Polyimide fiber with bending form and preparation method thereof

Abstract

The invention provides a polyimide fiber with a bent form and a preparation method thereof, and belongs to the field of polyimide fibers.The preparation method comprises the steps that pyromellitic dianhydride, 4, 4 '-diaminodiphenyl ether and triethylamine are added into an N, N-dimethylformamide solvent, condensation polymerization is conducted at the preset temperature, a polyamide acid solution is obtained, and the polyimide fiber with the bent form is obtained; the polyamide acid fiber is prepared by adopting a centrifugal spinning technology, the polyamide acid fiber is placed in an oxygen-containing environment for cyclization reaction, the curvature radius of the fiber is regulated and controlled through oxygen concentration, and the polyimide fiber with a bent form is obtained. Under the condition of no exogenous reagent intervention, macroscopic fibers are induced to generate controllable bending deformation through regulation and control of a polyimide molecule microstructure, the two-phase interface bonding defect can be effectively avoided, it is ensured that the fiber bending structure is long-acting and stable, and high elastic limit strain and high fatigue resistance of polyimide fiber textiles are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyimide fibers, and in particular to a polyimide fiber with a curved shape and a preparation method thereof. Background Art

[0002] Polyimide fibers are widely used in aerospace, flexible electronic devices, high-temperature filtration and other fields due to their excellent high-temperature resistance and chemical corrosion resistance. Traditional polyimide fibers are usually prepared by sol-gel spinning or wet spinning technology, which is achieved by spinning polyamide acid solution and subsequent high-temperature imidization treatment. However, the fibers in the existing technology are mostly straight fibers, and their mechanical properties (such as elastic limit strain and fatigue resistance) are limited, making it difficult to meet the flexibility requirements under complex working conditions.

[0003] Patent publication number CN114560709B proposes using electrostatic direct spraying technology to control specific temperature and humidity so that the pH of the jet in the electrostatic direct spraying process is far less than the zero charge point of the inorganic source, inducing rapid polycondensation of the hydroxyl groups present in the inorganic source in the jet, thereby causing the jet to quickly solidify and fully whip and stretch in the spinning area to form curved deformed fibers. The production of these curved fibers is mainly caused by the whipping and stretching of the jet, which is caused by physical factors. Compared with the curved structure formed by chemical action, the curved structure formed by physical action has poor stability. In Adv. Mater. (2024, 36: 2313444), researchers proposed to construct polyamic acid curved fibers by regulating the electrostatic field intensity and phase separation process during the electrospinning process, and to prepare polyimide curved fibers through cyclization reaction. The formation of these curved fibers is due to the large Flory-Huggins interaction parameter between the hydrophobic polymer added to the spinning solution and the water molecules in the air, which accelerates the phase separation rate during the electrospinning process, thereby exacerbating the entanglement of the polyamic acid polymer and forming a curved fiber morphology. The study shows that the production of this curved fiber mainly relies on phase separation and is caused by physical factors. In this system, when there is no hydrophobic polymer, the fiber has almost no curved structure. Therefore, the formation of polyamic acid curved fibers is highly dependent on hydrophobic polymers. However, due to the polarity difference between hydrophilic polyamic acid and hydrophobic polymers, this inherent contradiction may lead to macroscopic phase separation during solvent volatilization and curing molding, affecting the uniformity of chemical components in the curved fiber assembly and the long-term stability of the structure.

[0004] In view of this, it is necessary to design a polyimide fiber with a curved morphology and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides a polyimide fiber with a curved morphology and a preparation method thereof, aiming to solve the technical problems of poor structural stability and limited mechanical properties of curved fibers.

[0006] In a first aspect, the present application provides a method for preparing a polyimide fiber having a curved morphology, comprising the following steps:

[0007] S1. Pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and triethylamine are added to N,N-dimethylformamide solvent and subjected to polycondensation reaction at a predetermined temperature to obtain a polyamic acid solution;

[0008] S2. The polyamic acid solution is prepared into polyamic acid fibers using centrifugal spinning technology;

[0009] S3. Placing the polyamic acid fiber in an oxygen-containing environment for a cyclization reaction, and regulating the curvature radius of the fiber by adjusting the oxygen concentration to obtain a polyimide fiber with a curved morphology.

[0010] As a further improvement of the present application, in step S1, the mass fraction of the pyromellitic dianhydride is 5-10%, the mass fraction of the 4,4'-diaminodiphenyl ether is 5-10%, and the mass fraction of the triethylamine is 1-8%.

[0011] As a further improvement of the present application, the temperature of the polycondensation reaction is 0-10°C.

[0012] As a further improvement of the present application, the viscosity of the polyamic acid solution is 30 to 55 Pa·S.

[0013] As a further improvement of the present application, in step S2, the spinning speed of the centrifugal spinning technology is 3000-4000 rpm, the spinning temperature is 30-40°C, and the spinning humidity is 30-40% RH.

[0014] As a further improvement of the present application, in step S3, the temperature of the cyclization reaction is 300-450° C., and the time is 1-3 hours.

[0015] As a further improvement of the present application, the oxygen concentration in the oxygen-containing environment is 5-50%, and the remaining component is nitrogen.

[0016] As a further improvement of the present application, the control range of the curvature radius is 10 to 300 μm.

[0017] In a second aspect, the present application provides a polyimide fiber with a curved morphology, which is prepared by the preparation method described in the first aspect. The diameter of the polyimide fiber with a curved morphology is 0.05 to 0.7 μm.

[0018] As a further improvement of the present application, the elastic limit strain of the polyimide fiber with a curved shape is ≥70%, and the number of fatigue resistance cycles is ≥1000 times.

[0019] The beneficial effects of this application are:

[0020] The present application provides a polyimide fiber with a curved morphology and a preparation method thereof, wherein pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and triethylamine are added to an N,N-dimethylformamide solvent, a polycondensation reaction is carried out at a predetermined temperature to obtain a polyamic acid solution, a centrifugal spinning technique is used to prepare polyamic acid fibers, the polyamic acid fibers are placed in an oxygen-containing environment for a cyclization reaction, and the curvature radius of the fibers is regulated by the oxygen concentration to obtain a polyimide fiber with a curved morphology. The present application, without the intervention of exogenous reagents, induces controllable bending deformation of macroscopic fibers by regulating the microstructure of polyimide molecules, which can effectively circumvent the two-phase interface bonding defects, ensure the long-term stability of the fiber bending structure, and achieve high elastic limit strain and high fatigue resistance of polyimide fiber textiles.

[0021] The present application improves the thermal stability of the fiber by carrying out a cyclization reaction in a high-temperature oxygen-containing environment, so that it can still maintain its performance in a high-temperature environment. By regulating the oxygen concentration, the radius of curvature of the polyimide fiber can be accurately controlled, thereby achieving fibers with different bending shapes to meet the needs of different application fields. The quinone structure and local crystal structure formed during the cyclization reaction can improve the stiffness and strength of the fiber, while the non-crosslinked area remains flexible, giving the fiber excellent mechanical properties. Since the crystal structure of the crosslinked area can reduce the thermal expansion coefficient, the prepared polyimide fiber has good dimensional stability.

[0022] The process of this application is simple and easy to realize industrial production. It can be used in many fields such as aerospace, electronics, biomedicine, filtration materials, etc., and has high market value.

[0023] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0025] Figure 1 This is a SEM image of the polyimide fiber with a curved morphology obtained in Example 1 of the present application;

[0026] Figure 2 This is a SEM image of the polyimide fiber with a curved morphology obtained in Comparative Example 2;

[0027] Figure 3 The XRD diagrams of the crystal structures of the polyimide fibers in Example 1 and Comparative Example 2 are shown. DETAILED DESCRIPTION

[0028] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0030] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0031] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0032] In the existing technology, most polyimide fibers are in the form of straight fibers, with limited mechanical properties, making it difficult to meet the flexibility requirements under complex working conditions. The formation of curved fibers prepared by electrostatic direct injection technology or electrospinning processes mainly relies on physical effects such as whipping and phase separation, resulting in poor stability of the resulting curved structure. At the same time, the formation of polyamic acid curved fibers is highly dependent on the addition of hydrophobic polymers. Due to the polarity difference between hydrophilic polyamic acid and hydrophobic polymers, macroscopic phase separation may occur during the solvent volatilization and curing process, which not only affects the uniformity of the chemical components in the fiber aggregate, but also reduces the long-term stability of the structure, limiting its use in applications requiring high stability and uniformity.

[0033] In order to solve the technical problems of poor structural stability and limited mechanical properties of curved fibers, the present application provides a polyimide fiber with a curved morphology and a preparation method thereof, wherein the curvature radius of the polyimide fiber is precisely controlled by regulating the cyclization reaction conditions, thereby realizing fibers with different curved morphologies to meet the needs of different application fields.

[0034] In a first aspect, an embodiment of the present application provides a method for preparing a polyimide fiber having a curved morphology, comprising the following steps:

[0035] S1. Pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and triethylamine are added to N,N-dimethylformamide solvent and subjected to polycondensation reaction at a predetermined temperature to obtain a polyamic acid solution;

[0036] S2 using centrifugal spinning technology to prepare polyamic acid solution into polyamic acid fibers;

[0037] S3. Place the polyamic acid fiber in an oxygen-containing environment for a cyclization reaction, and regulate the curvature radius of the fiber by adjusting the oxygen concentration to obtain a polyimide fiber with a curved shape.

[0038] In the technical solution of the embodiment of the present application, a polyamic acid solution is prepared by a polycondensation reaction, and the contents of pyromellitic dianhydride (PMDA), 4,4'-diaminodiphenyl ether (ODA) and triethylamine (TEA) are controlled to adjust the viscosity of the polyamic acid solution, thereby affecting the performance of the final fiber. By adopting centrifugal spinning technology and controlling the spinning parameters, fibers with specific morphology and properties can be obtained. By regulating the curvature radius of the fiber through a cyclization reaction, the obtained polyimide fiber has a more stable curved morphology and can maintain its shape and performance under various environments.

[0039] Furthermore, in some embodiments, in step S1, the mass fraction of pyromellitic dianhydride is 5-10%, the mass fraction of 4,4'-diaminodiphenyl ether is 5-10%, and the mass fraction of triethylamine is 1-8%. The viscosity of the polyamic acid solution is 30-55 Pa·s.

[0040] In the technical solution of the present embodiment, by adjusting the contents of pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, and triethylamine, the viscosity of the polyamic acid solution can be effectively controlled. The appropriate raw material ratio helps improve reaction efficiency, shorten reaction time, and thus increase production efficiency. By precisely controlling the raw material ratio and viscosity, polyimide fibers with superior mechanical properties can be produced.

[0041] Furthermore, in some embodiments, the temperature of the polycondensation reaction is 0-10°C.

[0042] In the technical solution of the embodiment of the present application, the polycondensation reaction is carried out at low temperature, which can reduce the risk of gelation or precipitation of the polyamic acid solution during the reaction, improve the stability of the solution, and is conducive to obtaining polyamic acid with a more uniform molecular weight distribution.

[0043] Furthermore, in some embodiments, in step S2, the spinning speed of the centrifugal spinning technology is 3000-4000 rpm, the spinning temperature is 30-40° C., and the spinning humidity is 30-40% RH.

[0044] In the technical solutions of the embodiments of this application, high-speed spinning helps stretch the molecular chains, improving the fiber's orientation and crystallinity, thereby enhancing the fiber's strength and modulus. Appropriate spinning temperature and humidity provide a mild spinning environment, avoiding thermal degradation of the fiber caused by excessive temperature and loose fiber structure caused by excessive humidity, thereby facilitating the formation of fibers with a compact structure and excellent mechanical properties.

[0045] Furthermore, in some embodiments, in step S3, the cyclization reaction temperature is 300-450° C., the reaction time is 1-3 hours, the oxygen concentration is 5-50%, and the remaining component is nitrogen.

[0046] In the technical solution of the embodiment of the present application, the suitable temperature range provides enough thermal energy to activate the molecules, promote the dehydration cyclization reaction within or between the polyamic acid molecules, and generate a polyimide with an imide ring structure. Sufficient reaction time ensures that the cyclization reaction is fully carried out, so that the polyamic acid can be converted into polyimide as completely as possible, thereby improving the conversion rate of the polyimide and the performance of the fiber. In a high-temperature oxygen-containing environment, the aromatic rings of the polyimide macromolecular main chain can trigger oxidative dehydrogenation and cyclization cross-linking through free radical chain reactions to form a quinone structure, which can be stacked to induce the orderly arrangement of local segments to form a local crystal structure. The crystal structure of the cross-linked region can reduce the thermal expansion coefficient (1 to 15 ppm / °C) through the grain boundary constraint effect and has a larger rigidity (4 to 10 GPa); while the non-cross-linked region still maintains a flexible amorphous state, has a larger thermal expansion coefficient (16 to 50 ppm / °C), and has a smaller rigidity (1 to 3 GPa). When the polyimide fiber undergoes temperature changes, the internal stress difference caused by the difference in thermal expansion coefficient causes the fiber to bend toward the cross-linked region. The curvature radius of the curved fiber obtained under different cyclization reaction parameters was measured, and a quantitative relationship between the cyclization reaction parameters and the bending behavior was established, so that the curvature radius could be precisely controlled by regulating the cyclization reaction parameters.

[0047] Furthermore, in some embodiments, the curvature radius of the fiber is controlled in the range of 10 to 300 μm.

[0048] In the technical solutions of the embodiments of this application, the mechanical properties, surface properties, and chemical stability of the fiber can be optimized by adjusting the curvature radius. A smaller curvature radius indicates a greater degree of fiber curvature; conversely, a larger curvature radius indicates a lesser degree of fiber curvature. Moderate curvature increases the fiber's elasticity, enabling it to better disperse stress when subjected to external forces, thereby improving its durability.

[0049] In a second aspect, an embodiment of the present application provides a polyimide fiber with a curved shape, which is prepared using the preparation method described in the first aspect, and the diameter of the fiber is 0.05 to 0.7 μm.

[0050] In the technical solutions of the embodiments of this application, by controlling the diameter of polyimide fibers and combining their curvature, the functionality and application range of the fibers can be significantly improved. This precise diameter control enables the fibers to demonstrate great potential in a variety of fields, including filtration materials, catalytic supports, tissue engineering scaffolds, sensors and actuators, and optical devices.

[0051] Furthermore, in some embodiments, the polyimide fiber having a curved shape has an elastic limit strain of ≥70% and an anti-fatigue cycle number of ≥1000 times.

[0052] In the technical solution of the embodiment of the present application, the controllable bending deformation of the macro fiber is induced by regulating the microstructure of the polyimide molecules, thereby achieving high elastic limit strain and high fatigue resistance of the polyimide fiber.

[0053] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0054] Example 1

[0055] This embodiment provides a method for preparing a polyimide fiber having a curved morphology, comprising the following steps:

[0056] S1. PMDA, ODA, and TEA were added to N,N-dimethylformamide solvent and subjected to polycondensation reaction at 3°C to obtain a polyamic acid solution; wherein the mass fraction of PMDA was 8%, the mass fraction of ODA was 8%, the mass fraction of TEA was 2%, and the viscosity of the obtained polyamic acid solution was 42 Pa·s;

[0057] S2. The polyamic acid solution was prepared into polyamic acid fibers using centrifugal spinning technology at a spinning speed of 3500 rpm, a spinning temperature of 35°C, and a spinning humidity of 40% RH.

[0058] S3. The polyamic acid fiber was placed in an oxygen-containing environment for cyclization reaction. The cyclization reaction temperature was 350 ° C, the time was 2 h, the oxygen concentration was 20%, and the remaining components were nitrogen. The polyimide fiber with a curved morphology was obtained, and its SEM image is shown as follows Figure 1 shown.

[0059] Example 2

[0060] This embodiment provides a method for preparing a polyimide fiber having a curved morphology, comprising the following steps:

[0061] S1. PMDA, ODA, and TEA were added to N,N-dimethylformamide solvent and subjected to polycondensation reaction at 2 ° C to obtain a polyamic acid solution; wherein the mass fraction of PMDA was 5%, the mass fraction of ODA was 5%, the mass fraction of TEA was 2%, and the viscosity of the obtained polyamic acid solution was 33 Pa·S;

[0062] S2 using centrifugal spinning technology to prepare a polyamic acid solution of polyamic acid fiber, the spinning speed of 3000rmp, the spinning temperature of 30 ℃, the spinning humidity of 30% RH;

[0063] S3. The polyamic acid fiber is placed in an oxygen-containing environment for a cyclization reaction. The cyclization reaction temperature is 300°C, the time is 2 hours, the oxygen concentration is 5%, and the remaining component is nitrogen, to obtain a polyimide fiber with a curved morphology.

[0064] Example 3

[0065] This embodiment provides a method for preparing a polyimide fiber having a curved morphology, comprising the following steps:

[0066] S1. PMDA, ODA, and TEA were added to N,N-dimethylformamide solvent and subjected to polycondensation reaction at 4 ° C to obtain a polyamic acid solution; wherein the mass fraction of PMDA was 10%, the mass fraction of ODA was 10%, and the mass fraction of TEA was 6%. The viscosity of the obtained polyamic acid solution was 55 Pa·S;

[0067] S2 using centrifugal spinning technology to prepare a polyamic acid solution of polyamic acid fibers, the spinning speed of 4000rmp, the spinning temperature of 40 ℃, the spinning humidity of 40% RH;

[0068] S3. The polyamic acid fiber is placed in an oxygen-containing environment for a cyclization reaction at a temperature of 450° C. for 2 hours, an oxygen concentration of 50%, and the remaining component is nitrogen, to obtain a polyimide fiber with a curved morphology.

[0069] Examples 4-6 and Comparative Examples 1-3

[0070] Examples 4-6 and Comparative Examples 1-3 respectively provide a method for preparing a polyimide fiber with a curved morphology. Compared with Example 1, the only difference is that the oxygen concentration is different, as shown in Table 1. Other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0071] Comparative Examples 4-5

[0072] Comparative Examples 4-5 respectively provide a method for preparing a polyimide fiber with a curved morphology. Compared with Example 1, the only difference is that the mass fractions of PMDA, ODA and TEA are different. In Comparative Example 3, the mass fraction of PMDA is 15%, the mass fraction of ODA is 5%, and the mass fraction of TEA is 2%. In Comparative Example 4, the mass fraction of PMDA is 5%, the mass fraction of ODA is 15%, and the mass fraction of TEA is 2%. The other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0073] The performance testing method of the polyimide fibers prepared in each embodiment and comparative example is as follows:

[0074] Elastic limit strain and fatigue resistance cycles: tested according to GB / T 18942.1-2003 Polymeric porous elastic materials - Determination of compressive stress-strain characteristics - Part 1: Low-density materials.

[0075] The tensile strength is tested according to GB / T 3923.1-2013 Textile fabrics tensile properties Part 1: Determination of breaking force and elongation at break (strip method).

[0076] The test results are shown in Table 1.

[0077] Table 1 Performance test results

[0078]

[0079] As can be seen from Table 1, the curvature radius is mainly affected by the oxygen concentration. As the oxygen concentration increases, the free radical chain reaction intensifies and the local cross-linking structure formed increases, which reduces the fiber curvature radius, thereby improving the elastic limit strain and fatigue resistance cycle number. In Comparative Example 1, the cyclization reaction was carried out in an oxygen-free environment, and the average curvature radius of the fiber was the largest, indicating that the degree of bending was the smallest. Figure 2 As shown, in Comparative Example 2, the cyclization reaction was carried out under a 1% O2 atmosphere, and the average curvature radius of the polyimide fiber was 380 μm, which was less curvature than that of Example 1. In Comparative Example 3, the O2 concentration was excessive, and the aromatic rings in the polyimide reacted with the excess oxygen, causing the polyimide molecular chains to break, resulting in oxidative degradation of the polyimide fiber, and weakening the elastic limit strain and fatigue resistance of the fiber. In Comparative Examples 4-5, due to the change in the mass ratio of the raw materials PMDA and ODA, the reaction was unbalanced during the synthesis of polyamic acid, the molecular structure of the polyimide fiber changed, and the mechanical properties of the fiber decreased.

[0080] from Figure 3 It can be seen that by adjusting the oxygen concentration to prepare polyimide fibers with different curvature radii, their crystal structure undergoes partial changes, and new diffraction peaks appear, indicating that their molecular chains may rearrange to form new ordered regions. Under 1% O2 atmosphere conditions, polyimide exhibits diffraction peaks at 18.7° and 21.9°, while under 20% O2 conditions, the diffraction peak positions shift to 16.2° and 22.3°, and sharp new diffraction peaks appear, indicating that the crystal structure of the polyimide has changed.

[0081] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a polyimide fiber having a curved shape, characterized in that: The following steps are involved: S1. Pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and triethylamine are added to N,N-dimethylformamide solvent and subjected to polycondensation reaction at a predetermined temperature to obtain a polyamic acid solution; S2. The polyamic acid solution is prepared into polyamic acid fibers using centrifugal spinning technology; S3. Placing the polyamic acid fiber in an oxygen-containing environment for a cyclization reaction, and regulating the curvature radius of the fiber by adjusting the oxygen concentration to obtain a polyimide fiber with a curved morphology.

2. The method for preparing a polyimide fiber having a curved shape according to claim 1, wherein: In step S1 , the mass fraction of the pyromellitic dianhydride is 5-10%, the mass fraction of the 4,4'-diaminodiphenyl ether is 5-10%, and the mass fraction of the triethylamine is 1-8%.

3. The method for preparing a polyimide fiber having a curved shape according to claim 2, wherein: The temperature of the polycondensation reaction is 0-10°C.

4. The method for preparing a polyimide fiber having a curved shape according to claim 3, wherein: The viscosity of the polyamic acid solution is 30-55 Pa·S.

5. The method for preparing a polyimide fiber having a curved shape according to claim 1, wherein: In step S2, the spinning speed of the centrifugal spinning technology is 3000-4000 rpm, the spinning temperature is 30-40°C, and the spinning humidity is 30-40% RH.

6. The method for preparing a polyimide fiber having a curved shape according to claim 1, wherein: In step S3, the cyclization reaction temperature is 300-450° C., and the time is 1-3 hours.

7. The method for preparing a polyimide fiber having a curved shape according to claim 6, wherein: The oxygen concentration in the oxygen-containing environment is 5-50%, and the remaining component is nitrogen.

8. The method for preparing a polyimide fiber having a curved shape according to claim 7, wherein: The control range of the curvature radius is 10 to 300 μm.

9. A polyimide fiber having a curved shape, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8, the polyimide fiber with a curved shape has a diameter of 0.05 to 0.7 μm.

10. The polyimide fiber having a curved shape according to claim 9, characterized in that: The elastic limit strain of the polyimide fiber with a curved shape is ≥70%, and the number of fatigue resistance cycles is ≥1000 times.

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