A method for improving the dielectric gradient uniformity of a high dielectric constant filler modified anti-flashover coating

Abstract

The application discloses a method for improving dielectric gradient uniformity of a pollution flashover prevention coating modified by high dielectric constant fillers, and belongs to the technical field of pollution flashover prevention coatings. The method comprises the following steps: preparing silicon oxide particles with first active groups and high dielectric constant fillers with second active groups, wherein the first active groups and the second active groups can be chemically bonded under the action of a catalyst; and mixing the silicon oxide particles with the first active groups and the high dielectric constant fillers with the second active groups with polydimethylsiloxane, a crosslinking agent, a solvent and a catalyst to prepare a pollution flashover prevention coating modified by high dielectric constant fillers. The method can reduce the difference in dielectric properties between high dielectric constant filler particles and a silicone rubber film-forming material, form a continuous and uniformly changing dielectric gradient structure, avoid local electric field distortion, and is simple and has remarkable effects.

Description

Technical Field

[0001] This invention relates to the field of anti-flashover coating technology, and in particular to a method for improving the dielectric uniformity of anti-flashover coatings modified with high dielectric constant fillers. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Power system external insulation equipment operates outdoors for extended periods, and flashover due to pollution is one of the main fault types threatening the safe and stable operation of the power system. Flashover is determined by two factors: first, the accumulation of pollutants in the atmosphere on the surface of the external insulation; and second, the wetting of the surface after the deposited contaminants have accumulated under humid weather conditions. In dry environments, the contaminants on the external insulation surface still possess high insulation strength. However, under conditions such as light rain, snow, fog, frost, and dew, after wetting, soluble electrolytes and other substances in the contaminant layer gradually dissolve in water, forming a conductive film. This increases the conductivity of the external insulation surface, leading to flashover along the surface, i.e., flashover due to pollution. Flashover due to pollution can cause line tripping, power outages, and other accidents, seriously endangering the safe operation of the power grid and causing huge economic losses. Therefore, preventing flashover due to pollution on the surface of power system external insulation equipment is crucial for ensuring the safe operation of power system lines.

[0004] Silicone rubber (RTV) anti-flashover coatings are an effective measure for preventing flashover due to their excellent hydrophobicity and hydrophobic migration properties. However, RTV anti-flashover coatings are organic polymer materials with poor aging resistance, flame retardancy, arc resistance, and mechanical properties. After 3-5 years of operation, they are prone to aging, cracking, peeling, tracking, and electrolytic erosion, leading to a decline in insulation protection performance and causing flashover accidents, seriously threatening the safe operation of the power grid. To improve the service performance of RTV anti-flashover coatings, nanomaterials are usually added to the system, giving them the characteristics of both organic and inorganic materials. This can significantly improve the performance and service life of RTV anti-flashover coatings. For example, patents such as CN109233620B, CN102321434B, and CN116855170B disclose the addition of inorganic fillers such as silicon oxide, iron oxide red, aluminum hydroxide, boron nitride, and titanium dioxide as reinforcing agents, flame retardants, and pigments to RTV anti-flashover coatings. However, the introduction of inorganic fillers will form a large number of interface regions between the silicone rubber film-forming material and the filler. Due to the huge difference in dielectric constant between the film-forming material and the inorganic filler, and the poor compatibility between the two due to factors such as filler agglomeration or defects, severe local electric field distortion will occur at the interface between the film-forming material and the inorganic filler, thereby causing breakdown and reducing the insulation strength of the outer insulating coating. Moreover, the reduction in insulation strength is more obvious with the increase of particle type and content.

[0005] Modifying the surface of filler particles using physicochemical methods is a major approach to improving the interfacial properties between the film-forming material and the inorganic filler particles. However, this method is only effective for silica particles (relative permittivity: 3.9–4.0), whose dielectric constant is not significantly different from that of silicone rubber (relative permittivity: 2.7–3.3). For filler particles with higher dielectric constants, such as alumina (relative permittivity: 9–10), iron oxide red (relative permittivity: 14.2), and titanium oxide (relative permittivity: 110–120), even after modification using physicochemical methods, problems such as poor continuity of dielectric gradient and uneven change of electric field gradient still exist.

[0006] Therefore, how to provide a method to improve the uniformity of dielectric constant of anti-flashover coatings modified with high dielectric constant, and solve the electric field distortion caused by high dielectric constant, so as to prepare anti-flashover coatings with good comprehensive performance, is an urgent problem to be solved. Summary of the Invention

[0007] In view of this, the present invention provides a method for improving the dielectric uniformity of anti-flashover coatings modified with high dielectric constant fillers, thereby solving the problem of uneven electric field distribution when using high dielectric constant fillers to modify anti-flashover coatings.

[0008] In a first aspect, the present invention provides a method for improving the dielectric uniformity of an anti-flashover coating modified with a high dielectric constant filler, comprising the following steps:

[0009] A method for preparing silica particles having a first active group and a high dielectric constant filler having a second active group is described, wherein the first and second active groups are capable of chemical bonding under the action of a catalyst; the high dielectric constant filler comprises one or more of alumina, iron oxide red, titanium oxide, magnesium oxide, or magnesium hydroxide.

[0010] A high-dielectric-constant filler-modified anti-flashover coating is prepared by mixing silica particles with a first active group and a high-dielectric-constant filler with a second active group with polydimethylsiloxane, a crosslinking agent, a solvent, and a catalyst.

[0011] Preferably, the particle size of the silicon oxide particles is 10-100 nm, and the particle size of the high dielectric constant filler is 1-10 μm.

[0012] Preferably, the first active group and the second active group are selected from any combination of the following functional groups:

[0013] a. Epoxy groups and amino groups;

[0014] b. Epoxy groups and mercapto groups;

[0015] c. Vinyl groups and thiol groups.

[0016] Furthermore, the method for preparing the silica particles having the first active group is as follows: reacting silica particles with a silane coupling agent containing epoxy, amino, vinyl or mercapto groups;

[0017] The high dielectric constant filler with the second active group is prepared by reacting the high dielectric constant filler with a silane coupling agent containing epoxy, amino, vinyl or mercapto groups.

[0018] Preferably, the crosslinking agent is selected from one or more of methyltributanone oxime silane, phenyltributanone oxime silane, or tetrabutanone oxime silane.

[0019] Preferably, the solvent is selected from one or more of toluene, xylene, ethyl acetate, butyl acetate, or acetone.

[0020] Preferably, the catalyst is selected from one or more of acetic acid, oxalic acid, or propionic acid.

[0021] Preferably, the mass ratio of the silica particles with the first active group, the high dielectric constant filler with the second active group, the polydimethylsiloxane, the crosslinking agent, the solvent, and the catalyst is (5-10):(5-10):(70-75):(0.5-1):(10-20):(0.5-2).

[0022] Preferably, the specific method for preparing the high dielectric constant filler-modified anti-flashover coating includes the following steps:

[0023] Silica particles with a first active group and a high dielectric constant filler with a second active group are added to a solvent and stirred to disperse to obtain a particle dispersion.

[0024] The particle dispersion was added to polydimethylsiloxane, then a crosslinking agent was added, and the mixture was stirred until homogeneous to obtain a mixed slurry.

[0025] A catalyst is added to the mixed slurry, and after stirring evenly, it is poured and cured to obtain a high dielectric constant filler-modified anti-flashover coating.

[0026] Secondly, the present invention provides a high dielectric constant filler-modified anti-flashover coating prepared by the above method.

[0027] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0028] (1) This invention utilizes the chemical bonding between the active groups of the high dielectric constant filler and the active groups of the silicon oxide particles to achieve chemical bonding between the high dielectric constant particles and the silicon oxide particles, forming a complete chemical bonding layer, avoiding phase interface defects in the coating and improving the uniformity of the internal structure of the anti-flashover coating.

[0029] (2) In this invention, silica particles are encapsulated on the surface of high dielectric constant filler through chemical bonding, which effectively achieves a gradual decrease in dielectric constant of high dielectric constant filler, silica particles and silicone rubber matrix. Through the change of dielectric constant in multiple levels, the difference in dielectric properties between high dielectric constant filler particles and silicone rubber film is reduced, forming a continuous and uniformly changing dielectric constant structure, realizing the control of electric field distribution of anti-flashover coating, and avoiding local electric field distortion caused by sudden change in dielectric properties of filler particles and silicone rubber film due to interface region.

[0030] (3) The construction of the intermediate degree structure of the anti-flashover coating in this invention is based on chemical bonding self-assembly technology. It does not require stacking or external electric or magnetic fields. The method is simple and convenient, with significant effects and universality. Attached Figure Description

[0031] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0032] Figure 1 This is a diagram showing the compatibility test results of Embodiment 1 of the present invention;

[0033] Figure 2 This is a schematic diagram of the chemical bonding self-assembly process in Examples 1 and 2 of the present invention;

[0034] Figure 3 This is a schematic diagram of the dielectric gradient structure of the coatings formed in Embodiments 1 and 2 of the present invention;

[0035] Figure 4 This is a graph showing the compatibility test results of Comparative Example 2 of the present invention;

[0036] Figure 5 This is a graph showing the compatibility test results of Comparative Example 3 of the present invention. Detailed Implementation

[0037] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0038] Terminology Explanation

[0039] Dielectric constant and relative permittivity: The dielectric constant is the main parameter reflecting the dielectric or polarization properties of piezoelectric materials under the influence of an electrostatic field, usually represented by ε. It indicates that when an external electric field is applied, the dielectric will generate induced charges, weakening the electric field. The ratio of the original external electric field (in vacuum) to the electric field in the dielectric is the relative permittivity (or relative permittivity), also known as the induced charge, which is frequency-dependent. The dielectric constant is the product of the relative permittivity and the absolute permittivity in vacuum. If a material with a high dielectric constant is placed in an electric field, the intensity of the electric field will decrease considerably within the dielectric. Generally, substances with a relative permittivity greater than 3.6 are polar substances; substances with a relative permittivity in the range of 2.8 to 3.6 are weakly polar substances; and substances with a relative permittivity less than 2.8 are non-polar substances. In this invention, fillers with a relative permittivity higher than 5.0 are called high dielectric constant fillers.

[0040] As described in the background section, existing anti-flashover coatings modified with high dielectric constant fillers suffer from problems such as poor dielectric constant continuity and uneven electric field gradient. Therefore, this invention provides a method for improving the dielectric constant uniformity of anti-flashover coatings modified with high dielectric constant fillers, comprising the following steps:

[0041] Silica particles with a first active group and high dielectric constant fillers with a second active group are prepared, wherein the first active group and the second active group can undergo chemical bonding under the action of a catalyst;

[0042] The high dielectric constant filler includes one or more of alumina, iron oxide red, titanium oxide, magnesium oxide, or magnesium hydroxide;

[0043] A high-dielectric-constant filler-modified anti-flashover coating is prepared by mixing silica particles with a first active group and a high-dielectric-constant filler with a second active group with polydimethylsiloxane, a crosslinking agent, a solvent, and a catalyst.

[0044] In this invention, the high dielectric constant filler particles have greater polarity and more modified functional groups on their surface, thus reacting with more silica particles to form a coating structure. This invention uses silica particles with a dielectric constant between that of silicone rubber and the high dielectric constant filler as a transitional stage for dielectric gradient. The silica particles form a coating on the surface of the high dielectric constant filler through chemical bonding, effectively achieving a gradual decrease in dielectric gradient between the high dielectric constant filler, silica particles, and the silicone rubber matrix. Through multi-level dielectric gradient changes, the difference in dielectric properties between the high dielectric constant filler particles and the silicone rubber film is reduced, forming a continuous and uniformly varying dielectric gradient structure. This allows for the control of the electric field distribution in the anti-flashover coating, avoiding local electric field distortion caused by abrupt changes in the dielectric properties of the interface region between the filler particles and the silicone rubber film, thereby improving the electrical properties of the coating.

[0045] Meanwhile, under the chemical bonding of active groups, a complete chemical bond layer is formed at the particle-particle interface, which enhances the compatibility between the particle-particle interface and the particle-silicone rubber interface, thereby avoiding the generation of phase interface defects inside the coating, improving the uniformity of the coating, and making the coating more durable and stable.

[0046] The silica particles of this invention have a particle size of 10–100 nm, and the high dielectric constant filler has a particle size of 1–10 μm. Particle size primarily affects steric hindrance; selecting small-sized silica particles is mainly to reduce steric hindrance, allowing more silica particles to react with the high dielectric constant filler particles.

[0047] In this invention, the first active group and the second active group are selected from any combination of the following functional groups:

[0048] a. Epoxy groups and amino groups;

[0049] b. Epoxy groups and mercapto groups;

[0050] c. Vinyl groups and thiol groups.

[0051] The present invention does not impose any special restrictions on the selection order of the first active group and the second active group in the above-listed combinations. For example, the first active group can be an epoxy group and the second active group can be an amino group, or the first active group can be an amino group and the second active group can be an epoxy group.

[0052] Furthermore, it is understood that the active groups capable of chemical bonding can also be selected from any combination of isocyanate groups and hydroxyl, amino, or carboxyl groups. All of these combinations can achieve chemical bonding at room temperature under the action of a catalyst. Given the ease of modification, the present invention preferably uses combinations of epoxy and amino or mercapto groups, and vinyl and mercapto functional groups.

[0053] In this invention, the method for preparing the silica particles having the first active group is as follows: reacting silica particles with a silane coupling agent having an epoxy group, amino group, vinyl group or mercapto group;

[0054] The high dielectric constant filler with the second active group is prepared by reacting the high dielectric constant filler with a silane coupling agent containing epoxy, amino, vinyl or mercapto groups.

[0055] This invention does not impose any special limitations on the reaction process of the aforementioned silica particles or high dielectric constant fillers with silane coupling agents. Those skilled in the art can implement the above reaction using conventional methods in the field. The reaction process mainly includes the dispersion of silica particles or high dielectric constant fillers, the hydrolysis of silane coupling agents, and the reaction of silica particles or high dielectric constant fillers with the hydrolysate of silane coupling agents.

[0056] In one or more embodiments of the present invention, the preparation method of the silica particles having the first active group and the high dielectric constant filler having the second active group is as follows: silica particles or high dielectric constant filler are dispersed in a solvent (water and / or ethanol), and after ultrasonic and shear dispersion, a silane coupling agent hydrolysate is added under stirring at 60–90°C, and the reaction is carried out for 10–30 hours. After centrifugation, washing, and drying, the solution is ready for use. The present invention does not impose special limitations on the preparation process of the silane coupling agent hydrolysate; commonly used preparation methods in the art can be used. For example, ultrasonic dispersion in water or hydrolysis under acidic conditions can be employed. Those skilled in the art can choose the appropriate method according to actual needs.

[0057] In this invention, the epoxy-containing silane coupling agents include, but are not limited to, γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), γ-glycidoxypropyltriethoxysilane (KH-561), 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (KH-1770), 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (KH-1771), and 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane (KH-781).

[0058] In this invention, amino-containing silane coupling agents include, but are not limited to, γ-aminopropyltriethoxysilane (KH-550), γ-aminopropyltrimethoxysilane (KH-540), γ-aminopropylsilanetriol (KH-553), N-2-aminoethyl-3-aminopropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

[0059] In this invention, silane coupling agents with thiol groups include, but are not limited to, 3-mercaptopropyltrimethoxysilane (KH-591), γ-mercaptopropyltriethoxysilane (KH-592), and 3-mercaptopropylmethyldimethoxysilane.

[0060] In this invention, vinyl-containing silane coupling agents include, but are not limited to, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, etc.

[0061] In this invention, the crosslinking agent is selected from one or more of methyltributanone oxime silane, phenyltributanone oxime silane, or tetrabutanone oxime silane. The crosslinking agent can promote the curing and crosslinking of the silicone rubber film-forming material polydimethoxysilane.

[0062] In this invention, the solvent is selected from one or more of toluene, xylene, ethyl acetate, butyl acetate, or acetone. The main function of the solvent is to dilute and disperse, allowing the substances to mix better and improving the uniformity of the coating.

[0063] In this invention, the catalyst is selected from one or more of acetic acid, oxalic acid, or propionic acid, and the acidic conditions it provides can promote the chemical bonding reaction between the first and second active groups. In principle, other acids can also be chosen, as long as they can promote the chemical bonding reaction.

[0064] In this invention, the mass ratio of the silica particles with the first active group, the high dielectric constant filler with the second active group, the polydimethylsiloxane, the crosslinking agent, the solvent, and the catalyst is (5-10):(5-10):(70-75):(0.5-1):(10-20):(0.5-2). It is understood that those skilled in the art can add other additives beneficial to coating preparation or application performance, such as defoamers, flame retardants, and water-repellent agents; this invention does not impose any special limitations on this.

[0065] In this invention, the specific method for preparing the high dielectric constant filler-modified anti-flashover coating includes the following steps:

[0066] Silica particles with a first active group and a high dielectric constant filler with a second active group are added to a solvent and stirred to disperse to obtain a particle dispersion.

[0067] The particle dispersion was added to polydimethylsiloxane, then a crosslinking agent was added, and the mixture was stirred until homogeneous to obtain a mixed slurry (component A).

[0068] A catalyst (component B) is added to the mixed slurry, stirred evenly, and then poured. After curing, a high dielectric constant filler-modified anti-flashover coating is obtained.

[0069] This invention does not impose any special restrictions on the specific methods of stirring, dispersing, and curing; any method commonly used in the field may be adopted.

[0070] This invention allows for the formulation of high dielectric constant filler-modified anti-flashover coatings according to the following formula:

[0071] Component A:

[0072] 5-10 parts of silica particles with the first active group,

[0073] 5-10 parts of high dielectric constant filler with a second active group,

[0074] 70-75 parts of polydimethylsiloxane

[0075] Crosslinking agent 0.5-1 part,

[0076] Solvent 10-20 parts;

[0077] Component B: Catalyst;

[0078] The mass ratio of component A to component B is 100:(0.5~2).

[0079] When preparing the coating, components A and B are mixed and then poured to obtain a high dielectric constant filler-modified anti-flashover coating.

[0080] This invention also provides a high-dielectric-constant filler-modified anti-flashover coating prepared by the above method. The high-dielectric-constant filler-modified anti-flashover coating provided by this invention can improve the overall performance of the anti-flashover coating while maintaining a relative dielectric constant below 4.0, good insulation performance and dielectric uniformity, and a dielectric strength above 20 kV / mm.

[0081] The technical solution of the present invention will be further described below with reference to specific embodiments. The present invention does not impose any special restrictions on the source of the reagents used below; commercially available products well known to those skilled in the art can be used.

[0082] Example 1

[0083] This embodiment provides a method for preparing an anti-flashover coating modified with a high dielectric constant filler.

[0084] (1) Preparation of epoxy-modified silica particles:

[0085] ① Disperse silica particles (average particle size of 20nm) into an ethanol solution at a mass ratio of 1:20, stir under magnetic stirring for 5 minutes, then shear disperse at a speed of 1000r / min for 10 minutes, and then transfer to an ultrasonic bath and ultrasonic disperse at a power of 1kW for 10 minutes to obtain a particle dispersion.

[0086] ② Prepare the silane coupling agent hydrolysate by weighing γ-glycidyl etheroxypropyltrimethoxysilane (KH-560) at 20% of the mass of silicon oxide and adding it to deionized water. After stirring and dispersing evenly, adjust the pH to 4.0-5.0 to obtain the silane coupling agent hydrolysate.

[0087] ③ Transfer the particle dispersion from step ① to an 80℃ oil bath, and add the silane coupling agent hydrolysate from step ② dropwise while stirring continuously. After the addition is complete, continue stirring and react for 24 hours.

[0088] ④ After washing the modified silica particles three times by centrifugation with ethanol, transfer them to a 60℃ oven to dry for later use.

[0089] (2) Preparation of amino-modified alumina:

[0090] ① Alumina particles (average particle size of 2 μm) were dispersed in an ethanol solution at a mass ratio of 1:30 and stirred under magnetic stirring for 5 min. Then, the mixture was sheared and dispersed at a speed of 1000 r / min for 10 min. Finally, the mixture was transferred to an ultrasonic bath and ultrasonically dispersed at a power of 1 kW for 10 min to obtain a particle dispersion.

[0091] ② Prepare the silane coupling agent hydrolysate by weighing 30% of the mass of alumina into deionized water, stirring and dispersing evenly, and adjusting the pH to 4.0-5.0 to obtain the silane coupling agent hydrolysate.

[0092] ③ Transfer the particle dispersion from step ① to an 80℃ oil bath, and add the silane coupling agent hydrolysate from step ② dropwise while stirring continuously. After the addition is complete, continue stirring and react for 24 hours.

[0093] ④ After washing the modified alumina particles three times by centrifugation with ethanol, transfer them to a 60℃ oven to dry for later use.

[0094] (3) Anti-flashover coating formulation (all parts below are by weight):

[0095] Component A:

[0096] Polydimethylsiloxane: 70 parts;

[0097] Xylene: 14 parts;

[0098] Epoxy-modified silica particles: 10 parts;

[0099] Amino-modified alumina: 5 parts;

[0100] Methyltributanone oxime silane: 1 part;

[0101] Component B is acetic acid.

[0102] (4) Preparation of anti-flashover coating:

[0103] ① Add epoxy-modified silica particles and amino-modified alumina to xylene, stir evenly, shear for 20 min, and ultrasonically disperse for 10 min to obtain a particle dispersion;

[0104] ② Add the particle dispersion to polydimethylsiloxane and add methyl tributanone oxime silane, and stir and disperse evenly in a vacuum reactor at a speed of 500 r / min;

[0105] ③According to the mass ratio of component A to component B of 100:1, acetic acid is added to component A, stirred evenly, poured into a mold, and cured at room temperature for 72 hours to obtain the sample.

[0106] Example 2

[0107] This embodiment provides a method for preparing an anti-flashover coating modified with a high dielectric constant filler.

[0108] (1) Preparation of epoxy-modified silica particles:

[0109] ① Disperse silica particles (average particle size of 50nm) in an ethanol solution at a mass ratio of 1:20, stir under magnetic stirring for 5 minutes, then shear disperse at a speed of 1000r / min for 10 minutes, and then transfer to an ultrasonic bath and ultrasonic disperse at a power of 1kW for 10 minutes to obtain a particle dispersion.

[0110] ② Prepare the silane coupling agent hydrolysate by weighing γ-glycidyl etheroxypropyltrimethoxysilane (KH-560) at 20% of the mass of silicon oxide and adding it to deionized water. After stirring and dispersing evenly, adjust the pH to 4.0-5.0 to obtain the silane coupling agent hydrolysate.

[0111] ③ Transfer the particle dispersion from step ① to an 80℃ oil bath, and add the silane coupling agent hydrolysate from step ② dropwise while stirring continuously. After the addition is complete, continue stirring and react for 24 hours.

[0112] ④ After washing the modified silica particles three times by centrifugation with ethanol, transfer them to a 60℃ oven to dry for later use.

[0113] (2) Preparation of mercapto-modified titanium dioxide:

[0114] ① At a mass ratio of 1:30, titanium oxide particles (average particle size of 10 μm) were dispersed in an ethanol solution and stirred under magnetic stirring for 5 min. Then, the mixture was sheared and dispersed at a speed of 1000 r / min for 10 min. Finally, the mixture was transferred to an ultrasonic bath and ultrasonically dispersed at a power of 1 kW for 10 min to obtain a particle dispersion.

[0115] ② Prepare the silane coupling agent hydrolysate by weighing γ-mercaptopropyltrimethoxysilane (KH-591) at 25% of the mass of titanium dioxide and adding it to deionized water. After stirring and dispersing evenly, adjust the pH to 4.0-5.0 to obtain the silane coupling agent hydrolysate.

[0116] ③ Transfer the particle dispersion from step ① to an 80℃ oil bath, and add the silane coupling agent hydrolysate from step ② dropwise while stirring continuously. After the addition is complete, continue stirring and react for 24 hours.

[0117] ④ After washing the modified alumina particles three times by centrifugation with ethanol, transfer them to a 60℃ oven to dry for later use.

[0118] (3) Anti-flashover coating formulation (all parts below are by weight):

[0119] Component A:

[0120] Polydimethylsiloxane: 75 parts;

[0121] Toluene: 10 parts;

[0122] Epoxy-modified silica particles: 8 parts;

[0123] Thiol-modified alumina: 6 parts;

[0124] Methyltributanone oxime silane: 1 part;

[0125] Component B is acetic acid.

[0126] (4) Preparation of anti-flashover coating:

[0127] ① Add epoxy-modified silica particles and mercapto-modified alumina to toluene, stir evenly, shear for 20 min, and ultrasonically disperse for 10 min to obtain a particle dispersion;

[0128] ② Add the particle dispersion to polydimethylsiloxane and add methyl tributanone oxime silane, and stir and disperse evenly in a vacuum reactor at a speed of 500 r / min;

[0129] ③According to the mass ratio of component A to component B of 100:1, acetic acid is added to component A, stirred evenly, poured into a mold, and cured at room temperature for 72 hours to obtain the sample.

[0130] Comparative Example 1

[0131] Compared with Example 1, this comparative example does not contain epoxy-modified silica particles or amino-modified alumina.

[0132] (1) The formulation of the anti-flashover coating (all parts below are by weight) is as follows:

[0133] Component A:

[0134] Polydimethylsiloxane: 70 parts;

[0135] Xylene: 14 parts;

[0136] Methyltributanone oxime silane: 1 part;

[0137] Component B is acetic acid.

[0138] (2) Preparation of anti-flashover coating:

[0139] ① Add xylene to polydimethylsiloxane and add methyl tributanone oxime silane, and stir and disperse evenly in a vacuum reactor at a speed of 500 r / min;

[0140] ②According to the mass ratio of component A to component B of 100:1, acetic acid is added to component A, stirred evenly, poured into a mold, and cured at room temperature for 72 hours to obtain the sample.

[0141] Comparative Example 2

[0142] The difference between this comparative example and Example 1 is that this comparative example does not contain epoxy-modified silica particles.

[0143] (1) Formulation of anti-flashover coating (all parts below are by weight):

[0144] Component A:

[0145] Polydimethylsiloxane: 70 parts;

[0146] Xylene: 14 parts;

[0147] Amino-modified alumina: 5 parts;

[0148] Methyltributanone oxime silane: 1 part;

[0149] Component B is acetic acid.

[0150] (2) Preparation of anti-flashover coating:

[0151] ① Add amino-modified alumina to xylene, stir evenly, shear for 20 min, and ultrasonically disperse for 10 min to obtain a particle dispersion;

[0152] ② Add the particle dispersion to polydimethylsiloxane and add methyl tributanone oxime silane, and stir and disperse evenly in a vacuum reactor at a speed of 500 r / min;

[0153] ③According to the mass ratio of component A to component B of 100:1, acetic acid is added to component A, stirred evenly, poured into a mold, and cured at room temperature for 72 hours to obtain the sample.

[0154] Comparative Example 3

[0155] The difference between this comparative example and Example 1 is that this comparative example does not modify silica and alumina, and epoxy silane coupling agent (KH-560) is added as an additive to the coating formulation.

[0156] (1) Formulation of anti-flashover coating (all parts below are by weight):

[0157] Component A:

[0158] Polydimethylsiloxane: 70 parts;

[0159] Xylene: 14 parts;

[0160] Silica particles (20nm): 10 parts;

[0161] Alumina (2μm): 5 parts;

[0162] KH-560: 2 copies;

[0163] Methyltributanone oxime silane: 1 part;

[0164] Component B is acetic acid.

[0165] (2) Preparation of anti-flashover coating:

[0166] ① Add silica particles and alumina to xylene, then add KH-560, stir evenly, shear for 20 minutes, and ultrasonically disperse for 10 minutes to obtain a particle dispersion;

[0167] ② Add the particle dispersion to polydimethylsiloxane and add methyl tributanone oxime silane, and stir and disperse evenly in a vacuum reactor at a speed of 500 r / min;

[0168] ③ Add acetic acid to component A at a mass ratio of 100:1 for component A: component B, stir well, pour into a mold, and obtain the sample after curing.

[0169] Comparative Example 4

[0170] The difference between this comparative example and Example 1 is that amino-modified silica particles are used instead of epoxy-modified silica particles (i.e., the modification methods for silica and alumina are the same), while the other steps and formulations are the same as in Example 1.

[0171] The preparation method of the amino-modified silica particles in this comparative example is as follows:

[0172] ① Disperse silica particles (average particle size of 20nm) into an ethanol solution at a mass ratio of 1:20, stir under magnetic stirring for 5 minutes, then shear disperse at a speed of 1000r / min for 10 minutes, and then transfer to an ultrasonic bath and ultrasonic disperse at a power of 1kW for 10 minutes to obtain a particle dispersion.

[0173] ② Prepare the silane coupling agent hydrolysate by weighing γ-aminopropyltriethoxysilane (KH-550) at 20% of the mass of silicon oxide and adding it to deionized water. After stirring and dispersing evenly, adjust the pH to 4.0-5.0 to obtain the silane coupling agent hydrolysate.

[0174] ③ Transfer the particle dispersion from step ① to an 80℃ oil bath, and add the silane coupling agent hydrolysate from step ② dropwise while stirring continuously. After the addition is complete, continue stirring and react for 24 hours.

[0175] ④ After washing the modified silica particles three times by centrifugation with ethanol, transfer them to a 60℃ oven to dry for later use.

[0176] Comparative Example 5

[0177] The difference between this comparative example and Example 1 is that the alumina particles in this comparative example are nano-alumina with an average particle size of 20 nm, while the rest are the same as in Example 1.

[0178] Comparative Example 6

[0179] The difference between this comparative example and Example 1 is that the anti-flashover coating formulation of this comparative example does not contain component B (i.e., no acetic acid is added), while the rest is the same as Example 1.

[0180] Test case

[0181] The anti-flashover coatings of Examples 1-2 and Comparative Examples 1-6 were tested for appearance, compatibility, electrical properties, and UV aging resistance. Compatibility was determined through a sedimentation test. After the prepared component A coating was left to stand at room temperature for 24 hours, compatibility was assessed by observing whether the coating delaminated internally. Aging resistance was evaluated using the method specified in GB / T16422.3-2022 Plastics Laboratory Light Source Exposure Test Method Part 3: Fluorescent UV Lamp standard, with 30 exposure cycles. The results were then assessed according to GB / T1766-2008 Paints and Varnishes—Aging Rating Method for Coatings. The test results are shown in Table 1.

[0182] Table 1 Performance determination of anti-flashover coatings in Examples 1-2 and Comparative Examples 1-6

[0183]

[0184] Examples 1 and 2, due to the addition of modified filler particles, significantly improved the compatibility between the filler particles and organic film-forming materials within the anti-flashover coating. Figure 1 (Based on the compatibility test results of Example 1), the anti-flashover coating's aging resistance was improved, with the aging level increasing from level 2 in Comparative Example 1 to level 0. Simultaneously, under the action of chemical bonding self-assembly, a dielectric gradient structure was formed inside the coating, avoiding local distortion of the electric field, thus maintaining the electrical insulation performance. A schematic diagram of the chemical bonding self-assembly process is shown below. Figure 2 As shown in the diagram, the resulting coating dielectric gradient structure is illustrated in the figure below. Figure 3 As shown in the figure. Comparative Example 1, having no added filler particles, exhibits excellent electrical insulation properties but poor aging resistance. Comparative Examples 2 and 4 contain modified silica and alumina. Due to the high density of alumina, it settles significantly in the coating, resulting in generally poor internal compatibility. The compatibility test diagram for Comparative Example 2 is shown in the figure. Figure 4 As shown. In Comparative Example 3, the silica and alumina particles were not modified, and a clear interface existed between the inorganic filler particles and the organic film-forming material system, such as... Figure 5As shown, poor compatibility leads to significant delamination of the coating after standing, resulting in a marked decrease in electrical performance. In Comparative Example 5, although silica and alumina can chemically bond due to their similar particle size, steric hindrance prevents silica from forming a coating on the alumina surface. This results in the high dielectric constant alumina remaining in direct contact with the film-forming material, causing electric field distortion within the coating and a decrease in electrical performance. In Comparative Example 6, the lack of an acidic catalyst prevents the active groups between silica and alumina from chemically bonding to form a dielectric gradient structure, leading to a decrease in electrical insulation.

[0185] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving the dielectric uniformity of anti-flashover coatings modified with high dielectric constant fillers, characterized in that, The steps include the following: A method for preparing silica particles having a first active group and a high dielectric constant filler having a second active group is described, wherein the first and second active groups are capable of chemical bonding under the action of a catalyst; the high dielectric constant filler comprises one or more of alumina, iron oxide red, titanium oxide, magnesium oxide, or magnesium hydroxide. A high-dielectric-constant filler-modified anti-flashover coating is prepared by mixing silica particles with a first active group and a high-dielectric-constant filler with a second active group with polydimethylsiloxane, a crosslinking agent, a solvent, and a catalyst. The silica particles have a particle size of 10~100nm, and the high dielectric constant filler has a particle size of 1~10μm; The first and second active groups are selected from any combination of the following functional groups: a. Epoxy groups and amino groups; b. Epoxy groups and mercapto groups; c. Vinyl groups and thiol groups; The method for preparing the silica particles with the first active group is as follows: reacting silica particles with a silane coupling agent containing epoxy, amino, vinyl or mercapto groups. The high dielectric constant filler with the second active group is prepared by reacting the high dielectric constant filler with a silane coupling agent containing epoxy, amino, vinyl or mercapto groups. The mass ratio of the silica particles with the first active group, the high dielectric constant filler with the second active group, the polydimethylsiloxane, the crosslinking agent, the solvent and the catalyst is (5~10): (5~10): (70~75): (0.5~1): (10~20): (0.5~2).

2. The method as described in claim 1, characterized in that, The crosslinking agent is selected from one or more of methyl tributanone oxime silane, phenyl tributanone oxime silane, or tetrabutanone oxime silane.

3. The method as described in claim 1, characterized in that, The solvent is selected from one or more of toluene, xylene, ethyl acetate, butyl acetate, or acetone.

4. The method as described in claim 1, characterized in that, The catalyst is selected from one or more of acetic acid, oxalic acid, or propionic acid.

5. The method as described in claim 1, characterized in that, The specific method for preparing the high dielectric constant filler-modified anti-flashover coating includes the following steps: Silica particles with a first active group and a high dielectric constant filler with a second active group are added to a solvent and stirred to disperse to obtain a particle dispersion. The particle dispersion was added to polydimethylsiloxane, then a crosslinking agent was added, and the mixture was stirred until homogeneous to obtain a mixed slurry. A catalyst is added to the mixed slurry, and after stirring evenly, it is poured and cured to obtain a high dielectric constant filler-modified anti-flashover coating.

6. A high dielectric constant filler-modified anti-flashover coating prepared by the method according to any one of claims 1 to 5.

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