A device and method for preparing a foldable curved polyimide fiber film

Abstract

The present invention discloses a preparation device and method for a foldable curved polyimide fiber film, comprising the steps of: installing a pretreated crease positioning post onto a crease positioning hole on a mold base, and installing a fiber fixing post onto the remaining fiber fixing holes of the mold base; passing the two ends of a main fiber through the positioning holes of the crease positioning post and fixing them; placing a polyimide fiber in a polyamic acid solution, winding a secondary fiber onto the fiber fixing post and the main fiber, preparing a polyimide fiber grid, and subjecting the polyimide solution to thermal imidization; demoulding and drying the thermally imidized polyimide composite film to obtain a fiber-reinforced foldable curved polyimide fiber film. The film has excellent properties such as high strength, high toughness, high heat resistance, and corrosion resistance, and has good foldability and processability, and has broad application prospects in the fields of aerospace, electronic information, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar antenna film forming, relates to a high-performance reflective material, and specifically relates to a device and method for preparing a foldable curved polyimide fiber film. Background Art

[0002] Polyimide (PI) films are widely used in aerospace, electronic information, smart wearables and other fields, and have excellent thermal stability, chemical stability, mechanical strength and low dielectric constant. However, traditional polyimide films have limitations in certain specific application scenarios. For example, in the application of curved structures, traditional polyimide films are difficult to maintain uniform mechanical properties and good adhesion. The reflective surfaces of satellites in space are mostly curved structures, and they often face problems of planarization and singularization during the preparation process. At the same time, there are inevitable vibrations and shocks during the unfolding and folding process in the space environment, so there is also the problem of substandard strength, which makes it difficult to meet the requirements of modern electronic equipment for curved surfaces, foldability and other characteristics.

[0003] Therefore, developing fiber-reinforced polyimide films with foldability and surface adaptability has become a research hotspot in the field. Fiber reinforcement involves the addition of fiber reinforcement and thermoplastic molding, which not only improves mechanical properties but also enhances the adaptability and stability of the film's reflective surface during folding. While there have been some reports on fiber-reinforced polyimide films, these studies primarily focus on the preparation of flat films, with few reports on methods and apparatus for preparing polyimide films with curved structures.

[0004] In this context, a device and method for preparing a foldable curved polyimide fiber film are proposed to achieve uniform distribution and effective compounding of fiber reinforcement in the curved polyimide film, thereby improving the mechanical properties and stability of the curved polyimide film, and providing possibilities for its application in the field of radar antenna film manufacturing. Summary of the Invention

[0005] To address the aforementioned deficiencies in the prior art, the present invention aims to provide an apparatus and method for preparing a foldable, curved polyimide fiber film. By optimizing the composite process for combining fibers with a polyimide matrix and combining this with a molding method, the present invention produces a fiber-reinforced, curved polyimide film that not only exhibits high strength, toughness, heat resistance, and corrosion resistance, but also exhibits excellent foldability and processability, meeting the demands of applications in a variety of complex environments.

[0006] The present invention is achieved through the following technical solutions.

[0007] One aspect of the present invention provides a method for preparing a foldable curved polyimide fiber film, comprising the following steps:

[0008] Clean the surface of the mold base, crease positioning column and fiber fixing column and dry them;

[0009] Install the two processed crease positioning columns onto the crease positioning holes on the mold base respectively;

[0010] Installing the treated fiber fixing posts onto the remaining fiber fixing holes of the mold base;

[0011] Pass both ends of the main fiber through the positioning holes of the crease positioning column and fix them;

[0012] The polyimide fiber is placed in a polyamic acid solution to obtain a polyimide fiber with a coating liquid; the secondary fiber is wound onto a fiber fixing column and a main fiber, and the secondary fibers on the left and right sides are interlocked with each other to form a polyimide fiber grid;

[0013] Performing a preliminary heat setting treatment on the polyimide fiber mesh to obtain a polyimide fiber mesh;

[0014] spraying the polyimide solution onto the mold using a spray gun to obtain a polyimide composite film attached to the polyimide fiber grid;

[0015] The sprayed mold is subjected to thermal imidization;

[0016] The polyimide composite film after thermal imidization is demoulded and dried to obtain a fiber-reinforced, foldable, curved polyimide fiber film.

[0017] Preferably, the polyamic acid solution is prepared as follows:

[0018] According to a mass ratio of 100:1.2-2.0, a polyimide solution with a mass concentration of 15-25% and triphenyl phosphite are fully stirred and mixed, and sealed for storage.

[0019] Preferably, the polyimide fiber mesh is subjected to a preliminary heat setting treatment by heating the temperature from room temperature to 250-280° C. at a heating rate of 1-5° C. / min, keeping the temperature for 2-3 hours, and then naturally cooling to room temperature.

[0020] Preferably, the sprayed mold is thermally imidized, including: the first stage is a desolventizing treatment stage, which requires heating to 80°C, 120°C and 150°C at a rate of 1 to 2°C / min, and baking in an oven for 60 minutes respectively to perform a desolventizing operation; the second stage is a thermal imidization stage, which requires heating to 180°C, 210°C, 240°C, 270°C and 300°C at a rate of 3 to 4°C / min, and performing each heat treatment for 30 to 40 minutes under each temperature condition.

[0021] Preferably, the mold base is divided into six equal parts, one part is a module, and film making is performed multiple times. The edge of the demolded film has small holes for crease positioning columns and fiber fixing columns. Fibers are passed through the small holes to splice the six films into a grid to form a whole film reflective surface, thereby obtaining a polyimide film.

[0022] Preferably, the grid is a tri-directional fiber grid, a diamond grid, a cage grid or a right-angle grid.

[0023] Another aspect of the present invention provides a device used in the method for preparing the foldable curved polyimide fiber film, comprising a mold base, two crease positioning columns located on both sides of the upper surface of the mold base, and a plurality of fiber fixing columns arranged at intervals on the peripheral edge of the upper surface of the mold base; the upper surface of the mold base is a convex arc surface, the two crease positioning columns are symmetrically arranged in the middle of the edge of the convex arc surface, and the plurality of fiber fixing columns are arranged at equal intervals along the edge of the convex arc surface of the mold base.

[0024] Preferably, fold positioning holes and fiber fixing holes are distributed on the mold base, and the fiber fixing columns are inserted into the fixing holes for fixing.

[0025] Preferably, a fiber retaining groove is provided on the fiber fixing column, and the fiber retaining groove is flush with the parabola of the mold base.

[0026] Preferably, a positioning hole for the main fiber to pass through is provided on the crease positioning post, and the crease positioning post is inserted into the crease positioning hole and fixed.

[0027] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects:

[0028] 1. The resulting polyimide fiber film possesses a precisely curved surface, better meeting the requirements of antenna reflective surfaces than flat films and better adapting to the propagation characteristics of electromagnetic waves. Directly molded from the raised arc surface of the mold base, the curved film achieves more efficient electromagnetic wave reflection and focusing, thereby improving the antenna's gain and directivity. The curved shape reduces electromagnetic wave scattering during reflection, optimizing the antenna's beam shape and resulting in a more concentrated and stable antenna signal, better meeting specific communication needs.

[0029] 2. The crease positioning posts create precise crease points on the film. These crease points become natural bending points when the film needs to be opened, making it easier to unfold along the creases, reducing the required force and difficulty of operation. The crease positioning posts also guide the film to fold along the predetermined path, avoiding unnecessary twisting or deformation, reducing the probability of wrinkles, improving folding efficiency and the film's ease of use, and improving folding efficiency.

[0030] 3. By spraying a polyamic acid solution composed of polyimide and triphenyl phosphite solution on the polyimide fiber, the effective reinforcement effect of the fiber is ensured, so that the polyimide fiber has the characteristics of high strength and high modulus, low density, and impact resistance.

[0031] 4. By controlling both the thermal imidization desolventization stage and the thermal imidization stage, the stability and performance of the polyimide composite film at high temperatures are ensured. This process not only imparts excellent mechanical properties to the film, but also ensures its high-temperature and corrosion resistance, significantly improving the film's tensile strength, flexural strength, and shear strength.

[0032] 5. This fiber-reinforced structure makes the polyimide fiber-reinforced thermoplastic polyimide film more outstanding in mechanical properties. Its foldability and spatial adaptability make it show great advantages in applications where space is limited or frequent changes in form are required. It is particularly suitable for fields that need to withstand impact loads, such as aerospace, foldable electronic devices, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute an improper limitation of the present invention. In the drawings:

[0034] Figure 1 It is a schematic diagram of the overall assembly of the embodiment of the present invention;

[0035] Figure 2 is a perspective assembly drawing of the embodiment of the present invention as a whole;

[0036] Figure 3 is a schematic diagram of a mold base according to an embodiment of the present invention;

[0037] Figure 4 is a cross-sectional view of a mold base according to an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of a crease positioning column according to an embodiment of the present invention;

[0039] Figure 6 This is a schematic diagram of a fiber fixing column according to an embodiment of the present invention;

[0040] Figure 7Schematic diagram of fiber winding on a mold according to an embodiment of the present invention;

[0041] Figure 8 This is a schematic diagram of a fiber winding method according to an embodiment of the present invention;

[0042] Figure 9 This is a heating schematic diagram of thermal imidization according to an embodiment of the present invention;

[0043] Figure 10 is a schematic diagram of a mold using spliced ​​films according to the present invention;

[0044] Figure 11 Schematic diagram of the spliced ​​film fibers of the present invention being wound on a mold;

[0045] Figure 12 The invention provides a splicing method for splicing films;

[0046] Figure 13 Schematic diagram of the splicing film of the present invention after splicing;

[0047] Figure 14 (a)-(d) are several other common fiber-reinforced grids provided by the present invention; among them, (a) is a diamond grid, (b) is a three-dimensional grid, (c) is a cage grid, and (d) is a rectangular grid.

[0048] In the figure: 1. mold base; 2. crease positioning column; 3. fiber fixing column; 4. crease positioning hole; 5. fiber fixing hole; 6. positioning hole; 7. fiber slot; 8. main fiber; 9. secondary fiber. DETAILED DESCRIPTION

[0049] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0050] like Figure 1 、 Figure 2 The figure shows an apparatus for preparing a foldable curved polyimide fiber film according to an embodiment of the present invention. The apparatus comprises a mold base 1, two crease positioning posts 2 located on either side of the upper surface of the mold base 1, and a plurality of fiber fixing posts 3 spaced apart along the periphery of the upper surface of the mold base 1. The upper surface of the mold base 1 is a convex arc-shaped surface, and the two crease positioning posts 2 are symmetrically arranged in the middle of the edge of the convex arc-shaped surface. The plurality of fiber fixing posts 3 are evenly spaced along the edge of the convex arc-shaped surface of the mold base 1.

[0051] The mold base 1 is at the bottom of the entire device and is used to fix the crease positioning column 2 and the fiber fixing column 3. It also serves as a carrier for the imidization process of the polyamic acid solution.

[0052] like Figure 3 、 Figure 4As shown, the mold base 1 is provided with fold positioning holes 4 and fiber fixing holes 5 . The fiber fixing columns 3 are used to fix the fibers around the device and can be directly inserted into the fiber fixing holes 5 during installation.

[0053] like Figure 5 、 Figure 6 As shown, the crease positioning column 2 is provided with a positioning hole 6 through which the main fiber 8 passes. The crease positioning column 2 in this embodiment is located in the middle of the long section of the mold base. It can be replaced with different installation positions according to different requirements. When installing, it can be directly inserted into the crease positioning hole 4. When fixing the main fiber 8, the main fiber 8 needs to pass through the middle positioning hole 6 to ensure that the fiber does not slide up and down during processing. Figure 6 The positioning hole 6 is flush with the parabolic edge of the mold base 1, which can ensure that the fold is in the ideal position.

[0054] A fiber retaining slot 7 is provided on the fiber fixing column 3. The fiber retaining slot 7 is flush with the parabola of the mold base 1. When winding the fiber, the fiber needs to be placed in the fiber retaining slot 7 to prevent the fiber from being displaced due to thermal expansion during the thermal imidization process, thereby causing deformation of the formed film.

[0055] The present invention further provides a method for preparing a fiber-reinforced polyimide curved film, comprising the following steps:

[0056] Step 1: Clean the surfaces of the mold base 1, the crease positioning column 2, and the fiber fixing column 3 with alcohol and place them in a drying oven for drying.

[0057] Step 2: Install the two processed crease positioning columns 2 onto the crease positioning holes 4 on the mold base 1 respectively.

[0058] Step 3: Install the treated fiber fixing columns 3 onto the remaining fiber fixing holes 5 of the mold base 1 .

[0059] In steps 2 and 3, two crease positioning posts 2 are respectively installed in crease positioning holes 4 on the mold base 1; fiber fixing posts 3 are installed in the remaining fiber fixing holes in the mold base; and the two ends of the main fiber are respectively passed through the positioning holes of the crease positioning posts and fixed. Compared with the current salivation stretching method used in industrial film production, the present application uses crease positioning posts and fiber fixing posts to ensure that the creases of the produced film are positioned in the desired engineering application. For example, the crease can be controlled to a location with weak reflectivity without significantly affecting the electrical performance of the antenna reflective surface. In step 4, the two ends of the main fiber 8 are respectively passed through the positioning holes 6 of the crease positioning posts 2 and fixed.

[0060] Step 5: Place the polyimide fiber in a polyamic acid solution to obtain a polyimide fiber with a coating liquid, wind the secondary fiber 9 onto the fiber fixing column 3 and the main fiber 8, and interlock the secondary fibers 9 on the left and right sides, and make the polyimide fiber with the coating liquid into a polyimide fiber grid.

[0061] In the above steps, the polyimide solution is a mixed solution, and the preparation method is:

[0062] According to the mass ratio, 100g of polyimide solution with a mass concentration of 15-25% and 1.2-2.0g of triphenyl phosphite are added. After sufficient stirring, the prepared solution is transferred to a sealed bottle and stored at a low temperature for later use. In this range, the film can fall off normally. When the mass fraction of triphenyl phosphite is too high, the edge of the film will automatically separate.

[0063] Step 6: subjecting the polyimide fiber mesh to a preliminary heat setting treatment by heating it from room temperature to 250-280° C. at a heating rate of 1-5° C. / min, keeping it warm for 2-3 hours, and then naturally cooling it to room temperature to obtain a polyimide fiber mesh.

[0064] Step 7: spraying the polyimide solution onto the mold using a spray gun to obtain a polyimide fiber grid and a polyimide composite film;

[0065] Step 8, placing the sprayed mold horizontally in an oven to complete thermal imidization; specifically comprising:

[0066] The first stage is the desolvation stage, which requires heating to 80°C, 120°C and 150°C at a rate of 1 to 2°C / min, and baking in an oven for 60 minutes respectively to perform the desolvation operation; the second stage is the thermal imidization stage, which requires heating at a rate of 3 to 4°C / min, and performing each heat treatment at 180°C, 210°C, 240°C, 270°C and 300°C for 30 to 40 minutes.

[0067] Step 9: After the heating furnace is cooled to room temperature, the mold is taken out and demoulded, and the film after demoulding is dried to finally obtain a fiber-reinforced polyimide film.

[0068] Among them, in step 8, the polyimide fiber grid and the polyimide composite film are subjected to the desolventizing stage and the thermal imidization process; the temperature is raised and baked in stages. Considering that the solution is in the stage of eliminating the solvent when it is below 150°C, the solvent in the polyamic acid solution can be effectively removed by gradually raising the temperature to 80°C, 120°C and 150°C and baking for 60 minutes respectively before thermal imidization. Gradual heating helps the solvent to evaporate smoothly, avoiding the rapid volatilization of the solvent and the generation of internal stress in the film caused by rapid heating, which leads to the production of bubbles, gel stripes and other drawbacks in the finished film. Appropriately reducing the heating rate and extending the heating time helps the polyamic acid molecular chains to gradually align at low temperatures, forming a more stable polyimide structure, which helps to improve the mechanical properties, heat resistance and electrical properties of the film.

[0069] When the temperature rises above 150°C, polyamic acid begins to imidize under temperature conditions of 180°C, 210°C, 240°C, 270°C, and 300°C. During the thermal imidization stage, a heating rate of 3-4°C / min can be used to precisely control the conversion of polyamic acid to polyimide. This heating rate helps ensure a uniform reaction and avoids side reactions or degradation of film properties caused by local overheating. Heat treatment at different temperature stages (180°C, 210°C, 240°C, 270°C, and 300°C) can promote the gradual cyclization and crosslinking of the polyamic acid molecular chains. Each temperature stage provides sufficient energy and time to allow the reaction to proceed fully, while avoiding degradation or excessive crosslinking that may occur at high temperatures. This method is suitable for the preparation of different types of polyamic acid and polyimide films. By adjusting the heating rate and heat treatment temperature, it can be adapted to different material properties and application requirements. The present invention is further illustrated below through specific examples.

[0070] Example 1

[0071] (1) Clean and dry the mold base 1, crease positioning column 2, and fiber fixing column 3;

[0072] (2) Install the two crease positioning columns 2 onto the crease positioning holes 4 on the mold base 1 respectively;

[0073] (3) Install the fiber fixing columns 3 onto the remaining fiber fixing holes 5 of the mold base 1;

[0074] (4) Pass both ends of the main fiber through the positioning holes of the crease positioning column and fix them;

[0075] (5) placing the polyimide fiber in 100 g of a 20% polyimide solution and a polyamic acid solution containing 2.0 g of triphenyl phosphite to obtain a polyimide fiber coated with the solution, and winding the secondary fiber onto a fiber fixing post and the primary fiber, with the secondary fibers on the left and right sides interlocking with each other to form a polyimide fiber grid;

[0076] (6) subjecting the polyimide fiber mesh to a heat setting treatment by heating the mesh from room temperature to 280°C at a heating rate of 3°C / min, maintaining the temperature for 2 hours, and cooling the mesh to room temperature to obtain a polyimide fiber mesh;

[0077] (7) spraying the polyimide solution onto the mold to obtain a polyimide fiber grid and a polyimide composite film;

[0078] (8) Place the sprayed mold horizontally in an oven for thermal imidization:

[0079] In the first stage, the temperature was raised to 80℃, 120℃ and 150℃ at a rate of 2℃ / min, and baked for 60min respectively; in the second stage, the temperature was raised to 180℃, 210℃, 240℃, 270℃ and 300℃ at a rate of 4℃ / min, and heat treated for 30min each. Figure 9 shown.

[0080] (9) After cooling to room temperature, demoulding, and film drying treatment are carried out to obtain a fiber-reinforced polyimide film.

[0081] Example 2

[0082] (1) Clean and dry the mold base, crease positioning column, and fiber fixing column;

[0083] (2) Install two crease positioning columns onto the crease positioning holes on the mold base;

[0084] (3) Install the fiber fixing posts on the remaining fiber fixing holes of the mold base;

[0085] (4) Pass both ends of the main fiber through the positioning holes of the crease positioning column and fix them;

[0086] (5) placing the polyimide fiber in a polyamic acid solution containing 100 g of a 25% polyimide solution and 1.5 g of triphenyl phosphite to obtain a polyimide fiber coated with the solution, and winding the secondary fiber onto a fiber fixing column and the main fiber, with the secondary fibers on the left and right sides interlocking with each other to form a polyimide fiber grid;

[0087] (6) subjecting the polyimide fiber mesh to a heat setting treatment by heating the temperature from room temperature to 250° C. at a heating rate of 1° C. / min, keeping the temperature for 3 h, and cooling the temperature to room temperature to obtain a polyimide fiber mesh;

[0088] (7) spraying the polyimide solution onto the mold to obtain a polyimide fiber grid and a polyimide composite film;

[0089] (8) Place the sprayed mold horizontally in an oven for thermal imidization:

[0090] In the first stage, the temperature was raised to 80°C, 120°C and 150°C at a rate of 2°C / min and baked for 60 minutes respectively; in the second stage, the temperature was raised to 180°C, 210°C, 240°C, 270°C and 300°C at a rate of 3°C / min and heat treated for 40 minutes each.

[0091] (9) After cooling to room temperature, demoulding, and film drying treatment are carried out to obtain a fiber-reinforced polyimide film.

[0092] Example 3

[0093] (1) Clean and dry the mold base, crease positioning column, and fiber fixing column;

[0094] (2) Install two crease positioning columns onto the crease positioning holes on the mold base;

[0095] (3) Install the fiber fixing posts on the remaining fiber fixing holes of the mold base;

[0096] (4) Pass both ends of the main fiber through the positioning holes of the crease positioning column and fix them;

[0097] (5) placing the polyimide fiber in 100 g of a 15% polyimide solution and a polyamic acid solution containing 1.2 g of triphenyl phosphite to obtain a polyimide fiber coated with the solution, and winding the secondary fiber onto a fiber fixing column and the main fiber, with the secondary fibers on the left and right sides interlocking with each other to form a polyimide fiber grid;

[0098] (6) subjecting the polyimide fiber mesh to a heat setting treatment by heating the mesh from room temperature to 270°C at a heating rate of 5°C / min, maintaining the temperature for 2 hours, and cooling the mesh to room temperature to obtain a polyimide fiber mesh;

[0099] (7) spraying the polyimide solution onto the mold to obtain a polyimide fiber grid and a polyimide composite film;

[0100] (8) Place the sprayed mold horizontally in an oven for thermal imidization:

[0101] In the first stage, the temperature was raised to 80°C, 120°C and 150°C at a rate of 1°C / min and baked for 60 minutes respectively; in the second stage, the temperature was raised to 180°C, 210°C, 240°C, 270°C and 300°C at a rate of 3.5°C / min and heat treated for 35 minutes each at each temperature.

[0102] (9) After cooling to room temperature, demoulding, and film drying treatment are carried out to obtain a fiber-reinforced polyimide film.

[0103] The specific heating curve of this embodiment can be seen Figure 9 .

[0104] Figure 7 、 Figure 8 In the polyimide fiber winding method shown in FIG, the black vertical thick line represents the main fiber 8, the black horizontal line and the dotted line represent the secondary fiber 9, and the blocked part can illustrate the upper and lower relationship of the fibers.

[0105] For the film reflector of large-diameter antenna, the cost of making a large mold and a heating furnace is high. The present invention proposes a splicing solution as follows: Since there is no solution in the original fiber fixing column, no film will be produced after imidization, so there will be some small holes in the film after demoulding. When processing the mold, the mold is divided into six equal parts from the center of the mold, such as Figure 10 , one part is a module, when making the mold, you only need to make one module, and perform the film making process multiple times. After making it, follow the Figure 11 、 Figure 12 The six films are spliced ​​together into a whole reflective film surface by passing fibers through the holes. Figure 13 .

[0106] In the present invention, polyimide fibers are first coated with a polyamic acid solution to form a fiber mesh. The mesh is then fixed in shape by utilizing the viscosity of the polyamic acid solution. The mesh is then heated for a preliminary heat setting treatment, causing the polyimide fibers to fully shrink. Simultaneously, the polyamic acid solution heat sets the mesh. The polyimide fiber mesh is then composited with a polyimide film, which is then subjected to a further heat treatment at elevated temperatures to complete the thermal imidization of the entire film. This ensures that the thermal dimensional changes of the polyimide fiber mesh and the film are substantially synchronized, minimizing internal stress during the molding process. This results in a composite film structure with a smooth surface and no warping or wrinkles.

[0107] Research has found that using a triaxial mesh as a reinforcement material results in composite materials with advantages such as structural orthotropy, good overall structural properties, excellent rigidity, and structural design. Therefore, the present invention first uses a triaxial fiber mesh as an example, as shown in Figures 14(a)-(d). The fiber arrangement can also be replaced with diamond meshes, cage meshes, or rectangular meshes, which can be considered as other implementations of the present invention.

[0108] The splicable polyimide film proposed in the present invention can be flexibly spliced ​​according to the specific needs of the antenna reflective surface, thereby constructing reflective surfaces of various shapes and sizes. This design freedom enables the antenna to better adapt to different application scenarios and performance requirements. In the design of antennas that require non-standard shapes or large-area reflective surfaces, the integrity and performance of the reflective surface can be ensured. Through modular production of splicable film elements, production efficiency can be significantly improved and manufacturing costs can be reduced. At the same time, it is also convenient for subsequent maintenance and replacement. When the antenna reflective surface is locally damaged or its performance degrades, the splicable design allows only the damaged part to be replaced without replacing the entire reflective surface, thereby reducing maintenance costs and time. The prepared curved film has broad application prospects in aerospace, electronic information and other fields.

[0109] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features therein according to the disclosed technical content without creative labor, and these substitutions and modifications are all within the protection scope of the present invention.

Claims

1. A method for preparing a foldable curved polyimide fiber film, characterized in that: The steps include: Clean the surface of the mold base, crease positioning column and fiber fixing column and dry them; Install the two processed crease positioning columns onto the crease positioning holes on the mold base respectively; Installing the treated fiber fixing posts onto the remaining fiber fixing holes of the mold base; Pass both ends of the main fiber through the positioning holes of the crease positioning column and fix them; The polyimide fiber is placed in a polyamic acid solution to obtain a polyimide fiber with a coating liquid; the secondary fiber is wound onto a fiber fixing column and a main fiber, and the secondary fibers on the left and right sides are interlocked with each other to form a polyimide fiber grid; Performing a preliminary heat setting treatment on the polyimide fiber mesh to obtain a polyimide fiber mesh; spraying the polyimide solution onto the mold using a spray gun to obtain a polyimide composite film attached to the polyimide fiber grid; The sprayed mold is subjected to thermal imidization; The polyimide composite film after thermal imidization is demoulded and dried to obtain a fiber-reinforced foldable curved polyimide fiber film.

2. The method for preparing a foldable curved polyimide fiber film according to claim 1, wherein: The preparation method of polyamic acid solution is: According to the mass ratio of 15-25% polyimide solution to triphenyl phosphite being 100:(1.2-2.0), the polyimide solution with a mass concentration of 15-25% and triphenyl phosphite are fully stirred and mixed, and the mixture is sealed and stored.

3. The method for preparing a foldable curved polyimide fiber film according to claim 1, wherein: The polyimide fiber mesh was subjected to a preliminary heat setting treatment by heating from room temperature to 250-280°C at a heating rate of 1-5°C / min, keeping the temperature for 2-3 hours, and then naturally cooling to room temperature.

4. The method for preparing a foldable curved polyimide fiber film according to claim 1, wherein: The sprayed mold is subjected to thermal imidization, including: the first stage of solvent removal treatment, heating to 80°C, 120°C and 150°C at a rate of 1~2°C / min, and baking in an oven for 60 minutes respectively; the second stage of thermal imidization, heating to 180°C, 210°C, 240°C, 270°C and 300°C at a rate of 3~4°C / min, and heat treatment at each temperature condition for 30~40 minutes.

5. The method for preparing a foldable curved polyimide fiber film according to claim 1, wherein: The mold base is divided into six equal parts, one part is a module, and the film is made multiple times. The edge of the demolded film has small holes for crease positioning columns and fiber fixing columns. Fibers are passed through the small holes to splice the six films into a grid to form a whole film reflective surface, thus obtaining a polyimide film.

6. The method for preparing a foldable curved polyimide fiber film according to claim 5, characterized in that: The grid is a tri-directional fiber grid, a diamond grid, a cage grid or a right-angle grid.

7. A device used in the method for preparing a foldable curved polyimide fiber film according to any one of claims 1 to 6, characterized in that: It includes a mold base, two crease positioning columns located on both sides of the upper surface of the mold base, and several fiber fixing columns arranged at intervals on the peripheral edge of the upper surface of the mold base; the upper surface of the mold base is a convex arc surface, the two crease positioning columns are symmetrically arranged in the middle of the edge of the convex arc surface, and the several fiber fixing columns are arranged at equal intervals along the edge of the convex arc surface of the mold base.

8. The device for preparing a foldable curved polyimide fiber film according to claim 7, characterized in that: Crease positioning holes and fiber fixing holes are distributed on the mold base, and the fiber fixing columns are inserted into the fixing holes for fixing.

9. The device for preparing a foldable curved polyimide fiber film according to claim 7, characterized in that: A fiber clamping groove is provided on the fiber fixing column, and the fiber clamping groove is flush with the parabola of the mold base.

10. The device for preparing a foldable curved polyimide fiber film according to claim 7, characterized in that: A positioning hole for the main fiber to pass through is provided on the crease positioning column, and the crease positioning column is inserted into the crease positioning hole for fixation.

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