Far infrared nanocarbon fiber film and preparation method thereof

Abstract

The application discloses a far-infrared nanometer carbon fiber film and a preparation method thereof, and belongs to the technical field of nanometer carbon fiber films; the far-infrared nanometer carbon fiber film is prepared by mixing, stirring and uniformly mixing modified nanometer carbon fibers and modified polytetrafluoroethylene according to a mass ratio, then performing airflow pulverization, and then performing high-speed rotary cutting fiberization after heating, and then being placed into a material spreading device to be uniformly spread and flat and to be formed into a shape by hot roller pressing; wherein the modified nanometer carbon fibers are obtained by reacting 3,4-diamino benzoic acid methyl ester with hydroxylated nanometer carbon fibers; the modified polytetrafluoroethylene is obtained by grafting modification of 4-allyl benzoic acid on pre-irradiation treated PTFE; the nanometer carbon fibers in the far-infrared nanometer carbon fiber film prepared by the application are uniformly dispersed, have good conductivity, have a small current density difference under working voltage, have more perfect current distribution, and have more uniform heating.

Description

Technical Field

[0001] This invention relates to a far-infrared carbon nanofiber membrane and its preparation method. Background Technology

[0002] With the rapid development of far-infrared heating technology, its applications in healthcare, smart wearables, and industrial heating are becoming increasingly widespread. As a core heating material, carbon nanofiber membranes have attracted significant attention due to their excellent electrical and thermal conductivity. This material not only provides stable far-infrared radiation but also possesses good mechanical flexibility and a long service life, making it an ideal choice for achieving efficient heating.

[0003] However, the traditional fabrication process of carbon nanofiber membranes still has many problems, limiting their practical application. Currently, the mainstream fabrication methods include chemical vapor deposition and electrospinning, which construct conductive networks by controlling the carbon fiber diameter (50-500 nm) and orientation (±15° deviation). Nevertheless, existing technologies still face some significant drawbacks, such as insufficient fiber dispersion uniformity: due to process limitations, the distribution of carbon nanofibers on the substrate is uneven, with local density differences exceeding 30%. This leads to uneven distribution of conductive pathways, with current density differences exceeding 25% under operating voltage, resulting in localized overheating, with temperature differences reaching up to 10°C. This uneven heating problem seriously affects the user experience and safety of the product.

[0004] Therefore, the applicant prepared a far-infrared carbon nanofiber membrane to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a far-infrared carbon nanofiber film and its preparation method to solve the technical problems mentioned in the background section.

[0006] The technical solution to achieve the purpose of the present invention is as follows: In the first aspect, the present invention provides a far-infrared nanofiber membrane, which is obtained by mixing and stirring modified nanofiber and modified polytetrafluoroethylene evenly, then air-jetting and pulverizing, then heating and high-speed rotary cutting and fiberization, and then placing it into a spreader to spread it evenly and hot roll forming.

[0007] Furthermore, the modified carbon nanofibers are obtained by reacting methyl 3,4-diaminobenzoate with hydroxylated carbon nanofibers.

[0008] Furthermore, the modified polytetrafluoroethylene is obtained by grafting 4-allylbenzoic acid onto pre-irradiated PTFE.

[0009] In a second aspect, the present invention provides a method for preparing a far-infrared carbon nanofiber film according to the first aspect, comprising the following preparation steps:

[0010] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.4 to 1.6:2 and stir until homogeneous;

[0011] S2. The material obtained in step S1 is subjected to air jet milling;

[0012] S3. The material obtained in step S2 is heated and then rapidly rotary-cut into fibers;

[0013] S4. Place the material obtained in step S3 into a spreader and spread it evenly, and then perform hot roll forming.

[0014] Furthermore, the preparation steps of the modified carbon nanofibers are as follows:

[0015] (1) The carbon nanofibers and acid mixture were mixed at a mass ratio of 1:18-22 and ultrasonically treated for 10 min. Then, the mixture was heated to 115-125℃ and stirred under reflux for 1.8-2.2 h. Subsequently, 70-90 times the mass of the carbon nanofibers were added to dilute the mixture with deionized water, and the mixture was filtered. The mixture was then repeatedly washed with deionized water and filtered until the filtrate was neutral. The filtrate was then vacuum dried at 78-82℃ for 23-25 ​​h to obtain acidified carbon nanofibers. The acid mixture was obtained by mixing 60 wt% concentrated nitric acid and 98 wt% concentrated sulfuric acid at a volume ratio of 1:3.

[0016] (2) The acidified carbon nanofibers obtained in step (1) and sulfoxide were mixed at a mass ratio of 1:38-42 and ultrasonically treated for 10 min. Then the temperature was raised to 70-80℃ and stirred and refluxed for 23-25 ​​h. Excess sulfoxide was removed by vacuum distillation to obtain acylated carbon nanofibers.

[0017] (3) The acylated carbon nanofibers obtained in step (2) are mixed with ethylene glycol at a mass ratio of 1:48-52 and ultrasonically treated for 10 min. Then the temperature is raised to 115-125℃ and stirred for 47-49 h. After the reaction is completed, the mixture is diluted with deionized water and filtered. After washing with deionized water and filtering 4-6 times, the mixture is vacuum dried at 78-82℃ for 23-25 ​​h to obtain hydroxylated carbon nanofibers.

[0018] (4) Under nitrogen protection, the hydroxylated carbon nanofibers obtained in step (3), methyl 3,4-diaminobenzoate, p-toluenesulfonic acid, and toluene were mixed in a mass ratio of 1:1.3-1.5:0.006-0.008:5.8-6.2 and ultrasonically treated for 10 min. Then, the temperature was raised to 120-140℃ and refluxed for 6-12 h. After cooling to room temperature, 5% sodium bicarbonate solution was added to adjust the pH of the reaction system to 7-8. Then, the mixture was diluted with deionized water and filtered. The mixture was then washed with deionized water and filtered 2-4 times. Finally, the mixture was vacuum dried at 78-82℃ for 23-25 ​​h to obtain the modified carbon nanofibers.

[0019] Furthermore, the preparation steps of the modified polytetrafluoroethylene are as follows:

[0020] A1: Polytetrafluoroethylene micropowder with a particle size of 0.5–20 μm was placed in an air atmosphere at room temperature with an activity of 1.85 × 10⁻⁶. 14 BQ 60 Pre-irradiated PTFE was obtained by irradiating a Co radioactive source with gamma rays. The absorbed dose of the irradiated PTFE was 100 kGy and the free radical concentration was 8.37 × 10⁻⁶. 17 spins / g;

[0021] A2: Mix 100 parts by weight of deionized water and 0.5-1 parts by weight of surfactant ethoxyperfluorooctyl ethanol, stir and disperse evenly, then add 8-12 parts by weight of pre-irradiated PTFE, continue stirring to suspend the pre-irradiated PTFE evenly in the aqueous solution, then add 18-22 parts by weight of 4-allylbenzoic acid, 0.008-0.012 parts by weight of polymerization inhibitor ferrous ammonium sulfate, and 0.08-0.12 parts by weight of concentrated sulfuric acid. Under nitrogen protection, stir and react in a water bath at 68-72℃ for 4.5-5.5 hours. After the reaction is complete, centrifuge to separate the supernatant, remove the supernatant, and redisperse the obtained precipitate with water and centrifuge again. Repeat the above steps 9-11 times. Then dry in a forced-air oven at 55-65℃ for 23-25 ​​hours to obtain modified polytetrafluoroethylene.

[0022] The modification mechanism of modified polytetrafluoroethylene is as follows:

[0023]

[0024] Further, the specific steps of mixing and stirring in step S1 are as follows: S1.1 Revolution speed 800-1200 r / min, time 8-12 min, revolution-to-rotation speed ratio 90%-110%; S1.2 Revolution speed 1800-2200 r / min, time 14-16 min, revolution-to-rotation speed ratio 110%-130%; S1.3 Revolution speed 1200-1800 r / min, time 8-12 min, revolution-to-rotation speed ratio 110%-130%.

[0025] Furthermore, in step S2, the feeding air pressure for air jet milling is 0.5–0.7 MPa, the milling pressure is 0.3–0.5 MPa, and the feeding air pressure is greater than the milling pressure.

[0026] Furthermore, the heating in step S3 adopts a two-stage heating method. The first stage heating temperature is 210-230℃, and the heating time is 10-20 min. The second stage heating temperature is 300-320℃, and the heating time is 40-50 min. The high-speed rotary cutting steps in step S3 are as follows: S3.2.1 Rotation speed 1800-2200 r / min, time 4-6 min; S3.2.2 Rotation speed 3500-4500 r / min, time 8-12 min; S3.2.3 Rotation speed 5500-6500 r / min, time 4-6 min.

[0027] Further, the specific steps of step S4 are as follows: under nitrogen protection, the material is placed in a spreader and evenly spread, and then hot-rolled to form a film. The rolling temperature is 345-355℃, the pressure is 1-100t, the gap between the hot rollers is 0-2mm, the hot rolling is performed 2-3 times, and the rolling thickness is 135-145μm, thus obtaining a far-infrared carbon nanofiber film.

[0028] By adopting the above technical solution, the present invention has the following beneficial effects:

[0029] (1) The far-infrared carbon nanofiber membrane of the present invention is made by first mixing and stirring modified carbon nanofiber and modified polytetrafluoroethylene evenly, then air-jetting, then heating and high-speed rotary cutting. During the high-speed rotary cutting process, the modified carbon nanofiber and the adhesive modified polytetrafluoroethylene form fibers and complete the fiberization. Then, it is placed in a spreader and evenly spread and hot-rolled to form the far-infrared carbon nanofiber membrane. The carbon nanofiber in the membrane is evenly dispersed, has good conductivity, and has a small difference in current density under working voltage, resulting in more perfect current distribution and more uniform heating.

[0030] (2) The modified carbon nanofibers of the present invention are obtained by transesterification reaction of methyl 3,4-diaminobenzoate and hydroxylated carbon nanofibers. The modified polytetrafluoroethylene is obtained by grafting 4-allylbenzoic acid onto pre-irradiated PTFE. A large number of amino and other active groups are introduced on the surface of the carbon nanofibers, and a large number of carboxyl groups are grafted onto the surface of the modified polytetrafluoroethylene to make the mixture of modified carbon nanofibers and modified polytetrafluoroethylene more uniform. The dispersibility of the modified carbon nanofibers in the far-infrared carbon nanofiber film makes the heating of the far-infrared carbon nanofiber film more uniform under the working voltage.

[0031] (3) In this invention, the modified carbon nanofibers and modified polytetrafluoroethylene are first mixed and stirred evenly, then air-jet pulverized, then heated and high-speed rotary-cut into fibers, and then placed in a spreader to be evenly spread and hot-rolled to obtain a far-infrared carbon nanofiber membrane. In this invention, the o-phenylenediamine on the modified carbon nanofibers reacts with the benzoic acid on the modified polytetrafluoroethylene to form a benzimidazole polymer network in the far-infrared carbon nanofiber membrane, which evenly disperses the modified carbon nanofibers in the modified polytetrafluoroethylene to form a uniform conductive network, thereby enhancing the conductivity of the far-infrared carbon nanofiber membrane. This also makes the heating of the far-infrared carbon nanofiber membrane under the working voltage more uniform and enhances the mechanical properties of the far-infrared carbon nanofiber membrane.

[0032] (4) The present invention uses a method to prepare far-infrared carbon nanofiber membrane by first mixing and stirring the modified carbon nanofiber and modified polytetrafluoroethylene evenly, then performing air jet pulverization, followed by heating and high-speed rotary cutting and fiberization, and then placing it into a spreader for even spreading and hot rolling molding. The process is convenient and, compared with the traditional carbon nanofiber membrane preparation process, no solvent is required, which reduces VOC emissions, improves environmental protection performance, and the yield of the obtained carbon nanofiber membrane is high. It produces stable far-infrared rays, has good conductivity, and has a long life. Detailed Implementation

[0033] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0034] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0035] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0036] The following are the raw materials used in the embodiments and comparative examples of this invention:

[0037] The diameter of the carbon nanofiber is about 150 nm and the length is between 10 and 20 μm.

[0038] (Example 1)

[0039] A method for preparing a far-infrared carbon nanofiber film includes the following preparation steps:

[0040] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.4:2 until homogeneous; the specific mixing steps are as follows: S1.1 Revolution speed 800 r / min, time 8 min, revolution-to-rotation speed ratio 90%; S1.2 Revolution speed 1800 r / min, time 14 min, revolution-to-rotation speed ratio 110%; S1.3 Revolution speed 1200 r / min, time 8 min, revolution-to-rotation speed ratio 110%.

[0041] S2. The material obtained in step S1 is subjected to airflow pulverization, wherein the feeding airflow pressure is 0.5 MPa and the pulverization pressure is 0.3 MPa;

[0042] S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting for fiberization. The heating is carried out in two stages: the first stage heating temperature is 210℃ and the heating time is 10 min; the second stage heating temperature is 300℃ and the heating time is 40 min. The specific steps of high-speed rotary cutting are as follows: S3.2.1 Rotation speed 1800 r / min, time 4 min; S3.2.2 Rotation speed 3500 r / min, time 8 min; S3.2.3 Rotation speed 5500 r / min, time 4 min.

[0043] S4. Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled to form a film. The rolling temperature is 345℃, the pressure is 50t, the gap between the hot rollers is 1mm, the hot rolling is performed twice, and the rolling thickness is 135μm, thus preparing a far-infrared carbon nanofiber membrane.

[0044] The preparation steps of the modified carbon nanofibers are as follows:

[0045] (1) After mixing carbon nanofibers and acid mixture at a mass ratio of 1:18, the mixture was treated with ultrasonic waves at 25 kHz for 10 min, then heated to 115 °C and stirred under reflux for 1.8 h. Subsequently, 70 times the mass of carbon nanofibers was added to dilute the mixture with deionized water, and the mixture was filtered through a mixed fiber microporous membrane with a pore size of 0.22 μm. The mixture was then repeatedly washed with deionized water and filtered until the filtrate was neutral. The filtrate was then vacuum dried at 78 °C for 23 h to obtain acidified carbon nanofibers. The acid mixture was obtained by mixing 60 wt% concentrated nitric acid and 98 wt% concentrated sulfuric acid at a volume ratio of 1:3.

[0046] (2) The acidified carbon nanofibers obtained in step (1) and sulfoxide were mixed at a mass ratio of 1:38, and then treated with ultrasonic waves at 25 kHz for 10 min. After that, the temperature was raised to 70 °C and stirred and refluxed for 23 h. Excess sulfoxide was removed by vacuum distillation to obtain acylated carbon nanofibers.

[0047] (3) The acylated carbon nanofibers obtained in step (2) were mixed with ethylene glycol at a mass ratio of 1:48, and then treated with ultrasonic waves at 25 kHz for 10 min. After that, the temperature was raised to 115 °C and stirred for 47 h. After the reaction was completed, the mixture was diluted with deionized water and filtered to remove excess ethylene glycol and reaction byproducts. The mixture was washed with deionized water and filtered 4 times. Then, it was vacuum dried at 78 °C for 23 h to obtain hydroxylated carbon nanofibers.

[0048] (4) Under nitrogen protection, the hydroxylated carbon nanofibers obtained in step (3), methyl 3,4-diaminobenzoate, p-toluenesulfonic acid and toluene were mixed in a mass ratio of 1:1.3:0.006:5.8 and ultrasonically treated for 10 min. Then the temperature was raised to 120℃ and refluxed for 6 h. After cooling to room temperature, 5% sodium bicarbonate solution was added to adjust the pH of the reaction system to 7. Then the mixture was diluted with deionized water and filtered. The mixture was then washed and filtered twice with deionized water. Finally, it was vacuum dried at 78℃ for 23 h to obtain the modified carbon nanofibers.

[0049] The preparation steps of the modified polytetrafluoroethylene are as follows:

[0050] A1: Polytetrafluoroethylene micropowder with a particle size of 1 μm was placed in an air atmosphere at room temperature with an activity of 1.85 × 10⁻⁶. 14 BQ 60 Pre-irradiated PTFE was obtained by irradiating a Co radioactive source with gamma rays. The absorbed dose of the irradiated PTFE was 100 kGy and the free radical concentration was 8.37 × 10⁻⁶. 17 spins / g;

[0051] A2: Mix 100 parts by weight of deionized water and 0.5 parts by weight of surfactant ethoxyperfluorooctyl ethanol, stir and disperse evenly, then add 8 parts by weight of pre-irradiated PTFE, continue stirring to suspend the pre-irradiated PTFE evenly in the aqueous solution, then add 18 parts by weight of 4-allylbenzoic acid, 0.008 parts by weight of polymerization inhibitor ferrous ammonium sulfate, and 0.08 parts by weight of concentrated sulfuric acid. Under nitrogen protection, stir and react in a water bath at 68°C for 4.5 hours. After the reaction is completed, centrifuge to separate the supernatant, remove the supernatant, and redisperse the obtained precipitate with water and centrifuge again. Repeat the above steps 9 times. Then dry in a forced-air oven at 55°C for 23 hours to obtain modified polytetrafluoroethylene.

[0052] (Example 2)

[0053] A method for preparing a far-infrared carbon nanofiber film includes the following preparation steps:

[0054] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.5:2 until homogeneous; the specific mixing steps are as follows: S1.1 Revolution speed 1000 r / min, time 10 min, revolution-to-rotation speed ratio 100%; S1.2 Revolution speed 2000 r / min, time 15 min, revolution-to-rotation speed ratio 120%; S1.3 Revolution speed 1500 r / min, time 10 min, revolution-to-rotation speed ratio 120%.

[0055] S2. The material obtained in step S1 is subjected to airflow pulverization, wherein the feeding airflow pressure is 0.6 MPa and the pulverization pressure is 0.4 MPa;

[0056] S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting for fiberization. The heating is carried out in two stages: the first stage heating temperature is 220℃ and the heating time is 15 min; the second stage heating temperature is 310℃ and the heating time is 45 min. The specific steps of high-speed rotary cutting are as follows: S3.2.1 Rotation speed 2000 r / min, time 5 min; S3.2.2 Rotation speed 4000 r / min, time 10 min; S3.2.3 Rotation speed 6000 r / min, time 5 min.

[0057] S4. Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled to form a film. The rolling temperature is 350℃, the pressure is 30t, the gap between the hot rollers is 2mm, the hot rolling is performed twice, and the rolling thickness is 140μm, thus preparing a far-infrared carbon nanofiber membrane.

[0058] The preparation steps of the modified carbon nanofibers are as follows:

[0059] (1) After mixing carbon nanofibers and acid mixture at a mass ratio of 1:20, the mixture was treated with ultrasonic waves at 25 kHz for 10 min, then heated to 120 ℃ and stirred under reflux for 2 h. Subsequently, deionized water at a mass ratio of 80 times that of carbon nanofibers was added for dilution, and the mixture was filtered through a mixed fiber microporous membrane with a pore size of 0.22 μm. The mixture was then repeatedly washed with deionized water and filtered until the filtrate was neutral. The filtrate was then vacuum dried at 80 ℃ for 24 h to obtain acidified carbon nanofibers. The acid mixture was obtained by mixing 60 wt% concentrated nitric acid and 98 wt% concentrated sulfuric acid at a volume ratio of 1:3.

[0060] (2) The acidified carbon nanofibers obtained in step (1) and sulfonium chloride were mixed at a mass ratio of 1:40, and then treated with ultrasonic waves at 25 kHz for 10 min. After that, the temperature was raised to 75 °C and stirred and refluxed for 24 h. Excess sulfonium chloride was removed by vacuum distillation to obtain acylated carbon nanofibers.

[0061] (3) The acylated carbon nanofibers obtained in step (2) were mixed with ethylene glycol at a mass ratio of 1:50, and then treated with ultrasonic waves at 25 kHz for 10 min. After that, the temperature was raised to 120 °C and stirred for 48 h. After the reaction was completed, the mixture was diluted with deionized water and filtered to remove excess ethylene glycol and reaction byproducts. The mixture was washed with deionized water and filtered 5 times. Then, it was vacuum dried at 80 °C for 234 h to obtain hydroxylated carbon nanofibers.

[0062] (4) Under nitrogen protection, the hydroxylated carbon nanofibers obtained in step (3), methyl 3,4-diaminobenzoate, p-toluenesulfonic acid and toluene were mixed in a mass ratio of 1:1.4:0.007:6 and ultrasonically treated for 10 min. Then the temperature was raised to 130℃ and refluxed for 9 h. After cooling to room temperature, 5% sodium bicarbonate solution was added to adjust the pH of the reaction system to 7.5. Then the mixture was diluted with deionized water and filtered. The mixture was then washed with deionized water and filtered three times. Finally, the mixture was vacuum dried at 80℃ for 24 h to obtain the modified carbon nanofibers.

[0063] The preparation steps of the modified polytetrafluoroethylene are as follows:

[0064] A1: Polytetrafluoroethylene micropowder with a particle size of 10 μm was placed in an air atmosphere at room temperature with an activity of 1.85 × 10⁻⁶. 14 BQ 60 Pre-irradiated PTFE was obtained by irradiating a Co radioactive source with gamma rays. The absorbed dose of the irradiated PTFE was 100 kGy and the free radical concentration was 8.37 × 10⁻⁶. 17 spins / g;

[0065] A2: Mix 100 parts by weight of deionized water and 0.8 parts by weight of surfactant ethoxyperfluorooctyl ethanol, stir and disperse evenly, then add 10 parts by weight of pre-irradiated PTFE, continue stirring to suspend the pre-irradiated PTFE evenly in the aqueous solution, then add 20 parts by weight of 4-allylbenzoic acid, 0.01 parts by weight of polymerization inhibitor ferrous ammonium sulfate, and 0.1 parts by weight of concentrated sulfuric acid. Under nitrogen protection, stir and react in a 70°C water bath for 5 hours. After the reaction is completed, centrifuge to separate the supernatant, remove the supernatant, and redisperse the obtained precipitate with water and centrifuge again. Repeat the above steps 10 times, then dry in a forced-air oven at 60°C for 24 hours to obtain modified polytetrafluoroethylene.

[0066] (Example 3)

[0067] A method for preparing a far-infrared carbon nanofiber film includes the following preparation steps:

[0068] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.6:2 until homogeneous; the specific mixing steps are as follows: S1.1 Revolution speed 1200 r / min, time 12 min, revolution-to-rotation speed ratio 110%; S1.2 Revolution speed 2200 r / min, time 16 min, revolution-to-rotation speed ratio 130%; S1.3 Revolution speed 1800 r / min, time 12 min, revolution-to-rotation speed ratio 130%.

[0069] S2. The material obtained in step S1 is subjected to airflow pulverization, wherein the feeding airflow pressure is 0.7 MPa and the pulverization pressure is 0.5 MPa;

[0070] S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting for fiberization. The heating is carried out in two stages: the first stage heating temperature is 230℃ and the heating time is 20 min; the second stage heating temperature is 320℃ and the heating time is 50 min. The specific steps of high-speed rotary cutting are as follows: S3.2.1 Rotation speed 2200 r / min, time 6 min; S3.2.2 Rotation speed 4500 r / min, time 12 min; S3.2.3 Rotation speed 6500 r / min, time 6 min.

[0071] S4. Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled to form a film. The rolling temperature is 355℃, the pressure is 100t, the gap between the hot rollers is 2mm, the hot rolling is performed 3 times, and the rolling thickness is 145μm, thus preparing a far-infrared carbon nanofiber film.

[0072] The preparation steps of the modified carbon nanofibers are as follows:

[0073] (1) After mixing carbon nanofibers and acid mixture at a mass ratio of 1:22, the mixture was treated with ultrasonic waves at 25 kHz for 10 min, then heated to 125 °C and stirred under reflux for 2.2 h. Subsequently, 90 times the mass of carbon nanofibers of deionized water was added for dilution, and the mixture was filtered through a mixed fiber microporous membrane with a pore size of 0.22 μm. The mixture was then repeatedly washed with deionized water and filtered until the filtrate was neutral. The filtrate was then vacuum dried at 82 °C for 25 h to obtain acidified carbon nanofibers. The acid mixture was obtained by mixing 60 wt% concentrated nitric acid and 98 wt% concentrated sulfuric acid at a volume ratio of 1:3.

[0074] (2) The acidified carbon nanofibers obtained in step (1) and sulfoxide were mixed at a mass ratio of 1:42, and then treated with ultrasonic waves at 25 kHz for 10 min. After that, the temperature was raised to 80 °C and stirred and refluxed for 25 h. Excess sulfoxide was removed by vacuum distillation to obtain acylated carbon nanofibers.

[0075] (3) The acylated carbon nanofibers obtained in step (2) were mixed with ethylene glycol at a mass ratio of 1:52, and then treated with ultrasonic waves at 25 kHz for 10 min. After that, the temperature was raised to 125 °C and stirred for 49 h. After the reaction was completed, the mixture was diluted with deionized water and filtered to remove excess ethylene glycol and reaction byproducts. The mixture was washed with deionized water and filtered 6 times. Then, it was vacuum dried at 82 °C for 25 h to obtain hydroxylated carbon nanofibers.

[0076] (4) Under nitrogen protection, the hydroxylated carbon nanofibers obtained in step (3), methyl 3,4-diaminobenzoate, p-toluenesulfonic acid and toluene were mixed in a mass ratio of 1:1.5:0.008:6.2 and ultrasonically treated for 10 min. Then the temperature was raised to 140℃ and refluxed for 12 h. After cooling to room temperature, 5% sodium bicarbonate solution was added to adjust the pH of the reaction system to 8. Then the mixture was diluted with deionized water and filtered. The mixture was then washed and filtered repeatedly with deionized water 4 times. Finally, the mixture was vacuum dried at 82℃ for 25 h to obtain the modified carbon nanofibers.

[0077] The preparation steps of the modified polytetrafluoroethylene are as follows:

[0078] A1: Polytetrafluoroethylene micropowder with a particle size of 20 μm was placed in an air atmosphere at room temperature with an activity of 1.85 × 10⁻⁶. 14 BQ 60 Pre-irradiated PTFE was obtained by irradiating a Co radioactive source with gamma rays. The absorbed dose of the irradiated PTFE was 100 kGy and the free radical concentration was 8.37 × 10⁻⁶. 17 spins / g;

[0079] A2: Mix 100 parts by mass of deionized water and 1 part by mass of surfactant ethoxyperfluorooctyl ethanol, stir and disperse evenly, then add 12 parts by mass of pre-irradiated PTFE, continue stirring to suspend the pre-irradiated PTFE evenly in the aqueous solution, then add 22 parts by mass of 4-allylbenzoic acid, 0.012 parts by mass of polymerization inhibitor ferrous ammonium sulfate, and 0.12 parts by mass of concentrated sulfuric acid. Under nitrogen protection, stir and react in a water bath at 72°C for 5.5 hours. After the reaction is completed, centrifuge to separate the supernatant, remove the supernatant, and redisperse the obtained precipitate with water and centrifuge again. Repeat the above steps 11 times, then dry in a forced-air oven at 65°C for 25 hours to obtain modified polytetrafluoroethylene.

[0080] (Comparative Example 1)

[0081] The difference between Comparative Example 1 and Example 2 is that the far-infrared carbon nanofiber membrane of Comparative Example 1 was prepared using carbon nanofiber and modified polytetrafluoroethylene as raw materials, while the remaining components and steps were the same as those of Example 2.

[0082] (Comparative Example 2)

[0083] The difference between Comparative Example 2 and Example 2 is that the far-infrared carbon nanofiber membrane of Comparative Example 2 was prepared using modified carbon nanofiber and polytetrafluoroethylene as raw materials, while the other components and steps were the same as those of Example 2.

[0084] (Comparative Example 3)

[0085] The difference between Comparative Example 3 and Example 2 lies in the preparation steps of the far-infrared carbon nanofiber film; the remaining components and steps are the same as in Example 2. The preparation steps of the far-infrared carbon nanofiber film in Comparative Example 3 are as follows:

[0086] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.5:2 until homogeneous; the specific mixing steps are as follows: S1.1 Revolution speed 1000 r / min, time 10 min, revolution-to-rotation speed ratio 100%; S1.2 Revolution speed 2000 r / min, time 15 min, revolution-to-rotation speed ratio 120%; S1.3 Revolution speed 1500 r / min, time 10 min, revolution-to-rotation speed ratio 120%.

[0087] S2. The material obtained in step S1 is subjected to airflow pulverization, wherein the feeding airflow pressure is 0.6 MPa and the pulverization pressure is 0.4 MPa;

[0088] S3. Perform high-speed rotary cutting on the material obtained in step S2. The specific steps of high-speed rotary cutting are as follows: S3.2.1 Rotation speed 2000 r / min, time 5 min; S3.2.2 Rotation speed 4000 r / min, time 10 min; S3.2.3 Rotation speed 6000 r / min, time 5 min;

[0089] S4. Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled to form a film. The rolling temperature is 350℃, the pressure is 30t, the gap between the hot rollers is 2mm, the hot rolling is performed twice, and the rolling thickness is 140μm, thus preparing a far-infrared carbon nanofiber membrane.

[0090] (Comparative Example 4)

[0091] The difference between Comparative Example 4 and Example 2 lies in the preparation steps of the far-infrared carbon nanofiber film; the remaining components and steps are the same as in Example 2. The preparation steps of the far-infrared carbon nanofiber film in Comparative Example 4 are as follows:

[0092] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.5:2 until homogeneous; the specific mixing steps are as follows: S1.1 Revolution speed 1000 r / min, time 10 min, revolution-to-rotation speed ratio 100%; S1.2 Revolution speed 2000 r / min, time 15 min, revolution-to-rotation speed ratio 120%; S1.3 Revolution speed 1500 r / min, time 10 min, revolution-to-rotation speed ratio 120%.

[0093] S2. The material obtained in step S1 is subjected to airflow pulverization, wherein the feeding airflow pressure is 0.6 MPa and the pulverization pressure is 0.4 MPa;

[0094] S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting for fiberization. The heating temperature is 220℃ and the heating time is 60 min. The specific steps of high-speed rotary cutting are as follows: S3.2.1 Rotation speed 2000 r / min, time 5 min; S3.2.2 Rotation speed 4000 r / min, time 10 min; S3.2.3 Rotation speed 6000 r / min, time 5 min.

[0095] S4. Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled to form a film. The rolling temperature is 350℃, the pressure is 30t, the gap between the hot rollers is 2mm, the hot rolling is performed twice, and the rolling thickness is 140μm, thus preparing a far-infrared carbon nanofiber membrane.

[0096] (Comparative Example 5)

[0097] The difference between Comparative Example 5 and Example 2 lies in the preparation steps of the far-infrared carbon nanofiber film; the remaining components and steps are the same as in Example 2. The preparation steps of the far-infrared carbon nanofiber film in Comparative Example 5 are as follows:

[0098] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.5:2 until homogeneous; the specific mixing steps are as follows: S1.1 Revolution speed 1000 r / min, time 10 min, revolution-to-rotation speed ratio 100%; S1.2 Revolution speed 2000 r / min, time 15 min, revolution-to-rotation speed ratio 120%; S1.3 Revolution speed 1500 r / min, time 10 min, revolution-to-rotation speed ratio 120%.

[0099] S2. The material obtained in step S1 is subjected to airflow pulverization, wherein the feeding airflow pressure is 0.6 MPa and the pulverization pressure is 0.4 MPa;

[0100] S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting for fiberization. The heating temperature is 310℃ and the heating time is 60 min. The specific steps of high-speed rotary cutting are as follows: S3.2.1 Rotation speed 2000 r / min, time 5 min; S3.2.2 Rotation speed 4000 r / min, time 10 min; S3.2.3 Rotation speed 6000 r / min, time 5 min.

[0101] S4. Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled to form a film. The rolling temperature is 350℃, the pressure is 30t, the gap between the hot rollers is 2mm, the hot rolling is performed twice, and the rolling thickness is 140μm, thus preparing a far-infrared carbon nanofiber membrane.

[0102] (Comparative Example 6)

[0103] The difference between Comparative Example 6 and Example 2 lies in the preparation steps of the far-infrared carbon nanofiber film; the remaining components and steps are the same as in Example 2. The preparation steps of the far-infrared carbon nanofiber film in Comparative Example 6 are as follows:

[0104] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.5:2 until homogeneous; the specific mixing steps are as follows: S1.1 Revolution speed 1000 r / min, time 10 min, revolution-to-rotation speed ratio 100%; S1.2 Revolution speed 2000 r / min, time 15 min, revolution-to-rotation speed ratio 120%; S1.3 Revolution speed 1500 r / min, time 10 min, revolution-to-rotation speed ratio 120%.

[0105] S2. The material obtained in step S1 is subjected to airflow pulverization, wherein the feeding airflow pressure is 0.6 MPa and the pulverization pressure is 0.4 MPa;

[0106] S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting for fiberization. The heating is carried out in two stages: the first stage heating temperature is 220℃ and the heating time is 15 min; the second stage heating temperature is 310℃ and the heating time is 45 min. The specific steps of high-speed rotary cutting are as follows: S3.2.1 Rotation speed 2000 r / min, time 5 min; S3.2.2 Rotation speed 4000 r / min, time 10 min; S3.2.3 Rotation speed 6000 r / min, time 5 min.

[0107] S4. Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled to form a film. The rolling temperature is 340℃, the pressure is 30t, the gap between the hot rollers is 2mm, the hot rolling is performed twice, and the rolling thickness is 140μm, thus preparing a far-infrared carbon nanofiber membrane.

[0108] (Comparative Example 7)

[0109] The difference between Comparative Example 7 and Example 2 lies in the preparation steps of the far-infrared carbon nanofiber film; the remaining components and steps are the same as in Example 2. The preparation steps of the far-infrared carbon nanofiber film in Comparative Example 7 are as follows:

[0110] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.5:2 until homogeneous; the specific mixing steps are as follows: S1.1 Revolution speed 1000 r / min, time 10 min, revolution-to-rotation speed ratio 100%; S1.2 Revolution speed 2000 r / min, time 15 min, revolution-to-rotation speed ratio 120%; S1.3 Revolution speed 1500 r / min, time 10 min, revolution-to-rotation speed ratio 120%.

[0111] S2. The material obtained in step S1 is subjected to airflow pulverization, wherein the feeding airflow pressure is 0.6 MPa and the pulverization pressure is 0.4 MPa;

[0112] S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting for fiberization. The heating is carried out in two stages: the first stage heating temperature is 220℃ and the heating time is 15 min; the second stage heating temperature is 310℃ and the heating time is 45 min. The specific steps of high-speed rotary cutting are as follows: S3.2.1 Rotation speed 2000 r / min, time 5 min; S3.2.2 Rotation speed 4000 r / min, time 10 min; S3.2.3 Rotation speed 6000 r / min, time 5 min.

[0113] S4. Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled to form a film. The rolling temperature is 335℃, the pressure is 30t, the gap between the hot rollers is 2mm, the hot rolling is performed twice, and the rolling thickness is 140μm, thus preparing a far-infrared carbon nanofiber membrane.

[0114] (Comparative Example 8)

[0115] The difference between Comparative Example 8 and Example 2 lies in the preparation steps of the far-infrared carbon nanofiber film; the remaining components and steps are the same as in Example 2. The preparation steps of the far-infrared carbon nanofiber film in Comparative Example 8 are as follows:

[0116] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.5:2 until homogeneous; the specific mixing steps are as follows: S1.1 Revolution speed 1000 r / min, time 10 min, revolution-to-rotation speed ratio 100%; S1.2 Revolution speed 2000 r / min, time 15 min, revolution-to-rotation speed ratio 120%; S1.3 Revolution speed 1500 r / min, time 10 min, revolution-to-rotation speed ratio 120%.

[0117] S2. The material obtained in step S1 is subjected to airflow pulverization, wherein the feeding airflow pressure is 0.6 MPa and the pulverization pressure is 0.4 MPa;

[0118] S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting for fiberization. The heating is carried out in two stages: the first stage heating temperature is 220℃ and the heating time is 15 min; the second stage heating temperature is 310℃ and the heating time is 45 min. The specific steps of high-speed rotary cutting are as follows: S3.2.1 Rotation speed 2000 r / min, time 5 min; S3.2.2 Rotation speed 4000 r / min, time 10 min; S3.2.3 Rotation speed 6000 r / min, time 5 min.

[0119] S4. Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled to form a film. The rolling temperature is 360℃, the pressure is 30t, the gap between the hot rollers is 2mm, the hot rolling is performed twice, and the rolling thickness is 140μm, thus preparing a far-infrared carbon nanofiber membrane.

[0120] (Comparative Example 9)

[0121] The difference between Comparative Example 9 and Example 2 lies in the preparation steps of the far-infrared carbon nanofiber film; the remaining components and steps are the same as in Example 2. The preparation steps of the far-infrared carbon nanofiber film in Comparative Example 9 are as follows:

[0122] S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.5:2 until homogeneous; the specific mixing steps are as follows: S1.1 Revolution speed 1000 r / min, time 10 min, revolution-to-rotation speed ratio 100%; S1.2 Revolution speed 2000 r / min, time 15 min, revolution-to-rotation speed ratio 120%; S1.3 Revolution speed 1500 r / min, time 10 min, revolution-to-rotation speed ratio 120%.

[0123] S2. The material obtained in step S1 is subjected to airflow pulverization, wherein the feeding airflow pressure is 0.6 MPa and the pulverization pressure is 0.4 MPa;

[0124] S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting for fiberization. The heating is carried out in two stages: the first stage heating temperature is 220℃ and the heating time is 15 min; the second stage heating temperature is 310℃ and the heating time is 45 min. The specific steps of high-speed rotary cutting are as follows: S3.2.1 Rotation speed 2000 r / min, time 5 min; S3.2.2 Rotation speed 4000 r / min, time 10 min; S3.2.3 Rotation speed 6000 r / min, time 5 min.

[0125] S4. Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled to form a film. The rolling temperature is 365℃, the pressure is 30t, the gap between the hot rollers is 2mm, the hot rolling is performed twice, and the rolling thickness is 140μm, thus preparing a far-infrared carbon nanofiber membrane.

[0126] Example of effect

[0127] Tensile strength test: The far-infrared carbon nanofiber films prepared in the examples and comparative examples were made into specimens with a width of (10+0.1) mm and a length of 80±2 mm. Tensile strength was then tested using a tensile testing machine with an initial distance of (80±5) mm between the clamps and a testing speed of 3 mm / min.

[0128] Resistivity test: The far-infrared carbon nanofiber films prepared in the examples and comparative examples were cut into 3×3cm squares and placed under the four-probe needle for testing to obtain the resistance value of the material. The resistivity of the material can be calculated according to the resistivity formula ρ=R·s / L=R·d·ω / L, where ρ represents the resistivity of the material (mΩ·cm), R represents the resistance of the material (mΩ / sq), d represents the thickness of the material (cm), ω represents the width of the material (cm), and L represents the length of the material (cm).

[0129] Table 1 below shows the performance test results of the far-infrared carbon nanofiber films prepared in Examples 1-3 and Comparative Examples 1-9:

[0130] Table 1

[0131] Tensile strength (MPa) Resistivity (mΩ*cm) Example 1 8.70 28.69 Example 2 8.86 28.36 Example 3 8.64 29.02 Comparative Example 1 2.64 336.32 Comparative Example 2 2.59 335.87 Comparative Example 3 3.03 322.36 Comparative Example 4 4.36 69.05 Comparative Example 5 3.34 66.96 Comparative Example 6 8.06 28.73 Comparative Example 7 7.83 28.92 Comparative Example 8 7.66 28.56 Comparative Example 9 6.98 28.83

[0132] Comparing the data from Examples 1-3 and Comparative Examples 1-9 in Table 1, it can be seen that the far-infrared carbon nanofiber films prepared in Examples 1-3 have better mechanical and electrical properties.

[0133] Compared with Example 2, the far-infrared carbon nanofiber membrane of Comparative Example 1 was made from carbon nanofiber and modified polytetrafluoroethylene. The tensile strength of the far-infrared carbon nanofiber membrane was 3.03 MPa and the resistivity was 336.32 mΩ*cm. The mechanical properties and electrical conductivity of the far-infrared carbon nanofiber membrane of Comparative Example 1 were weaker than those of Example 2.

[0134] Compared with Example 2, the far-infrared carbon nanofiber membrane of Comparative Example 2 was made from modified carbon nanofiber and polytetrafluoroethylene. The tensile strength of the far-infrared carbon nanofiber membrane was 3.03 MPa and the resistivity was 335.87 mΩ*cm. The mechanical properties and electrical conductivity of the far-infrared carbon nanofiber membrane of Comparative Example 2 were weaker than those of Example 2.

[0135] Compared with Example 2, Comparative Examples 3-5 show that in the preparation of the far-infrared carbon nanofiber membrane in Comparative Example 3, high-speed dispersion was carried out without heating after air jet pulverization. The resulting far-infrared carbon nanofiber membrane had a tensile strength of 3.03 MPa and a resistivity of 322.36 mΩ*cm. This may be because the high-speed dispersion of the far-infrared carbon nanofiber membrane in Comparative Example 3 without heating after air jet pulverization prevented the formation of a polymer network within the membrane, resulting in weaker dispersibility of the carbon nanofibers. Therefore, the mechanical properties and electrical conductivity of the far-infrared carbon nanofiber membrane in Comparative Example 3 were significantly different from those in Example 2. The performance is relatively weak. In the process of preparing far-infrared carbon nanofiber membrane in Comparative Example 4, the heating was carried out only at 220°C after air jet pulverization. In the process of preparing far-infrared carbon nanofiber membrane in Comparative Example 5, the heating was carried out only at 310°C after air jet pulverization. The tensile strengths of the far-infrared carbon nanofiber membranes prepared in Comparative Examples 4 and 5 are 4.36 MPa and 3.34 MPa, respectively; the resistivity is 69.05 mΩ*cm and 66.96 mΩ*cm, respectively. Compared with Example 2, the far-infrared carbon nanofiber membrane prepared by two-stage heating in Example 2 has better mechanical and electrical properties.

[0136] Compared with Example 2, Comparative Examples 6-10 had hot rolling temperatures of 340°C, 335°C, 360°C, and 365°C respectively during the preparation of far-infrared carbon nanofiber films. The tensile strengths of the far-infrared carbon nanofiber films obtained in Comparative Examples 6-10 were 8.06 MPa, 7.83 MPa, 7.66 MPa, and 6.98 MPa respectively, which were lower than the tensile strength of 8.86 MPa of the far-infrared carbon nanofiber film obtained in Example 2. This may be because the polytetrafluoroethylene in the far-infrared carbon nanofiber film partially decomposes at high temperatures above 355°C, resulting in weaker mechanical properties of the far-infrared carbon nanofiber film; and the incomplete reaction to form a benzimidazole polymer network at temperatures below 345°C resulted in weaker mechanical properties of the far-infrared carbon nanofiber film compared to Example 2.

[0137] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A far-infrared carbon nanofiber membrane, characterized in that, The far-infrared carbon nanofiber membrane is obtained by mixing modified carbon nanofibers and modified polytetrafluoroethylene evenly, then air-jetting and pulverizing, followed by heating and high-speed rotary cutting and fiberization, and then spreading it evenly in a spreader and hot rolling to form a film; the modified carbon nanofibers are obtained by reacting methyl 3,4-diaminobenzoate with hydroxylated carbon nanofibers; the modified polytetrafluoroethylene is obtained by grafting 4-allylbenzoic acid onto pre-irradiated PTFE.

2. A method for preparing a far-infrared carbon nanofiber film as described in claim 1, characterized in that, The preparation steps include the following: S1. Mix the modified carbon nanofibers and modified polytetrafluoroethylene at a mass ratio of 1.4 to 1.6:2 and stir until homogeneous; S2. The material obtained in step S1 is subjected to air jet milling; S3. The material obtained in step S2 is heated and then rapidly rotary-cut into fibers; S4. Place the material obtained in step S3 into a spreader and spread it evenly, and then perform hot roll forming.

3. The method for preparing far-infrared carbon nanofiber film according to claim 2, characterized in that, The preparation steps of the modified carbon nanofibers are as follows: (1) The carbon nanofibers and acid mixture were mixed at a mass ratio of 1:18-22 and ultrasonically treated for 10 min. Then, the mixture was heated to 115-125℃ and stirred under reflux for 1.8-2.2 h. Subsequently, 70-90 times the mass of the carbon nanofibers were added to dilute the mixture with deionized water, and the mixture was filtered. The mixture was then repeatedly washed with deionized water and filtered until the filtrate was neutral. The filtrate was then vacuum dried at 78-82℃ for 23-25 ​​h to obtain acidified carbon nanofibers. The acid mixture was obtained by mixing 60 wt% concentrated nitric acid and 98 wt% concentrated sulfuric acid at a volume ratio of 1:

3. (2) The acidified carbon nanofibers obtained in step (1) and sulfoxide were mixed at a mass ratio of 1:38-42 and ultrasonically treated for 10 min. Then the temperature was raised to 70-80℃ and stirred and refluxed for 23-25 ​​h. Excess sulfoxide was removed by vacuum distillation to obtain acylated carbon nanofibers. (3) The acylated carbon nanofibers obtained in step (2) are mixed with ethylene glycol at a mass ratio of 1:48-52 and ultrasonically treated for 10 min. Then the temperature is raised to 115-125℃ and stirred for 47-49 h. After the reaction is completed, the mixture is diluted with deionized water and filtered. After washing with deionized water and filtering 4-6 times, the mixture is vacuum dried at 78-82℃ for 23-25 ​​h to obtain hydroxylated carbon nanofibers. (4) Under nitrogen protection, the hydroxylated carbon nanofibers obtained in step (3), methyl 3,4-diaminobenzoate, p-toluenesulfonic acid, and toluene were mixed in a mass ratio of 1:1.3-1.5:0.006-0.008:5.8-6.2 and ultrasonically treated for 10 min. Then, the temperature was raised to 120-140℃ and refluxed for 6-12 h. After cooling to room temperature, 5% sodium bicarbonate solution was added to adjust the pH of the reaction system to 7-8. Then, the mixture was diluted with deionized water and filtered. The mixture was then washed with deionized water and filtered 2-4 times. Finally, the mixture was vacuum dried at 78-82℃ for 23-25 ​​h to obtain the modified carbon nanofibers.

4. The method for preparing far-infrared carbon nanofiber film according to claim 2, characterized in that, The preparation steps of the modified polytetrafluoroethylene are as follows: A1: Polytetrafluoroethylene (PTFE) micropowder with a particle size of 0.5–20 μm was subjected to gamma-ray irradiation in air at room temperature using a 60Co radiation source with an activity of 1.85 × 10¹⁴ Bq to obtain pre-irradiated PTFE. The absorbed dose of the irradiated PTFE was 100 kGy, and the free radical concentration was 8.

37. 1017 spins / g; A2: Mix 100 parts by weight of deionized water and 0.5-1 parts by weight of surfactant ethoxyperfluorooctyl ethanol, stir and disperse evenly, then add 8-12 parts by weight of pre-irradiated PTFE, continue stirring to suspend the pre-irradiated PTFE evenly in the aqueous solution, then add 18-22 parts by weight of 4-allylbenzoic acid, 0.008-0.012 parts by weight of polymerization inhibitor ferrous ammonium sulfate, and 0.08-0.12 parts by weight of concentrated sulfuric acid. Under nitrogen protection, stir and react in a water bath at 68-72℃ for 4.5-5.5 hours. After the reaction is complete, centrifuge to separate the supernatant, remove the supernatant, and redisperse the obtained precipitate with water and centrifuge again. Repeat the above steps 9-11 times. Then dry in a forced-air oven at 55-65℃ for 23-25 ​​hours to obtain modified polytetrafluoroethylene.

5. The method for preparing far-infrared carbon nanofiber film according to claim 2, characterized in that, The specific steps of mixing and stirring in step S1 are as follows: S1.1 Revolution speed 800-1200 r / min, time 8-12 min, revolution-to-rotation speed ratio 90%-110%; S1.2 Revolution speed 1800-2200 r / min, time 14-16 min, revolution-to-rotation speed ratio 110%-130%; S1.3 Revolution speed 1200-1800 r / min, time 8-12 min, revolution-to-rotation speed ratio 110%-130%.

6. The method for preparing far-infrared carbon nanofiber film according to claim 2, characterized in that, The feeding air pressure in step S2 air jet milling is 0.5-0.7 MPa, and the milling pressure is 0.3-0.5 MPa. The feeding air pressure is greater than the milling pressure.

7. The method for preparing far-infrared carbon nanofiber film according to claim 2, characterized in that, The heating in step S3 is a two-stage heating process. The first stage heating temperature is 210-230℃ and the heating time is 10-20 min. The second stage heating temperature is 300-320℃ and the heating time is 40-50 min. The high-speed rotary cutting steps in step S3 are as follows: S3.2.1 Rotation speed 1800-2200 r / min, time 4-6 min; S3.2.2 Rotation speed 3500-4500 r / min, time 8-12 min; S3.2.3 Rotation speed 5500-6500 r / min, time 4-6 min.

8. The method for preparing far-infrared carbon nanofiber film according to claim 2, characterized in that, The specific steps of step S4 are as follows: Under nitrogen protection, the material obtained in step S3 is placed into a spreader and spread evenly, and then hot-rolled. The rolling temperature is 345-355℃, the pressure is 1-100t, the gap between the hot rollers is 0-2mm, the hot rolling is performed 2-3 times, and the rolling thickness is 135-145μm, thus preparing a far-infrared carbon nanofiber membrane.

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