Nano-aerogel / ceramicized silicone rubber composite materials, their preparation methods, and fire-resistant cables

Abstract

This invention belongs to the field of fire-resistant composite material preparation technology, and provides a nano-aerogel ceramicized silicone rubber composite material, its preparation method, and fire-resistant cables. A silicon carbide layer is deposited on the surface of nano-silica aerogel using atomic layer deposition technology, enhancing the mechanical stability and high-temperature oxidation resistance of the aerogel. A silane coupling agent is used to chemically modify the aerogel surface, improving its interfacial compatibility. An Al-doped ceramicized precursor is prepared by reacting polynitrosilane with various functional silanes and metal compounds, enabling the material to form a dense ceramic protective layer at high temperatures. A phosphorus-containing silicon polymer is synthesized with DOPO as the core, further enhancing the flame-retardant properties of the material. By introducing the modified aerogel, Al-doped ceramicized precursor, and phosphorus-silicon polymer into phenyl silicone rubber and methylphenyl silicone resin, followed by vulcanization and ceramicization, a nano-aerogel / ceramized silicone rubber composite material is obtained for application in the field of fire-resistant cables.

Description

Technical Field

[0001] This invention belongs to the field of fire-resistant composite material preparation technology, and relates to nano-aerogel / ceramicized silicone rubber composite materials and their preparation methods, as well as fire-resistant cables. Background Technology

[0002] Cables are core components of modern power transmission and communication systems, widely used in industry, construction, transportation, energy, and other fields. However, because cables are typically made of organic polymer materials, which are easily flammable under high temperatures or fire conditions, they pose significant challenges to fire rescue and evacuation. Therefore, developing fire-resistant cables with excellent flame-retardant properties is of great importance. Traditional flame-retardant solutions mainly include halogen flame-retardant systems and metal hydroxide flame-retardant systems. Halogen flame-retardant systems use halogen compounds as flame retardants, and their flame-retardant mechanism mainly occurs in the gas phase region of combustion, capturing free radicals generated during combustion by releasing hydrogen halide gas and inhibiting the combustion chain reaction. Metal hydroxide flame-retardant systems utilize materials such as aluminum hydroxide and magnesium hydroxide, and their flame-retardant mechanism relies on high-temperature decomposition to release water molecules, while simultaneously absorbing combustion heat and forming a carbonized protective layer to isolate oxygen and heat. These two traditional solutions have shown some flame-retardant effects in past applications, but they also have significant drawbacks and cannot meet the high-performance and environmental protection requirements of modern fire-resistant cables.

[0003] Halogenated flame retardant systems release large amounts of toxic gases and corrosive products during combustion, posing a serious threat to human health and potentially causing a sharp decrease in visibility at fire scenes, hindering evacuation and rescue efforts. The hydrogen chloride released during combustion readily combines with water vapor to form hydrochloric acid, severely irritating the respiratory tract and even causing suffocation. Furthermore, incomplete combustion at high temperatures can produce dioxins, a carcinogen, further exacerbating the environmental hazards of fires. Metal hydroxides, as physical flame retardants, require high dosages to achieve ideal flame-retardant effects. However, high filler content reduces the tensile strength and ductility of cable materials, affecting their service life in practical applications. Excessive filler also increases material viscosity, reducing processing fluidity. The flame-retardant effect of metal hydroxides primarily relies on high-temperature decomposition endothermics and the release of water vapor, but this process requires significant heat to initiate, resulting in low flame-retardant efficiency, especially under high flame temperatures where combustion is difficult to suppress. Therefore, using metal hydroxides alone is insufficient to meet modern high-standard flame-retardant requirements. Nano-aerogels are among the solid materials with the lowest known thermal conductivity, far lower than traditional fire-resistant and heat-insulating materials. As an inorganic material, nano-aerogels do not decompose and release toxic gases or smoke during a fire, meeting the environmental and safety requirements of low smoke and halogen-free materials. Silicone rubber, as the matrix material, possesses extremely high thermal stability, with a decomposition temperature typically above 300-400℃, far exceeding that of most organic polymers. Ceramicized silicone rubber further enhances its temperature resistance, allowing it to withstand even higher temperatures in a fire. Silicone rubber is halogen-free and does not release toxic gases or corrosive fumes during combustion. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a nano-aerogel / ceramized silicone rubber composite fire-resistant cable. It utilizes nano-SiO2 aerogel as the base material, introducing a SiC coating through atomic layer deposition to enhance the aerogel's structural strength and high-temperature oxidation resistance. Simultaneously, a silane coupling agent modifies the aerogel surface, improving its interfacial compatibility with the silicone rubber matrix. Secondly, an Al-doped ceramicized precursor is prepared through a multi-component reaction of polynitrosilanes, providing excellent thermal insulation and flame erosion resistance. Furthermore, a phosphorus-silicon synergistic flame-retardant functional polymer is synthesized using DOPO as the core to enhance the material's charring effect and flame-retardant efficiency under fire conditions. Through optimized composite processes, the modified aerogel, ceramicized precursor, and phosphorus-silicon polymer are uniformly dispersed in phenyl silicone rubber and methylphenyl silicone resin, then compounded, extruded, and vulcanized using a twin-screw extruder, and applied to the fire-resistant cable, thus meeting the needs of practical production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a nano-aerogel / ceramized silicone rubber composite material, the preparation method comprising:

[0007] S1. Place the dried nano-SiO2 aerogel on an ALD substrate tray and deposit a SiC layer using a cyclic method to obtain SiC aerogel. Immerse the SiC aerogel in KH-560 solution, adjust the pH to 4.5, and then vacuum dry and solidify it to obtain modified aerogel.

[0008] S2, inside the glove box, polynitrosilane is dispersed in diethylene glycol dimethyl ether. After installing the condenser, the temperature is adjusted to the first temperature and ammonia is introduced. Trimethyl borate is added to react. The temperature is lowered to 40°C and aluminum isopropoxide is added and stirred to react. The temperature is adjusted to the first temperature and vinyltriethoxysilane is added and stirred to continue the reaction. After the reaction is completed, vacuum distillation is performed to obtain the Al-doped ceramic precursor.

[0009] S3, mix DOPO with pentaerythritol, under nitrogen atmosphere, adjust the temperature to the second temperature and stir to disperse, adjust the temperature to 80°C, add vinyltrimethoxysilane and mercaptoacetic acid, add azobisisobutyronitrile under light-protected conditions, continue stirring in the dark, adjust the temperature to 60°C and add trimethyl borate, continue stirring, after the reaction is completed, distill under reduced pressure to obtain phosphosilicate polymer.

[0010] S4. Phenyl silicone rubber and methyl phenyl silicone resin were added to a twin-screw internal mixer. The temperature was set at 40℃ and the speed at 200 rpm. The mixture was plasticized for 5 minutes. Modified aerogel was added and mixed for 10 minutes. The temperature was adjusted to 60℃. Molten Al-doped ceramic precursor was added and mixed for 5 minutes. The temperature was adjusted to 50℃. Phosphorus-silicon polymer was added and mixed for 8 minutes. Diisopropylbenzene peroxide was added and mixed for 2 minutes. After mixing, the mixture was added to an extruder for extrusion and cooling. Vulcanization and ceramicization were carried out sequentially to obtain a nano-aerogel / ceramized silicone rubber composite material.

[0011] Atomic layer deposition (ALD) technology was used to construct a silicon carbide coating on the surface of nano-SiO2 aerogels under plasma-activated conditions using trimethylsilane and methane as precursors. The Si–C bonds within the trimethylsilane molecule broke under high-energy electron bombardment by the plasma, forming an initial silicon adsorption layer. Subsequently, carbon radicals gradually formed a Si–C covalent network through insertion or substitution mechanisms. The introduction of the SiC coating significantly improved the physicochemical properties of the nano-aerogels. On the one hand, SiC, as a material with high mechanical strength and thermal stability, enhanced the structural integrity of the aerogels, significantly improving their compressive strength and crack resistance at high temperatures. On the other hand, the silicon carbide coating exhibited excellent antioxidant properties at high temperatures, effectively preventing the oxidative decomposition of the aerogels under extreme temperature conditions, thereby extending their service life. Furthermore, the high chemical inertness of the SiC coating enhanced the stability of the aerogels in complex chemical environments, providing greater applicability for subsequent composite material processing. The introduction of the silane coupling agent KH-560 further optimized the interfacial compatibility between the aerogels and the polymer matrix. The methoxy group in the KH-560 molecule hydrolyzes in an ethanol-water system to generate a silanol group, which then undergoes a condensation reaction with the active silicon or carbon sites on the SiC coating surface to form a strong covalent bond. The epoxy group at the end of the coupling agent undergoes a ring-opening reaction with the functional groups of the silicone rubber during subsequent composite material processing, generating ether or urethane bonds. This achieves chemical bonding between the aerogel and the polymer matrix, resulting in a strong interfacial bond between the aerogel and the matrix. This improves the mechanical properties and interfacial stability of the composite material. Furthermore, the shielding effect of the hydrophobic long-chain alkyl group reduces the moisture absorption rate of the aerogel, thus preventing performance degradation under humid and hot conditions.

[0012] Polynitrosilanes are core materials for ceramicization precursors. Their molecular framework is mainly composed of Si-N bonds, exhibiting superior high-temperature pyrolysis characteristics. Under high-temperature conditions, polynitrosilanes can pyrolyze to generate ceramic phases such as silicon nitride, silicon oxide, or silicon oxynitrides. The formation of these phases endows the materials with good thermal stability and oxidation resistance. However, the ceramic products generated by the pyrolysis of polynitrosilanes alone usually suffer from high porosity, easy crack initiation, and insufficient density, which weakens the shielding performance of the ceramic protective layer under extreme high-temperature conditions. The core mechanism of the ammonolysis reaction is the reaction between ammonia molecules and the active sites in polynitrosilane molecules, especially the chemical interaction with Si-H or Si-Cl bonds. Ammonia attacks the Si-H bonds in polynitrosilane molecules through nucleophilic attack, generating Si-NH bonds, increasing the degree of cross-linking between molecules, forming a more stable Si-N network structure, enhancing the thermal stability of polynitrosilane molecules, and providing a highly active and stable precursor for subsequent functionalization reactions. After the ammonolysis reaction, trimethyl borate is introduced. The BO bonds in its molecule can chemically react with the active sites in the polynitrosilane molecule to form BO-Si and BN bonds. The introduction of boron plays several important roles in the ceramization process. First, boron oxide is an effective flux that significantly lowers the melting point of the system during ceramization, thereby promoting the densification and homogenization of the ceramic layer. Low-melting-point boron oxide has high fluidity at high temperatures, which can fill microcracks and pores in the ceramic layer, thus improving the mechanical integrity and thermal crack resistance of the ceramic protective layer. Second, boron oxide and silicon oxide can form a borosilicate covalent network structure at high temperatures. This network has excellent thermal stability and resistance to chemical corrosion, thereby improving the overall performance of the ceramic protective layer. Furthermore, boron oxide can also react with other oxides such as alumina during ceramization to form composite ceramic phases, further enhancing the multifunctionality of the ceramic layer. Aluminum isopropoxide possesses highly reactive Al-O bonds, enabling it to chemically exchange with Si-H or Si-NH bonds in polynitrosilane molecules to form Al-O-Si and Al-ON bonds, further enhancing the three-dimensional network structure of the polynitrosilane molecules. During high-temperature ceramization, aluminum oxides can significantly improve the mechanical strength and thermal shock resistance of the ceramic protective layer by generating a stable ceramic phase. Furthermore, alumina can form composite ceramic phases with silicon oxides or boron oxides at high temperatures, further enhancing the thermal stability and chemical corrosion resistance of the ceramic layer, improving the density and refractory properties of the ceramization product, and enabling more effective thermal shielding under extreme high-temperature conditions. By functionalizing the precursor with vinyltriethoxysilane, the vinyl groups in the vinyltriethoxysilane molecule can chemically combine with polynitrosilane molecules through free radical polymerization or covalent bonding, introducing organosilicon groups and improving the dispersibility of the ceramization precursor, resulting in higher interfacial compatibility when subsequently composited with an organic matrix.In addition, the triethoxysilane group in the molecule can generate silicon-oxygen bonds through hydrolysis and condensation reactions, which further enhances the crosslinking degree of the precursor and optimizes its structural stability.

[0013] In the DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) molecule, the phosphorus atom forms a rigid planar structure with the benzoxoxane ring via a phosphorooxy bond. Its highly reactive PH bond undergoes a nucleophilic substitution reaction with the hydroxyl group of pentaerythritol at high temperatures. The tetrafunctional hydroxyl group of pentaerythritol provides multiple reaction sites. The PH bond of DOPO breaks under acidic or free radical conditions, releasing H₂. + It combines with hydroxyl oxygen atoms to form water molecules, creating stable phosphoester bonds. The benzo[a]oxoheterocyclic structure of DOPO not only endows the material with intrinsic flame retardancy but also enhances the rigidity of the molecular chain through π-π stacking, inhibiting chain segment movement at high temperatures. After the initial reaction of DOPO with pentaerythritol, vinyltrimethoxysilane and mercaptoacetic acid are added for further chemical modification. Vinyltrimethoxysilane is a functional silane whose molecular structure contains both active vinyl and trimethoxysilane groups. In the reaction medium, the trimethoxysilane group is first converted into a silanol intermediate through hydrolysis. The mechanism of this hydrolysis reaction is that the methoxy group reacts with hydrogen in the water molecule, leaving behind an active silanol group. The silanol group has extremely high chemical reactivity and can form silicon-oxygen bonds with other silanol groups through condensation reactions, thereby forming a preliminary silicon oxide network structure in the reaction system.

[0014] Meanwhile, the vinyl groups in the vinyltrimethoxysilane molecule undergo further functionalization through an addition reaction with mercaptoacetic acid. The thiol group in mercaptoacetic acid acts as a nucleophile, reacting with the carbon-carbon double bond of the vinyl group to form a new C–S bond, conferring higher thermal stability to the system and introducing sulfur-containing groups to improve the polymer's flame-retardant properties. In this stage of the reaction, the free radicals generated from the decomposition of the free radical initiator azobisisobutyronitrile (AIBN) can further initiate the free radical polymerization of the vinyl groups, forming a cross-linked organosilicon network structure. Under the action of the free radical initiator, the degree of cross-linking of the siloxane segments is further enhanced, forming a three-dimensional phosphorosilicon polymer network with a high cross-linking density. The introduction of trimethyl borate integrates boron into the polymer chain through transesterification. Under high-temperature conditions, the methoxy group of trimethyl borate reacts with the hydroxyl or thiol group at the polymer terminal to form BOC or BSC bonds. The empty boron atom... pThe orbitals can accept lone pairs of electrons, forming coordinate bonds with neighboring oxygen or sulfur atoms, further crosslinking the molecular chain. These dynamic borate ester bonds can reversibly break and recombine at high temperatures, endowing the material with self-healing capabilities: when the material is heated, the borate ester bonds in localized stress concentration areas break and absorb energy, subsequently rebonding during cooling, inhibiting microcrack propagation. Furthermore, the introduction of boron enhances the polymer's high-temperature oxidation resistance; the B2O3 generated from boron oxidation effectively blocks oxygen penetration, delaying the material's thermal decomposition. The polymer's flame-retardant properties are mainly reflected in two aspects: the phosphorus-oxygen bonds in DOPO decompose under high-temperature conditions, releasing phosphoric acid-like chemicals. These substances catalyze carbonization to form a stable char layer, effectively isolating heat and oxygen; the silicon oxides and boron oxides in the polymer further form a dense ceramic protective layer at high temperatures, working synergistically with the char layer to provide additional thermal shielding.

[0015] Using phenyl silicone rubber as the matrix material, the introduction of SiC aerogel enhances the thermal stability of the composite material. In the composite system, the epoxy groups on the aerogel surface can chemically react with the end groups in the silicone rubber matrix, strengthening the interfacial bonding between the inorganic filler and the organic matrix. Furthermore, the SiC coating imparts higher heat resistance to the aerogel, enabling it to maintain stable physicochemical properties under high-temperature conditions. Aluminum-doped ceramic precursors generate a dense ceramic layer through pyrolysis and chemical rearrangement reactions at high temperatures. The polynitrosilane in the precursor decomposes during high-temperature pyrolysis to generate ceramic phases such as silicon nitride and alumina, forming a ceramic protective layer with high mechanical strength and thermal stability. Boron oxide in the precursor can lower the ceramicization temperature of the system at high temperatures and further enhance the density of the ceramic layer by filling cracks and pores. In addition, aluminum doping can form a composite ceramic phase with silicon oxide and boron oxide at high temperatures. This composite phase exhibits excellent thermal stability and chemical corrosion resistance, improving the material's flame retardancy and high-temperature protection capabilities. In composite materials, aluminum-doped ceramic precursors not only provide protection through their own high-temperature ceramicization reaction, but also further enhance the overall performance of the composite material through interfacial interaction with the silicone rubber matrix.

[0016] As a preferred technical solution of the present invention, in S1, the cyclic deposition method is as follows: trimethylsilane pulse for 0.1s, nitrogen purging for 5s, nitrogen flow rate for 200sccm, methane pulse for 0.05s, methane flow rate for 20sccm, H2 flow rate for 50sccm, power for 200W, activation for 5s, nitrogen purging for 5s, and 100 cycles.

[0017] In some optional examples, the mass-to-volume ratio of the SiC aerogel to the KH-560 solution is 1 g: 10 mL.

[0018] In some optional examples, the KH-560 solution has a mass fraction of 5 wt.%, the solvent is anhydrous ethanol and deionized water, the volume ratio of the solvent components is 85:10, and the KH-560 solution is pre-hydrolyzed for 30 min before use.

[0019] In some optional embodiments, the duration of the ultrasonic treatment is 30-40 minutes, for example, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, 35 minutes, 36 minutes, 37 minutes, 38 minutes, 39 minutes or 40 minutes, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0020] In some optional embodiments, the vacuum curing and drying temperature is 80-90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0021] In some optional embodiments, the vacuum drying and curing time is 2-3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0022] As a preferred embodiment of the present invention, in S2, the mass-to-volume ratio of the polynitrosilane, diethylene glycol dimethyl ether, trimethyl borate, aluminum isopropoxide, and vinyltriethoxysilane is 10g:20mL:3g:5mL:2g.

[0023] In some alternative embodiments, the first temperature is 60-70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the reaction time for adding trimethyl borate is 4-5 hours, for example, 4.0 hours, 4.1 hours, 4.2 hours, 4.3 hours, 4.4 hours, 4.5 hours, 4.6 hours, 4.7 hours, 4.8 hours, 4.9 hours, or 5.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] In some alternative embodiments, the stirring reaction time is 2-3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0026] In some optional embodiments, the continued stirring reaction time is 1-2 hours, for example, 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, or 2.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0027] As a preferred embodiment of the present invention, in S3, the mass ratio of DOPO, pentaerythritol, vinyltrimethoxysilane, mercaptoacetic acid, azobisisobutyronitrile and trimethyl borate is 5:2:3:0.5:0.05:1.

[0028] In some alternative embodiments, the second temperature is 120-130°C, for example, it can be 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C or 130°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the stirring and dispersion time is 1-2 hours, for example, it can be 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the stirring time in the dark is 3-4 hours, for example, 3.0 hours, 3.1 hours, 3.2 hours, 3.3 hours, 3.4 hours, 3.5 hours, 3.6 hours, 3.7 hours, 3.8 hours, 3.9 hours or 4.0 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the continuous stirring time is 2-3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] As a preferred embodiment of the present invention, in S4, the phenyl content of the phenyl silicone rubber is >10%.

[0033] In some optional examples, the mass ratio of the phenyl silicone rubber, methylphenyl silicone resin, modified aerogel, Al-doped ceramic precursor, phosphosilicate polymer and dicumyl peroxide is 100:20:15:12:8:1.5.

[0034] In some alternative examples, the extruder is configured with the following conditions: feed zone 50°C, melt zone 80°C, die head zone 110°C, screw speed 20 rpm, and traction speed 2 m / min.

[0035] In some optional examples, the vulcanization conditions are 150°C, 15 MPa, and 25 min.

[0036] In some optional examples, the ceramization conditions are 300°C for 10 min at a heating rate of 5°C / min.

[0037] In a second aspect, the present invention provides a nano-aerogel / ceramized silicone rubber composite material prepared by the preparation method described in the first aspect.

[0038] Thirdly, the present invention provides a fire-resistant cable, comprising a conductor, an insulation layer, and a sheath material for covering the insulation layer, wherein the sheath material is a nano-aerogel / ceramized silicone rubber composite material prepared by the preparation method described in the first aspect.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) By introducing SiC coating through atomic layer deposition technology, the mechanical strength and high temperature anti-oxidation performance of nano-aerogel are enhanced. At the same time, the surface of aerogel is chemically modified by silane coupling agent, which effectively improves its interfacial compatibility with silicone rubber matrix; (2) Al-doped ceramic precursor is successfully prepared by reaction of polynitrosilane, trimethyl borate and aluminum isopropoxide. A dense and stable alumina-silica composite ceramic protective layer is generated under high temperature conditions, which improves the ceramicization efficiency and thermal shielding performance of the material; (3) Phosphorus silicon polymer with high flame retardant performance is designed by chemical combination of DOPO and siloxane groups, which realizes excellent synergistic effect of carbonization and flame retardancy, avoids the high toxicity and smoke problems of traditional halogenated flame retardants, and effectively enhances the carbonization stability and thermal protection capability of the material in fire environment. Attached Figure Description

[0040] Figure 1 The following is a flowchart of the preparation method of nano-aerogel / ceramicized silicone rubber composite material for Examples 1-4 of the present invention. Detailed Implementation

[0041] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0042] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0043] Example 1

[0044] This embodiment provides a method for preparing nano-aerogel / ceramized silicone rubber composite material, the preparation method specifically including the following steps:

[0045] S1. Place the dried nano-SiO2 aerogel on an ALD substrate tray and deposit a SiC layer using a cyclic method. The cyclic method is as follows: trimethylsilane pulse for 0.1s, nitrogen purging for 5s, nitrogen flow rate 200sccm, methane pulse for 0.05s, methane flow rate 20sccm, H2 flow rate 50sccm, power 200W, activation for 5s, nitrogen purging for 5s, and 100 cycles to obtain SiC aerogel. Immerse 10g of SiC aerogel in 100mL of 5wt% KH-560 solution, adjust the pH to 4.5, sonicate for 30min, and then vacuum dry and cure at 84℃ for 2.2h to obtain modified aerogel.

[0046] S2, In a glove box, 10g of polynitrosilane was dispersed in 20mL of diethylene glycol dimethyl ether. After installing a condenser, the temperature was adjusted to 60℃ and ammonia was introduced. 3g of trimethyl borate was added and the reaction was carried out for 4.3h. The temperature was lowered to 40℃ and 5mL of aluminum isopropoxide was added and the reaction was stirred for 2.0h. The temperature was adjusted to 66℃ and 2g of vinyltriethoxysilane was added and the reaction was stirred for another 1.3h. After the reaction was completed, the Al-doped ceramic precursor was obtained by vacuum distillation.

[0047] S3, 5g DOPO and 2g pentaerythritol were mixed under a nitrogen atmosphere and the temperature was adjusted to 122℃ and stirred for 1.6h. The temperature was then adjusted to 80℃, 3g vinyltrimethoxysilane and 0.5g mercaptoacetic acid were added, and 0.05g azobisisobutyronitrile was added under light-protected conditions. The mixture was stirred continuously under light-protected conditions for 3-4h. The temperature was then adjusted to 60℃ and 1g trimethyl borate was added. The mixture was stirred continuously for 2.3h. After the reaction was completed, the phosphorus-silicon polymer was obtained by vacuum distillation.

[0048] S4. 1000g of phenyl silicone rubber and 200g of methylphenyl silicone resin were added to a twin-screw internal mixer. The temperature was set at 40℃ and the speed at 200rpm. After plasticizing for 5min, 150g of modified aerogel was added and mixed for 10min. The temperature was adjusted to 60℃. 120g of molten Al-doped ceramicized precursor was added and mixed for 5min. The temperature was adjusted to 50℃. 80g of phosphosilicate polymer was added and mixed for 8min. 15g of dicumyl peroxide was added and mixed for 2min. After mixing, the mixture was fed into an extruder for extrusion and cooling. The extruder conditions were: feed zone 50℃, melt zone 80℃, die head zone 110℃, screw speed 20rpm, and traction speed 2m / min. Vulcanization and ceramicization were carried out sequentially. The vulcanization conditions were 150℃ and 15MPa, held for 25min. The ceramicization conditions were 300℃, held for 10min, and heating rate 5℃ / min, to obtain a nano-aerogel / ceramized silicone rubber composite material.

[0049] Example 2

[0050] This embodiment provides a method for preparing nano-aerogel / ceramized silicone rubber composite material, the preparation method specifically including the following steps:

[0051] S1. Place the dried nano-SiO2 aerogel on an ALD substrate tray and deposit a SiC layer using a cyclic method. The cyclic method is as follows: trimethylsilane pulse for 0.1s, nitrogen purging for 5s, nitrogen flow rate 200sccm, methane pulse for 0.05s, methane flow rate 20sccm, H2 flow rate 50sccm, power 200W, activation for 5s, nitrogen purging for 5s, and 100 cycles to obtain SiC aerogel. Immerse 10g of SiC aerogel in 100mL of 5wt% KH-560 solution, adjust the pH to 4.5, sonicate for 40min, and then vacuum dry and cure at 80℃ for 2.0h to obtain modified aerogel.

[0052] S2, In a glove box, 10g of polynitrosilane was dispersed in 20mL of diethylene glycol dimethyl ether. After installing a condenser, the temperature was adjusted to 64℃ and ammonia was introduced. 3g of trimethyl borate was added and reacted for 4.0h. The temperature was lowered to 40℃ and 5mL of aluminum isopropoxide was added and stirred for 2.8h. The temperature was adjusted to 60℃ and 2g of vinyltriethoxysilane was added and stirred for another 1.0h. After the reaction was completed, the Al-doped ceramic precursor was obtained by vacuum distillation.

[0053] S3, 5g DOPO and 2g pentaerythritol were mixed under a nitrogen atmosphere and the temperature was adjusted to 120℃ and stirred for 1.0h. The temperature was then adjusted to 80℃, 3g vinyltrimethoxysilane and 0.5g mercaptoacetic acid were added, and 0.05g azobisisobutyronitrile was added under light-protected conditions. The mixture was stirred continuously under light-protected conditions for 3-4h. The temperature was then adjusted to 60℃ and 1g trimethyl borate was added. The mixture was stirred continuously for 2.0h. After the reaction was completed, the phosphorus-silicon polymer was obtained by vacuum distillation.

[0054] S4. 1000g of phenyl silicone rubber and 200g of methylphenyl silicone resin were added to a twin-screw internal mixer. The temperature was set at 40℃ and the speed at 200rpm. After plasticizing for 5min, 150g of modified aerogel was added and mixed for 10min. The temperature was adjusted to 60℃. 120g of molten Al-doped ceramicized precursor was added and mixed for 5min. The temperature was adjusted to 50℃. 80g of phosphosilicate polymer was added and mixed for 8min. 15g of dicumyl peroxide was added and mixed for 2min. After mixing, the mixture was fed into an extruder for extrusion and cooling. The extruder conditions were: feed zone 50℃, melt zone 80℃, die head zone 110℃, screw speed 20rpm, and traction speed 2m / min. Vulcanization and ceramicization were carried out sequentially. The vulcanization conditions were 150℃ and 15MPa, held for 25min. The ceramicization conditions were 300℃, held for 10min, and heating rate 5℃ / min, to obtain a nano-aerogel / ceramized silicone rubber composite material.

[0055] Example 3

[0056] This embodiment provides a method for preparing nano-aerogel / ceramized silicone rubber composite material, the preparation method specifically including the following steps:

[0057] S1. Place the dried nano-SiO2 aerogel on an ALD substrate tray and deposit a SiC layer using a cyclic method. The cyclic method is as follows: trimethylsilane pulse for 0.1s, nitrogen purging for 5s, nitrogen flow rate 200sccm, methane pulse for 0.05s, methane flow rate 20sccm, H2 flow rate 50sccm, power 200W, activation for 5s, nitrogen purging for 5s, and 100 cycles to obtain SiC aerogel. Immerse 10g of SiC aerogel in 100mL of 5wt% KH-560 solution, adjust the pH to 4.5, sonicate for 37min, and then vacuum dry and cure at 90℃ for 2.6h to obtain modified aerogel.

[0058] S2, In a glove box, 10g of polynitrosilane was dispersed in 20mL of diethylene glycol dimethyl ether. After installing a condenser, the temperature was adjusted to 70℃ and ammonia was introduced. 3g of trimethyl borate was added and reacted for 5.0h. The temperature was lowered to 40℃ and 5mL of aluminum isopropoxide was added and stirred for 3.0h. The temperature was adjusted to 70℃ and 2g of vinyltriethoxysilane was added and stirred for another 1.8h. After the reaction was completed, the Al-doped ceramic precursor was obtained by vacuum distillation.

[0059] S3, 5g DOPO and 2g pentaerythritol were mixed under a nitrogen atmosphere and the temperature was adjusted to 128℃ and stirred for 2.0h. The temperature was then adjusted to 80℃, 3g vinyltrimethoxysilane and 0.5g mercaptoacetic acid were added, and 0.05g azobisisobutyronitrile was added under light-protected conditions. The mixture was stirred continuously under light-protected conditions for 3-4h. The temperature was then adjusted to 60℃ and 1g trimethyl borate was added. The mixture was stirred continuously for 2.7h. After the reaction was completed, the phosphorus-silicon polymer was obtained by vacuum distillation.

[0060] S4. 1000g of phenyl silicone rubber and 200g of methylphenyl silicone resin were added to a twin-screw internal mixer. The temperature was set at 40℃ and the speed at 200rpm. After plasticizing for 5min, 150g of modified aerogel was added and mixed for 10min. The temperature was adjusted to 60℃. 120g of molten Al-doped ceramicized precursor was added and mixed for 5min. The temperature was adjusted to 50℃. 80g of phosphosilicate polymer was added and mixed for 8min. 15g of dicumyl peroxide was added and mixed for 2min. After mixing, the mixture was fed into an extruder for extrusion and cooling. The extruder conditions were: feed zone 50℃, melt zone 80℃, die head zone 110℃, screw speed 20rpm, and traction speed 2m / min. Vulcanization and ceramicization were carried out sequentially. The vulcanization conditions were 150℃ and 15MPa, held for 25min. The ceramicization conditions were 300℃, held for 10min, and heating rate 5℃ / min, to obtain a nano-aerogel / ceramized silicone rubber composite material.

[0061] Example 4

[0062] This embodiment provides a method for preparing nano-aerogel / ceramized silicone rubber composite material, the preparation method specifically including the following steps:

[0063] S1. Place the dried nano-SiO2 aerogel on an ALD substrate tray and deposit a SiC layer using a cyclic method. The cyclic method is as follows: trimethylsilane pulse for 0.1s, nitrogen purging for 5s, nitrogen flow rate of 200sccm, methane pulse for 0.05s, methane flow rate of 20sccm, H2 flow rate of 50sccm, power of 200W, activation for 5s, nitrogen purging for 5s, and 100 cycles to obtain SiC aerogel. Immerse 10g of SiC aerogel in 100mL of 5wt% KH-560 solution, adjust the pH to 4.5, sonicate for 33min, and then vacuum dry and cure at 87℃ for 3.0h to obtain modified aerogel.

[0064] S2, In a glove box, 10g of polynitrosilane was dispersed in 20mL of diethylene glycol dimethyl ether. After installing a condenser, the temperature was adjusted to 68℃ and ammonia was introduced. 3g of trimethyl borate was added and reacted for 4.7h. The temperature was lowered to 40℃ and 5mL of aluminum isopropoxide was added and stirred for 2.4h. The temperature was adjusted to 62℃ and 2g of vinyltriethoxysilane was added and stirred for another 2.0h. After the reaction was completed, the Al-doped ceramic precursor was obtained by vacuum distillation.

[0065] S3, 5g DOPO and 2g pentaerythritol were mixed under a nitrogen atmosphere and the temperature was adjusted to 130℃ and stirred for 1.4h. The temperature was then adjusted to 80℃, 3g vinyltrimethoxysilane and 0.5g mercaptoacetic acid were added, and 0.05g azobisisobutyronitrile was added under light-protected conditions. The mixture was stirred continuously under light-protected conditions for 3-4h. The temperature was then adjusted to 60℃ and 1g trimethyl borate was added. The mixture was stirred continuously for 3.0h. After the reaction was completed, the phosphorus-silicon polymer was obtained by vacuum distillation.

[0066] S4. 1000g of phenyl silicone rubber and 200g of methylphenyl silicone resin were added to a twin-screw internal mixer. The temperature was set at 40℃ and the speed at 200rpm. After plasticizing for 5min, 150g of modified aerogel was added and mixed for 10min. The temperature was adjusted to 60℃. 120g of molten Al-doped ceramicized precursor was added and mixed for 5min. The temperature was adjusted to 50℃. 80g of phosphosilicate polymer was added and mixed for 8min. 15g of dicumyl peroxide was added and mixed for 2min. After mixing, the mixture was fed into an extruder for extrusion and cooling. The extruder conditions were: feed zone 50℃, melt zone 80℃, die head zone 110℃, screw speed 20rpm, and traction speed 2m / min. Vulcanization and ceramicization were carried out sequentially. The vulcanization conditions were 150℃ and 15MPa, held for 25min. The ceramicization conditions were 300℃, held for 10min, and heating rate 5℃ / min, to obtain a nano-aerogel / ceramized silicone rubber composite material.

[0067] Comparative Example 1

[0068] This comparative example provides a method for preparing nano-aerogel / ceramized silicone rubber composite material. The difference between this method and Example 1 is that the mass of the Al-doped ceramized precursor in S4 is 220g, which is 100g more than in Example 1. Other process parameters and operating conditions are exactly the same as in Example 1.

[0069] Comparative Example 2

[0070] This comparative example provides a method for preparing a nano-aerogel / ceramized silicone rubber composite material. The difference between this method and Example 1 is that the mass of the Al-doped ceramized precursor in S4 is 20g, which is 100g less than that in Example 1. Other process parameters and operating conditions are exactly the same as in Example 1.

[0071] Comparative Example 3

[0072] This comparative example provides a method for preparing a nano-aerogel / ceramicized silicone rubber composite material. The difference between this method and Example 1 is that the mass of the phosphorus-silicon polymer in S4 is 150g, which is 70g more than that in Example 1. Other process parameters and operating conditions are exactly the same as in Example 1.

[0073] Comparative Example 4

[0074] This comparative example provides a method for preparing a nano-aerogel / ceramicized silicone rubber composite material. The difference between this method and Example 1 is that the mass of the phosphorus-silicon polymer in S4 is 10g, which is 70g less than that in Example 1. Other process parameters and operating conditions are exactly the same as in Example 1.

[0075] The limiting oxygen index test method is GB / T 2406.2-2009; the flame retardant performance test method is GB / T 2408-2021; and the maximum smoke density (flameless) test method is GB / T 32129-2015. The test results are shown in Table 1.

[0076] Table 1. Test results of nano-aerogel / ceramized silicone rubber composites in Examples 1-4 and Comparative Examples 1-4

[0077]

[0078] As shown in Table 1, compared to Example 1, Comparative Example 1 showed a decrease in limiting oxygen index (LOI), unchanged flame retardancy rating, and decreased maximum smoke density (flameless); Comparative Example 2 showed a decrease in both LIO and flame retardancy rating, but an increase in maximum smoke density (flameless). This is because in Comparative Example 1, the excessive Al-doped ceramic precursor resulted in a dense and continuous ceramic layer, preventing oxygen penetration and isolating heat transfer, thus maintaining a stable flame retardancy rating. Excessive Al-doped ceramic precursor may prematurely crosslink, hindering silicone rubber vulcanization and leading to increased porosity within the matrix and a decrease in LIO. In Comparative Example 2, insufficient Al-doped ceramic precursor prevented the formation of an effective barrier at high temperatures, making it difficult for the carbonized layer to maintain structural integrity, thereby reducing the flame retardancy rating, accelerating thermal decomposition, and increasing maximum smoke density (flameless). Compared to Example 1, Comparative Example 3 showed an increase in LIO, a decrease in flame retardancy rating, and an increase in maximum smoke density (flameless); Comparative Example 4 showed a decrease in both LIO and flame retardancy rating, but an increase in maximum smoke density (flameless). In Comparative Example 3, excessive phosphorus-silicon polymer and high phosphorus content promote the formation of a large amount of dense char layer, increasing the limiting oxygen index. However, an excessively thick char layer is prone to cracking, leading to exposure of internal combustibles and thus reducing the flame retardant rating. In Comparative Example 4, insufficient phosphorus-silicon polymer results in incomplete char layer formation, reduced density and integrity of the char layer, and insufficient synergistic flame retardancy from phosphorus and boron.

[0079] 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing nano-aerogel / ceramized silicone rubber composite material, characterized in that, The preparation method includes: S1, dry nano-SiO2 aerogel is cyclically deposited with SiC layer to obtain SiC aerogel, and SiC aerogel is immersed in KH-560 solution to obtain modified aerogel; S2, polynitrosilane is dispersed in diethylene glycol dimethyl ether, ammonia is introduced, and trimethyl borate, aluminum isopropoxide and vinyltriethoxysilane are added to react and obtain Al-doped ceramic precursor; S3, DOPO is mixed with pentaerythritol, and vinyltrimethoxysilane, mercaptoacetic acid, azobisisobutyronitrile and trimethyl borate are added and reacted to obtain a phosphosilicate polymer; S4, phenyl silicone rubber and methyl phenyl silicone resin are added to a twin-screw mixer, and modified aerogel, Al-doped ceramic precursor, phosphosilicate polymer and dicumyl peroxide are added. After mixing, the mixture is added to an extruder for extrusion and cooling, and then vulcanized and ceramicized in sequence to obtain a nano-aerogel / ceramized silicone rubber composite material.

2. The preparation method of the nano-aerogel / ceramized silicone rubber composite material according to claim 1, characterized in that, In S1, The cyclic deposition method is as follows: trimethylsilane pulse for 0.1s, nitrogen purging for 5s, nitrogen flow rate of 200 sccm, methane pulse for 0.05s, methane flow rate of 20 sccm, H2 flow rate of 50 sccm, power of 200 W, activation for 5s, nitrogen purging for 5s, and 100 cycles.

3. The method for preparing the nano-aerogel / ceramized silicone rubber composite material according to claim 1, characterized in that, In S2, The mass-to-volume ratio of the polynitrosilane, diethylene glycol dimethyl ether, trimethyl borate, aluminum isopropoxide, and vinyltriethoxysilane is 10g:20mL:3g:5mL:2g.

4. The method for preparing the nano-aerogel / ceramized silicone rubber composite material according to claim 1, characterized in that, In S3 The mass ratio of DOPO, pentaerythritol, vinyltrimethoxysilane, mercaptoacetic acid, azobisisobutyronitrile, and trimethyl borate is 5:2:3:0.5:0.05:

1.

5. The method for preparing the nano-aerogel / ceramized silicone rubber composite material according to claim 1, characterized in that, In S4, The phenyl content of the phenyl silicone rubber is >10%.

6. The method for preparing the nano-aerogel / ceramized silicone rubber composite material according to claim 1, characterized in that, In S4, The mass ratio of the phenyl silicone rubber, methyl phenyl silicone resin, modified aerogel, Al-doped ceramic precursor, phosphosilicate polymer and dicumyl peroxide is 100:20:15:12:8:1.

5.

7. The method for preparing the nano-aerogel / ceramized silicone rubber composite material according to claim 1, characterized in that, In S4, The vulcanization conditions were 150°C, 15 MPa, and 25 min.

8. The method for preparing the nano-aerogel / ceramized silicone rubber composite material according to claim 1, characterized in that, In S4, The ceramization conditions are 300℃ for 10 min, with a heating rate of 5℃ / min.

9. The nano-aerogel / ceramized silicone rubber composite material obtained by the preparation method according to any one of claims 1-8.

10. A fire-resistant cable, comprising a conductor, an insulation layer, and a sheath material for covering the insulation layer, characterized in that: The sheath material is obtained by melt extrusion of the nano-aerogel / ceramized silicone rubber composite material as described in claim 9.

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