Aramid nanofiber-cellulose composite aerogel as well as preparation method and application thereof

Abstract

The invention discloses an aramid nanofiber-cellulose composite aerogel and a preparation method and application thereof, the preparation method comprises the following steps: respectively putting aramid fibers and cellulose into a solvent containing organic alkali to obtain an aramid nanofiber dispersion liquid and a cellulose dispersion liquid; mixing the aramid nanofiber dispersion liquid and the cellulose dispersion liquid to obtain a composite dispersion liquid; and gelatinizing the composite dispersion liquid, replacing a solvent, and drying to obtain the aramid nanofiber-cellulose composite aerogel. The preparation process is simple and easy to implement, and the obtained composite aerogel has extremely low apparent density, is adjustable in the range of 5-500 mg / cm < 3 >, has high porosity, excellent mechanical properties and low heat conductivity coefficient, and has wide application prospects in the fields of mechanical compression, heat management, sound absorption and noise reduction, environmental governance, electronic information and the like.

Description

Technical Field

[0001] This invention relates to the field of porous aerogel technology, and particularly to an aramid nanofiber-cellulose composite aerogel, its preparation method, and its application. Background Technology

[0002] Aerogels are a class of three-dimensional nanoporous materials with ultra-high specific surface area, low density, and interconnected pore structure, showing broad application prospects in fields such as thermal insulation, adsorption, separation, energy storage, buffering, and filtration. However, although traditional inorganic aerogels (such as silica aerogels) exhibit excellent thermal properties and surface characteristics, they generally suffer from problems such as high brittleness, insufficient mechanical properties, limited processability, and poor resistance to damp heat, which seriously restricts their long-term stable application under complex working conditions.

[0003] Aramid nanofibers (ANFs) have been widely used in recent years to construct high-performance aerogel structures due to their high strength, high modulus, excellent high-temperature resistance, and chemical stability. However, ANFs mainly rely on hydrogen bonds and van der Waals forces to form a network structure, which is prone to structural collapse during wet processing and drying. Simultaneously, their dispersion stability is highly sensitive to the solvent system, leading to problems such as unstable pore structure, insufficient mechanical properties, or difficulty in forming the prepared aerogels. Cellulose, as a widely available, renewable, and biocompatible natural polymer material, is rich in hydroxyl groups in its molecular chain, enabling effective cross-linking through hydrogen bonding. This, to a certain extent, improves the structural stability of aerogels, making it an excellent mechanical reinforcing material.

[0004] Based on these characteristics, researchers have attempted to combine aramid fibers with cellulose to combine the excellent mechanical properties of aramid materials with the processing advantages of cellulose. For example, the process reported by Wang et al. in "Thermal insulating, light-weight and conductive cellulose / aramid nanofibers composite aerogel for pressure sensing" requires first exfoliating the aramid fibers for about a week and preparing colloidal ANFs before combining them with cellulose to obtain the ANF / cellulose composite aerogel. This method has an excessively long preparation cycle and is time-consuming and labor-intensive. Liu et al. reported a method for 3D printing aramid / cellulose aerogels in "3D-printed shapeable hybrid Nanocellulose / aramid nanofiberaerogels for thermal insulation of portable electronics," but their aramid fibers and cellulose dispersions were prepared using different solvents, and the subsequent aerogels were prepared by forming a suspension after water dispersion. The overall process was time-consuming and not conducive to large-scale preparation. In addition, patent CN201911358518.1 reports a method for preparing aramid fiber / cellulose aerogel, but it uses a suspension system and introduces an external crosslinking agent, making the preparation process complex and difficult to meet the requirements of efficient and simplified preparation.

[0005] However, the existing technology still has many shortcomings, mainly in the following aspects: (1) The peeling process of aramid fibers by traditional solvent systems (such as DMSO and KOH, NaOH or potassium tert-butoxide) takes a long time, and the preparation cycle is often measured in weeks; (2) Existing solvent systems are difficult to achieve simultaneous dissolution of aramid and cellulose, and usually require multi-step and step-by-step processing, with a long process route; (3) Existing preparation processes are highly sensitive to dispersion uniformity and gelation rate, with harsh process conditions and poor scalability.

[0006] Therefore, there is an urgent need to develop a solvent system capable of simultaneously dissolving and dispersing cellulose and aramid fibers, constructing a structurally stable and uniformly dispersed composite dispersion to prepare aramid fiber-cellulose composite aerogels with excellent structural stability and superior mechanical properties. This is of great significance for the preparation of aerogels with high mechanical properties, the recycling and reuse of aramid and cellulose, and their high-value applications. Summary of the Invention

[0007] The purpose of this invention is to develop a solvent system capable of simultaneously dissolving and dispersing cellulose and aramid, constructing a structurally stable and uniformly dispersed composite dispersion to prepare aramid nanofiber-cellulose composite aerogels with excellent structural stability and superior mechanical properties, and to realize the recycling and reuse of aramid and cellulose and their high-value applications.

[0008] To achieve the above objectives, the present invention provides a method for preparing aramid nanofiber-cellulose composite aerogel, comprising: Aramid fibers and cellulose were placed in solvents containing organic bases to obtain aramid nanofiber dispersions and cellulose dispersions, respectively. Aramid nanofiber dispersion and cellulose dispersion were mixed to obtain a composite dispersion; The composite dispersion was gelled, solvent replaced, and dried to obtain an aramid nanofiber-cellulose composite aerogel. The aramid nanofiber dispersion contains 0.1wt%-30wt% aramid nanofibers, and the mass ratio of aramid nanofibers to organic alkali is 1-20:20. The cellulose dispersion contains 0.1wt%-30wt% cellulose and the cellulose organic base mass ratio is 1-5:5-6. The aramid nanofiber dispersion contains 1wt%-10wt% aramid fibers; the cellulose dispersion contains 1wt%-10wt% cellulose. The volume ratio of the aramid nanofiber dispersion to the cellulose dispersion is 1-9:9-1; The organic base includes at least one of organic amines and organic amine hydrates; The organic amines include at least one of tetrabutylammonium fluoride, tetrabutylammonium chloride, tetrabutylammonium bromide, tetraethylammonium chloride, and tetraethylammonium fluoride; The solvent includes at least one of dimethyl sulfoxide, sulfolane, dibutyl sulfone, diethyl sulfone, and ethyl methyl sulfone.

[0009] Furthermore, the aramid fiber includes at least one of waste aramid, aramid 1414, aramid 1313 and heterocyclic aramid; the waste aramid includes at least one of waste aramid 1414, waste aramid 1313 and waste hybrid aramid.

[0010] Furthermore, the cellulose includes at least one of cotton fiber, microcrystalline cellulose, and carboxymethyl cellulose.

[0011] Furthermore, the aramid nanofiber dispersion and the cellulose dispersion are obtained by mixing the corresponding mixture and stirring at a speed of 800-1500 r / min for 2-5 h.

[0012] Furthermore, the gelation of the composite dispersion is achieved by sealing and allowing it to stand at room temperature for 2-24 hours.

[0013] Furthermore, the solvent used for solvent replacement includes at least one of water, ethanol, tert-butanol, and acetone, and the number of replacements is at least 3 times, with an interval of at least 3 hours between each replacement.

[0014] Furthermore, the drying process includes at least one of supercritical drying, freeze drying, vacuum drying, pressure drying, spray drying, and microwave drying.

[0015] It should be noted that the shape of aramid fibers and cellulose is not strictly limited in this invention and can be any shape. For example, the morphology of aramid fibers includes at least one of bulk, fiber, paper, pulp, and powder; the morphology of cellulose includes at least one of fibrous, powder, and bulk. The source of aramid fibers and cellulose is also not strictly limited in this invention; aramid fibers and cellulose can be virgin, semi-virgin products, or waste materials. Using waste aramid fibers and cellulose enables the recycling and reuse of aramid and cellulose, and their high-value applications.

[0016] The present invention also provides an aramid nanofiber-cellulose composite aerogel, which is obtained by the above preparation method.

[0017] This invention also provides applications of the above-mentioned aramid nanofiber-cellulose composite aerogel in mechanical compression, thermal management, sound absorption and noise reduction, environmental remediation, and electronic information fields.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a solvent containing an organic alkali to dissolve aramid fibers and cellulose separately, enabling the formation of a gel without the addition of an external crosslinking agent or cryogenic casting. The resulting aramid nanofiber-cellulose composite aerogel is lightweight, heat-insulating, thermally insulating, and exhibits an extremely short peeling time. The preparation process of this invention is simple and easy to implement, and the obtained composite aerogel possesses an extremely low apparent density, ranging from 5 to 500 mg / cm³. 3 It is adjustable, has high porosity, excellent mechanical properties and low thermal conductivity, and has broad application prospects in mechanical compression, thermal management, sound absorption and noise reduction, environmental management and electronic information. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The appearance of the aramid nanofiber-cellulose composite aerogel prepared in Example 1 of the present invention is shown; Figure 2 A scanning electron microscope image of the aramid nanofiber-cellulose composite aerogel prepared in Example 1 of the present invention is shown. Figure 3 The tensile stress-strain curve of the aramid nanofiber-cellulose composite aerogel prepared in Example 3 of the present invention is shown. Figure 4 The compressive stress-strain curve of the aramid nanofiber-cellulose composite aerogel prepared in Example 3 of the present invention is shown. Figure 5 The adsorption amount-relative pressure curve of the aramid nanofiber-cellulose composite aerogel prepared in Example 5 of the present invention is shown. Detailed Implementation

[0021] In view of the shortcomings of the existing technology, the inventors have conducted long-term research and proposed the preparation method of the present invention. The method mainly uses aramid and cellulose as raw materials, and prepares a lightweight, heat-insulating, and mechanically excellent aramid nanofiber-cellulose composite aerogel by chemical exfoliation with dimethyl sulfoxide organic base solvent, compounding gel, and solvent replacement.

[0022] The following will further explain the technical solution, its implementation process, and its principles. Specific preparation methods include: Step 1: Preparation of aramid nanofiber dispersion: Aramid fibers and dimethyl sulfoxide organic base solvent are mixed and stirred in a sealed container to obtain an aramid nanofiber dispersion dispersed in dimethyl sulfoxide. Step 2: Preparation of cellulose dispersion: The cellulose and dimethyl sulfoxide in an organic base solvent (the same as in Step 1 above) are sealed and stirred to obtain a cellulose dispersion dispersed in dimethyl sulfoxide. Step 3: Preparation of aramid nanofiber-cellulose composite dispersion: The cellulose dispersion obtained in step 2 is compounded with the aramid nanofiber dispersion obtained in step 1, and after homogenization, the aramid fiber-cellulose composite dispersion is obtained. Step 4: Preparation of aramid nanofiber-cellulose composite gel: The aramid nanofiber-cellulose composite dispersion obtained in Step 3 is subjected to static gelation and solvent replacement to obtain aramid nanofiber-cellulose composite gel. Step 5: Preparation of aramid nanofiber-cellulose composite aerogel: The aramid nanofiber-cellulose composite gel obtained in Step 4 is subjected to special drying to obtain aramid nanofiber-cellulose composite aerogel.

[0023] The present invention will be further described in detail below with reference to the embodiments: The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to specific embodiments and the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 A method for preparing aramid nanofiber-cellulose composite aerogel includes the following steps: S1. Weigh 3g of aramid 1313, 15g of tetraethylammonium fluoride, and 147g of dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium fluoride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add aramid 1313. Stir and react at 1000r / min for 3 hours to obtain an aramid nanofiber dispersion with a concentration of 2% dispersed in dimethyl sulfoxide.

[0025] S2. Weigh 3g of cellulose powder, 17.5g of tetraethylammonium fluoride, and 147g of dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium fluoride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add the cellulose powder. Stir and react at 1200r / min for 3 hours to obtain a cellulose dispersion with a concentration of 2% dispersed in dimethyl sulfoxide.

[0026] S3. Using a syringe, the obtained cellulose dispersion is injected into the aramid nanofiber dispersion at a stirring speed of 1200 r / min, with a volume ratio of 40:60 between the aramid nanofiber dispersion and the cellulose dispersion. The mixture is stirred at 80℃ for 1 h to obtain an aramid nanofiber-cellulose composite dispersion.

[0027] S4. The obtained aramid nanofiber-cellulose composite dispersion was placed in a glass dish and allowed to stand and gel for 8 hours. After complete gelation, it was placed in deionized water for solvent replacement. Subsequently, it was placed in a solvent with a volume ratio of tert-butanol to water of 3:1 for solvent replacement for at least 24 hours to remove the dimethyl sulfoxide solvent in the system, thus preparing the aramid nanofiber-cellulose composite gel.

[0028] S5. Place the aramid nanofiber-cellulose composite gel in a freeze dryer for vacuum freeze drying to obtain aramid nanofiber-cellulose composite aerogel.

[0029] Example 2 A method for preparing aramid nanofiber-cellulose composite aerogel includes the following steps: S1. Weigh 6g of heterocyclic aramid, 15g of tetrabutylammonium bromide, and 144g of dimethyl sulfoxide. In a sealed beaker, first add tetrabutylammonium bromide, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add the heterocyclic aramid. Stir and react at 1000r / min for 3 hours to obtain an aramid nanofiber dispersion with a concentration of 4% dispersed in dimethyl sulfoxide.

[0030] S2. Weigh 6g of cellulose powder, 17.5g of tetrabutylammonium bromide, and 144g of dimethyl sulfoxide. In a sealed beaker, first add tetrabutylammonium bromide, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add cellulose powder. Stir and react at 1200r / min for 3 hours to obtain a cellulose dispersion with a concentration of 4% dispersed in dimethyl sulfoxide.

[0031] S3. Using a syringe, the obtained cellulose dispersion is stirred at a speed of 1100 r / min, and the cellulose dispersion is injected into the aramid fiber dispersion at a volume ratio of 30:70. The mixture is stirred at 80℃ for 1 h to obtain an aramid nanofiber-cellulose composite dispersion.

[0032] S4. The obtained aramid nanofiber-cellulose composite dispersion was placed in a glass dish and allowed to stand and gel for 8 hours. After complete gelation, it was placed in deionized water for solvent replacement. Subsequently, it was placed in a solvent with a volume ratio of tert-butanol to water of 3:1 for solvent replacement for at least 24 hours to remove the dimethyl sulfoxide solvent in the system, thus preparing the aramid nanofiber-cellulose composite gel.

[0033] S5. Place the aramid nanofiber-cellulose composite gel in a freeze dryer for vacuum freeze drying to obtain aramid nanofiber-cellulose composite aerogel.

[0034] Example 3 A method for preparing aramid nanofiber-cellulose composite aerogel includes the following steps: S1. Weigh 1.5g of aramid 1414, 15g of tetrabutylammonium fluoride, and 148.5g of dimethyl sulfoxide. In a sealed beaker, first add tetrabutylammonium fluoride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add aramid 1414. Stir and react at 1000r / min for 3 hours to obtain an aramid nanofiber dispersion with a concentration of 1% dispersed in dimethyl sulfoxide.

[0035] S2. Weigh 1.5g cellulose powder, 17.5g tetrabutylammonium fluoride, and 148.5g dimethyl sulfoxide. In a sealed beaker, first add tetrabutylammonium fluoride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add cellulose powder. Stir and react at 1200r / min for 3 hours to obtain a cellulose dispersion with a concentration of 1% dispersed in dimethyl sulfoxide.

[0036] S3. Using a syringe, the obtained cellulose dispersion is stirred at a speed of 1300 r / min, and the cellulose dispersion is injected into the aramid nanofiber dispersion at a volume ratio of 70:30. The mixture is stirred at 80℃ for 1 h to obtain an aramid nanofiber-cellulose composite dispersion.

[0037] S4. The obtained aramid nanofiber-cellulose composite dispersion was placed in a glass dish and allowed to stand and gel for 8 hours. After complete gelation, it was placed in deionized water for solvent replacement. Subsequently, it was placed in a solvent with a volume ratio of tert-butanol to water of 1:1 for solvent replacement for at least 24 hours to remove the dimethyl sulfoxide solvent in the system, thus preparing the aramid nanofiber-cellulose composite gel.

[0038] S5. Place the aramid nanofiber-cellulose composite gel in a freeze dryer for vacuum freeze drying to obtain aramid nanofiber-cellulose composite aerogel.

[0039] Example 4 A method for preparing aramid nanofiber-cellulose composite aerogel includes the following steps: S1. Weigh 12g heterocyclic aramid, 15g tetrabutylammonium chloride, and 138g dimethyl sulfoxide. In a sealed beaker, first add tetrabutylammonium chloride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add heterocyclic aramid. Stir and react at 1000r / min for 3 hours to obtain an aramid nanofiber dispersion with a concentration of 8% dispersed in dimethyl sulfoxide.

[0040] S2. Weigh 12g of cellulose powder, 17.5g of tetrabutylammonium chloride, and 138g of dimethyl sulfoxide. In a sealed beaker, first add tetrabutylammonium chloride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add cellulose powder. Stir and react at 1200r / min for 3 hours to obtain a cellulose dispersion with a concentration of 8% dispersed in dimethyl sulfoxide.

[0041] S3. Using a syringe, the obtained cellulose dispersion is stirred at a speed of 1200 r / min, and the cellulose dispersion is injected into the aramid nanofiber dispersion at a volume ratio of 50:50. The mixture is stirred at 80℃ for 1 h to obtain an aramid nanofiber-cellulose composite dispersion.

[0042] S4. The obtained aramid nanofiber-cellulose composite dispersion was placed in a glass dish and allowed to stand and gel for 8 hours. After complete gelation, it was placed in deionized water for solvent replacement. Subsequently, it was placed in a solvent with a volume ratio of tert-butanol to water of 3:2 for solvent replacement for at least 24 hours to remove the dimethyl sulfoxide solvent in the system, thus preparing the aramid nanofiber-cellulose composite gel.

[0043] S5. Place the aramid nanofiber-cellulose composite gel in a freeze dryer for vacuum freeze drying to obtain aramid nanofiber-cellulose composite aerogel.

[0044] Example 5 A method for preparing aramid nanofiber-cellulose composite aerogel includes the following steps: S1. Weigh 1.5g of waste aramid 1414 fiber, 15g of tetraethylammonium fluoride, and 148.5g of dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium fluoride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add heterocyclic aramid 1414 fiber. Stir and react at 1000r / min for 3 hours to obtain an aramid nanofiber dispersion with a concentration of 1% dispersed in dimethyl sulfoxide.

[0045] S2. Weigh 1.5g cellulose powder, 17.5g tetraethylammonium fluoride, and 148.5g dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium fluoride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add cellulose powder. Stir and react at 1200r / min for 3 hours to obtain a cellulose dispersion with a concentration of 1% dispersed in dimethyl sulfoxide.

[0046] S3. Using a syringe, the obtained cellulose dispersion is stirred at a speed of 1200 r / min, and the cellulose dispersion is injected into the aramid nanofiber dispersion at a volume ratio of 60:40. The mixture is stirred at 80℃ for 1 h to obtain an aramid nanofiber-cellulose composite dispersion.

[0047] S4. The obtained aramid nanofiber-cellulose composite dispersion was placed in a glass dish and allowed to stand and gel for 8 hours. After complete gelation, it was placed in deionized water for solvent replacement. Subsequently, it was placed in a solvent with a volume ratio of tert-butanol to water of 2:1 for solvent replacement for at least 24 hours to remove the dimethyl sulfoxide solvent in the system, thus preparing the aramid nanofiber-cellulose composite gel.

[0048] S5. Place the aramid nanofiber-cellulose composite gel in a freeze dryer for vacuum freeze drying to obtain aramid nanofiber-cellulose composite aerogel.

[0049] Example 6 A method for preparing aramid nanofiber-cellulose composite aerogel includes the following steps: S1. Weigh 0.75g of aramid 1313, 15g of tetraethylammonium chloride, and 149.25g of dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium chloride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add aramid 1313. Stir and react at 1000r / min for 3 hours to obtain an aramid nanofiber dispersion with a concentration of 0.5% dispersed in dimethyl sulfoxide.

[0050] S2. Weigh 0.75g carboxymethyl cellulose, 17.5g tetraethylammonium chloride, and 149.25g dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium chloride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add carboxymethyl cellulose. Stir and react at 1200r / min for 3 hours to obtain a cellulose dispersion with a concentration of 0.5% dispersed in dimethyl sulfoxide.

[0051] S3. Using a syringe, the obtained cellulose dispersion is stirred at a speed of 1100 r / min, and the cellulose dispersion is injected into the aramid nanofiber dispersion at a volume ratio of 20:80. The mixture is stirred at 80℃ for 1 h to obtain an aramid nanofiber-cellulose composite dispersion.

[0052] S4. The obtained aramid nanofiber-cellulose composite dispersion was placed in a glass dish and allowed to stand and gel for 8 hours. After complete gelation, it was placed in deionized water for solvent replacement. Subsequently, it was placed in a solvent with a volume ratio of tert-butanol to water of 5:1 for solvent replacement for at least 24 hours to remove the dimethyl sulfoxide solvent in the system, thus preparing the aramid nanofiber-cellulose composite gel.

[0053] S5. Place the aramid nanofiber-cellulose composite gel in a freeze dryer for vacuum freeze drying to obtain aramid nanofiber-cellulose composite aerogel.

[0054] Example 7 A method for preparing aramid nanofiber-cellulose composite aerogel includes the following steps: S1. Weigh 9g of aramid 1414, 15g of tetrabutylammonium chloride, and 141g of dimethyl sulfoxide. In a sealed beaker, first add tetrabutylammonium chloride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add aramid 1414. Stir and react at 1000r / min for 3 hours to obtain an aramid nanofiber dispersion with a concentration of 6% dispersed in dimethyl sulfoxide.

[0055] S2. Weigh 9g of carboxymethyl cellulose, 17.5g of tetrabutylammonium chloride, and 141g of dimethyl sulfoxide. In a sealed beaker, first add tetrabutylammonium chloride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add carboxymethyl cellulose. Stir and react at 1200r / min for 3 hours to obtain a cellulose dispersion with a concentration of 6% dispersed in dimethyl sulfoxide.

[0056] S3. Using a syringe, the obtained cellulose dispersion is stirred at a speed of 1100 r / min, and the cellulose dispersion is injected into the aramid nanofiber dispersion at a volume ratio of 70:30. The mixture is stirred at 80℃ for 1 h to obtain an aramid nanofiber-cellulose composite dispersion.

[0057] S4. The obtained aramid nanofiber-cellulose composite dispersion was placed in a glass dish and allowed to stand and gel for 8 hours. After complete gelation, it was placed in deionized water for solvent replacement. Subsequently, it was placed in a solvent with a volume ratio of tert-butanol to water of 4:3 for solvent replacement. The dimethyl sulfoxide solvent in the system was removed for at least 24 hours to prepare the aramid nanofiber-cellulose composite gel.

[0058] S5. Place the aramid nanofiber-cellulose composite gel in a freeze dryer for vacuum freeze drying to obtain aramid nanofiber-cellulose composite aerogel.

[0059] Example 8 A method for preparing aramid nanofiber-cellulose composite aerogel includes the following steps: S1. Weigh 15g of heterocyclic aramid, 15g of tetraethylammonium chloride, and 135g of dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium chloride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add heterocyclic aramid. Stir and react at 1000r / min for 3 hours to obtain an aramid nanofiber dispersion with a concentration of 10% dispersed in dimethyl sulfoxide.

[0060] S2. Weigh 15g of cellulose powder, 17.5g of tetraethylammonium chloride, and 141g of dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium chloride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add cellulose powder. Stir and react at 1200r / min for 3 hours to obtain a cellulose dispersion with a concentration of 10% dispersed in dimethyl sulfoxide.

[0061] S3. Using a syringe, the obtained cellulose dispersion is stirred at a speed of 1100 r / min, and the cellulose dispersion is injected into the aramid nanofiber dispersion at a volume ratio of 60:40. The mixture is stirred at 80℃ for 1 h to obtain an aramid nanofiber-cellulose composite dispersion.

[0062] S4. The obtained aramid nanofiber-cellulose composite dispersion was placed in a glass dish and allowed to stand and gel for 8 hours. After complete gelation, it was placed in deionized water for solvent replacement. Subsequently, it was placed in a solvent with a volume ratio of tert-butanol to water of 2:3 for solvent replacement for at least 24 hours to remove the dimethyl sulfoxide solvent in the system, thus preparing the aramid nanofiber-cellulose composite gel.

[0063] S5. Place the aramid nanofiber-cellulose composite gel in a freeze dryer for vacuum freeze drying to obtain aramid nanofiber-cellulose composite aerogel.

[0064] Example 9 A method for preparing aramid nanofiber-cellulose composite aerogel includes the following steps: S1. Weigh 1.5g heterocyclic aramid, 15g tetraethylammonium bromide, and 148.5g dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium bromide, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add heterocyclic aramid. Stir and react at 1000r / min for 3 hours to obtain an aramid nanofiber dispersion with a concentration of 1% dispersed in dimethyl sulfoxide.

[0065] S2. Weigh 1.5g cellulose powder, 17.5g tetraethylammonium chloride, and 148.5g dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium bromide, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add cellulose powder. Stir and react at 1200r / min for 3 hours to obtain a cellulose dispersion with a concentration of 1% dispersed in dimethyl sulfoxide.

[0066] S3. Using a syringe, the obtained cellulose dispersion is stirred at a speed of 1100 r / min, and the cellulose dispersion is injected into the aramid nanofiber dispersion at a volume ratio of 50:50. The mixture is stirred at 80℃ for 1 h to obtain an aramid nanofiber-cellulose composite dispersion.

[0067] S4. The obtained aramid nanofiber-cellulose composite dispersion was placed in a glass dish and allowed to stand and gel for 8 hours. After complete gelation, it was placed in deionized water for solvent replacement. Subsequently, it was placed in a solvent with a volume ratio of tert-butanol to water of 4:3 for solvent replacement. The dimethyl sulfoxide solvent in the system was removed for at least 24 hours to prepare the aramid nanofiber-cellulose composite gel.

[0068] S5. Place the aramid nanofiber-cellulose composite gel in a freeze dryer for vacuum freeze drying to obtain aramid nanofiber-cellulose composite aerogel.

[0069] Example 10 A method for preparing aramid nanofiber-cellulose composite aerogel includes the following steps: S1. Weigh 3g of aramid 1313, 15g of tetraethylammonium fluoride, and 147g of dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium fluoride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add aramid 1313. Stir and react at 1000r / min for 3 hours to obtain an aramid nanofiber dispersion with a concentration of 2% dispersed in dimethyl sulfoxide.

[0070] S2. Weigh 3g of cotton fiber, 17.5g of tetraethylammonium fluoride, and 148.5g of dimethyl sulfoxide. In a sealed beaker, first add tetraethylammonium fluoride, then add dimethyl sulfoxide. Mix and stir with a magnetic stirrer for 5 minutes, then add cotton fiber. Stir and react at 1200r / min for 3 hours to obtain a cellulose dispersion with a concentration of 2% dispersed in dimethyl sulfoxide.

[0071] S3. Using a syringe, the obtained cellulose dispersion is stirred at a speed of 1100 r / min, and the cellulose dispersion is injected into the aramid nanofiber dispersion at a volume ratio of 50:50. The mixture is stirred at 80℃ for 1 h to obtain an aramid nanofiber-cellulose composite dispersion.

[0072] S4. The obtained aramid nanofiber-cellulose composite dispersion was placed in a glass dish and allowed to stand and gel for 8 hours. After complete gelation, it was placed in deionized water for solvent replacement. Subsequently, it was placed in a solvent with a volume ratio of tert-butanol to water of 1:1 for solvent replacement for at least 24 hours to remove the dimethyl sulfoxide solvent in the system, thus preparing the aramid nanofiber-cellulose composite gel.

[0073] S5. Place the aramid nanofiber-cellulose composite gel in a freeze dryer for vacuum freeze drying to obtain aramid nanofiber-cellulose composite aerogel.

[0074] Figure 1 and Figure 2 The images show the appearance and scanning electron microscope (SEM) images of the aramid nanofiber-cellulose composite aerogel prepared in Example 1 of this invention. It can be seen that the aramid nanofiber-cellulose composite aerogel has a well-structured macroscopically and exhibits a rich, three-dimensionally interconnected pore structure at the microscopic level.

[0075] Figure 3 and Figure 4 The tensile stress-strain and compressive stress-strain curves of the aramid nanofiber-cellulose composite aerogel prepared in Example 3 of the present invention are shown respectively, which can be seen that it has excellent compression resilience and high tensile strength.

[0076] To further study the properties of the material, the aramid nanofiber-cellulose composite aerogel prepared in the embodiments of the present invention was characterized, and the test results are shown in Table 1.

[0077] Table 1 Performance parameters of aramid nanofiber-cellulose composite aerogels prepared in Examples 1-10 As can be seen from the results in Table 1, the aramid nanofiber-cellulose composite aerogel obtained by this invention has an extremely low apparent density, ranging from 5 to 500 mg / cm³. 3 Adjustable, with high porosity and low thermal conductivity.

[0078] In summary, this invention dissolves aramid fibers and cellulose separately in a solvent containing an organic base, enabling the formation of a gel without the addition of an external crosslinking agent or cryogenic casting. This results in a lightweight, heat-insulating, and thermally insulating aramid nanofiber-cellulose composite aerogel with an extremely short peeling time. The preparation process of this invention is simple and easy to implement. The resulting composite aerogel exhibits extremely low apparent density, high porosity, excellent mechanical properties, and low thermal conductivity, showing broad application prospects in fields such as mechanical compression, thermal management, sound absorption and noise reduction, environmental remediation, and electronic information.

[0079] Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various modifications, deletions, or additions can be made without departing from the core principles and scope of the invention, and substantially equivalent technical means can be used to replace elements in the described embodiments. Furthermore, many adjustments can be made to the present invention to adapt to specific application scenarios or material needs, and such adjustments do not depart from the protection scope of the present invention. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed, but should cover all technical solutions defined by the appended claims.

Claims

1. A method for preparing an aramid nanofiber-cellulose composite aerogel, characterized in that, include: Aramid fibers and cellulose were placed in solvents containing organic bases to obtain aramid nanofiber dispersions and cellulose dispersions, respectively. Aramid nanofiber dispersion and cellulose dispersion were mixed to obtain a composite dispersion; The composite dispersion was gelled, solvent replaced, and dried to obtain an aramid nanofiber-cellulose composite aerogel. The aramid nanofiber dispersion contains 0.1wt%-30wt% aramid nanofibers, and the mass ratio of aramid nanofibers to organic alkali is 1-20:

20. The cellulose dispersion contains 0.1wt%-30wt% cellulose and the cellulose-organic base mass ratio is 0.1-2:2-6. The volume ratio of the aramid nanofiber dispersion to the cellulose dispersion is 1-9:9-1; The organic base includes at least one of organic amines and organic amine hydrates; The organic amines include at least one of tetrabutylammonium fluoride, tetrabutylammonium chloride, tetrabutylammonium bromide, tetraethylammonium chloride, and tetraethylammonium fluoride; The solvent includes at least one of dimethyl sulfoxide, sulfolane, dibutyl sulfone, diethyl sulfone, and ethyl methyl sulfone.

2. The preparation method of the aramid nanofiber-cellulose composite aerogel according to claim 1, characterized in that, The aramid fiber includes at least one of waste aramid, aramid 1414, aramid 1313, and heterocyclic aramid; The waste aramid includes at least one of waste aramid 1414, waste aramid 1313, and waste hybrid aramid.

3. The preparation method of the aramid nanofiber-cellulose composite aerogel according to claim 1, characterized in that, The cellulose includes at least one of cotton fiber, microcrystalline cellulose, and carboxymethyl cellulose.

4. The method for preparing aramid nanofiber-cellulose composite aerogel according to any one of claims 1-3, characterized in that, The aramid nanofiber dispersion and the cellulose dispersion are obtained by mixing the corresponding mixtures and stirring at a speed of 800-1500 r / min for 2-5 h.

5. An aramid nanofiber-cellulose composite aerogel, characterized in that, It is obtained by the preparation method described in any one of claims 1-4.

6. The application of the aramid nanofiber-cellulose composite aerogel as described in claim 5 in the fields of mechanical compression, thermal management, sound absorption and noise reduction, environmental remediation, and electronic information.

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