A highly flexible fire-resistant cable and its preparation method

Abstract

This application provides a highly flexible fire-resistant cable and its preparation method. The highly flexible fire-resistant cable includes a core, an outer sheath, and a sheath layer. The core is composed of multiple conductors twisted together. Each conductor is covered with an inner sheath and an insulation layer from the inside out. By selecting ceramicized silicone rubber as the material for the outer sheath and thermoplastic elastomer as the material for the sheath layer, and extruding each layered structure around the core, the cable's flexibility and flame retardancy can be improved simultaneously, meeting the requirements for cables used in new energy vehicles. The preparation method of the highly flexible fire-resistant cable provided in this application includes four steps: conductor preparation, sheath extrusion preparation, core preparation, and cable preparation. By secondary twisting of the conductor, the conductor's ductility is improved, ensuring the cable's flexibility. It has the advantages of simple operation, low improvement cost, and ease of promotion and implementation.

Description

Technical Field

[0001] This application belongs to the field of flexible cable manufacturing technology, specifically relating to a highly flexible fire-resistant cable and its preparation method. Background Technology

[0002] In the existing technology, cables are widely used in fields such as construction, shipbuilding, aerospace and new energy vehicles. Their design quality is directly related to the safe and stable operation of equipment. With the popularization of new energy vehicles, the demand for cables for new energy vehicles has increased significantly. In order to ensure the driving safety and charging safety of new energy vehicles, the requirements for flexibility and fire resistance of cables for new energy vehicles are getting higher and higher.

[0003] In existing technologies, cables typically include a fire-resistant layer, a conductor layer, an insulation layer, a filler layer, a wrapping layer, and a sheath layer. The conductor, copper, is usually a type of conductor with poor ductility. Using copper as the core results in cables with poor flexibility, which does not meet the requirements for cables used in new energy vehicles. The insulation layer is typically made of polyethylene, the wrapping layer is usually non-woven fabric, and the sheath layer is usually a halogen-free elastomer material. On the one hand, these materials have low flexibility, which does not meet the design requirements for cables used in new energy vehicles and is not conducive to cable routing in confined spaces. On the other hand, existing cables have low flame retardant ratings, making them prone to fire during prolonged operation under high load conditions. Furthermore, when a fire occurs, the burning cable produces large amounts of dense smoke and pungent odors, greatly increasing the difficulty of escape and posing a significant hazard. Therefore, improvements are urgently needed. Summary of the Invention

[0004] To address the technical problems in the prior art where cables for new energy vehicles have high requirements for flexibility and flame retardancy, and where the core of existing cables is usually made of a type of conductor with poor ductility, resulting in low flexibility after cable fabrication, which does not meet the requirements of new energy vehicles, and where the sheath layer of existing cables is usually made of halogen-free elastomer and wrapped with non-woven fabric, which cannot meet the requirements of new energy vehicles for flame retardancy and flexibility after cable fabrication, this application proposes a highly flexible fire-resistant cable. To further address the technical problems proposed in this application, this application also proposes a method for preparing the highly flexible fire-resistant cable.

[0005] This application adopts the following scheme: a highly flexible fireproof cable, including a conductor, an outer sheath covering the outer periphery of the conductor, and a sheath covering the outer sheath. The conductor is made of multiple conductors twisted together, and each conductor is covered with an inner sheath and an insulation layer from the inside to the outside. The outer sheath is made of ceramicized silicone rubber, and the insulation layer is made of silicone rubber.

[0006] Furthermore, the ceramicized silicone rubber is composed of the following components by weight: 200-400 parts of base material, 50-100 parts of filler, 40-60 parts of dimethyl silicone oil, 40-50 parts of crosslinking agent, and 60-80 parts of stabilizer.

[0007] The base material is silicone rubber, which is an organosilicon compound, and is any one or more of vinyl-terminated methyl vinyl silicone rubber, methyl vinyl silicone rubber, and polyurethane-modified silicone rubber.

[0008] Furthermore, the filler is a mixture of silica and ceramic body, with silica particle size of 55-230μm and ceramic body particle size of 110-350μm. The silica and ceramic body are mixed in a mass ratio of 1:3-7.

[0009] Furthermore, the conductor is a Class 5 conductor, and the conductor is made of multiple copper wires twisted together multiple times, with each copper wire having a cross-sectional diameter of 0.3mm-0.4mm.

[0010] Furthermore, the conductor is formed by two stranding processes. In the first stranding process, the stranding direction of the multiple copper wires in the conductor is to the left, and the pitch ratio of the first stranding is 30-40 times. In the second stranding process, the stranding direction of the multiple copper wires is to the left, and the pitch ratio of the second stranding is 20-30 times. The elongation S of the conductor satisfies the following relationship: 30% ≤ S < 60%.

[0011] Furthermore, a filler is provided between the outer wrapping layer and the insulating layer. The filler is a mixture of magnesium hydroxide and cotton rope, and the mixing ratio of magnesium hydroxide and cotton rope is 4-10:1 by mass.

[0012] Furthermore, the length-to-diameter ratio of the cotton rope is 8-15:1, and the cross-sectional diameter of the cotton rope is 0.05mm-0.15mm.

[0013] Furthermore, the sheath layer is made of one or more of the following materials: ceramicized polyurethane elastomer, ceramicized acrylate elastomer, and ceramicized castor oil resin elastomer.

[0014] To address the technical problems raised in this application, this application also proposes a method for preparing a highly flexible fire-resistant cable, comprising the following steps:

[0015] Step 101. Conductor preparation: After the bundled copper wire units are arranged in a regular 1+9 or 1+12 pattern, they are stranded into a pre-made conductor in one step using a cage stranding machine. Then the pre-made conductor is stranded into a conductor in a second step.

[0016] Step 102. Preparation of wrapped extruded material: The base material, filler, dimethyl silicone oil, crosslinking agent and stabilizer are put into the mixer in sequence. Under the conditions of -0.01Mpa, 80-100℃ and 1600-2100rpm, the mixture is stirred for 10-20min to obtain the wrapped extruded material.

[0017] Step 103. Core preparation: The extruded material of the wrapping layer prepared in step 102 is used as the inner wrapping layer and extruded around the outer periphery of the conductor prepared in step 101. After extruding the insulation layer around the outer periphery of the inner wrapping layer, a single core is obtained. Multiple cores are arranged in a regular 1+6 pattern and then stranded into a core using a cage stranding machine.

[0018] Step 104. Cable preparation: The extruded material of the wrapping layer prepared in step 102 is extruded around the outer periphery of the wire core prepared in step 103 to obtain the outer wrapping layer. Then, the ceramicized elastomer is extruded as the sheath layer around the outer periphery of the outer wrapping layer to obtain a highly flexible fireproof cable.

[0019] Furthermore, in step 101, after the copper wire monomers are stranded into a conductor, the conductor is annealed at a temperature of 500°C for 3 hours.

[0020] Compared with the prior art, this application has the following beneficial effects:

[0021] This application provides a highly flexible fire-resistant cable and its preparation method. The highly flexible fire-resistant cable includes a core, an outer sheath, and a sheath layer. The core is composed of multiple conductors twisted together. Each conductor is covered with an inner sheath and an insulation layer from the inside out. By selecting ceramicized silicone rubber as the material for the outer sheath and thermoplastic elastomer as the material for the sheath layer, and extruding each layered structure around the core, the cable's flexibility can be improved while ensuring its flame retardancy, meeting the requirements for cables used in new energy vehicles. The preparation method of the highly flexible fire-resistant cable provided in this application includes four steps: conductor preparation, sheath extrusion preparation, core preparation, and cable preparation. By secondary twisting of the conductor, the conductor's ductility is improved, ensuring the cable's flexibility. It has the advantages of simple operation, low improvement cost, and ease of promotion and implementation. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0023] Figure 1 This is a cross-sectional view of a highly flexible fireproof cable according to this application. Detailed Implementation

[0024] Combination such as Figure 1As shown, to further illustrate this technical solution, a highly flexible fireproof cable includes a conductor 1, an outer sheath 2 covering the outer periphery of the conductor 1, and a sheath layer 3 covering the outer sheath 2. The conductor 1 is formed by twisting multiple conductors 10 together. Each conductor 10 is covered with an inner sheath 11 and an insulation layer 12 from the inside out. The outer sheath 2 is made of ceramicized silicone rubber, and the insulation layer 12 is made of silicone rubber.

[0025] In actual implementation, silicone rubber is used as the insulating layer material. By setting the extrusion parameters as follows: the outer mold corridor length is 12mm and the extrusion distance between the outer mold and the inner mold is 11mm, the insulation layer has good density and the material plasticization is much higher than that of the tube extrusion method. The hardness of this silicone rubber material is 66A.

[0026] In actual implementation, the insulation layer obtained by silicone rubber extrusion has high heat resistance and excellent cold resistance, as well as excellent fire resistance and insulation. When combined with high dielectric silica and metal oxides, it can effectively improve the flame retardancy and insulation of the insulation layer. In the event of a cable fire, it can also maintain the integrity and reliability of normal current transmission.

[0027] In this embodiment, the material of the inner cladding layer is the same as that of the outer cladding layer.

[0028] In this embodiment, the space between the outer wrapping layer 2 and the insulating layer 12 is filled with a filler 4. The filler 4 is a mixture of magnesium hydroxide and cotton rope, and the mixing ratio of magnesium hydroxide and cotton rope is 7.5:1 by mass.

[0029] In this embodiment, the length-to-diameter ratio of the cotton rope is 12.2:1, and the cross-sectional diameter of the cotton rope is 0.08mm.

[0030] In practical application, the mixture of magnesium hydroxide and cotton rope has advantages such as high chemical purity, good suspension performance, low hydration rate, and good flame retardant properties. When the cable is energized and heated, the magnesium hydroxide is activated to produce active magnesium oxide. Active magnesium oxide can prevent combustion, and its decomposition products can also absorb a large amount of harmful gases and fumes produced by the combustion of polymers such as rubber and plastics. When ceramicized silicone rubber is exposed to ablation or high temperature, the silicone rubber matrix first decomposes into amorphous SiO2, producing pores of varying sizes. Then, as the temperature rises, the low-melting-point filler gradually melts first, and a liquid phase appears in the silicone rubber system, connecting the amorphous SiO2 produced by the matrix and the heat-resistant ceramicized filler, forming a "eutectic mixture" at the filler boundary. The eutectic mixture acts as a bridge between amorphous SiO2 and the filler, allowing them to maintain their original state at the ignition temperature. Finally, as the temperature rises further with time, the interpenetration between the ceramicized filler and the amorphous SiO2 with the eutectic mixture becomes more complete, the filler boundaries disappear, and new inorganic phases are generated, forming a continuous, complete, and dense ceramic structure. In the event of a cable fire, this reduces the smoke density generated by the combustion of the material, protecting the health of personnel.

[0031] In this embodiment, the conductor 10 is a Class 5 conductor, which is formed by multiple copper wires twisted together, and the cross-sectional diameter of each copper wire is 0.4 mm.

[0032] In actual implementation, the conductor 10 is formed by two stranding processes. The flexibility of the Class 5 conductor is much higher than that of the Class 1 conductor on the market. By extruding ceramicized silicone rubber and secondary stranding, the conductor's ductility is improved, so that it can meet the wiring requirements of new energy vehicles in confined spaces.

[0033] In this embodiment, the sheath layer 3 is made of one or more of the following: ceramicized polyurethane elastomer, ceramicized acrylate elastomer, and ceramicized castor oil resin elastomer.

[0034] In actual implementation, the sheath layer is made of ceramicized castor oil resin elastomer.

[0035] In practical applications, ceramicized castor oil resin elastomers have the following advantages:

[0036] Firstly, castor oil-based prepolymers have lower viscosity than other types of prepolymers, resulting in elastomers with better heat resistance. When used to make cable sheaths, this can prevent the cable sheath from aging due to temperature increases, extend cable lifespan, and prevent cable damage and leakage.

[0037] Secondly, ceramicized castor oil resin elastomer has good mechanical properties, strong reprocessability, good elasticity, and tensile strength exceeding 200 MPa. When made into a sheath, it can improve the flexibility of the cable.

[0038] Example 1

[0039] A) Prepare ceramicized silicone rubber according to the weight parts shown in Table 1:

[0040] The base material is a mixture of vinyl-terminated methyl vinyl silicone and polyurethane-modified silicone in a mass ratio of 3:7.

[0041] The filler is a mixture of silica and ceramic body. The silica has a particle size of 68 μm and the ceramic body has a particle size of 121 μm. The silica and ceramic body are mixed in a mass ratio of 1:3.5.

[0042] The preparation method of polyurethane-modified silicone includes the following steps:

[0043] Step a. Add silicone oil, polyisopropyl alcohol ether and methacrylate in a mass ratio of 10:3:2 into a stirred tank and stir for 25 minutes at a water bath temperature of 70℃ and 214 rpm to obtain the activated prepolymer.

[0044] Step b. The activated prepolymer obtained in step a and polypropylene glycol are added to the reactor in a mass ratio of 7:3. After pre-reaction for 11 min at a water bath temperature of 50℃ and a vacuum degree of 0.01 MPa, nitrogen gas is introduced into the reactor. Isophorone diisocyanate is added dropwise under a nitrogen atmosphere, and the temperature is raised to 80℃ and kept at that temperature for 2 h to obtain the pre-chain extended product.

[0045] Step c. Add butanediol and triethylamine dropwise to the pre-extended chain body prepared in step b, react for 3.5 h in a water bath at 90 °C and 830 rpm, then transfer it to a mold to dry, cure, and granulate to obtain polyurethane modified silicone, wherein the mass ratio of butanediol to triethylamine is 3:1.

[0046] Step d. The polyurethane-modified silicone rubber and styrene-butadiene rubber prepared in step c are fed into an extruder in a mass ratio of 1:3.1. After mixing, extruding and granulating at 95°C and 1250 rpm, polyurethane-modified silicone rubber is obtained.

[0047] B) The ceramicized silicone rubber was prepared according to the weight parts shown in Table 1, including the following steps:

[0048] The base material, filler, dimethyl silicone oil, crosslinking agent, and stabilizer are sequentially fed into an extruder and mixed, extruded, and granulated under the conditions of -0.01 MPa, 85°C, and 1740 rpm to obtain ceramicized silicone rubber.

[0049] C) The high-flexibility fire-resistant cable is prepared according to the weight proportions shown in Table 1, including the following steps:

[0050] Step 101. Conductor preparation: After the bundled copper wire units are arranged in a regular 1+9 pattern, they are stranded into a pre-made conductor in one step using a cage stranding machine. Then, the pre-made conductor is stranded into a conductor in a second step.

[0051] Step 102. Preparation of wrapped extruded material: The base material, filler, dimethyl silicone oil, crosslinking agent and stabilizer are put into the mixer in sequence and stirred for 12 minutes under the conditions of -0.01Mpa, 85℃ and 1740rpm to obtain the wrapped extruded material.

[0052] Step 103. Core preparation: The extruded material of the wrapping layer prepared in step 102 is used as the inner wrapping layer and extruded around the outer periphery of the conductor prepared in step 101. After extruding the insulation layer around the outer periphery of the inner wrapping layer, a single core is obtained. Multiple cores are arranged in a regular 1+6 pattern and then stranded into a core using a cage stranding machine.

[0053] Step 104. Cable preparation: The extruded material of the wrapping layer prepared in step 102 is extruded around the outer periphery of the wire core prepared in step 103 to obtain the outer wrapping layer. Then, the ceramicized elastomer is extruded as a sheath layer and wrapped around the outer periphery of the outer wrapping layer to obtain a highly flexible fireproof cable.

[0054] In step 101, after the copper wires are stranded into a conductor, the conductor is annealed at a temperature of 500°C for 3 hours.

[0055] In step 101, the twisting direction of the copper wire in the first twisting process is to the left, the twisting pitch ratio is 30 times, the twisting direction of the multiple copper wires in the second twisting process is to the left, the twisting pitch ratio is 22 times, and the elongation of the conductor is S=35%.

[0056] Example 2

[0057] A) Prepare ceramicized silicone rubber according to the weight parts shown in Table 1:

[0058] The base material is a mixture of vinyl-terminated methyl vinyl silicone and polyurethane-modified silicone in a mass ratio of 3:7.

[0059] The filler is a mixture of silica and ceramic body, with silica having a particle size of 125 μm and ceramic body having a particle size of 266 μm. The silica and ceramic body are mixed in a mass ratio of 1:5.

[0060] The preparation method of polyurethane-modified silicone includes the following steps:

[0061] Step a. Add silicone oil, polyisopropyl alcohol ether and methacrylate to a stirred tank in a mass ratio of 10:3:2. Stir for 33 minutes at a water bath temperature of 70℃ and 350 rpm to obtain the activated prepolymer.

[0062] Step b. The activated prepolymer obtained in step a and polypropylene glycol are added to the reactor in a mass ratio of 7:3. After pre-reaction for 15 min at a water bath temperature of 50℃ and a vacuum degree of 0.01 MPa, nitrogen gas is introduced into the reactor. Isophorone diisocyanate is added dropwise under a nitrogen atmosphere, and the temperature is raised to 80℃ and kept at that temperature for 2 h to obtain the pre-chain extended product.

[0063] Step c. Add butanediol and triethylamine dropwise to the pre-extended chain body prepared in step b, react for 4 hours at 90°C and 1100 rpm in a water bath, transfer it to a mold to dry, cure, and granulate to obtain polyurethane modified silicone, wherein the mass ratio of butanediol to triethylamine is 3:1.

[0064] Step d. The polyurethane-modified silicone rubber and styrene-butadiene rubber prepared in step c are fed into an extruder in a mass ratio of 1:3.1. After mixing, extruding and granulating at 110°C and 1420 rpm, polyurethane-modified silicone rubber is obtained.

[0065] B) Prepare ceramicized silicone rubber according to the weights shown in Table 1, including the following steps:

[0066] The base material, filler, dimethyl silicone oil, crosslinking agent, and stabilizer are sequentially fed into an extruder and mixed, extruded, and granulated under the conditions of -0.01 MPa, 89°C, and 1850 rpm to obtain ceramicized silicone rubber.

[0067] C) The high-flexibility fire-resistant cable is prepared according to the weight proportions shown in Table 1, including the following steps:

[0068] Step 101. Conductor preparation: After the bundled copper wire units are arranged in a regular 1+12 pattern, they are stranded into a pre-made conductor in one step using a cage stranding machine. Then, the pre-made conductor is stranded into a conductor in a second step.

[0069] Step 102. Preparation of wrapped extruded material: The base material, filler, dimethyl silicone oil, crosslinking agent and stabilizer are put into the mixer in sequence and stirred for 15 minutes under the conditions of -0.01Mpa, 89℃ and 1850rpm to obtain the wrapped extruded material.

[0070] Step 103. Core preparation: The extruded material of the wrapping layer prepared in step 102 is used as the inner wrapping layer and extruded around the outer periphery of the conductor prepared in step 101. After extruding the insulation layer around the outer periphery of the inner wrapping layer, a single core is obtained. Multiple cores are arranged in a regular 1+6 pattern and then stranded into a core using a cage stranding machine.

[0071] Step 104. Cable preparation: The extruded material of the wrapping layer prepared in step 102 is extruded around the outer periphery of the wire core prepared in step 103 to obtain the outer wrapping layer. Then, the ceramicized elastomer is extruded as the sheath layer around the outer periphery of the outer wrapping layer to obtain a highly flexible fireproof cable.

[0072] In step 101, after the copper wires are stranded into a conductor, the conductor is annealed at a temperature of 500°C for 3 hours.

[0073] In step 101, the twisting direction of the copper wire in the first twisting process is to the left, the twisting pitch ratio is 35 times, the twisting direction of the multiple copper wires in the second twisting process is to the left, the twisting pitch ratio is 26 times, and the elongation of the conductor is S=47%.

[0074] Example 3

[0075] A) Prepare ceramicized silicone rubber according to the weight parts shown in Table 1:

[0076] The base material is a mixture of vinyl-terminated methyl vinyl silicone and polyurethane-modified silicone in a mass ratio of 3:7.

[0077] The filler is a mixture of silica and ceramic body, with silica having a particle size of 225 μm and ceramic body having a particle size of 338 μm. The silica and ceramic body are mixed in a mass ratio of 1:5.5.

[0078] The preparation method of polyurethane-modified silicone includes the following steps:

[0079] Step a. Add silicone oil, polyisopropyl alcohol ether and methacrylate to a stirred tank in a mass ratio of 10:3:2. Stir for 38 minutes at a water bath temperature of 70℃ and 482 rpm to obtain the activated prepolymer.

[0080] Step b. The activated prepolymer obtained in step a and polypropylene glycol are added to the reactor in a mass ratio of 7:3. After pre-reaction for 18 minutes at a water bath temperature of 50°C and a vacuum degree of 0.01 MPa, nitrogen gas is introduced into the reactor. Isophorone diisocyanate is added dropwise under a nitrogen atmosphere, and the temperature is raised to 80°C and kept at that temperature for 2 hours to obtain the pre-chain extended product.

[0081] Step c. Add butanediol and triethylamine dropwise to the pre-extended chain obtained in step b, react in a water bath at 90°C and 1180 rpm for 5.5 h, transfer it to a mold to dry, cure, and granulate to obtain polyurethane modified silicone, wherein the mass ratio of butanediol to triethylamine is 3:1.

[0082] Step d. The polyurethane-modified silicone rubber and styrene-butadiene rubber prepared in step c are fed into an extruder in a mass ratio of 1:3.5. After mixing, extruding and granulating at 115℃ and 1580rpm, polyurethane-modified silicone rubber is obtained.

[0083] B) The ceramicized silicone rubber was prepared according to the weight parts shown in Table 1, including the following steps:

[0084] The base material, filler, dimethyl silicone oil, crosslinking agent, and stabilizer are sequentially fed into an extruder and mixed, extruded, and granulated under the conditions of -0.01 MPa, 92°C, and 2050 rpm to obtain ceramicized silicone rubber.

[0085] C) The high-flexibility fire-resistant cable is prepared according to the weight proportions shown in Table 1, including the following steps:

[0086] Step 101. Conductor preparation: After the bundled copper wire units are arranged in a regular 1+9 pattern, they are stranded into a pre-made conductor in one step using a cage stranding machine. Then, the pre-made conductor is stranded into a conductor in a second step.

[0087] Step 102. Preparation of wrapped extruded material: The base material, filler, dimethyl silicone oil, crosslinking agent and stabilizer are put into the mixer in sequence and stirred for 17 minutes under the conditions of -0.01Mpa, 92℃ and 2050rpm to obtain the wrapped extruded material.

[0088] Step 103. Core preparation: The extruded material of the wrapping layer prepared in step 102 is used as the inner wrapping layer and extruded around the outer periphery of the conductor prepared in step 101. After extruding the insulation layer around the outer periphery of the inner wrapping layer, a single core is obtained. Multiple cores are arranged in a regular 1+6 pattern and then stranded into a core using a cage stranding machine.

[0089] Step 104. Cable preparation: The extruded material of the wrapping layer prepared in step 102 is extruded around the outer periphery of the wire core prepared in step 103 to obtain the outer wrapping layer. Then, the ceramicized elastomer is extruded as the sheath layer around the outer periphery of the outer wrapping layer to obtain a highly flexible fireproof cable.

[0090] In step 101, after the copper wires are stranded into a conductor, the conductor is annealed at a temperature of 500°C for 3 hours.

[0091] In step 101, the twisting direction of the copper wire in the first twisting process is to the left, the twisting pitch ratio is 40 times, the twisting direction of the multiple copper wires in the second twisting process is to the left, the twisting pitch ratio is 30 times, and the elongation of the conductor is S=52%.

[0092] Comparative Example 1

[0093] The outer and inner wrapping layers prepared from ceramicized silicone rubber in Example 3 were replaced with nonwoven outer and inner wrapping layers of the same size and specifications, and the sheath layer was replaced with a 90-degree low-smoke halogen-free material, while the rest of the structure and composition remained unchanged.

[0094] Comparative Example 2

[0095] In Example 3, the base material was replaced with ordinary silicone to prepare a ceramicized silicone rubber, which was used as the inner and outer wrapping layers, while the rest of the structure and composition remained unchanged.

[0096] Comparative Example 3

[0097] In Example 3, the secondary stranding of the copper wire in step 101 is replaced with a single stranding, while the rest of the structure, components and operation steps remain unchanged.

[0098] Table 1. Composition of each component in the ceramicized silicone rubber of Examples 1-3 and Comparative Examples 1-3

[0099]

[0100] The highly flexible flame-retardant cables prepared in Examples 1-3 and Comparative Examples 1-3 were tested for flame retardancy and elongation at break according to GB 31247-2014 and GB / T 4074.3-2008. The elongation at break measured according to GB / T 4074.3-2008 was used to evaluate the flexibility of the cable. The test results are shown in the table below.

[0101] Table 2 Test Results

[0102]

[0103] By using vinyl-terminated methyl vinyl silicone and polyurethane-modified silicone as base materials for ceramicizing and then preparing the wrapping material, flexible groups can be added to ordinary silicone. Firstly, the addition of flexible groups gives the cable excellent heat resistance and flame retardant properties, enabling it to operate under high-temperature conditions. Secondly, by supplementing with vinyl and polyurethane groups, the tensile strength and elongation at break of silicone rubber can be effectively improved, giving the cable better mechanical properties and facilitating cable routing in confined spaces. Thirdly, by introducing vinyl and polyurethane groups into ordinary silicone, the vulcanization characteristics of silicone rubber during the preparation process can be effectively improved. Vinyl-terminated methyl vinyl silicone can be vulcanized through addition vulcanization, while polyurethane-based vulcanization can be vulcanized through peroxide vulcanization. The combined use of these two vulcanization systems... Synergistic effects can be achieved, improving the overall performance of silicone rubber. The advantages of polyurethane-modified silicone rubber are evident in Comparative Example 1, where replacing the ceramicized silicone rubber wrapping layer with a non-woven fabric wrapping layer significantly reduces the mechanical and flame-retardant properties of the cable. In Comparative Example 2, replacing the base material with ordinary silicone rubber prepares ceramicized silicone rubber, which is used as both the inner and outer wrapping layers. The remaining structure and components remain unchanged. Without vinyl-terminated methyl vinyl silicone and polyurethane-modified silicone as the base material for ceramic modification, the mechanical flexible groups within the cable material decrease, reducing the cable's flame-retardant and mechanical properties. In Comparative Example 3, replacing the secondary stranding of the copper wire with primary stranding, without pre-stretching the copper wire to improve its ductility, results in a significantly reduced flexibility in the prepared cable, making it unsuitable for operation in confined spaces.

[0104] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A highly flexible fire-resistant cable, characterized in that, It includes a wire core (1), an outer wrapping layer (2) covering the outer periphery of the wire core (1), and a sheath layer (3) covering the outer wrapping layer (2). The wire core (1) is made of multiple conductors (10) twisted together. Each conductor (10) is covered with an inner wrapping layer (11) and an insulation layer (12) from the inside to the outside. The outer wrapping layer (2) and the inner wrapping layer (11) are both made of ceramicized silicone rubber, and the insulation layer (12) is made of silicone rubber. The ceramicized silicone rubber, by weight, is composed of the following components: 200-400 parts base material, 50-100 parts filler, 40-60 parts dimethyl silicone oil, 40-50 parts crosslinking agent, and 60-80 parts stabilizer. The base material is a mixture of vinyl-terminated methyl vinyl silicone rubber and polyurethane-modified silicone rubber; The conductor (10) is a Class 5 conductor. The conductor (10) is made by twisting multiple copper wires together multiple times. The cross-sectional diameter of each copper wire is 0.3mm-0.4mm. The conductor (10) is made by twisting multiple copper wires twice. The twisting direction of the multiple copper wires in the conductor (10) during the first twisting process is to the left, and the twisting pitch ratio is 30 to 40 times. The twisting direction of the multiple copper wires during the second twisting process is to the left, and the twisting pitch ratio is 20 to 30 times. The elongation S of the conductor (10) satisfies the following relationship: 30% ≤ S < 60%.

2. The highly flexible fire-resistant cable according to claim 1, characterized in that, The filler is a mixture of silica and ceramic body. The silica has a particle size of 55-230 μm and the ceramic body has a particle size of 110-350 μm. The silica and ceramic body are mixed in a mass ratio of 1:3-7.

3. The highly flexible fire-resistant cable according to claim 1, characterized in that, The outer wrapping layer (2) and the insulating layer (12) are filled with a filler (4). The filler (4) is a mixture of magnesium hydroxide and cotton rope, and the mixing ratio of magnesium hydroxide and cotton rope is 4-10:1 by mass.

4. The highly flexible fire-resistant cable according to claim 3, characterized in that, The length-to-diameter ratio of the cotton rope is 8-15:1, and the cross-sectional diameter of the cotton rope is 0.05mm-0.15mm.

5. A highly flexible fire-resistant cable according to claim 1, characterized in that, The sheath layer (3) is made of one or more of the following materials: ceramicized polyurethane elastomer, ceramicized acrylate elastomer, and ceramicized castor oil resin elastomer.

6. A method for preparing a highly flexible fire-resistant cable according to any one of claims 1-5, characterized in that, Includes the following steps: Step 101. Conductor preparation: After the bundled copper wire units are arranged in a regular 1+9 or 1+12 pattern, they are stranded into a pre-made conductor in one step using a cage stranding machine. Then the pre-made conductor is stranded into a conductor in a second step. Step 102. Preparation of wrapped extruded material: The base material, filler, dimethyl silicone oil, crosslinking agent and stabilizer are put into the mixer in sequence. Under the conditions of -0.01Mpa, 80-100℃ and 1600-2100rpm, the mixture is stirred for 10-20min to obtain the wrapped extruded material. Step 103. Core preparation: The extruded material of the wrapping layer prepared in step 102 is used as the inner wrapping layer and extruded around the outer periphery of the conductor prepared in step 101. After extruding the insulation layer around the outer periphery of the inner wrapping layer, a single core is obtained. Multiple cores are arranged in a regular 1+6 pattern and then stranded into a core using a cage stranding machine. Step 104. Cable preparation: The extruded material of the wrapping layer prepared in step 102 is extruded around the outer periphery of the wire core prepared in step 103 to obtain the outer wrapping layer. Then, the ceramicized elastomer is extruded as the sheath layer around the outer periphery of the outer wrapping layer to obtain a highly flexible fireproof cable.

7. The method for preparing a highly flexible fire-resistant cable according to claim 6, characterized in that, In step 101, after the copper wires are stranded into a conductor, the conductor is annealed at a temperature of 500°C for 3 hours.

Images