Insulating gasket for nuclear power plants and method for manufacturing same

Abstract

This application relates to the field of sealing materials, specifically disclosing an insulating sealing gasket for nuclear power equipment and its preparation method. The insulating sealing gasket for nuclear power equipment of this application comprises an outer layer material and an inner layer material, with the outer layer material covering the surface of the inner layer material. The outer layer material is composed of the following components by mass percentage: 50%-60% silane coupling agent modified phenolic resin, 35%-45% composite fiber, and 3%-5% epoxy functionalized silane bonding accelerator. The inner layer material is composed of the following components by mass percentage: 45%-55% fluorine-modified epoxy resin, 30%-40% polyimide fiber, and 10%-20% high-temperature resistant nano-reinforced microspheres. The insulating sealing gasket for nuclear power equipment of this application has the advantages of high pressure resistance and high temperature resistance.

Description

Technical Field

[0001] This application relates to the field of sealing materials, and more specifically, to an insulating sealing gasket for nuclear power equipment and a method for preparing the same. Background Technology

[0002] In the field of nuclear power generation, the safe and stable operation of nuclear power equipment is of paramount importance. As key sealing components, the sealing rings in nuclear power equipment play a crucial role in preventing media leakage, maintaining stable internal pressure, and ensuring nuclear safety. Their operating environment is extremely harsh, requiring them to withstand high temperatures, high pressures, strong radiation, and various corrosive chemical media, while maintaining excellent sealing and mechanical properties during long-term operation.

[0003] Currently available sealing materials, such as ordinary rubber and polyurethane, are widely used in conventional industrial settings and possess a certain sealing capability. However, their pressure resistance and temperature resistance have significant shortcomings. Ordinary rubber generally has a temperature resistance range of -20℃ to 120℃. When the temperature exceeds this range, the rubber gradually hardens or softens, leading to a sharp decline in sealing performance. Its pressure resistance is typically only a few megapascals, making it difficult to cope with high-pressure environments. While polyurethane materials perform reasonably well in terms of wear resistance, their upper temperature limit is generally 80℃-150℃, and they are prone to creep under high pressure, affecting the sealing effect.

[0004] The nuclear power industry has extremely stringent requirements for sealing. During operation, the reactor cooling system of a nuclear power plant experiences internal pressures reaching 15 MPa and temperatures exceeding 300°C, accompanied by intense neutron radiation. Under these extreme conditions, ordinary sealing materials are simply inadequate. Even a tiny leak in a nuclear power plant due to the failure of ordinary sealing materials can trigger a serious safety accident, leading to the leakage of radioactive materials and causing incalculable harm to the environment and human health. Therefore, a new type of sealing gasket needs to be developed for use in nuclear power equipment. Summary of the Invention

[0005] In order to improve the high pressure resistance and high temperature resistance of sealing materials so that they can meet the requirements for safe use of nuclear power equipment, this application provides an insulating sealing gasket for nuclear power equipment and a method for preparing the same.

[0006] The technical solution provided in this application for an insulating sealing gasket for nuclear power equipment is as follows:

[0007] An insulating sealing gasket for nuclear power equipment includes an outer layer material and an inner layer material, wherein the outer layer material covers the surface of the inner layer material; the outer layer material is composed of the following components in weight percentage: 50%-60% silane coupling agent modified phenolic resin, 35%-45% composite fiber, and 3%-5% epoxy functionalized silane bonding accelerator; the inner layer material is composed of the following components in weight percentage: 45%-55% fluorine-containing modified epoxy resin, 30%-40% polyimide fiber, and 10%-20% high-temperature resistant nano-reinforced microspheres;

[0008] The fluorinated modified epoxy resin is prepared by a method comprising the following steps: by weight, 80-120 parts of bisphenol A type epoxy resin and 5-10 parts of reactive diluent are mixed at 80-85°C, 0.5-1.5 parts of catalyst are added, and then 8-12 parts of fluoroanhydride modifier are added, and the mixture is reacted at 80-90°C for 2-3 hours.

[0009] By adopting the above technical solutions, the outer layer material uses silane coupling agent-modified phenolic resin as the matrix. The silane coupling agent modifies the phenolic resin, effectively toughening the matrix and reducing brittleness. A high proportion of composite fibers is introduced to form a dense reinforcing network, greatly improving fracture toughness through crack pinning and deflection mechanisms, and forming a load-bearing skeleton to withstand extreme high pressure. The inner layer material uses fluorine-modified epoxy resin as the matrix. The introduction of fluorine-containing segments significantly improves the resin matrix's resistance to chemical corrosion while maintaining excellent adhesion and toughness. This ensures the bonding between the inner and outer layers and allows for a certain degree of deformation under pressure, improving the sealing effect. The addition of polyimide fibers greatly enhances the high-temperature resistance and radiation resistance of the inner layer material, preventing rapid aging in strong radiation environments. High-temperature resistant nano-reinforced microspheres, through nanoscale dispersion, effectively induce crazes and pinning cracks, playing a dual role of toughening and strengthening, improving the fatigue resistance and crack resistance of the inner layer material under harsh working conditions.

[0010] Optionally, the composite fiber includes aramid fiber and insulating carbon fiber, and the mass ratio of the insulating carbon fiber to the aramid fiber is (3-4):2.

[0011] By adopting the above technical solution, aramid fibers possess high strength, high modulus, and excellent heat resistance, effectively distributing external loads and preventing compression failure of the gasket under high pressure. Insulated carbon fibers retain their high modulus, excellent heat resistance, and creep resistance, while surface insulation treatment completely eliminates their conductivity, ensuring the overall electrical insulation performance of the gasket. Combining the two in a (3-4):2 mass ratio ensures that carbon fibers provide the main rigid support skeleton, while aramid fibers fill the skeleton gaps and contribute their excellent toughness. Their synergistic effect achieves the optimal distribution of the fiber reinforcement phase in the phenolic resin matrix, thus forming a stable reinforcing network in the outer layer material that effectively disperses stress and inhibits crack propagation, maximizing the pressure resistance and structural integrity of the gasket.

[0012] Optionally, the insulating carbon fiber is prepared by the following method: reflux oxidation of the carbon fiber in concentrated nitric acid at 60-80°C, followed by washing and drying, impregnation in tetraethyl orthosilicate hydrolysate, and then heat treatment at 500-600°C for 1-2 hours.

[0013] By employing the above technical solution, the concentrated nitric acid reflux oxidation step effectively etches and introduces oxygen-containing functional groups onto the carbon fiber surface. This significantly improves the surface energy of the carbon fiber, providing a foundation for the firm adhesion of subsequent coatings. The sol-gel method constructs a dense, continuous, and chemically extremely stable inorganic insulating layer on the carbon fiber surface. Silica itself is an excellent insulator, resistant to high temperatures and radiation, and can completely isolate the internal conductive graphite crystals. The high-temperature heat treatment step promotes further condensation and solidification of the amorphous silica coating, eliminating microscopic defects, thereby achieving higher coating density, bonding strength, and insulation reliability.

[0014] Optionally, the high-temperature resistant nano-reinforced microspheres are polyimide microspheres or silica nano-microspheres modified with a silane coupling agent, and the particle size of the high-temperature resistant nano-reinforced microspheres is 100-300 nm.

[0015] By adopting the above technical solution and selecting polyimide microspheres, the effect is that the microspheres themselves possess ultra-high heat resistance and radiation resistance comparable to polyimide fibers. They can act as "elastic nodes" and be uniformly dispersed in the epoxy resin matrix, absorbing energy through their own deformation, thus improving the material's toughness without sacrificing its temperature resistance. Silica nanospheres modified with a silane coupling agent are selected. The rigid nanoparticles can greatly restrict the movement of polymer chain segments through interfacial interactions, thereby improving the modulus, hardness, and heat resistance of the matrix material. Simultaneously, the silane coupling agent ensures the interfacial compatibility between the nano-silica and the epoxy resin matrix, preventing agglomeration. Limiting the particle size to 100-300 nm ensures that the microspheres can be fully and uniformly dispersed in the matrix; too small a particle size easily leads to agglomeration, while too large a particle size may become a stress concentration point.

[0016] Optionally, the inner layer material may also contain a three-dimensional mesh reinforcement skeleton, which is prepared by 3D printing technology from one or two of silicon carbide ceramic powder and silicon nitride ceramic powder.

[0017] By employing the above technical solution, when the sealing gasket is subjected to excessive pressure, the polymer composite material may undergo irreversible plastic deformation or creep. The three-dimensional mesh skeleton composed of silicon carbide or silicon nitride ceramics, as a rigid internal support structure with a temperature resistance exceeding 2000℃, bears the majority of the mechanical load and limits the excessive deformation of the polymer matrix. This ensures the stability of the gasket thickness and the integrity of the sealing interface under long-term high-pressure service conditions.

[0018] Optionally, the method for preparing the three-dimensional mesh-reinforced skeleton includes:

[0019] By weight, 60-80 parts of ceramic powder, 1-5 parts of dispersant and 20-40 parts of solvent are mixed and ball-milled, and then 25-35 parts of short-cut carbon fibers are added and dispersed to form a slurry.

[0020] The slurry was 3D printed using binder jetting technology, with a layer thickness of 100-150μm. After printing, it was cured and set by infrared curing.

[0021] The shaped green body is degreased and then sintered at 1800-2000℃ for 2-3 hours under argon protection.

[0022] By employing the aforementioned technical solutions, binder jet 3D printing technology can precisely manufacture a continuous three-dimensional mesh-like porous structure. This design ensures both the macroscopic strength of the skeleton and provides space for the injection and anchoring of the polymer matrix, achieving mechanical interlocking. Adding chopped carbon fibers to the slurry primarily enhances toughness. Pure ceramic skeletons are inherently brittle; the introduction of chopped carbon fibers effectively hinders crack propagation through bridging and pull-out mechanisms, transforming brittle fracture into quasi-plastic fracture, significantly improving the fracture toughness and thermal shock resistance of the skeleton. The final high-temperature sintering step ensures that ceramic particles form a strong neck and a dense sintered body through diffusion mass transfer, thereby achieving the final high strength and stability.

[0023] Secondly, this application provides a method for preparing an insulating sealing gasket for nuclear power equipment, employing the following technical solution:

[0024] A method for preparing an insulating sealing gasket for nuclear power equipment includes the following steps:

[0025] S1: Silane coupling agent modified phenolic resin, composite fiber and bonding accelerator are blended at 100-120℃ and then hot-pressed at 140-160℃ and 8-12MPa pressure for 15-25 minutes to obtain the outer layer material preform.

[0026] S2: Heat the fluorinated modified epoxy resin to 80-85℃, add high-temperature resistant nano-reinforced microspheres and ultrasonically disperse for 20-30 minutes, then add polyimide fiber and stir to mix, to obtain an inner layer material premix, and pre-cur it at 95-105℃ for 60-80 minutes to obtain an inner layer material preform.

[0027] S3: Place the inner layer material preform in the outer layer material preform and hot-press it at 145-155℃ and 13-15MPa pressure for 40-50 minutes; then perform step-curing under nitrogen protection: heat up to 120-130℃ at a rate of 1-2℃ / min and hold for 2 hours, continue to heat up to 150-160℃ and hold for 4 hours, then heat up to 180-190℃ and hold for 6 hours, and then cool with the furnace to obtain the insulating sealing gasket.

[0028] By employing the above technical solutions, the hot-pressing process of the outer pre-forming layer allows the phenolic resin to fully flow and impregnate the fibers, achieving initial cross-linking and forming a dense pre-shaped body. The dispersion and pre-curing of the inner premix ensures uniform dispersion of the nanospheres and polyimide fibers, preventing agglomeration, and pre-curing provides the system with sufficient initial strength for subsequent operations. The stepped post-curing process, through programmed temperature control, ensures a stable and thorough cross-linking reaction of the epoxy resin. Slow heating avoids internal stress and bubbles caused by intense exothermic reactions; phased, long-term holding at different temperatures ensures the gradual formation and improvement of the cross-linking network from low to high, ultimately resulting in a cured epoxy resin with high cross-linking density, low internal stress, and excellent thermal stability. This is the core process ensuring that the inner layer material maintains excellent sealing and mechanical properties even at high temperatures.

[0029] Optionally, the three-dimensional mesh reinforcement skeleton is placed into the inner layer material premix before the pre-curing described in step S2.

[0030] By employing the above technical solution, the skeleton is placed in the uncured inner layer material premix before pre-curing, allowing the highly fluid resin slurry to fully penetrate and fill the three-dimensional network pores of the skeleton. The subsequent pre-curing process causes the resin to initially gel around the skeleton, fixing it in the predetermined position. This method effectively prevents skeleton displacement during subsequent composite processes and ensures that, after final curing, the polymer matrix and ceramic skeleton achieve an ideal state of mechanical interlocking and stress transfer.

[0031] Optionally, after the step-curing process described in step S3, the obtained insulating sealing gasket is subjected to surface plasma treatment. The plasma treatment uses a mixture of argon and oxygen in a volume ratio of (7-4):1. The plasma power is 300-400W, the treatment time is 120-140 seconds, and the pressure is 45-55Pa.

[0032] By employing the above technical solution, the use of an argon-oxygen mixed gas achieves the effect of physically bombarding the polymer surface of the sealing gasket with argon ions, generating microscopic roughness and increasing the effective contact area. Simultaneously, the oxygen plasma introduces a large number of oxygen-containing polar functional groups onto the surface through chemical reactions, significantly increasing the surface energy. Optimized power, time, and pressure settings ensure that the activation process is efficient and uniform, achieving sufficient activation depth while avoiding excessive damage to the material. The wettability of the treated sealing gasket surface with the metal flange is improved, effectively preventing capillary penetration of the medium at the interface, thus maintaining an extremely reliable static sealing effect under long-term vibration and thermal cycling conditions.

[0033] In summary, this application has the following beneficial effects:

[0034] 1. Because this application uses a composite structure design with a rigid outer layer covering an elastic inner layer, and combines the reinforcing network formed by a high proportion of composite fibers in the outer layer with the rigid support of the three-dimensional ceramic skeleton in the inner layer, a multi-level pressure-bearing system is constructed. Together, these systems endow the gasket with excellent resistance to compression creep and mechanical strength, enabling it to withstand pressure stably for a long time while maintaining structural integrity and reliable sealing.

[0035] 2. In this application, a fully insulating material system is preferably used and the resin matrix is ​​modified to be heat resistant, so that the sealing gasket not only remains stable under high temperature of 300°C and strong radiation conditions, but also has a long-lasting high volume resistivity.

[0036] 3. This application preferably employs an interface modification and optimized step-curing process to ensure a strong chemical bond and mechanical interlock between the polymer matrix and various reinforcing fibers, inner and outer layer materials, and the ceramic skeleton. This strong interfacial bonding ensures that stress can be effectively transferred and dispersed under thermal cycling and mechanical vibration, preventing interlayer delamination. This allows the complementary performance advantages of each component to achieve a synergistic increase in overall performance and an extended service life. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the insulating sealing gasket obtained by the scheme of Embodiment 1 of this application. Detailed Implementation

[0038] 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.

[0039] Preparation Example 1

[0040] A method for preparing a fluorinated modified epoxy resin:

[0041] In a dry container, add 100 kg of bisphenol A type epoxy resin (E-51) with an epoxy value of 0.51 eq / 100 g and 7.5 kg of butyl glycidyl ether as an active diluent.

[0042] Heat the container to 83±2℃ and mechanically stir at 250r / min until the system is homogeneous and transparent.

[0043] While maintaining the temperature and stirring, add 1.0 kg of triethylamine catalyst to the system and continue stirring for 12 minutes.

[0044] Using a constant pressure dropping device, slowly add 10 kg of perfluorooctanoic anhydride (PFOA). After the addition is complete, increase the stirring speed to 550 r / min, control the reaction temperature at 85±5℃, and continue the reaction for 2.5 hours.

[0045] After the reaction was completed, the reaction product was allowed to cool naturally to room temperature (25°C) in the container to obtain fluorine-modified epoxy resin.

[0046] Preparation Example 2

[0047] A method for preparing a fluorinated modified epoxy resin: The difference from preparation example 1 is that 80 kg of bisphenol A type epoxy resin, 8 kg of perfluorooctanoic anhydride, 0.5 kg of triethylamine, and 5 kg of butyl glycidyl ether are weighed.

[0048] Preparation Example 3

[0049] A method for preparing a fluorinated modified epoxy resin: The difference from preparation example 1 is that 120 kg of bisphenol A type epoxy resin, 12 kg of perfluorooctanoic anhydride, 1.5 kg of triethylamine, and 10 kg of butyl glycidyl ether are weighed.

[0050] Preparation Example 4

[0051] A method for insulating carbon fiber:

[0052] Raw materials to be prepared: PAN-based carbon fiber cloth (T300 grade, 1K), concentrated nitric acid (68wt%), tetraethyl orthosilicate (TEOS), anhydrous ethanol, deionized water, ammonia (28wt%).

[0053] Take 10 kg of carbon fiber cloth and immerse it completely in a container containing 200 L of concentrated nitric acid. Turn on the reflux condenser and place the reaction system at a constant temperature of 70°C. Turn on the electric stirrer at 150 r / min for reflux oxidation treatment for 3 hours. After the reaction is complete, allow the system to cool, remove the carbon fiber, and transfer it to a large amount of deionized water for repeated filtration and washing until the filtrate is neutral (pH≈7). Place the washed carbon fiber in a forced-air drying oven and dry it at 80°C for 2 hours to obtain oxidized carbon fiber.

[0054] In a dry, clean environment, add 100L of anhydrous ethanol, 20L of deionized water, and 10L of tetraethyl orthosilicate (TEOS) sequentially. Under magnetic stirring, add ammonia to adjust the pH of the mixture to 9-10, at which point the solution becomes a translucent sol. Completely immerse the dried oxidized carbon fibers in the prepared TEOS hydrolysate, ensuring complete fiber wetting. Allow the mixture to stand at room temperature (25±5℃) for 24 hours to allow the sol-gel reaction to proceed fully, forming a silica (SiO2) gel coating in situ on the carbon fiber surface. After impregnation, remove the carbon fibers and allow excess liquid to drip naturally onto a stainless steel mesh frame. Then, age the mixture in air for 6 hours to further cure the coating.

[0055] The aged carbon fibers with gel coating were placed in a heating furnace. High-purity nitrogen was introduced into the furnace tubes as a protective gas at a flow rate of 50 L / min. The temperature was increased from room temperature to 150°C at a rate of 3°C / min and held for 30 minutes to thoroughly remove residual solvents and moisture. The temperature was then increased to 550°C at a rate of 5°C / min and held at this temperature for 1.5 hours. After heat treatment, the carbon fibers were cooled to 30°C (room temperature) in the furnace before being removed.

[0056] Preparation Example 5

[0057] A method for insulating carbon fiber: The method differs from Preparation Example 4 in that the temperature is increased from room temperature to 150°C at a rate of 3°C / min and held for 30 minutes to thoroughly remove residual solvent and moisture. The temperature is then increased to 500°C at a rate of 5°C / min and held at this temperature for 1.5 hours.

[0058] Preparation Example 6

[0059] A method for insulating carbon fiber: The method differs from Preparation Example 4 in that the temperature is increased from room temperature to 150°C at a rate of 3°C / min and held for 30 minutes to thoroughly remove residual solvent and moisture. The temperature is then increased to 600°C at a rate of 5°C / min and held at this temperature for 1.5 hours.

[0060] Preparation Example 7

[0061] A method for fabricating a three-dimensional mesh-reinforced skeleton:

[0062] Raw material preparation:

[0063] Silicon carbide ceramic powder: purity ≥ 99%, D50 = 5μm;

[0064] Short-cut carbon fibers with a length of 2-4 mm and a diameter of 10-50 μm are selected, soaked in 3% nitric acid solution for 1 hour, washed with water until neutral, and then dried.

[0065] Polyvinyl alcohol is used as the binder, and ammonium polyacrylate is used as the dispersant.

[0066] 70 kg of silicon carbide ceramic powder, 3 kg of ammonium polyacrylate, and 30 kg of deionized water were loaded into a large ball mill, and 210 kg of zirconia grinding balls were added (ball-to-material ratio 3:1). The mixture was ball-milled at 300 r / min for 2.5 hours to obtain a uniform ceramic slurry.

[0067] Add 30 kg of short-cut carbon fiber to the ceramic slurry, and then ultrasonically disperse the mixture in an industrial ultrasonic dispersion device at 800 W power for 25 minutes to form a uniform printing slurry.

[0068] The printing paste was loaded into the feed system of the binder jet 3D printer. The layer thickness was set to 125 μm, the printing speed to 65 mm / s, and the binder jet volume to be 15% of the printing paste weight. Printing was performed layer by layer according to the preset 3D mesh structure. After printing, the green body was transferred to an infrared curing device and cured at 80°C for 30 minutes.

[0069] The cured green body was placed in an industrial atmosphere furnace and degreased by heating to 400±10℃ at 2℃ / min and holding for 2 hours under air atmosphere. Then, high-purity argon gas (99.99% purity) was switched to protection, and the temperature was increased to 1900±50℃ at 5℃ / min and held for 2.5 hours for sintering. After cooling to below 100℃ in the furnace, the green body was removed, yielding a three-dimensional mesh-reinforced skeleton.

[0070] Preparation Example 8

[0071] A method for preparing a three-dimensional mesh-reinforced skeleton: The difference from preparation example 7 is that 60 kg of silicon carbide ceramic powder and 25 kg of deionized water are used, while the other components and preparation method remain the same.

[0072] Preparation Example 9

[0073] A method for preparing a three-dimensional mesh-reinforced skeleton: The difference from preparation example 7 is that 80 kg of silicon carbide ceramic powder and 35 kg of deionized water are used, while the other components and preparation method remain the same.

[0074] Preparation Example 10

[0075] A method for preparing a three-dimensional mesh-reinforced skeleton: The difference from preparation example 7 is that 25 kg of short-cut carbon fiber is used, while the other components and preparation method remain the same.

[0076] Preparation Example 11

[0077] A method for preparing a three-dimensional mesh-reinforced skeleton: The difference from preparation example 7 is that 35 kg of short-cut carbon fiber is used, while the other components and preparation method remain the same.

[0078] Preparation Example 12

[0079] A method for preparing a three-dimensional mesh-reinforced skeleton: The difference from preparation example 7 is that 70 kg of silicon nitride ceramic powder is used, while the other components and preparation method remain the same.

[0080] Preparation Example 13

[0081] A method for preparing a three-dimensional mesh-reinforced skeleton: The difference from preparation example 7 is that a composite powder of 35 kg silicon carbide + 35 kg silicon nitride is used, while the other components and preparation method remain the same.

[0082] Preparation Example 14

[0083] A method for preparing a three-dimensional mesh-reinforced skeleton: the difference from preparation example 7 is that short-cut carbon fibers are not added.

[0084] Example 1

[0085] A method for preparing an insulating sealing gasket for nuclear power equipment:

[0086] Prepare the following materials:

[0087] Outer layer material raw materials: 55 kg of silane coupling agent modified phenolic resin (blended and modified by PSI-520 type silane coupling agent), 14.5 kg of 1313 aramid fiber, 25.5 kg of insulating carbon fiber (prepared according to the method of preparation example 4), and 4 kg of Silquest™ A-186 epoxy functionalized silane bonding accelerator.

[0088] Inner layer material raw materials: 50 kg of fluorine-modified epoxy resin (prepared according to the method of Preparation Example 1), 35 kg of Vespel® SP-1 polyimide fiber, and 15 kg of high-temperature resistant nano-reinforced microspheres (using polyimide microspheres with a particle size of 200 nm).

[0089] Three-dimensional mesh-reinforced skeleton: prepared by the method of Preparation Example 7.

[0090] Outer preform preparation:

[0091] Silane coupling agent-modified phenolic resin, aramid fiber, insulating carbon fiber, and bonding accelerator were blended in an internal mixer at 110°C for 45 minutes. The mixture was then loaded into a mold and hot-pressed at 150°C and 10 MPa for 20 minutes. After pressing, the mixture was water-cooled to below 50°C and demolded to obtain the outer preform.

[0092] Inner layer preform preparation:

[0093] Fluorine-modified epoxy resin was heated to 83°C, and high-temperature resistant nano-reinforced microspheres were added and ultrasonically dispersed for 25 minutes. Polyimide fibers were then added, and the mixture was mechanically stirred at 120 rpm for 30 minutes. The mixture was poured into a mold to half its capacity, and a pre-fabricated three-dimensional mesh reinforcement skeleton was placed inside. The remaining mixture was then poured in. The mixture was pre-cured at 100°C for 70 minutes to obtain an inner layer preform containing the reinforcement skeleton.

[0094] Hot pressing composite:

[0095] The inner preform is accurately placed in the outer preform, and then hot-pressed in a hot press mold at 150°C and 14.5MPa pressure for 45 minutes.

[0096] Stepped post-curing:

[0097] Transfer the composite to a temperature-controlled oven and perform post-curing under nitrogen protection according to the following procedure:

[0098] Increase the temperature to 125℃ at a rate of 1.5℃ / min and hold for 2 hours, then increase the temperature to 155℃ and hold for 4 hours, and finally increase the temperature to 185℃ and hold for 6 hours.

[0099] The furnace is cooled to room temperature to obtain the final insulating sealing gasket product.

[0100] Example 2

[0101] A method for preparing an insulating sealing gasket for nuclear power equipment: The difference from Example 1 is that the outer layer material consists of 50 kg of silane coupling agent modified phenolic resin, 45 kg of composite fiber, and 5 kg of epoxy functionalized silane bonding accelerator.

[0102] Example 3

[0103] A method for preparing an insulating sealing gasket for nuclear power equipment: The difference from Example 1 is that the outer layer material includes 60 kg of silane coupling agent modified phenolic resin, 35 kg of composite fiber, and 5 kg of epoxy functionalized silane bonding accelerator.

[0104] Example 4

[0105] A method for preparing an insulating sealing gasket for nuclear power equipment: The difference from Example 1 is that the inner layer material includes 50 kg of fluorinated modified epoxy resin, 30 kg of polyimide fiber and 20 kg of high temperature resistant nano-reinforced microspheres.

[0106] Example 5

[0107] A method for preparing an insulating sealing gasket for nuclear power equipment: The difference from Example 1 is that the inner layer material includes 45 kg of epoxy resin, 40 kg of polyimide fiber and 15 kg of nanopolymer microspheres containing dynamic covalent bonds.

[0108] Example 6

[0109] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the mass ratio of the insulating carbon fiber to the aramid fiber is 3:2.

[0110] Example 7

[0111] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the mass ratio of the insulating carbon fiber to the aramid fiber is 4:2.

[0112] Example 8

[0113] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the fluorine-modified epoxy resin is prepared by Example 2.

[0114] Example 9

[0115] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that it is a fluorinated modified epoxy resin, prepared by Preparation Example 3.

[0116] Example 10

[0117] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the insulating carbon fiber is prepared by Example 5.

[0118] Example 11

[0119] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the insulating carbon fiber is prepared by Preparation Example 6.

[0120] Example 12

[0121] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the three-dimensional mesh reinforcing skeleton is prepared by Example 8.

[0122] Example 13

[0123] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the three-dimensional mesh reinforcing skeleton is prepared by Example 9.

[0124] Example 14

[0125] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the three-dimensional mesh reinforcing skeleton is prepared by Example 10.

[0126] Example 15

[0127] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the three-dimensional mesh reinforcing skeleton is prepared by Example 11.

[0128] Example 16

[0129] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the three-dimensional mesh reinforcing skeleton is prepared by Example 12.

[0130] Example 17

[0131] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the three-dimensional mesh reinforcing skeleton is prepared by Example 13.

[0132] Example 18

[0133] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the three-dimensional mesh reinforcing skeleton is prepared by Example 14.

[0134] Example 19

[0135] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that a three-dimensional mesh reinforcing skeleton is not added.

[0136] Example 20

[0137] A method for preparing an insulating sealing gasket for nuclear power equipment: The difference from Example 1 is that the insulating sealing gasket, after step-curing treatment, is fed into the working chamber of a plasma processing device and processed according to the following precise parameters:

[0138] Secure the sealing gasket to the sample stage, ensuring the surface to be treated is fully exposed. Close the chamber and activate the vacuum system to reduce the pressure inside the chamber to below 5 Pa.

[0139] A mixture of high-purity argon and oxygen is introduced, with the volume ratio of the two gases strictly controlled at 6:1.

[0140] The gas flow rate is precisely controlled by a mass flow meter to maintain a total gas flow rate of 500 sccm.

[0141] Maintaining a stable working pressure of 50Pa, using 350W radio frequency power to excite plasma, processing time of 130 seconds, keeping the electrodes at a fixed electrode spacing of 100mm, and maintaining the processing temperature below 40℃ through a water cooling system.

[0142] After the treatment is completed, stop the radio frequency power and gas supply, re-evacuate the chamber to below 5 Pa, maintain this state for 10 minutes to remove residual active materials, and slowly fill the chamber with high-purity nitrogen to atmospheric pressure. Remove the treated insulating sealing gasket.

[0143] Example 21

[0144] A method for preparing an insulating sealing gasket for nuclear power equipment: The difference from Example 20 is that after the step-curing treatment, the obtained insulating sealing gasket is subjected to surface plasma treatment using a mixture of argon and oxygen in a volume ratio of 7:1.

[0145] Example 22

[0146] A method for preparing an insulating sealing gasket for nuclear power equipment: The difference from Example 20 is that after the step-curing treatment, the obtained insulating sealing gasket is subjected to surface plasma treatment using a mixture of argon and oxygen in a volume ratio of 4:1.

[0147] Example 23

[0148] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 20 is that the plasma power is 300W, the processing time is 120 seconds, and the pressure is 45Pa in the plasma treatment.

[0149] Example 24

[0150] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 20 is that the plasma power is 400W, the processing time is 140 seconds, and the pressure is 55Pa in the plasma treatment.

[0151] Example 25

[0152] A method for preparing an insulating sealing gasket for nuclear power equipment: The difference from Example 1 is that the high-temperature resistant nano-reinforced microspheres are silica nanospheres modified with KH-550 silane coupling agent.

[0153] Comparative Example 1

[0154] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the phenolic resin is not modified by a silane coupling agent.

[0155] Comparative Example 2

[0156] A method for preparing an insulating sealing gasket for nuclear power equipment: the difference from Example 1 is that the composite fiber in the outer layer material component is replaced with aramid fiber.

[0157] Comparative Example 3

[0158] A preparation method of an insulating gasket for nuclear power equipment: The difference from Example 1 is that nano-polymer microspheres containing dynamic covalent bonds are not added to the inner layer material.

[0159] Comparative Example 4

[0160] A preparation method of an insulating gasket for nuclear power equipment: The difference from Example 1 is that polyimide fibers are not added to the inner layer material.

[0161] Comparative Example 5

[0162] A preparation method of an insulating gasket for nuclear power equipment: The difference from Example 1 is that the carbon fibers in the composite fibers are not treated at all.

[0163] Comparative Example 6

[0164] A preparation method of an insulating gasket for nuclear power equipment: The difference from Example 1 is that the fluorine-modified epoxy resin is replaced with a conventional epoxy resin.

[0165] Testing method

[0166] Place the gasket sample in a high-temperature test chamber, set the test chamber temperature to 300 °C, and control the heating rate at about 5 °C / min. The sample is maintained at 300 °C for 24 hours, and the appearance of the sample is observed every 1 hour during this period to check for any deformation, cracking, color change, etc. After the high-temperature treatment is completed, take out the sample, wait for it to cool to room temperature, and then conduct an appearance inspection and size measurement of the sample again, and compare it with the initial state. If the change in the sample diameter does not exceed ±2%, and the change rate of hardness does not exceed ±10%, it is considered that the high-temperature resistance performance of the gasket meets the requirements.

[0167] Install the gasket sample in a specific test mold. The mold simulates the actual installation method of the gasket in nuclear power equipment to ensure that the gasket is installed tightly and correctly. Slowly apply pressure through a hydraulic testing machine, and set the pressure increase rate to 0.5 MPa / min. Continuously observe the deformation of the gasket. When the pressure reaches 15 MPa, maintain this pressure for 24 hours, and closely monitor the pressure change and the state of the gasket during this period. After the pressure holding is completed, slowly release the pressure, measure the thickness of the gasket again, compare it with the initial thickness, and calculate the thickness change rate. If the thickness change rate does not exceed ±5%, it is considered qualified.

[0168] The insulating gasket is installed within the sealing groove of the sealing cavity, ensuring correct installation and that the gasket is free from twisting or damage. Helium gas is introduced into the sealing cavity at 1 MPa using a pressurized gas source, gradually increasing the pressure to 15 MPa to simulate the operating pressure of nuclear power equipment, while a pressure regulator is used to maintain pressure stability. A helium mass spectrometer leak detector is then used to perform a comprehensive inspection of the sealing cavity for 120 minutes. If the helium mass spectrometer leak detector does not detect a leak signal during the inspection, meaning the leak rate is below the equipment's detection limit, the gasket is considered to have good sealing performance.

[0169] Table 1 Test Results

[0170] Sample number High temperature resistance (diameter change rate, %) High temperature resistance (hardness change rate, %) High pressure resistance (thickness change rate, %) Sealing performance assessment Example 1 +1.1 -3.8 -2.5 qualified Example 2 +1.5 -5.1 -3.1 qualified Example 3 +1.2 -4.0 -2.8 qualified Example 4 +1.8 -6.2 -3.5 qualified Example 5 +1.4 -5.5 -3.3 qualified Example 6 +1.3 -4.8 -2.9 qualified Example 7 +1.6 -5.8 -3.6 qualified Example 8 +1.7 -6.0 -3.4 qualified Example 9 +1.1 -4.2 -2.7 qualified Example 10 +1.4 -5.3 -3.0 qualified Example 11 +1.5 -5.6 -3.2 qualified Example 12 +1.3 -4.9 -2.8 qualified Example 13 +1.2 -4.6 -2.6 qualified Example 14 +1.5 -5.4 -3.1 qualified Example 15 +1.4 -5.1 -2.9 qualified Example 16 +1.1 -4.4 -2.5 qualified Example 17 +1.2 -4.7 -2.7 qualified Example 18 +1.8 -7.0 -6.8 qualified Example 19 +2.0 -7.5 -7.2 qualified Example 20 +1.1 -4.0 -2.4 qualified Example 21 +1.0 -3.9 -2.3 qualified Example 22 +1.3 -4.6 -2.6 qualified Example 23 +1.2 -4.3 -2.5 qualified Example 24 +1.1 -4.1 -2.4 qualified Example 25 +1.3 -4.9 -2.9 qualified Comparative Example 1 +2.6 -9.5 -5.2 Unqualified Comparative Example 2 +2.1 -7.0 -4.5 Unqualified Comparative Example 3 +1.7 -8.8 -4.1 Unqualified Comparative Example 4 +2.3 -10.6 -3.5 Unqualified Comparative Example 5 +1.8 -7.0 -4.5 Unqualified Comparative Example 6 +2.8 -11.8 -5.0 Unqualified

[0171] As can be seen from Examples 1 and 2-3 and Table 1, adjusting the ratio of resin to fiber in the outer layer material does not affect the performance of the examples. This indicates that the formulation range of this application is reasonable and the process tolerance is good.

[0172] As can be seen from Examples 1 and 4-5 and Table 1, adjusting the ratio of polyimide fibers to nanospheres in the inner layer material does not affect the performance of the prepared sealing gaskets. Moreover, when the proportion of polyimide fibers is higher (Example 5), the overall performance is better.

[0173] As can be seen from Examples 1 and 6-7 and Table 1, adjusting the mass ratio of insulating carbon fiber to aramid fiber in the outer composite fiber ensures that the material properties meet the requirements. However, an excessively high proportion of carbon fiber (Example 7) will slightly increase the permanent compression deformation of the material.

[0174] As can be seen from Examples 1 and 8-11 and Table 1, the sealing gaskets prepared with fluorinated modified epoxy resin (Examples 8-9) or insulating carbon fibers treated with different heat treatment temperatures (Examples 10-11) all have qualified performance. The overall performance of the raw materials used in Examples 1 and 9 and the 550℃ treatment conditions (comparison of Examples 1, 10, and 11) is better.

[0175] As can be seen from Examples 1 and 12-19, and in conjunction with Table 1, the introduction of a three-dimensional mesh reinforcement skeleton can significantly improve the compressive strength and creep resistance of the material (comparison between Examples 1 and 19). The type and amount of ceramic powder in the skeleton (Examples 12, 13, 16, 17) and the addition of chopped carbon fibers (Examples 14, 15) all affect the performance. Among them, the skeleton without chopped carbon fiber toughening (Example 18) is qualified, but its performance is the worst among the examples, which proves the importance of fiber toughening for ceramic skeletons.

[0176] As can be seen from Examples 1 and 20-24, and in conjunction with Table 1, the performance of the sealing gasket was slightly improved after adding plasma surface treatment (Example 20). Adjusting the plasma treatment parameters (Examples 21-24) maintained excellent product performance, indicating that the process has good operational flexibility.

[0177] As can be seen from Examples 1 and 25 and Table 1, the use of surface-modified silica nanospheres or polyimide microspheres for the inner layer can both achieve good reinforcement and toughening effects, with comparable performance.

[0178] As can be seen from Examples 1 and Comparative Examples 1-6, combined with Table 1, the absence of any key component or process will lead to unsatisfactory performance. Specifically: unmodified phenolic resin (Comparative Example 1) results in high brittleness and significant deformation; the outer layer using only aramid fiber (Comparative Example 2) results in insufficient rigidity and large compression deformation; the lack of nanospheres in the inner layer (Comparative Example 3) results in decreased toughness and poor hardness retention; the lack of polyimide fiber in the inner layer (Comparative Example 4) results in severely insufficient heat resistance; the lack of insulation treatment on carbon fiber (Comparative Example 5) results in poor interfacial bonding and performance degradation; and the use of conventional epoxy resin (Comparative Example 6) results in poor matrix heat resistance and overall performance deterioration. This, from the opposite perspective, collectively confirms the necessity and synergy of the overall system design of this application.

[0179] 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. An insulating sealing gasket for nuclear power equipment, characterized in that, The insulating sealing gasket comprises an outer layer material and an inner layer material, wherein the outer layer material covers the surface of the inner layer material; the outer layer material is composed of the following components by mass percentage: 50%-60% silane coupling agent modified phenolic resin, 35%-45% composite fiber, and 3%-5% epoxy functionalized silane bonding accelerator; the inner layer material is composed of the following components by mass percentage: 45%-55% fluorine-containing modified epoxy resin, 30%-40% polyimide fiber, and 10%-20% high-temperature resistant nano-reinforced microspheres; The fluorinated modified epoxy resin is prepared by a method comprising the following steps: by weight, 80-120 parts of bisphenol A type epoxy resin and 5-10 parts of reactive diluent are mixed at 80-85°C, 0.5-1.5 parts of catalyst are added, and then 8-12 parts of fluoroanhydride modifier are added, and the mixture is reacted at 80-90°C for 2-3 hours.

2. The insulating sealing gasket for nuclear power equipment according to claim 1, characterized in that, The composite fiber includes aramid fiber and insulating carbon fiber, and the mass ratio of the insulating carbon fiber to the aramid fiber is (3-4):

2.

3. The insulating sealing gasket for nuclear power equipment according to claim 2, characterized in that, The insulating carbon fiber is prepared by the following method: the carbon fiber is refluxed and oxidized in concentrated nitric acid at 60-80°C, washed and dried, then impregnated in tetraethyl orthosilicate hydrolysate, and subsequently heat-treated at 500-600°C for 1-2 hours.

4. The insulating sealing gasket for nuclear power equipment according to claim 1, characterized in that, The high-temperature resistant nano-reinforced microspheres are polyimide microspheres or silica nanospheres modified with a silane coupling agent, and the particle size of the high-temperature resistant nano-reinforced microspheres is 100-300 nm.

5. The insulating sealing gasket for nuclear power equipment according to claim 1, characterized in that, The inner layer material also contains a three-dimensional mesh reinforcement skeleton, which is prepared by 3D printing technology from one or two of silicon carbide ceramic powder and silicon nitride ceramic powder.

6. The insulating sealing gasket for nuclear power equipment according to claim 5, characterized in that, The method for preparing the three-dimensional mesh-reinforced skeleton includes: By weight, 60-80 parts of ceramic powder, 1-5 parts of dispersant and 20-40 parts of solvent are mixed and ball-milled, and then 25-35 parts of short-cut carbon fibers are added and dispersed to form a slurry. The slurry was 3D printed using binder jetting technology, with a layer thickness of 100-150μm. After printing, it was cured and set by infrared curing. The shaped green body is degreased and then sintered at 1800-2000℃ for 2-3 hours under argon protection.

7. A method for preparing an insulating sealing gasket for nuclear power equipment as described in any one of claims 1-6, characterized in that, Includes the following steps: S1: Silane coupling agent modified phenolic resin, composite fiber and bonding accelerator are blended at 100-120℃ and then hot-pressed at 140-160℃ and 8-12MPa pressure for 15-25 minutes to obtain the outer layer material preform. S2: Heat the fluorinated modified epoxy resin to 80-85℃, add high-temperature resistant nano-reinforced microspheres and ultrasonically disperse for 20-30 minutes, then add polyimide fiber and stir to mix, to obtain an inner layer material premix, and pre-cur it at 95-105℃ for 60-80 minutes to obtain an inner layer material preform. S3: Place the inner layer material preform in the outer layer material preform and hot-press composite it at 145-155℃ and 13-15MPa pressure for 40-50 minutes. Subsequently, under nitrogen protection, a stepped post-curing process was carried out: the temperature was increased to 120-130℃ at a rate of 1-2℃ / min and held for 2 hours, then increased to 150-160℃ and held for 4 hours, and then increased to 180-190℃ and held for 6 hours before being cooled in the furnace to obtain the insulating sealing gasket.

8. The method for preparing an insulating sealing gasket for nuclear power equipment according to claim 7, characterized in that, Before pre-curing as described in step S2, the three-dimensional mesh reinforcement skeleton is placed into the inner layer material premix.

9. The method for preparing an insulating sealing gasket for nuclear power equipment according to claim 7, characterized in that, After the step-curing process described in step S3, the obtained insulating sealing gasket is subjected to surface plasma treatment. The plasma treatment uses a mixture of argon and oxygen in a volume ratio of (7-4):

1. The plasma power is 300-400W, the treatment time is 120-140 seconds, and the pressure is 45-55Pa.

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