Weatherproof cable with integrated insulation and shield

Abstract

The application belongs to the field of power cables, and discloses a kind of weather-proof overhead cables of insulation shielding integration, from inside to outside, including aluminum alloy conductor, conductor-insulation interface layer, insulation shielding integration layer and weather-proof protective layer in proper order;The purpose of the application is to provide a kind of weather-proof overhead cables of insulation shielding integration and preparation method thereof, adopt EMA and LLDPE thermodynamics incompatible to form two-phase co-continuous structure, conductive carbon black selective distribution realizes the scheme of integration of shielding and insulation, zinc stannate / nano yttrium oxide composite filler and nano barium titanate are introduced to form deep-shallow trap gradient cooperation to inhibit space charge, adopt perfluoro octyl triethoxysilane modified synthesis fluorine mica and KH-560 modified boehmite nanosheet to construct laminated water-blocking interface layer, adopt PVDF-HFP and POE blend to add KH-550 modified nano neodymium oxide to construct fluoropolymer / polyolefin composite weather-proof protective layer.

Description

Technical Field

[0001] This invention relates to the field of power cable technology, specifically to an integrated insulation and shielding weather-resistant overhead cable. Background Technology

[0002] Overhead cables are power transmission lines laid in the air and exposed to the outdoor environment for extended periods, requiring them to simultaneously meet insulation, shielding, and weather resistance requirements. Traditional medium-voltage overhead cables employ a three-layer co-extruded structure consisting of a conductor shield, an insulation layer, and an insulation-shielding layer. The conductor shield and insulation-shielding layers are semi-conductive layers used to distribute the electric field evenly, while the insulation layer provides the main insulation. This three-layer structure suffers from problems such as interlayer interface defects, complex manufacturing processes, and water tree growth along the interfaces.

[0003] In the prior art, CN122103718A discloses a multi-level synergistic grafted insulation material, which uses SiO2@Nylon core-shell particles and MAH-g-POE ternary grafting to improve insulation performance, but it is still a three-layer split structure and the interlayer interface problem has not been solved.

[0004] CN202511754848 discloses a gradient interface nano-MgO for high-voltage cables, which is modified with poly(glycidyl methacrylate)-poly(1-octene) block, but this scheme focuses on the gradient interface inside the insulation layer and does not involve the integration of shielding and insulation.

[0005] CN202411644282 discloses a water-tree resistant insulating material blended with SEBS and SEBS-g-MAH, which uses an elastomeric phase to toughen and suppress water tree initiation. However, the purpose of blending SEBS in this scheme is to resist water tree rather than to achieve integrated shielding function.

[0006] CN103059378B discloses an EMA+POE+LDPE blend system for use in magnetic levitation feeder cables, which improves flexibility. However, this system does not involve shielding functionality, nor does it utilize the selective distribution of fillers in the blend system. CN202511979655 discloses the synergistic use of nano-Si and nano-SiO2 in high-voltage cables to achieve thermal conductivity and dielectric composite properties. However, this scheme is a thermally conductive design rather than a space charge suppression design.

[0007] Regarding weather protection, CN109181083A discloses a reinforced polyolefin cable material blended with fluoropolymers, POE, and EMA. However, this solution focuses on enhancing the mechanical properties of the cable and does not address the functional design of the weather protection layer or rare earth nanofillers. Existing weather-resistant layers often employ a simple blending of LLDPE and EBA with the addition of TiO2, resulting in limited weather resistance.

[0008] In terms of space charge suppression, existing technologies mostly adopt nonlinear conductive and depletion-type schemes of ZnO whiskers or synergistic anti-depletion schemes of SiC whiskers and MgO. There is a lack of space charge capture schemes based on dielectric traps, and even more so a lack of design ideas for deep-shallow trap gradient coordination. Summary of the Invention

[0009] The purpose of this invention is to provide an integrated insulation and shielding weather-resistant overhead cable and its preparation method. The method employs a two-phase co-continuous structure formed by the thermodynamic incompatibility of EMA and LLDPE, and selective distribution of conductive carbon black to achieve integrated shielding and insulation. Simultaneously, it introduces zinc stannate / nano-yttrium oxide composite filler and nano-barium titanate to form a deep-shallow trap gradient to suppress space charge. A "brick-and-mortar" layered water-blocking interface is constructed using perfluorooctyltriethoxysilane-modified fluoromica and KH-560-modified boehmite nanosheets. Finally, a fluoropolymer / polyolefin composite weather-resistant protective layer is constructed by blending PVDF-HFP and POE with KH-550-modified nano-neodymium oxide.

[0010] To achieve the above objectives, the present invention provides the following technical solution: The technical solution provided by this invention is: An integrated insulation and shielding weather-resistant overhead cable comprises, from the inside out, an aluminum alloy conductor, a conductor-insulation interface layer, an integrated insulation and shielding layer, and a weather-resistant protective layer.

[0011] The integrated insulation and shielding layer is a single composite layer composed of the following raw materials in parts by weight: 60-80 parts linear low-density polyethylene, 8-18 parts ethylene-methyl acrylate copolymer, 8-15 parts ethylene-vinyl acetate copolymer, 12-25 parts conductive carbon black, 1-4 parts nano barium titanate, 3-8 parts zinc stannate / nano yttrium oxide composite filler, 1.5-2.5 parts dicumyl peroxide, and 0.3-0.8 parts antioxidant.

[0012] Ethylene-methyl acrylate copolymer and linear low-density polyethylene are thermodynamically incompatible, forming a two-phase co-continuous structure during blending. Conductive carbon black is preferentially dispersed in the polar ethylene-methyl acrylate copolymer phase, reaching a concentration above the percolation threshold to form a through-type semi-conductive network. The linear low-density polyethylene phase constitutes the insulating continuous phase.

[0013] The ethylene-vinyl acetate copolymer is distributed at the interface between the ethylene-methyl acrylate copolymer phase and the linear low-density polyethylene phase.

[0014] The zinc stannate / nano yttrium oxide composite filler is prepared by ball milling zinc stannate and nano yttrium oxide in a mass ratio of 1:1 to 3:1, with the nano yttrium oxide loaded on the surface of the zinc stannate particles.

[0015] The volume resistivity of the integrated insulating shielding layer increases continuously from the side closer to the conductor to the side farther from the conductor, with the volume resistivity being 10⁻⁶ on the side closer to the conductor. 1 ~10 4 Ω·cm, volume resistivity on the side away from the conductor ≥10 12 Ω·cm.

[0016] The conductor-insulator interface layer is composed of the following raw materials in parts by weight: 70-85 parts of ethylene-vinyl acetate copolymer, 5-12 parts of perfluorooctyltriethoxysilane modified synthetic fluoromica, 3-8 parts of KH-560 modified boehmite nanosheets, 2-5 parts of vinyltriethoxysilane, 0.8-1.5 parts of dicumyl peroxide, and 0.3-0.5 parts of antioxidant.

[0017] The synthetic fluoromica is a fluorophlogopite-type synthetic mica with a sheet diameter of 10~50 μm and a thickness of 0.5~2 μm. After surface modification with perfluorooctyltriethoxysilane, a hydrophobic fluorosilane layer is formed on the surface.

[0018] Boehmite nanosheets are γ-alumina hydrates with a diameter of 100~500 nm and a thickness of 10~30 nm. After surface modification with KH-560, they are bonded to the ethylene-vinyl acetate copolymer matrix through epoxy groups.

[0019] Synthetic fluoromica and boehmite nanosheets form a "brick-and-mortar" stacked structure in an ethylene-vinyl acetate copolymer matrix, wherein the synthetic fluoromica is the large-sized "brick" layer, and the boehmite nanosheets are the small-sized "mortar" layer filling the gaps between the fluoromica layers.

[0020] Vinyltriethoxysilane undergoes hydrolysis and condensation upon the penetration of moisture, forming a siloxane cross-linked network within the interfacial layer.

[0021] The weather-resistant protective layer is a blend of polyvinylidene fluoride-hexafluoropropylene copolymer and polyolefin elastomer, composed of the following raw materials in parts by weight: 25-40 parts of polyvinylidene fluoride-hexafluoropropylene copolymer, 35-50 parts of polyolefin elastomer, 8-15 parts of ethylene-methyl acrylate copolymer grafted with maleic anhydride, 1-3 parts of nano-cerium dioxide, 2-5 parts of nano-titanium dioxide, 1-4 parts of KH-550 modified nano-neodymium oxide, 0.5-1.5 parts of hindered amine light stabilizer, 0.8-1.5 parts of dicumyl peroxide, and 0.5-1 part of antioxidant.

[0022] Ethylene-methyl acrylate copolymer grafted with maleic anhydride is a reactive compatibilizer. Its maleic anhydride groups undergo a grafting reaction with the defluorination sites on the polyvinylidene fluoride-hexafluoropropylene copolymer chain. The ethylene-methyl acrylate copolymer segment is compatible with the polyolefin elastomer, achieving chemical bonding at the two-phase interface.

[0023] The average particle size of nano-cerium dioxide is 10~50 nm, and the cerium ions in cerium dioxide can reversibly switch between the trivalent and tetravalent cerium ions.

[0024] The average particle size of KH-550 modified nano-neodymium oxide is 30~100 nm. After surface modification with γ-aminopropyltriethoxysilane, its amino groups react with the acidic degradation products generated by the thermal aging of polyvinylidene fluoride-hexafluoropropylene copolymer.

[0025] The barium titanate nanoparticles have an average particle size of 50~200 nm and are surface-modified by glycidyl methacrylate grafted with ethylene-vinyl acetate copolymer.

[0026] During the crosslinking process of dicumyl peroxide, the epoxy groups of glycidyl methacrylate form covalent bonds with the linear low-density polyethylene matrix, thereby anchoring the nano-barium titanate to the matrix through chemical bonds.

[0027] Nano-barium titanate introduces deep trap levels in the integrated insulation and shielding layer. Nano-yttrium oxide in the zinc stannate / nano-yttrium oxide composite filler introduces shallow trap levels in the integrated insulation and shielding layer, forming a deep-shallow trap gradient coordination with the deep trap levels of nano-barium titanate.

[0028] The aluminum alloy conductor is a high-strength aluminum alloy compacted round conductor, and its outer surface is treated with micro-arc oxidation to form an alumina ceramic transition layer with a thickness of 2~8 μm. The surface roughness Ra of the alumina ceramic transition layer is 0.5~2.0 μm.

[0029] The conductor-insulator interface layer has a thickness of 0.3~0.8 mm and a volume resistivity ≤500 Ω·cm. The total thickness of the integrated insulation and shielding layer is 3.5~6.0 mm, with the volume resistivity on the side closest to the conductor being less than 10 Ω·cm. 4 The semiconductive region with a volume resistivity of Ω·cm accounts for 8-20% of the total thickness of the integrated insulation and shielding layer, the transition region with continuously increasing volume resistivity accounts for 15-30%, and the volume resistivity on the side away from the conductor is higher than 10 Ω·cm. 12 The insulation area with an Ω·cm coverage rate is 50-77%. The thickness of the weather-resistant protective layer is 1.0-2.5 mm.

[0030] The present invention also provides a method for preparing the above-mentioned integrated insulation and shielding weather-resistant overhead cable, comprising the following steps: S1: Modified fluoromica, modified boehmite nanosheets, ethylene-vinyl acetate copolymer, vinyltriethoxysilane, dicumyl peroxide, and antioxidant are mixed and kneaded in an internal mixer at 110~130℃ for 6~10 min, and then granulated by twin-screw extrusion to obtain interfacial layer granules.

[0031] S2: First, ethylene-methyl acrylate copolymer and conductive carbon black are premixed in a mixer at 120~140℃ for 8~12min to fully wet and disperse the conductive carbon black in the ethylene-methyl acrylate copolymer, thus obtaining carbon black masterbatch; then, the carbon black masterbatch is melt-blended and granulated in a twin-screw extruder at 140~160℃ with linear low-density polyethylene, ethylene-vinyl acetate copolymer, GMA-grafted EVA surface-modified nano barium titanate, zinc stannate / nano yttrium oxide composite filler, dicumyl peroxide, and antioxidant to obtain integrated layered granules.

[0032] S3: Polyvinylidene fluoride-hexafluoropropylene copolymer, polyolefin elastomer, ethylene-methyl acrylate copolymer grafted with maleic anhydride, modified nano-cerium dioxide, modified nano-titanium dioxide, KH-550 modified nano-neodymium oxide, hindered amine light stabilizer, dicumyl peroxide, and antioxidant are mixed in an internal mixer at 150~170℃ for 10~15 min, and then granulated in a twin-screw extruder at 150~170℃ to obtain weather-resistant granules.

[0033] S4: Micro-arc oxidation treatment is performed on the outer surface of the aluminum alloy conductor to form an alumina ceramic transition layer.

[0034] S5: The interface layer granules and the integrated layer granules are sequentially extruded through a three-channel co-extrusion die onto the aluminum alloy conductor that has undergone micro-arc oxidation treatment, and then cross-linked and cured through a cross-linking tube. During the cross-linking and curing process, the ethylene-methyl acrylate copolymer phase and the linear low-density polyethylene phase undergo phase separation. The conductive carbon black remains in the ethylene-methyl acrylate copolymer phase to form a semi-conductive network. Dicumyl peroxide initiates the cross-linking of the linear low-density polyethylene and the ethylene-vinyl acetate copolymer, locking the two-phase co-continuous structure.

[0035] S6: Weather-resistant granules are extruded onto the outside of the cross-linked and cured cable core. While dicumyl peroxide initiates the cross-linking of the polyolefin elastomer, maleic anhydride groups react with polyvinylidene fluoride-hexafluoropropylene copolymer to achieve two-phase chemical bonding. After segmented cooling, the cable is wound up.

[0036] The beneficial effects of this technical solution are: 1. The integrated insulation and shielding layer utilizes a two-phase co-continuous structure formed by the thermodynamic incompatibility of EMA and LLDPE. Conductive carbon black is preferentially dispersed in the polar EMA phase, reaching above the percolation threshold to form a semi-conductive network. The LLDPE phase is the insulating continuous phase, and EVA is distributed at the interface between the two phases. The extrusion shear gradient connects the EMA phase near the conductor, while stretching the EMA phase away from the conductor into isolated micro-regions. This single-layer material achieves a continuous increase in resistivity from semi-conductive to insulating. Compared with traditional three-layer co-extrusion, this scheme eliminates interlayer interface defects. The shielding structure is determined by composition selection and phase separation behavior rather than process-driven, unlike existing technologies that use premixed gradient formulations or electric field-induced self-assembly.

[0037] 2. In the zinc stannate / nano-yttrium oxide composite filler, the Zn₂SnO₄ spinel structure provides a nonlinear dielectric response through reversible ion displacement polarization under an electric field. Nano-Y₂O₃ introduces shallow trap energy levels, forming a deep-shallow trap gradient with the deep trap energy levels of nano-BaTiO₃. Deep traps capture slow space charges far from the electrode, while shallow traps capture rapidly injected charges near the electrode. Together, they stratify and trap space charges within the insulating layer, suppressing electric field distortion. Compared to existing nonlinear conductive and depleting ZnO whisker or SiC whisker and MgO synergistic anti-depletion schemes, this approach is a dielectric trap trapping type with a different working mechanism.

[0038] 3. The conductor-insulator interface layer utilizes perfluorooctyltriethoxysilane-modified fluoromica as the "brick" and KH-560-modified boehmite nanosheets as the "mortar" to construct a "brick-mortar" laminated structure. Large-sized fluoromica sheets provide barrier pathways, while small-sized boehmite nanosheets fill the gaps to form a dense barrier. Fluorosilane imparts hydrophobicity, and A-151 hydrolyzes and condenses upon contact with water to seal micropores. Compared to self-healing organic microcapsules or HNT-loaded silane systems, this approach employs a combined mechanism of physical barrier from inorganic sheet-like fillers and chemical sealing with silane, eliminating the problem of wall material aging and failure.

[0039] 4. The weather-resistant protective layer employs a blend of PVDF-HFP and POE, with EMA-g-MAH acting as a reactive compatibilizer to achieve two-phase chemical bonding. Nano-CeO2 provides UV absorption and free radical scavenging, while KH-550-modified nano-neodymium oxide absorbs near-infrared thermal radiation to reduce the cable's temperature rise under sunlight. Its amino groups react with acidic degradation products such as HF generated during the thermal aging of PVDF-HFP to neutralize acidic chain degradation. This scheme is the first to introduce PVDF-HFP fluoropolymer and rare earth Nd2O3 into the weather-resistant layer of overhead cables, significantly improving weather resistance and heat aging resistance compared to the existing simple blending scheme of LLDPE+EBA+TiO2. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the manufacturing process of the integrated insulation and shielding weather-resistant overhead cable proposed in this invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The specific implementation process is as follows: Example 1:

[0043] Please see Figure 1 The present invention provides a technical solution: the integrated insulation and shielding weather-resistant overhead cable of this embodiment consists of, from the inside out, an aluminum alloy conductor, an alumina ceramic transition layer, a conductor-insulation interface layer, an integrated insulation and shielding layer, and a weather-resistant protection layer.

[0044] The formulas for each layer are as follows: 1. Integrated insulation and shielding layer: Linear low-density polyethylene (type 7042, density 0.920 g / cm³) 3 The following materials were prepared: 574 g of melt flow rate 2.0 g / 10 min, 107 g of ethylene-methyl acrylate copolymer (type 1125, MA content 8%), 90 g of ethylene-vinyl acetate copolymer (type 18-3, VA content 24%), 148 g of conductive carbon black N550 (DBP absorption value 130 ml / 100g, particle size 30 nm), 20.5 g of nano barium titanate (average particle size 120 nm, surface modified with GMA grafted EVA), and 41 g of zinc stannate / nano yttrium oxide composite filler (preparation method: 27.3 g of zinc stannate (Zn2SnO4 spinel structure) and 13.7 g of nano yttrium oxide (average particle size 50 nm) were mixed in deionized water, 0.41 g of PEG-400 dispersant was added, and the mixture was ball-milled for 10 h at a ball mill speed of 400 rpm). Prepared by spray drying at rpm (inlet temperature 200℃, outlet temperature 90℃), 16.4 g of dicumyl peroxide, and 4.1 g of antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)).

[0045] 2. Conductor-insulator interface layer: 817 g of ethylene-vinyl acetate copolymer (type 18-3, VA content 24%), 84 g of perfluorooctyltriethoxysilane-modified synthetic fluoromica (preparation method: 70 g of synthetic fluoromica (fluorophlogopite type, flake diameter 30 μm, thickness 1 μm) was dispersed in a 10% ethanol solution of 14 g of perfluorooctyltriethoxysilane (purity ≥97%), stirred at 80℃ for 3 h, filtered, and vacuum dried at 60℃ for 12 h), and 52 g of KH-560-modified boehmite nanosheets (preparation method: 43.3 g of boehmite nanosheets (γ-AlO(OH), flake diameter 300 nm, thickness 20 nm) were dispersed in an ethanol aqueous solution of 8.7 g of KH-560, with a volume ratio of ethanol to water of 9:1, the pH was adjusted to 4.5 with acetic acid, reacted at 70℃ for 4 h, filtered, and vacuum dried at 60℃ for 12 h). h), vinyltriethoxysilane (A-151) 31 g, dicumyl peroxide 10.5 g, antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)) 4.2 g.

[0046] 3. Weather-resistant protective layer: Polyvinylidene fluoride-hexafluoropropylene copolymer (type 6010, MFR 15 g / 10min) 334 g, polyolefin elastomer (type 8003, density 0.870 g / cm³) 3 439 g of ethylene-methyl acrylate copolymer grafted maleic anhydride (type 1420, MAH grafting rate 1.2%), 125 g of nano-cerium dioxide (average particle size 30 nm, surface modified with KH-570 silane coupling agent: KH-570 5% ethanol solution, pH 4.5, 70℃ for 3 h, filtered and dried), 21 g of nano-titanium dioxide (average particle size 200 nm, surface modified with KH-570 silane coupling agent: KH-570 5% ethanol solution, pH 4.5, 70℃ for 3 h, filtered and dried), and 21 g of KH-550 modified nano-neodymium oxide (preparation method: 19.4 g of nano-neodymium oxide (average particle size 60 nm) dispersed in KH-550 1.6 In a 10.5 g aqueous solution of ethanol and water with a volume ratio of 8.5:1.5, the pH was adjusted to 9.5 with ammonia, the mixture was stirred at 75°C for 4 h, filtered, washed 3 times with ethanol, and dried at 110°C for 5 h. The solution also included 10.5 g of hindered amine light stabilizer (type 770), 10.5 g of dicumyl peroxide, and 7.3 g of antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)).

[0047] The preparation method is as follows: S1: Preparation of conductor-insulator interface layer granules. 84 g of modified fluoromica, 52 g of modified boehmite nanosheets, 817 g of EVA, 31 g of A-151, 10.5 g of DCP, and 4.2 g of antioxidant 300 were mixed and kneaded in a mixer at 120°C for 8 min. The mixture was then granulated by twin-screw extrusion to obtain the interface layer granules.

[0048] S2: Preparation of integrated insulating and shielding granules. 107 g of EMA and 148 g of conductive carbon black N550 were premixed in a Banbury mixer at 130°C for 10 min to fully wet and disperse the conductive carbon black in the EMA, yielding carbon black masterbatch. The concentration of carbon black in the EMA reached twice the percolation threshold. The carbon black masterbatch was then melt-blended and granulated in a twin-screw extruder at 150°C with 574 g of LLDPE, 90 g of EVA, 20.5 g of GMA-grafted EVA surface-modified nano-barium titanate, 41 g of zinc stannate / nano-yttrium oxide composite filler, 16.4 g of DCP, and 4.1 g of antioxidant 300 to obtain integrated granules.

[0049] S3: Preparation of weather-resistant protective layer granules. PVDF-HFP 334 g, POE 439 g, EMA-g-MAH 125 g, modified nano-cerium dioxide 21 g, modified nano-titanium dioxide 31 g, KH-550 modified nano-neodymium oxide 21 g, HALS 10.5 g, DCP 10.5 g, and antioxidant 300 7.3 g were mixed in an internal mixer at 160℃ for 12 min, and then granulated in a twin-screw extruder at 160℃ to obtain the weather-resistant layer granules.

[0050] S4: Micro-arc oxidation treatment is performed on the outer surface of the aluminum alloy conductor. The electrolyte is sodium silicate solution (concentration 15 g / L), the voltage is 350 V, and the treatment time is 5 min to form an alumina ceramic transition layer with a thickness of 5 μm and a surface roughness Ra of 1.2 μm.

[0051] S5: The interface layer granules and integrated layer granules are sequentially extruded through a three-channel co-extrusion die onto an aluminum alloy conductor that has undergone micro-arc oxidation treatment. The temperatures of the three-channel co-extrusion die are set as follows: feeding section 135℃, compression section 150℃, metering section 165℃, and die head 175℃. Crosslinking and curing are performed through a crosslinking tube at a temperature of 200℃ for 450 seconds. During the crosslinking and curing process, the EMA phase and LLDPE phase undergo phase separation. The conductive carbon black remains in the EMA phase, forming a semi-conductive network. DCP initiates crosslinking of LLDPE and EVA, locking the two-phase co-continuous structure.

[0052] S6: Weather-resistant granules are extruded onto the outside of the cross-linked and cured cable core. While DCP initiates POE cross-linking, MAH groups react with PVDF-HFP to achieve two-phase chemical bonding. The segmented cooling process is as follows: the first segment is cooled by 60°C warm water, the second segment by 40°C warm water, and the third segment by 20°C cold water, followed by winding.

[0053] The thickness of each layer of the cable is as follows: conductor-insulation interface layer 0.5 mm, integrated insulation and shielding layer 4.5 mm, and weather-resistant protection layer 1.5 mm.

[0054] This embodiment employs a three-phase blend system of EMA / LLDPE / EVA. EMA (type 1125, MA content 8%) and LLDPE (type 7042) are thermodynamically incompatible, forming a two-phase co-continuous structure. In the carbon black premixing process, carbon black and EMA are premixed in a mixer at 130°C for 10 min. The carbon black preferentially wets the polar EMA phase, resulting in carbon black masterbatch with a concentration in EMA of twice the percolation threshold. During subsequent blending with LLDPE, the carbon black remains in the EMA phase, and the carbon black concentration in the LLDPE phase is below the percolation threshold, maintaining insulation. During extrusion, the shear rate is low near the conductor, and the EMA phase maintains a continuous semi-conductive network; the shear rate is high away from the conductor, and the EMA phase is stretched and dispersed into isolated micro-regions, breaking the semi-conductive network. DCP in the crosslinking tube initiates crosslinking, locking the phase separation structure and causing the volume resistivity of the integrated insulation shielding layer to decrease from 10 ohms on the conductor side. 2 Ω·cm increases continuously to 10 on the outer side 13 With a strength of Ω·cm or higher, it achieves the functional transition from semiconducting to insulating within a single-layer material.

[0055] In the zinc stannate / nano-yttrium oxide composite filler, 27.3 g of zinc stannate (Zn₂SnO₄ spinel structure) and 13.7 g of nano-yttrium oxide (average particle size 50 nm) were ball-milled together. Nano-Y₂O₃ introduced shallow trap energy levels, forming a deep-shallow gradient coordination with the deep trap energy levels of BaTiO₃ (average particle size 120 nm). The shallow traps near the electrode side preferentially capture rapidly injected charges, while the deep traps capture slow space charges in the insulating region. Together, they suppress electric field distortion.

[0056] In the conductor-insulator interface layer, 84 g of modified fluoromica (70 g of synthetic fluoromica + 14 g of perfluorooctyltriethoxysilane modification, sheet diameter 30 μm, thickness 1 μm) and 52 g of modified boehmite nanosheets (43.3 g of boehmite nanosheets + 8.7 g of KH-560 modification, sheet diameter 300 nm, thickness 20 nm) form a "brick-and-mortar" stacked structure in the EVA (18-3 type) matrix. The large-sized fluoromica sheets provide a barrier pathway, the boehmite nanosheets fill the gaps between the sheets, the hydrophobic fluorosilane layer reduces the driving force for water molecule penetration, and A-151 hydrolyzes and condenses upon contact with water to seal residual micropores. This triple mechanism synergistically blocks water.

[0057] In the weather-resistant protective layer, PVDF-HFP (type 6010) provides an extremely weather-resistant matrix, POE (type 8003) provides low-temperature flexibility, and EMA-g-MAH (type 1420) achieves two-phase chemical bonding through grafting MAH with PVDF-HFP de-HF sites and the compatibility of EMA segments with POE. CeO2 (average particle size 30 nm) contains Ce... 3+ / Ce 4+Reversible redox reactions scavenge UV free radicals. KH-550 modified Nd2O3 (19.4 g of nano-neodymium oxide + 1.6 g of KH-550 modification, average particle size 60 nm) reduces the temperature rise of cables under sunlight by absorbing near-infrared thermal radiation. The amino groups react with the HF acidic degradation products generated by the thermal aging of PVDF-HFP, interrupting the acidic chain degradation.

[0058] Example 2:

[0059] Please see Figure 1 The present invention provides a technical solution: The difference between this embodiment and Embodiment 1 is that the formulation of each layer is as follows: the lower value is taken, specifically as follows: The formulas for each layer are as follows: 1. Integrated insulation and shielding layer: Linear low-density polyethylene (type 7042, density 0.920 g / cm³) 3 The following materials were prepared: 640 g of melt flow rate 2.0 g / 10 min, 85 g of ethylene-methyl acrylate copolymer (type 1125, MA content 6%), 85 g of ethylene-vinyl acetate copolymer (type 18-3, VA content 18%), 128 g of conductive carbon black N220 (DBP absorption value 150 ml / 100g, particle size 25 nm), 10.7 g of nano barium titanate (average particle size 120 nm, surface modified with GMA grafted EVA), and 32 g of zinc stannate / nano yttrium oxide composite filler (preparation method: 16 g of zinc stannate (Zn2SnO4 spinel structure) and 16 g of nano yttrium oxide (average particle size 50 nm) were mixed in deionized water, 0.26 g of PEG-400 dispersant was added, and the mixture was ball-milled for 8 h at a ball milling speed of 350 rpm). Prepared by spray drying at rpm (inlet temperature 190℃, outlet temperature 85℃), 16 g of dicumyl peroxide, and 3.2 g of antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)).

[0060] 2. Conductor-insulator interface layer: 863 g of ethylene-vinyl acetate copolymer (type 18-3, VA content 20%), 62 g of perfluorooctyltriethoxysilane-modified synthetic fluoromica (preparation method: 56.4 g of synthetic fluoromica (fluorophlogopite type, flake diameter 30 μm, thickness 1 μm) was dispersed in an 8% (w / w) ethanol solution of 5.6 g of perfluorooctyltriethoxysilane (purity ≥97%), stirred at 75℃ for 2.5 h, filtered and dried), 37 g of KH-560-modified boehmite nanosheets (preparation method: 33.6 g of boehmite nanosheets (γ-AlO(OH), flake diameter 300 nm, thickness 20 nm) was dispersed in an ethanol aqueous solution of 3.4 g of KH-560, pH adjusted to 4, reacted at 65℃ for 3 h, filtered and dried), 25 g of vinyltriethoxysilane (A-151), and 9.9 g of dicumyl peroxide. g, Antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)) 3.7 g.

[0061] 3. Weather-resistant protective layer: Polyvinylidene fluoride-hexafluoropropylene copolymer (type 6010, MFR 15 g / 10min) 339 g, polyolefin elastomer (type 8003, density 0.870 g / cm³) 3 474 g of ethylene-methyl acrylate copolymer grafted maleic anhydride (type 1420, MAH grafting rate 1.2%), 108 g of nano-cerium dioxide (average particle size 30 nm, surface modified with KH-570 silane coupling agent), 13.6 g of nano-titanium dioxide (average particle size 200 nm, surface modified with KH-570 silane coupling agent), 27 g of KH-550 modified nano-neodymium oxide, 13.6 g of KH-550 modified nano-neodymium oxide (preparation method: 12.8 g of nano-neodymium oxide (average particle size 60 nm) was dispersed in 0.85 g of KH-550 in an ethanol-water solution, the volume ratio of ethanol to water was 8:2, pH 9, reaction was carried out at 70℃ for 3 h, filtered and washed, and dried at 105℃ for 4 h), 6.8 g of hindered amine light stabilizer (type 770), and 10.8 g of dicumyl peroxide. g, Antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)) 6.8 g.

[0062] The preparation method is as follows: S1: Preparation of conductor-insulator interface layer granules. The components are mixed and kneaded in a Banbury mixer at 115°C for 7 min, followed by twin-screw extrusion granulation.

[0063] S2: Preparation of integrated insulating and shielding granules. 85 g of EMA and 128 g of conductive carbon black N220 were premixed in a Banbury mixer at 125°C for 9 min to obtain carbon black masterbatch. The concentration of carbon black in EMA reached 1.5 times the percolation threshold. The carbon black masterbatch was melt-blended and granulated in a twin-screw extruder at 145°C with 640 g of LLDPE, 85 g of EVA, 10.7 g of GMA-grafted EVA surface-modified nano-barium titanate, 32 g of zinc stannate / nano-yttrium oxide composite filler, 16 g of DCP, and 3.2 g of antioxidant 300.

[0064] S3: Preparation of weather-resistant protective layer granules. PVDF-HFP 339 g, POE 474 g, EMA-g-MAH 108 g, modified nano-cerium dioxide 13.6 g, modified nano-titanium dioxide 27 g, KH-550 modified nano-neodymium oxide 13.6 g, HALS 6.8 g, DCP 10.8 g, and antioxidant 300 6.8 g were mixed in an internal mixer at 155℃ for 11 min, and then granulated in a twin-screw extruder at 155℃.

[0065] S4: Same as Example 1.

[0066] S5: Three-channel co-extrusion die head temperatures: feeding section 132℃, compression section 148℃, metering section 162℃, die head 172℃. Crosslinking pipe temperature 190℃, crosslinking curing time 500 s.

[0067] S6: Segmented cooling: first segment 55℃ warm water, second segment 35℃ warm water, third segment 18℃ cold water.

[0068] The thickness of each layer of the cable is as follows: conductor-insulation interface layer 0.4 mm, integrated insulation and shielding layer 4.0 mm, and weather-resistant protection layer 1.2 mm.

[0069] In this embodiment, the lower values ​​of each component are used: EMA 85 g (type 1125, MA content 6%), LLDPE 640 g (type 7042). The volume ratio of EMA phase to LLDPE phase is relatively small. The EMA phase can still form a semiconductive network, but the connectivity is lower than in Example 1. In the zinc stannate / nano-yttrium oxide composite filler, 16 g of zinc stannate and 16 g of nano-yttrium oxide are combined in equal amounts. The proportion of Y2O3 increases, the shallow trap density increases, but the nonlinear dielectric response of Zn2SnO3 weakens. The filler content of the interface layer and weather-resistant layer is relatively low. The water-blocking and weather-resistant functions are still within an acceptable range, but the margin is small. This embodiment is suitable for cost-sensitive applications.

[0070] Example 3:

[0071] Please see Figure 1The present invention provides a technical solution: The difference between this embodiment and Embodiment 1 is that the formulation of each layer is as follows: taking the higher value, specifically as follows: The formulas for each layer are as follows: 1. Integrated insulation and shielding layer: Linear low-density polyethylene (type 7042, density 0.920 g / cm³) 3 The following materials were prepared: 522 g of melt flow rate 2.0 g / 10 min, 117 g of ethylene-methyl acrylate copolymer (type 1125, MA content 10%), 98 g of ethylene-vinyl acetate copolymer (type 18-3, VA content 28%), 163 g of conductive carbon black N550 (DBP absorption value 130 ml / 100g, particle size 30 nm), 26 g of nano barium titanate (average particle size 120 nm, surface modified with GMA grafted EVA), and 52 g of zinc stannate / nano yttrium oxide composite filler (preparation method: 39 g of zinc stannate (Zn2SnO4 spinel structure) and 13 g of nano yttrium oxide (average particle size 50 nm) were mixed in deionized water, 0.78 g of PEG-400 dispersant was added, and the mixture was ball-milled for 12 h at a ball milling speed of 450 rpm). Prepared by spray drying at rpm (inlet temperature 215℃, outlet temperature 95℃), 16.3 g of dicumyl peroxide, and 5.2 g of antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)).

[0072] 2. Conductor-insulator interface layer: 759 g of ethylene-vinyl acetate copolymer (type 18-3, VA content 26%), 107 g of perfluorooctyltriethoxysilane-modified synthetic fluoromica (preparation method: 82.3 g of synthetic fluoromica (fluorophlogopite type, flake diameter 30 μm, thickness 1 μm) was dispersed in a 12% ethanol solution containing 24.7 g of perfluorooctyltriethoxysilane (purity ≥97%), and the reaction was stirred at 85℃ for 3.5 h), 71 g of KH-560-modified boehmite nanosheets (preparation method: 54.6 g of boehmite nanosheets (γ-AlO(OH), flake diameter 300 nm, thickness 20 nm) was dispersed in an ethanol aqueous solution containing 16.4 g of KH-560, and the reaction was carried out at pH 4.5 and 75℃ for 4.5 h), 45 g of vinyltriethoxysilane (A-151), and 13.4 g of dicumyl peroxide. g, Antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)) 4.5 g.

[0073] 3. Weather-resistant protective layer: 331 g of polyvinylidene fluoride-hexafluoropropylene copolymer (type 6010, MFR 15 g / 10min) and polyolefin elastomer (type 8003, density 0.870 g / cm³). 3413 g of ethylene-methyl acrylate copolymer grafted maleic anhydride (type 1420, MAH grafting rate 1.2%), 124 g of nano-cerium dioxide (average particle size 30 nm, surface modified with KH-570 silane coupling agent), 41 g of nano-titanium dioxide (average particle size 200 nm, surface modified with KH-570 silane coupling agent), 33 g of KH-550 modified nano-neodymium oxide (preparation method: 29.3 g of nano-neodymium oxide (average particle size 60 nm) was dispersed in 3.7 g of KH-550 in an ethanol-water solution, the volume ratio of ethanol to water was 9:1, pH 10, the reaction was carried out at 78℃ for 4.5 h, filtered and washed, and dried at 115℃ for 5 h), 12.4 g of hindered amine light stabilizer (type 770), and 12.4 g of dicumyl peroxide. g, Antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)) 8.3 g.

[0074] The preparation method is as follows: S1: Preparation of conductor-insulator interface layer granules. After mixing all components, the mixture is kneaded in an internal mixer at 125°C for 9 min, and then granulated by twin-screw extrusion.

[0075] S2: Preparation of integrated insulating and shielding granules. 117 g of EMA and 163 g of conductive carbon black N550 were premixed in a Banbury mixer at 135°C for 11 min to obtain carbon black masterbatch. The concentration of carbon black in EMA reached 2.5 times the percolation threshold. The carbon black masterbatch was melt-blended and granulated in a twin-screw extruder at 155°C with 522 g of LLDPE, 98 g of EVA, 26 g of GMA-grafted EVA surface-modified nano-barium titanate, 52 g of zinc stannate / nano-yttrium oxide composite filler, 16.3 g of DCP, and 5.2 g of antioxidant 300.

[0076] S3: Preparation of weather-resistant protective layer granules. PVDF-HFP 331 g, POE 413 g, EMA-g-MAH 124 g, modified nano-cerium dioxide 24.8 g, modified nano-titanium dioxide 41 g, KH-550 modified nano-neodymium oxide 33 g, HALS 12.4 g, DCP 12.4 g, and antioxidant 300 8.3 g were mixed in an internal mixer at 165℃ for 14 min, and then granulated in a twin-screw extruder at 165℃.

[0077] S4: Same as Example 1.

[0078] S5: Three-channel co-extrusion die head temperatures: feeding section 138℃, compression section 153℃, metering section 168℃, die head 178℃. Crosslinking pipe temperature 210℃, crosslinking curing time 380 s.

[0079] S6: Segmented cooling: first segment 65℃ warm water, second segment 45℃ warm water, third segment 22℃ cold water.

[0080] The thickness of each layer of the cable is as follows: conductor-insulation interface layer 0.7 mm, integrated insulation and shielding layer 5.5 mm, and weather-resistant protection layer 2.0 mm.

[0081] This embodiment uses the higher values ​​of each component. EMA content is 117 g (type 1125, 10% MA content), increasing the EMA phase volume ratio, improving the connectivity of the semiconductive network, and lowering the resistivity on the conductor side. Carbon black content is 163 g, and the premixed concentration reaches 2.5 times the percolation threshold, ensuring sufficient conductivity in the semiconductive region. In the zinc stannate / nano-yttrium oxide composite filler, 39 g of zinc stannate and 13 g of nano-yttrium oxide are combined, resulting in a high Zn2SnO4 content and strong nonlinear dielectric response, but the low Y2O3 content leads to a lower shallow trap density. The high filler content in the interface and weather-resistant layers provides ample margin for water blocking and weather resistance. KH-550 modified Nd2O3 content is 33 g (29.3 g nano-neodymium oxide + 3.7 g KH-550 modification), exhibiting the strongest near-infrared thermal radiation absorption and neutralization ability against acidic degradation products. This embodiment is suitable for high-voltage levels and scenarios with extreme weather resistance requirements.

[0082] Comparative Example 1: Please see Figure 1 The present invention provides a comparative scheme: the only difference between Comparative Example 1 and Example 1 is that the integrated insulating and shielding layer does not contain zinc stannate / nano-yttrium oxide composite filler, and this part is supplemented by linear low-density polyethylene (type 7042). The rest of the formulation and preparation method are exactly the same as those in Example 1.

[0083] Comparative Example 1 was used to investigate the contribution of zinc stannate / nano-yttrium oxide composite filler.

[0084] Comparative Example 2: Please see Figure 1 The present invention provides a comparative scheme: the only difference between Comparative Example 2 and Example 1 is that the weather-resistant protective layer does not contain KH-550 modified nano-neodymium oxide, and this part is made up by polyolefin elastomer (type 8003). The rest of the formulation and preparation method are exactly the same as those in Example 1.

[0085] Comparative Example 2 was used to examine the contribution of KH-550-modified nano-neodymium oxide.

[0086] Comparative Example 3: Please see Figure 1The present invention provides a comparative scheme: Comparative Example 3 differs from Example 1 in that the integrated insulation and shielding layer adopts a traditional three-layer co-extrusion structure, namely, a conductor shielding layer (EVA 18-3 type + conductive carbon black N550 148 g + DCP 16.4 g + antioxidant 300 4.1 g), an insulation layer (LLDPE 7042 type + DCP 16.4 g + antioxidant 300 4.1 g), and an insulation shielding layer (EVA 18-3 type + conductive carbon black N550 148 g + DCP 16.4 g + antioxidant 300 4.1 g), without EMA, EVA, nano barium titanate, and zinc stannate / nano yttrium oxide composite filler. The conductor-insulation interface layer and the weather-resistant protective layer are the same as in Example 1. The preparation method is a conventional three-layer co-extrusion crosslinking process.

[0087] Comparative Example 3 was used to examine the differences between the phase-separated integrated layer and the traditional three-layer split structure.

[0088] Comparative Example 4: Please see Figure 1 The present invention provides a comparative scheme: Comparative Example 4 differs from Example 1 only in that the integrated insulating and shielding layer does not contain nano-barium titanate, and this portion is supplemented by linear low-density polyethylene (type 7042). The remaining formulation and preparation method are exactly the same as those in Example 1.

[0089] Comparative Example 4 was used to examine the contribution of nano-barium titanate deep traps.

[0090] Comparative Example 5: Please see Figure 1 The present invention provides a comparative scheme: Comparative Example 5 differs from Example 1 only in that: in the conductor-insulator interface layer, unmodified natural mica powder (30 μm particle size) is used instead of perfluorooctyltriethoxysilane-modified fluoromica, and unmodified alumina powder (300 nm particle size) is used instead of KH-560 modified boehmite nanosheets; A-151 is not included. The remaining formulation and preparation method are exactly the same as in Example 1.

[0091] Comparative Example 5 was used to examine the contribution of the "brick-mud" layered structure and silane modification.

[0092] Comparative Example 6: Please see Figure 1 The present invention provides a comparative scheme: Comparative Example 6 differs from Example 1 only in that: in the weather-resistant protective layer, linear low-density polyethylene (type 7042) is used instead of polyvinylidene fluoride-hexafluoropropylene copolymer (type 6010), and KH-550 modified nano-neodymium oxide is not present; this portion is supplemented by linear low-density polyethylene. The remaining formulation and preparation method are exactly the same as in Example 1.

[0093] Comparative Example 6 was used to investigate the synergistic contribution of PVDF-HFP fluoropolymer and KH-550 modified nano-neodymium oxide.

[0094] To further illustrate the beneficial technical effects of the various embodiments of the present invention, relevant performance tests were conducted on Embodiments 1-3 and Comparative Examples 1-6; The testing method is as follows: The cables prepared in Examples 1-3 and Comparative Examples 1-6 were subjected to the following performance tests, and the test results are shown in Table 1.

[0095] 1. Volume resistivity gradient: On the cross-section of the integrated insulation and shielding layer, the volume resistivity is measured at 0.5 mm intervals from the side closest to the conductor to the side furthest from the conductor. The resistivity on the conductor side (Ω·cm) and the resistivity on the outer side (Ω·cm) are recorded, and the resistivity from 10... 4 Ω·cm increases to 10 12 The proportion of the transition zone width (Ω·cm) to the layer thickness.

[0096] 2. Space charge: The maximum space charge density (C / m²) inside the integrated insulation and shielding layer was measured using the PEA method under a DC electric field strength of 50 kV / mm. 3 ).

[0097] 3. Water absorption rate: The cable sample was immersed in deionized water at 23°C for 168 h, and the water absorption rate (%) of the conductor-insulation interface layer was measured.

[0098] 4. Elongation at break retention rate after UV aging: UV aging was performed for 1000 h according to GB / T 12527, and the elongation at break retention rate (%) of the weather-resistant protective layer was measured.

[0099] 5. Elongation at break retention rate after heat aging: After heat aging at 135℃ for 168 h, the elongation at break retention rate (%) of the weather-resistant protective layer was measured.

[0100] 6. Solar radiation temperature rise: Under simulated solar radiation (1 kW / m²), 2 The steady-state temperature (°C) of the cable surface was measured under the full spectrum of ultraviolet, visible and near-infrared radiation, with an ambient temperature of 40°C.

[0101] 7. Low temperature bending: After bending around a 6D mandrel 3 times at -40℃, observe whether the surface cracks.

[0102] 8. Water tree growth length: After accelerated aging for 180 days in a 15 kV / mm power frequency electric field and a 50℃ water bath, the maximum growth length (μm) of the water tree was measured.

[0103]

[0104] In Comparative Example 1, after removing the zinc stannate / nano-yttrium oxide composite filler, the space charge density decreased from 0.8 C / m². 3 Rise to 2.5C / m 3 The increase exceeded 200%. This is because the absence of shallow Y₂O₃ traps prevents the rapid injection of charge near the electrode from being preferentially captured by these traps. Instead, the deep BaTiO₃ traps capture the charge far from the electrode, leading to an accumulation of space charge near the electrode and exacerbating electric field distortion. The lack of nonlinear dielectric response in Zn₂SnO₄ also weakens the insulating layer's adaptability to localized high electric fields. This comparison demonstrates that the zinc stannate / nano-yttrium oxide composite filler suppresses space charge through a dual mechanism of shallow and deep trap gradient coordination and nonlinear dielectric response, which cannot be replaced by simply increasing the amount of BaTiO₃.

[0105] In Comparative Example 2, after removing KH-550-modified nano-neodymium oxide, the retention rate of elongation at break during thermal aging plummeted from 86% to 71%, and the temperature rise under sunlight increased from 52℃ to 58℃. The loss of near-infrared thermal radiation absorption by Nd2O3 led to a 6℃ increase in the cable surface temperature under sunlight, exacerbating the thermal aging of PVDF-HFP. The neutralization effect of the KH-550 amino groups on the Nd2O3 surface on the acidic degradation products generated by HF removal from PVDF-HFP was lost, accelerating the acidic chain degradation and significantly reducing the retention rate during thermal aging. This comparison demonstrates that KH-550-modified nano-neodymium oxide plays a dual role in the weathering layer, providing near-infrared thermal radiation cooling and neutralizing acidic degradation products.

[0106] Comparative Example 3, employing a traditional three-layer co-extrusion structure, achieves a space charge density as high as 3.8 C / m². 3 The water tree reached a length of 250 μm. In the traditional three-layer structure, the insulating layer is homogeneous XLPE, lacking a phase separation-driven semiconducting-insulating functional transition and deep-shallow trap coordination, allowing space charge to accumulate unimpeded within the insulating layer. The interlayer interface becomes the channel for water tree germination and growth, with the water tree length nearly three times that of Example 1. This comparison demonstrates that the phase-separated integrated layer plays a crucial role in suppressing water trees and space charge by eliminating the interlayer interface.

[0107] Comparative Example 4 analysis showed that after removing nano-barium titanate, the space charge density decreased from 0.8 C / m². 3 Increased to 2.8 C / m 3 Y₂O₃ shallow traps alone capture rapidly injected charges near the electrode, but the charges captured by shallow traps have a high probability of thermal detrapping and cannot be stably anchored deep within the insulating region. Without BaTiO₃ deep traps, slow space charges cannot be effectively captured deep within the insulating region, exacerbating electric field distortion. This comparison contrasts with Comparative Example 1: using deep traps or shallow traps alone is less effective than a deep-shallow trap gradient combination.

[0108] In Comparative Example 5, replacing modified fluoromica and modified boehmite nanosheets with unmodified natural mica and alumina powder, and removing A-151, increased the water absorption rate from 0.03% to 0.18%, and the water tree length from 85 μm to 210 μm. Unmodified natural mica has a hydrophilic surface and cannot form a hydrophobic barrier; alumina powder is non-flaky and cannot form a "brick-and-mortar" layered structure with mica, allowing water molecules to penetrate along the interparticle gaps. Without A-151, no siloxane cross-linking network seals the micropores when water penetrates. This comparison demonstrates that the "brick-and-mortar" layered structure, the hydrophobic modification with fluorosilanes, and the hydrolytic condensation sealing mechanism of A-151 are all indispensable.

[0109] In Comparative Example 6, replacing PVDF-HFP (6010 type) with LLDPE (7042 type) and removing Nd2O3 resulted in a decrease in UV aging retention rate from 92% to 62%, a decrease in thermal aging retention rate from 86% to 55%, low-temperature bending cracking at -40℃, and a rise in temperature due to sunlight from 52℃ to 59℃. The CH bonds in the LLDPE molecular chain break under UV radiation, generating free radicals, leading to an aging rate far higher than that of fluoropolymers. LLDPE enters its brittle temperature range at -40℃, failing to meet low-temperature bending requirements. The lack of near-infrared absorption by Nd2O3 further exacerbates the temperature rise. This comparison demonstrates that the blend system of PVDF-HFP and POE (8003 type) and the KH-550 modified nano-neodymium oxide play a decisive role in the performance of the weather-resistant protective layer.

[0110] Performance data from Examples 1-3 show that the integrated insulation and shielding weather-resistant overhead cable of the present invention can achieve a conductor-side volume resistivity of 10 Ω·cm within the formulation range defined in the claims. 1 ~10 4 Ω·cm, outer volume resistivity ≥10 12 A continuous increasing transition of Ω·cm, with a space charge density below 1.2 C / m. 3 It has a water absorption rate of less than 0.05%, a UV aging retention rate of more than 88%, a heat aging retention rate of more than 82%, no cracking when bent at -40℃, and a water tree growth length of less than 120 μm.

[0111] Each of the six comparative examples removed one of the key innovations of this invention, and all showed a significant decrease in performance: Comparative Examples 1 and 4 demonstrate that the deep-shallow trap gradient combination is indispensable for space charge suppression; Comparative Example 2 demonstrates the key role of KH-550 modified nano-neodymium oxide in controlling thermal aging and solar radiation temperature rise; Comparative Example 3 demonstrates the fundamental advantage of the phase-separated integrated layer in eliminating interlayer interface defects and suppressing water treeing; Comparative Example 5 demonstrates the synergistic contribution of the "brick-mud" laminated structure and silane modification to water-blocking performance; Comparative Example 6 demonstrates the decisive role of PVDF-HFP fluoropolymer and KH-550 modified nano-neodymium oxide in weather protection.

[0112] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A weather-resistant overhead cable with integrated insulation and shielding, comprising, from the inside out, an aluminum alloy conductor, a conductor-insulation interface layer, an integrated insulation and shielding layer, and a weather-resistant protective layer, characterized in that: The integrated insulation and shielding layer is a single composite layer composed of the following raw materials in parts by weight: 60-80 parts linear low-density polyethylene, 8-18 parts ethylene-methyl acrylate copolymer, 8-15 parts ethylene-vinyl acetate copolymer, 12-25 parts conductive carbon black, 1-4 parts nano barium titanate, 3-8 parts zinc stannate / nano yttrium oxide composite filler, 1.5-2.5 parts dicumyl peroxide, and 0.3-0.8 parts antioxidant; The ethylene-methyl acrylate copolymer is thermodynamically incompatible with linear low-density polyethylene, and a two-phase co-continuous structure is formed during the blending process; The linear low-density polyethylene phase constitutes an insulating continuous phase; the ethylene-vinyl acetate copolymer is distributed at the interface between the ethylene-methyl acrylate copolymer phase and the linear low-density polyethylene phase. The zinc stannate / nano yttrium oxide composite filler is prepared by ball milling zinc stannate and nano yttrium oxide in a mass ratio of 1:1 to 3:1, with the nano yttrium oxide loaded on the surface of the zinc stannate particles; The volume resistivity of the integrated insulating shielding layer increases continuously from the side closer to the conductor to the side farther from the conductor, with the volume resistivity being 10⁻⁶ on the side closer to the conductor. 1 ~10 4 Ω·cm, volume resistivity on the side away from the conductor ≥10 12 Ω·cm.

2. The integrated insulation and shielding weather-resistant overhead cable according to claim 1, characterized in that: The conductive carbon black is N220 or N550 type acetylene black, with a DBP absorption value of 100~160ml / 100g and a particle size of 20~50nm; the conductive carbon black preferentially wets the polar ethylene-methyl acrylate copolymer phase, and its concentration in the linear low-density polyethylene phase is lower than the percolation threshold. The ethylene-methyl acrylate copolymer has a methyl acrylate content of 6-10% and a melt flow rate of 2-8 g / 10 min; the ethylene-vinyl acetate copolymer has a vinyl acetate content of 18-28% and its polarity is between that of ethylene-methyl acrylate copolymer and linear low-density polyethylene. In the zinc stannate / nano-yttrium oxide composite filler, the zinc stannate has a Zn2SnO4 spinel structure, and the average particle size of the nano-yttrium oxide is 20~80nm; the volume ratio of the ethylene-methyl acrylate copolymer phase to the linear low-density polyethylene phase is 15~35:65~85; during the extrusion process, the shear rate is low near the conductor, and the ethylene-methyl acrylate copolymer phase maintains a connected semi-conductive network morphology. The shear rate is high far from the conductor, and the ethylene-methyl acrylate copolymer phase is stretched and dispersed into isolated micro-regions, breaking the semiconductive network.

3. The integrated insulation and shielding weather-resistant overhead cable according to claim 1, characterized in that: The conductor-insulator interface layer is composed of the following raw materials in parts by weight: 70-85 parts of ethylene-vinyl acetate copolymer, 5-12 parts of perfluorooctyltriethoxysilane modified synthetic fluoromica, 3-8 parts of KH-560 modified boehmite nanosheets, 2-5 parts of vinyltriethoxysilane, 0.8-1.5 parts of dicumyl peroxide, and 0.3-0.5 parts of antioxidant; The synthetic fluoromica is a fluorophlogopite-type synthetic mica with a sheet diameter of 10~50μm and a thickness of 0.5~2μm. After surface modification with perfluorooctyltriethoxysilane, a hydrophobic fluorosilane layer is formed on the surface. The boehmite nanosheets are γ-alumina hydrate with a diameter of 100~500 nm and a thickness of 10~30 nm. After surface modification with KH-560, they are bonded to the ethylene-vinyl acetate copolymer matrix through epoxy groups.

4. The integrated insulation and shielding weather-resistant overhead cable according to claim 1, characterized in that: The weather-resistant protective layer is a blend of polyvinylidene fluoride-hexafluoropropylene copolymer and polyolefin elastomer, composed of the following raw materials in parts by weight: 25-40 parts of polyvinylidene fluoride-hexafluoropropylene copolymer, 35-50 parts of polyolefin elastomer, 8-15 parts of ethylene-methyl acrylate copolymer grafted with maleic anhydride, 1-3 parts of nano-cerium dioxide, 2-5 parts of nano-titanium dioxide, 1-4 parts of KH-550 modified nano-neodymium oxide, 0.5-1.5 parts of hindered amine light stabilizer, 0.8-1.5 parts of dicumyl peroxide, and 0.5-1 part of antioxidant; The polyvinylidene fluoride-hexafluoropropylene copolymer is blended with a polyolefin elastomer; the ethylene-methyl acrylate copolymer grafted with maleic anhydride is a reactive compatibilizer, and its maleic anhydride groups undergo a grafting reaction with the defluorination sites on the polyvinylidene fluoride-hexafluoropropylene copolymer chain, so that the ethylene-methyl acrylate copolymer segment is compatible with the polyolefin elastomer and achieves chemical bonding at the two-phase interface. The average particle size of the nano-cerium dioxide is 10~50nm, and the cerium ions in the cerium dioxide can be reversibly converted between the trivalent and tetravalent cerium. The average particle size of the KH-550 modified nano-neodymium oxide is 30~100nm. After surface modification with γ-aminopropyltriethoxysilane, its amino groups react with the acidic degradation products generated by the thermal aging of polyvinylidene fluoride-hexafluoropropylene copolymer.

5. The integrated insulation and shielding weather-resistant overhead cable according to claim 1, characterized in that: The barium titanate nanoparticles have an average particle size of 50-200 nm and are surface-modified by glycidyl methacrylate grafted with ethylene-vinyl acetate copolymer. The epoxy groups of the glycidyl methacrylate form covalent bonds with the linear low-density polyethylene matrix during the crosslinking process of dicumyl peroxide, so that the barium titanate nanoparticles are anchored to the matrix by chemical bonds.

6. The integrated insulation and shielding weather-resistant overhead cable according to claim 1, characterized in that: The aluminum alloy conductor is a high-strength aluminum alloy compacted round conductor, and its outer surface is treated with micro-arc oxidation to form an alumina ceramic transition layer with a thickness of 2~8μm; the surface roughness Ra of the alumina ceramic transition layer is 0.5~2.0μm.

7. The integrated insulation and shielding weather-resistant overhead cable according to claim 1, characterized in that: The conductor-insulator interface layer has a thickness of 0.3~0.8 mm and a volume resistivity of ≤500 Ω·cm; The total thickness of the integrated insulating and shielding layer is 3.5~6.0 mm, with the volume resistivity on the side closest to the conductor being less than 10. 4 The semiconductive region with a volume resistivity of Ω·cm accounts for 8-20% of the total thickness of the integrated insulating and shielding layer, the transition region with continuously increasing volume resistivity accounts for 15-30%, and the volume resistivity on the side away from the conductor is higher than 10 Ω·cm. 12 The insulation region with an Ω·cm insulation area accounts for 50~77%; The thickness of the weather-resistant protective layer is 1.0~2.5mm.

8. A method for preparing an integrated insulation and shielding weather-resistant overhead cable as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Preparation of conductor-insulator interface layer granules: The synthesized fluoromica was dispersed in an ethanol solution of perfluorooctyltriethoxysilane, stirred at 70~90℃ for 2~4h, filtered and dried to obtain modified fluoromica; Boehmite nanosheets were dispersed in an ethanol-water solution of KH-560, the pH was adjusted to 4-5, and the reaction was carried out at 60-80℃ for 3-5 hours. The mixture was then filtered and dried to obtain modified boehmite nanosheets. Modified fluoromica, modified boehmite nanosheets, ethylene-vinyl acetate copolymer, vinyltriethoxysilane, dicumyl peroxide, and antioxidant are mixed and kneaded in an internal mixer at 110-130°C for 6-10 minutes. The mixture is then extruded and granulated by twin screws to obtain interfacial layer granules. S2: First, zinc stannate and nano-yttrium oxide are mixed in deionized water at a mass ratio of 1:1 to 3:1, polyethylene glycol dispersant is added, ball milling is performed for 8 to 12 hours, and spray drying is carried out to obtain zinc stannate / nano-yttrium oxide composite filler; Preparation of integrated insulating and shielding granules: First, ethylene-methyl acrylate copolymer and conductive carbon black are premixed in an internal mixer at 120~140℃ for 8~12min to fully wet and disperse the conductive carbon black in the ethylene-methyl acrylate copolymer, thus obtaining carbon black masterbatch. Carbon black masterbatch was melt-blended and granulated with linear low-density polyethylene, ethylene-vinyl acetate copolymer, GMA-grafted EVA surface-modified nano barium titanate, zinc stannate / nano yttrium oxide composite filler, dicumyl peroxide, and antioxidant in a twin-screw extruder at 140~160℃ to obtain integrated layered granules. S3: Disperse nano-neodymium oxide in an ethanol-water solution of KH-550, adjust the pH to 9-10, stir and react at 70-80℃ for 3-5 hours, filter, wash with ethanol, and dry at 100-120℃ for 4-6 hours to obtain KH-550 modified nano-neodymium oxide. Preparation of weather-resistant protective layer granules: Nano-cerium dioxide and nano-titanium dioxide were surface modified with KH-570 silane coupling agent respectively; Polyvinylidene fluoride-hexafluoropropylene copolymer, polyolefin elastomer, ethylene-methyl acrylate copolymer grafted with maleic anhydride, modified nano-cerium dioxide, modified nano-titanium dioxide, KH-550 modified nano-neodymium oxide, hindered amine light stabilizer, dicumyl peroxide, and antioxidant are mixed in an internal mixer at 150-170℃ for 10-15 minutes, and then granulated in a twin-screw extruder at 150-170℃ to obtain weather-resistant granules. S4: Micro-arc oxidation treatment is performed on the outer surface of the aluminum alloy conductor to form an alumina ceramic transition layer; S5: The interface layer granules and the integrated layer granules are sequentially extruded through a three-channel co-extrusion die head onto the aluminum alloy conductor that has undergone micro-arc oxidation treatment, and then cross-linked and cured through a cross-linking tube; During the cross-linking and curing process, the ethylene-methyl acrylate copolymer phase and the linear low-density polyethylene phase undergo phase separation. The conductive carbon black remains in the ethylene-methyl acrylate copolymer phase to form a semi-conductive network. Dicumyl peroxide initiates the cross-linking of linear low-density polyethylene and ethylene-vinyl acetate copolymer, locking the co-continuous structure of the two phases. S6: The weather-resistant layer granules are extruded onto the outside of the cross-linked and cured cable core. While dicumyl peroxide initiates the cross-linking of the polyolefin elastomer, the maleic anhydride groups react with the polyvinylidene fluoride-hexafluoropropylene copolymer to achieve two-phase chemical bonding. After segmented cooling, the material is wound up.

9. The preparation method according to claim 8, characterized in that: In step S2, the premixing ratio of ethylene-methyl acrylate copolymer and conductive carbon black is such that the concentration of carbon black in ethylene-methyl acrylate copolymer reaches 1.5 to 3 times the percolation threshold. In the preparation of the zinc stannate / nano yttrium oxide composite filler, the amount of polyethylene glycol dispersant added is 0.5~2% of the total mass of zinc stannate and nano yttrium oxide, the ball milling speed is 300~500 rpm, the inlet temperature of the spray drying is 180~220℃, and the outlet temperature is 80~100℃. In step S5, the temperature settings of the three-channel co-extrusion die head are as follows: feeding section 130~140℃, compression section 145~155℃, metering section 160~170℃, and die head 170~180℃; the temperature of the crosslinking tube is 180~220℃, and the crosslinking curing time is 300~600s.

10. The preparation method according to claim 8, characterized in that: In step S1, the mass concentration of the ethanol solution of perfluorooctyltriethoxysilane is 5-15%, and the mass ratio of synthesized fluoromica to perfluorooctyltriethoxysilane is 10:1-10:

3. The volume ratio of ethanol to water in the KH-560 aqueous solution is 9:1, and the mass ratio of KH-560 to boehmite nanosheets is 1:10 to 3:

10. In step S3, the melt flow rate of the polyvinylidene fluoride-hexafluoropropylene copolymer is 5~25 g / 10 min, and the density of the polyolefin elastomer is 0.865~0.875 g / cm³. 3 ; The grafting rate of maleic anhydride in the ethylene-methyl acrylate copolymer grafted with maleic anhydride is 0.8~1.5%; the volume ratio of ethanol to water in the KH-550 ethanol aqueous solution is 8:2~9:1, and the mass ratio of KH-550 to nano-neodymium oxide is 1:15~1:

8. In step S6, the segmented cooling is as follows: the first segment is 50~70℃ warm water, the second segment is 30~50℃ warm water, and the third segment is 15~25℃ cold water.

Images