A carbon nanotube / polyaniline / aramid composite microwave absorbing fiber, its preparation method and application

Abstract

This invention provides a carbon nanotube / polyaniline / aramid composite microwave absorbing fiber, its preparation method, and its application, comprising the following steps: A) dispersing polyvinylpyrrolidone, carbon nanotubes, and silane-modified fumed silica in water to obtain a carbon nanotube dispersion; B) mixing the carbon nanotube dispersion, sodium dodecylbenzenesulfonate, and aniline to obtain a carbon nanotube / aniline dispersion; C) adding an initiator to the carbon nanotube / aniline dispersion and polymerizing to obtain carbon nanotube / polyaniline; D) mixing carbon nanotube / polyaniline, an alkali, and aramid in a solvent to obtain a spinning solution and spinning to obtain the carbon nanotube / polyaniline / aramid composite microwave absorbing fiber. This invention achieves integrated molding by chemically bonding polyaniline and carbon nanotubes through in-situ polymerization, followed by blending and spinning with an aramid matrix. Modification of fumed silica with a silane coupling agent significantly enhances the interfacial bonding force between fumed silica and carbon nanotubes / polyaniline.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, and particularly relates to a carbon nanotube / polyaniline / aramid composite microwave absorbing fiber, its preparation method and application. Background Technology

[0002] With the rapid development of modern communication technology, the problem of electromagnetic radiation is becoming increasingly serious. It not only affects the normal operation of equipment, but long-term exposure to electromagnetic radiation can also damage the human nervous, reproductive and cardiovascular systems. Therefore, developing practical and portable electromagnetic protection products has become an inevitable choice for people to prevent and control the hazards of electromagnetic radiation.

[0003] Microwave-absorbing materials can convert electromagnetic waves into other forms of energy for dissipation, thereby achieving the effect of attenuating electromagnetic waves. When electromagnetic waves are incident on the surface of a microwave-absorbing material, a small portion of the electromagnetic waves are reflected or transmitted, while most of the electromagnetic waves enter the interior of the material. After multiple reflections and scatterings, they are converted into heat energy or dissipated in other forms of energy. Therefore, the design of high-performance microwave-absorbing materials needs to consider the following two aspects: 1) good impedance matching characteristics, so that as many electromagnetic waves as possible enter the interior of the absorber; 2) strong attenuation and loss capabilities, so that as many electromagnetic waves as possible are attenuated from the absorber.

[0004] In recent years, with the rapid development of smart wearable devices, the goal of developing flexible microwave absorbing materials has been proposed. Fabric-type microwave absorbing materials have advantages such as wide applicability, customizable shapes and sizes to match the shape and size of the protected target; flexibility and ease of use, enabling rapid coverage; and multifunctionality, integrating breathability, waterproofing, heat insulation, and electromagnetic absorption. In recent years, modern textiles woven from conductive fibers / yarns have made significant progress in the field of electromagnetic radiation protection fabrics. However, due to the poor feel of traditional metal conductive fibers and the difficulty in color reprocessing of traditional carbon fibers, their poor wearability limits the development and application of traditional conductive fibers in modern textiles, especially smart textiles. Traditional fibers such as aramid, polyamide, and polyester have better wearability, but are insulating materials and lack microwave absorption capabilities. They are typically impregnated, coated, or have active materials grown in situ to impart conductivity and microwave absorption properties, but this results in the conductive layer easily peeling off, leading to poor stability and severely impacting usability. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing carbon nanotube / polyaniline / aramid composite microwave absorbing fibers. This preparation method is simple, the fibers are integrally formed, avoiding the problem of conductive layer detachment, and the fibers are lightweight, have good flexibility and microwave absorption properties.

[0006] This invention provides a method for preparing carbon nanotube / polyaniline / aramid composite microwave absorbing fibers, comprising the following steps:

[0007] A) Polyvinylpyrrolidone, carbon nanotubes, and silane-modified fumed silica were dispersed in water to obtain a carbon nanotube dispersion.

[0008] B) Mix carbon nanotube dispersion, sodium dodecylbenzenesulfonate and aniline to obtain carbon nanotube / aniline dispersion;

[0009] C) An initiator is added to the carbon nanotube / aniline dispersion to carry out polymerization and obtain carbon nanotube / polyaniline;

[0010] D) Carbon nanotubes / polyaniline, alkali and aramid are mixed in a solvent to obtain a spinning solution. The spinning solution is then spun to obtain carbon nanotube / polyaniline / aramid composite microwave absorbing fiber.

[0011] Preferably, the silane-modified fumed silica is prepared according to the following steps:

[0012] The silane coupling agent was mixed with water to obtain a silane coupling agent dispersion. Then, fumed silica was added and stirred to carry out the reaction. After solid-liquid separation, the mixture was dried to obtain a silane-modified silane coupling agent.

[0013] Preferably, the mass ratio of the silane coupling agent to fumed silica is 1:(10~20).

[0014] Preferably, in step A), the mass ratio of polyvinylpyrrolidone to carbon nanotubes is (3~5):1, and the mass ratio of silane-modified fumed silica to carbon nanotubes is 1:(40~60).

[0015] Preferably, in step B), the mass ratio of aniline to carbon nanotubes is 1:(1~8).

[0016] The molar ratio of aniline to sodium dodecylbenzenesulfonate is 1:(1~2.5).

[0017] Preferably, in step C), the initiator is ammonium persulfate; the mass ratio of ammonium persulfate to aniline is (2~3):1.

[0018] Preferably, in step C), the polymerization temperature is 20~30℃ and the polymerization time is 8~14 hours.

[0019] Preferably, in step D), aramid fibers, alkali, water and dimethyl sulfoxide are mixed to obtain an aramid fiber dispersion, and then carbon nanotubes / polyaniline are mixed with the aramid fiber dispersion to obtain a spinning solution;

[0020] The mass ratio of the aramid fiber to the alkali is 1:(1~2).

[0021] The mass ratio of the aramid fiber to the carbon nanotube / polyaniline is 80:(1~10).

[0022] This invention provides a carbon nanotube / polyaniline / aramid composite microwave absorbing fiber, which is prepared according to the preparation method described above.

[0023] The present invention provides a microwave absorbing fabric, comprising the carbon nanotube / polyaniline / aramid composite microwave absorbing fiber described above.

[0024] This invention provides a method for preparing carbon nanotube / polyaniline / aramid composite microwave absorbing fibers, comprising the following steps: A) dispersing polyvinylpyrrolidone, carbon nanotubes, and silane-modified fumed silica in water to obtain a carbon nanotube dispersion; B) mixing the carbon nanotube dispersion, sodium dodecylbenzenesulfonate, and aniline to obtain a carbon nanotube / aniline dispersion; C) adding an initiator to the carbon nanotube / aniline dispersion and polymerizing to obtain carbon nanotube / polyaniline; D) mixing carbon nanotube / polyaniline, an alkali, and aramid in a solvent to obtain a spinning solution, and spinning the spinning solution to obtain carbon nanotube / polyaniline / aramid composite microwave absorbing fibers. This invention uses carbon nanotubes as the core carrier, with an impedance matching layer formed by in-situ polymerized polyaniline on the surface, achieving in-situ polymerization to construct a "core-shell" structure. This invention chemically combines polyaniline and carbon nanotubes through in-situ polymerization, and then blends and spins them with an aramid matrix to achieve integrated molding. Furthermore, this invention modifies fumed silica with a silane coupling agent, allowing the surface hydroxyl groups to form chemical bonds with the silane coupling agent, significantly enhancing the interfacial bonding between fumed silica and carbon nanotubes / polyaniline. Moreover, fumed silica, acting as rigid nanoparticles, bears stress and improves the tensile strength of the composite fiber. The insulating properties of fumed silica neutralize the excessively high dielectric constant of carbon nanotubes, improving the impedance matching between the material and air. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figure 1 Here is a scanning electron microscope image of the carbon nanotube / polyaniline / aramid composite fiber prepared in Example 3;

[0027] Figure 2 The stress-strain curves of the carbon nanotube / polyaniline / aramid composite fibers prepared in Examples 1-3 are shown.

[0028] Figure 3 Two-dimensional reflection loss diagrams of carbon nanotube / polyaniline / aramid composite fibers prepared in Examples 1-3;

[0029] Figure 4 Thermogravimetric curve of the carbon nanotube / polyaniline / aramid composite fiber prepared in Example 3 of the present invention;

[0030] Figure 5 The stress-strain curves and two-dimensional reflection loss diagrams of the carbon nanotube / polyaniline / aramid composite fibers without modified fumed silica prepared in Comparative Example 1 are shown.

[0031] Figure 6 The stress-strain curves and two-dimensional reflection loss diagrams of the graphene / polyaniline / aramid composite fibers prepared in Comparative Example 2 are shown. Detailed Implementation

[0032] This invention provides a method for preparing carbon nanotube / polyaniline / aramid composite microwave absorbing fibers, comprising the following steps:

[0033] A) Polyvinylpyrrolidone, carbon nanotubes, and silane-modified fumed silica were dispersed in water to obtain a carbon nanotube dispersion.

[0034] B) Mix carbon nanotube dispersion, sodium dodecylbenzenesulfonate and aniline to obtain carbon nanotube / aniline dispersion;

[0035] C) An initiator is added to the carbon nanotube / aniline dispersion to carry out polymerization and obtain carbon nanotube / polyaniline;

[0036] D) Carbon nanotubes / polyaniline, alkali and aramid are mixed in a solvent to obtain a spinning solution. The spinning solution is then spun to obtain carbon nanotube / polyaniline / aramid composite microwave absorbing fiber.

[0037] This invention first modifies fumed silica using a silane coupling agent to obtain silane-modified fumed silica. Specifically, the silane coupling agent is mixed with water and ultrasonically dispersed to obtain a dispersion of the silane coupling agent. Then, fumed silica is added, and the mixture is stirred to react. After solid-liquid separation, the solid is washed until neutral and dried to obtain silane-modified fumed silica. Unlike conventional methods that directly mix fumed silica and the silane coupling agent, this application prioritizes the hydrolysis of the silane coupling agent. The silane coupling agent is first hydrolyzed to generate Si-OH, which then condenses with the hydroxyl groups on the surface of fumed silica. If directly mixed, the silane coupling agent is not fully hydrolyzed and reacts with silica, resulting in silane self-polymerization, which reduces the modification efficiency.

[0038] In this invention, the fumed silica is prepared by flame hydrolysis and its surface is rich in isolated, uncondensed silanol groups (density approximately 2-3 per nm). 2The SiO2 purity is >99.8%, with no residual metal ions. The silane coupling agent is preferably γ-aminopropyltriethoxysilane (KH550), and the mass ratio of the silane coupling agent to fumed silica is preferably 1:(10~20), more preferably 1:(15~16), such as 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, preferably within a range where any of the above values ​​is the upper or lower limit.

[0039] In this invention, the amino group (-NH2) in the silane coupling agent forms hydrogen bonds with the amide bond (-CONH-) of the aramid fiber, and simultaneously interacts with the polar groups of polyaniline to enhance the adhesion of the filler-matrix interface. The silane coupling agent enhances the bonding between fumed silica and carbon nanotubes through chemical bonding, reduces agglomeration, and ensures the continuity of the conductive network.

[0040] In this invention, the frequency of ultrasonication of the mixed solution of silane coupling agent and water is preferably 30-50 kHz, more preferably 40-45 kHz; the ultrasonication time is preferably 10-30 min, more preferably 12-25 min. The reaction temperature of the silane coupling agent with fumed silica is preferably 50-70°C, more preferably 55-60°C, and the reaction time is preferably 40-60 min, more preferably 50-55 min; the drying temperature is preferably 50-70°C, more preferably 55-60°C, and the drying time is preferably 10-12 hours.

[0041] The silane-modified fumed silica obtained by this invention has a high surface hydroxyl density. After forming chemical bonds, it can effectively prevent filler agglomeration. The nanoscale of fumed silica gives it a large specific surface area, which can enhance the interfacial bonding with aramid nanofibers.

[0042] After obtaining silane-modified fumed silica, the present invention mixes polyvinylpyrrolidone, carbon nanotubes and silane-modified fumed silica in water, and disperses them by ultrasonication to obtain a carbon nanotube dispersion. Then, dodecylbenzenesulfonic acid is added to the carbon nanotube dispersion, and aniline is added dropwise after stirring. Stirring is continued until the system is homogenized to obtain a carbon nanotube / aniline dispersion.

[0043] In this invention, polyvinylpyrrolidone (PVP) can disperse carbon nanotubes (CNTs). CNTs have a high specific surface area and strong van der Waals forces, making them easy to aggregate. The pyrrolidone rings on the surface of PVP molecules can be adsorbed onto the CNT surface through π–π stacking. At the same time, the hydrophilic long chains (polyvinyl groups) extend into the water to form steric hindrance, preventing CNTs from re-aggregating. Furthermore, the adsorption layer of PVP provides electrostatic repulsion and steric stability, ensuring that CNTs are uniformly dispersed in subsequent polymerization reactions.

[0044] The polyaniline (PANI) used in this invention has conductivity between that of aramid and carbon nanotubes, serving as an impedance transition layer. Furthermore, the conductivity of PANI is modulated by doping with sodium dodecylbenzenesulfonate. The introduction of PANI significantly enhances interfacial polarization loss (CNT / PANI interface, PANI / aramid interface), forming a continuous conductive pathway between CNTs and PANI. Simultaneously, the fibrous pleated structure effectively improves electromagnetic wave scattering. In addition, the benzene rings of PANI form strong π-π stacking with the carbon nanotube walls, ensuring a tight core-shell structure. The imino groups (-NH-) of PANI form multiple hydrogen bonds with the amino groups (-NH2) and aramid amide bonds (-CONH-) of silane coupling agent-modified silica. This multi-level interfacial interaction significantly improves filler dispersibility, reduces CNT agglomeration, enhances stress transmission, and prevents conductive layer detachment.

[0045] Furthermore, this invention uses dodecylbenzenesulfonic acid as a dopant and emulsifier to adsorb sulfonate anions onto the surface of carbon nanotubes. After aniline is added, it is preferentially protonated at the carbon nanotube interface, guiding the polyaniline to grow directionally along the carbon nanotube surface. The dodecylbenzenesulfonic acid in this invention can simultaneously achieve emulsification and doping, avoiding the introduction of impurities. Its sulfonic acid group (-SO3H) provides protonated acid doping for PANI, endowing the microwave absorbing filler with conductivity. The sulfonic acid group is directly embedded in the PANI molecular chain, forming a highly efficient conductive pathway.

[0046] In this invention, the preferred mass ratio of polyvinylpyrrolidone to carbon nanotubes is (3~5):1, more preferably (3.5~4.5):1, such as 3:1, 3.5:1, 4:1, 4.5:1, 5:1, and preferably any of the above values ​​as the upper or lower limit; the preferred mass ratio of silane-modified fumed silica to carbon nanotubes is 1:(40~60), more preferably 1:(45~55), such as 1:40, 1:45, 1:50, 1:55, 1:60, and preferably any of the above values ​​as the upper limit. The mass ratio of aniline to carbon nanotubes is preferably 1:(1~8), more preferably 1:(2~6), such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, and preferably a range of values ​​with the upper or lower limit of any of the above values; the molar ratio of aniline to sodium dodecylbenzenesulfonate is preferably 1:(1~2.5), more preferably 1:(1.5~2), such as 1:1, 1:1.5, 1:2, 1:2.5, and preferably a range of values ​​with the upper or lower limit of any of the above values.

[0047] In this invention, the ultrasonic dispersion time of the polyvinylpyrrolidone, carbon nanotubes, and silane-modified fumed silica in water is preferably 10-30 min, more preferably 15-20 min. Compared with other materials, the one-dimensional conductive pathway of carbon nanotubes is more suitable for wet spinning fiber forming processes, which is more conducive to the construction of continuous conductive networks, improving the polyaniline coating effect, and enhancing mechanical properties.

[0048] After obtaining the carbon nanotube / aniline dispersion, the present invention mixes the carbon nanotube / aniline dispersion with an initiator and carries out a polymerization reaction. After the reaction is completed, ethanol is added to break the emulsion. The precipitate obtained after solid-liquid separation is washed and dried to obtain carbon nanotube / polyaniline powder.

[0049] In this invention, the initiator is preferably ammonium persulfate. Preferably, the initiator is first dissolved in deionized water to obtain an initiator solution, and then the initiator solution is added dropwise to the carbon nanotube / aniline dispersion to carry out the polymerization reaction.

[0050] In this invention, the mass ratio of ammonium persulfate to aniline is preferably (2~3):1, more preferably (2.2~2.8):1, such as 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, preferably any of the above values ​​as the upper or lower limit range. The polymerization reaction temperature is preferably room temperature, such as 20~30℃, and the polymerization reaction time is 8~14 hours, more preferably 10~12 hours. The drying is preferably freeze drying, the drying temperature is preferably -50~-60℃, and the drying time is preferably 24~28 hours.

[0051] After obtaining carbon nanotube / polyaniline powder, the present invention disperses the carbon nanotube / polyaniline powder in a dispersion of aramid nanofibers, stirs for 6 to 24 hours, and then defoams by ultrasonication to obtain a spinning solution.

[0052] In this invention, the dispersion of the aramid nanofibers is preferably prepared according to the following steps:

[0053] Aramid nanofibers, alkali, water, and dimethyl sulfoxide are mixed and stirred for 4-8 hours to obtain an aramid nanofiber dispersion.

[0054] In this invention, the aramid fibers are preferably pretreated before the aramid nanofiber dispersion is prepared. The pretreatment includes cutting, washing and drying in sequence. The washing is preferably performed by ultrasonically washing the aramid nanofibers with methanol and deionized water for 20-30 min in sequence. The drying temperature is preferably 50-65℃, more preferably 55-60℃, and the drying time is preferably 10-12 hours. The length of the cut aramid nanofibers is preferably 5-10 mm, and the diameter is preferably 5-7 μm.

[0055] In this invention, the alkali is preferably potassium hydroxide, and the mass ratio of the alkali to the alkali is preferably 1:(1~2), more preferably 1:(1.2~1.8), such as 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, 1:2, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0056] In this invention, the mass ratio of aramid fiber to carbon nanotube / polyaniline is preferably 80:(1~10), more preferably 80:(3~9), such as 80:1, 80:2, 80:3, 80:4, 80:5, 80:6, 80:7, 80:8, 80:9, 80:10, and preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0057] After obtaining the spinning solution, the spinning solution is injected into the coagulation bath through a needle, and the solvent on the fiber surface is removed by washing with deionized water. The fiber is collected by a winding device and placed in an oven to dry, thus obtaining carbon nanotube / polyaniline / aramid composite microwave absorbing fiber.

[0058] In this invention, the inner diameter of the needle is preferably 20-23G, and the fiber diameter obtained by the needle with this inner diameter is 0.34-0.6mm. If the diameter is <0.34mm, it will lead to excessive shear force and breakage of aramid nanofibers (reduced strength); if the diameter is >0.6mm, it will lead to slower solvent diffusion and delamination of the core-sheath structure. The extrusion speed of the spinning solution is preferably 5-20mL / h, more preferably 10-15mL / h; low speed (<5ml / h) may cause excessive swelling in the coagulation bath and loss of fiber diameter control; high speed (>20ml / h) may cause solvent retention and increased porosity after drying; the drying temperature is preferably 40-80℃, more preferably 50-60℃.

[0059] This invention first pre-synthesizes the microwave absorbing filler (CNT / PANI) and then blends it with aramid fiber through spinning, forming a single integral molding process. Compared with in-situ polymerization on the surface of aramid fibers, this method offers higher structural stability, better interfacial bonding, effectively improved breaking strength, and a wider effective microwave absorption bandwidth. Furthermore, the microwave absorbing filler is embedded within the fiber, resulting in better stability of microwave absorption performance.

[0060] The present invention also provides a carbon nanotube / polyaniline / aramid composite microwave absorbing fiber, which is prepared according to the preparation method of carbon nanotube / polyaniline / aramid composite microwave absorbing fiber described above.

[0061] In this invention, the diameter of the carbon nanotube / polyaniline / aramid composite microwave absorbing fiber is preferably 0.34~0.6mm.

[0062] The present invention also provides a microwave absorbing fabric, comprising the carbon nanotube / polyaniline / aramid composite microwave absorbing fiber described above.

[0063] This invention provides a method for preparing carbon nanotube / polyaniline / aramid composite microwave absorbing fibers, comprising the following steps: A) dispersing polyvinylpyrrolidone, carbon nanotubes, and silane-modified fumed silica in water to obtain a carbon nanotube dispersion; B) mixing the carbon nanotube dispersion, sodium dodecylbenzenesulfonate, and aniline to obtain a carbon nanotube / aniline dispersion; C) adding an initiator to the carbon nanotube / aniline dispersion and polymerizing to obtain carbon nanotube / polyaniline; D) mixing carbon nanotube / polyaniline, an alkali, and aramid in a solvent to obtain a spinning solution, and spinning the spinning solution to obtain carbon nanotube / polyaniline / aramid composite microwave absorbing fibers. This invention uses carbon nanotubes as the core carrier, with an impedance matching layer formed by in-situ polymerized polyaniline on the surface, achieving in-situ polymerization to construct a "core-shell" structure. This invention chemically combines polyaniline and carbon nanotubes through in-situ polymerization, and then blends and spins them with an aramid matrix to achieve integrated molding. Furthermore, this invention modifies fumed silica with a silane coupling agent, allowing the surface hydroxyl groups to form chemical bonds with the silane coupling agent, significantly enhancing the interfacial bonding between fumed silica and carbon nanotubes / polyaniline. Moreover, fumed silica, acting as rigid nanoparticles, bears stress and improves the tensile strength of the composite fiber. The insulating properties of fumed silica neutralize the excessively high dielectric constant of carbon nanotubes, improving the impedance matching between the material and air.

[0064] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, describes a carbon nanotube / polyaniline / aramid composite microwave absorbing fiber provided by the present invention, its preparation method, and its application, but this should not be construed as limiting the scope of protection of the present invention.

[0065] Example 1

[0066] (1) Preparation of carbon nanotube / polyaniline microwave absorbing filler

[0067] Add 0.067g of silane coupling agent KH550 to 20ml of deionized water and ultrasonically disperse it for 10min to obtain a uniform dispersion. Add 1g of fumed silica and magnetically stir at 70°C for 40min. After the reaction is complete, centrifuge, wash and dry the product to obtain modified fumed silica.

[0068] Add 2g of polyvinylpyrrolidone, 0.5g of carbon nanotubes and 0.01g of modified fumed silica to 70ml of deionized water, sonicate for 30min to obtain a carbon nanotube dispersion, add 7g of dodecylbenzenesulfonic acid, stir, add 1g of aniline dropwise to the dispersion, continue stirring, and obtain solution A after the system is homogenized.

[0069] Dissolve 2.5g of ammonium persulfate in 15ml of deionized water and stir for 5min to ensure complete dissolution, thus obtaining solution B;

[0070] B was added dropwise to A, and the mixture was stirred for 12 hours to polymerize. After the reaction was completed, ethanol was added to break the emulsion, and the precipitate was washed and dried to obtain carbon nanotube / polyaniline powder.

[0071] (2) Preparation of aramid nanofiber dispersion

[0072] Aramid fibers were cut into small pieces and ultrasonically washed with methanol and deionized water for 30 minutes in sequence. The washed fibers were then dried in an oven at 60°C for 24 hours. 2.4 g of dried aramid fibers, 3.6 g of potassium hydroxide and 4 ml of deionized water were added to 96 ml of dimethyl sulfoxide and stirred for 5 hours to obtain an aramid nanofiber / dimethyl sulfoxide dispersion.

[0073] (3) Preparation of carbon nanotube / polyaniline / aramid microwave absorbing fiber

[0074] 0.09g of carbon nanotube / polyaniline powder was added to 9g of aramid nanofiber / dimethyl sulfoxide dispersion, stirred for 18h, and ultrasonically defoamed for 30min to obtain spinning solution. The spinning solution was injected into a deionized water coagulation bath at a rate of 10ml / h through a 22G needle. The solvent on the fiber surface was removed by washing with deionized water. The fibers were collected by a winding device and dried in a 50℃ oven to obtain carbon nanotube / polyaniline / aramid composite microwave absorbing fiber.

[0075] Example 2

[0076] (1) Preparation of carbon nanotube / polyaniline microwave absorbing filler

[0077] The preparation process of modified fumed silica is the same as in Example 1.

[0078] Add 2g of polyvinylpyrrolidone, 0.5g of carbon nanotubes and 0.01g of modified fumed silica to 70ml of deionized water, sonicate for 30min to obtain a carbon nanotube dispersion, add 7g of dodecylbenzenesulfonic acid, stir, add 1g of aniline dropwise to the dispersion, continue stirring, and obtain solution A after the system is homogenized.

[0079] Dissolve 2.5g of ammonium persulfate in 15ml of deionized water and stir for 5min to ensure complete dissolution, thus obtaining solution B;

[0080] B was added dropwise to A, and the mixture was stirred for 12 hours to polymerize. After the reaction was completed, ethanol was added to break the emulsion, and the precipitate was washed and dried to obtain carbon nanotube / polyaniline powder.

[0081] (2) Preparation of aramid nanofiber dispersion

[0082] Aramid fibers were cut into small pieces and ultrasonically washed with methanol and deionized water for 30 minutes in sequence. The washed fibers were then dried in an oven at 60°C for 24 hours. 2.4 g of dried aramid fibers, 3.6 g of potassium hydroxide and 4 ml of deionized water were added to 96 ml of dimethyl sulfoxide and stirred for 5 hours to obtain an aramid nanofiber / dimethyl sulfoxide dispersion.

[0083] (3) Preparation of carbon nanotube / polyaniline / aramid microwave absorbing fiber

[0084] 0.18g of carbon nanotube / polyaniline powder was added to 9g of aramid nanofiber / dimethyl sulfoxide dispersion, stirred for 18h, and ultrasonically defoamed for 30min to obtain spinning solution. The spinning solution was injected into a deionized water coagulation bath at a rate of 10ml / h through a 22G needle. The solvent on the fiber surface was removed by washing with deionized water. The fibers were collected by a winding device and dried in a 50℃ oven to obtain carbon nanotube / polyaniline / aramid composite microwave absorbing fiber.

[0085] Example 3

[0086] (1) Preparation of carbon nanotube / polyaniline microwave absorbing filler

[0087] The preparation process of modified fumed silica is the same as in Example 1.

[0088] Add 2g of polyvinylpyrrolidone, 0.5g of carbon nanotubes and 0.01g of modified fumed silica to 70ml of deionized water, sonicate for 30min to obtain a carbon nanotube dispersion, add 7g of dodecylbenzenesulfonic acid, stir, add 1g of aniline dropwise to the dispersion, continue stirring, and obtain solution A after the system is homogenized.

[0089] Dissolve 2.5g of ammonium persulfate in 15ml of deionized water and stir for 5min to ensure complete dissolution, thus obtaining solution B;

[0090] B was added dropwise to A, and the mixture was stirred for 12 hours to polymerize. After the reaction was completed, ethanol was added to break the emulsion, and the precipitate was washed and dried to obtain carbon nanotube / polyaniline powder.

[0091] (2) Preparation of aramid nanofiber dispersion

[0092] Aramid fibers were cut into small pieces and ultrasonically washed with methanol and deionized water for 30 minutes in sequence. The washed fibers were then dried in an oven at 60°C for 24 hours. 2.4 g of dried aramid fibers, 3.6 g of potassium hydroxide and 4 ml of deionized water were added to 96 ml of dimethyl sulfoxide and stirred for 5 hours to obtain an aramid nanofiber / dimethyl sulfoxide dispersion.

[0093] (3) Preparation of carbon nanotube / polyaniline / aramid microwave absorbing fiber

[0094] 0.27g of carbon nanotube / polyaniline powder was added to 9g of aramid nanofiber / dimethyl sulfoxide dispersion, stirred for 18h, and ultrasonically defoamed for 30min to obtain spinning solution. The spinning solution was injected into a deionized water coagulation bath at a rate of 10ml / h through a 22G needle. The solvent on the fiber surface was removed by washing with deionized water. The fibers were collected by a winding device and dried in a 50℃ oven to obtain carbon nanotube / polyaniline / aramid composite microwave absorbing fiber.

[0095] Comparative Example 1

[0096] (1) Preparation of carbon nanotube / polyaniline microwave absorbing filler

[0097] Add 2g of polyvinylpyrrolidone and 0.5g of carbon nanotubes to 70ml of deionized water, sonicate for 30min to obtain a carbon nanotube dispersion, add 7g of dodecylbenzenesulfonic acid, stir, add 1g of aniline dropwise to the dispersion, continue stirring, and obtain solution A after the system is homogenized.

[0098] Dissolve 2.5g of ammonium persulfate in 15ml of deionized water and stir for 5min to ensure complete dissolution, thus obtaining solution B;

[0099] B was added dropwise to A, and the mixture was stirred for 12 hours to polymerize. After the reaction was completed, ethanol was added to break the emulsion, and the precipitate was washed and dried to obtain carbon nanotube / polyaniline powder.

[0100] (2) Preparation of aramid nanofiber dispersion

[0101] Aramid fibers were cut into small pieces and ultrasonically washed with methanol and deionized water for 30 minutes in sequence. The washed fibers were then dried in an oven at 60°C for 24 hours. 2.4 g of dried aramid fibers, 3.6 g of potassium hydroxide and 4 ml of deionized water were added to 96 ml of dimethyl sulfoxide and stirred for 5 hours to obtain an aramid nanofiber / dimethyl sulfoxide dispersion.

[0102] (3) Preparation of carbon nanotube / polyaniline / aramid microwave absorbing fiber

[0103] 0.27g of carbon nanotube / polyaniline powder was added to 9g of aramid nanofiber / dimethyl sulfoxide dispersion, stirred for 18h, and ultrasonically defoamed for 30min to obtain spinning solution. The spinning solution was injected into a deionized water coagulation bath at a rate of 10ml / h through a 22G needle. The solvent on the fiber surface was removed by washing with deionized water. The fibers were collected by a winding device and dried in a 50℃ oven to obtain carbon nanotube / polyaniline / aramid composite microwave absorbing fiber without the addition of modified silica.

[0104] Comparative Example 2

[0105] (1) Preparation of graphene / polyaniline microwave absorbing filler

[0106] The preparation process of modified fumed silica is the same as in Example 1.

[0107] Add 2g of polyvinylpyrrolidone and 0.5g of graphene oxide to 70ml of deionized water, sonicate for 30min to obtain a graphene oxide dispersion, add 7g of dodecylbenzenesulfonic acid, stir, add 1g of aniline dropwise to the dispersion, continue stirring, and obtain solution A after the system is homogenized.

[0108] Dissolve 2.5g of ammonium persulfate in 15ml of deionized water and stir for 5min to ensure complete dissolution, thus obtaining solution B;

[0109] B was added dropwise to A, and the mixture was stirred for 12 hours to polymerize. After the reaction was completed, ethanol was added to break the emulsion, and the precipitate was washed and dried to obtain graphene oxide / polyaniline powder.

[0110] (2) Preparation of aramid nanofiber dispersion

[0111] Aramid fibers were cut into small pieces and ultrasonically washed with methanol and deionized water for 30 minutes in sequence. The washed fibers were then dried in an oven at 60°C for 24 hours. 2.4 g of dried aramid fibers, 3.6 g of potassium hydroxide and 4 ml of deionized water were added to 96 ml of dimethyl sulfoxide and stirred for 5 hours to obtain an aramid nanofiber / dimethyl sulfoxide dispersion.

[0112] (3) Preparation of graphene / polyaniline / aramid microwave absorbing fibers

[0113] 0.27g of graphene oxide / polyaniline powder was added to 9g of aramid nanofiber / dimethyl sulfoxide dispersion, stirred for 18h, and ultrasonically defoamed for 30min to obtain spinning solution. The spinning solution was injected into a deionized water coagulation bath at a rate of 10ml / h through a 22G needle. The solvent on the fiber surface was removed by washing with deionized water. The fibers were collected by a winding device and dried in a 50℃ oven to obtain graphene oxide / polyaniline / aramid composite microwave absorbing fiber.

[0114] Figure 1The image shows a scanning electron microscope (SEM) image of the carbon nanotube / polyaniline / aramid composite fiber prepared in Example 3. The composite fiber surface exhibits wrinkles, possibly due to rapid moisture evaporation during drying, leading to excessive fiber shrinkage and tightening of the outer layer. The cross-section reveals rod-shaped carbon nanotubes / polyaniline dispersed within the fiber, forming a conductive network.

[0115] Figure 2 The stress-strain curves of the carbon nanotube / polyaniline / aramid composite fibers prepared in Examples 1-3 show that as the relative content of carbon nanotubes / polyaniline in the composite fiber increases, the breaking strength and breaking elongation of the fiber both show a continuous decreasing trend. The breaking strength of the composite fiber prepared in Example 3 is 139 MPa.

[0116] Figure 3 The image shows two-dimensional reflection loss diagrams of the carbon nanotube / polyaniline / aramid composite fibers prepared in Examples 1-3. In Example 3, the carbon nanotubes / polyaniline form a conductive path in the composite fiber, thus the composite fiber prepared in Example 3 has good wave absorption performance. It exhibits the best effective wave absorption bandwidth of 6.85 GHz and the minimum reflection loss of -45.83 dB at a simulated thickness of 2.10 mm.

[0117] Figure 4 The thermogravimetric curve of the carbon nanotube / polyaniline / aramid composite fiber prepared in Example 3 of the present invention is shown. The weight loss of the fiber at 200°C is attributed to the loss of residual moisture or solvent in the fiber. The significant weight loss at around 400°C may be due to the pyrolysis of polyaniline after 400°C. The residual mass fraction at 800°C is 49.1%.

[0118] Figure 5 The stress-strain curves and two-dimensional reflection loss diagrams of the carbon nanotube / polyaniline / aramid composite fibers prepared in Comparative Example 1 without the addition of modified fumed silica are shown. The comparison reveals that the composite fiber prepared without modified fumed silica exhibits a tensile strength of 135 MPa, demonstrates the best effective absorption bandwidth of 3.74 GHz at a simulated thickness of 2.23 mm, and a minimum reflection loss of -40.27 dB. Figure 2 , 3 It is evident that the composite microwave absorbing fiber with modified fumed silica prepared in this invention exhibits superior tensile strength and microwave absorption performance.

[0119] In this invention, the "simulated thickness" refers to the ideal thickness required for the material to achieve optimal microwave absorption performance, as predicted by theoretical calculations or simulation models. A smaller simulated thickness indicates a higher microwave absorption efficiency per unit thickness of the material.

[0120] Fumed silica modified with silane coupling agent KH550 can effectively improve the dispersibility and continuity of the conductive network in the composite system. KH550 enhances the interfacial bonding between fumed silica and the matrix through chemical bonding, reduces agglomeration, and makes carbon nanotubes and polyaniline more uniformly dispersed, promoting the continuity and integrity of the conductive network, thereby improving dielectric loss capability. The insulating properties of fumed silica can partially neutralize the excessively high dielectric constant of carbon nanotubes, improve the impedance matching between the material and air, and reduce electromagnetic wave reflection.

[0121] In addition, the amino group (-NH2) of KH550 forms hydrogen bonds with the amide bond (-CONH-) of aramid and interacts with the polar groups of polyaniline, which improves the interfacial adhesion between the filler and the matrix, reduces stress concentration, and improves the fracture strength and modulus.

[0122] Figure 6 The stress-strain curves and two-dimensional reflection loss diagrams of the graphene / polyaniline / aramid composite fibers prepared in Comparative Example 2 are shown. The comparison reveals that the composite fiber prepared using graphene instead of carbon nanotubes exhibits a tensile strength of 125 MPa, demonstrates the best effective absorption bandwidth of 1.82 GHz at a simulated thickness of 1.5 mm, and a minimum reflection loss of -36.41 dB. Figure 2 , 3 It is evident that composite fibers with added carbon nanotubes exhibit superior mechanical and wave absorption properties. The one-dimensional conductive pathways of carbon nanotubes are better suited to wet spinning fiber forming processes, which is more conducive to the construction of continuous conductive networks, improving the polyaniline coating effect, and enhancing mechanical properties.

[0123] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon nanotube / polyaniline / aramid composite microwave absorbing fiber, comprising the following steps: A) Polyvinylpyrrolidone, carbon nanotubes, and silane-modified fumed silica were dispersed in water to obtain a carbon nanotube dispersion. The silane-modified fumed silica was prepared according to the following steps: The silane coupling agent was mixed with water to obtain a silane coupling agent dispersion. Then, fumed silica was added and stirred to carry out the reaction. After solid-liquid separation, the mixture was dried to obtain a silane-modified silane coupling agent. The mass ratio of the silane coupling agent to fumed silica is 1:(10~20). B) Mix carbon nanotube dispersion, sodium dodecylbenzenesulfonate and aniline to obtain carbon nanotube / aniline dispersion; C) An initiator is added to the carbon nanotube / aniline dispersion to carry out polymerization and obtain carbon nanotube / polyaniline; D) Carbon nanotubes / polyaniline, alkali and aramid are mixed in a solvent to obtain a spinning solution. The spinning solution is then spun to obtain carbon nanotube / polyaniline / aramid composite microwave absorbing fiber.

2. The method for preparing carbon nanotube / polyaniline / aramid composite microwave absorbing fiber according to claim 1, characterized in that, In step A), the mass ratio of polyvinylpyrrolidone to carbon nanotubes is (3~5):1, and the mass ratio of silane-modified fumed silica to carbon nanotubes is 1:(40~60).

3. The method for preparing carbon nanotube / polyaniline / aramid composite microwave absorbing fiber according to claim 1, characterized in that, In step B), the mass ratio of aniline to carbon nanotubes is 1:(1~8). The molar ratio of aniline to sodium dodecylbenzenesulfonate is 1:(1~2.5).

4. The method for preparing carbon nanotube / polyaniline / aramid composite microwave absorbing fiber according to claim 1, characterized in that, In step C), the initiator is ammonium persulfate; the mass ratio of ammonium persulfate to aniline is (2~3):

1.

5. The method for preparing carbon nanotube / polyaniline / aramid composite microwave absorbing fiber according to claim 1, characterized in that, In step C), the polymerization temperature is 20~30℃ and the polymerization time is 8~14 hours.

6. The method for preparing carbon nanotube / polyaniline / aramid composite microwave absorbing fiber according to claim 1, characterized in that, In step D), aramid fibers, alkali, water and dimethyl sulfoxide are mixed to obtain an aramid fiber dispersion, and then carbon nanotubes / polyaniline are mixed with the aramid fiber dispersion to obtain a spinning solution. The mass ratio of the aramid fiber to the alkali is 1:(1~2). The mass ratio of the aramid fiber to the carbon nanotube / polyaniline is 80:(1~10).

7. A carbon nanotube / polyaniline / aramid composite microwave absorbing fiber, prepared according to the preparation method described in any one of claims 1 to 6.

8. A microwave absorbing fabric comprising the carbon nanotube / polyaniline / aramid composite microwave absorbing fiber as described in claim 7.

Images