A polytetrafluoroethylene film for aerospace cable wrapping and a method of manufacturing the same

Abstract

This invention discloses a polytetrafluoroethylene (PTFE) film for wrapping aerospace cables and its preparation method, belonging to the field of PTFE film technology. The invention uses dispersed-grade PTFE resin as raw material, and obtains the target product through raw material tape forming, two-step differentiated argon plasma activation, perfluorinated (2-naphthoxypropyl vinyl ether) grafting, and sintering. This invention achieves the directional and controllable generation of crosslinking active sites by directionally activating the grafted perfluoronaphthalene rings of the side chains using low-power secondary plasma, without destroying the bulk crystalline structure of PTFE. The resulting film fully retains the low dielectric insulation properties of pure PTFE, while simultaneously improving high-temperature creep resistance, ionizing radiation resistance, and interlayer bonding performance, making it suitable for the extreme service requirements of aerospace cables.

Description

Technical Field

[0001] This invention relates to the field of polytetrafluoroethylene (PTFE) film technology, and more particularly to a PTFE film for wrapping aerospace cables and its preparation method. Background Technology

[0002] Polytetrafluoroethylene (PTFE), with its extremely low dielectric constant and dielectric loss, stable dielectric properties over a wide temperature range, excellent chemical inertness, and intrinsic flame retardant characteristics, has become the core substrate for insulation layers in aerospace cables. Currently, the mainstream manufacturing process for aerospace-grade PTFE wrapping films is the paste extrusion calendering method. The resulting raw material tape is wrapped and then sintered at high temperature to fuse the interlayers, forming a dense insulation layer. PTFE film wrapping insulation structures are widely used in high-end applications such as aviation installation cables, coaxial cables, high-temperature conductors, and aerospace environment wiring, and are a key material for ensuring the integrity of signal transmission and long-term reliability of aerospace electrical systems.

[0003] However, the molecular structure of PTFE exposes several unavoidable performance shortcomings in the extreme service environments of aerospace. PTFE molecules have a linear helical configuration with extremely weak intermolecular forces. Under long-term loads, they are prone to relative slippage and deentanglement of molecular chains, exhibiting significant creep behavior, the so-called "cold flow" phenomenon. This defect is further amplified in the high-temperature service scenarios of aerospace cables. When the cable operating temperature is consistently above 200°C, the thermal motion of the molecular chain segments in the amorphous region of PTFE intensifies. Under continuous stress, the wrapping layer undergoes irreversible thinning and interlayer misalignment, leading to a decrease in dielectric strength and, in severe cases, insulation breakdown failure. Furthermore, PTFE is extremely sensitive to ionizing radiation. Under high-energy electron, proton, and atomic oxygen irradiation in the space environment, the molecular backbone is prone to chain breakage and degradation, resulting in a sharp deterioration in mechanical properties. Studies have shown that PTFE's mechanical properties significantly decrease after receiving even extremely low doses of ionizing radiation in air, severely limiting its application in irradiated environments. The erosive effect of atomic oxygen on PTFE is also significant. After atomic oxygen irradiation, the surface roughness of PTFE increases, the mass loss increases, and the integrity and sealing of the insulation layer are damaged.

[0004] At the wrapping process level, the overlap interface after wrapping with pure PTFE film can only achieve physical adhesion through intermolecular van der Waals forces during sintering. This physically bonded interlayer interface is prone to delamination under thermal cycling and mechanical vibration conditions, and cannot effectively prevent spatial atomic oxygen and water vapor from penetrating into the interior along microscopic gaps, accelerating the aging and failure of the cable insulation layer. Simultaneously, PTFE film exhibits a certain degree of thermal shrinkage during sintering; the effective contact area of ​​the wrapping overlap interface decreases under high-temperature shrinkage, further weakening the interlayer bonding strength and the overall sealing performance of the insulation structure.

[0005] To address the aforementioned shortcomings, existing technologies primarily focus on two directions for improvement. First, inorganic particle-filled modification involves adding fillers such as glass fiber, graphite, silica, and graphene to the PTFE matrix to enhance creep resistance and wear resistance. However, PTFE resin particles have extremely low surface energy and poor interfacial compatibility with inorganic fillers, making uniform dispersion and agglomeration difficult. Furthermore, the lack of effective chemical bonding between the filler and the matrix leads to interfacial debonding during long-term service, resulting in a continuous decline in the modification effect. Second, multilayer composite structure design involves stacking PTFE films with high-temperature resistant materials such as polyimide (PI) to improve overall performance through structural assembly. However, this approach is essentially a simple physical layering, with the risk of interlayer delamination remaining. Additionally, the introduced PI layer increases the overall dielectric constant, affecting the transmission characteristics of high-frequency signals. Therefore, there is an urgent need to develop a modification scheme that can simultaneously address the core issues of high-temperature creep, radiation degradation, and insufficient interlayer bonding at the molecular level, without sacrificing the low dielectric advantage of PTFE. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a polytetrafluoroethylene film for wrapping aerospace cables and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a polytetrafluoroethylene film for wrapping aerospace cables, comprising the following steps:

[0008] (1) Mix the dispersion-grade polytetrafluoroethylene resin and the extrusion aid evenly, seal and cure at 30-35℃ for 24-36h to obtain a paste-like mixture;

[0009] (2) The paste mixture is cold-pressed into a cylindrical blank, extruded into a uniform thick sheet by an extruder, and then gradually calendered to a thickness of 0.05-0.12 mm by a multi-roll calendering unit to obtain PTFE raw material strip;

[0010] (3) The PTFE raw material tape is fed into the continuous roll-to-roll low temperature plasma reaction chamber and plasma treatment is carried out in an argon atmosphere to obtain the activated raw material tape;

[0011] (4) The activated raw material tape is transferred to the grafting tank under inert gas protection throughout the process, and immersed in a perfluoroalkane solution of perfluoro(2-naphthoxypropyl vinyl ether) for 3-8 min at 35-50℃ to obtain the grafted raw material tape.

[0012] (5) The grafted raw material tape is washed by countercurrent spraying of perfluoroalkane and then vacuum dried at 40-50℃ to obtain the grafted modified raw material tape.

[0013] (6) The grafted modified raw material tape is fed back into the continuous roll-to-roll low temperature plasma reaction chamber and plasma treatment is carried out in an argon atmosphere to obtain a secondary activated raw material tape.

[0014] (7) The secondary activated raw material belt is fed into a three-stage continuous sintering furnace, and nitrogen micro-positive pressure protection is applied throughout the process. It is processed in sequence through a low-temperature degreasing section, a medium-temperature heating transition section, and a high-temperature sintering section. After forced cooling and shaping, the primary finished product is obtained.

[0015] (8) After vacuum annealing to eliminate internal stress, the primary finished product is slit after thickness testing and dust-free cleaning to obtain polytetrafluoroethylene film for wrapping aerospace cables.

[0016] Preferably, the number average molecular weight of the dispersion-grade polytetrafluoroethylene resin in (1) is 2 × 10⁻⁶. 6 -5×10 6 .

[0017] Preferably, in (1), the mass ratio of the dispersion-grade polytetrafluoroethylene resin and the extrusion aid is 1:0.17-0.24.

[0018] Preferably, the extrusion aid in (1) is selected from industrial-grade paraffin oil or isoalkanes with 12-16 carbon atoms.

[0019] More preferably, the extrusion aid in (1) is selected from isoalkanes with 12-16 carbon atoms.

[0020] Preferably, the pressure of the argon atmosphere in (3) is 10-30 Pa.

[0021] Preferably, the radio frequency power of the plasma treatment in (3) is 100-200W and the treatment time is 30-90s.

[0022] Preferably, the inert gas in (4) is nitrogen or argon.

[0023] Preferably, the mass concentration of the perfluoroalkane solution of perfluoro(2-naphthoxypropyl vinyl ether) in (4) is 2%-5%.

[0024] Preferably, the perfluoroalkane in (4) is one of perfluorohexane or perfluorooctane.

[0025] More preferably, the perfluoroalkane in (4) is perfluorohexane.

[0026] Preferably, the preparation method of the perfluorinated (2-naphthoxypropyl vinyl ether) in (4) is as follows:

[0027] Anhydrous sulfolane, heptafluoro-2-naphthol, and anhydrous cesium carbonate were added to a reaction vessel. Stirring was started, and the temperature was raised to 40-50°C. The mixture was stirred at this temperature for 40-60 minutes. After purging with nitrogen three times, 3-bromoperfluoropropyl vinyl ether was added dropwise. After the addition was complete, the temperature was raised to 80-90°C, and the reaction was stirred for 8-12 hours. After the reaction was complete, the system was cooled to room temperature. The reaction solution was poured into deionized water at 0°C, stirred for 10-20 minutes, and allowed to stand to separate the layers. The organic phase was separated and washed 2-3 times with 5wt% dilute hydrochloric acid and then with deionized water until neutral. Anhydrous sulfur was added to the washed organic phase. Magnesium sulfate was dried, filtered, and the solvent was removed by rotary evaporation to obtain a crude product. The crude product was transferred to a jacketed crystallizer, heated to 55-60℃, and a mixed solvent of perfluorohexane / perfluorooctane in a volume ratio of 5-7:3-5 was added until just completely dissolved. 0.3% (by weight) of activated carbon was added for decolorization. The mixture was kept at this temperature and filtered. The filtrate was cooled to below 0℃ at a rate of 1-2℃ / min and allowed to stand at this temperature for crystallization for 8-12 hours. The primary crystalline product was obtained by suction filtration. The primary crystalline product was recrystallized once more, dried, and perfluoro(2-naphthoxypropyl vinyl ether) was obtained. The chemical reaction equation is as follows:

[0028] ; Heptafluoro-2-naphthol has seven fluorine substituents on its naphthalene ring. The combined effect of strong electron-withdrawing inductive properties and conjugation reduces the electron cloud density of the oxygen atom in the phenolic hydroxyl group, enhancing the polarity of the OH bond. Anhydrous cesium carbonate acts as an acid-binding agent; the pKa of the bicarbonate ion, the conjugate acid of the carbonate ion, is higher than that of the fluorophenol, allowing it to abstract a proton from the phenolic hydroxyl group, generating an ion pair between the heptafluoronaphthyl anion and the cesium cation. The aprotic polar solvent sulfolane used in the reaction only solvates the cesium cation and does not form hydrogen bonds with the phenoxy anion. Simultaneously, the soft acid nature of the cesium ion forms a weak coordination with the phenoxy anion. This process allows the anion to exhibit a highly reactive "naked nucleophilic" state, providing a highly active site for subsequent substitution reactions. The generated heptafluoronaphthyl anion launches a nucleophilic attack on the α-bromocarbon atom at the end of the 3-bromoperfluoropropyl vinyl ether. This α-carbon atom is directly bonded to the electronegative bromine atom. At the same time, the strong electron-withdrawing effect of the perfluoroalkyl side chain further enhances the positive charge of the carbon atom, reducing the steric hindrance and reaction energy barrier of the nucleophilic attack. As an excellent leaving group, the bromine atom undergoes C-Br bond cleavage simultaneously with the formation of the CO bond, ultimately generating the target ether product and cesium bromide byproduct.

[0029] More preferably, in the method for preparing the perfluoro(2-naphthoxypropyl vinyl ether), the molar ratio of heptafluoro-2-naphthol, anhydrous cesium carbonate, and 3-bromoperfluoropropyl vinyl ether is 1:1.2-2:1.05-1.2.

[0030] Preferably, the perfluoroalkane in (5) is one of perfluorohexane or perfluorooctane.

[0031] Preferably, the pressure of the argon atmosphere in (6) is 10-20 Pa.

[0032] Preferably, the radio frequency power of the plasma treatment in (6) is 50-100W and the treatment time is 20-60s.

[0033] Preferably, in the (7) low-temperature degreasing section, the furnace temperature is 180-200℃ and the residence time is 30-60min.

[0034] Preferably, in the intermediate temperature transition section of (7), the furnace temperature gradually increases from 200℃ to 370℃, with a heating rate of 2-5℃ / min.

[0035] Preferably, in the high-temperature sintering section of (7), the furnace temperature is 370-390℃ and the residence time is 2-4min.

[0036] Preferably, the vacuum annealing temperature in step (8) is 200-250℃ and the annealing time is 10-30min.

[0037] Furthermore, the present invention also provides a polytetrafluoroethylene film for wrapping aerospace cables, which is prepared by the above-described method.

[0038] Preferably, the mechanism of action of the polytetrafluoroethylene film for wrapping aerospace cables according to the present invention is explained as follows:

[0039] The thin film of the present invention, through a combination of two-step plasma process and sintering crosslinking, achieves simultaneous improvement in high-temperature creep resistance, radiation resistance, and interlayer bonding performance without destroying the bulk crystalline structure of PTFE.

[0040] The core basis of the modification is the differentiated and directional activation by two-step argon plasma. In the first step, high-power plasma acts on the amorphous main chain of the PTFE raw material strip. The high-energy particles of the argon plasma selectively break the CF bonds of the amorphous molecular chains, generating carbon-centered free radicals. Due to the highly ordered stacking of the PTFE crystalline molecular chains and the dense crystalline structure, high-energy particles can be blocked from penetrating. The bond-breaking reaction is limited to the amorphous region and grain boundaries, without damaging the crystalline lamellar structure that bears the main mechanical load, thus ensuring the basic mechanical and dielectric properties of the film. In the second step, low-power plasma acts on the grafted side chain perfluoronaphthalene rings. Utilizing the preferential trapping effect of the naphthalene ring conjugated π system on high-energy particles, the CF bonds on the aromatic rings are selectively broken, generating conjugated and stable perfluoronaphthalene free radicals. The plasma power in this stage is lower than in the first step, and the probability of additional main chain bond-breaking damage to the PTFE main chain is extremely small, achieving the directional and controllable generation of crosslinking active sites.

[0041] After the PTFE raw material tape is heated to above the melting temperature in the sintering furnace, the crystalline layers gradually melt, and the mobility of the molecular chain segments in the amorphous region is greatly enhanced. The perfluoronaphthyl free radicals that were originally fixed on the molecular chains diffuse with the chain segment movement. When two naphthyl free radicals located on different molecular chains approach each other, a bimodal coupling reaction occurs between the free radicals, forming a stable aryl-aryl CC covalent bond. This connects the independent PTFE molecular chains through the perfluoronaphthyl structure, ultimately constructing a sparse three-dimensional micro-crosslinked network in the amorphous region. The mechanism of this reaction is illustrated below:

[0042] ; The conjugated delocalization effect of perfluoronaphthyl free radicals exhibits excellent stability. It will not be prematurely quenched during the sintering and heating process under inert protection throughout. No small molecule byproducts are generated in the coupling reaction, and all crosslinking sites are concentrated in the amorphous side chains, which will not invade the crystalline region and damage the crystallinity of the material.

[0043] In terms of creep resistance, the large-volume rigid structure of the perfluoronaphthalene ring itself can restrict the relative slippage of molecular chains through steric hindrance. Combined with the constraint effect of chemical cross-linking points, it doubly hinders the disentanglement and slippage of molecular chains in the amorphous region at high temperatures, reducing high-temperature cold flow deformation and solving the creep failure problem of pure PTFE wrapping films under long-term high-temperature service. In terms of radiation resistance, the conjugated π system of the perfluoronaphthalene ring can act as a radiation energy trapping site, absorbing high-energy electrons and active free radicals generated by ionizing radiation. Through electron delocalization, the radiation energy is dissipated as heat energy, avoiding direct attack of high-energy particles on the PTFE main chain, which would cause chain breakage and degradation, thus improving the service stability of the material under space irradiation. In terms of interlayer bonding performance, at the overlap interface after cable wrapping, the side chain free radicals of different film layers can undergo inter-interface coupling reactions during sintering, transforming the original purely van der Waals bonded interlayer interface into a covalently bonded whole, improving the peel strength of the overlap layer, and blocking the intrusion path of atomic oxygen and corrosive media. In terms of dielectric properties, the perfluoronaphthalene ring and the entire side chain are perfluoro structures with no polar groups introduced. Furthermore, the grafting and crosslinking occur in the amorphous region, without disrupting the uniformity of the material's crystallinity. Therefore, the film retains the low dielectric constant and low dielectric loss characteristics of pure PTFE, fully meeting the insulation requirements of high-frequency signal cables in aerospace applications.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] 1. This invention employs a two-step differentiated argon plasma activation process to construct a directional micro-crosslinked network of perfluoronaphthalene ring side groups in the amorphous region without damaging the bulk crystalline structure of polytetrafluoroethylene (PTFE). The entire modification process involves the introduction of no polar functional groups, and both the grafted side chains and crosslinking nodes are perfluoro structures. This process does not degrade the material's inherent low dielectric insulation properties, while simultaneously improving high-temperature creep resistance, radiation resistance, and dimensional stability. It combines the original advantages of PTFE with the performance gains from modification, making it suitable for the insulation requirements of high-frequency signal cables.

[0046] 2. This invention utilizes the steric hindrance effect of the rigid side groups of the perfluoronaphthalene ring and the chemical constraint of the micro-crosslinked network in the amorphous region to dually restrict the slippage and deentanglement of the polytetrafluoroethylene (PTFE) amorphous molecular chains at high temperatures, effectively suppressing high-temperature cold flow defects in the material. Simultaneously, the crosslinked network can constrain the high-temperature shrinkage of the molecular chains, and in conjunction with the annealing process, eliminate processing stress, reduce the high-temperature thermal shrinkage rate of the film, and improve the high-temperature service stability and dimensional accuracy of the wrapping process.

[0047] 3. The perfluoronaphthalene ring side groups and the amorphous region micro-crosslinking network constructed in this invention form a synergistic radiation-resistant system. The conjugated π system of the perfluoronaphthalene ring can capture high-energy particles of ionizing radiation and dissipate radiation energy through electron delocalization, reducing the direct impact and bond breakage of the main chain. The crosslinking network can anchor the trace chain breaks caused by irradiation, inhibiting defect diffusion and chain degradation. The two work together to improve the mechanical retention rate and service life of the material under ionizing radiation environment, making it suitable for extreme space service scenarios.

[0048] 4. The modified polytetrafluoroethylene film of this invention can enhance the intermolecular bonding force through the π-π stacking effect of the perfluoronaphthalene rings at the interface during the wrapping and sintering process. At the same time, the low shrinkage characteristics can ensure that the overlap interface is always tightly attached, effectively improving the peel strength of the wrapping overlap layer and the structural integrity of the insulation layer. The overall preparation process adopts a continuous roll-to-roll production mode, which is highly compatible with existing polytetrafluoroethylene calendering and sintering production lines and has good potential for industrial promotion. Attached Figure Description

[0049] Figure 1 The nuclear magnetic resonance fluorine spectrum of the perfluorinated (2-naphthoxypropyl vinyl ether) prepared in Example 2 of this invention. Detailed Implementation

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0051] Preparation Example 1: A specific method for preparing perfluorinated (2-naphthoxypropyl vinyl ether) includes the following steps:

[0052] 2.0 L of anhydrous sulfolane, 1 mol of heptafluoro-2-naphthol, and 1.2 mol of anhydrous cesium carbonate were added to a reaction vessel. Stirring was started, and the temperature was raised to 40 °C. The mixture was stirred at this temperature for 40 min. After purging with nitrogen three times, 1.05 mol of [a specific substance] was added dropwise. After the addition of 3-bromoperfluoropropyl vinyl ether, the temperature was raised to 80°C and the reaction was stirred for 8 hours. After the reaction, the system was cooled to room temperature, and the reaction solution was poured into 8.0 L of 0°C deionized water. The mixture was stirred for 10 minutes, allowed to stand and separate into layers, and the organic phase was separated. The organic phase was washed twice with 5 wt% dilute hydrochloric acid (3.0 L each time) and washed with deionized water until neutral. The washed organic phase was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was transferred to a jacketed crystallizer, heated to 55°C, and a mixed solvent of perfluorohexane / perfluorooctane in a volume ratio of 5:5 was added until it was just completely dissolved. 0.3% of the crude product mass of activated carbon was added for decolorization, and the mixture was kept at the same temperature and filtered. The filtrate was cooled to below 0°C at a rate of 1°C / min and allowed to stand at the same temperature for 8 hours to crystallize. The primary crystalline product was obtained by vacuum filtration. The primary crystalline product was recrystallized once and dried to obtain perfluoro(2-naphthoxypropyl vinyl ether).

[0053] Preparation Example 2: A specific method for preparing perfluorinated (2-naphthoxypropyl vinyl ether) includes the following steps:

[0054] 2.0 L of anhydrous sulfolane, 1 mol of heptafluoro-2-naphthol, and 1.6 mol of anhydrous cesium carbonate were added to a reaction vessel. Stirring was started, and the temperature was raised to 45 °C. The mixture was stirred at this temperature for 50 min, and after purging with nitrogen three times, 1.125 mol of 3-bromoperfluoropropyl vinyl ether was added dropwise. After the addition was complete, the temperature was raised to 85 °C, and the reaction was stirred for 10 h. After the reaction was completed, the system was cooled to room temperature, and the reaction solution was poured into an 8.0 L container. Stir for 15 min in deionized water at 0℃, allow to stand and separate the organic phase, wash twice with 5wt% dilute hydrochloric acid (3.0 L each time) and wash with deionized water until neutral. Dry the washed organic phase with anhydrous magnesium sulfate, filter and remove the solvent by rotary evaporation to obtain crude product. Transfer the crude product to a jacketed crystallizer, heat to 58℃, add a mixed solvent of perfluorohexane / perfluorooctane in a volume ratio of 6:4 until just completely dissolved, add 0.3% activated carbon by mass of crude product for decolorization, keep warm and filter, cool the filtrate to below 0℃ at a rate of 1.5℃ / min, keep at constant temperature and crystallize for 10 h, filter to obtain primary crystalline product, repeat the recrystallization operation once for primary crystalline product, dry to obtain perfluoro(2-naphthoxypropyl vinyl ether).

[0055] Preparation Example 3: A specific method for preparing perfluorinated (2-naphthoxypropyl vinyl ether) includes the following steps:

[0056] 2.0 L of anhydrous sulfolane, 1 mol of heptafluoro-2-naphthol, and 2.0 mol of anhydrous cesium carbonate were added to a reaction vessel. Stirring was started, and the temperature was raised to 50 °C. The mixture was stirred at this temperature for 60 min, and after purging with nitrogen three times, 1.2 mol of 3-bromoperfluoropropyl vinyl ether was added dropwise. After the addition was complete, the temperature was raised to 90 °C, and the reaction was stirred for 12 h. After the reaction was completed, the system was cooled to room temperature, and the reaction solution was poured into an 8.0 L container. Stir for 20 min in deionized water at 0℃, allow to stand and separate the organic phase, wash three times with 5wt% dilute hydrochloric acid (3.0 L each time), wash with deionized water until neutral, dry the washed organic phase with anhydrous magnesium sulfate, filter and remove solvent by rotary evaporation to obtain crude product, transfer the crude product to a jacketed crystallizer, heat to 60℃, add 1.4 L of a mixed solvent of perfluorohexane / perfluorooctane in a volume ratio of 7:3 until just completely dissolved, add 0.3% of activated carbon by mass of crude product for decolorization, keep warm and filter, cool the filtrate to below 0℃ at a rate of 2℃ / min, keep at constant temperature and crystallize for 12 h, filter to obtain primary crystalline product, repeat recrystallization operation once for primary crystalline product, dry to obtain perfluoro(2-naphthoxypropyl vinyl ether).

[0057] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and Preparation Example 2 is that heptafluoro-2-naphthol is replaced with pentafluorophenol.

[0058] Comparative Preparation Example 2: The difference between Comparative Preparation Example 2 and Preparation Example 2 is that heptafluoro-2-naphthol is replaced with heptafluoro-1-propanol.

[0059] Comparative Preparation Example 3: The difference between Comparative Preparation Example 3 and Preparation Example 2 is that 3-bromoperfluoropropyl vinyl ether is replaced with heptafluoropropyl bromide.

[0060] Example 1: A specific method for preparing a polytetrafluoroethylene film for wrapping aerospace cables, comprising the following steps:

[0061] (1) 1 kg of a number-average molecular weight of 2×10 6 Dispersed polytetrafluoroethylene resin and 170g of isoalkane extrusion aid with 12-16 carbon atoms were mixed evenly, sealed, and cured at 30℃ for 24h to obtain a paste-like mixture.

[0062] (2) The paste mixture is cold-pressed into a cylindrical blank, extruded into a uniform thick sheet by an extruder, and then gradually calendered to a thickness of 0.05 mm by a multi-roll calendering unit to obtain PTFE raw material strip;

[0063] (3) The PTFE raw material tape is fed into the continuous roll-to-roll low temperature plasma reaction chamber and plasma-treated for 30s with 100W radio frequency power under 10Pa argon atmosphere to obtain the activated raw material tape.

[0064] (4) The activated raw material tape was transferred to the grafting tank under argon protection throughout the process and immersed in a perfluorohexane solution of perfluoro(2-naphthoxypropyl vinyl ether) prepared in Preparation Example 1 with a mass concentration of 2% and immersed at 35°C for 3 min to obtain the grafted raw material tape.

[0065] (5) The grafted raw material tape is washed by countercurrent spraying of perfluorohexane and dried under vacuum at 40°C to obtain the grafted modified raw material tape.

[0066] (6) The grafted modified raw material tape is fed back into the continuous roll-to-roll low temperature plasma reaction chamber and plasma-treated for 20s with 50W radio frequency power under 10Pa argon atmosphere to obtain a secondary activated raw material tape.

[0067] (7) The secondary activated raw material belt is fed into a three-stage continuous sintering furnace under full nitrogen micro-positive pressure protection. It is processed sequentially through a low-temperature degreasing section, a medium-temperature heating transition section, and a high-temperature sintering section. The furnace temperature in the low-temperature degreasing section is 180℃ and the residence time is 30min. The furnace temperature in the medium-temperature heating transition section is gradually increased from 200℃ to 370℃ at a heating rate of 2℃ / min. The furnace temperature in the high-temperature sintering section is 370℃ and the residence time is 2min. After forced cooling and shaping, the primary finished product is obtained.

[0068] (8) The primary finished product is vacuum annealed at 200℃ for 10 minutes to eliminate the internal stress of processing. After thickness testing and dust-free cleaning, it is cut to obtain polytetrafluoroethylene film for wrapping aerospace cables.

[0069] Example 2: A specific method for preparing a polytetrafluoroethylene film for wrapping aerospace cables, comprising the following steps:

[0070] (1) 1 kg of a number-average molecular weight of 3.5 × 10 6 Dispersed polytetrafluoroethylene resin and 205g of isoalkane extrusion aid with 12-16 carbon atoms were mixed evenly, sealed, and cured at 32℃ for 30h to obtain a paste-like mixture.

[0071] (2) The paste mixture is cold-pressed into a cylindrical blank, extruded into a uniform thick sheet by an extruder, and then gradually calendered to a thickness of 0.08 mm by a multi-roll calendering unit to obtain PTFE raw material strip;

[0072] (3) The PTFE raw material tape is fed into the continuous roll-to-roll low temperature plasma reaction chamber and plasma-treated for 60s with 150W radio frequency power under an argon atmosphere of 20Pa to obtain the activated raw material tape.

[0073] (4) The activated raw material tape was transferred to the grafting tank under argon protection throughout the process and immersed in a perfluorohexane solution of perfluoro(2-naphthoxypropyl vinyl ether) prepared in Preparation Example 2 with a mass concentration of 3.5% and immersed at 42°C for 5.5 min to obtain the grafted raw material tape.

[0074] (5) The grafted raw material tape is washed by countercurrent spraying of perfluorohexane and then vacuum dried at 45°C to obtain the grafted modified raw material tape.

[0075] (6) The grafted modified raw material tape is fed back into the continuous roll-to-roll low temperature plasma reaction chamber and plasma-treated for 40s with 75W radio frequency power under an argon atmosphere of 15Pa to obtain a secondary activated raw material tape.

[0076] (7) The secondary activated raw material belt is fed into a three-stage continuous sintering furnace under nitrogen micro-positive pressure protection throughout the process. It is processed sequentially through a low-temperature degreasing section, a medium-temperature heating transition section, and a high-temperature sintering section. The furnace temperature in the low-temperature degreasing section is 190℃, and the residence time is 45min. The furnace temperature in the medium-temperature heating transition section is gradually increased from 200℃ to 370℃ at a heating rate of 3.5℃ / min. The furnace temperature in the high-temperature sintering section is 380℃, and the residence time is 3min. After forced cooling and shaping, the primary finished product is obtained.

[0077] (8) The primary finished product is vacuum annealed at 220℃ for 20 minutes to eliminate the internal stress of processing. After thickness testing and dust-free cleaning, it is cut to obtain polytetrafluoroethylene film for wrapping aerospace cables.

[0078] Example 3: A specific method for preparing a polytetrafluoroethylene film for wrapping aerospace cables, comprising the following steps:

[0079] (1) 1 kg of a number-average molecular weight of 5×10 6 Dispersed polytetrafluoroethylene resin and 240g of isoalkane extrusion aid with 12-16 carbon atoms were mixed evenly, sealed, and cured at 35℃ for 36h to obtain a paste-like mixture.

[0080] (2) The paste mixture is cold-pressed into a cylindrical blank, extruded into a uniform thick sheet by an extruder, and then gradually calendered to a thickness of 0.12 mm by a multi-roll calendering unit to obtain PTFE raw material strip;

[0081] (3) The PTFE raw material tape is fed into the continuous roll-to-roll low temperature plasma reaction chamber and plasma-treated for 90s with 200W radio frequency power under an argon atmosphere of 30Pa to obtain the activated raw material tape.

[0082] (4) The activated raw material tape was transferred to the grafting tank under argon protection throughout the process and immersed in a perfluorohexane solution of perfluoro(2-naphthoxypropyl vinyl ether) prepared in Preparation Example 3 with a mass concentration of 5% and immersed at 50°C for 8 min to obtain the grafted raw material tape.

[0083] (5) The grafted raw material tape is washed by countercurrent spraying of perfluorohexane and dried under vacuum at 50°C to obtain the grafted modified raw material tape.

[0084] (6) The grafted modified raw material tape is fed back into the continuous roll-to-roll low temperature plasma reaction chamber and plasma-treated for 60s with 100W radio frequency power under an argon atmosphere of 20Pa to obtain a secondary activated raw material tape.

[0085] (7) The secondary activated raw material belt is fed into a three-stage continuous sintering furnace under full nitrogen micro-positive pressure protection. It is processed sequentially through a low-temperature degreasing section, a medium-temperature heating transition section, and a high-temperature sintering section. The furnace temperature in the low-temperature degreasing section is 200℃ and the residence time is 60min. The furnace temperature in the medium-temperature heating transition section is gradually increased from 200℃ to 370℃ at a heating rate of 5℃ / min. The furnace temperature in the high-temperature sintering section is 390℃ and the residence time is 4min. After forced cooling and shaping, the primary finished product is obtained.

[0086] (8) The primary finished product is vacuum annealed at 250°C for 30 minutes to eliminate the internal stress of processing. After thickness testing and dust-free cleaning, it is cut to obtain polytetrafluoroethylene film for wrapping aerospace cables.

[0087] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that steps (3)-(6) are omitted. The PTFE raw material strip obtained in step (2) is directly fed into a three-section continuous sintering furnace for degreasing, sintering and annealing. The remaining steps and parameters are the same as in Example 2.

[0088] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that step (6) is omitted, and the grafted modified raw material belt is directly fed into the three-section continuous sintering furnace. The remaining steps and parameters are the same as in Example 2.

[0089] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the radio frequency power of plasma treatment in step (6) is adjusted to 150W, while the remaining steps and parameters are completely consistent with Example 2.

[0090] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the perfluorinated (2-naphthoxypropyl vinyl ether) prepared in Preparation Example 1 was replaced with the product prepared in Comparative Preparation Example 1.

[0091] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the perfluorinated (2-naphthoxypropyl vinyl ether) prepared in Preparation Example 1 was replaced with the product prepared in Comparative Preparation Example 2.

[0092] Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that the perfluorinated (2-naphthoxypropyl vinyl ether) prepared in Preparation Example 1 was replaced with the product prepared in Comparative Preparation Example 3.

[0093] Performance testing:

[0094] The following systematic tests were performed on the thin film samples prepared in Examples 1-3 and Comparative Examples 1-6:

[0095] 1. Tensile mechanical property test: The films prepared in each example and comparative example were cut into standard dumbbell-shaped specimens and tested using a universal electronic testing machine at room temperature of 25℃ and tensile rate of 100mm / min. Each group of specimens was tested in parallel 5 times, and the average value was recorded as the tensile strength and elongation at break of the specimen.

[0096] 2. High-temperature creep resistance test: The test was conducted using a high-temperature creep testing machine for thin films. The test conditions were set to a constant temperature environment of 250℃. A constant axial tensile stress of 5MPa was applied to the sample, and the creep strain value of the sample was recorded after 100h of continuous loading. That is, the ratio of the deformation length to the original gauge length.

[0097] 3. Electron irradiation resistance test: The sample was irradiated with a total dose of 100 kGy using an electron accelerator. After irradiation, the tensile strength of the sample was determined under the same test conditions as the room temperature tensile properties. The strength retention rate was calculated by the ratio of the tensile strength after irradiation to the initial strength before irradiation.

[0098] 4. Peel strength test of the wrapping overlap layer: The peel strength test of the wrapping overlap layer simulates the actual cable wrapping process. Each sample is spirally wrapped on the surface of a clean aluminum core wire with a 50% overlap rate. After being sintered at a constant temperature of 380℃ for 3 minutes, it is naturally cooled. A 180° peel test is performed using a universal electronic testing machine with a peel rate of 50mm / min. The average peel strength between the overlap layers is recorded.

[0099] 5. Dielectric performance test: The relative permittivity and dielectric loss tangent of each sample are measured using a high-frequency dielectric constant tester at a room temperature of 25℃ and a test frequency of 1MHz. Before the test, the samples need to be vacuum dried to remove surface adsorbed moisture.

[0100] 6. High-temperature heat shrinkage rate test: Cut the sample into strips of 100mm×10mm and mark the original gauge length. Place them in a 200℃ constant temperature oven without restraint for 30 minutes. After cooling to room temperature, measure the gauge length again and calculate the longitudinal heat shrinkage rate.

[0101] The experimental results are shown in Table 1.

[0102] Table 1 Performance Test Results

[0103]

[0104] Data Analysis:

[0105] As can be seen from the performance test data in Table 1, the three sample examples prepared using the technical solution of this invention have achieved significant improvements in various service performances compared to pure PTFE, and can fully meet the stringent requirements of high temperature, radiation, high frequency and other dimensions for aerospace cable wrapping. Among them, Example 2 has the best overall performance.

[0106] In terms of room temperature mechanical properties, the amorphous region directional side chain crosslinking process used in this invention does not damage the main load-bearing structure of the PTFE crystalline layer. The uniformly distributed crosslinking points can improve the stress transfer efficiency during the stretching process and reduce the slippage and unentanglement of molecular chains. Therefore, the tensile strength of the film is improved compared with pure PTFE, while still maintaining excellent elongation at break and bending toughness, which can meet the processing and service requirements of repeated bending during cable wrapping.

[0107] High-temperature creep resistance is a key area for improvement in this invention. Pure PTFE is prone to amorphous molecular chain slippage and disentanglement at high temperatures, resulting in significant cold flow defects. This invention addresses this by introducing large-volume rigid side groups of perfluoronaphthalene rings through grafting. These side groups can restrict the relative slippage of molecular chains through steric hindrance. Combined with the chemical constraint of the amorphous micro-crosslinked network formed by naphthyl radical coupling during sintering, this double inhibition of molecular chain movement at high temperatures significantly suppresses high-temperature cold flow deformation and substantially improves the long-term high-temperature service stability of the film.

[0108] Regarding resistance to electron irradiation, this invention achieves a synergistic effect of conjugated structure protection and cross-linked network constraint. The conjugated π system of the perfluoronaphthalene ring can serve as a radiation energy trapping site, absorbing high-energy electrons and active free radicals generated by ionizing radiation. Through electron delocalization, the radiation energy is dissipated as heat, reducing the direct attack of high-energy particles on the PTFE backbone. At the same time, the micro-cross-linked network in the amorphous region can anchor the trace chain breaks caused by irradiation, inhibiting defect diffusion and chain degradation reactions. The synergy of these two factors significantly improves the mechanical retention rate and service life of the film under space irradiation environment.

[0109] Regarding the peel strength of the wrapping and overlapping layer, the overlapping interface of pure PTFE after wrapping and sintering relies solely on intermolecular van der Waals forces for bonding. Furthermore, pure PTFE has a high thermal shrinkage rate at high temperatures. During the wrapping and sintering process, the film shrinks longitudinally, which reduces the effective contact area of ​​the overlapping interface. The interlayer bonding force is extremely weak, making it prone to delamination failure. The enhanced interlayer bonding strength of the modified film of this invention stems from multiple synergistic effects. First, there is the intermolecular interaction of the perfluoronaphthalene ring side groups. Under the high temperature of wrapping and sintering, the perfluoronaphthalene ring side groups on both sides of the film at the overlap interface can form stronger intermolecular forces through π-π stacking, resulting in a bonding strength higher than that of pure PTFE. Second, there is the low shrinkage characteristic brought about by the cross-linked network. The high-temperature thermal shrinkage rate of the film of this invention is much lower than that of pure PTFE. No significant interface shrinkage occurs during the wrapping and sintering process, and the overlap layer always maintains a large contact area of ​​tight adhesion, avoiding interface debonding caused by shrinkage. Finally, the molecular chains in the amorphous region still have a certain degree of mobility at high temperatures, and slight chain segment diffusion entanglement can occur at the interface, further enhancing the interlayer bonding strength. These multiple effects together make the peel strength of the overlap layer much higher than that of pure PTFE film, ensuring the structural integrity of the cable insulation layer.

[0110] In terms of dielectric properties, the grafted side chains and cross-linking structures introduced in this invention are all perfluorinated nonpolar structures, without introducing any polar functional groups. Furthermore, the grafting and cross-linking reactions are limited to the amorphous region, without compromising the crystal uniformity and film density of PTFE. Therefore, the film completely retains the intrinsic low dielectric constant and low dielectric loss characteristics of pure PTFE, which can meet the insulation requirements of high-frequency signal cables in aerospace.

[0111] Regarding high-temperature dimensional stability, the amorphous micro-crosslinked network constructed in this invention can restrict the free retraction of molecular chains at high temperatures. Combined with the subsequent vacuum annealing process, it can fully eliminate the processing internal stress introduced during calendering and winding, making the high-temperature thermal shrinkage rate of the film much lower than that of pure PTFE. The dimensional stability is significantly improved, which can meet the process requirements of high-precision cable wrapping and avoid defects such as dimensional deviations and wrinkles after sintering.

[0112] Comparative Example 1 is a pure PTFE blank control group, which has not undergone any grafting and crosslinking modification. It lacks the constraint effect of perfluoronaphthalene ring side groups and crosslinking network. Its high-temperature creep resistance, radiation resistance and peel strength of the cover layer are far lower than those of the embodiments of the present invention. It suffers from severe high-temperature cold flow, is easily degraded under irradiation environment and has weak interlayer bonding force, and cannot meet the stringent service requirements of aerospace cables. Only its dielectric properties are at the same level as those of the embodiments of the present invention.

[0113] Comparative Example 2 omitted the second step of plasma-directed activation, only completing the grafting of the perfluoronaphthalene ether monomer. It failed to generate stable cross-linked active free radicals on the naphthalene ring, and thus could not form an effective chemical cross-linking network during the sintering stage. Therefore, its high-temperature creep resistance, capping layer peel strength, and dimensional stability were significantly lower than those of the embodiments of this invention. It only retained a certain degree of radiation protection effect relying on the conjugated structure of the naphthalene ring, but the protection level was far inferior to the synergistic system of the conjugated structure and the cross-linking network. This verifies the necessity of the second-step plasma activation process for constructing the cross-linking network and improving overall performance.

[0114] Comparative Example 3 increased the plasma treatment power in the second step to match that in the first step, thus losing the effect of low-power differentiated directional activation. The plasma energy indiscriminately bombarded the PTFE main chain and side-chain naphthalene rings, ultimately forming a mixed crosslinking system in which random crosslinking of the main chain and crosslinking of the side-chain naphthalene rings coexist. Although the total degree of crosslinking increased slightly, random crosslinking of the main chain disrupted the uniformity of the crystal structure, leading to a decrease in the film's elongation at break and a deterioration in its flexural toughness. At the same time, the proportion of directional naphthalene ring crosslinking decreased, and the radiation resistance and creep resistance were slightly inferior to the directional side-chain crosslinking system of the embodiments of the present invention.

[0115] Comparative Example 4 replaced heptafluoro-2-naphthol with pentafluorophenol, resulting in a monocyclic perfluorobenzene structure at the end of the grafted side chain. The conjugated system of the monocyclic benzene ring is much smaller than that of the bicyclic naphthalene structure, leading to poor stability of the generated aryl radicals, which are prone to premature quenching during sintering and significantly reduced crosslinking efficiency. Therefore, its high-temperature creep resistance, interlayer bonding strength, and radiation resistance are all weaker than those of the embodiment of this invention using the perfluoronaphthalene ring system. This verifies that the large conjugated structure of the perfluoronaphthalene ring is the key structural basis for achieving efficient crosslinking and excellent radiation resistance.

[0116] Comparative Example 5 replaced heptafluoro-2-naphthol with heptafluoro-1-propanol, and the grafted side chains were saturated perfluoroalkyl structures, completely removing the aromatic ring conjugated system. The second-step plasma treatment could not generate stable aryl radicals, making it almost impossible to form an effective cross-linked network. Therefore, its modified properties were close to those of pure PTFE, with only a very weak side group steric hindrance effect, failing to effectively improve creep resistance, radiation resistance, and interlayer bonding properties. This verifies the indispensability of the conjugated aromatic ring structure in the modified system of this invention.

[0117] Comparative Example 6, where 3-bromoperfluoropropyl vinyl ether was replaced with heptafluoropropyl bromide, produced a product lacking terminal perfluoropropyl ether double bonds. This product did not possess the reactivity to undergo addition grafting with PTFE backbone radicals; the monomer could only adhere to the film surface through physical adsorption and was almost completely removed after washing. The film did not form effective grafted side chains or cross-linked structures. Therefore, its properties were essentially consistent with the pure PTFE blank control group, showing no significant performance improvement. This verifies that the perfluoropropyl ether double bond is a necessary reaction site for achieving monomer covalent grafting and exerting the modification effect.

[0118] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a polytetrafluoroethylene film for wrapping aerospace cables, characterized in that, Includes the following steps: (1) Mix the dispersion-grade polytetrafluoroethylene resin and the extrusion aid evenly, seal and cure at 30-35℃ for 24-36h to obtain a paste-like mixture; (2) The paste mixture is cold-pressed into a cylindrical blank, extruded into a uniform thick sheet by an extruder, and then gradually calendered to a thickness of 0.05-0.12 mm by a multi-roll calendering unit to obtain PTFE raw material strip; (3) The PTFE raw material tape is fed into the continuous roll-to-roll low temperature plasma reaction chamber and plasma treatment is carried out in an argon atmosphere to obtain the activated raw material tape; (4) The activated raw material tape is transferred to the grafting tank under inert gas protection throughout the process, and immersed in a perfluoroalkane solution of perfluoro(2-naphthoxypropyl vinyl ether) for 3-8 min at 35-50℃ to obtain the grafted raw material tape. (5) The grafted raw material tape is washed by countercurrent spraying of perfluoroalkane and then vacuum dried at 40-50℃ to obtain the grafted modified raw material tape. (6) The grafted modified raw material tape is fed back into the continuous roll-to-roll low temperature plasma reaction chamber and plasma treatment is carried out in an argon atmosphere to obtain a secondary activated raw material tape. (7) The secondary activated raw material belt is fed into a three-stage continuous sintering furnace, and nitrogen micro-positive pressure protection is applied throughout the process. It is processed in sequence through a low-temperature degreasing section, a medium-temperature heating transition section, and a high-temperature sintering section. After forced cooling and shaping, the primary finished product is obtained. (8) After vacuum annealing to eliminate internal stress, the primary finished product is slit after thickness testing and dust-free cleaning to obtain polytetrafluoroethylene film for wrapping aerospace cables.

2. The method for preparing polytetrafluoroethylene film for wrapping aerospace cables according to claim 1, characterized in that, The number average molecular weight of the dispersed polytetrafluoroethylene resin in (1) is 2 × 10⁻⁶. 6 -5×10 6 ; The mass ratio of dispersible polytetrafluoroethylene resin and extrusion aid is 1:0.17-0.24; the extrusion aid is selected from industrial-grade paraffin oil or isoparaffins with 12-16 carbon atoms.

3. The method for preparing polytetrafluoroethylene film for wrapping aerospace cables according to claim 1, characterized in that, The pressure of the argon atmosphere in (3) is 10-30 Pa; the radio frequency power of the plasma treatment is 100-200 W, and the treatment time is 30-90 s.

4. The method for preparing polytetrafluoroethylene film for wrapping aerospace cables according to claim 1, characterized in that, The inert gas in (4) is nitrogen or argon; the mass concentration of the perfluoroalkane solution of perfluoro(2-naphthoxypropyl vinyl ether) is 2%-5%; the perfluoroalkane is one of perfluorohexane or perfluorooctane.

5. The method for preparing polytetrafluoroethylene film for wrapping aerospace cables according to claim 1, characterized in that, The preparation method of the perfluorinated (2-naphthoxypropyl vinyl ether) in (4) is as follows: Anhydrous sulfolane, heptafluoro-2-naphthol, and anhydrous cesium carbonate were added to a reaction vessel. Stirring was started, and the temperature was raised to 40-50°C. The mixture was stirred at this temperature for 40-60 minutes. After purging with nitrogen three times, 3-bromoperfluoropropyl vinyl ether was added dropwise. After the addition was complete, the temperature was raised to 80-90°C, and the reaction was stirred for 8-12 hours. After the reaction was completed, the system was cooled to room temperature, and the reaction solution was poured into deionized water at 0°C. The mixture was stirred for 10-20 minutes, allowed to stand, and the layers were separated. The organic phase was washed 2-3 times with 5wt% dilute hydrochloric acid and then with deionized water until neutral. The washed organic phase... Anhydrous magnesium sulfate was added for drying, and the solvent was removed by rotary evaporation after filtration to obtain a crude product. The crude product was transferred to a jacketed crystallizer and heated to 55-60℃. A mixed solvent of perfluorohexane / perfluorooctane in a volume ratio of 5-7:3-5 was added until it was just completely dissolved. 0.3% of activated carbon by mass of the crude product was added for decolorization. The mixture was kept at the temperature and filtered. The filtrate was cooled to below 0℃ at a rate of 1-2℃ / min and allowed to stand at the temperature for crystallization for 8-12 hours. The primary crystalline product was obtained by suction filtration. The primary crystalline product was recrystallized once and dried to obtain perfluoro(2-naphthoxypropyl vinyl ether). The molar ratio of heptafluoro-2-naphthol, anhydrous cesium carbonate, and 3-bromoperfluoropropyl vinyl ether is 1:1.2-2:1.05-1.

2.

6. The method for preparing polytetrafluoroethylene film for wrapping aerospace cables according to claim 1, characterized in that, The perfluoroalkane in (5) is one of perfluorohexane or perfluorooctane.

7. The method for preparing polytetrafluoroethylene film for wrapping aerospace cables according to claim 1, characterized in that, The pressure of the argon atmosphere in (6) is 10-20 Pa; the radio frequency power of the plasma treatment is 50-100 W, and the treatment time is 20-60 s.

8. The method for preparing polytetrafluoroethylene film for wrapping aerospace cables according to claim 1, characterized in that, In section (7), the furnace temperature of the low-temperature degreasing section is 180-200℃, and the residence time is 30-60min; the furnace temperature of the medium-temperature heating transition section is gradually increased from 200℃ to 370℃, and the heating rate is 2-5℃ / min; the furnace temperature of the high-temperature sintering section is 370-390℃, and the residence time is 2-4min.

9. The method for preparing polytetrafluoroethylene film for wrapping aerospace cables according to claim 1, characterized in that, The vacuum annealing temperature in (8) is 200-250℃, and the annealing time is 10-30min.

10. A polytetrafluoroethylene film for wrapping aerospace cables, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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