Para-aramid nanosheet and preparation method thereof
The preparation of paraposition aramid nanosheets through high-energy physical sand grinding technology solves the difficulties of processing on the nanoscale and two-dimensional morphology control, and achieves efficient preparation and application potential in multiple fields.
Patent Information
- Application Number
- CN202510183337.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-19
- Publication Date
- 2025-05-27
AI Technical Summary
In the prior art, the processing of para-abras on the nanoscale and control of two-dimensional morphology is relatively difficult, resulting in limited application of para-abras in complex structural products.
Using high-energy physical sand grinding technology, para-aramid microfibers and alkali powder are sanded in a dispersant to prepare a high-concentration para-aramid nanosheet slurry, and para-aramid nanosheets are obtained through washing and drying steps.
It realizes efficient preparation and high yield of para-aramid nanosheets, improves its processability and controllability of two-dimensional morphology, maintains the original high strength, high modulus, heat resistance and chemical corrosion resistance, and is suitable for the application of a variety of high-performance materials.
Smart Images
Figure HDA0005277778010000011 
Figure HDA0005277778010000012 
Figure HDA0005277778010000021
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of nanomaterials, and particularly relates to a para-aramid nanoflake and a preparation method thereof. Background Art
[0002] Para-aramid, also known as poly(p-phenylene terephthalamide) (PPTA), is a high-performance polymer material. In its molecular structure, benzene rings are connected in a para position to form long and straight molecular chains, endowing para-aramid with properties such as high strength, high modulus, low thermal expansion, good heat resistance, and chemical corrosion resistance. These properties enable para-aramid to have broad application prospects in multiple fields such as aerospace, automotive industry, electronics and electrical, sports goods, and medical devices. In the aerospace field, para-aramid is widely used to manufacture lightweight and high-strength structural materials and protective materials due to its lightweight, high strength, high temperature resistance, and chemical corrosion resistance. In the automotive industry, para-aramid can be used to manufacture lightweight components to improve vehicle performance and reduce energy consumption. In the electronics and electrical field, para-aramid, as a high-temperature insulating material and battery separator, exhibits excellent performance. In addition, in the sports goods field, para-aramid is used to manufacture high-strength sports equipment such as ropes and protective gear; in the medical device field, para-aramid is used to manufacture biomedical materials to replace traditional organic materials.
[0003] However, despite the many excellent properties of para-aramid, its processability is relatively poor, which limits its application in some complex-structured products. To overcome this problem, researchers have been committed to developing new forms of para-aramid, and among them, para-aramid nanofibers are an important innovation. Para-aramid nanofibers not only retain the original high strength, high modulus, and high temperature resistance of para-aramid but also significantly improve its processability, enabling the preparation of products with complex structures. The preparation of para-aramid nanofibers is mainly through a top-down method, where para-micron fibers or aramid pulp are dispersed in an alkaline aprotic solvent, and by controlling temperature, pressure, and concentration, etc., para-aramid nanofibers with uniform size and good dispersibility can be prepared. In addition, through self-assembly technology, the nanofibers can be further assembled into materials with specific structures and functions, such as all-aromatic blocks, all-aromatic honeycombs, and all-aromatic aerogels, etc. These materials show potential application values in fields such as high-performance insulating paper, lithium-ion battery separators, and thermal insulation adsorption materials.
[0004] In recent years, two-dimensional (2D) sheet-like nanomaterials have shown broad application prospects in various fields such as electronic devices, optoelectronic devices, sensors, energy conversion and storage, due to their excellent mechanical strength, unique structural characteristics, good film-forming properties, and rich tunability. With the continuous innovation of synthesis methods, in-depth performance research, and acceleration of the industrialization process, 2D nanomaterials are gradually moving from the laboratory to practical applications, becoming a research hotspot and frontier direction in the field of materials science. However, for para-aramid fibers, a large number of researchers have focused on the study of their one-dimensional nanoforms, and there is little research on their two-dimensional form (nanosheets).
[0005] Due to the high degree of order and stability of the molecular structure, it is very difficult to process para-aramid at the nanoscale and control its two-dimensional form. Therefore, developing an efficient, low-cost, and simple-process method for preparing para-aramid nanosheets has become an urgent problem to be solved in the current scientific research and industrial circles. Summary of the Invention
[0006] The purpose of the present invention is to provide a method for preparing para-aramid nanosheets to solve the problem that it is difficult to process para-aramid at the nanoscale and control its two-dimensional form in the prior art.
[0007] The present invention also provides a para-aramid nanosheet to solve the problem that para-aramid is difficult to exist in a two-dimensional form in the prior art.
[0008] To solve the above problems, the present invention proposes a method for preparing para-aramid nanosheets, and the technical solution adopted is as follows:
[0009] A method for preparing para-aramid nanosheets includes the following steps: adding para-aramid microfibers and alkali powder into a dispersant for high-energy physical sanding to obtain a high-concentration para-aramid nanosheet slurry; washing and drying the high-concentration para-aramid nanosheet slurry to obtain para-aramid nanosheets.
[0010] The beneficial effects of the present invention are as follows:
[0011] 1) High-efficiency preparation and high yield: The present invention adopts high-energy physical sanding technology to sand para-aramid microfibers and alkali powder in a dispersant, and successfully prepares a high-concentration para-aramid nanosheet slurry. This method has a simple process and convenient operation, can greatly improve the yield of nanosheets, meet the needs of large-scale production, and not only overcomes the problems of poor processability and difficult two-dimensional form control of para-aramid nanosheets in the prior art, but also significantly improves the preparation efficiency and performance of para-aramid nanosheets.
[0012] 2) Excellent properties of para-aramid nanoflakes: The para-aramid nanoflakes prepared by the present invention have uniform size, good dispersibility, and no obvious agglomeration phenomenon. The thickness of the para-aramid nanoflakes is 1 - 30 nanometers, and both the width and length are in the range of 50 - 5000 nanometers. The surface is flat, without obvious defects or damages, maintaining the high strength, high modulus, heat resistance, and chemical corrosion resistance of the original para-aramid, and having a two-dimensional nanostructure. The two-dimensional nanostructure endows the nanoflakes with an enhanced specific surface area and better film-forming property, providing the possibility for their applications in high-performance composite materials, coating materials, filtration materials, and other fields.
[0013] 3) Stability and long-term storage property of the slurry: The para-aramid nanoflake slurry prepared by the present invention has excellent stability and can be stored at room temperature for at least 6 months. During this period, the size, dispersibility, and properties of the para-aramid nanoflakes in the para-aramid nanoflake slurry remain basically unchanged. This long-term stability enables the para-aramid nanoflake slurry to be conveniently stored and transported, providing convenience for industrial applications.
[0014] 4) Wide application prospects: The para-aramid nanoflakes prepared by the present invention, due to their unique two-dimensional nanostructure and excellent properties, are suitable for preparing high-performance composite materials, coating materials, filtration materials, electrode materials, and energy storage and conversion materials, etc. In many fields such as aerospace, automotive industry, electronics and electrical, sports goods, and medical devices, the para-aramid nanoflakes are expected to show wide application prospects and important practical values.
[0015] In order to further improve the uniformity and dispersibility of the size of the para-aramid nanoflakes and obtain a two-dimensional morphology, preferably, the mass ratio of the para-aramid microfibers, alkali powder, and dispersant is 1:(0.5 - 2):(4 - 200).
[0016] In order to deprotonate the amino groups on the para-aramid molecular chains, further weaken the intermolecular forces of the para-aramid, be more conducive to dissociating from the microscale morphology into the nanoscale morphology, and thus improve the processability and controllability of the two-dimensional morphology of the para-aramid nanoflakes, preferably, the low-alkali powder is selected from one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium ethoxide, sodium ethoxide, potassium tert-butoxide, and sodium tert-butoxide.
[0017] In order to further improve the uniformity and dispersibility of the size of the para-aramid nanoflakes, preferably, the diameter of the para-aramid microfibers is 5 - 25 microns, and the length is 1 - 10 millimeters.
[0018] In order to improve the high-energy physical sanding effect and enable the para-aramid nanoflakes to be fully and uniformly dispersed in the high-concentration para-aramid nanoflake slurry without obvious agglomeration, preferably, the dispersant is composed of an aprotic solvent and a proton donor agent. The aprotic solvent is selected from one or more of acetonitrile, benzene, diethyl ether, carbon tetrachloride, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric triamide, and 1,3-dimethyl-2-imidazolidinone; the proton donor agent is selected from water, alcohol solvents, or a mixture thereof, where the alcohol solvents are selected from one or more of methanol, ethanol, and propanol; the mass ratio of the aprotic solvent to the proton donor agent is 1:(0.01 - 0.05).
[0019] In order to improve the processing efficiency of para-aramid nanoflakes, preferably, the mass concentration of para-aramid nanoflakes in the high-concentration para-aramid nanoflake slurry is 0.5 - 20%.
[0020] In order to improve the high-energy physical sanding efficiency and avoid the degradation of para-aramid caused by excessive temperature, preferably, the sanding time of the high-energy physical sanding is 2 - 15 hours, the sanding speed is 2000 - 8000 revolutions per minute, and the sanding temperature is 0 - 50 °C.
[0021] In order to thoroughly remove the residual dispersant and the sanding aids in the high-energy physical sanding process, preferably, the washing step includes: first, performing preliminary washing with a solvent that is the same as or compatible with the dispersant in the slurry, and then performing final washing with deionized water or pure water.
[0022] In order to more effectively obtain loose, porous para-aramid nanoflakes that maintain the original nanoflake structure, preferably, the drying step includes: freezing the washed high-concentration para-aramid nanoflake slurry into a solid at a low temperature and then sublimating to remove moisture under vacuum conditions.
[0023] Preferably, a sanding aid is added during the high-energy physical sanding process. The sanding aid is selected from one or two of polyvinylpyrrolidone and polyacrylamide to improve the sanding efficiency of para-aramid microfibers.
[0024] Preferably, the conditions for the high-energy physical sanding include: the sanding medium is a hard sphere with a hardness higher than that of para-aramid, and the hard sphere is selected from one of zirconia beads, zirconium silicate beads, tungsten carbide beads, or silicon carbide beads.
[0025] Preferably, the diameter of the hard sphere is 0.1 - 5 mm, and the ratio of the volume of the hard sphere to the total volume of para-aramid microfibers, alkali powder, and dispersant is 1:(3 - 10).
[0026] The present invention also proposes a kind of para-aramid nanoflakes, and the technical solution adopted is as follows:
[0027] A para-aramid nanoflake, which is prepared by the preparation method of the para-aramid nanoflake described above.
[0028] The beneficial effects of the present invention are as follows: The para-aramid nanoflakes of the present invention have a two-dimensional nanostructure, which retains the high strength, high modulus, heat resistance and chemical corrosion resistance of the original para-aramid, and at the same time has an enhanced specific surface area and better film-forming properties, and is suitable for preparing high-performance composite materials, coating materials, filtration materials, electrode materials, and energy storage and conversion materials, etc. Description of the Drawings
[0029] Figure 1 It is a SEM image of the para-aramid microfiber used in the preparation method of the para-aramid nanoflakes of the present invention.
[0030] Figure 2 It is a SEM image of the para-aramid nanoflakes prepared in Example 1 of the preparation method of the para-aramid nanoflakes of the present invention.
[0031] Figure 3 It is a SEM image of the para-aramid nanoflakes prepared in Example 2 of the preparation method of the para-aramid nanoflakes of the present invention.
[0032] Figure 4 It is a SEM image of the para-aramid nanoflakes prepared in Example 3 of the preparation method of the para-aramid nanoflakes of the present invention.
[0033] Figure 5 It is a SEM image of the para-aramid nanoflakes prepared in Example 4 of the preparation method of the para-aramid nanoflakes of the present invention.
[0034] Figure 6 It is an AFM image of the para-aramid nanoflakes prepared in Example 1 of the preparation method of the para-aramid nanoflakes of the present invention.
[0035] Figure 7 It is an image of the dispersion of the para-aramid nanoflakes prepared in Example 1 of the preparation method of the para-aramid nanoflakes of the present invention in water. Detailed Embodiments
[0036] In the prior art, it is difficult to process para-aramid at the nanoscale and control its two-dimensional morphology. The present invention provides a preparation method of para-aramid nanoflakes, which includes the following steps: adding para-aramid microfibers and alkali powder into a dispersant for high-energy physical sanding to obtain a high-concentration para-aramid nanoflake slurry; washing and drying the high-concentration para-aramid nanoflake slurry to obtain para-aramid nanoflakes.
[0037] The technical concept of the present invention is as follows: Para-aramid microfibers have higher high strength, high modulus, heat resistance and chemical corrosion resistance. After being prepared into para-aramid nanosheets, they have a loose and uniform porous structure; the alkaline powder deprotonates the amino groups on the para-aramid molecular chains, weakening the intermolecular forces of para-aramid, which is beneficial to dissociating from the micro-scale into the nano-scale, thereby improving the processability and two-dimensional morphology controllability of para-aramid nanosheets; adding para-aramid microfibers and alkaline powder into the dispersant enables the para-aramid microfibers and alkaline powder to be fully dispersed. At the same time, the dispersant can reduce the surface activity of para-aramid nanosheets, prevent agglomeration, and under the condition of high-energy physical sanding, a high-concentration para-aramid nanosheet slurry with a porous structure is obtained; after washing and drying, the thickness of the obtained para-aramid nanosheets is 1-30 nanometers, and the width and length are both in the range of 50-5000 nanometers. The surface is flat, without obvious defects or damages, maintaining the high strength, high modulus, heat resistance and chemical corrosion resistance of the original para-aramid, and having a two-dimensional nanostructure. The two-dimensional nanostructure endows the nanosheets with an enhanced specific surface area and better film-forming properties, providing the possibility for their applications in high-performance composite materials, coating materials, filtration materials and other fields.
[0038] Specifically, the preparation method of para-aramid nanosheets includes the following steps:
[0039] First, add para-aramid microfibers and alkaline powder into the dispersant, and perform high-energy physical sanding under the conditions of a sanding time of 2-15 hours, a sanding speed of 2000-8000 revolutions per minute, and a sanding temperature of 0-50 °C to obtain a high-concentration para-aramid nanosheet slurry; among them, the mass ratio of para-aramid microfibers, alkaline powder and dispersant is 1:(0.5-2):(4-200); the alkaline powder is selected from one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium ethoxide, sodium ethoxide, potassium tert-butoxide, sodium tert-butoxide; the diameter of the para-aramid microfibers is 5-25 microns, and the length is 1-10 millimeters; the dispersant is composed of an aprotic solvent and a proton donor agent. The aprotic solvent is selected from one or more of acetonitrile, benzene, ether, carbon tetrachloride, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide and 1,3-dimethyl-2-imidazolidinone; the proton donor agent is selected from water, alcohol solvents or a mixture thereof, and among them, the alcohol solvents are selected from one or more of methanol, ethanol, and propanol; the mass ratio of the aprotic solvent and the proton donor agent is 1:(0.01-0.05).
[0040] Secondly, wash the above high-concentration para-aramid nanosheet slurry. Among them, the washing steps include: first, perform preliminary washing with a solvent that is the same as or compatible with the dispersant in the slurry, and then perform final washing with deionized water or pure water to thoroughly remove the residual dispersant and sanding aids;
[0041] Finally, the washed high-concentration para-aramid nanoflake slurry is dried to obtain para-aramid nanoflakes; wherein, the drying step includes: freezing the washed high-concentration para-aramid nanoflake slurry into a solid at a low temperature, and then sublimating and removing water under vacuum conditions.
[0042] Preferably, during the washing process, the solvent compatible with the dispersant in the slurry is tert-butanol.
[0043] Preferably, during the drying process, the low temperature is -18°C, and the sublimation temperature under vacuum conditions is -101°C.
[0044] The implementation process of the present invention will be described in detail below in conjunction with specific embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Additionally, it should be noted that for the sake of description, only the parts related to the invention are shown in the embodiments.
[0045] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the embodiments.
[0046] It should be noted that, in the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.
[0047] In the following embodiments, among the raw materials used, the diameter of the para-aramid microfibers is 5 - 25 microns, and the length is 1 - 10 millimeters; the remaining raw materials are all ordinary commercially available products that can be directly purchased or can be prepared according to conventional techniques in the art.
[0048] I. Specific embodiments of the preparation method of the para-aramid nanoflakes of the present invention
[0049] Example 1
[0050] The preparation method of the para-aramid nanoflakes provided in this example includes the following steps:
[0051] First, first, add para-aramid microfibers and sodium hydroxide powder into a mixed solution of acetonitrile and methanol, and perform high-energy physical sanding under the conditions of a sanding time of 2 hours, a sanding speed of 8,000 revolutions per minute, and a sanding temperature of 50 °C to obtain a high-concentration para-aramid nanoflake slurry; among them, the sanding aid added in the high-energy physical sanding is polyvinylpyrrolidone with an average molecular weight of 1,300,000, the hard spheres in the high-energy physical sanding are zirconia beads, the diameter of the hard spheres is 0.1 mm, and the ratio of the volume of the hard spheres to the total volume of para-aramid microfibers, alkali powder, and dispersant is 1:3; the mass ratio of para-aramid microfibers, alkali powder, and dispersant is 1:0.5:4; the mass ratio of acetonitrile and methanol is 1:0.01; the mass concentration of para-aramid nanoflakes in the high-concentration para-aramid nanoflake slurry is 0.5%.
[0052] Secondly, wash the above high-concentration para-aramid nanoflake slurry. Among them, the washing steps include: first, perform preliminary washing with a mixed solution of acetonitrile and methanol, and then perform final washing with deionized water to thoroughly remove the residual dispersant and sanding aid;
[0053] Finally, dry the above washed high-concentration para-aramid nanoflake slurry to obtain para-aramid nanoflakes; among them, the drying steps include: freeze the washed high-concentration para-aramid nanoflake slurry into a solid at -18 °C, and then sublime and remove water under a vacuum condition of -101 °C.
[0054] Example 2
[0055] The preparation method of para-aramid nanoflakes provided in this example includes the following steps:
[0056] First, first, add para-aramid microfibers, lithium hydroxide, and potassium ethoxide powder into a mixed solution of benzene, ether, and water, and perform high-energy physical sanding under the conditions of a sanding time of 15 hours, a sanding speed of 2,000 revolutions per minute, and a sanding temperature of 0 °C to obtain a high-concentration para-aramid nanoflake slurry; among them, the sanding aid added in the high-energy physical sanding is polyacrylamide with an average molecular weight of 10,000,000, the hard spheres in the high-energy physical sanding are zirconium silicate beads, the diameter of the hard spheres is 5 mm, and the ratio of the volume of the hard spheres to the total volume of para-aramid microfibers, alkali powder, and dispersant is 1:10; the mass ratio of para-aramid microfibers, alkali powder, and dispersant is 1:2:100; the mass ratio of the mixed solution of benzene and ether and water is 1:0.05; the mass concentration of para-aramid nanoflakes in the high-concentration para-aramid nanoflake slurry is 20%.
[0057] Secondly, wash the above-mentioned high-concentration para-aramid nanoflake slurry. The washing steps include: first, conduct preliminary washing with a mixed solution of acetonitrile and methanol, and then conduct final washing with deionized water to thoroughly remove the residual dispersant and sanding aid.
[0058] Finally, dry the above-mentioned washed high-concentration para-aramid nanoflake slurry to obtain para-aramid nanoflakes. The drying steps include: freeze the washed high-concentration para-aramid nanoflake slurry into a solid at -18°C, and then sublime and remove the moisture under a vacuum condition of -101°C.
[0059] Example 3
[0060] The preparation method of para-aramid nanoflakes provided in this example includes the following steps:
[0061] First, add para-aramid microfibers and potassium tert-butoxide powder to a mixed solution of N,N-dimethylformamide and ethanol, and conduct high-energy physical sanding under the conditions of a sanding time of 8 hours, a sanding speed of 4000 revolutions per minute, and a sanding temperature of 20°C to obtain a high-concentration para-aramid nanoflake slurry. Among them, the sanding aid added in the high-energy physical sanding is polyvinylpyrrolidone with an average molecular weight of 1,300,000. The hard spheres in the high-energy physical sanding are tungsten carbide beads, the diameter of the hard spheres is 2 mm, and the ratio of the volume of the hard spheres to the total volume of para-aramid microfibers, alkali powder, and dispersant is 1:5. The mass ratio of para-aramid microfibers, alkali powder, and dispersant is 1:1:200. The mass ratio of N,N-dimethylformamide and ethanol is 1:0.03. The mass concentration of para-aramid nanoflakes in the high-concentration para-aramid nanoflake slurry is 15%.
[0062] Secondly, wash the above-mentioned high-concentration para-aramid nanoflake slurry. The washing steps include: first, conduct preliminary washing with a mixed solution of acetonitrile and methanol, and then conduct final washing with deionized water to thoroughly remove the residual dispersant and sanding aid.
[0063] Finally, dry the above-mentioned washed high-concentration para-aramid nanoflake slurry to obtain para-aramid nanoflakes. The drying steps include: freeze the washed high-concentration para-aramid nanoflake slurry into a solid at -18°C, and then sublime and remove the moisture under a vacuum condition of -101°C.
[0064] Example 4
[0065] The preparation method of para-aramid nanoflakes provided in this example includes the following steps:
[0066] First, first, para-aramid microfibers and sodium tert-butoxide powder are added to a mixed solution of hexamethylphosphoramide and propanol, and high-energy physical sanding is carried out under the conditions of a sanding time of 10 hours, a sanding speed of 6000 revolutions per minute, and a sanding temperature of 40 °C to obtain a high-concentration para-aramid nanoflake slurry; among them, the sanding aid added in the high-energy physical sanding is polyvinylpyrrolidone with an average molecular weight of 1,300,000, the hard spheres in the high-energy physical sanding are silicon carbide beads, the diameter of the hard spheres is 4 mm, and the ratio of the volume of the hard spheres to the total volume of para-aramid microfibers, alkali powder and dispersant is 1:8; the mass ratio of para-aramid microfibers, alkali powder and dispersant is 1:2:150; the mass ratio of hexamethylphosphoramide and propanol is 1:0.04; the mass concentration of para-aramid nanoflakes in the high-concentration para-aramid nanoflake slurry is 15%.
[0067] Secondly, the above high-concentration para-aramid nanoflake slurry is washed. Among them, the washing steps include: first, preliminary washing is carried out with a mixed solution of acetonitrile and methanol, and then final washing is carried out with deionized water to thoroughly remove the residual dispersant and sanding aid;
[0068] Finally, the above washed high-concentration para-aramid nanoflake slurry is dried to obtain para-aramid nanoflakes; among them, the drying steps include: after freezing the washed high-concentration para-aramid nanoflake slurry into a solid at -18 °C, water is sublimated and removed under a vacuum condition of -101 °C.
[0069] In this application, when the alkali powder is selected from one or two of potassium hydroxide and sodium ethoxide, the technical effects obtained are the same as those of the above embodiments.
[0070] In this application, when the aprotic solvent is selected from one or more of carbon tetrachloride, N,N-dimethylacetamide, dimethyl sulfoxide and 1,3-dimethyl-2-imidazolidinone, the technical effects obtained are the same as those of the above embodiments.
[0071] II. Experimental Examples
[0072] Experimental Example 1
[0073] The surface morphologies of the para-aramid nanoflakes prepared in the above Examples 1-4 were detected. Specifically, a scanning electron microscope was used to characterize the micro-morphologies of the raw para-aramid microfiber raw materials and the prepared para-aramid nanoflake samples, and the acceleration voltage was 10 kV. The detection results are as Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 shown; at the same time, an atomic force microscope was used to detect the micro-morphology of the para-aramid nanoflake sample prepared in Example 1, and the detection results are asFigure 6 as shown; the figure of the dispersion of the para-aramid nanoflakes prepared in Example 1 in water was taken with a camera as Figure 7 shown.
[0074] It can be seen that in the SEM image of the para-aramid microfiber raw material, there are long strips with a certain diameter; in the SEM images of the para-aramid nanoflakes prepared in Examples 1-4, the para-aramid nanoflakes have a two-dimensional structure, with a thickness of 1-30 nanometers, a width of 50-5000 nanometers, and a length of 50-5000 nanometers. Moreover, the surface of the nanoflakes is flat and there are no obvious defects or damages, indicating that the para-aramid nanoflakes prepared by the method for preparing para-aramid nanoflakes of the present application form a stable two-dimensional morphology; and under different process conditions, para-aramid nanoflakes with different pore structures can be obtained. At the same time, in the AFM image of the para-aramid nanoflakes prepared in Example 1, it can be further seen that the para-aramid presents a two-dimensional flaky morphology, with a thickness of about 17 nm, and the length and width can reach several micrometers, having a high aspect ratio.
[0075] This shows that the para-aramid nanoflakes prepared by the method for preparing para-aramid nanoflakes provided by the present application have a thickness of 1-30 nanometers, and both the width and length are in the range of 50-5000 nanometers. The surface is flat and there are no obvious defects or damages. It maintains the high strength, high modulus, heat resistance, and chemical corrosion resistance of the original para-aramid, and has a two-dimensional nanostructure. The two-dimensional nanostructure endows the nanoflakes with an enhanced specific surface area and better film-forming properties, providing the possibility for its application in high-performance composite materials, coating materials, filtration materials and other fields.
[0076] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A method for preparing a para-aramid nanosheet, characterized in that: The following steps are involved: Para-aramid micron fibers and alkali powder are added to a dispersant for high-energy physical sand grinding to obtain a high-concentration para-aramid nanosheet slurry; the high-concentration para-aramid nanosheet slurry is washed and dried to obtain a para-aramid nanosheet.
2. The method for preparing the para-aramid nanosheet according to claim 1, characterized in that: The mass ratio of the para-aramid micron fiber, the alkali powder and the dispersant is 1:(0.5-2):(4-200).
3. The method for preparing the para-aramid nanosheet according to claim 1, characterized in that: The alkali powder is selected from one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium ethoxide, sodium ethoxide, potassium tert-butoxide, and sodium tert-butoxide.
4. The method for preparing the para-aramid nanosheet according to claim 1, characterized in that: The diameter of the para-aramid micron fiber is 5-25 microns, and the length is 1-10 millimeters.
5. The method for preparing para-aramid nanosheets according to claim 1, characterized in that: The dispersant is composed of a non-protonic solvent and a proton donor, wherein the non-protonic solvent is selected from one or more of acetonitrile, benzene, ether, carbon tetrachloride, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric triamide and 1,3-dimethyl-2-imidazolidinone; the proton donor is selected from water, alcohol solvents or mixtures thereof, wherein the alcohol solvent is selected from one or more of methanol, ethanol and propanol; the mass ratio of the non-protonic solvent to the proton donor is 1:(0.01-0.05).
6. The method for preparing para-aramid nanosheets according to claim 1, characterized in that: The mass concentration of the para-aramid nanosheets in the high-concentration para-aramid nanosheet slurry is 0.5-20%.
7. The method for preparing para-aramid nanosheets according to claim 1, characterized in that: The high-energy physical sanding has a sanding time of 2-15 hours, a sanding speed of 2000-8000 rpm, and a sanding temperature of 0-50°C.
8. The method for preparing para-aramid nanosheets according to claim 1, characterized in that: The washing step comprises: firstly performing preliminary washing with a solvent that is the same as or compatible with the dispersant in the slurry, and then performing final washing with deionized water or purified water.
9. The method for preparing para-aramid nanosheets according to claim 1, characterized in that: The drying step comprises: freezing the washed high-concentration para-aramid nanosheet slurry into a solid at low temperature, and then sublimating to remove moisture under vacuum conditions.
10. A para-aramid nanosheet, characterized in that: The nanosheet is prepared by the method for preparing the para-aramid nanosheet according to any one of claims 1 to 9.