A water-based acrylic resin modified polysilazane alkyl high-temperature resistant ceramic coating and its preparation method
By combining a graft copolymer of vinyl polysilazane modified with waterborne acrylic resin with nano-silicate filler and employing a stepped heating ceramization process, the problems of poor film-forming properties and poor workability of vinyl polysilazane coatings were solved, and a ceramic coating suitable for high-temperature environments was prepared, exhibiting good adhesion and density.
Patent Information
- Application Number
- CN202610382105.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-26
- Publication Date
- 2026-05-26
AI Technical Summary
Existing vinyl polysilazane coatings have poor film-forming properties, demanding curing conditions, and poor workability. Furthermore, traditional systems are not environmentally friendly and are difficult to apply to large components, complex curved surfaces, and lack sufficient density for high-temperature ceramicization.
A water-based acrylic resin was used to modify vinyl polysilazane, and a graft copolymer was formed by a free radical-initiated grafting reaction. The copolymer was then crosslinked with an isocyanate curing agent at room temperature. Combined with nano-silicate fillers, Si-O-Si covalent bonds were generated at high temperature. A high-temperature resistant ceramic coating was prepared using a stepped heating ceramization process.
It achieves a water-based, environmentally friendly, easy-to-apply, compatibility-friendly, uniformly dense ceramic coating with excellent adhesion and high-temperature resistance, suitable for aerospace, metallurgical high-temperature components and marine engineering fields.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of coating technology, specifically to a water-based acrylic resin modified polysilazane alkyl high-temperature resistant ceramic coating and its preparation method. Background Technology
[0002] Ceramic coatings have irreplaceable application value in aerospace, high-temperature metallurgical components, new energy equipment, and marine engineering. Vinyl polysilazane, as one of the best-performing Si3N4 ceramic precursors, has advantages such as designable molecular structure, high ceramicization yield, high temperature resistance, oxidation resistance, and outstanding corrosion resistance, and has become a research hotspot in the field of high-performance ceramic coatings.
[0003] Currently, the preparation of ceramic coatings using polysilazane as a precursor still faces several common key technical challenges in the industry: First, pure polysilazane has high bulk viscosity, poor film-forming properties, and demanding curing conditions, making it difficult to achieve room temperature coating directly, thus limiting its application in large components, complex curved surfaces, and on-site construction scenarios; Second, polysilazane has poor compatibility with conventional water-based resins, and simple physical blending easily leads to phase separation, weak interfacial bonding, and easy cracking of the coating. After high-temperature ceramization, it is prone to forming pores and defects, making it difficult to obtain a continuous and dense ceramic coating; Third, existing systems mostly rely on organic solvents, resulting in high VOC emissions and poor environmental performance, which does not conform to the development trend of green coating and safe production.
[0004] Therefore, developing a novel polysiloxane alkyl ceramic coating that is water-based, environmentally friendly, can be applied at room temperature, has excellent compatibility, and exhibits uniform and dense ceramicization is of significant practical importance and application value. Summary of the Invention
[0005] In view of the technical problems existing in the background art, the present invention provides a water-based acrylic resin modified polysilazane high-temperature resistant ceramic coating and its preparation method, aiming to solve the technical problems of poor film-forming properties, harsh curing conditions and poor workability of vinyl polysilazane coatings in the prior art.
[0006] In a first aspect, the present invention provides a method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating, comprising the following steps: S1. Disperse aqueous acrylic resin, vinyl polysilazane, and nano silicate filler in water to obtain a mixed dispersion; S2. Add a free radical initiator to the mixed dispersion to carry out a grafting reaction to obtain a grafted product of waterborne acrylic resin grafted with vinyl polysilazane. S3. After uniformly mixing the grafted product with the curing agent, the mixture is coated onto the surface of the substrate to form a wet film. After curing at room temperature, an organic-inorganic hybrid coating is obtained. S4. The organic-inorganic hybrid coating is subjected to high-temperature ceramicization treatment. In the first stage, the temperature is raised to 180~220℃ and held for 20~40 min. In the second stage, the temperature is raised to 750~850℃ and held for 20~60 min to obtain the ceramic coating.
[0007] Preferably, in step S1, the mass ratio of waterborne acrylic resin, vinyl polysilazane, nano silicate filler and water is (50~60):(20~30):(5~10):(40~70).
[0008] Preferably, in step S1, the nano-silicate filler includes at least one of nano-mica, nano-montmorillonite, and nano-kaolinite.
[0009] Preferably, in step S2, the free radical initiator includes an organic peroxide or an azo compound; the amount of free radical initiator added is 0.01% to 0.15% of the total mass of the aqueous acrylic resin and vinyl polysilazane.
[0010] Preferably, in step S2, the grafting reaction temperature is 60~80℃, the reaction time is 4~6h, and the grafting reaction is carried out under an inert atmosphere.
[0011] Preferably, in step S3, the amount of curing agent added is 7% to 15% of the mass of the waterborne acrylic resin; the curing agent includes isocyanate curing agents or aziridine curing agents.
[0012] Preferably, in step S3, the thickness of the wet film is 100~200μm; the thickness of the organic-inorganic hybrid coating is 50~100μm; and the room temperature curing time is 24~48h.
[0013] Preferably, in step S4, the high-temperature ceramicization treatment specifically involves: heating from room temperature to 180-220°C at a rate of 1-3°C / min, holding at that temperature for 20-40 min, then heating to 750-850°C at a rate of 4-6°C / min, holding at that temperature for 20-60 min, and then cooling to room temperature with the furnace.
[0014] Preferably, the atmosphere for high-temperature ceramicization includes at least one of nitrogen and argon.
[0015] In a second aspect, the present invention provides a ceramic coating prepared by the preparation method described in the first aspect.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses water-based acrylic resin as the grafting host. The molecular chain is rich in unsaturated double bonds. Under the initiation of free radicals, it can undergo efficient addition grafting with vinyl groups of vinyl polysilazane, which significantly improves the grafting rate. The resulting grafted product has good film-forming properties and strong coating adhesion.
[0017] (2) The present invention uses isocyanate or aziridine curing agents, which can be rapidly cross-linked with acrylic resin at room temperature, and the construction process is simple and the film-forming properties are good.
[0018] (3) The present invention uses silicate materials as inorganic fillers, which are different from traditional nano-oxide fillers. Its surface is rich in active silanol groups, which can react in situ with the Si-N structure generated by the cracking of vinyl polysilazane at high temperature to generate Si-O-Si covalent bonds, which greatly improves the coating density, salt spray resistance and high temperature thermal shock resistance.
[0019] (4) The present invention adopts a stepped heating ceramicization process to achieve low-temperature crosslinking and high-temperature pyrolysis transformation in stages to form a continuous and complete ceramic phase.
[0020] (5) The present invention uses water as the dispersion medium throughout the process, with low VOC content, environmental protection and safety, and easy construction; the prepared ceramic coating has both excellent high temperature resistance and long-term corrosion resistance, and can be applied to high-end protection fields such as aerospace, metallurgical high temperature components, new energy equipment and marine engineering, and has broad application prospects. Detailed Implementation
[0021] The embodiments of the technical solution of the present invention will be described in detail below. These embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore merely examples and should not be used to limit the scope of protection of the present invention.
[0022] To address the technical problems of poor film-forming properties, demanding curing conditions, and poor workability of existing vinyl polysilazane coatings, this invention provides a waterborne acrylic resin-modified polysilazane high-temperature resistant ceramic coating and its preparation method. The method involves grafting and modifying vinyl polysilazane with waterborne acrylic resin, using an isocyanate-based curing agent to achieve rapid curing at room temperature, followed by high-temperature firing to achieve ceramicization. This results in a waterborne, environmentally friendly, room-temperature-easy-to-apply, highly compatible, and uniformly dense ceramicized polysilazane high-temperature resistant ceramic coating.
[0023] In a first aspect, embodiments of the present invention provide a method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating, comprising the following steps: S1. Disperse aqueous acrylic resin, vinyl polysilazane, and nano silicate filler in water to obtain a mixed dispersion; S2. Add a free radical initiator to the mixed dispersion to carry out a grafting reaction to obtain a grafted product of waterborne acrylic resin grafted with vinyl polysilazane. S3. After uniformly mixing the grafted product with the curing agent, the mixture is coated onto the surface of the substrate to form a wet film. After curing at room temperature, an organic-inorganic hybrid coating is obtained. S4. The organic-inorganic hybrid coating is subjected to high-temperature ceramicization treatment. In the first stage, the temperature is raised to 180~220℃ and held for 20~40 min. In the second stage, the temperature is raised to 750~850℃ and held for 20~60 min to obtain the ceramic coating.
[0024] In the technical solution of this invention embodiment, the principle of the technical solution is as follows: (1) Reaction grafting: Under the action of the initiator, the vinyl double bond in the vinyl polysilazane molecular chain opens to form an active free radical; at the same time, the unsaturated double bond in the waterborne acrylic resin molecular chain is also activated by the initiator to generate free radicals. The two free radicals are connected by covalent bonds to form a graft copolymer. (2) Room temperature curing: The hydroxyl / carboxyl groups in the grafted product and the isocyanate / aziridine curing agent crosslink rapidly at room temperature to medium temperature to form a dense crosslinking network, which anchors the vinyl polysilazane and the nano silicate filler. The coating has strong adhesion and dense film formation, providing a stable skeleton for high-temperature ceramization. (3) High-temperature ceramization: The low-temperature section completes further crosslinking, and the high-temperature section polysilazane is cracked and converted into Si3N4 ceramic phase and fully densified. (4) Synergistic reinforcement of fillers: The surface of nano-silicate fillers is rich in active silanol groups. At high temperature, they can react in situ with the Si-N structure of polysilazane to generate Si-O-Si covalent ceramic phase, achieving chemical bonding rather than physical filling, which significantly improves density, salt spray resistance and thermal shock resistance.
[0025] Furthermore, in some embodiments, in step S1, the mass ratio of waterborne acrylic resin, vinyl polysilazane, nano-silicate filler and water is (50~60):(20~30):(5~10):(40~70).
[0026] Furthermore, in some embodiments, in step S1, the temperature during dispersion is controlled at 60~80°C.
[0027] In the technical solution of this invention embodiment, heating to 60-80℃ can effectively reduce the viscosity of the system, promote the uniform dispersion of each component, and create favorable conditions for the subsequent grafting reaction. This invention does not impose any particular limitation on the dispersion method; mechanical stirring, ultrasonic dispersion, or high-speed shear dispersion can be used.
[0028] Furthermore, in some embodiments, in step S1, the solid content of the waterborne acrylic resin is 40%~60%, and the hydroxyl value is 60~150mgKOH / g.
[0029] Furthermore, in some embodiments, in step S1, the nano-silicate filler includes at least one of nano-mica, nano-montmorillonite, and nano-kaolinite.
[0030] In the technical solution of the present invention, the surface of the above-mentioned nano-silicate filler is rich in silanol groups, which can undergo in-situ chemical reaction with polysilazane pyrolysis products during the high-temperature ceramicization stage to form a Si-O-Si / Si-N-Si ceramic network, rather than simple physical filling, thereby significantly improving the density and interfacial bonding strength of the coating.
[0031] Furthermore, in some embodiments, in step S2, the free radical initiator includes an organic peroxide or an azo compound; the amount of free radical initiator added is 0.01% to 0.15% of the total mass of the aqueous acrylic resin and vinyl polysilazane.
[0032] Furthermore, in some embodiments, in step S2, the grafting reaction temperature is 60~80°C, the reaction time is 4~6h, and the grafting reaction is carried out under an inert atmosphere.
[0033] Furthermore, in some embodiments, in step S3, the amount of curing agent added is 7% to 15% of the mass of the waterborne acrylic resin.
[0034] Furthermore, in some embodiments, in step S3, the curing agent includes an isocyanate curing agent or an aziridine curing agent.
[0035] Furthermore, in some embodiments, in step S3, the thickness of the wet film is 100~200μm, and the thickness of the organic-inorganic hybrid coating is 50~100μm.
[0036] Furthermore, in some embodiments, in step S3, the room temperature curing time is 24~48h.
[0037] Furthermore, in some embodiments, in step S4, the high-temperature ceramicization treatment specifically involves: heating from room temperature to 180-220°C at a rate of 1-3°C / min, holding at that temperature for 20-40 min, then heating to 750-850°C at a rate of 4-6°C / min, holding at that temperature for 20-60 min, and then cooling to room temperature with the furnace.
[0038] In the technical solution of this invention embodiment, the first stage of low-temperature heating rate is relatively slow, which is conducive to the complete removal of residual moisture in the coating and the further improvement of the cross-linking network, avoiding defects such as bubbles caused by rapid heating; the second stage heats up to 750~850℃ more quickly, the polysilazane undergoes thermal decomposition and rearrangement, the Si-N bond breaks and recombines to form the Si3N4 ceramic phase, and at the same time the silanols on the surface of the nano silicate filler react with the decomposition products to generate Si-O-Si bonds, realizing chemical bonding; holding at this temperature range for a certain period of time can ensure that the ceramicization reaction is fully carried out and improve the density of the coating.
[0039] Furthermore, in some embodiments, in step S4, the atmosphere for the high-temperature ceramicizing treatment includes at least one of nitrogen and argon.
[0040] Secondly, embodiments of the present invention provide a ceramic coating prepared by the preparation method described in the first aspect.
[0041] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.
[0042] In the following examples, the aqueous acrylic resin was purchased from Dow Chemical's Maincote. TM HG-100, solid content 45%, hydroxyl value 103mgKOH / g; vinyl polysilazane purchased from Hangzhou Qingci New Material Technology Co., Ltd. TC-P11.
[0043] Example 1 Raw material preparation: 55 parts of water-based acrylic resin, 25 parts of vinyl polysilazane, 6 parts of isocyanate curing agent (Bayer Desmodur N3390), 0.08 parts of BPO (benzoyl peroxide), and 8 parts of mica powder (BT-4 mica powder from Baota Sericite Mining).
[0044] A method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating, the specific steps of which are as follows: (1) Pre-dispersion of raw materials: 55 parts of waterborne acrylic resin and 50 parts of deionized water were added to the reactor at 60°C and stirred at 800 rpm for 30 minutes until uniform. Then 25 parts of vinyl polysilazane and 8 parts of mica powder were added and dispersed at 2000 rpm for 30 minutes under high shear. (2) Grafting reaction: Add 0.08 parts of initiator BPO to the reactor and react at 70°C and 2000 rpm for 5 hours to obtain the graft copolymer solution. Monitor the viscosity of the reaction system. If the viscosity is too high, add deionized water to adjust the viscosity to 25~35 seconds (Ford cup 4 method, 25°C). (3) Curing film at room temperature: Mix the obtained graft copolymer solution with 6 parts of isocyanate curing agent evenly, stir at room temperature for 30 min and then coat it on the surface of high temperature resistant substrate. The wet film thickness is controlled at 100~120μm. Curing at room temperature for 24 hours yields an organic-inorganic hybrid coating with a dry film thickness of about 50~60μm. (4) High-temperature firing ceramicization: The hybrid coating is placed in a nitrogen atmosphere and heated from room temperature to 200℃ at a rate of 2℃ / min and held for 30min (NCO / OH crosslinking stage), then heated to 800℃ at a rate of 5℃ / min (polysilazane ceramicization transformation stage), held for 30min (ceramic phase densification stage), and cooled to room temperature in the furnace to obtain the ceramic coating.
[0045] Example 2 Raw material preparation: 50 parts of waterborne acrylic resin, 30 parts of vinyl polysilazane, 7 parts of isocyanate curing agent (Covestro Imprafix 2794 blocked isocyanate), 0.05 parts of AIBN (azobisisobutyronitrile), and 6 parts of nano-kaolin.
[0046] A method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating, the specific steps of which are as follows: (1) Pre-dispersion of raw materials: 50 parts of waterborne acrylic resin and 50 parts of deionized water were added to the reactor at 60°C and stirred at 800 rpm for 30 minutes until uniform. Then, 30 parts of vinyl polysilazane and 6 parts of nano kaolin powder were added and dispersed at 2000 rpm for 30 minutes under high shear. (2) Grafting reaction: Add 0.05 parts of initiator AIBN to the reactor and react at 65°C and 1500 rpm for 6 hours to obtain the grafted copolymer solution. Monitor the viscosity of the reaction system. If the viscosity is too high, add deionized water to adjust the viscosity to 25~35 seconds (Ford cup 4 method, 25°C). (3) Curing film at room temperature: Mix the obtained graft copolymer solution with 7 parts of isocyanate curing agent evenly, stir at room temperature for 30 min and then coat it on the surface of high temperature resistant substrate. The wet film thickness is controlled at 100~120μm. Curing at room temperature for 24 hours yields an organic-inorganic hybrid coating with a dry film thickness of about 50~60μm. (4) High-temperature firing ceramicization: The hybrid coating is placed in a nitrogen atmosphere and heated from room temperature to 200℃ at a rate of 2℃ / min and held for 20min (NCO / OH crosslinking stage), then heated to 800℃ at a rate of 5℃ / min (polysilazane ceramicization transformation stage), held for 30min (ceramic phase densification stage), and cooled to room temperature in the furnace to obtain the ceramic coating.
[0047] Example 3 Raw material preparation: The ingredients are: 60 parts waterborne acrylic resin, 20 parts vinyl polysilazane, 5 parts aziridine curing agent (aziridine crosslinking agent XR-100), 0.1 parts BPO (benzoyl peroxide), and 5 parts mica powder (BT-4 mica powder from Baota Sericite Mining).
[0048] A method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating, the specific steps of which are as follows: (1) Pre-dispersion of raw materials: 60 parts of waterborne acrylic resin and 60 parts of deionized water were added to the reactor at 60°C and stirred at 800 rpm for 30 minutes until uniform. Then 20 parts of vinyl polysilazane and 5 parts of mica powder were added and dispersed at 2000 rpm for 30 minutes under high shear. (2) Grafting reaction: Add 0.1 parts of initiator BPO to the reactor and react at 75°C and 3000 rpm for 4 hours to obtain the graft copolymer solution. Monitor the viscosity of the reaction system. If the viscosity is too high, add deionized water to adjust the viscosity to 25~35 seconds (Ford cup 4 method, 25°C). (3) Curing film at room temperature: Mix the obtained graft copolymer solution with 5 parts of aziridine curing agent evenly, stir at room temperature for 30 min and then coat it on the surface of high temperature resistant substrate. The wet film thickness is controlled at 100~120μm. Curing at room temperature for 24 hours yields an organic-inorganic hybrid coating with a dry film thickness of about 50~60μm. (4) High-temperature firing ceramicization: The hybrid coating is placed in a nitrogen atmosphere and heated from room temperature to 200℃ at a rate of 2℃ / min and held for 30min (NCO / OH crosslinking stage), then heated to 800℃ at a rate of 5℃ / min (polysilazane ceramicization transformation stage), held for 30min (ceramic phase densification stage), and cooled to room temperature in the furnace to obtain the ceramic coating.
[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that the waterborne acrylic resin and vinyl polysilazane were not grafted together. Specifically: Raw material preparation: Same as in Example 1, but without initiator.
[0050] The preparation method, with specific steps as follows: (1) Pre-dispersion of raw materials: 55 parts of waterborne acrylic resin and 50 parts of deionized water were added to the reactor at 60°C and stirred at 800 rpm for 30 minutes until uniform. Then 25 parts of vinyl polysilazane and 8 parts of mica powder were added and dispersed at 2000 rpm for 30 minutes under high shear. (2) Curing film at room temperature: Mix the obtained dispersion with 6 parts of isocyanate curing agent evenly, stir at room temperature for 30 min and then coat it on the surface of high temperature resistant substrate. The wet film thickness is controlled at 100~120μm. Curing at room temperature for 24 hours yields an organic-inorganic hybrid coating with a dry film thickness of about 50~60μm. (3) High-temperature firing ceramicization: The hybrid coating is placed in a nitrogen atmosphere and heated from room temperature to 200℃ at a rate of 2℃ / min and held for 20min (NCO / OH crosslinking stage), then heated to 800℃ at a rate of 5℃ / min (polysilazane ceramicization transformation stage), held for 30min (ceramic phase densification stage), and cooled to room temperature in the furnace to obtain the ceramic coating.
[0051] Comparative Example 2 The difference between this comparative example and Example 1 is that the waterborne acrylic resin was replaced with a waterborne epoxy resin (model E-44, epoxy value 0.44, solid content 60%), and the curing agent was replaced with (cashew phenol modified amine curing agent, Kramar brand ZY-A1); the specific steps are as follows: (1) Pre-dispersion of raw materials: 55 parts of waterborne epoxy resin and 50 parts of deionized water were added to the reactor at 60°C and stirred at 800 rpm for 30 minutes until uniform. Then, 25 parts of vinyl polysilazane and 8 parts of mica powder were added and dispersed at 2000 rpm for 30 minutes under high shear. (2) Grafting reaction: Add 0.08 parts of initiator BPO to the reactor and react at 70°C and 2000 rpm for 5 hours to obtain the graft copolymer solution. Monitor the viscosity of the reaction system. If the viscosity is too high, add deionized water to adjust the viscosity to 25~35 seconds (Ford cup 4 method, 25°C). (3) Curing at room temperature: The obtained graft copolymer solution is mixed with 6 parts of cashew phenol modified amine curing agent, stirred at room temperature for 30 min and then coated on the surface of high temperature resistant substrate. The wet film thickness is controlled at 100~120μm. Curing at room temperature for 24 hours yields an organic-inorganic hybrid coating with a dry film thickness of about 50~60μm. (4) High-temperature firing ceramicization: The hybrid coating is placed in a nitrogen atmosphere and heated from room temperature to 200℃ at a rate of 2℃ / min and held for 20min (NCO / OH crosslinking stage), then heated to 800℃ at a rate of 5℃ / min (polysilazane ceramicization transformation stage), held for 30min (ceramic phase densification stage), and cooled to room temperature in the furnace to obtain the ceramic coating.
[0052] Comparative Example 3 The difference between this comparative example and Example 1 is that mica powder was not added in step (1); the parameters of the other steps are the same as those in Example 1.
[0053] Comparative Example 4 The difference between this comparative example and Example 1 is that in step (1), mica powder is replaced with nano-silica; the other step parameters are the same as in Example 1.
[0054] Comparative Example 5 Compared with Example 1, the difference in this comparative example is that in step (4), the step heating is cancelled, and the temperature is directly increased from 25°C to 800°C at 5°C / min, and held for 30min (without the 200°C NCO / OH crosslinking stage); the other step parameters are the same as those in Example 1.
[0055] Performance testing 1. Grafting rate test Test method: Quantitative analysis of Si-N bond characteristic peaks (1020 cm⁻¹) using Fourier transform infrared spectroscopy (FTIR). -1 ) and OH / COOH groups (3350cm) -1 +1720 cm -1 The characteristic peak area ratio of (-OH). The characteristic peak wavenumber of (-OH) in the infrared spectrum is around 3350 cm⁻¹. -1 In -COOH, the characteristic peak wavenumber of the -C=O portion is around 1720 cm⁻¹. -1 The characteristic peaks of the -OH group are relatively diffuse, with a wavenumber range of 2500 cm⁻¹. -1 -3500 cm -1 Therefore, 3350 cm -1 Peak area and 1720 cm -1 (Compare them together).
[0056] The test results are shown in Table 1 below.
[0057] Table 1
[0058] Table 1 shows that, compared to the waterborne epoxy resin system, the waterborne acrylic resin used in this invention exhibits higher grafting efficiency and stronger interfacial bonding with vinyl polysilazane, ensuring the uniformity and stability of the ceramicized precursor at the molecular structure level. The waterborne acrylic resin molecular chain contains numerous unsaturated double bonds, which, under free radical initiation, can undergo highly efficient addition grafting with the vinyl groups on vinyl polysilazane, resulting in higher reactivity and less steric hindrance.
[0059] 2. Coating performance test The ceramic yield was tested using a TG-DSC thermogravimetric analyzer; temperature resistance was tested using a 1500℃ thermal shock test in a muffle furnace; and salt spray resistance was tested according to GB / T 1771-2021 standard. The test results are shown in Table 2 below.
[0060] Table 2
[0061] The results in Table 2 show that, in Examples 1-3 of the present invention, the free radical grafting reaction between waterborne acrylic resin and vinyl polysilazane achieved chemical bonding of organic and inorganic phases at the molecular level. Combined with room temperature crosslinking of isocyanate or aziridine curing agents and a step-by-step high-temperature ceramization process, the overall performance of the coating was significantly improved.
[0062] Comparative Example 1 did not undergo free radical grafting reaction, but was only physically blended. The waterborne acrylic resin and vinyl polysilazane have a large polarity difference, which easily leads to phase separation and makes it impossible to form a molecularly homogeneous system. During the high-temperature ceramization process, a large amount of organic components are lost through pyrolysis, resulting in a discontinuous ceramic phase and many internal pores and defects in the coating, leading to low ceramic yield and poor adhesion and corrosion resistance.
[0063] Comparison of Example 2 and Example 1 shows that the waterborne acrylic resin has higher reactivity and grafting efficiency, which can significantly improve the overall performance of the coating.
[0064] Comparative Example 3 did not add mica powder. The coating lacked reinforcing components during the ceramization process, resulting in decreased density and easy generation of micro-defects inside.
[0065] Comparative Example 4 replaced the filler with nano-silica. Nano-SiO2 is an inert oxide with a stable structure and no active hydroxyl groups. It can only play a physical filling role and cannot chemically react with the Si-N skeleton formed by the cracking of vinyl polysilazane to generate Si-O-Si covalent bonds. Its interfacial bonding force is not as good as that of the mica powder system.
[0066] The ceramicization process of Comparative Example 5 involved rapidly heating the material from room temperature to 800°C, resulting in incomplete cross-linking. The residual active groups decomposed violently at high temperatures, and the sudden increase in thermal stress caused the coating to crack, leading to insufficient ceramicization and deterioration of overall performance.
[0067] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.
Claims
1. A method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating, characterized in that, Includes the following steps: S1. Disperse aqueous acrylic resin, vinyl polysilazane, and nano-silicate filler in water to obtain a mixed dispersion; S2. Add a free radical initiator to the mixed dispersion to carry out a grafting reaction to obtain a grafted product of waterborne acrylic resin grafted with vinyl polysilazane. S3. After uniformly mixing the grafted product with the curing agent, the mixture is coated onto the surface of the substrate to form a wet film. After curing at room temperature, an organic-inorganic hybrid coating is obtained. S4. The organic-inorganic hybrid coating is subjected to high-temperature ceramicization treatment. In the first stage, the temperature is raised to 180~220℃ and held for 20~40 min. In the second stage, the temperature is raised to 750~850℃ and held for 20~60 min to obtain the ceramic coating.
2. The method for preparing a waterborne acrylic resin-modified polysilazane-based high-temperature resistant ceramic coating according to claim 1, characterized in that, In step S1, the mass ratio of the waterborne acrylic resin, vinyl polysilazane, nano silicate filler and water is (50~60):(20~30):(5~10):(40~70).
3. The method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating according to claim 1, characterized in that, In step S1, the nano-silicate filler includes at least one of nano-mica, nano-montmorillonite, and nano-kaolinite.
4. The method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating according to claim 1, characterized in that, In step S2, the free radical initiator includes organic peroxides or azo compounds; And / or, the amount of the free radical initiator added is 0.01% to 0.15% of the total mass of the aqueous acrylic resin and the vinyl polysilazane.
5. The method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating according to claim 1, characterized in that, In step S2, the grafting reaction is carried out at a temperature of 60-80°C for 4-6 hours, and the grafting reaction is conducted under an inert atmosphere.
6. The method for preparing a waterborne acrylic resin-modified polysilazane-based high-temperature resistant ceramic coating according to claim 1, characterized in that, In step S3, the amount of curing agent added is 7% to 15% of the mass of the water-based acrylic resin; And / or, the curing agent includes isocyanate curing agents or aziridine curing agents.
7. The method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating according to claim 1, characterized in that, In step S3, the thickness of the wet film is 100~200μm; the thickness of the organic-inorganic hybrid coating is 50~100μm; and the room temperature curing time is 24~48h.
8. The method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating according to claim 1, characterized in that, In step S4, the high-temperature ceramicization treatment specifically involves: heating from room temperature to 180-220°C at a rate of 1-3°C / min, holding at that temperature for 20-40 minutes, then heating to 750-850°C at a rate of 4-6°C / min, holding at that temperature for 20-60 minutes, and then cooling to room temperature in the furnace.
9. The method for preparing a waterborne acrylic resin-modified polysilazane alkyl high-temperature resistant ceramic coating according to claim 1, characterized in that, In step S4, the atmosphere for the high-temperature ceramicization treatment includes at least one of nitrogen and argon.
10. A ceramic coating, characterized in that, It is prepared by the method for preparing waterborne acrylic resin modified polysilazane alkyl high-temperature resistant ceramic coating according to any one of claims 1 to 9.