A double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance, as well as its preparation method and application

Abstract

A double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance, as well as its preparation method and application, is intended to solve the technical problems of the existing microcapsule phase change materials being prone to leakage, having a single source of heat energy, and achieving monotonous functions. The double-layer composite microcapsule of the present invention is composed of an inner phase change microcapsule core, an inner phase change microcapsule shell, an outer self-repairing microcapsule core, and an outer self-repairing microcapsule shell from the inside to the outside; wherein the inner phase change microcapsule core is composed of n-octanoic acid and tetradecane; the outer self-repairing microcapsule core is a mixture of hydrophobic hexamethylene diisocyanate and carbon nanotubes; the inner and outer phase change microcapsule shells are a mixture of carbon nanotubes and a double polymer, and the double polymer is prepared from polyvinyl alcohol and methylated hexahydroxymethyl melamine resin; first prepare an inner high energy storage phase change microcapsule, then add it to the outer microcapsule core solution, and then add it dropwise to the outer microcapsule shell solution to form a double-layer composite microcapsule; use the microcapsule to prepare a coating, which can be used in the field of coating self-repair and ice and snow resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of coating material preparation, and in particular to a double-layer composite microcapsule coating with self-repairing, high energy storage and ice and snow resistance, and a preparation method thereof. Background Art

[0002] Icing on outdoor power transmission lines, photovoltaic equipment, and transportation vehicles not only reduces the efficiency of these facilities and increases energy consumption, but is also more likely to cause serious accidents involving life and property. Current anti-icing methods can be divided into two types: active and passive. Active anti-icing methods include the use of mechanical devices, heating, and lowering the freezing point by spreading salt. However, these methods are often accompanied by problems such as high workload, low conversion efficiency, environmental pollution, and corrosion to building materials. Passive anti-icing methods, especially anti-icing coating technology, are widely used in practical engineering due to their low cost, low energy consumption, environmental friendliness, and high application value. Applying anti-icing coatings on the surfaces of outdoor power transmission lines, photovoltaic equipment, transportation vehicles, and other facilities is an efficient and economical anti-icing method.

[0003] Anti-icing coatings incorporate photothermal materials that effectively convert absorbed light energy into heat, significantly accelerating the melting of ice on surfaces. While these coatings exhibit excellent de-icing performance under bright sunlight, they readily lose this ability in darkness. Consequently, their anti-icing / de-icing capabilities are significantly reduced, or even completely lost in the absence of light, such as on cloudy days or at night. This limits their practical use. Phase-change materials, as a promising latent heat storage material, can effectively regulate material temperature. To this end, researchers have combined phase-change materials with anti-icing / de-icing coatings to achieve energy storage. Part of the photothermal energy is stored in the phase-change material within the coating, which is then released at night or on rainy days, achieving all-weather anti-icing and de-icing performance. However, when phase-change materials are directly incorporated into the coating matrix, they are prone to leakage, reducing the coating's service life. Furthermore, microcapsules—microcontainers used to encapsulate active substances—encapsulate phase-change materials, preventing direct contact between the phase-change material and the matrix, thus preventing leakage. Furthermore, the microcapsule structure exhibits high mechanical strength and thermal stability. However, while the phase-change material microcapsules currently under research can store heat, they typically only obtain heat energy through heating, resulting in a single source of heat energy. Furthermore, when the surface coating materials of outdoor power transmission lines, photovoltaic equipment, transportation vehicles, and other facilities are exposed to strong sunlight, ozone, and other chemicals, the low-surface-energy substances on the coating surface can be chemically damaged, causing the coating to lose its anti-icing properties. Summary of the Invention

[0004] The present invention aims to solve the technical problems of existing microcapsule phase change materials, such as easy leakage, single heat energy source, and monotonous function, and provides a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance, as well as its preparation method and application.

[0005] The double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance of the present invention is composed of an inner phase change microcapsule core, an inner phase change microcapsule shell, an outer self-repairing microcapsule core and an outer self-repairing microcapsule shell from the inside to the outside.

[0006] The core of the internal phase-change microcapsule is a mixture of octanoic acid, tetradecane, sodium polyacrylate emulsifier and deionized water; octanoic acid and tetradecane change from liquid to solid under low-temperature conditions. This process releases heat, slows the cooling rate of the coating, regulates the low-temperature environment of the coating material, and effectively improves the anti-icing and de-icing effect of the coating.

[0007] The inner phase-change microcapsule shell is made from a mixture of carbon nanotubes, a dual polymer (prepared from polyvinyl alcohol and methylated hexamethylolmelamine resin), and deionized water. The carbon nanotubes are entangled with the dual polymer and deposited within the inner shell wall. The dual polymer as the inner shell material improves the strength and chemical stability of the phase-change microcapsules. The carbon nanotubes, as a photothermal material, convert light energy into heat, enhancing the energy storage efficiency of the phase-change material. Furthermore, the carbon nanotubes generate heat under the influence of an external electric or magnetic field, further enhancing the energy storage of the phase-change material.

[0008] The external self-healing microcapsule core is made of a mixture of hydrophobic hexamethylene diisocyanate, carbon nanotubes, styrene maleic anhydride emulsifier, polyether F127 surfactant and deionized water; among them, hydrophobic hexamethylene diisocyanate is a low-surface-energy substance that will gradually release and repair the damaged parts of the coating after the coating is damaged; carbon nanotubes will increase the release of hydrophobic hexamethylene diisocyanate, promote its repair of the damaged parts of the coating, and improve the self-healing effect of the coating material.

[0009] The shell of the self-healing microcapsule is made from a mixture of carbon nanotubes, a dual polymer made from polyvinyl alcohol (PVA) and methylated hexamethylolmelamine resin, and deionized water. The carbon nanotubes are entangled with the dual polymer and deposited in the shell wall. The dual polymer as the shell material improves the self-healing microcapsule's responsiveness to the external environment. Polyvinyl alcohol, as a vulnerable component of the shell material, is more susceptible to damage and can accelerate the release of the core material. The methylated hexamethylolmelamine resin offers high stability and harmlessness due to its high crosslinking density and low formaldehyde content. The carbon nanotubes impart dual thermal induction and self-healing mechanisms to the self-healing microcapsules, enhancing the shell's damage resistance and the core's release efficiency.

[0010] Furthermore, in the core of the internal phase change microcapsule, the mass ratio of sodium polyacrylate emulsifier, n-octanoic acid, tetradecane and deionized water is 1:(95-100):(95-100):(190-210).

[0011] Furthermore, in the shell of the internal phase change microcapsule, the mass ratio of polyvinyl alcohol, methylated hexahydroxymethyl melamine resin, carbon nanotubes and deionized water is 1:(65-70):(1.2-1.5):(140-155).

[0012] Furthermore, in the external self-healing microcapsule core, the mass ratio of polyether F127 surfactant with a concentration of 15-20 g / L, carbon nanotubes, styrene maleic anhydride emulsifier, hydrophobic hexamethylene diisocyanate and deionized water is 1:(1.5-2):(2-3):(85-95):(185-200).

[0013] Furthermore, in the external self-repairing microcapsule shell, the mass ratio of polyvinyl alcohol, methylated hexahydroxymethyl melamine resin, carbon nanotubes and deionized water is 1:(65-70):(1.2-1.5):(140-155).

[0014] The preparation method of the above-mentioned double-layer composite microcapsules with self-repairing, high energy storage and ice and snow resistance is carried out according to the following steps:

[0015] 1. Preparation of internal phase change microcapsule core solution: Sodium polyacrylate emulsifier, n-octanoic acid, tetradecane and deionized water are taken respectively in a mass ratio of 1:(95-100):(95-100):(190-210); n-octanoic acid and tetradecane are mixed, added to deionized water and mixed evenly, and heated until the raw materials are completely dissolved to obtain a mixed solution; the pH value of the mixed solution is then adjusted to 3.5-4.5 with citric acid solution; sodium polyacrylate emulsifier is then added to the mixed solution, and stirred at a temperature of 65-75°C for 20-40 minutes for emulsification to obtain a uniform and stable internal phase change microcapsule core solution;

[0016] 2. Preparation of internal phase change microcapsule shell solution: polyvinyl alcohol, methyl ether hexahydroxymethyl melamine resin, carbon nanotubes and deionized water are taken respectively in a mass ratio of 1: (65-70): (1.2-1.5): (140-155); polyvinyl alcohol is added to deionized water and mixed evenly, and then methyl ether hexahydroxymethyl melamine resin is added and mixed evenly to obtain a mixed solution; the pH value of the mixed solution is adjusted to 7.5-8.5 with sodium hydroxide solution, and then stirred at a temperature of 65-75°C and a stirring speed of 500-700 r / min for 20-40 minutes; finally, carbon nanotubes are added to the mixed solution, and ultrasonically treated to entangle the carbon nanotubes and the double polymer and mix evenly to obtain an internal phase change microcapsule shell solution;

[0017] 3. Preparation of internal high energy storage phase change microcapsules: the internal phase change microcapsule shell solution is added dropwise to the internal phase change microcapsule core solution, and citric acid solution is added at the same time to adjust the solution pH value to 3.5-4.5; after the internal phase change microcapsule shell solution is added dropwise, stirring is carried out at a temperature of 65-75°C and a stirring speed of 1000-1500 r / min for 60-90 minutes to allow the inner wall material to undergo a cross-linking and curing reaction on the surface of the core material, and the carbon nanotubes and the double polymer are entangled and deposited in the inner shell wall. The stirring is stopped after the solution temperature is naturally cooled to room temperature; the reaction solution is then filtered, washed with anhydrous ethanol, and then dried in a vacuum drying oven at a temperature of 20-30°C for 20-24 hours to obtain internal high energy storage phase change microcapsules;

[0018] 4. Preparation of external self-repairing microcapsule core solution: take polyether F127 surfactant, carbon nanotubes, styrene maleic anhydride emulsifier, hydrophobic hexamethylene diisocyanate and deionized water with a concentration of 15-20 g / L respectively according to the mass ratio of 1: (1.5-2): (2-3): (85-95): (185-200); first styrene maleic anhydride emulsifier is swollen in deionized water for 20-24 hours, the expanded styrene maleic anhydride solution is heated to 45-55 ° C, and then sodium hydroxide solution is added to adjust the pH of the solution to 9.5-10.5; hydrophobic hexamethylene diisocyanate, carbon nanotubes, 15-20 g / L polyether F127 surfactant are added to the styrene maleic anhydride solution, and then stirred with a high-speed shearing machine at a stirring speed of 500-700 r / min for 25-35 minutes to obtain a stable and uniform external self-repairing microcapsule core solution;

[0019] 5. Preparation of external self-repairing microcapsule shell solution: polyvinyl alcohol, methylated hexahydroxymethyl melamine resin, carbon nanotubes and deionized water are taken respectively in a mass ratio of 1: (65-70): (1.2-1.5): (140-155); polyvinyl alcohol and deionized water are stirred evenly, and added to the methylated hexahydroxymethyl melamine resin, stirred evenly to obtain a mixed solution; the pH value of the mixed solution is adjusted to 7.5-8.5 with sodium hydroxide solution; and then stirred at a stirring speed of 500-700 r / min for 20-40 min at a temperature of 65-75°C; carbon nanotubes are then added and ultrasonically treated to entangle with the double polymer and deposited in the outer shell wall to prepare an external microcapsule shell solution;

[0020] 6. Preparation of double-layer composite microcapsules: Add the inner high energy storage phase change microcapsules to the outer self-repairing microcapsule core solution at a temperature of 20-30°C, and then add it dropwise to the outer self-repairing microcapsule shell solution. The outer self-repairing microcapsule core material containing the inner high energy storage phase change microcapsules attracts the outer wall material to the surrounding area through electrostatic adsorption; after the outer self-repairing microcapsule shell solution is added, the temperature is increased at a rate of 1-5°C / min. When the solution temperature rises to 65°C, citric acid solution is added to adjust the solution pH value to 4-5, and the temperature is continued to be increased at a rate of 1-5°C / min until the solution temperature reaches 80°C and stirred at this temperature at a stirring speed of 1000-1500r / min for 60-90min. The outer wall material undergoes a cross-linking and curing reaction on the surface of the core material through mechanical stirring. The solution temperature is naturally cooled to room temperature and stirring is stopped; finally, the reaction solution is filtered, washed with anhydrous ethanol, and vacuum dried to obtain a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance.

[0021] Furthermore, the ultrasonic treatment in steps 2 and 5 is performed using a cell disruptor, with an ultrasonic power of 85 to 95 W, an amplitude of 50% to 60%, and a duration of 60 to 90 min.

[0022] Furthermore, in step three, the mass ratio of the internal phase change microcapsule shell solution to the internal phase change microcapsule core solution is 1:(1.4-1.6).

[0023] Furthermore, the concentration of the citric acid solution in step 1, step 3 and step 6 is 1 to 1.5 mol / L.

[0024] Furthermore, the concentration of the sodium hydroxide solution in step 2, step 4 and step 5 is 1-2 mol / L.

[0025] Furthermore, the mass ratio of the external self-repairing microcapsule shell solution to the external self-repairing microcapsule core solution in step six is ​​1:(1.4-1.6).

[0026] Furthermore, the vacuum drying in step six is ​​carried out in a vacuum drying oven at a temperature of 20 to 30° C. for 20 to 24 hours.

[0027] The application of the above-mentioned double-layer composite microcapsules with both self-repairing, high energy storage and ice and snow resistance is to use the double-layer composite microcapsules with both self-repairing, high energy storage and ice and snow resistance to prepare a coating with both self-repairing, high energy storage and ice and snow resistance; the specific method is carried out according to the following steps:

[0028] 1. Weigh, by mass percentage, 57% to 75% of E51 epoxy resin, 10% to 15% of a curing agent, 5% to 8% of methacryloxypropyltrimethoxysilane as a surface modifier, 3% to 5% of hydrophobic nano-silica, and 7% to 15% of a double-layer composite microcapsule with self-repairing, high energy storage, and ice and snow resistance; wherein the curing agent is isophorone diamine or triethylenetetramine;

[0029] Second, E51 epoxy resin, a curing agent, a surface modifier, hydrophobic nano-silica, and double-layer composite microcapsules with self-repairing, high energy storage, and ice and snow resistance properties were mixed to obtain a mixture. Acetone was then added as a diluent and stirred for 60 to 90 minutes using a mechanical stirrer at a stirring speed of 1000 to 1500 rpm. The mixture was then ultrasonically treated to obtain a coating with self-repairing, high energy storage, and ice and snow resistance properties. The coating contains double-layer composite microcapsules with self-repairing, high energy storage, and long-lasting ice and snow resistance properties, giving the coating self-repairing, high energy storage, and long-lasting ice and snow resistance properties.

[0030] Furthermore, the ultrasonic treatment in step 2 is performed using a cell disruptor, and the ultrasonic power is 85-95 W, the amplitude is 50%-60%, and the time is 30-40 min.

[0031] Furthermore, the added mass of the acetone diluent described in step 2 is 80% to 90% of the total mass of the mixture of E51 epoxy resin, curing agent, surface modifier, hydrophobic nano-silica and double-layer composite microcapsules with self-repairing, high energy storage and ice and snow resistance.

[0032] The method for using the self-repairing, high-energy-storage, and ice- and snow-resistant coating is to spray the self-repairing, high-energy-storage, and ice- and snow-resistant coating on a substrate through a spray gun, and then cure it at room temperature or heat-cure it at 70 to 90°C for 100 to 120 minutes to obtain a double-shell microcapsule coating that is self-repairing, high-energy-storage, and long-lasting ice- and snow-resistant.

[0033] Furthermore, the substrate is one or more of concrete, metal, asphalt, glass, fiber, plastic, wall, and wire;

[0034] Furthermore, the spraying amount of the self-repairing, high energy storage and ice and snow resistance coating is 0.015-0.04 mL / cm 2 .

[0035] Compared with existing technologies, this invention overcomes the single-function limitations of traditional microcapsule composite materials, achieving multifunctionality with self-repairing, high energy storage, and long-term anti-ice and snow protection. The self-repairing, high energy storage, and long-term anti-ice and snow protection double-layer composite microcapsules prepared by this invention not only repair chemical damage to the coating, but also offer advantages such as high encapsulation efficiency, high photothermal conversion efficiency, high thermal conductivity, excellent sealing performance, good thermal stability, and excellent mechanical properties. The generated heat and high energy storage increase the temperature of the coating material, melting ice and snow on the coating surface and inhibiting ice formation, ultimately achieving a self-repairing, high energy storage, and long-term anti-ice and snow protection mechanism.

[0036] The coating prepared by the double-layer composite microcapsules with self-repairing, high energy storage and ice and snow resistance of the present invention has a working process of two stages, such as Figure 2 shown.

[0037] Phase 1: When the coating is damaged by external forces, the shell structure of the double-layer composite microcapsule is destroyed, and the repair agent contained in the outer core is released to repair the damaged coating. At the same time, the conductive nanomaterials contained in the shell structure will generate heat energy under the action of the external electric field or magnetic field, increasing the fluidity of the repair agent, promoting the self-repair effect of the damaged coating, and achieving the purpose of long-term durability of the coating.

[0038] The second stage: The released repair agent contains undamaged high-energy storage phase change microcapsules. After the composite microcapsule shell and outer core structure realize thermal induction and self-repair functions, the high-energy storage phase change microcapsules in the repair agent continue to play a high energy storage role. The photothermal material contained in the wall of the high-energy storage phase change microcapsule not only stores light and heat in the phase change material, but also generates heat energy under the action of an external electric field or magnetic field and then stores it in the phase change material, jointly realizing comprehensive properties such as high heat storage capacity, excellent light-to-heat conversion performance and good thermal conductivity, realizing the temperature regulation function of the coating in a low-temperature environment, and effectively inhibiting the formation of ice on the coating surface.

[0039] At -20°C, the time it takes for small droplets on the surface of the coating containing 10 wt.% of the double-layer composite microcapsules of the present invention to freeze is 742 seconds, while the time it takes for small droplets on the surface of the blank coating to freeze is 56 seconds. The time it takes for small droplets on the coating containing 10 wt.% of the double-layer composite microcapsules of the present invention to freeze is about 13.3 times that of the blank coating. 2Under near-infrared light, droplets of a coating containing 10 wt.% of the present invention's double-layer composite microcapsules melted in 1.9 seconds, compared to 21 seconds for a blank coating. This represents approximately 1 / 11 of the time required for a blank coating to melt. Compared to a coating without the double-layer composite microcapsules, the coating containing the double-layer composite microcapsules exhibited superior anti-icing / de-icing properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic structural diagram of the double-layer composite microcapsule of the present invention that has both self-repairing, high energy storage and ice and snow resistance. In the figure, 1 is the inner phase change microcapsule core, 2 is the inner phase change microcapsule shell, 3 is the outer self-repairing microcapsule core, and 4 is the outer self-repairing microcapsule shell.

[0041] Figure 2 It is a schematic diagram of the two-stage action of a double-layer composite microcapsule with self-repairing, high energy storage and anti-ice / de-icing properties on the substrate surface. DETAILED DESCRIPTION

[0042] The beneficial effects of the present invention are demonstrated with the following examples.

[0043] Example 1: The preparation method of the double-layer composite microcapsules with self-repairing, high energy storage and ice and snow resistance of this embodiment is carried out according to the following steps:

[0044] 1. Preparation of internal phase change microcapsule core solution:

[0045] Sodium polyacrylate emulsifier, n-octanoic acid, tetradecane, and deionized water were weighed according to a mass ratio of 1:95:95:190; n-octanoic acid and tetradecane were mixed, then added to deionized water and mixed evenly, and heated until the raw materials were completely dissolved to obtain a mixed solution; the pH value of the mixed solution was then adjusted to 4 with a 1 mol / L citric acid solution; the sodium polyacrylate emulsifier was then added to the mixed solution, and the mixture was stirred at 70° C. for 30 minutes for emulsification to obtain a uniform and stable internal phase change microcapsule core solution;

[0046] 2. Preparation of internal phase change microcapsule shell solution: Polyvinyl alcohol, methylated hexahydroxymethyl melamine resin, carbon nanotubes and deionized water were weighed respectively according to the mass ratio of polyvinyl alcohol, methylated hexahydroxymethyl melamine resin, carbon nanotubes and deionized water of 1:65:1.2:140; polyvinyl alcohol was added to deionized water and mixed evenly, and then methylated hexahydroxymethyl melamine resin was added and mixed evenly to obtain a mixed solution; the pH value of the mixed solution was adjusted to 8 with a sodium hydroxide solution having a concentration of 1.5 mol / L, and then stirred at a temperature of 70°C and a stirring speed of 600 r / min for 30 minutes; finally, carbon nanotubes were added to the mixed solution, and the carbon nanotubes were entangled with the double polymer and mixed evenly by ultrasonic treatment to obtain an internal phase change microcapsule shell solution;

[0047] 3. Preparation of internal high energy storage phase change microcapsules: according to the mass ratio of the internal phase change microcapsule shell solution to the internal phase change microcapsule core solution of 1:1.5, the internal phase change microcapsule shell solution was added dropwise to the internal phase change microcapsule core solution, and a citric acid solution with a concentration of 1 mol / L was added to adjust the pH value of the solution to 4; after the internal phase change microcapsule shell solution was added dropwise, the mixture was stirred at a temperature of 70°C and a stirring speed of 1500 r / min for 70 minutes to allow the inner wall material to undergo a cross-linking and curing reaction on the surface of the core material, and the carbon nanotubes and the double polymer were entangled and deposited in the inner shell wall. The stirring was stopped after the solution temperature naturally cooled to room temperature; the reaction solution was then filtered, washed with anhydrous ethanol, and then dried in a vacuum drying oven at a temperature of 25°C for 24 hours to obtain internal high energy storage phase change microcapsules;

[0048] 4. Preparation of external self-repairing microcapsule core solution:

[0049] 15g / L of polyether F127 surfactant, carbon nanotubes, styrene maleic anhydride emulsifier, hydrophobic hexamethylene diisocyanate, and deionized water were weighed in a mass ratio of 1:1.5:2:85:185. The styrene maleic anhydride emulsifier was first swelled in deionized water for 24 hours, and the expanded styrene maleic anhydride solution was heated to 50°C. Then, a 1.5mol / L sodium hydroxide solution was added to adjust the pH of the solution to 10. The hydrophobic hexamethylene diisocyanate, carbon nanotubes, and polyether F127 were added to the styrene maleic anhydride solution, and then stirred for 30 minutes using a high-speed shearing machine at a stirring speed of 700r / min to obtain a stable and uniform external self-healing microcapsule core solution.

[0050] 5. Preparation of external self-repairing microcapsule shell solution:

[0051] According to the mass ratio of polyvinyl alcohol, methylated hexahydroxymethyl melamine resin, carbon nanotubes and deionized water of 1:65:1.2:140, polyvinyl alcohol, methylated hexahydroxymethyl melamine resin, carbon nanotubes and deionized water were weighed respectively; polyvinyl alcohol and deionized water were stirred evenly, and added to the methylated hexahydroxymethyl melamine resin, and stirred evenly to obtain a mixed solution; the pH value of the mixed solution was adjusted to 8 with a sodium hydroxide solution having a concentration of 1.5 mol / L; then, the mixture was stirred at a stirring speed of 600 r / min at a temperature of 70° C. for 30 minutes; carbon nanotubes were then added, and ultrasonic treatment was performed for 30 minutes using a cell crusher at an ultrasonic power of 90 W and an amplitude of 50% to entangle the carbon nanotubes and the double polymer and mix them evenly to obtain an external self-repairing microcapsule shell solution;

[0052] 6. Preparation of double-layer composite microcapsules

[0053] According to the mass ratio of the external self-repairing microcapsule shell solution to the external self-repairing microcapsule core solution of 1:1.5, the internal high energy storage phase change microcapsules were added to the external self-repairing microcapsule core solution at a temperature of 25°C, and then added dropwise to the external self-repairing microcapsule shell solution. The external self-repairing microcapsule core material containing the internal high energy storage phase change microcapsules attracted the outer wall material to the surrounding area through electrostatic adsorption, and the carbon nanotubes and the double polymer were entangled and deposited on the outer shell wall. After the external self-repairing microcapsule shell solution was added, the temperature was increased at a rate of 2°C / min. When the solution temperature rose to 65°C, the solution was heated. 1 mol / L citric acid solution was added to adjust the pH value of the solution to 4, and the temperature was continued to be raised at a rate of 2°C / min until the solution temperature reached 80°C and stirred at this temperature at a stirring speed of 1500r / min for 60min. The outer wall material was cross-linked and cured on the surface of the core material through mechanical stirring. The solution temperature was naturally cooled to room temperature and stirring was stopped; finally, the reaction liquid was filtered, washed with anhydrous ethanol, and vacuum dried in a vacuum drying oven at a temperature of 25°C for 24 hours to obtain a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance.

[0054] Comparative Example 1: This comparative example is to prepare a single self-repairing microcapsule, and the specific steps are as follows:

[0055] 1. Preparation of self-repairing microcapsule core solution:

[0056] According to the mass ratio of 15 g / L polyether F127 surfactant, carbon nanotubes, styrene maleic anhydride emulsifier, hydrophobic hexamethylene diisocyanate and deionized water of 1:1.5:2:85:185, polyether F127 surfactant, carbon nanotubes, styrene maleic anhydride emulsifier, hydrophobic hexamethylene diisocyanate and deionized water were taken respectively; the styrene maleic anhydride emulsifier was first swelled in deionized water for 24 hours, the expanded styrene maleic anhydride solution was heated to 50°C, and then a 1.5 mol / L sodium hydroxide solution was added to adjust the pH of the solution to 10; hydrophobic hexamethylene diisocyanate, carbon nanotubes and polyether F127 were added to the styrene maleic anhydride solution, and then stirred for 30 minutes using a high-speed shearing machine at a stirring speed of 700 r / min to obtain a stable and uniform external self-healing microcapsule core solution;

[0057] 2. Preparation of self-repairing microcapsule shell solution:

[0058] Polyvinyl alcohol, methylated hexahydroxymethyl melamine resin, carbon nanotubes and deionized water are taken respectively according to the mass ratio of polyvinyl alcohol, methylated hexahydroxymethyl melamine resin, carbon nanotubes and deionized water of 1:65:1.2:140; polyvinyl alcohol and deionized water are stirred evenly, and added to the methylated hexahydroxymethyl melamine resin, and stirred evenly to obtain a mixed solution; the pH value of the mixed solution is adjusted to 8 with 1.5 mol / L sodium hydroxide solution; the mixture is stirred at a temperature of 70°C and a stirring speed of 600 r / min for 30 minutes; carbon nanotubes are then added, and ultrasonic treatment is carried out for 70 minutes using a cell crusher at an ultrasonic power of 90 W and an amplitude of 50%, so that the carbon nanotubes are entangled with the double polymer and deposited in the shell wall to obtain a self-repairing microcapsule shell solution;

[0059] 3. Preparation of self-repairing microcapsules:

[0060] According to the mass ratio of self-repairing microcapsule shell solution to self-repairing microcapsule core solution of 1:1.5, the self-repairing microcapsule shell solution was added dropwise to the self-repairing microcapsule core solution. After the self-repairing microcapsule shell solution was added, the temperature was increased at a rate of 2°C / min. When the solution temperature rose to 65°C, 1 mol / L citric acid solution was added to adjust the pH value of the solution to 4. The temperature was continued to be increased at a rate of 2°C / min until the solution temperature reached 80°C and stirred at a stirring speed of 1000 r / min for 60 minutes. The outer wall material was cross-linked and cured on the surface of the core material through mechanical stirring. The solution temperature was naturally cooled to room temperature and stirring was stopped. Finally, the reaction solution was filtered, washed with anhydrous ethanol, and vacuum dried at 25°C for 24 hours to obtain a single self-repairing microcapsule.

[0061] The single self-healing microcapsules prepared in Comparative Example 1 and the double-layer composite microcapsules prepared in Example 1 were tested for their impermeability and thermal stability. After the single self-healing microcapsules and the double-layer composite microcapsules were immersed in ethanol for the same time, the mass loss rate of the core of the two microcapsules before and after immersion was tested to evaluate their impermeability.

[0062] The thermal stability of single self-healing microcapsules and double-layer composite microcapsules was analyzed by thermogravimetric analyzer at temperatures of 230-300°C, and their mass loss rate was used as an evaluation indicator.

[0063] The exothermic enthalpy of single phase change microcapsules and double-layer composite microcapsules was tested by differential scanning calorimetry.

[0064] The yield stress of single phase-change microcapsules and double-layer composite microcapsules was tested using a nanoindentation tester. The load-displacement curves were set to 50 nN for 10 seconds with a displacement resolution of 0.01 nm. The yield stress values ​​of the single phase-change microcapsules and double-layer composite microcapsules at a pH of 5.0 were calculated based on the load-displacement curves.

[0065] The test results are listed in Table 1.

[0066] Table 1 Performance comparison of the single phase change microcapsules of Comparative Example 1 and the double-layer composite microcapsules of Example 1

[0067]

[0068] Compared to single self-healing microcapsules, double-layer composite microcapsules exhibit greater impermeability and thermal stability, indicating greater stability and greater support for the self-healing function of the microcapsules. Compared to single phase-change microcapsules, double-layer composite microcapsules exhibit greater yield stress and exothermic enthalpy, indicating improved mechanical properties and a greater ability to regulate low-temperature environments in coating materials, mitigating ice buildup on the coating surface.

[0069] The double-layer composite microcapsules with self-repairing, high energy storage and ice and snow resistance prepared in Example 1 were used to prepare a coating with self-repairing, high energy storage and ice and snow resistance. The specific method was carried out according to the following steps:

[0070] 1. Weigh 63 grams of E51 epoxy resin, 15 grams of triethylenetetramine as a curing agent, 8 grams of methacryloxypropyltrimethoxysilane as a surface modifier, 4 grams of hydrophobic nano-silica, and 10 grams of double-layer composite microcapsules with self-repairing, high energy storage and ice and snow resistance;

[0071] 2. E51 epoxy resin, triethylenetetramine, methacryloxypropyltrimethoxysilane, hydrophobic nano-silica and double-layer composite microcapsules with self-repairing, high energy storage and anti-ice and snow properties were mixed to obtain a mixture; 110 mL of acetone diluent (density 0.79 g / cm 3 ), stirred for 80 minutes using a mechanical stirring device at a stirring speed of 1000 r / min; then subjected to ultrasonic treatment for 30 minutes using a cell crusher at an ultrasonic power of 90 W and an amplitude of 50% to obtain a coating with self-repairing, high energy storage and anti-ice and snow properties.

[0072] At the same time, the double-layer composite microcapsules with self-repairing, high energy storage and ice and snow resistance were not added to prepare the comparative coating.

[0073] The self-repairing, high energy storage and ice and snow resistance coatings and the comparative coatings were sprayed on the same substrate, which was a plexiglass plate (area 100cm 2 ), droplet freezing and deicing tests were conducted on the two coatings.

[0074] The droplet freezing test was performed by placing the two coatings in an environmental chamber at a temperature of -20°C and a relative humidity of 30%; then placing a small droplet of 5 μl on the surface of each coating.

[0075] De-icing test method: The two coatings were placed in an environmental chamber with a temperature of -5°C and a relative humidity of 85%. An air humidifier was placed in the environmental chamber to promote the formation of water droplets on the coating surface. Subsequently, the air humidifier was turned off and the coating was heated under near-infrared (200mW / cm 2 ) and observed the melting time of water droplets on the surfaces of the two coatings.

[0076] The test results of the two coatings are as follows:

[0077] At -20°C, it takes 742 seconds for small droplets on the surface of the coating containing 10 wt.% of double-layer composite microcapsules to freeze, while it takes 56 seconds for small droplets on the surface of the blank coating to freeze. The time taken for small droplets on the coating containing 10 wt.% of double-layer composite microcapsules to freeze is approximately 13.3 times that of the blank coating.

[0078] At 200mW / cm 2 Under the irradiation of near-infrared lamp, the time taken for the small droplets of the double-layer composite microcapsule coating containing 10wt.% to melt is 1.9 seconds, and the time taken for the small droplets of the blank coating to melt is 21 seconds. The time taken for the small droplets of the double-layer composite microcapsule coating containing 10wt.% to melt is about 1 / 11 of the time taken for the small droplets of the blank coating to melt.

[0079] In summary, the coating containing double-layer composite microcapsules has excellent anti-icing / de-icing effect compared with the coating without double-layer composite microcapsules.

Claims

1. A method for preparing a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance, characterized in that: The method proceeds as follows:

1. Preparation of internal phase change microcapsule core solution: Sodium polyacrylate emulsifier, octanoic acid, tetradecane and deionized water are respectively taken in a mass ratio of 1: (95-100): (95-100): (190-210); octanoic acid and tetradecane are mixed, added to deionized water and mixed evenly, and heated until the raw materials are completely dissolved to obtain a mixed solution; the pH value of the mixed solution is then adjusted to 3.5-4.5 with citric acid solution; sodium polyacrylate emulsifier is then added to the mixed solution, and stirred at a temperature of 65-75°C for 20-40 minutes for emulsification to obtain a uniform and stable internal phase change microcapsule core solution; 2. Preparation of internal phase change microcapsule shell solution: polyvinyl alcohol, methyl ether hexahydroxymethyl melamine resin, carbon nanotubes and deionized water are taken respectively in a mass ratio of 1: (65~70): (1.2~1.5): (140~155); polyvinyl alcohol is added to deionized water and mixed evenly, and then methyl ether hexahydroxymethyl melamine resin is added and mixed evenly to obtain a mixed solution; the pH value of the mixed solution is adjusted to 7.5~8.5 with sodium hydroxide solution, and then stirred at a temperature of 65~75℃ and a stirring speed of 500~700r / min for 20~40min; finally, carbon nanotubes are added to the mixed solution, and ultrasonic treatment is performed to entangle the carbon nanotubes and the double polymer and mix them evenly to obtain an internal phase change microcapsule shell solution; 3. Preparation of internal high energy storage phase change microcapsules: the internal phase change microcapsule shell solution is added dropwise to the internal phase change microcapsule core solution, and citric acid solution is added at the same time to adjust the solution pH value to 3.5-4.5; after the internal phase change microcapsule shell solution is added dropwise, stirring is carried out at a temperature of 65-75°C and a stirring speed of 1000-1500 r / min for 60-90 minutes to allow the inner wall material to undergo a cross-linking and curing reaction on the surface of the core material, and the carbon nanotubes and the double polymer are entangled and deposited in the inner shell wall. The stirring is stopped after the solution temperature is naturally cooled to room temperature; the reaction solution is then filtered, washed with anhydrous ethanol, and then dried in a vacuum drying oven at a temperature of 20-30°C for 20-24 hours to obtain internal high energy storage phase change microcapsules; Preparation of external self-healing microcapsule core solution: polyether F127 surfactant, carbon nanotubes, styrene maleic anhydride emulsifier, hydrophobic hexamethylene diisocyanate and deionized water with a mass ratio of 1: (1.5-2): (2-3): (85-95): (185-200) were respectively taken at a concentration of 15-20 g / L; the styrene maleic anhydride emulsifier was first swelled in deionized water for 20-24 h, the expanded styrene maleic anhydride solution was heated to 45-55 °C, and then sodium hydroxide solution was added to adjust the solution pH to 9.5-10.5; hydrophobic hexamethylene diisocyanate, carbon nanotubes and polyether F127 surfactant were added to the styrene maleic anhydride solution, and then stirred for 25-35 min using a high-speed shearing machine at a stirring speed of 500-700 r / min to obtain a stable and uniform external self-healing microcapsule core solution; 5. Preparation of external self-repairing microcapsule shell solution: polyvinyl alcohol, methyl ether hexahydroxymethyl melamine resin, carbon nanotubes and deionized water are respectively taken in a mass ratio of 1: (65-70): (1.2-1.5): (140-155); polyvinyl alcohol and deionized water are stirred evenly, and then added to the methyl ether hexahydroxymethyl melamine resin and stirred evenly to obtain a mixed solution; the pH value of the mixed solution is adjusted to 7.5-8.5 with sodium hydroxide solution; and then stirred at a temperature of 65-75 ° C and a stirring speed of 500-700 r / min for 20-40 min; carbon nanotubes are then added and ultrasonically treated to entangle with the double polymer and deposited in the outer shell wall to prepare an external microcapsule shell solution; 6. Preparation of double-layer composite microcapsules: Add the inner high energy storage phase change microcapsules to the outer self-repairing microcapsule core solution at a temperature of 20-30°C, and then add them dropwise to the outer self-repairing microcapsule shell solution. The outer self-repairing microcapsule core material containing the inner high energy storage phase change microcapsules attracts the outer wall material to the surrounding area through electrostatic adsorption; After the external self-repairing microcapsule shell solution is added, the temperature is increased at a rate of 1~5 ℃ / min. When the solution temperature reaches 65 ℃, citric acid is added to adjust the solution pH value to 4~5. The temperature is continued to be increased at a rate of 1~5 ℃ / min until the solution temperature reaches 80 ℃ and stirred at this temperature at a stirring speed of 1000~1500 r / min for 60~90 minutes. The outer wall material undergoes a cross-linking and curing reaction on the surface of the core material through mechanical stirring. The solution temperature is naturally cooled to room temperature and stirring is stopped. Finally, the reaction liquid is filtered, washed with anhydrous ethanol, and vacuum dried to obtain a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance. The double-layer composite microcapsule is composed of an internal phase change microcapsule core, an internal phase change microcapsule shell, an external self-repairing microcapsule core and an external self-repairing microcapsule shell from the inside to the outside.

2. The method for preparing a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance according to claim 1, characterized in that: The ultrasonic treatment described in steps 2 and 5 is performed using a cell disruptor with an ultrasonic power of 85-95 W, an amplitude of 50%-60%, and a duration of 60-90 min.

3. The method for preparing a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance according to claim 1 or 2, characterized in that: In step three, the mass ratio of the internal phase change microcapsule shell solution to the internal phase change microcapsule core solution is 1:(1.4~1.6).

4. The method for preparing a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance according to claim 1 or 2, characterized in that: The concentration of the citric acid solution in step 1, step 3 and step 6 is 1-1.5 mol / L.

5. The method for preparing a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance according to claim 1 or 2, characterized in that: The concentration of the sodium hydroxide solution in step 2, step 4 and step 5 is 1-2 mol / L.

6. The method for preparing a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance according to claim 1 or 2, characterized in that: The mass ratio of the external self-repairing microcapsule shell solution to the external self-repairing microcapsule core solution described in step six is ​​1:(1.4~1.6).

7. Application of a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance prepared by the method of claim 1, characterized in that: This application is to use double-layer composite microcapsules with self-repairing, high energy storage and ice and snow resistance to prepare a coating with self-repairing, high energy storage and ice and snow resistance.

8. The use of a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance according to claim 7, characterized in that: The specific method for preparing a coating with self-repairing, high energy storage and anti-ice and snow properties by using double-layer composite microcapsules with self-repairing, high energy storage and anti-ice and snow properties is carried out in the following steps:

1. Weigh, by mass percentage, 57% to 75% of E51 epoxy resin, 10% to 15% of a curing agent, 5% to 8% of methacryloxypropyltrimethoxysilane as a surface modifier, 3% to 5% of hydrophobic nano-silica, and 7% to 15% of a double-layer composite microcapsule with self-repairing properties, high energy storage properties, and ice and snow resistance; wherein the curing agent is isophorone diamine or triethylenetetramine; 2. Mix E51 epoxy resin, curing agent, surface modifier, hydrophobic nano-silica and double-layer composite microcapsules with self-repairing, high energy storage and ice and snow resistance to obtain a mixture; then add acetone diluent, and stir with a mechanical stirring device at a stirring speed of 1000~1500r / min for 60~90min; then ultrasonically treat to obtain a coating with self-repairing, high energy storage and ice and snow resistance.

9. The use of a double-layer composite microcapsule with self-repairing, high energy storage and ice and snow resistance according to claim 8, characterized in that: The added mass of the acetone diluent described in step 2 is 80% to 90% of the total mass of the mixture of E51 epoxy resin, curing agent, surface modifier, hydrophobic nano-silica and double-layer composite microcapsules with self-repairing, high energy storage and ice and snow resistance.

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