Fluoroplastic insulated high-temperature resistant fireproof cable and preparation method thereof

Abstract

The application relates to the technical field of electric wire and cable, and discloses a fluoroplastic insulation high-temperature-resistant fireproof cable and a preparation method, the cable comprises a conductor layer, the conductor layer is twisted by multiple copper wires, the conductor layer is coated with a fluoroplastic insulation layer, the fluoroplastic insulation layer is coated with a shielding layer, the shielding layer is a copper-belt woven structure, the shielding layer is coated with an armor layer, the armor layer is woven by stainless steel wires, the armor layer is coated with a sheath layer, and the sheath layer comprises the following components in mass fractions: functionalized ethylene-tetrafluoroethylene copolymer, 50-70 parts by mass. The application constructs an interpenetrating polymer network formed by in-situ crosslinking of a functionalized fluoropolymer and an organic silicon elastomer in the sheath layer, and adopts an energy field gradient response vulcanization process, so that the prepared cable sheath keeps the inherent high-temperature resistance of fluoroplastic, and the flexibility and mechanical strength of the material are improved.

Description

Technical Field

[0001] This invention relates to the field of wire and cable technology, specifically to a fluoroplastic insulated high-temperature fire-resistant cable and its preparation method. Background Technology

[0002] Fluoroplastics, such as ethylene-tetrafluoroethylene copolymer (ETFE) and fusible polytetrafluoroethylene (PFA), are widely used as insulation and sheathing materials for special cables due to their excellent high-temperature resistance, chemical stability and electrical insulation properties. They are especially suitable for fields with harsh operating environments, such as aerospace, petrochemical and nuclear industries.

[0003] However, fluoroplastics have relatively rigid molecular chains and high crystallinity, resulting in significant bending stiffness. Cables using this material as their sheath layer suffer from limited overall flexibility, causing inconvenience in laying and installing them in confined and complex spaces. Furthermore, in dynamic applications requiring repeated bending, this can potentially impact the cable's lifespan.

[0004] To improve the flexibility of fluoroplastics, existing technologies employ physical blending methods with flexible polymers such as silicone elastomers. However, due to differences in molecular structure, polarity, and surface energy, fluoroplastics and silicone polymers exhibit poor thermodynamic compatibility. This incompatibility makes it difficult for the two phases to form a uniform microstructure during melt blending, resulting in weak interfacial bonding. The resulting blended material is prone to stress concentration points at its internal phase interfaces, leading to failure under external forces. This results in a decrease in key mechanical properties such as tensile strength and elongation at break, failing to meet the requirements of high-performance cable sheaths. Therefore, this invention provides a fluoroplastic-insulated high-temperature fire-resistant cable and its preparation method to address the shortcomings of existing technologies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a fluoroplastic insulated high-temperature fire-resistant cable and its preparation method, solving the problems of discontinuous control trajectory, static and unadjustable emotion mapping, lack of user feedback closed loop, weak adaptive capability, and insufficient fusion of multi-dimensional control information in existing technologies.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The first aspect of this invention provides a fluoroplastic insulated high-temperature fire-resistant cable, the cable comprising a conductor layer formed by multiple strands of copper wire, a fluoroplastic insulation layer surrounding the conductor layer, a shielding layer having a copper tape braided structure surrounding the fluoroplastic insulation layer, an armor layer having a stainless steel wire braid surrounding the shielding layer, and a sheath layer having the sheath layer comprising the following components in parts by weight:

[0008] Functionalized ethylene-tetrafluoroethylene copolymer: 50-70 parts by weight;

[0009] Vinyl-terminated polydimethylsiloxane: 30-50 parts by weight;

[0010] Hydrogen-containing silicone oil: 1.5-3.0 parts by weight;

[0011] Energy field gradient-responsive synergistic catalysis / crosslinking system: 2.05-2.7 parts by mass;

[0012] Fluorinated silane coupling agent: 0.5-2.0 parts by weight.

[0013] The functionalized ethylene-tetrafluoroethylene copolymer is a graft copolymer of ethylene-tetrafluoroethylene copolymer and 4-hydroxystyrene.

[0014] In another technical solution, the energy field gradient-responsive synergistic catalysis / crosslinking system is composed of a microwave-sensitive inhibiting platinum catalyst and an infrared-sensitive organic peroxide. The microwave-sensitive inhibiting platinum catalyst comprises 0.05-0.2 parts by mass, and the infrared-sensitive organic peroxide comprises 1.0-2.5 parts by mass.

[0015] In another specific technical solution, the vinyl-terminated polydimethylsiloxane has a kinematic viscosity of 30,000-60,000 mm³ at 25°C. 2 / s, wherein the vinyl content is 0.04-0.08 mmol / g.

[0016] A second aspect of this invention provides a method for preparing a fluoroplastic insulated high-temperature fire-resistant cable, comprising the following steps:

[0017] S1. Preparation of cable core: Multiple strands of copper wire are twisted into a conductor layer; a fluoroplastic insulation layer, a shielding layer, and an armor layer are sequentially wrapped around the outer periphery of the conductor layer to obtain the cable core to be sheathed; the shielding layer is formed by weaving copper strips around the outer periphery of the fluoroplastic insulation layer, and the armor layer is formed by weaving stainless steel wires around the outer periphery of the shielding layer.

[0018] S2. Preparation of sheath premix: Functionalized ethylene-tetrafluoroethylene copolymer, vinyl-terminated polydimethylsiloxane, hydrogen-containing silicone oil, energy field gradient-responsive synergistic catalysis / crosslinking system and fluorinated silane coupling agent are blended and granulated to obtain sheath premix particles.

[0019] S3. Sheath extrusion: The sheath premixed material particles are extruded and coated onto the armor layer of the cable core to form an uncrosslinked sheath layer.

[0020] S4. Energy field gradient crosslinking: The cable covered with an uncrosslinked sheath layer is continuously passed through an energy field gradient response vulcanization pipe, and crosslinking and curing are carried out in the first and second zones in succession within the pipe.

[0021] The first region is a microwave activation region, where a microwave field with a frequency of 2.45 GHz ± 50 MHz and a power of 20-40 kW is applied.

[0022] The second region is an infrared curing region, where infrared rays with a peak wavelength of 3-8μm are applied, and the total radiant power is 80-120kW.

[0023] Step S4 enables the sequential crosslinking of two different chemical systems. In the first region, the applied microwave energy is selectively absorbed by a microwave-sensitive, inhibiting platinum catalyst, thereby initiating a crosslinking reaction between the terminal vinyl polydimethylsiloxane and the hydrogen-containing silicone oil, forming a second polymer network. Subsequently, in the second region, the applied infrared energy is absorbed by an infrared-sensitive organic peroxide, thereby initiating a crosslinking reaction of the functionalized ethylene-tetrafluoroethylene copolymer, forming a first polymer network. This sequential crosslinking process, differentiated by energy field, avoids chemical interference between the two crosslinking reaction systems at the same time point, thus generating the aforementioned interpenetrating polymer network structure in situ within the sheath layer.

[0024] In one specific embodiment, the fluoroplastic insulation layer in step S1 is a fusible polytetrafluoroethylene insulation layer, which is formed by coating at an extrusion temperature of 390-410°C.

[0025] In one specific embodiment, the specific process of preparing the sheath premix in step S2 is as follows: the functionalized ethylene-tetrafluoroethylene copolymer, vinyl-terminated polydimethylsiloxane, hydrogen-containing silicone oil and fluorinated silane coupling agent are melt-blended using a twin-screw extruder at a temperature of 110-150°C; at the end of the blending, the energy field gradient-responsive synergistic catalysis / crosslinking system is added through the side feed port of the twin-screw extruder, and then rapidly dispersed and granulated at a temperature of 110-120°C.

[0026] In one specific embodiment, the process parameters for sheath extrusion in step S3 are: feeding zone 120-140℃, compression zone 140-160℃, and die head 150-170℃.

[0027] In one specific embodiment, in step S4, the cable continuously passes through the energy field gradient response vulcanization pipe at a speed of 5-15 m / min, and after leaving the pipe, it is sent into a circulating water tank with a water temperature of 20-40℃ for cooling and shaping.

[0028] This invention provides a fluoroplastic insulated high-temperature fire-resistant cable and its preparation method. It has the following beneficial effects:

[0029] 1. The fluoroplastic insulated high-temperature fire-resistant cable of the present invention employs an interpenetrating polymer network structure formed in situ from a functionalized ethylene-tetrafluoroethylene copolymer and an organosilicon prepolymer. In this structure, the cross-linked fluoropolymer network provides excellent high-temperature resistance, chemical corrosion resistance, and mechanical strength, while the physically entangled organosilicon elastomer network imparts excellent flexibility to the material. This structural design achieves synergy between the properties of the two materials at the molecular level, solving the technical problem of high rigidity and poor flexibility in traditional fluoroplastic cables. This allows the cable to maintain high protective performance while being easy to install in confined or complex spaces.

[0030] 2. The preparation method employed in this invention achieves precise and sequential control of two different chemical crosslinking systems by setting up an energy field gradient-response vulcanization channel. The microwave field in the first region selectively activates the platinum catalyst, preferentially completing the crosslinking of the organosilicon network; the infrared radiation field in the second region specifically induces the decomposition of organic peroxides, completing the crosslinking of the fluoropolymer network. This non-contact, stepwise energy input method effectively avoids chemical interference problems such as catalyst poisoning or reaction runaway that may occur when the two reaction systems are heated simultaneously, ensuring that both polymer networks can be formed completely and uniformly, thereby guaranteeing the stability and reliability of the final sheath product performance.

[0031] 3. This invention prepares functionalized ethylene-tetrafluoroethylene copolymers by introducing functional groups into the molecular chains of inert ethylene-tetrafluoroethylene copolymers. This design provides the necessary active sites for subsequent peroxide crosslinking reactions, significantly improving the crosslinking efficiency and density of the fluoropolymer network. This not only ensures the effective formation of a rigid network, providing a solid performance foundation for the final material, but also makes it possible to achieve efficient crosslinking under relatively mild industrial continuous production conditions, which is of great significance to the feasibility and economy of the entire process. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the preparation method of the present invention. Detailed Implementation

[0033] The following is in conjunction with the appendix Figure 1 This application will be described in further detail below.

[0034] Ethylene-tetrafluoroethylene copolymer, prepared in-house according to the present invention, see Preparation Example 1;

[0035] 4-Hydroxystyrene, CAS No.: 2628-17-3;

[0036] 2,5-Dimethyl-2,5-bis(tert-butylperoxy)hexane, CAS No.: 78-63-7;

[0037] N,N-Dimethylformamide, CAS No.: 68-12-2;

[0038] Meltable polytetrafluoroethylene, CAS No.: 26655-00-5;

[0039] Microwave-sensitive inhibited platinum catalyst: CAS No.: 68478-92-2;

[0040] Fluorinated silane coupling agent (3-(heptafluoroisopropoxy)propyltriethoxysilane), CAS No.: 83048-65-1;

[0041] Infrared-sensitive organic peroxide (dicumyl peroxide, DCP), CAS No.: 80-43-3.

[0042] Preparation steps:

[0043] In a 20L stainless steel reactor equipped with a mechanical stirrer, reflux condenser, and nitrogen inlet / outlet, add 10L of N,N-dimethylformamide (DMF). Start stirring and heat the reactor to 125°C. At this temperature, slowly add 2kg of ethylene-tetrafluoroethylene copolymer (ETFE) particles, and continue stirring for 5 hours until the ETFE is completely dissolved and a homogeneous solution is formed.

[0044] The temperature of the reactor was lowered to 95°C. Under nitrogen protection, 150g of 4-hydroxystyrene (4-HBS) and 60g of potassium tert-butoxide were added to the reactor and stirred for 30 minutes to disperse them evenly.

[0045] 30 g of the initiator 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPH) was dissolved in 200 mL of DMF and added dropwise to the reaction vessel over 1.5 hours using a constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 95 °C for 7 hours.

[0046] After the reaction was complete, heating was stopped, and the reaction solution was cooled to room temperature. The product in the reactor was slowly poured into 100 L of deionized water, and a large amount of white solid precipitated. The solid product was collected by vacuum filtration and washed four times each with deionized water and ethanol. The washed product was placed in a vacuum oven and dried under vacuum at 85 °C for 24 hours to obtain functionalized ethylene-tetrafluoroethylene copolymer powder for later use.

[0047] Please see the appendix Figure 1 :

[0048] Examples 1-3:

[0049] Example 1:

[0050] Raw material components (by mass parts):

[0051] Functionalized ethylene-tetrafluoroethylene copolymer (f-ETFE): 50;

[0052] Vinyl-terminated polydimethylsiloxane (PDMS-Vi): 30;

[0053] Hydrogen-containing silicone oil: 1.5;

[0054] Microwave-sensitive inhibition of platinum catalyst: 0.05;

[0055] Infrared-sensitive organic peroxide (DCP): 1.0;

[0056] Fluorinated silane coupling agent: 0.5.

[0057] Preparation steps:

[0058] S1. Cable core preparation: 19 strands of copper wire with a diameter of 0.18 mm are twisted into a conductor layer; fusible polytetrafluoroethylene (PFA) is extruded at an extrusion temperature of 400°C to coat the outer periphery of the conductor layer to form a fluoroplastic insulation layer; a copper strip is braided around the outer periphery of the fluoroplastic insulation layer to form a shielding layer; a stainless steel wire is braided around the outer periphery of the shielding layer to form an armor layer, thus obtaining the cable core to be covered with a sheath.

[0059] S2. Preparation of Sheath Premix: 50 parts f-ETFE, 30 parts PDMS-Vi, 1.5 parts hydrogen-containing silicone oil, and 0.5 parts fluorosilane coupling agent were added to a twin-screw extruder, and the melt blending zone temperature was set to 130℃ for blending. At the end of the blending process, 0.05 parts microwave-sensitive platinum catalyst and 1.0 part DCP were added through the side feed port of the extruder, and the temperature in this zone was controlled at 115℃. After rapid dispersion, the material was extruded from the die head, cooled, and pelletized to obtain sheath premix granules.

[0060] S3. Sheath Extrusion: The sheath premix granules obtained in step (S2) are added to the extruder and coated onto the armor layer of the cable core obtained in step (S1). The extruder temperature is set as follows: feeding zone 130℃, compression zone 150℃, and die head 160℃.

[0061] S4. Energy Field Gradient Crosslinking and Post-treatment: The cable covered with an uncrosslinked sheath is continuously passed through an energy field gradient response vulcanization pipe at a speed of 5 m / min. First, it passes through the first zone (microwave activation zone), where a microwave field with a frequency of 2.45 GHz and a power of 20 kW is applied; then it passes through the second zone (infrared curing zone), where infrared radiation with a peak wavelength of 3-8 μm and a total radiant power of 80 kW is applied. After leaving the vulcanization pipe, the cable enters a circulating water tank at a temperature of 30℃ for cooling and shaping, and is then wound up to obtain the finished cable.

[0062] Example 2:

[0063] Raw material components (by mass parts):

[0064] Functionalized ethylene-tetrafluoroethylene copolymer (f-ETFE): 60;

[0065] Vinyl-terminated polydimethylsiloxane (PDMS-Vi): 40;

[0066] Hydrogen-containing silicone oil: 2.2;

[0067] Microwave-sensitive inhibition of platinum catalyst: 0.12;

[0068] Infrared-sensitive organic peroxide (DCP): 1.7;

[0069] Fluorinated silane coupling agent: 1.2.

[0070] Preparation steps:

[0071] S1. Cable core preparation: 19 strands of copper wire with a diameter of 0.18 mm are twisted into a conductor layer; fusible polytetrafluoroethylene (PFA) is extruded at an extrusion temperature of 400°C to coat the outer periphery of the conductor layer to form a fluoroplastic insulation layer; a copper strip is braided around the outer periphery of the fluoroplastic insulation layer to form a shielding layer; a stainless steel wire is braided around the outer periphery of the shielding layer to form an armor layer, thus obtaining the cable core to be covered with a sheath.

[0072] S2. Preparation of Sheath Premix: 50 parts f-ETFE, 30 parts PDMS-Vi, 1.5 parts hydrogen-containing silicone oil, and 0.5 parts fluorosilane coupling agent were added to a twin-screw extruder, and the melt blending zone temperature was set to 130℃ for blending. At the end of the blending process, 0.05 parts microwave-sensitive platinum catalyst and 1.0 part DCP were added through the side feed port of the extruder, and the temperature in this zone was controlled at 115℃. After rapid dispersion, the material was extruded from the die head, cooled, and pelletized to obtain sheath premix granules.

[0073] S3. Sheath Extrusion: The sheath premix granules obtained in step (S2) are added to the extruder and coated onto the armor layer of the cable core obtained in step (S1). The extruder temperature for sheath extrusion is set as follows: feeding zone 135℃, compression zone 155℃, and die head 165℃.

[0074] S4. Energy field gradient crosslinking and post-processing: Cable travel speed 10m / min, microwave power of zone 1 30kW, total infrared radiation power of zone 2 100kW, cooling water tank temperature 35℃.

[0075] Example 3:

[0076] Raw material components (by mass parts):

[0077] Functionalized ethylene-tetrafluoroethylene copolymer (f-ETFE): 70;

[0078] Vinyl-terminated polydimethylsiloxane (PDMS-Vi): 50;

[0079] Hydrogen-containing silicone oil: 3.0;

[0080] Microwave-sensitive inhibited platinum catalyst: 0.2;

[0081] Infrared-sensitive organic peroxide (DCP): 2.5;

[0082] Fluorinated silane coupling agent: 2.0.

[0083] Preparation steps:

[0084] S1. Cable core preparation: 19 strands of copper wire with a diameter of 0.18 mm are twisted into a conductor layer; fusible polytetrafluoroethylene (PFA) is extruded at an extrusion temperature of 410°C to coat the outer periphery of the conductor layer to form a fluoroplastic insulation layer; a copper strip is braided around the outer periphery of the fluoroplastic insulation layer to form a shielding layer; a stainless steel wire is braided around the outer periphery of the shielding layer to form an armor layer, thus obtaining the cable core to be covered with a sheath.

[0085] S2. Preparation of Sheath Premix: 50 parts f-ETFE, 30 parts PDMS-Vi, 1.5 parts hydrogen-containing silicone oil, and 0.5 parts fluorosilane coupling agent were added to a twin-screw extruder, and the melt blending zone temperature was set to 130℃ for blending. At the end of the blending process, 0.05 parts microwave-sensitive platinum catalyst and 1.0 part DCP were added through the side feed port of the extruder, and the temperature in this zone was controlled at 115℃. After rapid dispersion, the material was extruded from the die head, cooled, and pelletized to obtain sheath premix granules.

[0086] S3. Sheath Extrusion: The sheath premix granules obtained in step (S2) are added to the extruder and coated onto the armor layer of the cable core obtained in step (S1). The extruder temperature is set as follows: feeding zone 140℃, compression zone 160℃, and die head 170℃.

[0087] S4. Energy Field Gradient Crosslinking and Post-treatment: The cable covered with an uncrosslinked sheath is continuously passed through an energy field gradient response vulcanization pipe at a speed of 15 m / min. First, it passes through the first zone (microwave activation zone), where a microwave field with a frequency of 2.45 GHz and a power of 40 kW is applied; then it passes through the second zone (infrared curing zone), where infrared radiation with a peak wavelength of 3-8 μm and a total radiant power of 120 kW is applied. After leaving the vulcanization pipe, the cable enters a circulating water tank at a temperature of 40℃ for cooling and shaping, and is then wound up to obtain the finished cable.

[0088] Comparative Examples 1-3:

[0089] Comparative Example 1:

[0090] Compared with Example 1, the difference is that in the sheath layer formulation, 50 parts of unfunctionalized ethylene-tetrafluoroethylene copolymer (ETFE) are used instead of functionalized ethylene-tetrafluoroethylene copolymer (f-ETFE), while the other components and preparation steps are the same.

[0091] Comparative Example 2:

[0092] Compared with Example 1, the difference is that no fluorinated silane coupling agent is added to the sheath layer formulation, while the remaining components and preparation steps are the same.

[0093] Comparative Example 3:

[0094] Compared with Example 1, the difference is that in step (S4) energy field gradient crosslinking, instead of using microwave and infrared dual-zone pipelines, the cable is passed through a single hot air circulating vulcanization pipeline with a temperature set at 200°C at a speed of 5 m / min. The remaining components and preparation steps are the same.

[0095] Experiments 1-3:

[0096] Experiment 1:

[0097] Experimental objective: To determine the tensile strength and elongation at break of the cable sheath.

[0098] Experimental steps:

[0099] This is conducted in accordance with the national standard GB / T1040.2-2006. The specific operating steps are as follows:

[0100] Sample preparation: The sheath layer was stripped from each cable sample, and dumbbell-shaped 5A specimens were cut using a cutter.

[0101] Testing equipment: A universal testing machine was used, with the testing rate set to 100 mm / min.

[0102] Test procedure: Clamp the two ends of the specimen onto the fixtures of the testing machine, start the testing machine to apply tension until the specimen breaks. Record the maximum force at which the specimen breaks and the change in distance between the markings.

[0103] Data calculation: Tensile strength (MPa) was calculated based on the recorded force values ​​and the initial cross-sectional area of ​​the specimen. Elongation at break (%) was calculated based on the recorded change in the distance between the markings and the initial distance between the markings. Five valid data points were tested for each group of samples, and their arithmetic mean was taken.

[0104] The experimental results are shown in Table 1.

[0105] Table 1

[0106] sample Tensile strength (MPa) Elongation at break (%) Example 1 21.3 458 Example 2 23.8 492 Example 3 25.1 515 Comparative Example 1 10.7 213 Comparative Example 2 14.2 288 Comparative Example 3 12.5 241

[0107] As shown in Table 1, the sheath materials of Examples 1-3 exhibit improved tensile strength and elongation at break compared to Comparative Examples 1-3. This indicates that the technical solution provided by the present invention, by introducing functional groups into the ethylene-tetrafluoroethylene copolymer molecular chain, provides the necessary active sites for the subsequent peroxide crosslinking reaction, promoting the effective formation of the first polymer network. This fluoropolymer network, together with the second organosilicon polymer network formed through a platinum-catalyzed addition reaction, constitutes an interpenetrating polymer network structure within the material. This structure allows the physical properties of the two networks to be combined, thereby achieving higher mechanical strength and ductility.

[0108] Comparative Example 1, which did not use a functionalized ethylene-tetrafluoroethylene copolymer, had a low degree of cross-linking of the fluoropolymer phase, resulting in an incomplete network structure and lower tensile strength and elongation at break values. Comparative Example 2, which did not contain a fluorosilane coupling agent, had weakened interfacial bonding between the fluoropolymer network and the organosilicon network, making the interface prone to separation under external forces and thus reducing the overall mechanical properties of the material.

[0109] Comparative Example 3 employed a single hot-air circulating vulcanization process. The high temperature simultaneously triggered two crosslinking reactions, potentially reducing the activity of the platinum catalyst due to the influence of peroxide decomposition products. This caused interference between the formation processes of the two polymer networks, preventing the formation of a regular interpenetrating network structure. Consequently, the mechanical properties of this material were lower than those of the example sample prepared using the energy field gradient crosslinking method of this invention. This energy field gradient crosslinking method, through the sequential application of microwave and infrared energy fields, achieves stepwise and targeted execution of the two crosslinking reactions, ensuring the integrity of their respective network structures and thus obtaining the desired material properties.

[0110] Experiment 2:

[0111] Experimental objective: To conduct low-temperature bending tests on the finished cables prepared in Examples 1-3 and Comparative Examples 1-3.

[0112] Experimental steps:

[0113] This is conducted in accordance with the national standard GB / T2951.14-2008. The specific operating steps are as follows:

[0114] Sample preparation: Cut a sample with a length of not less than 300 mm from each finished cable.

[0115] Equipment preparation: Prepare a low-temperature test chamber and a test rod with a diameter of 4 times the outer diameter of the cable being tested.

[0116] Test procedure: Place the cable sample and test rod together in a -40°C low-temperature test chamber for 4 hours. After removing the sample from the test chamber, tightly wrap it 3 times around the test rod, which is also being cooled in the low-temperature chamber, within 1 minute.

[0117] Results observation: After the wound sample is removed from the test bar and allowed to return to room temperature, its sheath surface is examined under normal vision to check for any form of cracking.

[0118] The experimental results are shown in Table 2.

[0119] Table 2

[0120]

[0121]

[0122] As shown in Table 2, the cables prepared in Examples 1-3 did not exhibit cracking on their sheath surface after bending at -40°C, while the cable sheaths in Comparative Examples 1-3 showed varying degrees of cracking or breakage. This result indicates that the sheath material prepared by the technical solution of this invention possesses flexibility in low-temperature environments. This property stems from the interpenetrating polymer network structure formed within the material. The organosilicon network formed by the crosslinking of terminal vinyl polydimethylsiloxane and hydrogen-containing silicone oil maintains the mobility of polymer chain segments at low temperatures, thereby endowing the entire material system with bending flexibility at low temperatures.

[0123] Comparative Example 1, due to the use of unfunctionalized ethylene-tetrafluoroethylene copolymer, failed to form an effective fluoropolymer cross-linking network, resulting in a material that was essentially a poorly compatible physical blend. Its rigid fluoroplastic matrix underwent brittle fracture at low temperatures. Comparative Example 2, lacking a fluorosilane coupling agent, resulted in insufficient interfacial bonding between the fluoropolymer and organosilicon networks. Under low-temperature bending stress, delamination occurred at the interface between the two phases, leading to the generation and propagation of microcracks.

[0124] Comparative Example 3 used a single high-temperature heating method for crosslinking. The two crosslinking reaction systems occurred simultaneously and interfered with each other, resulting in insufficient crosslinking of the organosilicon network and failure to form a complete flexible network structure to resist low-temperature brittleness. The preparation method of this invention utilizes energy field gradient crosslinking, taking advantage of the different response characteristics of microwave and infrared fields, to achieve the stepwise and sequential formation of the two networks, ensuring the structural integrity of the flexible organosilicon network. This is a prerequisite for the example samples to maintain flexibility at low temperatures.

[0125] Experiment 3:

[0126] Experimental objective: To evaluate the heat aging resistance of the cable sheaths prepared in Examples 1-3 and Comparative Examples 1-3.

[0127] Experimental steps:

[0128] This is conducted in accordance with the national standard GB / T2951.12-2008. The specific operating steps are as follows:

[0129] Sample preparation: The sheath layer was stripped from each cable sample, and dumbbell-shaped 5A specimens were cut using a cutter.

[0130] Initial performance test: Take a portion of the samples and determine their tensile strength and elongation at break before aging according to the method described in Test 1.

[0131] Thermal aging treatment: The remaining samples were suspended in a forced-ventilation oven and aged at 260°C for 168 hours.

[0132] Post-aging performance testing: The aged samples were removed from the oven and placed at room temperature for at least 16 hours for conditioning. Subsequently, the tensile strength and elongation at break after aging were determined according to the method described in Test 1.

[0133] Data calculation: Calculate the ratio of tensile strength after aging to tensile strength before aging, and the ratio of elongation at break after aging to elongation at break before aging. The results are expressed as percentages (%), which is the performance retention rate.

[0134] The experimental results are shown in Table 3.

[0135] Table 3

[0136]

[0137] As shown in Table 3, the sheath materials of Examples 1-3 exhibited high retention rates of tensile strength and elongation at break under high-temperature aging conditions at 260℃. This is because an interpenetrating polymer network composed of cross-linked functionalized ethylene-tetrafluoroethylene copolymers and cross-linked organosilicon polymers was formed within the material. The chemically bonded three-dimensional network structure of the fluoropolymer provides the structural basis for the material's resistance to high-temperature thermal oxidative degradation. Simultaneously, the physically entangled organosilicon network restricts the movement of molecular chain segments at high temperatures, further suppressing the degradation of material properties.

[0138] The sheath material in Comparative Example 1 exhibited the lowest performance retention rate because the ethylene-tetrafluoroethylene copolymer used was not functionalized, preventing effective cross-linking under the peroxide system and the formation of a stable fluoropolymer network. Consequently, severe molecular chain breakage occurred at high temperatures. Comparative Example 2 lacked a fluorosilane coupling agent, resulting in insufficient interfacial bonding between the fluoropolymer and organosilicon phases. Under thermal stress, separation easily occurred at the interface between the two phases, accelerating the deterioration of the overall material performance; therefore, its performance retention rate was lower than that of the examples.

[0139] The sheath material in Comparative Example 3, crosslinked using a single hot air heating method, also exhibited lower performance retention than the examples. Under these conditions, the platinum catalyst and organic peroxide were simultaneously activated, leading to interference between the two chemical reaction systems. This resulted in insufficient crosslinking of both the fluoropolymer and organosilicon networks, resulting in defects in the overall network structure and reduced thermal stability. The energy field gradient crosslinking method employed in this invention, through the sequential action of microwave and infrared fields, initiates the two crosslinking reactions respectively, ensuring the complete formation of both network structures. This is a structural prerequisite for achieving high thermal aging stability in the material.

Claims

1. A fluoroplastic insulated high-temperature fire-resistant cable, characterized in that, The cable includes a conductor layer composed of multiple strands of copper wire, an outer circumference covered by a fluoroplastic insulation layer, an outer circumference covered by a shielding layer of copper tape braiding, an outer circumference covered by an armor layer made of stainless steel wire braiding, and an outer circumference covered by a sheath layer comprising the following components in parts by weight: Functionalized ethylene-tetrafluoroethylene copolymer: 50-70 parts by weight; Vinyl-terminated polydimethylsiloxane: 30-50 parts by weight; Hydrogen-containing silicone oil: 1.5-3.0 parts by weight; Energy field gradient-responsive synergistic catalysis / crosslinking system: 2.05-2.7 parts by weight; Fluorinated silane coupling agent: 0.5-2.0 parts by weight; The energy field gradient-responsive synergistic catalysis / crosslinking system consists of a microwave-sensitive inhibiting platinum catalyst and an infrared-sensitive organic peroxide. The microwave-sensitive inhibiting platinum catalyst has a mass fraction of 0.05-0.2 parts; The infrared-sensitive organic peroxide is present in a mass fraction of 1.0-2.5 parts.

2. The fluoroplastic insulated high-temperature fire-resistant cable according to claim 1, characterized in that, The functionalized ethylene-tetrafluoroethylene copolymer is a graft copolymer of ethylene-tetrafluoroethylene copolymer and 4-hydroxystyrene.

3. The fluoroplastic insulated high-temperature fire-resistant cable according to claim 1, characterized in that, The vinyl-terminated polydimethylsiloxane has a kinematic viscosity of 30,000-60,000 mm⁻¹ at 25°C. 2 / s, wherein the content of the terminal vinyl polydimethylsiloxane is 0.04-0.08 mmol / g.

4. A method for preparing a fluoroplastic insulated high-temperature fire-resistant cable, used to prepare the fluoroplastic insulated high-temperature fire-resistant cable according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Preparation of cable core: Multiple strands of copper wire are twisted into a conductor layer, and a fluoroplastic insulation layer, a shielding layer, and an armor layer are sequentially wrapped around the outer periphery of the conductor layer to obtain the cable core to be sheathed; the shielding layer is formed by weaving copper strips around the outer periphery of the fluoroplastic insulation layer, and the armor layer is formed by weaving stainless steel wires around the outer periphery of the shielding layer. S2. Preparation of sheath premix: Functionalized ethylene-tetrafluoroethylene copolymer, vinyl-terminated polydimethylsiloxane, hydrogen-containing silicone oil, energy field gradient-responsive synergistic catalysis / crosslinking system and fluorinated silane coupling agent are blended and granulated to obtain sheath premix particles. S3. Sheath extrusion: The sheath premixed material particles are extruded and coated onto the armor layer of the cable core to form an uncrosslinked sheath layer. S4. Energy field gradient crosslinking: The cable covered with an uncrosslinked sheath layer is continuously passed through an energy field gradient response vulcanization pipe, and crosslinking and curing are carried out in the first and second zones in succession within the pipe. The first region is a microwave activation region, where a microwave field with a frequency of 2.45 GHz ± 50 MHz and a power of 20-40 kW is applied. The second region is an infrared curing region, where infrared rays with a peak wavelength of 3-8μm are applied, and the total radiant power is 80-120kW.

5. The method for preparing a fluoroplastic insulated high-temperature fire-resistant cable according to claim 4, characterized in that, In step S2, the preparation of the sheath premix includes: The functionalized ethylene-tetrafluoroethylene copolymer, vinyl-terminated polydimethylsiloxane, hydrogen-containing silicone oil, and fluorinated silane coupling agent are melt-blended using a twin-screw extruder at a temperature of 110-150°C. At the end of the blending process, the energy field gradient-responsive synergistic catalysis / crosslinking system is added through the side feed port of the twin-screw extruder and rapidly dispersed at a temperature of 110-120°C before being discharged and granulated.

6. The method for preparing a fluoroplastic insulated high-temperature fire-resistant cable according to claim 4, characterized in that, In step S3, the process parameters for extruding the sheath are: feeding zone 120-140℃, compression zone 140-160℃, and die head 150-170℃.

7. The method for preparing a fluoroplastic insulated high-temperature fire-resistant cable according to claim 4, characterized in that, In step S4, the continuous passage through an energy field gradient-response vulcanization pipe includes: The control cable travels at a speed of 5-15 m / min; After the cable leaves the energy field gradient response vulcanization pipe, it is sent into a circulating water tank for cooling and shaping, and the water temperature of the circulating water tank is controlled at 20-40℃.

8. The method for preparing a fluoroplastic insulated high-temperature fire-resistant cable according to claim 4, characterized in that, In step S1, the fluoroplastic insulation layer is a melt-cured polytetrafluoroethylene insulation layer, which is formed by coating at an extrusion temperature of 390-410°C.

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