Nanofiber with aerogel coating layer and method of making the same
By coating nanofibers with an aramid aerogel layer, the mechanical properties and thermal stability of aerogel fibers were solved, resulting in aerogel fibers with high strength and good flexibility, suitable for phase change materials and smart wearable materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN TEXTILE UNIV
- Filing Date
- 2024-05-24
- Publication Date
- 2026-05-19
AI Technical Summary
Existing aerogel fibers have low skeletal strength, poor mechanical properties and thermal stability, making it difficult to maintain good flexibility and mechanical properties while retaining the characteristics of aerogel.
Nanofibers with an aerogel coating were prepared by wet spinning. By coating the core nanofibers with an aramid aerogel layer, nanofibers with a diameter of 100-150 μm and an aerogel coating layer of 20-200 μm were formed. The mechanical properties of the fibers were improved by using a specific coagulation bath composition and freeze-drying treatment.
The mechanical and thermal insulation properties of nanofibers were significantly improved, with the tensile strength increasing from 0.1~0.5 MPa to 6.0~9.0 MPa, thus broadening their application prospects in phase change materials and smart wearable materials.
Smart Images
Figure CN118480879B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of natural or chemical yarn or fiber technology, and specifically relates to a nanofiber with an aerogel coating layer and its preparation method. Background Technology
[0002] Aerogels are porous materials synthesized from gels, where the liquid is replaced by gas, with an air content reaching up to 99.8%. They possess ultra-high porosity, ultra-low density, high specific surface area, and excellent thermal insulation properties. Furthermore, aerogels have a micro / nanoporous three-dimensional structure, making them highly promising for applications in adsorption, filtration, catalysis, and air purification. However, most aerogel research focuses on bulk, membrane, and microsphere materials. If aerogels were prepared into fibrous forms, retaining their aerogel properties while also acquiring fibrous characteristics (such as an aspect ratio thousands of times greater and good flexibility), it would be possible to weave them and endow them with flexible, wearable properties, thereby further broadening the application pathways and fields of aerogel materials.
[0003] However, aerogel fibers prepared solely from aerogel have a porous network structure and low skeletal strength, resulting in low mechanical properties and poor thermal stability. Therefore, how to prepare aerogel fibers with both excellent thermal stability and good mechanical properties is an urgent problem to be solved. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a nanofiber with an aerogel coating and its preparation method. The nanofiber not only has the advantages of aerogel, such as abundant pores, ultra-low density and ultra-high specific surface area, but also has good mechanical properties and flexibility. It has good application prospects in the fields of phase change materials and smart wearable materials. Its preparation method is easy to implement and has good reproducibility.
[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:
[0006] A nanofiber with an aerogel coating is provided, which is composed of nanofibers located in the core and an aerogel coating surrounding the core. The nanofibers have a diameter of 100-150 μm and the aerogel coating has a thickness of 20-200 μm.
[0007] According to the above scheme, the nanofibers include bamboo nanocellulose fibers or bacterial cellulose fibers.
[0008] According to the above scheme, the aerogel coating layer is aramid aerogel, which has a porous structure with a pore size of 10~50nm.
[0009] This invention also includes a method for preparing the above-mentioned nanofibers with an aerogel coating, the specific steps of which are as follows:
[0010] 1) Preparation of core layer spinning solution: Add nanocellulose to deionized water and ultrasonically disperse it evenly to obtain core layer spinning solution;
[0011] 2) Preparation of outer spinning solution: Add aramid fiber, alkaline substance and water to an aprotic solvent to dissolve and obtain outer spinning solution;
[0012] 3) Using a wet spinning process, the core spinning solution obtained in step 1) and the outer spinning solution obtained in step 2) are injected into a coagulation bath through a coaxial spinning needle. The outer shaft of the spinning needle contains the outer spinning solution, and the inner shaft of the spinning needle contains the core spinning solution. After full coagulation, aramid-coated nanofiber gel is obtained. The obtained aramid-coated nanofiber gel is wound and collected, and then placed in a displacement solution for solvent replacement. Then, it is freeze-treated and freeze-dried in sequence to obtain nanofibers with an aerogel coating layer.
[0013] According to the above scheme, the nanocellulose in step 1) is plant cellulose or bacterial cellulose, with a diameter of 10~20nm and a length of 80~120μm.
[0014] According to the above scheme, the concentration of nanocellulose in the core spinning solution in step 1) is 0.1~1wt%.
[0015] According to the above scheme, the aramid fiber in step 2) is para-aramid fiber or meta-aramid fiber.
[0016] According to the above scheme, the alkaline substance in step 2) is one or two of sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide.
[0017] According to the above scheme, the aprotic solvent in step 2) is acetonitrile (CH3CN). N , N One or more of dimethylformamide (DMF), 1,3-dimethyl-2-imidazolinone (DMI), dimethyl sulfoxide (DMSO), and hexamethylphosphoric triamine (HMPA).
[0018] According to the above scheme, in step 2), the concentration of aramid fiber in the outer spinning solution is 0.5~5wt%, the concentration of alkaline substance is 2~4wt%, and the concentration of water is 1~2wt%.
[0019] According to the above scheme, in step 3), the core spinning solution and the outer spinning solution are injected into the coagulation bath through the coaxial spinning needle. The propulsion speed of the core spinning solution is 15~30mL / h, and the propulsion speed of the outer spinning solution is 30~60mL / h.
[0020] According to the above scheme, the coagulation bath in step 3) is a mixture of calcium chloride solution, ethanol solution, acetic acid solution, dimethyl sulfoxide solution and ethylene glycol solution, wherein the concentration of calcium chloride solution is 10~40wt%, the concentration of ethanol solution is 10~20wt%, the concentration of acetic acid solution is 5~10wt%, the concentration of dimethyl sulfoxide solution is 20~30wt%, and the concentration of ethylene glycol solution is 5~10wt%. The volume ratio of calcium chloride solution, ethanol solution, acetic acid solution, dimethyl sulfoxide solution and ethylene glycol solution is 9~13:1~3:0.5~2:4~6:1. The present invention adds dimethyl sulfoxide solution to the coagulation bath to slow down the protonation process of aerogel fibers during coagulation and molding, making the fibers more compact. Without the addition of dimethyl sulfoxide solution, the aramid solution (outer spinning solution) will quickly coagulate and form upon contact with the proton solution. The rapid coagulation of the outer fibers will prevent the coagulation bath from further contacting the inner fibers, resulting in poor coagulation and molding of the inner fibers and insufficient mechanical properties. In addition, the acetic acid solution added to the coagulation bath of the present invention can help the aerogel fibers to be molded better and form a dense structure.
[0021] According to the above scheme, the replacement solution in step 3) is deionized water, the replacement time is 5~10 hours each time, and the number of replacements is 6~10 times.
[0022] According to the above scheme, the freezing temperature in step 3) is in the range of -60~-20℃, and the freezing time is 12~24h.
[0023] According to the above scheme, the freeze-drying process conditions for step 3) are: vacuum degree of 0.05~0.1mbar, freeze-drying temperature of -65~-50℃, and freeze-drying time of 24~48h.
[0024] The present invention also includes the application of the above-mentioned nanofibers with aerogel coating in the fields of phase change materials and smart wearable materials.
[0025] In the coagulation stage of the spinning solution of this invention, the composition of the coagulation bath affects the coagulation time and the transformation process of the solution into a gel. The applicant has found that adding acetic acid solution to the coagulation bath can remove impurities generated on the fiber, resulting in a smoother fiber surface and a dense network of pores without impurities occupying space, thus significantly improving the fiber's mechanical properties. In addition, adding DMSO solution to the coagulation bath slows down protonation. Aramid solutions coagulate very quickly in existing coagulation baths, causing the outer layer of the fiber to solidify rapidly while the inner layer is difficult to form, greatly reducing the tensile properties of the gel fiber. By adding DMSO solution, the outer layer coagulation speed is slowed down, allowing the inner layer to form better, thus greatly improving the overall mechanical properties of the nanofiber.
[0026] The beneficial effects of this invention are as follows: 1. This invention coats the surface of nanofibers with an aramid aerogel coating layer, which improves the mechanical properties and thermal insulation properties of the nanofibers. The tensile strength of nanofibers without the aerogel coating layer is 0.1~0.5 MPa, while the tensile strength after coating with the aramid aerogel coating layer reaches 6.0~9.0 MPa. The obtained nanofibers with the aerogel coating layer have good application prospects in the fields of phase change materials and smart wearable materials. 2. The preparation method of this invention is easy to implement and has good reproducibility. Attached Figure Description
[0027] Figure 1 This is a cross-sectional SEM image of the aerogel coating layer of the sample in Example 1 of the present invention;
[0028] Figure 2 This is a cross-sectional SEM image of the aerogel coating layer of the sample in Example 2;
[0029] Figure 3 This is a cross-sectional SEM image of the aerogel coating layer of the sample in Example 3;
[0030] Figure 4 The image shows a scanning electron microscope (SEM) image of the nanofibers with an aerogel coating prepared in Comparative Example 4.
[0031] Figure 5 The image shows a scanning electron microscope (SEM) image of the nanofibers with an aerogel coating prepared in Comparative Example 5.
[0032] Figure 6 The tensile properties of the nanofibers with aerogel coating prepared in Examples 1-4 are shown in the figure.
[0033] Figure 7 The pore size distribution diagram of the sample with an aerogel coating prepared in Example 1;
[0034] Figure 8 The pore size distribution diagram of the sample with an aerogel coating prepared in Example 2;
[0035] Figure 9 The nitrogen adsorption-desorption curve of the sample with an aerogel coating prepared in Example 1;
[0036] Figure 10 The nitrogen adsorption-desorption curves are for the sample with an aerogel coating prepared in Example 2. Detailed Implementation
[0037] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.
[0038] Example 1
[0039] A nanofiber with an aerogel coating is prepared by the following method:
[0040] 1) Bamboo nanocellulose (10nm in diameter and 100μm in length) was added to deionized water and ultrasonically dispersed to obtain a nanocellulose dispersion with a concentration of 0.5wt%.
[0041] 2) Add 2g of aramid fiber (1000 denier, cut into 1-2mm lengths), 2g of potassium hydroxide, and 1g of water to 95g of dimethyl sulfoxide to dissolve and obtain a nano-aramid fiber solution, wherein the aramid fiber concentration is 2%;
[0042] 3) A wet spinning process is used. The nanocellulose dispersion obtained in step 1) is used as the core spinning solution, and the nanoaramid fiber solution obtained in step 2) is used as the outer spinning solution. These solutions are injected into a coaxial spinning needle into a coagulation bath. The outer shaft of the spinning needle contains the outer spinning solution, and the inner shaft contains the core spinning solution. During coaxial spinning, the core spinning solution is propelled at a speed of 22 mL / h, and the outer spinning solution is propelled at a speed of 45 mL / h. The coagulation bath is a mixture of calcium chloride solution, ethanol solution, acetic acid solution, dimethyl sulfoxide solution, and ethylene glycol solution, wherein the calcium chloride solution concentration is 30 wt% and the ethanol solution concentration is 15 wt%. The concentrations of the calcium chloride solution, ethanol solution, acetic acid solution, dimethyl sulfoxide solution, and ethylene glycol solution were 10 wt%, 25 wt%, and 5 wt%, respectively. The volume ratio of the calcium chloride solution, ethanol solution, acetic acid solution, dimethyl sulfoxide solution, and ethylene glycol solution was 11:2:1:5:1. After solidification for 8 hours, aramid-coated nanofiber gel was obtained. The obtained aramid-coated nanofiber gel was collected by winding and then placed in a replacement solution (deionized water) for solvent replacement (replacement 9 times, 8 hours each time). Then, it was successively frozen (freezing temperature -40℃, freezing time 24 hours) and freeze-dried (vacuum degree 0.1 mbar, freeze-drying temperature -50℃, freeze-drying time 36 hours) to obtain nanofibers with an aerogel coating.
[0043] Examples 2-4
[0044] Adjust the concentration of the nanocellulose dispersion in step 1) and the concentration of the nanoaramid fiber solution in step 2) as detailed in Table 1. The remaining conditions are the same as in Example 1 to prepare nanofibers with different aerogel coating layers.
[0045] Comparative Examples 1-3
[0046] Comparative Examples 1 and 2 were prepared with an aerogel coating layer, and Comparative Example 3 was prepared with an inner nanofiber layer. The preparation method was different from that of Example 1, except that only the corresponding nano-aramid fiber solution or nano-cellulose dispersion was prepared. The concentration is detailed in Table 1.
[0047] Comparative Examples 4-5
[0048] In Comparative Example 4, no acetic acid solution was added to the coagulation bath, and the fiber used was aramid fiber instead of bamboo nanocellulose. The other conditions were the same as in Example 1.
[0049] In Comparative Example 5, no dimethyl sulfoxide solution was added to the coagulation bath, and the fiber used was aramid fiber instead of bamboo nanocellulose. The other conditions were the same as in Example 1.
[0050] The proportions of raw materials used in Examples 1-4 and Comparative Examples 1-5 and the test results of the obtained products are shown in Table 1.
[0051] Table 1
[0052]
[0053] As can be seen from Table 1, compared with Comparative Examples 1-3, Examples 1-4, by adding an aerogel coating layer, not only improve the fiber breaking strength but also reduce the thermal conductivity, while the fiber reinforces the aerogel. Compared with Example 1, Comparative Examples 4-5 show a decrease in both mechanical and thermal insulation properties, indicating that the adjustment of the coagulation bath composition in this invention can improve the performance of the spun products.
[0054] like Figure 1 The image shows a cross-sectional SEM image of the aerogel coating layer of the sample from Example 1. As can be seen from the image, the aerogel coating layer has a thickness of 50–200 μm and possesses a dense, porous network structure with pore sizes below 40–50 nm. The diameter of the original inner layer of nanofibers is approximately 100–150 μm. The aerogel coating layer improves the mechanical properties of the nanofibers, and the network structure of the aerogel coating layer restricts air circulation, resulting in nanofibers with a low thermal conductivity.
[0055] The nanofibers with an aerogel coating prepared in Example 1 had a density of 6 mg / cm³, as tested. 3 .
[0056] Figure 2 The image shows a cross-sectional SEM image of the aerogel coating layer of the sample in Example 2. As can be seen from the image, the aerogel coating layer has a thickness of 30–160 μm and a dense, porous network structure with pore sizes of 25–40 nm. The inner layer originally coated with nanofibers has a diameter of approximately 120–150 μm.
[0057] Figure 3 The image shows a cross-sectional SEM image of the aerogel coating layer of the sample in Example 3. As can be seen from the image, the aerogel coating layer has a thickness of 20–180 μm and a dense, porous network structure with pore sizes of 20–35 nm. The inner layer originally coated with nanofibers has a diameter of approximately 110–150 μm.
[0058] Figure 4 The image shows a scanning electron microscope (SEM) image of the nanofibers with an aerogel coating prepared in Comparative Example 4. As can be seen from the image, the nanofibers and the coating contain clustered impurities, and the presence of these impurities affects their mechanical properties.
[0059] Figure 5 The image shows a scanning electron microscope (SEM) image of the nanofibers with an aerogel coating prepared in Comparative Example 5. As can be seen from the image, the nanofibers and coating are not fully solidified and do not solidify completely, which leads to a sharp decline in the performance of the aerogel fibers.
[0060] like Figure 6 The figures shown are tensile property test diagrams of the nanofibers with aerogel coating prepared in Examples 1-4. The instrument used for tensile testing was an Instron 5969 electronic universal testing machine. It can be seen that as the concentration of aramid solution gradually increases, the strength of the aerogel fiber also gradually increases.
[0061] Figure 7 The pore size distribution of the sample with aerogel coating prepared in Example 1 was obtained by measuring the specific surface area and micropore size through nitrogen adsorption testing. As can be seen from the figure, most of the pores are distributed in the range of 10~30nm, which belongs to the microporous structure.
[0062] Figure 8 The image shows the pore size distribution of the sample with an aerogel coating prepared in Example 2. As can be seen from the image, most of the pores are distributed in the range of 10-30 nm. Compared with Example 1, the pore size range of 0-10 nm is more dense, which corresponds to the lower thermal conductivity. The pore size range belongs to the microporous structure.
[0063] Figure 9 The nitrogen adsorption-desorption curve is shown for the sample with an aerogel coating prepared in Example 1, with a specific surface area of 658.81 cm³. 3 / g.
[0064] Figure 10 The nitrogen adsorption-desorption curve is shown for the sample with an aerogel coating prepared in Example 2, with a specific surface area of 700.12 cm³. 3 / g.
Claims
1. A method for preparing nanofibers with an aerogel coating, wherein the nanofibers with an aerogel coating consist of nanofibers located in a core and an aerogel coating surrounding the core, wherein the nanofibers have a diameter of 100-150 μm and the aerogel coating has a thickness of 20-200 μm, characterized in that, The specific steps are as follows: 1) Preparation of core layer spinning solution: Add nanocellulose to deionized water and ultrasonically disperse it evenly to obtain core layer spinning solution; 2) Preparation of outer spinning solution: Add aramid fiber, alkaline substance and water to an aprotic solvent to dissolve and obtain outer spinning solution; 3) Using a wet spinning process, the core spinning solution obtained in step 1) and the outer spinning solution obtained in step 2) are injected into a coagulation bath through a coaxial spinning needle. The outer shaft of the spinning needle contains the outer spinning solution, and the inner shaft contains the core spinning solution. During the injection of the core spinning solution and the outer spinning solution into the coagulation bath through the coaxial spinning needle, the propulsion speed of the core spinning solution is 15~30 mL / h, and the propulsion speed of the outer spinning solution is 30~60 mL / h. The coagulation bath is a mixture of calcium chloride solution, ethanol solution, acetic acid solution, dimethyl sulfoxide solution, and ethylene glycol solution, wherein the concentration of the calcium chloride solution is 10~40w. The concentrations of the calcium chloride solution, ethanol solution, acetic acid solution, dimethyl sulfoxide solution, and ethylene glycol solution are 10-20 wt%, 5-10 wt%, 20-30 wt%, and 5-10 wt%, respectively. The volume ratio of the calcium chloride solution, ethanol solution, acetic acid solution, dimethyl sulfoxide solution, and ethylene glycol solution is 9-13:1-3:0.5-2:4-6:
1. After complete solidification, aramid-coated nanofiber gel is obtained. The obtained aramid-coated nanofiber gel is collected by winding and then placed in a displacement solution for solvent replacement. Then, it is subjected to freeze treatment and freeze-drying treatment in sequence to obtain nanofibers with an aerogel coating layer.
2. The method for preparing nanofibers with an aerogel coating according to claim 1, characterized in that, The nanocellulose in step 1) is plant cellulose or bacterial cellulose, with a diameter of 10~20nm and a length of 80~120μm; the concentration of nanocellulose in the core spinning solution in step 1) is 0.1~1wt%.
3. The method for preparing nanofibers with an aerogel coating according to claim 1, characterized in that, Step 2) The aramid fiber is para-aramid fiber or meta-aramid fiber; Step 2) The alkaline substance is one or two of sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide; Step 2) The aprotic solvent is acetonitrile, N , N - One or more of dimethylformamide, 1,3-dimethyl-2-imidazolinone, dimethyl sulfoxide, and hexamethylphosphoric triamine; the concentration of aramid fiber in the outer spinning solution in step 2) is 0.5~5wt%, the concentration of alkaline substance is 2~4wt%, and the concentration of water is 1~2wt%.
4. The method for preparing nanofibers with an aerogel coating according to claim 1, characterized in that, Step 3) The replacement solution is deionized water, the replacement time is 5~10h each time, and the number of replacements is 6~10 times; Step 3) The freezing treatment temperature is in the range of -60~-20℃, and the freezing treatment time is 12~24h; Step 3) The freeze-drying process conditions are: vacuum degree of 0.05~0.1mbar, freeze-drying temperature of -65~-50℃, and freeze-drying time of 24~48h.
5. A nanofiber with an aerogel coating prepared by the preparation method according to any one of claims 1-4.
6. The nanofibers with an aerogel coating according to claim 5, characterized in that, The nanofibers include bamboo nanocellulose fibers or bacterial cellulose fibers.
7. The nanofibers with an aerogel coating according to claim 5, characterized in that, The aerogel coating layer is aramid aerogel, which has a porous structure with a pore size of 10~50nm.
8. The application of nanofibers with aerogel coating as described in any one of claims 5-7 in the fields of phase change materials and smart wearable materials.