Low-wear PTFE-based sealing element and preparation method thereof

Abstract

The invention discloses a low-wear PTFE-based sealing element and a preparation method thereof, belongs to the technical field of PTFE-based material preparation, and aims to solve the technical problem that the sealing performance and the low-wear performance of a PTFE-based sealing element in the prior art need to be further improved. Reversible connection structures are introduced into particle layers, interface coupling and bridging units are constructed on sheet layers, a dynamic thioether network skeleton is embedded into a continuous phase, a multi-layer structure system from point to surface to body is formed, and the structure participates in force transmission, interface regulation and control and deformation constraint in the forming and running process, so that the mechanical performance of the structure is improved, and the mechanical performance of the structure is improved. The material shows a collaborative optimization trend in the aspects of frictional wear, thermal-mechanical coupling stability and gas barrier behavior, and comprehensive performance improvement brought by structural integrated construction is embodied.

Description

Technical Field

[0001] This invention relates to the field of PTFE-based material preparation technology, specifically to a low-wear PTFE-based seal and its preparation method. Background Technology

[0002] Polytetrafluoroethylene (PTFE) is widely used in the field of fluid sealing for gaskets, annular seals and valve sealing structures due to its regular molecular chain, low surface energy and outstanding chemical inertness. However, pure PTFE material is prone to molecular chain slippage, cold flow deformation and surface wear accumulation under long-term friction and load coupling, which in turn causes changes in dimensional stability and fluctuations in interface bonding.

[0003] Under high-pressure gas or high-frequency opening and closing conditions, the above-mentioned structural evolution is more significant, which may lead to increased wear rate and fluctuations in sealing reliability. In order to improve its service performance, the industry usually modifies the structure of PTFE through filling reinforcement, blending modification or surface modification. However, different modification paths still have differences in dispersion uniformity, interfacial bonding efficiency and long-term stability. Therefore, structural optimization and system construction of low-wear PTFE-based seals continue to be an important research direction in the field of sealing materials.

[0004] Currently, PTFE-based seals mostly use physical filling or simple blending modification to improve wear resistance. However, the dispersion state and interfacial bonding of fillers in the matrix are limited. Under frictional loads, interfacial deintercalation or particle peeling is prone to occur, resulting in material removal mainly through brittle wear. The shear path at the contact interface is unstable. At the same time, the particles mainly rely on physical compaction to form a bond structure, lacking continuous constraints on the interfacial connection state. Under repeated start-stop or alternating load conditions, micro-damage accumulation and surface structure destruction are likely to occur.

[0005] Furthermore, under thermo-mechanical coupling conditions, traditional PTFE materials are affected by molecular chain slippage and cold flow effects, making it easy for the force transmission path within the continuous phase to rearrange and be interrupted. Local deformation is difficult to control effectively, and the fillers mostly exist in an isolated and dispersed state, making it difficult to form a continuous structural support or planar confinement structure. This results in limited suppression of chain segment movement under high-temperature conditions. In addition, the lack of structural constraints on the evolution of micro-gap and gas migration paths within the material means that there is still room for improvement in the density and long-term stability of the microstructure under high-pressure gas sealing conditions.

[0006] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a low-wear PTFE-based seal and its preparation method, in order to solve the technical problem that the sealing performance and low-wear performance of PTFE-based seals in the prior art need to be further improved.

[0008] The objective of this invention can be achieved through the following technical solution: a low-wear PTFE-based sealant, comprising the following raw material components by weight: 80-85 parts reversibly cross-linked PTFE particles, 8-12 parts fluoroarylized-boron nitrogen-bridged graphene, 8-10 parts dynamic sulfide network framework, 1-2 parts polyvinyl alcohol, 1-2 parts dioctyl phthalate, and 0.2-0.4 parts 2,6-di-tert-butylhydroquinone; The method for preparing the reversible cross-linked PTFE particles is as follows: furan-grafted PTFE particles, 4,4'-bismaleimide diphenylmethane and N-methyl-2-pyrrolidone are added to a reaction vessel and stirred until evenly dispersed. The reaction vessel is then heated to 140-150℃ and stirred for 5-6 hours. The reversible cross-linked PTFE particles are obtained after post-treatment.

[0009] Furthermore, the ratio of furan-grafted PTFE particles, 4,4'-bismaleimide diphenylmethane, and N-methyl-2-pyrrolidone is 20g:4-5g:160mL. The post-treatment includes: cooling to room temperature after the reaction, filtering to collect the solid, washing and drying to obtain reversibly cross-linked PTFE particles.

[0010] Furthermore, the furan-grafted PTFE particles are prepared by the following method: A1. Polytetrafluoroethylene powder, sodium, naphthalene and tetrahydrofuran are added to a reaction vessel, nitrogen gas is introduced for protection, and then post-processing is performed to obtain activated PTFE particles. A2. Activated PTFE particles, 2-tetrahydrofuranol methacrylate, azobisisobutyronitrile and N,N-dimethylformamide are added to a reaction vessel and stirred until evenly dispersed. The reaction vessel is then heated to 60-70℃ and stirred for 3-4 hours. After the reaction is completed, the filter cake is collected by filtration, washed and dried to obtain furan-grafted PTFE particles.

[0011] Furthermore, in step A1, the ratio of polytetrafluoroethylene powder, sodium, naphthalene and tetrahydrofuran is 20-24g:1-2g:2-3g:200mL. The post-treatment includes: after the reaction is completed, adding three times the mass of deionized water to quench the reaction, filtering to collect the solid, washing and drying to obtain activated PTFE particles. Furthermore, in step A2, the ratio of activated PTFE particles, 2-tetrahydrofuranol methacrylate, azobisisobutyronitrile, and N,N-dimethylformamide is 20g:10-12mL:0.8-1.2g:180mL.

[0012] Furthermore, the preparation method of the dynamic sulfide network material is as follows: 1,4-benzenedithiol, 4,4'-difluorodiphenyl sulfone, 4,4'-thiodiphenylthiol, cesium carbonate and N-methyl-2-pyrrolidone are added to a reaction vessel, the reaction vessel is heated to 100-110℃, and stirred for 4-5 hours. The dynamic sulfide network framework is then obtained through post-treatment.

[0013] Furthermore, in the preparation of the dynamic sulfide network framework, the ratio of 1,4-benzenedithiol, 4,4'-difluorodiphenyl sulfone, 4,4'-thiodiphenylthiol, cesium carbonate, and N-methyl-2-pyrrolidone is 6-8 g:10-12 g:3-4 g:8-10 g:150 mL. The post-treatment includes: cooling to room temperature after the reaction, pouring the reaction solution into five times its volume of deionized water to precipitate, washing and drying after precipitation to obtain the dynamic sulfide network framework.

[0014] Furthermore, the fluoroaryl-boron nitrogen-bridged graphene is prepared by the following method: B1. After adding graphene oxide and deionized water to the reaction vessel and stirring evenly, add 4-fluoroaniline and 10wt% hydrochloric acid aqueous solution. Stir in an ice bath and add sodium nitrite in ten equal batches. After the addition is completed, heat the reaction vessel to 20-25℃ and keep it at the temperature for 3-4 hours. Post-treatment yields fluoroarylated graphene oxide. B2. Fluoroarylated graphene oxide, 3-(aminopropyl)triethoxysilane and anhydrous toluene are added to a reaction vessel and stirred until evenly dispersed. The reaction vessel is then heated to 75-85℃ and stirred for 1-2 hours. Boric acid is added and the reaction is continued for 2-3 hours. The resulting product is fluoroarylated-boron-nitrogen-bridged graphene.

[0015] Further, in step B1, the ratio of graphene oxide, deionized water, 4-fluoroaniline, 10wt% hydrochloric acid aqueous solution, and sodium nitrite is 5-6g:500mL:4-5g:15-20mL:4-5g. The post-processing includes: after the reaction is completed, filtering and collecting the filter cake, washing and drying it to obtain fluoroarylized graphene oxide. Furthermore, in step B2, the ratio of the fluoroarylized graphene oxide, 3-(aminopropyl)triethoxysilane, anhydrous toluene, and boric acid is 5g:8-10mL:150mL:4g. The post-treatment includes: after the reaction is completed, filtering and collecting the filter cake, washing and drying it to obtain fluoroarylized-boron nitrogen-bridged graphene.

[0016] The present invention also proposes a method for preparing a low-wear PTFE-based seal, comprising the following steps: S1. Reversible cross-linked PTFE particles, fluoroarylated-boron nitrogen-bridged graphene, dynamic sulfide network framework, polyvinyl alcohol, dioctyl phthalate and 2,6-di-tert-butylhydroquinone are added to a mixer and mixed evenly to obtain composite sealing material powder. S2. Add the composite sealing material powder into the mold, and hot press it at 320-340℃ and 15-25MPa for 20-30 minutes. Then demold to obtain the PTFE-based sealing component.

[0017] The present invention has the following beneficial effects: 1. The fluoroarylated-boron-nitrogen-bridged graphene prepared by this invention is dispersed in the system in the form of sheet-like structures between the reversibly cross-linked PTFE continuous phase. The fluorinated aryl structure constructed on its surface forms a compatible interface with the matrix. Under the action of friction load, it preferentially distributes in the contact area and participates in the stress sharing of the interface. Its sheet-like structure tends to be oriented during sliding, which makes the shear path at the contact interface tend to be stable. At the same time, the reversible cross-linked structure constrains the connection state between particles, reducing the occurrence of micro-detachment and interface damage. Moreover, the dynamic sulfide network skeleton is embedded in it, which provides support and buffer for local stress concentration areas. This changes the material removal mode during the friction process from brittle peeling to a relatively stable surface transfer mode, and the overall operation tends to be stable.

[0018] 2. The reversible cross-linked PTFE particles prepared by this invention achieve interface rearrangement and structural integration during the hot pressing stage. During the subsequent loading and heating process, the interparticle connection structure continuously constrains the chain segment movement, enabling the continuous phase to maintain a relatively complete force transmission path under external load. At the same time, the dynamic sulfide network skeleton, with aromatic sulfone units as the main chain skeleton embedded in it, maintains the spatial support framework under thermal action and forms structural resistance to local deformation regions. The fluoroaryl graphene sheets form a planar confinement structure in the matrix, suppressing chain segment slippage and local flow under high temperature conditions. Finally, through multiple structural units forming a mutually cooperating load-bearing system under thermo-mechanical coupling, the material exhibits a relatively stable deformation evolution process during loading and heating.

[0019] 3. In the preparation process of PTFE-based sealing components, the reversibly cross-linked PTFE particles are integrated by hot pressing to form a continuous phase structure. The connecting units between the particles constitute a stable internal load-bearing network, enabling the material to maintain a relatively uniform structural response under external stress and maintain a tight contact state in the interface region. Furthermore, the fluoroaryl-boron nitrogen-bridged graphene dispersed in the matrix is ​​embedded in the continuous phase in a layered form. Its two-dimensional sheets construct a multi-level interface transition structure inside the material, causing the gas to exhibit path extension and direction change characteristics during transport. At the same time, the dynamic sulfide network skeleton participates in the stress regulation of the overall structure, constraining the structural relaxation and gap evolution at the microscale. Finally, by utilizing the inherent synergistic relationship formed between the multiple components during operation, the internal structure of the material is kept continuous and dense, the gas migration behavior is correspondingly restricted, and the overall structural stability is maintained. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In this application, the polyvinyl alcohol used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number P729145; the polytetrafluoroethylene powder used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number 767377; and the graphene oxide used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number G699141.

[0022] Example 1: This example provides a method for preparing reversibly cross-linked PTFE particles, including the following steps: Step ①: Preparation of activated PTFE particles Weigh out 20.0g of polytetrafluoroethylene powder, 1.0g of sodium, 2.0g of naphthalene and 200.0mL of tetrahydrofuran and add them to the reaction vessel. After purging with nitrogen, stir at room temperature for 2 hours. After the reaction is complete, add three times the mass of deionized water to quench the reaction. Filter to collect the solid, wash and dry it to obtain activated PTFE particles.

[0023] Step 2: Preparation of furan-grafted PTFE particles Weigh out 20.0g of activated PTFE particles, 10.0mL of 2-tetrahydrofuran alcohol methacrylate, 0.8g of azobisisobutyronitrile and 180.0mL of N,N-dimethylformamide and add them to the reaction vessel. Stir until the mixture is evenly dispersed. Heat the reaction vessel to 60℃ and keep it at that temperature for 3 hours. After the reaction is complete, filter and collect the filter cake. After washing and drying, furan-grafted PTFE particles are obtained.

[0024] Step 3: Preparation of reversibly cross-linked PTFE particles Weigh out 20.0g of furan-grafted PTFE particles, 4.0g of 4,4'-bismaleimide diphenylmethane, and 160.0mL of N-methyl-2-pyrrolidone and add them to a reaction vessel. Stir until the mixture is evenly dispersed. Heat the reaction vessel to 140℃ and keep it at that temperature for 5 hours. After the reaction is complete, cool it to room temperature, filter and collect the solid. After washing and drying, reversible cross-linked PTFE particles are obtained.

[0025] The reaction principle for preparing reversibly cross-linked PTFE particles is as follows: Under the action of the sodium / naphthalene system, an electron transfer process occurs on the surface of polytetrafluoroethylene powder, and the local C–F bonds are activated to form carbon sites with certain reactivity. In the presence of a free radical initiator, 2-tetrahydrofuranol methacrylate can undergo a grafting reaction near the above-mentioned active sites, introducing furan-containing segments into the surface layer of polytetrafluoroethylene powder. Under heating conditions, the introduced furan groups undergo a cycloaddition reaction with the maleimide structure in 4,4'-bismaleimide diphenylmethane to form a connecting unit containing a six-membered ring structure, thereby constructing a cross-linked structure with reversible covalent bond characteristics between particles.

[0026] The mechanism of action of reversibly cross-linked PTFE particles in PTFE-based seals is as follows: The activation step introduces a small amount of reactive carbon structure into the surface of polytetrafluoroethylene powder, giving the originally inert low surface energy interface a certain degree of chemical activity and providing binding sites for subsequent grafting reactions. The furan grafting reaction introduces side group structures with cycloaddition activity into the particle surface, forming functional units on the particle surface that can participate in reversible covalent bonding. Further, a cycloaddition reaction occurs with bismaleimide, constructing connection nodes containing six-membered ring structures between particles. The above structural regulation transforms the particle interface from simple physical fusion to a composite interface structure containing covalent bonding characteristics. During hot pressing, the interface rearrangement and recombination are achieved, thereby improving the overall structural continuity and density.

[0027] Example 2: This example provides a method for preparing reversibly cross-linked PTFE particles, including the following steps: Step ①: Preparation of activated PTFE particles Weigh out 24.0g of polytetrafluoroethylene powder, 2.0g of sodium, 3.0g of naphthalene and 200.0mL of tetrahydrofuran and add them to the reaction vessel. After purging with nitrogen, stir at room temperature for 3 hours. After the reaction is complete, add three times the mass of deionized water to quench the reaction. Filter to collect the solid, wash and dry it to obtain activated PTFE particles.

[0028] Step 2: Preparation of furan-grafted PTFE particles Weigh out 20.0g of activated PTFE particles, 12.0mL of 2-tetrahydrofuran alcohol methacrylate, 1.2g of azobisisobutyronitrile and 180.0mL of N,N-dimethylformamide and add them to the reaction vessel. Stir until the mixture is evenly dispersed. Heat the reaction vessel to 70℃ and keep it at that temperature for 4 hours. After the reaction is complete, filter and collect the filter cake. After washing and drying, furan-grafted PTFE particles are obtained.

[0029] Step 3: Preparation of reversibly cross-linked PTFE particles Weigh out 20.0g of furan-grafted PTFE particles, 4.0g of 4,4'-bismaleimide diphenylmethane, and 160.0mL of N-methyl-2-pyrrolidone and add them to a reaction vessel. Stir until the mixture is evenly dispersed. Heat the reaction vessel to 140℃ and keep it at that temperature for 5 hours. After the reaction is complete, cool it to room temperature, filter and collect the solid. After washing and drying, reversible cross-linked PTFE particles are obtained.

[0030] Example 3: This example provides a method for preparing reversibly cross-linked PTFE particles, including the following steps: Step ①: Preparation of activated PTFE particles Weigh out 21.0g of polytetrafluoroethylene powder, 1.6g of sodium, 2.5g of naphthalene and 200.0mL of tetrahydrofuran and add them to the reaction vessel. After purging with nitrogen, stir at room temperature for 3 hours. After the reaction is completed, add three times the mass of deionized water to quench the reaction. Filter to collect the solid, wash and dry it to obtain activated PTFE particles.

[0031] Step 2: Preparation of furan-grafted PTFE particles Weigh out 20.0g of activated PTFE particles, 11.0mL of 2-tetrahydrofuran alcohol methacrylate, 1.0g of azobisisobutyronitrile and 180.0mL of N,N-dimethylformamide and add them to the reaction vessel. Stir until the mixture is evenly dispersed. Heat the reaction vessel to 65℃ and keep it at that temperature for 4 hours. After the reaction is complete, filter and collect the filter cake. After washing and drying, furan-grafted PTFE particles are obtained.

[0032] Step 3: Preparation of reversibly cross-linked PTFE particles Weigh out 20.0g of furan-grafted PTFE particles, 4.5g of 4,4'-bismaleimide diphenylmethane, and 160.0mL of N-methyl-2-pyrrolidone and add them to a reaction vessel. Stir until the mixture is evenly dispersed. Heat the reaction vessel to 145℃ and keep it at that temperature for 6 hours. After the reaction is complete, cool it to room temperature, filter and collect the solid. After washing and drying, reversible cross-linked PTFE particles are obtained.

[0033] Example 4: This example provides a method for preparing fluoroaryl-boron nitrogen-bridged graphene, including the following steps: Step I: Preparation of fluoroarylized graphene oxide Weigh out 5.0 g of graphene oxide and 500.0 mL of deionized water and add them to the reaction vessel. Stir well, then add 4.0 g of 4-fluoroaniline and 15.0 mL of 10 wt% hydrochloric acid aqueous solution. Stir in an ice bath and add sodium nitrite in ten equal batches, with a total addition of 4.0 g. After the addition is complete, heat the reaction vessel to 20 °C and keep it at that temperature for 3 h. After the reaction is complete, filter and collect the filter cake. After washing and drying, fluoroaryl graphene oxide is obtained.

[0034] Step II: Preparation of fluoroaryl-boron nitrogen-bridged graphene Weigh out 5.0 g of fluoroarylized graphene oxide, 8.0 mL of 3-(aminopropyl)triethoxysilane and 150.0 mL of anhydrous toluene and add them to the reaction vessel. Stir until the mixture is evenly dispersed. Heat the reaction vessel to 75 °C and stir for 1 h. Then add 4.0 g of boric acid and continue to stir for 2 h. After the reaction is complete, filter and collect the filter cake. After washing and drying, fluoroarylized-boron nitrogen-bridged graphene is obtained.

[0035] The reaction principle for preparing fluoroaryl-boron nitrogen-bridged graphene is as follows: Under acidic conditions, 4-fluoroaniline undergoes a diazotization reaction to generate an aryl diazonium salt. The intermediate decomposes on the surface of graphene oxide, forming aryl radicals. These radicals react with sps on the graphene oxide sheets. 2 Carbon structures or oxygen-containing functional groups undergo covalent bonding to introduce fluorinated aryl structures; subsequently, 3-(aminopropyl)triethoxysilane undergoes hydrolysis and condensation to form silicon-oxygen structures, which are then linked to functional groups on the graphene surface. At the same time, coordination or condensation reactions occur between amino groups and boric acid to form structural units with boron-nitrogen bond characteristics, thus constructing a connection system containing silicon-oxygen bonds and boron-nitrogen structures on the surface of the sheet.

[0036] The mechanism of action of fluoroarylated-boron-nitrogen-bridged graphene in PTFE-based seals is as follows: Fluorinated aryl groups are covalently introduced into the surface of graphene oxide through diazotization, transforming the graphene sheets from a simple oxygen-containing structure to a surface structure containing aromatic substituents. This modulates the surface energy and chemical activity, improving the interfacial compatibility between the graphene sheets and the fluoropolymer matrix. Furthermore, through silane hydrolysis and condensation and the involvement of boric acid, a connection structure containing silicon-oxygen bonds and boron-nitrogen structural units is constructed on the sheet surface, enhancing the interfacial bonding ability between sheets and between the sheets and the matrix. The above structural regulation helps to improve the dispersion state of graphene in the PTFE matrix, promote interfacial stress transfer, reduce the formation of interfacial defects, and thus improve the overall structural stability and mechanical continuity of the composite seal.

[0037] Example 5: This example provides a method for preparing fluoroaryl-boron nitrogen-bridged graphene, including the following steps: Step I: Preparation of fluoroarylized graphene oxide Weigh out 6.0 g of graphene oxide and 500.0 mL of deionized water and add them to the reaction vessel. Stir well, then add 5.0 g of 4-fluoroaniline and 20.0 mL of 10 wt% hydrochloric acid aqueous solution. Stir in an ice bath and add sodium nitrite in ten equal batches, with a total addition of 5.0 g. After the addition is complete, heat the reaction vessel to 25 °C and keep it at that temperature for 4 h. After the reaction is complete, filter and collect the filter cake. After washing and drying, fluoroaryl graphene oxide is obtained.

[0038] Step II: Preparation of fluoroaryl-boron nitrogen-bridged graphene Weigh out 5.0 g of fluoroarylized graphene oxide, 10.0 mL of 3-(aminopropyl)triethoxysilane and 150.0 mL of anhydrous toluene and add them to the reaction vessel. Stir until the mixture is evenly dispersed. Heat the reaction vessel to 85 °C and stir for 2 h. Then add 4.0 g of boric acid and continue to stir for 3 h. After the reaction is complete, filter and collect the filter cake. After washing and drying, fluoroarylized-boron nitrogen-bridged graphene is obtained.

[0039] Example 6: This example provides a method for preparing fluoroaryl-boron nitrogen-bridged graphene, including the following steps: Step I: Preparation of fluoroarylized graphene oxide Weigh out 5.4 g of graphene oxide and 500.0 mL of deionized water and add them to the reaction vessel. Stir well, then add 4.5 g of 4-fluoroaniline and 18.0 mL of 10 wt% hydrochloric acid aqueous solution. Stir in an ice bath and add sodium nitrite in ten equal batches, with a total addition of 4.5 g. After the addition is complete, heat the reaction vessel to 25 °C and keep it at that temperature for 4 h. After the reaction is complete, filter and collect the filter cake. After washing and drying, fluoroarylated graphene oxide is obtained.

[0040] Step II: Preparation of fluoroaryl-boron nitrogen-bridged graphene Weigh out 5.0 g of fluoroarylized graphene oxide, 9.0 mL of 3-(aminopropyl)triethoxysilane and 150.0 mL of anhydrous toluene and add them to the reaction vessel. Stir until the mixture is evenly dispersed. Heat the reaction vessel to 80 °C and stir for 2 h. Then add 4.0 g of boric acid and continue to stir for 3 h. After the reaction is complete, filter and collect the filter cake. After washing and drying, fluoroarylized-boron nitrogen-bridged graphene is obtained.

[0041] Example 7: This example provides a method for preparing a PTFE-based seal, including the following steps: Step 1: Preparation of dynamic sulfide network framework Weigh out 6.0 g of 1,4-benzenedithiol, 10.0 g of 4,4'-difluorodiphenyl sulfone, 3.0 g of 4,4'-thiodiphenylthiol, 8.0 g of cesium carbonate, and 150.0 mL of N-methyl-2-pyrrolidone and add them to a reaction vessel. Heat the reaction vessel to 100 °C and stir for 5 h. After the reaction is complete, cool to room temperature and pour the reaction solution into five times its volume of deionized water to precipitate. After precipitation, wash and dry to obtain a dynamic sulfide network framework.

[0042] The reaction principle for preparing the dynamic sulfide network framework is as follows: Under the action of cesium carbonate, the thiol groups in 1,4-benzenedithiol and 4,4'-thiodibenzenedithiol undergo deprotonation to generate sulfonates. These sulfonates act as nucleophiles, inducing nucleophilic aromatic substitution reactions on the aromatic rings in the 4,4'-difluorodiphenyl sulfone molecule that are activated by the strong electron-withdrawing effect of the sulfone groups. Fluorine atoms, as leaving groups, are gradually substituted, forming an aromatic sulfide bond linkage structure. As the reaction proceeds, the multifunctional monomers undergo gradual condensation, causing the aromatic structural units containing sulfone groups to alternately connect with the aromatic sulfide bonds. The system gradually transforms from a linear growth structure to a spatially linked structure, constructing a cross-linked network structure at the molecular level with the aromatic sulfone structure as the main backbone and sulfide bonds as the connecting nodes.

[0043] The mechanism of action of the dynamic sulfide network skeleton in PTFE-based seals is as follows: The aromatic sulfide network framework formed under the action of cesium carbonate has aromatic sulfone structures as the main chain units and sulfide bonds as connecting nodes. It exhibits a spatial structure feature of alternating rigid aromatic rings and flexible sulfide bonds. On the one hand, this structure has high structural stability and can exist as a relatively rigid supporting framework in the composite system. On the other hand, the sulfide bonds have a certain degree of bond angle adjustability and molecular chain flexibility, which can undergo micro-conformation adjustment during stress or thermo-pressing. After the introduction of this network framework, it forms a dispersed phase structure in the PTFE continuous phase. Through physical interlocking and interfacial contact, it participates in the stress transfer process, reduces local stress concentration in the matrix, and plays a role in structural filling and restricting chain segment slippage at the interparticle interface, thereby improving the overall structural stability and dimensional retention of the composite seal.

[0044] Step 2: Preparation of composite sealing material powder By weight, weigh 80 parts of the reversible cross-linked PTFE particles prepared in Example 1, 8 parts of the fluoroarylized-boron nitrogen-bridged graphene prepared in Example 4, 8 parts of the dynamic sulfide network skeleton, 1 part of polyvinyl alcohol, 1 part of dioctyl phthalate and 0.2 parts of 2,6-di-tert-butylhydroquinone and add them to a mixer and mix evenly to obtain composite sealing material powder.

[0045] Step 3: Preparation of PTFE-based sealing components The composite sealing material powder is added into the mold and hot-pressed at 320℃ and 15MPa for 20 minutes. After demolding, a PTFE-based seal with an inner diameter of 89mm, an outer diameter of 142mm, and a thickness of 1.5mm is obtained.

[0046] The reaction principle for preparing the dynamic sulfide network framework is as follows: Under heating and pressure, the reversibly cross-linked polytetrafluoroethylene powder undergoes melting and softening, and chain segment migration. The interparticle interfaces gradually fuse and densify, forming a continuous phase structure. The cycloaddition structure between furan groups and maleimide groups is in a dynamic equilibrium state of dissociation and recombination at high temperature, enabling the molecular chains to have a certain rearrangement ability during hot pressing and to reform six-membered ring-structured connecting units during cooling. At the same time, fluoroarylated-boron nitrogen-modified graphene is dispersed in the system, and its surface oxygen-containing groups, silicon-oxygen bonds, and boron nitrogen structural units form interfacial interactions with the polymer matrix. The aromatic sulfide skeleton is embedded in the continuous phase structure in the composite system, participating in the overall structure construction through physical interlocking between molecular chains and local interfacial bonding. Finally, the multi-component system completes spatial rearrangement and structural integration under hot pressing conditions, ultimately forming a composite network system containing reversible covalent connecting units and multiphase interface structures.

[0047] Example 8: This example provides a method for preparing a PTFE-based seal, including the following steps: Step 1: Preparation of dynamic sulfide network framework Weigh out 8.0 g of 1,4-benzenedithiol, 12.0 g of 4,4'-difluorodiphenyl sulfone, 4.0 g of 4,4'-thiodiphenylthiol, 10.0 g of cesium carbonate, and 150.0 mL of N-methyl-2-pyrrolidone and add them to a reaction vessel. Heat the reaction vessel to 110 °C and stir for 5 h. After the reaction is complete, cool to room temperature and pour the reaction solution into five times its volume of deionized water to precipitate. After precipitation, wash and dry to obtain a dynamic sulfide network framework.

[0048] Step 2: Preparation of composite sealing material powder By weight, 85 parts of the reversible cross-linked PTFE particles prepared in Example 2, 12 parts of the fluoroarylized-boron nitrogen-bridged graphene prepared in Example 5, 10 parts of the dynamic sulfide network skeleton, 2 parts of polyvinyl alcohol, 2 parts of dioctyl phthalate and 0.4 parts of 2,6-di-tert-butylhydroquinone were weighed and added to a mixer and mixed evenly to obtain composite sealing material powder.

[0049] Step 3: Preparation of PTFE-based sealing components The composite sealing material powder is added into the mold and hot-pressed at 340℃ and 25MPa for 30 minutes. After demolding, a PTFE-based sealing component with an inner diameter of 89mm, an outer diameter of 142mm, and a thickness of 1.5mm is obtained.

[0050] Example 9: This example provides a method for preparing a PTFE-based seal, including the following steps: Step 1: Preparation of dynamic sulfide network framework Weigh out 7.0 g of 1,4-benzenedithiol, 11.0 g of 4,4'-difluorodiphenyl sulfone, 3.5 g of 4,4'-thiodiphenylthiol, 9.0 g of cesium carbonate, and 150.0 mL of N-methyl-2-pyrrolidone and add them to a reaction vessel. Heat the reaction vessel to 105 °C and stir for 5 h. After the reaction is complete, cool to room temperature and pour the reaction solution into five times its volume of deionized water to precipitate. After precipitation, wash and dry to obtain a dynamic sulfide network framework.

[0051] Step 2: Preparation of composite sealing material powder By weight, 81 parts of the reversible cross-linked PTFE particles prepared in Example 3, 10 parts of the fluoroarylized-boron nitrogen-bridged graphene prepared in Example 6, 9 parts of the dynamic sulfide network skeleton, 2 parts of polyvinyl alcohol, 2 parts of dioctyl phthalate and 0.3 parts of 2,6-di-tert-butylhydroquinone were weighed and added to a mixer and mixed evenly to obtain composite sealing material powder.

[0052] Step 3: Preparation of PTFE-based sealing components The composite sealing material powder is added into the mold and hot-pressed at 330℃ and 20MPa for 25 minutes. After demolding, a PTFE-based sealing component with an inner diameter of 89mm, an outer diameter of 142mm, and a thickness of 1.5mm is obtained.

[0053] Comparative Example 1: The difference between this comparative example and Example 9 is that in the preparation process of the reversible cross-linked PTFE particles used in step 2, step ③ is omitted, and the furan-grafted PTFE particles prepared in step ② are used to replace the reversible cross-linked PTFE particles in an equal amount.

[0054] Comparative Example 2: The difference between this comparative example and Example 9 is that, in the preparation process of the fluoroaryl-boron-nitrogen-bridged graphene used in step two, step II is omitted, and the fluoroaryl-derived graphene oxide prepared in step I is used to replace the fluoroaryl-boron-nitrogen-bridged graphene in an equal amount.

[0055] Comparative Example 3: The difference between this comparative example and Example 9 is that the dynamic sulfide network framework is not used in step two.

[0056] Performance testing: The mass wear and coefficient of friction of the PTFE-based seals prepared in Examples 7-9 and Comparative Examples 1-3 were tested in accordance with the standard GB / T 3960-2016 "Test Method for Sliding Friction and Wear of Plastics". The deformation temperature of the PTFE-based seals prepared in Examples 7-9 and Comparative Examples 1-3 under a load of 1.8 MPa was tested in accordance with the standard GB / T 1634.1-2025 "Determination of deformation temperature of plastics under load - Part 1: General test method". The sealing performance of the PTFE-based seals prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 9126.1-2023 "Non-metallic flat gaskets for pipe flanges - Part 1: PN series". The specific data are shown in Table 1. Table 1 - Performance Test Data for Each Sample

[0057] Data Analysis: Comparative analysis of the data in Table 1 reveals that the PTFE-based seal prepared by this invention exhibits a wear rate of 0.011g, a friction coefficient of 0.09, and a deformation temperature of 158℃ under a load of 1.8MPa. Simultaneously, under test conditions of 4.0MPa pressure, 99.9% helium gas as the medium, and a test temperature of 23℃, the gas leakage rate is 0.05cm. 3 ·s -1 All data points are better than the comparative data, indicating that: In Comparative Example 1, after step ③ was removed during the preparation of reversibly crosslinked PTFE particles, the PTFE particles lost their reversible crosslinked structural characteristics. This caused the interparticle connection to change from a dynamically reconfigurable crosslinked structure to a looser physical contact. This particle structure, lacking crosslinking, could not form a continuous internal force transmission network during hot pressing, and the interfacial bonding force was significantly reduced. Under the action of force and friction, the slippage and relative displacement between particles were more likely to occur, leading to interfacial instability. Furthermore, due to the lack of adaptive rearrangement ability of reversible crosslinking, the material could not effectively cope with local deformation caused by external stress, which in turn led to the rapid expansion of microcracks and pores. Ultimately, this resulted in a decrease in overall wear resistance, thermal stability, and sealing performance, and directly affected the durability and long-term operational stability of the material. In Comparative Example 2, after step II was omitted in the preparation of fluoroarylized-boron-nitrogen-bridged graphene, the fluoroarylized graphene oxide did not undergo boron-nitrogen bridging and silane interface treatment, resulting in a significant weakening of its dispersion and interfacial bonding in the matrix. This led to a lack of support from the bridging structure, reduced stability of the graphene sheets within the material, and an inability to effectively construct multi-level transitional gas permeation pathways. Furthermore, under high pressure or friction, the graphene sheets were prone to delamination or local aggregation, affecting the uniformity and stability of the gas barrier effect. In addition, the stress transfer efficiency between the sheets and the matrix decreased, leading to interfacial mismatch, which affected the sealing and heat resistance of the material, thus degrading its overall performance. In Comparative Example 3, after the dynamic sulfide network skeleton was removed in step two, the material lost its structural support and stress regulation function throughout the entire matrix. The stress distribution and local relaxation suppression effect that could originally be achieved through the dynamic sulfide skeleton were weakened, resulting in the inability to effectively regulate the deformation of local areas inside the material after being compressed. Without this kind of skeleton support, the material is more prone to microstructural relaxation and pore expansion during heating or friction, which leads to a decrease in the overall structural stability of the material. In addition, without the structural support network, local damage cannot be effectively repaired, further reducing the long-term durability and sealing performance of the material. In conclusion, the material system constructed in this scheme exhibits a well-defined and interlocking configuration at the structural level. Specifically, the reversibly cross-linked PTFE particles form a continuous phase basic structure with connecting units during the molding stage, ensuring relatively stable force transmission and constraint relationships between particles during subsequent loading and temperature rise. Fluoroarylated-boron-nitrogen-bridged graphene participates in the construction of the continuous phase through interfacial coupling and layer embedding, introducing multi-level interfacial structures and path adjustment factors at the microscale. The dynamic sulfide network framework permeates the continuous phase, continuously participating in stress distribution and deformation evolution. These three structural units act at the particle interface level, the layer interface level, and the overall framework level, respectively, forming a progressive internal connection during operation. When any level of structure is omitted, the corresponding structural constraints and response paths change, and the system shifts from its original multi-level collaborative state to a relatively independent unit response state, resulting in different development trends in material behavior.

[0058] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A low-wear PTFE-based seal, characterized in that, The raw material composition includes the following parts by weight: 80-85 parts reversibly cross-linked PTFE particles, 8-12 parts fluoroarylized-boron nitrogen-bridged graphene, 8-10 parts dynamic sulfide network framework, 1-2 parts polyvinyl alcohol, 1-2 parts dioctyl phthalate and 0.2-0.4 parts 2,6-di-tert-butylhydroquinone; The method for preparing the reversible cross-linked PTFE particles is as follows: furan-grafted PTFE particles, 4,4'-bismaleimide diphenylmethane, and N-methyl-2-pyrrolidone are added to a reaction vessel and stirred until uniformly dispersed. The reaction vessel is then heated to 140-150℃ and stirred for 5-6 hours. The reversible cross-linked PTFE particles are obtained after post-treatment. The ratio of furan-grafted PTFE particles, 4,4'-bismaleimide diphenylmethane, and N-methyl-2-pyrrolidone is 20g:4-5g:160mL.

2. The low-wear PTFE-based seal according to claim 1, characterized in that, The furan-grafted PTFE particles were prepared by the following method: A1. Polytetrafluoroethylene powder, sodium, naphthalene and tetrahydrofuran are added to a reaction vessel, nitrogen gas is introduced for protection, and then post-processing is performed to obtain activated PTFE particles. A2. Activated PTFE particles, 2-tetrahydrofuranol methacrylate, azobisisobutyronitrile and N,N-dimethylformamide are added to a reaction vessel and stirred until evenly dispersed. The reaction vessel is then heated to 60-70℃ and stirred for 3-4 hours. After the reaction is completed, the filter cake is collected by filtration, washed and dried to obtain furan-grafted PTFE particles.

3. The low-wear PTFE-based seal according to claim 2, characterized in that, In step A1, the ratio of polytetrafluoroethylene powder, sodium, naphthalene, and tetrahydrofuran is 20-24g:1-2g:2-3g:200mL; in step A2, the ratio of activated PTFE particles, 2-tetrahydrofuran alcohol methacrylate, azobisisobutyronitrile, and N,N-dimethylformamide is 20g:10-12mL:0.8-1.2g:180mL.

4. The low-wear PTFE-based seal according to claim 1, characterized in that, The preparation method of the dynamic sulfide network material is as follows: 1,4-benzenedithiol, 4,4'-difluorodiphenyl sulfone, 4,4'-thiodiphenylthiol, cesium carbonate and N-methyl-2-pyrrolidone are added to a reaction vessel, the reaction vessel is heated to 100-110℃, and stirred for 4-5 hours. The dynamic sulfide network framework is then obtained after post-treatment.

5. A low-wear PTFE-based seal according to claim 4, characterized in that, In the preparation of the dynamic sulfide network framework, the ratio of 1,4-benzyl dithiol, 4,4'-difluorodiphenyl sulfone, 4,4'-thiodiphenyl thiol, cesium carbonate and N-methyl-2-pyrrolidone was 6-8 g:10-12 g:3-4 g:8-10 g:150 mL.

6. A low-wear PTFE-based seal according to claim 1, characterized in that, The fluoroaryl-boron nitrogen-bridged graphene was prepared by the following method: B1. After adding graphene oxide and deionized water to the reaction vessel and stirring evenly, add 4-fluoroaniline and 10wt% hydrochloric acid aqueous solution. Stir in an ice bath and add sodium nitrite in ten equal batches. After the addition is completed, heat the reaction vessel to 20-25℃ and keep it at the temperature for 3-4 hours. Post-treatment yields fluoroarylated graphene oxide. B2. Fluoroarylated graphene oxide, 3-(aminopropyl)triethoxysilane and anhydrous toluene are added to a reaction vessel and stirred until evenly dispersed. The reaction vessel is then heated to 75-85℃ and stirred for 1-2 hours. Boric acid is added and the reaction is continued for 2-3 hours. The resulting product is fluoroarylated-boron-nitrogen-bridged graphene.

7. A low-wear PTFE-based seal according to claim 6, characterized in that, In step B1, the ratio of graphene oxide, deionized water, 4-fluoroaniline, 10wt% hydrochloric acid aqueous solution, and sodium nitrite is 5-6g:500mL:4-5g:15-20mL:4-5g; in step B2, the ratio of fluoroarylized graphene oxide, 3-(aminopropyl)triethoxysilane, anhydrous toluene, and boric acid is 5g:8-10mL:150mL:4g.

8. A method for preparing a low-wear PTFE-based seal as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Reversible cross-linked PTFE particles, fluoroarylated-boron nitrogen-bridged graphene, dynamic sulfide network framework, polyvinyl alcohol, dioctyl phthalate and 2,6-di-tert-butylhydroquinone are added to a mixer and mixed evenly to obtain composite sealing material powder. S2. Add the composite sealing material powder into the mold, and hot press it at 320-340℃ and 15-25MPa for 20-30 minutes. Then demold to obtain the PTFE-based sealing component.

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