MXene-coated aramid fiber of coaxial cable structure, preparation method and application thereof in coating flame-retardant polyurethane sponge

Abstract

MXene-coated aramid fiber of coaxial cable structure, preparation method and application thereof in flame-retardant polyurethane sponge coating, relate to the field of MXene-coated aramid fiber preparation. ANF aqueous dispersion is prepared by protonation, the fiber is surface functionalized by generating a polydopamine nanometer thin layer on the surface of ANF through dopamine self-polymerization, and the MXene nanosheet layer is bridged and coated on the surface of ANF to generate coaxial cable structure ANF@MXene nanofiber by using the hydrogen bond action between polydopamine and MXene. Meanwhile, the nanofiber is attached to the surface of FPU by using the dipping method to construct a flame-retardant coating. The hollow tubular structure MXene formed in the pyrolysis and combustion process of ANF@MXene has a limited catalytic effect, can promote the generation of carbon layer and graphitized carbon, thereby reducing the thickness and use amount of the coating and significantly improving the fire safety of FPU, and thus has a wide application prospect in the field of flame-retardant polymers.

Description

Technical Field

[0001] This invention relates to the field of MXene-coated aramid fiber preparation, specifically to an MXene-coated aramid fiber with a coaxial cable structure, its preparation method, and its application in coated flame-retardant polyurethane foam. Background Technology

[0002] Polyurethane foam (FPU) has wide applications in automobiles and home furnishings, but its flammability poses a serious threat to people's lives and property. Applying one or more layers of flame-retardant coating to the three-dimensional skeleton surface of FPU through impregnation technology can effectively improve its flame-retardant properties. However, high flame-retardant efficiency generally requires a large coating thickness and application rate, which not only affects the adhesion between the coating and the substrate but also damages the overall performance of the substrate. Therefore, designing and synthesizing flame-retardant coatings with high flame-retardant efficiency is an urgent problem to be solved. Improving the char formation rate of the coating during pyrolysis and combustion, and promoting the transformation of amorphous carbon into graphitized carbon materials, is one of the effective ways to improve the fire safety of materials.

[0003] MXene nanosheets are highly favored in catalytic dehydrogenation and carbonization due to their diverse surface functional groups and C-Ti-O active sites. Chinese invention patent ZL202110821947.9 describes the construction of MXene-coated positively charged polystyrene (CPS) core-shell nanospheres (CPS@MXene) using a template method. The spatial confinement effect of the MXene shell is utilized to regulate the pyrolysis process of the CPS and promote the conversion of pyrolysis products into graphitized carbon quantum dots (CQDs) at low temperatures (<500℃). This strategy has potential applications in reducing polymer carbonization temperatures and in the catalytic carbonization of flame-retardant polymers.

[0004] Aramid fibers possess excellent mechanical properties, high-temperature resistance, and flame retardancy, making them widely used in aerospace, military defense, and security protection fields. However, due to their limited surface-active functional groups and high inertness, they often exhibit defects such as difficulty in dispersion and weak interfacial bonding strength with the matrix during practical applications, severely impacting the performance improvement of composite materials. Currently, physical methods such as plasma treatment and chemical methods such as surface grafting are commonly used to treat their surfaces. Dopamine (DA) can self-polymerize to form polydopamine (PDA) through chemical reactions. Due to its excellent adhesion, it can form a uniform nanofilm on almost any fiber surface, increasing the fiber's external surface area and improving its bonding ability. Simultaneously, the -NH2 and -OH groups contained in PDA can form hydrogen bonds with the active groups on the surface of nanomaterials such as MXene.

[0005] However, there are few reports on the preparation of ANF@MXene nanofibers with coaxial cable structures by "bridging" MXene nanosheets on the surface of ANF using PDA, and the construction of flame-retardant coatings on the surface of FPU by impregnation method, thereby utilizing the confined catalytic effect of the hollow tubular structure of MXene formed during pyrolysis and combustion to promote the formation of carbon layers or even graphitized carbon to improve the fire safety of FPU. Summary of the Invention

[0006] The purpose of this invention is to provide an MXene-coated aramid fiber coaxial cable structure, its preparation method, and its application in flame-retardant coated polyurethane foam. This invention uses protonated aqueous ANF fiber as the matrix and PDA as the surface treatment agent. MXene is coated onto the ANF surface through hydrogen bonding to form an ANF@MXene coaxial cable structure. Simultaneously, an impregnation method is used to attach ANF@MXene to the FPU surface to form a flame-retardant coating. The hollow tubular MXene structure formed during pyrolysis and combustion of ANF@MXene has a confined catalytic effect, promoting the formation of char layers and graphitized carbon, thereby forming a highly thermally stable barrier layer on the FPU surface to significantly improve the fire safety of the FPU.

[0007] In addition, this invention also provides a method for preparing MXene-coated aramid fibers with a coaxial cable structure. An ANF aqueous dispersion is prepared by protonation. A polydopamine (PDA) nanosheet (PDA-ANF) is generated on the ANF surface through dopamine (DA) self-polymerization to functionalize the fiber. The hydrogen bonding between PDA and MXene "bridges" the MXene nanosheets, which then coat the ANF surface to form MXene-coated aramid fibers (ANF@MXene).

[0008] As a preferred technical solution of the present invention, in the preparation method:

[0009] The method for preparing an ANF aqueous dispersion by protonation is as follows: Poly(p-phenylene terephthalamide) cellulose (PPTA), potassium hydroxide (KOH), dimethyl sulfoxide (DMSO), and deionized water are mixed and protonated by stirring. Excess KOH and DMSO are removed by filtration and washing until pH=7. Then, deionized water is added and dispersed at high speed to obtain an ANF aqueous dispersion. Specifically, 1g of PPTA and 1.5g of KOH are weighed and added to a three-necked flask, followed by the addition of 480mL of DMSO and 20mL of deionized water. The mixture is mechanically stirred for 2–4 hours to obtain an ANF / DMSO dispersion with a concentration of 2mg / mL. 100mL of the ANF / DMSO dispersion is then placed in a three-necked flask, and 200mL of deionized water is added. The mixture is mechanically stirred for 2–4 hours. Excess KOH and DMSO are removed by alternating filtration and washing with anhydrous ethanol and deionized water through an organic microporous membrane until pH=7. The product is then redispersed with deionized water for 1–2 minutes to obtain an ANF aqueous dispersion with a concentration of 1mg / mL.

[0010] The preparation method of PDA-ANF dispersion is as follows: ANF aqueous dispersion, Tris-hydrochloric acid solution and DA solution are mixed and stirred to obtain PDA-ANF dispersion, wherein the mass ratio of DA to ANF is 3:97 to 7:93. Specifically, 100 mL of 1 mg / mL ANF aqueous dispersion is measured into a three-necked flask, and 200 mL of Tris-hydrochloric acid solution and 1.5 to 3.5 mL of 2 mg / mL DA solution are added sequentially. After mechanical stirring in a water bath at 60 to 70 °C for 10 to 15 h, excess Tris-hydrochloric acid solution is removed by filtration through an aqueous microporous membrane until pH = 7. The product is then redispersed with deionized water to obtain PDA-ANF dispersion with a concentration of 1 mg / mL.

[0011] The MXene nanosheet dispersion was prepared by chemical etching: lithium fluoride was added to concentrated hydrochloric acid, and the hydrofluoric acid generated by the reaction was used to etch carbon aluminum titanium. The product was repeatedly centrifuged and washed with deionized water until neutral, and the precipitate was collected. Deionized water was added to the precipitate, and the mixture was sonicated to obtain a dark green dispersion. The dispersion was separated by centrifugation, and the supernatant was taken to obtain a dispersion containing monolayers and / or multiple layers of MXene nanosheets. Specifically, weigh 0.3–0.6 g each of aluminum titanium carbon and lithium fluoride powder and add them to a 50 mL centrifuge tube. Add 2–4 mL of deionized water and 6–8 mL of concentrated hydrochloric acid in sequence. Seal the centrifuge tube opening with plastic wrap and then poke a hole. Stir magnetically at 20–60 rpm for 40–60 h. Centrifuge and wash until the pH reaches 7. Take 100–120 mL of deionized water to dissolve the precipitate. Sonicate the precipitate at 10–20 °C for 40–60 min. Centrifuge at 3000–5000 rpm for 4–8 min and collect the supernatant to obtain a MXene nanosheet dispersion with a concentration of 3–5 mg / mL.

[0012] Preparation method of ANF@MXene dispersion: PDA-ANF dispersion and MXene nanosheet dispersion are stirred to obtain ANF@MXene dispersion, wherein the mass ratio of PDA-ANF to MXene is 1:0.25-1. Specifically, 100 mL of PDA-ANF dispersion with a concentration of 1 mg / mL is measured into a beaker, and 5-33 mL of MXene nanosheet dispersion with a concentration of 3-5 mg / mL is added. After magnetic stirring for 3 h, an ANF@MXene dispersion with a concentration of 1.2-1.7 mg / mL is obtained.

[0013] In addition, this invention also provides the application of ANF@MXene dispersion in the field of flame retardancy. Polyurethane sponge (FPU) is impregnated in an ANF@MXene dispersion with a concentration of 1.2–1.7 mg / mL for 5–10 min, then dried in an oven at 55–65°C for 11–15 h to obtain an ANF@MXene-coated flame-retardant FPU composite material (FPU / ANF@MXene). After combustion, the prepared FPU / ANF@MXene composite material yields hollow tubular MXene with a diameter of 208.4 ± 9.0 nm and carbon quantum dots with a particle size of 4–15 nm in the char layer.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] This invention encapsulates MXene onto the surface of ANF to form a coaxial cable structure ANF@MXene through self-assembly, and then attaches it to the surface of FPU using an impregnation technique to construct a flame-retardant coating. It can utilize the confined catalytic effect of the hollow tubular structure MXene formed by ANF@MXene during pyrolysis and combustion to promote the formation of char layer and graphitized carbon, thereby reducing the coating thickness and usage amount and significantly improving the fire safety of FPU. It has broad application prospects in the field of flame-retardant polymers. Attached Figure Description

[0016] Figure 1 These are scanning electron microscope images of ANF(a) and ANF@MXene(b) nanofibers prepared in Example 1.

[0017] Figure 2 The graphs show the heat release rate curves of the ANF@MXene coated flame-retardant FPU composite material (FPU / ANF@MXene) and the MXene coated flame-retardant FPU composite material (FPU / MXene) prepared in Examples 5 and 6, respectively.

[0018] Figure 3 This is a transmission electron microscope (TEM) image of the hollow tubular MXene formed after combustion of FPU / ANF@MXene prepared in Example 5.

[0019] Figure 4 This is a transmission electron microscope (TEM) image of graphitized carbon (carbon quantum dots) generated after combustion of FPU / ANF@MXene prepared in Example 5. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0021] Example 1

[0022] The preparation of ANF@MXene dispersion includes the following steps:

[0023] 1. Weigh 1g PPTA and 1.5g KOH into a three-necked flask, then add 480mL DMSO and 20mL deionized water sequentially. Stir mechanically for 4h to obtain an ANF / DMSO dispersion with a concentration of 2mg / mL. Take 100mL of the ANF / DMSO dispersion into a three-necked flask, add 200mL deionized water, and stir mechanically for 2h. Filter the product through an organic microporous membrane using alternating suction filtration with anhydrous ethanol and deionized water to remove excess KOH and DMSO until pH=7. Redisperse the product with deionized water for 1min to obtain an ANF aqueous dispersion with a concentration of 1mg / mL.

[0024] 2. Weigh 0.5g each of carbon aluminum titanium and lithium fluoride powder and add them to a 50mL centrifuge tube. Add 2.5mL of deionized water and 7.5mL of concentrated hydrochloric acid. Seal the centrifuge tube with plastic wrap and make a hole. Stir magnetically at 40rpm for 48h. Centrifuge and wash until the pH is 7. Take 100mL of deionized water to dissolve the precipitate. Disperse it ultrasonically at 19℃ for 40min. Centrifuge at 4000rpm for 5min and take the supernatant to obtain MXene nanosheet dispersion with a concentration of 4mg / mL.

[0025] 3. Measure 100 mL of a 1 mg / mL ANF aqueous dispersion into a three-necked flask, and add 200 mL of Tris-hydrochloric acid solution and 1.5 mL of a 2 mg / mL DA solution sequentially. Stir mechanically in a water bath at 65°C for 12 hours. Filter through an aqueous microporous membrane to remove excess Tris-hydrochloric acid solution until the pH reaches 7. Redisperse the product with deionized water to obtain a 1 mg / mL PDA-ANF dispersion, where the mass ratio of DA to ANF is 3:97.

[0026] 4. Measure 100 mL of PDA-ANF dispersion with a concentration of 1 mg / mL into a beaker, add 10.7 mL of MXene nanosheet dispersion with a concentration of 4 mg / mL, and stir magnetically for 3 h to obtain ANF@MXene dispersion with a concentration of 1.3 mg / mL, wherein the mass ratio of PDA-ANF to MXene is 1:0.43.

[0027] Figure 1 These are scanning electron microscope (SEM) images of the ANF(a) and ANF@MXene(b) nanofibers prepared in Example 1. Figure 1 As shown, the prepared ANF@MXene exhibits a coaxial cable structure, with the MXene layered structure completely covering the ANF fibers. Compared to the diameter of ANF (142.1 ± 1.5 nm), the diameter of the ANF@MXene nanofibers increases to 242.6 ± 22.0 nm.

[0028] Example 2

[0029] The preparation of ANF@MXene dispersion includes the following steps:

[0030] 1. Weigh 1g PPTA and 1.5g KOH into a three-necked flask, then add 480mL DMSO and 20mL deionized water sequentially. Stir mechanically for 4h to obtain an ANF / DMSO dispersion with a concentration of 2mg / mL. Take 100mL of the ANF / DMSO dispersion into a three-necked flask, add 200mL deionized water, and stir mechanically for 2h. Filter the product through an organic microporous membrane using alternating suction filtration with anhydrous ethanol and deionized water to remove excess KOH and DMSO until pH=7. Redisperse the product with deionized water for 1min to obtain an ANF aqueous dispersion with a concentration of 1mg / mL.

[0031] 2. Weigh 0.5g each of carbon aluminum titanium and lithium fluoride powder and add them to a 50mL centrifuge tube. Add 2.5mL of deionized water and 7.5mL of concentrated hydrochloric acid. Seal the centrifuge tube with plastic wrap and make a hole. Stir magnetically at 40rpm for 48h. Centrifuge and wash until the pH is 7. Take 100mL of deionized water to dissolve the precipitate. Disperse it ultrasonically at 19℃ for 40min. Centrifuge at 4000rpm for 5min and take the supernatant to obtain MXene nanosheet dispersion with a concentration of 4mg / mL.

[0032] 3. Measure 100 mL of a 1 mg / mL ANF aqueous dispersion into a three-necked flask, add 200 mL of Tris-hydrochloric acid solution and 2.5 mL of a 2 mg / mL DA solution sequentially, and mechanically stir for 12 h in a water bath at 65°C. Filter through an aqueous microporous membrane to remove excess Tris-hydrochloric acid solution until the pH reaches 7. Redisperse the product with deionized water to obtain a 1 mg / mL PDA-ANF dispersion, where the mass ratio of DA to ANF is 5:95.

[0033] 4. Measure 100 mL of PDA-ANF dispersion with a concentration of 1 mg / mL into a beaker, add 10.7 mL of MXene nanosheet dispersion with a concentration of 4 mg / mL, and stir magnetically for 3 h to obtain ANF@MXene dispersion with a concentration of 1.3 mg / mL, wherein the mass ratio of PDA-ANF to MXene is 1:0.43.

[0034] Example 3

[0035] The preparation of ANF@MXene dispersion includes the following steps:

[0036] 1. Weigh 1g PPTA and 1.5g KOH into a three-necked flask, then add 480mL DMSO and 20mL deionized water sequentially. Stir mechanically for 4h to obtain an ANF / DMSO dispersion with a concentration of 2mg / mL. Take 100mL of the ANF / DMSO dispersion into a three-necked flask, add 200mL deionized water, and stir mechanically for 2h. Filter the product through an organic microporous membrane using alternating suction filtration with anhydrous ethanol and deionized water to remove excess KOH and DMSO until pH=7. Redisperse the product with deionized water for 1min to obtain an ANF aqueous dispersion with a concentration of 1mg / mL.

[0037] 2. Weigh 0.5g each of carbon aluminum titanium and lithium fluoride powder and add them to a 50mL centrifuge tube. Add 2.5mL of deionized water and 7.5mL of concentrated hydrochloric acid. Seal the centrifuge tube with plastic wrap and make a hole. Stir magnetically at 40rpm for 48h. Centrifuge and wash until the pH is 7. Take 100mL of deionized water to dissolve the precipitate. Disperse it ultrasonically at 19℃ for 40min. Centrifuge at 4000rpm for 5min and take the supernatant to obtain MXene nanosheet dispersion with a concentration of 4mg / mL.

[0038] 3. Measure 100 mL of a 1 mg / mL ANF aqueous dispersion into a three-necked flask, and add 200 mL of Tris-hydrochloric acid solution and 1.5 mL of a 2 mg / mL DA solution sequentially. Stir mechanically in a water bath at 65°C for 12 hours. Filter through an aqueous microporous membrane to remove excess Tris-hydrochloric acid solution until the pH reaches 7. Redisperse the product with deionized water to obtain a 1 mg / mL PDA-ANF dispersion, where the mass ratio of DA to ANF is 3:97.

[0039] 4. Measure 100 mL of PDA-ANF dispersion with a concentration of 1 mg / mL into a beaker, add 6.25 mL of MXene nanosheet dispersion with a concentration of 4 mg / mL, and stir magnetically for 3 h to obtain ANF@MXene dispersion with a concentration of 1.2 mg / mL, wherein the mass ratio of PDA-ANF to MXene is 1:0.25.

[0040] Example 4

[0041] The preparation of ANF@MXene dispersion includes the following steps:

[0042] 1. Weigh 1g PPTA and 1.5g KOH into a three-necked flask, then add 480mL DMSO and 20mL deionized water sequentially. Stir mechanically for 4h to obtain an ANF / DMSO dispersion with a concentration of 2mg / mL. Take 100mL of the ANF / DMSO dispersion into a three-necked flask, add 200mL deionized water, and stir mechanically for 2h. Filter the product through an organic microporous membrane using alternating suction filtration with anhydrous ethanol and deionized water to remove excess KOH and DMSO until pH=7. Redisperse the product with deionized water for 1min to obtain an ANF aqueous dispersion with a concentration of 1mg / mL.

[0043] 2. Weigh 0.5g each of carbon aluminum titanium and lithium fluoride powder and add them to a 50mL centrifuge tube. Add 2.5mL of deionized water and 7.5mL of concentrated hydrochloric acid. Seal the centrifuge tube with plastic wrap and make a hole. Stir magnetically at 40rpm for 48h. Centrifuge and wash until the pH is 7. Take 100mL of deionized water to dissolve the precipitate. Disperse it ultrasonically at 19℃ for 40min. Centrifuge at 4000rpm for 5min and take the supernatant to obtain MXene nanosheet dispersion with a concentration of 4mg / mL.

[0044] 3. Measure 100 mL of a 1 mg / mL ANF aqueous dispersion into a three-necked flask, and add 200 mL of Tris-hydrochloric acid solution and 1.5 mL of a 2 mg / mL DA solution sequentially. Stir mechanically in a water bath at 65°C for 12 hours. Filter through an aqueous microporous membrane to remove excess Tris-hydrochloric acid solution until the pH reaches 7. Redisperse the product with deionized water to obtain a 1 mg / mL PDA-ANF dispersion, where the mass ratio of DA to ANF is 3:97.

[0045] 4. Measure 100 mL of PDA-ANF dispersion with a concentration of 1 mg / mL into a beaker, add 25 mL of MXene nanosheet dispersion with a concentration of 4 mg / mL, and stir magnetically for 3 h to obtain ANF@MXene dispersion with a concentration of 1.6 mg / mL, wherein the mass ratio of PDA-ANF to MXene is 1:1.

[0046] Example 5

[0047] The preparation of ANF@MXene coated flame-retardant FPU composite material (FPU / ANF@MXene) includes the following steps:

[0048] A 100mm×100mm×10mm FPU sample was impregnated in an ANF@MXene dispersion with a concentration of 1.3mg / mL prepared in Example 1 for 5 minutes. After removal, it was placed in an oven at 60℃ for 12 hours to dry, thus obtaining a flame-retardant coated FPU / ANF@MXene composite material.

[0049] Example 6

[0050] In comparison, the preparation of MXene-coated flame-retardant FPU composite material (FPU / MXene) includes the following steps:

[0051] A 100mm×100mm×10mm FPU sheet was immersed in a 0.4mg / mL MXene nanosheet dispersion for 5 minutes. After removal, it was placed in a 60℃ oven for 12 hours to dry, thus obtaining a flame-retardant coated FPU / MXene composite material.

[0052] Figure 2 These are the heat release rate curves of the ANF@MXene coated flame-retardant FPU composite material (FPU / ANF@MXene) and the MXene coated flame-retardant FPU composite material (FPU / MXene) prepared in Examples 5 and 6, respectively. Figure 2 As shown, the peak heat release rates of FPU / MXene and FPU / ANF@MXene are 259 and 176 kW / m, respectively. 2 Compared to the pure FPU's 459kW / m 2 The fire safety performance of the FPU was reduced by 43.6% and 61.7% respectively. This indicates that ANF@MXene can more effectively improve the fire safety performance of the FPU compared to adding MXene alone.

[0053] Figure 3 and 4 This is a transmission electron microscope (TEM) image of the FPU / ANF@MXene prepared in Example 5 after combustion. The image shows hollow tubular MXene with a diameter of approximately 208.4 ± 9.0 nm and carbon quantum dots with a particle size of approximately 4–15 nm formed within the char layer. This indicates that the hollow tubular MXene structure formed during the pyrolysis and combustion of ANF@MXene has a confined catalytic effect, promoting the formation of the char layer and graphitized carbon. This not only improves the thermal stability of the char layer and significantly enhances the fire safety of the FPU, but also reduces the thickness and amount of flame-retardant coating required.

[0054] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing an ANF@MXene dispersion liquid of MXene-coated aramid fibers, characterized in that, An aqueous dispersion of ANF was prepared by protonation. A polydopamine-PDA nanosheet (PDA-ANF) was then generated on the ANF surface via dopamine (DA) self-polymerization to functionalize the fiber. Hydrogen bonding between PDA and MXene was used to "bridge" the MXene nanosheets, which were then coated onto the ANF surface to form MXene-coated aramid fibers (ANF@MXene) with a coaxial cable structure. The specific steps are as follows: Poly(p-phenylene terephthalamide) cellulose (PPTA), potassium hydroxide (KOH), dimethyl sulfoxide (DMSO), and deionized water were mixed, stirred to protonate, and excess KOH and DMSO were removed by vacuum filtration and washing until pH=7. Then, deionized water was added and dispersed at high speed to obtain an ANF aqueous dispersion. ANF ​​aqueous dispersion, Tris-hydrochloric acid solution and DA solution were mixed and stirred to obtain PDA-ANF dispersion, wherein the mass ratio of DA to ANF was 3:97~7:93; ANF@MXene dispersion was obtained by stirring PDA-ANF dispersion and MXene nanosheet dispersion, wherein the mass ratio of PDA-ANF to MXene was 1:0.25~1; The prepared MXene-coated aramid fiber ANF@MXene has a coaxial cable structure, consisting of MXene nanosheets coated on the surface of the ANF fiber.

2. The method of claim 1, wherein, The specific method for preparing ANF aqueous dispersion by protonation is as follows: Weigh 1g PPTA and 1.5g KOH into a three-necked flask, add 480mL DMSO and 20mL deionized water sequentially, and mechanically stir for 2-4h to obtain an ANF / DMSO dispersion with a concentration of 2mg / mL; Take 100mL of ANF / DMSO dispersion into a three-necked flask, add 200mL of deionized water, and mechanically stir for 2-4h; Filter and wash with anhydrous ethanol and deionized water alternately through an organic microporous membrane to remove excess KOH and DMSO until pH=7; After redispersing the product with deionized water for 1-2min, an ANF aqueous dispersion with a concentration of 1mg / mL is obtained.

3. The method of claim 1, wherein, The specific preparation method of PDA-ANF dispersion is as follows: 100 mL of ANF aqueous dispersion with a concentration of 1 mg / mL is measured into a three-necked flask, and 200 mL of Tris-hydrochloric acid solution and 1.5~3.5 mL of DA solution with a concentration of 2 mg / mL are added sequentially. After mechanical stirring in a water bath at 60~70℃ for 10~15 h, excess Tris-hydrochloric acid solution is removed by filtration through an aqueous microporous membrane until pH=7. The product is redispersed with deionized water to obtain PDA-ANF dispersion with a concentration of 1 mg / mL.

4. The method as described in claim 1, characterized in that, The specific preparation method of ANF@MXene dispersion is as follows: 100 mL of PDA-ANF dispersion with a concentration of 1 mg / mL is measured into a beaker, and 5~33 mL of MXene nanosheet dispersion with a concentration of 3~5 mg / mL is added. After magnetic stirring for 3 h, ANF@MXene dispersion with a concentration of 1.2~1.7 mg / mL is obtained.

5. Use of the ANF@MXene dispersion prepared according to the method of claim 1 in a coating flame-retardant polyurethane sponge, characterized in that, The polyurethane sponge FPU is immersed in the ANF@MXene dispersion liquid with a concentration of 1.2-1.7 mg / mL for 5-10 min, and after being taken out, it is placed in an oven at 55-65 DEG C for 11-15 h for drying, to obtain the ANF@MXene coating flame-retardant FPU composite FPU / ANF@MXene.

6. The use according to claim 5, wherein the compound is ###0002### After the FPU / ANF@MXene composite is burned, hollow tubular MXene with a diameter of 208.4±9.0 nm and carbon quantum dots with a particle size of 4-15 nm are obtained in the carbon layer.

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