Inorganic high-temperature-resistant ceramic coating based on siloxane low-temperature polycondensation and precursor pyrolysis and preparation method thereof

Abstract

The application belongs to the technical field of novel inorganic functional coating materials, and discloses an inorganic baking-free high-temperature-resistant ceramic coating based on siloxane low-temperature polycondensation and precursor cracking and a preparation method thereof. The coating comprises a matrix phase, a precursor reinforcing phase, a functional filler and an auxiliary agent. The matrix phase is a siloxane prepolymer solution. The precursor reinforcing phase is a PSZ solution containing aluminum / zirconium. The functional filler comprises core-shell structure heat-insulating antibacterial filler, yttrium oxide stabilized zirconium oxide powder and flaky mica powder. The core of the core-shell structure heat-insulating antibacterial filler is a hollow glass microsphere, and the shell is a TiO2 / ZnO composite coating layer. The coating integrates broad-spectrum antibacterial and mildew-proof and photocatalytic self-cleaning capabilities. After curing, the pencil hardness of the coating reaches 9H or above, the wear resistance is strong, and there is no VOC release in the whole life cycle. The system is water-based or reactive, and the coating can be firmly attached to the surfaces of various polar or non-polar substrates such as concrete, cement mortar, wood, glass, ceramic and metal.

Description

Technical Field

[0001] This invention relates to the field of novel inorganic functional coating materials, specifically to a composite ceramic coating that can be applied and cured at low temperatures and can withstand extreme high temperatures, and its preparation method. It is particularly suitable for applications in the fields of construction, industrial equipment, aerospace, etc., where there are stringent requirements for fire resistance, heat insulation, weather resistance, and multifunctional surfaces. More specifically, it relates to an inorganic, non-fired, high-temperature resistant ceramic coating based on low-temperature polycondensation of siloxanes and precursor pyrolysis, and its preparation method. Background Technology

[0002] Currently, inorganic high-temperature resistant coatings on the market are mainly divided into the following three categories: (1) Silicate / phosphate-based coatings: rely on high temperature (usually >400℃) dehydration condensation or sintering to form a ceramic structure. Its fundamental defect is that it cannot be effectively cured at low temperature, the coating strength is low, and the maximum service temperature is mostly limited to below 1200℃, which is difficult to meet the ultra-high temperature scenarios.

[0003] (2) Organic-inorganic hybrid coatings: The workability is improved by modifying organic resins, but the organic components decompose and carbonize at 300-600℃, resulting in coating failure and smoke release, which cannot meet the requirements of extreme fire resistance and zero VOC at 2000℃.

[0004] (3) Traditional ceramic coatings (such as thermal barrier coatings): usually employ plasma spraying or high-temperature sintering processes, which have harsh construction conditions, high energy consumption, and cannot be applied to heat-sensitive substrates such as wood and concrete.

[0005] Polymers such as polysiloxanes and polycarbosilanes can undergo high-temperature pyrolysis (1000-1600℃) under an inert atmosphere to generate non-oxide ceramics such as SiC and SiOC, which exhibit excellent high-temperature performance. However, this process typically requires high-temperature heat treatment (sintering) under a protective atmosphere, and the precursors themselves are expensive. Existing technologies either focus on the low-temperature bonding applications of siloxanes (temperature resistance <600℃) or on the preparation of high-temperature ceramic fibers / bulk materials from precursor polymers. There is currently no deep coupling of these two technologies to design a coating system that can be applied and cured in air through low-temperature polycondensation, and then transformed into a higher-performance ceramic phase through pyrolysis-oxidation synergy upon exposure to ultra-high temperatures.

[0006] Overall, existing coating systems exhibit an irreconcilable contradiction between the two performance dimensions of "applicable and curable at low temperatures (above 0°C)" and "resistant to ultra-high temperatures (2000°C)". The root cause lies in the fact that low-temperature curing relies on organic reactions or physical drying, while ultra-high temperature stability depends on a well-developed inorganic ceramic network structure. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a novel coating material design and preparation strategy to achieve the following comprehensive objectives: 1. Revolutionary construction performance: Enables normal brushing or spraying in low-temperature environments of 0℃ and above, and relies on chemical reaction to complete curing at low temperatures, forming a coating with initial service strength.

[0008] 2. Extreme high temperature stability: After the coating is exposed to 2000℃ high temperature (such as fire) for 30 minutes, the mass loss rate is less than 1%, the structure remains intact, and there is no melting, dripping or powdering.

[0009] 3. Active and passive thermal insulation: Through a unique microstructure design, the coating is endowed with a low thermal conductivity, which blocks the transfer of heat to the substrate and can undergo an endothermic reaction in a specific temperature range to actively consume heat.

[0010] 4. Long-lasting and multifunctional: It integrates broad-spectrum antibacterial and antifungal properties with photocatalytic self-cleaning capabilities, ensuring that the surface remains clean and hygienic for a long time in humid and highly polluted environments.

[0011] 5. Excellent mechanical and environmental performance: After curing, the coating has a pencil hardness of 9H or higher, strong wear resistance, and no VOC release throughout its entire life cycle. It is a fully water-based or reactive system.

[0012] 6. Wide adaptability to various substrates: It can firmly adhere to the surfaces of various polar or non-polar substrates such as concrete, cement mortar, wood, glass, ceramics, and metals.

[0013] To achieve the objectives of this invention, an inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation of siloxanes and precursor pyrolysis is provided. The coating comprises a matrix phase, a precursor reinforcing phase, functional fillers, and additives. The matrix phase is a siloxane prepolymer solution, the precursor reinforcing phase is an aluminum / zirconium-containing polysilazane (PSZ) solution, and the functional fillers include a core-shell structured thermally insulating and antibacterial filler, yttrium oxide-stabilized zirconia (YSZ) powder, and flake mica powder. The core of the core-shell structured thermally insulating and antibacterial filler is a hollow glass microsphere, and the shell is a TiO2 / ZnO composite coating layer.

[0014] Furthermore, in some embodiments of the present invention, the mass ratio of the matrix phase, reinforcing phase, functional filler and additive is 30-45:10-15:35-50:4-8.

[0015] Furthermore, in some embodiments of the present invention, the siloxane prepolymer solution comprises an epoxy-based siloxane, a long-chain alkyl siloxane, and a solvent. The epoxy-based siloxane provides reactive epoxy groups, enhancing low-temperature reactivity and adhesion to the substrate; the long-chain alkyl siloxane introduces hydrophobic segments, improving coating flexibility, hydrophobicity, and compatibility with the precursor; and the solvent is used to control the hydrolysis rate and system viscosity.

[0016] Furthermore, in some embodiments of the present invention, the mass ratio of epoxy siloxane, long-chain alkyl siloxane and solvent in the siloxane prepolymer solution is 15-20:8-12.

[0017] Furthermore, in some embodiments of the present invention, the epoxy siloxane is γ-glycidoxypropyltrimethoxysilane (KH560).

[0018] Furthermore, in some embodiments of the present invention, the long-chain alkylsiloxane is n-octyltriethoxysilane.

[0019] Furthermore, in some embodiments of the present invention, the solvent is a mixture of deionized water and alcohol.

[0020] Furthermore, in some embodiments of the present invention, the preparation method of the aluminum / zirconium-containing polysilazane (PSZ) solution is as follows: methyldichlorosilane (CH3SiHCl2) and dimethyldichlorosilane ((CH3)2SiCl2) are mixed in a reaction vessel at a molar ratio of 5-9:2-4, diluted with toluene, and the reaction system is cooled to -83°C to -72°C. Excess anhydrous ammonia gas is introduced or liquid ammonia is added dropwise while stirring. The reaction is violently exothermic, generating a large amount of white ammonium chloride precipitate. The reaction is maintained at a low temperature for 4-6 hours, then raised to room temperature, and the solid NH4+ is filtered out. Add 4Cl to the filtrate with a catalyst amount of triethylamine, reflux and stir at 80-90℃ for 12-24 hours, cool the system to 55-65℃, and add a toluene solution of aluminum / zirconium alkoxide dropwise at a silicon:aluminum / zirconium molar ratio of 8-12:0.8-1.2. After the addition is complete, raise the temperature to 100-110℃ and reflux for 8-12 hours. Stop heating and cool to room temperature. Filter the reaction solution under N2 protection, evaporate the filtrate until a viscous liquid is obtained with a solid content controlled at 50-60%. This is the target aluminum / zirconium-containing polysilazane (PSZ) solution.

[0021] Furthermore, in some embodiments of the present invention, the mass ratio of the core-shell structured thermally insulating and antibacterial filler, yttrium-stabilized zirconia (YSZ) powder, and flake mica powder in the functional filler is 20-30:8-12:5-8. The yttrium-stabilized zirconia (YSZ) powder, as a high-temperature reinforcing phase and oxygen ion conductor, can improve the high-temperature phase stability and thermal shock resistance of the coating, while the flake mica powder can improve the barrier properties of the coating and reduce internal stress.

[0022] Furthermore, in some embodiments of the present invention, the molar ratio of TiO2 to ZnO in the core-shell structured heat-insulating and antibacterial filler is (6.5:3.5) to (9.5:0.5), preferably (7.5:2.5) to (8.5:1.5). Experiments show that when the molar ratio of TiO2 to ZnO is 8.5:1.5, compared with a pure TiO2 shell, its antibacterial rate against Escherichia coli is increased by 15%, and its inhibition rate against Aspergillus niger is increased from less than 50% to over 95%. Simultaneously, it accelerates the photocatalytic degradation rate of methylene blue, and its performance shows no degradation after 1000 hours of damp heat aging. This precise ratio design is one of the key details of the present invention in achieving long-lasting, stable, and multifunctional self-cleaning antibacterial performance.

[0023] Furthermore, in some embodiments of the present invention, the TiO2 mass percentage in the core-shell structure heat-insulating and antibacterial filler is 4-6% of the total weight of the hollow glass microspheres.

[0024] Furthermore, in some embodiments of the present invention, the core of the core-shell structure heat-insulating and antibacterial filler is a hollow glass microsphere with a particle size of 10-50 μm, and the shell is a TiO2 / ZnO composite coating layer of 3-5 nm.

[0025] Furthermore, in some embodiments of the present invention, the preparation method of the core-shell structure heat-insulating and antibacterial filler is as follows: hollow glass microspheres are dispersed in ethanol, a mixed solution of tetrabutyl titanate and zinc acetate is added, and under ultrasonication and stirring, the microspheres are hydrolyzed by ammonia catalysis to form a uniform TiO2 / ZnO composite gel layer. After drying and calcination at 400-500℃, a core-shell structure heat-insulating and antibacterial filler with good photocatalytic activity is obtained.

[0026] Furthermore, in some embodiments of the present invention, the mass ratio of tetrabutyl titanate to zinc acetate is 6-10:0.8-1.2, preferably 7.5-8.5:0.9-1.1.

[0027] Furthermore, in some embodiments of the present invention, the particle size of the yttrium-stabilized zirconium oxide (YSZ) powder is 50-200 nm.

[0028] Furthermore, in some embodiments of the present invention, the additives include a catalyst, a pH adjuster, a leveling agent / defoamer, and a thixotropic agent; preferably, the mass ratio of the catalyst, pH adjuster, leveling agent / defoamer, and thixotropic agent is 0.5-1.5:0.2-0.5:0.3-0.8:2-4.

[0029] Further preferably, in some embodiments of the present invention, the catalyst is a catalyst composed of dibutyltin dilaurate and an organic amine; preferably, the mass ratio of dibutyltin dilaurate to the organic amine is 0.9-1.1:0.3-2, more preferably 1:0.5-1.2. Within the above range, the coating can most reliably achieve storage stability of more than 6 months at 5-25°C, while achieving full curing within 24-72 hours after application at 0°C.

[0030] Further preferably, in some embodiments of the present invention, the organic amine is one of a sterically hindered secondary amine, an aliphatic primary amine, or an alicyclic amine; more preferably, the organic amine is one or more of N-methylcyclohexylamine, diisopropylamine, N,N-dimethylcyclohexylamine, n-butylamine, isopropylamine, cyclohexylamine, or aminoethylethanolamine.

[0031] More preferably, in some embodiments of the present invention, the pH adjuster is glacial acetic acid.

[0032] More preferably, in some embodiments of the present invention, the leveling agent / defoamer is a polyether-modified polysiloxane leveling agent / defoamer.

[0033] More preferably, in some embodiments of the present invention, the thixotropic agent is fumed silica.

[0034] On the other hand, the present invention also provides a method for preparing the aforementioned inorganic non-sintering high-temperature resistant ceramic coating based on low-temperature polycondensation of siloxanes and precursor pyrolysis, the preparation method comprising: (1) Pre-hydrolysis of siloxanes: Under nitrogen protection, epoxy siloxanes and long-chain alkyl siloxanes are added to a reactor, along with a mixed solvent of water and ethanol (water:ethanol = 1:3) and a portion (40%-60% of the total amount of glacial acetic acid) of the auxiliaries. The mixture is stirred slowly at 5-10°C for 4-6 hours to obtain a clear and transparent pre-hydrolyzed siloxane solution. The low-temperature operation is intended to control the hydrolysis rate and avoid excessive self-polymerization.

[0035] (2) Coating preparation: Transfer the siloxane pre-hydrolyzed solution to a high-speed disperser. Under low-speed stirring, add the aluminum / zirconium-containing polysilazane (PSZ) solution and the remaining additives except glacial acetic acid in sequence. Slowly add the functional filler and increase the speed to 2000-3000 rpm. Disperse for 30-45 minutes until the system is uniform and the fineness is ≤50μm. Adjust the final pH value to 4.5-5.5 with the remaining glacial acetic acid (this pH range is the key window to ensure storage stability and rapid curing after construction).

[0036] (3) Curing and application: The coating can be used after being sealed and cured at 5-25℃ for 20-28 hours. It can be applied by brushing, rolling or spraying. The ambient temperature during application must be ≥0℃ and the relative humidity ≤80%.

[0037] (4) Curing: In an environment above 0°C, the wet film triggers a deep polycondensation reaction of siloxanes through moisture evaporation and pH changes. It reaches surface dryness and a transportable hardness within 24-72 hours (the lower the temperature, the longer the time). After 7 days, the polycondensation reaction is basically complete, and the coating reaches its maximum initial strength (hardness > 6H). Full performance (hardness 9H) requires 28 days of curing under environmental conditions, or can be accelerated by baking at a low temperature below 80°C (2-4 hours).

[0038] In this invention, organosiloxanes (such as ethyl silicate and methyltrimethoxysilane) can undergo hydrolysis and condensation at low temperatures or even room temperature under the action of a catalyst to form a three-dimensional Si-O-Si network (sol-gel process). This network has inorganic properties and good thermal stability. However, pure siloxane gels will crack and pulverize due to excessive shrinkage at high temperatures (>1200℃), and their initial hardness and wear resistance are insufficient.

[0039] Compared with the prior art, the advantages of the present invention include, but are not limited to: 1. Mechanism Innovation – “Low-Temperature Polycondensation Network” and “High-Temperature Cracking-Oxidation Synergistic Enhancement” Achieve Dual Mechanism Coupling: (1) First mechanism (low temperature): Functional siloxanes (such as epoxy siloxanes and long-chain alkyl siloxanes) undergo rapid hydrolysis and condensation at temperatures above 0°C under the action of a catalyst to form a tough, organic-inorganic hybrid three-dimensional network skeleton. This network provides the coating with initial strength, adhesion, flexibility and application window.

[0040] (2) Second mechanism (high temperature): Carefully designed introduction of "pyrolysis precursors" (such as polysilazane containing specific metals) and "oxidation-enhancing fillers" (such as ultrafine zircon powder and rare earth oxides). When exposed to ultra-high temperatures, the organic components and precursors in the siloxane network undergo pyrolysis, generating active silicon species and carbides; simultaneously, in the presence of air, these active species undergo in-situ oxidation reactions with the fillers and matrix, generating new and more stable silicate, oxide, or non-oxide ceramic phases (such as ZrSiO4, Y2SiO5, etc.), filling the pores left by the decomposition of organic components, achieving "self-healing" and "secondary reinforcement" of the coating, rather than simple inorganic skeleton collapse. This is the key to achieving "sintered" performance without firing.

[0041] 2. Material System Innovation – Precise Design and Compounding of Multifunctional Components: (1) Core-shell structured multifunctional filler: The filler is designed with hollow ceramic microspheres as the core and an outer shell of nano-titanium dioxide (TiO2) and nano-zinc oxide (ZnO) composite layer coated by sol-gel method. The core layer provides excellent thermal insulation performance (low thermal conductivity), and the shell layer provides photocatalytic self-cleaning and antibacterial functions. This design solves the problem of easy agglomeration of nanoparticles and uneven distribution in the coating.

[0042] (2) Environmentally responsive curing regulator: A composite catalytic system is used, which includes a low-temperature active metal-organic catalyst (such as organotin) and a pH adjuster. The system maintains low activity at a low temperature of 0-5℃ to ensure the storage stability of the coating; once the film is formed, as the moisture evaporates, the pH of the system changes, which quickly activates the concentration polymerization reaction of siloxanes and achieves rapid curing.

[0043] 3. Structural Innovation – Gradient Functional Coating Design: By controlling the rheology and application process of the coating, a micro-gradient structure is guided to form during the curing process: the surface layer is enriched with wear-resistant hard fillers and photocatalysts to achieve high hardness and self-cleaning; the middle layer is a dense siloxane-precursor composite network, providing the main strength and airtightness; the bottom layer (near the substrate) is rich in flexible siloxanes and interfacial coupling agents to ensure strong adhesion and stress buffering with different substrates. This self-assembled gradient structure is the basis for a single formulation to achieve multiple conflicting properties (such as hardness and adhesion). Attached Figure Description

[0044] Figure 1 The coating of this invention is burned with a flame torch. The coating of this invention does not produce smoke, does not catch fire, and its color changes slightly. Figure 2 The epoxy coating was burned by using a flame torch, causing it to bubble and quickly catch fire. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. It should be understood that the following description is merely illustrative and not intended to limit the invention.

[0046] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0047] The singular form includes the plural objects of discussion unless the context clearly indicates otherwise. "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.

[0048] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0049] Furthermore, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., described below refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms are not necessarily directed at the same embodiment or example. Moreover, the technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0050] The preparation method of the inorganic non-sintering high-temperature resistant ceramic coating based on low-temperature polycondensation of siloxane and precursor pyrolysis in this invention embodiment is as follows: (1) Pre-hydrolysis of siloxanes: Under nitrogen protection, epoxy siloxanes and long-chain alkyl siloxanes are added to a reaction vessel, along with a mixed solvent of water and ethanol (water:ethanol = 1:3) and half the amount of glacial acetic acid. The mixture is stirred slowly at 5-10°C for 4-6 hours to obtain a clear and transparent pre-hydrolyzed siloxane solution. The low-temperature operation is intended to control the hydrolysis rate and avoid excessive self-polymerization.

[0051] (2) Coating preparation: Transfer the siloxane pre-hydrolyzed solution to a high-speed disperser. Under low-speed stirring, add the aluminum / zirconium-containing polysilazane (PSZ) solution and the remaining additives except glacial acetic acid in sequence. Slowly add the functional filler and increase the speed to 2000-3000 rpm. Disperse for 30-45 minutes until the system is uniform and the fineness is ≤50μm. Adjust the final pH value to 4.5-5.5 with the remaining glacial acetic acid (this pH range is the key window to ensure storage stability and rapid curing after construction).

[0052] (3) Curing and application: The coating can be used after being sealed and cured at 5-25℃ for 24 hours. It can be applied by brushing, rolling or spraying. The ambient temperature during application must be ≥0℃ and the relative humidity ≤80%.

[0053] (4) Curing: In an environment above 0°C, the wet film triggers a deep polycondensation reaction of siloxanes through moisture evaporation and pH changes. It reaches surface dryness and a transportable hardness within 24-72 hours (the lower the temperature, the longer the time). After 7 days, the polycondensation reaction is basically complete, and the coating reaches its maximum initial strength (hardness > 6H). Full performance (hardness 9H) requires 28 days of curing under environmental conditions, or can be accelerated by baking at a low temperature below 80°C (2-4 hours).

[0054] The preparation method of the aluminum / zirconium polysilazane (PSZ) solution in this embodiment of the invention is as follows: I. Chemical nature and design objectives of PSZ solution 1. Chemical nature: PSZ is an abbreviation for "Poly(silyl)zarane", referring to an organic-inorganic hybrid polymer containing a silicon (Si) and nitrogen (N) backbone, with aluminum (Al) or zirconium (Zr) elements bonded at the molecular level. Its ideal molecular structure can be simplified to [-Si(R1,R2)-N-]n-[-M(OR)x-] (M=Al, Zr), that is, metal alkoxide units are introduced into the polysilazane backbone through chemical bonds.

[0055] 2. Design Objectives: Low temperature stability: The solution can be stored stably at room temperature (≥6 months) and is well compatible with siloxanes.

[0056] High-temperature reactivity: When pyrolyzed at temperatures above 600℃, it can produce nanoclusters rich in active Si, N, Al / Zr. These nanoclusters are the key "reaction source" for in-situ reactions with fillers (such as YSZ) at high temperatures to generate high-temperature reinforcing phases such as zircon (ZrSiO4), aluminosilicate, or aluminum oxynitride.

[0057] II. Laboratory Preparation Method Main monomers: methyldichlorosilane CH3SiHCl2 (M1) and dimethyldichlorosilane (CH3)2SiCl2 (M2). M1 provides reactive Si-H bonds, while M2 regulates polymer flexibility and solubility.

[0058] Metal source: Aluminum sec-butoxide Al(OC4H9)3. Its alkoxy group has moderate reactivity and readily undergoes exchange reactions with silazane intermediates.

[0059] Reaction medium: dry toluene or xylene.

[0060] Core reagent: Anhydrous liquid ammonia NH3 (or ammonia gas).

[0061] Catalyst: a small amount of triethylamine (C2H5)3N.

[0062] Post-treatment: Nitrogen (N2).

[0063] Experimental steps: 1. Establishment of an inert environment: The entire process shall be carried out in a dry Schlenk line or glove box protected by N2, and all glassware must be thoroughly dried.

[0064] 2. Ammonolysis reaction: Methyldichlorosilane CH3SiHCl2 and dimethyldichlorosilane (CH3)2SiCl2 were mixed in a reaction vessel at a molar ratio of 7:3, and then diluted with dry toluene to a concentration of about 30%.

[0065] Cool the reaction system to -78°C (dry ice / acetone bath).

[0066] Under vigorous stirring, slowly introduce excess anhydrous ammonia gas (or add liquid ammonia dropwise). The reaction is violently exothermic, producing a large amount of white ammonium chloride precipitate. Maintain the reaction at a low temperature for 4-6 hours.

[0067] Schematic diagram of the reaction: ≡Si-Cl + NH3→ ≡Si-NH2 + NH4Cl↓ 3. Desalination and condensation: Bring to room temperature and filter out solid NH4Cl.

[0068] Add a catalyst amount of triethylamine to the filtrate and reflux and stir at 80-90℃ for 12-24 hours. During this time, the generated aminosilane (≡Si-NH2) undergoes condensation polymerization to form a polysilazane prepolymer with alternating [-Si-NH-] and [-Si-N-] structures, and the viscosity gradually increases.

[0069] 4. Introduction of aluminum (key step): Cool the system to 60°C.

[0070] A toluene solution of aluminum sec-butoxide is slowly added dropwise at a Si:Al molar ratio of 10:1.

[0071] After the addition is complete, the temperature is raised to 100-110℃ and refluxed for 8-12 hours. During this process, the -NH- or -NH2 at the ends of the polysilazane chain undergoes alcohol exchange and condensation reactions with Al(OR)3 to form Si-N-Al-O- bonds, thus "grafting" aluminum atoms onto the polymer backbone at the molecular level.

[0072] Schematic diagram of the reaction: ≡Si-NH2+ Al(OR)3→ ≡Si-NH-Al(OR)2+ ROH 5. Termination and purification: Stop heating and allow to cool to room temperature.

[0073] The reaction solution was filtered through a 0.2μm polytetrafluoroethylene filter membrane under high-purity N2 protection to remove any trace amounts of gel that might be generated.

[0074] The filtrate was slowly evaporated by rotary evaporation at 40°C and a vacuum below 10 Pa to remove most of the solvent and reaction byproduct alcohol, until a pale yellow to amber, transparent, viscous liquid was obtained, with a solid content controlled at 50-60%. This is the target aluminum-containing polysilazane (Al-PSZ) concentrate.

[0075] 6. Dilution and Storage: Dilute with anhydrous xylene or propylene glycol methyl ether acetate to the required working concentration (e.g., 30%), depending on the coating formulation requirements.

[0076] Store in a nitrogen-filled, sealed container at a low temperature (<10℃) and protected from light.

[0077] Note: The preparation of zirconium-containing PSZ (Zr-PSZ) is similar, but the metal source needs to be replaced with a zirconium alkoxide, such as tetrapropyl zirconate Zr(OCH2CH2CH3)4. Due to the higher reactivity of the Zr-O bond, the reaction conditions (temperature, dropping rate) need to be milder to avoid vigorous cross-linking and gelation.

[0078] In this embodiment of the invention, the mass ratio of epoxy-based siloxane, long-chain alkyl siloxane, and solvent in the siloxane prepolymer solution is 15-20:8-12. The epoxy-based siloxane is γ-glycidoxypropyltrimethoxysilane (KH560), the long-chain alkyl siloxane is n-octyltriethoxysilane, and the solvent is a mixture of deionized water and an alcohol. Within the above range, the performance of the final product obtained by this invention shows no significant difference.

[0079] In this embodiment of the invention, the core of the core-shell structured heat-insulating and antibacterial filler is a hollow glass microsphere with a particle size of 10-50 μm, and the shell is a TiO2 / ZnO composite coating layer of 3-5 nm. The TiO2 content in the core-shell structured heat-insulating and antibacterial filler is 4-6% of the total weight of the hollow glass microspheres. Within the above range, the performance of the final product obtained by this invention shows no significant difference.

[0080] The preparation method of the core-shell structure heat-insulating and antibacterial filler is as follows: hollow glass microspheres are dispersed in ethanol, a mixed solution of tetrabutyl titanate and zinc acetate is added, and under ultrasonication and stirring, the microspheres are hydrolyzed by ammonia catalysis to form a uniform TiO2 / ZnO composite gel layer. After drying and calcination at 400-500℃, a core-shell structure heat-insulating and antibacterial filler with good photocatalytic activity is obtained.

[0081] The particle size of the yttrium-stabilized zirconia (YSZ) powder is 50-200 nm.

[0082] The mass ratio of tetrabutyl titanate to zinc acetate is 6-10:0.8-1.2, preferably 7-9:0.9-1.1, which is essentially equivalent to the molar ratio of TiO2 to ZnO in the core-shell structured heat-insulating and antibacterial filler being (6.5:3.5) to (9.5:0.5), preferably (7.5:2.5) to (8.5:1.5). The composite photocatalyst prepared at the specified ratio exhibits both excellent photocatalytic activity and broad-spectrum antibacterial properties, efficiently decomposing organic pollutants (oil stains), providing self-cleaning functionality, and without ZnO corrosion failure.

[0083] The catalyst described in this embodiment of the invention is a composite catalyst of dibutyltin dilaurate and an organic amine. Compared to a single catalyst, the storage period of the coating at 5°C can be extended from less than one month to more than six months, while the surface drying time at 0°C is shortened from seven days to 36 hours, achieving an optimal balance between storage stability and low-temperature curing activity. The organic amine ensures sufficient silanol groups are provided before application and in the early stages of film formation; after application, as moisture evaporates and the system concentrates, the dibutyltin dilaurate (DBTL) efficiently catalyzes the combination of these silanol groups to form a robust Si-O-Si network, creating a relay-style catalytic cycle. The organic amine is one or more of N-methylcyclohexylamine, diisopropylamine, N,N-dimethylcyclohexylamine, n-butylamine, isopropylamine, cyclohexylamine, or aminoethylethanolamine. In this invention, the performance of the final product obtained using these organic amines is not significantly different.

[0084] The mass ratio of dibutyltin dilaurate to organic amine is 0.9-1.1:0.3-2, more preferably 1:0.5-1.2. Within the above range, the coating can reliably achieve storage stability of more than 6 months at 5-25°C, and complete curing within 24-72 hours after application at 0°C. When the proportion of organic amine is too high, hydrolysis is strongly promoted, resulting in an excessively rapid reaction in the mixed system, a sharp increase in viscosity, a significantly shortened shelf life (possibly <1 month), and even a risk of gelation. When the proportion of dibutyltin dilaurate (DBTL) is too high, although it is beneficial for storage, the polycondensation reaction is excessively inhibited, resulting in the inability of the generated silanol groups to effectively dehydrate and crosslink at low temperatures of 0-5°C, leading to slow coating curing (possibly requiring several weeks) and poor hardness development.

[0085] In embodiments of the present invention, the additives include a catalyst composed of dibutyltin dilaurate and an organic amine, glacial acetic acid, a polyether-modified polysiloxane leveling agent / defoamer, and fumed silica; preferably, the mass ratio of the catalyst composed of dibutyltin dilaurate and an organic amine, glacial acetic acid, polyether-modified polysiloxane leveling agent / defoamer, and fumed silica is 0.5-1.5:0.2-0.5:0.3-0.8:2-4. Within the above range, the performance of the final product obtained by the present invention does not differ significantly.

[0086] Example 1 1. Formulation: 40% siloxane prepolymer (KH560 18%, octylsiloxane 10%, deionized water and alcohol mixture), 12% aluminum-containing polysilazane solution, 25% core-shell structured heat-insulating and antibacterial filler, 10% YSZ powder, 6% mica powder, and 7% additives (a catalyst composed of dibutyltin dilaurate and N-methylcyclohexylamine, glacial acetic acid, polyether-modified polysiloxane leveling agent / defoamer, and fumed silica, in a mass ratio of 1:0.3:0.5:3.2). The percentages represent the proportion of the coating raw materials used to their total weight. The mass ratio of dibutyltin dilaurate to N-methylcyclohexylamine is 1:0.8. 2. Preparation: Prepared according to the method described in this invention.

[0087] 3. Application and Testing: Apply the coating to the pretreated concrete slab (or pine board and glass board) at 5℃, with a wet film thickness of 150μm. Curing conditions: Cure for 28 days at 5℃ and 50%RH.

[0088] 4. Test Results: (1) Low temperature curing: At 5℃, the surface drying time is 4 hours, and it can be polished after 7 days.

[0089] (2) High temperature performance: In a muffle furnace, the temperature is increased to 2000℃ at 10℃ / min, heated for 30 minutes, and then cooled naturally.

[0090] (3) Mass loss rate: 0.82% for coating on concrete substrate.

[0091] (4) Coating condition: intact, without cracks or peeling, and the color has turned light grayish-white. Microscopic observation shows that the coating is dense and the interface with the substrate is intact.

[0092] (5) Thermal insulation performance: Using the heat flow meter method, it was found that when the hot side of the coating was at 1000℃, the cold side (substrate side) temperature was 280℃ lower than that of the uncoated sample.

[0093] (6) Surface properties: Pencil hardness: 9H (GB / T 6739-2006).

[0094] Abrasion resistance: 12mg mass loss after 500 revolutions under 750g load.

[0095] Antibacterial rate: The antibacterial rate against Escherichia coli and Staphylococcus aureus was >99.9% after 24 hours.

[0096] Self-cleaning: After 24 hours of UV irradiation, the coating exhibits a degradation rate of >85% for methylene blue solution; water contact angle >105°.

[0097] (7) VOC test: Not detected.

[0098] Comparative Example 1 Design: Same as Example 1, except that the composite matrix of epoxy siloxane (KH560) and long-chain alkyl siloxane is completely replaced with an equal mass of ordinary tetraethyl orthosilicate (TEOS).

[0099] Test results: Curing and Adhesion: The coating cures significantly slower at low temperatures and remains soft even after 7 days. It exhibits extremely poor adhesion to various substrates (especially wood and metal) and is prone to peeling off in large sheets.

[0100] High-temperature performance: After burning at 2000℃, the coating cracked and powdered severely, with a mass loss rate of >15%. The reason is that the silica network formed by pure TEOS is brittle, lacks the buffer of organic flexible segments, and lacks reactive groups to achieve strong bonding with precursors and fillers.

[0101] Conclusion: This study verified that specific functional siloxane (epoxy group, long-chain alkyl group) composites are indispensable for achieving low-temperature rapid curing, strong adhesion, high flexibility and high-temperature stability.

[0102] Comparative Example 2 Design: Same as Example 1, except that: no aluminum-containing polysilazane (PSZ) precursor solution is added, and its mass is made up by an equal amount of siloxane prepolymer solution.

[0103] Test results: High-temperature performance: After being burned at 2000℃, the mass loss rate increased to about 5-8%. Although the coating did not peel off, a large number of microcracks appeared on the surface, and the structure was loose.

[0104] Mechanism analysis: At high temperatures, relying solely on the siloxane network and fillers, the lack of active Al / Si / N substances generated from precursor decomposition to participate in the high-temperature in-situ reaction prevents the coating from achieving "self-healing" and "secondary reinforcement." The pores left by the decomposition of organic matter cannot be effectively filled, leading to structural deterioration.

[0105] Conclusion: This study demonstrates that the precursor is a key component for achieving the "pyrolysis-oxidation synergistic enhancement" mechanism, ultra-low mass loss rate (<1%), and structural integrity.

[0106] Comparative Example 3 Design: Same as Example 1, except that the self-made core-shell structure heat-insulating and antibacterial filler was replaced with an equal mass of uncoated ordinary hollow glass microspheres and nano-TiO2 powder that was simply physically mixed (high-speed mechanical dry mixing, 3000 rpm, 15 minutes). To ensure a fair comparison and highlight the advantages of the "core-shell structure," the mass ratio of ordinary hollow glass microspheres to nano-TiO2 powder was determined based on the theoretical content of the TiO2 functional component in the self-made core-shell filler in Example 1, and the mass ratio of ordinary hollow glass microspheres to nano-TiO2 powder was 94:6.

[0107] Test results: Dispersion and performance: Nano-TiO2 is severely agglomerated and unevenly distributed in the coating.

[0108] Thermal insulation effect: The thermal insulation performance decreased by about 15% (because TiO2 did not form an effective radiation scattering layer on the surface).

[0109] Antibacterial and self-cleaning: The antibacterial rate and photocatalytic degradation rate drop to below 70%, and the performance deteriorates rapidly.

[0110] Conclusion: This study validates the importance of core-shell structure design in ensuring uniform dispersion of nanofunctional components, long-term effective thermal insulation and antibacterial self-cleaning functions, and maintaining coating density. Physically mixed TiO2 only has physical contact with microspheres and the coating matrix, which can easily become defect points during curing or heating, affecting coating density and durability.

[0111] Comparative Example 4 Design: Same as Example 1, except that the ultrafine yttrium-stabilized zirconium oxide (YSZ) powder is replaced with an equal mass of ordinary fumed silica (white carbon black).

[0112] Test results: High-temperature performance: After being burned at 2000℃, the coating severely deformed, shrank, and cracked. Although the mass loss rate was low (due to the stability of silica), the coating lost its structural strength.

[0113] Mechanism analysis: Silica softens at high temperatures and promotes excessive shrinkage of the silicon-oxygen network. Lacking the phase-stabilizing and reinforcing effects of YSZ and its role as a reaction precursor for zircon (ZrSiO4), the coating cannot form a stable framework at ultra-high temperatures.

[0114] Conclusion: This study demonstrates that YSZ not only serves as a nano-reinforcing phase but also participates in high-temperature in-situ reactions to generate a high-melting-point second phase, thus ensuring the dimensional stability and structural strength of the coating under extreme temperatures.

[0115] Comparative Example 5 Design: Same as Example 1, except that no flake mica powder is added, and its mass is made up by an equal amount of YSZ powder.

[0116] Test results: Application and Curing: Slight sagging occurred during the application of the coating on the vertical surface.

[0117] Coating performance: After curing, the internal stress of the coating increases, and its crack resistance decreases during thermal cycling tests. After high-temperature burning, the number of cracks increases compared to Example 1.

[0118] Mechanism analysis: The physical barrier, stress release and anti-sagging effects of sheet mica are lacking.

[0119] Conclusion: This study verified the auxiliary but important role of flaky mica powder filler in improving workability, reducing coating internal stress, and enhancing thermal shock resistance.

[0120] Comparative Example 6 Design: Same as Example 1, except that the composite catalyst (a mixture of dibutyltin dilaurate and organic amine) is replaced with an equal mass of the single catalyst glacial acetic acid.

[0121] Test results: Storage stability: The coating's storage stability deteriorates, with a significant increase in viscosity or gelation occurring within one week.

[0122] Low-temperature curing: At 5℃, the surface drying and hard drying time of the coating is extended by more than double, and it may even fail to cure completely.

[0123] Conclusion: This study verifies the key regulatory role of the composite catalytic system of the present invention in precisely controlling the balance between hydrolysis and polycondensation rates, thereby achieving the contradictory properties of stable coating storage and rapid curing at low temperatures.

[0124] Comparative Example 7 Design: Same as Example 1, except that the entire siloxane prepolymer and precursor system is replaced with room temperature curing silicone resin with equal solids (common type with a temperature resistance of about 300°C on the market).

[0125] Test results: Environmental friendliness: There is a significant release of VOCs during construction.

[0126] High-temperature performance: It begins to decompose and smoke at 400℃, and is completely carbonized at 600℃. After testing at 2000℃, only ash remains.

[0127] Conclusion: This extreme but clear comparison delineates the essential boundary between the "inorganic non-fired ceramic coating" of this invention and the traditional "organic high-temperature resistant coating", highlighting the revolutionary breakthrough of the coating material of this invention in terms of environmental protection and temperature resistance.

[0128] Comparative Example 8 Design: Same as Example 1, except that all functional fillers (core-shell structure heat-insulating and antibacterial filler, YSZ powder, mica powder) are replaced by an equal volume with a conventional filler combination. The conventional filler is composed of quartz powder (200 mesh), kaolin and calcium carbonate in a mass ratio of 6:3:1, which are added after being uniformly mixed by high-speed dispersion.

[0129] Test results: Coating appearance: The coating surface is rough and has low gloss.

[0130] Mechanical properties: maximum hardness not exceeding 4H, poor wear resistance.

[0131] High-temperature performance: When heated to 2000℃, the decomposition of calcium carbonate produces gas, causing the coating to bubble. The crystal transformation of quartz powder causes volume changes, leading to cracking. The mass loss rate is >10%.

[0132] Conclusion: This study verifies that the finely designed nano / micro composite functionalized filler system of this invention is irreplaceable in achieving top-tier comprehensive performance such as high hardness, wear resistance, high-temperature stability, and low thermal conductivity, which cannot be achieved by ordinary fillers. This result not only demonstrates the necessity of single-functional fillers but also strongly proves that combining the functional fillers described in this invention through specific design can produce synergistic effects beyond simple addition (e.g., core-shell fillers provide "thermal insulation + antibacterial properties," YSZ provides "reinforcement + high-temperature reaction," and mica provides "barrier + crack resistance").

[0133] The properties of the coatings (ceramic substrates) prepared in Example 1 and Comparative Examples 1-8 are shown in the table below: I. Verification of the core innovation mechanism: 1. Comparative Example 2 (mass loss of 5.3%) directly demonstrates the core role of the precursor in achieving self-healing through "pyrolysis-oxidation synergy" at high temperatures, and its absence leads to significant performance degradation.

[0134] 2. Comparative Example 4 (loss rate 8.1%, cracking) verified the irreplaceable nature of YSZ as a high-temperature reactive phase precursor, and its absence caused the coating to lose its structural skeleton at extreme temperatures.

[0135] 3. Comparative Example 7 (completely burned, high VOC) completely distinguishes the boundary between the "inorganic non-burning" system of this invention and traditional organic coatings, highlighting the dual breakthrough of environmental protection and temperature resistance.

[0136] II. Verification of Multifunctional Integrated Design: 1. Comparative Example 3 (75% antibacterial rate, 92° contact angle) shows that simple physical mixing cannot bring out the effectiveness of nano-photocatalysts, and the core-shell structure design is the key to integrating long-lasting self-cleaning and antibacterial functions.

[0137] 2. Comparative Example 1 (adhesion grade 3, hardness 2H) and Comparative Example 6 (construction temperature >10℃, hardness 4H) jointly verified the decisive role of functional siloxane compound and composite catalytic system in achieving low-temperature construction, strong adhesion and high hardness.

[0138] III. Demonstration of Superior Overall Performance: Example 1 achieves optimal performance at both extreme performance points of "0℃ construction" and "2000℃ tolerance", and has no shortcomings in various indicators such as hardness, heat insulation, self-cleaning, adhesion, wear resistance, and environmental protection, which proves the high degree of synergy and non-obviousness of the entire material system design.

[0139] In summary, this invention, through its original material system and reaction pathway design, successfully bridges the performance gap between "low-temperature curing" and "ultra-high temperature stable service," providing an unprecedented multifunctional coating solution adaptable to extreme environments, possessing strong practical value and broad industrialization prospects.

[0140] Those skilled in the art will readily understand that the above description is merely a partial example of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation of siloxanes and precursor pyrolysis, characterized in that, The coating comprises a matrix phase, a precursor reinforcing phase, functional fillers, and additives. The matrix phase is a siloxane prepolymer solution, the precursor reinforcing phase is an aluminum / zirconium-containing polysilazane solution, and the functional fillers include a core-shell structured thermal insulation and antibacterial filler, yttrium oxide-stabilized zirconia powder, and flake mica powder. The core of the core-shell structured thermal insulation and antibacterial filler is a hollow glass microsphere, and the shell is a TiO2 / ZnO composite coating layer.

2. The inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation and precursor pyrolysis of siloxanes according to claim 1, characterized in that, The mass ratio of the matrix phase, reinforcing phase, functional filler, and additives is 30-45:10-15:35-50:4-8.

3. The inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation and precursor pyrolysis of siloxanes according to claim 1, characterized in that, The siloxane prepolymer solution contains an epoxy siloxane, a long-chain alkyl siloxane, and a solvent; preferably, the mass ratio of the epoxy siloxane, the long-chain alkyl siloxane, and the solvent in the siloxane prepolymer solution is 15-20:8-12; preferably, the epoxy siloxane is γ-glycidoxypropyltrimethoxysilane; preferably, the long-chain alkyl siloxane is n-octyltriethoxysilane; preferably, the solvent is a mixture of deionized water and an alcohol.

4. The inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation and precursor pyrolysis of siloxanes according to claim 1, characterized in that, The preparation method of the aluminum / zirconium-containing polysilazane solution is as follows: Methyldichlorosilane and dimethyldichlorosilane are mixed in a molar ratio of 5-9:2-4 in a reaction vessel, diluted with toluene, and the reaction system is cooled to -83°C to -72°C. Excess anhydrous ammonia gas is introduced or liquid ammonia is added dropwise while stirring. The reaction is violently exothermic, generating a large amount of white ammonium chloride precipitate. The reaction is maintained at a low temperature for 4-6 hours, then raised to room temperature. Solid NH4Cl is filtered off, and a catalyst amount of triethylamine is added to the filtrate. The mixture is then reacted at 80°C. Reflux and stir at -90℃ for 12-24 hours. Cool the system to 55-65℃ and add a toluene solution of aluminum / zirconium alkoxide dropwise at a silicon:aluminum / zirconium molar ratio of 8-12:0.8-1.

2. After the addition is complete, heat to 100-110℃ and reflux for 8-12 hours. Stop heating and cool to room temperature. Filter the reaction solution under N2 protection. Evaporate the filtrate until a viscous liquid is obtained with a solid content of 50-60%. This is the target aluminum / zirconium-containing polysilazane solution.

5. The inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation and precursor pyrolysis of siloxanes according to claim 1, characterized in that, The mass ratio of the core-shell structured heat-insulating and antibacterial filler, yttrium oxide-stabilized zirconia powder, and flake mica powder in the functional filler is 20-30:8-12:5-8; preferably, the molar ratio of TiO2 to ZnO in the core-shell structured heat-insulating and antibacterial filler is (6.5:3.5) to (9.5:0.5), more preferably (7.5:2.5) to (8.5:1.5); preferably, the mass percentage of TiO2 in the core-shell structured heat-insulating and antibacterial filler is 4-6% of the total weight of the hollow glass microspheres; preferably, the core of the core-shell structured heat-insulating and antibacterial filler is a hollow glass microsphere with a particle size of 10-50 μm, and the shell is a TiO2 / ZnO composite coating layer of 3-5 nm.

6. The inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation and precursor pyrolysis of siloxanes according to claim 1, characterized in that, The preparation method of the core-shell structure heat-insulating and antibacterial filler is as follows: hollow glass microspheres are dispersed in ethanol, a mixed solution of tetrabutyl titanate and zinc acetate is added, and under ultrasonication and stirring, the microspheres are hydrolyzed by ammonia catalysis to form a uniform TiO2 / ZnO composite gel layer. After drying and calcination at 400-500℃, a core-shell structure heat-insulating and antibacterial filler with good photocatalytic activity is obtained. Preferably, the mass ratio of tetrabutyl titanate to zinc acetate is 6-10:0.8-1.2, and more preferably 7.5-8.5:0.9-1.

1.

7. The inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation and precursor pyrolysis of siloxanes according to claim 1, characterized in that, The additives include a catalyst, a pH adjuster, a leveling agent / defoamer, and a thixotropic agent; preferably, the mass ratio of the catalyst, pH adjuster, leveling agent / defoamer, and thixotropic agent is 0.5-1.5:0.2-0.5:0.3-0.8:2-4; preferably, the catalyst is a catalyst composed of dibutyltin dilaurate and an organic amine; preferably, the mass ratio of dibutyltin dilaurate to organic amine is 0.9-1.1:0.3-2, more preferably 1:0.5-1.

2.

8. The inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation and precursor pyrolysis of siloxanes according to claim 1, characterized in that, The organic amine is one of a sterically hindered secondary amine, an aliphatic primary amine, or an alicyclic amine; more preferably, the organic amine is one or more of N-methylcyclohexylamine, diisopropylamine, N,N-dimethylcyclohexylamine, n-butylamine, isopropylamine, cyclohexylamine, or aminoethylethanolamine.

9. The inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation and precursor pyrolysis of siloxanes according to claim 1, characterized in that, The pH adjuster is glacial acetic acid; preferably, the leveling agent / defoamer is a polyether-modified polysiloxane leveling agent / defoamer; preferably, the thixotropic agent is fumed silica.

10. The method for preparing an inorganic, non-sintering, high-temperature resistant ceramic coating based on low-temperature polycondensation and precursor pyrolysis of siloxanes according to any one of claims 1-9, characterized in that, The preparation method includes: (1) Pre-hydrolysis of siloxanes: Under nitrogen protection, epoxy siloxanes and long-chain alkyl siloxanes are added to the reaction vessel, along with a mixed solvent of water and ethanol and glacial acetic acid from some of the additives. The mixture is stirred slowly at 5-10°C for 4-6 hours to obtain a clear and transparent pre-hydrolyzed siloxane solution. (2) Coating preparation: Transfer the siloxane pre-hydrolyzed solution to a high-speed disperser. Under low-speed stirring, add the aluminum / zirconium-containing polysilazane solution and the remaining additives except glacial acetic acid in sequence. Slowly add the functional filler and increase the speed to 2000-3000 rpm. Disperse for 30-45 minutes until the system is uniform and the fineness is ≤50μm. Adjust the final pH value to 4.5-5.5 with the remaining glacial acetic acid. (3) Curing and application: The coating can be used after being cured in a sealed environment at 5-25℃ for 20-28 hours. It can be applied by brushing, rolling or spraying. The ambient temperature during application must be ≥0℃ and the relative humidity ≤80%. (4) Curing: In an environment above 0°C, the wet film triggers a deep polycondensation reaction of siloxane through water evaporation and pH changes. It is surface dry and reaches a transportable hardness within 24-72 hours. After 7 days, the polycondensation reaction is basically complete, and the coating reaches its highest initial strength. The full performance needs to be cured under environmental conditions for 28 days or accelerated by low-temperature baking below 80°C.

Images