An ultralight hollow carbon nanotube composite fiber, an electromagnetic shielding material based on a shuttle-shaped supramolecular structure and a preparation method thereof

Abstract

The present application relates to a kind of ultra-light hollow carbon nanotube composite fiber, electromagnetic shielding material based on shuttle-shaped supramolecular structure and its preparation method.The preparation of ultra-light hollow carbon nanotube composite fiber is: using DMAC and LiCl to uniformly disperse purified carbon nanotube, obtain the carbon nanotube dispersion system containing 2-3.5wt% LiCl, add 0.1-4wt% PBIA solution and uniformly disperse, obtain carbon nanotube-PBIA dispersion, add DMAC to reduce the content of LiCl to 0.1-1wt% and shear processing under 5000-10000rpm for 10-30min, then centrifugal separation and freeze-drying, obtain carbon nanotube-PBIA polymer supramolecule and prepare into spinning solution, by wet spinning, ultra-light hollow carbon nanotube composite fiber is prepared.The density of carbon nanotube composite fiber prepared by the present application is greatly reduced, and the strength, toughness and electromagnetic shielding efficiency are obviously improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of carbon nanotube composite fiber preparation, and particularly relates to a super-light hollow carbon nanotube composite fiber, an electromagnetic shielding material based on a shuttle-shaped supramolecular structure and a preparation method thereof. BACKGROUND

[0002] Carbon nanotubes (CNTs) are an important member of the family of nanocarbon materials, and have attracted much attention due to their outstanding mechanical, electrical and optical properties. As a one-dimensional nanomaterial, carbon nanotubes have a length-diameter ratio of more than 1000, a high strength of about 100 GPa and an elastic modulus close to 1000 GPa, and an electrical conductivity of up to 1800 S·cm -1 , making them ideal nanofillers for composite materials. As a typical representative of new high-performance fibers, one-dimensional macroscopic material carbon nanotube fiber (CNTF) composed of aligned carbon nanotubes exhibits excellent properties such as high strength and high thermal conductivity. Compared with traditional metal or alloy materials, carbon nanotube fiber reinforced composites have higher specific performance (specific strength and specific modulus), and have wide application and demand in the fields of aerospace, wind power blades, new energy vehicles, high-speed trains and sports goods. Lightweight, high strength, high toughness, high electrical conductivity and high thermal conductivity are key performance indicators and core technical problems that need to be solved in the application and development of fiber materials, and have attracted widespread attention from researchers and the industry.

[0003] However, although pure hollow carbon nanotube fibers have advantages such as low density and high electrical conductivity, the elongation at break of pure carbon nanotube fibers is generally low, which means that it lacks ductility when subjected to tensile stress, which limits its use in certain applications. To overcome these limitations, the ductility of carbon nanotube fibers can be improved by composite modification, for example, the toughness and ductility can be improved by forming a composite fiber with a high molecular polymer, making it more suitable for use in applications requiring high strength and toughness. Currently, the carbon nanotube / high molecular polymer composite fibers formed are generally solid structures, which are determined by the preparation method and material properties of the carbon nanotube / high molecular polymer composite fiber. During the preparation of the carbon nanotube / high molecular polymer composite fiber, carbon nanotubes and high molecular chains as structural units are formed by double diffusion, which usually causes carbon nanotubes and high molecular chains to fill the entire fiber, resulting in a solid structure. For example, Chinese Patent Application CN115787304A discloses a preparation method of a carbon nanotube / high molecular composite fiber, but the carbon nanotube / high molecular composite fiber prepared thereby is also a solid structure. Although the carbon nanotube / high molecular composite fiber has high tensile strength and elongation at break, the solid structure of the carbon nanotube / high molecular composite fiber has a high density, which does not meet the lightweight preparation scene requirements.

[0004] Therefore, as a composite material reinforcer with obvious performance advantages, it is of great significance to develop carbon nanotube composite fibers with adjustable electrical conductivity, more lightweight requirements and better electromagnetic shielding performance on the basis of maintaining the original performance of the fibers for the further development of carbon nanotube fiber preparation technology. SUMMARY

[0005] In order to solve one or more technical problems existing in the prior art, the present application provides an ultralight hollow carbon nanotube composite fiber, an electromagnetic shielding material based on a shuttle-shaped supramolecular structure and a preparation method thereof. The present application prepares a new shuttle-shaped carbon nanotube-PBIA polymer supramolecule, and an ultralight hollow carbon nanotube composite fiber is prepared by a wet spinning technology. Meanwhile, based on the adjustable dielectric property of the shuttle-shaped carbon nanotube-PBIA polymer supramolecular structure, an electromagnetic shielding material with periodic and multi-level structure is prepared.

[0006] The present application provides, in a first aspect, a preparation method of an ultralight hollow carbon nanotube composite fiber, comprising the following steps:

[0007] (1) purifying carbon nanotubes to obtain purified carbon nanotubes;

[0008] (2) uniformly dispersing the purified carbon nanotubes with N,N-dimethylacetamide and lithium chloride to obtain a carbon nanotube dispersion system containing 2-3.5% of lithium chloride by mass percentage, then adding a polymer PBIA solution with a concentration of 0.1-4wt% to the carbon nanotube dispersion system and uniformly dispersing to obtain a carbon nanotube-PBIA dispersion liquid;

[0009] (3) adding N,N-dimethylacetamide to the carbon nanotube-PBIA dispersion liquid to reduce the mass percentage of lithium chloride contained in the carbon nanotube-PBIA dispersion liquid to 0.1-1%, and shearing at a speed of 5000-10000 rpm for 10-30 min, then centrifuging and freeze-drying to obtain a carbon nanotube-PBIA polymer supramolecule;

[0010] (4) preparing the carbon nanotube-PBIA polymer supramolecule into a carbon nanotube-PBIA polymer supramolecule solution with a strong acid, and then preparing an ultralight hollow carbon nanotube composite fiber by wet spinning.

[0011] The present application provides, in a second aspect, a preparation method of an electromagnetic shielding material based on a shuttle-shaped supramolecular structure, comprising the following steps:

[0012] (1) purifying carbon nanotubes to obtain purified carbon nanotubes;

[0013] (2) dispersing the purified carbon nanotubes uniformly with N,N-dimethylacetamide and lithium chloride to obtain a carbon nanotube dispersion system containing 2-3.5% lithium chloride by mass percentage, then adding a polymer PBIA solution with a concentration of 0.1-4wt% into the carbon nanotube dispersion system and dispersing uniformly to obtain a carbon nanotube-PBIA dispersion liquid;

[0014] (3) adding N,N-dimethylacetamide into the carbon nanotube-PBIA dispersion liquid to reduce the mass percentage of lithium chloride contained in the carbon nanotube-PBIA dispersion liquid to 0.1-1%, and shearing at a speed of 5000-10000 rpm for 10-30 min, then centrifuging and freeze-drying to obtain carbon nanotube-PBIA polymer supramolecules;

[0015] (4) preparing the carbon nanotube-PBIA polymer supramolecules into a carbon nanotube-PBIA polymer supramolecule solution with a strong acid, and then coating into a film layer by layer to obtain an electromagnetic shielding material based on the shuttle-shaped supramolecular structure.

[0016] Preferably, the step (3) obtains shuttle-shaped carbon nanotube-PBIA polymer supramolecules.

[0017] Preferably, in the step (1), the carbon nanotubes are single-walled carbon nanotubes and / or multi-walled carbon nanotubes; and / or the purification treatment is mixing the carbon nanotubes with hydrogen peroxide and stirring for 1-2 h, then mixing with hydrochloric acid and stirring for 2-4 h, and then washing and freeze-drying to obtain the purified carbon nanotubes; preferably, when the purification treatment is performed, the use amount ratio of the carbon nanotubes, hydrogen peroxide and hydrochloric acid is (5-10) g:(300-500) mL:(400-600) mL; preferably, the concentration of the hydrogen peroxide is 20-40%; and preferably, the concentration of the hydrochloric acid is 36-38wt%.

[0018] Preferably, in the step (2), the polymer PBIA solution uses N,N-dimethylacetamide and lithium chloride as the solvent, and the mass percentage of lithium chloride contained in the polymer PBIA solution is 2-3.5%; the mass ratio of the purified carbon nanotubes to the polymer PBIA contained in the polymer PBIA solution is (0.2-2):1; and / or when the purified carbon nanotubes are dispersed uniformly with N,N-dimethylacetamide and lithium chloride, the ratio of the total use amount of N,N-dimethylacetamide and lithium chloride to the use amount of the purified carbon nanotubes is (250-500) mL:(250-500) mg.

[0019] Preferably, in the step (4), the strong acid is chlorosulfonic acid; and / or the carbon nanotube-PBIA polymer supramolecule solution contains 2-5% carbon nanotube-PBIA polymer supramolecules by mass percentage.

[0020] Preferably, in step (4): when wet spinning is performed, the extrusion rate is 100-300 μL / min, the draw ratio is 1.2-1.5, and the coagulation bath is acetone.

[0021] Preferably, in step (4): when layer-by-layer blade coating is performed, the thickness of each layer of film is 0.4-0.6 μm, preferably 0.5 μm; when blade coating is performed, each layer of film is sequentially coated through an N,N-dimethylacetamide / water system with a volume ratio of 8:2, an N,N-dimethylacetamide / water system with a volume ratio of 1:1, and pure water as a coagulation bath; when blade coating is performed, each layer of film is oriented in the same direction, and the angle between adjacent two layers of film is 15-90°; and / or the total number of layers of film is 4-30.

[0022] The present application provides, in a third aspect, an ultralight hollow carbon nanotube composite fiber prepared by the preparation method described in the first aspect of the present application.

[0023] The present application provides, in a fourth aspect, an electromagnetic shielding material based on a fusiform supramolecular structure prepared by the preparation method described in the second aspect of the present application.

[0024] Compared with the prior art, the present application has at least the following beneficial effects:

[0025] (1) After obtaining the carbon nanotube-PBIA dispersion liquid, the present application can make the carbon nanotubes coated with polymers (PBIA polymers) orderly assembled into a fusiform supramolecular structure (fusiform nanosupramolecular structure) by regulating the content of LiCl in the dispersion liquid and simultaneously adding high-speed shearing, thereby obtaining a novel fusiform carbon nanotube-PBIA polymer supramolecule, and the present application can regulate the size of the fusiform carbon nanotube-PBIA polymer supramolecule by shearing rate and shearing time, and adjust the electrical performance of the fusiform supramolecular structure by regulating the content of carbon nanotubes.

[0026] (2) The present application is based on the fusiform carbon nanotube-PBIA polymer supramolecule obtained by wet spinning process to prepare an ultralight hollow carbon nanotube composite fiber, and the present application can obtain continuous ultralight hollow carbon nanotube composite fibers with different mechanical and electrical properties by regulating the extrusion rate, draw ratio, and coagulation bath composition; the ultralight hollow carbon nanotube composite fiber prepared by the present application has a significantly reduced density, significantly improved strength and toughness, and is beneficial to improving the electromagnetic shielding performance of the composite fiber.

[0027] (3) The application obtains the electromagnetic shielding film (electromagnetic shielding material) with periodicity and multi-level structure based on the obtained shuttle-shaped carbon nanotube-PBIA polymer supramolecule through the doctor blade film forming technology, so that the electromagnetic shielding material has high shielding efficiency, high strength and light weight, and fully meets the requirements of "strong, light and thin" materials at the present stage. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the SEM image of the carbon nanotube-PBIA polymer supramolecule obtained in Example 1 of the application;

[0029] Figure 2 is the SEM image of the ultra-light hollow carbon nanotube composite fiber prepared in Example 1 of the application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the application clearer, the technical scheme of the application will be described clearly and completely below in combination with the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0031] The application adopts a lossless dispersion method of polymer macromolecule non-covalent functionalized carbon nanotubes suitable for organic systems to obtain a uniform and stable dispersion system, and self-assembles a new shuttle-shaped carbon nanotube-polymer PBIA supramolecular structure through external force and cosolvent regulation; and designs and prepares an ultra-light hollow carbon nanotube composite fiber based on the shuttle-shaped supramolecular structure as a building unit, and at the same time, based on the shuttle-shaped supramolecular structure and the adjustable characteristics of its dielectric properties, an electromagnetic shielding material with periodicity and multi-level structure is prepared.

[0032] In a first aspect, the application provides a preparation method of an ultra-light hollow carbon nanotube composite fiber, which comprises the following steps:

[0033] (1) the carbon nanotubes are purified to obtain purified carbon nanotubes; the metal catalyst and other impurities in the carbon nanotube raw material can affect the final performance of the material, therefore, in the present application, the carbon nanotubes are purified, preferably, the carbon nanotubes are purified by using the oxidation-acid washing method; in the present application, for example, the carbon nanotubes are mixed with hydrogen peroxide in a certain proportion, and stirred at room temperature, the carbon nanotubes are weakly oxidized to remove the amorphous carbon attached to the surface of the catalyst and the carbon nanotubes, and expose the metal catalyst; then, the weakly oxidized carbon nanotubes are mixed with hydrochloric acid at room temperature and stirred to remove the metal catalyst; finally, the carbon nanotubes are cleaned with deionized water by using centrifugation and ultrasonic filtration (centrifugation-ultrasonic filtration method) until the filtrate is neutral, and then the carbon nanotubes are freeze-dried to obtain the purified carbon nanotube raw material, i.e. the purified carbon nanotubes; the centrifugation, ultrasonic filtration and freeze-drying are not specifically limited, which are the conventional techniques in the field;

[0034] (2) using N,N-dimethylacetamide (DMAC) and lithium chloride (LiCl) to uniformly disperse the purified carbon nanotubes to obtain a carbon nanotube dispersion system containing 2-3.5% (for example, 2%, 2.5%, 3% or 3.5%) lithium chloride by mass percentage, and then adding a polymer PBIA solution with a concentration of 0.1-4wt% (for example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt% or 4wt%) to the carbon nanotube dispersion system and uniformly dispersing to obtain a carbon nanotube-PBIA dispersion; in the present application, for example, using N,N-dimethylacetamide and lithium chloride to uniformly disperse the purified carbon nanotubes by ultrasonic cell pulverizer, specifically, using the ultrasonic cavitation effect of the N,N-dimethylacetamide and lithium chloride solvent to pretreat (for example, for 20-40 min) the purified carbon nanotubes by the ultrasonic cell pulverizer, so that the purified carbon nanotubes are fully infiltrated and untangled to obtain the carbon nanotube dispersion system; then, adding PBIA molecules with a certain concentration, further opening the carbon nanotube bundles by the ultrasonic cell pulverizer (for example, for 60-120 min), and wrapping the PBIA molecules on the surface of the carbon nanotubes through π-π interaction to prevent the carbon nanotubes from re-aggregating, so as to form a stable dispersion, i.e. to obtain the carbon nanotube-PBIA dispersion; in the present application, the π-π interaction between the polymer PBIA macromolecule and the carbon nanotubes is used to adsorb the polymer PBIA macromolecule on the surface of the carbon nanotubes, and then to assist the dispersion of the carbon nanotubes in the solvent system of the polymer; in the present application, the adsorption of the polymer PBIA macromolecule on the surface of the carbon nanotubes forms a steric hindrance effect, which effectively prevents the aggregation of the carbon nanotubes; the present application finds that this dispersion method of the carbon nanotubes in step (2) is a lossless dispersion method for the non-covalent functionalization of the carbon nanotubes by the polymer macromolecule in the organic system; the carbon nanotubes are non-covalently modified by the polymer matrix molecules, the π-electron interaction between the PBIA molecules and the carbon nanotubes is used to losslessly disperse the carbon nanotubes in the solvent system of the polymer PBIA macromolecule; in the present application, the polymer PBIA refers to polybenzimidazole terephthalamide;

[0035] (3) adding N,N-dimethylacetamide to the carbon nanotube-PBIA dispersion to reduce the mass percentage of lithium chloride contained in the carbon nanotube-PBIA dispersion to 0.1-1% (for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%) and shearing at a speed of 5000-10000 rpm (for example, 5000, 6000, 7000, 8000, 9000 or 10000 rpm) for 10-30 min (for example, 10, 15, 20, 25 or 30 min), and then centrifuging, separating and freeze-drying to obtain the carbon nanotube-PBIA polymer supramolecule; in the present application, the obtained carbon nanotube-PBIA polymer supramolecule is a fusiform carbon nanotube-PBIA polymer supramolecule, for example, as shown in Figure 1 The present application finds that, by adding high-speed shearing (shearing at 5000-10000 rpm for 10-30 min) and adjusting the content of the cosolvent LiCl to the carbon nanotube-PBIA dispersion, the carbon nanotubes wrapped with PBIA molecules in the carbon nanotube-PBIA dispersion can be uniformly self-assembled to form a fusiform supramolecular structure; the good dispersibility of the PBIA molecules in the DMAC / LiCl system is derived from the large cations formed by the coordination of DMAC and LiCl, which can effectively prevent the formation of hydrogen bonds between molecules, and thus the PBIA high molecules can be stably dispersed in the solvent; the present application finds that, among them, the cosolvent LiCl plays a crucial role in the dispersion stability of the system, by increasing the DMAC solvent and reducing the proportion of the LiCl solvent, and simultaneously adding high-speed shearing, the carbon nanotubes wrapped with PBIA high molecules can be orderly assembled into a fusiform nanosupramolecular structure; and in the present application, the size and aspect ratio of the fusiform supramolecular structure can be regulated by the shearing rate and shearing time, and the electrothermal performance of the fusiform supramolecular structure can be adjusted by the content of the carbon nanotubes; the present application does not make specific limitations on the centrifugation and freeze-drying operations involved in step (3), which can be routinely selected by those skilled in the art; specifically, in step (3), N,N-dimethylacetamide is added to the carbon nanotube-PBIA dispersion to reduce the mass percentage of lithium chloride contained in the carbon nanotube-PBIA dispersion to 0.1-1%, and the homogenizer is rapidly stirred at a speed of 5000-10000 rpm for 10-30 min, and then the lower precipitate is separated by centrifugation and freeze-dried to obtain the carbon nanotube-PBIA polymer supramolecule;

[0036] (4) The carbon nanotube-PBIA polymer supramolecule is prepared into a carbon nanotube-PBIA polymer supramolecule solution by using a strong acid, and then a super-light hollow carbon nanotube composite fiber (also referred to as a super-light hollow carbon nanotube composite fiber based on a fusiform supramolecular structure) is prepared by wet spinning; in the present application, the prepared super-light hollow carbon nanotube composite fiber has a hollow structure, for example, as shown in Figure 2 In the present application, the carbon nanotube-PBIA polymer supramolecule is protonated in a strong acid (for example, chlorosulfonic acid), due to the strong rigidity of the supramolecular structure and the charge on the protonated surface, a liquid crystal state structure with anisotropic distribution can be formed in a strong acid system, and by using a strong acid such as chlorosulfonic acid stripping technology, a carbon nanotube-PBIA polymer supramolecule solution with different carbon nanotube / PBIA contents can be obtained as a composite nanospinning solution; in the present application, a wet spinning technology is used, and by adjusting the extrusion rate, the draw ratio and the components of the coagulation bath, a continuous super-light hollow carbon nanotube composite fiber with different mechanical and electrical properties can be prepared. In the present application, the density of the prepared super-light hollow carbon nanotube composite fiber is not more than 0.87 g / cm 3 , preferably not more than 0.85 g / cm 3 , and the fiber has the characteristics of super-lightness, while the density of the solid carbon nanotube / polymer composite fiber reported in the prior art is generally 1.3-1.4 g / cm 3 .

[0037] The application is just based on the obtained fusiform carbon nanotube-PBIA polymer supramolecule to prepare the ultra-light hollow carbon nanotube composite fiber by using a wet spinning process, and it is found that the ultra-light hollow carbon nanotube composite fiber can be prepared by taking the fusiform carbon nanotube-PBIA polymer supramolecule as raw material. The unique fusiform structure has higher surface area and unique morphology, which can effectively promote the directional arrangement of the carbon nanotube in the composite fiber, and the morphology of the fusiform supramolecular structure makes it easier to support each other in the fiber forming process, which is beneficial to form a hollow structure, thereby reducing the density of the composite fiber, making the composite fiber material more lightweight, and obtaining the ultra-light hollow carbon nanotube composite fiber. The density of the ultra-light hollow carbon nanotube composite fiber prepared by the application is greatly reduced, the strength and toughness are obviously improved, and the electrical conductivity is controllable, which is beneficial to improve the electromagnetic shielding performance of the composite fiber. It is found that the ultra-light hollow carbon nanotube composite fiber is beneficial to adjust the dielectric loss and electromagnetic shielding efficiency of the composite fiber compared with the solid carbon nanotube composite fiber. The carbon nanotube itself has extremely high electrical conductivity, and PBIA is not conductive. By controlling the content of the two, the fusiform supramolecule with different dielectric properties can be prepared, and then the hollow composite fiber with adjustable dielectric performance is obtained. The electromagnetic shielding efficiency mainly depends on the electrical conductivity and the ability to reflect and absorb electromagnetic waves. The hollow carbon nanotube composite fiber can more effectively absorb and reflect electromagnetic waves due to its large specific surface area. Its porous and hollow structure also helps to reflect and scatter electromagnetic waves multiple times, so that they are gradually absorbed by the material, further improving the shielding efficiency. Compared with the solid carbon nanotube composite fiber, the inner and outer interfaces of the hollow carbon nanotube composite fiber can realize multiple reflections, effectively reducing the transmission of electromagnetic waves and improving the electromagnetic shielding efficiency.

[0038] The application provides a preparation method of an electromagnetic shielding material based on a fusiform supramolecular structure in a second aspect.

[0039] (1) The carbon nanotube is subjected to a purification treatment to obtain a purified carbon nanotube;

[0040] (2) The purified carbon nanotube is uniformly dispersed by using N,N-dimethylacetamide and lithium chloride to obtain a carbon nanotube dispersion system containing 2-3.5% of lithium chloride by mass percentage, then a polymer PBIA solution with a concentration of 0.1-4wt% is added to the carbon nanotube dispersion system and uniformly dispersed to obtain a carbon nanotube-PBIA dispersion liquid;

[0041] (3) N,N-dimethylacetamide is added to the carbon nanotube-PBIA dispersion liquid to reduce the mass percentage of lithium chloride contained in the carbon nanotube-PBIA dispersion liquid to 0.1-1%, and the carbon nanotube-PBIA dispersion liquid is subjected to shearing treatment at a speed of 5000-10000 rpm for 10-30 min, and then subjected to centrifugal separation and freeze-drying to obtain a carbon nanotube-PBIA polymer supramolecule;

[0042] (4) The carbon nanotube-PBIA polymer supramolecule is prepared into a carbon nanotube-PBIA polymer supramolecule solution by using a strong acid, and then a film is formed by layer-by-layer doctor blading to obtain an electromagnetic shielding material based on a fusiform supramolecular structure; in the application, the carbon nanotube-PBIA polymer supramolecule solution can be layer-by-layer doctor bladed to obtain a composite material with periodicity and a multi-level structure.

[0043] The fusiform carbon nanotube-PBIA polymer supramolecule is formed by doctor blading, and an electromagnetic shielding film (electromagnetic shielding material) with periodicity and a multi-level structure is prepared based on the obtained fusiform carbon nanotube-PBIA polymer supramolecule; the electromagnetic shielding material has high shielding efficiency, high strength and light weight, and fully meets the requirements of strength, lightness and thinness of the material at the present stage; the application finds that the electromagnetic shielding material prepared based on the fusiform carbon nanotube-PBIA polymer supramolecule can significantly improve the electromagnetic shielding efficiency of the electromagnetic shielding material compared with the electromagnetic shielding material prepared by using a common structure of carbon nanotube-PBIA polymer supramolecule; the possible reason is that the fusiform carbon nanotube-PBIA polymer supramolecule is arranged more orderly in the material, and a better conductive channel can be formed, thereby improving the conductivity and electromagnetic shielding efficiency of the electromagnetic shielding material; and the unique shape of the fusiform carbon nanotube-PBIA polymer supramolecule helps to more efficiently absorb and reflect electromagnetic waves; the fusiform structure can increase the contact area with electromagnetic waves, and the shape is easy to form multiple scattering, thereby increasing the absorption effect on electromagnetic waves and improving the overall performance of the electromagnetic shielding material.

[0044] In the present application, by layer-by-layer doctor-blading carbon nanotube-PBIA polymer supramolecular solution with different carbon nanotube contents, by controlling the carbon nanotube content in each layer of carbon nanotube-PBIA polymer supramolecular, the conductive property of each layer can be changed, the interlayer conductive gradient is formed, the incident surface conductivity is low, the impedance matching with the environment is improved, the reflection is reduced, the incident electromagnetic wave is more into the material interior, the electromagnetic wave is dissipated in the form of internal dielectric loss and interface polarization loss, the secondary pollution to the environment is reduced, and the electromagnetic wave absorption efficiency is improved; the conductivity gradient makes the electromagnetic wave attenuate layer by layer in the material interior, thereby effectively dispersing the electromagnetic wave energy, the conductivity of the inner layer of the material is gradually increased, the electromagnetic wave absorption in the interior can be enhanced, the electromagnetic wave energy is converted into heat energy dissipation by using dielectric loss and interface polarization loss, compared with the electromagnetic shielding material with uniform conductivity, the electromagnetic shielding material with gradient conductivity more fully utilizes the absorption and dissipation properties of the electromagnetic wave in the whole thickness, and the electromagnetic shielding efficiency is improved; and the design of the conductivity gradient can form different polarization regions in the multi-layer structure, increase the interface polarization loss in the material interior, the interlayer interface further absorbs electromagnetic wave energy by producing different polarization responses, which is particularly effective in high frequency applications, and this property makes the electromagnetic shielding material with gradient conductivity have better shielding performance in a wide frequency range, and is suitable for absorption of electromagnetic wave of various frequencies.

[0045] According to some preferred embodiments, step (3) obtains shuttle-shaped carbon nanotube-PBIA polymer supramolecular.

[0046] According to some preferred embodiments, in step (1): the carbon nanotube is single-walled carbon nanotube and / or multi-walled carbon nanotube; and / or the purification treatment is: mixing the carbon nanotube with hydrogen peroxide and stirring for 1-2 h, then mixing with hydrochloric acid and stirring for 2-4 h, and then washing and freeze-drying to obtain the purified carbon nanotube; preferably, when the purification treatment is performed, the use amount ratio of the carbon nanotube, the hydrogen peroxide and the hydrochloric acid is (5-10) g:(300-500) mL:(400-600) mL; preferably, the concentration of the hydrogen peroxide is 20-40%; in the present application, the concentration of the hydrogen peroxide refers to the mass percentage content of hydrogen peroxide in the hydrogen peroxide; preferably, the concentration of the hydrochloric acid is 36-38 wt%, that is, the mass percentage content of hydrogen chloride in the hydrochloric acid is 36-38%.

[0047] According to some specific embodiments, step (1) is: mixing 5-10 g of carbon nanotubes with 300-500 mL of hydrogen peroxide and stirring at room temperature for 1-2 h to weakly oxidize the carbon nanotubes to remove amorphous carbon attached to the catalyst and the surface of the carbon nanotubes and expose the metal catalyst; then mixing the weakly oxidized carbon nanotubes with 500 mL of hydrochloric acid at room temperature and stirring for 2-4 h to remove the metal catalyst; finally, washing the oxidized and acid-washed carbon nanotubes with deionized water by centrifugation-ultrasonic filtration until the filtrate is neutral, and then freeze-drying the carbon nanotubes to obtain purified carbon nanotube powder; in the present application, the room temperature refers to a room temperature of 15-35 °C.

[0048] According to some preferred embodiments, in step (2): the polymer PBIA solution has N,N-dimethylacetamide and lithium chloride as solvents, and the mass percentage of lithium chloride contained in the polymer PBIA solution is 2-3.5%; the mass ratio of the purified carbon nanotubes to the polymer PBIA contained in the polymer PBIA solution is (0.2-2): 1 (for example, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1), preferably (0.5-2):1; and / or when the purified carbon nanotubes are uniformly dispersed in N,N-dimethylacetamide and lithium chloride, the ratio of the total amount of N,N-dimethylacetamide and lithium chloride to the amount of the purified carbon nanotubes is (250-500) mL:(250-500) mg.

[0049] According to some specific embodiments, step (2) is: using the π-π interaction between PBIA molecules and carbon nanotubes to make PBIA polymers adsorbed on the surface of carbon nanotubes, thereby assisting the dispersion of carbon nanotubes in the solvent system of the polymer; specifically, the purified carbon nanotubes are pretreated in a DMAC / LiCl system by an ultrasonic cell pulverizer for 30 min in an anhydrous environment to obtain a uniformly dispersed carbon nanotube dispersion system containing 2-3.5% of lithium chloride by mass percentage, then a polymer PBIA solution with a concentration of 0.1-4 wt% is added to the carbon nanotube dispersion system and uniformly dispersed by an ultrasonic cell pulverizer to obtain a carbon nanotube-PBIA dispersion; in the present application, the polymer PBIA solution with a concentration of 0.1-4 wt% refers to the mass percentage of polymer PBIA contained in the polymer PBIA solution being 0.1-4 wt%.

[0050] According to some preferred embodiments, in step (4): the strong acid is chlorosulfonic acid; and / or the mass percentage of the carbon nanotube-PBIA polymer supramolecular in the carbon nanotube-PBIA polymer supramolecular solution is 2-5% (for example 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%).

[0051] According to some preferred embodiments, in step (4): when wet spinning is performed, the extrusion rate is 100-300 μL / min (for example 100, 150, 200, 250 or 300 μL / min), the draw ratio is 1.2-1.5 (for example 1.2, 1.3, 1.4 or 1.5), and the coagulation bath is acetone.

[0052] According to some specific embodiments, in step (4) of preparing the ultra-lightweight hollow carbon nanotube composite fiber, carbon nanotube-PBIA polymer supramolecular powder is added to chlorosulfonic acid, and magnetic stirring is performed for 2 h to prepare a carbon nanotube-PBIA polymer supramolecular solution with a solid content (mass percentage) of 2%-5%, and then the carbon nanotube-PBIA polymer supramolecular solution is used as a spinning solution to prepare the ultra-lightweight hollow carbon nanotube composite fiber by wet spinning; when wet spinning is performed, a micro-flow pump is used to control the extrusion rate, acetone is used as the coagulation bath, the draw ratio is adjusted by adjusting the winding rate, and after washing, the ultra-lightweight hollow carbon nanotube composite fiber can be obtained by natural drying to a constant weight; in the present application, the stirring and / or magnetic stirring speed can be, for example, 400-800 r / min, unless otherwise specified.

[0053] According to some preferred embodiments, in step (4): when layer-by-layer blade coating is performed, the thickness of each layer of film is 0.4-0.6 μm, and preferably 0.5 μm; when blade coating is performed, each layer of film is sequentially coated on a coagulation bath of an N,N-dimethylacetamide / water system with a volume ratio of 8:2, an N,N-dimethylacetamide / water system with a volume ratio of 1:1 and pure water; in the present application, the N,N-dimethylacetamide / water system with a volume ratio of 8:2 refers to a system in which N,N-dimethylacetamide and water are mixed in a volume ratio of 8:2, and the N,N-dimethylacetamide / water system with a volume ratio of 1:1 refers to a system in which N,N-dimethylacetamide and water are mixed in a volume ratio of 1:1; when blade coating is performed, the carbon nanotube-PBIA polymer supramolecular solution is oriented in the same direction for each layer of film, and the blade coating angle of adjacent two layers of film differs by 15-90°, and specifically, in the present application, for example, the blade coating direction of each layer of film forms a clockwise angle of 15-90° with the blade coating direction of the previous layer of film; and / or the total number of layers of blade coating is 4-30 layers.

[0054] According to some specific embodiments, in the step (4) of preparing the electromagnetic shielding material based on the shuttle-shaped supramolecular structure, the thickness of each layer of film is 0.5 μm when the film is formed by doctor blading; after the film of each layer is formed by using an N,N-dimethylacetamide / water system with a volume ratio of 8:2, an N,N-dimethylacetamide / water system with a volume ratio of 1:1 and pure water as the coagulation bath, and then dried at room temperature to a constant weight, the electromagnetic shielding material based on the shuttle-shaped supramolecular structure is obtained by doctor blading the layers one by one; during the doctor blading process, the carbon nanotube-PBIA polymer supramolecule is oriented parallel to the doctor blading direction, and the doctor blading direction of each layer of film is at a certain angle, so that the carbon nanotube-PBIA polymer supramolecule is oriented at a certain angle in the film, the difference between the doctor blading angles of two adjacent layers of film is 15-90°, the total number of layers of the film is 4-30, and preferably 5-30.

[0055] The present application provides, in a third aspect, the ultra-light hollow carbon nanotube composite fiber prepared by the preparation method described in the first aspect of the present application; the ultra-light hollow carbon nanotube composite fiber prepared by the present application not only has a low density, but also has a significantly improved strength and toughness, and the electromagnetic shielding performance is also significantly improved.

[0056] The present application provides, in a fourth aspect, the electromagnetic shielding material based on the shuttle-shaped supramolecular structure prepared by the preparation method described in the second aspect of the present application; the multi-layer film material with controllable dielectric performance gradient can be prepared by the doctor blading method, and the prepared electromagnetic shielding material has outstanding electromagnetic shielding performance.

[0057] The present application will be further described below by way of examples, but the protection scope of the present application is not limited to these examples. The present application can have other various embodiments, and those skilled in the art can make various corresponding changes and modifications according to the present application without departing from the spirit and essence of the present application, and these corresponding changes and modifications shall all belong to the protection scope of the claims attached to the present application. In the following examples, the experimental methods used are conventional methods unless otherwise specified. In the following examples, the materials, reagents, etc. can be obtained from commercial channels or prepared by existing methods unless otherwise specified.

[0058] Example 1

[0059] ① 5 g of carbon nanotubes were mixed with 300 mL of hydrogen peroxide (the concentration of the hydrogen peroxide was 25 wt%) and stirred at room temperature for 1 h to obtain weakly oxidized carbon nanotubes; then, the weakly oxidized carbon nanotubes were mixed with 500 mL of hydrochloric acid (the concentration of the hydrochloric acid was 37 wt%) at room temperature and stirred for 4 h to obtain oxidized and acid-washed carbon nanotubes; finally, the oxidized and acid-washed carbon nanotubes were cleaned with deionized water by centrifugation and ultrasonic filtration until the filtrate was neutral, and then freeze-dried to obtain purified carbon nanotube powder.

[0060] ② 500 mg of the purified carbon nanotubes obtained in step ① were added to 500 mL of a system composed of DMAC and LiCl under anhydrous environment and pretreated by an ultrasonic cell pulverizer for 30 min to obtain a carbon nanotube dispersion system containing 2% of lithium chloride by mass percentage; then, 12.5 g of a 4 wt% polymer PBIA solution was added to the carbon nanotube dispersion system and dispersed by an ultrasonic cell pulverizer for 90 min to obtain a carbon nanotube-PBIA dispersion liquid; the polymer PBIA solution was prepared by using N,N-dimethylacetamide and lithium chloride as solvents, and the polymer PBIA solution contained 2% of lithium chloride by mass percentage.

[0061] ③ 5000 rpm, and then the lower precipitate was taken out by centrifugation and freeze-dried to obtain carbon nanotube-PBIA polymer supramolecular powder; the carbon nanotube-PBIA polymer supramolecular powder prepared in this embodiment had a shuttle-shaped supramolecular structure, as shown in FIG. 3. Figure 1

[0062] ④ 200 mg of the carbon nanotube-PBIA polymer supramolecular powder obtained in step ③ was added to chlorosulfonic acid and magnetically stirred for 2 h to obtain a carbon nanotube-PBIA polymer supramolecular solution with a mass percentage of 2%; then, wet spinning was performed by using the obtained carbon nanotube-PBIA polymer supramolecular solution as a spinning solution to prepare ultra-light hollow carbon nanotube composite fibers, as shown in FIG. 4; when wet spinning was performed, a micro-flow pump was used to control the extrusion rate to be 100 μL / min, acetone was used as a coagulation bath, the draw ratio was adjusted to be 1.2 by adjusting the winding rate, and the ultra-light hollow carbon nanotube composite fibers were obtained after washing with water and naturally drying to a constant weight. Figure 2

[0063] The tensile strength of the ultra-light hollow carbon nanotube composite fibers prepared in this embodiment was 2.1 GPa, the elongation at break was 6.3%, and the density was 0.72 g / cm 3 ​​The conductivity of the prepared ultra-lightweight hollow carbon nanotube composite fiber was tested by four-probe method, and the conductivity was 6118.32 S / m.

[0064] Example 2

[0065] ① 5 g of carbon nanotubes were mixed with 400 mL of hydrogen peroxide (the concentration of the hydrogen peroxide was 25 wt%) and stirred at room temperature for 2 h to obtain weakly oxidized carbon nanotubes; then, the weakly oxidized carbon nanotubes were mixed with 500 mL of hydrochloric acid (the concentration of the hydrochloric acid was 37 wt%) at room temperature and stirred for 4 h to obtain carbon nanotubes after oxidation and acid washing; finally, the carbon nanotubes after oxidation and acid washing were washed with deionized water by centrifugation and ultrasonic filtration until the filtrate was neutral, and then freeze-drying was performed to obtain purified carbon nanotube powder.

[0066] ② 250 mg of the purified carbon nanotubes obtained in step ① were added into 250 mL of a system composed of DMAC and LiCl under anhydrous environment and pretreated by an ultrasonic cell pulverizer for 30 min to obtain a carbon nanotube dispersion system containing 3.5 wt% of lithium chloride; then, 50 g of a 1 wt% polymer PBIA solution was added into the carbon nanotube dispersion system and dispersed by an ultrasonic cell pulverizer for 90 min to obtain a carbon nanotube-PBIA dispersion liquid; the polymer PBIA solution used N,N-dimethylacetamide and lithium chloride as solvents, and the mass percentage of lithium chloride contained in the polymer PBIA solution was 3.5 wt%.

[0067] ③ 50 g of a 1 wt% polymer PBIA solution was added into the carbon nanotube-PBIA dispersion liquid obtained in step ② to reduce the mass percentage of LiCl contained in the carbon nanotube-PBIA dispersion liquid to 0.875%, and then the mixture was rapidly stirred by a homogenizer at a stirring rate of 8000 rpm for 30 min; finally, the lower precipitate was taken out by centrifugation and freeze-dried to obtain a carbon nanotube-PBIA polymer supramolecular powder; the carbon nanotube-PBIA polymer supramolecular powder prepared in this example had a shuttle-shaped supramolecular structure.

[0068] ④ 200 mg of the carbon nanotube-PBIA polymer supramolecular powder obtained in step ③ was added into chlorosulfonic acid and magnetically stirred for 2 h to obtain a carbon nanotube-PBIA polymer supramolecular solution with a mass percentage of 2%; then, wet spinning was performed by using the obtained carbon nanotube-PBIA polymer supramolecular solution as a spinning solution to prepare an ultra-lightweight hollow carbon nanotube composite fiber; when the wet spinning was performed, a micro-flow pump was used to control the extrusion rate to be 100 μL / min, acetone was used as a coagulation bath, the draw ratio was adjusted to be 1.3 by adjusting the winding rate, and the ultra-lightweight hollow carbon nanotube composite fiber was obtained after washing with water and naturally drying to a constant weight.

[0069] The tensile strength of the prepared ultra-lightweight hollow carbon nanotube composite fiber is 2.8 GPa, the elongation at break is 7.2%, and the density is 0.81 g / cm 3 The conductivity of the prepared ultra-lightweight hollow carbon nanotube composite fiber is tested by the four-probe method, and the conductivity is measured to be 3390.60 S / m.

[0070] Example 3

[0071] ① 5 g of carbon nanotubes were mixed with 300 mL of hydrogen peroxide (the concentration of the hydrogen peroxide was 25 wt%) and stirred at room temperature for 1 h to obtain weakly oxidized carbon nanotubes; then, the weakly oxidized carbon nanotubes were mixed with 500 mL of hydrochloric acid (the concentration of the hydrochloric acid was 37 wt%) at room temperature and stirred for 4 h to obtain oxidized and acid-washed carbon nanotubes; finally, the oxidized and acid-washed carbon nanotubes were washed with deionized water by centrifugation and ultrasonic filtration until the filtrate was neutral, and then freeze-dried to obtain purified carbon nanotube powder.

[0072] ② 500 mg of the purified carbon nanotubes obtained in step ① were added to 500 mL of a system composed of DMAC and LiCl under anhydrous environment and pretreated by an ultrasonic cell pulverizer for 30 min to obtain a uniformly dispersed carbon nanotube dispersion system containing 2 wt% of lithium chloride; then, 12.5 g of a 2 wt% polymer PBIA solution was added to the carbon nanotube dispersion system and dispersed by an ultrasonic cell pulverizer for 90 min to obtain a carbon nanotube-PBIA dispersion; the polymer PBIA solution used N,N-dimethylacetamide and lithium chloride as solvents, and the polymer PBIA solution contained 2 wt% of lithium chloride.

[0073] ③ 500 mg of the purified carbon nanotubes obtained in step ① were added to 500 mL of a system composed of DMAC and LiCl under anhydrous environment and pretreated by an ultrasonic cell pulverizer for 30 min to obtain a uniformly dispersed carbon nanotube dispersion system containing 2 wt% of lithium chloride; then, 12.5 g of a 2 wt% polymer PBIA solution was added to the carbon nanotube dispersion system and dispersed by an ultrasonic cell pulverizer for 90 min to obtain a carbon nanotube-PBIA dispersion; the polymer PBIA solution used N,N-dimethylacetamide and lithium chloride as solvents, and the polymer PBIA solution contained 2 wt% of lithium chloride.

[0074] ④ Add 200 mg of the carbon nanotube-PBIA polymer supramolecular powder obtained in step ③ to chlorosulfonic acid and stir magnetically for 2 hours to obtain a carbon nanotube-PBIA polymer supramolecular solution with a mass percentage of 3%. Then, use the obtained carbon nanotube-PBIA polymer supramolecular solution as the spinning solution for wet spinning to obtain ultralight hollow carbon nanotube composite fibers. During wet spinning, a microfluidic pump is used to control the extrusion rate at 100 μL / min, acetone is used as the coagulation bath, and the draw ratio is adjusted to 1.2 by controlling the winding rate. After washing with water, the fibers are naturally dried to a constant weight to obtain the ultralight hollow carbon nanotube composite fibers.

[0075] The ultralight hollow carbon nanotube composite fiber prepared in this embodiment has a tensile strength of 2.23 GPa, an elongation at break of 7.8%, and a density of 0.68 g / cm³. 3 In this embodiment, the electrical conductivity of the prepared ultralight hollow carbon nanotube composite fiber was also tested using the four-probe method, and the measured electrical conductivity was 12850.45 S / m.

[0076] In this embodiment, the ultralight hollow carbon nanotube composite fiber prepared in this embodiment is pulverized and cut into microfibers with a length of 20-100 micrometers. Then, 200 mg of microfibers are mixed with 100 mL of a 1 wt% polymer PBIA solution (the polymer PBIA solution uses N,N-dimethylacetamide and lithium chloride as solvents, and the polymer PBIA solution contains 2% lithium chloride by mass) and thoroughly mixed. The mixture is then coated onto a glass slide and formed by sequentially passing it through an N,N-dimethylacetamide / water system with a volume ratio of 8:2, an N,N-dimethylacetamide / water system with a volume ratio of 1:1, and a pure water system as coagulation baths. After being dried at room temperature to constant weight, a membrane material is obtained. The tensile strength of the membrane material is measured to be 680 MPa and the conductivity is 2850 S / m.

[0077] Example 4

[0078] Example 4 is basically the same as Example 1, except that:

[0079] ② 200 mg of the purified carbon nanotubes obtained in step ① were added to 500 mL of a system composed of DMAC and LiCl under anhydrous conditions and pretreated for 30 min using an ultrasonic cell pulverizer to obtain a uniformly dispersed carbon nanotube dispersion containing 2% lithium chloride by mass. Then, 25 g of a 4 wt% polymer PBIA solution was added to the carbon nanotube dispersion and dispersed for 90 min using an ultrasonic cell pulverizer to obtain a carbon nanotube-PBIA dispersion. The polymer PBIA solution used N,N-dimethylacetamide and lithium chloride as solvents, and the polymer PBIA solution contained 2% lithium chloride by mass.

[0080] The tensile strength of the prepared ultra-lightweight hollow carbon nanotube composite fiber is 3.2 GPa, the elongation at break is 7.5%, and the density is 0.85 g / cm 3 The conductivity of the prepared ultra-lightweight hollow carbon nanotube composite fiber is tested by the four-probe method, and the conductivity is 913.32 S / m.

[0081] Example 5

[0082] Example 5 is basically the same as Example 1, except that:

[0083] ② 100 mg of the purified carbon nanotubes obtained in step ① are added to 500 mL of a system composed of DMAC and LiCl under anhydrous environment and pretreated by ultrasonic cell pulverizer for 30 min to obtain a uniformly dispersed carbon nanotube dispersion system containing 2% lithium chloride by mass percentage, then 25 g of a 4 wt% polymer PBIA solution is added to the carbon nanotube dispersion system and dispersed by ultrasonic cell pulverizer for 90 min to obtain a carbon nanotube-PBIA dispersion; the polymer PBIA solution uses N,N-dimethylacetamide and lithium chloride as the solvent, and the mass percentage of lithium chloride contained in the polymer PBIA solution is 2%.

[0084] The tensile strength of the prepared carbon nanotube composite fiber is 3.3 GPa, the elongation at break is 7.6%, and the density is 0.87 g / cm 3 The conductivity of the prepared carbon nanotube composite fiber is tested by the four-probe method, and the carbon nanotube composite fiber is basically non-conductive.

[0085] Example 6

[0086] ① 5 g of carbon nanotubes are mixed with 300 mL of hydrogen peroxide (the concentration of the hydrogen peroxide is 25 wt%) and stirred at room temperature for 1 h to obtain weakly oxidized carbon nanotubes; then, the weakly oxidized carbon nanotubes are mixed with 500 mL of hydrochloric acid (the concentration of the hydrochloric acid is 37 wt%) at room temperature and stirred for 4 h to obtain oxidized and acid-washed carbon nanotubes; finally, the oxidized and acid-washed carbon nanotubes are cleaned with deionized water by centrifugation and ultrasonic filtration until the filtrate is neutral, and then freeze-dried to obtain purified carbon nanotube powder.

[0087] ii) 500 mg of the purified carbon nanotubes obtained in step i) were added to 500 mL of a system comprising DMAC and LiCl under anhydrous conditions and pre-treated for 30 min using an ultrasonic cell disruptor to obtain a carbon nanotube dispersion system containing 2% of LiCl by mass percentage, and then 12.5 g of a 4 wt% polymer PBIA solution was added to the carbon nanotube dispersion system and dispersed for 90 min using an ultrasonic cell disruptor to obtain a carbon nanotube-PBIA dispersion; the polymer PBIA solution used N,N-dimethylacetamide and lithium chloride as solvents, and the polymer PBIA solution contained 2% of lithium chloride by mass percentage.

[0088] iii) 500 mg of the purified carbon nanotubes obtained in step i) were added to 500 mL of a system comprising DMAC and LiCl under anhydrous conditions and pre-treated for 30 min using an ultrasonic cell disruptor to obtain a carbon nanotube dispersion system containing 2% of LiCl by mass percentage, and then 12.5 g of a 4 wt% polymer PBIA solution was added to the carbon nanotube dispersion system and dispersed for 90 min using an ultrasonic cell disruptor to obtain a carbon nanotube-PBIA dispersion; the polymer PBIA solution used N,N-dimethylacetamide and lithium chloride as solvents, and the polymer PBIA solution contained 2% of lithium chloride by mass percentage.

[0089] iv) 200 mg of the carbon nanotube-PBIA polymer supramolecular powder obtained in step iii) was added to chlorosulfonic acid and magnetically stirred for 2 h to obtain a carbon nanotube-PBIA polymer supramolecular solution with a mass percentage of 2%; a carbon nanotube-PBIA polymer supramolecular solution was used as a coating material for layer-by-layer blade coating to form a film, and the thickness of each layer of the film was 0.5 μm; during the blade coating, each layer of the film passed through a system comprising N,N-dimethylacetamide / water (8:2 by volume ratio), a system comprising N,N-dimethylacetamide / water (1:1 by volume ratio), and pure water as a coagulation bath in sequence to form a film, and then dried at room temperature to a constant weight; a carbon nanotube-PBIA polymer supramolecular material with a periodic and multi-level structure based on a shuttle-shaped supramolecular structure was obtained by layer-by-layer blade coating; during the blade coating, the carbon nanotube-PBIA polymer supramolecular material was oriented parallel to the blade coating direction, and the blade coating direction of each layer of the film was at a clockwise 45° angle with respect to the blade coating direction of the previous layer of the film, and a total of 10 layers were coated.

[0090] The mechanical properties and electrical conductivity of the carbon nanotube-PBIA polymer supramolecular material with a periodic and multi-level structure based on a shuttle-shaped supramolecular structure obtained in this example were tested, and the tensile strength of the carbon nanotube-PBIA polymer supramolecular material with a periodic and multi-level structure based on a shuttle-shaped supramolecular structure was measured to be 530 MPa, and the electrical conductivity was 3390 S / m.

[0091] Example 7

[0092] ① 5 g of carbon nanotubes were mixed with 400 mL of hydrogen peroxide (the concentration of the hydrogen peroxide was 25 wt%) and stirred at room temperature for 2 h to obtain weakly oxidized carbon nanotubes; then, the weakly oxidized carbon nanotubes were mixed with 500 mL of hydrochloric acid (the concentration of the hydrochloric acid was 37 wt%) at room temperature and stirred for 4 h to obtain oxidized and acid-washed carbon nanotubes; finally, the oxidized and acid-washed carbon nanotubes were cleaned with deionized water by centrifugation and ultrasonic filtration until the filtrate was neutral, and then freeze-dried to obtain purified carbon nanotube powder.

[0093] ② 250 mg of the purified carbon nanotubes obtained in step ① were added to 500 mL of a system composed of DMAC and LiCl under anhydrous environment and pretreated by an ultrasonic cell pulverizer for 30 min to obtain a carbon nanotube dispersion system containing 3.5 wt% of lithium chloride; then, 50 g of a 1 wt% polymer PBIA solution was added to the carbon nanotube dispersion system and dispersed by an ultrasonic cell pulverizer for 90 min to obtain a carbon nanotube-PBIA dispersion liquid; the polymer PBIA solution was prepared by using N,N-dimethylacetamide and lithium chloride as solvents, and the polymer PBIA solution contained 3.5 wt% of lithium chloride.

[0094] ③ 50 g of a 1 wt% polymer PBIA solution was added to the carbon nanotube-PBIA dispersion liquid obtained in step ② to reduce the content of LiCl in the carbon nanotube-PBIA dispersion liquid to 0.875 wt%, and then the mixture was rapidly stirred by a homogenizer at a stirring rate of 8000 rpm for 30 min; finally, the lower precipitate was obtained by centrifugation and freeze-dried to obtain a carbon nanotube-PBIA polymer supramolecular powder; the carbon nanotube-PBIA polymer supramolecular powder prepared in this embodiment had a shuttle-shaped supramolecular structure.

[0095] ④ 200 mg of the carbon nanotube-PBIA polymer supramolecular powder obtained in step ③ was added to chlorosulfonic acid and magnetically stirred for 2 h to obtain a carbon nanotube-PBIA polymer supramolecular solution with a mass percentage of 2%; the carbon nanotube-PBIA polymer supramolecular solution was used as a coating raw material to perform layer-by-layer blade coating to form a film; during the blade coating, the thickness of each layer of the film was 0.5 μm; during the blade coating, each layer of the film was sequentially passed through an N,N-dimethylacetamide / water system with a volume ratio of 8:2, an N,N-dimethylacetamide / water system with a volume ratio of 1:1, and a pure water system as a coagulation bath to form a film, and then dried at room temperature to a constant weight; a periodic and multi-level electromagnetic shielding material based on a shuttle-shaped supramolecular structure was obtained by layer-by-layer blade coating; during the blade coating, the carbon nanotube-PBIA polymer supramolecular was oriented parallel to the blade coating direction, and the blade coating direction of each layer of the film was at a clockwise angle of 30° with the blade coating direction of the previous layer of the film, and a total of 15 layers were blade coated.

[0096] The mechanical properties and electrical conductivity of the prepared electromagnetic shielding material based on the pike-shaped supermolecular structure were tested. The tensile strength of the prepared electromagnetic shielding material based on the pike-shaped supermolecular structure was 650 MPa, and the electrical conductivity was 2130 S / m.

[0097] Example 8

[0098] ①The same method as in steps ① to ③ in Example 3 was used to obtain carbon nanotube-PBIA polymer supermolecular powder (the mass ratio of purified carbon nanotubes to PBIA was 2:1); 200 mg of the obtained carbon nanotube-PBIA polymer supermolecular powder was added to chlorosulfonic acid, and magnetic stirring was performed for 2 h to obtain a carbon nanotube-PBIA polymer supermolecular solution with a mass percentage of 2%.

[0099] ②The same method as in steps ① to ③ in Example 1 was used to obtain carbon nanotube-PBIA polymer supermolecular powder (the mass ratio of purified carbon nanotubes to PBIA was 1:1); 200 mg of the obtained carbon nanotube-PBIA polymer supermolecular powder was added to chlorosulfonic acid, and magnetic stirring was performed for 2 h to obtain a carbon nanotube-PBIA polymer supermolecular solution with a mass percentage of 2%.

[0100] ③The same method as in steps ① to ③ in Example 2 was used to obtain carbon nanotube-PBIA polymer supermolecular powder (the mass ratio of purified carbon nanotubes to PBIA was 0.5:1); 200 mg of the obtained carbon nanotube-PBIA polymer supermolecular powder was added to chlorosulfonic acid, and magnetic stirring was performed for 2 h to obtain a carbon nanotube-PBIA polymer supermolecular solution with a mass percentage of 2%.

[0101] ④The same method as in steps ① to ③ in Example 4 was used to obtain carbon nanotube-PBIA polymer supermolecular powder (the mass ratio of purified carbon nanotubes to PBIA was 0.2:1); 200 mg of the obtained carbon nanotube-PBIA polymer supermolecular powder was added to chlorosulfonic acid, and magnetic stirring was performed for 2 h to obtain a carbon nanotube-PBIA polymer supermolecular solution with a mass percentage of 2%.

[0102] ⑤ The carbon nanotube-PBIA polymer supramolecular solution obtained in step 1, step 2, step 3 and step 4 in turn is used as the coating raw material for layer-by-layer coating film formation. During the coating film formation, the thickness of each layer is 0.5 μm. The carbon nanotube-PBIA polymer supramolecular solution with each ratio is coated in the same direction for 5 layers, and then the carbon nanotube-PBIA polymer supramolecular solution with the next ratio is coated. During the coating film formation, each layer of film is successively coated through the N,N-dimethylacetamide / water system with a volume ratio of 8:2, the N,N-dimethylacetamide / water system with a volume ratio of 1:1 and pure water system as the coagulation bath film formation, and then dried at room temperature to constant weight. The carbon nanotube-PBIA polymer supramolecular electromagnetic shielding material with periodic and multi-level structure based on the plectonemic supramolecular structure is obtained by layer-by-layer coating. During the coating process, the carbon nanotube-PBIA polymer supramolecular is oriented parallel to the coating direction. The coating direction of each layer of film is at a clockwise 72° angle with the coating direction of the previous layer of film. A total of 20 layers are coated.

[0103] The mechanical properties and electrical conductivity of the prepared electromagnetic shielding material based on the plectonemic supramolecular structure are tested. The tensile strength of the prepared electromagnetic shielding material based on the plectonemic supramolecular structure is 720 MPa, and the electrical conductivity distribution range is 9816.5-680.3 S / m.

[0104] Comparative Example 1

[0105] Comparative Example 1

[0106] The carbon nanotube / PBO composite fiber obtained in the comparative example is a solid structure, and the density is about 1.3 g / cm 3 .

[0107] Comparative Example 2

[0108] ① The same as step 1 of Example 1.

[0109] ② 500 mg of the purified carbon nanotubes obtained in step ① were added to 500 mL of a system formed by mixing DMAC and LiCl in anhydrous environment and pretreated for 30 min by ultrasonic cell pulverizer to obtain a carbon nanotube dispersion system containing 2% of LiCl by mass percentage, then 12.5 g of a 4 wt% polymer PBIA solution was added to the carbon nanotube dispersion system and dispersed for 90 min by ultrasonic cell pulverizer to obtain a carbon nanotube-PBIA dispersion liquid, the polymer PBIA solution was solvent by N,N-dimethylacetamide and lithium chloride, the polymer PBIA solution contained 2% of lithium chloride by mass percentage; then the carbon nanotube-PBIA dispersion liquid was centrifuged to take the lower precipitate and freeze-dried to obtain a carbon nanotube / PBIA polymer powder, the carbon nanotube / PBIA polymer powder obtained in the present comparative example does not have a shuttle-shaped structure.

[0110] ③ 200 mg of the carbon nanotube / PBIA polymer powder obtained in step ② was added to chlorosulfonic acid and magnetically stirred for 2 h to obtain a carbon nanotube / PBIA polymer solution with a mass percentage of 2%; then wet spinning was performed with the obtained carbon nanotube / PBIA polymer solution as the spinning solution to prepare a solid carbon nanotube composite fiber; when wet spinning was performed, a micro-flow pump was used to control the extrusion rate to be 100 μL / min, acetone was used as a coagulation bath, the draw ratio was adjusted to be 1.2 by adjusting the winding rate, and the solid carbon nanotube composite fiber was obtained after washing and naturally drying to constant weight.

[0111] The tensile strength of the solid carbon nanotube composite fiber prepared in the present comparative example was 1.2 GPa, the elongation at break was 3.5%, and the density was 1.35 g / cm 3 ; the conductivity of the solid carbon nanotube composite fiber prepared in the present comparative example was tested, and the conductivity was measured to be 1380.7 S / m.

[0112] Comparative Example 3

[0113] Comparative Example 3 is basically the same as Example 1, except that:

[0114] ③ LiCl was added to the carbon nanotube-PBIA dispersion liquid obtained in step ② to increase the mass percentage of LiCl in the carbon nanotube-PBIA dispersion liquid to 4% and rapidly stirred with a homogenizer for 30 min at a stirring rate of 5000 rpm, then centrifuged to take the lower precipitate and freeze-dried to obtain a carbon nanotube / PBIA polymer powder; the carbon nanotube / PBIA polymer powder prepared in the present comparative example does not have a shuttle-shaped structure.

[0115] ④ 200 mg of the carbon nanotube / PBIA polymer powder obtained in step ③ was added into chlorosulfonic acid and magnetically stirred for 2 h to obtain a carbon nanotube / PBIA polymer solution with a mass percentage of 2%; then wet spinning was performed using the obtained carbon nanotube / PBIA polymer solution as a spinning solution; when step ④ was performed, it was found that the carbon nanotube / PBIA polymer solution prepared in the present comparative example could not be continuously spun.

[0116] Comparative Example 4

[0117] Comparative Example 4 was basically the same as Example 1, except that:

[0118] ③ The carbon nanotube-PBIA dispersion liquid obtained in step ② was rapidly stirred with a homogenizer for 30 min at a stirring rate of 5000 rpm, and then the lower precipitate was taken out by centrifugation and freeze-dried to obtain a carbon nanotube / PBIA polymer powder; the carbon nanotube / PBIA polymer powder prepared in the present comparative example did not have a shuttle-shaped structure.

[0119] ④ 200 mg of the carbon nanotube / PBIA polymer powder obtained in step ③ was added into chlorosulfonic acid and magnetically stirred for 2 h to obtain a carbon nanotube / PBIA polymer solution with a mass percentage of 2%; then wet spinning was performed using the obtained carbon nanotube / PBIA polymer solution as a spinning solution; when step ④ was performed, it was found that the carbon nanotube / PBIA polymer solution prepared in the present comparative example could not be continuously spun.

[0120] The solid carbon nanotube composite fiber prepared in the present comparative example was tested, and the tensile strength thereof was 1.3 GPa, the elongation at break thereof was 3.6%, and the density thereof was 1.34 g / cm 3 ; the conductivity of the solid carbon nanotube composite fiber prepared in the present comparative example was also tested, and the conductivity thereof was 1542.8 S / m.

[0121] Comparative Example 5

[0122] Comparative Example 5 was basically the same as Example 1, except that:

[0123] ③ LiCl in the carbon nanotube-PBIA dispersion liquid obtained in step ② was reduced to a mass percentage of 1% by adding DMAC into the carbon nanotube-PBIA dispersion liquid, and then the lower precipitate was taken out by centrifugation and freeze-dried to obtain a carbon nanotube / PBIA polymer powder; the carbon nanotube / PBIA polymer powder prepared in the present comparative example did not have a shuttle-shaped structure, but formed uneven aggregates in size and shape, which affected the subsequent wet spinning.

[0124] IV. 200 mg of the carbon nanotube / PBIA polymer powder obtained in step III was added into chlorosulfonic acid and stirred magnetically for 2 h to obtain a carbon nanotube / PBIA polymer solution with a mass percentage of 2%; then wet spinning was performed using the obtained carbon nanotube / PBIA polymer solution as a spinning solution to prepare a solid carbon nanotube composite fiber; during the wet spinning, a micro-flow pump was used to control the extrusion rate to be 100 μL / min, acetone was used as a coagulation bath, the draw ratio was adjusted to be 1.2 by adjusting the winding rate, and the solid carbon nanotube composite fiber was obtained after washing with water and naturally dried to a constant weight.

[0125] The tensile strength of the solid carbon nanotube composite fiber prepared in the present comparative example was 0.92 GPa, the elongation at break was 2%, and the density was 1.30 g / cm 3 The conductivity of the solid carbon nanotube composite fiber prepared in the present comparative example was tested, and the conductivity was measured to be 960.6 S / m.

[0126] Comparative Example 6

[0127] I. The same as step I in Example 3.

[0128] II. 500 mg of the purified carbon nanotubes obtained in step I were added into 500 mL of a system prepared by mixing DMAC and LiCl under anhydrous environment and pretreated by an ultrasonic cell pulverizer for 30 min to obtain a carbon nanotube dispersion system with a mass percentage of 2% of lithium chloride, then 12.5 g of a polymer PBIA solution with a concentration of 4 wt% was added into the carbon nanotube dispersion system and dispersed by an ultrasonic cell pulverizer for 90 min to obtain a carbon nanotube-PBIA dispersion liquid, the polymer PBIA solution used N,N-dimethylacetamide and lithium chloride as a solvent, and the mass percentage of lithium chloride in the polymer PBIA solution was 2%; then the carbon nanotube-PBIA dispersion liquid was subjected to centrifugal separation, and the lower precipitate was taken out and freeze-dried to obtain a carbon nanotube / PBIA polymer powder, and the carbon nanotube / PBIA polymer powder obtained in the present comparative example did not have a shuttle-shaped structure.

[0129] ③ Add 200 mg of the carbon nanotube / PBIA polymer powder obtained in step ② to chlorosulfonic acid and stir magnetically for 2 h to obtain a carbon nanotube / PBIA polymer solution with a mass percentage of 2%. Use the carbon nanotube / PBIA polymer solution as the coating material to form a film layer by layer. The thickness of each film layer is 0.5 μm. During the film formation, each film layer is successively passed through an N,N-dimethylacetamide / water system with a volume ratio of 8:2, an N,N-dimethylacetamide / water system with a volume ratio of 1:1, and a pure water system as coagulation baths. After film formation, it is dried at room temperature to constant weight. Through layer-by-layer coating, an electromagnetic shielding material with a periodic and multi-level structure is obtained. During the coating process, the carbon nanotube / PBIA polymer is oriented parallel to the coating direction. The coating direction of each film layer is at a 45° clockwise angle to the coating direction of the previous film layer. A total of 10 layers are coated.

[0130] The mechanical properties and conductivity of the prepared electromagnetic shielding material were tested in this comparative example. The tensile strength of the prepared electromagnetic shielding material was measured to be 350 MPa and the conductivity was 1860.8 S / m.

[0131] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an ultralight hollow carbon nanotube composite fiber, characterized by, The method comprises the following steps: (1) purifying the carbon nanotubes to obtain purified carbon nanotubes; (2) uniformly dispersing the purified carbon nanotubes with N,N-dimethylacetamide and lithium chloride to obtain a carbon nanotube dispersion system containing 2-3.5% lithium chloride by mass percentage, then adding a polymer PBIA solution with a concentration of 0.1-4wt% into the carbon nanotube dispersion system and uniformly dispersing to obtain a carbon nanotube-PBIA dispersion liquid; (3) adding N,N-dimethylacetamide into the carbon nanotube-PBIA dispersion liquid to reduce the mass percentage of lithium chloride contained in the carbon nanotube-PBIA dispersion liquid to 0.1-1%, and shearing at a speed of 5000-10000 rpm for 10-30 min, then centrifuging and freeze-drying to obtain carbon nanotube-PBIA polymer supramolecules; (4) preparing the carbon nanotube-PBIA polymer supramolecules into a carbon nanotube-PBIA polymer supramolecule solution with a strong acid, and then performing layer-by-layer blade coating to form a film to obtain an electromagnetic shielding material based on the shuttle-shaped supramolecular structure.

2. A method for preparing an electromagnetic shielding material based on a shuttle-shaped supramolecular structure, characterized by, The method comprises the following steps: (1) purifying the carbon nanotubes to obtain purified carbon nanotubes; (2) uniformly dispersing the purified carbon nanotubes with N,N-dimethylacetamide and lithium chloride to obtain a carbon nanotube dispersion system containing 2-3.5% lithium chloride by mass percentage, then adding a polymer PBIA solution with a concentration of 0.1-4wt% into the carbon nanotube dispersion system and uniformly dispersing to obtain a carbon nanotube-PBIA dispersion liquid; (3) adding N,N-dimethylacetamide into the carbon nanotube-PBIA dispersion liquid to reduce the mass percentage of lithium chloride contained in the carbon nanotube-PBIA dispersion liquid to 0.1-1%, and shearing at a speed of 5000-10000 rpm for 10-30 min, then centrifuging and freeze-drying to obtain carbon nanotube-PBIA polymer supramolecules; (4) preparing the carbon nanotube-PBIA polymer supramolecules into a carbon nanotube-PBIA polymer supramolecule solution with a strong acid, and then performing layer-by-layer blade coating to form a film to obtain an electromagnetic shielding material based on the shuttle-shaped supramolecular structure.

3. The preparation method according to claim 1 or 2, characterized in that: the step (3) obtains shuttle-shaped carbon nanotube-PBIA polymer supramolecules.

4. The production method according to claim 1 or 2, characterized by, In the step (1): the carbon nanotubes are single-walled carbon nanotubes and / or multi-walled carbon nanotubes; and / or the purification treatment is that the carbon nanotubes are mixed with hydrogen peroxide and stirred for 1-2 h, then mixed with hydrochloric acid and stirred for 2-4 h, and then washed and freeze-dried to obtain the purified carbon nanotubes.

5. The preparation method according to claim 4, characterized in that: when the purification treatment is performed, the use amount ratio of the carbon nanotubes, the hydrogen peroxide and the hydrochloric acid is (5-10) g:(300-500) mL:(400-600) mL.

6. The preparation method according to claim 4, characterized in that: the concentration of the hydrogen peroxide is 20-40%.

7. The preparation method according to claim 4, characterized in that: The concentration of the hydrochloric acid is 36-38 wt%.

8. The production method according to claim 1 or 2, characterized by, In step (2): The polymer PBIA solution is dissolved in N,N-dimethylacetamide and lithium chloride, and the mass percentage of lithium chloride in the polymer PBIA solution is 2-3.5%; The mass ratio of the purified carbon nanotubes to the polymer PBIA contained in the polymer PBIA solution is (0.2-2):1; and / or When the purified carbon nanotubes are uniformly dispersed in N,N-dimethylacetamide and lithium chloride, the ratio of the total amount of N,N-dimethylacetamide and lithium chloride to the amount of purified carbon nanotubes is (250-500) mL:(250-500) mg.

9. The production method according to claim 1 or 2, characterized by, In step (4): The strong acid is chlorosulfonic acid; and / or The mass percentage of carbon nanotube-PBIA polymer supramolecules in the carbon nanotube-PBIA polymer supramolecular solution is 2-5%.

10. The method of claim 1, wherein, In step (4): When wet spinning is performed, the extrusion rate is 100-300 μL / min, the draw ratio is 1.2-1.5, and the coagulation bath is acetone.

11. The method of claim 2, wherein, In step (4): When the film is formed by layer-by-layer blade coating, the thickness of each layer of film is 0.4-0.6 μm; When the film is formed by blade coating, each layer of film is sequentially formed by passing through an N,N-dimethylacetamide / water system with a volume ratio of 8:2, an N,N-dimethylacetamide / water system with a volume ratio of 1:1, and a pure water system as a coagulation bath; When the film is formed by blade coating, the carbon nanotube-PBIA polymer supramolecular solution is oriented in the same direction for each layer of film, and the blade coating angle of adjacent two layers of film differs by 15-90°; and / or The total number of layers of the film formed by blade coating is 4-30 layers.

12. The preparation method of claim 11, wherein: When the film is formed by layer-by-layer blade coating, the thickness of each layer of film is 0.5 μm.

13. The ultra-light hollow carbon nanotube composite fiber prepared by the preparation method of any one of claims 1 or 3-10.

14. The electromagnetic shielding material based on a fusiform supramolecular structure prepared by the preparation method of any one of claim 2 or 3-9 or any one of claims 11-12.

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