Low dielectric wire harness and method of making same

Abstract

This invention discloses a low-dielectric wire harness and its preparation method, relating to the field of polyethylene cable technology and belonging to patent classification number H01B13 / 012. The method includes: performing a free radical grafting reaction between plasma-activated high-density polyethylene and dodecafluoroheptyl methacrylate and vinyltriethoxysilane to obtain fluorosilicone co-grafted modified polyethylene; preparing hollow silica microspheres using calcium carbonate as a template and amination; compounding organic intercalated montmorillonite with the amination hollow silica microspheres using a bridging agent and then surface fluorinating to obtain fluorinated hollow silica-montmorillonite composite filler; mixing and melt-extruding a mixture of fluorosilicone co-grafted modified polyethylene, ethylene-octene copolymer, maleic anhydride grafted polyethylene, composite filler, polyethylene wax, dimethyl silicone oil, antioxidant, and calcium stearate to obtain granules; and finally, melt-coating the granules onto the surface of a copper core conductor to obtain a low-dielectric wire harness. This invention significantly reduces the dielectric constant and dielectric loss of the wire harness and exhibits good moisture resistance and stability.

Description

Technical Field

[0001] This invention relates to the field of polyethylene cable technology, belonging to patent classification number H01B13 / 012, specifically to a low-dielectric wire harness and its preparation method. Background Technology

[0002] As the fundamental carrier of electrical signal transmission, wire harnesses play an irreplaceable role in fields such as 5G communication base stations, high-frequency radar systems, precision instruments, and high-speed data transmission equipment. With the continuous evolution of electronic devices towards higher frequencies, smaller sizes, and higher integration, signal transmission frequencies are constantly increasing, placing unprecedentedly stringent requirements on the dielectric properties of wire harness insulation layers. Currently, polyethylene is widely used in industry as the base material for wire harness insulation layers. This material has good electrical insulation properties, chemical stability, and processability, and is widely used in conventional wire harness applications. However, although polyethylene is a non-polar polymer, its dielectric constant (approximately 2.3–2.4) is sufficient for use under low-frequency conditions. In high-frequency applications, the trace amounts of polar groups remaining on the polyethylene molecular chain and the polar impurities inevitably introduced during processing can generate dipole orientation polarization and interfacial polarization effects in high-frequency alternating electric fields, leading to a significant increase in dielectric loss and severely affecting signal transmission fidelity and efficiency. In addition, traditional polyethylene wire harnesses are prone to absorbing trace amounts of moisture in humid environments. The extremely high polarity of water molecules will drastically deteriorate the dielectric properties of the material, further exacerbating the attenuation and distortion of high-frequency signals.

[0003] In existing technologies, methods for reducing the dielectric constant of wire harness insulation mainly include physical foaming and inorganic filler doping. Physical foaming reduces the effective dielectric constant by introducing air bubbles into the matrix; however, the size and distribution of the bubbles are difficult to control precisely, and the foamed structure is prone to collapse and deformation during long-term use, leading to significant fluctuations in dielectric properties over time. Inorganic filler doping faces problems such as poor compatibility between the filler and the polymer matrix and numerous interface defects, often resulting in a significant increase in dielectric loss while reducing the dielectric constant. Therefore, addressing the technical shortcomings of existing polyethylene wire harnesses—high dielectric constant, high dielectric loss, and poor environmental adaptability under high-frequency operating conditions—developing a wire harness fabrication method with low dielectric constant, low dielectric loss, and long-term stable performance has become a key technical objective to meet the application requirements of high-frequency communication and precision electronics. Summary of the Invention

[0004] The purpose of this invention is to provide a low-dielectric wire harness and its preparation method to solve the technical problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a low-dielectric wire harness includes the following steps: 1) High-density polyethylene powder was subjected to plasma activation treatment, and then subjected to free radical grafting reaction with dodecafluoroheptyl methacrylate, vinyltriethoxysilane and benzoyl peroxide to obtain fluorosilicone co-grafted modified polyethylene. 2) Using calcium carbonate microspheres as a template, tetraethyl orthosilicate is hydrolyzed and condensed under alkaline catalysis to form a shell. The calcium carbonate template is dissolved and removed to obtain hollow silica microspheres. Then, γ-aminopropyltriethoxysilane is used to modify them by amination to obtain amination-modified hollow silica microspheres. Sodium-based montmorillonite was organically intercalated with octadecyltrimethylammonium chloride; the aminated hollow silica microspheres and organically intercalated montmorillonite were compositely reacted with hexamethylene diisocyanate as a bridging agent under the action of a catalyst, and then the surface was fluorinated with tridecafluorooctyltriethoxysilane to obtain fluorinated hollow silica-montmorillonite composite filler. 3) The fluorosilicone co-grafted modified polyethylene, ethylene-octene copolymer, maleic anhydride grafted polyethylene, fluorinated hollow silica-montmorillonite composite filler, polyethylene wax, dimethyl silicone oil, antioxidant and calcium stearate are mixed evenly and then melt-extruded to obtain low dielectric polyethylene wire harness particles. 4) The low-dielectric polyethylene wire harness particles are melt-coated onto the surface of the copper core conductor to obtain a low-dielectric wire harness.

[0006] In the technical solution of this invention, the dielectric properties of polyethylene wire harnesses are improved synergistically from the following two aspects: (1) By modifying the polyethylene matrix with fluorosilicone co-graft, the polarization of the matrix is ​​reduced at the molecular level, thereby improving the low dielectric properties of the wire harness. Benzoyl peroxide decomposes at the reaction temperature to generate benzoyloxy radicals. These radicals abstract hydrogen atoms from the polyethylene molecular chain to generate macromolecular carbon radicals. At the same time, the peroxide groups introduced on the polyethylene surface by plasma pre-activation undergo OO bond thermal homolytic cracking under heating conditions, which also generates macromolecular active radicals in situ on the molecular chain. The above macromolecular radicals serve as active species for the grafting reaction, initiating the free radical addition polymerization reaction of carbon-carbon double bonds in dodecylfluoroheptyl methacrylate and vinyltriethoxysilane, and simultaneously grafting the two monomers onto the polyethylene molecular chain in the form of covalent bonds. The numerous carbon-fluorine bonds in the dodecafluoroheptyl methacrylate molecule possess extremely high bond energies and a highly symmetrical electron cloud distribution, endowing the fluoroalkyl segments with extremely low electronic polarizability and a very small permanent dipole moment. After grafting onto the polyethylene backbone, it can replace or shield the trace polar groups on the original molecular chain at the microscopic level with low-polarizability fluorocarbon segments, fundamentally weakening the contribution of dipole orientation polarization to the dielectric constant. After grafting, the ethoxy groups of vinyltriethoxysilane will gradually hydrolyze and condense when exposed to trace amounts of moisture in subsequent processing and use environments, constructing a three-dimensional cross-linked network with Si-O-Si as the backbone between the polyethylene molecular chains. This network restricts the relaxation motion amplitude of the molecular chain segments in the high-frequency alternating electric field through physical constraint effects, effectively suppressing the generation of dielectric loss. At the same time, the polarizability of the Si-O bond itself is lower than that of the C-C bond, further diluting the overall polarization intensity of the matrix. The synergistic grafting of the two monomers constructs a modified polyethylene matrix with both low polarizability and restricted molecular motion characteristics, providing a material basis for the low dielectric properties of the wire harness.

[0007] (2) By using a fluorinated hollow silica-montmorillonite composite filler system, the dielectric constant of the composite material is further reduced from the filler structure level. The hollow silica microspheres encapsulate closed air cavities with a dielectric constant close to 1. When these microspheres are uniformly dispersed in the polyethylene matrix, according to the effective dielectric theory, a large number of low dielectric cavities at the nanometer to micrometer scale can significantly reduce the effective dielectric constant of the composite system. Montmorillonite treated with octadecyltrimethylammonium chloride organic intercalation has a significantly expanded interlayer spacing and its surface changes from hydrophilic to hydrophobic. It can fully peel and unfold in the matrix to form a sheet barrier structure, effectively extending the path of external water molecules and polar small molecule impurities to penetrate and diffuse into the material, reducing the dielectric constant caused by water intrusion. Risk of increased electrical constant; Hexamethylene diisocyanate integrates hollow microspheres and montmorillonite sheets into a composite structure through chemical bonds, avoiding macroscopic stratification and local agglomeration caused by density differences when each component is used alone, ensuring that the dual functions of cavity dielectric reduction and sheet moisture barrier work uniformly and synergistically within the material; the surface fluorination treatment of tridecafluorooctyltriethoxysilane covers the outer surface of the composite filler with a dense, low-polarity fluoroalkyl molecular film, completely blocking the adverse effects of residual polar silanol groups on dielectric properties, making the composite filler itself a functional unit with extremely low polarizability.

[0008] Preferably, in step 1), the plasma activation power is 100-130W and the plasma activation time is 10-15min.

[0009] Preferably, in step 1), the mass ratio of dodecafluoroheptyl methacrylate to vinyltriethoxysilane is 10:(3-6); the free radical grafting reaction temperature is 80-90℃, and the reaction time is 3-5h.

[0010] Preferably, in step 2), the hydrolysis and condensation reaction of tetraethyl orthosilicate is carried out under alkaline catalytic conditions, with ammonia as the alkaline catalyst and a pH of 9-10 in the reaction system.

[0011] Preferably, in step 2), the mass ratio of sodium montmorillonite to octadecyltrimethylammonium chloride is 10:(3-5).

[0012] Preferably, in step 2), the catalyst used for the bridging composite reaction is dibutyltin dilaurate.

[0013] Preferably, in step 2), the surface fluorination treatment is carried out under slightly acidic conditions, with the pH of the system adjusted to 4-5 by glacial acetic acid, and the reaction solvent is a mixture of ethanol and water.

[0014] Preferably, in step 3), the mass ratio of fluorosilicone co-grafted modified polyethylene, ethylene-octene copolymer, maleic anhydride grafted polyethylene, and fluorinated hollow silica-montmorillonite composite filler is 60:(12-18):(6-10):(12-18).

[0015] Preferably, in step 3), the mass ratio of polyethylene wax to dimethyl silicone oil is 3:(0.5-2).

[0016] In experiments, this invention found that when fluorosilicone co-grafted modified polyethylene matrix and fluorinated composite filler are melt-blended in a twin-screw extruder, the surface energy of both is at a low level, resulting in insufficient wetting and spreading ability of the matrix melt on the filler surface. Nanoscale micropores are easily left at the interface between the filler and the matrix. These micropores are prone to accumulating free water molecules in the humid environment of daily use. Since the dielectric constant of water is as high as about 80, even trace amounts of water intrusion can cause a sudden increase in the local dielectric constant of the interface region and generate an interface polarization effect under the excitation of an alternating electric field. This leads to a significant increase in the dielectric loss tangent of the composite material in the mid-to-low frequency range, partially offsetting the low dielectric effect achieved by the synergistic effect of the two aspects mentioned above. To address the aforementioned technical problems, this invention introduces polyethylene wax and dimethyl silicone oil into the blend system, resulting in a synergistic effect: Polyethylene wax has a low molecular weight, low melting temperature, and extremely low melt viscosity, allowing it to melt first during extrusion and rapidly penetrate the micropores between the filler and matrix. This physical filling effectively closes the voids and defects at the interface, cutting off the adsorption and aggregation channels for water molecules, thus making the interface region dense and complete. Dimethyl silicone oil itself has an extremely low dielectric constant and excellent surface wetting and spreading properties. During processing, it spontaneously migrates to the filler-matrix interface and forms a uniform, low-dielectric transition layer. This transition layer, on the one hand, mitigates the abrupt gradient of the dielectric constant between the filler and the matrix, effectively suppressing the occurrence of interfacial polarization effects. On the other hand, the strong hydrophobic properties of the Si-O-Si backbone in the silicone oil molecules endow the interface region with a lasting water-repellent capability, thereby maintaining the overall low dielectric level of the material system while eliminating microscopic defects at the interface.

[0017] A low-dielectric wire harness is prepared by the method described above.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. By modifying polyethylene with fluorosilicone co-graft, low polarizability carbon-fluorine bonds and three-dimensional cross-linking networks are introduced, which weakens dipole polarization and restricts the relaxation movement of molecular chains at the molecular level, significantly improving the low dielectric properties of the matrix.

[0019] 2. Fluorinated hollow silica-montmorillonite composite filler is used. The closed cavity lowers the dielectric constant, while the peeled montmorillonite sheets prevent moisture and polar impurities from entering, thus avoiding the degradation of dielectric properties.

[0020] 3. The synergistic effect of polyethylene wax and dimethyl silicone oil is introduced to fill the micropores between the filler and the matrix and form a low-dielectric hydrophobic transition layer, eliminating the interfacial polarization effect and ensuring the stability of the overall low dielectric level of the material. Attached Figure Description

[0021] Figure 1 This is a low-magnification SEM image of the cross-section of the low-dielectric wire harness prepared in Example 1 of the present invention.

[0022] Figure 2 This is a medium-magnification SEM image of the cross-section of the low-dielectric wire harness prepared in Example 1 of the present invention.

[0023] Figure 3 This is a high-magnification SEM image of the cross-section of the low-dielectric wire harness prepared in Example 1 of the present invention.

[0024] Figure 4 The image shows the XRD pattern of the low-dielectric wire bundle prepared in Example 1 of this invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1 A method for preparing a low-dielectric wire harness includes the following steps: Step 1: Weigh 50g of high-density polyethylene powder (particle size about 100 mesh), put it into a low-temperature plasma treatment instrument, introduce high-purity argon gas (purity ≥99.999%), set the activation power to 120W and the activation time to 12min, and obtain activated polyethylene after treatment; 10g of dodecafluoroheptyl methacrylate, 5g of vinyltriethoxysilane, and 180mL of anhydrous xylene were added to a three-necked flask and stirred at 55℃ for 30min to prepare a monomer premix. 50g of activated polyethylene, 300mL of anhydrous xylene, and 0.25g of benzoyl peroxide were added to a four-necked flask. After purging with nitrogen three times, the temperature was raised to 85℃, and the monomer premix was slowly added dropwise (dropping rate of about 1.5mL / min). After the addition was complete, the mixture was kept at the temperature and stirred for 4h. After the reaction, the mixture was poured into 600mL of methanol while hot to precipitate. The precipitate was collected by suction filtration, washed three times with methanol, and dried under vacuum at 70℃ for 12h to obtain fluorosilicone co-grafted modified polyethylene.

[0027] Step 2: Weigh 60g of calcium carbonate microspheres (particle size approximately 3μm), add 1000mL of ethanol-water solution (ethanol:water = 1:1), and ultrasonically disperse for 20min. Add concentrated ammonia (25% by mass) dropwise to adjust the pH to approximately 9.5. Slowly add 40mL of tetraethyl orthosilicate (dropwise for approximately 1h), and stir at 40℃ for 6h. Centrifuge at 5000r / min for 10min to collect the precipitate. Add the precipitate to 1200mL of 2mol / L hydrochloric acid solution and stir at room temperature for 4h to dissolve the calcium carbonate template. Centrifuge at 5000r / min to collect the product, wash with deionized water until neutral, and vacuum dry at 80℃ for 10h to obtain hollow silica microspheres. Weigh 10g of hollow silica microspheres, add 300mL of ethanol aqueous solution (ethanol:water = 1:1), ultrasonically disperse for 20min, add 0.5g of γ-aminopropyltriethoxysilane, stir and react at 70℃ for 3h, centrifuge (7000r / min, 10min), wash 3 times with ethanol, and vacuum dry at 75℃ for 8h to obtain aminated hollow silica; Weigh 10g of sodium montmorillonite, add 200mL of deionized water and ultrasonically disperse for 30min, add 4.5g of octadecyltrimethylammonium chloride, stir and react at 80℃ for 3h, centrifuge (8000r / min, 15min), wash with deionized water until no chloride ions are present, and vacuum dry at 85℃ for 10h to obtain organic intercalated montmorillonite; 10g of aminated hollow silica, 6g of organic intercalated montmorillonite, 0.35g of hexamethylene diisocyanate, 0.01g of dibutyltin dilaurate, and 150mL of anhydrous toluene were added to a four-necked flask. Under nitrogen protection, the mixture was reacted at 65℃ for 3h, then the temperature was raised to 75℃ and the reaction continued for 5h. The mixture was centrifuged (9000r / min, 20min), washed four times with ethanol, dried under vacuum at 90℃ for 12h, and then heat-treated at 150℃ under nitrogen atmosphere for 2h to obtain hollow silica-montmorillonite composite filler. Take 10g of composite filler, add 200mL of ethanol aqueous solution (ethanol:water = 4:1), ultrasonically disperse for 15min, add glacial acetic acid to adjust pH to 4.5, add 1.2g of tridecafluorooctyltriethoxysilane, stir and react at 65℃ for 3h, centrifuge (7500r / min, 12min), wash 3 times with ethanol, and vacuum dry at 80℃ for 8h to obtain fluorinated composite filler.

[0028] Step 3: Dry the fluorosilicone co-grafted modified polyethylene and the fluorinated composite filler separately in a vacuum drying oven at 75℃ for 4 hours. Weigh out 60 parts by weight of fluorosilicone co-grafted modified polyethylene, 17 parts by weight of ethylene-octene copolymer (octene content approximately 20wt%), 9 parts by weight of maleic anhydride grafted polyethylene (grafting rate approximately 1.0%), 16 parts by weight of fluorinated composite filler, 3 parts by weight of polyethylene wax, 0.8 parts by weight of antioxidant (antioxidant 1010 and antioxidant 168 are compounded at a mass ratio of 1:1), and 0.5 parts by weight of calcium stearate, and add them to a high-speed mixer. Set the speed to 1500 r / min and the temperature to 80℃. Mix for 15 minutes; add the mixture to the main feed port of the twin-screw extruder, and simultaneously inject 1.5 parts of dimethyl silicone oil online through the third section side feed port via a liquid metering pump. Set the temperatures of each zone as follows: Zone 1 155℃, Zone 2 170℃, Zone 3 180℃, Zone 4 185℃, and die head 180℃. Set the screw speed to 280 r / min. After melt extrusion, cool the mixture in a 20℃ water cooling tank and pelletize it into low-dielectric polyethylene wire harness granules with a particle size of 3-5 mm using a pelletizer.

[0029] Step 4: Add low-dielectric polyethylene wire harness granules to a single-screw extruder and coating machine. Set the barrel temperature to 180℃, the die head temperature to 185℃, and the die temperature to 180℃. Introduce 1.5mm diameter copper core wires (after degreasing and preheating at 60℃) into the die at a speed of 3m / min using a traction device. This allows the molten wire harness granules to evenly coat the surface of the wires, forming a 0.35mm thick coating layer. After coating, the wire harness is cooled in a 25℃ water cooling bath, dried at 75℃ for 1 hour, and finally wound up using a winding device to obtain the low-dielectric wire harness.

[0030] Figure 1 This is a low-magnification SEM image of the cross-section of the low-dielectric wire harness prepared in Example 1 of the present invention, showing the overall cross-sectional structure of the wire harness. It can be seen that the copper core wire and the insulation layer are tightly bonded and the insulation layer has a uniform thickness. Figure 2 The image shown is a medium-magnification SEM image of the cross-section of the low dielectric wire harness prepared in Example 1 of the present invention, which shows the microstructure inside the insulation layer. It can be seen that the composite filler is uniformly dispersed in the matrix and there is no obvious agglomeration. Figure 3 The high-magnification SEM image of the cross-section of the low dielectric wire harness prepared in Example 1 of the present invention shows the morphology of the fluorinated hollow silica-montmorillonite composite filler and its interfacial bonding with the matrix. It can be seen that the interface is clear and dense with no obvious micropores.

[0031] Figure 4 The XRD pattern of the low-dielectric wire bundle prepared in Example 1 of this invention shows that the characteristic peaks at 2θ = 21.6° and 23.8° correspond to the crystallization peaks of polyethylene; the broad envelope peak near 2θ = 22° corresponds to amorphous hollow silica; the diffraction peak near 2θ = 3.5° corresponds to the crystal plane of organic intercalated montmorillonite, and the shift of this peak to a lower angle proves that octadecyltrimethylammonium chloride has successfully entered the interlayer of montmorillonite, thus expanding its interlayer spacing; in addition, the strong and sharp peaks near 2θ = 43°, 50°, and 74° come from the copper core wire inside the wire bundle.

[0032] Example 2 A method for preparing a low-dielectric wire harness includes the following steps: Step 1: Weigh 50g of high-density polyethylene powder (particle size about 100 mesh), put it into a low-temperature plasma treatment instrument, introduce high-purity argon gas (purity ≥99.999%), set the activation power to 120W and the activation time to 12min, and obtain activated polyethylene after treatment; 10g of dodecafluoroheptyl methacrylate, 4g of vinyltriethoxysilane, and 180mL of anhydrous xylene were added to a three-necked flask and stirred at 55℃ for 30min to prepare a monomer premix. 50g of activated polyethylene, 300mL of anhydrous xylene, and 0.25g of benzoyl peroxide were added to a four-necked flask. After purging with nitrogen three times, the temperature was raised to 85℃, and the monomer premix was slowly added dropwise (dropping rate of about 1.5mL / min). After the addition was complete, the mixture was kept at the temperature and stirred for 4h. After the reaction, the mixture was poured into 600mL of methanol while hot to precipitate. The precipitate was collected by suction filtration, washed three times with methanol, and dried under vacuum at 70℃ for 12h to obtain fluorosilicone co-grafted modified polyethylene.

[0033] Step 2: Weigh 60g of calcium carbonate microspheres (particle size approximately 3μm), add 1000mL of ethanol-water solution (ethanol:water = 1:1), and ultrasonically disperse for 20min. Add concentrated ammonia (25% by mass) dropwise to adjust the pH to approximately 9.5. Slowly add 40mL of tetraethyl orthosilicate (dropwise for approximately 1h), and stir at 40℃ for 6h. Centrifuge at 5000r / min for 10min to collect the precipitate. Add the precipitate to 1200mL of 2mol / L hydrochloric acid solution and stir at room temperature for 4h to dissolve the calcium carbonate template. Centrifuge at 5000r / min to collect the product, wash with deionized water until neutral, and vacuum dry at 80℃ for 10h to obtain hollow silica microspheres. Weigh 10g of hollow silica microspheres, add 300mL of ethanol aqueous solution (ethanol:water = 1:1), ultrasonically disperse for 20min, add 0.5g of γ-aminopropyltriethoxysilane, stir and react at 70℃ for 3h, centrifuge (7000r / min, 10min), wash 3 times with ethanol, and vacuum dry at 75℃ for 8h to obtain aminated hollow silica; Weigh 10g of sodium montmorillonite, add 200mL of deionized water and ultrasonically disperse for 30min, add 3.5g of octadecyltrimethylammonium chloride, stir and react at 80℃ for 3h, centrifuge (8000r / min, 15min), wash with deionized water until no chloride ions are present, and vacuum dry at 85℃ for 10h to obtain organic intercalated montmorillonite; 10g of aminated hollow silica, 6g of organic intercalated montmorillonite, 0.35g of hexamethylene diisocyanate, 0.01g of dibutyltin dilaurate, and 150mL of anhydrous toluene were added to a four-necked flask. Under nitrogen protection, the mixture was reacted at 65℃ for 3h, then the temperature was raised to 75℃ and the reaction continued for 5h. The mixture was centrifuged (9000r / min, 20min), washed four times with ethanol, dried under vacuum at 90℃ for 12h, and then heat-treated at 150℃ under nitrogen atmosphere for 2h to obtain hollow silica-montmorillonite composite filler. Take 10g of composite filler, add 200mL of ethanol aqueous solution (ethanol:water = 4:1), ultrasonically disperse for 15min, add glacial acetic acid to adjust pH to 4.5, add 1.2g of tridecafluorooctyltriethoxysilane, stir and react at 65℃ for 3h, centrifuge (7500r / min, 12min), wash 3 times with ethanol, and vacuum dry at 80℃ for 8h to obtain fluorinated composite filler.

[0034] Step 3: Dry the fluorosilicone co-grafted modified polyethylene and the fluorinated composite filler separately in a vacuum drying oven at 75℃ for 4 hours. Weigh out 60 parts by weight of fluorosilicone co-grafted modified polyethylene, 14 parts by weight of ethylene-octene copolymer (octene content approximately 20wt%), 7 parts by weight of maleic anhydride grafted polyethylene (grafting rate approximately 1.0%), 14 parts by weight of fluorinated composite filler, 3 parts by weight of polyethylene wax, 0.8 parts by weight of antioxidant (antioxidant 1010 and antioxidant 168 are compounded at a mass ratio of 1:1), and 0.5 parts by weight of calcium stearate. Add these to a high-speed mixer, set the speed to 1500 r / min and the temperature to 80℃. Mix for 15 minutes; add the mixture to the main feed port of the twin-screw extruder, and simultaneously inject 0.8 parts of dimethyl silicone oil online through the third section side feed port via a liquid metering pump. Set the temperatures of each zone as follows: Zone 1 155℃, Zone 2 170℃, Zone 3 180℃, Zone 4 185℃, and die head 180℃. Set the screw speed to 280 r / min. After melt extrusion, cool the mixture in a 20℃ water cooling tank and then pelletize it into low-dielectric polyethylene wire harness granules with a particle size of 3-5 mm using a pelletizer.

[0035] Step 4: Add low-dielectric polyethylene wire harness granules to a single-screw extruder and coating machine. Set the barrel temperature to 180℃, the die head temperature to 185℃, and the die temperature to 180℃. Introduce 1.5mm diameter copper core wires (after degreasing and preheating at 60℃) into the die at a speed of 3m / min using a traction device. This allows the molten wire harness granules to evenly coat the surface of the wires, forming a 0.35mm thick coating layer. After coating, the wire harness is cooled in a 25℃ water cooling bath, dried at 75℃ for 1 hour, and finally wound up using a winding device to obtain the low-dielectric wire harness.

[0036] Example 3 A method for preparing a low-dielectric wire harness includes the following steps: Step 1: Weigh 50g of high-density polyethylene powder (particle size about 100 mesh), put it into a low-temperature plasma treatment instrument, introduce high-purity argon gas (purity ≥99.999%), set the activation power to 120W and the activation time to 12min, and obtain activated polyethylene after treatment; 10g of dodecafluoroheptyl methacrylate, 4.5g of vinyltriethoxysilane, and 180mL of anhydrous xylene were added to a three-necked flask and stirred at 55℃ for 30min to prepare a monomer premix. 50g of activated polyethylene, 300mL of anhydrous xylene, and 0.25g of benzoyl peroxide were added to a four-necked flask. After purging with nitrogen three times, the temperature was raised to 85℃, and the monomer premix was slowly added dropwise (dropping rate of about 1.5mL / min). After the addition was complete, the mixture was kept at the temperature and stirred for 4h. After the reaction, the mixture was poured into 600mL of methanol while hot to precipitate. The precipitate was collected by filtration, washed three times with methanol, and dried under vacuum at 70℃ for 12h to obtain fluorosilicone co-grafted modified polyethylene.

[0037] Step 2: Weigh 60g of calcium carbonate microspheres (particle size approximately 3μm), add 1000mL of ethanol-water solution (ethanol:water = 1:1), and ultrasonically disperse for 20min. Add concentrated ammonia (25% by mass) dropwise to adjust the pH to approximately 9.5. Slowly add 40mL of tetraethyl orthosilicate (dropwise for approximately 1h), and stir at 40℃ for 6h. Centrifuge at 5000r / min for 10min to collect the precipitate. Add the precipitate to 1200mL of 2mol / L hydrochloric acid solution and stir at room temperature for 4h to dissolve the calcium carbonate template. Centrifuge at 5000r / min to collect the product, wash with deionized water until neutral, and vacuum dry at 80℃ for 10h to obtain hollow silica microspheres. Weigh 10g of hollow silica microspheres, add 300mL of ethanol aqueous solution (ethanol:water = 1:1), ultrasonically disperse for 20min, add 0.5g of γ-aminopropyltriethoxysilane, stir and react at 70℃ for 3h, centrifuge (7000r / min, 10min), wash 3 times with ethanol, and vacuum dry at 75℃ for 8h to obtain aminated hollow silica; Weigh 10g of sodium montmorillonite, add 200mL of deionized water and ultrasonically disperse for 30min, add 4g of octadecyltrimethylammonium chloride, stir and react at 80℃ for 3h, centrifuge (8000r / min, 15min), wash with deionized water until no chloride ions are present, and vacuum dry at 85℃ for 10h to obtain organic intercalated montmorillonite. 10g of aminated hollow silica, 6g of organic intercalated montmorillonite, 0.35g of hexamethylene diisocyanate, 0.01g of dibutyltin dilaurate, and 150mL of anhydrous toluene were added to a four-necked flask. Under nitrogen protection, the mixture was reacted at 65℃ for 3h, then the temperature was raised to 75℃ and the reaction continued for 5h. The mixture was centrifuged (9000r / min, 20min), washed four times with ethanol, dried under vacuum at 90℃ for 12h, and then heat-treated at 150℃ under nitrogen atmosphere for 2h to obtain hollow silica-montmorillonite composite filler. Take 10g of composite filler, add 200mL of ethanol aqueous solution (ethanol:water = 4:1), ultrasonically disperse for 15min, add glacial acetic acid to adjust pH to 4.5, add 1.2g of tridecafluorooctyltriethoxysilane, stir and react at 65℃ for 3h, centrifuge (7500r / min, 12min), wash 3 times with ethanol, and vacuum dry at 80℃ for 8h to obtain fluorinated composite filler.

[0038] Step 3: Dry the fluorosilicone co-grafted modified polyethylene and the fluorinated composite filler separately in a vacuum drying oven at 75℃ for 4 hours. Weigh out 60 parts by weight of fluorosilicone co-grafted modified polyethylene, 15 parts by weight of ethylene-octene copolymer (octene content approximately 20wt%), 8 parts by weight of maleic anhydride grafted polyethylene (grafting rate approximately 1.0%), 15 parts by weight of fluorinated composite filler, 3 parts by weight of polyethylene wax, 0.8 parts by weight of antioxidant (antioxidant 1010 and antioxidant 168 are compounded at a mass ratio of 1:1), and 0.5 parts by weight of calcium stearate. Add these to a high-speed mixer, set the speed to 1500 r / min and the temperature to 80℃. Mix for 15 minutes; add the mixture to the main feed port of the twin-screw extruder, and simultaneously inject 1 part of dimethyl silicone oil online from the side feed port of the third section through a liquid metering pump. Set the temperature of each zone as follows: Zone 1 155℃, Zone 2 170℃, Zone 3 180℃, Zone 4 185℃, and die head 180℃. Set the screw speed to 280 r / min. After melt extrusion, cool the mixture in a 20℃ water cooling tank and cut it into low-dielectric polyethylene wire harness granules with a particle size of 3-5 mm using a pelletizer.

[0039] Step 4: Add low-dielectric polyethylene wire harness granules to a single-screw extruder and coating machine. Set the barrel temperature to 180℃, the die head temperature to 185℃, and the die temperature to 180℃. Introduce 1.5mm diameter copper core wires (after degreasing and preheating at 60℃) into the die at a speed of 3m / min using a traction device. This allows the molten wire harness granules to evenly coat the surface of the wires, forming a 0.35mm thick coating layer. After coating, the wire harness is cooled in a 25℃ water cooling bath, dried at 75℃ for 1 hour, and finally wound up using a winding device to obtain the low-dielectric wire harness.

[0040] Example 4 A method for preparing a low-dielectric wire harness includes the following steps: Step 1: Weigh 50g of high-density polyethylene powder (particle size about 100 mesh), put it into a low-temperature plasma treatment instrument, introduce high-purity argon gas (purity ≥99.999%), set the activation power to 130W and the activation time to 15min, and obtain activated polyethylene after treatment; 10g of dodecafluoroheptyl methacrylate, 6g of vinyltriethoxysilane, and 180mL of anhydrous xylene were added to a three-necked flask and stirred at 55℃ for 30min to prepare a monomer premix. 50g of activated polyethylene, 300mL of anhydrous xylene, and 0.25g of benzoyl peroxide were added to a four-necked flask. After purging with nitrogen three times, the temperature was raised to 90℃, and the monomer premix was slowly added dropwise (dropping rate of about 1.5mL / min). After the addition was complete, the mixture was kept at the temperature and stirred for 5h. After the reaction, the mixture was poured into 600mL of methanol while hot to precipitate. The precipitate was collected by suction filtration, washed three times with methanol, and dried under vacuum at 70℃ for 12h to obtain fluorosilicone co-grafted modified polyethylene.

[0041] Step 2: Weigh 60g of calcium carbonate microspheres (particle size approximately 3μm), add 1000mL of ethanol-water solution (ethanol:water = 1:1), and ultrasonically disperse for 20min. Add concentrated ammonia (25% by mass) dropwise to adjust the pH to approximately 10. Slowly add 40mL of tetraethyl orthosilicate (dropwise for approximately 1h), and stir at 40℃ for 6h. Centrifuge at 5000r / min for 10min to collect the precipitate. Add the precipitate to 1200mL of 2mol / L hydrochloric acid solution and stir at room temperature for 4h to dissolve the calcium carbonate template. Centrifuge at 5000r / min to collect the product, wash with deionized water until neutral, and vacuum dry at 80℃ for 10h to obtain hollow silica microspheres. Weigh 10g of hollow silica microspheres, add 300mL of ethanol aqueous solution (ethanol:water = 1:1), ultrasonically disperse for 20min, add 0.5g of γ-aminopropyltriethoxysilane, stir and react at 70℃ for 3h, centrifuge (7000r / min, 10min), wash 3 times with ethanol, and vacuum dry at 75℃ for 8h to obtain aminated hollow silica; Weigh 10g of sodium montmorillonite, add 200mL of deionized water and ultrasonically disperse for 30min, add 5g of octadecyltrimethylammonium chloride, stir and react at 80℃ for 3h, centrifuge (8000r / min, 15min), wash with deionized water until no chloride ions are present, and vacuum dry at 85℃ for 10h to obtain organic intercalated montmorillonite. 10g of aminated hollow silica, 6g of organic intercalated montmorillonite, 0.35g of hexamethylene diisocyanate, 0.01g of dibutyltin dilaurate, and 150mL of anhydrous toluene were added to a four-necked flask. Under nitrogen protection, the mixture was reacted at 65℃ for 3h, then the temperature was raised to 75℃ and the reaction continued for 5h. The mixture was centrifuged (9000r / min, 20min), washed four times with ethanol, dried under vacuum at 90℃ for 12h, and then heat-treated at 150℃ under nitrogen atmosphere for 2h to obtain hollow silica-montmorillonite composite filler. Take 10g of composite filler, add 200mL of ethanol aqueous solution (ethanol:water = 4:1), ultrasonically disperse for 15min, add glacial acetic acid to adjust pH to 5, add 1.2g of tridecafluorooctyltriethoxysilane, stir and react at 65℃ for 3h, centrifuge (7500r / min, 12min), wash 3 times with ethanol, and vacuum dry at 80℃ for 8h to obtain fluorinated composite filler.

[0042] Step 3: Dry the fluorosilicone co-grafted modified polyethylene and the fluorinated composite filler separately in a vacuum drying oven at 75℃ for 4 hours. Weigh out 60 parts by weight of fluorosilicone co-grafted modified polyethylene, 18 parts by weight of ethylene-octene copolymer (octene content approximately 20wt%), 10 parts by weight of maleic anhydride grafted polyethylene (grafting rate approximately 1.0%), 18 parts by weight of fluorinated composite filler, 3 parts by weight of polyethylene wax, 0.8 parts by weight of antioxidant (antioxidant 1010 and antioxidant 168 are compounded at a mass ratio of 1:1), and 0.5 parts by weight of calcium stearate, and add them to a high-speed mixer. Set the speed to 1500 r / min and the temperature to 80℃. Mix for 15 minutes; add the mixture to the main feed port of the twin-screw extruder, and simultaneously inject 2 parts of dimethyl silicone oil online from the side feed port of the third section through a liquid metering pump. Set the temperature of each zone as follows: Zone 1 155℃, Zone 2 170℃, Zone 3 180℃, Zone 4 185℃, and die head 180℃. Set the screw speed to 280 r / min. After melt extrusion, cool the mixture in a 20℃ water cooling tank and cut it into low-dielectric polyethylene wire harness granules with a particle size of 3-5 mm using a pelletizer.

[0043] Step 4: Add low-dielectric polyethylene wire harness granules to a single-screw extruder and coating machine. Set the barrel temperature to 180℃, the die head temperature to 185℃, and the die temperature to 180℃. Introduce 1.5mm diameter copper core wires (after degreasing and preheating at 60℃) into the die at a speed of 3m / min using a traction device. This allows the molten wire harness granules to evenly coat the surface of the wires, forming a 0.35mm thick coating layer. After coating, the wire harness is cooled in a 25℃ water cooling bath, dried at 75℃ for 1 hour, and finally wound up using a winding device to obtain the low-dielectric wire harness.

[0044] Example 5 A method for preparing a low-dielectric wire harness includes the following steps: Step 1: Weigh 50g of high-density polyethylene powder (particle size about 100 mesh), put it into a low-temperature plasma treatment instrument, introduce high-purity argon gas (purity ≥99.999%), set the activation power to 100W and the activation time to 10min, and obtain activated polyethylene after treatment; 10g of dodecafluoroheptyl methacrylate, 3g of vinyltriethoxysilane, and 180mL of anhydrous xylene were added to a three-necked flask and stirred at 55℃ for 30min to prepare a monomer premix. 50g of activated polyethylene, 300mL of anhydrous xylene, and 0.25g of benzoyl peroxide were added to a four-necked flask. After purging with nitrogen three times, the temperature was raised to 80℃, and the monomer premix was slowly added dropwise (dropping rate of about 1.5mL / min). After the addition was complete, the mixture was kept at the temperature and stirred for 3h. After the reaction, the mixture was poured into 600mL of methanol while hot to precipitate. The precipitate was collected by suction filtration, washed three times with methanol, and dried under vacuum at 70℃ for 12h to obtain fluorosilicone co-grafted modified polyethylene.

[0045] Step 2: Weigh 60g of calcium carbonate microspheres (particle size approximately 3μm), add 1000mL of ethanol-water solution (ethanol:water = 1:1), and ultrasonically disperse for 20min. Add concentrated ammonia (25% by mass) dropwise to adjust the pH to approximately 9. Slowly add 40mL of tetraethyl orthosilicate (dropwise for approximately 1h), and stir at 40℃ for 6h. Centrifuge at 5000r / min for 10min to collect the precipitate. Add the precipitate to 1200mL of 2mol / L hydrochloric acid solution and stir at room temperature for 4h to dissolve the calcium carbonate template. Centrifuge at 5000r / min to collect the product, wash with deionized water until neutral, and vacuum dry at 80℃ for 10h to obtain hollow silica microspheres. Weigh 10g of hollow silica microspheres, add 300mL of ethanol aqueous solution (ethanol:water = 1:1), ultrasonically disperse for 20min, add 0.5g of γ-aminopropyltriethoxysilane, stir and react at 70℃ for 3h, centrifuge (7000r / min, 10min), wash 3 times with ethanol, and vacuum dry at 75℃ for 8h to obtain aminated hollow silica; Weigh 10g of sodium montmorillonite, add 200mL of deionized water and ultrasonically disperse for 30min, add 3g of octadecyltrimethylammonium chloride, stir and react at 80℃ for 3h, centrifuge (8000r / min, 15min), wash with deionized water until no chloride ions are present, and vacuum dry at 85℃ for 10h to obtain organic intercalated montmorillonite. 10g of aminated hollow silica, 6g of organic intercalated montmorillonite, 0.35g of hexamethylene diisocyanate, 0.01g of dibutyltin dilaurate, and 150mL of anhydrous toluene were added to a four-necked flask. Under nitrogen protection, the mixture was reacted at 65℃ for 3h, then the temperature was raised to 75℃ and the reaction continued for 5h. The mixture was centrifuged (9000r / min, 20min), washed four times with ethanol, dried under vacuum at 90℃ for 12h, and then heat-treated at 150℃ under nitrogen atmosphere for 2h to obtain hollow silica-montmorillonite composite filler. Take 10g of composite filler, add 200mL of ethanol aqueous solution (ethanol:water = 4:1), ultrasonically disperse for 15min, add glacial acetic acid to adjust pH to 4, add 1.2g of tridecafluorooctyltriethoxysilane, stir and react at 65℃ for 3h, centrifuge (7500r / min, 12min), wash 3 times with ethanol, and vacuum dry at 80℃ for 8h to obtain fluorinated composite filler.

[0046] Step 3: Dry the fluorosilicone co-grafted modified polyethylene and the fluorinated composite filler separately in a vacuum drying oven at 75℃ for 4 hours. Weigh out 60 parts by weight of fluorosilicone co-grafted modified polyethylene, 12 parts by weight of ethylene-octene copolymer (octene content approximately 20wt%), 6 parts by weight of maleic anhydride grafted polyethylene (grafting rate approximately 1.0%), 12 parts by weight of fluorinated composite filler, 3 parts by weight of polyethylene wax, 0.8 parts by weight of antioxidant (antioxidant 1010 and antioxidant 168 are compounded at a mass ratio of 1:1), and 0.5 parts by weight of calcium stearate. Add these to a high-speed mixer, set the speed to 1500 r / min and the temperature to 80℃. Mix for 15 minutes; add the mixture to the main feed port of the twin-screw extruder, and simultaneously inject 0.5 parts of dimethyl silicone oil online through the third section side feed port via a liquid metering pump. Set the temperatures of each zone as follows: Zone 1 155℃, Zone 2 170℃, Zone 3 180℃, Zone 4 185℃, and die head 180℃. Set the screw speed to 280 r / min. After melt extrusion, cool the mixture in a 20℃ water cooling tank and then pelletize it into low-dielectric polyethylene wire harness granules with a particle size of 3-5 mm using a pelletizer.

[0047] Step 4: Add low-dielectric polyethylene wire harness granules to a single-screw extruder and coating machine. Set the barrel temperature to 180℃, the die head temperature to 185℃, and the die temperature to 180℃. Introduce 1.5mm diameter copper core wires (after degreasing and preheating at 60℃) into the die at a speed of 3m / min using a traction device. This allows the molten wire harness granules to evenly coat the surface of the wires, forming a 0.35mm thick coating layer. After coating, the wire harness is cooled in a 25℃ water cooling bath, dried at 75℃ for 1 hour, and finally wound up using a winding device to obtain the low-dielectric wire harness.

[0048] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the grafting modification in step 1 is omitted in the preparation of the low dielectric wire harness, and the fluorosilicone co-grafted modified polyethylene in step 3 is replaced with an equal amount of ordinary high-density polyethylene.

[0049] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that all operations in step 2 are omitted in the preparation process of the low dielectric wire harness, and the fluorinated composite filler in step 3 is removed.

[0050] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that in the preparation process of the low dielectric wire harness, step 3 involves the removal of polyethylene wax and dimethyl silicone oil.

[0051] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that polyethylene wax is removed in step 3 during the preparation of the low dielectric wire harness.

[0052] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that dimethyl silicone oil is removed in step 3 during the preparation of the low dielectric wire harness.

[0053] Performance testing: 1. Dielectric constant and dielectric loss tangent tests: The cladding layer was peeled off from the wire harnesses prepared in each embodiment and comparative example, and cut into circular samples with a diameter of 25 mm and a thickness of 0.35 mm. Measurements were performed using a precision impedance analyzer with a dielectric testing fixture. Five samples were tested in parallel for each group. The test conditions were: test frequency 1 MHz, test temperature 23 ± 1 ℃. Before testing, the samples were conditioned for 24 hours in a standard environment of 23 ℃ and relative humidity of 50 ± 5% to eliminate the influence of moisture absorption and thermal history on the test results. The relative dielectric constant (εr) and dielectric loss tangent (tanδ) of each sample at 1 MHz were recorded, and the arithmetic mean of the five samples was taken as the final test result. A lower dielectric constant indicates a smaller polarization of the material in a high-frequency electric field and a smaller signal transmission attenuation; a lower dielectric loss tangent indicates less electromagnetic energy dissipated as heat in an alternating electric field, which is more beneficial to the fidelity of high-frequency signal transmission. The test results are shown in Table 1.

[0054] 2. Water Absorption Test: The coating layer was peeled off from the wire harnesses prepared in each embodiment and comparative example, and cut into square standard samples of 50mm × 50mm × 0.35mm. Five samples were tested in parallel for each group. Before the test, the samples were dried in a vacuum drying oven at 50±2℃ (vacuum degree not lower than -85kPa) for 24±1h. After being removed, they were cooled to room temperature in a desiccator, and the initial mass m0 after drying was weighed using an analytical balance (accuracy 0.0001g). Then, the samples were completely immersed in distilled water at 23±1℃ for 24±1h. After soaking, the samples were removed, and the water droplets adhering to the surface of the samples were quickly wiped off with clean filter paper. Weighing was completed within 30s, and the mass m1 after water absorption was recorded. The water absorption rate was calculated using the formula W = (m1 - m0) / m0 × 100%. The arithmetic mean of the five samples was taken as the final test result. The lower the water absorption rate, the stronger the material's ability to resist moisture intrusion in a humid environment, and the better the stability of its dielectric properties under different humidity conditions. The test results are shown in Table 1.

[0055] 3. Dielectric constant change rate test after damp heat aging: The coating layer was peeled off from the wire harnesses prepared in each embodiment and comparative example, and cut into circular samples with a diameter of 25 mm and a thickness of 0.35 mm. Five samples were tested in parallel for each group. First, the initial dielectric constant εr0 of each sample was determined according to test method 1 above. Then, samples of the same specifications were placed in a constant temperature and humidity chamber, with the temperature set at 85±2℃ and the relative humidity at 85±5%, and aged continuously for 500 h under no-load conditions. After aging, the samples were taken out and conditioned in a standard environment of 23℃ and 50% relative humidity for 2 h, and the dielectric constant εr1 was re-determined under the same test conditions. The dielectric constant change rate was calculated according to the formula Δεr=(εr1-εr0) / εr0×100%, and the arithmetic mean of the five samples was taken. This index reflects the stability of the dielectric properties of the material under long-term high temperature and high humidity harsh environment. The smaller the change rate, the better the resistance to damp heat aging of the material and the higher the reliability for long-term use. The test results are shown in Table 1.

[0056] Table 1: Comparative Examples 4 and 5 were used to remove polyethylene wax and dimethyl silicone oil separately to verify their independent effects and synergistic effects. After removing polyethylene wax, Comparative Example 4 showed a dielectric loss tangent of 2.8 × 10⁻⁴, a water absorption rate of 0.015%, and a dielectric constant change rate of 5.26% after damp heat aging. Comparative Example 5 showed a dielectric loss tangent of 2.5 × 10⁻⁴, a water absorption rate of 0.013%, and a dielectric constant change rate of 4.31% after damp heat aging. All indicators for both were inferior to Example 1 but superior to Comparative Example 3, indicating that polyethylene wax and dimethyl silicone oil each have independent abilities to improve interface defects, but the absence of either component significantly reduces the interface optimization effect. Further comparison reveals that Comparative Example 4 (lacking polyethylene wax) exhibits inferior water absorption and damp heat aging change rates compared to Comparative Example 5 (lacking dimethyl silicone oil), indicating that the physical filling of polyethylene wax plays a more crucial role in bridging interfacial micropores and preventing moisture intrusion. Meanwhile, Comparative Example 5's dielectric loss tangent is inferior to Example 1 but superior to Comparative Example 4, demonstrating that the low-dielectric transition layer formed by silicone oil is irreplaceable in suppressing interfacial polarization effects. When both work synergistically (Example 1), all indicators reach optimal levels, verifying the synergistic necessity of the dual mechanism of physical filling of polyethylene wax and low-dielectric wetting of dimethyl silicone oil proposed in this invention.

[0057] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a low-dielectric wire harness, characterized in that, Includes the following steps: 1) High-density polyethylene powder was subjected to plasma activation treatment, and then subjected to free radical grafting reaction with dodecafluoroheptyl methacrylate, vinyltriethoxysilane and benzoyl peroxide to obtain fluorosilicone co-grafted modified polyethylene. 2) Using calcium carbonate microspheres as a template, tetraethyl orthosilicate is hydrolyzed and condensed under alkaline catalysis to form a shell. The calcium carbonate template is dissolved and removed to obtain hollow silica microspheres. Then, γ-aminopropyltriethoxysilane is used to modify them by amination to obtain amination-modified hollow silica microspheres. Sodium-based montmorillonite was organically intercalated with octadecyltrimethylammonium chloride; the aminated hollow silica microspheres and organically intercalated montmorillonite were compositely reacted with hexamethylene diisocyanate as a bridging agent under the action of a catalyst, and then the surface was fluorinated with tridecafluorooctyltriethoxysilane to obtain fluorinated hollow silica-montmorillonite composite filler. 3) The fluorosilicone co-grafted modified polyethylene, ethylene-octene copolymer, maleic anhydride grafted polyethylene, fluorinated hollow silica-montmorillonite composite filler, polyethylene wax, dimethyl silicone oil, antioxidant and calcium stearate are mixed evenly and then melt-extruded to obtain low dielectric polyethylene wire harness particles. 4) The low-dielectric polyethylene wire harness particles are melt-coated onto the surface of the copper core conductor to obtain a low-dielectric wire harness.

2. The method for preparing a low-dielectric wire harness according to claim 1, characterized in that, In step 1), the plasma activation power is 100-130W and the plasma activation time is 10-15min.

3. The method for preparing a low-dielectric wire harness according to claim 1, characterized in that, In step 1), the mass ratio of dodecafluoroheptyl methacrylate to vinyltriethoxysilane is 10:(3-6); the free radical grafting reaction temperature is 80-90℃, and the reaction time is 3-5h.

4. The method for preparing a low-dielectric wire harness according to claim 1, characterized in that, In step 2), the hydrolysis and condensation reaction of tetraethyl orthosilicate is carried out under alkaline catalytic conditions, with ammonia as the alkaline catalyst and a pH of 9-10 in the reaction system.

5. The method for preparing a low-dielectric wire harness according to claim 1, characterized in that, In step 2), the mass ratio of sodium montmorillonite to octadecyltrimethylammonium chloride is 10:(3-5).

6. The method for preparing a low-dielectric wire harness according to claim 1, characterized in that, In step 2), the catalyst used in the bridging composite reaction is dibutyltin dilaurate.

7. The method for preparing a low-dielectric wire harness according to claim 1, characterized in that, In step 2), the surface fluorination treatment is carried out under slightly acidic conditions, with the pH of the system adjusted to 4-5 by glacial acetic acid, and the reaction solvent is a mixture of ethanol and water.

8. The method for preparing a low-dielectric wire harness according to claim 1, characterized in that, In step 3), the mass ratio of fluorosilicone co-grafted modified polyethylene, ethylene-octene copolymer, maleic anhydride grafted polyethylene, and fluorinated hollow silica-montmorillonite composite filler is 60:(12-18):(6-10):(12-18).

9. The method for preparing a low-dielectric wire harness according to claim 1, characterized in that, In step 3), the mass ratio of polyethylene wax to dimethyl silicone oil is 3:(0.5-2).

10. A low-dielectric wire harness, characterized in that, It is prepared by the method described in any one of claims 1 to 9 above.

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