Carbon nanotube / polyaniline / aramid fiber composite wave-absorbing fiber as well as preparation method and application thereof

Abstract

The invention provides a carbon nanotube / polyaniline / aramid fiber composite wave-absorbing fiber as well as a preparation method and application thereof. Comprising the following steps: A) dispersing polyvinylpyrrolidone, carbon nanotubes and silane modified fumed silica in water to obtain a carbon nanotube dispersion liquid, B) mixing the carbon nanotube dispersion liquid, sodium dodecyl benzene sulfonate and aniline to obtain a carbon nanotube / aniline dispersion liquid; c) adding an initiator into the carbon nanotube / aniline dispersion liquid, and carrying out polymerization to obtain carbon nanotube / polyaniline; and D) mixing the carbon nano tube / polyaniline, alkali and aramid fiber in a solvent to obtain a spinning solution, and spinning to obtain the carbon nano tube / polyaniline / aramid fiber composite wave-absorbing fiber. According to the invention, polyaniline and carbon nanotubes are chemically combined through in-situ polymerization, and then blended spinning with an aramid matrix is carried out, so that integral forming is realized. The fumed silica is modified by the silane coupling agent, so that the interface bonding force between the fumed silica and the carbon nanotube / polyaniline is remarkably enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of absorbing materials, and in particular relates to a carbon nanotube / polyaniline / aramid composite absorbing fiber, a preparation method and application thereof. Background Art

[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 cause damage to the human nervous, reproductive, and cardiovascular systems. Therefore, the development of electromagnetic protection products with strong practicality and high portability has become an inevitable choice for people to prevent and control the hazards of electromagnetic radiation.

[0003] Absorbing materials can attenuate electromagnetic waves by converting them into other forms of energy for dissipation. When electromagnetic waves strike the surface of an absorbing material, a small portion is reflected or transmitted, while the majority enters the material's interior. After multiple reflections and scattering, they are converted into heat or dissipated as other forms of energy. Therefore, the design of high-performance absorbing materials requires considering two key aspects: 1) good impedance matching to maximize electromagnetic wave penetration; 2) strong attenuation to minimize the loss of electromagnetic waves that do enter the absorber.

[0004] In recent years, with the rapid development of smart wearable devices, the goal of developing flexible absorbing materials has been proposed. Textile absorbing materials offer a wide range of applications, with shapes and sizes tailored to the shape and size of the target being protected; flexibility and ease of use, enabling quick coverage; and multifunctionality, integrating multiple functions such as breathability, waterproofing, thermal 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 hand feel of traditional metal conductive fibers and the difficulty in color reprocessing of traditional carbon fibers, their wearability is poor, limiting their development and application in modern textiles, especially smart textiles. Traditional fibers such as aramid, polyamide, and polyester offer good wearability, but are insulating materials and lack absorbency. These fibers are typically impregnated with conductive materials, coated with impregnation materials, or grown with in-situ active materials to impart conductive properties and enhance their absorbency. However, these materials suffer from the problem of the conductive layer easily detaching, and their poor stability severely impacts their usability. Summary of the Invention

[0005] The present invention aims to provide a method for preparing a carbon nanotube / polyaniline / aramid composite absorbing fiber. This method is simple, the fibers are integrally formed, and the problem of conductive layer shedding is avoided. Furthermore, the fibers are lightweight, flexible, and exhibit good absorbing properties.

[0006] The present invention provides a method for preparing a carbon nanotube / polyaniline / aramid composite absorbing fiber, comprising the following steps:

[0007] A) dispersing polyvinyl pyrrolidone, carbon nanotubes and silane-modified fumed silica in water to obtain a carbon nanotube dispersion,

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

[0009] C) adding an initiator to the carbon nanotube / aniline dispersion to carry out polymerization to obtain carbon nanotube / polyaniline;

[0010] D) mixing carbon nanotubes / polyaniline, alkali and aramid in a solvent to obtain a spinning solution, and spinning the spinning solution to obtain a carbon nanotube / polyaniline / aramid composite absorbing fiber.

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

[0012] The silane coupling agent is mixed with water to obtain a silane coupling agent dispersion, and then fumed silica is added, stirred to react, and the solid-liquid separation is followed by drying to obtain a silane-modified silane coupling agent.

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

[0014] Preferably, in step A), the mass ratio of the polyvinyl pyrrolidone to the carbon nanotubes is (3-5):1, and the mass ratio of the silane-modified fumed silica to the 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; and the mass ratio of ammonium persulfate to aniline is (2-3):1.

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

[0019] Preferably, in step D), aramid fiber, 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] The present invention provides a carbon nanotube / polyaniline / aramid composite absorbing fiber, which is prepared according to the preparation method described above.

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

[0024] The present invention provides a method for preparing a carbon nanotube / polyaniline / aramid composite absorbing fiber, comprising the following steps: A) dispersing polyvinyl pyrrolidone, 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 to polymerize the dispersion to obtain a carbon nanotube / polyaniline; and D) mixing the carbon nanotubes / polyaniline, a base, and aramid in a solvent to obtain a spinning solution, and spinning the spinning solution to obtain a carbon nanotube / polyaniline / aramid composite absorbing fiber. The present invention utilizes carbon nanotubes as a core carrier, with an impedance matching layer formed by in-situ polymerization of polyaniline on the surface, achieving in-situ polymerization to construct a "core-shell" structure. The polyaniline and carbon nanotubes are chemically bonded through in-situ polymerization, and then the fibers are blended and spun with the aramid matrix to achieve integrated molding. Furthermore, the present 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 the fumed silica and the carbon nanotubes / polyaniline. Furthermore, the fumed silica, as a rigid nanoparticle, supports stress and increases the tensile strength of the composite fiber. The insulating properties of the fumed silica neutralize the excessively high dielectric constant of the carbon nanotubes, improving the impedance matching between the material and air. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

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

[0027] Figure 2 1 is a stress-strain curve of the carbon nanotube / polyaniline / aramid composite fiber prepared in Examples 1-3;

[0028] Figure 3 2D reflection loss graph of the carbon nanotube / polyaniline / aramid composite fiber prepared in Examples 1-3;

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

[0030] Figure 5 The stress-strain curve and two-dimensional reflection loss diagram of the carbon nanotube / polyaniline / aramid composite fiber prepared in Comparative Example 1 without the addition of modified fumed silica;

[0031] Figure 6 The stress-strain curve and two-dimensional reflection loss diagram of the graphene / polyaniline / aramid composite fiber prepared in Comparative Example 2. DETAILED DESCRIPTION

[0032] The present invention provides a method for preparing a carbon nanotube / polyaniline / aramid composite absorbing fiber, comprising the following steps:

[0033] A) dispersing polyvinyl pyrrolidone, carbon nanotubes and silane-modified fumed silica in water to obtain a carbon nanotube dispersion,

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

[0035] C) adding an initiator to the carbon nanotube / aniline dispersion to carry out polymerization to obtain carbon nanotube / polyaniline;

[0036] D) mixing carbon nanotubes / polyaniline, alkali and aramid in a solvent to obtain a spinning solution, and spinning the spinning solution to obtain a carbon nanotube / polyaniline / aramid composite absorbing fiber.

[0037] The present 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, ultrasonically dispersed to obtain a dispersion of the silane coupling agent, and then the fumed silica is added, stirred for reaction, and after solid-liquid separation, the solid is washed to neutrality and dried to obtain the silane-modified fumed silica. Unlike conventional methods that directly mix fumed silica with a silane coupling agent, the present invention preferentially hydrolyzes the silane coupling agent, first hydrolyzing it to form Si-OH groups, which then condense with hydroxyl groups on the surface of the fumed silica. If the silane coupling agent is not fully hydrolyzed and reacts with the silica, silane self-polymerization will occur, reducing the modification efficiency.

[0038] In the present invention, the fumed silica is prepared by flame hydrolysis and is rich in isolated, uncondensed silanol groups (density of about 2 to 3 per nm). 2), SiO2 purity >99.8%, with no metal ion residue. The silane coupling agent is preferably γ-aminopropyltriethoxysilane (KH550). The mass ratio of the silane coupling agent to the 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, and 1:20. The range with any of the above values ​​as the upper or lower limit is preferably a value.

[0039] In this invention, the amino groups (-NH2) in the silane coupling agent form hydrogen bonds with the amide bonds (-CONH-) of the aramid fiber, while also interacting with the polar groups of the polyaniline to enhance filler-matrix interfacial adhesion. The silane coupling agent strengthens the bond between the fumed silica and carbon nanotubes through chemical bonding, reducing agglomeration and ensuring the continuity of the conductive network.

[0040] In the present invention, the frequency of the ultrasonic treatment of the mixed solution of the silane coupling agent and water is preferably 30-50 kHz, more preferably 40-45 kHz; the ultrasonic treatment time is preferably 10-30 minutes, more preferably 12-25 minutes. The temperature of the reaction of the silane coupling agent with the fumed silica is preferably 50-70°C, more preferably 55-60°C, and the reaction time is preferably 40-60 minutes, more preferably 50-55 minutes. 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 the present invention has a high surface hydroxyl density, and after forming chemical bonds, it can effectively prevent filler agglomeration. The nanometer scale of the fumed silica gives it a large specific surface area, which can enhance the interface bonding with the aramid nanofiber.

[0042] After obtaining silane-modified fumed silica, the present invention mixes polyvinyl pyrrolidone, carbon nanotubes and silane-modified fumed silica in water, performs ultrasonic dispersion to obtain a carbon nanotube dispersion, then adds dodecylbenzenesulfonic acid to the carbon nanotube dispersion, stirs, and then adds aniline dropwise, continues stirring, and after the system is homogenized, obtains a carbon nanotube / aniline dispersion.

[0043] In the present invention, the polyvinyl pyrrolidone can disperse carbon nanotubes. CNTs have a high specific surface area and strong van der Waals force and are easy to agglomerate. The pyrrolidone ring on the surface of the PVP molecule can be adsorbed on the surface of the CNT through π-π stacking. At the same time, the hydrophilic long chain (polyethylene group) extends into the water to form a steric hindrance, preventing the CNTs from reaggregating. Secondly, the adsorption layer of PVP provides electrostatic repulsion and steric stability, ensuring that the CNTs are evenly dispersed in the subsequent polymerization reaction.

[0044] The polyaniline (PANI) used in this invention has a conductivity intermediate between that of aramid and carbon nanotubes, making it suitable for use as an impedance transition layer. Furthermore, the conductivity of PAI can be controlled by doping with sodium dodecylbenzenesulfonate. The introduction of PAI significantly enhances interfacial polarization losses (at the CNT / PANI interface and the PANI / aramid interface), forming a continuous conductive pathway between the CNTs and PANI. The wrinkled fiber structure effectively enhances electromagnetic wave scattering. Furthermore, the benzene rings of PAI form strong π-π stacking with the carbon nanotube walls, ensuring a tight core-shell structure. The imino groups (-NH-) of PAI form multiple hydrogen bonds with the amino groups (-NH2) of the silane-modified silica and the amide bonds (-CONH-) of the aramid. This multi-level interfacial interaction significantly improves filler dispersion, reduces CNT agglomeration, and enhances stress transfer, preventing shedding of the conductive layer.

[0045] Furthermore, the present invention uses dodecylbenzenesulfonic acid as a dopant and emulsifier to adsorb sulfonate anions on the carbon nanotube surface. Aniline, after dropwise addition, preferentially protonates at the carbon nanotube interface, guiding the directional growth of polyaniline along the carbon nanotube surface. The dodecylbenzenesulfonic acid in the present invention simultaneously achieves emulsification and doping, avoiding the introduction of impurities. Its sulfonic acid groups (-SO3H) provide proton acid doping for the PANI, imparting conductivity to the absorbing filler. The sulfonic acid groups are directly embedded in the PANI molecular chains, forming efficient conductive pathways.

[0046] In the present invention, the mass ratio of polyvinyl pyrrolidone to carbon nanotubes is preferably (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 a range value with any of the above values ​​as the upper or lower limit; the mass ratio of silane-modified fumed silica to carbon nanotubes is preferably 1:(40-60), more preferably 1:(45-55), such as 1:40, 1:45, 1:50, 1:55, 1:60, and preferably a range value with any of the above values ​​as the upper limit. or lower limit range value; 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, preferably a range value with any of the above values ​​as the upper or lower limit; 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, preferably a range value with any of the above values ​​as the upper or lower limit.

[0047] In the present invention, the ultrasonic dispersion time of the polyvinyl pyrrolidone, carbon nanotubes, and silane-modified fumed silica in water is preferably 10 to 30 minutes, more preferably 15 to 20 minutes. Compared to other materials, the one-dimensional conductive pathways of carbon nanotubes are more suitable for wet spinning fiber forming processes, are more conducive to the construction of a continuous conductive network, improve the polyaniline coating effect, and enhance mechanical properties.

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

[0049] In the present invention, the initiator is preferably ammonium persulfate. In the present invention, the initiator is preferably 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 the present 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, and 3:1, preferably with any of the above values ​​as the upper or lower limit of the range value. The temperature of the polymerization reaction is preferably room temperature, such as 20-30°C, 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°C, and the drying time is preferably 24-28 hours.

[0051] After obtaining the 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 removes bubbles by ultrasonication to obtain a spinning solution.

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

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

[0054] The present invention preferably pre-treats the aramid fibers before preparing the aramid nanofiber dispersion, wherein the pre-treatment sequentially comprises shredding, washing, and drying, wherein the washing is preferably ultrasonically washing the aramid nanofibers using methanol and deionized water in sequence for 20 to 30 minutes; the drying temperature is preferably 50 to 65°C, more preferably 55 to 60°C, and the drying time is preferably 10 to 12 hours. The length of the shredded aramid nanofibers is preferably 5 to 10 mm, and the diameter is preferably 5 to 7 μm.

[0055] In the present invention, the base is preferably potassium hydroxide, and the mass ratio of the base to the base 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 value with any of the above values ​​as the upper or lower limit.

[0056] In the present invention, the mass ratio of the aramid fiber to the 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 value with any of the above values ​​as the upper or lower limit.

[0057] After the spinning solution is obtained, the spinning solution is injected into a coagulation bath through a needle, washed with deionized water to remove the solvent on the fiber surface, and the fiber is collected by a winding device and placed in an oven for drying to obtain a carbon nanotube / polyaniline / aramid composite absorbing fiber.

[0058] In the present invention, the inner diameter of the needle is preferably 20-23G, and the fiber diameter obtained with this inner diameter needle is 0.34-0.6mm. If the diameter is less than 0.34mm, excessive shear force will result in breakage of the aramid nanofibers (reduced strength); if the diameter is greater than 0.6mm, the solvent diffusion rate will slow down and the skin-core structure will delaminate. The spinning solution extrusion speed is preferably 5-20mL / h, more preferably 10-15mL / h. Slow speeds (<5ml / h) may cause excessive swelling of the coagulation bath and uncontrolled fiber diameter; high speeds (>20ml / h) may cause solvent retention and increase porosity after drying. The drying temperature is preferably 40-80°C, more preferably 50-60°C.

[0059] The present invention pre-synthesizes the absorbing filler (CNT / PANI) and then blends it with aramid to form an integral fiber. Compared with in-situ polymerization on the surface of aramid fibers, the present invention has higher structural stability, better interface bonding, can effectively improve the breaking strength, and has a wider effective absorbing bandwidth. In addition, the absorbing filler is embedded in the fiber, and the absorbing performance is more stable.

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

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

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

[0063] The present invention provides a method for preparing a carbon nanotube / polyaniline / aramid composite absorbing fiber, comprising the following steps: A) dispersing polyvinyl pyrrolidone, 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 to polymerize the dispersion to obtain a carbon nanotube / polyaniline; and D) mixing the carbon nanotubes / polyaniline, a base, and aramid in a solvent to obtain a spinning solution, and spinning the spinning solution to obtain a carbon nanotube / polyaniline / aramid composite absorbing fiber. The present invention utilizes carbon nanotubes as a core carrier, with an impedance matching layer formed by in-situ polymerization of polyaniline on the surface, achieving in-situ polymerization to construct a "core-shell" structure. The polyaniline and carbon nanotubes are chemically bonded through in-situ polymerization, and then the fibers are blended and spun with the aramid matrix to achieve integrated molding. Furthermore, the present 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 the fumed silica and the carbon nanotubes / polyaniline. Furthermore, the fumed silica, as a rigid nanoparticle, supports stress and increases the tensile strength of the composite fiber. The insulating properties of the fumed silica neutralize the excessively high dielectric constant of the carbon nanotubes, improving the impedance matching between the material and air.

[0064] To further illustrate the present invention, a carbon nanotube / polyaniline / aramid composite absorbing fiber, its preparation method and application provided by the present invention are described in detail below in conjunction with examples, but it should not be understood as limiting the scope of protection of the present invention.

[0065] Example 1

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

[0067] 0.067 g of silane coupling agent KH550 was added to 20 ml of deionized water and ultrasonically dispersed for 10 min to obtain a uniform dispersion. 1 g of fumed silica was added and magnetically stirred at 70°C for 40 min. After the reaction was completed, the product was centrifuged, washed, and dried to obtain modified fumed silica.

[0068] 2 g of polyvinyl pyrrolidone, 0.5 g of carbon nanotubes, and 0.01 g of modified fumed silica were added to 70 ml of deionized water and sonicated for 30 min to obtain a carbon nanotube dispersion. 7 g of dodecylbenzenesulfonic acid was added and stirred. 1 g of aniline was added dropwise to the dispersion and continued stirring until the system was homogenized to obtain Solution A.

[0069] Dissolve 2.5 g of ammonium persulfate in 15 ml of deionized water and stir for 5 minutes to fully dissolve to obtain solution B;

[0070] B was added dropwise to A and stirred for 12 h for polymerization. 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] The aramid fibers were chopped and ultrasonically washed with methanol and deionized water for 30 min, respectively. The washed fibers were dried in a 60°C oven for 24 h. 2.4 g of the 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 h to obtain an aramid nanofiber / dimethyl sulfoxide dispersion.

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

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

[0075] Example 2

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

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

[0078] 2 g of polyvinyl pyrrolidone, 0.5 g of carbon nanotubes, and 0.01 g of modified fumed silica were added to 70 ml of deionized water and sonicated for 30 min to obtain a carbon nanotube dispersion. 7 g of dodecylbenzenesulfonic acid was added and stirred. 1 g of aniline was added dropwise to the dispersion and continued stirring until the system was homogenized to obtain Solution A.

[0079] Dissolve 2.5 g of ammonium persulfate in 15 ml of deionized water and stir for 5 minutes to fully dissolve to obtain solution B;

[0080] B was added dropwise to A and stirred for 12 h for polymerization. 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] The aramid fibers were chopped and ultrasonically washed with methanol and deionized water for 30 min, respectively. The washed fibers were dried in a 60°C oven for 24 h. 2.4 g of the 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 h to obtain an aramid nanofiber / dimethyl sulfoxide dispersion.

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

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

[0085] Example 3

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

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

[0088] 2 g of polyvinyl pyrrolidone, 0.5 g of carbon nanotubes, and 0.01 g of modified fumed silica were added to 70 ml of deionized water and sonicated for 30 min to obtain a carbon nanotube dispersion. 7 g of dodecylbenzenesulfonic acid was added and stirred. 1 g of aniline was added dropwise to the dispersion and continued stirring until the system was homogenized to obtain Solution A.

[0089] Dissolve 2.5 g of ammonium persulfate in 15 ml of deionized water and stir for 5 minutes to fully dissolve to obtain solution B;

[0090] B was added dropwise to A and stirred for 12 h for polymerization. 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] The aramid fibers were chopped and ultrasonically washed with methanol and deionized water for 30 min, respectively. The washed fibers were dried in a 60°C oven for 24 h. 2.4 g of the 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 h to obtain an aramid nanofiber / dimethyl sulfoxide dispersion.

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

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

[0095] Comparative Example 1

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

[0097] 2 g of polyvinyl pyrrolidone and 0.5 g of carbon nanotubes were added to 70 ml of deionized water and sonicated for 30 min to obtain a carbon nanotube dispersion. 7 g of dodecylbenzenesulfonic acid was added and stirred. 1 g of aniline was added dropwise to the dispersion and stirred continuously until the system was homogenized to obtain solution A.

[0098] Dissolve 2.5 g of ammonium persulfate in 15 ml of deionized water and stir for 5 minutes to fully dissolve to obtain solution B;

[0099] B was added dropwise to A and stirred for 12 h for polymerization. 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] The aramid fibers were chopped and ultrasonically washed with methanol and deionized water for 30 min, respectively. The washed fibers were dried in a 60°C oven for 24 h. 2.4 g of the 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 h to obtain an aramid nanofiber / dimethyl sulfoxide dispersion.

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

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

[0104] Comparative Example 2

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

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

[0107] 2 g of polyvinyl pyrrolidone and 0.5 g of graphene oxide were added to 70 ml of deionized water and ultrasonicated for 30 min to obtain a graphene oxide dispersion. 7 g of dodecylbenzenesulfonic acid was added and stirred. 1 g of aniline was added dropwise to the dispersion and stirred continuously until the system was homogenized to obtain solution A.

[0108] Dissolve 2.5 g of ammonium persulfate in 15 ml of deionized water and stir for 5 minutes to fully dissolve to obtain solution B;

[0109] B was added dropwise to A and stirred for 12 h for polymerization. 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] The aramid fibers were chopped and ultrasonically washed with methanol and deionized water for 30 min, respectively. The washed fibers were dried in a 60°C oven for 24 h. 2.4 g of the 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 h to obtain an aramid nanofiber / dimethyl sulfoxide dispersion.

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

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

[0114] Figure 1This is a scanning electron microscope image of the carbon nanotube / polyaniline / aramid composite fiber produced in Example 3. The composite fiber exhibits wrinkles on its surface, likely due to rapid water evaporation during drying, resulting in excessive fiber shrinkage and a tightening of the cortex. A cross-section reveals the presence of rod-shaped carbon nanotubes / polyaniline dispersed throughout 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 fibers increases, the breaking strength and elongation at break of the fibers both show a decreasing trend. The breaking strength of the composite fibers prepared in Example 3 is 139 MPa.

[0116] Figure 3 Figure 3 is a two-dimensional reflection loss diagram of the carbon nanotube / polyaniline / aramid composite fibers prepared in Examples 1-3. The carbon nanotubes / polyaniline in the composite fiber of Example 3 constitute a conductive path, so the composite fiber prepared in Example 3 has good wave absorption performance, showing an optimal effective absorption bandwidth of 6.85 GHz and a minimum reflection loss of -45.83 dB at a simulated thickness of 2.10 mm.

[0117] Figure 4 This is a thermogravimetric curve of the carbon nanotube / polyaniline / aramid composite fiber prepared in Example 3 of the present invention. The decrease in fiber weight loss at 200°C is attributed to the loss of residual water or solvent in the fiber. The obvious decrease in weight loss at around 400°C may be due to the fact that polyaniline begins to pyrolyze after 400°C. The residual mass fraction is 49.1% at 800°C.

[0118] Figure 5 The stress-strain curve and two-dimensional reflection loss diagram of the carbon nanotube / polyaniline / aramid composite fiber without modified fumed silica prepared in Comparative Example 1. By comparison, it can be seen that the composite fiber prepared without modified fumed silica has a breaking strength of 135 MPa, an optimal 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 can be seen that the composite absorbing fiber added with modified fumed silica prepared in the present invention exhibits better breaking strength and absorbing performance.

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

[0120] Fumed silica modified with the silane coupling agent KH550, as a modifier, effectively improves the dispersion of the composite system and the continuity of the conductive network. KH550 strengthens the interface between the fumed silica and the substrate through chemical bonding, reducing agglomeration and achieving a more uniform dispersion of carbon nanotubes and polyaniline. This promotes the continuity and integrity of the conductive network, thereby enhancing dielectric loss capacity. The insulating properties of fumed silica partially neutralize the excessively high dielectric constant of carbon nanotubes, improving the impedance match between the material and air and reducing 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, thereby improving the interfacial adhesion between the filler and the matrix, reducing stress concentration, and increasing the breaking strength and modulus.

[0122] Figure 6 The stress-strain curve and two-dimensional reflection loss diagram of the graphene / polyaniline / aramid composite fiber prepared in Comparative Example 2. By comparison, it can be seen that the composite fiber prepared using graphene instead of carbon nanotubes as raw material has a breaking strength of 125 MPa, and exhibits an optimal effective absorption bandwidth of 1.82 GHz and a minimum reflection loss of -36.41 dB at a simulated thickness of 1.5 mm. Figure 2 、 3 It can be seen that composite fibers containing carbon nanotubes exhibit superior mechanical and microwave absorption properties. The one-dimensional conductive pathways of carbon nanotubes are more suitable for wet spinning fiber forming processes, which is more conducive to the construction of a continuous conductive network, improve the polyaniline coating effect, and enhance mechanical properties.

[0123] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon nanotube / polyaniline / aramid composite absorbing fiber, comprising the following steps: A) dispersing polyvinyl pyrrolidone, 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 to carry out polymerization to obtain carbon nanotube / polyaniline; D) mixing carbon nanotubes / polyaniline, alkali and aramid in a solvent to obtain a spinning solution, and spinning the spinning solution to obtain a carbon nanotube / polyaniline / aramid composite absorbing fiber.

2. The method for preparing the carbon nanotube / polyaniline / aramid composite absorbing fiber according to claim 1, characterized in that: The silane-modified fumed silica is prepared according to the following steps: The silane coupling agent is mixed with water to obtain a silane coupling agent dispersion, and then fumed silica is added, stirred to react, and the solid-liquid separation is followed by drying to obtain a silane-modified silane coupling agent.

3. The method for preparing the carbon nanotube / polyaniline / aramid composite absorbing fiber according to claim 2, characterized in that: The mass ratio of the silane coupling agent to the fumed silica is 1:(10-20).

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

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

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

1.

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

8. The method for preparing the carbon nanotube / polyaniline / aramid composite absorbing fiber according to claim 1, characterized in that: In the 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).

9. A carbon nanotube / polyaniline / aramid composite absorbing fiber prepared according to the preparation method according to any one of claims 1 to 8.

10. A microwave-absorbing fabric comprising the carbon nanotube / polyaniline / aramid composite microwave-absorbing fiber according to claim 9.

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