Carbon nanotube composite fiber, method for preparing the same, and use thereof

Abstract

The application provides a preparation method of carbon nanotube composite fiber, comprising the following steps: S1, preparation of core layer fiber: mixing to obtain polymer / carbon nanotube composite raw material, dispersing in chlorosulfonic acid to form a spinning stock solution; preparing a flexible high-thermal-conductivity core layer fiber with densification and high-orientation structure through wet spinning; S2, preparation of sheath layer: vacuum plating film is carried out on the fiber prepared in S1 to deposit a layer of insulating film on the surface of the fiber through monomer polymerization, and the carbon nanotube composite fiber is prepared. The carbon nanotube composite fiber prepared by the application has flexibility, high thermal conductivity and high resistivity, and has a very broad application prospect in the fields of thermal interface materials and electronic device thermal management materials.

Description

Technical Field

[0001] This invention relates to the fields of composite materials and thermal interface materials, and particularly to a carbon nanotube composite fiber, its preparation method and application, specifically to a flexible, highly thermally conductive and highly insulating carbon nanotube composite fiber based on a core-sheath structure, its preparation method and application. Background Technology

[0002] With the rapid development of artificial intelligence, electronic devices are experiencing explosive growth in integration and power density. However, this has led to a continuous increase in heat flux density in high-power chips, becoming a key bottleneck restricting the development of electronic technology. Therefore, the accumulation of heat within a limited space severely impairs the operating efficiency, safety, reliability, and lifespan of electronic devices. Thermal interface materials (TIMs), due to their ability to reduce minute irregularities between solid contact surfaces and replace poorly thermally conductive air, have become crucial for solving the heat dissipation problem of electronic devices. Vertically aligned fiber structures are considered highly promising TIM filling structures because they can establish continuous heat transfer paths along the main heat flow direction.

[0003] Due to the excellent axial thermal conductivity and corrosion resistance of carbon fiber, various carbon fiber-based TIMs preparation technologies have been developed in related fields, such as Chinese invention patent applications CN120623789A and CN120484288A. However, this material system has many bottlenecks: (1) The longitudinal thermal conductivity of commonly used carbon fiber fillers is generally limited (about 600 W / m). -1 K -1 (1) High-performance carbon fibers rely on imports; (2) The interaction between carbon fibers and polymers is weak, and a large number of pores are generated during the curing process, which leads to a significant increase in the interfacial scattering of phonons; (3) Carbon fibers have a high Young's modulus (about 960 GPa), and the TIMs compressive modulus and contact thermal resistance are significantly increased. Summary of the Invention

[0004] To address the shortcomings of existing technologies, such as the high stiffness and low thermal conductivity of carbon fiber fillers in TIMs, this invention provides a carbon nanotube composite fiber, its preparation method, and its application. By uniformly and densely distributing the insulating layer on the fiber surface, the composite fiber possesses excellent flexibility, thermal properties, mechanical strength, and resistivity.

[0005] To achieve the above-mentioned objective, this invention provides a method for preparing carbon nanotube composite fibers, comprising the following steps: S1. Preparation of core fiber: The polymer / carbon nanotube composite raw material is mixed and dispersed in chlorosulfonic acid to form a spinning solution; after wet spinning, a flexible high thermal conductivity core fiber with a dense and highly oriented structure is prepared. S2, Preparation of the sheath layer: The fibers obtained in S1 are vacuum coated, and a layer of insulating film is formed by monomer polymerization deposition on the fiber surface to obtain carbon nanotube composite fibers.

[0006] In some embodiments, the composite raw material in step S1 includes the following components by weight: 10-30 parts polymer and 70-90 parts carbon nanotubes.

[0007] In some embodiments, in step S1, the polymer is selected from one or more combinations of poly(p-phenylenebenzodioxazole), polyimide, polyamide, polybenzimidazole, polyaniline, poly(p-phenylene terephthalamide), and poly(m-phenylene isophthalamide). Alternatively, the polymer may be selected from one of poly(p-phenylenebenzodioxazole), polyimide, polyamide, polybenzimidazole, polyaniline, poly(p-phenylene terephthalamide), and poly(m-phenylene isophthalamide).

[0008] In some of these embodiments, the polymer is selected from poly(p-phenylenebenzodioxazole).

[0009] In some embodiments, the carbon nanotubes in step S1 are few-walled carbon nanotubes.

[0010] In some embodiments, the mass fraction of carbon nanotubes in the spinning solution in step S1 is 0.5%-1%.

[0011] In some embodiments, the wet spinning process conditions in step S1 are: ambient temperature and pressure, winding speed of 1 m / min-5 m / min, coagulation bath of acetone, and coagulation time of 10-20 s.

[0012] In some embodiments, the vacuum coating process conditions in step S2 are as follows: solid p-xylene raw material gradually absorbs heat and sublimates in the evaporation chamber as the temperature rises; the sublimated dimer gas enters the pyrolysis chamber, and at a temperature of about 680°C, the molecular bonds of the dimer are broken to form an active p-xylene monomer with two dangling bonds; finally, the p-xylene monomer is sent to a vacuum deposition chamber at room temperature to polymerize and deposit on the fiber surface, ultimately forming a dense insulating film layer.

[0013] In another aspect, the present invention provides a carbon nanotube composite fiber, prepared using the method described above, wherein the thermal conductivity of the carbon nanotube composite fiber is >600 W·m. −1 ·K −1 Tensile strength > 2 GPa, Young's modulus < 300 GPa, toughness > 40 MJ·m −3 Resistivity > 10 7 Ω·cm.

[0014] In another aspect, the present invention provides the application of the above-mentioned carbon nanotube composite fiber in thermal interface materials and thermal management materials for electronic devices.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention achieves the controllable assembly of polymers on the surface of carbon nanotubes through wet spinning technology, constructing a thermally conductive continuous dual-network structure with carbon nanotubes as the high thermal conductivity skeleton and polymers as the reinforcing phase. This structure not only improves the fiber density and orientation through the interfacial interaction between polymers and carbon nanotubes, but also forms a stable two-phase thermally conductive pathway, thereby achieving a unity of flexibility, high thermal conductivity and high mechanical strength in the fiber core layer.

[0016] (2) In terms of insulation layer construction, the present invention adopts vacuum coating-assisted in-situ polymerization technology to achieve uniform deposition and polymerization of monomers on the fiber surface, forming a dense, controllable thickness and firmly bonded insulating sheath layer; this method avoids interface defects that may be caused by solution coating and significantly improves the integrity and breakdown resistance of the insulation layer.

[0017] (3) The present invention solves the key problem that traditional carbon fiber filled thermal interface materials cannot simultaneously achieve compression resistance, thermal conductivity and electrical breakdown resistance through the integrated structural design of "double network core layer + dense insulating sheath layer". The composite fiber can achieve comprehensive performance of flexibility, high thermal conductivity, high insulation and high strength without the need to add toxic flame retardants or insulating additives, and has clear environmentally friendly attributes and engineering application prospects. Attached Figure Description

[0018] Figure 1 This is a morphological characterization diagram of carbon nanotube composite fibers according to an embodiment of the present invention. Figure 2 This is a resistivity test diagram of carbon nanotube composite fibers according to an embodiment of the present invention. Figure 3 This is a statistical chart of the mechanical properties of carbon nanotube composite fibers according to an embodiment of the present invention. Figure 4 This is a comparison diagram of the thermal conductivity of carbon nanotube composite fibers according to an embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise specified, the test materials used in the following embodiments were purchased from conventional biochemical reagent stores. Unless otherwise stated, percentages and parts are by weight. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar with the art. Furthermore, any methods and materials similar to or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0020] 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.

[0021] Carbon nanotube fibers are formed by assembling millions of parallel-aligned carbon nanotubes. Benefiting from the large inter-tube contact area and interactions, as well as the excellent properties of carbon nanotubes themselves, carbon nanotube fibers possess flexibility, high strength, and high thermal conductivity. The composite of carbon nanotubes with other polymers, attributed to reduced porosity, increased orientation, and enhanced inter-tube contact, can further improve mechanical and thermal conductivity properties. In addition, to avoid electrical breakdown of TIMs, the fibers can be designed with high resistivity.

[0022] Therefore, by using carbon nanotube composite fibers as the core layer and vacuum-depositing a high-insulation sheath layer, the fibers as a whole can have low stiffness, high mechanical strength, high thermal conductivity and high insulation properties. When the fibers are vertically arranged in TIMs, they can significantly improve the compressive strength, thermal conductivity and electrical breakdown resistance of TIMs.

[0023] The present invention provides a method for preparing carbon nanotube composite fibers, wherein the carbon nanotube composite fibers are flexible, highly thermally conductive, and highly insulating carbon nanotube composite fibers based on a core-sheath structure. The preparation method includes the following steps: S1. Preparation of core fiber: The polymer / carbon nanotube composite raw material is mixed and dispersed in chlorosulfonic acid to form a spinning solution; after wet spinning, a flexible high thermal conductivity core fiber with a dense and highly oriented structure is prepared. S2, Preparation of the sheath layer: The fibers obtained in S1 are vacuum coated, and a layer of insulating film is formed by monomer polymerization deposition on the fiber surface to obtain carbon nanotube composite fibers.

[0024] In this embodiment, the polymer / carbon nanotube composite raw material is mixed with chlorosulfonic acid to form a spinning solution. Wet spinning technology is used to assemble the polymer on the surface of the carbon nanotubes, enhance the interfacial interaction between carbon nanotubes, and thus prepare a high thermal conductivity core fiber with a dense and highly oriented structure.

[0025] In this embodiment, a uniform and dense insulating sheath layer is formed on the fiber surface by vacuum coating of a fiber with a dense and highly oriented structure, thereby obtaining a flexible, highly thermally conductive and highly insulating carbon nanotube composite fiber.

[0026] In this embodiment, the composite raw material in step S1 includes the following components by weight: 10-30 parts polymer and 70-90 parts carbon nanotubes. Preferably, the composite raw material includes the following components by weight: 20 parts polymer and 80 parts carbon nanotubes.

[0027] In step S1 of this embodiment, the polymer is selected from one or more combinations of poly(p-phenylene benzodioxazole), polyimide, polyamide, polybenzimidazole, polyaniline, poly(p-phenylene terephthalamide), and poly(m-phenylene isophthalamide); or the polymer is selected from one of poly(p-phenylene benzodioxazole), polyimide, polyamide, polybenzimidazole, polyaniline, poly(p-phenylene terephthalamide), and poly(m-phenylene isophthalamide). The polymer is assembled on the surface of carbon nanotubes to enhance the interfacial interaction between carbon nanotubes, thereby enabling the fiber to form a dense and highly oriented structure. In specific experiments, appropriate selections can be made according to the circumstances, which will not be elaborated here.

[0028] In this embodiment, the polymer is preferably selected from poly(p-phenylenebenzodioxazole).

[0029] In this embodiment, the carbon nanotubes in step S1 are few-walled carbon nanotubes.

[0030] In this embodiment, the mass fraction of carbon nanotubes in the spinning solution in step S1 is 0.5%-1%. The wet spinning process conditions in step S1 are: ambient temperature and pressure, winding speed of 1 m / min-5 m / min, coagulation bath of acetone, and coagulation time of 10-20 s.

[0031] In this embodiment, the vacuum coating process conditions in step S2 are as follows: the solid p-xylene raw material gradually absorbs heat and sublimates in the evaporation chamber as the temperature rises; the sublimated dimer gas enters the pyrolysis chamber, and at a temperature of about 680°C, the molecular bonds of the dimer are broken to form an active p-xylene monomer with two dangling bonds; finally, the p-xylene monomer is sent to the vacuum deposition chamber at room temperature to polymerize and deposit on the fiber surface, ultimately forming a dense insulating film layer.

[0032] Another embodiment of the present invention provides a carbon nanotube composite fiber, prepared using the method described above. The carbon nanotube composite fiber comprises a high thermal conductivity core layer and an insulating sheath layer, wherein the sheath layer is uniformly and densely distributed on the surface of the core layer. The flexible, high thermal conductivity, and high insulating carbon nanotube composite fiber of the present invention is based on the excellent flexibility and thermal conductivity of carbon nanotubes and the high insulating properties of parylene. The composite fiber possesses excellent flexibility, thermal properties, mechanical strength, and resistivity, with the insulating layer uniformly and densely distributed on the fiber surface.

[0033] The thermal conductivity of the carbon nanotube composite fiber described in this embodiment is >600 W·m. −1 ·K −1 Tensile strength > 2 GPa, Young's modulus < 300 GPa, toughness > 40 MJ·m −3 Resistivity > 10 7 The carbon nanotube fibers have a diameter of 5–15 μm, a tensile breaking strength of 2.3–2.8 GPa, a tensile modulus of 240–260 GPa, and a thermal conductivity of 650–700 W·m. −1 ·K −1 Resistivity 10 7 Ω·cm ~ 10 8 Ω·cm.

[0034] Another embodiment of the present invention provides the application of the above-mentioned carbon nanotube composite fiber in thermal interface materials and thermal management materials for electronic devices.

[0035] This invention employs wet spinning and vacuum deposition to prepare coaxial composite fibers. A polymer / carbon nanotube composite material is mixed with chlorosulfonic acid to form a spinning solution. Wet spinning technology is used to assemble the polymer on the surface of the carbon nanotubes, enhancing the interfacial interactions between the carbon nanotubes. This results in a high-thermal-conductivity core fiber with a dense, highly oriented structure. Vacuum deposition is then used to form a uniform and dense insulating sheath layer on the fiber surface. The resulting composite fiber exhibits flexibility, high thermal conductivity, and high resistivity, and has broad application prospects in the fields of thermal interface materials and thermal management materials for electronic devices.

[0036] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0037] Example 1 1) Prepare a 1% carbon nanotube dispersion: Accurately weigh 0.35 g of carbon nanotubes into a 50 ml sample bottle, measure 20 ml of chlorosulfonic acid, and stir magnetically until homogeneous.

[0038] 2) Transfer the spinning solution prepared in step 1) into the syringe of the extrusion device, set the extrusion speed to 0.01 ml / min, and the maximum draw ratio ≥3. The resulting spinning solution is extruded into an acetone coagulation bath to prepare nascent fibers. The coagulation time is 10-20 s. After water bath treatment and heat treatment at 70℃, residual chlorosulfonic acid, acetone and reaction products are removed to obtain carbon nanotube composite fibers.

[0039] 3) Vacuum coating of insulating layer on carbon nanotube composite fibers: solid para-xylene raw material gradually absorbs heat and sublimates in the evaporation chamber as the temperature rises; the sublimated dimer gas enters the pyrolysis chamber, and at a temperature of about 680℃, the molecular bonds of the dimer are broken to form an active para-xylene monomer with two dangling bonds; finally, the para-xylene monomer is sent to the vacuum deposition chamber at room temperature to polymerize and deposit on the fiber surface, ultimately forming a dense insulating film layer.

[0040] The properties of the pure carbon nanotube fibers in this embodiment were characterized, as shown in the mechanical property statistics chart. Figure 3 ) and thermal conductivity diagram ( Figure 4 The results showed that the tensile breaking strength of the carbon nanotube composite fiber was 1.59 GPa, the Young's modulus was 131.3 GPa, and the thermal conductivity of the fiber, determined using the third harmonic method, was 214.9 W·m. −1 ·K −1 .

[0041] Example 2 1) Prepare a 1% carbon nanotube dispersion: Accurately weigh 0.35 g of carbon nanotubes into a 50 ml sample bottle, measure 20 ml of chlorosulfonic acid, and stir magnetically until homogeneous.

[0042] 2) Weigh 0.035 g of poly(p-phenylenebenzodioxazole) into the dispersion prepared in step 1), and then perform magnetic stirring to obtain a uniformly dispersed spinning solution.

[0043] 3) Transfer the spinning solution prepared in step 2) into the syringe of the extrusion device, set the extrusion speed to 0.01 ml / min, and the maximum draw ratio ≥3. The resulting spinning solution is extruded into an acetone coagulation bath to prepare nascent fibers. The coagulation time is 10-20 s. After water bath treatment and heat treatment at 70℃, residual chlorosulfonic acid, acetone and reaction products are removed to obtain carbon nanotube composite fibers.

[0044] 4) Vacuum coating of insulating layer on carbon nanotube composite fibers: solid para-xylene raw material gradually absorbs heat and sublimates in the evaporation chamber as the temperature rises; the sublimated dimer gas enters the pyrolysis chamber, and at a temperature of about 680℃, the molecular bonds of the dimer are broken to form an active para-xylene monomer with two dangling bonds; finally, the para-xylene monomer is sent to the vacuum deposition chamber at room temperature to polymerize and deposit on the fiber surface, ultimately forming a dense insulating film layer.

[0045] The properties of the pure carbon nanotube fibers in this embodiment were characterized, as shown in the mechanical property statistics chart. Figure 3 ) and thermal conductivity diagram ( Figure 4 The results showed that the tensile breaking strength of the carbon nanotube composite fiber was 2.12 GPa, the Young's modulus was 184.0 GPa, and the thermal conductivity of the fiber, determined using the third harmonic method, was 404.8 W·m. −1 ·K −1 .

[0046] Example 3 1) Prepare a 1% carbon nanotube dispersion: Accurately weigh 0.35 g of carbon nanotubes into a 50 ml sample bottle, measure 20 ml of chlorosulfonic acid, and stir magnetically until homogeneous.

[0047] 2) Weigh 0.0525 g of poly(p-phenylenebenzodioxazole) into the dispersion prepared in step 1), and then perform magnetic stirring to obtain a uniformly dispersed spinning solution.

[0048] 3) Transfer the spinning solution prepared in step 2) into the syringe of the extrusion device, set the extrusion speed to 0.01 ml / min, and the maximum draw ratio ≥3. The resulting spinning solution is extruded into an acetone coagulation bath to prepare nascent fibers. The coagulation time is 10-20 s. After water bath treatment and heat treatment at 70℃, residual chlorosulfonic acid, acetone and reaction products are removed to obtain carbon nanotube composite fibers.

[0049] 4) Vacuum coating of insulating layer on carbon nanotube composite fibers: solid para-xylene raw material gradually absorbs heat and sublimates in the evaporation chamber as the temperature rises; the sublimated dimer gas enters the pyrolysis chamber, and at a temperature of about 680℃, the molecular bonds of the dimer are broken to form an active para-xylene monomer with two dangling bonds; finally, the para-xylene monomer is sent to the vacuum deposition chamber at room temperature to polymerize and deposit on the fiber surface, ultimately forming a dense insulating film layer.

[0050] The properties of the pure carbon nanotube fibers in this embodiment were characterized, as shown in the mechanical property statistics chart. Figure 3 ) and thermal conductivity diagram ( Figure 4The results showed that the tensile breaking strength of the carbon nanotube composite fiber was 2.47 GPa, the Young's modulus was 187.2 GPa, and the thermal conductivity of the fiber, determined using the third harmonic method, was 527.0 W·m. −1 ·K −1 .

[0051] Example 4 1) Prepare a 1% carbon nanotube dispersion: Accurately weigh 0.35 g of carbon nanotubes into a 50 ml sample bottle, measure 20 ml of chlorosulfonic acid, and stir magnetically until homogeneous.

[0052] 2) Weigh 0.07 g of poly(p-phenylenebenzodioxazole) into the dispersion prepared in step 1), and then perform magnetic stirring to obtain a uniformly dispersed spinning solution.

[0053] 3) Transfer the spinning solution prepared in step 2) into the syringe of the extrusion device, set the extrusion speed to 0.01 ml / min, and the maximum draw ratio ≥3. The resulting spinning solution is extruded into an acetone coagulation bath to prepare nascent fibers. The coagulation time is 10-20 s. After water bath treatment and heat treatment at 70℃, residual chlorosulfonic acid, acetone and reaction products are removed to obtain carbon nanotube composite fibers.

[0054] 4) Vacuum coating of insulating layer on carbon nanotube composite fibers: solid para-xylene raw material gradually absorbs heat and sublimates in the evaporation chamber as the temperature rises; the sublimated dimer gas enters the pyrolysis chamber, and at a temperature of about 680℃, the molecular bonds of the dimer are broken to form an active para-xylene monomer with two dangling bonds; finally, the para-xylene monomer is sent to the vacuum deposition chamber at room temperature to polymerize and deposit on the fiber surface, ultimately forming a dense insulating film layer.

[0055] SEM images of carbon nanotube composite fibers before and after chemical vapor deposition in this embodiment ( Figure 1 ).like Figure 1 As shown, a uniform and dense insulating film with a thickness of only 2.8 μm is formed on the fiber surface.

[0056] The performance of the carbon nanotube composite fiber in this embodiment was characterized, as shown in the resistivity test graph (). Figure 2 ), Mechanical property statistics chart ( Figure 3 ) and thermal conductivity diagram ( Figure 4 The results showed that the tensile breaking strength of the carbon nanotube composite fiber was 2.64 GPa, the Young's modulus was 247.3 GPa, and the thermal conductivity of the fiber, determined using the third harmonic method, was 632.5 W·m. −1 ·K −1 The resistance can reach 2.56 TΩ, which translates to a resistivity of 4.08*10. 7Ω·cm.

[0057] Example 5 1) Prepare a 1% carbon nanotube dispersion: Accurately weigh 0.35 g of carbon nanotubes into a 50 ml sample bottle, measure 20 ml of chlorosulfonic acid, and stir magnetically until homogeneous.

[0058] 2) Weigh 0.105 g of poly(p-phenylenebenzodioxazole) into the dispersion prepared in step 1), and then stir magnetically to obtain a uniformly dispersed spinning solution.

[0059] 3) Transfer the spinning solution prepared in step 2) into the syringe of the extrusion device, set the extrusion speed to 0.01 ml / min, and the maximum draw ratio ≥3. The resulting spinning solution is extruded into an acetone coagulation bath to prepare nascent fibers. The coagulation time is 10-20 s. After water bath treatment and heat treatment at 70℃, residual chlorosulfonic acid, acetone and reaction products are removed to obtain carbon nanotube composite fibers.

[0060] 4) Vacuum coating of insulating layer on carbon nanotube composite fibers: solid para-xylene raw material gradually absorbs heat and sublimates in the evaporation chamber as the temperature rises; the sublimated dimer gas enters the pyrolysis chamber, and at a temperature of about 680℃, the molecular bonds of the dimer are broken to form an active para-xylene monomer with two dangling bonds; finally, the para-xylene monomer is sent to the vacuum deposition chamber at room temperature to polymerize and deposit on the fiber surface, ultimately forming a dense insulating film layer.

[0061] The properties of the pure carbon nanotube fibers in this embodiment were characterized, as shown in the mechanical property statistics chart. Figure 3 ) and thermal conductivity diagram ( Figure 4 The results showed that the tensile breaking strength of the carbon nanotube composite fiber was 2.16 GPa, the Young's modulus was 199.2 GPa, and the thermal conductivity of the fiber, determined using the third harmonic method, was 502.5 W·m. −1 ·K −1 .

[0062] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A method for preparing carbon nanotube composite fibers, characterized in that: Includes the following steps: S1. Preparation of core fiber: The polymer / carbon nanotube composite raw material is mixed and dispersed in chlorosulfonic acid to form a spinning solution; after wet spinning, a flexible high thermal conductivity core fiber with a dense and highly oriented structure is prepared. S2, Preparation of the sheath layer: The fibers obtained in S1 are vacuum coated, and a layer of insulating film is formed by monomer polymerization deposition on the fiber surface to obtain carbon nanotube composite fibers.

2. The method for preparing carbon nanotube composite fibers according to claim 1, characterized in that: The composite raw material in step S1 includes the following components by weight: 10-30 parts polymer and 70-90 parts carbon nanotubes.

3. The method for preparing carbon nanotube composite fibers according to claim 1, characterized in that: In step S1, the polymer is selected from one or more combinations of poly(p-phenylenebenzodioxazole), polyimide, polyamide, polybenzimidazole, polyaniline, poly(p-phenylene terephthalamide), and poly(m-phenylene isophthalamide). Alternatively, the polymer may be selected from one of poly(p-phenylenebenzodioxazole), polyimide, polyamide, polybenzimidazole, polyaniline, poly(p-phenylene terephthalamide), and poly(m-phenylene isophthalamide).

4. The method for preparing carbon nanotube composite fibers according to claim 3, characterized in that: The polymer is selected from poly(p-phenylenebenzodioxazole).

5. The method for preparing carbon nanotube composite fibers according to claim 1, characterized in that: In step S1, the carbon nanotubes are few-walled carbon nanotubes.

6. The method for preparing carbon nanotube composite fibers according to claim 1, characterized in that: In step S1, the mass fraction of carbon nanotubes in the spinning solution is 0.5%-1%.

7. The method for preparing carbon nanotube composite fibers according to claim 1, characterized in that: The wet spinning process conditions in step S1 are: ambient temperature and pressure, winding speed of 1 m / min-5 m / min, coagulation bath of acetone, and coagulation time of 10-20 s.

8. The method for preparing carbon nanotube composite fibers according to claim 1, characterized in that: The vacuum coating process conditions in step S2 are as follows: solid p-xylene raw material gradually absorbs heat and sublimates in the evaporation chamber as the temperature rises; the sublimated dimer gas enters the pyrolysis chamber, and at a temperature of about 680°C, the molecular bonds of the dimer are broken to form an active p-xylene monomer with two dangling bonds; finally, the p-xylene monomer is sent to a vacuum deposition chamber at room temperature to polymerize and deposit on the fiber surface, ultimately forming a dense insulating film layer.

9. A carbon nanotube composite fiber, characterized in that: The carbon nanotube composite fiber is prepared by the method described in any one of claims 1-8, and the thermal conductivity of the carbon nanotube composite fiber is >600 W·m. −1 ·K −1 Tensile strength > 2 GPa, Young's modulus < 300 GPa, toughness > 40 MJ·m −3 Resistivity > 10 7 Ω·cm.

10. The application of the carbon nanotube composite fiber according to claim 9 in thermal interface materials and thermal management materials for electronic devices.

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