A polytetrafluoroethylene sealing material and a method for producing the same

Abstract

The application relates to the field of high polymer materials, and particularly discloses a polytetrafluoroethylene sealing material and a preparation method thereof. The polytetrafluoroethylene sealing material comprises the following raw materials in parts by weight: 60-80 parts of polytetrafluoroethylene resin, 15-20 parts of modified carbon fiber, 5-10 parts of polyether ether ketone, 1-5 parts of ultrahigh molecular weight polyethylene fiber, 20-30 parts of bronze powder, 1.5-5 parts of inorganic nano filler and 0.05-0.2 parts of a coupling agent. The modified carbon fiber comprises the following raw materials in parts by weight: 5-10 parts of boron nitride, 5-10 parts of polyamide acid solution, 0.5-1.5 parts of attapulgite, 10-15 parts of polyacrylonitrile and 0.5-1.5 parts of PPS fiber powder. The polytetrafluoroethylene sealing material has the advantages of strong wear resistance, high toughness, anti-creep and long service life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, and more particularly to a polytetrafluoroethylene sealing material and a preparation method thereof. BACKGROUND

[0002] Polytetrafluoroethylene is widely used in many fields due to its excellent chemical stability, high temperature resistance and low friction coefficient, especially for making seals for aircraft engines. The seals for aircraft engines are mainly applied to hydraulic systems and mainly play the roles of protection, lubrication and wear resistance. The seals play a crucial role in the related mechanical equipment of the aircraft engine, and the seals applied to the hydraulic system often need to withstand extreme pressure, load and temperature, but the PTFE has poor wear resistance, is easy to wear and has a short service life. If any form of failure occurs in these seals, it will affect the normal work of the hydraulic system or even cause serious damage, for example, oil leakage will cause great harm to the aircraft engine. Therefore, it is necessary to modify the PTFE material.

[0003] In the prior art, the Chinese patent application file with the application number 2006100475006 discloses a carbon fiber filled polytetrafluoroethylene and a manufacturing method thereof. The carbon fiber filled polytetrafluoroethylene is composed of 60-80% of polytetrafluoroethylene, 10-35% of carbon fiber and carbon powder, and a filler with a content not exceeding 15%, wherein the mass ratio of the carbon fiber and the carbon powder is 1:0.5-1.5, and the filler is one or a combination of more than one of graphite, glass fiber, molybdenum disulfide and copper powder.

[0004] In view of the above related technologies, the inventors find that the use of carbon fiber, carbon powder and glass fiber as filling modification materials has the problems that the polarity difference between the filling materials and the polytetrafluoroethylene is large, the filling materials have poor wettability in the polytetrafluoroethylene, are not uniformly dispersed, and are difficult to form effective bonding, so that the prepared material is easy to crack and wear. Once worn out, it will backfire on the hydraulic mechanism, causing wear of the piston or piston rod, and further causing greater harm to the aircraft engine. SUMMARY

[0005] In order to improve the toughness and wear resistance of the polytetrafluoroethylene sealing material, the present application provides a polytetrafluoroethylene sealing material and a preparation method thereof.

[0006] In the first aspect, the present application provides a polytetrafluoroethylene sealing material, which adopts the following technical scheme:

[0007] A polytetrafluoroethylene sealing material comprises the following raw materials by weight: 60-80 parts of polytetrafluoroethylene resin, 15-20 parts of modified carbon fiber, 5-10 parts of polyether ether ketone, 1-5 parts of ultra-high molecular weight polyethylene fiber, 20-30 parts of bronze powder, 1.5-5 parts of inorganic nano filler, and 0.05-0.2 parts of coupling agent;

[0008] The preparation method of the modified carbon fiber comprises the following steps:

[0009] Dissolve polyacrylonitrile with an organic solvent to prepare a spinning solution with a concentration of 8-12 wt%;

[0010] Mix boron nitride, PPS fiber powder, attapulgite and polyamide acid solution, ultrasonically disperse, add to the spinning solution, electrospinning after uniform mixing, then heat to 260-280 DEG C and keep for 4-5h, then heat to 700-750 DEG C under argon protection, keep for 1-2h, naturally cool to room temperature, to prepare the modified carbon fiber.

[0011] By adopting the above technical scheme, the polytetrafluoroethylene base material is added with polyether ether ketone, modified carbon fiber, polytetrafluoroethylene fiber and other materials, the polyether ether ketone has high strength, wear resistance, creep resistance and good dimensional stability, and has toughness and rigidity, and has high thermal deformation temperature, and can form a polymer transfer film on the metal surface, thereby having a self-lubricating effect, thereby improving the lubricity of the polytetrafluoroethylene sealing material, achieving the effect of reducing friction and wear resistance, the ultrahigh molecular weight polyethylene fiber has special wear resistance, very low friction coefficient, impact resistance and strong corrosion resistance, and has better anti-creep performance than polytetrafluoroethylene, the addition of the ultrahigh molecular weight polyethylene fiber can improve the lubricity and wear resistance of the polytetrafluoroethylene sealing material, the bronze powder serves as a hard support, in the friction process, can promote the friction chemistry, quickly form a transfer film, reduce the real contact between the polytetrafluoroethylene and the metal edge, and reduce the wear rate, the inorganic nano filler is a rigid particle, is filled into the sealing material, after treatment by the coupling agent, the agglomeration of the inorganic nano filler is reduced, so that the inorganic nano filler is uniformly dispersed in the polytetrafluoroethylene matrix, fully contacts the polytetrafluoroethylene, has good interfacial adhesion, reduces internal defects, so that the tensile strength of the sealing material is improved, the surface of the nano particle treated by the coupling agent forms a soft interface layer, when the sealing material is stressed, the part can play a role in inhibiting crack growth and absorbing part of the impact energy, and the inorganic nano filler preferentially bears the load, and can also adsorb macromolecular chains, the macromolecular chains adsorbed between the inorganic nano filler particles are intertwined, thereby preventing large-area damage of the sealing material and improving wear resistance; the use of the coupling agent can improve the compatibility of the modified carbon fiber, the ultrahigh molecular weight polyethylene fiber, the bronze powder and the inorganic nano filler with the polytetrafluoroethylene, improve the interfacial bonding strength of each component with the polytetrafluoroethylene, reduce the wear rate of the polytetrafluoroethylene sealing material, and improve wear resistance.The modified carbon fiber is made by carbonizing after spinning polyacrylonitrile, and boron nitride and palygorskite with lubricating effect are added in the spinning solution, and polyamide acid solution is used to improve the agglomeration of boron nitride and palygorskite, so that the tensile strength of the carbon fiber is increased, and the polyamide acid solution is amide after spinning and heating, forming polyimide, and the modulus and hardness of polyimide are higher than those of pure polytetrafluoroethylene, so that the rigidity of the sealing material is increased, the plastic deformation resistance of the sealing material is improved, the wear resistance of the sealing material is increased, the thermal conductivity of boron nitride is good, the thermal conductivity of the sealing material is improved, the service life of the sealing material at high temperature is improved, the micro-enhanced area of palygorskite is larger, which is more conducive to preventing the wear of the sealing material caused by shear failure of the friction surface, PPS fiber powder in the matrix preferentially bears the load, and the compressive stress and shear stress on the friction surface are transmitted to the inside of the matrix without stress concentration on the surface layer, effectively preventing large-area damage of polytetrafluoroethylene and improving wear resistance, but the hardness of the fiber powder is large, which will make the hardness of the sealing material large, the friction torque will increase, the friction coefficient will increase, and the fiber powder will be easily detached under the load, causing abrasive wear, but palygorskite and boron nitride can form a lubricating film at the wear site to reduce the friction coefficient and improve the wear resistance of the material, and also can reduce the friction force on the PPS fiber powder and reduce the tendency of PPS fiber to fall off; the macromolecular chains in the structure of PPS fiber powder contain many rigid benzene rings, so the formed fibers contain a high proportion of straight rigid chains, are highly oriented along the fiber axis, and have a large molecular packing density, so they have high tensile modulus and strength, palygorskite and boron nitride reduce the friction coefficient and improve the friction and wear resistance of PPS fiber powder, the friction coefficient is reduced, and the wear rate is reduced; the adhesion of polyimide formed by high-temperature amidation of polyamide acid is large, and the compatibility with polytetrafluoroethylene is good, when the modified carbon fiber is mixed with polytetrafluoroethylene, boron nitride, palygorskite and PPS powder attached to the carbon fiber are randomly embedded in the polytetrafluoroethylene matrix, improving the interfacial adhesion between the modified carbon fiber and polytetrafluoroethylene, and the high-adhesion polyimide can firmly adhere boron nitride, palygorskite and PPS fiber powder to the carbon fiber, which is not easy to be worn and separated, further improving the wear resistance and reducing the wear rate.

[0012] Optionally, the modified carbon fiber includes the following raw materials by weight: 5-10 parts of boron nitride, 5-10 parts of polyamide acid solution, 0.5-1.5 parts of palygorskite, 10-15 parts of polyacrylonitrile, and 0.5-1.5 parts of PPS fiber powder.

[0013] By adopting the technical scheme and using the above-mentioned raw materials, the modified carbon fiber with high interfacial adhesion to the polytetrafluoroethylene matrix can be prepared, the strong and tough interface layer can effectively exert the reinforcing effect of the modified carbon fiber, the load bearing capacity of the sealing material is improved, the boron nitride, the attapulgite and the PPS fiber powder are embedded in the polyimide and uniformly dispersed, the nanometer effect is fully exerted, the comprehensive performance of the material is improved, the wear rate is reduced, the friction chemical reaction of the boron nitride and the attapulgite promotes the formation of the transfer film of the sealing material on the metal surface, the lubricating effect is improved, and the wear of the carbon fiber is reduced.

[0014] Optionally, the spinning voltage is 16-20kv, the receiving distance is 18-20cm, and the spinning speed is 0.75-0.9mL / h.

[0015] By adopting the technical scheme and using the above-mentioned spinning process, the modified carbon fiber with good tensile strength and excellent mechanical properties can be obtained, and when the modified carbon fiber is added to the polytetrafluoroethylene sealing material, the toughness of the sealing material can be improved, and the anti-creep ability can be improved.

[0016] Optionally, the ultra-high molecular weight fiber is made by the following method:

[0017] The ultra-high molecular weight polyethylene is dissolved to prepare a spinning solution with a mass concentration of 2-10%, and the initial fiber is prepared by spinning at 170-175℃;

[0018] 1.7-2 parts of polyvinyl alcohol, 0.8-1 part of polyethylene glycol 1000 and 10 parts of deionized water are uniformly stirred, 0.17-0.2 parts of polytetrafluoroethylene emulsion, 0.1-0.3 parts of silicon nitride and 0.3-0.6 parts of rare earth compound are added, and the mixture is uniformly stirred at 60-65℃, then 0.2-0.25 parts of glutaraldehyde is added after acidification, the mixture is kept for 50-60min, and defoaming is performed to prepare a treatment solution;

[0019] The initial fiber is immersed in the treatment solution for 10-12h and dried to prepare the ultra-high molecular weight polyethylene fiber.

[0020] By adopting the technical scheme, the ultra-high molecular weight polyethylene is dissolved and spun to prepare primary fibers with high mechanical strength and excellent toughness, then polyvinyl alcohol, polytetrafluoroethylene emulsion and other components are prepared into a treatment liquid, the primary fibers are immersed and treated in the treatment liquid, due to the existence of a large number of hydroxyl groups on the polyvinyl alcohol molecular chain, the polyvinyl alcohol can produce self-crosslinking, and glutaraldehyde and polyvinyl alcohol can also produce crosslinking, so that the treatment liquid can form a treatment film with a spatial crosslinking structure, the polytetrafluoroethylene particles are covered or adhered by the polyvinyl alcohol film, and play a role similar to a ball bearing on the ultra-high molecular weight polyethylene fiber, thereby increasing the roughness of the ultra-high molecular weight polyethylene fiber and improving the interfacial bonding force between the ultra-high molecular weight polyethylene fiber and the polytetrafluoroethylene, the rare earth compound is added to the treatment liquid, the rare earth element can be chemically coordinated with the oxygen atoms in the oxygen-containing groups on the surface of the carbon fiber and the fluorine atoms in the polytetrafluoroethylene to form a rare earth mixed complex with a ring-shaped stable structure, which plays a bridge role between the ultra-high molecular weight polyethylene fiber and the polytetrafluoroethylene, improves the interfacial strength between the ultra-high molecular weight polyethylene fiber and the polytetrafluoroethylene, inhibits the flaky peeling and large-scale transfer of the polytetrafluoroethylene, reduces the wear rate, and improves the tensile strength and elongation at break of the sealing material and improves the toughness.

[0021] Optionally, the coupling agent comprises KH550 and Z6124 in a mass ratio of 1:3-4.

[0022] By adopting the technical scheme, Z6124 is phenyltrimethoxysilane, which is embedded in the long chain of polytetrafluoroethylene through the phenyl group in the molecular structure to form a special network structure, thereby increasing the interface contact and enhancing the bonding force between polytetrafluoroethylene and modified carbon fiber, ultra-high molecular weight polyethylene fiber, inorganic nano filler and other components, KH550 is gamma-aminopropyltriethoxysilane, which can improve the dispersibility of modified carbon fiber, ultra-high molecular weight polyethylene fiber and inorganic nano filler in polytetrafluoroethylene and enhance the bonding ability, and the two work together to achieve the best dispersion and interface enhancement of modified carbon fiber, ultra-high molecular weight polyethylene fiber and inorganic nano filler.

[0023] Optionally, the particle size of the inorganic nano filler is 15-40 nm, and the particle size of the bronze powder is 1-2 μm.

[0024] By adopting the technical scheme, the crystal nucleus effect of the inorganic nano filler helps polytetrafluoroethylene to form small size crystals, thereby effectively reducing the size of the friction damage unit of the sealing material and reducing the wear rate of polytetrafluoroethylene.

[0025] Optionally, the inorganic nano filler is selected from at least one of nano molybdenum disulfide, nano silicon carbide and nano silicon dioxide.

[0026] In a second aspect, the application provides a preparation method of a polytetrafluoroethylene sealing material, which uses the following technical scheme:

[0027] A preparation method of a polytetrafluoroethylene sealing material, comprising the following steps:

[0028] The coupling agent is dissolved in anhydrous ethanol, inorganic nano-filler, bronze powder, modified glass fiber and ultra-high molecular weight fiber are added, and after mixing, polytetrafluoroethylene and polyether ether ketone are added, and after sufficient mixing, the polytetrafluoroethylene sealing material is prepared by molding and sintering.

[0029] By using the above technical scheme, the polytetrafluoroethylene sealing material is prepared by mixing, molding and sintering, and the components in the sealing material are closely and uniformly distributed, the friction reduction effect is strong, and the wear rate is low.

[0030] Optionally, the molding is cold molding, the pressure is 15-25 MPa, and the pressure holding time is 2-6 min.

[0031] Optionally, the sintering process is as follows: the temperature is raised to 270-280 DEG C at a rate of 10-20 DEG C / min, the temperature is kept for 20-40 min, the temperature is raised to 320-340 DEG C at a rate of 3-8 DEG C / min, the temperature is kept for 20-30 min, the temperature is raised to 360-365 DEG C at a rate of 1-2 DEG C / min, the temperature is kept for 100-120 min, the temperature is lowered to 270-280 DEG C at a rate of 10-20 DEG C / min, the temperature is kept for 150-200 min, and the furnace is cooled down.

[0032] By using the above technical scheme, the sealing material prepared by the segmented sintering process has high strength and strong creep resistance.

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

[0034] 1. In the polytetrafluoroethylene base material, polyether ether ketone, ultra-high molecular weight polyethylene fiber, inorganic nano-filler, bronze powder, modified carbon fiber and other components are added, and the coupling agent is used to improve the interfacial bonding force between polytetrafluoroethylene and each raw material, reduce the wear rate, and the modified carbon fiber is dissolved by polyacrylonitrile, then boron nitride, attapulgite, PPS fiber and polyamide acid solution are added, and then the modified carbon fiber is spun, oxidized and carbonized, the dispersion of boron nitride, PPS fiber and attapulgite in the spinning solution is improved after the polyamide acid solution is amidated, thereby improving the lubricity and wear resistance of the modified carbon fiber, and the compatibility of polyimide and polytetrafluoroethylene is good, which can improve the dispersion of the modified carbon fiber in the polytetrafluoroethylene and the interfacial bonding force between the modified carbon fiber and the polytetrafluoroethylene, reduce the wear of the carbon fiber, and reduce the wear rate of the sealing material.

[0035] 2. In this application, ultra-high molecular weight polyethylene (UHMWPE) fibers are preferably prepared using ultra-high molecular weight polyethylene (UHMWPE), silicon nitride, and rare earth compounds. Silicon nitride, as a rigid particle, can be uniformly dispersed in polytetrafluoroethylene (PTFE) resin under the action of polyvinyl alcohol, thereby improving the tensile strength and wear resistance of the sealing material. Rare earth compounds can improve the interfacial adhesion between UHMWPE fibers and PTFE resin, thereby improving wear resistance. The added PTFE emulsion can act as a ball bearing on the film formed by polyvinyl alcohol, increasing lubricity and reducing the wear rate. Detailed Implementation

[0036] Preparation Examples of Modified Carbon Fibers 1-6

[0037] Preparation Example 1: 15 kg of polyacrylonitrile was dissolved in the organic solvent N,N-dimethylformamide to prepare a spinning solution with a concentration of 12 wt% and a relative molecular weight of 150,000 for the polyacrylonitrile.

[0038] 10 kg of boron nitride, 1.5 kg of PPS fiber powder, 1.5 kg of attapulgite clay, and 10 kg of polyamic acid solution were mixed and ultrasonically dispersed for 30 min at 200 W. The mixture was then added to the spinning solution and mixed evenly before electrospinning. The mixture was then heated to 260 °C and held for 5 h, followed by heating to 750 °C and holding for 1 h under argon protection. The mixture was then allowed to cool naturally to room temperature to obtain modified carbon fibers. The polyamic acid solution was prepared by stirring 4,4'-diaminodiphenyl ether and pyromellitic dianhydride in N,N-dimethylacetamide at a molar ratio of 1:1 for 1 h at 70 °C. The solid content of the polyamic acid was 12%. The particle size of the PPS fiber powder was 300 mesh, the particle size of the boron nitride was 30 nm, and the particle size of the attapulgite clay was 50 nm. The electrospinning voltage was 16 kV, the receiving distance was 18 cm, and the spinning speed was 0.75 mL / h.

[0039] Preparation Example 2: 10 kg of polyacrylonitrile was dissolved in the organic solvent N,N-dimethylformamide to prepare a spinning solution with a concentration of 8 wt% and a relative molecular weight of 150,000 for the polyacrylonitrile.

[0040] 5 kg of boron nitride, 0.5 kg of attapulgite, 0.5 kg of PPS fiber powder and 5 kg of polyamide acid solution were mixed and ultrasonically dispersed for 30 min under a power of 200 W, added to the spinning solution, uniformly mixed and electrospun, then heated to 280°C and kept for 4 h, then heated to 700°C under argon protection, kept for 2 h, and naturally cooled to room temperature to obtain modified carbon fibers. The polyamide acid solution was prepared by stirring 4,4'-diamino diphenyl ether and pyromellitic dianhydride in a molar ratio of 1:1 in N,N-dimethylacetamide at 70°C for 1 h. The solid content of the polyamide acid was 12%, the particle size of the PPS fiber was 300 mesh, the particle size of the boron nitride was 30 nm, the particle size of the attapulgite was 50 nm, the voltage of the electrospinning was 20 kV, the receiving distance was 20 cm, and the spinning speed was 0.9 mL / h.

[0041] Preparation Example 3: Different from Preparation Example 1, no attapulgite was added.

[0042] Preparation Example 4: Different from Preparation Example 1, no boron nitride was added.

[0043] Preparation Example 5: Different from Preparation Example 1, no polyamide acid solution was added.

[0044] Preparation Example 6: Different from Preparation Example 1, no PPS fiber powder was added.

[0045] Preparation Examples 7-12 of ultra-high molecular weight polyethylene fibers

[0046] Preparation Example 7: Ultra-high molecular weight polyethylene was dissolved in decalin with a mass concentration of 10% spinning solution, 0.1% antioxidant 2,6-di-tert-butyl-p-cresol was added to the ultra-high molecular weight polyethylene, stirred and heated at a rate of 2°C / min until a gel was formed, heated to 170°C after stabilizing at 135°C for 1.5 h, degassed by pouring into a spinning machine, extruded through a spinneret at 170°C, cooled in air for 20 cm, then entered a water bath and wound at a speed of 3000 m / min to obtain a primary fiber. The molecular weight of the ultra-high molecular weight polyethylene was 4.5 million;

[0047] 2 kg of polyvinyl alcohol-1799 and 1 kg of polyethylene glycol 1000 were added to 10 kg of deionized water and stirred uniformly, 0.2 parts of polytetrafluoroethylene emulsion, 0.3 kg of silicon nitride and 0.6 parts of rare earth compound were added, stirred at 65°C for 5 h, acidified, 0.25 parts of glutaraldehyde were added, kept for 60 min, and degassed to obtain a treatment solution. The polytetrafluoroethylene emulsion was with a product number of CD113195, the rare earth compound was lanthanum chloride, and the particle size of the silicon nitride was 100 nm.

[0048] The primary fiber was immersed in the treatment solution for 12 h and dried at 120°C for 4 h to obtain an ultra-high molecular weight polyethylene fiber.

[0049] Preparation Example 8: The ultra-high molecular weight polyethylene is dissolved in decalin to form a spinning solution with a mass concentration of 2%, 0.1% of antioxidant 2,6-di-tert-butyl-p-cresol is added to the ultra-high molecular weight polyethylene, the solution is stirred and heated at a rate of 2°C / min until a gel is formed, the temperature is then raised to 175°C after the gel is stabilized at 135°C for 1.5 h, the solution is then degassed in a spinning machine, the gel is extruded through a spinneret at 175°C, passes through 20 cm of air cooling, enters a water bath, and is wound at a speed of 3000 m / min to form a primary fiber, the molecular weight of the ultra-high molecular weight polyethylene is 4.5 million;

[0050] 1.7 kg of polyvinyl alcohol-1799 and 0.8 kg of polyethylene glycol 1000 are added to 10 kg of deionized water, stirred until uniform, 0.17 parts of polytetrafluoroethylene emulsion, 0.1 kg of silicon nitride, and 0.3 parts of a rare earth compound are added, stirred at 60°C for 6 h, acidified, 0.2 parts of glutaraldehyde are added, incubated for 50 min, degassed, and a treatment solution is prepared, the polytetrafluoroethylene emulsion has a product number of CD113195, the rare earth compound is lanthanum oxide, and the particle size of the silicon nitride is 100 nm;

[0051] The primary fiber is immersed in the treatment solution for 10 h, dried at 120°C for 4 h, and an ultra-high molecular weight polyethylene fiber is prepared.

[0052] Preparation Example 9: The difference from Preparation Example 7 is that no silicon nitride is added to the treatment solution.

[0053] Preparation Example 10: The difference from Preparation Example 7 is that no rare earth compound is added to the treatment solution.

[0054] Preparation Example 11: The difference from Preparation Example 7 is that no polytetrafluoroethylene emulsion is added to the treatment solution.

[0055] Preparation Example 12: The difference from Preparation Example 7 is that no polyvinyl alcohol and glutaraldehyde are added to the treatment solution.

[0056] Example

[0057] Example 1: A polytetrafluoroethylene sealing material, the amounts of raw materials are shown in Table 1, the modified carbon fiber is prepared according to Preparation Example 1, has a diameter of 3 μm, and an aspect ratio of 3:1, the ultra-high molecular weight polyethylene fiber is prepared according to Preparation Example 7, has a diameter of 8 μm, and an aspect ratio of 8:1, the coupling agent includes KH550 and Z6124 in a mass ratio of 1:4, the inorganic nano-filler is nano-molybdenum disulfide with a particle size of 15 nm, and the particle size of the bronze powder is 2 μm.

[0058] The above method for preparing a polytetrafluoroethylene sealing material includes the following steps:

[0059] The coupling agent is dissolved in anhydrous ethanol, inorganic nano-filler, bronze powder, modified glass fiber and ultra-high molecular weight fiber are added, and after mixing, polytetrafluoroethylene and polyether ether ketone are added, and after sufficient mixing, the polytetrafluoroethylene sealing material is prepared by molding and sintering. The molding is cold pressing, the pressure is 25 MPa, the pressure holding time is 2 min, and the sintering process is: heating at a rate of 20 ℃ / min to 280 ℃, holding for 20 min, heating at a rate of 8 ℃ / min to 340 ℃, holding for 20 min, heating at a rate of 2 ℃ / min to 365 ℃, holding for 100 min, heating at a rate of 20 ℃ / min to 280 ℃, holding for 150 min, and cooling in the furnace.

[0060] Table 1 Raw material amount of polytetrafluoroethylene sealing material in examples 1-3

[0061]

[0062]

[0063] Example 2: A polytetrafluoroethylene sealing material, which is different from example 1 in that the raw material amount is shown in table 1, the modified carbon fiber is made by preparation example 2, the ultra-high molecular weight polyethylene fiber is made by preparation example 8, and the coupling agent includes KH550 and Z6124 with a mass ratio of 1:3, the inorganic nano-filler is nano-silicon carbide with a particle size of 40 nm, and the bronze powder has a particle size of 1 μm.

[0064] The preparation method of the polytetrafluoroethylene sealing material, comprising the following steps:

[0065] The coupling agent is dissolved in anhydrous ethanol, inorganic nano-filler, bronze powder, modified glass fiber and ultra-high molecular weight fiber are added, and after mixing, polytetrafluoroethylene and polyether ether ketone are added, and after sufficient mixing, the polytetrafluoroethylene sealing material is prepared by molding and sintering. The molding is cold pressing, the pressure is 25 MPa, the pressure holding time is 2 min, and the sintering process is: heating at a rate of 20 ℃ / min to 280 ℃, holding for 20 min, heating at a rate of 8 ℃ / min to 340 ℃, holding for 20 min, heating at a rate of 2 ℃ / min to 365 ℃, holding for 100 min, heating at a rate of 20 ℃ / min to 280 ℃, holding for 150 min, and cooling in the furnace.

[0066] Example 3: A polytetrafluoroethylene sealing material, which is different from example 1 in that the raw material amount is shown in table 1.

[0067] Example 4: A polytetrafluoroethylene sealing material, which is different from example 1 in that the modified carbon fiber is made by preparation example 3.

[0068] Example 5: A polytetrafluoroethylene sealing material, which differs from Example 1 in that the modified carbon fiber is made from Preparation Example 4.

[0069] Example 6: A polytetrafluoroethylene sealing material, which differs from Example 1 in that the modified carbon fiber is made from Preparation Example 5.

[0070] Example 7: A polytetrafluoroethylene sealing material, which differs from Example 1 in that the modified carbon fiber is made from Preparation Example 6.

[0071] Example 8: A polytetrafluoroethylene sealing material, which differs from Example 1 in that the ultra-high molecular weight polyethylene fiber is made from Preparation Example 9.

[0072] Example 9: A polytetrafluoroethylene sealing material, which differs from Example 1 in that the ultra-high molecular weight polyethylene fiber is made from Preparation Example 10.

[0073] Example 10: A polytetrafluoroethylene sealing material, which differs from Example 1 in that the ultra-high molecular weight polyethylene fiber is made from Preparation Example 11.

[0074] Example 11: A polytetrafluoroethylene sealing material, which differs from Example 1 in that the ultra-high molecular weight polyethylene fiber is made from Preparation Example 12.

[0075] Example 12: A polytetrafluoroethylene sealing material, which differs from Example 1 in that the coupling agent is all KH550, and Z6124 is not used.

[0076] Comparative Example

[0077] Comparative Example 1: A polytetrafluoroethylene sealing material, which differs from Example 1 in that no modified carbon fiber is added.

[0078] Comparative Example 2: A polytetrafluoroethylene sealing material, which differs from Example 1 in that an equal amount of unmodified carbon fiber is used instead of the modified carbon fiber.

[0079] Comparative Example 3: A polytetrafluoroethylene sealing material, which differs from Example 1 in that no ultra-high molecular weight polyethylene fiber is added.

[0080] Comparative Example 4: A polytetrafluoroethylene sealing material, which differs from Example 1 in that no polyether ether ketone is added.

[0081] Comparative Example 5: A polytetrafluoroethylene sealing ring material, using a polytetrafluoroethylene suspension resin powder as the base material, using one of barium ferrite, strontium ferrite, cobalt ferrite, and neodymium iron boron as the filler, requiring the particle size of the magnetic powder to be 100 μm, and then adding glass fiber, carbon fiber, and molybdenum disulfide powder as modifiers, and the modifiers are sieved to 200 mesh. The weight percentage content of each component is: polytetrafluoroethylene 60%, magnetic powder 20%, carbon fiber 10%, molybdenum disulfide 5%, and glass fiber 5%.

[0082] The raw materials prepared according to the above content are mixed uniformly, and then molded under a pressure of 20 MPa and a heating temperature of 360°C for 10 minutes, and then cooled to room temperature to obtain the prepared sealing ring.

[0083] Performance test

[0084] The sealing material is prepared according to the method in the examples and comparative examples, and the performance of the sealing material is detected according to the following method, and the test results are recorded in Table 2.

[0085] 1. Tensile strength and elongation at break: detected according to GB / T1040.2-2006 "Determination of tensile properties of plastics";

[0086] 3. Friction coefficient: detected according to GB / T3960-2016 "Plastics - Determination of the friction and wear characteristics of plastics sliding against each other in reciprocating motion under lubricated contact conditions";

[0087] 4. Creep rate: detected according to GB / T41061-2021 "Test method for creep properties of fiber reinforced plastics".

[0088] Table 2 Performance test results of polytetrafluoroethylene sealing material

[0089]

[0090]

[0091] In Examples 1 and 2, modified carbon fibers prepared by Preparation Examples 1 and 2, and ultra-high molecular weight polyethylene fibers prepared by Preparation Examples 7 and 8 are used, and as shown in Table 2, the sealing materials prepared in Examples 1 and 2 have excellent tensile strength and creep resistance, and have the advantages of self-lubrication and low wear rate,

[0092] Example 3 is compared with Example 1, only the amount of raw materials is different, and the sealing material prepared in Example 3 has similar performance test results to Example 1.

[0093] The modified carbon fiber prepared in Preparation Example 3 is used in Example 4, and no attapulgite is added in Preparation Example 3. Compared with Example 1, the mechanical strength of the sealing material prepared in Example 4 is decreased, and the volume wear rate is increased. It is indicated that the attapulgite pretreated by the coupling agent can be uniformly dispersed in the spinning solution, so as to improve the tensile strength of the modified carbon fiber and reduce the wear rate.

[0094] The modified carbon fiber prepared in Preparation Example 4 is used in Example 5, and no boron nitride is added in Preparation Example 4. Compared with Example 1, the friction coefficient of the sealing material prepared in Example 5 is increased, the tensile strength is decreased, and the volume wear rate is increased. It is indicated that the addition of the boron nitride treated by the coupling agent can effectively reduce the wear resistance of the sealing material and improve the creep resistance.

[0095] The modified carbon fiber prepared in Preparation Example 5 is used in Example 6, and no polyamide acid solution is added in the modified carbon fiber. The mechanical strength of the sealing material is decreased, and the wear rate and the creep rate are increased. It is indicated that the polyamide acid solution is blended and spun with the polyacrylonitrile, and then is subjected to amidation and carbonization to prepare the modified carbon fiber. The modified carbon fiber can have good interfacial bonding force with the polytetrafluoroethylene, so as to reduce the wear rate and improve the tensile strength of the sealing material.

[0096] The modified carbon fiber prepared in Preparation Example 6 is used in Example 7, and no PPS fiber powder is added. The tensile strength and the elongation at break of the sealing material are decreased, although the friction coefficient is improved, and the wear rate is increased significantly.

[0097] The ultrahigh molecular weight polyethylene fiber prepared in Preparation Example 9 is used in Example 8, and no silicon nitride is added in Preparation Example 9 compared with Preparation Example 7. As shown in Table 2, the wear rate of the sealing material prepared in Example 8 is increased, and the mechanical strength is weakened.

[0098] The ultrahigh molecular weight polyethylene fiber prepared in Preparation Example 10 is used in Example 9, and no rare earth compound is added. As shown in Table 2, the tensile strength and the elongation at break of the sealing material prepared in Example 9 are decreased, the volume wear rate is increased, and the friction coefficient and the creep rate are increased.

[0099] The ultrahigh molecular weight polyethylene fiber prepared in Preparation Example 11 is used in Example 10, and no polytetrafluoroethylene emulsion is added. Compared with Example 1, the volume wear rate of the sealing material prepared in Example 10 is increased, and the mechanical strength is deteriorated.

[0100] The ultrahigh molecular weight polyethylene fiber prepared in Preparation Example 12 is used in Example 11, and no polyvinyl alcohol and glutaraldehyde are added in Preparation Example 12 compared with Preparation Example 7. As shown in Table 2, the mechanical strength of the sealing material prepared in Example 11 is deteriorated, the creep resistance is weakened, and the volume wear rate is increased.

[0101] No Z6124 was added in the coupling agent in Example 12, and it is shown in Table 2 that the mechanical strength of the sealing material prepared in Example 12 decreased and the volume wear rate increased, which indicates that Z6124 can improve the affinity of the modified carbon fiber and other raw materials with polytetrafluoroethylene and reduce the generation of wear debris.

[0102] Comparative Example 1 was compared with Example 1, wherein no modified carbon fiber was added, and unmodified carbon fiber was used in Comparative Example 2. The tensile strength of the sealing material prepared in Comparative Examples 1 and 2 decreased, and the volume wear rate increased.

[0103] No ultra-high molecular weight polyethylene fiber was added in Comparative Example 3, and the tensile strength of the sealing material significantly decreased, the creep resistance decreased, the volume wear rate increased, and the wear resistance decreased.

[0104] No polyether ether ketone was added in Comparative Example 4, and the friction coefficient of the sealing material increased, the wear resistance decreased, and the tensile strength decreased.

[0105] Comparative Example 5 was a sealing material prepared by the prior art, which contained carbon fiber and glass fiber. The mechanical properties of the sealing ring material prepared therefrom were checked, and the wear rate was large, and the wear resistance was not as good as that of the present application.

[0106] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, as long as the modifications are within the scope of the claims of the present application.

Claims

1. A polytetrafluoroethylene sealing material, characterized by, The raw materials include the following components by weight: 80 parts of polytetrafluoroethylene resin, 20 parts of modified carbon fiber, 10 parts of polyether ether ketone, 5 parts of ultra-high molecular weight polyethylene fiber, 30 parts of bronze powder, 5 parts of inorganic nano filler, and 0.2 parts of coupling agent. The method for preparing the modified carbon fiber includes the following steps: Dissolve polyacrylonitrile with an organic solvent to prepare a spinning solution with a concentration of 8-12wt%; Mix boron nitride, PPS fiber powder, attapulgite, and polyamide acid solution, ultrasonically disperse, add to the spinning solution, and electrospun after uniform mixing, then heat to 260-280℃ and keep for 4-5h, then heat to 700-750℃ under argon protection, keep for 1-2h, and naturally cool to room temperature to prepare the modified carbon fiber. The ultra-high molecular weight fiber is prepared by the following method: Dissolve ultra-high molecular weight polyethylene to prepare a spinning solution with a mass concentration of 2-10%, and spin at 170-175℃ to prepare the primary fiber. Add 1.7-2 parts of polyvinyl alcohol, 0.8-1 part of polyethylene glycol 1000 to 10 parts of deionized water, stir uniformly, add 0.17-0.2 parts of polytetrafluoroethylene emulsion, 0.1-0.3 parts of silicon nitride, and 0.3-0.6 parts of rare earth compound, stir uniformly at 60-65℃, add 0.2-0.25 parts of glutaraldehyde after acidification, keep for 50-60min, and defoam to prepare the treatment solution. Soak the primary fiber in the treatment solution for 10-12h, dry, and prepare the ultra-high molecular weight polyethylene fiber.

2. The polytetrafluoroethylene sealing material according to claim 1, characterized by: The modified carbon fiber includes the following components by weight: 5-10 parts of boron nitride, 5-10 parts of polyamide acid solution, 0.5-1.5 parts of attapulgite, 10-15 parts of polyacrylonitrile, and 0.5-1.5 parts of PPS fiber powder.

3. The polytetrafluoroethylene sealing material according to claim 1, wherein The spinning voltage is 16-20kv, the receiving distance is 18-20cm, and the spinning speed is 0.75-0.9mL / h.

4. The polytetrafluoroethylene sealing material according to claim 1, wherein The coupling agent includes KH550 and Z6124 with a mass ratio of 1:3-4.

5. The polytetrafluoroethylene sealing material according to claim 1, wherein The particle size of the inorganic nano filler is 15-40nm, and the particle size of the bronze powder is 1-2μm.

6. The polytetrafluoroethylene sealing material according to claim 1, wherein The inorganic nano filler is selected from at least one of nano molybdenum disulfide, nano silicon carbide, and nano silicon dioxide.

7. A process for the production of a polytetrafluoroethylene sealing material as claimed in any one of claims 1 to 6, characterized in that The method includes the following steps: Dissolve the coupling agent with anhydrous ethanol, add the inorganic nano filler, bronze powder, modified carbon fiber, and ultra-high molecular weight fiber, mix uniformly, add polytetrafluoroethylene and polyether ether ketone, mix thoroughly, mold, sinter, and prepare the polytetrafluoroethylene sealing material.

8. The method of claim 7, wherein the polytetrafluoroethylene sealing material is prepared by a process comprising: The mold forming is cold pressing, the pressure is 15-25MPa, and the pressure keeping time is 2-6min.

9. The method for preparing the polytetrafluoroethylene sealing material according to claim 7, characterized in that, The sintering process is as follows: heat to 270-280℃ at a rate of 10-20℃ / min, keep for 20-40min, heat to 320-340℃ at a rate of 3-8℃ / min, keep for 20-30min, heat to 360-365℃ at a rate of 1-2℃ / min, keep for 100-120min, cool to 270-280℃ at a rate of 10-20℃ / min, keep for 150-200min, and cool with the furnace.

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