Preparation method of high-performance polyacrylonitrile pre-oxidized fiber

Abstract

The invention provides a preparation method of high-performance polyacrylonitrile pre-oxidized fibers, and belongs to the technical field of preparation of carbon filaments from polyacrylonitrile. The preparation method comprises the following steps: adding hydroxylated carbon nanotubes into deionized water, performing ultrasonic dispersion, adding a modifier and a catalyst, continuing ultrasonic dispersion, heating to 80-90 DEG C, performing constant-temperature reaction, fully washing with water, and drying to obtain modified carbon nanotubes; dispersing the modified carbon nanotube in an N, N '-dimethylformamide solution, adding an acrylonitrile monomer, hydroxyethyl acrylate and an initiator, copolymerizing to form a carbon nanotube / acrylonitrile copolymer, and spinning to obtain a carbon nanotube / acrylonitrile copolymer fiber; the carbon nano tube / acrylonitrile copolymer fiber is placed in a microwave treatment device, and a plurality of microwave generators are arranged in the microwave treatment device and are used for carrying out segmented pre-oxidation on the carbon nano tube / acrylonitrile copolymer fiber. The problems that an existing polyacrylonitrile fiber pre-oxidation technology is high in energy consumption and low in strength, poor in flame retardance and the like due to the difference between internal and external pre-oxidation effects can be solved.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of high-performance acrylonitrile pre-oxidized fiber, and belongs to the technical field of carbon fiber manufacturing from polyacrylonitrile. BACKGROUND

[0002] Fire accidents not only directly threaten human life safety, but also cause incalculable economic losses. Therefore, the development of long-acting flame-retardant textiles has always attracted attention from all walks of life.

[0003] Polyacrylonitrile pre-oxidized fiber is a high-performance flame-retardant fiber with heat-resistant ladder structure formed after polyacrylonitrile fiber is treated by oxidation. It is widely used in flame-retardant fabrics, high-temperature resistant filter materials, carbon / carbon composites, activated carbon fiber and other fields due to its intrinsic flame retardancy, high temperature resistance, acid and alkali resistance, and relatively low price. At present, conventional pre-oxidation mainly places PAN original wire in an electric heating furnace for pre-oxidation. Heat is from a heating source, and then is transferred from the outside to the inside of the PAN original wire through heat convection, heat conduction and heat radiation. As the temperature rises, the surface layer of the PAN original wire is first pre-oxidized, and the ladder structure is formed preferentially, and then a dense network structure is formed, which hinders the further diffusion of oxygen to the core. As the heating time increases, the skin-core structure of the PAN original wire becomes more and more obvious, and then the strength, flame retardant performance and uniformity of the fiber are affected.

[0004] Microwave heating is a heating method that uses microwave energy absorbed by materials to realize internal and external heating at the same time. Compared with traditional heating methods, microwave heating has the advantages of energy saving, easy control, selective heating, fast heating speed and high efficiency. Domestic and foreign researchers have tried to apply microwaves to the pre-oxidation of PAN. However, polyacrylonitrile original wire itself does not absorb microwaves, and if you want to improve its wave absorption performance, you need to coat a wave-absorbing material (such as carbon black, carbon nanotubes, graphene, etc.) on its surface. Zhang Zeyang et al. (Aerospace Materials and Technology, 2011, 41(4): 11-14.) found that carbon nanotubes are the best wave-absorbing material among carbon materials. For example, CN111691012A performs microwave oxidation on polyacrylonitrile original wire immersed in a binding solution, and reduces the processing cost through power supply; CN118498009A performs temperature-incremental segmented microwave on polyacrylonitrile fiber felt coated with a microwave sensitizer. However, most fibers are solid structures, and the above-mentioned coating of wave-absorbing materials can solve the consistency of heating of the inner core and the surface layer of the fiber, but it is difficult to achieve uniformity of the entire cross-section treatment effect. CN120061016A introduces cyano carbon nanotubes into the polyacrylonitrile matrix through in-situ polymerization to improve the pre-oxidation efficiency by introducing wave-absorbing materials, but ignores the important role of microwave in rapid transmission and uniform distribution in the fiber. SUMMARY

[0005] Therefore, the application provides a preparation method of high-performance polyacrylonitrile pre-oxidized fiber, which effectively solves the problem of high energy consumption of polyacrylonitrile fiber pre-oxidation, and effectively eliminates the problems of small strength, poor flame retardant performance and easy ash and residue caused by the difference in pre-oxidation effect inside and outside the fiber.

[0006] Specifically, the application is realized by the following scheme:

[0007] A preparation method of high-performance polyacrylonitrile pre-oxidized fiber, the steps are as follows:

[0008] Step one, hydroxylated carbon nanotubes are added to deionized water, and after ultrasonic dispersion, a modifier and a catalyst are added, and ultrasonic dispersion is continued, and then heated to 80-90℃, and after constant temperature reaction, fully washed with water, and dried to obtain modified carbon nanotubes;

[0009] Step two, the modified carbon nanotubes obtained in step one are dispersed in N,N'-dimethylformamide solution, acrylonitrile monomer, hydroxy acrylate and initiator are added, and carbon nanotube / acrylonitrile copolymer is formed by copolymerization, and the copolymer is obtained by conventional wet spinning to obtain carbon nanotube / acrylonitrile copolymer fiber;

[0010] Step three, the carbon nanotube / acrylonitrile copolymer fiber is placed in a microwave treatment device, a plurality of microwave generators are arranged in the microwave treatment device, and the carbon nanotube / acrylonitrile composite fiber is subjected to segmented pre-oxidation: first segment pre-oxidation: 600-800W for 5-10min, second segment pre-oxidation: 1000-1300W for 10-20min, and third segment pre-oxidation: 2000-2500W for 20-30min.

[0011] The above scheme first modifies the hydroxylated carbon nanotubes with unsaturated acid, and introduces into the polyacrylonitrile structure by copolymerization, solves the problem of easy aggregation of carbon nanotubes, provides the uniformity of carbon nanotubes in the fiber, so as to strengthen the absorption of microwave energy into heat energy in the microwave pre-oxidation of the fiber by means of the microwave absorption performance of carbon nanotubes, fundamentally guarantee the uniformity of the pre-oxidation effect, and improve the pre-oxidation efficiency and reduce the energy consumption. The polar molecules of hydroxyethyl acrylate are easy to interact with the microwave electric field, improve the dielectric constant and loss factor, so that more microwave energy is converted into heat energy, thereby enhancing the microwave absorption effect. In addition, the carboxylate group in the hydroxyethyl acrylate decomposes at high temperature, and the carboxylate group decomposes into carboxyl group, which can promote the pre-oxidation reaction in the fiber, especially the cyclization reaction. Moreover, the hydroxyethyl acrylate contains a large amount of oxygen, which can release oxygen elements at high temperature to promote the oxidation reaction. In the segmented microwave process, the first pre-oxidation is carried out at a lower power to promote uniform heating of the fiber and initiate the cyclization reaction and form a stable structure prototype; the second pre-oxidation is carried out at a medium power to cause oxidation reaction and introduce oxygen-containing groups to improve thermal stability; the third pre-oxidation is carried out at a high power to release oxygen elements from the hydroxyethyl acrylate and strengthen the oxidation reaction and complete the structure stabilization.

[0012] Further, as preferred:

[0013] In step one,

[0014] The modifier is an unsaturated carboxylic acid, specifically including one or a mixture of several of itaconic acid, acrylic acid, 2-methyl 3-butenoic acid, and preferably itaconic acid. The itaconic acid molecule contains two carboxyl groups (-COOH), and after modifying the hydroxyl (-OH) carbon nanotubes, the amount of double bonds (C=C) contained on the surface of the modified carbon nanotubes is easy to control, so that the conditions for its participation in the copolymerization of acrylonitrile are easy to control, and a complex spatial network structure is not formed.

[0015] The catalyst is concentrated sulfuric acid with a mass percentage content of 95%.

[0016] The mass ratio of hydroxylated carbon nanotubes, modifier, and catalyst is 5-10:20-50:10-20. Preferably, the molar ratio of carboxyl groups (-COOH) to hydroxyl groups (-OH) satisfies 1:1, and accordingly, the amount of modifier is related to the number of hydroxyl groups in the carbon nanotubes.

[0017] In step two,

[0018] The mass ratio of modified carbon nanotubes, acrylonitrile monomer, and hydroxyethyl acrylate is 0.5-1:90-98:1-3.

[0019] The initiator is azobisisobutyronitrile.

[0020] In step three,

[0021] The microwave pre-oxidation treatment device is provided with eight microwave generators. In the direction of the carbon nanotube / acrylonitrile copolymer fiber entering, the frequency of the front four microwave generators is 915MHz, and the frequency of the rear four microwave generators is 2.45GHz. Different frequencies of microwaves have different penetration depths. High frequency penetrates shallowly, and low frequency penetrates deeply. Simultaneous use of high frequency and low frequency can cover different depth layers, thereby realizing more uniform heating.

[0022] The first pre-oxidation is 600W for 10min, the second pre-oxidation is 1000W for 10min, and the third pre-oxidation is 2000W for 20min.

[0023] Before being placed in the microwave treatment device, the carbon nanotube / acrylonitrile copolymer fiber is also subjected to a humidification treatment, and the water content of the carbon nanotube / acrylonitrile copolymer fiber is controlled to be 5-15%, and preferably 12%. Water is a typical wave-absorbing material. In combination with hydroxy acrylate, the presence of a small amount of water can improve the pre-oxidation efficiency and reduce energy consumption.

[0024] In the segmented microwave treatment of this process, the higher the microwave power, the faster the heating speed. Under the condition of low power (600-800W) for 5-10min, the fiber can be uniformly heated, and the cyclization reaction can be initiated to form a stable structure prototype. Then, under the condition of medium power (1000-1300W) for 10-20min, the oxidation reaction is started, oxygen-containing groups are introduced, and the thermal stability is improved. Finally, under the condition of high power (2000-2500W) for 20-30min, the hydroxy acrylate releases oxygen elements, the oxidation reaction is strengthened, and the structure is stabilized. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0026] Figure 1 The structure of the microwave treatment device in the present application is shown in the figure,

[0027] In the figure, 1 is the first microwave generator, 2 is the second microwave generator, 3 is the third microwave generator, 4 is the fourth microwave generator, 5 is the fifth microwave generator, 6 is the sixth microwave generator, 7 is the seventh microwave generator, 8 is the eighth microwave generator, and 9 is the body.

[0028] Figure 2SEM image of the polyacrylonitrile pre-oxidized fiber in Example 1. DETAILED DESCRIPTION

[0029] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application clearer, the technical solutions in the embodiments of the present application will be further described in detail below in combination with the drawings in the embodiments of the present application. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the technical solutions of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0030] The standards and detection methods on which the present application is based:

[0031] The tensile breaking strength and its coefficient of variation of the polyacrylonitrile fiber are tested according to the national standard GB / T 14337-2022 "Chemical fiber short fiber tensile property test method". Specifically, a YG 006 type electronic single fiber strength machine is used for testing, the gauge is 20 mm, the tensile speed is 10 mm / min, and each sample is tested 50 times for the average value. The coefficient of variation of breaking strength refers to the degree of difference between the breaking strengths of multiple samples under the same conditions. It is usually represented by the standard deviation divided by the average value, and its numerical range is 0 to 1. When the coefficient of variation is close to 0, it indicates that the breaking strength of the sample is relatively concentrated, and the variability is small; when the coefficient of variation is close to 1, it indicates that the breaking strength of the sample is widely distributed, and the variability is large.

[0032] The limiting oxygen index is determined according to the national standard GB / T 5454-1997 "Textile burning property test oxygen index method", and each sample is tested 3 times for the average value.

[0033] The reagents used are commercially available unless otherwise specified.

[0034] Example 1

[0035] The present embodiment provides a preparation method of high-performance polyacrylonitrile pre-oxidized fiber, which is described below in combination with the drawings.

[0036] Step one, carbon nanotube modification: 10 g of hydroxylated carbon nanotubes (provided by Wuhan Kemike Biomedical Technology Co., Ltd.) is added to 1000 mL of deionized water at room temperature, ultrasonic dispersion for about 20 min, then 40 g of itaconic acid, 15 g of concentrated sulfuric acid (98%) are added, and ultrasonic dispersion is continued for 10 min. Heat to 85℃ and keep the temperature for 180 min, wash thoroughly with water, and dry to obtain modified carbon nanotubes.

[0037] Step two, copolymer fiber preparation: 0.8 parts by mass of the modified carbon nanotubes obtained in step one were dispersed in 500 parts by mass of N,N'-dimethylformamide solution, 97 parts by mass of acrylonitrile monomer, 2.2 parts by mass of hydroxyethyl acrylate, and 0.3 parts by mass of azobisisobutyronitrile were added, and under the initiation of azobisisobutyronitrile, copolymerization was carried out at 70°C to form carbon nanotube / acrylonitrile copolymer. The carbon nanotube / acrylonitrile copolymer was subjected to conventional wet spinning to obtain carbon nanotube / acrylonitrile copolymer fiber.

[0038] Step three, pre-oxidation: the moisture content of the carbon nanotube / acrylonitrile copolymer fiber was controlled to be 12%, and the fiber was transferred into the microwave treatment device along the arrow direction for segmented microwave pre-oxidation treatment. First segment: 600W for 10min, second segment: 1000W for 10min, and in the third segment, 2000W for 20min. Figure 1

[0039] The structure of the microwave treatment device is shown in Figure 1 Figure 1, which includes a body 9, and distributed in the body 9: a first microwave generator 1, a second microwave generator 2, a third microwave generator 3, a fourth microwave generator 4, a fifth microwave generator 5, a sixth microwave generator 6, a seventh microwave generator 7, and an eighth microwave generator 8. The frequencies of the first microwave generator 1, the fourth microwave generator 4, the sixth microwave generator 6, and the seventh microwave generator 7 are 915MHz, and the frequencies of the second microwave generator 2, the third microwave generator 3, the fifth microwave generator 5, and the eighth microwave generator 8 are 2.45GHz.

[0040] The pre-oxidized polyacrylonitrile fiber of Example 1 was observed by electron microscopy to observe the pre-oxidation effect, and the results are shown in Figure 2: although there were a small amount of shallow grooves on the surface of the fiber after pre-oxidation treatment, there was no obvious powder residue adhesion, and the small amount of solid particles deposited on the surface of the fiber were probably oligomers of polyacrylonitrile. In addition, no residue fiber was observed when the fiber was shaken by hand.

[0041] Example 2

[0042] This example has the same settings as Example 1, except that in step two, the mass fraction of modified carbon nanotubes is adjusted to 0.2, 0.5, 1.0, and 1.5.

[0043] Table 1 Effect of mass fraction of modified carbon nanotubes

[0044]

[0045] ​As can be seen from Table 1, with the increase of the mass fraction of modified carbon nanotubes, the breaking strength shows a trend of first increasing and then decreasing, and the breaking strength variation coefficient shows a trend of first decreasing and then increasing. At the same time, the limiting oxygen index increases with the increase of the mass fraction of modified carbon nanotubes, and when the mass fraction of modified carbon nanotubes exceeds 1.0 and continues to increase, the limiting oxygen index will obviously decrease. This is because the mass fraction of modified carbon nanotubes is low, which is not enough to achieve uniform distribution inside the fiber, and when the mass fraction is too high, the modified carbon nanotubes will also be aggregated and difficult to be uniformly distributed, which may lead to local excessive oxidation, and then affect the breaking strength and breaking strength variation coefficient. Therefore, the optimal value of the mass fraction of modified carbon nanotubes is 0.8.

[0046] Example 3

[0047] The settings of this example and Example 1 are the same, the difference is that in step two, the mass fraction of hydroxyethyl acrylate is adjusted from 2.2 to 0.5, 1.5, 3.0 and 4.0.

[0048] Table 2: Influence of the mass fraction of modified carbon nanotubes

[0049]

[0050] As can be seen from Table 2, with the increase of the mass fraction of hydroxyethyl acrylate, the breaking strength shows a trend of first increasing and then decreasing, and the breaking strength variation coefficient shows a trend of first decreasing and then increasing. At the same time, the limiting oxygen index increases with the increase of the mass fraction of hydroxyethyl acrylate, and when the mass fraction of hydroxyethyl acrylate exceeds 3 and continues to increase, the limiting oxygen index no longer changes obviously. This is because the lower mass fraction of hydroxyethyl acrylate is not enough to achieve uniform distribution inside the fiber, and when the mass fraction of hydroxyethyl acrylate reaches 2.2, the hydroxyethyl acrylate is uniformly distributed inside the fiber. Therefore, the optimal value of the mass fraction of hydroxyethyl acrylate is 2.2.

[0051] Example 4

[0052] The settings of this example and Example 1 are the same, the difference is that in the pre-oxidation process, the water content of the fiber is replaced from 12% to 4%, 5%, 15% and 20%

[0053] Table 3: Influence of fiber moisture content

[0054]

[0055] As can be seen from Table 3, with the increase of water content, the breaking strength and limiting oxygen index show a trend of first increasing and then decreasing, and the coefficient of variation of breaking strength shows a trend of first decreasing and then increasing. In addition, too low (3%) or too high (20%) water content may cause slight slagging. This is because water molecules have strong polarity and can efficiently absorb microwave energy and convert it into heat energy. When the water content is low, the heating efficiency is low, and the pre-oxidation is insufficient, and when the water content is too high, the steam generated by water evaporation volatilizes rapidly from the inside to the outside of the fiber, resulting in uneven distribution of water content in the fiber, leading to uneven pre-oxidation. Therefore, the optimal value of water content in the fiber is 12%.

[0056] Comparative Example 1

[0057] This comparative example is the same as the setting of Example 1, except that the carbon nanotubes are not modified.

[0058] Comparative Example 2

[0059] This comparative example is the same as the setting of Example 1, except that only the microwave generator with a frequency of 915 MHz, i.e. the first microwave generator 1, the fourth microwave generator 4, the sixth microwave generator 6 and the seventh microwave generator 7, is turned on during pre-oxidation.

[0060] Comparative Example 3

[0061] This comparative example is the same as the setting of Example 1, except that only the microwave generator with a frequency of 2.45 GHz, i.e. the second microwave generator 2, the third microwave generator 3, the fifth microwave generator 5 and the eighth microwave generator 8, is turned on during pre-oxidation.

[0062] Comparative Example 4

[0063] This comparative example is the same as the setting of Example 1, except that no segmented pre-oxidation is performed, and the fibers with a water content of 12% are directly transferred into the microwave treatment device for microwave pre-oxidation treatment at 600 W for 40 min.

[0064] Comparative Example 5

[0065] This comparative example is the same as the setting of Example 1, except that no segmented pre-oxidation is performed, and the fibers with a water content of 12% are directly transferred into the microwave treatment device for microwave pre-oxidation treatment at 1000 W for 40 min.

[0066] Comparative Example 6

[0067] This comparative example is the same as the setting of Example 1, except that no segmented pre-oxidation is performed, and the fibers with a water content of 12% are directly transferred into the microwave treatment device for microwave pre-oxidation treatment at 2000 W for 40 min.

[0068] Comparative Example 7

[0069] CN120061016A was used as Comparative Example 7.

[0070] Table 4: Properties of polyacrylonitrile pre-oxidized fibers prepared in Comparative Examples 1-7 and Example 1

[0071]

[0072]

[0073] As can be seen from Table 4, the breaking strength and limiting oxygen index of Comparative Example 1 were smaller than those of Example 1, and the coefficient of variation of breaking strength was larger. This is because the unmodified carbon nanotubes do not have double bonds that can react with acrylonitrile, and the structure contains more hydroxyl groups, which are prone to aggregation, so it is difficult to disperse uniformly in polyacrylonitrile, and then the oxidation is not uniform. In addition, the places where the carbon nanotubes are deposited are prone to excessive oxidation, and are prone to breakage during stretching.

[0074] Compared with Example 1, the breaking strength of the polyacrylonitrile pre-oxidized fiber prepared by only turning on the microwave generator with a frequency of 915 MHz (Comparative Example 2) or only turning on the microwave generator with a frequency of 2.45 GHz (Comparative Example 3) is smaller, the coefficient of variation of breaking strength is larger, and the limiting oxygen index value is smaller. This is because the penetration depth of microwaves with different frequencies is different, and high frequency penetrates shallowly and low frequency penetrates deeply. At the same time, the use of high frequency and low frequency waves can cover different depth layers, thereby achieving more uniform heating. In addition, 2.45 GHz microwaves can cause excessive oxidation on the surface of the fiber, and a slight slagging phenomenon occurs.

[0075] The data in Table 4 also shows that when the segmented pre-oxidation is not used, the breaking strength of the pre-oxidized fiber gradually decreases with the increase of power, but the limiting oxygen index value gradually increases, but a slight slagging phenomenon occurs when the power is too large (Comparative Example 6). This is because, if the power is too low, the pre-oxidation is not sufficient, and the flame retardant performance is poor, but the fiber strength is large; the pre-oxidation degree is gradually improved with the increase of power, and the flame retardant performance is improved, but if the power is too large, it will cause uneven pre-oxidation, and excessive oxidation occurs in local places, resulting in a slagging phenomenon.

[0076] As can be seen from the data in Example 1 and Table 4, the breaking strength and limiting oxygen index value of Comparative Example 7 are relatively low, and the coefficient of variation of breaking strength is large. This is because in Comparative Example 7, although the cyanated carbon nanotubes are introduced into the fiber structure to improve the microwave pre-oxidation efficiency through the wave absorption effect of carbon nanotubes, the segmented pre-oxidation is not used, so the oxidation uniformity is poor, and the damage to the fiber is large.

[0077] The above-described embodiments only express several possible implementation manners of the present application, the description is relatively specific and detailed, but it cannot be understood as the limitation of the patent scope of the present application, and the embodiments are not used to limit the protection scope in the claims of the present application. For ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, and any equivalent implementation or change made without departing from the present application shall be included in the present application.

Claims

1. A process for the production of high performance polyacrylonitrile pre-oxidized fibers, characterized by, The steps are as follows: Step one, hydroxylated carbon nanotubes are added to deionized water, ultrasonic dispersion is carried out after adding a modifier and a catalyst, ultrasonic dispersion is continued, heating is carried out to 80-90 DEG C, constant temperature reaction is carried out, sufficient water washing is carried out, drying is carried out, and modified carbon nanotubes are obtained; Step two, the modified carbon nanotubes obtained in step one are dispersed in a N,N'-dimethylformamide solution, acrylonitrile monomers, hydroxyethyl acrylate, and an initiator are added, copolymerization is carried out to form carbon nanotube / acrylonitrile copolymer, and spinning is carried out to obtain carbon nanotube / acrylonitrile copolymer fibers; Step three, the carbon nanotube / acrylonitrile copolymer fibers are placed in a microwave treatment device, a plurality of microwave generators are arranged in the microwave treatment device, and the carbon nanotube / acrylonitrile composite fibers are subjected to segmented pre-oxidation: first segment pre-oxidation: 600-800 W for 5-10 min, second segment pre-oxidation: 1000-1300 W for 10-20 min, and third segment pre-oxidation: 2000-2500 W for 20-30 min.

2. The process for the preparation of high performance polyacrylonitrile pre-oxidized fibers according to claim 1, characterized in that: In step one, the modifier is one or a mixture of several of itaconic acid, acrylic acid, and 2-methyl 3-butenoic acid.

3. The process for the preparation of high performance polyacrylonitrile pre-oxidized fibers according to claim 1, characterized in that: In step one, the catalyst is one of sulfuric acid, phosphoric acid, and benzene sulfonic acid.

4. The process for the preparation of high performance polyacrylonitrile pre-oxidized fibers according to claim 1, characterized in that: In step one, the addition mass ratio of the hydroxylated carbon nanotubes, the modifier, and the catalyst is 5-10:20-50:10-20.

5. The process for the preparation of high performance polyacrylonitrile pre-oxidized fibers according to claim 1, characterized in that: In step one, the catalyst is concentrated sulfuric acid with a mass percentage content of 95%.

6. The process for the preparation of high performance polyacrylonitrile pre-oxidized fibers according to claim 1, characterized in that: In step two, the addition mass ratio of the modified carbon nanotubes, the acrylonitrile monomers, and the hydroxyethyl acrylate is 0.5-1:90-98:1-3.

7. The method for preparing high-performance polyacrylonitrile pre-oxidized fiber according to claim 1, characterized in that: The microwave treatment device is provided with eight microwave generators, which respectively emit two frequencies of 915 MHz and 2.45 GHz.

8. A process for the preparation of high performance polyacrylonitrile pre-oxidized fibers according to claim 7, characterized by the fact that: In the direction of the polyacrylonitrile fibers entering the microwave treatment device, the frequencies of the four microwave generators in the front are 915 MHz, and the frequencies of the four microwave generators in the back are 2.45 GHz.

9. The preparation method of the high-performance polyacrylonitrile pre-oxidized fiber according to claim 1, characterized in that, first segment pre-oxidation: 600 W for 10 min, second segment pre-oxidation: 1000 W for 10 min, third segment pre-oxidation: 2000 W for 20 min.

10. The method for preparing high-performance polyacrylonitrile pre-oxidized fiber according to any one of claims 1-9, characterized in that: Before being placed in the microwave treatment device, the water content of the carbon nanotube / acrylonitrile copolymer fibers is controlled to be 5-15%.

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