Unsintered PTFE microporous film and wrapping tape with high dielectric strength and low friction coefficient

Abstract

The utility model discloses a kind of unsintered PTFE microporous film and wrapping tape with high dielectric strength and low friction coefficient, film includes: microporous area: by PTFE resin fiber nodule and fiber network constitute, its microporous hole area proportion is 28% to 70%, micropore inner size is between 8nm to 2.7 μm, fiber width is 0.5nm to 1nm;Dense area: by PTFE resin fiber nodule and mutually fused by faceted connection mode, form continuous, high-density faceted PTFE area;Overall density is between 0.6 g / cm³ to 5.0 g / cm³.Wrapping tape is made by cutting unsintered PTFE microporous film, after wrapping in cable conductor, after sintering process, for manufacturing the insulating layer or sheath layer of cable.By the above-mentioned mode, the utility model can be integrated with high dielectric strength, low friction coefficient, low dielectric loss and good mechanical property, and meet the harsh requirements of high-end cable to low loss, low friction and high reliability in final application level.

Description

Technical Field

[0001] This utility model relates to the field of high-performance insulating materials, and in particular to an unsintered PTFE microporous film and wrapping tape that has both high dielectric strength and low coefficient of friction. Background Technology

[0002] With the rapid development of strategic industries such as aviation, intelligent robotics, new energy, and high-end equipment manufacturing, the demand for high-performance cables is becoming increasingly urgent. These applications require cable insulation materials to achieve efficient and stable signal and power transmission under extreme environments. Specifically, this manifests as low dielectric loss to reduce signal attenuation, low coefficient of friction for easy installation and improved wear resistance, high dielectric strength to ensure insulation reliability, and performance stability over a wide temperature range. However, existing common polymer insulation materials often struggle to simultaneously meet these demanding performance combinations, exhibiting significant performance shortcomings and forming a technological bottleneck restricting the development of high-end cables.

[0003] Currently, polytetrafluoroethylene (PTFE) is considered one of the preferred materials for high-frequency cable insulation due to its inherent low dielectric constant, low loss factor, and excellent chemical stability. However, in practical applications, traditional PTFE dense insulating films present inherent contradictions in cable manufacturing: while traditional PTFE dense film tapes maintain excellent insulation performance, they cannot be tightly bonded to the conductor during the wrapping process, and the loose semi-overlap joints allow moisture to enter, affecting cable performance in humid environments. This contradiction of "incompatible wrapping insulation strength and low dielectric loss" makes it difficult for existing technologies to provide a cable insulation material that combines excellent machinability and top-notch electrical performance.

[0004] Therefore, current technology cannot provide an ideal cable wrapping material that can maintain a low dielectric constant and low loss similar to unsintered PTFE, while also possessing sufficient mechanical strength and a low coefficient of friction to meet the requirements of high-speed, reliable wrapping processes. The wrapped cable, through a sintering process, ensures a tight bond between the unsintered PTFE and the conductor, with the semi-overlapping joints fused together to prevent moisture penetration. Developing a new material that can overcome these performance contradictions has become an urgent need in the industry. Utility Model Content

[0005] The main technical problem solved by this utility model is to provide an unsintered PTFE microporous film and a cable wrapping tape that can overcome the above-mentioned performance contradictions, integrating high dielectric strength, low coefficient of friction, low dielectric loss and good mechanical properties, and meeting the stringent requirements of high-end cables for low loss, low friction and high reliability at the final application level.

[0006] To solve the above-mentioned technical problems, one technical solution adopted by this utility model is: to provide an unsintered PTFE microporous film with both high dielectric strength and low coefficient of friction, the microstructure of which includes: Microporous region: Composed of PTFE resin fiber nodules and fiber network, the micropore area accounts for 28% to 70%, the micropore size is between 8nm and 2.7μm, and the fiber width is between 0.5nm and 1nm; Dense region: formed by the fusion of PTFE resin fiber nodules through planar connections, creating a continuous, high-density planar PTFE region; The microporous and dense regions are intertwined, collectively forming the microstructure of the film, resulting in an overall density between 0.6 g / cm³ and 5.0 g / cm³. The dense regions provide the main mechanical support for the film, while the microporous regions contribute excellent dielectric properties and low friction characteristics.

[0007] In a preferred embodiment of this invention, the thickness of the unsintered PTFE microporous film is 0.03 mm to 0.38 mm, and the thickness deviation is controlled within ±0.005 mm.

[0008] In a preferred embodiment of the present invention, the dielectric strength of the thin film is between 30kV / mm and 170kV / mm, the dielectric constant Dk is between 1.3 and 2.9, and the loss tangent Df is between 0.00005 and 0.001.

[0009] In a preferred embodiment of the present invention, the static friction coefficient of the film under dry friction conditions is 0.04 to 0.1, and the dynamic friction coefficient is 0.05 to 0.15.

[0010] To solve the above-mentioned technical problems, another technical solution adopted by this utility model is to provide a wrapping tape, including the unsintered PTFE microporous film, with a wrapping tape width of 2.3mm to 20mm and a continuous length of more than 500 meters.

[0011] In a preferred embodiment of this invention, the wrapping tape is wrapped around the cable conductor and sintered to form the cable's insulation or sheath layer. After sintering, approximately 80% of the film's microporous structure is retained, the tensile strength is greater than 15 MPa, and the long-term operating temperature range can reach -150°C to 260°C.

[0012] In a preferred embodiment of this utility model, the cable is a radio frequency coaxial cable, aviation wire, wear-resistant cable for robots, data cable, or power feeder.

[0013] The beneficial effects of this invention are as follows: The unsintered PTFE microporous film provided by this invention, through its unique two-phase microstructure composed of interwoven dense and microporous regions, not only fills the high-porosity microporous regions with air, giving the material extremely low dielectric constant and loss factor, which can significantly reduce high-frequency signal transmission loss; but also provides a solid mechanical skeleton for the material through the continuous dense region formed by the planar connection of PTFE resin fiber nodules, enabling it to obtain high strength and excellent dimensional stability after wrapping and sintering, while maintaining the inherent low friction, high temperature resistance and chemical corrosion resistance of PTFE.

[0014] This invention wraps a thin film around a cable wrapping tape material, exhibiting significant processing and usage advantages: its low coefficient of friction helps to increase the wrapping speed in cable production, improve production efficiency, and reduce wear on the conductor; at the same time, the material's low density characteristics are conducive to achieving cable lightweighting, meeting the stringent weight control requirements of aerospace and other fields, and providing key basic material support for the manufacturing of high-performance, high-reliability aviation cables, robot cables and other high-end cables. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a scanning electron microscope (SEM) image of the unsintered PTFE microporous film described in Embodiment 1 of this utility model at a magnification of 15000x. Figure 2 This is a scanning electron microscope (SEM) image of the unsintered PTFE microporous film described in Embodiment 2 of this utility model at 15000x magnification; Figure 3 This is a scanning electron microscope (SEM) image of the unsintered PTFE microporous film described in Embodiment 3 of this utility model at a magnification of 15000x. Figure 4 This is a schematic diagram of the structure of the present invention, showing the wrapping tape being wound onto the tray. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0017] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0018] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0019] In the description of this utility model, it should be noted that the terms "front," "rear," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the utility model product is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this utility model. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0020] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0021] In this invention, unless otherwise expressly specified and limited, "above or below" the first feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on" the first feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the first feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0022] The embodiments of this utility model include: Example 1:

[0023] S1: Material preparation and mixing: At a constant temperature of 22℃, PTFE fine powder (particle size 25μm) and aviation kerosene (distillation range 180-260℃) are mixed at a weight ratio of 100:22 and stirred at low speed in a double cone mixer for 40 minutes to form a uniform paste.

[0024] S2: Maturation: Transfer the mixed paste to a sealed container and let it stand at a constant temperature of 22°C for 20 hours to allow the additives to fully penetrate.

[0025] S3: Pre-forming: The matured material is fed into a plunger extruder and initially extruded into a cylindrical blank with a diameter of 80mm under a pressure of 1.5MPa. Then, the mold is changed and the material is extruded into a dense, fine-diameter cylindrical disc with a diameter of 8mm under a pressure of 3.0MPa.

[0026] S4: Calendering: After the coil material is placed in a constant temperature environment of 25℃ until the temperature is uniform, it is immediately fed into a three-roll calender at the same temperature. The roller spacing is adjusted to 0.05mm, and calendering is performed to form a continuous narrow strip with a width of 12mm.

[0027] S5: Degreasing and Pore Formation: The calendered narrow strip is passed through a stepped heating oven with a length of 8 meters and temperature zones of 100℃, 150℃ and 200℃ at a speed of 0.8 meters / minute, so that the aviation kerosene is completely evaporated and removed, and the PTFE resin expands to form a microporous structure.

[0028] S6: Post-processing: The thickness of the film after pore formation is measured online and then wound up. The resulting film thickness is 0.05 mm, apparent density is 0.75 g / cm³, and the micropore area ratio is approximately 70% to 90%. Example 2:

[0029] S1: Material preparation and mixing: At a constant temperature of 25°C, mix PTFE resin powder and aviation kerosene at a weight ratio of 100:18 and stir at high speed for 30 minutes to form a paste.

[0030] S2: Curing: The paste is cured in a sealed container at 25°C for 36 hours.

[0031] S3: Preforming and calendering: Following the method in Example 1, the material is extruded into a 10mm diameter disc, then left to stand in a constant temperature environment of 30℃ until the temperature is balanced, and then fed into a calendering roller (the roller spacing can be selected as 0.12mm) to form a narrow strip with a width of 15mm.

[0032] S4: Degreasing and Pore Forming: The narrow strip is degreased at a rate of 0.5 m / min through a 250°C hot air circulating oven.

[0033] S5: Rapid cooling: The degreased film is immediately subjected to rapid cooling and quenching in a 10°C cooling water bath.

[0034] S6: Post-processing: The cooled film is measured and wound up. The resulting film has a thickness of 0.15 mm, an apparent density of 1.8 g / cm³, a micropore area ratio of approximately 40% to 60%, and a crystallinity of 62% as determined by DSC. Example 3:

[0035] S1: Preparation and mixing: At a constant temperature of 18°C, high molecular weight PTFE resin and aviation kerosene are mixed at a weight ratio of 100:15 and stirred at low speed for a long time for 60 minutes to form a high viscosity paste.

[0036] S2: Curing: Extend the curing time to 48 hours at 18°C.

[0037] S3: Preforming and Calendering: The material is extruded into a dense disc with a diameter of 12mm using higher pressure (optional 4.0MPa), and then left to stand at 35°C until the temperature is uniform. After that, it is calendered under high pressure through a small roller gap (optional 0.25mm) to form a narrow strip with a width of 18mm.

[0038] S4: Degreasing and Pore Forming: Passing through a 280°C high-temperature oven at a lower speed (optional 0.3 m / min) ensures thorough degreasing while partially melting PTFE resin fiber nodules.

[0039] S5: Cooling: The narrow strip is naturally cooled to room temperature at room temperature. This natural cooling process is conducive to the regular arrangement of molecular chains, resulting in higher crystallinity, thereby improving the mechanical strength and density of the film.

[0040] S6: Post-processing: The film is wound up to obtain a thickness of 0.30 mm. Its apparent density is 2.5 g / cm³, the micropore area ratio is about 28% to 40%, the structure is more compact, and the mechanical strength is higher. Example 4:

[0041] This embodiment describes in detail the method for controlling the preparation of unsintered PTFE microporous films with different microstructures by adjusting the preparation process parameters of Examples 1 to 3, and the structural characteristics of the resulting products.

[0042] The microstructure of the unsintered PTFE microporous films consists of a two-phase system composed of dense regions and microporous regions interwoven with each other.

[0043] The microporous region is composed of PTFE resin fiber nodules and fiber networks, with the micropore area accounting for 28% to 70%, the micropore size ranging from 8 nm to 2.7 μm, and the width of the PTFE fibers constituting the micropores ranging from 0.5 nm to 1 nm. The dense regions are formed by the fusion of PTFE resin fiber nodules through planar connections, creating a continuous, high-density PTFE phase. These dense regions provide the primary mechanical support for the film, while the microporous regions impart excellent dielectric properties and low friction characteristics. By adjusting the relative proportions and morphological characteristics of these two regions, the overall density of the film can be adjusted between 0.6 g / cm³ and 5.0 g / cm³, thus meeting diverse application requirements.

[0044] Specifically, by adjusting the ratio of PTFE resin to aviation kerosene, calendering parameters, deoiling temperature and speed, and other process conditions, precise control of the microstructure can be achieved.

[0045] The high lubricant content and rapid degreasing process of Example 1 were used. The resulting film was dominated by microporous regions, and its morphology can be referenced. Figure 1 The characteristics include: abundant and fine fibers (approximately 0.5-0.8 nm in width), irregular and interconnected micropore morphology, wide pore size distribution (tens of nanometers to 2.0 μm), and micropore area accounting for 70% to 90%. This structure enables the film to have extremely low apparent density (approximately 0.6-1.2 g / cm³) and dielectric constant (Dk as low as 1.6), making it highly suitable for applications with extremely high requirements for lightweight design and ultra-low signal loss.

[0046] The uniform process parameters of Example 2 were used. The resulting film exhibits a uniform and interwoven distribution of dense and microporous regions, the morphology of which can be referenced. Figure 2 The characteristics include: relatively thick fibers (width approximately 0.8-1.0 nm), increased and uniformly distributed PTFE resin fiber nodules, relatively regular micropore morphology, concentrated pore size distribution (mainly between 0.1 μm and 1.0 μm), and a micropore area ratio of approximately 40% to 60%. This structure allows the film to maintain a low dielectric constant (Dk as low as 1.5) while possessing excellent mechanical strength, dimensional stability, and overall performance, making it suitable for most high-end cable insulation applications.

[0047] The low lubricant content, high-pressure calendering, and slow-temperature degreasing process of Example 3 were used. The resulting film exhibited a predominantly dense region, and its morphology can be referenced. Figure 3 The characteristics are: the PTFE resin fiber nodules are further enlarged and connected to form a more complete continuous matrix, the fiber network is denser, the micropore size is reduced, and the micropore area accounts for approximately 28% to 40%. This structure increases the apparent density of the film (up to 1.3 g / cm³ or more), provides optimal mechanical strength, and retains the chemical resistance and insulation properties of PTFE material, making it suitable for sheathing or insulation applications with special requirements for mechanical protection.

[0048] In summary, by precisely controlling the preparation process parameters, this invention can directionally adjust the relative ratio, connection method, and scale of the dense region and the microporous region in the unsintered PTFE microporous film, thereby preparing a series of products with gradient adjustable key parameters such as dielectric properties, mechanical strength, and density to meet the specific needs of different application scenarios.

[0049] Example 5: Wrapping tape and its application Preparation of wrapping tape: Using the unsintered PTFE microporous film rolls obtained in Examples 1 to 3 as raw materials, the wrapping tape manufacturing process is as follows: Production line process preparation includes: film roll 1, winding tray 2 - unwinding - using sharp carbide blades to continuously cut the film into the specific width required by the customer - winding onto tray 2 - inspection - warehousing.

[0050] This process can produce wrapped tape products with a bandwidth ranging from 2.3mm to 20mm and a continuous length of over 500 meters, which are then wound onto tray 2. Figure 4 As shown.

[0051] The aforementioned wrapping tape is wrapped around the cable conductor and then sintered to manufacture the cable's insulation or sheath layer. After sintering, the film retains a microporous structure, has a tensile strength greater than 15 MPa, and a long-term operating temperature range of -150℃ to 260℃.

[0052] Furthermore, after wrapping and sintering, this material, as a pure material with low polarization capability, exhibits a rich microporous structure that increases the internal void density, thereby reducing its overall density and significantly decreasing the number of polarized molecules per unit volume. This characteristic leads to a reduction in its dielectric constant, effectively lowering the dielectric loss between the cable and conductor, and thus significantly improving the transmission performance of high-frequency, high-speed communication cables and devices.

[0053] The main performance indicators of this wrapping tape product are shown in the table below:

[0054] After sintering, the wrapping tape of this invention can also be widely used in the following high-end cable applications: It is used as the main insulation layer of control cables to ensure the stability of signal transmission.

[0055] As an outer sleeve for the spiral hose, it provides abrasion resistance and flexibility.

[0056] Used to manufacture insulation and sheathing for wires and cables that are resistant to high temperatures and chemical corrosion, suitable for harsh industrial environments.

[0057] As insulation and sheathing for wiring systems in commercial and military aircraft, it meets the extremely high requirements of the aviation industry for weight, reliability and environmental resistance.

[0058] Insulation and sheathing used in data cables to ensure low-loss transmission of high-frequency signals.

[0059] It is particularly suitable for the insulation and sheathing of low-friction, wear-resistant cables used in AI robots. Its low coefficient of friction can effectively cope with the wear caused by frequent bending and movement.

[0060] Used as insulation and sheathing for power feeders, providing high dielectric strength and heat resistance.

[0061] The complete examples and performance data from preparation to application above demonstrate that the unsintered PTFE microporous film and wrapping tape provided by this invention are high-end cable insulation and sheathing materials with comprehensive performance and wide application, capable of meeting the needs of various demanding application scenarios.

[0062] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made using the content of this utility model specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. An unsintered PTFE microporous film with both high dielectric strength and low coefficient of friction, characterized in that, Its microstructure includes: Microporous region: Composed of PTFE resin fiber nodules and fiber network, the micropore area accounts for 28% to 70%, the micropore size is between 8nm and 2.7μm, and the fiber width is 0.5nm to 1nm; Dense region: formed by the fusion of PTFE resin fiber nodules through planar connections, creating a continuous, high-density planar PTFE region; The microporous regions and dense regions are intertwined to form the microstructure of the film, resulting in an overall density between 0.6 g / cm³ and 5.0 g / cm³.

2. The unsintered PTFE microporous film according to claim 1, characterized in that, The thickness of the unsintered PTFE microporous film is from 0.03 mm to 0.38 mm.

3. The unsintered PTFE microporous film according to claim 1, characterized in that, The dielectric strength of the unsintered PTFE microporous film is between 30kV / mm and 170kV / mm, the dielectric constant Dk is between 1.3 and 2.9, and the loss tangent Df is between 0.00005 and 0.

001.

4. The unsintered PTFE microporous film according to claim 1, characterized in that, The unsintered PTFE microporous film has a static friction coefficient of 0.04 to 0.1 and a dynamic friction coefficient of 0.05 to 0.15 under dry friction conditions.

5. A wrapping tape, characterized in that, The unsintered PTFE microporous film included in any one of claims 1 to 4, wherein the wrapping tape has a bandwidth of 2.3 mm to 20 mm and a continuous length of more than 500 meters.

6. The wrapping tape according to claim 5, characterized in that, The wrapping tape is wrapped around the cable conductor and, through a sintering process, forms the cable's insulation layer or sheath layer.

7. The wrapping tape according to claim 6, characterized in that, The cable may be a radio frequency coaxial cable, aviation wire, wear-resistant cable for robots, data cable, or power feeder.

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