Silicone rubber sheath material capable of being vitrified as well as preparation method and application of silicone rubber sheath material

Abstract

The invention belongs to the technical field of cable sheath materials, and provides a ceramic silicone rubber sheath material and a preparation method and application thereof. Polycarbosilane is subjected to staged heat treatment, so that the polycarbosilane is crosslinked, pyrolyzed and ceramized to obtain SiOC powder, and the SiOC powder has excellent crack resistance and heat stability; boric acid and phosphate are mixed and then are subjected to high-temperature melting and rapid cooling, borophosphate glass powder is prepared, the low-temperature softening characteristic of the borophosphate glass powder can fill pores in the ceramization process, and the compactness and mechanical performance of a ceramic layer are improved; molybdenum powder and silicon powder are mixed, and molybdenum disilicide powder is prepared through high-temperature reaction, so that the oxidation resistance of the material is improved; methyl vinyl silicone rubber is uniformly mixed with SiOC powder, borophosphate glass powder and molybdenum disilicide powder in sequence, a vulcanizing agent, an antioxidant and an auxiliary agent are added, the ceramic silicone rubber sheath material is prepared through a vulcanization process, and the material has excellent fire resistance at high temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of cable sheath materials and relates to a ceramic silicone rubber sheath material and a preparation method and application thereof. Background Art

[0002] With the rapid development of modern industry, energy, and transportation, the performance requirements for cable sheathing materials in extreme environments are becoming increasingly stringent. Traditional cable sheathing materials such as polyvinyl chloride and polyethylene, while offering excellent flexibility and electrical insulation, are prone to burning, losing structural integrity, and releasing large amounts of toxic fumes under extreme conditions such as high temperatures and fires, making them difficult to meet stringent safety and high-temperature resistance requirements. For this reason, ceramicized silicone rubber sheathing materials, which can be converted into a ceramic layer at high temperatures, maintaining the material's structural integrity and flame retardancy, have become an important solution. In ceramicized silicone rubber, the density of the ceramic layer directly determines its protective effect under high-temperature conditions. However, the inorganic fillers in traditional ceramicized silicone rubber (such as single wollastonite or alumina) often have difficulty forming a dense ceramic layer, causing the material to crack or fall off easily in a fire, making it difficult to achieve the desired fire protection effect. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a ceramic silicone rubber sheath material and its preparation method and application. By using SiOC powder, borophosphate glass powder and MoSi2 powder as functional fillers and compounding them with a methyl vinyl silicone rubber matrix, the ceramicization ability, flame retardant properties and mechanical strength of the material at high temperatures are improved. The prepared silicone rubber sheath material can be quickly ceramicized in a fire or high-temperature environment to form a dense protective layer, thereby meeting the needs of actual production.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a method for preparing a ceramic silicone rubber sheath material, the preparation method comprising:

[0006] S1, dispersing polycarbosilane in anhydrous toluene, pouring it into a glass dish, ventilating and volatilizing the solvent to form a thin film of polycarbosilane, placing the thin film of polycarbosilane in a tube furnace under an argon atmosphere, adjusting the temperature to a first temperature and holding it, then adjusting the temperature to a second temperature and holding it, and continuing to increase the temperature to a third temperature and holding it, to obtain SiOC powder;

[0007] S2, ball-milling B2O3 and P2O5 to obtain a mixed powder, placing the mixed powder in a platinum crucible and adjusting the temperature to the fourth temperature for insulation, and quickly pouring the melt in the crucible onto the surface of a room temperature steel plate to obtain borophosphate glass powder;

[0008] S3, mixing molybdenum powder and silicon powder and ball-milling and pre-pressing to obtain a bulk mixture, placing the bulk mixture in a tube furnace under an argon atmosphere, heating it to a fifth temperature and holding it, and then heating it to a sixth temperature and holding it to obtain MoSi2 powder;

[0009] S4, add methyl vinyl silicone rubber, white carbon black, SiOC powder, borophosphate glass powder and MoSi2 powder into an open mill in sequence, mix them evenly, then add vulcanizer, antioxidant, zinc stearate and silicone oil, pass the mixture through a thin tube to obtain a sheet, place the sheet in a flat vulcanizer and maintain pressure to obtain a ceramic silicone rubber sheath material.

[0010] Specifically include:

[0011] S1, dispersing polycarbosilane in anhydrous toluene, pouring it into a glass dish, ventilating to volatilize the solvent to form a polycarbosilane film, placing the polycarbosilane film in a tube furnace under an argon atmosphere, adjusting the temperature to a first temperature and holding it, then adjusting the temperature to a second temperature and holding it, and continuing to increase the temperature to a third temperature and holding it, while maintaining the argon flow, naturally cooling it to below 200° C. and then turning off the argon flow to obtain a bulk SiOC ceramic, which is then ball-milled and sieved to obtain SiOC powder;

[0012] S2, ball-milling the dried B2O3 and P2O5 to obtain a mixed powder, placing the mixed powder in a platinum crucible and adjusting the temperature to the fourth temperature for insulation, heating the crucible at 300°C and 600°C for 30 minutes each, quickly pouring the melt in the crucible onto the surface of a room-temperature steel plate, cooling it to form a glass block, ball-milling the glass block, sieving it, and drying it to obtain borophosphate glass powder;

[0013] S3, mixing molybdenum powder and silicon powder and ball-milling and pre-pressing to obtain a block mixture, placing the block mixture in an argon atmosphere in a tube furnace, heating it to the fifth temperature and holding it, then heating it to the sixth temperature and holding it, and continuously passing argon during the cooling process to obtain a sintered block, crushing the sintered block by ball milling and sieving to obtain MoSi2 powder;

[0014] S4, add methyl vinyl silicone rubber, white carbon black, SiOC powder, borophosphate glass powder and MoSi2 powder into an open mill in sequence, mix them evenly, then add vulcanizer, antioxidant, zinc stearate and silicone oil, pass the mixture through a thin tube to obtain a sheet, place the sheet in a flat vulcanizer and maintain pressure to obtain a ceramic silicone rubber sheath material.

[0015] Polycarbosilane, an organic polymer containing a carbon-silicon backbone, is an ideal precursor for preparing SiOC ceramics due to its unique structure and thermal decomposition properties. First, polycarbosilane is dispersed in anhydrous toluene to fully separate the molecular chains and form a uniform dispersion. The use of anhydrous toluene also effectively avoids the introduction of water, thereby preventing unwanted cross-linking reactions during the solvent evaporation process. After the solvent evaporates, the resulting film-like polycarbosilane structure provides a uniform material morphology for subsequent heat treatment reactions, ensuring the adequacy and consistency of the pyrolysis process.

[0016] During the subsequent heat treatment, polycarbosilane undergoes three major chemical transformation stages. In the first, lower temperature range, the organic side groups of polycarbosilane begin to be removed. During this process, organic groups such as methyl and ethyl groups in the polycarbosilane release small gases through thermal decomposition. This process is accompanied by the partial recombination of silicon and carbon elements in the backbone, forming a preliminary three-dimensional cross-linked network structure. As the temperature increases further, entering the second stage, the thermal decomposition of polycarbosilane intensifies, and more organic groups such as methyl, ethyl, and hydrogen groups are removed, gradually forming an amorphous inorganic structure dominated by silicon, oxygen, and carbon. During this stage, the density of the cross-linked network increases further, and the organic properties of the material significantly decrease. This heat treatment not only involves the recombination of silicon-oxygen and carbon-silicon bonds in the backbone, but also the precipitation of some carbon, forming a preliminary silicon-oxygen-carbon inorganic network structure. Finally, under the high-temperature treatment conditions of the third stage, the material undergoes a ceramic transformation. In this stage, the high temperature promotes further recombination of silicon, oxygen, and carbon in the system, forming a thermodynamically stable SiOC ceramic network structure. This structure is a typical amorphous ceramic material, featuring a highly cross-linked silicon-oxygen-carbon network, exhibiting excellent thermal stability and mechanical strength. The bulk SiOC ceramic obtained through heat treatment is then ball-milled and sieved to produce a uniform SiOC powder. This powder not only exhibits high-temperature stability and excellent mechanical properties, but also possesses good dispersibility and composite processing characteristics, providing an ideal inorganic filler for subsequent compounding with silicone rubber matrices.

[0017] B2O3 and P2O5, two highly chemically active inorganic oxides with low melting points, were ball-milled. During the ball-milling process, the two powders were thoroughly mixed mechanically, forming fine crystals, which improved their homogeneity and reactivity. When the mixed powders were placed in a platinum crucible and heated to a high temperature to melt, significant chemical reactions and structural reorganization occurred between the B2O3 and P2O5. As the temperature gradually increased, the B2O3 and P2O5 first melted, forming molten boron-oxygen networks and phosphorus-oxygen networks. During this process, B2O3 formed a boron-oxygen network through its triangular BO3 groups and tetrahedral BO4 groups, while P2O5 formed a phosphorus-oxygen network through its tetrahedral PO4 groups. At high temperatures, these structural units cross-linked through the formation of bridging oxygen and co-oxygen bonds, forming a highly cross-linked boron-phosphorus-oxygen network. The formation of this boron-phosphorus-oxygen network is crucial for the entire vitrification process. In the molten state, the interaction between B2O3 and P2O5 imparts a low viscosity and high fluidity to the system, effectively filling the crucible and significantly enhancing its glass-forming ability. After melting, the melt is rapidly poured onto a room-temperature steel plate for rapid cooling. The purpose of this rapid cooling is to allow the melt to solidify directly without fully crystallizing, forming an amorphous glass structure. During this process, due to the extremely rapid cooling rate, the molecular structures of B2O3 and P2O5 do not have time to rearrange to form crystals, and instead solidify in a disordered state, forming borophosphate glass with amorphous characteristics. This effectively inhibits the formation and growth of crystal nuclei, ensuring the material's amorphous structure. The low melting point of the borophosphate glass powder allows it to soften rapidly at high temperatures, filling the pores in the ceramic layer and improving the density and mechanical strength of the ceramic layer. Furthermore, the presence of B2O3 and P2O5 enhances the uniformity and thermal shock resistance of the ceramic layer by promoting sintering.

[0018] Molybdenum (Mo) and silicon (Si) both have high melting points, making it difficult for them to react at room temperature through diffusion alone. Therefore, the ball milling process physically refines and evenly distributes the two metal particles. The mixed molybdenum and silicon powders are then pre-pressed into a block mixture to enhance contact between the particles, reduce interparticle gaps during the reaction, and improve reaction efficiency during high-temperature sintering. In the first stage, at a relatively low temperature, an initial diffusion reaction occurs on the surfaces of the molybdenum and silicon particles. Here, silicon atoms gradually diffuse onto the molybdenum particle surfaces, forming a preliminary intermetallic compound with the molybdenum atoms. As the temperature rises to higher sintering temperatures, the reaction between molybdenum and silicon intensifies, and a stable molybdenum disilicide structure begins to form. During this process, silicon atoms further diffuse into the molybdenum particles, forming a thermodynamically stable MoSi2 phase. The formation of MoSi2 is an exothermic reaction, and some of the heat generated during the reaction further promotes the diffusion reaction. Molybdenum disilicide has a high melting point and excellent antioxidant properties. In an oxidizing atmosphere, a dense silicon dioxide film will quickly form on the surface of molybdenum disilicide, preventing oxygen from further diffusing into the material, thereby improving the material's antioxidant ability. Molybdenum disilicide also has good thermal stability, making it an ideal high-temperature functional material.

[0019] As an amorphous ceramic material, SiOC powder exhibits excellent high-temperature crack resistance due to its highly cross-linked network of silicon-oxygen and silicon-carbon bonds. During the ceramicization process and in high-temperature operating environments, SiOC effectively resists cracks caused by thermal expansion and mechanical stress concentration. When subjected to external thermal stress, SiOC's amorphous structure absorbs and disperses stress, preventing crack initiation and propagation. Furthermore, SiOC ceramics have an extremely low coefficient of thermal expansion, maintaining remarkable structural stability when subjected to high-temperature gradients, providing long-term mechanical support for the ceramic layer in high-temperature environments. Furthermore, SiOC's heat resistance provides a skeletal support for the overall material, ensuring the mechanical strength and integrity of the ceramicized silicone rubber under high-temperature conditions. Borophosphate glass powder acts as a low-temperature sintering aid within the material system. Its unique low melting point enables it to melt at relatively low temperatures and participate in the ceramicization process. When the material is exposed to high temperatures, the borophosphate glass powder first softens and transforms into a molten state, flowing through the ceramic system to fill microcracks, pores, or other defective areas. This significantly improves the density of the ceramic layer and reduces the crack propagation path. The molten glass filler also exhibits excellent fluidity and adhesion, enhancing the mechanical strength and thermal shock resistance of the ceramic layer at high temperatures. The low-temperature sintering properties of borophosphate glass powder also reduce the temperature requirements of the overall ceramicization process, reducing the risk of thermal decomposition of the silicone rubber matrix due to excessively high temperatures, thereby improving the preparation efficiency and stability of the ceramic material.

[0020] MoSi2 provides a key antioxidant function within the material system. Molybdenum disilicide (MoSi2) is a classic high-temperature antioxidant. In high-temperature oxidizing environments, it forms a dense SiO2 protective film covering the material surface, preventing further oxygen diffusion into the material, thereby protecting the SiOC ceramic and silicone rubber matrix from oxidative degradation. This antioxidant mechanism is particularly important in high-temperature environments, particularly under flames or prolonged high-temperature operating conditions. MoSi2 significantly slows the material's oxidation rate, maintaining its mechanical properties and thermal stability. The synergistic effect of these three components significantly enhances the overall performance of the ceramicized silicone rubber. The SiOC powder provides a strong framework through its crack resistance and high-temperature stability. The borophosphate glass powder enhances the density and crack resistance of the ceramic layer through low-temperature sintering, while the MoSi2 provides a long-lasting protective barrier through its antioxidant properties. During the ceramicization process, the melt-filled borophosphate glass powder combines with the SiOC ceramic framework to form a uniform and dense ceramic layer, enhancing the material's mechanical properties and thermal stability.

[0021] As a preferred technical solution of the present invention, in S1, the first temperature is 300-310°C, for example, it can be 300°C, 301°C, 302°C, 303°C, 304°C, 305°C, 306°C, 307°C, 308°C, 309°C or 310°C, and the heating rate is 3°C / min, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0022] In some optional examples, the first temperature insulation time is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] In some optional instances, the second temperature is 600-610°C, for example, it can be 600°C, 601°C, 602°C, 603°C, 604°C, 605°C, 606°C, 607°C, 608°C, 609°C or 610°C, and the heating rate is 3°C / min, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0024] In some optional examples, the second temperature insulation time is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] In some optional instances, the third temperature is 1100-1110°C, for example, it can be 1100°C, 1101°C, 1102°C, 1103°C, 1104°C, 1105°C, 1106°C, 1107°C, 1108°C, 1109°C or 1110°C, and the heating rate is 5°C / min, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0026] In some optional examples, the third temperature insulation time is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] In some optional examples, the flow rate of the argon gas is 120-150 mL / min, for example, it can be 120 mL / min, 123 mL / min, 126 mL / min, 129 mL / min, 132 mL / min, 135 mL / min, 138 mL / min, 141 mL / min, 144 mL / min, 147 mL / min or 150 mL / min, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0028] In some optional examples, the mesh size of the sieve is 300 mesh or 400 mesh.

[0029] As a preferred technical solution of the present invention, in S2, the mass ratio of B2O3 to P2O5 is (0.8-1.2):1, for example, it can be (0.80, 0.84, 0.88, 0.92, 0.96, 1.00, 1.04, 1.08, 1.12, 1.16 or 1.20):1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] In some optional instances, the fourth temperature is 1150-1170°C, for example, it can be 1150°C, 1152°C, 1154°C, 1156°C, 1158°C, 1160°C, 1162°C, 1164°C, 1166°C, 1168°C or 1170°C, and the heating rate is 5°C / min, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0031] In some optional examples, the fourth temperature insulation time is 40-60 minutes, for example, it can be 40 minutes, 42 minutes, 44 minutes, 46 minutes, 48 ​​minutes, 50 minutes, 52 minutes, 54 minutes, 56 minutes, 58 minutes or 60 minutes, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] In some optional examples, the mesh size of the sieve is 300 mesh or 400 mesh.

[0033] As a preferred technical solution of the present invention, in S3, the mass ratio of the molybdenum powder to the silicon powder is (1.7-1.8):1, for example, it can be (1.7, 1.71, 1.72, 1.73, 1.74, 1.75, 1.76, 1.77, 1.78, 1.79 or 1.8):1, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0034] In some optional instances, the fifth temperature is 900-910°C, for example, it can be 900°C, 901°C, 902°C, 903°C, 904°C, 905°C, 906°C, 907°C, 908°C, 909°C or 910°C, and the heating rate is 5°C / min, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0035] In some optional examples, the fifth temperature insulation time is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] In some optional instances, the sixth temperature is 1350-1370°C, for example, it can be 1350°C, 1352°C, 1354°C, 1356°C, 1358°C, 1360°C, 1362°C, 1364°C, 1366°C, 1368°C or 1370°C, and the heating rate is 5°C / min, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0037] In some optional examples, the sixth temperature insulation time is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] In some optional examples, the mesh size of the sieve is 300 mesh or 400 mesh.

[0039] As a preferred technical solution of the present invention, in S4, the mass ratio of the methyl vinyl silicone rubber, white carbon black, SiOC powder, borophosphate glass powder, MoSi2 powder, vulcanizing agent, antioxidant, zinc stearate and silicone oil is 1000: (150-200): (150-200): (100-150): (200-260): (10-15): 10: (10-15): (10-20), for example, it can be 1000: (150, 155, 160, 165, 170, 175, 180, 185, 190, 195 or 200): (150, 155, 160, 165, 170, 175, 180, 185, 190, 195 or 200): (100, 105, 110, 115, 120, 125, 130, 135, 140, 145 or 150): (200, 206, 212, 218, 224, 230, 236, 242, 248, 254 or 260): (10-15): 10: (10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5 or 15.0): (10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20), but are not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0040] In some optional examples, the vulcanizing agent is dibenzoyl peroxide.

[0041] In some optional examples, the antioxidant is any one or more of antioxidant 1010 , antioxidant 1076 , and antioxidant 1024 .

[0042] In a second aspect, the present invention provides a ceramicizable silicone rubber sheath material prepared by the preparation method described in the first aspect.

[0043] In a third aspect, the present invention provides an application of a ceramicizable silicone rubber sheath material in a fireproof cable.

[0044] Compared with the prior art, the present invention has the following beneficial effects: (1) SiOC powder has high-temperature stability and mechanical strength, and can play a skeletal supporting role in the material. Under high-temperature conditions, SiOC powder can further enhance the density and heat resistance of the ceramic layer through high-temperature sintering, thereby ensuring that the sheath material still maintains structural integrity and effective protective performance under extreme high-temperature conditions; (2) Borophosphate glass powder can form a low-melting-point glass phase at high temperature, fill the pores in the ceramic layer, enhance the density and thermal shock resistance, and at the same time, B2O3 and P2O5 in the borophosphate glass powder exhibit excellent fluidity and wettability at high temperatures, further improving the mechanical strength and crack resistance of the ceramic layer, thereby significantly improving the durability and flame retardant effect of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a physical picture of the ceramicizable silicone rubber sheath material prepared by the preparation method described in Example 1 of this application. DETAILED DESCRIPTION

[0046] The technical solutions of the present invention are described in detail below with reference to specific embodiments. The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be understood as limiting the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments described herein.

[0047] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products and have not been subjected to any further purification treatment.

[0048] Example 1

[0049] This embodiment provides a ceramic silicone rubber sheath material and a preparation method thereof, wherein the preparation method specifically comprises the following steps:

[0050] S1, dispersing polycarbosilane in anhydrous toluene, pouring it into a glass dish, and ventilating to evaporate the solvent to form a thin film of polycarbosilane. The thin film of polycarbosilane is placed in a tube furnace with an argon atmosphere, adjusting the temperature to 300°C and holding it for 1 hour at a heating rate of 3°C / min, then adjusting the temperature to 600°C and holding it for 1 hour at a heating rate of 3°C / min, and then continuing to heat it to 1100°C and holding it for 2 hours at a heating rate of 5°C / min, while maintaining the argon flow at a flow rate of 120 mL / min. The mixture is naturally cooled to below 200°C and the argon flow is turned off to obtain a bulk SiOC ceramic, which is then ball-milled through a 300-mesh sieve to obtain SiOC powder;

[0051] S2, 80g of dried B2O3 and 100g of P2O5 were ball-milled to obtain a mixed powder, the mixed powder was placed in a platinum crucible and the temperature was adjusted to 1150°C and kept warm for 40 min at a heating rate of 5°C / min. The temperature was then increased to 300°C and 600°C for 30 min each. The melt in the crucible was quickly poured onto the surface of a room temperature steel plate. After cooling, a glass block was formed. The glass block was ball-milled through a 400-mesh sieve and dried to obtain borophosphate glass powder;

[0052] S3, 170g of molybdenum powder and 100g of silicon powder were mixed and ball-milled and pre-pressed to obtain a block mixture. The block mixture was placed in an argon atmosphere in a tube furnace, heated to 900°C and kept for 1h at a heating rate of 5°C / min, then heated to 1350°C and kept for 2h at a heating rate of 5°C / min. Argon was continuously introduced during the cooling process to obtain a sintered block, which was crushed and ball-milled through a 300-mesh sieve to obtain MoSi2 powder;

[0053] S4, 1000g of methyl vinyl silicone rubber, 150g of white carbon black, 150g of SiOC powder, 100g of borophosphate glass powder and 200g of MoSi2 powder were added to an open mill in sequence, mixed evenly, and then 10g of dibenzoyl peroxide, 10g of antioxidant 1010, 10g of zinc stearate and 10g of silicone oil were added. The mixture was thinly slurried to obtain a sheet, which was placed in a flat vulcanizer to maintain pressure to obtain a ceramic silicone rubber sheath material. The actual picture of the ceramic silicone rubber sheath material is as follows: Figure 1 shown.

[0054] Example 2

[0055] This embodiment provides a ceramic silicone rubber sheath material and a preparation method thereof, wherein the preparation method specifically comprises the following steps:

[0056] S1, dispersing polycarbosilane in anhydrous toluene, pouring it into a glass dish, and ventilating to evaporate the solvent to form a thin film of polycarbosilane. The thin film of polycarbosilane is placed in a tube furnace with an argon atmosphere, adjusting the temperature to 303°C and holding it for 1.3 hours at a heating rate of 3°C / min, then adjusting the temperature to 602°C and holding it for 1.4 hours at a heating rate of 3°C / min, and then continuing to heat it to 1105°C and holding it for 3 hours at a heating rate of 5°C / min, while maintaining the argon flow at a flow rate of 130 mL / min. Naturally cooling to below 200°C, the argon gas is turned off to obtain a bulk SiOC ceramic, and the SiOC powder is ball-milled through a 400-mesh sieve.

[0057] S2, 120g of dried B2O3 and 100g of P2O5 were ball-milled to obtain a mixed powder, the mixed powder was placed in a platinum crucible and the temperature was adjusted to 1160°C and kept warm for 50min at a heating rate of 5°C / min. The temperature was then increased to 300°C and 600°C for 30min each. The melt in the crucible was quickly poured onto a room temperature steel plate surface, and after cooling, a glass block was formed. The glass block was ball-milled through a 400-mesh sieve and dried to obtain borophosphate glass powder;

[0058] S3, 180g of molybdenum powder and 100g of silicon powder were mixed and ball-milled and pre-pressed to obtain a block mixture. The block mixture was placed in an argon atmosphere in a tube furnace, heated to 903°C and kept warm for 2.0h at a heating rate of 5°C / min, then heated to 1360°C and kept warm for 3h at a heating rate of 5°C / min. Argon was continuously introduced during the cooling process to obtain a sintered block, which was crushed and ball-milled through a 400-mesh sieve to obtain MoSi2 powder;

[0059] S4, add 1000g of methyl vinyl silicone rubber, 200g of white carbon black, 170g of SiOC powder, 150g of borophosphate glass powder and 260g of MoSi2 powder into an open mill in sequence, mix well, then add 15g of dibenzoyl peroxide, 10g of antioxidant 1076, 15g of zinc stearate and 20g of silicone oil, pass the mixture through a thin tube to obtain a sheet, place the sheet in a flat vulcanizer and maintain pressure to obtain a ceramic silicone rubber sheath material.

[0060] Example 3

[0061] This embodiment provides a ceramic silicone rubber sheath material and a preparation method thereof, wherein the preparation method specifically comprises the following steps:

[0062] S1, dispersing polycarbosilane in anhydrous toluene, pouring it into a glass dish, and ventilating to evaporate the solvent to form a thin film of polycarbosilane. The thin film of polycarbosilane is placed in a tube furnace with an argon atmosphere, adjusting the temperature to 310°C and holding it for 2 hours at a heating rate of 3°C / min, then adjusting the temperature to 610°C and holding it for 2 hours at a heating rate of 3°C / min, and then further increasing the temperature to 1110°C and holding it for 2.2 hours at a heating rate of 5°C / min, while maintaining the argon flow at a flow rate of 150 mL / min. The mixture is naturally cooled to below 200°C and then the argon is turned off to obtain a bulk SiOC ceramic, which is then ball-milled through a 300-mesh sieve to obtain SiOC powder;

[0063] S2, 110g of dried B2O3 and 100g of P2O5 were ball-milled to obtain a mixed powder, the mixed powder was placed in a platinum crucible and the temperature was adjusted to 1170°C and kept warm for 60min at a heating rate of 5°C / min. The temperature was then increased to 300°C and 600°C for 30min each. The melt in the crucible was quickly poured onto the surface of a room temperature steel plate, and after cooling, a glass block was formed. The glass block was ball-milled through a 300-mesh sieve and dried to obtain borophosphate glass powder;

[0064] S3, 174g of molybdenum powder and 100g of silicon powder were mixed and ball-milled and pre-pressed to obtain a block mixture. The block mixture was placed in an argon atmosphere in a tube furnace, heated to 910°C and kept warm for 1.3h at a heating rate of 5°C / min, then heated to 1370°C and kept warm for 2.4h at a heating rate of 5°C / min. Argon was continuously introduced during the cooling process to obtain a sintered block, which was crushed and ball-milled through a 300-mesh sieve to obtain MoSi2 powder;

[0065] S4, 1000g of methyl vinyl silicone rubber, 160g of white carbon black, 200g of SiOC powder, 120g of borophosphate glass powder and 220g of MoSi2 powder are added to an open mill in sequence, and after mixing evenly, 12g of dibenzoyl peroxide, 10g of antioxidant 1024, 11g of zinc stearate and 17g of silicone oil are added. The mixture is thinly passed through a tube to obtain a sheet, and the sheet is placed in a flat vulcanizer to maintain pressure to obtain a ceramic silicone rubber sheath material.

[0066] Example 4

[0067] This embodiment provides a ceramic silicone rubber sheath material and a preparation method thereof, wherein the preparation method specifically comprises the following steps:

[0068] S1, dispersing polycarbosilane in anhydrous toluene, pouring it into a glass dish, and ventilating to evaporate the solvent to form a thin film of polycarbosilane. The thin film of polycarbosilane is placed in a tube furnace with an argon atmosphere, adjusting the temperature to 308°C and holding it for 1.7 hours at a heating rate of 3°C / min, then adjusting the temperature to 609°C and holding it for 1.8 hours at a heating rate of 3°C / min, and then continuing to heat it to 1102°C and holding it for 2.7 hours at a heating rate of 5°C / min, while maintaining argon flow at a flow rate of 140 mL / min. The mixture is naturally cooled to below 200°C and then the argon is turned off to obtain a bulk SiOC ceramic, which is then ball-milled through a 400-mesh sieve to obtain SiOC powder;

[0069] S2, 90g of dried B2O3 and 100g of P2O5 were ball-milled to obtain a mixed powder, the mixed powder was placed in a platinum crucible and the temperature was adjusted to 1165°C and kept warm for 45min at a heating rate of 5°C / min. The temperature was then increased to 300°C and 600°C for 30min each. The melt in the crucible was quickly poured onto the surface of a room temperature steel plate. After cooling, a glass block was formed. The glass block was ball-milled through a 400-mesh sieve and dried to obtain borophosphate glass powder;

[0070] S3, 178g of molybdenum powder and 100g of silicon powder were mixed and ball-milled and pre-pressed to obtain a block mixture. The block mixture was placed in an argon atmosphere in a tube furnace, heated to 907°C and kept warm for 1.6h at a heating rate of 5°C / min, then heated to 1365°C and kept warm for 2.8h at a heating rate of 5°C / min. Argon was continuously introduced during the cooling process to obtain a sintered block, which was crushed and ball-milled through a 400-mesh sieve to obtain MoSi2 powder;

[0071] S4, 1000g of methyl vinyl silicone rubber, 180g of white carbon black, 190g of SiOC powder, 140g of borophosphate glass powder and 250g of MoSi2 powder are added to an open mill in sequence, and after mixing evenly, 14g of dibenzoyl peroxide, 10g of antioxidant 1076, 13g of zinc stearate and 14g of silicone oil are added. The mixture is thinly passed through a tube to obtain a sheet, and the sheet is placed in a flat vulcanizer to maintain pressure to obtain a ceramic silicone rubber sheath material.

[0072] Comparative Example 1

[0073] This comparative example provides a ceramicizable silicone rubber sheath material and a preparation method thereof. The difference between this comparative example and Example 1 is that the mass of the SiOC powder in S4 is 0, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0074] Comparative Example 2

[0075] This comparative example provides a ceramicizable silicone rubber sheath material and a preparation method thereof. The difference between the comparative example and Example 1 is that the mass of the borophosphate glass powder in S4 is 0, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0076] Comparative Example 3

[0077] This comparative example provides a ceramicizable silicone rubber sheath material and a preparation method thereof. The difference between the comparative example and Example 1 is that the mass of the MoSi2 powder in S4 is 0, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0078] The limiting oxygen index test method is GB / T 2406.2-2009; the tensile strength test method is GB / T 528-2009; and the flame retardancy test method is GB / T 2408-2021. The ceramic transition temperature test method is as follows: 10 mg ± 1 mg of sample is placed in a ceramic crucible and secured to the sample holder of the thermogravimetric analyzer. Ensure that the sample is evenly distributed across the bottom of the crucible, without any overlap or protrusion beyond the edge. High-purity argon is introduced as a shielding gas at a flow rate of 40 mL / min. The temperature is raised from room temperature (approximately 25°C) to 1200°C at a rate of 10°C / min. The ceramic transition temperature is determined by identifying the point in the TGA curve where the sample mass begins to significantly decrease. The test results are shown in Table 1.

[0079] Table 1 Test results of a ceramic silicone rubber sheath material of Examples 1-4 and Comparative Examples 1-3

[0080]

[0081] It can be seen from Table 1 that compared with Example 1, the limiting oxygen index of Comparative Example 1 decreases, the ceramicization temperature increases, the tensile strength decreases, and the flame retardant grade decreases; the limiting oxygen index of Comparative Example 2 decreases, the ceramicization temperature increases, the tensile strength decreases, and the flame retardant grade decreases; the limiting oxygen index of Comparative Example 3 decreases, the ceramicization temperature increases, the tensile strength decreases, and the flame retardant grade decreases.

[0082] This is because the mass of SiOC powder in Comparative Example 1 is zero, and the material cannot be quickly ceramicized at high temperatures. It will decompose and carbonize more easily during combustion, resulting in a lower limiting oxygen index and a lower flame retardant rating. Without SiOC powder, the material mainly relies on the thermal decomposition of the silicone rubber matrix, and the residual carbon rate of silicone rubber is low, making it difficult to form sufficient ceramic residues, and the ceramicization temperature rises. SiOC powder can act as an inorganic reinforcing component in the material. The lack of SiOC powder in Comparative Example 1 reduces the tensile strength. The mass of borophosphate glass powder in Comparative Example 2 is zero. Borophosphate glass powder softens at high temperatures and fills pores, improving the density of the ceramic layer. Without borophosphate glass powder, oxygen can more easily penetrate into the material, reducing the limiting oxygen index and the flame retardant rating. Borophosphate glass powder softens and fills pores upon heating, promoting the densification of the ceramic layer. Without borophosphate glass powder, the ceramicization temperature increases. The mass of MoSi2 powder in Comparative Example 3 is 0. MoSi2 powder generates a SiO2 protective film at high temperature to inhibit oxidation diffusion. The lack of MoSi2 powder will accelerate the oxidation of the material, reduce the limiting oxygen index, and reduce the flame retardant grade. The SiO2 protective film generated by MoSi2 powder at high temperature improves the high-temperature stability of the ceramic layer. Without MoSi2 powder, the thermodynamic stability of the ceramic layer formed is reduced.

[0083] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a ceramic silicone rubber sheath material, characterized in that: The preparation method comprises: S1, dispersing polycarbosilane in anhydrous toluene, pouring it into a glass dish, ventilating and volatilizing the solvent to form a thin film of polycarbosilane, placing the thin film of polycarbosilane in a tube furnace under an argon atmosphere, adjusting the temperature to a first temperature and holding it, then adjusting the temperature to a second temperature and holding it, and continuing to increase the temperature to a third temperature and holding it, to obtain SiOC powder; S2, ball-milling B2O3 and P2O5 to obtain a mixed powder, placing the mixed powder in a platinum crucible and adjusting the temperature to the fourth temperature for insulation, and quickly pouring the melt in the crucible onto the surface of a room temperature steel plate to obtain borophosphate glass powder; S3, mixing molybdenum powder and silicon powder and ball-milling and pre-pressing to obtain a bulk mixture, placing the bulk mixture in a tube furnace under an argon atmosphere, heating it to a fifth temperature and holding it, and then heating it to a sixth temperature and holding it to obtain MoSi2 powder; S4, add methyl vinyl silicone rubber, white carbon black, SiOC powder, borophosphate glass powder and MoSi2 powder into an open mill in sequence, mix them evenly, then add vulcanizer, antioxidant, zinc stearate and silicone oil, pass the mixture through a thin tube to obtain a sheet, place the sheet in a flat vulcanizer and maintain pressure to obtain a ceramic silicone rubber sheath material.

2. The method for preparing a ceramic silicone rubber sheath material according to claim 1, characterized in that: In S1: The first temperature is 300-310°C, and the heating rate is 3°C / min; The second temperature is 600-610° C., and the heating rate is 3° C. / min.

3. The method for preparing a ceramic silicone rubber sheath material according to claim 1, characterized in that: In S1: The third temperature is 1100-1110° C., and the heating rate is 5° C. / min.

4. The method for preparing a ceramic silicone rubber sheath material according to claim 1, characterized in that: In S2: The mass ratio of B2O3 to P2O5 is (0.8-1.2):1; The fourth temperature is 1150-1170° C., and the heating rate is 5° C. / min.

5. The method for preparing a ceramic silicone rubber sheath material according to claim 1, characterized in that: In S3: The mass ratio of the molybdenum powder to the silicon powder is (1.7-1.8):

1.

6. The method for preparing a ceramic silicone rubber sheath material according to claim 1, characterized in that: In S3: The fifth temperature is 900-910°C, and the heating rate is 5°C / min; The sixth temperature is 1350-1370° C., and the heating rate is 5° C. / min.

7. The method for preparing a ceramic silicone rubber sheath material according to claim 1, characterized in that: In S4: The mass ratio of the methyl vinyl silicone rubber, white carbon black, SiOC powder, borophosphate glass powder, MoSi2 powder, vulcanizer, antioxidant, zinc stearate and silicone oil is 1000: (150-200): (150-200): (100-150): (200-260): (10-15): 10: (10-15): (10-20).

8. The method for preparing a ceramic silicone rubber sheath material according to claim 1, characterized in that: In S4: The vulcanizing agent is dibenzoyl peroxide; The antioxidant is any one or more of antioxidant 1010 , antioxidant 1076 , and antioxidant 1024 .

9. A ceramic silicone rubber sheath material, characterized in that: Obtained according to the preparation method according to any one of claims 1 to 8.

10. Use of a ceramicizable silicone rubber sheath material prepared by the preparation method according to any one of claims 1 to 8 in fireproof cables.

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