Amphiphilic carbon fibers, methods of making and using the same

Abstract

The application relates to the technical field of carbon fiber surface modification, and discloses amphiphilic carbon fibers and a preparation method thereof, wherein the amphiphilic carbon fibers comprise a carbon fiber matrix and hydrophilic functional groups and hydrophobic functional groups modified on the surface of the carbon fiber matrix; the hydrophilic functional groups are selected from one or more of amino-substituted ionic liquid groups, hydroxyl groups and carboxyl groups; ionic liquid is electrochemically grafted, and ion exchange reaction is utilized to form the amphiphilic carbon fibers, so that the reaction efficiency can be effectively improved. The obtained amphiphilic carbon fibers and resins have good combination capacity, and the water dispersion performance is improved, the performance expression of the carbon fibers is improved, and the application range is widened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon fiber surface modification, and particularly relates to an amphiphilic carbon fiber and a preparation method thereof. BACKGROUND

[0002] As a kind of high-performance fiber, carbon fiber has the characteristics of high strength, high modulus, good thermal stability and corrosion resistance. In the application process, the interfacial bonding capacity of carbon fiber is one of the important factors affecting its use. Conventional carbon fiber has few active functional groups on the surface, which is difficult to combine with the matrix resin, the performance cannot be effectively expressed, and it is hydrophobic, which is difficult to disperse in water or polar solvents, limiting the expansion of its application field.

[0003] And the surface modification can make up for this shortcoming, such as sizing treatment of carbon fiber to adapt to different resins and enhance hydrophilicity. But the sizing agent has the problems of narrow application of special sizing agent and short board of performance of conventional sizing agent. Therefore, the research on enhancing the universality of carbon fiber is also gradually carried out. The amphiphilic carbon fiber can interact with hydrophilic and hydrophobic groups, which can effectively improve the surface bonding capacity of carbon fiber. However, the current method of oxidation-chemical grafting has a complex reaction process and needs heating energy, which is not conducive to industrial production. Therefore, a simpler modification method is urgently needed. Moreover, the current carbon fiber has poor comprehensive performance of interfacial shear strength and poor water dispersibility. Therefore, it is urgent to research a modified carbon fiber with good comprehensive performance of interfacial shear strength and good water dispersibility. SUMMARY

[0004] The purpose of the present application is to overcome the problems of poor comprehensive performance of interfacial shear strength and poor water dispersibility of carbon fiber in the prior art, and to provide an amphiphilic carbon fiber and a preparation method and application thereof.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides an amphiphilic carbon fiber, wherein the amphiphilic carbon fiber comprises a carbon fiber matrix and a hydrophilic functional group and a hydrophobic functional group modified on the surface of the carbon fiber matrix, and the hydrophilic functional group is selected from one or more of an amino-substituted ionic liquid group, a hydroxyl group and a carboxyl group.

[0006] The second aspect of the present application provides a preparation method of an amphiphilic carbon fiber, comprising the following steps:

[0007] (1) oxidizing carbon fiber to obtain oxidized carbon fiber;

[0008] (2) contacting the oxidized carbon fiber with a mixed solution containing ionic liquid, first organic solvent, condensing agent and conductive agent to perform electrochemical reaction, to obtain covalently grafted carbon fiber;

[0009] (3) The covalently grafted carbon fiber is mixed with a solution containing hydrophobic anions and immersed, and then dried to obtain the amphiphilic carbon fiber.

[0010] A third aspect of the present invention provides an amphiphilic carbon fiber obtained by the preparation method described above.

[0011] The fourth aspect of this invention provides the application of the aforementioned amphiphilic carbon fiber in thermoplastic composite materials and carbon fiber composite paper.

[0012] Through the above technical solution, this invention provides an amphiphilic carbon fiber and its preparation method. The method employs electrochemical grafting of ionic liquids and utilizes ion exchange reactions to form amphiphilic carbon fibers, effectively improving reaction efficiency. The resulting amphiphilic carbon fibers exhibit significantly enhanced interfacial shear strength compared to unmodified carbon fibers, and also improve the water dispersibility of the carbon fibers. Attached Figure Description

[0013] Figure 1 This is a comparison chart of the dispersion results of Example 2 and Comparative Examples 1 and 2.

[0014] Figure 2 This is a schematic diagram of the preparation of amphiphilic carbon fibers. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] The first aspect of the present invention provides an amphiphilic carbon fiber, wherein the amphiphilic carbon fiber comprises a carbon fiber matrix and hydrophilic and hydrophobic functional groups modified on the surface of the carbon fiber matrix, wherein the hydrophilic functional groups are selected from one or more of amino-substituted ionic liquid groups, hydroxyl groups and carboxyl groups.

[0017] This invention provides an amphiphilic carbon fiber, comprising a carbon fiber matrix and hydrophilic and hydrophobic functional groups modified on the surface of the carbon fiber matrix. The carbon fiber surface is rich in oxygen-containing functional groups. While retaining hydrophilic hydroxyl and carboxyl groups, cations from an ionic liquid are introduced as hydrophilic functional groups through the condensation of carboxyl and amino groups, and lipophilic anions are introduced through ion exchange with the ionic liquid. The resulting amphiphilic carbon fiber exhibits significantly improved interfacial shear strength compared to unmodified carbon fiber and also enhances its water dispersibility.

[0018] In some specific embodiments of the present invention, the amphiphilic carbon fiber comprises: carbon fiber and hydrophilic and hydrophobic functional groups modified on the surface of the carbon fiber, wherein the presence is as follows: Figure 2 As shown, taking aminopropylaminopropyl-3-methylimidazolium chloride and sodium dodecyl sulfonate as examples, the amphiphilic structure on the surface of carbon fiber is illustrated. Its hydrophilic functional groups are ionized amino, carboxyl, hydroxyl groups and ionic liquid cations, and its hydrophobic functional group is the hydrophobic anion dodecyl sulfonate ion.

[0019] In some specific embodiments of the present invention, the amino-substituted ionic liquid group is selected from one or more of amino-substituted imidazole cations, amino-substituted pyridine cations, amino-substituted quaternary ammonium salt cations, amino-substituted quaternary phosphonium salt cations, and amino-substituted pyrrole cations, and the hydrophobic functional group is selected from one or more of laurate ion, dodecyl sulfonate ion, decanoate ion, dioctyl dibutyrate sulfonate ion, and bis(trifluoromethanesulfonyl)imide ion (LiNTf2).

[0020] Preferably, based on the total amount of the amphiphilic carbon fibers, the content of the hydrophilic functional groups and the content of the hydrophobic functional groups vary according to the actual amount of feed. In reality, the amphiphilicity varies depending on the number of ionized hydrophilic groups, the number of condensations, and the number of substitutions.

[0021] In some specific embodiments of the present invention, the interfacial shear strength of the amphiphilic carbon fiber is 84-95 MPa, the interlaminar shear strength of the polypropylene resin (POK) is 20-33 MPa, the interlaminar shear strength of nylon 6 (PA6) is 58-68 MPa, and the interlaminar shear strength of the aliphatic polyketone resin (POK) is 68-78 MPa; the interfacial shear strength of the amphiphilic carbon fiber obtained by the present invention is significantly improved compared with that of the unmodified carbon fiber.

[0022] A second aspect of the present invention provides a method for preparing amphiphilic carbon fibers, comprising the following steps:

[0023] (1) Oxidize the carbon fiber to obtain oxidized carbon fiber (OCF);

[0024] (2) The oxidized carbon fiber is contacted with a mixed solution containing an ionic liquid, a first organic solvent, a condensing agent and a conductive agent to carry out an electrochemical reaction to obtain covalently grafted carbon fiber (IL-OCF);

[0025] (3) The covalently grafted carbon fiber is mixed with a salt containing hydrophobic anions and immersed, and then dried to obtain the amphiphilic carbon fiber (DIL-OCF).

[0026] This invention provides a method for preparing amphiphilic carbon fibers. The carbon fibers are pretreated and then oxidized to obtain oxidized carbon fibers with hydrophilic oxygen-containing functional groups on their surface. The oxidized carbon fibers are then added to an electrolyte containing an amino-substituted ionic liquid and a condensing agent for electrolytic condensation. After the reaction, an ion exchange reaction is performed to introduce lipophilic anions while retaining the hydrophilic hydroxyl, carboxyl, and cation groups, ultimately yielding the amphiphilic carbon fibers. The interfacial shear strength of the amphiphilic carbon fibers obtained by this method is significantly improved compared to unmodified carbon fibers, and it also enhances the water dispersibility of the carbon fibers.

[0027] In some specific embodiments of the present invention, the carbon fiber is selected from carbon fiber tow or short carbon fiber.

[0028] In some specific embodiments of the present invention, the carbon fiber is first degummed before performing step (1).

[0029] In some specific embodiments of the present invention, in step (1), the oxidation is carried out by contacting an electrolyte, wherein the electrolyte is selected from one or more aqueous solutions of ammonium bicarbonate, ammonium sulfate and ammonium nitrate, and wherein the concentration of the electrolyte is 0.05-1 mol / L.

[0030] In some specific embodiments of the present invention, in step (1), the current density of the oxidation is 0.1-30 A·m. 2 Preferably 1-15 A·m 2 The oxidation time is 1-30 minutes. The oxidation current density has good controllability and oxidation efficiency within this range.

[0031] In some specific embodiments of the present invention, in step (2), the oxidized carbon fiber is used as the cathode, graphite is used as the anode, and a mixed solution containing an amino ionic liquid, a first organic solvent, a condensing agent and a conductive agent is used as the electrolyte to carry out an electrochemical reaction so as to covalently graft the ionic liquid onto the surface of the carbon fiber.

[0032] In some specific embodiments of the present invention, in step (2), the cation of the amino-substituted ionic liquid is selected from one or more of amino-substituted imidazole cations, amino-substituted pyridine cations, amino-substituted quaternary ammonium salt cations, amino-substituted quaternary phosphonium salt cations, and amino-substituted pyrrole cations; the anion is selected from one or more of halide ions, tetrafluoroborate ions, hexafluorophosphate ions, and hexafluoroantimonate ions. By covalently grafting amino-containing ionic liquids onto the surface of carbon fibers, the interfacial shear strength of the carbon fibers can be significantly improved, and the water dispersibility of their chopped fibers can be enhanced. Furthermore, suitable cations can be selected according to actual applications to obtain better material performance.

[0033] In some specific embodiments of the present invention, in step (2), the first organic solvent is selected from one or more of N,N-dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF) and carbon tetrachloride.

[0034] In some specific embodiments of the present invention, in step (2), the condensing agent is selected from one or more of 2-(7-azabenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate (HATU), O-benzotriazole-N,N,N',N'-tetramethylurea tetrafluoroboric acid (TBTU), O-benzotriazole-tetramethylurea hexafluorophosphate (HBTU), 1-hydroxybenzotriazole (HOBT), dicyclohexylcarbodiimide (DCC), and 4-dimethylaminopyridine (DMAP).

[0035] In some specific embodiments of the present invention, in step (2), the conductive agent is selected from one or more of potassium chloride, potassium sulfate, sodium chloride and potassium nitrate.

[0036] In some specific embodiments of the present invention, in step (2), the mass ratio of the oxidized carbon fiber to the amino-substituted ionic liquid, the first organic solvent, the condensing agent and the conductive agent is 1:1-50:10-100:0.01-5:0.001-3.

[0037] In some specific embodiments of the present invention, in step (2), the current density of the electrochemical reaction is 0.1-30 A × m. 2 The electrochemical reaction takes 0.1-300 min.

[0038] In some specific embodiments of the present invention, the solution of the hydrophobic anion is obtained by dissolving the hydrophobic anion in a second solvent.

[0039] In some specific embodiments of the present invention, in step (3), the mass ratio of the covalently grafted carbon fiber to the salt containing the hydrophobic anion and the second solvent is 1:0.5-100:10-100.

[0040] In some specific embodiments of the present invention, the solution of the hydrophobic anion can also be obtained by dissolving the hydrophobic anion in a mixture of a second solvent and water, wherein the mass ratio of the second solvent to water is 5-95:5-95.

[0041] In some specific embodiments of the present invention, in step (3), the salt containing the hydrophobic anion is selected from one or more of laurate, dodecyl sulfonate, decanoate, dioctyl dibutyrate sulfonate, and bis(trifluoromethanesulfonyl)imide (LiNTf2), preferably dodecyl sulfonate and / or bis(trifluoromethanesulfonyl)imide. Different hydrophobic anion modifications can enhance the bonding ability of carbon fibers to different degrees. Appropriate anions can be selected based on actual applications to obtain better material performance.

[0042] In some specific embodiments of the present invention, in step (3), the second solvent is selected from one or more of dichloromethane, trichloromethane, ethanol, methanol and tetrahydrofuran.

[0043] In some specific embodiments of the present invention, in step (3), the mass ratio of the covalently grafted carbon fiber, the hydrophobic anion and the mixed liquid is 1:0.5-100:10-100.

[0044] In some specific embodiments of the present invention, in step (3), the immersion is selected from ultrasound, microwave or stirring, wherein the power of ultrasound is 1-2000W, the power of microwave is 10-2000W, and the stirring rate is 10-2000rpm.

[0045] In some specific embodiments of the present invention, in step (3), the immersion time is 0.1-72h and the immersion temperature is 0-55℃.

[0046] A third aspect of the present invention provides an amphiphilic carbon fiber obtained by the preparation method described above.

[0047] The fourth aspect of this invention provides the application of the aforementioned amphiphilic carbon fiber in thermoplastic composite materials and carbon fiber composite paper.

[0048] The present invention will be described in detail below through embodiments.

[0049] The aminopropyl-3-methylimidazolium chloride was purchased from a chemical synthesis reagent factory.

[0050] N-aminopropylpyridine chloride was purchased from a chemical synthesis reagent factory.

[0051] Sodium dodecyl sulfonate, purchased from Aladdin.

[0052] LiNTf2, HATU and HBTU were purchased from Bailingwei.

[0053] Potassium chloride, sodium chloride, ammonium bicarbonate, and ammonium bisulfate were purchased from Sinopharm.

[0054] DMF, DMAc, and DCM were purchased from Sinopharm.

[0055] The 550E and 555H were purchased from Orin.

[0056] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0057] Example 1

[0058] Methods for preparing amphiphilic carbon fibers include:

[0059] (1) Carbon fiber is passed through a continuous heating furnace with inert gas and reacted at 500℃ for 10 min to obtain degummed carbon fiber.

[0060] (2) Using degummed carbon fiber as the anode and graphite as the cathode, with 0.1M ammonium bisulfate as the electrolyte, at a temperature of 25℃ and an A·m 2 Under current conditions, electrolysis for 5 minutes yields OCF.

[0061] (3) Take 1.2g of carbon dioxide as the cathode and graphite as the anode, and place it in a mixed solution containing 6g of aminopropyl-3-methylimidazolium chloride, 100mL of DMF, 18mg of HATU, and 10mg of KCl. The temperature is 25℃ and the current density is 25A×m. 2 The reaction was carried out under the specified conditions for 2 hours. Then, it was washed repeatedly with DMF and deionized water and dried to obtain IL-OCF.

[0062] (4) Place 0.6g of IL-OCF in 30mL of dichloromethane, add 1.2g of LiNTf2, and immerse at 35℃ for 6h. Remove the carbon fiber, wash with ethanol and water, and dry to obtain DIL-OCF.

[0063] Example 2

[0064] Methods for preparing amphiphilic carbon fibers include:

[0065] (1) Carbon fiber is passed through a continuous heating furnace with inert gas and reacted at 500℃ for 10 min to obtain degummed carbon fiber.

[0066] (2) Using degummed carbon fiber as the anode and graphite as the cathode, with 0.1M ammonium bisulfate as the electrolyte, at a temperature of 25℃ and an A·m 2 Under current conditions, electrolysis for 5 minutes yields OCF.

[0067] (3) Take 1.2g of carbon dioxide as the cathode and graphite as the anode, and place it in a mixed solution containing 6g of aminopropyl-3-methylimidazolium chloride, 100mL of DMAC, 18mg of HATU, and 10mg of KCl. The temperature is 25℃ and the current density is 5A×m. 2 The reaction was carried out under the specified conditions for 2 hours. Then, it was washed repeatedly with DMF and deionized water and dried to obtain IL-OCF.

[0068] (4) Place 0.6g of IL-OCF in 30mL of dichloromethane, add 1.2g of LiNTf2, and immerse at 35℃ for 6h. Remove the carbon fiber, wash with ethanol and water, and dry to obtain DIL-OCF.

[0069] Example 3

[0070] Methods for preparing amphiphilic carbon fibers include:

[0071] (1) Carbon fiber is passed through a continuous heating furnace with inert gas and reacted at 500℃ for 10 min to obtain degummed carbon fiber.

[0072] (2) Using degummed carbon fiber as the anode and graphite as the cathode, with 0.1M ammonium bisulfate as the electrolyte, at a temperature of 25℃ and an A·m 2 Under current conditions, electrolysis for 5 minutes yields OCF.

[0073] (3) Take 1.2g of carbon dioxide as the cathode and graphite as the anode, and place it in a mixed solution containing 6g of aminopropyl-3-methylimidazolium chloride, 100mL of DMAC, 18mg of HBTU and 10mg of KCl. The temperature is 25℃ and the current density is 25A·m. 2 The reaction was carried out under the specified conditions for 2 hours. Then, it was washed repeatedly with DMF and deionized water and dried to obtain IL-OCF.

[0074] (4) Place 0.6g of IL-OCF in 30mL of ethanol, add 2.3g of sodium dodecyl sulfonate, and immerse for 6h at 25℃. Remove the carbon fiber, wash with ethanol and water, and dry to obtain DIL-OCF.

[0075] Example 4

[0076] Methods for preparing amphiphilic carbon fibers include:

[0077] (1) Carbon fiber is passed through a continuous heating furnace with inert gas and reacted at 500℃ for 10 min to obtain degummed carbon fiber.

[0078] (2) Using degummed carbon fiber as the anode and graphite as the cathode, with 0.1M ammonium bisulfate as the electrolyte, at a temperature of 25℃ and an A·m 2 Under current conditions, electrolysis for 5 minutes yields OCF.

[0079] (3) Take 1.2g of carbon dioxide as the cathode and graphite as the anode, and place it in a mixed solution containing 6g of aminopropyl-3-methylimidazolium chloride, 100mL of DMAC, 18mg of HBTU and 10mg of KCl. The temperature is 25℃ and the current density is 5A·m. 2 The reaction was carried out under the specified conditions for 2 hours. Then, it was washed repeatedly with DMF and deionized water and dried to obtain IL-OCF.

[0080] (4) Place 0.6g of IL-OCF in 30mL of dichloromethane, add 1.2g of LiNTf2, and immerse at 35℃ for 6h. Remove the carbon fiber, wash with ethanol and water, and dry to obtain DIL-OCF.

[0081] Example 5

[0082] Methods for preparing amphiphilic carbon fibers include:

[0083] (1) Carbon fiber is passed through a continuous heating furnace with inert gas and reacted at 500℃ for 10 min to obtain degummed carbon fiber.

[0084] (2) Using degummed carbon fiber as the anode and graphite as the cathode, with 0.1M ammonium bisulfate as the electrolyte, at a temperature of 25℃ and an A·m 2 Under current conditions, electrolysis for 5 minutes yields OCF.

[0085] (3) Take 1.2g of carbon dioxide as the cathode and graphite as the anode, and place it in a mixed solution containing 6.4g of N-aminopropylpyridine chloride, 100mL of DMF, 18mg of HATU and 10mg of KCl. The temperature is 25℃ and the current density is 25A·m. 2 The reaction was carried out under the specified conditions for 2 hours. Then, it was washed repeatedly with DMF and deionized water and dried to obtain IL-OCF.

[0086] (4) Place 0.6g of IL-OCF in 30mL of dichloromethane, add 1.2g of LiNTf2, and immerse at 35℃ for 6h. Remove the carbon fiber, wash with ethanol and water, and dry to obtain DIL-OCF.

[0087] Example 6

[0088] Methods for preparing amphiphilic carbon fibers include:

[0089] (1) Carbon fiber is passed through a continuous heating furnace with inert gas and reacted at 500℃ for 10 min to obtain degummed carbon fiber.

[0090] (2) Using degummed carbon fiber as the anode and graphite as the cathode, with 0.1M ammonium bicarbonate as the electrolyte, at a temperature of 25℃ and an A·m 2 Under current conditions, electrolysis for 5 minutes yields OCF.

[0091] (3) Take 1.2g of carbon dioxide as the cathode and graphite as the anode, and place it in a mixed solution containing 6.4g of N-aminopropylpyridine chloride, 100mL of DMF, 18mg of HATU, and 10mg of NaCl. The temperature is 25℃ and the current density is 25A·m. 2 The reaction was carried out under the specified conditions for 2 hours. Then, it was washed repeatedly with DMF and deionized water and dried to obtain IL-OCF.

[0092] (4) Place 0.6 g of IL-OCF in 30 mL of ethanol, add 2.3 g of sodium dodecyl sulfonate, and immerse for 6 h at 25 °C. Remove the carbon fiber, wash with water, and dry to obtain DIL-OCF.

[0093] Example 7

[0094] Methods for preparing amphiphilic carbon fibers include:

[0095] (1) Carbon fiber is passed through a continuous heating furnace with inert gas and reacted at 500℃ for 10 min to obtain degummed carbon fiber.

[0096] (2) Using degummed carbon fiber as the anode and graphite as the cathode, with 0.1M ammonium bicarbonate as the electrolyte, at a temperature of 25℃ and an A·m 2 Under current conditions, electrolysis for 5 minutes yields OCF.

[0097] (3) Take 1.2g of carbon dioxide as the cathode and graphite as the anode, and place it in a mixed solution containing 6g of aminopropyl-3-methylimidazolium chloride, 100mL of DMF, 23mg of HATU and 10mg of KCl. The temperature is 25℃ and the current density is 25A·m. 2 The reaction was carried out under the specified conditions for 2 hours. Then, it was washed repeatedly with DMF and deionized water and dried to obtain IL-OCF.

[0098] (4) Place 0.6g of IL-OCF in 30mL of dichloromethane, add 1.2g of LiNTf2, and immerse at 35℃ for 6h. Remove the carbon fiber, wash with ethanol and water, and dry to obtain DIL-OCF.

[0099] Comparative Example 1

[0100] Commercial carbon fiber, grade SCF-35S.

[0101] Comparative Example 2

[0102] (1) Carbon fiber is passed through a continuous heating furnace with inert gas and reacted at 500℃ for 10 min to obtain degummed carbon fiber.

[0103] (2) Using degummed carbon fiber as the anode and graphite as the cathode, with 0.1M ammonium bisulfate as the electrolyte, at a temperature of 25℃ and an A·m 2 Under current conditions, electrolysis for 5 minutes yields OCF.

[0104] (3) Take 1.2g of oxidized carbon fiber as the cathode and graphite as the anode, and place it in a mixed solution containing 6.0g of N-aminopropylpyridine chloride, 6.4g of DMF, 100mL of DMF, 18mg of HATU, and 10mg of NaCl. The solution is heated at 25℃ and the current density is 25A·m. 2 The reaction was carried out under the specified conditions for 2 hours. Then, it was washed repeatedly with DMF and deionized water and dried to obtain IL-OCF.

[0105] Dispersion test:

[0106] Water dispersibility tests were performed on Example 2 and Comparative Examples 1 and 2, as follows: Figure 1 As shown in the results, the amphiphilic carbon fiber of Example 2 has better dispersibility in water, while the commercial carbon fiber, i.e., Comparative Example 1, has the worst dispersibility. Comparative Example 2 has better hydrophilicity because it is grafted with ionic liquid and can be dispersed in water, but its uniformity is not as good as that of the amphiphilic carbon fiber.

[0107] Interface performance testing:

[0108] Interlaminar shear strength test method: A single fiber is fixed on a self-made glass mold. A small amount of thermoplastic resin (such as polypropylene resin (POK), nylon 6 (PA6), or aliphatic polyketone resin (POK) in this invention) is applied to the fiber to form a dot. The fiber is heated to 300°C on a flat vulcanizing machine to melt and spontaneously form microbeads. The interlaminar shear strength is tested according to the micro-debonding test method. The coating length of the microbeads is observed under a microscope. Fibers with a coating length between 100-170 μm are selected and passed through a self-made clamp with micropores. The microbeads are fixed in the micropores of the clamp. The clamp is placed on a single fiber strength tester with a length of 10 mm and a tensile speed of 2 mm / min. The interlaminar shear strength of polypropylene resin (POK), nylon 6 (PA6), and aliphatic polyketone resin (POK) are measured respectively.

[0109] Epoxy resin interfacial shear strength: 550E epoxy resin, 555H curing agent and 2-ethylimidazolium accelerator are mixed in a certain proportion to obtain a resin mixture. The resin mixture is coated on the surface of modified carbon fiber to prepare a composite material. The epoxy resin interfacial shear strength of the obtained composite material is measured.

[0110] Interfacial strength tests were conducted on the amphiphilic carbon fibers obtained in the examples and comparative examples, including epoxy resin interfacial shear strength, polypropylene interlaminar shear strength (PP interlaminar shear strength, grade M800E), nylon 6 interlaminar shear strength (PA6 interlaminar shear strength, grade BL3190H), and aliphatic polyketide resin interlaminar shear strength (POK interlaminar shear strength, grade Hyosung M330A from South Korea). The results are shown in Table 1.

[0111] Table 1

[0112]

[0113]

[0114] As can be seen from the results in Table 1, the carbon fibers obtained by this invention all exhibit good interfacial bonding ability with epoxy resin. Examples 1-6 show varying degrees of improvement compared to conventional commercial carbon fibers. Example 7 shows a low current in step (1), resulting in insufficient surface activation and oxidation, fewer active groups, and a low subsequent grafting modification ratio, ultimately leading to weak bonding with epoxy. Comparative Example 2 exhibits high interfacial shear strength because no ion exchange reaction was performed. Hydrophobic anions do not significantly enhance the bonding with epoxy resin; instead, they have a weakening effect, resulting in this outcome. Therefore, this application can specifically set different anions for bonding with different resins.

[0115] For PP, as clearly demonstrated in Examples 3 and 6, the dodecyl sulfonate group, being a hydrophobic anion, showed the best effect because its long hydrophobic chain can bind well with PP. In contrast, NTf2... - It also showed good interlaminar shear strength of PP, but was weaker than that of dodecyl sulfonate. Comparative Example 2, which lacked hydrophobic anions, showed an improvement over Comparative Example 1 because the effect of the imidazole ring and PP was stronger than that of ordinary carbon fiber.

[0116] For PA6, the more carboxyl and hydroxyl groups on the carbon fiber surface, the better the interlaminar shear strength. Amide bonds generated by grafted ionic liquids can also form good bonds with PA6, thus improving the bonding ability compared to the carbon fibers in Comparative Example 1. NTf2 - The binding affinity with PA6 is higher than that with dodecyl sulfonate, hence the data shown in the table.

[0117] POK is a thermoplastic resin with a high proportion of aromatic rings, so it bonds better with pyridine rings. However, imidazole also has directionality, so the modified fibers all have improved bonding ability. Example 7 showed the best results because it was less modified and was closest to carbon fiber. The disordered graphite structure of carbon fiber has aromaticity and bonds best with POK.

[0118] In summary, the advantages of the amphiphilic carbon fiber described in this invention are that it has good bonding ability with various resins, good water dispersibility, and different modified carbon fiber structures can be designed according to different resins to improve the bonding ability with the corresponding resins.

[0119] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for producing amphiphilic carbon fibers, characterized by, The method comprises the following steps: (1) oxidizing carbon fibers to obtain oxidized carbon fibers; (2) contacting the oxidized carbon fibers with a mixed solution containing an amino-substituted ionic liquid, a first organic solvent, a condensing agent and a conductive agent to perform an electrochemical reaction, thereby obtaining covalently grafted carbon fibers; (3) immersing the covalently grafted carbon fibers in a salt containing hydrophobic anions, and then drying to obtain the amphiphilic carbon fibers; The cation of the amino-substituted ionic liquid is selected from one or more of amino-substituted imidazole cation, amino-substituted pyridine cation, amino-substituted quaternary ammonium salt cation, amino-substituted quaternary phosphonium salt cation and amino-substituted pyrrole cation; and the anion is selected from one or more of halide ion, tetrafluoroborate ion, hexafluorophosphate ion and hexafluoroantimonate ion. The salt containing hydrophobic anions is selected from one or more of laurate salt, dodecylsulfonate salt, caprate salt, dioctyl bisulfonate salt and bistrifluoromethylsulfonylimide salt.

2. The production method according to claim 1, wherein, The carbon fibers are selected from carbon fiber tows or short carbon fibers.

3. The production method according to claim 1, wherein Before performing the step (1), the carbon fibers are subjected to a degumming treatment.

4. The production method according to claim 1, wherein In the step (1), the oxidation is performed by contacting an electrolyte, wherein the electrolyte is selected from one or more of aqueous solutions of ammonium bicarbonate, ammonium sulfate and ammonium nitrate.

5. The production method according to claim 1, wherein In step (1), the current density of the oxidation is 0.1-30 A x m 2 and the time of the oxidation is 1-30 min.

6. The production method according to claim 5, wherein The current density of the oxidation is 1-15 A x m 2 .

7. The production method according to claim 1, wherein In the step (2), the first organic solvent is selected from one or more of N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran and carbon tetrachloride.

8. The production method according to claim 1, wherein In the step (2), the condensing agent is selected from one or more of 2-(7-azabenzotriazol)-N,N,N',N'-tetramethyluronium hexafluorophosphate, O-benzotriazol-N,N,N',N'-tetramethyluronium tetrafluoroborate, O-benzotriazol-tetramethyluronium hexafluorophosphate, 1-hydroxybenzotriazole, dicyclohexyl carbodiimide and 4-dimethylamino pyridine.

9. The production method according to claim 1, wherein In the step (2), the conductive agent is selected from one or more of potassium chloride, potassium sulfate, sodium chloride and potassium nitrate.

10. The method of making according to any one of claims 1-9, wherein, In the step (2), the mass ratio of the oxidized carbon fibers to the amino-substituted ionic liquid, the first organic solvent, the condensing agent and the conductive agent is 1:1-50:10-100:0.01-5:0.001-3.

11. The method of producing according to claim 1, wherein, In step (2), the current density of the electrochemical reaction is 0.1-30 A·m 2 , and the time of the electrochemical reaction is 0.1-300 min.

12. The method of producing according to claim 1, wherein, In the step (3), the solution of the hydrophobic anion is obtained by dissolving the hydrophobic anion in a second solvent.

13. The method of producing according to claim 1, wherein, In the step (3), the mass ratio of the covalently grafted carbon fibers, the salt containing hydrophobic anions and the second solvent is 1:0.5-100:10-100.

14. The method of producing according to claim 1, wherein, In the step (3), the second solvent is selected from one or more of dichloromethane, trichloromethane, ethanol, methanol and tetrahydrofuran.

15. The method of producing according to claim 1, wherein, In the step (3), the method of immersion is selected from ultrasonic, microwave or stirring; wherein the power of ultrasonic is 1-2000 W, the power of microwave is 10-2000 W, the stirring rate is 10-2000 rpm, the time of immersion is 0.1-72 h, and the temperature of immersion is 0-55℃.

16. The amphiphilic carbon fibers obtained by the preparation method of any one of claims 1-15.

17. The amphiphilic carbon fiber according to claim 16, wherein, The amphiphilic carbon fiber includes a carbon fiber base and a hydrophilic functional group and a hydrophobic functional group modified on the surface of the carbon fiber base.

18. The amphiphilic carbon fiber according to claim 17, wherein, The hydrophilic functional group is selected from one or more of an amino-substituted ionic liquid group, a hydroxyl group, and a carboxyl group.

19. The amphiphilic carbon fiber of claim 18, wherein, The amino-substituted ionic liquid group is selected from one or more of an amino-substituted imidazole cation, an amino-substituted pyridine cation, an amino-substituted quaternary ammonium salt cation, an amino-substituted quaternary phosphonium salt cation, and an amino-substituted pyrrole cation.

20. The amphiphilic carbon fiber of claim 17, wherein, The hydrophobic functional group is selected from one or more of a laurate ion, a dodecylsulfonate ion, a decanoate ion, a dioctyl butyrate sulfonate ion, and a bistrifluoromethylsulfonylimide ion.

21. The amphiphilic carbon fiber of claim 16, wherein, The amphiphilic carbon fiber has an epoxy resin interfacial shear strength of 84-95 MPa, a polypropylene interlaminar shear strength of 20-33 MPa, a nylon 6 interlaminar shear strength of 58-68 MPa, and an aliphatic polyketone resin interlaminar shear strength of 68-78 MPa.

22. Use of the amphiphilic carbon fiber according to any one of claims 16-21 in thermoplastic composites and carbon fiber composite paper.

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