An electrically insulated cable and a method for producing the same

Abstract

The present application relates to high voltage and ultra-high voltage power cable insulation material and cable manufacturing technical field, concretely relates to a kind of electrical insulation cable and preparation method thereof.The present application discloses a kind of electrical insulation cable and preparation method thereof, the cable includes conductor, conductor shield layer, insulation layer, insulation shield layer and sheath layer, the surface of conductor is equipped with micron level annular groove that can adapt to different line diameter, conductor shield layer fills groove and forms embedded anchor, and realizes interface fusion with insulation layer by homologous material.Insulation material includes polypropylene, polyolefin elastomer, reactive compatibilizer, functionalized nanohybrid particle, reactive voltage stabilizer and antioxidant, functionalized nanohybrid particle is hexagonal boron nitride as core, polydopamine as intermediate layer, and beta nucleating agent as functional layer.The present application is enhanced by embedded anchor and chemical anchor, and the interface bonding strength and operation reliability of cable are improved.

Description

Technical Field

[0001] This invention relates to the field of insulation materials and cable manufacturing technology for high-voltage and ultra-high-voltage transmission cables, specifically to an electrically insulated cable and its preparation method. Background Technology

[0002] In the field of high-voltage and ultra-high-voltage power transmission, especially in special service environments such as outdoor, high-altitude, and underground applications, cables must withstand complex conditions such as high electric fields, frequent thermal cycling, mechanical stress, and environmental erosion for extended periods. Their insulation performance and interface stability directly determine the safe and reliable operation of the transmission system. In traditional high-voltage and ultra-high-voltage cable structures, the conductor-insulation interface relies solely on physical bonding, which easily peels off under thermal cycling, forming air gaps and inducing partial discharge. Although cross-linked polyethylene is widely used in high-voltage cable insulation, its thermosetting defects are significant: it cannot be recycled after its service life, and the residual cross-linking byproducts lead to space charge accumulation, requiring weeks of high-temperature degassing, resulting in high energy consumption and cost. Therefore, recyclable thermoplastic polypropylene has become a research hotspot. However, pure polypropylene has two major bottlenecks: high crystallinity leads to high brittleness, easily causing microcracks during production and installation; and material defects under high-voltage DC conditions easily induce space charge accumulation, leading to insulation breakdown due to distorted electric fields. Therefore, there is an urgent need to develop new thermoplastic insulation materials and cable structures that combine high flexibility, space charge suppression, and interface reinforcement.

[0003] To address the issues of high brittleness in polypropylene and easy delamination at the conductor-insulation interface in traditional cable structures, the industry widely employs a method of physical blending polyolefin elastomers into the polypropylene matrix. For example, CN118522497A discloses a low-halogen standard-thickness insulated cable for internal combustion engine vehicles, comprising: a conductor and a low-halogen flame-retardant insulating sheath layer covering the outer surface of the conductor. The low-halogen flame-retardant insulating sheath layer is composed of the following components in parts by weight: 100 parts ethylene-vinyl acetate copolymer, 20-35 parts ethylene propylene diene monomer (EPDM) rubber, 8-20 parts low-density polyethylene resin, 6-10 parts high-density polyethylene resin, 3-8 parts maleic anhydride-grafted polyolefin elastomer, 0.2-1 part antioxidant, 0.3-1.5 parts irradiated crosslinking agent, 5-10 parts zinc borate, 10-25 parts flame retardant, 2-5 parts 1,2-polybutadiene, and 1-3 parts ethylene glycol dimethacrylate. The cables prepared using this method, after being immersed in mineral oil at 100°C for 70 hours, exhibit a tensile strength retention rate exceeding 85% and an elongation at break retention rate reaching 90% after aging, thus improving the oil resistance of the cables and meeting the oil resistance requirements of iron and national standards for insulated cables. However, existing technologies primarily focus on improving the oil resistance and mechanical properties of cables, neglecting the space charge accumulation problem caused by shallow interfacial traps in polypropylene and elastomer blends, and also failing to address the design of conductor-insulator interface reinforcement structures.

[0004] In summary, how to innovate a new insulating material system and its preparation method that can retain the advantages of polypropylene's recyclability and thermoplasticity while synergistically improving the material's flexibility, thermal conductivity, space charge suppression ability, and interfacial bonding strength has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an electrically insulated cable and its preparation method, so as to solve the technical problems in the prior art, such as the difficulty in balancing the weather resistance and insulation of the insulating material and the difficulty in controlling the dispersion and interface of the nanofiller.

[0006] The specific technical solution is as follows: An electrically insulated cable and its manufacturing method are disclosed, comprising, from the inside out, a conductor, a conductor shielding layer, an insulation layer, an insulation shielding layer, and a sheath layer; the conductor has a micron-sized annular groove on its surface; the conductor shielding layer is composed of a semi-conductive shielding material and fills the micron-sized annular groove, forming an embedded anchoring structure between the conductor shielding layer and the conductor; the insulation layer is composed of an insulating material composition and is chemically anchored to the conductor shielding layer through fusion at a homologous material interface; the insulating material composition includes polypropylene, a polyolefin elastomer, a reactive compatibilizer, functionalized nano-hybrid particles, a reactive voltage stabilizer, and an antioxidant; the functionalized nano-hybrid particles have an inorganic particle core, a polyphenolic compound as an intermediate layer, and a β-nucleating agent as a load layer, stabilizing the load through hydrogen bonding and π-π stacking; the reactive compatibilizer includes glycidyl methacrylate-grafted polyolefin elastomer and maleic anhydride-grafted polypropylene; the reactive voltage stabilizer is grafted and fixed onto the polyolefin elastomer molecular chain.

[0007] Furthermore, the micron-sized annular groove has a depth of 0.5% to 2% of the conductor diameter, a width of 2% to 5% of the conductor diameter, and a center-to-center distance between adjacent grooves of 8% to 15% of the conductor diameter.

[0008] Further, the inorganic particles are selected from boron nitride and aluminum oxide; the polyphenolic compound is selected from dopamine hydrochloride and tannic acid; the β-nucleating agent is selected from N,N'-dicyclohexyl-2,6-naphthalenediamide and sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate; and the reactive voltage stabilizer is selected from 4-allyloxybenzophenone and 9-vinylcarbazole.

[0009] Further, the insulating material composition, calculated by total percentage, comprises the following components by mass: 100 parts of blended resin matrix, wherein polypropylene resin accounts for 60-70 parts and polyolefin elastomer resin accounts for 30-40 parts; 6-13 parts of reactive compatibilizer; 2-4 parts of the functionalized nano-hybrid particles; 0.5-2 parts of the reactive voltage stabilizer; 0.8 parts of antioxidant stabilizer combination; and 0.01-0.03 parts of free radical initiator.

[0010] An electrically insulated cable and its manufacturing method, comprising the following steps: S1: Hexagonal boron nitride was added to deionized water and ultrasonically dispersed for 30 minutes. Dopamine hydrochloride was added, and the pH was adjusted with Tris buffer solution. After stirring, the mixture was centrifuged and washed until neutral. The mixture was then vacuum dried at 60°C for 12 hours to obtain polydopamine-coated boron nitride. Polydopamine-coated boron nitride was then dispersed in a mixed solvent of ethanol and water. N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide was added and stirred for impregnation and adsorption. After centrifugation and washing to remove unloaded nucleating agent, the mixture was vacuum dried at 60°C for 12 hours to obtain functionalized nano-hybrid particles.

[0011] S2: Polypropylene is melt-grafted with maleic anhydride and dicumyl peroxide, and then extruded and granulated to obtain maleic anhydride-grafted polypropylene; polyolefin elastomer is melt-grafted with glycidyl methacrylate and dicumyl peroxide to obtain glycidyl methacrylate-grafted polyolefin elastomer; functionalized nano-hybrid particles and glycidyl methacrylate-grafted polyolefin elastomer are then added to a mixer for melt premixing to form a premix, which is then cooled and crushed for later use.

[0012] S3: Polypropylene, polyolefin elastomer, maleic anhydride-grafted polypropylene, premix, 4-allyloxybenzophenone, dicumyl peroxide, antioxidant 1010, and antioxidant 168 are added to a twin-screw extruder for melt blending, extrusion granulation, and drying to obtain insulating material composition granules.

[0013] S4: Take a copper conductor and process micron-level annular grooves on the conductor surface using a laser grooving device; first, extrude conductor shielding material onto the grooved conductor surface to form a conductor shielding layer; then, extrude the insulating material composition granules onto the conductor shielding layer. Set the extrusion temperature as follows: feeding section 175℃, compression section 185℃, metering section 190℃, die head 195℃, and die temperature 200℃. Simultaneously set the extrusion linear speed to ensure the molten insulating material is tightly bonded to the outer surface of the conductor shielding layer; subsequently, extrude insulating shielding material onto the outside of the insulating layer to form an insulating shielding layer. After cooling and shaping, extrude a low-density polyethylene outer sheath onto the outside of the insulating shielding layer at an extrusion temperature of 170℃. After extrusion, pull and wind to obtain an electrically insulated cable.

[0014] Further, in S1, the pH adjustment needs to be adjusted to 8-9; the inorganic particles, the polyphenolic compound, and the β-nucleating agent have a mass ratio of (2-5):(0.4-0.8):(0.1-0.5); the impregnation adsorption is performed under the following conditions: temperature 35-45℃, stirring time 2-6 hours.

[0015] Further, in step S2, the conditions for melt grafting polypropylene with maleic anhydride and dicumyl peroxide are set as follows: temperature 170~190℃, rotation speed 50~70rpm, and reaction time 6~10 minutes; the conditions for melt grafting polyolefin elastomer with glycidyl methacrylate and dicumyl peroxide are set as follows: temperature 160~180℃, rotation speed 40~60rpm, and reaction time 5~7 minutes.

[0016] Furthermore, the melt blending described in S3 is performed under the following conditions: rotation speed 100-200 rpm, temperature 170-190°C, and reaction time 3-5 minutes.

[0017] Furthermore, the extrusion line speed set in S4 is set to 10~20m / min; the cooling and shaping is set to a first stage of 50~70℃ warm water, a second stage of 30~50℃ warm water, and a third stage of 15~25℃ cold water.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) Enhance the bonding strength of the conductor-insulator interface: The conductor surface has micron-level grooves that form an embedded anchoring structure with the insulating material. This works synergistically with the chemical anchoring at the material interface to significantly improve the interface's anti-peeling performance, effectively suppress partial discharge at the interface, and extend the cable's service life.

[0019] (2) Significantly improve the breakdown strength and thermal stability of insulating materials: Through the “one agent, multiple functions” design of functionalized nano-hybrid particles, the functions of thermal conduction, nucleation and interface modification are integrated into a single particle, which effectively induces polypropylene to form a high proportion of β crystal form, greatly improving the toughness and heat resistance of the material. At the same time, the uniformly distributed thermal conductive network significantly improves the heat dissipation capacity of the insulation layer.

[0020] (3) Effectively suppress space charge accumulation: By grafting reactive voltage stabilizers onto the elastomer chain, the problem of small molecule migration is completely solved. The voltage stabilizing group can efficiently capture high-energy electrons, significantly reduce space charge density, avoid local electric field distortion, and improve the long-term reliability of the cable.

[0021] (4) Achieving environmental protection, recyclability and process simplification: The use of a fully thermoplastic system eliminates the need for cross-linking reactions and the generation of no polar byproducts, saving the high-temperature degassing process, significantly reducing production energy consumption and cycle time, and allowing the cable to be melted and recycled after its service life, which meets the requirements of green and low-carbon development. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of the insulated cable in Embodiment 1 of the present invention.

[0023] Figure 2 The image shows the infrared spectrum of the functionalized nano-hybrid particles in Example 1 of this invention.

[0024] Figure 3 This is the infrared spectrum of the insulating material composition granules in Example 1 of the present invention. Detailed Implementation

[0025] This invention proposes an electrically insulated cable and its manufacturing method, the detailed manufacturing steps of which are as follows: 1. Preparation of Functionalized Nanohybrid Particles Hexagonal boron nitride was dispersed in a Tris-hydroxymethylaminomethane (Tris) buffer solution, and dopamine hydrochloride was added. Under weakly alkaline conditions, dopamine underwent a self-polymerization reaction, forming a polydopamine coating layer on the surface of the hexagonal boron nitride. The polydopamine-coated boron nitride was then dispersed in a mixed solvent of ethanol and water, and N,N'-dicyclohexyl-2,6-naphthalenediamide was added for impregnation and adsorption. Supramolecular physical loading was achieved by utilizing the hydrogen bonds and π-π stacking interactions between polydopamine and the nucleating agent. After centrifugation, washing, and drying, functionalized nano-hybrid particles were obtained.

[0026] 2. Preparation and pre-reaction anchoring of reactive compatibilizers Polypropylene was melt-grafted with maleic anhydride and dicumyl peroxide in a mixer to obtain maleic anhydride-grafted polypropylene. Polyolefin elastomers were melt-grafted with glycidyl methacrylate and dicumyl peroxide in a mixer to obtain epoxy-group-grafted polyolefin elastomers. Functionalized nano-hybrid particles and epoxy-group-grafted polyolefin elastomers were added to a mixer and premixed under high shear at 140–160 °C. The ring-opening reaction between the epoxy groups and the amino groups on the surface of polydopamine chemically anchored the nano-hybrid particles to the elastomer phase, forming a premix.

[0027] 3. Melt blending and granulation Polypropylene, polyolefin elastomer, maleic anhydride-grafted polypropylene, premix, reactive voltage stabilizer, peroxide initiator and antioxidant are added to a twin-screw extruder and melt-blended at 180~200℃. The reactive voltage stabilizer undergoes graft copolymerization with the polyolefin elastomer under the initiation of peroxide and is chemically fixed on the elastomer chain. At the same time, functionalized nano-hybrid particles are uniformly distributed at the elastomer phase interface, inducing polypropylene to form β crystal form. After extrusion granulation, the insulating material composition granules are obtained.

[0028] 4. Cable extrusion molding Micron-level annular grooves are machined on the surface of a copper conductor using laser grooving equipment. First, thermoplastic polyolefin-based semiconductive conductor shielding material is extruded onto the surface of the grooved conductor using an extruder, so that the shielding material fills the grooves to form an embedded anchoring structure. Then, the granular insulating material composition is dried and extruded onto the grooved conductor with the shielding layer using a single-screw extruder. The extrusion temperature is controlled in stages to ensure a tight bond with the outer surface of the conductor shielding layer. Subsequently, thermoplastic polyolefin-based semiconductive insulating shielding material is extruded onto the outside of the insulating layer and water-cooled for shaping. Finally, a low-density polyethylene outer sheath is extruded onto the outside of the insulating shielding layer. After extrusion, the material is pulled and wound to obtain an electrically insulated cable.

[0029] The technical solution designed by this invention to solve the existing problems includes the following key points: 1. "Multi-functional" design of functionalized nano-hybrid particles In traditional cable insulation materials, thermally conductive fillers, β-nucleating agents, and interface modifiers are usually added individually as multiple components, which leads to problems such as uneven dispersion, poor interfacial compatibility, and limited functionality. Furthermore, multi-component systems are prone to additive migration and interfacial defects, affecting the long-term stability of the insulation layer. This invention uses hexagonal boron nitride (h-BN) as a thermally conductive core, and through the self-polymerization reaction of dopamine under weakly alkaline conditions, coats its surface with a polydopamine (PDA) layer approximately 10 nm thick. The PDA layer contains abundant phenolic hydroxyl and amino functional groups, which serve two purposes: firstly, as an interfacial modification layer, improving the compatibility between inorganic particles and the polymer matrix; and secondly, providing active sites for the loading of β-nucleating agents. Subsequently, the polydopamine-coated hexagonal boron nitride support (PDA@h-BN) was dispersed in a solvent, and the specified β-nucleating agent N,N'-dicyclohexyl-2,6-naphthalenediamide (DCTNA) was added for thorough isothermal impregnation. High-intensity supramolecular physical loading was achieved by utilizing the multiple hydrogen bonds and π-π electron stacking between the phenolic hydroxyl groups and the large-area conjugated system on the PDA network surface and the amide groups and naphthalene ring skeleton of the nucleating agent. Since no chemical crosslinking agent was added to the system, the passivation of the active sites of the nucleating agent was avoided, and highly active functionalized nano-hybrid particles could be obtained directly by centrifugation and drying.

[0030] To verify the successful encapsulation of h-BN in PDA and the successful loading of the β-nucleating agent N,N'-dicyclohexyl-2,6-naphthalenediamide onto the surface of the PDA layer, the chemical structure of the functionalized nano-hybrid particles was characterized by Fourier transform infrared spectroscopy (FTIR). Figure 2 This is the FTIR spectrum of the functionalized nano-hybrid particles in Example 1 of this invention. As shown in the figure, pure h-BN at 1370 cm⁻¹... -1 The characteristic absorption peak of the BN bond appears at 3400 cm⁻¹; after dopamine self-polymerization coating, PDA@h-BN shows an absorption peak at 3400 cm⁻¹. -1 A broad absorption peak for the phenolic hydroxyl and amino groups appears at 1620 cm⁻¹. -1 The presence of the characteristic C=C peak of the aromatic ring at 1640 cm⁻¹ indicates that PDA was successfully coated onto the h-BN surface; further loading with a β nucleating agent resulted in functionalized nano-hybrid particles exhibiting a peak at 1640 cm⁻¹. -1 The characteristic peak of amide C=O appears at 1550 cm⁻¹. -1 The presence of a characteristic peak of amide II (C-N+NH) indicates that the β-nucleating agent was successfully loaded onto the PDA layer surface via hydrogen bonding and π-π stacking interactions. Infrared spectroscopy results confirmed the successful construction of the functionalized nanohybrid particles.

[0031] 2. Grafting and Immobilization Techniques for Reactive Voltage Stabilizers Traditional voltage stabilizers are added through physical blending, relying on intermolecular forces to disperse them within the polymer matrix. Under the high temperature and strong electric field conditions of long-term cable operation, these small-molecule additives are prone to migration and diffusion, precipitating from the insulation layer to the surface or interface. This leads to a gradual decrease in the space charge suppression effect, and may even cause partial discharge and insulation breakdown. This invention uses voltage stabilizers containing reactive groups, specifically 4-allyloxybenzophenone or 9-vinylcarbazole compounds. These molecules contain both voltage-stabilizing functional groups and unsaturated double bonds that can participate in polymerization reactions. During melt blending, a trace amount of peroxide initiator is added. The free radicals generated by the initiator decomposition promote the opening of the double bonds in the reactive voltage stabilizer, causing a graft copolymerization reaction with the polyolefin elastomer molecular chain, chemically fixing the voltage stabilizer to the polyolefin elastomer chain via covalent bonds. The benzophenone or carbazole group can act as a charge carrier trapping center, capturing and dissipating high-energy electrons. Through electron transfer or energy relaxation mechanisms, it inhibits charge injection and accumulation, reducing the bombardment damage of high-energy electrons to the polymer backbone, thereby delaying the initiation and growth of electrical trees. Because the voltage stabilizer is chemically grafted onto the elastomer chain, the small molecule migration problem of traditional physical blending methods is completely solved, ensuring the long-term stability of the space charge suppression effect.

[0032] To verify the graft copolymerization effect of the reactive voltage stabilizer and the polyolefin elastomer matrix in this invention, the prepared insulating material was characterized by FTIR, and the results are as follows: Figure 3As shown. Among them, 2944cm -1 and 2889cm -1 The strong absorption peak at 1464 cm⁻¹ is a characteristic peak of the stretching vibration of saturated CH bonds in polyolefin segments. -1 and 1395cm -1 The absorption peak at 1741 cm⁻¹ corresponds to the bending vibrations of the methylene and methyl groups, confirming the presence of the polyolefin elastomer matrix; -1 The absorption peak at 1243 cm⁻¹ is a characteristic peak of the carbonyl group introduced by the grafting reaction. -1 The absorption peak at 1658 cm⁻¹ corresponds to the stretching vibration of the COC bond, indicating that the reactive voltage stabilizer has been successfully grafted onto the polyolefin chain; -1 The absorption peak at this location corresponds to the aromatic ring structure or a small amount of incompletely reacted C=C double bonds in the voltage stabilizer, confirming the effective introduction of the 4-allyloxybenzophenone functional group. The coexistence of the above-mentioned characteristic peaks of the polyolefin matrix and the characteristic peaks of the voltage stabilizer directly proves that the voltage stabilizer is grafted onto the polyolefin elastomer molecular chain through covalent bonding, rather than simple physical blending, providing structural experimental evidence for solving the migration problem of small molecule additives.

[0033] 3. Embedded anchoring structure at the conductor-shielding layer interface Traditional cables rely solely on physical adhesion between the conductor and insulation layer. Under thermal cycling and mechanical stress, this adhesion easily leads to interfacial peeling, creating gaps and potentially causing partial discharge or even insulation breakdown. In contrast, this invention uses laser grooving equipment to perform microstructural processing on the copper conductor surface before cable forming. This process enables continuous automated production and large-scale industrial processing capabilities. Figure 1 As shown, this groove design allows the molten conductor shielding material to completely fill the conductor groove under extrusion pressure without forming air gaps. After filling, the outer surface of the conductor shielding layer returns to a smooth cylindrical surface. During extrusion molding, the conductor shielding material is first extruded onto the surface of the grooved conductor, filling the groove to form an embedded anchoring structure. Then, the insulating material composition is coated onto the outside of the conductor shielding layer in a high-temperature molten state, tightly adhering to the smooth outer surface of the shielding layer. Subsequently, an insulating shielding layer is extruded onto the outside of the insulating layer, forming a complete shield-insulation-shielding structure. After cooling and solidification, a smooth and flat interface is formed between the insulating layer and the conductor shielding layer. This embedded anchoring structure and the chemical anchoring of the material interface form a dual reinforcement mechanism, significantly improving the bonding strength and peel resistance of the conductor-insulation interface. The insulating shielding layer further homogenizes the electric field, protects the insulation layer, and synergistically ensures interface stability. The improved interface bonding strength effectively suppresses interface peeling under thermal cycling and mechanical stress, eliminating the root cause of partial discharge and ensuring the long-term reliability of the cable.

[0034] In practical implementation, the groove dimensions corresponding to the micron-level annular grooves on the conductor surface need to be adapted to the cable conductor diameter. In this invention, the groove depth is 0.5% to 2% of the conductor diameter, the width is 2% to 5% of the conductor diameter, and the spacing between adjacent grooves is 8% to 15% of the conductor diameter. Based on this range, for thin-diameter conductors, the groove dimensions should ideally be at the lower limit to avoid excessively weakening the conductor's cross-sectional area and mechanical strength; for thick conductors with large cross-sections, the upper limit can be appropriately chosen to ensure sufficient interlocking contact area and interfacial bonding force between the conductor shielding layer and the insulation layer. Through the matching design of the groove geometry parameters, the annular groove structure of this invention is applicable to power cables of different specifications and diameters. While ensuring the conductor's conductivity and mechanical properties, it achieves stable embedded anchoring between the conductor and the conductor shielding layer, while maintaining a continuous and smooth cylindrical shape on the outer surface of the conductor shielding layer, avoiding electric field distortion and tip discharge. It has good versatility and industrial-scale batch adaptation capabilities.

[0035] To achieve the synergistic effect of embedded anchoring and seamless interface integration, this invention further incorporates a homologous design for the shielding layer material. By employing a fully thermoplastic polypropylene and polyolefin elastomer system with extremely high molecular homology to the main insulation matrix as the inner and outer semiconductive shielding material, this not only eliminates the extremely energy-intensive and time-consuming high-temperature vulcanization and long-term degassing crosslinking processes in cable manufacturing, but also effectively avoids the risks of melting eccentricity and thermal oxidative degradation of polypropylene insulation at high temperatures in the vulcanization tube. This homologous design endows the shielding layer and insulation layer with extremely similar material melting point distributions, almost identical coefficients of thermal expansion and contraction, and extremely low interfacial tension. During extrusion molding, the molten macromolecular chains can undergo deep mutual diffusion and entanglement at the geometric interface between the semiconductive layer and the insulation layer. After cooling and solidification, seamless fusion of the macromolecular interface is achieved, eliminating microscopic air gap peeling caused by differences in thermal contraction of heterogeneous materials. This ensures that the entire cable system can be completely shredded and melted after its service life, enabling recycling.

[0036] Example 1 Table 1 Raw Material Information Table An electrically insulated cable and its manufacturing method, comprising the following steps: S1: Add 3 parts hexagonal boron nitride to 300 parts deionized water, sonicate for 30 minutes, add 0.6 parts dopamine hydrochloride, adjust pH to 8.5 with Tris buffer, stir at 25℃ for 18 hours, centrifuge and wash until neutral, and vacuum dry at 60℃ for 12 hours to obtain polydopamine-coated boron nitride with a polydopamine coating thickness of about 10 nm; then disperse PDA@h-BN in a mixed solvent of 150 parts ethanol and water in a 1:1 volume ratio, add 0.24 parts N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide, stir at 40℃ for 4 hours for impregnation and adsorption, and realize supramolecular physical loading by utilizing the hydrogen bonding and π-π stacking effect between polydopamine and nucleating agent; centrifuge and wash to remove unloaded nucleating agent, and vacuum dry at 60℃ for 12 hours to obtain functionalized nano-hybrid particles.

[0037] S2: Add 5 parts polypropylene, 0.5 parts maleic anhydride, and 0.1 parts dicumyl peroxide to a mixer and melt-graft at 180°C and 60 rpm for 8 minutes. Extrude and granulate to obtain maleic anhydride-grafted polypropylene. Separately, add 4 parts polyolefin elastomer, 0.5 parts glycidyl methacrylate, and 0.05 parts dicumyl peroxide to a mixer and melt-graft at 170°C and 50 rpm for 6 minutes to obtain glycidyl methacrylate-grafted polyolefin elastomer. Then, add 3 parts functionalized nano-hybrid particles and 4 parts glycidyl methacrylate-grafted polyolefin elastomer to a mixer and melt-premix at 160°C and 40 rpm for 5 minutes. Utilize the ring-opening reaction between epoxy groups and amino groups on the surface of polydopamine to anchor the nano-hybrid particles in the glycidyl methacrylate-grafted polyolefin elastomer matrix to form a premix. Cool and crush for later use.

[0038] S3: Add 65 parts polypropylene, 35 parts polyolefin elastomer, 5 parts maleic anhydride-grafted polypropylene, 7 parts premix, 1.2 parts 4-allyloxybenzophenone, 0.05 parts dicumyl peroxide, 0.5 parts antioxidant 1010, and 0.3 parts antioxidant 168 to a twin-screw extruder. Set the screw speed to 150 rpm and melt-blend at 180°C for 4 minutes. Then extrude and granulate to obtain granules of the insulating material composition, and dry them for later use.

[0039] S4: Take a copper conductor and process micron-level annular grooves on the conductor surface using a laser grooving device; then, first, extrude thermoplastic polyolefin-based semiconductive conductor shielding material onto the grooved conductor surface using an extruder, so that the shielding material fills the grooves to form an embedded anchoring structure; then, extrude the insulating material composition granules onto the outside of the conductor shielding layer, setting the extrusion temperature as follows: feeding section 175℃, compression section 185℃, metering section 190℃, die head 195℃, and mold temperature 200℃, setting the extrusion line speed to 15m / min, so that the molten insulating material is tightly bonded to the outer surface of the conductor shielding layer; then, extrude thermoplastic polyolefin-based semiconductive insulating shielding material onto the outside of the insulating layer, and cool and shape it through a three-stage water cooling tank: the first stage is 60℃ warm water, the second stage is 40℃ warm water, and the third stage is 20℃ cold water; finally, extrude a low-density polyethylene outer sheath onto the outside of the insulating shielding layer at an extrusion temperature of 170℃, and after extrusion, pull and wind it to obtain an electrical insulated cable with a nominal insulation layer thickness of 1.0mm and a micro-interlocking anchoring structure at the conductor-insulation interface.

[0040] Example 2 The preparation method is the same as in Example 1, except that: S1: 2 parts hexagonal boron nitride, 0.4 parts dopamine hydrochloride, 0.1 parts N,N'-dicyclohexyl-2,6-naphthalenediamide; S2: 2 parts functionalized nano-hybrid particles and 3 parts glycidyl methacrylate grafted polyolefin elastomer; S3: 60 parts polypropylene, 30 parts polyolefin elastomer, 3 parts maleic anhydride-grafted polypropylene, 5 parts premix, 0.5 parts 4-allyloxybenzophenone; All other steps are the same.

[0041] Example 3 The preparation method is the same as in Example 1, except that: S1: 5 parts hexagonal boron nitride, 0.8 parts dopamine hydrochloride, 0.5 parts N,N'-dicyclohexyl-2,6-naphthalenediamide; S2: 4 parts functionalized nano-hybrid particles and 5 parts glycidyl methacrylate grafted polyolefin elastomer; S3: 70 parts polypropylene, 40 parts polyolefin elastomer, 8 parts maleic anhydride-grafted polypropylene, 10 parts premix, 2.0 parts 4-allyloxybenzophenone; All other steps are the same.

[0042] Example 4 The preparation method is the same as in Example 1, except that: S1: Adjust pH to 8 with Tris buffer; impregnate and adsorb at 35°C for 2 hours with stirring. S2: 170℃, 50rpm for 6 minutes of fusion grafting; 160℃, 40rpm for 5 minutes of fusion grafting; S3: Set the screw speed to 100 rpm and melt-blend at 170°C for 3 minutes; S4: Set the extrusion line speed to 10m / min; first stage: 50℃ warm water, second stage: 30℃ warm water, third stage: 15℃ cold water; All other steps are the same.

[0043] Example 5 The preparation method is the same as in Example 1, except that: S1: Adjust pH to 9 with Tris buffer; impregnate and adsorb at 45°C for 6 hours with stirring. S2: 190℃, 70rpm fusion grafting for 10 minutes; 180℃, 60rpm fusion grafting for 7 minutes; S3: Set the screw speed to 200 rpm and melt-blend at 190°C for 5 minutes; S4: Set the extrusion line speed to 20m / min; first stage: 70℃ warm water, second stage: 50℃ warm water, third stage: 25℃ cold water; All other steps are the same.

[0044] Example 6 The preparation method is the same as in Example 1, except that: S1: Replacing hexagonal boron nitride with aluminum oxide provides both high thermal conductivity and electrical insulation. All other steps are the same.

[0045] Example 7 The preparation method is the same as in Example 1, except that: S1: Replace dopamine hydrochloride with tannic acid. Both contain pyrogallol groups and can form a coating layer through self-polymerization. All other steps are the same.

[0046] Example 8 The preparation method is the same as in Example 1, except that: S1: Replace N,N'-dicyclohexyl-2,6-naphthalenedicarbamide with N,N'-dicyclohexyl-terephthalamide; All other steps are the same.

[0047] Example 9 The preparation method is the same as in Example 1, except that: S3: 4-Allyloxybenzophenone is replaced with 9-vinylcarbazole, both of which contain vinyl groups and can be graft copolymerized with polyolefin elastomers. All other steps are the same.

[0048] Comparative Example 1 The insulated cable was prepared using a traditional process: 3 parts hexagonal boron nitride, 0.24 parts N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide, 1.2 parts 4-allyloxybenzophenone, 70 parts polypropylene, 30 parts polyolefin elastomer, 0.5 parts antioxidant 1010, and 0.3 parts antioxidant 168 were directly mixed and then melt-blended and granulated in a twin-screw extruder at 180°C. The granules were then extruded with a copper conductor at 175-195°C and coated, followed by water cooling and shaping to obtain the insulated cable. This comparative example did not construct functionalized nano-hybrid particles, did not undergo pre-reaction anchoring, did not graft and fix the voltage stabilizer, and lacked grooved structures on the conductor surface.

[0049] Comparative Example 2 The preparation method is the same as in Example 1, except that: S2: Omit the melt premixing step and directly add the functionalized nano-hybrid particles, epoxy group-grafted polyolefin elastomer, maleic anhydride-grafted polypropylene and other components into the twin-screw extruder for melt blending and extrusion granulation. All other steps are the same.

[0050] Comparative Example 3 The preparation method is the same as in Example 1, except that: S3: The step of adding 1.2 parts of 4-allyloxybenzophenone is omitted; All other steps are the same.

[0051] Comparative Example 4 The preparation method is the same as in Example 1, except that: S4: The step of laser grooving the copper conductor is omitted, and the smooth conductor surface is directly extruded and coated. All other steps are the same.

[0052] Experimental Example 1 The insulating cable materials prepared in Examples 1-9 and Comparative Examples 1-4 were measured: (1) Space charge density: Referring to IEC TS 62758:2012 "Calibration of space charge measurement equipment based on pulse electroacoustic (PEA) measurement principle", the pulse electroacoustic (PEA) test system was used. The sample was placed between the test electrodes and a DC electric field of 60 kV / mm was applied. The pressure wave signal generated by the space charge distribution was detected by the piezoelectric sensor. The waveform was reconstructed and the charge density was calculated by the computer data acquisition system. The test temperature was room temperature. Each group of valid samples should have no less than 5 samples, and the final result is the average.

[0053] (2) DC breakdown strength: Referring to IEC 60243-2-2013 "Electrical strength test method for insulating materials - Part 2: DC voltage test", a ball-ball electrode system was used with an electrode diameter of 20 mm and a sample thickness of 0.5 ± 0.05 mm. The voltage rise rate was 1 kV / s. The test was conducted in transformer oil at room temperature to prevent surface flashover. Ten points were tested on each sample, and the breakdown voltage value was recorded. The breakdown strength was calculated as the ratio of breakdown voltage to sample thickness, and the Weibull distribution statistical value was used. At least 5 parallel samples were tested in each group, and the average value was taken.

[0054] (3) β-crystal content: Referring to ISO 11357-3:2025 "Plastics—Differential scanning calorimetry (DSC)—Part 3: Determination of melting and crystallization temperatures and enthalpy", a differential scanning calorimeter was used. 5-10 mg of the sample was weighed and placed in an aluminum crucible. Under nitrogen protection, the temperature was increased from 30℃ to 200℃ at a rate of 10℃ / min, and the melting curve was recorded. The β-crystal melting peak was located at approximately 150-155℃, and the α-crystal melting peak was located at approximately 165-170℃. The β-crystal content K β According to formula K β =H β / (H α +H β ) × 100% calculation, where H β and H α The values ​​are the enthalpy of fusion for β-crystal and α-crystal, respectively. Each sample was tested three times and the average value was taken. To obtain reliable data, at least three parallel samples were tested in each group, and the results were averaged.

[0055] Table 2 Comparison of experimental results of Examples 1-9 and Comparative Examples 1-4 The experimental results of Examples 1-9 and Comparative Examples 1-4 are shown in Table 2. The space charge density of the insulating cable material prepared by the present invention is 5.68 C / m. 3 The DC breakdown strength reached 298.53 kV / mm, and the β crystal content reached 81.67%, demonstrating the technical effect of pre-reaction anchoring of functionalized nano-hybrid particles, grafting and fixing of reactive voltage stabilizers, and synergistic reinforcement of micro-interlocking interface structure.

[0056] Example 2 reduced the amount of hybrid particles and nucleating agent, increasing the space charge density to 7.12 C / m. 3The β-crystal content decreased to 73.28%, demonstrating the crucial role of functional filler dosage in charge suppression and nucleation efficiency. Insufficient dosage resulted in decreased anchoring density and performance degradation. Example 3 increased the hybrid particle dosage, increasing the breakdown strength to 313.46 kV / mm, demonstrating the beneficial effect of high thermal conductivity filler on insulation performance. However, the β-crystal content remained the same as in Example 1, indicating that the nucleation efficiency had reached a plateau. Example 4 reduced the reaction temperature and time, resulting in a significant decrease in all properties, demonstrating the importance of complete reaction for epoxy-amino ring-opening anchoring and nucleating agent fixation; the process window needs strict control. Example 5 optimized the entire set of process parameters, achieving optimal overall performance, demonstrating the ultimate potential of process-material synergistic optimization, but production costs and energy consumption increased accordingly. Example 6 replaced boron nitride with alumina, reducing the breakdown strength to 284.67 kV / mm, demonstrating the unique advantages of boron nitride's high thermal conductivity and deep trapping effect on insulation performance. Example 7 replaced dopamine with tannic acid, increasing the space charge to 6.78 C / m. 3 This demonstrates that the dopamine coating exhibits superior interfacial activity and reactivity compared to tannic acid. Example 8, using sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate instead of DCTNA, showed a β-crystal content of 78.21%, demonstrating that different β-nucleating agents can achieve effective nucleation, but amide-based nucleation agents are more efficient. Example 9, using 9-vinylcarbazole instead of 4-allyloxybenzophenone, showed a space charge of 5.89 C / m. 3 This demonstrates that aromatic compounds containing double bonds can all be used as reactive voltage stabilizers, with carbazoles having slightly less electron-trapping ability than benzophenones.

[0057] Due to the lack of key technologies, the overall effect of Comparative Examples 1 to 4 was reduced to varying degrees compared with the Examples. Comparative Example 1 did not construct functionalized nano-hybrid particles, did not perform pre-reaction anchoring, did not graft and fix the voltage stabilizer, and did not have a grooved structure on the conductor surface. Direct blending of hexagonal boron nitride resulted in easy agglomeration and uneven dispersion, with limited improvement in thermal conductivity. Direct blending of the β-nucleating agent DCTNA led to easy migration and precipitation during processing and operation, significantly reducing the β-crystal induction effect and drastically decreasing the β-crystal content. Ungrafted 4-allyloxybenzophenone migrated and precipitated under high-temperature electric fields, exhibiting poor space charge suppression and a significant increase in space charge density. Without compatibilizers, the interfacial bonding between polypropylene and polyolefin elastomer was weak, and interfacial defects led to a significant reduction in DC breakdown strength. The conductor surface was smooth, and interfacial bonding relied solely on physical adhesion. Comparative Example 2 omitted the melt premixing step, and the functionalized nano-hybrid particles and epoxy-grafted polyolefin elastomer did not react beforehand, reacting randomly during melt blending. Incomplete reactions resulted in some hybrid particles remaining free in the polypropylene phase or interface, exhibiting uneven distribution and failing to concentrate at the polyolefin elastomer phase interface. This reduced the nucleation efficiency of the β-nucleating agent on polypropylene, leading to a decrease in β-crystal content. The nanoparticles exhibited poor dispersibility, easily agglomerating and forming defects, thus affecting thermal conductivity. The path is discontinuous, the space charge density is increased, and the DC breakdown strength is reduced. In Comparative Example 3, the addition of 4-allyloxybenzophenone is omitted. The non-reactive voltage stabilizer is grafted and fixed onto the polyolefin elastomer chain. The lack of benzophenone groups to capture high-energy electrons leads to a large accumulation of space charge under the action of the electric field, resulting in a significant increase in space charge density. This causes local electric field distortion, accelerates insulation aging, and significantly reduces the DC breakdown strength. At the same time, due to the lack of maleic anhydride-grafted polypropylene to adsorb and fix free nucleating agents, the β crystal content is also reduced. In Comparative Example 4, laser grooving of the copper conductor is omitted. The conductor surface is smooth and there are no micron-level annular grooves. The conductor-insulator interface relies solely on the physical adhesion of the material itself and lacks an embedded anchoring structure. Under thermal cycling or mechanical bending conditions, micro gaps are easily generated at the interface, becoming the starting point of partial discharge. The increased charge injection at the interface leads to an increase in space charge density and a decrease in DC breakdown strength. At the same time, interface defects affect the crystallization behavior of the polypropylene phase, resulting in a decrease in β crystal content.

[0058] In summary, this invention achieves integrated functionality of thermal conductivity, nucleation, and interface modification, as well as synergistic improvement of electrical, thermal, and mechanical properties, by constructing a "one-agent-multi-functional" structure of functionalized nano-hybrid particles, employing a grafting fixation technique with reactive voltage stabilizers, and designing a micro-interlocking anchoring structure at the conductor-insulation interface. The functionalized nano-hybrid particles, with hexagonal boron nitride as the core, polydopamine as the interface layer, and a β-nucleating agent as the loading layer, stabilize the load through hydrogen bonding and π-π stacking interactions, solving the problem of uneven dispersion of multiple components. The reactive voltage stabilizer is grafted onto the polyolefin elastomer chain, completely solving the problem of small molecule migration and effectively suppressing space charge accumulation. The micron-level grooves on the conductor surface form an embedded anchoring structure with the shielding material, significantly improving the interfacial bonding strength. Comparative results show that the key technologies synergistically ensure the excellent performance of the cable insulation layer in terms of space charge suppression, breakdown strength improvement, and β-crystal induction, making it suitable for power transmission in high-voltage and special environments.

[0059] In this invention, the terms "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0060] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An electrically insulated cable, comprising, from the inside out, a conductor, a conductor shielding layer, an insulation layer, an insulation shielding layer, and a sheath layer, characterized in that, The conductor has micron-sized annular grooves on its surface; the conductor shielding layer is made of a semi-conductive shielding material and fills the micron-sized annular grooves, forming an embedded anchoring structure between the conductor shielding layer and the conductor; the insulating layer is made of an insulating material composition and is chemically anchored to the conductor shielding layer through fusion at the interface of homologous materials. The insulating material composition includes polypropylene, polyolefin elastomer, reactive compatibilizer, functionalized nano-hybrid particles, reactive voltage stabilizer, and antioxidant. The functionalized nano-hybrid particles have inorganic particles as the core, polyphenolic compounds as the intermediate layer, and β-nucleating agents as the loading layer, and the loading is stabilized through hydrogen bonding and π-π stacking. The reactive compatibilizer includes glycidyl methacrylate-grafted polyolefin elastomer and maleic anhydride-grafted polypropylene. The reactive voltage stabilizer is grafted and fixed onto the polyolefin elastomer molecular chain.

2. The electrically insulated cable as described in claim 1, characterized in that, The micron-sized annular groove has a depth of 0.5% to 2% of the conductor diameter, a width of 2% to 5% of the conductor diameter, and a center-to-center distance of 8% to 15% of the conductor diameter between adjacent grooves.

3. The electrically insulated cable as described in claim 1, characterized in that, The inorganic particles are selected from one of hexagonal boron nitride and aluminum oxide; the polyphenolic compound is selected from one of dopamine hydrochloride and tannic acid; the β-nucleating agent is selected from one of N,N'-dicyclohexyl-2,6-naphthalenedicarboxylamide and N,N'-dicyclohexylterephthalamide; and the reactive voltage stabilizer is selected from one of 4-allyloxybenzophenone and 9-vinylcarbazole.

4. The electrically insulated cable as described in claim 1, characterized in that, The insulating material composition, calculated by total percentage, comprises the following components by mass: 100 parts of blended resin matrix, of which 60-70 parts are polypropylene resin and 30-40 parts are polyolefin elastomer resin; 6-13 parts of reactive compatibilizer; 2-4 parts of the functionalized nano-hybrid particles; and 0.5-2 parts of the reactive voltage stabilizer. Antioxidant stabilizer combination 0.8 parts; 0.02 parts of free radical initiator.

5. A method for manufacturing an electrically insulated cable as described in any one of claims 1 to 4, characterized in that, The insulated cable is prepared by: processing micron-level annular grooves on the surface of a copper conductor; firstly, extruding conductor shielding material onto the surface of the grooved conductor to form a conductor shielding layer; then extruding the insulating material composition granules onto the grooved conductor to cover it, setting the extrusion temperature as follows: feeding section 175°C, compression section 185°C, metering section 190°C, die head 195°C, and die temperature 200°C, while simultaneously setting the extrusion linear speed; subsequently, extruding insulating shielding material onto the outside of the insulating layer to form an insulating shielding layer, and after cooling and shaping, extruding a low-density polyethylene outer sheath onto the outside of the insulating shielding layer at an extrusion temperature of 170°C; after extrusion, pulling and winding to obtain an electrically insulated cable.

6. The method for preparing an electrically insulated cable as described in claim 5, characterized in that, The set extrusion line speed is set to 10~20m / min; the cooling and shaping is set to a first stage of 50~70℃ warm water, a second stage of 30~50℃ warm water, and a third stage of 15~25℃ cold water.

7. The method for preparing an electrically insulated cable as described in claim 5, characterized in that, The preparation method of the insulating material composition granules includes the following steps: S1: Inorganic nanoparticles were added to deionized water and ultrasonically dispersed for 30 minutes. Polyphenolic compounds were added, pH was adjusted and stirred, and the mixture was centrifuged and washed until neutral. The nanoparticles were then vacuum-dried at 60°C for 12 hours to obtain polyphenolic compound-coated inorganic particles. The polyphenolic compound-coated inorganic particles were then dispersed in a mixed solvent of ethanol and water, and a β-nucleating agent was added and stirred for impregnation and adsorption. The unloaded nucleating agent was removed by centrifugation and washing, and the nanoparticles were vacuum-dried at 60°C for 12 hours to obtain functionalized nano-hybrid particles. S2: Polypropylene is melt-grafted with maleic anhydride and dicumyl peroxide, and then extruded and granulated to obtain maleic anhydride-grafted polypropylene; separately, polyolefin elastomer is melt-grafted with glycidyl methacrylate and dicumyl peroxide to obtain glycidyl methacrylate-grafted polyolefin elastomer; then, functionalized nano-hybrid particles and glycidyl methacrylate-grafted polyolefin elastomer are added to a mixer for melt premixing to form a premix, which is then cooled and crushed for later use. S3: Polypropylene, polyolefin elastomer, maleic anhydride-grafted polypropylene, premix, 4-allyloxybenzophenone, dicumyl peroxide, antioxidant 1010, and antioxidant 168 are added to a twin-screw extruder for melt blending, extrusion granulation, and drying to obtain insulating material composition granules.

8. The method for manufacturing an electrically insulated cable as described in claim 7, characterized in that, S1 The pH adjustment needs to be adjusted to 8~9; the inorganic particles, the polyphenolic compound and the β nucleating agent have a mass ratio of (2~5):(0.4~0.8):(0.1~0.5); the impregnation adsorption is set to a temperature of 35~45℃ and a stirring time of 2~6 hours.

9. The method for preparing an electrically insulated cable as described in claim 7, characterized in that, S2 describes the melt grafting of polypropylene with maleic anhydride and dicumyl peroxide, with conditions set at a temperature of 170-190℃, a rotation speed of 50-70 rpm, and a reaction time of 6-10 minutes; S2 describes the melt grafting of polyolefin elastomer with glycidyl methacrylate and dicumyl peroxide, with conditions set at a temperature of 160-180℃, a rotation speed of 40-60 rpm, and a reaction time of 5-7 minutes.

10. The method for preparing an electrically insulated cable as described in claim 7, characterized in that, The melt blending described in S3 is performed under the following conditions: rotation speed 100-200 rpm, temperature 170-190℃, and reaction time 3-5 minutes.

Images