Polyimide film with high vacuum surface flashover performance and preparation method and application thereof

Abstract

The invention discloses a polyimide film with high vacuum surface flashover performance and a preparation method and application thereof, and belongs to the technical field of preparation of high-voltage insulating materials. The diamine monomer and the dianhydride monomer used in the invention can effectively increase the cross sectional area of a polyimide molecular chain, inhibit charge transport of the material, and lay a foundation for improving the vacuum surface flashover performance of the insulating material; according to the polyimide film prepared by adopting the method provided by the invention, a deep trap can be introduced into a dielectric surface insulator, secondary electron emission and surface electric field distortion of a material are reduced, and then the vacuum surface flashover performance of the polyimide film is improved; the provided preparation method is simple in synthesis principle, required equipment is common equipment in the field, raw materials can be directly purchased, operability is high, and the preparation method is suitable for application and popularization.

Description

Technical Field

[0001] The invention relates to the technical field of high-voltage insulating material preparation, and in particular to a polyimide film with high vacuum surface flashover performance, a preparation method and application thereof. Background Art

[0002] Spacecraft solar cell arrays absorb solar energy and generate power to drive spacecraft in space to explore the universe. The main insulating material of solar cell arrays is polyimide film, which is prone to surface flashover in the space environment, causing serious failures of spacecraft and seriously hindering the exploration of space science. Recent studies have shown that the surface flashover problem of polyimide materials in spacecraft solar cell arrays is one of the main forms of spacecraft failure. Therefore, it is necessary to develop polyimide films with high vacuum surface flashover performance and study their preparation technology.

[0003] The surface insulation improvement technologies for vacuum surface flashover voltage mainly include: nano-modification, electric field optimization at the triple junction, surface coating, chemical intrinsic modification, etc. Among them, chemical intrinsic modification can directly change the molecular chain structure on the surface of polyimide film, thereby affecting the surface insulation performance of the material. The polyimide molecular chain is linear and is synthesized by the condensation reaction of dianhydride monomers and diamine monomers. Finding a suitable diamine and dianhydride monomer structure can effectively increase the cross-sectional area of ​​the polyimide molecular chain, prevent the charge transport of carriers in polyimide, form deep surface traps and hinder secondary electron emission, which is expected to improve the surface flashover voltage in vacuum.

[0004] Therefore, it is of great significance to find suitable diamine and dianhydride monomers, synthesize polyimide structures with deep trap energy levels, and effectively improve the vacuum surface flashover voltage of polyimide. Summary of the invention

[0005] The purpose of the present invention is to provide a polyimide film with high vacuum surface flashover performance and a preparation method and application thereof, so as to provide a new combination of diamine monomer and dianhydride monomer to prepare a polyimide film with deep trap energy levels, thereby effectively improving the vacuum surface flashover voltage of the polyimide.

[0006] To achieve the above-mentioned purpose, the present invention provides a polyimide film with high vacuum surface flashover performance. The material for preparing the polyimide film with high vacuum surface flashover performance includes a diamine monomer and a dianhydride monomer; the diamine monomer is 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and the dianhydride monomer is bisphenol A diether dianhydride.

[0007] Preferably, the molar ratio of diamine monomer:dianhydride monomer is 1:1.

[0008] A method for preparing the polyimide film with high vacuum surface flashover performance as described above comprises the following steps:

[0009] S1, dissolving a diamine monomer in a polar organic solvent, and stirring under a nitrogen atmosphere to obtain a diamine solution;

[0010] S2, adding the dianhydride monomer to the diamine solution prepared in step S1 in 4-6 portions and stirring to obtain a polyamic acid solution;

[0011] S3, vacuumizing the polyamic acid solution obtained in step S2, coating and drying.

[0012] Preferably, in step S1, the polar organic solvent is N,N-dimethylacetamide, and the stirring is performed at 24-26° C. and at a rate of 145-155 r / min for 15-25 minutes.

[0013] Preferably, in step S2, the dianhydride monomer is added to the diamine solution at intervals of 15-25 minutes each time.

[0014] Preferably, the stirring in step S2 is performed at a rate of 145-155 r / min for 6.5-7.5 hours.

[0015] Preferably, the vacuuming in step S3 is performed at a pressure of 5-15 Pa for 4.5-6.5 hours.

[0016] Preferably, the drying in step S3 is completed in an oven, the heating rate is 1.75-2.25°C / min, and the heating process is: 79-81°C constant temperature for 59.5-60.5min, 119-121°C constant temperature for 29.5-30.5min, 159-161°C constant temperature for 29.5-30.5min, 199-201°C constant temperature for 29.5-30.5min, 249-251°C constant temperature for 29.5-30.5min, 299-301°C constant temperature for 29.5-30.5min.

[0017] Preferably, in step S3, the coating speed is 1-3 mm / s, and the coating thickness is 0.149-0.151 mm.

[0018] An application of the polyimide film with high vacuum surface flashover performance as described above in insulating materials, wherein the polyimide film with high vacuum surface flashover performance is coated on the surface of the target material and then dried.

[0019] Therefore, the polyimide film with high vacuum surface flashover performance and its preparation method and application provided by the present invention have the following specific technical effects:

[0020] (1) The diamine monomer and dianhydride monomer used in the present invention can effectively increase the cross-sectional area of ​​the polyimide molecular chain, inhibit the charge transport of the material, and lay a foundation for improving the vacuum surface flashover performance of the insulating material;

[0021] (2) The polyimide film prepared by the method provided by the present invention can introduce deep traps into the dielectric surface insulator, reduce the secondary electron emission and surface electric field distortion of the material, and thus improve the vacuum surface flashover performance of the polyimide film;

[0022] (3) The preparation method provided by the present invention has a simple synthesis principle, the required equipment is commonly used in the field, the raw materials can be purchased directly, the operability is strong, and it is suitable for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0024] Figure 1 This is a flow chart for preparing a polyimide film provided by the present invention;

[0025] Figure 2 It is a schematic diagram of the chemical synthesis principle of the polyimide film of Example 1, Comparative Example 1 and Comparative Example 2 in the experimental test (I) of the present invention;

[0026] Figure 3 The optimized molecular monomer structure (a) and the statistical result of the cross-sectional area (b) of the polyimide film prepared in Example 1, Comparative Example 1 and Comparative Example 2 in the experimental test (II) of the present invention are shown in FIG.

[0027] Figure 4 It is the infrared spectra of the polyimide films prepared in Example 1, Comparative Example 1 and Comparative Example 2 in the experimental test (III) of the present invention;

[0028] Figure 5 The surface potential decay curve (a) and the trap energy level density distribution diagram (b) of the polyimide film prepared in Example 1, Comparative Example 1 and Comparative Example 2 in the experimental test (IV) of the present invention;

[0029] Figure 6 It is the vacuum DC surface flashover voltage of the polyimide film prepared in Example 1, Comparative Example 1 and Comparative Example 2 in the experimental test (V) of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0031] In order to make the purpose, technical scheme and advantages of the present application clearer, more thorough and more complete, the technical scheme of the present invention is clearly and completely described below through the accompanying drawings and examples. The following detailed descriptions are all descriptions of the embodiments, and are intended to provide further detailed descriptions of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present application belongs.

[0032] The polyimide film provided by the present invention uses bisphenol A diether dianhydride (BPADA) as the dianhydride monomer and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) as the diamine monomer. The dianhydride monomer is added to the polar organic solvent solution of the diamine monomer in multiple times, stirred for a certain period of time under certain conditions, and then vacuumed, coated, and dried. The flow chart is as follows Figure 1 shown.

[0033] The instruments, equipment, reagents and materials used in the examples were all obtained through commercial channels.

[0034] Example 1

[0035] The polyimide film was prepared using BPADA as a dianhydride monomer and BAPP as a diamine monomer. The specific steps are as follows:

[0036] 1) Dissolve diamine monomer (BAPP) (2.39 g) in 50 mL of polar organic solvent N,N-dimethylacetamide (DMAC), and stir at 25° C. for 20 minutes at a stirring rate of 150 r / min under nitrogen protection to obtain a diamine solution.

[0037] 2) dianhydride monomer (BPADA) (3.03 g) was added to the diamine solution prepared in step 1) in 5 portions, once every 20 minutes, and stirred for 7 hours at a stirring rate of 150 r / min to obtain a polyamic acid solution.

[0038] 3) The polyamic acid solution obtained in step 2) was treated at a pressure of 10 Pa for 5 hours and then vacuumed.

[0039] 4) The polyamic acid solution after vacuum treatment in step 3) is coated on a glass plate at a speed of 2 mm / s with a coating thickness of 0.150 mm to obtain a coated glass plate.

[0040] 5) The coated glass plate prepared in step 4) is heated in an oven at a heating rate of 2°C / min. The heating process is as follows: 80°C for 60 min, 120°C for 30 min, 160°C for 30 min, 200°C for 30 min, 250°C for 30 min, and 300°C for 30 min.

[0041] 6) Soaking the coated glass plate after the oven treatment in step 5) in deionized water for 30 minutes to remove the film, thereby obtaining a polyimide film.

[0042] Example 2

[0043] The polyimide film was prepared using BPADA as a dianhydride monomer and BAPP as a diamine monomer. The specific steps are as follows:

[0044] 1) Dissolve the diamine monomer BAPP (2.39 g) in 50 mL of polar organic solvent DMAC, and stir at 24° C. for 15 minutes at a stirring rate of 145 r / min under nitrogen protection to obtain a diamine solution.

[0045] 2) BPADA (3.03 g), a dianhydride monomer, was added into the diamine solution obtained in step 1) in 4 portions, once every 15 minutes, and stirred for 6.5 hours at a stirring rate of 145 r / min to obtain a polyamic acid solution.

[0046] 3) The polyamic acid solution obtained in step 2) was treated at a pressure of 5 Pa for 4.5 hours and then vacuumed.

[0047] 4) The polyamic acid solution after vacuum treatment in step 3) is coated on a glass plate at a speed of 1 mm / s with a coating thickness of 0.149 mm to obtain a coated glass plate.

[0048] 5) The coated glass plate prepared in step 4) is heated in an oven at a heating rate of 1.75°C / min. The heating process is as follows: 79°C for 59.5 min, 119°C for 29.5 min, 159°C for 29.5 min, 199°C for 29.5 min, 249°C for 29.5 min, and 299°C for 29.5 min.

[0049] 6) Soaking the coated glass plate after the oven treatment in step 5) in deionized water for 25 minutes to remove the film, thereby obtaining a polyimide film.

[0050] Example 3

[0051] The polyimide film was prepared using BPADA as a dianhydride monomer and BAPP as a diamine monomer. The specific steps are as follows:

[0052] 1) Dissolve the diamine monomer BAPP (2.39 g) in 50 mL of polar organic solvent DMAC, and stir at 26° C. for 25 minutes at a stirring rate of 155 r / min under nitrogen protection to obtain a diamine solution.

[0053] 2) BPADA (3.03 g), a dianhydride monomer, was added into the diamine solution prepared in step 1) in 6 portions, once every 25 minutes, and stirred for 7.5 hours at a stirring rate of 155 r / min to obtain a polyamic acid solution.

[0054] 3) The polyamic acid solution obtained in step 2) was treated at a pressure of 15 Pa for 5.5 hours and then vacuumed.

[0055] 4) The polyamic acid solution after vacuum treatment in step 3) is coated on a glass plate at a speed of 3 mm / s with a coating thickness of 0.151 mm to obtain a coated glass plate.

[0056] 5) The coated glass plate prepared in step 4) is heated in an oven at a heating rate of 2.25°C / min. The heating process is as follows: 81°C for 60.5 min, 121°C for 30.5 min, 161°C for 30.5 min, 201°C for 30.5 min, 251°C for 30.5 min, and 301°C for 30.5 min.

[0057] 6) Soaking the coated glass plate treated in the oven in step 5) in deionized water for 35 minutes to remove the film and obtain a polyimide film.

[0058] Comparative Example 1

[0059] The polyimide film was prepared using BPADA as a dianhydride monomer and 4,4'-diaminodiphenyl ether (ODA) as a diamine monomer. The specific steps are as follows:

[0060] 1) Dissolve the diamine monomer ODA (3.47 g) in 50 mL of polar organic solvent DMAC, and stir at 25° C. for 20 minutes at a stirring rate of 150 r / min under nitrogen protection to obtain a diamine solution.

[0061] 2) BPADA (9.02 g) was added into the diamine solution prepared in step 1) in 5 portions, once every 20 minutes, and stirred for 7 hours at a stirring rate of 150 r / min to obtain a polyamic acid solution.

[0062] 3) The polyamic acid solution obtained in step 2) was treated at a pressure of 10 Pa for 5 hours and then vacuumed.

[0063] 4) The polyamic acid solution after vacuum treatment in step 3) is coated on a glass plate at a speed of 2 mm / s with a coating thickness of 0.150 mm to obtain a coated glass plate.

[0064] 5) The coated glass plate prepared in step 4) is heated in an oven at a heating rate of 2°C / min. The heating process is as follows: 80°C for 60 min, 120°C for 30 min, 160°C for 30 min, 200°C for 30 min, 250°C for 30 min, and 300°C for 30 min.

[0065] 6) Soaking the coated glass plate after the oven treatment in step 5) in deionized water for 30 minutes to remove the film, thereby obtaining a polyimide film.

[0066] Comparative Example 2

[0067] The polyimide film is prepared using pyromellitic anhydride (PMDA) as the dianhydride monomer and ODA as the diamine monomer. The specific steps are as follows:

[0068] 1) Dissolve the diamine monomer ODA (4.40 g) in 50 mL of polar organic solvent DMAC, and stir at 25° C. for 20 minutes at a stirring rate of 150 r / min under nitrogen protection to obtain a diamine solution.

[0069] 2) PMDA (4.79 g) was added into the diamine solution prepared in step 1) in 5 portions, once every 20 minutes, and stirred for 7 hours at a stirring rate of 150 r / min to obtain a polyamic acid solution.

[0070] 3) The polyamic acid solution obtained in step 2) was treated at a pressure of 10 Pa for 5 hours and then vacuumed.

[0071] 4) The polyamic acid solution after vacuum treatment in step 3) is coated on a glass plate at a speed of 2 mm / s with a coating thickness of 0.150 mm to obtain a coated glass plate.

[0072] 5) The coated glass plate prepared in step 4) is heated in an oven at a heating rate of 2°C / min. The heating process is as follows: 80°C for 60 min, 120°C for 30 min, 160°C for 30 min, 200°C for 30 min, 250°C for 30 min, and 300°C for 30 min.

[0073] 6) Soaking the coated glass plate after the oven treatment in step 5) in deionized water for 30 minutes to remove the film, thereby obtaining a polyimide film.

[0074] Experimental Testing (one)

[0076] Figure 2 It is a chemical synthesis principle diagram of Example 1, Comparative Example 1 and Comparative Example 2. It can be seen from the figure that the dianhydride monomer PMDA and diamine monomer ODA, BPADA and BAPP monomers used in the preparation of polyimide film in the prior art (Comparative Example 2) contain a benzene-isopropyl-benzene structure. (two)

[0078] Density functional theory (DFT) of Gaussian quantum chemical simulation software was used to perform geometry optimization on the polyimide monomers prepared in Example 1, Comparative Example 1 and Comparative Example 2, and the functional used was B3LYP with a basis set of 6-311G (d, p). Multiwfn software was used to statistically analyze the length, width, height and chain length of the polyimide monomer unit cell, and the cross-sectional area of ​​the polyimide monomer was length × width × height / chain length.

[0079] The results are as follows Figure 3 As shown in part (a), when the benzene-isopropyl-benzene structure is added to the dianhydride and diamine monomers, the dihedral angle between the benzene rings inside the molecular chain will increase significantly, and the molecular chain inside the material will be easier to fold, resulting in an increase in the cross-sectional area of ​​the polyimide. Figure 3 From part (b), it can be seen that when the dianhydride and diamine monomers are BPABA and BAPP, the equivalent area of ​​the material increases to Significantly larger than the polyimide prepared by PMDA+ODA in the prior art (three)

[0081] The infrared spectra of the polyimide prepared in Example 1, Comparative Example 1 and Comparative Example 2 were measured by Fourier spectral transmission method. The test used a wave number of 4000-400 cm -1 , scanning interval 1cm -1 , the results are as follows Figure 4 As shown. Figure 4 It can be seen that with the introduction of BPADA and BAPP monomers, the methyl content inside the material gradually increased, indicating that BPADA and BAPP were successfully condensed during preparation, and the prepared polyimide film can be used for subsequent tests. (Four)

[0083] The surface potential decay test was used to characterize the trap characteristics inside the polyimide film materials prepared in Example 1, Comparative Example 1 and Comparative Example 2, with a needle voltage of -4 kV, a gate voltage of -2 kV, and a charging time of 15 min. The surface potential test device was Trek 341B, the measurement time was 10000 s, the sampling time was 1 s, and the experimental test temperature was 15°C.

[0084] Figure 5 Part (a) shows the surface potential decay diagram of the insulator treated with ozone at different times. It can be seen that with the increase of benzene-isopropyl-benzene structure in the polyimide molecular chain, the surface potential decay rate of the material decreases significantly. Figure 5 Part (b) is the trap energy level-density distribution diagram of the polyimide composite material. It can be seen from the figure that with the increase of benzene-isopropyl-benzene structure, the overall energy level peak of the material shifts to the right, indicating that the deep trap energy level of the polyimide film increases. Therefore, after the introduction of BPADA and BAPP, the trap energy level of the polyimide film increases significantly. (five)

[0086] The vacuum DC surface flashover voltage of the polyimide film prepared in Example 1, Comparative Example 1 and Comparative Example 2 was measured using finger-type electrodes. The electrode spacing was 4 mm, the diameter of the finger-type electrode end was 20 mm, and the vacuum pressure was 1×10 -3 Pa. The experiment uses the continuous voltage boost method to apply voltage, and the voltage growth rate is 1kV / s. 20 groups of vacuum surface flashover voltages are measured for each sample, and the experimental results are shown in Table 1.

[0087] Table 1 Vacuum surface flashover voltage of polyimide film (unit kV)

[0088]

[0089]

[0090] Figure 6 The vacuum DC surface flashover voltage of the polyimide film prepared in Example 1, Comparative Example 1 and Comparative Example 2. It can be seen from the figure that with the introduction of BPADA and BAPP, the surface flashover voltage continues to increase. The surface flashover voltage of the polyimide film prepared in Example 1 reaches 24.70 kV, which is 17.33% higher than the surface flashover voltage of the polyimide prepared in Comparative Examples 1 and 2.

[0091] Therefore, the diamine monomer and dianhydride monomer used in the present invention can effectively increase the cross-sectional area of ​​the polyimide molecular chain, inhibit the charge transport of the material, and lay a foundation for improving the vacuum surface flashover performance of the insulating material; the polyimide film prepared by the method provided by the present invention can introduce deep traps into the dielectric surface insulator, reduce the secondary electron emission and surface electric field distortion of the material, and thus improve the vacuum surface flashover performance of the polyimide film; the preparation method provided has a simple synthesis principle, the required equipment is commonly used equipment in this field, the raw materials can be purchased directly, the operability is strong, and it is suitable for popularization and application.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A polyimide film with high vacuum surface flashover performance, characterized in that: The materials for preparing the polyimide film with high vacuum surface flashover performance include diamine monomer and dianhydride monomer; the diamine monomer is 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and the dianhydride monomer is bisphenol A diether dianhydride.

2. The polyimide film with high vacuum surface flashover performance according to claim 1, characterized in that: The molar ratio of diamine monomer:dianhydride monomer is 1:

1.

3. A method for preparing a polyimide film with high vacuum surface flashover performance as claimed in claim 1 or 2, characterized in that: Here are the steps: S1, dissolving a diamine monomer in a polar organic solvent, and stirring under a nitrogen atmosphere to obtain a diamine solution; S2, adding the dianhydride monomer to the diamine solution prepared in step S1 in 4-6 portions and stirring to obtain a polyamic acid solution; S3, vacuumizing the polyamic acid solution obtained in step S2, coating and drying.

4. The method for preparing a polyimide film with high vacuum surface flashover performance according to claim 3, characterized in that: In the step S1, the polar organic solvent is N,N-dimethylacetamide, and the stirring is performed at 24-26° C. and a stirring rate of 145-155 r / min for 15-25 minutes.

5. The method for preparing a polyimide film with high vacuum surface flashover performance according to claim 3, characterized in that: In step S2, the dianhydride monomer is added to the diamine solution at intervals of 15-25 minutes each time.

6. The method for preparing a polyimide film with high vacuum surface flashover performance according to claim 3, characterized in that: The stirring in step S2 is performed at a rate of 145-155 r / min for 6.5-7.5 hours.

7. The method for preparing a polyimide film with high vacuum surface flashover performance according to claim 3, characterized in that: The vacuuming in step S3 is performed at a pressure of 5-15 Pa for 4.5-6.5 hours.

8. The method for preparing a polyimide film with high vacuum surface flashover performance according to claim 3, characterized in that: In step S3, the drying is completed in an oven with a heating rate of 1.75-2.25°C / min, and the heating process is: constant temperature of 79-81°C for 59.5-60.5min, constant temperature of 119-121°C for 29.5-30.5min, constant temperature of 159-161°C for 29.5-30.5min, constant temperature of 199-201°C for 29.5-30.5min, constant temperature of 249-251°C for 29.5-30.5min, and constant temperature of 299-301°C for 29.5-30.5min.

9. The method for preparing a polyimide film with high vacuum surface flashover performance according to claim 3, characterized in that: In the step S3, the coating speed is 1-3 mm / s, and the coating thickness is 0.149-0.151 mm.

10. Use of the polyimide film with high vacuum surface flashover performance as claimed in claim 1 or 2 in insulating materials, characterized in that: The polyimide film with high vacuum surface flashover performance is coated on the surface of the target material and then dried.

Images