Aircraft surface ablation-resistant anti-aging coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of coating materials, and particularly relates to an ablation-resistant anti-aging coating on the surface of an aircraft and a preparation method of the ablation-resistant anti-aging coating. A silane coupling agent containing an epoxy group and vinyl and boric acid are used as raw materials, an organic silicon-boron hybrid oligomer with a Si-O-Si and Si-O-B bond stereo structure is obtained by adjusting the ratio of the silane coupling agent to the boric acid and serves as a bridge, and phenolic resin, hydrogen-containing silane and vinyl silicone rubber are combined together to form the ablation-resistant anti-aging coating. Wherein an epoxy group and a phenolic hydroxyl group are subjected to a condensation reaction, vinyl and a platinum catalyst form a compact cross-linked structure through hydrogen-containing silane, and the obtained coating has a lower ablation rate, better anti-UV weather resistance and higher flexibility, is suitable for long-time protection of the surface of an aircraft, and has a better ablation protection effect under shear airflow impact.

Description

Technical Field

[0001] This application belongs to the field of coating materials technology, specifically relating to an ablation-resistant and anti-aging coating, its preparation method, and its application. Background Technology

[0002] New-generation aircraft possess greater maneuverability and precision strike capabilities, resulting in significantly increased atmospheric flight time and more demanding thermal environments, primarily characterized by high shear and prolonged high heat flux. Therefore, higher requirements are placed on the shear resistance and ablation protection efficiency of thermal protection materials coated on aircraft surfaces under medium-to-high heat flux. Among aircraft ablation protection solutions, organic coatings are easy to apply and are the preferred option for thermal protection of aircraft with complex aerodynamic shapes. Therefore, there is an urgent need to develop a new generation of ablation protection coating materials that can meet long-term thermal protection requirements under medium-to-high heat flux.

[0003] The resin matrix determines the mechanical properties, weather resistance, and ablation resistance of the heat-resistant coating, making it the most crucial component of ablation protection coatings. Currently, resin matrices used in ablation protection coatings are mainly divided into two categories: high-carbon-residue resin matrices, represented by epoxy resins and phenolic resins, and silicone rubber matrices. High-carbon-residue resin matrices offer advantages such as high ablation efficiency and the formation of a dense carbonized layer after ablation. However, they suffer from rapid ablation rates, narrow pyrolysis temperature ranges, and poor toughness. Furthermore, these coatings exhibit poor stability under UV light, and long-term exposure to sunlight can easily lead to irreversible discoloration, loss of gloss, chalking, or cracking. Therefore, these coatings are unsuitable for long-term heat protection, especially under medium to high heat fluxes where their reliability is low. Additionally, while silicone rubber has high temperature resistance, its heat protection efficiency is low. After ablation, it chalks to form a ash layer, resulting in very poor ablation protection under shear airflow impact. Its heat protection primarily relies on thermal barrier mechanisms. Therefore, the ablation protection coatings prepared by using either of the above two types of resin matrices alone have significant problems when applied under new heat flow conditions.

[0004] Based on the thermal protection requirements of current-generation aircraft for long-term, high-heat-flux, and high-shear environments, a resin matrix combining high-carbon-residue resins with organosilicon is synthesized, possessing high temperature resistance, high toughness, high weather resistance, and low ablation rate. This is expected to significantly improve the ablation thermal efficiency of ablation-resistant coatings, laying the foundation for the development of highly efficient ablation-protective coatings. However, the corresponding challenge lies in addressing the extremely low compatibility between high-carbon-residue resins such as phenolic or epoxy resins and silicone rubber matrices. Direct physical blending results in severe phase separation, necessitating prior chemical modification to link the two through chemical bonds before use as an ablation-protective coating.

[0005] Regarding chemical modification, CN109265684B proposes using phenolic-modified silicone rubber resin to solve the problem of easy pulverization during the ablation process of traditional silicone rubber. CN116462975B proposes using diisocyanate to pre-react with hydroxypropyl silicone oil and phenolic resin, introducing polysiloxane segments into the phenolic resin, thus making it easier to disperse stably in silicone rubber. However, these modification steps are relatively cumbersome, and the improvement in coating flexibility and weather resistance is not significant, making it difficult to cope with long-term ablation protection under shear gas flow impact. Summary of the Invention

[0006] The purpose of this application is to overcome the shortcomings of the prior art by designing and synthesizing organosilicon-boron hybrid oligomers containing epoxy groups and vinyl groups as a bridge to chemically crosslink phenolic resin, hydrogen-containing silanes and vinyl silicone rubber to form an ablation-resistant and anti-aging coating. This coating has a lower ablation rate, better UV resistance and weather resistance and higher flexibility, making it suitable for long-term protection of aircraft surfaces and providing better protection against ablation under shear airflow impact.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: In a first aspect, an ablation-resistant and anti-aging coating for aircraft surfaces is provided, the raw materials of which include: organosilicon-boron hybrid oligomers, phenolic resins, vinyl silicone rubber, hydrogen-containing silanes, and platinum catalysts. The organosilicon-boron hybrid oligomer is obtained by condensation reaction of silane coupling agent and boric acid at 60-100℃, followed by vacuum distillation to remove small molecule products. The molar ratio of silane coupling agent to boric acid is (1-2):1; Preferably, the molar ratio of silane coupling agent to boric acid is (1.2-1.8):1; The silane coupling agent is composed of an epoxy-containing silane coupling agent and a vinyl-containing silane coupling agent; The epoxy-containing silane coupling agent molecule contains at least one epoxy group and at least one hydrolyzable Si-OR group or Si-OH group, wherein R is selected from a hydrocarbon group with 1 to 6 carbon atoms; Preferably, the epoxy-containing silane coupling agent is selected from one or more of the following: 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane; More preferably, the epoxy-containing silane coupling agent is selected from one or more of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane; The vinyl silane coupling agent molecule contains at least one vinyl group and at least one hydrolyzable Si-OR group or Si-OH group, wherein R is selected from a hydrocarbon group with 1 to 6 carbon atoms or a hydrocarbon group containing an ether bond; Preferably, the vinyl silane coupling agent is selected from one or more of vinyltriisopropoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(2-methoxyethoxy)silane; The phenolic resin is selected from hydrocarbon-based or hydrocarbon-modified phenolic resins, which have strong hydrophobicity and non-polarity, and have a certain compatibility with silicone rubber. Preferably, the phenolic resin is selected from one or more of alkylphenolic resins, rosin phenolic resins, and terpene phenolic resins; More preferably, the alkylphenol resin is selected from p-tert-butylphenol resin.

[0008] The vinyl silicone rubber is selected from one or more of vinyl-terminated poly(dimethylsiloxane), vinyl-terminated poly(methylphenylsiloxane), and vinyl-terminated poly(diphenylsiloxane); Preferably, the silicone rubber is selected from vinyl-terminated poly(dimethylsiloxane); Preferably, the vinyl-terminated poly(dimethylsiloxane) includes one or more of monovinyl-terminated poly(dimethylsiloxane) and divinyl-terminated poly(dimethylsiloxane); The hydrogen-containing silane is selected from one or more of tetramethylcyclotetrasiloxane and hydrogen-terminated polydimethylsiloxane; The platinum catalyst is selected from platinum-olefin complex catalysts; Preferably, the platinum-olefin complex catalyst is selected from platinum-divinyltetramethyldisiloxane complex.

[0009] Preferably, the raw materials for the ablation-resistant and anti-aging coating include a solvent, which is selected from C6-C12 nonpolar hydrocarbon solvents; Further preferred, the solvent is selected from toluene, xylene, n-hexane, or cyclohexane; Preferably, the raw material for the ablation-resistant and anti-aging coating includes low-temperature glass powder, the softening temperature of which does not exceed 400°C. Preferably, the softening temperature of the low-temperature glass powder is 300-350℃; Preferably, the raw materials for the ablation-resistant and anti-aging coating include inorganic fillers, which are selected from one or more of mica powder and fumed silica. Preferably, the raw material for the ablation-resistant and anti-aging coating includes chopped glass fibers with a chopped length of 0.5-10 mm.

[0010] More preferably, the chopped length of the chopped glass fiber is 0.5-6 mm.

[0011] Furthermore, the raw materials of the ablation-resistant and anti-aging coating, by weight, include: 10-20 parts by weight of organosilicon-boron hybrid oligomer, 15-30 parts by weight of phenolic resin, 20-40 parts by weight of vinyl silicone rubber, 5-15 parts by weight of hydrogen-containing silane, and 0.5-3 parts by weight of platinum catalyst. Preferably, the raw materials of the ablation-resistant and anti-aging coating include, by weight, 20-40 parts of solvent; Preferably, the raw materials of the ablation-resistant and anti-aging coating include, by weight, 5-15 parts of low-temperature glass powder. Preferably, the raw materials of the ablation-resistant and anti-aging coating include, by weight, 10-20 parts of inorganic filler; Preferably, the raw materials of the ablation-resistant and anti-aging coating include, by weight, 1-10 parts of chopped glass fiber.

[0012] Secondly, the preparation method of the above-mentioned ablation-resistant and anti-aging coating on the surface of the aircraft includes: mixing organosilicon-boron hybrid oligomer, phenolic resin, vinyl silicone rubber, hydrogen-containing silane, low-temperature glass powder, solvent, inorganic filler and chopped glass fiber evenly, evaporating the solvent, adding platinum catalyst, kneading the mixture, scraping it onto the surface of the substrate, and curing it at 100-200℃. Preferably, the solvent evaporates under conditions ranging from room temperature to 130°C; Preferably, different types of solvents are used to dissolve the organosilicon-boron hybrid oligomer and phenolic resin, as well as vinyl silicone rubber and hydrogen-containing silanes, respectively; Preferably, a disperser is used to uniformly mix the organosilicon-boron hybrid oligomer, phenolic resin, vinyl silicone rubber, hydrogen-containing silane, low-temperature glass powder, solvent, inorganic filler, and chopped glass fiber; Preferably, a two-roll open mill is used to mix the mixture; Preferably, the mixing time is 10-60 minutes; Preferably, the curing temperature is 140-200℃.

[0013] Thirdly, the above-mentioned ablation-resistant and anti-aging coatings for aircraft surfaces are applied to aircraft surface coating.

[0014] The beneficial effects of the technical solution proposed in this application are as follows: A condensation reaction is carried out using an epoxy- and vinyl silane coupling agent and boric acid as raw materials. By adjusting the molar ratio of the silane coupling agent to boric acid, an organosilicon-boron hybrid oligomer with Si-O-Si and Si-OB bond stereostructures is obtained as a bridge. This bridge connects phenolic resin, hydrogen-containing silane, and vinyl silicone rubber through chemical crosslinking to form an ablation-resistant and anti-aging coating. The epoxy and phenolic hydroxyl groups form a dense crosslinked structure through a condensation reaction, and the vinyl groups form a dense crosslinked structure through hydrogen-containing silane and a platinum catalyst. The resulting coating exhibits a lower ablation rate, better UV resistance, and higher flexibility, making it suitable for long-term protection of aircraft surfaces and providing better protection against ablation under shear airflow impact. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The GPC spectra of the organosilicon-boron hybrid oligomers prepared in Examples 1, 4 and Comparative Example 1 are shown.

[0017] Figure 2 The ATR-FTIR spectra of the organosilicon-boron hybrid oligomers prepared in Examples 1, 4 and Comparative Example 1 are shown. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention. It should be noted that the terminology used herein is only for describing specific implementation methods and is not intended to limit the exemplary implementation methods according to the present invention.

[0019] Unless otherwise specified, the experimental conditions used in the examples are generally in accordance with conventional conditions in the art or the conditions recommended by the reagent company. Unless otherwise specified, the materials and reagents used in the examples can be purchased commercially.

[0020] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings: The terms "and / or," "or / and," and "and / or" as used herein include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND," and also undoubtedly includes technical solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0021] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0022] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0023] In this application, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions containing the listed features.

[0024] Example 1 Synthesis of organosilicon-boron hybrid oligomers: 3-glycidyl etheroxypropyltrimethoxysilane (KH560), vinyltris(2-methoxyethoxy)silane and boric acid in a molar ratio of 0.6:0.6:1 were stirred and refluxed at 80°C for 1 hour. Then the temperature was lowered to 60°C and the volatile small molecule byproducts generated in the condensation reaction were removed by vacuum distillation to obtain viscous and transparent organosilicon-boron hybrid oligomers.

[0025] Example 2 The synthesis method of organosilicon-boron hybrid oligomers is the same as in Example 1, except that the raw materials are changed to 3-glycidyl etheroxypropyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane and boric acid in a molar ratio of 0.75:0.75:1.

[0026] Example 3 The synthesis method of organosilicon-boron hybrid oligomers is the same as in Example 1, except that the raw materials are changed to 3-glycidoxypropyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane and boric acid in a molar ratio of 0.7:0.8:1.

[0027] Example 4 The method for synthesizing organosilicon-boron hybrid oligomers is the same as in Example 1, except that the raw materials are changed to 3-glycidoxypropyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane and boric acid in a molar ratio of 0.8:1:1.

[0028] Example 5 The synthesis method of organosilicon-boron hybrid oligomers is the same as in Example 1, except that the raw materials are changed to 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane and boric acid in a molar ratio of 0.6:0.7:1.

[0029] Example 6 The method for synthesizing organosilicon-boron hybrid oligomers is the same as in Example 1, except that the raw materials are changed to 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane and boric acid in a molar ratio of 0.8:0.8:1.

[0030] Example 7 The ablation-resistant and anti-aging coating comprises, by weight, the following raw materials: 16 parts by weight of the organosilicon-boron hybrid oligomer prepared in Example 1, 24 parts by weight of p-tert-butylphenol formaldehyde resin (A2402, Shanghai Lisen Chemical), 20 parts by weight of xylene solvent, 25 parts by weight of divinyl-terminated poly(dimethylsiloxane) (vinyl content 0.24 wt%), 5 parts by weight of monovinyl-terminated poly(dimethylsiloxane) (vinyl content 0.12 wt%), 8 parts by weight of cyclohexane solvent, 10 parts by weight of low-temperature glass powder (Jiangsu Zhengqiu, softening temperature 320-340℃), 7.5 parts by weight of mica powder, 7.5 parts by weight of fumed silica, 5 parts by weight of chopped glass fiber (monofilament diameter 11±1 μm, chopped length 3±1 mm), 9 parts by weight of tetramethylcyclotetrasiloxane, and 1 part by weight of PT-5000 platinum-divinyltetramethyldisiloxane complex.

[0031] A method for preparing an ablation-resistant and anti-aging coating includes: dissolving a formulated amount of organosilicon-boron hybrid oligomer and p-tert-butylphenol formaldehyde resin in xylene; dissolving a formulated amount of divinyl-terminated poly(dimethylsiloxane), monovinyl-terminated poly(dimethylsiloxane), and tetramethylcyclotetrasiloxane in cyclohexane; then turning on a high-speed disperser and adding a formulated amount of xylene solution of organosilicon-boron hybrid oligomer and p-tert-butylphenol formaldehyde resin, low-temperature glass powder, mica powder, fumed silica, and chopped glass fibers to the mixture; after high-speed dispersion for 30 minutes, placing the mixture in a vacuum oven and baking at 90°C for 1 hour to remove the solvent; then adding a formulated amount of platinum catalyst PT-5000; placing the mixture in a two-roll mill and kneading for 30 minutes; scraping the kneaded sample onto the surface of an aluminum substrate with a thickness of 3 mm; and curing at 150°C for 20 minutes to obtain an ablation-resistant and anti-aging coating on the surface of the aluminum substrate.

[0032] Example 8 The ablation-resistant and anti-aging coating comprises, by weight, 13 parts of the organosilicon-boron hybrid oligomer prepared in Example 1, 27 parts of 901 terpene phenolic resin (Arakawa Chemical), and the remaining components and amounts are the same as in Example 7.

[0033] A method for preparing an ablation-resistant and anti-aging coating includes: dissolving a formulated amount of organosilicon-boron hybrid oligomer and terpene phenolic resin in xylene; dissolving a formulated amount of divinyl-terminated poly(dimethylsiloxane), monovinyl-terminated poly(dimethylsiloxane), and tetramethylcyclotetrasiloxane in cyclohexane; then turning on a high-speed disperser and adding a formulated amount of xylene solution of organosilicon-boron hybrid oligomer and p-tert-butylphenol formaldehyde resin, low-temperature glass powder, mica powder, fumed silica, and chopped glass fibers to the mixture; after high-speed dispersion for 30 minutes, the mixture is placed in a vacuum oven and baked at 100°C for 1 hour to remove the solvent; then a formulated amount of platinum catalyst PT-5000 is added; the mixture is placed in a two-roll mill and kneaded for 30 minutes; the kneaded sample is scraped onto the surface of an aluminum substrate with a thickness of 3 mm; and cured at 150°C for 20 minutes to obtain an ablation-resistant and anti-aging coating on the surface of the aluminum substrate.

[0034] Example 9 The ablation-resistant and anti-aging coating comprises, by weight, 16 parts of the organosilicon-boron hybrid oligomer prepared in Example 2, and the remaining components and amounts are the same as in Example 7.

[0035] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 7.

[0036] Example 10 The ablation-resistant and anti-aging coating comprises, by weight, 13 parts of the organosilicon-boron hybrid oligomer prepared in Example 2, and the remaining components and amounts are the same as in Example 8.

[0037] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 8.

[0038] Example 11 The ablation-resistant and anti-aging coating comprises, by weight, 16 parts of the organosilicon-boron hybrid oligomer prepared in Example 3, with the remaining components and amounts being the same as in Example 7.

[0039] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 7.

[0040] Example 12 The ablation-resistant and anti-aging coating comprises, by weight, 13 parts of the organosilicon-boron hybrid oligomer prepared in Example 3, and the remaining components and amounts are the same as in Example 8.

[0041] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 8.

[0042] Example 13 The ablation-resistant and anti-aging coating comprises, by weight, 16 parts of the organosilicon-boron hybrid oligomer prepared in Example 4, with the remaining components and amounts being the same as in Example 7.

[0043] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 7.

[0044] Example 14 The ablation-resistant and anti-aging coating comprises, by weight, 13 parts of the organosilicon-boron hybrid oligomer prepared in Example 4, with the remaining components and amounts being the same as in Example 8.

[0045] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 8.

[0046] Example 15 The ablation-resistant and anti-aging coating comprises, by weight, 16 parts of the organosilicon-boron hybrid oligomer prepared in Example 5, and the remaining components and amounts are the same as in Example 7.

[0047] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 7.

[0048] Example 16 The ablation-resistant and anti-aging coating comprises, by weight, 13 parts of the organosilicon-boron hybrid oligomer prepared in Example 5, and the remaining components and amounts are the same as in Example 8.

[0049] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 8.

[0050] Example 17 The ablation-resistant and anti-aging coating comprises, by weight, 16 parts of the organosilicon-boron hybrid oligomer prepared in Example 6, with the remaining components and amounts being the same as in Example 7.

[0051] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 7.

[0052] Example 18 The ablation-resistant and anti-aging coating comprises, by weight, 13 parts of the organosilicon-boron hybrid oligomer prepared in Example 6, with the remaining components and amounts being the same as in Example 8.

[0053] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 8.

[0054] Comparative Example 1 The synthesis method of organosilicon-boron hybrid oligomers is the same as in Example 1, except that the raw materials are changed to 3-glycidoxypropyltrimethoxysilane (KH560), vinyltris(2-methoxyethoxy)silane and boric acid in a molar ratio of 1.25:1.25:1.

[0055] Comparative Example 2 The ablation-resistant and anti-aging coating comprises, by weight, 16 parts of the organosilicon-boron hybrid oligomer prepared in Comparative Example 1, with the remainder being the same as those in Example 7 in terms of composition and dosage.

[0056] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 7.

[0057] Comparative Example 3 The ablation-resistant and anti-aging coating comprises, by weight, 13 parts of organosilicon-boron hybrid oligomer prepared in Comparative Example 1, and the remaining components and amounts are the same as in Example 8.

[0058] The preparation method of the ablation-resistant and anti-aging coating is the same as that in Example 8.

[0059] Characterization of organosilicon-boron hybrid oligomers The organosilicon-boron hybrid oligomers prepared in Examples 1, 4, and Comparative Example 1 were characterized by GPC. Tetrahydrofuran was used as the solvent to dissolve the corresponding organosilicon-boron hybrid oligomers. The corresponding GPC test results are listed below. Figure 1 And in Table 1.

[0060] Table 1 The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of the organosilicon-boron hybrid oligomers prepared in Examples 1, 4 and Comparative Example 1 are listed below. Figure 2 .right Figure 2 Analysis of the ATR-FTIR spectrum shows that 'a' is 760 cm⁻¹. -1 The nearby Si-O-Si bending vibration absorption peak, b is 880 cm⁻¹ -1 The absorption peak of the Si-OB stretching vibration nearby, with c at 920-930 cm⁻¹. -1 The peak is the hallmark of the epoxy group, i.e., the asymmetric stretching vibration peak of COC, with a value of 1080 cm⁻¹. -1 The absorption peak of the Si-O-Si stretching vibration nearby, with an e value of 1270 cm⁻¹. -1 The absorption peak of the CH bending vibration in the nearby CH=CH2 has an f value of 1430 cm⁻¹. -1 The bending vibration absorption peak of COC in the nearby epoxy group is 1485 cm⁻¹. -1 The absorption peak of the bending vibration of CH in the methylene group attached to the epoxide in the nearby -CH2-CH(O)-CH2 group, with an h of 1610 cm⁻¹. -1 The absorption peak of the C=C stretching vibration in the nearby CH=CH2, with an i value of 2930 cm⁻¹. -1 The absorption peak of the CH stretching vibration of the nearby methylene group, j = 3230 cm⁻¹ -1 The absorption peak of the stretching vibration of the nearby boron hydroxyl group B-OH confirms the successful synthesis of the organosilicon-boron hybrid oligomer, which introduces vinyl and epoxy functional groups through the condensation reaction of boric acid with a silane coupling agent.

[0061] Performance testing of ablation-resistant and anti-aging coatings Oxy-acetylene ablation test: The coating was ablated according to ASTM E285-08 standard. The sample was placed perpendicular to the nozzle. The volume ratio of oxygen to acetylene was 1.35:1, the nozzle diameter was 2 mm, and the heat flux was 1.6 MW / m. 2 The ablation time was 1 minute, and the mass ablation rate and linear ablation rate of different coating samples were tested.

[0062] Weather resistance test: The artificial ultraviolet aging performance of the aluminum plate surface coating was tested according to GB / T 14522-2008 standard. The test time was 1000 hours, and the fluorescent ultraviolet lamp type was UVA-340 with an irradiance of 0.76±0.02 (W / m²). 2 ×nm), the exposure section is 8 hours of drying and 4 hours of condensation cycle.

[0063] Mechanical properties: Tensile strength and elongation at break were determined using an electronic universal testing machine according to GB / T 528-2009 standard. The sample was placed in a dumbbell-shaped mold and heat-cured at 150℃ for 20 minutes. The mold thickness was 2mm. The tensile rate was 100mm / min. The mechanical properties were tested after the cured sample was left at room temperature for 12 hours.

[0064] The test results for Examples 7-18 and Comparative Examples 2-3 are summarized in Table 2.

[0065] First, the GPC test results in Table 1 were analyzed. In Examples 1-4, by adjusting the molar ratio of silane coupling agent to boric acid to 1.2-1.8:1, the higher the relative proportion of boric acid, the higher the molecular weight of the synthesized organosilicon-boron hybrid oligomers. This indicates that a higher boric acid content facilitates the condensation reaction, forming Si-O-Si and Si-OB hybrid structures. In contrast, Comparative Example 1, with a designed molar ratio of silane coupling agent to boric acid of 2.5:1, resulted in a significantly lower molecular weight of the synthesized organosilicon-boron hybrid oligomers, indicating that some silane coupling agent did not undergo the condensation reaction with boric acid.

[0066] Table 2 Analysis of the experimental data in Table 2 shows that the coatings formed after thermosetting using phenolic resin, vinyl-terminated poly(dimethylsiloxane), and organosilicon-boron hybrid oligomers prepared in Examples 7-18 as film-forming materials exhibit better ablation resistance and weather resistance. This is because the organosilicon-boron hybrid oligomers themselves possess Si-O-Si and Si-OB structures, and the vinyl groups undergo hydrosilylation reactions with vinyl-terminated poly(dimethylsiloxane). Simultaneously, epoxy groups can undergo ring-opening reactions with the phenolic hydroxyl groups of the phenolic resin at high temperatures, resulting in a highly cross-linked coating. The Si-O-Si and Si-OB structures, along with the aromatic rings of the phenolic resin itself, provide ablation resistance. The cross-linked vinyl-terminated poly(dimethylsiloxane) provides a large amount of Si-O-Si, exhibiting high bond energy, heat oxidation resistance, and UV resistance, which forms the basis for the coating's weather resistance. Although Comparative Examples 2-3 also used the same vinyl-terminated poly(dimethylsiloxane), the silane coupling agent molar ratio designed in Comparative Example 1 was too high, resulting in incomplete reaction with boric acid. This led to a large number of unreacted low-molecular-weight components in the prepared organosilicon-boron hybrid oligomers. These components could not act as a bridge during the subsequent curing process to connect the incompatible phenolic resin and vinyl silicone rubber. Therefore, the coatings obtained after curing in Comparative Examples 2-3 using the organosilicon-boron hybrid oligomers from Comparative Example 1 showed a significant decrease in weather resistance and ablation resistance.

[0067] Finally, in Examples 1-4, organosilicon-boron hybrid oligomers were synthesized using 3-glycidyl etheroxypropyltrimethoxysilane, and in Examples 5-6, organosilicon-boron hybrid oligomers were synthesized using 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. This introduced alicyclic structures into the coating, resulting in better mechanical properties and weather resistance in the cured coatings (Examples 15-18). The tensile strength and elongation at break were more balanced. Although the introduction of alicyclic structures slightly increased the ablation rate, it also improved the weather resistance and mechanical balance of the coating, making it more suitable for long-term ablation protection under ultraviolet exposure and shear airflow impact conditions.

[0068] Finally, it should be noted that the above-described embodiments are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be pointed out that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Furthermore, it should be understood that after reading the above teachings of this application, those skilled in the art can make various alterations or modifications to this application, and the equivalent forms obtained also fall within the scope of protection of this application. It should also be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. An ablation-resistant and anti-aging coating for aircraft surfaces, characterized in that, The raw materials include: organosilicon-boron hybrid oligomers, phenolic resins, vinyl silicone rubber, hydrogen-containing silanes, and platinum catalysts; The organosilicon-boron hybrid oligomer is obtained by condensation reaction of silane coupling agent and boric acid at 60-100℃, followed by vacuum distillation to remove small molecule products. The molar ratio of silane coupling agent to boric acid is (1-2):1; The silane coupling agent is composed of an epoxy-containing silane coupling agent and a vinyl-containing silane coupling agent; The phenolic resin is selected from hydrocarbon-based or hydrocarbon-modified phenolic resins; The vinyl silicone rubber is selected from one or more of vinyl-terminated poly(dimethylsiloxane), vinyl-terminated poly(methylphenylsiloxane), and vinyl-terminated poly(diphenylsiloxane); The hydrogen-containing silane is selected from one or more of tetramethylcyclotetrasiloxane and hydrogen-terminated polydimethylsiloxane; The platinum catalyst is selected from platinum-olefin complex catalysts.

2. The ablation-resistant and anti-aging coating for aircraft surfaces according to claim 1, characterized in that, The molar ratio of the silane coupling agent to boric acid is (1.2-1.8):1; And / or, the epoxy-containing silane coupling agent molecule contains at least one epoxy group and at least one hydrolyzable Si-OR group or Si-OH group, wherein R is selected from hydrocarbon groups with 1 to 6 carbon atoms; And / or, the vinyl silane coupling agent molecule contains at least one vinyl group and at least one hydrolyzable Si-OR group or Si-OH group, wherein R is selected from hydrocarbon groups with 1 to 6 carbon atoms or hydrocarbon groups containing ether bonds.

3. The ablation-resistant and anti-aging coating for aircraft surfaces according to claim 1, characterized in that, The epoxy-containing silane coupling agent is selected from one or more of the following: 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane. And / or, the vinyl silane-containing coupling agent is selected from one or more of vinyltriisopropoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(2-methoxyethoxy)silane.

4. The ablation-resistant and anti-aging coating for aircraft surfaces according to claim 1, characterized in that, The phenolic resin is selected from one or more of alkyl phenolic resin, rosin phenolic resin and terpene phenolic resin; And / or, platinum-olefin complex catalysts are selected from platinum-divinyltetramethyldisiloxane complexes.

5. The ablation-resistant and anti-aging coating for aircraft surfaces according to claim 1, characterized in that, The raw materials for the ablation-resistant and anti-aging coating include solvents, which are selected from C6-C12 non-polar hydrocarbon solvents; And / or, the raw materials for the ablation-resistant and anti-aging coating include low-temperature glass powder, the softening temperature of which does not exceed 400°C; And / or, the raw materials of the ablation-resistant and anti-aging coating include inorganic fillers, which are selected from one or more of mica powder and fumed silica; And / or, the raw materials for the ablation-resistant and anti-aging coating include chopped glass fibers with a chopped length of 0.5-10 mm.

6. The ablation-resistant and anti-aging coating for aircraft surfaces according to claim 1, characterized in that, The ablation-resistant and anti-aging coating comprises, by weight, 10-20 parts of organosilicon-boron hybrid oligomer, 15-30 parts of phenolic resin, 20-40 parts of vinyl silicone rubber, 5-15 parts of hydrogen-containing silane, and 0.5-3 parts of platinum catalyst.

7. The ablation-resistant and anti-aging coating for aircraft surfaces according to claim 6, characterized in that, The ablation-resistant and anti-aging coating comprises, by weight, 20-40 parts of solvent; And / or, the raw materials of the ablation-resistant and anti-aging coating include, by weight, 5-15 parts by weight of low-temperature glass powder; And / or, the raw materials of the ablation-resistant and anti-aging coating include, by weight, 10-20 parts by weight of inorganic filler; And / or, the raw materials of the ablation-resistant and anti-aging coating include, by weight, 1-10 parts by weight of chopped glass fiber.

8. A method for preparing an ablation-resistant and anti-aging coating for an aircraft surface as described in any one of claims 1-7, characterized in that, The mixture is prepared by uniformly mixing organosilicon-boron hybrid oligomer, phenolic resin, vinyl silicone rubber, hydrogen-containing silane, low-temperature glass powder, solvent, inorganic filler and chopped glass fiber, evaporating the solvent, adding platinum catalyst, kneading the mixture, scraping it onto the surface of the substrate and curing it at 100-200℃.

9. The method for preparing the ablation-resistant and anti-aging coating on the surface of an aircraft according to claim 8, characterized in that, The solvent evaporates under conditions ranging from room temperature to 130°C; And / or, different types of solvents are used to dissolve organosilicon-boron hybrid oligomers and phenolic resins, as well as vinyl silicone rubber and hydrogen-containing silanes, respectively; And / or, use a disperser to mix the organosilicon-boron hybrid oligomer, phenolic resin, vinyl silicone rubber, hydrogen-containing silane, low-temperature glass powder, solvent, inorganic filler and chopped glass fiber evenly; And / or, the mixture is compounded using a two-roll open mill; And / or, the mixing time is 10-60 minutes; And / or, the curing temperature is 140-200℃.

10. The application of the ablation-resistant and anti-aging coating for aircraft surfaces as described in any one of claims 1-7 in aircraft surface coating.

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