A radio frequency microwave test cable and method of making the same

Abstract

The application discloses a radio frequency microwave test cable and a preparation method thereof, and relates to the technical field of cables.The method comprises the following steps: first, an inner conductor is prepared by adopting oxygen-free copper rods through drawing, annealing and electrolytic polishing; then, silane modified nano silicon dioxide is prepared, and modified PI composite resin is obtained through a chemical imidization reaction; then, amino functionalized reduced graphene oxide is added into the modified PI composite resin, and modified PI insulating material is obtained through cross-linking and curing; finally, the insulating material is extruded to be coated on the inner conductor, a copper wire shielding layer is braided after cooling and shaping, and a polyurethane sheath is coated, so that the test cable is prepared.The radio frequency microwave test cable prepared by the application has excellent dielectric properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cables, in particular to a radio frequency microwave test cable and a preparation method thereof. BACKGROUND

[0002] As an indispensable core transmission component in high-frequency signal test systems, radio frequency microwave test cables play an irreplaceable role in multiple key fields such as communication, radar, and electronic measurement. Whether it is the radio frequency performance test of 5G / 6G base stations, the signal transceiver link of military radars, or the connection between electronic measuring instruments (such as oscilloscopes and spectrum analyzers) and the measured devices, it directly determines the reliability of high-frequency signal transmission and the accuracy of test data. The high-frequency signal bands transmitted by such cables usually cover 1GHz-40GHz, and some scenarios even extend to higher frequency bands. The wavelength of signals in this frequency band is extremely short, the anti-interference ability is weak, and the performance of the transmission medium is extremely sensitive. Therefore, the core requirement is not only to ensure the physical path of signal transmission, but also to maximize the integrity of high-frequency signal transmission and minimize signal attenuation and distortion during transmission. Any slight signal loss or waveform distortion may cause test result deviation, communication link error rate increase, or even core device failure.

[0003] As one of the core functional layers of radio frequency microwave test cables, the insulating layer has dual key responsibilities: on the one hand, it needs to achieve reliable electrical isolation between the inner conductor and the external shielding layer to avoid short circuit or electric leakage risks; on the other hand, it needs to provide a stable and uniform medium environment for high-frequency signal transmission. The stability of its dielectric properties (especially dielectric constant and dielectric loss tangent) directly determines the impedance consistency and signal transmission loss of the cable. From a physical principle point of view, the characteristic impedance of the cable is inversely proportional to the square root of the dielectric constant of the insulating layer. A slight fluctuation in the dielectric constant will directly cause impedance deviation, and impedance mismatch will cause signal reflection during transmission, further exacerbating signal attenuation. At the same time, the higher the dielectric constant, the slower the signal transmission speed in the insulating layer, and the signal energy will be more converted into heat energy due to dielectric polarization loss, resulting in increased dielectric loss, which is particularly significant at ultra-high frequency bands, directly limiting the effective transmission distance and signal fidelity of the cable.

[0004] In the prior art, the insulating layer of the radio frequency microwave test cable mostly adopts polyimide (PI) material, which is due to a series of outstanding advantages of the PI material: excellent high-temperature resistance, capable of adapting to extreme working environments such as aerospace and industrial high-temperature testing; excellent mechanical strength, capable of meeting the mechanical stress requirements in the process of cable laying and bending, and not prone to cracking or damage; and good chemical stability, capable of resisting the erosion of common chemical media and prolonging the service life of the cable. However, the intrinsic characteristics of the PI material have obvious shortcomings, and the intrinsic dielectric constant thereof is still relatively high for the low-loss requirement of ultra-high frequency signal transmission, which is difficult to meet the stringent requirements of modern radio frequency microwave test systems on cable impedance consistency, signal transmission rate and low loss, and becomes a core bottleneck restricting the further improvement of the performance of the cable. SUMMARY

[0005] The present application aims to provide a radio frequency microwave test cable and a preparation method thereof to solve the technical problems in the background art. The PI material prepared by the present application has a relatively low dielectric constant.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] A preparation method of a radio frequency microwave test cable, comprising the following steps:

[0008] S1, using an oxygen-free copper rod, after continuous drawing, annealing treatment, and electrolytic polishing, an inner conductor is obtained;

[0009] S2, dispersing nano-silicon dioxide in anhydrous ethanol, adding γ-glycidoxypropyltrimethoxysilane, and performing reflux reaction under acidic conditions, and after the reaction, centrifugation, washing and drying, a silane-modified nano-silicon dioxide is obtained;

[0010] adding the silane-modified nano-silicon dioxide into a DMAc solvent, after dispersion treatment, adding 4,4'-diamino diphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and then adding pyromellitic dianhydride, and generating a PAA hybrid solution under the protection of nitrogen, adding acetic anhydride and isoquinoline to the PAA hybrid solution, and performing chemical imidization reaction, and after deionized water precipitation, washing and drying, a modified PI composite resin is obtained;

[0011] S3, dispersing graphene oxide in deionized water, adding hydrazine hydrate for reflux reduction to obtain reduced graphene oxide; dispersing the reduced graphene oxide in anhydrous ethanol again, adding 3-aminopropyltriethoxysilane for reaction, and after centrifugation, washing and drying, amino-functionalized reduced graphene oxide is obtained;

[0012] After melting the modified PI composite resin, the amino-functionalized reduced graphene oxide is added and stirred and dispersed, then the dianhydride crosslinking agent is added and stirred, and then the modified PI insulating material is obtained after heat curing.

[0013] S4, the modified PI insulating material is extruded and coated on the surface of the inner conductor, and is cooled and shaped to obtain an inner conductor-insulating layer composite; an oxygen-free copper wire is used to coat a shielding layer on the surface of the inner conductor-insulating layer composite by a braiding machine to obtain a core wire-shielding layer composite, and a polyurethane material is extruded and coated on the surface of the core wire-shielding layer composite, and is cooled and shaped to obtain the radio frequency microwave test cable.

[0014] In the technical scheme of the present application, the dielectric constant of the polyimide material of the insulating layer of the radio frequency microwave test cable is reduced in multiple ways. On the one hand, the fluorine group has a very low polarizability, and after being introduced into the PI molecular chain, it can significantly reduce the dielectric contribution of the molecular chain itself, and reduce the dielectric constant caused by polarization from the structural root. On the other hand, the nano-particles modified by silane have a relatively low dielectric constant and a greatly improved compatibility with the PI matrix, and can be uniformly dispersed in the matrix and form a continuous nanoscale low dielectric region, further diluting the overall dielectric strength through spatial distribution optimization. The two mechanisms cooperate with each other, effectively reducing the dielectric constant of the composite resin without damaging the basic properties of the PI matrix, while ensuring the film-forming property and mechanical strength of the material. On the other hand, the amino-functionalized reduced graphene oxide has a super-high specific surface area and a layered structure, and can form a labyrinthine barrier network after being uniformly dispersed in the PI matrix, which can effectively inhibit the charge migration and polarization relaxation process, reduce the dielectric loss and dielectric constant caused by the directional movement of charges; at the same time, the construction of the crosslinking network can fix the PI molecular chain structure, limit the free movement of the molecular chain, and avoid the dielectric property fluctuations caused by the vibration and orientation changes of the molecular chain, further stabilizing and reducing the dielectric constant.

[0015] Preferably, in step S1, the annealing temperature is 320-350°C, and the annealing time is 1-2h.

[0016] Preferably, in step S2, the mass ratio of nano-silicon dioxide to γ-glycidoxypropyltrimethoxysilane is 10:(0.2-0.8).

[0017] Preferably, in step S3, the mass ratio of graphene oxide to hydrazine hydrate is 5:(0.5-1.0).

[0018] Preferably, in step S3, the addition amount of the amino-functionalized reduced graphene oxide is (2-5)wt% of the modified PI composite resin.

[0019] As preferred, in the step S3, after the modified PI composite resin is melted, perfluorohexyl ethyl amino triethoxysilane is added.

[0020] In the technical solution of the present application, through further in-depth research, it is found that the steric hindrance effect of the fluorine-containing group of the modified PI composite resin and the rigid characteristics of the PI molecular chain hinder the full spreading of the amino-functionalized reduced graphene oxide sheet in the molten PI matrix, making it difficult to form a continuous maze-like barrier network, directly weakening the dielectric optimization effect of the amino-functionalized reduced graphene oxide on the cable insulation layer. To further solve this technical problem, perfluorohexyl ethyl amino triethoxysilane is added after the modified PI composite resin is melted, the length of the molecular chain is moderate, and it can fill the space gap between the fluorine-containing group and the amino-functionalized reduced graphene oxide, weaken the steric hindrance of the fluorine-containing group, guide the full spreading of the amino-functionalized reduced graphene oxide sheet in the PI matrix, and form a continuous two-dimensional barrier network, thereby further improving the dielectric properties of the cable.

[0021] As preferred, the amount of perfluorohexyl ethyl amino triethoxysilane added is (1-2) wt% of the modified PI composite resin.

[0022] A radio frequency microwave test cable prepared by the above method.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. By grafting a low-polarizability fluorine-containing group to the polyimide (PI) molecular chain and uniformly dispersing silane-modified nano-silicon dioxide to form a low-dielectric region, the dielectric constant of the insulation material is significantly reduced through the synergistic effect of molecular structure and material composite, thereby improving the high-frequency signal transmission performance of the cable.

[0025] 2. The amino-functionalized reduced graphene oxide has a super-high specific surface area and a layered structure, and can form a maze-like barrier network after being uniformly dispersed in the PI matrix, which can effectively inhibit the charge migration and polarization relaxation process, and reduce the dielectric loss and dielectric constant increase caused by the directional movement of charges.

[0026] 3. By adding perfluorohexyl ethyl amino triethoxysilane as an interface modifier, the steric hindrance caused by the fluorine-containing group is effectively alleviated, the full spreading of the amino-functionalized reduced graphene oxide sheet in the PI matrix and the establishment of a continuous network are promoted, and the dielectric properties of the cable are further improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM image of the surface of the cable insulation layer prepared in Example 4 of the present application.

[0028] Figure 2The XPS spectrum of the cable insulating layer prepared in Example 4 of the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0030] Example 1

[0031] A preparation method of a radio frequency microwave test cable, comprising the following steps:

[0032] Step 1: take oxygen-free copper rods with copper content ≥ 99.99%, process to a diameter of 0.5 mm through a continuous drawing process, put the drawn copper conductor into an annealing furnace, complete annealing treatment at 330℃ for 1.5 h, and then treat the surface by electrolytic polishing process, control the electrolytic polishing voltage at 12 V, the current density at 2 A / dm 2 , and the polishing time at 15 min to obtain an inner conductor.

[0033] Step 2: take nano-silicon dioxide with a particle size of 30 nm, disperse in anhydrous ethanol, and ultrasonically disperse at a power of 350 W for 35 min to obtain a dispersion liquid with a mass fraction of 5%, add γ-glycidoxypropyltrimethoxysilane to the dispersion liquid, the mass ratio of nano-silicon dioxide to γ-glycidoxypropyltrimethoxysilane is 10:0.7, adjust the pH of the system to 5.0 with 0.1 mol / L hydrochloric acid solution, place the mixed system in a reflux device, and reflux at a constant temperature of 80℃ for 2.5 h, after the reaction is completed, centrifuge at a speed of 10000 r / min for 15 min, collect the precipitate, wash with anhydrous ethanol for 4 times, and then dry in a vacuum drying oven at 108℃ for 5 h to obtain silane-modified nano-silicon dioxide.

[0034] The silane-modified nano-silica was added into DMAc solvent according to the mass-volume ratio of 6 g / 500 mL, and ultrasonic dispersion was performed for 45 min. Then, 4,4'-diamino diphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (molar ratio of 7:3) were added in sequence, the mass ratio of 4,4'-diamino diphenyl ether to silane-modified nano-silica was 5:1, the system was controlled to be cooled to 5 ℃, and pyromellitic dianhydride (molar ratio of pyromellitic dianhydride to 4,4'-diamino diphenyl ether was 1:0.7) was added in batches. The PAA hybrid solution was generated after reaction for 6 h under nitrogen protection. Finally, the dehydrating agent and catalyst were prepared according to the mass ratio of acetic anhydride to isoquinoline of 11.5:1 (the mass ratio of acetic anhydride to pyromellitic dianhydride was about 2.1:1), and were added into the system in sequence. The chemical imidization was completed after the temperature was increased to 80 ℃ and heat preservation for 3 h. The obtained glue solution was precipitated, washed, and vacuum dried at 180 ℃ to obtain the modified PI composite resin.

[0035] Step 3: The graphene oxide was dispersed in deionized water, and a uniform GO dispersion with a mass fraction of 0.5% was obtained by ultrasonic dispersion at a power of 450 W for 18 min. Hydrazine hydrate was added to the dispersion, and the mass ratio of graphene oxide to hydrazine hydrate was 5:0.9. The reduction was performed at 98 ℃ under constant temperature reflux for 2.5 h. After the reaction was completed, the precipitate was collected by filtration, washed with deionized water until the filtrate was neutral to obtain reduced graphene oxide (rGO). The rGO was redispersed in anhydrous ethanol according to the mass-volume ratio of 1 g / 100 mL, and 3-aminopropyl triethoxysilane was added. The mass ratio of rGO to 3-aminopropyl triethoxysilane was 5:0.4. The reaction was performed under stirring at a speed of 50 r / min at 85 ℃ for 2.2 h. After the reaction, the mixture was centrifuged, washed with anhydrous ethanol for 3 times, and then vacuum dried at 102 ℃ for 3.5 h to obtain the amino-functionalized rGO.

[0036] The modified PI composite resin was added into a reaction kettle, the temperature was set to 350 ℃, and after the resin was completely melted, the amino-functionalized rGO with a mass of 4% of the resin and the perfluorohexylethylaminotriethoxysilane with a mass of 1.8 wt% of the resin were added through a side feeding port. The stirring speed was controlled to be 300 r / min, and the stirring and dispersion were performed for 35 min. Then, the crosslinking agent pyromellitic dianhydride with a mass of 4% of the resin was added, and the stirring was continuously performed at a speed of 300 r / min for 18 min. Then, the barrel temperature was maintained at 290 ℃ for heat curing for 1.2 h to obtain the modified PI insulating material.

[0037] Step 4: The modified PI insulation material is added to a single screw extruder, and the barrel temperature is set to 280°C at the feeding port, 300°C at the middle section, 310°C at the rear section, and 320°C at the head. The pretreated inner conductor is introduced into the head as a core wire, and the pulling speed is controlled at 2.5 m / min to uniformly extrude the insulation material on the surface of the inner conductor. Then, the inner conductor-insulation layer composite is cooled and shaped by a water cooling device at 25°C. A 0.09 mm diameter oxygen-free copper wire is selected, and the inner conductor-insulation layer composite is coated with a shielding layer by a braiding machine. The braiding density is controlled at 96%, the tension is maintained at 6N during the coating process, and the braiding speed is consistent with the pulling speed in the insulation layer forming stage (2.5 m / min). Finally, the core wire-shielding layer composite is formed. Polyurethane material is selected as the outer sheath raw material and added to a single screw extruder. The barrel temperature is set to 140°C at the feeding port, 160°C at the middle section, 170°C at the rear section, and 180°C at the head. The core wire-shielding layer composite is introduced into the head, and the pulling speed is controlled at 2.5 m / min to uniformly extrude the PU material on the surface of the shielding layer. Then, the RF microwave test cable coated with an outer sheath is obtained by cooling and shaping the shielding layer with an air cooling device.

[0038] Example 2

[0039] A method for preparing a RF microwave test cable, comprising the following steps:

[0040] Step 1: An oxygen-free copper rod with a copper content of ≥99.99% is processed into a diameter of 0.5 mm by a continuous drawing process. The drawn copper conductor is placed in an annealing furnace and annealed at 330°C for 1.5 h. Then, the surface is treated by electrolytic polishing process, with an electrolytic polishing voltage of 12V, a current density of 2A / dm 2 , and a polishing time of 15 min to obtain an inner conductor.

[0041] Step 2: Nanosilica with a particle size of 30 nm is dispersed in anhydrous ethanol, and an ultrasonic dispersion is obtained at a power of 350W for 35 min to obtain a dispersion liquid with a mass fraction of 5%. γ-glycidoxypropyltrimethoxysilane is added to the dispersion liquid, and the mass ratio of nanosilica to γ-glycidoxypropyltrimethoxysilane is 10:0.3. The pH of the system is adjusted to 5.0 with 0.1 mol / L hydrochloric acid solution. The mixed system is placed in a reflux device and refluxed at 80°C for 2.5 h. After the reaction is completed, centrifugal separation is performed at a speed of 10000 r / min for 15 min. The precipitate is washed with anhydrous ethanol for 4 times, and then dried in a vacuum drying oven at 108°C for 5 h to obtain silane-modified nanosilica.

[0042] The silane-modified nano-silica was added into DMAc solvent in a mass-volume ratio of 6 g / 500 mL, and ultrasonic dispersion was performed for 45 min. Then, 4,4'-diamino diphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (molar ratio of 7:3) were added in sequence, the mass ratio of 4,4'-diamino diphenyl ether to silane-modified nano-silica was 5:1, the system was controlled to be cooled to 5 ℃, and pyromellitic dianhydride (molar ratio of pyromellitic dianhydride to 4,4'-diamino diphenyl ether was 1:0.7) was added in batches. The PAA hybrid solution was generated after reaction for 6 h under nitrogen protection. Finally, a dehydrating agent and a catalyst were prepared in a mass ratio of acetic anhydride to isoquinoline of 11.5:1 (the mass ratio of acetic anhydride to pyromellitic dianhydride was about 2.1:1), which were added to the system in sequence, and the chemical imidization was completed after being heated to 80 ℃ for 3 h. The obtained glue solution was precipitated, washed with deionized water, and vacuum dried at 180 ℃ to obtain a modified PI composite resin.

[0043] Step 3: The graphene oxide was dispersed in deionized water, and a uniform GO dispersion with a mass fraction of 0.5% was obtained by ultrasonic dispersion at a power of 450 W for 18 min. Hydrazine hydrate was added to the dispersion, and the mass ratio of graphene oxide to hydrazine hydrate was 5:0.6. The reduction was performed at 98 ℃ for 2.5 h. After the reaction was completed, the precipitate was collected by filtration, washed with deionized water until the filtrate was neutral to obtain reduced graphene oxide (rGO). The rGO was re-dispersed in anhydrous ethanol in a mass-volume ratio of 1 g / 100 mL, and 3-aminopropyl triethoxysilane was added. The mass ratio of rGO to 3-aminopropyl triethoxysilane was 5:0.4. The reaction was performed at 85 ℃ with stirring at a speed of 50 r / min for 2.2 h. After the reaction, the mixture was centrifuged and washed with anhydrous ethanol for 3 times. Then, the mixture was vacuum dried at 102 ℃ for 3.5 h to obtain amino-functionalized rGO.

[0044] The modified PI composite resin was added into a reaction kettle, and the temperature was set to 350 ℃. After the resin was completely melted, amino-functionalized rGO with a mass of 3% of the resin and perfluorohexylethylaminotriethoxysilane with a mass of 1.2 wt% of the resin were added through a side feeding port. The stirring speed was controlled to be 300 r / min, and the stirring and dispersion were performed for 35 min. Then, the crosslinking agent pyromellitic dianhydride with a mass of 4% of the resin was added, and the stirring was continuously performed at a speed of 300 r / min for 18 min. Then, the barrel temperature was maintained at 290 ℃ for 1.2 h for curing to obtain a modified PI insulating material.

[0045] Step 4: The modified PI insulation material is added to a single screw extruder, the barrel temperature is set to 280°C at the feeding port, 300°C at the middle section, 310°C at the rear section, and 320°C at the head, the pretreated inner conductor is introduced into the head as a core wire, the pulling speed is controlled to be 2.5 m / min, the insulation material is uniformly extruded on the surface of the inner conductor, and then cooled and shaped by a water cooling device at 25°C to obtain an inner conductor-insulation layer composite. A diameter of 0.09 mm of oxygen-free copper wire is selected, and the inner conductor-insulation layer composite is coated with a shielding layer by a braiding machine, the braiding density is controlled to be 96%, the tension is kept at 6N during the coating process, the braiding speed is consistent with the pulling speed in the insulation layer forming stage (2.5 m / min), and finally a core wire-shielding layer composite is formed. Polyurethane material is selected as the outer sheath raw material, which is added to a single screw extruder, the barrel temperature is set to 140°C at the feeding port, 160°C at the middle section, 170°C at the rear section, and 180°C at the head, the core wire-shielding layer composite is introduced into the head, the pulling speed is controlled to be 2.5 m / min, the PU material is uniformly extruded on the surface of the shielding layer, and then cooled and shaped by an air cooling device to obtain a radio frequency microwave test cable coated with an outer sheath.

[0046] Example 3

[0047] A preparation method of a radio frequency microwave test cable, comprising the following steps:

[0048] Step 1: An oxygen-free copper rod with a copper content of ≥99.99% is processed into a diameter of 0.5 mm by a continuous drawing process, the drawn copper conductor is placed in an annealing furnace, annealing treatment is completed at 330°C for 1.5 h, and then the surface is treated by an electrolytic polishing process, the electrolytic polishing voltage is controlled to be 12V, the current density is controlled to be 2A / dm 2 , the polishing time is 15 min, and an inner conductor is obtained.

[0049] Step 2: Nanometer silicon dioxide with a particle size of 30 nm is dispersed in anhydrous ethanol, ultrasonic dispersion is performed at 350W power for 35 min to obtain a dispersion liquid with a mass fraction of 5%, γ-glycidoxypropyltrimethoxysilane is added to the dispersion liquid, the mass ratio of nanometer silicon dioxide to γ-glycidoxypropyltrimethoxysilane is 10:0.5, 0.1 mol / L hydrochloric acid solution is used to adjust the pH of the system to 5.0, the mixed system is placed in a reflux device, and reflux reaction is performed at 80°C for 2.5 h, after the reaction is completed, centrifugal separation is performed at a speed of 10000 r / min for 15 min, the precipitate is washed with anhydrous ethanol for 4 times, and then dried in a vacuum drying oven at 108°C for 5 h to obtain silane modified nanometer silicon dioxide.

[0050] The silane-modified nano-silica was added into DMAc solvent according to the mass-volume ratio of 6 g / 500 mL, and ultrasonic dispersion was performed for 45 min. Then, 4,4'-diamino diphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (molar ratio of 7:3) were added in sequence, the mass ratio of 4,4'-diamino diphenyl ether to silane-modified nano-silica was 5:1, the system was controlled to be cooled to 5 ℃, and pyromellitic dianhydride (molar ratio of pyromellitic dianhydride to 4,4'-diamino diphenyl ether was 1:0.7) was added in batches. The PAA hybrid solution was generated after reaction for 6 h under nitrogen protection. Finally, the dehydrating agent and catalyst were prepared according to the mass ratio of acetic anhydride to isoquinoline of 11.5:1 (the mass ratio of acetic anhydride to pyromellitic dianhydride was about 2.1:1), and were added into the system in sequence. The chemical imidization was completed after the temperature was increased to 80 ℃ and heat preservation for 3 h. The obtained glue solution was precipitated, washed with deionized water, and vacuum dried at 180 ℃ to obtain the modified PI composite resin.

[0051] Step 3: The graphene oxide was dispersed in deionized water, and a uniform GO dispersion with a mass fraction of 0.5% was obtained by ultrasonic dispersion at a power of 450 W for 18 min. Hydrazine hydrate was added to the dispersion, and the mass ratio of graphene oxide to hydrazine hydrate was 5:0.7. The reduction was performed at 98 ℃ under constant temperature reflux for 2.5 h. After the reaction was completed, the precipitate was collected by filtration, washed with deionized water until the filtrate was neutral to obtain reduced graphene oxide (rGO). The rGO was redispersed in anhydrous ethanol according to the mass-volume ratio of 1 g / 100 mL, and 3-aminopropyl triethoxysilane was added. The mass ratio of rGO to 3-aminopropyl triethoxysilane was 5:0.4. The reaction was performed at 85 ℃ under stirring at a speed of 50 r / min for 2.2 h. After the reaction, the mixture was centrifuged, washed with anhydrous ethanol for 3 times, and vacuum dried at 102 ℃ for 3.5 h to obtain the amino-functionalized rGO.

[0052] The modified PI composite resin was added into a reaction kettle, the temperature was set to 350 ℃, and after the resin was completely melted, the amino-functionalized rGO with a mass of 3.5% of the resin and the perfluorohexylethylaminotriethoxysilane with a mass of 1.5 wt% of the resin were added through a side feeding port. The stirring speed was controlled to be 300 r / min, and stirring and dispersion were performed for 35 min. Then, the crosslinking agent pyromellitic dianhydride with a mass of 4% of the resin was added, and the stirring was continuously performed at a speed of 300 r / min for 18 min. Then, the barrel temperature was maintained at 290 ℃ for heat curing for 1.2 h to obtain the modified PI insulating material.

[0053] Step 4: The modified PI insulation material is added to a single screw extruder, the barrel temperature is set to 280℃ at the feeding port, 300℃ at the middle section, 310℃ at the rear section, and 320℃ at the head, the pretreated inner conductor is introduced into the head as a core wire, the pulling speed is controlled to be 2.5 m / min, the insulation material is uniformly extruded on the surface of the inner conductor, and then cooled and shaped by a water cooling device at 25℃, to obtain an inner conductor-insulation layer composite. A diameter of 0.09 mm oxygen-free copper wire is selected, and the inner conductor-insulation layer composite is coated with a shielding layer by a braiding machine, the braiding density is controlled to be 96%, the tension is kept at 6N during the coating process, the braiding speed is consistent with the pulling speed in the insulation layer forming stage (2.5 m / min), and finally a core wire-shielding layer composite is formed. Polyurethane material is selected as the outer sheath raw material, added to a single screw extruder, the barrel temperature is set to 140℃ at the feeding port, 160℃ at the middle section, 170℃ at the rear section, and 180℃ at the head, the core wire-shielding layer composite is introduced into the head, the pulling speed is controlled to be 2.5 m / min, the PU material is uniformly extruded on the surface of the shielding layer, and then cooled and shaped by an air cooling device, to obtain a radio frequency microwave test cable coated with an outer sheath.

[0054] Example 4

[0055] A preparation method of a radio frequency microwave test cable, comprising the following steps:

[0056] Step 1: An oxygen-free copper rod with a copper content of ≥99.99% is processed into a diameter of 0.5 mm by a continuous drawing process, the drawn copper conductor is placed into an annealing furnace, annealing treatment is completed at 320℃ for 2 h, and then the surface is treated by an electrolytic polishing process, the electrolytic polishing voltage is controlled to be 12V, the current density is controlled to be 2A / dm 2 , the polishing time is 15 min, and an inner conductor is obtained.

[0057] Step 2: Nanometer silicon dioxide with a particle size of 30 nm is dispersed in anhydrous ethanol, an ultrasonic dispersion is obtained at a power of 350W for 35 min, the mass fraction of the dispersion is 5%, γ-glycidoxypropyltrimethoxysilane is added to the dispersion, the mass ratio of nanometer silicon dioxide to γ-glycidoxypropyltrimethoxysilane is 10:0.8, the pH of the system is adjusted to 5.0 by using a 0.1 mol / L hydrochloric acid solution, the mixed system is placed in a reflux device, and reflux reaction is performed at a constant temperature of 80℃ for 2.5 h, after the reaction is completed, centrifugal separation is performed at a speed of 10000 r / min for 15 min, the precipitate is washed with anhydrous ethanol for 4 times, and then dried in a vacuum drying oven at 108℃ for 5 h, to obtain silane modified nanometer silicon dioxide.

[0058] The silane-modified nano-silica was added into the DMAc solvent in a mass-volume ratio of 6 g / 500 mL, and ultrasonic dispersion was performed for 45 min. Then, 4,4'-diamino diphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (molar ratio of 7:3) were added in sequence, the mass ratio of 4,4'-diamino diphenyl ether to silane-modified nano-silica was 5:1, the system was controlled to be cooled to 5°C, and phthalic anhydride (molar ratio of phthalic anhydride to 4,4'-diamino diphenyl ether was 1:0.7) was added in batches. The PAA hybrid solution was generated after reaction for 6 h under nitrogen protection. Finally, the dehydrating agent and catalyst were prepared in a mass ratio of acetic anhydride to isoquinoline of 11.5:1 (the mass ratio of acetic anhydride to phthalic anhydride was about 2.1:1), and were added into the system in sequence. The temperature was increased to 80°C, and chemical imidization was completed after holding for 3 h. The obtained glue solution was precipitated, washed, and vacuum dried at 180°C to obtain the modified PI composite resin.

[0059] Step 3: The graphene oxide was dispersed in deionized water, and a uniform GO dispersion with a mass fraction of 0.5% was obtained by ultrasonic dispersion at a power of 450 W for 18 min. Hydrazine hydrate was added to the dispersion, and the mass ratio of graphene oxide to hydrazine hydrate was 5:1.0. The reduction was carried out at 98°C under constant temperature reflux for 2.5 h. After the reaction was completed, the precipitate was collected by filtration, and washed with deionized water until the filtrate was neutral to obtain reduced graphene oxide (rGO). The rGO was redispersed in anhydrous ethanol in a mass-volume ratio of 1 g / 100 mL, and 3-aminopropyl triethoxysilane was added. The mass ratio of rGO to 3-aminopropyl triethoxysilane was 5:0.4. The reaction was carried out at 85°C under stirring at a speed of 50 r / min for 2.2 h. After the reaction, the mixture was centrifuged, washed with anhydrous ethanol for 3 times, and vacuum dried at 102°C for 3.5 h to obtain the amino-functionalized rGO.

[0060] The modified PI composite resin was added into a reaction kettle, the temperature was set to 350°C, and after the resin was completely melted, amino-functionalized rGO with a mass of 5% of the resin and perfluorohexylethylaminotriethoxysilane with a mass of 2 wt% of the resin were added through a side feeding port. The stirring speed was controlled at 300 r / min, and stirring and dispersion were performed for 35 min. Then, the crosslinking agent phthalic anhydride with a mass of 4% of the resin was added, and the stirring was continued at a speed of 300 r / min for 18 min. Then, the barrel temperature was maintained at 290°C for 1.2 h for curing to obtain the modified PI insulating material.

[0061] Step 4: The modified PI insulation material is added to a single screw extruder, the barrel temperature is set to 280°C at the feeding port, 300°C at the middle section, 310°C at the rear section, and 320°C at the head, the pretreated inner conductor is introduced into the head as a core wire, the pulling speed is controlled to be 2.5 m / min, the insulation material is uniformly extruded on the surface of the inner conductor, and then cooled and shaped by a water cooling device at 25°C to obtain an inner conductor-insulation layer composite. A diameter of 0.09 mm of oxygen-free copper wire is selected, and the inner conductor-insulation layer composite is coated with a shielding layer by a braiding machine, the braiding density is controlled to be 96%, the tension is kept at 6N during the coating process, the braiding speed is consistent with the pulling speed in the insulation layer forming stage (2.5 m / min), and finally a core wire-shielding layer composite is formed. The polyurethane material is selected as the outer sheath raw material, which is added to a single screw extruder, the barrel temperature is set to 140°C at the feeding port, 160°C at the middle section, 170°C at the rear section, and 180°C at the head, the core wire-shielding layer composite is introduced into the head, the pulling speed is controlled to be 2.5 m / min, the PU material is uniformly extruded on the surface of the shielding layer, and then cooled and shaped by an air cooling device to obtain a radio frequency microwave test cable coated with an outer sheath.

[0062] Example 5

[0063] A preparation method of a radio frequency microwave test cable, comprising the following steps:

[0064] Step 1: An oxygen-free copper rod with a copper content of ≥99.99% is processed into a diameter of 0.5 mm by a continuous drawing process, the drawn copper conductor is placed into an annealing furnace, annealing treatment is completed at 350°C for 1 h, and then the surface is treated by an electrolytic polishing process, the electrolytic polishing voltage is controlled to be 12V, the current density is controlled to be 2A / dm 2 , the polishing time is 15 min, and an inner conductor is obtained.

[0065] Step 2: Nanometer silicon dioxide with a particle size of 30 nm is dispersed in anhydrous ethanol, ultrasonic dispersion is performed at 350W for 35 min to obtain a dispersion liquid with a mass fraction of 5%, γ-glycidoxypropyltrimethoxysilane is added to the dispersion liquid, the mass ratio of nanometer silicon dioxide to γ-glycidoxypropyltrimethoxysilane is 10:0.2, 0.1 mol / L hydrochloric acid solution is used to adjust the pH of the system to 5.0, the mixed system is placed in a reflux device, constant temperature reflux reaction is performed at 80°C for 2.5 h, after the reaction is completed, centrifugal separation is performed at a speed of 10000 r / min for 15 min, the precipitate is washed with anhydrous ethanol for 4 times, and then dried in a vacuum drying oven at 108°C for 5 h to obtain silane modified nanometer silicon dioxide.

[0066] The silane-modified nano-silica was added into DMAc solvent according to the mass-volume ratio of 6 g / 500 mL, and ultrasonic dispersion was performed for 45 min. Then, 4,4'-diamino diphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (molar ratio of 7:3) were added in sequence, the mass ratio of 4,4'-diamino diphenyl ether to silane-modified nano-silica was 5:1, the system was controlled to be cooled to 5 ℃, and pyromellitic dianhydride (molar ratio of pyromellitic dianhydride to 4,4'-diamino diphenyl ether was 1:0.7) was added in batches. The PAA hybrid solution was generated after reaction for 6 h under nitrogen protection. Finally, the dehydrating agent and catalyst were prepared according to the mass ratio of acetic anhydride to isoquinoline of 11.5:1 (the mass ratio of acetic anhydride to pyromellitic dianhydride was about 2.1:1), and were added into the system in sequence. The chemical imidization was completed after the temperature was increased to 80 ℃ and heat preservation for 3 h. The obtained glue solution was precipitated, washed, and vacuum dried at 180 ℃ to obtain the modified PI composite resin.

[0067] Step 3: The graphene oxide was dispersed in deionized water, and a uniform GO dispersion with a mass fraction of 0.5% was obtained by ultrasonic dispersion at a power of 450 W for 18 min. Hydrazine hydrate was added to the dispersion, and the mass ratio of graphene oxide to hydrazine hydrate was 5:0.5. The reduction was performed at 98 ℃ under constant temperature reflux for 2.5 h. After the reaction was completed, the precipitate was collected by filtration, washed with deionized water until the filtrate was neutral to obtain reduced graphene oxide (rGO). The rGO was redispersed in anhydrous ethanol according to the mass-volume ratio of 1 g / 100 mL, and 3-aminopropyl triethoxysilane was added. The mass ratio of rGO to 3-aminopropyl triethoxysilane was 5:0.4. The reaction was performed at 85 ℃ under stirring at a speed of 50 r / min for 2.2 h. After the reaction, the mixture was centrifuged, washed with anhydrous ethanol for 3 times, and vacuum dried at 102 ℃ for 3.5 h to obtain the amino-functionalized rGO.

[0068] The modified PI composite resin was added into a reaction kettle, the temperature was set to 350 ℃, and after the resin was completely melted, the amino-functionalized rGO with a mass of 2% of the resin and perfluorohexylethylaminotriethoxysilane with a mass of 1 wt% of the resin were added through a side feeding port. The stirring speed was controlled to be 300 r / min, and the stirring and dispersion were performed for 35 min. Then, the crosslinking agent pyromellitic dianhydride with a mass of 4% of the resin was added, and the stirring was continuously performed at a speed of 300 r / min for 18 min. After that, the barrel temperature was maintained at 290 ℃ for heat curing for 1.2 h to obtain the modified PI insulating material.

[0069] Step 4: The modified PI insulating material was added into a single screw extruder, and the barrel temperature was set to 280°C at the feeding port, 300°C at the middle section, 310°C at the rear section, and 320°C at the head. The pre-processed inner conductor was introduced into the head as a core wire, and the pulling speed was controlled at 2.5 m / min to make the insulating material uniformly extruded on the surface of the inner conductor. Then, the inner conductor-insulating layer composite was cooled and shaped by a water cooling device at 25°C. A copper wire with a diameter of 0.09 mm was selected, and the inner conductor-insulating layer composite was coated with a shielding layer by a braiding machine. The braiding density was controlled at 96%, and the tension was maintained at 6 N during the coating process. The braiding speed was consistent with the pulling speed in the insulating layer forming stage (2.5 m / min). Finally, the core wire-shielding layer composite was formed. Polyurethane material was selected as the outer sheath raw material, which was added into a single screw extruder. The barrel temperature was set to 140°C at the feeding port, 160°C at the middle section, 170°C at the rear section, and 180°C at the head. The core wire-shielding layer composite was introduced into the head, and the pulling speed was controlled at 2.5 m / min to make the PU material uniformly extruded on the surface of the shielding layer. Then, the RF microwave test cable coated with an outer sheath was cooled and shaped by an air cooling device.

[0070] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that step 2 is omitted in the cable preparation process, and the modified PI composite resin in step 3 is replaced by an equal amount of polyimide resin.

[0071] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the amino-functionalized rGO in step 3 is replaced by an equal amount of graphene oxide in the cable preparation process.

[0072] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that perfluorohexylethylaminotriethoxysilane is not added in step 3 in the cable preparation process.

[0073] Performance Test:

[0074] 1. Insulating layer dielectric constant and dielectric loss tangent test: The parallel plate capacitor method was used to test. A circular sample with a thickness of 0.2 mm and a diameter of 20 mm was peeled off from the cable insulating layer. The dielectric constant (εr) and dielectric loss tangent (tan δ) were measured by a precision dielectric constant tester at 25°C and 1 MHz frequency. Each sample was tested 3 times, and the average value was taken. The test results are shown in Table 1.

[0075] 2. Signal transmission loss test at 40 GHz: The insertion loss method was used, and the network analyzer was used to measure the signal transmission loss of a 10 m long cable at 40 GHz frequency, with the unit of dB / m. The test environment temperature was 25°C, and the relative humidity was 50%. Each sample was tested 3 times, and the average value was taken. The test results are shown in Table 1.

[0076] 3. Cut dumbbell type I sample (25mm gauge, 4mm width) from the insulation layer, and test the tensile strength and elongation at break using a universal material testing machine at a tensile speed of 5mm / min. Test each sample 5 times and take the average. The test results are shown in Table 1.

[0077] 4. Dielectric property temperature stability test: Place the insulation layer sample in a high-low temperature test chamber, and measure εr at -55℃, -35℃, -15℃, 5℃, 25℃, 45℃, 65℃, 85℃, 105℃, 125℃, 150℃, respectively, after 30min of incubation. Calculate the maximum fluctuation value of the dielectric constant in the full temperature range, and the fluctuation value = (maximum value - minimum value) / average value x 100%. The test results are shown in Table 1.

[0078] Table 1:

[0079]

[0080] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can make modifications to the technical solutions described in the foregoing embodiments, or make equivalent replacements to some of the technical features, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for manufacturing an RF microwave test cable, characterized in that, Includes the following steps: S1. Using oxygen-free copper rod, after continuous drawing, it undergoes annealing treatment and then electrolytic polishing to obtain the inner conductor; S2. Disperse nano-silica in anhydrous ethanol, add γ-glycidoxypropyltrimethoxysilane, and reflux under acidic conditions. After the reaction, centrifuge, wash and dry to obtain silane-modified nano-silica. Silane-modified nano-silica was added to DMAc solvent and dispersed. Then, 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane were added, followed by the addition of pyromellitic dianhydride. The reaction was carried out under nitrogen protection to generate a PAA hybrid solution. Acetic anhydride and isoquinoline were added to the PAA hybrid solution to carry out a chemical imidization reaction. After precipitation with deionized water, washing and drying, the modified PI composite resin was obtained. S3. Graphene oxide is dispersed in deionized water, and hydrazine hydrate is added for reflux reduction to obtain reduced graphene oxide. It was redispersed in anhydrous ethanol, and 3-aminopropyltriethoxysilane was added to carry out the reaction. After the reaction, it was centrifuged, washed and dried to obtain amino-functionalized reduced graphene oxide. After the modified PI composite resin is melted, amino-functionalized reduced graphene oxide is added and stirred to disperse it. Then, the crosslinking agent pyromellitic dianhydride is added and stirred again. Subsequently, it is kept warm and cured to obtain the modified PI insulating material. S4. The modified PI insulating material is extruded and coated onto the surface of the inner conductor, and then cooled and shaped to obtain an inner conductor-insulating layer composite. Using oxygen-free copper wire, a shielding layer is wrapped around the surface of the inner conductor-insulation layer composite using a braiding machine to obtain a core wire-shielding layer composite. Polyurethane material is then extruded and wrapped around the surface of the core wire-shielding layer composite. After cooling and shaping, an RF microwave test cable is obtained.

2. The method for preparing an RF microwave test cable according to claim 1, characterized in that, In step S1, the annealing temperature is 320–350°C and the annealing time is 1–2 hours.

3. The method for preparing an RF microwave test cable according to claim 1, characterized in that, In step S2, the mass ratio of nano-silica to γ-glycidoxypropyltrimethoxysilane is 10:(0.2-0.8).

4. The method for preparing an RF microwave test cable according to claim 1, characterized in that, In step S3, the mass ratio of graphene oxide to hydrazine hydrate is 5:(0.5-1.0).

5. The method for preparing an RF microwave test cable according to claim 1, characterized in that, In step S3, the amount of amino-functionalized reduced graphene oxide added is (2-5) wt% of the modified PI composite resin.

6. The method for preparing an RF microwave test cable according to claim 1, characterized in that, In step S3, perfluorohexylethylaminotriethoxysilane is added after the modified PI composite resin is melted.

7. The method for preparing an RF microwave test cable according to claim 6, characterized in that, The amount of perfluorohexylethylaminotriethoxysilane added is (1-2) wt% of the modified PI composite resin.

8. A radio frequency microwave test cable, characterized in that, It is prepared by the method described in any one of claims 1-7.

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