CN114907609A - Super-elastic aramid nanofiber aerogel, and preparation method and application thereof - Google Patents
Super-elastic aramid nanofiber aerogel, and preparation method and application thereof Download PDFInfo
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2377/00—Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers
- C08J2377/10—Polyamides derived from aromatically bound amino and carboxyl groups of amino carboxylic acids or of polyamines and polycarboxylic acids
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Abstract
The invention discloses a super-elastic aramid nano-fiber aerogel, and a preparation method and application thereof. The preparation method comprises the following steps: dissolving aramid fiber in alkali and an organic solvent and reacting to form homogeneous aramid nanofiber dispersion liquid; compounding the aramid nano-fiber dispersion liquid and the slow-release gelling agent, standing for gelling after homogenization, and aging to obtain aramid nano-fiber wet gel; and (3) carrying out solvent replacement and gas-liquid exchange drying on the aerogel, and then carrying out high-temperature heat treatment in a selected atmosphere to prepare the super-elastic aramid nano-fiber aerogel. The super-elastic aramid nano-fiber aerogel provided by the invention has extremely low apparent density, high porosity, excellent mechanical property, low thermal conductivity, excellent compression resilience, heat insulation and heat preservation, and has wide application prospects in the fields of mechanical compression, thermal management, sound absorption and noise reduction, environmental management, intelligent sensing, clean energy, electronic information and the like.
Description
Technical Field
The invention relates to a super-elastic aramid nano-fiber aerogel and a preparation method and application thereof, belonging to the technical field of porous aerogel materials.
Background
Aerogel materials have evolved rapidly since the kistler invention, and their low density, high porosity and large specific surface area characteristics have given aerogels a wide range of applications, such as adsorption, filtration, shock absorption, thermal insulation and energy applications. Currently, aerogel not only pursues excellent comprehensive performance, thermal stability and low thermal conductivity, but also pursues a simple and flexible preparation method with high elasticity so as to meet the requirements of national defense, aerospace and civil fields. However, due to the inherent brittleness of inorganic aerogels, severe strength reduction or structural collapse occurs during compression or stretching, limiting their use under special conditions. Compared with inorganic aerogel, polymer aerogel has better flexibility, but general polymer has poor thermal stability and is easy to decompose, so that the application of the polymer aerogel is greatly limited.
Aramid fiber has unique performance, obviously higher strength than other organic materials, excellent mechanical performance, chemical stability, solvent resistance, thermal stability (decomposition temperature up to 550 ℃) and the like, and is widely applied to the fields of national defense and civil use. After the aramid nano-fiber aerogel is prepared by Kotov et al, some researchers at home and abroad have successfully applied the kevlar nano-fiber to lithium ion battery diaphragms, nano-fiber reinforced fillers and super capacitor electrodes, however, the mechanical exploration of the aerogel body is generally ignored in the current stage of research. Currently, although various applications of aramid aerogel are reported, a block of superelastic aramid aerogel has not been reported. Tuo et al in From Monomers to a Lasagna-like Aerogel monoliths: an Assembling strand for Aramid fibers reports that a monomer method is adopted to prepare Aramid fiber aerogel, but the obtained aerogel has low elasticity which is not more than 50 percent, high thermal conductivity, complex preparation process from bottom to top and no industrial value. Therefore, the development of the super-elastic aramid aerogel has important significance.
Disclosure of Invention
The invention mainly aims to provide a light, heat-insulating, heat-preserving and super-elastic aramid nanofiber aerogel and a preparation method and application thereof, so as to overcome the defects in the prior art.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a preparation method of a super-elastic aramid nanofiber aerogel, which comprises the following steps:
dissolving aramid fiber in alkali and an organic solvent and reacting to form homogeneous aramid nanofiber dispersion liquid;
compounding the aramid nano-fiber dispersion liquid and the slow-release gelling agent, standing for gelling after homogenizing, and aging to obtain aramid nano-fiber wet gel;
and carrying out solvent replacement and gas-liquid exchange drying on the aramid nano fiber wet gel, and then carrying out high-temperature heat treatment in a selected atmosphere to prepare the super-elastic aramid nano fiber aerogel.
In some embodiments, the sustained release gel comprises a combination of any two or more of dimethyl sulfoxide, sulfolane, ethyl formate, ethyl acetate, ethyl butyrate, methanol, ethanol, and water.
The embodiment of the invention also provides the super-elastic aramid nano-fiber aerogel prepared by the preparation method.
Furthermore, the super-elastic aramid nano-fiber aerogel is formed by assembling aramid nano-fiber building modules and simultaneously forms a hierarchical pore structure, wherein the hierarchical pore structure consists of micropores with the pore diameter of less than 2nm, mesopores with the pore diameter of 2-50 nm and macropores with the pore diameter of 50 nm-100 mu m; the density of the super-elastic aramid nano-fiber aerogel is 0.1-200 mg/cm 3 The porosity is 70-99.99%, and the specific surface area is 10-1000 m 2 (g), the compression rebound rate is 1-99%, the tensile strength is 0.1-30 MPa, and the thermal conductivity is 10-100 mw/(m × k).
The embodiment of the invention also provides application of the super-elastic aramid nano-fiber aerogel in the fields of mechanical compression, thermal management, sound absorption and noise reduction, environmental management, intelligent sensing, clean energy, wearable materials or electronic information and the like.
Compared with the prior art, the invention has the beneficial effects that:
the light, heat-insulating, heat-preserving and super-elastic aramid nanofiber aerogel provided by the invention has extremely low apparent density of 0.1-200 mg/cm 3 The composite material is adjustable, has high porosity, excellent mechanical property and low heat conductivity coefficient, has excellent compression resilience and thermal insulation performance, and has wide application prospect in the fields of mechanical compression, thermal management, sound absorption and noise reduction, environmental management, intelligent sensing, clean energy, electronic information and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is an appearance diagram of the super-elastic aramid nanofiber aerogel material prepared in example 1 of the present invention.
Fig. 2 is a scanning electron microscope image of the super-elastic aramid nanofiber aerogel material prepared in example 1 of the present invention.
Fig. 3 is a graph of adsorption capacity-relative pressure curve of the super-elastic aramid nanofiber aerogel material prepared in example 3 of the present invention.
Fig. 4 is an infrared image of the super-elastic aramid nanofiber aerogel material prepared in example 3 of the present invention at 350 ℃ for 1 hour.
Fig. 5 is a scanning electron microscope image of the super-elastic aramid nanofiber aerogel material prepared in example 6 of the present invention.
Fig. 6 is a stress-strain curve diagram of the super-elastic aramid nanofiber aerogel material prepared in example 5 of the present invention.
Detailed Description
In view of the defects of the prior art, the inventor of the present invention provides a preparation method of the invention through long-term research, and mainly takes an aramid polymer and a copolymer thereof as raw materials, prepares aramid nanofibers through deprotonation, and prepares a light, heat-insulating, heat-preserving and super-elastic aramid nanofiber aerogel through a slow-release gel method, a gas-liquid interaction drying method and a thermal crosslinking method, wherein the obtained aramid nanofiber aerogel has excellent compression resilience and heat-insulating and heat-preserving properties.
The technical solution, its implementation and principles, etc. will be further explained as follows.
One aspect of the embodiment of the present invention provides a method for preparing a superelastic aramid nanofiber aerogel, which includes:
dissolving aramid fiber in alkali and an organic solvent and reacting to form homogeneous aramid nanofiber dispersion liquid;
compounding the aramid nano-fiber dispersion liquid and the slow-release gelling agent, standing for gelling after homogenizing, and aging to obtain aramid nano-fiber wet gel;
and carrying out solvent replacement and gas-liquid exchange drying on the aramid nano fiber wet gel, and then carrying out high-temperature heat treatment in a selected atmosphere to prepare the super-elastic aramid nano fiber aerogel.
In some embodiments, the method of making comprises: firstly, mixing aramid fiber, pulp or powder, alkali and an organic solvent, then reacting the mixture at a certain temperature to form homogeneous aramid fiber nano-fiber dispersion liquid, compounding the aramid fiber nano-fiber dispersion liquid and a slow-release gelling agent, standing for gelling after homogenization, and aging to obtain aramid fiber nano-fiber wet gel; and then, obtaining the super-elastic aramid nano-fiber aerogel through solvent replacement, gas-liquid exchange drying and high-temperature heat treatment.
In some more specific embodiments, the preparation method of the super-elastic aramid nanofiber aerogel comprises the following steps:
(1) dissolving aramid fiber in alkali and an organic solvent, and then reacting the mixture at a certain temperature to form homogeneous aramid nanofiber dispersion liquid;
(2) compounding the aramid nano-fiber dispersion liquid and the slow-release gelling agent in a certain proportion, violently stirring in the compounding process, standing for gelling after homogenizing, and aging to obtain aramid nano-fiber wet gel;
(3) and (3) performing solvent replacement and gas-liquid exchange drying on the obtained aramid nano fiber wet gel, and performing high-temperature heat treatment under the flow of a selected atmosphere to obtain the light, temperature-resistant and excellent-mechanical-property super-elastic aramid nano fiber aerogel.
The preparation mechanism of the invention may be that: after the aramid fiber is treated by an alkali organic solvent, deprotonation is carried out, the repulsion force between chains is increased, the fiber is generated, and finally the aramid nanofiber dispersion liquid is formed in the solvent under the action of a long time. The slow-release gel can slowly give protons to the dispersion liquid to slowly generate gelation, and the inner part and the outer part are synchronously performed to form uniform gel. And then obtaining the super-elastic aramid nano-fiber aerogel through solvent exchange and gas-liquid interactive drying.
In some embodiments, in step (1), the aramid fiber includes at least one of poly-p-phenylene terephthalamide, poly-p-phenylene terephthalamide co-poly-phenylene terephthalamide, and the like, and specifically, the aramid fiber includes at least one of Kevlar, Nomex, Twaron, Technora, Terlon, tapran, and the like, but is not limited thereto.
In some embodiments, the aramid fiber has a morphology including, but not limited to, at least one of bulk, fiber, paper, pulp, or powder. The preparation method has wide range of material selection directions and has no direct relation with the shape and appearance of raw materials.
In some embodiments, in step (1), the base comprises at least one of sodium hydroxide, potassium hydroxide, sodium tert-butoxide, potassium tert-butoxide, sodium amide, lithium amide, etc., preferably at least one of potassium hydroxide, sodium hydroxide, potassium tert-butoxide, but not limited thereto.
In some embodiments, in the step (1), the mass ratio of the aramid fiber to the alkali is 1: 0.1-1: 20, and the mass ratio of the alkali to the organic solvent is 1: 2-1: 500. According to the invention, the microstructure of the nanofiber can be regulated and controlled by controlling the proportion and the matching mode of different organic solvents and alkali, and the overall structure of the aerogel can be regulated and controlled.
In some embodiments, in step (1), the organic solvent includes at least one of dimethyl sulfoxide, sulfolane, dibutyl sulfone, diethyl sulfone, ethanol, ethyl methyl sulfone, and the like, but is not limited thereto.
In some embodiments, the mass fraction of the aramid fibers (preferably poly-p-phenylene terephthalamide) in the aramid nanofiber dispersion is 0.01 to 30 wt%, preferably 0.1 to 10 wt%. According to the invention, the uniformly distributed and completely dispersed aramid nanofiber dispersion can be obtained, and the aerogel density can be regulated and controlled by regulating and controlling the mass fraction, particularly, the aerogel density is high and is improved along with the improvement of the mass fraction.
In some embodiments, in the step (1), the reaction temperature is 25-80 ℃ and the reaction time is 10 h-7 days.
In some embodiments, in step (2), the sustained release gel comprises any two or more combinations of dimethyl sulfoxide, sulfolane, ethyl formate, ethyl acetate, ethyl butyrate, methanol, ethanol, water, and the like, but is not limited thereto. The mass percentages of the dimethyl sulfoxide, the sulfolane, the ethyl formate, the ethyl acetate, the ethyl butyrate, the methanol, the ethanol and the water are (0-80): (0-60): (0-40): (0-20): (0-10): and the configuration scheme under a large window can obtain the aramid nano fiber wet gel which is more uniform and stable.
In some embodiments, in step (2), the standing time is 1 to 3 days.
In some embodiments, in the step (2), the aging time is 0.5-48 h, preferably 0.5-24 h, and the nanofiber framework structure can be sufficiently improved and the strength of the aerogel can be increased as the aging time is prolonged.
In some embodiments, in step (3), the solvent used for solvent replacement includes at least one of water, ethanol, tert-butanol, dioxane, phenol, acetone, etc., but is not limited thereto, the number of replacements is at least 3, and the time interval is at least 5 h. The invention adopts solvent replacement to reduce the interfacial tension in the drying process, thereby obtaining more complete nanofiber morphology and aerogel integral structure.
In some embodiments, in step (3), the gas-liquid exchange drying manner includes at least one of supercritical drying, freeze drying, vacuum drying, atmospheric drying, spray drying, thermal drying, radiation drying, and the like, but is not limited thereto.
In some embodiments, in step (3), the selected atmosphere includes an atmosphere formed by at least one of nitrogen, argon, air, helium, carbon dioxide, and hydrogen, but is not limited thereto.
In some embodiments, in the step (3), the temperature of the high-temperature heat treatment is 200-600 ℃ and the time is 10 min-10 h, and the high-temperature heat treatment process generates thermal crosslinking and micro-carbonization to generate crosslinking points, so that the skeleton strength is increased.
As another aspect of the technical scheme of the invention, the invention also relates to the super-elastic aramid nano-fiber aerogel prepared by the preparation method.
Furthermore, the super-elastic aramid nano-fiber aerogel is formed by assembling aramid nano-fiber building modules and simultaneously forms a hierarchical pore structure, and the hierarchical pore structure consists of micropores with the pore diameter smaller than 2nm, mesopores with the pore diameter of 2-50 nm and macropores with the pore diameter of 50 nm-100 mu m.
Furthermore, the nanofiber structure obtained by the deprotonation method is controllable, the shrinkage rate of the material is extremely low by the slow-release gel method, and the density of the obtained super-elastic aramid nanofiber aerogel has extremely low apparent density of 0.1-200 mg/cm 3 Adjustable, has high porosity of 70-99.99 percent and specific surface area of 10-1000 m 2 The super-elastic aramid fiber nano-fiber aerogel has excellent mechanical properties (the compression rebound rate is 1-99%) and high tensile strength (specifically 0.1-30 MPa), and has a low heat conductivity coefficient, specifically 10-100 mw/(m × k). The preparation method provided by the invention is simple and easy to apply.
The embodiment of the invention also provides application of the super-elastic aramid nanofiber aerogel.
Further, the application includes: the super-elastic aramid nano-fiber aerogel has wide application prospects in the fields of mechanical compression, thermal management (such as heat insulation), sound absorption and noise reduction, environmental management, intelligent sensing, clean energy, wearable materials or electronic information and the like.
By the technical scheme, the super-elastic aramid nano-fiber aerogel provided by the invention has the advantages of good mechanical strength, high specific surface area, high porosity, excellent thermal stability, excellent heat-insulating property and the like, and has a very wide application prospect.
The technical solutions of the present invention will be described in further detail below with reference to several preferred embodiments and accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. It is to be noted that the following examples are intended to facilitate the understanding of the present invention, and do not set forth any limitation thereto. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers.
Example 1
Weighing 1g of poly-p-phenylene terephthalamide fiber and 1g of potassium hydroxide, adding the poly-p-phenylene terephthalamide fiber and the potassium hydroxide into a sample bottle, adding 49g of dimethyl sulfoxide, stirring and reacting at 1200rpm at room temperature (25 ℃) for 4 days until a uniform aramid fiber nanofiber dispersion liquid is formed, wherein the mass fraction of the aramid fiber nanofiber is 2%.
Weighing 3.0g of dimethyl sulfoxide, 1.0g of ethyl formate, 1.0g of water and 0.2g of ethanol, uniformly mixing to obtain a slow-release gel, adding 5g of the prepared aramid nano-fiber dispersion liquid, stirring at 1200rpm, homogenizing, standing for gelling for 1 day, aging for 48 hours to obtain aramid nano-fiber wet gel, and then adding sufficient tert-butyl alcohol and water (V/V is 1: 1) for replacement for 5 times at an interval of 5 hours each time. Finally, freeze-drying at-50 deg.C. Obtaining aerogel, and carrying out high-temperature heat treatment on the aerogel at 350 ℃ for 10 hours under nitrogen to obtain the aramid nano-fiber aerogel.
The appearance of the super-elastic aramid nanofiber aerogel prepared in this example is shown in fig. 1, the scanning electron microscope image is shown in fig. 2, and other performance parameters are shown in table 1.
Example 2
Weighing 1g of poly-p-phenylene terephthalamide pulp and 1g of potassium tert-butoxide, adding into a sample bottle, adding 49g of dimethyl sulfoxide, stirring at 1200rpm at room temperature, and reacting for 7 days until a uniform aramid nano-fiber dispersion liquid is formed, wherein the mass fraction of the aramid nano-fiber is 2%.
Weighing 2.0g of dimethyl sulfoxide, 2.0g of ethyl acetate, 1.0g of water and 1.0g of ethanol, uniformly mixing to obtain a slow-release gel, adding 5g of the prepared aramid nano-fiber dispersion liquid, stirring and homogenizing at 1200rpm, standing for gelling for 2 days, aging for 24 hours to obtain an aramid nano-fiber wet gel, and then adding sufficient phenol and water (V/V is 2: 1) for replacement for 5 times, wherein the interval is 5 hours each time. Finally, freeze-drying at-50 deg.C. Obtaining aerogel, and carrying out high-temperature heat treatment on the aerogel at 550 ℃ for 1h under hydrogen to obtain the aramid nano-fiber aerogel.
Example 3
Weighing 2g of poly-p-phenylene terephthalamide fiber and 3g of potassium tert-butoxide, adding into a sample bottle, adding 48g of dimethyl sulfoxide, stirring at 2400rpm at room temperature, and reacting for 7 days until a uniform aramid nano-fiber dispersion liquid is formed, wherein the mass fraction of the aramid nano-fiber is 4%.
Weighing 5.0g of dimethyl sulfoxide, 2.0g of ethyl acetate, 1.0g of water and 1.0g of ethanol, uniformly mixing to obtain a slow-release gel, adding 5g of the prepared aramid nano-fiber dispersion liquid, stirring at 1200rpm, homogenizing, standing for gelling for 2 days, aging for 30 hours to obtain aramid nano-fiber wet gel, and adding sufficient ethanol for replacement for 3 times at intervals of 5 hours each time. And finally drying in supercritical carbon dioxide for 12 h. Obtaining aerogel, and carrying out high-temperature heat treatment on the aerogel at 400 ℃ for 5h under argon to obtain the super-elastic aramid nano-fiber aerogel.
The adsorption capacity-relative pressure curve prepared in this example is shown in fig. 3, the infrared graph after 1h at 350 ℃ is shown in fig. 4, and other performance parameters are shown in table 1.
Example 4
Weighing 15g of poly-p-phenylene terephthalamide fiber and 10g of potassium tert-butoxide, adding into a sample bottle, adding 35g of dimethyl sulfoxide, stirring at 2400rpm at room temperature, and reacting for 7 days until a uniform aramid nano-fiber dispersion liquid is formed, wherein the mass fraction of the aramid nano-fiber is 30%.
Weighing 6.0g of dimethyl sulfoxide, 2.0g of ethyl acetate, 3.0g of water and 1.0g of ethanol, uniformly mixing to obtain a slow-release gel, adding 5g of the prepared aramid nano-fiber dispersion liquid, stirring at 1200rpm, homogenizing, standing for gelling for 2 days, aging for 48 hours to obtain aramid nano-fiber wet gel, and adding sufficient ethanol for replacement for 4 times at an interval of 5 hours each time. And finally drying in supercritical carbon dioxide for 12 h. Obtaining aerogel, and carrying out high-temperature heat treatment on the aerogel at 400 ℃ for 5h under argon to obtain the super-elastic aramid nano-fiber aerogel.
Example 5
Weighing 3g of poly (p-phenylene terephthalamide) co-poly (p-phenylene terephthalamide) and 2g of sodium amide, adding into a sample bottle, adding 47g of sulfolane, stirring at 1200rpm at 50 ℃ for reaction for 2 days until a uniform aramid nano-fiber dispersion liquid is formed, wherein the mass fraction of the aramid nano-fiber is 6%.
Weighing 5.0g of dimethyl sulfoxide, 1.0g of ethyl butyrate, 0.2g of water and 0.5g of ethanol, uniformly mixing to obtain a slow-release gel, adding 5g of the prepared aramid nano-fiber dispersion liquid, stirring at 1200rpm, homogenizing, standing for gelling for 1 day, aging for 12 hours to obtain aramid nano-fiber wet gel, and adding sufficient acetone for replacement for 5 times at intervals of 5 hours. And finally drying in supercritical carbon dioxide for 12 h. Obtaining aerogel, carrying out high-temperature heat treatment on the aerogel at 500 ℃ for 10min under nitrogen to obtain the super-elastic aramid nano-fiber aerogel, wherein the stress-strain curve (compression curve) is shown in figure 6, and other performance parameters are shown in table 1.
Example 6
Weighing 5g of poly (p-phenylene terephthalamide) co-poly (p-phenylene terephthalamide) and 5g of sodium tert-butoxide, adding 45g of dimethyl sulfoxide, stirring at room temperature and 1200rpm for 5 days, and reacting until a uniform aramid nano-fiber dispersion liquid is formed, wherein the mass fraction of the aramid nano-fiber is 10%.
Weighing 3.0g of dimethyl sulfoxide, 1.5g of ethyl butyrate, 1.5g of water and 0.5g of methanol, uniformly mixing to obtain a slow-release gel, adding 5g of the prepared aramid nanofiber dispersion liquid, stirring at 1200rpm, homogenizing, standing for gelling, aging for 24 hours to obtain aramid nanofiber wet gel, and adding sufficient acetone for replacing for 5 times at intervals of 5 hours. And finally drying in supercritical carbon dioxide for 12 h. Obtaining aerogel, carrying out high-temperature heat treatment on the aerogel at 450 ℃ for 6h under nitrogen to obtain the super-elastic aramid nano-fiber aerogel, wherein a scanning electron microscope image of the super-elastic aramid nano-fiber aerogel is shown in figure 5, and other performance parameters are shown in table 1.
Example 7
0.1g of poly-p-phenylene terephthalamide fiber and 1g of potassium tert-butoxide are weighed and added into a sample bottle, 49.9g of dimethyl sulfoxide is added, and the mixture is stirred and reacted for 12 hours at room temperature and 2400rpm until uniform aramid fiber nano-fiber dispersion liquid is formed, wherein the mass fraction of the aramid fiber nano-fiber is 0.2%.
Weighing 2.0g of dimethyl sulfoxide, 2.0g of ethyl acetate, 2.0g of water and 1.0g of ethanol, uniformly mixing to obtain a slow-release gel, adding 5g of the prepared aramid nano-fiber dispersion liquid, stirring at 1200rpm, homogenizing, standing for gelling for 1 day, aging for 12 hours to obtain aramid nano-fiber wet gel, and then adding sufficient dioxane for replacement for 6 times at intervals of 5 hours. Finally, freeze-drying at-50 deg.C. Obtaining aerogel, and carrying out high-temperature heat treatment on the aerogel at 400 ℃ for 5h under argon to obtain the super-elastic aramid nano-fiber aerogel.
Table 1 performance parameters of the super-elastic aramid nanofiber aerogels obtained in examples 1 to 7
Example 8
Weighing poly (p-phenylene terephthalamide) fibers and lithium amide, adding into a sample bottle, adding sulfolane, stirring at 2400rpm at 80 ℃ for 10 hours to react until a uniform aramid fiber nanofiber dispersion liquid is formed, wherein the mass fraction of the aramid fiber nanofiber is 0.01%, the mass ratio of the poly (p-phenylene terephthalamide) fibers to the lithium amide is 1: 0.1, and the mass ratio of the sulfolane to the lithium amide is 1: 2.
Weighing 2.0g of sulfolane, 2.0g of ethyl formate, 2.0g of water and 1.0g of methanol, uniformly mixing to obtain a slow-release gel, adding the prepared aramid nano-fiber dispersion liquid, wherein the mass ratio of the aramid nano-fiber dispersion liquid to the slow-release gel is 1: 0.6, standing for gelling for 1 day after stirring and homogenizing at 1200rpm, aging for 12 hours to obtain aramid nano-fiber wet gel, and adding sufficient dioxane for replacement for 4 times at an interval of 8 hours. And finally, carrying out vacuum drying to obtain aerogel, and carrying out high-temperature heat treatment on the aerogel at 200 ℃ for 10 hours under helium to obtain the super-elastic aramid nano-fiber aerogel.
Example 9
Weighing poly-p-phenylene terephthalamide fiber and sodium hydroxide, adding the poly-p-phenylene terephthalamide fiber and the sodium hydroxide into a sample bottle, adding ethyl methyl sulfone, stirring and reacting at the temperature of 25 ℃ and the rpm for 7 days until a uniform aramid fiber nano-fiber dispersion liquid is formed, wherein the mass fraction of the aramid fiber nano-fiber is 20%, the mass ratio of the poly-p-phenylene terephthalamide fiber to the sodium hydroxide is 1: 20, and the mass ratio of the ethyl methyl sulfone to the sodium hydroxide is 1: 500.
Weighing 2.0g of dimethyl sulfoxide, 2.0g of ethyl butyrate, 2.0g of methanol and 1.0g of ethanol, uniformly mixing to obtain a slow-release gel, adding the prepared aramid nano-fiber dispersion liquid, wherein the mass ratio of the aramid nano-fiber dispersion liquid to the slow-release gel is 1: 5, stirring at 1200rpm, homogenizing, standing for gelling for 3 days, aging for 0.5h to obtain aramid nano-fiber wet gel, and then adding sufficient ethanol for replacing for 5 times, wherein the interval is 6h each time. And finally, carrying out freeze drying at-50 ℃ to obtain aerogel, and carrying out high-temperature heat treatment on the aerogel at 600 ℃ for 10min under carbon dioxide to obtain the super-elastic aramid nano-fiber aerogel.
In addition, the inventors of the present invention have also made experiments with other materials, process operations, and process conditions described in the present specification with reference to the above examples, and have obtained preferable results.
While the invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (10)
1. A preparation method of the super-elastic aramid nanofiber aerogel is characterized by comprising the following steps:
dissolving aramid fiber in alkali and an organic solvent and reacting to form homogeneous aramid nanofiber dispersion liquid;
compounding the aramid nano-fiber dispersion liquid and the slow-release gelling agent, standing for gelling after homogenizing, and aging to obtain aramid nano-fiber wet gel;
and carrying out solvent replacement and gas-liquid exchange drying on the aramid nano fiber wet gel, and then carrying out high-temperature heat treatment in a selected atmosphere to prepare the super-elastic aramid nano fiber aerogel.
2. The method of claim 1, wherein: the aramid fiber is made of at least one of poly-p-phenylene terephthalamide, poly-p-phenylene terephthalamide and poly-p-phenylene terephthalamide co-poly-p-phenylene terephthalamide, and preferably, the aramid fiber comprises at least one of Kevlar, Nomex, Twaron, Tehnora, Terlon and Taparan;
and/or the aramid fiber has a form including at least one of a block, a fiber, a paper, a pulp, and a powder.
3. The method of claim 1, wherein: the alkali comprises at least one of sodium hydroxide, potassium hydroxide, sodium tert-butoxide, potassium tert-butoxide, sodium amide and lithium amide, preferably at least one of potassium hydroxide, sodium hydroxide and potassium tert-butoxide; and/or the organic solvent comprises at least one of dimethyl sulfoxide, sulfolane, dibutyl sulfone, diethyl sulfone, ethanol and ethyl methyl sulfone.
4. The method of claim 1, wherein: the mass fraction of the aramid fiber in the aramid nanofiber dispersion liquid is 0.01-30 wt%, preferably 0.1-10 wt%;
and/or the mass ratio of the aramid fiber to the alkali is 1: 0.1-1: 20;
and/or the mass ratio of the alkali to the organic solvent is 1: 2-1: 500;
and/or the reaction temperature is 25-80 ℃, and the reaction time is 10 h-7 days.
5. The method of claim 1, wherein: the slow release gel comprises a mixture of at least any two or more than three of dimethyl sulfoxide, sulfolane, ethyl formate, ethyl acetate, ethyl butyrate, methanol, ethanol and water;
preferably, the mass ratio of dimethyl sulfoxide, sulfolane, ethyl formate, ethyl acetate, ethyl butyrate, methanol, ethanol and water in the sustained-release gel is (0-80): (0-60): (0-40): (0-20): (0-10): (0-10);
and/or the mass ratio of the aramid nano-fiber dispersion liquid to the slow-release gel is 1: 0.6-1: 5;
and/or the standing time is 1-3 days;
and/or the aging time is 0.5-48 hours, preferably 0.5-24 hours.
6. The method of claim 1, wherein: the solvent adopted by the solvent replacement comprises at least one of water, ethanol, tert-butyl alcohol, dioxane, phenol and acetone, the replacement frequency is at least 3 times, and the interval time of each time is at least 5 hours; and/or the gas-liquid exchange drying mode comprises at least one of supercritical drying, freeze drying, vacuum drying, normal pressure drying, spray drying, heat drying and radiation drying.
7. The method of claim 1, wherein: the selected atmosphere comprises an atmosphere of at least one of nitrogen, argon, air, helium, carbon dioxide, hydrogen.
8. The method of claim 1, wherein: the temperature of the high-temperature heat treatment is 200-600 ℃, and the time is 10 min-10 h.
9. The super-elastic aramid nano-fiber aerogel prepared by the preparation method of any one of claims 1 to 8, preferably, the super-elastic aramid nano-fiber aerogel is assembled by aramid nano-fiber building modules and forms a hierarchical pore structure, and the hierarchical pore structure consists of micropores with the pore diameter of less than 2nm, mesopores with the pore diameter of 2-50 nm and macropores with the pore diameter of 50 nm-100 μm; the density of the super-elastic aramid nano-fiber aerogel is 0.1-200 mg/cm 3 The porosity is 70-99.99%, and the specific surface area is 10-1000 m 2 (g), the compression rebound rate is 1-99%, the tensile strength is 0.1-30 MPa, and the thermal conductivity is 10-100 mw/(m × k).
10. The use of the superelastic aramid nanofiber aerogel according to claim 9 in the fields of mechanical compression, thermal management, sound absorption and noise reduction, environmental remediation, smart sensing, clean energy, wearable materials, or electronic information.
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