Preparation method of Kevlar fiber composite aerogel

Abstract

The invention provides a preparation method of Kevlar fiber composite aerogel, and belongs to the technical field of aerogel. According to the preparation method, Kevlar fiber (ANF) is taken as a substrate, and Kevlar nanofiber hydrogel without protonation is prepared; pVA-co-PE nanofiber is used as a reinforcing material, and the prepared PVA-co-PE nanofiber dispersion liquid is added into the deprotonated Kevlar nanofiber hydrogel; then adding the prepared carboxylated carbon nanotube dispersion liquid, and fully reacting and cross-linking; finally, suction filtration, freezing and drying are conducted, ANF / PVA-co-PE / CNT composite aerogel is obtained, and the prepared composite aerogel has a stable three-dimensional skeleton porous structure and is excellent in thermal stability and electromagnetic shielding performance.

Description

Technical Field

[0001] The invention relates to the technical field of aerogels, and in particular to a method for preparing a Kevlar fiber composite aerogel. Background Art

[0002] Aerogel is a nanoscale porous material with excellent properties such as ultra-low density, low dielectric constant, low thermal conductivity, multiple pores, and large specific surface area. It is known as one of the "10 magical materials that changed the world". Common preparation methods include sol-gel method, chemical crosslinking method, decomposition method, emulsion template method, etc. Aerogel can be divided into block aerogel, film aerogel and granular aerogel according to its morphology. Since the discovery of silica aerogel, various aerogels have been widely studied, such as polymer aerogel, nanocellulose aerogel, aramid nanofiber (ANF) aerogel, MXene aerogel, etc.

[0003] High-performance polymer-based aerogel aramid nanofibers have good mechanical strength, porosity and excellent thermal stability. Studies have shown that aramid nanofiber aerogels have good application prospects in the fields of thermal insulation, flame retardancy, electromagnetic shielding, etc.

[0004] In the prior art, the patent with publication number CN111333900B discloses an aramid nanofiber aerogel and a preparation method thereof. The patent first mixes the aramid nanofiber dispersion with water and filters it to obtain the aramid nanofiber gel, and then uses the ice template method to freeze and vacuum dry to obtain the aramid nanofiber aerogel. The disadvantage of this invention is that the hydrogen bonding force between the single-component aramid nanofibers in the ice template method is weak, and the pore structure inside the aramid nanofiber aerogel is not firm, which easily leads to uneven pore distribution in the aramid nanofiber aerogel, reducing the mechanical properties and durability of the aerogel. Summary of the invention

[0005] In view of the technical problems existing in the background technology, the present application provides a method for preparing a Kevlar fiber composite aerogel, aiming to solve the problems of poor mechanical properties and durability of existing Kevlar nanofiber aerogels.

[0006] The present application provides a method for preparing a Kevlar fiber composite aerogel, which is characterized by comprising the following steps:

[0007] S1. Preparation of Kevlar nanofiber hydrogel;

[0008] S2. Preparation of PVA-co-PE nanofiber dispersion;

[0009] S3. preparing a carbon nanotube dispersion;

[0010] S4. Preparation of ANF / PVA-co-PE / CNT hydrogel: Add PVA-co-PE nanofiber dispersion to Kevlar nanofiber hydrogel, stir evenly, then add 0.02-0.04% of concentrated hydrochloric acid, 2-4% of glutaraldehyde and 7-10% of ultrapure water by volume fraction of ANF / PVA-co-PE composite solution, then add carbon nanotube dispersion, stir evenly, and react for 2-4 hours to obtain ANF / PVA-co-PE / CNT hydrogel;

[0011] S5. Preparation of ANF / PVA-co-PE / CNT / composite aerogel: The ANF / PVA-co-PE / CNT hydrogel was filtered, frozen and dried to obtain the ANF / PVA-co-PE / CNT composite aerogel.

[0012] In the technical solution of the embodiment of the present application, Kevlar fiber is used as a substrate to prepare a Kevlar nanofiber hydrogel; PVA-co-PE nanofiber is used as a reinforcing material, and the prepared PVA-co-PE nanofiber dispersion is added to the Kevlar nanofiber hydrogel; then the prepared carbon nanotube dispersion is added, and the cross-linking is fully reacted. The incomplete chemical bonds and oxygen-containing functional groups on the surface of the carbon nanotubes, the amide groups (-CONH-) in the Kevlar fiber molecules, and the hydroxyl groups (-OH) in the PVA-co-PE are used to support the three-dimensional network structure of the aerogel through chemical bonds, thereby strengthening the interfacial bonding force between each other, improving the mechanical strength and comprehensive performance of the aerogel material, and ensuring the effective transfer of stress; finally, filtration and freeze-drying are performed to obtain the ANF / PVA-co-PE / CNT composite aerogel, and the prepared composite aerogel has a stable three-dimensional skeleton porous structure, and has excellent thermal stability and electromagnetic shielding performance.

[0013] In some embodiments, in step S4, the PVA-co-PE nanofibers account for 40-60% of the mass fraction of the Kevlar nanofibers; and the carbon nanotubes account for 20-40% of the mass fraction of the Kevlar nanofibers.

[0014] In this embodiment, a specific ratio of Kevlar nanofibers, PVA-co-PE nanofibers and carbon nanotubes is composited, so that the incomplete chemical bonds and oxygen-containing functional groups on the surface of the carbon nanotubes, the amide groups (-CONH-) in the Kevlar fiber molecules, and the hydroxyl groups (-OH) in the PVA-co-PE can fully react and cross-link, and jointly support the three-dimensional network structure of the aerogel through chemical bonds, thereby obtaining an aerogel with a porous structure with a stable three-dimensional skeleton.

[0015] In some embodiments, in step S1, the preparation of the Kevlar nanofiber hydrogel comprises the following steps:

[0016] The Kevlar fiber was cut into small segments of 3 to 5 cm, washed and dried with sodium dodecylbenzene sulfonate, immersed in a KOH solution, and then poured into dimethyl sulfoxide, stirred evenly, and then added with ultrapure water, stirred, filtered, washed, and then exchanged with a tert-butyl alcohol aqueous solution solvent to prepare a Kevlar nanofiber hydrogel.

[0017] In this embodiment, a stable deprotonated Kevlar nanofiber hydrogel can be obtained by this method, and the deprotonation treatment can improve the purity and performance of the Kevlar nanofiber, making it have a high specific surface area, high mechanical strength and good chemical stability.

[0018] In some embodiments, in step S1, the mass volume ratio of KOH to dimethyl sulfoxide is 0.1-1 g:100 mL, and the volume ratio of ultrapure water to dimethyl sulfoxide is 1:5-1:400.

[0019] In this embodiment, the Kevlar chopped fibers are immersed in a KOH solution to provide an alkaline environment for the deprotonation of the Kevlar fibers; dimethyl sulfoxide can dissolve the Kevlar fibers, and finally obtain deprotonated Kevlar nanofibers.

[0020] In some embodiments, in step S1, the mass volume fraction of the Kevlar nanofiber hydrogel is 0.2-1%.

[0021] In some embodiments, in step S2, the preparation of the PVA-co-PE nanofiber dispersion comprises the following steps:

[0022] Cellulose acetate butyrate and PVA-co-PE in a mass ratio of 70-80:20-30 are added to a co-rotating twin-screw extruder, extruded, hot stretched, and curled to obtain PVA-co-PE / CAB composite fibers, and then CAB is removed from the PVA-co-PE / CAB composite fibers using acetone as a solvent to obtain PVA-co-PE nanofibers. Subsequently, the PVA-co-PE nanofibers are dispersed in an aqueous solution of isopropanol to prepare a PVA-co-PE nanofiber dispersion.

[0023] In this embodiment, a uniformly dispersed PVA-co-PE nanofiber dispersion can be obtained by this method.

[0024] In some embodiments, in step S2, the mass volume fraction of the PVA-co-PE nanofiber dispersion is 0.1-0.5%.

[0025] In some embodiments, in step S3, the preparation of the carbon nanotube dispersion comprises the following steps:

[0026] Multi-walled carbon nanotubes are added to a mixture of concentrated sulfuric acid and nitric acid, stirred, and then ultrasonically treated. The mixture is then diluted with ultrapure water, filtered, and rinsed until the pH value of the filtrate is 7. The resulting black precipitate is vacuum dried to obtain carboxylated carbon nanotubes. The mixture is then mixed with ultrapure water and ultrasonically shaken to obtain a carboxylated carbon nanotube dispersion.

[0027] In this embodiment, this step can change the surface properties of the carbon nanotubes to obtain a carboxylated carbon nanotube dispersion, enhance its dispersibility in the solvent, and introduce conductive active groups on the surface of the carbon nanotubes to improve its conductivity and enhance the interface interaction between the carbon nanotubes and the matrix.

[0028] In some embodiments, in step S3, the mass volume fraction of the carbon nanotube dispersion is 0.1-0.5%.

[0029] In some embodiments, in step S5, the filter membrane used for the filtration is any one of a nylon filter membrane, a polypropylene filter membrane, and a polyethersulfone filter membrane; the diameter of the filter membrane is 68 to 72 mm, and the pore size is 0.1 to 0.5 um.

[0030] In this embodiment, the cross-linked fibers are filtered out through a filter membrane with a specific pore size to obtain a cross-linked ANF / PVA-co-PE / CNT composite aerogel.

[0031] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 This is a process flow chart for preparing Kevlar composite aerogel in Example 1.

[0034] Figure 2 This is a physical picture of the Kevlar composite aerogel prepared in Example 1.

[0035] Figure 3 (a), (b) and (c) are SEM images of the Kevlar composite aerogel prepared in Example 1 at 200 times, 500 times and 1000 times, respectively.

[0036] Figure 4 This is a composite principle diagram of the Kevlar composite aerogel prepared in Example 1.

[0037] Figure 5 The infrared spectra of the Kevlar composite aerogels prepared in Example 1 and Comparative Example 6 are shown. DETAILED DESCRIPTION

[0038] The following is a detailed description of the embodiments of the technical solution of the present application. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms "including" and "having" and any variations thereof used herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0040] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0041] In order to solve the problem of poor mechanical properties and durability of existing Kevlar nanofiber aerogels, the present application provides a method for preparing a Kevlar fiber composite aerogel. Kevlar fiber is used as a substrate to prepare a Kevlar nanofiber hydrogel; PVA-co-PE nanofiber is used as a reinforcing material, and the prepared PVA-co-PE nanofiber dispersion is added to the Kevlar nanofiber hydrogel; then the prepared carbon nanotube dispersion is added, fully reacted and cross-linked, and the incomplete chemical bonds and oxygen-containing photoenergy groups on the surface of the carbon nanotubes, the amide groups (-CONH-) in the Kevlar fiber molecules, and the hydroxyl groups (-OH) in the PVA-co-PE are used. The three are combined through chemical bonds to jointly support the three-dimensional network structure of the aerogel, strengthen the interface bonding force between each other, improve the mechanical strength and comprehensive performance of the aerogel material, and ensure the effective transmission of stress; finally, the ANF / PVA-co-PE / CNT composite aerogel is obtained by filtration and freeze drying. The prepared composite aerogel has a stable three-dimensional skeleton porous structure, excellent thermal stability and electromagnetic shielding performance.

[0042] The present application provides a method for preparing a Kevlar fiber composite aerogel, which is characterized by comprising the following steps:

[0043] S1. Preparation of Kevlar nanofiber hydrogel;

[0044] S2. Preparation of PVA-co-PE nanofiber dispersion;

[0045] S3. preparing a carbon nanotube dispersion;

[0046] S4. Preparation of ANF / PVA-co-PE / CNT hydrogel: Add PVA-co-PE nanofiber dispersion to Kevlar nanofiber hydrogel, stir evenly, then add 0.02-0.04% of concentrated hydrochloric acid, 2-4% of glutaraldehyde and 7-10% of ultrapure water by volume fraction of ANF / PVA-co-PE composite solution, then add carbon nanotube dispersion, stir evenly, and react for 2-4 hours to obtain ANF / PVA-co-PE / CNT hydrogel;

[0047] S5. Preparation of ANF / PVA-co-PE / CNT / composite aerogel: The ANF / PVA-co-PE / CNT hydrogel was filtered, frozen and dried to obtain the ANF / PVA-co-PE / CNT composite aerogel.

[0048] In the technical solution of the embodiment of the present application, Kevlar fiber is used as a substrate to prepare a Kevlar nanofiber hydrogel; PVA-co-PE nanofiber is used as a reinforcing material, and the prepared PVA-co-PE nanofiber dispersion is added to the Kevlar nanofiber hydrogel; then the prepared carbon nanotube dispersion is added, and the cross-linking is fully reacted. The incomplete chemical bonds and oxygen-containing functional groups on the surface of the carbon nanotubes, the amide groups (-CONH-) in the Kevlar fiber molecules, and the hydroxyl groups (-OH) in the PVA-co-PE are used to support the three-dimensional network structure of the aerogel through chemical bonds, thereby strengthening the interfacial bonding force between each other, improving the mechanical strength and comprehensive performance of the aerogel material, and ensuring the effective transfer of stress; finally, filtration and freeze-drying are performed to obtain the ANF / PVA-co-PE / CNT composite aerogel, and the prepared composite aerogel has a stable three-dimensional skeleton porous structure, and has excellent thermal stability and electromagnetic shielding performance.

[0049] Furthermore, in some embodiments, in step S4, the PVA-co-PE nanofibers account for 40-60% of the mass fraction of the Kevlar nanofibers; and the carbon nanotubes account for 20-40% of the mass fraction of the Kevlar nanofibers.

[0050] In the technical solution of the embodiment of the present application, a specific proportion of Kevlar nanofibers, PVA-co-PE nanofibers and carbon nanotubes are composited, so that the incomplete chemical bonds on the surface of the carbon nanotubes, the oxygen-containing photoenergy groups, the amide groups (-CONH-) in the Kevlar fiber molecules, and the hydroxyl groups (-OH) in the PVA-co-PE can fully react and cross-link, and jointly support the three-dimensional network structure of the aerogel through chemical bonds, thereby obtaining an aerogel with a porous structure with a stable three-dimensional skeleton.

[0051] Furthermore, in some embodiments, in step S1, the preparation of the Kevlar nanofiber hydrogel comprises the following steps:

[0052] The Kevlar fiber was cut into small segments of 3 to 5 cm, washed and dried with sodium dodecylbenzene sulfonate, immersed in a KOH solution, and then poured into dimethyl sulfoxide, stirred evenly, and then added with ultrapure water, stirred, filtered, washed, and then exchanged with a tert-butyl alcohol aqueous solution solvent to prepare a Kevlar nanofiber hydrogel.

[0053] In the technical solution of the embodiment of the present application, a stable deprotonated Kevlar nanofiber hydrogel can be obtained by this method, and the deprotonation treatment can improve the purity and performance of the Kevlar nanofiber, so that it has a high specific surface area, high mechanical strength and good chemical stability.

[0054] Furthermore, in some embodiments, in step S1, the mass volume ratio of KOH to dimethyl sulfoxide is 0.1-1 g:100 mL, and the volume ratio of ultrapure water to dimethyl sulfoxide is 1:5-1:400.

[0055] In the technical solution of the embodiment of the present application, the Kevlar chopped fibers are immersed in a KOH solution to provide an alkaline environment for the deprotonation of the Kevlar fibers; dimethyl sulfoxide can dissolve the Kevlar fibers, and finally obtain deprotonated Kevlar nanofibers.

[0056] Furthermore, in some embodiments, in step S1, the mass volume fraction of the Kevlar nanofiber hydrogel is 0.2-1%.

[0057] Further, in some embodiments, in step S2, the preparation of the PVA-co-PE nanofiber dispersion comprises the following steps:

[0058] Cellulose acetate butyrate and PVA-co-PE in a mass ratio of 70-80:20-30 are added to a co-rotating twin-screw extruder, extruded, hot stretched, and curled to obtain PVA-co-PE / CAB composite fibers, and then CAB is removed from the PVA-co-PE / CAB composite fibers using acetone as a solvent to obtain PVA-co-PE nanofibers. Subsequently, the PVA-co-PE nanofibers are dispersed in an aqueous solution of isopropanol to prepare a PVA-co-PE nanofiber dispersion.

[0059] In the technical solution of the embodiment of the present application, a uniformly dispersed PVA-co-PE nanofiber dispersion can be obtained by this method.

[0060] Furthermore, in some embodiments, in step S2, the mass volume fraction of the PVA-co-PE nanofiber dispersion is 0.1-0.5%.

[0061] Furthermore, in some embodiments, in step S3, the preparation of the carbon nanotube dispersion comprises the following steps:

[0062] Multi-walled carbon nanotubes are added to a mixture of concentrated sulfuric acid and nitric acid, stirred, and then ultrasonically treated. The mixture is then diluted with ultrapure water, filtered, and rinsed until the pH value of the filtrate is 7. The resulting black precipitate is vacuum dried to obtain carboxylated carbon nanotubes. The mixture is then mixed with ultrapure water and ultrasonically shaken to obtain a carboxylated carbon nanotube dispersion.

[0063] In the technical solution of the embodiment of the present application, this step can change the surface properties of the carbon nanotubes to obtain a carboxylated carbon nanotube dispersion, enhance its dispersibility in the solvent, and introduce conductive active groups on the surface of the carbon nanotubes, thereby improving its conductivity and enhancing the interface interaction between the carbon nanotubes and the matrix.

[0064] Furthermore, in some embodiments, in step S3, the mass volume fraction of the carbon nanotube dispersion is 0.1-0.5%.

[0065] Furthermore, in some embodiments, in step S5, the filter membrane used for the filtration is any one of a nylon filter membrane, a polypropylene filter membrane, and a polyethersulfone filter membrane; the diameter of the filter membrane is 68 to 72 mm, and the pore size is 0.1 to 0.5 um.

[0066] In the technical solution of the embodiment of the present application, the cross-linked fibers are filtered out through a filter membrane with a specific pore size to obtain a cross-linked ANF / PVA-co-PE / CNT composite aerogel.

[0067] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0068] Example 1

[0069] This embodiment provides a method for preparing a Kevlar fiber composite aerogel. Figure 1 As shown, the specific steps include:

[0070] (1) Preparation of Kevlar nanofiber hydrogel: Weigh 0.6 g of Kevlar fiber and cut it into small pieces of about 3 cm. Wash the chopped Kevlar fiber with sodium dodecylbenzene sulfonate for 30 min and then dry it in a 60°C oven. Dissolve 0.9 g of KOH in 4 mL of ultrapure water and immerse the dried Kevlar fiber in the KOH solution. After immersion for 30 s, pour in 100 ml of dimethyl sulfoxide for mechanical stirring to prepare a Kevlar nanofiber dispersion. Take 25 ml of the dispersion, add 300 ml of ultrapure water, stir, wash, filter, and then exchange with a tert-butyl alcohol aqueous solution solvent to obtain a Kevlar nanofiber hydrogel with a mass volume fraction of 0.6%.

[0071] (2) Preparation of PVA-co-PE nanofiber dispersion: A mixture of CAB and PVA-co-PE in a mass ratio of 80:20 was added into a co-rotating twin-screw extruder, and the blend was extruded. The mixture was heat-stretched and curled at 30°C to obtain PVA-co-PE / CAB composite fibers. The PVA-co-PE / CAB composite fibers were then added into an acetone solution and stirred to obtain PVA-co-PE nanofibers. Subsequently, the PVA-co-PE nanofibers were dispersed in an aqueous solution of isopropanol using a high-speed shearing machine to prepare a PVA-co-PE nanofiber dispersion with a mass volume fraction of 0.3%.

[0072] (3) Preparation of carbon nanotube dispersion: Weigh 100 mg of multi-walled carbon nanotubes, add to a mixture of 200 ml of concentrated sulfuric acid and 200 ml of nitric acid, stir at 60° C. for 4 hours, and then ultrasonically vibrate; then add ultrapure water, filter through a microporous filter membrane, and rinse the solid on the membrane until the filtrate has a pH of 7, and vacuum dry the solid on the membrane to obtain carboxylated carbon nanotubes; take 75 mg of the carboxylated carbon nanotubes, mix with 50 ml of ultrapure water, and ultrasonically vibrate to obtain a carbon nanotube dispersion with a mass volume fraction of 0.15%.

[0073] (4) Preparation of ANF / PVA-co-PE / CNT hydrogel: 25 ml of PVA-co-PE nanofiber dispersion was added to the Kevlar nanofiber hydrogel, and after stirring with a blender, 0.02 ml of concentrated hydrochloric acid, 2 ml of glutaraldehyde and 10 ml of ultrapure water were added, and then 30 ml of carbon nanotube dispersion was added and stirred with a blender to obtain ANF / PVA-co-PE / CNT hydrogel.

[0074] (5) Preparation of ANF / PVA-co-PE / CNT / composite aerogel: The ANF / PVA-co-PE / CNT hydrogel was filtered through a nylon filter membrane with a diameter of 70 mm and a pore size of 0.3 um, and then freeze-dried to obtain the ANF / PVA-co-PE / CNT composite aerogel.

[0075] The physical image and SEM images of the ANF / PVA-co-PE / CNT composite aerogel prepared in this example at 200 times, 500 times, and 1000 times are shown in Figure 2 , respectively. Figure 2 and Figure 3 As shown in (a), (b) and (c).

[0076] Depend on Figure 3 It can be seen from the SEM image in that the prepared ANF / PVA-co-PE / CNT composite aerogel has a special three-dimensional network structure. ANF and PVA-co-PE are cross-linked to form a porous nanofiber network, and CNTs are entangled with the two and randomly distributed in the entire nanofiber network, thus forming a continuous three-dimensional network structure with conductive effect.

[0077] The formation principle diagram of this structure is shown in Figure 4 As shown, Kevlar nanofibers are first cross-linked with PVA-co-PE nanofibers to form a stable two-dimensional cross-linked structure, and then modified with carbon nanotubes to form an aerogel with a porous structure having a stable three-dimensional skeleton.

[0078] Examples 2 to 3 and Comparative Examples 1 to 2

[0079] Examples 2 to 3 and Comparative Examples 1 to 2 respectively provide a method for preparing a Kevlar fiber composite aerogel. Compared with Example 1, the difference is that the mass fraction of PVA-co-PE nanofibers in the Kevlar nanofibers is different, as shown in Table 1. The other steps are roughly the same as those in Example 1 and will not be repeated here.

[0080] Table 1 Mass fraction of PVA-co-PE nanofibers to Kevlar nanofibers in Examples 2 to 3 and Comparative Example 1

[0081] Example / Comparative Example Example 2 Example 3 Comparative Example 1 Comparative Example 2 Proportion 40％ 60％ 30％ 70％

[0082] Examples 4 to 5 and Comparative Examples 3 to 4

[0083] Examples 4 to 5 and Comparative Examples 3 to 4 respectively provide a method for preparing a Kevlar fiber composite aerogel. Compared with Example 1, the difference is that the mass fraction of carbon nanotubes in the Kevlar nanofibers is different, as shown in Table 2. The other steps are roughly the same as those in Example 1 and will not be repeated here.

[0084] Table 2 Mass fraction of carbon nanotubes in Kevlar nanofibers in Examples 4-5 and Comparative Examples 3-4

[0085] Example / Comparative Example Example 4 Example 5 Comparative Example 3 Comparative Example 4 Proportion 20％ 40％ 10％ 50％

[0086] Comparative Example 5

[0087] This comparative example provides a method for preparing a Kevlar fiber composite aerogel. Compared with Example 1, the difference is that PVA-co-PE nanofibers are not added, and the other steps are substantially the same as those in Example 1, which will not be repeated here.

[0088] Comparative Example 6

[0089] This comparative example provides a method for preparing a Kevlar fiber composite aerogel. Compared with Example 1, the difference is that no carbon nanotubes are added. The other steps are substantially the same as those in Example 1 and will not be described again.

[0090] The ANF / PVA-co-PE / CNT and ANF / PVA-co-PE composite aerogels prepared in Example 1 and Comparative Example 6 were subjected to FTIR analysis. The analysis results are as follows: Figure 5 shown.

[0091] Depend on Figure 5 It can be seen that with the introduction of CNT, h is at 1544.9 cm -1 and 1514cm -1 The related stronger absorption peaks are attributed to the in-plane vibration of the CC bond and the stretching vibration of the CC ring of CNT, which indirectly proves that Kevlar nanofibers form stronger hydrogen bonds with carbon nanotubes and promote stress transfer.

[0092] The electromagnetic shielding performance and mechanical properties of the Kevlar fiber composite aerogels prepared in Examples 1 to 5 and Comparative Examples 1 to 6 were tested, and the test results are shown in Table 3.

[0093] Table 3 Test results of electromagnetic shielding performance and mechanical properties of Kevlar fiber composite aerogels prepared in Examples 1 to 5 and Comparative Examples 1 to 6

[0094]

[0095]

[0096] It can be seen from Examples 1 to 3 and Comparative Examples 1 to 2 in Table 3 that with the increase of the PVA-co-PE ratio, the mechanical properties of the Kevlar fiber composite aerogel increase accordingly, but when it exceeds 60%, the porosity decreases; it can be seen from Example 1, Examples 4 to 5 and Comparative Example 4 that with the increase of the CNT ratio, the electromagnetic shielding effect of the Kevlar fiber composite aerogel increases accordingly, all exceeding 20 dB, indicating that the aerogel with the addition of CNT has good absorption loss, but when the CNT content exceeds 40%, the CNT will agglomerate, and the mechanical properties of the Kevlar fiber composite aerogel will be greatly reduced, and the porosity will also be reduced; it can be seen from Example 1 and Comparative Example 5 that when PVA-co-PE nanofibers are not added, the mechanical properties of the composite aerogel are extremely poor, and the porosity is also very low; it can be seen from Example 1 and Comparative Example 6 that when CNT is not added, the mechanical properties of the composite aerogel are also poor, and the porosity is also very low.

[0097] In summary, the present application provides a method of preparing a Kevlar nanofiber hydrogel with Kevlar fiber as a substrate; using PVA-co-PE nanofiber as a reinforcing material, adding the prepared PVA-co-PE nanofiber dispersion to the Kevlar nanofiber hydrogel; then adding the prepared carbon nanotube dispersion, fully reacting and cross-linking, utilizing the incomplete chemical bonds and oxygen-containing photoenergy groups on the surface of the carbon nanotubes, the amide groups (-CONH-) in the Kevlar fiber molecules, and the hydroxyl groups (-OH) in the PVA-co-PE, the three of which are combined through chemical bonds to jointly support the three-dimensional network structure of the aerogel, strengthen the interface bonding force between each other, improve the mechanical strength and comprehensive performance of the aerogel material, and ensure the effective transfer of stress; finally, filtering and freeze-drying are performed to obtain the ANF / PVA-co-PE / CNT composite aerogel, and the prepared composite aerogel has a stable three-dimensional skeleton porous structure, and has excellent thermal stability and electromagnetic shielding performance.

[0098] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a Kevlar fiber composite aerogel, characterized in that: The following steps are involved: S1. Preparation of Kevlar nanofiber hydrogel; S2. Preparation of PVA-co-PE nanofiber dispersion; S3. preparing a carbon nanotube dispersion; S4. Preparation of ANF / PVA-co-PE / CNT hydrogel: Add PVA-co-PE nanofiber dispersion to Kevlar nanofiber hydrogel, stir evenly, then add 0.02-0.04% of concentrated hydrochloric acid, 2-4% of glutaraldehyde and 7-10% of ultrapure water by volume fraction of ANF / PVA-co-PE composite solution, then add carbon nanotube dispersion, stir evenly, and react for 2-4 hours to obtain ANF / PVA-co-PE / CNT hydrogel; S5. Preparation of ANF / PVA-co-PE / CNT composite aerogel: The ANF / PVA-co-PE / CNT hydrogel was filtered, frozen and dried to obtain the ANF / PVA-co-PE / CNT composite aerogel.

2. The method for preparing the Kevlar fiber composite aerogel according to claim 1, characterized in that: In step S4, the PVA-co-PE nanofibers account for 40 to 60% of the mass fraction of the Kevlar fibers; and the carbon nanotubes account for 20 to 40% of the mass fraction of the Kevlar fibers.

3. The method for preparing the Kevlar fiber composite aerogel according to claim 1, characterized in that: In step S1, the preparation of the Kevlar nanofiber hydrogel comprises the following steps: The Kevlar fiber was cut into small segments of 3 to 5 cm, washed and dried with sodium dodecylbenzene sulfonate, immersed in a KOH solution, and then poured into dimethyl sulfoxide and stirred evenly. Ultrapure water was added, stirred, filtered, washed, and then solvent exchanged with tert-butyl alcohol aqueous solution to prepare a deprotonated Kevlar nanofiber hydrogel.

4. The method for preparing the Kevlar fiber composite aerogel according to claim 3, characterized in that: The mass volume fraction of the Kevlar nanofiber hydrogel is 0.2-1%.

5. The method for preparing the Kevlar fiber composite aerogel according to claim 3, characterized in that: The mass volume ratio of the KOH to the dimethyl sulfoxide is 0.1-1 g:100 mL, and the volume ratio of the ultrapure water to the dimethyl sulfoxide is 1:5-1:

400.

6. The method for preparing the Kevlar fiber composite aerogel according to claim 1, characterized in that: In step S2, the preparation of the PVA-co-PE nanofiber dispersion comprises the following steps: Cellulose acetate butyrate and PVA-co-PE in a mass ratio of 70-80:20-30 are added to a co-rotating twin-screw extruder, extruded, hot stretched, and curled to obtain PVA-co-PE / CAB composite fibers, and then CAB is removed from the PVA-co-PE / CAB composite fibers using acetone as a solvent to obtain PVA-co-PE nanofibers. Subsequently, the PVA-co-PE nanofibers are dispersed in an aqueous solution of isopropanol to prepare a PVA-co-PE nanofiber dispersion.

7. The method for preparing the Kevlar fiber composite aerogel according to claim 6, characterized in that: The mass volume fraction of the PVA-co-PE nanofiber dispersion is 0.1-0.5%.

8. The method for preparing the Kevlar fiber composite aerogel according to claim 1, characterized in that: In step S3, the preparation of the carbon nanotube dispersion comprises the following steps: Multi-walled carbon nanotubes are added to a mixture of concentrated sulfuric acid and nitric acid, stirred, and then ultrasonically treated. The mixture is then diluted with ultrapure water, filtered, and rinsed until the pH value of the filtrate is 7. The resulting black precipitate is vacuum dried to obtain carboxylated carbon nanotubes. The mixture is then mixed with ultrapure water and ultrasonically shaken to obtain a carboxylated carbon nanotube dispersion.

9. The method for preparing the Kevlar fiber composite aerogel according to claim 8, characterized in that: The mass volume fraction of the carbon nanotube dispersion is 0.1-0.5%.

10. The method for preparing the Kevlar fiber composite aerogel according to claim 1, characterized in that: In step S5, the filter membrane used for the filtration is any one of a nylon filter membrane, a polypropylene filter membrane, and a polyethersulfone filter membrane; the diameter of the filter membrane is 68 to 72 mm, and the pore size is 0.1 to 0.5 um.

Images