An aramid aerogel, its preparation method, macroscopic assembly method and application

Abstract

This invention provides an aramid aerogel, its preparation method, macroscopic assembly method, and applications. The preparation method includes: inducing a sol-gel transition of aramid using a coagulation bath containing a first solvent and a non-solvent; or dissolving aramid in a mixed solvent containing a first solvent and a non-solvent, allowing it to stand to induce a sol-gel transition, forming a wet gel; and sequentially subjecting the wet gel to solvent replacement and drying to obtain the aramid aerogel. The method of this invention can obtain a lightweight, porous aramid aerogel material with excellent thermal stability and flame-retardant and heat-insulating properties. Furthermore, by applying a solvent to the aerogel surface, without destroying the overall porous framework, the surface aramid molecular chains are selectively activated, promoting solvent diffusion between the interfaces to be assembled, inducing interpenetration of aramid chain segments at the interfaces, and realizing macroscopic structural assembly between aerogels. This provides a pathway for shape editing, encapsulation repair, and engineering of aramid aerogels.

Description

Technical Field

[0001] This invention belongs to the field of aerogel materials technology, specifically relating to an aramid aerogel, its preparation method, macroscopic assembly method and application. Background Technology

[0002] Aramidamide (PAF) fiber is a high-performance heat-resistant fiber independently developed in my country, possessing excellent heat resistance, flame retardancy, and electrical insulation. Aerogel, on the other hand, is an ultralight porous material formed by the aggregation of nanoparticles or polymer chains, characterized by high porosity, high specific surface area, and low density. If PAF can be constructed into an aerogel structure, it is hoped that the high-temperature resistance and flame retardancy of PAF can be combined with the lightweight and porous advantages of aerogel. However, constructing PAF into an aerogel faces many challenges. Traditional PAF processing typically relies on a "solvent dissolution-non-solvent coagulation and regeneration" process. In this process, the gelation behavior of the polymer is difficult to precisely control, easily leading to uneven aerogel pore structure and making it difficult to obtain a structurally complete and performance-controllable porous network. Furthermore, aerogel materials are inherently brittle and have limited macroscopic structural stability, making it difficult to process complex shapes and stably assemble multiple blocks. Therefore, how to achieve controllable fabrication of aramid aerogel structures and further solidify the small-sized aerogel units into macroscopic components with complex morphologies is one of the problems that urgently need to be solved. Summary of the Invention

[0003] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions: A first aspect of the present invention provides a method for preparing arylsulfonyl aerogel, comprising: A coagulation bath containing a first solvent and a non-solvent is provided, and the coagulation bath is used to induce the aramid fiber to undergo a sol-gel transition to form a wet gel; The wet gel was subjected to solvent replacement and drying treatment in sequence to obtain aramid aerogel.

[0004] In some embodiments, the preparation method specifically includes: Aramidone is dissolved in a second solvent to obtain a first aramidone solution; the second solvent is the same as or compatible with the first solvent. The first aramid solution is brought into contact with the coagulation bath to induce the aramid to undergo a sol-gel transition, resulting in the wet gel.

[0005] In some embodiments, the volume ratio of the first solvent to the non-solvent in the coagulation bath is 30~60:40~70.

[0006] In some embodiments, the first solvent includes one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0007] In some embodiments, the second solvent includes one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0008] In some embodiments, the non-solvent includes one or more of tert-butanol, methanol, ethanol, propanol, and ethylene glycol.

[0009] In some embodiments, the first aramid solution is coated onto a substrate and then immersed in the coagulation bath to form a thin-film aramid aerogel.

[0010] In some embodiments, the mass percentage of aramid in the first aramid solution is 6~16 wt.%.

[0011] In some embodiments, the solvent used for solvent replacement includes one or a combination of ethanol, tert-butanol, and acetone.

[0012] In some embodiments, the drying process may include one or more of supercritical drying, freeze drying, or atmospheric pressure drying.

[0013] A second aspect of the present invention provides a method for preparing arylsulfonyl aerogel, comprising: A aramid fiber is dissolved in a mixed solvent, which includes a first solvent and a non-solvent, to obtain a second aramid fiber solution; The second aramid solution was injected into the mold and left to stand until a wet gel was formed; The wet gel was subjected to solvent replacement and drying treatment in sequence to obtain aramid aerogel.

[0014] The above-mentioned method for preparing aramid aerogels using a mold casting process can obtain aramid aerogels with smooth surfaces, controllable dimensions, complete structures, and diverse shapes, and is suitable for preparing complex three-dimensional aramid aerogel materials.

[0015] In some embodiments, the mass percentage of aramid in the second aramid solution is 6-12 wt.%.

[0016] In some embodiments, the volume ratio of the first solvent to the non-solvent in the mixed solvent is 60~80:20~40.

[0017] In some embodiments, the first solvent includes one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0018] In some embodiments, the non-solvent includes one or more of tert-butanol, methanol, ethanol, propanol, and ethylene glycol.

[0019] In some embodiments, the settling time is 24 hours or more, preferably 24 hours to 72 hours.

[0020] In some embodiments, the solvent used for solvent replacement includes one or a combination of ethanol, tert-butanol, and acetone.

[0021] In some embodiments, the drying process may include one or more of supercritical drying, freeze drying, or atmospheric pressure drying.

[0022] The preparation method provided by this invention enables control over the gelation process and pore structure of aramid fibers, resulting in aramid fiber aerogels with adjustable specific surface area and complete structure. The obtained aramid fiber aerogels are not only lightweight and porous with excellent thermal stability, but also exhibit superior flame retardant and thermal insulation properties.

[0023] A third aspect of the present invention provides an aramid aerogel, which is prepared by the preparation method described in any of the technical solutions.

[0024] A fourth aspect of the present invention provides a method for macroscopic assembly of arylsulfonyl aerogel, comprising: A third solvent is applied at the assembly interface of the first aramid aerogel unit, and the assembly interface of the second aramid aerogel unit is brought into contact with the assembly interface of the first aramid aerogel unit having the third solvent. The third solvent is removed to allow the first aramid aerogel unit and the second aramid aerogel unit to combine, thereby obtaining an aramid aerogel assembly. The third solvent includes one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0025] In some embodiments, the first aramid aerogel unit and the second aramid aerogel unit are prepared by the aramid aerogel preparation method described in any of the technical solutions of the present invention.

[0026] The aforementioned macroscopic assembly method is based on a solvent-induced aerogel surface molecular activation mechanism: by applying a solvent to the surface of the aramid aerogel, the surface aramid molecular chains are selectively activated without damaging the overall porous framework, promoting solvent diffusion between the interfaces to be assembled. This induces interpenetration of aramid chain segments at the interfaces, achieving stable adhesion and macroscopic structural assembly between aerogels. This method enables adhesive-free bonding of aramid aerogels and is simple and rapid, applicable to shape editing, encapsulation repair, and fabrication of complex engineering components using aramid aerogels.

[0027] In some embodiments, the method of applying a third solvent at the assembly interface may include one or a combination of liquid phase coating, dripping, impregnation, spraying, or solvent vapor annealing.

[0028] The fifth aspect of the present invention provides an aramid aerogel assembly, which is obtained by assembling at least two aramid aerogel units using the macroscopic assembly method described in any of the technical solutions.

[0029] A sixth aspect of the present invention provides a surface-encapsulated aramid aerogel, comprising: Aramidyl sulfone aerogel; An encapsulation structure is formed on the surface of the aramid aerogel. The encapsulation structure is formed by applying a fourth solvent to the surface of the aramid aerogel, causing local densification and reconstruction of the aramid segments on the surface, and then removing the fourth solvent. The fourth solvent includes one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0030] In some embodiments, the first aramid aerogel unit and the second aramid aerogel unit are prepared by the aramid aerogel preparation method described in any of the technical solutions of the present invention.

[0031] The above method can be used to obtain aramid aerogels with a surface encapsulation structure, which significantly improves the surface integrity and environmental stability of the material while maintaining the internal porous network characteristics.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The present invention uses a mixture of solvent and non-solvent to prepare aramid aerogel with adjustable specific surface area and complete structure; the obtained aramid aerogel is not only lightweight and porous with excellent thermal stability, but also has excellent flame retardant and heat insulation properties.

[0033] (2) In this invention, a solvent is applied to the surface of the aramid aerogel. Without damaging the overall porous framework, the surface aramid molecular chains are selectively activated, promoting the diffusion of the solvent between the interfaces to be assembled. This induces the interpenetration of aramid chain segments at the interface, achieving stable adhesion and macroscopic structural assembly between aerogels. This method can achieve adhesive-free bonding of aramid aerogels, and is simple and fast. It can be applied to the shape editing, encapsulation and repair, and preparation of complex engineering components of aramid aerogels.

[0034] (3) The present invention uses a solvent to act on the surface of aramid aerogel, which promotes the local densification and reconstruction of aramid segments to form a continuous surface encapsulation structure. While maintaining the internal porous network characteristics, it significantly improves the surface integrity and stability of aramid aerogel material. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the process for preparing arylsulfonyl aerogel films in Example 1; Figure 2 This is a comparison chart of the specific surface area of ​​the aramid aerogel films prepared in Examples 1-4; Figure 3 This is a macroscopic schematic diagram of the arylsulfonyl aerogel film prepared in Example 1; Figure 4 Here is a SEM image of the arylsulfonyl aerogel film prepared in Example 1; Figure 5 The stress-strain curves of the aramid aerogel films prepared in Examples 1-4 are shown. Figure 6 The nitrogen adsorption-desorption isotherms of the arylsulfonyl aerogel blocks prepared in Examples 5-9 are shown. Figure 7 The pore size distribution diagram of the arylsulfonyl fiber aerogel block prepared by method 5-9 is shown. Figure 8 This is a SEM image of the arylsulfonyl aerogel prepared in Example 6; Figure 9 This is a SEM image of the sulfolane aerogel prepared in Example 8; Figure 10 These are comparative diagrams of the density distribution of sulfolane aerogel blocks prepared in Examples 5-9; Figure 11 The graph shows the thermal conductivity of aramid aerogel blocks of different densities in Examples 5-9 at 25 °C. Figure 12 This is a graph showing the trend of thermal conductivity variation of the aramid aerogel blocks in Examples 5-9 under different temperature conditions; Figure 13 This is a temperature diagram of the measured temperature of the aramid aerogel in Example 7 on the upper and lower surfaces of the hot plate using thermocouples. Figure 14 This is an infrared camera image of the aramid aerogel of Example 7 on a hot stage; Figure 15 It is a model of arylsulfonyl aerogel in the shape of a "large cauldron"; Figure 16It is a model of arylsulfonium aerogel in the shape of "Tengwang Pavilion"; Figure 17 This is the ternary phase diagram for the preparation of arylsulfonyl aerogels using the DMSO-TBA system; Figure 18 This is a ternary phase diagram for the preparation of arylsulfonyl aerogels using the NMP-TBA system; Figure 19 This is the ternary phase diagram for the preparation of arylsulfonyl aerogels using the DMF-TBA system; Figure 20 This is the ternary phase diagram for the preparation of arylsulfonyl aerogels using the DMSO-MeOH system; Figure 21 This is the ternary phase diagram for the preparation of arylsulfonyl aerogels using the DMSO-EtOH system; Figure 22 This is a schematic flowchart of the macroscopic assembly method of the arylsulfonyl aerogel in Example 14; Figure 23 It is an aramid aerogel model in the shape of the Eiffel Tower, obtained by assembling the components using a macroscopic assembly method; Figure 24 It is a cylindrical aramid aerogel model obtained by splicing together using a macroscopic assembly method. Detailed Implementation

[0037] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0038] In addition, unless otherwise specified, all raw materials used in the following embodiments can be purchased from the market or other sources, and all production and testing equipment used are known in the art, as are the testing methods used.

[0039] Example 1 This embodiment provides an aramid aerogel film and its preparation method. Figure 1 This is a schematic diagram of the preparation process of Example 1, which specifically includes the following steps: Aryl sulfone short-cut fiber raw material was dissolved in DMSO to prepare a homogeneous DMSO solution of aramid, wherein the mass concentration of aramid was 10 wt.%. The DMSO solution of aramid was poured onto a glass substrate and coated with a blade coater to a thickness of about 500 μm. After coating, the substrate was placed in a coagulation bath containing 60% DMSO and 40% tert-butanol by volume to gel, resulting in a wet gel film. Then, solvent replacement was performed with ethanol, with ethanol being replaced every 2 hours. After more than 5 ethanol replacements, the substrate was subjected to supercritical drying to obtain an aramid aerogel film.

[0040] Examples 2-4 Examples 2-4 are basically the same as Example 1, except that the composition of the good solvent and non-solvent in the mixed coagulation bath is changed according to Table 1. The rest are the same as in Example 1 and will not be repeated here. The specific surface area of ​​the arylsulfonyl aerogel films prepared in Examples 1-4 is summarized in Table 1.

[0041] Table 1. Composition of the coagulation bath and specific surface area of ​​the aerogels obtained in Examples 1-4 This invention, through systematic research, has discovered that in the preparation system of aramid aerogels, if water or acid is used as the coagulation bath, the high hydrogen bonding content of water and acid, combined with their significant solubility differences, leads to instantaneous phase separation, easily forming a loosely structured membrane (such as a finger-like structure). Furthermore, the high surface tension of water easily disrupts the overall membrane structure. Using a simple alcohol as the coagulation bath results in volume shrinkage and the formation of macropores due to phase separation. This invention further reveals that by introducing a suitable solvent (dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone), the solvent exchange rate can be slowed down, reducing the rate of phase separation and allowing more time for the aramid to complete physical processes such as hydrogen bonding and benzene ring stacking. Tert-butanol, with its low surface tension, is suitable as a poor solvent in the coagulation bath. Moreover, by adjusting the ratio of tert-butanol to a good solvent (such as DMSO), hydrogels with a pore size distribution primarily between 2-50 nm can be obtained. By further solvent replacement and drying, the pore size is kept from collapsing, thus obtaining an aramid aerogel with a certain specific surface area and a pore size distribution mainly consisting of mesopores.

[0042] Experimental results show that when the volume fraction of the non-solvent tert-butanol in the coagulation bath is 40%-70% (corresponding to a DMSO content of 30%-60%), an aerogel structure with a certain specific surface area can be obtained. When the tert-butanol content is too low, i.e., the DMSO content in the system is high, the solvation effect is too strong, making it difficult for polymer segments to effectively aggregate into a film and form a porous structure. Conversely, when the tert-butanol content is too high, the non-solventization effect dominates, the system undergoes rapid phase separation, and a dense structure or blind pores are easily formed, making it difficult to form a considerable specific surface area. Therefore, the non-solvent content must be controlled within a suitable range, and combined with subsequent solvent replacement and specific drying processes, to prepare aerogel films with a high specific surface area. In the non-solvent-induced sol-gel transition, the gelation rate is crucial. This gelation process is related to the double diffusion rate; the faster the diffusion rate, the faster the gelation rate. However, if the solvent exchange rate is too fast, it usually causes rapid phase separation, forming a precipitate. The structure of this precipitate is usually a dense blind-pore structure with no surface area. The diffusion rate depends on the amount of non-solvent in the coagulation bath. The higher the amount of non-solvent, the faster the diffusion rate, and therefore the faster the gelation rate.

[0043] Figure 2 This is a comparison chart of the specific surface areas of the aramid aerogel films prepared in Examples 1-4. It can be seen that the specific surface area of ​​the film prepared in Example 1 is larger, at 288 m² / g. Furthermore, from... Figure 2 As can be seen, the specific surface area gradually decreases with the increase of tert-butanol content in the coagulation bath. The pore size distribution of the prepared arylsulfonyl aerogel is mainly concentrated in the range of 2-50 nm. Therefore, considering the need to obtain a higher specific surface area, the preferred volume ratio of DMSO to tert-butanol in the coagulation bath is 50-60:40-50.

[0044] Figure 3 This is a macroscopic schematic diagram of the arylsulfonyl aerogel film prepared in Example 1. Figure 3 As can be seen, the aramid aerogel film is white in color and has a uniform surface. Figure 4 This is a SEM image of the arylsulfonyl aerogel film prepared in Example 1. Figure 4 As can be seen, the interior of the aramid aerogel film is a three-dimensional skeleton, and its building blocks are mainly fibers.

[0045] Figure 5 This is a comparison chart of the tensile properties of the aramid aerogel films prepared in Examples 1-4. Figure 5 As can be seen, the fracture strength and elongation at break increase with the increase of tert-butanol content in the coagulation bath. Therefore, considering the need to obtain higher fracture strength and elongation at break, the preferred volume ratio of DMSO to tert-butanol in the coagulation bath is 30~50:50~70.

[0046] Example 5 Example 5 provides a method for preparing three-dimensional aramid aerogels using a casting molding process, specifically including the following steps: A mixed solvent of 70% DMSO and 30% tert-butanol was used to dissolve aramid fibers, with the mass fraction of aramid fibers controlled at 6 wt.%. The solution was heated and stirred thoroughly to form a homogeneous solution. The solution was then injected into a mold of a predetermined shape and allowed to stand for about 2 days to allow the system to undergo a gelation reaction, generating a wet gel with a three-dimensional network structure. Subsequently, the wet gel sample was subjected to ethanol solvent exchange to remove residual solvent and impurities, and then dried using a supercritical drying process to obtain a structurally complete aramid fiber aerogel block with well-developed pores.

[0047] This invention introduces a casting process into the preparation of aerogel materials. By pouring aramid sol into a mold, a sol-gel transition is induced within the confined space. Combined with subsequent solvent replacement and drying steps, the three-dimensional structure of aramid aerogel is formed. This method not only enables the construction of the unique porous structure of aerogels but also provides an effective way to prepare aramid aerogel blocks with controllable dimensions, complete structures, and diverse shapes.

[0048] Examples 6-9 Examples 6-9 are basically the same as Example 5, except that the volume ratios of DMSO and tert-butanol are varied according to Table 2, and the mass fraction of arylsulfonyl ether in the solution is changed. The rest are the same as in Example 5, and will not be described again here.

[0049] The specific surface area of ​​the aramid aerogel blocks prepared in Examples 6-9 was tested, and the test results are summarized in Table 2.

[0050] Table 2. Solvent composition, aramid mass fraction, and specific surface area used in the preparation of aramid aerogel blocks. As shown in Table 2, the specific surface area of ​​the aramid aerogel blocks is mainly concentrated in the range of 150-170 m² / g. Figure 6 The nitrogen adsorption-desorption isotherms of the arylsulfonyl aerogel blocks prepared in Examples 5-9 show that they typically exhibit Type IV curve characteristics, indicating that the samples mainly have mesoporous structure characteristics. Figure 7 The pore size distribution curves of the aerogel blocks under different preparation parameters in Examples 5-9 are shown. The results show that the pore size of all samples is mainly concentrated in the mesoporous range of 2-50 nm, and the distribution peak is located around 20 nm. This indicates that the prepared arylsulfonyl aerogels generally have well-developed mesoporous structures, which is beneficial for achieving excellent specific surface area and adsorption performance.

[0051] Figure 8This is a SEM image of the sulfolane aerogel prepared in Example 6. Figure 9 This is a SEM image of the arylsulfonyl aerogel prepared in Example 8. (Comparison) Figure 8 , Figure 9 It can be seen that the microstructure of the aerogel changes significantly as the concentration of aramid in the solution decreases: when the concentration of aramid in the solution is 10 wt.%, the building units of the aerogel exhibit a distinct fibrous structure, with fibers interwoven to form a three-dimensional network skeleton; while when the concentration of aramid in the solution is 6 wt.% PSA, the building units of the aerogel mainly exhibit a lamellar structure, with the lamellars stacked on top of each other to form a relatively loose porous network.

[0052] This structural evolution can be explained by solvent action and thermodynamic mechanisms. In the DMSO solution system, DMSO has good solubility for aramid fibers, effectively dispersing the polymer chains and maintaining high system stability. When tert-butanol (TBA) is added to the system, its non-solvent nature reduces the overall solubility, prompting spontaneous gelation of the solution. From a thermodynamic perspective, the gelation process can be described by the formula ΔG = ΔH. The process is described using TΔS. When interactions occur between aramid molecular chains (such as hydrogen bonding, π-π stacking, or van der Waals interactions), the system releases a significant amount of energy, leading to a substantial decrease in enthalpy (ΔH < 0), resulting in a free energy change ΔG < 0. The system then tends to spontaneously form a gel network structure. Therefore, the main driving force for gelation originates from the decrease in system enthalpy, i.e., the release of intermolecular interaction energy. In high-concentration systems (e.g., 10 wt.% aramid), the polymer chains are closer together, and the intermolecular interactions (such as chain entanglement and hydrogen bonding) are stronger. During gelation, the molecular chains tend to align and aggregate along the direction of least resistance. Due to the high rigidity and linear structure of aramid molecular chains, this aggregation tendency makes them easily stacked in an ordered manner along a one-dimensional direction to form a fibrous structure. Conversely, in low-concentration systems (e.g., 6 wt.% aramid), the polymer chains are sparsely distributed, the intermolecular interactions are significantly weakened, and the stability of the gel network decreases. During the subsequent ethanol replacement process, the system exhibits weak resistance to phase separation, making it more prone to local aggregation of molecular chains to form a polymer-rich phase, which ultimately stacks into a lamellar structure during drying. It is evident that the solution concentration directly influences the gelation process and microstructure of aramid aerogel by regulating the strength and spatial distribution of interactions between polymer chains, demonstrating a significant morphological evolution from fibrous to lamellar structure, which also significantly affects its thermal conductivity. To obtain a three-dimensional network framework formed by interwoven fibrous structures, the mass fraction of aramid in the solution can be controlled at 10–12 wt.%. To obtain a framework formed by stacked lamellar structures, the mass fraction of aramid in the solution can be controlled at 6–10 wt.%.

[0053] Figure 10 This is a comparison diagram of the density distribution of arylsulfonyl aerogel blocks prepared in Examples 5-9. Figure 10 It is known that, under the same mixed solvent (70% DMSO, 30% TBA), the lower the mass concentration of arylsulfonyl fiber in the solution, the lower the density of the resulting aerogel. The densities of the arylsulfonyl fiber aerogel blocks obtained in Examples 5-9 are, in order, 0.092 g / cm³. 3 0.131 g / cm 3 0.153g / cm 3 0.182 g / cm 3 0.227 g / cm 3 . Figure 11 The results show the thermal conductivity of aramid aerogel blocks of different densities obtained in Examples 5-9 at 25°C. To ensure data reliability, each sample was tested three times and the average value was used for analysis. The thermal conductivity of the aramid aerogel blocks obtained in Examples 5-9 were 0.033 W / (m·K), 0.027 W / (m·K), 0.026 W / (m·K), 0.029 W / (m·K), and 0.032 W / (m·K), respectively. The change in thermal conductivity shows that the thermal conductivity of the aerogel gradually decreases with increasing aramid polymer concentration, indicating that the aerogel prepared at higher concentrations has a denser and more uniform pore structure, which can effectively suppress heat conduction between gas molecules, thus significantly improving its thermal insulation performance. Therefore, from the perspective of obtaining excellent thermal insulation, the preferred mass fraction of aramid in the solution is 8-11 wt.%.

[0054] Figure 12 The results show the trend of thermal conductivity variation of the aramid aerogel blocks in Examples 5-9 under different temperature conditions. The results indicate that the thermal conductivity of the aerogel gradually increases with increasing test temperature. This is because at higher temperatures, the thermal motion of gas molecules is enhanced, resulting in a corresponding increase in the thermal conductivity of the gas, thus improving the overall thermal conductivity. Despite this, the aramid aerogel as a whole maintains a relatively low thermal conductivity, demonstrating that its excellent porous structure can effectively block heat transfer at high temperatures.

[0055] To further verify the thermal insulation performance of the aerogel, actual thermal insulation characterization was performed using a hot stage and thermocouples. The results are as follows: Figure 13As shown. Test method: The hot stage temperature was set to 100 ℃. The aramid aerogel block of Example 7 was placed on the hot stage, and the change in its upper surface temperature over time was tested. The results showed that the temperature of the upper surface of the aramid aerogel remained relatively stable at approximately 48 ℃ within 20 min, with a temperature difference of up to 52 ℃ compared to the hot stage temperature. This indicates that the aerogel can effectively block heat transfer and maintain stable thermal insulation performance for a relatively long period of time. In addition, the test process was characterized using an infrared thermal imager, and the results are shown below. Figure 14 As shown in the image, the infrared image shows that the temperature of the hot stage is 99.9 ℃, while the temperature of the upper surface of the aerogel is 47.9 ℃, which is highly consistent with the thermocouple measurement results, further verifying the excellent thermal insulation ability and thermal stability of the aramid aerogel.

[0056] To evaluate its flame-retardant properties, the limiting oxygen index (LOI) of the aramid aerogel blocks in Examples 5-9 was tested, and the LOI was measured to be 25-27%. According to the aramid fiber technical handbook, the limiting oxygen index of pure aramid fiber is approximately 33%, while the oxygen index of the aerogel samples is slightly lower. This phenomenon is mainly attributed to the aerogel's extremely high specific surface area and open porous structure, which significantly increases the contact area between the sample and oxygen, thereby accelerating the oxidation reaction rate and reducing the oxygen index value. Nevertheless, its limiting oxygen index is still higher than that of most common polymer materials, indicating that the aramid aerogel still possesses good intrinsic flame-retardant properties and thermal protection capabilities.

[0057] As can be seen from the above thermal conductivity and flame retardant test results, the aramid aerogel prepared by this invention has both low thermal conductivity and excellent flame retardant properties, and has potential application value in the fields of thermal insulation and protection, high temperature insulation, etc.

[0058] Based on the solvent-to-nonsolvent volume ratio and aramid mass fraction in Example 5 of Table 2, this invention also produces aramid aerogel three-dimensional materials of different shapes by using molds of different shapes. Figure 15 , Figure 16 These are detailed aramid aerogel models of the "Da Ke Ding" and "Tengwang Pavilion" obtained using this method. This demonstrates that aramid aerogel materials not only possess excellent formability and structural retention capabilities, but also exhibit potential feasibility in complex structure molding and cultural and creative applications.

[0059] Examples 10-13 The only difference between Examples 10-13 and Example 5 is that the good solvent, non-solvent type and mass ratio of aramid polymer used in the preparation of aramid aerogel are varied according to Table 3. The rest are the same as in Example 1, and will not be repeated here.

[0060] Table 3 When the solvent-to-nonsolvent volume ratio and aramid polymer mass ratio are within the range shown in Table 3, aramid aerogels can be successfully prepared using the NMP-TBA system, DMF-TBA system, DMSO-MeOH system, and DMSO-EtOH system.

[0061] Figures 17-21 It is a universal ternary phase diagram for preparing arylsulfonyl aerogels using mixed solvents of different solvents and non-solvents. Figures 17-21 The aerogel is divided into three regions: sol, gel, and precipitation. In the sol region, due to the small amount of non-solvent added, solvation ability remains dominant, and the polymer chains maintain good solubility. The system remains stable as a single phase, exhibiting a transparent sol overall. With continued addition of non-solvent, the effective solvent mass decreases, and the polymer chains begin to shrink, generating enhanced interchain attraction (interaction forces). The system represents the gel point in the ternary phase diagram, forming a spatial network structure spanning the system, but without macroscopic phase separation, thus exhibiting a soft, elastic gel—the region required for aerogel preparation. Excess non-solvent causes the system to enter the phase separation region, where the polymer locally concentrates to form a solid "polymer-enriched phase," coexisting with the remaining solvent-enriched phase. Macroscopically, this manifests as a solid-liquid composite phase with both solid blocks and liquid (macroscopic phase separation), i.e., the precipitation region. This is something to be avoided in aerogel preparation. Therefore, by rationally controlling the ratio of solvent, non-solvent, and polymer in the solvent-polymer system, polymer aerogels can be prepared.

[0062] Example 14 This embodiment provides a macroscopic assembly method for aramid aerogel. Figure 22 This is a flowchart of Example 14, which specifically includes: Take a block of aramid aerogel prepared in Example 5, and apply DMSO to a portion of its surface. Take another block of aramid aerogel and place its surface in contact with the area of ​​the aforementioned aerogel coated with DMSO. Then, remove the DMSO by natural evaporation or heating to achieve the splicing of the aerogels. Repeat the above steps to assemble the desired shape.

[0063] Figure 23 The "Eiffel Tower" is assembled based on this macroscopic assembly method. Figure 24 The process involves first casting aramid aerogel sol into a cylindrical groove mold to obtain a cylindrical aerogel, and then bonding the cylinders together using a solvent-induced method to obtain a three-dimensional structure of aramid aerogel.

[0064] As demonstrated by the macroscopic assembly method for aramid aerogels in this application, solvents play a crucial role in the secondary processing after aerogel molding. The suitable solvent provided by this invention can induce localized plasticization and rearrangement of surface polymer segments, thereby improving the mobility of surface segments. After coating the aramid aerogel surface with this solvent, solvent molecules can penetrate the aerogel surface without damaging the overall porous framework, causing relaxation and activation of surface segments. In this state, segment diffusion and interpenetration can occur at the contact interface of adjacent aerogel blocks, thus forming a stable physical entanglement structure. After solvent removal, this interface structure gradually solidifies, achieving a strong connection between aerogel blocks. This macroscopic assembly method has promising application prospects. Firstly, this process can be used for the repair of aerogel structures: by improving the mobility and migration ability of surface segments, solvent-induced segment recombination can effectively bridge microcracks and structural defects generated during molding or service, thereby restoring local continuity and inhibiting further defect propagation. Secondly, based on the same molecular rearrangement mechanism, solvent treatment on the aerogel surface can induce local densification and reconstruction of aramid segments, forming a continuous surface encapsulation structure. This significantly improves the surface integrity and environmental stability of the material while maintaining the internal porous network characteristics. Furthermore, when solvent treatment is applied to the contact interface of multiple aerogel blocks, the activated segments can diffuse and interpenetrate with each other in the interface region and re-associate after solvent removal, thereby achieving a stable bond between adjacent aerogel blocks.

[0065] Therefore, the decisive regulatory role of non-solvents in the sol-gel transition and skeleton construction during the primary molding stage, synergistically with the repair, encapsulation, and adhesion functions imparted by solvents through segment dissolution and recombination in the secondary processing stage, jointly construct a complete technical path for aramid aerogels from structural molding to interface engineering and reprocessing, providing a new material strategy for their repairability and encapsulation. Furthermore, the casting molding combined with solvent-induced macroscopic assembly strategy expands the design freedom of the macroscopic morphology of aramid aerogels, providing a new approach for the modular assembly of aerogel materials. The method provided by this invention, while maintaining the intrinsic porous structure advantages of aerogels, achieves the controllable construction of complex structural components, possessing certain engineering application potential.

[0066] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0067] All aspects, embodiments, features, and examples of this invention should be considered illustrative and used to explain and illustrate the invention, but not to limit the invention. The scope of the invention is defined only by the claims.

[0068] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims.

Claims

1. A method for preparing an aramid aerogel, characterized in that, include: A coagulation bath containing a first solvent and a non-solvent is provided, and the coagulation bath is used to induce the aramid fiber to undergo a sol-gel transition to form a wet gel; The wet gel was subjected to solvent replacement and drying treatment in sequence to obtain aramid aerogel.

2. The preparation method according to claim 1, characterized in that, Specifically, it includes: Aramidone is dissolved in a second solvent to obtain a first aramidone solution; the second solvent is the same as or compatible with the first solvent. The first aramid solution is brought into contact with the coagulation bath to induce the aramid to undergo a sol-gel transition, resulting in the wet gel.

3. The preparation method according to claim 1, characterized in that: The volume ratio of the first solvent to the non-solvent in the coagulation bath is 30~60:40~70; And / or, the first solvent includes one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; And / or, the non-solvent includes one or more of tert-butanol, methanol, ethanol, propanol, and ethylene glycol.

4. The preparation method according to claim 2, characterized in that, Specifically, it includes: The first aramid solution is coated onto a substrate and then immersed in the coagulation bath to form a thin film of aramid aerogel. And / or, the mass percentage of aramid in the first aramid solution is 6~16 wt.%.

5. A method for preparing an aramid aerogel, characterized in that, include: A aramid fiber is dissolved in a mixed solvent, which includes a first solvent and a non-solvent, to obtain a second aramid fiber solution; The second aramid solution was injected into the mold and left to stand until a wet gel was formed; The wet gel was subjected to solvent replacement and drying treatment in sequence to obtain aramid aerogel.

6. The preparation method according to claim 5, characterized in that: The mass percentage of aramid in the second aramid solution is 6~12 wt.%. And / or, the volume ratio of the first solvent to the non-solvent in the mixed solvent is 60~80:20~40; And / or, the first solvent includes one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; And / or, the non-solvent includes one or more of tert-butanol, methanol, ethanol, propanol, and ethylene glycol; And / or, the settling time is more than 24 hours.

7. An aramid aerogel, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. A macroscopic assembly method for arylsulfonyl aerogel, characterized in that, include: A third solvent is applied at the assembly interface of the first aramid aerogel unit, and the assembly interface of the second aramid aerogel unit is brought into contact with the assembly interface of the first aramid aerogel unit having the third solvent. The third solvent is removed to allow the first aramid aerogel unit and the second aramid aerogel unit to combine, thereby obtaining an aramid aerogel assembly. The third solvent includes one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

9. An aramid aerogel assembly, characterized in that, It is obtained by assembling at least two aramid aerogel units using the macroscopic assembly method described in claim 8.

10. A surface-encapsulated arylsulfonyl aerogel, characterized in that, include: Aramidyl sulfone aerogel; An encapsulation structure is formed on the surface of the aramid aerogel. The encapsulation structure is formed by applying a fourth solvent to the surface of the aramid aerogel, causing local densification and reconstruction of the aramid segments on the surface, and then removing the fourth solvent. The fourth solvent includes one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

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