High-temperature-resistant sealing material applied to working conditions above 900 DEG C and preparation method thereof

Abstract

The application relates to the field of sealing materials, and particularly discloses a high-temperature-resistant sealing material applied to a working condition above 900 DEG C and a preparation method thereof. The high-temperature-resistant sealing material raw materials include polysilazane rubber 20-30%, organic cation modified bentonite 30-40%, reinforcing fiber 10-20%, aluminum hydroxide 5-10% and additives 1-5% in percentage by mass; the preparation method is as follows: the polysilazane rubber is stirred, the organic cation modified bentonite is added, the reinforcing fiber is added into the mixed materials, the stirring speed is increased, and then the aluminum hydroxide and the additives are added to form a uniform mixture; the mixed materials are placed into a mold preheated to 150-200 DEG C, a pressure of 4-6 MPa is applied after the mold is closed, and the pressure is kept for 30-60 minutes to obtain the high-temperature-resistant sealing material. The high-temperature-resistant sealing material applied to the working condition above 900 DEG C has the advantages of high-temperature resistance and good sealing performance in a high-temperature environment.

Description

Technical Field

[0001] This application relates to the field of sealing materials, and more specifically, to a high-temperature resistant sealing material for use in conditions above 900°C and a method for preparing the same. Background Technology

[0002] Sealing materials play a vital role in industrial production and daily life. From the operation of various mechanical equipment to the waterproofing and moisture-proofing of building structures, the use of sealing materials is ubiquitous. Their core function is to prevent the leakage of fluids (gases, liquids, etc.) and ensure the normal operation and safety of the system.

[0003] With the continuous advancement of industrial technology, the performance requirements for sealing materials are becoming increasingly stringent. Temperature is one of the key factors affecting the performance of sealing materials in various applications. Currently, the application temperature of most sealing materials on the market is limited to below 250℃. These materials can perform well in typical industrial environments and everyday life scenarios, are relatively inexpensive, and have a wide range of applications, such as common rubber gaskets and some organic polymer sealants.

[0004] However, in some specialized high-temperature industrial fields, such as metallurgy, glass manufacturing, ceramic firing, and aerospace engines, operating temperatures often far exceed 250°C. To address these high-temperature conditions, researchers and material manufacturers have continuously developed and improved sealing materials, and those capable of withstanding temperatures of 500-600°C are now available. These materials are mostly made from special inorganic fibers, ceramic materials, or metal alloys, and to a certain extent, meet the sealing requirements in moderately high-temperature environments.

[0005] However, when the temperature exceeds 800℃, existing sealing materials generally experience a sharp decline in sealing performance. High temperatures cause significant changes in the physical and chemical properties of materials, such as alterations in the coefficient of thermal expansion leading to deformation of the sealing structure, softening, melting, or even decomposition of the material, thus failing to maintain an effective seal and meet practical application requirements. This technological bottleneck restricts the further development of related high-temperature industries and the improvement of equipment performance, necessitating the development of new high-temperature resistant sealing materials or improvements to the performance of existing materials to overcome this predicament. Summary of the Invention

[0006] To address the problem of poor high-temperature resistance of existing sealing materials, this application provides a high-temperature resistant sealing material applicable to working conditions above 900℃ and its preparation method.

[0007] The high-temperature resistant sealing material provided in this application for use in conditions above 900℃ adopts the following technical solution:

[0008] A high-temperature resistant sealing material for use in conditions above 900℃, the raw materials of which, by mass percentage, include 20-30% polysilazane rubber, 30-40% organic cationic modified bentonite, 10-20% reinforcing fiber, 5-10% aluminum hydroxide, and 1-5% additives.

[0009] By adopting the above technical solution, the Si-N bond energy in the molecular structure of polysilazane rubber is relatively high, making it more difficult to break at high temperatures compared to the Si-O bond in traditional silicone rubber. As a precursor, polysilazane rubber undergoes a ceramic transformation at high temperatures (e.g., above 400℃), generating an inorganic ceramic phase mainly composed of silicon nitride and silicon carbide. This ceramic phase maintains extremely high structural stability and chemical inertness even above 900℃, providing a high-temperature skeletal support for the sealing material. Its excellent formability and flowability as a precursor ensure a tight fit between the molded material and the sealing interface, laying the foundation for effective sealing at high temperatures and guaranteeing a tight seal to prevent media leakage. At high temperatures, polysilazane rubber can form a complex and stable cross-linked network structure. This cross-linked structure not only enhances the strength and hardness of the rubber itself but also improves its resistance to harsh environments such as high temperatures and oxidation. Bentonite itself has a layered structure; after modification with organic cations, the organic cations enter the interlayer spaces of bentonite, increasing the interlayer spacing. This expanded interlayer structure not only accommodates more small molecules but also increases the specific surface area and adsorption capacity of bentonite. During material preparation and at medium and low temperatures, the layered structure of modified bentonite effectively blocks and adsorbs small molecules, improving sealing performance. Under high-temperature conditions, it acts as a high-temperature resistant inorganic filler, combining with polysilazane-converted ceramics to fill the material's voids, improving overall density and synergistically enhancing high-temperature performance with other components. Organic cationic modified bentonite can form good interfacial bonds with organic components such as polysilazane rubber. Reinforcing fibers act as a skeleton in the sealing material. Aluminum hydroxide decomposes at high temperatures, absorbing a large amount of heat. This endothermic effect lowers the surface temperature of the sealing material, slows down the thermal degradation process, and provides a flame-retardant effect. The resulting alumina is a high-temperature resistant substance that can form a heat-insulating layer on the surface of the sealing material, preventing further heat transfer to the interior, reducing the damage to the internal structure of the material caused by high temperatures, and improving the material's high-temperature resistance.

[0010] Optionally, the preparation method of the organic cationic modified bentonite is as follows:

[0011] Sodium carbonate is dissolved in water to prepare a sodium carbonate solution with a mass fraction of 2%-5%;

[0012] Bentonite and sodium-modifying agent solution are mixed and stirred at a solid-liquid ratio of 1:(5-10). After stirring, the mixture is allowed to stand for 12-24 hours, then filtered and washed until no carbonate ions are present in the washing liquid to obtain sodium-modified bentonite.

[0013] Dissolve hexadecyltrimethylammonium bromide in water to prepare an organic cationic surfactant solution with a mass fraction of 3%-8%. Mix sodium bentonite with the organic cationic surfactant solution at a mass ratio of 1:(8-12) and react at a temperature of 50-80℃ for 3-5 hours.

[0014] After the reaction was completed, the product was filtered and washed until no bromide ions were found in the eluent. The washed product was then dried at 60-80℃ to constant weight to obtain organic cationic modified bentonite.

[0015] By employing the above technical solution, bentonite typically contains polyvalent cations such as calcium and magnesium ions. These cations result in a compact interlayer structure and poor dispersibility in bentonite. Sodium carbonate, as a sodizing agent, allows its sodium ions in solution to undergo ion exchange reactions with calcium and magnesium ions in bentonite, displacing them and transforming the bentonite into sodium-based bentonite. This ion exchange increases the interlayer spacing of the bentonite, improving its dispersibility and swelling properties, making it easier to react with subsequent organic cationic surfactants. The static aging process allows for a more complete and uniform ion exchange reaction. During aging, sodium ions have sufficient time to diffuse into the interlayer of bentonite, fully exchanging with other cations. Simultaneously, the crystal structure of the bentonite undergoes certain adjustments and optimizations, improving the stability and performance of the sodized bentonite. Hexadecyltrimethylammonium bromide, as an organic cationic surfactant, allows its cationic portion (hexadecyltrimethylammonium ions) to undergo ion exchange reactions with sodium ions in the sodized bentonite, inserting itself into the interlayer of the bentonite. The insertion of these organic cations not only increases the interlayer spacing of bentonite but also transforms its surface properties from hydrophilic to lipophilic, improving its compatibility with organic components such as polysilazane rubber. Reacting at 50-80℃ for 3-5 hours ensures a stable reaction rate while preventing the decomposition or volatilization of the organic cationic surfactant due to excessive heat. A suitable reaction time allows the organic cations to fully penetrate the interlayer of bentonite, forming a stable organic-inorganic composite structure, thereby enhancing the performance of organically cationic modified bentonite.

[0016] Optionally, the reinforcing fiber includes either PBO fiber or PI fiber.

[0017] By employing the above technical solutions, PBO fibers (poly(p-phenylenebenzodioxazole) fibers), when used as a skeleton in sealing materials, can effectively prevent material deformation or collapse caused by high temperatures, maintaining the integrity of the sealing structure. PBO fibers have low thermal conductivity, reducing heat transfer to the interior of the sealing material under high-temperature environments. PI fibers exhibit strong resistance to oxygen, acids, alkalis, and other media. PI fibers combine rigidity and flexibility, forming a tight interfacial bond with polysilazane rubber and organic cationic modified bentonite.

[0018] Optionally, both the PBO fiber and the PI fiber undergo pre-oxidation treatment. The pre-oxidation temperature of the PBO fiber is 300-400℃ and the time is 1-2h. The pre-oxidation temperature of the PI fiber is 250-350℃ and the time is 2-3h. Argon gas is used for protection during the pre-oxidation process.

[0019] By employing the above technical solutions, PBO or PI fibers, after undergoing a specific pre-oxidation treatment, exhibit enhanced high-temperature instantaneous stability and improved bonding strength with the matrix. During the initial stages of material service at high temperatures, as the temperature rises from room temperature to 900°C, these fibers effectively provide mechanical support, preventing cracking or deformation due to insufficient strength during the ceramization transformation. Their remaining form and the transformed carbides continue to provide reinforcement.

[0020] Optionally, the aluminum hydroxide has a particle size of 100-500 nm.

[0021] By employing the above technical solution, nano-sized aluminum hydroxide particles possess an extremely large specific surface area. According to the relationship between specific surface area and particle size, the smaller the particle size, the larger the specific surface area. When the aluminum hydroxide particle size is in the range of 100-500 nm, its specific surface area is much larger than that of ordinary aluminum hydroxide. At high temperatures, a larger specific surface area means a greater contact area between aluminum hydroxide and oxygen, heat, etc., resulting in a more rapid and complete decomposition reaction, enabling more effective heat absorption and thus exerting a flame-retardant effect.

[0022] Optionally, the additives include nano-titanium dioxide and cerium oxide.

[0023] By adopting the above technical solution, the core function of the material changes when it enters the high-temperature stage (>500℃). Nano-titanium dioxide is a very stable ceramic phase at high temperatures, serving as a heat-resistant filler and improving the thermal stability of the matrix. More importantly, it can interact with components such as silica generated from the pyrolysis of polysilazane rubber, promoting the formation of a denser and more stable Si-O-Ti composite ceramic structure. This composite structure can effectively fill the pores and cracks generated during the high-temperature transformation process, improving the density and high-temperature structural strength of the sealing material. In high-temperature applications of sealing materials, under locally oxygen-rich conditions, cerium oxide can oxidize Ce³⁺ to Ce.4 Cerium oxide absorbs and fixes excess oxygen, preventing excessive oxygen erosion of organic components and reinforcing fibers, thereby inhibiting the oxidative degradation of the material. Under conditions of localized oxygen deficiency or the presence of pyrolytic carbon, cerium oxide can also absorb and fix excess oxygen by absorbing and fixing cerium. 4 The reduction of ⁺ to Ce³⁺ releases active oxygen, promoting the complete oxidation of residual carbonaceous components within the material and preventing structural loosening and strength reduction caused by carbon buildup. The composite ceramic phase formed by the synergistic effect of nano-titanium dioxide and cerium oxide at high temperatures exhibits superior thermal stability and density compared to single components, thus ensuring that the material maintains excellent sealing performance and service life even under extreme operating conditions above 900℃.

[0024] Secondly, this application provides a method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃, using the following technical solution:

[0025] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃ includes the following steps:

[0026] Place the polysilazane rubber into a high-speed mixer, start the mixer, and stir at 100-200 r / min. During the stirring process, add organic cationic modified bentonite and continue stirring for 10-15 minutes.

[0027] Add the reinforcing fiber to the above mixture, and increase the stirring speed to 300-500 r / min. Continue stirring for 15-20 minutes, then add aluminum hydroxide and additives, keep the stirring speed constant, and stir for another 20-30 minutes to form a uniform mixture.

[0028] Place the mixed material into a mold preheated to 150-200℃, close the mold, apply a pressure of 4-6MPa, and maintain for 30-60 minutes to obtain a high-temperature resistant sealing material.

[0029] Optionally, the molded sealing material is heated to 300-400°C in the furnace at a heating rate of 5-10°C / min, held at that temperature for 2-4 hours, and then cooled to room temperature in the furnace.

[0030] By employing the above technical solution, holding the material at 300-400℃ for 2-4 hours can further promote the complete crosslinking reaction of polysilazane rubber, increasing the crosslinking density of the material. Cooling the material to room temperature in the furnace allows it to shrink slowly, reducing internal stress caused by thermal expansion and contraction, and improving the dimensional stability and overall performance of the material. Detailed Implementation

[0031] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0032] Preparation Example 1

[0033] Weigh 20g of sodium carbonate and slowly add it to a beaker containing 980g of deionized water. Stir continuously with a glass rod until the sodium carbonate is completely dissolved to obtain a sodium carbonate solution with a mass fraction of 2%.

[0034] Weigh 200g of bentonite and add it to the prepared sodium-modifying agent solution. Stir at 200 rpm for 2 hours using an electric stirrer to ensure thorough mixing of the bentonite and the sodium-modifying agent solution. After stirring, transfer the mixture to a plastic container, seal it, and let it stand for 12 hours. Then, filter the mixture using a Buchner funnel and a vacuum pump to obtain a filter cake. Wash the filter cake repeatedly with deionized water, filtering after each wash and testing the eluent with barium chloride solution until no white precipitate (i.e., no carbonate ions) is produced in the eluent, thus obtaining sodium-modified bentonite.

[0035] Weigh 30g of hexadecyltrimethylammonium bromide and add it to a beaker containing 970g of deionized water. Heat to 50°C and stir until the hexadecyltrimethylammonium bromide is completely dissolved to obtain an organic cationic surfactant solution with a mass fraction of 3%.

[0036] The prepared sodium bentonite was added to the organic cationic surfactant solution at a mass ratio of 1:8. The mixture was then transferred to a reactor equipped with a stirrer and a heating device, and stirred at 300 r / min for 3 hours at 50°C.

[0037] After the reaction was complete, the reaction product was filtered using a Buchner funnel and a vacuum pump to obtain a filter cake. The filter cake was repeatedly washed with deionized water, filtered after each wash, and the eluent was tested with silver nitrate solution until no white precipitate (i.e., no bromide ions) was produced in the eluent. The washed filter cake was placed in an oven and dried at 60°C to constant weight to finally obtain organic cationic modified bentonite.

[0038] Preparation Example 2

[0039] Weigh 35g of sodium carbonate and add it to 965g of deionized water. Stir thoroughly to dissolve completely, thus preparing a sodium carbonate solution with a mass fraction of 3.5%.

[0040] Weigh 150g of bentonite and pour it into the sodium-modifying agent solution. Stir at 250 rpm for 2.5 hours. After stirring, place the mixture in a cool place to age for 18 hours. Then, perform filtration and washing operations. Test the washing solution with calcium chloride solution to ensure that there are no carbonate ions in the washing solution, thus obtaining sodium-modified bentonite.

[0041] Weigh 55g of cetyltrimethylammonium bromide and add it to 945g of deionized water. Heat the solution to 65°C and stir continuously until it is completely dissolved to obtain an organic cationic surfactant solution with a mass fraction of 5.5%.

[0042] Sodium bentonite was added to an organic cationic surfactant solution at a mass ratio of 1:10. The mixture was placed in a reactor and stirred at 350 rpm for 4 hours at 65°C.

[0043] After the reaction was complete, the mixture was filtered, and the filter cake was washed with deionized water. The washings were tested with silver nitrate solution until no bromide ions were found. The filter cake was then dried in an oven at 70°C to constant weight to obtain organic cationic modified bentonite.

[0044] Preparation Example 3

[0045] Weigh 50g of sodium carbonate, dissolve it in 950g of deionized water, stir well, and prepare a 5% sodium carbonate solution.

[0046] Weigh 100g of bentonite and add it to the sodium-modifying agent solution. Stir at 300 rpm for 3 hours using a high-speed stirrer. After stirring, seal the mixture and let it stand for 24 hours. Then filter and wash the mixture. Test the eluent with magnesium carbonate solution to confirm the absence of carbonate ions, thus obtaining sodium-modified bentonite.

[0047] Weigh 80g of hexadecyltrimethylammonium bromide and add it to 920g of deionized water. Heat the solution to 80°C and stir continuously until it is completely dissolved to obtain an organic cationic surfactant solution with a mass fraction of 8%.

[0048] Sodium bentonite was added to an organic cationic surfactant solution at a mass ratio of 1:12. The mixture was transferred to a reaction vessel and stirred at 400 rpm for 5 hours at 80°C.

[0049] After the reaction was complete, the filter cake was repeatedly washed with deionized water, and the washings were tested with silver nitrate solution until no bromide ions were found. The filter cake was then dried in an oven at 80°C to constant weight to obtain organic cationic modified bentonite.

[0050] Example 1

[0051] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃:

[0052] Raw material preparation:

[0053] Polysilazane rubber: Accurately weigh 250g.

[0054] Organic cationic modified bentonite: 350g of the bentonite prepared in Preparation Example 1 was weighed.

[0055] Reinforcing fiber: 150g of PBO fiber is used.

[0056] Aluminum hydroxide: Particle size 100-500nm, weigh 80g.

[0057] Additives: 12g of nano titanium dioxide and 8g of cerium oxide.

[0058] Mixing steps:

[0059] Place the polysilazane rubber into a high-speed mixer, start the mixer, and stir at a speed of 150 rpm. During the stirring process, slowly add the organic cationic modified bentonite and continue stirring for 12 minutes to allow the two to be initially mixed evenly.

[0060] Add silicon carbide fibers to the above mixture and increase the stirring speed to 400 r / min. Continue stirring for 18 minutes to ensure that the silicon carbide fibers are evenly dispersed in the mixture.

[0061] Next, add aluminum hydroxide and additives, and keep the stirring speed constant at 400 r / min for another 25 minutes to form a uniform mixture.

[0062] Molding steps:

[0063] The mixed material is placed into a mold preheated to 180°C. After the mold is closed, a pressure of 5MPa is applied and maintained for 45 minutes, so that the material is initially formed into the desired sealing material shape under high temperature and high pressure.

[0064] Post-processing steps:

[0065] The molded sealing material is removed from the mold and placed in a high-temperature furnace. The furnace temperature is raised to 350°C at a heating rate of 8°C / min and held for 3 hours, then cooled to room temperature in the furnace. Post-treatment further promotes the cross-linking reaction of the polysilazane rubber, improving the high-temperature resistance and mechanical properties of the sealing material. The final product is a high-temperature resistant sealing material suitable for applications above 900°C.

[0066] Example 2

[0067] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that it uses 200g of polysilazane rubber, 400g of organic cationic modified bentonite, 150g of reinforcing fiber, 80g of aluminum hydroxide, and 20g of additives.

[0068] Example 3

[0069] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that it uses 300g of polysilazane rubber, 300g of organic cationic modified bentonite, 150g of reinforcing fiber, 80g of aluminum hydroxide, and 20g of additives.

[0070] Example 4

[0071] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that no post-processing step is performed.

[0072] Example 5

[0073] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that the organic cationic modified bentonite is prepared by Example 2, while the other parameters remain unchanged.

[0074] Example 6

[0075] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900°C: The difference from Example 1 is that the organic cationic modified bentonite is prepared by Example 3, while the other parameters remain unchanged.

[0076] Example 7

[0077] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that the reinforcing fiber is PI fiber, while the other parameters remain unchanged.

[0078] Example 8

[0079] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that the reinforcing fiber is PBO fiber that has undergone pre-oxidation treatment. The pre-oxidation temperature of the PBO fiber is 350℃ and the time is 1.5h, while the other parameters remain unchanged.

[0080] Example 9

[0081] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that the reinforcing fiber is PBO fiber that has undergone pre-oxidation treatment. The pre-oxidation temperature of the PBO fiber is 300℃ and the time is 1h, while the other parameters remain unchanged.

[0082] Example 10

[0083] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that the reinforcing fiber is PBO fiber that has undergone pre-oxidation treatment. The pre-oxidation temperature of the PBO fiber is 400℃ and the time is 2h, while the other parameters remain unchanged.

[0084] Example 11

[0085] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that the reinforcing fiber is PI fiber after pre-oxidation treatment. The pre-oxidation temperature of the PI fiber is 300℃ and the time is 2.5h. Argon gas is used for protection during the pre-oxidation process. All other parameters remain unchanged.

[0086] Example 12

[0087] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that the reinforcing fiber is PI fiber after pre-oxidation treatment. The pre-oxidation temperature of the PI fiber is 250℃ and the time is 2h. Argon gas is used for protection during the pre-oxidation process. All other parameters remain unchanged.

[0088] Example 13

[0089] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that the reinforcing fiber is PI fiber after pre-oxidation treatment. The pre-oxidation temperature of the PI fiber is 350℃ and the time is 3h. Argon gas is used for protection during the pre-oxidation process. All other parameters remain unchanged.

[0090] Comparative Example 1

[0091] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900℃: The difference from Example 1 is that the organic cationic modified bentonite is replaced with an equal mass of bentonite with a purity > 95%.

[0092] Comparative Example 2

[0093] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900°C: The difference from Example 1 is that the polysilazane rubber is replaced with natural latex.

[0094] Comparative Example 3

[0095] A method for preparing a high-temperature resistant sealing material applicable to working conditions above 900°C: The difference from Example 1 is that the reinforcing fiber is replaced with an equal amount of acrylic fiber.

[0096] Performance testing methods

[0097] 1. High temperature resistance test

[0098] Thermogravimetric analysis (TGA): The temperature was increased to 1000℃ in a nitrogen atmosphere at a rate of 10℃ / min, and the mass retention rate at 900℃ was recorded.

[0099] High-temperature dimensional stability: The sample was placed in a muffle furnace at 900℃ and kept at that temperature for 24 hours. The dimensional change rate before and after heating was measured.

[0100] 2. Mechanical performance testing

[0101] A cylindrical specimen with a diameter of 50 mm and a thickness of 5 mm was used and loaded at a rate of 10 mm / min on a 200 kN press until failure.

[0102] 3. Sealing performance test

[0103] The differential pressure method was used to measure the volume of gas passing through the sample per unit time at 900℃ and 0.5MPa nitrogen pressure.

[0104] Group Mass retention rate at 900℃ (%) Dimensional change rate at 900℃ (%) Compressive strength (MPa) Gas leakage rate (ml / h) Example 1 92.3 +0.8 85 306 Example 2 91.5 +0.9 87 331 Example 3 93.1 +0.7 83 292 Example 4 90.3 +1.0 81 345 Example 5 92.8 +0.8 86 259 Example 6 93.0 +0.7 86 270 Example 7 91.7 +0.9 82 317 Example 8 95.6 +0.5 92 191 Example 9 94.8 +0.6 90 209 Example 10 95.2 +0.5 91 198 Example 11 94.8 +0.6 88 223 Example 12 94.2 +0.7 86 234 Example 13 94.5 +0.6 87 227 Comparative Example 1 78.2 +2.3 60 1872 Comparative Example 2 45.7 +5.8 -(break down) - (Invalid) Comparative Example 3 88.5 +1.5 83 416

[0105] Combining Example 1 and Comparative Examples 1-3 with Table 1, it can be seen that compared with Example 1, Comparative Example 1, which replaced the organic cationic modified bentonite with an equal mass of ordinary bentonite, experienced a decrease in its 900℃ mass retention rate from 92.3% to 78.2%, an increase in dimensional change rate from +0.8% to +2.3%, a decrease in compressive strength from 85 MPa to 60 MPa, and a surge in gas leakage rate to 1872 ml / h. This indicates that the unmodified bentonite, due to its tight interlayer structure and poor dispersibility, cannot form a good interfacial bond with the polysilazane rubber, resulting in insufficient density of the material at high temperatures, making it prone to thermal degradation and media leakage. Comparative Example 2, which replaced the polysilazane rubber with natural latex, showed a material mass retention rate of only 45.7% at 900℃, a dimensional change rate of +5.8%, and compressive strength that could not be measured due to decomposition, resulting in complete failure of sealing performance. This confirms the high bond energy advantage of Si-N bonds in polysilazane rubber. The cross-linked network formed at high temperatures is the core of maintaining the material's structural stability. In contrast, the molecular chains of natural latex are prone to breakage and degradation at high temperatures, making it unsuitable for operating conditions above 900℃. Comparative Example 3 replaced the reinforcing fiber with acrylic fiber. The test data shows that all performance characteristics were slightly weaker than those of the fiber used in this application.

[0106] Based on Examples 1-3 and Table 1, it can be seen that when the content of polysilazane rubber increased from 25% (Example 1) to 30% (Example 3) and the content of organic cationic modified bentonite decreased from 35% to 30%, the mass retention rate at 900℃ increased from 92.3% to 93.1%, the compressive strength increased from 85 MPa to 87 MPa, and the gas leakage rate decreased from 306 ml / h to 292 ml / h. This indicates that a moderate increase in the content of polysilazane rubber can strengthen the cross-linking network density and improve high-temperature stability, but it needs to be balanced with the filling effect of modified bentonite. Excessive rubber may lead to excessive flexibility and insufficient mechanical strength. The optimal ratio range (20-30% polysilazane rubber, 30-40% modified bentonite) can balance the stability of the cross-linking network and the filling reinforcement effect.

[0107] Combining Examples 1 and 4 with Table 1, it can be seen that Example 4 did not undergo post-processing, and all test results were lower than those of Example 1. Post-processing can improve the cross-linking density of the material. The untreated material is prone to structural relaxation under long-term high temperature due to insufficient cross-linking, resulting in faster degradation of sealing performance.

[0108] Combining Examples 1 and 5-6 with Table 1, it can be seen that the gas leakage rate of Example 5 (Preparation Example 2) decreased to 259 ml / h, and that of Example 6 (Preparation Example 3) decreased to 270 ml / h, both lower than the 306 ml / h of Example 1. This indicates that optimizing the sodium-modifying agent concentration (3.5-5%), reaction temperature (65-80℃), and time (4-5h) can improve the interlayer spacing and oleophilicity of the modified bentonite, making it more tightly bonded to the rubber matrix, thereby reducing the media penetration path. The higher concentration of sodium-modifying agent and the higher reaction temperature in Preparation Example 3 further improved the specific surface area and adsorption performance of the modified bentonite. The mass retention rate of Example 6 reached 93.0%, slightly higher than that of Example 1, indicating that more complete ion exchange and organic cation insertion can enhance the high-temperature oxidation resistance of the material.

[0109] Combining Examples 1 and 7-13 with Table 1, it can be seen that in Example 7, after using PI fiber, the mass retention rate at 900℃ was 91.7% and the compressive strength was 82 MPa, slightly lower than that of PBO fiber (Example 1), but the gas leakage rate of 317 ml / h was slightly higher. This is because although PI fiber is resistant to chemical corrosion, its tensile strength (lower than 5.8 GPa of PBO fiber) and modulus are relatively low, and its skeletal support is slightly weaker, making it more suitable for working conditions with high requirements for media resistance but low mechanical load. Pre-oxidized PBO fiber (Examples 8-10) increased the mass retention rate to 94.8-95.6%, the compressive strength to 90-92 MPa, and reduced the leakage rate to 191-209 ml / h. This is because pre-oxidation at 300-400℃ promotes the cyclization and cross-linking of PBO fiber molecular chains, forming a more stable aromatic structure and reducing chain segment breakage at high temperatures. After pre-oxidation at 250-350℃ (argon protection) (Examples 11-13), the PI fiber exhibits a mass retention rate of 94.2-94.8%, a compressive strength of 86-88 MPa, and a leakage rate of 223-234 ml / h. Argon protection prevents oxidative degradation of the PI fiber, and the three-dimensional network structure formed by pre-oxidation significantly improves its dimensional stability at high temperatures.

[0110] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high temperature resistant sealing material applied to a working condition above 900℃, characterized in that, The raw materials include polysilazane rubber 20-30%, organic cation modified bentonite 30-40%, reinforcing fiber 10-20%, aluminum hydroxide 5-10%, and auxiliary agent 1-5% by mass percentage, and the sum of the weights of the components in the raw materials is 100%; the preparation method of the organic cation modified bentonite is as follows: Dissolve sodium carbonate in water to prepare a sodiumizing agent solution with a mass fraction of 2%-5%; Mix bentonite and the sodiumizing agent solution according to a solid-liquid ratio of 1: (5-10) and stir, after stirring is completed, let the mixed solution stand for 12-24 h, then filter and wash until no carbonate ions are present in the washing liquid, to obtain sodiumized bentonite; Dissolve cetyltrimethylammonium bromide in water to prepare an organic cation surfactant solution with a mass fraction of 3%-8%, mix the sodiumized bentonite and the organic cation surfactant solution according to a mass ratio of 1: (8-12), and react at a temperature of 50-80℃ for 3-5 h; After the reaction is completed, filter the product and wash until no bromide ions are present in the washing liquid, dry the washed product at a temperature of 60-80℃ to constant weight, to obtain organic cation modified bentonite.

2. The high temperature resistant sealing material for operating conditions above 900℃ of claim 1, characterized in that: The reinforcing fiber includes one of PBO fiber or PI fiber.

3. The high temperature resistant sealing material for operating conditions above 900 °C according to claim 2, characterized in that: Both the PBO fiber and the PI fiber are subjected to pre-oxidation treatment, the pre-oxidation temperature of the PBO fiber is 300-400℃ and the time is 1-2 h, the pre-oxidation temperature of the PI fiber is 250-350℃ and the time is 2-3 h, and argon is used for protection during the pre-oxidation process.

4. The high temperature resistant sealing material for operating conditions above 900℃ of claim 1, characterized in that: The particle size of the aluminum hydroxide is 100-500 nm.

5. The high temperature resistant sealing material for operating conditions above 900 °C according to claim 1, characterized in that: The auxiliary agent includes nanometer titanium dioxide and cerium oxide.

6. A method for preparing the high-temperature-resistant sealing material for use in a temperature above 900 °C according to any one of claims 1 to 5, characterized in that: The method includes the following steps: Put polysilazane rubber into a high-speed mixer, start the mixer, and stir at 100-200 r / min, and add organic cation modified bentonite during stirring, and continuously stir for 10-15 min; Add reinforcing fiber to the above mixture, increase the stirring speed to 300-500 r / min, continue to stir for 15-20 min, add aluminum hydroxide and auxiliary agent, keep the stirring speed unchanged, and stir for another 20-30 min to form a uniform mixture; Put the mixed material into a mold preheated to 150-200℃, apply a pressure of 4-6 MPa after the mold is closed, and keep for 30-60 min to obtain a high-temperature-resistant sealing material.

7. The method according to claim 6, characterized in that: After the sealing material is formed, increase the furnace temperature to 300-400℃ at a heating rate of 5-10℃ / min, keep for 2-4 h, and then cool to room temperature with the furnace.