An ultrafine aerogel fiber, its preparation method and application

Abstract

This invention discloses an ultrafine aerogel fiber, its preparation method, and its applications. The ultrafine polymer aerogel fiber is obtained by wet spinning of a polymer solution through a gradient phase separation bath and stepwise drawing, followed by coagulation in a coagulation bath and drying at room temperature and pressure. The polymer aerogel fiber of this invention has an average diameter of less than 10 μm, excellent mechanical properties, good weavability, and an average internal pore size of less than 60 nm, which can effectively reduce gas heat conduction. The preparation method has the advantages of simplicity, safety, environmental friendliness, speed, and low cost. Thermal insulation textiles based on ultrafine fibers combine lightweight and high strength, good thermal insulation performance, and good flexibility, showing great application potential in the field of thermal insulation.

Description

Technical Field

[0001] This invention relates to the field of aerogel preparation technology, specifically to an ultrafine aerogel fiber, its preparation method, and its application. Background Technology

[0002] Aerogel fiber is a novel material with high porosity, low density, and excellent thermal insulation properties. Due to its diverse functions and ease of weaving or integration into textiles and composite materials, it is suitable for applications such as thermal clothing, filter materials, personal protective fabrics, and smart textiles. Furthermore, finer aerogel fibers can be woven into denser fabrics that effectively insulate against cold air while reflecting body heat at a high density, resulting in textiles with superior thermal insulation performance.

[0003] Currently, aerogel fibers prepared via cryo-spinning exhibit low porous backbone strength, low pore wall orientation, and poor mechanical properties. During preparation, the gel fiber strength is insufficient to withstand the tension of industrial spinning equipment, and its fragile mechanical properties limit its continuous production. Therefore, it is difficult to achieve high draw ratios to produce ultrafine fibers during the preparation process, resulting in poor weavability. Fibers prepared through a single-step draw process in conventional wet spinning suffer from extremely strong inter-chain interactions between polymers. The instantaneous solidification and rapid hardening of the gel precursor inhibits subsequent stretching and refining processes, leading to fibers with diameters exceeding 10 micrometers. Such large diameters significantly reduce the mechanical properties of the polymer fibers. Currently prepared aerogel fibers have large pore sizes, a narrow processing range, and are difficult to optimize in terms of thermal insulation performance. Summary of the Invention

[0004] To address the problem that existing technologies struggle to produce ultrafine aerogel fibers with small pore sizes and excellent mechanical properties, this invention provides an ultrafine aerogel fiber, its preparation method, and its application, resulting in aerogel fibers with good mechanical strength, flexibility, and thermal insulation properties.

[0005] One of the technical solutions of this invention is to provide a method for preparing ultrafine aerogel fibers. This method involves traction stretching in a phase separation bath with high solvent content. Due to the low degree of phase separation and large distance between polymer chains, the intermolecular interactions are weak. The stretching force allows for partial orientation of the polymer chains. Further stretching in a phase separation bath with lower solvent content results in a more compact arrangement of the polymer chains, thereby improving the strength of the porous polymer fiber skeleton. The stretching force during the stepwise phase separation process effectively suppresses the nucleation size of the polymer-depleted phase, ensuring the fine pore size inside the aerogel fiber. Testing shows that this invention can effectively control the internal pore size of the aerogel within 60 nm. With an average internal pore size of less than 60 nm, the aerogel fiber effectively reduces gas heat conduction and exhibits excellent thermal insulation properties.

[0006] Specifically, the method includes: extruding a polymer solution, stretching it in a multi-stage phase separation bath system, then solidifying it in a coagulation bath to obtain nascent fibers, and drying the nascent fibers to obtain ultrafine polymer aerogel fibers; the multi-stage phase separation bath system includes multiple phase separation baths, each phase separation bath being a mixed solution of polymer solvent and non-solvent, wherein the mass fraction of the solvent is 30% to 90%, the mass fraction of the solvent in the first phase separation bath is not less than 40%, and the mass fraction of the solvent in each phase separation bath decreases sequentially; the coagulation bath is a non-solvent of the polymer; the stretching ratio in each phase separation bath is 30% to 200%.

[0007] Further, the polymer solution is a 10wt%~15wt% polyimide solution, a 0.1wt%~2.5wt% heterocyclic aramid solution, a 15wt%~25wt% polyurethane solution, or a 15wt%~25wt% polyacrylonitrile solution.

[0008] Further, the solvent is one or more of DMF, DMAC, NMP, DMSO, HMPA, TEP, TMP, and TMU; the non-solvent is one or more of water, ethanol, isopropanol, methanol, diethyl ether, ethyl acetate, ethylene glycol, and glycerol.

[0009] Furthermore, the drying process is carried out at room temperature and atmospheric pressure.

[0010] In some embodiments of the present invention, polyimide acid is used as a polymer solution to prepare polyimide aerogel fibers. After drying, the polyimide acid aerogel fibers need to be transferred to a tube furnace for imidization at 300°C for one hour to obtain polyimide aerogel fibers.

[0011] The second technical solution of the present invention is to provide polymer aerogel fibers prepared by the above method, wherein the polymer aerogel fibers have a thickness of 3µm to 10µm, a strength of 40Mpa to 200Mp, and a porosity of 40% to 70%.

[0012] Furthermore, the pores inside the polymer aerogel fibers are nanopores with an average pore size of less than 60 nm. The air inside these small pores is generally in a static state, which can effectively reduce gas heat conduction and play a significant role in thermal insulation.

[0013] The third technical solution of the present invention is to provide a filament bundle composed of the above-mentioned ultrafine aerogel fibers.

[0014] The fourth technical solution of the present invention is to provide a woven fabric prepared from the above-mentioned filament bundles.

[0015] The beneficial effects of this invention are as follows: By using a multi-stage phase separation bath and step-by-step stretching to precisely control the pore structure of the aerogel, the prepared polymer aerogel fibers have a small diameter, good mechanical strength and flexibility, thus endowing the aerogel fibers with good weavability. Furthermore, the average pore size inside the aerogel fibers is less than 60 nm, effectively reducing gas heat conduction and exhibiting good thermal insulation performance. The preparation method of this invention is simple and efficient, providing a feasible solution for large-scale preparation of weavable aerogel fibers at room temperature and atmospheric pressure. It is highly repeatable and shows broad application prospects in the field of thermal insulation textiles. Attached Figure Description

[0016] Figure 1 SEM image of the polyimide aerogel fiber obtained in Example 1;

[0017] Figure 2 This is a picture of the polyimide aerogel knotted in Example 1. Detailed Implementation

[0018] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.

[0019] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0020] The embodiments of the present invention will be further described below with reference to several examples.

[0021] The spinning needle described in this invention is a commercially available national standard needle.

[0022] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0023] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. Example 1

[0024] (1) A 15% N,N-dimethylacetamide solution of polyimide was extruded through a 34G needle, passed through a three-stage gradient phase separation bath and drawn, and finally wet-spun through a pure water coagulation bath to obtain nascent polyimide fibers. The mass ratios of N,N-dimethylacetamide and water in the gradient phase separation bath were 9:1, 1:1, and 3:7, respectively, and the corresponding draw ratios in each bath were 50%, 200%, and 100%, respectively.

[0025] (2) Polyimide fibers were dried at room temperature and normal pressure to obtain polyimide aerogel fibers, which were then thermally imidized to obtain polyimide aerogels. The imidization temperature was 300℃ and the imidization time was 1 h. The prepared fibers had a diameter of approximately 9 micrometers, and the microstructure of the obtained aerogel fibers was as follows. Figure 1 As shown, the average pore size is 37 nm, the orientation degree is 0.72, the porosity is 70%, and the tensile strength is 157 MPa. The polyimide aerogel fibers from Example 1 were knotted, and the results are as follows... Figure 2 As shown. The fibers from Example 1 were prepared into tows and then woven into fabrics, with a vertical thermal conductivity of 39 mw / mK at room temperature. Example 2

[0026] The only difference from Example 1 is the use of a 10 wt% solution of polyimide N,N-dimethylacetamide. Example 3

[0027] (1) A 0.1% (w / w) heterocyclic aramid N,N-dimethylacetamide solution was extruded through a 32G needle, passed through a three-stage gradient phase separation bath and drawn, and finally wet-spun through a pure ethanol coagulation bath to obtain heterocyclic aramid nascent fibers. The mass ratios of dimethyl sulfoxide and ethanol in the gradient phase separation bath were 8:2, 6:4, and 4:6, respectively, and the corresponding draw ratios in each bath were 30%, 150%, and 100%, respectively.

[0028] (2) The heterocyclic aramid nascent fibers were dried at room temperature and normal pressure to obtain heterocyclic aramid aerogel fibers. The average pore size was 51 nm, the fiber diameter was 3 μm, the orientation degree was 0.75, the porosity was 40%, and the tensile strength was 200 MPa. The fibers from Example 2 were prepared into tows and then woven into fabrics. The vertical thermal conductivity at room temperature was 55 mw / mK. Example 4

[0029] The only difference from Example 3 is the use of a 2.5 wt% heterocyclic aramid N,N-dimethylacetamide solution. Example 5

[0030] (1) A 15% N,N-dimethylformamide polyurethane solution was extruded through a 30G needle, passed through a four-stage gradient phase separation bath and stretched, and finally wet-spun through a pure ethanol coagulation bath to obtain polyurethane nascent fibers. The mass ratios of N,N-dimethylformamide to water in the gradient phase separation bath were 8:2, 6:4, 4:6, and 3:7, respectively, and the corresponding stretching ratios in each bath were 80%, 200%, 100%, and 100%, respectively. The coagulation bath consisted of ethanol and water in a 1:1 miscible ratio.

[0031] (2) The nascent polyurethane fibers were dried at room temperature and normal pressure to obtain polyurethane aerogel fibers. The average pore size was 60 nm, the fiber diameter was 10 μm, the orientation degree was 0.87, and the tensile strength was 40 MPa. The fibers from Example 3 were prepared into tows and then woven into fabrics. The vertical thermal conductivity at room temperature was 45 mw / mK. Example 6

[0032] The only difference from Example 5 is the use of a 25% (w / w) polyurethane N,N-dimethylformamide solution. Example 7

[0033] (1) A 15% (w / w) polyacrylonitrile dimethyl sulfoxide solution was extruded through a 34G needle, passed through a three-stage gradient phase separation bath and stretched, and finally wet-spun through a pure water coagulation bath to obtain nascent polyacrylonitrile fibers. The mass ratio of N-methylpyrrolidone solution to water in the gradient phase separation bath was 8:2, 6:4, and 1:1, with corresponding stretching ratios of 50%, 200%, and 100% in each bath.

[0034] (2) The nascent polyacrylonitrile fibers were dried at room temperature and normal pressure to obtain polyacrylonitrile aerogel fibers. The average pore size was 37 nm, the fiber diameter was 6 μm, the orientation degree was 0.77, and the strength was 125 MPa. The fibers from Example 4 were prepared into tows and then woven into fabrics. The vertical thermal conductivity at room temperature was 38 mw / mK. Example 8

[0035] The only difference from Example 7 is the use of a 25% (w / w) polyacrylonitrile dimethyl sulfoxide solution. Example 9

[0036] (1) A 15% (w / w) polyacrylonitrile dimethyl sulfoxide solution was extruded through a 34G needle, passed through a three-stage gradient phase separation bath and stretched, and finally wet-spun through a pure water coagulation bath to obtain polyacrylonitrile nascent fibers. The mass ratio of N-methylpyrrolidone solution to water in the gradient phase separation bath was 4:6, 7:13, and 3:7, with corresponding stretching ratios of 50%, 200%, and 100% in each bath.

[0037] (2) The nascent polyacrylonitrile fibers were dried at room temperature and normal pressure to obtain polyacrylonitrile aerogel fibers.

[0038] Comparative Example 1

[0039] The difference from Example 1 is that the mass ratios of N,N-dimethylacetamide and water in the three-stage gradient phase separation bath are 3:7, 2:8, and 1:9, respectively, and the corresponding stretching ratios in each bath are 50%, 200%, and 100%, respectively. The prepared fibers are solid fibers without porous structures.

[0040] The above embodiments describe in detail the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall still fall within the scope of protection of the present invention if they do not exceed the scope covered by the specification.

Claims

1. A method for producing ultrafine aerogel fibers, characterized by, The polymer solution is extruded, drawn in a multi-stage phase separation bath system, and then solidified by a coagulation bath to obtain a primary fiber, and the primary fiber is dried to obtain the ultrafine polymer aerogel fiber; the polymer solution is a 10wt%-15wt% polyimide acid solution, a 0.1wt%-2.5wt% heterocyclic aramid solution, a 15wt%-25wt% polyurethane solution, or a 15wt%-25wt% polyacrylonitrile solution; the multi-stage phase separation bath system comprises a plurality of phase separation baths, which are mixed solutions of a solvent and a non-solvent of the polymer, wherein the mass fraction of the solvent is 30%-90%, the mass fraction of the solvent in the first phase separation bath is not less than 40%, and the mass fraction of the solvent in each phase separation bath decreases successively; the coagulation bath is a non-solvent of the polymer; and the draw ratio in each phase separation bath is 30%-200%.

2. The production method according to claim 1, characterized by, The solvent is one or more of DMF, DMAC, NMP, DMSO, HMPA, TEP, TMP, and TMU; and the non-solvent is one or more of water, ethanol, isopropanol, methanol, diethyl ether, ethyl acetate, ethylene glycol, and glycerol.

3. The preparation method according to claim 1, characterized in that, The drying process is normal pressure at room temperature.

4. An ultrafine aerogel fiber prepared by the production method according to claim 1, characterized by The polymer aerogel fiber has a diameter of 3µm-10µm, a strength of 40Mpa-200Mpa, and a porosity of 40%-70%.

5. The sub-fϊne aerogel fiber of claim 4, wherein, The pores in the polymer aerogel fiber are nanopores, and the average pore size is less than 60 nm.

6. A tow consisting of the ultrafine aerogel fiber according to claim 4 or 5.

7. A woven fabric prepared from the tow according to claim 6.

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