Carbon fiber with amine-containing molecules grafted on surface and preparation method and application thereof

Abstract

The invention discloses a carbon fiber grafted with amine-containing molecules on the surface and a preparation method and application thereof, and belongs to the technical field of carbon fiber preparation and surface treatment thereof. According to the method, in an ammonium salt and amine-containing molecule compound electrolyte, electrode alternating electrochemical pulse surface treatment is carried out on carbon fibers. A nucleophilic reaction energy barrier between amine-containing molecules in the electrolyte and oxygen-containing active sites on the surface of the carbon fiber is overcome by using the instantaneous energy of the pulse current, and the reaction kinetics is accelerated. The carbon fiber with the surface grafted with amine-containing molecules can be obtained after cleaning and drying only within 20 s, and the surface nitrogen content can reach 19.22 at.%. A strong chemical bonding effect and a gradient modulus interface phase can be generated between the carbon fiber of which the surface is grafted with abundant amine-containing molecules and a resin matrix, so that the carbon fiber reinforced resin matrix composite material shows excellent mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon fiber preparation and its surface treatment, and particularly relates to a carbon fiber grafted with amine-containing molecules on the surface, and a preparation method and application thereof. Background Art

[0002] Carbon fiber is a strategic functional material with high modulus and high strength containing more than 90% carbon. The carbon fiber composite material made by compounding with matrix resin has been widely used in many fields such as sports, aviation, aerospace, new energy and national defense. However, after the fiber precursor is carbonized at high temperature in an inert gas, the carbon fiber with a low surface energy and an inert graphite surface has poor wettability with the resin, which further restricts the improvement of the overall mechanical properties of the composite material. Therefore, it is necessary to treat the surface of the carbon fiber to increase the number of surface active groups and roughness, so as to improve the interfacial bonding strength with the resin. Surface treatment is a crucial link in the carbon fiber manufacturing process. As early as the 1960s, foreign countries have started research on carbon fiber surface treatment technology. At present, carbon fiber production powers such as Japan and the United States have mastered the core technology of carbon fiber surface treatment. Improving the surface roughness of carbon fiber and increasing the number of surface chemical functional groups are the keys to improving the surface properties of the fiber. The surface treatment technologies of carbon fiber by foreign carbon fiber enterprises and research institutions mainly include: electrochemical oxidation treatment technology, polymer coating technology, high-energy irradiation technology and chemical grafting technology.

[0003] A modified carbon fiber / phenolic resin composite material and a preparation method thereof (CN 114874470 B) disclose that the carbon fiber is first subjected to electrochemical anodic oxidation treatment for 15-20 minutes, washed and dried, and then impregnated in a polyisocyanate solution; the dried carbon fiber is taken out as the anode material and redeposited in an electrodeposition reaction tank for 10-12 minutes to obtain a carbon fiber sample with carbon nanotubes grown on the surface. This method is carried out in multiple steps, involves a relatively cumbersome process, takes a long time and the reagents are not easy to obtain, and is not suitable for large-scale continuous industrial production of carbon fiber.

[0004] A carbon fiber surface treatment process (CN 119553497 A) discloses that nano-silica is carboxylated modified with silane coupling agent KH550 and succinic anhydride, and melamine is used as the coupling agent to graft nano-silica on the carbon fiber, which can fill the surface defects on the carbon fiber surface, thereby improving the mechanical properties of the carbon fiber. This process is divided into 3 steps, and each step requires at least 3-5 hours of treatment.

[0005] Feng et al. disclosed a method for hydrothermally treating carbon fibers in an amine-containing polymer solution (Compos. Part B Eng, 2024, 271, 111190-111202), which can graft polynaphthalene ether nitrile ketone and polyethyleneimine onto the surface of carbon fibers. The nitrogen element content on the surface of the treated carbon fibers can reach up to 14.3 at%, and the surface inertness is significantly reduced. However, the implementation conditions of this method require relatively high industrial production equipment, and the treatment duration exceeding 2 h cannot meet the industrial demand for high efficiency.

[0006] Electrochemical oxidation treatment technology has the advantages of easy control, high efficiency, and continuous treatment, and is widely used in the large-scale continuous production of high-performance carbon fibers in industrial production. However, in the existing carbon fiber electrochemical surface treatment methods, the increase in the number of active groups on the surface of modified carbon fibers is relatively small. The carbon fibers and the resin matrix are mainly combined by mechanical interlocking and weak intermolecular interactions, and almost no chemical bonding occurs between the two. Chemical grafting technology can introduce rich active groups on the surface of carbon fibers, but this technology usually requires multiple steps of treatment, extremely long time-consuming, and a large amount of reagents. Therefore, on the premise of not requiring major modifications to the existing carbon fiber electrochemical oxidation device and meeting the operating speed of the existing industrial production line, it is urgent to develop a technology for electrochemically grafting target molecules onto the surface of carbon fibers that is one-step, ultra-fast (within 20 s), and efficient (ultra-high nitrogen content on the surface: ~20 at.%). Summary of the Invention

[0007] The technical problems to be solved by the present invention are as follows: to provide a method for preparing carbon fibers grafted with amine-containing molecules on the surface, which is suitable for electrochemically grafting any amine-containing molecule on the surface of carbon fibers, with a total treatment time within 20 s, fully meeting the operating speed of the existing industrial carbon fiber production line and the electrochemical oxidation surface treatment device. Another technical problem to be solved by the present invention is to provide carbon fibers grafted with amine-containing molecules on the surface, which have uniformly distributed amine-containing molecules on the surface, with a nitrogen element content reaching 19.22 at%, and the intrinsic mechanical properties of the carbon fibers are not reduced and no hairiness is generated. Another technical problem to be solved by the present invention is to provide the application of carbon fibers grafted with amine-containing molecules on the surface in the preparation of carbon fiber composites. By introducing a large number of active groups on the surface of carbon fibers, the chemical bonding between carbon fibers and resin molecules is enhanced, thereby greatly improving the interfacial bonding performance of carbon fiber reinforced resin matrix composites.

[0008] Technical Solution: To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0009] A preparation method of carbon fiber grafted with amine-containing molecules on the surface, wherein an ammonium salt and an amine-containing molecule are compounded to obtain a compounded electrolyte solution; using the carbon fiber as the working electrode and the graphite plate as the counter electrode, immersing the two in the compounded electrolyte solution to perform ultrafast electrochemical pulse surface treatment with alternating electrodes, and after the reaction is completed, washing and drying are carried out to obtain carbon fiber grafted with amine-containing molecules on the surface; specifically including the following steps:

[0010] Step 1, select carbon fiber after high-temperature carbonization;

[0011] Step 2, compound an ammonium salt and an amine-containing molecule to obtain a compounded electrolyte solution;

[0012] Step 3, using the carbon fiber as the working electrode and the graphite plate as the counter electrode, immersing the two in the compounded electrolyte solution, and under the condition of energization, the amine-containing molecule undergoes a grafting reaction on the surface of the carbon fiber;

[0013] Step 4: After the electrochemical treatment is completed, place the carbon fiber after the grafting reaction into a water washing tank for washing to remove the excess electrolyte adhered to the surface of the carbon fiber, and then dry it.

[0014] In the preparation method of the carbon fiber grafted with amine-containing molecules on the surface, when performing the electrochemical pulse surface treatment with alternating electrodes, the power supply used is one of a DC power supply, a high-frequency pulse power supply or a low-frequency square wave power supply, the treatment method is alternating cathode and anode treatment, the treatment voltage range is 5 - 200V, the pulse width ratio of cathode and anode treatment is 1:1 - 1:20, the pulse interval duration is 50 - 1000 μs, and the total treatment duration is 1 - 20 s; preferably, the treatment voltage range is 10 - 48V, the pulse width ratio of cathode and anode treatment is 1:1 - 1:5; further preferably, the treatment voltage range is 36V, the pulse width ratio of cathode and anode treatment is 1:5, the pulse interval duration is selected as 50 μs, and the total treatment duration is 20 s.

[0015] In the preparation method of the carbon fiber grafted with amine-containing molecules on the surface, the mass fraction of the ammonium salt in the compounded electrolyte solution is 0.1 - 10 wt%, and the mass fraction of the amine-containing molecule is 0.1 - 10 wt%; preferably, the mass fraction of the ammonium salt in the compounded electrolyte solution is 1.5 - 5.0 wt%, and the mass fraction of the amine-containing molecule is 2.0 - 4.0 wt%; further preferably, the mass fraction of the ammonium salt in the compounded electrolyte solution is 1.5 wt%, and the mass fraction of the amine-containing molecule is 2.0 wt%.

[0016] In the preparation method of the carbon fiber grafted with amine-containing molecules on the surface, the carbon fiber is a polyacrylonitrile-based carbon fiber after high-temperature carbonization.

[0017] In the preparation method of the carbon fiber grafted with amine-containing molecules on the surface, the carbon fiber tow is 6k, 12k, 24k or 48k, and the carbon fiber model is T300, T400, T700 or T800.

[0018] The preparation method of the carbon fiber grafted with amine-containing molecules on the surface, wherein the ammonium salt is one or more of ammonium bicarbonate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium sulfate, ammonium phosphate or ammonium thiosulfate; the amine-containing molecules are one or more of aliphatic, heterocyclic, aromatic diamines, polyamines, high molecular polymers and their derivatives.

[0019] The preparation method of the carbon fiber grafted with amine-containing molecules on the surface, wherein the amine-containing molecules are one or more of methylamine, ethylamine, propylamine, cyclohexylamine, piperazine, aniline, o / m / p-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, polypropyleneimine, polyaminoamine or polyetheramine.

[0020] The preparation method of the carbon fiber grafted with amine-containing molecules on the surface, place the carbon fiber grafted with amine-containing molecules on the surface after washing with water for 20 - 60 s in a drying device, and dry it at 110 - 130 °C for 60 - 360 s; preferably, place the carbon fiber grafted with amine-containing molecules on the surface after washing with water for 30 s in a drying device, and dry it at 120 °C for 120 s.

[0021] The carbon fiber grafted with amine-containing molecules on the surface is prepared by the above method.

[0022] The application of the above carbon fiber grafted with amine-containing molecules on the surface in the preparation of carbon fiber composites.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0024] (1) By means of an instantaneous high-energy pulsed current, the present invention overcomes the grafting reaction energy barrier of amine-containing molecules on the carbon fiber surface, accelerates the reaction kinetics, and realizes the preparation of carbon fiber with ultra-high nitrogen content on the surface within 20 s.

[0025] (2) The graftable amine-containing molecules involved in the present invention can be one or more of methylamine, ethylamine, propylamine, cyclohexylamine, piperazine, aniline, o / m / p-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, polypropyleneimine, polyaminoamine or polyetheramine, and have strong universality; cheap reagents can be selected according to actual needs for electrochemical grafting treatment on the carbon fiber surface.

[0026] (3) After surface treatment, the nitrogen element on the obtained carbon fiber surface is evenly distributed, the nitrogen element content can reach 19.22 at.%, and the intrinsic mechanical properties of the carbon fiber are not reduced and there are fewer hair-like filaments.

[0027] (4) The ultrafast electrochemical pulse treatment method for grafting amine-containing molecules on the carbon fiber surface can be well integrated with the electrochemical oxidation treatment equipment in the current carbon fiber industrial production process, without the need for major modifications, and can still match the operating speed of the entire production line, having excellent application prospects.

[0028] (5) A covalent bond interface molecular layer with C-N crosslinking can be formed between the surface-modified carbon fiber and the resin matrix, effectively enhancing the interfacial bonding performance, chemical / thermal stability, and overall mechanical properties of the composite material. Brief Description of the Drawings

[0029] Figure 1 It is the total XPS spectrum of the carbon fibers prepared in Example 1, Example 2, Example 3, Example 4, Example 5, and Comparative Example 1;

[0030] Figure 2 It is the maximum load of the carbon fiber tows prepared in Comparative Example 1, Example 1, Example 2, Example 3, Example 4, and Example 5;

[0031] Figure 3 It is the tensile strength of the carbon fiber-reinforced epoxy resin matrix composites prepared in Comparative Example 1, Example 1, Example 2, Example 3, Example 4, and Example 5;

[0032] Figure 4 It is the interlaminar shear strength of the carbon fiber-reinforced epoxy resin matrix composites prepared in Comparative Example 1, Example 1, Example 2, Example 3, Example 4, and Example 5;

[0033] Figure 5 It is the distribution map of C, N, and O elements on the surface of the carbon fiber prepared in Example 3;

[0034] Figure 6 It is the appearance diagram of the carbon fiber prepared in Example 3;

[0035] Figure 7 It is the thermal stability performance diagram of the tensile strength of the carbon fiber-reinforced epoxy resin matrix composites prepared in Comparative Example 1, Example 1, Example 3, and Example 5. Detailed Embodiments

[0036] The following further clarifies the present invention in conjunction with specific embodiments. The embodiments are implemented on the premise of the technical solution of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0037] Performance tests were carried out on the carbon fibers grafted with amine-containing molecules and carbon fiber-reinforced epoxy resin matrix composites prepared in Examples 1-5, as well as the carbon fibers and carbon fiber-reinforced epoxy resin matrix composites prepared in Comparative Example 1. The test methods and test results are as follows:

[0038] The elemental content on the surface of carbon fiber was tested using an X-ray photoelectron spectrometer, and the results are as Figure 1 shown; the maximum load of the carbon fiber tow was tested using a universal testing machine, and the results are as Figure 2 shown; according to the national standards of the People's Republic of China GB / T 3362-2017 and GB / T 35100-2018, the tensile strength and interlaminar shear strength of the carbon fiber reinforced epoxy resin matrix composite were tested respectively, and the results are as Figure 3 and Figure 4 shown.

[0039] UCF, CF-1, CF-2, CF-3, CF-4 and CF-5 marked in the attached drawings of the specification respectively represent the carbon fibers obtained after treatment in Comparative Example 1, Example 1, Example 2, Example 3, Example 4 and Example 5; UCF / EP, CF-1 / EP, CF-2 / EP, CF-3 / EP, CF-4 / EP and CF-5 / EP respectively represent the carbon fiber reinforced epoxy resin matrix composites prepared from the carbon fibers obtained after treatment in Comparative Example 1, Example 1, Example 2, Example 3, Example 4 and Example 5 and epoxy resin.

[0040] Example 1

[0041] Step 1: Prepare a compound electrolyte of 2.0 wt% diammonium hydrogen phosphate and 2.5 wt% diethylenetriamine, and then completely immerse the T400 carbon fiber (24k) as the working electrode in the compound electrolyte, with the counter electrode being graphite;

[0042] Step 2: Use a high-frequency pulse power supply to treat the carbon fiber both as the anode and as the cathode. The treatment voltage is 25V, the pulse width ratio of the cathode and anode treatments is 1:4, the pulse interval duration is selected as 100 μs, and the total treatment duration is 10 s;

[0043] Step 3: Place the treated carbon fiber in a water washing pool for 60 s, and then dry it in an environment of 120 °C for 360 s to obtain the carbon fiber CF-1 grafted with amine molecules on the surface;

[0044] Step 4: Using CF-1 as the raw material, prepare the carbon fiber reinforced epoxy resin matrix composite CF-1 / EP according to the national standard of the People's Republic of China (GB / T 3362-2017).

[0045] The nitrogen content on the surface of the obtained carbon fiber CF-1 grafted with amine molecules is 13.51 at.%, and the oxygen content is 11.65 at.%; the maximum load of the CF-1 tow is 1.64 kN; the tensile strength of the composite material CF-1 / EP is 3.71 GPa, and the interlaminar shear strength is 100.5 MPa.

[0046] Example 2

[0047] Step 1: Prepare a compound electrolyte of 5.0 wt% diammonium hydrogen phosphate and 3.0 wt% diethylenetriamine. Then, completely immerse T300 carbon fiber (12k) as the working electrode in the compound electrolyte, and the counter electrode is graphite;

[0048] Step 2: Use a high-frequency pulse power supply to treat the carbon fiber as both the anode and the cathode. The treatment voltage is 20V, the pulse width ratio of the cathode and anode treatments is 1:3, the pulse interval duration is selected as 100 μs, and the total treatment duration is 3s;

[0049] Step 3: Place the treated carbon fiber in a water washing tank and wash for 30s, then place it in an environment at 120 °C and dry for 120s to obtain carbon fiber CF-2 grafted with amine molecules on the surface;

[0050] Step 4: Use CF-2 as the raw material to prepare carbon fiber reinforced epoxy resin matrix composite CF-2 / EP according to the National Standard of the People's Republic of China (GB / T 3362-2017).

[0051] The surface nitrogen content of the obtained carbon fiber CF-2 grafted with amine molecules is 3.14 at.%, and the oxygen content is 14.43 at.%; the maximum load of the CF-2 tow is 1.53 kN; the tensile strength of the composite material CF-2 / EP is 3.54 GPa, and the interlaminar shear strength is 87.2 MPa.

[0052] Example 3

[0053] Step 1: Prepare a compound electrolyte of 1.5 wt% diammonium hydrogen phosphate and 2.0 wt% piperazine. Then, completely immerse T800 carbon fiber (24k) as the working electrode in the compound electrolyte, and the counter electrode is graphite;

[0054] Step 2: Use a high-frequency pulse power supply to treat the carbon fiber as both the anode and the cathode. The treatment voltage is 36V, the pulse width ratio of the cathode and anode treatments is 1:5, the pulse interval duration is selected as 50 μs, and the total treatment duration is 20s;

[0055] Step 3: Place the treated carbon fiber in a water washing tank and wash for 30s, then place it in an environment at 120 °C and dry for 120s to obtain carbon fiber CF-3 grafted with amine molecules on the surface;

[0056] Step 4: Use CF-3 as the raw material to prepare carbon fiber reinforced epoxy resin matrix composite CF-3 / EP according to the National Standard of the People's Republic of China (GB / T 3362-2017).

[0057] The surface nitrogen content of the obtained carbon fiber CF-3 grafted with amine-containing molecules is 19.22 at.%, and the oxygen content is 16.32 at.%; the maximum load of the CF-3 tow is 1.75 kN; the tensile strength of the composite material CF-3 / EP is 4.12 GPa, and the interlaminar shear strength is 127.5 MPa.

[0058] Figure 5 and Figure 6 are the distribution maps of C, N, and O elements on the surface of carbon fiber CF-3 and the appearance map of the carbon fiber, respectively. From Figure 5 and Figure 6 it can be seen that after surface treatment, the nitrogen element on the surface of the obtained carbon fiber is evenly distributed, and there are fewer hairy filaments on the appearance of the carbon fiber.

[0059] Example 4

[0060] Step 1: Prepare a compound electrolyte of 2.0 wt% ammonium bicarbonate and 4.0 wt% polyetheramine. Then, immerse the T700 carbon fiber (24k) as the working electrode completely in the compound electrolyte, and the counter electrode is graphite;

[0061] Step 2: Use a high-frequency pulse power supply to treat the carbon fiber as both the anode and the cathode. The treatment voltage is 48 V, the pulse width ratio of the cathode and anode treatments is 1:2, the pulse interval duration is selected as 200 μs, and the total treatment duration is 15 s;

[0062] Step 3: Place the treated carbon fiber in a water washing tank and wash it for 20 s, then place it in an environment of 110 °C and dry it for 120 s to obtain the carbon fiber CF-4 grafted with amine-containing molecules on the surface;

[0063] Step 4: Use CF-4 as the raw material to prepare the carbon fiber reinforced epoxy resin matrix composite material CF-4 / EP according to the national standard of the People's Republic of China (GB / T 3362-2017).

[0064] The surface nitrogen content of the obtained carbon fiber CF-4 grafted with amine-containing molecules is 18.67 at.%, and the oxygen content is 19.33 at.%; the maximum load of the CF-4 tow is 1.68 kN; the tensile strength of the composite material CF-4 / EP is 4.01 GPa, and the interlaminar shear strength is 119.8 MPa.

[0065] Example 5

[0066] Step 1: Prepare a compound electrolyte of 4.0 wt% ammonium bicarbonate and 2.5 wt% ethylenediamine. Then, immerse the T300 carbon fiber (6k) as the working electrode completely in the compound electrolyte, and the counter electrode is graphite;

[0067] Step 2: Use a high-frequency pulse power supply to treat carbon fiber as both the anode and the cathode. The treatment voltage is 10 V, the pulse width ratio of the cathode and anode treatments is 1:1, the pulse interval duration is selected as 1000 μs, and the total treatment duration is 1 s.

[0068] Step 3: Place the treated carbon fiber in a water washing tank and wash it for 20 s, then place it in an environment of 130 °C and dry it for 60 s to obtain carbon fiber CF-5 with amine-containing molecules grafted on the surface.

[0069] Step 4: Use CF-5 as the raw material to prepare carbon fiber reinforced epoxy resin matrix composite CF-5 / EP according to the National Standard of the People's Republic of China (GB / T 3362-2017).

[0070] The surface nitrogen content of the obtained carbon fiber CF-5 with amine-containing molecules grafted on the surface is 4.12 at.%, and the oxygen content is 11.11 at.%; the maximum load of the CF-5 tow is 1.56 kN; the tensile strength of the composite material CF-5 / EP is 3.59 GPa, and the interlaminar shear strength is 85.4 MPa.

[0071] Comparative Example 1

[0072] Step 1: Prepare a compound electrolyte of 1.5 wt% diammonium hydrogen phosphate and 2.0 wt% piperazine, and then completely immerse T800 carbon fiber (24k) as the working electrode in the compound electrolyte for 20 s. The counter electrode is graphite, but no electrochemical treatment is carried out.

[0073] Step 2: Place the untreated carbon fiber in a water washing tank and wash it for 30 s, then place it in an environment of 120 °C and dry it for 120 s to obtain carbon fiber UCF.

[0074] Step 3: Use UCF as the raw material to prepare carbon fiber reinforced epoxy resin matrix composite UCF / EP according to the National Standard of the People's Republic of China (GB / T 3362-2017).

[0075] The surface nitrogen content of the obtained carbon fiber UCF is 2.31 at.%, and the oxygen content is 4.46 at.%; the maximum load of the UCF tow is 1.25 kN; the tensile strength of the composite material UCF / EP is 3.12 GPa, and the interlaminar shear strength is 57.98 MPa.

[0076] Figure 7 Thermal stability performance diagram of the tensile strength of the carbon fiber reinforced epoxy resin matrix composites prepared in Comparative Example 1, Example 1, Example 3, and Example 5. From Figure 7It can be observed that with the increase in temperature, the tensile strength of all composite materials shows a downward trend. When the test temperature exceeds the interfacial transformation temperature (Tg, which is positively correlated with the interfacial crosslinking density) of the composite material, the mechanical properties of the material will fail. As the temperature increases from 25 °C to 100 °C, the tensile strength of the composite material UCF / EP prepared from untreated carbon fibers rapidly decreases by 41%, while the composite material prepared from treated carbon fibers with a higher nitrogen content has good thermal stability. For CF-3 / EP, even when the temperature rises to 150 °C, the tensile strength retention rate is still as high as 61%. This indicates that after electrochemical pulse treatment, a large number of amine-containing molecules grafted on the surface of CF-3 significantly increase the interfacial crosslinking density between it and epoxy resin, and the higher Tg value enhances the thermal stability of CF-3 / EP.

[0077] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of carbon fiber grafted with amine-containing molecules on the surface, characterized in that, In the ammonium salt and amine-containing molecule complex electrolyte, electrochemical pulse surface treatment with electrode alternation is carried out on carbon fiber. After the reaction, it is washed and dried to obtain carbon fiber with amine-containing molecules grafted on the surface.

2. The preparation method of the carbon fiber with amine-containing molecules grafted on the surface according to claim 1, characterized in that, For the electrochemical pulse surface treatment with electrode alternation, carbon fiber is used as the working electrode, and a graphite plate is used as the counter electrode. The power supply used is one of a DC power supply, a high-frequency pulse power supply, or a low-frequency square-wave power supply. The treatment method is cathode and anode alternation treatment. The treatment voltage range is 5 - 200 V, the pulse width ratio of cathode and anode treatment is 1:1 - 1:20, the pulse interval duration is 50 - 1000 μs, and the total treatment duration is 1 - 20 s.

3. The preparation method of the carbon fiber with amine-containing molecules grafted on the surface according to claim 1, characterized in that, In the complex electrolyte, the mass fraction of the ammonium salt is 0.1 - 10 wt%, and the mass fraction of the amine-containing molecule is 0.1 - 10 wt%.

4. The preparation method of the carbon fiber with amine-containing molecules grafted on the surface according to claim 1, characterized in that, The carbon fiber is a polyacrylonitrile-based carbon fiber after high-temperature carbonization.

5. The preparation method of the carbon fiber with amine-containing molecules grafted on the surface according to claim 1, characterized in that, The carbon fiber tow is 6k, 12k, 24k, or 48k, and the carbon fiber model is T300, T400, T700, or T800.

6. The preparation method of the carbon fiber with surface-grafted amine-containing molecules according to claim 1, wherein, The ammonium salt is one or more of ammonium bicarbonate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium sulfate, ammonium phosphate, or ammonium thiosulfate; the amine-containing molecule is one or more of aliphatic, heterocyclic, aromatic diamines, polyamines, high molecular polymers, and their derivatives.

7. The preparation method of the carbon fiber with amine-containing molecules grafted on the surface according to claim 1, characterized in that, The amine-containing molecule is one or more of methylamine, ethylamine, propylamine, cyclohexylamine, piperazine, aniline, o- / m- / p-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, polypropyleneimine, polyaminoamine, or polyetheramine.

8. The preparation method of the carbon fiber with amine-containing molecules grafted on the surface according to claim 1, characterized in that, The carbon fiber with amine-containing molecules grafted on the surface after being washed with water for 20 - 60 s is placed in a drying device and dried at 110 - 130 °C for 60 - 360 s.

9. Carbon fiber with amine-containing molecules grafted on the surface prepared by the method according to any one of claims 1 - 8.

10. Application of the carbon fiber with amine-containing molecules grafted on the surface according to claim 9 in the preparation of carbon fiber composites.

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