Self-healing superhydrophobic photothermal anti-icing coating based on hindered urea bond, preparation method and application thereof

Abstract

The application provides a self-repairing super-hydrophobic photothermal anti-icing coating based on a blocked urea bond, a preparation method and application thereof, the coating is prepared by using a two-step method of blade coating-spraying, and comprises a bottom layer self-repairing resin and a surface layer micro-nano composite structure; the bottom layer is a polyurethane urea acrylate resin containing a dynamic blocked urea bond; the resin can realize reversible dissociation-recombination under heating or photothermal conditions by introducing a large steric tert-butyl urea bond, and endows the coating with intrinsic self-repairing capability; the surface layer is composed of modified carbon nanotubes and hydrophobic nano-silicon dioxide to form a micro-nano hierarchical rough structure, and realizes super-hydrophobic performance; meanwhile, the carbon nanotubes serve as a photothermal conversion medium, rapidly heat up to above 100 DEG C under near-infrared light, and can activate the self-repairing of the blocked urea bond and realize rapid active deicing. The coating integrates passive anti-icing, active deicing and damage self-repairing, and solves the problems of poor durability and single function of the existing super-hydrophobic anti-icing coating.

Description

Technical Field

[0001] This invention relates to the field of functional coatings and anti-icing technology, and in particular to a self-healing superhydrophobic photothermal anti-icing coating based on hindered urea bonds, its preparation method, and its application. Background Technology

[0002] Icing and icing severely threaten the safe operation of aviation, power transmission, wind power generation, and transportation. Traditional de-icing methods (mechanical vibration, electric heating, and chemical de-icing agents) suffer from high energy consumption, low efficiency, and environmental pollution. Superhydrophobic coatings, as a passive anti-icing strategy, capture the air layer through micro-nano rough structures, significantly delaying icing and reducing ice adhesion strength. However, superhydrophobic surfaces are highly susceptible to damage from mechanical wear and scratches, leading to the destruction of micro-nano structures and the loss of low surface energy components, resulting in the loss of superhydrophobic properties. Poor durability is a major bottleneck in their engineering applications.

[0003] To improve durability, researchers have attempted to introduce self-healing capabilities into superhydrophobic coatings. Existing self-healing superhydrophobic coatings mostly rely on the migration and replenishment of low surface energy substances or microencapsulated repair agents, which suffer from limitations such as limited repair cycles, irreversible repair processes, or harsh repair conditions. In recent years, intrinsic self-healing materials based on dynamic covalent bonds (such as Diels-Alder bonds, disulfide bonds, and imine bonds) have attracted attention due to their ability to repair multiple times without the need for external repair agents. Among them, hindered urea bonds (HUBs) exhibit unique advantages in self-healing polymers because they can undergo reversible dissociation-recombination at mild temperatures (100–140 °C) without the need for catalysts. However, research combining the self-healing properties of hindered urea bonds with superhydrophobic surfaces and photothermal active de-icing functions has not yet been reported.

[0004] Furthermore, superhydrophobic coatings that rely solely on passive anti-icing may still fail under extreme low-temperature and high-humidity environments, necessitating the introduction of active de-icing mechanisms. Carbon nanotubes (CNTs) possess excellent photothermal conversion efficiency and broad-spectrum light absorption characteristics, and can be used as photothermal fillers to endow coatings with remote and controllable active de-icing capabilities.

[0005] Based on the above-mentioned technical problems, this invention proposes a coating design scheme that synergistically integrates the dynamic self-healing of hindered urea bonds, the photothermal effect of carbon nanotubes, and the superhydrophobic surface. Summary of the Invention

[0006] The purpose of this invention is to provide a self-healing superhydrophobic photothermal anti-icing coating based on hindered urea bonds, which integrates the photothermal effect of carbon nanotubes to achieve active de-icing, and is particularly suitable for anti-icing and de-icing protection of metal or composite material surfaces in cold environments. The invention also includes its preparation method and application. The aim is to solve the problems of poor mechanical durability, irreversible function after damage, and inability of single passive anti-icing to cope with extreme environments in existing superhydrophobic anti-icing coatings, and to achieve synergistic protection of damage self-repair, long-lasting superhydrophobicity and active photothermal de-icing.

[0007] The technical solution adopted by this invention to solve its technical problem is: In a first aspect, the present invention provides a self-healing superhydrophobic photothermal anti-icing coating based on hindered urea bonds, the coating being composed of a base layer and a top layer: The underlying layer is a dynamic covalent polymer matrix resin containing hindered urea bonds; The surface layer is a functional layer composited on the bottom surface, comprising modified carbon nanotubes and hydrophobic nano-silica, which together constitute a micro-nano hierarchical rough structure. The modified carbon nanotubes have photothermal conversion function, which raises the surface temperature of the coating to over 100°C under near-infrared light irradiation, while activating the dynamic reversible exchange of hindered urea bonds to achieve self-repair and melt the ice layer.

[0008] Furthermore, the dynamic covalent polymer containing hindered urea bonds is polyurethane urea acrylate, which is prepared by stepwise polymerization of a reaction product containing polytrimethylene ether glycol, isophorone diisocyanate, chain extender trimethylolethane and methacrylate end-capping agent 2-(tert-butylamino)ethyl methacrylate containing secondary amine groups; wherein the ethyl ester forms hindered urea bonds by reacting its secondary amine groups with isocyanate groups, and introduces photocurable carbon-carbon double bonds into the resin.

[0009] Furthermore, the modified carbon nanotubes are carboxylated multi-walled carbon nanotubes modified with organosilanes for hydrophobicity, and their surfaces are further coated with a silica layer in situ by a sol-gel method, and grafted with hexadecyltrimethoxysilane or other long-chain alkyl / fluoroalkyl silanes.

[0010] Furthermore, the primary particle size of the hydrophobic nano-silica is 7–40 nm, and the surface is modified with fluorosilane or long-chain alkylsilane.

[0011] Furthermore, the surface static water contact angle of the coating is ≥150° and the roll-off angle is ≤10°; under irradiation with an 808 nm near-infrared laser, the surface of the coating heats up to ≥100°C within 5 seconds, and the maximum temperature can reach 110~125°C; in an environment of -15°C, the freezing delay time of 5μL water droplets on the surface is ≥400 seconds, and the time for the frozen ice beads to completely melt by photothermal means is ≤30 seconds.

[0012] Furthermore, when the coating is heated at 135°C for 30 minutes or irradiated with near-infrared light, surface scratches can be basically healed, and the water contact angle can be restored to more than 90% of its initial value.

[0013] In a second aspect, the present invention provides a method for preparing a coating as described in any one of the above claims, characterized by comprising the following steps: Step a) Synthesis of polyurethane urea acrylate resin containing hindered urea bonds: Under an inert atmosphere, dehydrated PO3G is mixed with the catalyst dibutyltin dilaurate and the solvent acetone, heated to 60-80°C, and IPDI is added dropwise for a prepolymerization reaction for 3-4 hours; the chain extender trimethylolethane is added and the reaction continues for 3-4 hours; finally, the end-capping agent 2-(tert-butylamino)ethyl methacrylate is added and the reaction continues for 1-2 hours to obtain the polyurethane urea acrylate resin; Step b) Preparation of modified carbon nanotube composite particles: Carboxylated multi-walled carbon nanotubes were dispersed in ethanol, and ammonia and tetraethyl orthosilicate were added to carry out a sol-gel reaction, in situ generating silica on the surface of carbon nanotubes; then hexadecyltrimethoxysilane was added for hydrophobic modification, and the reaction was carried out for 6-12 hours. After filtration, washing and drying, modified carbon nanotubes were obtained. Step c) Coating application: The polyurethane urea acrylate resin obtained in step a) is uniformly coated onto the substrate surface using a scraping method to form a bottom wet film; the modified carbon nanotubes obtained in step b) are dispersed in petroleum ether to form a first spray liquid, which is then sprayed onto the surface of the bottom wet film; hydrophobic nano-silica is then dispersed in petroleum ether to form a second spray liquid, which is then sprayed onto the surface of the carbon nanotube layer; finally, the polyurethane urea acrylate resin is cross-linked and cured by irradiation with ultraviolet light for 10-15 minutes to anchor the surface particles.

[0014] Furthermore, in step c), the first spray liquid can be sprayed once or multiple times between the application of the first spray liquid and the second spray liquid to adjust the microstructure and photothermal properties of the surface layer.

[0015] Thirdly, the present invention provides an application of the coating described in any of the above in preventing icing on the surfaces of aircraft, wind turbine blades, power transmission lines, ship decks, etc., and in active de-icing.

[0016] In summary, the beneficial effects of the present invention are as follows: The present invention relates to a self-healing superhydrophobic photothermal anti-icing coating based on hindered urea bonds, its preparation method, and its application. 1. Intrinsic self-healing and superhydrophobic properties are structurally separated but functionally synergistic: The underlying PUUA resin achieves multiple repairs of scratches and cracks through the dynamic and reversible exchange of hindered urea bonds, restoring the coating integrity and physical barrier function; the surface micro-nano rough structure provides stable superhydrophobic properties, effectively blocking water and corrosive media. The two do not interfere with each other, and the self-healing process does not damage the surface superhydrophobic structure.

[0017] 2. Photothermal Effect Simultaneously Triggers Self-Healing and Active De-icing: Utilizing the efficient photothermal conversion of carbon nanotubes, the coating surface rapidly heats to over 100℃ under near-infrared light irradiation. This meets the thermal activation temperature (130℃) required for the dynamic dissociation of hindered urea bonds and is far above the freezing point, enabling remote, non-contact, rapid de-icing. Experiments show that ice beads frozen at -15℃ completely melt within 26 seconds under 808nm light irradiation.

[0018] 3. Excellent passive anti-icing performance: Thanks to the extremely low solid-liquid contact area and air layer insulation effect of the superhydrophobic surface, the freezing delay time of water droplets in the -15℃ environment can reach 420 seconds, which is more than 1.8 times that of ordinary hydrophilic surfaces.

[0019] 4. Good thermal stability and environmental adaptability: The introduction of carbon nanotubes and nano-silica increases the maximum thermal decomposition temperature of the composite coating by about 54°C compared with pure PUUA resin, meeting the requirements for outdoor service. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Figure 1 This is a schematic diagram of the coating structure of the present invention; Figure 2 This is a schematic diagram of PUUA resin synthesis and hindered urea bond formation. Figure 3 Photograph of water contact angle test on the coating surface of one embodiment (showing superhydrophobic state, contact angle of about 160°). Figure 4 Photograph of water contact angle test on the coating surface of one embodiment (showing superhydrophobic state, contact angle of about 160°). Figure 5 Photograph of water contact angle test on the coating surface of one embodiment (showing superhydrophobic state, contact angle of about 160°). Figure 6 Optical microscope images of the coating self-healing process (comparison of scratches before and after heating at 135℃ for 30 minutes); Figure 7 The photothermal heating curve and infrared thermograph of the coating are shown. Figure 8 A bar chart comparing the coating icing delay time of one embodiment; Figure 9 A schematic diagram illustrating the coating icing delay time according to one embodiment; Figure 10 This is a schematic diagram of the photothermal de-icing time of the coating in another embodiment. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0023] Please see Figures 1-10 In a first aspect, the present invention provides a self-healing superhydrophobic photothermal anti-icing coating based on hindered urea bonds, the coating being composed of a base layer and a top layer: The underlying layer is a dynamic covalent polymer matrix resin containing hindered urea bonds; The surface layer is a functional layer composited on the bottom surface, comprising modified carbon nanotubes and hydrophobic nano-silica, which together constitute a micro-nano hierarchical rough structure. The modified carbon nanotubes have photothermal conversion function, which raises the surface temperature of the coating to over 100°C under near-infrared light irradiation, while activating the dynamic reversible exchange of hindered urea bonds to achieve self-repair and melt the ice layer.

[0024] Furthermore, the dynamic covalent polymer containing hindered urea bonds is polyurethane urea acrylate (PUUA), which is prepared by stepwise polymerization of reactants containing polytrimethylene ether glycol (PO3G), isophorone diisocyanate (IPDI), chain extender trimethylolethane (TME), and methacrylate end-capping agent 2-(tert-butylamino)ethyl methacrylate (TBEMA) containing secondary amine groups; wherein TBEMA forms hindered urea bonds by reacting its secondary amine groups with isocyanate groups, and introduces photocurable carbon-carbon double bonds into the resin.

[0025] Furthermore, the modified carbon nanotubes are carboxylated multi-walled carbon nanotubes modified with organosilanes for hydrophobicity, and their surfaces are further coated with a silica layer in situ by a sol-gel method, and grafted with hexadecyltrimethoxysilane or other long-chain alkyl / fluoroalkyl silanes.

[0026] Furthermore, the primary particle size of the hydrophobic nano-silica is 7–40 nm, and the surface is modified with fluorosilane or long-chain alkylsilane.

[0027] Furthermore, the surface static water contact angle of the coating is ≥150° and the roll-off angle is ≤10°; under irradiation by an 808nm near-infrared laser (power 1W), the surface of the coating heats up to ≥100°C within 5 seconds, with a maximum temperature of 110~125°C; in an environment of -15°C, the freezing delay time of a 5μL water droplet on the surface is ≥400 seconds, and the time for the frozen ice droplet to completely melt by photothermal means is ≤30 seconds.

[0028] Furthermore, when the coating is heated at 135°C for 30 minutes or irradiated with near-infrared light, surface scratches can be basically healed, and the water contact angle can be restored to more than 90% of the initial value.

[0029] Specifically, the base layer is a dynamically covalent polymer matrix resin containing hindered urea bonds, specifically polyurethane urea acrylate (PUUA). Its synthetic route is as follows: using polytrimethylene ether glycol (PO3G, Mn=2000) as the soft segment, isophorone diisocyanate (IPDI) as the hard segment, trimethylolpropane (TME) as the chain extender, and 2-(tert-butylamino)ethyl methacrylate (TBEMA) as the end-capping agent. The secondary amine group in the TBEMA molecule reacts with the isocyanate group at the prepolymer chain end to form a hindered urea bond with significant steric hindrance, while simultaneously introducing photocurable methacrylate end groups.

[0030] Top layer: Composed of modified carbon nanotubes and hydrophobic nano-silica layer by layer. The modified carbon nanotubes are carboxylated multi-walled carbon nanotubes hydrophobically modified with organosilanes (such as hexadecyltrimethoxysilane, HDTMS), and a silica coating layer can be further generated on their surface in situ using a sol-gel method to improve their dispersibility and compatibility with resins. The hydrophobic nano-silica is commercially available or self-made fluorosilane / alkylsilane modified fumed silica (such as R812S). The carbon nanotubes intertwine to form a micron-scale porous network framework, and the nano-silica fills the gaps and surface of the network, forming nanoscale protrusions. Together, they construct a micro-nano hierarchical rough structure that satisfies the Cassie-Baxter model.

[0031] The coating preparation method includes the following steps: Synthesis of PUUA resin: In a reaction vessel equipped with a mechanical stirrer, a constant-pressure dropping funnel, a condenser, and a nitrogen gas delivery pipe, dehydrated PO3G, catalyst DBTDL, and solvent acetone were added, and the mixture was stirred and heated to 70°C. Under nitrogen protection, IPDI was slowly added dropwise, and the prepolymerization reaction was carried out for 3–4 hours. Chain extender TME was added, and the reaction was continued for 3–4 hours. Finally, end-capping agent TBEMA was added, and the reaction was carried out for 1–2 hours. After the reaction was completed, acetone was removed by rotary evaporation to obtain PUUA resin.

[0032] Preparation of modified carbon nanotubes: Carboxylated multi-walled carbon nanotubes were dispersed in anhydrous ethanol, and ammonia and tetraethyl orthosilicate (TEOS) were added. The mixture was stirred at room temperature for 10 hours to allow TEOS to hydrolyze and condense on the surface of the carbon nanotubes, forming a silica coating layer. Then, hexadecyltrimethoxysilane (HDTMS) was added, and the reaction was continued for another 10 hours to perform hydrophobic modification. The reaction product was filtered, washed with ethanol, and dried to obtain modified carbon nanotube composite particles.

[0033] Coating application: Apply PUUA resin evenly to a clean glass or metal substrate using a scraper, and allow it to level at room temperature for 10 minutes.

[0034] The modified carbon nanotube composite particles were dispersed in petroleum ether (concentration of about 0.2 g / 5 mL), ultrasonically dispersed, and then sprayed onto the surface of the uncured PUUA wet film using a spray gun.

[0035] Hydrophobic nano-silica was dispersed in petroleum ether (concentration approximately 0.2 g / 5 mL), ultrasonically dispersed, and then sprayed onto the surface of the carbon nanotube layer.

[0036] The coating is irradiated under a UV lamp for 10-15 minutes to crosslink and cure the methacrylate groups in the PUUA resin, thereby firmly anchoring the functional particles.

[0037] Optimized solution: First, spray a layer of modified carbon nanotubes, then spray a second layer of modified carbon nanotubes, and finally spray a layer of silica to adjust the photothermal heating rate and superhydrophobic properties.

[0038] In a second aspect, the present invention provides a method for preparing a coating as described in any one of the above claims, comprising the following steps: Step a) Synthesis of PUUA resin containing hindered urea bonds: Under an inert atmosphere, dehydrated PO3G is mixed with catalyst dibutyltin dilaurate (DBTDL) and solvent acetone, heated to 60-80°C, and IPDI is added dropwise for prepolymerization reaction for 3-4 hours; chain extender TME is added and the reaction continues for 3-4 hours; finally, end-capping agent TBEMA is added and the reaction continues for 1-2 hours to obtain PUUA resin; Step b) Preparation of modified carbon nanotube composite particles: Carboxylated multi-walled carbon nanotubes were dispersed in ethanol, and ammonia and tetraethyl orthosilicate (TEOS) were added to carry out a sol-gel reaction, generating silica in situ on the surface of the carbon nanotubes; then hexadecyltrimethoxysilane (HDTMS) was added for hydrophobic modification, and the reaction was carried out for 6-12 hours. After filtration, washing and drying, modified carbon nanotubes were obtained. Step c) Coating application: The PUUA resin obtained in step a) is uniformly coated onto the substrate surface using a scraping method to form a bottom wet film; the modified carbon nanotubes obtained in step b) are dispersed in petroleum ether to form a first spray liquid, which is then sprayed onto the surface of the bottom wet film; hydrophobic nano-silica is then dispersed in petroleum ether to form a second spray liquid, which is then sprayed onto the surface of the carbon nanotube layer; finally, the PUUA resin is cross-linked and cured by irradiation with ultraviolet light for 10-15 minutes to anchor the surface particles.

[0039] Furthermore, in step c), the first spray liquid can be sprayed once or multiple times between the application of the first spray liquid and the second spray liquid to adjust the microstructure and photothermal properties of the surface layer.

[0040] Thirdly, the present invention provides an application of the coating described in any of the above in preventing icing on the surfaces of aircraft, wind turbine blades, power transmission lines, ship decks, etc., and in active de-icing.

[0041] Example 1 I. Synthesis of PUUA Resin In a 250 mL four-necked flask, add 36.0 g of dehydrated PO3G (Mn=2000), 0.02 g of DBTDL, and 10 mL of acetone. Stir mechanically and purge with nitrogen. Heat to 70 °C, and slowly add 6.67 g of IPDI dropwise using a constant-pressure dropping funnel. After the addition is complete, react for 3 hours. Add 0.13 g of TME and continue the reaction for 4 hours. Finally, add 3.89 g of TBEMA and react for 1 hour. After the reaction is complete, remove the acetone by rotary evaporation, and dry under vacuum at 40 °C to obtain a pale yellow, transparent PUUA resin.

[0042] II. Preparation of Modified Carbon Nanotubes 0.2 g of carboxylated multi-walled carbon nanotubes were added to 50 mL of anhydrous ethanol and stirred for 30 min to ensure uniform dispersion. 4 mL of ammonia water was added, and 3 mL of LTEOS was slowly added while stirring. The reaction was carried out at room temperature for 10 h. Then, 0.15 g of HDTMS was added, and the reaction was continued for another 10 h. The reaction product was filtered, washed three times with anhydrous ethanol, and dried at 60 °C to constant weight to obtain modified carbon nanotube composite particles.

[0043] III. Coating Preparation Substrate treatment: The glass slide and Q235 iron sheet were cleaned with anhydrous ethanol and alkali-acid-alcohol washing respectively, and then dried with nitrogen.

[0044] Apply the base coat: Use a tetrahedral applicator to evenly coat the PUUA resin onto the substrate, with a film thickness of about 100 μm, and allow it to level at room temperature for 10 min.

[0045] Topcoat application: Disperse 0.2g of modified carbon nanotubes in 5g of petroleum ether, sonicate for 15s, and spray onto the PUUA wet film surface using a spray gun. Then disperse 0.2g of hydrophobic nano-silica (R812S, Evonik) in 5g of petroleum ether, sonicate for 15s, and spray onto the carbon nanotube layer surface.

[0046] Photocuring: The coating was placed under a UV LED lamp (48W, 365nm) for 10 minutes to crosslink and cure the PUUA. The final product was a PUUA-CNT-SiO2 coating.

[0047] IV. Performance Testing Surface wettability: Using an optical contact angle meter, with a 5μL deionized water droplet, the contact angles at three measuring points were 166.7°, 161.3°, and 152.2°, with an average of 160.1°, and a roll-off angle of <5°.

[0048] Self-healing properties: A 10-15 μm wide scratch was made on the coating surface with a scalpel. The coating was then heated on a 135°C hot plate for 30 minutes. Optical microscopy showed that the scratch was basically closed and the water contact angle recovered to 93% of its initial value.

[0049] Photothermal performance: The coating surface was irradiated with an 808nm near-infrared laser (1W power, 5mm spot diameter), and the temperature was recorded by an infrared thermal imager. The surface temperature rose to 111.7℃ within 5 seconds of irradiation, and the equilibrium temperature was approximately 112℃.

[0050] Freezing delay test: The coating was placed on a -15℃ cold stage, 5μL of deionized water was added, and the freezing time was observed under a microscope. The time to complete freezing was recorded as 420 seconds.

[0051] Photothermal de-icing test: After the water droplets are completely frozen, keep the temperature at -15°C and turn on the near-infrared laser to irradiate the frozen ice beads. Record the time for complete melting as 26 seconds.

[0052] Thermal analysis: DSC shows that the glass transition temperature of PUUA resin is about 65℃, and the endothermic peak of hindered urea bond dissociation is located at 139℃; TGA shows that the maximum thermal decomposition temperature of the composite coating is about 404℃, which is 54℃ higher than that of pure PUUA.

[0053] Example 2 The process is basically the same as in Example 1, except that only modified carbon nanotubes are sprayed on the surface layer, and no silica layer is sprayed, resulting in a PUUA-CNT coating.

[0054] Test results: average water contact angle 109.3° (hydrophobic but not superhydrophobic), freezing delay time 296 seconds, maximum photothermal temperature 121.3℃, and defrosting time 63 seconds. These results indicate that nano-silica is crucial for achieving superhydrophobicity and rapid defrosting.

[0055] Example 3 The process is basically the same as in Example 1, except that the spraying sequence is as follows: first, a layer of modified carbon nanotubes is sprayed, then a second layer of modified carbon nanotubes is sprayed, and finally a silicon dioxide layer, namely the PUUA-CNT-CNT-SiO2 coating, is sprayed.

[0056] Test results: average water contact angle 153.8° (superhydrophobic), freezing delay time 240 seconds, maximum photothermal temperature 116.4℃, and defrosting time 57 seconds. This indicates that while bilayer carbon nanotubes increase the photothermal temperature, they reduce the freezing delay performance; a balance needs to be struck between superhydrophobicity and photothermal performance.

[0057] Comparative Example 1 (Pure PUUA coating) Only apply PUUA resin by scraping and light curing, without spraying any fillers.

[0058] Test results: Water contact angle 82.3° (hydrophilic), freezing delay time 230 seconds, maximum photothermal temperature 35.3℃, defrosting time 90 seconds. No self-healing test showed that scratches could partially heal at 135℃, but it lacked superhydrophobicity and active defrosting capabilities.

[0059] Comparative Example 2 (Q235 bare iron sheet) Use the cleaned Q235 iron sheet directly.

[0060] Test results: Icing delay time 203 seconds, maximum photothermal temperature 28.8℃, defrosting time 74 seconds.

[0061] Performance Summary Comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the PUUA-CNT-SiO2 coating of the present invention has the best overall performance: it maintains a superhydrophobic state (contact angle 160.1°) and a long icing delay time (420 seconds), and can rapidly heat up and efficiently de-ic under near-infrared light irradiation (26 seconds), and its self-healing ability makes the coating durable. This coating achieves a three-in-one synergistic protection of "passive anti-icing - active de-icing - damage self-repair".

[0062] The present invention relates to a self-healing superhydrophobic photothermal anti-icing coating based on hindered urea bonds, its preparation method, and its application. 1. Intrinsic self-healing and superhydrophobic properties are structurally separated but functionally synergistic: The underlying PUUA resin achieves multiple repairs of scratches and cracks through the dynamic and reversible exchange of hindered urea bonds, restoring the coating integrity and physical barrier function; the surface micro-nano rough structure provides stable superhydrophobic properties, effectively blocking water and corrosive media. The two do not interfere with each other, and the self-healing process does not damage the surface superhydrophobic structure.

[0063] 2. Photothermal Effect Simultaneously Triggers Self-Healing and Active De-icing: Utilizing the efficient photothermal conversion of carbon nanotubes, the coating surface rapidly heats to over 100℃ under near-infrared light irradiation. This meets the thermal activation temperature (130℃) required for the dynamic dissociation of hindered urea bonds and is far above the freezing point, enabling remote, non-contact, rapid de-icing. Experiments show that ice beads frozen at -15℃ completely melt within 26 seconds under 808nm light irradiation.

[0064] 3. Excellent passive anti-icing performance: Thanks to the extremely low solid-liquid contact area and air layer insulation effect of the superhydrophobic surface, the freezing delay time of water droplets in the -15℃ environment can reach 420 seconds, which is more than 1.8 times that of ordinary hydrophilic surfaces.

[0065] 4. Good thermal stability and environmental adaptability: The introduction of carbon nanotubes and nano-silica increases the maximum thermal decomposition temperature of the composite coating by about 54°C compared with pure PUUA resin, meeting the requirements for outdoor service.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or equivalent variations to the disclosed technical content and apply them to other fields. However, any simple modifications, equivalent variations, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention. For those skilled in the art, the specific meaning of the above terms in the present invention can be understood through specific circumstances.

Claims

1. A self-healing superhydrophobic photothermal anti-icing coating based on hindered urea bonds, its preparation method, and its application, characterized in that, The coating is composed of a base layer and a top layer: The underlying layer is a dynamic covalent polymer matrix resin containing hindered urea bonds; The surface layer is a functional layer composited on the bottom surface, comprising modified carbon nanotubes and hydrophobic nano-silica, which together constitute a micro-nano hierarchical rough structure. The modified carbon nanotubes have photothermal conversion function, which raises the surface temperature of the coating to over 100°C under near-infrared light irradiation, while activating the dynamic reversible exchange of hindered urea bonds to achieve self-repair and melt the ice layer.

2. The coating according to claim 1, characterized in that, The dynamic covalent polymer containing hindered urea bonds is polyurethane urea acrylate, which is prepared by stepwise polymerization of a reaction product containing polytrimethylene ether glycol, isophorone diisocyanate, chain extender trimethylolethane and methacrylate end-capping agent 2-(tert-butylamino)ethyl methacrylate containing secondary amine groups; wherein the ethyl ester forms hindered urea bonds by reacting its secondary amine groups with isocyanate groups, and introduces photocurable carbon-carbon double bonds into the resin.

3. The coating according to claim 1, characterized in that, The modified carbon nanotubes are carboxylated multi-walled carbon nanotubes modified with organosilanes for hydrophobicity, and their surfaces are further coated with a silica layer in situ by a sol-gel method, and grafted with hexadecyltrimethoxysilane or other long-chain alkyl / fluoroalkyl silanes.

4. The coating according to claim 1, characterized in that, The hydrophobic nano-silica has a primary particle size of 7–40 nm and its surface is modified with fluorosilane or long-chain alkylsilane.

5. The coating according to claim 1, characterized in that, The surface static water contact angle of the coating is ≥150° and the roll-off angle is ≤10°. Under irradiation with an 808nm near-infrared laser, the surface of the coating heats up to ≥100°C within 5 seconds, and the maximum temperature can reach 110~125°C. In an environment of -15°C, the freezing delay time of 5μL water droplets on the surface is ≥400 seconds, and the time for the frozen ice beads to completely melt by photothermal means is ≤30 seconds.

6. The coating according to claim 1, characterized in that, When the coating is heated at 135°C for 30 minutes or irradiated with near-infrared light, surface scratches can be basically healed, and the water contact angle can be restored to more than 90% of the initial value.

7. A method for preparing the coating as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step a) Synthesis of polyurethane urea acrylate resin containing hindered urea bonds: Under an inert atmosphere, dehydrated PO3G is mixed with the catalyst dibutyltin dilaurate and the solvent acetone, heated to 60-80°C, and IPDI is added dropwise for a prepolymerization reaction for 3-4 hours; the chain extender trimethylolethane is added and the reaction continues for 3-4 hours; finally, the end-capping agent 2-(tert-butylamino)ethyl methacrylate is added and the reaction continues for 1-2 hours to obtain the polyurethane urea acrylate resin; Step b) Preparation of modified carbon nanotube composite particles: Carboxylated multi-walled carbon nanotubes were dispersed in ethanol, and ammonia and tetraethyl orthosilicate were added to carry out a sol-gel reaction, in situ generating silica on the surface of carbon nanotubes; then hexadecyltrimethoxysilane was added for hydrophobic modification, and the reaction was carried out for 6-12 hours. After filtration, washing and drying, modified carbon nanotubes were obtained. Step c) Coating application: The polyurethane urea acrylate resin obtained in step a) is uniformly coated onto the substrate surface using a scraping method to form a bottom wet film; the modified carbon nanotubes obtained in step b) are dispersed in petroleum ether to form a first spray liquid, which is then sprayed onto the surface of the bottom wet film; hydrophobic nano-silica is then dispersed in petroleum ether to form a second spray liquid, which is then sprayed onto the surface of the carbon nanotube layer; finally, the polyurethane urea acrylate resin is cross-linked and cured by irradiation with ultraviolet light for 10-15 minutes to anchor the surface particles.

8. The method according to claim 7, characterized in that, In step c), the first spray liquid can be sprayed once or multiple times between the application of the first spray liquid and the second spray liquid to adjust the microstructure and photothermal properties of the surface layer.

9. The application of the coating according to any one of claims 1 to 6 in preventing icing on the surfaces of aircraft, wind turbine blades, power transmission lines, ship decks, etc., and in active de-icing.

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