Method for preparing kevlar fiber composite aerogel

Abstract

The application provides a preparation method of Kevlar fiber composite aerogel and belongs to the technical field of aerogel. The application takes Kevlar fiber (ANF) as a substrate to prepare deprotonated Kevlar nanofiber hydrogel; takes PVA-co-PE nanofiber as a reinforcing material, adds the prepared PVA-co-PE nanofiber dispersion liquid into the deprotonated Kevlar nanofiber hydrogel; then adds the prepared carboxylated carbon nanotube dispersion liquid, fully reacts and crosslinks; finally, carries out suction filtration, freezing and drying to obtain ANF / PVA-co-PE / CNT composite aerogel, and the prepared composite aerogel has a stable three-dimensional skeleton porous structure, excellent thermal stability and electromagnetic shielding performance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of aerogels, and in particular to a preparation method of a Kevlar fiber composite aerogel. BACKGROUND

[0002] An aerogel is a nanoscale porous material with excellent properties such as ultralow density, low dielectric constant, low thermal conductivity, porous pores, and large specific surface area, and is known as one of the "top ten magical materials changing the world". Common preparation methods include sol-gel method, chemical crosslinking method, decomposition method, and emulsion template method, and the aerogels can be classified into block aerogels, film aerogels and granular aerogels according to the shape. Since the discovery of silica aerogels, various aerogels have been widely studied, such as polymer aerogels, nanocellulose aerogels, aramid nanofiber (ANF) aerogels, MXene aerogels and the like.

[0003] High-performance polymer-based aramid nanofiber aerogels 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 retardation, electromagnetic shielding and the like.

[0004] In the prior art, the patent with the publication number CN111333900B discloses an aramid nanofiber aerogel and a preparation method thereof. In the patent, aramid nanofiber dispersion liquid is mixed with water uniformly, filtered to obtain aramid nanofiber gel, and then an ice template method is adopted to obtain aramid nanofiber aerogel through freezing and vacuum drying. The disadvantage of the application is that the hydrogen bond binding force between single-component aramid nanofibers in the ice template method is weak, the pore structure inside the aramid nanofiber aerogel is not firm, and the aramid nanofiber aerogel is prone to uneven pore distribution, which reduces the mechanical properties and durability of the aerogel. SUMMARY

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

[0006] The application provides a preparation method of a Kevlar fiber composite aerogel, characterized by comprising the following steps:

[0007] S1. Preparing a Kevlar nanofiber hydrogel;

[0008] S2. Preparing a PVA-co-PE nanofiber dispersion liquid;

[0009] S3. Preparing a carbon nanotube dispersion liquid;

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

[0011] S5. Preparation of ANF / PVA-co-PE / CNT / complex aerogel: the ANF / PVA-co-PE / CNT hydrogel is subjected to suction filtration, freezing and drying to obtain the ANF / PVA-co-PE / CNT complex aerogel.

[0012] In the technical scheme of the embodiment, the Kevlar fiber is used as the substrate to prepare the Kevlar nanofiber hydrogel, the PVA-co-PE nanofiber is used as the reinforcing material, the prepared PVA-co-PE nanofiber dispersion liquid is added into the Kevlar nanofiber hydrogel, and then the prepared carbon nanotube dispersion liquid is added for full reaction and crosslinking. The incomplete chemical bonds and oxygen-containing functional groups on the surface of the carbon nanotube, the amide groups (-CONH-) in the Kevlar fiber molecules and the hydroxyl groups (-OH) in the PVA-co-PE are combined through chemical bonds to jointly support the three-dimensional network structure of the aerogel, the interface bonding force between them is strengthened, the mechanical strength and comprehensive performance of the aerogel material are improved, and the effective transmission of stress is ensured. Finally, the ANF / PVA-co-PE / CNT complex aerogel is obtained by suction filtration, freezing and drying, and the prepared complex aerogel has a stable three-dimensional skeleton porous structure, excellent thermal stability and electromagnetic shielding performance.

[0013] In some embodiments, in step S4, the PVA-co-PE nanofiber accounts for 40-60% of the mass fraction of the Kevlar nanofiber, and the carbon nanotube accounts for 20-40% of the mass fraction of the Kevlar nanofiber.

[0014] In this embodiment, the Kevlar nanofiber, the PVA-co-PE nanofiber and the carbon nanotube are compounded in a specific ratio, the incomplete chemical bonds and oxygen-containing functional groups on the surface of the carbon nanotube, the amide groups (-CONH-) in the Kevlar fiber molecules and the hydroxyl groups (-OH) in the PVA-co-PE are fully reacted and crosslinked, and are combined through chemical bonds to jointly support the three-dimensional network structure of the aerogel, so that the aerogel with a stable three-dimensional skeleton porous structure can be prepared.

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

[0016] The Kevlar fiber is cut into 3-5 cm short pieces, and the Kevlar short fibers are washed, dried, and then immersed in a KOH solution, followed by pouring dimethyl sulfoxide, stirring uniformly, adding ultrapure water, stirring, filtering, washing, and then solvent exchanging with a tert-butyl alcohol aqueous solution to prepare the Kevlar nanofiber hydrogel.

[0017] In this embodiment, the method can obtain stable deprotonated Kevlar nanofiber hydrogel, and the deprotonation treatment can improve the purity and performance of the Kevlar nanofiber, so that the Kevlar nanofiber has 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 short fibers are immersed in a KOH solution to provide an alkaline environment for the deprotonation of the Kevlar fibers, and dimethyl sulfoxide can dissolve the Kevlar fibers to 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 liquid includes the following steps:

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

[0023] In this embodiment, the method can obtain a PVA-co-PE nanofiber dispersion liquid with uniform dispersion.

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

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

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

[0027] In this embodiment, the surface properties of the carbon nanotubes can be changed by this step to obtain a carboxylated carbon nanotube dispersion, enhance the dispersibility of the carbon nanotubes in the solvent, and introduce conductive active groups on the surface of the carbon nanotubes to improve the conductivity and the interfacial 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 suction filtration is any one of a nylon filter membrane, a polypropylene filter membrane, and a polyether sulfone filter membrane; the diameter of the filter membrane is 68-72 mm, and the pore size is 0.1-0.5 um.

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

[0031] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented according to the content of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating any creative labor.

[0033] Figure 1 The process flow chart for preparing the Kevlar composite aerogel in Example 1.

[0034] Figure 2 The physical map of the Kevlar composite aerogel prepared in Example 1.

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

[0036] Figure 4 A composite schematic diagram of the Kevlar composite aerogel prepared in Example 1.

[0037] Figure 5 An infrared spectrum of the Kevlar composite aerogel prepared in Example 1 and Comparative Example 6. DETAILED DESCRIPTION

[0038] The embodiments of the technical solutions of the present application are described in detail below. The following examples are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

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

[0040] In this document, reference to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. Those skilled in the art will appreciate that embodiments described herein can be combined with one another.

[0041] In order to solve the problem of poor mechanical properties and durability of existing Kevlar nanofiber aerogels, the present application provides a preparation method of Kevlar fiber composite aerogel. Kevlar nanofiber hydrogel is prepared with Kevlar fiber as the substrate; PVA-co-PE nanofiber dispersion liquid is added to the prepared Kevlar nanofiber hydrogel; then the prepared carbon nanotube dispersion liquid is added, and the three are combined through chemical bonds to support the three-dimensional network structure of the aerogel, strengthen the interfacial bonding force between them, and improve the mechanical strength and comprehensive performance of the aerogel material, ensuring effective stress transfer; finally, ANF / PVA-co-PE / CNT composite aerogel is obtained by vacuum filtration and freeze-drying, and 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 preparation method of Kevlar fiber composite aerogel, characterized in that it comprises the following steps:

[0043] S1. preparing Kevlar nanofiber hydrogel;

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

[0045] S3. Preparation of carbon nanotube dispersion liquid;

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

[0047] S5. Preparation of ANF / PVA-co-PE / CNT / complex aerogel: perform suction filtration, freezing and drying on the ANF / PVA-co-PE / CNT hydrogel to obtain ANF / PVA-co-PE / CNT complex aerogel.

[0048] In the technical scheme of the embodiments of the present application, Kevlar fiber is used as a substrate to prepare Kevlar nanofiber hydrogel, PVA-co-PE nanofiber is used as a reinforcing material, PVA-co-PE nanofiber dispersion liquid is added to the Kevlar nanofiber hydrogel, and then carbon nanotube dispersion liquid is added for sufficient reaction and crosslinking. The incomplete chemical bonds, oxygen-containing functional groups on the surface of the carbon nanotubes, amide groups (-CONH-) in the Kevlar fiber molecules and hydroxyl groups (-OH) in the PVA-co-PE are combined through chemical bonds to jointly support the three-dimensional network structure of the aerogel, strengthen the interfacial bonding force between them, improve the mechanical strength and comprehensive performance of the aerogel material, and ensure effective stress transmission. Finally, suction filtration, freezing and drying are performed to obtain ANF / PVA-co-PE / CNT complex aerogel, and the prepared complex aerogel has a stable three-dimensional skeleton porous structure, excellent thermal stability and electromagnetic shielding performance.

[0049] Further, in some embodiments, in step S4, the PVA-co-PE nanofiber accounts for 40-60% of the mass fraction of the Kevlar nanofiber; and the carbon nanotube accounts for 20-40% of the mass fraction of the Kevlar nanofiber.

[0050] In the technical scheme of the embodiment of the present application, the specific proportion of the Kevlar nanofiber, the PVA-co-PE nanofiber and the carbon nanotube is combined, so that the incomplete chemical bond, the oxygen-containing light group on the surface of the carbon nanotube, the amide group (-CONH-) in the Kevlar fiber molecule and the hydroxyl group (-OH) in the PVA-co-PE are fully reacted and crosslinked, and the three are chemically bonded to jointly support the three-dimensional network structure of the aerogel, so that the aerogel with the porous structure of the stable three-dimensional skeleton can be prepared.

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

[0052] The Kevlar fiber is cut into small pieces of 3-5 cm, the Kevlar short-cut fiber is washed and dried by sodium dodecyl benzene sulfonate, then is immersed in a KOH solution, followed by pouring dimethyl sulfoxide, stirring uniformly, adding ultrapure water, stirring, filtering, washing, and then solvent exchanging by an aqueous tert-butyl alcohol solution to prepare the Kevlar nanofiber hydrogel.

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

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

[0055] In the technical scheme of the embodiment of the present application, the Kevlar short-cut fiber is immersed in the KOH solution, which can provide an alkaline environment for the deprotonation of the Kevlar fiber, and the dimethyl sulfoxide can dissolve the Kevlar fiber, so that the deprotonated Kevlar nanofiber is finally obtained.

[0056] Further, 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 liquid comprises the following steps:

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

[0059] In the technical scheme of the embodiment, the method can obtain the PVA-co-PE nanofiber dispersion with uniform dispersion.

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

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

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

[0063] In the technical scheme of the embodiment, the step can change the surface properties of the carbon nanotubes, obtain the carboxylated carbon nanotube dispersion, enhance the dispersibility of the carbon nanotubes in the solvent, introduce conductive active groups on the surface of the carbon nanotubes to improve the conductivity, and improve the interfacial interaction between the carbon nanotubes and the matrix.

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

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

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

[0067] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are intended to explain the present application only and are not to be construed as limiting the present application. The technical or conditions not specified in the examples are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained commercially.

[0068] Example 1

[0069] The present example provides a preparation method of Kevlar fiber composite aerogel, as shown in Figure 1 The preparation method specifically comprises the following steps:

[0070] (1) Preparation of Kevlar nanofiber hydrogel: 0.6 g of Kevlar fiber was weighed, and the weighed Kevlar fiber was cut into small pieces of about 3 cm. The Kevlar short-cut fiber was washed with sodium dodecyl benzene sulfonate for 30 min, and then placed in a 60°C oven for drying. 0.9 g of KOH was dissolved in 4 mL of ultrapure water, and the dried Kevlar fiber was immersed in the KOH solution. After 30 s of immersion, 100 ml of dimethyl sulfoxide was poured into the mechanical stirring to prepare a Kevlar nanofiber dispersion. 25 ml of the dispersion was taken, 300 ml of ultrapure water was added, and the mixture was stirred, washed, filtered, and solvent exchanged with a tert-butyl alcohol aqueous solution to obtain a Kevlar nanofiber hydrogel with a mass fraction of 0.6%.

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

[0072] (3) Preparation of carbon nanotube dispersion: 100 mg of multi-walled carbon nanotubes was weighed and added to a mixture of 200 ml of concentrated sulfuric acid and 200 ml of nitric acid. The mixture was stirred at 60°C for 4 hours, and then ultrasonically shaken. Then, ultrapure water was added, the mixture was filtered through a microporous membrane, and the solid on the membrane was washed until the filtrate pH was 7. The solid on the membrane was vacuum dried to obtain carboxylated carbon nanotubes. 75 mg of the carboxylated carbon nanotubes was mixed with 50 ml of ultrapure water and ultrasonically shaken to obtain a carbon nanotube dispersion with a mass fraction of 0.15%.

[0073] (4) Preparation of ANF / PVA-co-PE / CNT hydrogel: 25 ml of PVA-co-PE nanofiber dispersion liquid was added to the Kevlar nanofiber hydrogel, and after stirring by the beater, 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 liquid was added, and after stirring by the beater, ANF / PVA-co-PE / CNT hydrogel was obtained.

[0074] (5) Preparation of ANF / PVA-co-PE / CNT / complex aerogel: the ANF / PVA-co-PE / CNT hydrogel was subjected to suction filtration 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 ANF / PVA-co-PE / CNT complex aerogel.

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

[0076] As can be seen from the SEM map in Figure 3 , the prepared ANF / PVA-co-PE / CNT complex aerogel has a special three-dimensional network structure, ANF and PVA-co-PE are crosslinked with each other to form a porous nanofiber network, CNT is entangled with both and randomly distributed in the entire nanofiber network, thereby forming a continuous three-dimensional network structure with conductive effect.

[0077] The formation principle diagram of the structure is shown in Figure 4 , the Kevlar nanofiber is first crosslinked with the PVA-co-PE nanofiber to form a stable two-dimensional crosslinked structure, and then modified with the carbon nanotube to form a porous structure aerogel with a stable three-dimensional skeleton.

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

[0079] Examples 2-3 and Comparative Examples 1-2 respectively provide a preparation method of Kevlar fiber composite aerogel, compared with Example 1, the difference is that the mass fraction of PVA-co-PE nanofiber in Kevlar nanofiber is different, see Table 1 for details, and other steps are substantially the same as those of Example 1, which will not be repeated here.

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

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

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

[0083] Examples 4-5 and Comparative Examples 3-4 respectively provide a preparation method of Kevlar fiber composite aerogel, compared with Example 1, the difference is that the mass fraction of carbon nanotubes in Kevlar nanofiber is different, see Table 2 for details, and other steps are substantially the same as Example 1, which will not be repeated here.

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

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

[0086] Comparative Example 5

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

[0088] Comparative Example 6

[0089] This comparative example provides a preparation method of Kevlar fiber composite aerogel, compared with Example 1, the difference is that carbon nanotubes are not added, and other steps are substantially the same as Example 1, which will not be repeated here.

[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, and the analysis results are shown in Figure 5 .

[0091] From Figure 5 It can be seen that with the introduction of CNT, h shows a stronger absorption peak at 1544.9 cm -1 and 1514 cm -1 , which are respectively attributed to the in-plane vibration of C-C bond and the stretching vibration of C-C ring of CNT, indirectly proving that Kevlar nanofiber and carbon nanotube form stronger hydrogen bond, promoting stress transfer.

[0092] The Kevlar fiber composite aerogels prepared in Examples 1-5 and Comparative Examples 1-6 were subjected to electromagnetic shielding performance and mechanical property detection, and the detection results are shown in Table 3.

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

[0094]

[0095]

[0096] As can be seen from Table 3, with the increase of the PVA-co-PE ratio, the mechanical properties of the Kevlar fiber composite aerogel increase, but when it exceeds 60%, the porosity decreases; as can be seen from Example 1, Examples 4-5 and Comparative Example 4, with the increase of the CNT ratio, the electromagnetic shielding effect of the Kevlar fiber composite aerogel increases, all exceeding 20 dB, indicating that the aerogel with CNT has good absorption loss, but when the CNT content exceeds 40%, the CNT will agglomerate, the mechanical properties of the Kevlar fiber composite aerogel will be greatly reduced, and the porosity will also be reduced; as can be seen from Example 1 and Comparative Example 5, when no PVA-co-PE nanofiber is added, the mechanical properties of the composite aerogel are very poor, and the porosity is also very low; as can be seen from Example 1 and Comparative Example 6, when no CNT is added, the mechanical properties of the composite aerogel are also very poor, and the porosity is also very low.

[0097] In summary, the present application provides a Kevlar nanofiber hydrogel prepared by taking Kevlar fiber as a substrate; a PVA-co-PE nanofiber is used as a reinforcing material, and the prepared PVA-co-PE nanofiber dispersion liquid is added to the Kevlar nanofiber hydrogel; then the prepared carbon nanotube dispersion liquid is added, and cross-linking is fully reacted, the incomplete chemical bonds on the surface of the carbon nanotube, the oxygen-containing light groups, the amide groups (-CONH-) in the Kevlar fiber molecules, and the hydroxyl groups (-OH) in the PVA-co-PE are combined through chemical bonds to jointly support the three-dimensional network structure of the aerogel, strengthen the interfacial bonding force between them, and improve the mechanical strength and comprehensive performance of the aerogel material, ensuring effective stress transfer; finally, the ANF / PVA-co-PE / CNT composite aerogel is obtained by vacuum filtration and freeze-drying, and the prepared composite aerogel has a stable three-dimensional skeleton porous structure, 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 embodiments having the same technical idea and playing the same role and 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, within the scope of the main idea of the present application, various modifications of the embodiments, combination of part of the components in the embodiments to construct other ways can also be included in the scope of the present application.

Claims

1. A method for preparing a Kevlar fiber composite aerogel, characterized by, Comprising the following steps: S1. Preparation of Kevlar nanofiber hydrogel; S2. Preparation of PVA-co-PE nanofiber dispersion; S3. Preparation of carboxylated 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% concentrated hydrochloric acid, 2~4% glutaraldehyde and 7~10% ultrapure water based on the volume fraction of ANF / PVA-co-PE composite solution, then add carboxylated carbon nanotube dispersion, stir evenly, and react for 2~4h to obtain ANF / PVA-co-PE / CNT hydrogel; S5. Preparation of ANF / PVA-co-PE / CNT composite aerogel: filter, freeze and dry the ANF / PVA-co-PE / CNT hydrogel to obtain ANF / PVA-co-PE / CNT composite aerogel; The preparation of the PVA-co-PE nanofiber dispersion comprises the following steps: The PVA-co-PE / CAB composite fiber is obtained by adding cellulose acetate butyrate and PVA-co-PE with a mass ratio of 70~80:20~30 into a co-rotating twin-screw extruder for extrusion, hot stretching and curling, then CAB is removed from the PVA-co-PE / CAB composite fiber with acetone as the solvent to obtain PVA-co-PE nanofiber, and then the PVA-co-PE nanofiber is dispersed in an isopropanol aqueous solution to obtain the PVA-co-PE nanofiber dispersion; The PVA-co-PE nanofiber accounts for 40~60% of the mass fraction of the Kevlar fiber; and the carboxylated carbon nanotube accounts for 20~40% of the mass fraction of the Kevlar fiber.

2. The method for preparing 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 is cut into 3~5cm short pieces, washed and dried with sodium dodecyl benzene sulfonate, then immersed in a KOH solution, followed by pouring into dimethyl sulfoxide, stirring evenly, adding ultrapure water, stirring and filtering, washing, and then solvent exchanging with an aqueous tert-butyl alcohol solution to obtain the deprotonated Kevlar nanofiber hydrogel.

3. The method of claim 2, wherein the Kevlar fiber composite aerogel is prepared by the steps of: The mass volume fraction of the Kevlar nanofiber hydrogel is 0.2~1%.

4. The method of claim 2, wherein the Kevlar fiber composite aerogel is prepared by the steps of: The mass volume ratio of the KOH to the dimethyl sulfoxide is 0.1~1g:100mL, and the volume ratio of the ultrapure water to the dimethyl sulfoxide is 1:5~1:

400.

5. The method for preparing Kevlar fiber composite aerogel according to claim 1, characterized in that, The mass volume fraction of the PVA-co-PE nanofiber dispersion is 0.1~0.5%.

6. The method of claim 1, wherein the Kevlar fiber composite aerogel is prepared by the steps of: In step S3, the preparation of the carbon nanotube dispersion comprises the following steps: The multi-walled carbon nanotube is added into a concentrated sulfuric acid and nitric acid mixture, stirred, then ultrasonically treated, then diluted with ultrapure water, filtered and rinsed until the pH of the filtrate is 7, the obtained black precipitate is vacuum dried to obtain carboxylated carbon nanotubes, then mixed with ultrapure water and ultrasonically shaken to obtain the carboxylated carbon nanotube dispersion.

7. The method for preparing Kevlar fiber composite aerogel according to claim 6, characterized in that, The mass-volume fraction of the carboxylated carbon nanotube dispersion liquid is 0.1-0.5%.

8. The method for preparing 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 polyether sulfone filter membrane; the diameter of the filter membrane is 68-72 mm, and the pore size is 0.1-0.5 um.

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