Carbon fiber felt reinforced aramid fiber aerogel as well as preparation method and application thereof

Abstract

The invention relates to a carbon fiber felt reinforced aramid fiber aerogel as well as a preparation method and application thereof, and solves the technical problems that an existing material is not ideal enough in mechanical property, low in compression strength of a product, required to be improved in rebound resilience and low in tensile strength, the carbon fiber felt reinforced aramid fiber aerogel is composed of chopped carbon fiber felt and aramid fiber nanofibers, and the shrinkage rate of the aerogel is 20%-30%; the compression strength is greater than or equal to 267 kPa under the strain of 80%, the maximum stress retention rate is greater than or equal to 75% after 500 cycles under the strain of 50%, and the energy loss factor is greater than or equal to 19%; the tensile strength is greater than or equal to 5MPa. The prepared aerogel has high strength and thermal insulation performance, and can be widely applied to the fields of aerospace, building materials and the like.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber reinforced composite materials, and in particular to a carbon fiber felt reinforced aramid aerogel, its preparation method, and its application. Background Technology

[0002] With the continuous growth of my country's economy and the expansion of domestic demand, my country has gradually emerged as a major user and consumer of carbon fiber reinforced composite materials. Against this backdrop, the large-scale recycling of chopped carbon fiber mats from carbon fiber reinforced composite materials awaits development and utilization to fully unleash the potential value of recycled products, further implement the "carbon neutrality" concept, and achieve the low-carbon goal throughout the entire life cycle of carbon fiber reinforced composite materials.

[0003] Aramid fiber is a synthetic fiber with excellent heat resistance and high specific strength. Kevlar fiber fabrics assembled from aramid fibers are widely used in the cushioning layer of bulletproof vests and the restraint layer of spacesuits due to their excellent tensile strength and flexibility. Since Kotov et al. dissociated nanoscale monomers of aramid fibers using a polar alkaline solution in 2011, composite materials constructed based on aramid fibers have gradually increased. Given the growing demand for lightweight, high-strength, and thermally insulating materials in aerospace, environmental remediation, and other fields, aramid aerogels have become a research hotspot due to their excellent properties such as high temperature resistance and low density.

[0004] Chinese invention patent application CN117164936A discloses a method for preparing a hydrophobic and oleophilic aramid / porous carbon fiber composite aerogel material, comprising: 1) preparing porous carbon fibers using PVP, aluminum sol, PTFE emulsion, etc., as raw materials, and employing electrostatic solution jet spinning technology combined with heat treatment; 2) preparing aramid nanofibers using aramid short fibers as raw materials, KOH as an alkali agent, and dimethyl sulfoxide as a solvent; 3) uniformly mixing the obtained porous carbon fibers and aramid nanofibers in a certain proportion, and preparing the hydrophobic and oleophilic aramid / porous carbon fiber composite aerogel material by freeze-drying. The prepared composite aerogel material has a three-dimensional honeycomb network structure, ultra-low density, and high oil absorption performance.

[0005] However, the above method has the following problems: (1) The carbon fibers prepared by electrospinning need to be treated; (2) The aerogel forming process does not use acid-assisted forming method; (3) The mechanical properties of the aerogel are not ideal, and the product has low compressive strength and low tensile strength. Summary of the Invention

[0006] To address the technical problems of insufficient mechanical properties of existing materials, such as low compressive strength, need for improved resilience, and low tensile strength, this invention provides a low-cost carbon fiber felt-reinforced aramid aerogel with high compressive strength, improved resilience, and high tensile strength, along with its preparation method and applications.

[0007] Therefore, the present invention provides a carbon fiber felt reinforced aramid aerogel, which is composed of chopped carbon fiber felt and aramid nanofibers, with a shrinkage rate of 20% to 30%; a compressive strength of ≥267 kPa at 80% strain, a maximum stress retention rate of ≥75% after 500 cycles at 50% strain, an energy loss factor of ≥19%, and a tensile strength of ≥5 MPa.

[0008] Preferably, the carbon fiber used in the carbon fiber felt is one or more of high modulus and high strength fibers such as T700, T800, and T1000.

[0009] Preferably, the chopped fibers used in the carbon fiber felt have a length of 0.2 to 8 mm; and the number of carbon fiber felt layers is 4 to 36.

[0010] If the chopped fiber length is too short, the tensile strength of the prepared aerogel will decrease, while if the chopped fiber length is too long, the compression resilience of the prepared aerogel will decrease. Depending on the type and content of the chopped fiber in the carbon fiber felt and the proportion of the aramid nanofiber solution, different numbers of carbon fiber felt layers should be selected. Only aerogels prepared according to this selection will have excellent performance.

[0011] The present invention also provides a method for preparing carbon fiber felt reinforced aramid aerogel, the specific steps of which are as follows: (1) using dimethyl sulfoxide solvent and potassium hydroxide, aramid fibers are peeled off under heating and stirring conditions to obtain a mixed solution of aramid nanofibers; (2) carbon fiber felt is immersed in the mixed solution of aramid nanofibers obtained in step (1), and the immersed carbon fiber felt and the mixed solution of aramid nanofibers are formed into a freezing solution; (3) the freezing solution obtained in step (2) is immersed in an ethanol solution of acetic acid for solvent replacement, and is washed with water to remove excess acid / alcohol solvent and dimethyl sulfoxide solvent, and water in the freezing solution is removed by freeze drying method to finally obtain carbon fiber felt reinforced aramid aerogel.

[0012] Preferably, in step (1), the mass ratio of the aramid fiber to potassium hydroxide is 1:(0.5-1.5).

[0013] Aramid fibers possess high crystallinity and extremely high orientation, making them difficult to directly disperse in solvents to form nanoscale dispersions. Deprotonation is a key technology for solving this problem. In the process of preparing aramid nanofibers through deprotonation of aramid fibers, potassium hydroxide, as a strong base reagent, is the core substance for achieving the deprotonation reaction. Its role is consistent throughout the entire process of disrupting the intermolecular forces of aramid fibers and promoting fiber exfoliation. The repeating units of the aramid molecular chain contain amide bonds, where the hydrogen atoms connected to the aromatic rings have a certain acidity. Potassium hydroxide dissociates into hydroxide ions in dimethyl sulfoxide. These hydroxide ions, as strong nucleophiles, attack the hydrogen atoms in the amide bonds, resulting in a deprotonation reaction. However, if the amount of potassium hydroxide is too small, deprotonation will be insufficient; if too much is used, it will lead to the breakage of the aramid nanofiber molecular chains, reducing the strength of the prepared aerogel.

[0014] Preferably, in step (1), the heating temperature is 20 to 80°C.

[0015] Heating can increase the activity and penetration rate of hydroxide ions and accelerate the deprotonation of amide groups. However, if the temperature is too high, the aramid molecular chains will thermally degrade, resulting in a decrease in strength. The evaporation of dimethyl sulfoxide solvent will cause the viscosity of the system to be too high. If the temperature is too low, the deprotonation rate will be slow.

[0016] Preferably, in step (1), the stirring speed is 100-700 r / min.

[0017] Stirring provides uniform shearing, avoiding localized overheating and excessive fiber breakage. Excessive rotation speed results in excessive shear force, leading to excessive breakage of aramid nanofibers and a decrease in the mechanical strength of the aerogel. Too low a rotation speed will result in uneven mixing, with hydroxide ions reacting only on the fiber surface and not being deprotonated inside, leading to severe agglomeration of aramid nanofibers.

[0018] Preferably, in step (1), the stirring time is 2 to 96 hours.

[0019] Insufficient stirring time will result in uneven mixing of the system, thereby reducing the strength of the aerogel; while excessive stirring time will prolong the preparation cycle.

[0020] Preferably, in step (1), the mass ratio of the aramid fiber to the dimethyl sulfoxide solvent is (1-3):100.

[0021] In the deprotonation process of aramid fibers, dimethyl sulfoxide (DMSO) solvent, as a polar aprotic solvent, dissolves and disperses potassium hydroxide to provide a uniform reaction environment. Through solvation, it stabilizes the negatively charged aramid molecular chains, preventing their re-aggregation and aiding in the nanofiber exfoliation process. Insufficient DMSO solvent leads to excessively high viscosity of the reaction system, incomplete deprotonation, and agglomeration of the aramid nanofibers; excessive DMSO reduces reaction efficiency, resulting in a porous aerogel structure and decreased performance.

[0022] Preferably, in step (2), the carbon fiber felt is stacked in a conventional stacking manner, such as parallel stacking, staggered stacking, directional staggered stacking, gradient thickness stacking, etc.

[0023] Different carbon fiber felt stacking methods will affect the performance of the prepared aerogel products. Parallel stacking: laid in parallel; staggered stacking: adjacent layers are stacked alternately and staggered; directional staggered stacking: formed by crisscrossing to form a grid; gradient thickness stacking: stacked in order of different thicknesses.

[0024] Preferably, in step (3), the soaking temperature is -20°C, and the acid / alcohol solvent is acetic acid solvent and ethanol solvent with a mass ratio of 7:3.

[0025] Aramid nanofibers that have not undergone reprotonation typically exhibit poor mechanical properties. Therefore, an acetic acid / ethanol solvent is used for reprotonation. During the cryogenic solution replacement process, the acetic acid solvent acts as a proton donor, providing abundant hydrogen ions for the formation of hydrogen bonds between the exfoliated aramid nanofibers; the ethanol solvent alleviates the volume shrinkage caused by low surface tension during reprotonation. A low-temperature environment is maintained during reprotonation to ensure the stability of the cryogenic solution. Excessive temperature leads to changes in the pore size of the cryogenic solution, while excessively low temperature slows down the reprotonation rate.

[0026] This invention also provides an application of carbon fiber felt reinforced aramid aerogel as a thermal insulation material.

[0027] The present invention has the following beneficial effects:

[0028] This invention provides a method for recycling and reusing chopped carbon fiber mat, combining it with aramid fibers to achieve a synergistic effect of high-performance fibers. Compared with existing technologies, this invention can effectively reduce the shrinkage rate of aramid nano-aerogels while significantly improving their compressive strength, resilience, and tensile strength. Attached Figure Description

[0029] Figure 1A and Figure 1B These are comparison diagrams of the compressive strength of the samples prepared in Example 2 and Comparative Example 2 of the present invention;

[0030] Figure 2A and Figure 2B These are comparison diagrams of the cyclic compression of samples prepared in Example 2 and Comparative Example 2 of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments, so that those skilled in the art can easily implement the present invention.

[0032] Example 1

[0033] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 0.5 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0034] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0035] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0036] The carbon fiber felt-reinforced aerogel prepared in this embodiment has a shrinkage rate of 33.3%, a compressive strength of 508.6 kPa (strain of 80%), a maximum stress retention rate of 80.3% after 500 cycles at 50% strain, an energy loss factor of 25.6%, and a tensile strength of 7.6 MPa.

[0037] Example 2

[0038] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0039] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0040] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0041] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 20.0%, a compressive strength of 289.9 kPa (60% strain) and 682.7 kPa (80% strain), a maximum stress retention rate of 89.0% after 500 cycles at 50% strain, an energy loss factor of 31.7%, and a tensile strength of 11.8 MPa.

[0042] Example 3

[0043] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.5 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0044] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0045] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0046] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 22.3%, a compressive strength of kPa (strain of 80%), a maximum stress retention rate of 84.0% after 500 cycles at 50% strain, an energy loss factor of 30.2%, and a tensile strength of 9.4 MPa.

[0047] Example 4

[0048] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 20°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0049] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0050] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0051] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 22.2%, a compressive strength of 600.7 kPa (strain of 80%), a maximum stress retention rate of 86.3% after 500 cycles at 50% strain, an energy loss factor of 20.3%, and a tensile strength of 10.8 MPa.

[0052] Example 5

[0053] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 80°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0054] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0055] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0056] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 23.3%, a compressive strength of 550.6 kPa (strain of 80%), a maximum stress retention rate of 82.6% after 500 cycles at 50% strain, an energy loss factor of [missing value], and a tensile strength of 9.2 MPa.

[0057] Example 6

[0058] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 100 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0059] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0060] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0061] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 32.5%, a compressive strength of 420.6 kPa (strain of 80%), a maximum stress retention rate of 75.2% after 500 cycles at 50% strain, an energy loss factor of 25.6%, and a tensile strength of 6.3 MPa.

[0062] Example 7

[0063] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 700 r / min, and stir continuously for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0064] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0065] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0066] The carbon fiber felt-reinforced aerogel prepared in this embodiment has a shrinkage rate of 26.3%, a compressive strength of 521.6 kPa (strain of 80%), a maximum stress retention rate of 79.6% after 500 cycles at 50% strain, an energy loss factor of 26.8%, and a tensile strength of 6.9 MPa.

[0067] Example 8

[0068] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 2 h until the solution color changes from yellow to red to obtain aramid nanofiber solution.

[0069] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0070] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0071] The carbon fiber felt-reinforced aerogel prepared in this embodiment has a shrinkage rate of 29.6%, a compressive strength of 400.6 kPa (strain of 80%), a maximum stress retention rate of 78.6% after 500 cycles at 50% strain, an energy loss factor of 26.6%, and a tensile strength of 6.8 MPa.

[0072] Example 9

[0073] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 96 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0074] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0075] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0076] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 21.2%, a compressive strength of 665.3 kPa (strain of 80%), a maximum stress retention rate of 88.5% after 500 cycles at 50% strain, an energy loss factor of 27.6%, and a tensile strength of 10.8 MPa.

[0077] Example 10

[0078] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 0.5 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 0.5 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0079] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0080] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0081] The carbon fiber felt-reinforced aerogel prepared in this embodiment has a shrinkage rate of 25.2%, a compressive strength of 267.5 kPa (strain of 80%), a maximum stress retention rate of 87.1% after 500 cycles at 50% strain, an energy loss factor of 25.8%, and a tensile strength of 5.0 MPa.

[0082] Example 11

[0083] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.5 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.5 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0084] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0085] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0086] The carbon fiber felt-reinforced aerogel prepared in this embodiment has a shrinkage rate of 22.8%, a compressive strength of 481.5 kPa (strain of 80%), a maximum stress retention rate of 85.0% after 500 cycles at 50% strain, an energy loss factor of 19.8%, and a tensile strength of 8.5 MPa.

[0087] Example 12

[0088] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0089] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 0.2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0090] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0091] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 21.3%, a compressive strength of 669.6 kPa (strain of 80%), a maximum stress retention rate of 88.6% after 500 cycles at 50% strain, an energy loss factor of 31.5%, and a tensile strength of 8.9 MPa.

[0092] Example 13

[0093] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0094] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 8 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0095] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0096] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 21.6%, a compressive strength of 670.6 kPa (strain of 80%), a maximum stress retention rate of 88.5% after 500 cycles at 50% strain, an energy loss factor of 28.6%, and a tensile strength of 10.2 MPa.

[0097] Example 14

[0098] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0099] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution in a staggered stacking manner, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0100] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0101] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 21.2%, a compressive strength of 675.3 kPa (strain of 80%), a maximum stress retention rate of 88.5% after 500 cycles at 50% strain, an energy loss factor of 31.6%, and a tensile strength of 11.5 MPa.

[0102] Example 15

[0103] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0104] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, stack them in the aramid nanofiber solution in an oriented interlaced manner, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0105] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0106] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 21.6%, a compressive strength of 679.6 kPa (strain of 80%), a maximum stress retention rate of 88.7% after 500 cycles at 50% strain, an energy loss factor of 31.8%, and a tensile strength of 11.4 MPa.

[0107] Example 16

[0108] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0109] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 20 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a gradient thickness stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0110] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0111] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 21.5%, a compressive strength of 670.6 kPa (strain of 80%), a maximum stress retention rate of 88.2% after 500 cycles at 50% strain, an energy loss factor of 31.7%, and a tensile strength of 10.9 MPa.

[0112] Example 17

[0113] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0114] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 4 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution in a parallel layer stacking manner, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0115] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0116] The carbon fiber felt-reinforced aerogel prepared in this embodiment has a shrinkage rate of 28.9%, a compressive strength of 310.5 kPa (strain of 80%), a maximum stress retention rate of 85.3% after 500 cycles at 50% strain, an energy loss factor of 25.6%, and a tensile strength of 5.9 MPa.

[0117] Example 18

[0118] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0119] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, take 36 layers of carbon fiber felt with a T700 fiber length of 2 mm, distribute them in the aramid nanofiber solution using a parallel layer stacking method, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, so that the solution freezes slowly along the axial direction to form a freezing solution.

[0120] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and perform reprotonation treatment at -20℃ for 24 hours. Wash with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution, and finally obtain carbon fiber felt reinforced aramid aerogel.

[0121] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 20.6%, a compressive strength of 675.6 kPa (strain of 80%), a maximum stress retention rate of 88.4% after 500 cycles at 50% strain, an energy loss factor of 24.9%, and a tensile strength of 11.6 MPa.

[0122] Comparative Example 1

[0123] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 0.5 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 0.5 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0124] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, and let the solution freeze slowly along the axial direction to form a freezing solution.

[0125] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and reprotonate it at -20℃ for 24 hours. Wash it with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution to finally obtain aramid aerogel.

[0126] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 29.9%, a compressive strength of 120.6 kPa (strain of 80%), a maximum stress retention rate of 84.6% after 500 cycles at 50% strain, an energy loss factor of 22.3%, and a tensile strength of 3.3 MPa.

[0127] Comparative Example 2

[0128] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.0 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.0 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0129] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, and let the solution freeze slowly along the axial direction to form a freezing solution.

[0130] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and reprotonate it at -20℃ for 24 hours. Wash it with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution to finally obtain aramid aerogel.

[0131] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 25.7%, a compressive strength of 603.2 kPa (strain of 80%), a maximum stress retention rate of 84.2% after 500 cycles at 50% strain, an energy loss factor of 13.6%, and a tensile strength of 5.7 MPa.

[0132] Comparative Example 3

[0133] (1) Take 50 ml of dimethyl sulfoxide solvent, weigh 1.5 g of potassium hydroxide, and stir thoroughly until the solution is clear and transparent; put 1.5 g of aramid fiber into the prepared mixed solution of dimethyl sulfoxide and potassium hydroxide, heat at 60°C, set the speed to 400 r / min, and continue stirring for 48 h until the solution color changes from yellow to red, and obtain aramid nanofiber solution.

[0134] (2) Inject 10 ml of the pre-prepared aramid nanofiber solution into the polytetrafluoroethylene mold, place the metal base of the polytetrafluoroethylene mold in liquid nitrogen, and let the solution freeze slowly along the axial direction to form a freezing solution.

[0135] (3) Prepare an acetic acid / ethanol solvent with a volume ratio of 7:3, place the freezing solution in the solvent, and reprotonate it at -20℃ for 24 hours. Wash it with deionized water to remove excess acetic acid / ethanol solvent and dimethyl sulfoxide solvent. Place the treated freezing solution in a refrigerator and use freeze-drying technology to remove the water in the freezing solution to finally obtain aramid aerogel.

[0136] The carbon fiber felt-reinforced aerogel prepared in this embodiment was tested and found to have a shrinkage rate of 25.5%, a compressive strength of 465.6 kPa (strain of 80%), a maximum stress retention rate of 81.5% after 500 cycles at 50% strain, an energy loss factor of 20.5%, and a tensile strength of 3.2 MPa.

[0137] Comparative Example 4

[0138] (1) 2g PVP and 14g deionized water were mixed to form a 12.5wt% solution. 5g aluminum sol and 10g PTFE emulsion were added and stirred at 30℃ for 6h to obtain spinning solution. Electrostatic jet spinning (1mm nozzle, 30kV electric field, 0.08MPa wind pressure, 80cm receiving distance) was carried out and dried at 80℃ for 12h. The temperature was raised to 200℃ in an air furnace at 2℃ / min and held for 1h (pre-oxidation). The temperature was raised to 1000℃ in a nitrogen furnace at 3℃ / min and held for 2h (carbonization) to obtain porous carbon fibers.

[0139] (2) 1g aramid short fiber, 1.5g KOH, 20mL water, 500mL dimethyl sulfoxide, stir at 30℃ for 4h until dark red; add deionized water and filter and wash 4 times until neutral to obtain aramid nanofibers; add deionized water and stir to prepare a 0.5wt% dispersion.

[0140] (3) 0.4g porous carbon fiber, 20g aramid dispersion, and 40g water were dispersed at 8000r / min for 5min, and 0.475g silane and 0.075g acetic acid were added and stirred for 2h. The solution was transferred to a mold and frozen at -60℃ for 24h. It was then freeze-dried at -60℃ for 72h and vacuum-dried at 160℃ for 6h to obtain composite aerogel.

[0141] The prepared aerogel composite material has a compressive stress of 11.55 kPa under a compressive strain of 60%.

[0142] Table 1. Performance parameters of the aerogels prepared in each example and comparative example.

[0143]

[0144]

[0145] Combining Examples 2 and 2, it can be seen that the addition of carbon fiber felt significantly improves the compressive and tensile strength of the aerogel product, while also improving the shrinkage rate. Combining Examples 1-9, it can be seen that the amount of potassium hydroxide, heating temperature, stirring speed, and stirring time affect the degree of dissolution of aramid fibers, thus affecting the mechanical properties of the aerogel product. The optimal conditions are achieved when the ratio of aramid fiber to potassium hydroxide is 1:1, the heating temperature is 60℃, the stirring speed is 400 r / min, and the stirring time is 48 h.

[0146] As can be seen from Examples 2, 12-18, the length of the carbon fiber felt, the number of carbon fiber felt layers, and the stacking method of the carbon fiber felt will affect the mechanical properties of the formed carbon fiber felt aerogel product.

[0147] Combining Example 2 and Comparative Example 4, the aerogel composite material prepared in Comparative Example 4 exhibits a compressive stress of 11.55 kPa under a compressive strain of 60%; the carbon fiber felt-reinforced aramid aerogel prepared in Example 2 exhibits a compressive stress of 289.9 kPa under a compressive strain of 60%. It can be seen that the compressive strength of the carbon fiber felt-reinforced aramid aerogel is significantly improved.

[0148] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the scope of the claims of the present invention should be within the protection scope of the present invention.

Claims

1. A carbon fiber felt reinforced aramid aerogel, characterized in that, It is composed of chopped carbon fiber mat and aramid nanofibers. The shrinkage rate of the carbon fiber mat-reinforced aramid aerogel is 20% to 30%. The compressive strength at 80% strain is ≥267 kPa, the maximum stress retention rate after 500 cycles at 50% strain is ≥75%, the energy loss factor is ≥19%, and the tensile strength is ≥5 MPa.

2. The carbon fiber felt reinforced aramid aerogel according to claim 1, characterized in that... The carbon fiber felt used is one or more of high modulus and high strength fibers such as T700, T800, and T1000.

3. The carbon fiber felt reinforced aramid aerogel according to claim 1, characterized in that... The chopped fibers used in the carbon fiber felt have a length of 0.2 to 8 mm; the carbon fiber felt has 4 to 36 layers.

4. The preparation method of carbon fiber felt reinforced aramid aerogel as described in claim 1, characterized in that... Includes the following steps: (1) Using dimethyl sulfoxide solvent and potassium hydroxide, aramid fibers were exfoliated under heating and stirring conditions to obtain a mixed solution of aramid nanofibers; (2) The carbon fiber felt is immersed in the aramid nanofiber mixed solution obtained in step (1), and the immersed carbon fiber felt and aramid nanofiber mixed solution are formed into a freezing solution. (3) The freezing solution obtained in step (2) is immersed in an ethanol solution of acetic acid for solvent replacement and washed with water to remove excess acid / alcohol solvent and dimethyl sulfoxide solvent. Water in the freezing solution is removed by freeze drying to finally obtain carbon fiber felt reinforced aramid aerogel.

5. The method for preparing carbon fiber felt reinforced aramid aerogel according to claim 4, characterized in that, In step (1), the mass ratio of the aramid fiber to potassium hydroxide is 1:(0.5-1.5).

6. The method for preparing carbon fiber felt reinforced aramid aerogel according to claim 4, characterized in that, In step (1), the heating temperature is 20-80℃.

7. The method for preparing carbon fiber felt reinforced aramid aerogel according to claim 4, characterized in that, In step (1), the stirring speed is 100-700 r / min; the stirring time is 2-96 h.

8. The method for preparing carbon fiber felt reinforced aramid aerogel according to claim 4, characterized in that, In step (1), the mass ratio of aramid fiber to dimethyl sulfoxide solvent is (1-3):

100.

9. The method for preparing carbon fiber felt reinforced aramid aerogel according to claim 4, characterized in that, In step (3), the soaking temperature is -20℃, and the mass ratio of acetic acid solvent to ethanol solvent is 7:

3.

10. The application of carbon fiber felt reinforced aramid aerogel as described in claim 1 as a thermal insulation material.

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