PTFE composite material with high strength and high wear resistance and preparation method thereof

Abstract

The application discloses a kind of high-strength, high wear resistance PTFE composite material and preparation method, the PTFE composite material includes PTFE resin powder 80~90%;Surface treatment glass fiber 8~15%;Molybdenum disulfide powder 2~5%.The application is synergistically enhanced with molybdenum disulfide by surface-treated glass fiber and lubrication modification, and combined with optimized surface treatment and multi-stage precision process, realizes the comprehensive balance of high strength, high modulus, low friction, high wear resistance and excellent creep resistance.The PTFE composite material has significantly improved mechanical strength, creep resistance, wear life and stable low friction coefficient, can effectively improve the dispersion uniformity of filler in PTFE matrix, and strengthen the interface bonding between filler and matrix, so as to ensure the reliability and consistency of composite material performance, especially suitable for manufacturing long-life, high-reliability dynamic seals, bearing bushings and mechanical parts such as sliding block.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, and relates to a high-performance polytetrafluoroethylene (PTFE) composite material, specifically a modified PTFE composite material for aerospace hydraulic seals used in harsh friction conditions and its preparation method. Background Technology

[0002] PTFE holds an important position in the fields of sealing and tribology due to its excellent chemical stability, wide operating temperature range, and the lowest coefficient of friction among known solid materials. However, its inherent low mechanical strength, high cold flow tendency, and poor wear resistance make pure PTFE products prone to excessive wear, plastic deformation, and even premature failure under high-speed, high-load, or long-term operating conditions.

[0003] To overcome these shortcomings, existing technologies generally employ filler modification methods. Common reinforcing fillers include glass fiber (GF), carbon fiber (CF), and bronze powder, while lubricating fillers include graphite and molybdenum disulfide (MoS2). For example, Fang Hongqiang's research on the molding process and performance of GF wave-transparent composite materials disclosed a glass fiber-reinforced PTFE sealing material, which improved the material's hardness and creep resistance to a certain extent, but had limited improvement on the coefficient of friction and wear rate. Another paper by Gong Jun on the tribological properties of polytetrafluoroethylene and its graphite and MoS2-filled composites revealed that PTFE composites with added molybdenum disulfide and graphite showed improved self-lubricating properties, but decreased mechanical strength, especially impact resistance.

[0004] In summary, the main problems with existing technologies are: First, single or simple blended filler systems struggle to simultaneously and synergistically improve mechanical load-bearing capacity and tribological properties, often resulting in trade-offs. Second, poor interfacial compatibility between inorganic fillers and the non-polar PTFE matrix leads to weak interfacial bonding, easy filler agglomeration, and low stress transfer efficiency, limiting the modification effect. Third, conventional mechanical blending-hot pressing processes are insufficient to achieve uniform dispersion and robust interfacial bonding of nano / microscale fillers. Therefore, developing a PTFE composite material that achieves complementary advantages between the reinforcing and lubricating phases and possesses a stable interfacial structure, along with its efficient preparation method, is of great significance for promoting the development of high-end sealing and bearing technologies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-strength, high-wear-resistant PTFE composite material and its preparation method. By synergistic reinforcement and lubrication modification of surface-treated glass fiber (GF) and molybdenum disulfide (MoS2), combined with optimized surface treatment and multi-stage precision processes, a comprehensive balance of high strength, high modulus, low friction, high wear resistance, and excellent creep resistance is achieved. This PTFE composite material simultaneously possesses significantly improved mechanical strength, creep resistance, wear life, and a stable low coefficient of friction. It effectively improves the uniformity of filler dispersion in the PTFE matrix and strengthens the interfacial bonding between the filler and the matrix, thereby ensuring the reliability and consistency of the composite material's performance. It is particularly suitable for manufacturing mechanical components such as dynamic seals, bearing bushings, and sliders that require long service life and high reliability.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A high-strength, high-wear-resistant PTFE composite material, by weight percentage, comprises: PTFE resin powder: 80-90%; surface-treated glass fiber: 8-15%; molybdenum disulfide (MoS2) powder: 2-5%.

[0008] A method for preparing the above-mentioned high-strength, high-wear-resistant PTFE composite material includes the following steps:

[0009] Step 1, Multi-stage precision mixing: PTFE resin powder, surface-treated glass fiber and molybdenum disulfide powder are placed in a high-speed mixer and initially mixed under inert gas protection; then transferred to a three-dimensional rotary mixer for long-term low-temperature mixing to ensure uniform dispersion of multiple components;

[0010] Step 2, Pre-pressing: The uniformly mixed composite powder is loaded into a mold and cold isostatically pressed at a pressure of 40~80MPa at room temperature to form a dense preform.

[0011] Step 3, temperature-controlled sintering: Place the preformed blank in a sintering furnace and sinter it in an air or nitrogen atmosphere according to the following multi-stage temperature curve: raise the temperature to 300-330℃ at a rate of 30-50℃ / h and hold for 1-2 hours; continue to raise the temperature to 370-385℃ at a rate of 20-40℃ / h and hold for 2-4 hours; finally, slowly cool to room temperature.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] 1. Synergistic Reinforcement and Lubrication Effect: Glass fiber, as a rigid reinforcement, effectively bears mechanical stress, significantly improving the tensile strength, compressive modulus, and creep resistance of the composite material. Molybdenum disulfide, as a solid lubricant, forms a continuous transfer film at the friction interface, significantly improving the wear resistance and self-lubricating properties of the composite material, reducing the coefficient of friction and wear rate (wear rate reduction of over 50%). The synergistic effect of these two components allows the material to maintain excellent self-lubricating and wear-resistant properties even under high loads.

[0014] 2. Optimized interface structure: By treating the glass fiber with a silane coupling agent, organic functional groups that can physically entangle or weakly chemically interact with PTFE molecules are introduced onto its surface. This greatly improves the interfacial compatibility and bonding force between the hydrophilic glass fiber and the hydrophobic PTFE matrix, enhances stress transfer efficiency, and prevents interfacial delamination.

[0015] 3. Uniform microstructure: The multi-stage mixing process of "high-speed initial mixing + three-dimensional low-temperature long-term mixing" effectively solves the problem of agglomeration and sedimentation of micron-sized fillers caused by differences in density and polarity, ensuring the uniformity of the microstructure of the composite material, thereby resulting in stable performance and high isotropy.

[0016] 4. Controllable sintering process: Through staged temperature-controlled sintering, the full melting and recrystallization of PTFE resin are ensured, while avoiding internal stress cracking and damage to filler distribution caused by excessively rapid heating. The final product has high density, few internal defects, and good dimensional stability. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0018] This invention provides a high-strength, high-wear-resistant PTFE composite material, comprising, by weight percentage: 80-90% PTFE resin powder as a continuous matrix; 8-15% surface-treated glass fiber as the main reinforcing phase for stress bearing and creep inhibition; and 2-5% molybdenum disulfide (MoS2) powder as a solid lubricant for reducing friction and improving wear resistance. The surface-treated glass fiber is a short-cut, alkali-free glass fiber treated with a silane coupling agent (KH-550 or KH-560), with a fiber length of 40±3μm and a single filament particle size of 10±3μm. Surface pretreatment with the silane coupling agent enhances the interfacial bonding between the glass fiber and the PTFE matrix. The molybdenum disulfide powder has a particle size of 1-10μm, preferably 1-5μm, and a purity of not less than 99.5%.

[0019] The preparation method of the above-mentioned high-strength, high-wear-resistant PTFE composite material includes the following steps:

[0020] Step 1, Packing Pretreatment:

[0021] Step 11: Dry the PTFE powder in an oven at 110~130℃ for 3~5 hours to remove adsorbed moisture.

[0022] Step 12: Place the chopped alkali-free glass fibers in an ethanol solution containing 1-3 wt% silane coupling agent (such as γ-aminopropyltriethoxysilane, KH-550), disperse them by ultrasonication, drain them, and then heat-treat them at 100-120℃ for 1-2 hours to complete the surface modification and obtain surface-treated glass fibers.

[0023] Step 2, Multi-stage precision mixing:

[0024] Step 21: Place PTFE resin powder, surface-treated glass fiber and molybdenum disulfide powder in a high-speed mixer and perform initial mixing under inert gas protection.

[0025] Step 22: The mixture is then transferred to a three-dimensional rotary mixer for prolonged low-temperature mixing to ensure uniform dispersion of the multiple components. The prolonged low-temperature mixing procedure is as follows: First, it runs at a low speed (150~250 r / min) for 1~2 minutes to achieve initial mixing of the glass fiber and molybdenum disulfide powder in the PTFE resin powder; then, it is quickly switched to a high speed (1300~1500 r / min) for 90~120 seconds. Utilizing strong shear and convection, the filler is highly uniformly dispersed in the PTFE powder. Simultaneously, the low-temperature environment prevents the PTFE resin from softening and sticking due to frictional heat, ensuring the stability and uniformity of the mixture. The entire mixing process is conducted in a dry air environment.

[0026] Step 3, Pre-pressing: The uniformly mixed composite powder is loaded into the mold and subjected to unidirectional cold isostatic pressing at a pressure of 40~80MPa at room temperature for 10~20 minutes to produce a dense preform with sufficient initial strength.

[0027] Step 4, Temperature-Controlled Sintering: Place the preformed green body in a temperature-controlled sintering furnace and sinter under an air or nitrogen atmosphere according to the following multi-stage temperature curve: First stage (heating and desorption): Heat to 300-330℃ at a rate of 30-50℃ / h and hold for 1-2 hours to remove low molecular weight substances; Second stage (melting and crystallization): Continue to heat to above the melting peak temperature of PTFE (370-385℃) at a rate of 20-40℃ / h and hold for 2-4 hours to ensure full melting of the matrix, interface fusion, and crystal structure reorganization; Third stage (controlled cooling): Finally, cool from the sintering temperature to approximately 300℃ at a controlled rate (≤20℃ / h), and then cool with the furnace or further slowly to room temperature according to the set program to eliminate thermal stress and obtain a structurally stable product.

[0028] Step 5, Post-processing and shaping (optional): For seals with precise dimensional requirements, the sintered blank can be placed in a flat vulcanizing machine and molded for a short time (e.g., 1-5 minutes) using a precision die at a low pressure of 2-5 MPa and a temperature below the melting point of PTFE (e.g., 200-250°C) to calibrate the dimensions and improve the surface morphology.

[0029] The aforementioned PTFE material system uses polytetrafluoroethylene (PTFE) as the matrix and glass fibers treated with a silane coupling agent as the reinforcing phase to improve the tensile strength, flexural modulus, and creep resistance of the composite material. Simultaneously, micron-sized molybdenum disulfide is added as a solid lubricating phase, forming a continuous transfer film on the contact surface during friction, thereby significantly reducing the coefficient of friction and wear rate of the composite material and endowing it with excellent self-lubricating properties. This invention effectively solves the technical problems of difficulty in simultaneously achieving mechanical and tribological properties when modifying with a single filler, and uneven dispersion of the filler in the matrix, through the synergistic effect of the two-phase filler and the optimization of interfacial compatibility by the coupling agent. Ultimately, it obtains a PTFE composite material with high strength, high wear resistance, and stable low friction characteristics. This material is particularly suitable for high-performance seals, bearing bushings, and sliders, and other tribological components with stringent requirements for mechanical strength, wear life, and operational reliability, and can operate stably for long periods under harsh conditions such as high speed and high load.

[0030] Example 1:

[0031] 1. Raw material ratio

[0032] PTFE resin: 88wt%; surface-treated glass fiber: 10wt%; molybdenum disulfide: 2wt%.

[0033] 2. Preparation process

[0034] Step 1, Packing Pretreatment:

[0035] Step 11: Select suspension polytetrafluoroethylene (PTFE) resin powder with an average particle size of 25~35μm and a molecular weight of 3 million~5 million, place it in a clean stainless steel tray with a thickness not exceeding 3cm, put it into an electric heating drying oven, and dry it at a constant temperature of 120℃ for 4 hours to remove adsorbed moisture and volatile impurities. After drying, immediately place it in a desiccator to cool for later use.

[0036] Step 12: Short chopped alkali-free glass fibers with a length of 40±3μm and a single filament diameter of 7~10μm are placed in an ethanol solution containing 2wt% silane coupling agent KH-550. After ultrasonic dispersion and leaching, the fibers are heat-treated at 110℃ for 1.5 hours to complete surface modification and obtain surface-treated glass fibers.

[0037] Step 2, Multi-stage precision mixing:

[0038] Step 21: Place PTFE resin powder, surface-treated glass fiber and molybdenum disulfide powder in a high-speed mixer and mix at room temperature for 20 minutes. Perform initial mixing under inert gas protection to ensure uniform dispersion.

[0039] Step 22: The mixture is then transferred to a three-dimensional rotary mixer for prolonged low-temperature mixing to ensure uniform dispersion of the multiple components. The prolonged low-temperature mixing procedure is as follows: First, it runs at 200 r / min for 2 minutes to initially mix the components; then, it is quickly switched to 1400 r / min for 100 seconds. Utilizing strong shear force, impact force, and convection, the PTFE suspended fine powder, glass fiber, and MoS2 agglomerates are depolymerized, achieving nanoscale uniform dispersion of the filler in the PTFE matrix. Finally, the mixture is decelerated and stopped within 30 seconds. The entire mixing process is conducted in a dry air environment.

[0040] Step 3, Pre-compression molding: The uniformly mixed composite powder is loaded into a cold isostatic pressing mold. The pressure increase rate is set as follows: at room temperature, the pressure is slowly increased to the target pressure of 80 MPa at a rate of 0.5 MPa / s, held for 10 minutes, and then slowly depressurized to atmospheric pressure at a rate of 0.6 MPa / s. The slow pressure increase and depressurization help to expel gas, eliminate internal stress, and prevent delamination and cracking of the pressed bar, thus producing a dense preform with sufficient initial strength.

[0041] Step 4, Program-controlled temperature sintering: Place the preformed green body in a program-controlled temperature sintering furnace and sinter it under an air or nitrogen atmosphere according to the following multi-stage temperature profile:

[0042] Heating stage 1: Increase the temperature from room temperature to 330℃ at a rate of 40℃ / h and hold for 1 hour to remove the moisture adsorbed by the resin and any small amount of low molecular weight additives that may be present, and to prevent bubbles and cracks from forming in the product due to excessive evaporation.

[0043] Heating stage 2: Continue heating at a rate of 30℃ / h to 370℃. This temperature exceeds the melt transition temperature of PTFE (327℃). PTFE resin changes from a crystalline state to an amorphous state, and the melt viscosity decreases significantly. Hold at this temperature for 3 hours to ensure that the matrix is ​​fully melted, the interface is fused, and the crystal structure is reorganized to form a complete crystal structure.

[0044] Cooling stage: After the heat preservation is completed, the temperature is reduced from the sintering temperature to about 300℃ at a rate of ≤20℃ / h. Then the product is slowly cooled to room temperature with the furnace to eliminate the thermal stress caused by uneven shrinkage, prevent the product from warping and deforming, and obtain suitable crystallinity and dimensional stability, that is, to obtain a product with stable structure.

[0045] 3. Performance Testing

[0046] Coefficient of friction: 0.37;

[0047] Tensile strength: 32.8 MPa;

[0048] Elongation at break: 342.3%.

[0049] Example 2:

[0050] 1. Raw material ratio

[0051] PTFE resin: 90wt%; surface-treated glass fiber: 8wt%; molybdenum disulfide: 2wt%.

[0052] 2. Preparation process

[0053] The steps are the same as in Example 1.

[0054] 3. Performance Testing

[0055] Coefficient of friction: 0.45

[0056] Tensile strength: 33.8 MPa

[0057] Elongation at break: 344.7%.

[0058] Example 3:

[0059] 1. Raw material ratio

[0060] PTFE resin: 85wt%; glass fiber: 10wt%; molybdenum disulfide: 5wt%.

[0061] 2. Preparation method

[0062] The steps are the same as in Example 1.

[0063] 3. Performance Testing

[0064] Coefficient of friction: 0.42;

[0065] Tensile strength: 29.8 MPa;

[0066] Elongation at break: 359.9%.

[0067] Example 4:

[0068] 1. Raw material ratio

[0069] PTFE resin: 80wt%; surface-treated glass fiber: 15wt%; molybdenum disulfide: 5wt%.

[0070] 2. Preparation process

[0071] The steps are the same as in Example 1.

[0072] 3. Performance Testing

[0073] Coefficient of friction: 0.43;

[0074] Tensile strength: 28.3 MPa;

[0075] Elongation at break: 339.6%.

Claims

1. A PTFE composite material with high strength and high wear resistance, characterized in that... The PTFE composite material, by weight percentage, comprises: PTFE resin powder: 80-90%; surface-treated glass fiber: 8-15%; molybdenum disulfide powder: 2-5%.

2. The high-strength, high-wear-resistant PTFE composite material according to claim 1, characterized in that... The surface-treated glass fiber is a short-cut alkali-free glass fiber treated with a silane coupling agent.

3. The high-strength, high-wear-resistant PTFE composite material according to claim 2, characterized in that... The silane coupling agent is KH-550 or KH-560, the fiber length is 40±3μm, and the monofilament particle size is 10±3μm.

4. The high-strength, high-wear-resistant PTFE composite material according to claim 1, characterized in that... The molybdenum disulfide powder has a particle size of 1~10μm and a purity of not less than 99.5%.

5. The high-strength, high-wear-resistant PTFE composite material according to claim 4, characterized in that... The particle size of the molybdenum disulfide powder is 1~5μm.

6. A method for preparing a high-strength, high-wear-resistant PTFE composite material according to any one of claims 1-5, characterized in that... The method includes the following steps: Step 1, Multi-stage precision mixing: PTFE resin powder, surface-treated glass fiber and molybdenum disulfide powder are placed in a high-speed mixer and initially mixed under inert gas protection; then transferred to a three-dimensional rotary mixer for long-term low-temperature mixing to ensure uniform dispersion of multiple components; Step 2, Pre-pressing: The uniformly mixed composite powder is loaded into a mold and cold isostatically pressed at room temperature to form a dense preform. Step 3, temperature-controlled sintering: Place the preformed blank in a sintering furnace and sinter it in an air or nitrogen atmosphere.

7. The method for preparing the high-strength, high-wear-resistant PTFE composite material according to claim 6, characterized in that... In step 1, the surface-treated glass fiber is prepared as follows: short-cut alkali-free glass fiber is placed in an ethanol solution containing 1-3 wt% silane coupling agent, ultrasonically dispersed and drained, and then heat-treated at 100-120℃ for 1-2 hours to complete surface modification and obtain surface-treated glass fiber.

8. The method for preparing the high-strength, high-wear-resistant PTFE composite material according to claim 6, characterized in that... In step 1, the long-term low-temperature mixing procedure is as follows: First, run at 150~250 r / min for 1~2 minutes to achieve preliminary mixing of glass fiber and molybdenum disulfide powder in PTFE resin powder; then quickly switch to 1300~1500 r / min for 90~120 seconds of mixing.

9. The method for preparing the high-strength, high-wear-resistant PTFE composite material according to claim 6, characterized in that... In step 2, the pressure of cold isostatic pressing is 40~80MPa.

10. The method for preparing the high-strength, high-wear-resistant PTFE composite material according to claim 6, characterized in that... In step 3, sintering is carried out according to the following multi-stage temperature curve: the temperature is increased to 300-330℃ at a rate of 30-50℃ / h and held for 1-2 hours; the temperature is further increased to 370-385℃ at a rate of 20-40℃ / h and held for 2-4 hours; finally, the temperature is slowly cooled to room temperature.