Preparation method and application of anti-ultraviolet radiation polyimide insulating composite material with surface coated with titanium dioxide inorganic layer

Abstract

The invention discloses a preparation method and application of an anti-ultraviolet radiation polyimide insulation composite material with the surface coated with a titanium dioxide inorganic layer, and relates to the technical field of polyimide insulation composite media. The invention aims to solve the problems that the normal operation of a space detector is affected due to the fact that a pure polyimide material is easy to degrade, and when inorganic particles are doped into a polyimide matrix to serve as a protective material, filler dispersion is not uniform or agglomerated, and interfacial compatibility is poor. The high-speed electrostatic spinning technology enables the titanium oxide nanosheets to be directionally arranged on the surface of the substrate to form a compact protective layer, so that the absorption and reflection efficiency of ultraviolet light can be maximized, and the ultraviolet light penetrating into the polyimide substrate can be effectively reduced; in addition, closer interface bonding can be formed between the directionally arranged TiO2 nanosheets and the polyimide matrix, and interface defects are reduced. The invention can obtain the preparation method and the application of the anti-ultraviolet radiation polyimide insulating composite material with the surface coated with the titanium dioxide inorganic layer.

Description

Technical Field

[0001] The invention relates to the technical field of ultraviolet aging of polyimide insulating composite media, and in particular to a preparation method and application of a polyimide insulating composite material with a surface covered with a titanium dioxide inorganic layer and resistant to ultraviolet radiation. Background Art

[0002] With the rapid development of my country's aerospace industry, polyimide is widely used in the insulation layer of spacecraft cables and wires and in spacecraft electronic equipment. Therefore, the research on the protection modification of polyimide in space radiation environment is of great significance. The study found that through nanocomposite, surface coating, copolymerization modification and functional modification technologies, the radiation resistance, atomic oxygen resistance and electrical insulation performance of polyimide can be significantly improved, thereby meeting the high performance requirements of spacecraft in extreme environments. This research not only helps to improve the reliability and life of spacecraft, but also provides important support for the innovative development of my country's aerospace materials.

[0003] At present, there are still problems that pure polyimide is easily degraded, which affects the normal operation of space probes, and when inorganic particles are doped into polyimide as protective materials, there are problems such as uneven filler dispersion or agglomeration and poor interface compatibility. Based on this, how to solve the above technical problems has become a difficult problem that technicians in the industry need to solve urgently. Summary of the invention

[0004] The purpose of the present invention is to solve the problems that pure polyimide materials are easily degraded, thereby affecting the normal operation of space probes, and that when inorganic particles are doped into a polyimide matrix as a protective material, there are problems of uneven filler dispersion or agglomeration and poor interface compatibility, and to provide a method for preparing and applying a polyimide insulating composite material with a surface coated with an inorganic layer of titanium dioxide that is resistant to ultraviolet radiation.

[0005] A method for preparing a polyimide insulating composite material having a surface coated with an inorganic titanium dioxide layer and resistant to ultraviolet radiation, comprising the following steps:

[0006] Step S1, preparing a polyimide film:

[0007] Adding polyimide powder to N-methylpyrrolidone solution, stirring thoroughly and evacuating overnight to obtain a mixed solution a; pouring the mixed solution a onto a cleaned glass plate, coating it evenly with a scraper, and then drying and stripping the film to obtain a polyimide film;

[0008] Step S2, preparing spinning solution:

[0009] Adding titanium dioxide nanosheets to N-methylpyrrolidone solution, and performing ultrasonic dispersion to obtain a mixed solution b; then adding polyimide powder to the mixed solution b, stirring the mixed solution fully, and then standing the mixed solution to obtain a spinning solution c;

[0010] The mass fraction of the titanium dioxide nanosheets in the polyimide powder in step S2 is 0.25%, 0.5%, 0.75% or 1%;

[0011] Step S3, preparing a polyimide insulating composite material having a surface covered with an inorganic titanium dioxide layer:

[0012] The polyimide film obtained in step S1 is cut and pasted on the surface of the high-speed receiver roller of the electrospinning device, and then the spinning solution c obtained in step S2 is evenly sprayed on the polyimide film using the electrospinning technology until both sides of the polyimide film are evenly sprayed with the spinning solution c; then the film is peeled off, placed in a flat-plate vulcanizer for hot pressing, and after the hot pressing is completed, placed in an oven for curing to obtain a polyimide insulating composite material with a surface covered with an inorganic layer of titanium dioxide.

[0013] The invention discloses an application of a polyimide insulating composite material with a surface coated with a titanium dioxide inorganic layer to resist ultraviolet radiation, and an application of the polyimide insulating composite material with a surface coated with a titanium dioxide inorganic layer to resist ultraviolet radiation in the preparation of a spacecraft anti-ultraviolet radiation material.

[0014] Principle of the present invention:

[0015] Different from the conventional electrostatic spinning technology which uses three layers of fibers with different concentration structures to form a film with poor mechanical properties when hot pressed, the substrate of the present invention is formed by scraping and coating, and the substrate thickness is better controlled, the structure is denser, and it has higher mechanical strength and toughness.

[0016] Beneficial effects of the present invention:

[0017] (1) The method for preparing the polyimide insulating composite material with a surface coated with titanium dioxide inorganic layer that is resistant to ultraviolet radiation of the present invention innovatively utilizes high-speed electrospinning technology to coat the polyimide doped with titanium oxide nanosheets on a pure polyimide matrix, effectively solving the problems of uneven filler dispersion or agglomeration and poor interface compatibility when polyimide-based doped inorganic particles are used as protective materials.

[0018] The high-speed electrospinning technology of the present invention enables titanium oxide nanosheets to be oriented and arranged on the surface of the substrate to form a dense protective layer, which can not only maximize the absorption and reflection efficiency of ultraviolet light, but also effectively reduce the penetration of ultraviolet light into the polyimide substrate. Moreover, a tighter interface bonding can be formed between the oriented TiO2 nanosheets and the polyimide substrate, thereby reducing interface defects.

[0019] (2) The polyimide insulating composite material with a surface coated with titanium dioxide inorganic layer and resistant to ultraviolet radiation prepared by the process of the present invention has improved breakdown and dielectric properties compared to pure polyimide, and can still maintain relatively good performance after ultraviolet radiation treatment, and can be widely used in electrical and aerospace fields.

[0020] The invention can obtain a preparation method and application of a polyimide insulating composite material with a surface covered with a titanium dioxide inorganic layer and resistant to ultraviolet radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The SEM image of the polyimide insulating composite material having a surface covered with an inorganic titanium dioxide layer prepared in Example 1;

[0022] Figure 2 A diagram showing the DC breakdown Weibull distribution result of the polyimide insulating composite material (without irradiation treatment) with a surface coated with a titanium dioxide inorganic layer in the present invention, wherein ■ represents a pure polyimide-based film, ● represents a titanium dioxide nanosheet with a mass fraction of 0.25%, ▲ represents a titanium dioxide nanosheet with a mass fraction of 0.5%, ▼ represents a titanium dioxide nanosheet with a mass fraction of 0.75%, and ◆ represents a titanium dioxide nanosheet with a mass fraction of 1%;

[0023] Figure 3 A diagram showing the DC breakdown Weibull distribution result of the polyimide insulating composite material (irradiated with UV light for 7 days) with a surface coated with an inorganic titanium dioxide layer in the present invention, wherein ■ represents a pure polyimide-based film, ● represents a titanium dioxide nanosheet having a mass fraction of 0.25%, ▲ represents a titanium dioxide nanosheet having a mass fraction of 0.5%, ▼ represents a titanium dioxide nanosheet having a mass fraction of 0.75%, and ◆ represents a titanium dioxide nanosheet having a mass fraction of 1%;

[0024] Figure 4 A graph showing the dielectric constant test results of the polyimide insulating composite material with a titanium dioxide inorganic layer on the surface in the present invention, wherein ■ represents a pure polyimide-based film, ● represents a titanium dioxide nanosheet with a mass fraction of 0.25%, ▲ represents a titanium dioxide nanosheet with a mass fraction of 0.5%, ▼ represents a titanium dioxide nanosheet with a mass fraction of 0.75%, and ◆ represents a titanium dioxide nanosheet with a mass fraction of 1%;

[0025] Figure 5 A graph showing the dielectric loss test results of the polyimide insulating composite material with a titanium dioxide inorganic layer on the surface in the present invention, wherein ■ represents a pure polyimide-based film, ● represents a titanium dioxide nanosheet with a mass fraction of 0.25%, ▲ represents a titanium dioxide nanosheet with a mass fraction of 0.5%, ▼ represents a titanium dioxide nanosheet with a mass fraction of 0.75%, and ◆ represents a titanium dioxide nanosheet with a mass fraction of 1%;

[0026] Figure 6 A graph showing the Fourier transform infrared spectrum characterization result of the polyimide insulating composite material with a titanium dioxide inorganic layer on the surface in the present invention, 000 represents a pure polyimide-based film, 2-1 represents a titanium dioxide nanosheet with a mass fraction of 0.25%, 2-2 represents a titanium dioxide nanosheet with a mass fraction of 0.5%, 2-3 represents a titanium dioxide nanosheet with a mass fraction of 0.75%, and 2-4 represents a titanium dioxide nanosheet with a mass fraction of 1%;

[0027] Figure 7 A graph showing the tensile test results of the polyimide insulating composite material having a surface-covered titanium dioxide inorganic layer in the present invention, wherein 000 represents a pure polyimide-based film, 2-1 represents a titanium dioxide nanosheet with a mass fraction of 0.25%, 2-2 represents a titanium dioxide nanosheet with a mass fraction of 0.5%, 2-3 represents a titanium dioxide nanosheet with a mass fraction of 0.75%, and 2-4 represents a titanium dioxide nanosheet with a mass fraction of 1%. DETAILED DESCRIPTION

[0028] Specific implementation method 1: In this implementation method, a method for preparing a polyimide insulating composite material with a surface covered with a titanium dioxide inorganic layer that is resistant to ultraviolet radiation is carried out according to the following steps:

[0029] Step S1, preparing a polyimide film:

[0030] Adding polyimide powder to N-methylpyrrolidone solution, stirring thoroughly and evacuating overnight to obtain a mixed solution a; pouring the mixed solution a onto a cleaned glass plate, coating it evenly with a scraper, and then drying and stripping the film to obtain a polyimide film;

[0031] Step S2, preparing spinning solution:

[0032] Adding titanium dioxide nanosheets to N-methylpyrrolidone solution, and performing ultrasonic dispersion to obtain a mixed solution b; then adding polyimide powder to the mixed solution b, stirring the mixed solution fully, and then standing the mixed solution to obtain a spinning solution c;

[0033] The mass fraction of the titanium dioxide nanosheets in the polyimide powder in step S2 is 0.25%, 0.5%, 0.75% or 1%;

[0034] Step S3, preparing a polyimide insulating composite material having a surface covered with an inorganic titanium dioxide layer:

[0035] The polyimide film obtained in step S1 is cut and pasted on the surface of the high-speed receiver roller of the electrospinning device, and then the spinning solution c obtained in step S2 is evenly sprayed on the polyimide film using the electrospinning technology until both sides of the polyimide film are evenly sprayed with the spinning solution c; then the film is peeled off, placed in a flat-plate vulcanizer for hot pressing, and after the hot pressing is completed, placed in an oven for curing to obtain a polyimide insulating composite material with a surface covered with an inorganic layer of titanium dioxide.

[0036] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that in step S1, polyimide powder is added to N-methylpyrrolidone solution and stirred at a temperature of 60-65° C. and a rotation speed of 600-650 r / min for 10-12 hours.

[0037] The other steps are the same as those in the first specific implementation.

[0038] Specific embodiment three: The difference between this embodiment and specific embodiment one or two is that in step S2, polyimide powder is added to the mixed solution b, and a magnetic stirrer is used to continuously stir for 9 to 10 hours at a temperature of 80 to 85° C. and a rotation speed of 400 to 500 r / min.

[0039] The other steps are the same as those in the first or second embodiment.

[0040] Specific embodiment 4: The difference between this embodiment and specific embodiments 1 to 3 is that the ratio of the mass of the polyimide powder described in step S1 to the volume of the N-methylpyrrolidone solution is (1.8~2) g: (8~12) mL; the ratio of the mass of the polyimide powder described in step S2 to the volume of the N-methylpyrrolidone solution is (1.5~1.6) g: (4~6) mL.

[0041] The other steps are the same as those in Specific Embodiments 1 to 3.

[0042] Specific embodiment 5: The difference between this embodiment and specific embodiments 1 to 4 is that in step S1, the mixed solution a is poured onto a glass plate with a length of 5 to 6 cm and a width of 1.5 to 2.5 cm, and the scraper thickness is 14 to 16 μm.

[0043] The other steps are the same as those in Specific Embodiments 1 to 4.

[0044] Specific embodiment 6: The difference between this embodiment and specific embodiments 1 to 5 is that the drying conditions in step S1 are: first drying in an oven at 80-85°C for 7-8h, and then continuing drying in a vacuum oven at 115-120°C for 1-2h.

[0045] The other steps are the same as those in Specific Embodiments 1 to 5.

[0046] Specific embodiment seven: The difference between this embodiment and any one of specific embodiments one to six is ​​that in step S3, 5 mL of the spinning solution c in step S2 is first extracted with a syringe, and then the syringe is placed on the push column A of the electrospinning equipment, and then the electrospinning equipment is set: the push speed of the push injection A is 1 to 1.2 mm / min, the left and right translation distances are both 8 to 12 mm, the rotation speed of the high-speed receiver is 1800 to 2000 r / min, the humidity in the spinning machine is 20 to 25%, the temperature is 25 to 30°C, and the pressure is increased to 11 to 12V.

[0047] The other steps are the same as those in Specific Embodiments 1 to 6.

[0048] Specific embodiment eight: The difference between this embodiment and specific embodiments one to seven is that in step S3, the film is peeled off and placed in a flat vulcanizer, and hot-pressed at a temperature of 80 to 85° C. and a pressure of 12 to 15 MPa for 5 to 8 minutes.

[0049] The other steps are the same as those in Specific Embodiments 1 to 7.

[0050] Specific embodiment 9: The difference between this embodiment and specific embodiments 1 to 8 is: the curing conditions in step S3: first dry in a vacuum oven at 75-85°C for 220-240 min, and then continue drying in a vacuum oven at 115-125°C for 180-200 min.

[0051] The other steps are the same as those in Specific Embodiments 1 to 8.

[0052] Specific embodiment ten: This embodiment discloses an application of a polyimide insulating composite material having an anti-ultraviolet radiation surface coated with an inorganic titanium dioxide layer, and an application of the polyimide insulating composite material having an anti-ultraviolet radiation surface coated with an inorganic titanium dioxide layer in the preparation of spacecraft anti-ultraviolet radiation materials.

[0053] The following examples are used to verify the beneficial effects of the present invention:

[0054] Example 1: A method for preparing a polyimide insulating composite material having a surface coated with an inorganic titanium dioxide layer and resistant to ultraviolet radiation, comprising the following steps:

[0055] Step S1, preparing a polyimide film:

[0056] 1.8 g of polyimide powder and 10 mL of N-methylpyrrolidone solution were added to a beaker in sequence, and stirred for 10 h at 60° C. and 600 r / min using a magnetic stirrer, and then vacuumed overnight to obtain a mixed solution a; the mixed solution a was poured onto a cleaned glass plate with a length of 5 cm and a width of 1.5 cm, and evenly coated with a scraper (thickness of 16 μm), and then the glass plate was first dried in an oven at 80° C. for 8 h, and then continued to be dried in a vacuum oven at 120° C. for 1 h, and finally soaked in deionized water for 10 min, the polyimide group was peeled off, and a polyimide film was obtained;

[0057] The glass plate is treated according to the following steps before use: prepare a glass plate with a size of 200 mm*16 mm*4 mm, first wash the glass plate with detergent once, then rinse with clean water twice, then rinse with deionized water twice, then wash with anhydrous ethanol once, and finally dry at 80°C for 15 minutes;

[0058] Step S2, preparing a spinning solution:

[0059] 0.0038 g of titanium dioxide nanosheets and 5 mL of N-methylpyrrolidone solution were added to a beaker in sequence, and ultrasonically dispersed for 1 hour to obtain a mixed solution b; 1.5 g of polyimide powder was added to the mixed solution b, and a magnetic stirrer was used to continuously stir for 9 hours at a temperature of 80° C. and a speed of 400 r / min. After sufficient stirring, the magnetic stirrer was adjusted to 0 speed at 80° C. and allowed to stand for 30 minutes to obtain a spinning solution c;

[0060] The mass fraction of the titanium dioxide nanosheets in the polyimide powder described in step S2 is 0.25%;

[0061] Step S3, preparing a polyimide insulating composite material having a surface covered with an inorganic titanium dioxide layer:

[0062] The polyimide film was cut into a rectangle with a width of 4.5 cm and a length of 12 cm, and fixed on the surface of the high-speed receiver roller of the electrospinning device. Then, 5 mL of spinning solution c was drawn with a syringe, and then the syringe was placed on the push column A of the electrospinning device. Then, the electrospinning device was set up: the push speed of the push column A was 1 mm / min, the left and right translation distances were both 8 mm, the speed of the high-speed receiver was 1800 r / min, the voltage was ±11 V, the humidity in the spinning machine was 20%, and the temperature was 25 °C; the heating was turned on. A piezoelectric power source is used to evenly spray the spinning solution c on the polyimide film. After spraying for 10 minutes, the polyimide film is turned over and sprayed for another 10 minutes, until both sides of the polyimide film are evenly sprayed with the spinning solution c; then the film is peeled off, placed in a flat-plate vulcanizer, and hot-pressed at a temperature of 81°C and a pressure of 15 MPa for 6 minutes. After the hot pressing, it is first dried in a vacuum oven at 80°C for 4 hours, and then further dried in a vacuum oven at 120°C for 3 hours to obtain a polyimide insulating composite material with a surface covered with an inorganic layer of titanium dioxide.

[0063] Example 2: The mass fraction of the titanium dioxide nanosheets in step S2 (ie, spinning solution c) of the polyimide powder is 0.5%. Other conditions are the same as those in Example 1.

[0064] Example 3: The mass fraction of the titanium dioxide nanosheets in step S2 (ie, spinning solution c) of the polyimide powder is 0.75%. Other conditions are the same as those in Example 1.

[0065] Example 4: The mass fraction of the titanium dioxide nanosheets in step S2 (ie, spinning solution c) of the polyimide powder is 1%. Other conditions are the same as those in Example 1.

[0066] Comparative Example 1: In this comparative example, steps S2 and S3 are not performed, and titanium dioxide is not coated, that is, a pure polyimide film is prepared. Other conditions are the same as those in Example 1.

[0067] Figure 1 The SEM image of the polyimide insulating composite material with a titanium dioxide inorganic layer on its surface prepared in Example 1 is shown; Figure 1 As shown in the figure, the titanium dioxide nanosheets after peeling are oriented on the surface of the polyimide base, with good interface compatibility, and a thin layer of coating on the upper and lower surfaces of the polyimide base, without obvious stratification. It can not only maximize the absorption and reflection efficiency of ultraviolet light, but also effectively reduce the penetration of ultraviolet light into the polyimide matrix, and the oriented TiO2 nanosheets and the polyimide matrix can form a tighter interface and reduce interface defects.

[0068] Figure 2A graph showing the DC breakdown Weibull distribution results of the polyimide insulating composite material (without irradiation treatment) having a surface covered with an inorganic titanium dioxide layer in the present invention, wherein ■ represents a pure polyimide-based film, ● represents a titanium dioxide nanosheet having a mass fraction of 0.25%, ▲ represents a titanium dioxide nanosheet having a mass fraction of 0.5%, ▼ represents a titanium dioxide nanosheet having a mass fraction of 0.75%, and ◆ represents a titanium dioxide nanosheet having a mass fraction of 1%.

[0069] Figure 3 The figure shows the DC breakdown Weibull distribution results of the polyimide insulating composite material (irradiated with UV light for 7 days) with a surface covered with an inorganic layer of titanium dioxide in the present invention, wherein ■ represents a pure polyimide-based film, ● represents a titanium dioxide nanosheet with a mass fraction of 0.25%, ▲ represents a titanium dioxide nanosheet with a mass fraction of 0.5%, ▼ represents a titanium dioxide nanosheet with a mass fraction of 0.75%, and ◆ represents a titanium dioxide nanosheet with a mass fraction of 1%.

[0070] like Figure 2-3 As shown in the figure, when not irradiated, as the mass fraction of titanium dioxide nanosheets increases, the breakdown field strength first increases and then decreases, and the breakdown field strength of pure polyimide is 550kV / mm; when the mass fraction of titanium dioxide nanosheets is 0.75%, the breakdown field strength reaches the maximum value of 639kV / mm; and after 6 days of ultraviolet irradiation, the breakdown field strength of pure polyimide film decreases to 402kV / mm; and the composite material of polyimide-based titanium dioxide coating with a mass fraction of 1% of titanium dioxide nanosheets has excellent radiation shielding performance, and the breakdown field strength only slightly decreases to 587kV / mm compared with the non-irradiated. This shows that with the addition of inorganic filler titanium dioxide nanosheets with good insulation and radiation resistance, the breakdown field strength of the composite material of polyimide-based titanium dioxide coating has not only been intrinsically improved, but also has a strong ultraviolet radiation shielding performance.

[0071] Figure 4 A graph showing the dielectric constant test results of the polyimide insulating composite material having a surface covered with an inorganic titanium dioxide layer in the present invention, wherein ■ represents a pure polyimide-based film, ● represents a titanium dioxide nanosheet having a mass fraction of 0.25%, ▲ represents a titanium dioxide nanosheet having a mass fraction of 0.5%, ▼ represents a titanium dioxide nanosheet having a mass fraction of 0.75%, and ◆ represents a titanium dioxide nanosheet having a mass fraction of 1%.

[0072] like Figure 4 As shown, at a frequency of 100 Hz, with the increase of the mass fraction of titanium dioxide nanosheets, the dielectric constant shows an increasing trend; when the mass fraction of titanium dioxide nanosheets is 0.75%, the dielectric constant reaches a maximum of 3.85.

[0073] Figure 5A graph showing the dielectric loss test results of the polyimide insulating composite material having a surface-covered titanium dioxide inorganic layer in the present invention, wherein ■ represents a pure polyimide-based film, ● represents a titanium dioxide nanosheet having a mass fraction of 0.25%, ▲ represents a titanium dioxide nanosheet having a mass fraction of 0.5%, ▼ represents a titanium dioxide nanosheet having a mass fraction of 0.75%, and ◆ represents a titanium dioxide nanosheet having a mass fraction of 1%.

[0074] like Figure 5 As shown in the figure, the dielectric loss tends to decrease with the increase of the mass fraction of titanium dioxide nanosheets. In pure polyimide, charges are easily accumulated inside the material to form charge traps, which leads to increased dielectric loss. The added TiO2 nanosheets have good conductivity and charge dispersion ability, which can effectively capture and disperse charges, reduce the formation of charge traps, and thus reduce dielectric loss.

[0075] Figure 6 A graph showing the Fourier transform infrared spectrum characterization results of the polyimide insulating composite material having a surface-covered titanium dioxide inorganic layer in the present invention, wherein 000 represents a pure polyimide-based film, 2-1 represents a titanium dioxide nanosheet with a mass fraction of 0.25%, 2-2 represents a titanium dioxide nanosheet with a mass fraction of 0.5%, 2-3 represents a titanium dioxide nanosheet with a mass fraction of 0.75%, and 2-4 represents a titanium dioxide nanosheet with a mass fraction of 1%.

[0076] like Figure 6 As shown in the figure, by comparing the infrared absorption peak positions of composite materials with different mass fractions of titanium dioxide nanosheets as polyimide-based coatings, it was found that the increase in the content of titanium dioxide nanosheets did not lead to a significant change in the characteristic peaks of the composite film, among which the film had a peak at 725 cm -1 、1100cm -1 、1230cm -1 、1367cm -1 、1720cm -1 and 1780cm -1 Obvious absorption peaks appeared at the same wave number positions, which corresponded to the C=O bending vibration in the imide ring, the symmetric and asymmetric stretching vibration of COC, the CN stretching vibration, and the symmetric and asymmetric stretching vibration of the C=O bond, indicating that the introduction of titanium dioxide nanosheets did not change the polyimide matrix itself. However, when the intensity of the above characteristic peaks was further compared, it was found that many characteristic peaks showed lower intensities when the content of titanium dioxide nanosheets increased, indicating that the addition of titanium dioxide nanosheets may have weakened the effectiveness of these chemical bonds to a certain extent, which may be closely related to the presence of stretching vibration peaks such as Ti-O in titanium dioxide nanosheets.

[0077] Figure 7A graph showing the tensile test results of the polyimide insulating composite material having a surface-covered titanium dioxide inorganic layer in the present invention, wherein 000 represents a pure polyimide-based film, 2-1 represents a titanium dioxide nanosheet with a mass fraction of 0.25%, 2-2 represents a titanium dioxide nanosheet with a mass fraction of 0.5%, 2-3 represents a titanium dioxide nanosheet with a mass fraction of 0.75%, and 2-4 represents a titanium dioxide nanosheet with a mass fraction of 1%.

[0078] like Figure 7 As shown in the figure, by comparing the polyimide insulating composite materials coated with different mass fractions of titanium dioxide on the surface and the pure polyimide matrix, it was found that the addition of titanium dioxide nanosheets reduced the tensile strength of the composite materials, while when the mass fraction of titanium dioxide nanosheets was 1%, the effect on the tensile properties was minimal. The tensile strength of the composite materials with titanium dioxide nanosheets as polyimide coating was as low as 88 MPa and as high as 121 MPa. This is because the modulus of the TiO2 nanosheets and the polyimide matrix is ​​quite different, and the stress is not evenly transmitted at the interface, which can easily lead to local stress concentration and reduce the tensile properties of the material.

Claims

1. A method for preparing a polyimide insulating composite material having a surface coated with an inorganic titanium dioxide layer and resistant to ultraviolet radiation, characterized in that The preparation method is carried out according to the following steps: Step S1, preparing a polyimide film: Adding polyimide powder to N-methylpyrrolidone solution, stirring thoroughly and evacuating overnight to obtain a mixed solution a; pouring the mixed solution a onto a cleaned glass plate, coating it evenly with a scraper, and then drying and stripping the film to obtain a polyimide film; Step S2, preparing spinning solution: Adding titanium dioxide nanosheets to N-methylpyrrolidone solution, and performing ultrasonic dispersion to obtain a mixed solution b; then adding polyimide powder to the mixed solution b, stirring the mixed solution fully, and then standing the mixed solution to obtain a spinning solution c; The mass fraction of the titanium dioxide nanosheets in the polyimide powder in step S2 is 0.25%, 0.5%, 0.75% or 1%; Step S3, preparing a polyimide insulating composite material having a surface covered with an inorganic titanium dioxide layer: The polyimide film obtained in step S1 is cut and pasted on the surface of the high-speed receiver roller of the electrospinning device, and then the spinning solution c obtained in step S2 is evenly sprayed on the polyimide film using the electrospinning technology until both sides of the polyimide film are evenly sprayed with the spinning solution c; then the film is peeled off, placed in a flat-plate vulcanizer for hot pressing, and after the hot pressing is completed, placed in an oven for curing to obtain a polyimide insulating composite material with a surface covered with an inorganic layer of titanium dioxide.

2. The method for preparing a polyimide insulating composite material having a surface-coated titanium dioxide inorganic layer and resistant to ultraviolet radiation according to claim 1, characterized in that In step S1, the polyimide powder is added to the N-methylpyrrolidone solution, and stirred at a temperature of 60 to 65° C. and a rotation speed of 600 to 650 r / min for 10 to 12 hours.

3. The method for preparing a polyimide insulating composite material having a surface-coated titanium dioxide inorganic layer and resistant to ultraviolet radiation according to claim 1, characterized in that In step S2, polyimide powder is added to the mixed solution b, and the mixture is stirred continuously for 9 to 10 hours at a temperature of 80 to 85° C. and a rotation speed of 400 to 500 r / min using a magnetic stirrer.

4. The method for preparing a polyimide insulating composite material having a surface-coated titanium dioxide inorganic layer and resistant to ultraviolet radiation according to claim 1 or 2, characterized in that The ratio of the mass of the polyimide powder described in step S1 to the volume of the N-methylpyrrolidone solution is (1.8-2) g: (8-12) mL; the ratio of the mass of the polyimide powder described in step S2 to the volume of the N-methylpyrrolidone solution is (1.5-1.6) g: (4-6) mL.

5. The method for preparing a polyimide insulating composite material having a surface-coated titanium dioxide inorganic layer and resistant to ultraviolet radiation according to claim 1, characterized in that In step S1, the mixed solution a is poured onto a glass plate with a length of 5 to 6 cm and a width of 1.5 to 2.5 cm, and the scraper thickness is 14 to 16 μm.

6. The method for preparing a polyimide insulating composite material having a surface-coated titanium dioxide inorganic layer and resistant to ultraviolet radiation according to claim 1, characterized in that The drying conditions in step S1 are: first drying in an oven at 80-85° C. for 7-8 hours, and then continuing drying in a vacuum oven at 115-120° C. for 1-2 hours.

7. The method for preparing a polyimide insulating composite material having a surface-coated titanium dioxide inorganic layer and resistant to ultraviolet radiation according to claim 1, characterized in that In step S3, 5 mL of the spinning solution c in step S2 is first extracted with a syringe, and then the syringe is placed on the push column A of the electrospinning device, and then the electrospinning device is set: the push speed of the push column A is 1-1.2 mm / min, the left and right translation distances are both 8-12 mm, the speed of the high-speed receiver is 1800-2000 r / min, the humidity in the spinning machine is 20-25%, the temperature is 25-30°C, and the pressure is increased to 11-12V.

8. The method for preparing a polyimide insulating composite material having a surface coated with an inorganic titanium dioxide layer and resistant to ultraviolet radiation according to claim 1, characterized in that In step S3, the film is peeled off and placed in a flat vulcanizer for hot pressing at a temperature of 80 to 85° C. and a pressure of 12 to 15 MPa for 5 to 8 minutes.

9. The method for preparing a polyimide insulating composite material having a surface-coated titanium dioxide inorganic layer and resistant to ultraviolet radiation according to claim 1, characterized in that The curing conditions in step S3 are: first drying in a vacuum oven at 75-85° C. for 220-240 min, and then continuing drying in a vacuum oven at 115-125° C. for 180-200 min.

10. Use of a polyimide insulating composite material having a surface coated with an inorganic titanium dioxide layer and resistant to ultraviolet radiation, prepared by the method according to any one of claims 1 to 9, characterized in that The invention discloses an application of the polyimide insulating composite material with a surface coated with a titanium dioxide inorganic layer and resistant to ultraviolet radiation in the preparation of a spacecraft anti-ultraviolet radiation material.

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