A high voltage silicone rubber cold shrink cable termination and method of manufacture

Abstract

The application discloses a high-voltage silicone rubber cold-shrink cable terminal insulator and a manufacturing method thereof, and relates to the technical field of cable terminal insulators.The application is prepared by using terpolymer ethylene propylene rubber as a base body, matching epoxy silicone rubber, DOPO modified Schiff base intermediate and various additives, and reasonably matching the mass fractions of the components.The DOPO modified Schiff base intermediate is prepared by reacting p-aminodiphenylamine with salicylaldehyde to generate a Schiff base, and then reacting with 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide;the epoxy silicone rubber is prepared by epoxidation reaction of high-vine rubber.The manufacturing method realizes full fusion of the components by step-by-step mixing and gradient temperature control vulcanization.The application solves the problem that the mechanical toughness, aging resistance and flame resistance of the existing insulator are difficult to be considered simultaneously, improves the material density and interface bonding strength, and has excellent comprehensive performance of the product, is suitable for high-voltage power transmission scenes, is convenient to install and has a long service life.

Description

Technical Field

[0001] This invention relates to the field of cable termination insulation technology, specifically to a high-voltage silicone rubber cold-shrink cable termination insulation and its manufacturing method. Background Technology

[0002] With the rapid development of the power industry towards high voltage and ultra-high voltage, cable terminals, as key connecting components of power transmission systems, directly determine the safety and stability of power transmission through their insulation, mechanical properties, aging resistance, and flame retardant properties. High-voltage silicone rubber cold-shrink cable terminal insulators, due to their excellent elasticity, resistance to high and low temperatures, and convenient installation, have been widely used in power, rail transportation, and new energy fields. Currently, the industry mostly uses a blend of silicone rubber and rubber with the addition of inorganic fillers to prepare this type of insulator. The core requirement is to balance the material's mechanical toughness, aging resistance, flame retardant safety, and structural stability to adapt to complex outdoor and underground service environments and meet the long-term use requirements of high-voltage power transmission. However, existing technologies for preparing high-voltage silicone rubber cold-shrink cable terminal insulation still have significant shortcomings, making it difficult to meet the high-performance requirements of high-voltage scenarios. Firstly, existing insulation materials often employ single modified components or conventional blending systems, lacking efficient synergistic modification mechanisms. This results in a difficulty in achieving a balance between material mechanical toughness and aging resistance, leading to problems such as breakage and hardening after long-term service. Secondly, flame-retardant modification often uses single flame retardants, resulting in low flame-retardant efficiency, making it difficult to meet flame-retardant requirements, and easily affecting the material's mechanical properties. Thirdly, in some preparation processes, the modified intermediates react insufficiently, grafting efficiency is low, or the rubber matrix is ​​not effectively modified, leading to insufficient material density and weak interfacial bonding, further affecting the comprehensive properties of insulation, mechanical properties, and flame retardancy. These technical shortcomings restrict the performance improvement and application expansion of high-voltage silicone rubber cold-shrink cable terminal insulation. This technical solution, through a specific compounding system and optimized processes, can effectively solve the above problems. Summary of the Invention

[0003] The purpose of this invention is to provide a high-voltage silicone rubber cold-shrink cable terminal insulator and its manufacturing method, so as to solve the problems existing in the prior art.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A high-voltage silicone rubber cold-shrink cable terminal insulator, wherein the components of the insulator are in the following proportions by weight: 100 parts of EPDM rubber, 8-12 parts of epoxidized silicone rubber, 3-4 parts of DOPO modified Schiff base intermediate, 45-60 parts of silica, 12-25 parts of kaolin, 8-15 parts of mica powder, 2-4 parts of γ-aminopropyltriethoxysilane, 3-5 parts of peroxide vulcanizing agent, 1.5-3 parts of crosslinking agent, and 8-16 parts of paraffin oil.

[0005] Further, preferably, the DOPO-modified Schiff base intermediate is first prepared by reacting the primary amine in p-aminodiphenylamine with the aldehyde group in salicylaldehyde to generate p-aminodiphenylamine-salicylaldehyde Schiff base, and then by reacting the C=N bond in the p-aminodiphenylamine-salicylaldehyde Schiff base with 9,10-dihydro-9-oxo-10-phosphophenanthrene-10 oxide to obtain the DOPO-modified Schiff base intermediate.

[0006] Further, preferably, the epoxy silicone rubber comprises the following preparation steps: weighing high vinyl rubber and m-chloroperoxybenzoic acid at a mass ratio of 1:0.4~0.6, adding the high vinyl silicone rubber to 10~15 times the mass of the high vinyl silicone rubber in chloroform, stirring evenly, then adding m-chloroperoxybenzoic acid, and then stirring at a temperature of 25~35℃ for 96~100h. After the reaction is completed, the mixture is settled by methanol flocculation method, filtered and washed with methanol 3~5 times, and vacuum dried to obtain epoxy silicone rubber.

[0007] Further, preferably, the vinyl content of the high vinyl rubber is greater than 20%.

[0008] Further, preferably, the p-aminodiphenylamine-salicylaldehyde Schiff base comprises the following preparation steps: p-aminodiphenylamine and salicylaldehyde are weighed at a mass ratio of 1:1~1.2; p-aminodiphenylamine is added to N,N-dimethylformamide at a mass ratio of 10~15 times that of p-aminodiphenylamine and stirred until completely dissolved; then salicylaldehyde is added; the mixture is refluxed and stirred at a temperature of 110~120℃ for 3.5~4.5h; after the reaction is completed, the reaction solution is added to toluene and allowed to stand to precipitate; the mixture is filtered and washed 3~5 times with a mixed solvent; and then dried under vacuum to obtain the p-aminodiphenylamine-salicylaldehyde Schiff base.

[0009] Furthermore, preferably, the mixed solvent is prepared by mixing toluene and methanol in a volume ratio of 1:1.

[0010] Further, preferably, the DOPO-modified Schiff base intermediate comprises the following preparation steps: p-aminodiphenylamine-salicylaldehyde Schiff base and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide are weighed at a mass ratio of 1:1.5~1.8; p-aminodiphenylamine-salicylaldehyde Schiff base and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide are added to ethanol at a mass ratio of 50~60 times that of p-aminodiphenylamine-salicylaldehyde Schiff base; after stirring evenly, the temperature is raised to 85~95℃ and the reaction is carried out for 12~14 hours; after the reaction is completed, deionized water is added to precipitate the precipitate; the precipitate is filtered and purified by chromatography to obtain the DOPO-modified Schiff base intermediate.

[0011] Further, preferably, the peroxide sulfiding agent is dicumyl peroxide.

[0012] Further, preferably, the crosslinking agent is triallyl isocyanurate.

[0013] A method for manufacturing a high-voltage silicone rubber cold-shrink cable termination insulator, applicable to the high-voltage silicone rubber cold-shrink cable termination insulator described above, includes the following steps: S1. First, put the epoxidized silicone rubber and the DOPO modified Schiff base intermediate into a mixer, heat it to 110~130℃ and mix it at a constant temperature for 8~12 minutes to obtain the grafted modified composite rubber. S2. Continue to add EPDM rubber, silica, kaolin, mica powder and γ-aminopropyltriethoxysilane into the internal mixer, and continue mixing at 120~150℃ for 5~10 minutes. S3. Cool down to 80~100℃, add paraffin oil, and mix for 3-5 minutes; S4. Cool down to 70~85℃ again, add dicumyl peroxide and triallyl isocyanurate, mix for 2~4 minutes to obtain a uniform compound. S5. Place the compounded rubber in a mold and vulcanize it at 160~180℃ and 10~15MPa pressure for 10~30min. Cool it to room temperature to obtain a high-voltage silicone rubber cold shrink cable terminal insulator.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are: This technical solution uses EPDM rubber as the base material, compounded with an appropriate amount of epoxidized silicone rubber, effectively combining the excellent insulation and elastic properties of the two types of rubber. It also incorporates silica, kaolin, and mica powder as multi-element inorganic fillers, simultaneously achieving reinforcement, toughening, improved processing performance, and enhanced corona resistance. The addition of γ-aminopropyltriethoxysilane optimizes the interface between the filler and the rubber compound, while paraffin oil improves processing fluidity. Finally, a composite vulcanization system is formed using dicumyl peroxide and triallyl isocyanurate. The proportions of each component are adapted to the production requirements of high-voltage cable terminal insulation products, exhibiting strong material synergy, balanced and stable formability, mechanical properties, and basic electrical properties, making it suitable for the actual operating conditions of high-voltage cold-shrink cable terminals. The intermediate was first prepared by a condensation reaction of p-aminodiphenylamine and salicylaldehyde to form a Schiff base matrix, and then grafted to modify the matrix by an addition reaction of DOPO with the carbon-nitrogen double bond of the Schiff base. The synthetic route was clear and controllable. The modified intermediate obtained by the two-step ordered reaction successfully introduced phosphorus and nitrogen elements into the molecular structure simultaneously, constructing a stable phosphorus-nitrogen synergistic flame retardant system that is not easily precipitated or migrated in the rubber matrix. At the same time, the intermediate molecular structure is rich in conjugated active groups, which have excellent free radical scavenging ability. It can effectively inhibit the thermo-oxidative breakage of rubber molecular chains, endowing the material with excellent antioxidant, thermo-oxidative aging resistance and UV aging resistance. It effectively delays the aging phenomena such as hardening, embrittlement and cracking of insulation materials under high voltage conditions and outdoor environments. While enhancing the flame retardant and smoke suppression effect, it significantly extends the service life of cable terminal insulation components and improves the safe and stable operation of power equipment. In the preparation process, epoxy silicone rubber and DOPO-modified Schiff base intermediate are premixed. The epoxy groups carried by the epoxy silicone rubber can undergo an epoxy ring-opening grafting reaction with the polar active groups on the DOPO-modified Schiff base intermediate to form a stable chemical bond structure, which thoroughly improves the compatibility and bonding force of the two functional components and effectively prevents problems such as additive agglomeration, uneven dispersion, and later migration and loss. After the two are combined through ring-opening grafting, they are then incorporated into the main rubber compound, which allows the flame retardant and anti-aging properties to be deeply integrated with the advantages of silicone rubber in high and low temperature resistance, high elasticity, and weather resistance. This not only further improves the overall density of the rubber compound and enhances the high voltage insulation, corona resistance, and cold shrinkage sealing performance of the product, but also allows the flame retardant, anti-oxidation, and anti-aging properties to be evenly distributed throughout the material. The final product has excellent construction adaptability, high voltage electrical performance, and long-term environmental resistance. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1 S1. Weigh high-vinyl silicone rubber and m-chloroperoxybenzoic acid at a mass ratio of 1:0.4. Add the high-vinyl silicone rubber to 10 times its mass of chloroform and stir until homogeneous. Then add m-chloroperoxybenzoic acid and stir at 25°C for 96 hours. After the reaction is complete, settle the mixture using the methanol flocculation method, filter, wash three times with methanol, and vacuum dry to obtain epoxidized silicone rubber. The vinyl content of the high-vinyl rubber is greater than 20%. S2. Weigh p-aminodiphenylamine and salicylaldehyde at a mass ratio of 1:1. Add p-aminodiphenylamine to N,N-dimethylformamide at a mass ratio of 10 times that of p-aminodiphenylamine and stir until completely dissolved. Then add salicylaldehyde and reflux at 110℃ for 3.5 h. After the reaction is complete, add the reaction solution to toluene and let it stand to precipitate. Filter and wash three times with a mixed solvent. Dry under vacuum to obtain the p-aminodiphenylamine-salicylaldehyde Schiff base. The mixed solvent is prepared by mixing toluene and methanol at a volume ratio of 1:1. S3. Weigh p-aminodiphenylamine-salicylaldehyde Schiff base and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide at a mass ratio of 1:1.5. Add p-aminodiphenylamine-salicylaldehyde Schiff base and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide to ethanol at a mass of 50 times that of p-aminodiphenylamine-salicylaldehyde Schiff base. After stirring evenly, heat to 85℃ and react for 12 hours. After the reaction is completed, add deionized water to precipitate the precipitate. Filter the precipitate and separate and purify it by chromatography to obtain the DOPO modified Schiff base intermediate. S4. Weigh out the following materials: 100 parts EPDM rubber, 8 parts epoxidized silicone rubber, 3 parts DOPO modified Schiff base intermediate, 45 parts silica, 12 parts kaolin, 8 parts mica powder, 2 parts γ-aminopropyltriethoxysilane, 3 parts peroxide vulcanizing agent, 1.5 parts crosslinking agent, and 8 parts paraffin oil. First, add the epoxidized silicone rubber and DOPO modified Schiff base intermediate to a mixer and heat to 110℃ for 8 minutes to obtain the grafted modified composite rubber. Continue to add the following materials to the mixer: Ethylene propylene diene monomer (EPDM) rubber, silica, kaolin, mica powder, and γ-aminopropyltriethoxysilane were mixed at 120°C for 5 minutes. The mixture was then cooled to 80°C, paraffin oil was added, and the mixture was mixed for 3 minutes. The mixture was then cooled to 70°C, dicumyl peroxide and triallyl isocyanurate were added, and the mixture was mixed for 2 minutes to obtain a homogeneous compound. The compound was placed in a mold and vulcanized at 160°C and 10 MPa for 10 minutes. After cooling to room temperature, a high-voltage silicone rubber cold-shrink cable terminal insulation was obtained.

[0017] Example 2 S1. Weigh high-vinyl silicone rubber and m-chloroperoxybenzoic acid at a mass ratio of 1:0.5. Add the high-vinyl silicone rubber to 12.5 times its mass of chloroform and stir until homogeneous. Then add m-chloroperoxybenzoic acid and stir at 30°C for 98 hours. After the reaction is complete, settle the mixture using the methanol flocculation method, filter, wash four times with methanol, and vacuum dry to obtain epoxidized silicone rubber. The vinyl content of the high-vinyl rubber is greater than 20%. S2. Weigh p-aminodiphenylamine and salicylaldehyde at a mass ratio of 1:1.1. Add p-aminodiphenylamine to N,N-dimethylformamide at a mass ratio of 12.5 times that of p-aminodiphenylamine and stir until completely dissolved. Then add salicylaldehyde and reflux at 115℃ for 4 hours. After the reaction is complete, add the reaction solution to toluene and let it stand to precipitate. Filter and wash 4 times with a mixed solvent. Dry under vacuum to obtain the p-aminodiphenylamine-salicylaldehyde Schiff base. The mixed solvent is prepared by mixing toluene and methanol at a volume ratio of 1:1. S3. Weigh p-aminodiphenylamine-salicylaldehyde Schiff base and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide at a mass ratio of 1:1.65. Add p-aminodiphenylamine-salicylaldehyde Schiff base and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide to ethanol at a mass ratio of 55 times that of p-aminodiphenylamine-salicylaldehyde Schiff base. After stirring evenly, heat to 90℃ and react for 13 hours. After the reaction is completed, add deionized water to precipitate the precipitate. Filter the precipitate and separate and purify it by chromatography to obtain the DOPO modified Schiff base intermediate. S4. Weigh out the following materials: 100 parts EPDM rubber, 10 parts epoxidized silicone rubber, 3.5 parts DOPO modified Schiff base intermediate, 52.5 parts silica, 18.5 parts kaolin, 11.5 parts mica powder, 3 parts γ-aminopropyltriethoxysilane, 4 parts peroxide vulcanizing agent, 2.25 parts crosslinking agent, and 12 parts paraffin oil. First, put the epoxidized silicone rubber and DOPO modified Schiff base intermediate into a mixer and heat to 120℃ for 10 minutes to obtain the grafted modified composite rubber. Continue mixing in the mixer... EPDM rubber, silica, kaolin, mica powder, and γ-aminopropyltriethoxysilane were added to the machine and mixed at 135°C for 7.5 minutes. The temperature was then lowered to 90°C, paraffin oil was added, and the mixture was mixed for 4 minutes. The temperature was then lowered again to 77.5°C, dicumyl peroxide and triallyl isocyanurate were added, and the mixture was mixed for 3 minutes to obtain a homogeneous compound. The compound was placed in a mold and vulcanized at 170°C and 12.5 MPa for 20 minutes. After cooling to room temperature, a high-voltage silicone rubber cold-shrink cable terminal insulation was obtained.

[0018] Example 3 S1. Weigh high-vinyl silicone rubber and m-chloroperoxybenzoic acid at a mass ratio of 1:0.6. Add the high-vinyl silicone rubber to 15 times its mass of chloroform and stir until homogeneous. Then add m-chloroperoxybenzoic acid and stir at 35°C for 100 hours. After the reaction is complete, settle the mixture using the methanol flocculation method, filter, wash five times with methanol, and vacuum dry to obtain epoxidized silicone rubber. The vinyl content of the high-vinyl rubber is greater than 20%. S2. Weigh p-aminodiphenylamine and salicylaldehyde at a mass ratio of 1:1.2. Add p-aminodiphenylamine to N,N-dimethylformamide at a mass ratio of 15 times that of p-aminodiphenylamine and stir until completely dissolved. Then add salicylaldehyde and reflux at 120℃ for 4.5 h. After the reaction is complete, add the reaction solution to toluene and let it stand to precipitate. Filter and wash 5 times with a mixed solvent. Dry under vacuum to obtain the p-aminodiphenylamine-salicylaldehyde Schiff base. The mixed solvent is prepared by mixing toluene and methanol at a volume ratio of 1:1. S3. Weigh p-aminodiphenylamine-salicylaldehyde Schiff base and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide at a mass ratio of 1:1.8. Add p-aminodiphenylamine-salicylaldehyde Schiff base and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide to ethanol at a mass ratio of 60 times that of p-aminodiphenylamine-salicylaldehyde Schiff base. After stirring evenly, heat to 95℃ and react for 14 hours. After the reaction is completed, add deionized water to precipitate the precipitate. Filter the precipitate and separate and purify it by chromatography to obtain the DOPO modified Schiff base intermediate. S4. Weigh out the following materials: 100 parts EPDM rubber, 12 parts epoxidized silicone rubber, 4 parts DOPO modified Schiff base intermediate, 60 parts silica, 25 parts kaolin, 15 parts mica powder, 4 parts γ-aminopropyltriethoxysilane, 5 parts peroxide vulcanizing agent, 3 parts crosslinking agent, and 16 parts paraffin oil. First, put the epoxidized silicone rubber and DOPO modified Schiff base intermediate into a mixer and heat to 130℃ for 12 minutes to obtain the grafted modified composite rubber. Continue to add the following materials into the mixer: Ethylene propylene diene monomer (EPDM) rubber, silica, kaolin, mica powder, and γ-aminopropyltriethoxysilane were mixed at 150°C for 10 minutes. The mixture was then cooled to 100°C, paraffin oil was added, and the mixture was mixed for 5 minutes. The mixture was then cooled to 85°C, dicumyl peroxide and triallyl isocyanurate were added, and the mixture was mixed for 4 minutes to obtain a homogeneous compound. The compound was placed in a mold and vulcanized at 180°C and 15 MPa for 30 minutes. After cooling to room temperature, a high-voltage silicone rubber cold-shrink cable terminal insulation was obtained.

[0019] Example 4 The only difference from Example 2 is step S4: Materials are weighed according to the following formula: 100 parts EPDM rubber, 10 parts epoxidized silicone rubber, 52.5 parts silica, 18.5 parts kaolin, 11.5 parts mica powder, 3 parts γ-aminopropyltriethoxysilane, 4 parts peroxide vulcanizing agent, 2.25 parts crosslinking agent, and 12 parts paraffin oil. Epoxidized silicone rubber, EPDM rubber, silica, kaolin, mica powder, and γ-aminopropyltriethoxysilane are then added to an internal mixer. Aminopropyltriethoxysilane was mixed at 135°C for 7.5 minutes; the temperature was lowered to 90°C, paraffin oil was added, and the mixture was mixed for 4 minutes; the temperature was lowered to 77.5°C, dicumyl peroxide and triallyl isocyanurate were added, and the mixture was mixed for 3 minutes to obtain a uniform compound; the compound was placed in a mold and vulcanized at 170°C and 12.5 MPa pressure for 20 minutes, and then cooled to room temperature to obtain a high-voltage silicone rubber cold-shrink cable terminal insulation.

[0020] Example 5 The only difference from Example 2 is step S4: Materials are weighed according to the following formula: 100 parts EPDM rubber, 10 parts epoxidized silicone rubber, 3.5 parts p-aminodiphenylamine-salicylaldehyde Schiff base, 52.5 parts silica, 18.5 parts kaolin, 11.5 parts mica powder, 3 parts γ-aminopropyltriethoxysilane, 4 parts peroxide vulcanizing agent, 2.25 parts crosslinking agent, and 12 parts paraffin oil. The epoxidized silicone rubber and p-aminodiphenylamine-salicylaldehyde Schiff base are first added to a mixer and heated to 120°C for 10 minutes to obtain the grafted modified composite. Add EPDM rubber, silica, kaolin, mica powder, and γ-aminopropyltriethoxysilane to the internal mixer and continue mixing at 135°C for 7.5 minutes. Cool down to 90°C, add paraffin oil, and mix for 4 minutes. Cool down again to 77.5°C, add dicumyl peroxide and triallyl isocyanurate, and mix for 3 minutes to obtain a homogeneous compound. Place the compound in a mold and vulcanize at 170°C and 12.5 MPa for 20 minutes. Cool to room temperature to obtain a high-voltage silicone rubber cold-shrink cable terminal insulation.

[0021] Example 6 The only difference from Example 2 is step S4: Materials are weighed according to the following formula: 100 parts EPDM rubber, 10 parts epoxidized silicone rubber, 3.5 parts 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide, 52.5 parts silica, 18.5 parts kaolin, 11.5 parts mica powder, 3 parts γ-aminopropyltriethoxysilane, 4 parts peroxide vulcanizing agent, 2.25 parts crosslinking agent, and 12 parts paraffin oil. First, the epoxidized silicone rubber and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide are added to an internal mixer and heated to 120°C for 10 minutes of constant-temperature mixing. n, to obtain grafted modified composite rubber; continue to add EPDM rubber, silica, kaolin, mica powder and γ-aminopropyltriethoxysilane into the internal mixer, and continue mixing at 135℃ for 7.5 min; cool down to 90℃, add paraffin oil, and mix for 4 min; cool down again to 77.5℃, add dicumyl peroxide and triallyl isocyanurate, and mix for 3 min to obtain a uniform compound; place the compound in a mold, vulcanize at 170℃ and 12.5MPa pressure for 20 min, and cool to room temperature to obtain high-voltage silicone rubber cold shrink cable terminal insulation.

[0022] Example 7 The difference from Example 2 lies only in step S4: Materials are weighed according to the following formula: 100 parts EPDM rubber, 10 parts epoxidized silicone rubber, 3.5 parts p-aminodiphenylamine, 52.5 parts silica, 18.5 parts kaolin, 11.5 parts mica powder, 3 parts γ-aminopropyltriethoxysilane, 4 parts peroxide vulcanizing agent, 2.25 parts crosslinking agent, and 12 parts paraffin oil. First, the epoxidized silicone rubber and p-aminodiphenylamine are added to a mixer and heated to 120°C for 10 minutes to obtain the grafted modified composite rubber. The mixture is then further mixed in a mixer. EPDM rubber, silica, kaolin, mica powder, and γ-aminopropyltriethoxysilane were added to the machine and mixed at 135°C for 7.5 minutes. The temperature was then lowered to 90°C, paraffin oil was added, and the mixture was mixed for 4 minutes. The temperature was then lowered again to 77.5°C, dicumyl peroxide and triallyl isocyanurate were added, and the mixture was mixed for 3 minutes to obtain a homogeneous compound. The compound was placed in a mold and vulcanized at 170°C and 12.5 MPa for 20 minutes. After cooling to room temperature, a high-voltage silicone rubber cold-shrink cable terminal insulation was obtained.

[0023] Example 8 The only difference from Example 2 is step S4: Materials are weighed according to the following formula: 100 parts EPDM rubber, 12 parts epoxidized silicone rubber, 2.2 parts DOPO, 1.1 parts p-aminodiphenylamine, 0.7 parts salicylaldehyde, 60 parts silica, 25 parts kaolin, 15 parts mica powder, 4 parts γ-aminopropyltriethoxysilane, 5 parts peroxide vulcanizing agent, 3 parts crosslinking agent, and 16 parts paraffin oil. The epoxidized silicone rubber, DOPO, p-aminodiphenylamine, and salicylaldehyde are first added to a mixer and heated to 130°C for 12 minutes for constant temperature mixing. Simultaneously, Schiff base synthesis and... Phosphorus-based grafting reaction was performed to prepare grafted modified composite rubber. EPDM rubber, silica, kaolin, mica powder, and γ-aminopropyltriethoxysilane were added to a mixer, and the mixture was kept at 150°C for 10 minutes. The temperature was lowered to 100°C, paraffin oil was added, and the mixture was stirred for 5 minutes. The temperature was lowered again to 85°C, dicumyl peroxide and triallyl isocyanurate were added, and the mixture was stirred for 4 minutes to obtain a homogeneous compound. The compound was placed in a mold and vulcanized at 180°C and 15 MPa for 30 minutes. After cooling to room temperature, a high-voltage silicone rubber cold-shrink cable terminal insulation was obtained.

[0024] Performance testing: The high-voltage silicone rubber cold-shrink cable terminal insulators prepared in Examples 1 to 8 above were tested according to the following standards, and the test results are shown in Table 1 below. Hardness test: The Shore hardness of the sample at room temperature was determined according to GB / T 39693.4-2025. The test results are shown in Table 1. Tensile mechanical property test: The room temperature tensile strength of the specimen was tested according to GB / T 528-2009. Another specimen from the same batch was placed in a composite environment of 135℃ hot air, 35% oxygen concentration and UV-A lamp irradiation. After 200h accelerated aging, the specimen was retested. The relevant test data are detailed in Table 1. Flame retardant performance test: The limiting oxygen index of the prepared insulator samples was tested according to GB / T 10707-2008 using the oxygen index method to determine the flame retardant level of the material. The test results are summarized in Table 1.

[0025] Table 1 Performance Test Results Examples 1-3 exhibit excellent overall performance, demonstrating outstanding hardness, toughness, aging resistance, and flame retardancy. Among them, Example 2 shows the most balanced and excellent performance, with a hardness of 68 Shore A, an elongation at break of 605%, an elongation at break of 540% after aging, and a limiting oxygen index of 32.8%. The performance of Example 4 was significantly reduced compared to Example 2, with the hardness dropping to 60 Shore A, the elongation at break to 450%, and the limiting oxygen index to 21.0%. The core reason is that the DOPO-modified Schiff base intermediate of this invention was not used, resulting in a lack of phosphorus-nitrogen synergy and grafting reinforcement, and the performance could not meet the requirements for use. Examples 5-7 showed poor performance, with Example 7 being the worst, exhibiting a hardness of 61 Shore A, an elongation at break of 460%, and a limiting oxygen index of 21.5%. This was due to the lack of a phosphorus-nitrogen synergistic system, as only a single modified component was added, which could not achieve effective grafting, resulting in significant performance shortcomings. Example 8 has performance between Examples 1-3 and 5-7, with a hardness of 65 Shore A, an elongation at break of 530%, and a limiting oxygen index of 27.0%. Due to the lack of prior preparation of the DOPO-modified Schiff base intermediate, the in-situ reaction grafting efficiency was insufficient, and its performance was slightly inferior to Groups 1-3.

[0026] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A high-voltage silicone rubber cold-shrink cable terminal insulator, characterized in that, The components of the insulator are as follows: 100 parts EPDM rubber, 8-12 parts epoxidized silicone rubber, 3-4 parts DOPO modified Schiff base intermediate, 45-60 parts silica, 12-25 parts kaolin, 8-15 parts mica powder, 2-4 parts γ-aminopropyltriethoxysilane, 3-5 parts peroxide vulcanizing agent, 1.5-3 parts crosslinking agent, and 8-16 parts paraffin oil.

2. The high-voltage silicone rubber cold-shrink cable terminal insulator according to claim 1, characterized in that, The DOPO-modified Schiff base intermediate is first prepared by reacting the primary amine in p-aminodiphenylamine with the aldehyde group in salicylaldehyde to generate p-aminodiphenylamine-salicylaldehyde Schiff base. Then, the C=N bond in the p-aminodiphenylamine-salicylaldehyde Schiff base is reacted with 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide to obtain the DOPO-modified Schiff base intermediate.

3. The high-voltage silicone rubber cold-shrink cable terminal insulator according to claim 1, characterized in that, The epoxy silicone rubber comprises the following preparation steps: weigh high vinyl rubber and m-chloroperoxybenzoic acid at a mass ratio of 1:0.4~0.6, add the high vinyl silicone rubber to 10~15 times the mass of the high vinyl silicone rubber in chloroform, stir evenly, then add m-chloroperoxybenzoic acid, and then stir at a temperature of 25~35℃ for 96~100h. After the reaction is completed, settle by methanol flocculation method, filter and wash with methanol 3~5 times, and vacuum dry to obtain epoxy silicone rubber.

4. The high-voltage silicone rubber cold-shrink cable terminal insulator according to claim 3, characterized in that, The high vinyl rubber has a vinyl content of more than 20%.

5. The high-voltage silicone rubber cold-shrink cable terminal insulator according to claim 2, characterized in that, The p-aminodiphenylamine-salicylaldehyde Schiff base comprises the following preparation steps: p-aminodiphenylamine and salicylaldehyde are weighed at a mass ratio of 1:1 to 1.

2. The p-aminodiphenylamine is added to N,N-dimethylformamide at a mass ratio of 10 to 15 times that of the p-aminodiphenylamine and stirred until completely dissolved. Then, salicylaldehyde is added and the mixture is refluxed and stirred at a temperature of 110 to 120°C for 3.5 to 4.5 hours. After the reaction is completed, the reaction solution is added to toluene and allowed to stand to precipitate. The mixture is filtered and washed 3 to 5 times with a mixed solvent and then dried under vacuum to obtain the p-aminodiphenylamine-salicylaldehyde Schiff base.

6. The high-voltage silicone rubber cold-shrink cable terminal insulator according to claim 5, characterized in that, The mixed solvent is prepared by mixing toluene and methanol in a volume ratio of 1:

1.

7. The high-voltage silicone rubber cold-shrink cable terminal insulator according to claim 2, characterized in that, The DOPO-modified Schiff base intermediate comprises the following preparation steps: p-aminodiphenylamine-salicylaldehyde Schiff base and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide are weighed at a mass ratio of 1:1.5~1.

8. The p-aminodiphenylamine-salicylaldehyde Schiff base and 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide are added to ethanol at a mass ratio of 50~60 times that of p-aminodiphenylamine-salicylaldehyde Schiff base. After stirring evenly, the temperature is raised to 85~95℃ and the reaction is carried out for 12~14 hours. After the reaction is completed, deionized water is added to precipitate the precipitate. The precipitate is filtered and purified by chromatography to obtain the DOPO-modified Schiff base intermediate.

8. The high-voltage silicone rubber cold-shrink cable terminal insulator according to claim 1, characterized in that, The peroxide sulfiding agent is dicumyl peroxide.

9. The high-voltage silicone rubber cold-shrink cable terminal insulator according to claim 1, characterized in that, The crosslinking agent is triallyl isocyanurate.

10. A method for manufacturing a high-voltage silicone rubber cold-shrink cable terminal insulator, applied to the high-voltage silicone rubber cold-shrink cable terminal insulator of claims 1-7, characterized in that, Includes the following steps: S1. First, put the epoxidized silicone rubber and the DOPO modified Schiff base intermediate into a mixer, heat it to 110~130℃ and mix it at a constant temperature for 8~12 minutes to obtain the grafted modified composite rubber. S2. Continue to add EPDM rubber, silica, kaolin, mica powder and γ-aminopropyltriethoxysilane into the internal mixer, and continue mixing at 120~150℃ for 5~10 minutes. S3. Cool down to 80~100℃, add paraffin oil, and mix for 3-5 minutes; S4. Cool down to 70~85℃ again, add dicumyl peroxide and triallyl isocyanurate, mix for 2~4 minutes to obtain a uniform compound. S5. Place the compounded rubber in a mold and vulcanize it at 160~180℃ and 10~15MPa pressure for 10~30min. Cool it to room temperature to obtain a high-voltage silicone rubber cold shrink cable terminal insulator.

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