Highly thermally-conductive epoxy resin scratch self-repairing material doped with phase-change microspheres and preparation method therefor

Abstract

Disclosed in the present invention are a highly thermally-conductive epoxy resin scratch self-repairing material doped with phase-change microspheres and a preparation method therefor. The preparation method comprises using n-octacosane having a phase-change capability as microsphere main bodies; modified oleophilic nano SiC particles are added to the microsphere main bodies so that the microspheres can obtain a non-contact targeted heating function; and modified oleophilic BN particles are added to an epoxy matrix so that the high thermal conductivity of the modified oleophilic BN particles increases the thermal conductivity of a composite material, helping the microspheres absorb heat and undergo a phase change. When damage occurs, phase-change microcapsules in the damaged area are induced, by means of targeted heating, to rapidly melt so as to fill in damaged channels, and are cooled and cured to achieve self-repairing of the material.

Description

A high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres and its preparation method Technical Field

[0001] This invention belongs to the field of self-healing materials science, specifically relating to a high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres and its preparation method. Background Technology

[0002] Polymer materials are 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, and circuit board manufacturing due to its excellent adhesion, heat resistance, and chemical stability. However, epoxy resin materials often face various external environmental factors during their service life, such as mechanical stress, temperature changes, and humidity. These factors can lead to micro-damage, resulting in insulation failure. Such insulation failures not only affect the normal operation of equipment but may also pose a serious threat to the safety and stability of power systems.

[0003] To improve the durability and safety of epoxy resin materials, self-healing technology has become a research hotspot in recent years, especially microcapsule self-healing technology. This technology effectively releases repair agents when materials are damaged, achieving automatic repair, making it particularly suitable for epoxy resin materials. This technology not only extends the service life of materials but also reduces the risks caused by insulation failure in power systems to a certain extent, providing effective protection for the reliability and safety of electrical equipment.

[0004] Microcapsule self-healing technology enables insulating materials to autonomously repair microscale damage, marking a milestone in the development of smart insulating materials. However, its industrial application has yet to be realized due to the following factors: 1. The liquid healing agent filling the damage channel requires external stimulation or chemical reaction to induce curing, which is irreversible and can only repair damage once. 2. Encapsulating the liquid repair agent requires introducing it into the microcapsule shell, which not only affects the intrinsic properties of the matrix material but also requires a strong external force to passively trigger shell rupture, leading to problems such as untimely release of the microcapsule repair agent and low damage repair rate. 3. Current microcapsule self-healing technology still struggles to prevent premature curing of the internal repair agent, resulting in the inability to maintain its self-healing efficacy in the long term. 4. The weak electrical and mechanical properties of the liquid repair agent inside the microcapsule lead to a decline in the intrinsic properties of the composite material.

[0005] To achieve efficient self-repair of micro-damage in epoxy resin materials and minimize the impact of microcapsule introduction on the intrinsic properties of composite materials, it is urgent to improve existing technologies and develop an innovative and 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 embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

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

[0008] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres, characterized in that it includes:

[0010] The emulsifier was dissolved in deionized water, and modified lipophilic nano-SiC particles were added and stirred evenly to form a silicon carbide emulsion.

[0011] Octacosane was added to the above silicon carbide emulsion, heated in an oil bath, and cooled to obtain octacosane solid microspheres doped with nano-SiC particles.

[0012] Epoxy resin monomers and curing agents are mixed, and modified oleophilic BN particles and n-octadecane solid microspheres doped with nano-SiC particles are added. After curing, a high thermal conductivity epoxy resin scratch self-healing material with doped phase change microspheres is obtained.

[0013] In a preferred embodiment of the preparation method described in this invention, the emulsifier is tetradecyltrimethylammonium bromide, and its dosage is 0.01 mol per 100 ml of deionized water.

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

[0015] In a preferred embodiment of the preparation method described in this invention, the mass of the octadecane solid microspheres with added doped nano-SiC particles is 0.1% to 3%.

[0016] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing modified oleophilic nano-SiC particles, characterized by comprising: mixing SiC particles with anhydrous ethanol aqueous solution, adding dodecyltrimethoxysilane, reflux reaction, filtration, washing, and drying to obtain the modified oleophilic SiC particles.

[0017] In a preferred embodiment of the preparation method described in this invention, the volume ratio of the anhydrous ethanol aqueous solution to dodecyltrimethoxysilane is 100:0.2-0.4; and the amount of SiC particles added per 100 mL of mixed solution is 1-2 g.

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

[0019] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing modified lipophilic BN particles, characterized by comprising: mixing BN particles with anhydrous ethanol aqueous solution, adding dodecyltrimethoxysilane, reflux reaction, filtration, washing, and drying to obtain modified lipophilic BN particles.

[0020] In a preferred embodiment of the preparation method described in this invention, the mass of the nano-BN particles is 2% of the total mass of the epoxy monomer and curing agent.

[0021] Another objective of this invention is to overcome the shortcomings of the prior art and provide a high thermal conductivity epoxy resin scratch self-healing material for doped phase change microspheres prepared by a preparation method, characterized in that: the breakdown voltage of the high thermal conductivity epoxy resin scratch self-healing material is 35.89 kV / mm, and the repair efficiency is 92.72%.

[0022] Beneficial effects of this invention:

[0023] This invention provides a method for preparing a high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres. The method uses n-octacosane, which has phase change capability, as the microsphere matrix, and incorporates oleophilic nano-SiC particles modified with an organosilicon coupling agent. The SiC particles can absorb light of specific wavelengths (especially the ultraviolet and visible light range), enabling the microspheres to achieve non-contact targeted heating. Oleophilic BN particles modified with an organosilicon coupling agent are added to the epoxy matrix; their high thermal conductivity increases the thermal conductivity of the composite material, facilitating the microspheres' endothermic phase change. When damage occurs, targeted heating induces the rapid melting of the phase change microcapsules in the damaged area to fill the damage channels. Cooling and solidification achieve self-repair of the material. Furthermore, the solid-liquid transformation of the octacosane repair agent is reversible, which to some extent overcomes the shortcomings of traditional repair agents, such as irreversible curing and the limitation to single-use repair. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0025] Figure 1 is a SEM image showing the distribution of the phase change microspheres prepared in Example 1 of this invention.

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

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

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

[0029] Figure 5 shows the SEM characterization results of the scratch damage repaired in Experiment Example 3 of this invention.

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

[0031] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available. See Table 1 for details.

[0032] Table 1

[0033] The performance testing methods for the high thermal conductivity epoxy resin scratch self-healing materials with doped phase change microspheres prepared in the various embodiments and comparative examples of this invention refer to:

[0034] Tensile property testing is conducted in accordance with GB / T 1040.1-2018 and GB / T 1040.2-2022. The testing instrument is a computer-controlled electronic universal testing machine. The testing method is as follows: clamp the dumbbell-shaped standard specimen, ensure centering, and stretch the specimen at a constant speed until it breaks. Record the maximum load and the elongation at break. The tensile strength is obtained by dividing the maximum load by the cross-sectional area of ​​the specimen.

[0035] Insulation performance test standard: GB / T 1048.1-2016, test instrument: microcomputer-controlled voltage breakdown tester, test method: place the standard sample between power frequency electrodes, ensure good contact between the sample and the electrodes, gradually increase the voltage at 1kV / s until the sample breaks down, record the breakdown voltage value, and calculate the electrical strength by using the breakdown voltage and the sample thickness.

[0036] Thermal conductivity testing is conducted according to GB / T 22588-2008 and ISO 22007-4:2017. The testing instrument is a laser thermal conductivity meter. The testing method involves irradiating the sample surface with a short-pulse laser to cause it to absorb energy and generate an instantaneous temperature rise. At the same time, an infrared detector is used to measure the temperature rise curve on the back of the sample. The thermal diffusivity (α) is calculated based on the temperature rise curve, and the thermal conductivity (λ) is calculated by combining the material's density (ρ) and specific heat capacity (Cp).

[0037] Example 1

[0038] This embodiment provides a method for preparing a high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres:

[0039] (1) Mix 3g of SiC particles with 100ml of anhydrous ethanol and 100ml of deionized water, add 0.3% dodecyltrimethoxysilane by volume, reflux at 70℃ for 3h, filter, wash and dry to obtain modified lipophilic SiC particles.

[0040] (2) Dissolve 3g tetradecyltrimethylammonium bromide in 100ml deionized water, and add 1.5g modified nano SiC particles. Heat in a water bath at 45℃ and stir at 600r / min for 30min until tetradecyltrimethylammonium bromide is completely dissolved to form Pickering emulsion.

[0041] (3) Take 3.2g of octadecane and add it to the above emulsion. Keep the oil bath heating at 90°C. After the octadecane is completely melted, stir at 900r / min for 25min. Then stop stirring and transfer the mixture to a new beaker to cool and stand. When the octadecane cools to room temperature, the SiC particles are wrapped and embedded on the outer surface of the solid octadecane, thus forming phase change microspheres.

[0042] (4) Mix 3g of BN particles with 100ml of anhydrous ethanol and 100ml of deionized water, add 0.3% dodecyltrimethoxysilane by volume, reflux at 70℃ for 3h, filter, wash and dry to obtain modified lipophilic BN particles.

[0043] (5) Mix 20g of E51 epoxy resin and 6g of D230 curing agent and mechanically stir until uniform; add 0.52g of modified BN particles (2wt%) and 0.52g (2wt%) of phase change microspheres, disperse uniformly by ultrasonication at 300w, degas under vacuum, pour into a mold, and cure at 30℃ for 12h to obtain a high thermal conductivity epoxy resin composite material doped with phase change microspheres.

[0044] Example 2

[0045] The difference from Example 1 is that the mass fraction of phase change microspheres in step (5) is 1 wt%, and the remaining steps are all the same as in Example 1, so as to obtain the high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres in this example.

[0046] Example 3

[0047] The difference from Example 1 is that the mass fraction of phase change microspheres in step (5) is 3wt%, and the remaining steps are all the same as in Example 1, so as to obtain the high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres in this example.

[0048] Example 4

[0049] The difference from Example 1 is that the mass fraction of phase change microspheres in step (5) is 4wt%, and the remaining steps are all the same as in Example 1, so as to obtain the high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres in this example.

[0050] Comparative Example 1

[0051] The difference from Example 1 is that the mass fraction of phase change microspheres in step (5) is 0 wt%, and the remaining steps are the same as in Example 1, so as to obtain the high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres in this comparative example.

[0052] Comparative Example 2

[0053] Mix 20g of E51 epoxy resin and 6g of D230 curing agent, stir mechanically until uniform, degas under vacuum, pour into a mold, and cure at 30℃ for 12h to obtain a pure epoxy resin sample.

[0054] Comparative Example 3

[0055] The difference from Example 1 is that the added SiC (silicon carbide) particles were not modified in step (1), and the remaining steps were performed in accordance with the example to obtain the doped phase change microspheres of this example.

[0056] Comparative Example 4

[0057] The difference from Example 1 is that the water bath heating in step (2) is adjusted to room temperature, while the remaining steps are the same as in Example 1, thus obtaining the doped phase change microspheres of this example.

[0058] Comparative Example 5

[0059] The difference from Example 1 is that the oil bath heating temperature in step (3) is adjusted to 75°C, while the remaining steps are the same as in Example 1, thus obtaining the doped phase change microspheres of this example.

[0060] The phase change microspheres prepared in step 3 of Example 1 were observed by SEM. Their distribution and surface morphology are shown in Figures 1 and 2(a). The microspheres showed good dispersion, relatively uniform size, and an overall spherical shape with a slightly rough surface. The particle size of the phase change microspheres was statistically analyzed by a particle size analyzer. The results are shown in Figure 3. The diameter of the microspheres ranged from 50 to 150 μm, with an average diameter of 104.28 μm. When the SiC (silicon carbide) particles added in Comparative Example 3 were not modified in step (1), the microspheres prepared were as shown in Figure 2(b). Since SiC has poor compatibility with the oil phase when it is not modified, it agglomerates on the surface of the microspheres, affecting the overall thermal conductivity of the material. The microspheres prepared in Comparative Example 4 were as shown in Figure 2(c). Since the emulsification process was not heated, the emulsification was insufficient, and the coating effect of the prepared microspheres was poor. They were not regular spheres. The microspheres prepared in Comparative Example 5 were as shown in Figure 2(d). The low temperature during the formation of microspheres reduced the dispersion effect of octacosane, resulting in the inability to form spheres.

[0061] The thermal conductivity of the composite materials prepared in Example 1 and Comparative Example 2 and pure epoxy resin was tested using a laser thermal conductivity meter. The thermal conductivity of pure epoxy resin was 0.217 W / (m·K), while the thermal conductivity of the 2% microsphere / 2% BN / EP composite material was 0.287 W / (m·K), which is 32.26% higher than that of pure epoxy resin.

[0062] The composite samples prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to tensile tests using a universal testing machine. The stress-strain curves are shown in Figure 4. The mechanical tensile properties of the composite material decreased continuously with increasing microsphere doping concentration. When the microsphere doping concentration was 2 wt%, the tensile strength of the composite material was 73.68 MPa, which was 89.71% of that of pure epoxy resin (0 wt%), and the mechanical properties of the composite material remained good. When the microsphere doping concentration exceeded 3 wt%, the mechanical properties of the composite material decreased significantly.

[0063] The composite sample prepared in Example 1 was scratched with a medical #11 scalpel to simulate micro-damage. Then, the microspheres were melted by infrared heating to fill the damaged channels. The filling result is shown in Figure 5. As can be seen from the figure, the damaged channels were basically completely filled at this time.

[0064] The samples prepared in Example 1 and Comparative Example 2 were subjected to power frequency breakdown voltage tests. Eight groups of undamaged Sample 1 samples, eight groups of undamaged Comparative Example 2 samples, eight groups of Sample 1 samples with scratch damage but not repaired, and eight groups of Sample 1 samples with scratch damage repaired were tested. The breakdown voltage patterns were statistically analyzed using Weibull statistics. The results are shown in Figure 6. The breakdown probability of 63.2% was taken as the characteristic breakdown voltage of the sample. The data are 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 to 35.89 kV / mm. This may be due to the partial aggregation of microspheres during the doping process, which introduced defects and led to a decrease in breakdown voltage, but the decrease was not significant. The breakdown voltage of the sample with scratch damage but no repair decreased significantly to 29.12 kV / mm. This is because the scratch damage reduced the thickness of the damaged area on the one hand, and increased the electric field distortion of the damaged area on the other hand. The breakdown voltage of the sample after damage repair was 33.28 kV / mm, which recovered to 92.72% of the original value. The repair effect was good, which is beneficial for the application of the composite epoxy resin provided in this application in fields such as power equipment.

[0065] Table 2

[0066] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a high thermal conductivity epoxy resin scratch self-healing material doped with phase change microspheres, characterized in that: include, The emulsifier was dissolved in deionized water, and modified lipophilic nano-SiC particles were added and stirred evenly to form a silicon carbide emulsion. Octacosane was added to the above silicon carbide emulsion, heated in an oil bath, and cooled to obtain octacosane solid microspheres doped with nano-SiC particles. Epoxy resin monomers and curing agents are mixed, and modified oleophilic BN particles and n-octadecane solid microspheres doped with nano-SiC particles are added. After curing, a high thermal conductivity epoxy resin scratch self-healing material with doped phase change microspheres is obtained.

2. The preparation method according to claim 1, characterized in that: The emulsifier is tetradecyltrimethylammonium bromide, and its dosage 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 type epoxy resin, the curing agent is polyetheramine, and the mass ratio of epoxy resin monomer to curing agent is 10:2.5~3.

5.

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

5. A method for preparing modified oleophilic nano-SiC particles, characterized in that: The process includes mixing SiC particles with anhydrous ethanol aqueous solution, adding dodecyltrimethoxysilane, 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 amount of SiC particles added per 100 mL of 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 lipophilic BN particles, characterized in that: The process involves mixing BN particles with anhydrous ethanol aqueous solution, adding dodecyltrimethoxysilane, refluxing, filtering, washing, and drying to obtain modified lipophilic 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 curing agent.

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

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