A super-permeable PTFE microporous raw material tape for cables and its preparation method

Abstract

This invention discloses an ultra-permeable PTFE microporous raw material tape for cables and its preparation method, relating to the field of cable materials. The microporous raw material tape comprises polytetrafluoroethylene (PTFE), a propellant, and hydrophobic porous particles. The hydrophobic porous particles are prepared by hydrophobic modification of porous particles with silane. Each porous particle includes a core layer and a shell layer; the core layer is naphthalene, and the shell layer is silica, with a molar ratio of (2-8):1. This application incorporates hydrophobic porous particles into the PTFE raw material tape. The naphthalene in the core layer can volatilize at high temperatures to form hollow particles, which, combined with the micropores of the silica shell layer, improves the air permeability of the raw material tape. When applied to cables, this increases temperature diffusion efficiency. Simultaneously, the porous particles provide a rigid framework, reducing irreversible deformation and improving tear resistance. The micropores of the hydrophobic porous particles can block water molecules with high surface tension, and, combined with the hydrophobic groups on the surface, enhance the water-blocking effect of the raw material tape, meeting the requirements of cable applications.

Description

Technical Field

[0001] This invention relates to the field of cable materials, and more particularly to an ultra-permeable PTFE microporous raw material tape for cables and its preparation method. Background Technology

[0002] Polytetrafluoroethylene (PTFE) is widely used in cable wrapping insulation protection due to its excellent high-temperature resistance, superior insulation properties, strong corrosion resistance, and good flame retardancy. It is particularly crucial in high-end applications with stringent material performance requirements, such as aerospace, new energy vehicles, 5G communications, and chemical industries, where it is a key material for ensuring the safe and stable operation of cables. Unsintered PTFE raw tape, with its good flexibility, bending resistance, and shock resistance, facilitates tight bonding during cable wrapping, effectively improving the electrical performance and structural stability of cables, making it an indispensable component in cable manufacturing.

[0003] During actual cable operation, especially in high-temperature, high-humidity, or highly enclosed environments, heat is generated inside the cable due to current transmission. In such cases, the air permeability of the PTFE raw material tape used for cable wrapping becomes particularly crucial. Good air permeability helps dissipate the heat generated inside the cable in a timely manner, preventing excessively high local temperatures caused by heat accumulation, which could affect insulation performance. Simultaneously, it promotes the expulsion of internal moisture and residual gases, reducing the corrosion of the cable conductor by moisture condensation, thereby extending the cable's service life and improving operational safety.

[0004] However, existing PTFE raw material tapes for cables generally suffer from insufficient air permeability. This is mainly due to the molecular structure of PTFE itself. Its molecular chains are composed of carbon atoms tightly wrapped by fluorine atoms, forming a dense mixed crystalline and amorphous structure with extremely small intermolecular gaps, making it difficult for gases and moisture to permeate. Traditional production processes often focus on improving the insulation strength, dimensional stability, and mechanical properties of the raw material tape, frequently optimizing these properties by increasing material density. This further exacerbates the densification of the raw material tape structure, resulting in a further reduction in air permeability. Summary of the Invention

[0005] This invention provides an ultra-permeable PTFE microporous raw material tape for cables and its preparation method. By doping hydrophobic porous particles into the PTFE raw material tape, a hollow, breathable rigid support skeleton can be formed during the subsequent high-temperature degreasing process due to the full volatilization of naphthalene, thereby improving the tear resistance of the raw material tape, improving its air permeability, increasing heat dissipation efficiency, and providing a certain water-blocking effect, which can be used for cable protection.

[0006] To address the aforementioned technical problems, one objective of this invention is to provide an ultra-permeable PTFE microporous raw material tape for cables, comprising the following components by weight: Polytetrafluoroethylene: 100 parts; Propellant: 15-25 parts; Hydrophobic porous particles: 2-4 parts; The hydrophobic porous particles are prepared by hydrophobic modification of porous particles with silane. The porous particles include a core layer and a shell layer. The core layer is naphthalene and the shell layer is silicon dioxide. The molar ratio of the core layer to the shell layer is (2-8):1.

[0007] This application incorporates hydrophobic porous particles into PTFE raw material tape. During the degreasing stage of the preparation process, high-temperature treatment completely volatilizes the naphthalene in the hydrophobic porous particles, forming micropores on the silica layer to improve the overall air permeability of the raw material tape. Simultaneously, these hollow hydrophobic porous particles act as a rigid support skeleton within the raw material tape, reducing compression set and irreversible deformation, improving tear resistance, and enhancing its sealing performance. Furthermore, the silica wall layer of these hydrophobic porous particles contains pores that allow gas diffusion, effectively improving the air permeability of the raw material tape and allowing gas passage to a certain extent. When applied to cables, this improves heat dissipation efficiency, balances internal pressure changes, and enhances operational safety. In addition, the micropores of these hydrophobic porous particles effectively block water molecules with high surface tension, and the hydrophobic groups on the surface of the particles further enhance water resistance, maintaining internal dryness and making them suitable for cable protection.

[0008] As a preferred embodiment, the silane is a fluorinated silane coupling agent.

[0009] The porous particles in this application are hydrophobically modified using fluorinated silanes. The fluorinated silane coupling agent can form silanized groups with the hydroxyl groups on the surface of silica, thereby introducing hydrophobic groups on the surface. This not only improves the water-blocking effect of the raw material tape, but also reduces the surface energy of the porous particles and improves the compatibility with polytetrafluoroethylene, thus ensuring uniform particle distribution in the system and ultimately improving the mechanical properties of the material.

[0010] As a preferred embodiment, the fluorinated silane coupling agent includes at least one of trifluoropropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and heptadecafluorodecyltriethoxysilane.

[0011] As a preferred embodiment, the molar ratio of the core layer to the shell layer is (4-6):1.

[0012] This application controls the molar ratio of naphthalene in the core layer and silica in the shell layer, which can simultaneously improve air permeability and tensile strength. This is because if the amount of silica raw material increases, the thickness of the shell layer will increase and the porosity will decrease, resulting in a decrease in the overall air permeability of the raw material tape. If the amount of silica raw material is too small, the thickness of the silica shell layer formed will be small, which will lead to a decrease in the overall compressive strength of the hydrophobic porous particles, an increase in the permanent compression deformation and irreversible deformation of the raw material tape, and a deficiency in mechanical properties.

[0013] As a preferred embodiment, the D50 particle size of the porous particles is 30-100 nm.

[0014] As a preferred embodiment, the propellant includes at least one of naphtha, paraffin oil, and petroleum ether.

[0015] As a preferred embodiment, the method for preparing the porous particles includes the following steps: dispersing the naphthalene in a non-polar solvent to prepare a naphthalene solution, then adding the naphthalene solution dropwise to an aqueous solution, while simultaneously adding ammonia and a surfactant to prepare a suspension, then slowly adding a silicon source solution and stirring the reaction, followed by filtration, washing, drying, and sieving to obtain porous particles.

[0016] This application dissolves naphthalene in a non-polar solvent, and after being added dropwise to an aqueous phase, it precipitates out tiny crystal nuclei due to changes in solubility. A porous silica coating layer is then formed on the surface of these nuclei using ammonia water as a catalyst, which improves the supporting strength of the porous particles and also enhances the air permeability of the raw material belt.

[0017] As a preferred embodiment, in the method for preparing the porous particles, the surfactant accounts for 0.1wt%-0.2wt% of the mass of the suspension.

[0018] As a preferred embodiment, in the method for preparing the porous particles, the surfactant includes at least one of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and hydroxyethyl cellulose.

[0019] This application utilizes surfactants to form micelles in aqueous solution, allowing silicate ions to undergo condensation reactions around the micelles and deposit to form a silica framework, leaving regular nanopores. This results in porous particles with high surface porosity, and also reduces the surface tension of the particles, improving the uniformity of the porous particle surface.

[0020] As a preferred embodiment, in the method for preparing the porous particles, the mass ratio of the naphthalene solution to the aqueous solution is 1:(10-20), and the naphthalene solution comprises naphthalene with a mass fraction of 5wt%-15wt%.

[0021] As a preferred embodiment, in the method for preparing the porous particles, the nonpolar solvent is cyclohexane.

[0022] As a preferred embodiment, in the method for preparing the porous particles, the ammonia water accounts for 2%-4% of the mass of the suspension.

[0023] As a preferred embodiment, in the method for preparing the porous particles, the concentration of the ammonia water is 25%-28%.

[0024] As a preferred embodiment, in the method for preparing the porous particles, the silicon source in the silicon source solution is at least one of tetraethyl orthosilicate, tetrabutyl orthosilicate, and tetrapropyl orthosilicate.

[0025] As a preferred embodiment, in the method for preparing the porous particles, the drying temperature is 30-50 ℃ and the drying time is 2-8 h.

[0026] As a preferred embodiment, the method for preparing the hydrophobic porous particles includes the following steps: adding the porous particles to an aqueous solution containing 3wt%-8wt% silane, stirring and reacting, filtering, washing, and drying to obtain the hydrophobic porous particles.

[0027] This application modifies porous particles with silane, which introduces hydrophobic groups into the surface by reacting with hydroxyl groups on the surface of the shell silica to form silanized groups. This not only improves the water-blocking effect of the raw material tape, but also enhances its compatibility with polytetrafluoroethylene, thereby ensuring uniform particle distribution in the system and improving the mechanical properties of the material.

[0028] To solve the above-mentioned technical problems, the second objective of this invention is to provide a method for preparing ultra-permeable PTFE microporous raw material tape for cables, comprising the following steps: mixing polytetrafluoroethylene, hydrophobic porous particles and a propellant evenly, maturing the mixture and then extruding it in an extrusion device to obtain a polytetrafluoroethylene strip, which is then calendered and degreased to prepare the microporous raw material tape.

[0029] As a preferred option, the curing temperature is 40-60 ℃ and the time is 12-30 h.

[0030] As a preferred option, the degreasing temperature is 200-280 ℃.

[0031] Compared with the prior art, the present invention has the following beneficial effects: 1. This application involves doping hydrophobic porous particles into polytetrafluoroethylene (PTFE) raw material tape. After high-temperature degreasing, the naphthalene in the core layer completely volatilizes to form hollow particles, and the silica shell layer forms micropores. This not only improves the overall air permeability of the raw material tape but also serves as a rigid support skeleton, improving mechanical properties such as tear resistance. When applied to cables, it can improve heat dissipation efficiency, balance internal pressure changes, and is suitable for cable protection, thereby improving operational safety.

[0032] 2. In this application, the shell of the porous particles is a porous silica layer. Its tiny pores can resist water molecules with a large specific surface area to a certain extent. At the same time, silane is used for surface hydrophobic modification treatment. The silane reacts with the hydroxyl groups on the surface of the silica shell to form silanized groups, thereby introducing hydrophobic groups on the surface, further improving the water-blocking effect of the raw material tape, improving the compatibility between the porous particles and polytetrafluoroethylene, ensuring uniform particle distribution in the system, and improving the mechanical properties of the material.

[0033] 3. In this application, a surfactant is added to the aqueous phase of the porous particle preparation. This surfactant can reduce the specific surface area of ​​the aqueous solution, improve the uniformity of the condensation reaction, and form micelles in the aqueous solution. Silica can be deposited around the micelles to form a shell framework, leaving regular nanopores, thereby improving the porosity of the porous particles and the uniformity of the thickness of the silica deposited on the surface. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] Example 1 A method for preparing ultra-permeable PTFE microporous raw material tape for cables includes the following steps: (1) 1 kg of naphthalene was ultrasonically dispersed in 10 kg of cyclohexane solution to prepare a naphthalene solution. Then, all the naphthalene solution was added dropwise to 150 kg of aqueous solution, and 5 kg of ammonia and 0.2 kg of sodium dodecyl sulfate were added at the same time. The ammonia concentration was 25% to prepare a suspension. Then, a silicon source solution was slowly added dropwise to the suspension. The silicon source solution was an ethanol solution containing 50 wt% tetraethyl orthosilicate. The molar ratio of tetraethyl orthosilicate to naphthalene was 1:5. The reaction was stirred for 14 h. After filtration and washing, the solution was dried in an oven at 40 °C for 5 h. The porous particles with a D50 particle size of 50 nm were obtained by sieving. (2) Add 10 kg of porous particles to 50 kg of an aqueous solution containing 5 wt% trifluoropropyltrimethoxysilane, stir for 2 h, filter and wash, and dry in an oven at 40 ℃ for 2 h to obtain hydrophobic porous particles. (3) Mix 100 kg of polytetrafluoroethylene (PTFE), 3 kg of hydrophobic porous particles and 20 kg of propellant evenly. The propellant is paraffin oil. Then, let it stand at 50 ℃ for 24 h to mature. Then, add it to the extruder to extrude the PTFE strip. Press it into a film by a calender. Then, degrease it at 250 ℃ to remove the propellant and prepare microporous raw material tape.

[0038] Example 2 A method for preparing ultra-permeable PTFE microporous raw material tape for cables includes the following steps: (1) 1 kg of naphthalene was ultrasonically dispersed in 10 kg of cyclohexane solution to prepare a naphthalene solution. Then, all the naphthalene solution was added dropwise to 100 kg of aqueous solution, and 3 kg of ammonia and 0.1 kg of sodium dodecyl sulfate were added at the same time. The concentration of ammonia was 25% to prepare a suspension. Then, a silicon source solution was slowly added dropwise to the suspension. The silicon source solution was an ethanol solution containing 40 wt% tetraethyl orthosilicate. The molar ratio of tetraethyl orthosilicate to naphthalene was 1:6. The reaction was stirred for 12 h. After filtration and washing, the solution was dried in an oven at 40 °C for 5 h. The porous particles with a D50 particle size of 50 nm were obtained by sieving. (2) 10 kg of porous particles were added to 50 kg of an aqueous solution containing 3 wt% trifluoropropyltrimethoxysilane, stirred for 3 h, filtered and washed, and dried in an oven at 40 ℃ for 2 h to obtain hydrophobic porous particles. (3) Mix 100 kg of polytetrafluoroethylene (PTFE), 2 kg of hydrophobic porous particles and 15 kg of propellant evenly. The propellant is paraffin oil. Then, let it stand at 50 ℃ for 24 h to mature. Then, add it to the extruder to extrude the PTFE strip. Press it into a film by calendering. Then, degrease it at 250 ℃ to remove the propellant and prepare microporous raw material tape.

[0039] Example 3 A method for preparing ultra-permeable PTFE microporous raw material tape for cables includes the following steps: (1) 1 kg of naphthalene was ultrasonically dispersed in 10 kg of cyclohexane solution to prepare a naphthalene solution. Then, all the naphthalene solution was added dropwise to 200 kg of aqueous solution, and 6 kg of ammonia and 0.4 kg of sodium dodecyl sulfate were added at the same time. The ammonia concentration was 25% to prepare a suspension. Then, a silicon source solution was slowly added dropwise to the suspension. The silicon source solution was an ethanol solution containing 30 wt% tetraethyl orthosilicate. The molar ratio of tetraethyl orthosilicate to naphthalene was 1:4. The reaction was stirred for 16 h. After filtration and washing, the solution was dried in an oven at 40 °C for 5 h. The porous particles with a D50 particle size of 50 nm were obtained by sieving. (2) 10 kg of porous particles were added to 50 kg of an aqueous solution containing 8 wt% trifluoropropyltrimethoxysilane, stirred for 1 h, filtered and washed, and dried in an oven at 40 ℃ for 2 h to obtain hydrophobic porous particles. (3) Mix 100 kg of polytetrafluoroethylene (PTFE), 4 kg of hydrophobic porous particles and 25 kg of propellant evenly. The propellant is paraffin oil. Then, let it stand at 50 ℃ for 24 h to mature. Then, add it to the extruder to extrude the PTFE strip. Press it into a film by calendering. Then, degrease it at 250 ℃ to remove the propellant and prepare microporous raw material tape.

[0040] Example 4 A method for preparing ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (1), the molar ratio of tetraethyl orthosilicate and naphthalene is 1:2.

[0041] Example 5 A method for preparing ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (1), the molar ratio of tetraethyl orthosilicate and naphthalene is 1:4.

[0042] Example 6 A method for preparing ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (1), the molar ratio of tetraethyl orthosilicate and naphthalene is 1:6.

[0043] Example 7 A method for preparing ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (1), the molar ratio of tetraethyl orthosilicate and naphthalene is 1:8.

[0044] Example 8 A method for preparing an ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (1), the amount of sodium dodecyl sulfate added to the suspension is 0.

[0045] Example 9 A method for preparing ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (2), the aqueous solution containing 5 wt% trifluoropropyltrimethoxysilane is replaced by an aqueous solution containing 5 wt% heptadecafluorodecyltrimethoxysilane.

[0046] Example 10 A method for preparing an ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (2), an aqueous solution containing 5 wt% trifluoropropyltrimethoxysilane is replaced by an aqueous solution containing 5 wt% methyltrimethoxysilane.

[0047] Example 11 A method for preparing an ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (3), the amount of hydrophobic porous particles added is 2 kg.

[0048] Example 12 A method for preparing an ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (3), the amount of hydrophobic porous particles added is 4 kg.

[0049] Comparative Example 1 A method for preparing ultra-permeable PTFE microporous raw material tape for cables includes the following steps: 100 kg of polytetrafluoroethylene (PTFE) and 20 kg of a propellant (paraffin oil) were stirred and mixed evenly. The mixture was then allowed to stand at 50 °C for 24 h to mature. The mixture was then extruded in an extruder to obtain PTFE strips. The strips were then pressed into films using a calender. Finally, the film was degreased at 250 °C to remove the propellant, thus preparing a microporous raw material tape.

[0050] Comparative Example 2 A method for preparing ultra-permeable PTFE microporous raw material tape for cables includes the following steps: (1) 10 kg of silica was added to 50 kg of an aqueous solution containing 5 wt% trifluoropropyltrimethoxysilane. The D50 particle size of silica was 50 nm. The mixture was stirred for 2 h, filtered, washed, and dried in an oven at 40 ℃ for 2 h to obtain hydrophobic silica. (2) Mix 100 kg of polytetrafluoroethylene (PTFE), 3 kg of filler particles and 20 kg of propellant evenly. The filler particles include hydrophobic silica and naphthalene in a molar ratio of 1:5. The propellant is paraffin oil. Then, let it stand at 50 ℃ for 24 h to mature. Then, add it to the extruder to extrude the PTFE strip. Press it into a film by a calender. Then, degrease it at 250 ℃ to remove the propellant and prepare microporous raw material tape.

[0051] Comparative Example 3 A method for preparing ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (1), the molar ratio of tetraethyl orthosilicate and naphthalene is 1:1.

[0052] Comparative Example 4 A method for preparing ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (1), the molar ratio of tetraethyl orthosilicate and naphthalene is 1:10.

[0053] Comparative Example 5 A method for preparing ultra-permeable PTFE microporous raw material tape for cables includes the following steps: (1) 1 kg of naphthalene was ultrasonically dispersed in 10 kg of cyclohexane solution to prepare a naphthalene solution. Then, all the naphthalene solution was added dropwise to 150 kg of aqueous solution, and 5 kg of ammonia and 0.2 kg of sodium dodecyl sulfate were added at the same time. The ammonia concentration was 25% to prepare a suspension. Then, a silicon source solution was slowly added dropwise to the suspension. The silicon source solution was an ethanol solution containing 50 wt% tetraethyl orthosilicate. The molar ratio of tetraethyl orthosilicate to naphthalene was 1:5. The reaction was stirred for 14 h. After filtration and washing, the solution was dried in an oven at 40 °C for 5 h. The porous particles with a D50 particle size of 50 nm were obtained by sieving. (2) Mix 100 kg of polytetrafluoroethylene (PTFE), 3 kg of porous particles and 20 kg of propellant evenly. The propellant is paraffin oil. Then, let it stand at 50 ℃ for 24 h to mature. Then, add it to the extruder to extrude the PTFE strip. Press it into a film by a calender. Then, degrease it at 250 ℃ to remove the propellant and prepare microporous raw material tape.

[0054] Comparative Example 6 A method for preparing an ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (3), the amount of hydrophobic porous particles added is 0.5 kg.

[0055] Comparative Example 7 A method for preparing an ultra-permeable PTFE microporous raw material tape for cables differs from Example 1 in that, in step (3), the amount of hydrophobic porous particles added is 7 kg.

[0056] Performance testing 1. Air permeability: The air permeability of the microporous raw material tapes prepared in the examples and comparative examples was tested according to GB / T 1038.1-2022 "Test method for gas permeability of plastic films and sheets - Part 1: Differential pressure method". The test results are shown in Table 1 below.

[0057] 2. Waterproofing rate: According to GB / T 1034-2008 standard, the microporous raw material tape prepared in the examples and comparative examples was cut into samples of specified size, dried to constant weight at 40 ℃, and then soaked in distilled water at 25 ℃ for 24 h. After taking them out, the surface moisture was wiped off with filter paper and weighed immediately. The percentage increase in mass was calculated as the water absorption rate. The test results are shown in Table 1 below.

[0058] 3. Tensile strength: The tensile strength of the microporous raw material tapes prepared in the examples and comparative examples was tested according to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The test results are shown in Table 1 below.

[0059] Table 1 - Performance test results of microporous raw material tapes in the embodiments and comparative examples of this application As shown in Table 1, in Examples 1-3 of this application, hydrophobic porous particles are doped into the polytetrafluoroethylene raw material tape. The high-temperature treatment during the degreasing stage can completely volatilize the naphthalene in the core layer and form micropores on the silica shell layer, forming hollow hydrophobic porous particles. These particles serve as a rigid support skeleton in the raw material tape to improve tensile strength. At the same time, the silica shell layer of the hydrophobic porous particles has pores that allow gas diffusion, which effectively improves the air permeability of the raw material tape. When applied to cables, it can improve heat dissipation efficiency. Furthermore, the smaller pores can reduce the passage rate of high surface tension water molecules. Combined with the hydrophobic groups on the surface, it reduces the water absorption rate and improves the water-blocking and sealing effect.

[0060] By comparing the schemes of Example 1 and Comparative Example 1 in Table 1, it can be seen that the polytetrafluoroethylene raw material tape of Comparative Example 1 does not contain hydrophobic porous particles. The polytetrafluoroethylene raw material tape has extremely low air permeability. When used as a wrapping material for cables, the heat generated inside the cable is difficult to dissipate from the inside, which can easily lead to excessive local heat and affect the insulation performance, thus reducing the safety of cable operation.

[0061] Comparing the schemes of Example 1 and Comparative Example 2 in Table 1, it can be seen that the polytetrafluoroethylene raw material tape of Comparative Example 2 simultaneously incorporates naphthalene and hydrophobic silica particles. Since the surface of the naphthalene particles is not coated with a silica shell, after complete volatilization during the high-temperature degreasing stage, it leaves tiny pores inside the raw material tape. The presence of these pores increases the compressive deformation and irreversible deformation of the raw material tape, thereby reducing the tensile strength of the material and resulting in insufficient mechanical properties. Secondly, the pores left inside the raw material tape also allow water molecules to gradually penetrate, increasing the material's water absorption rate and thus reducing its water-blocking performance, limiting its application in cables.

[0062] A comparison of the schemes in Examples 1, 4-7, and Comparative Examples 3-4 in Table 1 shows that Examples 1 and 4-7 controlled the molar ratio of tetraethyl orthosilicate to naphthalene to be 1:(2-8) during the preparation of porous particles, while Comparative Example 3 used a molar ratio of 1:1, resulting in an excessively thick silica shell layer in the prepared porous particles and a reduced porosity of the silica shell layer. This led to a significant decrease in the air permeability of the raw material tape and a reduction in heat diffusion efficiency. Comparative Example 4 used a molar ratio of 1:10 for tetraethyl orthosilicate to naphthalene, resulting in an excessively thin silica shell layer in the prepared porous particles. This insufficient strength as a rigid framework resulted in a decrease in the tensile strength of the material and an increase in water absorption.

[0063] Comparing the schemes of Example 1 and Comparative Example 5 in Table 1, it can be seen that the porous particles of Comparative Example 5 were not surface modified with trifluoropropyltrimethoxysilane. The hydrophilic groups such as hydroxyl groups on the surface of the porous particles will increase the contact angle with water, promote the penetration of water molecules, and lead to an increase in the water absorption rate of the material. Secondly, polytetrafluoroethylene is a non-polar material, while the silica shell coating on the surface of the porous particles is a polar material. The compatibility between the two is poor, which makes the material prone to agglomeration, and ultimately the tensile strength of the raw material tape is greatly reduced.

[0064] Comparing the schemes of Examples 1, 11-12 and Comparative Examples 6-7 in Table 1, it can be seen that the amount of hydrophobic porous particles added to the raw material tape in Examples 1 and 11-12 is 2-4 kg, while the amount of hydrophobic porous particles added to the raw material tape in Comparative Example 6 is 0.5 kg. The content of hydrophobic porous particles is too low, resulting in low air permeability and low heat diffusion efficiency of the raw material tape. The amount of hydrophobic porous particles added to the raw material tape in Comparative Example 7 is 7 kg. The content of hydrophobic porous particles is too high, which will form a large number of "stress concentration points" in the matrix. When the material is subjected to tensile force, the stress cannot be evenly distributed in the matrix and is concentrated at the interface around the particles, resulting in premature microcracks and reduced tensile strength.

[0065] Comparing the schemes of Examples 1 and 8 in Table 1, it can be seen that in Example 1, the addition of sodium dodecyl sulfate surfactant in the aqueous phase during the porous particle preparation process can reduce the specific surface area, improve the uniformity of the condensation reaction, and form micelles in the aqueous solution. Silica is deposited around the micelles to form a shell framework, forming regular nanopores in the silica shell, thereby improving the porosity of the porous particles and the uniformity of the silica thickness, and improving air permeability and tensile strength. In Example 8, because sodium dodecyl sulfate surfactant was not added to the aqueous phase, the porosity of the silica shell deposited on the naphthalene surface was lower and the thickness was uneven, resulting in a decrease in air permeability and tensile strength.

[0066] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A super-permeable PTFE microporous raw material tape for cables, characterized in that, Includes the following components by weight: Polytetrafluoroethylene: 100 parts; Propellant: 15-25 parts; Hydrophobic porous particles: 2-4 parts; The hydrophobic porous particles are prepared by hydrophobic modification of porous particles with silane. The porous particles include a core layer and a shell layer. The core layer is naphthalene and the shell layer is silicon dioxide. The molar ratio of the core layer to the shell layer is (2-8):

1.

2. The ultra-permeable PTFE microporous raw material tape for cables as described in claim 1, characterized in that, The silane is a fluorinated silane coupling agent.

3. The ultra-permeable PTFE microporous raw material tape for cables as described in claim 1, characterized in that, The D50 particle size of the porous particles is 30-100 nm.

4. The ultra-permeable PTFE microporous raw material tape for cables as described in claim 1, characterized in that, The propellant includes at least one of naphtha, paraffin oil, and petroleum ether.

5. The ultra-permeable PTFE microporous raw material tape for cables as described in claim 1, characterized in that, The method for preparing the porous particles includes the following steps: dispersing the naphthalene in a non-polar solvent to prepare a naphthalene solution, then adding the naphthalene solution dropwise to an aqueous solution, while adding ammonia and a surfactant to prepare a suspension, then slowly adding a silicon source solution and stirring the reaction, and finally filtering, washing, drying, and sieving to obtain porous particles.

6. The ultra-permeable PTFE microporous raw material tape for cables as described in claim 5, characterized in that, In the method for preparing the porous particles, the surfactant accounts for 0.1wt%-0.2wt% of the suspension mass; And / or, in the method for preparing the porous particles, the surfactant includes at least one of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and hydroxyethyl cellulose.

7. The ultra-permeable PTFE microporous raw material tape for cables as described in claim 5, characterized in that, In the method for preparing the porous particles, the mass ratio of the naphthalene solution to the aqueous solution is 1:(10-20), and the naphthalene solution comprises naphthalene with a mass fraction of 5wt%-15wt%. And / or, in the method for preparing the porous particles, the nonpolar solvent is cyclohexane; And / or, in the method for preparing the porous particles, the ammonia water accounts for 2%-4% of the mass of the suspension; And / or, in the method for preparing porous particles, the silicon source in the silicon source solution is at least one of tetraethyl orthosilicate, tetrabutyl orthosilicate, and tetrapropyl orthosilicate.

8. The ultra-permeable PTFE microporous raw material tape for cables as described in claim 1, characterized in that, The preparation method of the hydrophobic porous particles includes the following steps: adding the porous particles to an aqueous solution containing 3wt%-8wt% silane, stirring and reacting, filtering, washing and drying to obtain hydrophobic porous particles.

9. A method for preparing an ultra-permeable PTFE microporous raw material tape for cables as described in any one of claims 1-8, characterized in that, Includes the following steps: Polytetrafluoroethylene (PTFE), hydrophobic porous particles, and a propellant are stirred and mixed evenly, and after maturation, they are added to an extrusion device to extrude PTFE strips. After calendering and degreasing, microporous raw material tapes are prepared.

10. The method for preparing ultra-permeable PTFE microporous raw material tape for cables as described in claim 9, characterized in that, The curing temperature is 40-60 ℃, and the time is 12-30 h; And / or, the defatting temperature is 200-280 ℃.

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