A ceramifiable silicone rubber fast flame retardant fire resistant composition and composite belt based on its principles

Abstract

The application discloses a kind of ceramization silicone rubber quick fire resistance fireproof composition and composite tape based on its principle, the composition includes: methyl phenyl vinyl silicone rubber raw rubber, alpha, omega-dihydroxy polydimethylsiloxane, superfine acicular wollastonite powder, lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder, nano yttrium aluminum garnet powder, Sn-Bi-In low melting point alloy micro powder, silane coupling agent modified beta-spodumene powder, vinyl modified polycarbosilane, barium strontium titanate nano powder, active aluminum hydroxide, zinc borate, fumed silica, low viscosity hydroxyl silicone oil.The composite tape is made of the covering layer made of the composition described above with no-alkali glass fiber cloth as the intermediate reinforcing layer.The composite tape is not cracked after ablation in 950 DEG C flame, has high density, excellent insulation resistance, and the fire penetration time is more than 80 minutes, suitable for the wrapping protection of fire-resistant cable.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer composite materials for fire-resistant cables, specifically relating to a ceramicized silicone rubber rapid fire-retardant and fire-resistant composition and a composite tape based on its principle. Background Technology

[0002] With the development of modern buildings towards high-rise, large-scale, and intelligent structures, fire safety requirements for the fire resistance of electrical wires and cables are becoming increasingly stringent. While traditional mineral-insulated cables possess excellent fire resistance, they suffer from complex manufacturing processes, high costs, and difficulties in bending and installation. Ceramicized silicone rubber composites, as a new type of fire-resistant material that can be ceramicized, retain the flexibility and processability of silicone rubber at room temperature, but transform into a hard, dense ceramic-like shell when exposed to high temperatures, coating the conductor surface to continue providing insulation and mechanical protection. Therefore, they are widely used in the insulation layer or wrapping tape of fire-resistant cables.

[0003] The basic principle of ceramicized silicone rubber to achieve ceramicization is as follows: ceramic fillers, fluxes, and flame retardants are added to the silicone rubber matrix. When subjected to high-temperature flame ablation, the silica produced by the decomposition of silicone rubber undergoes a eutectic or sintering reaction with the ceramic fillers under the action of the liquid phase formed by the flux, ultimately forming a ceramic body with a certain strength. However, this technical route has long faced two core contradictions in practical applications. One is the contradiction between "dense ceramicization" and "resistance to thermal shock cracking": the high-temperature decomposition of silicone rubber is accompanied by significant volume shrinkage, while conventional ceramic fillers are mostly positive thermal expansion materials. During rapid heating, both generate enormous internal stress, which easily leads to cracking and detachment of the ceramic protective layer, allowing flames and high temperatures to directly penetrate the internal core. Secondly, there is a contradiction between "fully liquid-phase sintering" and "high-temperature insulation retention": In order to reduce the porosity of ceramic bodies, it is usually necessary to add sufficient low-melting-point glass powder and other fluxes to generate sufficient liquid phase to fill the pores. However, the presence of alkali metal ions in the glass phase and their migration at high temperatures will significantly reduce the volume resistivity of the ceramic body, causing the ceramic layer, which should play an insulating role, to become a semiconductor or even a conductor at fire temperatures, seriously threatening the safe operation of fire-fighting power lines.

[0004] To address the aforementioned issues, the industry has undertaken various improvement attempts. Chinese patent CN109181317A discloses a low-shrinkage, high-ceramization-rate silicone rubber composite material. This material introduces β-spodumene powder as a negative thermal expansion filler, utilizing its minimal or even micro-expansion at high temperatures to partially offset the volume shrinkage caused by silicone rubber decomposition and other fillers, thereby improving the crack resistance of the ceramic layer. While this solution alleviates the shrinkage cracking problem to some extent, it still focuses on physical expansion compensation and lacks active control over the densification process of the ceramic microstructure. The ablation-treated ceramic layer still contains interconnected micropores with high gas permeability, making it difficult to maintain insulation resistance above the safe threshold for extended periods at high temperatures. Chinese patent CN107722634A discloses a polycarbosilane-modified ceramizable silicone rubber. This material utilizes the pyrolysis of polycarbosilane at high temperatures to generate silicon carbide microcrystals, constructing an interfacial bridge between the residual carbon and the silicate ceramic phase, thus improving the density and mechanical strength of the ceramization product. However, the polycarbosilane used in this scheme is dispersed in the silicone rubber matrix through a simple physical blending method, resulting in limited interfacial bonding. Under the severe thermal shock in the early stage of combustion, the interfacial bridging phase cannot play a full role, and the single interfacial reinforcement cannot simultaneously solve the problems of volume shrinkage cracking and high-temperature insulation degradation.

[0005] Furthermore, no existing technology has yet demonstrated a ceramicized silicone rubber system that simultaneously achieves zero cracking of the ceramic layer, ultra-low gas permeability, and excellent high-temperature insulation performance under dynamic flame conditions. Various improvement methods often target a single performance aspect in isolation, lacking multi-level sequential response mechanisms and synergistic designs across different temperature ranges. Consequently, the overall fire resistance and insulation performance of the final product still fails to meet increasingly stringent fire safety standards.

[0006] Therefore, there is an urgent need for a ceramicized silicone rubber composition that can simultaneously achieve low shrinkage cracking, high density, and excellent high-temperature insulation of the ceramic layer after high-temperature ablation. Summary of the Invention

[0007] This invention addresses the problems existing in the prior art by providing a ceramicized silicone rubber rapid fire-retardant and fire-resistant composition and a composite tape based on its principle. It aims to simultaneously solve the problems of easy cracking of the ceramic layer, insufficient density, and low high-temperature insulation resistance of existing ceramicized silicone rubber materials after high-temperature ablation, so that the formed ceramic protective layer has both structural integrity and electrical insulation reliability.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of this invention provides a ceramicized silicone rubber rapid fire-retardant and refractory composition, comprising, by weight: 60-80 parts of methylphenyl vinyl silicone rubber raw rubber, 20-40 parts of α,ω-dihydroxypolydimethylsiloxane, 15-25 parts of ultrafine needle-like wollastonite powder, 10-20 parts of lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder, 2-4 parts of nano-yttrium aluminum garnet powder, 3-8 parts of Sn-Bi-In low-melting-point alloy micro powder, 6-12 parts of silane coupling agent modified β-spodumene powder, 3-5 parts of vinyl-modified polycarbosilane, 1-3 parts of barium strontium titanate nanoparticles, 25-40 parts of activated aluminum hydroxide, 10-15 parts of zinc borate, 25-40 parts of fumed silica, 3-6 parts of low-viscosity hydroxyl silicone oil, and 1-2.5 parts of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0010] Furthermore, in the lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder, the doping amount of La is 1%-3% of the total mass of the glass powder, and the mass ratio of Bi2O3, B2O3 to SiO2 is 1:(0.42-0.88):(0.17-0.50).

[0011] Furthermore, the lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder is prepared by the following method: Bi2O3, B2O3, SiO2 and La2O3 are weighed according to the ratio, wet ball milled and mixed for 4-8 hours and then dried. The mixture is melted at 1100-1300℃ and kept at that temperature for 1-3 hours. The glass fragments are obtained by water quenching, wet ball milled until the average particle size is ≤10μm, dried and sieved.

[0012] Furthermore, in the Sn-Bi-In low-melting-point alloy micro powder, the mass ratio of Sn, Bi, and In is 1:(0.35-0.60):(0.10-0.25), the melting point is 70-120℃, and the surface of the alloy micro powder is coated with a nano-Al2O3 oxidation inhibition film.

[0013] Furthermore, the Sn-Bi-In low-melting-point alloy micro powder is prepared by the following method: Sn, Bi, and In metal ingots are weighed according to the ratio, melted and stirred evenly at 300-400℃ under a nitrogen atmosphere, powdered by inert gas atomization, and screened to obtain powder with an average particle size ≤10μm; dispersed in isopropanol, aluminum sol is added, pH is adjusted to 8-9, stirred and hydrolyzed for 1-3 hours, filtered and dried, and then calcined at 200-300℃ for 0.5-1 hours to obtain Sn-Bi-In low-melting-point alloy micro powder.

[0014] Furthermore, the silane coupling agent modified β-spodumene powder is prepared by surface modification treatment of β-spodumene powder with γ-methacryloxypropyltrimethoxysilane.

[0015] Further, the vinyl-modified polycarbosilane is prepared by the following method: polydimethylsilane is pyrolyzed and rearranged at 450-500℃ and 5-10MPa for 8-12 hours to obtain crude liquid polycarbosilane, and the fraction at 280-350℃ is obtained by vacuum distillation; the obtained fraction is subjected to hydrosilylation reaction with vinyltrimethoxysilane under the catalysis of isopropanol chloroplatinate solution, the amount of vinyltrimethoxysilane is 5%-15% of the fraction mass, the reaction temperature is 80-120℃, the reaction time is 4-8 hours, and the unreacted substances are removed under vacuum to obtain the final product.

[0016] The mechanism of action of the composition of the present invention in the high-temperature ablation process can be roughly divided into the following stages according to the temperature range.

[0017] In the initial stage of combustion, the Sn-Bi-In low-melting-point alloy micropowder is the first to respond. This alloy has a melting point of only 70-120℃, far lower than the softening temperature of other inorganic fillers. After melting upon heating, the alloy droplets migrate towards the hotter, flame-facing side under the influence of the temperature gradient. Upon reaching the surface, they rapidly oxidize upon contact with air, forming a continuous oxide film primarily composed of SnO2-Bi2O3-In2O3. This film is dense and firmly bonded to the underlying substrate, effectively blocking the escape channels of decomposition gases from the silicone rubber in the early stages of combustion and preventing external oxygen from diffusing into the material. While metal powder is generally considered a conductive phase, its introduction into insulating materials seems unreasonable. However, this method utilizes the mechanism of surface oxidation into a glaze after alloy melting and infiltration; the resulting oxide film on the surface is itself insulating.

[0018] When the temperature rises to the range of 420-480℃, lanthanum-doped bismuth-boron glass powder softens and forms a liquid phase. The addition of a small amount of La₂O₃ here serves to suppress premature crystallization of the glass at high temperatures, allowing the liquid phase to exist stably over a wider temperature range. The presence of the liquid phase fills some of the pores and also slightly erodes the surface of the acicular wollastonite powder, causing some components in the wollastonite to dissolve. The dissolved calcium and silicon ions recrystallize on the surface of the nano-yttrium aluminum garnet powder and strontium barium titanate powder particles, forming smaller secondary whiskers. These newly formed whiskers interlock with the remaining acicular wollastonite framework, forming a network reinforcement structure within the ceramic body, thus improving the flexural strength of the fired ceramic.

[0019] At higher temperatures, vinyl-modified polycarbosilanes undergo pyrolysis. Unlike ordinary polycarbosilanes, the vinyl groups on their molecular chains participate in cross-linking reactions during the vulcanization stage of silicone rubber, allowing the polycarbosilanes to chemically integrate into the matrix network rather than being simply dispersed within the matrix. The Si-C phase generated during pyrolysis lies between the residual carbon from the decomposition of silicone rubber and the newly formed silicate phase, acting as a bridge and reducing the tendency for the carbon layer to detach at high temperatures.

[0020] Nano-yttrium aluminum garnet powder has a melting point exceeding 1900℃ and maintains a solid particle morphology at firing temperatures around 1000℃. These particles are distributed at the grain boundaries of the ceramic body, exerting a pinning effect on grain boundary slip and helping to maintain the shape stability of the ceramic body at high temperatures. Strontium barium titanate nanoparticles are enriched in the grain boundary region, utilizing their high dielectric constant to form electron trapping centers, suppressing the decrease in insulation resistance caused by thermionic emission at high temperatures.

[0021] Silane coupling agent-modified β-spodumene powder has a very low average coefficient of thermal expansion, resulting in minimal volume change during heating. When silicone rubber decomposes and causes the matrix to shrink, β-spodumene powder can offset some of the shrinkage, reducing thermal stress within the ceramic layer and lowering the risk of cracking.

[0022] The above components take effect sequentially during the temperature rise process. The final ceramic body is sealed on the fire-facing side by a dense glaze layer formed by alloy oxidation, while the interior is supported by a microcrystalline glass reinforced with whiskers. The outer layer is dense and the interior is reinforced, which takes into account the requirements of crack resistance, high density and high temperature insulation.

[0023] A second aspect of the present invention provides a ceramicized silicone rubber rapid fire-retardant and refractory composite tape, comprising an intermediate reinforcing layer and a cover layer coated on the upper and lower surfaces of the intermediate reinforcing layer, wherein the cover layer is made of the ceramicized silicone rubber rapid fire-retardant and refractory composition of the present invention, and the intermediate reinforcing layer is alkali-free glass fiber cloth.

[0024] Furthermore, the covering layer includes a fire-facing covering layer bonded to one side of the intermediate reinforcing layer and a back-facing covering layer bonded to the other side; both the fire-facing and back-facing covering layers are made of the ceramicized silicone rubber rapid fire-retardant and refractory composition of the present invention, wherein the fire-facing covering layer uses a composition containing 5-8 parts of Sn-Bi-In low-melting-point alloy micro powder and 2-3 parts of barium strontium titanate nanopowder; the back-facing covering layer uses a composition containing 15-20 parts of lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder and 3-4 parts of nano-yttrium aluminum garnet powder.

[0025] The flame-facing cover layer, which is in direct contact with the flame, needs to form a dense, sealed layer as quickly as possible in the early stages of combustion to prevent the intrusion of flame and oxygen. Therefore, the amount of Sn-Bi-In low-melting-point alloy micropowder and barium strontium titanate nanopowder was appropriately increased. The former enhances the surface's active pore-sealing ability, while the latter improves high-temperature insulation. The unflammable cover layer, which is not in direct contact with the flame, mainly serves as structural support and insulation protection. Therefore, the amount of lanthanum-doped bismuth-boron glass powder and nano-yttrium aluminum garnet powder was increased to generate a more complete liquid phase to promote sintering densification and enhance creep resistance at high temperatures. The two side formulations have different focuses, together forming a gradient structure that is dense on the outside and reinforced on the inside.

[0026] Furthermore, the thickness of the fire-facing covering layer is 0.10-0.15 mm, the thickness of the unfired covering layer is 0.20-0.30 mm, and the thickness of the alkali-free glass fiber cloth is 0.08-0.12 mm; the outer side of the unfired covering layer is also coated with a self-adhesive layer, which is a semi-vulcanized silicone rubber layer containing MQ silicone resin, with a thickness of 0.02-0.05 mm.

[0027] The ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape of the present invention can be wrapped around the outside of fire-resistant cables, and its typical assembly structure is as follows: Figure 7 As shown, during assembly, the self-adhesive layer of the composite tape back-side covering layer adheres to the cable substrate, while the fire-facing covering layer faces outwards, directly exposed to the high-temperature environment of the flame as the core fire-resistant insulation barrier. Figure 7 The inner cable layer is equipped with a self-adhesive coating, and the middle mica layer is an optional auxiliary fire-resistant structure for the cable. It is not part of the composite tape of this invention, but can be used to improve the overall fire resistance of the cable. The outermost integral block is the ceramicized silicone rubber rapid fire-retardant composite tape of this invention.

[0028] Compared with the prior art, the present invention has the following beneficial effects: This invention introduces Sn-Bi-In low-melting-point alloy micropowder into the formulation, allowing it to actively melt and infiltrate to the surface in the early stages of a fire, forming a dense glaze layer. This effectively seals gas escape channels, preventing cracking of the ceramic layer due to volume shrinkage, significantly reducing gas permeability after ablation, and maintaining high-temperature insulation. The addition of lanthanum-doped bismuth-boron glass powder delays high-temperature crystallization of the glass phase, allowing the liquid phase to fully fill the pores and promote in-situ growth of secondary whiskers, thus improving the density and flexural strength of the ceramic body. Vinyl-modified polycarbosilane is chemically bonded to the matrix network, and the interfacial bridging phase formed after pyrolysis enhances the bonding force between the residual char layer and the ceramic layer, reducing char layer peeling at high temperatures. Nano-yttrium aluminum garnet powder and strontium barium titanate nanopowder enhance the overall performance of the ceramic body at fire temperatures from two dimensions: high-temperature structural stability and intrinsic insulation, respectively. Through the asymmetrical design of the fire-facing and unfire-facing covering layers, a gradient ceramic structure with an outer density and inner reinforcement is ultimately formed. This simultaneously achieves the comprehensive goals of crack-free ceramic layers, high density, and excellent high-temperature insulation performance, significantly extending the fire-resistant burn-through time and providing long-lasting and reliable protection for cable cores under fire conditions. Attached Figure Description Figure 1 This is a schematic diagram of the structure of the ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape of the present invention, wherein 1-fire-facing surface covering layer, 2-intermediate reinforcing layer, 3-fire-repellent surface covering layer, and 4-self-adhesive layer.

[0029] Figure 2A photograph of the ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape prepared in Example 1.

[0030] Figure 3 This is a scene photo of the composite tape of the present invention being tested for fire resistance and burn-through on a cable.

[0031] Figure 4 Photographs of the composite strip prepared for Example 1 before (a), during (b), and after (c) ablation.

[0032] Figure 5 Photographs of the composite strip prepared for Comparative Example 1 after ablation.

[0033] Figure 6 Photographs showing the appearance of the composite strip prepared for Comparative Example 3 after ablation.

[0034] Figure 7 This is a schematic diagram of the assembly structure of the ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape-covered cable of the present invention. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the raw materials used in the embodiments are all commercially available products.

[0036] Example 1 This embodiment provides a ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape, such as... Figure 1 As shown, it includes a fire-facing covering layer 1, an unfacing covering layer 3, an intermediate reinforcing layer 2, and a self-adhesive layer 4.

[0037] The formulation and raw material parameters of the coating composition for the fire-facing and unfire-facing sides are shown in Table 1.

[0038] Table 1

[0039] (1) Preparation of lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder: Bi₂O₃, B₂O₃, and SiO₂ were weighed in a mass ratio of 1:0.65:0.33, and La₂O₃ was weighed in at 2% of the total mass of the glass powder. The mixture was wet-milled for 6 hours, dried, placed in a crucible, melted at 1200℃ and held for 2 hours, and then water-quenched to obtain glass fragments. The fragments were wet-milled to an average particle size of 8μm, dried, and sieved to obtain the final product.

[0040] (2) Preparation of Sn-Bi-In low-melting-point alloy micro powder: Sn, Bi, and In metal ingots were weighed at a mass ratio of 1:0.47:0.17, melted and stirred uniformly at 350°C under a nitrogen atmosphere, and then powdered by inert gas atomization. Powder with an average particle size ≤10μm was screened. The powder was dispersed in isopropanol, aluminum sol was added, the pH was adjusted to 8.5, and the mixture was stirred and hydrolyzed for 2 hours. After filtration and drying, the powder was calcined at 250°C for 0.5 hours to obtain Sn-Bi-In low-melting-point alloy micro powder with a nano-Al2O3 film on the surface.

[0041] (3) Preparation of vinyl-modified polycarbosilane: Polydimethylsilane was pyrolyzed and rearranged in a high-pressure reactor at 480°C and 8MPa for 10 hours to obtain crude liquid polycarbosilane. The fraction obtained at 300-350°C was collected by vacuum distillation. The fraction was then hydrosilylated with vinyltrimethoxysilane in the presence of isopropanol chloroplatinate solution as a catalyst. The amount of vinyltrimethoxysilane was 10% of the fraction mass, and the amount of isopropanol chloroplatinate was 0.1% of the fraction mass. The reaction temperature was 100°C, and the reaction time was 6 hours. Unreacted substances were removed under reduced pressure to obtain the final product.

[0042] (4) Preparation of β-spodumene powder modified with silane coupling agent: Place β-spodumene powder in a high-speed mixer and preheat it to 100°C. Spray in γ-methacryloyloxypropyltrimethoxysilane (KH-570) at 1.0% of the mass of β-spodumene powder while stirring. Continue mixing and stirring for 30 minutes, then discharge the material to obtain silane coupling agent modified β-spodumene powder.

[0043] The preparation method of ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape is as follows: (1) Weigh 70 parts of methyl phenyl vinyl silicone rubber raw rubber and 30 parts of α,ω-dihydroxy polydimethylsiloxane according to the formula for the fire-facing side, add 4 parts of low viscosity hydroxyl silicone oil, mix evenly in a kneader, and then add 30 parts of fumed silica in batches and knead until it becomes a paste to obtain the fire-facing side base rubber mixture; prepare the back-facing side base rubber mixture in the same way according to the formula for the back-facing side. (2) According to the formula for the fire-facing side, add ultrafine needle-shaped wollastonite powder, lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder, nano-yttrium aluminum garnet powder, Sn-Bi-In low-melting-point alloy micro powder, silane coupling agent modified β-spodumene powder, vinyl-modified polycarbosilane, strontium barium titanate nanoparticles, active aluminum hydroxide, and zinc borate to the fire-facing side base adhesive mixture and stir to mix evenly; according to the formula for the unfired side, prepare the unfired side mixture in the same way; (3) Mix the fire-facing mixture in an internal mixer at 70°C for 30 minutes, add 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, continue mixing for 8 minutes, and discharge the fire-facing compound; the unfired compound is prepared by the same method. (4) Calender the rubber compound on the fire-facing side into a sheet with a thickness of 0.12 mm and the rubber compound on the unfired side into a sheet with a thickness of 0.25 mm. (5) Using alkali-free glass fiber cloth with a thickness of 0.10 mm and a warp and weft density of 60×58 threads / inch as the intermediate reinforcing layer, the fire-facing film and the unfacing film are respectively bonded to the upper and lower surfaces of the glass fiber cloth and hot-pressed at 60°C. (6) Curl the composite sheet at 160°C for 20 minutes; (7) Coat the outside of the unexposed surface with a semi-vulcanized silicone rubber slurry containing MQ silicone resin, dry it to form a self-adhesive layer with a thickness of 0.03 mm, cut and roll it up to obtain a ceramicized silicone rubber fast fire-retardant composite tape.

[0044] A photograph of the ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape is shown below. Figure 2 As shown.

[0045] Example 2 This embodiment provides a ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape, including a fire-facing covering layer, an unfire-facing covering layer, an intermediate reinforcing layer, and a self-adhesive layer.

[0046] The formulation and raw material parameters of the coating composition for the fire-facing and unfire-facing sides are shown in Table 2.

[0047] Table 2

[0048] The preparation methods for lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder, Sn-Bi-In low-melting-point alloy micro powder, vinyl-modified polycarbosilane, silane coupling agent-modified β-spodumene powder, and ceramicized silicone rubber rapid fire-retardant and refractory composite tape are the same as in Example 1.

[0049] Example 3 This embodiment provides a ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape, including a fire-facing covering layer, an unfire-facing covering layer, an intermediate reinforcing layer, and a self-adhesive layer.

[0050] The formulation and raw material parameters of the coating composition for the fire-facing and unfire-facing sides are shown in Table 3.

[0051] Table 3

[0052] The preparation methods for lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder, Sn-Bi-In low-melting-point alloy micro powder, vinyl-modified polycarbosilane, silane coupling agent-modified β-spodumene powder, and ceramicized silicone rubber rapid fire-retardant and refractory composite tape are the same as in Example 1.

[0053] Comparative Example 1 The difference between this comparative example and Example 1 is that the Sn-Bi-In low-melting-point alloy micro powder is replaced with an equal amount of low-melting-point borate glass powder (B2O3-ZnO-SiO2 system, softening point 480℃, average particle size 8μm), and the amount used on the fire-facing side is 6 parts, while the amount used on the unfired side is 4 parts. The rest is the same as in Example 1.

[0054] Comparative Example 2 The difference between this comparative example and Example 1 is that the lanthanum-doped Bi₂O₃-B₂O₃-SiO₂ ternary glass powder is replaced with an equal amount of undoped La Bi₂O₃-B₂O₃-SiO₂ ternary glass powder, with 12 parts used on the fire-facing side and 18 parts used on the unfired side. The preparation method of the Bi₂O₃-B₂O₃-SiO₂ ternary glass powder is as follows: Bi₂O₃, B₂O₃, and SiO₂ are weighed at a mass ratio of 1:0.65:0.33, wet-milled for 6 hours, dried, placed in a crucible, melted at 1200℃ and held for 2 hours, water-quenched to obtain glass fragments, wet-milled to an average particle size of 8 μm, dried, and sieved.

[0055] The rest is the same as in Example 1.

[0056] Comparative Example 3 The difference between this comparative example and Example 1 is that the vinyl-modified polycarbosilane is replaced with an equal amount of commercially available ordinary polycarbosilane (number average molecular weight 1500, vinyl-free), and the amount used on both the fire-facing and unfire-facing sides is 4 parts. Everything else is the same as in Example 1.

[0057] Comparative Example 4 The difference between this comparative example and Example 1 is that the nano-yttrium aluminum garnet powder is replaced with an equal amount of nano-silicon carbide powder (average particle size 200 nm), and the amount used on the fire-facing side is 3 parts, while the amount used on the unfired side is 3.5 parts. The rest is the same as in Example 1.

[0058] Comparative Example 5 The difference between this comparative example and Example 1 is that the barium strontium titanate nanoparticles are replaced with an equal amount of nano-titanium dioxide powder (average particle size 300 nm, anatase type), with 2.5 parts used on the fire-facing side and 1.5 parts used on the unfired side. Everything else is the same as in Example 1.

[0059] Performance testing The composite tapes prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to the following performance tests: 1. Tensile strength The test was conducted according to GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber". The composite tape was cut into dumbbell-shaped specimens, and the tensile strength was recorded at a tensile speed of 500 mm / min.

[0060] 2. Elongation at break The test was conducted in accordance with GB / T 528-2009, and the tensile strength test was performed simultaneously, with the elongation at break recorded.

[0061] 3. Breakdown strength The test was conducted according to GB / T 1695-2005, "Determination of Power Frequency Breakdown Voltage Strength and Withstand Voltage of Vulcanized Rubber". The composite tape was placed in insulating oil, and a continuous voltage increase method was used with a voltage increase rate of 2kV / s. The breakdown voltage was recorded and the breakdown strength was calculated.

[0062] 4. Gas permeability The gas permeability of the ceramic layer after ablation was tested using the differential pressure method. After the composite tape was ablated at 950℃ for 30 minutes, a circular piece with a diameter of 50 mm was cut out, and its gas permeability was tested with nitrogen at room temperature at a pressure of 0.1 MPa.

[0063] 5. Insulation resistance at 950℃ The test was conducted in accordance with GB / T 31838.7-2021 "Dielectric and resistive properties of solid insulating materials - Part 3-4: Determination of resistive properties (DC method) - Measurement of volume resistivity and volume resistivity at high temperature". To simulate the actual wrapping conditions of the composite tape, the composite tape was wrapped around a copper rod with a diameter of 5 mm in 3 layers. The rod was placed in a tube furnace and heated to 950 °C at a rate of 10 °C / min. After holding at that temperature for 15 minutes, a DC voltage of 500 V was applied, and the insulation resistance value of a 1 m long sample was measured.

[0064] 6. Bending strength after ablation The composite tape was cut into strips of 100mm×20mm and placed in a muffle furnace. The temperature was increased to 950℃ at 10℃ / min and held for 30 minutes. After cooling in the furnace, the strips were removed and the bending strength of the ceramic layer was tested using the three-point bending method with a span of 60mm and a loading speed of 2mm / min.

[0065] 7. Fire-resistant burn-through time Referring to the test principle of BS 6387 "Performance requirements for cables to maintain circuit integrity under flame conditions", a cable wrapping simulation test was conducted: the composite tape of this invention was tightly wrapped around the outer surface of the cable (3 layers). The wrapped sample was placed directly above a flame torch and continuously burned with a flame at 950°C. A 300V AC voltage was applied to both ends of the cable, and the time from flame contact to the occurrence of a short circuit was recorded as the fire-resistant burn-through time of the composite tape. The test procedure is as follows: Figure 3 As shown.

[0066] 8. Appearance after ablation The composite tape was cut into samples, placed in a muffle furnace, heated to 950°C at 10°C / min, held for 30 minutes, cooled with the furnace, and then removed to visually observe the surface condition of the ceramic layer.

[0067] Figure 4 These are photographs of the composite strip prepared in Example 1 before (a), during (b), and after (c) ablation. Figure 4 As can be seen from the ablation (c), the sample is intact and unbroken, with only a few independent closed micropores. A continuous and dense glaze layer is formed on the surface, and the structure has excellent stability.

[0068] Figure 5 The image shows the appearance of the composite strip prepared for Comparative Example 1 after ablation. The sample lacked Sn-Bi-In low-melting-point alloy micro powder, which prevented the formation of a low-temperature sealed pore glaze layer. The surface was covered with a large number of interconnected honeycomb-like bubbles, and the ceramic layer was loose and porous with no continuous barrier.

[0069] Figure 6 The image shows the appearance of the composite strip prepared in Comparative Example 3 after ablation. The sample used ordinary polycarbosilane instead of vinyl-modified polycarbosilane. The carbon layer debonded from the interface of the inorganic ceramic skeleton, a large amount of black residual carbon accumulated on the surface, dense deep through-holes, and severe fragmentation and defects at the edge of the sample.

[0070] The remaining test results are shown in Table 4.

[0071] Table 4

[0072] The test results show that the overall performance indicators of Examples 1-3 are at a relatively good level. The tensile strength, elongation at break and breakdown strength can meet the basic requirements of composite tape wrapping construction and normal insulation. At the same time, after high temperature ablation, they exhibit extremely low gas permeability, high high temperature insulation resistance and flexural strength. The fire resistance burn-through time exceeds 80 minutes, indicating that the composition of the present invention can form a dense, crack-free ceramic protective layer with excellent high temperature insulation performance under fire conditions, and the overall fire resistance effect is significant.

[0073] In Comparative Example 1, the lack of an active melting and infiltration surface sealing mechanism from alloy micropowder resulted in a significant decrease in the density of the ceramic layer after ablation, leading to a substantial decline in various properties. In Comparative Example 2, replacing lanthanum-doped glass powder with undoped glass powder resulted in premature crystallization of the glass phase at high temperatures, leading to insufficient liquid phase filling, decreased ceramic layer density, and significantly lower insulation resistance and refractory time compared to the examples. In Comparative Example 3, replacing vinyl-modified polycarbosilane with ordinary polycarbosilane resulted in insufficient interfacial bonding after pyrolysis due to the lack of chemical bond anchoring, and a significant decrease in flexural strength after ablation, indicating that V-PCS plays a crucial role in maintaining the structural integrity of the ceramic body. In Comparative Example 4, replacing yttrium aluminum garnet powder with silicon carbide resulted in an extremely low high-temperature insulation resistance. This is because the semiconductor properties of silicon carbide itself become a conductive path at high temperatures, and its gradual consumption in an oxidizing atmosphere also weakens the high-temperature pinning effect. In Comparative Example 5, replacing barium strontium titanate with titanium dioxide significantly deteriorated the high-temperature insulation performance, demonstrating that the perovskite structure electron trapping effect of BST plays an irreplaceable role in suppressing high-temperature leakage current.

[0074] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A ceramicized silicone rubber rapid fire-retardant and refractory composition, characterized in that, By weight, it includes: 60-80 parts of methylphenyl vinyl silicone rubber raw rubber, 20-40 parts of α,ω-dihydroxy polydimethylsiloxane, 15-25 parts of ultrafine needle-like wollastonite powder, 10-20 parts of lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder, 2-4 parts of nano-yttrium aluminum garnet powder, 3-8 parts of Sn-Bi-In low-melting-point alloy micro powder, 6-12 parts of silane coupling agent modified β-spodumene powder, 3-5 parts of vinyl-modified polycarbosilane, 1-3 parts of barium strontium titanate nanoparticles, 25-40 parts of activated aluminum hydroxide, 10-15 parts of zinc borate, 25-40 parts of fumed silica, 3-6 parts of low-viscosity hydroxyl silicone oil, and 1-2.5 parts of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

2. The ceramicized silicone rubber rapid fire-retardant and refractory composition according to claim 1, characterized in that: In the lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder, the doping amount of La is 1%-3% of the total mass of the glass powder, and the mass ratio of Bi2O3, B2O3 to SiO2 is 1:(0.42-0.88):(0.17-0.50).

3. The ceramicized silicone rubber rapid fire-retardant and refractory composition according to claim 2, characterized in that: The lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder is prepared by the following method: Bi2O3, B2O3, SiO2 and La2O3 are weighed according to the ratio, wet ball milled and mixed for 4-8 hours and then dried. The mixture is melted at 1100-1300℃ and kept at that temperature for 1-3 hours. The glass fragments are obtained by water quenching, wet ball milled until the average particle size is ≤10μm, dried and sieved.

4. The ceramicized silicone rubber rapid fire-retardant and refractory composition according to claim 1, characterized in that: The Sn-Bi-In low-melting-point alloy micro powder has a mass ratio of Sn, Bi, and In of 1:(0.35-0.60):(0.10-0.25), a melting point of 70-120℃, and a nano-Al2O3 oxidation inhibition film coated on the surface of the alloy micro powder.

5. The ceramicized silicone rubber rapid fire-retardant and refractory composition according to claim 4, characterized in that: The Sn-Bi-In low-melting-point alloy micro powder is prepared by the following method: Sn, Bi, and In metal ingots are weighed according to the formula, melted and stirred evenly at 300-400℃ under a nitrogen atmosphere, and powdered by inert gas atomization. Powder with an average particle size ≤10μm is screened. The powder is dispersed in isopropanol, aluminum sol is added, the pH is adjusted to 8-9, and the mixture is stirred and hydrolyzed for 1-3 hours. After filtration and drying, the powder is calcined at 200-300℃ for 0.5-1 hours to obtain the Sn-Bi-In low-melting-point alloy micro powder.

6. The ceramicized silicone rubber rapid fire-retardant and refractory composition according to claim 1, characterized in that: The silane coupling agent modified β-spodumene powder is prepared by surface modification treatment of β-spodumene powder with γ-methacryloxypropyltrimethoxysilane.

7. The ceramicized silicone rubber rapid fire-retardant and refractory composition according to claim 1, characterized in that: The vinyl-modified polycarbosilane is prepared by the following method: polydimethylsilane is pyrolyzed and rearranged at 450-500℃ and 5-10MPa for 8-12 hours to obtain crude liquid polycarbosilane. The fraction obtained at 280-350℃ is then distilled under reduced pressure. The fraction obtained is then subjected to a hydrosilylation reaction with vinyltrimethoxysilane under the catalysis of isopropanol chloroplatinate solution. The amount of vinyltrimethoxysilane used is 5%-15% of the fraction mass, the reaction temperature is 80-120℃, the reaction time is 4-8 hours, and unreacted substances are removed under reduced pressure to obtain the final product.

8. A ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape, characterized in that, include: The intermediate reinforcing layer and the cover layer covering the upper and lower surfaces of the intermediate reinforcing layer, wherein the cover layer is made of the ceramicized silicone rubber rapid fire-retardant and fire-resistant composition according to any one of claims 1-7, and the intermediate reinforcing layer is alkali-free glass fiber cloth.

9. The ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape according to claim 8, characterized in that: The covering layer includes a fire-facing covering layer coated on one side of the intermediate reinforcing layer and a back-facing covering layer coated on the other side; both the fire-facing and back-facing covering layers are made of the ceramicized silicone rubber rapid fire-retardant and refractory composition according to any one of claims 1-7, wherein the composition used in the fire-facing covering layer contains 5-8 parts of Sn-Bi-In low-melting-point alloy micro powder and 2-3 parts of barium strontium titanate nanopowder; the composition used in the back-facing covering layer contains 15-20 parts of lanthanum-doped Bi2O3-B2O3-SiO2 ternary glass powder and 3-4 parts of nano-yttrium aluminum garnet powder.

10. The ceramicized silicone rubber rapid fire-retardant and fire-resistant composite tape according to claim 8, characterized in that, The thickness of the fire-facing covering layer is 0.10-0.15 mm, the thickness of the unfired covering layer is 0.20-0.30 mm, and the thickness of the alkali-free glass fiber cloth is 0.08-0.12 mm. The outer side of the unfired covering layer is also coated with a self-adhesive layer, which is a semi-vulcanized silicone rubber layer containing MQ silicone resin with a thickness of 0.02-0.05 mm.

Images