High-thermal-conductivity epoxy resin scratch self-repairing material doped with phase change microspheres and preparation method of high-thermal-conductivity epoxy resin scratch self-repairing material

Abstract

The invention discloses a phase change microsphere-doped high-thermal-conductivity epoxy resin scratch self-repairing material and a preparation method thereof.The preparation method comprises the steps that n-octacosane with phase change capacity is used as a microsphere main body, and modified oleophylic nano SiC particles are added, so that microspheres can obtain a non-contact targeted heating function; the modified oleophylic BN particles are added into the epoxy matrix, the heat conductivity of the composite material is improved due to the high heat conductivity characteristic of the modified oleophylic BN particles, and phase change caused by heat absorption of the microspheres is facilitated. When the damage occurs, the phase change microcapsules in the damage area are induced to be rapidly melted through targeted heating so as to fill a damage channel, and self-repairing of the material is achieved through cooling and curing.

Description

Technical Field

[0001] The invention belongs to the field of self-repairing material science, and specifically relates to a high thermal conductivity epoxy resin scratch self-repairing material doped with phase change microspheres and a preparation method thereof. Background Art

[0002] Polymer materials have been widely used in the electrical field due to their excellent mechanical properties, electrical insulation and ease of processing. Epoxy resin, as an important polymer material, is widely used in electrical insulation, electronic component packaging, circuit board manufacturing, etc. due to its excellent adhesion, heat resistance and chemical stability. However, during its service, epoxy resin materials are often affected by various external environmental factors, such as mechanical stress, temperature changes and humidity. These factors may cause micro-damage and thus cause insulation failure. This type of insulation failure not only affects the normal operation of the equipment, but may also pose a serious threat to the safety and stability of the power system.

[0003] In order to improve the durability and safety of epoxy resin materials, self-repair technology has gradually become a research hotspot in recent years, especially microcapsule self-repair technology, which is particularly suitable for application in epoxy resin materials because it can effectively release repair agents when the material is damaged, thereby achieving automatic repair. This technology can not only extend the service life of the material, but also reduce the risk of insulation failure in the power system to a certain extent, providing effective protection for the reliability and safety of electrical equipment.

[0004] Microcapsule self-repair technology realizes the autonomous repair of microscale damage by insulating materials, which is a milestone in the development of intelligent insulating materials. However, it has not yet been able to achieve industrial application due to the following factors: 1. The liquid healing agent filled in the damaged channel requires external stimulation or chemical reaction to induce solidification, and the solidification is irreversible and can only be repaired once. 2. The encapsulated liquid repair agent must be introduced into the microcapsule shell, which not only affects the intrinsic properties of the matrix material, but also the rupture of the shell needs to be passively triggered by a strong external force, resulting in problems such as untimely release of the microcapsule repair agent and low damage repair rate. 3. The current microcapsule self-repair technology still finds it difficult to avoid premature solidification of the internal repair agent, and its self-repair performance cannot be maintained for a long time. 4. The electrical and mechanical properties of the liquid repair agent inside the microcapsule are weak, resulting in a decrease in the intrinsic performance of the composite material.

[0005] In order to achieve efficient self-repair of micro-damage in epoxy resin materials and avoid the influence of the introduction of microcapsules on the intrinsic properties of composite materials as much as possible, it is urgent to improve the existing technology and innovatively develop an efficient self-repair technology for micro-damage in epoxy resin composite materials. Summary of the invention

[0006] The purpose of this section is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this section, the abstract, and the title, and such simplifications or omissions shall not be used to limit the scope of the present invention.

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

[0008] Therefore, an object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a highly thermally conductive epoxy resin scratch self-healing material doped with phase change microspheres.

[0009] To solve the above technical problems, the present invention provides the following technical solution: A method for preparing a highly thermally conductive epoxy resin scratch self-healing material doped with phase change microspheres, characterized by comprising:

[0010] Dissolve the emulsifier in deionized water, add modified lipophilic nano-SiC particles, and stir evenly to form a silicon carbide emulsion.

[0011] Add n-octacosane to the above silicon carbide emulsion, heat it in an oil bath, and obtain solid microspheres of n-octacosane doped with nano-SiC particles after cooling.

[0012] Mix the epoxy resin monomer and the curing agent, add modified lipophilic BN particles and solid microspheres of n-octacosane doped with nano-SiC particles, and obtain the highly thermally conductive epoxy resin scratch self-healing material doped with phase change microspheres after curing.

[0013] As a preferred embodiment of the preparation method of the present invention, wherein: the emulsifier is tetradecyltrimethylammonium bromide, and its dosage is 0.01 mol per 100 ml of deionized water.

[0014] As a preferred embodiment of the preparation method of the present invention, wherein: the epoxy resin monomer is E51 type epoxy resin, the curing agent is polyetheramine, and the mass ratio of the epoxy resin monomer to the curing agent is 10:2.5 - 3.5.

[0015] As a preferred embodiment of the preparation method of the present invention, wherein: the mass of the solid microspheres of n-octacosane doped with nano-SiC particles added is 0.1% - 3%.

[0016] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing modified lipophilic nano-SiC particles, characterized by comprising: mixing SiC particles with an aqueous solution of absolute ethanol, adding dodecyltrimethoxysilane, carrying out a reflux reaction, filtering, washing, and drying to obtain the modified lipophilic SiC particles.

[0017] As a preferred embodiment of the preparation method of the present invention, wherein: the volume ratio of the anhydrous ethanol aqueous solution to dodecyltrimethoxysilane is 100:0.2 to 0.4; the addition amount of SiC particles per 100 mL of the mixed solution is 1 to 2 g.

[0018] As a preferred embodiment of the preparation method of the present invention, wherein: the volume ratio of ethanol to deionized water in the anhydrous ethanol aqueous solution is 1 to 1.2:1.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide a preparation method for modified lipophilic BN particles, which is characterized in that: it includes mixing BN particles with an anhydrous ethanol aqueous solution and then adding dodecyltrimethoxysilane, refluxing, filtering, washing, and drying to obtain modified lipophilic BN particles.

[0020] As a preferred embodiment of the preparation method of the present invention, wherein: the mass of the nano BN particles is 2% of the total mass of the epoxy monomer and the curing agent.

[0021] Another object of the present invention is to overcome the deficiencies in the prior art and provide a highly thermally conductive epoxy resin scratch self-healing material prepared by a preparation method, which is characterized in that: the breakdown voltage of the highly thermally conductive epoxy resin scratch self-healing material is 35.89 kV / mm, and the repair efficiency is 92.72%.

[0022] Advantages of the present invention:

[0023] The present invention provides a preparation method for a highly thermally conductive epoxy resin scratch self-healing material doped with phase change microspheres. Using n-octacosane with phase change ability as the microsphere main body, lipophilic nano SiC particles modified by an organosilane coupling agent are added. The SiC particles can absorb light of specific wavelengths (especially in the ultraviolet and visible light ranges), enabling the microspheres to obtain a non-contact targeted heating function. Lipophilic BN particles modified by an organosilane coupling agent are added to the epoxy matrix, and their high thermal conductivity characteristics increase the thermal conductivity of the composite material, helping the microspheres absorb heat and undergo a phase change. When damage occurs, targeted heating is used to induce the phase change microcapsules in the damaged area to quickly melt to fill the damage channel, and cooling and curing achieve the autonomous repair of the material. At the same time, the solid-liquid conversion of the octacosane repair agent is reversible, which can solve the shortcomings of traditional repair agents with irreversible curing and only single repair to a certain extent. Description of the drawings

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the attached drawings required for the description of the embodiments. Obviously, the attached drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other attached drawings can also be obtained based on these attached drawings. Among them:

[0025] Figure 1 SEM characterization diagram of the phase change microsphere distribution prepared in Example 1 of the present invention.

[0026] Figure 2 SEM characterization diagram of a single phase change microsphere prepared in Example 1 and Comparative Examples 3-5 of the present invention.

[0027] Figure 3 Statistical results of the particle size distribution of the phase change microspheres prepared in Example 1 of the invention.

[0028] Figure 4 Stress-strain curves of epoxy resin composites with different microsphere contents in the examples and comparative examples of the present invention.

[0029] Figure 5 SEM characterization results after scratch damage repair in Experimental Example 3 of the present invention.

[0030] Figure 6 Weibull statistical results of the breakdown voltage before and after scratch damage repair of the composite material in Experimental Example 4 of the present invention. Detailed implementation manners

[0031] Except as otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available. For details, see Table 1.

[0032] Table 1

[0033]

[0034] The performance test method of the high thermal conductivity epoxy resin scratch self-repairing material doped with phase change microspheres prepared in each example and comparative example of the present invention refers to:

[0035] Tensile property test basis: GB / T 1040.1-2018, GB / T 1040.2-2022. Test instrument: microcomputer controlled electronic universal testing machine. Test method: Clamp dumbbell-shaped standard specimens, ensure centering, stretch the specimens at a constant speed until fracture, record the maximum load and the elongation at fracture. The tensile strength is obtained by dividing the maximum load by the cross-sectional area of the specimen.

[0036] Basis for insulation performance test: GB / T 1048.1-2016, test instrument: microcomputer controlled voltage breakdown tester, test method: Place the standard specimen between the power frequency electrodes, ensure good contact between the specimen and the electrodes, gradually increase the voltage at a rate of 1 kV / s until the specimen breaks down, record the breakdown voltage value, and calculate the electrical strength through the breakdown voltage and the specimen thickness.

[0037] Basis for thermal conductivity test: GB / T 22588-2008, ISO 22007-4:2017, test instrument: laser thermal conductivity meter, test method: Irradiate the surface of the sample with a short pulse laser to make it absorb energy and generate an instantaneous temperature rise. At the same time, use an infrared detector to measure the temperature rise curve on the back of the sample, calculate the thermal diffusivity (α) based on the temperature rise curve, and then calculate the thermal conductivity (λ) in combination with the density (ρ) and specific heat capacity (Cp) of the material.

[0038] Example 1

[0039] This example provides a preparation method of a highly thermally conductive epoxy resin scratch self-healing material doped with phase change microspheres:

[0040] (1) Mix 3 g of SiC particles with 100 ml of absolute ethanol and 100 ml of deionized water, add 0.3% by volume of dodecyltrimethoxysilane, reflux at 70 °C for 3 h, filter, wash, and dry to obtain modified lipophilic SiC particles.

[0041] (2) Dissolve 3 g of tetradecyltrimethylammonium bromide in 100 ml of deionized water, and at the same time add 1.5 g of modified nano-SiC particles, heat in a water bath at 45 °C, and stir at 600 r / min for 30 min until the tetradecyltrimethylammonium bromide is completely dissolved to form a Pickering emulsion.

[0042] (3) Take 3.2 g of octacosane and add it to the above emulsion, and maintain an oil bath at 90 °C. After the octacosane is completely melted, stir at 900 r / min for 25 min; then stop stirring, transfer the mixture to a new beaker and cool and let it stand. When the octacosane cools to room temperature, the SiC particles are wrapped and embedded on the outer surface of the solid octacosane, thus forming phase change microspheres.

[0043] (4) Mix 3 g of BN particles with 100 ml of absolute ethanol and 100 ml of deionized water, add 0.3% by volume of dodecyltrimethoxysilane, reflux at 70 °C for 3 h, filter, wash, and dry to obtain modified lipophilic BN particles.

[0044] (5) Mix 20 g of E51 epoxy resin and 6 g of D230 curing agent, and mechanically stir to mix evenly; add 0.52 g of modified BN particles (2 wt%) and 0.52 g (2 wt%) of phase change microspheres, disperse evenly by ultrasonic wave, with an ultrasonic power of 300 w, degas under vacuum, pour into a mold, and cure at 30 °C for 12 h to obtain a high thermal conductivity epoxy resin composite doped with phase change microspheres.

[0045] Example 2

[0046] The difference from Example 1 is that the mass fraction of the phase change microspheres in step (5) is 1 wt%, and the process of the remaining steps refers to Example 1 to obtain the high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres in this example.

[0047] Example 3

[0048] The difference from Example 1 is that the mass fraction of the phase change microspheres in step (5) is 3 wt%, and the process of the remaining steps refers to Example 1 to obtain the high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres in this example.

[0049] Example 4

[0050] The difference from Example 1 is that the mass fraction of the phase change microspheres in step (5) is 4 wt%, and the process of the remaining steps refers to Example 1 to obtain the high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres in this example.

[0051] Comparative Example 1

[0052] The difference from Example 1 is that the mass fraction of the phase change microspheres in step (5) is 0 wt%, and the process of the remaining steps refers to Example 1 to obtain the high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres in this comparative example.

[0053] Comparative Example 2

[0054] Mix 20 g of E51 epoxy resin and 6 g of D230 curing agent, mechanically stir to mix evenly, degas under vacuum, pour into a mold, and cure at 30 °C for 12 h to obtain a pure epoxy resin sample.

[0055] Comparative Example 3

[0056] The difference from Example 1 is that the added SiC (silicon carbide) particles are not subjected to the modification treatment in step (1), and the process of the remaining steps refers to Example 1 to obtain the doped phase change microspheres in this example.

[0057] Comparative Example 4

[0058] The difference from Example 1 is that the water bath heating in step (2) is adjusted to room temperature, and the processes of the remaining steps refer to Example 1 to obtain the doped phase change microspheres of this example.

[0059] Comparative Example 5

[0060] The difference from Example 1 is that the oil bath heating temperature in step (3) is adjusted to 75 °C, and the processes of the remaining steps refer to Example 1 to obtain the doped phase change microspheres of this example.

[0061] The phase change microspheres prepared in step 3 of Example 1 were observed by SEM, and their distribution and surface morphology are as Figure 1 、 Figure 2 (a) shows that the microspheres have good dispersibility, relatively uniform size, are generally spherical, and the surface is slightly rough. The particle size of the phase change microspheres was statistically analyzed by a particle size analyzer, and the results are as Figure 3 shown. The diameter of the microspheres is distributed in the range of 50 - 150 μm, and the average diameter is 104.28 μm. When the SiC (silicon carbide) particles added in Comparative Example 3 were not subjected to the modification treatment in step (1), the prepared microspheres are as Figure 2 (b) shows that since the compatibility of unmodified SiC with the oil phase is poor, it agglomerates on the surface of the microspheres, affecting the thermal conductivity of the overall material; the microspheres prepared in Comparative Example 4 are as Figure 2 (c) shows that since the emulsification process was not heated, the emulsification was insufficient, and the coating effect of the prepared microspheres was poor, and they were not regular spheres; the microspheres prepared in Comparative Example 5 are as Figure 2 (d) shows that a lower temperature during the formation of the microspheres will reduce the dispersion effect of octacosane, resulting in the inability to form spheres;

[0062] A laser thermal conductivity meter was used to test the thermal conductivity of the composite materials prepared in Example 1 and Comparative Example 2 and pure epoxy resin. The thermal conductivity of pure epoxy resin was measured to be 0.217 W / (m·K), while the thermal conductivity of the 2% microspheres / 2% BN / EP composite material was 0.287 W / (m·K), and the thermal conductivity increased by 32.26% compared with pure epoxy resin.

[0063] The composite samples prepared in Examples 1 - 4 and Comparative Examples 1 - 2 were subjected to a tensile test by a universal testing machine, and the stress-strain curves are as Figure 4 shown. The mechanical tensile properties of the composite materials continuously decrease with the increase in the doping concentration of the microspheres. When the microsphere doping concentration is 2 wt%, the tensile strength of the composite material is 73.68 MPa, which is 89.71% of pure epoxy resin (0 wt%), and the mechanical properties of the composite material remain good; when the microsphere doping concentration exceeds 3 wt%, the mechanical properties of the composite material significantly decrease.

[0064] The composite sample prepared in Example 1 was scratched with a No. 11 medical scalpel to simulate micro-damage, and then infrared heating was used to melt the microspheres to fill the damage channels. The filling results are as Figure 5 shown. It can be seen from the figure that the damage channels are basically completely filled at this time.

[0065] The power frequency breakdown voltage tests were carried out on the samples prepared in Example 1 and Comparative Example 2. There were 8 groups of undamaged Example 1 samples, 8 groups of undamaged Comparative Example 2 samples, 8 groups of Example 1 samples with scratch damage but not repaired, and 8 groups of Example 1 samples with scratch damage repaired. By Weibull statistics of the breakdown voltage law, the results are as Figure 6 shown. Taking the breakdown probability of 63.2% as the characteristic breakdown voltage of the sample. The data is shown in Table 2 below. The breakdown voltage of pure epoxy resin is 37.93 kV / mm. After adding microspheres, the characteristic breakdown voltage of the composite material decreased slightly, dropping to 35.89 kV / mm. This may be because some microspheres agglomerated during the doping process, introducing defects and resulting in a decrease in the breakdown voltage, but the decrease is not significant. The breakdown voltage of the sample with scratch damage but not repaired decreased significantly to 29.12 kV / mm. This is because the scratch damage reduced the thickness of the damaged part on the one hand and increased the electric field distortion of the damaged part on the other hand. The breakdown voltage of the sample after damage repair was 33.28 kV / mm, recovering to 92.72% before the damage. The repair effect is good, which is beneficial to the application of the composite epoxy resin provided by this application in fields such as power equipment.

[0066] Table 2

[0067]

[0068] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a high thermal conductivity epoxy resin scratch self-repairing material doped with phase change microspheres, characterized in that: include, The emulsifier is dissolved in deionized water, and the modified oleophilic nano-SiC particles are added and stirred to form a silicon carbide emulsion; The n-octacosane is added into the silicon carbide emulsion, heated in an oil bath, and cooled to obtain the n-octacosane solid microspheres doped with nano-SiC particles. The epoxy resin monomer is mixed with a curing agent, and modified oleophilic BN particles and solid microspheres of n-octacosane doped with nano-SiC particles are added, and after curing, the high thermal conductivity epoxy resin scratch self-repairing material doped with phase change microspheres is obtained.

2. The preparation method according to claim 1, characterized in that: The emulsifier is tetradecyltrimethylammonium bromide, and the amount thereof is 0.01 mol per 100 ml of deionized water.

3. The preparation method according to claim 1, characterized in that: The epoxy resin monomer is E51 epoxy resin, the curing agent is polyetheramine, and the mass ratio of the epoxy resin monomer to the curing agent is 10:2.5-3.

5.

4. The preparation method according to claim 1, characterized in that: The mass of the n-octacosane solid microspheres added with doped nano-SiC particles is 0.1% to 3%.

5. A method for preparing modified oleophilic nano-SiC particles, characterized in that: The method comprises the steps of mixing SiC particles with anhydrous ethanol aqueous solution, adding dodecyltrimethoxysilane, and performing reflux reaction, filtering, washing, and drying to obtain the modified oleophilic SiC particles.

6. The preparation method according to claim 5, characterized in that: The volume ratio of the anhydrous ethanol aqueous solution to dodecyltrimethoxysilane is 100:0.2-0.4; the added amount of SiC particles per 100 mL of the mixed solution is 1-2 g.

7. The preparation method according to claim 5, characterized in that: The volume ratio of ethanol to deionized water in the anhydrous ethanol aqueous solution is 1 to 1.2:

1.

8. A method for preparing modified oleophilic BN particles, characterized in that: The method comprises the steps of mixing BN particles with anhydrous ethanol aqueous solution, adding dodecyltrimethoxysilane, and performing reflux reaction, filtering, washing, and drying to obtain modified oleophilic BN particles.

9. The preparation method according to claim 7, characterized in that: The mass of the nano BN particles is 2% of the total mass of the epoxy monomer and the curing agent.

10. The high thermal conductivity epoxy resin scratch self-repairing material doped with phase change microspheres prepared by the preparation method of claims 1 to 4, characterized in that: The high thermal conductivity epoxy resin scratch self-repairing material has a breakdown voltage of 35.89 kV / mm and a repair efficiency of 92.72%.

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