Liquid silicone rubber for cold-shrink cable accessories and preparation method of liquid silicone rubber

Abstract

The invention provides liquid silicone rubber for a cold-shrink cable accessory and a preparation method of the liquid silicone rubber. The preparation raw materials of the silicone rubber comprise a component A and a component B, the component A is prepared from the following components in parts by weight: 100 to 150 parts of vinyl polydimethylsiloxane, 20 to 50 parts of white carbon black, 0.01 to 20.00 parts of surface treating agent, 0.01 to 10.00 parts of composite modifying agent and 0.001 to 0.500 part of platinum catalyst; the component B is prepared from the following components in parts by weight: 100 to 150 parts of vinyl polydimethylsiloxane, 20 to 50 parts of white carbon black, 0.01 to 20.00 parts of a surface treating agent, 0.01 to 10.00 parts of a composite modifier, 0.1 to 10.0 parts of a cross-linking agent and 0.001 to 0.500 part of an inhibitor. The composite modifier is prepared by carrying out ball milling treatment on nano zinc oxide and a modifier, and the modifier is prepared by reacting a polyamino compound with monoisocyanate. The silicone rubber adopts a specific modifier, has the characteristics of gas-phase flame retardance and condensed-phase flame retardance mechanisms, and can greatly improve the compatibility and dispersity of the silicone rubber in a silicone rubber matrix, thereby realizing long-acting and stable tracking resistance.

Description

Technical Field

[0001] This invention relates to the field of electrical insulation materials technology, and in particular to liquid silicone rubber for cold-shrink cable accessories and its preparation method. Background Technology

[0002] With rapid economic development, people's demand for electricity is increasing, as are their requirements for the reliability and stability of power. Silicone rubber, due to its excellent weather resistance, aging resistance, and hydrophobicity, is widely used in cold-shrink cable accessories. However, cold-shrink cable accessories are affected by various factors such as moisture, salt spray, oxidation, thermal stress, and mechanical stress during long-term use, which places higher demands on the electrical insulation, gas insulation, and mechanical properties of silicone rubber.

[0003] In existing technologies, the tracking resistance of silicone rubber is often improved by adding inorganic fillers such as alumina and titanium dioxide, or nitrogen-based flame retardants. However, these fillers have poor compatibility with the silicone rubber matrix, making it difficult to disperse uniformly within the matrix, and excessive filling can impair the mechanical properties of the silicone rubber. Alternatively, organic-inorganic hybrid materials can be used to modify silicone rubber to improve its performance, but this process is complex and costly. Therefore, it is of great significance to optimize the process and develop novel modifiers using composite technologies to modify silicone rubber and improve the electrical insulation and mechanical properties of liquid silicone rubber for cold-shrink cable accessories. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a liquid silicone rubber for cold-shrink cable accessories and its preparation method. The liquid silicone rubber for cold-shrink cable accessories of this invention employs a specific modifier, possessing both gas-phase and condensed-phase flame-retardant mechanisms, and significantly improving its compatibility and dispersibility within the silicone rubber matrix, thereby achieving long-lasting and stable resistance to tracking.

[0005] To achieve the above objectives, the present invention provides a liquid silicone rubber for cold-shrink cable accessories, the raw materials of which include component A and component B. By mass parts, component A comprises 100-150 parts vinyl polydimethylsiloxane, 20-50 parts silica, 0.01-20.00 parts surface treatment agent, 0.01-10.00 parts composite modifier, and 0.001-0.500 parts platinum catalyst. Component B comprises 100-150 parts vinyl polydimethylsiloxane, 20-50 parts silica, 0.01-20.00 parts surface treatment agent, 0.01-10.00 parts composite modifier, 0.1-10.0 parts crosslinking agent, and 0.001-0.500 parts inhibitor. The composite modifier is prepared by ball milling nano-zinc oxide with the modifier, and the modifier is formed by reacting a polyamine compound with a monoisocyanate. The liquid silicone rubber for cold-shrink cable accessories of the present invention utilizes a composite modifier prepared by ball milling nano-zinc oxide and a modifier in a conventional two-component system of components A and B. In this composite modifier, nano-zinc oxide improves the mechanical properties of the liquid silicone rubber for cold-shrink cable accessories, and through modification by the modifier, it can also be uniformly dispersed in the silicone rubber matrix and exhibit good flow properties. Without altering the original molding process, it can also produce a silicone rubber with both gas-phase and condensed-phase flame-retardant mechanisms, achieving long-lasting and stable resistance to tracking. The specific mechanism is as follows.

[0006] (1) This modifier is formed by reacting a polyamine compound with a monoisocyanate. It utilizes the monoisocyanate to perform surface grafting on the polyamine compound, allowing the isocyanate group (-NCO) of the monoisocyanate to react with the primary amino group of the polyamine compound to form a stable chemical bond. The organic functional group of the monoisocyanate imparts good affinity between the product and the silicone rubber matrix. Furthermore, by ball milling and combining it with nano zinc oxide, the compatibility and dispersion uniformity of nano zinc oxide in the hydrophobic silicone rubber matrix can be greatly improved, avoiding agglomeration and thus fully exerting its resistance to tracking. (2) The nano-zinc oxide and the modifier were prepared by ball milling. The ball milling process not only achieved uniform mixing of the nano-zinc oxide and the modifier, but also enabled the zinc oxide particles to firmly adhere to the surface of the polyamine compound grafted with organic chains through mechanochemical action, thus constructing an organic-inorganic hybrid composite structure. This structure enhances the interfacial interaction between the filler and the matrix, providing a foundation for the long-term stability of performance. (3) The use of nano-zinc oxide instead of other inorganic fillers and modifiers is because, under high-temperature electric arc conditions, nano-zinc oxide can catalytically decompose flammable gases (such as alkanes and alkenes) produced by silicone rubber, promoting their conversion into non-flammable carbon dioxide and water, thereby effectively intervening in the gas-phase combustion process. Many other nano-inorganic fillers do not possess this gas-phase intervention capability. Furthermore, some fillers also have certain photocatalytic activity, which may have adverse effects on the silicone rubber matrix under long-term use or specific environments, thus being detrimental to long-term electrical stability.

[0007] (4) The modifier is formed by the reaction of polyamine compounds and monoisocyanates. Therefore, the modifier can exert the flame retardant effect of condensed phase due to the polyamine structure and -NCO structure. Combined with the gas phase flame retardant intervention ability generated by nano zinc oxide, it can greatly improve the tracking resistance of silicone rubber.

[0008] As one technical solution of the present invention, the particle size of the nano zinc oxide is 20~100nm.

[0009] As a technical solution of the present invention, the polyamino compound is selected from one or more of melamine, octa-aminophenyl cage-like silsesquioxane and octa-aminopropyl cage-like silsesquioxane.

[0010] As a technical solution of the present invention, the monoisocyanate is selected from one or more of aliphatic monoisocyanates, phenyl isocyanates and 3-isocyanatopropyltrimethoxysilane.

[0011] As one technical solution of the present invention, the viscosity of the vinyl polydimethylsiloxane is 500~100000mPa.s and the vinyl content is 0.06~0.43wt.%.

[0012] As a technical solution of the present invention, the crosslinking agent is a hydrogen-containing silicone oil, and the hydrogen content of the hydrogen-containing silicone oil is 0.10~0.75 wt.%.

[0013] As one technical solution of the present invention, the silica is fumed silica produced by gasification and has a specific surface area of ​​200~400 m². 2 / g.

[0014] As one technical solution of the present invention, the platinum catalyst is a Karstedt catalyst or a Speier catalyst, and the platinum content in the platinum catalyst is 1000~5000ppm.

[0015] As a technical solution of the present invention, the surface treatment agent is selected from one or more of dimethyldimethoxysilane, dimethyldiethoxysilane and hexamethyldisilazane.

[0016] As one technical solution of the present invention, the inhibitor is an alkynyl alcohol inhibitor. Further, the alkynyl alcohol inhibitor is selected from at least one of 1-ethynyl-cyclohexanol, 2-methyl-3-butyn-2-ol, and 3-methyl-1-dodecyn-3-ol.

[0017] A second aspect of the present invention provides a method for preparing liquid silicone rubber for cold-shrink cable accessories, comprising the steps of: (1) Preparation of composite modifier The monoisocyanate is grafted onto the surface of the polyamino compound to obtain the modifier. The modifier and the nano zinc oxide are mixed and ball-milled to obtain a composite modifier. The ball milling is carried out in a ball mill at a speed of 350~500 rpm for 3~6 hours. (2) Preparation of component A The silica, surface treatment agent, composite modifier, and a portion of the vinyl polydimethylsiloxane are mixed in an intensive manner, and then the platinum catalyst and the remaining vinyl polydimethylsiloxane are added and mixed. (3) Preparation of component B The silica, surface treatment agent, composite modifier, and a portion of the vinyl polydimethylsiloxane are mixed in an intensive kneading process, and then the crosslinking agent, the inhibitor, and the remaining vinyl polydimethylsiloxane are added and mixed. (4) Preparation of the composition The components A and B are mixed in the same mass ratio and then heated and cured.

[0018] The composite modifier of this invention is prepared through the following steps: First, the modifier is converted into a stable urea bond by reacting a polyamine compound with a monoisocyanate. Then, nano-zinc oxide and the modifier are ball-milled at 350-500 rpm for 3-6 hours. During this process, the intense collisions and friction not only achieve efficient dispersion and uniform mixing of the nano-zinc oxide and the modifier at the microscale, but also significantly enhance the interfacial interaction between them through mechanochemical effects. This results in a tight and stable bond between the modifier molecular chains and the surface of the nano-zinc oxide particles, constructing a structurally robust organic-inorganic hybrid composite. This "mechanochemical activation" process achieves a robust physical composite between the modifier and nano-zinc oxide.

[0019] As one technical solution of the present invention, the polyamino compound and the monoisocyanate are reacted under the action of a catalyst and an inert organic solvent to perform surface grafting. The catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, dibutyltin maleate, dimethyltin maleate, dioctyltin maleate, and monobutyltin oxide. The inert organic solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0020] As one technical solution of the present invention, the surface grafting is carried out at a temperature of 60~85℃ for 3~5h, and the ball milling uses zirconia balls as grinding balls with a ball-to-material ratio of 5~15:1.

[0021] As one technical solution of the present invention, the mass ratio of the modifier to the nano zinc oxide is 1:0.5~3.0.

[0022] As one technical solution of the present invention, the maximum temperature of the mixing is 120~180℃, the mixing time is 1~6h, the curing temperature is 100~150℃, and the curing time is 5~30min. Detailed Implementation

[0023] This invention employs a novel modifier for use in liquid silicone rubber for cold-shrink cable accessories. This modifier has both gas-phase and condensed-phase flame-retardant properties and can be uniformly dispersed in the silicone rubber matrix, thereby achieving long-lasting and stable resistance to tracking in silicone rubber.

[0024] The raw materials for preparing the liquid silicone rubber for cold-shrink cable accessories of the present invention include component A and component B. By mass parts, component A comprises 100-150 parts vinyl polydimethylsiloxane, 20-50 parts silica, 0.01-20.00 parts surface treatment agent, 0.01-10.00 parts composite modifier, and 0.001-0.500 parts platinum catalyst. Component B comprises 100-150 parts vinyl polydimethylsiloxane, 20-50 parts silica, 0.01-20.00 parts surface treatment agent, 0.01-10.00 parts composite modifier, 0.1-10.0 parts crosslinking agent, and 0.001-0.500 parts inhibitor.

[0025] In component A, the content of vinyl polydimethylsiloxane may be, but is not limited to, 100 parts, 105 parts, 110 parts, 115 parts, 120 parts, 125 parts, 130 parts, 135 parts, 140 parts, 145 parts, or 150 parts. The viscosity of vinyl polydimethylsiloxane is 500~100000 mPa·s, and the vinyl content is 0.06~0.43 wt.%. The content of silica may be, but is not limited to, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, or 50 parts. The silica is fumed silica with a specific surface area of ​​200~400 m² / g. 2 / g. The content of the surface treatment agent may be, but is not limited to, 0.01 parts, 0.05 parts, 0.10 parts, 0.50 parts, 1.00 parts, 3.00 parts, 5.00 parts, 8.00 parts, 10.00 parts, 12.00 parts, 14.00 parts, 16.00 parts, 18.00 parts, or 20.00 parts. The surface treatment agent is selected from one or more of dimethyldimethoxysilane, dimethyldiethoxysilane, and hexamethyldisilazane. The content of the composite modifier may be, but is not limited to, 0.01 parts, 0.05 parts, 0.10 parts, 0.50 parts, 1.00 parts, 3.00 parts, 5.00 parts, 8.00 parts, or 10.00 parts. The content of platinum catalyst may be, but is not limited to, 0.001 parts, 0.005 parts, 0.010 parts, 0.050 parts, 0.100 parts, 0.200 parts, 0.300 parts, 0.400 parts, or 0.500 parts. The platinum catalyst is a Karstedt catalyst or a Speier catalyst, and the platinum content in the platinum catalyst is 1000~5000 ppm.

[0026] In component B, the content of vinyl polydimethylsiloxane may be, but is not limited to, 100 parts, 105 parts, 110 parts, 115 parts, 120 parts, 125 parts, 130 parts, 135 parts, 140 parts, 145 parts, or 150 parts. The viscosity of vinyl polydimethylsiloxane is 500~100000 mPa·s, and the vinyl content is 0.06~0.43 wt.%. The content of silica may be, but is not limited to, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, or 50 parts. The silica is fumed silica with a specific surface area of ​​200~400 m². 2 / g. The content of the surface treatment agent may be, but is not limited to, 0.01 parts, 0.05 parts, 0.10 parts, 0.50 parts, 1.00 parts, 3.00 parts, 5.00 parts, 8.00 parts, 10.00 parts, 12.00 parts, 14.00 parts, 16.00 parts, 18.00 parts, or 20.00 parts. The surface treatment agent is selected from one or more of dimethyldimethoxysilane, dimethyldiethoxysilane, and hexamethyldisilazane. The content of the composite modifier may be, but is not limited to, 0.01 parts, 0.05 parts, 0.10 parts, 0.50 parts, 1.00 parts, 3.00 parts, 5.00 parts, 8.00 parts, or 10.00 parts. The content of the crosslinking agent may be, but is not limited to, 0.1 parts, 0.5 parts, 1.0 parts, 2.0 parts, 3.0 parts, 4.0 parts, 5.0 parts, 6.0 parts, 7.0 parts, 8.0 parts, 9.0 parts, or 10.0 parts. The crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.10~0.75 wt.%. The content of the inhibitor may be, but is not limited to, 0.001 parts, 0.005 parts, 0.010 parts, 0.050 parts, 0.100 parts, 0.200 parts, 0.300 parts, 0.400 parts, or 0.500 parts. The inhibitor is an alkynyl alcohol inhibitor, and further, the inhibitor is selected from at least one of 1-ethynyl-cyclohexanol, 2-methyl-3-butyn-2-ol, and 3-methyl-1-dodecyn-3-ol.

[0027] The composite modifier of this invention is prepared by ball milling nano-zinc oxide and a modifier. The modifier is formed by reacting a polyamine compound with a monoisocyanate. The polyamine compound is selected from one or more of melamine, octa-aminophenyl cage-type silsesquioxane, and octa-aminopropyl cage-type silsesquioxane. The monoisocyanate is selected from one or more of aliphatic monoisocyanates, phenyl isocyanates, and 3-isocyanopropyltrimethoxysilane. The structural formula of the aliphatic monoisocyanate may be CH3(CH2). nNCO, where n is 5-17, and further, the aliphatic monoisocyanate can be hexyl isocyanate, dodecyl isocyanate, or octadecyl isocyanate. The polyamino compound and the monoisocyanate react in the presence of a catalyst and an inert organic solvent to perform surface grafting. This surface grafting is carried out at a temperature of 60-85°C for 3-5 hours, wherein the molar ratio of the isocyanate group to the amino group is 1:1, and the molar ratio of 3-isocyanatopropyltrimethoxysilane to the polyamino compound is between 1 and 2 (inclusive). The catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, dibutyltin maleate, dimethyltin maleate, dioctyltin maleate, and monobutyltin oxide. The inert organic solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone. Ball milling is performed in a ball mill at a speed of 350-500 rpm for 3-6 hours. For example, the speed can be, but is not limited to, 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm, 400 rpm, 410 rpm, 420 rpm, 430 rpm, 440 rpm, 450 rpm, 460 rpm, 470 rpm, 480 rpm, 490 rpm, or 500 rpm. The time can be, but is not limited to, 3 hours, 4 hours, 5 hours, or 6 hours. The ball milling speed and time need to generate sufficient energy to avoid insufficient energy, which would prevent effective dispersion of nano-zinc oxide and poor composite effect between nano-zinc oxide and the modifier. Excessive speed or time should also be avoided, as it can lead to over-grinding. This may damage the molecular structure of the modifier, reducing its flame retardant efficiency, and may also reduce the size of the nano-zinc oxide grains or even cause a crystal transformation. Excessive surface energy can lead to re-agglomeration during subsequent processing. The particle size of nano zinc oxide is 20~100nm, the mass ratio of modifier to nano zinc oxide is 1:0.5~3.0, and zirconia balls are used as grinding balls during ball milling with a ball-to-material ratio of 5~15:1.

[0028] The preparation method of liquid silicone rubber for cold shrink cable accessories of the present invention includes the following steps: (1) preparation of composite modifier; (2) preparation of component A; (3) preparation of component B and (4) preparation of composition.

[0029] The preparation of the composite modifier in step (1) is the same as described above.

[0030] Step (2) Preparation of component A involves mixing silica, surface treatment agent, composite modifier, and a portion of vinyl polydimethylsiloxane in an intensive mixing process, followed by adding a platinum catalyst and the remaining vinyl polydimethylsiloxane for further mixing. The maximum mixing temperature is 120-180℃, and the mixing time is 1-6 hours. Pre-mixing can be performed first, followed by further mixing at a higher temperature. Two-thirds of the vinyl polydimethylsiloxane by mass can be mixed with silica, surface treatment agent, and composite modifier initially, and the remaining one-third by mass is added when the platinum catalyst is added. The parameters of the vinyl polydimethylsiloxane added before and after intensive mixing can be the same or different.

[0031] Step (3) Preparation of component B involves mixing silica, surface treatment agent, composite modifier, and a portion of vinyl polydimethylsiloxane in an intensive mixing process, followed by adding a crosslinking agent, inhibitor, and the remaining vinyl polydimethylsiloxane for further mixing. The maximum mixing temperature is 120-180℃, and the mixing time is 1-6 hours. Pre-mixing can be performed first, followed by increasing the temperature for further intensive mixing. Two-thirds of the vinyl polydimethylsiloxane mass can be mixed with silica, surface treatment agent, and composite modifier initially, and the remaining one-third mass is mixed when adding the crosslinking agent and inhibitor. The parameters of the vinyl polydimethylsiloxane added before and after intensive mixing can be the same or different.

[0032] In step (2) preparation of component A and step (3) preparation of component B, silica, surface treatment agent, composite modifier and part of vinyl polydimethylsiloxane can be mixed to obtain base rubber, and then platinum catalyst can be added to the base rubber to obtain component A, and crosslinking agent and inhibitor can be added to the base rubber to obtain component B.

[0033] Step (4) involves preparing the composition by mixing component A and component B in the same mass ratio and then heating and curing. The curing temperature is 100~150℃ and the curing time is 5~30min.

[0034] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0035] Example 1 This embodiment describes a liquid silicone rubber for cold-shrink cable accessories, prepared from raw materials including component A and component B. By mass, component A comprises 100 parts of vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 13 parts of vinyl polydimethylsiloxane (viscosity 50000 mPa·s, vinyl content 0.075 wt.%), and 30 parts of silica (BET 300 m...). 2Component B consists of 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 7 parts vinyl polydimethylsiloxane (viscosity 80000 mPa·s, vinyl content 0.07 wt.%), and 30 parts silica (BET 300 m... 2 The ingredients include 5 parts of dimethyldiethoxysilane, 3 parts of composite modifier, 6 parts of hydrogen-containing silicone oil (hydrogen content of 0.25 wt.%), and 0.01 parts of 1-ethynyl-1-cyclohexanol.

[0036] The preparation method of the liquid silicone rubber for the cold-shrink cable accessory includes the following steps.

[0037] (1) Preparation of composite modifier 3.47 g of octaaminophenyl cage-type silsesquioxane was dissolved in 250 mL of N,N-dimethylformamide and sonicated for 15 min. Under nitrogen protection and stirring, 0.018 g of dibutyltin dilaurate was added, followed by the slow dropwise addition of 1.23 g of 3-isocyanatopropyltrimethoxysilane and 5.32 g of octadecyl isocyanate. The temperature was raised to 75 °C and the reaction was carried out for 4 h. After the reaction was completed, the mixture was cooled to room temperature, and 200 mL of petroleum ether was slowly poured in and stirred for 30 min. The mixture was then filtered through a Buchner funnel and the solid product was washed three times with a large amount of petroleum ether to completely remove unreacted 3-isocyanatopropyltrimethoxysilane, octadecyl isocyanate, and N,N-dimethylformamide to obtain the modified product. The modified material was then mixed with nano zinc oxide (particle size 50nm) at a mass ratio of 1:1 and placed in a ball mill (using zirconia grinding balls, ball-to-material ratio of 10:1) and ball-milled at 400rpm for 5h to obtain the composite modifier.

[0038] (2) Preparation of component A Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 50,000 mPa·s and a platinum catalyst were added to the base rubber and mixed evenly.

[0039] (3) Preparation of component B Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 80,000 mPa·s, hydrogen-containing silicone oil, and 1-ethynyl-1-cyclohexanol were added to the base rubber and mixed evenly.

[0040] (4) Preparation of the composition Mix components A and B at a mass ratio of 1:1 and cure at 120°C for 10 minutes.

[0041] Example 2 This embodiment describes a liquid silicone rubber for cold-shrink cable accessories, prepared from raw materials including component A and component B. By mass, component A comprises 100 parts of vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 13 parts of vinyl polydimethylsiloxane (viscosity 50000 mPa·s, vinyl content 0.075 wt.%), and 30 parts of silica (BET 300 m...). 2 Component B consists of 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 7 parts vinyl polydimethylsiloxane (viscosity 80000 mPa·s, vinyl content 0.07 wt.%), and 30 parts silica (BET 300 m... 2 The ingredients include 5 parts of dimethyldiethoxysilane, 3 parts of composite modifier, 6 parts of hydrogen-containing silicone oil (hydrogen content of 0.25 wt.%), and 0.01 parts of 1-ethynyl-1-cyclohexanol.

[0042] The preparation method of the liquid silicone rubber for the cold-shrink cable accessory includes the following steps.

[0043] (1) Preparation of composite modifier 18.9 g of melamine was dissolved in 250 mL of N,N-dimethylformamide and sonicated for 15 min. Under nitrogen protection and stirring, 0.165 g of dibutyltin dilaurate was added, followed by the slow dropwise addition of 30.8 g of 3-isocyanatopropyltrimethoxysilane and 35.7 g of phenyl isocyanate. The mixture was heated to 75 °C and reacted for 4 h. After the reaction was completed, the mixture was cooled to room temperature, and 200 mL of petroleum ether was slowly poured in and stirred for 30 min. The mixture was then filtered through a Buchner funnel and the solid product was washed three times with a large amount of petroleum ether to completely remove unreacted 3-isocyanatopropyltrimethoxysilane, phenyl isocyanate, and N,N-dimethylformamide, yielding the modified product. The modified material was then mixed with nano zinc oxide (particle size 50nm) at a mass ratio of 1:1 and placed in a ball mill (using zirconia grinding balls, ball-to-material ratio of 10:1) and ball-milled at 400rpm for 5h to obtain the composite modifier.

[0044] (2) Preparation of component A Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 50,000 mPa·s and a platinum catalyst were added to the base rubber and mixed evenly.

[0045] (3) Preparation of component B Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 80,000 mPa·s, hydrogen-containing silicone oil, and 1-ethynyl-1-cyclohexanol were added to the base rubber and mixed evenly.

[0046] (4) Preparation of the composition Mix components A and B at a mass ratio of 1:1 and cure at 120°C for 10 minutes.

[0047] Example 3 This embodiment describes a liquid silicone rubber for cold-shrink cable accessories, prepared from raw materials including component A and component B. By mass, component A comprises 100 parts of vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 13 parts of vinyl polydimethylsiloxane (viscosity 50000 mPa·s, vinyl content 0.075 wt.%), and 30 parts of silica (BET 300 m...). 2Component B consists of 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 7 parts vinyl polydimethylsiloxane (viscosity 80000 mPa·s, vinyl content 0.07 wt.%), and 30 parts silica (BET 300 m... 2 The ingredients include 5 parts of dimethyldiethoxysilane, 3 parts of composite modifier, 6 parts of hydrogen-containing silicone oil (hydrogen content of 0.25 wt.%), and 0.01 parts of 1-ethynyl-1-cyclohexanol.

[0048] The preparation method of the liquid silicone rubber for the cold-shrink cable accessory includes the following steps.

[0049] (1) Preparation of composite modifier 6.56 g of octaaminopropyl cage-like silsesquioxane was dissolved in 250 mL of N,N-dimethylformamide and sonicated for 15 min. Under nitrogen protection and stirring, 0.026 g of dibutyltin dilaurate was added, followed by the slow dropwise addition of 3.08 g of 3-isocyanopropyltrimethoxysilane and 5.72 g of hexyl isocyanate. The temperature was raised to 75 °C and the reaction was carried out for 4 h. After the reaction was completed, the mixture was cooled to room temperature, and 200 mL of petroleum ether was slowly poured in and stirred for 30 min. The mixture was then filtered through a Buchner funnel and the solid product was washed three times with a large amount of petroleum ether to completely remove unreacted 3-isocyanopropyltrimethoxysilane, hexyl isocyanate, and N,N-dimethylformamide to obtain the modified product. The modified material was then mixed with nano zinc oxide (particle size 50nm) at a mass ratio of 1:1 and placed in a ball mill (using zirconia grinding balls, ball-to-material ratio of 10:1) and ball-milled at 400rpm for 5h to obtain the composite modifier.

[0050] (2) Preparation of component A Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 50,000 mPa·s and a platinum catalyst were added to the base rubber and mixed evenly.

[0051] (3) Preparation of component B Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 80,000 mPa·s, hydrogen-containing silicone oil, and 1-ethynyl-1-cyclohexanol were added to the base rubber and mixed evenly.

[0052] (4) Preparation of the composition Mix components A and B at a mass ratio of 1:1 and cure at 120°C for 10 minutes.

[0053] Example 4 This embodiment describes a liquid silicone rubber for cold-shrink cable accessories, prepared from raw materials including component A and component B. By mass, component A comprises 100 parts vinyl polydimethylsiloxane (viscosity 80000 mPa·s, vinyl content 0.07 wt.%), 13 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), and 30 parts silica (BET 300 m...). 2 Component B consists of 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 7 parts vinyl polydimethylsiloxane (viscosity 50000 mPa·s, vinyl content 0.075 wt.%), and 30 parts silica (BET 300 m... 2 / g), 5 parts dimethyldiethoxysilane, 3 parts composite modifier, 6.2 parts hydrogen-containing silicone oil (hydrogen content of 0.25wt.%) and 0.01 parts 1-ethynyl-1-cyclohexanol.

[0054] The preparation method of the liquid silicone rubber for the cold-shrink cable accessory includes the following steps.

[0055] (1) Preparation of composite modifier 3.47 g of octaaminophenyl cage-type silsesquioxane was dissolved in 250 mL of dimethyl sulfoxide and sonicated for 20 min. Under nitrogen protection and stirring, 0.010 g of dibutyltin diacetate was added, followed by the slow dropwise addition of 1.23 g of 3-isocyanopropyltrimethoxysilane and 2.15 g of phenyl isocyanate. The temperature was raised to 85 °C and the reaction was carried out for 3 h. After the reaction was completed, the mixture was cooled to room temperature, and 150 mL of petroleum ether was slowly poured in and stirred for 45 min. The mixture was then filtered through a Buchner funnel and the solid product was washed twice with a large amount of petroleum ether to completely remove unreacted phenyl isocyanate and 3-isocyanopropyltrimethoxysilane, obtaining the modified product. The modified product was then mixed with nano-zinc oxide (particle size 100 nm) at a mass ratio of 1:1.5 and placed in a ball mill (using zirconia grinding balls, ball-to-material ratio 15:1) at a speed of 350 rpm for 6 h to obtain the composite modifier.

[0056] (2) Preparation of component A Vinyl polydimethylsiloxane with a viscosity of 80000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 100°C for 1 hour, then heated to 160°C and stirred for another 3 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 100000 mPa·s and a platinum catalyst were added to the base rubber and mixed evenly.

[0057] (3) Preparation of component B Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 3 hours, then heated to 150°C and stirred for another 3 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 50,000 mPa·s, hydrogen-containing silicone oil, and 1-ethynyl-1-cyclohexanol were added to the base rubber and mixed evenly.

[0058] (4) Preparation of the composition Mix components A and B at a mass ratio of 1:1 and cure at 120°C for 10 minutes.

[0059] Example 5 This embodiment describes a liquid silicone rubber for cold-shrink cable accessories, prepared from raw materials including component A and component B. By mass, component A comprises 100 parts of vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 10 parts of vinyl polydimethylsiloxane (viscosity 50000 mPa·s, vinyl content 0.075 wt.%), 10 parts of vinyl polydimethylsiloxane (viscosity 500 mPa·s, vinyl content 0.43 wt.%), and 45 parts of silica (BET 400 m...2 Component B consists of 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 16 parts vinyl polydimethylsiloxane (viscosity 80000 mPa·s, vinyl content 0.07 wt.%), and 45 parts silica (BET 250 m... 2 / g), 10 parts hexamethyldisilazane, 8 parts composite modifier, 4 parts hydrogen-containing silicone oil (hydrogen content of 0.50wt.%) and 0.05 parts 3-methyl-1-dodecyn-3-ol.

[0060] The preparation method of the liquid silicone rubber for the cold-shrink cable accessory includes the following steps.

[0061] (1) Preparation of composite modifier 3.47 g of octaaminophenyl cage-type silsesquioxane was dissolved in 250 mL of N,N-dimethylformamide and sonicated for 15 min. Under nitrogen protection and stirring, 0.018 g of dibutyltin dilaurate was added, followed by the slow dropwise addition of 1.23 g of 3-isocyanatopropyltrimethoxysilane and 3.81 g of dodecyl isocyanate. The temperature was raised to 85 °C and the reaction was carried out for 3 h. After the reaction was completed, the mixture was cooled to room temperature, and 200 mL of petroleum ether was slowly poured in and stirred for 30 min. The mixture was then filtered through a Buchner funnel and the solid product was washed three times with a large amount of petroleum ether to completely remove unreacted 3-isocyanatopropyltrimethoxysilane, dodecyl isocyanate, and N,N-dimethylformamide to obtain the modified product. The modified material was then mixed with nano zinc oxide (particle size 50nm) at a mass ratio of 1:1 and placed in a ball mill (using zirconia grinding balls, ball-to-material ratio of 13:1) and ball-milled at 450rpm for 3h to obtain the composite modifier.

[0062] (2) Preparation of component A Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and hexamethyldisilazane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 50,000 mPa·s, vinyl polydimethylsiloxane with a viscosity of 500 mPa·s, and platinum catalyst were added to the base rubber and mixed evenly.

[0063] (3) Preparation of component B Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), and silica were added to a mixer. The mixture was stirred at 80°C for 3 hours, then heated to 135°C and stirred for another 6 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 80,000 mPa·s, hydrogen-containing silicone oil, and 3-methyl-1-dodecyn-3-ol were added to the base rubber and mixed evenly.

[0064] (4) Preparation of the composition Mix components A and B at a mass ratio of 1:1 and cure at 150°C for 5 minutes.

[0065] Comparative Example 1 This comparative example is a liquid silicone rubber for cold-shrink cable accessories, prepared from raw materials including component A and component B. By mass parts, component A comprises 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 16 parts vinyl polydimethylsiloxane (viscosity 50000 mPa·s, vinyl content 0.075 wt.%), and 30 parts silica (BET 300 m... 2 Component B consists of 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 10 parts vinyl polydimethylsiloxane (viscosity 80000 mPa·s, vinyl content 0.07 wt.%), and 30 parts silica (BET 300 m... 2 / g), 5 parts dimethyldiethoxysilane, 6.2 parts hydrogen-containing silicone oil (hydrogen content of 0.25wt.%) and 0.01 parts 1-ethynyl-1-cyclohexanol.

[0066] The preparation method of the liquid silicone rubber for the cold-shrink cable accessory includes the following steps.

[0067] (1) Preparation of component A Vinyl polydimethylsiloxane, silica, and dimethyldiethoxysilane with a viscosity of 100,000 mPa·s were added to a mixer and mixed at 80°C for 2 hours. The temperature was then raised to 150°C and mixed for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 50,000 mPa·s and a platinum catalyst were added to the base rubber and mixed thoroughly.

[0068] (2) Preparation of component B Vinyl polydimethylsiloxane, silica, and dimethyldiethoxysilane with a viscosity of 100,000 mPa·s were added to a mixer and mixed at 80°C for 2 hours. The temperature was then raised to 150°C and mixed for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 80,000 mPa·s, hydrogen-containing silicone oil, and 1-ethynyl-1-cyclohexanol were added to the base rubber and mixed thoroughly.

[0069] (3) Preparation of the composition Mix components A and B at a mass ratio of 1:1 and cure at 120°C for 10 minutes.

[0070] Comparative Example 2 This embodiment describes a liquid silicone rubber for cold-shrink cable accessories, prepared from raw materials including component A and component B. By mass, component A comprises 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 16 parts vinyl polydimethylsiloxane (viscosity 50000 mPa·s, vinyl content 0.075 wt.%), and 30 parts silica (BET 300 m...). 2 Component B consists of 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 10 parts vinyl polydimethylsiloxane (viscosity 80000 mPa·s, vinyl content 0.07 wt.%), and 30 parts silica (BET 300 m... 2 / g), 5 parts dimethyldiethoxysilane, 3 parts modifier, 6.2 parts hydrogen-containing silicone oil (hydrogen content of 0.25wt.%) and 0.01 parts 1-ethynyl-1-cyclohexanol.

[0071] The preparation method of the liquid silicone rubber for the cold-shrink cable accessory includes the following steps.

[0072] (1) Preparation of modifier 3.47 g of octaaminophenyl cage-type silsesquioxane was dissolved in 250 mL of N,N-dimethylformamide and sonicated for 15 min. Under nitrogen protection and stirring, 0.018 g of dibutyltin dilaurate was added, followed by the slow dropwise addition of 1.23 g of 3-isocyanatopropyltrimethoxysilane and 5.32 g of octadecyl isocyanate. The temperature was raised to 75 °C and the reaction was carried out for 4 h. After the reaction was completed, the mixture was cooled to room temperature, and 200 mL of petroleum ether was slowly poured in and stirred for 30 min. The mixture was then filtered through a Buchner funnel and the solid product was washed three times with a large amount of petroleum ether to completely remove unreacted 3-isocyanatopropyltrimethoxysilane, octadecyl isocyanate, and N,N-dimethylformamide to obtain the modified product.

[0073] (2) Preparation of component A Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 50,000 mPa·s and a platinum catalyst were added to the base rubber and mixed evenly.

[0074] (3) Preparation of component B Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 80,000 mPa·s, hydrogen-containing silicone oil, and 1-ethynyl-1-cyclohexanol were added to the base rubber and mixed evenly.

[0075] (4) Preparation of the composition Mix components A and B at a mass ratio of 1:1 and cure at 120°C for 10 minutes.

[0076] Comparative Example 3 This comparative example is a liquid silicone rubber for cold-shrink cable accessories, prepared from raw materials including component A and component B. By mass parts, component A comprises 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 16 parts vinyl polydimethylsiloxane (viscosity 50000 mPa·s, vinyl content 0.075 wt.%), and 30 parts silica (BET 300 m... 2 Component B consists of 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 10 parts vinyl polydimethylsiloxane (viscosity 80000 mPa·s, vinyl content 0.07 wt.%), and 30 parts silica (BET 300 m... 2 / g), 5 parts dimethyldiethoxysilane, 3 parts nano zinc oxide (particle size 50nm), 6.2 parts hydrogen-containing silicone oil (hydrogen content 0.25wt.%) and 0.01 parts 1-ethynyl-1-cyclohexanol.

[0077] The preparation method of the liquid silicone rubber for the cold-shrink cable accessory includes the following steps.

[0078] (1) Preparation of component A Vinyl polydimethylsiloxane (100,000 mPa·s), nano zinc oxide, silica, and dimethyldiethoxysilane were added to a mixer and mixed at 80°C for 2 hours. The temperature was then increased to 150°C and mixed for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane (50,000 mPa·s) and a platinum catalyst were added to the base rubber and mixed thoroughly.

[0079] (2) Preparation of component B Vinyl polydimethylsiloxane (100,000 mPa·s), nano zinc oxide, silica, and dimethyldiethoxysilane were added to a Banbury mixer and mixed at 80°C for 2 hours. The temperature was then raised to 150°C and mixed for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane (80,000 mPa·s), hydrogen-containing silicone oil, and 1-ethynyl-1-cyclohexanol were added to the base rubber and mixed thoroughly.

[0080] (3) Preparation of the composition Mix components A and B at a mass ratio of 1:1 and cure at 120°C for 10 minutes.

[0081] Comparative Example 4 This comparative example is a liquid silicone rubber for cold-shrink cable accessories, prepared from raw materials including component A and component B. By mass parts, component A comprises 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 16 parts vinyl polydimethylsiloxane (viscosity 50000 mPa·s, vinyl content 0.075 wt.%), and 30 parts silica (BET 300 m... 2 Component B consists of 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 10 parts vinyl polydimethylsiloxane (viscosity 80000 mPa·s, vinyl content 0.07 wt.%), and 30 parts silica (BET 300 m...g). The composition of component B includes 5 parts dimethyldiethoxysilane, 3 parts composite modifier, and 0.15 parts Karstedt catalyst with a platinum concentration of 3000 ppm. 2 / g), 5 parts dimethyldiethoxysilane, 3 parts composite modifier, 6.2 parts hydrogen-containing silicone oil (hydrogen content of 0.25wt.%) and 0.01 parts 1-ethynyl-1-cyclohexanol.

[0082] The preparation method of the liquid silicone rubber for the cold-shrink cable accessory includes the following steps.

[0083] (1) Preparation of composite modifier 3.47 g of octaaminophenyl cage-type silsesquioxane was dissolved in 250 mL of N,N-dimethylformamide and sonicated for 15 min. Under nitrogen protection and stirring, 0.018 g of dibutyltin dilaurate was added, followed by the slow dropwise addition of 1.23 g of 3-isocyanatopropyltrimethoxysilane and 5.32 g of octadecyl isocyanate. The temperature was raised to 75 °C and the reaction was carried out for 4 h. After the reaction was completed, the mixture was cooled to room temperature, and 200 mL of petroleum ether was slowly poured in and stirred for 30 min. The mixture was then filtered through a Buchner funnel and the solid product was washed three times with a large amount of petroleum ether to completely remove unreacted 3-isocyanatopropyltrimethoxysilane, octadecyl isocyanate, and N,N-dimethylformamide to obtain the modified product. The modified material was then mixed with alumina (particle size 5 μm) at a mass ratio of 1:1 and placed in a ball mill (using zirconia grinding balls, ball-to-material ratio of 10:1) and ball-milled at 400 rpm for 5 hours to obtain the composite modifier.

[0084] (2) Preparation of component A Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 50,000 mPa·s and a platinum catalyst were added to the base rubber and mixed evenly.

[0085] (3) Preparation of component B Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 80,000 mPa·s, hydrogen-containing silicone oil, and 1-ethynyl-1-cyclohexanol were added to the base rubber and mixed evenly.

[0086] (4) Preparation of the composition Mix components A and B at a mass ratio of 1:1 and cure at 120°C for 10 minutes.

[0087] Comparative Example 5 This comparative example is a liquid silicone rubber for cold-shrink cable accessories, prepared from raw materials including component A and component B. By mass parts, component A comprises 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 16 parts vinyl polydimethylsiloxane (viscosity 50000 mPa·s, vinyl content 0.075 wt.%), and 30 parts silica (BET 300 m... 2Component B consists of 100 parts vinyl polydimethylsiloxane (viscosity 100000 mPa·s, vinyl content 0.06 wt.%), 10 parts vinyl polydimethylsiloxane (viscosity 80000 mPa·s, vinyl content 0.07 wt.%), and 30 parts silica (BET 300 m...g). The composition of component B includes 5 parts dimethyldiethoxysilane, 3 parts composite modifier, and 0.15 parts Karstedt catalyst with a platinum concentration of 3000 ppm. 2 / g), 5 parts dimethyldiethoxysilane, 3 parts composite modifier, 6.2 parts hydrogen-containing silicone oil (hydrogen content of 0.25wt.%) and 0.01 parts 1-ethynyl-1-cyclohexanol.

[0088] The preparation method of the liquid silicone rubber for the cold-shrink cable accessory includes the following steps.

[0089] (1) Preparation of composite modifier 3.47 g of octaaminophenyl cage-type silsesquioxane was dissolved in 250 mL of N,N-dimethylformamide and sonicated for 15 min. Under nitrogen protection and stirring, 0.018 g of dibutyltin dilaurate was added, followed by the slow dropwise addition of 1.23 g of 3-isocyanatopropyltrimethoxysilane and 5.32 g of octadecyl isocyanate. The temperature was raised to 75 °C and the reaction was carried out for 4 h. After the reaction was completed, the mixture was cooled to room temperature, and 200 mL of petroleum ether was slowly poured in and stirred for 30 min. The mixture was then filtered through a Buchner funnel and the solid product was washed three times with a large amount of petroleum ether to completely remove unreacted 3-isocyanatopropyltrimethoxysilane, octadecyl isocyanate, and N,N-dimethylformamide to obtain the modified product. The modified product was then mixed with nano-zinc oxide (particle size 50 nm) at a mass ratio of 1:1 and stirred at 600 rpm for 3 h in a high-speed mixer to obtain the composite modifier.

[0090] (2) Preparation of component A Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 50,000 mPa·s and a platinum catalyst were added to the base rubber and mixed evenly.

[0091] (3) Preparation of component B Vinyl polydimethylsiloxane with a viscosity of 100,000 mPa·s, the composite modifier obtained in step (1), silica, and dimethyldiethoxysilane were added to a mixer. The mixture was stirred at 80°C for 2 hours, then heated to 150°C and stirred for another 4 hours. The mixture was then cooled to obtain the base rubber. Vinyl polydimethylsiloxane with a viscosity of 80,000 mPa·s, hydrogen-containing silicone oil, and 1-ethynyl-1-cyclohexanol were added to the base rubber and mixed evenly.

[0092] (4) Preparation of the composition Mix components A and B at a mass ratio of 1:1 and cure at 120°C for 10 minutes.

[0093] The silicone rubbers prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to performance tests, and the results are shown in Table 1. Hardness was tested according to GB / T 531.1-2008 Test method for indentation hardness of vulcanized rubber or thermoplastic rubber—Part 1: Shore hardness tester method (Shore hardness) standard. Tensile strength and elongation were tested according to GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber standard. Tear strength was tested according to GB / T 529-2008 Determination of tear strength of vulcanized rubber or thermoplastic rubber (trouser-shaped, right-angled, and crescent-shaped specimens) standard. Breakdown strength was tested according to GB / T 1695-2005 Determination of power frequency breakdown voltage strength and withstand voltage of vulcanized rubber standard. The tracking resistance level was tested according to the standard GB / T 6553-2014 "Test Methods for Evaluation of Tracking and Corrosion Resistance of Electrical Insulation Materials Used in Harsh Environmental Conditions". Flame retardancy was tested according to the standard UL94-2023 "Test for Flammability of Plastic Materials for Equipment and Electrical Components".

[0094] Table 1. Performance test results of silicone rubbers prepared in Examples 1-5 and Comparative Examples 1-5

[0095] As shown in Table 1, the liquid silicone rubber for cold-shrink cable accessories of the present invention, in the conventional two-component system of component A and component B, uses a composite modifier prepared by ball milling nano zinc oxide and modifier, which enables the silicone rubber to have better mechanical properties as well as better resistance to tracking and flame retardancy.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A liquid silicone rubber for cold-shrink cable accessories, characterized in that, The raw materials for preparation include component A and component B. By mass, component A comprises 100-150 parts vinyl polydimethylsiloxane, 20-50 parts silica, 0.01-20.00 parts surface treatment agent, 0.01-10.00 parts composite modifier, and 0.001-0.500 parts platinum catalyst. Component B comprises 100-150 parts vinyl polydimethylsiloxane, 20-50 parts silica, 0.01-20.00 parts surface treatment agent, 0.01-10.00 parts composite modifier, 0.1-10.0 parts crosslinking agent, and 0.001-0.500 parts inhibitor. The composite modifier is prepared by ball milling nano-zinc oxide and the modifier, and the modifier is formed by reacting a polyamine compound with a monoisocyanate.

2. The liquid silicone rubber for cold-shrink cable accessories according to claim 1, characterized in that, The particle size of the nano zinc oxide is 20~100nm.

3. The liquid silicone rubber for cold-shrink cable accessories according to claim 1, characterized in that, The polyamino compound is selected from one or more of melamine, octa-aminophenyl cage silsesquioxane, and octa-aminopropyl cage silsesquioxane.

4. The liquid silicone rubber for cold-shrink cable accessories according to claim 1, characterized in that, The monoisocyanate is selected from one or more of aliphatic monoisocyanates, phenyl isocyanates, and 3-isocyanatopropyltrimethoxysilane.

5. The liquid silicone rubber for cold-shrink cable accessories according to claim 1, characterized in that, Includes at least one of the following features (I) to (VI): (I) The vinyl polydimethylsiloxane has a viscosity of 500~100000 mPa·s and a vinyl content of 0.06~0.43 wt.%; (II) The crosslinking agent is a hydrogen-containing silicone oil, wherein the hydrogen content of the hydrogen-containing silicone oil is 0.10~0.75 wt.%; (III) The silica is fumed silica produced by the gas phase method, and has a specific surface area of ​​200~400 m². 2 / g; (IV) The platinum catalyst is a Karstedt catalyst or a Speier catalyst, and the platinum content in the platinum catalyst is 1000~5000ppm; (V) The surface treatment agent is selected from one or more of dimethyldimethoxysilane, dimethyldiethoxysilane, and hexamethyldisilazane; (VI) The inhibitor is an alkynyl alcohol inhibitor.

6. A method for preparing liquid silicone rubber for cold-shrink cable accessories according to any one of claims 1 to 5, characterized in that, Including the following steps: (1) Preparation of composite modifier The monoisocyanate is grafted onto the surface of the polyamino compound to obtain the modifier. The modifier and the nano zinc oxide are mixed and ball-milled to obtain a composite modifier. The ball milling is carried out in a ball mill at a speed of 350~500 rpm for 3~6 hours. (2) Preparation of component A The silica, surface treatment agent, composite modifier, and a portion of the vinyl polydimethylsiloxane are mixed in an intensive manner, and then the platinum catalyst and the remaining vinyl polydimethylsiloxane are added and mixed. (3) Preparation of component B The silica, surface treatment agent, composite modifier, and a portion of the vinyl polydimethylsiloxane are mixed in an intensive kneading process, and then the crosslinking agent, the inhibitor, and the remaining vinyl polydimethylsiloxane are added and mixed. (4) Preparation of the composition The components A and B are mixed in the same mass ratio and then heated and cured.

7. The method for preparing liquid silicone rubber for cold-shrink cable accessories according to claim 6, characterized in that, The polyamino compound and the monoisocyanate are reacted in the presence of a catalyst and an inert organic solvent to perform surface grafting. The catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, dibutyltin maleate, dimethyltin maleate, dioctyltin maleate, and monobutyltin oxide. The inert organic solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

8. The method for preparing liquid silicone rubber for cold-shrink cable accessories according to claim 6, characterized in that, The surface grafting is carried out at a temperature of 60~85℃ for 3~5 hours, and the ball milling uses zirconia balls as grinding balls with a ball-to-material ratio of 5~15:

1.

9. The method for preparing liquid silicone rubber for cold-shrink cable accessories according to claim 6, characterized in that, The mass ratio of the modifier to the nano zinc oxide is 1:0.5~3.

0.

10. The method for preparing liquid silicone rubber for cold-shrink cable accessories according to claim 6, characterized in that, The maximum temperature of the mixing process is 120~180℃, the mixing time is 1~6h, the curing temperature is 100~150℃, and the curing time is 5~30min.

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