Highly heat-conductive silicone rubber composite material for cable accessories and method for preparing the same

Abstract

The application belongs to the technical field of electric power engineering, and particularly relates to a high-thermal-conductivity silicone rubber composite material for cable accessories and a preparation method thereof. The high-thermal-conductivity silicone rubber composite material for cable accessories has methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber and boron-silicon rubber as base rubber, has modified boron nitride whisker, modified fluoromicaschist sheet and modified spherical nano magnesium oxide as fillers, has 2,5-di-tert-butyl peroxide hexane as vulcanizing agent, has N,N',N''-triallyl melamine as auxiliary crosslinking agent, has end-vinyl polydimethylsiloxane as processing aid, and has bis(2,4 di-cumyl phenyl) pentaerythritol diphosphite as antioxidant, so that the raw materials synergize with each other, and the high-thermal-conductivity silicone rubber composite material for cable accessories prepared has good thermal conductivity and mechanical strength.

Description

Technical Field

[0001] This invention belongs to the field of power engineering technology, specifically relating to a high thermal conductivity silicone rubber composite material for cable accessories and its preparation method. Background Technology

[0002] High-voltage power cables are core and critical equipment for large-capacity power grid interconnection, ultra-high-voltage power transmission, and urban underground power distribution networks. In the actual operation and maintenance of power systems, cable accessories are the weakest link in the overall line structure, directly affecting the long-term operational safety and stability of high-voltage transmission lines.

[0003] Silicone rubber, with its excellent insulation properties, elasticity, and processing characteristics, is widely used as the main reinforcing insulation material for high-voltage cable accessories. During actual operation, cable accessories experience significant heat generation near the conductor core. Furthermore, the low thermal conductivity and poor heat dissipation of pure silicone rubber result in a large temperature difference between the inside and outside of the cable accessory. Since the conductivity of the reinforcing silicone rubber material in cable accessories is a function of temperature, the significant temperature difference between the internal and external areas leads to a persistent mismatch in the conductivity of the reinforcing insulation, causing localized electric field concentration and increasing the likelihood of cable accessory failure.

[0004] However, the silicone rubber commonly used in cable accessories typically has low mechanical strength and poor thermal conductivity. While adding fillers such as metal oxides to silicone rubber can further improve its thermal conductivity, problems arise such as poor compatibility, uneven dispersion, and easy particle agglomeration, which impairs the mechanical and processing properties of the silicone rubber. Therefore, it is necessary to explore a novel high thermal conductivity silicone rubber composite material for cable accessories. Summary of the Invention

[0005] The purpose of this invention is to provide a high thermal conductivity silicone rubber composite material for cable accessories, which has good thermal conductivity and mechanical properties. In addition, this invention also provides a method for its preparation.

[0006] The high thermal conductivity silicone rubber composite material for cable accessories described in this invention is composed of the following raw materials in parts by weight: 63-65 parts of methyl vinyl silicone rubber, 30-32 parts of methyl phenyl vinyl silicone rubber, 4-5 parts of borosilicate rubber, 16-18 parts of modified boron nitride whiskers, 10-11 parts of modified fluorophlogopite flakes, 12-13 parts of modified spherical nano magnesium oxide, 1.8-2.0 parts of 2,5-di-tert-butylperoxide, 0.8-1.0 parts of N,N',N''-triallylmelamine, 1.8-2.0 parts of vinyl-terminated polydimethylsiloxane, and 0.3-0.5 parts of bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0007] The method for preparing the modified boron nitride whiskers comprises the following steps: (1) Pre-activation treatment of hexagonal boron nitride whiskers Hexagonal boron nitride whiskers were added to dilute hydrochloric acid for acid washing. After the reaction, the mixture was filtered under reduced pressure, and the filter cake was washed with deionized water until the pH of the filtrate was 7.0. Then, the neutral hexagonal boron nitride whiskers were added to anhydrous ethanol-deionized water mixture for ultrasonic dispersion. Sodium hydroxide-hydrogen peroxide mixture was added dropwise to the reaction system at a stirring speed of 400 r / min. The temperature was raised to 64℃ for isothermal etching. After etching, the mixture was filtered under reduced pressure, and the mixture was washed alternately with deionized water and anhydrous ethanol until the filtrate was neutral. Finally, the mixture was dried under vacuum to prepare pre-activated hexagonal boron nitride whiskers. (2) Preparation of precursor sol Methyltriethoxysilane was dissolved in anhydrous ethanol, deionized water was added, and then hydrochloric acid was added to adjust the pH of the system to 4.5. The system was hydrolyzed at 40°C for 1 hour, and then tributyl borate was added. The system was hydrolyzed at 40°C for 2 hours to prepare the precursor sol. (3) The hexagonal boron nitride whiskers pre-activated in step (1) are ultrasonically dispersed in the precursor sol prepared in step (2), and stirred at 50°C for 10 h, and then aged at room temperature for 20 h to prepare a core-shell structured gel. (4) The prepared core-shell structured gel was dried under vacuum and sintered under a nitrogen atmosphere to prepare modified boron nitride whiskers.

[0008] Wherein: the concentration of dilute hydrochloric acid in step (1) is 0.8 mol / L, the mass-to-volume ratio of hexagonal boron nitride whiskers to dilute hydrochloric acid is 1:20, and the unit is g / mL.

[0009] In step (1), the stirring speed during pickling is 350 r / min, the pickling temperature is room temperature, and the pickling time is 3.2 h.

[0010] In step (1), the volume ratio of anhydrous ethanol to deionized water in the anhydrous ethanol-deionized water mixture is 3.5:1.

[0011] In step (1), the mass-to-volume ratio of neutral hexagonal boron nitride whiskers to anhydrous ethanol-deionized water mixture is 1:20, with units of g / mL.

[0012] In step (1), the ultrasonic dispersion power is 350W, the ultrasonic dispersion frequency is 40kHz, and the ultrasonic dispersion time is 28min.

[0013] In step (1), the concentration of sodium hydroxide solution is 0.5 mol / L and the mass concentration of hydrogen peroxide is 10%. The sodium hydroxide-hydrogen peroxide mixture is prepared by mixing sodium hydroxide solution and hydrogen peroxide solution at a volume ratio of 1:1 under room temperature and light-protected conditions.

[0014] In step (1), the mass-volume ratio of neutral hexagonal boron nitride whiskers to sodium hydroxide-hydrogen peroxide mixture is 1:20, with units of g / mL.

[0015] The isothermal etching time in step (1) is 3.0 h.

[0016] In step (1), the vacuum drying temperature is 80℃ and the vacuum drying time is 7h.

[0017] In step (2), the molar ratio of tributyl borate to methyltriethoxysilane is 1:2.5.

[0018] In step (2), the mass ratio of anhydrous ethanol to deionized water is 5:1.

[0019] In step (2), the mass ratio of methyltriethoxysilane to tributyl borate and to anhydrous ethanol is 1:3.0.

[0020] In step (3), the mass ratio of the pretreated activated hexagonal boron nitride whiskers to the precursor sol is 1:4.

[0021] The ultrasonic dispersion power in step (3) is 350W, the ultrasonic dispersion frequency is 40kHz, and the ultrasonic dispersion time is 25min.

[0022] In step (4), the vacuum drying temperature is 100℃ and the vacuum drying time is 8h.

[0023] The sintering in step (4) involves heating from room temperature to 600°C at a heating rate of 5°C / min and holding at that temperature for 1.5 hours, and then heating from 600°C to 730°C at a heating rate of 3°C / min and holding at that temperature for 1.5 hours.

[0024] The method for preparing the modified fluorophlogopite flakes comprises the following steps: fluorophlogopite flakes are ultrasonically dispersed in a mixture of anhydrous ethanol and deionized water, then ammonia is added to adjust the pH of the system to 9.0, KH-550 silane coupling agent is added, and the mixture is stirred at 60°C for 3.0 h. After the reaction is completed, the mixture is filtered under reduced pressure, and the resulting filter cake is washed four times alternately with ethanol and deionized water. Finally, the mixture is vacuum dried at 80°C for 7 h to obtain the modified fluorophlogopite flakes.

[0025] In the preparation method of the modified fluorophlogopite sheets, the volume ratio of anhydrous ethanol to deionized water is 3:1, and the mass of KH-550 silane coupling agent accounts for 3.0% of the mass of the fluorophlogopite sheets.

[0026] In the preparation method of the modified fluorophlogopite flakes, the mass-to-volume ratio of the fluorophlogopite flakes to the mixture of anhydrous ethanol and deionized water is 1:10, with units of g / mL.

[0027] In the preparation method of the modified fluorophlogopite sheet, the ultrasonic dispersion power is 350W, the ultrasonic dispersion frequency is 40kHz, and the ultrasonic dispersion time is 25min.

[0028] The modified fluorophlogopite sheet preparation method involves a constant temperature stirring reaction at 60°C for 3 hours, with a stirring speed of 400 r / min.

[0029] The method for preparing modified spherical nano-magnesium oxide consists of the following steps: anhydrous ethanol and deionized water are mixed to prepare a mixed solution, acetic acid is added to adjust the pH of the system to 4.5, KH-570 silane coupling agent is added and the mixture is stirred at room temperature for 1.5 h, then spherical nano-magnesium oxide is added to the reaction system and ultrasonically dispersed at room temperature for 30 min, then the temperature is raised to 80℃ and stirred for 2.5 h, after the reaction is completed, the mixture is filtered under reduced pressure, the resulting filter cake is washed 6 times alternately with ethanol and deionized water, and finally dried under vacuum at 80℃ for 8 h to prepare modified spherical nano-magnesium oxide.

[0030] In the preparation method of the modified spherical nano-magnesium oxide, the volume ratio of anhydrous ethanol to deionized water is 4:1, and the mass of KH-570 silane coupling agent accounts for 2.5% of the mass of spherical nano-magnesium oxide.

[0031] In the preparation method of the modified spherical nano-magnesium oxide, the mass-to-volume ratio of the spherical nano-magnesium oxide to the mixture of anhydrous ethanol and deionized water is 1:8, with units of g / mL.

[0032] The method for preparing the modified spherical nano-magnesium oxide involves a constant temperature stirring reaction at 80°C for 2.5 hours, with a stirring speed of 400 r / min.

[0033] The preparation method of the high thermal conductivity silicone rubber composite material for cable accessories according to the present invention comprises the following steps: (1) Modified boron nitride whiskers, modified fluorophlogopite sheets and modified spherical nano magnesium oxide were vacuum dried and then cooled to room temperature for later use; (2) Start the open mixing mill, add methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber and borosilicate rubber according to the ratio, and plasticize in a thin pass for 6-8 minutes to prepare a composite rubber matrix; (3) Add vinyl-terminated polydimethylsiloxane to the composite rubber matrix prepared in step (2) and pass it through the mixture 3-5 times. Then add modified fluorophlogopite sheets and mix for 8-10 min. Add modified boron nitride whiskers and mix for 10-12 min. Add modified spherical nano magnesium oxide and mix for 6-8 min. Add bis(2,4-dicumylphenyl) pentaerythritol diphosphite and mix for 5 min. Add 2,5-di-tert-butylperoxyhexane and N,N',N''-triallylmelamine and pass it through the mixture 6-8 times. Immediately after mixing, sheet the mixture and seal it in a package. Let it stand at room temperature for 24 h. (4) Preheat the mold to 168-172℃, put in the compound prepared in step (3), apply a pressure of 15MPa, vulcanize for 12-15min, and obtain a vulcanized sample; (5) Place a vulcanized sample into an oven, first heat it from room temperature to 120-125℃ and keep it at that temperature for 1 hour, then heat it from 120-125℃ to 150-155℃ and keep it at that temperature for 1 hour, then heat it from 150-155℃ to 200-205℃ and keep it at that temperature for 4 hours, and finally turn off the heat source and cool it to room temperature before taking it out of the oven to prepare a high thermal conductivity silicone rubber composite material for cable accessories.

[0034] Wherein: the vacuum drying temperature in step (1) is 80-85℃, the vacuum drying time is 6h, and the vacuum drying pressure is -0.085MPa.

[0035] The surface temperature of the rollers of the open rubber mixing mill in step (2) is 40-45℃ and the roller speed is 16-18r / min.

[0036] In step (3), the roller speed is controlled at 12-14 r / min during the mixing process, and the rubber temperature is controlled at 35-40℃ throughout the process.

[0037] In step (3), add 2,5-di-tert-butylperoxide and N,N',N''-triallylmelamine, and quickly pass through the mixture 6-8 times, controlling the total mixing time of this section to 3-5 minutes.

[0038] In step (5), the heating rate is controlled at 1.5℃ / min throughout the process.

[0039] Compared with the prior art, the present invention has the following advantages: (1) The high thermal conductivity silicone rubber composite material for cable accessories described in this invention uses methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber and borosilicate rubber as matrix rubber, modified boron nitride whiskers, modified fluorophlogopite flakes and modified spherical nano magnesium oxide as fillers, 2,5-di-tert-butylhexane peroxide as vulcanizing agent, N,N',N''-triallylmelamine as co-crosslinking agent, terminal vinyl polydimethylsiloxane as processing aid, and bis(2,4-dicumylphenyl)pentaerythritol diphosphite as antioxidant. The synergistic effect between the raw materials ensures that the prepared high thermal conductivity silicone rubber composite material for cable accessories has good thermal conductivity and mechanical strength.

[0040] (2) The high thermal conductivity silicone rubber composite material for cable accessories of the present invention, wherein the methyl vinyl silicone rubber serves as the main matrix, providing a large number of vinyl crosslinking reaction sites and endowing the material with basic mechanical strength; the methyl phenyl vinyl silicone rubber introduces phenyl side groups, enhancing the rigidity of the molecular chain and the intermolecular forces, and synergistically optimizing the tensile and tear strength of the composite material; the borosilicate rubber introduces boron-oxygen characteristic structures, strengthening the high-temperature stability of the crosslinking network and ensuring the stable retention of mechanical properties after long-term thermal aging. The three rubber materials are synergistically co-crosslinked by oxide free radicals to form a hybrid dense crosslinking system, so that the prepared silicone rubber composite material has comprehensive properties of high strength, high insulation and high thermal conductivity; the N,N',N''-trimethylene melamine serves as a co-crosslinking agent, and the allyl group in its molecule undergoes a copolymerization reaction with the vinyl side chain of the methyl vinyl silicone rubber under the initiation of free radicals generated by the decomposition of peroxide, forming a stable three-dimensional network structure. This co-crosslinking agent not only improves the crosslinking efficiency of 2,5-di-tert-butylhexane peroxide, but also endows the composite material with better thermal stability due to its triazine ring structure.

[0041] (3) The high thermal conductivity silicone rubber composite material for cable accessories described in this invention uses modified boron nitride whiskers to construct a main thermal conduction path that penetrates the silicone rubber matrix through longitudinal and transverse overlap, thereby achieving rapid and efficient heat conduction and providing fiber reinforcement as a one-dimensional whisker. The layered structure of modified fluorophlogopite flakes can block crack propagation, effectively inhibit matrix cracking, maintain and improve the toughness and structural strength of the material, and also act as an electrical insulation barrier. Modified spherical nano-magnesium oxide fills the microscopic voids formed by the interweaving of one-dimensional whiskers and two-dimensional flakes, repairs the breaks in the thermal conduction network, and realizes the continuity of the thermal conduction channel. In addition, the smooth spherical particles can disperse the stress concentration at the interface and avoid the decrease in mechanical properties caused by voids through interface synergistic densification. Thus, the synergistic effect of the three ensures the mechanical strength and thermal conductivity of the prepared silicone rubber composite material.

[0042] (4) In the preparation of the modified boron nitride whiskers in the high thermal conductivity silicone rubber composite material for cable accessories of the present invention, the modified boron nitride whiskers are first prepared by acid washing to remove impurities, followed by alkaline etching and ultrasonic treatment to generate active hydroxyl groups on the surface of hexagonal boron nitride. When preparing the precursor sol, the molar ratio of methyltriethoxysilane to tributyl borate is controlled to generate B-Si-O hybrid sol. Then, through in-situ coating, the hydroxyl groups on the surface of boron nitride are covalently condensed with B-OH and Si-OH in the sol to form a core-shell structure in situ. The shell structure is homologous to the molecular structure of borosilicate rubber. After aging treatment, the cross-linked network of the shell is densified. Finally, after drying and sintering, the shell is made into a stable glassy structure, while protecting the hexagonal boron nitride whiskers from oxidation, thus obtaining the modified boron nitride whiskers.

[0043] (5) The preparation method of the high thermal conductivity silicone rubber composite material for cable accessories described in this invention is simple, the parameters are easy to control, and it is easy to realize industrial production. Detailed Implementation

[0044] The preparation methods of the modified boron nitride whiskers, modified fluorophlogopite sheets, and modified spherical nano-magnesium oxide used in the following examples and comparative examples are shown below: The method for preparing the modified boron nitride whiskers comprises the following steps: (1) Pre-activation treatment of hexagonal boron nitride whiskers Hexagonal boron nitride whiskers were added to dilute hydrochloric acid for acid washing. After the reaction, the mixture was filtered under reduced pressure, and the filter cake was washed with deionized water until the pH of the filtrate was 7.0. Then, the neutral hexagonal boron nitride whiskers were added to anhydrous ethanol-deionized water mixture for ultrasonic dispersion. Sodium hydroxide-hydrogen peroxide mixture was added dropwise to the reaction system at a stirring speed of 400 r / min. The temperature was raised to 64℃ for isothermal etching. After etching, the mixture was filtered under reduced pressure, and the mixture was washed alternately with deionized water and anhydrous ethanol until the filtrate was neutral. Finally, the mixture was dried under vacuum to prepare pre-activated hexagonal boron nitride whiskers. (2) Preparation of precursor sol Methyltriethoxysilane was dissolved in anhydrous ethanol, deionized water was added, and then hydrochloric acid was added to adjust the pH of the system to 4.5. The system was hydrolyzed at 40°C for 1 hour, and then tributyl borate was added. The system was hydrolyzed at 40°C for 2 hours to prepare the precursor sol. (3) The hexagonal boron nitride whiskers pre-activated in step (1) are ultrasonically dispersed in the precursor sol prepared in step (2), and stirred at 50°C for 10 h, and then aged at room temperature for 20 h to prepare a core-shell structured gel. (4) The prepared core-shell structured gel was dried under vacuum and sintered under a nitrogen atmosphere to prepare modified boron nitride whiskers.

[0045] Wherein: the concentration of dilute hydrochloric acid in step (1) is 0.8 mol / L, the mass-to-volume ratio of hexagonal boron nitride whiskers to dilute hydrochloric acid is 1:20, and the unit is g / mL.

[0046] In step (1), the stirring speed during pickling is 350 r / min, the pickling temperature is room temperature, and the pickling time is 3.2 h.

[0047] In step (1), the volume ratio of anhydrous ethanol to deionized water in the anhydrous ethanol-deionized water mixture is 3.5:1.

[0048] In step (1), the mass-to-volume ratio of neutral hexagonal boron nitride whiskers to anhydrous ethanol-deionized water mixture is 1:20, with units of g / mL.

[0049] In step (1), the ultrasonic dispersion power is 350W, the ultrasonic dispersion frequency is 40kHz, and the ultrasonic dispersion time is 28min.

[0050] In step (1), the concentration of sodium hydroxide solution is 0.5 mol / L and the mass concentration of hydrogen peroxide is 10%. The sodium hydroxide-hydrogen peroxide mixture is prepared by mixing sodium hydroxide solution and hydrogen peroxide solution at a volume ratio of 1:1 under room temperature and light-protected conditions.

[0051] In step (1), the mass-volume ratio of neutral hexagonal boron nitride whiskers to sodium hydroxide-hydrogen peroxide mixture is 1:20, with units of g / mL.

[0052] The isothermal etching time in step (1) is 3.0 h.

[0053] In step (1), the vacuum drying temperature is 80℃ and the vacuum drying time is 7h.

[0054] In step (2), the molar ratio of tributyl borate to methyltriethoxysilane is 1:2.5.

[0055] In step (2), the mass ratio of anhydrous ethanol to deionized water is 5:1.

[0056] In step (2), the mass ratio of methyltriethoxysilane to tributyl borate and to anhydrous ethanol is 1:3.0.

[0057] In step (3), the mass ratio of the pretreated activated hexagonal boron nitride whiskers to the precursor sol is 1:4.

[0058] The ultrasonic dispersion power in step (3) is 350W, the ultrasonic dispersion frequency is 40kHz, and the ultrasonic dispersion time is 25min.

[0059] In step (4), the vacuum drying temperature is 100℃ and the vacuum drying time is 8h.

[0060] The sintering in step (4) involves heating from room temperature to 600°C at a heating rate of 5°C / min and holding at that temperature for 1.5 hours, and then heating from 600°C to 730°C at a heating rate of 3°C / min and holding at that temperature for 1.5 hours.

[0061] The method for preparing the modified fluorophlogopite flakes comprises the following steps: fluorophlogopite flakes are ultrasonically dispersed in a mixture of anhydrous ethanol and deionized water, then ammonia is added to adjust the pH of the system to 9.0, KH-550 silane coupling agent is added, and the mixture is stirred at 60°C for 3.0 h. After the reaction is completed, the mixture is filtered under reduced pressure, and the resulting filter cake is washed four times alternately with ethanol and deionized water. Finally, the mixture is vacuum dried at 80°C for 7 h to obtain the modified fluorophlogopite flakes.

[0062] In the preparation method of the modified fluorophlogopite sheets, the volume ratio of anhydrous ethanol to deionized water is 3:1, and the mass of KH-550 silane coupling agent accounts for 3.0% of the mass of the fluorophlogopite sheets.

[0063] In the preparation method of the modified fluorophlogopite flakes, the mass-to-volume ratio of the fluorophlogopite flakes to the mixture of anhydrous ethanol and deionized water is 1:10, with units of g / mL.

[0064] In the preparation method of the modified fluorophlogopite sheet, the ultrasonic dispersion power is 350W, the ultrasonic dispersion frequency is 40kHz, and the ultrasonic dispersion time is 25min.

[0065] The modified fluorophlogopite sheet preparation method involves a constant temperature stirring reaction at 60°C for 3 hours, with a stirring speed of 400 r / min.

[0066] The method for preparing modified spherical nano-magnesium oxide consists of the following steps: anhydrous ethanol and deionized water are mixed to prepare a mixed solution, acetic acid is added to adjust the pH of the system to 4.5, KH-570 silane coupling agent is added and the mixture is stirred at room temperature for 1.5 h, then spherical nano-magnesium oxide is added to the reaction system and ultrasonically dispersed at room temperature for 30 min, then the temperature is raised to 80℃ and stirred for 2.5 h, after the reaction is completed, the mixture is filtered under reduced pressure, the resulting filter cake is washed 6 times alternately with ethanol and deionized water, and finally dried under vacuum at 80℃ for 8 h to prepare modified spherical nano-magnesium oxide.

[0067] In the preparation method of the modified spherical nano-magnesium oxide, the volume ratio of anhydrous ethanol to deionized water is 4:1, and the mass of KH-570 silane coupling agent accounts for 2.5% of the mass of spherical nano-magnesium oxide.

[0068] In the preparation method of the modified spherical nano-magnesium oxide, the mass-to-volume ratio of the spherical nano-magnesium oxide to the mixture of anhydrous ethanol and deionized water is 1:8, with units of g / mL.

[0069] The method for preparing the modified spherical nano-magnesium oxide involves a constant temperature stirring reaction at 80°C for 2.5 hours, with a stirring speed of 400 r / min.

[0070] Example 1

[0071] The high thermal conductivity silicone rubber composite material for cable accessories described in Example 1 is composed of the following raw materials by weight: 64 parts methyl vinyl silicone rubber, 31 parts methyl phenyl vinyl silicone rubber, 4.5 parts borosilicate rubber, 17 parts modified boron nitride whiskers, 10.5 parts modified fluorophlogopite flakes, 12.5 parts modified spherical nano magnesium oxide, 1.9 parts 2,5-di-tert-butylhexane peroxide, 0.9 parts N,N',N''-triallylmelamine, 1.9 parts vinyl-terminated polydimethylsiloxane, and 0.4 parts bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0072] The preparation method of the high thermal conductivity silicone rubber composite material for cable accessories described in Example 1 consists of the following steps: (1) Modified boron nitride whiskers, modified fluorophlogopite sheets and modified spherical nano magnesium oxide were vacuum dried and then cooled to room temperature for later use; (2) Start the open mixing mill, add methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber and borosilicate rubber according to the ratio, and plasticize for 7 minutes to prepare the composite rubber matrix; (3) Add vinyl-terminated polydimethylsiloxane to the composite rubber matrix prepared in step (2) and pass it through the mixture 4 times. Then add modified fluorophlogopite sheets and mix for 9 min. Add modified boron nitride whiskers and mix for 11 min. Add modified spherical nano magnesium oxide and mix for 7 min. Add bis(2,4-dicumylphenyl) pentaerythritol diphosphite and mix for 5 min. Add 2,5-di-tert-butylhexane peroxide and N,N',N''-triallylmelamine and pass it through the mixture 7 times. Immediately after mixing, sheet the mixture and seal it in a package. Let it stand at room temperature for 24 h. (4) Preheat the mold to 170°C, put in the compound prepared in step (3), apply a pressure of 15MPa, vulcanize for 13min, and obtain a vulcanized sample; (5) A vulcanized sample was placed in an oven. First, the temperature was raised from room temperature to 123°C and kept for 1 hour. Then, the temperature was raised from 123°C to 153°C and kept for 1 hour. Subsequently, the temperature was raised from 153°C to 203°C and kept for 4 hours. Finally, the heat source was turned off and the sample was cooled to room temperature before being taken out of the oven. The high thermal conductivity silicone rubber composite material for cable accessories was prepared.

[0073] Wherein: the vacuum drying temperature in step (1) is 83℃, the vacuum drying time is 6h, and the vacuum drying pressure is -0.085MPa.

[0074] The surface temperature of the rollers of the open rubber mixing mill in step (2) is 43°C and the roller speed is 17 r / min.

[0075] In step (3), the roller speed is controlled at 13 r / min during the mixing process, and the rubber temperature is controlled at 37℃ throughout the process.

[0076] In step (3), 2,5-di-tert-butylperoxide and N,N',N''-triallylmelamine are added and rapidly passed through a thin stream 7 times, controlling the total mixing time of this section to 4 minutes.

[0077] In step (5), the heating rate is controlled at 1.5℃ / min throughout the process.

[0078] Example 2

[0079] The high thermal conductivity silicone rubber composite material for cable accessories described in Example 2 is composed of the following raw materials by weight: 63 parts methyl vinyl silicone rubber, 32 parts methyl phenyl vinyl silicone rubber, 4 parts borosilicate rubber, 16 parts modified boron nitride whiskers, 11 parts modified fluorophlogopite flakes, 13 parts modified spherical nano magnesium oxide, 1.8 parts 2,5-di-tert-butylperoxide, 1.0 part N,N',N''-triallylmelamine, 1.8 parts vinyl-terminated polydimethylsiloxane, and 0.3 parts bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0080] The preparation method of the high thermal conductivity silicone rubber composite material for cable accessories described in Example 2 consists of the following steps: (1) Modified boron nitride whiskers, modified fluorophlogopite sheets and modified spherical nano magnesium oxide were vacuum dried and then cooled to room temperature for later use; (2) Start the open rubber mixing mill, add methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber and borosilicate rubber according to the ratio, and plasticize in thin pass for 6 minutes to prepare the composite rubber matrix; (3) Add vinyl-terminated polydimethylsiloxane to the composite rubber matrix prepared in step (2) and pass it through the mixture 3 times. Then add modified fluorophlogopite sheets and mix for 10 min. Add modified boron nitride whiskers and mix for 10 min. Add modified spherical nano magnesium oxide and mix for 8 min. Add bis(2,4-dicumylphenyl) pentaerythritol diphosphite and mix for 5 min. Add 2,5-di-tert-butylhexane peroxide and N,N',N''-triallylmelamine and pass it through the mixture 6 times. Immediately after mixing, sheet the mixture and seal it in a package. Let it stand at room temperature for 24 h. (4) Preheat the mold to 168°C, put in the compound prepared in step (3), apply a pressure of 15MPa, vulcanize for 15min, and obtain a vulcanized sample; (5) Place a vulcanized sample into an oven, first raise the temperature from room temperature to 120°C and keep it at that temperature for 1 hour, then raise the temperature from 120°C to 150°C and keep it at that temperature for 1 hour, then raise the temperature from 150°C to 200°C and keep it at that temperature for 4 hours, and finally turn off the heat source and cool it to room temperature before taking it out of the oven to prepare a high thermal conductivity silicone rubber composite material for cable accessories.

[0081] Wherein: the vacuum drying temperature in step (1) is 80℃, the vacuum drying time is 6h, and the vacuum drying pressure is -0.085MPa.

[0082] The surface temperature of the rollers of the open rubber mixing mill in step (2) is 45°C and the roller speed is 16 r / min.

[0083] In step (3), the roller speed is controlled at 12 r / min during the mixing process, and the rubber temperature is controlled at 40℃ throughout the process.

[0084] In step (3), 2,5-di-tert-butylperoxide and N,N',N''-triallylmelamine are added and rapidly passed through a thin stream 6 times, controlling the total mixing time of this section to 3 minutes.

[0085] In step (5), the heating rate is controlled at 1.5℃ / min throughout the process.

[0086] Example 3

[0087] The high thermal conductivity silicone rubber composite material for cable accessories described in Example 3 is composed of the following raw materials by weight: 65 parts methyl vinyl silicone rubber, 30 parts methyl phenyl vinyl silicone rubber, 5 parts borosilicate rubber, 18 parts modified boron nitride whiskers, 10 parts modified fluorophlogopite flakes, 12 parts modified spherical nano magnesium oxide, 2.0 parts 2,5-di-tert-butylperoxide, 0.8 parts N,N',N''-triallylmelamine, 2.0 parts vinyl-terminated polydimethylsiloxane, and 0.5 parts bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0088] The preparation method of the high thermal conductivity silicone rubber composite material for cable accessories described in Example 3 consists of the following steps: (1) Modified boron nitride whiskers, modified fluorophlogopite sheets and modified spherical nano magnesium oxide were vacuum dried and then cooled to room temperature for later use; (2) Start the open rubber mixing mill, add methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber and borosilicate rubber according to the ratio, and plasticize for 8 minutes to prepare the composite rubber matrix; (3) Add vinyl-terminated polydimethylsiloxane to the composite rubber matrix prepared in step (2) and pass it through 5 times. Then add modified fluorophlogopite sheets and mix for 8 min. Add modified boron nitride whiskers and mix for 12 min. Add modified spherical nano magnesium oxide and mix for 6 min. Add bis(2,4-dicumylphenyl) pentaerythritol diphosphite and mix for 5 min. Add 2,5-di-tert-butylhexane peroxide and N,N',N''-triallylmelamine and pass it through 8 times. After mixing, immediately sheet the mixture and seal it in a package. Let it stand at room temperature for 24 h. (4) Preheat the mold to 172°C, put in the compound prepared in step (3), apply a pressure of 15MPa, vulcanize for 12min, and obtain a vulcanized sample; (5) A vulcanized sample was placed in an oven. First, the temperature was raised from room temperature to 125°C and kept for 1 hour. Then, the temperature was raised from 125°C to 155°C and kept for 1 hour. After that, the temperature was raised from 155°C to 205°C and kept for 4 hours. Finally, the heat source was turned off and the sample was cooled to room temperature before being taken out of the oven. The high thermal conductivity silicone rubber composite material for cable accessories was prepared.

[0089] Wherein: the vacuum drying temperature in step (1) is 85℃, the vacuum drying time is 6h, and the vacuum drying pressure is -0.085MPa.

[0090] The surface temperature of the rollers of the open rubber mixing mill in step (2) is 40°C and the roller speed is 18 r / min.

[0091] In step (3), the roller speed is controlled at 14 r / min during the mixing process, and the rubber temperature is controlled at 35℃ throughout the process.

[0092] In step (3), 2,5-di-tert-butylperoxide and N,N',N''-triallylmelamine are added and rapidly passed through a thin stream 8 times, controlling the total mixing time of this section to 5 minutes.

[0093] In step (5), the heating rate is controlled at 1.5℃ / min throughout the process.

[0094] Comparative Example 1 The preparation method of the high thermal conductivity silicone rubber composite material for cable accessories described in Comparative Example 1 is the same as that in Example 1, except that the raw material composition is different. The high thermal conductivity silicone rubber composite material for cable accessories described in Comparative Example 1, by weight, is composed of the following raw materials: 64 parts of methyl vinyl silicone rubber, 31 parts of methyl phenyl vinyl silicone rubber, 4.5 parts of borosilicate rubber, 10.5 parts of modified fluorophlogopite flakes, 12.5 parts of modified spherical nano magnesium oxide, 1.9 parts of 2,5-di-tert-butylperoxide, 0.9 parts of N,N',N''-triallylmelamine, 1.9 parts of vinyl-terminated polydimethylsiloxane, and 0.4 parts of bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0095] Comparative Example 2 The preparation method of the high thermal conductivity silicone rubber composite material for cable accessories described in Comparative Example 2 is the same as that in Example 1, except that the raw material composition is different. The high thermal conductivity silicone rubber composite material for cable accessories described in Comparative Example 2, by weight, consists of the following raw materials: 64 parts methyl vinyl silicone rubber, 31 parts methyl phenyl vinyl silicone rubber, 4.5 parts borosilicate rubber, 17 parts modified boron nitride whiskers, 12.5 parts modified spherical nano magnesium oxide, 1.9 parts 2,5-di-tert-butylperoxide, 0.9 parts N,N',N''-triallylmelamine, 1.9 parts vinyl-terminated polydimethylsiloxane, and 0.4 parts bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0096] Comparative Example 3 The preparation method of the high thermal conductivity silicone rubber composite material for cable accessories described in Comparative Example 3 is the same as that in Example 1, except that the raw material composition is different. The high thermal conductivity silicone rubber composite material for cable accessories described in Comparative Example 3, by weight, consists of the following raw materials: 64 parts methyl vinyl silicone rubber, 31 parts methyl phenyl vinyl silicone rubber, 4.5 parts borosilicate rubber, 17 parts modified boron nitride whiskers, 10.5 parts modified fluorophlogopite flakes, 1.9 parts 2,5-di-tert-butylperoxide, 0.9 parts N,N',N''-triallylmelamine, 1.9 parts vinyl-terminated polydimethylsiloxane, and 0.4 parts bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0097] The high thermal conductivity silicone rubber composites for cable accessories prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests. Tensile strength was tested according to GB / T 528 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber", tear strength was tested according to GB / T 529 "Determination of Tear Strength of Vulcanized Rubber or Thermoplastic Rubber (Pants-Shaped, Right-Angle, and Crescent-Shaped Specimens)", and thermal conductivity was tested according to GB / T 11205 "Determination of Thermal Conductivity of Rubber". The results are shown in Table 1 below. Table 1. Performance test results of high thermal conductivity silicone rubber composite materials for cable accessories

[0098] As shown in Table 1, the performance of the high thermal conductivity silicone rubber composite materials for cable accessories prepared in Examples 1-3 is significantly better than that in Comparative Examples 1-3. In Comparative Examples 1-3, the absence of any one of boron nitride whiskers, modified fluorophlogopite sheets, or modified spherical nano-magnesium oxide led to a significant decrease in the mechanical properties and thermal conductivity of the prepared silicone rubber composite materials.

[0099] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high thermal conductivity silicone rubber composite material for cable accessories, characterized in that: The product, by weight, is composed of the following raw materials: 63-65 parts of methyl vinyl silicone rubber, 30-32 parts of methyl phenyl vinyl silicone rubber, 4-5 parts of borosilicate rubber, 16-18 parts of modified boron nitride whiskers, 10-11 parts of modified fluorophlogopite flakes, 12-13 parts of modified spherical nano magnesium oxide, 1.8-2.0 parts of 2,5-di-tert-butylperoxide, 0.8-1.0 parts of N,N',N''-trimethylene melamine, 1.8-2.0 parts of vinyl-terminated polydimethylsiloxane, and 0.3-0.5 parts of bis(2,4-dicumylphenyl)pentaerythritol diphosphite. The method for preparing the modified boron nitride whiskers comprises the following steps: (1) Pre-activation treatment of hexagonal boron nitride whiskers Hexagonal boron nitride whiskers were added to dilute hydrochloric acid for acid washing. After the reaction, the mixture was filtered under reduced pressure, and the filter cake was washed with deionized water until the pH of the filtrate was 7.

0. Then, the neutral hexagonal boron nitride whiskers were added to anhydrous ethanol-deionized water mixture for ultrasonic dispersion. Sodium hydroxide-hydrogen peroxide mixture was added dropwise to the reaction system at a stirring speed of 400 r / min. The temperature was raised to 64℃ for isothermal etching. After etching, the mixture was filtered under reduced pressure, and the mixture was washed alternately with deionized water and anhydrous ethanol until the filtrate was neutral. Finally, the mixture was dried under vacuum to prepare pre-activated hexagonal boron nitride whiskers. (2) Preparation of precursor sol Methyltriethoxysilane was dissolved in anhydrous ethanol, deionized water was added, and then hydrochloric acid was added to adjust the pH of the system to 4.

5. The system was hydrolyzed at 40°C for 1 hour, and then tributyl borate was added. The system was hydrolyzed at 40°C for 2 hours to prepare the precursor sol. (3) The hexagonal boron nitride whiskers pre-activated in step (1) are ultrasonically dispersed in the precursor sol prepared in step (2), and stirred at 50°C for 10 h, and then aged at room temperature for 20 h to prepare a core-shell structured gel. (4) The prepared core-shell structured gel was dried under vacuum and sintered under a nitrogen atmosphere to prepare modified boron nitride whiskers; The method for preparing the modified fluorophlogopite sheets comprises the following steps: fluorophlogopite sheets are ultrasonically dispersed in a mixture of anhydrous ethanol and deionized water, then ammonia is added to adjust the pH of the system to 9.0, KH-550 silane coupling agent is added and the mixture is stirred at 60°C for 3.0 h, after which the reaction is completed, the mixture is filtered under reduced pressure, and the resulting filter cake is washed four times alternately with ethanol and deionized water, and finally dried under vacuum at 80°C for 7 h to obtain the modified fluorophlogopite sheets. The method for preparing the modified spherical nano-magnesium oxide comprises the following steps: mixing anhydrous ethanol and deionized water to prepare a mixed solution, adding acetic acid to adjust the pH of the system to 4.5, adding KH-570 silane coupling agent and stirring at room temperature for 1.5 h, then adding spherical nano-magnesium oxide to the reaction system and ultrasonically dispersing at room temperature for 30 min, followed by heating to 80℃ and stirring for 2.5 h, after which the reaction is completed, filtering under reduced pressure, washing the obtained filter cake alternately with ethanol and deionized water 6 times, and finally drying under vacuum at 80℃ for 8 h to prepare the modified spherical nano-magnesium oxide.

2. The high thermal conductivity silicone rubber composite material for cable accessories according to claim 1, characterized in that: In step (1) of the preparation method of the modified boron nitride whiskers, the concentration of dilute hydrochloric acid is 0.8 mol / L, and the mass-volume ratio of hexagonal boron nitride whiskers to dilute hydrochloric acid is 1:20, with units of g / mL. In step (1) of the preparation method of the modified boron nitride whiskers, the stirring speed during acid washing is 350 r / min, the acid washing temperature is room temperature, and the acid washing time is 3.2 h. In step (1) of the method for preparing the modified boron nitride whiskers, the volume ratio of anhydrous ethanol to deionized water in the anhydrous ethanol-deionized water mixture is 3.5:

1. In step (1) of the preparation method of the modified boron nitride whiskers, the mass-volume ratio of neutral hexagonal boron nitride whiskers to anhydrous ethanol-deionized water mixture is 1:20, with units of g / mL. In step (1) of the preparation method of the modified boron nitride whiskers, the ultrasonic dispersion power is 350W, the ultrasonic dispersion frequency is 40kHz, and the ultrasonic dispersion time is 28min. In step (1) of the method for preparing modified boron nitride whiskers, the concentration of sodium hydroxide solution is 0.5 mol / L and the mass concentration of hydrogen peroxide is 10%. The sodium hydroxide-hydrogen peroxide mixture is prepared by mixing sodium hydroxide solution and hydrogen peroxide solution at a volume ratio of 1:1 under room temperature and light-protected conditions. In step (1) of the preparation method of the modified boron nitride whiskers, the mass-volume ratio of neutral hexagonal boron nitride whiskers to sodium hydroxide-hydrogen peroxide mixture is 1:20, and the unit is g / mL. The isothermal etching time in step (1) of the method for preparing the modified boron nitride whiskers is 3.0 h; In step (1) of the preparation method of the modified boron nitride whiskers, the vacuum drying temperature is 80℃ and the vacuum drying time is 7h.

3. The high thermal conductivity silicone rubber composite material for cable accessories according to claim 1, characterized in that: In step (2) of the method for preparing the modified boron nitride whiskers, the molar ratio of tributyl borate to methyltriethoxysilane is 1:2.

5. In step (2) of the preparation method of the modified boron nitride whiskers, the mass ratio of anhydrous ethanol to deionized water is 5:

1. In step (2) of the preparation method of the modified boron nitride whiskers, the mass ratio of methyltriethoxysilane to tributyl borate and to anhydrous ethanol is 1:3.

0. In step (3) of the preparation method of the modified boron nitride whiskers, the mass ratio of the pretreated and activated hexagonal boron nitride whiskers to the precursor sol is 1:

4. In step (3) of the preparation method of the modified boron nitride whiskers, the ultrasonic dispersion power is 350W, the ultrasonic dispersion frequency is 40kHz, and the ultrasonic dispersion time is 25min. In step (4) of the preparation method of the modified boron nitride whiskers, the vacuum drying temperature is 100℃ and the vacuum drying time is 8h. In step (4) of the method for preparing the modified boron nitride whiskers, the sintering is performed by heating from room temperature to 600℃ at a heating rate of 5℃ / min and holding for 1.5h, and then heating from 600℃ to 730℃ at a heating rate of 3℃ / min and holding for 1.5h.

4. The high thermal conductivity silicone rubber composite material for cable accessories according to claim 1, characterized in that: In the preparation method of the modified fluorophlogopite flakes, the volume ratio of anhydrous ethanol to deionized water is 3:1, and the mass of KH-550 silane coupling agent accounts for 3.0% of the mass of the fluorophlogopite flakes. In the preparation method of the modified fluorophlogopite flakes, the mass-to-volume ratio of the fluorophlogopite flakes to the mixture of anhydrous ethanol and deionized water is 1:10, with units of g / mL. In the preparation method of the modified fluorophlogopite sheet, the ultrasonic dispersion power is 350W, the ultrasonic dispersion frequency is 40kHz, and the ultrasonic dispersion time is 25min. The modified fluorophlogopite sheet preparation method involves a constant temperature stirring reaction at 60°C for 3 hours, with a stirring speed of 400 r / min.

5. The high thermal conductivity silicone rubber composite material for cable accessories according to claim 1, characterized in that: In the preparation method of the modified spherical nano-magnesium oxide, the volume ratio of anhydrous ethanol to deionized water is 4:1, and the mass of KH-570 silane coupling agent accounts for 2.5% of the mass of the spherical nano-magnesium oxide. In the preparation method of the modified spherical nano magnesium oxide, the mass-to-volume ratio of the spherical nano magnesium oxide to the mixture of anhydrous ethanol and deionized water is 1:8, and the unit is g / mL. The method for preparing the modified spherical nano-magnesium oxide involves a constant temperature stirring reaction at 80°C for 2.5 hours, with a stirring speed of 400 r / min.

6. A method for preparing the high thermal conductivity silicone rubber composite material for cable accessories according to claim 1, characterized in that: It consists of the following steps: (1) Modified boron nitride whiskers, modified fluorophlogopite sheets and modified spherical nano magnesium oxide were vacuum dried and then cooled to room temperature for later use; (2) Start the open mixing mill, add methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber and borosilicate rubber according to the ratio, and plasticize in a thin pass for 6-8 minutes to prepare a composite rubber matrix; (3) Add vinyl-terminated polydimethylsiloxane to the composite rubber matrix prepared in step (2) and pass it through the mixture 3-5 times. Then add modified fluorophlogopite sheets and mix for 8-10 min. Add modified boron nitride whiskers and mix for 10-12 min. Add modified spherical nano magnesium oxide and mix for 6-8 min. Add bis(2,4-dicumylphenyl) pentaerythritol diphosphite and mix for 5 min. Add 2,5-di-tert-butylhexane peroxide and N,N',N''-triallylmelamine and pass it through the mixture 6-8 times. Immediately after mixing, sheet the mixture and seal it in a package. Let it stand at room temperature for 24 h. (4) Preheat the mold to 168-172℃, put in the compound prepared in step (3), apply a pressure of 15MPa, vulcanize for 12-15min, and obtain a vulcanized sample; (5) Place a vulcanized sample into an oven, first heat it from room temperature to 120-125℃ and keep it at that temperature for 1 hour, then heat it from 120-125℃ to 150-155℃ and keep it at that temperature for 1 hour, then heat it from 150-155℃ to 200-205℃ and keep it at that temperature for 4 hours, and finally turn off the heat source and cool it to room temperature before taking it out of the oven to prepare a high thermal conductivity silicone rubber composite material for cable accessories.

7. The method for preparing the high thermal conductivity silicone rubber composite material for cable accessories according to claim 6, characterized in that: The vacuum drying temperature in step (1) is 80-85℃, the vacuum drying time is 6h, and the vacuum drying pressure is -0.085MPa; The surface temperature of the rollers of the open rubber mixing mill in step (2) is 40-45℃, and the roller speed is 16-18r / min; In step (3), the roller speed is controlled at 12-14 r / min during the mixing process, and the rubber temperature is controlled at 35-40℃ throughout the process; In step (3), add 2,5-di-tert-butylperoxide and N,N',N''-triallylmelamine, and quickly pass through the mixture 6-8 times, controlling the total mixing time of this section to be 3-5 minutes; In step (5), the heating rate is controlled at 1.5℃ / min throughout the process.

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