CNT composite fiber, and preparation method therefor and use thereof

Abstract

The present application provides a CNT composite fiber, and a preparation method therefor and a use thereof. The CNT composite fiber comprises the following components in percentage by weight: 80%-95% of a CNT and 5%-20% of a thermoplastic resin. The preparation method comprises the following steps: (1) uniformly mixing a CNT and a solvent, adding a thermoplastic resin into the mixture, and uniformly mixing to obtain a spinning solution; and (2) performing wet spinning on the spinning solution obtained in the step (1) to obtain the CNT composite fiber. According to the present application, a CNT composite fiber with high CNT content, high CNT orientation degree, and excellent mechanical property is prepared by using a liquid crystal spinning method.

Description

A CNT composite fiber and its preparation method and application Technical Field

[0001] The present application relates to the technical field of carbon nanotube materials, for example, a CNT composite fiber and its preparation method and application. Background Art

[0002] Carbon nanotubes (CNTs), thanks to their unique one-dimensional tubular structure and exceptionally strong C-C covalent bonds, possess low density, a high aspect ratio, and excellent strength, modulus, electrical conductivity, and thermal properties. However, in practical applications, CNTs present two challenges that need to be addressed: first, strong van der Waals forces between CNT tubes, which lead to agglomeration; second, the inert surface of CNTs, which hinders the formation of a strong interfacial bond with the resin. Polyetheretherketone (PEEK) resin, a specialty thermoplastic engineering plastic, has garnered widespread attention for its high-temperature resistance, high strength, corrosion resistance, creep resistance, and high flame retardancy. Its products are widely used in aerospace, automotive, and medical device industries.

[0003] Currently, there are two broad methods for preparing CNT composites: mixing CNT powder with polymers; and polymer-infiltrating CNT macropreforms. These include one-dimensional CNT fibers, two-dimensional CNT films, and three-dimensional CNT sponges. Compared to films and foams, CNTs in fibers are more highly oriented, which facilitates their superior mechanical properties.

[0004] CNT has a high degree of orientation in the macroscopic body of fiber, which is beneficial to improve the mechanical properties of the material. In the related art, there are literature reports on the preparation of CNT composite fibers (Latko-Dura ek P, Bertasius P, Macutkevic J, et al. Fibers of thermoplastic copolyamides with carbon nanotubes for electromagnetic shielding applications [J]. Materials, 2021, 14 (19): 5699), but the CNT agglomeration in this composite fiber is more serious, and the CNT content is only 7wt%, which is not conducive to the excellent performance of CNT, and the mechanical properties of the prepared composite fiber are poor. CN115787304A discloses a method for preparing a carbon nanotube / PBO composite fiber, the method being that the carbon nanotube fiber is contacted with a composite solution and protonated to obtain an intermediate fiber. The solvent in the intermediate fiber is then removed to finally obtain a carbon nanotube / polymer composite fiber, but the resin in this composite fiber is difficult to enter the interior of the fiber, the resin is unevenly distributed in the fiber, and the mechanical properties are poor.

[0005] Therefore, how to provide a CNT composite fiber with uniform CNT dispersion and high mechanical properties, and then prepare a CNT composite material with excellent mechanical properties, has become a technical problem that needs to be solved urgently.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] In view of the shortcomings of the related art, the purpose of this application is to provide a CNT composite fiber and its preparation method and application. This application uses a liquid crystal spinning method to prepare a CNT composite fiber with high CNT content, high CNT orientation and excellent mechanical properties.

[0009] To achieve this goal, this application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a CNT composite fiber, which includes the following components in weight percentage: 80-95% CNT and 5-20% thermoplastic resin.

[0011] In the related art, when CNT powder and polymer are blended and melt-spun to prepare CNT composite fibers, the problems are: CNTs are not easy to disperse and are prone to agglomeration, which leads to reduced mechanical properties of the CNT composite fibers. At the same time, the CNT content of the composite fibers is low, making it difficult to exert the excellent performance of CNTs. There are a large number of CNT bundles in the CNT fibers. The composite fibers prepared by immersing the CNT fibers in a polymer solution have CNT bundles as reinforcements, and the performance of CNT bundles is far lower than that of CNTs. At the same time, it is difficult for the polymers to be evenly distributed, and it is difficult for the polymers to penetrate into the internal area of ​​the bundles. As a result, the performance of the CNT composite fibers prepared in this way is also poor.

[0012] In this application, a liquid crystal spinning method is used to prepare CNT composite fibers with high CNT content, high CNT orientation and excellent mechanical properties.

[0013] In the present application, the weight percentage of CNT in the CNT composite fiber can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94% or 95%, etc.

[0014] In the CNT composite fiber, the weight percentage of the thermoplastic resin can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc.

[0015] The following are optional technical solutions for this application, but are not intended to limit the technical solutions provided in this application. Through the following optional technical solutions, the objectives and beneficial effects of this application can be better achieved and realized.

[0016] As an optional technical solution of the present application, the CNT includes single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

[0017] In one embodiment, the diameter of the CNT is 2 to 10 nm (for example, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm), and can further be 7 to 9 nm.

[0018] In one embodiment, the length of the CNT is 100-200 μm, for example, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm or 200 μm.

[0019] As an optional technical solution of the present application, the thermoplastic resin is selected from any one of polyetheretherketone (PEEK), polyimide, polystyrene or polyetherketoneketone, or a combination of at least two thereof.

[0020] It should be noted that the present application does not have any special restrictions on the number average molecular weight range of the thermoplastic resin, and all thermoplastic resins within the number average molecular weight range commonly used in the field are applicable.

[0021] In a second aspect, the present application provides a method for preparing the CNT composite fiber as described in the first aspect, the preparation method comprising the following steps:

[0022] (1) After CNT and solvent are uniformly mixed, thermoplastic resin is added thereto and mixed uniformly to obtain a spinning solution;

[0023] (2) wet spinning the spinning solution obtained in step (1) to obtain the CNT composite fiber.

[0024] In this application, the CNTs and solvent are pre-mixed to disperse the CNT bundles within the system into individual CNTs as much as possible, facilitating subsequent interaction between the thermoplastic resin molecules and each CNT. If the CNTs, solvent, and thermoplastic resin are mixed simultaneously, the CNTs may not fully disperse, and the resin molecules may surround the CNT bundles. Once the bundles are dispersed, the resin molecules may not be able to interact with the CNTs within. Furthermore, CNT dispersion relies on the protonation of chlorosulfonic acid. If the CNTs and resin molecules are added to the chlorosulfonic acid simultaneously, the resin molecules may wrap around the CNTs, weakening the protonation of the chlorosulfonic acid and preventing the CNTs from fully dispersing.

[0025] In this application, a liquid crystal spinning method of blending CNTs and thermoplastic resins is adopted. This method makes the CNTs uniformly and monodispersed in the spinning solution and highly oriented in the composite fibers, which is beneficial to load transfer and thus obtains CNT composite fibers with high mechanical properties.

[0026] As an optional technical solution of the present application, the solvent is selected from any one of chlorosulfonic acid, concentrated sulfuric acid or fuming sulfuric acid, or a combination of at least two thereof.

[0027] Chlorosulfonic acid, concentrated sulfuric acid, and fuming sulfuric acid will protonate CNTs without causing any other effects on the CNT surface. The protonated CNTs can be evenly dispersed due to electrostatic repulsion.

[0028] In one embodiment, the concentration of the CNT in the spinning solution is 5 to 15 mg / mL, for example, 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL or 15 mg / mL.

[0029] In one embodiment, in the spinning solution, the mass ratio of the thermoplastic resin to the CNT is 1:(4-25), for example, it can be 1:4, 1:6, 1:9, 1:10, 1:12, 1:15, 1:18, 1:20, 1:22, 1:24 or 1:25, etc., and can further be 1:(9-20).

[0030] It should be noted that in the present application, there is no special restriction on the mixing method of CNT and solvent in step (1) and the subsequent mixing method after adding thermoplastic resin. The mixing methods commonly used in the art are applicable, including but not limited to: using a rotary mixer for homogenous rotation, the rotation speed can be 1000 to 2000 r / min, for example, 1000 r / min, 1200 r / min, 1400 r / min, 1600 r / min, 1800 r / min or 2000 r / min, etc.

[0031] In one embodiment, the mixing time of the CNTs and the solvent is 20 to 30 minutes, for example, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes or 30 minutes.

[0032] In one embodiment, the mixing time after adding the thermoplastic resin is 10 to 20 minutes, for example, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes or 20 minutes.

[0033] As an optional technical solution of the present application, the wet spinning method specifically includes the following steps: placing the spinning solution in a syringe, fixing the syringe on a syringe pump, extruding, and coagulating in a coagulation bath to obtain the CNT composite fiber.

[0034] In one embodiment, the extrusion speed is 60 to 90 μL / min, for example, it can be 60 μL / min, 63 μL / min, 66 μL / min, 69 μL / min, 72 μL / min, 75 μL / min, 78 μL / min, 81 μL / min, 84 μL / min, 86 μL / min, 88 μL / min or 90 μL / min, etc.

[0035] It should be noted that there is no special restriction on the needle specifications of the syringe in this application, and exemplary ones include 25G, 27G, and 30G.

[0036] In one embodiment, the solvent used in the coagulation bath is selected from any one of acetone, deionized water, or ethanol, or a combination of at least two thereof.

[0037] In one embodiment, the method further includes a post-processing step after coagulation in the coagulation bath, and the post-processing method includes collecting and winding.

[0038] In one embodiment, the winding speed is 10 to 30 r / min, for example, it can be 10 r / min, 12 r / min, 14 r / min, 16 r / min, 18 r / min, 20 r / min, 22 r / min, 24 r / min, 26 r / min, 28 r / min or 30 r / min.

[0039] As an optional technical solution of the present application, a pre-treatment step is also included before the wet spinning in step (2).

[0040] In one embodiment, the pre-treatment method includes filtration;

[0041] The present application does not have any special restrictions on the pore size of the filter used for filtration. All commonly used filter screens in the field are applicable, including but not limited to: 400-800 mesh, for example, it can be 400 mesh, 500 mesh, 600 mesh, 700 mesh or 800 mesh, etc.

[0042] In one embodiment, the pore size of the filter used for filtration is 400 mesh or 600 mesh.

[0043] In the present application, partially agglomerated CNTs in the spinning solution can be removed by filtration to ensure that the CNTs are uniformly and monodispersed in the spinning solution, and CNT composite fibers with high orientation and excellent mechanical properties are prepared.

[0044] It should also be noted that, since filtration can remove some of the agglomerated CNTs in the spinning solution, the mass ratio of CNTs to thermoplastic resin in the unfiltered spinning solution obtained in step (1) is greater than the mass ratio of CNTs to thermoplastic resin in the CNT composite fiber finally prepared.

[0045] As an optional technical solution of the present application, the preparation method of the CNT composite fiber specifically includes the following steps:

[0046] (1) After CNT and solvent are uniformly mixed, thermoplastic resin is added thereto and mixed uniformly to obtain a spinning solution;

[0047] (2) After filtering the spinning solution obtained in step (1) using a filter, place it in a syringe, fix the syringe on the injection pump, set the speed to 60 to 90 μL / min, extrude, coagulate in a coagulation bath, collect, and roll up to obtain the CNT composite fiber.

[0048] Furthermore, the preparation method of the CNT composite fiber specifically includes the following steps:

[0049] (1) placing CNT and solvent in a rotary mixer and rotating them homogenously for 20 to 30 minutes to mix them evenly, then adding thermoplastic resin and continuing to rotate for 10 to 20 minutes to obtain a spinning solution;

[0050] (2) After filtering the spinning solution obtained in step (1) using a filter with a pore size of 400 to 800 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 60 to 90 μL / min, extrude, coagulate in a coagulation bath, collect, and obtain the CNT composite fiber.

[0051] In a third aspect, the present application provides a CNT composite material. The CNT composite material is prepared from the CNT composite fiber as described in the first aspect.

[0052] This application uses CNT composite fibers with high CNT content, high CNT orientation, and excellent mechanical properties prepared by liquid crystal spinning as raw materials. Without the need to introduce additional resins, a CNT composite material with excellent mechanical properties can be obtained by hot pressing or winding.

[0053] In a fourth aspect, the present application provides a method for preparing the CNT composite material according to the third aspect, the preparation method comprising the following steps:

[0054] The CNT composite fibers described in the first aspect are bundled and then formed to obtain the CNT composite material.

[0055] In one embodiment, the molding method includes hot pressing molding and winding molding.

[0056] In one embodiment, the temperature of the hot pressing molding is 160-175°C (for example, it can be 160°C, 163°C, 164°C, 166°C, 167°C, 168°C, 170°C, 172°C, 174°C or 175°C, etc.), and the pressure is 12-16 MPa (for example, it can be 12 MPa, 12.5 MPa, 13 MPa, 13.5 MPa, 14 MPa, 14.5 MPa, 15 MPa, 15.5 MPa or 16 MPa, etc.).

[0057] Compared with the related art, this application has the following beneficial effects:

[0058] (1) This application adopts liquid crystal spinning method and controls the mass ratio of CNT and thermoplastic resin in the spinning solution within a specific range to prepare CNT composite fibers with high CNT content, high CNT orientation and excellent mechanical properties. The orientation degree of CNT in the CNT composite fibers is 1 G∥ / I G⊥ ≥16.56, single fiber tensile strength ≥1GPa.

[0059] (2) This application uses CNT composite fibers with high CNT content, high CNT orientation, and excellent mechanical properties prepared by liquid crystal spinning as raw materials. Without the need to introduce other resins, a CNT composite film material with excellent mechanical properties can be obtained by hot pressing or winding. The orientation degree of CNT in the composite film is 1 G∥ / I G⊥ ≥8.67, tensile strength ≥460MPa.

[0060] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0062] FIG1 is a SEM photograph of the CNT composite fiber provided in Example 1 of the present application;

[0063] FIG2 is a stress-strain curve diagram of the CNT composite fibers provided in Examples 1-4 of the present application and the CNT fibers provided in Comparative Example 3;

[0064] FIG3 is a polarized light image of mixed solutions 1-4 provided in the present application;

[0065] FIG4 is a stress-strain curve diagram of the CNT composite material provided in Application Examples 1-4 of the present application;

[0066] FIG5 is a SEM photograph of the CNT composite film provided in Application Example 1 of the present application;

[0067] FIG6 is a SEM photograph of the CNT composite film provided in Comparative Application Example 4 of the present application;

[0068] FIG7 is a SEM photograph of the CNT composite film provided in Comparative Application Example 5 of the present application. DETAILED DESCRIPTION

[0069] The technical solution of the present application will be further described below with reference to the accompanying drawings and through specific implementation methods. Those skilled in the art should understand that the embodiments are only for the purpose of helping to understand the present application and should not be regarded as specific limitations of the present application.

[0070] The sources of some components in the following examples and comparative examples are as follows:

[0071] CNT: OCSiAL, tubal;

[0072] Polyetheretherketone: Zhongyan High Performance Engineering Plastics Co., Ltd., 330PF;

[0073] Polyimide: polyamic acid (whkmk-2658968) was purchased from Kemi Biopharmaceuticals. The starting temperature was 20°C, and the mixture was heated to 350°C at a heating rate of 10°C / min. The mixture was kept at 350°C for 1 h to obtain polyimide.

[0074] Polystyrene: New Yida Technology Co., Ltd., XYD-204.

[0075] Example 1

[0076] This embodiment provides a CNT composite fiber and a preparation method thereof. The CNT composite fiber includes the following components in percentage by weight: 95% CNT and 5% polyetheretherketone.

[0077] The preparation method of the above-mentioned CNT composite fiber is as follows:

[0078] (1) CNT (0.15 g) and chlorosulfonic acid (10 mL) were placed in a rotary mixer and homogenized and rotated for 20 min to mix uniformly. Then, polyetheretherketone (0.0075 g) was added thereto and the mixture was rotated for another 10 min to obtain a spinning solution.

[0079] (2) After filtering the spinning solution obtained in step (1) using a filter with a pore size of 400 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 60 μL / min, extrude it, coagulate it in an acetone coagulation bath, collect and reel it in, and the reeling speed is 10 r / min to obtain the CNT composite fiber.

[0080] The appearance of the CNT composite fiber provided in this embodiment was characterized using a scanning electron microscope (Quanta 250FEG). The result is shown in FIG1 . As can be seen from FIG1 , the CNT composite fiber was successfully prepared using the preparation method provided in this application.

[0081] Example 2

[0082] This embodiment provides a CNT composite fiber and a preparation method thereof. The CNT composite fiber includes the following components in percentage by weight: 90% CNT and 10% polyetheretherketone.

[0083] The preparation method of the above-mentioned CNT composite fiber is as follows:

[0084] (1) CNT (0.15 g) and solvent (10 mL) were placed in a rotary mixer and homogenized for 20 min to mix uniformly. Then, polyetheretherketone (0.0148 g) was added thereto and the mixture was rotated for another 10 min to obtain a spinning solution.

[0085] (2) After filtering the spinning solution obtained in step (1) using a filter with a pore size of 400 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 60 μL / min, extrude it, coagulate it in an acetone coagulation bath, collect and reel it in, and the reeling speed is 10 r / min to obtain the CNT composite fiber.

[0086] Example 3

[0087] This embodiment provides a CNT composite fiber and a preparation method thereof. The CNT composite fiber includes the following components in percentage by weight: 85% CNT and 15% polyetheretherketone.

[0088] The preparation method of the above-mentioned CNT composite fiber is as follows:

[0089] (1) CNT (0.15 g) and solvent (10 mL) were placed in a rotary mixer and homogenized and rotated for 20 min to mix uniformly. Then, polyetheretherketone (0.0244 g) was added thereto and the mixture was rotated for another 10 min to obtain a spinning solution.

[0090] (2) After filtering the spinning solution obtained in step (1) using a filter with a pore size of 400 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 60 μL / min, extrude it, coagulate it in an acetone coagulation bath, collect and reel it in, and the reeling speed is 10 r / min to obtain the CNT composite fiber.

[0091] Example 4

[0092] This embodiment provides a CNT composite fiber and a preparation method thereof. The CNT composite fiber includes the following components in percentage by weight: 80% CNT and 20% polyetheretherketone.

[0093] The preparation method of the above-mentioned CNT composite fiber is as follows:

[0094] (1) CNT (0.15 g) and solvent (10 mL) were placed in a rotary mixer and homogenized for 20 min to mix uniformly. Then, polyetheretherketone (0.035 g) was added thereto and the mixture was rotated for another 10 min to obtain a spinning solution.

[0095] (2) After filtering the spinning solution obtained in step (1) using a filter with a pore size of 400 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 60 μL / min, extrude it, coagulate it in an acetone coagulation bath, collect and reel it in, and the reeling speed is 10 r / min to obtain the CNT composite fiber.

[0096] Example 5

[0097] This embodiment provides a CNT composite fiber and a preparation method thereof. The CNT composite fiber includes the following components in percentage by weight: 92% CNT and 8% polyimide.

[0098] The preparation method of the above-mentioned CNT composite fiber is as follows:

[0099] (1) CNT (0.15 g) and solvent (10 mL) were placed in a rotary mixer and homogenized for 30 min to mix uniformly. Then, polyimide (0.012 g) was added thereto and the mixture was rotated for another 20 min to obtain a spinning solution.

[0100] (2) After filtering the spinning solution obtained in step (1) using a filter with a pore size of 600 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 70 μL / min, extrude it, coagulate it in a coagulation bath, collect and reel it in, and the reeling speed is 15 r / min to obtain the CNT composite fiber.

[0101] Example 6

[0102] This embodiment provides a CNT composite fiber and a preparation method thereof. The CNT composite fiber includes the following components in percentage by weight: 88% CNT and 12% polystyrene.

[0103] The preparation method of the above-mentioned CNT composite fiber is as follows:

[0104] (1) CNT (0.15 g) and solvent (10 mL) were placed in a rotary mixer and homogenized for 25 min to mix uniformly. Then, polystyrene (0.019 g) was added and the mixture was rotated for another 15 min to obtain a spinning solution.

[0105] (2) After filtering the spinning solution obtained in step (1) using a filter with a pore size of 600 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 90 μL / min, extrude, coagulate in a coagulation bath, collect, and reel at a reeling speed of 20 r / min to obtain the CNT composite fiber.

[0106] Comparative Example 1

[0107] This comparative example provides a CNT composite fiber and a preparation method thereof. The CNT composite fiber includes the following components in percentage by weight: 97% CNT and 3% polyetheretherketone.

[0108] The preparation method of the above-mentioned CNT composite fiber is as follows:

[0109] (1) CNT (0.15 g) and solvent (10 mL) were placed in a rotary mixer and homogenized and rotated for 20 min to mix uniformly. Then, polyetheretherketone (0.0038 g) was added thereto and the mixture was rotated for another 10 min to obtain a spinning solution.

[0110] (2) After filtering the spinning solution obtained in step (1) using a filter with a pore size of 400 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 60 μL / min, extrude it, coagulate it in an acetone coagulation bath, collect and reel it in, and the reeling speed is 10 r / min to obtain the CNT composite fiber.

[0111] Comparative Example 2

[0112] This comparative example provides a CNT composite fiber and a preparation method thereof. The CNT composite fiber includes the following components in percentage by weight: 75% CNT and 25% polyetheretherketone.

[0113] The preparation method of the above-mentioned CNT composite fiber is as follows:

[0114] (1) CNT (0.15 g) and solvent (10 mL) were placed in a rotary mixer and homogenized and rotated for 20 min to mix uniformly. Then, polyetheretherketone (0.049 g) was added thereto and the mixture was rotated for another 10 min to obtain a spinning solution.

[0115] (2) After filtering the spinning solution obtained in step (1) using a filter with a pore size of 400 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 60 μL / min, extrude it, coagulate it in an acetone coagulation bath, collect and reel it in, and the reeling speed is 10 r / min to obtain the CNT composite fiber.

[0116] Comparative Example 3

[0117] This comparative example provides a CNT fiber and a preparation method thereof. The preparation method of the CNT fiber is as follows:

[0118] (1) CNT (0.15 g) and solvent (10 mL) were placed in a rotary mixer and homogenized for 20 min to obtain a spinning solution.

[0119] (2) After filtering the spinning solution obtained in step (1) using a filter with a pore size of 400 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 60 μL / min, extrude, coagulate in an acetone coagulation bath, collect and reel, and reel at a reeling speed of 10 r / min to obtain the CNT fiber.

[0120] The mechanical properties of the CNT composite fibers provided in Examples 1-4 and the CNT fibers provided in Comparative Example 3 were tested using Instron 3365, and their stress-strain curves are shown in FIG2 . As can be seen from FIG2 , the CNT composite fibers prepared by the method provided in the present application have good mechanical properties.

[0121] CNT (0.15 g) and chlorosulfonic acid (10 mL) were mixed to obtain a mixed solution 1;

[0122] CNT (0.15 g) and chlorosulfonic acid (10 mL) were mixed uniformly, and polyetheretherketone (0.0375 g) was added thereto and mixed uniformly to obtain a mixed solution 2;

[0123] CNT (0.15 g) and chlorosulfonic acid (10 mL) were mixed uniformly, and polyetheretherketone (0.225 g) was added thereto and mixed uniformly to obtain a mixed solution 3;

[0124] Polyetheretherketone (0.225 g) and chlorosulfonic acid (10 mL) were mixed to obtain a mixed solution 4;

[0125] Mixed solutions 1-4 were tested using a polarizing microscope, and their polarized light images are shown in Figure 3. As shown in Figure 3, CNTs can show a liquid crystal phase in chlorosulfonic acid. After adding PEEK, the liquid crystal phase gradually becomes blurred, which shows that excessive PEEK will affect the formation of liquid crystals by CNTs, thereby causing their orientation to decrease. PEEK alone will not produce a liquid crystal phase in chlorosulfonic acid. This shows that in this application, liquid crystal spinning can be achieved by controlling the amount of CNT and PEEK added to the spinning solution, and CNT and PEEK can be evenly dispersed in chlorosulfonic acid without phase separation.

[0126] The properties of the CNT composite fibers or CNT fibers provided in the above examples and comparative examples were tested. The specific testing methods are as follows:

[0127] (1) Orientation degree of CNT in CNT composite fiber I G∥ / I G⊥ :

[0128] The Raman intensity of the composite fiber under polarized light of different angles was measured using a Renishaw invia Qontor laser Raman spectrometer at room temperature. When the incident polarized light was parallel to the fiber axis, the Raman intensity was defined as I G∥ When the incident polarized light is perpendicular to the fiber axis, the Raman intensity is defined as I G⊥ .

[0129] (2) Single filament tensile strength:

[0130] The CNT composite fiber was cut into 10 mm long strips and fixed in a sample frame. The tensile properties were then characterized using an Instron 3365 tensile testing machine. The tensile speed was set to 0.5 mm / min, and the load-displacement curve was detected and recorded simultaneously.

[0131] The above performance test results are shown in Table 1 below:

[0132] Table 1

[0133] From the above, it can be seen that the present invention adopts the liquid crystal spinning method and controls the mass ratio of CNT and thermoplastic resin in the spinning solution within a specific range to prepare CNT composite fibers with high CNT content, high CNT orientation and excellent mechanical properties. G∥ / I G⊥ ≥16.56, specifically 16.56~24.62, single fiber tensile strength ≥1GPa, specifically 1.2~3GPa.

[0134] If the mass ratio of CNT to thermoplastic resin in the spinning solution is too large or too small, the performance of the prepared CNT composite fiber will be poor.

[0135] Application Examples 1-6 and Comparative Application Examples 1-2

[0136] Application Examples 1-6 and Comparative Application Examples 1-2 respectively provide a CNT composite film and a preparation method thereof. The CNT composite film is prepared from the CNT composite fibers provided in Examples 1-6 and Comparative Examples 1-2, respectively, in sequence. The preparation methods are as follows:

[0137] After the CNT composite fibers are bundled, they are hot-pressed at 160° C. and 12 MPa for 3 hours to form the CNT composite film.

[0138] Comparative Application Example 3

[0139] This comparative application example provides a CNT film and a preparation method thereof. The CNT film is prepared from the CNT fiber provided in Comparative Example 3, and the preparation method is the same as that of Application Example 1.

[0140] Comparative Application Example 4

[0141] This comparative application example provides a CNT composite film and a preparation method thereof. The CNT composite film is composed of the following components in percentage by weight: 89.8% CNT and 10.2% polyetheretherketone.

[0142] The preparation method of the above-mentioned CNT composite fiber is as follows:

[0143] PEEK was dried in a vacuum oven for 6 h, the temperature was set to 150 °C, and CNTs were placed in a vacuum oven and dried for 12 h;

[0144] Weigh polyetheretherketone (0.17 g) and CNT (1.5 g) and grind them separately at room temperature until there is no particle feeling. Dissolve the ground polyetheretherketone in an appropriate amount of DMF (50 mL) and perform ultrasonic dispersion at 30°C and 10 W for 1 hour. Then add CNT and stir evenly. Then ultrasonicate at 30°C for 1 hour. After uniform dispersion, filter (filter membrane pore size is 0.22 μm), wash with deionized water 4 times to remove the DMF solution, and finally dry thoroughly in a vacuum oven at 80°C to obtain a CNT composite material.

[0145] Comparative Application Example 5

[0146] This comparative application example provides a CNT composite film and a preparation method thereof. The CNT composite film is composed of the following components in percentage by weight: 90% CNT and 10% polyetheretherketone.

[0147] The preparation method of the above-mentioned CNT composite film is as follows:

[0148] (1) Preparation of CNT fibers: CNT (0.15 g) and chlorosulfonic acid (10 mL) were placed in a rotary mixer and homogenized for 20 min to obtain a spinning solution.

[0149] After filtering the spinning solution obtained in step (1) using a filter with a pore size of 400 mesh, place it in a syringe, fix the syringe on the injection pump, set the speed to 60 μL / min, extrude, coagulate in an acetone coagulation bath, collect and reel, and the reeling speed is 10 r / min to obtain the CNT fiber.

[0150] (2) Preparation of CNT composite film: Weigh 0.0166 g of polyetheretherketone and grind them separately at room temperature until they are free of particles. Dissolve the ground PEEK in 50 mL of DMF. Soak the CNT fibers prepared in step (1) in the DMF solution for 2 h. Then soak them in deionized water for 2 h. Finally, dry them in a vacuum oven at 80°C to obtain a CNT composite film.

[0151] The mechanical properties of the CNT composite films provided in Examples 1-4 were tested using an Instron 3365, and their stress-strain curves are shown in Figure 4. As shown in Figure 4, the CNT composite films prepared by the method provided in this application have good mechanical properties.

[0152] Scanning electron microscopy (Quanta 250FEG) was used to characterize the appearance of the CNT composite films provided in Example 1 and Comparative Examples 4-5. The results are shown in Figures 5 (Application Example 1), 6 (Comparative Example 4), and 7 (Comparative Example 5), respectively. Figures 5-7 show that the film in Figure 5, prepared by hot-pressing the fiber bundles, exhibits greater density and a certain degree of orientation. The materials in Figures 6 and 7 exhibit less density. Because the composite film in Figure 7 is prepared from CNT fibers, its orientation is slightly better than that in Figure 6.

[0153] The performance of the CNT composite films or CNT films provided in the above application examples and comparative application examples was tested. The specific testing methods are as follows:

[0154] (1) Orientation degree of CNT in CNT composite film I G∥ / I G⊥ :

[0155] The Raman intensity of the composite fiber under polarized light of different angles was measured using a Renishaw invia Qontor laser Raman spectrometer at room temperature. When the incident polarized light was parallel to the fiber axis, the Raman intensity was defined as I G∥ When the incident polarized light is perpendicular to the fiber axis, the Raman intensity is defined as I G⊥ .

[0156] (2) Tensile strength:

[0157] The CNT composite film or CNT film was cut into 2mm×10mm strips and fixed in the sample frame. The tensile properties were then characterized using an Instron 3365 tensile testing machine. The tensile speed was set to 0.5mm / min, and the load-displacement curve was detected and recorded.

[0158] The above performance test results are shown in Table 2 below:

[0159] Table 2

[0160] As can be seen from the above, in this application, the CNT composite fiber with high CNT content, high CNT orientation and excellent mechanical properties prepared by the liquid crystal spinning method is used as the raw material. Without the need to introduce other resins, a CNT composite film material with excellent mechanical properties can be obtained by hot pressing or winding. The orientation degree of CNT in the composite film is 1 G∥ / I G⊥ ≥8.67, specifically 8.67~15.52, tensile strength ≥460MPa, specifically 460~1030MPa.

[0161] If the mass ratio of CNT to thermoplastic resin in the spinning solution for preparing the composite membrane is too large or too small (Comparative Application Examples 1-2), the performance of the prepared CNT composite fiber is poor.

[0162] However, CNT films cannot be prepared using CNT fibers (Comparative Application Example 3); the CNT composite membranes prepared by grinding and drying CNT and polyetheretherketone as raw materials (Comparative Application Example 4), or the CNT composite membranes prepared by using CNT fibers and polyetheretherketone as raw materials (Comparative Application Example 5), all have poor performance.

[0163] In summary, the present application adopts the liquid crystal spinning method and controls the mass ratio of CNT and thermoplastic resin in the spinning solution within a specific range to prepare CNT composite fibers with high CNT content, high CNT orientation and excellent mechanical properties. Furthermore, without the need to introduce additional resins, CNT composite materials with excellent mechanical properties can be obtained by hot pressing or winding.

[0164] The applicant declares that while the above-mentioned embodiments are used to illustrate the detailed process flow of the present application, the present application is not limited to the above-mentioned detailed process flow, which does not mean that the present application must rely on the above-mentioned detailed process flow in order to be implemented. Those skilled in the art should understand that any improvements to the present application, equivalent replacements for the raw materials of the present application's products, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present application.

Claims

1. A CNT composite fiber, wherein, The CNT composite fiber comprises components in the following weight percentages: 80-95% of CNT and 5%-20% of thermoplastic resin.

2. The CNT composite fiber according to claim 1, wherein, The CNT includes single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

3. The CNT composite fiber according to claim 1 or 2, wherein, The diameter of the CNT is 2-10 nm, and further optionally 7-9 nm.

4. The CNT composite fiber according to any one of claims 1-3, wherein, The length of the CNT is 100-200 μm.

5. The CNT composite fiber according to any one of claims 1-4, wherein, The thermoplastic resin is selected from any one or a combination of at least two of polyether ether ketone, polyimide, polystyrene, or polyether ketone ketone.

6. A method for preparing the CNT composite fiber according to any one of claims 1-5, comprising the following steps: (1) After uniformly mixing CNT and a solvent, add the thermoplastic resin thereto and mix uniformly to obtain a spinning solution; (2) Perform wet spinning on the spinning solution obtained in step (1) to obtain the CNT composite fiber.

7. The preparation method according to claim 6, wherein The solvent is selected from any one or a combination of at least two of chlorosulfonic acid, concentrated sulfuric acid, or fuming sulfuric acid.

8. The preparation method according to claim 6 or 7, wherein In the spinning solution, the concentration of the CNT is 5-15 mg / mL.

9. The preparation method according to any one of claims 6-8, wherein, In the spinning solution, the mass ratio of the thermoplastic resin to the CNT is 1:(4-25), and further optionally 1:(9-20).

10. The preparation method according to any one of claims 6-9, wherein, The method of wet spinning specifically comprises the following steps: Place the spinning solution in a syringe, fix the syringe on an injection pump, extrude it, and coagulate it in a coagulation bath to obtain the CNT composite fiber; Optionally, the extrusion speed is 60-90 μL / min; Optionally, the solvent used in the coagulation bath is selected from any one or a combination of at least two of acetone, deionized water, or ethanol.

11. The preparation method according to any one of claims 6-10, wherein, Before the wet spinning in step (2), a pretreatment step is further included; Optionally, the pretreatment method includes filtration.

12. The preparation method according to any one of claims 6-11, wherein, The method for preparing the CNT composite fiber specifically comprises the following steps: (1) After uniformly mixing CNT and a solvent, add the thermoplastic resin thereto and mix uniformly to obtain a spinning solution; (2) Filter the spinning solution obtained in step (1) using a filter screen, place it in a syringe, fix the syringe on an injection pump, set the speed to 60-90 μL / min, extrude it, coagulate it in a coagulation bath, collect it, and wind it up to obtain the CNT composite fiber.

13. A CNT composite material, wherein, The CNT composite material is prepared from the CNT composite fiber according to any one of claims 1-5.

14. A method for preparing the CNT composite material according to claim 13, comprising the following steps: After bundling the CNT composite fiber according to any one of claims 1-5, perform shaping to obtain the CNT composite material.

15. The preparation method of the CNT composite material according to claim 14, wherein, The shaping method includes hot pressing and winding; Optionally, the temperature of the hot pressing is 160-175 °C and the pressure is 12-16 MPa.

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