Surface damage self-diagnosis insulating material as well as preparation method and application thereof

Abstract

The invention provides a surface damage self-diagnosis insulating material as well as a preparation method and application thereof. The surface damage self-diagnosis insulating material comprises a silicon rubber base material, microcapsules and an alkali reagent, wherein the microcapsules and the alkali reagent are dispersed in the silicon rubber base material; the microcapsule comprises a shell and a core material, the shell is a urea-formaldehyde resin polymer, and the core material comprises 2 ', 7'-dichlorofluorescein and ethyl phenylacetate. The mass fraction of the microcapsule in the silicone rubber matrix is 1-10%, and the mass fraction of the alkali reagent in the silicone rubber matrix is 1-10%. According to the surface damage self-diagnosis insulating material provided by the invention, the microcapsule component is added into an existing silicone rubber material, so that the composite material has a damage self-diagnosis function on the premise that the mechanical property and the insulating property are kept good, and red can be displayed as an indication after the material is damaged; the method is of great significance in detection of insulation damage of power equipment, early warning of faults and improvement of use safety and reliability of polymer insulation materials.

Description

Technical Field

[0001] This invention belongs to the field of electrical materials technology, and particularly relates to a self-diagnostic insulating material for surface damage, its preparation method and application. Background Technology

[0002] During the operation of electrical equipment, polymer insulation materials are subjected to various forms of damage under the influence of environmental stress, mechanical stress, and electrical stress. Early damage may not affect normal use, but it will gradually reduce the material's performance, leading to deterioration or degradation. If the insulation material could autonomously report such damage after it is damaged, it would prevent eventual large-scale failure and effectively improve the safety and reliability of polymer applications.

[0003] Polymer insulating materials are susceptible to mechanical damage such as cracks and deformation due to internal and external mechanical stresses. On the other hand, when dielectric polymers are exposed to localized high electric fields, electrical damage occurs, such as electrical treeing and partial discharge within the insulation, as well as corona discharge, surface discharge, and erosion / corrosion on the insulation surface. Accumulated damage leads to a decline in the material's insulating properties, ultimately causing insulation failure and equipment malfunction.

[0004] Current methods for detecting damage to external insulation include electric field distribution measurement, infrared imaging, ultraviolet imaging, and leakage current measurement. These methods all require equipment for detection and are only effective for specific damage conditions. Current research on self-diagnostic materials mainly focuses on the self-diagnostic effects after mechanical damage. For power equipment, electrical damage to the material surface, such as corona discharge, tracking, electrical erosion, surface discharge, localized arcing, and flashover, is the main cause of insulation material failure. Therefore, research on self-diagnosis of surface electrical damage is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a surface damage self-diagnostic insulating material, its preparation method and application. The surface damage self-diagnostic insulating material of this invention can realize the visualization effect of autonomous reporting and diagnosis of insulating materials after being subjected to various forms of electrical and mechanical damage.

[0006] This invention provides a surface damage self-diagnostic insulating material, comprising a silicone rubber substrate and microcapsules and an alkaline reagent dispersed in the silicone rubber substrate;

[0007] The microcapsule comprises a shell and a core material, wherein the shell is a urea-formaldehyde resin polymer and the core material comprises 2',7'-dichlorofluorescein and ethyl phenylacetate.

[0008] The microcapsules have a mass fraction of 1-10% in the silicone rubber matrix, and the alkaline reagent has a mass fraction of 1-10% in the silicone rubber matrix.

[0009] Preferably, the alkaline reagent includes one or more of aluminum hydroxide, sodium carbonate, sodium hydroxide, and sodium dodecylbenzenesulfonate.

[0010] Preferably, the mass ratio of the outer shell to the core material is 1:(4~8).

[0011] Preferably, the mass fraction of 2',7'-dichlorofluorescein in the core material is 0.01~0.1%.

[0012] This invention provides a method for preparing a surface damage self-diagnostic insulating material as described in the "Sprinkling Flower Girl" method, comprising the following steps:

[0013] A) Mix emulsifier, alkaline medium and water to obtain an emulsion with a pH of 3 to 4;

[0014] B) Mix the emulsion, urea, resorcinol and ammonium chloride, add the core material dropwise under stirring, and emulsify at room temperature;

[0015] The core material comprises 2',7'-dichlorofluorescein, ethyl phenylacetate, and a curing agent;

[0016] C) After emulsifying at room temperature for 10-60 minutes, add formaldehyde aqueous solution to the solution, raise the temperature to 50-60℃, and continue the reaction for 3-6 hours to obtain microcapsules;

[0017] D) Mix silicone rubber, microcapsules, alkaline reagents and optional additives, and cure to obtain a surface damage self-diagnostic insulating material.

[0018] Preferably, in step A), the emulsifier is a poly(ethylene-maleic anhydride) aqueous solution with a mass fraction of 1-5%, and the alkaline medium is sodium hydroxide.

[0019] Preferably, the mass ratio of urea, resorcinol and ammonium chloride is (8~12):(0.5~2):1.

[0020] Preferably, in step D), the curing is heat curing, condensation curing, or addition curing.

[0021] Preferably, in step D), the optional additives include one or more of functional fillers, vulcanizing agents, coupling agents, pigments, silicone oils, and anti-aging agents.

[0022] This invention provides the application of the surface damage self-diagnostic insulating material as described above in the self-diagnosis of electrical damage in electrical insulation materials.

[0023] This invention provides a surface damage self-diagnostic insulating material, comprising a silicone rubber substrate and microcapsules and an alkaline reagent dispersed in the silicone rubber substrate. The microcapsules comprise a shell and a core material; the shell is a urea-formaldehyde resin polymer, and the core material comprises 2',7'-dichlorofluorescein and ethyl phenylacetate. The mass fraction of the microcapsules and the alkaline reagent in the silicone rubber matrix is ​​1-10% by mass. The surface damage self-diagnostic insulating material provided in this application adds a microcapsule component to existing silicone rubber materials. This composite material, while maintaining good mechanical and insulating properties, possesses a self-diagnostic function for damage, displaying a red indicator after the material is damaged. This is of great significance for detecting insulation damage in power equipment, providing early warning of faults, and improving the safety and reliability of polymer insulating materials.

[0024] In view of the fact that existing self-diagnostic materials are only applicable to mechanical damage, the surface damage self-diagnostic material provided in this application can achieve the effect of self-diagnosis in both electrical and mechanical damage cases, and has greater application value for various forms of surface damage to the insulation materials of power equipment.

[0025] Existing insulation damage detection technologies employ various instruments for offline or online detection and analysis. The surface damage self-diagnostic insulation material provided in this application does not require the use of complex instruments and equipment for testing. After the material is damaged, it can report, indicate, and convey the damaged area through color changes, providing an intuitive visual diagnostic effect. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure and mechanism of the self-diagnostic insulation material.

[0028] Figure 2 The tensile curves of the surface damage self-diagnostic insulating materials in Examples 2-4 of this invention are shown.

[0029] Figure 3 The dielectric constant variation curves of the surface damage self-diagnostic insulating materials in Examples 2-4 of this invention are shown.

[0030] Figure 4 The curves showing the variation of the dielectric loss tangent of the surface damage self-diagnostic insulating material in Examples 2-4 of this invention are shown.

[0031] Figure 5 The Weibull distribution of the breakdown field strength of the surface damage self-diagnostic insulating material in Examples 2-4 of this invention;

[0032] Figure 6 Thermogravimetric curves of the surface damage self-diagnostic insulating materials in Examples 2-4 of this invention;

[0033] Figure 7 This demonstrates the diagnostic effect of the self-diagnostic insulating material for surface damage under different AC voltages in Embodiment 3 of the present invention.

[0034] Figure 8 This demonstrates the diagnostic effect of surface damage self-diagnostic insulating material on surface discharge in Embodiment 3 of the present invention.

[0035] Figure 9 This demonstrates the diagnostic effect of surface damage self-diagnosis of insulation material breakdown discharge in Embodiment 3 of the present invention.

[0036] Figure 10 The surface damage self-diagnosis of insulating materials in Examples 2-4 of this invention demonstrates the mechanical damage diagnosis effect. Detailed Implementation

[0037] This invention provides a surface damage self-diagnostic insulating material, comprising a silicone rubber substrate and microcapsules and an alkaline reagent dispersed in the silicone rubber substrate;

[0038] The microcapsule comprises a shell and a core material, wherein the shell is a urea-formaldehyde resin polymer and the core material comprises 2',7'-dichlorofluorescein and ethyl phenylacetate.

[0039] The microcapsules have a mass fraction of 1-10% in the silicone rubber matrix, and the alkaline reagent has a mass fraction of 1-10% in the silicone rubber matrix.

[0040] In this invention, the silicone rubber substrate is silicone rubber with insulating properties commonly used in the art, and will not be described in detail here.

[0041] In this invention, the microcapsule comprises a shell and a core material. The shell is a urea-formaldehyde resin polymer, and the core material comprises 2',7'-dichlorofluorescein and ethyl phenylacetate. In this invention, 2',7'-dichlorofluorescein is dissolved in ethyl phenylacetate as the core material, and the urea-formaldehyde resin polymer is used as the shell, encapsulating to form a microcapsule. The microcapsule and an alkaline reagent are incorporated into a silicone rubber substrate. After the material surface is subjected to mechanical or electrical damage, the microcapsule wall ruptures directly or gradually, releasing the core material. The 2',7'-dichlorofluorescein comes into contact with the alkaline sodium carbonate in the matrix, and its structure changes from a lactone form to a quinone form, turning the damaged area red. The principle is shown in Formula I:

[0042] Formula I.

[0043] In this invention, the mass fraction of the microcapsules in the silicone rubber matrix is ​​preferably 1-10%, more preferably 3-8%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, preferably within the range of any of the above values ​​as the upper or lower limit. The alkaline reagent is preferably one or more of aluminum hydroxide, sodium carbonate, sodium hydroxide, and sodium dodecylbenzenesulfonate. The mass fraction of the alkaline reagent in the silicone rubber matrix is ​​preferably 1-10%, more preferably 3-8%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, preferably within the range of any of the above values ​​as the upper or lower limit.

[0044] In this invention, the mass ratio of the shell to the core material of the microcapsule is preferably 1:(4~8), more preferably 1:(6~7), such as 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, preferably within the range of any of the above values ​​as the upper or lower limit; the mass fraction of 2',7'-dichlorofluorescein in the core material is preferably 0.01~0.1%, more preferably 0.03~0.08%, such as 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, preferably within the range of any of the above values ​​as the upper or lower limit.

[0045] In this invention, the particle size of the microcapsules is preferably 60-80 μm, more preferably 70-75 μm, and the shell thickness is preferably, more preferably 650-750 nm, more preferably 680-720 nm.

[0046] This invention provides a method for preparing the surface damage self-diagnostic insulating material described above, comprising the following steps:

[0047] A) Mix emulsifier, alkaline medium and water to obtain an emulsion with a pH of 3 to 4;

[0048] B) Mix the emulsion, urea, resorcinol and ammonium chloride, add the core material dropwise under stirring, and emulsify at room temperature;

[0049] The core material comprises 2',7'-dichlorofluorescein, ethyl phenylacetate, and a curing agent;

[0050] C) After emulsifying at room temperature for 10-60 minutes, add formaldehyde aqueous solution to the solution, raise the temperature to 50-60℃, and continue the reaction for 3-6 hours to obtain microcapsules;

[0051] D) Mix silicone rubber, microcapsules, alkaline reagents and optional additives, and cure to obtain a surface damage self-diagnostic insulating material.

[0052] The present invention first prepares an emulsifier and a core material. The emulsifier is prepared by dissolving poly(ethylene-maleic anhydride) in water. The core material is obtained by mixing 2',7'-dichlorofluorescein, ethyl phenylacetate and curing agent.

[0053] In this invention, the mass fraction of poly(ethylene-maleic anhydride) in the emulsifier is preferably 1-5%, more preferably 2-4%, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, preferably within the range of any of the above values ​​as the upper or lower limit; the mass ratio of 2',7'-dichlorofluorescein to ethyl phenylacetate is preferably 1:(1500-2500), more preferably 1:(2000-2200), such as 1:1500, 1:1600, 1:1700, 1:1800, 1:1900, 1:2000. The ratio of curing agent to ethyl phenylacetate is preferably 1:2100, 1:2200, 1:2300, 1:2400, 1:2500, or more preferably, within the range of values ​​with any of the above values ​​as the upper or lower limit; the curing agent is preferably a polyisocyanate curing agent, such as Bayer curing agent L75, and the mass ratio of the curing agent to ethyl phenylacetate is preferably 1:(10~20), more preferably 1:(15~18), such as 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, or more preferably, within the range of values ​​with any of the above values ​​as the upper or lower limit.

[0054] After obtaining the emulsifier and core material, the present invention mixes the emulsifier and alkaline medium in water to obtain an emulsion. Preferably, the present invention mixes the emulsifier and water, and adds an alkaline medium dropwise to adjust the pH value of the solution to 3-4, preferably 3.5, to obtain an emulsion.

[0055] In this invention, the alkaline medium is preferably sodium hydroxide, more preferably an aqueous solution of sodium hydroxide. This invention does not impose any special restrictions on the concentration and amount of the sodium hydroxide aqueous solution, as long as the pH value of the emulsion can be adjusted to the required range.

[0056] After obtaining the emulsion, the present invention adds urea, resorcinol and ammonium chloride to the emulsion, and then adds the prepared core material to the mixed solution under stirring conditions for emulsification. After the emulsification is completed, formaldehyde is added and the temperature is raised to continue the reaction to obtain microcapsules.

[0057] In this invention, the preferred mass ratio of urea, resorcinol, and ammonium chloride is (8~12):(0.5~2):1, more preferably (9~11):(1~1.5):1. Specifically, in some embodiments of this invention, it can be 10:1:1. The preferred mass ratio of 2',7'-dichlorofluorescein to urea is (1~5):250, more preferably (2~4):250, such as 1:250, 2:250, 3:250, 4:250, 5:250, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0058] In this invention, the stirring speed is preferably 500-600 rpm, more preferably 550-600 rpm, the emulsification temperature is preferably room temperature, such as 20-35℃, more preferably 25-30℃, and the emulsification time is preferably 10-60 min, more preferably 20-50 min, such as 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, preferably within the range of any of the above values ​​as the upper or lower limit.

[0059] In this invention, the mass ratio of formaldehyde to core material is preferably 1:(8~12), more preferably 1:(9~11), such as 1:8, 1:9, 1:10, 1:11, 1:12, and preferably within the range of any of the above values ​​as the upper or lower limit; in this invention, an aqueous formaldehyde solution is preferably added, and after adding formaldehyde, the temperature is raised to 50~60℃, more preferably 55~60℃, and the rate of heating is preferably 1~3℃ / min, more preferably 1~2℃ / min; the reaction time after heating is preferably 3~6 hours, more preferably 4~5 hours.

[0060] After the reaction is complete, the reaction product is washed, filtered and dried to obtain microcapsules.

[0061] After obtaining the microcapsules, the present invention mixes silicone rubber, microcapsules, alkaline reagent and optional additives, and cures them to obtain a surface damage self-diagnostic insulating material.

[0062] In this invention, the optional additives include one or more of the following: functional fillers (such as silica, aluminum hydroxide), vulcanizing agents, coupling agents, pigments, silicone oils, and anti-aging agents.

[0063] In this invention, the types and amounts of the alkali reagent, microcapsules, and silicone rubber are the same as those described above, and will not be repeated here.

[0064] In this invention, the curing can be heat curing, condensation curing, or addition curing, all of which are commonly used curing methods in the art. Curing can be carried out according to conventional operations in the art, and this invention does not impose any special limitations on them.

[0065] This invention also provides an application of the aforementioned surface damage self-diagnostic insulating material in the self-diagnosis of electrical damage in electrical insulation materials. The surface damage self-diagnostic material of this invention can produce color changes in the damaged area under various forms of electrical and mechanical damage, achieving a self-diagnostic effect.

[0066] The self-diagnostic insulating material for surface damage provided by this invention adds microcapsule components to existing silicone rubber materials. This composite material, while maintaining good mechanical and insulating properties, possesses a self-diagnostic function for damage. It can display a red indicator after the material is damaged, which is of great significance for detecting insulation damage in power equipment, early warning of faults, and improving the safety and reliability of polymer insulating materials.

[0067] In view of the fact that existing self-diagnostic materials are only applicable to mechanical damage, the surface damage self-diagnostic material provided in this application can achieve the effect of self-diagnosis in both electrical and mechanical damage cases, and has greater application value for various forms of surface damage to the insulation materials of power equipment.

[0068] Existing insulation damage detection technologies employ various instruments for offline or online detection and analysis. The surface damage self-diagnostic insulation material provided in this application does not require the use of complex instruments and equipment for testing. After the material is damaged, it can report, indicate, and convey the damaged area through color changes, providing an intuitive visual diagnostic effect.

[0069] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, describes a surface damage self-diagnostic insulating material, its preparation method, and its application, but this should not be construed as limiting the scope of protection of the present invention.

[0070] Example 1

[0071] A 2.5% (w / w) aqueous solution of poly(ethylene-maleic anhydride) was prepared as an emulsifier for the reaction. 120 mg of 2',7'-dichlorofluorescein, 60 g of ethyl phenylacetate, and 4 g of Bayer curing agent L75 were mixed evenly to form the core material of the microcapsules.

[0072] Place 100 mL of deionized water and 30 mL of poly(ethylene-maleic anhydride) aqueous solution into a three-necked flask, and add sodium hydroxide aqueous solution dropwise to adjust the pH of the solution to 3.5;

[0073] Add 2.5 g of urea, 0.25 g of resorcinol and 0.25 g of ammonium chloride to the above flask, and emulsify the core material by dropping it into the flask at a speed of 550 rpm.

[0074] After emulsification for 30 min, 6.9 g of formaldehyde aqueous solution was added to the solution. The oil bath temperature was increased from room temperature to 55 °C at a rate of 1 °C / min, and the reaction was continued for 4 hours. The microcapsules were obtained by washing, filtering and drying.

[0075] The synthesis steps for heat-cured self-diagnostic silicone rubber materials are as follows:

[0076] Add 25 g of SYLGARD 182 two-component addition-type silicone rubber component A (uncrosslinked linear polydimethylsiloxane precursor) to a beaker, add 3 g of silica, stir evenly with a glass rod, then add 3 g of aluminum hydroxide, 1 g of titanium dioxide and 1.5 g of sodium carbonate, stir, and then add 1.5 g of the synthesized microcapsules and 2.5 g of silicone rubber component B (silicone rubber crosslinking agent); place the mixture in a vacuum drying oven to degas for 10 min; place a polyimide film on each of two flat molds, place a 1 mm thick hollow sheet mold on one of the flat molds, spread the mixture evenly on the hollow part of the sheet mold, and cover with the other flat mold; place the mold on a flat vulcanizing machine, heat and cure for 75 min at 15 MPa pressure and 100°C to obtain a surface damage self-diagnostic insulating material.

[0077] Example 2

[0078] The surface damage self-diagnostic insulating material was prepared according to the method in Example 1, except that the surface damage self-diagnostic insulating material was prepared according to the following formulation:

[0079] 25g of SYLGARD 182 two-component addition-type silicone rubber, component A (uncrosslinked linear polydimethylsiloxane precursor), 3g of silica were added, and the mixture was stirred evenly with a glass rod. Then, 3g of aluminum hydroxide, 1g of titanium dioxide, and 1.5g of sodium carbonate were added, and the mixture was stirred. Finally, 0.735g of the microcapsules synthesized above and 2.5g of silicone rubber component B (silicone rubber crosslinking agent) were added.

[0080] Place the mixture in a vacuum drying oven to degas for 10 min; place a polyimide film on each of the two flat molds, place a 1 mm thick hollow sheet mold on one of the flat molds, spread the mixture evenly in the hollow part of the sheet mold, and cover it with the other flat mold; place the mold on a flat vulcanizing machine, and heat and cure it for 75 min at a pressure of 15 MPa and a temperature of 100°C to obtain a surface damage self-diagnostic insulating material.

[0081] Example 3

[0082] The surface damage self-diagnostic insulating material was prepared according to the method in Example 1, except that the surface damage self-diagnostic insulating material was prepared according to the following formulation:

[0083] 25g of SYLGARD 182 two-component addition-type silicone rubber, component A (uncrosslinked linear polydimethylsiloxane precursor), 3g of silica were added, and the mixture was stirred evenly with a glass rod. Then, 3g of aluminum hydroxide, 1g of titanium dioxide, and 1.5g of sodium carbonate were added, and the mixture was stirred. Finally, 2.298g of the microcapsules synthesized above and 2.5g of silicone rubber component B (silicone rubber crosslinking agent) were added.

[0084] Place the mixture in a vacuum drying oven to degas for 10 min; place a polyimide film on each of the two flat molds, place a 1 mm thick hollow sheet mold on one of the flat molds, spread the mixture evenly in the hollow part of the sheet mold, and cover it with the other flat mold; place the mold on a flat vulcanizing machine, and heat and cure it for 75 min at a pressure of 15 MPa and a temperature of 100°C to obtain a surface damage self-diagnostic insulating material.

[0085] Example 4

[0086] The surface damage self-diagnostic insulating material was prepared according to the method in Example 1, except that the surface damage self-diagnostic insulating material was prepared according to the following formulation:

[0087] 25g of SYLGARD 182 two-component addition-cure silicone rubber component A (uncrosslinked linear polydimethylsiloxane precursor) was mixed with 3g of silica and stirred with a glass rod. Then, 3g of aluminum hydroxide, 1g of titanium dioxide and 1.5g of sodium carbonate were added and stirred. Finally, 4g of the synthesized microcapsules and 2.5g of silicone rubber component B (silicone rubber crosslinking agent) were added.

[0088] Place the mixture in a vacuum drying oven to degas for 10 min; place a polyimide film on each of the two flat molds, place a 1 mm thick hollow sheet mold on one of the flat molds, spread the mixture evenly in the hollow part of the sheet mold, and cover it with the other flat mold; place the mold on a flat vulcanizing machine, and heat and cure it for 75 min at a pressure of 15 MPa and a temperature of 100°C to obtain a surface damage self-diagnostic insulating material.

[0089] Example 5

[0090] The synthesis steps for condensation-cured self-diagnostic silicone rubber materials are as follows:

[0091] Add 25 g of polydimethylsiloxane liquid DMS-S35 component with silanol end caps, 1.5 g of microcapsules synthesized in Example 1 and 1.5 g of sodium carbonate to a beaker, stir well, add 2.5 g of crosslinking agent poly(diethoxysiloxane), add two drops of dimethyltin dodecanoate catalyst, place the mixture in a vacuum drying oven to degas for 1 min, then pour it into a mold and place it at room temperature to cure for 4 hours to obtain a surface damage self-diagnostic insulating material.

[0092] Example 6

[0093] Add 25 g of silicone rubber component A (uncrosslinked linear polydimethylsiloxane precursor) of SYLGARD 182 two-component addition-type silicone rubber with vinyl end to a beaker, 1.5 g of the microcapsules synthesized in Example 1 and 1.5 g of sodium carbonate, stir well, and then add 2.5 g of silicone rubber component B (silicone rubber crosslinking agent). Place the mixture in a vacuum drying oven to degas for 10 min, then pour it into a mold and place it in an oven at 60 ℃ to cure for 4 hours to obtain a surface damage self-diagnostic insulating material.

[0094] Comparative Example 1

[0095] A surface damage self-diagnostic insulating material was prepared according to the method in Example 1, except that no microcapsules were added to the surface damage self-diagnostic insulating material.

[0096] Mechanical properties (tensile data):

[0097] For each surface damage self-diagnostic insulating material sample obtained in Examples 2-4, the above measurements were performed at least three times to obtain the average tensile strength and elongation at break, as shown in Table 1. The tensile strength of the matrix sample (Comparative Example 1) was 7.37 MPa, and the elongation at break was 213%. The tensile strength and elongation at break of the 2% sample (Example 2), 6% sample (Example 3), and 10% sample (Example 4) decreased sequentially. The addition of microcapsules reduced the mechanical properties of the samples to a certain extent, and the higher the content of microcapsules, the greater the decrease in mechanical properties. Figure 2 The curve in the middle is the tensile process of each sample, and it can be directly seen that the tensile strength and elongation at break decrease with the increase of microcapsule content.

[0098] Table 1 Mechanical property data of samples in Examples 2-4

[0099]

[0100] Dielectric properties:

[0101] A dielectric spectrometer was used to apply an AC voltage of 1 V, and the frequency was scanned from 104 Hz to 1 Hz to obtain curves showing the changes in dielectric constant and dielectric loss tangent, as follows: Figures 3-4 As shown, at a power frequency of 50 Hz, the dielectric constant of the matrix sample is 4.02, and the dielectric constants of the 2%, 6%, and 10% samples are 4.29, 4.32, and 4.68, respectively. After incorporating microcapsules and sodium carbonate, the dielectric constant of the samples increases, and the greater the mass of microcapsules added, the greater the dielectric constant.

[0102] At a power frequency of 50 Hz, the dielectric loss tangent of the matrix sample was 0.0156, while the dielectric loss tangents of the 2%, 6%, and 10% samples were 0.0243, 0.0288, and 0.0717, respectively. These values ​​were all higher than those of the matrix sample, indicating that the incorporation of microcapsules increased the dielectric loss of the samples. Furthermore, the tanδ values ​​of the 2% and 6% samples were relatively close, while the tanδ value of the 10% sample was relatively high compared to the other three samples, suggesting that a higher microcapsule content resulted in a greater dielectric loss.

[0103] Breakthrough Field Strength:

[0104] The Weibull distributions of the breakdown field strength of the samples in Examples 2-4 are as follows: Figure 5 As shown in Table 2, the characteristic breakdown field strength and shape parameters are obtained.

[0105] Table 2. Characteristic breakdown field strength and shape parameters of samples in Examples 2-4

[0106]

[0107] Thermogravimetric curve:

[0108] like Figure 6 As shown, with a heating rate of 10℃ / min, the self-diagnostic silicone rubber sample maintained a mass of over 90% during the temperature rise from room temperature to 400℃. The weight loss was mainly due to the decomposition of fillers such as microcapsules and aluminum hydroxide. Between 400 and 600℃, the sample mass began to decrease significantly, indicating that the silicone rubber matrix structure was damaged and the molecular chains broke down. The test ended after heating to 1000℃; the sample was not completely carbonized and still maintained a certain mass. Thermogravimetric analysis results show that the self-diagnostic silicone rubber material can maintain good thermal stability at around 400℃.

[0109] Diagnostic efficacy of corona damage under different AC voltages:

[0110] Four identical sample pieces were cut from a single 6% self-diagnostic silicone rubber sample. AC voltages with peak values ​​of 7.5 kV, 10 kV, 12.5 kV, and 15 kV were applied to each sample to induce corona discharge. Each sample was continuously pressurized for 24 hours. Afterward, the pressurization was stopped, and the samples were removed for observation. Figure 7 As shown. From Figure 7 As can be seen, a small area around the needle tip turned red, while areas farther from the needle tip remained largely unchanged. This indicates that the area within the corona damage zone showed a significant diagnostic effect of color change, while the area outside the damage zone was largely unaffected. The color change diagnosis result corresponds to the damage area. The range of reddening varied depending on the applied AC voltage. The sample with a peak voltage of 7.5 kV showed a relatively small red range, while samples at 10 kV, 12.5 kV, and 15 kV showed a larger red range after corona treatment, and the color was also slightly darker than that at 7.5 kV. With increasing AC voltage, the reddening range and the intensity of the red color slightly increased after corona damage, indicating a relatively good diagnostic effect on the damage site. Additionally, the substrate sample without the indicator remained white after corona treatment.

[0111] Diagnostic effect of surface discharge (17.5kV voltage, 5h discharge):

[0112] A 6% self-diagnostic silicone rubber sample was cut into 25mm × 25mm × 1mm pieces and placed on a flat electrode. The height of the conical electrode was adjusted so that the tip of the cone was tightly fitted to the surface of the sample piece. The applied voltage was gradually increased, starting from 2.5kV. When the peak voltage reached 17.5kV, a bright discharge channel could be seen extending from the tip of the cone along the sample surface to the sample edge. A yellow arc was observed along the sample edge. After applying the voltage for 5 hours, the sample was observed to show scattered red marks on some areas of the sample surface, as shown below. Figure 8 As shown.

[0113] Diagnostic effect of breakdown discharge (black represents breakdown points, and each breakdown point is subjected to repeated discharge breakdown several times):

[0114] The breakdown test was conducted using ball-to-ball electrodes immersed in silicone oil. The sample was placed between the two ball electrodes, and both the electrodes and the sample were immersed in silicone oil. The AC voltage was increased from 0 until the sample broke down. The process from the start of the pressure application to the sample breakdown took approximately 10 to 20 seconds.

[0115] Each sample (microcapsule content 6%) in Example 3 was subjected to 20 breakdown tests. After the tests, it was found that the area around each breakdown point turned red, as shown in the image. Figure 9As shown, within a circle of approximately 5 mm radius centered on the breakdown point, the area turns almost entirely red, and the distribution is quite dense. The sheds of the composite insulator can develop small holes due to electrolytic erosion or flashover due to localized arcing. These are similar to the localized concentrated electrical stress between the ball electrodes. Within the area covered by the ball electrodes, high-energy electrons bombard the sample surface in a short time, causing the microcapsules to rupture and the area to turn red. Compared to the corona experiment, this produces greater damage and disruption, resulting in a more pronounced color change effect; compared to surface discharge, the energy of the charged particles is more concentrated, and the distribution of the red spots is also more concentrated.

[0116] Diagnostic efficacy of mechanical damage:

[0117] A blade is used to create uniform scratches on the sample surface to test the sample's diagnostic effectiveness against mechanical damage. For example... Figure 10 As shown, the matrix sample remained white after damage. Under the premise that the depth and range of mechanical damage were basically the same, the red color at the damaged area gradually deepened in the 2%, 6%, and 10% samples, which is equivalent to the gradual improvement of the color change performance. This indicates that the diagnostic effect on mechanical damage gradually improves with the increase of microcapsule content in the sample.

[0118] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A surface damage self-diagnostic insulating material, comprising a silicone rubber substrate and microcapsules and an alkaline reagent dispersed in the silicone rubber substrate; The microcapsule comprises a shell and a core material, wherein the shell is a urea-formaldehyde resin polymer and the core material comprises 2',7'-dichlorofluorescein and ethyl phenylacetate; The microcapsules have a mass fraction of 1-10% in the silicone rubber matrix, and the alkaline reagent has a mass fraction of 1-10% in the silicone rubber matrix.

2. The surface damage self-diagnostic insulating material according to claim 1, characterized in that, The alkaline reagent includes one or more of aluminum hydroxide, sodium carbonate, sodium hydroxide, and sodium dodecylbenzenesulfonate.

3. The surface damage self-diagnostic insulating material according to claim 1, characterized in that, The mass ratio of the outer shell to the core material is 1:(4~8).

4. The surface damage self-diagnostic insulating material according to claim 1, characterized in that, The mass fraction of 2',7'-dichlorofluorescein in the core material is 0.01~0.1%.

5. The method for preparing the surface damage self-diagnostic insulating material as described in claim 1, comprising the following steps: A) Mix emulsifier, alkaline medium and water to obtain an emulsion with a pH of 3 to 4; B) Mix the emulsion, urea, resorcinol and ammonium chloride, add the core material dropwise under stirring, and emulsify at room temperature; The core material comprises 2',7'-dichlorofluorescein, ethyl phenylacetate, and a curing agent; C) After emulsifying at room temperature for 10-60 minutes, add formaldehyde aqueous solution to the solution, raise the temperature to 50-60℃, and continue the reaction for 3-6 hours to obtain microcapsules; D) Mix silicone rubber, microcapsules, alkaline reagents and optional additives, and cure to obtain a surface damage self-diagnostic insulating material.

6. The method for preparing a surface damage self-diagnostic insulating material according to claim 1, characterized in that, In step A), the emulsifier is a poly(ethylene-maleic anhydride) aqueous solution with a mass fraction of 1-5%, and the alkaline medium is sodium hydroxide.

7. The method for preparing a surface damage self-diagnostic insulating material according to claim 1, characterized in that, The mass ratio of urea, resorcinol and ammonium chloride is (8~12):(0.5~2):

1.

8. The method for preparing a surface damage self-diagnostic insulating material according to claim 1, characterized in that, In step D), the curing is heat curing, condensation curing, or addition curing.

9. The method for preparing a surface damage self-diagnostic insulating material according to claim 1, characterized in that, In step D), the optional additives include one or more of the following: functional fillers, vulcanizing agents, coupling agents, pigments, silicone oils, and anti-aging agents.

10. The application of the surface damage self-diagnostic insulating material as described in claim 1 in the self-diagnosis of electrical damage in electrical insulation materials.

Images