A shock-resistant and heat-stable polytetrafluoroethylene composite material and its preparation method

Abstract

The present invention belongs to the technical field of polytetrafluoroethylene composite material preparation, and provides a polytetrafluoroethylene composite material that is impact-resistant and thermally stable, and a preparation method thereof. Montmorillonite enhances material strength and barrier properties through the physical crosslinking and barrier effect of its layered structure, and improves dispersibility, interfacial bonding, and thermal stability through grafting modification and metal ion exchange. Nanoparticles enhance the strength, toughness, and wear resistance of composite materials due to their high specific surface area and small size effect, and optimize interfacial compatibility and impact resistance through silane coupling agents, toughening monomers, and rubber coating modification. Polyacrylonitrile-based carbon fibers enhance the mechanical and conductive properties of composite materials due to their high strength and heat resistance, and further enhance interfacial bonding and mechanical locking through mixed acid oxidation and chemical vapor deposition modification. The three work synergistically to achieve optimization of the mechanical, thermal, and functional properties of the composite material.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of polytetrafluoroethylene composite materials, and relates to an impact-resistant and heat-stable polytetrafluoroethylene composite material and a preparation method thereof. Background Art

[0002] As an exceptional high-performance material, polytetrafluoroethylene (PTFE) is widely used in chemical, electronic, mechanical, and aerospace industries due to its excellent chemical stability, electrical insulation, and low friction coefficient. However, despite its outstanding performance in many applications, its deficiencies in mechanical properties and thermal stability significantly limit its performance in specific applications.

[0003] First, the mechanical properties of PTFE are primarily reflected in its tensile strength and toughness. Although PTFE has high tensile strength, enabling it to withstand high pressures under certain static load conditions, its inherent brittleness significantly limits the material's application range. When subjected to impact or stress concentration, PTFE is prone to crack propagation, leading to material fracture. This brittleness is often the main cause of material failure in practical applications, especially in environments that need to withstand dynamic loads or shock. For example, in the aerospace and automotive industries, PTFE is often used as a seal and insulation material, but its brittle nature can cause components to fail unexpectedly during use, thereby affecting the safety and reliability of the overall system. Such failures can not only result in economic losses but can also, in some cases, endanger personal safety. Therefore, improving the mechanical properties of PTFE is particularly important.

[0004] Secondly, while PTFE performs well under high-temperature conditions, rapid temperature changes or sustained high temperatures can cause its molecular structure to change during these dramatic temperature fluctuations, leading to a decrease in the material's mechanical properties. In certain high-temperature industrial applications, prolonged exposure to high temperatures can lead to material fatigue, which not only affects the material's physical properties but can also lead to failure. Therefore, PTFE's lack of thermal stability is particularly evident in extreme temperature environments, limiting its application in high-temperature processes or equipment. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide an impact-resistant and heat-stable polytetrafluoroethylene composite material and a preparation method thereof. The present invention significantly improves the comprehensive performance of polytetrafluoroethylene composite materials by introducing and modifying montmorillonite, nanoparticles and polyacrylonitrile-based carbon fibers. Montmorillonite enhances the strength and barrier properties of the material through the physical cross-linking and barrier effect of the layered structure, and improves the dispersibility, interface bonding and thermal stability through grafting modification and metal ion exchange; nanoparticles improve the strength, toughness and wear resistance of the composite material due to their high specific surface area and small size effect, and optimize the interface compatibility and impact resistance through silane coupling agents, toughening monomers and rubber coating modifications; polyacrylonitrile-based carbon fibers enhance the mechanical and conductive properties of the composite material due to their high strength and heat resistance, and further enhance the interface bonding and mechanical locking effect through mixed acid oxidation and chemical vapor deposition modification. The synergistic effect of these multiple modification strategies enables the three reinforcing materials to fully exert their performance advantages in the polytetrafluoroethylene matrix, achieving comprehensive optimization of the mechanical, thermal and functional properties of the composite material.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material, the preparation method comprising:

[0008] S1: mixing a montmorillonite dispersion with a grafting monomer solution and an initiator to obtain a reaction solution A, reacting and treating the mixture to obtain surface-modified montmorillonite, which is then reacted with a metal salt to obtain modified montmorillonite;

[0009] S2: reacting the nanoparticles with a coupling agent to obtain surface-modified nanoparticles, which are then reacted with a toughening functional monomer to obtain surface-toughened nanoparticles; preparing a dispersion of the surface-toughened nanoparticles, adding a rubber latex and a cross-linking agent, and reacting to obtain rubber-coated toughened nanoparticles;

[0010] S3: Mixing concentrated nitric acid and concentrated sulfuric acid to obtain a mixed acid solution, adding the solution to the polyacrylonitrile-based carbon fiber to react and obtain acid-treated polyacrylonitrile-based carbon fiber; performing chemical vapor deposition on the acid-treated polyacrylonitrile-based carbon fiber using a CVD reactor to obtain carbon-deposited acid-treated polyacrylonitrile-based carbon fiber;

[0011] S4: Modified montmorillonite, carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers, rubber-coated toughened nanoparticles and polytetrafluoroethylene powder are mixed and ball-milled to obtain a composite powder, which is then cold-pressed and sintered to obtain an impact-resistant and thermally stable polytetrafluoroethylene composite material.

[0012] Specifically: S1: dispersing montmorillonite in deionized water to obtain a montmorillonite dispersion; dissolving a grafting monomer in deionized water to obtain a grafting monomer solution; preparing an initiator solution and adding it to the grafting monomer solution to obtain a mixed solution A; dropping the mixed solution A into the montmorillonite dispersion to obtain a reaction solution A, stirring at a constant temperature, and filtering, washing, and drying the reaction solution A after cooling to obtain surface-modified montmorillonite; preparing a metal salt solution, dispersing the surface-modified montmorillonite in the metal salt solution, stirring to obtain a mixed solution B, adjusting the pH of the mixed solution B with aqueous ammonia to obtain a reaction solution B, stirring at a constant temperature, and then filtering, washing, and drying to obtain the modified montmorillonite;

[0013] S2: dispersing the nanoparticles in anhydrous ethanol to obtain a nanoparticle dispersion, adding deionized water and a coupling agent to obtain a reaction solution C, stirring at a constant temperature, filtering, washing, and drying to obtain surface-modified nanoparticles; dissolving a toughening functional monomer in deionized water to obtain a toughening functional monomer solution, adding potassium persulfate, stirring at a constant temperature to obtain a toughening functional solution, adding surface-modified nanoparticles, continuing to stir, and then filtering, washing, and drying to obtain surface-toughened nanoparticles; preparing a surface-toughened nanoparticle dispersion, adding a rubber latex, stirring to react to obtain a rubber latex system, and then adding a cross-linking agent to obtain a reaction solution D, stirring at a constant temperature, and then filtering, washing, and drying to obtain rubber-coated toughened nanoparticles;

[0014] S3: Mixing concentrated nitric acid and concentrated sulfuric acid to obtain a mixed acid solution, adding polyacrylonitrile-based carbon fibers to the mixed acid solution, stirring in a constant temperature water bath, filtering, washing, and drying to obtain acid-treated polyacrylonitrile-based carbon fibers; performing chemical vapor deposition treatment on the acid-treated polyacrylonitrile-based carbon fibers using a CVD reactor to obtain carbon-deposited acid-treated polyacrylonitrile-based carbon fibers;

[0015] S4: Modified montmorillonite, carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers, rubber-coated toughened nanoparticles and polytetrafluoroethylene powder are mixed and ball-milled to obtain a composite powder, which is then cold-pressed and sintered to obtain an impact-resistant and thermally stable polytetrafluoroethylene composite material.

[0016] As a preferred technical solution of the present invention, in S1, the mass ratio of montmorillonite to deionized water is 1:(10-20), for example, it can be 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] In some optional examples, the feed amount of the grafting monomer is 10-15% of the montmorillonite, for example, it can be 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5% or 15%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] In some optional examples, the concentration of the grafted monomer solution is 0.1-1wt%, for example, it can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt% or 1wt%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0019] In some optional examples, the amount of the initiator added is 1-2% of the grafted monomer, for example, it can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0020] In some optional examples, the temperature of the constant temperature stirring of the reaction liquid A is 60-70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0021] In some optional examples, the constant temperature stirring time of the reaction solution A is 4-5 hours, for example, it can be 4 hours, 4.1 hours, 4.2 hours, 4.3 hours, 4.4 hours, 4.5 hours, 4.6 hours, 4.7 hours, 4.8 hours, 4.9 hours or 5 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] In some optional examples, the drying temperature of the surface-modified montmorillonite is 60-70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0023] In some optional examples, the drying time of the surface-modified montmorillonite is 12-24 hours, for example, it can be 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] In some optional examples, the concentration of the metal salt solution is 0.05-0.1M, for example, it can be 0.05M, 0.06M, 0.07M, 0.08M, 0.09M or 0.1M, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] In some optional examples, the mass ratio of the surface modified montmorillonite to the metal salt is (1-2):1, for example, it can be 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0026] In some optional examples, the surface modified montmorillonite is dispersed in the metal salt solution and stirred for 30-60 min, for example, 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min, 50 min, 52 min, 54 min, 56 min, 58 min or 60 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] In some optional examples, the pH of the mixed solution B is adjusted to 9-10 using ammonia water, for example, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9 or 10, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] In some optional examples, the temperature of the constant temperature stirring of the reaction liquid B is 70-80°C, for example, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0029] In some optional examples, the constant temperature stirring time of the reaction liquid B is 2-3 hours, for example, it can be 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] In some optional examples, the drying temperature of the modified montmorillonite is 70-80°C, for example, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] In some optional examples, the drying time of the modified montmorillonite is 10-20 hours, for example, it can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] As a preferred technical solution of the present invention, in S2, the feeding amount of the nanoparticles in the nanoparticle dispersion is 0.1-1 mg / mL, for example, it can be 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL or 1 mg / mL, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In some optional examples, the amount of deionized water added is 1-2 mL, for example, 1 mL, 1.1 mL, 1.2 mL, 1.3 mL, 1.4 mL, 1.5 mL, 1.6 mL, 1.7 mL, 1.8 mL, 1.9 mL or 2 mL, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0034] In some optional examples, the mass ratio of the coupling agent to the nanoparticles is (1-2):1, for example, it can be 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] In some optional examples, the temperature of the constant temperature stirring of the reaction liquid C is 50-60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0036] In some optional examples, the constant temperature stirring time of the reaction liquid C is 4-5h, for example, it can be 4h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h or 5h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] In some optional embodiments, the drying temperature of the surface-modified nanoparticles is 75-85°C, for example, it can be 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C or 85°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0038] In some optional examples, the drying time of the surface-modified nanoparticles is 12-20 hours, for example, it can be 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In some optional examples, the concentration of the toughening functional monomer solution is 0.05-0.1M, for example, 0.05M, 0.06M, 0.07M, 0.08M, 0.09M or 0.1M, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In some optional examples, the mass ratio of potassium persulfate to toughening functional monomer is (0.05-0.1):1, for example, it can be 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1 or 0.1:1, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0041] In some optional examples, the temperature of the constant temperature stirring of the toughening functional solution is 65-75°C, for example, it can be 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C or 75°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0042] In some optional examples, the toughening functional solution is stirred at a constant temperature for 5-10 minutes, for example, 5 minutes, 5.5 minutes, 6 minutes, 6.5 minutes, 7 minutes, 7.5 minutes, 8 minutes, 8.5 minutes, 9 minutes, 9.5 minutes or 10 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] In some optional examples, the mass ratio of the surface modified nanoparticles to the toughening functional monomer is 1:(5-15), for example, it can be 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14 or 1:15, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0044] In some optional examples, the surface-modified nanoparticles are added to the toughening functional solution and the stirring time is 4-5 hours, for example, 4h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h or 5h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] In some optional examples, the drying temperature of the surface toughened modified nanoparticles is 50-60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0046] In some optional examples, the drying time of the surface toughened modified nanoparticles is 8-12 hours, for example, it can be 8 hours, 8.5 hours, 9.0 hours, 9.5 hours, 10.0 hours, 10.5 hours, 11.0 hours, 11.5 hours or 12 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] In some optional examples, the feeding amount of the rubber latex accounts for 10-30wt% of the surface toughened and modified nanoparticles, for example, it can be 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt% or 30wt%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0048] In some optional examples, the temperature of the stirring reaction of the rubber latex system is 25-35°C, for example, it can be 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C or 35°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0049] In some optional examples, the stirring reaction time of the rubber latex system is 6-8h, for example, it can be 6h, 6.2h, 6.4h, 6.6h, 6.8h, 7.0h, 7.2h, 7.4h, 7.6h, 7.8h or 8h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] In some optional examples, the amount of the crosslinking agent is 1-5wt% of the surface toughened modified nanoparticles, for example, it can be 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0051] In some optional examples, the temperature of the constant temperature stirring of the reaction liquid D is 65-75°C, for example, it can be 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C or 75°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0052] In some optional examples, the constant temperature stirring time of the reaction liquid D is 2-3 hours, for example, it can be 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] In some optional examples, the drying temperature of the rubber-coated toughening nanoparticles is 50-60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0054] In some optional examples, the drying time of the rubber-coated toughened nanoparticles is 8-12 hours, for example, it can be 8 hours, 8.5 hours, 9.0 hours, 9.5 hours, 10.0 hours, 10.5 hours, 11.0 hours, 11.5 hours or 12 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] As a preferred technical solution of the present invention, in S3, the volume ratio of the mixed concentrated nitric acid and concentrated sulfuric acid is 1:(3-4), for example, it can be 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9 or 1:4, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] In some optional examples, the mass ratio of the polyacrylonitrile-based carbon fiber to the mixed acid solution is 1:(10-15), for example, it can be 1:10, 1:11, 1:12, 1:13, 1:14 or 1:15, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0057] In some optional examples, after the polyacrylonitrile-based carbon fiber is added to the mixed acid solution and stirred in a constant temperature water bath, the temperature is 60-70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0058] In some optional examples, the polyacrylonitrile-based carbon fiber is added to the mixed acid solution and stirred in a constant temperature water bath for 2-3 hours, for example, 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3h, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0059] In some optional examples, the drying temperature of the acid-treated polyacrylonitrile-based carbon fiber is 70-80°C, for example, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0060] In some optional examples, the drying time of the acid-treated polyacrylonitrile-based carbon fiber is 8-12 hours, for example, it can be 8 hours, 8.5 hours, 9.0 hours, 9.5 hours, 10.0 hours, 10.5 hours, 11.0 hours, 11.5 hours or 12 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0061] In some optional examples, the precursor gas flow rate in the chemical vapor deposition process is 10-20 sccm, for example, it can be 10 sccm, 11 sccm, 12 sccm, 13 sccm, 14 sccm, 15 sccm, 16 sccm, 17 sccm, 18 sccm, 19 sccm or 20 sccm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0062] In some optional examples, the reaction time in the chemical vapor deposition process is 1-2h, for example, it can be 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] In some optional examples, the reaction temperature in the chemical vapor deposition process is 800-900°C, for example, it can be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C or 900°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0064] As a preferred technical solution of the present invention, in S4, the pressure of cold pressing of the composite powder is 15-30 MPa, for example, it can be 15 MPa, 17 MPa, 19 MPa, 21 MPa, 23 MPa, 25 MPa, 27 MPa, 29 MPa or 30 MPa, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0065] In some optional examples, the cold pressing time of the composite powder is 5-10 minutes, for example, it can be 5 minutes, 5.5 minutes, 6 minutes, 6.5 minutes, 7 minutes, 7.5 minutes, 8 minutes, 8.5 minutes, 9 minutes, 9.5 minutes or 10 minutes, but it is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0066] In some optional examples, the first temperature for sintering the composite powder is 325-330°C, for example, it can be 325°C, 325.5°C, 326°C, 326.5°C, 327°C, 327.5°C, 328°C, 328.5°C, 329°C, 329.5°C or 330°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0067] In some optional examples, the first sintering time of the composite powder is 30-60 min, for example, it can be 30 min, 33 min, 36 min, 39 min, 42 min, 45 min, 48 min, 51 min, 54 min, 57 min or 60 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0068] In some optional examples, the second temperature for sintering the composite powder is 360-400°C, for example, it can be 360°C, 365°C, 370°C, 375°C, 380°C, 385°C, 390°C, 395°C or 400°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0069] In some optional examples, the second sintering time of the composite powder is 2-3h, for example, it can be 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0070] In a second aspect, the present invention provides an impact-resistant and heat-stable polytetrafluoroethylene composite material, which comprises polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers, wherein the mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is: (80-90): (2-4): (3-8): (2-5).

[0071] The present invention introduces montmorillonite to modify polytetrafluoroethylene to enhance the overall performance of the composite material. Montmorillonite is a layered silicate mineral with a crystal structure consisting of alternating layers of silicon dioxide tetrahedrons and aluminum oxide octahedrons, bonded electrostatically and containing exchangeable cations. This unique layered structure gives montmorillonite a large specific surface area, excellent chemical stability, and good thermal stability, making it an ideal inorganic reinforcement material.

[0072] The role of montmorillonite in polytetrafluoroethylene matrix is ​​mainly manifested in several aspects. First, its layered structure can form physical cross-linking points by being evenly dispersed in the polytetrafluoroethylene matrix, limiting the slip behavior of the polytetrafluoroethylene molecular chain, thereby significantly improving the tensile strength and modulus of the composite material, while enhancing the rigidity and deformation resistance of the material. Secondly, the layered structure of montmorillonite acts as a physical barrier of the "maze effect" in the composite material, extending the permeation path of gas or liquid, helping to improve the barrier properties of the composite material, making it excellent in chemical corrosion resistance and sealing performance. In addition, the high thermal stability of montmorillonite itself can effectively delay the thermal degradation process of polytetrafluoroethylene matrix in high temperature environment, and its interlayer structure can absorb and disperse heat, further improving the thermal stability and high temperature adaptability of the material.

[0073] However, montmorillonite itself has significant limitations. Its strong hydrophilicity and interlayer electrostatic interactions make it easy to agglomerate, making it difficult to form a uniform dispersion in the hydrophobic polytetrafluoroethylene matrix and having poor interfacial bonding, thus limiting its reinforcement effect. Therefore, surface modification of montmorillonite is the key to ensuring its effectiveness in polytetrafluoroethylene matrices.

[0074] The present invention utilizes both grafting and ion exchange modification to optimize montmorillonite from the perspectives of dispersibility and interfacial compatibility. By grafting monomers containing polar groups, such as acrylic acid, methyl acrylate, or methacrylic acid, polar functional groups such as carboxyl and hydroxyl groups can be introduced onto the montmorillonite surface, or flexible segments can be introduced through polymerization reactions. This modification not only improves the surface polarity of the montmorillonite, enabling better compatibility with the polytetrafluoroethylene matrix, but also enhances the interfacial bonding between the montmorillonite and the matrix through physical entanglement or chemical interactions between the polar groups or flexible segments and the polytetrafluoroethylene molecular chains. Furthermore, grafting significantly reduces the montmorillonite's tendency to agglomerate, enabling a more uniform dispersion within the matrix and fully exerting its reinforcing effect.

[0075] In order to further optimize the performance of montmorillonite, the present invention also adopts metal ion exchange modification. By dispersing montmorillonite in a metal salt solution and using metal ions to carry out ion exchange reactions with interlayer exchangeable cations, the interlayer spacing of montmorillonite can be effectively adjusted, and metal ions with specific functions can be introduced. This modification method brings about performance improvements in many aspects. First, the interlayer spacing of montmorillonite after ion exchange increases, the electrostatic effect is weakened, and the interlayer bonding force is reduced, thereby promoting the exfoliation and dispersion of montmorillonite in the polytetrafluoroethylene matrix, so that it forms a more stable dispersed state in the matrix. Secondly, the introduction of metal ions gives montmorillonite new functional properties, such as Zn 2+ Can further improve the thermal stability of montmorillonite, Al 3+ and Mg 2+The mechanical reinforcement effect of montmorillonite can be significantly improved by enhancing interlayer electrostatic interactions or forming new chemical bonds. In addition, metal ions may also catalyze the interfacial reaction of the composite material, thereby further improving the interfacial bonding performance of montmorillonite and polytetrafluoroethylene matrix.

[0076] Nanoparticles are introduced into the present invention to significantly improve the overall performance of polytetrafluoroethylene composite materials. Nanoparticles are an important reinforcing phase in composite materials due to their unique physical and chemical properties, such as high specific surface area, small size effect, and quantum effect. The high specific surface area of ​​the nanoparticles provides a larger interface contact area between them and the matrix, thereby significantly improving the interfacial bonding performance; the small size effect enables them to be evenly distributed in the matrix, forming a fine reinforcement network; and the quantum effect enables them to exhibit excellent functionality in thermal and electrical aspects. After the introduction of nanoparticles, the mechanical properties, thermal properties, wear resistance and other aspects of the composite material have been significantly improved.

[0077] The role of nanoparticles in composite materials is mainly reflected in the following aspects. First, nanoparticles can play a reinforcing role in the matrix. Their high hardness and high strength hinder the movement of polytetrafluoroethylene molecular chains through the microscopic "pinning effect", thereby effectively improving the tensile strength and modulus of the composite material. In addition, the nanoparticles are small in size and evenly distributed. They can absorb stress concentration in the microstructure, delay the initiation and expansion of cracks, and thus enhance the toughness and impact resistance of the composite material. Secondly, nanoparticles with good thermal conductivity can significantly improve the thermal conductivity of the composite material through their high thermal conductivity path, accelerate the transfer of heat in the material, reduce the thermal expansion coefficient, and improve the thermal stability of the composite material. In addition, the high hardness of nanoparticles can significantly improve the wear resistance of the composite material, delay surface wear in a dynamic friction environment, and extend the service life of the material.

[0078] However, nanoparticles typically have a large number of hydroxyl groups or other polar functional groups on their surfaces. These functional groups make it easy for hydrogen bonding or van der Waals forces to occur between the particles, causing them to agglomerate in the matrix, forming large particle clusters, which significantly reduces their reinforcing effect. In addition, nanoparticles have poor interfacial compatibility with hydrophobic polytetrafluoroethylene substrates and poor dispersion in the matrix. Therefore, surface modification of nanoparticles is a key step to ensure their uniform dispersion in composite materials, improve interfacial compatibility, and fully realize their functionality.

[0079] To address the above issues, the present invention applies multiple surface modification treatments to the nanoparticles. First, the nanoparticle surface is modified using a silane coupling agent. The siloxane groups in the silane coupling agent can chemically react with the hydroxyl groups on the nanoparticle surface, stably bonding to the particle surface. Simultaneously, the organic functional groups in the coupling agent can form a stable interfacial bond with the molecular chains in the polytetrafluoroethylene matrix through physical entanglement or chemical interaction. Through silane coupling agent modification, the surface polarity of the nanoparticles is regulated, thereby reducing the tendency of particles to agglomerate and significantly improving their dispersibility in the polytetrafluoroethylene matrix.

[0080] Secondly, the nanoparticles are further modified using toughening functional monomers such as acrylic acid or ethylene glycol. After introducing flexible segments or polar groups on the surface of the nanoparticles, these flexible segments can alleviate the stress concentration phenomenon of the matrix material under the action of external forces, thereby significantly improving the toughness of the composite material. In addition, the introduction of polar groups can enhance the interfacial bonding between the nanoparticles and the polytetrafluoroethylene matrix, improving the overall mechanical properties of the composite material. Through this treatment with toughening functional monomers, not only the interfacial properties of the nanoparticles are improved, but also the composite material has higher impact resistance.

[0081] In addition, the present invention also carries out coating modification to nanoparticles by nitrile rubber or natural rubber emulsion.The rubber coating can form a flexible interface structure between nanoparticles and polytetrafluoroethylene based matrix, effectively absorbs external stress, alleviates the stress concentration phenomenon at the interface, thereby improves the impact resistance of composite material.The flexible segment of rubber further strengthens the dispersibility of nanoparticles in matrix, prevents the generation of particle agglomeration, and gives composite material higher toughness and flexibility simultaneously.Through this modification process, nanoparticles not only show excellent reinforcement in composite material, can also be used as the flexible buffer phase of absorbing stress, further improved the overall performance of composite material.

[0082] In the present invention, polyacrylonitrile-based carbon fibers are introduced to modify polytetrafluoroethylene. Polyacrylonitrile-based carbon fibers are a high-performance carbon fiber material prepared by high-temperature carbonization treatment using polyacrylonitrile as a precursor. They have extremely high tensile strength and modulus, and are high-quality fillers currently widely used in the field of composite material reinforcement. Their high strength and high modulus properties give them a significant reinforcing effect in composite materials, which can significantly improve the rigidity and strength of composite materials; at the same time, the high thermal stability and heat resistance of carbon fibers can enhance the mechanical properties and thermal stability of composite materials in high-temperature environments; in addition, the electrical conductivity of carbon fibers provides composite materials with potential conductive functions or antistatic properties, enabling them to adapt to the needs of some special scenarios, such as electronic equipment housings, antistatic sealing materials, etc. The introduction of polyacrylonitrile-based carbon fibers has resulted in multi-dimensional improvements in the mechanical, thermal and electrical properties of polytetrafluoroethylene composite materials.

[0083] The reinforcement mechanism of polyacrylonitrile-based carbon fibers in polytetrafluoroethylene composites is mainly reflected in the following aspects. First, carbon fibers have extremely high tensile strength and modulus. As a rigid skeleton, they are dispersed in the polytetrafluoroethylene matrix, which can evenly share the stress applied by the outside world, limit the deformation of the matrix material, and significantly improve the tensile and bending resistance of the composite material. Secondly, the dimensional stability and heat resistance of carbon fibers enable them to maintain high mechanical properties in high temperature environments, thereby giving the composite material better high-temperature stability. In addition, the conductivity of carbon fibers provides additional functional properties for the material, enabling the composite material to be used in environments requiring antistatic or a certain degree of conductivity. However, the surface of polyacrylonitrile-based carbon fibers is generally inert, with low surface energy and weak interfacial bonding ability with the hydrophobic polytetrafluoroethylene matrix, making it difficult to achieve effective load transfer and interfacial adhesion. Therefore, surface chemical modification of carbon fibers to enhance their interfacial compatibility with the polytetrafluoroethylene matrix is ​​the key to ensuring their reinforcement effect.

[0084] The present invention adopts oxidation treatment with concentrated nitric acid and concentrated sulfuric acid as the preliminary surface modification method of carbon fiber. By immersing the carbon fiber in a mixed acid solution for oxidation treatment, polar functional groups such as hydroxyl, carboxyl and carbonyl groups can be introduced on its surface. These polar functional groups can significantly improve the surface chemical activity of the carbon fiber, enabling it to chemically bond or hydrogen bond with the molecular chains in the polytetrafluoroethylene matrix or other components, thereby enhancing interfacial adhesion. In addition, the oxidation treatment can also increase the hydrophilicity and wettability of the carbon fiber surface, further improving its dispersibility in the matrix. Through this oxidation modification, the chemical inertness of the carbon fiber surface is significantly reduced, laying the foundation for the subsequent reinforcement effect.

[0085] In order to further improve the interfacial bonding performance and reinforcement effect of carbon fiber, the present invention also uses chemical vapor deposition technology to perform surface modification on the carbon fiber after oxidation treatment. In a CVD reactor, a carbon-based deposition layer is formed on the surface of the carbon fiber by chemical vapor deposition technology. The deposition layer can significantly improve the activity and roughness of the carbon fiber surface, thereby enhancing its mechanical locking effect with the polytetrafluoroethylene-based matrix. This mechanical locking effect is one of the key mechanisms of interface enhancement. The presence of the deposition layer enables the carbon fiber and the matrix to effectively transfer external loads through the physical interlocking of the microstructure. In addition, the formation of the carbon-based deposition layer can further improve the heat resistance and thermal stability of the carbon fiber, making it exhibit even better performance under high temperature environments.

[0086] In the composite material, montmorillonite, nanoparticles, and polyacrylonitrile-based carbon fibers form a multiscale reinforcement structure, which is the core source of the improved mechanical properties. The synergistic effect of this multiscale structure is as follows: the modified montmorillonite and nanoparticles are evenly distributed in the polytetrafluoroethylene matrix, exerting layered reinforcement and point reinforcement, respectively. Montmorillonite, through its layered structure, forms physical crosslinks in the matrix, limiting the slippage of the polytetrafluoroethylene molecular chains; while the nanoparticles further hinder the movement of the molecular chains through the "pinning effect." This synergistic effect enables the composite material to exhibit higher tensile strength and modulus under stress, while also reducing stress concentration and improving the material's toughness.

[0087] Polyacrylonitrile-based carbon fibers serve as the composite's rigid backbone, significantly improving the material's tensile strength and flexural resistance. The modified montmorillonite is evenly distributed around the carbon fibers, acting as a filler and interfacial reinforcement. The montmorillonite's layered structure creates a "bridging effect" between the carbon fibers and the polytetrafluoroethylene matrix, ensuring effective stress transfer from the matrix to the carbon fibers, further enhancing the composite's overall rigidity and strength.

[0088] Carbon fibers and nanoparticles form a multi-level reinforcement system of "rigidity enhancement + local reinforcement" in composite materials. The carbon fibers bear the primary stress, while the nanoparticles, through their uniform distribution and high hardness, reinforce the matrix surrounding the carbon fibers at a microscopic level, further enhancing the material's resistance to crack growth and fatigue.

[0089] The rubber-coated toughening nanoparticles work together with carbon fibers and montmorillonite to form a flexible-rigid composite reinforcement system. The flexible rubber segments absorb impact energy and alleviate stress concentration, while the carbon fibers and montmorillonite provide rigid reinforcement. This synergistic combination of rigidity and flexibility significantly improves the material's impact resistance and toughness.

[0090] In terms of thermal properties: the layered structure of montmorillonite acts as a thermal barrier, slowing the diffusion of heat in the matrix; while nanoparticles with excellent thermal conductivity (such as nano-alumina) accelerate the transfer of heat within the material through their high thermal conductivity paths. The synergistic effect of the two significantly improves the thermal conductivity and thermal stability of the composite material. In addition, after montmorillonite is modified with metal ions, its thermal stability is further enhanced, which complements the thermal conductivity of the nanoparticles. Carbon fiber itself has high thermal stability and excellent thermal conductivity, and its rigid skeleton structure can efficiently transfer heat. In high temperature environments, the interaction between carbon fiber and montmorillonite prevents the premature decomposition of the polytetrafluoroethylene matrix. Specifically, the thermal conductivity path of carbon fiber and the thermal barrier effect of montmorillonite work synergistically to reduce the thermal expansion coefficient of the material and improve the dimensional stability of the material.

[0091] The improved barrier performance is primarily due to the synergistic shielding effect of montmorillonite, nanoparticles, and the PTFE matrix. The layered structure of montmorillonite creates a "maze effect" within the composite, significantly extending the permeation path for gases or liquids. The introduction of nanoparticles further densifies the material structure and reduces the porosity within the matrix. This synergistic effect significantly enhances the composite's gas barrier properties and chemical resistance. The high density and low porosity of carbon fibers play a significant role in preventing the permeation of gases or chemicals. The uniform distribution of montmorillonite on the carbon fiber surface and within the PTFE matrix further enhances the barrier properties. This synergistic effect of "rigid skeleton + layered barrier" enables the composite to perform exceptionally well in corrosive environments.

[0092] Compared with the prior art, the present invention has the following beneficial effects:

[0093] The present invention modifies polytetrafluoroethylene by introducing montmorillonite, significantly improving the mechanical properties, thermal stability and barrier properties of the composite material. The layered structure of montmorillonite forms physical crosslinks and barrier effects through uniform dispersion, thereby improving the strength and permeability resistance of the material. However, the dispersibility and interfacial compatibility of montmorillonite in polytetrafluoroethylene matrix are poor, so polar functional groups and flexible chain segments are introduced through grafting modification to improve its dispersibility and interfacial bonding strength, while metal ion exchange is used to expand the interlayer spacing and enhance its thermal stability and mechanical reinforcement effect. These modification measures synergistically optimize the performance of montmorillonite, allowing it to fully exert its reinforcing effect in polytetrafluoroethylene composite materials;

[0094] The present invention significantly improves the mechanical properties, thermal stability and wear resistance of polytetrafluoroethylene composite materials by introducing and modifying nanoparticles. Due to their high specific surface area and small size effect, the nanoparticles are evenly distributed in the matrix, enhancing the strength and toughness of the material while improving thermal conductivity and impact resistance. To overcome the problems of easy agglomeration and poor interface compatibility, silane coupling agent modification, toughening monomer modification and rubber coating treatment are used to improve dispersibility and interface bonding, and enhance flexibility and impact resistance. The synergistic effect of multiple modifications allows the nanoparticles to fully exert their reinforcing effect, significantly optimizing the comprehensive performance of polytetrafluoroethylene composite materials;

[0095] The present invention significantly improves the mechanical properties, thermal stability, and electrical conductivity of polytetrafluoroethylene composites by introducing and modifying polyacrylonitrile-based carbon fibers. Carbon fibers have high strength, high modulus, and good heat resistance, but their surface inertness leads to poor interfacial bonding. Polar functional groups are introduced through mixed acid oxidation treatment to improve interfacial adhesion and dispersibility; simultaneously, a carbon-based deposition layer is formed using chemical vapor deposition to enhance mechanical locking and load transfer capabilities. This multiple modification strategy effectively optimizes interfacial properties, allowing carbon fibers to fully exert their reinforcing role in composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Figure 1 A flow chart of a method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material provided by an embodiment of the present invention;

[0097] Figure 2 This is the infrared spectrum of the acid-treated polyacrylonitrile-based carbon fiber in Example 1 of the present invention. DETAILED DESCRIPTION

[0098] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be understood as limiting the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments described herein.

[0099] Example 1

[0100] This embodiment provides a shock-resistant and heat-stable polytetrafluoroethylene composite material and a preparation method thereof. The preparation method of the shock-resistant and heat-stable polytetrafluoroethylene composite material specifically comprises the following steps:

[0101] S1: dispersing montmorillonite in deionized water to obtain a montmorillonite dispersion, wherein the mass ratio of montmorillonite to deionized water is 1:10; dissolving a graft monomer acrylic acid in deionized water to obtain a graft monomer solution, wherein the amount of the graft monomer acrylic acid is 15% of the montmorillonite, and the concentration of the graft monomer solution is 1wt%; preparing a potassium persulfate solution and adding it to the graft monomer solution to obtain a mixed solution A, wherein the amount of the potassium persulfate is 1% of the graft monomer acrylic acid; dropping the mixed solution A into the montmorillonite dispersion to obtain a reaction solution A, and heating at 68°C. The mixture was stirred for 4.2 hours, and after the reaction solution A was cooled, it was filtered, washed, and dried at 70°C for 12 hours to obtain surface-modified montmorillonite. A zinc nitrate solution with a concentration of 0.05M was prepared, and the surface-modified montmorillonite was dispersed in the zinc nitrate solution, wherein the mass ratio of the surface-modified montmorillonite to zinc nitrate was 1:1, and stirred for 30 minutes to obtain a mixed solution B. The pH of the mixed solution B was adjusted to 9 with ammonia water to obtain a reaction solution B, which was stirred at a constant temperature of 80°C for 2 hours, and then filtered, washed, and dried to obtain the modified montmorillonite, wherein the drying temperature was 80°C and the time was 10 hours.

[0102] S2: Nano-silica was dispersed in anhydrous ethanol to obtain a nano-particle dispersion, wherein the feeding amount of nano-silica was 1 mg / mL, 1 mL of deionized water and 3-aminopropyltriethoxysilane were added to obtain a reaction solution C, wherein the mass ratio of 3-aminopropyltriethoxysilane to nano-silica was 1:1, and the mixture was stirred at a constant temperature of 50°C for 5 hours, filtered, washed, and dried at 75°C for 20 hours to obtain surface-modified nano-particles; acrylic acid was dissolved in deionized water to obtain an acrylic acid solution with a concentration of 0.1M, potassium persulfate with a mass ratio of 0.1:1 to acrylic acid was added, and the mixture was stirred at a constant temperature of 75°C for 5 minutes to obtain a toughening function. solution, adding surface-modified nanoparticles in a mass ratio of 1:5 to acrylic acid, continuing stirring for 4 hours, then filtering, washing, and drying at 50°C for 12 hours to obtain surface-toughened nanoparticles; preparing a surface-toughened nanoparticle dispersion, adding nitrile rubber accounting for 10 wt% of the surface-toughened nanoparticles, stirring and reacting to obtain a rubber latex system, wherein the stirring reaction temperature is 25°C and the time is 8 hours, and then adding sulfur accounting for 5 wt% of the surface-toughened nanoparticles to obtain a reaction solution D, stirring at a constant temperature of 70°C for 2.5 hours, then filtering, washing, and drying at 55°C for 10 hours to obtain rubber-coated toughened nanoparticles;

[0103] S3: Concentrated nitric acid and concentrated sulfuric acid are mixed in a volume ratio of 1:3 to obtain a mixed acid solution, polyacrylonitrile-based carbon fiber is added to the mixed acid solution, the mass ratio of polyacrylonitrile-based carbon fiber to the mixed acid solution is 1:10, stirred in a water bath at a constant temperature of 68°C for 2.2h, filtered, washed, and dried at 77°C for 9h to obtain acid-treated polyacrylonitrile-based carbon fiber; a chemical vapor deposition reactor is used to perform chemical vapor deposition treatment on the acid-treated polyacrylonitrile-based carbon fiber to obtain carbon-based deposited acid-treated polyacrylonitrile-based carbon fiber, wherein the chemical vapor deposition coating precursor in the chemical vapor deposition treatment is methane; the precursor gas flow rate is 10sccm; the reaction time is 2h; the reaction temperature is 800°C; the protective gas is hydrogen; wherein the infrared spectrum of the acid-treated polyacrylonitrile-based carbon fiber is as shown Figure 2 Shown: Located at 1650-1600cm -1 and 3000-2830cm -1 The signal peaks near 1740-1700 cm -1 and 1150-1040cm -1 The signal peaks at correspond to the saturated aliphatic carboxyl groups and tertiary hydroxyl bonds of the acid-treated polyacrylonitrile-based carbon fibers, respectively, which indicates that carboxyl groups and hydroxyl groups are formed on the surface of the polyacrylonitrile-based carbon fibers under the action of acid treatment.

[0104] S4: Modified montmorillonite, carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers, rubber-coated toughening nanoparticles and polytetrafluoroethylene powder are mixed and ball-milled to obtain a composite powder, which is cold-pressed at a pressure of 15 MPa for 5 minutes and sintered to obtain an impact-resistant and heat-stable polytetrafluoroethylene composite material, wherein the first sintering temperature is 325°C, the first time is 30 minutes, the second temperature is 380°C, and the second time is 2 hours. The mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is 85:3:5:3.

[0105] Example 2

[0106] This embodiment provides a shock-resistant and heat-stable polytetrafluoroethylene composite material and a preparation method thereof. The preparation method of the shock-resistant and heat-stable polytetrafluoroethylene composite material specifically comprises the following steps:

[0107] S1: dispersing montmorillonite in deionized water to obtain a montmorillonite dispersion, wherein the mass ratio of montmorillonite to deionized water is 1:20; dissolving a grafting monomer methyl acrylate in deionized water to obtain a grafting monomer solution, wherein the amount of the grafting monomer methyl acrylate accounts for 12% of the montmorillonite, and the concentration of the grafting monomer solution is 0.1wt%; preparing a potassium persulfate solution and adding it to the grafting monomer solution to obtain a mixed solution A, wherein the amount of the potassium persulfate accounts for 2% of the grafting monomer methyl acrylate; dropping the mixed solution A into the montmorillonite dispersion to obtain a reaction solution A, and stirring at 60°C. The mixture was stirred at a constant temperature for 5 hours, and after the reaction solution A was cooled, it was filtered, washed, and dried at 60°C for 24 hours to obtain surface-modified montmorillonite; a 0.08M aluminum chloride solution was prepared, and the surface-modified montmorillonite was dispersed in the aluminum chloride solution, wherein the mass ratio of the surface-modified montmorillonite to the aluminum chloride was 1:2, and stirred for 40 minutes to obtain a mixed solution B, and the pH of the mixed solution B was adjusted to 9.5 with ammonia water to obtain a reaction solution B, which was stirred at a constant temperature for 2.2 hours at 78°C, and then filtered, washed, and dried to obtain modified montmorillonite, wherein the drying temperature was 78°C and the time was 12 hours;

[0108] S2: Nano-alumina was dispersed in anhydrous ethanol to obtain a nano-particle dispersion, wherein the feeding amount of nano-alumina was 0.1 mg / mL, 1.4 mL of deionized water and 3-aminopropyltriethoxysilane were added to obtain a reaction solution C, wherein the mass ratio of 3-aminopropyltriethoxysilane to nano-alumina was 2:1, and the mixture was stirred at a constant temperature of 60°C for 4 hours, filtered, washed, and dried at 85°C for 10 hours to obtain surface-modified nanoparticles; acrylic acid was dissolved in deionized water to obtain an acrylic acid solution with a concentration of 0.05 M, potassium persulfate was added at a mass ratio of 0.05:1 to acrylic acid, and the mixture was stirred at a constant temperature of 70°C for 6 minutes to obtain a toughened functional solution, adding surface-modified nanoparticles at a mass ratio of 1:15 to acrylic acid, continuing stirring for 4.5 hours, then filtering, washing, and drying at 55°C for 10 hours to obtain surface-toughened nanoparticles; preparing a surface-toughened nanoparticle dispersion, adding nitrile rubber accounting for 20 wt% of the surface-toughened nanoparticles, stirring and reacting to obtain a rubber latex system, wherein the stirring reaction temperature is 30°C and the time is 7 hours, and then adding sulfur accounting for 1 wt% of the surface-toughened nanoparticles to obtain a reaction solution D, stirring at a constant temperature of 75°C for 2 hours, then filtering, washing, and drying at 58°C for 8 hours to obtain rubber-coated toughened nanoparticles;

[0109] S3: Concentrated nitric acid and concentrated sulfuric acid are mixed in a volume ratio of 1:4 to obtain a mixed acid solution, polyacrylonitrile-based carbon fiber is added to the mixed acid solution, the mass ratio of polyacrylonitrile-based carbon fiber to the mixed acid solution is 1:12, the mixture is stirred in a water bath at a constant temperature of 60°C for 3 hours, filtered, washed, and dried at 75°C for 10 hours to obtain acid-treated polyacrylonitrile-based carbon fiber; a chemical vapor deposition reactor is used to perform chemical vapor deposition on the acid-treated polyacrylonitrile-based carbon fiber to obtain carbon-based deposited acid-treated polyacrylonitrile-based carbon fiber, wherein the chemical vapor deposition coating precursor in the chemical vapor deposition treatment is methane; the precursor gas flow rate is 18 sccm; the reaction time is 1.2 hours; the reaction temperature is 850°C; and the protective gas is hydrogen;

[0110] S4: Modified montmorillonite, carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers, rubber-coated toughening nanoparticles and polytetrafluoroethylene powder are mixed and ball-milled to obtain a composite powder, which is cold-pressed at a pressure of 25 MPa for 8 minutes and sintered to obtain an impact-resistant and heat-stable polytetrafluoroethylene composite material, wherein the first sintering temperature is 327°C, the first time is 50 minutes, the second temperature is 390°C, and the second time is 2.5 hours. The mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is 80:2:7:5.

[0111] Example 3

[0112] This embodiment provides a shock-resistant and heat-stable polytetrafluoroethylene composite material and a preparation method thereof. The preparation method of the shock-resistant and heat-stable polytetrafluoroethylene composite material specifically comprises the following steps:

[0113] S1: dispersing montmorillonite in deionized water to obtain a montmorillonite dispersion, wherein the mass ratio of montmorillonite to deionized water is 1:15; dissolving a grafting monomer methacrylic acid in deionized water to obtain a grafting monomer solution, wherein the amount of the grafting monomer methacrylic acid is 10% of the montmorillonite, and the concentration of the grafting monomer solution is 0.5wt%; preparing a sodium persulfate solution and adding it to the grafting monomer solution to obtain a mixed solution A, wherein the amount of the sodium persulfate is 1.7% of the grafting monomer methacrylic acid; dropping the mixed solution A into the montmorillonite dispersion to obtain a reaction solution A, and stirring at 70°C. The mixture was stirred at a constant temperature for 4 hours, and after the reaction solution A was cooled, it was filtered, washed, and dried at 65°C for 21 hours to obtain surface-modified montmorillonite; a magnesium chloride solution with a concentration of 0.06M was prepared, and the surface-modified montmorillonite was dispersed in the magnesium chloride solution, wherein the mass ratio of the surface-modified montmorillonite to magnesium chloride was 1:1.5, and stirred for 50 minutes to obtain a mixed solution B, and the pH of the mixed solution B was adjusted to 9.7 with ammonia water to obtain a reaction solution B, which was stirred at a constant temperature for 3 hours at 70°C, and then filtered, washed, and dried to obtain modified montmorillonite, wherein the drying temperature was 70°C and the time was 20 hours;

[0114] S2: Nano-calcium carbonate was dispersed in anhydrous ethanol to obtain a nano-particle dispersion, wherein the feeding amount of nano-calcium carbonate was 0.5 mg / mL, 1.7 mL of deionized water and γ-methacryloxypropyltrimethoxysilane were added to obtain a reaction solution C, wherein the mass ratio of γ-methacryloxypropyltrimethoxysilane to nano-calcium carbonate was 1.5:1, and the mixture was stirred at a constant temperature of 55°C for 4.5 hours, filtered, washed, and dried at 80°C for 15 hours to obtain surface-modified nanoparticles; ethylene glycol was dissolved in deionized water to obtain an ethylene glycol solution with a concentration of 0.07 M, potassium persulfate was added at a mass ratio of 0.06:1 to ethylene glycol, and stirred at a constant temperature of 72°C for 8 minutes to obtain A toughening functional solution was prepared, and surface-modified nanoparticles were added in a mass ratio of 1:10 to ethylene glycol, and the mixture was stirred for 4.8 hours, followed by filtration, washing, and drying at 58°C for 9 hours to obtain surface-toughened nanoparticles; a surface-toughened nanoparticle dispersion was prepared, and a natural rubber latex accounting for 25 wt% of the surface-toughened nanoparticles was added, and the mixture was stirred to obtain a rubber latex system, wherein the stirring reaction temperature was 32°C and the time was 7.8 hours, and then an epoxy resin accounting for 2.5 wt% of the surface-toughened nanoparticles was added to obtain a reaction solution D, which was stirred at a constant temperature of 72°C for 2.2 hours, and then filtered, washed, and dried at 50°C for 11 hours to obtain rubber-coated toughened nanoparticles;

[0115] S3: Concentrated nitric acid and concentrated sulfuric acid are mixed in a volume ratio of 1:3.5 to obtain a mixed acid solution, polyacrylonitrile-based carbon fiber is added to the mixed acid solution, the mass ratio of polyacrylonitrile-based carbon fiber to the mixed acid solution is 1:14, the mixture is stirred in a water bath at a constant temperature of 65°C for 2.5 hours, filtered, washed, and dried at 70°C for 12 hours to obtain acid-treated polyacrylonitrile-based carbon fiber; a chemical vapor deposition reactor is used to perform chemical vapor deposition on the acid-treated polyacrylonitrile-based carbon fiber to obtain carbon-based deposited acid-treated polyacrylonitrile-based carbon fiber, wherein the chemical vapor deposition coating precursor in the chemical vapor deposition treatment is acetylene; the precursor gas flow rate is 15 sccm; the reaction time is 1.5 hours; the reaction temperature is 870°C; and the protective gas is argon;

[0116] S4: Modified montmorillonite, carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers, rubber-coated toughening nanoparticles and polytetrafluoroethylene powder are mixed and ball-milled to obtain a composite powder, which is cold-pressed at a pressure of 20 MPa for 7 minutes and sintered to obtain an impact-resistant and heat-stable polytetrafluoroethylene composite material, wherein the first sintering temperature is 328°C, the first time is 40 minutes, the second temperature is 360°C, and the second time is 2.8 hours. The mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is 90:3.5:3:4.

[0117] Example 4

[0118] This embodiment provides a shock-resistant and heat-stable polytetrafluoroethylene composite material and a preparation method thereof. The preparation method of the shock-resistant and heat-stable polytetrafluoroethylene composite material specifically comprises the following steps:

[0119] S1: dispersing montmorillonite in deionized water to obtain a montmorillonite dispersion, wherein the mass ratio of montmorillonite to deionized water is 1:18; dissolving a graft monomer acrylic acid in deionized water to obtain a graft monomer solution, wherein the amount of the graft monomer acrylic acid is 14% of the montmorillonite, and the concentration of the graft monomer solution is 0.7 wt %; preparing a sodium persulfate solution and adding it to the graft monomer solution to obtain a mixed solution A, wherein the amount of the sodium persulfate is 1.5% of the graft monomer acrylic acid; dropping the mixed solution A into the montmorillonite dispersion to obtain a reaction solution A, and stirring at a constant temperature of 65°C. Stir for 4.5 hours, and after the reaction solution A is cooled, filter, wash, and dry at 67°C for 18 hours to obtain surface-modified montmorillonite; prepare a zinc nitrate solution with a concentration of 0.1M, disperse the surface-modified montmorillonite in the zinc nitrate solution, wherein the mass ratio of the surface-modified montmorillonite to zinc nitrate is 1:1.8, stir for 60 minutes to obtain a mixed solution B, adjust the pH of the mixed solution B to 10 with ammonia water to obtain a reaction solution B, stir at a constant temperature of 75°C for 2.5 hours, then filter, wash, and dry to obtain modified montmorillonite, wherein the drying temperature is 75°C and the time is 15 hours;

[0120] S2: Nano-silica was dispersed in anhydrous ethanol to obtain a nano-particle dispersion, wherein the feeding amount of nano-silica was 0.7 mg / mL, 2 mL of deionized water and γ-methacryloxypropyltrimethoxysilane were added to obtain a reaction solution C, wherein the mass ratio of γ-methacryloxypropyltrimethoxysilane to nano-silica was 1.8:1, and the mixture was stirred at a constant temperature of 57°C for 4.2 hours, filtered, washed, and dried at 82°C for 18 hours to obtain surface-modified nano-particles; ethylene glycol was dissolved in deionized water to obtain an ethylene glycol solution with a concentration of 0.09 M, potassium persulfate was added at a mass ratio of 0.08:1 to ethylene glycol, and the mixture was stirred at a constant temperature of 65°C for 10 minutes. in to obtain a toughening functional solution, adding surface-modified nanoparticles at a mass ratio of 1:12 to ethylene glycol, continuing stirring for 5 hours, then filtering, washing, and drying at 60°C for 8 hours to obtain surface-toughened nanoparticles; preparing a surface-toughened nanoparticle dispersion, adding natural rubber latex accounting for 30 wt% of the surface-toughened nanoparticles, stirring and reacting to obtain a rubber latex system, wherein the stirring reaction temperature is 35°C and the time is 6 hours, and then adding epoxy resin accounting for 3.2 wt% of the surface-toughened nanoparticles to obtain a reaction solution D, stirring at a constant temperature of 65°C for 3 hours, then filtering, washing, and drying at 60°C for 12 hours to obtain rubber-coated toughened nanoparticles;

[0121] S3: Concentrated nitric acid and concentrated sulfuric acid are mixed in a volume ratio of 1:3.8 to obtain a mixed acid solution, polyacrylonitrile-based carbon fiber is added to the mixed acid solution, the mass ratio of polyacrylonitrile-based carbon fiber to the mixed acid solution is 1:15, the mixture is stirred in a water bath at a constant temperature of 70°C for 2 hours, filtered, washed, and dried at 80°C for 8 hours to obtain acid-treated polyacrylonitrile-based carbon fiber; a chemical vapor deposition reactor is used to perform chemical vapor deposition on the acid-treated polyacrylonitrile-based carbon fiber to obtain carbon-based deposited acid-treated polyacrylonitrile-based carbon fiber, wherein the chemical vapor deposition coating precursor in the chemical vapor deposition treatment is acetylene; the precursor gas flow rate is 20 sccm; the reaction time is 1 hour; the reaction temperature is 900°C; and the protective gas is argon;

[0122] S4: Modified montmorillonite, carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers, rubber-coated toughening nanoparticles and polytetrafluoroethylene powder are mixed and ball-milled to obtain a composite powder, which is cold-pressed at a pressure of 30 MPa for 10 minutes and sintered to obtain an impact-resistant and heat-stable polytetrafluoroethylene composite material, wherein the first sintering temperature is 330°C, the first time is 60 minutes, the second temperature is 400°C, and the second time is 3 hours. The mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is 87:4:8:2.

[0123] Comparative Example 1

[0124] This embodiment provides an impact-resistant and thermally stable polytetrafluoroethylene composite material, which differs from Example 1 in that, in S4, the mass ratio of polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is 85:6:5:3, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0125] Comparative Example 2

[0126] This embodiment provides an impact-resistant and thermally stable polytetrafluoroethylene composite material, which differs from Example 1 in that, in S4, the mass ratio of polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is 85:1:5:3, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0127] Comparative Example 3

[0128] This embodiment provides an impact-resistant and thermally stable polytetrafluoroethylene composite material, which differs from Example 1 in that, in S4, the mass ratio of polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is 85:3:10:3, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0129] Comparative Example 4

[0130] This embodiment provides an impact-resistant and thermally stable polytetrafluoroethylene composite material, which differs from Example 1 in that, in S4, the mass ratio of polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is 85:3:1:3, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0131] Comparative Example 5

[0132] This embodiment provides an impact-resistant and thermally stable polytetrafluoroethylene composite material, which differs from Example 1 in that, in S4, the mass ratio of polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is 85:3:5:7, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0133] Comparative Example 6

[0134] This embodiment provides an impact-resistant and thermally stable polytetrafluoroethylene composite material, which differs from Example 1 in that, in S4, the mass ratio of polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is 85:3:5:1, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0135] The performance test of the impact-resistant and heat-stable polytetrafluoroethylene composite materials of Examples 1-4 and Comparative Examples 1-6 was conducted, and the specific process is as follows:

[0136] The notched impact strength of the samples was tested according to the national standard GB / T1043.1-2008. For each example or comparative example, five samples with a size of 100 mm × 10 mm × 3 mm were prepared for testing, and the results were averaged. The impact energy was set to 75 J, and the hammer lifting angle was set to 150°.

[0137] The tensile strength of the samples was tested according to the national standard GB / T1040.1-2018;

[0138] The bending strength test of the samples was carried out according to the national standard GB / T9341-2008 "Determination of Flexural Properties of Plastics";

[0139] The heat deformation temperature of the samples was tested according to the national standard GB / T1634.2-2004. Five samples were tested for each embodiment or comparative example, and the average value was taken. The test results are shown in Table 1.

[0140] Table 1: Performance test results of impact-resistant and heat-stable polytetrafluoroethylene composite materials of Examples 1-4 and Comparative Examples 1-6

[0141]

[0142]

[0143] The test results of Example 1 and Comparative Examples 1 and 2 show that when the amount of modified montmorillonite is too high, the layered silicate agglomerates in the matrix, resulting in the notched impact strength of the impact-resistant and heat-stable polytetrafluoroethylene composite material decreasing to 85 kJ / m 2 , the tensile strength decreased to 25MPa, and the flexural strength decreased to 18MPa; the heat deformation temperature increased slightly to 98℃; when the modified montmorillonite feed rate was too low, the heat deformation temperature was only 75℃ due to the inability to form an effective layered network structure, and the improvement effects of notched impact strength, tensile strength and flexural strength were not obvious, which were 120kJ / m 2 , 35MPa and 25MPa.

[0144] From the test results of Example 1 and Comparative Examples 3 and 4, it can be seen that when the amount of rubber-coated toughening nanoparticles is too high, the continuity of the matrix is ​​destroyed due to excessive soft phase, resulting in a decrease in tensile strength to 28 MPa, a decrease in flexural strength to 20 MPa, a decrease in heat deformation temperature to 74°C, and a slight increase in notched impact strength to 140 kJ / m 2 When the amount of rubber-coated toughening nanoparticles is too low, the notched impact strength is only 95kJ / m due to insufficient toughness phase content. 2 , other mechanical properties remain basically unchanged.

[0145] From the test results of Example 1 and Comparative Examples 5 and 6, it can be seen that when the feed rate of carbon-based deposited carbon fibers is too high, the notched impact strength is reduced to 90 kJ / m due to the agglomeration of the fibers in the matrix. 2 Although the tensile strength is slightly increased to 40MPa, the flexural strength drops to 20MPa due to inconsistent fiber orientation, and the heat deformation temperature increases slightly to 97°C. When the carbon-based deposited carbon fiber feed rate is too low, the tensile strength drops to 32MPa, the flexural strength drops to 22MPa, and the heat deformation temperature drops to 80°C due to the inability to form an effective skeleton support structure.

[0146] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material, characterized in that: The preparation method is: S1: mixing a montmorillonite dispersion with a grafting monomer solution and an initiator to obtain a reaction solution A, reacting and treating the mixture to obtain surface-modified montmorillonite, which is then reacted with a metal salt solution to obtain modified montmorillonite; S2: reacting the nanoparticles with a coupling agent to obtain surface-modified nanoparticles, which are then reacted with a toughening functional monomer to obtain surface-toughened nanoparticles; preparing a dispersion of the surface-toughened nanoparticles, adding a rubber latex and a cross-linking agent, and reacting to obtain rubber-coated toughened nanoparticles; S3: Mixing concentrated nitric acid and concentrated sulfuric acid to obtain a mixed acid solution, adding the solution to the polyacrylonitrile-based carbon fiber to react and obtain acid-treated polyacrylonitrile-based carbon fiber; performing chemical vapor deposition on the acid-treated polyacrylonitrile-based carbon fiber using a CVD reactor to obtain carbon-deposited acid-treated polyacrylonitrile-based carbon fiber; S4: Modified montmorillonite, carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers, rubber-coated toughened nanoparticles, and polytetrafluoroethylene powder are mixed and ball-milled to obtain a composite powder, which is then cold-pressed and sintered to obtain an impact-resistant and thermally stable polytetrafluoroethylene composite material; The grafting monomer in the grafting monomer solution is any one of acrylic acid, methyl acrylate, and methacrylic acid; The metal salt in the metal salt solution is any one of zinc nitrate, aluminum chloride, and magnesium chloride; The nanoparticles are any one of nano-silicon dioxide, nano-aluminum oxide, and nano-calcium carbonate; The toughening functional monomer is acrylic acid and / or ethylene glycol. When the toughening functional monomer is acrylic acid, the crosslinking agent is sulfur; when the toughening functional monomer is ethylene glycol, the crosslinking agent is epoxy resin. The mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is: (80-90): (2-4): (3-8): (2-5).

2. The method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material according to claim 1, characterized in that: In S1, The feeding amount of the grafting monomer accounts for 10-15% of the montmorillonite; The initiator is potassium persulfate and / or sodium persulfate; The amount of the initiator added is 1-2% of the grafting monomer.

3. The method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material according to claim 1, characterized in that: In S1, The mass ratio of the surface-modified montmorillonite to the metal salt is (1-2):

1.

4. The method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material according to claim 1, characterized in that: In S2, The coupling agent is 3-aminopropyltriethoxysilane and / or γ-methacryloxypropyltrimethoxysilane; The mass ratio of the coupling agent to the nanoparticles is (1-2):

1.

5. The method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material according to claim 1, characterized in that: In S2, The mass ratio of the surface modified nanoparticles to the toughening functional monomer is 1:(5-15).

6. The method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material according to claim 1, characterized in that: In S2, The rubber latex is nitrile rubber and / or natural rubber latex; The feeding amount of the rubber latex accounts for 10-30wt% of the surface toughened and modified nanoparticles.

7. The method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material according to claim 1, characterized in that: In S2, The amount of the cross-linking agent is 1-5 wt % of the surface toughened and modified nanoparticles.

8. The method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material according to claim 1, characterized in that: In S3, The volume ratio of the mixed concentrated nitric acid and concentrated sulfuric acid is 1: (3-4); The mass ratio of the polyacrylonitrile-based carbon fiber to the mixed acid solution is 1:(10-15); The chemical vapor deposition coating precursor in the chemical vapor deposition process is methane and / or acetylene; The protective gas in the chemical vapor deposition process is hydrogen and / or argon.

9. A shock-resistant and heat-stable polytetrafluoroethylene composite material prepared by the method for preparing a shock-resistant and heat-stable polytetrafluoroethylene composite material according to claims 1 to 8.

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