Glass fiber filled and modified PTFE composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a glass fiber filled and modified PTFE composite material as well as a preparation method and application thereof. The glass fiber filled and modified PTFE composite material comprises modified glass fibers and PTFE, wherein the use amount of the modified glass fibers is 15-25% of the mass of the glass fiber filled and modified PTFE composite material; the modified glass fiber is obtained by modifying glass fiber through an amino silane coupling agent. The modified PTFE composite material is filled with the amino silane coupling agent modified glass fibers, and the use amount of the modified glass fibers is controlled to be 15%-25%, so that the PTFE composite material can maintain the original excellent performance, the hardness, the compression modulus, the 5% compression strength and other mechanical performance indexes of the composite material are improved, the friction coefficient is reduced, and the service life of the composite material is prolonged. The wear resistance is improved, so that the application range of the PTFE composite material is widened.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a glass fiber-filled modified PTFE composite material and a preparation method and application thereof. Background Art

[0002] Polytetrafluoroethylene (PTFE), commonly known as the "King of Plastics," is a polymer material with exceptional performance. Its chemical stability is exceptional, maintaining its properties over a wide temperature range (-200°C to +260°C). PTFE also possesses excellent self-lubricating and electrical insulating properties, making it widely used in numerous fields, including chemical engineering, machinery, electronics, and aerospace.

[0003] However, PTFE is not without flaws. In practical applications, it exhibits several significant drawbacks that significantly limit its scope of use. For example, pure PTFE has low mechanical strength, and its wear resistance and thermal conductivity are unsatisfactory. Furthermore, its relatively weak creep resistance and high coefficient of thermal expansion make it susceptible to deformation when subjected to high pressure or long-term stress. This presents a serious problem in applications requiring high dimensional stability and sealing performance.

[0004] To overcome these shortcomings, researchers have developed a variety of methods for modifying PTFE, among which filler modification is considered an effective and commonly used technique. Filler modification primarily involves adding various inorganic fillers to the PTFE matrix to enhance its performance. These fillers must meet certain requirements, such as being able to withstand the high-temperature sintering process of PTFE (typically above 350°C), not chemically react with PTFE, and possessing an appropriate particle size and shape for uniform dispersion within the PTFE matrix, thereby optimizing the physical and chemical properties of the composite material.

[0005] Glass fiber (GF), a common inorganic filler, shows great potential for application in PTFE composites. GF ​​boasts advantages such as high strength, high modulus, low density, and excellent heat resistance and chemical stability. Its addition to PTFE significantly enhances the material's mechanical properties, such as tensile strength, hardness, and wear resistance. It also improves its dimensional stability and creep resistance, preventing seals from deforming and failing under high pressure or long-term stress. Furthermore, the addition of GF optimizes the tribological properties of PTFE composites, reducing the coefficient of friction and minimizing stick-slip, which is particularly important in dynamic sealing applications (such as rotary shaft seals and piston rings).

[0006] However, in GF-enhanced PTFE composites, the interface bonding performance between GF and the PTFE matrix is ​​poor. Due to the low surface energy of PTFE and the poor affinity with GF, the compatibility between the two is poor. The deficiency of this interface bonding can cause a series of problems. When composite material is subjected to external force, interfacial debonding easily occurs between GF and the PTFE matrix, thereby causing the mechanical properties of the material to decline, affecting its reliability and durability in practical applications. Therefore, how to improve the interfacial bonding between GF and the PTFE matrix has become a key technical problem in preparing high-performance GF / PTFE composites. Summary of the Invention

[0007] The present invention provides a glass fiber filled modified PTFE composite material and a preparation method and application thereof, which are used to solve the problem of poor interface bonding performance between GF and PTFE matrix in existing GF reinforced PTFE composite materials.

[0008] According to a first aspect of the present invention, the present invention provides a glass fiber-filled modified PTFE composite material, comprising modified glass fiber and PTFE, wherein the amount of the modified glass fiber is 15-25% of the mass of the glass fiber-filled modified PTFE composite material; the modified glass fiber is obtained by modifying glass fiber (GF) with an aminosilane coupling agent.

[0009] In GF-reinforced PTFE composites, surface treatment with an aminosilane coupling agent significantly improves the interfacial bonding between GF and the PTFE matrix, thereby enhancing the overall performance of the seal. Due to PTFE's low surface energy and poor affinity with GF, direct composite bonding can easily lead to interfacial debonding. However, the organic-inorganic hybrid structure of the silane coupling agent forms chemical bonds (—Si—O—Si—) on the GF surface. Its NH₂⁻ provides organic reactivity, forming physical or chemical interactions with the PTFE matrix and enhancing compatibility. This treatment significantly enhances the composite's tensile strength, creep resistance, and wear resistance, ensuring more uniform load transfer and reducing fiber debonding and wear in dynamic seals such as shaft seals and piston rings. Furthermore, the silane treatment improves the dispersion of GF in PTFE, reduces processing defects, and ensures the long-term stability of the seal in high-pressure, corrosive, or high-temperature environments. By optimizing interfacial bonding, the aminosilane coupling agent makes GF / PTFE composites more suitable for high-performance sealing applications in demanding operating conditions.

[0010] By filling a modified PTFE composite with glass fiber modified with an aminosilane coupling agent and controlling the amount of modified glass fiber to 15% to 25% of the PTFE mass, this invention significantly enhances the mechanical and tribological properties of the PTFE composite while maintaining its original excellent properties. Specifically, the composite's mechanical properties, including hardness, compression modulus, and 5% compressive strength, are improved, while the coefficient of friction is reduced and wear resistance is enhanced, thereby broadening the application of PTFE composites in high-performance sealing materials and other fields.

[0011] Furthermore, the aminosilane coupling agent is used in an amount of 1-4%, preferably 1-2%, of the glass fiber mass. This ensures the desired modification effect while avoiding the increased costs and other negative issues that may arise from excessive amounts of coupling agent, such as uneven material properties. Within this dosage range, the interfacial bonding between the glass fiber and the PTFE matrix can be more precisely controlled, further optimizing the overall performance of the composite material.

[0012] Furthermore, the aminosilane coupling agent has a molecular formula of H2N-(CH2)2-N(CH3)-(CH2)3-Si(CH3)(OCH3)2. This coupling agent, corresponding to this molecular formula, possesses a specific organic and inorganic structure, capable of forming a strong chemical bond with the glass fiber surface while simultaneously allowing its organic end to physically or chemically interact with the PTFE matrix. This specific structure of the coupling agent effectively enhances the compatibility and bonding between the glass fiber and PTFE, thereby improving the mechanical properties and stability of the composite material, ensuring more reliable performance in practical applications.

[0013] In some specific embodiments, the aminosilane coupling agent is selected from KBM602.

[0014] Furthermore, the glass fiber is powdered glass fiber prepared from chopped glass fiber or continuous glass fiber.

[0015] Furthermore, the particle size of the glass fiber is 10-30 mesh, preferably 15-25 mesh. Glass fibers in a specific particle size range can be better dispersed and distributed in the PTFE matrix, thereby improving the filling effect and enhancing the mechanical properties of the composite material.

[0016] In some specific embodiments, the glass fiber has a particle size of 20 mesh.

[0017] Furthermore, the PTFE is TFM1700 suspension resin with an average particle size of 15-45 μm. Using TFM1700 suspension resin with an average particle size of 15-45 μm as the PTFE ensures the inherent properties of the PTFE and better matches it with the modified glass fiber, creating a closer bond between the two and fully leveraging the reinforcing effect of the glass fiber to enhance the overall performance of the composite material.

[0018] Furthermore, the glass fiber-filled modified PTFE composite material exhibits a hardness of 66.8-68.5 HD, a compression modulus of 624.72-1070.08 MPa, a 5% compressive strength of 17.93-23.18 MPa, and a friction coefficient of 0.126-0.138. These indicators demonstrate the composite material's excellent mechanical and tribological properties. Compared with pure PTFE, its compression modulus and 5% compressive strength are significantly improved, while its friction coefficient and mass wear rate are significantly reduced. This demonstrates that the glass fiber-filled modified PTFE composite material modified with an aminosilane coupling agent has significantly enhanced wear resistance, deformation resistance, and load-bearing capacity, enabling it to better meet the demanding material requirements in applications such as high-performance sealing materials.

[0019] According to a second aspect of the present invention, the present invention provides a method for preparing the above-mentioned glass fiber-filled modified PTFE composite material, comprising the following steps: Step 1: Using an aminosilane coupling agent to perform surface modification on the glass fiber to obtain modified glass fiber; Step 2, mixing the modified glass fiber with PTFE, and pressing the obtained mixture to obtain a PTFE-based composite material precursor; Step 3: sintering the PTFE-based composite material precursor at high temperature.

[0020] The present invention provides a method for preparing a glass fiber-filled modified PTFE composite material. By sequentially performing three key steps: surface modification, mixed compression molding, and high-temperature sintering, the modified glass fiber and PTFE are effectively combined to produce a composite material with excellent properties. This method is simple, feasible, and amenable to industrial production. It also ensures the quality and performance stability of the composite material, providing a reliable approach for preparing high-performance PTFE composite materials.

[0021] Furthermore, in step 1, an aminosilane coupling agent is added to a mixed solution of water and ethanol, the pH of the solution is adjusted to weak acidity, and then hydrolyzed at 60-80° C. for 20-40 min. After hydrolysis, the mixture is mixed with glass fiber, and then reacted at 60-80° C. for 3-5 h, washed, and dried.

[0022] The above protocol defines the specific conditions for surface modification of glass fibers with an aminosilane coupling agent in step 1, including adjusting the solution pH to a weakly acidic state, the hydrolysis temperature and time, and the reaction temperature and time. The volume ratio of the coupling agent, water, and anhydrous ethanol is also optimized. These controlled conditions ensure that the coupling agent is fully hydrolyzed and undergoes a uniform and stable chemical reaction with the glass fiber surface, forming a uniform and dense modified layer on the glass fiber surface. This effectively improves the interfacial bonding between the glass fiber and the PTFE matrix, further enhancing the performance of the composite material.

[0023] To ensure sufficient hydrolysis of the aminosilane coupling agent and the formation of effective chemical bonds, the volume ratio of the aminosilane coupling agent, water, and anhydrous ethanol is preferably 1:(10-20):(100-200). Water, as the medium for the hydrolysis reaction, provides sufficient hydroxyl groups to promote the hydrolysis and condensation reactions of the coupling agent molecules, while anhydrous ethanol, as the solvent, helps control the reaction rate and evenly disperse the coupling agent, allowing it to be uniformly coated on the glass fiber surface. By precisely controlling the ratio of these three components, a uniform and dense modified layer can be formed on the glass fiber surface, significantly enhancing the interfacial bonding between the glass fiber and the PTFE matrix. This optimized coupling agent dosage and formulation not only improves the mechanical properties and wear resistance of the composite material, but also enhances its processability and stability. It also avoids the problems of agglomeration or uneven material properties that can result from excessive coupling agent, ensuring the reliability and consistency of the composite material in practical applications.

[0024] More preferably, the volume ratio of the aminosilane coupling agent, water, and anhydrous ethanol is 1:(12-18):(130-170). Even more preferably, the volume ratio of the aminosilane coupling agent, water, and anhydrous ethanol is 1:(15-17):(140-150). In some specific embodiments, the volume ratio of the aminosilane coupling agent, water, and anhydrous ethanol is 1:16:144.

[0025] Furthermore, in step 2, the press molding is performed by cold pressing; preferably, the cold pressing pressure is 20-30 MPa, and the holding time is 1-2 minutes. Appropriate cold pressing pressure and holding time enable the mixture of modified glass fiber and PTFE to be evenly compacted in the mold, forming a dense composite precursor. This ensures sufficient contact and bonding between the components, lays a good foundation for the subsequent high-temperature sintering process, and helps improve the density and mechanical properties of the final composite material.

[0026] Furthermore, in step 3, the high-temperature sintering is carried out by heating the material to 350-390°C at a heating rate of 0.5-1.5°C / min, keeping the temperature at 350-390°C for 1-3 hours, cooling the temperature to 300-340°C at a cooling rate of 0.5-1.5°C / min, keeping the temperature at 300-340°C for 1-3 hours, and then cooling the material to room temperature with the furnace. This precisely controlled sintering process can ensure that the PTFE fully melts, flows, and solidifies at high temperatures, allowing it to better combine with the modified glass fiber, while avoiding the occurrence of adverse phenomena such as oxidation and decomposition of the material at high temperatures, thereby ensuring the quality and performance of the composite material. By keeping the temperature and cooling the material under specific temperature and time conditions, the PTFE macromolecular chains can be fully entangled and crystallized, thereby improving the density and mechanical properties of the material, thereby making the prepared composite material have better comprehensive performance.

[0027] Preferably, the high-temperature sintering is protected by N2 atmosphere. Before heating, the air in the furnace is repeatedly replaced with N2 until the air is completely replaced by N2. After that, N2 with a pressure of 0.2 MPa is opened for 1 min every hour to keep the pressure in the furnace in a positive pressure state. Such an operation can effectively isolate the air and prevent the PTFE material from undergoing oxidation reaction at high temperature, thereby avoiding the degradation of material properties. At the same time, maintaining the positive pressure state in the furnace can prevent external impurities from entering, ensuring the purity of the sintering environment, helping to improve the density and uniformity of the composite material after sintering, and further improving the mechanical properties and stability of the material.

[0028] According to a third aspect of the present invention, the present invention also provides the use of the above-mentioned glass fiber-filled modified PTFE composite material or the glass fiber-filled modified PTFE composite material prepared by the above-mentioned preparation method in a sealing material.

[0029] Since the glass fiber-filled modified PTFE composite material of the present invention has excellent mechanical properties, good self-lubricating properties and wear resistance, it has broad application prospects in the field of sealing materials and can meet the high performance requirements of sealing materials under various harsh working conditions, such as sealing applications in high temperature, high pressure, corrosive media and other environments, which can improve the service life and reliability of seals and reduce the maintenance cost and failure rate of equipment.

[0030] The glass fiber-filled modified PTFE composite material of the present invention can be used in seals in dry gas sealing systems. Specifically, the glass fiber-filled modified PTFE composite material of the present invention can be used in spring energy storage seals as a jacket material.

[0031] Beneficial effects of the present invention: (1) The glass fiber-filled modified PTFE composite material provided by the present invention has excellent mechanical properties. The maximum compression modulus and 5% compressive strength reach 1070.08 MPa and 23.18 MPa, respectively, which are 109.8% and 38.4% higher than those of pure PTFE (compression modulus and 5% compressive strength are 510.04 MPa and 16.75 MPa, respectively).

[0032] (2) The glass fiber filled modified PTFE composite material of the present invention has a minimum friction coefficient of 0.123 and a mass wear rate of 0.11%, which are respectively reduced by 39.4% and 99.3% compared with pure PTFE (friction coefficient of 0.203 and mass wear rate of 16.50%). The material has better self-lubricating properties and greatly improved wear resistance, making it more suitable for sealing materials.

[0033] (3) The glass fiber filled modified PTFE composite material of the present invention, the compression performance and wear resistance of the PTFE / eGF material treated with aminosilane coupling agent are improved to varying degrees compared with the untreated PTFE / GF material. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a diagram of the thermal sintering process parameters of the GF-filled modified PTFE composite material in Example 1 provided by the present invention.

[0036] Figure 2 This is a compression performance test curve chart of the PTFE materials of Example 1, Example 4, Comparative Example 1 and Comparative Example 2 provided by the present invention.

[0037] Figure 3 This is a compression performance test curve chart of the PTFE materials of Example 2, Example 5, Comparative Example 1 and Comparative Example 3 provided by the present invention.

[0038] Figure 4 This is a compression performance test curve chart of the PTFE materials of Example 3, Example 6, Comparative Example 1 and Comparative Example 4 provided by the present invention.

[0039] Figure 5 This is a test chart of the friction coefficient of the PTFE materials of Example 1, Example 4, Comparative Example 1 and Comparative Example 2 provided by the present invention.

[0040] Figure 6This is a test chart of the friction coefficient of the PTFE materials of Example 2, Example 5, Comparative Example 1 and Comparative Example 3 provided by the present invention.

[0041] Figure 7 This is a test chart of the friction coefficient of the PTFE materials of Example 3, Example 6, Comparative Example 1 and Comparative Example 4 provided by the present invention. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0043] Sources of raw materials used in the embodiments and comparative examples: PTFE: specification 45 μm, brand TFM1700, purchased from 3M Company, USA.

[0044] GF powder: particle size 20 mesh, purchased from Zhuzhou Hongda Polymer Materials Co., Ltd., brand t005.

[0045] Example 1 This embodiment provides a GF-filled modified PTFE composite material, and the preparation method of the composite material comprises the following steps: (1) The aminosilane coupling agent KBM602 was added to a mixed solution of water and ethanol, with the volume ratio of aminosilane coupling agent: water: anhydrous ethanol = (1:16:144). Acetic acid was added to adjust the pH value to weak acidity, and the mixture was hydrolyzed at 70 °C for 30 min. After hydrolysis, the mixture was mixed with GF (wherein the content of aminosilane coupling agent was 1% of the mass fraction of GF), stirred at 70 °C for 4 h, and the aminosilane coupling agent remaining on the surface of GF was filtered and washed. The mixture was then placed in a vacuum drying oven and dried at 70 °C for 10 h to obtain the modified eGF.

[0046] (2) The mixture of eGF and dried PTFE was stirred evenly and then added to a mold. The powder was scraped flat and pressed into shape to obtain a PTFE-based composite material precursor. The eGF content was 15% of the mixture mass.

[0047] At room temperature, weigh 50 g of the dried mixture and transfer it to a dedicated mold. Apply a pressure of 25 MPa and maintain pressure for 1 minute to complete the molding process. During the molding process, the material for each pressed part should be evenly distributed into the mold cavity. Do not use vibration or pounding to fill the material tightly to prevent segregation caused by uneven filler weight. Also, do not add material in batches to prevent delamination of the product. Maintain an appropriate unit pressure during molding to ensure that the resulting pressed part is dense, free of pores, and has high yield strength and wear resistance. The unit pressure is related to the filler type, properties, and content. During the molding process, apply pressure slowly and avoid using impact pressure. Perform 2-4 pressure relief cycles to expel air from the sample. Maintain pressure for 1 minute to ensure even pressure distribution, then slowly reduce pressure. Finally, use a demolding frame to slowly remove the upper and lower molds, and remove the molded part from the mold cavity using appropriate tools.

[0048] (3) The PTFE-based composite material precursor is sintered at high temperature. The sintering process parameters are as follows: Figure 1 As shown, a PTFE composite material filled with multiple inorganic materials and modified is obtained.

[0049] During the heating stage, the sintering heating rate is controlled at 1°C / min within 370°C to ensure that the internal and external temperature difference of PTFE is small during the heating process, to prevent the internal and external expansion of PTFE products from being inconsistent and causing cracking, and the temperature is kept at 370°C for 2 hours.

[0050] Holding the preform at this temperature for a period of time after it has reached the sintering and curing temperature. As the temperature rises, the PTFE macromolecular chains begin to entangle irregularly. The holding temperature and duration determine the density of the molecular entanglement. Temperatures below 370°C or holding times below 50 minutes result in poor PTFE chain activity and poor product density. Sintering at excessively long temperatures can lead to excessive PTFE decomposition and blistering. During the holding process, PTFE molecular motion intensifies, eliminating the interfaces between particles and forming a dense, continuous whole. Therefore, a sintering temperature of 370°C and a holding time of 2 hours were used in this experiment.

[0051] Cooling is the process of cooling a sintered preform from its holding temperature to room temperature. During this process, the PTFE resin transforms from an amorphous phase to a crystalline phase, causing the product to shrink in volume. Within the temperature range of 320-370°C, the cooling rate is controlled at 1°C / min. Maintaining the temperature at 320°C for 2 hours allows the PTFE's internal and external temperatures to drop to the recrystallization temperature, promoting its shrinkage and improving its performance. The product is then cooled to room temperature in the furnace.

[0052] Example 2 This embodiment provides a GF-filled modified PTFE composite material. The preparation method of the composite material is different from that of Example 1 only in that the eGF content in step (2) is 20% of the mass of the mixture.

[0053] Example 3 This embodiment provides a GF-filled modified PTFE composite material. The preparation method of the composite material is different from that of Example 1 only in that the eGF content in step (2) is 25% of the mass of the mixture.

[0054] Example 4 This embodiment provides a GF-filled modified PTFE composite material. The preparation method of the composite material is different from that of Example 1 only in that: in step (1), the content of the aminosilane coupling agent is 2% of the mass fraction of GF, and the modified mGF is obtained.

[0055] Example 5 This embodiment provides a GF-filled modified PTFE composite material. The preparation method of the composite material is different from that of Example 2 only in that: in step (1), the content of the aminosilane coupling agent is 2% of the mass fraction of GF, and the modified mGF is obtained.

[0056] Example 6 This embodiment provides a GF-filled modified PTFE composite material. The preparation method of the composite material is different from that of Example 3 only in that: in step (1), the content of the aminosilane coupling agent is 2% of the mass fraction of GF, and the modified mGF is obtained.

[0057] Comparative Example 1 This comparative example provides a PTFE composite material. No GF is added to the formula, that is, a pure PTFE material is prepared. The preparation method is the same as that of Example 1.

[0058] Comparative Example 2 This comparative example provides a PTFE / GF composite material. This comparative example is prepared according to the preparation method of Example 1, wherein GF that has not been modified with an aminosilane coupling agent is directly added to PTFE and the PTFE / GF composite material is prepared according to steps (2) and (3).

[0059] Comparative Example 3 This comparative example provides a PTFE / GF composite material. This comparative example is to prepare the PTFE / GF composite material according to the preparation method of Example 2, wherein GF that has not been modified with an aminosilane coupling agent is directly added to PTFE according to steps (2) and (3).

[0060] Comparative Example 4 This comparative example provides a PTFE / GF composite material. This comparative example is prepared according to the preparation method of Example 3, wherein GF that has not been modified with an aminosilane coupling agent is directly added to PTFE and the PTFE / GF composite material is prepared according to steps (2) and (3).

[0061] Next, the following performance tests were performed on the PTFE materials of Examples 1 to 6 and Comparative Examples 1 to 4: The density test standard is carried out in accordance with the national standard GT / T1463-2005 "Fiber reinforced plastic density and relative density test".

[0062] The hardness test standard is based on the national standard GB / T2411-2008 "Determination of indentation hardness (Shore hardness) of plastics and hard rubber using a hardness tester". The hardness of the same sample is measured 5 times at a distance of 6 mm and the average value is calculated.

[0063] The compression performance test standard is carried out in accordance with GB / T1041-2008 "Plastics - Determination of Compression Properties", the compression rate is 1 mm / min, and the final result is the average value of 5 parallel samples.

[0064] The friction coefficient test standard is based on the national standard GB / T 10006-2021 "Determination of the coefficient of friction of plastic films and sheets", and the test is carried out using a MWF-05 reciprocating friction and wear testing machine.

[0065] Specifically: The test load was 500 N, the friction rate was 200 mm / s, the time was 60 min, the sample size was Φ12 mm × 12 mm cylinder, and the specimen was made of 45# steel (surface roughness 0.12). During the experiment, the friction coefficient of the composite material was recorded, and the sample mass before and after friction was measured to calculate the mass wear rate. Each sample was repeated 5 times and the average value was taken.

[0066] (1) Density detection Table 1 Density of PTFE materials of Examples 1 to 6 and Comparative Examples 1 to 4

[0067] The experimental data in Table 1 show that density increases with increasing GF content. Specifically, the density of pure PTFE is 2.195 g / cm³. When unmodified GF is added, the density increases at all concentrations, reaching 2.275 g / cm³ for PTFE + 25% GF. The density of PTFE composites filled with GF (eGF or mGF) modified with an aminosilane coupling agent also increases with GF content. At the same GF content, the density of the modified mGF-filled material is higher than that of the unmodified and eGF-filled materials. This is likely due to the tighter bonding of the modified glass fiber to the PTFE matrix, resulting in a denser overall material. This suggests that aminosilane-modified glass fiber helps improve the density of the composite, which in turn may have a positive impact on the material's mechanical properties.

[0068] (2) Hardness test The hardness of the same sample was measured 5 times at intervals of 6 mm and the average value was calculated. The results are shown in Table 2.

[0069] Table 2 Hardness of PTFE materials in Examples 1 to 6 and Comparative Examples 1 to 4

[0070] The experimental data in Table 2 show that PTFE composites filled with glass fibers modified with aminosilane coupling agents (eGF or mGF) generally exhibit higher hardness than those filled with unmodified glass fibers (GF). Specifically, the hardness of pure PTFE is 66.5 HD, while the addition of unmodified GF increases the hardness with increasing GF content, reaching a hardness of 71.0 HD for PTFE + 25% GF. In contrast, the modified glass fiber-filled composites exhibited higher hardness at the same GF content, with mGF modification slightly outperforming eGF. This indicates that the modification of glass fibers with aminosilane coupling agents significantly enhances the bond between the fibers and the PTFE matrix, thereby effectively improving the hardness of the composite. This increase in hardness is crucial for improving the material's wear resistance and dimensional stability, further demonstrating that modified glass fibers can significantly optimize the mechanical properties of PTFE composites.

[0071] (3) Compression performance test The stress-strain curves of the PTFE materials in the compression process of Examples 1 to 6 and Comparative Example 1 are as follows: Figures 2-4 shown.

[0072] Table 3 Compression modulus and yield strength of PTFE materials of Examples 1 to 6 and Comparative Examples 1 to 4

[0073] The data in Table 3 show that PTFE composites filled with aminosilane-modified glass fibers (eGF or mGF) significantly outperformed unmodified GF-filled composites and pure PTFE in terms of both compression modulus and 5% compressive strength. Specifically, pure PTFE exhibited a compression modulus of 510.04 MPa and a 5% compressive strength of 16.75 MPa. While the addition of unmodified GF improved both the compression modulus and 5% compressive strength, the effect was limited. For example, the compression modulus of PTFE with 25% GF was 945.60 MPa and the 5% compressive strength was 22.24 MPa. In contrast, the performance of composites filled with modified glass fibers was even more pronounced, particularly the PTFE with 25% mGF, which achieved a compression modulus of 1070.08 MPa and a 5% compressive strength of 23.18 MPa, both significantly higher than pure PTFE. This shows that the modification of glass fiber with aminosilane coupling agent greatly enhances the interfacial bonding between glass fiber and PTFE matrix, thereby enabling the composite material to transfer load more effectively and significantly improving the material's compression resistance and mechanical strength, making it more suitable for application scenarios such as sealing materials with high mechanical performance requirements.

[0074] (4) Friction performance test The friction coefficient of the composite material was recorded during the friction test, and each sample was repeated 5 times. The friction coefficient changed during the experiment as follows Figures 5-7 The friction coefficient is calculated as shown in Table 4.

[0075] Table 4 Friction coefficients of PTFE materials of Examples 1 to 6 and Comparative Examples 1 to 4

[0076] The experimental data in Table 4 demonstrate that PTFE composites filled with aminosilane-modified glass fibers (eGF or mGF) significantly outperform unmodified GF-filled composites and pure PTFE in terms of friction coefficient and wear resistance. Specifically, pure PTFE exhibits a friction coefficient of 0.203 and a mass wear rate of 16.50%, demonstrating high friction resistance and poor wear resistance. Adding unmodified GF reduces the friction coefficient somewhat, but only slightly improves the mass wear rate. For example, the friction coefficient of PTFE with 25% GF is 0.138, and the mass wear rate is 0.12%. In contrast, the performance of the modified glass fiber-filled composites is even more pronounced, particularly the PTFE with 25% mGF, which achieves a friction coefficient of only 0.126 and a mass wear rate as low as 0.11%, both significantly lower than those of pure PTFE. This shows that the modification of glass fiber with aminosilane coupling agent not only enhances the interfacial bonding between the fiber and the PTFE matrix, but also significantly improves the self-lubricating properties and wear resistance of the composite material, making it more suitable for application scenarios such as sealing materials with high requirements for friction performance and durability.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A glass fiber filled modified PTFE composite material, characterized in that, The composite material comprises modified glass fiber and PTFE, wherein the amount of the modified glass fiber is 15-25% of the mass of the glass fiber-filled modified PTFE composite material; and the modified glass fiber is obtained by modifying the glass fiber with an aminosilane coupling agent.

2. The glass fiber filled modified PTFE composite material according to claim 1, characterized in that The amount of the aminosilane coupling agent used is 1-4% of the mass of the glass fiber, preferably 1-2%.

3. The glass fiber filled modified PTFE composite material according to claim 1 or 2, characterized in that The molecular formula of the aminosilane coupling agent is H2N-(CH2)2-N(CH3)-(CH2)3-Si(CH3)(OCH3)2.

4. The glass fiber filled modified PTFE composite material according to any one of claims 1 to 3, characterized in that: The glass fiber is a powdered glass fiber prepared from chopped glass fiber or continuous glass fiber; And / or, the particle size of the glass fiber is 10-30 mesh; And / or, the PTFE is TFM1700 suspension resin with an average particle size of 15-45 μm.

5. The glass fiber filled modified PTFE composite material according to any one of claims 1 to 4, characterized in that: The glass fiber-filled modified PTFE composite material has a hardness of 66.8-68.5 HD, a compression modulus of 624.72-1070.08 MPa, a 5% compression strength of 17.93-23.18 MPa, and a friction coefficient of 0.126-0.

138.

6. The method for preparing the glass fiber-filled modified PTFE composite material according to any one of claims 1 to 5, characterized in that: The steps include: Step 1: Using an aminosilane coupling agent to perform surface modification on the glass fiber to obtain modified glass fiber; Step 2, mixing the modified glass fiber with PTFE, and pressing the obtained mixture to obtain a PTFE-based composite material precursor; Step 3: sintering the PTFE-based composite material precursor at high temperature.

7. The preparation method according to claim 6, characterized in that In the step 1, an aminosilane coupling agent is added to a mixed solution of water and ethanol, the pH of the solution is adjusted to weak acidity, and then hydrolyzed at 60-80° C. for 20-40 minutes. After hydrolysis, the mixture is mixed with glass fiber, and then reacted at 60-80° C. for 3-5 hours, washed, and dried. Preferably, the volume ratio of the aminosilane coupling agent, water and anhydrous ethanol is 1: (10-20): (100-200).

8. The preparation method according to claim 6, characterized in that In step 2, the pressing is performed by cold pressing. Preferably, the pressure of the cold pressing is 20-30 MPa, and the holding time is 1-2 min.

9. The preparation method according to claim 6, characterized in that In step 3, the high-temperature sintering is performed by heating the temperature to 350-390°C at a heating rate of 0.5-1.5°C / min, keeping the temperature at 350-390°C for 1-3 hours, cooling the temperature to 300-340°C at a cooling rate of 0.5-1.5°C / min, keeping the temperature at 300-340°C for 1-3 hours, and then cooling the temperature to room temperature with the furnace; Preferably, the high-temperature sintering is protected by N2 atmosphere. Before heating, the air in the furnace is repeatedly replaced by N2 until all the air is replaced by N2. Thereafter, N2 with a pressure of 0.2 MPa is turned on for 1 minute every hour to keep the pressure in the furnace in a positive pressure state.

10. Use of the glass fiber filled modified PTFE composite material according to any one of claims 1 to 5 or the glass fiber filled modified PTFE composite material prepared by the preparation method according to any one of claims 6 to 9 in sealing materials.

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