A high-content stretchable silica aerogel composite fiber

Abstract

The present invention relates to a high-content, stretchable silica aerogel composite fiber, produced by the following methods: 1) preparing a silica aerogel composite fiber precursor by coaxial melt spinning; 2) thermally stretching the silica aerogel composite fiber precursor; and 3) hot-pressing and sealing the fibers into a bamboo-like shape. By adjusting the diameter of the hollow fibers, silica aerogel composite fibers of varying diameters can be produced. The fibers maintain their thermal insulation properties after 10,000 cycles of 100% strain stretching.

Description

Technical Field

[0001] The invention relates to an aerogel fiber material, in particular to a high-content stretchable silica aerogel composite fiber. Background Art

[0002] Aerogel is a special solid material formed by the interaction between colloidal particles or polymer molecules. This material has a three-dimensional nanoporous structure filled with a gaseous dispersion medium. Aerogel is known for its unique characteristics such as ultra-lightness, low density and nano-pores, and is known as "solidified smoke". Aerogel has shown important application value in the fields of building insulation, heat insulation, catalysis, aerospace, etc. Especially in the field of thermal insulation, the application of aerogel powder materials has further expanded to aerogel coatings, aerogel felts, aerogel boards, aerogel special-shaped parts and other composite materials that can be used in industry. However, it also has some disadvantages, such as high brittleness, low mechanical strength and poor processability. These shortcomings limit its application in the wearable field.

[0003] To overcome these issues with aerogels in the wearable field, existing technologies have attempted to improve their performance. One approach involves adding an appropriate amount of nanofibers, such as ceramic fibers, to aerogel mats to enhance their mechanical strength, thereby improving their reliability and durability. However, this approach still cannot avoid the problem of powder shedding, and the low aerogel loading limits improvements in thermal insulation performance. Another approach involves blending aerogel powder with thermoplastic polymers and melt-extruding them to create composite aerogels. However, such composite aerogels typically have an aerogel loading of less than 50%, an elongation at break of less than 3%, and poor mechanical properties. Due to these poor mechanical properties, aerogel fibers are easily broken, rendering them unusable. Furthermore, the human body dissipates most of its heat through infrared radiation, but the nanopores within aerogels cannot modulate infrared radiation. This can lead to insufficient thermal insulation performance, making aerogel fibers incapable of meeting higher thermal insulation requirements. Therefore, there is an urgent need to develop new processes for preparing aerogel fibers with superior mechanical properties, resulting in improved flexibility, durability, adaptability, and comfort. Summary of the Invention

[0004] The present invention addresses the shortcomings of the prior art by encapsulating aerogel powder within hollow fibers to produce tensile-resistant, pressure-resistant, weavable, and washable aerogel fibers. Due to the excellent resilience of the shell layer and the friction between the aerogel powder in the core layer and the shell layer, the aerogel powder in the core layer can return to its unstretched state as the shell layer recovers after stretching the aerogel fiber, ensuring the same thermal insulation properties. Furthermore, due to the interfacial reflection between the core and shell layers, infrared radiation is reflected at the interface, thereby enhancing the thermal insulation effect.

[0005] The present invention provides a high-content stretchable silica aerogel composite fiber, comprising a polymer shell layer and aerogel powder filled in the polymer shell layer; the shell layer has a diameter of 400 to 700 μm; the aerogel powder is silica aerogel, which is prepared by the following method:

[0006] 1) Using a double annular nozzle, a composite fiber with a core-shell structure is extruded from top to bottom, wherein molten polymer is injected into the double annular nozzle to form a shell layer, and aerogel powder is injected into the double annular nozzle to form a core layer;

[0007] 2) heating and softening the composite fiber obtained in step 1) and then thermally stretching the composite fiber at a stretching ratio of 3 to 6;

[0008] 3) The stretched fiber obtained in step 2) is heat-sealed every 1 to 5 cm to obtain an aerogel composite fiber with a bamboo structure.

[0009] Furthermore, the molten polymer is one of thermoplastic polyurethane (TPU), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), and polyester (PET). The aerogel is silica aerogel.

[0010] Furthermore, the inner diameter of the inner ring of the double-annular nozzle is 200-500 μm, and the inner diameter of the outer ring is 400-700 μm.

[0011] Furthermore, the silica aerogel powder has a diameter of 20 μm.

[0012] The present invention also provides a high-content stretchable silica aerogel composite fiber, which has the advantages of being washable and dyeable, and has applications in the field of thermal insulation materials.

[0013] Compared to existing technologies, the present invention achieves this by encapsulating aerogel powder within hollow fibers, which provide the fiber's mechanical properties, ensuring the fiber's mechanical properties even with a high silica aerogel powder content. The silica aerogel powder provides the fiber's thermal insulation properties. Simultaneously, due to the reflection of infrared radiation by the core-shell interface, the fiber's infrared transmittance can be reduced by 65%, while its thermal insulation rate is increased by 64.7%. The bamboo-shaped heat seal also avoids the problem of large-scale leakage of aerogel powder due to hollow fiber breakage. The flexibility of the fiber material is also crucial for the application of aerogel materials in wearable applications.

[0014] In addition, the present invention has the following beneficial effects:

[0015] (1) The preparation method of the present invention is simple, can be prepared continuously on a large scale, and is suitable for industrial scale-up applications. Different materials can be designed according to actual needs.

[0016] (2) The preparation method of the present invention can prepare silica aerogel composite fibers of different diameters by adjusting the diameter of the hollow fibers. The fibers can still maintain unchanged thermal insulation performance after 10,000 cycles of 100% strain stretching.

[0017] (3) The silica aerogel composite fiber prepared by the present invention has a dense outer shell and a silica aerogel powder as the inner core; at the same time, the aerogel fiber has the characteristics of pressure resistance, tension resistance, and washability, which expands the application range of the aerogel fiber and can be widely used in thermal insulation fabrics, with broad development prospects. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described below through specific embodiments.

[0019] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the embodiments, unless otherwise specified, are all conventional methods in the art.

[0020] The silica aerogel composite fiber prepared by the present invention is a hollow fiber wrapped with silica aerogel powder. The dense wall of the hollow fiber provides mechanical properties, and the silica aerogel powder provides thermal insulation performance.

[0021] The hollow fiber material used in the following examples is TPU.

[0022] Example 1

[0023] The method for preparing the silica aerogel composite fiber of the present invention comprises the following steps:

[0024] 1) TPU particles are fed into a screw extruder and extruded after being fully melted. The melt enters the spinning assembly after passing through a metering pump. At the same time, silica aerogel powder (about 20 μm in diameter) falls to the spinning assembly through a pipeline by gravity. The two are ejected from top to bottom through a coaxial spinneret to form a hollow fiber precursor tow injected with silica aerogel powder, which is collected by a motor. The inner diameter of the inner ring of the double annular nozzle of the spinneret is 200 μm, and the inner diameter of the outer ring is 400 μm.

[0025] 2) Fixing one end of the precursor tow obtained in step 1) on another motor, heating the fiber between the two motors until the fiber precursor softens, adjusting the speed ratio of the two motors to 1:3, that is, the fiber stretching ratio is 3, and obtaining a fiber diameter of 150 μm.

[0026] 3) Fixing one end of the silica aerogel composite fiber obtained in step 2) to another motor, axially hot-pressing and sealing the fibers between the two motors every 3 cm to encapsulate the silica aerogel in the bamboo-like fibers, and adjusting the speed ratio of the two motors to 1:1.

[0027] The fibers were cut into 1cm samples and subjected to axial tensile testing on a mechanical testing machine at a stretching rate of 1mm / min. The tensile strength was 15MPa, the elongation at break was 875%, and the silica aerogel content was 69%. The fibers maintained their thermal insulation properties after 10,000 cycles of 100% strain. The fibers were woven into a 5cm×5cm fabric and tested for its radiant transmittance, which was only 0.0013%, while its thermal insulation was 85.2%.

[0028] Comparative Example 1

[0029] The preparation steps of this comparative example are as follows:

[0030] The method for preparing the silica aerogel composite fiber of the present invention comprises the following steps:

[0031] 1) The TPU particles are fed into a screw extruder and extruded after being fully melted. The melt enters the spinning assembly after passing through a metering pump. At the same time, the silica aerogel powder (about 20 μm in diameter) falls to the spinning assembly through a pipeline by gravity. The two are ejected through a coaxial spinneret to form a hollow fiber precursor tow injected with silica aerogel powder, which is collected by a motor. The spinneret has an inner diameter of 50 μm and an outer diameter of 300 μm.

[0032] 2) Fixing one end of the precursor tow obtained in step 1) on another motor, heating the fiber between the two motors until the fiber precursor softens, adjusting the speed ratio of the two motors to 1:4, that is, the fiber stretching ratio is 4, and obtaining a fiber diameter of 150 μm.

[0033] 3) Fixing one end of the silica aerogel composite fiber obtained in step 2) to another motor, axially hot-pressing and sealing the fibers between the two motors every 3 cm to encapsulate the silica aerogel in the bamboo-like fibers, and adjusting the speed ratio of the two motors to 1:1.

[0034] The fibers were cut into 1cm samples and subjected to axial tensile testing on a mechanical testing machine at a stretching rate of 1mm / min. The tensile strength was 27MPa, the elongation at break was 1064%, and the silica aerogel content was 3%. The fibers maintained their thermal insulation properties after 10,000 cycles of 100% strain. When the fibers were woven into a 5cm×5cm fabric, the radiant transmittance was 21.43% and the thermal insulation was 12.5%.

[0035] From Example 1 and Comparative Example 1 above, it can be seen that the core-shell ratio of composite aerogel fibers significantly affects thermal insulation performance. When the core layer aerogel ratio is too low, the fabric's radiation transmittance increases, while the thermal insulation rate decreases. This is because when the core layer aerogel ratio is too low, the radiation is reflected at the core-shell interface and mostly transmits through the shell layer. However, when the aerogel ratio increases, the radiation reflected at the core-shell interface is scattered and absorbed by the aerogel layer, preventing heat loss.

[0036] Comparative Example 2

[0037] The preparation steps of this comparative example are as follows:

[0038] The method for preparing the silica aerogel composite fiber of the present invention comprises the following steps:

[0039] 1) TPU particles are fed into a screw extruder and extruded after being fully melted. The melt enters the spinning assembly after passing through a metering pump. At the same time, silica aerogel powder (about 20 μm in diameter) falls to the spinning assembly through a pipeline by gravity. The two are ejected through a coaxial spinneret to form a hollow fiber precursor tow injected with silica aerogel powder, which is collected by a motor. The spinneret has an inner diameter of 600 μm and an outer diameter of 650 μm.

[0040] 2) Fixing one end of the precursor tow obtained in step 1) on another motor, heating the fiber between the two motors until the fiber precursor softens, adjusting the speed ratio of the two motors to 1:4, that is, the fiber stretching ratio is 4, and obtaining a fiber diameter of 325 μm.

[0041] 2) Fixing one end of the silica aerogel composite fiber obtained in step 1) on another motor, performing axial hot pressing and sealing on the fiber between the two motors every 3 cm to encapsulate the silica aerogel in the bamboo-like fiber, and adjusting the speed ratio of the two motors to 1:1.

[0042] The fibers were cut into 1 cm samples and subjected to axial tensile testing on a mechanical testing machine at a rate of 1 mm / min. The tensile strength was 0.3 MPa, the elongation at break was 12%, and the silica aerogel content was 85%. The fibers broke after 10 cycles of 100% strain. The fibers were woven into a 5 cm x 5 cm fabric and tested for radiation transmittance, which was only 0.0011%, while the thermal insulation rating was 89.7%.

[0043] From Example 1 and Comparative Example 2 above, it can be seen that the core-shell ratio of the composite aerogel fiber has a significant impact on the mechanical properties. When the core aerogel accounts for too large a proportion, the fiber's elongation at break and tensile cycle performance decrease significantly. This is because when the core aerogel accounts for too large a proportion, the shell material cannot provide good mechanical protection. At the same time, the shell is prone to notching during stretching, failing to protect the core aerogel fiber.

[0044] Example 2

[0045] The method for preparing the silica aerogel composite fiber of the present invention comprises the following steps:

[0046] 1) TPU particles are fed into a screw extruder and extruded after being fully melted. The melt enters the spinning assembly after passing through a metering pump. At the same time, silica aerogel powder (about 20 μm in diameter) falls to the spinning assembly through a pipeline by gravity. The two are ejected through a coaxial spinneret to form a hollow fiber precursor tow injected with silica aerogel powder, which is collected by a motor. The inner diameter of the inner ring of the double annular nozzle is 500 μm, and the inner diameter of the outer ring is 700 μm.

[0047] 2) Fixing one end of the precursor tow obtained in step 1) on another motor, heating the fiber between the two motors until the fiber precursor softens, adjusting the speed ratio of the two motors to 1:6, that is, the fiber stretching ratio is 6, and obtaining a fiber diameter of 360 μm.

[0048] 3) Fixing one end of the silica aerogel composite fiber obtained in step 2) to another motor, axially hot-pressing and sealing the fibers between the two motors every 3 cm to encapsulate the silica aerogel in the bamboo-like fibers, and adjusting the speed ratio of the two motors to 1:1.

[0049] The fibers were cut into 1cm samples and subjected to axial tensile testing on a mechanical testing machine at a stretching rate of 1mm / min. The tensile strength was 15MPa, the elongation at break was 798%, and the silica aerogel content was 51%. The fibers maintained their thermal insulation properties after 10,000 cycles of 100% strain. The fibers were woven into a 5cm×5cm fabric and tested for its radiant transmittance, which was only 0.0002%, while its thermal insulation was 87.2%.

[0050] Comparative Example 3

[0051] The method for preparing the graphene aerogel composite fiber of the present invention comprises the following steps:

[0052] 1) The TPU particles are fed into a screw extruder and extruded after being fully melted. The melt enters the spinning assembly after passing through a metering pump and is ejected through a coaxial spinneret to form a hollow fiber precursor tow injected with graphene aerogel powder. At the same time, the graphene aerogel powder (about 15 μm in diameter) falls to the spinning assembly through a pipeline by gravity. The two are ejected through the coaxial spinneret to form a hollow fiber precursor tow of graphene aerogel powder, which is collected by a motor. The inner diameter of the inner ring of the double annular nozzle is 500 μm, and the inner diameter of the outer ring is 700 μm.

[0053] 2) Fixing one end of the precursor tow obtained in step 1) on another motor, heating the fiber between the two motors until the fiber precursor softens, adjusting the speed ratio of the two motors to 1:6, that is, the fiber stretching ratio is 6, and obtaining a fiber diameter of 360 μm.

[0054] The fibers were cut into 1cm samples and subjected to axial tensile testing on a mechanical testing machine at a stretching rate of 1mm / min. The tensile strength was 13.1MPa, the elongation at break was 776%, and the graphene aerogel content was 51%. The fibers maintained their thermal insulation properties after 10,000 cycles of 100% strain. The fibers were woven into a 5cm×5cm fabric and tested for radiant transmittance of 15.14% and thermal insulation of 65.5%.

[0055] From the above Example 2 and Comparative Example 3, it can be seen that the aerogel material in the composite aerogel fiber has a great influence on the thermal insulation performance of the fiber. Using silica aerogel as the core layer aerogel material can effectively reduce the radiation transmittance of the fiber and enhance the thermal insulation effect. However, if the core layer is replaced with other aerogel materials such as graphene, the infrared radiation cannot be regulated at the core-shell interface, and therefore the thermal insulation rate cannot be improved.

[0056] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-content stretchable silica aerogel composite fiber, the silica aerogel composite fiber comprising a polymer shell and aerogel powder filled in the polymer shell; the shell diameter is 400-700 μm; the aerogel powder is silica aerogel; the method comprising the following steps: 1) Using a double annular nozzle, composite fibers with a core-shell structure are extruded from top to bottom, wherein: injecting molten polymer into the double annular nozzle to form a shell layer, and injecting aerogel powder into the double annular nozzle to form a core layer; 2) heating and softening the composite fiber obtained in step 1) and then thermally stretching the composite fiber at a stretching ratio of 3 to 6; 3) heat-sealing the stretched fiber obtained in step 2) every 1 to 5 cm to obtain an aerogel composite fiber with a bamboo structure; The molten polymer is one of thermoplastic polyurethane (TPU), styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), and polyester (PET), and the aerogel is silica aerogel.

2. The method for preparing silica aerogel composite fibers according to claim 1, wherein: The inner diameter of the double annular nozzle is 200~500 μm, and the inner diameter of the outer ring is 400~700 μm.

3. The method for preparing silica aerogel composite fibers according to claim 1, wherein: The silica aerogel powder has a diameter of 20 μm.