Sealing ring filled with PTFE (Polytetrafluoroethylene) material and preparation process of sealing ring

Abstract

The invention relates to the technical field of sealing rings, in particular to a sealing ring filled with a PTFE material and a preparation process of the sealing ring. The sealing ring filled with the PTFE material comprises the following raw materials in parts by mass: 60-100 parts of polytetrafluoroethylene, 1-5 parts of nanoscale talcum powder, 5-15 parts of nano silicon dioxide, 3-7 parts of a carbon nanotube / mesoporous silicon dioxide composite material, 7-15 parts of activated carbon fibers, 1-2 parts of a dispersing agent and 0.1-1.5 parts of a coloring agent. The sealing ring has excellent high-temperature creep resistance, high tensile strength and good rebound resilience, and compared with a traditional mold pressing polytetrafluoroethylene sealing ring, the sealing capability of the sealing ring is remarkably improved, the leakage risk is greatly reduced, the comprehensive performance advantage is prominent, and the sealing ring has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of sealing rings, in particular to a sealing ring filled with PTFE material and a preparation process thereof. Background Art

[0002] Since its commercialization in the 1930s, polytetrafluoroethylene (PTFE), a high-performance engineering plastic, has been widely used in chemical reactor seals, pharmaceutical equipment pipe linings, environmental dust removal filters, corrosion-resistant components for the nuclear industry, and high-end consumer goods. PTFE, particularly in the sealing industry, has long served as the core matrix of sealing materials due to its ability to effectively prevent media leakage and its non-corrosive properties on metal substrates.

[0003] However, despite the outstanding comprehensive performance of PTFE, its application in the sealing field still faces significant bottlenecks - poor creep relaxation resistance and insufficient compression resilience. The so-called creep relaxation refers to the phenomenon that the material undergoes slow plastic deformation over time under constant stress or high temperature environment; compression resilience reflects the ability of the material to return to its original shape after being compressed. For seals, these two properties directly determine their long-term reliability: if the PTFE sealing material has insufficient creep relaxation resistance, it will undergo irreversible deformation under high temperature or continuous pressure, resulting in a decrease in the contact pressure of the sealing surface, and eventually causing leakage; if the compression resilience is poor, the material will not be able to effectively rebound to fill the microscopic surface defects after installation and compression, and the fit of the sealing interface will be greatly reduced, which will also increase the risk of leakage.

[0004] In response to the above problems, existing technologies mainly attempt to improve the performance of PTFE through two methods: filling modification and expansion modification. Filling modification is to improve the mechanical properties by utilizing the synergistic effect of fillers and matrix. For example, the addition of graphite can reduce the friction coefficient, and glass fiber can improve rigidity, but the interfacial bonding force between these fillers and PTFE is weak, and agglomeration is prone to occur, resulting in an increase in internal defects of the material, which may in turn reduce tensile strength and dimensional stability. In addition, some fillers (such as glass fiber) are prone to interfacial reaction with PTFE at high temperatures, further deteriorating the material properties. Expansion modification is to form a porous structure of PTFE by controlling the sintering process (such as rapid cooling), and using the gas in the pores to buffer stress. Although it can improve compression resilience, excessive porosity will lead to a decrease in material density, and the tensile strength and resistance to medium permeability will be significantly reduced, making it difficult to meet the needs of high-pressure sealing scenarios.

[0005] As industrial equipment evolves toward higher temperatures and longer cycle times, higher requirements are placed on the comprehensive performance of sealing materials: not only must they exhibit excellent tensile properties, but they must also maintain low creep relaxation and high compression resilience even in high-temperature environments. Traditional PTFE and its simple modified materials are no longer able to meet these requirements. Developing a new PTFE sealing material and preparation process that combines high mechanical properties, low creep relaxation, and excellent dimensional stability has become a pressing technical challenge for the sealing industry. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a sealing ring filled with PTFE material and a preparation process thereof.

[0007] A sealing ring filled with PTFE material. The raw materials thereof include, by mass, 60-100 parts of polytetrafluoroethylene, 1-5 parts of nano-grade talc powder, 5-15 parts of nano-silicon dioxide, 3-7 parts of carbon nanotube / mesoporous silicon dioxide composite material, 7-15 parts of activated carbon fiber, 1-2 parts of dispersant, and 0.1-1.5 parts of colorant.

[0008] Preferably, the dispersant is polyvinyl alcohol.

[0009] Preferably, activated carbon fiber is prepared by the following steps: adding carbon fiber, tetraethyl orthosilicate, and hydroxypropyl β-cyclodextrin to an ethanol aqueous solution and stirring evenly, adjusting the pH value of the system to 5-6, ultrasonic treatment for 1-2 hours, adjusting the pH value of the system to 9-10, continuing ultrasonic treatment for 3-6 hours, aging at 50-60°C for 5-10 hours, filtering, washing, and vacuum drying.

[0010] More preferably, the mass ratio of carbon fiber, tetraethyl orthosilicate, and hydroxypropyl β-cyclodextrin is 5-10:1-3:1-2.

[0011] More preferably, the ultrasound frequency is 60-80 kHz.

[0012] Preferably, the carbon nanotube / mesoporous silica composite material is prepared by the following steps: adding mesoporous silica to anhydrous ethanol and ultrasonically dispersing it for 5-10 minutes at an ultrasonic frequency of 80-100 kHz, adding nickelocene, refluxing and stirring at 60-65°C for 1-2 hours, vacuum drying, adding to a chemical vapor deposition chamber, passing argon to purge, reducing in a hydrogen atmosphere for 2-5 minutes, controlling the deposition power to 400-450W, the deposition pressure to 50-120Pa, passing a mixed gas of argon and hydrogen, heating to 700-750°C, passing methane to grow for 4-8 minutes, and cooling to room temperature.

[0013] More preferably, the total flow rate of argon and hydrogen is 120-480 sccm, and the flow ratio of argon to hydrogen is 5-15:1.

[0014] More preferably, the methane flow rate is 15-20 sccm.

[0015] The preparation process of the sealing ring filled with PTFE material comprises the following steps: S1. Mix polytetrafluoroethylene, nano-grade talc powder and nano-silicon dioxide, ball-mill and sieve, dry, sinter at 320-350°C for 1-2h, cool to room temperature, and crush and sieve to obtain a prefabricated material; S2, stirring the preform, carbon nanotube / mesoporous silica composite, activated carbon fiber, dispersant, and colorant for 5-15 minutes, sieving, and pressing at 15-25 MPa for 5-15 minutes, releasing air 1-3 times during the pressurization process to obtain a blank; S3, heating the blank to 300-340°C, sintering for 1-2 hours, heating to 380-400°C, sintering for 1-3 hours, cooling to 200-260°C, and cooling to room temperature with the furnace to obtain a sintered material; S4. Heat the sintering material to 300-350℃, keep it warm for 10-20min, cool it down to 150-200℃, heat it up to 380-400℃, keep it warm for 5-15min, and cool it to room temperature along with the furnace.

[0016] Preferably, in S3, during the process of heating to 300-340°C, the heating rate is 1-3°C / min.

[0017] Preferably, in S3, during the process of heating to 380-400°C, the heating rate is 5-10°C / min.

[0018] Preferably, in S3, during the process of cooling to 200-260°C, the cooling rate is 1-5°C / min.

[0019] Preferably, in S4, during the process of heating to 300-350°C, the heating rate is 1-5°C / min.

[0020] Preferably, in S4, during the process of heating to 380-400°C, the heating rate is 2-6°C / min. Beneficial effects

[0021] The present invention uses ethyl orthosilicate to form a silica deposition layer on the surface of the carbon fiber, and cooperates with hydroxypropyl beta-cyclodextrin to form a large number of active hydroxyl sites on its surface, which cooperate with the silica deposition layer to form a skeleton support network. Not only does the tensile strength of the carbon fiber greatly enhance, but also, in combination with the prefabricated material, the interlayer shear strength is improved.

[0022] This invention utilizes a ball-milled pre-sintering process to combine polytetrafluoroethylene with nano-scale talc and nano-silica, effectively improving the uniformity of raw material dispersion and resolving the performance fluctuations caused by uneven material dispersion in traditional mixing processes, laying the foundation for subsequent material performance enhancements. The carbon nanotube film generated by a catalytic reaction within the mesoporous silica channels forms a synergistically reinforced structure with the preform, significantly increasing the material's tensile strength. The nanoscale reinforcement effect of the carbon nanotubes also enhances the dimensional stability of the sealing ring, allowing it to quickly rebound after deformation under stress, effectively reducing the risk of leakage at the sealing interface.

[0023] This invention utilizes a preformed material, a carbon nanotube / mesoporous silica composite, and activated carbon fibers to form a composite system. This system undergoes a staged sintering process (including low-temperature, high-temperature, and low-temperature tempering stages). Compared to conventional single-high-temperature sintering processes, this process is more effective in releasing the internal stresses generated by structural transformation during sintering, resulting in a denser, smoother surface and a more regular structure. This process optimization not only increases the overall tensile strength of the material but also effectively reduces its creep relaxation rate at both room and high temperatures, significantly enhancing dimensional stability. This overall improvement in mechanical properties and durability of the sealing product extends its service life.

[0024] The sealing ring obtained by the present invention has excellent high-temperature creep resistance, high tensile strength and good resilience. Compared with traditional molded polytetrafluoroethylene sealing rings, its sealing ability is significantly improved, the leakage risk is greatly reduced, the comprehensive performance advantages are outstanding, and it has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a comparison chart of the tensile strength of the sealing rings obtained in Example 5 and Comparative Examples 1-3.

[0026] Figure 2 The figure is a comparison chart of the compression rate and rebound rate of the sealing rings obtained in Example 5 and Comparative Examples 1-3.

[0027] Figure 3 1 is a comparison chart of the room temperature creep relaxation rate and the 200°C creep relaxation rate of the sealing rings obtained in Example 5 and Comparative Examples 1-3.

[0028] Figure 4 This is a photo of the finished sealing ring obtained in Example 5. DETAILED DESCRIPTION

[0029] The present invention will be further explained below with reference to specific embodiments.

[0030] The polytetrafluoroethylene used in the following is from Daikin, Japan, with the designation PTFE M-111. The pore size of the mesoporous silica used in the following is 5-20 nm. Example 1

[0031] A sealing ring filled with PTFE material, whose raw materials include: 60g of polytetrafluoroethylene, 1g of nano-grade talc powder, 5g of nano-silicon dioxide, 3g of carbon nanotube / mesoporous silica composite material, 7g of activated carbon fiber, 1g of polyvinyl alcohol, and 0.1g of colorant.

[0032] The carbon nanotube / mesoporous silica composite material was prepared by the following steps: 1 g of mesoporous silica was added to 20 g of anhydrous ethanol and ultrasonically dispersed for 5 minutes at an ultrasonic frequency of 80 kHz, 0.01 g of nickelocene was added, and the mixture was refluxed and stirred at 60°C for 1 hour, dried in vacuo, added to a chemical vapor deposition chamber, purged with argon, and reduced in a hydrogen atmosphere for 2 minutes. The deposition power was controlled to 400 W, the deposition pressure was 50 Pa, a mixed gas of argon and hydrogen was introduced (argon flow rate was 100 sccm, hydrogen flow rate was 20 sccm), heated to 700°C, and methane (methane flow rate was 15 sccm) was introduced for growth for 4 minutes, and then cooled to room temperature.

[0033] Activated carbon fiber was prepared by the following steps: 5 g of carbon fiber, 1 g of ethyl orthosilicate, and 1 g of hydroxypropyl β-cyclodextrin were added to 20 g of 40% ethanol aqueous solution and stirred evenly, 1 mol / L hydrochloric acid was used to adjust the pH value of the system to 5.5, ultrasonic treatment was performed for 1 h, the ultrasonic frequency was 60 kHz, and the pH value of the system was adjusted to 9.5 with ammonia water, and ultrasonic treatment was continued for 3 h. The mixture was aged at 50 ° C for 5 h, filtered, washed, and vacuum dried.

[0034] The preparation process of the sealing ring filled with PTFE material comprises the following steps: S1. Mix polytetrafluoroethylene, nano-grade talc powder and nano-silicon dioxide, send them into a ball mill, grind them through a 400-mesh sieve, dry them, send them into a sintering furnace, sinter them at a temperature of 320° C. for 1 hour, cool them to room temperature, and grind them through a 400-mesh sieve to obtain a prefabricated material; S2. The preform, carbon nanotube / mesoporous silica composite, activated carbon fiber, polyvinyl alcohol, and colorant were fed into a high-speed mixer and stirred at a speed of 500 r / min for 5 min. The resulting mixture was passed through a 60-mesh sieve and placed in a sealing ring mold. The mixture was pressed at a pressure of 15 MPa for 5 min, and the air was released once during the pressurization process to obtain a billet with a thickness of 2.5 mm. S3, feeding the blank into a sintering furnace, heating it to 300°C at a rate of 1°C / min, sintering it for 1 hour, then heating it to 380°C at a rate of 5°C / min, sintering it for 1 hour, cooling it to 200°C at a rate of 1°C / min, and cooling it to room temperature with the furnace to obtain a sintered material; S4. Raise the temperature of the sintering material to 300°C at a rate of 1°C / min, keep it warm for 10 minutes, cool it down to 150°C, raise the temperature to 380°C at a rate of 2°C / min, keep it warm for 5 minutes, and cool it to room temperature with the furnace. Example 2

[0035] A sealing ring filled with PTFE material, whose raw materials include: 100g of polytetrafluoroethylene, 5g of nano-grade talc powder, 15g of nano-silicon dioxide, 7g of carbon nanotube / mesoporous silica composite material, 15g of activated carbon fiber, 2g of polyvinyl alcohol, and 0.2g of colorant.

[0036] The carbon nanotube / mesoporous silica composite material was prepared by the following steps: 5 g of mesoporous silica was added to 40 g of anhydrous ethanol and ultrasonically dispersed for 10 min at an ultrasonic frequency of 100 kHz, 0.1 g of nickelocene was added, refluxed and stirred at a temperature of 65 ° C for 2 h, vacuum dried, added to a chemical vapor deposition chamber, purged with argon, reduced in a hydrogen atmosphere for 3 min, the deposition power was controlled to 450 W, the deposition pressure was 120 Pa, a mixed gas of argon and hydrogen was introduced (argon flow rate was 450 sccm, hydrogen flow rate was 30 sccm), heated to 750 ° C, methane was introduced (methane flow rate was 20 sccm) and grown for 8 min, and cooled to room temperature.

[0037] Activated carbon fiber was prepared by the following steps: 10 g of carbon fiber, 3 g of ethyl orthosilicate, and 2 g of hydroxypropyl β-cyclodextrin were added to 50 g of 60% ethanol aqueous solution and stirred evenly, 2 mol / L hydrochloric acid was used to adjust the pH value of the system to 5.5, ultrasonic treatment was performed for 2 h, the ultrasonic frequency was 80 kHz, and the pH value of the system was adjusted to 9.5 with ammonia water, and ultrasonic treatment was continued for 6 h. The mixture was aged at 60 ° C for 10 h, filtered, washed, and vacuum dried.

[0038] The preparation process of the sealing ring filled with PTFE material comprises the following steps: S1. Mix polytetrafluoroethylene, nano-grade talc powder and nano-silicon dioxide, send them into a ball mill, grind them through a 400-mesh sieve, dry them, send them into a sintering furnace, sinter them at a temperature of 350° C. for 2 hours, cool them to room temperature, and grind them through a 400-mesh sieve to obtain a prefabricated material; S2. The preform, carbon nanotube / mesoporous silica composite, activated carbon fiber, polyvinyl alcohol, and colorant were fed into a high-speed mixer and stirred at a speed of 1000 r / min for 15 min. The resulting mixture was passed through a 60-mesh sieve and placed in a sealing ring mold. The mixture was pressed at a pressure of 25 MPa for 15 min, and the air was released three times during the pressurization process to obtain a billet with a thickness of 3.5 mm. S3, feeding the blank into a sintering furnace, heating it to 340°C at a rate of 3°C / min, sintering it for 2 hours, then heating it to 400°C at a rate of 10°C / min, sintering it for 3 hours, cooling it to 260°C at a rate of 5°C / min, and cooling it to room temperature with the furnace to obtain a sintered material; S4. Heat the sintering material to 350°C at a rate of 5°C / min, keep it warm for 20 minutes, cool it to 200°C, heat it to 400°C at a rate of 6°C / min, keep it warm for 15 minutes, and cool it to room temperature with the furnace. Example 3

[0039] A sealing ring filled with PTFE material, whose raw materials include: 70g of polytetrafluoroethylene, 4g of nano-grade talc powder, 8g of nano-silicon dioxide, 6g of carbon nanotube / mesoporous silica composite material, 9g of activated carbon fiber, 1.8g of polyvinyl alcohol, and 0.5g of colorant.

[0040] The carbon nanotube / mesoporous silica composite material was prepared by the following steps: 2 g of mesoporous silica was added to 35 g of anhydrous ethanol and ultrasonically dispersed for 7 minutes at an ultrasonic frequency of 95 kHz, 0.03 g of nickelocene was added, refluxed and stirred at a temperature of 63°C for 80 minutes, vacuum dried, added to a chemical vapor deposition chamber, purged with argon, reduced in a hydrogen atmosphere for 4 minutes, the deposition power was controlled to 430 W, the deposition pressure was 60 Pa, a mixed gas of argon and hydrogen was introduced (argon flow rate was 400 sccm, hydrogen flow rate was 22 sccm), heated to 730°C, introduced methane (methane flow rate was 17 sccm) and grown for 7 minutes, and cooled to room temperature.

[0041] Activated carbon fiber was prepared by the following steps: 7 g of carbon fiber, 2.5 g of ethyl orthosilicate, and 1.2 g of hydroxypropyl β-cyclodextrin were added to 40 g of 45% ethanol aqueous solution and stirred evenly, 1.8 mol / L hydrochloric acid was used to adjust the pH value of the system to 5.5, ultrasonic treatment was performed for 80 min at an ultrasonic frequency of 75 kHz, and ammonia water was used to adjust the pH value of the system to 9.5, and ultrasonic treatment was continued for 4 h. The mixture was aged at 58 ° C for 7 h, filtered, washed, and vacuum dried.

[0042] The preparation process of the sealing ring filled with PTFE material comprises the following steps: S1. Mix polytetrafluoroethylene, nano-grade talc and nano-silicon dioxide, send them into a ball mill, grind them through a 400-mesh sieve, dry them, send them into a sintering furnace, sinter them at a temperature of 340° C. for 80 min, cool them to room temperature, and grind them through a 400-mesh sieve to obtain a prefabricated material; S2. The preform, carbon nanotube / mesoporous silica composite, activated carbon fiber, polyvinyl alcohol, and colorant were fed into a high-speed mixer and stirred at a speed of 900 r / min for 8 min. The resulting mixture was passed through a 60-mesh sieve and placed in a sealing ring mold. The mixture was pressed at a pressure of 22 MPa for 8 min, and the air was released twice during the pressurization process to obtain a billet with a thickness of 3.0 mm. S3, feeding the blank into a sintering furnace, heating it to 310°C at a rate of 2.5°C / min, sintering it for 100 min, then heating it to 395°C at a rate of 7°C / min, sintering it for 1.5 h, cooling it to 210°C at a rate of 4°C / min, and cooling it to room temperature with the furnace to obtain a sintered material; S4. Heat the sintering material to 310°C at a rate of 4°C / min, keep it warm for 18 minutes, cool it to 160°C, heat it to 385°C at a rate of 5°C / min, keep it warm for 12 minutes, and cool it to room temperature with the furnace. Example 4

[0043] A sealing ring filled with PTFE material, whose raw materials include: 90g of polytetrafluoroethylene, 2g of nano-grade talc powder, 12g of nano-silicon dioxide, 4g of carbon nanotube / mesoporous silica composite material, 13g of activated carbon fiber, 1.2g of polyvinyl alcohol, and 0.8g of colorant.

[0044] The carbon nanotube / mesoporous silica composite material was prepared by the following steps: 4 g of mesoporous silica was added to 25 g of anhydrous ethanol and ultrasonically dispersed for 9 minutes at an ultrasonic frequency of 85 kHz, 0.07 g of nickelocene was added, refluxed and stirred at a temperature of 61°C for 100 minutes, vacuum dried, added to a chemical vapor deposition chamber, purged with argon, reduced in a hydrogen atmosphere for 5 minutes, the deposition power was controlled to 410 W, the deposition pressure was 100 Pa, a mixed gas of argon and hydrogen was introduced (argon flow rate was 150 sccm, hydrogen flow rate was 28 sccm), heated to 710°C, introduced methane (methane flow rate was 19 sccm) and grown for 5 minutes, and cooled to room temperature.

[0045] Activated carbon fiber was prepared by the following steps: 9 g of carbon fiber, 1.5 g of ethyl orthosilicate, and 1.8 g of hydroxypropyl β-cyclodextrin were added to 30 g of 55% ethanol aqueous solution and stirred evenly, 1.2 mol / L hydrochloric acid was used to adjust the pH value of the system to 5.5, ultrasonic treatment was performed for 100 min at an ultrasonic frequency of 65 kHz, and ammonia water was used to adjust the pH value of the system to 9.5, and ultrasonic treatment was continued for 5 h. The mixture was aged at 52 ° C for 9 h, filtered, washed, and vacuum dried.

[0046] The preparation process of the sealing ring filled with PTFE material comprises the following steps: S1, polytetrafluoroethylene, nano-grade talc and nano-silicon dioxide were mixed, sent into a ball mill, ball-milled and passed through a 400-mesh sieve, dried, sent into a sintering furnace, sintered at a temperature of 330° C. for 100 min, cooled to room temperature, and crushed through a 400-mesh sieve to obtain a prefabricated material; S2. The preform, carbon nanotube / mesoporous silica composite, activated carbon fiber, polyvinyl alcohol, and colorant were fed into a high-speed mixer and stirred at a speed of 700 r / min for 12 min. The resulting mixture was passed through a 60-mesh sieve and placed in a sealing ring mold. The mixture was pressed at a pressure of 18 MPa for 12 min, and the air was released twice during the pressurization process to obtain a billet with a thickness of 3.0 mm. S3. The blank was placed in a sintering furnace, heated to 330°C at a rate of 1.5°C / min, sintered for 80 min, then heated to 385°C at a rate of 9°C / min, sintered for 2.5 h, cooled to 250°C at a rate of 2°C / min, and cooled to room temperature in the furnace to obtain a sintered material; S4. Heat the sintering material to 330°C at a rate of 2°C / min, keep it warm for 12 minutes, cool it to 180°C, heat it to 395°C at a rate of 3°C / min, keep it warm for 8 minutes, and cool it to room temperature with the furnace. Example 5

[0047] A sealing ring filled with PTFE material, whose raw materials include: 80g of polytetrafluoroethylene, 3g of nano-grade talc powder, 10g of nano-silicon dioxide, 5g of carbon nanotube / mesoporous silica composite material, 11g of activated carbon fiber, 1.5g of polyvinyl alcohol, and 1.5g of titanium dioxide.

[0048] The carbon nanotube / mesoporous silica composite material was prepared by the following steps: 3 g of mesoporous silica was added to 30 g of anhydrous ethanol and ultrasonically dispersed for 8 minutes at an ultrasonic frequency of 90 kHz, 0.05 g of nickelocene was added, refluxed and stirred at a temperature of 62°C for 90 minutes, vacuum dried, added to a chemical vapor deposition chamber, purged with argon, reduced in a hydrogen atmosphere for 4 minutes, the deposition power was controlled to 420 W, the deposition pressure was 80 Pa, a mixed gas of argon and hydrogen was introduced (argon flow rate was 275 sccm, hydrogen flow rate was 25 sccm), heated to 720°C, introduced methane (methane flow rate was 18 sccm) and grown for 6 minutes, and cooled to room temperature.

[0049] Activated carbon fiber was prepared by the following steps: 8 g of carbon fiber, 2 g of ethyl orthosilicate, and 1.5 g of hydroxypropyl β-cyclodextrin were added to 35 g of 50% ethanol aqueous solution and stirred evenly, 1.5 mol / L hydrochloric acid was used to adjust the pH value of the system to 5.5, ultrasonic treatment was performed for 90 min at an ultrasonic frequency of 70 kHz, and ammonia water was used to adjust the pH value of the system to 9.5, and ultrasonic treatment was continued for 4.5 h. The mixture was aged at 55 ° C for 8 h, filtered, washed, and vacuum dried.

[0050] The preparation process of the sealing ring filled with PTFE material comprises the following steps: S1, polytetrafluoroethylene, nano-grade talc, and nano-silicon dioxide were mixed, sent to a ball mill, ball-milled through a 400-mesh sieve, dried, sent to a sintering furnace, sintered at a temperature of 335° C. for 90 min, cooled to room temperature, and crushed through a 400-mesh sieve to obtain a prefabricated material; S2. The preform, carbon nanotube / mesoporous silica composite, activated carbon fiber, polyvinyl alcohol, and titanium dioxide were fed into a high-speed mixer and stirred at a speed of 800 r / min for 10 min. The resulting mixture was passed through a 60-mesh sieve and placed in a sealing ring mold. The mixture was pressed at a pressure of 20 MPa for 10 min, and the air was released twice during the pressurization process to obtain a billet with a thickness of 3.0 mm. S3, feeding the blank into a sintering furnace, heating it to 320°C at a rate of 2°C / min, sintering it for 90 min, then heating it to 390°C at a rate of 8°C / min, sintering it for 2 h, cooling it to 230°C at a rate of 3°C / min, and cooling it to room temperature with the furnace to obtain a sintered material; S4, the sintering material was heated to 320℃ at a rate of 3℃ / min, kept at this temperature for 15min, cooled to 170℃, heated to 390℃ at a rate of 4℃ / min, kept at this temperature for 10min, and cooled to room temperature with the furnace; the photo of the finished sealing ring is as follows: Figure 4 shown.

[0051] Comparative Example 1 A sealing ring filled with PTFE material, whose raw materials include: 80g of polytetrafluoroethylene, 3g of nano-grade talc powder, 10g of nano-silicon dioxide, 5g of carbon nanotube / mesoporous silica composite material, 11g of activated carbon fiber, 1.5g of polyvinyl alcohol, and 1.5g of titanium dioxide.

[0052] The carbon nanotube / mesoporous silica composite material was prepared by the following steps: 3 g of mesoporous silica was added to 30 g of anhydrous ethanol and ultrasonically dispersed for 8 minutes at an ultrasonic frequency of 90 kHz, 0.05 g of nickelocene was added, refluxed and stirred at a temperature of 62°C for 90 minutes, vacuum dried, added to a chemical vapor deposition chamber, purged with argon, reduced in a hydrogen atmosphere for 4 minutes, the deposition power was controlled to 420 W, the deposition pressure was 80 Pa, a mixed gas of argon and hydrogen was introduced (argon flow rate was 275 sccm, hydrogen flow rate was 25 sccm), heated to 720°C, introduced methane (methane flow rate was 18 sccm) and grown for 6 minutes, and cooled to room temperature.

[0053] Activated carbon fiber was prepared by the following steps: 8 g of carbon fiber, 2 g of ethyl orthosilicate, and 1.5 g of hydroxypropyl β-cyclodextrin were added to 35 g of 50% ethanol aqueous solution and stirred evenly, 1.5 mol / L hydrochloric acid was used to adjust the pH value of the system to 5.5, ultrasonic treatment was performed for 90 min at an ultrasonic frequency of 70 kHz, and ammonia water was used to adjust the pH value of the system to 9.5, and ultrasonic treatment was continued for 4.5 h. The mixture was aged at 55 ° C for 8 h, filtered, washed, and vacuum dried.

[0054] The preparation process of the sealing ring filled with PTFE material comprises the following steps: S1. Mix polytetrafluoroethylene, nano-grade talc and nano-silicon dioxide, dry them, and grind them through a 400-mesh sieve to obtain a prefabricated material; S2. The preform, carbon nanotube / mesoporous silica composite, activated carbon fiber, polyvinyl alcohol, and titanium dioxide were fed into a high-speed mixer and stirred at a speed of 800 r / min for 10 min. The resulting mixture was passed through a 60-mesh sieve and placed in a sealing ring mold. The mixture was pressed at a pressure of 20 MPa for 10 min, and the air was released twice during the pressurization process to obtain a billet with a thickness of 3.0 mm. S3, feeding the blank into a sintering furnace, heating it to 320°C at a rate of 2°C / min, sintering it for 90 min, then heating it to 390°C at a rate of 8°C / min, sintering it for 2 h, cooling it to 230°C at a rate of 3°C / min, and cooling it to room temperature with the furnace to obtain a sintered material; S4. Heat the sintering material to 320°C at a rate of 3°C / min, keep it warm for 15 minutes, cool it to 170°C, heat it to 390°C at a rate of 4°C / min, keep it warm for 10 minutes, and cool it to room temperature with the furnace.

[0055] Comparative Example 2 A sealing ring filled with PTFE material, whose raw materials include: 80g of polytetrafluoroethylene, 3g of nano-grade talc powder, 10g of nano-silicon dioxide, 5g of mesoporous silica, 11g of activated carbon fiber, 1.5g of polyvinyl alcohol, and 1.5g of titanium dioxide.

[0056] Activated carbon fiber was prepared by the following steps: 8 g of carbon fiber, 2 g of ethyl orthosilicate, and 1.5 g of hydroxypropyl β-cyclodextrin were added to 35 g of 50% ethanol aqueous solution and stirred evenly, 1.5 mol / L hydrochloric acid was used to adjust the pH value of the system to 5.5, ultrasonic treatment was performed for 90 min at an ultrasonic frequency of 70 kHz, and ammonia water was used to adjust the pH value of the system to 9.5, and ultrasonic treatment was continued for 4.5 h. The mixture was aged at 55 ° C for 8 h, filtered, washed, and vacuum dried.

[0057] The preparation process of the sealing ring filled with PTFE material comprises the following steps: S1, polytetrafluoroethylene, nano-grade talc, and nano-silicon dioxide were mixed, sent to a ball mill, ball-milled through a 400-mesh sieve, dried, sent to a sintering furnace, sintered at a temperature of 335° C. for 90 min, cooled to room temperature, and crushed through a 400-mesh sieve to obtain a prefabricated material; S2. The prefabricated material, mesoporous silica, activated carbon fiber, polyvinyl alcohol, and titanium dioxide were fed into a high-speed mixer and stirred at a speed of 800 r / min for 10 min. The resulting mixture was passed through a 60-mesh sieve and placed in a sealing ring mold. The mixture was pressed at a pressure of 20 MPa for 10 min, and the pressure was released twice during the pressurization process to obtain a billet with a thickness of 3.0 mm. S3, feeding the blank into a sintering furnace, heating it to 320°C at a rate of 2°C / min, sintering it for 90 min, then heating it to 390°C at a rate of 8°C / min, sintering it for 2 h, cooling it to 230°C at a rate of 3°C / min, and cooling it to room temperature with the furnace to obtain a sintered material; S4. Heat the sintering material to 320°C at a rate of 3°C / min, keep it warm for 15 minutes, cool it to 170°C, heat it to 390°C at a rate of 4°C / min, keep it warm for 10 minutes, and cool it to room temperature with the furnace.

[0058] Comparative Example 3 A sealing ring filled with PTFE material, whose raw materials include: 80g of polytetrafluoroethylene, 3g of nano-grade talc powder, 10g of nano-silicon dioxide, 5g of carbon nanotube / mesoporous silica composite material, 11g of activated carbon fiber, 1.5g of polyvinyl alcohol, and 1.5g of titanium dioxide.

[0059] The carbon nanotube / mesoporous silica composite material was prepared by the following steps: 3 g of mesoporous silica was added to 30 g of anhydrous ethanol and ultrasonically dispersed for 8 minutes at an ultrasonic frequency of 90 kHz, 0.05 g of nickelocene was added, refluxed and stirred at a temperature of 62°C for 90 minutes, vacuum dried, added to a chemical vapor deposition chamber, purged with argon, reduced in a hydrogen atmosphere for 4 minutes, the deposition power was controlled to 420 W, the deposition pressure was 80 Pa, a mixed gas of argon and hydrogen was introduced (argon flow rate was 275 sccm, hydrogen flow rate was 25 sccm), heated to 720°C, introduced methane (methane flow rate was 18 sccm) and grown for 6 minutes, and cooled to room temperature.

[0060] Activated carbon fiber was prepared by the following steps: 8 g of carbon fiber, 2 g of ethyl orthosilicate, and 1.5 g of hydroxypropyl β-cyclodextrin were added to 35 g of 50% ethanol aqueous solution and stirred evenly, 1.5 mol / L hydrochloric acid was used to adjust the pH value of the system to 5.5, ultrasonic treatment was performed for 90 min at an ultrasonic frequency of 70 kHz, and ammonia water was used to adjust the pH value of the system to 9.5, and ultrasonic treatment was continued for 4.5 h. The mixture was aged at 55 ° C for 8 h, filtered, washed, and vacuum dried.

[0061] The preparation process of the sealing ring filled with PTFE material comprises the following steps: S1, polytetrafluoroethylene, nano-grade talc, and nano-silicon dioxide were mixed, sent to a ball mill, ball-milled through a 400-mesh sieve, dried, sent to a sintering furnace, sintered at a temperature of 335° C. for 90 min, cooled to room temperature, and crushed through a 400-mesh sieve to obtain a prefabricated material; S2. The preform, carbon nanotube / mesoporous silica composite, activated carbon fiber, polyvinyl alcohol, and titanium dioxide were fed into a high-speed mixer and stirred at a speed of 800 r / min for 10 min. The resulting mixture was passed through a 60-mesh sieve and placed in a sealing ring mold. The mixture was pressed at a pressure of 20 MPa for 10 min, and the air was released twice during the pressurization process to obtain a billet with a thickness of 3.0 mm. S3. Place the blank into a sintering furnace, heat it to 320°C at a rate of 2°C / min, sinter for 90 minutes, continue heating it to 390°C at a rate of 8°C / min, sinter for 2 hours, cool it to 230°C at a rate of 3°C / min, and cool it to room temperature along with the furnace.

[0062] The performance of the sealing rings obtained in Example 5 and Comparative Examples 1-3 was measured as follows: (1) The tensile strength of each group of specimens was measured with reference to ASTM D4894-19 (2024).

[0063] (2) Refer to JB / T 10688-2020 "Polytetrafluoroethylene Gasket" for the compression rate and rebound rate of each group of samples.

[0064] (3) Refer to GB / T 20671.5-2020 "Classification system and test methods for non-metallic gasket materials Part 5: Test method for creep relaxation rate of gasket materials" for the creep relaxation rate at room temperature and the creep relaxation rate at 200℃ of each group of samples.

[0065] like Figure 1 、 Figure 2 and Figure 3 As shown, the sealing ring obtained in Example 5 has the highest tensile strength and resilience, and the lowest compression rate and creep relaxation rate, which is better than that of Comparative Examples 1-3 (P < 0.05).

[0066] The reason for the above results is that the present invention uses tetraethyl orthosilicate to form a silica deposition layer on the surface of carbon fiber, and cooperates with hydroxypropyl beta-cyclodextrin to form a large number of active hydroxyl sites on its surface, which cooperates with the silica deposition layer to form a skeleton support network, which greatly enhances not only the tensile strength of carbon fiber, but also cooperates with the prefabricated material to improve the interlaminar shear strength. The present invention adopts a ball milling pre-sintering process of polytetrafluoroethylene, nano-scale talc and nano-silica, which effectively improves the dispersion uniformity of raw materials, solves the performance fluctuation problem caused by uneven dispersion of materials in traditional mixing processes, and lays the foundation for subsequent material performance improvement. The carbon nanotube film generated by catalytic reaction in the mesoporous silica channel forms a synergistic reinforcement structure with the prefabricated material, which not only significantly improves the tensile strength of the material, but also strengthens the dimensional stability of the sealing ring through the nanoscale reinforcement effect of the carbon nanotubes, so that it can rebound quickly after being deformed by force, effectively reducing the leakage risk of the sealing interface. This invention utilizes a preformed material, a carbon nanotube / mesoporous silica composite, and activated carbon fibers to form a composite system. This system undergoes a staged sintering process (including low-temperature, high-temperature, and low-temperature tempering stages). Compared to conventional single-high-temperature sintering processes, this process is more effective in releasing the internal stresses generated by structural transformation during sintering, resulting in a denser, smoother surface and a more regular structure. This process optimization not only increases the overall tensile strength of the material but also effectively reduces its creep relaxation rate at both room and high temperatures, significantly enhancing dimensional stability. This overall improvement in mechanical properties and durability of the sealing product extends its service life.

[0067] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A sealing ring filled with PTFE material, characterized in that: The raw materials include, by mass, 60-100 parts of polytetrafluoroethylene, 1-5 parts of nano-grade talc, 5-15 parts of nano-silicon dioxide, 3-7 parts of carbon nanotube / mesoporous silicon dioxide composite material, 7-15 parts of activated carbon fiber, 1-2 parts of dispersant, and 0.1-1.5 parts of colorant.

2. The sealing ring filled with PTFE material according to claim 1, characterized in that: The dispersant is polyvinyl alcohol.

3. The sealing ring filled with PTFE material according to claim 1, characterized in that: Activated carbon fiber is prepared by the following steps: adding carbon fiber, tetraethyl orthosilicate, and hydroxypropyl beta-cyclodextrin to an ethanol aqueous solution and stirring evenly, adjusting the pH value of the system to 5-6, ultrasonic treatment for 1-2 hours, adjusting the pH value of the system to 9-10, continuing ultrasonic treatment for 3-6 hours, aging at 50-60°C for 5-10 hours, filtering, washing, and vacuum drying.

4. The sealing ring filled with PTFE material according to claim 3, characterized in that: The mass ratio of carbon fiber, tetraethyl orthosilicate and hydroxypropyl beta-cyclodextrin is 5-10:1-3:1-2.

5. The sealing ring filled with PTFE material according to claim 3, characterized in that: The ultrasonic frequency is 60-80kHz.

6. The sealing ring filled with PTFE material according to claim 1, characterized in that: The carbon nanotube / mesoporous silica composite material is prepared by the following steps: adding mesoporous silica to anhydrous ethanol and ultrasonically dispersing it for 5-10 minutes at an ultrasonic frequency of 80-100 kHz, adding nickelocene, refluxing at 60-65°C with stirring for 1-2 hours, vacuum drying, adding it to a chemical vapor deposition chamber, passing argon to purge it, reducing it in a hydrogen atmosphere for 2-5 minutes, controlling the deposition power to 400-450W, the deposition pressure to 50-120 Pa, passing a mixed gas of argon and hydrogen, heating it to 700-750°C, passing methane to grow it for 4-8 minutes, and cooling it to room temperature.

7. The sealing ring filled with PTFE material according to claim 6, characterized in that: The total flow rate of argon and hydrogen is 120-480 sccm, and the flow ratio of argon to hydrogen is 5-15:

1.

8. The sealing ring filled with PTFE material according to claim 6, characterized in that: The methane flow rate is 15-20 sccm.

9. A process for preparing a sealing ring filled with PTFE material as claimed in any one of claims 1 to 8, characterized in that: The steps include: S1. Mix polytetrafluoroethylene, nano-grade talc powder and nano-silicon dioxide, ball-mill and sieve, dry, sinter at 320-350°C for 1-2h, cool to room temperature, and crush and sieve to obtain a prefabricated material; S2, stirring the preform, carbon nanotube / mesoporous silica composite, activated carbon fiber, dispersant, and colorant for 5-15 minutes, sieving, and pressing at 15-25 MPa for 5-15 minutes, releasing air 1-3 times during the pressurization process to obtain a blank; S3, heating the blank to 300-340°C, sintering for 1-2 hours, heating to 380-400°C, sintering for 1-3 hours, cooling to 200-260°C, and cooling to room temperature with the furnace to obtain a sintered material; S4. Heat the sintering material to 300-350℃, keep it warm for 10-20min, cool it down to 150-200℃, heat it up to 380-400℃, keep it warm for 5-15min, and cool it to room temperature along with the furnace.

10. The process for preparing a sealing ring filled with PTFE material according to claim 9, characterized in that: In S3, during the process of heating to 300-340°C, the heating rate is 1-3°C / min; during the process of heating to 380-400°C, the heating rate is 5-10°C / min; during the process of cooling to 200-260°C, the cooling rate is 1-5°C / min.

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