A process for the preparation of a silicone rubber / crosslinked polyethylene composite medium for cable accessories and its use

Abstract

A method for preparing and applying a silicone rubber / crosslinked polyethylene composite dielectric for cable accessories is disclosed, belonging to the field of composite dielectric preparation methods and applications. The purpose of this invention is to solve the problem in existing technologies where, with long-term cable operation, silicone grease diffuses into the silicone rubber, causing swelling, leading to a decrease in the insulation performance of the silicone rubber and an increase in the failure rate. The method includes: 1. Preparing silicone rubber; 2. Preparing crosslinked polyethylene; 3. Preparing a doped and modified silicone grease; 4. Coating the modified silicone grease onto the surface of the silicone rubber, and then covering it with crosslinked polyethylene. 2,3,5,6-Tetrafluoro-7,7',8,8'-Tetracyanodimethyl-p-benzoquinone is introduced into the silicone grease as a filler to construct carrier traps, hindering carrier injection and transport. Under the synergistic effect of this filler and silicone grease, intermolecular forces are enhanced, silicone grease slippage is reduced, and thus the electrical insulation properties of the silicone rubber-crosslinked polyethylene composite interface are further increased.

Description

Technical Field

[0001] This invention pertains to the preparation method and application of composite media. Background Technology

[0002] In the actual operation of cable systems, cable accessories are weak points in insulation and prone to failure. According to statistics from the State Grid Corporation of China on cable operation failures, ignoring external force damage, 70% of cable failures are caused by the failure of cable accessory insulation. Therefore, improving the insulation performance of cable accessories is of great significance. Silicone rubber, due to its excellent insulation properties and superior mechanical strength, is commonly used as the main insulation material for cable accessories and has been widely applied. Statistics on domestic cable accessory and cable body failures show that the failure rate at cable joints accounts for 31%, and 97% of joint failures originate from interface discharge. The interface characteristics at cable joints are closely related to the optimized design of the joint structure, the clamping force during cable accessory assembly, and also to the installation process and the cable operating environment. During the actual installation of medium and low voltage cables, a layer of silicone grease is applied to the inside of the cable joint and the cable insulation contact surface to increase the sealing of the interface and the lubrication of the installation process. It also enhances the insulation performance between the cable and the cable joint at the interface. However, with long-term operation of the cable, the silicone grease diffuses into the silicone rubber, causing swelling and leading to a decrease in the insulation performance of the silicone rubber. Currently, there is no solution to address the degradation of silicone rubber insulation performance caused by silicone grease swelling, thus reducing the failure rate of composite interfaces in cable accessories. Summary of the Invention

[0003] The purpose of this invention is to solve the problem in the prior art that as cables operate for a long time, silicone grease diffuses into the silicone rubber, causing swelling, which leads to a decrease in the insulation performance of the silicone rubber and an increase in the failure rate. The invention provides a method for preparing and applying a silicone rubber / cross-linked polyethylene composite medium for cable accessories.

[0004] A method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories is specifically carried out according to the following steps:

[0005] I. Preparation of silicone rubber:

[0006] ① Weigh out component A and component B of the silicone rubber;

[0007] ② Stir component A of silicone rubber under a frequency converter for a period of time to obtain stirred component A of silicone rubber; stir component B of silicone rubber under a frequency converter for a period of time to obtain stirred component B of silicone rubber; mix the stirred component A of silicone rubber and the stirred component B of silicone rubber, and stir under a frequency converter for a period of time to obtain a uniformly mixed silicone rubber composite material.

[0008] ③ Place the uniformly mixed silicone rubber composite material in a stirring and vacuuming device, stirring and vacuuming simultaneously to remove air bubbles introduced during the mixing process. Continue vacuuming and stirring for a period of time to obtain a uniformly mixed silicone rubber.

[0009] ④ Apply the uniformly mixed silicone rubber evenly into the mold, and then place the mold into a flat vulcanizing machine for a first vulcanization to obtain the composite medium after the first vulcanization.

[0010] ⑤ Place the composite medium after primary vulcanization in a high-temperature forced-air drying oven for secondary vulcanization to obtain the composite medium after secondary vulcanization; let the composite medium after secondary vulcanization stand at room temperature for a period of time to obtain silicone rubber.

[0011] II. Preparation of cross-linked polyethylene:

[0012] ① Place the cross-linked polyethylene granules in a vacuum oven and dry them for a period of time to obtain dried cross-linked polyethylene granules;

[0013] ② Place the dried cross-linked polyethylene granules into a mold at a temperature of 110℃~115℃, and then place the mold into a flat vulcanizing machine for melting. The specific process is as follows: first, melt for 10min~15min under a pressure of 0MPa, then melt for 10min~15min under a pressure of 5MPa, then melt for 10min~15min under a pressure of 10MPa, and finally melt for 10min~15min under a pressure of 15MPa to obtain cross-linked polyethylene after one melting.

[0014] ③ The cross-linked polyethylene after one melting is placed in a flat vulcanizing machine at a temperature of 175℃ and a pressure of 15MPa for a period of time to cross-link and obtain a cross-linked polyethylene film.

[0015] ④ The cross-linked polyethylene film is placed in a vacuum oven and dried for a period of time to obtain cross-linked polyethylene;

[0016] III. Preparation of doped modified silicone grease:

[0017] The silicone grease was mixed with 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and stirred for a period of time to obtain the modified silicone grease.

[0018] 4. The modified silicone grease is coated onto the surface of the silicone rubber, and then cross-linked polyethylene is covered to obtain a silicone rubber / cross-linked polyethylene composite medium for cable accessories.

[0019] The silicone rubber / crosslinked polyethylene composite dielectric for cable accessories prepared by this invention improves the interfacial insulation performance between silicone rubber and crosslinked polyethylene, enabling it to meet the higher electrical resistance requirements of cable accessories in engineering applications.

[0020] This reduces the failure rate of composite interfaces in cable accessories.

[0021] This invention utilizes the synergistic effect of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silicone grease to play a role at the interface between silicone rubber and cross-linked polyethylene, thereby further improving the electrical insulation performance of the composite interface.

[0022] The principle of this invention:

[0023] I. This invention selects a low LUMO energy level and high electron affinity organic molecular semiconductor, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone (F4TCNQ), as a filler and introduces it into silicone grease to construct carrier traps, thereby hindering carrier injection and transport. Under the synergistic effect of this filler and silicone grease, the electrical insulation properties of the silicone rubber-crosslinked polyethylene composite interface are further enhanced. Applying the modified silicone grease to the interface between silicone rubber and crosslinked polyethylene, under the synergistic effect of the high electron affinity of F4TCNQ and the silicone grease, constructs carrier traps, effectively limiting carrier injection and transport, thereby improving the interface breakdown voltage, surface breakdown voltage, and DC breakdown field strength of the silicone rubber-crosslinked polyethylene composite interface.

[0024] II. This invention, through measurements of multiple doping concentrations, explored the optimal doping ratio of F4TCNQ to be 0.6 wt%. The results show that the interfacial breakdown voltage of the silicone grease-coated silicone rubber and cross-linked polyethylene composite interface after modification with the optimal doping ratio is 22.61 kV at 0.3 MPa, 25.51 kV at 0.4 MPa, and 27.02 kV at 0.5 MPa. The DC breakdown field strength is 164.7 kV / mm at 30°C, 158.8 kV / mm at 50°C, and 150.8 kV / mm at 70°C. The surface breakdown voltage is 11.22 kV.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] I. This invention selects an organic molecular semiconductor with low LUMO energy level and high electron affinity as a filler, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone, and introduces it into silicone grease to construct a carrier trap, thereby hindering the injection and transport of carriers. Under the synergistic effect of this filler and silicone grease, the intermolecular forces are enhanced, the silicone grease slippage is reduced, and the electrical insulation properties of the silicone rubber-crosslinked polyethylene composite interface are further increased.

[0027] Second, this invention belongs to a fully organic system, which is suitable for large-scale production and manufacturing. It is easy to produce and the modified silicone grease gives the silicone rubber and cross-linked polyethylene composite interface high interfacial breakdown performance, which greatly improves its insulation performance. It provides a new research and development idea for matching the insulation performance and electrical strength of accessory-reinforced silicone rubber and cross-linked polyethylene. Attached Figure Description

[0028] Figure 1 Interfacial breakdown voltage of silicone rubber / cross-linked polyethylene composite dielectric for cable accessories prepared with different proportions after swelling for different times at 0.3 MPa;

[0029] Figure 2 (a) Weibull distribution diagrams of the interface breakdown voltage of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 0.3 MPa pressure; (b) Weibull distribution diagrams of the interface breakdown voltage of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 0.4 MPa pressure; (c) Weibull distribution diagrams of the interface breakdown voltage of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 0.5 MPa pressure.

[0030] Figure 3 Weibull distribution diagrams of surface breakdown voltage of silicone rubber coated with silicone grease in different comparative examples;

[0031] Figure 4 (a) Weibull distribution of DC breakdown field strength of silicone rubber coated with different silicone greases in different comparative examples at 30°C; (b) Weibull distribution of DC breakdown field strength of silicone rubber coated with different silicone greases in different comparative examples at 50°C; (c) Weibull distribution of DC breakdown field strength of silicone rubber coated with different silicone greases in different comparative examples at 70°C.

[0032] Figure 5 (a) The graph shows the change of interfacial conductivity current with electric field strength for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different proportions at 30°C; (b) The graph shows the change of interfacial conductivity current with electric field strength for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different proportions at 50°C; (c) The graph shows the change of interfacial conductivity current with electric field strength for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different proportions at 70°C.

[0033] Figure 6(a) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments at a pressure of 0.3 MPa; (b) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments at a pressure of 0.4 MPa; (c) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments at a pressure of 0.5 MPa.

[0034] Figure 7 Weibull distribution diagrams of surface breakdown voltage of silicone rubber coated with different modified silicone greases in different embodiments;

[0035] Figure 8 (a) is a Weibull distribution diagram of the DC breakdown field strength of silicone rubber coated with different modified silicone greases in different embodiments at 30°C; (b) is a Weibull distribution diagram of the DC breakdown field strength of silicone rubber coated with different modified silicone greases in different embodiments at 50°C; and (c) is a Weibull distribution diagram of the DC breakdown field strength of silicone rubber coated with different modified silicone greases in different embodiments at 70°C.

[0036] Figure 9 (a) shows the variation of interfacial conductivity current with electric field strength at 30°C for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments; (b) shows the variation of interfacial conductivity current with electric field strength at 50°C for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments; and (c) shows the variation of interfacial conductivity current with electric field strength at 70°C for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments.

[0037] Figure 10 Infrared spectra of different types of silicone grease;

[0038] Figure 11 XRD patterns of different types of silicone grease;

[0039] Figure 12 (a) is a surface electron microscope image of the silicone rubber coated with silicone grease in Comparative Example 4, and (b) is a surface electron microscope image of the silicone rubber coated with silicone grease in Comparative Example 4 after thermal aging for 240 hours.

[0040] Figure 13 (a) is the surface electrostatic potential cloud diagram of silicone grease, and (b) is the surface electrostatic potential cloud diagram of F4TCNQ organic small molecules;

[0041] Figure 14 (a) shows the surface LUMO and HUMO distribution cloud maps of silicone grease and F4TCNQ organic small molecules, and (b) shows the energy level distribution maps of silicone grease and F4TCNQ organic small molecules in comparison.

[0042] Figure 15 Diagram of the interface breakdown voltage test setup;

[0043] Figure 16 Diagram of the interface conductivity testing device;

[0044] Figure 17 This is a diagram of a surface breakdown voltage testing device. Detailed Implementation

[0045] Specific Implementation Method 1: This implementation method provides a method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories, which is specifically completed according to the following steps:

[0046] I. Preparation of silicone rubber:

[0047] ① Weigh out component A and component B of the silicone rubber;

[0048] ② Stir component A of silicone rubber under a frequency converter for a period of time to obtain stirred component A of silicone rubber; stir component B of silicone rubber under a frequency converter for a period of time to obtain stirred component B of silicone rubber; mix the stirred component A of silicone rubber and the stirred component B of silicone rubber, and stir under a frequency converter for a period of time to obtain a uniformly mixed silicone rubber composite material.

[0049] ③ Place the uniformly mixed silicone rubber composite material in a stirring and vacuuming device, stirring and vacuuming simultaneously to remove air bubbles introduced during the mixing process. Continue vacuuming and stirring for a period of time to obtain a uniformly mixed silicone rubber.

[0050] ④ Apply the uniformly mixed silicone rubber evenly into the mold, and then place the mold into a flat vulcanizing machine for a first vulcanization to obtain the composite medium after the first vulcanization.

[0051] ⑤ Place the composite medium after primary vulcanization in a high-temperature forced-air drying oven for secondary vulcanization to obtain the composite medium after secondary vulcanization; let the composite medium after secondary vulcanization stand at room temperature for a period of time to obtain silicone rubber.

[0052] II. Preparation of cross-linked polyethylene:

[0053] ① Place the cross-linked polyethylene granules in a vacuum oven and dry them for a period of time to obtain dried cross-linked polyethylene granules;

[0054] ② Place the dried cross-linked polyethylene granules into a mold at a temperature of 110℃~115℃, and then place the mold into a flat vulcanizing machine for melting. The specific process is as follows: first, melt for 10min~15min under a pressure of 0MPa, then melt for 10min~15min under a pressure of 5MPa, then melt for 10min~15min under a pressure of 10MPa, and finally melt for 10min~15min under a pressure of 15MPa to obtain cross-linked polyethylene after one melting.

[0055] ③ The cross-linked polyethylene after one melting is placed in a flat vulcanizing machine at a temperature of 175℃ and a pressure of 15MPa for a period of time to cross-link and obtain a cross-linked polyethylene film.

[0056] ④ The cross-linked polyethylene film is placed in a vacuum oven and dried for a period of time to obtain cross-linked polyethylene;

[0057] III. Preparation of doped modified silicone grease:

[0058] The silicone grease was mixed with 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and stirred for a period of time to obtain the modified silicone grease.

[0059] 4. The modified silicone grease is coated onto the surface of the silicone rubber, and then cross-linked polyethylene is covered to obtain a silicone rubber / cross-linked polyethylene composite medium for cable accessories.

[0060] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the mass ratio of component A to component B of the silicone rubber in step one ① is 1:1; the type of component A of the silicone rubber in step one ① is: 745-LG-7046-A-CN, purchased from Wacker Chemie (China) Co., Ltd., is the model number for component B. Product code 745-LG-7046-B-CN was purchased from Wacker Chemie (China) Co., Ltd. Other steps are the same as in Specific Implementation Method 1.

[0061] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the stirring time in step one ② is 1 to 2 hours, and the stirring speed is 2.8 to 3 rpm; the continuous vacuuming and stirring operation in step one ③ lasts for 2 to 3 hours. Other steps are the same as in Specific Implementation Method One or Two.

[0062] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the temperature for the primary vulcanization in step one (④) is 160℃~170℃, and the pressure is 15MPa~20MPa; the mold in step one (④) has dimensions of 100mm×100mm×0.175mm. Other steps are the same as in Specific Implementation Methods One to Three.

[0063] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the temperature for secondary vulcanization in step one (⑤) is 190℃~210℃; the standing time in step one (⑤) is 4h~5h. The other steps are the same as in Specific Implementation Methods One to Four.

[0064] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the cross-linked polyethylene mentioned in step two ① is of type LD200GH, purchased from Beijing Yanshan Petrochemical Co., Ltd. of China Petrochemical Corporation; the drying temperature mentioned in step two ① is 80℃, and the drying time is 24 hours. Other steps are the same as in Specific Implementation Methods One to Five.

[0065] Specific Implementation Method Seven: The difference between this implementation method and Specific Implementation Methods One to Six is ​​that: the dried cross-linked polyethylene particles described in step two ② are placed in a mold with dimensions of 100mm×100mm×0.175mm and filled according to a mass of 2.5g to 2.7g; the cross-linking time described in step two ③ is 30min; the temperature of the vacuum oven described in step two ④ is 80℃ and the vacuum drying time is 24h.

[0066] The other steps are the same as those in Specific Implementation Methods 1 to 6.

[0067] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the mass ratio of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silicone grease in step three is (0.2-0.8):100; the stirring time in step three is 20 minutes until uniformly mixed; the silicone grease in step three is psaitong, Great Wall 7051, Boer, or Aladdin, all purchased from Beijing Innocare Technology Co., Ltd. Other steps are the same as in Specific Implementation Methods One to Seven.

[0068] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the mass of the modified silicone grease applied in step four is 1g, and the dimensions of both the silicone rubber and the cross-linked polyethylene are 100mm × 100mm × 0.175mm. The other steps are the same as in Specific Implementation Methods One to Eight.

[0069] Specific Implementation Method 10: This implementation method is widely used in the fields of power transmission, submarine cables, and rail transportation for cable accessories.

[0070] The beneficial effects of the present invention are verified using the following embodiments:

[0071] Example 1: A method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories, specifically comprising the following steps:

[0072] I. Preparation of silicone rubber:

[0073] ① Weigh out component A and component B of the silicone rubber;

[0074] The mass ratio of component A to component B of the silicone rubber mentioned in step 1① is 1:1.

[0075] The type of component A of the silicone rubber mentioned in step 1①: 745-LG-7046-A-CN, purchased from Wacker Chemie (China) Co., Ltd., is the model number for component B. 745-LG-7046-B-CN, purchased from Wacker Chemie (China) Co., Ltd.

[0076] ② Stir component A of silicone rubber in a frequency converter for 1 hour to obtain stirred component A of silicone rubber; stir component B of silicone rubber in a frequency converter for 1 hour to obtain stirred component B of silicone rubber; mix the stirred component A of silicone rubber and the stirred component B of silicone rubber, and stir in a frequency converter for 1 hour to obtain a uniformly mixed silicone rubber composite material.

[0077] The stirring speed mentioned in step 1② is 2.8 rpm;

[0078] ③ Place the uniformly mixed silicone rubber composite material in a stirring and vacuuming device, stirring and vacuuming simultaneously to remove air bubbles introduced during the mixing process. Continue vacuuming and stirring for 1 hour to obtain a uniformly mixed silicone rubber.

[0079] ④ Apply the uniformly mixed silicone rubber evenly into the mold, and then place the mold into a flat vulcanizing machine for a first vulcanization to obtain the composite medium after the first vulcanization.

[0080] The temperature for the primary vulcanization described in step 1④ is 165℃ and the pressure is 15MPa;

[0081] The mold mentioned in step 1, section 4 has dimensions of 100mm × 100mm × 0.175mm;

[0082] ⑤ Place the composite medium after primary vulcanization in a high-temperature forced-air drying oven for secondary vulcanization to obtain the composite medium after secondary vulcanization; let the composite medium after secondary vulcanization stand at room temperature for a period of time to obtain silicone rubber.

[0083] The temperature for the secondary vulcanization described in step 1, ⑤ is 200℃;

[0084] The settling time mentioned in step 1, ⑤ is 4 hours;

[0085] II. Preparation of cross-linked polyethylene:

[0086] ① Place the cross-linked polyethylene granules in a vacuum oven and dry them for a period of time to obtain dried cross-linked polyethylene granules;

[0087] The cross-linked polyethylene mentioned in step 2① is of type LD200GH and was purchased from Beijing Yanshan Petrochemical Co., Ltd. of China Petrochemical Corporation.

[0088] The drying temperature described in step 2① is 80℃, and the drying time is 24 hours;

[0089] ② Place the dried cross-linked polyethylene granules into a mold at a temperature of 110℃, and then place the mold into a flat vulcanizing machine for melting. The specific process is as follows: first, melt for 10 minutes under a pressure of 0 MPa, then melt for 10 minutes under a pressure of 5 MPa, then melt for 10 minutes under a pressure of 10 MPa, and finally melt for 10 minutes under a pressure of 15 MPa to obtain cross-linked polyethylene after one melting.

[0090] The dried cross-linked polyethylene granules mentioned in step 2② are placed in a mold with dimensions of 100mm×100mm×0.175mm and filled according to a mass of 2.6g.

[0091] ③ The cross-linked polyethylene after one melting is placed in a flat vulcanizing machine at a temperature of 175℃ and a pressure of 15MPa for a period of time to cross-link and obtain a cross-linked polyethylene film.

[0092] The cross-linking time mentioned in step 2③ is 30 minutes;

[0093] ④ The cross-linked polyethylene film is placed in a vacuum oven and dried for a period of time to obtain cross-linked polyethylene;

[0094] The temperature of the vacuum oven mentioned in step 2④ is 80℃, and the vacuum drying time is 24 hours;

[0095] III. Preparation of doped modified silicone grease:

[0096] The silicone grease was mixed with 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and stirred for 2 hours to obtain the modified silicone grease.

[0097] The mass ratio of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silicone grease in step three is 0.2:100;

[0098] The stirring time mentioned in step three is 2 hours;

[0099] The silicone grease selected in step three is No. 4 silicone grease, which is Aladdin brand high vacuum silicone grease and was purchased from Beijing Innocare Technology Co., Ltd.

[0100] IV. The modified silicone grease is coated onto the surface of silicone rubber, and then cross-linked polyethylene is covered to obtain silicone rubber / cross-linked polyethylene composite medium for cable accessories (denoted as 0.2wt% / No. 4);

[0101] The amount of modified silicone grease used in step four is 1g, and the dimensions of both silicone rubber and cross-linked polyethylene are 100mm×100mm×0.175mm.

[0102] Example 2: The difference between this example and Example 1 is that the mass ratio of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silicone grease in step three is 0.4:100; the silicone rubber / crosslinked polyethylene composite dielectric for cable accessories obtained in step four is denoted as 0.4wt% / No. 4. All other steps and parameters are the same as in Example 1.

[0103] Example 3: The difference between this example and Example 1 is that the mass ratio of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silicone grease in step three is 0.6:100; the silicone rubber / crosslinked polyethylene composite dielectric for cable accessories obtained in step four is denoted as 0.6wt% / No. 4. All other steps and parameters are the same as in Example 1.

[0104] Example 4: The difference between this example and Example 1 is that the mass ratio of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silicone grease in step three is 0.8:100; the silicone rubber / crosslinked polyethylene composite dielectric for cable accessories obtained in step four is denoted as 0.8wt% / No. 4. All other steps and parameters are the same as in Example 1.

[0105] Example 5: The difference between this example and Example 1 is that the mass ratio of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silicone grease in step three is 1:100; the silicone rubber / crosslinked polyethylene composite dielectric for cable accessories obtained in step four is denoted as 1.0wt% / No. 4. All other steps and parameters are the same as in Example 1.

[0106] Comparative Example 1: A method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories, specifically comprising the following steps:

[0107] I. Preparation of silicone rubber:

[0108] ① Weigh out component A and component B of the silicone rubber;

[0109] The mass ratio of component A to component B of the silicone rubber mentioned in step 1① is 1:1.

[0110] The type of component A of the silicone rubber mentioned in step 1①: 745-LG-7046-A-CN, purchased from Wacker Chemie (China) Co., Ltd., is the model number for component B. 745-LG-7046-B-CN, purchased from Wacker Chemie (China) Co., Ltd.

[0111] ② Stir component A of silicone rubber in a frequency converter for 1 hour to obtain stirred component A of silicone rubber; stir component B of silicone rubber in a frequency converter for 1 hour to obtain stirred component B of silicone rubber; mix the stirred component A of silicone rubber and the stirred component B of silicone rubber, and stir in a frequency converter for 1 hour to obtain a uniformly mixed silicone rubber composite material.

[0112] The stirring speed mentioned in step 1② is 2.8 rpm;

[0113] ③ Place the uniformly mixed silicone rubber composite material in a stirring and vacuuming device, stirring and vacuuming simultaneously to remove air bubbles introduced during the mixing process. Continue vacuuming and stirring for 1 hour to obtain a uniformly mixed silicone rubber.

[0114] ④ Apply the uniformly mixed silicone rubber evenly into the mold, and then place the mold into a flat vulcanizing machine for a first vulcanization to obtain the composite medium after the first vulcanization.

[0115] The temperature for the primary vulcanization described in step 1④ is 165℃ and the pressure is 15MPa;

[0116] The mold mentioned in step 1, section 4 has dimensions of 100mm × 100mm × 0.175mm;

[0117] ⑤ Place the composite medium after primary vulcanization in a high-temperature forced-air drying oven for secondary vulcanization to obtain the composite medium after secondary vulcanization; let the composite medium after secondary vulcanization stand at room temperature for a period of time to obtain silicone rubber.

[0118] The temperature for the secondary vulcanization described in step 1, ⑤ is 200℃;

[0119] The settling time mentioned in step 1, ⑤ is 4 hours;

[0120] II. Preparation of cross-linked polyethylene:

[0121] ① Place the cross-linked polyethylene granules in a vacuum oven and dry them for a period of time to obtain dried cross-linked polyethylene granules;

[0122] The cross-linked polyethylene mentioned in step 2① is of type LD200GH and was purchased from Beijing Yanshan Petrochemical Co., Ltd. of China Petrochemical Corporation.

[0123] The drying temperature described in step 2① is 80℃, and the drying time is 24 hours;

[0124] ② Place the dried cross-linked polyethylene granules into a mold at a temperature of 110℃, and then place the mold into a flat vulcanizing machine for melting. The specific process is as follows: first, melt for 10 minutes under a pressure of 0 MPa, then melt for 10 minutes under a pressure of 5 MPa, then melt for 10 minutes under a pressure of 10 MPa, and finally melt for 10 minutes under a pressure of 15 MPa to obtain cross-linked polyethylene after one melting.

[0125] The dried cross-linked polyethylene granules mentioned in step 2② are placed in a mold with dimensions of 100mm×100mm×0.175mm and filled according to a mass of 2.6g.

[0126] ③ The cross-linked polyethylene after one melting is placed in a flat vulcanizing machine at a temperature of 175℃ and a pressure of 15MPa for a period of time to cross-link and obtain a cross-linked polyethylene film.

[0127] The cross-linking time mentioned in step 2③ is 30 minutes;

[0128] ④ The cross-linked polyethylene film is placed in a vacuum oven and dried for a period of time to obtain cross-linked polyethylene;

[0129] The temperature of the vacuum oven mentioned in step 2④ is 80℃, and the vacuum drying time is 24 hours;

[0130] 3. Apply silicone grease to the surface of silicone rubber, and then cover it with cross-linked polyethylene to obtain silicone rubber / cross-linked polyethylene composite medium for cable accessories (referred to as No. 1 or No. 1 silicone grease).

[0131] The amount of silicone grease used in step three is 1g, and the dimensions of both silicone rubber and cross-linked polyethylene are 100mm×100mm×0.175mm;

[0132] The silicone grease selected in step three is No. 1, which is high-vacuum silicone grease psaitong, purchased from Beijing Innocare Technology Co., Ltd.

[0133] Comparative Example 2: The difference between this comparative example and Comparative Example 1 is that the silicone grease used in step three is No. 2, a high-vacuum silicone grease from the Great Wall 7501 brand, purchased from Beijing Innocare Technology Co., Ltd.; the silicone rubber / cross-linked polyethylene composite dielectric for cable accessories obtained in step three is denoted as No. 2 or No. 2 silicone grease. All other steps and parameters are the same as in Comparative Example 1.

[0134] Comparative Example 3: The difference between this comparative example and Comparative Example 1 is that the silicone grease used in step three is No. 3, a high-vacuum silicone grease from the Boer brand, purchased from Beijing Innocare Technology Co., Ltd.; the silicone rubber / cross-linked polyethylene composite dielectric for cable accessories obtained in step three is denoted as No. 3 or No. 3 silicone grease. All other steps and parameters are the same as in Comparative Example 1.

[0135] Comparative Example 4: The difference between this comparative example and Comparative Example 1 is that the silicone grease used in step three is No. 4, a high-vacuum silicone grease from the Aladdin brand, purchased from Beijing Innocare Technology Co., Ltd.; the silicone rubber / cross-linked polyethylene composite dielectric for the cable accessories obtained in step three is denoted as No. 4 or No. 4 silicone grease. All other steps and parameters are the same as in Comparative Example 1.

[0136] Figure 1 Interfacial breakdown voltage of silicone rubber / cross-linked polyethylene composite dielectric for cable accessories prepared with different proportions after swelling for different times at 0.3 MPa;

[0137] Depend on Figure 1It is known that when silicone grease is applied to the interface between silicone rubber and cross-linked polyethylene for a prolonged period, swelling occurs due to the similarity in molecular formula between the silicone grease and silicone rubber, causing the silicone grease to integrate into the silicone rubber. This swelling effect is beneficial for good interfacial contact in the short term, but under long-term operation, the cross-linked structure of the silicone rubber is damaged, forming electrically weak areas. The swelling effect degrades the electrical and mechanical properties of the silicone rubber. As shown in the figure, after applying four different silicone greases to the interface between silicone rubber and cross-linked polyethylene for a certain period, their interfacial breakdown voltages all showed varying degrees of decrease. Among them, silicone grease No. 4 showed the most gradual decrease, from 24.9 kV at 0 h to 22.1 kV after 24 h. Compared to the other three silicone greases, the change in interfacial breakdown voltage of silicone grease No. 4 was less than 20% of its own interfacial breakdown voltage value. Therefore, silicone grease No. 4 showed the least impact from swelling. Thus, through experimental testing, silicone grease No. 4 was selected as the silicone grease with excellent anti-swelling properties, exhibiting the least swelling effect on silicone rubber.

[0138] Figure 2 (a) Weibull distribution diagrams of the interface breakdown voltage of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 0.3 MPa pressure; (b) Weibull distribution diagrams of the interface breakdown voltage of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 0.4 MPa pressure; (c) Weibull distribution diagrams of the interface breakdown voltage of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 0.5 MPa pressure.

[0139] Depend on Figure 2 It is known that applying silicone grease to the interface between silicone rubber and cross-linked polyethylene at a pressure of 0.3 MPa increases the interface breakdown voltage. Among the four silicone greases selected, grease No. 4 exhibits the highest interface breakdown voltage, demonstrating its superior interfacial electrical insulation performance at this pressure. At this pressure, the interface breakdown voltage of SIR is 18.96 kV, No. 1 is 19.81 kV, No. 2 is 20.18 kV, No. 3 is 20.39 kV, and No. 4 is 21.05 kV. With increasing pressure, the interface breakdown voltage increases to some extent. This is because at lower interfacial pressures, the composite interface contains numerous gaps, and the dielectric constant of the gas within these gaps is lower than that of SIR or XLPE, resulting in a highly uneven interfacial electric field distribution. Since the breakdown field strength of the gas gaps is much lower than that of solid materials, the interface is more prone to discharge. Increasing the interfacial pressure increases the actual contact area at the interface between the silicone rubber and the cross-linked polyethylene composite, thus reducing the gas volume in the gap. This results in a more uniform distribution of the interfacial electric field, making discharge less likely. Therefore, increasing the interfacial pressure is beneficial for improving the insulation performance of the interface.

[0140] Figure 3Weibull distribution diagrams of surface breakdown voltage of silicone rubber coated with silicone grease in different comparative examples;

[0141] Depend on Figure 3 It is known that applying silicone grease to the surface of silicone rubber increases its surface breakdown voltage. Among the four selected silicone greases, grease No. 4 has the highest surface breakdown voltage, at 10.57 kV. This demonstrates that grease No. 4 exhibits the best electrical insulation performance when applied to the surface of silicone rubber. The increase in surface breakdown voltage due to the higher the smoothness of the XLPE / silicone rubber interface, the higher the interface breakdown voltage. Applying silicone grease reduces interface roughness and lowers the local electric field strength, thereby increasing the surface breakdown voltage. Silicone grease and silicone rubber have similar structures, and similar structures tend to dissolve each other. Small molecule silicone grease molecules, acting as solvents, penetrate into the silicone rubber polymer chains, causing swelling. This swelling disrupts the cross-linked structure of the silicone rubber. This swelling may alter the surface properties of the silicone rubber, thus increasing its surface breakdown voltage.

[0142] Figure 4 (a) Weibull distribution of DC breakdown field strength of silicone rubber coated with different silicone greases in different comparative examples at 30°C; (b) Weibull distribution of DC breakdown field strength of silicone rubber coated with different silicone greases in different comparative examples at 50°C; (c) Weibull distribution of DC breakdown field strength of silicone rubber coated with different silicone greases in different comparative examples at 70°C.

[0143] Depend on Figure 4 It is known that applying silicone grease to the surface of silicone rubber increases its DC breakdown field strength, with the highest DC breakdown field strength observed when applying silicone grease No. 4: 158.3 KV / mm at 30°C, 157.6 KV / mm at 50°C, and 156.5 KV / mm at 70°C. The reason for this increase is that the silicone grease forms a protective film on the surface, reducing direct contact and influence from the external environment. Furthermore, the similarity between the silicone grease and silicone rubber molecular structures allows the grease to penetrate the silicone rubber polymer chains, causing swelling. This swelling effect can enhance the insulation performance of silicone rubber in a short time. Additionally, silicone grease application reduces surface inhomogeneity, resulting in a more uniform electric field distribution and reducing localized excessively high electric field strength, thus increasing the DC breakdown field strength of the silicone rubber. The breakdown field strength of silicone rubber decreases with increasing temperature. This is because charge carriers gain more kinetic energy at higher temperatures. Under the influence of a high field, charge carriers are more likely to undergo collisional ionization, and breakdown paths are more likely to form. Therefore, the breakdown field strength decreases with increasing temperature.

[0144] Figure 5(a) The graph shows the change of interfacial conductivity current with electric field strength for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different proportions at 30°C; (b) The graph shows the change of interfacial conductivity current with electric field strength for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different proportions at 50°C; (c) The graph shows the change of interfacial conductivity current with electric field strength for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different proportions at 70°C.

[0145] Depend on Figure 5 It is known that applying silicone grease to the interface between silicone rubber and cross-linked polyethylene increases the interfacial conductivity of the composite interface. At 30°C, a comparison of the interfacial conductivity of four different types of silicone grease showed that the interface with silicone rubber coated with grease No. 4 had the lowest conductivity. Under both low and high field conditions, its interfacial conductivity remained consistently around 10. -15 -10 -14 Between S / m, the interfacial conductivity did not change significantly with the electric field strength. With increasing temperature, at 50℃ and 70℃, the interfacial conductivity of all four types of silicone greases applied increased slightly. However, the overall distribution of interfacial conductivity among the different silicone greases was the same as at 30℃. This is because increasing temperature causes electrons in the silicone rubber-crosslinked polyethylene composite interface to transition from the valence band to the conduction band, increasing the number of charge carriers. Furthermore, increasing temperature may lower the activation energy for conductivity, making it easier for charge carriers to transition, thereby improving the interfacial conductivity.

[0146] Figure 6 (a) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments at a pressure of 0.3 MPa; (b) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments at a pressure of 0.4 MPa; (c) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments at a pressure of 0.5 MPa.

[0147] Depend on Figure 6It is known that coating the silicone grease with F4TCNQ-doped organic semiconductor filler at the interface of silicone rubber and cross-linked polyethylene increases its interfacial breakdown voltage. Furthermore, with increasing F4TCNQ doping content, the interfacial breakdown voltage at the silicone rubber-cross-linked polyethylene interface initially increases and then decreases. Among the selected filler doping concentrations, the highest interfacial breakdown voltage is achieved at an F4TCNQ concentration of 0.6 wt%, reaching 22.61 kV at 0.3 MPa, 25.51 kV at 0.4 MPa, and 27.02 kV at 0.5 MPa. The increased interfacial breakdown voltage is due to the high electron affinity of F4TCNQ, which introduces deep traps at the silicone rubber-cross-linked polyethylene interface. These deep traps hinder carrier migration, reduce collisional ionization, and synergize with the silicone grease, thereby increasing intermolecular forces and reducing silicone grease slippage. However, higher F4TCNQ content can enhance the conjugation effect between fillers, which in turn promotes carrier transport. Furthermore, smaller intermolecular spacing in F4TCNQ can easily lead to localized crystalline phase formation, resulting in localized defects. This, in turn, reduces the interfacial breakdown voltage.

[0148] Figure 7 Weibull distribution diagrams of surface breakdown voltage of silicone rubber coated with different modified silicone greases in different embodiments;

[0149] Depend on Figure 7 It is known that coating the silicone grease with F4TCNQ-doped organic semi-polymer filler on the surface of silicone rubber increases its surface breakdown voltage. Furthermore, as the F4TCNQ doping content increases, the surface breakdown voltage of the coated silicone rubber first increases and then decreases. Among the selected filler doping concentrations, the surface breakdown voltage reaches its highest value of 11.22 kV when the F4TCNQ concentration is 0.6 wt%. The improved breakdown performance after F4TCNQ doping is due to the high electron affinity of F4TCNQ, which successfully constructs deep electron traps to capture free electrons. Because of the Coulomb force between electrons in the low unoccupied molecular orbitals (LUMOs) of these fillers and holes in the highest occupied molecular orbitals (HOMOs) of the polymer matrix, the captured electrons have difficulty escaping. The silicone grease and F4TCNQ work synergistically to reduce the accumulation of space charge inside the sample, thereby increasing the breakdown field strength of the silicone rubber. When the concentration of the introduced filler reaches 0.6 wt% or more, the DC breakdown field strength of silicone rubber decreases. This is because excessive filler with high electron affinity may increase the accumulation of space charge, which will lead to uneven electric field distribution, increase the local electric field strength, and thus reduce the breakdown field strength.

[0150] Figure 8(a) is a Weibull distribution diagram of the DC breakdown field strength of silicone rubber coated with different modified silicone greases in different embodiments at 30°C; (b) is a Weibull distribution diagram of the DC breakdown field strength of silicone rubber coated with different modified silicone greases in different embodiments at 50°C; and (c) is a Weibull distribution diagram of the DC breakdown field strength of silicone rubber coated with different modified silicone greases in different embodiments at 70°C.

[0151] Depend on Figure 8 It is known that coating the silicone rubber surface with F4TCNQ-doped organic semi-polymer filler increases its DC breakdown field strength. Furthermore, as the F4TCNQ doping content increases, the DC breakdown field strength coated on the silicone rubber surface initially increases and then decreases. Among the selected filler doping concentrations, the highest DC breakdown field strength is achieved at an F4TCNQ doping concentration of 0.6 wt%. This field strength reaches 164.7 kV / mm at 30°C, 158.8 kV / mm at 50°C, and 150.8 kV / mm at 70°C. The improved breakdown performance after F4TCNQ doping is due to the high electron affinity of F4TCNQ, which allows it to successfully construct deep electron traps to capture free electrons. Due to the Coulomb force between electrons in the low unoccupied molecular orbitals (LUMOs) of these fillers and holes in the highest occupied molecular orbitals (HOMOs) of the polymer matrix, trapped electrons have difficulty escaping. The silicone grease and F4TCNQ work synergistically to reduce space charge accumulation within the sample, thereby increasing the breakdown field strength of the silicone rubber. When the concentration of the introduced filler reaches above 0.6 wt%, the DC breakdown field strength of the silicone rubber decreases. This is because excessive high electron affinity fillers may increase space charge accumulation, leading to uneven electric field distribution, increased local electric field strength, and consequently, a decrease in breakdown field strength. The breakdown field strength of silicone rubber decreases with increasing temperature. This is because charge carriers gain more kinetic energy at higher temperatures. Under the influence of a high field, charge carriers are more prone to collisional ionization, and breakdown paths are more easily formed; therefore, the breakdown field strength decreases with increasing temperature.

[0152] Figure 9 (a) shows the variation of interfacial conductivity current with electric field strength at 30°C for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments; (b) shows the variation of interfacial conductivity current with electric field strength at 50°C for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments; and (c) shows the variation of interfacial conductivity current with electric field strength at 70°C for silicone rubber / cross-linked polyethylene composite media for cable accessories prepared with modified silicone grease coated with different doping ratios in different embodiments.

[0153] Depend on Figure 9It is known that coating the silicone grease doped with F4TCNQ organic semi-polymer filler at the interface of silicone rubber and cross-linked polyethylene reduces its interfacial conductivity. This is because F4TCNQ, as a high electron affinity filler, may help improve the charge transfer efficiency in the silicone grease. This filler can capture and transfer more charge, leading to an increase in charge density at the interface, thereby reducing conductivity. Furthermore, as the F4TCNQ doping content increases, the interfacial conductivity at the silicone rubber and cross-linked polyethylene composite interface shows a trend of first decreasing and then increasing. This is because the relatively low LUMO energy level of F4TCNQ can establish carrier traps in the electron transport path, thereby capturing carriers and restricting their free path, thus reducing interfacial conductivity. However, when the filler doping content is high, excessive high electron affinity filler may increase the accumulation of space charge, which can lead to uneven electric field distribution, increase local electric field strength, and thus cause an increase in interfacial conductivity.

[0154] Figure 10 Infrared spectra of different types of silicone grease;

[0155] Depend on Figure 10 It can be known that 700cm -1 The absorption peak at 790-816 cm⁻¹ belongs to the Si(CH₃)₃ vibration. -1 The absorption peak at 2965.40 cm⁻¹ belongs to the CH vibration. -1 The absorption peak belongs to the asymmetric stretching vibration of the CH2 functional group, at 2905.71 cm⁻¹. -1 The absorption peak belongs to the symmetric stretching vibration of the CH2 functional group, 1000-1100 cm⁻¹ -1 The absorption peak belongs to the stretching vibration of the Si-O functional groups. The absorption peak for silicone grease No. 3 is at 2965.40 cm⁻¹. -1 The high intensity of the absorption peak at 800-1000 cm⁻¹ indicates a high concentration of organic molecules. -1 1000-1100cm -1 The presence of relatively broad and strong peaks at these locations indicates strong molecular interactions between silicon and oxygen bonds, suggesting a more regular silicon-oxygen structure and potentially stronger mechanical properties. The peaks at 2965.40 and 1000-1100 cm⁻¹ of silicone grease #2 and #1 are also relevant. -1 It exhibits a moderately strong absorption peak at 2965.4 cm⁻¹, with relatively regular peak intensity. Therefore, its structure is simple, with few silicon-oxygen cross-linked structures. Silicone grease No. 4 has an absorption peak at 2965.4 cm⁻¹. -1 The absorption peak intensity is lowest at 790-816 cm⁻¹. -1 1000-1100cm -1The strongest absorption peak and narrowest peak width are observed at this location, indicating a relatively simple vibrational mode and the highest concentration. Therefore, this type of silicone grease has the highest organic content and the lowest degree of cross-linking, thus indicating the best insulation performance.

[0156] Figure 11 XRD patterns of different types of silicone grease;

[0157] Depend on Figure 11 It can be seen that these four types of silicone grease exhibit diffraction peaks at similar 2θ angles, indicating that they may have similar crystal structures or lattice parameters. The higher peak intensities of silicone greases No. 4 and No. 3 suggest higher crystallinity, which increases the chemical and physical stability of the grease, crucial for maintaining its insulating properties. Highly stable materials are less prone to decomposition or degradation under an electric field, thus maintaining their insulating characteristics. Conversely, the lower peak intensities of silicone greases No. 1 and No. 2 indicate lower crystallinity, suggesting that their physical structures are less stable than those of No. 3 and No. 4. Therefore, their insulating properties are lower than those of No. 3 and No. 4.

[0158] Figure 12 (a) is a surface electron microscope image of the silicone rubber coated with silicone grease in Comparative Example 4, and (b) is a surface electron microscope image of the silicone rubber coated with silicone grease in Comparative Example 4 after thermal aging for 240 hours.

[0159] Depend on Figure 12 It is known that the surface of silicone rubber itself is very regular and free of cracks. However, after 240 hours of heat aging with silicone grease, obvious cracks appeared on the surface of the silicone rubber, and even fracture occurred. This indicates that the microstructure of silicone rubber changes with increasing aging. Furthermore, during heat aging, the swelling effect of silicone grease on silicone rubber intensifies the transport of molecular chains, and when this exceeds the dissociation energy of molecular bonds, thermal degradation occurs. Heat aging is more damaging to silicone rubber materials because the applied load causes deeper damage to the silicone rubber molecular chains, and the presence of force load leads to a reduction in free volume, affecting the free path of charge movement, thereby affecting its insulation properties.

[0160] Figure 14 (a) shows the surface LUMO and HUMO distribution cloud maps of silicone grease and F4TCNQ organic small molecules, and (b) shows the energy level distribution maps of silicone grease and F4TCNQ organic small molecules in comparison.

[0161] pass Figure 14(b) The energy level comparison diagram shows that the introduction of F4TCNQ filler can introduce traps to weaken electron jump transport, making it more difficult for electrons to jump, weakening intrinsic excitation ability, resulting in poorer electron transport, fewer electron transport paths, and a lower probability of collisional ionization. This fully explains the phenomenon that F4TCNQ filler-modified silicone grease phase has good breakdown performance.

[0162] The present invention demonstrates that doping silicone grease with high electron affinity filler F4TCNQ can significantly improve the insulation performance of the silicone rubber-crosslinked polyethylene composite interface in cable accessories.

[0163] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories, characterized in that... The preparation method is specifically carried out according to the following steps: I. Preparation of silicone rubber: ① Weigh out component A and component B of the silicone rubber; ② Stir component A of the silicone rubber under a frequency converter for a period of time to obtain component A of the stirred silicone rubber; The B component of the silicone rubber was stirred for a period of time under a variable frequency disperser to obtain the stirred B component of the silicone rubber. The A component and B component of the stirred silicone rubber were mixed and stirred for a period of time under a frequency converter to obtain a uniformly mixed silicone rubber composite material. ③ Place the uniformly mixed silicone rubber composite material in a stirring and vacuuming device, stirring and vacuuming simultaneously to remove air bubbles introduced during the mixing process. Continue vacuuming and stirring for a period of time to obtain a uniformly mixed silicone rubber. ④ Apply the uniformly mixed silicone rubber evenly into the mold, and then place the mold into a flat vulcanizing machine for a first vulcanization to obtain the composite medium after the first vulcanization. ⑤ Place the composite medium after primary vulcanization in a high-temperature forced-air drying oven for secondary vulcanization to obtain the composite medium after secondary vulcanization; let the composite medium after secondary vulcanization stand at room temperature for a period of time to obtain silicone rubber. II. Preparation of cross-linked polyethylene: ① Place the cross-linked polyethylene granules in a vacuum oven and dry them for a period of time to obtain dried cross-linked polyethylene granules; ② Place the dried cross-linked polyethylene granules into a mold at a temperature of 110℃~115℃, and then place the mold into a flat vulcanizing machine for melting. The specific process is as follows: first, melt for 10min~15min under a pressure of 0MPa, then melt for 10min~15min under a pressure of 5MPa, then melt for 10min~15min under a pressure of 10MPa, and finally melt for 10min~15min under a pressure of 15MPa to obtain cross-linked polyethylene after one melting. ③ The cross-linked polyethylene after one melting is placed in a flat vulcanizing machine at a temperature of 175℃ and a pressure of 15MPa for a period of time to cross-link and obtain a cross-linked polyethylene film. ④ The cross-linked polyethylene film is placed in a vacuum oven and dried for a period of time to obtain cross-linked polyethylene; III. Preparation of doped modified silicone grease: The silicone grease was mixed with 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and stirred for a period of time to obtain the modified silicone grease. The mass ratio of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silicone grease in step three is (0.2~0.8):100; 4. The modified silicone grease is coated onto the surface of the silicone rubber, and then cross-linked polyethylene is covered to obtain a silicone rubber / cross-linked polyethylene composite medium for cable accessories.

2. The method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories according to claim 1, characterized in that... The mass ratio of component A to component B of the silicone rubber mentioned in step 1① is 1:1; the model of component A of the silicone rubber mentioned in step 1① is POWERSIL®745-LG-7046-A-CN, purchased from Wacker Chemie (China) Co., Ltd., and the model of component B is POWERSIL®745-LG-7046-B-CN, purchased from Wacker Chemie (China) Co., Ltd.

3. The method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories according to claim 1, characterized in that... The stirring time in step 1② is 1h~2h, and the stirring speed is 2.8rps~3rps; the continuous vacuuming and stirring operation in step 1③ lasts for 2h~3h.

4. The method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories according to claim 1, characterized in that... The temperature for the primary vulcanization in step 1, section 4 is 160℃~170℃, and the pressure is 15MPa~20MPa; the mold mentioned in step 1, section 4 is 100mm in size. 100mm 0.175mm.

5. The method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories according to claim 1, characterized in that... The temperature for secondary vulcanization in step 1.5 is 190℃~210℃; the settling time in step 1.5 is 4h~5h.

6. The method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories according to claim 1, characterized in that... The cross-linked polyethylene mentioned in step 2① is of type LD200GH and was purchased from Beijing Yanshan Petrochemical Co., Ltd. of China Petrochemical Corporation; the drying temperature mentioned in step 2① is 80℃ and the drying time is 24h.

7. The method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories according to claim 1, characterized in that... In step 2②, the dried cross-linked polyethylene granules are placed in a mold with dimensions of 100mm×100mm×0.175mm at a mass of 2.5g~2.7g; in step 2③, the cross-linking time is 30min; in step 2④, the temperature of the vacuum oven is 80℃ and the vacuum drying time is 24h.

8. The method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories according to claim 1, characterized in that... The stirring time in step three is 20 minutes, until the mixture is homogeneous; the silicone grease mentioned in step three is psaitong, Great Wall 7051, boer or Aladdin, all of which were purchased from Beijing Innocare Technology Co., Ltd.

9. The method for preparing a silicone rubber / cross-linked polyethylene composite dielectric for cable accessories according to claim 1, characterized in that... The mass of the modified silicone grease applied in step four is 1g, and the dimensions of both the silicone rubber and the cross-linked polyethylene are 100mm. 100mm 0.175mm.

10. The application of the silicone rubber / crosslinked polyethylene composite dielectric for cable accessories prepared by the method described in claim 1, characterized in that... Silicone rubber / cross-linked polyethylene composite media for cable accessories are widely used in the fields of power transmission, submarine cables, and rail transportation.

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