Valve conductive PTFE-based sealing material and preparation method thereof

Abstract

The invention discloses a valve conductive PTFE-based sealing material and a preparation method thereof, and relates to the field of valve conductive sealing materials. The preparation method comprises the following steps: respectively pretreating the thermoplastic resin (PTFE and PEEK), the carbon nanotubes and the conductive carbon spheres, weighing and mixing the pretreated thermoplastic resin (PTFE and PEEK), the carbon nanotubes and the conductive carbon spheres according to a certain proportion, and then mixing in a high-speed mixer to obtain a uniformly dispersed mixture; weighing a certain amount of the mixture, and carrying out compression molding to obtain a molded blank; and carrying out high-temperature sintering treatment on the molded blank to obtain the conductive PTFE-based sealing material. Two fillers, namely the carbon nanotubes and the conductive carbon balls, are added into a PTFE / PEEK matrix for synergistic modification, so that the conductive sealing material has good conductivity, wear resistance, mechanical property, creep resistance and sealing property.

Description

A conductive PTFE-based sealing material for valves and its preparation method Technical Field

[0001] This invention belongs to the field of conductive sealing materials technology, and particularly relates to a conductive PTFE-based sealing material for valves and its preparation method. Background Technology

[0002] Valves play a crucial role in the petrochemical industry, used to regulate and control the flow of liquids, gases, and vapors, ensuring stable fluid transport during petrochemical processes. Different types of valves (such as ball valves, gate valves, globe valves, and check valves) allow for precise flow control to meet process requirements. The valve industry involves large quantities of flammable and explosive gases and liquids; static electricity buildup can potentially trigger fires or explosions.

[0003] Polytetrafluoroethylene (PTFE) is widely used in valve sealing due to its excellent properties such as self-lubrication, high temperature resistance, and chemical corrosion resistance. However, the low hardness and poor wear resistance of PTFE greatly limit the application of single-phase PTFE materials. To improve the hardness and wear resistance of PTFE, the most effective way is to composite PTFE, that is, to form PTFE-based composite materials by introducing fillers such as bronze, graphite, glass fiber, and carbon fiber.

[0004] The introduction of conductive fillers not only improves the wear resistance and mechanical strength of materials, but also effectively enhances antistatic properties, avoiding safety hazards caused by static electricity accumulation. By controlling the type, particle size, and content of nanofillers, long-term sealing of sealing materials can be achieved under high temperature, high pressure, and strong corrosive environments, meeting the stringent requirements of the petrochemical industry for high-performance and long-life valve sealing materials.

[0005] Carbon nanomaterials have gained favor among researchers due to their excellent mechanical, electrical, and thermal properties. Carbon nanotubes, with their high aspect ratio, excellent conductivity, and interfacial reinforcement effect, form a three-dimensional conductive network in a PTFE matrix, significantly reducing the material's volume resistivity and enabling rapid electrostatic discharge. However, because carbon nanotubes have extremely high surface energy, excessive addition easily leads to agglomeration, intrinsically creating pore-like structural defects that readily become crack initiators, often resulting in reduced mechanical properties and wear resistance. Designing conductive fillers that synergistically improve the conductivity and mechanical strength of the PTFE matrix with carbon nanotubes, forming multiphase composite materials, has significant practical implications. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, the present invention aims to provide a conductive PTFE-based sealing material for valves and its preparation method. This conductive PTFE-based sealing material for valves is produced by synergistic modification of a PTFE / PEEK matrix by adding carbon nanotubes and conductive carbon balls as fillers. This conductive sealing material exhibits excellent conductivity, wear resistance, mechanical properties, creep resistance, and sealing performance.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a conductive PTFE-based sealing material for valves includes the following steps:

[0009] S1: The thermoplastic resin (PTFE and PEEK), carbon nanotubes and conductive carbon balls are pretreated separately, and the pretreated thermoplastic resin (PTFE, PEEK), carbon nanotubes and conductive carbon balls are weighed and mixed in a certain proportion, and then placed in a high-speed mixer to mix and obtain a uniformly dispersed mixture.

[0010] S2: Weigh a certain amount of the mixture obtained above and mold it to obtain a molded blank;

[0011] S3: The molded blank obtained above is subjected to high-temperature sintering treatment to obtain conductive PTFE-based sealing material.

[0012] Preferably, in S1, the thermoplastic resin, PTFE or PEEK powder has a particle size of 20-40 micrometers, the carbon nanotubes are single-walled carbon nanotubes (SWCNTs) with a diameter of 10-40 nm, and the conductive carbon spheres have a diameter of 20-100 nm.

[0013] Preferably, the conductive carbon sphere in S1 has many nano-voids inside and the overall structure is cauliflower-shaped. It is composed of curved carbon sheet layers wrapped together. The interplanar spacing d002 of the (002) crystal plane of the carbon sphere is about 0.34 nm. The carbon sphere is mainly amorphous carbon structure.

[0014] Preferably, the conductive carbon spheres in S1 are synthesized by catalysis, with the carbon source being a CaC2-CHCl3 system raw material and the catalyst being at least one of iron(II,III) oxide, ferric chloride, ferrocene, Pt, Fe, Co, Ni, and Au.

[0015] Preferably, the pretreatment of the S1 thermoplastic resin is as follows: drying the thermoplastic resin at 80°C for 3 hours.

[0016] Preferably, the pretreatment of carbon nanotubes in S1 involves surface functionalization to improve their dispersibility and interfacial bonding in the PTFE matrix. The specific surface functionalization method is as follows:

[0017] S11: Weigh 4.0g of carbon nanotubes and add them to 3L of a mixed acid solution with a sulfuric acid:nitric acid volume ratio of 3:1. After sonication for 15min, stir magnetically at room temperature for 24h. Then wash and filter repeatedly with deionized water until the pH value is 7. Dry the filter cake to obtain carboxylated carbon nanotubes, denoted as c-GCNT.

[0018] S12: Subsequently, amino groups were grafted onto c-GCNTs. A certain amount of DCC was dissolved in 3.0 L of anhydrous ethanol, and 900 mg of c-GCNTs were added. The mixture was sonicated for 30 min, then incubated in a water bath at 55 °C for 30 min. 750 mL of saturated p-aminobenzenesulfonic acid aqueous solution was added to the system and incubated in a water bath at 60 °C for 24 h. The mixture was then repeatedly washed with ethanol and deionized water and filtered until the pH value was 7. The filter cake was dried to obtain aminated carbon nanotubes, denoted as a-GCNTs.

[0019] Preferably, the pretreatment of the conductive carbon balls in S1 is a surface modification treatment, the purpose of which is to improve their compatibility and adhesion in the PTFE matrix. The specific method is as follows:

[0020] Step 1, Solution preparation: Dissolve 50g of polyvinyl alcohol (PVA) in 450ml of DMF (N,N-dimethylformamide) to prepare a PVA solution with a concentration of 10% (w / v). Stir and heat to 60-80℃ until completely dissolved.

[0021] Step 2, Coating process: Place 100g of conductive carbon balls into the 10% PVA solution prepared above and perform ultrasonic vibration for 12 hours to make PVA uniformly adhere to the surface of the conductive carbon balls.

[0022] Step 3, drying and curing: repeatedly wash and filter the PVA-coated conductive carbon ball solution with deionized water until the pH value is 7. Place the filter paper in a constant temperature drying oven at 120℃ for 3 hours to cure the PVA on the surface of the conductive carbon balls.

[0023] Preferably, in S1, the pretreated thermoplastic resin (PTFE, PEEK), carbon nanotubes, and conductive carbon spheres are in the following proportions by weight: PTFE resin 86-98.5 parts, PEEK resin 0.5-8 parts, pretreated carbon nanotubes 0.5-3.0 parts, and pretreated conductive carbon spheres 0.5-3 parts.

[0024] Preferably, in step S2, the mixture is molded by compression molding, which is a cold pressing process with a pressure of 50-70 MPa, a pressing speed of 15-25 mm / min, and a holding time of 30 s-30 min. Then, the mixture is demolded to obtain a molded blank.

[0025] Preferably, in step S3, the obtained molded blank undergoes high-temperature sintering treatment, specifically as follows:

[0026] The sintering temperature is 375℃, the holding time is 4-6h, the heating rate is 10-20℃ / min, and then it is naturally cooled to obtain a conductive PTFE-based sealing material.

[0027] Compared with the effects of existing technologies, the beneficial effects of this invention are as follows:

[0028] 1. Carbon nanotubes are formed by rolling up a single layer of graphene (single-walled carbon nanotubes) or by coaxially nesting multiple layers of graphene (multi-walled carbon nanotubes). Due to their high aspect ratio, excellent conductivity, and interfacial reinforcement effect, they form a three-dimensional conductive network in the PTFE matrix, significantly reducing the material's volume resistivity and enabling rapid electrostatic discharge. Because carbon nanotubes have extremely high surface energy, excessive addition can easily lead to agglomeration. Surface functionalization of carbon nanotubes, introducing carboxyl and amino groups, can enhance the interaction between carbon nanotubes and the PTFE matrix, thereby improving their dispersibility.

[0029] 2. Conductive carbon spheres, with a diameter of 20-50 nm, are synthesized from CaC2-CHCl3 system raw materials through catalysis with catalysts (Fe3O4 and ferric chloride). The carbon spheres contain numerous nanopores and have a cauliflower-like overall structure, composed of entangled layers of bent carbon sheets. The interplanar spacing d002 of the (002) crystal plane of the carbon sphere is approximately 0.34 nm. The carbon spheres are primarily amorphous carbon structures. Coating the surface of the conductive carbon spheres with polyvinyl alcohol (PVA) can improve their compatibility and adhesion in a PTFE matrix while maintaining their good conductivity.

[0030] 3. Different forms of carbon materials play different roles in PTFE. Surface-functionalized carbon nanotubes and conductive carbon spheres are added to the PTFE matrix. The conductive carbon spheres provide local conductive points, while the carbon nanotubes connect these conductive points through their long chain structure, thereby forming a continuous conductive network and improving the overall conductivity and mechanical strength of PTFE. Attached Figure Description

[0031] Figure 1 is a schematic diagram of the structure of the single-walled carbon nanotube in this invention;

[0032] Figure 2 shows the SEM and TEM analysis results of the conductive carbon spheres in this invention;

[0033] Figure 3 shows the EDS composition analysis of the conductive PTFE-based sealing material;

[0034] Figure 4 is the EDS composition analysis spectrum of the conductive PTFE-based sealing material. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0037] The test methods used in Examples 1-6 and Comparative Examples 1-3 of the present invention are as follows:

[0038] Mechanical property testing: Tensile properties were tested according to ASTM D4745, at a room temperature of 23±2℃, an ambient humidity of 50%RH, and a test speed of 50mm / min.

[0039] Friction and wear performance: Tested according to GB 3960—2016. Before the test, the surface was polished with 1200-grit metallographic sandpaper. The test conditions were: positive load 196N, friction torque 5N·m, rotation speed 200r / min, test time 120min, dry friction, room temperature 23±2℃.

[0040] Electrical performance conforms to GB / T 1410-2006 / IEC 60093:1980. Test environment: temperature 23±2℃, relative humidity RH≤75%, conductive electrode: copper plate, insulating pad: marble table.

[0041] Example 1

[0042] S1: The thermoplastic resins (PTFE and PEEK), carbon nanotubes, and conductive carbon balls are pretreated separately. 92.5 parts of the pretreated PTFE resin, 5 parts of PEEK resin, 2 parts of carbon nanotubes, and 0.5 parts of conductive carbon balls are placed in a high-speed mixer according to their weight parts and mixed. The mixture is then tamped once with a tamping machine to obtain a uniformly dispersed mixture.

[0043] S2: Weigh 260g of the mixture obtained above and mold it. The molding pressure is 55MPa, the pressing speed is 20mm / min, the holding time is 2min, and then demold to obtain the molded blank.

[0044] S3: The molded blank obtained above is subjected to high-temperature sintering treatment at a temperature of 375°C and a holding time of 4 hours to obtain a conductive PTFE-based sealing material.

[0045] The PTFE resin and PEEK powder have a particle size of 20-40 micrometers. Both PTFE and PEEK are pretreated by drying at 80℃ for 3 hours.

[0046] The pretreatment method for carbon nanotubes is as follows:

[0047] Weigh 4.0g of single-walled carbon nanotubes (10-40nm in diameter) and add them to 3L of a mixed acid solution with a sulfuric acid:nitric acid volume ratio of 3:1. After sonication for 15min, stir magnetically at room temperature for 24h. Then wash and filter repeatedly with deionized water until the pH value is 7. Dry the filter cake to obtain carboxylated carbon nanotubes c-GCNT.

[0048] Take 150-500g (preferably 300g) of N,N , - Dicyclohexylcarbodiimide (DCC) was dissolved in 3.0 L of anhydrous ethanol, and 900 mg of c-GCNT was added. The mixture was sonicated for 30 min, then heated in a water bath at 55 °C for 30 min. 750 mL of saturated p-aminobenzenesulfonic acid aqueous solution was added to the system and heated in a water bath at 60 °C for 24 h. The mixture was then repeatedly washed with ethanol and deionized water and filtered until the pH value was 7. The filter cake was dried to obtain aminated carbon nanotubes a-GCNT.

[0049] The method for preparing conductive carbon balls is as follows:

[0050] 10 ml of CHCl3 or CCl4, 20 g of powdered CaC2, and 15-75 g (preferably 50 g) of iron(III) oxide catalyst were placed in a 150 ml 316 L stainless steel autoclave (argon gas was introduced beforehand to purge air from the autoclave). The temperature was raised to 550 °C and held for 12 h, then allowed to cool naturally to room temperature. After collecting the samples, they were repeatedly washed with deionized water, dilute hydrochloric acid, and anhydrous ethanol until the pH of the filtered water was 7. The resulting black product was dried at 120 °C for 8 h. Some samples were subjected to high-temperature heat treatment at 2100 °C to finally obtain conductive carbon spheres.

[0051] The pretreatment method for the conductive carbon spheres prepared above is as follows:

[0052] Solution preparation: Dissolve 50g of polyvinyl alcohol (PVA) in 450ml of N,N-dimethylformamide (DMF), stir and heat to 60-80℃ until completely dissolved;

[0053] Coating process: 100g of conductive carbon balls are placed in the PVA solution prepared above and subjected to ultrasonic vibration for 12h to make PVA uniformly adhere to the surface of the conductive carbon balls.

[0054] Drying and curing: The PVA-coated conductive carbon ball solution is repeatedly washed and filtered with deionized water until the pH value is 7. The filter paper is placed in a constant temperature drying oven at 120℃ and dried for 3 hours. The PVA is cured on the surface of the conductive carbon balls, and the pretreated conductive carbon balls are obtained.

[0055] Figure 2-4 shows that thermogravimetric analysis of the conductive PTFE-based sealing material revealed that the elemental composition of the residue after the black conductive carbon filler was burned off was mainly C, O, and F. Combined with TEM analysis, the conductive carbon consisted of irregular cauliflower-shaped carbon spheres with diameters ranging from 20 to 50 nm. The diameter distribution was relatively uneven, with most being spherical particles and some carbon spheres agglomerated to form chains or multiple bonded spheres. The electron diffraction pattern showed a disordered structure with multiple diffuse diffractions and broadened rings, indicating that these carbon spheres were mainly composed of amorphous carbon structures.

[0056] Example 2

[0057] S1: Pre-treat the thermoplastic resins (PTFE and PEEK), carbon nanotubes, and conductive carbon balls respectively. Then, place 92 parts of the pre-treated PTFE resin, 5 parts of PEEK resin, 2 parts of carbon nanotubes, and 1 part of conductive carbon balls into a high-speed mixer according to their weight parts and mix them. Then, tamp the mixture once with a tamping machine to obtain a uniformly dispersed mixture.

[0058] S2: Weigh 260g of the mixture obtained above and mold it. The molding pressure is 55MPa, the pressing speed is 20mm / min, the holding time is 2min, and then demold to obtain the molded blank.

[0059] S3: The molded blank obtained above is subjected to high-temperature sintering treatment at a temperature of 375°C and a holding time of 4 hours to obtain a conductive PTFE-based sealing material.

[0060] The pretreatment methods for thermoplastic resin (PTFE or PEEK), carbon nanotubes, and conductive carbon spheres in Example 2 are the same as those in Example 1.

[0061] Example 3

[0062] S1: The thermoplastic resins (PTFE and PEEK), carbon nanotubes, and conductive carbon balls are pretreated separately. 91 parts of the pretreated PTFE resin, 5 parts of PEEK resin, 2 parts of carbon nanotubes, and 2 parts of conductive carbon balls are placed in a high-speed mixer according to their weight and mixed. The mixture is then tamped once with a tamping machine to obtain a uniformly dispersed mixture.

[0063] S2: Weigh 260g of the mixture obtained above and mold it. The molding pressure is 55MPa, the pressing speed is 20mm / min, the holding time is 2min, and then demold to obtain the molded blank.

[0064] S3: The molded blank obtained above is subjected to high-temperature sintering treatment at a temperature of 375°C and a holding time of 4 hours to obtain a conductive PTFE-based sealing material.

[0065] The pretreatment methods for thermoplastic resin (PTFE or PEEK), carbon nanotubes, and conductive carbon spheres in Example 3 are the same as those in Example 1.

[0066] Example 4

[0067] S1: Pre-treat thermoplastic resins (PTFE and PEEK), carbon nanotubes, and conductive carbon balls respectively. Then, place 90 parts of pre-treated PTFE resin, 5 parts of PEEK resin, 2 parts of carbon nanotubes, and 3 parts of conductive carbon balls into a high-speed mixer according to their weight parts and mix them. Then, tamp the mixture once with a tamping machine to obtain a uniformly dispersed mixture.

[0068] S2: Weigh 260g of the mixture obtained above and mold it. The molding pressure is 55MPa, the pressing speed is 20mm / min, the holding time is 2min, and then demold to obtain the molded blank.

[0069] S3: The molded blank obtained above is subjected to high-temperature sintering treatment at a temperature of 375°C and a holding time of 4 hours to obtain a conductive PTFE-based sealing material.

[0070] The pretreatment methods for the thermoplastic resin (PTFE or PEEK), carbon nanotubes, and conductive carbon spheres in Example 4 are the same as those in Example 1.

[0071] Example 5

[0072] S1: Pre-treat thermoplastic resins (PTFE and PEEK), carbon nanotubes, and conductive carbon balls respectively. Then, place 92 parts of pre-treated PTFE resin, 5 parts of PEEK resin, 1 part of carbon nanotubes, and 2 parts of conductive carbon balls into a high-speed mixer according to their weight parts and mix them. Then, tamp the mixture once with a tamping machine to obtain a uniformly dispersed mixture.

[0073] S2: Weigh 260g of the mixture obtained above and mold it. The molding pressure is 55MPa, the pressing speed is 20mm / min, the holding time is 2min, and then demold to obtain the molded blank.

[0074] S3: The molded blank obtained above is subjected to high-temperature sintering treatment at a temperature of 375°C and a holding time of 4 hours to obtain a conductive PTFE-based sealing material.

[0075] The pretreatment methods for thermoplastic resin (PTFE or PEEK), carbon nanotubes, and conductive carbon spheres in Example 5 are the same as those in Example 1.

[0076] Example 6

[0077] S1: Pre-treat thermoplastic resins (PTFE and PEEK), carbon nanotubes, and conductive carbon balls respectively. Then, place 91 parts of pre-treated PTFE resin, 5 parts of PEEK resin, 1 part of carbon nanotubes, and 3 parts of conductive carbon balls into a high-speed mixer according to their weight parts and mix them. Then, tamp the mixture once with a tamping machine to obtain a uniformly dispersed mixture.

[0078] S2: Weigh 260g of the mixture obtained above and mold it. The molding pressure is 55MPa, the pressing speed is 20mm / min, the holding time is 2min, and then demold to obtain the molded blank.

[0079] S3: The molded blank obtained above is subjected to high-temperature sintering treatment at a temperature of 375°C and a holding time of 4 hours to obtain a conductive PTFE-based sealing material.

[0080] The pretreatment methods for the thermoplastic resin (PTFE or PEEK), carbon nanotubes, and conductive carbon spheres in Example 6 are the same as those in Example 1.

[0081] The PTFE-based sealing materials obtained in Examples 1-6 were tested, and the results are shown in Table 1.

[0082] Comparative Example 1

[0083] For comparison with this technical solution, the comparative example is counted by weight ratio: 95 parts PTFE, 5 parts PEEK resin, and the other preparation methods are exactly the same as in Example 1. The performance test results are shown in Table 1.

[0084] Comparative Example 2

[0085] For comparison with this technical solution, the comparative example is calculated by weight ratio as follows: 94 parts PTFE, 5 parts PEEK resin, and 2 parts carbon nanotubes. The carbon nanotubes are not surface-functionalized. The other preparation methods are exactly the same as in Example 1. The performance test results are shown in Table 1.

[0086] Comparative Example 3

[0087] For comparison with this technical solution, the comparative example is calculated by weight ratio as follows: 93 parts PTFE, 5 parts PEEK resin, 1 part carbon nanotube, and 2 parts conductive carbon spheres. The conductive carbon spheres are not surface modified. The other preparation methods are exactly the same as in Example 1. The performance test results are shown in Table 1.

[0088] Table 1 shows the effect of the addition amount of carbon nanotubes and conductive carbon spheres of different components on the performance of PTFE-based sealing materials:

[0089]

[0090] As can be seen from the results of the above embodiments and comparative examples:

[0091] As can be seen from Examples 1-6 and Comparative Examples 1-3, the addition of surface-modified carbon nanotubes and conductive carbon balls to the PTFE matrix greatly improves the conductivity, mechanical properties, and friction properties of the PTFE sealing material. The overall performance is optimal when 1 part of surface-functionalized carbon nanotubes and 2 parts of conductive carbon balls are added. This is because the conductive carbon balls and carbon nanotubes form a multiphase composite structure with the PTFE matrix. The conductive carbon balls provide local conductive points, while the carbon nanotubes connect these conductive points through their long-chain structure, thereby forming a continuous conductive network and improving the overall conductivity of PTFE.

[0092] Furthermore, from Example 5 and Comparative Examples 2 and 3, it can be concluded that surface functionalization and surface chemical modification of carbon nanotubes and conductive carbon spheres can effectively improve the dispersion and interfacial bonding ability of carbon nanotubes in the PTFE matrix, improve the compatibility and adhesion of conductive carbon spheres in the PTFE matrix, and significantly reduce wear resistance and friction reduction, that is, the overall friction performance is improved.

[0093] This invention discloses a conductive PTFE-based sealing material for valves and its preparation method, relating to the field of conductive sealing materials for valves. Its purpose is to solve the technical problems of poor dispersibility and poor interfacial bonding of carbon nanotubes in a PTFE matrix. The technical solution involves carboxylating or amylating single-walled carbon nanotubes to improve their interaction with PTFE and enhance their dispersibility. Additionally, conductive carbon spheres synthesized from a carbon source via catalysis are added and their surface chemically modified (coated with polyvinyl alcohol) to improve adhesion to the PTFE resin matrix. These two different forms of carbon materials play different roles in PTFE. The surface-functionalized carbon nanotubes and conductive carbon spheres, added to the PTFE matrix, provide localized conductive points, while the carbon nanotubes connect these conductive points through their long-chain structure, forming a continuous conductive network. This improves the overall conductivity and mechanical strength of PTFE, enabling this multiphase composite material to fully exert its conductive sealing function in valves and other fields in the petrochemical industry.

Claims

1. A method for preparing a conductive PTFE-based sealing material for valves, characterized in that, Includes the following steps: S1: Pre-treat thermoplastic resin PTFE and PEEK, carbon nanotubes, and conductive carbon balls respectively. Weigh the pre-treated thermoplastic resin, carbon nanotubes, and conductive carbon balls in a certain proportion, and then mix them in a high-speed mixer to obtain a uniformly dispersed mixture. S2: Weigh a certain amount of the mixture and mold it to obtain a molded blank. S3: Perform high-temperature sintering treatment on the molded blank to obtain a conductive PTFE-based sealing material.

2. The method for preparing a valve conductive PTFE-based sealing material according to claim 1, characterized in that: In step S1, the thermoplastic resin, PTFE or PEEK powder has a particle size of 20-40 micrometers, the carbon nanotubes are single-walled carbon nanotubes with a diameter of 10-40 nm, and the conductive carbon spheres have a diameter of 20-100 nm.

3. The method for preparing a valve conductive PTFE-based sealing material according to claim 1, characterized in that: The conductive carbon sphere in step S1 has many nano-voids inside and the overall structure is cauliflower-shaped. It is composed of curved carbon sheet layers wrapped together. The interplanar spacing d002 of the (002) crystal plane of the carbon sphere is about 0.34 nm. The carbon sphere is mainly composed of amorphous carbon structure.

4. The method for preparing a valve conductive PTFE-based sealing material according to claim 1, characterized in that: The pretreatment of thermoplastic resin in step S1 is as follows: the thermoplastic resin is dried at 80°C for 3 hours.

5. The method for preparing a valve conductive PTFE-based sealing material according to claim 2, characterized in that: The pretreatment of carbon nanotubes in step S1 involves surface functionalization. The specific surface functionalization method is as follows: S11: Weigh 4.0g of carbon nanotubes and add them to 3L of a mixed acid solution with a sulfuric acid:nitric acid volume ratio of 3:

1. After sonication for 15min, stir magnetically at room temperature for 24h. Then, wash and filter repeatedly with deionized water until the pH value is 7. Dry the filter cake to obtain carboxylated carbon nanotubes, denoted as c-GCNT. S12: Dissolve a certain amount of DCC in 3.0L of anhydrous ethanol, add 900mg of c-GCNT, sonicate for 30min, and then heat in a 55℃ water bath for 30min. Add 750mL of saturated p-aminobenzenesulfonic acid aqueous solution to the system and heat in a 60℃ water bath for 24h. Then, wash and filter repeatedly with ethanol and deionized water until the pH value is 7. Dry the filter cake to obtain ammoniated carbon nanotubes, denoted as a-GCNT.

6. The method for preparing a valve conductive PTFE-based sealing material according to claim 2, characterized in that: In step S1, the pretreatment of the conductive carbon balls is a surface modification treatment. The specific method is as follows: Step 1, solution preparation: Dissolve 50g of polyvinyl alcohol (PVA) in 450ml of N,N-dimethylformamide (DMF), stir and heat to 60-80℃ until completely dissolved; Step 2, coating process: Place 100g of conductive carbon balls into the above-prepared PVA solution and ultrasonically vibrate for 12h to make the PVA uniformly adhere to the surface of the conductive carbon balls; Step 3, drying and curing: Wash the conductive carbon ball solution with PVA coating repeatedly with deionized water and filter until the pH value is 7. Place the filter paper in a constant temperature drying oven at 120℃ and dry for 3h to cure the PVA on the surface of the conductive carbon balls.

7. The method for preparing a valve conductive PTFE-based sealing material according to claim 2, characterized in that: In step S1, the pretreated thermoplastic resin, carbon nanotubes, and conductive carbon spheres are in the following proportions by weight: 86-98.5 parts PTFE resin, 0.5-8 parts PEEK resin, 0.5-3.0 parts pretreated carbon nanotubes, and 0.5-3 parts pretreated conductive carbon spheres.

8. The method for preparing a valve conductive PTFE-based sealing material according to claim 1, characterized in that: In step S2, the mixture is molded into a cold pressing mold with a pressure of 50-70 MPa, a pressing speed of 15-25 mm / min, and a holding time of 30 s-30 min. Then, it is demolded to obtain a molded blank.

9. The method for preparing a valve conductive PTFE-based sealing material according to claim 1, characterized in that: In step S3, the obtained molding blank is subjected to high-temperature sintering treatment, specifically: the sintering temperature is 375℃, the holding time is 4-6h, the heating rate is 10-20℃ / min, and then it is naturally cooled to obtain conductive PTFE-based sealing material.

10. The valve conductive PTFE-based sealing material prepared according to the preparation method of the valve conductive PTFE-based sealing material according to claim 1.

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