Manufacturing method of wire insulating layer for automobile and combined wire

Abstract

The invention relates to the technical field of high-voltage automobile wire insulating materials, in particular to a manufacturing method of an automobile wire insulating layer and a combined wire, and aims to solve the problems that in the prior art, a traditional crosslinked polyethylene material is insufficient in breakdown voltage in an extremely thin wall state, and the interface adhesive force is remarkably reduced after damp-heat aging; and although ceramic silicone rubber has high dielectric strength, the material density is too high, the flexibility is poor, and the requirements of light weight and bending resistance cannot be met. Through the synergistic effect of the gradient cross-linked structure and the axially and directionally arranged nano boron nitride sheet layers, the breakdown voltage is increased while the mechanical strength of the thin-wall insulating layer is ensured, and the interface bonding force is enhanced in combination with the molecular anchoring layer; the method has the advantages that the breakdown strength of the insulating layer is improved, the conductor-insulating layer interface bonding force is enhanced, and a lightweight thin-wall structure is realized.

Description

Technical Field

[0001] This application relates to the technical field of high-voltage automotive wire insulation materials, and more specifically, to a method for manufacturing an insulation layer for automotive wires and a combined wire. Background Technology

[0002] As new energy vehicles move towards 800V high-voltage platforms, higher requirements are placed on the insulation performance of high-voltage wires such as battery connection lines and motor control lines. An ideal insulation layer needs to simultaneously meet three core indicators: high breakdown strength, excellent damp heat aging performance, and lightweight design.

[0003] Traditional cross-linked polyethylene materials struggle to balance electrical and mechanical properties in extremely thin-walled applications, while ceramicized silicone rubber, despite its excellent electrical properties, suffers from excessive density and significant brittleness. Adding nanofillers carries the risk of extrusion defects due to uneven filler dispersion. These technological bottlenecks severely restrict the reliability and lightweight development of high-voltage automotive wiring harnesses.

[0004] Particularly regarding the interfacial bonding strength between the conductor and the insulation layer, existing processes struggle to maintain the thin-walled characteristics of the insulation layer while ensuring high adhesion. Furthermore, the uniform distribution of cross-linking within the insulation layer also limits further improvements in material properties. Therefore, existing technologies urgently need improvement to address these issues. Summary of the Invention

[0005] (a) Technical problems to be solved To address the aforementioned issues, this invention proposes a method for manufacturing an insulation layer for automotive electrical wires and a combined electrical wire. The aim is to resolve the problems of insufficient breakdown voltage and significantly reduced interfacial adhesion of traditional cross-linked polyethylene materials in extremely thin-walled conditions, and the inability of ceramicized silicone rubber to meet the requirements for lightweighting and bending resistance, despite its high dielectric strength.

[0006] (II) Technical Solution The present invention discloses a method for manufacturing an insulation layer for automotive electrical wires, the technical solution of which is as follows: the raw material formulation of the insulation layer comprises, by weight percentage: 91.5%~97.2% polyolefin elastomer substrate, 2.0%~4.0% nano boron nitride flakes, 0.7%~1.6% crosslinking agent, and 0.1%~0.3% antioxidant; the manufacturing method includes the following steps: S100, modification and preparation of insulation substrate: the components in the raw material formulation are mixed and melt-blended and granulated by a screw extruder; wherein, a directional magnetic field of 0.2~0.5T is applied at the extruder die to orient the nano boron nitride flakes along the conductor axis to obtain modified insulation masterbatch; S200, conductor surface anchoring treatment: the surface of the metal conductor is subjected to plasma activation treatment with a treatment power of 500~700W and a treatment time of 5~15s to form a micro-rough surface with active groups; subsequently, a polyamide-amine dendritic molecular solution is coated on the activated conductor surface to form a layer with a thickness of 0.2~0.4μm. Molecular anchoring layer; S300, gradient insulation layer molding: The modified insulation masterbatch is coated onto the conductor treated in step S200 through an extruder with a coaxial double-layer flow channel, wherein the crosslinking agent concentration of the inner flow channel is 40%~60% higher than that of the outer flow channel; by controlling the temperature to make the inner flow channel temperature 210~230℃ and the outer flow channel temperature 180~200℃, the extruded insulation layer forms a gradient curing structure with an inner crosslinking degree of 80%~90% and an outer crosslinking degree of 45%~55%; after extrusion, it is first cooled with warm water at 70~90℃ for 5~15s, and then cured a second time by ultraviolet light with a wavelength of 250~260nm and a power of 90~110W.

[0007] Furthermore, this application also proposes that the particle size of the boron nitride nanosheets is 40~60nm, and the surface is treated with silane coupling agent KH-560.

[0008] Furthermore, this application also proposes that the crosslinking agent includes di-tert-butyl peroxide and a crosslinking accelerator, and the mass ratio of the two is (1.5~2.5):1.

[0009] Furthermore, this application also proposes that, in step S100, the screw speed of the screw extruder is 280~320 r / min and the shear rate is 450~550 s⁻¹.

[0010] Furthermore, this application also proposes that, in step S200, the plasma activation treatment uses argon as the working gas to achieve a conductor surface roughness Ra of 0.1~0.3μm.

[0011] Furthermore, this application also proposes that the polyolefin elastomer substrate is a low-density polyolefin elastomer with a density of 0.86~0.91 g / cm³.

[0012] Furthermore, this application also proposes that the antioxidant is antioxidant 1010; and that after secondary curing with ultraviolet light, a dense protective film with a thickness of 0.04~0.06mm is formed on the outer layer of the insulating layer.

[0013] Furthermore, this application also proposes a composite wire, comprising a metal conductor and an insulating layer covering the metal conductor, wherein the insulating layer contains nano-boron nitride sheets oriented along the conductor axis, and the insulating layer has a gradient cross-linking structure with an inner layer cross-linking degree of 80% to 90% and an outer layer cross-linking degree of 45% to 55%; the insulating layer is prepared by the above-described manufacturing method.

[0014] Furthermore, this application also proposes that the total thickness of the insulation layer is no more than 0.4 mm.

[0015] Furthermore, this application also proposes that the metal conductor is a copper or copper alloy conductor, and a polyamide-amine dendritic molecular anchoring layer with a thickness of 0.2~0.4μm is provided between the surface of the metal conductor and the insulating layer.

[0016] (III) Beneficial Effects Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, the gradient cross-linking structure and the axially oriented boron nitride nanosheets work synergistically to improve the breakdown voltage while ensuring the mechanical strength of the thin-walled insulation layer. Combined with the molecular anchoring layer to enhance the interfacial bonding force, this invention has the advantages of improving the breakdown strength of the insulation layer, enhancing the interfacial bonding force between the conductor and the insulation layer, and achieving a lightweight thin-walled structure.

[0017] This invention effectively improves the breakdown strength of high-voltage insulation layers, ensuring voltage withstand performance in extremely thin-walled states; maintains low-density characteristics to meet the lightweight requirements of automobiles; and through gradient cross-linking structures and composite interface treatment, maintains high interfacial bonding strength after damp heat aging while avoiding brittle cracking. The synergistic effect of each process step solves the problem of performance constraints in traditional solutions. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram illustrating the logical steps of a method for manufacturing electrical insulation layers for automotive applications. Detailed Implementation

[0020] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0021] In existing technologies, high-voltage automotive wire insulation layers face the challenge of a performance imbalance. Traditional cross-linked polyethylene materials have insufficient breakdown voltage in extremely thin-walled states, and their interfacial adhesion decreases significantly after humid heat aging. While ceramicized silicone rubber possesses high dielectric strength, its excessively high density and poor flexibility fail to meet the requirements for lightweighting and bending resistance. Existing processes optimize individual properties by adding nanofillers or adjusting curing parameters, but uneven filler dispersion and thermal runaway issues make it difficult to achieve breakthroughs in overall performance.

[0022] The research and development focus is on the deep coupling of material function and process control. Traditionally, the directional alignment of nanofillers and gradient curing processes are considered independent optimization paths. However, in practical applications, it has been found that the thermal conductivity of directional fillers can assist in controlling the temperature field during gradient curing. By combining the axial alignment of boron nitride nanoparticles with the gradient distribution of crosslinking agent concentration, insulation performance is enhanced while avoiding localized overheating. Simultaneously, a dendritic molecular anchoring layer is used to enhance interfacial bonding stability, creating a synergistic effect.

[0023] Therefore, this application proposes a method for manufacturing an insulation layer for automotive electrical wires, characterized in that the raw material formulation of the insulation layer comprises, by weight percentage: The polyolefin elastomer substrate comprises 91.5%~97.2%, the nano boron nitride sheet comprises 2.0%~4.0%, the crosslinking agent comprises 0.7%~1.6%, and the antioxidant comprises 0.1%~0.3%. The crosslinking agent is composed of di-tert-butyl peroxide (the main crosslinking agent) and trimethylolpropane triacrylate (the crosslinking accelerator), with a mass ratio of (1.5~2.5):1, which can ensure precise control of the crosslinking degree of the inner and outer layers during the gradient curing process.

[0024] The manufacturing method includes the following steps: S100, Preparation of modified insulating substrate: The components in the raw material formula are mixed and melt-blended and granulated using a screw extruder; In this process, a directional magnetic field of 0.2~0.5T is applied at the extruder die head to orient the nano boron nitride sheets along the conductor axis, thereby obtaining a modified insulating masterbatch. In the insulation substrate modification stage, melt blending and magnetic field orientation are used to form an ordered filler distribution, solving the problem of uneven dielectric properties caused by the random distribution of traditional fillers. Specifically, the screw extruder barrel employs three-stage temperature control: 160℃ (feeding section), 180℃ (melting section), and 200℃ (homogenization section), ensuring complete melting of the substrate and preventing degradation of the nanofillers. The directional magnetic field is applied through a permanent magnet module embedded in the outer wall of the die, with the magnetic field direction parallel to the extrusion channel axis. The uniformity error of the magnetic field strength at the die exit is ≤5%, ensuring that the nano-boron nitride sheets are arranged in an orderly manner along the conductor length.

[0025] S200, Conductor Surface Anchoring Treatment: The surface of the metal conductor is subjected to plasma activation treatment with a power of 500~700W and a treatment time of 5~15s to form a micro-rough surface with active groups; then, a polyamide-amine dendritic molecular solution is coated on the activated conductor surface to form a molecular anchoring layer with a thickness of 0.2~0.4μm. S300, Gradient Insulation Layer Forming: The modified insulation masterbatch is coated onto the conductor treated in step S200 through an extruder with coaxial double-layer flow channels, wherein the crosslinking agent concentration in the inner flow channel is 40%~60% higher than that in the outer flow channel; By controlling the temperature to make the inner flow channel temperature 210~230℃ and the outer flow channel temperature 180~200℃, the extruded insulating layer forms a gradient curing structure with an inner crosslinking degree of 80%~90% and an outer crosslinking degree of 45%~55%. After extrusion, the material is first cooled in warm water at 70~90℃ for 5~15s, and then cured a second time by ultraviolet light with a wavelength of 250~260nm and a power of 90~110W.

[0026] Among them, polyolefin elastomer substrate refers to elastic materials mainly composed of low-density polyolefins. Specifically, substrates with a density range that meets the requirements for lightweighting can be used to reduce the overall density of the insulation layer. Nano-boron nitride sheets refer to two-dimensional nanomaterials whose surfaces are treated with silane coupling agents. They are oriented and aligned by a magnetic field to form an axially conductive thermally insulating network, enhancing dielectric strength and thermal management capabilities.

[0027] The crosslinking agent concentration gradient distribution refers to the difference in crosslinking agent content between the inner and outer flow channels. Adjusting the concentration difference achieves a difference in the degree of crosslinking between the inner and outer layers, balancing mechanical strength and flexibility. Plasma activation treatment utilizes inert gas discharge to generate high-energy particles that bombard the conductor surface, forming a rough interface with active groups, enhancing the bonding strength of subsequent anchoring layers. The dendritic molecular anchoring layer is an ultrathin interface layer formed by a polyamide-amine dendritic molecular solution, which improves interface stability through intermolecular forces and mechanical interlocking effects.

[0028] Specifically, the insulation substrate modification stage achieves an ordered filler distribution through melt blending and magnetic field orientation, thus solving the problem of uneven dielectric properties caused by the random distribution of traditional fillers. The conductor surface treatment establishes a stable interface through a combination of physical roughening and chemical bonding, overcoming adhesion degradation defects under humid and hot environments.

[0029] During the gradient insulation layer molding process, the high concentration of cross-linking agent in the inner layer, combined with high-temperature extrusion, forms a dense structure, while the low degree of cross-linking in the outer layer maintains the material's ductility and prevents bending and cracking. The staged treatment of warm water cooling and UV curing controls the distribution of curing stress and seals surface micro-defects, forming a complete protective system.

[0030] Traditional cross-linked polyethylene solutions suffer from insufficient breakdown voltage due to uneven filler dispersion, while ceramicized silicone rubber cannot meet lightweight requirements due to its excessively high density. This solution, through synergistic directional filler arrangement and gradient curing, improves dielectric strength while maintaining low density, without requiring the development of new substrates. Existing dual-zone curing processes suffer from structural inhomogeneity due to temperature field fluctuations; this solution utilizes the thermal conductivity of the filler to stabilize the temperature distribution, ensuring precise and controllable gradient cross-linking structure. Traditional interface treatments rely on single roughening or chemical modification; this solution combines physical activation and molecular anchoring to form a composite reinforcement effect.

[0031] This application achieves an effective improvement in the breakdown strength of high-voltage insulation layers, ensuring voltage withstand performance in extremely thin-walled states; maintains low-density characteristics to meet the lightweight requirements of automobiles; and maintains high interfacial bonding strength after damp heat aging through gradient cross-linking structures and composite interface treatment, while avoiding the problem of brittle cracking of materials. The synergistic effect of each process step solves the problem of mutual performance constraints in traditional solutions.

[0032] This application further proposes a technical solution in which the particle size of the boron nitride nanosheets is 40~60nm and the surface is treated with silane coupling agent KH-560.

[0033] The 40-60 nm particle size of the boron nitride nanosheets refers to controlling the size range of the filler within a specific range, which can be achieved through a combination of mechanical exfoliation and graded screening. This particle size range avoids agglomeration caused by excessively small particle sizes due to high surface energy, while also preventing stress concentration caused by excessively large particle sizes. The silane coupling agent KH-560 treatment refers to the chemical modification of the nanosheet surface, which can be achieved through solution impregnation. This treatment involves the reaction of the siloxane groups in the coupling agent molecule with the hydroxyl groups on the boron nitride surface to form chemical bonds, while its epoxy groups physically entangle with the polyolefin substrate, thereby establishing a stable interfacial transition layer between the filler and the matrix.

[0034] Specifically, during melt blending, a particle size range of 40–60 nm allows for effective dispersion of the nanosheets under screw shearing, avoiding increased van der Waals forces due to excessively small particle size or increased flow resistance due to excessively large particle size. The surface-treated boron nitride nanosheets, through a combination of chemical bonding and physical entanglement, reduce the interfacial energy difference between the filler and the substrate, inhibiting secondary agglomeration of the filler during processing. The resulting uniformly dispersed system, under the subsequent application of a directional magnetic field, achieves an ordered arrangement of the sheets along the conductor axis, thus preventing localized electric field distortion caused by agglomeration or pinhole defects during extrusion molding.

[0035] Traditional methods typically employ nanofillers with undefined particle sizes and often use amino-based coupling agents for surface treatment. Such approaches struggle to balance dispersibility and interfacial bonding strength, easily leading to microscopic defects due to filler agglomeration during extrusion. This solution, through the synergistic effect of a defined particle size range and a specific coupling agent, enhances interfacial bonding while maintaining dispersion efficiency, enabling the insulating layer to maintain a dense structure even under extremely thin-walled conditions.

[0036] This application effectively solves the problem of pinhole defects caused by uneven dispersion of nanofillers in the insulating layer, while improving the interfacial bonding strength between the filler and the substrate. The resulting insulating layer exhibits a more uniform electric field distribution under a high-voltage electric field, and pinhole defects are significantly reduced during extrusion molding, thereby improving product reliability and service life.

[0037] This application further proposes that the crosslinking agent includes di-tert-butyl peroxide and a crosslinking accelerator, and the mass ratio of the two is 1.5~2.5:1.

[0038] Di-tert-butyl peroxide refers to an organic peroxide-based main crosslinking agent whose decomposition temperature range matches the processing temperature of polyolefin elastomer substrates. Specifically, it can be achieved using commercially available industrial-grade peroxides. This component decomposes at high temperatures to generate free radicals, which then initiate the crosslinking reaction of polyolefin molecular chains.

[0039] The crosslinking accelerator TMPTA refers to trimethylolpropane triacrylate, which can be achieved using liquid additives containing acrylate functional groups. This component accelerates the crosslinking reaction process by capturing free radicals, while simultaneously reducing the viscosity of the melt system to improve extrusion flowability. The unsaturated acrylate bonds in the TMPTA molecule do not fully react during gradient curing, reserving reaction sites for subsequent UV secondary curing and achieving a seamless transition between primary gradient curing and secondary surface curing.

[0040] The mass ratio of 1.5 to 2.5:1 refers to the weight ratio range of the main crosslinking agent and the accelerator. This can be achieved by adjusting the feeding ratio of the two. This range ensures that the main crosslinking agent is fully decomposed in the high-temperature environment of the inner flow channel, while avoiding excessive accelerator that would cause premature over-crosslinking of the outer layer.

[0041] Specifically, under the influence of a gradient temperature field, the high-temperature environment of the inner flow channel causes rapid decomposition of di-tert-butyl peroxide. Combined with the free radical scavenging effect of the crosslinking accelerator, this promotes the formation of a highly crosslinked structure in the polyolefin substrate within a short time. The low-temperature environment of the outer flow channel inhibits the decomposition rate of the main crosslinking agent. At this point, the dilution effect of the crosslinking accelerator becomes dominant, maintaining melt fluidity to achieve thin-wall coating while retaining some unreacted active groups. Thus, the highly crosslinked structure of the inner layer improves the voltage resistance of the insulating layer, while the incompletely cured active sites in the outer layer provide a reaction basis for subsequent UV secondary curing, thereby balancing crosslinking efficiency and material flexibility.

[0042] Traditional methods using amino-based accelerators can easily cause phase separation in polyolefin substrates, leading to microcracks inside the insulation layer. However, the acrylate-based accelerators used in this solution have better compatibility with polyolefins. Combined with a specific mass ratio range, this avoids sudden changes in flowability during processing and ensures a precise match between the difference in crosslinking degree between the inner and outer layers and the gradient temperature field. This solves the problem of decreased interlayer bonding caused by the mismatch between the crosslinking agent concentration gradient and temperature distribution in existing technologies.

[0043] This application achieves synergistic control of crosslinking reaction rate and material processing performance, maintaining the active state of the outer layer that can be cured a second time while ensuring high crosslinking degree of the inner layer. This allows the insulation layer to maintain stable interfacial adhesion under high temperature and high humidity conditions, while avoiding the risk of brittle cracking caused by excessive crosslinking.

[0044] This application further proposes that, in the preparation step of modifying the insulating substrate, the screw speed of the screw extruder be set to 280 to 320 rpm, and the shear rate be controlled at 450 to 550 s⁻¹. A laser scattering online monitoring system is used for detection, with the shear rate ranging from 450 to 550 s⁻¹. -1 At a shear rate of ≥90%, the dispersion uniformity of the boron nitride nanosheets is maintained; if the shear rate is <450 s⁻¹, the uniformity is maintained. -1When the dispersion uniformity drops below 70%, it is easy to form agglomerates, leading to pinhole defects. When the rotation speed exceeds 320 r / min, it will cause the molecular chain of the polyolefin substrate to break, producing small molecule volatiles.

[0045] Screw speed refers to the rotational speed of the extruder screw per unit time. This can be achieved using a variable frequency speed-regulating motor in conjunction with a reduction gearbox. By adjusting the motor input frequency, the screw speed is changed, thereby controlling the residence time and shear intensity of the material within the extruder. This speed range provides sufficient mechanical shear force to disperse the nanofillers while preventing excessive speed from causing thermal degradation of the substrate. Shear rate refers to the rate of shear strain experienced by the molten material flowing within the extruder channel. This can be achieved by adjusting the ratio of screw thread depth to pitch. This parameter directly affects the melt flow state and the filler dispersion effect. Controlling the shear rate within this range optimizes melt viscosity, ensuring that the nanosheets remain uniformly dispersed and structurally intact before magnetic field orientation.

[0046] Specifically, during melt blending, the synergistic effect of screw speed and shear rate is used to match the addition ratio and particle size characteristics of the boron nitride nanosheets. By limiting the speed range, the material undergoes moderate shearing within the extruder, effectively breaking down the initial agglomerates of the nanofillers while avoiding the breakage of polyolefin matrix molecular chains due to excessive shearing. Simultaneously, the compatibility between the shear rate and melt viscosity ensures a stable flow field at the die, providing sufficient time for the subsequent magnetic field orientation process, allowing the nanosheets to align orderly along the conductor axis.

[0047] Traditional processes often adjust screw speed or shear rate in isolation, without considering the synergistic relationship between these parameters and filler dosage, particle size, and subsequent processes. For example, some solutions use excessively high speeds to improve dispersion, but this leads to substrate degradation and the generation of small-molecule volatiles; other solutions use excessively low shear rates, which fail to effectively deagglomerate, resulting in uneven filler dispersion. This solution achieves a balance between dispersion effect, substrate protection, and process adaptability through precise parameter range design, forming a closed-loop control logic.

[0048] This application effectively solves the problem of pinhole defects in the insulating layer caused by uneven dispersion of nanofillers during melt blending, ensuring that the nanosheets are uniformly distributed and structurally intact in the substrate, providing a reliable basis for subsequent magnetic field orientation and gradient curing processes, thereby improving the dielectric strength and thermal conductivity of the insulating layer.

[0049] This application further proposes that in the conductor surface anchoring process, argon gas is used as the working gas in the plasma activation treatment to achieve a conductor surface roughness Ra of 0.1~0.3μm.

[0050] Plasma activation treatment refers to the process of bombarding the conductor surface with high-energy particles generated by ionized gas. This can be achieved using a radio frequency glow discharge device. By adjusting the gas type and processing parameters, specific microstructures are formed on the conductor surface. Using argon as the working gas means using an inert gas as the plasma source; specifically, argon with a purity ≥99.99% can be used. The argon ions generated after ionization have sufficient kinetic energy to break the atomic bonds on the conductor surface. Surface roughness Ra refers to the arithmetic mean deviation of the surface profile, which can be measured using a white light interferometer. This parameter range is adapted to the thickness of the subsequent anchoring layer.

[0051] Plasma treatment employed a 13.56MHz radio frequency glow discharge device, with argon gas flow rate controlled at 12L / min and vacuum maintained at 0.1~0.3MPa to ensure uniform bombardment of the conductor surface by high-energy particles. X-ray photoelectron spectroscopy analysis showed that the density of -OH groups on the conductor surface after treatment was ≥5×10⁻⁶. 14 The number of sites per cm² provides ample sites for the covalent bonding of polyamide-amine dendritic molecules.

[0052] Specifically, during argon plasma treatment, high-energy argon ions physically bombard the conductor surface, removing the oxide layer and forming a uniformly distributed micron-sized pit structure. The active sites exposed after the atomic bonds on the conductor surface break combine with water molecules in the air to generate hydroxyl groups. When the roughness Ra is controlled within the range of 0.1~0.3 μm, the depth of the surface pits matches the thickness of the subsequently coated molecular anchoring layer, allowing the anchoring layer material to fully penetrate to the bottom of the pits. When the polyamide-amine dendritic molecular solution is coated, the amino groups at the ends of its molecular chains covalently bond with the hydroxyl groups on the conductor surface, while the solution fills the pits to form a mechanically interlocked structure.

[0053] Traditional acid pickling and roughening processes use strong acids to corrode the conductor surface, creating a rough structure, but this leads to intergranular corrosion and wastewater pollution. While oxygen plasma treatment can introduce active groups, it generates an excessively thick oxide layer, which is prone to interfacial delamination in humid and hot environments. This solution, however, uses argon plasma treatment, achieving both surface activation and roughening while avoiding chemical corrosion. The resulting interfacial structure exhibits higher environmental stability.

[0054] This application effectively solves the problem of insufficient adhesion between metallic conductors and insulating layers in humid and hot environments. The active groups on the conductor surface form stable chemical bonds with the anchoring layer molecules, and combined with the mechanical interlocking effect brought about by appropriate roughness, significantly improving the interfacial bonding strength. This process poses no risk of chemical corrosion, avoids the damage to the mechanical properties of the conductor caused by traditional processes, and simultaneously meets environmentally friendly production requirements.

[0055] This application further proposes that the polyolefin elastomer substrate is a low-density polyolefin elastomer with a density of 0.86~0.91 g / cm³.

[0056] Low-density polyolefin elastomers (LDPEs) are materials formed by the random copolymerization of ethylene and α-olefins. Their molecular chains have no crystalline regions or extremely low crystallinity. Specifically, they can be achieved using polyolefin elastomers (POEs). This structural characteristic allows them to maintain low density while also possessing flexibility and resistance to damp heat. The density range of 0.86~0.91 g / cm³ refers to optimizing the substrate density by controlling the proportion of comonomers and polymerization process parameters. Specifically, this can be achieved by adjusting the α-olefin content and molecular weight distribution. This density range can be adapted to the amount of nanofiller added and the processing technology, ensuring that the overall density of the insulation layer meets lightweight requirements.

[0057] The low-density polyolefin elastomer selected is Dow Engage8780, which is a random copolymer of ethylene and 1-octene with a crystallinity of ≤5%. Based on a total insulation layer thickness of 0.4mm, this density range results in an insulation layer weight of ≤1.5g / m per unit length, which is 25% lighter than ceramicized silicone rubber, meeting the requirements for lightweighting of the entire vehicle.

[0058] Specifically, the random copolymer structure of low-density polyolefin elastomers makes their molecular chain flexibility significantly superior to that of traditional crystalline polyolefins, facilitating uniform mixing with nanofillers during extrusion molding. The lower limit of the density range is set at 0.86 g / cm³ to prevent insufficient intermolecular forces due to excessively low matrix density, which would prevent the filler from being supported; the upper limit is set at 0.91 g / cm³ to prevent excessively high density from weakening the lightweight effect. This density range matches the shear rate in the screw extrusion process, and the low viscosity facilitates the directional alignment of nanofillers during melt blending, while also providing a foundation for the flexibility of the low-crosslinked outer layer structure in the gradient curing process.

[0059] While traditional solutions using cross-linked polyethylene offer similar substrate densities, their crystalline structure leads to decreased interfacial adhesion in humid and hot environments. Ceramicized silicone rubber, despite its excellent insulation properties, suffers from excessive density and brittleness. This solution, by selecting a specific type of low-density polyolefin elastomer, achieves superior resistance to humid heat and processing fluidity at the same density, while avoiding the cracking risk of highly crystalline materials under bending conditions.

[0060] This application resolves the contradiction between the need for lightweight automotive wire insulation and the control of material density. It significantly reduces material density while ensuring dielectric strength and mechanical properties. At the same time, it improves the interfacial stability of the insulation layer in humid and hot environments through the flexibility of the substrate, avoiding problems such as uneven filler dispersion or deterioration of mechanical properties caused by excessively low density.

[0061] This application further proposes that the antioxidant is antioxidant 1010, and that after secondary curing under ultraviolet light, a dense protective film with a thickness of 0.04~0.06mm is formed on the outer layer of the insulating layer.

[0062] Antioxidant 1010 refers to pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which can be achieved by blending commercially available powdered antioxidants with a polyolefin substrate. The polyhydroxy groups in its molecular structure effectively capture free radicals generated by oxidation reactions. This antioxidant remains stable under high-temperature processing conditions, preventing protective failure due to volatilization or decomposition. The dense protective film refers to a cross-linked network structure formed on the surface of the insulating layer by ultraviolet light irradiation. Specifically, it can be achieved by secondary curing of the low-crosslinking outer substrate using an ultraviolet light source with a wavelength of 250-260 nm. This film layer forms a physical barrier by enhancing the cross-linking density of the surface molecular chains, while maintaining an elastic connection with the underlying material.

[0063] Specifically, antioxidant 1010 is uniformly dispersed within the insulation layer, continuously neutralizing free radicals generated within the substrate during humid heat aging and blocking the diffusion of the oxidation chain reaction. During secondary UV curing, the irradiation time is controlled at 4 seconds. Fourier transform infrared spectroscopy (FTIR) analysis shows that the crosslinking density of the protective film is ≥80%, and the water vapor permeability is ≤1×10⁻⁶. -12 g / (m・s・Pa); According to high performance liquid chromatography (HPLC), the migration rate of antioxidant 1010 in the insulating layer is ≤0.5μm / year, and it can form a stable concentration (≥0.05wt%) on the surface of the protective film, thus continuously exerting its antioxidant effect.

[0064] Specifically, antioxidant 1010 is uniformly dispersed within the insulation layer, continuously neutralizing free radicals generated within the substrate during humid heat aging and blocking the diffusion of the oxidation chain reaction. During secondary UV curing, the unreacted crosslinking agent pre-reserved in the outer polyolefin substrate undergoes a polymerization reaction under specific wavelength irradiation, forming a continuous and dense surface structure. This protective film reduces the internal humidity of the substrate by blocking external moisture penetration, while its surface crosslinking network forms a stronger chemical bond with the conductor anchoring layer. Antioxidant molecules remain stable during high-temperature processing and gradually migrate to the surface of the protective film during long-term use, forming a dynamic antioxidant interface.

[0065] Traditional solutions, which only add antioxidants, cannot prevent interfacial delamination caused by moisture intrusion, while the thick protective film formed by simple UV curing can easily lead to material brittleness. Existing technologies lack compatibility between antioxidant selection and curing processes, and are prone to failure during high-temperature processing. This solution, through the synergy of the high-temperature resistance of antioxidants and a secondary curing process, creates a complementary protective mechanism of internal oxidation resistance and external moisture protection.

[0066] This application effectively inhibits oxidative degradation within the insulation layer under humid and hot conditions, maintaining the bonding strength between the conductor and the insulation layer interface. The dense protective film blocks moisture while preventing a decrease in material flexibility, and the dynamic migration characteristics of the antioxidant extend the protective duration, enabling the insulation layer to maintain stable mechanical and electrical properties even after long-term humid and hot aging.

[0067] Example 1

[0068] First, the raw materials are pretreated and mixed: Weigh out the following components by weight percentage: 95.0% low-density POE substrate, 3.0% nano boron nitride sheets treated with silane coupling agent KH-560, 1.7% crosslinking agent, and 0.3% antioxidant 1010. Add the above components to a high-speed mixer in sequence, set the speed to 1000 r / min, and mix for 10 min until the material is uniform in color, ensuring that each additive is initially dispersed in the POE substrate. The low-density POE substrate has a density of 0.89 g / cm³, is copolymerized with ethylene-1-octene, has a crystallinity of ≤5%, and is a crosslinking agent consisting of di-tert-butyl peroxide (DTBP-50) and trimethylolpropane triacrylate (TMPTA-98) mixed in a 2:1 mass ratio.

[0069] Next, we proceed to the S100 insulation substrate modification and preparation stage: the mixed materials are fed into a twin-screw extruder for melt blending. The extruder barrel adopts a three-stage temperature gradient control: the feeding stage is 160°C to ensure stable material conveying and prevent premature melting and agglomeration; the melting stage is 180°C to achieve complete melting of POE and avoid premature decomposition of additives; and the homogenization stage is 200°C to ensure that the material and nano boron nitride are fully and uniformly mixed.

[0070] The screw speed is set to 300 r / min, corresponding to a shearing rate of 500 s. -1 This parameter can break the initial agglomerates of nano-boron nitride through mechanical shearing force, while avoiding the generation of small volatile molecules due to excessive rotation speed causing POE molecular chain breakage. The extruder vacuum port maintains a negative pressure of -0.08MPa to promptly remove micro-bubbles generated during the melting process. After the material is extruded from the barrel, it enters the die head, where a permanent magnet module is embedded in the outer wall of the die head. A uniform magnetic field of 0.3T parallel to the extrusion channel axis is applied, using magnetic force to induce the nano-boron nitride sheets to align axially along the conductor axis. Subsequently, it is cooled in a cooling water bath at 25℃ for 15s, and then cut into cylindrical modified insulating masterbatch with a particle size of 3mm×3mm by a pelletizer. Particles with a particle size deviation of ±0.5mm are screened out for later use.

[0071] Subsequently, S200 conductor surface anchoring treatment was performed: A 2.0mm diameter oxygen-free copper conductor with a purity ≥99.9% was selected. First, surface oil was removed by wiping with alcohol, then dried with hot air at 100℃ for 5 seconds. The dried conductor was then placed into a plasma treatment chamber, with 99.99% pure argon gas introduced as the working gas at a flow rate controlled at 12L / min, maintaining a vacuum of 0.2MPa. A 13.56MHz radio frequency glow discharge device was activated, set to a power of 600W, and a treatment time of 10 seconds. High-energy argon ion bombardment removed the oxide layer from the conductor surface, simultaneously forming a micro-rough surface with Ra=0.2μm and a surface introduction density ≥5×10¹. 4 The conductor has 1 -OH active group per cm². After treatment, the conductor immediately enters the coating station and is coated with a fourth-generation polyamide-amine (PAMAM) dendritic molecular solution using a micro-grooved roller coating process. The solution uses anhydrous ethanol as solvent, has a mass concentration of 2.5%, a viscosity of 6 mPa·s, a coating speed of 8 m / min, and a roller gap pressure of 0.1 MPa to ensure the formation of a uniform anchoring layer with a thickness of 0.3 μm on the conductor surface. Finally, the conductor is dried with hot air at 60℃ for 8 s to complete the conductor pretreatment.

[0072] Finally, the S300 gradient insulation layer is formed and post-treated: the modified insulation masterbatch is first fed into a dryer and dried at 80℃ and -0.09MPa for 4 hours to remove the adsorbed moisture in the masterbatch; the dried masterbatch is fed into a coaxial double-layer flow channel extruder through a double hopper feeder, wherein the diameter of the inner flow channel close to the conductor is 0.2mm and the diameter of the outer flow channel is 0.2mm. The concentration of the crosslinking agent in the inner layer is 50% higher than that in the outer layer through precise control of the feeder; the extruder barrel temperature is set to 160℃ to 180℃ to 200℃ along the material conveying direction, the inner layer temperature of the die is controlled at 220℃ to promote the full crosslinking reaction, with a target crosslinking degree of 85%, and the outer layer temperature is controlled at 190℃ to inhibit crosslinking, with a target crosslinking degree of 50%. The die outlet pressure is maintained at 5MPa to ensure that the insulation layer tightly covers the pre-treated conductor. After extrusion, the wire is first cooled in an 80℃ warm water bath for 10 seconds to quickly fix the gradient cross-linked structure. Then it enters the UV curing station, where a 254nm wavelength, 100W UV lamp is used, with the lamp 5cm away from the wire surface and the irradiation time 4 seconds, to further polymerize the outer layer of incompletely cross-linked substrate, forming a dense protective film with a thickness of 0.05mm. Finally, the total thickness of the insulation layer is detected online by a laser thickness gauge to ensure that it is ≤0.4mm. The wire is then wound up under tension control to complete the preparation of the composite wire.

[0073] Example 2

[0074] Compared with Example 1, the difference in this disclosure lies in the complete difference in both formulation and process. In terms of formulation, the substrate is replaced with cross-linked polyethylene, which has a density of 0.92 g / cm³ and a content of 98.0%. The low-density polyolefin elastomer in Example 1 is no longer used. At the same time, the nano boron nitride sheet layer is deleted. The cross-linking agent is replaced with dicumyl peroxide, with a content of 2.0%. The combination cross-linking agent of di-tert-butyl peroxide and trimethylolpropane triacrylate in Example 1 is removed, and antioxidant 1010 is not added.

[0075] In terms of process, the melt blending equipment was replaced with a single-screw extruder, the screw speed was adjusted to 250 r / min, and the shear rate was reduced to 300 s. -1 The three-stage temperature control mode of the twin-screw extruder in Example 1 is no longer used. No directional magnetic field is applied at the extrusion die. The conductor surface is roughened by pickling with 10% sulfuric acid for 10 seconds. The argon plasma activation and polyamide-amine dendritic molecular anchoring layer coating steps in Example 1 are deleted. The insulation layer is cured at a single-zone temperature of 200°C with the crosslinking degree controlled at 70%. The gradient temperature control of the coaxial double-layer flow channel and the concentration difference design of the inner and outer crosslinking agent are cancelled. The post-treatment is only natural cooling. The 80°C warm water cooling and 254nm ultraviolet curing steps are no longer performed.

[0076] Example 3

[0077] Compared with Example 1, the difference in this disclosure lies in the amount of boron nitride nanosheets added to the formulation. In Example 1, the content of boron nitride nanosheets was 3.0%, while in this example it was reduced to 1.0%. To maintain the total proportion of the formulation at 100%, the content of the polyolefin elastomer substrate was increased from 95.0% in Example 1 to 97.0%. The other components in the formulation, including the mass ratio of di-tert-butyl peroxide to trimethylolpropane triacrylate in the crosslinking agent, the content of antioxidant 1010, and all process steps, such as the melt blending parameters of the twin-screw extruder, the application of the directional magnetic field at the extrusion die, the argon plasma activation of the conductor surface and the coating of the polyamide-amine dendritic molecular anchoring layer, the gradient curing parameters of the insulating layer, and the subsequent warm water cooling and ultraviolet curing steps, are all completely consistent with Example 1.

[0078] Example 4

[0079] Compared with Example 1, the difference in this disclosure lies in the different mass ratios of the crosslinking agent components in the formulation. In Example 1, the mass ratio of di-tert-butyl peroxide to trimethylolpropane triacrylate was 2:1, while in this embodiment, the ratio was adjusted to 1:1, and the total amount of crosslinking agent added remained unchanged at 1.7%. Other components in the formulation, such as the content of polyolefin elastomer substrate, the content and specifications of nano boron nitride sheets, the content of antioxidant 1010, and all process steps, from the melt blending of raw materials and magnetic field orientation at the extrusion die, to the anchoring treatment of the conductor surface, the gradient curing of the insulation layer, and finally the ultraviolet curing step, have not changed and are completely the same as in Example 1. Example 5

[0080] Compared with Example 1, the difference in this disclosure is that no directional magnetic field is applied in the preparation step of the modified insulating substrate. In Example 1, a permanent magnet module is embedded in the die of a twin-screw extruder, and a uniform magnetic field with a strength of 0.3T parallel to the flow channel axis is applied to achieve the directional arrangement of the boron nitride nanosheets along the conductor axis. In this embodiment, the permanent magnet module is deleted, and no directional magnetic field is formed at the extrusion die. All components in the formulation, including the content and specifications of the polyolefin elastomer substrate, the boron nitride nanosheets, the crosslinking agent and the antioxidant, as well as other process steps, such as the melt blending parameters of the twin-screw extruder, the argon plasma activation of the conductor surface and the coating of the polyamide-amine dendritic molecular anchoring layer, the gradient curing parameters of the insulating layer, and the subsequent warm water cooling and ultraviolet curing treatment, are consistent with those of Example 1.

[0081] Example 6

[0082] Compared with Example 1, the difference in this disclosure is that the formulation design and process steps have been adjusted. In terms of formulation, the design in Example 1 in which the concentration of crosslinking agent in the inner layer flow channel is 40% to 60% higher than that in the outer layer has been eliminated. All crosslinking agents are uniformly mixed with other raw materials to keep the concentration of crosslinking agents in the inner and outer layers consistent.

[0083] In terms of process, a single-channel extrusion die is used when molding the insulation layer, instead of the coaxial double-layer flow channel structure in Example 1. The curing temperature control is changed to a single-zone temperature of 200°C, and the crosslinking degree target is 70%. The gradient temperature control mode of 220°C for the inner layer and 190°C for the outer layer in Example 1 is deleted. However, the polyolefin elastomer substrate, nano boron nitride flakes, total content of crosslinking agent, content of antioxidant 1010, and other process steps, such as melt blending of raw materials, magnetic field orientation at the extrusion die, anchoring treatment of conductor surface, subsequent warm water cooling and ultraviolet curing, are all the same as in Example 1, and the total thickness of the insulation layer is still controlled at 0.4 mm.

[0084] Table 1: Core Performance Test Results at Normal Temperature and Stability Example Breakdown voltage (kV) Insulation layer density (g / cm³) Bending life (times, no cracking) Pinhole rate (pinholes / m) 1 17.2 1.15 185 0.08 2 12.1 0.92 82 0.75 3 14.2 1.13 182 0.09 4 15.1 1.15 98 0.15 5 13.5 1.15 178 0.12 6 15.8 1.15 65 0.10 7 17.0 1.15 180 0.09 Table 1 presents the core performance data of the seven examples under normal temperature and conditions, highlighting the impact of different formulations and processes on the basic performance of the insulation layer. Example 1 achieved a breakdown voltage of 17.2 kV, significantly higher than the other examples, especially Example 2 using the conventional process, indicating that its ultra-thin-walled insulation layer maintains excellent high-voltage resistance while ensuring lightweight design. The insulation layer density is 1.15 g / cm³, slightly higher than the 0.92 g / cm³ of conventional XLPE (Example 2), but far lower than high-voltage insulation materials such as ceramicized silicone rubber, meeting the lightweight requirements.

[0085] In terms of mechanical properties, Example 1 exhibited a bending life of 185 cycles, which is 2.26 times that of Example 2 and significantly superior to Example 6 without gradient curing. This confirms the design advantage of maintaining flexibility in the outer layer with low crosslinking degree in the gradient crosslinked structure. The pinhole rate of Example 1 was only 0.08 pins / m, a reduction of 89.3% compared to Example 2, indicating that the synergistic effect of directional nano-boron nitride and gradient curing effectively reduced insulation layer defects.

[0086] Comparing the single-variable groups reveals that: Example 5, without magnetic field orientation, has a breakdown voltage reduced to 13.5kV, a 21.5% decrease compared to Example 1, verifying the crucial role of boron nitride orientation in improving dielectric strength. Example 3, with low boron nitride content, has a breakdown voltage of 14.2kV, a 17.4% decrease, indicating that 3.0% boron nitride content is the optimal value for balancing dispersibility and insulation. Example 4, with an unbalanced crosslinking agent ratio, has a bending life of only 98 cycles, a 47.0% reduction, highlighting the importance of a 2:1 crosslinking agent ratio for material toughness.

[0087] Table 2: Performance test results after damp heat aging (40℃ + 95% humidity, aging for 3000h) Example Adhesion force with conductor (N) Breakdown voltage retention rate (%) Oxidative degradation rate (%) <![CDATA[Water vapor permeability (×10 -12 g / (m·s·Pa))]]> 1 52.3 96.5 14.8 0.85 2 27.8 72.7 68.2 5.62 3 51.8 84.5 15.0 0.86 4 45.2 88.7 18.3 0.92 5 51.5 82.2 15.2 0.88 6 48.5 92.4 16.5 0.90 7 35.6 95.8 15.5 0.91 Table 2 presents the performance degradation data of the seven examples after aging at 40℃ and 95% humidity for 3000 hours, reflecting the damp heat resistance stability of the insulation layer. The adhesion force to the conductor maintained by Example 1 is 52.3N, which is much higher than that of Example 2 and Example 7 without anchoring treatment, proving that the chemical bonding and mechanical interlocking formed by plasma activation and PAMAM anchoring layer can effectively resist interfacial peeling under damp heat conditions.

[0088] Regarding the breakdown voltage retention rate, Example 1 achieved 96.5%, which is 32.7% higher than Example 2 and better than Example 8 without UV curing, demonstrating the synergistic antioxidant effect of antioxidant 1010 and the UV outer protective film; the oxidative degradation rate was only 14.8%, which is 21.7% of Example 2, indicating that the free radical scavenging effect of antioxidant 1010 significantly delayed the aging of the substrate.

[0089] Water vapor permeability data show that Example 1 has a permeability of only 0.85 × 10⁻⁶. -12 The g / (m・s・Pa) was 74.1% lower than that of Example 8, confirming that the dense protective film formed by UV secondary curing can effectively block moisture intrusion; while the adhesion of Example 6 without gradient curing was 48.5 N, which was 7.3% lower than that of Example 1, indicating that the elastic buffer of the low cross-linking structure of the outer layer also contributes to the interface stability.

[0090] Example 7

[0091] This application further proposes a composite wire, including a metal conductor and an insulating layer covering the metal conductor. The insulating layer contains nano-boron nitride sheets oriented along the conductor axis, and the insulating layer has a gradient cross-linking structure with an inner layer cross-linking degree of 80%~90% and an outer layer cross-linking degree of 45%~55%.

[0092] Among them, the boron nitride nanosheets oriented along the conductor axis refer to a structure in which sheet-like nanoparticles are arranged in an orderly manner along the length of the conductor through a magnetic field-assisted dispersion process. Specifically, this can be achieved by applying a directional magnetic field during extrusion. This arrangement can extend the path length of leakage channels inside the insulation layer and disperse the local electric field intensity. The gradient crosslinking structure refers to a cured form in which the degree of crosslinking in the insulation layer gradually decreases from the inside to the outside. This can be achieved through a double-layer flow channel extrusion process. The inner flow channel uses a combination of high temperature and high crosslinking agent concentration to promote the formation of a dense crosslinked network, while the outer flow channel uses a combination of low temperature and low crosslinking agent concentration to retain the material's elasticity. The polyamide-amine dendritic molecular anchoring layer refers to an interfacial transition layer that connects the conductor and the insulation layer through chemical bonding. Specifically, this can be achieved by coating a dendritic polymer solution after plasma activation. This layer enhances interfacial adhesion through molecular chain entanglement and the combination of active groups.

[0093] Specifically, the axial alignment of the boron nitride nanosheets forms a multi-level insulation barrier within the extremely thin insulating layer, effectively suppressing breakdown caused by concentrated electric fields. The highly cross-linked inner layer provides mechanical support through a dense cross-linked network, resisting stress generated by the thermal expansion of the conductor, while the low-cross-linked outer layer buffers external bending loads through elastic deformation. The anchoring layer on the conductor surface prevents interface delamination under humid and hot conditions through a combination of chemical bonding and physical anchoring. During manufacturing, a directional magnetic field induces the orderly arrangement of the nanosheets, the temperature difference between the two-layer flow channels and the concentration difference of the cross-linking agent creates a gradient curing process, and plasma activation and dendritic molecular coating construct a stable interface. These three elements work synergistically to optimize the insulating layer structure.

[0094] Traditional ultra-thin insulation layers suffer from an imbalance between mechanical strength and flexibility due to their single cross-linked structure, and the disordered dispersion of fillers easily creates weak points in the electric field. This solution combines gradient cross-linking with directional fillers to maintain the material's lightweight nature while giving the insulation layer both high voltage resistance and deformation resistance. Furthermore, it overcomes the decrease in adhesion caused by humid heat aging through interface anchoring technology.

[0095] This application addresses the issue of insufficient breakdown voltage in ultra-thin insulation layers under high-voltage conditions, avoids the decrease in adhesion caused by interfacial peeling after humid and hot aging, and simultaneously meets the lightweight requirements of automotive wiring harnesses. The gradient cross-linked structure within the insulation layer balances mechanical strength and flexibility, the oriented nanosheets effectively disperse electric field stress, and the interfacial anchoring layer enhances the bonding stability between the conductor and the insulation layer, ultimately achieving a comprehensive performance improvement in high-voltage resistance, strong adhesion, and low density.

[0096] This application further proposes that the total thickness of the insulation layer is no more than 0.4 mm.

[0097] The total thickness of the insulation layer refers to the vertical distance from the inner surface to the outer surface of the insulating material layer covering the metal conductor. Specifically, it can be achieved by adjusting the coordinating control of the extruder die gap and the traction speed. This parameter is directly related to the dielectric strength and mechanical properties of the insulation layer.

[0098] Specifically, based on the axially formed gradient cross-linked structure of the conductor, a synergistic optimization of high-voltage resistance and lightweight requirements is achieved by limiting the upper limit of the total thickness. The inner layer with a high degree of cross-linking forms a dense insulating barrier, while the outer layer with a low degree of cross-linking maintains flexibility; the two complement each other at a specific thickness ratio. When the total thickness exceeds the set threshold, the material density will exceed the lightweight requirements; below this threshold, a sufficient dielectric barrier cannot be constructed. By precisely controlling the extrusion process parameters, the thickness of the inner and outer layers is kept evenly distributed, ensuring that the breakdown voltage meets the requirements while avoiding interface stress concentration.

[0099] In some specific embodiments, the molecular anchoring layer formed by the pretreatment of the conductor surface can enhance the bonding force between the thin insulating layer and the substrate, and the directional magnetic field applied during the extrusion process causes the nanofillers to be arranged in an orderly manner along the conductor axis, further enhancing the dielectric properties of the thin-walled insulating layer.

[0100] Traditional cross-linked polyethylene materials cannot meet the breakdown voltage requirements at the same thickness, while ceramicized silicone rubber, although meeting the withstand voltage index, results in excessive density. This solution overcomes the performance limitations of the material itself through structural innovation, achieving simultaneous optimization of multiple performance indicators at an extremely thin thickness.

[0101] This application effectively reduces material usage while ensuring that the withstand voltage strength of the insulation layer meets the requirements of high-voltage platforms. It solves the problems of reduced breakdown voltage and insufficient adhesion caused by thinning the insulation layer in traditional processes, and at the same time meets the density control requirements of lightweight design.

[0102] This application further proposes that the metal conductor is copper or copper alloy conductor, and a polyamide-amine dendritic molecular anchoring layer is provided between the surface of the metal conductor and the insulating layer, with the thickness of the anchoring layer controlled in the range of 0.2~0.4μm.

[0103] Among them, copper or copper alloy conductors refer to wires with copper or copper-based alloys as the conductive core. Specifically, oxygen-free copper or copper-nickel alloys with a purity ≥99.9% can be used, which have high conductivity and tensile strength, meeting the basic performance requirements of high-voltage automotive wires for conductor materials. The polyamide-amine dendritic molecular anchoring layer refers to a three-dimensional dendritic polymer interface layer formed by solution coating. Specifically, it can be achieved using a fourth-generation polyamide-amine dendritic molecular solution via spin coating. The amino functional groups at the molecular ends can form multiple bonds with the active groups on the conductor surface and the insulating substrate. The thickness range of 0.2~0.4μm refers to the thickness of the anchoring layer covering the conductor surface. This can be achieved by adjusting the solution concentration and coating speed. This range can fully fill the microscopic rough structure of the conductor surface while avoiding an increase in the insulation layer density due to excessive thickness.

[0104] Specifically, after plasma activation treatment, a micro-groove structure with active hydroxyl groups is formed on the conductor surface. Polyamide-amine dendritic molecules achieve chemical anchoring through covalent bonding of amino and hydroxyl groups, while their three-dimensional dendritic structure simultaneously forms hydrogen bonds with the insulating substrate. The anchoring layer thickness is slightly greater than the peak surface roughness of the conductor, allowing the molecular chains to fully embed into the grooves and form mechanical interlocking. During damp heat aging, the dense network structure of the dendritic molecules prevents water molecules from penetrating to the interface, preventing the chemical bonds from hydrolyzing and breaking. The low cross-linking design of the outer insulating material buffers bending stress, preventing the anchoring layer from peeling off due to stress concentration.

[0105] Traditional processes, employing acid pickling or single coupling agent treatment, can only achieve physical adsorption or single-point chemical bonding, resulting in a sharp decline in interfacial bonding strength with humid and heat aging. Existing dendritic molecular coating technologies do not consider the compatibility between thickness and conductor roughness, easily leading to localized unfilled or over-stacking areas and uneven interfacial bonding. This solution, through the synergistic effect of plasma activation, molecular structure design, and thickness control, constructs a stable composite interfacial bonding system.

[0106] This application effectively maintains the bonding strength between the conductor and insulation layer of high-voltage automotive wires in humid and hot environments, preventing insulation failure due to interface peeling. While achieving long-term bonding, the submicron-level thickness and low density of the anchoring layer ensure that the overall weight of the insulation layer meets lightweight requirements, resolving the technical challenge of the contradiction between traditional interface reinforcement solutions and lightweight objectives.

[0107] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for manufacturing an electric wire insulating layer for an automobile, characterized by comprising: The raw material formula of the insulation layer includes, in percentage by weight: 91.5%-97.2% of polyolefin elastomer base material, 2.0%-4.0% of nano boron nitride sheet layer, 0.7%-1.6% of crosslinking agent, and 0.1%-0.3% of antioxidant; The manufacturing method includes the following steps: S100, mixing the components in the raw material formula, melt blending and granulating through a screw extruder; wherein, a directional magnetic field of 0.2-0.5T is applied at the extruder die to make the nano boron nitride sheet layer directionally arrange along the conductor axis to obtain modified insulation master batch; S200, plasma activation treatment is performed on the surface of the metal conductor, the treatment power is 500-700W, and the treatment time is 5-15s to form a micro rough surface with active groups; then a polyamide-amine dendrimer solution is coated on the activated conductor surface to form a molecular anchoring layer with a thickness of 0.2-0.4μm; S300, the modified insulation master batch is coated on the conductor treated in step S200 through an extruder with coaxial double-layer flow channel, wherein the crosslinking agent concentration of the inner layer flow channel is 40%-60% higher than that of the outer layer flow channel; By controlling the temperature, the inner layer flow channel temperature is 210-230℃, and the outer layer flow channel temperature is 180-200℃, so that the extruded insulation layer forms a gradient curing structure with an inner layer crosslinking degree of 80%-90% and an outer layer crosslinking degree of 45%-55%; After extrusion, the insulation layer is first cooled in warm water at 70-90℃ for 5-15s, and then subjected to secondary curing by ultraviolet light with a wavelength of 250-260nm and a power of 90-110W.

2. The manufacturing method according to claim 1, characterized by, The particle size of the nano boron nitride sheet layer is 40-60nm, and the surface is treated with silane coupling agent KH-560.

3. The production method according to claim 1, characterized by The crosslinking agent includes di-tert-butyl peroxide and a crosslinking promoter, and the mass ratio of the two is (1.5-2.5):

1.

4. The production method according to claim 1, characterized by In step S100, the screw rotation speed of the screw extruder is 280-320 r / min, and the shear rate is 450-550 s -1 .

5. The production method according to claim 1, characterized by In step S200, the plasma activation treatment uses argon as the working gas to make the conductor surface roughness Ra reach 0.1-0.3μm.

6. The production method according to claim 1, characterized by The polyolefin elastomer base material is a low-density polyolefin elastomer with a density of 0.86-0.91g / cm³.

7. The production method according to claim 1, characterized by The antioxidant is antioxidant 1010; and after the ultraviolet light secondary curing, a dense protective film with a thickness of 0.04-0.06mm is formed on the outer layer of the insulation layer.

8. A combination wire comprising a metal conductor and an insulating layer covering the metal conductor, characterized in that, The insulation layer contains nano boron nitride sheet layers directionally arranged along the conductor axis, and has a gradient crosslinking structure with an inner layer crosslinking degree of 80%-90% and an outer layer crosslinking degree of 45%-55%; the insulation layer is prepared by the manufacturing method of any one of claims 1-7.

9. The combination electrical cord of claim 8, wherein, The total thickness of the insulation layer is not more than 0.4mm.

10. The combination electrical cord of claim 8, wherein, The metal conductor is a copper or copper alloy conductor, and a polyamide-amine dendrimer anchoring layer with a thickness of 0.2-0.4μm is arranged between the surface of the metal conductor and the insulation layer.

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