Composite insulator and method for manufacturing the same

Abstract

The present disclosure relates to the technical field of insulators, and particularly relates to a composite insulator and a preparation method thereof. The preparation method comprises the following steps: setting a fitting on both ends of a core rod, then sequentially performing roughening treatment, plasma activation treatment, silane coupling agent coating and adhesive coating on the surface of the core rod, drying to obtain a core A; loading the core A into a forming mold, closing the mold, injecting vulcanized rubber material after forming the cavity of the forming mold into a vacuum condition, sequentially performing vulcanization treatment at a first temperature, a second temperature and a third temperature, opening the mold to obtain a core B; and performing post-vulcanization treatment on the core B to obtain the composite insulator. The preparation method of the composite insulator provided by the present disclosure takes integral and integrated vulcanization molding as the core, realizes high-strength combination and uniform molding of the outer insulating umbrella and the core through the cooperation of the whole process of interface ordered modification, vacuum injection glue step vulcanization and post-vulcanization stability.

Description

Technical Field

[0001] This disclosure relates to the field of insulator technology, and in particular to a composite insulator and its preparation method. Background Technology

[0002] Composite insulators, with their excellent resistance to flashover, lightweight and high strength, and maintenance-free advantages, have become the core insulation components in high-voltage and ultra-high-voltage power transmission and transformation systems. The vulcanization quality of the silicone rubber outer insulating sheath directly determines the electrical insulation performance, mechanical stability, and long-term service life of the insulator, and is the core process in the manufacturing of composite insulators.

[0003] Currently, the molding of silicone rubber sheds for composite insulators in the industry mostly adopts segmented molding vulcanization or extrusion segmented vulcanization processes. These processes have gradually revealed several technical shortcomings in long-term production and engineering applications, making them unsuitable for the high reliability requirements of ultra-high voltage products. In the segmented vulcanization mode, the product forms multiple splicing seams, making it difficult to guarantee stable interfacial adhesion at these seams, which can easily lead to sealing failure. During long-term outdoor service, moisture can gradually penetrate the interior along the splicing seams, inducing a series of failure problems such as core rod brittle fracture, insulation breakdown, and end fitting corrosion, becoming a major factor affecting the operational safety of composite insulators. Furthermore, segmented vulcanization requires multiple mold closing and changing operations, which can easily cause molding deviations such as core eccentricity and uneven shed wall thickness distribution. Multiple heating and cooling cycles can also accumulate internal stress within the silicone rubber, easily leading to shed cracking, skirt detachment, and decreased surface hydrophobicity during long-term operation, resulting in performance degradation problems such as shed cracking, skirt detachment, and decreased surface hydrophobicity.

[0004] Although the industry has attempted to eliminate seam defects through whole-piece vulcanization molding, core challenges such as precise coaxial positioning of long molds, adequate cavity venting, and uniform vulcanization temperature control have not yet been effectively solved. Whole-piece molding is prone to defects such as insufficient rubber filling, internal air bubbles, and inconsistent vulcanization levels at different locations, resulting in poor batch stability and difficulty in supporting large-scale stable production. Furthermore, existing vulcanization processes often employ a single constant temperature control method, leading to insufficient matching between process parameters and the crosslinking reaction process of silicone rubber. This can easily result in localized under-vulcanization or over-vulcanization, causing a decrease in the tracking resistance and aging resistance of silicone rubber, thus limiting the long-term service life of the product.

[0005] Overall, existing technologies are mostly limited to local optimization of single mold structure or vulcanization parameters, and have not formed a whole-process collaborative optimization system for molding positioning, vulcanization control and post-processing. It is difficult to achieve stable mass production of vulcanized composite insulators of UHV level, and cannot fully meet the core requirements of new power systems for high reliability and long service life of insulation components. Summary of the Invention

[0006] To address the aforementioned technical problems, this disclosure provides a composite insulator and its preparation method. The preparation method of the composite insulator provided in this disclosure is based on integral vulcanization molding, achieving high-strength bonding and uniform molding of the outer insulating sheath and core through a comprehensive process involving ordered interface modification, vacuum injection step vulcanization, and post-vulcanization stabilization.

[0007] This disclosure provides a method for preparing a composite insulator, including the following steps: Fittings are installed at both ends of the mandrel. Then, the surface of the mandrel is subjected to roughening treatment, plasma activation treatment, coating with silane coupling agent and coating with adhesive in sequence, and then dried to obtain core A. The core A is inserted into the molding mold, the mold is closed, and a vacuum condition is formed in the cavity of the molding mold before vulcanizing rubber is injected. The vulcanization process is carried out in sequence at the first temperature, the second temperature and the third temperature. The mold is then opened to obtain the core B. The core B is subjected to post-vulcanization treatment to obtain the composite insulator; The first temperature is 110℃~120℃, the second temperature is 165℃~175℃, and the third temperature is 140℃~150℃.

[0008] This disclosure provides a method for preparing composite insulators. First, fittings are assembled at both ends of a core rod to pre-assemble the core's basic components. Then, the surface of the core rod to be coated is subjected to roughening treatment, plasma activation treatment, silane coupling agent coating, and adhesive coating in sequence. After drying, a core A with interface pretreatment is obtained. The roughening treatment constructs a micro-rough structure on the core rod surface, providing a physical basis for subsequent interface coating and improving coating adhesion. The plasma activation treatment modifies the polarity of the core rod surface, introducing active functional groups, increasing surface reactivity, and providing reaction sites for chemical bonding. The silane coupling agent forms a molecular bridge between the inorganic core rod and the silicone rubber material, while the adhesive further enhances the adhesion performance of the interface layer. After drying and curing, a stable interface transition layer is formed, ensuring the long-term reliability of the bond between the core and the outer insulation layer.

[0009] Then, core A is placed into the molding mold. After the mold is closed, the cavity of the mold is first made into a vacuum condition, and then vulcanizing rubber is injected into the cavity. Then, the vulcanization process is completed by using the first temperature, the second temperature and the third temperature in sequence. After the mold is opened, core B with an outer insulating umbrella sleeve (silicone rubber umbrella sleeve) structure is obtained. Vacuum treatment before injection can fully remove air from the cavity, preventing air bubbles from forming internal pore defects during the filling process and ensuring uniform and stable electrical performance of the outer insulation layer. A three-stage gradient temperature vulcanization process allows for precise control of the crosslinking reaction of the silicone rubber: the first temperature of 110℃~120℃ is the pre-vulcanization and shaping stage, where the rubber undergoes initial crosslinking, fixing the shape of the umbrella sleeve and preventing shape deviations caused by rubber flow during subsequent temperature increases; the second temperature of 165℃~175℃ is the main crosslinking stage, where the vulcanization reaction proceeds efficiently, forming a complete three-dimensional crosslinked network that constitutes the main body of the material's mechanical and insulating properties; the third temperature of 140℃~150℃ is the stabilization and adjustment stage, where a slight temperature drop allows the crosslinking reaction to end smoothly, resulting in more uniform vulcanization of the entire product and initial release of internal stress generated during the high-temperature crosslinking process.

[0010] Finally, core B undergoes post-vulcanization treatment to further improve the cross-linked network structure of silicone rubber, completely eliminate the internal stress remaining from the vulcanization process, and stabilize the bonding state of the interface transition layer, ultimately producing a composite insulator with uniform and stable overall performance.

[0011] In some embodiments, the silane coupling agent includes KH550 and KH570.

[0012] Two silane coupling agents work synergistically to construct a bidirectional, adaptive molecular bridging structure between the inorganic core surface and the silicone rubber matrix: the amino functional groups in KH550 can chemically bond with active sites such as hydroxyl groups generated after activation on the core surface, firmly adhering to the core surface; the methacryloyloxy functional groups in KH570 can participate in the cross-linking reaction during the silicone rubber vulcanization process, forming a stable chemical bond with the outer insulating silicone rubber matrix. The combined use of these two agents can simultaneously strengthen the bonding force between the inorganic and organic ends of the interface. Compared with single coupling agent treatment, it can further improve the interfacial adhesion strength and water penetration resistance, ensuring the structural integrity of the interfacial layer during long-term service. Preferably, the mass ratio of KH550 to KH570 is 1:(12-15).

[0013] In some embodiments, the adhesive comprises bisphenol A type epoxy resin.

[0014] This type of epoxy resin exhibits excellent wetting affinity with the mandrel surface. After coating and curing, it forms a dense and continuous adhesive film layer. This film layer can form a strong interlayer bond with the underlying silane coupling agent layer, and can also be tightly integrated with the subsequently injected silicone rubber matrix through intermolecular forces and some chemical bonds, constructing a gradient transition interface from the mandrel to the silicone rubber. This epoxy adhesive layer can effectively alleviate the interfacial stress caused by the difference in thermal expansion coefficients between the core and the silicone rubber, reducing the risk of interlayer delamination. Simultaneously, it can prevent external moisture from penetrating to the mandrel surface, further improving the insulator's watertightness and long-term operational reliability. Preferably, the solid content of the bisphenol A type epoxy resin is 10%~15%.

[0015] In some embodiments, the vulcanized compound is obtained by mixing a base material and additives, wherein the base material comprises, by weight: 100 parts of methyl vinyl silicone rubber raw rubber, 35-55 parts of fumed silica, 3-8 parts of structure control agent, and 0.8-2.0 parts of bis(2,5)-vinyl chloride agent; The additives, by weight, include: 60-120 parts of modified aluminum hydroxide, 2-5 parts of flame retardant, 0.5-2 parts of water repellent, 0.3-1.0 parts of internal release agent, and 0.5-1.5 parts of color paste; the modified aluminum hydroxide is obtained by coating and modifying aluminum hydroxide with vinyl silane.

[0016] The substrate is mainly composed of methyl vinyl silicone rubber raw rubber, which provides basic electrical insulation, high and low temperature resistance, and aging resistance for the vulcanized silicone rubber matrix. Fumed silica is used as a reinforcing filler, which can significantly improve the tensile strength, tear strength, and other mechanical properties of the cured silicone rubber. The structure control agent can suppress the structuring effect between silica and raw rubber, and maintain the good processing fluidity and storage stability of the rubber compound. The bis(2,5) vulcanizing agent is used as a high-temperature crosslinking initiator, which is suitable for the temperature range of step vulcanization and can precisely control the crosslinking reaction process. Based on this, the modified aluminum hydroxide in the compounded additives can chemically crosslink with silicone rubber, achieving uniform dispersion in methyl vinyl silicone rubber, improving vulcanization uniformity and thermal aging stability, while reducing the water absorption rate of the rubber compound. This, combined with the integrated vulcanization and mandrel interface treatment processes, ensures the long-term watertightness and operational reliability of the composite insulator. The flame retardant synergistically enhances the flame retardancy rating of the silicone rubber, meeting the fire safety requirements of high-voltage scenarios. The water-repellent agent imparts durable water-repellent properties to the silicone rubber surface, reducing the risk of flashover. The internal release agent improves the release performance of the rubber compound from the mold cavity, ensuring a smooth and intact umbrella sleeve surface after mold opening. The colorant is used to adjust the appearance color of the umbrella sleeve and also helps improve the material's weather resistance. After vulcanization, this compounded system forms a uniformly crosslinked and stable silicone rubber outer insulation layer, meeting the long-term service requirements of composite insulators in ultra-high voltage scenarios.

[0017] It should be noted that unmodified aluminum hydroxide is hydrophilic and prone to agglomeration, which will cause internal porosity of the vulcanized rubber, increase partial discharge, and reduce mechanical and tracking resistance.

[0018] In some embodiments, the mixing of the substrate and the additives includes the following steps: The substrate and the additives are mixed, filtered, and vacuum degassed to obtain the vulcanized rubber compound; The mixing parameters include: internal mixing temperature 70℃~90℃, internal mixing time 15min~25min, open mill roll temperature 40℃~50℃, and open mill thin pass 6~8 times. The filtration process involves passing the material through 100-mesh and 200-mesh filters in sequence. The vacuum degassing is carried out under conditions of -0.08MPa to -0.1MPa, and the vacuum degassing time is 4h to 8h.

[0019] In some embodiments, the parameters of the plasma activation treatment include: using a helium / argon mixed plasma, a processing power of 800W~1200W, a spray gun moving speed of 5mm / s~10mm / s, and a processing distance of 10mm~15mm.

[0020] In some embodiments, the silane coupling agent is coated sequentially, the binder is coated, and after drying, an interface transition layer is formed on the surface of the mandrel, the total thickness of the interface transition layer being 5 μm to 15 μm.

[0021] In some embodiments, the holding time for the first temperature is 20 min to 30 min, the holding time for the second temperature is 30 min to 60 min, and the holding time for the third temperature is 15 min to 20 min.

[0022] In some embodiments, the vulcanization process is completed and the temperature is lowered to below 90°C before the mold is opened.

[0023] In some embodiments, the post-vulcanization treatment includes: holding at 120°C for 1 hour, then raising the temperature to 180°C and holding for 2 to 4 hours, then cooling down to 80°C at a rate of 10°C / hour, and finally naturally cooling to room temperature.

[0024] This stepped post-curing process synergizes with the three-stage pre-curing process, further optimizing the cross-linking structure of silicone rubber and completely releasing internal stress after molding. The initial 120℃ holding stage ensures synchronized and uniform temperature of the insulator core and sheath, avoiding internal and external temperature stress caused by direct high-temperature treatment. Simultaneously, it promotes the slow migration and escape of residual small-molecule additives and curing byproducts from the rubber compound, supplementing areas with lower cross-linking levels in the pre-curing stage and initially regulating the cross-linking network structure. The 180℃ holding stage is the core processing area of ​​post-curing. At this temperature, the cross-linking reaction of silicone rubber can proceed fully, further refining and densifying the three-dimensional network structure. Simultaneously, the internal stress accumulated during curing can be fully released, effectively improving the tensile strength, aging resistance, and dimensional stability of the silicone rubber, and also making the bonding state of the interface transition layer more stable. The subsequent slow cooling at a rate of 10℃ / h avoids thermal shrinkage stress caused by rapid cooling, allowing the silicone rubber and core to maintain interfacial bonding during synchronous and gentle shrinkage. This prevents interfacial peeling or shed deformation cracking caused by differences in thermal expansion coefficients. After the temperature drops to 80℃, natural cooling is adopted, which can ensure structural stability while taking into account processing efficiency. The final product is a composite insulator with uniform cross-linking, extremely low internal stress, and strong interfacial bonding. Its performance stability and weather resistance during long-term service can be further improved.

[0025] In some embodiments, the roughening treatment involves sandblasting the surface of the mandrel with 80-120 mesh white corundum sand at a pressure of 0.3 MPa-0.5 MPa. After the roughening treatment, the surface roughness Ra of the mandrel is 6.3 μm-12.5 μm.

[0026] In some embodiments, the vacuum conditions formed in the cavity of the molding die are -0.095MPa to -0.1MPa, and the vulcanized rubber is injected after holding the pressure for 10 to 15 minutes.

[0027] In some embodiments, the injection temperature of the vulcanized rubber compound is 70℃~80℃, the injection pressure is 8MPa~15MPa, the injection speed is 5mm / s~10mm / s, and the holding pressure after injection is 3MPa~5MPa.

[0028] This disclosure also provides a composite insulator prepared by the above-described method.

[0029] Compared to products manufactured using traditional segmented vulcanization, this composite insulator offers significant improvements in structural integrity, interface reliability, and long-term service stability. The seamless, integral umbrella-sheath structure completely eliminates weak paths for moisture penetration, fundamentally preventing problems such as core corrosion, insulation breakdown, and hardware rust caused by moisture intrusion during long-term operation, resulting in a substantial improvement in watertightness. A robust interface bonding layer ensures strong adhesion between the core and silicone rubber, effectively reducing the level of partial discharge at the interface and minimizing the risk of interface debonding, thus meeting the low partial discharge requirements of ultra-high voltage (UHV) applications. The uniform and dense cross-linked structure and fully released internal stress give the silicone rubber superior mechanical properties, resistance to tracking, and aging resistance. The product has high mechanical property redundancy, making it less prone to failure issues such as umbrella-sheath cracking and decreased hydrophobicity during long-term service, effectively extending its service life. It is widely adaptable to various demanding application scenarios, including AC / DC UHV transmission, converter stations, and new energy grid connection.

[0030] The technical solution provided in this disclosure has the following advantages compared with the prior art: First, the integral vulcanization molding method can complete the overall molding of the outer insulating shed of the insulator in one go, eliminating multiple splicing seams caused by the segmented vulcanization process from the root, completely avoiding the hidden dangers of poor adhesion and sealing failure at the seams, effectively blocking the path of moisture intrusion into the interior, and significantly reducing the risk of failure such as core rod corrosion, insulation breakdown, and hardware corrosion during long-term operation. At the same time, it eliminates the need for multiple mold closing and mold changing operations, avoiding molding deviations such as core eccentricity and uneven shed wall thickness caused by repeated mold assembly, and also eliminates the accumulation of internal stress caused by multiple heating and cooling cycles, reducing the occurrence of problems such as shed cracking, shed falling off, and water repellency attenuation.

[0031] Secondly, through the synergistic effect of a multi-step interface treatment process involving roughening, plasma activation, silane coupling agent coating, and adhesive coating, a firmly bonded interface transition layer can be constructed on the surface of the core rod. This process enhances the mechanical interlocking of the interface through physical roughening and strengthens the bond between the core and silicone rubber through surface activation and chemical coating, significantly improving the interfacial bonding strength and ensuring the long-term reliability of the bond between the core and the outer insulation layer. This also helps reduce the partial discharge level of the product and meets the insulation performance requirements of high-voltage and ultra-high-voltage scenarios.

[0032] Third, after mold closing, a vacuum condition is created before injecting the vulcanizing rubber compound. This fully removes air from the mold cavity, preventing air bubbles from being trapped during the filling process and creating internal pore defects. This ensures a dense and uniform outer insulation layer. Combined with a three-stage gradient temperature vulcanization process, the cross-linking reaction of the silicone rubber can be precisely controlled in stages. The pre-vulcanization and shaping, the main cross-linking reaction, and the structural stabilization adjustment are completed sequentially. This ensures the full progress of the cross-linking reaction of the silicone rubber and avoids the under-vulcanization or over-vulcanization problems that are prone to occur with single constant temperature vulcanization. This makes the vulcanization degree of the entire product more uniform and consistent, effectively improving the mechanical properties, tracking resistance, and aging resistance of the silicone rubber.

[0033] Fourth, adding post-curing treatment on top of the above can further improve the three-dimensional cross-linked network structure of silicone rubber, fully release the residual internal stress generated during the curing process, and stabilize the bonding state of the interface transition layer, making the product's structure and performance more stable and effectively extending its long-term service life. The entire process forms a fully synergistic optimization system of interface modification, precise molding, curing control, and post-stabilization, resulting in excellent product performance consistency and batch stability. It can adapt to the needs of large-scale mass production and fully meet the core requirements of new power systems for high reliability and long service life of composite insulators. Attached Figure Description

[0034] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0035] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram and a comparison diagram of the composite insulator molding process disclosed in this paper; Figure 2 This is a comparison diagram of the sulfurization distribution of composite insulators prepared in the embodiments and comparative examples of this disclosure; Figure 3 The graphs show the partial discharge characteristics of the composite insulators prepared according to the embodiments and comparative examples of this disclosure. Detailed Implementation

[0037] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0038] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0039] Example This embodiment provides a method for preparing a composite insulator, including the following steps: S1. Fittings are installed at both ends of the core rod. Then, the surface of the core rod is subjected to roughening treatment, plasma activation treatment, coating with silane coupling agent and coating with adhesive in sequence, and then dried to obtain core A. S2. The core A is placed into the molding mold, the mold is closed, and the cavity of the molding mold is made into a vacuum condition before the vulcanizing material is injected. The vulcanizing treatment is carried out in sequence at the first temperature, the second temperature and the third temperature. The mold is opened to obtain the core B. S3. Perform post-vulcanization treatment on the core B to obtain the composite insulator.

[0040] Specifically, in step S1, the core rod is an epoxy glass fiber core rod for ±800kV rod-shaped suspension composite insulators, with a diameter of 24mm and a total length of 5500mm; high-strength fittings are fitted at both ends of the core rod, and after crimping, the coaxiality deviation of the whole is 0.3‰, and it passes the water pressure test and tensile load test.

[0041] After fittings are installed at both ends of the mandrel, it is fixed on a special tooling frame for roughening treatment. The surface of the mandrel (the area to be vulcanized is defined on the mandrel surface according to the design requirements) is sandblasted with 100-mesh white corundum abrasive. The sandblasting pressure is 0.4MPa and the spray gun moving speed is 8mm / s. The surface roughness Ra after treatment is 8.5μm. Then, the sandblasted surface is ultrasonically cleaned three times with anhydrous ethanol for 10 minutes each time. Then, it is placed in an 80℃ vacuum drying oven for 2 hours to thoroughly remove surface oil, dust and residual solvent.

[0042] The plasma activation treatment was carried out using an atmospheric pressure plasma treatment device. The parameters of the plasma activation treatment included: using a helium / argon mixed plasma (the volume ratio of helium to argon was 7:3), a treatment power of 1000W, a spray gun moving speed of 8mm / s, a treatment distance of 12mm, moving at a uniform speed along the core axis, and treating one side twice.

[0043] Within 10 minutes after plasma activation treatment, a layer of silane coupling agent is uniformly coated, left to air at room temperature for 30 minutes, and then dried at 80°C for 20 minutes. Then, a layer of adhesive is uniformly coated, left to air at room temperature for 30 minutes, and then dried at 80°C for 30 minutes, finally forming an interface transition layer with a total thickness of 10 μm.

[0044] The silane coupling agent is obtained by compounding KH550 and KH570 at a mass ratio of 1:13; the binder is bisphenol A type epoxy resin with a solid content of 12%.

[0045] The vulcanizing compound required in step S2 includes a base material and additives. The base material, by weight, includes: 100 parts of methyl vinyl silicone rubber raw rubber (vinyl content 0.18%, molecular weight 650,000) and fumed silica (specific surface area 200m²). 2 The mixture contains 45 parts by weight of modified aluminum hydroxide (3 μm particle size), 5 parts by weight of hydroxyl silicone oil structuring control agent, and 1.2 parts by weight of bis(2,5-dimethyl)sulfide agent; the additives include, by weight, 100 parts by weight of modified aluminum hydroxide (3 μm particle size), 3 parts by weight of nitrogen-phosphorus flame retardant, 1 part by weight of methyl hydrogen silicone oil hydrophobic agent, 0.5 parts by weight of zinc stearate internal release agent, and 1 part by weight of iron red paste. The modified aluminum hydroxide is obtained by coating aluminum hydroxide with vinyl silane. Specifically, the aluminum hydroxide is first dried at 110℃ to remove water, then a 2% (w / w) ethanol hydrolysate of KH570 is prepared. The KH570 ethanol hydrolysate is sprayed onto the aluminum hydroxide, and the coating reaction is carried out with stirring at 80℃. After completion, the mixture is filtered, vacuum dried, and sieved to obtain the modified aluminum hydroxide. The surface of the modified aluminum hydroxide is grafted with vinyl hydrophobic groups.

[0046] The preparation of vulcanized rubber compounds includes the following steps: Weigh out the methyl vinyl silicone rubber raw rubber, fumed silica and hydroxyl silicone oil structure control agent according to the above formula, put them into a mixer, and mix at 80°C for 20 minutes. Then add aluminum hydroxide, nitrogen and phosphorus flame retardant, methyl hydrogen silicone oil water repellent, zinc stearate internal release agent and iron red paste, and continue mixing at 80°C for 15 minutes. After mixing evenly, discharge the rubber to obtain the compound. Transfer the compound to a two-roll mill, roll at 45°C, and pass through it 7 times. Add the bis(2,5) vulcanizing agent, mix evenly, and filter it through a 100-mesh + 200-mesh double-layer filter to obtain the sheet. Place the filtered rubber in a vacuum oven and let it stand at -0.098MPa for 6 hours to completely remove the air bubbles inside the rubber to obtain the vulcanized rubber.

[0047] In step S2, the core A obtained in step S1 is horizontally installed into a 6000mm long-stroke integrated vulcanizing mold. The hardware at both ends of the core A is fixed by high-precision V-shaped positioning fixtures at both ends of the mold. The position of the core A is adjusted to ensure that the coaxiality deviation between the core A and the mold cavity is 0.3‰. After the mold is closed, the mold is locked with a hydraulic locking device. The mold cavity is evacuated to -0.098MPa and held for 12 minutes. The pressure rise in the cavity is checked to be ≤0.001MPa to confirm that there is no leakage in the cavity. The vacuum state is maintained for later use. Then, the vulcanized rubber compound is injected into the mold cavity using a silicone rubber injection molding machine at an injection temperature of 75℃, an injection pressure of 12MPa, and an injection speed of 8mm / s. After injection, the pressure is maintained at 4MPa to keep the cavity in a vacuum state. Subsequently, the mold temperature control system is activated to execute a three-stage stepped temperature-increasing vulcanization process: the first stage is to heat up to 115℃ (first temperature) and pre-vulcanize for 25 minutes to complete the initial shaping and flow filling of the rubber compound; the second stage is to heat up to 170℃ (second temperature) and set the shape for 45 minutes to complete the main cross-linking reaction of the silicone rubber; the third stage is to cool down to 145℃ (third temperature) and hold for 18 minutes to achieve the initial stabilization of the cross-linking structure; after vulcanization, the temperature is naturally cooled to 85℃, the mold is released, and the core B is obtained by opening the mold.

[0048] In step S3, the core B obtained in step S2 is placed horizontally into a stepped post-vulcanization oven and post-vulcanization treatment is performed: first, the temperature is raised to 120℃ and held for 1 hour, then the temperature is raised to 180℃ at a uniform rate and held for 3 hours, and then the temperature is stepped down to 80℃ at a rate of 10℃ / h. The oven power is turned off and the oven is allowed to cool naturally to room temperature to complete interface stabilization and internal stress elimination.

[0049] Finally, the flash on the surface of the insulator sheath is cleaned, and appearance defects are repaired. Dimensional inspection, appearance inspection, routine electrical and mechanical tests are completed in accordance with GB / T19519-2014 and IEC 61109 standards, and the composite insulator (±800kV integral vulcanized rod-shaped suspension composite insulator) is finally produced.

[0050] Comparative Example 1 The only difference from the example is that a traditional three-stage segmented molding vulcanization process is used. Everything else is the same as the example.

[0051] Comparative Example 2 The only difference from the example is that plasma activation is not performed, and only KH550 is coated after roughening treatment. Everything else is the same as the example.

[0052] Comparative Example 3 The only difference from the example is that the vulcanization process uses a traditional constant temperature vulcanization process at 170°C for 60 minutes. Everything else is the same as the example.

[0053] Performance testing The composite insulators prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests to verify the effect of the preparation method of this disclosure on improving product performance and to prove its applicability in harsh ultra-high voltage scenarios.

[0054] 1. Testing Standards and Conditions This test was conducted in accordance with GB / T 19519-2014 "Composite insulators for AC overhead lines with nominal voltage above 1000V - Definitions, test methods and acceptance criteria" and IEC 61109:2020 standard. Three samples were tested in each group, and the average value was taken. The core test indicators include: core-silicone rubber interface bonding strength, partial discharge at 1.1 times the rated voltage, water tightness, mechanical breaking load, vulcanization uniformity, resistance to tracking and electrical erosion, and tensile strength retention rate (after thermal aging).

[0055] 2. Test Results Figure 1 The above are schematic diagrams and comparison diagrams of the composite insulator molding process of the embodiments and comparative examples 1-3. Figure 1 In the diagram: 1-Umbrella sleeve; 2-Core rod; 3-Mold cavity. The composite insulator in this embodiment is integrally vulcanized, with a continuous, seamless umbrella sleeve and a complete, dense interface between the core rod and silicone rubber. Comparative Example 1 uses a traditional segmented molding process, resulting in multiple seams in the umbrella sleeve, which easily create moisture penetration channels. Comparative Example 2 did not undergo core rod plasma interface activation treatment, resulting in a significant interface gap between the core rod and silicone rubber. Comparative Example 3 uses a single constant-temperature vulcanization process, leading to uneven cross-linking within the silicone rubber and localized weak interface bonding areas. Through a direct comparison of these four structures, the advantages of the integral molding and multi-level interface modification process disclosed in eliminating seams and improving interface bonding integrity are clearly demonstrated.

[0056] The core performance test results of each group of samples are shown in Table 1, and the sulfurization distribution comparison diagram is shown in Figure 2. Figure 2 As shown in the figure, the partial discharge characteristic curve is as follows: Figure 3 As shown.

[0057] Table 1

[0058] From Table 1, Figure 2 , Figure 3 The test results show that the present invention is significantly superior to the comparative samples in terms of uniformity and aging resistance. The embodiment achieves chemical bonding between the core and silicone rubber through a gradient interface modification process. The interface bonding strength is increased by 67.7% compared to comparative example 1 and by 136.4% compared to comparative example 2, fundamentally solving the problems of interface debonding and moisture intrusion. The partial discharge at 1.1 times the rated voltage is only 2.3 pC, far below the requirement of ≤10 pC for ultra-high voltage products.

[0059] The integral vulcanization molding process used in the preparation of composite insulators disclosed herein completely eliminates the splicing defects of segmented vulcanization, significantly improving water tightness and mechanical properties. The mechanical breaking load reaches 138% of the rated value, which is 23.2% higher than that of Comparative Example 1. The three-stage stepped vulcanization treatment and subsequent post-vulcanization treatment achieve uniform control of the vulcanization degree of the entire product, with a vulcanization degree uniformity of 98.7%. At the same time, it effectively eliminates vulcanization internal stress, and the tensile strength retention rate after thermal aging reaches 94.2%. The aging resistance and tracking resistance are significantly better than those of the traditional constant temperature vulcanization process.

[0060] In summary, this disclosure, centered on integral vulcanization molding, successfully overcomes the industry bottlenecks of traditional segmented vulcanization processes—namely, numerous interface defects, uneven vulcanization, poor batch stability, and insufficient long-term reliability—through comprehensive optimization of the entire process, including interface gradient modification, high-precision mold positioning, stepped temperature-controlled vulcanization, and post-vulcanization stabilization. This process produces composite insulators with seamless joints, high interfacial bonding strength, low partial discharge, and long lifespan. This technology is suitable for the large-scale production of composite insulators across all voltage levels, providing a novel technical solution for the preparation of high-reliability composite insulators for ultra-high voltage power transmission and transformation systems, and possesses significant engineering application value and broad market prospects.

[0061] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0062] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a composite insulator, characterized in that, Includes the following steps: Fittings are installed at both ends of the mandrel. Then, the surface of the mandrel is subjected to roughening treatment, plasma activation treatment, coating with silane coupling agent and coating with adhesive in sequence, and then dried to obtain core A. The core A is inserted into the molding mold, the mold is closed, and a vacuum condition is formed in the cavity of the molding mold before vulcanizing rubber is injected. The vulcanization process is carried out in sequence at the first temperature, the second temperature and the third temperature. The mold is then opened to obtain the core B. The core B is subjected to post-vulcanization treatment to obtain the composite insulator; The first temperature is 110℃~120℃, the second temperature is 165℃~175℃, and the third temperature is 140℃~150℃.

2. The method for preparing a composite insulator according to claim 1, characterized in that, The silane coupling agents include KH550 and KH570; And / or, the adhesive comprises bisphenol A type epoxy resin.

3. The method for preparing a composite insulator according to claim 1, characterized in that, The vulcanized rubber compound is obtained by mixing a base material and additives. The base material comprises, by weight, 100 parts of methyl vinyl silicone rubber raw rubber, 35-55 parts of fumed silica, 3-8 parts of structure control agent, and 0.8-2.0 parts of bis(2,5)-vinyl chloride agent. The additives, by weight, include: 60-120 parts of modified aluminum hydroxide, 2-5 parts of flame retardant, 0.5-2 parts of water repellent, 0.3-1.0 parts of internal release agent, and 0.5-1.5 parts of color paste; the modified aluminum hydroxide is obtained by coating and modifying aluminum hydroxide with vinyl silane.

4. The method for preparing a composite insulator according to claim 3, characterized in that, The mixing of the substrate and the additives includes the following steps: The substrate and the additives are mixed, filtered, and vacuum degassed to obtain the vulcanized rubber compound; The mixing parameters include: internal mixing temperature 70℃~90℃, internal mixing time 15min~25min, open mill roll temperature 40℃~50℃, and open mill thin pass 6~8 times. The filtration process involves passing the material through 100-mesh and 200-mesh filters in sequence. The vacuum degassing is carried out under conditions of -0.08MPa to -0.1MPa, and the vacuum degassing time is 4h to 8h.

5. The method for preparing a composite insulator according to claim 1, characterized in that, The parameters for the plasma activation treatment include: using a helium / argon mixed plasma, a processing power of 800W~1200W, a spray gun moving speed of 5mm / s~10mm / s, and a processing distance of 10mm~15mm.

6. The method for preparing a composite insulator according to claim 1, characterized in that, The silane coupling agent is coated sequentially, the binder is coated, and after drying, an interface transition layer is formed on the surface of the mandrel. The total thickness of the interface transition layer is 5 μm to 15 μm.

7. The method for preparing a composite insulator according to claim 1, characterized in that, The holding time at the first temperature is 20-30 minutes, the holding time at the second temperature is 30-60 minutes, and the holding time at the third temperature is 15-20 minutes. And / or, after completing the vulcanization treatment, cool down to below 90°C before opening the mold.

8. The method for preparing a composite insulator according to claim 1, characterized in that, The post-vulcanization treatment includes: holding at 120°C for 1 hour, then raising the temperature to 180°C and holding for 2 to 4 hours, then cooling down to 80°C at a rate of 10°C / hour, and finally naturally cooling to room temperature.

9. The method for preparing a composite insulator according to claim 1, characterized in that, The roughening treatment involves sandblasting the surface of the mandrel with 80-120 mesh white corundum sand at a pressure of 0.3 MPa-0.5 MPa. After the roughening treatment, the surface roughness Ra of the mandrel is 6.3 μm-12.5 μm. And / or, the vacuum condition formed in the cavity of the molding die is -0.095MPa to -0.1MPa, and the pressure is maintained for 10min to 15min before the vulcanized rubber material is injected; And / or, the injection temperature of the vulcanized rubber compound is 70℃~80℃, the injection pressure is 8MPa~15MPa, the injection speed is 5mm / s~10mm / s, and the holding pressure after injection is 3MPa~5MPa.

10. A composite insulator, characterized in that, The composite insulator is prepared by the method according to any one of claims 1 to 9.

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