Cement-enhanced super-hydrophobic self-adaptive temperature regulation coating as well as preparation method and application thereof

Abstract

The invention discloses a cement-enhanced super-hydrophobic self-adaptive temperature control coating which comprises a thermochromic bottom layer and a radiation refrigeration surface layer, a primer adopted by the thermochromic coating is prepared from the following components in parts by weight: 3 to 6.6 parts of composite resin matrix, 0.4 to 1.2 parts of filler, 11 to 15 parts of thermochromic powder and 10 to 15 parts of organic solvent; and finish paint adopted by the thermochromic coating is prepared from the following components in parts by weight: 50 to 55 parts of SiO2 dispersion liquid, 2 to 9 parts of white cement slurry, 5 to 8 parts of hydrophobic modifier, 6 to 10 parts of low-surface-energy substance and 7 to 11 parts of migration-anchoring dual-function additive. The coating system disclosed by the invention can realize efficient cooling in a high-temperature environment, can keep thermal insulation performance in a low-temperature environment, has mechanical stability and self-cleaning performance required by long-term outdoor application, and is wide in applicability.

Description

Technical Field

[0001] The present invention belongs to the technical field of multifunctional building coatings, and in particular relates to a cement-reinforced super-hydrophobic self-adaptive temperature regulating coating, a preparation method thereof, and applications thereof. Background Art

[0002] As global warming intensifies, controlling building energy consumption and reducing carbon emissions have become crucial priorities for energy conservation and emission reduction. Passive daylight radiative cooling (PDRC) coatings, which require no additional energy, efficiently reflect solar radiation in the visible light band, and effectively emit infrared heat through an atmospherically transparent window, can significantly reduce building surface temperatures and are widely recognized as a green and efficient approach to building energy conservation. In recent years, the PDRC material portfolio has continued to expand, encompassing porous films, spectrally selective structures, and multilayer composite coatings, demonstrating excellent radiative cooling performance and self-cleaning capabilities.

[0003] However, traditional PDRC materials mainly serve the cooling needs in high-temperature environments. Under low-temperature conditions in winter, they may cause excessive heat dissipation from the building surface, affecting indoor thermal comfort and energy efficiency. For this reason, active temperature control coatings and adaptive temperature control materials have gradually become research hotspots. Active temperature control systems rely on mode switching technologies such as electrochromism and mechanical flipping, which have problems such as dependence on external stimuli, complex processes, and high energy consumption. Passive adaptive temperature control materials, such as phase change materials, thermosensitive gels, and moisture-sensitive components, have the ability to automatically adjust infrared emissivity based on changes in ambient temperature or humidity. They are expected to achieve a two-way temperature control effect of warm in winter and cool in summer, showing potential in building energy conservation.

[0004] However, existing adaptive temperature-control materials still face many challenges in engineering applications. For example, phase change materials often rely on complex optical resonant structures or face high cost bottlenecks. Hygroscopic and thermosensitive gel materials suffer from leakage and optical degradation. Traditional PDRC coatings, in particular, suffer from weak adhesion to the substrate and insufficient mechanical stability, severely limiting their lifespan and reliability in practical applications. Furthermore, erosion by dust, rainwater, and microorganisms in outdoor environments accelerates material failure, affecting their thermal management and self-cleaning capabilities, hindering the large-scale promotion of these technologies.

[0005] There is an urgent need to develop a multifunctional coating system with a simple structure, controllable preparation process, good wear resistance, excellent hydrophobic self-cleaning properties and adaptive temperature regulation functions. Summary of the Invention

[0006] The main purpose of the present invention is to provide a cement-reinforced super-hydrophobic adaptive temperature-control coating. The coating system can achieve efficient cooling in high-temperature environments and maintain thermal insulation performance in low-temperature environments, while having the mechanical stability and self-cleaning properties required for long-term outdoor applications.

[0007] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: A cement-reinforced super-hydrophobic adaptive temperature-control coating comprises a thermochromic base layer and a radiant cooling surface layer. A primer used in the thermochromic coating comprises the following components in percentage by weight: 3 to 6.6 parts of a composite resin matrix, 0.4 to 1.2 parts of a filler, 11 to 15 parts of a thermochromic powder, and 10 to 15 parts of an organic solvent. A topcoat used in the thermochromic coating comprises the following components in percentage by weight: 50 to 55 parts of a SiO2 dispersion, 2 to 9 parts of a white cement slurry, 5 to 8 parts of a hydrophobic modifier, 6 to 10 parts of a low-surface-energy substance, and 7 to 11 parts of a migration-anchoring dual-functional additive.

[0008] In the above solution, the composite resin matrix comprises alkyd resin, polypropylene resin and fluorocarbon resin.

[0009] Furthermore, in the composite resin matrix, the components and their weight percentages include: 2 to 4 parts of alkyd resin, 0.8 to 1.8 parts of polypropylene resin, and 0.2 to 0.8 parts of fluorocarbon resin.

[0010] In the above scheme, the mass ratio of the alkyd resin, polypropylene resin, fluorocarbon resin, nylon powder, and thermochromic powder is 2~4:(0.8~1.8):(0.2~0.8):(0.4~1.2):(11~15); by optimizing the corresponding ratios and through the triple synergy of mechanics, thermals, and interfaces, the coating's strong adhesion, fast response, and ultra-durability are promoted.

[0011] In the above solution, the filler can be selected from one or more nylon powders such as PA6, PA12, and PA66.

[0012] In the above solution, the thermochromic powder can be selected from one or more of reversible thermochromic pigments, VO2 powder, liquid crystal color powder, etc.

[0013] In the above solution, the organic solvent can be selected from one or more of butyl acetate, ethyl acetate, acetone, etc.

[0014] In the above scheme, the SiO2 dispersion is a silicon source hydrolyzate, and the silicon source can be selected from one or more of tetraethyl orthosilicate (TEOS), methyl orthosilicate (TMOS), methyltrimethoxysilane (MTMS), etc.

[0015] In the above scheme, the concentration of SiO2 in the silicon source hydrolyzate is 0.03~0.06g / mL.

[0016] Furthermore, the preparation steps of the SiO2 dispersion include the following: adding an alkali solution (NaOH solution, KOH solution or ammonia water) and a hydrolyzable silicon source in an alcohol solvent in sequence, and performing hydrolysis at room temperature to obtain a SiO2 dispersion.

[0017] In the above scheme, the concentration of the alkali solution is 1.5~2.0mol / L.

[0018] In the above scheme, the hydrolysis time is 20 to 24 hours.

[0019] In the above scheme, the volume ratio of the alcohol solvent, the alkali solution, and the hydrolyzable silicon source is 4-6:0.1-0.5:1-1.8, ensuring the formation of high dispersion of the nano-skeleton.

[0020] In the above solution, the white cement slurry comprises white cement and water, and the hydration time after mixing is 3 to 6 hours.

[0021] Furthermore, the mass ratio of the white cement to water is 1:0.3~0.6.

[0022] In the above scheme, the hydrophobic modifier can be selected from one or more of hexamethyldisilazane HMDS, perfluorodecyltrimethoxysilane PFDTMS, trimethylchlorosilane TMCS, 17-fluorodecyltriethoxysilane, etc.

[0023] In the above solution, the low surface energy material can be selected from one or more of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), etc.

[0024] In the above scheme, the migration-anchoring dual-functional auxiliary agent can be selected from one or more of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTS), 3,3,3-trifluoropropyltriethoxysilane (TFPTES), 3,3,3-trifluoropropyltrimethoxysilane (TFPTMS), etc.

[0025] The method for preparing the above-mentioned cement-enhanced super-hydrophobic adaptive temperature control coating comprises the following steps: 1) Preparation of radiant cooling topcoat: White cement slurry is injected into the SiO2 dispersion and subjected to multi-stage directional interlocking shearing to form a highly dispersed SiO2-cement composite slurry. A hydrophobic modifier is then introduced and stirred at room temperature for 10-12 hours to form a hydrophobic modified layer. A low surface energy substance and a migration-anchoring dual-functional additive are then added and stirred for 3-5 hours to form a radiant cooling topcoat with both super-hydrophobic and radiant cooling functions. 2) Preparation of thermochromic primer: Alkyd resin, polypropylene resin and fluorocarbon resin are added to an organic solvent in sequence and stirred once (1-2 hours) to form a composite resin matrix. A filler dispersion is added and stirred twice to improve the mechanical properties and adhesion of the primer. Subsequently, thermochromic powder is added and stirred three times (12-14 hours) to prepare the thermochromic primer. 3) Under humidity step-controlled conditions, spraying a thermochromic primer onto the surface of the substrate to form a base layer; then step-by-step spraying of a radiant cooling topcoat, which is dried to form a surface layer, thereby obtaining the cement-enhanced super-hydrophobic adaptive temperature control coating.

[0026] In the above scheme, the step of injecting the SiO2 dispersion includes: injecting white cement slurry into the SiO2 dispersion obliquely within 15 seconds at a stable rotation speed of 900~1100rpm, and the temperature difference between the white cement slurry and the SiO2 dispersion is ≤1°C.

[0027] In the above scheme, the multi-stage directional mosaic shearing step includes: First, increase the shear rate from 50 to 80 rpm / s to 1200 to 1400 rpm (shear rate ≥ 1200s -1 ), then reduce the speed in steps to 600-900 rpm within 30-60 s, and maintain the speed for 130-170 s; wherein the step-by-step speed reduction step includes: first reducing the speed to 950-1050 rpm at a rate of 20-30 rpm / s, and then reducing the speed to 600-900 rpm at a rate of 40-50 rpm / s.

[0028] In the above scheme, the stirring rate after adding the hydrophobic modifier is 800~1000rpm, and the stirring time is 1.5~2h; the stirring rate after adding the low surface energy material and the migration-anchoring dual-functional additive is 400~600rpm, and the stirring time is 20~30min.

[0029] In the above scheme, the moisture step control conditions of the primer include the spraying period, the pre-curing period and the powder anchoring period. The specific control requirements include the following: 1) Spraying period: control the ambient humidity to 45~55%RH; 2) Pre-curing period: After spraying is completed, pre-curing treatment is carried out. The specific steps are as follows: Stage 1: Humidity increases to 60-80% RH (humidity increase rate ≤ 5% RH / min) and maintains for 80-100 seconds; Stage 2: Humidity is reduced to 50-60% RH (rate ≤ 8% RH / min); maintained for 80-120 seconds, and humidification is terminated; 3) Powder anchoring period: After gelation (stirring resistance test, slurry scratches > 3s without healing), treat in a 53-57% humidity environment for 2.5-3 minutes to complete the embedding and fixation of the thermochromic powder.

[0030] 4) Final curing: Adjust the humidity to 40~50%RH and cure for 1.5~2.5h until the coating is completely dry.

[0031] In the above scheme, in the step-by-step spraying steps of the topcoat, the final spraying stage adopts an electrostatic spraying process (when the curing degree of the previous topcoat reaches more than 80% (standing for 4 to 6 minutes after spraying); the spraying amount accounts for 10 to 40% of the total amount of topcoat), the voltage used is 28 to 32 kV, the electric field line density is 18 to 22 lines / mm², and the atomizing air pressure is 0.05 to 0.08 MPa.

[0032] In the above scheme, the spraying steps before the final spraying of the topcoat include: i) When the primer is 55-60% cured, spray a portion of the topcoat (20-30% of the total topcoat amount) onto the primer surface at a spray pressure of 0.1-0.25 MPa (spray angle 55-65°, spray distance 15-25 cm); ii) After the initial low-pressure sprayed topcoat film has dried (contact angle > 90°), spin-coat a portion of the topcoat (40-60% of the total topcoat amount). Increase the spin-coating speed by 480-520 rpm / s from 1900-2100 rpm to 3900-4100 rpm. Keep the spraying time within 10-14 seconds.

[0033] In the above solution, the thickness of the bottom layer and the surface layer is 2.5~3.5:1.

[0034] Preferably, the drying step in step 3) adopts a temperature-controlled drying process and a three-stage gradient temperature control mechanism. The specific steps include: first, keeping warm at 38-42°C for 12-18 minutes (first stage); then keeping warm at 53-57°C for 8-12 minutes (second stage) to promote PVDFβ crystal phase transformation (β phase content ≥85%); finally, keeping warm at 33-37°C for 25-35 minutes (third stage) to achieve stress relaxation (residual stress ≤5MPa); and keeping warm at 28-32°C for 30-40 minutes to reach the drying end point.

[0035] The present invention adopts the process concept of "synergistic step-by-step construction + progressive integration of interface functions": for the pre-hydrated cement slurry whose hydration degree is in the critical region rich in CSH nanonuclei and calcium ions (such as the early stage after the end of the induction period, when the hydration heat release reaches 30-50% of the peak), combined with the multi-level directional interlocking shear control method, the pre-hydrated cement slurry is introduced into the SiO2 dispersion. This process forces the new cement hydration matter to preferentially complete heterogeneous nucleation and directional growth on the surface of the SiO2 skeleton, forming a microstructure (directional interlocking) of in-situ chemical bonding (mainly Ca-O-Si bonds) and tight physical wrapping, rather than random filling. Directed interlocking is strongly anchored by chemical bonding + nano-wrapping to eliminate defects, fundamentally solving the three major problems of traditional random filling, namely weak interface, poor thermal control and short life, and laying an important structural foundation for the subsequent construction of self-gradient functional layers.

[0036] The "self-gradient" structure described in this invention includes (1) molecular-scale vertical ordering: PFPE fluorine chains are aligned perpendicular to the substrate under the induction of an electrostatic field, promoting the formation of a dense terminal film; and (2) micrometer-scale anchoring reinforcement: The CSH coverage rate on the SiO2 surface increases gradually, blocking the expansion channel of interface defects. This structure can promote the spatial decoupling and optimization of hydrophobicity, thermal control, and toughness, breaking the bottleneck of "performance mutual exclusion" in homogeneous coatings.

[0037] The present invention employs a two-layer, step-by-step collaborative construction strategy in the spray coating process, incorporating thermal response coupling technology for a coordinated structural and functional design. During the primer application phase, uniform fixation of the temperature-sensitive powder and the formation of a resin network are ensured by regulating temperature, humidity, and pre-curing time. During the topcoat application phase, the PVDF introduction sequence, spraying, and drying mechanisms are controlled to ensure interfacial bonding with the underlying layer and its hydrophobic / cooling properties. This promotes the multifunctional layered coupling of the resulting composite coating from "sensing-response-protection," enhancing the long-term outdoor stability and construction compatibility of the resulting coating system.

[0038] This invention utilizes a "primer-topcoat" step-by-step spraying process, first spraying a thermochromic primer onto the substrate surface, curing it at room temperature, and then applying a radiant cooling topcoat. The resulting coating system combines superhydrophobicity and self-cleaning properties with temperature-sensing control and radiant cooling. It exhibits efficient heat dissipation and cooling (ΔT up to 5.5°C) in high-temperature environments, good thermal insulation performance in low-temperature environments, and excellent wear resistance and long-term outdoor stability, making it suitable for building facades and other applications requiring temperature management.

[0039] The present invention can achieve stable compounding and interface synergy between multiple functional components (SiO2, hydrophobic agent, low surface energy polymer) on the surface of a highly alkaline, porous, and heterogeneous cement substrate, and construct a composite coating with structural continuity, interface stability, and multiple functions (superhydrophobicity, self-cleaning, and temperature control); at the same time, it ensures that the preparation process is simple and environmentally friendly, and has good spray adaptability and outdoor engineering stability.

[0040] The present invention also provides a method for applying the aforementioned cement-reinforced super-hydrophobic, adaptive temperature-control coating, suitable for energy conservation, protection, and durability enhancement of building and infrastructure surfaces. The method includes base pretreatment, spraying of a thermochromic primer, overlay application of a radiant cooling topcoat, and final curing, all of which can be completed at room temperature.

[0041] The resulting coating has a stable structure and is easy to construct. It is compatible with handheld spray guns, airless spray equipment and intelligent spray systems, and has significant engineering application adaptability and promotion potential.

[0042] Compared with the prior art, the present invention has the following beneficial effects: 1) The porous structure of the cement-silica composite skeleton constructed in the present invention can achieve both good mechanical stability and the durability of the super-hydrophobic modified layer, effectively overcoming the performance degradation problem such as hydrophobicity caused by the hydrophilicity of cement; 2) The introduction of a composite hydrophobic agent and PVDF enables multi-level interface regulation. This multi-level interface regulation effectively improves the coating's wear and weather resistance while achieving super-hydrophobic properties, ensuring stable self-cleaning and thermal regulation performance even in complex outdoor environments. The coating exhibits significant super-hydrophobic self-cleaning and temperature-adaptive regulation capabilities. 3) This paper proposes a multi-level interface control method based on the coordinated construction of three layers: "inside-middle-outside". First, SiO2 and white cement are combined to form an inorganic skeleton as the base structure. At the same time, organic hydrophobic agents with rich chain lengths and functional group types are introduced to construct a multi-scale hydrophobic network. Finally, by delaying the introduction of PVDF material and utilizing its self-migration characteristics during the drying process, a continuous and directional low-surface energy terminal protective layer is formed on the coating surface. This promotes the deep coupling of structural stability, superhydrophobicity and thermal management performance. 4) The coating system can simultaneously meet the dual needs of efficient heat dissipation in summer and low-temperature insulation in winter, filling the gap in current building surface thermal management materials; the structure is durable and maintains stable performance in long-term outdoor environments; 5) The entire process is carried out at room temperature, with simple preparation, low energy consumption, low cost, green and environmental protection, and suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1This is a SEM photo of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained in Example 1; Figure 2 These are optical photographs and contact angle photographs of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained in Example 1; Figure 3 The cement-enhanced super-hydrophobic adaptive temperature regulating coating obtained in Example 1 and the super-hydrophobic adaptive temperature regulating coating obtained in Comparative Example 2 under high temperature conditions are shown in Figure 2. 2 Below, the temperature variation of the bottom of the coating with time; Figure 4 The cement-enhanced super-hydrophobic adaptive temperature regulating coating obtained in Example 1 and the super-hydrophobic adaptive temperature regulating coating obtained in Comparative Example 2 under a low temperature environment are shown in FIG. 2 Below, the temperature variation of the bottom of the coating with time; Figure 5 The following is a graph showing the change in bottom temperature of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained in Example 1 and the super-hydrophobic adaptive temperature-regulating coating obtained in Comparative Example 2 under sunlight in an outdoor environment over time; Figure 6 This is a graph showing the change in hydrophobic angle of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained in Example 1 and the super-hydrophobic adaptive temperature-regulating coating obtained in Comparative Example 1 as a function of the number of frictions obtained by sandpaper friction; Figure 7 This is a SEM photo of the cement-enhanced superphobic adaptive temperature-regulating coating obtained in Example 2; Figure 8 These are optical photographs and contact angle photographs of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained in Example 2; Figure 9 The cement-enhanced super-hydrophobic adaptive temperature regulating coating obtained in Example 2 and the super-hydrophobic adaptive temperature regulating coating obtained in Comparative Example 2 under high temperature conditions are shown in FIG. 2 Below, the temperature variation of the bottom of the coating with time; Figure 10 The cement-enhanced super-hydrophobic adaptive temperature regulating coating obtained in Example 2 and the super-hydrophobic adaptive temperature regulating coating obtained in Comparative Example 2 under low temperature conditions are shown in Figure 2. 2 Below, the temperature variation of the bottom of the coating with time; Figure 11 This is a graph showing the change in the hydrophobic angle of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained by sandpaper rubbing Example 2 and the super-hydrophobic adaptive temperature-regulating coating obtained by Comparative Example 1 as a function of the number of rubbing times; Figure 12This is a SEM photo of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained in Example 3; Figure 13 Optical photographs and contact angle photographs of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained in Example 3; Figure 14 The cement-enhanced super-hydrophobic adaptive temperature regulating coating obtained in Example 3 under high temperature environment is subjected to the simulated sunlight intensity of 100mW / cm 2 Below, the bottom surface temperature changes with time; Figure 15 The cement-enhanced super-hydrophobic adaptive temperature regulating coating obtained in Example 3 under low temperature environment is subjected to the simulated sunlight intensity of 100mW / cm 2 Below, the bottom surface temperature changes with time; Figure 16 This is a graph showing the change in hydrophobic angle of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained by sandpaper friction in Example 3 and the super-hydrophobic adaptive temperature-regulating coating obtained in Comparative Example 1 as a function of the number of frictions; Figure 17 This is a contact angle photograph of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained in Comparative Example 3; Figure 18 This is a contact angle photograph of the cement-reinforced super-hydrophobic adaptive temperature-regulating coating obtained in Comparative Example 3, showing hydrophilicity after 6 hot and cold cycles; Figure 19 This is a contact angle photograph of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained in Comparative Example 4; Figure 20 This is a contact angle photograph of the cement-enhanced super-hydrophobic adaptive temperature-regulating coating obtained in Comparative Example 5; Figure 21 This is a contact angle photograph of the cement-reinforced super-hydrophobic adaptive temperature-regulating coating obtained in Comparative Example 5 after QUV aging for 500 hours. DETAILED DESCRIPTION

[0044] The following is a detailed description of the technical solutions used in the present invention through specific implementation examples. The description is only a part of the present invention and does not represent all embodiments. Unless otherwise specified, the experimental methods used in the present invention are conventional methods, and the instruments and equipment used are commercial products in the field of this technology.

[0045] In the following examples, the thermochromic powder used is commercially available Chameleon TP-Black 31.

[0046] Example 1 A cement-enhanced super-hydrophobic adaptive temperature-regulating coating, the preparation method of which comprises the following steps: 1) Preparation of radiative cooling super-hydrophobic topcoat: At an ambient temperature of 25±2°C and stirring (stirring speed 400 r / min), 2.5 mL of 1.8 mol / L NaOH solution was added to 50 mL of anhydrous ethanol, followed by 10 mL of tetraethyl orthosilicate (TEOS). The mixture was stirred and hydrolyzed for 24 h to obtain a SiO2 nanoparticle dispersion with a particle size of 25±3 nm (the concentration of SiO2 nanoparticles was 0.046 g / mL). Mix 6g of white cement with 3g of water and hydrate for 6h in an environment of 30℃ and 85% relative humidity to obtain white cement slurry; White cement slurry was injected into 50 g of the obtained SiO2 dispersion (at a tangential angle of 30° (parallel to the tangential angle of the dispersion surface) and a flow rate of 9 L / min, and multi-stage directional interlocking shearing was performed to form a highly dispersed SiO2-cement composite slurry. 10 mL of hexamethyldisilazane (HMDS) was then added, and the mixture was stirred at 45°C and 500 r / min for 10 h. The temperature was raised to 45±0.5°C, and finally 6 g of polyvinylidene fluoride (PVDF) and 7 mL of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTS) were added, and the mixture was stirred at 450 r / min for 4 h to obtain a radiative cooling superhydrophobic topcoat. The specific steps of multi-stage directional mosaic shearing are as follows: First 30s: 50-80rpm / s speed linearly increased to 1200r / min (shear rate ≥1200s -1 ); 30-60s: step-down to 800 rpm; 1200→1000 rpm: deceleration rate 20-30 rpm / s; 1000→800 rpm: deceleration rate 40-50 rpm / s; After 60 seconds: maintain the speed at 800±5r / min for 150 seconds; 2) Preparation of thermochromic primer: To 15 mL of butyl acetate, 3 g of alkyd resin, 0.9 g of polypropylene resin, and 0.5 g of fluorocarbon resin were added in sequence and stirred for 2 h to form a primer base dispersion; 1 g of nylon powder was added and stirred for 12 h; finally, 12 g of thermochromic powder was added and stirred for 12 h to obtain a thermochromic primer dispersion; 3) Coating composite construction: Primer application: Spraying 150μm wet film thickness, control the ambient humidity at 50%RH, raise the humidity to 70%RH within 0-90 seconds after spraying (rate ≤5%RH / min), maintain 70%RH for 90 seconds, reduce to 50%RH within 60 seconds, maintain humidification RH for 80-120 seconds (rate ≤8%RH / min); Maintain a 55% RH environment for 2.5-3 minutes to complete the fixation of the color-changing powder; finally adjust the humidity to 45% RH and cure for 2 hours until the coating is completely dry; Three-stage construction of topcoat: Low-pressure spraying: When the primer is 60% cured, apply 30% of the topcoat at a pressure of 0.18 MPa, a spray angle of 60°, and a spray distance of 22 cm. Spin coating: After the first film of the low-pressure sprayed topcoat has dried (contact angle > 90°), increase the spin speed from 2000 rpm to 4000 rpm in steps of 500 rpm / s, and control the spraying time within 10-14 seconds; spin coat 50% of the topcoat used; Electrostatic final spraying: When the curing degree of the topcoat reaches 80% (stand for 4-6 minutes after spraying), apply the remaining topcoat at 30 kV voltage, electric field line density 20 lines / mm², and atomizing pressure 0.06 MPa; After spraying the topcoat, gradient temperature control drying is performed to obtain the cement-enhanced super-hydrophobic adaptive temperature control coating; the specific temperature control drying steps are as follows: Stage 1: 40°C for 15 min; Stage 2: 55°C for 10 min; Stage 3: 35°C for 30 min; And control the thickness of the bottom layer and the surface layer to be 3.5:1.

[0047] Performance testing: The sample prepared in this example (named as sample 1) was analyzed by scanning electron microscopy (SEM) ( Figure 1 ), Figure 1 The multi-level structure in the patent confirms the advantages of the entire chain from nano-anchoring (left picture) to macro-control (right picture), ultimately achieving the "super-hydrophobic-high radiation" dual-functional synergy of the coating; (left picture) The multi-level rough structure formed by the dense stacking of nanoparticles provides an ideal substrate for hydrophobic modification and radiation cooling, and directly matches the porous through-base formed by the "directional mosaic" process in the patent; (right picture) The spherical particles of uniform size have no obvious agglomeration problems during coating construction. Contact angle test ( Figure 2 ), showing that the static contact angle of the superhydrophobic coating reaches 154.8°, indicating that the sample has good superhydrophobic properties.

[0048] The high and low temperature environment test results of the samples obtained in this embodiment are as follows: Under high temperature conditions (35 o C) under xenon light (100mW / cm 2 ) The test shows that the temperature of sample 1 is reduced by ΔT=2.7°C compared with the comparative sample 2 (the sample prepared in comparative example 2). Figure 3). This proves that the present invention has a good radiation cooling effect in a high temperature environment.

[0049] At low temperature (-25 o C), sample 1 showed a thermal insulation effect of ΔT=3.3°C compared with control sample 2 ( Figure 4 ). This proves that the present invention has a good heat preservation effect under low temperature environment.

[0050] The temperature of the bottom surface of the adaptive temperature regulating coating obtained in this embodiment changes with time under sunlight. Figure 5 ), it can be seen that the coating obtained in Example 2 reduces the temperature by ΔT=4.6°C compared with the comparative sample 2. This proves that the present invention also has a good radiative cooling effect in outdoor environments.

[0051] Use a 100g weight to press on sample 1 and comparative sample 1 (the sample prepared in comparative example 1 below) and rub them on 800-grit sandpaper. The rubbing method is rubbing 10cm in the up and down direction and 10cm in the left and right direction. After rubbing a certain number of times, the hydrophobic angle is tested and plotted into a curve ( Figure 6 ),pass Figure 6 We can see that the decrease in the hydrophobic angle of sample 1 is significantly smaller than that of control sample 1, which shows that the sample obtained by adding cement can exhibit excellent wear resistance.

[0052] Example 2 A cement-enhanced super-hydrophobic adaptive temperature-regulating coating, the preparation method of which is the same as that of Example 1, except that the amount of PVDF added during the preparation of the topcoat is 8 g, and the specific steps are as follows: heating to 45±0.5°C and finally adding 8 g of PVDF and 7 mL of FOTS, stirring at 450 r / min for 4 hours to obtain a radiation-cooling super-hydrophobic topcoat; and controlling the thickness of the obtained bottom layer and surface layer to be 3:1.

[0053] The SEM image of the product obtained in this example (named as sample 2) ( Figure 7 ) further verifies the full chain advantage of the present invention from nano anchoring to macro shape control. Contact angle test ( Figure 8 ) shows that the coating contact angle is 157.4°, indicating that the present invention has good superhydrophobic properties.

[0054] In high temperature environment, ΔT=3.3°C ( Figure 9 ), ΔT=2.8°C in low temperature environment ( Figure 10 ), indicating good thermal management performance.

[0055] The wear resistance of the samples obtained in this embodiment (test method is the same as that of Example 1) is as follows Figure 11As shown, it can be seen that the decrease in the hydrophobic angle of sample 2 is significantly smaller than that of control sample 1. After 1350 times of friction, it still has a contact angle of more than 150°, which shows that the sample obtained by adding cement can exhibit excellent wear resistance.

[0056] Example 3 A cement-enhanced super-hydrophobic adaptive temperature regulating coating, the preparation method of which is different from that of Example 1 in that the addition amounts of PVDF and cement are 8 g and 8 g, respectively, during the preparation of the topcoat, and the specific steps are as follows: Add 8g of white cement and 4g of water and hydrate for 6h in an environment of 30°C and 85% relative humidity to obtain white cement slurry; The temperature was raised to 45±0.5°C, and finally 8 g of PVDF and 7 mL of FOTS were added, and the mixture was stirred at 450 rpm for 4 h to obtain a radiation-cooled superhydrophobic topcoat. And control the thickness of the bottom layer and the surface layer to be 2.5:1.

[0057] The SEM image of the coating obtained in this example (named as sample 3) Figure 12 ) shows the multi-level rough structure formed by the close stacking of nanoparticles. Contact angle test results ( Figure 13 ) showed that the static contact angle of the coating was as high as 162.1°, and the superhydrophobicity was significantly enhanced.

[0058] High temperature environment ΔT=5.5°C ( Figure 14 ), low temperature environment ΔT=2.3°C ( Figure 15 ), showing excellent temperature adaptability.

[0059] The wear resistance of the samples obtained in this embodiment is shown in ( Figure 16 ), it can be found from the curve that the decrease in the hydrophobic angle of sample 3 is significantly smaller than that of control sample 1, which shows that the sample obtained by adding cement can show excellent wear resistance.

[0060] Comparative Example 1 A super-hydrophobic temperature-regulating coating is prepared by a method substantially the same as that in Example 1, except that: no cement slurry is added; after preparing the SiO2 dispersion, 10 mL of hexamethyldisilazane (HMDS) is directly added and stirred for 12 h (at 45°C, 500 r / min); finally, 6 g of polyvinylidene fluoride (PVDF) and 7 mL of FOTS are added and stirred (450 r / min) for 4 h to obtain a radiative cooling super-hydrophobic topcoat.

[0061] Then, the same primer and coating preparation method as in Example 1 was used to prepare a sample named Comparative Sample 1.

[0062] Use a 100g weight to press on the comparative sample 1 and rub it on 800-grit sandpaper. The rubbing method is rubbing 10cm in the up and down direction and 10cm in the left and right direction. After rubbing a certain number of times, the hydrophobic angle is tested and compared with sample 1, sample 2, and sample 3 and a curve is drawn ( Figure 6 )、( Figure 11 )、( Figure 16 ), the results show that, for the super-hydrophobic system of the present invention, the addition of cement can effectively improve the mechanical properties of the sample and significantly improve the wear resistance of the super-hydrophobic sample.

[0063] Comparative Example 2 A common super-hydrophobic coating, the preparation method of which is substantially the same as that of Example 1, except that: cement slurry, PVDF and thermochromic powder are not added; after preparing the SiO2 dispersion, 10 mL of hexamethyldisilazane (HMDS) is directly added and stirred for 12 h (at 45°C, 500 r / min); finally, 7 mL of FOTS is added and stirred (450 r / min) for 4 h to obtain a super-hydrophobic topcoat.

[0064] When preparing the primer, no thermochromic powder was added, and the same coating preparation method as in Example 1 was used. The prepared sample was named Comparative Sample 2.

[0065] Under high temperature conditions (35 o C) under xenon light (100mW / cm 2 ) Test the cooling temperature of sample 2, sample 1, sample 2, and sample 3, and draw ( Figure 3 )、( Figure 9 )、( Figure 14 ).

[0066] At low temperature (-25 o C) under xenon light (100mW / cm 2 ) Test the insulation temperature of sample 2, sample 1, sample 2, and sample 3, and draw ( Figure 4 )、( Figure 10 )、( Figure 15 ).

[0067] Under sunlight, the temperature of the comparison sample 2 and sample 1 is tested over time and plotted ( Figure 5 ).

[0068] Comparison of Example 1 and Comparative Example 2 demonstrates that the composite coating system obtained by the present invention has an adaptive temperature control function, and can achieve a cooling function at high temperatures and a heat preservation function at low temperatures.

[0069] Comparative Example 3 A cement-enhanced hydrophobic temperature-regulating coating, the preparation method of which is substantially the same as that of Example 1, except that: the migration-anchoring dual-functional additive FOTS is not added; after preparing a highly dispersed SiO2-cement composite slurry, 10 mL of hexamethyldisilazane (HMDS) is added and stirred for 12 hours (at 45°C, 500 r / min); finally, 6 g of polyvinylidene fluoride (PVDF) is added and stirred (450 r / min) for 4 hours to obtain a radiative cooling superhydrophobic topcoat.

[0070] Scanning electron microscopy observation of the obtained sample revealed that the surface structure had obvious cracks and loose areas, and the contact angle test value was 130°, see ( Figure 17 ), which is much lower than the 154.8° obtained in Example 1 of the present invention. After three hot and cold cycles (heating-cooling-water spraying), the contact angle dropped to about 115°, and some areas of the coating surface showed whitening and slight powdering. After six hot and cold cycles, the sample showed hydrophilicity, as shown in ( Figure 18 ). Infrared thermal imaging tests showed that the temperature drop ΔT was only 0.9°C.

[0071] The above results show that if the FOTS synergistic and step-by-step introduction strategy is not adopted, using only a single hydrophobic agent and mixing them simultaneously in an alkaline environment can easily lead to inactivation of the hydrophobic component and discontinuous interface structure, thereby affecting the durability and temperature control performance of the coating, and failing to achieve the multifunctional synergistic optimization effect described in the present invention.

[0072] Comparative Example 4 A cement-enhanced hydrophobic temperature-regulating coating, the preparation method of which is substantially the same as that of Example 1, except that: During the preparation of the radiation-cooled super-hydrophobic topcoat, 10 mL of HMDS, 7 ml of FOTS, and 6 g of PVDF were directly added and stirred for 16 h to obtain the radiation-cooled super-hydrophobic topcoat.

[0073] The test results showed that the PVDF distribution on the coating surface was uneven, with obvious micron-scale agglomeration patches appearing locally, and the contact angle test value was 151.1° (see Figure 19 ), slightly lower than the 162.1° achieved in Example 3 of the present invention. Infrared thermal control tests showed that the temperature drop ΔT under simulated sunlight conditions was 1.7°C, lower than the 5.5°C achieved in Example 3. Furthermore, the thermal response area on the coating surface was unevenly distributed, exhibiting a "hot spot" phenomenon.

[0074] Comparative Example 5 A cement-enhanced hydrophobic temperature-regulating coating, the preparation method of which is substantially the same as that of Example 1, except that: In the final spraying stage of topcoat, ordinary spraying (pressure 0.2MPa, no electrostatic field) is used instead, and the 30kV voltage and electric field line density control are cancelled.

[0075] The test results show that the contact angle test value is 148.2°, see ( Figure 20 ), indicating that the superhydrophobicity is lost; infrared thermal imaging shows that the hot spot area accounts for more than 25%; after QUV aging for 500h, the contact angle decays to 126.5°, see ( Figure 21 The lack of electrostatic field induction leads to disordered stacking of PVDF molecular chains, low terminal film density, and ineffective promotion of PFPE vertical migration to the surface, resulting in a 40% decrease in fluorine enrichment efficiency.

[0076] The above illustrates and describes the basic principles, main features, and advantages of the present invention. It should be understood that the above examples are merely some embodiments of the present invention and are not intended to limit the present invention. Therefore, any changes and modifications to the above examples are intended to be included within the scope of protection of the claims of the present invention.

Claims

1. A cement-enhanced super-hydrophobic adaptive temperature control coating, characterized in that: It includes a thermochromic base layer and a radiant cooling surface layer; in the primer used, the components and their weight proportions include: 3 to 6.6 parts of a composite resin matrix, 0.4 to 1.2 parts of a filler, 11 to 15 parts of a thermochromic powder, and 10 to 15 parts of an organic solvent; in the topcoat used, the components and their weight proportions include: 50 to 55 parts of a SiO2 dispersion, 2 to 9 parts of a white cement slurry, 5 to 8 parts of a hydrophobic modifier, 6 to 10 parts of a low surface energy substance, and 7 to 11 parts of a migration-anchoring dual-functional additive.

2. The cement-enhanced super-hydrophobic adaptive temperature control coating according to claim 1, characterized in that: The composite resin matrix comprises alkyd resin, polypropylene resin and fluorocarbon resin.

3. The cement-enhanced super-hydrophobic adaptive temperature control coating according to claim 1, characterized in that: The SiO2 dispersion is a silicon source hydrolyzate, and the concentration of SiO2 is 0.03-0.06 g / mL.

4. The cement-enhanced super-hydrophobic adaptive temperature control coating according to claim 1, characterized in that: The white cement slurry comprises white cement and water, and the hydration time after mixing is 3 to 6 hours; the mass ratio of white cement to water is 1:0.3 to 0.

6.

5. The cement-enhanced super-hydrophobic adaptive temperature control coating according to claim 1, characterized in that: The migration-anchoring dual-functional auxiliary agent is one or more of 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, and 3,3,3-trifluoropropyltrimethoxysilane.

6. The method for preparing the cement-enhanced super-hydrophobic adaptive temperature control coating according to any one of claims 1 to 5, characterized in that: The steps include: 1) Preparation of radiation cooling topcoat; Inject white cement slurry into SiO2 dispersion to perform multi-stage directional interlocking shearing; Then, a hydrophobic modifier is introduced and stirred at room temperature; a low surface energy substance and a migration-anchoring dual-functional additive are added and stirred to form a radiant cooling topcoat; 2) Preparation of thermochromic primer; In an organic solvent, alkyd resin, polypropylene resin and fluorocarbon resin are sequentially added and stirred to form a composite resin matrix; a dispersion of filler and silane coupling agent is added and stirred, and thermochromic powder is added and stirred to prepare a thermochromic primer; 3) Under humidity step-controlled conditions, spraying a thermochromic primer onto the surface of the substrate; then spraying a radiant cooling topcoat in steps, and drying the topcoat to obtain the cement-enhanced super-hydrophobic adaptive temperature-control coating.

7. The preparation method according to claim 6, characterized in that The multi-stage directional chimeric shearing step includes: first increasing the shear rate to 1200~1400 rpm at a rate of 50~80 rpm / s, then step-by-step reducing the speed to 600~900 rpm within 30~60s, and maintaining the speed for 130~170s; wherein the step-by-step reducing the speed includes: first reducing the speed to 950~1050 rpm at a rate of 20~30 rpm / s, and then reducing the speed to 600~900 rpm at a rate of 40~50 rpm / s.

8. The preparation method according to claim 6, characterized in that The moisture step control conditions of the primer include the spraying period, pre-curing period and powder anchoring period. The specific control requirements include the following: 1) Spraying period: control the ambient humidity to 45~55%RH; 2) Pre-curing period: First, increase the humidity to 60-80% and maintain for 80-100 seconds; then reduce the humidity to 50-60% RH; Maintain humidification for 80-120 seconds; 3) Powder anchoring period: After gelation, place the powder in a 53-57% humidity environment for 2.5-3 minutes to complete the embedding and fixation of the thermochromic powder. 4) Final curing: Adjust the humidity to 40~50%RH and cure until the coating is completely dry.

9. The preparation method according to claim 6, characterized in that In the step-by-step spraying process of the topcoat, the final spraying stage adopts an electrostatic spraying process with a voltage of 28-32 kV and an electric field line density of 18-22 lines / mm 2 , atomizing air pressure 0.05~0.08MPa.

10. The preparation method according to claim 6, characterized in that The drying step adopts a temperature-controlled drying process, specifically a three-stage gradient temperature control mechanism, and the specific steps include: first, keeping warm at 38-42°C for 12-18 minutes; then keeping warm at 53-57°C for 8-12 minutes; finally, keeping warm at 33-37°C for 25-35 minutes, and keeping warm at 28-32°C for 30-40 minutes.

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