionized water to form an aqueous phase, and slowly add it dropwise to the oil phase at a rate of 30 mL / hr. Stir continuously at 700 rpm during this process. After the addition is completed, continue stirring at room temperature for 30 minutes to obtain a uniform water-in-oil silicone oil emulsion.

[0056] Step 2: Mix 5 parts acetone diluent and 6 parts water-based epoxy resin (4,5-epoxytetrahydrophthalic acid diglycidyl ester) and stir until evenly combined. Then, add 2 parts polyamide 650 curing agent and continue stirring until evenly combined to obtain a coating binder. Spray the coating binder evenly onto the substrate surface (using compressed air pressure of 0.3 MPa, a 0.3 mm airbrush diameter, and a distance of 5 cm from the nozzle to the substrate) and pre-cure for 8 hours.

[0057] Step 3: After evenly applying the water-in-oil silicone oil emulsion on the surface of the bonding layer, perform vacuum defoaming treatment at room temperature (defoaming for 12 minutes at an air pressure of -0.07 MPa); after defoaming, cure at 60°C for 4 hours, and then dry at 105°C for 24 hours to obtain a porous PDMS coating; finally, slightly polish the cured coating surface with 800-grit sandpaper to obtain SHC-PDMS.

[0058] Comparative Example 1

[0059] The difference from Example 1 is that no polyethylene powder is added, and the other preparation methods are exactly the same as those in Example 1.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that the aqueous phase is prepared by mixing 0.6 parts of ethanol and 3.4 parts of deionized water. The other preparation methods are exactly the same as those in Example 1.

[0062] Comparative Example 3

[0063] The difference from Example 1 is that the aqueous phase is prepared by mixing 1.9 parts of ethanol and 12.1 parts of deionized water. The other preparation methods are exactly the same as those in Example 1.

[0064] Comparative Example 4

[0065] The difference from Example 1 is that the aqueous phase is prepared by mixing 0 parts of ethanol and 10 parts of deionized water. The other preparation methods are exactly the same as those in Example 1.

[0066] Comparative Example 5

[0067] The difference from Example 1 is that the aqueous phase is prepared by mixing 10 parts of ethanol and 0 parts of deionized water. The other preparation methods are exactly the same as those in Example 1.

[0068] Comparative Example 6

[0069] Unlike Example 1, only the water-in-oil silicone oil emulsion was prepared, without a coating binder. The water-in-oil silicone oil emulsion was directly applied to the surface of the base material and then defoamed under vacuum at room temperature. After defoaming, the coating was cured at 60°C for 4 hours and then dried at 105°C for 24 hours to obtain a porous PDMS coating. Finally, the cured coating surface was lightly polished with 800-grit sandpaper to obtain SHC-PDMS. The remaining preparation methods were identical to those in Example 1.

[0070] Comparative Example 7

[0071] The difference from Example 1 is that only the coating binder is applied without preparing the water-in-oil silicone oil emulsion, and the coating binder is directly sprayed evenly on the substrate surface and then pre-cured for 8 hours. The other preparation methods are exactly the same as those in Example 1.

[0072] The following properties were measured on the fluorine-free integral super-hydrophobic coating materials of the examples and comparative examples.

[0073] Material contact angle and rolling angle tests: Contact angle tests use a contact angle tester to measure the contact angle between a horizontal coating surface and water. The rolling angle test measures the angle between the specimen surface and the horizontal plane when a water droplet begins to roll spontaneously across the specimen surface (as the specimen's tilt angle gradually increases), which is the rolling angle. Three specimen surfaces with the same ratio are measured three times per surface. The average of the nine contact angles or rolling angles represents the contact angle or rolling angle between the coating surface and water.

[0074] Material Abrasion Resistance Test: Under a pressure of 20 kPa, a coated sample was moved horizontally 300 cm on a surface of 1000-grit sandpaper. The contact angle after abrasion was then measured using the contact angle and rolling angle test methods. Three sample surfaces were taken from the same mix, and each surface was measured three times. The average of the nine contact angles or rolling angles represents the contact angle or rolling angle of the coated material after abrasion.

[0075] Material Hardness Test: Hardness testing refers to the GB / T 6739-2022 standard. A pencil lead of specified geometry is pressed downward at a 45° angle against the coating surface under a load of (7.35 ± 0.15) N. The pencil is pushed horizontally, and the scratches made by pencils of varying hardness on the coating surface are measured. The hardest pencil that produces no visible scratch marks represents the coating hardness. Pencil hardness indicators are shown in Table 1.

[0076] Table 1 Pencil hardness index

[0077]

[0078] The present invention is fluorine-free overall super-hydrophobic coating material each implementation and comparative example performance test data, test results are shown in Table 2, the present invention uses PDMS, polyethylene as oily material, ethanol / water solution as aqueous phase material, adopts non-solvent phase separation method to prepare a class of fluorine-free overall super-hydrophobic coating material. Such coating has overall super-hydrophobicity, high wear resistance, and does not contain fluorine and other advantages. The aqueous solution has excellent protective properties. The water contact angle is greater than 153 °, and the rolling angle is less than 7 °; Thanks to the overall super-hydrophobicity of the coating material itself, 1000 mesh sand is used. After rubbing 300cm horizontal distance under 20kPa pressure, the contact angle and rolling angle are basically unchanged.

[0079] As can be seen from the comparison of Example 1, Example 3, Comparative Example 3 and Comparative Example 4, the mixing ratio of water relative to oil phase increases, and super-hydrophobicity first increases and then decreases, and material hardness continuously decreases.As can be seen from the comparison of Example 1 and Comparative Example 1, the polyethylene powder mixing ratio increases, and super-hydrophobicity is slightly promoted, and coating material hardness significantly increases, which is conducive to improving the wear resistance of solidified material itself. However, it should be noted that mixing excessive polyethylene powder can cause coating emulsion rheological variation to deteriorate, which is unfavorable for subsequent applications.

[0080] As can be seen from the comparison of Example 1, Comparative Example 4 and Comparative Example 5, the proportion of ethanol in the aqueous phase cannot be too small, otherwise the pore content in the upper part of the coating is very low, resulting in weak hydrophobicity in the upper part. This is because the ethanol content is low, and the density of the aqueous phase will be significantly greater than that of the oil phase, causing the vacuole to sink. However, if the proportion of ethanol in the aqueous phase is too high, the aqueous phase vacuole in the PDMS layer will continue to gather in the upper part due to excessive buoyancy, and it is very easy to merge into large vacuole, eventually leading to demulsification, and there is no microporous rough structure inside the cured PDMS.

[0081] A comparison of Example 1, Comparative Example 6, and Comparative Example 7 shows that the PDMS top layer is the core component that provides superhydrophobicity; the epoxy adhesive layer is insufficient to achieve superhydrophobicity. However, if only the PDMS top layer is used, its adhesion to the substrate is poor. For example, the coating prepared using the method of Comparative Example 6 can be easily removed from the substrate surface.

[0082] Table 2 Performance test data of various embodiments and comparative examples of the fluorine-free overall super-hydrophobic coating material of the present invention

[0083]

[0084] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A fluorine-free overall super-hydrophobic coating material, characterized in that, It includes an epoxy resin bonding layer and a super-hydrophobic polydimethylsiloxane surface layer supported on the surface thereof; the epoxy resin bonding layer is composed of an epoxy resin main agent, an epoxy resin curing agent and acetone; the super-hydrophobic polydimethylsiloxane surface layer is composed of a PDMS main agent, a PDMS curing agent, polyethylene powder and an aqueous solvent; The aqueous phase solvent is a solvent composed of ethanol and water; The mass ratio of the PDMS main agent to the PDMS curing agent is 10: (0.8-1.5); the mass ratio of the polyethylene powder to the PDMS main agent is (1-3): 5; the mass ratio of the ethanol to water is (0.15-0.25): 1; the mass ratio of the PDMS main agent to the aqueous solvent is 1: (0.6-1.2); The preparation method of the fluorine-free overall super-hydrophobic coating material comprises the following steps: (1) Polyethylene powder, PDMS main agent, and PDMS curing agent are mixed to prepare mixed silica gel, and then an aqueous phase solvent mixed with water and ethanol is added dropwise to the mixed silica gel to prepare a water-in-oil silicone oil emulsion; (2) Acetone, epoxy resin main agent and epoxy curing agent are mixed to prepare epoxy resin adhesive; the epoxy resin adhesive is sprayed on the surface of the substrate and pre-cured to form an epoxy resin adhesive layer; (3) Applying water-in-oil silicone oil emulsion on the surface of the epoxy resin bonding layer, and forming a super-hydrophobic polydimethylsiloxane surface layer after vacuum defoaming, curing and drying; and polishing the super-hydrophobic polydimethylsiloxane surface layer to form a fluorine-free overall super-hydrophobic coating material.

2. The fluorine-free overall super-hydrophobic coating material according to claim 1, wherein The epoxy resin main agent is one or more of bisphenol A epoxy resin E12, E20, E44, E51, bisphenol F epoxy resin NPEF-170, NPEF-187 or 4,5-epoxytetrahydrophthalic acid diglycidyl ester; Alternatively, the epoxy resin curing agent is one or more of polyetheramine curing agent D230, T403, D400, D2000, FL1000, polyamide curing agent 650, 651, T31 modified amine curing agent, ethylenediamine curing agent or xylenediamine curing agent.

3. The fluorine-free overall super-hydrophobic coating material according to claim 1, wherein The mass ratio of the epoxy resin main agent to the epoxy resin curing agent is (2.5-3.5):1; the mass ratio of the epoxy resin main agent to acetone is (1-1.8):

1.

4. The fluorine-free overall super-hydrophobic coating material according to claim 1, wherein The PDMS main agent and PDMS curing agent are one or more of Dow Corning SYLGARD 184 and its supporting curing agent, Dow Corning SYLGARD 182 and its supporting curing agent, or Momentive RTV615 and its supporting curing agent; Alternatively, the particle size of the polyethylene powder is 5-7 μm, and the number average molecular weight of the polyethylene powder is 50,000-80,000.

5. A method for preparing a fluorine-free overall super-hydrophobic coating material according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Polyethylene powder, PDMS main agent, and PDMS curing agent are mixed to prepare mixed silica gel, and then an aqueous phase solvent mixed with water and ethanol is added dropwise to the mixed silica gel to prepare a water-in-oil silicone oil emulsion; (2) Acetone, epoxy resin main agent and epoxy curing agent are mixed to prepare epoxy resin adhesive; the epoxy resin adhesive is sprayed on the surface of the substrate and pre-cured to form an epoxy resin adhesive layer; (3) Applying water-in-oil silicone oil emulsion on the surface of the epoxy resin bonding layer, and forming a super-hydrophobic polydimethylsiloxane surface layer after vacuum defoaming, curing and drying; and polishing the super-hydrophobic polydimethylsiloxane surface layer to form a fluorine-free overall super-hydrophobic coating material.

6. The method for preparing a fluorine-free overall super-hydrophobic coating material according to claim 5, wherein In step (2), the compressed air pressure used for spraying is 0.15-0.35 MPa, the diameter of the spray pen is 0.3 mm, and the distance between the nozzle and the substrate is 4-6 cm; Alternatively, the pre-curing step is: curing at 20-28° C. for 6-10 h.

7. The method for preparing a fluorine-free overall super-hydrophobic coating material according to claim 5, wherein In step (3), the vacuum defoaming is performed at room temperature under an air pressure of -0.09 to -0.05 MPa for 10 to 20 minutes; Alternatively, the curing step is: curing at 55-70°C for 4-8 hours; Alternatively, the drying step is: drying at 100-115° C. for 12-24 hours.

8. according to the preparation method of the fluorine-free overall super-hydrophobic coating material of claim 5, it is characterised in that, In step (3), the polishing is performed using 300-1000 grit sandpaper at a pressure of 15-25 kPa; Alternatively, the thickness of the fluorine-free overall super-hydrophobic coating material is 0.5 to 2 mm.

9. Use of the fluorine-free integral super-hydrophobic coating material according to any one of claims 1 to 4 in special engineering structure protection, metal mechanical corrosion protection or oil-water separation.

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