Electromagnetic shielding cable for radio altimeter and preparation method thereof

Abstract

The invention discloses an electromagnetic shielding cable for a radio altimeter and a preparation method thereof, and relates to the technical field of cables. The preparation method comprises the following steps: treating ethylene-tetrafluoroethylene copolymer particles, a mixed compatilizer, a chemical foaming agent and a nano nucleating agent by using mixed gas low-temperature plasma containing acrylic acid, performing melt blending by using a double-screw extruder, injecting supercritical carbon dioxide, and performing slow cooling and shock cooling to obtain a three-dimensional porous matrix containing micro-nano cells; the preparation method comprises the following steps: synthesizing ferroferric oxide particles by a solvothermal method, coating a silicon dioxide dielectric layer, and then chemically silvering to prepare ternary core-shell composite particles; modifying the particles with aminopropyltriethoxysilane and a block copolymer to obtain modified composite particles; melting, mixing and granulating the porous matrix and the modified composite particles to obtain the electromagnetic shielding composite material. And performing extrusion molding on a conductor to form an insulation shielding layer, thereby obtaining the cable. The cable has an excellent electromagnetic shielding effect.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, in particular to an electromagnetic shielding cable for a radio altimeter and a preparation method thereof. Background Art

[0002] Electromagnetic shielding cables play a vital role in modern electronic equipment and communication systems, especially in devices such as radio altimeters that have extremely strict electromagnetic requirements. Their primary function is to effectively shield against external electromagnetic interference, ensuring stable and accurate signals transmitted internally and preventing problems such as signal distortion and bit errors caused by external electromagnetic fields.

[0003] Currently, most common electromagnetic shielding cables on the market feature a multi-layer structure. Generally speaking, from the inside out, they consist of a core, insulation layer, shielding layer, and sheath. The shielding layer may be composed of a variety of materials, including metal foil (such as aluminum foil or copper foil) and metal braid (such as tinned copper wire braid or aluminum-magnesium alloy wire braid). While this multi-layer structure can achieve a certain degree of electromagnetic shielding effectiveness, it also has several drawbacks. For example, the multi-layer structure makes the cable's structural design extremely complex. Manufacturing requires the selection of multiple materials and processing techniques, such as wrapping the metal foil and braiding the wire, significantly increasing production complexity and cost. Furthermore, the multi-layer structure increases the cable's weight and reduces its flexibility. In practical applications, this can significantly limit cable installation space and flexibility, particularly in applications where high flexibility is required, such as wiring within aerospace equipment. This increases the complexity of installation and maintenance. Summary of the Invention

[0004] The purpose of the present invention is to provide an electromagnetic shielding cable for a radio altimeter and a method for preparing the same, so as to solve the technical problem of the complex structure of multi-layer cables mentioned in the background art. The single-layer electromagnetic shielding cable prepared by the present invention has excellent electromagnetic shielding effect.

[0005] To achieve the above object, the present invention provides the following technical solutions: A method for preparing an electromagnetic shielding cable for a radio altimeter comprises the following steps: S1. Treating ethylene-tetrafluoroethylene copolymer particles with a low-temperature plasma using a mixed gas containing acrylic acid, then mixing the treated particles with a compatibilizer, a chemical foaming agent, and a nano-nucleating agent, melt-blending the mixture through a twin-screw extruder, and injecting supercritical carbon dioxide during the extrusion process. After slow cooling and quenching, a three-dimensional porous network structure matrix material containing micro-nano pores is obtained; S2. Using a solvothermal method to synthesize ferroferric oxide magnetic particles as the core, the surface of the core is coated with a silicon dioxide dielectric layer, and then a metallic silver conductive layer is deposited on the surface of the dielectric layer by chemical plating to obtain a ternary core-shell composite particle; S3, reacting the ternary core-shell composite particles with aminopropyltriethoxysilane and a block copolymer in sequence to modify the particle surface to obtain modified composite particles having a flexible polymer interface layer grafted onto the surface; S4, melt-mixing and granulating the three-dimensional porous network structure matrix material and the modified composite particles to obtain an electromagnetic shielding composite material; S5. Extruding the electromagnetic shielding composite material directly onto the conductor through an extruder to form an insulating shielding layer, thereby obtaining the electromagnetic shielding cable.

[0006] In the technical solution of the present invention, a large number of micro-nano-scale bubbles are first introduced into the ethylene-tetrafluoroethylene copolymer insulation layer. These bubbles create an air-ETFE interface. When electromagnetic waves are incident on this structure, repeated multiple reflections, refractions and scattering effects will occur on these heterogeneous interfaces, greatly extending the propagation path of the electromagnetic waves inside the material, thereby attenuating and dissipating the electromagnetic wave energy, and preliminarily improving the cable's shielding performance against electromagnetic waves. Then, the Fe3O4@SiO2@Ag ternary core-shell structure composite particles are used to further dissipate electromagnetic waves by taking advantage of their magnetic collection loss, dielectric loss and conductive loss. Specifically, the inner core Fe3O4 acts as a magnetic component, which efficiently dissipates the magnetic field component of the electromagnetic wave through mechanisms such as natural resonance and domain wall resonance, providing magnetic loss. The middle SiO2 dielectric layer not only isolates the magnetic core from the conductive silver shell, preventing the eddy current effect from causing magnetic loss failure, but also introduces strong interfacial polarization relaxation and consumes electromagnetic energy due to the dielectric layer itself and the heterogeneous interface formed with the inner and outer layers. The outermost continuous silver shell constitutes a highly conductive network, which converts electromagnetic energy into heat energy for consumption through ohmic loss. Finally, aminopropyl triethoxysilane and block copolymer (PFP-b-PA6) were used to modify the surface of the core-shell particles, solving the problem of easy agglomeration of nanoparticles and weak interface bonding with the matrix. Aminopropyl triethoxysilane was anchored on the particle surface through chemical bonding, grafting active amino groups on it; then, the PFP-b-PA6 block copolymer used its PA6 segment to form a strong hydrogen bond with the amino group of KH-550, while its PFP segment had excellent compatibility with the ETFE matrix. This "molecular bridge" design ensured the uniform and stable dispersion of functional particles in the matrix, forming a complete and efficient network, while greatly enhancing the bonding force of the filler-matrix interface, avoiding the sudden change of wave impedance and performance degradation caused by interface defects, which is beneficial to improving the electromagnetic shielding effect of the ternary core-shell structure composite particles, while ensuring the excellent mechanical properties and long-term reliability of the composite material. Figure 1This is a SEM image of the surface of the modified composite particles prepared in the present invention. It can be observed from the image that the surface of the modified composite particles presents a rough morphology.

[0007] Preferably, in step S1, the nano-nucleating agent is nano-SiO2 pretreated with KH-550.

[0008] Preferably, the amount of the nano nucleating agent added is 0.5 to 1.5 wt % of the ethylene-tetrafluoroethylene copolymer particles.

[0009] Preferably, in step S3, the mass ratio of the ternary core-shell composite particles to aminopropyltriethoxysilane is 10:0.3-0.8.

[0010] Preferably, in step S3, the ternary core-shell composite particles are modified with aminopropyltriethoxysilane and then subjected to the following reaction: The ternary core-shell composite particles modified with aminopropyltriethoxysilane are dispersed in a Tris-HCl buffer solution, and then dopamine hydrochloride is added and the reaction is continuously stirred at room temperature. After the reaction is completed, the product is collected by centrifugation and washed with deionized water to obtain the product.

[0011] In the technical solution of the present invention, the R&D team discovered through in-depth research that there is a mismatch between the macroscopic impedance gradient characteristics introduced by the porous matrix and the microscopic interface polarization characteristics of the ternary core-shell particles in terms of electromagnetic wave frequency response. That is, when the electromagnetic wave enters the outermost silver shell of the ternary core-shell particle from the matrix polymer, a huge microscopic interface impedance mutation occurs. This mutation causes a portion of the electromagnetic wave that has already entered the interior of the material to be strongly reflected back at the particle surface, thereby affecting the electromagnetic wave consumption effect of the ternary core-shell particle. To further solve this problem, the present invention further modifies the ternary core-shell composite particles modified with aminopropyltriethoxysilane, and constructs a polydopamine dielectric buffer layer on the particle surface. Its wave impedance is between that of the polymer matrix and the silver shell, thereby achieving a particle-level wave impedance gradient transition, ensuring that the electromagnetic wave can be efficiently and non-reflectively coupled into the interior of the core-shell particle and consumed. During the subsequent reaction process, the PA6 segment in PFP-b-PA6 is combined with the rich functional groups of the outermost polydopamine layer through hydrogen bonds, and its PFP segment is perfectly compatible with the ethylene-tetrafluoroethylene copolymer matrix. The presence of the polydopamine layer does not weaken the interfacial bonding. On the contrary, its rich functional groups enhance the interaction with the polymer.

[0012] Preferably, the mass ratio of the aminopropyltriethoxysilane-modified ternary core-shell composite particles to dopamine hydrochloride is 10:0.2-0.6.

[0013] Preferably, in step S3, the block copolymer is a PFP-b-PA6 block copolymer.

[0014] Preferably, the method for preparing the PFP-b-PA6 block copolymer comprises the following steps: S31. Under nitrogen protection, reacting sodium hydride with ε-caprolactam to generate sodium caprolactam, initiating a polymerization reaction, and adding 6-azidohexanoyl chloride as a capping agent to cap the ends after cooling; after the reaction, dissolving the product in hexafluoroisopropanol, precipitating it in cold methanol, washing, and drying to obtain an azide-terminated polycaprolactam prepolymer; S32, reacting perfluorononenyloxybenzenesulfonyl fluoride with propargylamine in acetonitrile, adding N,N-diisopropylethylamine, concentrating after the reaction, precipitating in methanol / water, washing and drying to obtain a fluorine-containing alkyne compound; S33. Dissolve the azide-terminated polycaprolactam prepolymer and the fluorine-containing alkyne compound in DMF, add cuprous bromide and PMDETA, and carry out an azide-alkyne cycloaddition reaction; the reaction solution is purified by a neutral alumina column, then treated with an EDTA aqueous solution or a copper-removing resin, and finally precipitated in methanol / water and dried to obtain a PFP-b-PA6 block copolymer.

[0015] Preferably, in step S4, the mass ratio of the three-dimensional porous network structure matrix material to the modified composite particles is 80:18-22.

[0016] An electromagnetic shielding cable for a radio altimeter is prepared by the method described above.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The single-layer insulation shield design is simpler than traditional multi-layer cables. In addition, through the multiple reflection and scattering effect of the three-dimensional porous network structure matrix, combined with the synergistic effect of the magnetic loss, dielectric loss, and conductive loss of the Fe3O4@SiO2@Ag ternary core-shell composite particles, the attenuation and dissipation capacity of electromagnetic waves is significantly improved, thereby enhancing the electromagnetic shielding effect.

[0018] 2. A gradual transition of wave impedance is achieved through the polydopamine dielectric buffer layer, ensuring that electromagnetic waves are efficiently coupled into the particles and consumed, further enhancing the electromagnetic shielding performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is an SEM image of the surface of the modified composite particles prepared in the present invention. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the implementation regulations described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0021] Example 1 Preparation of PFP-b-PA6 block copolymer: Under nitrogen, 50 mL of anhydrous THF and 2.0 g of sodium hydride were added to a dry Schlenk flask. The system was cooled in an ice-water bath, and 30 mL of anhydrous THF solution containing 11.3 g of ε-caprolactam was slowly added dropwise. After the addition was complete, the ice bath was removed, and the reaction mixture was allowed to warm to room temperature and stirred for 2 h until no bubbles formed, yielding a suspension of the sodium caprolactam salt. The reaction system was then heated to 80°C and refluxed for 12 h to carry out anionic ring-opening polymerization. After the reaction was complete, the system was cooled to 0°C, and 15 mL of anhydrous THF solution containing 1.88 g of 6-chlorohexanoyl chloride was slowly added dropwise via a constant pressure dropping funnel. After the addition was complete, the reaction mixture was allowed to warm to room temperature and stirred for another 6 h to perform end-capping. Subsequently, an excess of saturated ammonium chloride solution was added to quench the reaction. The organic phases were extracted with dichloromethane, combined, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation to yield the crude product. The crude product was redissolved in 30 mL of hexafluoroisopropanol and then added dropwise to 600 mL of ice-cold methanol with vigorous stirring for precipitation. The white precipitate was collected by filtration, washed three times with cold methanol, and dried under vacuum at 40°C for 24 h to obtain the acyl chloride-terminated polycaprolactam. This precipitate was dissolved in 50 mL of DMF, 1.5 g of sodium azide was added, and the reaction was stirred at 50°C for 12 h. After the reaction was completed, the reaction solution was poured into 600 mL of ice water to precipitate a white solid, which was filtered, washed thoroughly with water, and dried under vacuum at 40°C to obtain the azide-terminated polycaprolactam prepolymer.

[0022] To a dry round-bottom flask, add 5.0 g of perfluorononenyloxybenzenesulfonyl fluoride and 100 mL of anhydrous acetonitrile and stir to dissolve. Under nitrogen, add 1.0 mL of propargylamine and 2.5 mL of N,N-diisopropylethylamine, sequentially. The reaction mixture is stirred at room temperature in the dark for 24 hours. After completion of the reaction, remove most of the acetonitrile solvent using a rotary evaporator. The resulting viscous residue is dissolved in 50 mL of dichloromethane and washed with water and saturated brine. The organic phase is dried over anhydrous sodium sulfate, filtered, and concentrated by rotary evaporation. The concentrate is added dropwise to 500 mL of a mixture of methanol and water (4:1 by volume) with vigorous stirring, resulting in the precipitation of a white solid. The solid is collected by filtration, washed with a cold methanol / water mixture, and dried under vacuum at 40°C for 24 hours to yield the fluorinated alkyne compound as a white solid.

[0023] In a nitrogen glove box, 2.0 g of azide-terminated polycaprolactam prepolymer, 3.15 g of a fluorinated alkyne compound, and 40 mL of anhydrous DMF were added sequentially to a dry Schlenk tube. After tightening the stopper, the Schlenk tube was removed from the glove box and connected to a vacuum line system. Three cycles of evacuation and nitrogen refilling were repeated. Under nitrogen protection, the catalyst system was added sequentially via syringe: 2 mL of a DMF solution of CuBr (28.7 mg, 0.2 mmol) and 2 mL of a DMF solution of PMDETA (41.8 μL, 0.2 mmol). The reaction system was placed in a 50°C oil bath and stirred vigorously in the dark for 24 h. After the reaction, the reaction solution was passed through a short column filled with neutral alumina to remove the copper catalyst and rinsed with DMF. The effluent was collected and poured into 400 mL of ice-cold water containing 0.1 g of EDTA disodium salt. The mixture was stirred for 1 h to further complex any remaining copper ions. The precipitated polymer was filtered and redissolved in 30 mL of HFIP. This solution was then added dropwise to 600 mL of a vigorously stirred methanol / water (1:1, v / v) mixture for precipitation. The white fibrous solid was collected by filtration, washed with methanol, and dried under vacuum at 40°C to constant weight to obtain the final product, PFP-b-PA6 block copolymer.

[0024] Preparation of KH-550 pretreated nano-SiO2 nucleating agent: 100 g of nano-SiO2 powder (particle size 20 nm) was weighed and dispersed in a mixed solvent consisting of 400 mL of anhydrous ethanol and 100 mL of deionized water, and then fully dispersed by ultrasonic treatment at a power of 600 W for 30 minutes; then 1.5 mL of silane coupling agent KH-550 was added to the system, refluxed and condensed at 80 ° C and mechanically stirred at 300 rpm for 8 hours. After the reaction was completed, the product was collected by centrifugation and washed repeatedly with anhydrous ethanol three times. Finally, the product was placed in a vacuum drying oven at 80 ° C and dried for 12 hours.

[0025] Preparation of an electromagnetic shielding cable for a radio altimeter: Step 1: Take 500g of ETFE particles and evenly spread them in the sample chamber of a low-temperature plasma treatment instrument. After sealing, evacuate the system to a pressure of 80 Pa. Use a mixture of argon and acrylic acid with a volume ratio of 9:1 as the treatment gas. Adjust the gas flow rate to stabilize the chamber pressure at 80 Pa. Treat at 400W of radio frequency power for 10 minutes. After completion, remove the treated ETFE particles and place them in a high-speed blender with 2% of the ETFE-g-MAH compatibilizer, 1.5% of the chemical foaming agent OBSH, and 1.3% of the nano-SiO2 nucleating agent pretreated with KH-550. Mix at 800 rpm for 5 minutes at room temperature to obtain a premix. The premix was fed into the main feed port of a twin-screw extruder. The extruder's temperature zones were set at 270°C, 285°C, 295°C, 290°C, and 280°C, respectively, with a screw speed of 200 rpm. Simultaneously, supercritical carbon dioxide was injected into the fourth zone of the barrel via a supercritical fluid injection pump at a controlled injection rate of 0.5 kg / h. After extrusion through the die, the molten blend was immediately passed through a 120°C insulation channel for slow cooling. It then entered a 20°C cold water tank for quenching and shaping, and finally pelletized in a pelletizer to produce porous ETFE matrix particles containing a micro- and nano-scale cellular structure.

[0026] Step 2: Weigh 2.70 g of FeCl₃·6H₂O and dissolve it in 80 mL of ethylene glycol. Stir magnetically until completely dissolved. Then, add 7.20 g of anhydrous sodium acetate and 2.00 g of polyvinylpyrrolidone, sequentially, and continue stirring for 30 minutes to form a homogeneous yellow solution. The mixed solution is transferred to a polytetrafluoroethylene-lined hydrothermal reactor, sealed, and placed in a 200°C forced air drying oven for 10 hours. After cooling to room temperature, the resulting black product is collected using an external magnetic field and washed three times alternately with anhydrous ethanol and deionized water. Finally, dry it in a 60°C vacuum drying oven for 12 hours to obtain spherical Fe₃O₄ particles. 0.5 g of the dried Fe₃O₄ particles is dispersed in a mixture of 200 mL of ethanol and 50 mL of deionized water and treated with ultrasound for 30 minutes. 5 mL of concentrated aqueous ammonia (28 wt%) was then added to the solution. After mechanical stirring for 15 minutes, 2 mL of ethyl orthosilicate was slowly added dropwise using a constant pressure dropping funnel. The reaction was continued at 30°C for 6 hours. After the reaction, the product was magnetically separated, washed three times with ethanol, and dried under vacuum at 60°C to obtain Fe3O4@SiO2 powder. 0.5 g of Fe3O4@SiO2 powder was dispersed in 100 mL of deionized water and sonicated for 30 minutes to obtain a dispersion. To prepare the silver-ammonia solution, 2.0 g of silver nitrate was dissolved in 50 mL of water. Concentrated aqueous ammonia was added dropwise with stirring until the initial brown precipitate was dissolved, resulting in a clear silver-ammonia solution. The silver-ammonia solution was mixed with the Fe3O4@SiO2 dispersion and heated to 60°C in a water bath with continuous stirring. The pH of the system was then adjusted to 11 with NaOH solution. 20 mL of a 0.4 mol / L glucose-potassium sodium tartrate solution was quickly added, and the reaction was continued at 60°C for 40 minutes. After the solution turned gray-black, heating was stopped, the product was magnetically separated, washed thoroughly with deionized water and ethanol, and dried in a vacuum at 60 °C to finally obtain Fe3O4@SiO2@Ag composite powder.

[0027] Step 3: Disperse 20g of Fe3O4@SiO2@Ag composite powder in 400mL of a 4:1 ethanol / water mixture and sonicate for 1h to ensure thorough dispersion. Add 1.4g of KH-550 silane coupling agent and stir under reflux at 80°C for 8h. After the reaction, collect the product by centrifugation, wash three times with ethanol to remove physically adsorbed coupling agent, and dry it in a vacuum oven at 60°C.

[0028] 50 g of KH-550-modified particles were dispersed in 500 mL of Tris-HCl buffer (pH 8.5). Then, 2.5 g of dopamine hydrochloride was added and the mixture was stirred at room temperature for 10 hours. After the reaction, the product was collected by centrifugation and repeatedly washed with deionized water until the supernatant was colorless. The product was then dried under vacuum at 60°C.

[0029] The polydopamine-modified particles were dispersed with 4.0 g of PFP-b-PA6 block copolymer in 200 mL of DMF and sonicated for 30 minutes. The mixture was then mechanically stirred at 80°C for 6 hours. The temperature was then raised to 100°C and the DMF solvent was slowly evaporated under reduced pressure on a rotary evaporator. The resulting solid product was further dried in a vacuum oven at 80°C for 12 hours to completely remove any residual solvent, yielding modified composite particles coated with a flexible polymer interfacial layer.

[0030] Step 4: The porous ETFE matrix particles and the modified composite particles were mixed in a mass ratio of 80:21 and placed in an internal mixer for solid-state shear mixing at 265°C and 30 rpm for 5 minutes. The premix was fed into a twin-screw extruder for melt blending and pelletization at a temperature of 285°C and a screw speed of 150 rpm to obtain electromagnetic shielding composite particles.

[0031] Step 5: Using a single-screw extruder, extrude the electromagnetic shielding composite material pellets directly onto a silver-plated copper core wire (conductor diameter 0.5 mm) to form the insulating shielding layer. The extruder temperature was set at 285°C and the extrusion speed at 2 m / min, ensuring a uniform layer thickness of 0.3 mm. The extruded cable was cooled in a water-cooling tank and annealed at 100°C for 2 hours to eliminate internal stress.

[0032] Example 2 The preparation method of PFP-b-PA6 block copolymer and KH-550 pretreated nano-SiO2 nucleating agent is the same as that in Example 1.

[0033] Preparation of an electromagnetic shielding cable for a radio altimeter: Step 1: Take 500g of ETFE particles and evenly spread them in the sample chamber of a low-temperature plasma treatment instrument. After sealing, evacuate the system to a pressure of 80 Pa. Use a mixture of argon and acrylic acid with a volume ratio of 9:1 as the treatment gas. Adjust the gas flow rate to stabilize the chamber pressure at 80 Pa. Treat at 400W of radio frequency power for 10 minutes. After completion, remove the treated ETFE particles and place them in a high-speed blender with 2% of the ETFE-g-MAH compatibilizer, 1.5% of the chemical foaming agent OBSH, and 0.8% of the nano-SiO2 nucleating agent pretreated with KH-550. Mix at 800 rpm for 5 minutes at room temperature to obtain a premix. The premix was fed into the main feed port of a twin-screw extruder. The extruder's temperature zones were set at 270°C, 285°C, 295°C, 290°C, and 280°C, respectively, with a screw speed of 200 rpm. Simultaneously, supercritical carbon dioxide was injected into the fourth zone of the barrel via a supercritical fluid injection pump at a controlled injection rate of 0.5 kg / h. After extrusion through the die, the molten blend was immediately passed through a 120°C insulation channel for slow cooling. It then entered a 20°C cold water tank for quenching and shaping, and finally pelletized in a pelletizer to produce porous ETFE matrix particles containing a micro- and nano-scale cellular structure.

[0034] Step 2: Weigh 2.70 g of FeCl₃·6H₂O and dissolve it in 80 mL of ethylene glycol. Stir magnetically until completely dissolved. Then, add 7.20 g of anhydrous sodium acetate and 2.00 g of polyvinylpyrrolidone, sequentially, and continue stirring for 30 minutes to form a homogeneous yellow solution. The mixed solution is transferred to a polytetrafluoroethylene-lined hydrothermal reactor, sealed, and placed in a 200°C forced air drying oven for 10 hours. After cooling to room temperature, the resulting black product is collected using an external magnetic field and washed three times alternately with anhydrous ethanol and deionized water. Finally, dry it in a 60°C vacuum drying oven for 12 hours to obtain spherical Fe₃O₄ particles. 0.5 g of the dried Fe₃O₄ particles is dispersed in a mixture of 200 mL of ethanol and 50 mL of deionized water and treated with ultrasound for 30 minutes. 5 mL of concentrated aqueous ammonia (28 wt%) was then added to the solution. After mechanical stirring for 15 minutes, 2 mL of ethyl orthosilicate was slowly added dropwise using a constant pressure dropping funnel. The reaction was continued at 30°C for 6 hours. After the reaction, the product was magnetically separated, washed three times with ethanol, and dried under vacuum at 60°C to obtain Fe3O4@SiO2 powder. 0.5 g of Fe3O4@SiO2 powder was dispersed in 100 mL of deionized water and sonicated for 30 minutes to obtain a dispersion. To prepare the silver-ammonia solution, 2.0 g of silver nitrate was dissolved in 50 mL of water. Concentrated aqueous ammonia was added dropwise with stirring until the initial brown precipitate was dissolved, resulting in a clear silver-ammonia solution. The silver-ammonia solution was mixed with the Fe3O4@SiO2 dispersion and heated to 60°C in a water bath with continuous stirring. The pH of the system was then adjusted to 11 with NaOH solution. 20 mL of a 0.4 mol / L glucose-potassium sodium tartrate solution was quickly added, and the reaction was continued at 60°C for 40 minutes. After the solution turned gray-black, heating was stopped, the product was magnetically separated, washed thoroughly with deionized water and ethanol, and dried in a vacuum at 60 °C to finally obtain Fe3O4@SiO2@Ag composite powder.

[0035] Step 3: Disperse 20g of Fe3O4@SiO2@Ag composite powder in 400mL of a 4:1 ethanol / water mixture and sonicate for 1h to ensure thorough dispersion. Add 0.8g of KH-550 silane coupling agent and stir under reflux at 80°C for 8h. After the reaction, collect the product by centrifugation, wash three times with ethanol to remove physically adsorbed coupling agent, and dry it in a vacuum oven at 60°C.

[0036] 50 g of KH-550-modified particles were dispersed in 500 mL of Tris-HCl buffer (pH 8.5). 1.5 g of dopamine hydrochloride was then added and stirred at room temperature for 10 hours. After the reaction was complete, the product was collected by centrifugation and repeatedly washed with deionized water until the supernatant was colorless. The product was then dried under vacuum at 60°C.

[0037] The polydopamine-modified particles were dispersed with 4.0 g of PFP-b-PA6 block copolymer in 200 mL of DMF and sonicated for 30 minutes. The mixture was then mechanically stirred at 80°C for 6 hours. The temperature was then raised to 100°C and the DMF solvent was slowly evaporated under reduced pressure on a rotary evaporator. The resulting solid product was further dried in a vacuum oven at 80°C for 12 hours to completely remove any residual solvent, yielding modified composite particles coated with a flexible polymer interfacial layer.

[0038] Step 4: The porous ETFE matrix particles and the modified composite particles were mixed in a mass ratio of 80:19 and placed in an internal mixer for solid-state shear mixing at 265°C and 30 rpm for 5 minutes. The premix was fed into a twin-screw extruder for melt blending and pelletization at a temperature of 285°C and a screw speed of 150 rpm to obtain electromagnetic shielding composite particles.

[0039] Step 5: Using a single-screw extruder, extrude the electromagnetic shielding composite material pellets directly onto a silver-plated copper core wire (conductor diameter 0.5 mm) to form the insulating shielding layer. The extruder temperature was set at 285°C and the extrusion speed at 2 m / min, ensuring a uniform layer thickness of 0.3 mm. The extruded cable was cooled in a water-cooling tank and annealed at 100°C for 2 hours to eliminate internal stress.

[0040] Example 3 The preparation method of PFP-b-PA6 block copolymer and KH-550 pretreated nano-SiO2 nucleating agent is the same as that in Example 1.

[0041] Preparation of an electromagnetic shielding cable for a radio altimeter: Step 1: Take 500g of ETFE particles and evenly spread them in the sample chamber of a low-temperature plasma treatment instrument. After sealing, evacuate the system to a pressure of 80 Pa. Use a mixture of argon and acrylic acid with a volume ratio of 9:1 as the treatment gas. Adjust the gas flow rate to stabilize the chamber pressure at 80 Pa. Treat at 400W of radio frequency power for 10 minutes. After completion, remove the treated ETFE particles and place them in a high-speed blender with 2% of the ETFE-g-MAH compatibilizer, 1.5% of the chemical foaming agent OBSH, and 1.0% of the nano-SiO2 nucleating agent pretreated with KH-550. Mix at 800 rpm for 5 minutes at room temperature to obtain a premix. The premix was fed into the main feed port of a twin-screw extruder. The extruder's temperature zones were set at 270°C, 285°C, 295°C, 290°C, and 280°C, respectively, with a screw speed of 200 rpm. Simultaneously, supercritical carbon dioxide was injected into the fourth zone of the barrel via a supercritical fluid injection pump at a controlled injection rate of 0.5 kg / h. After extrusion through the die, the molten blend was immediately passed through a 120°C insulation channel for slow cooling. It then entered a 20°C cold water tank for quenching and shaping, and finally pelletized in a pelletizer to produce porous ETFE matrix particles containing a micro- and nano-scale cellular structure.

[0042] Step 2: Weigh 2.70 g of FeCl₃·6H₂O and dissolve it in 80 mL of ethylene glycol. Stir magnetically until completely dissolved. Then, add 7.20 g of anhydrous sodium acetate and 2.00 g of polyvinylpyrrolidone, sequentially, and continue stirring for 30 minutes to form a homogeneous yellow solution. The mixed solution is transferred to a polytetrafluoroethylene-lined hydrothermal reactor, sealed, and placed in a 200°C forced air drying oven for 10 hours. After cooling to room temperature, the resulting black product is collected using an external magnetic field and washed three times alternately with anhydrous ethanol and deionized water. Finally, dry it in a 60°C vacuum drying oven for 12 hours to obtain spherical Fe₃O₄ particles. 0.5 g of the dried Fe₃O₄ particles is dispersed in a mixture of 200 mL of ethanol and 50 mL of deionized water and treated with ultrasound for 30 minutes. 5 mL of concentrated aqueous ammonia (28 wt%) was then added to the solution. After mechanical stirring for 15 minutes, 2 mL of ethyl orthosilicate was slowly added dropwise using a constant pressure dropping funnel. The reaction was continued at 30°C for 6 hours. After the reaction, the product was magnetically separated, washed three times with ethanol, and dried under vacuum at 60°C to obtain Fe3O4@SiO2 powder. 0.5 g of Fe3O4@SiO2 powder was dispersed in 100 mL of deionized water and sonicated for 30 minutes to obtain a dispersion. To prepare the silver-ammonia solution, 2.0 g of silver nitrate was dissolved in 50 mL of water. Concentrated aqueous ammonia was added dropwise with stirring until the initial brown precipitate was dissolved, resulting in a clear silver-ammonia solution. The silver-ammonia solution was mixed with the Fe3O4@SiO2 dispersion and heated to 60°C in a water bath with continuous stirring. The pH of the system was then adjusted to 11 with NaOH solution. 20 mL of a 0.4 mol / L glucose-potassium sodium tartrate solution was quickly added, and the reaction was continued at 60°C for 40 minutes. After the solution turned gray-black, heating was stopped, the product was magnetically separated, washed thoroughly with deionized water and ethanol, and dried in a vacuum at 60 °C to finally obtain Fe3O4@SiO2@Ag composite powder.

[0043] Step 3: Disperse 20g of Fe3O4@SiO2@Ag composite powder in 400mL of a 4:1 ethanol / water mixture and sonicate for 1h to ensure thorough dispersion. Add 1.0g of KH-550 silane coupling agent and stir under reflux at 80°C for 8h. After the reaction, collect the product by centrifugation, wash three times with ethanol to remove physically adsorbed coupling agent, and dry it in a vacuum oven at 60°C.

[0044] 50 g of KH-550-modified particles were dispersed in 500 mL of Tris-HCl buffer (pH 8.5). Then, 2.0 g of dopamine hydrochloride was added and the mixture was stirred at room temperature for 10 hours. After the reaction, the product was collected by centrifugation and repeatedly washed with deionized water until the supernatant was colorless. The product was then dried under vacuum at 60°C.

[0045] The polydopamine-modified particles were dispersed with 4.0 g of PFP-b-PA6 block copolymer in 200 mL of DMF and sonicated for 30 minutes. The mixture was then mechanically stirred at 80°C for 6 hours. The temperature was then raised to 100°C and the DMF solvent was slowly evaporated under reduced pressure on a rotary evaporator. The resulting solid product was further dried in a vacuum oven at 80°C for 12 hours to completely remove any residual solvent, yielding modified composite particles coated with a flexible polymer interfacial layer.

[0046] Step 4: Mix the porous ETFE matrix particles and the modified composite particles in a mass ratio of 80:20. Place the mixture in an internal mixer and perform solid-state shear mixing at 265°C and 30 rpm for 5 minutes. The premix is ​​then fed into a twin-screw extruder for melt blending and pelletization at a temperature of 285°C and a screw speed of 150 rpm to obtain electromagnetic shielding composite particles.

[0047] Step 5: Using a single-screw extruder, extrude the electromagnetic shielding composite material pellets directly onto a silver-plated copper core wire (conductor diameter 0.5 mm) to form the insulating shielding layer. The extruder temperature was set at 285°C and the extrusion speed at 2 m / min, ensuring a uniform layer thickness of 0.3 mm. The extruded cable was cooled in a water-cooling tank and annealed at 100°C for 2 hours to eliminate internal stress.

[0048] Example 4 The preparation method of PFP-b-PA6 block copolymer and KH-550 pretreated nano-SiO2 nucleating agent is the same as that in Example 1.

[0049] Preparation of an electromagnetic shielding cable for a radio altimeter: Step 1: Take 500g of ETFE particles and evenly spread them in the sample chamber of a low-temperature plasma treatment instrument. After sealing, evacuate the system to a pressure of 80 Pa. Use a mixture of argon and acrylic acid with a volume ratio of 9:1 as the treatment gas. Adjust the gas flow rate to stabilize the chamber pressure at 80 Pa. Treat at 400W of radio frequency power for 10 minutes. After completion, remove the treated ETFE particles and place them in a high-speed blender with 2% of the ETFE-g-MAH compatibilizer, 1.5% of the chemical foaming agent OBSH, and 1.5% of the nano-SiO2 nucleating agent pretreated with KH-550. Mix at 800 rpm for 5 minutes at room temperature to obtain a premix. The premix was fed into the main feed port of a twin-screw extruder. The extruder's temperature zones were set at 270°C, 285°C, 295°C, 290°C, and 280°C, respectively, with a screw speed of 200 rpm. Simultaneously, supercritical carbon dioxide was injected into the fourth zone of the barrel via a supercritical fluid injection pump at a controlled injection rate of 0.5 kg / h. After extrusion through the die, the molten blend was immediately passed through a 120°C insulation channel for slow cooling. It then entered a 20°C cold water tank for quenching and shaping, and finally pelletized in a pelletizer to produce porous ETFE matrix particles containing a micro- and nano-scale cellular structure.

[0050] Step 2: Weigh 2.70 g of FeCl₃·6H₂O and dissolve it in 80 mL of ethylene glycol. Stir magnetically until completely dissolved. Then, add 7.20 g of anhydrous sodium acetate and 2.00 g of polyvinylpyrrolidone, sequentially, and continue stirring for 30 minutes to form a homogeneous yellow solution. The mixed solution is transferred to a polytetrafluoroethylene-lined hydrothermal reactor, sealed, and placed in a 200°C forced air drying oven for 10 hours. After cooling to room temperature, the resulting black product is collected using an external magnetic field and washed three times alternately with anhydrous ethanol and deionized water. Finally, dry it in a 60°C vacuum drying oven for 12 hours to obtain spherical Fe₃O₄ particles. 0.5 g of the dried Fe₃O₄ particles is dispersed in a mixture of 200 mL of ethanol and 50 mL of deionized water and treated with ultrasound for 30 minutes. 5 mL of concentrated aqueous ammonia (28 wt%) was then added to the solution. After mechanical stirring for 15 minutes, 2 mL of ethyl orthosilicate was slowly added dropwise using a constant pressure dropping funnel. The reaction was continued at 30°C for 6 hours. After the reaction, the product was magnetically separated, washed three times with ethanol, and dried under vacuum at 60°C to obtain Fe3O4@SiO2 powder. 0.5 g of Fe3O4@SiO2 powder was dispersed in 100 mL of deionized water and sonicated for 30 minutes to obtain a dispersion. To prepare the silver-ammonia solution, 2.0 g of silver nitrate was dissolved in 50 mL of water. Concentrated aqueous ammonia was added dropwise with stirring until the initial brown precipitate was dissolved, resulting in a clear silver-ammonia solution. The silver-ammonia solution was mixed with the Fe3O4@SiO2 dispersion and heated to 60°C in a water bath with continuous stirring. The pH of the system was then adjusted to 11 with NaOH solution. 20 mL of a 0.4 mol / L glucose-potassium sodium tartrate solution was quickly added, and the reaction was continued at 60°C for 40 minutes. After the solution turned gray-black, heating was stopped, the product was magnetically separated, washed thoroughly with deionized water and ethanol, and dried in a vacuum at 60 °C to finally obtain Fe3O4@SiO2@Ag composite powder.

[0051] Step 3: Disperse 20g of Fe3O4@SiO2@Ag composite powder in 400mL of a 4:1 ethanol / water mixture and sonicate for 1h to ensure thorough dispersion. Add 1.6g of KH-550 silane coupling agent and stir under reflux at 80°C for 8h. After the reaction, collect the product by centrifugation, wash three times with ethanol to remove physically adsorbed coupling agent, and dry it in a vacuum oven at 60°C.

[0052] 50 g of KH-550-modified particles were dispersed in 500 mL of Tris-HCl buffer (pH 8.5). Then, 3.0 g of dopamine hydrochloride was added and the mixture was stirred at room temperature for 10 hours. After the reaction, the product was collected by centrifugation and repeatedly washed with deionized water until the supernatant was colorless. The product was then dried under vacuum at 60°C.

[0053] The polydopamine-modified particles were dispersed with 4.0 g of PFP-b-PA6 block copolymer in 200 mL of DMF and sonicated for 30 minutes. The mixture was then mechanically stirred at 80°C for 6 hours. The temperature was then raised to 100°C and the DMF solvent was slowly evaporated under reduced pressure on a rotary evaporator. The resulting solid product was further dried in a vacuum oven at 80°C for 12 hours to completely remove any residual solvent, yielding modified composite particles coated with a flexible polymer interfacial layer.

[0054] Step 4: Mix the porous ETFE matrix particles and the modified composite particles in a mass ratio of 80:22. Place the mixture in an internal mixer and perform solid-state shear mixing at 265°C and 30 rpm for 5 minutes. The premix is ​​then fed into a twin-screw extruder for melt blending and pelletization at a temperature of 285°C and a screw speed of 150 rpm to obtain electromagnetic shielding composite particles.

[0055] Step 5: Using a single-screw extruder, extrude the electromagnetic shielding composite material pellets directly onto a silver-plated copper core wire (conductor diameter 0.5 mm) to form the insulating shielding layer. The extruder temperature was set at 285°C and the extrusion speed at 2 m / min, ensuring a uniform layer thickness of 0.3 mm. The extruded cable was cooled in a water-cooling tank and annealed at 100°C for 2 hours to eliminate internal stress.

[0056] Example 5 The preparation method of PFP-b-PA6 block copolymer and KH-550 pretreated nano-SiO2 nucleating agent is the same as that in Example 1.

[0057] Preparation of an electromagnetic shielding cable for a radio altimeter: Step 1: Take 500g of ETFE particles and evenly spread them in the sample chamber of a low-temperature plasma treatment instrument. After sealing, evacuate the system to a pressure of 80 Pa. Use a mixture of argon and acrylic acid with a volume ratio of 9:1 as the treatment gas. Adjust the gas flow rate to stabilize the chamber pressure at 80 Pa. Treat at 400W of radio frequency power for 10 minutes. After completion, remove the treated ETFE particles and place them in a high-speed blender with 2% of the ETFE-g-MAH compatibilizer, 1.5% of the chemical foaming agent OBSH, and 0.5% of the nano-SiO2 nucleating agent pretreated with KH-550. Mix at 800 rpm for 5 minutes at room temperature to obtain a premix. The premix was fed into the main feed port of a twin-screw extruder. The extruder's temperature zones were set at 270°C, 285°C, 295°C, 290°C, and 280°C, respectively, with a screw speed of 200 rpm. Simultaneously, supercritical carbon dioxide was injected into the fourth zone of the barrel via a supercritical fluid injection pump at a controlled injection rate of 0.5 kg / h. After extrusion through the die, the molten blend was immediately passed through a 120°C insulation channel for slow cooling. It then entered a 20°C cold water tank for quenching and shaping, and finally pelletized in a pelletizer to produce porous ETFE matrix particles containing a micro- and nano-scale cellular structure.

[0058] Step 2: Weigh 2.70 g of FeCl₃·6H₂O and dissolve it in 80 mL of ethylene glycol. Stir magnetically until completely dissolved. Then, add 7.20 g of anhydrous sodium acetate and 2.00 g of polyvinylpyrrolidone, sequentially, and continue stirring for 30 minutes to form a homogeneous yellow solution. The mixed solution is transferred to a polytetrafluoroethylene-lined hydrothermal reactor, sealed, and placed in a 200°C forced air drying oven for 10 hours. After cooling to room temperature, the resulting black product is collected using an external magnetic field and washed three times alternately with anhydrous ethanol and deionized water. Finally, dry it in a 60°C vacuum drying oven for 12 hours to obtain spherical Fe₃O₄ particles. 0.5 g of the dried Fe₃O₄ particles is dispersed in a mixture of 200 mL of ethanol and 50 mL of deionized water and treated with ultrasound for 30 minutes. 5 mL of concentrated aqueous ammonia (28 wt%) was then added to the solution. After mechanical stirring for 15 minutes, 2 mL of ethyl orthosilicate was slowly added dropwise using a constant pressure dropping funnel. The reaction was continued at 30°C for 6 hours. After the reaction, the product was magnetically separated, washed three times with ethanol, and dried under vacuum at 60°C to obtain Fe3O4@SiO2 powder. 0.5 g of Fe3O4@SiO2 powder was dispersed in 100 mL of deionized water and sonicated for 30 minutes to obtain a dispersion. To prepare the silver-ammonia solution, 2.0 g of silver nitrate was dissolved in 50 mL of water. Concentrated aqueous ammonia was added dropwise with stirring until the initial brown precipitate was dissolved, resulting in a clear silver-ammonia solution. The silver-ammonia solution was mixed with the Fe3O4@SiO2 dispersion and heated to 60°C in a water bath with continuous stirring. The pH of the system was then adjusted to 11 with NaOH solution. 20 mL of a 0.4 mol / L glucose-potassium sodium tartrate solution was quickly added, and the reaction was continued at 60°C for 40 minutes. After the solution turned gray-black, heating was stopped, the product was magnetically separated, washed thoroughly with deionized water and ethanol, and dried in a vacuum at 60 °C to finally obtain Fe3O4@SiO2@Ag composite powder.

[0059] Step 3: Disperse 20g of Fe3O4@SiO2@Ag composite powder in 400mL of a 4:1 ethanol / water mixture and sonicate for 1h to ensure thorough dispersion. Add 0.6g of KH-550 silane coupling agent and stir under reflux at 80°C for 8h. After the reaction, collect the product by centrifugation, wash three times with ethanol to remove physically adsorbed coupling agent, and dry it in a vacuum oven at 60°C.

[0060] 50 g of KH-550-modified particles were dispersed in 500 mL of Tris-HCl buffer (pH 8.5). Then, 1.0 g of dopamine hydrochloride was added and the mixture was stirred at room temperature for 10 hours. After the reaction, the product was collected by centrifugation and repeatedly washed with deionized water until the supernatant was colorless. The product was then dried under vacuum at 60°C.

[0061] The polydopamine-modified particles were dispersed with 4.0 g of PFP-b-PA6 block copolymer in 200 mL of DMF and sonicated for 30 minutes. The mixture was then mechanically stirred at 80°C for 6 hours. The temperature was then raised to 100°C and the DMF solvent was slowly evaporated under reduced pressure on a rotary evaporator. The resulting solid product was further dried in a vacuum oven at 80°C for 12 hours to completely remove any residual solvent, yielding modified composite particles coated with a flexible polymer interfacial layer.

[0062] Step 4: Mix the porous ETFE matrix particles and the modified composite particles in a mass ratio of 80:18. Place the mixture in an internal mixer and perform solid-state shear mixing at 265°C and 30 rpm for 5 minutes. The premix is ​​then fed into a twin-screw extruder for melt blending and pelletization at a temperature of 285°C and a screw speed of 150 rpm to obtain electromagnetic shielding composite particles.

[0063] Step 5: Using a single-screw extruder, extrude the electromagnetic shielding composite material pellets directly onto a silver-plated copper core wire (conductor diameter 0.5 mm) to form the insulating shielding layer. The extruder temperature was set at 285°C and the extrusion speed at 2 m / min, ensuring a uniform layer thickness of 0.3 mm. The extruded cable was cooled in a water-cooling tank and annealed at 100°C for 2 hours to eliminate internal stress.

[0064] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that step 1 is omitted, that is, the porous ETFE matrix particles in step 4 are replaced by ordinary ETFE matrix particles.

[0065] Comparative Example 2: The difference between Comparative Example 1 and Example 1 is that steps 2 and 3 are omitted, that is, the modified composite particles in step 4 are removed.

[0066] Comparative Example 3: The difference between Comparative Example 1 and Example 1 is that step 3 is omitted, that is, the modified composite particles in step 4 are replaced by Fe3O4@SiO2@Ag composite powder.

[0067] Comparative Example 4: The difference between Comparative Example 1 and Example 1 is that the particles modified with KH-550 in step 3 are not reacted with dopamine hydrochloride, but are directly reacted with the PFP-b-PA6 block copolymer.

[0068] Performance testing: 1. Electromagnetic shielding performance test: Based on the electromagnetic shielding effectiveness test standard in QB / T 18313-2022 "Copper tape for cable shielding", combined with the actual operating frequency band of the radio altimeter (1.2GHz~1.6GHz, belonging to the L band), the "coaxial transmission line method" was used for testing. The cable samples prepared in each embodiment and comparative example were cut into standard specimens with a length of 100mm, and the two ends were connected to coaxial connectors and fixed in a shielding effectiveness test system (including a signal generator, a spectrum analyzer, and a coaxial test fixture); the output power of the signal generator was set to 10dBm, and the "incident signal intensity (E0) without shielding" and the "transmitted signal intensity after cable shielding (E0)" were measured at the three characteristic frequency points of 1.2GHz, 1.4GHz, and 1.6GHz. i )”, according to the formula SE=20lg(E0 / E i Shielding effectiveness was calculated by taking the average of the three frequency points as the final result, expressed in decibels (dB). A larger value indicates better shielding effectiveness. The test results are shown in Table 1.

[0069] 2. Bending Performance Test: Based on the bending performance test method specified in GB / T 14049-2008, "Overhead Insulated Cables of Rated Voltage 10 kV and Below," complete cable samples were tested in actual radio altimeter cable installation scenarios. A 1-meter-long cable specimen was tested using a bending tester with a bend radius set at 5 times the cable's outer diameter. A reciprocating bend (a 90° bend from the initial position to one side, then back to the initial position, and then a 90° bend to the other side) was performed at a rate of 10 times / min. After 100 bends, the insulation shielding layer was inspected for signs of damage, such as cracks or detachment. The electromagnetic shielding effectiveness (EMI) of the bent cables at a frequency of 1.4 GHz was also tested. The change in EMI before and after bending was calculated as: ΔSE = (SE after bending - SE before bending) / SE before bending × 100%. A smaller change indicates better cable bending reliability. The test results are shown in Table 1.

[0070] Table 1: Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an electromagnetic shielding cable for a radio altimeter, characterized in that: The following steps are involved: S1. Treating ethylene-tetrafluoroethylene copolymer particles with a low-temperature plasma using a mixed gas containing acrylic acid, then mixing the treated particles with a compatibilizer, a chemical foaming agent, and a nano-nucleating agent, melt-blending the mixture through a twin-screw extruder, and injecting supercritical carbon dioxide during the extrusion process. After slow cooling and quenching, a three-dimensional porous network structure matrix material containing micro-nano pores is obtained; S2. Using a solvothermal method to synthesize ferroferric oxide magnetic particles as the core, the surface of the core is coated with a silicon dioxide dielectric layer, and then a metallic silver conductive layer is deposited on the surface of the dielectric layer by chemical plating to obtain a ternary core-shell composite particle; S3, reacting the ternary core-shell composite particles with aminopropyltriethoxysilane and a block copolymer in sequence to modify the particle surface to obtain modified composite particles having a flexible polymer interface layer grafted onto the surface; S4, melt-mixing and granulating the three-dimensional porous network structure matrix material and the modified composite particles to obtain an electromagnetic shielding composite material; S5. Extruding the electromagnetic shielding composite material directly onto the conductor through an extruder to form an insulating shielding layer, thereby obtaining the electromagnetic shielding cable.

2. The method for preparing an electromagnetic shielding cable for a radio altimeter according to claim 1, characterized in that: In the step S1, the nano nucleating agent is nano SiO2 pretreated with KH-550.

3. The method for preparing an electromagnetic shielding cable for a radio altimeter according to claim 2, wherein: The amount of the nano nucleating agent added is 0.5-1.5 wt % of the ethylene-tetrafluoroethylene copolymer particles.

4. The method for preparing an electromagnetic shielding cable for a radio altimeter according to claim 1, wherein: In step S3, the mass ratio of the ternary core-shell composite particles to aminopropyltriethoxysilane is 10:0.3-0.

8.

5. The method for preparing an electromagnetic shielding cable for a radio altimeter according to claim 1, wherein: In step S3, the ternary core-shell composite particles are modified with aminopropyltriethoxysilane and then subjected to the following reaction: The ternary core-shell composite particles modified with aminopropyltriethoxysilane are dispersed in a Tris-HCl buffer solution, and then dopamine hydrochloride is added and the reaction is continuously stirred at room temperature. After the reaction is completed, the product is collected by centrifugation and washed with deionized water to obtain the product.

6. The method for preparing an electromagnetic shielding cable for a radio altimeter according to claim 5, characterized in that: The mass ratio of the ternary core-shell composite particles modified with aminopropyltriethoxysilane to dopamine hydrochloride is 10:0.2-0.

6.

7. The method for preparing an electromagnetic shielding cable for a radio altimeter according to claim 1, wherein: In the step S3, the block copolymer is a PFP-b-PA6 block copolymer.

8. The method for preparing an electromagnetic shielding cable for a radio altimeter according to claim 7, characterized in that: The method for preparing the PFP-b-PA6 block copolymer comprises the following steps: S31. Under nitrogen protection, reacting sodium hydride with ε-caprolactam to generate sodium caprolactam, initiating a polymerization reaction, and adding 6-azidohexanoyl chloride as a capping agent to cap the ends after cooling; after the reaction, dissolving the product in hexafluoroisopropanol, precipitating it in cold methanol, washing, and drying to obtain an azide-terminated polycaprolactam prepolymer; S32, reacting perfluorononenyloxybenzenesulfonyl fluoride with propargylamine in acetonitrile, adding N,N-diisopropylethylamine, concentrating after the reaction, precipitating in methanol / water, washing and drying to obtain a fluorine-containing alkyne compound; S33. Dissolve the azide-terminated polycaprolactam prepolymer and the fluorine-containing alkyne compound in DMF, add cuprous bromide and PMDETA, and carry out an azide-alkyne cycloaddition reaction; the reaction solution is purified by a neutral alumina column, then treated with an EDTA aqueous solution or a copper-removing resin, and finally precipitated in methanol / water and dried to obtain a PFP-b-PA6 block copolymer.

9. The method for preparing an electromagnetic shielding cable for a radio altimeter according to claim 1, wherein: In step S4, the mass ratio of the three-dimensional porous network structure matrix material to the modified composite particles is 80:18-22.

10. An electromagnetic shielding cable for a radio altimeter, characterized in that: The method is prepared by any one of claims 1 to 9.

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