High-temperature-resistant and high-voltage-resistant PFA aviation cable insulation material and preparation method thereof
By introducing size-matched silica nanorods and end-group fluorination into PFA matrix resin, combined with a high-shear melt blending process, the problems of insufficient heat resistance, low mechanical strength, and poor electrical insulation performance of aviation cable insulation materials under high-temperature environments have been solved, achieving a comprehensive improvement in the material's performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HARBIN UNIV OF SCI & TECH
- Filing Date
- 2026-04-13
- Publication Date
- 2026-05-29
Smart Images
Figure CN122103783A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer insulation materials technology, and in particular to a high-temperature and high-voltage resistant PFA aviation cable insulation material and its preparation method. Background Technology
[0002] With the continuous development of aerospace technology, aviation electrical systems are evolving towards higher voltage, higher temperature, and lighter weight, which places higher demands on the comprehensive performance of cable insulation materials. As an important component of aviation cables, the insulation layer not only needs to have excellent high-temperature resistance, but also needs to maintain stable electrical insulation performance under high voltage and complex electromagnetic environments, while possessing good mechanical strength to adapt to service conditions such as vibration and bending.
[0003] Currently, aviation cable insulation layers mostly use fluoropolymer materials such as ethylene-tetrafluoroethylene copolymer (ETFE) or polytetrafluoroethylene (PTFE). ETFE, in particular, offers good processability and a certain level of mechanical strength, but its temperature resistance is typically limited to the range of 150℃ to 200℃. During long-term service in high-temperature areas such as aircraft engine nacelles, ETFE is prone to thermal aging and molecular chain breakage, leading to insulation embrittlement and even detachment, making it difficult to meet the application requirements of next-generation aircraft in extreme high-temperature environments.
[0004] To improve temperature resistance, some technical solutions use soluble polytetrafluoroethylene (PFA) as the insulation material. PFA has excellent high-temperature resistance, with a long-term operating temperature up to 260℃, which to some extent overcomes the insufficient temperature resistance of ETFE materials. However, pure PFA has a low Young's modulus and insufficient mechanical strength under high-temperature conditions. In the complex wiring and vibration environment of aviation cables, it is prone to cold creep, causing the insulation layer to thin in localized stress areas or even be punctured by the conductor, thus affecting the reliability of the cable. This is because PFA is a perfluoropolymer with weak intermolecular forces and a lack of effective reinforcing structures, making it difficult to restrict the movement of polymer chains.
[0005] Furthermore, under the influence of high-voltage DC and high-frequency pulsed electric fields, traditional polymer insulation materials generally suffer from space charge accumulation and insufficient corona resistance. For pure PFA materials, the internal free volume is relatively large, lacking deep trap structures that can effectively capture high-energy electrons. When partial discharge occurs, electrical trees are easily formed and rapidly propagate, eventually leading to material breakdown and reducing the electrical reliability of the cable.
[0006] To address the aforementioned issues, existing technologies attempt to improve material properties by introducing inorganic nanofillers into the polymer matrix. However, traditional nanomodification methods often employ micron-sized or larger (typically greater than 20 nm) particles, which are prone to aggregation within the polymer matrix, leading to poor interfacial bonding and the formation of microscopic air gaps within the material. These defects can become weak points in electrical breakdown, causing a decrease in the material's breakdown strength. Furthermore, the mismatch between the filler size and the polymer chain scale makes it difficult to achieve effective structural reinforcement at the molecular level, limiting further improvements in material properties.
[0007] In summary, existing aviation cable insulation materials struggle to achieve synergistic optimization among high-temperature resistance, mechanical properties, and electrical insulation performance. Furthermore, nano-modification techniques still suffer from poor filler dispersion and insufficient interface control. Therefore, there is an urgent need for an aviation cable insulation material capable of molecular-scale structural control, possessing high-temperature stability, excellent mechanical properties, and high electrical reliability to meet the increasingly stringent requirements of the aviation industry. Summary of the Invention
[0008] In view of this, the purpose of this invention is to provide a high-temperature, high-voltage PFA aviation cable insulation material and its preparation method, to solve the problems of insufficient heat resistance of existing aviation cable insulation materials under high-temperature environments, low mechanical strength and easy creep of pure PFA materials, insufficient resistance to high voltage DC and corona discharge of traditional polymer insulation materials, and easy agglomeration of fillers and weak interfacial bonding in existing nano-modification technologies, and to achieve a synergistic improvement in the high-temperature resistance, mechanical properties and electrical insulation properties of the insulation material. To achieve the above objectives, this invention provides the following technical solution: In one possible implementation, a high-temperature, high-voltage aviation cable insulation material is characterized in that the insulation material comprises the following components: (1) Perfluoropropyl vinyl ether-tetrafluoroethylene copolymer (PFA) matrix resin; (2) Silica nanorods dispersed in the PFA matrix resin; The silica nanorods have a mass fraction of 0.5 wt% to 2.0 wt%, preferably 1.0 wt% to 1.8 wt%, and more preferably about 1.5 wt%. The silica nanorods are one-dimensional cylindrical structures with a diameter of 0.5 nm to 2 nm, preferably about 1 nm, and a length of 1 nm to 5 nm, preferably about 2 nm. The microscopic free volume fraction of the insulating material is no higher than 1.2%.
[0009] In one possible implementation, the molecular chain ends of the PFA matrix resin have a trifluoromethyl (-CF3) structure.
[0010] In one possible implementation, the surface of the silica nanorods is subjected to hydrogen saturation treatment or equivalent modification treatment.
[0011] In one possible implementation, the Young's modulus of the insulating material is not less than 2.0 GPa, preferably not less than 2.5 GPa.
[0012] In one possible implementation, the breakdown field strength of the insulating material is not less than 6000 MV / m, preferably not less than 7000 MV / m.
[0013] In one possible implementation, the microscopic free volume fraction of the insulating material is not higher than 1.0%.
[0014] In one possible implementation, a method for preparing a high-temperature, high-voltage resistant aviation cable insulation material is characterized by comprising the following steps: (1) Preparation of PFA matrix resin; (2) The PFA matrix resin is subjected to end-group fluorination stabilization treatment to convert the ends of its molecular chains into trifluoromethyl structures; (3) The treated PFA matrix resin is mixed with silica nanorods and melt-blended by a twin-screw extruder at 350℃~380℃ to obtain nanocomposite insulating material.
[0015] In one possible implementation, step (1) employs an aqueous dispersion polymerization process, including: In a reactor, using deionized water as the medium, dispersants, buffers, and chain transfer agents are added, perfluoropropyl vinyl ether comonomers are introduced, and tetrafluoroethylene monomers are introduced. The polymerization reaction is carried out at a pressure of 1.5–2.5 MPa and a temperature of 70–85°C to obtain PFA coarse powder.
[0016] In one possible implementation, in step (2), fluorine gas or a mixture of fluorine gas and inert gas is introduced at 200°C to 250°C to perform end-group fluorination treatment.
[0017] In one possible implementation, in step (3), the silica nanorods and PFA matrix resin are premixed in a dry state before melt blending.
[0018] In one possible embodiment, the present invention also provides an aviation cable comprising a conductor and an insulating layer covering the outside of the conductor, the insulating layer being made of the insulating material described in any of the above embodiments.
[0019] Based on the above technical solution, the present invention provides a high-temperature and high-voltage aviation cable insulation material. By introducing one-dimensional silica nanorods with a specific mass fraction and size matching into a perfluoropropyl vinyl ether-tetrafluoroethylene copolymer (PFA) matrix resin, and combining end-group fluorination stabilization treatment and high-shear melt blending process, the nanofiller is uniformly dispersed in the matrix and the movement of polymer chains is effectively restricted.
[0020] Specifically, by controlling the size of silica nanorods within the nanoscale range that matches the scale of PFA molecular chains, stable physical cross-linking points are formed at the microscopic interface, thereby generating a significant molecular chain "constraint effect." This effectively suppresses the thermal motion and slippage behavior of polymer chain segments, significantly improving the rigidity and creep resistance of the material. Simultaneously, by performing end-group fluorination stabilization treatment on the PFA matrix, the original thermally unstable polar end groups are transformed into chemically inert trifluoromethyl end groups. This reduces the dielectric loss of the material under high temperature and high frequency electric fields at the molecular structure level and avoids the generation of micropores and bubble defects during high-temperature processing.
[0021] Furthermore, by controlling the doping ratio of nanorods within a specific range, the nanofiller forms a highly uniform and dense interfacial structure in the matrix, thereby significantly reducing the microscopic free volume fraction of the material, compressing the electron migration space, suppressing space charge accumulation and electron avalanche effects, and improving the electromechanical breakdown field strength and corona resistance of the material. At the same time, by utilizing the high shear effect in the twin-screw extrusion process, the problem of easy agglomeration of traditional nanofillers is overcome, and the nanorods are stably dispersed in high-viscosity PFA melt, further ensuring the uniformity and stability of the material properties.
[0022] Therefore, the present invention effectively solves the following problems existing in the prior art: First, the temperature resistance of traditional ETFE insulation materials is limited and it is difficult to adapt to extreme environments above 200°C; second, the mechanical properties of pure PFA materials are insufficient and they are prone to cold creep and thinning of the insulation layer; third, traditional polymer insulation materials have poor corona resistance and are prone to breakdown under high voltage DC and high frequency conditions; and fourth, the existing nano-modification technology has problems with filler agglomeration and poor interfacial bonding.
[0023] In summary, this invention achieves a comprehensive improvement in high-temperature resistance, mechanical properties, and electrical insulation properties through the synergistic effect of material composition design, microstructure control, and preparation process optimization. This enables the insulating material to maintain excellent stability and reliability under high temperature, high voltage, and complex vibration environments, making it particularly suitable for applications with extremely high insulation requirements, such as aviation cables. It has significant engineering application value and promising prospects for widespread application. Attached Figure Description
[0024] Figure 1The diagram shows the molecular dynamics microscopic models of silica nanorods and PFA polymer chains under different doping formulations according to the present invention. (a) is the model diagram with a doping mass fraction of 0.5 wt%, (b) is the model diagram with a doping mass fraction of 1.0 wt%, (c) is the model diagram with a doping mass fraction of 1.5 wt%, and (d) is the model diagram with a doping mass fraction of 2.0 wt%.
[0025] Figure 2 The graph shows the variation of the microscopic free volume fraction of modified PFA materials under different silica nanorod doping mass fractions.
[0026] Figure 3 The graph shows the Young's modulus variation of modified PFA materials with different silica nanorod doping mass fractions.
[0027] Figure 4 The graph shows the electromechanical breakdown field strength of modified PFA materials with different silica nanorod doping mass fractions. Detailed Implementation
[0028] I. General Description The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the scope of protection of the present invention.
[0029] This invention provides a high-temperature, high-voltage aviation cable insulation material, its preparation method, and its application. Through synergistic design of material composition, microstructure, and preparation process, the comprehensive performance of the insulation material under high temperature, high voltage, and complex service environments is improved. Specifically, by introducing one-dimensional silica nanorods of specific size and content into a perfluoropropyl vinyl ether-tetrafluoroethylene copolymer (PFA) matrix, combined with end-group fluorination stabilization treatment and high-shear melt blending, the material structure is controlled at the molecular scale, resulting in significantly improved mechanical, electrical, and thermal properties of the insulation material.
[0030] In this invention, by controlling the size of the silica nanorods to match the scale of the PFA molecular chains, the nanofillers can be effectively embedded in the gaps between the polymer chains, forming a stable physical constraint structure at the microscopic interface. This restricts the thermal motion of the molecular chains, thereby improving the overall rigidity and creep resistance of the material. Simultaneously, by end-group fluorination of the PFA matrix, the unstable polar groups at the ends of the molecular chains are transformed into chemically inert trifluoromethyl structures, thereby improving the thermal stability of the material and reducing dielectric loss.
[0031] Furthermore, by controlling the doping ratio and dispersion state of the nanofillers, a dense and uniform microstructure is formed within the material, effectively reducing the free volume fraction and suppressing the accumulation and migration of space charge, thereby improving the material's breakdown field strength and corona resistance. Combined with the high shear effect during twin-screw extrusion, the agglomeration of nanofillers can be effectively avoided, achieving nanoscale uniform dispersion and further enhancing the stability and consistency of the material's properties.
[0032] The accompanying drawings are used to further illustrate the technical solution and effects of the present invention. Figure 1 The molecular dynamics microstructure model of the PFA composite system with different silica nanorod doping ratios is shown to illustrate the dispersion state and interfacial structure characteristics of the nanofiller at different contents. Figure 2 The variation trend of microscopic free volume fraction of the material under different doping ratios is shown; Figure 3 The variation of Young's modulus of the material with the doping ratio is shown; Figure 4 The figure illustrates the trend of the electromechanical breakdown field strength of the material as a function of the doping ratio. The above figures visually demonstrate the influence of the nanofiller content on the microstructure and macroscopic properties of the material in this invention.
[0033] Furthermore, Table 1 compares the comprehensive performance differences of traditional ETFE materials, pure PFA materials, and the modified PFA materials of this invention, illustrating the significant advantages of this invention in terms of high-temperature resistance, mechanical properties, and electrical properties. Table 2 further provides the key performance parameters of the modified PFA materials under different silica nanorod doping ratios, including free volume fraction, Young's modulus, and breakdown field strength, to verify the rationality of the preferred doping range and the technical effect of this invention.
[0034] In summary, this invention achieves an effective balance between high-temperature resistance, mechanical properties, and electrical insulation properties through the synergistic effect of material system design and process optimization. It breaks through the technical bottleneck of existing technologies that make it difficult to balance multiple performance indicators, and provides a feasible technical solution for the reliable operation of aviation cables in extreme environments.
[0035] II. Example 1: Preparation of PFA matrix resin This embodiment provides a method for preparing PFA matrix resin for the insulating material of the present invention, wherein a PFA resin with good molecular structure uniformity is obtained by aqueous dispersion polymerization process.
[0036] 2.1 Raw materials and equipment The main raw materials used in this embodiment include: Deionized water is used as the polymerization reaction medium. Ammonium perfluorooctanoate, used as a dispersant; Buffer, used to adjust the pH value of the system; A chain transfer agent for adjusting the molecular weight of a polymer, wherein the chain transfer agent is selected from one or more of methanol or ethane; Tetrafluoroethylene (TFE) is used as the main monomer; Perfluoropropyl vinyl ether (PPVE) is used as a comonomer. A water-soluble persulfate initiator, preferably ammonium persulfate.
[0037] The reaction equipment used is a high-pressure resistant stainless steel polymerization reactor, equipped with a temperature control system, a pressure control system and a stirring device.
[0038] 2.2 Polymerization process Before the polymerization reaction begins, the reactor is first evacuated and nitrogen is introduced multiple times to completely remove oxygen from the reaction system and avoid the inhibitory effect of oxygen on the free radical polymerization reaction.
[0039] Subsequently, deionized water, ammonium perfluorooctanoate, a buffer, and a chain transfer agent were added to the reactor, and stirring was started to ensure thorough mixing of the components to form a homogeneous reaction system. Next, liquid perfluoropropyl vinyl ether (PPVE) comonomer was added to the reactor.
[0040] After completing the above preparations, gaseous tetrafluoroethylene (TFE) monomer is introduced into the reactor to raise the pressure of the reaction system to 1.5–2.5 MPa and the system temperature to 70–85°C. Once the set reaction conditions are met, a water-soluble persulfate initiator is added to the system to initiate a free radical copolymerization reaction between tetrafluoroethylene and perfluoropropyl vinyl ether.
[0041] During the polymerization reaction, since tetrafluoroethylene is more reactive than perfluoropropyl vinyl ether, in order to ensure the uniformity of the composition of the obtained copolymer, it is necessary to maintain the pressure inside the reactor at a basically constant level and continuously replenish tetrafluoroethylene gas according to the reaction progress, while dynamically replenishing perfluoropropyl vinyl ether in proportion to control the copolymerization rate of the two monomers and avoid compositional segregation problems caused by the difference in reactivity.
[0042] The polymerization reaction continues until the system reaches the predetermined solid content, at which point the monomer feed is stopped and the unreacted monomers are recovered.
[0043] 2.3 Post-processing After the polymerization reaction is complete, the resulting product is a PFA dispersion. To obtain a solid resin powder, the dispersion undergoes post-processing, including the following steps: First, the dispersion is demulsified mechanically to cause polymer particles to precipitate from the dispersion system; Subsequently, the precipitated polymer was washed multiple times with deionized water to remove impurities such as residual dispersants, initiators, and unreacted monomers. Finally, the washed polymer was dried at 150℃~200℃ to remove moisture and obtain PFA coarse powder.
[0044] 2.4 Technical Effects Description The PFA matrix resin prepared by the above-mentioned aqueous dispersion polymerization process has good molecular weight controllability and compositional uniformity, providing a stable material basis for subsequent end-group fluorination treatment and nanocomposite modification.
[0045] Meanwhile, by precisely controlling the reaction conditions and monomer feeding strategies during the polymerization process, the problem of uneven copolymerization caused by the differences in the reactivity of different monomers is effectively overcome, thereby ensuring the stability of PFA materials in terms of thermal and electrical properties.
[0046] III. Example 2: Terminal Fluorination Stabilization Treatment This embodiment is based on the PFA coarse powder prepared in Example 1, and the end groups are stabilized by fluorination to improve the thermal stability and electrical properties of the material, and to eliminate the adverse effects of unstable end groups on subsequent processing and performance.
[0047] 3.1 Purpose and Principle of Processing In the preparation of PFA resin using aqueous dispersion polymerization, the use of persulfate initiators often leaves a certain number of polar unstable groups, such as carboxyl groups (-COOH) and acyl fluoride groups (-COF), at the ends of the resulting PFA molecular chains. These polar end groups are prone to decomposition reactions under high-temperature processing or high-frequency electric field environments, which may lead to the following problems: Micropores or bubbles are generated during melt extrusion, affecting the density of the insulation layer; Increases the dielectric loss of the material and reduces its electrical insulation performance; This reduces the long-term thermal stability and service life of the material.
[0048] Therefore, it is necessary to stabilize the ends of the PFA molecular chain to transform the unstable end groups into end group structures with stronger chemical inertness and higher thermal stability.
[0049] 3.2 Processing Equipment and Conditions In this embodiment, a contact fluorination reactor is used to perform end-group fluorination treatment on PFA crude powder. The treatment conditions include: Reaction temperature: 200℃~250℃; Reaction atmosphere: a mixture of fluorine (F2) and nitrogen (N2), with nitrogen used as a diluent gas; Reaction method: gas-solid contact reaction.
[0050] By controlling the concentration of fluorine gas and the reaction temperature, the fluorine gas can be used to ensure that the reaction proceeds fully while avoiding damage to the PFA main chain structure.
[0051] 3.3 Processing Procedure The specific steps are as follows: First, the PFA coarse powder obtained in Example 1 was placed in a contact fluorination reactor, and the reaction system was sealed. Subsequently, the reactor was heated to 200℃~250℃, and a fluorine gas mixture diluted with nitrogen was introduced to ensure that the fluorine gas came into full contact with the PFA coarse powder. Under these conditions, the high reactivity of fluorine gas is utilized to cause the carboxyl group (-COOH) and acyl fluoride group (-COF) at the end of the PFA molecular chain to undergo a fluorination reaction, transforming them into trifluoromethyl (-CF3) end groups; After the reaction is complete, the fluorine gas supply is stopped, and the residual gas in the system is replaced with an inert gas. The treated PFA resin is then cooled to room temperature to obtain end-group stabilized PFA matrix resin.
[0052] 3.4 Technical Effects After end-group fluorination stabilization treatment, the molecular chain ends of the PFA matrix resin are mainly trifluoromethyl structures, which have excellent chemical inertness and thermal stability, thus bringing the following technical effects: (1) Significantly improves the thermal stability of the material, making it less prone to decomposition or structural degradation at high temperatures; (2) Effectively suppresses gas release during high-temperature melting and processing, avoids the formation of micropores or bubbles inside the insulation layer, and improves the density of the material; (3) Reduce the dielectric loss of the material under high frequency and high voltage conditions and improve its electrical insulation performance; (4) Provides a more stable matrix environment for the uniform dispersion and interfacial bonding of subsequent nanofillers.
[0053] 3.5 Explanation of the relationship with subsequent processes The end-group stabilized PFA matrix resin obtained in this embodiment serves as the base material for subsequent nanocomposite modification. The stability of its end-group structure directly affects the dispersion state and interfacial bonding effect of the nanofillers in the matrix. Therefore, this end-group fluorination treatment step is one of the important prerequisites for achieving the performance improvement of the material of this invention.
[0054] IV. Example 3: Preparation of Nanocomposite Materials Based on the end-group stabilized PFA matrix resin obtained in Example 2, this embodiment introduces silica nanorods of specific size and morphology and prepares nanocomposite insulating materials using a high-shear melt blending process.
[0055] 4.1 Selection and Characteristics of Nanofillers In this embodiment, silica (SiO2) nanorods are selected as the inorganic filler. The nanorods have a one-dimensional cylindrical structure, and their preferred geometric dimensions are as follows: The diameter is approximately 1 nm; Its length is approximately 2 nm.
[0056] This size range matches the segment scale of the PFA molecular chain, enabling the nanorods to be effectively embedded in the gaps between polymer chains, thereby forming a stable structural constraint at the microscopic interface.
[0057] Preferably, the surface of the silica nanorods is subjected to hydrogen saturation treatment or equivalent surface modification treatment to simulate the surface hydroxylation state, thereby improving the interfacial compatibility between them and the PFA matrix, enhancing the interfacial bonding strength, and avoiding the agglomeration of fillers in the composite system.
[0058] 4.2 Proportioning Design In this embodiment, the end-group stabilized PFA matrix resin and silica nanorods are mixed in a mass fraction ratio, preferably within the following range: PFA matrix resin: 98.0 wt%~99.5 wt%; Silica nanorods: 0.5 wt%~2.0 wt%.
[0059] More preferably, the silica nanorods have a mass fraction of about 1.5 wt%, which achieves an optimal balance of the overall material properties.
[0060] 4.3 Dry Premixing Process Prior to melt blending, the PFA matrix resin and silica nanorods were first subjected to a dry premixing treatment. Specifically: The terminal stabilized PFA resin powder and silica nanorods weighed according to the above proportions are added to a high-speed mixer and mechanically stirred at room temperature to uniformly disperse the nanorods in the PFA resin powder on a macroscopic scale, thus obtaining a premix.
[0061] This premixing step helps reduce local concentration gradients during subsequent melt blending, improving the uniformity of nanofiller dispersion.
[0062] 4.4 Melt Blending Process The above premix was added to a co-rotating twin-screw extruder for melt blending, with the specific process conditions as follows: Extrusion temperature: 350℃~380℃; Screw type: Co-directional twin-screw structure; Shearing method: High-shear mixing.
[0063] Within this temperature range, the PFA matrix is in a high-viscosity molten state. The strong shear stress field generated by the twin-screw extruder can effectively overcome the van der Waals forces between nanoparticles, enabling the silica nanorods to be dispersed at the nanoscale in the PFA melt.
[0064] During the melt blending process, the nanorods are gradually exfoliated and uniformly distributed in the matrix under shear force, while forming a stable interface structure with the PFA molecular chains, thus avoiding the filler agglomeration problem commonly found in traditional nano-modification.
[0065] 4.5 Molding and Granulation The thoroughly mixed melt is extruded through a die to form a continuous strip, and then the following processes are performed sequentially: Pull-up strips; Water cooling; Pelletizing process; The final product is a modified PFA insulating granule that can be used for extrusion coating of cable insulation layers.
[0066] 4.6 Technical Effects and Mechanism Analysis Through the above-described nanocomposite process, this embodiment achieves the following technical effects: (1) Nanoscale uniform dispersion High-shear melt blending allows silica nanorods to form a uniform distribution in the PFA matrix, avoiding interfacial defects caused by agglomeration. (2) Enhanced molecular chain constraint Size-matched nanorods are embedded between PFA chains to form "physical cross-linking points" at the interface, which restricts the cooperative movement of polymer chains and improves the rigidity and creep resistance of the material. (3) Free volume compression effect Nanofillers fill the gaps between chains, making the internal structure of the material more compact and significantly reducing the free volume fraction, thereby inhibiting electron migration pathways; (4) Improved electrical performance The formation of dense structures and deep interface traps helps to capture space charges, suppress the development of electrical trees, and improve the breakdown field strength and corona resistance of materials. (5) Performance Co-optimization By synergistically controlling the size, morphology, and content of the filler, the material's comprehensive optimization among high-temperature resistance, mechanical properties, and electrical properties can be achieved.
[0067] 4.7 Differences from traditional technologies Compared with traditional modification methods that use large-size nanoparticles or high doping ratios, this embodiment effectively avoids filler agglomeration and interface defects by controlling the size of the nanorods to match the scale of the PFA molecular chain, and combining low doping ratios and high shear dispersion processes, thus achieving a synergistic improvement in microstructure and macroscopic performance.
[0068] V. Example 4: Comparison of different doping ratios (in conjunction with...) Figure 1 Table 1) To verify the influence of the silica nanorod doping ratio on the performance of PFA-based composite materials in this invention and to determine the optimal doping range, this embodiment uses molecular dynamics simulation to systematically analyze the composite system with different doping mass fractions.
[0069] 5.1 Molecular model construction (corresponding to) Figure 1 ) A PFA-based composite system model was constructed using Materials Studio molecular simulation software, and microstructure models of different silica nanorod doping ratios were established, including: The model with a doping mass fraction of 0.5 wt%, such as Figure 1 As shown in (a); The model with a doping mass fraction of 1.0 wt%, such as Figure 1 As shown in (b); The model with a doping mass fraction of 1.5 wt%, such as Figure 1 As shown in (c); The model with a doping mass fraction of 2.0 wt%, such as Figure 1 As shown in (d).
[0070] In the above model, silica nanorods are embedded in the PFA molecular chain system in a one-dimensional cylindrical structure, and the microstructure of the actual material is simulated by constructing periodic boundary conditions.
[0071] 5.2 Performance parameters and data (corresponding to Table 1) Based on the constructed molecular model, the key performance parameters of the composite material under different doping ratios were calculated, including: Microscopic free volume fraction (FFV); Young's modulus; Theoretical electromechanical breakdown field strength.
[0072] The calculation results are shown in Table 1: <![CDATA[SiO2 content (wt%)]]> Free volume fraction (%) Young's modulus (GPa) Breakdown field strength (MV / m) 0.0 2.50 0.60 3408 0.5 1.85 1.45 5298 1.0 1.25 2.10 6375 1.5 0.95 2.65 7162 2.0 1.50 1.90 6063 5.3 Laws governing the variation of free volume fraction (corresponding to) Figure 2 ) like Figure 2As shown, the free volume fraction exhibits a typical "first decrease and then increase" trend with the change of nanorod doping ratio.
[0073] As the doping amount increased from 0.0 wt% to 1.5 wt%, the free volume fraction gradually decreased from 2.50% to 0.95%, indicating that the nanorods can effectively fill the gaps between PFA molecular chains, making the internal structure of the material more compact.
[0074] The mechanism is that nanorods with sizes matching the molecular chain scale can be embedded in the inter-chain gaps to form a highly dense interface layer, thereby compressing the free volume of the system.
[0075] When the doping ratio was further increased to 2.0 wt%, the free volume fraction rose back to 1.50%, indicating that the excess nanorods locally agglomerated, destroying the original uniform structure and introducing new interface defects and micropores.
[0076] 5.4 Young's modulus variation law (corresponding to) Figure 3 ) like Figure 3 As shown, the Young's modulus of the material exhibits an inverted U-shaped trend as the doping ratio changes.
[0077] The Young's modulus of pure PFA material is only 0.60 GPa, exhibiting low rigidity; as the doping ratio of nanorods increases, the Young's modulus increases significantly, reaching a maximum of 2.65 GPa at 1.5 wt%.
[0078] This improvement is mainly attributed to the "molecular chain constraint effect" formed by the nanorods at the microscopic interface. That is, the nanorods act as physical cross-linking points, restricting the movement of PFA molecular chains and improving the material's resistance to deformation.
[0079] When the doping ratio reaches 2.0 wt%, the Young's modulus decreases to 1.90 GPa due to the weakening of interfacial bonding and stress concentration caused by nanorod aggregation.
[0080] 5.5 Laws governing the variation of breakdown field strength (corresponding to) Figure 4 ) like Figure 4 As shown, the trend of the electromechanical breakdown field strength of the material is basically consistent with that of Young's modulus, and it also exhibits an "inverted U-shaped" characteristic.
[0081] The breakdown field strength of pure PFA material is 3408 MV / m, which gradually increases with the reinforcement of nanorods and reaches a peak of 7162 MV / m at 1.5 wt%.
[0082] The reason is: On the one hand, the reduction in free volume fraction restricts electron migration pathways, thereby suppressing the electron avalanche effect; On the other hand, the interfacial structure introduced by nanorods provides a large number of deep traps, which effectively capture space charge; In addition, a higher Young's modulus enhances the material's resistance to electric field-induced mechanical deformation (Maxwell stress), thereby improving its breakdown strength.
[0083] When the doping ratio increases to 2.0 wt%, the breakdown field strength decreases to 6063 MV / m due to increased structural defects and interface degradation.
[0084] 5.6 Optimal Doping Ratio Analysis Based on the data in Table 1 and Figures 2-4 The changing trend shows that: At a doping ratio of 1.5 wt%, the composite material simultaneously possesses: Minimum free volume fraction (0.95%); Highest Young's modulus (2.65 GPa); Maximum breakdown field strength (7162 MV / m).
[0085] The results show that at this doping ratio, the nanorods and PFA molecular chains achieve optimal spatial size matching and interface structure optimization, forming the most dense and uniform microstructure inside the system, thereby achieving a synergistic improvement in mechanical and electrical properties.
[0086] Therefore, the present invention preferably limits the doping ratio of silica nanorods to a range centered at 1.5 wt% to obtain the best overall performance.
[0087] 5.7 Technical Significance The comparative analysis of this embodiment verifies that the technical approach of this invention, which achieves microstructure regulation by precisely controlling the size and doping ratio of nanofillers, is effective. It also demonstrates that excessively high or low doping ratios cannot achieve optimal performance, further highlighting the rationality and advancement of the technical solution of this invention.
[0088] VI. Example 5: Comparison with existing materials (Table 2) To further verify the advantages of the modified PFA insulation material provided by this invention in terms of comprehensive performance, this embodiment selects the ethylene-tetrafluoroethylene copolymer (ETFE) material commonly used in existing aviation cables and the unmodified pure PFA material as comparative objects, and conducts a horizontal comparative analysis of their key performance.
[0089] 6.1 Explanation of Comparative Materials This embodiment selects the following three materials for comparison: (1) Traditional ETFE insulation materials; (2) Pure PFA material (without added nanofillers); (3) The modified PFA material of the present invention (PFA + 1.5 wt% silica nanorods).
[0090] The material of the present invention was prepared according to the method described in Example 3, and the optimal doping ratio determined in Example 4 was used.
[0091] 6.2 Comparison Indicators The following key indicators that reflect the overall performance of materials were selected for comparison: Young's modulus (GPa); Electromechanical breakdown field strength (MV / m); Comprehensive performance evaluation (combining temperature resistance, mechanical properties and electrical properties).
[0092] 6.3 Comparison Results (Table 2) Material type Young's modulus (GPa) Breakdown field strength (MV / m) Comprehensive performance evaluation ETFE 0.8～1.2 150 Low temperature resistance (≤200℃), prone to failure in high-temperature environments. Pure PFA 0.5～0.6 3408 It has excellent temperature resistance (approximately 260℃), but poor mechanical properties and is prone to creep. The material of this invention 2.65 7162 Significantly improved mechanical and electrical properties, suitable for extreme environments. 6.4 Comparative Analysis (1) Comparison with ETFE materials While traditional ETFE materials possess a certain level of mechanical strength, their molecular structure limits their temperature resistance, with long-term operating temperatures generally not exceeding 200°C. In high-temperature environments such as aircraft engine nacelles, ETFE materials are prone to thermal aging and softening failure, making it difficult to meet the demands of high-temperature service.
[0093] In contrast, this invention uses PFA as the matrix material, which has a temperature resistance of up to 260℃, significantly improving the heat resistance of the material and fundamentally solving the failure problem of ETFE material in high-temperature environments.
[0094] (2) Comparison with pure PFA material Although pure PFA material has excellent high temperature resistance, its Young's modulus is low (about 0.5 to 0.6 GPa), and the material is relatively soft. Under the complex vibration and stress environment of aviation cables, it is prone to cold flow creep, which leads to thinning or even failure of the insulation layer.
[0095] This invention significantly increases the Young's modulus of a material to 2.65 GPa by introducing silica nanorods of specific size and content, achieving a performance improvement of approximately four times. This improvement is mainly attributed to the molecular chain constraint effect formed by the nanorods at the microscopic interface, thereby significantly enhancing the material's resistance to deformation.
[0096] (3) Comparison of electrical performance In terms of electrical performance, ETFE material has a low breakdown field strength of only about 150 MV / m; although pure PFA material has some improvement, it still has problems with space charge accumulation and insufficient corona resistance.
[0097] The breakdown field strength of the material of this invention reaches 7162 MV / m, which is significantly higher than that of pure PFA material. The improvement is mainly due to the following factors: Nanorods fill the gaps between chains, reducing free volume and inhibiting electron migration; Nanoscale interfaces form deep traps that effectively capture space charge. Improve material rigidity and enhance its resistance to electric field stress.
[0098] (4) Comprehensive performance evaluation The above comparison shows that: ETFE materials have insufficient temperature resistance. Pure PFA materials have insufficient mechanical properties; The material of this invention achieves a synergistic improvement in high-temperature resistance, mechanical properties, and electrical properties through nanocomposite modification.
[0099] Especially under high temperature, high voltage and complex mechanical stress environments, the material of this invention exhibits superior stability and reliability.
[0100] 6.5 Summary of Technical Effects This embodiment demonstrates through comparative analysis that the modified PFA insulating material provided by the present invention has significant advantages in the following aspects: (1) Temperature resistance meets the requirements of extreme aviation environments; (2) The mechanical properties are significantly enhanced, and the creep resistance is improved; (3) Electrical insulation performance is greatly improved, and breakdown field strength is significantly enhanced; (4) Achieve synergistic optimization of multiple performance indicators.
[0101] Therefore, the present invention effectively overcomes the defects of different materials in the prior art, and has outstanding technical effects and application value.
[0102] VII. Summary of Key Mechanisms As can be seen from the above embodiments, the improved performance of the high-temperature and high-voltage aviation cable insulation material provided by this invention is not the result of a single factor, but rather a manifestation of the synergistic effect of material composition design, microstructure control, and optimized preparation process. Its key mechanisms are mainly reflected in the following aspects: 7.1 Size Matching Effect The one-dimensional silica nanorods selected in this invention preferably have a diameter of about 1 nm, which is comparable to the segment size of the PFA polymer chain, so that the nanorods can be effectively embedded in the gaps between the molecular chains.
[0103] This "size-matching" feature enables nanofillers not only to exist as simple filling phases, but also to participate in the construction of material structure at the molecular scale, forming a stable interfacial bonding structure between polymer chains, thereby significantly improving the structural compactness and stability of composite materials.
[0104] 7.2 Molecular chain constraint (molecular pin) effect Based on size matching, nanorods act as "physical cross-linking points" in the PFA matrix, effectively constraining the polymer chains by restricting the movement of molecular chain segments.
[0105] This effect can significantly reduce the slippage ability of molecular chains under external stress or high temperature conditions, thereby: Increase the Young's modulus of the material; Enhanced creep resistance; Improve the deformation stability of materials.
[0106] Therefore, this invention successfully overcomes the inherent defect of pure PFA material being "too soft".
[0107] 7.3 Free Volume Compression Effect The introduction of nanorods enables them to fill the free space between PFA molecular chains, significantly reducing the free volume fraction inside the material.
[0108] When nanorods are uniformly dispersed and their content is within a suitable range, a highly dense microstructure can be formed in the system, thereby: Shorten electron migration paths; Blocking electron acceleration channels; Suppressing the electron avalanche effect.
[0109] This mechanism directly leads to a significant increase in the material's breakdown field strength.
[0110] 7.4 Deep Trap Effect Because nanorods have a large specific surface area, the interface region formed between them and the PFA matrix can introduce a large number of deep-energy trap structures.
[0111] These deep traps can effectively capture space charges migrating under the influence of an electric field, thus: Reduce space charge accumulation; Suppress local electric field distortion; It slows down the formation and expansion of electrical tree trees.
[0112] Therefore, the corona resistance and high-voltage electrical reliability of the material are significantly improved.
[0113] 7.5 Synergistic Effect of Structural Densification and Interface Optimization When the nanorod doping ratio is controlled within a reasonable range (preferably about 1.5 wt%), an optimal interface structure is formed within the system: Nanorods are uniformly dispersed; No obvious reunion; The interface is tightly integrated.
[0114] At this point, the material exhibits the lowest free volume fraction and optimal mechanical and electrical properties.
[0115] However, when the doping ratio is too high, the nanorods are prone to aggregation, which introduces interfacial defects, undermines structural compactness, and leads to performance degradation. Therefore, this invention achieves an optimal balance of performance by precisely controlling the doping ratio.
[0116] 7.6 Synergistic Effect of End-Group Stabilization By fluorinating the end groups, the unstable polar groups at the ends of the PFA molecular chain are transformed into trifluoromethyl structures, thereby improving the chemical stability of the material at the molecular level.
[0117] This process not only: To avoid the formation of bubbles during high-temperature processing; Reduce dielectric loss; It also provides a more stable interfacial environment for nanofillers, which is conducive to achieving uniform dispersion and stable interfacial bonding.
[0118] 7.7 Process-enhanced dispersion effect By using a co-rotating twin-screw extruder for high-shear melt blending at 350℃~380℃, the nanorods are fully dispersed in the high-viscosity PFA melt.
[0119] High shear force can effectively overcome the mutual attraction between nanoparticles and avoid aggregation, thus: Ensure uniform distribution of nanofillers; Improve interface integration quality; Ensure the stability and consistency of material properties.
[0120] 7.8 Summary of Comprehensive Mechanisms In summary, this invention achieves a systematic improvement in material properties through the synergistic effect of multiple mechanisms, including "size matching effect, molecular chain constraint effect, free volume compression effect, deep trap effect, and process dispersion enhancement".
[0121] This multi-mechanism synergistic system breaks through the technical bottleneck of traditional insulating materials in achieving a balance between high-temperature resistance, mechanical properties, and electrical properties, resulting in materials with excellent comprehensive performance under high temperature, high voltage, and complex mechanical environments.
[0122] VIII. Application and Implementation Methods This embodiment applies the modified PFA insulation material prepared in the above embodiments to an aviation cable structure to verify its application effect in a real engineering environment.
[0123] 8.1 Structural Composition of Aviation Cables In this embodiment, the aviation cable includes: conductor; An insulating layer covering the outside of the conductor.
[0124] The conductor may be a copper conductor, a silver-plated copper conductor, or other conductive materials suitable for the aerospace environment; the insulating layer is formed by extrusion coating process using the modified PFA insulating material prepared in Embodiment 3 of the present invention.
[0125] Preferably, the insulation layer is uniformly coated on the outer surface of the conductor and has a continuous and dense structure to ensure the electrical insulation performance and mechanical protection performance of the cable.
[0126] 8.2 Insulation layer preparation and coating process In practical applications, the modified PFA insulating granules obtained in Example 3 are added to a cable extrusion device for melt processing. The specific process includes: First, the insulating granules are heated to a molten state, forming a melt with good fluidity; Subsequently, the molten material is uniformly extruded using an extruder and coated onto the outer surface of the conductor; During the extrusion process, temperature, pressure, and traction speed are controlled to ensure that the insulation layer has a uniform thickness and a dense structure. Finally, after cooling and shaping, a stable cable insulation layer structure is formed.
[0127] Through the above process, aviation cables with excellent interfacial bonding performance and structural integrity can be obtained.
[0128] 8.3 Service Environment and Performance Requirements The aviation cable in this embodiment is suitable for the following typical operating conditions: High-temperature environment (long-term operating temperature greater than 200℃, up to 260℃); High voltage environment (high voltage DC or high frequency pulsed electric field); Strong vibration and complex mechanical stress environment; High reliability requirements in scenarios such as aircraft engine compartments and electrical control systems.
[0129] Under the above operating conditions, cable insulation materials must simultaneously meet multiple requirements for heat resistance, mechanical strength, and electrical insulation performance.
[0130] 8.4 Application Effect By using the modified PFA insulating material of the present invention as the cable insulation layer, this embodiment achieves the following technical effects: (1) Improved high temperature resistance The insulation layer can work stably for a long time in a high-temperature environment of 260℃ without thermal aging or performance degradation. (2) Enhanced mechanical reliability Because the material’s Young’s modulus is significantly improved, the insulation layer is less prone to creep or local thinning under vibration and bending conditions, thus avoiding the risk of conductor puncture. (3) Improved electrical insulation performance The material has high breakdown field strength and excellent corona resistance, which can effectively prevent the development of electrical trees and insulation failure. (4) Improved structural stability The insulation layer has a dense internal structure with no obvious bubbles or defects, ensuring long-term operational stability. (5) Enhanced environmental adaptability It can adapt to the complex and ever-changing service environment in the aviation field, and improve the overall reliability of the cable.
[0131] 8.5 Significance in Engineering Applications As can be seen from this embodiment, the modified PFA insulation material provided by the present invention not only has excellent performance under experimental conditions, but can also be applied in engineering through conventional cable processing technology, and has good processing adaptability and promotion value.
[0132] This material is particularly suitable for the field of aviation cables, where extremely high insulation performance is required, and can be widely used in: Aircraft engine electrical systems; High-temperature electrical connection system; High-voltage power supply lines; Special avionics electronic equipment connection cables.
[0133] In summary, this invention, through the synergistic effect of material design and process optimization, enables insulating materials to achieve a balance of high-temperature resistance, mechanical properties, and electrical properties in practical applications, thereby meeting the usage requirements of aviation cables in extreme environments and demonstrating significant engineering application value.
[0134] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, various obvious modifications, substitutions or equivalent improvements can be made to the technical solution of the present invention without departing from the technical concept of the present invention, and such modifications, substitutions or improvements should all fall within the protection scope of the present invention.
[0135] Furthermore, the specific parameter ranges, material types, and process conditions described in this specification are only for illustrating the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
[0136] The scope of protection of this invention shall be determined by the claims. The description and drawings are for the purpose of interpreting the claims only.
Claims
1. A high-temperature, high-voltage resistant aviation cable insulation material, characterized in that, The insulating material comprises the following components: (1) Perfluoropropyl vinyl ether-tetrafluoroethylene copolymer (PFA) matrix resin; (2) Silica nanorods dispersed in the PFA matrix resin; The silica nanorods have a mass fraction of 0.5 wt% to 2.0 wt%, preferably 1.0 wt% to 1.8 wt%, and more preferably about 1.5 wt%. The silica nanorods are one-dimensional cylindrical structures with a diameter of 0.5 nm to 2 nm, preferably about 1 nm, and a length of 1 nm to 5 nm, preferably about 2 nm. The microscopic free volume fraction of the insulating material is no higher than 1.2%.
2. The insulating material according to claim 1, characterized in that, The molecular chain ends of the PFA matrix resin have a trifluoromethyl (-CF3) structure.
3. The insulating material according to claim 1 or 2, characterized in that, The surface of the silica nanorods is subjected to hydrogen saturation treatment or equivalent modification treatment to improve their interfacial bonding ability with the PFA matrix.
4. The insulating material according to any one of claims 1 to 3, characterized in that, The Young's modulus of the insulating material is not less than 2.0 GPa, preferably not less than 2.5 GPa.
5. The insulating material according to any one of claims 1 to 4, characterized in that, The breakdown field strength of the insulating material is not less than 6000 MV / m, preferably not less than 7000 MV / m.
6. The insulating material according to any one of claims 1 to 5, characterized in that, The microscopic free volume fraction of the insulating material is not higher than 1.0%.
7. A method for preparing a high-temperature, high-voltage resistant aviation cable insulation material, characterized in that, Includes the following steps: (1) Preparation of PFA matrix resin; (2) The PFA matrix resin is subjected to end-group fluorination stabilization treatment to convert the ends of its molecular chains into trifluoromethyl structures; (3) The treated PFA matrix resin is mixed with silica nanorods and melt-blended by a twin-screw extruder at 350℃~380℃ to obtain nanocomposite insulating material.
8. The preparation method according to claim 7, characterized in that, Step (1) employs an aqueous dispersion polymerization process, including: In a reactor, using deionized water as the medium, dispersants, buffers, and chain transfer agents are added, perfluoropropyl vinyl ether comonomers are introduced, and tetrafluoroethylene monomers are introduced. The polymerization reaction is carried out at a pressure of 1.5–2.5 MPa and a temperature of 70–85°C to obtain PFA coarse powder.
9. The preparation method according to claim 7 or 8, characterized in that, In step (2), fluorine gas or a mixture of fluorine gas and inert gas is introduced at 200℃~250℃ to perform end-group fluorination treatment.
10. The preparation method according to any one of claims 7 to 9, characterized in that, In step (3), the silica nanorods and PFA matrix resin are premixed in a dry state before melt blending.