Modified PTFE sealing material, preparation method and application thereof

Abstract

This invention belongs to the field of polymer sealing materials technology, specifically relating to a modified PTFE sealing material, its preparation method, and its application. The modified PTFE sealing material provided by this invention comprises the following components: polytetrafluoroethylene resin, bronze powder, nano-carbon materials, polyimide micropowder, potassium titanate whiskers, graphite, coupling agent, and lubricant. The modified PTFE sealing material provided by this invention exhibits high wear resistance, extremely low wear rate, excellent creep resistance, good self-lubrication, and thermal conductivity, enabling it to maintain excellent performance under various operating conditions (high-speed, high-temperature, and extreme-pressure conditions), thus extending the service life of the sealing components.

Description

Technical Field

[0001] This invention belongs to the field of polymer sealing materials technology, specifically relating to a modified PTFE sealing material, its preparation method, and its application. Background Technology

[0002] Polytetrafluoroethylene (PTFE) is known as the "King of Plastics" due to its excellent chemical resistance, low coefficient of friction (0.08~0.12) and wide operating temperature range (-200℃ to 260℃). It is widely used in the field of engineering machinery seals, such as hydraulic cylinder piston seals, piston rod seals, and guide belts.

[0003] However, pure PTFE has three inherent drawbacks: Poor abrasion resistance: Pure PTFE has an abrasion rate as high as 1×10⁻⁶. -3 mm 3 On the order of N·m, it is prone to rapid failure in working conditions containing particulate media; Poor creep resistance (cold flow): It is prone to permanent deformation under load, leading to seal failure; Low mechanical strength: The compressive strength is only about 12MPa, making it difficult to withstand high-pressure conditions.

[0004] To improve the performance of PTFE, the existing technologies mainly adopt the following modification methods, the advantages and disadvantages of which are shown in Table 1.

[0005] Table 1. Advantages and disadvantages of existing technologies

[0006] Existing technologies disclose PTFE modified with bronze powder and chromium trioxide, which has a certain degree of wear resistance but a high coefficient of friction; another existing technology discloses PTFE modified with PI and carbon fiber, but its resistance to high-pressure extrusion is insufficient. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a modified PTFE sealing material, its preparation method and application. The modified PTFE sealing material provided by this invention has high wear resistance, extremely low wear rate, excellent creep resistance, good self-lubrication and thermal conductivity, so that it can maintain excellent performance under different working conditions (high speed, high temperature and extreme pressure) and extend the service life of the seal.

[0008] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a modified PTFE sealing material, comprising the following components by weight: 100 parts of polytetrafluoroethylene resin, 30-80 parts of bronze powder, 1-8 parts of nano-carbon material, 5-20 parts of polyimide micro powder, 3-12 parts of potassium titanate whiskers, 3-10 parts of graphite, 0.5-2 parts of coupling agent, and 1-3 parts of lubricant.

[0009] Preferably, based on 1 part by weight of polytetrafluoroethylene resin, the modified PTFE sealing material further comprises 5 to 15 parts of carbon fiber.

[0010] Preferably, based on 1 part by weight of polytetrafluoroethylene resin, the modified PTFE sealing material further comprises: 5 to 10 parts of ceramic powder; the ceramic powder includes SiC and / or Al2O3.

[0011] Preferably, the modified PTFE sealing material includes modified PTFE sealing materials suitable for high-speed operating conditions, modified PTFE sealing materials suitable for high-temperature operating conditions, or modified PTFE sealing materials suitable for extreme pressure operating conditions.

[0012] Preferably, the modified PTFE sealing material suitable for high-speed operating conditions comprises, by weight, the following components: 100 parts of polytetrafluoroethylene resin 30-40 parts bronze powder 3-8 parts of nano-carbon material, 8-12 parts of polyimide micro powder 5-10 parts of potassium titanate whiskers, 5-10 parts graphite 5-10 parts carbon fiber 1 part coupling agent, Two parts lubricant.

[0013] Preferably, the modified PTFE sealing material suitable for high-temperature operating conditions comprises, by weight, the following components: 100 parts of polytetrafluoroethylene resin 50-70 parts bronze powder 2-4 parts of nano-carbon material, 15-20 parts of polyimide micro powder 5-10 parts of potassium titanate whiskers, 3-5 parts graphite 5-10 parts of ceramic powder 1 part coupling agent, Two parts lubricant.

[0014] Preferably, the modified PTFE sealing material suitable for extreme pressure conditions comprises, by weight, the following components: 100 parts of polytetrafluoroethylene resin 60-80 parts bronze powder 2-3 parts of nano-carbon material, 10-15 parts of polyimide micro powder 8-12 parts of potassium titanate whiskers, 5-8 parts graphite 5-15 parts carbon fiber 1-2 parts of coupling agent, Two parts lubricant.

[0015] This invention also provides a method for preparing the modified PTFE sealing material described in the above technical solution, comprising the following steps: (1) A coupling agent was added to the dispersion of nano-carbon materials to modify it, and a modified nano-carbon suspension was obtained; (2) The modified nano-carbon suspension and polytetrafluoroethylene resin are wet-premixed and then vacuum-dried at low temperature. The resulting nano-carbon material pre-coated polytetrafluoroethylene resin composite powder is dry-mixed with bronze powder, polyimide micro powder, potassium titanate whiskers, graphite and lubricant to obtain a mixture. (3) The mixture is molded to obtain a blank; (4) The blank is sintered to obtain the modified PTFE sealing material.

[0016] Preferably, the sintering includes sequentially performing low-temperature sintering, high-temperature sintering, and cooling; the low-temperature sintering temperature is 320~330℃, and the holding time is 1~2h; the high-temperature sintering temperature is 360~380℃, and the holding time is 3~5h; the cooling rate is controlled to be ≤40℃ / h during the cooling process.

[0017] The present invention also provides the application of the modified PTFE sealing material described in the above technical solution or the modified PTFE sealing material prepared by the preparation method described in the above technical solution in engineering machinery seals.

[0018] This invention provides a modified PTFE sealing material, comprising the following components by weight: 100 parts of polytetrafluoroethylene resin, 30-80 parts of bronze powder, 1-8 parts of nano-carbon material, 5-20 parts of polyimide micro powder, 3-12 parts of potassium titanate whiskers, 3-10 parts of graphite, 0.5-2 parts of coupling agent, and 1-3 parts of lubricant.

[0019] This invention employs a four-dimensional synergistic modification strategy consisting of "hard wear-resistant phase + organic wear-resistant phase + nano-reinforcing phase + fiber-reinforcing phase": Load-bearing layer (bronze powder): High-content bronze powder forms a continuous metal support network, which bears the main load, resists high-pressure extrusion, and at the same time improves thermal conductivity and quickly dissipates frictional heat.

[0020] Reinforcing skeleton (potassium titanate whiskers + carbon fiber): forms a three-dimensional fiber reinforcement network, improving impact resistance, creep resistance and dimensional stability, and preventing crack propagation.

[0021] Lubricating layer (graphite + nano-carbon materials): Graphite forms a basic lubricating film in the early stage of friction, while nano-carbon materials (such as graphene / MXene) are peeled off and transferred to the dual surface during the friction process to form a tough nanoscale transfer film, achieving "self-repairing" lubrication. High-temperature support (polyimide): Maintains high mechanical strength at high temperatures, supports the PTFE matrix, and prevents seal failure caused by thermal softening.

[0022] Synergistic effect: The components work together dynamically during friction – the hard phase bears the load, the reinforcing phase resists deformation, the lubricating phase reduces friction, and the nanophase optimizes the transfer film. This three-in-one synergistic mechanism of "load bearing-reinforcing-lubricating" makes the comprehensive performance of the material far exceed the linear superposition of single filler modification.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1) Extremely low wear rate: Through the synergistic design of the formulation and mixing process, this invention achieves a wear rate as low as 10%. -6 ~10 - 7 mm 3 The improvement is on the order of N·m, which is 3 to 4 orders of magnitude higher than that of pure PTFE, and 1 to 2 orders of magnitude higher than that of conventional modified PTFE (Comparative Example 2). 2) Excellent creep resistance: Compression set is significantly reduced at high temperatures (minimum 4.2%). 3) Good thermal conductivity: Frictional heat is effectively dissipated, preventing localized high temperatures; 4) Wide operating condition adaptability: By modifying the formula, its applicability is effectively improved, covering a variety of operating conditions such as high speed, high temperature, and extreme pressure; 5) Wear-resistant: The nano-transfer protective film formed during friction effectively reduces wear on mating parts; 6) Innovative mixing process: The wet-dry two-step mixing method solves the industry problem of easy agglomeration of nano-carbon materials, resulting in high batch-to-batch stability (wear rate CV value ≤ 5%), which is suitable for industrial production. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the preparation method of the modified PTFE sealing material in an embodiment of the present invention. Detailed Implementation

[0025] This invention provides a modified PTFE sealing material, comprising the following components by weight: 100 parts of polytetrafluoroethylene resin, 30-80 parts of bronze powder, 1-8 parts of nano-carbon material, 5-20 parts of polyimide micro powder, 3-12 parts of potassium titanate whiskers, 3-10 parts of graphite, 0.5-2 parts of coupling agent, and 1-3 parts of lubricant.

[0026] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0027] The modified PTFE sealing material provided by the present invention comprises, by weight, 100 parts of polytetrafluoroethylene resin (PTFE).

[0028] In one embodiment, the polytetrafluoroethylene (PTFE) resin is selected from PTFE resin polymerized by suspension polymerization; the particle size of the PTFE resin is 5~50μm, specifically 5~20μm in this embodiment, and the weight-average molecular weight is 1 million~6 million, specifically 2 million~4 million in this embodiment; the PTFE resin is selected from DF-16A molding grade fine powder from Shandong Dongyue Polymer Materials Co., Ltd., with a particle size of 5~20μm and a weight-average molecular weight of 2 million~4 million. PTFE resin, as a matrix material, provides basic chemical resistance and low friction properties.

[0029] Based on 1 part by weight of polytetrafluoroethylene resin, the modified PTFE sealing material provided by the present invention comprises: 30-80 parts of bronze powder, 45-55 parts in another embodiment, and 50 parts in a specific embodiment.

[0030] In one embodiment, the bronze powder is atomized spherical bronze powder, specifically 663 tin bronze powder from Shijiazhuang Jingyuan Powder Materials Co., Ltd. The particle size of the bronze powder is 25~100μm, specifically 25~75μm in this embodiment; the copper content is 60~90wt%, specifically 60~65wt% in this embodiment; the tin content is 10~40wt%, specifically 35~40wt% in this embodiment; and the purity is ≥99%. As a hard, wear-resistant phase, the bronze powder can form a metallic support network, disperse load, dissipate frictional heat, and improve load-bearing capacity, resistance to extrusion deformation, and thermal conductivity.

[0031] Based on 1 part by mass of polytetrafluoroethylene resin, the modified PTFE sealing material provided by the present invention comprises: 1 to 8 parts of nano-carbon material, or 2 to 4 parts in another embodiment, and 2 to 3 parts in a specific embodiment.

[0032] In one embodiment, the nanomaterial is selected from aminated graphene oxide, carboxylated carbon nanotubes, and MXene (Ti3C2T).x One or more combinations of nanosheets, specifically aminated graphene oxide in this embodiment; the aminated graphene oxide is selected from Matexcel D. 50 (15.5~16.8μm) powder (catalog number MGP-OG01); the MXene (Ti3C2T) x The nanosheets are selected from Jiangsu Xianfeng Nano's highly dispersed MXene nanosheet powder, with a diameter of 500~1500nm and a thickness of 5~10nm. The carboxylated carbon nanotubes are selected from Jiangsu Xianfeng Nano's long-diameter carboxylated multi-walled carbon nanotube XFM09 powder, with a diameter of 8~15nm, a length of ≈50μm, and a carboxyl content of 2.56wt%. Aminated graphene oxide contains -NH2 groups and has good compatibility with the PTFE matrix. During friction, the nanosheet layer structure is exfoliated and transferred to the dual surface to form a nanoscale transfer film. The self-lubricating properties of the transfer film greatly reduce the wear rate.

[0033] Based on 1 part by weight of polytetrafluoroethylene resin, the modified PTFE sealing material provided by the present invention comprises: 5 to 20 parts of polyimide micro powder (PI), 8 to 12 parts in another embodiment, and 10 parts in a specific embodiment.

[0034] In one embodiment, the polyimide micropowder (PI) has an average particle size of 5-50 μm, specifically 30-40 μm in this embodiment, and a thermal decomposition temperature ≥450℃, specifically 480-520℃ in this embodiment. The polyimide micropowder used is Solvay Torlon 4000TF, with a particle size of 30-40 μm. As an organic wear-resistant phase, the polyimide micropowder can form an interpenetrating network structure with PTFE, maintaining a supporting role at high temperatures and improving high-temperature mechanical strength and creep resistance.

[0035] Based on 1 part by mass of polytetrafluoroethylene resin, the modified PTFE sealing material provided by the present invention comprises: 3 to 12 parts of potassium titanate whiskers, 4 to 7 parts in another embodiment, and 5 parts in a specific embodiment.

[0036] In one embodiment, the potassium titanate whiskers have an aspect ratio of 10~20:1, specifically 15~20:1, a diameter of 0.2~2μm, specifically 0.2~0.6μm, and a length of 10~20μm. The potassium titanate whiskers are selected from Otsuka TISMOD potassium titanate octa-whisker powder, with a diameter of 0.2~0.6μm, a length of 10~20μm, and an aspect ratio of 15~20:1. As a fiber-reinforcing phase, potassium titanate whiskers can form a three-dimensional skeleton in the matrix, resisting deformation and crack propagation, thereby improving impact resistance and dimensional stability.

[0037] Based on 1 part by weight of polytetrafluoroethylene resin, the modified PTFE sealing material provided by the present invention comprises: 3 to 10 parts of graphite, 4 to 7 parts in another embodiment, and 5 parts in a specific embodiment.

[0038] In one embodiment, the graphite is flake graphite; the graphite particle size is 5~50μm, specifically 20~50μm in this embodiment, the thickness is 0.01~10μm, specifically 0.05~0.15μm in this embodiment, and the fixed carbon content (purity) is ≥99wt%, specifically 99.5wt% in this embodiment; the flake graphite is made from Japanese Toyo Carbon TSG-99 powder, with a flake size (diameter) of 20~50μm, a thickness of 0.05~0.15μm, and a purity ≥99%. The layered structure of graphite is easily sheared, forming a lubricating film at the friction interface, which reduces the coefficient of friction and improves self-lubrication.

[0039] Based on 1 part by mass of polytetrafluoroethylene resin, the modified PTFE sealing material provided by the present invention comprises: 0.5 to 2 parts of coupling agent, or 0.8 to 1.5 parts in another embodiment, and 1 part in a specific embodiment.

[0040] In one embodiment, the coupling agent is selected from one or more of silane coupling agents KH-550 and KH-560 and titanate coupling agents, with KH-550 or KH-560 being used in specific embodiments; the silane coupling agents KH-550 and KH-560 are industrial-grade products from Jiangxi Chenguang New Materials Co., Ltd. The coupling agent can improve the interfacial bonding ability between the inorganic filler and the PTFE matrix.

[0041] Based on 1 part by mass of polytetrafluoroethylene resin, the modified PTFE sealing material provided by the present invention comprises: 1 to 3 parts of lubricant, or 1.5 to 2.5 parts in another embodiment, and 2 parts in a specific embodiment.

[0042] In one embodiment, the lubricant is selected from one or more of liquid paraffin, zinc stearate, and calcium stearate, with liquid paraffin or zinc stearate being used in a specific embodiment. The liquid paraffin is a high flash point special liquid paraffin from Xinji Jingshan Petrochemical Co., Ltd., with a flash point ≥160℃. The zinc stearate is a high-temperature resistant zinc stearate from Jiangxi Chenguang New Materials Co., Ltd. The lubricant can improve the flowability of the mixture and enhance the uniformity of molding.

[0043] As one embodiment, based on 1 part by mass of polytetrafluoroethylene resin, the modified PTFE sealing material further includes: 5-10 parts of ceramic powder, specifically 8 parts in this embodiment; the ceramic powder includes SiC and / or Al2O3, specifically SiC in this embodiment; the SiC is nano-silicon carbide; the nano-silicon carbide is Cabot Cabot-SiC-50 powder with a particle size of 30-50 nm.

[0044] As one embodiment, based on 1 part by weight of polytetrafluoroethylene resin, the modified PTFE sealing material further comprises: 5-15 parts of carbon fiber, specifically 8-12 parts in this embodiment; the diameter of the carbon fiber is 5-20 μm, specifically 7-12 μm in this embodiment, and the length is 50-1500 μm, specifically 0.5 mm in this embodiment; the carbon fiber is Jiangsu Hengshen HF30-0.5, with an average fiber length of 0.5 mm and a diameter of 7-12 μm.

[0045] In one embodiment, the modified PTFE sealing material includes a modified PTFE sealing material suitable for high-speed operating conditions, a modified PTFE sealing material suitable for high-temperature operating conditions, or a modified PTFE sealing material suitable for extreme pressure operating conditions.

[0046] As one embodiment, the modified PTFE sealing material suitable for high-speed operating conditions comprises, by weight, the following components: 100 parts of polytetrafluoroethylene resin (PTFE) 30-40 parts bronze powder The nano-carbon material consists of 3 to 8 parts, with 4 parts used in the specific embodiment. 8-12 parts of polyimide micro powder, 10 parts in the specific example. Potassium titanate whiskers: 5-10 parts, 8 parts in the specific example. 5-10 parts graphite, specifically 8 parts in this embodiment. 5-10 parts of carbon fiber, specifically 8 parts in this embodiment. 1 part coupling agent, Two parts lubricant.

[0047] As one embodiment, the modified PTFE sealing material suitable for high-temperature operating conditions comprises, by weight, the following components: 100 parts of polytetrafluoroethylene resin (PTFE) 50-70 parts bronze powder, 60 parts in the specific embodiment. 2-4 parts of nano-carbon material, 3 parts in the specific embodiment. The amount of polyimide micro powder is 15-20 parts, with 18 parts used in the specific example. Potassium titanate whiskers: 5-10 parts, 8 parts in the specific example. 3-5 parts graphite, 4 parts in the specific embodiment. The ceramic powder consists of 5-10 parts, with 8 parts used in the specific embodiment. 1 part coupling agent, Two parts lubricant.

[0048] As one embodiment, the modified PTFE sealing material suitable for extreme pressure conditions comprises, by weight, the following components: 100 parts of polytetrafluoroethylene resin (PTFE) The bronze powder consists of 60-80 parts, with 70 parts used in the specific embodiment. Two to three parts of nano-carbon material, with two parts used in the specific embodiment. 10-15 parts of polyimide micro powder, 12 parts in the specific example. Potassium titanate whiskers: 8-12 parts, 10 parts in the specific example. 5-8 parts graphite, 6 parts in the specific embodiment. 5-15 parts of carbon fiber, with 12 parts in the specific embodiment. The coupling agent is 1-2 parts, specifically 1.5 parts in the example. Two parts lubricant.

[0049] High-speed operating conditions refer to operating conditions with a linear speed ≥5m / s, typical value 15~18m / s, working pressure 10~25MPa, and working temperature -20~80℃, such as high-speed hydraulic cylinders, high-speed injection molding machines, and high-speed stamping equipment. High-temperature operating conditions refer to operating conditions with a working temperature ≥120℃, typical value 150~200℃, linear velocity 0.5~4m / s, and working pressure 15~35MPa, such as continuous operation engineering machinery (excavators, loaders) and hydraulic systems of metallurgical equipment. Extreme pressure conditions refer to working conditions with working pressure ≥40MPa, typical value 50~70MPa, linear velocity 0.1~1m / s, and working temperature -10~100℃, such as large-tonnage presses, shield machine hydraulic systems, and heavy-duty lifting cylinders.

[0050] The above operating parameters are derived from actual operating data of hydraulic systems in construction machinery. The modified PTFE sealing material of this invention can maintain a wear rate of ≤1×10 under the above boundary conditions. -5 mm 3 Excellent performance with a compression set of ≤10% and a compressive set of ≤10%.

[0051] To address the sealing requirements of construction machinery under harsh conditions such as high speed, high temperature, and extreme pressure, this invention provides a modified PTFE material that combines high wear resistance, low friction, creep resistance, and good thermal conductivity. Through a multi-dimensional synergistic modification strategy, it can maintain excellent performance under different working conditions and extend the service life of the seals.

[0052] This invention also provides a method for preparing the modified PTFE sealing material described in the above technical solution, comprising the following steps: (1) A coupling agent was added to the dispersion of nano-carbon materials to modify it, and a modified nano-carbon suspension was obtained; (2) The modified nano-carbon suspension and polytetrafluoroethylene resin are wet-premixed and then vacuum-dried at low temperature. The resulting nano-carbon material pre-coated polytetrafluoroethylene resin composite powder is dry-mixed with bronze powder, polyimide micro powder, potassium titanate whiskers, graphite and lubricant to obtain a mixture. (3) The mixture is molded to obtain a blank; (4) The blank is sintered to obtain the modified PTFE sealing material.

[0053] As one embodiment, the method for preparing the dispersion of the nano-carbon material is to disperse the nano-carbon material in anhydrous ethanol; the modification is carried out under ultrasonic dispersion conditions; the ultrasonic dispersion power is 400~750W, specifically 500W in the embodiment, the frequency is 20~40kHz, specifically 40kHz in the embodiment, and the time is 10~60min, specifically 12~30min in the embodiment.

[0054] As one implementation method, the wet premixing is as follows: the modified nano-carbon suspension and all polytetrafluoroethylene resin are added to a high-speed shear mixer, and anhydrous ethanol is added to make the solid content of the system 30~50wt%. High-speed shear mixing is performed at room temperature to make the nano-carbon material uniformly coat the surface of the polytetrafluoroethylene resin particles; the high-speed shear mixing speed is 2000~4000rpm, specifically 2800rpm in this embodiment, and the time is 20~40min, specifically 30min in this embodiment; anhydrous ethanol is added to make the solid content of the system 40wt%; the equipment used for the low-temperature vacuum drying is a vacuum drying oven; the temperature of the low-temperature vacuum drying is 50~70℃, specifically 60℃ in this embodiment, the vacuum degree is ≤-0.08MPa, specifically -0.09MPa in this embodiment, and the time is 4~8h, specifically 6h in this embodiment.

[0055] As one implementation method, before the dry mixing, the process further includes: drying the bronze powder, polyimide micro powder, potassium titanate whiskers, and graphite to remove moisture; when the modified PTFE sealing material also includes ceramic powder and / or carbon fiber, the ceramic powder and / or carbon fiber are also dried; the drying equipment is a vacuum drying oven; the drying temperature is 80~100℃, specifically 85℃ in this embodiment, and the drying time is 2~4h, specifically 3.5h in this embodiment.

[0056] In one embodiment, when the modified PTFE sealing material further includes ceramic powder and / or carbon fiber, the ceramic powder and / or carbon fiber are dry-mixed with the obtained nano-carbon material pre-coated polytetrafluoroethylene resin composite powder, bronze powder, polyimide micro powder, potassium titanate whiskers, graphite, and lubricant to obtain a mixture.

[0057] In one implementation method, the equipment used for dry mixing is a high-speed mixer; the rotation speed of the dry mixing is 800~1500 rpm, specifically 1200 rpm in this embodiment, and the mixing time is 10~20 min, specifically 15 min in this embodiment. Unlike the one-step dry high-speed mixing commonly used in the prior art, this invention addresses the problem of easy agglomeration and difficulty in dispersion of nano-carbon materials and whisker-like fillers by employing a two-step wet-dry mixing method.

[0058] As one implementation, steps (1) and (2) can be replaced by gradient speed-low temperature mixing method or ball milling masterbatch method.

[0059] As one implementation method, the steps of the gradient speed-low temperature mixing method are as follows: after pre-cooling all powders, they are added to a high-speed mixer with jacketed cooling, and mixed sequentially at low speed, medium speed, and high speed; all powders include nano-carbon materials, polytetrafluoroethylene resin, coupling agent, bronze powder, polyimide micro powder, potassium titanate whiskers, graphite, and lubricant; when the components of the modified PTFE sealing material further include ceramic powder and / or carbon fiber, all powders also include ceramic powder and / or carbon fiber; the cooling temperature is -10~0℃, specifically -8℃ in this embodiment, and the time is 1~3h, specifically 2h in this embodiment; The temperatures for low-speed mixing, medium-speed mixing, and high-speed mixing are independently ≤10℃, specifically 8℃ in this embodiment; the rotation speed for low-speed mixing is 300~500rpm, specifically 390rpm in this embodiment, and the time is 5~10min, specifically 7min in this embodiment; the rotation speed for medium-speed mixing is 1000~1200rpm, specifically 1100rpm in this embodiment, and the time is 10~15min, specifically 12min in this embodiment; the rotation speed for low-speed mixing is 1500~2000rpm, specifically 1800rpm in this embodiment, and the time is 3~5min, specifically 4min in this embodiment.

[0060] As one implementation method, the steps of the ball milling masterbatch method are as follows: A portion of polytetrafluoroethylene resin is taken and added to a planetary ball mill along with all nano-carbon materials and potassium titanate whiskers for dry ball milling to obtain a masterbatch; the masterbatch is then mixed with the remaining components in a high-speed mixer; the remaining components include residual polytetrafluoroethylene resin, bronze powder, polyimide micro powder, graphite, coupling agent, and lubricant; when the modified PTFE sealing material further includes ceramic powder and / or carbon fiber, the remaining components also include ceramic powder and / or carbon fiber; the mass of the portion of polytetrafluoroethylene resin is 10-20% of the total mass of polytetrafluoroethylene resin, specifically 15% in this embodiment; the ball-to-material ratio of the ball milling is 3-6:1, specifically 5:1 in this embodiment, the rotation speed is 300-400 rpm, specifically 350 rpm in this embodiment, and the time is 1-2 hours, specifically 1.5 hours in this embodiment.

[0061] In one embodiment, the compression molding pressure is 20~30MPa, specifically 25MPa, and the holding time is 5~10min, specifically 8min. The compression molding steps are: filling the mixture into the mold and pressing it to obtain the blank. The equipment used for compression molding is a press. The holding time can be adjusted appropriately according to the blank size, and the mold design should consider the subsequent machining allowance.

[0062] In one implementation, the sintering atmosphere is air or nitrogen, specifically nitrogen; the sintering equipment is a sintering furnace; the sintering includes sequentially performing low-temperature sintering, high-temperature sintering, and cooling; the low-temperature sintering temperature is 320~330℃, specifically 325℃, and the holding time is 1~2h, specifically 1.5h; the heating rate to the low-temperature sintering temperature is 60~80℃ / h, specifically 65℃ / h; the high-temperature sintering temperature is 360~380℃, specifically 370℃, and the holding time is 3~5h, specifically 4h; the heating rate to the high-temperature sintering temperature is 40~60℃ / h, specifically 50℃ / h; the cooling is natural cooling to room temperature; the cooling rate during the cooling process is controlled to be ≤40℃ / h, specifically 25℃ / h. Low-temperature sintering is mainly used to remove residual stress, while high-temperature sintering is used to form the desired shape. The cooling rate is controlled at ≤40℃ / h to prevent internal stress.

[0063] As one implementation method, after sintering, the process further includes: sequentially performing post-processing, inspection, and warehousing on the sintered blank; the post-processing involves machining the blank according to inspection standards to obtain standard test pieces and seals of the required dimensions; the seals include guide strips, Step seals, or Glyd rings; the inspection involves inspecting the appearance and dimensions of the seals obtained from the post-processing according to the drawings; and the warehousing involves warehousing the qualified products after inspection according to the established process.

[0064] Figure 1 This is a schematic diagram of the preparation method of the modified PTFE sealing material in an embodiment of the present invention. Figure 1 As shown, the powder is pretreated, mixed, molded, sintered, and finally processed and inspected before being put into storage.

[0065] The present invention also provides the application of the modified PTFE sealing material described in the above technical solution or the modified PTFE sealing material prepared by the preparation method described in the above technical solution in engineering machinery seals.

[0066] As one implementation, the engineering machinery seal includes one or more of the following: hydraulic cylinder sealing system, compressor sealing system, rotary machinery sealing system, injection molding machine sealing system, valve sealing system, and reactor sealing system.

[0067] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments thereof, but they should not be construed as limiting the scope of protection of the present invention.

[0068] Example 1 The group assignments in the embodiments are shown in Table 2.

[0069] Table 2 Distribution ratio of each group

[0070] The characteristics of each component are as follows: The PTFE micro powder is selected from DF-16A molding grade fine powder from Shandong Dongyue Polymer Materials Co., Ltd., with a particle size of 5~20μm and a weight-average molecular weight of 2 million~4 million. The bronze powder used is 663 tin bronze powder from Shijiazhuang Jingyuan Powder Material Co., Ltd., which is atomized into spherical shape, with a copper content of 60~65wt%, a tin content of 35~40wt%, a purity of ≥99%, and a particle size of 25~75μm. The polyimide micro powder used is Solvay Torlon 4000TF, with a particle size of 30~40μm and a thermal decomposition temperature of 480~520℃; Aminated graphene oxide was selected from Matexcel D. 50 (15.5~16.8μm) powder (item number MGP-OG01); MXene (Ti3C2T) x The nanosheets are made from highly dispersed MXene nanosheet powder from Jiangsu Xianfeng Nano, with a sheet diameter of 500~1500nm and a thickness of 5~10nm; Carboxylated carbon nanotubes were selected from Jiangsu Xianfeng Nano's long-diameter carboxylated multi-walled carbon nanotube XFM09 powder, with a diameter of 8~15nm, a length of ≈50μm, and a carboxyl content of 2.56wt%. The potassium titanate whiskers are made from TISMOD potassium titanate octatate whisker powder from Otsuka, Japan, with a diameter of 0.2~0.6μm, a length of 10~20μm, and an aspect ratio of 15~20:1. The flake graphite used is TSG-99 from Toyo Carbon, Japan, with flake size of 20~50μm, thickness of 0.05~0.15μm, and purity ≥99%. Nano-silicon carbide is made from Cabot-SiC-50 powder with a particle size of 30~50nm; The carbon fiber used is Jiangsu Hengshen HF30-0.5, with a fiber length of 0.5mm and a diameter of 7~12μm. The silane coupling agents (KH-550, KH-560) are industrial-grade products from Jiangxi Chenguang New Materials Co., Ltd. The liquid paraffin used is a high flash point special liquid paraffin from Xinji Jingshan Petrochemical Co., Ltd., with a flash point ≥160℃; Zinc stearate is sourced from Jiangxi Chenguang New Materials Co., Ltd. (High-temperature resistant zinc stearate is used.) The specific steps are as follows: (1) Powder pretreatment: Disperse the nano-carbon material in anhydrous ethanol, add a coupling agent, and ultrasonically disperse it for 30 min at a power of 500W and a frequency of 40kHz to obtain a modified nano-carbon suspension; dry bronze powder, polyimide micro powder, potassium titanate whiskers, graphite (and carbon fiber and ceramic powder) in a vacuum drying oven at 85℃ for 3.5 h to remove moisture; (2) Mixing: (2-1) Wet premixing: The modified nano carbon suspension obtained in step (1) and all PTFE resin are added to a high shear mixer in proportion, and anhydrous ethanol is added to make the solid content of the system 40wt%. The mixture is sheared at 2800rpm for 30min at room temperature so that the nano carbon material is uniformly coated on the surface of PTFE particles. (2-2) Low temperature vacuum drying: The above mixture was transferred to a vacuum drying oven and dried at 60°C and a vacuum of -0.09MPa for 6 hours to obtain PTFE composite powder pre-coated with nano-carbon materials; (2-3) Secondary dry mixing: The dried composite powder, along with the bronze powder, polyimide micro powder, potassium titanate whiskers, graphite (and the carbon fiber and ceramic powder in the formula) and lubricant treated in step (1), are added to a high-speed mixer and mixed at 1200 rpm for 15 min to obtain a mixture. (3) Compression molding: The mixture is filled into the mold and held under pressure of 25MPa for 8 minutes to obtain the blank. The mold design should take into account the allowance for subsequent turning. (4) Sintering: In a nitrogen atmosphere, the billet is heated to 325°C at 65°C / h and held for 1.5h, then heated to 370°C at 50°C / h and held for 4h, and then naturally cooled to room temperature at a cooling rate of 25°C / h. (5) Post-processing, inspection and warehousing: After the sintered blanks are inspected according to the inspection standards, they are machined to produce standard test pieces and finished sealing parts (guide belts, Step seals, Glyd rings) of the required size. The appearance and size are inspected according to the drawings. After passing the inspection, they are put into the warehouse according to the process.

[0071] Comparative Examples 1-14 The group assignments in the comparative example are shown in Table 3.

[0072] Table 3 Distribution ratio of each group

[0073] The preparation methods for each comparative example are the same as in Example 1.

[0074] Performance testing The performance test results of each product in Example 1 are shown in Table 4.

[0075] Table 4 Performance test results of each product in Example 1

[0076] The performance test results of each product in Comparative Examples 1 to 14 are shown in Table 5.

[0077] Table 5 Performance test results of each product in Comparative Examples 1-14

[0078] Data analysis was performed on Tables 4 and 5, and the results are as follows: 1. Missing comparative examples (comparative examples 3-6): Comparative Example 3 (without bronze powder) showed a compressive strength of 14.2 MPa and a limiting PV value of only 0.4, demonstrating that bronze powder is crucial as a load-bearing layer for high-pressure extrusion resistance. Comparative Example 4 (without nano-carbon) had a wear rate as high as 38 × 10⁻⁶. -6 mm 3 / N·m, which is about 9 times higher than that in Example 1, proves that the transfer film formed by the nano-carbon material plays a decisive role in reducing wear; Comparative Example 5 (without PI) had a heat distortion temperature reduced to 118℃ and a high-temperature compression set of up to 42%, proving that PI is indispensable for high-temperature creep resistance. Comparative Example 6 (without potassium titanate whiskers) showed a decrease in compressive strength to 18.6 MPa and an increase in creep, demonstrating the contribution of whiskers to the three-dimensional reinforcing framework.

[0079] 2. Alternative Comparative Examples (Comparative Examples 7-8): Comparative Example 7 (glass fiber replacing whiskers) had a wear rate of 9.5 × 10⁻⁶. -6 mm 3 / N·m, compressive strength 19.8MPa, both inferior to Example 1, proving that potassium titanate whiskers are superior to glass fibers; Comparative Example 8 (unmodified graphene) had a wear rate of 7.8 × 10⁻⁶. -6 mm 3 / N·m demonstrates the necessity of amination-modified graphene for improving compatibility and dispersibility.

[0080] 3. Content boundary comparison examples (Comparative examples 9-11): Comparative Example 9 (20 parts bronze powder) had a compressive strength of only 18.5 MPa and a limiting PV value of 0.55, which was lower than that of Example 1; Comparative Example 10 (80 parts bronze powder) showed an increased coefficient of friction of 0.26, resulting in accelerated wear of the mating parts and increased machinability. Comparative Example 11 (0.5 parts nano-carbon) had a wear rate of 8.5 × 10⁻⁶. -6 mm 3 / N·m, which is still higher than that of Example 1, proves the necessity of the lower limit of 1 part.

[0081] 4. Validation of synergistic effect (Comparative Examples 12-13-14-Example 1): Comparative Example 12 (bronze powder + graphite only): Wear rate 92 × 10 -6 mm 3 / N·m, compressive strength 21.5MPa; Comparative Example 13 (+PI): Wear rate reduced to 32×10 -6 mm 3 / N·m, heat distortion temperature increased to 142℃; Comparative Example 14 (+whiskers): Wear rate further decreased to 8.2 × 10⁻⁶. -6 mm 3 / N·m, compressive strength 20.1MPa (slightly decreased due to the difficulty of whisker dispersion); Example 1 (+Nano Carbon): Wear rate drops sharply to 4.2 × 10 -6 mm3 / N·m, the compressive strength increased to 25.6MPa, and the coefficient of friction decreased to 0.18.

[0082] Conclusion: When the four dimensional components aggregate, the wear rate is reduced from 92 × 10⁻⁶. -6 mm 3 / N·m to 4.2×10 -6 mm 3 The two orders of magnitude increase in / N·m, along with the simultaneous optimization of compressive strength and friction coefficient, fully demonstrate that the four-dimensional synergy has produced unexpected technical effects, far exceeding the linear superposition of the properties of each component.

[0083] It should be noted that the limiting PV value is not the only indicator for evaluating the overall performance of a sealing material. Although Comparative Example 2 has a relatively high limiting PV value (1.1 MPa·m / s), its wear rate is as high as 78 × 10⁻⁶. -6 mm 3 The PV value of / N·m is relatively short in practical applications. Although the limiting PV value (0.8 MPa·m / s) of Example 1 of this invention is slightly low, it is sufficient to cover the normal operating conditions of most engineering machinery hydraulic systems (PV value is usually ≤0.6MPa·m / s), while the wear rate is reduced by about 18 times, achieving a longer service life. For extreme operating conditions that require higher PV values, this invention provides optimized formulations such as Example 2 (1.9 MPa·m / s) and Example 4 (2.3 MPa·m / s).

[0084] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A modified PTFE sealing material, characterized in that, By mass, it includes the following components: 100 parts polytetrafluoroethylene resin, 30-80 parts bronze powder, 1-8 parts nano-carbon material, 5-20 parts polyimide micro powder, 3-12 parts potassium titanate whiskers, 3-10 parts graphite, 0.5-2 parts coupling agent, and 1-3 parts lubricant.

2. The modified PTFE sealing material according to claim 1, characterized in that, Based on 1 part by weight of polytetrafluoroethylene resin, the modified PTFE sealing material also includes 5 to 15 parts of carbon fiber.

3. The modified PTFE sealing material according to claim 1, characterized in that, Based on 1 part by weight of polytetrafluoroethylene resin, the modified PTFE sealing material further comprises: 5 to 10 parts of ceramic powder; the ceramic powder includes SiC and / or Al2O3.

4. The modified PTFE sealing material according to claim 1, characterized in that, The modified PTFE sealing materials include modified PTFE sealing materials suitable for high-speed operating conditions, modified PTFE sealing materials suitable for high-temperature operating conditions, or modified PTFE sealing materials suitable for extreme pressure operating conditions.

5. The modified PTFE sealing material according to claim 4, characterized in that, The modified PTFE sealing material suitable for high-speed operating conditions comprises the following components by weight: 100 parts of polytetrafluoroethylene resin 30-40 parts bronze powder 3-8 parts of nano-carbon material, 8-12 parts of polyimide micro powder 5-10 parts of potassium titanate whiskers, 5-10 parts graphite 5-10 parts carbon fiber 1 part coupling agent, Two parts lubricant.

6. The modified PTFE sealing material according to claim 4, characterized in that, The modified PTFE sealing material suitable for high-temperature operating conditions comprises the following components by weight: 100 parts of polytetrafluoroethylene resin 50-70 parts bronze powder 2-4 parts of nano-carbon material, 15-20 parts of polyimide micro powder 5-10 parts of potassium titanate whiskers, 3-5 parts graphite 5-10 parts of ceramic powder 1 part coupling agent, Two parts lubricant.

7. The modified PTFE sealing material according to claim 4, characterized in that, The modified PTFE sealing material suitable for extreme pressure conditions comprises, by weight, the following components: 100 parts of polytetrafluoroethylene resin 60-80 parts bronze powder 2-3 parts of nano-carbon material, 10-15 parts of polyimide micro powder 8-12 parts of potassium titanate whiskers, 5-8 parts graphite 5-15 parts carbon fiber 1-2 parts of coupling agent, Two parts lubricant.

8. A method for preparing the modified PTFE sealing material according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) A coupling agent was added to the dispersion of nano-carbon materials to modify it, and a modified nano-carbon suspension was obtained; (2) The modified nano-carbon suspension and polytetrafluoroethylene resin are wet-premixed and then vacuum-dried at low temperature. The resulting nano-carbon material pre-coated polytetrafluoroethylene resin composite powder is dry-mixed with bronze powder, polyimide micro powder, potassium titanate whiskers, graphite and lubricant to obtain a mixture. (3) The mixture is molded to obtain a blank; (4) The blank is sintered to obtain the modified PTFE sealing material.

9. The preparation method according to claim 8, characterized in that, The sintering process includes sequential low-temperature sintering, high-temperature sintering, and cooling; the low-temperature sintering temperature is 320~330℃, and the holding time is 1~2h; the high-temperature sintering temperature is 360~380℃, and the holding time is 3~5h; the cooling rate is controlled to be ≤40℃ / h during the cooling process.

10. The application of the modified PTFE sealing material according to any one of claims 1 to 7 or the modified PTFE sealing material prepared by the preparation method according to claim 8 or 9 in engineering machinery seals.

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