Water self-healing microcapsule, electric tree damage self-repairing coating and preparation method of water self-healing microcapsule and electric tree damage self-repairing coating

Abstract

The invention discloses a water self-healing microcapsule, an electrical tree damage self-repairing coating and a preparation method thereof, and the preparation method comprises the following steps: mixing lauryl sodium sulfate, sodium hydroxide and deionized water, and stirring in a water bath to obtain a water phase solution; the preparation method comprises the following steps: adding polyisocyanate and octadecanol into ethyl phenylacetate, stirring, then adding isophorone diisocyanate, dropwise adding fluorescent dye, and stirring to obtain an oil phase solution; mixing the water-phase solution and the oil-phase solution, adding n-caprylic alcohol, cooling to room temperature, washing with absolute ethyl alcohol and deionized water respectively, removing residual liquid through low-pressure suction filtration, and drying a solid part to obtain the water self-healing microcapsule. The microcapsule disclosed by the invention is a water self-healing type microcapsule, and the microcapsule can be used for self-repairing electrical tree damage in the coating without a catalyst, and has a good self-repairing effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical coatings, and in particular relates to a water-based self-healing microcapsule, an electrical tree damage self-repairing coating and a preparation method thereof. Background Art

[0002] Silicone rubber coatings are widely used in power systems for flashover prevention and icing prevention due to their excellent electrical insulation properties, outstanding hydrophobicity, and good hydrophobic migration. However, in actual operation, silicone rubber coatings are inevitably exposed to pollution, radiation, humidity, and heat, which can cause dendritic damage on or within the coating. This can ultimately lead to aging phenomena such as peeling, shedding, and chalking, significantly reducing the coating's service life and seriously impacting the safe and stable operation of power systems.

[0003] Inspired by the self-healing phenomena of living organisms in nature, endowing coatings with self-healing properties, enabling them to autonomously repair microdamage during service, could effectively address the problem of premature coating failure. This idea has led to the emergence of a variety of novel self-healing systems. Currently, extensive research on coating self-healing has been conducted domestically and internationally, primarily by embedding nanofillers within the coating matrix to improve material properties and reduce the probability of damage. However, this approach has limitations in repairing early dendritic damage within the material. Therefore, a new approach is needed to address the challenge of self-healing coating damage. Among these self-healing systems, microcapsule self-healing systems have attracted considerable attention. This mechanism involves adding microcapsules to the coating without altering its original chemical structure. When environmental factors induce dendritic microdamage in the coating, the microcapsule shell ruptures, releasing a pre-encapsulated healing agent. Driven by capillary action, the healing agent rapidly penetrates and fills the damaged channels. Subsequently, under external stimuli (such as temperature and light), the agent solidifies, repairing the material damage and restoring its original mechanical and functional properties, ultimately achieving structural integrity and functional recovery. Summary of the Invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a water-self-healing microcapsule, an electrical tree damage self-repairing coating and a preparation method thereof.

[0007] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing water self-healing microcapsules, characterized in that: it comprises:

[0008] Sodium lauryl sulfate, sodium hydroxide and deionized water are mixed and stirred in a water bath to obtain an aqueous phase solution;

[0009] Polyisocyanate and octadecyl alcohol are added to ethyl phenylacetate and stirred, and then isophorone diisocyanate is added, and fluorescent dye is added dropwise and stirred to obtain an oil phase solution;

[0010] After mixing the aqueous phase solution and the oil phase solution, n-octanol is added and cooled to room temperature, and then washed with anhydrous ethanol and deionized water respectively, and then the residual liquid is removed by low-pressure filtration, and the solid part is dried to obtain the water self-healing microcapsules.

[0011] As a preferred embodiment of the preparation method of the present invention, the addition ratio of sodium lauryl sulfate, sodium hydroxide and deionized water in the aqueous phase solution is 6g-7g:5g-6g:180ml-220ml.

[0012] As a preferred embodiment of the preparation method of the present invention, the addition ratio of polyisocyanate, octadecanol, ethyl phenylacetate and isophorone diisocyanate in the oil phase solution is 4g-6g:2g-4g:25ml-32ml:16g-18g.

[0013] As a preferred embodiment of the preparation method of the present invention, the fluorescent dye is fluorescein isothiocyanate, and the added amount is 5% compared to the water self-healing microcapsules.

[0014] As a preferred embodiment of the preparation method of the present invention, the amount of n-octanol added is 2% compared to the water-healing microcapsules.

[0015] As a preferred embodiment of the preparation method of the present invention, the microcapsules are of a core-shell structure, wherein the core material is a mixed solution containing isocyanate groups and the shell material is sodium lauryl sulfate.

[0016] Another object of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a self-repairing coating for electrical tree damage based on water-healing microcapsules, which is characterized by: including adding water-healing microcapsules to high-temperature vulcanized silicone rubber, stirring in a water bath, vacuum degassing, and high-temperature curing to obtain the self-repairing coating for electrical tree damage based on water-healing microcapsules.

[0017] As a preferred solution of the preparation method of the present invention, the mass fraction of the water self-healing microcapsules is 0 to 6 wt%.

[0018] Another object of the present invention is to overcome the deficiencies in the prior art and provide a high-performance electrical tree damage self-repairing coating based on water self-healing microcapsules prepared by a preparation method.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of an electrical tree damage self-repairing coating based on water self-healing microcapsules in silicone rubber coatings.

[0020] Beneficial effects of the present invention:

[0021] The water self-healing microcapsules prepared by the present invention have good thermal stability below 200°C, will not be damaged during the coating preparation process, and can meet the temperature conditions of the coating during the actual operation of the equipment; after being doped with 4wt% of the water self-healing microcapsules, the breakdown field strength of the self-healing coating material becomes 92% of that of the pure coating, which basically does not affect the AC breakdown performance of the coating; the microcapsules are water self-healing microcapsules, which can self-repair electrical tree damage inside the coating without the need for a catalyst, and the self-repair effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0023] Figure 1 Schematic diagram of the water self-healing microcapsule in Example 1 of the present invention.

[0024] Figure 2 This is a scanning electron microscope characterization image of the water self-healing microcapsule in Example 1 of the present invention.

[0025] Figure 3 This is the thermogravimetric curve of the water self-healing microcapsules in Example 1 of the present invention.

[0026] Figure 4 is the relative dielectric constant of the self-repairing coating in Example 1 of the present invention.

[0027] Figure 5 This is the Weibull distribution diagram of the AC breakdown field strength of the self-healing coating in Example 1 of the present invention.

[0028] Figure 6 This is an image of self-repair of electrical tree damage in the self-repairing coating in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] 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.

[0030] 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.

[0031] 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.

[0032] Unless otherwise specified, all raw materials used in the examples of the present invention are commercially available. Details are shown in Table 1.

[0033] Table 1

[0034]

[0035]

[0036] Relative dielectric constant test: The instrument used for dielectric constant test is a wide-frequency domain dielectric spectrum tester. The wide-frequency domain dielectric spectrum tester consists of an AC voltage source and test electrodes. The electrode structure is a copper sheet electrode with a radius of 2 cm. During measurement, the test instrument is calibrated, and then the sample is placed between the two electrodes so that the electrodes are close to the surface of the sample. A sinusoidal voltage is applied to both ends of the sample, and the relative dielectric constant of the sample at each frequency is recorded.

[0037] AC breakdown test: The AC breakdown test platform primarily consists of a control system, test transformer, voltage divider, protective resistor, oscilloscope, test tank, and electrodes. The test tank contains insulating oil, and the sample is immersed in the oil during the test. Sample thickness must be recorded before the test. During the test, the voltage is increased at a rate of 1 kV / s until the sample breaks down, and the breakdown voltage is recorded. The breakdown field strength is calculated by dividing the breakdown voltage by the sample thickness.

[0038] Example 1

[0039] This embodiment provides a preparation method of water-based self-healing microcapsules:

[0040] (1) Preparation of aqueous solution: 7 g of sodium lauryl sulfate and 5 g of NaOH were placed in a round-bottom flask, and 200 ml of deionized water was added. The mixture was mechanically stirred at 60°C in a water bath for 40 min to completely dissolve the sodium lauryl sulfate. The resulting solution was used as the aqueous solution.

[0041] (2) Preparation of oil phase solution: 6 g of polyisocyanate and 3 g of octadecyl alcohol were weighed and added to 30 ml of ethyl phenylacetate. The mixture was mechanically stirred for 20 min. Then, 17 g of isophorone diisocyanate was added. 3 g of fluorescein isothiocyanate was added to the mixed solution in 45 drops. The mixture was mechanically stirred for 40 min until the solution became homogeneous, thereby obtaining a stable oil phase solution.

[0042] (3) Preparation of water-healing microcapsules: The oil phase solution prepared in step (2) was slowly and continuously poured into the aqueous phase solution prepared in step (1). During this process, mechanical stirring was maintained in a 70°C water bath for 70 minutes to fully emulsify the oil phase solution and the aqueous phase solution to form microcapsules. A large number of bubbles were generated during the reaction. To eliminate the bubbles, 1 ml of n-octanol was added dropwise. After the reaction was completed, the reaction solution was naturally cooled to room temperature and washed twice with anhydrous ethanol and deionized water, respectively. The residual liquid was then removed by low-pressure filtration. The solid portion was then dried to obtain a powdered microcapsule sample.

[0043] Example 2

[0044] This embodiment provides a method for preparing a high-performance self-repairing coating for electrical tree damage based on water-based self-healing microcapsules:

[0045] (1) Preparation of a high-performance self-healing coating for electrical tree damage: First, 10 g of high-temperature vulcanized silicone rubber was placed in a round-bottom flask and stirred in a water bath at 90°C. Subsequently, the water-based self-healing microcapsules prepared in step (3) were added to the silicone rubber and the microcapsules were uniformly mixed in the silicone rubber to obtain a mass fraction of 4 wt %. The uniformly mixed solution was first vacuum degassed to eliminate bubbles, poured into a mold, placed on a heating table, and cured at 150°C until the silicone rubber solidified. The solution was then cooled at room temperature and demolded to obtain a high-performance self-healing coating for electrical tree damage.

[0046] like Figure 1 As shown in the schematic diagram, the water-based self-healing microcapsules prepared by this invention have a double-layer structure. The outer shell primarily prevents the repair agent from prematurely curing and failing, and provides mechanical support for the microcapsules. The inner layer contains a fluorescent repair agent. After electrical tree microdamage occurs, the outer shell ruptures, allowing the repair agent to flow out and fill and cure the damaged channel.

[0047] This paper discusses the dielectric properties of self-repairing coatings and mainly tests the relative dielectric constant of composite insulating coatings. The experimental results are as follows Figure 4 As shown in the figure, the relative dielectric constant of the composite insulating coating decreases with increasing frequency. This phenomenon can be well explained by the material's polarization mechanism. At low frequencies, the electronic and impurity polarization within the material closely follows changes in the external electric field, responding well. However, as the frequency increases, the rate of change of the external electric field accelerates, and the response of the relaxation polarization lags, preventing the polarization process from completing quickly enough, resulting in a decrease in the material's relative dielectric constant. Figure 4 The experimental data also revealed the effect of the content of thermochromic microcapsules on the dielectric properties of composite insulating coatings. As the content of microcapsules increases, the dielectric constant of the coating shows an overall increasing trend, indicating that the doping concentration of microcapsules has a certain regulatory effect on the dielectric properties of the coating. However, when the content of microcapsules is 4wt%, the dielectric constant of the composite insulating coating is significantly lower than that of the coating with 2wt%. This shows that when the content of microcapsules is 4wt%, there is good compatibility between the microcapsules and the coating matrix, which enables the microcapsules to be better dispersed in the coating matrix, thereby improving the overall dielectric properties of the composite coating, which is manifested as a decrease in the relative dielectric constant. In summary, when preparing self-healing coatings, the optimal microcapsule doping concentration, i.e. 4wt%, should be selected to effectively improve the performance of the composite insulating coating.

[0048] This paper mainly studies the AC breakdown characteristics of self-repairing coatings and uses the Weibull statistical distribution method to conduct a detailed analysis of the test data. The experimental results are as follows Figure 5 As shown in the figure, it can be seen that the incorporation of water-based self-healing microcapsules has an impact on the AC breakdown field strength of the self-healing coating. Specifically, as the doping concentration of the microcapsules increases, the AC breakdown field strength of the composite coating gradually decreases. However, when the doping concentration of the microcapsules is 4wt%, the breakdown field strength of the self-healing coating is improved to a certain extent compared to when the doping concentration is 2wt%. The breakdown field strength of the constituent material of the microcapsules itself is lower than that of the pure coating, which leads to a decrease in the overall breakdown field strength of the composite insulating material after the microcapsules are incorporated. The incorporation of microcapsules introduces a large number of impurity groups, increases the carrier concentration, further promotes the collision ionization process, and accelerates the insulation failure of the material. The addition of microcapsules inevitably forms a defect structure, resulting in electric field distortion and the formation of new local discharge points. Under the action of high electric fields, these discharge points develop rapidly, further accelerating insulation failure. However, if appropriate microcapsules are doped into the self-healing coating, the dielectric properties and breakdown characteristics can be balanced, and the overall performance of the self-healing coating can be optimized.

[0049] The test results of the self-repairing of electrical tree damage of a high-performance self-repairing coating based on water self-healing microcapsules according to the present invention are as follows:

[0050] After the injection molding is completed, a needle electrode with a curvature radius of 25m is buried in the uncured self-healing coating mixture to ensure that the distance between the needle tip and the side surface of the mold is about 3mm, and then the curing treatment is carried out. Next, the electric tree test platform is used to induce the sample to generate electric trees. The needle electrode of the sample is connected to the high-voltage end to stimulate the growth of electric trees in the self-healing coating. The electric tree test platform includes an industrial frequency experimental transformer, a voltage regulator, a protective resistor, a voltage divider, an experimental sample and a real-time microscopic observation device. In order to prevent the sample from flashing along the surface during the generation of electric trees, thereby affecting the experimental results, the present invention immerses the sample and the electrode in insulating oil together. Electric trees are the result of gradual aging of insulating materials under long-term high electric field stress. In order to shorten the test time, the present invention adopts a step-by-step voltage boosting method. After the electric trees begin to grow, the applied voltage is immediately reduced and kept stable to promote the further growth of the electric trees. As Figure 6 In the experiment, it was observed that electrical trees began to grow from the tip of the needle electrode and continued to expand outward. When the trees reached the water-healing microcapsules, the microcapsule shell ruptured, the repair agent flowed out, and a chemical reaction occurred to generate new organic matter, filling and solidifying the damaged channels, restoring the performance of the insulating material. While the repair agent contained in the microcapsules can effectively repair the damage caused by electrical trees, the impurities and interface regions introduced by the microcapsules may disrupt the continuity of the original matrix structure, thereby hindering the expansion of electrical trees and limiting their size.

[0051] Example 3

[0052] The difference from Example 2 is that the mass fraction of the microcapsules in step (4) is 2 wt%.

[0053] Example 4

[0054] The difference from Example 2 is that the mass fraction of the microcapsules in step (4) is 6 wt %.

[0055] Comparative Example 1

[0056] The difference from Example 2 is that the mass fraction of the microcapsules in step (4) is 0 wt%.

[0057] from Figure 2 It can be clearly observed that the particle size distribution of the microcapsules is concentrated in the range of 210 to 330 μm, with an average particle size of 262.56 μm. The outer surface of the water self-healing microcapsules is smooth with almost no obvious protrusions. This is due to the selection of materials for the outer surface of the microcapsules. This material can form a uniform and flat surface during the molding process. The smooth outer surface of the microcapsules is conducive to the uniform distribution of the microcapsules inside the coating matrix, and is not prone to agglomeration or irregular accumulation, and is also conducive to the uniformity of the microcapsule size.

[0058] Example 5

[0059] The difference between this embodiment and embodiment 1 is that the mass of sodium lauryl sulfate is adjusted to 10 g, and the rest of the preparation process is the same as that of embodiment 1 to prepare microcapsules.

[0060] Example 6

[0061] The difference between this embodiment and embodiment 2 is that the water bath temperature for preparing microcapsules is adjusted to 50° C., and the rest of the preparation process is the same as that of embodiment 1 to prepare microcapsules.

[0062] Comparative Example 2

[0063] The difference between this embodiment and embodiment 1 is that the mass of n-octanol is adjusted to 0 ml, and the rest of the preparation process is the same as that of embodiment 1 to prepare microcapsules.

[0064] Comparative Example 3

[0065] The difference between this embodiment and embodiment 1 is that the fluorescent dye is changed to carboxyfluorescein, and the rest of the preparation process is the same as that of embodiment 1 to prepare microcapsules.

[0066] Table 2

[0067]

[0068]

[0069] Table 2 compares the conditions of the embodiments of the present invention and the comparative examples. Compared with Example 1, Examples 3 and 4 change the mass fraction of the microcapsules doped in the silicone rubber, but the breakdown and dielectric properties of the composite silicone rubber materials obtained in Examples 3 and 4 are not as good as those in Example 1. Compared with Example 1, Examples 5 and 6 change the mass of sodium lauryl sulfate and the water bath temperature in the microcapsule preparation process. The microcapsules prepared thereby are difficult to form and have an uneven particle size distribution. Compared with Example 1, Comparative Example 1 does not contain microcapsules in the silicone rubber. The silicone rubber is used for comparison with the composite silicone rubber material doped with microcapsules. The research shows that the various properties of the silicone rubber doped with microcapsules are improved to a certain extent. Compared with Example 1, Comparative Examples 2 and 3 change the amount of n-octanol added and the type of fluorescent dye in the preparation process. The structural integrity of the prepared microcapsules is impaired.

[0070] Figure 3 Thermogravimetric properties of self-healing microcapsules. Figure 3As can be seen from the figure, the water-healing microcapsule sample undergoes four distinct stages of mass loss over the temperature range of 0°C to 600°C. The mass change in each stage is closely related to the physicochemical transformations within the sample, effectively reflecting the thermal stability and thermal decomposition of the material. The first stage occurs between 0°C and 200°C, with a mass loss of approximately 4%. This mass loss is primarily attributed to the volatilization of adsorbed and crystalline water. The second stage, between 200°C and 350°C, features significant mass loss. During this stage, the chemical structure of the sample gradually decomposes, and the organic components begin to thermally decompose. The third stage, between 350°C and 450°C, features a significant mass loss, with an accelerated decomposition rate of the organic components. The fourth stage, between 450°C and 700°C, sees a slower mass loss, resulting in a final residual mass of 8%, indicating that the primary organic components of the microcapsules have been completely decomposed, leaving the remaining inorganic components to emerge. The formation of inorganic residues may be due to the greater stability of certain inorganic materials at high temperatures, making them less susceptible to further decomposition reactions. In summary, the thermal stability of the thermochromic microcapsule samples exhibits distinct phased characteristics. Throughout the thermal decomposition process, the sample's mass loss is primarily concentrated in the temperature range of 200°C to 450°C. The water-based self-healing microcapsules prepared in this invention exhibit excellent thermal stability below 200°C, meeting the temperature requirements of the coating during actual equipment operation.

[0071] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention 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 invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for preparing water-self-healing microcapsules, characterized in that: include, Sodium lauryl sulfate, sodium hydroxide and deionized water are mixed and stirred in a water bath to obtain an aqueous phase solution; Polyisocyanate and octadecyl alcohol are added to ethyl phenylacetate and stirred, and then isophorone diisocyanate is added, and fluorescent dye is added dropwise and stirred to obtain an oil phase solution; After mixing the aqueous phase solution and the oil phase solution, n-octanol is added and cooled to room temperature, and then washed with anhydrous ethanol and deionized water respectively, and then the residual liquid is removed by low-pressure filtration, and the solid part is dried to obtain the water self-healing microcapsules.

2. The preparation method according to claim 1, wherein: The addition ratio of sodium lauryl sulfate, sodium hydroxide and deionized water in the aqueous phase solution is 6g-7g:5g-6g:180ml-220ml.

3. The preparation method according to claim 1, wherein: The addition ratio of polyisocyanate, octadecyl alcohol, ethyl phenylacetate and isophorone diisocyanate in the oil phase solution is 4g-6g: 2g-4g: 25ml-32ml: 16g-18g.

4. The preparation method according to claim 1, wherein: The fluorescent dye is fluorescein isothiocyanate, and the added amount is 5% compared to the water self-healing microcapsules.

5. The preparation method according to claim 1, wherein: The amount of n-octanol added is 2% compared to the water self-healing microcapsules.

6. The water-healing microcapsules prepared by the preparation method according to claims 1 to 5, characterized in that: The microcapsule is a core-shell structure, wherein the core material is a mixed solution containing isocyanate groups, and the shell material is sodium lauryl sulfate.

7. A method for preparing a self-repairing coating for electrical tree damage based on water-repairing microcapsules, characterized by: The method comprises the steps of adding the water-based self-healing microcapsules according to claim 6 to high-temperature vulcanized silicone rubber, stirring in a water bath, vacuum degassing, and high-temperature curing to obtain the electrical tree damage self-repairing coating based on the water-based self-healing microcapsules.

8. The preparation method according to claim 7, wherein: The amount of the water self-healing microcapsules added to the high-temperature vulcanized rubber is 0 to 6 wt %.

9. A high-performance electrical tree damage self-repairing coating based on water self-healing microcapsules prepared by the preparation method according to claims 7 to 8.

10. Use of the electrical tree damage self-repairing coating based on water self-healing microcapsules as claimed in claim 9 in silicone rubber coating.

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