A thermally alternating adaptive coating and its preparation method

Abstract

This invention belongs to the field of protective coating technology, specifically disclosing a thermally adaptive coating and its preparation method. The method includes mixing a modified fluororubber matrix, oriented sheet filler, and a thermal expansion regulator by weight, followed by high-speed stirring for 15-20 minutes and ultrasonic dispersion for 8-12 minutes to obtain the coating. The modified fluororubber matrix is ​​selected from silicone-modified fluororubber; the oriented sheet filler is one or more of talc, vermiculite, and mica powder with a thickness-to-diameter ratio ≥ 50:1; and the thermal expansion regulator is one or more of cordierite, perovskite, and β-nepheline. The coating of this invention is composed of modified fluororubber, oriented sheet filler, and thermal expansion regulator. Through the synergistic effect of these three components, the fluororubber coating achieves an elongation at break >150%, an elasticity retention rate >90% after thermal cycling at 400℃ / 1h, and an interfacial adhesion strength ≥5MPa. After more than 300 thermal cycles, the coating remains crack-free and maintains its integrity, providing a long-life, highly reliable solution for extreme temperature cycling scenarios.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of protective coatings, and particularly relates to a cold-heat alternating self-adaptive coating and a preparation method thereof. BACKGROUND

[0002] Fluororubber has excellent high-temperature resistance, oil resistance, chemical medium resistance and aging resistance, and has been widely used in aerospace, petrochemical, automobile and other fields. Fluororubber anticorrosive coating has the characteristics of high temperature resistance, oil resistance, high vacuum resistance, acid and alkali resistance, and resistance to various chemicals, and is suitable for modern aviation, rockets, space travel, warships, atomic energy and other cutting-edge technologies, as well as automobiles, ships, chemicals, telecommunications, instruments, machinery, chemical plants, oil refineries, oil well drilling platforms and other fields; it can also be used for extremely corrosive and temperature-resistant storage tanks, pipes, pumps and valves, exhaust pipes, chimneys, etc.; it can also be used as a protective layer for various rubber and plastic materials, and a coating for various fiber fabrics and glass cloth; it is particularly suitable for internal corrosion protection of desulfurization towers, chemical storage tanks and other high-temperature harsh environments, as well as sealing gaskets for automobile engines, etc.

[0003] However, although the existing pure fluororubber matrix has excellent elasticity, it has poor temperature resistance and is prone to aging and crosslinking at temperatures above 400℃, resulting in a sudden decrease in elasticity, brittle cracking and peeling due to increased rigidity during rapid cold and heat changes, and after multiple rapid cold and heat changes, the matrix ages and the fillers agglomerate, resulting in a shortened overall service life of the coating, which cannot meet the use requirements in the application fields of aircraft engine nacelles, industrial heat exchangers, automobile exhaust purification devices and the like to withstand rapid cold and heat changes. In order to improve its temperature resistance, existing technical personnel modify the fluororubber with organosilicon, such as the high-thermal-resistance fluororubber material and its application disclosed in Chinese Patent Publication No. CN115819902B, which can be cured at room temperature and has temperature resistance, but the coating has a low elongation at break due to the high crosslinking density of the organosilicon modification, and the coating will become brittle and crack when the temperature changes rapidly, affecting the service life of the matrix; in addition to modifying the fluororubber with organosilicon, existing technology also adds fillers to the fluororubber coating, such as the preparation method of a special low-temperature-resistant fluororubber disclosed in Patent Publication No. CN112142902A, which adds white mica powder and diatomite to the fluororubber to improve the low-temperature resistance and mechanical properties of the fluororubber, but since it is a composite system, the added fillers are difficult to arrange directionally in the fluororubber matrix, and a continuous stress buffer layer cannot be formed, and due to the expansion and contraction difference between the coating and the metal matrix, an interfacial stress of up to 50MPa will be generated during rapid changes, far exceeding the adhesion limit of the coating. At the same time, the traditional matrix modification technology does not fully balance the temperature resistance and elasticity, and the elongation at break of the modified rubber is reduced to below 80% under the action of 400℃ short-term heat, which cannot cope with the coupling impact of "rapid cooling and heating → large deformation → strong stress".

[0004] In summary, it is urgent to develop a cold and hot alternating adaptive coating, which needs to resist room temperature-400℃ cold and hot sudden change conditions, while ensuring high elasticity for stress buffering and matching anti-crack through thermal expansion, breaking through the technical barriers of elastic retention, stress buffering and thermal expansion matching. SUMMARY

[0005] The purpose of the present application is to solve the technical problem of the contradiction between elasticity and temperature resistance of traditional cold and hot protective coating, and to propose a cold and hot alternating adaptive coating, which combines the synergistic effect of elastic matrix, directional filler and thermal expansion control to realize crack-free and peeling-free coating under cold and hot sudden change, and prolong the service life of metal matrix.

[0006] To achieve the above purpose, the present application provides the following technical scheme:

[0007] A cold and hot alternating adaptive coating, comprising the following raw materials by weight: modified fluororubber matrix 100 parts, directional flaky filler 28-32 parts, and negative thermal expansion regulator 10-12 parts.

[0008] Preferably, the modified fluororubber matrix is an organic silicon modified fluororubber matrix. Through graft polymerization or blending process, the organic silicon modified fluororubber matrix is constructed, and the elongation at break is >150%, and the elastic retention rate is >90% under 400℃ short-term thermal action, which greatly improves the high elasticity and temperature resistance of the coating, breaks through the technical bottleneck that the elasticity of traditional fluororubber is below 80% after 400℃ thermal aging, and the elongation at break of organic silicon coating is <100% and is easy to crack under temperature sudden change, and combines the temperature resistance of organic silicon segment and the high elastic retention of fluororubber soft segment, solves the core contradiction that rubber elasticity and temperature resistance cannot coexist under cold and hot sudden change, and ensures the deformation adaptability of the coating in room temperature-400℃ temperature sudden change cycle.

[0009] Preferably, the organic silicon modified fluororubber matrix is prepared by the following method:

[0010] 1) Dissolve 2-acryloyloxyethyl boronic acid and hydrogen-containing silicone oil in anhydrous toluene, add platinum catalyst, and stir under magnetic force for 3-4h, then distill under reduced pressure through a three-stage cold trap to obtain a dynamic linker;

[0011] 2) Select the fluororubber matrix after freeze-drying and organic silicon by weight parts, dissolve in butanone-toluene mixed solvent, and stir under nitrogen protection to form a uniform prepolymer solution;

[0012] 3) The prepolymer solution obtained in the above step is heated to 75-85℃, the dynamic linker prepared in the above step is added and stirred and dispersed, the platinum catalyst is slowly added dropwise, and the temperature is programmed to 90-100℃ for reaction for 4-5h, nitrogen is introduced for phase structure stabilization when the reaction is fast, and the silicone modified fluororubber matrix is obtained after filtration and concentration.

[0013] Preferably, the fluororubber matrix is any one of fluororubber, silicone rubber modified fluororubber, and acrylate modified fluororubber.

[0014] Preferably, the silicone includes one or both of methyl vinyl silicone rubber and phenyl silicone.

[0015] Preferably, the oriented sheet-shaped filler is one or more of talc powder, vermiculite, and mica powder with a thickness-diameter ratio of ≥ 50:1. The sheet-shaped mica powder with a thickness-diameter ratio of ≥ 50:1 is selected, and through flow casting, magnetic field induction or spray shear force control, the oriented layered accumulation of the filler in the coating is realized, the continuous stress buffer layer is constructed through the oriented arrangement, the internal stress peak value of the coating is reduced by more than 60%, the crack initiation strain threshold is increased to more than 15%, and the technical defects of coating cracking and peeling caused by stress concentration in cold and hot cycles are solved.

[0016] Preferably, the thermal expansion regulator is one or more of coesite, calcium titanium zirconium stone and beta-lithium feldspar. The thermal expansion regulator with negative thermal expansion characteristics is introduced to cooperatively regulate the thermal expansion coefficient of the coating to match the metal matrix, greatly reducing the difference between the thermal expansion coefficients of the coating and the metal matrix, thereby reducing the interfacial thermal stress generated during cold and hot changes, and avoiding interfacial peeling and cracking.

[0017] Another object of the present application provides a preparation method of a cold and hot alternating adaptive coating, including: mixing a modified fluororubber matrix, an oriented sheet-shaped filler and a thermal expansion regulator by weight parts, and then stirring at a high speed for 15-20min, and then ultrasonic dispersing for 8-12min to obtain the coating.

[0018] Preferably, the high-speed stirring rate is 1500-1800rpm.

[0019] Preferably, the ultrasonic power is 20-25kHz.

[0020] This invention also provides a method for using a thermally adaptive coating, comprising: applying the uniformly mixed thermally adaptive coating by air spraying; loading the pre-mixed and filtered paint into the spray gun reservoir; adjusting the atomization pressure (usually 3-4 bar), paint output, and fan-shaped amplitude of the spray gun; during spraying, maintaining a vertical distance of 15-20 cm between the spray gun nozzle and the workpiece surface; moving the spray gun at a stable and uniform speed to spray onto the metal substrate, ensuring that each coat overlaps the previous one by 1 / 2 to 2 / 3; achieving a coating thickness of 45-55 μm; and curing by baking at 140-160℃ for 40-90 minutes to form a thermally adaptive coating.

[0021] Preferably, the spraying method can also be magnetic field directional spraying, that is, a 0.5T permanent magnet is built into the spraying equipment, and the rest of the methods are the same as air spraying.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. The thermal cycling adaptive coating of this invention is composed of modified fluororubber, oriented sheet filler, and thermal expansion regulator. Through the synergistic effect of the three, the fluororubber coating achieves an elongation at break of >150%, an elasticity retention rate of >90% after thermal treatment at 400℃ / 1h, improved interfacial adhesion of the coating to ≥5MPa, and the coating can withstand strain of >15%. After more than 300 thermal cycles, the coating shows no cracks, and the interfacial peeling rate is <5%, maintaining the integrity of the coating. This provides a long-life and highly reliable protection solution for extreme temperature cycling scenarios.

[0024] 2. The modified fluororubber matrix of this invention introduces organosilicon segments into the fluororubber molecular chain to construct a block structure that has both soft segments of fluororubber and hard segments of organosilicon. Under the premise of ensuring that the elongation at break of fluororubber is >150%, the temperature resistance of the fluororubber coating is improved, and the elasticity retention rate is >90% under short-term heat treatment at 400℃.

[0025] 3. The present invention adds oriented sheet fillers with a diameter-to-thickness ratio ≥ 50:1 to the thermally alternating adaptive coating. Through casting or magnetic field induction, the fillers achieve oriented layered deposition in the coating. When the layered structure undergoes rapid thermal changes, it absorbs shear stress through sheet slippage, thereby inhibiting crack initiation and propagation and improving the crack resistance of the coating.

[0026] 4. The thermal expansion regulator in the adaptive coating of this invention, which has negative thermal expansion characteristics, is added and combined with the positive expansion characteristics of the modified fluororubber matrix to adjust the coefficient of thermal expansion of the coating to 15-18×10⁻⁶. -6 / ℃, close to the thermal expansion coefficient of the metal matrix, thereby reducing the interfacial thermal stress during rapid temperature changes, reducing the interfacial thermal stress from 80MPa to below 20MPa, and avoiding interfacial peeling and cracking.

[0027] 5. The coating of this invention is suitable for aircraft engine nacelles, can withstand rapid temperature changes from room temperature to 400℃, and has no failure after 3000 cycles, perfectly ensuring the sealing and heat insulation performance of the metal structure; when used in industrial heat exchangers, it can withstand temperature difference cycles of 350℃, improving the equipment's impact and vibration resistance by 50% and extending the equipment's maintenance cycle; when used in automotive exhaust systems, it adapts to the frequent rapid changes during vehicle start-up and shutdown, has the advantages of aging resistance and oil resistance, ensures the system is crack-free for 5 years, and improves the reliability of the entire vehicle. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a scanning electron microscope image of the cross-section of the coating prepared in Example 4 of the present invention;

[0030] Figure 2 This is a scanning electron microscope (SEM) image of the coating cross-section prepared in Example 4 of the present invention after 500 thermal cycles. Detailed Implementation

[0031] The technical solutions 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. In the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0032] A thermally adaptive coating comprises the following raw materials in parts by weight: 100 parts of modified fluororubber matrix, 28-32 parts of oriented lamellar filler, and 10-12 parts of thermal expansion regulator.

[0033] It should be noted that the modified fluororubber matrix is ​​an organosilicon-modified fluororubber matrix, wherein the fluororubber matrix can be any one of fluororubber, silicone rubber-modified fluororubber, or acrylate-modified fluororubber.

[0034] It should be noted that the fluororubber used is a copolymer of vinylidene fluoride and hexafluoropropylene, namely FKM-26 fluororubber, a high-performance fluoroelastomer known for its excellent chemical resistance, exhibiting outstanding tolerance to oils, fuels, various acids, and solvents. This material can operate stably for extended periods within a wide temperature range of -18℃ to 250℃, with short-term temperature resistance up to 300℃. However, its radiation resistance is relatively poor, its elasticity is limited at low temperatures, and contact with certain metal powders or amine compounds should be avoided.

[0035] The silicone rubber used in silicone-modified fluororubber is methyl vinyl silicone rubber, specifically MVQ-100 silicone rubber. Its main chain contains silicon-oxygen bonds and a small amount of vinyl groups, giving it a wide temperature adaptability (long-term use from -50℃ to 250℃) and excellent electrical insulation. It also maintains stable electrical properties under high temperature and humid conditions. Furthermore, this material has excellent biocompatibility and ozone aging resistance, and is non-toxic and odorless. Its drawback is that its mechanical strength (such as tensile and tear strength) is generally lower than that of ordinary rubber.

[0036] It should be noted that the acrylate-modified fluororubber is prepared by the following method: first, fluororubber is ultrasonically dispersed into an ethanol aqueous solution, then a core-shell type acrylate elastomer and a rubber reinforcing agent are added, nitrogen is used for bubbling to remove oxygen, and the mixture is placed under an ultrasonic initiation device and polymerized at a power of 55 kHz for 45 min. After washing with an ethanol aqueous solution, the mixture is filtered and vacuum dried to obtain the acrylate-modified fluororubber.

[0037] Example 1

[0038] A thermally adaptive coating comprises the following raw materials in parts by weight: 100 parts modified fluororubber matrix, 28 parts flaky mica powder, and 10 parts β-nepheline; the specific preparation steps include:

[0039] (1) Preparation of modified fluororubber matrix:

[0040] 1) 2-Acryloyloxyethylboronic acid and hydrogen-terminated silicone oil were dissolved in anhydrous toluene at a molar ratio of 1.05:1. Platinum catalyst was added and the mixture was reacted at 40°C and 250 rpm under magnetic stirring for 3 hours. The dynamic linker was obtained by vacuum distillation in a three-stage cold trap.

[0041] 2) Select 100 parts by weight of FKM-26 fluororubber and 15 parts by weight of methyl vinyl silicone rubber after freeze drying, dissolve them in a mixed solvent of butanone-toluene, and stir at 55°C and 400 rpm for 6 hours under nitrogen protection to form a homogeneous prepolymer solution.

[0042] 3) Heat the prepolymer solution obtained in step 2) to 75°C, add the dynamic linker prepared in step 1) and disperse at 500 rpm for 10 min, slowly add 200 ppm platinum catalyst over 30 min, and increase the temperature to 90°C at a programmed rate of 0.5°C / min for 4 hours. When the reaction is about to end, introduce 15% nitrogen gas to stabilize the phase structure. After the reaction is completed, filter and concentrate to obtain an organosilicon modified fluororubber matrix with a solid content of 65%.

[0043] (2) Weigh 28 parts by weight of flaky mica powder with a particle size of 10μm×0.2μm and a diameter-to-thickness ratio of 50:1; weigh 10 parts of β-nepheline with a particle size of 5μm;

[0044] (3) Add the material from step (2) to 100 parts of the organosilicon-modified fluororubber matrix prepared in step (1), and obtain the cold and heat alternating adaptive coating by high-speed stirring at 1500 rpm for 20 min and ultrasonic dispersion at 20 kHz for 12 min.

[0045] Example 2

[0046] A thermally adaptive coating comprises the following raw materials in parts by weight: 100 parts modified fluororubber matrix, 30 parts flaky mica powder, and 12 parts β-nepheline; the specific preparation steps include:

[0047] (1) Preparation of modified fluororubber matrix:

[0048] 1) 2-Acryloyloxyethylboronic acid and hydrogen-terminated silicone oil were dissolved in anhydrous toluene at a molar ratio of 1.05:1. Platinum catalyst was added and the mixture was reacted at 40°C and 250 rpm under magnetic stirring for 3 hours. The dynamic linker was obtained by vacuum distillation in a three-stage cold trap.

[0049] 2) 100 parts by weight of acrylate-modified fluororubber and 18 parts by weight of methyl vinyl silicone rubber after freeze-drying were dissolved in a mixed solvent of butanone-toluene and stirred at 55°C and 400 rpm for 6 hours under nitrogen protection to form a homogeneous prepolymer solution.

[0050] 3) Heat the prepolymer solution obtained in step 2) to 85°C, add the dynamic linker prepared in step 1) and disperse at 500 rpm for 10 min, slowly add 50 ppm platinum catalyst over 30 min, and increase the temperature to 90°C at a programmed rate of 0.5°C / min for 4 hours. When the reaction is about to end, introduce 15% nitrogen gas to stabilize the phase structure. After the reaction is completed, filter and concentrate to obtain an organosilicon modified fluororubber matrix with a solid content of 65%.

[0051] (2) Weigh 30 parts by weight of flaky mica powder with a particle size of 10μm×0.2μm and a diameter-to-thickness ratio of 50:1; weigh 12 parts by weight of β-nepheline with a particle size of 5μm;

[0052] (3) Add the material from step (2) to 100 parts of the organosilicon-modified fluororubber matrix prepared in step (1), and obtain the cold and heat alternating adaptive coating by high-speed stirring at 1700 rpm for 18 min and ultrasonic dispersion at 23 kHz for 10 min.

[0053] Example 3

[0054] A thermally adaptive coating comprises the following raw materials in parts by weight: 100 parts modified fluororubber matrix, 32 parts flake talc powder, and 10 parts β-nepheline; the specific preparation steps include:

[0055] (1) Preparation of modified fluororubber matrix:

[0056] 1) 2-Acryloyloxyethylboronic acid and hydrogen-terminated silicone oil were dissolved in anhydrous toluene at a molar ratio of 1.05:1. Platinum catalyst was added and the mixture was reacted at 40°C and 250 rpm under magnetic stirring for 3 hours. The dynamic linker was obtained by vacuum distillation in a three-stage cold trap.

[0057] 2) Select 70 parts by weight of FKM-26 fluororubber, 30 parts by weight of MVQ-100 silicone rubber and 20 parts by weight of methyl vinyl silicone rubber after freeze drying, dissolve them in a mixed solvent of butanone-toluene, and stir at 55°C and 400 rpm for 6 hours under nitrogen protection to form a homogeneous prepolymer solution.

[0058] 3) Heat the prepolymer solution obtained in step 2) to 80°C, add the dynamic linker prepared in step 1) and disperse at 500 rpm for 10 min, slowly add 100 ppm platinum catalyst over 30 min, and increase the temperature to 90°C at a programmed rate of 0.5°C / min for 4 hours. When the reaction is about to end, introduce 15% nitrogen gas to stabilize the phase structure. After the reaction is completed, filter and concentrate to obtain an organosilicon modified fluororubber matrix with a solid content of 70%.

[0059] (2) Weigh 32 parts by weight of flaky talc with a particle size of 10μm×0.2μm and a diameter-to-thickness ratio of 50:1; weigh 10 parts of β-nepheline with a particle size of 5μm;

[0060] (3) Add the material from step (2) to 100 parts of the modified fluororubber matrix prepared in step (1), and obtain the thermal alternation adaptive coating by high-speed stirring at 1800 rpm for 15 min and ultrasonic dispersion at 25 kHz for 8 min.

[0061] Example 4

[0062] A thermally adaptive coating comprises the following raw materials in parts by weight: 100 parts modified fluororubber matrix, 30 parts flaky mica powder, 8 parts β-lepidolite, and 2 parts cordierite; the specific preparation steps include:

[0063] (1) Preparation of modified fluororubber matrix:

[0064] 1) 2-Acryloyloxyethylboronic acid and hydrogen-terminated silicone oil were dissolved in anhydrous toluene at a molar ratio of 1.05:1. Platinum catalyst was added and the mixture was reacted at 40°C and 250 rpm under magnetic stirring for 3 hours. The dynamic linker was obtained by vacuum distillation in a three-stage cold trap.

[0065] 2) Select 80 parts by weight of FKM-26 fluororubber, 20 parts by weight of MVQ-100 silicone rubber and 20 parts by weight of phenyl organosilicon after freeze drying, dissolve them in a mixed solvent of butanone-toluene, and stir at 55°C and 400 rpm for 6 hours under nitrogen protection to form a homogeneous prepolymer solution.

[0066] 3) Heat the prepolymer solution obtained in step 2) to 80°C, add the dynamic linker prepared in step 1) and disperse at 500 rpm for 10 min, slowly add 100 ppm platinum catalyst over 30 min, and increase the temperature to 90°C at a programmed rate of 0.5°C / min for 4 hours. When the reaction is about to end, introduce 15% nitrogen gas to stabilize the phase structure. After the reaction is completed, filter and concentrate to obtain an organosilicon modified fluororubber matrix with a solid content of 65%.

[0067] (2) Weigh 30 parts by weight of flaky mica powder with a particle size of 10μm×0.2μm and a diameter-to-thickness ratio of 50:1; weigh 8 parts of β-nepheline with a particle size of 5μm and 2 parts of cordierite;

[0068] (3) Add the material from step (2) to 100 parts of the modified fluororubber matrix prepared in step (1), and obtain the thermal alternation adaptive coating by high-speed stirring at 1500 rpm for 20 min and ultrasonic dispersion at 20 kHz for 10 min.

[0069] Example 5

[0070] A thermally adaptive coating comprises the following raw materials in parts by weight: 100 parts modified fluororubber matrix, 30 parts flaky vermiculite, and 10 parts cordierite; the specific preparation steps include:

[0071] (1) Preparation of modified fluororubber matrix:

[0072] 1) 2-Acryloyloxyethylboronic acid and hydrogen-terminated silicone oil were dissolved in anhydrous toluene at a molar ratio of 1.05:1. Platinum catalyst was added and the mixture was reacted at 40°C and 250 rpm under magnetic stirring for 3 hours. The dynamic linker was obtained by vacuum distillation in a three-stage cold trap.

[0073] 2) Select 70 parts by weight of FKM-26 fluororubber, 30 parts by weight of MVQ-100 silicone rubber and 20 parts by weight of methyl vinyl silicone rubber after freeze drying, dissolve them in a mixed solvent of butanone-toluene, and stir at 55°C and 400 rpm for 6 hours under nitrogen protection to form a homogeneous prepolymer solution.

[0074] 3) Heat the prepolymer solution obtained in step 2) to 80°C, add the dynamic linker prepared in step 1) and disperse at 500 rpm for 10 min, slowly add 100 ppm platinum catalyst over 30 min, and increase the temperature to 90°C at a programmed rate of 0.5°C / min for 4 hours. When the reaction is about to end, introduce 15% nitrogen gas to stabilize the phase structure. After the reaction is completed, filter and concentrate to obtain an organosilicon modified fluororubber matrix with a solid content of 65%.

[0075] (2) Weigh 30 parts by weight of flaky vermiculite with a particle size of 10μm×0.2μm and a diameter-to-thickness ratio of 50:1; weigh 10 parts of cordierite with a particle size of 5μm;

[0076] (3) Add the material from step (2) to 100 parts of the modified fluororubber matrix prepared in step (1), and obtain the thermal alternation adaptive coating by high-speed stirring at 1500 rpm for 20 min and ultrasonic dispersion at 20 kHz for 10 min.

[0077] Example 6

[0078] A thermally adaptive coating comprises the following raw materials in parts by weight: 100 parts modified fluororubber matrix, 20 parts flake mica powder, 10 parts flake talc powder, and 10 parts perovskite; the specific preparation steps include:

[0079] (1) Preparation of modified fluororubber matrix:

[0080] 1) 2-Acryloyloxyethylboronic acid and hydrogen-terminated silicone oil were dissolved in anhydrous toluene at a molar ratio of 1.05:1. Platinum catalyst was added and the mixture was reacted at 40°C and 250 rpm under magnetic stirring for 3 hours. The dynamic linker was obtained by vacuum distillation in a three-stage cold trap.

[0081] 2) 100 parts by weight of acrylate-modified fluororubber and 20 parts by weight of methyl vinyl silicone rubber after freeze drying were dissolved in a mixed solvent of butanone-toluene and stirred at 55°C and 400 rpm for 6 hours under nitrogen protection to form a homogeneous prepolymer solution.

[0082] 3) Heat the prepolymer solution obtained in step 2) to 80°C, add the dynamic linker prepared in step 1) and disperse at 500 rpm for 10 min, slowly add 100 ppm platinum catalyst over 30 min, and increase the temperature to 90°C at a programmed rate of 0.5°C / min for 4 hours. When the reaction is about to end, introduce 15% nitrogen gas to stabilize the phase structure. After the reaction is completed, filter and concentrate to obtain an organosilicon modified fluororubber matrix with a solid content of 65%.

[0083] (2) Weigh 20 parts by weight of flaky mica powder with a particle size of 10μm×0.2μm and a diameter-to-thickness ratio of 50:1 and 10 parts by weight of flaky talc powder; weigh 10 parts by weight of perovskite with a particle size of 5μm;

[0084] (3) Add the material from step (2) to 100 parts of the organosilicon-modified fluororubber matrix prepared in step (1), and obtain the thermal-cooling adaptive coating by high-speed stirring at 1800 rpm for 15 min and ultrasonic dispersion at 20 kHz for 10 min.

[0085] Comparative Example 1

[0086] A coating comprises the following raw materials in parts by weight: 100 parts of FKM-26 fluororubber matrix, 30 parts of flake mica powder, 8 parts of β-nepheline, and 2 parts of cordierite; the specific preparation steps include: weighing 100 parts of FKM-26 fluororubber, 30 parts of flake mica powder with a particle size of 10μm×0.2μm and an aspect ratio of 50:1, 8 parts of β-nepheline with a particle size of 5μm, and 2 parts of cordierite; mixing the above materials and stirring at 1500rpm for 20min and ultrasonically dispersing at 20kHz for 10min to obtain the coating.

[0087] Comparative Example 2

[0088] A cold coating comprises the following raw materials in parts by weight: 100 parts modified fluororubber matrix, 8 parts β-lithium nepheline, and 2 parts cordierite; the specific preparation steps include:

[0089] (1) Preparation of modified fluororubber matrix: The preparation method is the same as in Example 3;

[0090] (2) Weigh out 8 parts by weight of β-nepheline with a particle size of 5 μm and 2 parts by weight of cordierite;

[0091] (3) Add the material from step (2) to 100 parts of the organosilicon-modified fluororubber matrix prepared in step (1), and obtain the coating by high-speed stirring at 1500 rpm for 20 min and ultrasonic dispersion at 20 kHz for 10 min.

[0092] Comparative Example 3

[0093] A coating comprising the following raw materials in parts by weight: 100 parts modified fluororubber matrix and 30 parts flake mica powder; the specific preparation steps include:

[0094] (1) Preparation of modified fluororubber matrix: The preparation method is the same as in Example 3;

[0095] (2) Weigh 30 parts by weight of flaky talc powder with a particle size of 10μm×0.2μm and a diameter-to-thickness ratio of 50:1;

[0096] (3) Add the material from step (2) to 100 parts of the organosilicon-modified fluororubber matrix prepared in step (1), and obtain the coating by high-speed stirring at 1500 rpm for 20 min and ultrasonic dispersion at 20 kHz for 10 min.

[0097] Comparative Example 4

[0098] A coating comprises the following raw materials in parts by weight: 100 parts modified fluororubber matrix, 30 parts flaky mica powder, 8 parts β-lepidolite, and 2 parts cordierite; the specific preparation steps include:

[0099] (1) Preparation of modified fluororubber matrix: The preparation method is the same as in Example 3;

[0100] (2) Weigh 30 parts by weight of conventional flaky mica powder with a diameter-to-thickness ratio <30:1; weigh 8 parts of β-lepidolite with a particle size of 5μm and 2 parts of cordierite;

[0101] (3) Add the material from step (2) to 100 parts of the modified fluororubber matrix prepared in step (1), and obtain the thermal alternation adaptive coating by high-speed stirring at 1500 rpm for 20 min and ultrasonic dispersion at 20 kHz for 10 min.

[0102] Comparative Example 5

[0103] A coating comprises the following raw materials in parts by weight: 100 parts of fluororubber (FKM-26) matrix, 30 parts of flake mica powder, 8 parts of β-nepheline, and 2 parts of cordierite; the specific preparation steps include: weighing 100 parts of fluororubber (FKM-26), 30 parts of conventional flake mica powder with an aspect ratio <50:1, 8 parts of β-nepheline with a particle size of 5μm, and 2 parts of cordierite; mixing the above materials and stirring at 1500rpm for 20min and ultrasonically dispersing at 20kHz for 10min to obtain the coating.

[0104] Comparative Example 6

[0105] A coating comprises the following raw materials in parts by weight: 100 parts of fluororubber (FKM-26) matrix and 30 parts of flake mica powder; the specific preparation steps include: weighing 100 parts of fluororubber (FKM-26) and 30 parts of conventional flake mica powder with an aspect ratio <50:1 according to the weight; mixing the above materials and stirring at 1500 rpm for 20 min and ultrasonically dispersing at 20 kHz for 10 min to obtain the coating.

[0106] Test case

[0107] The application performance of the prepared coatings was tested by spraying them onto aluminum alloy substrates and ceramic substrates, respectively. The specific spraying methods are as follows:

[0108] Aluminum alloy substrate: The coatings prepared above were sprayed onto sandblasted aluminum alloy substrates and cured by baking at 50°C for 1 hour to form a dense coating with a film thickness of 50 μm; at the same time, the coating prepared in Example 4 was sprayed using magnetic field directional spraying, that is, a 0.5T permanent magnet was built into the spraying equipment, and a magnetic field parallel to the substrate was applied during spraying. The coating was sprayed onto sandblasted aluminum alloy substrates and cured by baking at 50°C for 1 hour to form a dense coating with a film thickness of 50 μm; the performance difference of the coatings obtained by the two different spraying methods was tested.

[0109] The above-mentioned aluminum alloy substrates were subjected to surface characterization, mechanical property testing, thermal cycling testing, and thermal expansion matching testing, respectively. The specific testing methods are as follows:

[0110] Surface characterization: The coating prepared in Example 4 was subjected to cross-sectional scanning electron microscopy (SEM) testing, and the surface of the coating was also tested after 500 thermal cycles.

[0111] Mechanical properties: The elongation at break was tested according to GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber"; the adhesion was tested according to GB / T 9286-1998 "Cross-cut test of paint and varnish film".

[0112] Thermal cycling test: Referring to GB / T 42261-2022 and GB / T 42259-2022, the coated aluminum alloy specimen is placed in a thermal cycling test apparatus and cycled between room temperature (23±2℃) and 400℃. Each cycle includes: heating to 400℃ at a specified rate (e.g., 10℃ / min) and holding at that temperature for a certain time (e.g., 60 min), followed by cooling to room temperature and holding at that temperature. The test continues until the coating shows obvious failure (peeling area exceeds 20% of the total area), and the total number of cycles N is recorded. This method is relatively intuitive and suitable for large-area damage such as peeling and blistering.

[0113] Coating integrity (%) = (1 - Ad / At) × 100%

[0114] Ad: The total area (mm²) of the coating damaged by peeling, blistering, severe cracking, etc., after thermal cycling testing. This information is obtained by analyzing photographs of the samples using image analysis software (such as ImageJ).

[0115] At: Initial total test area of ​​the coating (mm²).

[0116] Thermal expansion matching: The coefficient of thermal expansion of the coating was tested according to the push-rod method specified in GB / T 7320-2018. The test temperature range was from room temperature to 400℃, and the heating rate was controlled at 10℃ / min.

[0117] Specific test results are as follows:Figure 1 , Figure 2 As shown in Table 1. From Figure 1 As can be seen from the scanning electron microscope image, the gray horizontal stripes are the oriented sheet-like fillers added to the coating of the present invention. It can be seen that the oriented arrangement of the sheet-like fillers added to the coating prepared in Example 4 of the present invention is successful. The negative thermal expansion regulator has a small particle size and the image contrast is not obvious in this mode. In addition, it can be seen from the image that the modified fluororubber matrix uniformly encapsulates the oriented sheet-like fillers and the negative thermal expansion regulator. Figure 2 The image shows the surface state of the coating in Example 4 of this invention after 500 thermal cycles. As can be seen from the image, the coating prepared by this invention only shows micro-cracks on the surface and no large-area peeling. This indicates that the coating prepared by this invention has high elasticity, crack resistance and impact resistance under rapid temperature change environment, ensuring the long-term stability and integrity of the coating.

[0118] As shown in Table 1, the elongation at break of the adaptive coatings prepared in Examples 1-6 of this invention all reached over 160%, which is much higher than the approximately 100% elongation at break of traditional fluororubber. The experimental test data from Comparative Examples 1, 5, and 6 show that when traditional fluororubber is mixed with the directional lamellar filler and negative thermal expansion regulator of this invention, the elongation at break is less than approximately 120%. The experimental test data from Comparative Examples 2 and 3 show that even with organosilicon modification of the fluororubber, if the directional lamellar filler or negative thermal expansion regulator of this invention is not added, the elongation at break of the coating is still less than 120%. This indicates that even when using a traditional composite system, i.e., using organosilicon-modified fluororubber instead of traditional fluororubber, or adding traditional fillers to the modified fluororubber, the lack of synergistic interaction between the elastic matrix, stress-buffering filler, and thermal expansion regulator leads to stress concentration in the coating. This results in random filler distribution, inability to provide directional buffering, or thermal expansion mismatch, leading to a large difference in expansion and contraction between the coating and the matrix, resulting in interface cracking of the coating.

[0119] Table 1 shows the coating integrity data. The coating integrity was tested after 300 and 500 thermal cycles. The results indicate that the coating prepared in this embodiment maintains over 98% integrity after 500 thermal cycles, and no cracking or peeling occurred. Comparative Examples 1, 5, and 6 show that using traditional fluororubber as the matrix resulted in cracking after 300 thermal cycles, and the integrity did not reach 50% after 500 cycles. Comparative Examples 2 and 3 show that even when using silicone-modified fluororubber as the matrix, without the addition of oriented lamellar fillers... The coating, even with materials or negative thermal expansion regulators, still cracked after 300 thermal cycles, and its integrity did not reach 60% after 500 thermal cycles. From the above test data, it can be seen that the coating prepared by this invention achieves the beneficial effect of improving the temperature resistance of the coating while ensuring high elasticity (elongation at break > 160%) by coordinating the interaction between the modified elastic matrix, directional stress buffer, and thermal expansion regulation, achieving an elasticity retention rate > 90% under 400℃ thermal action. Simultaneously, it absorbs shear stress through lamellar slip, inhibiting crack initiation and propagation, improving the coating's crack resistance, and reducing interfacial thermal stress during rapid temperature changes (from 80MPa to <20MPa), thus avoiding interfacial peeling and cracking.

[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A cold thermal alternating adaptive coating, characterized in that, The coating comprises the following raw materials by weight: a silicone-modified fluororubber matrix 100 parts, an oriented flaky filler 28-32 parts, and a thermal expansion regulator 10-12 parts; wherein the thickness-diameter ratio of the oriented flaky filler is ≥ 50:1; the silicone-modified fluororubber matrix is prepared by the following method: 1) Dissolve 2-acryloyloxyethyl boronic acid and hydrogen-terminated silicone oil in anhydrous toluene, add platinum gold catalyst, and react under magnetic stirring for 3-4 h, then obtain a dynamic linker after three-stage cold trap and reduced pressure distillation; 2) Select the fluororubber matrix after freeze-drying by weight, and dissolve silicone in butanone-toluene mixed solvent under nitrogen protection to form a uniform prepolymer solution; 3) Warm the prepolymer solution obtained above to 75-85℃, add the dynamic linker prepared above and stir to disperse, slowly add platinum gold catalyst, and program to 90-100℃ for reaction for 4-5 h, then pass nitrogen to stabilize the phase structure when the reaction is almost complete, filter and concentrate to obtain the silicone-modified fluororubber matrix after the reaction is completed.

2. The cold heat alternating adaptive coating of claim 1, wherein, The fluororubber matrix is any one of fluororubber, silicone-modified fluororubber, and acrylate-modified fluororubber.

3. The cold heat alternating adaptive coating of claim 1, wherein, The silicone includes one or both of methyl vinyl silicone rubber and phenyl silicone.

4. The cold heat alternating adaptive coating of claim 1, wherein, The oriented flaky filler is one or more of talc powder, vermiculite, and mica powder with a thickness-diameter ratio ≥ 50:

1.

5. The cold heat alternating adaptive coating of claim 1, wherein, The thermal expansion regulator is one or more of coelanite, calcium titanium zirconium stone, and β-lithium feldspar.

6. A method of making a cold thermal alternating adaptive coating as claimed in any one of claims 1 to 5, characterised by the steps of The coating comprises: The silicone-modified fluororubber matrix, the oriented flaky filler, and the thermal expansion regulator are stirred at a high speed for 15-20 min, and then ultrasonically dispersed for 8-12 min to obtain the coating.

7. The method of claim 6, wherein the cold thermal alternating self-adaptive coating is prepared by a process comprising: The high-speed stirring rate is 1500-1800 rpm.

8. The method of claim 6, wherein the cold thermal alternating adaptive coating is prepared by, The ultrasonic power is 20-25 kHz.

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