Preparation method and application of silicone rubber / crosslinked polyethylene composite medium for cable accessories

Abstract

The invention discloses a preparation method and application of a silicone rubber / crosslinked polyethylene composite medium for cable accessories, and belongs to a preparation method and application of a composite medium. The invention aims to solve the problems that in the prior art, along with long-term operation of a cable, silicone grease can be diffused into silicone rubber, the swelling phenomenon occurs, the insulating property of the silicone rubber is reduced, and the failure rate is increased. The method comprises: 1, preparing silicone rubber; 2, preparing crosslinked polyethylene; 3, preparing doped modified silicone grease; and 4, coating the modified silicone grease on the surface of the silicone rubber, and then covering crosslinked polyethylene. 2, 2, 3, 5, 6-tetrafluoro-7, 7 ', 8, 8'-tetracyanodimethyl p-benzoquinone is introduced into silicone grease as a filler to construct a carrier trap and hinder injection and transmission of carriers. Under the synergistic effect of the filler and the silicone grease, the acting force between molecules is enhanced, and the slippage of the silicone grease is reduced, so that the electrical insulation characteristic of a composite interface of the silicone rubber and the crosslinked polyethylene is further improved.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a composite medium. Background Art

[0002] In the actual operation of the cable system, cable accessories are the weak link of insulation and the part prone to failure. According to the statistics of cable operation failures by the State Grid Corporation of China, 70% of cable failures are caused by the damage of cable accessories insulation when external force damage is ignored. Therefore, it is of great significance to improve the insulation performance of cable accessories. Silicone rubber is often used as the main insulating material of cable accessories due to its excellent insulation performance and excellent mechanical strength, and has been widely used in cable accessories. Statistics on domestic cable accessories and body failures show that the failure rate at the cable joint accounts for 31%, and 97% of the joint failures are caused by interface discharge. The interface characteristics at the cable joint are closely related to the optimized design of the joint structure and the clamping force in the assembly of cable accessories, and are also closely related to the installation process and the cable operation environment. In the actual installation process of medium and low voltage cables, a layer of silicone grease will be applied to the inner side of the cable joint and the contact surface of the cable insulation to increase the sealing degree of the interface and the lubricity of the installation process. At the same time, it can enhance the insulation performance of the cable and the cable joint at the interface. However, with the long-term operation of the cable, the silicone grease will diffuse into the silicone rubber, swell, and cause the insulation performance of the silicone rubber to decrease. However, there is currently no solution to the degradation of silicone rubber insulation performance caused by silicone grease swelling, thereby reducing the failure rate of the composite interface of cable accessories. Summary of the invention

[0003] The purpose of the present invention is to solve the problem in the prior art that with the long-term operation of the cable, silicone grease will diffuse into the silicone rubber and swell, resulting in a decrease in the insulation performance of the silicone rubber and an increase in the failure rate, and to provide a preparation method and application of a silicone rubber / cross-linked polyethylene composite medium for cable accessories.

[0004] A method for preparing a silicone rubber / cross-linked polyethylene composite medium for cable accessories is specifically completed by the following steps:

[0005] 1. Preparation of silicone rubber:

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

[0007] ②, stirring the silicone rubber component A for a period of time under a variable frequency disperser to obtain the stirred silicone rubber component A; stirring the silicone rubber component B for a period of time under a variable frequency disperser to obtain the stirred silicone rubber component B; mixing the stirred silicone rubber component A and the stirred silicone rubber component B, stirring for a period of time under a variable frequency disperser 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, and vacuumize while stirring to remove bubbles introduced during the mixing and stirring process. Continue vacuuming and stirring for a period of time to obtain uniformly mixed silicone rubber;

[0009] ④. Apply the uniformly mixed silicone rubber evenly in the mold, and then put the mold into a flat vulcanizer for primary vulcanization to obtain a composite medium after primary vulcanization;

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

[0011] 2. Preparation of cross-linked polyethylene:

[0012] ①, placing the cross-linked polyethylene particles in a vacuum oven and drying them for a period of time to obtain dried cross-linked polyethylene particles;

[0013] ②, put the dried cross-linked polyethylene particles into a mold at a temperature of 110°C to 115°C, and then put the mold into a flat vulcanizer for melting. The specific process is: first melt at a pressure of 0MPa for 10min to 15min, then melt at a pressure of 5MPa for 10min to 15min, then melt at a pressure of 10MPa for 10min to 15min, and finally melt at a pressure of 15MPa for 10min to 15min to obtain a cross-linked polyethylene after primary melting;

[0014] ③, placing the once melted cross-linked polyethylene in a flat vulcanizer at a temperature of 175°C and a pressure of 15MPa for cross-linking for a period of time to obtain a cross-linked polyethylene film;

[0015] ④. Place the cross-linked polyethylene film in a vacuum oven and dry it for a period of time to obtain cross-linked polyethylene;

[0016] 3. Preparation of doped modified silicone grease:

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

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

[0019] The silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared by the present invention improves the interface insulation performance of silicone rubber and cross-linked polyethylene, so that it can meet the greater electrical resistance required by cable accessories in engineering.

[0020] And reduce the failure rate of the composite interface of cable accessories.

[0021] The present 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 composite interface of silicone rubber and cross-linked polyethylene, thereby further improving the electrical insulation performance of the composite interface.

[0022] Principle of the present invention:

[0023] 1. The present 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 (F4TCNQ) and introduces it into silicone grease, thereby constructing a carrier trap and hindering the injection and transmission of carriers. Under the synergistic effect of this filler and silicone grease, the electrical insulation properties of the composite interface between silicone rubber and cross-linked polyethylene will be further increased. The modified silicone grease is coated on the interface between silicone rubber and cross-linked polyethylene. Under the synergistic effect of F4TCNQ with high electron affinity and silicone grease, a carrier trap is constructed, which effectively limits the injection and transmission of carriers, thereby improving the interface breakdown voltage, surface breakdown voltage and DC body breakdown field strength of the composite interface between silicone rubber and cross-linked polyethylene;

[0024] 2. The present invention explores that the optimal doping ratio of F4TCNQ is 0.6wt% by measuring multiple doping concentrations; the results show that the interface breakdown voltage of the silicone grease-coated silicone rubber and cross-linked polyethylene composite interface modified by the optimal doping ratio is 22.61KV at a pressure of 0.3MPa, and the interface breakdown voltage is 25.51KV at a pressure of 0.4MPa. At a pressure of 0.5MPa, the interface breakdown voltage is 27.02KV. The DC body breakdown field strength is 164.7KV / mm at 30°C, and 158.8KV / mm at 50°C. The DC body breakdown field strength is 150.8KV / mm at 70°C. The surface breakdown voltage is 11.22KV.

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

[0026] 1. The present 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, thereby constructing a carrier trap and hindering the injection and transmission of carriers; under the synergistic effect of this filler and silicone grease, the intermolecular force is enhanced, the slippage of silicone grease is reduced, and the electrical insulation properties of the composite interface of silicone rubber and cross-linked polyethylene are further increased;

[0027] 2. The present invention belongs to a fully organic system, is suitable for large-scale production, has low production difficulty, and the modified silicone grease makes the composite interface of silicone rubber and cross-linked polyethylene have higher interface breakdown performance, which greatly improves its insulation performance; it provides a new research and development idea for the adaptation of the insulation performance and electrical strength of accessory-enhanced silicone rubber and cross-linked polyethylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The interfacial breakdown voltage of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative ratios at different swelling times at 0.3 MPa;

[0029] Figure 2 (a) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared in different comparative ratios 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 in different comparative ratios at a pressure of 0.4 MPa, and (c) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared in different comparative ratios at a pressure of 0.5 MPa;

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

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

[0032] Figure 5 (a) is a graph showing the interface conductivity current of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 30°C as a function of the electric field strength, (b) is a graph showing the interface conductivity current of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 50°C as a function of the electric field strength, and (c) is a graph showing the interface conductivity current of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 70°C as a function of the electric field strength;

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

[0034] Figure 7 Weibull distribution diagram 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 the silicone rubber coated with different modified silicone greases at 30°C in different embodiments, (b) is a Weibull distribution diagram of the DC breakdown field strength of the silicone rubber coated with different modified silicone greases at 50°C in different embodiments, (c) is a Weibull distribution diagram of the DC breakdown field strength of the silicone rubber coated with different modified silicone greases at 70°C in different embodiments;

[0036] Fig. 9 (a) is a graph showing the interface conductivity current of a silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared by coating modified silicone grease with different doping ratios in different embodiments at 30°C as a function of the electric field strength; (b) is a graph showing the interface conductivity current of a silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared by coating modified silicone grease with different doping ratios in different embodiments at 50°C as a function of the electric field strength; (c) is a graph showing the interface conductivity current of a silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared by coating modified silicone grease with different doping ratios in different embodiments at 70°C as a function of the electric field strength;

[0037] Fig.10 The following are infrared spectra of different types of silicone grease;

[0038] Fig.11 The following are XRD patterns of different types of silicone grease;

[0039] Fig.12 (a) is a surface electron micrograph of the silicone rubber just coated with silicone grease in Comparative Example 4, and (b) is a surface electron micrograph of the silicone rubber coated with silicone grease in Comparative Example 4 after heat aging for 240 hours;

[0040] Fig.13 (a) is the surface electrostatic potential cloud diagram of silicone grease, (b) is the F 4 Surface electrostatic potential cloud diagram of TCNQ organic small molecule;

[0041] Fig.14 (a) is silicone grease and F 4 Surface LUMO distribution cloud diagram and HUMO distribution cloud diagram of TCNQ organic small molecule, (b) silicone grease and F 4 Comparative energy level distribution diagram of TCNQ organic small molecule;

[0042] Fig.15 This is a diagram of the interface breakdown voltage test device;

[0043] Fig.16 This is a diagram of the interface conductivity test device;

[0044] Fig.17 This is a diagram of the surface breakdown voltage test device. DETAILED DESCRIPTION

[0045] Specific implementation method 1: This implementation method is a method for preparing a silicone rubber / cross-linked polyethylene composite medium for cable accessories, which is specifically completed by the following steps:

[0046] 1. Preparation of silicone rubber:

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

[0048] ②, stirring the silicone rubber component A for a period of time under a variable frequency disperser to obtain the stirred silicone rubber component A; stirring the silicone rubber component B for a period of time under a variable frequency disperser to obtain the stirred silicone rubber component B; mixing the stirred silicone rubber component A and the stirred silicone rubber component B, stirring for a period of time under a variable frequency disperser 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, and vacuumize while stirring to remove bubbles introduced during the mixing and stirring process. Continue vacuuming and stirring for a period of time to obtain uniformly mixed silicone rubber;

[0050] ④. Apply the uniformly mixed silicone rubber evenly in the mold, and then put the mold into a flat vulcanizer for primary vulcanization to obtain a composite medium after primary vulcanization;

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

[0052] 2. Preparation of cross-linked polyethylene:

[0053] ①, placing the cross-linked polyethylene particles in a vacuum oven and drying them for a period of time to obtain dried cross-linked polyethylene particles;

[0054] ②, put the dried cross-linked polyethylene particles into a mold at a temperature of 110°C to 115°C, and then put the mold into a flat vulcanizer for melting. The specific process is: first melt at a pressure of 0MPa for 10min to 15min, then melt at a pressure of 5MPa for 10min to 15min, then melt at a pressure of 10MPa for 10min to 15min, and finally melt at a pressure of 15MPa for 10min to 15min to obtain a cross-linked polyethylene after primary melting;

[0055] ③, placing the once melted cross-linked polyethylene in a flat vulcanizer at a temperature of 175°C and a pressure of 15MPa for cross-linking for a period of time to obtain a cross-linked polyethylene film;

[0056] ④. Place the cross-linked polyethylene film in a vacuum oven and dry it for a period of time to obtain cross-linked polyethylene;

[0057] 3. Preparation of doped modified silicone grease:

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

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

[0060] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that: the mass ratio of the silicone rubber component A to the silicone rubber component B described in step 1① is 1:1; the model of the silicone rubber component A described in step 1① is: 745-LG-7046-A-CN, purchased from Wacker Chemical (China) Co., Ltd., model of component B 745-LG-7046-B-CN, purchased from Wacker Chemical (China) Co., Ltd. The other steps are the same as those in the first embodiment.

[0061] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: the stirring time in step 1② is 1h to 2h, and the stirring speed is 2.8rps to 3rps; the vacuuming and stirring operation time in step 1③ is 2h to 3h. The other steps are the same as those in specific implementation method 1 or 2.

[0062] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that: the temperature of the primary vulcanization in step 1 ④ is 160°C to 170°C, and the pressure is 15MPa to 20MPa; the mold in step 1 ④ is 100mm×100mm×0.175mm in size. The other steps are the same as those in specific embodiments 1 to 3.

[0063] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the temperature of the secondary vulcanization in step 1 ⑤ is 190°C to 210°C, and the standing time in step 1 ⑤ is 4h to 5h. The other steps are the same as those in specific embodiments 1 to 4.

[0064] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that: the model of the cross-linked polyethylene described in step 2① is LD200GH, purchased from Beijing Yanshan Petrochemical Co., Ltd. of Sinopec Group; the drying temperature described in step 2① is 80°C, and the drying time is 24h. The other steps are the same as those of specific embodiments 1 to 5.

[0065] Specific embodiment seven: The difference between this embodiment and any one of specific embodiments one to six is ​​that: the dried cross-linked polyethylene particles described in step two ② are placed in a mold with a size of 100mm×100mm×0.175mm according to a mass of 2.5g to 2.7g for filling; the cross-linking time described in step two ③ is 30min; the temperature of the vacuum oven described in step two ④ is 80°C, and the vacuum drying time is 24h.

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

[0067] Specific embodiment eight: This embodiment differs from specific embodiments 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 the stirring is uniform; the silicone grease in step three is psaitong, Great Wall 7051, boer or Aladdin, all purchased from Beijing Inokai Technology Co., Ltd. The other steps are the same as specific embodiments one to seven.

[0068] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the mass of the modified silicone grease coated in step 4 is 1 g, and the dimensions of the silicone rubber and the cross-linked polyethylene are both 100 mm×100 mm×0.175 mm. The other steps are the same as those of specific embodiments 1 to 8.

[0069] Specific embodiment ten: This embodiment is that the silicone rubber / cross-linked polyethylene composite medium for cable accessories is widely used in the field of power transmission, submarine cable or rail transportation.

[0070] The following examples are used to verify the beneficial effects of the present invention:

[0071] Embodiment 1: A method for preparing a silicone rubber / cross-linked polyethylene composite medium for cable accessories is specifically completed by the following steps:

[0072] 1. Preparation of silicone rubber:

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

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

[0075] Model of component A of the silicone rubber described in step 1①: 745-LG-7046-A-CN, purchased from Wacker Chemical (China) Co., Ltd., model of component B 745-LG-7046-B-CN, purchased from Wacker Chemical (China) Co., Ltd.;

[0076] ②, stirring the silicone rubber component A under a variable frequency disperser for 1 hour to obtain the stirred silicone rubber component A; stirring the silicone rubber component B under a variable frequency disperser for 1 hour to obtain the stirred silicone rubber component B; mixing the stirred silicone rubber component A and the stirred silicone rubber component B, stirring for 1 hour under a variable frequency disperser to obtain a uniformly mixed silicone rubber composite material;

[0077] The stirring speed described in step 1② is 2.8 rps;

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

[0079] ④. Apply the uniformly mixed silicone rubber evenly in the mold, and then put the mold into a flat vulcanizer for primary vulcanization to obtain a composite medium after primary vulcanization;

[0080] The temperature of the primary vulcanization described in step 1④ is 165°C and the pressure is 15MPa;

[0081] The mold described in step 1④ has a size of 100mm×100mm×0.175mm;

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

[0083] The temperature of the secondary vulcanization described in step 1⑤ is 200°C;

[0084] The standing time described in step 1⑤ is 4h;

[0085] 2. Preparation of cross-linked polyethylene:

[0086] ①, placing the cross-linked polyethylene particles in a vacuum oven and drying them for a period of time to obtain dried cross-linked polyethylene particles;

[0087] The model of the cross-linked polyethylene described in step 2① is LD200GH, which is purchased from Beijing Yanshan Petrochemical Co., Ltd. of China Petrochemical Corporation;

[0088] The drying temperature in step 2① is 80°C and the drying time is 24h;

[0089] ②, put the dried cross-linked polyethylene particles into a mold at a temperature of 110°C, and then put the mold into a flat vulcanizer for melting. The specific process is: first melt at a pressure of 0MPa for 10min, then melt at a pressure of 5MPa for 10min, then melt at a pressure of 10MPa for 10min, and finally melt at a pressure of 15MPa for 10min to obtain a cross-linked polyethylene after primary melting;

[0090] The dried cross-linked polyethylene particles described in step 2② are placed in a mold with a size of 100 mm×100 mm×0.175 mm according to a mass of 2.6 g for filling;

[0091] ③, placing the once melted cross-linked polyethylene in a flat vulcanizer at a temperature of 175°C and a pressure of 15MPa for cross-linking for a period of time to obtain a cross-linked polyethylene film;

[0092] The cross-linking time described in step 2③ is 30min;

[0093] ④. Place the cross-linked polyethylene film in a vacuum oven and dry it for a period of time to obtain cross-linked polyethylene;

[0094] The temperature of the vacuum oven described in step 2④ is 80°C, and the vacuum drying time is 24h;

[0095] 3. Preparation of doped modified silicone grease:

[0096] The silicone grease and 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone were mixed 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 described in step 3 is 0.2:100;

[0098] The stirring time described in step 3 is 2h;

[0099] The silicone grease selected in step 3 is No. 4 silicone grease, which is a high vacuum silicone grease Aladdin brand, purchased from Beijing Inokai Technology Co., Ltd.;

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

[0101] The amount of the modified silicone grease described in step 4 is 1 g, and the dimensions of the silicone rubber and the cross-linked polyethylene are both 100 mm×100 mm×0.175 mm.

[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 3 is 0.4:100; the silicone rubber / cross-linked polyethylene composite medium for cable accessories obtained in step 4 (recorded as 0.4wt% / No. 4). The other steps and parameters are the same as those 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 3 is 0.6:100; the silicone rubber / cross-linked polyethylene composite medium for cable accessories obtained in step 4 (recorded as 0.6wt% / No. 4). The other steps and parameters are the same as those 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 3 is 0.8:100; the silicone rubber / cross-linked polyethylene composite medium for cable accessories obtained in step 4 (recorded as 0.8wt% / No. 4). The other steps and parameters are the same as those 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 3 is 1:100; the silicone rubber / cross-linked polyethylene composite medium for cable accessories obtained in step 4 (recorded as 1.0wt% / No. 4). The other steps and parameters are the same as those in Example 1.

[0106] Comparative Example 1: A method for preparing a silicone rubber / cross-linked polyethylene composite medium for cable accessories is specifically completed according to the following steps:

[0107] 1. Preparation of silicone rubber:

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

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

[0110] Model of component A of the silicone rubber described in step 1①: 745-LG-7046-A-CN, purchased from Wacker Chemical (China) Co., Ltd., model of component B 745-LG-7046-B-CN, purchased from Wacker Chemical (China) Co., Ltd.;

[0111] ②, stirring the silicone rubber component A under a variable frequency disperser for 1 hour to obtain the stirred silicone rubber component A; stirring the silicone rubber component B under a variable frequency disperser for 1 hour to obtain the stirred silicone rubber component B; mixing the stirred silicone rubber component A and the stirred silicone rubber component B, stirring for 1 hour under a variable frequency disperser to obtain a uniformly mixed silicone rubber composite material;

[0112] The stirring speed described in step 1② is 2.8 rps;

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

[0114] ④. Apply the uniformly mixed silicone rubber evenly in the mold, and then put the mold into a flat vulcanizer for primary vulcanization to obtain a composite medium after primary vulcanization;

[0115] The temperature of the primary vulcanization described in step 1④ is 165°C and the pressure is 15MPa;

[0116] The mold described in step 1④ has a size of 100mm×100mm×0.175mm;

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

[0118] The temperature of the secondary vulcanization described in step 1⑤ is 200°C;

[0119] The standing time described in step 1⑤ is 4h;

[0120] 2. Preparation of cross-linked polyethylene:

[0121] ①, placing the cross-linked polyethylene particles in a vacuum oven and drying them for a period of time to obtain dried cross-linked polyethylene particles;

[0122] The model of the cross-linked polyethylene described in step 2① is LD200GH, which is purchased from Beijing Yanshan Petrochemical Co., Ltd. of China Petrochemical Corporation;

[0123] The drying temperature in step 2① is 80°C and the drying time is 24h;

[0124] ②, put the dried cross-linked polyethylene particles into a mold at a temperature of 110°C, and then put the mold into a flat vulcanizer for melting. The specific process is: first melt at a pressure of 0MPa for 10min, then melt at a pressure of 5MPa for 10min, then melt at a pressure of 10MPa for 10min, and finally melt at a pressure of 15MPa for 10min to obtain a cross-linked polyethylene after primary melting;

[0125] The dried cross-linked polyethylene particles described in step 2② are placed in a mold with a size of 100 mm×100 mm×0.175 mm according to a mass of 2.6 g for filling;

[0126] ③, placing the once melted cross-linked polyethylene in a flat vulcanizer at a temperature of 175°C and a pressure of 15MPa for cross-linking for a period of time to obtain a cross-linked polyethylene film;

[0127] The cross-linking time described in step 2③ is 30min;

[0128] ④. Place the cross-linked polyethylene film in a vacuum oven and dry it for a period of time to obtain cross-linked polyethylene;

[0129] The temperature of the vacuum oven described in step 2④ is 80°C, and the vacuum drying time is 24h;

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

[0131] The amount of silicone grease used in step 3 is 1 g, and the dimensions of silicone rubber and cross-linked polyethylene are both 100 mm × 100 mm × 0.175 mm;

[0132] The silicone grease selected in step 3 is No. 1, which is high vacuum silicone grease psaitong, purchased from Beijing Inokai Technology Co., Ltd.

[0133] Comparative Example 2: The difference between this comparative example and comparative example 1 is that the silicone grease in step 3 is No. 2, which is a high vacuum silicone grease Great Wall 7501 brand purchased from Beijing Inokai Technology Co., Ltd.; the silicone rubber / cross-linked polyethylene composite medium for cable accessories obtained in step 3 (referred to as No. 2 or No. 2 silicone grease). The other steps and parameters are the same as those in comparative example 1.

[0134] Comparative Example 3: The difference between this comparative example and comparative example 1 is that the silicone grease in step 3 is No. 3, which is a high vacuum silicone grease of Boer brand purchased from Beijing Inokai Technology Co., Ltd.; the silicone rubber / cross-linked polyethylene composite medium for cable accessories obtained in step 3 (recorded as No. 3 or No. 3 silicone grease). The other steps and parameters are the same as those in comparative example 1.

[0135] Comparative Example 4: The difference between this comparative example and comparative example 1 is that the silicone grease in step 3 is No. 4, which is a high vacuum silicone grease Aladdin brand purchased from Beijing Inokai Technology Co., Ltd.; the silicone rubber / cross-linked polyethylene composite medium for cable accessories obtained in step 3 (recorded as No. 4 or No. 4 silicone grease). The other steps and parameters are the same as those in comparative example 1.

[0136] Figure 1 The interfacial breakdown voltage of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative ratios at different swelling times at 0.3 MPa;

[0137] Depend on Figure 1It can be seen that when silicone grease is coated on the composite interface of silicone rubber and cross-linked polyethylene for a long time, due to the similar molecular formula of silicone grease and silicone rubber, swelling will occur, so that silicone grease will be integrated into silicone rubber. This swelling effect is conducive to good contact of the interface in the short term, but the cross-linking structure of silicone rubber is destroyed in long-term operation, forming an electrically weak area, and the swelling effect deteriorates the electrical and mechanical properties of silicone rubber. As shown in the figure, after four different silicone greases are coated on the composite interface of silicone rubber and cross-linked polyethylene for a certain period of time, their interface breakdown voltages all show different degrees of decline. Among them, the decline trend of silicone grease No. 4 is the most gentle, from 24.9KV at 0h, to 22.1KV after 24h. Compared with the other three silicone greases, the change value of the interface breakdown voltage of silicone grease No. 4 is less than 20% of its own interface breakdown voltage value, so silicone grease No. 4 is least affected by swelling. Therefore, through experimental testing, silicone grease No. 4 is selected as a silicone grease with excellent anti-swelling properties. It has the smallest swelling effect on silicone rubber.

[0138] Figure 2 (a) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared in different comparative ratios 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 in different comparative ratios at a pressure of 0.4 MPa, and (c) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared in different comparative ratios at a pressure of 0.5 MPa;

[0139] Depend on Figure 2 It can be seen that under a pressure of 0.3MPa, coating silicone grease at the interface of silicone rubber and cross-linked polyethylene will increase its interfacial breakdown voltage. Among the four selected silicone greases, silicone grease No. 4 has the highest interfacial breakdown voltage, proving that its interfacial electrical insulation performance under this pressure is the best. Under this pressure, the interfacial breakdown voltage of SIR is 18.96KV, the interfacial breakdown voltage of No. 1 is 19.81KV, the interfacial breakdown voltage of No. 2 is 20.18KV, the interfacial breakdown voltage of No. 3 is 20.39KV, and the interfacial breakdown voltage of No. 4 is 21.05KV. As the pressure increases, the interfacial breakdown voltage is improved to a certain extent. This is because when the interfacial pressure is small, there are a large number of gaps at the composite interface, and the dielectric constant of the gas in the gap is smaller than that of SIR or XLPE, so the interfacial electric field distribution is extremely uneven. Since the breakdown field strength of the air gap is much lower than that of the solid material, the interface is more likely to discharge. When the interface pressure is increased, the actual contact area at the interface between silicone rubber and cross-linked polyethylene increases, so the volume of gas in the gap decreases. At this time, the distribution of the interface electric field becomes uniform, and discharge is not easy to occur. Therefore, increasing the interface pressure is beneficial to improving the insulation performance of the interface.

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

[0141] Depend on Figure 3 It can be seen that coating silicone grease on the surface of silicone rubber will increase its surface breakdown voltage. Among the four selected silicone greases, silicone grease No. 4 has the highest surface breakdown voltage of 10.57KV. It proves that the electrical insulation performance of silicone grease acting on the surface of silicone rubber is the best. Coating silicone grease on the surface of silicone rubber will increase the surface breakdown voltage of silicone rubber because the smoother the XLPE / silicone rubber interface, the higher the breakdown voltage value of the interface. The coating of silicone grease can reduce the roughness of the interface and reduce the local electric field strength, thereby increasing the surface breakdown voltage. Silicone grease has a similar structure to silicone rubber, and similar structures are prone to similar dissolution. Small molecule silicone grease, as a solvent molecule, penetrates into the silicone rubber polymer chain and causes swelling. The swelling of silicone grease destroys the cross-linked structure of silicone rubber. This swelling effect may change the surface properties of silicone rubber and increase its surface breakdown voltage.

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

[0143] Depend on Figure 4 It can be seen that coating silicone grease on the surface of silicone rubber will increase its DC breakdown field strength, and the DC breakdown field strength of coating No. 4 silicone grease is the highest, reaching 158.3KV / mm at a temperature of 30°C, 157.6KV / mm at a temperature of 50°C, and 156.5KV / mm at a temperature of 70°C. The reason why coating silicone grease will increase the DC breakdown field strength of silicone rubber is that silicone grease coated on the surface of silicone rubber can form a protective film to reduce the direct contact and influence of the external environment on silicone rubber. In addition, the molecular structure of silicone grease is similar to that of silicone rubber. This similarity allows silicone grease to penetrate into the polymer chain of silicone rubber and swell. This swelling effect can enhance the insulation performance of silicone rubber in a short time. Silicone grease coating can reduce the unevenness of the surface of silicone rubber, make the electric field distribution more uniform, and reduce the situation where the local electric field strength is too high, thereby improving the DC breakdown field strength of silicone rubber. The breakdown field strength of silicone rubber decreases as the temperature rises. This is because at high temperatures, carriers gain more high-temperature kinetic energy. Under the action of high fields, carriers are more likely to undergo collision ionization and breakdown paths are more likely to form. Therefore, the breakdown field strength decreases as the temperature rises.

[0144] Figure 5(a) is a graph showing the interface conductivity current of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 30°C as a function of the electric field strength, (b) is a graph showing the interface conductivity current of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 50°C as a function of the electric field strength, and (c) is a graph showing the interface conductivity current of silicone rubber / cross-linked polyethylene composite media for cable accessories prepared in different comparative proportions at 70°C as a function of the electric field strength;

[0145] Depend on Figure 5 It can be seen that coating silicone grease at the interface of silicone rubber and cross-linked polyethylene will increase the interfacial conductivity of the composite interface. At 30°C, by comparing the interfacial conductivity of four different types of silicone grease, the interfacial conductivity of the silicone rubber and cross-linked polyethylene composite interface coated with No. 4 silicone grease is the lowest. Under low and high field conditions, its interfacial conductivity is always within 10 -15 -10 -14 S / m, the interface conductivity does not change much with the electric field strength. With the increase of temperature, under the conditions of 50℃ and 70℃, the interface conductivity of the four silicone greases is slightly increased. However, the overall distribution of interface conductivity between different silicone greases is the same as that at 30℃. This is because as the temperature increases, the electrons in the composite interface of silicone rubber and cross-linked polyethylene will jump from the valence band to the conduction band, increasing the number of carriers, and the increase in temperature may reduce the conductivity activation energy, making it easier for carriers to jump, thereby improving the interface 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 by coating modified silicone grease with different doping ratios in different embodiments at a pressure of 0.3MPa, (b) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared by coating modified silicone grease with different doping ratios in different embodiments at a pressure of 0.4MPa, (c) is a Weibull distribution diagram of the interface breakdown voltage of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared by coating modified silicone grease with different doping ratios in different embodiments at a pressure of 0.5MPa;

[0147] Depend on Figure 6 It can be seen that the coating of doped F on the composite interface of silicone rubber and cross-linked polyethylene 4 The silicone grease after TCNQ organic semiconductor filling will increase its interface breakdown voltage. 4 With the increase of TCNQ doping content, the interface breakdown voltage of the silicone rubber and cross-linked polyethylene coated thereon increases first and then decreases. 4The interface breakdown voltage reaches the highest when the TCNQ concentration is 0.6wt%, which is 22.61KV at 0.3MPa, 25.51KV at 0.4MPa, and 27.02KV at 0.5MPa. The reason for the increase in interface breakdown voltage is that F has a high affinity for electrons. 4 TCNQ can introduce deep traps at the interface of silicone rubber and cross-linked polyethylene. The deep traps can hinder the migration of carriers, reduce the collision ionization of carriers, and work synergistically with silicone grease, thereby increasing the intermolecular force and reducing the slippage of silicone grease. 4 TCNQ can enhance the conjugation effect between fillers, which in turn promotes the transport of carriers. 4 When the distance between TCNQ molecules is small, it is easy to cause local crystalline phase composition, thus causing local defects, which in turn leads to a decrease in the interface breakdown voltage.

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

[0149] Depend on Figure 7 It can be seen that the surface of silicone rubber is coated with doped F 4 The silicone grease filled with TCNQ organic semi-body will increase its surface breakdown voltage. 4 With the increase of TCNQ doping content, the surface breakdown voltage of the silicone rubber coated on the surface shows a trend of first increasing and then decreasing. 4 The surface breakdown voltage reached the highest when the TCNQ concentration was 0.6wt%, reaching 11.22KV. 4 The reason for the improved breakdown performance of TCNQ is that the high electron affinity F 4 TCNQ can successfully construct deep electron traps to capture free electrons. Due to the Coulomb force between the electrons in the lower unoccupied molecular orbital (LUMO) of these fillers and the holes in the highest occupied molecular orbital (HOMO) in the polymer matrix, it is difficult for the trapped electrons to escape. 4 TCNQ works synergistically to reduce the accumulation of space charge inside the sample, thereby increasing the breakdown field strength of silicone rubber. When the concentration of the introduced filler reaches above 0.6wt%, the DC breakdown field strength of silicone rubber decreases. This is because too much high electron affinity filler may increase the accumulation of space charge, which will lead to uneven electric field distribution, increase 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 the silicone rubber coated with different modified silicone greases at 30°C in different embodiments, (b) is a Weibull distribution diagram of the DC breakdown field strength of the silicone rubber coated with different modified silicone greases at 50°C in different embodiments, (c) is a Weibull distribution diagram of the DC breakdown field strength of the silicone rubber coated with different modified silicone greases at 70°C in different embodiments;

[0151] Depend on Figure 8 It can be seen that the surface of silicone rubber is coated with doped F 4 The silicone grease doped with TCNQ organic semi-filler will increase its DC breakdown field strength. 4 With the increase of TCNQ doping content, the DC breakdown field strength of the silicone rubber coated on the surface shows a trend of first increasing and then decreasing. 4 The DC breakdown field strength reaches the highest when the TCNQ concentration is 0.6wt%. At 30℃, it reaches 164.7KV / mm, at 50℃, it reaches 158.8KV / mm, and at 70℃, it reaches 150.8KV / mm. 4 The reason for the improved breakdown performance of TCNQ is that the high electron affinity F 4 TCNQ can successfully construct deep electron traps to capture free electrons. Due to the Coulomb force between the electrons in the lower unoccupied molecular orbital (LUMO) of these fillers and the holes in the highest occupied molecular orbital (HOMO) in the polymer matrix, it is difficult for the trapped electrons to escape. 4 TCNQ works synergistically to reduce the accumulation of space charge inside the sample, thereby increasing the breakdown field strength of silicone rubber. When the concentration of the introduced filler reaches above 0.6wt%, the DC body breakdown field strength of silicone rubber decreases. This is because too much high electron affinity filler may increase the accumulation of space charge, which will lead to uneven electric field distribution, increase local electric field strength, and thus reduce the breakdown field strength. The breakdown field strength of silicone rubber decreases with increasing temperature. This is because at high temperatures, carriers gain more high-temperature kinetic energy. Under the action of high fields, carriers are more likely to undergo collision ionization and breakdown paths are more likely to form. Therefore, the breakdown field strength decreases with increasing temperature.

[0152] Fig. 9(a) is a graph showing the interface conductivity current of a silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared by coating modified silicone grease with different doping ratios in different embodiments at 30°C as a function of the electric field strength; (b) is a graph showing the interface conductivity current of a silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared by coating modified silicone grease with different doping ratios in different embodiments at 50°C as a function of the electric field strength; (c) is a graph showing the interface conductivity current of a silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared by coating modified silicone grease with different doping ratios in different embodiments at 70°C as a function of the electric field strength;

[0153] Depend on Fig. 9 It can be seen that the silicone grease doped with F4TCNQ organic semi-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 silicone grease. This filler can capture and transfer more charges, resulting in an increase in charge density at the interface, which in turn reduces the conductivity. And with the increase of F 4 With the increase of TCNQ doping content, the interfacial conductivity coated on the interface of silicone rubber and cross-linked polyethylene shows a trend of decreasing first and then increasing. This is because the relatively low LUMO energy level of F4TCNQ can establish carrier traps in the electron transmission path, thereby capturing carriers and limiting the free travel of carriers, which reduces the interfacial conductivity. When the doping content of the filler is high, too much high electron affinity filler may increase the accumulation of space charge, which will lead to uneven electric field distribution, increase the local electric field strength, and then form the phenomenon of increased interfacial conductivity.

[0154] Fig.10 The following are infrared spectra of different types of silicone grease;

[0155] Depend on Fig.10 It can be seen that 700cm -1 The absorption peak at belongs to Si(CH 3 ) 3 Vibration, 790-816cm -1 The absorption peak at 2965.40 cm belongs to CH vibration. -1 The absorption peak belongs to CH 2 Asymmetric stretching vibration of functional groups, 2905.71 cm -1 The absorption peak belongs to CH 2 Symmetric stretching vibration of functional groups, 1000-1100 cm -1 The absorption peak belongs to the stretching vibration of Si-O functional group. No. 3 silicone grease is at 2965.40cm -1 The absorption peak intensity at 800-1000cm -11000-1100cm -1 There is a relatively wide and strong peak band at 2965.40 and 1000-1100cm-1, indicating that there is a strong molecular effect of silicon-oxygen bond, indicating that its silicon-oxygen structure is more regular, and it is speculated that it has stronger mechanical properties. -1 There is a medium-intensity absorption peak at 2965.4cm, and the peak intensity is relatively regular. Therefore, its structure is simple and there are fewer silicon-oxygen cross-linked structures. -1 The absorption peak intensity is the lowest at 790-816cm -1 1000-1100cm -1 The strongest absorption peak is at , and the peak width is the narrowest, indicating that its vibration mode is relatively simple and its content concentration is the highest. Therefore, this type of silicone grease has the highest organic content and the least degree of cross-linking, so it is judged that this type of silicone grease has the best insulation performance.

[0156] Fig.11 The following are XRD patterns of different types of silicone grease;

[0157] Depend on Fig.11 It can be seen that these four silicone greases show diffraction peaks at similar 2θ angles, which indicates that they may have similar crystal structures or lattice parameters. The diffraction peaks of silicone grease No. 4 and No. 3 have higher peak intensities, indicating that they may have higher crystallinity. Higher crystallinity increases the chemical and physical stability of the silicone grease, which is essential for maintaining its insulating properties. Highly stable materials are less likely to decompose or degrade under the action of an electric field, thereby maintaining their insulating properties. The diffraction peaks of silicone grease No. 1 and No. 2 have lower peak intensities, indicating that they have lower crystallinity. Therefore, the physical structures of these two silicone greases are not as stable as those of silicone grease No. 3 and No. 4. Therefore, their insulating properties are lower than those of silicone grease No. 3 and No. 4.

[0158] Fig.12 (a) is a surface electron micrograph of the silicone rubber just coated with silicone grease in Comparative Example 4, and (b) is a surface electron micrograph of the silicone rubber coated with silicone grease in Comparative Example 4 after heat aging for 240 hours;

[0159] Depend on Fig.12 It can be seen that the surface of silicone rubber itself is very regular and there are no cracks. After the silicone rubber is coated with silicone grease and heat aged for 240 hours, obvious cracks appear on the surface of the silicone rubber, and even breaks. This shows that with the deepening of aging, the microstructure of silicone rubber has changed. In addition, during the heat aging process, due to the influence of silicone grease on the swelling of silicone rubber, the movement of the molecular chain will be aggravated, and when it exceeds the dissociation energy of the molecular bond, it will cause thermal degradation. The heat aging method is more serious in damaging silicone rubber materials, because the applied load has a deeper degree of damage to the silicone rubber molecular chain, and the presence of force load will cause the free volume to decrease, affecting the free travel of the charge movement, thereby affecting its insulation performance.

[0160] Fig.14 (a) is silicone grease and F 4 Surface LUMO distribution cloud diagram and HUMO distribution cloud diagram of TCNQ organic small molecule, (b) silicone grease and F 4 Comparative energy level distribution diagram of TCNQ organic small molecule;

[0161] pass Fig.14 (b) The energy level comparison distribution diagram shows that the introduction of F4TCNQ filler can introduce traps to weaken the electron jump transmission, which will make it difficult for electrons to jump, weaken the intrinsic excitation ability, and cause the electron transmission to deteriorate, the electron transmission path to decrease, and the probability of collision ionization to decrease. This fully explains the phenomenon that the F4TCNQ filler modified silicone grease phase has good breakdown performance.

[0162] The present invention dopes high electron affinity filler F into silicone grease 4 TCNQ can clearly improve the insulation performance of the composite interface of silicone rubber and cross-linked polyethylene in cable accessories.

[0163] Although the present invention has been disclosed as above in the preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing a silicone rubber / cross-linked polyethylene composite medium for cable accessories, characterized in that The preparation method is specifically completed according to the following steps:

1. Preparation of silicone rubber: ①. Weigh component A of silicone rubber and component B of silicone rubber; ②, stirring the silicone rubber component A in a variable frequency disperser for a period of time to obtain the stirred silicone rubber component A; Stirring the silicone rubber component B in a variable frequency disperser for a period of time to obtain the silicone rubber component B after stirring; The stirred silicone rubber component A and the stirred silicone rubber component B are mixed, and stirred for a period of time under a variable frequency disperser to obtain a uniformly mixed silicone rubber composite material; ③. Place the uniformly mixed silicone rubber composite material in a stirring and vacuuming device, and vacuumize while stirring to remove bubbles introduced during the mixing and stirring process. Continue vacuuming and stirring for a period of time to obtain uniformly mixed silicone rubber; ④. Apply the uniformly mixed silicone rubber evenly in the mold, and then put the mold into a flat vulcanizer for primary vulcanization to obtain a composite medium after primary vulcanization; ⑤. Place the composite medium after primary vulcanization in a high-temperature blast oven for secondary vulcanization to obtain a composite medium after secondary vulcanization; let the composite medium after secondary vulcanization stand for a period of time at room temperature to obtain silicone rubber; 2. Preparation of cross-linked polyethylene: ①, placing the cross-linked polyethylene particles in a vacuum oven and drying them for a period of time to obtain dried cross-linked polyethylene particles; ②, put the dried cross-linked polyethylene particles into a mold at a temperature of 110°C to 115°C, and then put the mold into a flat vulcanizer for melting. The specific process is: first melt at a pressure of 0MPa for 10min to 15min, then melt at a pressure of 5MPa for 10min to 15min, then melt at a pressure of 10MPa for 10min to 15min, and finally melt at a pressure of 15MPa for 10min to 15min to obtain a cross-linked polyethylene after primary melting; ③, placing the once melted cross-linked polyethylene in a flat vulcanizer at a temperature of 175°C and a pressure of 15MPa for cross-linking for a period of time to obtain a cross-linked polyethylene film; ④. Place the cross-linked polyethylene film in a vacuum oven and dry it for a period of time to obtain cross-linked polyethylene; 3. Preparation of doped modified silicone grease: The silicone grease and 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone are mixed and stirred for a period of time to obtain a modified silicone grease; Fourth, the modified silicone grease is coated on the surface of the silicone rubber, and then covered with cross-linked polyethylene 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 medium for cable accessories according to claim 1, characterized in that The mass ratio of the silicone rubber component A to the silicone rubber component B described in step 1① is 1:1; the model of the silicone rubber component A described in step 1① is: Purchased from Wacker Chemical (China) Co., Ltd., the model of component B Purchased from Wacker Chemicals (China) Co., Ltd.

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

4. The method for preparing a silicone rubber / cross-linked polyethylene composite medium for cable accessories according to claim 1, characterized in that The temperature of the primary vulcanization described in step 1④ is 160℃~170℃, and the pressure is 15MPa~20MPa; the mold described in step 1④ has a size of 100mm×100mm×0.175mm.

5. The method for preparing a silicone rubber / cross-linked polyethylene composite medium for cable accessories according to claim 1, characterized in that The temperature of the secondary vulcanization described in step 1⑤ is 190℃~210℃; the standing time described in step 1⑤ is 4h~5h.

6. The method for preparing a silicone rubber / cross-linked polyethylene composite medium for cable accessories according to claim 1, characterized in that The model of the cross-linked polyethylene described in step 2① is LD200GH, which is purchased from Beijing Yanshan Petrochemical Co., Ltd. of China Petrochemical Corporation; the drying temperature described in step 2① is 80° C., and the drying time is 24 hours.

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

8. The method for preparing a silicone rubber / cross-linked polyethylene composite medium for cable accessories according to claim 1, characterized in that The mass ratio of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silicone grease described in step three is (0.2-0.8):100; the stirring time described in step three is 20 minutes, until the stirring is uniform; the silicone grease described in step three is psaitong, Great Wall 7051, boer or Aladdin, all of which are purchased from Beijing Inokai Technology Co., Ltd.

9. The method for preparing a silicone rubber / cross-linked polyethylene composite medium for cable accessories according to claim 1, characterized in that The mass of the modified silicone grease coated in step 4 is 1 g, and the dimensions of the silicone rubber and the cross-linked polyethylene are both 100 mm×100 mm×0.175 mm.

10. Application of the silicone rubber / cross-linked polyethylene composite medium for cable accessories prepared by the preparation method according to 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 or rail transportation.

Images