Lightweight anti-pollution flashover insulating material for high-voltage transmission line, preparation method and application thereof

Abstract

This invention relates to the field of power transmission line technology, specifically to lightweight anti-flashover insulation materials for high-voltage transmission lines, their preparation methods, and applications. The materials include a composite insulation substrate and an anti-flashover coating applied to its surface. The composite insulation substrate uses methyl vinyl silicone rubber as a matrix, doped with micro / nano-level fillers, and undergoes modification treatment to improve interfacial adhesion with the substrate. The anti-flashover coating uses polydimethylsiloxane as a matrix, incorporating modified micro / nano-level fillers, hydrophobic monomers, and functional additives, and is prepared using surface grafting technology. This invention uses methyl vinyl silicone rubber as a matrix and employs single, composite, or gradient doping methods with "micro / nano-level fillers," breaking through the technical bottleneck of existing technologies that either emphasize lightweighting or performance, achieving simultaneous improvements in "lightweighting, insulation, and mechanical strength."

Description

Technical Field

[0001] This invention relates to the field of power transmission technology, specifically to lightweight anti-pollution flashover insulation materials for high-voltage transmission lines, their preparation methods, and their applications. Background Technology

[0002] In recent years, bird-related faults on power transmission lines have become the third largest type of power transmission line fault after lightning strikes and external damage. However, unlike these faults, bird-related faults often exhibit characteristics related to natural laws, bird habits, and human production and daily life. They are also closely related to the insulation configuration, tower structure, and dimensions of the transmission line. Currently, scholars have conducted relevant research on the mechanisms of bird-related faults and measures to strengthen line insulation to prevent bird damage.

[0003] International research on bird protection in power systems considers both power system safety and bird conservation. Currently available literature primarily focuses on the harm caused by transmission lines to birds, emphasizing bird protection. To prevent short circuits caused by large birds colliding with transmission lines, line research institutions have developed special colored tapes to wrap around conductors, allowing birds to see the lines during flight and effectively avoid them. Power companies have implemented numerous bird-attracting and deterrent measures, such as erecting simulated poles 30-50 meters away from towers to guide birds to nest on them, using ultrasonic bird deterrents, or employing specially structured crossarms. These measures are effective but very expensive.

[0004] Regarding bird-related faults, some domestic scholars believe that long strings of bird droppings falling near composite insulators may be the main cause of unexplained flashovers in composite insulators. Zhou Xueming et al. found that bird droppings flashovers are mainly caused by the breakdown of air gaps under instantaneous electric field distortion, rather than the surface flashovers previously thought. Yu Dongyang et al., through experiments, found that flashovers in insulators occur because arcs first appear at the end of the bird droppings trajectory and at the high-voltage end of the conductor. The arcs on both sides rapidly develop towards the middle along the trajectory of the bird droppings, with the arc on the conductor side developing more rapidly than that on the crossarm side. Finally, the bird droppings break down with the gap between the crossarm and the conductor, forming a stable arc. This view has now been accepted by most scholars.

[0005] Due to the frequent occurrence of bird-related faults on power transmission lines in recent years, provincial power grid companies have increasingly emphasized bird-related fault prevention and control. In the ongoing bird prevention work on transmission lines, bird-related fault prevention devices are constantly being updated and improved. Li Fan et al. from the State Grid Jiangxi Electric Power Research Institute analyzed factors related to bird-related faults on overhead transmission lines, including bird species, tower type, season, and time of day. Xue Bin et al. from the Inner Mongolia Ultra-High Voltage Power Supply Bureau classified bird-related fault levels based on ultra-high voltage transmission lines and proposed scientific bird prevention measures. Wang Shaohua et al. from the Zhejiang Provincial Electric Power Research Institute analyzed the characteristics, causes, formation process, and mechanisms of bird-related faults, and comprehensively analyzed and evaluated the bird prevention and control measures applied in China.

[0006] However, existing technologies for insulating materials in high-voltage transmission line bird protection devices suffer from three major drawbacks: First, it is difficult to balance lightweight design with insulation and mechanical properties. Traditional materials such as epoxy fiberglass are heavy, while lightweight materials (such as pure silicone rubber) suffer from insufficient insulation and mechanical strength. Second, the anti-flashover performance is poorly integrated with the main material, the coating is prone to peeling, and the anti-flashover durability is insufficient, making it unsuitable for complex outdoor pollution environments. Third, the materials have limited functionality, making it difficult to simultaneously meet multiple requirements such as lightweight design, insulation, anti-flashover, and weather resistance. Furthermore, there is a lack of targeted structural design and functional optimization, resulting in high operation and maintenance costs.

[0007] To address the long-standing problem of bird-induced power transmission line failures, this invention develops novel bird-proof devices and improves material performance to effectively reduce bird-induced tripping rates, ensuring the safe and stable operation of high-voltage (ultra-high-voltage) transmission lines and promoting the development of power transmission technology. In the field of materials science, it explores the application of novel composite insulation materials and anti-flashover coatings, studies and optimizes the properties of materials such as silicone rubber, and improves their insulation, weather resistance, and hydrophobicity. In the field of ecological protection and sustainable development, the project prioritizes bird protection while ensuring power grid safety, employing environmentally friendly materials and designs to reduce the impact on the ecological environment, achieving coordinated development of power facility construction and ecological protection, and providing technical support for sustainable development in related fields. Summary of the Invention

[0008] To address the problems of existing bird shield materials, such as heavy weight, insufficient insulation strength and mechanical strength, poor adhesion between anti-pollution flashover performance and the main material, easy peeling of coating, and insufficient anti-pollution flashover durability, this invention provides a lightweight anti-pollution flashover insulation material for high-voltage transmission lines, its preparation method, and its application, including a composite insulation main body and an anti-pollution flashover coating applied to its surface.

[0009] The composite insulation matrix uses methyl vinyl silicone rubber as the base material and is doped with micro-nano-scale fillers. The interfacial bonding force with the base material is improved through modification treatment.

[0010] The anti-flashover coating is prepared by surface grafting technology using polydimethylsiloxane as the matrix, with the addition of modified micro-nano fillers, hydrophobic monomers and functional additives.

[0011] Furthermore, the composite insulation body comprises the following raw materials in parts by weight: 55-75 parts of methyl vinyl silicone rubber, 8-25 parts of micro-nano filler, 4-9 parts of fumed silica, 1-2.5 parts of vulcanizing agent, 0.4-1.2 parts of silane coupling agent, and 0-1.8 parts of hydroxyl silicone oil.

[0012] Furthermore, the micro / nano-scale filler is one or more of micron-sized silicon nitride (Si3N4), micron-sized aluminum oxide (Al2O3), nano-sized aluminum oxide (Al2O3), and nano-silver-modified boron nitride.

[0013] Further, the anti-flashover coating comprises the following raw materials in parts by weight: 35-55 parts of polydimethylsiloxane, 8-16 parts of modified micro-nano filler, 5-14 parts of hydrophobic monomer, 0.3-0.7 parts of initiator, 0.5-1.2 parts of catalyst, 1-2.5 parts of dispersant, 0.5-3 parts of functional additive, and 30-45 parts of solvent;

[0014] The functional additives include one or more of the following: repair agents and weather-resistant agents.

[0015] Furthermore, the modified micro-nano grade filler is one of modified micro-nano fumed silica and modified nano calcium carbonate, which is modified by silane coupling agent and active silane; the hydrophobic monomer is a fluorinated (meth)acrylic acid monomer.

[0016] In addition, the present invention also provides a method for preparing lightweight anti-pollution flashover insulation material for high-voltage transmission lines, comprising the following steps:

[0017] S100 packing pretreatment

[0018] Micro-nano-grade fillers and anti-flashover coating micro-nano-grade fillers were subjected to alkaline washing and silane coupling agent modification treatments to remove impurities and introduce active groups, thereby improving the interfacial bonding force with the matrix; for nano-silver modified fillers, nano-silver loading treatment was performed.

[0019] Preparation of S200 composite insulation body

[0020] Methyl vinyl silicone rubber is fed into a two-roll mill and heated to 110-130℃. Pretreated micro-nano fillers, fumed silica and hydroxyl silicone oil are added. The mixture is then milled and passed through a thin sheet. A vulcanizing agent is added and the mixture is passed through a thin sheet again. After the sheet is extruded, it is molded and vulcanized to obtain the composite insulation body.

[0021] Preparation of S300 Anti-Flashover Coating

[0022] Using surface grafting technology, modified micro-nano-scale fillers, hydrophobic monomers, initiators, and functional additives are added to a solvent and stirred to carry out free radical polymerization; then polydimethylsiloxane, dispersant, and catalyst are added, and stirring is continued to obtain an anti-flashover coating.

[0023] S400 Integrated Composite

[0024] Anti-flashover coating is applied to the surface of the composite insulation body using spraying or brushing processes, and after curing, a lightweight anti-flashover insulation material for high-voltage transmission lines is obtained.

[0025] Furthermore, step S100 specifically includes the following steps:

[0026] S110 micron-level packing pretreatment

[0027] Micron-sized filler was added to sodium hydroxide solution and stirred at 100-120℃ for 40-48 hours. After stirring, it was repeatedly washed with deionized water until the pH of the washing solution was neutral. After drying and pulverizing, the pretreated micron-sized filler was obtained.

[0028] Modification of and / or S120 nano-scale fillers

[0029] The nano-sized filler was mixed with a silane coupling agent and stirred at high speed at 50-60℃ for 30-50 min. After drying, the modified nano-filler was obtained.

[0030] and / or S130 nano-silver modified filler pretreatment

[0031] S131: Add micron-sized boron nitride to sodium hydroxide solution and stir at 100-120℃ for 40-48h. After stirring, wash repeatedly with deionized water until the pH of the washing solution is neutral. After drying and pulverizing, pretreated micron-sized boron nitride is obtained.

[0032] S132: Add silane coupling agent to a 50% ethanol solution, stir at 50-60℃ for 30-50 min, add pretreated micron-sized boron nitride, heat to 100-120℃, continue stirring for 18-24 h, filter, wash with anhydrous ethanol, and then vacuum dry to obtain modified boron nitride.

[0033] S133: Modified boron nitride was added to DMF solvent at a solid-liquid ratio of 1:20. After ultrasonic dispersion, silver nitrate solution was slowly added dropwise. After stirring at 60-80℃ for 1-2 hours, the mixture was filtered, washed with deionized water until no silver ions were found, and then vacuum dried to obtain nano-silver modified boron nitride filler.

[0034] Pretreatment of S140 anti-flashover coating with micro / nano-level fillers

[0035] S141: Preparation of modified micro-nano fumed silica: Micro-nano fumed silica was added to silane coupling agent and hexamethylsilane, and mixed at high speed at 70-80℃ for 1 h. After vacuum drying, modified micro-nano fumed silica was obtained.

[0036] S142: Preparation of modified nano-calcium carbonate: Nano-calcium carbonate is added to a silane coupling agent and an active silane, stirred at 60-70℃ for 40 min, and then vacuum dried to obtain modified nano-calcium carbonate.

[0037] Furthermore, step S200 specifically includes the following steps:

[0038] S211: Preheat the open mill to 110-130℃, put the methyl vinyl silicone rubber into the open mill, plasticize until softened, add the pretreated micro-nano grade filler, fumed silica and hydroxyl silicone oil, and open mill for 20-35 minutes, passing through the mill 20-35 times during the process to ensure that the filler is evenly dispersed.

[0039] S212: Add vulcanizing agent, continue to pass through the thin sheet 20-35 times, and then pass through the thin sheet to produce the film;

[0040] S213: Place the sheet into a molding vulcanizing machine and mold it at 140-180℃ and 10-15MPa for 10-20 minutes. After taking it out, place it in an oven and vulcanize it again at 170-220℃ for 3-7 hours. Cool it to room temperature to obtain the composite insulation body.

[0041] Furthermore, step S200 specifically includes the following steps:

[0042] S221 Layered Mixing: Preheat the open mill to 110-130℃, put the methyl vinyl silicone rubber into the open mill, plasticize until softened, add the pretreated micro-nano grade filler, fumed silica, silane coupling agent and hydroxyl silicone oil, and open mill for 20-35 minutes, during which the filler is passed through 20-35 times to ensure uniform dispersion of the filler and obtain the inner layer.

[0043] Preheat the open mill to 110-130℃, put the methyl vinyl silicone rubber into the open mill, plasticize until softened, add the pretreated micro-nano grade filler, fumed silica, and silane coupling agent, and open mill for 20-35 minutes, passing through the mill 20-35 times during the process to ensure that the filler is evenly dispersed and to obtain the outer layer.

[0044] S222: Add vulcanizing agent to the inner and outer layers respectively, and continue to pass through the thin layer 20-35 times to produce thin sheets;

[0045] S223 Gradient Molding and Vulcanization: A layered molding process is adopted. First, the inner layer of compound rubber is placed into the mold and pressed into shape. Then, the outer layer of compound rubber is covered on the surface. The molding and vulcanization is carried out at 150-170℃ for 12-18 minutes. Finally, a second vulcanization is carried out at 180-200℃ for 2-3 hours to obtain a gradient doped composite insulating body. The inner layer thickness accounts for 60-70%, and the outer layer thickness accounts for 30-40%.

[0046] Furthermore, step S400 specifically includes the following steps:

[0047] S411 Surface Pretreatment: Wipe the prepared composite insulation body surface clean with anhydrous ethanol to remove oil and dust, and let it dry.

[0048] S412 coating process: The pre-treated composite insulation substrate is coated with a coating thickness controlled between 80-150μm.

[0049] S413 curing treatment: Allow to cure at room temperature for 24 hours, avoiding dust contamination during this period; or heat and cure in an oven at 60-80℃ for 1-2 hours, then cure at room temperature for 12 hours.

[0050] In addition, the present invention also provides the application of lightweight anti-flashover insulation material for high-voltage transmission lines, which is used as a bird cover for transmission lines.

[0051] Beneficial technical effects

[0052] (1) This invention uses methyl vinyl silicone rubber as the matrix and adopts single, composite or gradient doping methods of "micro-nano-level fillers" to break through the technical bottleneck of "either focusing on lightweighting or focusing on performance" in the prior art. In the prior art, silicone rubber-based composite materials mostly use single-size fillers for doping, which are prone to problems such as filler agglomeration and poor interfacial bonding. However, this invention achieves the simultaneous improvement of "lightweighting-insulation-mechanical strength" through technical solutions such as micro-nano doping (such as micron-sized Si3N4 combined with nano-sized Al2O3), nano-silver modification (nano-silver modified boron nitride), and gradient doping (inner layer focuses on lightweighting, outer layer focuses on insulation strength).

[0053] (2) This invention uses a polydimethylsiloxane anti-flashover coating combined with a silicone rubber-based substrate. By utilizing the characteristic that both contain siloxane structures, chemical bonding is achieved, solving the core pain point of poor adhesion and easy peeling of the coating to the substrate in the prior art. At the same time, the coating is modified with micro-nano fillers (such as modified micro-nano fumed silica and modified nano calcium carbonate) through surface grafting technology, and combined with fluorinated (meth)acrylic acid monomers to form a superhydrophobic surface. Combined with the hydrophobic migration characteristics of polydimethylsiloxane, long-term stability of anti-flashover performance is achieved.

[0054] (3) The present invention designs differentiated pretreatment processes for different types of fillers (micro-nano fillers, nano-silver modified fillers, and gradient doped fillers), such as alkaline washing activation of micron-sized Si3N4, silane coupling agent modification of nano-sized Al2O3, and stepwise modification of nano-silver modified boron nitride (alkaline washing-silane coupling-nano-silver loading). By removing filler impurities and introducing active groups through pretreatment, the interfacial bonding force between the filler and the matrix is ​​greatly improved, and the performance degradation caused by filler agglomeration is avoided. Detailed Implementation

[0055] Example 1

[0056] The composite insulation body comprises the following raw materials in parts by weight:

[0057] 65.0 parts of methyl vinyl silicone rubber, 17.5 parts of micron-sized silicon nitride (Si3N4, particle size 1.5μm, purity 99.8%), 4.0 parts of nano-alumina (Al2O3, particle size 13nm, purity 99.9%), 6.5 parts of fumed silica, 1.5 parts of vulcanizing agent (2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, purity 98%), 0.8 parts of silane coupling agent (KH550, purity 98%), and 1.2 parts of hydroxyl silicone oil.

[0058] The anti-flashover coating formulation includes the following raw materials in parts by weight:

[0059] 45.0 parts of polydimethylsiloxane (PDMS, viscosity 10000 mPa·s), 12.5 parts of modified micro / nano fumed silica (particle size 50 nm, modified with KH570 and hexamethylsilane), 10.0 parts of fluorinated (meth)acrylic acid monomer (perfluorooctyl acrylate, purity 98%), 0.4 parts of initiator (AIBN, purity 98%), 1.5 parts of dispersant (polyethylene glycol 400), 0.8 parts of catalyst (dibutyltin dilaurate, purity 98%), and 35.0 parts of solvent (butyl acetate, cyclohexanone, purity 99.5%).

[0060] A method for preparing lightweight anti-flashover insulation material for high-voltage transmission lines includes the following steps:

[0061] S100 packing pretreatment

[0062] S110 micron-level packing pretreatment

[0063] Pretreatment of micron-sized Si3N4: Add 5 mol / L sodium hydroxide solution, stir in a constant temperature water bath at 110℃ and 400 r / min for 44 h, add 100 mL of deionized water every 12 h, wash with deionized water until pH=7 after stirring, dry in a vacuum drying oven at 70℃ and vacuum degree -0.07 MPa for 5 h, and pulverize through a 100 mesh sieve to obtain the pretreated micron-sized Si3N4 filler;

[0064] Modification of S120 nanoscale fillers

[0065] Nano-Al₂O₃ was mixed with 0.04 parts of KH550, stirred in a high-speed mixer at 55℃ and 900 r / min for 40 min, and then dried in a vacuum drying oven at 100℃ and -0.07 MPa for 10 h to obtain modified nano-Al₂O₃. 3；

[0066] Preparation of modified micro / nano fumed silica: 0.31 parts KH570 and 0.31 parts hexamethylsilane were added to micro / nano fumed silica, stirred in a high-speed mixer at 70°C and 1200 r / min for 1 h, and then vacuum dried for 6 h to obtain modified micro / nano fumed silica.

[0067] Preparation of S200 composite insulation body

[0068] S211: Preheat the open mill to 125℃, add 65.0 parts of methyl vinyl silicone rubber, and plasticize for 6 minutes until softened. Add 17.5 parts of pretreated micron Si3N4, 4.0 parts of nano Al2O3, 6.5 parts of fumed silica and 1.2 parts of hydroxyl silicone oil, and open mill for 25 minutes, passing through a thin tube 25 times (thickness of 0.8 mm) to ensure uniform dispersion of fillers and no obvious agglomeration particles.

[0069] S212: Add 1.5 parts of vulcanizing agent, continue to pass through the thin sheet 25 times, and then pass through the thin sheet (thickness 2.5mm).

[0070] S213: The sheet material is placed in a compression molding vulcanizing machine and molded at 165℃ and 12MPa for 12 minutes. After removal, it is placed in an oven for a second vulcanization at 200℃ for 3 hours. After cooling to room temperature (25℃), the composite insulation matrix is ​​obtained, with a density of 1.15 g / cm³. 3 ,spare.

[0071] Preparation of S300 Anti-Flashover Coating

[0072] S311 Preparation of mixed solvent: 25.0 parts of butyl acetate and 10.0 parts of cyclohexanone are placed in a constant temperature stirrer and stirred at 40°C and 300 r / min for 10 min to ensure the solvent is uniform;

[0073] S312 graft polymerization: Add 12.5 parts of modified micro-nano fumed silica, 10.0 parts of fluorinated (meth)acrylic acid monomer, and 0.4 parts of AIBN. Heat to 65℃ and stir at 650 r / min for 2.5 h, during which ultrasonic dispersion is performed for 15 min (power 300W) to avoid filler agglomeration.

[0074] S313 Composite Formulation: Add 45.0 parts PDMS, 1.5 parts polyethylene glycol 400 and 0.8 parts dibutyltin dilaurate, continue stirring for 1.5 hours, ultrasonically disperse for 15 minutes, filter (through a 200-mesh sieve) to remove impurities, and obtain a uniform and delicate anti-flashover coating for later use (to be used within 20 hours).

[0075] S400 Integrated Composite

[0076] S411 Surface Pretreatment: Wipe the surface of the composite insulation body three times with anhydrous ethanol to remove oil and dust, and let it air dry for 15 minutes (no watermark on the surface).

[0077] S412 coating process: Spraying process is adopted, with a spray gun pressure of 0.4MPa, a spraying distance of 25cm, uniform spraying speed (5cm / s), and the coating thickness is controlled at 100μm (measured by a coating thickness gauge, with an error of ±5μm) to avoid missed coating and sagging.

[0078] S413 curing treatment: Curing is carried out at room temperature. Let it stand at room temperature (25℃) for 24 hours, and cover it with a dust cover during the process to avoid dust contamination.

[0079] Example 2

[0080] The composite insulation body comprises the following raw materials in parts by weight:

[0081] 60.0 parts of methyl vinyl silicone rubber, 22.5 parts of nano silver modified boron nitride (particle size 15μm, silver loading 0.5%), 7.5 parts of fumed silica, 2.0 parts of vulcanizing agent (platinum vulcanizing agent, effective content 1%), 1.0 part of silane coupling agent (KH540, purity 98%), and 1.5 parts of hydroxyl silicone oil.

[0082] The anti-flashover coating formulation includes the following raw materials in parts by weight:

[0083] PDMS (viscosity 15000 mPa·s) 40.0 parts, modified nano-calcium carbonate (particle size 80 nm, modified with KH602) 10.0 parts, active silane (hexamethylsilane, purity 99%) 5.0 parts, silane coupling agent (KH570, purity 98%) 12.5 parts, (meth)acrylic acid monomer (methyl methacrylate, purity 99%) 6.5 parts, initiator (BPO, purity 98%) 0.5 parts, functional additive (UV absorber UV-531) 0.8 parts, solvent (toluene, butyl acetate, purity 99.5%) 40.0 parts.

[0084] A method for preparing lightweight anti-flashover insulation material for high-voltage transmission lines includes the following steps:

[0085] S100 packing pretreatment

[0086] S130 nano-silver modified filler pretreatment

[0087] S131: Boron nitride is first added to 5 mol / L sodium hydroxide solution, stirred at 110℃ and 400 r / min for 44 h, washed until pH=7, and dried at 70℃ and vacuum degree-0.07MPa for 5 h;

[0088] S132: Prepare a 50% ethanol solution, add 0.34 parts of KH540, stir at 55℃ and 500 r / min for 40 min, add the treated boron nitride, heat to 110℃, stir for 21 h, filter, wash 4 times with anhydrous ethanol, and vacuum dry at 100℃ for 10 h.

[0089] S133: Prepare a 9 mmol / L silver nitrate solution, add modified boron nitride to DMF at a solid-liquid ratio of 1:20 (g / mL), sonicate for 30 min, add silver nitrate solution dropwise, stir at 70℃ and 400 r / min for 1.5 h, let stand at room temperature for 21 h, filter and wash until no silver ions are found, and vacuum dry at 80℃ for 6 h to obtain nano-silver modified boron nitride for later use;

[0090] Preparation of modified nano-calcium carbonate: Add 0.3 parts KH6O2 and 0.2 parts hexamethylsilane to nano-calcium carbonate, stir at 60℃ for 40 min, and vacuum dry for 8 h for later use.

[0091] Preparation of S200 composite insulation body

[0092] S211: Preheat the open mill to 115℃, add 60.0 parts of methyl vinyl silicone rubber, and plasticize for 7 minutes until softened. Add 22.5 parts of nano silver modified boron nitride, 7.5 parts of fumed silica and 1.5 parts of hydroxyl silicone oil, and open mill for 30 minutes, during which time pass through a thin tube 30 times (thickness of 0.7mm) to ensure uniform dispersion of the filler.

[0093] S212: Add 2.0 parts of platinum vulcanizing agent, continue thin-passing 30 times, and then pass through the thin-passing sheet (thickness 2.5mm).

[0094] S213: The sheet material is placed in a compression molding vulcanizing machine and molded at 150℃ and 13MPa for 17 minutes. After removal, it is placed in an oven and vulcanized a second time at 180℃ for 4 hours. After cooling to room temperature, the composite insulation matrix is ​​obtained, with a density of 1.12 g / cm³. 3 Thermal conductivity 1.8 W / (m·K), for standby.

[0095] Preparation of S300 Anti-Flashover Coating

[0096] S311 Preparation of mixed solvent: 30.0 parts toluene and 10.0 parts butyl acetate are placed in a constant temperature stirrer and stirred at 40°C and 300 r / min for 10 min to ensure the solvent is uniform;

[0097] S312 graft polymerization: Add 10.0 parts modified nano calcium carbonate, 6.5 parts methyl methacrylate, 0.5 parts BPO, and 0.8 parts UV-531, heat to 75℃, stir at 700 r / min for 3.5 h, and ultrasonically disperse for 15 min (power 300W) during the process to avoid filler agglomeration;

[0098] S313 Composite Formulation: Add 40.0 parts PDMS, 12.5 parts KH570, and 5.0 parts hexamethylsilane, continue stirring for 2 hours, ultrasonically disperse for 15 minutes, filter (through a 200-mesh sieve) to obtain the anti-flashover coating, for later use (within 22 hours).

[0099] S400 Integrated Composite

[0100] S411 Surface Pretreatment: Wipe the surface of the composite insulation body three times with anhydrous ethanol to remove oil and dust, and let it air dry for 15 minutes (no watermark on the surface).

[0101] S412 coating process: Use brush coating (2cm brush size), apply two coats evenly, with a coating thickness of 120μm (measured by coating thickness gauge), and avoid air bubbles.

[0102] S413 curing treatment: Heating curing is carried out by heating in an oven at 65℃ for 1.5 hours, followed by curing at room temperature for 12 hours; ④ Quality inspection: After curing, the coating adhesion is tested by cross-cut test and is grade 0. The surface is smooth. After passing the test, the composite insulation material is obtained.

[0103] Example 3

[0104] The composite insulation body comprises the following raw materials in parts by weight:

[0105] Inner layer: 72.5 parts methyl vinyl silicone rubber, 10.0 parts micron Al2O3 (particle size 1.8μm, purity 99.8%), 5.0 parts fumed silica, 1.2 parts vulcanizing agent (2,5-dimethyl-2,5-di(tert-butylperoxy)hexane), and 0.5 parts silane coupling agent (KH550);

[0106] Outer layer: 62.5 parts methyl vinyl silicone rubber, 14.0 parts micron Si3N4 (particle size 1.5μm, purity 99.8%), 5.0 parts nano Al2O3 (particle size 13nm, purity 99.9%), 6.0 parts fumed silica, 1.5 parts vulcanizing agent, 0.7 parts silane coupling agent (KH550);

[0107] The inner layer to outer layer mass ratio is 7:3, and the total thickness is 5mm (3.5mm for the inner layer and 1.5mm for the outer layer).

[0108] The anti-flashover coating formulation includes the following raw materials in parts by weight:

[0109] PDMS (viscosity 12000 mPa·s) 50.0 parts, modified micro / nano fumed silica (particle size 40 nm, modified with KH570 and hexamethylsilane) 14.0 parts, fluorinated (meth)acrylic acid monomer (perfluorodecyl acrylate, purity 98%) 12.0 parts, initiator (AIBN) 0.6 parts, catalyst (dibutyltin dilaurate) 1.0 part, dispersant (polyethylene glycol 600) 2.0 parts, aminosilane repair agent (aminosilane KH550, purity 98%) 2.5 parts, solvent (cyclohexanone, toluene, purity 99.5%) 35.0 parts;

[0110] Aminosilane repair agent: 10.0 parts aminosilane KH550, 85.0 parts ethanol, 0.5 parts catalyst, and 0.5 parts dispersant, mixed evenly and ready for use.

[0111] A method for preparing lightweight anti-flashover insulation material for high-voltage transmission lines includes the following steps:

[0112] S100 packing pretreatment

[0113] S110 micron-level packing pretreatment

[0114] Pretreatment of micron-sized Al2O3 and micron-sized Si3N4: According to the micro-nano-level filler pretreatment process in Embodiment 1, stir 5 mol / L sodium hydroxide solution at 110°C for 44 h, wash until neutral, vacuum dry at 70°C for 5 h, and pass through a 100-mesh sieve for later use.

[0115] Modification of S120 nanoscale fillers

[0116] Nano-Al2O3 was mixed with 0.05 parts of KH550, stirred at 55℃ and 900 r / min for 40 min, and then vacuum dried at 100℃ for 10 h to obtain modified nano-Al2O3.

[0117] Preparation of modified micro / nano fumed silica: 0.31 parts KH570 and 0.31 parts hexamethylsilane were added to micro / nano fumed silica, stirred in a high-speed mixer at 70°C and 1200 r / min for 1 h, and then vacuum dried for 6 h to obtain modified micro / nano fumed silica.

[0118] Preparation of S200 composite insulation body

[0119] S221 Layered Mixing:

[0120] At 120℃, 72.5 parts of methyl vinyl silicone rubber were added to a two-roll mill and plasticized for 6 minutes. Then, 10.0 parts of micron Al2O3, 5.0 parts of fumed silica, and 0.5 parts of KH550 were added and the milling was continued for 25 minutes. The mixture was then passed through a thin mill 25 times to ensure uniform dispersion of the filler and obtain the inner layer.

[0121] At 125℃, 62.5 parts of methyl vinyl silicone rubber were added to a two-roll mill and plasticized for 6 minutes. Then, 14.0 parts of micron-sized Si3N4, 5.0 parts of nano-sized Al2O3, 6.0 parts of fumed silica, and 0.7 parts of KH550 were added and the milling was continued for 25 minutes. The mixture was then passed through a thin pass 25 times to ensure uniform dispersion of the filler and obtain the outer layer.

[0122] S222: Add 1.2 parts of vulcanizing agent to the inner layer, pass through the thin layer 25 times, and produce a sheet (thickness 3.5mm).

[0123] Add 1.5 parts of vulcanizing agent to the outer layer, pass through the thin layer 25 times, and produce a sheet (1.5 mm thick).

[0124] S223 Gradient Molding Vulcanization: A layered molding process is used. The inner layer film is placed in the mold and pre-pressed at 160℃ and 9MPa for 6 minutes. After removal, the outer layer film is evenly covered (without deviation). It is then placed back into the molding vulcanizing machine and molded at 160℃ and 13MPa for 15 minutes. It is then placed in an oven for a second vulcanization at 190℃ for 2.5 hours. After cooling to room temperature, no delamination of the inner and outer layers is detected, and the overall density is 1.10 g / cm³. 3 ,spare.

[0125] Preparation of S300 Anti-Flashover Coating

[0126] S311 Preparation of mixed solvent: Place 25.0 parts of cyclohexanone and 10 parts of toluene into a constant temperature stirrer, stir at 40°C and 300 r / min for 10 min to ensure the solvent is uniform;

[0127] S312 graft polymerization: Add 14.0 parts of modified micro-nano fumed silica, 12.0 parts of fluorinated (meth)acrylic acid monomer, 0.6 parts of AIBN, and 2.5 parts of aminosilane repair agent. Heat to 70℃ and stir at 750 r / min for 3 hours. During this period, ultrasonically disperse for 15 minutes to avoid filler agglomeration.

[0128] S313 Composite Formulation: Add 50.0 parts PDMS, 2.0 parts polyethylene glycol 600, and 1.0 part dibutyltin dilaurate, continue stirring for 1.5 hours, ultrasonically disperse for 15 minutes, and filter (through a 200-mesh sieve) to obtain a repairable anti-flashover coating for later use (within 24 hours).

[0129] S400 Integrated Composite

[0130] S411 Surface Pretreatment: Wipe the surface of the composite insulation body three times with anhydrous ethanol to remove oil and dust, and let it air dry for 15 minutes (no watermark on the surface).

[0131] S412 coating process: Spraying process is adopted, with a spray gun pressure of 0.45MPa, a spraying distance of 25cm, a coating thickness of 110μm, uniform spraying, and no missed coating;

[0132] S413 curing treatment: cure at room temperature (25℃) for 24 hours, then cover with dustproof material.

[0133] Example 4

[0134] The composite insulation body comprises the following raw materials in parts by weight:

[0135] Inner layer: 75.0 parts methyl vinyl silicone rubber, 9.0 parts micron alumina (particle size 2.0 μm), 4.5 parts fumed silica, 1.0 part vulcanizing agent, 0.4 parts silane coupling agent KH550;

[0136] Outer layer: 63.0 parts of methyl vinyl silicone rubber, 13.0 parts of micron-sized silicon nitride (particle size 1.2μm), 4.5 parts of nano-alumina (particle size 13nm), 5.5 parts of fumed silica, 1.4 parts of vulcanizing agent, and 0.6 parts of silane coupling agent KH550;

[0137] The inner layer to outer layer mass ratio is 6.5:3.5, and the total thickness is 5mm (inner layer 3.5mm, outer layer 1.5mm).

[0138] The anti-flashover coating formulation includes the following raw materials in parts by weight:

[0139] PDMS (viscosity 15000 mPa・s) 48.0 parts, modified micro-nano fumed silica (particle size 45 nm) 13.5 parts, fluorinated methacrylic acid monomer 11.0 parts, initiator AIBN 0.55 parts, catalyst dibutyltin dilaurate 0.9 parts, dispersant polyethylene glycol 600 1.8 parts, ultraviolet absorber UV-327 1.2 parts, solvent (cyclohexanone 26.0 parts, toluene 10.0 parts).

[0140] The preparation method of lightweight anti-flashover insulation material for high-voltage transmission lines is the same as that in Example 3.

[0141] Example 5

[0142] The composite insulation body comprises the following raw materials in parts by weight:

[0143] 58.0 parts of methyl vinyl silicone rubber, 24.0 parts of nano silver modified boron nitride (particle size 12μm, silver loading 0.8%), 8.0 parts of fumed silica, 2.2 parts of platinum vulcanizing agent, 1.1 parts of silane coupling agent KH540, and 1.6 parts of hydroxyl silicone oil.

[0144] The anti-flashover coating formulation includes the following raw materials in parts by weight:

[0145] PDMS (viscosity 12000 mPa・s) 42.0 parts, modified nano calcium carbonate (particle size 70 nm) 11.0 parts, active silane 5.5 parts, silane coupling agent KH570 13.0 parts, fluorinated methacrylic acid monomer 7.0 parts, initiator BPO 0.55 parts, repair agent aminosilane KH79 22.8 parts, solvent toluene 38.0 parts, auxiliary agent moisture-resistant heat-resistant agent 0.9 parts.

[0146] The preparation method of lightweight anti-flashover insulation material for high-voltage transmission lines is the same as in Example 2.

[0147] Example 6

[0148] The composite insulation body comprises the following raw materials in parts by weight:

[0149] 66.0 parts of methyl vinyl silicone rubber, 16.0 parts of micron-sized silicon nitride (particle size 1.0 μm), 3.5 parts of nano-alumina (particle size 13 nm), 7.0 parts of fumed silica, 1.3 parts of vulcanizing agent, 0.7 parts of silane coupling agent KH550, and 1.3 parts of hydroxyl silicone oil.

[0150] The preparation method of lightweight anti-flashover insulation material for high-voltage transmission lines is the same as that in Example 1.

[0151] The anti-flashover coating formulation includes the following raw materials in parts by weight:

[0152] PDMS (viscosity 8000 mPa·s) 46.0 parts, modified micro-nano fumed silica (particle size 50 nm) 12.0 parts, low surface energy organosilicon monomer (methyltrichlorosilane) 8.0 parts, fluorinated methacrylate monomer 9.0 parts, initiator AIBN 0.45 parts, catalyst dibutyltin dilaurate 0.8 parts, solvent butyl acetate 34.0 parts.

[0153] Comparative Example 1

[0154] The main materials include the following raw materials in parts by weight:

[0155] The product contains 60 parts epoxy resin, 25 parts curing agent (polyamide 650), and 15 parts quartz powder. It has no anti-flashover coating, and contains no micro- or nano-level fillers, silane coupling agents, or modification treatments.

[0156] Preparation method:

[0157] Raw material pretreatment: Quartz powder was not subjected to any alkali washing or silane coupling modification. It was directly crushed and passed through an 80-mesh sieve to remove large particle impurities before use. Epoxy resin was preheated in a 60℃ oven for 30 minutes to soften it before use. Curing agent was placed at room temperature and did not require pretreatment.

[0158] Main body preparation: Preheat the open mill to 80℃, add softened epoxy resin, and plasticize for 5 minutes until uniform. Add quartz powder and open mill for 20 minutes, passing through a thin tube 15 times (thickness 1mm) during the process to ensure uniform dispersion of the quartz powder. Add polyamide 650 curing agent and continue opening mill for 10 minutes, passing through a thin tube 10 times. After mixing evenly, pass through a thin tube to produce a sheet (thickness 5mm). Place the sheet into a compression molding vulcanizing machine and mold it at 120℃ and 10MPa for 20 minutes. After removing it, allow it to cool naturally to room temperature. No secondary vulcanization is required to obtain the epoxy fiberglass main body. There is no anti-flashover coating step; the finished product is obtained directly.

[0159] Comparative Example 2

[0160] The main materials include the following raw materials in parts by weight:

[0161] 98 parts of methyl vinyl silicone rubber, 2 parts of vulcanizing agent (2,5-dimethyl-2,5-di(tert-butylperoxy)hexane), no fillers, silane coupling agents, and no anti-flashover coating.

[0162] Preparation method:

[0163] Raw material pretreatment: No fillers are used. Methyl vinyl silicone rubber is simply softened at room temperature for 2 hours. The vulcanizing agent is kept at room temperature. No modification or pretreatment steps are required.

[0164] Main body preparation: Preheat the open mill to 120℃, add methyl vinyl silicone rubber, and plasticize for 7 minutes until completely softened without adding any fillers. Continue open milling for 10 minutes to ensure uniform rubber texture. Add vulcanizing agent, pass through a thin pass 20 times (thickness of 0.8mm), and produce a sheet (thickness of 5mm). Place the sheet into a compression molding vulcanizing machine and compress and vulcanize at 160℃ and 12MPa for 15 minutes. After removal, place it in an oven and vulcanize again at 200℃ for 3 hours. Cool to room temperature to obtain pure silicone rubber main body. No anti-flashover coating step is required; the finished product is obtained directly.

[0165] Comparative Example 3

[0166] The main materials include the following raw materials in parts by weight:

[0167] The composition consists of 65 parts methyl vinyl silicone rubber, 21.5 parts micron-sized silicon nitride, 6.5 parts fumed silica, 1.5 parts vulcanizing agent, and 0.8 parts silane coupling agent KH550. It has no anti-flashover coating and no nanofiller doping.

[0168] Preparation method:

[0169] Raw material pretreatment: Micron-sized silicon nitride is added to 5 mol / L sodium hydroxide solution, stirred in a constant temperature water bath at 110℃ and 400 r / min for 44 h, washed until pH=7, dried in a vacuum drying oven at 70℃ and -0.07 MPa for 5 h, and then pulverized and passed through a 100 mesh sieve for later use.

[0170] Fumed silica produced by the gas phase process does not require modification and can be used directly; silane coupling agent KH550 can be used at room temperature.

[0171] Main body preparation: Preheat the open mill to 125℃, add methyl vinyl silicone rubber, and plasticize for 6 minutes until softened. Add pretreated micron-sized silicon nitride, fumed silica and silane coupling agent KH550, and open mill for 25 minutes, during which the material is passed through a thin tube 25 times (thickness of 0.8 mm) to ensure uniform dispersion of the filler. Add vulcanizing agent and continue to pass through a thin tube 25 times to produce a sheet (thickness of 5 mm). Place the sheet into a compression molding vulcanizing machine and compress and vulcanize at 165℃ and 12MPa for 15 minutes. After removal, place it in an oven and vulcanize again at 200℃ for 3 hours. Cool to room temperature to obtain a single micro-nano-level filler-doped silicone rubber main body.

[0172] There is no anti-flashover coating step, and the finished product is obtained directly.

[0173] Comparative Example 4:

[0174] The main materials include the following raw materials in parts by weight:

[0175] 65 parts methyl vinyl silicone rubber, 17.5 parts micron-sized silicon nitride, 4 parts nano-alumina, 6.5 parts fumed silica, 1.5 parts vulcanizing agent, 0.8 parts KH550; Coating material: commercially available conventional PDMS anti-flashover coating (without surface grafting modification, without fluorine-containing monomers).

[0176] Preparation method:

[0177] Raw material pretreatment: Micron-sized silicon nitride and nano-sized alumina are pretreated according to the process in Implementation Method 1 (alkali washing and silane coupling modification), and fumed silica is ready for immediate use; commercially available conventional PDMS anti-flashover coatings do not require any modification treatment and can be used directly after shaking.

[0178] Main body preparation: The preparation process was completely consistent with that of the composite insulating main body in Example 1 (open rolling, molding vulcanization, and secondary vulcanization), resulting in a silicone rubber main body with a density of 1.14 g / cm³. 3 spare.

[0179] Coating application and curing:

[0180] Wipe the main surface clean with anhydrous ethanol and let it air dry for 15 minutes.

[0181] The process involves spraying with a spray gun pressure of 0.4 MPa and a spraying distance of 25 cm. A commercially available PDMS anti-flashover coating is applied, with a coating thickness of 100 μm. The coating is cured at room temperature (25°C) for 24 hours. There is no siloxane structure adaptation design between the substrate and the coating. The finished product is obtained after curing.

[0182] Comparative Example 5

[0183] The composite insulation body comprises the following raw materials in parts by weight:

[0184] 65.0 parts of methyl vinyl silicone rubber, 21.5 parts of nano alumina (particle size 13nm), 6.5 parts of fumed silica, 1.5 parts of vulcanizing agent, 0.8 parts of silane coupling agent KH550, and 1.2 parts of hydroxyl silicone oil.

[0185] The anti-flashover coating formulation is the same as in Example 1.

[0186] The preparation method is the same as in Example 1.

[0187] Comparative Example 6

[0188] The formulations of the composite insulation body and the anti-flashover coating are the same as those in Example 2.

[0189] The preparation method differs from that in Example 2 in that step S132 is omitted.

[0190] Comparative Example 7

[0191] The formulation of the composite insulation body and the anti-flashover coating is the same as that in Example 3, except that the mass ratio of the inner layer to the outer layer is changed to 1:1 (total thickness 5mm, each 2.5mm).

[0192] The preparation method is the same as in Example 3.

[0193] Comparative Example 8

[0194] The difference from Example 1 is that the anti-flashover coating does not contain fluorinated (meth)acrylic monomers.

[0195] Comparative Example 9

[0196] The difference from Example 1 is that the micron-sized Si3N4, nano-sized Al2O3, and micro / nano-sized fumed silica were not pretreated.

[0197] Comparative Example 10

[0198] The difference from Example 3 is that the aminosilane repair agent is removed.

[0199] The performance tests of the embodiments and comparative examples of this invention, including specific test items and methods, are as follows:

[0200] Density test: Performed according to GB / T1033.1-2008 "Determination of density of non-foamed plastics - Part 1: Immersion method, liquid specific gravity bottle method and titration method", test temperature 25℃, sample size 10mm×10mm×4mm, 5 parallel tests and average value.

[0201] Breakdown field strength test: Performed according to GB / T1408.1-2016 "Electrical strength test method for insulating materials - Part 1: Test at power frequency", with a voltage rise rate of 2kV / s, and the average value of 3 parallel tests is taken;

[0202] Volume resistivity test: Performed according to GB / T1410-2006 "Test methods for volume resistivity and surface resistivity of solid insulating materials", apply 500V DC voltage, maintain for 10min under constant temperature and humidity environment, and take the average value of 3 parallel tests.

[0203] Tensile strength: Performed according to GB / T528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber", with dumbbell type 1 specimen, tensile rate of 500 mm / min, and average value of 5 parallel tests.

[0204] Shore hardness: Performed according to GB / T531.1-2008 "Test method for indentation hardness of vulcanized rubber or thermoplastic rubber - Part 1: Shore hardness tester method (Shore A and Shore D)". Before testing, the sample was placed in an environment of 23℃ for 24 hours. Five points were tested on each sample and the average value was taken. The average value of three samples was taken as the final result.

[0205] Thermal conductivity test: Performed according to GB / T10294-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - protective hot plate method". Take 3 standard samples and place them in a constant temperature and humidity chamber (25℃, 50% humidity) for 24 hours. Place the samples in the test chamber of the thermal conductivity meter, set the cold and hot surface temperatures to 30℃ and 20℃ respectively, and after the heat flow stabilizes (temperature difference fluctuation ≤0.1℃), record the thermal conductivity value and take the average value of the 3 samples as the final result.

[0206] Static water contact angle test: Performed according to GB / T30693-2014 "Determination of hydrophobic properties of plastic surfaces - contact angle method". Take 3 standard samples with coating and place them in a constant temperature and humidity chamber (25℃, 50% humidity) for 1 hour. Use a microsyringe to draw deionized water and drop 5μL of water droplets (drop height 5mm, avoid impacting the sample surface) onto the sample surface. After the water droplets stabilize (about 30s), take an image of the water droplets with a contact angle measuring instrument and measure the contact angle value. Select 5 different measuring points for each sample and take the average value of the 5 measuring points as the contact angle of a single sample. Then take the average value of the 3 samples as the final result.

[0207] Coating adhesion: Performed according to GB / T9286-2021 "Cross-cut test for paints and varnishes", with a cross-cut spacing of 2mm. Peel off with 3M tape. Rating standard: 0-5 (0 is the best). 5 parallel tests are conducted and the lowest rating is taken.

[0208] Flashover voltage and leakage current tests: Performed according to GB / T16927.1-2018 "High Voltage Testing Techniques Part 1: General Test Requirements" and GB / T4585-2004 "Artificial Pollution Tests for High Voltage Insulators for AC Systems". Three standard samples with the coating applied were taken and subjected to artificial pollution testing (pollution level 0.1 mg / cm³). 2 The sample was prepared by mixing NaCl and diatomaceous earth in a mass ratio of 1:2. The dirty liquid was sprayed evenly onto the sample surface using a spraying device and allowed to air dry for 1 hour. The sample was then mounted on a fixture, and a high-voltage power frequency was applied. The voltage was increased at a rate of 1 kV / s, and the voltage at flashover (flashover voltage) was recorded. At the same time, the leakage current on the sample surface (average current during the stable voltage increase phase) was recorded during the voltage increase. The average value of 3 samples was taken as the final result.

[0209] Hydrophobic migration time and self-cleaning rate test: Refer to DL / T864-2015 "Pollution Class of High Voltage External Insulation". Hydrophobic migration time: Take 3 samples of Implementation Method 2, add 5μL of deionized water to the coating surface and measure the initial contact angle; spray the sample surface with a pollutant solution (NaCl concentration 0.1%), let it stand and observe, and record the time required for the contact angle to recover to above 145°. Take the average value of the 3 samples as the final result.

[0210] Self-cleaning rate: Take 3 samples from Example 3 and weigh the initial mass of the samples (m0); evenly coat the surface of the samples with 0.1g of industrial dust (particle size 50-100μm) and place them under a simulated rainfall device (rainfall 10mm / h, rainfall time 30min); after the rainfall ends, let them air dry naturally and weigh the remaining mass of the samples (m1); calculate the self-cleaning rate according to the formula self-cleaning rate = [(m0+0.1-m1) / 0.1]×100%, and take the average value of the 3 samples as the final result;

[0211] Repairability test: Referring to GB / T30693-2014 "Determination of Hydrophobicity of Plastic Surfaces - Contact Angle Method", and combined with the repairability design supplement of this scheme, three repairable coating samples from Example 3 were taken. Damage scratches (2cm in length, 0.5mm in width, penetrating the coating to the base material) were made on the coating surface. The special repair agent was evenly sprayed onto the scratches using a micro-syringe and left to stand at room temperature (25℃) for 1.5h. After the repair was completed, the contact angle values ​​were measured in the scratch area and within 5mm of the surrounding area according to the static water contact angle test method. The average value of the three samples was taken as the final result.

[0212] High and low temperature resistance test: Perform the test according to GB / T1690-2010 "Test Method for Liquid Resistance of Vulcanized Rubber or Thermoplastic Rubber". Take 3 samples and place them in a high and low temperature test chamber. Set the temperature cycle as follows: -40℃ constant temperature for 2h → room temperature (25℃) standing for 1h → 120℃ (130℃ for Implementation Method 3) constant temperature for 2h → room temperature standing for 1h. Repeat the cycle 10 times. After the cycle, take out the samples and observe the surface with a magnifying glass for cracking, deformation, coating peeling, etc. At the same time, measure the density and tensile strength, compare with the initial data, and calculate the performance retention rate.

[0213] Salt spray resistance: The test was conducted according to GB / T10125-2021 "Salt spray test for corrosion in artificial atmosphere". The salt spray concentration was 5% NaCl solution. Three samples were placed in the salt spray test chamber and the test temperature was set to 35℃. The spraying was continuous (800h for Example 3, 500h for the others). After the test, the samples were taken out, the surface salt stains were rinsed with deionized water, and the samples were allowed to air dry. The surface was observed for any damage, rust, coating peeling, etc. The coating adhesion was measured and compared with the initial data.

[0214] The test results are as follows:

[0215]

[0216]

[0217] The density of the embodiments in this invention is 1.10-1.15 g / cm³. 3 The concentration was significantly lower than that of epoxy resin-based comparative example 1 (1.85 g / cm³). 3 The principle is as follows: methyl vinyl silicone rubber is selected as the matrix, which has a lower density; low-density insulating fillers such as Si3N4, Al2O3, and BN are used to replace traditional high-density quartz powder; Examples 3 and 4 adopt a gradient doping structure, with high rubber content and low filler content in the inner layer to reduce the overall density, and high filler content in the outer layer to ensure performance; at the same time, the dispersibility of the filler is greatly improved after alkaline washing activation and silane coupling, which can achieve high performance with low filler content, avoiding the increase in density caused by high filler content, thus achieving a balance between lightweight and high performance.

[0218] The breakdown field strength of the examples is 32.6-38.7 kV / mm, which is much higher than that of pure silicone rubber comparative example 2 (16.5 kV / mm) and untreated comparative example 9 (24.8 kV / mm). The principle is as follows: micron and nano fillers are compounded to form a dense insulating network. Micron builds the skeleton and nano fills the gaps, reducing internal air gaps and defects; the fillers are treated with alkali washing to remove impurities and silane coupling, resulting in tight interfacial bonding, eliminating interfacial voids, and inhibiting partial discharge and electrical tree growth; nano silver-modified BN can homogenize the electric field distribution and reduce charge accumulation; the gradient structure allows the outer high-insulation component to directly withstand the high electric field, further improving the surface breakdown strength.

[0219] The volume resistivity of the embodiment is 6.8 × 10⁻⁶. 16 -8.2×10 16 The resistivity (Ω·cm) is more than an order of magnitude higher than that of comparative examples 1 and 2. The principle behind this is that: the micro-nano composite filler forms a continuous insulating channel, reducing the probability of internal leakage current; interface modification eliminates interfacial defects between the filler and the matrix, reducing interfacial leakage current; nano-alumina, silicon nitride, and boron nitride are all high-resistivity inorganic fillers, which can significantly improve the bulk resistivity of the matrix; and the absence of filler agglomeration and void defects ensures a stable resistivity of 10 Ω·cm. 16 Ω·cm high grade.

[0220] The hardness of the example is 72-76, which is in the moderate hardness range. The principle is that: the micro-nano level filler is appropriately filled, which ensures rigidity without brittleness; the hydroxyl silicone oil improves the processing fluidity of the rubber and makes the cross-linking structure more uniform; the gradient structure has a softer inner layer and a harder outer layer, and the overall hardness is stable and controllable; compared with the pure rubber comparative example 2 (45) which is too soft and the epoxy comparative example 1 (85) which is too hard, this system can maintain moderate hardness under high insulation and high mechanical conditions, which meets the installation and operation requirements.

[0221] The thermal conductivity of the examples is 1.2-1.8 W / (m·K), which is much higher than that of the pure rubber comparative example 2 (0.2). The principle is that BN, Si3N4, and Al2O3 are all inorganic fillers with high thermal conductivity, forming a continuous thermal conduction path in the matrix; nano-silver modification of BN can reduce interfacial thermal resistance and enhance phonon transmission; the fillers are highly dispersed and do not agglomerate, reducing thermal barriers and voids, and enabling rapid Joule heat dissipation; Example 2 has a higher nano-silver loading, and the thermal conductivity reaches the highest of 1.8 W / (m·K).

[0222] The contact angle of the example was 152-158°, reaching the superhydrophobic standard; the comparative example 8 (fluorine-free monomer) was only 126°. The principle is as follows: PDMS + fluorine-containing (meth)acrylate constructs an extremely low surface energy layer; modified micro-nano fumed silica forms a micro-nano bilevel rough structure, stabilizing the Cassie-Baxter hydrophobic state; the hydrophobic migration of PDMS continuously replenishes the low-energy groups on the surface, so that the hydrophobic effect is maintained for a long time; the surface energy of the fluorine-free monomer is too high, and superhydrophobicity cannot be achieved.

[0223] In all examples, the coating adhesion was grade 0, compared to grade 3 for Comparative Example 4 and grade 4 for Comparative Example 9. The principle is as follows: both the substrate silicone rubber and the coating PDMS contain -Si-O-Si- structures, which can undergo chemical condensation and interfacial interpenetration, achieving chemical bonding; the coating filler is modified with silane, resulting in stronger compatibility with the resin; the substrate surface is cleaned and activated with ethanol, further enhancing interfacial adhesion; without pretreatment or using commercially available conventional coatings, only physical adhesion occurs, making them easily peeled off.

[0224] The flashover voltage of the example is 118-132kV, significantly higher than that of the comparative examples. The principle is as follows: the superhydrophobic surface inhibits the adsorption of dirt and the communication of the water film, thereby increasing the surface flashover voltage; the high insulating outer layer and high volume resistivity reduce the surface leakage current; the dense and defect-free filler interface reduces partial discharge; and the hydrophobic migration characteristics enable rapid recovery of hydrophobicity under dirt, maintaining a high flashover voltage.

[0225] The migration time in the examples was 1.2-2.1 hours, while that in Comparative Example 4 was as long as 6.8 hours. The principle is as follows: the PDMS molecular chains in the coating have the characteristic of spontaneous migration to the surface, continuously replenishing low surface energy groups; the micro-nano rough structure provides channels for migration, accelerating the hydrophobic recovery speed; the fluorinated components and siloxanes work synergistically to enable the contact angle to quickly recover to over 145°; conventional coatings have no migration design and hydrophobic recovery is extremely slow.

[0226] The self-cleaning rate of the example is 92.3-97.5%, which is much higher than that of Comparative Example 1 (45.2%). The principle is as follows: the superhydrophobic interface causes water droplets to roll off in a spherical shape, carrying dust off the surface; the micro-nano rough structure reduces the number of dirt adhesion points; the low surface energy of PDMS reduces the dust adhesion force; and dynamic self-cleaning can be achieved during rainfall to keep the surface clean and improve operational reliability.

[0227] The examples show that the repaired contact angle is 149-156° with a retention rate of over 98%; Comparative Example 10, without repair agent, has a contact angle of only 138°, and Comparative Example 9, without pretreatment, has a contact angle of only 121°. Principle: The aminosilane repair agent in the coating can rapidly undergo a condensation reaction at the damaged area, replenishing Si-O-Si and low surface energy groups, and reconstructing the superhydrophobic structure; comparative examples without repair agent, with unmodified fillers, or with poor interfacial bonding cannot form an effective repair layer, resulting in a significant loss of hydrophobic properties.

[0228] The strength retention rate of the example after high and low temperature cycling was 95.2%-97.3%, with no damage to the appearance; compared with Comparative Example 1, it was only 72.5%, and Comparative Example 2, it was only 68.3%. Principle: The silicone rubber matrix has a wide temperature resistance range; the chemical bonding at the filler interface reduces the risk of thermal stress cracking; the gradient structure releases internal stress and reduces the difference in thermal expansion; pure silicone rubber has insufficient strength, and the epoxy matrix is ​​brittle, both of which are prone to deformation and cracking.

[0229] Examples of examples show that the adhesion remained at level 0 after salt spray testing, and Example 3 withstood 800 hours without failure. Comparative Example 9 showed that the adhesion dropped to level 5 after salt spray testing, with large areas of the coating peeling off. Principle: The superhydrophobic coating blocks the penetration of salt spray and moisture; the filler pretreatment is thorough, eliminating impurities that could cause corrosion; PDMS and silicone rubber are chemically bonded, resulting in a dense, water-impermeable interface. Comparative examples without coatings, with unmodified fillers, or with poor adhesion were easily penetrated and damaged by salt spray, resulting in blistering, peeling, and powdering.

[0230] In summary, this invention improves upon traditional insulating materials from three aspects: molecular interface, micro-composite, and macro-structure. It solves the industry pain points of easy agglomeration of fillers, easy peeling of coatings, and difficulty in balancing lightweight and performance. Ultimately, it achieves an integrated system of "low density, high insulation, high mechanical strength, superhydrophobicity, long-lasting anti-pollution flashover, high reliability, and repairability", fully meeting the stringent requirements of high-voltage transmission lines.

[0231] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A lightweight anti-pollution flashover insulating material for high voltage transmission lines, characterized in that, It includes a composite insulation body and an anti-flashover coating applied to its surface; The composite insulation matrix uses methyl vinyl silicone rubber as the base material and is doped with micro-nano-scale fillers. The interfacial bonding force with the base material is improved through modification treatment. The anti-flashover coating is prepared by surface grafting technology with polydimethylsiloxane as the matrix, modified micro-nano fillers, hydrophobic monomers and functional additives. The composite insulation body comprises the following raw materials in parts by weight: 55-75 parts methyl vinyl silicone rubber, 8-25 parts micro-nano grade filler, 4-9 parts fumed silica, 1-2.5 parts vulcanizing agent, 0.4-1.2 parts silane coupling agent, and 0-1.8 parts hydroxyl silicone oil. The micro / nano-scale fillers are micron-sized silicon nitride (Si3N4), micron-sized aluminum oxide (Al2O3), nano-alumina (Al2O3), and nano-silver-modified boron nitride; The anti-flashover coating comprises the following raw materials in parts by weight: 35-55 parts polydimethylsiloxane, 8-16 parts modified micro-nano filler, 5-14 parts hydrophobic monomer, 0.3-0.7 parts initiator, 0.5-1.2 parts catalyst, 1-2.5 parts dispersant, 0.5-3 parts functional additive, and 30-45 parts solvent; The functional additives include one or more repair agents and weather-resistant additives; The modified micro / nano-grade filler is modified micro / nano fumed silica or modified nano calcium carbonate, which has been modified by silane coupling agent and active silane; the hydrophobic monomer is a fluorinated (meth)acrylic acid monomer.

2. A method for producing the lightweight anti-pollution flashover insulating material for high voltage transmission lines according to claim 1, characterized in that, Includes the following steps: S100 packing pretreatment Micro-nano-level fillers for composite insulation substrates and micro-nano-level fillers for anti-flashover coatings are subjected to alkaline washing and silane coupling agent modification treatments to remove impurities and introduce active groups, thereby improving the interfacial bonding force with the substrate; for nano-silver modified fillers, nano-silver loading treatment is performed. Preparation of S200 composite insulation body Methyl vinyl silicone rubber is fed into a two-roll mill and heated to 110-130℃. Pretreated micro-nano fillers, fumed silica and hydroxyl silicone oil are added. The mixture is then milled and passed through a thin sheet. A vulcanizing agent is added and the mixture is passed through a thin sheet again. After the sheet is extruded, it is molded and vulcanized to obtain the composite insulation body. Preparation of S300 Anti-Flashover Coating Using surface grafting technology, the modified anti-flashover coating is added to a solvent with micro-nano-level fillers, hydrophobic monomers, initiators, and functional additives, and then stirred to carry out free radical polymerization; then polydimethylsiloxane, dispersant, and catalyst are added, and stirring is continued to obtain the anti-flashover coating. S400 Integrated Composite Anti-flashover coating is applied to the surface of the composite insulation body using spraying or brushing processes, and after curing, a lightweight anti-flashover insulation material for high-voltage transmission lines is obtained.

3. The method for preparing lightweight anti-flashover insulation material for high-voltage transmission lines according to claim 2, characterized in that, Step S100 specifically includes the following steps: S110 micron-level packing pretreatment Micron-sized filler was added to sodium hydroxide solution and stirred at 100-120℃ for 40-48 hours. After stirring, it was repeatedly washed with deionized water until the pH of the washing solution was neutral. After drying and pulverizing, the pretreated micron-sized filler was obtained. Modification of and / or S120 nano-scale fillers The nano-sized filler was mixed with a silane coupling agent and stirred at high speed at 50-60℃ for 30-50 min. After drying, the modified nano-filler was obtained. and / or S130 nano-silver modified filler pretreatment S131: Add micron-sized boron nitride to sodium hydroxide solution and stir at 100-120℃ for 40-48h. After stirring, wash repeatedly with deionized water until the pH of the washing solution is neutral. After drying and pulverizing, pretreated micron-sized boron nitride is obtained. S132: Add silane coupling agent to a 50% ethanol solution, stir at 50-60℃ for 30-50 min, add pretreated micron-sized boron nitride, heat to 100-120℃, continue stirring for 18-24 h, filter, wash with anhydrous ethanol, and then vacuum dry to obtain modified boron nitride. S133: Modified boron nitride was added to DMF solvent at a solid-liquid ratio of 1:

20. After ultrasonic dispersion, silver nitrate solution was slowly added dropwise. After stirring at 60-80℃ for 1-2 hours, the mixture was filtered, washed with deionized water until no silver ions were found, and then vacuum dried to obtain nano-silver modified boron nitride filler. Pretreatment of S140 anti-flashover coating with micro / nano-level fillers S141: Preparation of modified micro-nano fumed silica: Micro-nano fumed silica was added to silane coupling agent and hexamethylsilane, and mixed at high speed at 70-80℃ for 1 h. After vacuum drying, modified micro-nano fumed silica was obtained. S142: Preparation of modified nano-calcium carbonate: Nano-calcium carbonate is added to a silane coupling agent and an active silane, stirred at 60-70℃ for 40 min, and then vacuum dried to obtain modified nano-calcium carbonate.

4. The method for preparing lightweight anti-flashover insulation material for high-voltage transmission lines according to claim 2, characterized in that, Step S200 specifically includes the following steps: S211: Preheat the open mill to 110-130℃, put the methyl vinyl silicone rubber into the open mill, plasticize until softened, add the pretreated micro-nano grade filler, fumed silica and hydroxyl silicone oil, and open mill for 20-35 minutes, passing through the mill 20-35 times during the process to ensure that the filler is evenly dispersed. S212: Add vulcanizing agent, continue to pass through the thin sheet 20-35 times, and then pass through the thin sheet to produce the film; S213: Place the sheet into a molding vulcanizing machine and mold it at 140-180℃ and 10-15MPa for 10-20 minutes. After taking it out, place it in an oven and vulcanize it again at 170-220℃ for 3-7 hours. Cool it to room temperature to obtain the composite insulation body.

5. The method for preparing lightweight anti-flashover insulation material for high-voltage transmission lines according to claim 2, characterized in that, Step S200 specifically includes the following steps: S221 Layered Mixing: Preheat the open mill to 110-130℃, put the methyl vinyl silicone rubber into the open mill, plasticize until softened, add the pretreated micron filler, fumed silica, silane coupling agent and hydroxyl silicone oil, and open mill for 20-35 minutes, passing through the mill 20-35 times during the process to ensure that the filler is evenly dispersed and to obtain the inner layer. Preheat the open mill to 110-130℃, put the methyl vinyl silicone rubber into the open mill, plasticize until softened, add the pretreated micro-nano grade filler, fumed silica, and silane coupling agent, and open mill for 20-35 minutes, passing through the mill 20-35 times during the process to ensure that the filler is evenly dispersed and to obtain the outer layer. S222: Add vulcanizing agent to the inner and outer layers respectively, and continue to pass through the thin layer 20-35 times to produce thin sheets; S223 Gradient Molding and Vulcanization: A layered molding process is adopted. First, the inner layer of compound rubber is placed into the mold and pressed into shape. Then, the outer layer of compound rubber is covered on the surface. The molding and vulcanization is carried out at 150-170℃ for 12-18 minutes. Finally, a second vulcanization is carried out at 180-200℃ for 2-3 hours to obtain a gradient doped composite insulating body. The inner layer thickness accounts for 60-70%, and the outer layer thickness accounts for 30-40%.

6. The method for preparing lightweight anti-flashover insulation material for high-voltage transmission lines according to claim 2, characterized in that, Step S300 specifically includes the following steps: S311 Solvent preparation: Prepare a mixed solvent by mixing butyl acetate, toluene, and cyclohexanone in a certain proportion, place it in a constant temperature stirrer, and stir for 10 minutes at 40-50℃ to ensure that the solvent is uniform. S312 graft polymerization: Add pretreated anti-flashover coating micro-nano-grade filler, hydrophobic monomers, initiators and functional additives, heat to 60-80℃, stir for 2-4 hours to carry out free radical polymerization reaction, and ultrasonically disperse during the process to avoid filler agglomeration. S313 Composite Formulation: Add polydimethylsiloxane, dispersant, and catalyst, continue stirring for 1-2.5 hours, ultrasonically disperse, filter to remove impurities, and obtain a uniform and delicate anti-flashover coating.

7. The method for preparing lightweight anti-flashover insulation material for high-voltage transmission lines according to claim 2, characterized in that, Step S400 specifically includes the following steps: S411 Surface Pretreatment: Wipe the prepared composite insulation body surface clean with anhydrous ethanol to remove oil and dust, and let it dry. S412 coating process: The pre-treated composite insulation substrate is coated with a coating thickness controlled between 80-150μm. S413 curing treatment: Allow to cure at room temperature for 24 hours, avoiding dust contamination during this period; or heat and cure in an oven at 60-80℃ for 1-2 hours, then cure at room temperature for 12 hours.

8. Use of the lightweight anti-pollution flashover insulating material for high voltage transmission lines according to claim 1, characterized in that, Bird protection covers for power transmission lines.

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