Modified graphene oxide-based aramid nanofiber paper and method of making and use thereof

Abstract

The application discloses a modified graphene oxide-based aramid nanofiber paper and a preparation method and application thereof, and belongs to the technical field of flame-retardant nanomaterials. The modified graphene oxide-based aramid nanofiber paper is prepared by the following method: uniformly mixing a nitrogen source and an acid compound by constant-temperature stirring to prepare a modifier mixed solution; hydrothermally mixing graphene oxide solution and the modifier mixed solution to obtain a modified graphene oxide gel; mixing strong alkali, dimethyl sulfoxide and aramid nanofiber to obtain aramid nanofiber suspension; mixing the modified graphene oxide gel and the aramid nanofiber suspension to obtain a hydrogel; and drying the hydrogel to obtain the modified graphene oxide-based aramid nanofiber paper. The modified graphene oxide-based aramid nanofiber paper has high electrical performance and mechanical performance, excellent insulation and flame-retardant property, and greatly improves the corresponding speed of a fire alarm. The working performance of a fire early warning sensor can be improved.

Description

Technical Field

[0001] This invention belongs to the field of flame-retardant nanomaterials technology, and specifically relates to a modified graphene oxide-based aramid nanofiber paper, its preparation method, and its application. Background Technology

[0002] Fires caused by flammable materials occur frequently, resulting not only in enormous loss of life and property and medical expenses, but also in harmful impacts on the global climate and living environment. Meanwhile, with population growth and increasing demand for modern high-rise buildings, the monitoring and early warning systems for high-rise fires have become indispensable. Currently, the mainstream fire prevention measures fall into two categories: one utilizes flame retardants to slow the combustion rate and flame spread, while also suppressing the release of toxic gases. However, although traditional flame retardants play a role in reducing fire hazards, these substances have negative impacts on the environment and biological health, and suffer from numerous drawbacks such as low fire resistance efficiency, high production costs, and complex processing conditions.

[0003] Another effective method is to use fire alarms to detect the scene and quickly issue an alarm signal upon detection of a fire, thereby achieving fire prevention through manual control. However, traditional (commercially available) fire alarms are limited by their working principle, with an alarm response time of up to 100 seconds. This long alarm time can render them ineffective, still resulting in loss of life and property. Therefore, the development of advanced fire alarm sensors is urgently needed. While common commercial temperature-sensitive fire alarm sensors are sensitive to ambient temperature and will revert to their original state at high temperatures, they still suffer from drawbacks such as response delay, low material utilization, false alarms, and susceptibility to damage. Therefore, it is necessary to develop a new type of flame-retardant material to meet safety requirements.

[0004] When graphene oxide is exposed to high temperatures or flames, the oxygen-containing functional groups on its surface are removed, resulting in conductive reduced graphene oxide. Based on this, thermally resistive graphene oxide-based early warning sensors for fires have attracted widespread attention from academia and industry. However, ordinary graphene oxide-based sensors cannot be widely used due to limitations in mechanical properties, response time, alarm duration, and environmental adaptability. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a modified graphene oxide-based aramid nanofiber paper, its preparation method, and its applications, thereby overcoming the shortcomings of existing fire alarm sensors, such as slow response time, short continuous alarm duration, and poor mechanical properties that limit its widespread applicability. The modified graphene oxide-based aramid nanofiber paper provided by this invention possesses high electrical and mechanical properties, excellent insulation and flame retardancy, significantly improving the response speed of fire alarms. It can improve the working performance of fire alarm sensors.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a modified graphene oxide-based aramid nanofiber paper; the modified graphene oxide-based aramid nanofiber paper has a response time of 0.7-1s at 200℃, a continuous alarm time of 60s, a tensile strength of 85-124MPa, an elongation at break of 3.2-11%, and remains morphologically stable after 90s of burning in an alcohol lamp.

[0008] The modified graphene oxide-based aramid nanofiber paper of the present invention is used as a sensor in a fire alarm.

[0009] This invention provides a method for preparing modified graphene oxide-based aramid nanofiber paper, comprising the following steps:

[0010] S1: The nitrogen source and acid compound are stirred and mixed evenly at a constant temperature to obtain a mixed solution of modifier;

[0011] S2: The graphene oxide solution and the modifier mixture are hydrothermally mixed to obtain the modified graphene oxide gel;

[0012] S3: Mix a strong alkali, dimethyl sulfoxide and aramid nanofibers to obtain an aramid nanofiber suspension;

[0013] S4: The modified graphene oxide gel and the aramid nanofiber suspension were mixed to obtain a hydrogel;

[0014] S5: The hydrogel is dried to obtain modified graphene oxide-based aramid nanofiber paper.

[0015] The above steps are merely an explanation of the operation process and do not constitute a restriction on the order of operations. The operation steps can be adjusted without affecting the final result.

[0016] In step S1, the nitrogen source is preferably one or more of melamine, urea, or ethylenediamine; and / or, the acidic compound is preferably one or more of boric acid, oxalic acid, phytic acid, or adenosine triphosphate.

[0017] In step S1, the molar ratio of nitrogen source to acid compound is 1:(1-4).

[0018] In step S1, the constant temperature is set to 50-100℃, the stirring rate is preferably 100-500 r / min, and the stirring time is preferably 0.5-2 h.

[0019] In step S2, the mass ratio of graphene oxide to modifier mixed solution is 1:(1-10). Preferably, the molar concentration of the graphene oxide solution is 0.3-0.5 mol / L.

[0020] In step S2, the temperature of the hydrothermal mixing is 20℃~80℃, and the hydrothermal time is preferably 10~30 minutes.

[0021] In step S3, the strong base is preferably one or more of potassium hydroxide, potassium ethoxide, or potassium tert-butoxide.

[0022] In step S3, the ratio of strong alkali to dimethyl sulfoxide is 1:(5-300) by mass; the ratio of strong alkali to aramid fiber is 1:(0.5-3) by mass.

[0023] In step S3, dimethyl sulfoxide can also be replaced by dimethylformamide.

[0024] In step S3, the aramid nanofibers have a diameter of 3-20 nm and an aspect ratio of 3000.

[0025] In step S3, the preparation process of the aramid nanofiber suspension is as follows: a strong alkali, dimethyl sulfoxide, and aramid nanofibers are stirred and mixed to obtain a mixed solution, which is then ball-milled and centrifuged to extract the supernatant to obtain an aramid nanofiber dispersion. The ball milling speed is preferably 300-700 r / min, and the ball milling time is preferably 2-4 h. Preferably, the centrifugation speed is 3000-7000 r / min, more preferably 4000-5000 r / min, and the centrifugation time is preferably 0.5-1 h.

[0026] The aramid nanofiber dispersion was diluted with a dimethyl sulfoxide solution, followed by solid-liquid separation to obtain an aramid nanofiber filter cake. The aramid nanofiber filter cake was then dispersed in deionized water and stirred at high speed to obtain an aramid nanofiber suspension. Preferably, the stirring speed was 7000–10000 r / min, and the stirring time was 20 min–1 h. The mass ratio of aramid nanofiber filter cake to deionized water was 1:(2–5).

[0027] In step S4, the modified graphene oxide gel and aramid nanofiber suspension are in a mass ratio of 1:(0.01-0.5).

[0028] In step S5, the drying temperature is 50–80°C and the drying time is 48–140 h.

[0029] Compared with the prior art, the modified graphene oxide-based aramid nanofiber paper of the present invention, its preparation method and application, have the following beneficial effects:

[0030] (1) In the modified graphene oxide-based aramid nanofiber paper provided by the present invention, the aramid nanofibers form a three-dimensional network structure, and the modified graphene oxide is located in the three-dimensional network structure. When the modified graphene oxide-based aramid nanofiber paper is stretched, the modified graphene oxide material slides together with the non-uniform (the pore size in the fiber network is large and small) aramid nanofiber network and is pulled out from the coiled aramid nanofibers. In this process, the hydrogen bond force between the aramid nanofibers is broken, and the elongation and orientation of the aramid nanofiber network will cause local deformation and hardening of the modified graphene oxide-based aramid nanofiber paper. Due to the high interconnectivity of the aramid nanofiber network and the multi-site cross-linking with the modified graphene oxide, the entire material will undergo uniform deformation, rather than deformation in a local area of ​​the material, thereby generating large fracture strain and ultra-high toughness.

[0031] (2) In addition, the cross-linking of aramid fibers and modified graphene oxide provides mechanical support for the modified graphene oxide. Therefore, the formation of a fiber network in the modified graphene oxide-based aramid nanofiber paper gives the paper high mechanical properties. In addition, the aramid fibers have high insulation properties. Therefore, the modified graphene oxide-based aramid nanofiber paper has excellent insulation properties and can maintain excellent stability in fire alarm sensors.

[0032] (3) Furthermore, due to the modified graphene oxide, compared to traditional graphene oxide alarms, the nitrogen atoms present in the modified graphene oxide can increase the active sites on the graphene surface, giving the graphene oxide superior electrochemical performance. This allows for more sensitive sensing of temperature changes and maintains a longer circuit response. The reaction between acidic compounds and nitrogen sources during combustion produces compounds that adhere to the graphene oxide surface, providing the possibility for continuous alarm operation over extended periods.

[0033] (4) The results of the embodiments show that, compared with the sensitive layer of commonly used fire alarm sensors, the modified graphene oxide-based aramid nanofiber paper provided by the present invention has significantly improved dielectric strength and tensile strength, and has a longer continuous alarm time. This indicates that the modified graphene oxide-based aramid nanofiber paper provided by the present invention has excellent electrical properties, insulation properties, and mechanical properties.

[0034] (5) This invention provides modified graphene oxide-based aramid nanofiber paper and its preparation method. The preparation method provided by this invention is simple, the preparation conditions are relatively relaxed, it has excellent operability, can be widely used, and further continuous manufacturing is conducive to industrial production. Attached Figure Description

[0035] Figure 1 A flowchart illustrating the operational steps of a method for preparing modified graphene oxide-based aramid nanofiber paper.

[0036] Figure 2This is a photograph of the modified graphene oxide-based aramid nanofiber paper prepared in Example 1 of this invention.

[0037] Figure 3 This is a magnified view of a portion of the modified graphene oxide-based aramid nanofiber paper prepared in Example 1 of the present invention.

[0038] Figure 4 The image shows a 60-second combustion test result of the modified graphene oxide-based aramid nanofiber paper prepared in Example 1 of this invention. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the embodiments.

[0040] This invention provides a modified graphene oxide-based aramid nanofiber paper, which comprises aramid fibers and modified graphene oxide.

[0041] This invention provides the aforementioned modified graphene oxide-based aramid nanofiber paper. The modified graphene oxide-based aramid nanofiber paper provided by this invention possesses high electrical and mechanical properties, excellent insulation and flame retardancy, greatly improving the response speed of fire alarms. It can improve the working performance of fire early warning sensors.

[0042] This invention provides a method for preparing the modified graphene oxide-based aramid nanofiber paper described above, comprising the following steps:

[0043] (1) Mix the nitrogen source and acid compound at a constant temperature and stir to prepare a modified agent mixed solution;

[0044] (2) The graphene oxide solution and the above-mentioned modifier mixture were hydrothermally mixed to obtain the modified graphene oxide gel.

[0045] (3) Mix strong alkali, dimethyl sulfoxide and aramid nanofibers to obtain an aramid nanofiber suspension;

[0046] (4) The modified graphene oxide gel and the aramid nanofiber suspension are mixed to obtain a hydrogel;

[0047] (5) The hydrogel was dried to obtain graphene-based aramid nanofiber paper.

[0048] This invention involves mixing a nitrogen source and an acidic compound at a constant temperature to obtain a modifier mixed solution. In this invention, the nitrogen source is selected from one or more of melamine, urea, and ethylenediamine; the acidic compound is selected from one or more of boric acid, oxalic acid, phytic acid, and adenosine triphosphate. The preferred molar ratio of the nitrogen source to the acidic substance is 1:1–4, more preferably 1:1.5–3. The preferred temperature is 50℃–100℃, more preferably 70℃–90℃. This invention does not have specific requirements regarding the source of the nitrogen source and the acidic compound; commercially available products in the art are acceptable. In specific embodiments of this invention, the mass concentration of the acidic compound is preferably ≥99.0%. This invention preferably mixes the nitrogen source and the acidic compound under stirring conditions, and the mixing time is preferably 0.5–2 hours. The resulting modified agent mixed solution is obtained after mixing.

[0049] This invention involves hydrothermal mixing of a graphene oxide solution and a modifier solution to obtain a modified graphene oxide gel. In this invention, the preferred mass ratio of graphene oxide to modifier is 1:1 to 10, more preferably 1:2 to 5. The graphene oxide solution is obtained by adding graphene oxide to water and ultrasonically dispersing it. The preferred hydrothermal temperature is 20℃ to 80℃, more preferably 30℃ to 60℃. This invention does not have special requirements regarding the source of the graphene oxide; commercially available products in the field are acceptable. The preferred hydrothermal time is 10 to 30 minutes. After hydrothermal treatment, a modified graphene oxide gel is obtained.

[0050] This invention mixes a strong alkali, dimethyl sulfoxide (DMSO), and aramid nanofibers to obtain an aramid nanofiber suspension. In this invention, the strong alkali is selected from one or more of potassium hydroxide, potassium ethoxide, or potassium tert-butoxide; the mass ratio of the strong alkali to DMSO is preferably 1:5–300, more preferably 1:10–200. The mass ratio of the strong alkali to aramid fibers is preferably 1:0.5–3, more preferably 1:1–2. This invention does not have special requirements regarding the source of the strong alkali and DMSO; commercially available products in the art are acceptable. In specific embodiments of this invention, the mass concentration of the strong alkali is preferably ≥99.0%, and the mass concentration of the DMSO is preferably ≥99.5%. This invention does not have special requirements regarding the source of the aramid fibers; commercially available aramid fibers in the art are acceptable. In this invention, a strong alkali, dimethyl sulfoxide (DMSO), and aramid nanofibers are preferably directly mixed and manually stirred for 5 minutes. Then, deionized water is added, with a preferred volume ratio of deionized water to DMSO of 1:10–40, more preferably 1:20–30. After adding deionized water, manual stirring continues for another 5 minutes to obtain a mixture of strong alkali, DMSO, and aramid nanofibers. This invention does not have specific requirements for the manual stirring rate; it is sufficient to achieve a preliminary mixture of the strong alkali, DMSO, and aramid nanofibers. Alternatively, this invention preferably ball-mills the mixture of strong alkali, DMSO, and aramid nanofibers to obtain a solution of strong alkali, DMSO, and aramid nanofibers. The preferred ball-milling speed is 300–700 r / min, and the preferred ball-milling time is 2–4 h. After ball milling, a solution of strong alkali, DMSO, and aramid nanofibers is obtained.

[0051] Furthermore, after obtaining the strong alkali, dimethyl sulfoxide, and aramid nanofiber solution, the present invention preferably uses a centrifugal filtration method to prepare the aramid nanofiber suspension. Preferably, the centrifugation speed is 3000–7000 r / min, more preferably 4000–5000 r / min, and the centrifugation time is preferably 0.5–1 h, to obtain an aramid nanofiber dispersion. In the present invention, the aramid nanofiber dispersion is mixed and diluted with the dimethyl sulfoxide solution and filtered to obtain an aramid nanofiber filter cake. In the present invention, the volume ratio of the aramid nanofiber dispersion to the dimethyl sulfoxide solution is not particularly required, as long as an aramid nanofiber filter cake is obtained.

[0052] In this invention, aramid nanofiber filter cake is dispersed in deionized water and stirred at high speed to obtain an aramid nanofiber suspension. The mass ratio of aramid nanofiber filter cake to deionized water is 1:2-5. The preferred stirring speed is 7000-10000 r / min, and the preferred stirring time is 20 min-1 h to obtain the aramid nanofiber suspension.

[0053] In this invention, an aramid nanofiber suspension is mixed with a modified graphene oxide sol and dried to obtain a modified graphene oxide-based aramid nanofiber paper. The preferred mass ratio of modified graphene oxide to aramid nanofibers is 1:0.01–0.5. No particular requirements are placed on the mixing method; sufficient mixing of the aramid nanofiber suspension and the modified graphene oxide gel is sufficient. After mixing, the solution is poured into a mold for drying. No particular requirements are placed on the shape and specifications of the mold; any mold known in the art for preparing thin films can be used. In specific embodiments, a flat-bottomed mold is preferred. The drying temperature is preferably 50–80°C, more preferably 70°C, and the drying time is preferably 48–140 h, more preferably 60–100 h. The drying atmosphere is preferably air. No particular requirements are placed on the drying method; any method known in the art can be used to ensure the required drying temperature and time. In this invention, during the drying process, modified graphene oxide and aramid nanofiber network together form a layered structure to obtain modified graphene oxide-based aramid nanofiber paper. This invention does not have specific requirements for the thickness of the modified graphene oxide-based aramid nanofiber paper; the layer thickness can be adjusted according to actual needs by changing the height of the mold.

[0054] This invention provides a method for preparing the modified graphene oxide-based aramid nanofiber paper described above. The preparation method provided by this invention is simple, has relatively relaxed requirements, possesses excellent operability, and can further achieve continuous preparation, facilitating industrial production.

[0055] The modified graphene oxide-based aramid nanofiber paper and its preparation method provided by the present invention will be described in detail below with reference to the embodiments. However, these should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] (1) Weigh 1.26g of melamine and 1.23g of boric acid and dissolve them in 250ml of deionized water. Stir and heat to 85℃ and maintain for 30 minutes to obtain a mixed solution of melamine and boric acid modifier.

[0058] (2) Dissolve 1g of commercial graphene oxide in 250ml of deionized water and sonicate for 10 minutes to obtain a graphene oxide solution. Mix the graphene oxide solution with the melamine and boric acid modifier mixed solution prepared in step (1) and stir hydrothermally at 60℃ for 10 minutes to obtain a modified graphene oxide gel.

[0059] (3) Weigh 50 ml of dimethyl sulfoxide solution, 0.75 g of potassium hydroxide and 0.5 g of aramid fiber. Place the weighed medicine in a beaker and stir manually for 5 minutes. Then add 2 ml of deionized water and continue stirring for 5 minutes. Place the resulting mixture into a ball mill jar and ball mill at 500 r / min for 2 hours. After ball milling, potassium hydroxide, dimethyl sulfoxide and aramid nanofiber solution are obtained.

[0060] (4) Centrifuge the solution obtained in step (3) at 4000 r / min for 30 minutes to obtain an aramid nanofiber dispersion. Dilute 50 ml of the aramid nanofiber dispersion with 450 ml of dimethyl sulfoxide solution and stir continuously for 30 minutes. Then filter to obtain an aramid nanofiber filter cake.

[0061] (5) Disperse the aramid nanofiber filter cake prepared in step (4) into 1000 ml of deionized water and mechanically stir at 9000 r / min for 25 minutes to obtain an aramid nanofiber suspension.

[0062] (6) Weigh 17.78 ml of the aramid nanofiber suspension prepared in step (5) and 20 ml of the modified graphene oxide gel prepared in step (2), mix and stir magnetically for 10 minutes, then put it into a petri dish and dry at 60°C for 52 hours to obtain modified graphene oxide-based aramid nanofiber paper.

[0063] The modified graphene oxide-based aramid nanofiber paper prepared in this embodiment has a thickness of 40 μm and a tensile strength of 85 MPa, according to the test results.

[0064] An alcohol lamp burning experiment was conducted on the modified graphene oxide-based aramid nanofiber paper prepared in this embodiment. The modified graphene oxide-based aramid nanofiber paper still maintained its morphological stability after 90 seconds.

[0065] The closed-loop response time of the modified graphene oxide-based aramid nanofiber paper prepared in this embodiment was tested. At 200°C, the response time of the modified graphene oxide-based aramid nanofiber paper was only 0.8 s. This indicates that the nanofiber paper prepared in this embodiment has excellent flame-retardant properties and outstanding rapid fire warning function.

[0066] Example 2

[0067] Preparation of modified graphene oxide-based aramid nanofiber paper

[0068] (1) Weigh 1.26g of melamine and 1.23g of boric acid and dissolve them in 250ml of deionized water. Stir and heat to 85℃ and maintain for 30 minutes to obtain a mixed solution of melamine and boric acid modifier.

[0069] (2) Dissolve 1g of commercial graphene oxide in 250ml of deionized water and sonicate for 10 minutes to obtain a graphene oxide solution. Mix the graphene oxide solution with the melamine and boric acid modifier mixed solution prepared in step (1) and stir hydrothermally at 60℃ for 10 minutes to obtain a modified graphene oxide gel.

[0070] (3) Weigh 50 ml of dimethyl sulfoxide solution, 0.75 g of potassium hydroxide and 0.5 g of aramid fiber. Place the weighed medicine in a beaker and stir manually for 5 minutes. Then add 2 ml of deionized water and continue stirring for 5 minutes. Place the resulting mixed solution into a ball mill jar and ball mill at 500 r / min for 2 hours. After ball milling, potassium hydroxide, dimethyl sulfoxide and aramid nanofiber solution are obtained.

[0071] (4) Centrifuge the solution obtained in step (3) at 4000 r / min for 30 minutes to obtain an aramid nanofiber dispersion. Dilute 50 ml of the aramid nanofiber dispersion with 450 ml of dimethyl sulfoxide solution and stir continuously for 30 minutes. Then filter to obtain an aramid nanofiber filter cake.

[0072] (5) Disperse the aramid nanofiber filter cake prepared in step (4) into 1000 ml of deionized water and mechanically stir at 9000 r / min for 25 minutes to obtain an aramid nanofiber suspension.

[0073] (6) Weigh 35.56 ml of the solution prepared in step (5) and 20 ml of the gel prepared in step (2), mix them and stir magnetically for 10 minutes, then put them in a petri dish and dry them to obtain modified graphene oxide-based aramid nanofiber paper.

[0074] Example 3

[0075] Preparation of modified graphene oxide-based aramid nanofiber paper

[0076] (1) Weigh 1.26g of melamine and 1.23g of boric acid and dissolve them in 250ml of deionized water. Stir and heat to 85℃ and maintain for 30 minutes to obtain melamine and boric acid modifier.

[0077] (2) Dissolve 1g of commercial graphene oxide in 250ml of deionized water and sonicate for 10 minutes to obtain a graphene oxide solution. Mix the graphene oxide solution with the melamine and boric acid modifier prepared in step (1) and stir hydrothermally at 60℃ for 10 minutes to obtain a modified graphene oxide gel.

[0078] (3) Weigh 50 ml of dimethyl sulfoxide solution, 0.75 g of potassium hydroxide and 0.5 g of aramid fiber. Place the weighed medicine in a beaker and stir manually for 5 minutes. Then add 2 ml of deionized water and continue stirring for 5 minutes. Place the resulting mixture into a ball mill jar and ball mill at 500 r / min for 2 hours. After ball milling, potassium hydroxide, dimethyl sulfoxide and aramid nanofiber solution are obtained.

[0079] (4) Centrifuge the solution obtained in step (3) at 4000 r / min for 30 minutes to obtain an aramid nanofiber dispersion. Dilute 50 ml of the aramid nanofiber dispersion with 450 ml of dimethyl sulfoxide solution and stir continuously for 30 minutes. Then filter to obtain an aramid nanofiber filter cake.

[0080] (5) Disperse the aramid nanofiber filter cake prepared in step (4) into 1000 ml of deionized water and mechanically stir at 9000 r / min for 25 minutes to obtain an aramid nanofiber suspension.

[0081] (6) Weigh 53.34 ml of the solution prepared in step (5) and 20 ml of the gel prepared in step (2), mix them and stir magnetically for 10 minutes, then put them in a petri dish and dry them to obtain modified graphene oxide-based aramid nanofiber paper.

[0082] Example 4

[0083] Preparation of modified graphene oxide-based aramid nanofiber paper

[0084] (1) Weigh 1.26g of melamine and 1.23g of boric acid and dissolve them in 250ml of deionized water. Stir and heat to 85℃ and maintain for 30 minutes to obtain melamine and boric acid modifier.

[0085] (2) Dissolve 1g of commercial graphene oxide in 250ml of deionized water and sonicate for 10 minutes to obtain a graphene oxide solution. Mix the graphene oxide solution with the melamine and boric acid modifier prepared in step (1) and stir hydrothermally at 60℃ for 10 minutes to obtain a modified graphene oxide gel.

[0086] (3) Weigh 50 ml of dimethyl sulfoxide solution, 0.75 g of potassium hydroxide and 0.5 g of aramid fiber. Place the weighed medicine in a beaker and stir manually for 5 minutes. Then add 2 ml of deionized water and continue stirring for 5 minutes. Place the resulting mixture into a ball mill jar and ball mill at 500 r / min for 2 hours. After ball milling, potassium hydroxide, dimethyl sulfoxide and aramid nanofiber solution are obtained.

[0087] (4) Centrifuge the solution obtained in step (3) at 4000 r / min for 30 minutes to obtain an aramid nanofiber dispersion. Dilute 50 ml of the aramid nanofiber dispersion with 450 ml of dimethyl sulfoxide solution and stir continuously for 30 minutes. Then filter to obtain an aramid nanofiber filter cake.

[0088] (5) Disperse the aramid nanofiber filter cake prepared in step (4) into 1000 ml of deionized water and mechanically stir at 9000 r / min for 25 minutes to obtain an aramid nanofiber suspension.

[0089] (6) Weigh 71.12 ml of the solution prepared in step (5) and 20 ml of the gel prepared in step (2), mix them and stir magnetically for 10 minutes, then put them in a petri dish to dry, and obtain modified graphene oxide-based aramid nanofiber paper.

[0090] Performance tests were conducted on the products obtained from the above embodiments. The results are shown in Table 1:

[0091] Example 1 85 3.2 0.7 Example 2 92 6.4 0.7 Example 3 110 8.5 0.8 Example 4 124 11 1

[0092] Comparative Example 1

[0093] The preparation of modified graphene oxide paper differs from that in Example 1 in that the modified graphene oxide paper prepared without the addition of aramid nanofibers has poor mechanical properties and is extremely easy to break.

[0094] Comparative Example 2

[0095] The preparation of graphene oxide aramid nanofiber paper differs from that in Example 1 in that the lack of modification of graphene oxide with nitrogen source and acid compounds leads to an increase in circuit alarm time and a decrease in flame retardant effect.

[0096] Comparative Example 3

[0097] The graphene oxide carbon fiber paper prepared by replacing aramid nanofibers with carbon fibers differs from that in Example 1 in that the prepared graphene oxide paper is easy to break and exhibits brittle mechanical properties.

[0098] Comparative Example 4

[0099] Aramid nanofiber suspension was prepared without the addition of a strong alkali, and then graphene oxide aramid nanofiber paper was prepared. The difference from Example 1 is that the mechanical properties of the prepared graphene oxide aramid nanofiber paper are not excellent, and the aramid fibers agglomerate.

[0100] Comparative Example 5

[0101] After preparing the aramid nanofiber dispersion, it was directly filtered to obtain an aramid nanofiber filter cake. If dimethyl sulfoxide solution was not added for mixing and dilution, the obtained aramid nanofiber filter cake contained impurities, which in turn led to contamination in the prepared graphene oxide aramid nanofiber paper and a decrease in mechanical properties.

Claims

1. A method for preparing modified graphene oxide-based aramid nanofiber paper, characterized in that, Includes the following steps: S1: The nitrogen source and acid compound are stirred and mixed evenly at a constant temperature to obtain a modified agent mixed solution; the molar ratio of nitrogen source to acid compound is 1:(1~4). S2: Hydrothermal mixing of graphene oxide solution and modifier mixed solution yields modified graphene oxide gel; the mass ratio of graphene oxide to modifier mixed solution is 1:(1~10). S3: A strong base, dimethyl sulfoxide, and aramid nanofibers are mixed to obtain an aramid nanofiber suspension; the mass ratio of strong base to dimethyl sulfoxide is 1:(5~300); the mass ratio of strong base to aramid nanofibers is 1:(0.5~3). S4: The modified graphene oxide gel and the aramid nanofiber suspension are mixed to obtain a hydrogel; the mass ratio of modified graphene oxide gel to aramid nanofiber suspension is 1:(0.01~0.5). S5: The hydrogel is dried to obtain modified graphene oxide-based aramid nanofiber paper.

2. The method for preparing modified graphene oxide-based aramid nanofiber paper according to claim 1, characterized in that, In step S1, the nitrogen source is selected from one or more of melamine, urea, or ethylenediamine; and / or, the acid compound is selected from one or more of boric acid, oxalic acid, phytic acid, or adenosine triphosphate; and / or, the constant temperature is set to 50~100℃, the stirring rate is 100~500r / min, and the stirring time is 0.5~2h.

3. The method for preparing modified graphene oxide-based aramid nanofiber paper according to claim 1, characterized in that, In step S2, the temperature of the hydrothermal mixing is 20℃~80℃, and the hydrothermal time is 10~30min.

4. The method for preparing modified graphene oxide-based aramid nanofiber paper according to claim 1, characterized in that, In step S3, the strong alkali is selected from one or more of potassium hydroxide, potassium ethoxide or potassium tert-butoxide; and / or, the aramid nanofiber has a fiber diameter of 3-20 nm and an aspect ratio of 3000.

5. The method for preparing modified graphene oxide-based aramid nanofiber paper according to claim 1, characterized in that, In step S3, dimethyl sulfoxide is replaced by dimethylformamide.

6. The method for preparing modified graphene oxide-based aramid nanofiber paper according to claim 1, characterized in that, In step S3, the preparation process of the aramid nanofiber suspension is as follows: strong alkali, dimethyl sulfoxide and aramid nanofiber are stirred and mixed to obtain a mixture, which is then ball-milled and centrifuged to obtain the supernatant to obtain the aramid nanofiber dispersion. After mixing and diluting the aramid nanofiber dispersion with a dimethyl sulfoxide solution, the mixture was filtered to obtain an aramid nanofiber filter cake. The aramid nanofiber filter cake was then dispersed in deionized water and stirred at high speed to obtain an aramid nanofiber suspension.

7. The method for preparing modified graphene oxide-based aramid nanofiber paper according to claim 1, characterized in that, In step S5, the drying temperature is 50~80℃ and the drying time is 48~140h.

8. A modified graphene oxide-based aramid nanofiber paper, characterized in that, The modified graphene oxide-based aramid nanofiber paper prepared by the preparation method described in claim 1 has a tensile strength of 85~124MPa and an elongation at break of 3.2~11%.

9. The application of the modified graphene oxide-based aramid nanofiber paper according to claim 8, used as a sensor for a fire alarm.

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