Polytetrafluoroethylene composite material with impact resistance and thermal stability and preparation method thereof

Abstract

The invention belongs to the technical field of preparation of polytetrafluoroethylene composite materials, and provides an impact-resistant and heat-stable polytetrafluoroethylene composite material and a preparation method thereof. Montmorillonite enhances the strength and barrier property of the material through physical crosslinking and barrier action of a layered structure, and improves the dispersity, interface bonding force and thermal stability through grafting modification and metal ion exchange; the strength, the toughness and the wear resistance of the composite material are improved due to the high specific surface area and the small-size effect of the nanoparticles, and the interfacial compatibility and the impact resistance are optimized through coating modification of the silane coupling agent, the toughening monomer and the rubber; the polyacrylonitrile-based carbon fiber enhances the mechanical and conductive properties of the composite material by virtue of high strength and heat resistance, and further improves the interface bonding force and mechanical locking effect by virtue of mixed acid oxidation and chemical vapor deposition modification; through the synergistic effect of the three components, the mechanical, thermal and functional optimization of the composite material is realized.

Description

Technical Field

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

[0002] As an excellent high-performance material, polytetrafluoroethylene is widely used in fields such as chemical industry, electronics, machinery, and aerospace due to its excellent chemical stability, electrical insulation, and low friction coefficient. However, although it performs well in many applications, its deficiencies in mechanical properties and thermal stability still significantly limit the performance of polytetrafluoroethylene in specific application scenarios.

[0003] Firstly, the mechanical properties of polytetrafluoroethylene are mainly reflected in its tensile strength and toughness. Although polytetrafluoroethylene has a relatively high tensile strength, enabling it to withstand relatively large pressures under certain static load conditions, its inherent brittleness severely limits the application scope of the material. When subjected to impact or stress concentration, polytetrafluoroethylene is prone to crack propagation, leading to material fracture. This brittleness often becomes the main cause of material failure in practical applications, especially in environments that need to withstand dynamic loads or impacts. For example, in the aerospace and automotive industries, polytetrafluoroethylene is often used as a sealant and insulation material, but its brittle characteristics may cause accidental failure of components during use, thereby affecting the safety and reliability of the overall system. Such failures may not only result in economic losses but also endanger personal safety in some cases. Therefore, it is particularly important to improve the mechanical properties of polytetrafluoroethylene.

[0004] Secondly, although polytetrafluoroethylene performs well under high-temperature conditions, when subjected to rapid temperature changes or continuous high-temperature action, the molecular structure of polytetrafluoroethylene may change during the sharp temperature fluctuations, resulting in a decline in the mechanical properties of the material. In some high-temperature industrial applications, when polytetrafluoroethylene is exposed to a high-temperature environment for a long time, material fatigue may occur, which not only affects the physical properties of the material but may also lead to failure. Therefore, the insufficient thermal stability of polytetrafluoroethylene is even more obvious in extreme temperature environments, which limits its application in high-temperature processes or equipment. Summary of the Invention

[0005] In view of the above problems, the object of the present invention is to provide an impact-resistant and thermally stable polytetrafluoroethylene composite material and a preparation method thereof. By introducing and modifying montmorillonite, nanoparticles and polyacrylonitrile-based carbon fibers, the comprehensive performance of the polytetrafluoroethylene composite material is significantly improved. Montmorillonite enhances the material strength and barrier properties through the physical crosslinking and barrier effects of its layered structure, and improves the dispersibility, interfacial bonding force and thermal stability through graft 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 interfacial compatibility and impact resistance through silane coupling agent, toughening monomer and rubber coating modification; polyacrylonitrile-based carbon fibers enhance the mechanical and electrical conductivity of the composite material by virtue of their high strength and heat resistance, and further improve the interfacial bonding force 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, realizing the comprehensive optimization of the mechanical, thermal and functional properties of the composite material.

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

[0007] In the first aspect, the present invention provides a preparation method of an impact-resistant and thermally stable polytetrafluoroethylene composite material, and the preparation method is as follows:

[0008] S1: Mix the montmorillonite dispersion liquid with the graft monomer solution and the initiator to obtain reaction liquid A, react and process to obtain surface-modified montmorillonite, and react it with metal salts to obtain modified montmorillonite;

[0009] S2: React the nanoparticles with the coupling agent to obtain surface-modified nanoparticles, and react them with the toughening functional monomer to obtain surface-toughened and modified nanoparticles; prepare a dispersion liquid of surface-toughened and modified nanoparticles, add rubber emulsion and crosslinking agent, and react to obtain rubber-coated toughened nanoparticles;

[0010] S3: Mix concentrated nitric acid and concentrated sulfuric acid to obtain a mixed acid solution, add polyacrylonitrile-based carbon fibers and react to obtain acid-treated polyacrylonitrile-based carbon fibers; perform chemical vapor deposition treatment on the acid-treated polyacrylonitrile-based carbon fibers using a CVD reactor to obtain acid-treated polyacrylonitrile-based carbon fibers with carbon-based deposition;

[0011] S4: Mix the modified montmorillonite, acid-treated polyacrylonitrile-based carbon fibers with carbon-based deposition, rubber-coated toughened nanoparticles and polytetrafluoroethylene powder, and ball mill to obtain composite powder, and obtain an impact-resistant and thermally stable polytetrafluoroethylene composite material after cold pressing, forming and sintering.

[0012] Specifically: S1: Disperse montmorillonite in deionized water to obtain a montmorillonite dispersion; dissolve the graft monomer in deionized water to obtain a graft monomer solution; prepare an initiator solution and add it to the graft monomer solution to obtain a mixed solution A; add the mixed solution A dropwise to the montmorillonite dispersion to obtain a reaction solution A, stir at a constant temperature, filter, wash, and dry after the reaction solution A cools to obtain surface-modified montmorillonite; prepare a metal salt solution, disperse the surface-modified montmorillonite in the metal salt solution, stir to obtain a mixed solution B, adjust the pH of the mixed solution B with ammonia water to obtain a reaction solution B, stir at a constant temperature, and then filter, wash, and dry to obtain modified montmorillonite;

[0013] S2: Disperse the nanoparticles in absolute ethanol to obtain a nanoparticle dispersion, add deionized water and a coupling agent to obtain a reaction solution C, stir at a constant temperature, filter, wash, and dry to obtain surface-modified nanoparticles; dissolve the toughening functional monomer in deionized water to obtain a toughening functional monomer solution, add potassium persulfate, stir at a constant temperature to obtain a toughening functional solution, add the surface-modified nanoparticles, continue to stir, and then filter, wash, and dry to obtain surface-toughened and modified nanoparticles; prepare a dispersion of surface-toughened and modified nanoparticles, add a rubber emulsion, stir and react to obtain a rubber emulsion system, add a crosslinking agent to obtain a reaction solution D, stir at a constant temperature, and then filter, wash, and dry to obtain rubber-coated toughened nanoparticles;

[0014] S3: Mix concentrated nitric acid and concentrated sulfuric acid to obtain a mixed acid solution, add polyacrylonitrile-based carbon fiber to the mixed acid solution, stir in a constant-temperature water bath, filter, wash, and dry to obtain acid-treated polyacrylonitrile-based carbon fiber; perform chemical vapor deposition treatment on the acid-treated polyacrylonitrile-based carbon fiber using a CVD reactor to obtain acid-treated polyacrylonitrile-based carbon fiber with carbon-based deposition;

[0015] S4: Mix the modified montmorillonite, acid-treated polyacrylonitrile-based carbon fiber with carbon-based deposition, rubber-coated toughened nanoparticles, and polytetrafluoroethylene powder, and ball mill to obtain a composite powder, and then cold press, form, and sinter 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 the montmorillonite to the 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 this numerical range are equally applicable.

[0017] In some alternative examples, the feeding amount of the graft monomer accounts for 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. Other unlisted values within this numerical range are equally applicable.

[0018] In some alternative examples, the concentration of the graft monomer solution is 0.1-1 wt%. For example, it can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt% or 1 wt%, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0019] In some alternative examples, the feeding amount of the initiator accounts for 1-2% of the graft 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. Other unlisted values within this numerical range are equally applicable.

[0020] In some alternative examples, the temperature for constant temperature stirring of the reaction solution 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. Other unlisted values within this numerical range are equally applicable.

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

[0022] In some alternative 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. Other unlisted values within this numerical range are equally applicable.

[0023] In some alternative examples, the drying time of the surface-modified montmorillonite is 12-24 h. For example, it can be 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h or 24 h, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

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

[0025] In some alternative 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0026] In some alternative examples, the stirring time of the surface-modified montmorillonite dispersed in the metal salt solution is 30 - 60 min. For example, it can be 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0027] In some alternative examples, the pH of the mixed solution B is adjusted to 9 - 10 using ammonia water. For example, it can be 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, or 10. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0028] In some alternative examples, the temperature of the constant-temperature stirring of the reaction solution 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0029] In some alternative examples, the constant-temperature stirring time of the reaction solution B is 2 - 3 h. For example, it can be 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h, or 3 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0030] In some optional examples, the temperature for drying 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

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

[0032] As a preferred technical solution of the present invention, in S2, the feeding amount of 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0033] In some optional examples, the feeding amount of deionized water is 1 - 2 mL. For example, it can be 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0035] In some optional examples, the temperature for constant temperature stirring of the reaction solution 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0036] In some alternative examples, the reaction solution C is stirred at a constant temperature for 4 - 5 h. For example, it can be 4 h, 4.1 h, 4.2 h, 4.3 h, 4.4 h, 4.5 h, 4.6 h, 4.7 h, 4.8 h, 4.9 h, or 5 h. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0037] In some alternative examples, the surface - modified nanoparticles are dried at a temperature of 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. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0038] In some alternative examples, the surface - modified nanoparticles are dried for 12 - 20 h. For example, it can be 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, or 20 h. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0039] In some alternative examples, the concentration of the toughening functional monomer solution is 0.05 - 0.1 M. For example, it can be 0.05 M, 0.06 M, 0.07 M, 0.08 M, 0.09 M, or 0.1 M. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0040] In some alternative examples, the mass ratio of potassium persulfate to the 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. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0041] In some alternative examples, the toughening functional solution is stirred at a constant temperature of 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. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0042] In some alternative examples, the toughening functional solution is stirred at a constant temperature for 5 - 10 min. For example, it can be 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min, or 10 min. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0043] In some alternative 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 equally applicable.

[0044] In some alternative examples, the stirring time after adding the surface-modified nanoparticles to the toughening functional solution is 4 - 5 h, for example, it can be 4 h, 4.1 h, 4.2 h, 4.3 h, 4.4 h, 4.5 h, 4.6 h, 4.7 h, 4.8 h, 4.9 h or 5 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0045] In some alternative 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 equally applicable.

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

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

[0048] In some alternative examples, the temperature of the stirring reaction of the rubber emulsion 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 equally applicable.

[0049] In some alternative examples, the stirring reaction time of the rubber emulsion system is 6 - 8 h. For example, it can be 6 h, 6.2 h, 6.4 h, 6.6 h, 6.8 h, 7.0 h, 7.2 h, 7.4 h, 7.6 h, 7.8 h, or 8 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

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

[0051] In some alternative examples, the temperature for constant temperature stirring of the reaction solution 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0052] In some alternative examples, the time for constant temperature stirring of the reaction solution D is 2 - 3 h. For example, it can be 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h, or 3 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0053] In some alternative examples, the drying temperature of the rubber-coated toughened 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0054] In some alternative examples, the drying time of the rubber-coated toughened nanoparticles is 8 - 12 h. For example, it can be 8 h, 8.5 h, 9.0 h, 9.5 h, 10.0 h, 10.5 h, 11.0 h, 11.5 h, or 12 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0055] As a preferred technical solution of the present invention, in S3, the volume ratio of concentrated nitric acid to concentrated sulfuric acid in the mixture 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. Other unlisted values within this numerical range are equally applicable.

[0056] In some alternative 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. Other unlisted values within this numerical range are equally applicable.

[0057] In some alternative examples, the temperature of the constant-temperature water bath stirring after adding the polyacrylonitrile-based carbon fiber to the mixed acid solution 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. Other unlisted values within this numerical range are equally applicable.

[0058] In some alternative examples, the time of the constant-temperature water bath stirring after adding the polyacrylonitrile-based carbon fiber to the mixed acid solution is 2 - 3 h. For example, it can be 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3 h, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0059] In some alternative 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. Other unlisted values within this numerical range are equally applicable.

[0060] In some alternative examples, the drying time of the acid-treated polyacrylonitrile-based carbon fiber is 8 - 12 h. For example, it can be 8 h, 8.5 h, 9.0 h, 9.5 h, 10.0 h, 10.5 h, 11.0 h, 11.5 h or 12 h, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0061] In some alternative examples, the flow rate of the precursor gas 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. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

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

[0063] In some alternative 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. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0064] As a preferred technical solution of the present invention, in S4, the pressure for cold pressing and forming 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. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0065] In some alternative examples, the time for cold pressing and forming the composite powder is 5 - 10 min. For example, it can be 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min, or 10 min. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0066] In some alternative 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. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

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

[0068] In some alternative examples, the second sintering temperature of 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 range are equally applicable.

[0069] In some alternative examples, the second sintering time of the composite powder 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 this range are equally applicable.

[0070] In a second aspect, the present invention provides an impact-resistant and thermally stable polytetrafluoroethylene composite material. The impact-resistant and thermally stable polytetrafluoroethylene composite material comprises polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers. The mass ratio of 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] In the present invention, montmorillonite is introduced to modify polytetrafluoroethylene to improve the comprehensive performance of the composite material. Montmorillonite is a layered silicate mineral, whose crystal structure consists of alternating silicon dioxide tetrahedral layers and aluminum oxide octahedral layers, which are combined by electrostatic interaction between layers and contain exchangeable cations. This unique layered structure endows montmorillonite with a large specific surface area, excellent chemical stability and good thermal stability, making it an ideal inorganic reinforcing material.

[0072] The role of montmorillonite in the polytetrafluoroethylene matrix is mainly manifested in multiple aspects. First of all, its layered structure can form physical cross-linking points by being uniformly dispersed in the polytetrafluoroethylene matrix, restricting the slip behavior of polytetrafluoroethylene molecular chains, thereby significantly improving the tensile strength and modulus of the composite material, and at the same time enhancing the rigidity and anti-deformation ability of the material. Secondly, the layered structure of montmorillonite plays a physical barrier role of the "labyrinth effect" in the composite material, prolonging the penetration path of gas or liquid, helping to improve the barrier performance of the composite material, and making it perform excellently in terms of chemical corrosion resistance and sealing performance. In addition, the high thermal stability of montmorillonite itself can effectively delay the thermal degradation process of the polytetrafluoroethylene matrix in a high-temperature environment, and its interlayer structure can absorb and disperse heat, further enhancing the thermal stability and high-temperature adaptability of the material.

[0073] However, montmorillonite itself has significant limitations. Its strong hydrophilicity and interlayer electrostatic interaction make it easy to agglomerate, resulting in difficulty in forming a uniform dispersion in the hydrophobic polytetrafluoroethylene matrix and poor interfacial bonding, thus limiting its strengthening effect. Therefore, surface modification of montmorillonite is the key to ensuring its role in the polytetrafluoroethylene matrix.

[0074] The present invention adopts two means of grafting modification and ion exchange modification to optimize montmorillonite from two aspects 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 groups and hydroxyl groups can be introduced onto the surface of montmorillonite, or flexible chain segments can be introduced through polymerization reactions. This modification method not only improves the surface polarity of montmorillonite, enabling it to be better compatible with the polytetrafluoroethylene matrix, but also enhances the interfacial bonding force between montmorillonite and the matrix through physical entanglement or chemical interaction between polar groups or flexible chain segments and polytetrafluoroethylene molecular chains. In addition, grafting modification significantly reduces the agglomeration tendency of montmorillonite, enabling it to achieve a more uniform dispersion in the matrix and fully exert its strengthening 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 layer 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 of all, after ion exchange, the layer spacing of montmorillonite increases, the electrostatic interaction weakens, and the interlayer bonding force decreases, thus promoting the exfoliation and dispersion of montmorillonite in the polytetrafluoroethylene matrix and forming a more stable dispersion state in the matrix. Secondly, the introduction of metal ions endows montmorillonite with new functional characteristics. For example, Zn 2+ can further improve the thermal stability of montmorillonite, Al 3+ and Mg 2+It can significantly enhance the mechanical reinforcement effect of montmorillonite by strengthening the interlayer electrostatic interaction or forming new chemical bonds. In addition, metal ions may also play a catalytic role in the interfacial reaction of the composite material, thereby further improving the interfacial bonding performance between montmorillonite and the polytetrafluoroethylene matrix.

[0076] In the present invention, nanoparticles are introduced to significantly improve the comprehensive performance of polytetrafluoroethylene composites. Due to their unique physical and chemical properties, nanoparticles become important reinforcing phases in the composites, such as high specific surface area, small size effect, and quantum effect. The high specific surface area of nanoparticles enables a larger interfacial contact area with the matrix, thus significantly enhancing the interfacial bonding performance; the small size effect allows them to be uniformly distributed in the matrix, forming a fine reinforcing network; and the quantum effect enables them to exhibit excellent functional properties in aspects such as thermics and electricity. After introducing nanoparticles, the mechanical properties, thermal properties, wear resistance, etc. of the composite materials have been significantly improved.

[0077] The roles of nanoparticles in the composite materials are mainly reflected in the following aspects. Firstly, nanoparticles can play a reinforcing role in the matrix. Their high hardness and 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 small size and uniform distribution of nanoparticles can absorb stress concentration in the microstructure, delay the initiation and propagation of cracks, and thus enhance the toughness and impact resistance of the composite material. Secondly, nanoparticles with good thermal conductivity can significantly increase the thermal conductivity of the composite material through their high thermal conductivity paths, accelerate the heat transfer in the material, reduce the coefficient of thermal expansion, 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, there are usually a large number of hydroxyl groups or other polar functional groups on the surface of nanoparticles. These functional groups cause easy hydrogen bonding or van der Waals force interactions between the particles, and then lead to their agglomeration in the matrix, forming larger particle clusters, which significantly reduces their reinforcement effect. In addition, the interfacial compatibility between nanoparticles and the hydrophobic polytetrafluoroethylene matrix is poor, and their dispersion in the matrix is not good. Therefore, surface modification of nanoparticles is a key step to ensure their uniform dispersion in the composite material, improve the interfacial compatibility, and fully exert their functional properties.

[0079] To solve the above problems, the present invention conducts various surface modification treatments on the nanoparticles. First, the surface of the nanoparticles is modified by using a silane coupling agent. The siloxane groups in the silane coupling agent can chemically react with the hydroxyl groups on the surface of the nanoparticles and stably bind to the particle surface; meanwhile, the organic functional groups in the coupling agent can form a firm interfacial bond with the molecular chains in the polytetrafluoroethylene matrix through physical entanglement or chemical interaction. Through the modification with the silane coupling agent, the surface polarity of the nanoparticles is regulated, thereby reducing the tendency of particle aggregation and significantly improving their dispersibility in the polytetrafluoroethylene matrix.

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

[0081] In addition, the present invention also conducts coating modification on the nanoparticles by using nitrile rubber or natural rubber latex. The rubber coating can form a flexible interfacial structure between the nanoparticles and the polytetrafluoroethylene matrix, effectively absorb external stress, and relieve the stress concentration phenomenon at the interface, thereby improving the impact resistance of the composite material. The flexible chain segments of the rubber further enhance the dispersibility of the nanoparticles in the matrix, prevent the occurrence of particle aggregation, and endow the composite material with higher toughness and flexibility. Through this modification process, the nanoparticles not only exhibit excellent reinforcement effects in the composite material, but also can act as a flexible buffer phase for absorbing stress, further improving the overall performance of the composite material.

[0082] In the present invention, polyacrylonitrile-based carbon fibers are introduced to modify polytetrafluoroethylene. Polyacrylonitrile-based carbon fibers are a kind of high-performance carbon fiber materials prepared by using polyacrylonitrile as a precursor and through high-temperature carbonization treatment. They have extremely high tensile strength and modulus and are high-quality fillers widely used in the field of composite material reinforcement at present. Their high strength and high modulus characteristics enable them to have a significant strengthening effect in the composite material and can significantly improve the rigidity and strength of the composite material; meanwhile, the high thermal stability and heat resistance of the carbon fibers can enhance the mechanical properties and thermal stability of the composite material in a high-temperature environment; in addition, the conductivity of the carbon fibers provides potential conductive functions or antistatic properties for the composite material, enabling it to meet the requirements of some special scenarios, such as electronic device casings, antistatic sealing materials, etc. The introduction of polyacrylonitrile-based carbon fibers has improved the polytetrafluoroethylene composite material in multiple dimensions such as mechanical, thermal, and electrical properties.

[0083] The reinforcement mechanism of polyacrylonitrile-based carbon fiber in polytetrafluoroethylene composites is mainly reflected in the following aspects. First of all, carbon fiber has extremely high tensile strength and modulus. As a rigid skeleton dispersed in the polytetrafluoroethylene matrix, it can evenly share the externally applied stress, limit the deformation of the matrix material, and significantly improve the tensile and flexural properties of the composite. Secondly, the dimensional stability and heat resistance of carbon fiber enable it to maintain high mechanical properties in high-temperature environments, thus endowing the composite with more excellent high-temperature stability. In addition, the conductivity of carbon fiber provides additional functional properties for the material, enabling the composite to be applied in environments where antistatic or certain conductivity is required. However, the surface of polyacrylonitrile-based carbon fiber is usually relatively 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 fiber to enhance its interfacial compatibility with the polytetrafluoroethylene matrix is the key to ensuring its reinforcement effect.

[0084] The present invention adopts the oxidation treatment with concentrated nitric acid and concentrated sulfuric acid as the preliminary surface modification method for carbon fiber. By immersing the carbon fiber in the mixed acid solution for oxidation treatment, polar functional groups such as hydroxyl, carboxyl, and carbonyl can be introduced on its surface. These polar functional groups can significantly improve the surface chemical activity of carbon fiber, enabling it to form chemical bonds or hydrogen bonds with the molecular chains in the polytetrafluoroethylene matrix or other components, thereby enhancing the interfacial adhesion force. In addition, the oxidation treatment can also increase the hydrophilicity and wettability of the carbon fiber surface, further improving its dispersion in the matrix. Through this oxidation modification, the chemical inertness of the carbon fiber surface is significantly reduced, laying a 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 adopts chemical vapor deposition technology to perform surface modification treatment on the oxidized carbon fiber. In the CVD reactor, a carbon-based deposition layer is formed on the surface of the carbon fiber through chemical vapor deposition technology. This deposition layer can significantly improve the surface activity and roughness of carbon fiber, thereby enhancing its mechanical locking effect with the polytetrafluoroethylene matrix. This mechanical locking effect is one of the key mechanisms for interfacial reinforcement. The existence of the deposition layer enables effective transfer of external loads between the carbon fiber and the matrix through physical interlocking of the microstructures. In addition, the formation of the carbon-based deposition layer can further improve the heat resistance and thermal stability of carbon fiber, enabling it to exhibit more excellent performance in high-temperature environments.

[0086] In the composite material, montmorillonite, nanoparticles and polyacrylonitrile-based carbon fibers form a multi-scale reinforcement structure, which is the core source of the improvement in mechanical properties. The synergistic effect of this multi-scale structure is as follows: The modified montmorillonite and nanoparticles are uniformly distributed in the polytetrafluoroethylene matrix, playing a layered reinforcement and a point-like reinforcement role respectively. Montmorillonite forms physical cross-linking points in the matrix through its layered structure, restricting the slippage of polytetrafluoroethylene molecular chains; while the nanoparticles further hinder the movement of molecular chains through the "pinning effect". This synergistic effect enables the composite material to exhibit higher tensile strength and modulus under stress, while slowing down the stress concentration phenomenon and improving the toughness of the material.

[0087] As the rigid framework of the composite material, polyacrylonitrile-based carbon fibers can significantly improve the tensile strength and bending resistance of the material. The modified montmorillonite is uniformly distributed around the carbon fibers, playing a role of filling and interfacial reinforcement. The layered structure of montmorillonite can form a "bridging effect" between the carbon fibers and the polytetrafluoroethylene matrix, ensuring the effective transfer of stress from the matrix to the carbon fibers, thereby further enhancing the overall rigidity and strength of the composite material.

[0088] The carbon fibers and nanoparticles form a multi-level reinforcement system of "rigid reinforcement + local reinforcement" in the composite material. The carbon fibers bear the main stress, and the nanoparticles, through their uniform distribution and high hardness, reinforce the matrix around the carbon fibers at the microscale, further enhancing the crack propagation resistance and fatigue resistance of the material.

[0089] The toughening nanoparticles coated with rubber act together with the carbon fibers and montmorillonite to form a flexible-rigid composite reinforcement system. The flexible chain segments of the rubber can absorb the external impact energy and relieve the stress concentration phenomenon; while the carbon fibers and montmorillonite provide a rigid reinforcement effect. This synergistic effect of combining rigidity and flexibility significantly improves the impact resistance and toughness of the material.

[0090] In terms of thermal properties: The layered structure of montmorillonite acts as a thermal barrier, delaying the diffusion of heat in the matrix; while the nanoparticles with excellent thermal conductivity (such as nano-aluminum oxide) accelerate the transfer of heat inside 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 being modified with metal ions, the thermal stability of montmorillonite is further enhanced, forming a complementary advantage with the thermal conductivity of the nanoparticles; the carbon fibers themselves have high thermal stability and excellent thermal conductivity, and their rigid framework structure can efficiently transfer heat. In a high-temperature environment, the interaction between the carbon fibers and montmorillonite prevents the premature decomposition of the polytetrafluoroethylene matrix. Specifically, the thermal conductivity path of the carbon fibers and the thermal barrier effect of montmorillonite act synergistically to reduce the thermal expansion coefficient of the material and improve the dimensional stability of the material.

[0091] The improvement in barrier performance is mainly due to the synergistic shielding effect of montmorillonite, nanoparticles, and polytetrafluoroethylene matrix: The layered structure of montmorillonite forms a "labyrinth effect" in the composite material, significantly extending the penetration path of gases or liquids; the introduction of nanoparticles makes the material structure more dense, further reducing the porosity in the matrix. This synergy significantly improves the gas barrier performance and chemical corrosion resistance of the composite material; the high density and low porosity of carbon fiber play an important role in preventing the penetration of gases or chemical substances. Montmorillonite is evenly distributed on the surface of carbon fiber and in the polytetrafluoroethylene matrix, further enhancing the barrier performance. This synergistic effect of "rigid skeleton + layered barrier" enables the composite material to perform excellently in corrosive environments.

[0092] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0093] The present invention modifies polytetrafluoroethylene by introducing montmorillonite, significantly improving the mechanical properties, thermal stability, and barrier performance of the composite material. The layered structure of montmorillonite forms physical cross-linking and barrier effects through uniform dispersion, improving the strength and permeability resistance of the material. However, the dispersibility and interfacial compatibility of montmorillonite in the polytetrafluoroethylene matrix are poor. Therefore, polar functional groups and flexible chain segments are introduced through graft modification to improve its dispersibility and interfacial binding force. At the same time, the layer spacing is expanded through metal ion exchange, and its thermal stability and mechanical enhancement effect are improved. These modification measures synergistically optimize the properties of montmorillonite, enabling it to fully play an enhancing role in the polytetrafluoroethylene composite material;

[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, nanoparticles are evenly distributed in the matrix, enhancing the strength and toughness of the material, while improving the thermal conductivity and impact resistance. To overcome the problems of easy agglomeration and poor interfacial compatibility, the dispersibility and interfacial binding force are improved through silane coupling agent modification, toughening monomer modification, and rubber coating treatment, strengthening the flexibility and impact resistance. The synergistic effect of various modifications enables nanoparticles to fully play a reinforcing role, 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 composite materials 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 binding. Polar functional groups are introduced through mixed acid oxidation treatment to improve its interfacial adhesion and dispersibility; at the same time, a carbon-based deposition layer is formed by chemical vapor deposition to enhance the mechanical locking effect and load transfer ability. This multiple modification strategy effectively optimizes the interfacial properties, enabling carbon fibers to fully play an enhancing role in the composite material. Description of the Drawings

[0096] Figure 1 Flow chart of the preparation method of the impact-resistant and thermally stable polytetrafluoroethylene composite provided by the embodiment of the present invention;

[0097] Figure 2 Infrared spectrum of the acid-treated polyacrylonitrile-based carbon fiber in Example 1 of the present invention. Specific embodiments

[0098] The technical solution of the present invention will be described in detail below with reference to specific embodiments and their accompanying drawings. The embodiments described herein are specific specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary and should not be construed as limiting the embodiments of the present invention and the protection scope of the present invention. Except for the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of the present application. These technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0099] Example 1

[0100] This example provides an impact-resistant and thermally stable polytetrafluoroethylene composite and a preparation method thereof. The preparation method of the impact-resistant and thermally stable polytetrafluoroethylene composite specifically includes the following steps:

[0101] S1: Disperse montmorillonite in deionized water to obtain a montmorillonite dispersion, where the mass ratio of montmorillonite to deionized water is 1:10; dissolve the graft monomer acrylic acid in deionized water to obtain a graft monomer solution, and the feeding amount of the graft monomer acrylic acid accounts for 15% of the montmorillonite, and the concentration of the graft monomer solution is 1 wt%; prepare a potassium persulfate solution and add it to the graft monomer solution to obtain a mixed solution A, where the feeding amount of potassium persulfate accounts for 1% of the graft monomer acrylic acid; drop the mixed solution A into the montmorillonite dispersion to obtain a reaction solution A, stir at a constant temperature of 68 °C for 4.2 h, filter, wash after the reaction solution A cools, and dry at 70 °C for 12 h to obtain surface-modified montmorillonite; prepare a zinc nitrate solution with a concentration of 0.05 M, disperse the surface-modified montmorillonite in the zinc nitrate solution, where the mass ratio of the surface-modified montmorillonite to zinc nitrate is 1:1, stir for 30 min to obtain a mixed solution B, adjust the pH of the mixed solution B to 9 with ammonia water to obtain a reaction solution B, stir at a constant temperature of 80 °C for 2 h, then filter, wash, and dry to obtain modified montmorillonite, where the drying temperature is 80 °C and the time is 10 h;

[0102] S2: Disperse nano-silica in absolute ethanol to obtain a nano-particle dispersion liquid. The feeding amount of nano-silica is 1 mg / mL. Add 1 mL of deionized water and 3-aminopropyltriethoxysilane to obtain reaction solution C. The mass ratio of 3-aminopropyltriethoxysilane to nano-silica is 1:1. Stir at a constant temperature of 50 °C for 5 h, then filter, wash, and dry at 75 °C for 20 h to obtain surface-modified nano-particles; dissolve acrylic acid in deionized water to obtain an acrylic acid solution with a concentration of 0.1 M. Add potassium persulfate with a mass ratio of 0.1:1 to acrylic acid, stir at a constant temperature of 75 °C for 5 min to obtain a toughening functional solution. Add surface-modified nano-particles with a mass ratio of 1:5 to acrylic acid, continue stirring for 4 h, then filter, wash, and dry at 50 °C for 12 h to obtain surface-toughened and modified nano-particles; prepare a dispersion liquid of surface-toughened and modified nano-particles, add acrylonitrile-butadiene rubber accounting for 10 wt% of the surface-toughened and modified nano-particles, and stir to react to obtain a rubber emulsion system. The temperature of the stirring reaction is 25 °C and the time is 8 h. Then add sulfur accounting for 5 wt% of the surface-toughened and modified nano-particles to obtain reaction solution D. Stir at a constant temperature of 70 °C for 2.5 h, then filter, wash, and dry at 55 °C for 10 h to obtain rubber-coated toughened nano-particles;

[0103] S3: Mix concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:3 to obtain a mixed acid solution. Add polyacrylonitrile-based carbon fiber to the mixed acid solution. The mass ratio of polyacrylonitrile-based carbon fiber to the mixed acid solution is 1:10. Stir in a water bath at a constant temperature of 68 °C for 2.2 h, filter, wash, and dry at 77 °C for 9 h to obtain acid-treated polyacrylonitrile-based carbon fiber; use a chemical vapor deposition reactor to perform chemical vapor deposition treatment on the acid-treated polyacrylonitrile-based carbon fiber to obtain acid-treated polyacrylonitrile-based carbon fiber with a carbon-based deposit. The chemical vapor deposition coating precursor in the chemical vapor deposition treatment is methane; the precursor gas flow rate is 10 sccm; the reaction time is 2 h; the chemical reaction temperature is 800 °C; the protective gas is hydrogen; the infrared spectrum of the acid-treated polyacrylonitrile-based carbon fiber is as Figure 2 shown: The signal peaks located at 1650 - 1600 cm -1 and 3000 - 2830 cm -1 correspond to the conjugated aryl chain and aliphatic chain of the polyacrylonitrile-based carbon fiber respectively, while the signal peaks at 1740 - 1700 cm -1 and 1150 - 1040 cm -1 correspond to the saturated aliphatic carboxyl group and tertiary hydroxyl bond of the acid-treated polyacrylonitrile-based carbon fiber respectively. This indicates that carboxyl groups and hydroxyl groups are formed on the surface of the polyacrylonitrile-based carbon fiber under the action of acid treatment.

[0104] S4: Mix the modified montmorillonite, carbon-based deposited acid-treated polyacrylonitrile-based carbon fiber, rubber-coated toughening nanoparticles, and polytetrafluoroethylene powder, and ball-mill to obtain a composite powder. Cold-press and form it for 5 min under a pressure of 15 MPa, and then sinter to obtain a polytetrafluoroethylene composite material with impact resistance and thermal stability. The first sintering temperature is 325 °C, the first time is 30 min, the second temperature is 380 °C, and the second time is 2 h. The mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles, and carbon-based deposited acid-treated polyacrylonitrile-based carbon fiber is: 85:3:5:3.

[0105] Example 2

[0106] This example provides a polytetrafluoroethylene composite material with impact resistance and thermal stability and its preparation method. The preparation method of the polytetrafluoroethylene composite material with impact resistance and thermal stability specifically includes the following steps:

[0107] S1: Disperse montmorillonite in deionized water to obtain a montmorillonite dispersion, where the mass ratio of montmorillonite to deionized water is 1:20; dissolve the graft monomer methyl acrylate in deionized water to obtain a graft monomer solution, and the feeding amount of the graft monomer methyl acrylate accounts for 12% of montmorillonite, and the concentration of the graft monomer solution is 0.1 wt%; prepare a potassium persulfate solution and add it to the graft monomer solution to obtain a mixed solution A, where the feeding amount of potassium persulfate accounts for 2% of the graft monomer methyl acrylate; drop the mixed solution A into the montmorillonite dispersion to obtain a reaction solution A, stir it at a constant temperature of 60 °C for 5 h, filter, wash, and dry it at 60 °C for 24 h to obtain surface-modified montmorillonite; prepare an aluminum chloride solution with a concentration of 0.08 M, disperse the surface-modified montmorillonite in the aluminum chloride solution, where the mass ratio of the surface-modified montmorillonite to aluminum chloride is 1:2, stir for 40 min to obtain a mixed solution B, use ammonia water to adjust the pH of the mixed solution B to 9.5 to obtain a reaction solution B, stir it at a constant temperature of 78 °C for 2.2 h, then filter, wash, and dry it to obtain modified montmorillonite, where the drying temperature is 78 °C and the time is 12 h;

[0108] S2: Disperse nano-aluminum oxide in absolute ethanol to obtain a nano-particle dispersion liquid. The feeding amount of nano-aluminum oxide is 0.1 mg / mL. Add 1.4 mL of deionized water and 3-aminopropyltriethoxysilane to obtain reaction liquid C. The mass ratio of 3-aminopropyltriethoxysilane to nano-aluminum oxide is 2:1. Stir at a constant temperature of 60 °C for 4 h, then filter, wash, and dry at 85 °C for 10 h to obtain surface-modified nano-particles; Dissolve acrylic acid in deionized water to obtain an acrylic acid solution with a concentration of 0.05 M. Add potassium persulfate with a mass ratio of 0.05:1 to acrylic acid, stir at a constant temperature of 70 °C for 6 min to obtain a toughening functional solution. Add surface-modified nano-particles with a mass ratio of 1:15 to acrylic acid, continue stirring for 4.5 h, then filter, wash, and dry at 55 °C for 10 h to obtain surface-toughened and modified nano-particles; Prepare a surface-toughened and modified nano-particle dispersion liquid, add nitrile rubber accounting for 20 wt% of the surface-toughened and modified nano-particles, and stir to react to obtain a rubber emulsion system. The temperature of the stirring reaction is 30 °C and the time is 7 h. Then add sulfur accounting for 1 wt% of the surface-toughened and modified nano-particles to obtain reaction liquid D. Stir at a constant temperature of 75 °C for 2 h, then filter, wash, and dry at 58 °C for 8 h to obtain rubber-coated toughened nano-particles;

[0109] S3: Mix concentrated nitric acid and concentrated sulfuric acid according to a volume ratio of 1:4 to obtain a mixed acid solution. Add polyacrylonitrile-based carbon fiber to the mixed acid solution. The mass ratio of polyacrylonitrile-based carbon fiber to the mixed acid solution is 1:12. Stir in a water bath at a constant temperature of 60 °C for 3 h, filter, wash, and dry at 75 °C for 10 h to obtain acid-treated polyacrylonitrile-based carbon fiber; Use a chemical vapor deposition reactor to perform chemical vapor deposition treatment on the acid-treated polyacrylonitrile-based carbon fiber to obtain acid-treated polyacrylonitrile-based carbon fiber with a carbon-based deposit. In the chemical vapor deposition treatment, the chemical vapor deposition coating precursor is methane; the precursor gas flow rate is 18 sccm; the reaction time is 1.2 h; the chemical reaction temperature is 850 °C; the protective gas is hydrogen;

[0110] S4: Mix modified montmorillonite, acid-treated polyacrylonitrile-based carbon fiber with a carbon-based deposit, rubber-coated toughened nano-particles, and polytetrafluoroethylene powder, and ball-mill to obtain a composite powder. Cold-press and form at a pressure of 25 MPa for 8 min and sinter to obtain an impact-resistant and thermally stable polytetrafluoroethylene composite material. The first sintering temperature is 327 °C, the first time is 50 min, the second temperature is 390 °C, and the second time is 2.5 h. The mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughened nano-particles, and acid-treated polyacrylonitrile-based carbon fiber with a carbon-based deposit is: 80:2:7:5.

[0111] Example 3

[0112] This embodiment provides an impact-resistant and thermally stable polytetrafluoroethylene composite material and a preparation method thereof. The preparation method of the impact-resistant and thermally stable polytetrafluoroethylene composite material specifically includes the following steps:

[0113] S1: Disperse montmorillonite in deionized water to obtain a montmorillonite dispersion, where the mass ratio of montmorillonite to deionized water is 1:15; dissolve the graft monomer methacrylic acid in deionized water to obtain a graft monomer solution, and the feeding amount of the graft monomer methacrylic acid accounts for 10% of the montmorillonite, and the concentration of the graft monomer solution is 0.5 wt%; prepare a sodium persulfate solution and add it to the graft monomer solution to obtain a mixed solution A, where the feeding amount of sodium persulfate accounts for 1.7% of the graft monomer methacrylic acid; drop the mixed solution A into the montmorillonite dispersion to obtain a reaction solution A, stir at a constant temperature of 70 °C for 4 h, filter, wash after the reaction solution A cools, and dry at 65 °C for 21 h to obtain surface-modified montmorillonite; prepare a magnesium chloride solution with a concentration of 0.06 M, disperse the surface-modified montmorillonite in the magnesium chloride solution, where the mass ratio of the surface-modified montmorillonite to magnesium chloride is 1:1.5, stir for 50 min to obtain a mixed solution B, adjust the pH of the mixed solution B to 9.7 with ammonia water to obtain a reaction solution B, stir at a constant temperature of 70 °C for 3 h, then filter, wash, and dry to obtain modified montmorillonite, where the drying temperature is 70 °C and the time is 20 h;

[0114] S2: Disperse nano calcium carbonate in absolute ethanol to obtain a nanoparticle dispersion, where the feeding amount of nano calcium carbonate is 0.5 mg / mL, add 1.7 mL of deionized water and γ-methacryloxypropyltrimethoxysilane to obtain a reaction solution C, where the mass ratio of γ-methacryloxypropyltrimethoxysilane to nano calcium carbonate is 1.5:1, stir at a constant temperature of 55 °C for 4.5 h, then filter, wash, and dry at 80 °C for 15 h to obtain surface-modified nanoparticles; dissolve ethylene glycol in deionized water to obtain an ethylene glycol solution with a concentration of 0.07 M, add potassium persulfate with a mass ratio of 0.06:1 to ethylene glycol, stir at a constant temperature of 72 °C for 8 min to obtain a toughening functional solution, add surface-modified nanoparticles with a mass ratio of 1:10 to ethylene glycol, continue to stir for 4.8 h, then filter, wash, and dry at 58 °C for 9 h to obtain surface-toughened and modified nanoparticles; prepare a dispersion of surface-toughened and modified nanoparticles, add natural rubber latex accounting for 25 wt% of the surface-toughened and modified nanoparticles, stir and react to obtain a rubber latex system, where the stirring and reaction temperature is 32 °C and the time is 7.8 h, then add epoxy resin accounting for 2.5 wt% of the surface-toughened and modified nanoparticles to obtain a reaction solution D, stir at a constant temperature of 72 °C for 2.2 h, then filter, wash, and dry at 50 °C for 11 h to obtain rubber-coated toughened nanoparticles;

[0115] S3: Mix concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:3.5 to obtain a mixed acid solution. Add polyacrylonitrile-based carbon fiber to the mixed acid solution, with the mass ratio of polyacrylonitrile-based carbon fiber to the mixed acid solution being 1:14. Stir in a water bath at a constant temperature of 65°C for 2.5 h, filter and wash, and dry at 70°C for 12 h to obtain acid-treated polyacrylonitrile-based carbon fiber; perform chemical vapor deposition treatment on the acid-treated polyacrylonitrile-based carbon fiber using a chemical vapor deposition reactor to obtain acid-treated polyacrylonitrile-based carbon fiber with a carbon-based deposit, where 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 h; the chemical reaction temperature is 870°C; the protective gas is argon;

[0116] S4: Mix modified montmorillonite, acid-treated polyacrylonitrile-based carbon fiber with a carbon-based deposit, rubber-coated toughening nanoparticles, and polytetrafluoroethylene powder, and ball-mill to obtain a composite powder. Cold-press and form at a pressure of 20 MPa for 7 min and sinter to obtain an impact-resistant and thermally stable polytetrafluoroethylene composite material, where the first sintering temperature is 328°C, the first time is 40 min, the second temperature is 360°C, and the second time is 2.8 h. The mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughening nanoparticles, and acid-treated polyacrylonitrile-based carbon fiber with a carbon-based deposit is: 90:3.5:3:4.

[0117] Example 4

[0118] This example provides an impact-resistant and thermally stable polytetrafluoroethylene composite material and a preparation method thereof. The preparation method of the impact-resistant and thermally stable polytetrafluoroethylene composite material specifically includes the following steps:

[0119] S1: Disperse montmorillonite in deionized water to obtain a montmorillonite dispersion, where the mass ratio of montmorillonite to deionized water is 1:18; dissolve graft monomer acrylic acid in deionized water to obtain a graft monomer solution, and the feeding amount of graft monomer acrylic acid accounts for 14% of montmorillonite, and the concentration of the graft monomer solution is 0.7 wt%; prepare a sodium persulfate solution and add it to the graft monomer solution to obtain a mixed solution A, where the feeding amount of sodium persulfate accounts for 1.5% of graft monomer acrylic acid; add the mixed solution A dropwise to the montmorillonite dispersion to obtain a reaction solution A, stir at a constant temperature of 65°C for 4.5 h, filter after the reaction solution A cools, wash, and dry at 67°C for 18 h to obtain surface-modified montmorillonite; prepare a zinc nitrate solution with a concentration of 0.1 M, disperse the surface-modified montmorillonite in the zinc nitrate solution, where the mass ratio of the surface-modified montmorillonite to zinc nitrate is 1:1.8, stir for 60 min to obtain a mixed solution B, adjust the pH of the mixed solution B to 10 using ammonia water to obtain a reaction solution B, stir at a constant temperature of 75°C for 2.5 h, and then filter, wash, and dry to obtain modified montmorillonite, where the drying temperature is 75°C and the time is 15 h;

[0120] S2: Disperse nano-silica in absolute ethanol to obtain a nano-particle dispersion liquid. The feeding amount of nano-silica is 0.7 mg / mL. Add 2 mL of deionized water and γ-methacryloxypropyltrimethoxysilane to obtain reaction solution C. The mass ratio of γ-methacryloxypropyltrimethoxysilane to nano-silica is 1.8:1. Stir at a constant temperature of 57 °C for 4.2 h, then filter, wash, and dry at 82 °C for 18 h to obtain surface-modified nano-particles; Dissolve ethylene glycol in deionized water to obtain an ethylene glycol solution with a concentration of 0.09 M. Add potassium persulfate with a mass ratio of 0.08:1 to ethylene glycol, stir at a constant temperature of 65 °C for 10 min to obtain a toughening functional solution. Add surface-modified nano-particles with a mass ratio of 1:12 to ethylene glycol, continue stirring for 5 h, then filter, wash, and dry at 60 °C for 8 h to obtain surface-toughened and modified nano-particles; Prepare a dispersion liquid of surface-toughened and modified nano-particles, add natural rubber latex accounting for 30 wt% of the surface-toughened and modified nano-particles, and stir to react to obtain a rubber latex system. The temperature of the stirring reaction is 35 °C and the time is 6 h. Then add epoxy resin accounting for 3.2 wt% of the surface-toughened and modified nano-particles to obtain reaction solution D. Stir at a constant temperature of 65 °C for 3 h, then filter, wash, and dry at 60 °C for 12 h to obtain rubber-coated toughened nano-particles;

[0121] S3: Mix concentrated nitric acid and concentrated sulfuric acid according to a volume ratio of 1:3.8 to obtain a mixed acid solution. Add polyacrylonitrile-based carbon fiber to the mixed acid solution. The mass ratio of polyacrylonitrile-based carbon fiber to the mixed acid solution is 1:15. Stir in a water bath at a constant temperature of 70 °C for 2 h, filter, wash, and dry at 80 °C for 8 h to obtain acid-treated polyacrylonitrile-based carbon fiber; Use a chemical vapor deposition reactor to perform chemical vapor deposition treatment on the acid-treated polyacrylonitrile-based carbon fiber to obtain acid-treated polyacrylonitrile-based carbon fiber with a carbon-based deposit. 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 h; The chemical reaction temperature is 900 °C; The protective gas is argon;

[0122] S4: Mix modified montmorillonite, acid-treated polyacrylonitrile-based carbon fiber with a carbon-based deposit, rubber-coated toughened nano-particles, and polytetrafluoroethylene powder, and ball mill to obtain a composite powder. Cold press and mold at a pressure of 30 MPa for 10 min and sinter to obtain an impact-resistant and thermally stable polytetrafluoroethylene composite material. The first sintering temperature is 330 °C, the first time is 60 min, the second temperature is 400 °C, and the second time is 3 h. The mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughened nano-particles, and acid-treated polyacrylonitrile-based carbon fiber with a carbon-based deposit is: 87:4:8:2.

[0123] Comparative Example 1

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

[0125] Comparative Example 2

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

[0127] Comparative Example 3

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

[0129] Comparative Example 4

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

[0131] Comparative Example 5

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

[0133] Comparative Example 6

[0134] This embodiment provides a poly(tetrafluoroethylene) composite material with impact resistance and thermal stability. The difference from Embodiment 1 is that in S4, the mass ratio of polytetrafluoroethylene powder, modified montmorillonite, toughening nanoparticle coated with rubber, and acid-treated polyacrylonitrile-based carbon fiber with carbon-based deposition is: 85:3:5:1, and other process parameters and operating conditions are exactly the same as those in Embodiment 1.

[0135] Perform performance tests on the impact-resistant and thermally stable poly(tetrafluoroethylene) composite materials of the above Embodiments 1-4 and Comparative Examples 1-6. The specific process is as follows:

[0136] Test the notched impact strength of the samples according to GB / T1043.1-2008 of the national standard. Among them, 5 specimens with dimensions of 100mm×10mm×3mm are prepared for each embodiment or comparative example for testing, and the results are averaged. The impact energy is set to 75J, and the lifting angle of the hammer is set to 150°;

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

[0138] Test the flexural strength of the samples according to GB / T9341-2008 "Determination of Flexural Properties of Plastics" of the national standard;

[0139] Test the heat distortion temperature of the samples according to GB / T1634.2-2004 of the national standard. 5 specimens are tested for each embodiment or comparative example, and the average value is taken; the test results are shown in Table 1.

[0140] Table 1: Performance test results of impact-resistant and thermally stable poly(tetrafluoroethylene) composite materials of Embodiments 1-4 and Comparative Examples 1-6

[0141]

[0142]

[0143] From the test results of Embodiment 1, Comparative Example 1, and Comparative Example 2, it can be seen that when the feeding amount of modified montmorillonite is too high, due to the agglomeration of layered silicates in the matrix, the notched impact strength of the impact-resistant and thermally stable poly(tetrafluoroethylene) composite material drops to 85 kJ / m 2 , the tensile strength decreases to 25 MPa, and the flexural strength decreases to 18 MPa; the heat distortion temperature slightly increases to 98 °C; when the feeding amount of modified montmorillonite is too low, due to the inability to form an effective layered network structure, the heat distortion temperature is only 75 °C, and the improvement effects of the notched impact strength, tensile strength, and flexural strength are not obvious, which are 120 kJ / m 2 , 35 MPa, and 25 MPa respectively.

[0144] From the test results of Example 1 and Comparative Example 3 and Comparative Example 4, when the feeding amount of rubber-coated toughened nanoparticles is too high, due to excessive soft phase damaging the continuity of the matrix, the tensile strength drops to 28 MPa, the flexural strength drops to 20 MPa, the heat distortion temperature drops to 74 °C, and the notched impact strength slightly increases to 140 kJ / m 2 . When the feeding amount of rubber-coated toughened nanoparticles is too low, due to insufficient content of the toughening phase, the notched impact strength is only 95 kJ / m 2 , and other mechanical properties basically remain unchanged.

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

[0146] The applicant declares that the above are only specific embodiments of the present invention, but the protection scope 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 any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope 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 to obtain a surface-modified montmorillonite, and reacting the montmorillonite with a metal salt to obtain a modified montmorillonite; S2: reacting the nanoparticles with a coupling agent to obtain surface-modified nanoparticles, reacting the nanoparticles with a toughening functional monomer to obtain surface-toughened nanoparticles; preparing a surface-toughened nanoparticle dispersion, adding a rubber latex and a crosslinking 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 mixed acid solution to the polyacrylonitrile-based carbon fiber to react and obtain acid-treated polyacrylonitrile-based carbon fiber; using a CVD reactor to perform chemical vapor deposition on the acid-treated polyacrylonitrile-based carbon fiber to obtain carbon-based 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 composite powder, which is then cold-pressed and sintered to obtain impact-resistant and thermally stable polytetrafluoroethylene composite materials.

2. The method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material according to claim 1, characterized in that: In S1, The grafting monomer in the grafting monomer solution is any one of acrylic acid, methyl acrylate, and methacrylic acid; 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 metal salt is any one of zinc nitrate, aluminum chloride and magnesium chloride; 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 nanoparticles are any one of nano-silicon dioxide, nano-aluminum oxide, and nano-calcium carbonate; 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 a shock-resistant and heat-stable polytetrafluoroethylene composite material according to claim 1, characterized in that: In S2, The toughening functional monomer is acrylic acid and / or ethylene glycol; 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 amount of the rubber latex added is 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 cross-linking agent is sulfur and / or epoxy resin; 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 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. The method for preparing an impact-resistant and heat-stable polytetrafluoroethylene composite material according to claim 1, characterized in that: In S4, the mass ratio of the polytetrafluoroethylene powder, modified montmorillonite, rubber-coated toughened nanoparticles and carbon-based deposited acid-treated polyacrylonitrile-based carbon fibers is: (80-90): (2-4): (3-8): (2-5).

10. A polytetrafluoroethylene composite material with impact resistance and heat stability prepared by the method for preparing a polytetrafluoroethylene composite material with impact resistance and heat stability as claimed in any one of claims 1 to 9.

Images