Preparation method of high-toughness carbon fiber and product thereof

Abstract

The invention relates to the field of composite materials, and discloses a preparation method of high-toughness carbon fiber and a product thereof, and the preparation method of the high-toughness carbon fiber comprises the following steps: ultrasonically dispersing a functional modification additive, tetraethoxysilane and ethanol uniformly, then immersing desized carbon fiber, adding ammonia water for ultrasonic treatment, then taking out, drying, heating and curing to prepare the high-toughness carbon fiber, the functional modified additive is prepared by grafting a modified hydrogenated cardanol derivative and polyethyleneimine, wherein the modified hydrogenated cardanol derivative is prepared by reacting gamma-aminopropyltriethoxysilane, paraformaldehyde and a hydrogenated cardanol derivative; the preparation method comprises the following steps: carrying out a reaction on 4, 4 '-dithio diphenylamine and ethyl 2-chloromethacrylate, carrying out a reaction on an obtained sulfur-containing intermediate and aldehyde group functionalized hydrogenated cardanol, and carrying out nucleophilic addition on the obtained product and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to prepare the hydrogenated cardanol derivative. The epoxy resin-based product prepared from the high-toughness carbon fibers has excellent mechanical properties, flame retardance, water resistance and heat resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite materials, and particularly relates to a preparation method of high-toughness carbon fibers and a product thereof. BACKGROUND

[0002] Carbon fiber reinforced epoxy resin composite materials are widely used in the fields of aerospace, new energy and high-grade civilian products due to their light weight, high specific strength, high specific stiffness and other excellent characteristics. However, the smooth and inert surface of carbon fibers and the poor interface between the carbon fibers and the resin affect the overall performance of the composite materials, so the surface of the carbon fibers must be modified to improve the interface bonding. The existing interface modification methods still have the problem of improving the interface strength at the expense of toughness, and the epoxy resin is a flammable material that produces a large amount of toxic gas during combustion. Adding a flame retardant is the most direct and simple method to improve the flame retardant performance. According to the type of the flame retardant, the flame retardants can be divided into halogen-containing flame retardants and halogen-free flame retardants. The halogen-containing flame retardants emit a large amount of toxic smoke during combustion, causing a "secondary disaster". The traditional halogen-free flame retardant system has the problems of low flame retardant efficiency, large addition amount and poor compatibility with the base material, which significantly reduces the mechanical properties of the material. In addition, the existing carbon fiber reinforced epoxy resin composite materials do not perform well in terms of impact resistance, heat resistance and water resistance, thereby limiting their application range. SUMMARY

[0003] To solve the problems mentioned in the background, the purpose of the present application is to provide a preparation method of high-toughness carbon fibers and a product thereof. The epoxy resin is used as the base material, and the epoxy resin-based product prepared by using the high-toughness carbon fibers has excellent mechanical properties, flame retardant properties, water resistance and heat resistance.

[0004] The purpose of the present application can be achieved by the following technical solutions. A preparation method of high-toughness carbon fibers, comprising the following steps: taking a functional modification additive, tetraethyl orthosilicate and ethanol in a reactor, uniformly ultrasonic dispersing, then immersing in the carbon fibers after desizing, adding ammonia water and continuing ultrasonic treatment, then taking out and drying in a 70-80℃ oven, and then heating to 180-190℃ and curing for 1-1.5h to obtain the high-toughness carbon fibers. The functional modification additive is a modified hydrogenated cardanol derivative prepared by Mannich condensation reaction of gamma-aminopropyl triethoxysilane, paraformaldehyde and hydrogenated cardanol derivative, and then the modified hydrogenated cardanol derivative is subjected to Michael addition reaction with polyethyleneimine to obtain the functional modification additive. The hydrogenated cardanol derivative is prepared by introducing an aldehyde group into the structure of hydrogenated cardanol using paraformaldehyde and tin tetrachloride, by a nucleophilic substitution reaction between 4,4'-dithiodianiline and 2-chloromethyl acrylate to prepare a sulfur-containing intermediate, and by a Schiff base reaction between the aldehyde group functionalized hydrogenated cardanol and the sulfur-containing intermediate to prepare the sulfur-containing Schiff base group hydrogenated cardanol, and by a further nucleophilic addition reaction between the sulfur-containing Schiff base group hydrogenated cardanol and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0005] Preferably, the addition ratio of the functional modification additive, tetraethyl orthosilicate and ammonia water is 4.5-5 g:1 g:0.15-0.25 mL.

[0006] Preferably, the preparation method of the functional modification additive comprises the following steps: I. γ-aminopropyl triethoxysilane, paraformaldehyde and 1,4-dioxane are taken into a reactor, and a hydrogenated cardanol derivative is dissolved in 1,4-dioxane and added dropwise into the reactor through a dropping funnel, and the reaction is carried out at 85-90°C for 7-9h, and after the reaction is completed, the solvent is removed by rotary evaporation to prepare a modified hydrogenated cardanol derivative; II. Polyethyleneimine and anhydrous dichloromethane are taken into a reactor, and a mixed solution of the modified hydrogenated cardanol derivative and anhydrous dichloromethane is added under stirring, and the reaction is carried out at 40-50°C for 20-24h, and after the reaction is completed, the solvent is removed by rotary evaporation to prepare a functional modification additive.

[0007] Preferably, the molar ratio of γ-aminopropyl triethoxysilane, paraformaldehyde and hydrogenated cardanol derivative in step I is 1:2:1.

[0008] Preferably, the mass ratio of the modified hydrogenated cardanol derivative and polyethyleneimine in step II is 4.6-5.8:1.

[0009] Preferably, the preparation method of the hydrogenated cardanol derivative in step I comprises the following steps: A. Hydrogenated cardanol is dissolved in toluene, then triethylamine and tin tetrachloride are added, and the mixture is stirred uniformly at room temperature under a nitrogen atmosphere, then paraformaldehyde is added, and the reaction is carried out at 95-100°C for 8-9h, and after the reaction is completed, the reaction mixture is transferred into deionized water, and the pH value is adjusted to 2, then the water phase is extracted with ethyl acetate, the organic layer is dried with anhydrous sodium sulfate, filtered and concentrated to dryness, and finally purified by chromatography to prepare aldehyde group functionalized hydrogenated cardanol; B, take 4,4'-dithiodianiline, tetrabutylammonium bromide and triethylamine in the reactor, add acetonitrile solvent, and pass nitrogen, then add a mixed solution of 2-chloromethyl acrylate and acetonitrile, stir at 75~80℃ for 3~5h, after reaction, spin, washing, purification, drying, to prepare a sulfur-containing intermediate; C, take the aldehyde functionalized hydrogenated cardanol, sulfur-containing intermediate and N,N-dimethylacetamide in the reactor, and protect the reaction with nitrogen, stir at 75~85℃ for 4~6h, cool to room temperature after reaction, slowly pour the reaction product into deionized water and stir, precipitate with deionized water, stand overnight, filter, dry, to prepare a sulfur-containing Schiff base hydrogenated cardanol; D, take the sulfur-containing Schiff base hydrogenated cardanol and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide respectively in N,N-dimethylformamide, stir at 80~90℃ for 10~12h under nitrogen atmosphere, filter, spin, recrystallize, dry after reaction, to prepare a hydrogenated cardanol derivative.

[0010] Preferably, the molar ratio of 4,4'-dithiodianiline and 2-chloromethyl acrylate in step B is 1:1~1.1.

[0011] The product of high-toughness carbon fiber as described above comprises the following components by weight: epoxy resin 70~95 parts, high-toughness carbon fiber 10~20 parts, curing agent 20~40 parts; the preparation method comprises the following steps: heating the epoxy resin to 55~70℃, then adding the high-toughness carbon fiber and the curing agent, stirring and mixing uniformly, then degassing in a vacuum oven under reduced pressure for 15~25min, and then curing: curing at 80℃ for 2h, curing at 130℃ for 4h, and curing at 180℃ for 3h, to obtain the product of high-toughness carbon fiber.

[0012] Preferably, the epoxy resin is bisphenol A type epoxy resin; and the curing agent is an amine curing agent.

[0013] The beneficial effects of the present application are: The aldehyde group functionalized hydrogenated cardanol is prepared by introducing aldehyde group at ortho position of phenolic hydroxyl group in hydrogenated cardanol structure under the action of paraformaldehyde and tin tetrachloride, meanwhile, one end of amino group in 4,4'-dithiodianiline is used to react with 2-chloromethyl ethyl acrylate to prepare a sulfur-containing intermediate through nucleophilic substitution reaction, then the aldehyde group functionalized hydrogenated cardanol and the ungrafted amino group in the sulfur-containing intermediate are used to react to prepare sulfur-containing Schiff base group hydrogenated cardanol through Schiff base reaction, and the -P-H bond in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is used to react with the Schiff base group (-N=CH) formed in the sulfur-containing Schiff base group hydrogenated cardanol to prepare the hydrogenated cardanol derivative. The hydrogenated cardanol derivative has excellent flame-retardant effect due to the introduction of synergistic flame-retardant nitrogen-phosphorus-sulfur elements in the structure, and contains hydrophobic long-chain alkyl groups and phenolic hydroxyl groups and double bond groups for next reaction.

[0014] The modified hydrogenated cardanol derivative is prepared by using Mannich condensation reaction of gamma-aminopropyl triethoxysilane, paraformaldehyde and phenolic hydroxyl group in the hydrogenated cardanol derivative, then the double bond group introduced in the modified hydrogenated cardanol derivative is used to react with polyethyleneimine to prepare a functional modified additive, and the functional modified additive and tetraethyl orthosilicate are used as raw materials to hydrolyze into silanol under the catalysis of ammonia water under the action of ultrasonic assistance, then two different silanols are dehydrated and condensed and further polycondensed to form composite nanoparticles on the surface of carbon fibers, and after further thermal curing, the benzoxazine introduced on the surface of the carbon fibers can form polybenzoxazine through ring-opening polymerization reaction, and the polybenzoxazine has good heat resistance and chemical resistance, low surface energy and adhesion, and the synergistic effect of the low surface energy of the functional modified additive and the rough structure of the composite nanoparticles endows the carbon fibers with excellent superhydrophobicity and heat resistance, meanwhile, the introduction of the flexible polyethyleneimine structure with rich amine groups and imine groups improves the toughness of the carbon fibers in the epoxy resin curing system, and the high-toughness carbon fibers have excellent compatibility with the epoxy resin, and the epoxy resin-based product prepared by using the high-toughness carbon fibers has excellent mechanical properties, flame-retardant properties, water resistance and heat resistance. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0016] A preparation method of a hydrogenated cardanol derivative in Example 1 comprises the following steps: A, 3.04 g of hydrogenated cardanol was dissolved in 20 mL of toluene, then 0.55 mL of triethylamine and 0.26 g of tin tetrachloride were added, the mixture was stirred uniformly at room temperature under nitrogen atmosphere, then 0.66 g of paraformaldehyde was added, heated to 100°C and reacted for 8 h, after the reaction was cooled, it was transferred into deionized water, and the pH value was adjusted to 2, then the water phase was extracted with ethyl acetate, the organic layer was dried with anhydrous sodium sulfate, filtered and concentrated to dryness, finally, the aldehyde functionalized hydrogenated cardanol was prepared by chromatography (purified using silica, eluent was hexane); B, 4.97 g of 4,4'-dithiodianiline, 0.64 g of tetrabutylammonium bromide and 2.8 mL of triethylamine were taken in a reactor, 50 mL of acetonitrile solvent was added, and nitrogen was introduced, then a mixed solution of 2.97 g of 2-chloromethyl ethyl acrylate and 10 mL of acetonitrile was added, and stirred at 80°C for 3 h, after the reaction was completed, it was rotary evaporated, washed, purified, dried, and the sulfur-containing intermediate was prepared; C, 6.64 g of aldehyde functionalized hydrogenated cardanol (Mr = 332), 7.21 g of sulfur-containing intermediate and 150 mL of N,N-dimethylacetamide were taken in a reactor, the reaction was protected by nitrogen, and stirred at 80°C for 5 h, after the reaction was completed, it was cooled to room temperature, the reaction product was slowly poured into deionized water and stirred, precipitated from deionized water, overnight, suction filtered and dried, and the sulfur-containing Schiff base-based hydrogenated cardanol was prepared; D, 6.74 g of sulfur-containing Schiff base-based hydrogenated cardanol and 2.17 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were respectively dissolved in 50 mL of N,N-dimethylformamide, stirred at 85°C for 12 h under nitrogen atmosphere, after the reaction was completed, it was filtered, rotary evaporated, recrystallized and dried, and the hydrogenated cardanol derivative was prepared.

[0017] The preparation method of the functional modified additive of Example 2 comprises the following steps: Ⅰ, 7.03 g of γ-aminopropyltriethoxysilane, 1.93 g of paraformaldehyde and 100 mL of 1,4-dioxane were taken in a reactor, 27.61 g of the hydrogenated cardanol derivative prepared in Example 1 was dissolved in 50 mL of 1,4-dioxane and added dropwise into the reactor through a dropping funnel, and stirred at 90°C for 8 h, after the reaction was completed, the solvent was removed by rotary evaporation, and the modified hydrogenated cardanol derivative was prepared; Ⅱ, 1.2 g of polyethyleneimine (molecular weight 600 Da) and 30 mL of anhydrous dichloromethane were taken in a reactor, a mixed solution of 5.8 g of the modified hydrogenated cardanol derivative and 40 mL of anhydrous dichloromethane was added under stirring, and stirred at 45°C for 24 h, after the reaction was completed, the solvent was removed by rotary evaporation, and the functional modified additive was prepared.

[0018] Example 3 A method for preparing high-toughness carbon fiber, comprising the following steps: taking 4.8 g of the functional modification additive prepared in Example 2, 1 g of tetraethyl orthosilicate and 100 mL of ethanol in a reactor, uniformly ultrasonic dispersing, then immersing 2 g of the carbon fiber after desizing, adding 0.2 mL of ammonia water and continuing ultrasonic treatment, then taking out and drying in a 70℃ oven, and then heating to 190℃ and curing for 1 h to prepare the high-toughness carbon fiber.

[0019] Example 4 A product of high-toughness carbon fiber, comprising the following components by weight: Epoxy resin E51 73 parts, high-toughness carbon fiber prepared in Example 3 10.8 parts, curing agent 4,4-diamino diphenyl sulfone 22 parts; the preparation method comprises the following steps: heating the epoxy resin to 60℃, then adding the high-toughness carbon fiber and the curing agent, stirring and mixing uniformly, then vacuum degassing in a vacuum oven for 20 min, and then curing: curing at 80℃ for 2 h, curing at 130℃ for 4 h, and curing at 180℃ for 3 h, to obtain the product of high-toughness carbon fiber.

[0020] Example 5 A product of high-toughness carbon fiber, comprising the following components by weight: Epoxy resin E51 86 parts, high-toughness carbon fiber prepared in Example 3 14.4 parts, curing agent 4,4-diamino diphenyl sulfone 31 parts; the preparation method comprises the following steps: heating the epoxy resin to 60℃, then adding the high-toughness carbon fiber and the curing agent, stirring and mixing uniformly, then vacuum degassing in a vacuum oven for 20 min, and then curing: curing at 80℃ for 2 h, curing at 130℃ for 4 h, and curing at 180℃ for 3 h, to obtain the product of high-toughness carbon fiber.

[0021] Example 6 A product of high-toughness carbon fiber, comprising the following components by weight: Epoxy resin E51 94 parts, high-toughness carbon fiber prepared in Example 3 18.9 parts, curing agent 4,4-diamino diphenyl sulfone 38 parts; the preparation method comprises the following steps: heating the epoxy resin to 60℃, then adding the high-toughness carbon fiber and the curing agent, stirring and mixing uniformly, then vacuum degassing in a vacuum oven for 20 min, and then curing: curing at 80℃ for 2 h, curing at 130℃ for 4 h, and curing at 180℃ for 3 h, to obtain the product of high-toughness carbon fiber.

[0022] Comparative Example 1 A method for preparing a functional modification additive, comprising the following steps: I. Take 7.03 g of γ-aminopropyl triethoxysilane, 1.93 g of polyformaldehyde and 100 mL of 1,4-dioxane in a reactor, take another 9.38 g of hydrogenated cardanol dissolved in 50 mL of 1,4-dioxane and add it drop by drop into the reactor through a dropping funnel, place it at 90°C for 8 h of continuous reaction, after the reaction is completed, remove the solvent by rotary evaporation, and prepare a modified hydrogenated cardanol derivative; II. Take 1.2 g of polyethyleneimine (molecular weight 600 Da) and 30 mL of anhydrous dichloromethane into the reactor, add a mixed solution of 5.8 g of the modified hydrogenated cardanol derivative and 40 mL of anhydrous dichloromethane under stirring, place it at 45°C for 24 h of stirring reaction, after the reaction is completed, remove the solvent by rotary evaporation, and prepare a functional modified additive.

[0023] The preparation method of a functional modified additive in Comparative Example 2 includes the following steps: Take 1.2 g of polyethyleneimine (molecular weight 600 Da) and 30 mL of anhydrous dichloromethane into the reactor, add a mixed solution of 5.8 g of the hydrogenated cardanol derivative prepared in Example 1 and 40 mL of anhydrous dichloromethane under stirring, place it at 45°C for 24 h of stirring reaction, after the reaction is completed, remove the solvent by rotary evaporation, and prepare a functional modified additive.

[0024] The preparation method of a high-toughness carbon fiber in Comparative Example 3 includes the following steps: take 4.8 g of the functional modified additive prepared in Comparative Example 1, 1 g of tetraethyl orthosilicate and 100 mL of ethanol into the reactor, ultrasonic dispersion is uniform, then immerse 2 g of desized carbon fiber, add 0.2 mL of ammonia water for continuous ultrasonic treatment, then take it out and put it into a 70°C oven for drying, then heat it to 190°C and solidify it for 1 h, and a high-toughness carbon fiber is prepared.

[0025] The preparation method of a high-toughness carbon fiber in Comparative Example 4 includes the following steps: take 4.8 g of the functional modified additive prepared in Comparative Example 2, 1 g of tetraethyl orthosilicate and 100 mL of ethanol into the reactor, ultrasonic dispersion is uniform, then immerse 2 g of desized carbon fiber, add 0.2 mL of ammonia water for continuous ultrasonic treatment, then take it out and put it into a 70°C oven for drying, then heat it to 190°C and solidify it for 1 h, and a high-toughness carbon fiber is prepared.

[0026] The product of a high-toughness carbon fiber in Comparative Example 5 includes the following components by weight: Epoxy resin E51 94 parts, high-toughness carbon fiber prepared in Comparative Example 3 18.9 parts, curing agent 4,4-diamino diphenyl sulfone 38 parts; the preparation method comprises the following steps: heating the epoxy resin to 60°C, then adding the high-toughness carbon fiber and the curing agent, stirring and uniformly mixing, vacuum degassing in a vacuum oven for 20 min, and then curing by a curing process: curing at 80°C for 2 h, curing at 130°C for 4 h, and curing at 180°C for 3 h, to obtain the high-toughness carbon fiber product.

[0027] Comparative Example 6: A high-toughness carbon fiber product, comprising the following components in parts by weight: Epoxy resin E51 94 parts, high-toughness carbon fiber prepared in Comparative Example 4 18.9 parts, curing agent 4,4-diamino diphenyl sulfone 38 parts; the preparation method comprises the following steps: heating the epoxy resin to 60°C, then adding the high-toughness carbon fiber and the curing agent, stirring and uniformly mixing, vacuum degassing in a vacuum oven for 20 min, and then curing by a curing process: curing at 80°C for 2 h, curing at 130°C for 4 h, and curing at 180°C for 3 h, to obtain the high-toughness carbon fiber product.

[0028] Comparative Example 7: A high-toughness carbon fiber product, comprising the following components in parts by weight: Epoxy resin E51 94 parts, high-toughness carbon fiber prepared in Comparative Example 4 18.9 parts, curing agent 4,4-diamino diphenyl sulfone 38 parts; the preparation method comprises the following steps: heating the epoxy resin to 60°C, then adding the high-toughness carbon fiber and the curing agent, stirring and uniformly mixing, vacuum degassing in a vacuum oven for 20 min, and then curing by a curing process: curing at 80°C for 2 h, curing at 130°C for 4 h, and curing at 180°C for 3 h, to obtain the high-toughness carbon fiber product.

[0029] Performance detection: The products prepared in Examples 4-6 and Comparative Examples 5-7 are subjected to performance detection: (1) Mechanical property test: using a UTM5305 material testing machine to measure, the size of the tensile test and bending test sample is 80 cm long, 10 cm wide and 4 cm thick, the tensile test rate is 5 mm / min, the notched impact property of the material is tested according to GB / T 1843-2008, and the data results are shown in Table 1.

[0030] (2) Heat resistance test: 5-10 mg of sample is weighed in a ceramic crucible, and a thermal gravimetric analyzer is used to measure the thermal decomposition curve, wherein the N2 flow rate is 50 mL / min, the temperature rising range is 50-800°C, the temperature rising rate is 20°C / min, and the heat resistance of the sample is evaluated by the initial thermal decomposition temperature, and the data results are shown in Table 1.

[0031] (3) Water resistance test: dry the sample to constant weight in a vacuum oven at 100°C, accurately weigh its dry weight m1, then immerse the sample in deionized water, remove and absorb the surface water, then accurately measure its wet weight m2, calculate the water absorption rate according to the formula, water absorption rate = (m2-m1) / m2 x 100%, and the data results are shown in Table 1 (4) Flame retardant performance test: according to the standard of ASTM D 2863, using JF-3 oxygen index tester to determine the limiting oxygen index (LOI), the sample size is 130x6.5x3.2mm 3 , and the data results are shown in Table 1.

[0032]

[0033] As can be seen from the data in Table 1, the products prepared in Examples 4-6 have excellent mechanical properties, flame retardant properties, water resistance and heat resistance. Among them, the functional modification additive introduced by the high-toughness carbon fiber added in Comparative Example 5 replaces the hydrogenated cardanol derivative with hydrogenated cardanol in the preparation process, and the measured mechanical properties and limiting oxygen index are lower than those of Examples 4-6, which shows that the addition of hydrogenated cardanol derivative can improve the mechanical properties and flame retardant properties of the product. In Comparative Example 6, the functional modification additive introduced by the high-toughness carbon fiber is not modified in the preparation process of the hydrogenated cardanol derivative, and the measured mechanical properties, initial thermal decomposition temperature and water resistance are lower than those of Examples 4-6, which is because the functional modification additive structure does not introduce benzoxazine and siloxane groups that can hydrolyze to generate silanol. In Comparative Example 7, ordinary commercially available carbon fiber is added, and the measured tensile strength, bending strength, impact strength, initial thermal decomposition temperature, flame retardant properties, water resistance and limiting oxygen index are significantly lower than those of Examples 4-6, which shows that the product prepared by the high-toughness carbon fiber of the application has excellent mechanical properties, flame retardant properties, water resistance and heat resistance.

[0034] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0035] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A method for preparing high-toughness carbon fiber, characterized in that, The process includes the following steps: functional modification additives, tetraethyl orthosilicate and ethanol are placed in a reactor, ultrasonically dispersed evenly, then immersed in desizing carbon fibers, then ammonia water is added for further ultrasonic treatment, then taken out and placed in an oven at 70~80℃ to dry, and then heated to 180~190℃ and cured for 1~1.5h to obtain high-toughness carbon fibers. The functional modification additive is prepared by a Mannich condensation reaction of γ-aminopropyltriethoxysilane, paraformaldehyde and hydrogenated cashew phenol derivative to obtain a modified hydrogenated cashew phenol derivative, and then by a Michael addition reaction of the modified hydrogenated cashew phenol derivative with polyethyleneimine. The hydrogenated cashew nut phenol derivative is prepared by introducing an aldehyde group into the structure of hydrogenated cashew nut phenol using paraformaldehyde and tin tetrachloride to prepare aldehyde-functionalized hydrogenated cashew nut phenol. At the same time, a sulfur-containing intermediate is prepared by nucleophilic substitution reaction of 4,4'-dithiodiphenylamine with ethyl 2-chloromethacrylate. Then, the sulfur-containing Schiff base hydrogenated cashew nut phenol prepared by Schiff base reaction with the aldehyde-functionalized hydrogenated cashew nut phenol and the sulfur-containing intermediate is further prepared by nucleophilic addition reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

2. The method for preparing high-toughness carbon fiber according to claim 1, characterized in that, The ratio of the functional modifier, tetraethyl orthosilicate, and ammonia is 4.5~5g:1g:0.15~0.25mL.

3. The method for preparing high-toughness carbon fiber according to claim 1, characterized in that, The preparation method of the functional modified additive includes the following steps: I. Take γ-aminopropyltriethoxysilane, paraformaldehyde and 1,4-dioxane in a reactor, and separately dissolve hydrogenated cashew phenol derivative in 1,4-dioxane and add it dropwise to the reactor through a dropping funnel. Place the reactor at 85~90℃ and continue to react for 7~9h. After the reaction is completed, remove the solvent by rotary evaporation to prepare the modified hydrogenated cashew phenol derivative. II. Take polyethyleneimine and anhydrous dichloromethane into a reactor, add a mixed solution of modified hydrogenated cashew phenol derivative and anhydrous dichloromethane while stirring, and stir the reaction at 40~50℃ for 20~24h. After the reaction is completed, remove the solvent by rotary evaporation to prepare the functional modified additive.

4. The method for preparing high-toughness carbon fiber according to claim 3, characterized in that, In step I, the molar ratio of γ-aminopropyltriethoxysilane, paraformaldehyde, and hydrogenated cashew phenol derivative is 1:2:

1.

5. The method for preparing high-toughness carbon fiber according to claim 3, characterized in that, In step II, the mass ratio of modified hydrogenated cashew nut extract to polyethyleneimine is 4.6~5.8:

1.

6. The method for preparing high-toughness carbon fiber according to claim 1, characterized in that, The preparation method of the hydrogenated cashew nut extract in step I includes the following steps: A. Dissolve hydrogenated cashew phenol in toluene, then add triethylamine and tin tetrachloride, stir and mix evenly under a nitrogen atmosphere at room temperature, then add paraformaldehyde, heat to 95~100℃ and continue to react for 8~9 hours, after cooling the reactants, transfer them to deionized water and adjust the pH to 2, then extract the aqueous phase with ethyl acetate, dry the organic layer with anhydrous sodium sulfate, filter and concentrate to dryness, and finally purify by chromatography to prepare aldehyde-functionalized hydrogenated cashew phenol; B. Take 4,4'-dithiodiphenylamine, tetrabutylammonium bromide and triethylamine in a reactor, add acetonitrile solvent and purge with nitrogen gas, then add a mixed solution of ethyl 2-chloromethacrylate and acetonitrile, and stir the reaction at 75~80℃ for 3~5h. After the reaction is completed, the sulfur-containing intermediate is prepared by rotary evaporation, washing, purification and drying. C. Place aldehyde-functionalized hydrogenated cashew nut phenol, sulfur-containing intermediate and N,N-dimethylacetamide in a reactor, purge the reaction under nitrogen protection, stir at 75~85℃ for 4~6h, cool to room temperature after the reaction is completed, slowly pour the reaction product into deionized water and stir, precipitate the deionized water, let stand overnight, filter and dry to prepare sulfur-containing Schiff base hydrogenated cashew nut phenol. D. Dissolve sulfur-containing Schiff base hydrogenated cashew phenol and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in N,N-dimethylformamide, respectively, and stir at 80~90℃ for 10~12h under nitrogen atmosphere. After the reaction is completed, filter, rotary evaporate, recrystallize and dry to prepare hydrogenated cashew phenol derivative.

7. The method for preparing high-toughness carbon fiber according to claim 6, characterized in that, In step B, the molar ratio of 4,4'-dithiodiphenylamine and ethyl 2-chloromethacrylate is 1:1 to 1.

1.

8. A product of high-toughness carbon fiber according to any one of claims 1 to 7, characterized in that, The product comprises the following components by weight: 70-95 parts epoxy resin, 10-20 parts high-toughness carbon fiber, and 20-40 parts curing agent. The preparation method includes the following steps: heating the epoxy resin to 55-70℃, then adding the high-toughness carbon fiber and curing agent, stirring and mixing evenly, and then degassing under reduced pressure in a vacuum oven for 15-25 minutes, followed by curing: curing at 80℃ for 2 hours, curing at 130℃ for 4 hours, and curing at 180℃ for 3 hours to obtain the high-toughness carbon fiber product.

9. The high-toughness carbon fiber product according to claim 8, characterized in that, The epoxy resin is a bisphenol A type epoxy resin; the curing agent is an amine curing agent.

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