CN115928268A - A kind of polyacrylonitrile primary thermal oxidation stabilized fiber and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of carbon fibers, and in particular relates to a polyacrylonitrile thermo-oxidatively stabilized fiber and a preparation method and application thereof. The present invention prepares polyacrylonitrile-based carbon fibers by controlling the orientation structure of polyacrylonitrile primary thermo-oxidatively stabilized fibers. The polyacrylonitrile precursor is firstly subjected to initial thermo-oxidative stabilization treatment at 170-240°C, and then at 220-280°C. The post-stage thermo-oxidative stabilization treatment is performed to obtain pre-oxidized polyacrylonitrile fibers, and the pre-oxidized polyacrylonitrile fibers are sequentially subjected to low-temperature carbonization and high-temperature carbonization to obtain high-performance polyacrylonitrile-based carbon fibers. The invention obtains carbon fibers with relatively excellent mechanical properties by controlling the molecular chain orientation structure of polyacrylonitrile initially thermo-oxidatively stabilized fibers, which has important guiding significance for the high-performance carbon fiber industry.

Description

A kind of polyacrylonitrile primary thermal oxidation stabilized fiber and its preparation method and application

technical field

The invention belongs to the technical field of carbon fibers, and in particular relates to a polyacrylonitrile primary thermo-oxidatively stabilized fiber and its preparation method and application.

Background technique

Polyacrylonitrile is prepared by the polymerization reaction mainly based on acrylonitrile monomer, and the polyacrylonitrile fiber precursor is prepared through a series of spinning processes. Then, the polyacrylonitrile precursor needs to undergo thermo-oxidative stabilization treatment to transform the macromolecular chains of the linear structure inside the fiber into a ladder-shaped molecular chain with thermal stability, which can make the fiber stable for subsequent low-temperature carbonization and carbonization. High-temperature carbonization treatment to obtain carbon fibers. The thermal-oxidative stabilization stage is a key step of high-performance polyacrylonitrile-based carbon fibers, which affects the mechanical properties of the final carbon fibers.

During the thermo-oxidative stabilization of polyacrylonitrile fiber precursors, cyclization reactions and oxidation reactions mainly occur. The occurrence of these chemical reactions will not only change the chemical structure but also change the orientation state of polyacrylonitrile molecular chains. Will significantly affect the mechanical properties of the final carbon fiber. If no draft is applied to the polyacrylonitrile precursor during the thermo-oxidative stabilization stage, the polyacrylonitrile fiber will reduce the orientation degree of the polyacrylonitrile molecular chain due to a series of complex physical and chemical reactions at this stage, and the "genetic "to the final carbon fiber, resulting in poor mechanical properties; if the polyacrylonitrile precursor is over-drawn during the thermal-oxidative stabilization stage, the molecular chains in the thermal-oxidative stabilized fiber may be damaged due to excessive The fracture occurs due to the stress, resulting in defects in the material structure, and it will also be "inherited" to the final carbon fiber, resulting in poor mechanical properties. In addition, the degree of stabilization of the polyacrylonitrile fiber needs to be considered for applying a draft ratio to the polyacrylonitrile fiber in the thermo-oxidative stabilization stage. Since the polyacrylonitrile fiber did not undergo a greater degree of cyclization reaction and oxidation reaction in the initial stage of the thermo-oxidative stabilization process, it would be relatively efficient to apply drafting and improve the orientation state of the polyacrylonitrile molecular chain; on the contrary, in the In the later stage of thermo-oxidative stabilization, because the polyacrylonitrile fiber has completed most of the cyclization reaction and oxidation reaction, its molecular chain has also changed from the original relatively soft long straight chain to a relatively rigid trapezoidal polymer chain. The efficiency of applying draft will decrease, and the degree of orientation of the final thermo-oxidatively stabilized polyacrylonitrile fiber is not high. Therefore, in order to improve the mechanical properties of the final carbon fiber, it is possible to obtain a suitable orientation structure of the polyacrylonitrile fiber by applying a suitable draft ratio to the polyacrylonitrile fiber in the thermo-oxidative stabilization stage.

Contents of the invention

What the present invention aims to solve is the control of the orientation structure of polyacrylonitrile fibers in the thermo-oxidative stabilization stage and the problems affecting the mechanical properties of the final carbon fibers existing in the prior art, and provides a polyacrylonitrile primary thermo-oxidatively stabilized fiber, And a method for preparing high-performance carbon fibers by controlling the molecular chain orientation structure in polyacrylonitrile fibers. In the present invention, the degree of orientation (F _i ) of the molecular chain in the polypropylene fiber reaches the optimum level by adopting the level of the additional draw ratio that can be applied to the polyacrylonitrile precursors of different deniers during the initial stage of thermo-oxidative stabilization. Optimum range, to achieve the purpose of preparing high-performance polyacrylonitrile-based carbon fiber.

One of the objectives of the present invention is to provide a primary thermo-oxidatively stabilized polyacrylonitrile fiber, the degree of crystal orientation of the polyacrylonitrile primary thermo-oxidatively stabilized fiber is 0.665-0.720, preferably 0.68-0.70.

The above-mentioned degree of crystal orientation F _i =(180-H)/180, wherein H is the half-height width ( FWHM) size.

The aforementioned polyacrylonitrile primary thermo-oxidatively stabilized fibers are obtained from polyacrylonitrile precursors subjected to thermo-oxidative stabilization treatment.

The second object of the present invention is to provide a method for preparing the above-mentioned polyacrylonitrile primary thermo-oxidatively stabilized fiber, which comprises performing initial thermal-oxidative stabilization treatment on the polyacrylonitrile precursor at 170-240°C to obtain the above-mentioned Polyacrylonitrile initially thermo-oxidatively stabilized fibers.

In the above preparation method, the initial thermo-oxidative stabilization treatment includes at least two temperature zones, wherein the temperature in the first temperature zone is 170-220°C, and the treatment time is 10-25min. Preferably, the temperature in the first temperature zone The temperature is 180-200°C, and the treatment time is 10-20 minutes; the draft ratio applied in the first temperature zone is not less than 10%, preferably 10-33%; the temperature in the second temperature zone is 190-240°C, and the treatment time is 10-25 minutes, preferably, the temperature of the second temperature zone is 200-210° C., and the treatment time is 10-20 minutes; the draft ratio applied in the second temperature zone is 0-5%, preferably 0-4.5%.

In the above preparation method, the polyacrylonitrile precursor is a copolymer, preferably, the comonomer of the copolymer is selected from at least two kinds of acids, esters, and amides; wherein, the acids At least one selected from unsaturated acids, preferably itaconic acid; the esters selected from at least one unsaturated esters, preferably methyl acrylate; the amides selected from unsaturated At least one of amides, preferably acrylamide;

The polyacrylonitrile precursor is prepared by wet method or dry jet wet spinning, which can be realized by wet spinning or dry jet wet spinning process commonly used in this field;

The mass fraction of acrylonitrile monomer in the polyacrylonitrile precursor is not less than 92%;

The fineness of the polyacrylonitrile precursor is 0.79-1.10dtex, preferably 0.85-1.10dtex;

The number of polyacrylonitrile precursors is within the range of parameters commonly used in this field, preferably 3-24K.

The third object of the present invention is to provide a kind of polyacrylonitrile pre-oxidized fiber, the polyacrylonitrile primary thermo-oxidatively stabilized fiber obtained by the above-mentioned polyacrylonitrile primary thermo-oxidatively stabilized fiber or the polyacrylonitrile primary thermo-oxidatively stabilized fiber obtained by the above-mentioned preparation method undergoes high-temperature thermal stabilization treatment after getting.

Specifically, the high-temperature thermal stabilization treatment temperature is 220-280°C; the high-temperature thermal stabilization treatment includes at least four temperature zones, and the treatment time in each temperature zone is 10-20 minutes; the high-temperature thermal stabilization treatment The total draft ratio was 0%.

The fourth object of the present invention is to provide a polyacrylonitrile-based carbon fiber obtained by carbonizing the above-mentioned polyacrylonitrile preoxidized fiber.

Specifically, the carbonization includes low-temperature carbonization and high-temperature carbonization; wherein, the low-temperature carbonization temperature is 300-700°C, the treatment time is 2-6 minutes, and the draft ratio is 0-6%; the high-temperature carbonization temperature The temperature is 1000-1400° C., the treatment time is 1-4 minutes, and the draw ratio is -4--1%. The carbonization is completed under the protection of inert gas.

Adopting the technical scheme of the present invention, in the stage of initial heat stabilization treatment, polyacrylonitrile fibers undergo complex physical and chemical reactions to reduce the degree of orientation of polyacrylonitrile molecular chains, and control the initial heat of polyacrylonitrile by applying appropriate drafting. Oxygen stabilizes the degree of orientation of the fiber molecular chain. When the precursor with a small degree of orientation is subjected to heat treatment, the stress concentration caused by the inappropriate arrangement of the molecular chain and internal defects will be more serious, which will lead to the mechanical properties of the final carbon fiber. Poor problem; on the contrary, the implementation of increased drafting ratio in the early stage of pre-oxidation for the precursor with a small degree of orientation can not only improve the orientation of the molecular chain, avoid the internal stress of the precursor in the initial stage of pre-oxidation, and improve the The degree of internal defects of the precursor can quickly reduce the diameter of the fiber at the beginning of the pre-oxidation stage, shorten the reaction distance of oxygen in the fiber, alleviate the problem of the skin-core structure in the later stage of pre-oxidation, and improve the mechanical properties of the final carbon fiber. The degree of crystal orientation (F _i ) of the polyacrylonitrile fiber stabilized by initial thermo-oxidative treatment is used as an indicator of orientation structure control, and the final polyacrylonitrile-based high-performance carbon fiber obtained has higher tensile strength and tensile modulus. The amount has a relatively good application effect.

In the present invention, the degree of orientation (F _i ) quantified in the XRD azimuth angle scanning spectrum of the polyacrylonitrile primary thermo-oxidatively stabilized fiber is used as an indicator for controlling the molecular chain orientation structure. When the present invention adopts polyacrylonitrile primary thermo-oxidatively stabilized fibers with crystal region orientation F _i value in the range of 0.665-0.720, the finally obtained polyacrylonitrile-based carbon fibers have better mechanical properties. When the polyacrylonitrile primary thermo-oxidative stabilized fiber crystal region orientation F _i value is higher than 0.68, the prepared carbon fiber tensile strength can be higher than 4900MPa, tensile modulus higher than 230GPa; but when the polyacrylonitrile initial stage When the crystal orientation degree F _i value of thermo-oxidatively stabilized fibers is higher than 0.72, the larger external load on the fiber will break the crystal phase inside the fiber and produce more structural defects, and the mechanical properties of the prepared carbon fiber will change. Difference. In addition, it is proved by examples that when the denier of the polyacrylonitrile precursor is large, a large draft ratio can be applied at the initial stage of the thermo-oxidative stabilization treatment at a lower temperature to increase the degree of orientation of the crystal region inside the fiber. As a result, the mechanical properties of the final polyacrylonitrile-based carbon fiber are further improved. The control standard of the molecular chain orientation structure of the polyacrylonitrile initially thermo-oxidatively stabilized fiber involved in the present invention can be used to obtain carbon fibers with relatively excellent mechanical properties, which has important guiding significance for the high-performance carbon fiber industry.

Description of drawings

Fig. 1 is the XRD azimuth angle test curve of the thermo-oxidatively stabilized fiber, wherein the abscissa is the azimuth angle, and the ordinate is the diffraction intensity of the azimuth scan of the initial thermo-oxidatively stabilized fiber of polyacrylonitrile.

Detailed ways

The present invention is specifically described below in conjunction with specific embodiment, it is necessary to point out here that following embodiment is only used for the further description of the present invention, can not be interpreted as the restriction to protection scope of the present invention, those skilled in the art can understand the present invention according to the content of the present invention Some non-essential improvements and adjustments made by the invention still belong to the protection scope of the present invention.

The raw materials used in the examples are all commercially available products.

[Comparative Example 1]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization precursors are used. The copolymerization composition of the precursors is 95.5% of acrylonitrile, 3.5% of methyl acrylate, and 1% of itaconic acid. The fineness is 0.8551dtex. Initial thermo-oxidative stabilization treatment is carried out in the first temperature zone with a temperature of 195°C and the second temperature zone with a temperature of 205°C. At the same time, a draft ratio of 5% is applied to the first temperature zone, and a draft is applied to the second temperature zone. The magnification is 0%, and the heat treatment time in each temperature zone is 15 minutes to obtain the initial thermo-oxidative stabilization of polyacrylonitrile fibers; and then carry out the post-thermal oxygen stabilization treatment in 4 temperature zones, the temperature of the third temperature zone is 225°C, and the temperature of the third temperature zone is 225°C. The temperature in the fourth temperature zone is 240°C, the temperature in the fifth temperature zone is 253°C, the temperature in the sixth temperature zone is 265°C, the applied total draw ratio is 0%, and the heat treatment time in each temperature zone is 15min, and the polyacrylonitrile preform is obtained. Oxidized fibers. The XRD produced by Shimadzu Corporation of Japan was used to scan the azimuthal angle of 2θ≈16.7° on the polyacrylonitrile primary thermo-oxidatively stabilized fiber, and obtain the azimuthal diffraction peak of the fiber (100) crystal plane. By quantifying the half-height width (H) of the diffraction peak of the XRD azimuth scanning, and substituting it into the mathematical formula F _i =(180-H)/180 for calculating the degree of orientation, the crystallinity of the initial thermal-oxidative stabilized fiber of polyacrylonitrile The domain orientation degree F _i . The pre-oxidized polyacrylonitrile fibers that have been stabilized by thermal oxygen are subjected to low-temperature carbonization and high-temperature carbonization in sequence in high-purity nitrogen to prepare the final polyacrylonitrile-based carbon fibers. The temperature of low-temperature carbonization is 320°C-400°C-550°C-700°C, the treatment time is 3min, and the draft ratio is 4%; the temperature of high-temperature carbonization is 1100°C-1200°C-1300°C-1450°C, and the heat treatment time is It is 2min, and the draft ratio is -4%. According to the national standard GB/T25749-2011, the mechanical properties of carbon fiber bundles were tested, and the test results are shown in Table 1.

【Comparative example 2】

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 1.0514dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 35%, the draft ratio in the second temperature zone is 4.5%, other The operating steps and process parameters are the same as in Comparative Example 1. However, due to the breakage of the original filament in the first temperature zone, the carbon fiber sample was not successfully collected.

[Comparative Example 3]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is adopted, and the fineness is 0.8551dtex; the initial stage of thermo-oxidative stabilization: the temperature in the first temperature zone is 220°C, the draft ratio is 15%, and the draft ratio in the second temperature zone It is 4.5%, and other operating steps and process parameters are the same as Comparative Example 1.

【Example 1】

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is adopted, and the fineness is 0.8551dtex; the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 10%, the draft ratio in the second temperature zone is 4.5%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 2]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is adopted, and the fineness is 0.7912dtex; the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 15%, the draft ratio in the second temperature zone is 0%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 3]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is adopted, and the fineness is 0.8551dtex; the initial stage of thermo-oxidative stabilization: the temperature in the first temperature zone is 170°C, the draft ratio is 15%, and the draft ratio in the second temperature zone It is 4.5%, and other operating steps and process parameters are the same as Comparative Example 1.

【Example 4】

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 0.8551dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 15%, the draft ratio in the second temperature zone is 0%, other The operating steps and process parameters are the same as in Comparative Example 1.

【Example 5】

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 0.8551dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 15%, the draft ratio in the second temperature zone is 2.5%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 6]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is adopted, the fineness is 0.8551dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 18%, the draft ratio in the second temperature zone is 0%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 7]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 0.9534dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 11%, the draft ratio in the second temperature zone is 3.5%, and others The operating steps and process parameters are the same as in Comparative Example 1.

[Embodiment 8]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 0.9534dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 16%, the draft ratio in the second temperature zone is 0%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 9]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 0.9534dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 16%, the draft ratio in the second temperature zone is 3.5%, other The operating steps and process parameters are the same as in Comparative Example 1.

【Example 10】

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 0.9534dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 21%, the draft ratio in the second temperature zone is 0%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 11]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 0.9534dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 21%, the draft ratio in the second temperature zone is 3.5%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 12]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is adopted, the fineness is 1.0514dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 12%, the draft ratio in the second temperature zone is 4.5%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 13]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 1.0514dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 17%, the draft ratio in the second temperature zone is 0%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 14]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 1.0514dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 17%, the draft ratio in the second temperature zone is 4.5%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 15]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 1.0514dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 23%, the draft ratio in the second temperature zone is 0%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 16]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 1.0514dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 23%, the draft ratio in the second temperature zone is 4.5%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 17]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 1.0514dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 30%, the draft ratio in the second temperature zone is 0%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 18]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 1.0514dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 30%, the draft ratio in the second temperature zone is 4.5%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 19]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 1.0514dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 33%, the draft ratio in the second temperature zone is 0%, other The operating steps and process parameters are the same as in Comparative Example 1.

[Example 20]

Domestic 3K wet-spun polyacrylonitrile ternary copolymerization raw yarn is used, the fineness is 1.0514dtex, and the initial stage of thermo-oxidative stabilization: the draft ratio in the first temperature zone is 33%, the draft ratio in the second temperature zone is 4.5%, other The operating steps and process parameters are the same as in Comparative Example 1.

The degree of crystal orientation (F _i ) of the polyacrylonitrile primary thermo-oxidatively stabilized fibers obtained in the above comparative examples and examples and the corresponding mechanical properties (including: tensile strength and tensile modulus) of polyacrylonitrile-based carbon fibers obtained The results are listed in Table 1.

Table 1. Comparative example and embodiment F _i value and corresponding carbon fiber mechanical property

Note: Samples were not successfully collected in Comparative Example 2, so there is no specific carbon fiber mechanical performance data

It can be seen from the carbon fiber mechanical property data in Table 1 that, compared with the comparative examples, the orientation degree provided by the present invention is 0.665-0.720, especially the carbon fiber mechanical properties prepared by the polyacrylonitrile primary thermo-oxidatively stabilized fiber at 0.68-0.70. Performance is better. In Comparative Example 2, the draft ratio in the first temperature zone was too high (35%), which caused the polyacrylonitrile precursor to break in the first temperature zone, and failed to prepare carbon fibers; When the magnification ratio is 10-33%, the prepared carbon fiber has better mechanical properties.

Claims (12)

1. A polyacrylonitrile initial thermal oxidation stabilized fiber, characterized in that the crystal orientation degree of the polyacrylonitrile initial thermal oxidation stabilized fiber is 0.665-0.720, preferably 0.68-0.70.

2. The polyacrylonitrile initial thermal oxidation stabilized fiber according to claim 1, characterized in that the polyacrylonitrile initial thermal oxidation stabilized fiber is obtained by performing thermal oxidation stabilization treatment on polyacrylonitrile precursor.

3. A preparation method of polyacrylonitrile initial thermal oxidation stabilized fiber as claimed in claim 1 or 2, which comprises subjecting polyacrylonitrile precursor to initial thermal oxidation stabilization treatment at 170-240 ℃ to obtain the polyacrylonitrile initial thermal oxidation stabilized fiber.

4. The production method according to claim 3,

the initial thermal oxidation stabilization treatment comprises at least two temperature zones.

5. The method according to claim 4, wherein the initial thermal oxidation stabilization treatment comprises:

the temperature of the first temperature zone is 170-220 ℃, and the treatment time is 10-25 min; preferably, the temperature of the first temperature zone is 180-200 ℃, and the treatment time is 10-20 min; and/or the presence of a gas in the gas,

the drafting magnification applied by the first temperature zone is not less than 10%, preferably 10-33%; and/or the presence of a gas in the gas,

the temperature of the second temperature zone is 190-240 ℃, and the treatment time is 10-25 min; preferably, the temperature of the second temperature zone is 200-210 ℃, and the treatment time is 10-20 min; and/or the presence of a gas in the atmosphere,

the second temperature zone is subjected to a draft of 0 to 5%, preferably 0 to 4.5%.

6. The production method according to claim 3,

the polyacrylonitrile protofilament is a copolymer, preferably, the comonomer of the copolymer is selected from at least two of acids, esters and amides; and/or the presence of a gas in the gas,

the polyacrylonitrile protofilament is prepared by wet method or dry-jet wet spinning; and/or the presence of a gas in the gas,

the mass fraction of acrylonitrile monomer in the polyacrylonitrile protofilament is not less than 92 percent; and/or the presence of a gas in the gas,

the fineness of the polyacrylonitrile protofilament is 0.79 to 1.10dtex; and/or the presence of a gas in the gas,

the number of the polyacrylonitrile protofilament is 3-24K.

7. The production method according to claim 6,

the acid is selected from at least one of unsaturated acids, preferably itaconic acid; and/or the presence of a gas in the gas,

the esters are at least one selected from unsaturated esters, and preferably are methyl acrylate; and/or the presence of a gas in the gas,

the amide is at least one selected from unsaturated amides, preferably acrylamide; and/or the presence of a gas in the gas,

the fineness of the polyacrylonitrile protofilament is 0.85 to 1.10dtex.

8. A polyacrylonitrile pre-oxidation fiber is obtained by performing high-temperature thermal stabilization treatment on the polyacrylonitrile initial thermal oxidation stabilization fiber according to claim 1 or 2 or the polyacrylonitrile initial thermal oxidation stabilization fiber precursor obtained by the preparation method according to any one of claims 3 to 7.

9. Polyacrylonitrile pre-oxidized fiber according to claim 8,

the temperature of the high-temperature heat stabilization treatment is 220-280 ℃; and/or the presence of a gas in the atmosphere,

the high-temperature heat stabilization treatment at least comprises four temperature areas, and the treatment time of each temperature area is 10-20 min; and/or the presence of a gas in the gas,

the total draft ratio of the high-temperature thermal stabilization treatment is 0%.

10. A polyacrylonitrile-based carbon fiber obtained by carbonizing the polyacrylonitrile pre-oxidized fiber according to claim 8 or 9.

11. Polyacrylonitrile-based carbon fiber according to claim 10,

the carbonization comprises low-temperature carbonization and high-temperature carbonization; and/or the presence of a gas in the gas,

the carbonization is finished under the protection of inert gas.

12. Polyacrylonitrile-based carbon fiber according to claim 11,

the low-temperature carbonization temperature is 300-700 ℃, the treatment time is 2-6 min, and the drafting multiplying power is 0-6%; and/or the presence of a gas in the atmosphere,

the high-temperature carbonization temperature is 1000-1400 ℃, the treatment time is 1-4 min, and the drafting multiplying power is-4 to-1 percent.

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