Anti-icing and deicing super-hydrophobic coating based on phase change energy storage and preparation method of anti-icing and deicing super-hydrophobic coating

Abstract

The invention discloses an anti-icing and deicing super-hydrophobic coating based on phase change energy storage and a preparation method of the anti-icing and deicing super-hydrophobic coating. The preparation method comprises the following steps: chambering a halloysite nanotube, and then filling a phase change material to obtain a first modified halloysite nanotube; carrying out microencapsulation packaging and structure regulation and control on the first modified halloysite nanotube through an in-situ growth method to obtain a second modified halloysite nanotube; uniformly mixing the second modified halloysite nanotube with a water-based resin dispersion liquid to obtain a mixed dispersion liquid; coating the surface of a base material with the mixed dispersion liquid, and then carrying out surface modification through alkyl siloxane, so as to obtain the anti-icing and deicing super-hydrophobic coating based on phase change energy storage. The super-hydrophobic coating is good in low-temperature using effect and excellent in hydrophobic and anti-icing performance, wall material microencapsulation packaging is compact, the surface microstructure is uniform, and the phase-change material is high in packaging rate and good in durability; the preparation process is simple and green, the requirement on production equipment is low, the cost is low, and large-scale industrial production can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of super-hydrophobic materials, and in particular relates to an anti-icing super-hydrophobic coating based on phase change energy storage and a preparation method thereof. Background Art

[0002] The ice problem has brought serious safety risks to aerospace, transportation, power systems and other fields and various types of equipment. Anti-icing is of great significance to people's daily production and life. Inspired by nature, such as the low adhesion and superhydrophobicity of the feet of geckos and the surface of lotus leaves, researchers have explored the application of superhydrophobic surfaces for anti-icing. On the superhydrophobic surface, the contact area between the droplet and the solid surface is reduced, which weakens the heat transfer efficiency between the two, thereby delaying the time for the droplet to freeze on the superhydrophobic surface; in addition, the reduction in the contact area between the solid surface and the droplet makes the interaction force between the rough structure surface and the droplet smaller, and the droplet can roll off the surface when the substrate is tilted at a certain angle, preventing the droplet from freezing on the surface. Although the superhydrophobic surface can improve the icing phenomenon, if it is exposed to low temperature and high humidity for a long time, the condensed droplets can easily penetrate into the micro / nanostructure and occupy the air layer, causing the contact state of the droplet to change from the low-adhesion Cassie state to the high-adhesion Wenzel state, and ultimately leading to the loss of anti-icing performance. If traditional mechanical or chemical deicing methods are used to remove ice on super-hydrophobic surfaces, the surface structure and chemical properties will be destroyed. Some researchers have tried to introduce phase change materials on super-hydrophobic surfaces, taking advantage of the high energy storage density and energy storage and release in a narrow temperature range of phase change materials, to achieve the excellent photothermal conversion performance of phase change materials and achieve the purpose of anti-icing and deicing. However, due to the low thermal conductivity of phase change materials themselves and the volume change during the phase change heat storage process, phase change materials often leak, which greatly limits their application.

[0003] By using microencapsulation technology, the heat transfer area of ​​the phase change material can be increased and the thermal conductivity of the phase change material can be improved. At present, there are many methods for preparing super hydrophobic coatings using microencapsulation technology, such as spray drying, solvent evaporation, emulsion polymerization, interfacial polymerization, etc. However, these methods generally have problems such as complex preparation process, easy shedding of super hydrophobic surface layer, generation of toxic substances during preparation process, and low encapsulation efficiency of phase change materials. It is impossible to obtain a super hydrophobic coating for anti-deicing that takes into account high phase change material encapsulation rate, high durability, simple preparation method, and safety.

[0004] Therefore, there is an urgent need to provide an anti-icing super-hydrophobic coating based on phase change energy storage and a preparation method thereof to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned technical deficiencies, propose an anti-icing super-hydrophobic coating based on phase change energy storage and a preparation method thereof, so as to solve the technical problems in the prior art that the super-hydrophobic coating based on microencapsulation cannot take into account high phase change material encapsulation rate, high durability and complex preparation method.

[0006] In a first aspect, the present invention provides a method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage, comprising the following steps: Performing pore expansion treatment on the halloysite nanotube, and then filling the phase change material to obtain the first modified halloysite nanotube; The first modified halloysite nanotube is microencapsulated and structure-controlled by an in-situ growth method to obtain a second modified halloysite nanotube; uniformly mixing the second modified halloysite nanotubes and the aqueous resin dispersion to obtain a mixed dispersion; The mixed dispersion is coated on the surface of the substrate, and then the surface is modified by alkyl siloxane to obtain an anti-icing superhydrophobic coating based on phase change energy storage.

[0007] In a second aspect, the present invention provides an anti-icing super-hydrophobic coating based on phase change energy storage, and the anti-icing super-hydrophobic coating based on phase change energy storage is obtained by the preparation method of the anti-icing super-hydrophobic coating based on phase change energy storage provided by the first aspect of the present invention.

[0008] Compared with the prior art, the beneficial effects of the present invention include: The present invention uses natural halloysite nanotubes as wall materials to encapsulate and store low-melting-point phase change materials in microcapsules, and uses an in-situ growth method to achieve morphological structure regulation (increasing roughness) and microcapsule encapsulation in one step, constructs a multi-level rough structure while encapsulating, and then composites it with an aqueous resin dispersion and coats it on the surface of a substrate, and then further uses alkyl siloxane for modification to obtain an anti-icing super-hydrophobic coating with high photothermal conversion efficiency; the super-hydrophobic coating of the present invention has good low-temperature use effect, excellent hydrophobic and anti-icing performance, dense wall material microencapsulation, uniform surface microstructure, high phase change material encapsulation rate, and good durability; the preparation process of the present invention is simple and green, has low requirements on production equipment, and is low in cost, and can achieve large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a static water contact angle photograph of the anti-icing superhydrophobic coating based on phase change energy storage prepared in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the first modified halloysite nanotube and the second modified halloysite nanotube prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0011] In a first aspect, the present invention provides a method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage, comprising the following steps: S1, performing pore expansion treatment on halloysite nanotubes (HNTs), and then filling phase change materials to obtain first modified halloysite nanotubes; S2, microencapsulating and structurally regulating the first modified halloysite nanotubes by an in-situ growth method to obtain second modified halloysite nanotubes; S3, uniformly mixing the second modified halloysite nanotubes and the aqueous resin dispersion to obtain a mixed dispersion containing the second modified halloysite nanotubes and the aqueous resin; S4. Applying a mixed dispersion containing the second modified halloysite nanotubes and an aqueous resin to the surface of the substrate, and then performing surface modification with alkyl siloxane to obtain an anti-icing superhydrophobic coating based on phase change energy storage.

[0012] In this embodiment, in step S1, halloysite (HNTs) is a silicate mineral with a tubular shape, an outer diameter of 40-60 nm, and a length of 700-1500 nm. HNTs are natural green materials with good crystallinity and low price. The inner and outer surfaces of HNTs are compounded with Al-OH and Si-OH groups, which makes it easy for HNTs to connect with other substances and have richer functional properties. The encapsulation process and the in-situ growth of nanoparticles (SiO2) are mainly cross-linked with the outer surface Si-OH. At the same time, HNTs also have good thermal stability and mechanical properties.

[0013] In this embodiment, in step S1, the hole enlarging treatment is performed by acid etching.

[0014] Preferably, the process of acid etching and pore enlargement includes: subjecting the halloysite nanotubes to acid etching and pore enlargement treatment using an acid solution, followed by filtering, washing and drying to obtain the acid-etched and pore-enlarged halloysite nanotubes.

[0015] Among them, during the acid etching and hole expansion process, the acid solution is dilute sulfuric acid or dilute hydrochloric acid with a concentration of 1~3 mol / L; the solid-liquid ratio is 1g: (10~30) ml; the acid etching temperature is 60~90℃, and the acid etching time is 2~4h; the acid etching is carried out under stirring conditions.

[0016] In this embodiment, in step S1, the melting point of the phase change material is 0-10° C. If the melting point of the phase change material is too high, anti-icing cannot be achieved through phase change energy storage in a low temperature environment.

[0017] Preferably, the phase change material is n-tetradecane, which belongs to the paraffin phase change material and has the characteristics of large heat storage capacity, low phase change temperature (melting point is 5.5°C), stable phase change behavior, abundant sources and low price. The present invention selects n-tetradecane with large latent heat, small supercooling, low melting point, stable phase change process and reversible phase change as the phase change material, which can make the coating have better performance in low temperature environment.

[0018] In this embodiment, in step S1, the process of filling the phase change material includes: preparing a first organic solvent solution of the phase change material, mixing the acid-etched and expanded halloysite nanotubes with the first organic solvent solution of the phase change material, and alternately performing vacuum extraction and standing at normal pressure to obtain a first modified halloysite nanotube. The present invention ensures that the halloysite is fully loaded with the phase change material by alternately performing vacuum extraction and standing at normal pressure.

[0019] Preferably, the usage ratio of the phase change material to the first organic solvent is 1 g: (2-4) ml.

[0020] Preferably, the first organic solvent is anhydrous ethanol.

[0021] Preferably, the mass ratio of the halloysite nanotubes after acid etching and pore expansion to the phase change material is 1:(1-1.5).

[0022] Preferably, the vacuum extraction temperature is 70-90° C., the vacuum extraction time is 1-2 h, and the vacuum pressure is 0.1-133 Pa.

[0023] Preferably, the temperature for standing at normal pressure is 20-30° C., and the time for standing at normal pressure is 0.5-1 h.

[0024] Preferably, the vacuum extraction and normal pressure standing are repeated 2 to 3 times.

[0025] In this embodiment, in step S2, the process of encapsulating and structurally regulating the first modified halloysite nanotubes by an in-situ growth method includes: S21, dispersing the first modified halloysite nanotubes in a second organic solvent, and ultrasonically dispersing the first modified halloysite nanotubes to obtain a second organic solvent suspension; S22, uniformly mixing tetraethyl orthosilicate, a third organic solvent and water, and then adjusting the pH to 3-4 for hydrolysis reaction to obtain a hydrolysis reaction liquid; S23, mixing the second organic solvent suspension of the first modified halloysite nanotubes and the hydrolysis reaction solution, and then adjusting the pH to 7-9 for polycondensation to obtain a second modified halloysite nanotube suspension.

[0026] The present invention uses a sol-gel method to utilize in-situ grown SiO2 nanospheres to achieve microencapsulation and structural regulation of halloysite nanotubes in one step; at the same time, by controlling the hydrolysis-polycondensation rate of tetraethyl orthosilicate (TEOS), the position and particle size of the generated SiO2 are regulated, and the particle size of the SiO2 spheres is obtained to be 5-20nm.

[0027] Preferably, the usage ratio of the first modified halloysite nanotube to the second organic solvent is (0.5-1.5) g:100 ml.

[0028] Preferably, the second organic solvent is anhydrous ethanol.

[0029] Preferably, the temperature of ultrasonic dispersion is 20-30° C., and the time of ultrasonic dispersion is 10-15 min.

[0030] Preferably, the mass ratio of the first modified halloysite nanotube to tetraethyl orthosilicate is 1:(0.6-0.8).

[0031] Preferably, in the process of uniformly mixing tetraethyl orthosilicate, the third organic solvent and water, the mass ratio of tetraethyl orthosilicate, the third organic solvent and water is (1.5-2.5):(3-4):1.

[0032] Preferably, the third organic solvent is anhydrous ethanol.

[0033] Preferably, the pH is adjusted to 3-4 by adding concentrated hydrochloric acid.

[0034] Preferably, the hydrolysis reaction temperature is 30-40° C., the hydrolysis reaction time is 30-60 min, and the hydrolysis reaction is carried out under stirring.

[0035] Preferably, the pH is adjusted to 7-9 by adding aqueous ammonia.

[0036] Specifically, the mass fraction of ammonia water is 25% to 28%.

[0037] Preferably, the temperature of the polycondensation reaction is 30-40° C., the time of the polycondensation reaction is 10-20 min, and the polycondensation reaction is carried out under stirring.

[0038] In this embodiment, in step S3, the aqueous resin dispersion is at least one of an aqueous polyurethane dispersion or an aqueous epoxy resin dispersion. The aqueous resin dispersion uses water as a solvent and has the advantages of being pollution-free, having good mechanical properties, strong adhesion, and good compatibility.

[0039] In this embodiment, in step S3, the mass solid content of the aqueous resin dispersion is 30%-40%, and the volume ratio of the suspension of the second modified halloysite nanotubes to the aqueous resin dispersion is (5-9):1.

[0040] In this embodiment, in step S3, the second modified halloysite nanotubes and the aqueous resin dispersion are uniformly mixed by stirring and then ultrasonically dispersing.

[0041] Preferably, the stirring time is 1 to 3 hours, the ultrasonic dispersion time is 30 to 60 minutes, and the stirring and ultrasonic dispersion temperatures are room temperature.

[0042] The present invention does not limit the type of substrate and the coating method, and those skilled in the art can choose according to actual conditions. In some specific embodiments of the present invention, the substrate is glass, wood, etc., and the coating method is spin coating, pulling, spraying, etc.

[0043] In some specific embodiments of the present invention, spin coating is adopted, and during the spin coating process, the rotation speed is 1000-1200 rpm and the spin coating time is 30-50 s.

[0044] In some specific embodiments of the present invention, a pulling method is adopted, and the pulling process includes: immersing the substrate in the coating solution for 2 to 3 minutes, and then pulling at a uniform speed.

[0045] In some specific embodiments of the present invention, a spraying method is adopted, and during the spraying process, the spray gun is 15 to 20 cm away from the substrate, and the spraying amount is 8 to 10 mL / min.

[0046] In this embodiment, in step S4, the coating thickness is 3-5 μm.

[0047] In this embodiment, in step S4, the alkyl siloxane is at least one of dodecyltrimethoxysilane, tetradecyltrimethoxysilane, hexadecyltrimethoxysilane, and octadecyltrimethoxysilane.

[0048] In this embodiment, in step S4, the surface modification process includes: preparing a fourth organic solvent solution of alkyl siloxane, immersing the substrate coated with a mixed dispersion containing second modified halloysite nanotubes and an aqueous resin into the fourth organic solvent solution of alkyl siloxane, and then drying to obtain an anti-icing superhydrophobic coating based on phase change energy storage.

[0049] Preferably, the fourth organic solvent is anhydrous ethanol.

[0050] Preferably, in the fourth organic solvent solution of alkyl siloxane, the mass concentration of alkyl siloxane is 1% to 2%.

[0051] Preferably, the soaking temperature is 20-30° C. and the soaking time is 2-3 min.

[0052] Preferably, the drying temperature is 80-110° C., and the drying time is 2-3 hours.

[0053] In a second aspect, the present invention provides an anti-icing super-hydrophobic coating based on phase change energy storage, and the anti-icing super-hydrophobic coating based on phase change energy storage is obtained by the preparation method of the anti-icing super-hydrophobic coating based on phase change energy storage provided by the first aspect of the present invention.

[0054] Example 1 (1) Weigh 5g of HNTs and add them to a flat-bottom flask containing 100ml of 2mol / L H2SO4. Etch them in a water bath at 90℃ for 2h under magnetic stirring, and then filter, wash and dry to obtain acid-etched HNTs powder. Then add it to a mixed solution prepared by 5g of n-tetradecane and 15mL of anhydrous ethanol, place it in a vacuum drying oven at 80℃ and 8Pa for 1h, and then let it stand at room temperature and pressure for 30min. Repeat this vacuum-normal pressure operation 3 times to obtain halloysite nanotubes filled with low melting point phase change material (i.e., first modified halloysite nanotubes).

[0055] (2) Disperse 5 g of halloysite nanotubes filled with low melting point phase change material in 500 ml of anhydrous ethanol and ultrasonically disperse for 10 min to obtain a HNTs / ethanol suspension; mix 4 g of tetraethyl orthosilicate, 7 g of anhydrous ethanol and 2 g of water in a beaker and pour into a three-necked flask; add concentrated hydrochloric acid to the flask to adjust the pH value of the solution to 3, stir in a water bath at 35°C for 40 min, then add the HNTs / ethanol suspension, and then add ammonia water (25~28wt%) dropwise to adjust the pH value of the solution to 8, continue stirring for 10 min, and obtain a suspension of halloysite nanotubes after microencapsulation and structural regulation (i.e., a suspension of the second modified halloysite nanotubes).

[0056] (3) 25 ml of the suspension of the microencapsulated and structure-controlled halloysite nanotubes was mixed with 5 ml of an aqueous polyurethane dispersion (mass solid content 38%), and the mixture was magnetically stirred for 2 h, followed by ultrasonic dispersion for 30 min to obtain a mixed dispersion containing the second modified halloysite nanotubes and an aqueous resin.

[0057] (4) The mixed dispersion containing the second modified halloysite nanotubes and the aqueous resin was coated on the surface of the glass slide by spin coating at a rotation speed of 1000 rpm for 30 s. The glass slide was then immersed in an ethanol solution of 1 wt% octadecyltrimethoxysilane at room temperature for 2 min and finally dried at 100 °C for 2 h to obtain an anti-icing superhydrophobic coating based on phase change energy storage.

[0058] Example 2 (1) Weigh 5g of HNTs and add them to a flat-bottom flask containing 100ml of 2mol / L H2SO4. Under magnetic stirring, acid-etch for 4h in a water bath at 60℃, and then filter, wash and dry to obtain acid-etched and pore-expanded HNTs powder. Then add it to a mixed solution prepared by 5g of n-tetradecane and 15mL of anhydrous ethanol, and then place it in a vacuum drying oven at 75℃ and 18Pa for 1h, and then stand at room temperature and pressure for 30min. Repeat this vacuum-normal pressure operation 3 times to obtain halloysite nanotubes filled with low melting point phase change material (i.e., first modified halloysite nanotubes).

[0059] (2) Disperse 5 g of halloysite nanotubes filled with low melting point phase change material in 500 ml of anhydrous ethanol and ultrasonically disperse for 15 min to obtain a HNTs / ethanol suspension; mix 4 g of tetraethyl orthosilicate, 8 g of anhydrous ethanol and 2 g of water in a beaker and pour into a three-necked flask; add concentrated hydrochloric acid to the flask to adjust the pH value of the solution to 4, stir in a water bath at 35°C for 40 min, then add the HNTs / ethanol suspension, and then add ammonia water (25~28wt%) dropwise to adjust the pH value of the solution to 8, continue stirring for 10 min, and obtain a suspension of halloysite nanotubes after microencapsulation and structural regulation (i.e., a suspension of the second modified halloysite nanotubes).

[0060] (3) 35 ml of the suspension of the microencapsulated and structure-controlled halloysite nanotubes was mixed with 5 ml of an aqueous polyurethane dispersion (mass solid content 38%), and the mixture was magnetically stirred for 2 h, and then ultrasonically dispersed for 30 min to obtain a mixed dispersion containing the second modified halloysite nanotubes and an aqueous resin.

[0061] (4) The wood was immersed in the coating solution for 3 min and then pulled at a constant speed. The wood was then immersed in a 2 wt% dodecyltrimethoxysilane ethanol solution at room temperature for 2 min and finally dried at 100 °C for 2 h to obtain an anti-icing superhydrophobic coating based on phase change energy storage.

[0062] Example 3 (1) Weigh 5g HNTs and add them to a flat-bottom flask containing 100ml, 2mol / L H2SO4. Under magnetic stirring, acid-etch for 3h in a water bath at 80℃, and then filter, wash and dry to obtain acid-etched HNTs powder. Then add it to a mixed solution prepared by 5g n-tetradecane and 15mL anhydrous ethanol, and then place it in a vacuum drying oven at 85℃ and 28Pa for 1.5h, and then stand at room temperature and pressure for 30min. Repeat this vacuum-normal pressure operation 3 times to obtain halloysite nanotubes filled with low melting point phase change material (i.e., first modified halloysite nanotubes).

[0063] (2) Disperse 5 g of halloysite nanotubes filled with low melting point phase change material in 500 ml of anhydrous ethanol and ultrasonically disperse for 10 min to obtain a HNTs / ethanol suspension; mix 3 g of tetraethyl orthosilicate, 7 g of anhydrous ethanol and 2 g of water in a beaker and pour into a three-necked flask; add concentrated hydrochloric acid to the flask to adjust the pH value of the solution to 3, stir in a water bath at 35°C for 40 min, then add the HNTs / ethanol suspension, and then add ammonia water (25~28wt%) dropwise to adjust the pH value of the solution to 7, continue stirring for 10 min, and obtain a suspension of halloysite nanotubes after microencapsulation and structural regulation (i.e., a suspension of the second modified halloysite nanotubes).

[0064] (3) 45 ml of the suspension of the microencapsulated and structure-controlled halloysite nanotubes was mixed with 5 ml of an aqueous polyurethane dispersion (mass solid content 38%), and the mixture was magnetically stirred for 2 h, followed by ultrasonic dispersion for 30 min to obtain a mixed dispersion containing the second modified halloysite nanotubes and an aqueous resin.

[0065] (4) The coating was applied by spraying, with the spray gun and the wood at a distance of 15 cm and a spraying volume of 8 mL / min. The coating thickness was 5 μm. The wood was then immersed in an ethanol solution of 2 wt% octadecyltrimethoxysilane at room temperature for 2 min and finally dried at 100 °C for 2 h to obtain an anti-icing superhydrophobic coating based on phase change energy storage.

[0066] Comparative Example 1 The only difference from Example 1 is that in step (1), the phase change material is replaced by n-octadecane from n-tetradecane.

[0067] Comparative Example 2 The only difference from Example 1 is that step (2) is adjusted as follows: 5 g of halloysite nanotubes filled with low melting point phase change material were dispersed in 500 ml of anhydrous ethanol and ultrasonically dispersed for 10 min to obtain HNTs / ethanol suspension; 4 g of SiO2 microspheres with a diameter ranging from 5 to 20 nm were added under stirring in a water bath at 35°C to obtain SiO2 / halloysite nanotube suspension.

[0068] Comparative Example 3 The only difference from Example 1 is that the halloysite nanotubes are replaced with attapulgite, and step (1) is adjusted as follows: 5 g of attapulgite was added to a mixed solution prepared by 5 g of n-tetradecane and 15 mL of anhydrous ethanol, and then placed in a vacuum drying oven at 80°C and 8 Pa for 1 hour, and then allowed to stand at room temperature and pressure for 30 minutes. This vacuum-normal pressure operation was repeated 3 times.

[0069] Comparative Example 4 The only difference from Example 1 is that in step (1), the halloysite nanotubes are not subjected to acid etching and pore expansion, but are directly filled with n-tetradecane.

[0070] Comparative Example 5 The only difference from Example 1 is that in step (2), 4 g of tetraethyl orthosilicate is replaced by 1 g of tetraethyl orthosilicate.

[0071] Comparative Example 6 The only difference from Example 1 is that in step (3), 5 ml of aqueous polyurethane dispersion (mass solid content 38%) is replaced by 10 ml of aqueous polyurethane dispersion (mass solid content 38%).

[0072] Comparative Example 7 The only difference from Example 1 is that in step (3), 5 ml of aqueous polyurethane dispersion (mass solid content 38%) is replaced by 2 ml of aqueous polyurethane dispersion (mass solid content 38%).

[0073] Performance Testing 1. Evaluation of the hydrophobic properties of the coating using static water contact angle (WCA) and sliding angle: The static WCA and sliding angle of the sample surface were measured at room temperature using a contact angle goniometer (DCA 35, Dataphysics, Germany) equipped with a digital camera. Five points were randomly selected on each sample surface, and 2uL of deionized water was used to measure the WCA on the surface using the droplet method. The average value of these points was taken as the representative value of the sample WCA.

[0074] 2. Static anti-icing test was used to test the anti-icing performance: the coating was placed in a 10°C environment and exposed to a xenon lamp (PLS, CME-SL500, CHINA) simulating sunlight (1 kW / m 2 ) for 4 hours, and then place the sample on a cold platform at -20°C and 35±5% relative humidity. Record the static freezing time of an 8ul water droplet on the sample surface to simulate the delayed freezing of the coating under low temperature conditions. The freezing time is defined as the time required for a water droplet to completely transform from liquid to solid.

[0075] Table 1 Wetting performance, initial anti-icing performance and anti-icing performance after 100 cycles of different coatings

[0076] See also Figure 1 , Figure 1 This is a static water contact angle photo of the anti-icing super-hydrophobic coating based on phase change energy storage prepared in Example 1 of the present invention. Figure 1It can be seen that the static contact angle of the coating reaches 161°, and combined with Table 1, it can be seen that the rolling angle of a water droplet on its surface is 4.8°, indicating that it has excellent superhydrophobic properties.

[0077] See also Figure 2 , Figure 2 The scanning electron microscope images of the first modified halloysite nanotube (a) and the second modified halloysite nanotube (b) prepared in Example 1 of the present invention. Figure 2 It can be seen that a large number of SiO2 spheres are gathered on the surface and ends of the second modified halloysite nanotubes after encapsulation and structural regulation, which not only realizes the effective encapsulation of the phase change material, but also constructs a multi-level rough structure on the surface of the material, which is beneficial to improve the hydrophobic performance.

[0078] Please refer to Table 1. It can be seen from Table 1 that the freezing delay time of the coating of Example 1 of the present invention at -20°C is as long as 3578s. After 100 cycles of anti-icing performance tests, the freezing delay time of the surface at -20°C is still 2736s. The reason is that the super hydrophobicity of the coating surface makes the contact area between the droplet and the surface extremely small, slowing down the heat transfer between the droplet and the substrate; in addition, the excellent photothermal performance of the surface can convert light energy into thermal energy so that the surface is maintained at a higher temperature and can transfer heat to the droplet, thereby delaying the freezing behavior of the droplet; in addition, the effective encapsulation of n-tetradecane ensures the effective cycle stability of the coating and good durability.

[0079] Please refer to Table 1. It can be seen from Table 1 that the static contact angle of the coating of Example 2 of the present invention reaches 158°, the rolling angle of water droplets on its surface is 5.8°, and the initial and 100-cycle freezing delay times of the surface at -20°C are as long as 3257s and 2579s respectively, showing excellent superhydrophobic properties and photothermal anti-icing properties.

[0080] Please refer to Table 1. It can be seen from Table 1 that the static contact angle of the coating of Example 3 of the present invention reaches 156°, the rolling angle of water droplets on its surface is 6.4°, and the initial and 100-cycle freezing delay times of the surface at -20°C are as long as 3037s and 2217s respectively, and it also has excellent superhydrophobic properties and photothermal anti-icing properties.

[0081] Please refer to Table 1. It can be seen from Table 1 that the static contact angle of the coating of Comparative Example 1 of the present invention reaches 160°, the rolling angle of water droplets on its surface is 4.9°, and the freezing delay time of the surface at -20°C is only 97s. The reason is that Comparative Example 1 uses n-octadecane as a phase change agent with a melting point of 28.18°C. Although it has a high heat storage performance, in a low temperature environment, no transition from solid phase to liquid phase occurs, and heat energy storage and release cannot be achieved through the phase change of the material. Therefore, although Comparative Example 1 has comparable hydrophobic properties to Example 1, the effect of delaying freezing is extremely poor.

[0082] Please refer to Table 1. It can be seen from Table 1 that the static contact angle of the coating of Comparative Example 2 of the present invention is only 148°, and the rolling angle of water droplets on its surface is 9.2°. The super hydrophobic effect is not achieved, and the anti-icing effect is also poor. The initial and 100-cycle freezing delay times of the surface at -20°C are only 2547s and 437s, respectively. The reason is that SiO2 spheres are directly incorporated in Comparative Example 2, and a multi-level rough structure is not constructed, and the phase change material is not effectively encapsulated, which is not conducive to improving the hydrophobic and anti-icing properties.

[0083] Please refer to Table 1. It can be seen from Table 1 that the static contact angle of the coating of Comparative Example 3 of the present invention reaches 159°, and the rolling angle of water droplets on its surface is 5.7°, but the freezing delay time of the surface at -20°C is only 224s. The reason is that Comparative Example 3 uses columnar attapulgite to replace halloysite nanotubes. Attapulgite is a solid structure. Although it can construct a multi-level rough structure, it cannot achieve the encapsulation of phase change materials, which is not conducive to improving the anti-icing performance.

[0084] Please refer to Table 1. It can be seen from Table 1 that the static contact angle of the coating prepared in Comparative Example 4 of the present invention reaches 160°, the rolling angle of water droplets on its surface is 5.0°, and the initial and 100-cycle freezing delay times of the surface at -20°C are 1278s and 1057s, respectively. The reason is that the halloysite nanotubes of Comparative Example 4 are not treated with acid etching and pore expansion, and the phase change material loading rate (phase change material weight in microcapsules / total weight of microcapsules×100%) is reduced from 16.5% (Example 1) to 5.7%, which is not conducive to improving the anti-icing performance.

[0085] Please refer to Table 1. It can be seen from Table 1 that the static contact angle of the coating prepared in Comparative Example 5 of the present invention is only 137°, the rolling angle of water droplets on its surface is 16.5°, and the initial and 100-cycle freezing delay times of the surface at -20°C are 468s and 257s, respectively, indicating that the concentration of SiO2 spheres is too low, which is not conducive to improving the hydrophobicity and anti-icing properties.

[0086] Please refer to Table 1. It can be seen from Table 1 that the static contact angle of the coating of Comparative Example 6 of the present invention is only 145°, the rolling angle of water droplets on its surface is 9.8°, and the initial and 100-cycle freezing delay times of the surface at -20°C are 2395s and 1847s, respectively, indicating that the amount of water-based polyurethane used is too much, the contact angle of the sample surface is reduced, and the rolling angle is also slightly increased. The reason is that although the water-based polyurethane acts as a binder of the coating to ensure the stability of the surface rough structure, too much water-based polyurethane is not conducive to the highlighting of the surface micro-nano structure, but will lead to a decrease in hydrophobicity, thereby affecting the anti-icing performance.

[0087] Please refer to Table 1. It can be seen from Table 1 that the static contact angle of the coating of Comparative Example 7 of the present invention reaches 162°, the rolling angle of water droplets on its surface is 4.6°, and the initial and 100-cycle freezing delay times of the surface at -20°C are 3612s and 2573s, respectively, indicating that the amount of water-based polyurethane used is too small, the contact angle of the sample surface is slightly increased, the rolling angle is also slightly decreased, and the initial anti-icing performance is enhanced, but the coating surface has peeling and powdering phenomenon. The reason is that although the reduction in the amount of water-based polyurethane is beneficial to highlighting the micro-nano structure of the coating surface and improving the hydrophobicity, the amount is too small, the binder cannot ensure the stability of the rough surface structure, the mechanical properties of the coating are significantly reduced, and the anti-icing performance is also reduced after 100 cycles, but this embodiment still shows good super hydrophobicity and anti-icing properties.

[0088] In summary, the present invention utilizes the property of low-melting-point phase change materials that can convert solar energy into thermal energy, uses natural green hollow tubular structured halloysite as a carrier to store low-melting-point phase change materials, and encapsulates and regulates the morphological structure of the halloysite nanotubes filled with phase change materials in one step through an in-situ growth method, and then composites it with an aqueous resin dispersion and coats it on the surface of a substrate, and then further modifies it with alkylsiloxane to obtain an anti-icing super-hydrophobic coating with high photothermal conversion efficiency, wherein the coating has a contact angle with water of 156~161°, a rolling angle of water droplets on its surface of 4.8~6.4°, an initial freezing delay time of more than 3000s at -20°C, and a freezing delay time of more than 2200s after 100 cycles, and the process has a wide range of material sources, good encapsulation effect, and high coating stability. The microencapsulation of the phase change material increases its heat transfer area and the stability of its volume change during the phase change process. The in-situ generated nanoparticles (such as SiO2, etc.) form a uniform and dense protrusion structure on the surface of the halloysite nanotube wall, which makes the surface of this type of coating material have very excellent water resistance and self-cleaning properties. In addition, since the low-melting point phase change material can store and release thermal energy, it also exhibits excellent anti-icing performance. In addition, the halloysite nanotube has excellent mechanical properties, which makes the coating have good wear resistance. The anti-icing super hydrophobic coating of the present invention can be widely used in aerospace, transportation, power systems and other fields.

[0089] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage, characterized in that: The following steps are involved: Performing pore expansion treatment on the halloysite nanotube, and then filling the phase change material to obtain the first modified halloysite nanotube; Microencapsulating and structurally regulating the first modified halloysite nanotubes by an in-situ growth method to obtain second modified halloysite nanotubes; uniformly mixing the second modified halloysite nanotubes and the aqueous resin dispersion to obtain a mixed dispersion; The mixed dispersion is coated on the surface of a substrate, and then the surface is modified by alkylsiloxane to obtain an anti-icing superhydrophobic coating based on phase change energy storage.

2. The method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage according to claim 1, characterized in that: The outer diameter of the halloysite nanotube is 40-60 nm and the length is 700-1500 nm; and / or, The melting point of the phase change material is 0-10°C.

3. The method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage according to claim 1, characterized in that: The hole enlargement treatment method is acid etching hole enlargement treatment, which specifically includes: The halloysite nanotubes are subjected to acid etching and pore enlargement treatment using an acid solution, and then filtered, washed, and dried to obtain the acid-etched and pore-enlarged halloysite nanotubes; wherein, The acid solution is dilute sulfuric acid or dilute hydrochloric acid with a concentration of 1-3 mol / L and a solid-liquid ratio of 1 g: (10-30) ml; and / or, The acid etching temperature is 60-90° C., the acid etching time is 2-4 hours, and the acid etching process is carried out under stirring.

4. The method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage according to claim 1, characterized in that: The process of filling the phase change material comprises: A first organic solvent solution of a phase change material is prepared, the expanded halloysite nanotubes are mixed with the first organic solvent solution of the phase change material, and vacuum extraction and normal pressure standing are performed alternately to obtain a first modified halloysite nanotube; wherein, The phase change material is n-tetradecane; and / or, The mass ratio of the expanded halloysite nanotubes to the phase change material is 1:(1-1.5); and / or, The ratio of the phase change material to the first organic solvent is 1 g: (2-4) ml; and / or, The first organic solvent is anhydrous ethanol; and / or, The vacuum extraction temperature is 70-90°C, the vacuum extraction time is 1-2h, and the vacuum pressure is 0.1-133Pa; and / or, The temperature of the normal pressure standing is 20-30° C., and the time of the normal pressure standing is 0.5-1 h.

5. The method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage according to claim 1, characterized in that: The process of encapsulating and structurally regulating the first modified halloysite nanotube by an in-situ growth method comprises: dispersing the first modified halloysite nanotubes in a second organic solvent, and dispersing by ultrasonication to obtain a second organic solvent suspension of the first modified halloysite nanotubes; Evenly mixing tetraethyl orthosilicate, a third organic solvent and water, and then adjusting the pH to 3-4 for hydrolysis reaction to obtain a hydrolysis reaction liquid; The second organic solvent suspension of the first modified halloysite nanotubes and the hydrolysis reaction solution are mixed, and then the pH is adjusted to 7-9 for polycondensation to obtain a second modified halloysite nanotube suspension.

6. The method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage according to claim 5, characterized in that: The dosage ratio of the first modified halloysite nanotube to the second organic solvent is (0.5-1.5) g: 100 ml; and / or, The mass ratio of the first modified halloysite nanotube to tetraethyl orthosilicate is 1:(0.6-0.8); and / or, In the process of uniformly mixing tetraethyl orthosilicate, the third organic solvent and water, the mass ratio of tetraethyl orthosilicate, the third organic solvent and water is (1.5-2.5): (3-4): 1; and / or, The second organic solvent and the third organic solvent are both anhydrous ethanol; and / or, Adjust the pH to 3-4 by adding concentrated hydrochloric acid; and / or, Adjust the pH to 7-9 by adding ammonia water; and / or, The hydrolysis reaction temperature is 30-40°C, the hydrolysis reaction time is 30-60 min, and the hydrolysis reaction is carried out under stirring; and / or, The temperature of the polycondensation reaction is 30-40° C., the time of the polycondensation reaction is 10-20 min, and the polycondensation reaction is carried out under stirring.

7. The method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage according to claim 6, characterized in that: The mass solid content of the aqueous resin dispersion is 30% to 40%, and the volume ratio of the second modified halloysite nanotube suspension to the aqueous resin dispersion is (5 to 9):

1.

8. The method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage according to claim 1, characterized in that: The aqueous resin dispersion is at least one of an aqueous polyurethane dispersion or an aqueous epoxy resin dispersion; and / or, The alkyl siloxane is at least one of dodecyltrimethoxysilane, tetradecyltrimethoxysilane, hexadecyltrimethoxysilane and octadecyltrimethoxysilane.

9. The method for preparing an anti-icing super-hydrophobic coating based on phase change energy storage according to claim 1, characterized in that: The surface modification process includes: A fourth organic solvent solution of alkyl siloxane is prepared, and the substrate coated with the mixed dispersion is immersed in the fourth organic solvent solution of alkyl siloxane, and then dried to obtain an anti-icing super-hydrophobic coating based on phase change energy storage; wherein, The fourth organic solvent is anhydrous ethanol; and / or, In the fourth organic solvent solution of alkyl siloxane, the mass concentration of alkyl siloxane is 1% to 2%; and / or, The soaking temperature is 20-30° C., and the soaking time is 2-3 min.

10. An anti-icing super-hydrophobic coating based on phase change energy storage, characterized in that: The anti-icing super-hydrophobic coating based on phase change energy storage is obtained by the preparation method of the anti-icing super-hydrophobic coating based on phase change energy storage according to any one of claims 1 to 9.

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