A yarn-reinforced nanofibril composite aerogel fiber and a preparation method and application thereof

Abstract

The application discloses yarn-reinforced nanometer aramid composite aerogel fibers and a preparation method and application thereof, and relates to the steps of spinning liquid preparation, coagulation bath preparation, spinning, solvent exchange and freeze drying, wherein nanometer aramid fiber spinning liquid and yarn are respectively used as an outer layer and an inner layer, wet spinning is carried out through coaxial needles into a coagulation bath, and yarn-reinforced nanometer aramid composite aerogel fibers are obtained after solvent exchange and freeze drying. The composite aerogel fibers have abundant micro-nano hole structures, store a large amount of static air, and have excellent heat insulation and warmth retention performance. Meanwhile, the yarn in the inner layer provides excellent mechanical support as the skeleton of the aerogel fibers, and provides reliable guarantee for subsequent textile weaving and processing. The strength of the composite aerogel fibers prepared by the method can be regulated by the inner layer yarn, the method is simple and easy to operate, and different properties of the yarn can also endow the aerogel with the potential of different special functions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aerogel fiber spinning preparation, and particularly relates to a yarn-reinforced nanometer aramid composite aerogel fiber and a preparation method and application thereof. BACKGROUND

[0002] Aerogel is a kind of porous material with micro-nano pore structure, and its micro-morphology presents a continuous porous network architecture with a pore size in the micro-nano range. Compared with conventional porous materials, aerogel has significantly reduced mass due to its ultra-low density, and has advantages in application scenarios with strict requirements for lightness. In addition, there is a large amount of still air in the aerogel, and the low thermal conductivity of the still air, combined with the blocking effect of the porous structure on heat convection, greatly limits the heat transfer. Therefore, aerogel can optimize the thermal performance of fabrics in the field of textile thermal insulation; in the field of heat protection and thermal insulation, it can resist high temperature and reduce heat conduction to ensure work safety and equipment stability; in the field of thermal management, it can precisely control the heat transfer path and distribution.

[0003] At present, aerogel fibers prepared by wet spinning are formed into aerogel fiber fabrics through textile processing, which has great potential to replace traditional thermal textiles and be applied in special protection fields. Aerogel fibers have a rich porous structure, and these micro-nano level pores provide a space for the storage of still air, thereby endowing the fibers with excellent thermal insulation performance. However, these pores also constitute the mechanical weakness of the fibers. During the weaving process of the textile machine, due to its brittleness and low mechanical strength, it is easy to break or deform, affecting the quality and stability of the final product, and seriously limiting the expansion of its production and application.

[0004] Existing methods for improving the mechanical properties of aerogel include introducing reinforcing nanofibers, crosslinking agents or modifying the matrix material of aerogel. Although these methods improve the mechanical properties of aerogel fibers to some extent, they are difficult to achieve qualitative changes and are difficult to meet the needs of actual production. SUMMARY

[0005] In view of the problem that the mechanical properties of the existing aerogel fibers are insufficient and difficult to meet the mechanical requirements of textile machine weaving and processing, the application provides a yarn-reinforced nanometer aramid composite aerogel fiber and a preparation method and application thereof, which can not only maintain the excellent thermal insulation performance of aerogel, but also significantly improve the mechanical properties thereof. The technology is of great significance for expanding the application range of aerogel. In particular, in the textile industry, it can be directly used for weaving, greatly expanding its application space in the fields of clothing, protective products and industrial textiles.

[0006] The application is implemented by the following technical solutions:

[0007] A preparation method of a yarn-reinforced nanometer aramid composite aerogel fiber, comprising the following steps:

[0008] Step 1) adding para-aramid fibers into a mixed solution of deionized water, potassium hydroxide and dimethyl sulfoxide, heating and stirring to disperse, to obtain an outer layer spinning solution of composite aerogel fibers, i.e. nanometer aramid fiber spinning solution;

[0009] Step 2) mixing an acid reagent with deionized water to obtain a spinning coagulation bath;

[0010] Step 3) connecting the nanometer aramid fiber spinning solution prepared in step 1) to the outer layer of a coaxial needle and injecting into the coagulation bath prepared in step 2) at a certain extrusion speed, while the inner layer of the coaxial needle is a yarn, which is wound and collected by a yarn winding drum, to obtain a yarn-reinforced nanometer aramid composite hydrogel fiber;

[0011] Step 4) placing the yarn-reinforced nanometer aramid composite hydrogel fiber prepared in step 3) in a solvent exchange bath for solvent exchange;

[0012] Step 5) placing the yarn-reinforced nanometer aramid composite hydrogel fiber treated in step 4) in a freezer, and freeze-drying to obtain the yarn-reinforced nanometer aramid composite aerogel fiber.

[0013] Preferably, the mass ratio between the potassium hydroxide and the para-aramid fibers in step 1) is 1:(1-5); the volume ratio between the dimethyl sulfoxide and the water is 49:1; and the concentration of the potassium hydroxide is 20 mg / mL.

[0014] Preferably, the acid reagent in step 2) is one or more of formic acid, acetic acid, hydrochloric acid, nitric acid, chlorosulfonic acid, phosphoric acid and sulfuric acid, and the concentration of the acid reagent is 0-4 mol / L.

[0015] Preferably, the inner core diameter of the coaxial needle in step 3) is 14-32G, and the outer core diameter is 6-24G; the extrusion speed is 10-300 mL / h; and the speed of the yarn winding drum is 1-20 m / min.

[0016] Preferably, the solvent exchange bath in step 4) is a solution of deionized water and tert-butyl alcohol, and the solvent exchange is specifically: exchanging in deionized water for 24 h, and then transferring to a 50% tert-butyl alcohol solution for 12 h.

[0017] Preferably, the temperature of the freezer in step 5) is -40℃, and the freezing time is 18-24 h; the temperature of the freeze-drying is below -40℃, the time is 24 h, and the vacuum degree is 8-12 Pa.

[0018] The yarn-reinforced nanofiber aramid composite aerogel fiber prepared by the preparation method has an outer layer of nanofiber aramid fiber and an inner layer of yarn, is prepared by wet spinning through a coaxial needle into a coagulation bath, and is prepared after solvent exchange and freeze drying; the yarn is pure spinning or more than one kind of blended strand or filament of one of cotton fiber, hemp fiber, wool fiber, polyester fiber, nylon fiber, acrylic fiber, carbon fiber, ultrahigh molecular weight polyethylene fiber, basalt fiber, aramid fiber, and stainless steel fiber.

[0019] The yarn-reinforced nanofiber aramid composite aerogel fiber is applied to warm textile products, and the yarn is cotton fiber.

[0020] The yarn-reinforced nanofiber aramid composite aerogel fiber is applied to high-strength protective products, and the yarn is carbon fiber.

[0021] The yarn-reinforced nanofiber aramid composite aerogel fiber is applied to conductive and heating industrial textiles, and the yarn is stainless steel fiber.

[0022] The yarn-reinforced nanofiber aramid composite aerogel fiber is applied to conductive and heating industrial textiles, and the yarn is stainless steel fiber.

[0023] (1) The yarn-reinforced nanofiber aramid composite aerogel fiber is applied to conductive and heating industrial textiles, and the yarn is stainless steel fiber.

[0024] (2) The yarn-reinforced nanofiber aramid composite aerogel fiber is applied to conductive and heating industrial textiles, and the yarn is stainless steel fiber.

[0025] (3) The yarn-reinforced nanofiber aramid composite aerogel fiber is applied to conductive and heating industrial textiles, and the yarn is stainless steel fiber. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a real photo of the nanofiber aramid fiber spinning solution in Example 1.

[0027] Figure 2 It is a real photo of the yarn-reinforced nanofiber aramid composite aerogel fiber wound on the yarn shaft in Example 2.

[0028] Figure 3SEM photos of different scales of the surface of the yarn-reinforced nanomesh composite aerogel fiber in Example 3: A is 200 μm, B is 10 μm, and C is 2 μm;

[0029] Figure 4 SEM photo of the cross section of the yarn-reinforced nanomesh composite aerogel fiber in Example 4;

[0030] Figure 5 SEM photos of different scales of the nanomesh aerogel part in the cross section of the yarn-reinforced nanomesh composite aerogel fiber in Example 4: A is 20 μm, and B is 5 μm;

[0031] Figure 6 Optical microscope photos of the surface (A) and the cross section (B) of the yarn-reinforced nanomesh composite aerogel fiber in Example 6;

[0032] Figure 7 Digital photo of the yarn-reinforced nanomesh composite aerogel fiber in Example 7 lifting a 2-kg water bucket;

[0033] Figure 8 Stress-strain curve of the yarn-reinforced nanomesh composite aerogel fiber prepared in Example 5 and Example 7;

[0034] Figure 9 Stress-strain curve of the aerogel fiber prepared in Comparative Example 1 (A) and Example 1 (B);

[0035] Figure 10 Thermal insulation performance test result of the yarn-reinforced nanomesh composite aerogel fiber in Example 3;

[0036] Figure 11 Electrothermal performance test result of the yarn-reinforced nanomesh composite aerogel fiber in Example 6: A is an infrared thermal imaging photo of the electrothermal fabric, and B is a curve of the electrothermal temperature change under different voltages. DETAILED DESCRIPTION

[0037] The application will be further described in detail below with reference to the accompanying drawings and specific examples.

[0038] Unless otherwise specified, the technical means used in the following examples are all conventional means known to those skilled in the art. The experimental methods not specified in detail are all conventional methods in the art.

[0039] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial channels.

[0040] Example 1

[0041] A yarn-reinforced nanometer aramid fiber composite aerogel fiber preparation method, the specific steps are as follows:

[0042] (1) Preparation of nanometer aramid fiber spinning solution

[0043] Control the temperature in the environment of 60℃, mix 2mL of deionized water and 98mL of dimethyl sulfoxide and stir for 30min, then add 2g of potassium hydroxide (concentration of 20mg / mL) and stir for 30min, finally add 1g of para-aramid fiber, continue to stir for 18h, to obtain a nanometer aramid fiber spinning solution with a content of 1wt%.

[0044] As Figure 1 The nanometer aramid fiber spinning fluid prepared in this embodiment is shown in the figure, the spinning solution is clear and transparent, the solution is uniform and stable, indicating that the nanometer aramid fiber (ANF) is uniformly dispersed, which is suitable for wet spinning.

[0045] (2) Preparation of spinning coagulation bath

[0046] Mix 500mL of acetic acid (concentration of 0-4mol / L, i.e. no acid can be added) with 4500mL of deionized water to obtain a coagulation bath with a concentration of 10% of 5000mL of acetic acid.

[0047] (3) Spinning

[0048] Pass the cotton yarn through the inner layer of the coaxial spinning needle with a diameter of 25G into the coagulation bath, connect the yarn guide and the winding drum, control the rotating speed of the winding drum to be 10m / min. At the same time, connect the outer layer of the coaxial needle head with the ANF nanometer aramid fiber spinning solution, and the outer layer of the spinneret with a diameter of 19G, under the action of the thrust of the pusher, extrude into the coagulation bath at a rate of 3.6mL / min, and wind the yarn onto the winding drum to obtain the yarn-reinforced hydrogel fiber.

[0049] (4) Solvent exchange

[0050] Take out the yarn-reinforced hydrogel fiber on the winding drum, put it into deionized water for 24h, and change the deionized water every 8h. Then change the deionized water into 50% tert-butyl alcohol solution and continue solvent exchange for 12h.

[0051] (5) Freeze-drying

[0052] Take out the yarn-reinforced hydrogel fiber from the 50% tert-butyl alcohol solution, put it into a-40℃ freezer for 18-24h. Place the frozen sample in a freeze dryer, control the freeze-drying temperature below-45℃, and the vacuum degree is 8-12Pa, after 24h, the yarn-reinforced nanometer aramid fiber composite aerogel fiber is obtained.

[0053] Example 2

[0054] A yarn-reinforced nanometer aramid composite aerogel fiber preparation method, the specific steps are the same as those of example 1, except that 2g of para-aramid fiber is added in the preparation of the nanometer aramid fiber spinning solution, and stirring is continued for 18h, to obtain a nanometer aramid fiber spinning solution with a content of 2wt%.

[0055] As Figure 2 shown is a digital photo of the yarn-reinforced nanometer aramid composite aerogel fiber prepared in this example being wound on a yarn spindle, and as can be seen from the figure, the composite aerogel fiber prepared in this example has good flexibility and mechanical properties, and can be smoothly wound on the yarn spindle, preparing for subsequent textile processing.

[0056] Example 3

[0057] A yarn-reinforced nanometer aramid composite aerogel fiber preparation method, the specific steps are the same as those of example 1, except that 3g of para-aramid fiber is added in the preparation of the nanometer aramid fiber spinning solution, and stirring is continued for 18h, to obtain a nanometer aramid fiber spinning solution with a content of 3wt%.

[0058] As Figure 3 shown is a scanning electron microscope picture of the surface of the yarn-reinforced nanometer aramid composite aerogel fiber prepared in this example, and as can be seen from the figure, due to the vigorous solvent exchange and protonation reduction, many tree bark-like stripes appear on the surface of the aerogel fiber.

[0059] Example 4

[0060] A yarn-reinforced nanometer aramid composite aerogel fiber preparation method, the specific steps are the same as those of example 1, except that 4g of para-aramid fiber is added in the preparation of the nanometer aramid fiber spinning solution, and stirring is continued for 18h, to obtain a nanometer aramid fiber spinning solution with a content of 4wt%.

[0061] As Figure 4 shown is a scanning electron microscope picture of the cross section of the yarn-reinforced nanometer aramid composite aerogel fiber prepared in this example, and as can be seen from the figure, the composite aerogel fiber is composed of a yarn skeleton and nanometer aramid fibers, wherein the yarn skeleton is in the center position and is surrounded by nanometer aramid fibers, forming a reinforcing fiber of the yarn-reinforced nanometer aramid aerogel.

[0062] As Figure 5 shown is an electron microscope picture of the aerogel part composed of nanometer aramid fibers in the yarn-reinforced nanometer aramid composite aerogel fiber prepared in this example, and as can be seen from the figure, the composite aerogel fiber contains rich micro-nano level pore structures, which provide space for the existence of electrostatic air, thereby reducing the overall thermal conductivity of the material and reducing the conduction of human body heat, playing a role in heat insulation and warmth retention.

[0063] Example 5

[0064] A method for preparing a yarn-reinforced nanomesh fiber composite aerogel fiber, the specific steps of which are the same as those of Example 1, except that the cotton yarn is replaced with meta-aramid yarn in the spinning step.

[0065] Example 6

[0066] A method for preparing a yarn-reinforced nanomesh fiber composite aerogel fiber, the specific steps of which are the same as those of Example 1, except that the cotton yarn is replaced with stainless steel wire yarn in the spinning step.

[0067] As Figure 6 shown is an optical microscope image of the nanomesh fiber composite aerogel fiber obtained in this embodiment, using stainless steel wire yarn as the inner layer. As can be seen from the figure, the stainless steel wire fiber is in the inner layer of the aerogel composite fiber, and the inner layer yarn exhibits the characteristic luster of metal materials; while the surface of the composite aerogel fiber is relatively flat, smooth and has no obvious depressions and pores.

[0068] Example 7

[0069] A method for preparing a yarn-reinforced nanomesh fiber composite aerogel fiber, the specific steps of which are the same as those of Example 1, except that the cotton yarn is replaced with carbon fiber filament in the spinning step.

[0070] In the composite aerogel fiber obtained in this embodiment, carbon fiber filaments are used as the inner layer, and the nanomesh fiber composite aerogel fiber obtained can lift a water bottle with a mass of 2 kg, as Figure 7 shown, the composite aerogel fiber has excellent mechanical properties, the main reason for which is that the carbon fiber filaments in the inner layer are high-strength and high-modulus fibers, which play a mechanical support role in the composite aerogel fiber and can withstand a large stress.

[0071] As Figure 8 shown is a stress-strain test curve of Example 5 and Example 7, from which it can be seen that the stress of the composite aerogel fiber changes with the change of the inner layer yarn. Example 5 uses meta-aramid as the inner layer, with a breaking stress of 8.03 N and a breaking strain of 23.03%; while Example 7 uses carbon fiber filaments as the inner layer, with a stress of 34.83 N and a breaking strain of 3.15%. This shows that the mechanical properties of the composite aerogel fiber can be regulated by the inner layer yarn, and based on this, the required yarn can be customized for special mechanical performance requirements.

[0072] Comparative Example 1

[0073] A method for preparing a nanomesh fiber composite aerogel fiber, the specific steps of which are the same as those of Example 1, except that no yarn is added to the coaxial inner layer in the spinning step. The spinning step is as follows:

[0074] The outer layer of the coaxial needle is connected to the spinneret of the 19G spinning solution of the ANF nanofiber, which is extruded into the coagulation bath at a speed of 3.6 mL / min under the thrust of the propeller, and is wound onto the winding drum at a speed of 10 m / min, to obtain a hydrogel fiber.

[0075] As Figure 9 The stress-strain test curve of Example 1 and Comparative Example 1 is shown in the figure, and it can be seen from the figure that the breaking stress of the pure nanofiber aerogel fiber is only 0.099 N Figure 9 (middle A) without adding the yarn skeleton, and the mechanical properties of the composite aerogel fiber are significantly increased Figure 9 (middle B) to 27.555 N, which proves that the yarn has the function of enhancing the mechanical properties of the composite aerogel fiber.

[0076] Test Example 1

[0077] The thermal insulation performance test of the fabric is to place the woven composite aerogel fabric on the thermocouple heating table, adjust the temperature of the heating table as the heat source, and record and analyze the surface temperature change of the composite aerogel fabric by an infrared camera.

[0078] The thermal insulation performance test of the yarn-reinforced nanofiber composite aerogel fiber prepared in Example 3 is shown in Figure 10 The composite aerogel fiber has excellent thermal insulation performance, and the thermal insulation effect is more obvious as the temperature rises. On a heating table at 200℃, the temperature of the composite aerogel fiber is only 100.8℃, which fully proves that the yarn-reinforced nanofiber composite aerogel fiber of the application has great application prospect in the field of thermal insulation.

[0079] Test Example 2

[0080] The electrothermal performance test of the fabric is to connect the two ends of part of the fibers of the woven composite aerogel fabric to a digital direct-current stabilized power supply, and to shoot, record and analyze the electrothermal performance of the fabric by an infrared camera.

[0081] The yarn-reinforced nanofiber composite aerogel fiber prepared in Example 6 is woven into a fabric, and the electrothermal performance test is carried out, as shown in Figure 11 Because the stainless steel fiber has good electrical conductivity, the voltage can be applied to the two ends of the fiber to realize electrothermal heating. As can be seen from the thermal imaging image Figure 11 (middle A) shot by the infrared camera, the composite aerogel fiber successfully realizes electrothermal heating, and the electrothermal effect is significant, which is significantly different from the surrounding fibers without voltage. And as Figure 11As shown in the middle B, with the increase of the applied voltage, the electrothermal temperature is higher, which proves that the yarn reinforced aerogel fiber of the application can also have other functions, and after increasing the electrothermal function, the clothing can be actively heated and kept warm, further expanding the application of the composite aerogel fiber.

[0082] The above-described embodiments are only some of the embodiments of the present application, not all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the application. The scope of protection of the present application is subject to the scope of claims, and all other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor fall within the scope of protection of the present application.

Claims

1. A method of making a yarn-reinforced nanofibril composite aerogel fiber, characterized by, Comprising the following steps: Step 1) adding para-aramid fibers into a mixed solution of deionized water, potassium hydroxide and dimethyl sulfoxide, heating and stirring to disperse, to obtain an outer layer of composite aerogel fiber spinning solution, i.e. nano aramid fiber spinning solution; Step 2) mixing an acid reagent with deionized water to obtain a spinning coagulation bath; Step 3) connecting the nano aramid fiber spinning solution prepared in step 1) to the outer layer of a coaxial needle and injecting it into the coagulation bath prepared in step 2) at a certain extrusion speed, while the inner layer of the coaxial needle is a yarn, which is wound and collected by a yarn winding drum, to obtain a yarn-reinforced nano aramid composite hydrogel fiber; Step 4) placing the yarn-reinforced nano aramid composite hydrogel fiber prepared in step 3) in a solvent exchange bath for solvent exchange; Step 5) placing the yarn-reinforced nano aramid composite hydrogel fiber treated in step 4) in a freezer, and freeze-drying to obtain the yarn-reinforced nano aramid composite aerogel fiber.

2. The method for preparing yarn-reinforced nano-aramid composite aerogel fiber according to claim 1, characterized in that, In step 1), the mass ratio between the potassium hydroxide and the para-aramid fiber is 1:(1-5); the volume ratio between the dimethyl sulfoxide and the water is 49:1; and the concentration of the potassium hydroxide is 20 mg / mL.

3. The method for preparing yarn-reinforced nano-aramid composite aerogel fiber according to claim 1, characterized in that, In step 2), the acid reagent is one or more of formic acid, acetic acid, hydrochloric acid, nitric acid, chlorosulfonic acid, phosphoric acid and sulfuric acid, and the concentration of the acid reagent is 0-4 mol / L.

4. The method of claim 1, wherein the nanofiber-reinforced aramid composite aerogel fiber is prepared by the steps of: In step 3), the inner core diameter of the coaxial needle is 14-32 G, and the outer core diameter is 6-24 G; the extrusion speed is 10-300 mL / h; and the speed of the yarn winding drum is 1-20 m / min.

5. The method for preparing yarn-reinforced nano-aramid composite aerogel fiber according to claim 1, characterized in that, In step 4), the solvent exchange bath is a deionized water and tert-butyl alcohol solution, and the solvent exchange is specifically: exchanging in deionized water for 24 h, and then transferring to a 50% tert-butyl alcohol solution for 12 h.

6. The method of claim 1, wherein the nanofiber-reinforced aramid composite aerogel fiber is prepared by the steps of: In step 5), the temperature of the freezer is -40°C, the freezing time is 18-24 h; the temperature of the freeze-drying is below -40°C, the time is 24 h, and the vacuum degree is 8-12 Pa.

7. The yarn-reinforced nanofiber aramid composite aerogel fiber prepared by the method according to any one of claims 1 to 6, characterized in that, The yarn-reinforced nano aramid composite aerogel fiber is prepared by wet spinning of the nano aramid fiber spinning solution and the yarn as the outer layer and the inner layer respectively through a coaxial needle into a coagulation bath, followed by solvent exchange and freeze-drying; the yarn is a pure spinning or a blended strand or filament of one or more of cotton fiber, hemp fiber, wool fiber, polyester fiber, nylon fiber, acrylic fiber, carbon fiber, ultra-high molecular weight polyethylene fiber, basalt fiber, aramid fiber and stainless steel fiber.

8. Use of the yarn-reinforced nanofiber aramid composite aerogel fiber according to claim 7 in thermal textile applications, characterized in that, The yarn is cotton fiber.

9. Use of the yarn-reinforced nanofiber aramid composite aerogel fiber according to claim 7 in high-strength protective equipment, characterized in that, The yarn is carbon fiber.

10. Use of the yarn-reinforced nanofiber aramid composite aerogel fiber according to claim 7 in electrically conductive, heated industrial textiles, characterized in that, The yarn is stainless steel fiber.

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