High-strength temperature-resistant self-cleaning polysilazane polyurea hybrid coating and preparation process thereof

Abstract

The invention relates to the technical field of high polymer materials and coatings thereof, and discloses a high-strength temperature-resistant self-cleaning polysilazane polyurea hybrid coating and a preparation process thereof. The coating is prepared by mixing an isocyanate-terminated polysilazane prepolymer and an amino component in proportion. The method is characterized in that a sequential gradient curing process is adopted, a deep interpenetrating network structure is constructed in a system, and molecular-level hybridization of an inorganic phase and an organic phase is achieved. By adopting the technical scheme, the problems of high brittleness of polysilazane and poor heat resistance of polyurea are solved, the strength, the heat stability and the hydrophobic self-cleaning performance of a coating are improved, the problem of thick coating cracking is solved, and the coating has excellent adhesive force and weather resistance and is suitable for the fields of aerospace, petrochemical corrosion prevention and the like.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and coatings technology, specifically relating to a high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating and its preparation process. Background Technology

[0002] Polysilazane coatings, due to their molecular backbone being composed of alternating Si-N bonds, undergo complex hydrolysis, condensation, and oxidation reactions during thermosetting or moisture curing, ultimately transforming into an inorganic-organic hybrid network with a silica-like structure. This unique transformation mechanism endows the coating with extremely high surface hardness, excellent oxidation resistance, and extremely low surface energy.

[0003] Polyurea systems are characterized by the rapid chemical reaction between their isocyanate components and terminal amino compounds, forming a large number of strongly polar urea bonds in the molecular chain. These urea bonds form physical cross-linking points through strong intermolecular hydrogen bonding, thereby endowing polyurea coatings with extremely excellent tensile strength, impact toughness, and good adaptability to substrate deformation.

[0004] However, during the curing process of polysilazane to form a high-hardness inorganic network, there is intense molecular chain rearrangement and chemical shrinkage. The side effect of this high cross-linking density is a large accumulation of internal stress. Due to the lack of sufficient flexible segments to buffer stress, polysilazane coatings exhibit a tendency to become brittle. Not only are spontaneous microcracks or even large-area peeling easily induced when the coating thickens, but they are also prone to brittle fracture under alternating hot and cold impact environments due to the mismatch between their coefficients of thermal expansion and those of the substrate.

[0005] While a single polyurea coating possesses excellent mechanical toughness, it is essentially still an organic polymer system. Under continuous high temperature or strong ultraviolet radiation, the organic segments in its molecular chain are prone to thermal oxidation degradation and thermal softening, resulting in a sharp drop in the mechanical strength of the coating in the high temperature range. Furthermore, its high surface energy makes it difficult to achieve long-term self-cleaning function.

[0006] When attempting to combine polysilazane and polyurea through physical blending, severe microphase separation is easily induced during film formation due to the significant differences in their chemical polarity, molecular weight distribution, and curing kinetics. This phase separation results in extremely weak interfacial bonding between the inorganic and organic phases, causing the coating to lose both the original high elasticity and toughness of polyurea and the ability to fully utilize the temperature resistance and hardness of polysilazane. Summary of the Invention

[0007] Addressing the technical problems mentioned in the background art, such as the high brittleness, easy cracking, and poor thick-coating performance of single polysilazane coatings, and to solve the defects of single polyurea coatings such as significant strength reduction under high-temperature environments, insufficient long-term heat resistance, and aging resistance, and further overcoming the systemic contradictions caused by the simple physical blending of polysilazane and polyurea, including severe microphase separation, weak interfacial bonding, and the inability to achieve synergistic performance enhancement, this invention provides a high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating and its preparation process. This invention utilizes molecular design to construct a deep interpenetrating network structure in the two-component system of polysilazane and polyurea, and combines this with a specific sequential gradient curing process to achieve a high degree of hybridization of the inorganic and organic phases at the molecular level, thereby improving the coating's overall mechanical strength, stability under extreme temperatures, and long-term hydrophobic self-cleaning function.

[0008] To achieve the above-mentioned objectives, this invention provides a high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating, which is composed of component A and component B mixed in a mass ratio of 1:0.8 to 1:1.5. Component A is an isocyanate-terminated polysilazane prepolymer component, and component B is an amino component.

[0009] Component A specifically includes the following components in parts by weight: 30 to 50 parts isocyanate monomer, 15 to 25 parts hydroxyl-terminated polysilazane, 10 to 20 parts reactive diluent, 0.5 to 1.5 parts antioxidant, and 0.2 to 0.8 parts defoamer.

[0010] The isocyanate monomer is selected from one or more of diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate. In a preferred embodiment of the present invention, the isocyanate monomer is a liquefied modified diphenylmethane diisocyanate, which has an isocyanate group content of 28% to 32% by mass and a dynamic viscosity of 40 to 80 mPa·s at 25 degrees Celsius.

[0011] The terminal hydroxyl polysilazane is an inorganic-organic hybrid polymer with a Si-H and Si-N bond backbone, and its molecular ends contain hydroxyl groups capable of reacting with isocyanate groups. The terminal hydroxyl polysilazane has a number-average molecular weight of 1500 to 3500, a hydroxyl value of 45 to 65 mg potassium hydroxide per gram, and a Si-H bond mass percentage of 0.8% to 1.5%. This component is introduced to pre-construct a polysilazane segment with flexible chain segments in component A, and to anchor the polysilazane to the main chain of the isocyanate prepolymer through the urethane esterification reaction of the hydroxyl groups and isocyanate groups, thereby solving the problem of two-phase incompatibility in the initial stage.

[0012] The reactive diluent is selected from one or more of dimethyl carbonate, butyl acetate, and propylene glycol methyl ether acetate. The water content of the reactive diluent is strictly controlled below 0.01% to prevent side reactions between water and isocyanate groups.

[0013] The B component specifically includes the following components in parts by weight: 40 to 60 parts of amino-terminated polyether, 10 to 20 parts of amino-terminated polysilazane, 15 to 25 parts of amine chain extender, 5 to 12 parts of nano self-cleaning functional additive, 1 to 3 parts of coupling agent, and 0.5 to 1.2 parts of ultraviolet absorber.

[0014] The terminal amine polyether is selected from terminal amine polyoxypropylene ethers, with a molecular weight distribution between 2000 and 5000 and a functionality of 2 or 3. As a soft segment in the polyurea network, the terminal amine polyether provides the coating with the necessary flexibility and impact resistance.

[0015] The terminal amino polysilazane is a key component of this invention. Its structure contains repeating silicon-nitrogen bond units, and the molecular chain ends with reactive primary or secondary amino groups. The dynamic viscosity of the terminal amino polysilazane is 100 to 300 mPa·s at 25 degrees Celsius, and the primary amino content is 1.2 to 2.5 mmol / g. During the coating curing process, this component reacts rapidly with the isocyanate groups in component A to form polyurea bonds. Simultaneously, the silicon-nitrogen structure in its molecular chain undergoes crosslinking during subsequent moisture or heat curing stages, thus spatially intertwining with the polyurea network.

[0016] The amine chain extender is selected from diethyltoluenediamine or dimethylthiotoluenediamine. These chain extenders have high reactivity, can regulate the gel time of the system, and increase the cohesive energy density of the polyurea hard segments.

[0017] The nano-self-cleaning functional additive is surface-modified nano-silica or nano-alumina with an average particle size of 20 to 50 nanometers. The surface modification uses a perfluoroalkylsilane coupling agent, which gives the nanoparticles low-surface-energy fluorocarbon segments. These nanoparticles migrate to the surface during the coating film formation process, constructing a micro-nano-scale rough structure. Combined with the inherent low surface energy properties of polysilazane, this gives the coating superhydrophobic properties, with a static water contact angle greater than 150 degrees.

[0018] The present invention discloses a preparation process for a high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating, characterized by comprising the following steps: Step 1, Preparation of Component A: The metered isocyanate monomer is added to a reactor equipped with a stirrer, thermometer, and nitrogen protection device. Stirring is started, and the temperature is raised to 60-70 degrees Celsius. Then, the dehydrated terminal hydroxyl polysilazane is added dropwise to the reactor, with the addition process completed within 1-2 hours. After the addition is complete, the reaction continues at 75-85 degrees Celsius for 3-4 hours until the measured isocyanate group content reaches the theoretical preset value. Finally, the temperature is lowered to below 40 degrees Celsius, and reactive diluent, antioxidant, and defoamer are added. After thorough mixing, the mixture is discharged and sealed for storage.

[0019] The second step, preparation of component B: Terminal amino polyether, terminal amino polysilazane, and amine chain extender are added to a high-speed disperser in a specific ratio and stirred for 30 minutes at 800-1200 rpm. Then, nano-self-cleaning functional additives, coupling agents, and ultraviolet absorbers are added, and the speed is increased to 2500-3500 rpm for high-shear dispersion. To ensure uniform dispersion of the nano-additives, a secondary grinding process using a sand mill can be performed to reduce the material fineness to less than 20 micrometers. After dispersion, degassing is performed under a vacuum of -0.09 MPa to remove microbubbles from the system.

[0020] The third step, mixing and application: Before application, mix component A and component B at a mass ratio of 1:0.8 to 1:1.5 in a two-component spraying device or forced mechanical mixer. Due to the extremely fast reaction speed of polyurea, the mixing process must be completed within a few seconds to tens of seconds, and spraying or brushing should be carried out immediately.

[0021] The fourth step, sequential gradient curing process: This is the core step in constructing the interpenetrating network structure of this invention. The coating after application undergoes the following three curing stages sequentially: Phase 1: Primary Polyurea Network Forming Stage. At an ambient temperature of 25 to 40 degrees Celsius, the isocyanate groups in component A undergo an addition polymerization reaction with the amino groups in component B, rapidly forming a flexible polyurea framework with a certain strength. This stage lasts for 15 to 30 minutes, ensuring the coating is surface dry and has anti-sagging capabilities.

[0022] Phase Two: Initial Construction of the Interpenetrating Network. The coating is placed in an environment with a humidity of 50% to 70% and a temperature of 50 to 70 degrees Celsius. At this stage, the Si-H and Si-N bonds in the polysilazane segments begin to undergo hydrolysis and condensation reactions under the influence of moisture and residual catalyst, generating siloxane crosslinking points. Since the polyurea network is not yet fully rigid at this point, the polysilazane segments can grow in the micropores of the polyurea network, forming a preliminary interpenetrating structure.

[0023] Phase Three: Deep Curing and Strengthening. The ambient temperature is further increased to 120-150 degrees Celsius and maintained for 3-5 hours. Under high-temperature induction, the polysilazane network undergoes deep cross-linking, transforming into an inorganic three-dimensional network similar to a ceramic structure. Simultaneously, polyurea segments and polysilazane segments achieve covalent bonding through previously pre-established chemical bonds (such as urethane bonds). Ultimately, a hybrid system is formed that is macroscopically uniform and stable, and microscopically consists of a deep interweaving of inorganic high-hardness networks and organic high-elasticity networks.

[0024] In a preferred embodiment of the present invention, the isocyanate-terminated polysilazane prepolymer in component A is prepared using a composite catalyst of an organotin catalyst and a tertiary amine catalyst, wherein the total mass fraction of the catalyst is 0.05% to 0.15% of component A. This composite catalytic system can precisely control the reaction rate ratios of isocyanate groups with OH and isocyanate groups with NH2, ensuring that excessive branching or gelation of the molecular chains does not occur during the prepolymer preparation stage.

[0025] In a preferred embodiment of the present invention, the nano-self-cleaning functional additive in component B needs to be pre-dispersed in anhydrous ethanol using ultrasound at a power of 400 to 600 watts for 1 to 2 hours before being added. The pre-dispersed nano-slurry is then mixed with the amino-terminated polyether, which improves the dispersion stability of the nanoparticles in the hybrid system and prevents them from agglomerating during the curing process.

[0026] In the formulation design of the coating described in this invention, fillers with specific functions can be added according to actual application requirements. For example, to enhance the shielding and corrosion protection performance of the coating, 5% to 10% by mass of flake mica powder or glass flakes can be added; to improve the thermal conductivity of the coating, 15% to 25% by mass of aluminum nitride or silicon carbide micro powder can be added. These fillers can be well encapsulated in the hybrid network composed of polysilazane and polyurea, have strong interfacial bonding with the matrix, and will not negatively affect the overall toughness of the coating.

[0027] In practical construction applications, the high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating provided by this invention exhibits extremely strong substrate adaptability. Whether it's a metal substrate such as carbon steel, stainless steel, or aluminum alloy, or a non-metallic substrate such as concrete or glass fiber reinforced plastics, the coating's molecular structure contains a large number of polar urea bonds, urethane bonds, and silicon-oxygen bonds. These groups can form strong physical adsorption and chemical bonding with the hydroxyl groups or oxides on the substrate surface.

[0028] To meet the needs of large-scale industrial construction, both components A and B of this invention exhibit excellent storage stability. Under conditions of isolation from air and moisture, component A has an effective shelf life of more than 6 months at room temperature, and component B has a shelf life of more than 12 months. During construction, high-pressure airless spraying equipment is used, with the spraying pressure controlled at 15 to 25 MPa and the material heating temperature controlled at 50 to 65 degrees Celsius, ensuring uniform mixing and excellent atomization.

[0029] This invention also relates to a substrate pretreatment method for the aforementioned coatings. For metal substrates, sandblasting to Sa2.5 grade is required, with the surface roughness Rz controlled between 40 and 75 micrometers. After sandblasting, surface dust must be blown away with compressed air, and the first coat of coating must be applied within 4 hours. For concrete substrates, the moisture content must be ensured to be below 6%, and a layer of highly penetrating modified epoxy sealing primer must be pre-applied to enhance the anchoring force between the hybrid coating and the porous substrate.

[0030] As a further supplement to the technical solution of the present invention, when the coating is applied to the surface of a structural component with high dynamic deformation, 2% to 5% by mass of terminal amino-terminated liquid nitrile rubber can be further introduced into component B. The introduction of liquid nitrile rubber can introduce more rubber phase micro-regions at the microscopic level without destroying the integrity of the interpenetrating network, thereby providing a stronger crack deflection and energy dissipation mechanism when the coating is subjected to cyclic fatigue loads.

[0031] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces terminally hydroxyl-terminated polysilazane into component A to react with isocyanate, and terminally amino-terminated polysilazane into component B to participate in the polyurea reaction. This design allows the inorganic phase of polysilazane to be covalently bonded to the main chain of the organic polymer in the initial stage of the reaction. This chemical grafting provides a large number of nucleation sites for the subsequent growth of the interpenetrating network, ensuring the uniform distribution of the inorganic and organic phases at the molecular scale and preventing macroscopic phase separation.

[0032] 2. This invention utilizes the time difference between the extremely rapid reaction kinetics of polyurea and the relatively slow crosslinking kinetics of polysilazane to first construct a flexible three-dimensional polyurea scaffold through a sequential gradient curing process. Subsequently, polysilazane grows in situ within the gaps of this scaffold and eventually hardens. This interpenetrating structure allows the flexible polyurea segments to dissipate energy through molecular extension and the breaking / recombining of hydrogen bonds when the coating is subjected to external impact, while the inorganic network formed by polysilazane acts to bear stress and restrict deformation. This synergistic effect gives the coating both the high strength and high toughness of polyurea and the high hardness and scratch resistance of polysilazane.

[0033] 3. The mechanical properties of a single polyurea coating degrade significantly above 100 degrees Celsius. However, the polysilazane introduced in this invention transforms into a siloxane and Si-C structure with extremely high thermal stability during gradient curing. This inorganic network acts like a ceramicized framework embedded in an organic system, greatly improving the coating's heat distortion temperature.

[0034] 4. Traditional polysilazane coatings are typically limited to a thickness of less than 10 micrometers due to high curing shrinkage and lack of toughness. This invention, by introducing a polyurea network, provides an effective stress buffer for the shrinkage of polysilazane. The elastic deformation of the polyurea segments can absorb the internal stress generated during the crosslinking process of polysilazane, thereby enabling the hybrid coating to achieve a single thick-coat application without generating any visible microcracks during drying and aging.

[0035] 5. The low surface energy of polysilazane itself, combined with the micro / nano structure constructed from nano-additives, gives the coating surface extremely high hydrophobicity. Since the polysilazane is interwoven throughout the entire coating as part of a unified network, rather than merely existing on the surface, this ensures that even after long-term physical wear, the exposed new surface still contains the polysilazane component, thus maintaining the durability of its self-cleaning function. Furthermore, the highly cross-linked inorganic-organic interpenetrating network forms a dense physical barrier, significantly improving the coating's resistance to the penetration of water molecules, oxygen, and various chemical corrosive media.

[0036] 6. The reliable operation capability of the coating of the present invention in extreme environments gives it great application potential in fields such as protection of aerospace engine components, high-temperature corrosion protection of petrochemical equipment, long-term protection of large marine engineering facilities, and self-cleaning surfaces of high-end buildings. Detailed Implementation

[0037] This invention provides a high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating and its preparation process. The coating system consists of component A and component B, which are mixed in a mass ratio of 1:0.8 to 1:1.5 during application. The core of this invention lies in achieving molecular-level hybridization of the inorganic silicon nitride structure and the organic polyurea structure through specific component selection and a sequential gradient curing process, thereby obtaining a protective coating that combines high mechanical strength, extreme temperature resistance, and long-lasting superhydrophobic self-cleaning properties.

[0038] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, so as to ensure that those skilled in the art can fully understand and implement the present invention.

[0039] Example 1: The mass ratio of component A to component B is 1:1.2; Component A contains 40 parts of isocyanate monomer (modified diphenylmethane diisocyanate, isocyanate group mass fraction 30%). 20 parts of hydroxyl-terminated polysilazane (number average molecular weight 2500, hydroxyl value 55mgKOH / g); 15 parts reactive diluent (dimethyl carbonate); 1.0 part antioxidant, 0.5 parts defoamer; 0.1 parts of composite catalyst (a combination of organotin and tertiary amines); Component B contains 50 parts of amino-terminated polyether (amino-terminated polyoxypropylene ether, molecular weight 3000). 15 parts of amino-terminated polysilazane (viscosity 200 mPa·s at 25℃); 20 parts of amine chain extender (diethyltoluene diamine); Eight parts of nano self-cleaning functional additive (surface-modified nano silica, particle size 35nm); 2 parts coupling agent; 0.8 parts of ultraviolet absorber; Preparation steps: S1: Preparation of component A: Isocyanate monomer is added to a reaction vessel under nitrogen protection, heated to 65°C, and dehydrated terminal hydroxyl polysilazane is added dropwise over 1.5 hours at a nitrogen flow rate of 0.3 reaction vessel volume units per minute. The reaction is carried out at 78°C for 3.5 hours. After the isocyanate group content reaches the standard, the temperature is lowered to 38°C, and active diluent, antioxidant, defoamer and composite catalyst are added. The mixture is stirred evenly and sealed for storage. S2: For the preparation of component B, amino-terminated polyether, amino-terminated polysilazane, and amine chain extender are added to a high-speed disperser and stirred at 1000 rpm for 30 minutes; nano self-cleaning functional additives, coupling agents, and ultraviolet absorbers are added after ultrasonic pre-dispersion at 400W for 1.5 hours, and high-shear dispersion is carried out at 3000 rpm. The mixture is then ground twice in a sand mill to a fineness of 18 μm and degassed under vacuum at -0.09 MPa. S3: Mixing and application: Add components A and B to the two-component spraying equipment at a mass ratio of 1:1.2, mix and spray at a spraying pressure of 18MPa and a material heating temperature of 58℃. S4: Sequential gradient curing. The coating is first cured at 25°C for 25 minutes to form a polyurea skeleton, then cured at 60°C and 60% humidity for 12 hours to build an interpenetrating network, and finally cured at 135°C for 4 hours to form a hybrid coating with an inorganic phase ratio of 25%.

[0040] Example 2: The mass ratio of component A to component B is 1:0.8, and the remaining components and proportions are the same as in Example 1; Preparation steps: Same as in Example 1.

[0041] Example 3: The mass ratio of component A to component B is 1:1.5, and the remaining components and proportions are the same as in Example 1; Preparation steps: Same as in Example 1.

[0042] Example 4: 15 parts of terminal hydroxyl polysilazane in component A, and the remaining components and proportions are the same as in Example 1; Preparation steps: Same as in Example 1.

[0043] Example 5: 25 parts of terminal hydroxyl polysilazane in component A, and the remaining components and proportions are the same as in Example 1; Preparation steps: Same as in Example 1.

[0044] Example 6: 5 parts of nano self-cleaning functional additive in component B, and the remaining components and proportions are the same as in Example 1; Preparation steps: Same as in Example 1.

[0045] Example 7: 12 parts of nano self-cleaning functional additive in component B, and the remaining components and proportions are the same as in Example 1; Preparation steps: Same as in Example 1.

[0046] Example 8: The remaining components and proportions are the same as in Example 1; Preparation steps: The temperature for the deep strengthening and curing stage is 150℃, and the temperature is maintained for 3 hours. The remaining steps are the same as in Example 1.

[0047] Comparative Example 1: Component A was modified by removing the terminal hydroxyl polysilazane, while the other components were the same as in Example 1; Preparation steps: When preparing component A, isocyanate monomers and other additives are directly mixed, without polysilazane grafting reaction. The remaining process parameters and steps are the same as in Example 1.

[0048] Comparative Example 2: Same as Example 1; Preparation steps: Segmented curing is eliminated. After spraying, the coating is directly cured at 80°C for 8 hours without a gradient heating process. The remaining steps are the same as in Example 1.

[0049] Test method: Tensile strength test: The tensile strength of the coating was tested according to the standard using a universal testing machine; Hardness test: The Shore D hardness of the coating was measured using a Rockwell hardness tester. Adhesion test: The adhesion grade of the coating was evaluated using the cross-cut test according to GB / T9286 standard; High-temperature mechanical strength retention test: The coating was placed at a constant temperature of 250℃ for 1000 hours, and the tensile strength retention rate was measured. Accelerated aging test: The coating gloss retention rate was tested after 4000 hours using a fluorescent ultraviolet lamp aging chamber. Static water contact angle test: The static water contact angle of the coating surface is measured using a contact angle measuring instrument; Abrasion resistance and hydrophobicity retention rate test: After wear of 500 revolutions in a Taber abrasion tester, the change rate of water contact angle was measured.

[0050] The test data comparisons are shown in Table 1 and Table 2.

[0051] Table 1 Comparison of Tensile Strength, Shore D Hardness, and Static Water Contact Angle Group Tensile strength (MPa) ShoreD hardness Static water contact angle (°) Example 1 32.5 75 156 Example 2 30.8 73 153 Example 3 33.2 76 158 Example 4 29.5 72 152 Example 5 34 77 159 Example 6 31.2 74 151 Example 7 33.5 76 160 Example 8 33.8 78 157 Comparative Example 1 22.3 60 105 Comparative Example 2 18.5 58 98 Table 2 Comparison of Strength Retention Rate, Adhesion Grade, Gloss Retention Rate, and Contact Angle After Abrasion Resistance at 250℃ Group Strength retention rate at 250℃ (%) Adhesion rating Gloss retention rate (%) Contact angle after wear resistance (°) Example 1 85 0 92 150 Example 2 83 0 90 148 Example 3 86 0 93 152 Example 4 81 1 89 146 Example 5 88 0 94 153 Example 6 84 0 91 147 Example 7 87 0 93 154 Example 8 89 0 94 151 Comparative Example 1 45 3 75 85 Comparative Example 2 38 4 68 72 Examples 1 to 8 utilize the covalent bonding between hydroxyl-terminated polysilazane and isocyanate to prevent phase separation. A sequential gradient curing process first forms a flexible polyurea framework, then induces the polysilazane to crosslink and form an inorganic network, achieving synergistic organic-inorganic reinforcement. Comparative Example 1, lacking hydroxyl-terminated polysilazane, cannot form effective chemical bonds, resulting in severe phase separation and a significant performance degradation. Comparative Example 2, lacking sequential gradient curing, fails to form an interpenetrating network, resulting in a brittle coating with poor temperature resistance.

[0052] The closer the mass ratio of components A and B is to 1:1.2, the more hydroxyl-terminated polysilazane is to 20-25 parts, and the more nano-additives are to 8-12 parts, the better the coating's tensile strength, hardness, and hydrophobic properties. The amount of hydroxyl-terminated polysilazane directly affects the proportion of the inorganic phase and the interfacial bonding force, while the amount of nano-additives determines the surface micro / nano structure roughness. Together, they ensure temperature resistance and self-cleaning properties.

[0053] Compared to Comparative Example 1 without polysilazane, the tensile strength of the example is increased by more than 45%, the strength retention rate at 250°C is increased by more than 89%, and the static water contact angle is increased by more than 48%. Compared to Comparative Example 2 without gradient curing, the tensile strength is increased by more than 82%, the adhesion grade is increased by more than 3 levels, the gloss retention rate is increased by more than 37%, and the thickness of a single application can reach 800μm without cracks, making it suitable for extreme environments such as aerospace and petrochemical corrosion protection.

[0054] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating, characterized in that, It is composed of isocyanate-terminated polysilazane prepolymer component and amino component mixed in a mass ratio of 1:0.8 to 1:1.

5.

2. The high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating according to claim 1, characterized in that, Component A comprises the following components in parts by weight: 30 to 50 parts of isocyanate monomer; 15 to 25 parts of hydroxyl-terminated polysilazane; 10 to 20 parts of reactive diluent; Antioxidant 0.5 to 1.5 parts; 0.2 to 0.8 parts of defoamer.

3. The high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating according to claim 1, characterized in that, Component B comprises the following components in parts by weight: 40 to 60 parts of amino-terminated polyether; 10 to 20 parts of amino-terminated polysilazane; 15 to 25 parts of amine chain extender; 5 to 12 parts of nano self-cleaning functional additive; 1 to 3 parts of coupling agent; 0.5 to 1.2 parts of ultraviolet absorber.

4. The high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating according to claim 2, characterized in that, The isocyanate monomer is selected from at least one of diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; preferably, the isocyanate monomer is modified diphenylmethane diisocyanate that has undergone liquefaction treatment.

5. The high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating according to claim 2, characterized in that, The terminal hydroxyl polysilazane is an inorganic-organic hybrid polymer with Si-H and Si-N bond backbones, and the molecular end contains hydroxyl groups that can react with isocyanate groups; the terminal hydroxyl polysilazane undergoes a carbamate reaction with the isocyanate groups in the isocyanate monomer through its terminal hydroxyl groups, thereby anchoring the polysilazane chain segment to the isocyanate prepolymer backbone.

6. The high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating according to claim 2, characterized in that, The active diluent is selected from at least one of dimethyl carbonate, butyl acetate, and propylene glycol methyl ether acetate, and the water content of the active diluent is less than 0.01%; the A component also contains a composite catalyst, which is composed of an organotin catalyst and a tertiary amine catalyst, and the total mass fraction of the composite catalyst is 0.05% to 0.15% of the total mass of the A component.

7. The high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating according to claim 3, characterized in that, The terminal amino polyether is selected from terminal amino polyoxypropylene ether, and its functionality is 2 or 3; or, the terminal amino polyether is a graded system composed of terminal amino polyether and terminal amino polyether mixed in a mass ratio of 1:

3.

8. The high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating according to claim 3, characterized in that, The structure of the terminal amino polysilazane contains repeating silicon-nitrogen bond units, and the molecular chain ends with primary or secondary amino groups.

9. The high-strength, high-temperature resistant, self-cleaning polysilazane-polyurea hybrid coating according to claim 3, characterized in that, The nano self-cleaning functional additive is surface-modified nano-silica or nano-alumina.

10. A high-strength, heat-resistant, self-cleaning polysilazane-polyurea hybrid coating according to claim 9, characterized in that, The surface modification uses a perfluoroalkylsilane coupling agent to give the nanoparticles low surface energy fluorocarbon segments; the nano self-cleaning functional aid is pre-dispersed in anhydrous ethanol using ultrasound before being added.