Preparation method of phase change microcapsule and epoxy resin self-repairing composite insulating material doped with phase change microcapsule

Abstract

The application discloses a kind of phase change microcapsules, preparation method of epoxy resin self-repairing composite insulating material doped with phase change microcapsules, comprising, the phase change microcapsule self-repairing epoxy resin composite material is core-shell structure, wherein, with 500nm silicon carbide particles and octacosane as core, outer layer is coated Fe3O4@SiO2 Nanoparticle.The application is in the aspect of heat conduction performance, with the content of microcapsule from 0wt% increases, the heat conduction performance of epoxy resin composite material gradually rises in tendency.Due to the microcapsule interconnection formed heat conduction network with Fe3O4@SiO2 Nanoparticle as shell is added, increase the overall heat conduction performance of material;The repairant of microencapsulation of the application not only can heal crack, can also provide higher tensile property for damaged part of epoxy resin composite material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of material science, and particularly relates to a preparation method of phase change microcapsules and epoxy resin self-repairing composite insulating material doped with the phase change microcapsules. BACKGROUND

[0002] Polymer-based composite material is a material composed of high molecular material and reinforcing material with high strength, high modulus, temperature resistance and other characteristics. This composite material usually has high specific strength and specific modulus, good chemical corrosion resistance and excellent mechanical processing performance, and thus has a wide application in the fields of aerospace, automobile and sports equipment. Epoxy resin is usually considered as a composite material matrix with excellent performance due to its good adhesive property and low curing shrinkage. However, in the context of insulation, the defect that the internal micro-damage of epoxy resin-based material cannot be detected or repaired in time seriously hinders its further application in the high-voltage field.

[0003] In the actual application process of epoxy resin-based composite insulating material, due to the defects of manufacturing process, transportation condition and installation mode and the influence of complex working environment of strong magnetic field and strong electric field, microcrack damage inevitably occurs in the internal insulation material. However, at present, there is a lack of effective solution to the problem of internal micro-damage degradation of epoxy resin-based insulating composite material. Most of the researches on effectively preventing the internal microcrack damage of epoxy resin-based composite insulating material focus on improving the electrical breakdown performance of epoxy resin-based composite insulating material and increasing the dielectric constant of the insulating material by means of nano-doping, and there is a lack of corresponding research on how to efficiently and autonomously repair the internal damage.

[0004] The curing mechanism of microcapsules in epoxy resin-based composite insulating material is usually to coat the liquid repair agent in the microcapsule wall. When the damage breaks the capsule wall, the repair agent flows out to fill the damage channel, and solidifies under the external conditions of temperature, light and the like, so as to realize the repair of the insulating material to the damage. Since the components of the existing repair agent after curing are not completely the same as the epoxy resin matrix, intrinsic defects will occur at the repair interface of the epoxy resin-based composite insulating material, which will cause the reduction of the mechanical properties of the epoxy resin-based composite insulating material, thereby limiting the wide application of the current microcapsule self-repairing technology in the field of high voltage and insulation technology.

[0005] The existing microcapsule self-repairing technology has made great progress in the field of self-repairing of epoxy resin-based composite insulating material. The microcapsule repair agent in the epoxy resin-based composite insulating material needs to be cured under external excitation or induced by chemical reaction. The curing process is irreversible and can only be repaired once. In order to solve the problem that the traditional repair agent is irreversible and can only be repaired once, it is urgent to improve the existing technology and innovatively develop a reusable high-performance epoxy resin self-repairing composite insulating material with a recycling path. SUMMARY

[0006] This section is intended to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification of the present application to avoid obscuring the purpose of this section, the abstract and the title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0007] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0008] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art, and to provide a preparation method of a phase change microcapsule and a doped phase change microcapsule epoxy resin self-repairing composite insulating material.

[0009] To solve the above technical problems, the present application provides the following technical scheme: a phase change microcapsule, characterized in that: the phase change microcapsule is a core-shell structure, wherein silicon carbide particles and octacosane are used as the core, and the outer layer is coated with Fe3O4@SiO2 nanoparticles.

[0010] Another purpose of the present application is to overcome the deficiencies in the prior art, and to provide a preparation method of a phase change microcapsule, characterized in that: it comprises,

[0011] Fe3O4 nanoparticles are dissolved in anhydrous ethanol to obtain a dispersion solution 1; concentrated ammonia water is added dropwise to the dispersion solution 1 to obtain a dispersion solution 2; and tetraethyl orthosilicate is added dropwise to the dispersion solution 2 to obtain a dispersion solution 3;

[0012] The dispersion solution 3 is mixed and stirred under heating conditions, and after solid-liquid separation, methanol and deionized water are used for filtration and washing, and room temperature drying is performed to obtain Fe3O4@SiO2 nanoparticles;

[0013] Fe3O4@SiO2 nanoparticles are dissolved in a solution of tetradecyl trimethyl ammonium bromide to obtain an aqueous solution; and silicon carbide particles are added to octacosane to obtain an oil phase solution;

[0014] The oil phase solution and the aqueous solution are stirred at room temperature to obtain an oil-water emulsion, which is filtered and washed with methanol and deionized water, and dried at room temperature to obtain the phase change microcapsule.

[0015] As a preferred scheme of the preparation method of the present application, the mass ratio of the Fe3O4 nanoparticles and the anhydrous ethanol is 1.0-1.1: 35-40.

[0016] As a preferred scheme of the preparation method of the present application, the mass ratio of the dispersion solution 1 and the concentrated ammonia water is 1.0-1.2: 1.5-1.7; and the mass ratio of the tetraethyl orthosilicate and the dispersion solution 2 is 1.0-1.1: 42-45.

[0017] As a preferred solution of the preparation method, the mass ratio of the aqueous phase solution to the oil phase solution is 18-22:12-15.

[0018] As a preferred solution of the preparation method, the mass ratio of the Fe3O4@SiO2 nanoparticles to the tetradecyl trimethyl ammonium bromide in the aqueous phase solution is 0.9-1.3:30-38. As a preferred solution of the preparation method, the mass ratio of the silicon carbide particles to the octacosane in the oil phase solution is 1.1-1.4:30-34.

[0019] Another object of the present application is to overcome the deficiencies in the prior art and provide a preparation method of a phase change microcapsule doped epoxy resin self-repairing composite insulating material, which is characterized by comprising,

[0020] The normal temperature curing epoxy resin and the curing agent are used as a matrix, the phase change microcapsules are mixed with the matrix, and the mixed sample is degassed and cured at room temperature to obtain the phase change microcapsule doped epoxy resin self-repairing composite insulating material.

[0021] As a preferred solution of the preparation method, the mass ratio of the normal temperature curing epoxy resin to the curing agent is 1.0-1.2:0.65-0.85.

[0022] As a preferred solution of the preparation method, the total content of the phase change microcapsules is 2-8wt%.

[0023] The present application has the following beneficial effects:

[0024] In terms of thermal conductivity, the thermal conductivity of the epoxy resin based composite insulating material shows an upward trend as the content of the microcapsules increases from 0wt%. The microcapsules with Fe3O4@SiO2 nanoparticles as the shell increase the overall thermal conductivity of the material. The microencapsulated repair agent not only heals cracks but also provides good thermal conductivity for the epoxy resin based composite insulating material. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. Among them:

[0026] Figure 1 The scanning electron microscope characterization diagram of the 500nm silicon carbide particles with Fe3O4@SiO2 nanoparticles as the shell and octacosane microcapsules.

[0027] Figure 2 Bar chart of the influence of different microcapsule contents on the thermal conductivity of the epoxy resin-based composite insulating material of the embodiments and the comparative examples of the present application.

[0028] Figure 3 Scratch damage self-repairing effect diagram of the phase change microcapsule self-repairing epoxy resin-based composite insulating material of the present application.

[0029] Figure 4 Bar chart of the tensile strength of the epoxy resin composite material of the embodiments and the comparative examples of the present application with different microcapsule contents.

[0030] Figure 5 Bar chart of the influence of different microcapsule contents of the repair agent on the self-repairing efficiency of the epoxy resin composite material of the embodiments and the comparative examples of the present application. DETAILED DESCRIPTION

[0031] In order to make the above objectives, features and advantages of the present application more apparent, the specific embodiments of the present application will be described in detail below with reference to the description and the embodiments.

[0032] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0033] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is separate or alternative to other embodiments.

[0034] The raw materials used in the embodiments of the present application are commercially available unless otherwise specified, and the details are shown in Table 1.

[0035] Table 1

[0036]

[0037]

[0038] The performance test method of the epoxy resin self-repairing composite insulating material doped with phase change microcapsules prepared in each embodiment and the comparative example of the present application is as follows:

[0039] Tensile strength test: The tensile strength test was conducted according to "GB / T 1040.2-2003 Determination of tensile properties of plastics - Part 2: test conditions for moulded and extruded plastics" and "GB / T 41929-2022 Test methods of plastics epoxy resin". According to the standard requirements, standard size epoxy resin samples were prepared, with specific dimensions as follows: length L = 150 mm, width b = 10 mm ± 0.1 mm, thickness d = 4 mm ± 0.1 mm, gauge length L0 = 50 mm (i.e. the initial distance between the two clamps). An electronic universal material testing machine was selected, model WDW-100E (maximum test force 100 kN, precision grade 1), equipped with standard tensile clamps and an extensometer (for measuring deformation). The experimental steps were as follows: First, use a vernier caliper or micrometer to measure the size of the sample, ensure that it meets the standard requirements, and record the data. Then clean the surface of the sample with alcohol and a cotton swab to remove dust and impurities, ensuring that the surface is clean and undamaged. Finally, check the power supply, sensors, and control system of the testing machine to ensure that the load sensor and displacement sensor have been calibrated. Install the appropriate tensile clamps and extensometer, adjust their position and gauge length. Clamping the ends of the sample in the upper and lower clamps, respectively, to ensure that the sample is centered and clamped firmly. Check whether the force direction of the sample is consistent with the tensile direction of the testing machine. Set the tensile speed to 5 mm / min and the test mode to stress-strain mode in the control software of the testing machine. Start the testing machine and begin the tensile test, observe the deformation of the sample, and record the changes in load and displacement. When the sample breaks, the testing machine automatically stops the test, and the maximum load at the time of breakage is recorded. Statistical analysis of the test data of multiple samples is performed to calculate the average value and standard deviation.

[0040] Thermal conductivity test: The thermal conductivity test was performed according to the ASTM E1461 Standard Test Method: Measurement of Thermal Diffusivity Using the Flash Method, and relevant thermal conductivity test standards were referred to. According to the standard requirements, circular epoxy resin samples were prepared, with the following specific dimensions: diameter D = 12.7 mm, thickness d = 2 mm. A laser thermal conductivity instrument, model LFA 447, was selected, which was designed based on the laser flash method (Flash Method) and was suitable for measuring the thermal diffusivity and thermal conductivity of materials. First, circular epoxy resin samples with a diameter of 12.7 mm and a thickness of 2 mm were prepared to ensure the smoothness of the sample surface. Then, the sample surface was sprayed with graphite to increase the absorption ratio of the sample surface to light energy and the infrared emissivity. The laser thermal conductivity instrument was started and the water bath device was turned on, and the equipment was kept in a stable state for more than 30 minutes. The sample tray was placed in the test position to ensure that the sample was tested in a protective atmosphere. The laser thermal conductivity instrument was started, and a light pulse was emitted from the laser source, uniformly irradiating the lower surface of the sample, causing the temperature to rise after absorbing light energy. The temperature rise of the upper surface of the sample was continuously measured using an infrared detector, and the temperature rise-time curve was recorded. The thermal diffusivity (a) was calculated by analysis software, and the thermal conductivity (l) was calculated by combining the specific heat capacity (Cp) and the density (p) of the sample: l = a x Cp x p, wherein the specific heat capacity can be obtained by differential scanning calorimetry (DSC) test.

[0041] Self-repairing efficiency test: The electrical performance test in this case is based on "GB / T 1408.1-2017 Measurement of the Dielectric Properties of Plastics Insulating Materials and Gelled Insulating Materials Part 1: General Guidelines" and "GB / T 1408.2-2017 Measurement of the Dielectric Properties of Plastics Insulating Materials and Gelled Insulating Materials Part 2: Measurement of Dielectric Loss Tangent". According to the standard requirements, circular epoxy resin samples are prepared with the following specific dimensions: diameter D = 25 mm, thickness d = 2 mm. A high-voltage breakdown platform with a model number of ZJC-50E is selected, which is suitable for the breakdown voltage test of solid insulating materials and has computer control function, and the voltage rising rate can be adjusted between 10 V / s and 5 kV / s. Circular epoxy resin samples with a diameter of 25 mm and a thickness of 2 mm are prepared to ensure the smoothness of the sample surface. Clean the surface of the sample to remove dust and impurities and ensure that the surface is defect-free. Turn on the high-voltage breakdown platform and preheat to ensure that the instrument is in a stable state. Place the sample between the test electrodes to ensure good contact between the sample and the electrodes. The entire electrode system needs to be placed in clean transformer oil to prevent corona discharge from affecting the breakdown voltage value. Set the voltage rising rate to 1 kV / s in the instrument control software. Start the test and gradually increase the voltage by rotating the voltage booster until the sample breaks down, and record the voltage value at the time of breakdown. Calculate the breakdown field strength (E) using the formula E = U / d, where U is the breakdown voltage and d is the thickness of the sample. Statistical analysis of test data from multiple samples is performed using the Weibull distribution model to analyze the breakdown data and obtain more accurate voltage resistance strength. The self-repairing efficiency is calculated by comparing the breakdown strength of the sample before and after the self-repairing process, with the formula η = E1 / E2, where E1 is the breakdown strength of the epoxy resin after self-repairing, and E2 is the original breakdown strength of the epoxy resin without damage.

[0042] Example 1

[0043] The present embodiment provides a preparation method of a self-repairing composite insulating material doped with phase change microcapsules:

[0044] (1) Dissolve 1 g of Fe3O4 nanoparticles in 50 ml of anhydrous ethanol, and ultrasonically disperse in an ultrasonic dispersion device with a frequency and power of 40 kHz and 200 W for 30 min to prepare dispersion solution 1;

[0045] Add 10 ml of concentrated ammonia water to 40 ml of dispersion solution 1 to obtain dispersion solution 2;

[0046] Add 5 ml of ethyl silicate solution to 30 ml of dispersion solution 2 to obtain dispersion solution 3;

[0047] The dispersion solution 3 was placed in a 50℃ water bath, stirred at a high speed of 1000 rpm for 8h, and then filtered, washed with methanol and deionized water, and dried at room temperature to obtain Fe3O4@SiO2nanoparticles.

[0048] (2) 2g of Fe3O4@SiO2nanoparticles were added to 100ml of tetradecyl trimethyl ammonium bromide with a concentration of 0.06mmol / L, stirred at a high speed of 1200 rpm for 2h at room temperature to obtain an aqueous solution;

[0049] 1g of 500nm silicon carbide particles were mixed with 20g of octacosane, stirred at a high speed of 1000 rpm in a 120℃ oil bath for 30min to obtain an oil phase solution;

[0050] (3) The prepared oil phase solution was mixed with the aqueous solution, and the addition ratio was 1.1:2.6. After the octacosane solidified, the mixture was washed with methanol and deionized water, and dried at room temperature to obtain microcapsules;

[0051] (4) 90 parts of E51 type room temperature curing epoxy resin and 20 parts of 593 curing agent were mixed as a matrix; the microcapsules prepared in step (3) were mixed with the matrix, and the content of the microcapsules was 2wt%; the mixed sample was degassed and poured into a dumbbell-shaped polytetrafluoroethylene mold, and cured at room temperature for 48h to obtain a phase change microcapsule doped epoxy resin self-repairing composite insulating material.

[0052] Example 2

[0053] The difference from Example 1 is that the content of the two-component microcapsules in step (4) is 4wt%, and the rest of the process refers to the example to obtain the phase change microcapsule doped epoxy resin self-repairing composite insulating material of this example.

[0054] Example 3

[0055] The difference from Example 1 is that the content of the two-component microcapsules in step (4) is 6wt%, and the rest of the process refers to the example to obtain the phase change microcapsule doped epoxy resin self-repairing composite insulating material of this example.

[0056] Example 4

[0057] The difference from Example 1 is that the content of the two-component microcapsules in step (4) is 8wt%, and the rest of the process refers to the example to obtain the phase change microcapsule doped epoxy resin self-repairing composite insulating material of this example.

[0058] Comparative Example 1

[0059] The difference between Example 1 is that only the pure epoxy resin sample is prepared, and the pure epoxy resin sample is prepared by mixing 90 parts of E51 type room temperature curing epoxy resin and 20 parts of 593 curing agent to obtain the pure epoxy resin sample.

[0060] Comparative Example 2

[0061] The difference between Example 1 is that the adjustment in step (1) uses an ultrasonic dispersion device with a frequency of 40 kHz and a power of 200 W to ultrasonically disperse the nanoparticles for 30 min, instead of using a mechanical stirrer to stir the nanoparticles at a speed of 500 r / min for 30 min. The rest of the process steps are the same as in Example 1. The nanoparticles of this comparative example have a serious agglomeration phenomenon and fail to successfully form a shell-coated microcapsule.

[0062] Comparative Example 3

[0063] The difference between Example 1 is that in step (2), 2 g of Fe3O4@SiO2 nanoparticles are added to 100 ml of tetradecyltrimethylammonium bromide with a concentration of 0.06 mmol / L, instead of 1 g of Fe3O4@SiO2 nanoparticles being added to 100 ml of tetradecyltrimethylammonium bromide with a concentration of 0.06 mmol / L. The rest of the process steps are the same as in Example 1. The microcapsules of this comparative example cannot be formed due to an imbalance in the ratio of shell material to core material.

[0064] Comparative Example 4

[0065] The difference between Example 1 is that in step (2), octacosane is replaced by docosane. The rest of the process steps are the same as in Example 1. The surface of the phase change microcapsules of this comparative example has a wrinkled morphology.

[0066] Comparative Example 5

[0067] The difference between Example 1 is that in step (2), 1 g of 500 nm silicon carbide particles is replaced by 1 g of 1 um carbon nanotubes. The rest of the process steps are the same as in Example 1. The carbon nanotube-modified phase change microcapsules of this comparative example are obtained.

[0068] Comparative Example 6

[0069] The difference between Example 1 is that in step (2), 1 g of 500 nm silicon carbide particles is replaced by 1 g of 1 um boron nitride particles. The rest of the process steps are the same as in Example 1. The boron nitride particle-modified phase change microcapsules of this comparative example are obtained.

[0070] Example 5

[0071] The samples prepared in Examples 1-4 and Comparative Example 1 were tested for thermal conductivity performance:

[0072] The thermal conductivity of the epoxy resin self-repairing composite insulation material doped with phase change microcapsules changes with the content of the microcapsules as follows:Figure 2 The thermal conductivity values are the average of 6 measurements. The thermal conductivity of pure epoxy resin is 0.2063 W / m·K. The results show that the thermal conductivity of the epoxy resin composite gradually increases to 0.3481 W / m·K as the microcapsule content increases from 0wt% to 8wt%. Compared with pure epoxy resin, the thermal conductivity of the self-repairing epoxy resin composite increases, which may be due to the cross-linking of the microcapsules with Fe3O4@SiO2 nanoparticles as the shell to form a thermal conduction network, improving the thermal conductivity of the composite. The significance of the improvement in thermal conductivity can be explained from two aspects. On the one hand, the introduction of phase change microcapsules allows the composite to maintain good insulation performance while improving thermal conductivity, expanding the application environment of the epoxy resin self-repairing composite insulation material. On the other hand, the improvement in thermal conductivity also enables the epoxy resin self-repairing composite insulation material to have the function of targeted heating, and octacosane can quickly melt and flow into the micro-damage channel, and solidify to repair the damage channel when cooled to room temperature.

[0073] Example 6

[0074] The samples prepared in Examples 1-4 and Comparative Example 1 were tested for self-repairing efficiency:

[0075] The self-repairing efficiency of the samples was evaluated according to the dumbbell-shaped sample fracture test.

[0076] The present application uses phase change microcapsules with 500nm silicon carbide particles and octacosane as the core, and Fe3O4@SiO2 nanoparticles as the outer coating to prepare self-repairing composite materials. The self-repairing efficiency of the epoxy resin composite with a dumbbell shape was measured using the same parameters to compare the self-repairing efficiency of the self-repairing epoxy resin composite samples with different microcapsule contents. Figure 4 The tensile strength bar chart of the epoxy resin composite with different microcapsule contents of the examples and comparative examples of the present application.

[0077] Figure 5 The bar chart of the influence of different microcapsule contents of the repair agent on the self-repairing efficiency of the epoxy resin composite of the examples and comparative examples of the present application. According to the dumbbell-shaped sample fracture test, Figure 5 As shown, the self-repairing efficiency of the epoxy resin composite significantly improves as the microcapsule content increases from 2wt% to 8wt%. When the content of the repair agent microcapsule is 8wt%, the self-repairing efficiency of the epoxy resin composite is 96.87%. Obviously, the self-repairing effect is related to the amount of repair agent released by the broken microcapsules on the crack surface.

[0078] The relevant properties of the products prepared in each example and comparative example were determined, and the results are shown in Table 2.

[0079] Table 2

[0080]

[0081] From Figure 1 It can be seen from the microcapsules are relatively uniform distribution, most of the spherical or nearly spherical, surface morphology is relatively smooth. The outer surface of the microcapsules smooth, almost no protrusions, which is due to the outer layer of the microcapsule Fe3O4@SiO2nanoparticle shell. From Table 2 can be seen, the comparative example 2 and comparative example 3 due to serious agglomeration and shell material core material ratio imbalance failed to successfully coated into the shell microcapsules, from the example to see this repair efficiency of rapid increase is due to the microcapsules released enough repair agent to fill the microcrack space. Phase change microcapsules embedded in the composite system for epoxy resin composite self-repair provides enough octacosane repair agent, and promotes the new epoxy resin and the original matrix interface bonding.

[0082] It should be noted that the above examples are merely intended to illustrate the technical solutions of the present application rather than limiting the same. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and all such modifications or replacements should be encompassed within the scope of the present application.

Claims

1. A method for preparing phase change microcapsules, characterized by: Comprising, Fe3O4 nanoparticles are dissolved in anhydrous ethanol to obtain a dispersion solution 1; concentrated ammonia is added dropwise to the dispersion solution 1 to obtain a dispersion solution 2; tetraethyl orthosilicate is added dropwise to the dispersion solution 2 to obtain a dispersion solution 3; The dispersion solution 3 is mixed and stirred under heating, and after solid-liquid separation, methanol and deionized water are used for filtration and washing, and the mixture is dried at room temperature to obtain Fe3O4@SiO2 nanoparticles; Fe3O4@SiO2 nanoparticles are dissolved in a solution of tetradecyl trimethyl ammonium bromide to obtain an aqueous solution; silicon carbide particles are added to octacosane to obtain an oil solution; The oil solution and the aqueous solution are stirred at room temperature to obtain an oil-water emulsion, which is filtered and washed with methanol and deionized water, and dried at room temperature to obtain the phase change microcapsule; The phase change microcapsule has a core-shell structure, wherein the core is composed of silicon carbide particles and octacosane, and the outer layer is coated with Fe3O4@SiO2 nanoparticles.

2. The production method according to claim 1, characterized by: The mass ratio of the Fe3O4 nanoparticles to anhydrous ethanol is 1.0-1.1:35-40.

3. The production method according to claim 1, wherein: The mass ratio of the dispersion solution 1 to concentrated ammonia is 1.0-1.2:1.5-1.7; the mass ratio of the tetraethyl orthosilicate to the dispersion solution 2 is 1.0-1.1:42-45.

4. The production method according to claim 1, wherein: The mass ratio of the aqueous solution to the oil solution is 18-22:12-15.

5. The production method according to claim 4, characterized by: The mass ratio of the Fe3O4@SiO2 nanoparticles to tetradecyl trimethyl ammonium bromide in the aqueous solution is 0.9-1.3:30-38.

6. The production method according to claim 4, characterized by: The mass ratio of the silicon carbide particles to octacosane in the oil solution is 1.1-1.4:30-34.

7. The phase change microcapsules prepared by the process according to any one of claims 1 to 6, characterized in that: The phase change microcapsule has a core-shell structure, wherein the core is composed of silicon carbide particles and octacosane, and the outer layer is coated with Fe3O4@SiO2 nanoparticles.

8. A method for preparing an epoxy resin self-repairing composite insulating material doped with phase change microcapsules, characterized in that: Comprising, The normal-temperature curing epoxy resin and the curing agent are used as a matrix; the phase change microcapsule of claim 7 is mixed with the matrix, and after degassing of the mixed sample, the normal-temperature curing epoxy resin self-repairing composite insulating material doped with the phase change microcapsule is obtained after curing at room temperature.

9. The production method according to claim 8, characterized by: The mass ratio of the normal-temperature curing epoxy resin to the curing agent is 1.0-1.2:0.65-0.

85.

10. The production method according to claim 8, characterized by: The total content of the phase change microcapsule is 2-8 wt%.

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