Cross-linked polyethylene insulated power cable capable of preventing strong ultraviolet rays as well as preparation method and application of cross-linked polyethylene insulated power cable

Abstract

The invention relates to the technical field of cables, in particular to a cross-linked polyethylene insulated power cable capable of preventing strong ultraviolet rays as well as a preparation method and application of the cross-linked polyethylene insulated power cable. According to the invention, through the synergistic effect of the brush-like polymer coated silicon dioxide and the reactive ultraviolet absorbent, a multi-layer protection network is constructed in the insulating layer. The brush-like polymer layer improves the dispersibility of silicon dioxide through a flexible chain segment and blocks ultraviolet light and oxygen diffusion; the reactive auxiliary agent is grafted to a polyethylene molecular chain in the crosslinking process, so that migration loss is avoided. The key raw materials comprise low-density polyethylene resin, eugenol-based methacrylate, an antioxidant 1010 and the like. The preparation method comprises the steps of brush-like polymer preparation, melt extrusion granulation, copper conductor coating and steam cross-linking shaping. The cable has the advantages of high breakdown strength, low dielectric loss and excellent aging resistance, and is suitable for power transmission in severe environments such as a photovoltaic power station.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and in particular to a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation, its preparation method, and its application. Background Technology

[0002] When cross-linked polyethylene (XLPE) insulated power cables operate for extended periods in environments with high ultraviolet radiation, such as high altitudes and desert photovoltaic power stations, the insulation layer is prone to synergistic acceleration of photo-oxidative and thermo-oxidative aging. Traditional cables often use carbon black shielding or single hindered amine light stabilizers as UV protection methods. However, high levels of carbon black significantly reduce the insulation resistivity and dielectric strength of the material, while single small-molecule light stabilizers are prone to migration and volatilization under long-term thermal and mechanical stress, resulting in insufficient protection durability. Especially under conditions of high-irradiance ultraviolet radiation and large diurnal temperature variations, the polyethylene molecular chains are excited by photon energy to generate alkyl free radicals, which then trigger a chain oxidation reaction, accompanied by surface pulverization, microcrack propagation, and a decrease in volume resistivity, accelerating the deterioration of insulation performance.

[0003] While the introduction of nano-inorganic fillers such as silica can improve thermal stability to some extent, unmodified nanoparticles tend to agglomerate in the polyethylene matrix, forming interfacial defects that become electric field concentration points and crack initiation sites. Some studies have used silane coupling agents to modify the surface of silica, but simple amino or alkylation modifications still fail to achieve full compatibility with the polymer matrix and lack active UV protection, failing to block the photo-oxidative aging chain reaction. Furthermore, in existing technologies, UV absorbers and antioxidants are mostly added through physical blending, resulting in low reactivity and poor dispersion uniformity during crosslinking, making it difficult to form a gradient protective network in the bulk and surface layers. This leads to a significant increase in the dielectric constant and dielectric loss of the material after long-term use, and a substantial decrease in breakdown strength.

[0004] Especially for cross-linked polyethylene cable insulation, the peroxide cross-linking system itself generates free radical byproducts during high-temperature cross-linking. If the light-stabilized system fails to effectively inhibit subsequent oxidation, it will actually accelerate initial aging. Currently, there is a lack of a synergistic protection solution that can balance long-term UV shielding, high-temperature cross-linking compatibility, high insulation reliability, and mechanical durability, which limits the service life and operational safety of cables in extreme environments. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation, its preparation method and its application, so as to solve the problem that existing cross-linked polyethylene cables suffer from insulation layer powdering and cracking and dielectric performance degradation due to the synergistic aging of multiple factors such as light, heat and oxygen in strong ultraviolet radiation environment, and that traditional carbon black or single stabilizer solutions are difficult to achieve both long-term protection and high insulation reliability.

[0006] To achieve the above objectives, the present invention provides a cross-linked polyethylene insulated power cable that is resistant to strong ultraviolet radiation, comprising: a copper conductor and a cross-linked polyethylene insulation layer covering the outer surface of the copper conductor;

[0007] The cross-linked polyethylene insulation layer, by mass parts, is prepared from the following raw materials: 1000 parts low-density polyethylene resin, 3-7 parts 4-allyloxy-2-hydroxybenzophenone, 3-5 parts eugenol methacrylate, 1 part antioxidant 1010, 6-10 parts brush-coated silica, and 14-18 parts dicumyl peroxide.

[0008] Preferably, the thickness of the cross-linked polyethylene insulation layer is 4 mm.

[0009] Preferably, the low-density polyethylene resin is grade LD200GH.

[0010] Preferably, the eugenol methacrylate is obtained by acid-catalyzed epoxy ring-opening etherification reaction of eugenol and glycidyl methacrylate; the mass ratio of eugenol to glycidyl methacrylate is 164:156.

[0011] Preferably, the brush-like polymer-coated silica is obtained by graft polymerization of N-(2-hydroxypropyl)methacrylamide, eugenol methacrylate, 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole and hindered amine methacrylate onto ATRP-initiated functionalized silica; the mass ratio of N-(2-hydroxypropyl)methacrylamide, eugenol methacrylate, 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, hindered amine methacrylate to ATRP-initiated functionalized silica is 25-35:18-22:8-12:8-12:50.

[0012] Preferably, the ATRP-initiating functionalized silica is obtained by grafting 2-bromoisobutyryl bromide onto silica after amination with 3-aminopropyltriethoxysilane; the mass ratio of silica, 3-aminopropyltriethoxysilane and 2-bromoisobutyryl bromide is 100:10:24.

[0013] Preferably, the specific surface area of ​​the silicon dioxide is 150-250 m². 2 / g.

[0014] Preferably, the hindered amine methacrylate is obtained by acylation reaction of 2,2,6,6-tetramethyl-4-piperidinol and methacryloyl chloride; the mass ratio of 2,2,6,6-tetramethyl-4-piperidinol to methacryloyl chloride is 172:120.

[0015] Furthermore, the present invention also provides a method for preparing a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation, comprising the following steps:

[0016] (1) Preparation of brush-shaped polymer-coated nano-silica;

[0017] (2) Low-density polyethylene resin, 4-allyloxy-2-hydroxybenzophenone, eugenol methacrylate, antioxidant 1010, brush-shaped polymer coated silica and dicumyl peroxide are mixed and melt-extruded into granules to obtain cross-linked UV-resistant insulating material granules.

[0018] (3) The cross-linked UV-resistant insulating material particles are melted, extruded, and coated onto the outer surface of the copper conductor to obtain a cable with an insulating layer;

[0019] (4) The cable covered with the insulation layer is cross-linked and shaped to obtain a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation.

[0020] Preferably, in step (2), the mixing is carried out in a high-speed mixer at a stirring speed of 500-700 rpm for 8-12 min.

[0021] Preferably, in step (2), the melt extrusion granulation adopts a co-rotating parallel twin-screw extruder. The temperatures of each temperature zone of the extruder are as follows: 75-85℃ in the feeding section, 85-95℃ in the melting section, 95-105℃ in the mixing section, 100-110℃ in the metering section, and 105-115℃ in the die head. The screw speed is 130-170 rpm, the barrel vacuum degree is -0.08 MPa, and the process is carried out under nitrogen protection.

[0022] Preferably, in step (3), the temperatures of each zone of the extruder barrel during melt extrusion are 65-75℃, 75-85℃, 85-95℃, 95-105℃, and 105-115℃ at the die head, respectively. The screw speed is 35-45 rpm, and the linear velocity is 35-45 m / min.

[0023] Preferably, in step (4), the crosslinking and shaping are carried out using a long crosslinking tube filled with steam. The temperature of the crosslinking tube is 245-255℃, the pressure is 0.9-1.1MPa, and the cable stays in the crosslinking tube for 13-17 minutes. After the crosslinking is completed, the cable is cooled to room temperature in a long water tank, then tempered in hot water at 80℃ for 1-3 hours, and finally left to stand at room temperature for 24 hours.

[0024] Furthermore, the present invention also provides an application of a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation in power transmission under strong ultraviolet radiation conditions.

[0025] The beneficial effects of this invention are:

[0026] This invention constructs a multi-layered protective network within a cross-linked polyethylene insulation layer through the synergistic effect of brush-like polymer coating of silica and reactive UV absorbers. The brush-like polymer layer, through its flexible segments fully entangled with the polyethylene matrix, significantly improves the dispersibility and interfacial compatibility of silica, effectively blocking the diffusion paths of oxygen and UV degradation products, thereby delaying surface pulverization and microcrack propagation. Simultaneously, the benzotriazole structural units and hindered amine units introduced into the brush-like polymer can form a directionally aligned UV shielding layer on the insulation layer surface, achieving efficient absorption and energy dissipation of high-energy photons and reducing the probability of photo-induced degradation of the polyethylene molecular chains.

[0027] The reactive UV absorber achieves uniform bulk distribution through grafting of allyl groups onto the polyethylene molecular chains during peroxide crosslinking, avoiding migration loss of small molecule additives and maintaining long-term UV absorption capacity. Synergistically with the eugenol methacrylate units in the brushed polymer, it effectively quenches free radicals generated by crosslinking side reactions, inhibits chain reactions induced by thermo-oxidative aging, and improves the oxidation-induced stability of the material. Furthermore, the composite structure of the silica core and the brushed polymer shell forms physical crosslinking points in the crosslinking network, enhancing chain segment constraint and improving the insulation layer's resistance to deformation at high temperatures, thereby maintaining the structural integrity of the cable under long-term thermomechanical stress.

[0028] This solution, through molecular design and multi-component synergy, significantly improves the aging resistance of cross-linked polyethylene under strong ultraviolet radiation while maintaining its excellent insulation properties. The interface modification effect of brushed polymer coating on silica reduces the negative impact of inorganic fillers on dielectric properties, while the combination of reactive ultraviolet absorbers and brushed polymer functional units achieves long-term synergy between ultraviolet shielding and oxidation resistance. Ultimately, this results in cable insulation with high breakdown strength, low dielectric loss, excellent mechanical retention, and resistance to surface cracking, meeting the long-term operational requirements of harsh environments such as high-altitude and desert photovoltaic power stations. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0030] Figure 1 The infrared spectra of fumed silica, brushed polymer-coated silica, and cross-linked UV-resistant insulating material provided in Example 2 of this invention are shown. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0032] Example 1:

[0033] Step 1: Preparation of brush-shaped polymer-coated silica

[0034] Step 1.1: Synthesis of eugenol methacrylate monomer

[0035] Add 164g of eugenol and 300mL of anhydrous toluene to a three-necked flask, stir and dissolve at 40℃, then add 156g of glycidyl methacrylate, followed by 2g of p-toluenesulfonic acid as a catalyst and 200g of 5A molecular sieve desiccant. Assemble a reflux condenser and a moisture separator, and reflux the reaction in an oil bath at 115℃ for 8h. After the reaction is complete, filter at 80℃, distill under reduced pressure, add 200mL of anhydrous diethyl ether to the residue for recrystallization, filter, and vacuum dry at 40℃ for 12h to obtain eugenol methacrylate.

[0036] Step 1.2: Synthesis of hindered amine methacrylate monomers

[0037] 172 g of 2,2,6,6-tetramethyl-4-piperidinol and 300 mL of anhydrous dichloromethane were added to a three-necked flask. The mixture was stirred in an ice-water bath at 0 °C. 120 g of triethylamine was added dropwise, followed by 120 g of methacryloyl chloride. The temperature of the system was kept below 5 °C during the addition process. After the addition was completed, the temperature was raised to room temperature and the mixture was stirred for 4 h. After the reaction was completed, the mixture was filtered. The filtrate was washed three times each with saturated sodium bicarbonate solution and deionized water. After separation, the organic phase was dried with anhydrous sodium sulfate, filtered, and distilled under reduced pressure to obtain hindered amine methacrylate.

[0038] Step 1.3: Introducing atom transfer radical polymerization initiation sites onto the silica surface

[0039] Add 100g of fumed silica (with a specific surface area of ​​approximately 200m²) to a three-necked flask equipped with a reflux condenser. 2 10 g of 3-aminopropyltriethoxysilane and 0.2 g of p-toluenesulfonic acid were added, and the mixture was stirred and ultrasonically dispersed at 80 °C for 30 min. The mixture was then refluxed and stirred at 110 °C for 6 h. After the reaction was complete, the mixture was cooled to room temperature, filtered, washed with 300 mL of toluene, and dried under vacuum at 80 °C for 8 h to obtain surface-aminated silica. The surface-aminated silica was then added to 400 mL of anhydrous dichloromethane, cooled to 0 °C in an ice-water bath, and 20 g of triethylamine was added. 24 g of 2-bromoisobutyryl bromide was added dropwise under stirring. After the addition was complete, the mixture was heated to room temperature and stirred for 4 h. After the reaction was complete, the mixture was filtered, washed three times with dichloromethane, and dried under vacuum at 80 °C for 8 h to obtain ATRP-initiated functionalized silica.

[0040] Step 1.4: In-situ growth of brush-shaped polymers to prepare brush-shaped polymer-coated silica

[0041] 50g of ATRP-initiating functionalized silica, 25g of N-(2-hydroxypropyl)methacrylamide, 18g of eugenol methacrylate, 8g of 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole and 8g of hindered amine methacrylate monomer were added to a three-necked flask equipped with a reflux condenser and a nitrogen inlet. 350mL of N,N-dimethylformamide / methanol mixed solvent (volume ratio 3:1) was added, and the mixture was stirred and dispersed for 25min under nitrogen protection. Then, 2g of cuprous bromide and 4g of 2,2′-bipyridine were added to the system, and the reaction was carried out at 65℃ for 6h under continuous nitrogen purging. After the reaction was completed, the mixture was filtered and washed three times each with deionized water and anhydrous ethanol. Finally, the mixture was dried under vacuum at 60℃ for 18h to obtain brush-like polymer-coated silica.

[0042] Step 2: Preparation of cross-linked UV-resistant insulating particles

[0043] Step 2.1: Drying and Premixing

[0044] 1000g of low-density polyethylene resin (LD200GH produced by Beijing Yanshan Branch of China Petroleum & Chemical Corporation) was vacuum dried at 80℃ for 4h, cooled to room temperature, and 1000g of dried low-density polyethylene resin was added to a high-speed mixer. 3g of 4-allyloxy-2-hydroxybenzophenone, 3g of eugenol methacrylate, 1g of antioxidant 1010, 6g of brush-coated silica, and 14g of dicumyl peroxide crosslinking agent were added. The mixture was stirred and premixed at 500rpm for 8min at room temperature to obtain the premix.

[0045] Step 2.2: Preparation of cross-linked insulating material by melt extrusion granulation

[0046] The premixed material is fed into a co-rotating parallel twin-screw extruder via a vacuum feeder. The temperatures of each zone of the extruder are set sequentially as follows: 75°C for the feeding section, 85°C for the melting section, 95°C for the mixing section, 100°C for the metering section, and 105°C for the die head. The screw speed is set to 130 rpm, the barrel vacuum is maintained at -0.08 MPa, and the entire line is protected by nitrogen. After the molten and mixed material is cooled by a water-cooled strip granulator, it is granulated to obtain cross-linked UV-resistant insulating material granules.

[0047] Step 3: Extrusion and cross-linking of UV-resistant cross-linked polyethylene insulated power cables

[0048] Step 3.1: Insulation extrusion and primary coating

[0049] Cross-linked UV-resistant insulating material granules are fed into the insulation extruder of a three-layer co-extrusion vertical cross-linking production line. The temperatures of each zone of the insulation extruder barrel are set to 65℃, 75℃, 85℃, 95℃, and 105℃ at the die head. The screw speed is controlled at 35 rpm. The melt is uniformly coated on the outer surface of the copper conductor through the die head mold. The designed insulation thickness is 4 mm, and the linear speed is controlled at 35 m / min to obtain a cable with an insulation layer.

[0050] Step 3.2: Tubular crosslinking and shaping

[0051] The cable with insulation layer is continuously fed into a long cross-linking tube filled with water vapor for cross-linking. The temperature of the cross-linking tube is set to 245℃ and the pressure is set to 0.9MPa. The residence time of the cable in the cross-linking tube is controlled to 13min. After cross-linking is completed, the cable is cooled to room temperature in a long water bath, then tempered in 80℃ hot water for 1h, and finally left to stand at room temperature for 24h to obtain a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation.

[0052] Example 2:

[0053] Step 1: Preparation of brush-shaped polymer-coated silica

[0054] Step 1.1: Synthesis of eugenol methacrylate monomer

[0055] Add 164g of eugenol and 300mL of anhydrous toluene to a three-necked flask, stir and dissolve at 40℃, then add 156g of glycidyl methacrylate, followed by 2g of p-toluenesulfonic acid as a catalyst and 200g of 5A molecular sieve desiccant. Assemble a reflux condenser and a moisture separator, and reflux the reaction in an oil bath at 115℃ for 8h. After the reaction is complete, filter at 80℃, distill under reduced pressure, add 200mL of anhydrous diethyl ether to the residue for recrystallization, filter, and vacuum dry at 40℃ for 12h to obtain eugenol methacrylate.

[0056] Step 1.2: Synthesis of hindered amine methacrylate monomers

[0057] 172 g of 2,2,6,6-tetramethyl-4-piperidinol and 300 mL of anhydrous dichloromethane were added to a three-necked flask. The mixture was stirred in an ice-water bath at 0 °C. 120 g of triethylamine was added dropwise, followed by 120 g of methacryloyl chloride. The temperature of the system was kept below 5 °C during the addition process. After the addition was completed, the temperature was raised to room temperature and the mixture was stirred for 4 h. After the reaction was completed, the mixture was filtered. The filtrate was washed three times each with saturated sodium bicarbonate solution and deionized water. After separation, the organic phase was dried with anhydrous sodium sulfate, filtered, and distilled under reduced pressure to obtain hindered amine methacrylate.

[0058] Step 1.3: Introducing atom transfer radical polymerization initiation sites onto the silica surface

[0059] Add 100g of fumed silica (with a specific surface area of ​​approximately 200m²) to a three-necked flask equipped with a reflux condenser. 2 10 g of 3-aminopropyltriethoxysilane and 0.2 g of p-toluenesulfonic acid were added, and the mixture was stirred and ultrasonically dispersed at 80 °C for 30 min. The mixture was then refluxed and stirred at 110 °C for 6 h. After the reaction was complete, the mixture was cooled to room temperature, filtered, washed with 300 mL of toluene, and dried under vacuum at 80 °C for 8 h to obtain surface-aminated silica. The surface-aminated silica was then added to 400 mL of anhydrous dichloromethane, cooled to 0 °C in an ice-water bath, and 20 g of triethylamine was added. 24 g of 2-bromoisobutyryl bromide was added dropwise under stirring. After the addition was complete, the mixture was heated to room temperature and stirred for 4 h. After the reaction was complete, the mixture was filtered, washed three times with dichloromethane, and dried under vacuum at 80 °C for 8 h to obtain ATRP-initiated functionalized silica.

[0060] Step 1.4: In-situ growth of brush-shaped polymers to prepare brush-shaped polymer-coated silica

[0061] 50g of ATRP-initiating functionalized silica, 30g of N-(2-hydroxypropyl)methacrylamide, 20g of eugenol methacrylate, 10g of 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole and 10g of hindered amine methacrylate monomer were added to a three-necked flask equipped with a reflux condenser and a nitrogen inlet. 400mL of N,N-dimethylformamide / methanol mixed solvent (volume ratio 3:1) was added, and the mixture was stirred and dispersed for 30min under nitrogen protection. Then, 3g of cuprous bromide and 6g of 2,2′-bipyridine were added to the system, and the reaction was carried out at 70℃ for 8h under continuous nitrogen purging. After the reaction was completed, the mixture was filtered and washed three times each with deionized water and anhydrous ethanol. Finally, the mixture was dried under vacuum at 60℃ for 24h to obtain brush-like polymer-coated silica.

[0062] Step 2: Preparation of cross-linked UV-resistant insulating particles

[0063] Step 2.1: Drying and Premixing

[0064] 1000g of low-density polyethylene resin (LD200GH produced by Beijing Yanshan Branch of China Petroleum & Chemical Corporation) was vacuum dried at 80℃ for 4h and cooled to room temperature. 1000g of the dried low-density polyethylene resin, 5g of 4-allyloxy-2-hydroxybenzophenone, 4g of eugenol methacrylate, 1g of antioxidant 1010, 8g of brush-coated silica, and 16g of dicumyl peroxide crosslinking agent were added to a high-speed mixer. The mixture was stirred and premixed at 600rpm for 10min at room temperature to obtain the premix.

[0065] Step 2.2: Preparation of cross-linked insulating material by melt extrusion granulation

[0066] The premixed material is fed into a co-rotating parallel twin-screw extruder via a vacuum feeder. The temperatures of each zone of the extruder are set sequentially as follows: 80°C for the feeding section, 90°C for the melting section, 100°C for the mixing section, 105°C for the metering section, and 110°C for the die head. The screw speed is set to 150 rpm, the barrel vacuum is maintained at -0.08 MPa, and the entire line is protected by nitrogen. After the molten and mixed material is cooled by a water-cooled strip granulator, it is granulated to obtain cross-linked UV-resistant insulating material granules.

[0067] Step 3: Extrusion and cross-linking of UV-resistant cross-linked polyethylene insulated power cables

[0068] Step 3.1: Insulation extrusion and primary coating

[0069] Cross-linked UV-resistant insulating material granules are fed into the insulation extruder of a three-layer co-extrusion vertical cross-linking production line. The temperatures of each zone of the insulation extruder barrel are set to 70℃, 80℃, 90℃, 100℃, and 110℃ at the die head. The screw speed is controlled at 40 rpm. The melt is uniformly coated on the outer surface of the copper conductor through the die head mold. The designed insulation thickness is 4 mm, and the linear speed is controlled at 40 m / min to obtain a cable with an insulation layer.

[0070] Step 3.2: Tubular crosslinking and shaping

[0071] The cable with the insulation layer is continuously fed into a long cross-linking tube filled with water vapor for cross-linking. The temperature of the cross-linking tube is set to 250℃ and the pressure is set to 1.0MPa. The residence time of the cable in the cross-linking tube is controlled to 15min. After the cross-linking is completed, it is cooled to room temperature in a long water bath, then tempered in 80℃ hot water for 2h, and finally left to stand at room temperature for 24h to obtain a cross-linked polyethylene insulated power cable resistant to strong ultraviolet rays.

[0072] Example 3:

[0073] Step 1: Preparation of brush-shaped polymer-coated silica

[0074] Step 1.1: Synthesis of eugenol methacrylate monomer

[0075] Add 164g of eugenol and 300mL of anhydrous toluene to a three-necked flask, stir and dissolve at 40℃, then add 156g of glycidyl methacrylate, followed by 2g of p-toluenesulfonic acid as a catalyst and 200g of 5A molecular sieve desiccant. Assemble a reflux condenser and a moisture separator, and reflux the reaction in an oil bath at 115℃ for 8h. After the reaction is complete, filter at 80℃, distill under reduced pressure, add 200mL of anhydrous diethyl ether to the residue for recrystallization, filter, and vacuum dry at 40℃ for 12h to obtain eugenol methacrylate.

[0076] Step 1.2: Synthesis of hindered amine methacrylate monomers

[0077] 172 g of 2,2,6,6-tetramethyl-4-piperidinol and 300 mL of anhydrous dichloromethane were added to a three-necked flask. The mixture was stirred in an ice-water bath at 0 °C. 120 g of triethylamine was added dropwise, followed by 120 g of methacryloyl chloride. The temperature of the system was kept below 5 °C during the addition process. After the addition was completed, the temperature was raised to room temperature and the mixture was stirred for 4 h. After the reaction was completed, the mixture was filtered. The filtrate was washed three times each with saturated sodium bicarbonate solution and deionized water. After separation, the organic phase was dried with anhydrous sodium sulfate, filtered, and distilled under reduced pressure to obtain hindered amine methacrylate.

[0078] Step 1.3: Introducing atom transfer radical polymerization initiation sites onto the silica surface

[0079] 100 g of fumed silica (specific surface area approximately 200 m² / g) and 500 mL of anhydrous toluene were added to a three-necked flask equipped with a reflux condenser. The mixture was stirred and ultrasonically dispersed at 80 °C for 30 min. Subsequently, 10 g of 3-aminopropyltriethoxysilane and 0.2 g of p-toluenesulfonic acid were added, and the mixture was refluxed and stirred at 110 °C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and washed with 300 mL of toluene. The mixture was then dried under vacuum at 80 °C for 8 h to obtain surface-aminated silica. The surface-aminated silica was then added to 400 mL of anhydrous dichloromethane and cooled to 0 °C in an ice-water bath. 20 g of triethylamine was added, and 24 g of 2-bromoisobutyryl bromide was added dropwise under stirring. After the addition was completed, the temperature was raised to room temperature and stirring was continued for 4 h. After the reaction was completed, the mixture was filtered, washed three times with dichloromethane, and dried under vacuum at 80 °C for 8 h to obtain ATRP-initiated functionalized silica.

[0080] Step 1.4: In-situ growth of brush-shaped polymers to prepare brush-shaped polymer-coated silica

[0081] 50g of ATRP-initiating functionalized silica, 35g of N-(2-hydroxypropyl)methacrylamide, 22g of eugenol methacrylate, 12g of 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole and 12g of hindered amine methacrylate monomer were added to a three-necked flask equipped with a reflux condenser and a nitrogen inlet. 450mL of N,N-dimethylformamide / methanol mixed solvent (volume ratio 3:1) was added, and the mixture was stirred and dispersed for 35min under nitrogen protection. Subsequently, 4g of cuprous bromide and 8g of 2,2′-bipyridine were added to the system, and the reaction was carried out at 75℃ for 10h under continuous nitrogen purging. After the reaction was completed, the mixture was filtered and washed three times each with deionized water and anhydrous ethanol. Finally, the mixture was dried under vacuum at 60℃ for 30h to obtain brush-like polymer-coated silica.

[0082] Step 2: Preparation of cross-linked UV-resistant insulating particles

[0083] Step 2.1: Drying and Premixing

[0084] 1000g of low-density polyethylene resin (LD200GH produced by Beijing Yanshan Branch of China Petroleum & Chemical Corporation) was vacuum dried at 80℃ for 4h, cooled to room temperature, and 1000g of dried low-density polyethylene resin was added to a high-speed mixer. 7g of 4-allyloxy-2-hydroxybenzophenone, 5g of eugenol methacrylate, 1g of antioxidant 1010, 10g of brush-coated silica, and 18g of dicumyl peroxide crosslinking agent were added. The mixture was stirred and premixed at 700rpm for 12min at room temperature to obtain the premix.

[0085] Step 2.2: Preparation of cross-linked insulating material by melt extrusion granulation

[0086] The premixed material is fed into a co-rotating parallel twin-screw extruder via a vacuum feeder. The temperatures of each zone of the extruder are set sequentially as follows: 85°C for the feeding section, 95°C for the melting section, 105°C for the mixing section, 110°C for the metering section, and 115°C for the die head. The screw speed is set to 170 rpm, the barrel vacuum is maintained at -0.08 MPa, and the entire line is protected by nitrogen. After the molten and mixed material is cooled by a water-cooled strip granulator, it is granulated to obtain cross-linked UV-resistant insulating material granules.

[0087] Step 3: Extrusion and cross-linking of UV-resistant cross-linked polyethylene insulated power cables

[0088] Step 3.1: Insulation extrusion and primary coating

[0089] Cross-linked UV-resistant insulating material granules are fed into the insulation extruder of a three-layer co-extrusion vertical cross-linking production line. The temperatures of each zone of the insulation extruder barrel are set to 75℃, 85℃, 95℃, 105℃, and 115℃ at the die head. The screw speed is controlled at 45 rpm. The melt is uniformly coated on the outer surface of the copper conductor through the die head mold. The designed insulation thickness is 4 mm, and the linear speed is controlled at 45 m / min to obtain a cable with an insulation layer.

[0090] Step 3.2: Tubular crosslinking and shaping

[0091] The cable with the insulation layer is continuously fed into a long cross-linking tube filled with water vapor for cross-linking. The temperature of the cross-linking tube is set to 255℃ and the pressure is set to 1.1MPa. The residence time of the cable in the cross-linking tube is controlled to 17min. After cross-linking is completed, the cable is cooled to room temperature in a long water bath, then tempered in 80℃ hot water for 3h, and finally left to stand at room temperature for 24h to obtain a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation.

[0092] Comparative Example 1:

[0093] The difference between Comparative Example 1 and Example 2 is that 5g of 4-allyloxy-2-hydroxybenzophenone was not added during the high-speed mixer premixing process in step 2.1. Instead, only 4g of eugenol methacrylate, 1g of antioxidant 1010, 8g of brush-coated silica, and 16g of dicumyl peroxide crosslinking agent were added. The other conditions were the same as in Example 2.

[0094] Comparative Example 2:

[0095] The difference between Comparative Example 2 and Example 2 is that 8g of brush-shaped polymer-coated silica was not added during the high-speed mixer premixing process in step 2.1. Instead, only 5g of 4-allyloxy-2-hydroxybenzophenone, 4g of eugenol methacrylate, 1g of antioxidant 1010 and 16g of dicumyl peroxide crosslinking agent were added. The remaining conditions were the same as in Example 2.

[0096] Comparative Example 3:

[0097] The difference between Comparative Example 3 and Example 2 is that the 8g of brush-coated silica added in step 2.1 was replaced with an equal amount of 8g of fumed silica, while the remaining raw materials were still 5g of 4-allyloxy-2-hydroxybenzophenone, 4g of eugenol methacrylate, 1g of antioxidant 1010 and 16g of dicumyl peroxide crosslinking agent, and the other conditions were the same as in Example 2.

[0098] Comparative Example 4:

[0099] The difference between Comparative Example 4 and Example 2 is that the 8g of brush-shaped polymer-coated silica added in step 2.1 is replaced with an equal amount of 8g of surface-aminated silica. The surface-aminated silica is prepared according to the first half of the method in step 1.3 of Example 2. The remaining raw materials in step 2.1 are still 5g of 4-allyloxy-2-hydroxybenzophenone, 4g of eugenol methacrylate, 1g of antioxidant 1010 and 16g of dicumyl peroxide crosslinking agent. The remaining conditions are the same as in Example 2.

[0100] Comparative Example 5:

[0101] The difference between Comparative Example 5 and Example 2 is that in step 1.4, when preparing the brush-like polymer-coated silica, 20g of eugenol-based methacrylate monomer was replaced with an equal amount of 20g of N-(2-hydroxypropyl)methacrylamide, so that the monomer system in step 1.4 became 50g of atom transfer radical polymerization initiator functionalized silica, 50g of N-(2-hydroxypropyl)methacrylamide, 10g of 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole and 10g of hindered amine methacrylate, and the remaining conditions were the same as in Example 2.

[0102] Comparative Example 6:

[0103] The difference between Comparative Example 6 and Example 2 is that in step 1.4, when preparing the brush-like polymer-coated silica, 10g of 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole monomer was replaced by 10g of N-(2-hydroxypropyl)methacrylamide, so that the monomer system in step 1.4 became 50g of atom transfer radical polymerization initiator functionalized silica, 40g of N-(2-hydroxypropyl)methacrylamide, 20g of eugenol methacrylate and 10g of hindered amine methacrylate, and the remaining conditions were the same as in Example 2.

[0104] Performance testing:

[0105] During testing and sampling, a 1000mm long middle section sample was cut along the axial direction of the cable prepared in the examples and comparative examples. After peeling off the copper conductor, only the cross-linked polyethylene insulation layer was retained, and the sample was conditioned for 24 hours in an environment of (23±2)℃ and (50±5)% relative humidity. Thermogravimetric analysis, cross-linking degree and oxidation induction time tests were performed using 2mm×2mm×2mm small sample pieces obtained by shearing. Dielectric properties and breakdown strength tests were performed using a slicer to cut two types of flat thin sheets with thicknesses of 0.50±0.05mm and 1.00±0.05mm, and the electrodes were pressed together in silicone oil for measurement. Ultraviolet aging and mechanical tests were performed using a cutter to prepare dumbbell-shaped samples with a width of 4.0±0.1mm, a gauge length of 20.0±0.5mm and a thickness of 2.0±0.1mm.

[0106] Fourier transform infrared spectroscopy characterization: The fumed silica, brush-like polymer-coated silica, and cross-linked UV-resistant insulating material provided in Example 2 were characterized using a Fourier transform infrared spectrometer. The results are as follows: Figure 1 As shown.

[0107] Thermogravimetric analysis: 5.0 mg of each sample was weighed and placed in an alumina crucible. The temperature was increased from 30 °C to 600 °C at a heating rate of 10 °C / min under a nitrogen atmosphere (flow rate 50 mL / min). The 5% weight loss temperature, the temperature corresponding to the maximum decomposition rate, and the residual mass fraction at 600 °C were recorded. The results are shown in Table 1.

[0108] Crosslinking degree (gel content) test: The crosslinking degree test was carried out according to GB / T 18474-2001. 0.3000±0.0100g of the sample after shearing the insulation layer of each sample was placed in a stainless steel mesh bag and then placed in xylene reflux solvent. The mixture was extracted at a constant temperature of 135℃ for 8h. After extraction, the mesh bag was removed and rinsed 3 times with xylene. Subsequently, it was vacuum dried at 80℃ to constant weight. The mass after extraction was recorded as m1 and the mass before extraction as m0. The gel content (crosslinking degree) G was calculated as G = m1 / m0 × 100%. The results are shown in Table 1.

[0109] Oxidation induction time test: The oxidation induction time was tested according to GB / T 19466.6-2009. 6.0 mg of each sample was weighed and placed in an open aluminum crucible. The temperature was raised to 200℃ at 20℃ / min under a nitrogen atmosphere (flow rate 50 mL / min) and held for 5 min. Then the oxygen atmosphere was switched to (flow rate 50 mL / min). The time from the start of switching to oxygen to the appearance of the obvious exothermic oxidation peak was recorded as the oxidation induction time. The results are shown in Table 1.

[0110] UV accelerated aging, surface cracking time, and mechanical property retention rate: UV accelerated aging was conducted according to GB / T 16422.3-2022, using a fluorescent UVA-340 lamp with an irradiance set at 0.76 W / (m²). 2 The test cycle was fixed as follows: 8 hours of UV irradiation at 340 nm (at the 340 nm mark), 4 hours of condensation at 50 °C, and a total exposure time of 1000 hours. The outer surface of the sample was visually inspected every 24 hours, and the time when the first continuous visible microcracks appeared was confirmed under a 10x magnifying glass. Tensile strength and elongation at break were tested according to GB / T 2951.11-2008 before aging and after 1000 hours of aging, respectively. The tensile speed was fixed at 50 mm / min, and the number of samples in each group was n=5. The retention rate of tensile strength and elongation at break were calculated. The results are shown in Table 1.

[0111] Dielectric constant and dielectric loss factor test: Dielectric properties were tested according to GB / T 1409-2006. The insulating sheet with a thickness of 1.00 mm was measured using a parallel plate electrode structure. An AC voltage of 1.0 kV was applied at a frequency of 50 Hz in an environment of (23±2) ℃, and the relative permittivity and dielectric loss tangent were recorded. The relative permittivity and dielectric loss tangent were then tested after UV accelerated aging test for 1000 h. The results are shown in Table 1.

[0112] DC breakdown strength test: The DC breakdown strength test was conducted according to GB / T 1408.1-2016 and in conjunction with GB / T 1408.2-2016. A ball-ball electrode structure was used and the test was conducted in silicone oil to avoid surface flashover. A 0.50 mm thick insulating sheet was used as the sample. The voltage rise rate was fixed at 1.0 kV / s until breakdown. The breakdown voltage was recorded and the DC breakdown strength was calculated. The DC breakdown strength was then tested after 1000 h of UV accelerated aging. The results are shown in Table 1.

[0113] Table 1 Performance Test Results

[0114]

[0115] Data Analysis:

[0116] As can be seen from the data of Examples 1-3 in Table 1, the UV-resistant cross-linked polyethylene insulating material prepared by the present invention exhibits stable comprehensive performance in terms of thermogravimetric decomposition characteristics, degree of cross-linking, oxidation-induced behavior, UV cracking and mechanical retention, as well as dielectric parameters and breakdown strength. The reasons are as follows: Low-density polyethylene resin forms a continuous cross-linking network under the action of dicumyl peroxide cross-linking agent, which improves chain segment constraint and thermal deformation stability; 4-allyloxy-2-hydroxybenzophenone enters the polyethylene molecular chain through free radical addition, which can absorb high-energy photons in the bulk phase and inhibit photo-oxidative chain breakage; the brush-like polymer coated with silica provides multi-point anchoring and blocking pathways at the interface; N-(2-hydroxypropyl)methacrylamide in the brush-like polymer improves interface wetting and dispersion; eugenol methacrylate and antioxidant 1010 jointly weaken the peroxide chain reaction; and 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole and hindered amine methacrylate form weather-resistant stable units on the surface, thereby achieving long-term reliable operation of the insulation layer in strong ultraviolet environment without significantly sacrificing electrical performance.

[0117] As can be seen from the data in Table 1 for Example 2 and Comparative Example 1, without the addition of 4-allyloxy-2-hydroxybenzophenone, the material exhibited surface cracking earlier during UV accelerated aging, with a simultaneous decrease in mechanical stability and dielectric stability, and a more significant decrease in breakdown strength after aging. The main reason for this is the lack of bulk absorption and energy dissipation channels. Photo-induced free radicals are more prone to hydrogen extraction and β-cleavage on the low-density polyethylene backbone, leading to an accumulation of oxidation products and an increase in polar groups, thus increasing the dielectric constant and dielectric loss. Therefore, the synergistic effect of 4-allyloxy-2-hydroxybenzophenone and brush-coated silica is key to improving UV resistance and dielectric properties.

[0118] As can be seen from the data in Table 1 for Example 2 and Comparative Example 2, although the dielectric loss or breakdown strength can be maintained in the initial state without the addition of brush-like polymer-coated silica, the dielectric constant and dielectric loss increase more significantly after UV aging, and the mechanical retention and cracking time are significantly shortened. The presumed reason is that the lack of interfacial barrier and multiple stabilizing groups provided by brush-like polymer-coated silica makes it easier for photo-oxidation products to diffuse inward and form defect channels; at the same time, insufficient improvement in interfacial traps and dispersion leads to a greater accumulation of space charge and local field strength after aging.

[0119] As can be seen from the data in Table 1 for Example 2 and Comparative Examples 3 and 4, replacing the brush-like polymer-coated silica with fumed silica or surface-aminated silica shortened the oxidation induction time, accelerated UV cracking, and resulted in a more significant deterioration in dielectric constant and dielectric loss. The presumed reason is that without the brush-like polymer layer, silica is more prone to agglomeration and the formation of micro-defects in the cross-linked network, becoming the starting point for electric field concentration and photo-oxidative decomposition; while surface-aminated silica introduces a stronger polar interface, increasing polarizability and hygroscopicity, further amplifying the dielectric loss after aging.

[0120] As can be seen from the data in Table 1 for Example 2 and Comparative Example 5, when replacing eugenol-based methacrylate with an equal amount of N-(2-hydroxypropyl)methacrylamide in the preparation of brush-like polymer-coated silica, the oxidation induction time was shortened, UV cracking occurred earlier, and the dielectric parameters fluctuated more significantly after aging. This may be because the aromatic structure of eugenol-based methacrylate is more conducive to inhibiting free radical chain oxidation, while the increased proportion of N-(2-hydroxypropyl)methacrylamide increases interfacial polarity and hygroscopicity, leading to a greater accumulation of photo-oxidation products and the formation of defect channels.

[0121] As can be seen from the data in Table 1 for Example 2 and Comparative Example 6, replacing 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole with N-(2-hydroxypropyl)methacrylamide resulted in decreased UV crack resistance and worsened stability of dielectric parameters and breakdown strength after aging. This is because 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole is located near the surface of the brush layer and can form a dual absorption and free radical inhibition effect with 4-allyloxy-2-hydroxybenzophenone in both the surface and bulk phases; its absence leads to insufficient surface protection, making it easier for oxidation products to accumulate and induce a concentrated electric field.

[0122] from Figure 1 It can be seen that fumed silica only grows at 1096, 800, and 467 cm⁻¹. -1 It exhibits typical Si-O-Si framework vibrational absorption peaks, accompanied by 3440 and 1630 cm⁻¹. -1 Water adsorption-related absorption; after being coated with brush-shaped polymer, the brush-shaped polymer-coated silica absorbs water at 2955-2854 cm⁻¹. -1 A distinct aliphatic CH stretching vibration peak appears at 1728 cm⁻¹. -1 Characteristic absorption of the ester group C=O appears at 1255 and 1162 cm⁻¹. -1 The appearance of a COC stretching vibration peak at 1600 and 1510 cm⁻¹, along with a slight broadening of the Si-O-Si absorption, indicates that the polymer brush-like segments have been successfully grafted and coated onto the silica surface; the further prepared cross-linked UV-resistant insulation material exhibits peaks at 1600 and 1510 cm⁻¹. -1A vibrational peak of the aromatic ring C=C skeleton appears at 1674 cm⁻¹. -1 A conjugated carbonyl absorption is observed nearby, accompanied by a 3060 cm⁻¹ absorption. -1 The aromatic CH stretching vibration indicates that the ultraviolet absorption structure has been introduced and participated in cross-linking, and all samples retain the characteristic peaks of the Si-O-Si framework, indicating that silica has been successfully embedded and formed a stable interfacial network with the organic phase.

[0123] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation, characterized in that, include: A copper conductor and a cross-linked polyethylene insulation layer covering the outer surface of the copper conductor; The cross-linked polyethylene insulation layer, by weight, is prepared from the following raw materials: 1000 parts low-density polyethylene resin, 3-7 parts 4-allyloxy-2-hydroxybenzophenone, 3-5 parts eugenol methacrylate, 1 part antioxidant 1010, 6-10 parts brushed polymer-coated silica, and 14-18 parts dicumyl peroxide; The brush-shaped polymer-coated silica is obtained by grafting N-(2-hydroxypropyl)methacrylamide, eugenol methacrylate, 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole and hindered amine methacrylate onto ATRP-initiated functionalized silica. The mass ratio of N-(2-hydroxypropyl)methacrylamide, eugenol methacrylate, 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, hindered amine methacrylate, and ATRP-initiating functionalized silica is 25-35:18-22:8-12:8-12:

50.

2. The cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation according to claim 1, characterized in that, The thickness of the cross-linked polyethylene insulation layer is 4 mm.

3. The cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation according to claim 1, characterized in that, The eugenol-based methacrylate is obtained by acid-catalyzed epoxy ring-opening etherification reaction of eugenol and glycidyl methacrylate; the mass ratio of eugenol to glycidyl methacrylate is 164:

156.

4. The cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation according to claim 1, characterized in that, The ATRP-initiating functionalized silica is obtained by grafting 2-bromoisobutyryl bromide onto silica after amylation with 3-aminopropyltriethoxysilane; the mass ratio of silica, 3-aminopropyltriethoxysilane and 2-bromoisobutyryl bromide is 100:10:

24.

5. The cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation according to claim 4, characterized in that, The specific surface area of ​​the silicon dioxide is 150-250 m². 2 / g.

6. The cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation according to claim 1, characterized in that, The hindered amine methacrylate is obtained by acylation of 2,2,6,6-tetramethyl-4-piperidinol and methacryloyl chloride; the mass ratio of 2,2,6,6-tetramethyl-4-piperidinol to methacryloyl chloride is 172:

120.

7. A method for preparing a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Preparation of brush-shaped polymer-coated nano-silica; (2) Low-density polyethylene resin, 4-allyloxy-2-hydroxybenzophenone, eugenol methacrylate, antioxidant 1010, brush-shaped polymer coated silica and dicumyl peroxide are mixed and melt-extruded into granules to obtain cross-linked UV-resistant insulating material granules. (3) The cross-linked UV-resistant insulating material particles are melted, extruded, and coated onto the outer surface of the copper conductor to obtain a cable with an insulating layer; (4) The cable with the insulation layer is cross-linked and shaped to obtain a cross-linked polyethylene insulated power cable that is resistant to strong ultraviolet radiation.

8. The method for preparing a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation according to claim 7, characterized in that, In step (2), the melt extrusion granulation adopts a co-rotating parallel twin-screw extruder. The temperatures of each temperature zone of the extruder are as follows: feeding section 75-85℃, melting section 85-95℃, mixing section 95-105℃, metering section 100-110℃, and die head 105-115℃. The screw speed is 130-170 rpm, the barrel vacuum degree is -0.08 MPa, and the process is carried out under nitrogen protection.

9. The method for preparing a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation according to claim 7, characterized in that, In step (4), crosslinking and shaping are carried out using a long crosslinking tube filled with steam. The temperature of the crosslinking tube is 245-255℃, the pressure is 0.9-1.1MPa, and the cable stays in the crosslinking tube for 13-17 minutes. After crosslinking is completed, the cable is cooled to room temperature in a long water bath, then tempered in 80℃ hot water for 1-3 hours, and finally left to stand at room temperature for 24 hours.

10. The application of a cross-linked polyethylene insulated power cable resistant to strong ultraviolet radiation according to any one of claims 1-6 in power transmission under strong ultraviolet radiation environment.

Images