Preparation method of a super-stretchable aerogel fiber with an oriented pore structure

Abstract

The present invention relates to a preparation method of a super-stretchable aerogel fiber with an oriented pore structure, comprising the following steps: 1) preparation of a spinning solution; 2) spinning the spinning solution, performing directional freezing during spinning, and collecting the frozen fibers; 3) removing ice crystals from the frozen fibers; 4) preparation of an encapsulation solution; 5) encapsulating the aerogel fiber. Through the encapsulation of the aerogel fiber, the overall diameter of the fiber, the ratio of the core layer diameter to the shell layer thickness are adjusted, affecting the thermal insulation performance and mechanical properties of the fiber. When the size ratio is matched, the thermal insulation performance and mechanical properties of the fiber reach a balance.

Description

Technical Field

[0001] The present invention relates to the field of aerogel fibers, and particularly to a preparation method of a super stretchable aerogel fiber with an oriented pore structure. Background Art

[0002] The optimal temperature for the normal physiological activities of the human body is between 36 and 37 °C. In a low-temperature environment, the heat dissipated through the skin increases significantly, and the heat production in the human body is insufficient to maintain the body temperature at the normal level. Once the core body temperature drops below 35 °C, symptoms of hypothermia such as severe shivering and confusion will occur, affecting normal physiological activities, and severe hypothermia may even endanger life. Traditional thermal insulation fibers are mainly divided into natural materials such as cotton, wool, and down, and synthetic fibers such as porous cotton and microfiber. Clothing made of traditional thermal insulation fibers needs to be relatively thick to meet the thermal insulation requirements in extremely cold regions, increasing the volume and weight of the clothing and restricting the movement of personnel.

[0003] Traditional thermal insulation fiber materials such as wool, down, and most synthetic fibers use porous structures for heat insulation, yet achieving the goals of environmental protection, lightness, and high-efficiency heat insulation for future thermal insulation clothing remains a huge challenge. Aerogel is a high-quality high-efficiency thermal insulation material with characteristics such as low density, high porosity, high specific surface area, and ultra-low thermal conductivity, and has great application potential in the field of thermal insulation.

[0004] Currently, common inorganic silica aerogels have excellent thermal insulation effects, but they have disadvantages such as high brittleness, poor mechanical strength, and poor processability, and cannot meet the requirements for wearability. The electrospinning technology can achieve the large-scale continuous preparation of aerogel fibers, but the obtained aerogel fibers have the disadvantage of poor mechanical strength, severely restricting the practical application of the fibers. Existing technologies have attempted to improve the mechanical properties of aerogel fibers. One method is to first prepare a hollow shell and then freeze-dry it, and then fill the shell with an aerogel precursor solution and freeze-dry it again; the other method is to coat PVP on the surface of the aerogel fiber to improve the fiber toughness, but still requires supercritical drying. These methods are challenging to operate, time-consuming, and the process is cumbersome and complex, and the improvement effect on the mechanical properties of the fibers is limited, and at the same time, it will affect the thermal insulation performance of the fibers.

[0005] The oriented pore structure is the same as the disordered pore structure, and both can isolate heat transfer by blocking heat conduction and restricting heat convection. In addition, the oriented pore structure reflects the infrared radiation emitted by the human body back to the human body through multiple reflections between the pore walls, thereby regulating heat through thermal radiation and finally achieving efficient heat preservation through the coupling of multiple heat transfer paths. Oriented pores can be prepared by directional freezing. During the directional freezing process, parameters such as the size of the cold source copper ring, the temperature of the cold source, and the freezing rate of the fiber will affect the orientation degree, pore diameter, and pore spacing of the oriented pores in the fiber, and thus affect the heat insulation ability of the fiber. In addition, due to the poor mechanical properties of high-porosity thermal insulation fibers, a dense shell layer needs to be coated on the outside to improve the mechanical properties of the fiber. However, the orientation degree and pore diameter of the fiber pores will directly affect the formation of the coating layer. If the pores in the fiber are disordered, it is easy to break during the coating process. If the pore diameter is too large, the coating solution is likely to penetrate into the fiber interior, resulting in the loss of heat insulation ability. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of a super-stretchable aerogel fiber with an oriented pore structure in view of the deficiencies of the prior art. By combining directional freezing and solution spinning, the diameter of the copper ring, the temperature of the cold source, and the spinning rate during the directional freezing process are precisely controlled to obtain an aerogel fiber with an oriented pore structure. At the same time, through fiber encapsulation coating, it has super-stretchable properties. The diameter of the aerogel fiber is 100-1000 μm, the pore diameter is 10-100 μm, and the shell layer thickness is 10-100 μm.

[0007] A preparation method of a super-stretchable aerogel fiber with an oriented pore structure includes the following steps:

[0008] 1) Preparation of the spinning solution;

[0009] 2) Spinning the spinning solution, performing directional freezing during spinning, and collecting the frozen fibers;

[0010] 3) Removing ice crystals from the frozen fibers;

[0011] 4) Preparation of the encapsulation solution;

[0012] 5) Encapsulating the aerogel fiber.

[0013] The aerogel fibers prepared by the above technical solution have excellent heat insulation and stretchable properties. After the spinning solution is extruded from the extrusion pump, due to the influence of the temperature gradient, the nucleation and growth of ice crystals are oriented in the extrusion direction, forming an oriented pore structure. At the same time, due to the occurrence of microphase separation in the system, the raw materials are displaced by the ice crystals and compressed in the voids between the ice crystals. After complete freezing, the ice crystals are removed, and aerogel fibers with an oriented pore structure are obtained using the ice crystals as a template. At the same time, encapsulation is carried out outside the fibers, endowing the aerogel fibers with excellent super stretchable properties.

[0014] The preparation method of the super stretchable aerogel fiber with an oriented pore structure in the present invention includes the following steps:

[0015] 1) Prepare a natural polymer solution for freeze spinning; the natural polymer solution is one or more of a sodium carboxymethyl cellulose solution, a starch solution, a chitosan solution, and a silk fibroin solution;

[0016] 2) Perform solution spinning on the natural polymer solution, carry out directional freezing during spinning, and collect the frozen fibers; the directional freezing specifically includes: after the spinning solution is extruded from the extrusion pump at a speed of 1 - 10 ml / h, it passes through a low-temperature copper ring for directional freezing; the temperature of the low-temperature copper ring is -90 to -60 °C, and the inner diameter of the inner ring of the low-temperature copper ring is 5 - 10 mm; on the basis of traditional directional freezing, combined with solution spinning, when the spinning solution is extruded from the extrusion pump and passes through the low-temperature copper ring, there is a temperature gradient in the vertical direction of the low-temperature copper ring. When the temperature drops below the crystallization temperature of the solvent, the solvent begins to crystallize, and finally the raw materials are displaced by the ice crystals and compressed in the voids between the ice crystals; the above temperature makes it easy for ice crystals to form a template, and the freezing temperature has an impact on the formed oriented porous structure. The lower the temperature, the greater the temperature gradient, the faster the ice crystal growth rate, and the smaller the pore diameter of the formed porous structure. The higher the temperature, the smaller the temperature gradient, the slower the ice crystal growth rate, and the larger the pore diameter of the formed porous structure. The directional freezing temperature in the present invention needs to be adjusted, and the directional freezing temperature will affect the growth of ice crystals, and thus affect the final fiber orientation structure; when the freezing temperature is too high, the ice crystal growth rate is slow and the size is large, the pore diameter of the oriented pores in the fiber is large, and the polymer solution is likely to penetrate into the oriented pores during the encapsulation process, destroying the oriented pore structure; when the freezing temperature is too low, the ice crystal growth rate is fast and the size is small, and a regular oriented pore structure cannot be obtained.

[0017] 3) Freeze-dry the frozen fibers to remove the ice crystals, obtaining aerogel fibers with an oriented pore structure;

[0018] 4) Prepare an encapsulation solution, which includes one of the following: a DMF solution of TPU, a dichloromethane solution of SIS rubber, or a formic acid solution of nylon. The concentration of the encapsulation solution in the present invention needs to be adjusted. The concentration of the encapsulation liquid affects the viscosity, thus affecting the uniformity of the encapsulation liquid on the fiber surface and the overall structure of the fiber. If the concentration of the encapsulation solution is too low, the viscosity is too low, and droplets are likely to form on the fiber surface due to Rayleigh instability. At the same time, during encapsulation, the solution may cause the encapsulation liquid to enter the fiber interior, damaging the pore structure. If the concentration of the encapsulation solution is too high, the viscosity is too high, and the resistance of the fiber during encapsulation is too large, easily causing the fiber to break.

[0019] 5) Immerse the aerogel fiber in the encapsulation solution, and after high-temperature drying, a dense shell layer is obtained to achieve encapsulation, resulting in a super-stretchable aerogel fiber with an oriented pore structure.

[0020] Furthermore, the overall diameter of the aerogel fiber is 100 - 1000 μm, the pore diameter is 10 - 100 μm, the core layer diameter is 80 - 800 μm, and the shell layer thickness is 10 - 100 μm. When the ratio of the core layer diameter to the shell layer thickness is 6 - 10:1, the fiber can balance mechanical properties and heat insulation performance. When the core layer diameter is too large and the shell layer is too thin, the mechanical properties of the fiber are poor; when the core layer diameter is too small and the shell layer is too thick, the heat insulation performance of the fiber is poor. When the ratio of the fiber core layer diameter to the shell layer thickness is matched, the heat insulation performance and mechanical properties of the fiber reach a balance. When the porosity is lower than 85.7%, the mechanical strength can exceed 20 MPa, but the heat insulation performance of the fiber decreases significantly. When the porosity is higher than 90.9%, the heat insulation performance of the fiber is excellent, but the mechanical strength is lower than 8 MPa, unable to meet the actual use requirements.

[0021] Furthermore, the sodium carboxymethyl cellulose solution is an aqueous solution of sodium carboxymethyl cellulose, and the mass fraction of the sodium carboxymethyl cellulose solution is 1% - 10%.

[0022] Furthermore, the starch solution is an aqueous solution of starch, and the mass fraction of the starch solution is 1% - 10%.

[0023] Furthermore, the chitosan solution is a chitosan acetic acid solution; the concentration of the chitosan solution is 20 - 60 mg / ml, and the mass concentration of the acetic acid solution is 0.5 - 1.5%.

[0024] Furthermore, the preparation of the silk fibroin solution: Cut the natural cocoon, boil and dry it in a sodium carbonate solution, dissolve it in a lithium bromide solution, and after complete dialysis, prepare a silk fibroin solution; the mass fraction of the silk fibroin solution is 10 - 30%, and the lithium bromide solution is 9 mol / L.

[0025] Furthermore, the natural polymer solution includes a chitosan solution and a silk protein solution, wherein the mass ratio of silk protein to chitosan is 4-10:1; the TPU solution is a DMF solution of TPU, and the mass ratio of TPU to DMF is 5-25:100; the SIS rubber solution is a dichloromethane solution of SIS rubber, and the mass ratio of SIS rubber to dichloromethane is 5-25:100; the nylon solution is a formic acid solution of nylon, and the mass ratio of nylon to formic acid is 5-30:100.

[0026] Furthermore, the step 5) encapsulation specifically includes: winding one end of the aerogel fiber on a feeding motor and the other end on a winding motor, providing a liquid tank filled with an encapsulation solution for immersing the aerogel fiber between the feeding motor and the winding motor, and providing a high-temperature drying area behind the liquid tank for drying and volatilizing the aerogel fiber immersed in the encapsulation solution, collecting the obtained fibers on another motor, and achieving continuous operation by adjusting the speeds of the two motors to obtain a compact encapsulation layer.

[0027] Furthermore, the temperature of the high temperature drying zone is 100-200°C. The above temperature can make the solvent volatilize at a suitable speed, and the drying temperature has an impact on the formation of a dense shell layer. The lower the temperature, the less the solvent evaporates, and the collected fibers are prone to adhesion. The higher the temperature, the more obvious the difference in the volatilization speed of the inner and outer layers of the solution, which is easy to generate bubbles on the encapsulation layer and destroy the encapsulation layer.

[0028] The present invention has the following beneficial effects:

[0029] (1) The preparation method of the present invention is simple, can be prepared continuously on a large scale, is suitable for industrial scale-up application, and different materials can be designed according to actual needs.

[0030] (2) The preparation method of the present invention can prepare aerogel fibers with different pore sizes by adjusting the temperature of directional freezing. In addition, the pore size, porosity and pore morphology of the porous structure of the fiber can also be adjusted over a wide range. Different pore sizes and porosities affect the heat conduction, heat convection and heat radiation inside the fiber, resulting in differences in thermal insulation performance. Through aerogel fiber encapsulation, the overall diameter of the fiber, the core layer diameter and the shell layer thickness ratio are adjusted, which affects the thermal insulation performance and mechanical properties of the fiber. When the size ratio matches, the thermal insulation performance and mechanical properties of the fiber are balanced.

[0031] (3) The ultra-stretchable aerogel fiber with an oriented pore structure prepared by the present invention has a dense outer shell and an inner core of an aerogel fiber with an oriented pore structure; at the same time, the encapsulation layer can greatly improve the mechanical properties of the aerogel fiber. When the porosity exceeds 80%, the strength can still exceed 20 MPa, and the elongation at break exceeds 1600%, which expands the application range of the aerogel fiber and can be widely used in wearable fabrics, with broad development prospects. Brief Description of the Drawings

[0032] Figure 1 is a flowchart of a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0033] Figure 2 is a structural diagram of an aerogel fiber in a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0034] Figure 3 SEM image of the fiber obtained in Example 1 of a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0035] Figure 4 Optical image of the fiber obtained in Example 2 of a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0036] Figure 5 SEM image of the fiber obtained in Example 3 of a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0037] Figure 6 SEM image of the fiber obtained in Example 4 of a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0038] Figure 7 Optical image of the glove knitted from the fiber obtained in Example 5 of a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0039] Figure 8 SEM image of the shell structure of the fiber obtained in Example 6 of a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0040] Figure 9 Optical image of the water-proof and hydrophobic property of the fiber obtained in Example 7 of a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0041] Figure 10 Thermal insulation performance image of the fiber obtained in Example 8 of a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0042] Figure 11 Mechanical property image of the glove knitted from the fiber obtained in Example 9 of a method for preparing a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0043] Figure 12Thermal insulation performance diagram of the fiber obtained in Example 10 of the preparation method of a super-stretchable aerogel fiber with an oriented pore structure according to the present invention;

[0044] Among them, the overall diameter is D, the pore diameter is d, the core layer diameter is t, and the shell layer thickness is T. Detailed implementation mode

[0045] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines the drawings and preferred embodiments to detail the specific implementation mode, structure, features and their effects of the present invention as follows.

[0046] Schematic diagrams of the directional freezing-spinning device and fiber encapsulation device used in the embodiment are as Figure 1 shown. The prepared aerogel fiber has excellent thermal insulation and mechanical properties at the same time. When the spinning solution is extruded from the extrusion pump, due to the influence of the temperature gradient, the nucleation and growth of ice crystals are oriented in the extrusion direction, forming an oriented pore structure. At the same time, due to the occurrence of microphase separation in the system, the raw materials are excluded by the ice crystals and compressed into the voids between the ice crystals. After complete freezing, the ice crystals are removed, and an aerogel fiber with an oriented pore structure is obtained using the ice crystals as a template. The collected aerogel fiber is immersed in a polymer solution, and the solvent in the polymer solution is volatilized by high-temperature drying to form a dense polymer encapsulation layer on the surface of the aerogel fiber, endowing the aerogel fiber with excellent mechanical properties. The structural schematic diagram of the aerogel fiber is as Figure 2 shown, its diameter is 100 - 1000 μm, the pore diameter is 10 - 100 μm, and the shell layer thickness is 5 - 100 μm.

[0047] Example 1

[0048] (1) Dissolve 1 g of sodium carboxymethylcellulose powder in 100 ml of deionized water. After complete dissolution, a sodium carboxymethylcellulose solution with a mass fraction of 1% is prepared.

[0049] (2) Place the solution in a syringe, extrude the solution through an extrusion pump, place the copper ring in a low-temperature reaction bath, the temperature of the copper ring is -90 °C, the solution passes through the copper ring for the freezing-spinning process, and the frozen fiber is collected by a motor. After the spinning solution is extruded from the extrusion pump at a speed of 5 ml, it passes through the low-temperature copper ring for directional freezing; the inner ring diameter of the low-temperature copper ring is 5 mm;

[0050] (3) Freeze-dry the frozen fiber obtained in step (2) for 24 h to remove the solvent, obtain the aerogel fiber, and perform SEM characterization. As Figure 3 shown, it shows that the aerogel fiber has an oriented pore structure.

[0051] (4) Dissolve 5 g of TPU particles in 100 ml of DMF. After complete dissolution, prepare a DMF solution of TPU with a mass fraction of 5%.

[0052] (5) Place the aerogel fibers obtained in step (3) into the TPU / DMF solution obtained in step (4). After high-temperature drying, super stretchable aerogel fibers with an oriented pore structure are obtained. The fiber diameter is about 720 μm, the pore diameter is about 50 μm, the core layer diameter is about 640 μm, the shell layer thickness is about 80 μm, the ratio of the core layer diameter to the shell layer thickness is 8:1, and the porosity is about 89%.

[0053] (6) Cut the super stretchable aerogel fibers into 1 cm lengths. Use a mechanical testing machine to measure the mechanical strength of the fibers as 13.1 MPa and the elongation at break as 2005%.

[0054] (7) Weave the super stretchable aerogel fibers into a fabric. Place the fabric on an 80 °C constant-temperature hot stage and use an infrared thermal imager to record the surface temperature of the fabric as 50.1 °C.

[0055] Example 2

[0056] (1) Dissolve 10 g of sodium carboxymethyl cellulose powder in 100 ml of deionized water. After complete dissolution, prepare a sodium carboxymethyl cellulose solution with a mass fraction of 10%.

[0057] (2) Place the solution in a syringe and extrude the solution through an extrusion pump. A copper ring is placed in a low-temperature reaction bath with a temperature of -90 °C. The solution passes through the copper ring for the freeze-spinning process, and the frozen fibers are collected by a motor. After the spinning solution is extruded from the extrusion pump at a speed of 6 ml / h, it passes through the low-temperature copper ring for directional freezing. The inner diameter of the low-temperature copper ring is 6 mm.

[0058] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent, obtaining aerogel fibers with an oriented porous structure.

[0059] (4) Dissolve 25 g of TPU particles in 100 ml of DMF. After complete dissolution, prepare a DMF solution of TPU with a mass fraction of 25%.

[0060] (5) Place the aerogel fibers obtained in step (3) into the TPU / DMF solution obtained in step (4). After high-temperature drying, super stretchable aerogel fibers with an oriented pore structure are obtained. The fiber diameter is about 720 μm, the pore diameter is about 80 μm, the core layer diameter is about 640 μm, the shell layer thickness is about 80 μm, the ratio of the core layer diameter to the shell layer thickness is 8:1, and the porosity is about 89%. Its optical diagram is as Figure 4 shown.

[0061] (6) Cut the super-stretchable aerogel fiber into 1 cm in length, and use a mechanical testing machine to measure that the mechanical strength of the fiber is 14.1 MPa and the elongation at break is 2014%.

[0062] (7) Weave the super-stretchable aerogel fiber into a fabric, place the fabric on an 80 °C constant temperature hot stage, and use an infrared thermal imager to record that the surface temperature of the fabric is 49.1 °C.

[0063] Example 3

[0064] (1) Dissolve 1 g of water-soluble starch powder in 100 ml of water. After complete dissolution, prepare a starch solution with a mass fraction of 1%.

[0065] (2) Place the solution in a syringe, extrude the solution through an extrusion pump. Place a copper ring in a low-temperature reaction bath with a temperature of -90 °C. The solution passes through the copper ring for the freeze-spinning process, and the frozen fiber is collected by a motor. After the spinning solution is extruded from the extrusion pump at a speed of 6 ml / h, it passes through the low-temperature copper ring for directional freezing; the inner diameter of the low-temperature copper ring is 8 mm;

[0066] (3) Freeze-dry the frozen fiber obtained in step (2) for 24 h to remove the solvent, obtaining an aerogel fiber with an oriented porous structure.

[0067] (4) Dissolve 5 g of SIS rubber particles in 100 ml of dichloromethane. After complete dissolution, prepare a dichloromethane solution of SIS rubber with a mass fraction of 5%.

[0068] (5) Place the aerogel fiber obtained in step (3) in the SIS / dichloromethane solution obtained in step (4), and obtain a super-stretchable aerogel fiber with an oriented pore structure after high-temperature drying. The fiber diameter is about 700 μm, the pore diameter is about 40 μm, the core layer diameter is about 600 μm, the shell layer thickness is about 100 μm, the ratio of the core layer diameter to the shell layer thickness is 6:1, and the porosity is about 86%. Conduct SEM characterization, as Figure 5 shown, indicating that the aerogel fiber has a core-shell oriented porous structure.

[0069] (6) Cut the super-stretchable aerogel fiber into 1 cm in length, and use a mechanical testing machine to measure that the mechanical strength of the fiber is 10.7 MPa and the elongation at break is 2060%.

[0070] (7) Weave the super-stretchable aerogel fiber into a fabric, place the fabric on an 80 °C constant temperature hot stage, and use an infrared thermal imager to record that the surface temperature of the fabric is 48.9 °C.

[0071] Example 4

[0072] (1) Dissolve 10 g of water-soluble starch powder in 100 ml of water. After complete dissolution, a starch solution with a mass fraction of 10% is prepared.

[0073] (2) Place the solution in a syringe and extrude the solution through an extrusion pump. The copper ring is placed in a low-temperature reaction bath, and the temperature of the copper ring is -90 °C. The solution passes through the copper ring for the freeze-spinning process, and the frozen fibers are collected by a motor. After the spinning solution is extruded from the extrusion pump at a speed of 1 ml / h, it passes through the low-temperature copper ring for directional freezing; the inner diameter of the low-temperature copper ring is 10 mm;

[0074] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent, obtaining aerogel fibers with an oriented porous structure.

[0075] (4) Dissolve 25 g of SIS rubber particles in 100 ml of dichloromethane. After complete dissolution, a dichloromethane solution of SIS rubber with a mass fraction of 25% is prepared.

[0076] (5) Place the aerogel fibers obtained in step (3) in the SIS / dichloromethane solution obtained in step (4), and after high-temperature drying, super stretchable aerogel fibers with an oriented pore structure are obtained. The fiber diameter is about 700 μm, the pore diameter is about 20 μm, the core layer diameter is about 600 μm, the shell layer thickness is about 100 μm, the ratio of the core layer diameter to the shell layer thickness is 6:1, and the porosity is about 86%. Perform SEM characterization, as Figure 6 shown to illustrate that the aerogel fibers have a core-shell oriented porous structure.

[0077] (6) Cut the super stretchable aerogel fibers into 1 cm lengths, and use a mechanical testing machine to measure the mechanical strength of the fibers as 13.7 MPa and the elongation at break as 2210%.

[0078] (7) Weave the super stretchable aerogel fibers into a fabric, place the fabric on an 80 °C constant-temperature hot stage, and use an infrared thermal imager to record the surface temperature of the fabric as 51.9 °C.

[0079] Example 5

[0080] (1) Dissolve 2 g of chitosan powder in 100 ml of 0.5% acetic acid solution, and stir at a speed of 800 rpm / min for 30 min to mix evenly, preparing a chitosan solution with a concentration of 20 mg / ml.

[0081] (2) Place the mixed solution in a syringe and extrude the solution through an extrusion pump. The copper ring is placed in a low-temperature reaction bath (-60 °C), the solution passes through the copper ring for the freeze-spinning process, and the frozen fibers are collected by a motor. After the spinning solution is extruded from the extrusion pump at a speed of 3 ml / h, it passes through the low-temperature copper ring for directional freezing; the inner diameter of the low-temperature copper ring is 8 mm;

[0082] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent, obtaining aerogel fibers, and perform SEM characterization.

[0083] (4) Dissolve 5 g of nylon powder in 100 ml of formic acid. After complete dissolution, prepare a formic acid solution of nylon with a mass fraction of 5%.

[0084] (5) Place the aerogel fibers obtained in step (3) into the nylon / formic acid solution obtained in step (4). After high-temperature drying, obtain super-stretchable aerogel fibers with an oriented pore structure. The fiber diameter is about 900 μm, the pore diameter is about 30 μm, the core layer diameter is about 800 μm, the shell layer thickness is about 100 μm, the ratio of the core layer diameter to the shell layer thickness is 8:1, and the porosity is about 89%.

[0085] (6) Cut the super-stretchable aerogel fibers into 1-cm lengths. Use a mechanical testing machine to measure that the mechanical strength of the fibers is 14.2 MPa and the elongation at break is 140%. As Figure 7 shown, gloves can be woven from such aerogel fibers, demonstrating their excellent processability.

[0086] (7) Weave the super-stretchable aerogel fibers into a fabric. Place the fabric on an 80°C constant-temperature hot stage and use an infrared thermal imager to record that the surface temperature of the fabric is 48.8°C.

[0087] Example 6

[0088] (1) Dissolve 6 g of chitosan powder in 100 ml of 1.5% acetic acid solution. Stir at a speed of 800 rpm / min for 30 min to mix evenly, preparing a chitosan solution with a concentration of 60 mg / ml.

[0089] (2) Place the mixed solution in a syringe and extrude the solution through an extrusion pump. Place a copper ring in a low-temperature reaction bath (-60°C). The solution passes through the copper ring for the freeze-spinning process, and the frozen fibers are collected by a motor. After the spinning solution is extruded from the extrusion pump at a speed of 5 ml / h, it passes through the low-temperature copper ring for directional freezing. The inner diameter of the low-temperature copper ring is 8 mm;

[0090] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent, obtaining aerogel fibers.

[0091] (4) Dissolve 30 g of nylon powder in 100 ml of formic acid. After complete dissolution, prepare a formic acid solution of nylon with a mass fraction of 30%.

[0092] (5) Place the aerogel fibers obtained in step (3) into the nylon / formic acid solution obtained in step (4), and after high-temperature drying, obtain super-stretchable aerogel fibers with an oriented pore structure. The fiber diameter is about 360 μm, the pore diameter is about 20 μm, the core layer diameter is about 320 μm, the shell layer thickness is about 40 μm, the ratio of the core layer diameter to the shell layer thickness is 8:1, and the porosity is about 89%.

[0093] (6) Cut the super-stretchable aerogel fibers into 1 cm lengths, and use a mechanical testing machine to measure that the mechanical strength of the fibers is 17.5 MPa and the elongation at break is 170%.

[0094] (7) Weave the super-stretchable aerogel fibers into a fabric, place the fabric on an 80 °C constant-temperature hot stage, and use an infrared thermal imager to record that the surface temperature of the fabric is 49.9 °C.

[0095] Example 7

[0096] (1) Cut 10 g of natural silkworm cocoons, boil and dry them in a 1% sodium carbonate solution, dissolve them in 100 ml of 9 mol / ml lithium bromide solution, and after dialysis for 24 h, prepare a silk fibroin solution with a mass fraction of 10%.

[0097] (2) Place the mixed solution in a syringe, extrude the solution through an extrusion pump, place the copper ring in a low-temperature reaction bath (-60 °C), pass the solution through the copper ring for the freeze-spinning process, and collect the frozen fibers with a motor. After the spinning solution is extruded from the extrusion pump at a speed of 6 ml / h, it passes through the low-temperature copper ring for directional freezing; the inner diameter of the low-temperature copper ring is 8 mm;

[0098] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent, and obtain aerogel fibers with an oriented pore structure.

[0099] (4) Dissolve 5 g of SIS rubber particles in 100 ml of dichloromethane, and after complete dissolution, prepare a dichloromethane solution of 5% mass fraction of SIS rubber.

[0100] (5) Place the aerogel fibers obtained in step (3) into the SIS / dichloromethane solution obtained in step (4), and after high-temperature drying, obtain super-stretchable aerogel fibers with an oriented pore structure. The fiber diameter is about 490 μm, the pore diameter is about 20 μm, the core layer diameter is about 420 μm, the shell layer thickness is about 70 μm, the ratio of the core layer diameter to the shell layer thickness is 6:1, and the porosity is about 86%. As Figure 9 shown, it is an optical picture of a water droplet on the fiber, proving the integrity of the encapsulation.

[0101] (6) Cut the super-stretchable aerogel fibers into 1 cm lengths, and use a mechanical testing machine to measure that the mechanical strength of the fibers is 11.5 MPa and the elongation at break is 1940%.

[0102] (7) Weave the super-stretchable aerogel fibers into a fabric, place the fabric on a constant-temperature hot stage at 80 °C, and use an infrared thermal imager to record the surface temperature of the fabric as 47.3 °C.

[0103] Example 8

[0104] (1) Cut 30 g of natural silkworm cocoons, boil and dry them in a 1% sodium carbonate solution, dissolve them in 100 ml of 9 mol / ml lithium bromide solution, and dialyze for 24 h to prepare a silk fibroin solution with a mass fraction of 30%.

[0105] (2) Place the mixed solution in a syringe, extrude the solution through an extrusion pump, place the copper ring in a low-temperature reaction bath (-60 °C), let the solution pass through the copper ring for the freeze-spinning process, and collect the frozen fibers with a motor. After the spinning solution is extruded from the extrusion pump at a speed of 6 ml / h, it passes through the low-temperature copper ring for directional freezing; the inner diameter of the low-temperature copper ring is 8 mm;

[0106] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent, obtaining aerogel fibers with an oriented pore structure.

[0107] (4) Dissolve 5 g of SIS rubber particles in 100 ml of dichloromethane. After complete dissolution, prepare a dichloromethane solution of SIS rubber with a mass fraction of 5%.

[0108] (5) Place the aerogel fibers obtained in step (3) in the SIS / dichloromethane solution obtained in step (4), and after high-temperature drying, obtain super-stretchable aerogel fibers with an oriented pore structure. The fiber diameter is about 490 μm, the pore diameter is about 50 μm, the core layer diameter is about 420 μm, the shell layer thickness is about 70 μm, the ratio of the core layer diameter to the shell layer thickness is 6:1, and the porosity is about 86%.

[0109] (6) Cut the super-stretchable aerogel fibers into 1 cm lengths, and use a mechanical testing machine to measure the mechanical strength of the fibers as 11.5 MPa and the elongation at break as 1940%.

[0110] (7) Weave the super-stretchable aerogel fibers into a fabric, place the fabric on a constant-temperature hot stage at 80 °C, and use an infrared thermal imager to record the surface temperature of the fabric as 47.3 °C, as Figure 10 shown in the infrared image of the heat insulation performance of a single fiber on an 80 °C hot stage.

[0111] Example 9

[0112] (1) Cut 10 g of natural silkworm cocoons, boil and dry them in a 1% sodium carbonate solution, dissolve them in 100 ml of 9 mol / ml lithium bromide solution, and dialyze for 24 h to prepare a silk fibroin solution with a mass fraction of 10%.

[0113] Dissolve 2.5 g of chitosan powder in 100 ml of 1% acetic acid solution, stir it at a speed of 800 rpm / min for 30 min to make it evenly mixed, and prepare a chitosan solution with a concentration of 25 mg / ml.

[0114] After mixing 100 ml of the above-mentioned silk fibroin solution and 100 ml of chitosan solution evenly, centrifuge to remove air bubbles to obtain a homogeneous solution, where the mass ratio of silk fibroin to chitosan is 4:1.

[0115] (2) Place the mixed solution in a syringe, extrude the solution through an extrusion pump, place the copper ring in a low-temperature reaction bath (-60 °C), let the solution pass through the copper ring for the freeze-spinning process, and collect the frozen fibers with a motor. After the spinning solution is extruded from the extrusion pump at a speed of 10 ml / h, it passes through the low-temperature copper ring for directional freezing; the inner diameter of the low-temperature copper ring is 5 mm;

[0116] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent and obtain aerogel fibers.

[0117] (4) Dissolve 10 g of TPU particles in 100 ml of DMF, and after complete dissolution, prepare a DMF solution of TPU with a mass fraction of 10%.

[0118] (5) Place the aerogel fibers obtained in step (3) in the TPU / DMF solution obtained in step (4), and after high-temperature drying, obtain super-stretchable aerogel fibers with an oriented pore structure. The fiber diameter is about 100 μm, the pore diameter is about 10 μm, the core layer diameter is about 88 μm, the shell layer thickness is about 12 μm, the ratio of the core layer diameter to the shell layer thickness is 7:1, and the porosity is about 87%.

[0119] (6) Cut the super-stretchable aerogel fibers into 1 cm lengths, and use a mechanical testing machine to measure that the mechanical strength of the fibers is 15.5 MPa and the elongation at break is 1340%, as Figure 11 is the mechanical property diagram of the fibers.

[0120] (7) Weave the super-stretchable aerogel fibers into a fabric, place the fabric on an 80 °C constant-temperature hot stage, and use an infrared thermal imager to record that the surface temperature of the fabric is 49.3 °C.

[0121] Example 10

[0122] (1) Cut 30 g of natural silkworm cocoons, boil and dry them in 1% sodium carbonate solution, dissolve them in 100 ml of 9 mol / ml lithium bromide solution, and after dialysis for 24 h, prepare a silk fibroin solution with a mass fraction of 30%.

[0123] Dissolve 3 g of chitosan powder in 100 ml of 1% acetic acid solution, and stir it at a speed of 800 rpm for 30 min to make it evenly mixed, so as to prepare a chitosan solution with a concentration of 30 mg / ml.

[0124] After mixing 100 ml of the above-mentioned silk fibroin solution and 100 ml of chitosan solution evenly, centrifuge to remove air bubbles to obtain a homogeneous solution, where the mass ratio of silk fibroin to chitosan is 10:1.

[0125] (2) Place the mixed solution in a syringe, extrude the solution through an extrusion pump, place the copper ring in a low-temperature reaction bath (-60 °C), and the solution passes through the copper ring for the freeze-spinning process, and the frozen fibers are collected by a motor. After the spinning solution is extruded from the extrusion pump at a speed of 10 ml / h, it passes through the low-temperature copper ring for directional freezing; the inner diameter of the low-temperature copper ring is 5 mm;

[0126] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent, and obtain aerogel fibers with an oriented pore structure.

[0127] (4) Dissolve 10 g of TPU particles in 100 ml of DMF, and after complete dissolution, prepare a DMF solution of TPU with a mass fraction of 10%.

[0128] (5) Place the aerogel fibers obtained in step (4) in the TPU / DMF solution obtained in step (5), and after high-temperature drying, obtain super-stretchable aerogel fibers with an oriented pore structure. The fiber diameter is about 100 μm, the pore diameter is about 15 μm, the core layer diameter is about 88 μm, the shell layer thickness is about 12 μm, the ratio of the core layer diameter to the shell layer thickness is 7:1, and the porosity is about 87%.

[0129] (6) Cut the super-stretchable aerogel fibers into 1 cm lengths, and use a mechanical testing machine to measure that the mechanical strength of the fibers is 16.7 MPa and the elongation at break is 1090%.

[0130] (7) Weave the super-stretchable aerogel fibers into a fabric, place the fabric on an 80 °C constant-temperature hot stage, and use an infrared thermal imager to record that the surface temperature of the fabric is 50.2 °C, as Figure 12 shown.

[0131] Comparative Example 1

[0132] (1) Dissolve 1 g of sodium carboxymethyl cellulose powder in 100 ml of deionized water, and after complete dissolution, prepare a sodium carboxymethyl cellulose solution with a mass fraction of 1%.

[0133] (2) Place the solution in a syringe and extrude the solution through an extrusion pump. The copper ring is placed in a low-temperature reaction bath with a temperature of -90 °C for the copper ring. The solution passes through the copper ring for the freeze-spinning process, and the frozen fibers are collected by a motor. After the spinning solution is extruded from the extrusion pump at a speed of 20 ml / h, it passes through the low-temperature copper ring for directional freezing; the temperature of the low-temperature copper ring is -50 °C, and the inner diameter of the low-temperature copper ring is 5 mm;

[0134] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent and obtain aerogel fibers. Due to the too-fast spinning speed, the pore size exceeds 100 μm, and the ice crystals grow disorderly, making it impossible to form fibers with an oriented lamellar pore structure.

[0135] (4) Dissolve 5 g of TPU particles in 100 ml of DMF. After complete dissolution, prepare a DMF solution of TPU with a mass fraction of 5%.

[0136] (5) Place the aerogel fibers obtained in step (3) in the TPU / DMF solution obtained in step (4). After high-temperature drying, super-stretchable aerogel fibers are obtained. The fiber diameter is about 720 μm, the pore diameter is about 130 μm, the core layer diameter is about 640 μm, the shell layer thickness is about 80 μm, the ratio of the core layer diameter to the shell layer thickness is 2:1, and the porosity is about 66%.

[0137] (6) Weave the super-stretchable aerogel fibers into a fabric, place the fabric on an 80 °C constant-temperature hot stage, and use an infrared thermal imager to record the surface temperature of the fabric as 66.8 °C.

[0138] (7) Cut the super-stretchable aerogel fibers into 1 cm lengths and use a mechanical testing machine to measure the mechanical strength of the fibers as 8.7 MPa and the elongation at break as 1150%.

[0139] Comparative Example 2

[0140] (1) Dissolve 1 g of sodium carboxymethylcellulose powder in 100 ml of deionized water. After complete dissolution, prepare a sodium carboxymethylcellulose solution with a mass fraction of 1%.

[0141] (2) Place the solution in a syringe and extrude the solution through an extrusion pump. The copper ring is placed in a low-temperature reaction bath with a temperature of -10 °C for the copper ring. The solution passes through the copper ring for the freeze-spinning process, and the frozen fibers are collected by a motor. After the spinning solution is extruded from the extrusion pump at a speed of 5 ml / h, it passes through the low-temperature copper ring for directional freezing; the inner diameter of the low-temperature copper ring is 5 mm;

[0142] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent and obtain aerogel fibers. Due to the too-high temperature of the copper ring, the pore size exceeds 100 μm, and the pore size exceeds 100 μm.

[0143] (4) Dissolve 5 g of TPU particles in 100 ml of DMF. After complete dissolution, prepare a DMF solution of TPU with a mass fraction of 5%.

[0144] (5) Place the aerogel fibers obtained in step (3) into the TPU / DMF solution obtained in step (4). After high-temperature drying, super-stretchable aerogel fibers with an oriented pore structure are obtained. The fiber diameter is about 720 μm, the pore diameter is about 140 μm, the core layer diameter is about 640 μm, the shell layer thickness is about 80 μm, the ratio of the core layer diameter to the shell layer thickness is 2:1, and the porosity is about 66%.

[0145] (6) Cut the super-stretchable aerogel fibers into 1 cm lengths. Use a mechanical testing machine to measure the mechanical strength of the fibers as 7.8 MPa and the elongation at break as 1010%.

[0146] (7) Weave the super-stretchable aerogel fibers into a fabric. Place the fabric on an 80 °C constant-temperature hot stage and use an infrared thermal imager to record the surface temperature of the fabric as 63.2 °C.

[0147] Comparative Example 3

[0148] (1) Dissolve 1 g of sodium carboxymethylcellulose powder in 100 ml of deionized water. After complete dissolution, prepare a sodium carboxymethylcellulose solution with a mass fraction of 1%.

[0149] (2) Place the solution in a syringe and extrude the solution through an extrusion pump. A copper ring is placed in a low-temperature reaction bath with a temperature of -50 °C. The solution passes through the copper ring for the freeze-spinning process, and the frozen fibers are collected by a motor. After the spinning solution is extruded from the extrusion pump at a speed of 5 ml / h, it passes through the low-temperature copper ring for directional freezing; the inner diameter of the low-temperature copper ring is 3 mm;

[0150] (3) Freeze-dry the frozen fibers obtained in step (2) for 24 h to remove the solvent, obtaining aerogel fibers. Due to the too small diameter of the copper ring, the ice crystal growth rate is too fast, the pore size is less than 10 μm, and an oriented lamellar pore structure cannot be formed.

[0151] (4) Dissolve 5 g of TPU particles in 100 ml of DMF. After complete dissolution, prepare a DMF solution of TPU with a mass fraction of 5%.

[0152] (5) Place the aerogel fibers obtained in step (3) into the TPU / DMF solution obtained in step (4). After high-temperature drying, super-stretchable aerogel fibers with a disordered pore structure are obtained. The fiber diameter is about 720 μm, the pore diameter is about 140 μm, the core layer diameter is about 640 μm, the shell layer thickness is about 80 μm, the ratio of the core layer diameter to the shell layer thickness is 8:1, and the porosity is about 89%.

[0153] (6) Cut the super-stretchable aerogel fiber into 1 cm in length, and measure the mechanical strength of the fiber to be 8.7 MPa and the elongation at break to be 1260% using a mechanical testing machine.

[0154] (7) Weave the super-stretchable aerogel fiber into a fabric, place the fabric on a constant temperature hot stage at 80 °C, and record the surface temperature of the fabric to be 68.4 °C using an infrared thermal imager.

[0155] The above is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the technical content disclosed above within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a super-stretchable aerogel fiber with an oriented pore structure, characterized in that, It includes the following steps: 1) Prepare a natural polymer solution for cryospinning; the natural polymer solution is one or more of a sodium carboxymethyl cellulose solution, a starch solution, a chitosan solution, and a silk fibroin solution; 2) Perform solution spinning on the natural polymer solution, carry out directional freezing during spinning, and collect the frozen fibers; The directional freezing specifically includes: after the spinning solution is extruded from the extrusion pump at a speed of 1-10 ml / h, it passes through a low-temperature copper ring for directional freezing; the temperature of the low-temperature copper ring is -90 to -60 °C, and the inner diameter of the low-temperature copper ring is 5-10 mm; 3) Freeze-dry the frozen fibers to remove ice crystals to obtain an aerogel fiber with an oriented pore structure; 4) Prepare an encapsulation solution, and the encapsulation solution includes: one of a DMF solution of TPU, a dichloromethane solution of SIS rubber, or a formic acid solution of nylon; 5) Immerse the aerogel fiber in the encapsulation solution, and after high-temperature drying, a dense shell layer is obtained to achieve encapsulation, obtaining a super-stretchable aerogel fiber with an oriented pore structure; the temperature of the high-temperature drying zone is 100-200 °C.

2. The preparation method of the super-stretchable aerogel fiber with an oriented pore structure according to claim 1, characterized in that, The overall diameter of the super-stretchable aerogel fiber is 100-1000 μm, the pore diameter is 10-100 μm, the core layer diameter is 80-800 μm, the shell layer thickness is 10-100 μm, and the ratio of the core layer diameter to the shell layer thickness is 6-10:

1.

3. The preparation method of the super-stretchable aerogel fiber with an oriented pore structure according to claim 1, wherein, The sodium carboxymethyl cellulose solution is an aqueous solution of sodium carboxymethyl cellulose, and the mass fraction of the sodium carboxymethyl cellulose solution is 1%-10%.

4. The preparation method of the super-stretchable aerogel fiber with an oriented pore structure according to claim 1, characterized in that, The starch solution is an aqueous solution of starch, and the mass fraction of the starch solution is 1%-10%.

5. The preparation method of the super-stretchable aerogel fiber with an oriented pore structure according to claim 1, characterized in that, The chitosan solution is a chitosan acetic acid solution; the concentration of the chitosan solution is 20-60 mg / ml, and the mass concentration of the acetic acid solution is 0.5-1.5%.

6. The preparation method of the super-stretchable aerogel fiber with an oriented pore structure according to claim 1, characterized in that, The preparation of the silk fibroin solution: Cut the natural silkworm cocoon, boil and dry it in a sodium carbonate solution, dissolve it in a 1 wt% lithium bromide solution, and after complete dialysis, prepare a silk fibroin solution; the mass fraction of the silk fibroin solution is 10-30%, and the lithium bromide solution is 9 mol / L.

7. The preparation method of the super-stretchable aerogel fiber with an oriented pore structure according to claim 1, wherein, The natural polymer solution includes a chitosan solution and a silk fibroin solution, and the mass ratio of silk fibroin to chitosan is 4-10:1; the TPU solution is a DMF solution of TPU, and the mass ratio of TPU to DMF is 5-25:100; the SIS rubber solution is a dichloromethane solution of SIS rubber, and the mass ratio of SIS rubber to dichloromethane is 5-25:100; the nylon solution is a formic acid solution of nylon, and the mass ratio of nylon to formic acid is 5-30:

100.

8. The preparation method of the super-stretchable aerogel fiber with an oriented pore structure according to claim 1, characterized in that, The encapsulation in step 5) specifically includes: winding one end of the aerogel fiber around the feeding motor and the other end around the winding motor. There is a liquid tank filled with encapsulation solution for immersing the aerogel fiber between the feeding motor and the winding motor. A high-temperature drying area for drying and volatilizing the aerogel fiber after immersion in the encapsulation solution is provided behind the liquid tank. The obtained fiber is collected on another motor, and continuous operation is achieved by adjusting the rotation speeds of the two motors to obtain a hermetic encapsulation layer.

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