Modified RPTFE gasket containing SILCAR62XT resin and preparation method thereof

Abstract

The invention relates to the technical field of sealing materials, and particularly discloses a modified RPTFE gasket containing SILCAR62XT resin and a preparation method of the modified RPTFE gasket. The composition of the gasket mainly comprises RPTFE (Resin Polytetrafluoroethylene) resin, SILCAR62XT Dupont resin, a 5B component, fluorinated graphene and an interface bridging agent. The preparation method mainly comprises the following steps: performing fluorine-containing gas plasma activation on the compound filler to improve the interfacial compatibility; uniform dispersion of all the components is realized through ultrasonic-assisted mixing and melting granulation; multi-section gradient pressurization hot press molding is combined with a programmed slow cooling and annealing process, so that the compactness of the material is optimized, and internal stress is eliminated. The gasket is suitable for complex sealing working conditions of high temperature, high pressure, strong corrosion and wide temperature range vibration, and the creep resistance, the chemical stability and the fatigue resistance are remarkably improved; the preparation method is stable in process, is beneficial to obtaining products with high dimensional precision and uniform structure, and is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sealing materials, more particularly, it relates to a modified RPTFE gasket containing SILCAR62XT resin and a preparation method thereof. BACKGROUND

[0002] Polytetrafluoroethylene has become the core basic material in the field of sealing gaskets due to its excellent chemical corrosion resistance, high temperature resistance and low friction coefficient, and is widely used in key industries such as chemical industry, petroleum, pharmaceutical industry, aerospace, etc. Among them, the reinforced polytetrafluoroethylene effectively improves the defect that the mechanical property of pure polytetrafluoroethylene is weak by introducing filling and reinforcing materials in the polytetrafluoroethylene matrix, and further expands its application in complex working condition scenes such as chemical reaction kettle, petroleum transportation pipeline and high temperature fluid sealing device. It is a key component to ensure the fluid transportation and reaction process sealing of various industrial equipment, and is directly related to the safety and stability of the production process, which can effectively avoid the risks of equipment damage, environmental pollution and economic loss caused by medium leakage.

[0003] However, the traditional reinforced polytetrafluoroethylene gasket and the existing modified products still have core technical bottlenecks that are difficult to break through in actual harsh working condition applications: under the superposition of high temperature and high pressure in static or dynamic working conditions, the material is prone to significant creep relaxation, accompanied by problems of insufficient mechanical strength and wear resistance, which leads to gradual deformation of the gasket sealing surface, increase of sealing gap, and further causes rapid decay of sealing performance, which cannot meet the long-term stable sealing use requirement. The modification scheme in the prior art for solving this problem mainly uses a single filler to optimize the performance. For example, although graphite filling can improve the sealing performance to a certain extent, it is easy to be oxidized and fail under high temperature working conditions. Glass fiber filling can enhance the mechanical strength, but it is easy to cause wear and damage to the sealing surface. Although carbon fiber modification can improve the rigidity, it significantly reduces the chemical corrosion resistance of the material, and it is difficult to realize the synergistic improvement of high temperature and high pressure anti-creep relaxation ability, mechanical strength and wear resistance. This performance shortcoming seriously restricts the reliable application of reinforced polytetrafluoroethylene gaskets in harsh sealing scenes such as high temperature and high pressure. SUMMARY

[0004] In order to solve the problem of weak anti-creep relaxation ability, insufficient mechanical strength and wear resistance of the RPTFE gasket under high temperature and high pressure in the prior art, the present application provides a modified RPTFE gasket containing SILCAR62XT resin and a preparation method thereof.

[0005] In the first aspect, the present application provides a modified RPTFE gasket containing SILCAR62XT resin, which adopts the following technical scheme:

[0006] A modified RPTFE gasket containing SILCAR62XT resin comprises the following components in parts by weight: 80-85 parts of RPTFE resin; 10-14 parts of SILCAR62XT DuPont resin; 4-6 parts of 5B component; 1-3 parts of fluorinated graphene; and 0.8 to 1 part of interfacial bridger.

[0007] By employing the above technical solution, RPTFE resin and a specific range of SILCAR62XT DuPont resin are used to construct the core blend matrix. The fluorine groups in SILCAR62XT DuPont resin form good structural compatibility with the fluorocarbon chains of RPTFE resin, enhancing the structural stability of the blend structure through intermolecular chain interactions and strengthening the matrix's high-temperature resistance and deformation resistance. The 5B component is a specific blend of boron nitride and silicon carbide. The layered structure of boron nitride optimizes sealing performance and improves heat conduction efficiency through interlayer slippage, while the high hardness of silicon carbide enhances the material's wear resistance and mechanical strength. The two components complement each other functionally to achieve a synergistic improvement in sealing, wear resistance, and thermal conductivity. The specific blending ratio ensures that the two components are uniformly dispersed in the matrix and fully exert their synergistic effect. Fluorinated graphene, leveraging its layered structure and compatibility with the fluorinated matrix, constructs a layer-particle-matrix composite structure. The layered barrier effect enhances sealing performance and thermal conductivity efficiency, while simultaneously forming spatial complementarity with the 5B component particles, filling the internal voids of the matrix to reduce system defects. The interface bridging agent is a silane-fluoroalkyl bifunctional compound. The silane functional group forms a chemical bond with the hydroxyl groups on the surface of component 5B and fluorinated graphene, while the fluoroalkyl functional group has a compatibility effect with the fluorocarbon chains of RPTFE and SILCAR62XT DuPont resin. The interfacial bonding strength between the inorganic filler component and the organic matrix is ​​improved through the synergistic bridging of the bifunctional group, avoiding the problems of uneven dispersion or interfacial delamination when blending multiple components. Through the precise selection and proportioning design of specific components, the structural compatibility and functional synergy between the components are achieved.

[0008] Preferably, the RPTFE resin has an average particle size of 20-50 μm and a melt index of 1.2-2.0 g / 10 min; the SILCAR62XT DuPont resin has a fluorine content of ≥65 wt% and a heat distortion temperature of ≥150℃.

[0009] By adopting the above technical solutions, the average particle size range of RPTFE resin is specifically adapted to balance the resin particle dispersion and matrix compactness, avoiding uneven mixing caused by particle agglomeration or excessively large particle gaps that affect the compactness of the blend matrix. Its melt index range is adapted to the process to ensure suitable fluidity at subsequent processing temperatures, guaranteeing uniform blending with other components and avoiding component stratification or molding defects during the molding process. The high fluorine content of DuPont SILCAR62XT resin ensures a sufficient proportion of fluorocarbon bonds in the molecular chain, forming high compatibility with the fluorocarbon chains of RPTFE resin. This enhances the interfacial bonding strength through intermolecular forces, while simultaneously strengthening the chemical corrosion resistance of the blend system to resist the erosion of strong acid and alkali media. The limited heat distortion temperature ensures that the resin maintains structural stability during processing stages such as raw material drying, heating and mixing, and hot pressing, preventing premature softening and deformation due to processing temperature, providing a fundamental support for the high-temperature resistance of the final gasket product.

[0010] Preferably, the 5B component is a compound of boron nitride and silicon carbide, and the weight ratio of boron nitride to silicon carbide is 1:1 to 1:3; the particle size D of the boron nitride is... 50 The particle size of silicon carbide is 5-15 μm, with a purity ≥99 wt%; 50 The particle size is 10-20 μm, and the purity is ≥98 wt%.

[0011] By adopting the above technical solution, the boron nitride and silicon carbide compound design of component 5B overcomes the performance limitations of single fillers through the complementary functions of the two components. A specific weight ratio range provides a key adaptation for fully realizing the synergistic effect, ensuring the formation of a uniformly dispersed composite filler structure and avoiding functional imbalance caused by excessive aggregation of a single component. The boron nitride particle size parameters are specifically optimized to match the particle size of the matrix resin, ensuring its layered structure is uniformly embedded in the blend system, fully utilizing the sealing optimization and heat conduction functions brought about by interlayer slippage. High purity limits prevent the introduction of impurities that affect the interfacial bonding effect and reduce defects in the blend system. The silicon carbide particle size range is reasonably matched with that of boron nitride, forming a space-filling advantage through complementary particle sizes, reducing internal voids in the matrix. Its high hardness characteristics improve the wear resistance and mechanical support strength of the system. High purity requirements ensure the structural integrity of silicon carbide and prevent impurities from weakening its mechanical properties. Through the synergistic limitation of the particle size and purity of the two components, combined with a specific compounding ratio, the 5B component is ensured to stably exert a synergistic effect of sealing, wear resistance, and thermal conductivity.

[0012] Preferably, the fluorinated graphene has a lateral dimension of 1-10 μm; the interface bridging agent is a silane-fluoroalkyl bifunctional compound.

[0013] By adopting the above technical solution, the lateral size range of fluorinated graphene is specifically optimized to precisely match the overall particle size of the blend system, ensuring that its sheet structure is uniformly dispersed in the matrix. This fully leverages the sheet barrier effect to enhance sealing performance and thermal conductivity, while simultaneously forming spatial complementarity with the 5B component particles, filling the internal voids of the matrix to reduce system defects and improve the structural integrity and density of the blend system. The interface bridger is a silane-fluoroalkyl bifunctional compound with precise interfacial compatibility. The silane functional groups form chemical bonds with the 5B component and the surface active groups of the fluorinated graphene, while the fluoroalkyl functional groups exhibit compatibility with the fluorocarbon chains of RPTFE and SILCAR62XT DuPont resin. This bifunctional synergistic bridging enhances the interfacial bonding strength between the inorganic filler component and the organic matrix, avoiding uneven dispersion or interfacial delamination problems during multi-component blending, and ensuring that each component forms a stable and synergistic system.

[0014] Secondly, this application provides a method for preparing a modified RPTFE gasket containing SILCAR62XT resin, using the following technical solution:

[0015] A method for preparing a modified RPTFE gasket containing SILCAR62XT resin includes the following steps:

[0016] S1. Raw material pretreatment: RPTFE resin and SILCAR62XT DuPont resin are dried separately; boron nitride and silicon carbide in component 5B are mixed to obtain a first mixture; fluorinated graphene and interfacial bridge agent are premixed with the first mixture to obtain a second mixture; the second mixture is subjected to plasma activation treatment in a fluorine-containing gas atmosphere.

[0017] S2. Mixing and Granulation: The dried RPTFE resin, SILCAR62XT DuPont resin, and the plasma-activated second mixture are mixed at room temperature in the first stage; then the mixture is heated and mixed at a higher temperature in the second stage, and ultrasonic-assisted dispersion is performed simultaneously in the heating and mixing stage to obtain a uniform blend; the uniform blend is melt-extruded and granulated to obtain modified RPTFE particles.

[0018] S3. Compression molding: The modified RPTFE particles are added to a preheated mold and pre-pressed to obtain a gasket blank; then the gasket blank is hot-pressed through a multi-stage gradient pressing method.

[0019] S4. Cooling and post-treatment: The hot-pressed gasket is slowly cooled to room temperature in a programmed manner; after demolding, the resulting gasket is annealed to finally obtain the modified RPTFE gasket.

[0020] By adopting the above technical solution, the raw material pretreatment stage employs a design combining segmented premixing and plasma activation in a fluorinated gas atmosphere: first, boron nitride and silicon carbide of component 5B are mixed to form a first mixture, then fluorinated graphene and an interfacial bridger are added and premixed to obtain a second mixture, avoiding agglomeration caused by direct mixing of multiple components; the second mixture is then activated by plasma in a fluorinated gas atmosphere, introducing fluorinated active groups on the surface of the filler component, enhancing its compatibility with the fluorinated resin matrix, improving the surface activity of the filler component to promote interaction with the interfacial bridger, and strengthening the interfacial bonding force between the inorganic filler phase and the organic matrix. The mixing and granulation stage employs a design combining segmented mixing with ultrasonic-assisted dispersion: the room temperature mixing stage achieves initial uniform dispersion of each component, avoiding stratification caused by differences in flowability of components in the early stage of heating; during the heating mixing stage, ultrasonic-assisted dispersion is applied simultaneously, using the ultrasonic cavitation effect to break up component agglomerates, further improving the uniformity of the blended material; subsequent melt extrusion granulation transforms the uniform blended material into modified particles with uniform particle size, ensuring consistency in subsequent pressing molding. The pressing and molding process employs a design combining pre-pressing and multi-stage gradient hot pressing: mold preheating and room-temperature pre-pressing initially densify the modified particles, forming a stable gasket blank and avoiding uneven particle slippage caused by direct hot pressing; multi-stage gradient pressing adapts to the structural changes of the blank during hot pressing, gradually applying pressure to promote blank densification while releasing internal stress generated during molding, reducing internal porosity and stress concentration. The programmed slow cooling and annealing processes in the cooling and post-processing stages work synergistically: programmed slow cooling adjusts the cooling rate according to the thermal expansion characteristics of the gasket in different temperature ranges, avoiding excessive internal and external temperature differences caused by rapid cooling, which generates thermal stress and prevents cracking and delamination defects in the gasket; subsequent annealing further eliminates residual stress inside the gasket, optimizes the internal crystal structure of the material, and improves the dimensional stability and structural integrity of the gasket. All process stages work together to form a complete quality control chain. By controlling key aspects such as mixing uniformity, interfacial bonding force, and molding stress, the synergistic effect of the multi-component system is fully realized, ensuring product molding stability and suitability for industrial production.

[0021] Preferably, in step S1, the drying is carried out at 80-100℃ for 2-3 hours; the plasma activation treatment takes 10-15 minutes and has a processing power of 300-500W; the fluorine-containing gas atmosphere is a mixture of argon and carbon tetrafluoride; and the volume ratio of argon to carbon tetrafluoride is 9:1-8:2.

[0022] By employing the above technical solutions, the drying parameters are specifically adapted to efficiently remove moisture from RPTFE resin and SILCAR62XT DuPont resin, avoiding defects such as bubbles generated during subsequent mixing and molding. Simultaneously, it ensures the structural stability of both resins during drying, preventing premature softening and deformation due to improper temperature or time. Plasma activation utilizes a mixed fluorinated gas atmosphere of argon and carbon tetrafluoride to introduce fluorinated active groups onto the surface of the filler component, enhancing its compatibility with the fluorinated resin matrix and increasing the surface activity of the filler component to promote interaction with the interfacial bridger. The activation time and power parameters are precisely controlled to balance the surface modification effect and structural integrity of the filler component, ensuring sufficient surface activation to strengthen interfacial bonding while avoiding over-activation that could damage the component structure. The optimized gas volume ratio ensures the precision of the fluorinated modification, ensuring that the surface characteristics of the activated filler component are compatible with the blend system, and improving the interfacial bonding strength between the inorganic filler phase and the organic matrix.

[0023] Preferably, in step S2, the room temperature mixing in the first stage is carried out at a rotation speed of 500-800 r / min for 5-8 min; the heating mixing involves heating the material to 120-140℃ and carrying it at a rotation speed of 1000-1200 r / min for 10-15 min; the ultrasonic-assisted dispersion treatment has a frequency of 25-35 kHz, a power of 300-400 W, and a treatment time of 5-10 min.

[0024] By adopting the above technical solution, the parameters for room temperature mixing are precisely matched to achieve initial uniform dispersion of each component. Through reasonable speed and time matching, the dried resin and pretreated filler components are fully contacted, avoiding component agglomeration caused by over-mixing. Simultaneously, the room temperature environment avoids stratification caused by differences in component flowability during the initial heating phase. The parameters for heating and mixing are synergistically matched: the heating temperature provides the resin with suitable flowability, enhancing the fusion ability between components; the corresponding speed and time promote deep blending of each component, strengthening the uniformity of the blend system; the simultaneously applied ultrasonic-assisted dispersion, through specific frequency and power matching, utilizes the cavitation effect to break up residual component agglomerates, supplementing the deficiencies of mechanical mixing. Combined with reasonable processing time, this improves the uniformity of the blended material dispersion, avoiding fluctuations in finished product performance due to uneven dispersion. Through the synergistic effect of segmented mixing and ultrasonic assistance, the uniformity and stability of the blended material are guaranteed.

[0025] Preferably, in step S2, the ultrasonic wave is applied through a probe immersed in the mixture, and the immersion depth of the probe is 1 / 3 to 1 / 2 of the height of the mixture; the extrusion temperature of the melt extrusion granulation is 300-350℃, and the screw speed is 150-200 r / min.

[0026] By adopting the above technical solution, the ultrasonic waves are applied using an immersion probe method, allowing the ultrasonic waves to act directly on the interior of the mixture, improving energy transfer efficiency, avoiding energy loss caused by indirect application, and ensuring that the ultrasonic dispersion effect is precisely applied to component agglomerates. The optimized design of the probe immersion depth ensures that the ultrasonic energy uniformly covers the material system, guaranteeing that most of the mixture is penetrated by the ultrasonic action to effectively break down residual agglomerates. Simultaneously, it avoids excessive immersion leading to excessive ultrasonic intensity in the bottom material causing component structure damage, or insufficient immersion preventing the upper material from receiving sufficient ultrasonic action. The temperature and screw speed parameters of melt extrusion granulation are synergistically matched. The extrusion temperature range ensures that the RPTFE resin and SILCAR62XT DuPont resin are fully melted, while avoiding excessively high temperatures that could lead to resin degradation or functional component failure. The screw speed range is precisely matched to the material flowability at that temperature, further enhancing the uniform mixing of each component through reasonable shearing action, controlling the material residence time in the screw, ensuring a stable and controllable granulation process, and producing modified granules with uniform particle size and composition.

[0027] Preferably, in step S3, the preheating temperature of the mold is 100-120℃; the pre-pressing is carried out at room temperature with a pressure of 15-20MPa and held for 5-10 minutes; the hot pressing is carried out at 380-420℃, and the multi-stage gradient pressurization method includes: firstly, holding at a pressure of 20-25MPa for 1-1.5 hours, then increasing the pressure to 28-32MPa at a rate of 0.5-1MPa / min, and continuing to hold at this pressure for 1-1.5 hours.

[0028] By adopting the above technical solutions, the mold preheating temperature is specifically adapted to avoid a sudden temperature drop caused by contact between the modified particles and the cold mold. This ensures that the particles maintain a suitable initial state after filling the mold, providing a temperature basis for the continuous pre-pressing and hot pressing, and reducing molding stress caused by temperature differences. The parameters for room temperature pre-pressing are adapted, and through appropriate pressure and holding time, the modified particles are rapidly and initially densified, forming a stable and uniformly structured gasket blank. This avoids particle slippage and misalignment caused by direct hot pressing, laying a structural foundation for subsequent densification enhancement during hot pressing. The temperature range for hot pressing ensures sufficient melting and flow of RPTFE resin and SILCAR62XT DuPont resin, providing thermodynamic conditions for deep integration and densification between components. The multi-stage gradient pressurization method adapts to the structural change pattern of the preform during hot pressing: the initial pressure and holding time allow the molten resin to fully impregnate the filler components and gradually remove the voids inside the preform; subsequently, by increasing the pressure at a stable rate and extending the holding time, the preform is further densified, while the internal stress generated during molding is gradually released, avoiding defects such as porosity and cracking in the preform due to stress concentration under constant pressure. Through the synergistic adaptation of temperature and gradient pressurization, the density of the finished gasket structure is ensured.

[0029] Preferably, in step S4, the programmed slow cooling is performed at a rate of 5-10°C / min; the programmed slow cooling specifically includes: a stage of cooling from the hot-pressing temperature to 250°C at a cooling rate of 8-10°C / min; a stage of cooling from 250°C to 100°C at a cooling rate of 5-8°C / min; a stage of cooling from 100°C to room temperature at a cooling rate of 3-5°C / min; the annealing treatment is performed at 200-220°C for 2-3 hours and under a nitrogen or argon protective atmosphere.

[0030] By adopting the above technical solution, the programmed slow cooling employs a staged rate control design to adapt to the thermophysical properties and structural transformation laws of the material in different temperature ranges. During the high-temperature stage after hot pressing, the material is in a critical transition period from a molten state to a solid state. The cooling rate at this stage avoids excessive molecular flow leading to structural inhomogeneity, laying the foundation for the subsequent crystallization process. The intermediate temperature range is the main stage of material crystallization; slowing down the cooling rate allows the molecular chains to arrange themselves in an orderly manner, reducing crystallization defects. In the low-temperature stage, the material structure gradually stabilizes, and further reducing the cooling rate eliminates residual thermal stress caused by the internal and external temperature differences. The annealing temperature range is specifically adapted to provide sufficient energy for the release of residual stress within the material, while avoiding excessively high temperatures that could damage the existing stable structure. Appropriate holding time optimizes the internal crystal arrangement of the material. A nitrogen or argon protective atmosphere effectively isolates the material from air, preventing the material surface from reacting with oxygen during high-temperature annealing and ensuring the structural stability of the fluorinated resin and filler components. The cooling and annealing processes work synergistically. Staged, rate-controlled cooling initially eliminates the main thermal stress, and then annealing under a protective atmosphere further releases residual stress and optimizes the structure.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. This application uses RPTFE resin blended with a specific ratio of SILCAR62XT DuPont resin, combined with a 5B component of boron nitride and silicon carbide, and adds fluorinated graphene and silane-fluoroalkyl bifunctional interfacial bridger. The components form a synergistic effect through structural compatibility and functional complementarity, thereby effectively improving the gasket's resistance to creep relaxation under high temperature and high pressure, while enhancing its overall mechanical strength and wear resistance, thus significantly improving the gasket's basic performance adaptability.

[0033] 2. The method of this application, through the fluorine-containing gas plasma activation treatment in the raw material pretreatment stage, combined with the mixed granulation method of segmented mixing and ultrasonic-assisted dispersion, and then through multi-stage gradient pressure hot pressing molding and programmed slow cooling and annealing treatment, effectively optimizes the internal structure of the material, thus achieving the effect of eliminating internal stress and achieving a dense and uniform structure in the gasket.

[0034] 3. Because this application uses a specific raw material compounding system and a precise and controllable preparation process, the modified RPTFE gasket can be adapted to a wide temperature range environment, while being resistant to the erosion of various strong chemical media and resisting the influence of vibration. Due to the synergistic optimization of raw materials and processes, a stable adaptability effect under multiple working conditions has been achieved.

[0035] 4. In this application, a parameter-controllable industrial preparation process is preferred. From raw material drying and plasma activation to melt extrusion granulation, compression molding and post-processing, the parameters of each step are set within a reasonable range. Due to the stable process route and strong repeatability, the gasket dimensional accuracy is high and it is suitable for mass production. Attached Figure Description

[0036] Figure 1 This is a flowchart of a method for preparing a modified RPTFE gasket containing SILCAR62XT resin, as provided in this application. Detailed Implementation

[0037] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0038] Technical concept:

[0039] In related technologies, modified RPTFE gaskets have problems such as weak creep relaxation resistance, insufficient mechanical strength and wear resistance under high temperature and high pressure. The core reason is that a single filler cannot achieve synergistic improvement of multiple properties, and the interface between inorganic filler components and organic matrix is ​​weak. At the same time, traditional preparation processes lack targeted multi-component mixing and molding stress control design, resulting in poor material structure uniformity and internal stress concentration.

[0040] This technical solution addresses the aforementioned issues through precise component matching and optimized process design: In terms of components, a stable matrix is ​​constructed by blending RPTFE resin with DuPont SILCAR62XT resin, combined with a 5B component of boron nitride and silicon carbide, and fluorinated graphene, with the aid of a bifunctional interfacial bridging agent to strengthen interfacial bonding; in terms of process, segmented raw material pretreatment, gradient mixing granulation, multi-stage pressure molding, and programmed cooling post-treatment ensure uniform dispersion of multiple components and release of internal stress, achieving a synergistic improvement in creep resistance, strong mechanical properties, and wear resistance.

[0041] Example 1

[0042] This embodiment provides a modified RPTFE gasket containing SILCAR62XT resin, comprising the following raw materials in parts by weight: 82.5 parts of RPTFE resin, 12 parts of SILCAR62XT DuPont resin, 5 parts of component 5B, 2 parts of fluorinated graphene, and 0.9 parts of interfacial bridger.

[0043] The RPTFE resin has an average particle size of 35 μm and a melt index of 1.6 g / 10 min; the SILCAR62XT DuPont resin has a fluorine content of 65 wt% and a heat distortion temperature of 150 °C.

[0044] Component 5B is a compound of boron nitride and silicon carbide, with a weight ratio of boron nitride to silicon carbide of 1:2; the particle size D50 of boron nitride is 10 μm and the purity is 99 wt%; the particle size D50 of silicon carbide is 15 μm and the purity is 98 wt%.

[0045] The lateral dimension of the fluorinated graphene is 5.5 μm; the interfacial bridger is a silane-fluoroalkyl bifunctional compound.

[0046] The preparation method of the modified RPTFE gasket containing SILCAR62XT resin includes the following steps:

[0047] S1. Raw material pretreatment: RPTFE resin and SILCAR62XT DuPont resin are dried separately; boron nitride and silicon carbide in component 5B are mixed to obtain a first mixture; fluorinated graphene and interfacial bridge agent are premixed with the first mixture to obtain a second mixture; the second mixture is subjected to plasma activation treatment in a fluorine-containing gas atmosphere.

[0048] The drying process was carried out at 90℃ for 2.5 hours; the plasma activation treatment lasted for 12.5 minutes with a power of 400W; and the fluorine-containing gas atmosphere was a mixture of argon and carbon tetrafluoride with a volume ratio of 8.5:1.5.

[0049] S2. Mixing and Granulation: The dried RPTFE resin, SILCAR62XT DuPont resin, and the plasma-activated second mixture are mixed at room temperature in the first stage; then the mixture is heated and mixed at a higher temperature in the second stage, and ultrasonic-assisted dispersion is performed simultaneously in the heating and mixing stage to obtain a uniform blend; the uniform blend is melt-extruded and granulated to obtain modified RPTFE particles.

[0050] The process involved several stages: First, room temperature mixing was performed at 650 rpm for 6.5 minutes; second, heating mixing involved raising the material to 130°C and performing the mixture at 1100 rpm for 12.5 minutes; third, ultrasonic-assisted dispersion was performed at 30 kHz with a power of 350 W for 7.5 minutes; ultrasonic waves were applied through a probe immersed in the mixture to a depth of 5 / 12 of the mixture's height; and fourth, melt extrusion granulation was performed at an extrusion temperature of 325°C and a screw speed of 175 rpm.

[0051] S3. Compression molding: Modified RPTFE particles are added to a preheated mold and pre-pressed to obtain a gasket blank; then the gasket blank is hot-pressed through a multi-stage gradient pressing method.

[0052] The mold preheating temperature is 110℃; pre-pressing is carried out at room temperature with a pressure of 17.5MPa and held for 7.5min; hot pressing is carried out at 400℃, and the multi-stage gradient pressurization method includes: first, holding at a pressure of 22.5MPa for 1.25h, then increasing the pressure to 30MPa at a rate of 0.75MPa / min, and continuing to hold at this pressure for 1.25h.

[0053] S4. Cooling and post-treatment: The hot-pressed gasket is slowly cooled to room temperature in a programmed manner; after demolding, the resulting gasket is annealed to finally obtain the modified RPTFE gasket.

[0054] The programmed slow cooling was carried out at a rate of 7.5℃ / min. Specifically, the programmed slow cooling included: a stage of cooling from the hot pressing temperature to 250℃ at a cooling rate of 9℃ / min; a stage of cooling from 250℃ to 100℃ at a cooling rate of 6.5℃ / min; and a stage of cooling from 100℃ to room temperature at a cooling rate of 4℃ / min. The annealing treatment was carried out at 210℃ for 2.5 hours under a nitrogen protective atmosphere.

[0055] Example 2

[0056] This embodiment provides a modified RPTFE gasket containing SILCAR62XT resin, comprising the following raw materials in parts by weight: 80 parts of RPTFE resin, 10 parts of SILCAR62XT DuPont resin, 4 parts of component 5B, 1 part of fluorinated graphene, and 0.8 parts of interfacial bridger.

[0057] The RPTFE resin has an average particle size of 20 μm and a melt index of 1.2 g / 10 min; the SILCAR62XT DuPont resin has a fluorine content of 65 wt% and a heat distortion temperature of 150 °C.

[0058] Component 5B is a compound of boron nitride and silicon carbide, with a weight ratio of boron nitride to silicon carbide of 1:1; the particle size D50 of boron nitride is 5 μm and the purity is 99 wt%; the particle size D50 of silicon carbide is 10 μm and the purity is 98 wt%.

[0059] The lateral dimension of the fluorinated graphene is 1 μm; the interfacial bridger is a silane-fluoroalkyl bifunctional compound.

[0060] The preparation method of the modified RPTFE gasket containing SILCAR62XT resin includes the following steps:

[0061] S1. Raw material pretreatment: RPTFE resin and SILCAR62XT DuPont resin are dried separately; boron nitride and silicon carbide in component 5B are mixed to obtain a first mixture; fluorinated graphene and interfacial bridge agent are premixed with the first mixture to obtain a second mixture; the second mixture is subjected to plasma activation treatment in a fluorine-containing gas atmosphere.

[0062] The drying process was carried out at 80℃ for 2 hours; the plasma activation treatment lasted for 10 minutes with a processing power of 300W; and the fluorine-containing gas atmosphere was a mixture of argon and carbon tetrafluoride with a volume ratio of 9:1.

[0063] S2. Mixing and Granulation: The dried RPTFE resin, SILCAR62XT DuPont resin, and the plasma-activated second mixture are mixed at room temperature in the first stage; then the mixture is heated and mixed at a higher temperature in the second stage, and ultrasonic-assisted dispersion is performed simultaneously in the heating and mixing stage to obtain a uniform blend; the uniform blend is melt-extruded and granulated to obtain modified RPTFE particles.

[0064] The process involves several stages: First, room temperature mixing is performed at 500 rpm for 5 minutes; second, heating mixing involves raising the material to 120°C and performing the mixture at 1000 rpm for 10 minutes; third, ultrasonic-assisted dispersion is performed at 25 kHz with a power of 300 W for 5 minutes; ultrasonic waves are applied through a probe immersed in the mixture to a depth of one-third of the mixture's height; and fourth, melt extrusion granulation is performed at an extrusion temperature of 300°C and a screw speed of 150 rpm.

[0065] S3. Compression molding: Modified RPTFE particles are added to a preheated mold and pre-pressed to obtain a gasket blank; then the gasket blank is hot-pressed through a multi-stage gradient pressing method.

[0066] The mold preheating temperature is 100℃; pre-pressing is carried out at room temperature with a pressure of 15MPa and held for 5 minutes; hot pressing is carried out at 380℃, and the multi-stage gradient pressurization method includes: first, holding at a pressure of 20MPa for 1 hour, then increasing the pressure to 28MPa at a rate of 0.5MPa / min, and continuing to hold at this pressure for 1 hour.

[0067] S4. Cooling and post-treatment: The hot-pressed gasket is slowly cooled to room temperature in a programmed manner; after demolding, the resulting gasket is annealed to finally obtain the modified RPTFE gasket.

[0068] The programmed slow cooling was carried out at a rate of 5℃ / min. Specifically, the programmed slow cooling included: a stage of cooling from the hot pressing temperature to 250℃ at a cooling rate of 8℃ / min; a stage of cooling from 250℃ to 100℃ at a cooling rate of 5℃ / min; a stage of cooling from 100℃ to room temperature at a cooling rate of 3℃ / min; and annealing was carried out at 200℃ for 2 hours under a nitrogen protective atmosphere.

[0069] Example 3

[0070] This embodiment provides a modified RPTFE gasket containing SILCAR62XT resin, comprising the following raw materials in parts by weight: 85 parts of RPTFE resin, 14 parts of SILCAR62XT DuPont resin, 6 parts of component 5B, 3 parts of fluorinated graphene, and 1 part of interfacial bridge agent.

[0071] The RPTFE resin has an average particle size of 50 μm and a melt index of 2.0 g / 10 min; the SILCAR62XT DuPont resin has a fluorine content of 65 wt% and a heat distortion temperature of 150 °C.

[0072] Component 5B is a compound of boron nitride and silicon carbide, with a weight ratio of boron nitride to silicon carbide of 1:3; the particle size D50 of boron nitride is 15 μm and the purity is 99 wt%; the particle size D50 of silicon carbide is 20 μm and the purity is 98 wt%.

[0073] The lateral dimension of the fluorinated graphene is 10 μm; the interfacial bridger is a silane-fluoroalkyl bifunctional compound.

[0074] The preparation method of the modified RPTFE gasket containing SILCAR62XT resin includes the following steps:

[0075] S1. Raw material pretreatment: RPTFE resin and SILCAR62XT DuPont resin are dried separately; boron nitride and silicon carbide in component 5B are mixed to obtain a first mixture; fluorinated graphene and interfacial bridge agent are premixed with the first mixture to obtain a second mixture; the second mixture is subjected to plasma activation treatment in a fluorine-containing gas atmosphere.

[0076] The drying process was carried out at 100℃ for 3 hours; the plasma activation treatment lasted for 15 minutes with a processing power of 500W; and the fluorine-containing gas atmosphere was a mixture of argon and carbon tetrafluoride with a volume ratio of 8:2.

[0077] S2. Mixing and Granulation: The dried RPTFE resin, SILCAR62XT DuPont resin, and the plasma-activated second mixture are mixed at room temperature in the first stage; then the mixture is heated and mixed at a higher temperature in the second stage, and ultrasonic-assisted dispersion is performed simultaneously in the heating and mixing stage to obtain a uniform blend; the uniform blend is melt-extruded and granulated to obtain modified RPTFE particles.

[0078] The process includes: 1) Room temperature mixing in the first stage, performed at 800 rpm for 8 minutes; 2) Heating mixing, where the material is heated to 140°C and mixed at 1200 rpm for 15 minutes; 3) Ultrasonic-assisted dispersion, performed at 35 kHz with a power of 400 W for 10 minutes; 4) Ultrasonic waves are applied through a probe immersed in the mixture to a depth of half the height of the mixture; and 5) Melt extrusion granulation, performed at 350°C with a screw speed of 200 rpm.

[0079] S3. Compression molding: Modified RPTFE particles are added to a preheated mold and pre-pressed to obtain a gasket blank; then the gasket blank is hot-pressed through a multi-stage gradient pressing method.

[0080] The mold preheating temperature is 120℃; pre-pressing is carried out at room temperature with a pressure of 20MPa and held for 10 minutes; hot pressing is carried out at 420℃, and the multi-stage gradient pressurization method includes: first, holding at a pressure of 25MPa for 1.5 hours, then increasing the pressure to 32MPa at a rate of 1MPa / min, and continuing to hold at this pressure for 1.5 hours.

[0081] S4. Cooling and post-treatment: The hot-pressed gasket is slowly cooled to room temperature in a programmed manner; after demolding, the resulting gasket is annealed to finally obtain the modified RPTFE gasket.

[0082] The programmed slow cooling was carried out at a rate of 10℃ / min. Specifically, the programmed slow cooling included: a stage of cooling from the hot pressing temperature to 250℃ at a cooling rate of 10℃ / min; a stage of cooling from 250℃ to 100℃ at a cooling rate of 8℃ / min; and a stage of cooling from 100℃ to room temperature at a cooling rate of 5℃ / min. The annealing treatment was carried out at 220℃ for 3 hours under an argon protective atmosphere.

[0083] Comparative Example 1

[0084] The only difference between this comparative example and Example 1 is that the SILCAR62XT DuPont resin is replaced with an equal part by weight of ordinary fluorinated modified resin. All other raw materials, proportions, and processes are the same as in Example 1.

[0085] Comparative Example 2

[0086] The only difference between this comparative example and Example 1 is that component 5B is replaced with an equal part by weight of a single graphite filler; all other raw materials, proportions, and processes are the same as in Example 1.

[0087] Comparative Example 3

[0088] The only difference between this comparative example and Example 1 is that the 5B component contains only boron nitride and does not contain silicon carbide, while the other raw materials, proportions, and processes are the same as in Example 1.

[0089] Comparative Example 4

[0090] The only difference between this comparative example and Example 1 is that fluorinated graphene is replaced with an equal part by weight of ordinary graphene; all other raw materials, proportions, and processes are the same as in Example 1.

[0091] Comparative Example 5

[0092] The only difference between this comparative example and Example 1 is that the interface bridging agent is replaced with an equal part by weight of ordinary silane coupling agent KH550. All other raw materials, proportions, and processes are the same as in Example 1.

[0093] Comparative Example 6

[0094] The only difference between this comparative example and Example 1 is that in step S3, the hot pressing is performed under constant pressure. Specifically, a pressure of 30 MPa is applied directly at 400°C and held for 2.5 hours. All other raw materials, proportions, and processes are the same as in Example 1.

[0095] Comparative Example 7

[0096] The only difference between this comparative example and Example 1 is that the fluorine-containing gas atmosphere used for plasma activation in step S1 is replaced with pure argon gas, which does not contain carbon tetrafluoride. All other raw materials, proportions, and processes are the same as in Example 1.

[0097] Comparative Example 8

[0098] This comparative example uses a commercially available glass fiber reinforced PTFE gasket, widely used for sealing chemical pipelines, as a comparison object. This product is a common filled PTFE sealing material in the prior art.

[0099] I. High Temperature and High Pressure Creep Resistance Test

[0100] The creep relaxation test was conducted according to ASTM F382-2019, "Standard for Creep Relaxation Testing of Flexible Graphite and Polytetrafluoroethylene Gaskets." Test samples included Examples 1-3 and Comparative Examples 1-8. Three annular gasket specimens (Φ50mm × Φ30mm × 3mm) were prepared for each sample, ensuring a smooth and defect-free surface. All specimens were mounted in a dedicated fixture of the creep relaxation testing machine. The test temperature was set to 280℃, the initial pressure was 12MPa, and the temperature and pressure were maintained for 24 hours. Pressure decay data was recorded in real-time during the test. The creep relaxation rate was calculated using the formula: Creep Relaxation Rate = (Initial Pressure - Residual Pressure after 24 hours) / Initial Pressure × 100%. The average value of three parallel specimens was taken as the final result. This indicator directly reflects the structural stability of the gasket under high temperature and high pressure static conditions; a lower value indicates better creep resistance.

[0101] II. Sealing performance test after immersion in strong chemical media

[0102] Immersion treatment was performed according to ASTM D471-2016, "Standard Test Method for Immersion of Rubber and Elastomers in Liquids," and sealing performance was tested according to GB / T 12385-2008, "Test Method for Sealing Performance of Gaskets for Pipe Flanges." Test samples included Examples 1-3 and Comparative Examples 1-8. Three specimens of the same size as those used in the high-temperature, high-pressure creep resistance test were prepared for each sample. All specimens were immersed in two strong chemical media: a 50% sodium hydroxide solution and concentrated hydrochloric acid. The immersion temperature was controlled at 25°C, and the immersion time was 72 hours. During immersion, it was ensured that the specimens were completely submerged and did not come into contact with the container wall. After soaking, the sample was removed, rinsed with deionized water, and air-dried. Then, the sample was installed in the flange sealing performance testing device, the sealing medium was set to compressed air, the test pressure was 1.6 MPa, and the pressure was maintained for 30 minutes. The leakage rate of the sample was detected by the soap film method. The average leakage rate of 3 parallel samples in the two media was taken as the final result. This index reflects the gasket's ability to retain sealing performance after strong acid and alkali corrosion. The lower the leakage rate, the better the chemical corrosion resistance and interfacial bonding stability.

[0103] III. Wide-temperature-range vibration post-mechanical-sealing synergistic performance test

[0104] Vibration treatment was performed according to ASTM G30-2017 "Methods for Vibration Fatigue Testing of Materials". Tensile strength testing was performed according to GB / T1040.4-2006 "Tension Properties of Plastics - Part 4: Isotropic and Orthotropic Fiber Reinforced Composites". Sealing performance testing was performed according to GB / T12385-2008. Test samples included Examples 1-3 and Comparative Examples 1-8. Six specimens were prepared for each sample, three for tensile testing and three for sealing testing. The tensile specimen size was 115mm × 10mm × 3mm, and the sealing specimen size was the same as the previous two tests. All specimens were mounted on an electromagnetic vibration test bench, with the vibration frequency range set from 10Hz to 2500Hz and the amplitude set at 0.5mm. Vibration was performed continuously for 100 hours. During the vibration, a wide temperature range of -200℃ to 280℃ was maintained during the vibration process, and a heating and cooling cycle from -200℃ to 280℃ was completed every 2 hours. After vibration, three tensile specimens were subjected to tensile testing at a high temperature of 200℃ with a tensile rate of 5 mm / min. The tensile strength retention rate was calculated as follows: tensile strength retention rate = tensile strength after vibration / tensile strength before vibration × 100%. The leakage rate of the other three sealing specimens was tested according to the sealing performance test conditions in the second test. The average of the tensile strength retention rate and leakage rate of the three parallel specimens was taken as the final result. This index reflects the mechanical stability and sealing synergy of the gasket under dynamic vibration conditions in a wide temperature range. A higher tensile strength retention rate and a lower leakage rate indicate better adaptability to multiple working conditions.

[0105] The key performance test results of Examples 1-3 and Comparative Examples 1-8 are shown in Table 1.

[0106] Table 1:

[0107]

[0108]

[0109] As can be seen from Examples 1-3 and Comparative Example 1, and Table 1, the specific fluorinated structure and high heat distortion temperature of DuPont SILCAR62XT resin play a decisive role in the creep resistance of the gasket under high temperature and high pressure conditions. This resin exhibits excellent molecular chain compatibility with the RPTFE matrix, effectively suppressing polymer chain slippage at high temperatures, thereby significantly enhancing the overall structural stability of the gasket. In contrast, using ordinary fluorinated modified resins cannot construct a similarly stable blend system, leading to greater plastic deformation of the material under long-term thermal stress.

[0110] As can be seen from Examples 1-3, Comparative Examples 2 and 3, and Table 1, the compounding of boron nitride and silicon carbide in component 5B is a key design element. The layered structure of boron nitride helps to form a dense barrier, improving the gasket's sealing performance and thermal conductivity uniformity; while the high hardness of silicon carbide provides the necessary mechanical support and wear resistance. The specific ratio of these two compounds achieves functional synergy and complementarity. When only a single filler such as graphite is used, or only boron nitride is used, it is impossible to simultaneously achieve the required flexibility and thermal conductivity for sealing, as well as the required rigidity and wear resistance for the structure, leading to a decline in the overall performance of the gasket under complex operating conditions.

[0111] As can be seen from Examples 1-3 and Comparative Example 4, and in conjunction with Table 1, the introduction of fluorinated graphene plays a dual role in nano-reinforcement and interface optimization. Its layered structure effectively hinders molecular chain migration, while the fluorine atoms on its surface have a very high affinity for the fluorinated resin matrix, which enhances the dispersibility and interfacial bonding of the nanofiller in the matrix. In contrast, unfluorinated ordinary graphene, due to its surface energy difference, has insufficient compatibility with the fluorocarbon matrix, easily leading to aggregation or interfacial weakening, thus affecting the long-term stability of the material and its resistance to extreme media.

[0112] As can be seen from Examples 1-3 and Comparative Example 5, and in conjunction with Table 1, the specific chemical structure of the interfacial bridging agent is crucial. The silane-fluoroalkyl bifunctional compound chemically bonds to the surface of inorganic fillers such as boron nitride and silicon carbide at one end via a silane group, and is tightly compatible with the fluorocarbon segments of RPTFE and SILCAR62XT resins at the other end via a fluoroalkyl chain, thus constructing a strong chemical bridge between the filler and the resin matrix. Ordinary silane coupling agents lack structural units that match fluorocarbon polymers, making it difficult to achieve interfacial adhesion of equal strength, leading to easier separation of the filler and matrix under chemical corrosion or stress.

[0113] As can be seen from Examples 1-3 and Comparative Example 6, and in conjunction with Table 1, the multi-stage gradient pressurization hot pressing process is crucial for obtaining gaskets with uniform internal structure and low internal stress. This process, by applying and increasing pressure in stages, allows the molten resin to flow fully and impregnate the filler, while also facilitating filler orientation and the elimination of pores, thereby forming a dense microstructure with a more rational stress distribution. Using a simple constant pressure method, the resin flow and compaction process may be insufficient or uneven, easily leading to internal defects or stress concentration, which in turn affects the dimensional stability and creep resistance of the gasket.

[0114] As can be seen from Examples 1-3 and Comparative Example 7, and in conjunction with Table 1, plasma treatment using a mixed gas containing carbon tetrafluoride is a key step for targeted modification of the filler surface. This process introduces active fluorine species onto the filler surface, achieving a certain degree of fluorination modification, thereby significantly improving its interfacial compatibility and bonding strength with the fluorinated resin matrix. If only inert pure argon gas is used for treatment, it mainly serves a physical cleaning and roughening function, lacking this chemical bonding enhancement effect, resulting in insufficient interfacial bonding strength between the filler and the resin, which may become a performance bottleneck under long-term use or corrosive environments.

[0115] As can be seen from Examples 1-3 and Comparative Example 8, and in conjunction with Table 1, the overall technical solution of this invention differs fundamentally from existing conventional reinforced PTFE gasket products. This invention constructs a completely new material system through specific resin combinations, multifunctional filler formulations, nano-reinforcement, interfacial chemical bonding, and a series of precisely controlled preparation processes. In contrast, traditional products using conventional fillers such as glass fiber and simple molding processes exhibit insufficient material structure and interfacial stability to maintain reliable sealing and mechanical properties under complex operating conditions such as high-temperature creep resistance, resistance to strong chemical corrosion, and withstanding wide-temperature-range alternating vibrations, demonstrating a significant performance gap.

[0116] 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 modified RPTFE gasket containing SILCAR62XT resin, characterized in that: It contains the following components in parts by weight: 80-85 parts RPTFE resin; 10-14 parts SILCAR62XT DuPont resin; 4-6 parts 5B component; 1-3 parts fluorinated graphene; and 0.8 to 1 part interfacial bridger.

2. The modified RPTFE gasket containing SILCAR62XT resin according to claim 1, characterized in that: The RPTFE resin has an average particle size of 20-50 μm and a melt index of 1.2-2.0 g / 10 min; the SILCAR62XT DuPont resin has a fluorine content of ≥65 wt% and a heat distortion temperature of ≥150℃.

3. The modified RPTFE gasket containing SILCAR62XT resin according to claim 1, characterized in that: The 5B component is a compound of boron nitride and silicon carbide, and the weight ratio of boron nitride to silicon carbide is 1:1 to 1:3; the particle size D of the boron nitride is... 50 The particle size of silicon carbide is 5-15 μm, with a purity ≥99 wt%; 50 The particle size is 10-20 μm, and the purity is ≥98 wt%.

4. The modified RPTFE gasket containing SILCAR62XT resin according to claim 1, characterized in that: The fluorinated graphene has a lateral dimension of 1-10 μm; the interface bridging agent is a silane-fluoroalkyl bifunctional compound.

5. A method for preparing a modified RPTFE gasket containing SILCAR62XT resin, characterized in that, The modified RPTFE gasket containing SILCAR62XT resin as described in any one of claims 1-4 comprises the following steps: S1. Raw material pretreatment: RPTFE resin and SILCAR62XT DuPont resin are dried separately; boron nitride and silicon carbide in component 5B are mixed to obtain a first mixture; fluorinated graphene and interfacial bridge agent are premixed with the first mixture to obtain a second mixture; the second mixture is subjected to plasma activation treatment in a fluorine-containing gas atmosphere. S2. Mixing and Granulation: The dried RPTFE resin, SILCAR62XT DuPont resin, and the plasma-activated second mixture are mixed at room temperature in the first stage; then the mixture is heated and mixed at a higher temperature in the second stage, and ultrasonic-assisted dispersion is performed simultaneously in the heating and mixing stage to obtain a uniform blend; the uniform blend is melt-extruded and granulated to obtain modified RPTFE particles. S3. Compression molding: The modified RPTFE particles are added to a preheated mold and pre-pressed to obtain a gasket blank; then the gasket blank is hot-pressed through a multi-stage gradient pressing method. S4. Cooling and post-treatment: The hot-pressed gasket is slowly cooled to room temperature in a programmed manner; after demolding, the resulting gasket is annealed to finally obtain the modified RPTFE gasket.

6. The method for preparing a modified RPTFE gasket containing SILCAR62XT resin according to claim 5, characterized in that: In step S1, the drying is carried out at 80-100℃ for 2-3 hours; the plasma activation treatment takes 10-15 minutes and the processing power is 300-500W; the fluorine-containing gas atmosphere is a mixed gas atmosphere of argon and carbon tetrafluoride; the volume ratio of argon to carbon tetrafluoride is 9:1-8:

2.

7. The method for preparing a modified RPTFE gasket containing SILCAR62XT resin according to claim 6, characterized in that: In step S2, the room temperature mixing in the first stage is carried out at a rotation speed of 500-800 r / min for 5-8 min; the heating mixing involves heating the material to 120-140℃ and carrying it out at a rotation speed of 1000-1200 r / min for 10-15 min; the ultrasonic-assisted dispersion treatment has a frequency of 25-35 kHz, a power of 300-400 W, and a treatment time of 5-10 min.

8. The method for preparing a modified RPTFE gasket containing SILCAR62XT resin according to claim 5, characterized in that: In step S2, the ultrasonic wave is applied through a probe immersed in the mixture, and the immersion depth of the probe is 1 / 3 to 1 / 2 of the height of the mixture; the extrusion temperature of the melt extrusion granulation is 300-350℃, and the screw speed is 150-200 r / min.

9. The method for preparing a modified RPTFE gasket containing SILCAR62XT resin according to claim 5, characterized in that: In step S3, the preheating temperature of the mold is 100-120℃; the pre-compression is carried out at room temperature with a pressure of 15-20MPa and held for 5-10 minutes. The hot pressing is carried out at 380-420℃. The multi-stage gradient pressurization method includes: first, maintaining a pressure of 20-25MPa for 1-1.5h, then increasing the pressure to 28-32MPa at a rate of 0.5-1MPa / min, and continuing to maintain the temperature and pressure at this pressure for 1-1.5h.

10. The method for preparing a modified RPTFE gasket containing SILCAR62XT resin according to claim 5, characterized in that: In step S4, the programmed slow cooling is performed at a rate of 5-10°C / min; the programmed slow cooling specifically includes: a stage of cooling from the hot pressing temperature to 250°C at a cooling rate of 8-10°C / min; a stage of cooling from 250°C to 100°C at a cooling rate of 5-8°C / min; and a stage of cooling from 100°C to room temperature at a cooling rate of 3-5°C / min; the annealing treatment is carried out at 200-220°C for 2-3 hours under a nitrogen or argon protective atmosphere.

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