Corona-resistant ceramic composite insulating material as well as preparation method and application thereof

Abstract

The invention discloses a corona-resistant ceramic composite insulating material as well as a preparation method and application thereof, and belongs to the technical field of high-performance composite insulating materials and preparation thereof. The problems that an existing insulating material is insufficient in corona resistance and difficult in powder doping are solved. BMI-DBA is used as a functional carrier to load ADP powder to obtain a BD-A system, the BD-A system is further compounded with PI by adopting a cospinning process, and after imidization treatment, the composite insulating material with remarkable corona resistance is obtained. Through PI and BD-A system co-spinning and imidization treatment and in combination with an ADP ceramization process, the corona resistance of the composite insulating material is remarkably improved. Experimental results show that the corona resistance time of the composite material reaches more than 650 hours, and is improved by more than 6500 times compared with that of a pure PI insulation paper material (about 0.1 hour).

Description

Technical Field

[0001] The invention relates to a corona-resistant ceramic composite insulating material and a preparation method and application thereof, belonging to the technical field of high-performance composite insulating materials and preparation thereof. Background Art

[0002] In high-voltage electrical equipment, the corona resistance of insulating materials directly determines the service life of the equipment. Although traditional polyimide (PI) materials have excellent heat resistance and mechanical strength, their corona resistance life is relatively short (the corona resistance time of pure PI insulating paper is only about 0.1h), which makes it difficult to meet the needs of high-voltage platforms above 35kV. Existing modification methods such as intrinsic modification, multi-layer structure or addition of nanofillers can partially improve the performance, but there are still problems such as complex synthesis, poor interface bonding, and uneven filler dispersion. For example, the multi-layer structure needs to solve the problem of interlayer bonding, and nanofillers are easy to agglomerate to form defects, which accelerates local discharge. In addition, when the traditional polyimide system is doped with large component powders, it is difficult to disperse due to the rigidity of the molecular structure, which limits the application of ceramic technology. Summary of the Invention

[0003] In order to solve the problems of insufficient corona resistance of existing insulating materials and difficulty in powder doping, the present invention provides a corona-resistant ceramic composite insulating material and a preparation method and application thereof.

[0004] The technical solution of the present invention:

[0005] One of the objects of the present invention is to provide a method for preparing a corona-resistant ceramic composite insulating material, the method comprising the following steps:

[0006] (1) Dissolve ODA (diaminodiphenyl ether) in DMAc (N,N-dimethylacetamide) in an ice-water bath, add PMDA (pyromellitic dianhydride) in batches, and react at 0-5°C for 1.5-2.5 hours to obtain glue solution I;

[0007] (2) Mix BMI (N,N'-(4,4'-methylenediphenyl)bismaleimide), DBA (diethylene glycol butyl ether acetate) and ADP (aluminum dihydrogen phosphate), add DMAA (N,N-dimethylacrylamide), and stir in an oil bath at 130-140°C for 30-40 minutes to obtain glue II;

[0008] (3) introducing glue solution I and glue solution II into the needle tube respectively, and preparing the composite membrane by electrospinning process;

[0009] (4) The composite film obtained in (3) is subjected to a stepwise temperature-raising imidization treatment to obtain a composite insulating material.

[0010] It is further defined that the mass ratio of ODA, PMDA and DMAc in (1) is (1.8-2.0):(2.0-2.1):(18-22).

[0011] It is further defined that the mass ratio of BMI, DBA, ADP and DMAA in (2) is (3-5):(2-4):(6-12):(1-3).

[0012] It is further defined that the mass ratio of BMI to DBA in (2) is (1.2-1.5):1.

[0013] It is further defined that the proportion of ADP in the glue solution II of (2) is 50 wt %, and the particle size of the ADP powder is 100-200 μm.

[0014] It is further defined that the electrospinning process parameters in (3) are: positive pressure 14-18 kV, negative pressure -3.5 kV, receiving distance 20-25 cm, propulsion speed 0.08-0.10 mm / min, and time 6-7 h.

[0015] It is further defined that the humidity of the electrospinning environment in (3) is 20-25%.

[0016] It is further defined that in (3), before electrospinning, the adhesive liquid I and the adhesive liquid II are degassed, the degassed pressure is -0.09 to -0.10 MPa, and the time is 60 to 80 min; and in the electrospinning process, the adhesive liquid I is spun first, and when the masses of the adhesive liquid I and the adhesive liquid II are the same, the electrospinning of the adhesive liquid I and the adhesive liquid II is carried out simultaneously.

[0017] It is further defined that the electrospinning receiving substrate in (3) is an aluminum foil with a thickness of 0.05 to 0.1 mm.

[0018] It is further defined that the mass ratio of the adhesive solution I to the adhesive solution II in the composite film obtained by (3) is (1-5):1.

[0019] It is further defined that the step-by-step imidization treatment process (4) is as follows: keeping at 80-100°C for 15-25 min, heating to 120-140°C for 15-25 min, heating to 160-180°C for 15-25 min, heating to 200-220°C for 15-25 min, heating to 250-270°C for 50-70 min, heating to 300-320°C for 50-70 min, heating to 340-360°C for 50-70 min, and the heating rate in each stage is 3-5°C / min.

[0020] A second object of the present invention is to provide a corona-resistant ceramic composite insulating material prepared by the above method.

[0021] A third object of the present invention is to provide an application of the above-mentioned corona-resistant ceramic composite insulating material, specifically for the preparation of high-voltage electrical equipment.

[0022] Beneficial effects of the present invention:

[0023] The present invention utilizes BMI-DBA as a functional carrier to load ADP powder to obtain a BD-A system, and further adopts a co-spinning process to compound it with PI, and after imidization treatment, a composite insulating material with significant corona resistance is obtained. By co-spinning and imidization treatment of PI and BD-A system, combined with ADP ceramic process, the corona resistance of the composite insulating material is significantly improved. Experimental results show that the corona resistance time of the composite material is more than 650h, which is more than 6500 times higher than that of pure PI material (about 0.1h). This performance improvement is mainly attributed to the formation of a dense phosphate ceramic layer by ADP under the corona thermal effect, which effectively suppresses the erosion of the material by corona discharge. At the same time, by optimizing the glue system and process parameters, the uniform dispersion of ADP powder and the stability of the material structure are ensured. Specifically, by using BMI-DBA as a functional carrier to load ADP powder, the addition amount of ADP powder can be significantly increased, avoiding the powder agglomeration problem caused by molecular chain rigidity in the traditional two-step synthesis PI process. At the same time, the use of an electrospinning process instead of conventional film-laying methods not only improves the uniformity and density of the material structure, but also enhances interfacial compatibility through a three-dimensional fiber network. This overcomes the performance defects caused by interlayer stress concentration in the film-laying process, effectively solving the problems of poor interfacial bonding and uneven dispersion of powder fillers. Furthermore, the composite membrane produced using the spinning process provides a structural foundation for the efficient formation of the ceramic layer, ensuring the long-term stability of the composite material in high-voltage environments, providing a high-performance insulation solution for high-voltage electrical equipment and promising broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FT-IR comparison spectra of PAA glue and PI prepared in Comparative Example 1;

[0025] Figure 2 Thermogravimetric analysis test charts of the composite insulation materials and BD-A glue prepared in Examples 1 to 5;

[0026] Figure 3 Differential thermogravimetric curve analysis diagram of the composite insulation material and BD-A glue prepared in Examples 1 to 5;

[0027] Figure 4 This is the SEM photo of the PI prepared in Comparative Example 1;

[0028] Figure 5 The SEM photograph and energy spectrum of the composite insulation material PI / 100wt% BD-A prepared in Example 5 after the corona resistance test;

[0029] Figure 6 This is the macroscopic state of the colloid solution of PAA loaded with 25 wt% ADP powder synthesized by the two-step method in Comparative Example 2. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0033] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0034] Example 1

[0035] Step 1, preparation of PAA glue:

[0036] In an ice-water bath, 1.88 g of ODA was dissolved in 20 mL of DMAc, and 2.05 g of PMDA was added in four portions. After stirring for 2 h, the mixture was vacuum degassed at 0.09 MPa for 120 min to obtain a PAA gel solution.

[0037] Step 2, preparation of BD-A glue:

[0038] 30 g of BMI and 20 g of DBA were mixed, 60 g of ADP powder with a particle size of 100-200 μm was added, and 10 g of DMAA was added. The mixture was stirred in an oil bath at 135° C. for 0.5 h to obtain BD-A glue.

[0039] Step 3, electrospinning:

[0040] The above-mentioned PAA glue and BD-A glue were respectively introduced into the needle tube at a mass ratio of 5:1, inserted into the spinning device, set the positive pressure to 15kV, the negative pressure to -3.5kV, the receiving distance to 24cm, the propulsion speed to 0.09mm / min, and the humidity to 20% for continuous spinning for 7h. In the electrospinning process, the PAA glue was electrospun first. When the mass of the PAA glue and the BD-A glue was the same, the PAA glue and the BD-A glue were electrospun simultaneously.

[0041] Step 4, imidization treatment:

[0042] The temperature was increased at a rate of 5°C / min, kept at 80°C for 20 min, heated to 120°C for 20 min, heated to 160°C for 20 min, heated to 200°C for 20 min, heated to 250°C for 60 min, heated to 300°C for 60 min, heated to 350°C for 60 min, and a composite insulating material with a thickness of 38 μm was obtained, which was named PI / 20wt% BD-A.

[0043] Example 2

[0044] The difference between this embodiment and Example 1 is that in step 3, the mass ratio of PAA glue to BD-A glue is 5:2, and the remaining process steps and parameter settings are the same as those in Example 1, resulting in a composite insulating material with a thickness of 43 μm, named PI / 40wt% BD-A.

[0045] Example 3

[0046] The difference between this embodiment and Example 1 is that in step 3, the mass ratio of PAA glue to BD-A glue is 5:3, and the remaining process steps and parameter settings are the same as those in Example 1, resulting in a composite insulating material with a thickness of 47 μm, named PI / 60wt% BD-A.

[0047] Example 4

[0048] The difference between this embodiment and Example 1 is that in step 3, the mass ratio of PAA glue to BD-A glue is 5:4, and the remaining process steps and parameter settings are the same as those in Example 1, resulting in a composite insulating material with a thickness of 51 μm, named PI / 80wt% BD-A.

[0049] Example 5

[0050] The difference between this embodiment and Example 1 is that in step 3, the mass ratio of PAA glue to BD-A glue is 1:1, and the remaining process steps and parameter settings are the same as those in Example 1, resulting in a composite insulating material with a thickness of 53 μm, named PI / 100 wt% BD-A.

[0051] Example 6

[0052] The difference between this embodiment and Example 1 is as follows: Step 2, the preparation of BD-A glue is as follows: 150g BMI and 100g DBA are mixed, 33.3g ADP powder with a particle size of 100-200μm (accounting for 10% of the total mass of the glue) is added, 50g DMAA is added, and the mixture is stirred in an oil bath at 135°C for 0.5h to obtain BD-A glue; the remaining process steps and parameter settings are the same as in Example 1, and a composite insulating material with a thickness of 46μm is obtained.

[0053] Comparative Example 1

[0054] The difference between this comparative example and Example 1 is that the amount of BD-A glue in step 3 is 0, and the other process steps and parameter settings are the same as those in Example 1. A composite insulating material with a thickness of 37 μm is obtained, which is named PI. The SEM photo of the obtained PI is shown in FIG. Figure 4 shown.

[0055] Comparative Example 2

[0056] 5.8 g of ADP powder with a particle size of 100-200 μm was added to 20 mL of DMAc and ultrasonically dispersed for 1 h. 1.88 g of ODA was added in an ice-water bath, and 2.05 g of PMDA was added in 4 portions with stirring to obtain the following: Figure 6 This shows that the traditional two-step process for synthesizing polyimide cannot produce a gel solution with an ADP powder content of 25 wt% that can be used for electrospinning.

[0057] Effect Examples

[0058] (1) Figure 1 Comparative FT-IR spectra of the PAA glue prepared in Comparative Example 1 and PI clearly show that the carbonyl (C═O) stretching vibration peak of PAA, located around 1700 cm⁻¹, is significantly weakened or absent in the PI spectrum, indicating that the carbonyl groups have largely participated in the reaction. Simultaneously, new absorption peaks appear in the PI spectrum in the 1360-1400 cm⁻¹ and 1650-1700 cm⁻¹ ranges, corresponding to the stretching vibration of the imino (C═N) group, further confirming the conversion of PAA to PI. Furthermore, a characteristic CH bending vibration peak in the 720-780 cm⁻¹ range is observed in the PI spectrum, a unique structural characteristic of PI. This demonstrates that the PIs in the aforementioned examples, using the same imidization treatment conditions as in Comparative Example 1, have been completely imidized.

[0059] (2) Figure 2Thermogravimetric analysis of the composite insulation materials and BD-A adhesive prepared in Examples 1-5 clearly shows that the thermal decomposition of the composite insulation material co-spun with PI and BD-A is slower, with the first drop in the curve occurring around 450°C and the second significant drop occurring near 600°C. In contrast, the BD-A adhesive not co-spun with PI shows a clear downward trend around 400°C. This indicates that the thermal decomposition temperature of BD-A is lower than that of the composite insulation material co-spun with PI and BD-A.

[0060] (3) is the differential thermogravimetric analysis diagram of the composite insulation material and BD-A glue prepared in Examples 1 to 5, Figure 3 It can be seen that in the low temperature region (<200°C), all materials show a weak weight loss peak caused by the desorption of adsorbed water or solvent molecules, among which ADP may show a more significant initial weight loss due to its higher hygroscopicity. In the medium temperature region (200-400°C), the CN bond breakage of the BMI resin in the BD-A system and the thermal decomposition of the ADP phosphate group lead to synergistic decomposition, forming multiple shoulder peaks, while PI shows a lower weight loss rate (2.5% min-1) due to the rigidity of the aromatic ring structure, which inhibits the volatilization of low molecules. In the high temperature region (600-800°C), the oxidation of the carbon skeleton and the aromatization of PI lead to the appearance of a sharp single peak, which is significantly higher than that of BD-A and ADP, indicating that its cross-linking density and aromatization dominate its carbonization ability.

[0061] (4) The composite insulating material PI / 100wt% BD-A prepared in Example 5 was subjected to a corona resistance test. The results showed that under the test conditions of 20kHz pulse square wave and 2kV peak-to-peak voltage, its corona resistance time exceeded 650h. The SEM photo of the composite insulating material PI / 100wt% BD-A after the corona resistance test is shown in FIG. Figure 5 As shown, the SEM photos show that a continuous and dense ceramic layer is formed on the surface of the insulating paper, and the P and Al elements in the ceramic layer are evenly distributed.

[0062] The composite insulating material PI / 20wt% BD-A prepared in Example 1 was subjected to a corona resistance test. The results showed that under the test conditions of 20kHz pulse square wave and 2kV peak-to-peak voltage, the corona resistance time was 210h.

[0063] The composite insulating material prepared in Example 6 was subjected to a corona resistance test. The results showed that under the test conditions of a 20 kHz pulse square wave and a 2 kV peak-to-peak voltage, the corona resistance time exceeded 105 h.

[0064] The above description is merely a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above. Some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a corona-resistant ceramic composite insulating material, characterized in that: include: (1) Dissolve ODA in DMAc in an ice-water bath, add PMDA in batches, and react at 0-5°C for 1.5-2.5 h to obtain gel solution I; (2) BMI, DBA, and ADP were mixed, DMAA was added, and the mixture was stirred in an oil bath at 130-140°C for 30-40 min to obtain gel solution II; (3) introducing glue solution I and glue solution II into the needle tube respectively, and preparing the composite membrane by electrospinning process; (4) The composite film obtained in (3) is subjected to a stepwise temperature-raising imidization treatment to obtain a composite insulating material.

2. The preparation method according to claim 1, characterized in that The mass ratio of ODA, PMDA and DMAc in (1) is (1.8~2.0):(2.0~2.1):(18~22).

3. The preparation method according to claim 1, characterized in that The mass ratios of BMI, DBA, ADP and DMAA in (2) are (3-5):(2-4):(6-12):(1-3).

4. The preparation method according to claim 3, characterized in that (2) The mass ratio of BMI and DBA is (1.2~1.5):

1.

5. The preparation method according to claim 3, characterized in that The proportion of ADP in the glue solution II of (2) is 50wt%, and the particle size of ADP powder is 100-200μm.

6. The preparation method according to claim 1, characterized in that (3) The electrospinning process parameters are: positive pressure 14-18 kV, negative pressure -3.5 kV, receiving distance 20-25 cm, propulsion speed 0.08-0.10 mm / min, and time 6-7 h; and in the electrospinning process, the electrospinning of glue solution I is carried out first, and when the mass of glue solution I and glue solution II is the same, the electrospinning of glue solution I and glue solution II is carried out simultaneously.

7. The preparation method according to claim 1, characterized in that (3) The mass ratio of glue solution I to glue solution II in the obtained composite film is (1-5):

1.

8. The preparation method according to claim 1, characterized in that (4) The medium-step temperature-raising imidization treatment process is as follows: keeping warm at 80-100°C for 15-25 min, heating to 120-140°C for 15-25 min, heating to 160-180°C for 15-25 min, heating to 200-220°C for 15-25 min, heating to 250-270°C for 50-70 min, heating to 300-320°C for 50-70 min, heating to 340-360°C for 50-70 min, and the heating rate in each stage is 3-5°C / min.

9. A corona-resistant ceramic composite insulating material prepared by the method according to any one of claims 1 to 8.

10. Use of the corona-resistant ceramic composite insulating material according to claim 9, characterized in that: Used for the preparation of high-voltage electrical equipment.

Images