Device and method for preparing foldable curved-surface polyimide fiber film

Abstract

The invention discloses a preparation device and method of a foldable curved-surface polyimide fiber film. Pretreated crease positioning columns are installed on crease positioning holes in a mold base, and fiber fixing columns are installed on other fiber fixing holes in the mold base; the two ends of the main fiber penetrate through positioning holes of the crease positioning columns respectively and are fixed; placing the polyimide fiber in a polyamide acid solution, winding the secondary fiber on the fiber fixing column and the main fiber to prepare a polyimide fiber grid, carrying out heat setting treatment, spraying the polyimide solution on the polyimide fiber grid, and carrying out thermal imidization; the polyimide composite film subjected to thermal imidization is demolded and dried, and the fiber-reinforced foldable curved surface polyimide fiber film is obtained. The film provided by the invention has excellent high strength, high toughness, high heat resistance, corrosion resistance and the like, has good foldability and machinability, and has wide application prospects in the fields of aerospace, electronic information and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of radar antenna film forming, relates to a high-performance reflective material, and specifically relates to a preparation device and method for 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, low dielectric constant and other characteristics. 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 a fiber-reinforced polyimide film with foldability and surface adaptability has become a research hotspot in the current field. Fiber reinforcement refers to the addition of fiber reinforcement and thermoplastic molding, which can not only improve its mechanical properties, but also improve the adaptability and stability of the film's reflective surface during the folding process. At present, although there have been some research reports on fiber-reinforced polyimide films, these studies mainly focus on the preparation of flat films, and there are few reports on the preparation method and preparation device of 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 possibility for its application in the field of radar antenna film manufacturing. Summary of the invention

[0005] In order to solve the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a device and method for preparing a foldable curved polyimide fiber film. The present invention optimizes the composite process of the fiber and the polyimide matrix and combines the molding method to prepare a fiber-reinforced polyimide curved film that not only has the characteristics of high strength, high toughness, high heat resistance, corrosion resistance, etc., but also has good foldability and processability, and can meet the application requirements in various 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 surfaces of the mold base, crease positioning columns and fiber fixing columns and dry them;

[0009] The two processed crease positioning columns are respectively installed on the crease positioning holes on the mold base;

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

[0011] Pass the two 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 solution; 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 thermally imidized;

[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 by:

[0018] According to the mass ratio of 100:1.2-2.0, the 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 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 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 at 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 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 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 through which the main fiber passes is provided on the crease positioning column, and the crease positioning column is inserted into the crease positioning hole for fixation.

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

[0028] 1. The prepared polyimide fiber film has a precise curved surface shape, which is more in line with the use requirements of the antenna reflective surface than the flat film, and can better adapt to the propagation characteristics of electromagnetic waves. The curved film is directly formed by the convex arc surface of the mold base, achieving more efficient electromagnetic wave reflection and focusing, thereby improving the gain and directivity of the antenna. The curved surface shape reduces the scattering of electromagnetic waves during the reflection process, optimizes the beam shape of the antenna, makes the antenna signal more concentrated and stable, and better meets specific communication needs.

[0029] 2. Through the setting of crease positioning columns, precise crease points are formed on the film. These crease points become natural bending points when the film needs to be opened, making it easier for the film to unfold along the crease, reducing the required force and difficulty of operation; the crease positioning columns also guide the film to fold along a predetermined path, avoiding unnecessary twisting or deformation, reducing the probability of wrinkles, improving folding efficiency and the ease of use of the film, and improving folding efficiency.

[0030] 3. By spraying a polyamic acid solution prepared from 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, high modulus, low density, and impact resistance.

[0031] 4. By controlling the two processes of thermal imidization desolventization and thermal imidization, the stability and performance of the polyimide composite film at high temperature are ensured. This process not only gives the film excellent mechanical properties, but also ensures its high temperature resistance and corrosion resistance; it significantly improves the tensile strength, bending strength and shear strength of the film.

[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 with limited space or requiring frequent changes in form. It is particularly suitable for aerospace, foldable electronic devices and other fields that need to withstand impact loads. 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 the present 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 diagram of an 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 is a schematic diagram of a crease positioning column according to an embodiment of the present invention;

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

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

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

[0042] Fig. 9 Schematic diagram of heating for thermal imidization according to an embodiment of the present invention;

[0043] Fig.10 is a schematic diagram of a mold using a spliced ​​film according to the present invention;

[0044] Fig.11 is a schematic diagram of the spliced ​​film fibers of the present invention being wound on a mold;

[0045] Fig.12 The invention discloses a splicing method for splicing films;

[0046] Fig.13 is a schematic diagram of the spliced ​​films of the present invention after being spliced;

[0047] Figure 14 (a)-(d) are several other common fiber-reinforced grids provided by the present invention; (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 in conjunction with 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 As shown, a preparation device for a foldable curved polyimide fiber film provided by an embodiment of the present invention comprises a mold base 1, two crease positioning columns 2 located on both sides of the upper surface of the mold base 1, and a plurality of fiber fixing columns 3 arranged at intervals on the peripheral edge of the upper surface of the mold base 1. The upper surface of the mold base 1 is a convex arc surface, and the two crease positioning columns 2 are symmetrically arranged in the middle of the edge of the convex arc surface. The plurality of fiber fixing columns 3 are arranged at equal intervals along the edge of the convex arc 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 , and 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, and 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 clamping groove 7 is provided on the fiber fixing column 3, and the fiber clamping groove 7 is flush with the parabola of the mold base 1. When winding the fiber, the fiber needs to be placed in the fiber clamping groove 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 embodiment of the present invention further provides a method for preparing a fiber-reinforced polyimide curved surface 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 put them into 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 processed fiber fixing columns 3 onto the remaining fiber fixing holes 5 of the mold base 1 .

[0059] Among them, in steps 2 and 3, two crease positioning posts 2 are respectively installed on the crease positioning holes 4 on the mold base 1; the fiber fixing post 3 is installed on the remaining fiber fixing holes of the mold base; the two ends of the main fiber are respectively passed through the positioning holes of the crease positioning posts and fixed; compared with the salivation stretching method currently used in industrially produced films, the present application uses crease positioning posts and fiber fixing posts to allow the creases of the produced films to be in the required positions in engineering applications, for example, the creases can be controlled in positions with weak reflective performance without having a significant impact on the electrical properties of the antenna reflective surface. Step 4, pass the two ends of the main fiber 8 through the positioning holes 6 of the crease positioning posts 2 and fix them.

[0060] Step 5, placing the polyimide fiber in a polyamic acid solution to obtain a polyimide fiber with a coating liquid, winding the secondary fiber 9 onto the fiber fixing column 3 and the main fiber 8, the secondary fibers 9 on the left and right sides are interlocked with each other, and the polyimide fiber with the coating liquid is made 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, add 100g of polyimide solution with a mass concentration of 15-25% and 1.2-2.0g of triphenyl phosphite. After fully stirring, transfer the prepared solution to a sealed bottle and store it at 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, 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 the temperature 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 desolventizing 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 for desolventizing operation; the second stage is the thermal imidization stage, which requires heating at a rate of 3 to 4°C / min, and performing heat treatments at 180°C, 210°C, 240°C, 270°C and 300°C for 30 to 40 minutes respectively.

[0067] Step 9, after waiting for the heating furnace to cool to room temperature, the mold is taken out and demolded, and the film after demolding 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 heating to 80°C, 120°C and 150°C and baking for 60 minutes respectively before thermal imidization. Gradually heating up helps the solvent to evaporate smoothly, avoiding the rapid volatilization of the solvent and the generation of internal stress of the film caused by the rapid temperature increase, which leads to the defects of bubbles and gel stripes 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 to above 150°C, under the temperature conditions of 180°C, 210°C, 240°C, 270°C and 300°C, polyamic acid begins to imidize. In the thermal imidization stage, a heating rate of 3 to 4°C / min is used to accurately control the conversion process of polyamic acid to polyimide. This heating rate helps to ensure that the reaction proceeds evenly and avoids side reactions or film performance degradation 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 polyamic acid molecular chains. Each temperature stage provides sufficient energy and time to enable 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, different material properties and application requirements can be adapted. The present invention is further illustrated below by specific embodiments.

[0070] Example 1

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

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

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

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

[0075] (5) placing the polyimide fiber in a polyamic acid solution containing 100 g of a 20% polyimide solution and 2.0 g of triphenyl phosphite to obtain a polyimide fiber coated with a coating 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;

[0076] (6) subjecting the polyimide fiber mesh to a heat setting treatment, heating the mesh from room temperature to 280° C. at a heating rate of 3° C. / min, maintaining the temperature for 2 h, 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 the samples were 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 the samples were heat treated for 30min respectively. Fig. 9 shown.

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

[0081] Example 2

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

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

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

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

[0086] (5) placing the polyimide fiber in 100 g of a polyimide solution having a mass concentration of 25% and a polyamic acid solution having 1.5 g of triphenyl phosphite to obtain a polyimide fiber with a coating 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, heating the mesh from room temperature to 250° C. at a heating rate of 1° C. / min, maintaining the temperature for 3 h, and cooling the mesh 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 at each temperature.

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

[0092] Example 3

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

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

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

[0096] (4) Pass the two 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 polyimide solution having a mass concentration of 15% and a polyamic acid solution having 1.2 g of triphenyl phosphite to obtain a polyimide fiber with a coating 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, heating the mesh from room temperature to 270° C. at a heating rate of 5° C. / min, maintaining the temperature for 2 h, 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 are performed to obtain a fiber-reinforced polyimide film.

[0103] The specific heating curve of this embodiment can be seen Fig. 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 reflective surface of the large-diameter antenna, the cost of making a large mold and a heating furnace is high. The present invention proposes a splicing scheme 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 Fig.10 , one part is a module. When making a mold, only one module needs to be made. The film making process is carried out many times. After it is made, Fig.11 , Fig.12 The six films are spliced ​​into a whole film reflective surface by using fibers to pass through these small holes. The spliced ​​film is visible Fig.13 .

[0106] In the present invention, firstly, the coated polyimide fiber obtained by coating the polyimide fiber with a polyamic acid solution is made into a fiber grid, the shape of the grid is fixed by using the viscosity of the polyamic acid solution, and then the grid is heated for preliminary heat setting treatment, so that the polyimide fiber is fully shrunk, and at the same time, the cyclization of the polyamic acid solution realizes heat setting of the grid. Then, the polyimide fiber grid is compounded with the polyimide film, and then the temperature is increased for heat treatment to complete the thermal imidization of the entire film, so that the thermal dimensional change behavior of the polyimide fiber grid and the film is basically synchronized, and the internal stress in the molding process is eliminated to the greatest extent, thereby obtaining a composite film structure with a smooth surface, no warping and no wrinkles.

[0107] Research has found that using a three-dimensional grid as a reinforcement material, the composite material has the advantages of structural orthogonal anisotropy, good overall bonding performance, excellent rigidity and structural design, etc. Therefore, the present invention first takes a three-dimensional fiber grid as an example, as shown in Figure 14 (a)-(d), the fiber arrangement method can also be replaced by a diamond grid, a cage grid, a right-angle grid, etc., which can be regarded as other implementation forms 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, so as to construct 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 partially damaged or the performance is degraded, 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 the fields of aerospace, electronic information, etc.

[0109] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations 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 surfaces of the mold base, crease positioning columns and fiber fixing columns and dry them; The two processed crease positioning columns are respectively installed on the crease positioning holes on the mold base; installing the treated fiber fixing posts onto the remaining fiber fixing holes of the mold base; Pass the two 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 solution; 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 thermally imidized; 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, characterized in that: The preparation method of polyamic acid solution is: According to the mass ratio of 100:1.2-2.0, the polyimide solution with a mass concentration of 15-25% and triphenyl phosphite are fully stirred and mixed, and sealed for storage.

3. The method for preparing a foldable curved polyimide fiber film according to claim 1, characterized in that: The polyimide fiber mesh is subjected to a preliminary heat setting treatment, and the temperature is increased from room temperature to 250-280°C at a heating rate of 1-5°C / min, and after being kept warm for 2-3 hours, it is naturally cooled to room temperature.

4. The method for preparing a foldable curved polyimide fiber film according to claim 1, characterized in that: The sprayed mold is subjected to thermal imidization, including: a first stage of solvent removal treatment, 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; a second stage of thermal imidization, heating to 180°C, 210°C, 240°C, 270°C and 300°C at a rate of 3 to 4°C / min, and heat treatment is performed at each temperature condition for 30 to 40 minutes.

5. The method for preparing a foldable curved polyimide fiber film according to claim 1, characterized in that: 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 demoulding film has small holes for crease positioning columns and fiber fixing columns. Fibers are passed through the small holes to splice 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 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.

8. The device for preparing a foldable curved polyimide fiber film according to claim 7, characterized in that: The mold base is provided with crease positioning holes and fiber fixing holes, 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 arranged 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 through which the main fiber passes is arranged on the crease positioning column, and the crease positioning column is inserted into the crease positioning hole for fixing.

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