Microwave pre-oxidation method based on cyanation carbon nanotube modified polyacrylonitrile-based carbon fiber precursor

Abstract

The invention provides a microwave pre-oxidation method based on a cyanation carbon nano tube modified polyacrylonitrile-based carbon fiber precursor, which comprises the following steps: firstly, carrying out surface modification on a carbon nano tube, and then introducing the cyanation carbon nano tube into a polyacrylonitrile matrix through in-situ polymerization to provide a certain wave-absorbing property for the carbon nano tube. The microwave reactor can absorb microwave energy in the microwave reactor and convert the microwave energy into heat energy, and the power and time of the microwave reactor are controlled, so that the microwave pre-oxidation of the polyacrylonitrile precursor is realized. Microwave pre-oxidation can complete pre-oxidation in a short time, and the production cost of the pre-oxidation stage during carbon fiber preparation can be greatly reduced when the microwave pre-oxidation is applied to industry. In addition, the dispersity of the carbon nano tube and the mechanical property of the precursor can be effectively improved through the interaction of the cyanation carbon nano tube and cyano groups on a polyacrylonitrile chain.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon fibers, and in particular relates to a microwave pre-oxidation method based on cyanated carbon nanotube modified polyacrylonitrile-based carbon fiber precursor filaments. Background Art

[0002] Carbon fiber (CF) is a high-performance fiber material with a carbon content exceeding 92%, having characteristics such as high specific strength, high specific modulus, high temperature resistance, and corrosion resistance, and is widely used in fields such as aerospace, rail transit, wind power generation, automotive industry, and leisure sports. At present, polyacrylonitrile (PAN) is the main precursor for carbon fiber production, accounting for more than 90% of the carbon fiber market. Its production process includes the polymerization of PAN copolymer, spinning, and then pre-oxidation in air (200 - 300 °C), and carbonization in an inert environment (1000 - 1700 °C). Among them, pre-oxidation is one of the most critical stages in the various processes of manufacturing carbon fibers, and it is also the stage with the largest energy consumption and the longest time-consuming in many processes. During this process, various complex physical and chemical reactions occur in the PAN precursor filaments, and the PAN macromolecular chains transform from a linear structure to a more heat-resistant ladder structure, which enables the PAN fibers to withstand higher-temperature carbonization treatment. However, the PAN precursor filaments incur huge cost consumption during pre-oxidation, severely restricting the reduction of the production cost of carbon fibers.

[0003] Currently, conventional pre-oxidation mainly places the PAN precursor filaments in an electric heating furnace for pre-oxidation. The heat comes from the heating source, and then is transferred from the outside to the inside of the PAN precursor filaments through heat convection, heat conduction, and heat radiation. As the temperature rises, the surface layer of the PAN precursor filaments first undergoes a pre-oxidation reaction, preferentially forming a ladder structure, and then forming a dense network structure, which hinders the further diffusion of oxygen to the core. As the heating time increases, the skin-core structure of the PAN precursor filaments becomes more and more obvious, making it difficult to obtain high-performance carbon fibers. In addition, the time of conventional pre-oxidation mostly needs to be controlled at about 2 h to achieve a better effect. Therefore, a large amount of energy consumption is generated, becoming one of the main reasons for the high cost of PAN-based carbon fibers. Summary of the Invention

[0004] The purpose of the present invention is to provide a microwave pre-oxidation method based on cyanated carbon nanotube modified polyacrylonitrile-based carbon fiber precursor filaments.

[0005] To achieve this, the above object of the present invention is realized through the following technical solutions:

[0006] A microwave pre-oxidation method based on cyanated carbon nanotube modified polyacrylonitrile-based carbon fiber precursor filaments, comprising the following steps:

[0007] S1. Preparation of cyanated carbon nanotubes: React an organic compound A with hydroxylated carbon nanotubes in a first organic solvent under the action of a catalyst to obtain cyanated carbon nanotubes;

[0008] The organic compound A contains a cyano group and an isocyanate group;

[0009] S2. In-situ polymerization preparation of cyanated carbon nanotube / acrylonitrile copolymer: Disperse the obtained cyanated carbon nanotubes in a second organic solvent, and copolymerize with acrylonitrile monomer and a second monomer under the action of an initiator to form a cyanated carbon nanotube / acrylonitrile copolymer;

[0010] S3. Preparation of cyanated carbon nanotube / acrylonitrile copolymer spinning dope: Stir and completely dissolve the obtained cyanated carbon nanotube / acrylonitrile copolymer and a third organic solvent at a certain temperature, remove monomers, remove bubbles, and filter to obtain a cyanated carbon nanotube / acrylonitrile copolymer spinning dope;

[0011] S4. Spinning preparation of cyanated carbon nanotube / acrylonitrile copolymer composite raw filaments: Spin the obtained cyanated carbon nanotube acrylonitrile copolymer spinning dope by solution spinning to obtain cyanated carbon nanotube / acrylonitrile copolymer composite raw filaments;

[0012] S5. Microwave pre-oxidation treatment of composite raw filaments: Perform microwave pre-oxidation treatment on the obtained cyanated carbon nanotube / acrylonitrile copolymer composite raw filaments.

[0013] While adopting the above technical solutions, the present invention can also adopt or combine the following technical solutions:

[0014] As a preferred technical solution of the present invention: In step S1, the chemical structural formula of the compound A is as follows:

[0015]

[0016] Wherein: R is one of a straight-chain alkyl group, a cycloalkyl group, an aromatic ring, and a heteroaromatic ring;

[0017] The aromatic ring is a benzene ring or a naphthalene ring; the heteroaromatic ring is one of furan, thiophene, pyrrole, and pyridine.

[0018] As a preferred technical solution of the present invention: In step S1, the first organic solvent is at least one of dichloromethane and dimethylformamide.

[0019] As a preferred technical solution of the present invention: In step S1, the catalyst is at least one of triethylamine, diacetyldiamine, and triethylenediamine.

[0020] As a preferred technical solution of the present invention: in step S2, the second organic solvent is at least one of dimethyl sulfoxide and dimethylformamide.

[0021] As a preferred technical solution of the present invention: in step S2, the second monomer is at least one of itaconic acid, methacrylic acid, methyl methacrylate, methyl acrylate, vinyl acetate, and 2-acrylamido-2-methylpropanesulfonic acid.

[0022] As a preferred technical solution of the present invention: in step S2, the initiator is at least one of azobisisobutyronitrile, benzoyl peroxide, dicumyl peroxide, potassium persulfate, ammonium persulfate, and sodium bisulfite.

[0023] As a preferred technical solution of the present invention: in step S2, the in-situ polymerization reaction temperature is 60°C to 100°C; the in-situ polymerization reaction time is 1 to 36 h.

[0024] As a preferred technical solution of the present invention: in step S3, the third organic solvent is at least one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, sodium thiocyanate aqueous solution, and zinc oxide aqueous solution.

[0025] As a preferred technical solution of the present invention: in step S5, in the microwave pre-oxidation treatment, the microwave power is 100 to 1000 w, and the treatment time is 1 to 60 min.

[0026] The present invention provides a microwave pre-oxidation method for polyacrylonitrile-based carbon fiber precursor modified by cyanated carbon nanotubes. First, the surface of the carbon nanotubes is modified, and then cyanated carbon nanotubes are introduced into the polyacrylonitrile matrix through in-situ polymerization to provide certain microwave absorption performance, enabling it to absorb microwave energy in a microwave reactor and convert it into heat energy, and realizing the microwave pre-oxidation of the polyacrylonitrile precursor by controlling the power and time of the microwave reactor. Microwave pre-oxidation can complete the pre-oxidation in a short time, and applying it in industry can greatly reduce the production cost in the pre-oxidation stage of carbon fiber preparation. In addition, the interaction between the cyanated carbon nanotubes and the cyano groups on the polyacrylonitrile chain can effectively improve the dispersion of the carbon nanotubes and the mechanical properties of the precursor. Description of the Drawings

[0027] Figure 1 FT-IR diagram of CNT-CN in Example 1.

[0028] Figure 2 Temperature rise program of microwave pre-oxidation of CNT-CN / P(AN-co-IA) precursor in Example 4 or Example 8.

[0029] Figure 3aInfrared spectra of 2 wt% CNT-CN / P(AN-co-IA) precursor A in Examples 1-4, the precursor A after being treated at different temperatures by microwave pre-oxidation, and the precursor A in Comparative Example 1 after being treated by conventional pre-oxidation.

[0030] Figure 3b Infrared spectra of 3 wt% CNT-CN / P(AN-co-IA) precursor B in Examples 5-8, the precursor B after being treated at different temperatures by microwave pre-oxidation, and the precursor B in Comparative Example 2 after being treated by conventional pre-oxidation.

[0031] Figure 4 Pre-oxidation degrees of 2 wt% and 3 wt% CNT-CN / P(AN-co-IA) precursors in Examples 1-8 after being treated at different temperatures by microwave pre-oxidation, and the conventional pre-oxidation treatments in Comparative Examples 1 and 2. Detailed implementation manners

[0032] The present invention provides a microwave pre-oxidation method for a polyacrylonitrile-based carbon fiber precursor modified by cyanated carbon nanotubes, comprising the following steps:

[0033] S1. Preparation of cyanated carbon nanotubes (CNT-CN): Add a certain amount of compound A containing cyanide and isocyanate groups into anhydrous dichloromethane (DCM), control the temperature at 0 °C, and then sequentially add a certain amount of triethylamine (Et 3 N) and hydroxylated carbon nanotubes (CNT-OH), heat the mixture to room temperature and stir for 1-24 h, and wash the obtained mixed solution with DCM, ethanol (EtOH) and deionized water (H 2 O), and dry to obtain cyanated carbon nanotubes (CNT-CN).

[0034]

[0035] Wherein, R is: an aromatic ring such as a benzene ring or a naphthalene ring; or an alkyl group, a cycloalkyl group, etc.; or a five- or six-membered aromatic heterocycle such as furan, thiophene, pyrrole, pyridine, etc.

[0036] S2. In-situ polymerization preparation of CNT-CN / PAN copolymer: Ultrasonically disperse a certain amount of CNT-CN in dimethyl sulfoxide (DMSO), then add monomer acrylonitrile (AN), a second monomer and an initiator respectively, and react at 60 °C - 100 °C under a nitrogen atmosphere for 1-36 h. Pour the reacted polymer solution into deionized H 2 O for washing, then transfer it to methanol (MeOH) for soaking, and make it into powder after drying treatment.

[0037] S3. Preparation of the spinning dope of CNT-CN / PAN copolymer: Add the powder obtained above and a certain amount of DMSO solution into a reaction kettle, stir at 60 °C until the powder is completely dissolved to obtain a 10-60 wt% CNT-CN / PAN copolymer spinning dope, transfer it to the dissolution kettle on the spinning production line, and carry out single monomer removal, degassing, and filtration treatments.

[0038] S4. Spinning preparation of CNT-CN / PAN copolymer composite raw filaments: The spinning dope passes through a screw and a metering pump in sequence, enters a coagulation bath through spinneret holes with 1 to 10,000 holes, and then undergoes multi-stage water washing and boiling water bath drawing, multi-stage thermal densification and heat setting processes, and finally winds and collects the filaments.

[0039] S5. Microwave pre-oxidation treatment of the raw filaments: Place the CNT-CN / PAN copolymer raw filaments in a microwave reactor for microwave pre-oxidation treatment, with a microwave power of 100-1000 w and a time of 1-60 min.

[0040] Specifically, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] S1. Preparation of CNT-CN: Add 0.5 g of 4-cyanophenyl isocyanate and 75 mL of anhydrous dichloromethane (DCM) to a completely dry flask, control the temperature at 0 °C, and then sequentially add 1.05 g of Et 3 N and 2 g of CNT-OH, heat the mixture to room temperature and stir for 12 h under a nitrogen atmosphere. The obtained mixed solution is centrifugally washed twice with DCM, EtOH, and H 2 O, and the washed and dried solid is obtained as CNT-CN.

[0043] S2. In-situ polymerization preparation of CNT-CN / P(AN-co-IA) copolymer: Add 10.1 g of CNT-CN (2 wt%) prepared above and 1710.7 g of DMSO into a 5 L beaker. After ultrasonic stirring and dispersion for 1 h, transfer it to a 5 L reaction kettle, and respectively add 26.5 g of itaconic acid (IA), 5.1 g of azobisisobutyronitrile (AIBN), and 479.5 g of acrylonitrile (AN), and react at 60 °C under a nitrogen atmosphere for 12 h. Pour the reacted polymer solution into deionized water and wash it repeatedly for about 12 h, then transfer it to methanol and soak it for 4 h, and obtain a powder after drying treatment.

[0044] S3. Preparation of CNT-CN / P(AN-co-IA) spinning dope: Dissolve 450 g of 2% CNT-CN / P(AN-co-IA) powder in 1800 g of DMSO to prepare a 20 wt% PAN spinning dope, transfer it to the dissolution kettle on the wet spinning production line, and conduct vacuum overnight defoaming treatment.

[0045] S4. Wet spinning preparation of CNT-CN / P(AN-co-IA) composite filaments: The spinning dope passes through a screw and a metering pump in sequence, enters the coagulation bath (60 wt% DMSO aqueous solution) from a spinneret with 100 holes (hole diameter is 60 μm), then undergoes two-stage boiling water bath stretching (90 °C, 100 °C), three-stage thermal densification (130 °C, 150 °C, 160 °C) and heat setting process (165 °C) in sequence, and finally winds and collects the filaments to obtain filament A.

[0046] S5. Microwave pre-oxidation treatment of CNT-CN / P(AN-co-IA) composite filaments: Take 30 cm of filament A and wind it around a quartz rod with a diameter of 10 mm, place it in a quartz test tube, and then put it into a microwave reactor for microwave treatment. The maximum microwave power is set to 180 w, and the program is set to rise to 180 °C in 3 min, keep warm for 1 min and then rise to 220 °C in 8 min, and the total treatment time is 12 min.

[0047] Example 2

[0048] In this example, steps S1 - S4 are the same as those in Example 1.

[0049] S5. Microwave pre-oxidation treatment of CNT-CN / P(AN-co-IA) composite filaments: Take 30 cm of filament A and wind it around a quartz rod with a diameter of 10 mm, place it in a quartz test tube, and then put it into a microwave reactor for microwave treatment. The maximum microwave power is set to 180 w, and the program is set to rise to 180 °C in 3 min, keep warm for 1 min and then rise to 240 °C in 12 min, and the total treatment time is 16 min.

[0050] Example 3

[0051] In this example, steps S1 - S4 are the same as those in Example 1.

[0052] S5. Microwave pre-oxidation treatment of CNT-CN / P(AN-co-IA) composite filaments: Take 30 cm of composite filament A and wind it around a quartz rod with a diameter of 10 mm, place it in a quartz test tube, and then put it into a microwave reactor for microwave treatment. The maximum microwave power is set to 200 w, and the program is set to rise to 180 °C in 3 min, keep warm for 1 min and then rise to 260 °C in 16 min, and the total treatment time is 20 min.

[0053] Example 4

[0054] In this example, steps S1 to S4 are the same as those in Example 1.

[0055] S5. Microwave pre-oxidation treatment of CNT-CN / P(AN-co-IA) composite precursor filaments: Take 30 cm of precursor filament A composite filaments and wind them around a quartz rod with a diameter of 10 mm. Place it in a quartz test tube, and then put it into a microwave reactor for microwave treatment. The maximum microwave power is set to 200 w. The program is set to rise to 180 °C in 3 min, keep warm for 1 min, and then rise to 280 °C in 20 min. The total treatment time is 24 min.

[0056] Example 5

[0057] S1. Preparation of CNT-CN: Add 1 g of 4-cyanophenyl isocyanate and 150 mL of anhydrous DCM to a completely dry flask, control the temperature at 0 °C, and then sequentially add 2.1 g of Et 3 N and 4 g of CNT-OH. Heat the mixture to room temperature and stir for 15 h under a nitrogen atmosphere. The resulting mixture is centrifugally washed twice with DCM, EtOH, and H 2 O, and the washed solid is dried to obtain CNT-CN.

[0058] S2. In-situ polymerization preparation of CNT-CN / P(AN-co-IA) copolymer: Add 13.6 g of CNT-CN (3 wt%) prepared above and 1539.6 g of DMSO to a 5 L beaker. After ultrasonic stirring and dispersion for 1.5 h, transfer it to a 5 L reaction kettle, and add 23.8 g of IA, 4.5 g of AIBN, and 431.5 g of AN respectively. React at 60 °C under a nitrogen atmosphere for 12 h. Pour the reacted polymer solution into deionized water and wash it repeatedly for about 12 h, and then transfer it to methanol and soak it for 4 h. After drying treatment, it is made into powder.

[0059] S3. Preparation of CNT-CN / P(AN-co-IA) spinning dope: Dissolve 400 g of 3% CNT-CN / P(AN-co-IA) powder in 1600 g of DMSO to prepare a 20 wt% PAN spinning dope, transfer it to a dissolution kettle on a wet spinning production line, and carry out vacuum overnight defoaming treatment before spinning.

[0060] S4. Wet spinning preparation of CNT-CN / P(AN-co-IA) composite precursor filaments: The spinning dope passes through a screw and a metering pump in sequence, enters a coagulation bath (60 wt% aqueous DMSO solution) from a spinneret with 100 holes (hole diameter 60 μm), then undergoes two-stage hot water bath drawing (90 °C, 100 °C), three-stage thermal densification (130 °C, 150 °C, 160 °C) and heat setting process (165 °C) in sequence, and finally the precursor filaments are wound and collected to obtain precursor filament B.

[0061] S5. Microwave pre-oxidation treatment of CNT-CN / P(AN-co-IA) composite precursor filaments: Take 30 cm of precursor filament B and wind it around a quartz rod with a diameter of 10 mm, place it in a quartz test tube, and then put it into a microwave reactor for microwave treatment. The maximum microwave power is set to 150 w, and the program is set to rise to 180 °C in 3 min, keep warm for 1 min and then rise to 220 °C in 8 min. The total treatment time is 12 min.

[0062] Example 6

[0063] In this example, steps S1 to S4 are the same as those in Example 5.

[0064] S5. Microwave pre-oxidation treatment of CNT-CN / P(AN-co-IA) composite precursor filaments: Take 30 cm of precursor filament B and wind it around a quartz rod with a diameter of 10 mm, place it in a quartz test tube, and then put it into a microwave reactor for microwave treatment. The maximum microwave power is set to 150 w, and the program is set to rise to 180 °C in 3 min, keep warm for 1 min and then rise to 240 °C in 12 min. The total treatment time is 16 min.

[0065] Example 7

[0066] In this example, steps S1 to S4 are the same as those in Example 5.

[0067] S5. Microwave pre-oxidation treatment of CNT-CN / P(AN-co-IA) composite precursor filaments: Take 30 cm of precursor filament B and wind it around a quartz rod with a diameter of 10 mm, place it in a quartz test tube, and then put it into a microwave reactor for microwave treatment. The maximum microwave power is set to 160 w, and the program is set to rise to 180 °C in 3 min, keep warm for 1 min and then rise to 260 °C in 16 min. The total treatment time is 20 min.

[0068] Example 8

[0069] In this example, steps S1 to S4 are the same as those in Example 5.

[0070] S5. Microwave pre-oxidation treatment of CNT-CN / P(AN-co-IA) composite precursor filaments: Take 30 cm of precursor filament B and wind it around a quartz rod with a diameter of 10 mm. Place it in a quartz test tube and then put it into a microwave reactor for microwave treatment. The maximum microwave power is set to 160 w, and the program is set to rise to 180 °C in 3 min, keep warm for 1 min and then rise to 280 °C in 20 min. The total treatment time is 24 min.

[0071] Comparative Example 1

[0072] In this example, steps S1 to S4 are the same as those in Example 1.

[0073] S5. Conventional pre-oxidation treatment of CNT-CN / P(AN-co-IA) composite precursor filaments: Place precursor filament A in a tube furnace for continuous temperature rise treatment. The program is set to rise to 180 °C in 15 min, keep warm for 5 min and then rise to 280 °C in 100 min. The total treatment time is 120 min.

[0074] Comparative Example 2

[0075] In this example, steps S1 to S4 are the same as those in Example 5.

[0076] S5. Conventional pre-oxidation treatment of CNT-CN / P(AN-co-IA) composite precursor filaments: Place precursor filament B in a tube furnace for continuous temperature rise treatment. The program is set to rise to 180 °C in 15 min, keep warm for 5 min and then rise to 280 °C in 100 min. The total treatment time is 120 min.

[0077] In Example 1, infrared spectroscopy tests were carried out on CNT-OH, CNT-CN and 4-cyanophenyl isocyanate in step S1. The results are as Figure 1 shown. Compared with the spectra of 4-cyanophenyl isocyanate and CNT-OH, the (-NCO) characteristic peak of CNT-CN at 2270 cm -1 disappeared after the reaction, the (-OH) characteristic peak at around 3450 cm -1 disappeared, and a characteristic peak belonging to (-NH) appeared at around 3320 cm -1 . The cyano (C≡N) characteristic peak was retained at around 2230 cm -1 . This indicates that the hydroxyl group on CNT-OH successfully underwent an esterification reaction with 4-cyanophenyl isocyanate, generating CNT-CN with a cyano functional group at the end.

[0078] In Examples 1-8, infrared spectroscopy tests were carried out on the precursor filaments in step S4 and the microwave pre-oxidized filaments in step S4. The results are as Figure 3a and 3bAs shown, the main chain characteristic absorption peaks of PAN at 2240 cm -1 , 1454 cm -1 , and 1360 cm -1 were respectively attributed to the cyano group C≡N, methylene -CH 2 , and methine -CH; the characteristic peak at 1736 cm -1 came from the carbonyl C=O on the comonomer IA; as the pre-oxidation temperature increased, the absorption peak of the cyano group -CN (2240 cm -1 ) under different conditions decreased with the increase of temperature, and the absorption peaks of the carbon-carbon double bond -C=C-, conjugated nitrile group -C=N-, and imino group -NH- (1580 cm -1 ) increased with the increase of temperature, indicating that the cyclization degree of the pre-oxidized fiber under both conditions was continuously increasing. In addition, as the treatment temperature increased, the absorption peak of methylene -CH 2 (1454 cm -1 ) decreased in intensity, and the absorption peak of methine -CH (1360 cm -1 ) increased in intensity, indicating that dehydrogenation reactions also occurred during the pre-oxidation of PAN.

[0079] The tensile strength, Young's modulus, and elongation at break of the polyacrylonitrile pre-oxidized fibers prepared from raw silk A, Example 1, Example 2, Example 3, Example 4, and raw silk B, Example 5, Example 6, Example 7, Example 8, Comparative Example 1, and Comparative Example 2 were measured, and characterized by infrared spectroscopy, and their pre-oxidation cyclization degrees were calculated. The results are shown in Table 1 below.

[0080] Table 1 Test Results

[0081] Tensile strength (MPa) Young's modulus (GPa) Elongation at break (%) Pre-oxidation cyclization degree (%) Precursor A 186.8 8.2 8.5 — Example 1 187.5 8.4 13.1 20.9 Example 2 179.2 7.5 7.1 39.8 Example 3 163.0 7.2 4.8 60.3 Example 4 153.3 9.1 2.1 80.4 Comparative Example 1 130.0 7.6 1.7 82.4 Precursor B 173.4 7.9 10.4 — Example 5 179.3 8.1 10.8 29.1 Example 6 163.2 7.3 7.7 40.0 Example 7 147.6 7.6 6.0 65.1 Example 8 125.1 8.1 1.9 81.0 Comparative Example 2 127.3 8.6 1.6 81.3

[0082] The results show that as the microwave temperature increased, the tensile strength, Young's modulus, and elongation at break of the polyacrylonitrile pre-oxidized fibers first increased and then decreased, and the pre-oxidation cyclization degree gradually increased, confirming the successful implementation of the microwave pre-oxidation of the present invention. In addition, by comparing with Comparative Examples 1 and 2, it was found that microwave pre-oxidation could achieve a cyclization degree close to that of conventional heating pre-oxidation in a short time (4 times shorter). Among them, the 2wt% CNT-CN / P(AN-co-IA) microwave pre-oxidized fiber had the best mechanical properties when the cyclization degrees were similar, and was more suitable for subsequent carbonization treatment.

[0083] The above specific embodiments are used to explain and illustrate the present invention, and are only the preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A microwave pre-oxidation method based on cyanated carbon nanotube-modified polyacrylonitrile-based carbon fiber precursor, characterized in that: The method comprises the following steps: S1. Preparation of cyanated carbon nanotubes: organic compound A and hydroxylated carbon nanotubes react in a first organic solvent under the action of a catalyst to obtain cyanated carbon nanotubes; The organic compound A contains a cyano group and an isocyanate group; S2, in-situ polymerization preparation of cyanated carbon nanotube / acrylonitrile copolymer: dispersing the obtained cyanated carbon nanotube in a second organic solvent, and copolymerizing with acrylonitrile monomer and a second monomer under the action of an initiator to form a cyanated carbon nanotube / acrylonitrile copolymer; S3, preparation of cyanated carbon nanotube / acrylonitrile copolymer spinning stock solution: stirring the obtained cyanated carbon nanotube / acrylonitrile copolymer and the third organic solvent to completely dissolve at a certain temperature, removing single atoms, degassing, and filtering to obtain the cyanated carbon nanotube / acrylonitrile copolymer spinning stock solution; S4, spinning preparation of cyanated carbon nanotube / acrylonitrile copolymer composite precursor: spinning the obtained cyanated carbon nanotube / acrylonitrile copolymer spinning stock solution to obtain cyanated carbon nanotube / acrylonitrile copolymer composite precursor; S5. Microwave pre-oxidation treatment of composite precursor: subjecting the obtained cyanated carbon nanotube / acrylonitrile copolymer composite precursor to microwave pre-oxidation treatment.

2. The method according to claim 1, characterized in that: In step S1, the chemical structural formula of compound A is as follows: Wherein: R is one of a straight chain alkyl, a cycloalkyl, an aromatic ring, and an aromatic heterocycle; The aromatic ring is a benzene ring or a naphthalene ring; the aromatic heterocyclic ring is one of furan, thiophene, pyrrole and pyridine.

3. The method according to claim 1, characterized in that: In step S1, the first organic solvent is at least one of dichloromethane and dimethylformamide.

4. The method according to claim 1, characterized in that: In step S1, the catalyst is at least one of triethylamine, diacetyl diamine, and triethylene diamine.

5. The method according to claim 1, characterized in that: In step S2, the second organic solvent is at least one of dimethyl sulfoxide and dimethylformamide.

6. The method according to claim 1, characterized in that: In step S2, the second monomer is at least one of itaconic acid, methacrylic acid, methyl methacrylate, methyl acrylate, vinyl acetate, and 2-acrylamide-2-methylpropanesulfonic acid.

7. The method according to claim 1, characterized in that: In step S2, the initiator is at least one of azobisisobutyronitrile, benzoyl peroxide, dicumyl peroxide, potassium persulfate, ammonium persulfate, and sodium bisulfite.

8. The method according to claim 1, characterized in that: In step S2, the in-situ polymerization reaction temperature is 60°C to 100°C; and the in-situ polymerization reaction time is 1 to 36 hours.

9. The method according to claim 1, characterized in that: In step S3, the third organic solvent is at least one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, sodium thiocyanate aqueous solution, and zinc oxide aqueous solution.

10. The method according to claim 1, characterized in that: In step S5, the microwave power in the microwave pre-oxidation treatment is 100-1000W, and the treatment time is 1-60min.

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