Far infrared nanometer carbon fiber film and preparation method thereof

Abstract

The invention discloses a far-infrared carbon nanofiber membrane and a preparation method thereof, and belongs to the technical field of carbon nanofiber membranes. The far infrared carbon nanofiber membrane is prepared by the following steps: uniformly mixing and stirring modified carbon nanofibers and modified polytetrafluoroethylene according to a mass ratio, carrying out airflow crushing, heating, carrying out high-speed rotary cutting and fibration, uniformly spreading in a spreading device, and carrying out hot rolling forming, thereby obtaining the far infrared carbon nanofiber membrane. Wherein the modified carbon nanofibers are obtained through a reaction between 3, 4-diaminobenzoic acid methyl ester and hydroxylated carbon nanofibers; the modified polytetrafluoroethylene is obtained by performing grafting modification on PTFE subjected to pre-irradiation treatment through 4-allylbenzoic acid; the nano carbon fibers in the prepared far-infrared nano carbon fiber film are uniformly dispersed, the conductivity is good, the current density difference under the working voltage is small, the current distribution is more perfect, and the heating is more uniform.

Description

Technical Field

[0001] The invention relates to a far-infrared carbon nanofiber film and a preparation method thereof. Background Art

[0002] With the rapid development of far-infrared heating technology, its application in healthcare, smart wearables and industrial heating is becoming more and more extensive. As the core heating material, nano carbon fiber film has attracted much attention due to its excellent electrical and thermal conductivity. This material not only provides stable far-infrared radiation, but also has good mechanical flexibility and long service life, making it an ideal choice for achieving efficient heating.

[0003] However, there are still many problems in the preparation process of traditional nanocarbon fiber membranes, which limits its practical application effect. The current mainstream preparation methods include chemical vapor deposition and electrospinning technology, which construct a conductive network by regulating the carbon fiber diameter (50-500nm) and orientation (±15° deviation). Despite this, the existing technology still faces some significant defects, such as insufficient fiber dispersion uniformity: due to process limitations, the nanocarbon fibers are unevenly distributed on the substrate, and the local density difference can reach more than 30%. This leads to an uneven distribution of conductive pathways, with a current density difference of more than 25% under the operating voltage, which causes local overheating, and the temperature difference can be as high as 10°C. This problem of uneven heating 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 the present invention is to provide a far-infrared carbon nanofiber film and a preparation method thereof to solve the technical problems mentioned in the above background technology.

[0006] The technical solution to achieve the purpose of the present invention is: in the first aspect, the present invention provides a far-infrared nano-carbon fiber film, which is prepared by mixing and stirring modified nano-carbon fibers and modified polytetrafluoroethylene, and then air flow crushing, followed by high-speed rotary cutting and fiberization after heating, and then evenly flattening and hot rolling forming in a spreader.

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

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

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

[0010] S1. Mix the modified carbon nanofiber and modified polytetrafluoroethylene in a mass ratio of 1.4 to 1.6:2 and stir evenly;

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

[0012] S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting and fiberization;

[0013] S4. Put the material obtained in step S3 into a spreading device, spread it evenly, and perform hot roller forming.

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

[0015] (1) Mixing nanocarbon fibers and an acid mixture in a mass ratio of 1:18-22, ultrasonically treating for 10 minutes, then heating to 115-125°C, stirring and refluxing for 1.8-2.2 hours, then adding deionized water 70-90 times the mass of the nanocarbon fibers to dilute and filter, then repeatedly washing with deionized water and filtering until the filtrate is neutral, and vacuum drying at 78-82°C for 23-25 ​​hours to obtain acidified nanocarbon fibers; wherein the acid mixture is obtained by mixing 60wt% concentrated nitric acid and 98wt% concentrated sulfuric acid in a volume ratio of 1:3;

[0016] (2) mixing the acidified carbon nanofibers obtained in step (1) with thionyl chloride in a mass ratio of 1:38-42, ultrasonically treating for 10 min, then heating to 70-80° C., stirring and refluxing for 23-25 ​​h, and removing excess thionyl chloride by vacuum distillation to obtain acylated carbon nanofibers;

[0017] (3) mixing the acylated carbon nanofibers obtained in step (2) with ethylene glycol in a mass ratio of 1:48-52, and then ultrasonically treating them for 10 minutes, then heating them to 115-125° C. and stirring them for 47-49 hours. After the reaction, diluting them with deionized water and filtering them, repeatedly washing them with deionized water and filtering them 4-6 times, and vacuum drying them at 78-82° C. for 23-25 ​​hours to obtain hydroxylated carbon nanofibers;

[0018] (4) Under nitrogen protection, the hydroxylated nano-carbon fibers obtained in step (3), methyl 3,4-diaminobenzoate, p-toluenesulfonic acid, and toluene are mixed in a mass ratio of 1:1.3-1.5:0.006-0.008:5.8-6.2, and then ultrasonically treated for 10 minutes, and then heated to 120-140°C, refluxed for 6-12 hours, cooled to room temperature, and added with 5% sodium bicarbonate solution to adjust the pH of the reaction system to 7-8, and then diluted with deionized water and filtered, and then repeatedly washed with deionized water and filtered for 2-4 times, and vacuum dried at 78-82°C for 23-25 ​​hours to obtain modified nano-carbon fibers.

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

[0020] A1: Place polytetrafluoroethylene powder with a particle size of 0.5 to 20 μm in an air atmosphere at room temperature and an activity of 1.85×10 14 Bq 60 The PTFE treated by γ-ray irradiation in a Co radiation source is obtained, wherein the absorbed dose of the PTFE treated by irradiation is 100 kGy and the free radical concentration is 8.37*10 17 spins / g;

[0021] A2: After 100 parts by mass of deionized water and 0.5-1 parts by mass of surfactant ethoxyperfluorooctylethanol are mixed and stirred to be uniformly dispersed, 8-12 parts by mass of pre-irradiated PTFE are added, and stirring is continued to make the pre-irradiated PTFE uniformly suspended in the aqueous solution, followed by adding 18-22 parts by mass of 4-allylbenzoic acid, 0.008-0.012 parts by mass of inhibitor ammonium ferrous sulfate, and 0.08-0.12 parts by mass of concentrated sulfuric acid. Under nitrogen protection, the mixture is stirred in a water bath at 68-72°C for 4.5-5.5 hours. After the reaction is completed, the mixture is centrifuged to remove the upper layer of liquid, and the obtained precipitate is re-dispersed with water and centrifuged again. The above steps are repeated 9-11 times, and then dried in a blast oven at 55-65°C for 23-25 ​​hours to obtain modified polytetrafluoroethylene.

[0022] Among them, the modification mechanism of modified polytetrafluoroethylene is as follows:

[0023]

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

[0025] Furthermore, in the step S2, the feed air flow pressure of the air flow crushing is 0.5-0.7 MPa, the crushing pressure is 0.3-0.5 MPa, and the feed air flow pressure is greater than the crushing pressure.

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

[0027] Furthermore, the specific steps of step S4 are as follows: under nitrogen protection, put it into a spreader and flatten it evenly, and perform hot rolling molding, wherein the rolling temperature is 345-355°C, the pressure is 1-100t, the gap between the hot pressing rollers is 0-2mm, hot rolling is performed 2-3 times, the rolling thickness is 135-145μm, and a far-infrared nano-carbon fiber film is prepared.

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

[0029] (1) The far-infrared nano-carbon fiber membrane of the present invention is first prepared by mixing the modified nano-carbon fiber and modified polytetrafluoroethylene evenly, and then performing air flow crushing, followed by heating and high-speed rotary cutting. During the high-speed rotary cutting process, the modified nano-carbon fiber and the adhesive modified polytetrafluoroethylene form fibers to complete fiberization. The fibers are then placed in a spreader and evenly flattened and hot rolled to obtain the far-infrared nano-carbon fiber membrane. The nano-carbon fibers are evenly dispersed, the conductivity is good, the current density difference is small under the working voltage, the current distribution is more perfect, and the heat generation is more uniform.

[0030] (2) The modified nano-carbon fibers of the present invention are obtained by ester exchange reaction between 3,4-diaminobenzoic acid methyl ester and hydroxylated nano-carbon fibers, and the modified polytetrafluoroethylene is obtained by grafting 4-allylbenzoic acid to modify pre-irradiated PTFE. A large number of active groups such as amino groups are introduced on the surface of the nano-carbon fibers, and a large number of carboxyl groups are grafted on the surface of the modified polytetrafluoroethylene to make the modified nano-carbon fibers and the modified polytetrafluoroethylene more evenly mixed, and the modified nano-carbon fibers are more dispersed in the far-infrared nano-carbon fiber film, thereby making the heat generation of the far-infrared nano-carbon fiber film more uniform under the working voltage.

[0031] (3) The modified nano-carbon fiber and modified polytetrafluoroethylene are first mixed and stirred evenly, and then air flow crushing is performed, followed by heating and high-speed rotary cutting to fiberize, and then the mixture is placed in a spreader to be evenly flattened and hot roller pressed to obtain a far-infrared nano-carbon fiber membrane, wherein the o-phenylenediamine on the modified nano-carbon fiber reacts with the benzoic acid on the modified polytetrafluoroethylene to form a benzimidazole polymer network in the far-infrared nano-carbon fiber membrane, and the modified nano-carbon fiber is evenly dispersed in the modified polytetrafluoroethylene to form a uniform conductive network, thereby enhancing the conductive properties of the far-infrared nano-carbon fiber membrane, making the heat generation of the far-infrared nano-carbon fiber membrane more uniform under the working voltage, and enhancing the mechanical properties of the far-infrared nano-carbon fiber membrane.

[0032] (4) The far-infrared carbon fiber film is prepared by the preparation method of the present invention, which comprises first mixing and stirring the modified carbon nanofiber and modified polytetrafluoroethylene evenly, and then subjecting them to air flow crushing, and then heating and high-speed rotary cutting for fiberization, and then placing them in a spreader for even flattening and hot rolling forming. The process is convenient to operate, and compared with the preparation process of the traditional carbon nanofiber film, no solvent is required, VOC emissions are reduced, and environmental protection performance is improved. The obtained carbon nanofiber film has a high yield rate, generates stable far-infrared rays, has good conductive effect, and has a long service life. DETAILED DESCRIPTION

[0033] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with specific implementation methods.

[0034] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

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

[0036] The following are some of the raw materials for the examples and comparative examples of the present invention:

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

[0038] (Example 1)

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

[0040] S1. The modified nano-carbon fiber and the modified polytetrafluoroethylene are mixed and stirred uniformly in a mass ratio of 1.4:2; wherein the specific steps of mixing and stirring are as follows: S1.1 revolution speed 800r / min, time 8min, revolution and rotation speed ratio 90%; S1.2 revolution speed 1800r / min, time 14min, revolution and rotation speed ratio 110%; S1.3 revolution speed 1200r / min, time 8min, revolution and rotation speed ratio 110%;

[0041] S2. The material obtained in step S1 is subjected to air flow pulverization, wherein the feed air flow pressure is 0.5 MPa and the pulverizing 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, wherein the heating is carried out in two stages, the first stage is heated at 210°C for 10 minutes, and the second stage is heated at 300°C for 40 minutes; the specific steps of high-speed rotary cutting are as follows: S3.2.1 speed 1800r / min, time 4min; S3.2.2 speed 3500r / min, time 8min; S3.2.3 speed 5500r / min, time 4min;

[0043] S4. Under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly flattened, and hot rolling is performed, wherein the rolling temperature is 345°C, the pressure is 50t, the gap between the hot pressing rollers is 1mm, the hot rolling is performed twice, the rolling thickness is 135μm, and a far-infrared nano-carbon fiber film is prepared.

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

[0045] (1) After mixing the nanocarbon fiber and the acid mixture in a mass ratio of 1:18, the mixture was treated with 25kHz ultrasound for 10 minutes, then heated to 115°C and stirred under reflux for 1.8 hours, then diluted with deionized water 70 times the mass of the nanocarbon fiber, filtered with a mixed fiber microporous filter membrane with a pore size of 0.22 μm, and then repeatedly washed with deionized water and filtered until the filtrate was neutral, and vacuum dried at 78°C for 23 hours to obtain acidified nanocarbon fiber; wherein the acid mixture was obtained by mixing 60wt% concentrated nitric acid and 98wt% concentrated sulfuric acid in a volume ratio of 1:3;

[0046] (2) mixing the acidified carbon nanofibers obtained in step (1) and thionyl chloride in a mass ratio of 1:38, treating with 25kHz ultrasonic waves for 10 minutes, then heating to 70°C, stirring and refluxing for 23 hours, and removing excess thionyl chloride by vacuum distillation to obtain acylated carbon nanofibers;

[0047] (3) mixing the acylated carbon nanofibers obtained in step (2) with ethylene glycol in a mass ratio of 1:48, treating with 25kHz ultrasonic waves for 10 minutes, then heating to 115°C and stirring for 47 hours, diluting with deionized water and filtering to remove excess ethylene glycol and reaction by-products after the reaction, repeatedly washing with deionized water and filtering for 4 times, and vacuum drying at 78°C for 23 hours to obtain hydroxylated carbon nanofibers;

[0048] (4) Under nitrogen protection, the hydroxylated nano-carbon fibers obtained in step (3), methyl 3,4-diaminobenzoate, p-toluenesulfonic acid, and toluene are mixed in a mass ratio of 1:1.3:0.006:5.8, and then ultrasonically treated for 10 minutes. The mixture is then heated to 120°C and refluxed for 6 hours. After cooling to room temperature, a 5% sodium bicarbonate solution is added to adjust the pH of the reaction system to 7. The mixture is then diluted with deionized water and filtered, and then repeatedly washed with deionized water and filtered twice. The mixture is vacuum dried at 78°C for 23 hours to obtain modified nano-carbon fibers.

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

[0050] A1: Place polytetrafluoroethylene powder with a particle size of 1 μm in an air atmosphere at room temperature and an activity of 1.85×10 14 Bq 60 The PTFE treated by γ-ray irradiation in a Co radiation source is obtained, wherein the absorbed dose of the PTFE treated by irradiation is 100 kGy and the free radical concentration is 8.37*10 17 spins / g;

[0051] A2: After 100 parts by mass of deionized water and 0.5 parts by mass of surfactant ethoxyperfluorooctylethanol are mixed and stirred to disperse evenly, 8 parts by mass of pre-irradiated PTFE are added, and stirring is continued to make the pre-irradiated PTFE evenly suspended in the aqueous solution, followed by adding 18 parts by mass of 4-allylbenzoic acid, 0.008 parts by mass of inhibitor ammonium ferrous sulfate, and 0.08 parts by mass of concentrated sulfuric acid. Under nitrogen protection, the mixture is stirred in a water bath at 68°C for 4.5 hours. After the reaction is completed, the mixture is centrifuged to remove the upper layer of liquid, and the obtained precipitate is re-dispersed with water and centrifuged again. The above steps are repeated 9 times, and then dried in a blast 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 comprises the following steps:

[0054] S1. The modified nano-carbon fiber and the modified polytetrafluoroethylene are mixed and stirred uniformly in a mass ratio of 1.5:2; wherein the specific steps of mixing and stirring are as follows: S1.1 revolution speed 1000r / min, time 10min, revolution and rotation speed ratio 100%; S1.2 revolution speed 2000r / min, time 15min, revolution and rotation speed ratio 120%; S1.3 revolution speed 1500r / min, time 10min, revolution and rotation speed ratio 120%;

[0055] S2. The material obtained in step S1 is subjected to air flow pulverization, wherein the feed air flow pressure is 0.6 MPa and the pulverizing 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, wherein the heating is carried out in two stages, the first stage is heated at 220°C for 15 minutes, and the second stage is heated at 310°C for 45 minutes; the specific steps of high-speed rotary cutting are as follows: S3.2.1 speed 2000r / min, time 5min; S3.2.2 speed 4000r / min, time 10min; S3.2.3 speed 6000r / min, time 5min;

[0057] S4. Under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly flattened, and hot rolling is performed, wherein the rolling temperature is 350°C, the pressure is 30t, the gap between the hot pressing rollers is 2mm, the hot rolling is performed twice, the rolling thickness is 140μm, and a far-infrared nano-carbon fiber film is prepared.

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

[0059] (1) After mixing the nanocarbon fiber and the acid mixture in a mass ratio of 1:20, the mixture was treated with 25kHz ultrasound for 10 minutes, then heated to 120°C and stirred under reflux for 2 hours, then diluted with deionized water 80 times the mass of the nanocarbon fiber, filtered with a mixed fiber microporous filter membrane with a pore size of 0.22 μm, and then repeatedly washed with deionized water and filtered until the filtrate was neutral, and vacuum dried at 80°C for 24 hours to obtain acidified nanocarbon fiber; wherein the acid mixture was obtained by mixing 60wt% concentrated nitric acid and 98wt% concentrated sulfuric acid in a volume ratio of 1:3;

[0060] (2) mixing the acidified carbon nanofibers obtained in step (1) and thionyl chloride in a mass ratio of 1:40, treating with 25kHz ultrasonic waves for 10 minutes, then heating to 75°C, stirring and refluxing for 24 hours, and removing excess thionyl chloride by vacuum distillation to obtain acylated carbon nanofibers;

[0061] (3) mixing the acylated carbon nanofibers obtained in step (2) with ethylene glycol in a mass ratio of 1:50, treating with 25kHz ultrasonic waves for 10 minutes, then heating to 120°C and stirring for 48 hours, diluting with deionized water and filtering to remove excess ethylene glycol and reaction by-products after the reaction, repeatedly washing with deionized water and filtering for 5 times, and vacuum drying at 80°C for 234 hours to obtain hydroxylated carbon nanofibers;

[0062] (4) Under nitrogen protection, the hydroxylated nano-carbon fibers obtained in step (3), methyl 3,4-diaminobenzoate, p-toluenesulfonic acid, and toluene are mixed in a mass ratio of 1:1.4:0.007:6, and then ultrasonically treated for 10 minutes. The mixture is then heated to 130°C and refluxed for 9 hours. After cooling to room temperature, a 5% sodium bicarbonate solution is added to adjust the pH of the reaction system to 7.5. The mixture is then diluted with deionized water and filtered, and then repeatedly washed with deionized water and filtered for 3 times. The mixture is then vacuum dried at 80°C for 24 hours to obtain modified nano-carbon fibers.

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

[0064] A1: Place polytetrafluoroethylene powder with a particle size of 10 μm in an air atmosphere at room temperature and an activity of 1.85×10 14 Bq 60 The PTFE treated by γ-ray irradiation in a Co radiation source is obtained, wherein the absorbed dose of the PTFE treated by irradiation is 100 kGy and the free radical concentration is 8.37*10 17 spins / g;

[0065] A2: After 100 parts by mass of deionized water and 0.8 parts by mass of surfactant ethoxyperfluorooctylethanol are mixed and stirred to disperse evenly, 10 parts by mass of pre-irradiated PTFE are added, and stirring is continued to make the pre-irradiated PTFE evenly suspended in the aqueous solution, followed by adding 20 parts by mass of 4-allylbenzoic acid, 0.01 parts by mass of inhibitor ammonium ferrous sulfate, and 0.1 parts by mass of concentrated sulfuric acid. Under nitrogen protection, the mixture is stirred in a water bath at 70°C for 5 hours. After the reaction is completed, the mixture is centrifuged to remove the upper layer of liquid, and the obtained precipitate is re-dispersed with water and centrifuged again. The above steps are repeated 10 times, and then dried in a blast 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 comprises the following steps:

[0068] S1. The modified nano-carbon fiber and the modified polytetrafluoroethylene are mixed and stirred uniformly in a mass ratio of 1.6:2; wherein the specific steps of mixing and stirring are as follows: S1.1 revolution speed 1200r / min, time 12min, revolution and rotation speed ratio 110%; S1.2 revolution speed 2200r / min, time 16min, revolution and rotation speed ratio 130%; S1.3 revolution speed 1800r / min, time 12min, revolution and rotation speed ratio 130%;

[0069] S2. The material obtained in step S1 is subjected to air flow pulverization, wherein the feed air flow pressure is 0.7 MPa and the pulverizing 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, wherein the heating is carried out in two stages, the first stage is heated at 230°C for 20 minutes, and the second stage is heated at 320°C for 50 minutes; the specific steps of high-speed rotary cutting are as follows: S3.2.1 speed 2200r / min, time 6min; S3.2.2 speed 4500r / min, time 12min; S3.2.3 speed 6500r / min, time 6min;

[0071] S4. Under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly flattened, and hot rolling is performed, wherein the rolling temperature is 355°C, the pressure is 100t, the gap between the hot pressing rollers is 2mm, the hot rolling is performed 3 times, the rolling thickness is 145μm, and a far-infrared nano-carbon fiber film is prepared.

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

[0073] (1) After mixing the nanocarbon fiber and the acid mixture in a mass ratio of 1:22, the mixture was treated with 25kHz ultrasound for 10 minutes, then heated to 125°C and stirred under reflux for 2.2 hours, then diluted with deionized water 90 times the mass of the nanocarbon fiber, filtered with a mixed fiber microporous filter membrane with a pore size of 0.22 μm, and then repeatedly washed with deionized water and filtered until the filtrate was neutral, and vacuum dried at 82°C for 25 hours to obtain acidified nanocarbon fiber; wherein the acid mixture was obtained by mixing 60wt% concentrated nitric acid and 98wt% concentrated sulfuric acid in a volume ratio of 1:3;

[0074] (2) mixing the acidified carbon nanofibers obtained in step (1) and thionyl chloride in a mass ratio of 1:42, treating with 25kHz ultrasonic waves for 10 minutes, then heating to 80°C, stirring and refluxing for 25 hours, and removing excess thionyl chloride by vacuum distillation to obtain acylated carbon nanofibers;

[0075] (3) mixing the acylated carbon nanofibers obtained in step (2) with ethylene glycol in a mass ratio of 1:52, treating with 25kHz ultrasonic waves for 10 minutes, then heating to 125°C and stirring for 49 hours, diluting with deionized water and filtering to remove excess ethylene glycol and reaction by-products after the reaction, repeatedly washing with deionized water and filtering for 6 times, and vacuum drying at 82°C for 25 hours to obtain hydroxylated carbon nanofibers;

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

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

[0078] A1: Place polytetrafluoroethylene powder with a particle size of 20 μm in an air atmosphere at room temperature and an activity of 1.85×10 14 Bq 60 The PTFE treated by γ-ray irradiation in a Co radiation source is obtained, wherein the absorbed dose of the PTFE treated by irradiation is 100 kGy and the free radical concentration is 8.37*10 17 spins / g;

[0079] A2: After 100 parts by mass of deionized water and 1 part by mass of surfactant ethoxyperfluorooctylethanol are mixed and stirred to be uniformly dispersed, 12 parts by mass of pre-irradiated PTFE are added, and stirring is continued to make the pre-irradiated PTFE uniformly suspended in the aqueous solution, followed by adding 22 parts by mass of 4-allyl benzoic acid, 0.012 parts by mass of inhibitor ammonium ferrous sulfate, and 0.12 parts by mass of concentrated sulfuric acid. Under nitrogen protection, the mixture is stirred in a 72°C water bath for 5.5 hours. After the reaction is completed, the mixture is centrifuged to remove the upper layer of liquid, and the obtained precipitate is re-dispersed with water and centrifuged again. The above steps are repeated 11 times, and then dried in a blast 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 is prepared using carbon nanofibers and modified polytetrafluoroethylene as raw materials, and the remaining components and steps are 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 is prepared using modified carbon nanofiber and polytetrafluoroethylene as raw materials, and the remaining components and steps are 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, and the remaining components and steps are the same as those of Example 2; wherein the preparation steps of the far-infrared carbon nanofiber film of Comparative Example 3 are as follows:

[0086] S1. The modified nano-carbon fiber and the modified polytetrafluoroethylene are mixed and stirred uniformly in a mass ratio of 1.5:2; wherein the specific steps of mixing and stirring are as follows: S1.1 revolution speed 1000r / min, time 10min, revolution and rotation speed ratio 100%; S1.2 revolution speed 2000r / min, time 15min, revolution and rotation speed ratio 120%; S1.3 revolution speed 1500r / min, time 10min, revolution and rotation speed ratio 120%;

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

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

[0089] S4. Under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly flattened, and hot rolling is performed, wherein the rolling temperature is 350°C, the pressure is 30t, the gap between the hot pressing rollers is 2mm, the hot rolling is performed twice, the rolling thickness is 140μm, and a far-infrared nano-carbon fiber film is prepared.

[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, and the remaining components and steps are the same as those of Example 2; wherein the preparation steps of the far-infrared carbon nanofiber film of Comparative Example 4 are as follows:

[0092] S1. The modified nano-carbon fiber and the modified polytetrafluoroethylene are mixed and stirred uniformly in a mass ratio of 1.5:2; wherein the specific steps of mixing and stirring are as follows: S1.1 revolution speed 1000r / min, time 10min, revolution and rotation speed ratio 100%; S1.2 revolution speed 2000r / min, time 15min, revolution and rotation speed ratio 120%; S1.3 revolution speed 1500r / min, time 10min, revolution and rotation speed ratio 120%;

[0093] S2. The material obtained in step S1 is subjected to air flow pulverization, wherein the feed air flow pressure is 0.6 MPa and the pulverizing 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, wherein the heating temperature is 220°C and the heating time is 60 min; the specific steps of high-speed rotary cutting are as follows: S3.2.1 speed 2000 r / min, time 5 min; S3.2.2 speed 4000 r / min, time 10 min; S3.2.3 speed 6000 r / min, time 5 min;

[0095] S4. Under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly flattened, and hot rolling is performed, wherein the rolling temperature is 350°C, the pressure is 30t, the gap between the hot pressing rollers is 2mm, the hot rolling is performed twice, the rolling thickness is 140μm, and a far-infrared nano-carbon fiber film is prepared.

[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, and the remaining components and steps are the same as those of Example 2; wherein, the preparation steps of the far-infrared carbon nanofiber film of Comparative Example 5 are as follows:

[0098] S1. The modified nano-carbon fiber and the modified polytetrafluoroethylene are mixed and stirred uniformly in a mass ratio of 1.5:2; wherein the specific steps of mixing and stirring are as follows: S1.1 revolution speed 1000r / min, time 10min, revolution and rotation speed ratio 100%; S1.2 revolution speed 2000r / min, time 15min, revolution and rotation speed ratio 120%; S1.3 revolution speed 1500r / min, time 10min, revolution and rotation speed ratio 120%;

[0099] S2. The material obtained in step S1 is subjected to air flow pulverization, wherein the feed air flow pressure is 0.6 MPa and the pulverizing 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, wherein the heating temperature is 310°C and the heating time is 60 min; the specific steps of high-speed rotary cutting are as follows: S3.2.1 speed 2000 r / min, time 5 min; S3.2.2 speed 4000 r / min, time 10 min; S3.2.3 speed 6000 r / min, time 5 min;

[0101] S4. Under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly flattened, and hot rolling is performed, wherein the rolling temperature is 350°C, the pressure is 30t, the gap between the hot pressing rollers is 2mm, the hot rolling is performed twice, the rolling thickness is 140μm, and a far-infrared nano-carbon fiber film is prepared.

[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, and the remaining components and steps are the same as those of Example 2; wherein the preparation steps of the far-infrared carbon nanofiber film of Comparative Example 6 are as follows:

[0104] S1. The modified nano-carbon fiber and the modified polytetrafluoroethylene are mixed and stirred uniformly in a mass ratio of 1.5:2; wherein the specific steps of mixing and stirring are as follows: S1.1 revolution speed 1000r / min, time 10min, revolution and rotation speed ratio 100%; S1.2 revolution speed 2000r / min, time 15min, revolution and rotation speed ratio 120%; S1.3 revolution speed 1500r / min, time 10min, revolution and rotation speed ratio 120%;

[0105] S2. The material obtained in step S1 is subjected to air flow pulverization, wherein the feed air flow pressure is 0.6 MPa and the pulverizing 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, wherein the heating is carried out in two stages, the first stage is heated at 220°C for 15 minutes, and the second stage is heated at 310°C for 45 minutes; the specific steps of high-speed rotary cutting are as follows: S3.2.1 speed 2000r / min, time 5min; S3.2.2 speed 4000r / min, time 10min; S3.2.3 speed 6000r / min, time 5min;

[0107] S4. Under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly flattened, and hot rolling is performed, wherein the rolling temperature is 340°C, the pressure is 30t, the gap between the hot pressing rollers is 2mm, the hot rolling is performed twice, the rolling thickness is 140μm, and a far-infrared nano-carbon fiber film is prepared.

[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, and the remaining components and steps are the same as those of Example 2; wherein, the preparation steps of the far-infrared carbon nanofiber film of Comparative Example 7 are as follows:

[0110] S1. The modified nano-carbon fiber and the modified polytetrafluoroethylene are mixed and stirred uniformly in a mass ratio of 1.5:2; wherein the specific steps of mixing and stirring are as follows: S1.1 revolution speed 1000r / min, time 10min, revolution and rotation speed ratio 100%; S1.2 revolution speed 2000r / min, time 15min, revolution and rotation speed ratio 120%; S1.3 revolution speed 1500r / min, time 10min, revolution and rotation speed ratio 120%;

[0111] S2. The material obtained in step S1 is subjected to air flow pulverization, wherein the feed air flow pressure is 0.6 MPa and the pulverizing 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, wherein the heating is carried out in two stages, the first stage is heated at 220°C for 15 minutes, and the second stage is heated at 310°C for 45 minutes; the specific steps of high-speed rotary cutting are as follows: S3.2.1 speed 2000r / min, time 5min; S3.2.2 speed 4000r / min, time 10min; S3.2.3 speed 6000r / min, time 5min;

[0113] S4. Under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly flattened, and hot rolling is performed, wherein the rolling temperature is 335°C, the pressure is 30t, the gap between the hot pressing rollers is 2mm, the hot rolling is performed twice, the rolling thickness is 140μm, and a far-infrared nano-carbon fiber film is prepared.

[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, and the remaining components and steps are the same as those of Example 2; wherein, the preparation steps of the far-infrared carbon nanofiber film of Comparative Example 8 are as follows:

[0116] S1. The modified nano-carbon fiber and the modified polytetrafluoroethylene are mixed and stirred uniformly in a mass ratio of 1.5:2; wherein the specific steps of mixing and stirring are as follows: S1.1 revolution speed 1000r / min, time 10min, revolution and rotation speed ratio 100%; S1.2 revolution speed 2000r / min, time 15min, revolution and rotation speed ratio 120%; S1.3 revolution speed 1500r / min, time 10min, revolution and rotation speed ratio 120%;

[0117] S2. The material obtained in step S1 is subjected to air flow pulverization, wherein the feed air flow pressure is 0.6 MPa and the pulverizing 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, wherein the heating is carried out in two stages, the first stage is heated at 220°C for 15 minutes, and the second stage is heated at 310°C for 45 minutes; the specific steps of high-speed rotary cutting are as follows: S3.2.1 speed 2000r / min, time 5min; S3.2.2 speed 4000r / min, time 10min; S3.2.3 speed 6000r / min, time 5min;

[0119] S4. Under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly spread, and hot rolling is performed, wherein the rolling temperature is 360°C, the pressure is 30t, the gap between the hot pressing rollers is 2mm, the hot rolling is performed twice, the rolling thickness is 140μm, and a far-infrared nano-carbon fiber film is prepared.

[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, and the remaining components and steps are the same as those of Example 2; wherein, the preparation steps of the far-infrared carbon nanofiber film of Comparative Example 9 are as follows:

[0122] S1. The modified nano-carbon fiber and the modified polytetrafluoroethylene are mixed and stirred uniformly in a mass ratio of 1.5:2; wherein the specific steps of mixing and stirring are as follows: S1.1 revolution speed 1000r / min, time 10min, revolution and rotation speed ratio 100%; S1.2 revolution speed 2000r / min, time 15min, revolution and rotation speed ratio 120%; S1.3 revolution speed 1500r / min, time 10min, revolution and rotation speed ratio 120%;

[0123] S2. The material obtained in step S1 is subjected to air flow pulverization, wherein the feed air flow pressure is 0.6 MPa and the pulverizing 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, wherein the heating is carried out in two stages, the first stage is heated at 220°C for 15 minutes, and the second stage is heated at 310°C for 45 minutes; the specific steps of high-speed rotary cutting are as follows: S3.2.1 speed 2000r / min, time 5min; S3.2.2 speed 4000r / min, time 10min; S3.2.3 speed 6000r / min, time 5min;

[0125] S4. Under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly spread, and hot rolling is performed, wherein the rolling temperature is 365°C, the pressure is 30t, the gap between the hot pressing rollers is 2mm, the hot rolling is performed twice, the rolling thickness is 140μm, and a far-infrared nano-carbon fiber film is prepared.

[0126] Effect example

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

[0128] Resistivity test: After cutting the far-infrared nano-carbon fiber film obtained in the embodiment and the comparative example into a square of 3×3 cm in size, place it 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 to 3 and Comparative Examples 1 to 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] From the comparison of the data of Examples 1 to 3 and Comparative Examples 1 to 9 in Table 1, it can be seen that the far-infrared carbon nanofiber films prepared in Examples 1 to 3 have better mechanical properties and conductive properties.

[0133] Compared with Example 2, the far-infrared nano-carbon fiber membrane of Comparative Example 1 is made of nano-carbon fibers and modified polytetrafluoroethylene as raw materials. The prepared far-infrared nano-carbon fiber membrane has a tensile strength of 3.03 MPa and a resistivity of 336.32 mΩ*cm. The mechanical properties and conductive properties of the far-infrared nano-carbon fiber membrane of Comparative Example 1 are weaker than those of Example 2.

[0134] Compared with Example 2, the far-infrared nanocarbon fiber membrane of Comparative Example 2 is made of modified nanocarbon fiber and polytetrafluoroethylene as raw materials. The prepared far-infrared nanocarbon fiber membrane has a tensile strength of 3.03 MPa and a resistivity of 335.87 mΩ*cm. The mechanical properties and conductive properties of the far-infrared nanocarbon fiber membrane of Comparative Example 2 are weaker than those of Example 2.

[0135] Compared with Example 2, in the process of preparing the far-infrared carbon nanofiber film in Example 3, the air flow was not heated before high-speed dispersion, and the tensile strength of the far-infrared carbon nanofiber film was 3.03MPa, and the resistivity was 322.36mΩ*cm. This may be because in the process of preparing the far-infrared carbon nanofiber film in Example 3, the air flow was not heated before high-speed dispersion, and a polymer network could not be formed in the far-infrared carbon nanofiber film, and the dispersion of the carbon nanofiber was weak. Compared with the far-infrared carbon nanofiber film in Example 2, the mechanical properties and conductivity of the far-infrared carbon nanofiber film in Example 3 are better than those in Example 2. The performance is weak; in the process of preparing the far-infrared nano-carbon fiber membrane in Comparative Example 4, the air flow crushing was only heated at 220°C after the air flow crushing, and in the process of preparing the far-infrared nano-carbon fiber membrane in Comparative Example 5, the air flow crushing was only heated at 310°C after the far-infrared nano-carbon fiber membrane. The tensile strengths of the far-infrared nano-carbon fiber membranes prepared in Comparative Examples 4 and 5 were 4.36MPa and 3.34MPa, respectively; the resistivities were 69.05mΩ*cm and 66.96mΩ*cm, respectively; Compared with Example 2, the far-infrared nano-carbon fiber membranes prepared in Example 2 using two-stage heating have better mechanical properties and conductive properties.

[0136] Compared with Example 2, the hot rolling temperatures in the process of preparing far-infrared nanocarbon fiber membranes in Comparative Examples 6 to 10 are 340°C, 335°C, 360°C, and 365°C, respectively, and the tensile strengths of the prepared far-infrared nanocarbon fiber membranes are 8.06MPa, 7.83MPa, 7.66MPa, and 6.98MPa, respectively, which are lower than the tensile strength of 8.86MPa of the far-infrared nanocarbon fiber membrane prepared in Example 2. This may be because when the temperature is higher than 355°C, the polytetrafluoroethylene of the far-infrared nanocarbon fiber membrane is partially decomposed at high temperature, making the mechanical properties of the far-infrared nanocarbon fiber membrane weaker; when the temperature is lower than 345°C, the benzimidazole polymer network is not completely reacted to form, making the mechanical properties of the far-infrared nanocarbon fiber membrane weaker than those in Example 2.

[0137] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is 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 in the protection scope of the present invention.

Claims

1. A far-infrared carbon nanofiber film, characterized in that: The far-infrared carbon nanofiber film is prepared by uniformly mixing modified carbon nanofiber and modified polytetrafluoroethylene, then air flow crushing, then heating and high-speed rotary cutting for fiberization, and then placing in a spreader for uniform flattening and hot rolling forming.

2. The far-infrared carbon nanofiber film according to claim 1, characterized in that: The modified carbon nanofiber is obtained by reacting 3,4-diaminobenzoic acid methyl ester with hydroxylated carbon nanofiber.

3. The far-infrared carbon nanofiber film according to claim 1, characterized in that: The modified polytetrafluoroethylene is obtained by grafting 4-allylbenzoic acid to modify the pre-irradiated PTFE.

4. A method for preparing a far-infrared carbon nanofiber film according to any one of claims 1 to 3, characterized in that: The method comprises the following preparation steps: S1. Mix the modified carbon nanofiber and modified polytetrafluoroethylene in a mass ratio of 1.4 to 1.6:2 and stir evenly; S2. The material obtained in step S1 is subjected to air flow pulverization; S3. The material obtained in step S2 is heated and then subjected to high-speed rotary cutting and fiberization; S4. Put the material obtained in step S3 into a spreading device, spread it evenly, and perform hot roller forming.

5. The method for preparing the far-infrared carbon nanofiber film according to claim 4, characterized in that: The preparation steps of the modified carbon nanofiber are as follows: (1) Mixing nanocarbon fibers and an acid mixture in a mass ratio of 1:18-22, ultrasonically treating for 10 minutes, then heating to 115-125°C, stirring and refluxing for 1.8-2.2 hours, then adding deionized water 70-90 times the mass of the nanocarbon fibers to dilute and filter, then repeatedly washing with deionized water and filtering until the filtrate is neutral, and vacuum drying at 78-82°C for 23-25 ​​hours to obtain acidified nanocarbon fibers; wherein the acid mixture is obtained by mixing 60wt% concentrated nitric acid and 98wt% concentrated sulfuric acid in a volume ratio of 1:3; (2) mixing the acidified carbon nanofibers obtained in step (1) with thionyl chloride in a mass ratio of 1:38-42, ultrasonically treating for 10 min, then heating to 70-80° C., stirring and refluxing for 23-25 ​​h, and removing excess thionyl chloride by vacuum distillation to obtain acylated carbon nanofibers; (3) mixing the acylated carbon nanofibers obtained in step (2) with ethylene glycol in a mass ratio of 1:48-52, and then ultrasonically treating them for 10 minutes, then heating them to 115-125° C. and stirring them for 47-49 hours. After the reaction, diluting them with deionized water and filtering them, repeatedly washing them with deionized water and filtering them 4-6 times, and vacuum drying them at 78-82° C. for 23-25 ​​hours to obtain hydroxylated carbon nanofibers; (4) Under nitrogen protection, the hydroxylated nano-carbon fibers obtained in step (3), methyl 3,4-diaminobenzoate, p-toluenesulfonic acid, and toluene are mixed in a mass ratio of 1:1.3-1.5:0.006-0.008:5.8-6.2, and then ultrasonically treated for 10 minutes, and then heated to 120-140°C, refluxed for 6-12 hours, cooled to room temperature, and added with 5% sodium bicarbonate solution to adjust the pH of the reaction system to 7-8, and then diluted with deionized water and filtered, and then repeatedly washed with deionized water and filtered for 2-4 times, and vacuum dried at 78-82°C for 23-25 ​​hours to obtain modified nano-carbon fibers.

6. The method for preparing the far-infrared carbon nanofiber film according to claim 4, characterized in that: The preparation steps of the modified polytetrafluoroethylene are as follows: A1: Place polytetrafluoroethylene powder with a particle size of 0.5 to 20 μm in an air atmosphere at room temperature and an activity of 1.85×10 14 Bq 60 The PTFE treated by γ-ray irradiation in a Co radiation source is obtained, wherein the absorbed dose of the PTFE treated by irradiation is 100 kGy and the free radical concentration is 8.37*10 17 spins / g; A2: After 100 parts by mass of deionized water and 0.5-1 parts by mass of surfactant ethoxyperfluorooctylethanol are mixed and stirred to be uniformly dispersed, 8-12 parts by mass of pre-irradiated PTFE are added, and stirring is continued to make the pre-irradiated PTFE uniformly suspended in the aqueous solution, followed by adding 18-22 parts by mass of 4-allylbenzoic acid, 0.008-0.012 parts by mass of inhibitor ammonium ferrous sulfate, and 0.08-0.12 parts by mass of concentrated sulfuric acid. Under nitrogen protection, the mixture is stirred in a water bath at 68-72°C for 4.5-5.5 hours. After the reaction is completed, the mixture is centrifuged to remove the upper layer of liquid, and the obtained precipitate is re-dispersed with water and centrifuged again. The above steps are repeated 9-11 times, and then dried in a blast oven at 55-65°C for 23-25 ​​hours to obtain modified polytetrafluoroethylene.

7. The method for preparing the far-infrared carbon nanofiber film according to claim 4, characterized in that: The specific steps of the mixing and stirring in step S1 are as follows: S1.1 revolution speed 800-1200r / min, time 8-12min, revolution and rotation speed ratio 90%-110%; S1.2 revolution speed 1800-2200r / min, time 14-16min, revolution and rotation speed ratio 110%-130%; S1.3 revolution speed 1200-1800r / min, time 8-12min, revolution and rotation speed ratio 110%-130%.

8. The method for preparing the far-infrared carbon nanofiber film according to claim 4, characterized in that: The feed air flow pressure of the air flow pulverization in step S2 is 0.5-0.7 MPa, and the pulverization pressure is 0.3-0.5 MPa, and the feed air flow pressure is greater than the pulverization pressure.

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

10. The method for preparing the far-infrared carbon nanofiber film according to claim 4, characterized in that: The specific steps of step S4 are as follows: under nitrogen protection, the material obtained in step S3 is placed in a spreader and evenly flattened, and hot rolling is performed, wherein the rolling temperature is 345-355°C and the pressure is 1-100t; the gap between the hot pressing rollers is 0-2mm, hot rolling is performed 2-3 times, and the rolling thickness is 135-145μm, to prepare a far-infrared nano-carbon fiber film.

Images