Carbon nanotube fiber sizing agent, carbon nanotube fiber interface modification method and application

Abstract

The application discloses a carbon nanotube fiber sizing agent, a carbon nanotube fiber interface modification method and application. The preparation method of the carbon nanotube fiber sizing agent comprises the following steps: mixing a carbon nanotube-philic compound, an intermediate compound and a solvent, and then adding an amine group-containing compound to react, so as to obtain the carbon nanotube fiber sizing agent. The carbon nanotube fiber interface modification method comprises the following steps: immersing the carbon nanotube fiber in the carbon nanotube fiber sizing agent, and then performing heating treatment on the sized carbon nanotube fiber. The application provides a sizing agent for the carbon nanotube fiber and a carbon nanotube fiber interface modification technology. The use of the sizing agent is not affected by the preparation method of the carbon nanotube fiber, and the finished carbon nanotube fiber is directly subjected to secondary sizing modification treatment. The preparation method is simple, the use efficiency is high, and the interface performance between the carbon nanotube fiber and the epoxy resin in the composite material can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite materials technology, and relates to a carbon nanotube fiber sizing agent and its preparation method, as well as the corresponding carbon nanotube fiber interface modification method and application. Background Technology

[0002] Carbon nanotubes (CNTs) are widely recognized as a highly promising reinforcing phase for composite materials, following carbon fibers, and carbon nanotube fibers are considered the most promising new nanofiber materials. The main failure mode of traditional carbon fiber materials is interfacial failure, requiring the use of sizing agents to improve the interfacial bonding between the fiber and resin. Similarly, when preparing composite materials using carbon nanotube fibers, the interfacial bonding strength between the carbon nanotube fibers and the resin matrix must be considered. Meanwhile, the density of carbon nanotube fibers is lower than that of carbon fibers, and the network structure composed of carbon nanotubes within the fiber also requires resin impregnation to achieve load transfer. The interfacial problems of carbon nanotube fiber composites are far more complex than those of carbon fibers, requiring consideration not only of the fiber-resin interface but also the design of the interface between the carbon nanotubes within the fiber and the resin.

[0003] Existing literature lacks reports on sizing agents for carbon nanotube fibers. Current techniques primarily involve directly modifying carbon nanotube powder using covalent or non-covalent modification methods, then using the modified carbon nanotubes to prepare carbon nanotube fiber materials. The mechanical properties of carbon nanotube fibers prepared by solution spinning after modification are relatively low. Therefore, a problem with this method is that the content of the modifying component is too high, ultimately affecting the mechanical properties of the carbon nanotube composite material. For example, the reported mechanical properties of carbon nanotube fibers prepared by chlorosulfonic acid spinning can reach 1–5 GPa, but the original modifying component cannot be retained under extremely acidic conditions.

[0004] Carbon nanotube fibers are currently in the research stage, and there are no commercial carbon nanotube fiber products. Research on sizing agents for carbon nanotube fibers is completely lacking. Summary of the Invention

[0005] The main objective of this invention is to provide a carbon nanotube fiber sizing agent and its preparation method, thereby overcoming the shortcomings of the prior art.

[0006] Another objective of this invention is to provide a method for modifying the interface of carbon nanotube fibers and its application.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] This invention provides a method for preparing a carbon nanotube fiber sizing agent, which includes: mixing a carbon nanotube-loving compound, an intermediate compound, and a solvent, and then adding an amine-containing compound to react and obtain the carbon nanotube fiber sizing agent.

[0009] In some preferred embodiments, the preparation method includes: mixing a carbon nanotube compound, an intermediate compound, and a solvent, then adding a buffer reagent to adjust the pH of the obtained mixed reaction system to 7.5-9, stirring for 6-12 hours, then adding an amine-containing compound, raising the temperature of the mixed reaction system to 45-60°C and stirring for 0.5-3 hours to obtain a carbon nanotube fiber sizing agent.

[0010] This invention also provides a carbon nanotube fiber sizing agent prepared by the aforementioned preparation method.

[0011] This invention also provides a method for modifying the interface of carbon nanotube fibers, which includes: impregnating carbon nanotube fibers in the aforementioned carbon nanotube fiber sizing agent, and then subjecting the sized carbon nanotube fibers to heat treatment.

[0012] This invention also provides modified carbon nanotube fibers prepared by the aforementioned carbon nanotube fiber interface modification method.

[0013] This invention also provides a method for preparing a carbon nanotube fiber composite material, comprising:

[0014] Epoxy resin and curing agent are dissolved in a solvent to obtain an epoxy resin solution, which is then subjected to ultrasound.

[0015] The modified carbon nanotube fibers are impregnated in the epoxy resin solution, and then the epoxy resin-impregnated carbon nanotube fibers are kept in a taut state and cured to obtain a carbon nanotube fiber composite material.

[0016] This invention also provides a carbon nanotube fiber composite material prepared by the aforementioned preparation method.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] This invention provides a sizing agent for carbon nanotube fibers and a carbon nanotube fiber interface modification technology. The use of this sizing agent is not affected by the carbon nanotube fiber preparation method. It directly performs secondary sizing modification treatment on the finished carbon nanotube fibers. The preparation method is simple and the use efficiency is high. It can effectively improve the interfacial properties between carbon nanotube fibers and epoxy resin in composite materials. Detailed Implementation

[0019] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention, which mainly provides a new sizing agent for carbon nanotube fibers and a new interface modification technology for carbon nanotube fibers. To further understand this invention, the technical solution, its implementation process, and principles will be further explained below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of this invention, and not for limiting the scope of the claims.

[0020] One aspect of the present invention provides a method for preparing a carbon nanotube fiber sizing agent, comprising: mixing a carbon nanotube-loving compound, an intermediate compound, and a solvent, and then adding an amine-containing compound to react and obtain a carbon nanotube fiber sizing agent.

[0021] In some preferred embodiments of the present invention, the carbonophilic nanotube compound includes any one or a combination of two or more of 1-(bromoacetyl)pyrene, 2-bromo-2-acetylnaphthalene, 1-bromoanthracene, 2-bromophenanthrene, etc., but is not limited thereto.

[0022] In some preferred embodiments of the present invention, the intermediate compound includes any one or a combination of two or more of polyethyleneimine, dopamine, chitosan, etc., but is not limited thereto.

[0023] In some preferred embodiments of the present invention, the amine-containing compound includes any one or a combination of two or more of ethylenediamine, hexamethylenediamine, diethylenetriamine, diethyltoluenediamine, 4',4-diaminodiphenylmethane, m-phenylenediamine, isophoronediamine, etc., but is not limited thereto.

[0024] Furthermore, the solvent includes, but is not limited to, any one or a combination of two or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), ethanol, diethyl ether, acetone, etc.

[0025] In some preferred embodiments of the present invention, the mass ratio of the carbonophilic nanotube compound, the intermediate compound, the solvent and the amine-containing compound is (1-20):(1-40):1000:(1-40).

[0026] In some more specific embodiments of the present invention, the preparation steps of a carbon nanotube fiber sizing agent include:

[0027] The carbon nanotube compound, intermediate compound, and solvent are mixed in a mass ratio of (1-20):(1-40):1000. The pH of the reaction system is adjusted to 7.5-9 by adding the buffer reagent Tris. After mechanical stirring for 6-12 hours, an amine-containing compound (1-40) Phr is added. The temperature of the reaction solution is raised to 45-60°C and stirred for 0.5-3 hours to obtain a carbon nanotube fiber sizing agent. This sizing agent needs to be sealed and stored.

[0028] Another aspect of the present invention provides a carbon nanotube fiber sizing agent prepared by the aforementioned preparation method.

[0029] Another aspect of the present invention provides a method for modifying the interface of carbon nanotube fibers, comprising: impregnating carbon nanotube fibers in the aforementioned carbon nanotube fiber sizing agent, and then subjecting the sized carbon nanotube fibers to heat treatment.

[0030] In some preferred embodiments of the present invention, the carbon nanotube fiber interface modification method specifically includes: applying ultrasound to the carbon nanotube fiber sizing agent, immersing the carbon nanotube fiber in the carbon nanotube fiber sizing agent for 10-60 seconds, and then heat-treating the sized carbon nanotube fiber at 60-100°C.

[0031] Furthermore, the power of the ultrasound is 20-100W.

[0032] Furthermore, the carbon nanotube fibers include carbon nanotube fibers prepared by chlorosulfonic acid spinning. This invention uses carbon nanotube fibers prepared by chlorosulfonic acid spinning as raw materials, with a tensile strength of 1.5 GPa and a single filament diameter of 10 μm.

[0033] In some more specific embodiments of the present invention, the steps of the carbon nanotube fiber interface modification method include: applying ultrasound to a beaker containing a carbon nanotube fiber sizing agent, with the ultrasound power set to 20-100W; immersing the acid-spun carbon nanotube fibers in the carbon nanotube fiber sizing agent for 10-60s; and subjecting the sized carbon nanotube fibers to heat treatment at 60-100°C until surface dry.

[0034] Another aspect of the present invention provides modified carbon nanotube fibers obtained by the carbon nanotube fiber interface modification method.

[0035] Another aspect of the present invention provides a method for preparing a carbon nanotube fiber composite material, comprising:

[0036] Epoxy resin and curing agent are dissolved in a solvent to obtain an epoxy resin solution, which is then subjected to ultrasound.

[0037] The modified carbon nanotube fibers are impregnated in the epoxy resin solution, and then the epoxy resin-impregnated carbon nanotube fibers are kept in a taut state and cured to obtain a carbon nanotube fiber composite material.

[0038] Furthermore, the epoxy resin includes, but is not limited to, epoxy resin E51.

[0039] Furthermore, the curing agent may be 4',4-diaminodiphenylmethane, but is not limited to this.

[0040] Furthermore, the mass ratio of the epoxy resin to the curing agent is 100:25 to 40.

[0041] Furthermore, the mass ratio of the epoxy resin and curing agent to the solvent is 10-40:100.

[0042] Furthermore, the power of the ultrasound is 20-100W.

[0043] Furthermore, the immersion time is 10–60 seconds.

[0044] Furthermore, the curing process can employ conventional curing conditions, such as first curing at 100°C for 1 hour, and then curing at 140°C for 4 hours.

[0045] In some more specific embodiments of the present invention, the steps of the method for preparing the carbon nanotube fiber composite material include:

[0046] Epoxy resin E51 and curing agent (epoxy resin / curing agent mass ratio of 100:25-40) are dissolved in acetone at a mass ratio of 10-40%. The epoxy resin solution is then subjected to ultrasound with an ultrasound power of 20-100W. The sized carbon nanotube fibers are then immersed in the epoxy resin solution for 10-60 seconds.

[0047] Carbon nanotube fibers impregnated with epoxy resin were kept in a taut state and cured according to a curing process of first curing at 100℃ for 1 hour and then curing at 140℃ for 4 hours to obtain carbon nanotube fiber composite materials. The tensile properties of the carbon nanotube fiber monofilaments were then measured.

[0048] Carbon nanotube fiber monofilament pull-out test samples were prepared based on the above resin system, and the micro-interface properties (IFSS) of carbon nanotube fibers were measured.

[0049] Another aspect of the present invention provides a carbon nanotube fiber composite material prepared by the aforementioned preparation method.

[0050] The single fiber tensile strength of the carbon nanotube fiber composite material is 2.1–2.6 GPa, and the single fiber pull-out interface strength is 82–124 MPa.

[0051] In summary, the sizing agent for carbon nanotube fibers provided by this invention is not affected by the carbon nanotube fiber preparation method. It directly performs secondary sizing modification treatment on the finished carbon nanotube fibers. Its preparation method is simple, its use efficiency is high, and it can effectively improve the interfacial properties between carbon nanotube fibers and epoxy resin in composite materials.

[0052] To further illustrate the present invention, the technical solutions of the present invention are described in detail below with reference to the embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solutions of the present invention, and detailed implementation methods and specific operation processes are given. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0053] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0054] All processes and equipment in this invention are conventional names in the field, and each name is clear and unambiguous in its relevant application. Those skilled in the art can understand the conventional process steps and corresponding equipment used based on the name.

[0055] Example 1

[0056] 1) Preparation of carbon nanotube fiber sizing agent

[0057] 1-(bromoacetyl)pyrene, dopamine, and ethanol were mixed in a mass ratio of 3:10:1000. The pH of the system was adjusted to 8.5 by adding the buffer reagent Tris. After mechanical stirring for 12 hours, 10 phr of diethyltoluene diamine was added. The solution temperature was raised to 45°C and stirred for 2 hours to obtain a carbon nanotube fiber sizing agent. This sizing agent needs to be sealed and stored.

[0058] 2) Sizing of carbon nanotube fibers

[0059] Carbon nanotube fibers prepared by chlorosulfonic acid spinning were selected as raw materials. The tensile strength of the fiber monofilament was 1.5 GPa and the diameter of the monofilament was 10 μm.

[0060] An ultrasonic treatment was applied to a beaker containing carbon nanotube fiber sizing agent, with the ultrasonic power set to 45W. The acid-spun carbon nanotube fibers were immersed in the sizing agent for 20 seconds, and the sized carbon nanotube fibers were then heated at 100°C until surface dry.

[0061] 3) Preparation of carbon nanotube fiber composite materials

[0062] Epoxy resin E51 and curing agent 4',4-diaminodiphenylmethane (the mass ratio of epoxy resin to curing agent is 100:32) were dissolved in acetone at a mass ratio of 25%. The resin solution was also subjected to ultrasound with an ultrasound power of 45W. The sized carbon nanotube fibers were then immersed in the above epoxy resin solution for 20 seconds.

[0063] Carbon nanotube fibers impregnated with epoxy resin were kept in a taut state and cured according to a curing process of first curing at 100℃ for 1 hour and then curing at 140℃ for 4 hours to obtain carbon nanotube fiber composite material.

[0064] The tensile strength of carbon nanotube fiber monofilaments was measured to be 2.6 GPa, and the interfacial strength (IFSS) of carbon nanotube fiber monofilaments was 96–113 MPa.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is that the carbon nanotube fiber sizing step is omitted, and carbon nanotube fiber composite material is prepared directly.

[0067] The tensile strength of carbon nanotube fiber monofilaments was measured to be 1.6 GPa, and the interfacial strength (IFSS) of carbon nanotube fiber monofilaments was 32–47 MPa.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that diethyltoluene diamine was not added during the preparation of the sizing agent, while the remaining steps were the same as in Example 1.

[0070] The tensile strength of carbon nanotube fiber monofilaments was measured to be 1.8 GPa, and the interfacial strength (IFSS) of carbon nanotube fiber monofilaments was 35–57 MPa.

[0071] Comparative Example 3

[0072] The difference between this comparative example and Example 1 is that 1-(bromoacetyl)pyrene is not added during the preparation of the sizing agent, while the other steps are the same as in Example 1.

[0073] The tensile strength of carbon nanotube fiber monofilaments was measured to be 1.6 GPa, and the interfacial strength (IFSS) of carbon nanotube fiber monofilaments was 27–44 MPa.

[0074] Comparative Example 4

[0075] The difference between this comparative example and Example 1 is that dopamine was not added during the preparation of the sizing agent, while the remaining steps were the same as in Example 1.

[0076] The tensile strength of carbon nanotube fiber monofilaments was measured to be 1.8 GPa, and the interfacial strength (IFSS) of carbon nanotube fiber monofilaments was 41-63 MPa.

[0077] Example 2

[0078] 1) Preparation of carbon nanotube fiber sizing agent

[0079] 2-Bromo-2-acetylnaphthalene, polyethyleneimine, and NMP were mixed in a mass ratio of 20:40:1000. The pH of the system was adjusted to 7.5 by adding the buffer reagent TTI. After mechanical stirring for 12 hours, 40 phr of diethylenetriamine was added. The solution temperature was raised to 60°C and stirred for 3 hours to obtain a carbon nanotube fiber sizing agent. This sizing agent needs to be sealed and stored.

[0080] 2) Sizing of carbon nanotube fibers

[0081] Carbon nanotube fibers prepared by chlorosulfonic acid spinning were selected as raw materials. The tensile strength of the fiber monofilament was 1.5 GPa and the diameter of the monofilament was 10 μm.

[0082] An ultrasonic treatment was applied to a beaker containing carbon nanotube fiber sizing agent, with the ultrasonic power set to 100W. The acid-spun carbon nanotube fibers were immersed in the sizing agent for 60 seconds, and the sized carbon nanotube fibers were then heated at 100°C until surface dry.

[0083] 3) Preparation of carbon nanotube fiber composite materials

[0084] Epoxy resin E51 and curing agent 4',4-diaminodiphenylmethane (the mass ratio of epoxy resin to curing agent is 100:25) were dissolved in acetone at a mass ratio of 10%. The resin solution was also subjected to ultrasound with an ultrasound power of 100W. The sized carbon nanotube fibers were then immersed in the epoxy resin solution for 10 seconds.

[0085] Carbon nanotube fibers impregnated with epoxy resin were kept in a taut state and cured according to a curing process of first curing at 100℃ for 1 hour and then curing at 140℃ for 4 hours to obtain carbon nanotube fiber composite material.

[0086] The tensile strength of carbon nanotube fiber monofilaments was measured to be 2.5 GPa, and the interfacial strength (IFSS) of carbon nanotube fiber monofilaments was 102–124 MPa.

[0087] Example 3

[0088] 1) Preparation of carbon nanotube fiber sizing agent

[0089] 1-Bromoanthracene, chitosan, and acetone were mixed in a mass ratio of 1:1:1000. The pH of the system was adjusted to 7.5 by adding the buffer reagent Tris. After mechanical stirring for 6 hours, 1 phr of 4',4-diaminodiphenylmethane was added. The solution temperature was raised to 45°C and stirred for 0.5 hours to obtain a carbon nanotube fiber sizing agent. This sizing agent needs to be sealed and stored.

[0090] 2) Sizing of carbon nanotube fibers

[0091] Carbon nanotube fibers prepared by chlorosulfonic acid spinning were selected as raw materials. The tensile strength of the fiber monofilament was 1.5 GPa and the diameter of the monofilament was 10 μm.

[0092] Ultrasonic treatment was applied to a beaker containing carbon nanotube fiber sizing agent. The ultrasonic power was set to 20W. The acid-spun carbon nanotube fiber was immersed in the sizing agent for 20 seconds. The sized carbon nanotube fiber was then heated at 100°C until it was surface dry.

[0093] 3) Preparation of carbon nanotube fiber composite materials

[0094] Epoxy resin E51 and curing agent 4',4-diaminodiphenylmethane (the mass ratio of epoxy resin to curing agent is 100:40) were dissolved in acetone at a mass ratio of 30%. The resin solution was also subjected to ultrasound with an ultrasound power of 20W. The sized carbon nanotube fibers were then immersed in the above epoxy resin solution for 60s.

[0095] Carbon nanotube fibers impregnated with epoxy resin were kept in a taut state and cured according to a curing process of first curing at 100℃ for 1 hour and then curing at 140℃ for 4 hours to obtain carbon nanotube fiber composite material.

[0096] The tensile strength of carbon nanotube fiber monofilaments was measured to be 2.1 GPa, and the interfacial strength (IFSS) of carbon nanotube fiber monofilaments was 82–100 MPa.

[0097] Example 4

[0098] 1) Preparation of carbon nanotube fiber sizing agent

[0099] 2-Bromophenanthrene, dopamine, and DMF were mixed in a mass ratio of 10:20:1000. The pH of the system was adjusted to 9 by adding the buffer reagent Tris. After mechanical stirring for 10 hours, 40 phr of isophorone diamine was added. The solution temperature was raised to 45°C and stirred for 3 hours to obtain a carbon nanotube fiber sizing agent. This sizing agent needs to be sealed and stored.

[0100] 2) Sizing of carbon nanotube fibers

[0101] Carbon nanotube fibers prepared by chlorosulfonic acid spinning were selected as raw materials. The tensile strength of the fiber monofilament was 1.5 GPa and the diameter of the monofilament was 10 μm.

[0102] An ultrasonic treatment was applied to a beaker containing carbon nanotube fiber sizing agent, with the ultrasonic power set to 60W. The acid-spun carbon nanotube fibers were immersed in the sizing agent for 10 seconds, and the sized carbon nanotube fibers were then heated at 60°C until surface dry.

[0103] 3) Preparation of carbon nanotube fiber composite materials

[0104] Epoxy resin E51 and curing agent 4',4-diaminodiphenylmethane (the mass ratio of epoxy resin to curing agent is 100:30) were dissolved in acetone at a mass ratio of 20%. The resin solution was also subjected to ultrasound with an ultrasound power of 30W. The sized carbon nanotube fibers were then immersed in the above epoxy resin solution for 30 seconds.

[0105] Carbon nanotube fibers impregnated with epoxy resin were kept in a taut state and cured according to a curing process of first curing at 100℃ for 1 hour and then curing at 140℃ for 4 hours to obtain carbon nanotube fiber composite material.

[0106] The tensile strength of carbon nanotube fiber monofilaments was measured to be 2.6 GPa, and the interfacial strength (IFSS) of carbon nanotube fiber monofilaments was 101–111 MPa.

[0107] In addition, the inventors of this case also conducted experiments with other raw materials, process operations and process conditions described in this specification, referring to the foregoing embodiments. For example, they replaced the amine-containing compounds with ethylenediamine, hexamethylenediamine, m-phenylenediamine, etc., and replaced the solvent with diethyl ether, and obtained relatively ideal results in all cases.

[0108] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims.

Claims

1. A method for preparing a carbon nanotube fiber sizing agent, characterized in that, include: A carbon nanotube-loving compound, an intermediate compound, and a solvent are mixed, and then an amine-containing compound is added to react and a carbon nanotube fiber sizing agent is prepared. The carbon nanotube-loving compound is selected from any one or a combination of two or more of 1-(bromoacetyl)pyrene, 2-bromo-2-acetylnaphthalene, 1-bromoanthracene, and 2-bromophenanthroline. The intermediate compound is selected from any one or a combination of two or more of polyethyleneimine, dopamine, and chitosan.

2. The preparation method according to claim 1, characterized in that: The amine-containing compound includes any one or a combination of two or more of ethylenediamine, hexamethylenediamine, diethylenetriamine, diethyltoluenediamine, 4',4-diaminodiphenylmethane, m-phenylenediamine, and isophoronediamine.

3. The preparation method according to claim 1, characterized in that: The solvent includes any one or a combination of two or more of N-methylpyrrolidone, N,N-dimethylformamide, ethanol, diethyl ether, and acetone.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the carbonophilic nanotube compound, the intermediate compound, the solvent, and the amine-containing compound is (1~20):(1~40):1000:(1~40).

5. The preparation method according to claim 1, characterized in that, Specifically, it includes: A carbon nanotube-loving compound, an intermediate compound, and a solvent are mixed. Then, a buffer reagent is added to adjust the pH of the resulting mixed reaction system to 7.5-9, and the mixture is stirred for 6-12 hours. After that, an amine-containing compound is added, and the temperature of the mixed reaction system is raised to 45-60°C and stirred for 0.5-3 hours to obtain a carbon nanotube fiber sizing agent.

6. A carbon nanotube fiber sizing agent prepared by any one of the preparation methods described in claims 1-5.

7. A method for modifying the interface of carbon nanotube fibers, characterized in that, include: The carbon nanotube fibers are impregnated in the carbon nanotube fiber sizing agent described in claim 5, and then the sized carbon nanotube fibers are subjected to heat treatment.

8. The method for modifying the interface of carbon nanotube fibers according to claim 7, characterized in that, Specifically, it includes: The carbon nanotube fiber sizing agent is subjected to ultrasound, and the carbon nanotube fiber is immersed in the carbon nanotube fiber sizing agent for 10~60s. Then, the sized carbon nanotube fiber is heat-treated at 60~100℃. The power of the ultrasound is 20~100W.

9. The method for modifying the interface of carbon nanotube fibers according to claim 7, characterized in that: The carbon nanotube fibers include carbon nanotube fibers prepared by chlorosulfonic acid spinning.

10. Modified carbon nanotube fibers obtained by the carbon nanotube fiber interface modification method according to any one of claims 7-9.

11. A method for preparing a carbon nanotube fiber composite material, characterized in that, include: Epoxy resin and curing agent are dissolved in a solvent to obtain an epoxy resin solution, which is then subjected to ultrasound. The modified carbon nanotube fibers of claim 10 are impregnated in the epoxy resin solution, and then the epoxy resin-impregnated carbon nanotube fibers are taut and cured to obtain a carbon nanotube fiber composite material.

12. The preparation method according to claim 11, characterized in that: The epoxy resin includes epoxy resin E51.

13. The preparation method according to claim 11, characterized in that: The mass ratio of epoxy resin to curing agent is 100:25~40.

14. The preparation method according to claim 11, characterized in that: The mass ratio of the epoxy resin and curing agent to the solvent is 10~30:

100.

15. The preparation method according to claim 11, characterized in that: The power of the ultrasound is 20~100W.

16. The preparation method according to claim 11, characterized in that: The immersion time is 10-60 seconds.

17. A carbon nanotube fiber composite material prepared by any one of claims 11-16.

18. The carbon nanotube fiber composite material according to claim 17, characterized in that: The single fiber tensile strength of the carbon nanotube fiber composite material is 2.1~2.6 GPa, and the single fiber pull-out interface strength is 82~124 MPa.