High-temperature-resistant silicone rubber cable material and preparation method thereof

Abstract

The invention provides a preparation method of a high-temperature-resistant silicone rubber cable material, which comprises the following steps: respectively immersing a fluorinated porous boron-nitrogen wafer and indium-titanium alloy particles into a surface modification solution in an inert atmosphere, stirring for 30 minutes, and drying to obtain a modified fluorinated porous boron-nitrogen wafer and modified indium-titanium alloy particles, the surface modification solution comprises a fluorinated intermediate, a silane reagent and a low-molecular interfacial agent; heating a poly-silicone matrix to a molten state, firstly adding the modified fluorinated porous boron-nitrogen crystal for mixing, then adding the modified indium-titanium alloy particles for mixing, and controlling the mixing temperature to be 80-100 DEG C and the mixing time to be 10-15 minutes to obtain a silicone rubber composite material; wrapping the outer surface of a cable core with the silica gel composite material, heating to 150-160 DEG C, keeping for 20-30 minutes, heating to 220-230 DEG C, and keeping for 2-4 hours, so as to obtain the high-temperature-resistant silicone rubber cable material. Therefore, the high-temperature resistance, insulativity and mechanical strength of the high-temperature-resistant silicone rubber cable material are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of cable materials, and particularly relates to a high-temperature resistant silicone rubber cable material and a preparation method thereof. Background Art

[0002] The composition of traditional cable materials includes a conductor core, an insulating layer, a sheath layer, etc. Among them, the insulating layer and the sheath layer are mainly made of polyvinyl chloride, rubber, polyethylene, etc., providing electrical insulation to prevent short circuits between conductors or between conductors and the external environment, and also being able to resist chemical environments such as moisture and oil stains to a certain extent.

[0003] However, in some scenarios, such as high-temperature workshops, steel mills, geothermal wells, aerospace, rail transit or engine compartments, the temperature can reach 200 - 300 °C, or even higher. Common thermoplastic materials such as polyvinyl chloride and polyethylene have poor heat resistance and will become soft or partially molten at around 120 - 180 °C, greatly weakening the mechanical strength and insulation performance. Although rubber can slightly increase the melting point and heat resistance, it is still difficult to be used for a long time above 200 °C. At high temperatures, the molecular chains are prone to thermal cracking and oxidation, making the material brittle and hard, losing its insulating properties and shortening the cable life. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-temperature resistant silicone rubber cable material and a preparation method thereof, aiming to solve the problem that the poor high-temperature resistance of the cable material leads to the decline of the insulation and mechanical strength of the cable material.

[0005] To solve the above technical problem, the present invention is implemented as follows. A preparation method of a high-temperature resistant silicone rubber cable material is proposed, and the steps include: S1. Respectively immerse fluorinated porous boron nitride wafers and indium-titanium alloy particles in a surface modification solution in an inert atmosphere, stir for 30 min, and obtain modified fluorinated porous boron nitride wafers and modified indium-titanium alloy particles after drying. Among them, the surface modification solution includes a fluorinated intermediate, a silane reagent, and a low-molecular surfactant; S2. Heat the polysiloxane matrix to a molten state, first add the modified fluorinated porous boron nitride wafers for mixing, and then add the modified indium-titanium alloy particles for mixing. The mixing temperature is controlled at 80 - 100 °C, and the mixing time is 10 - 15 min to obtain a silicone rubber composite; S3. Wrap the silicone composite around the outer surface of the cable core, heat it to 150 - 160 °C and keep it for 20 - 30 min, and then raise the temperature to 220 - 230 °C and keep it for 2 - 4 h to obtain a high-temperature resistant silicone rubber cable material.

[0006] In some embodiments of the present invention, in step S1, the fluorinated intermediate includes at least one of 2,2,3,3-tetrafluoro-1,4-butanediol, 3,3,4,4,5,5-hexafluoro-1,6-hexanediol, and 3,3,3-trifluoropropanol; the silane reagent includes at least one of 3-chloropropyltriethoxysilane, triethoxychlorosilane, and tris(methoxy)silane; the low-molecular surfactant includes at least one of sodium dodecyl sulfate, cetyltrimethylammonium bromide, and sorbitan monooleate.

[0007] In some embodiments of the present invention, step S1 includes: S1.1. Place the boron nitride powder in absolute ethanol or isopropanol for ultrasonic dispersion with a power of 200 - 400 W and a dispersion duration of 10 - 20 min, and then heat it to 100 - 120 °C for vacuum drying for 2 h; S1.2. Pass a dilute oxygen stream and heat it to 350 - 400 °C, keep it warm for 1 - 2 h, cool it and place it in a mixed acid solution for soaking for 30 min. After filtration, washing, and drying, obtain pretreated boron nitride; S1.3. Place the pretreated boron nitride in a plasma etching system, adjust the ambient pressure to 8 - 10 Pa, pass a fluorine-containing gas with a gas flow rate of 10 - 50 sccm, set the radio frequency power of the plasma etching system to 100 - 300 W, carry out the etching reaction for 10 - 30 min, heat it to 100 - 150 °C for drying, and obtain a fluorinated porous boron nitride wafer; S1.4. Add the fluorinated porous boron nitride wafer to the surface modification solution and stir it at a stirring speed of 100 - 150 rpm for 30 min to obtain a modified fluorinated porous boron nitride wafer, where the mass ratio of the fluorinated porous boron nitride wafer to the surface modification solution is 1:(5 - 10); S1.5. Add indium-titanium alloy particles to the surface modification solution and stir it at a stirring speed of 80 - 120 rpm, heat it to 40 °C, and stir for 30 min to obtain modified indium-titanium alloy particles, where the mass ratio of the indium-titanium alloy particles to the surface modification solution is 1:(3 - 8); S1.6. Heat the modified fluorinated porous boron nitride wafer and the modified indium-titanium alloy particles to 70 - 90 °C respectively, dry for 1 - 2 h, and then heat to 120 - 150 °C and keep it warm for 30 min.

[0008] In some embodiments of the present invention, in step S1.2, the dilute oxygen stream includes oxygen and nitrogen, and the volume ratio of oxygen to nitrogen is 1:(9 - 10), and the mixed acid solution includes sulfuric acid and hydrofluoric acid; In step S1.3, the fluorine-containing gas includes at least one of carbon tetrafluoride, trifluoromethane, and sulfur hexafluoride.

[0009] In some embodiments of the present invention, step S2 includes: S2.1. Heat the silicone matrix to 80 - 100°C, stir at a stirring speed of 50 - 80 rpm, add a dispersion aid, an antioxidant, and an anti-sticking agent, and stir until the viscosity of the silicone matrix reaches a preset viscosity to obtain a molten silicone matrix; S2.2. Add the modified fluorinated porous boron nitride wafer into the molten silicone matrix, increase the rotation speed to 100 - 150 rpm, and maintain at 80 - 100°C for 3 - 5 min; S2.3. Then add the modified indium-titanium alloy particles, reduce the rotation speed to 80 - 100 rpm, continue to stir for 5 - 10 min, and keep the temperature at 80 - 100°C to obtain a silica gel composite.

[0010] In some embodiments of the present invention, in step S2.1, the silicone matrix includes at least one of polydimethylsiloxane, polymethylphenylsiloxane, and multi-component copolymeric polysiloxane. The multi-component copolymeric polysiloxane includes at least two of silicon hydride groups, vinyl groups, and benzene ring groups. The dispersion aid includes at least one of polyether molecular dispersants, polyester polymer dispersants, and silicone-modified dispersants. The antioxidant includes at least one of hindered phenol antioxidants, hindered amine antioxidants, phosphite antioxidants, and phosphate antioxidants. The anti-sticking agent includes at least one of stearic acid, zinc stearate, erucamide, polydimethylsiloxane oil, silicone release agent, polyethylene wax, microcrystalline wax, and montan wax.

[0011] In some embodiments of the present invention, step S3 includes: S3.1. Put the silica gel composite into an extruder and coat it on the outer surface of the cable core; S3.2. Heat to 150 - 160°C and maintain for 20 - 30 min, apply a hot pressing pressure of 5 - 15 MPa; S3.3. After hot pressing, slowly heat to 220 - 230°C, maintain for 2 - 4 h, and slowly cool to room temperature at a rate of 1 - 2°C / min to obtain a high-temperature resistant silicone rubber cable material.

[0012] The present invention provides a high-temperature resistant silicone rubber cable material, which is made by the preparation method of a high-temperature resistant silicone rubber cable material as described above. The high-temperature resistant silicone rubber cable material includes fluorinated porous boron nitride wafers, indium-titanium alloy particles, and a silicone matrix; wherein, The fluorinated porous boron nitride wafers are used to improve the heat resistance of the high-temperature resistant silicone rubber cable material, enhance the insulation performance of the high-temperature resistant silicone rubber cable material, and improve its chemical inertness at high temperatures; The indium-titanium alloy particles are used to form a framework to improve the tensile strength and heat resistance of the high-temperature resistant silicone rubber cable material; The polysiloxane matrix serves as an elastic component to provide the processability and insulation of the high-temperature resistant silicone rubber cable material Compared with the prior art, a high-temperature resistant silicone rubber cable material and a preparation method thereof in the present invention have the beneficial effects that: Boron nitride originally has excellent thermal stability and can maintain the structural integrity in a high-temperature environment. The fluorination treatment reduces the polarization degree on the surface of the boron nitride sheet layer, while ensuring that its framework is not damaged, maintaining good dielectric and chemical inertness at high temperatures. The porous structure enables boron nitride to form a more uniformly dispersed reinforcing framework in the matrix, which can share the thermal stress and conduct the local heat generated in a high-temperature environment. Titanium forms a stable oxide film at high temperatures. The indium-titanium alloy particles have good overall high-temperature strength and are not easily oxidized or fail in an environment above 200 - 300 °C. The indium-titanium alloy particles can also maintain good mechanical support at high temperatures and are not easily detached or generate microcracks when heated or thermally shocked, ensuring the overall strength of the cable sheath layer. The polysiloxane matrix has a higher thermal decomposition temperature than general organic polymers. Through a segmented thermal curing process, the silicone rubber is further crosslinked to form a dense three-dimensional network, which can effectively improve the structural stability and antioxidant ability at high temperatures. First, medium-temperature pre-curing eliminates internal bubbles and pre-establishes a crosslinked framework; then high-temperature strengthening deepens the crosslinking degree, and finally a higher crosslinking degree and heat resistance stability are obtained. This process enables the filler and the matrix to still be firmly bonded at high temperatures and are not easily delaminated or cracked due to internal stress or thermal expansion and contraction. The overall material can maintain its functionality in an extreme temperature environment.

[0013] Introducing fluorine groups on the surface of boron nitride can reduce its surface energy and form strong BN−Si bonding during subsequent reactions with silane reagents. The pores and defect sites provide more bonding points for the subsequent infiltration and embedding of silane or organosilicon matrices, enhancing mechanical interlocking. The surface of the indium-titanium alloy particles is also treated with coupling agents such as fluorosilane, which can generate bridging bonds at the metal oxide layer or trace hydroxyl groups. Due to the presence of the fluoroalkyl segment and the silane coupling layer, the indium-titanium alloy particles remain stable at high temperatures and have better dispersibility and adhesion. The polysiloxane matrix not only provides a relatively high thermal decomposition temperature but also can complete chemical bonding or close physical embedding with the surface of the aforementioned modified fillers during the high-temperature curing stage. With the assistance of the surface modification solution, the fluorinated porous boron nitride wafers and the indium-titanium alloy particles respectively form strong interfacial coupling layers, which have stable chemical / physical bonding with the polysiloxane matrix during subsequent mixing and curing processes, thereby realizing the effective combination of the three, and further improving the high-temperature resistance, insulation, and mechanical strength of the high-temperature resistant silicone rubber cable material. Description of the Drawings

[0014] Figure 1It is a schematic flow chart of a preparation method of a high-temperature resistant silicone rubber cable material in an embodiment of the present invention. Detailed implementation manners

[0015] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] Please refer to Figure 1 , the present invention provides a preparation method of a high-temperature resistant silicone rubber cable material, and the steps include: S1. Respectively immerse fluorinated porous boron nitride wafers and indium-titanium alloy particles in a surface modification solution in an inert atmosphere, stir for 30 min, and obtain modified fluorinated porous boron nitride wafers and modified indium-titanium alloy particles after drying, wherein the surface modification solution includes a fluorinated intermediate, a silane reagent, and a low-molecular surfactant.

[0017] In step S1, the fluorinated intermediate includes at least one of 2,2,3,3-tetrafluoro-1,4-butanediol, 3,3,4,4,5,5-hexafluoro-1,6-hexanediol, and 3,3,3-trifluoropropanol; the silane reagent includes at least one of 3-chloropropyltriethoxysilane, triethoxysilane chloride, and tris(methoxy)silane; the low-molecular surfactant includes at least one of sodium dodecyl sulfate, cetyltrimethylammonium bromide, and sorbitan monooleate.

[0018] Step S1 includes: S1.1. Place boron nitride powder in absolute ethanol or isopropanol for ultrasonic dispersion, with a power of 200-400 W and a dispersion time of 10-20 min, and then heat up to 100-120 °C for vacuum drying for 2 h.

[0019] Ultrasonic dispersion can break up the aggregates formed by boron nitride powder during storage or transportation, reducing large particle agglomerates; after ultrasonic treatment in an organic solvent, heating and vacuum drying can remove residual moisture, organic impurities, etc. on the powder surface, creating a cleaner surface environment for subsequent oxidation / etching / fluorination reactions; after obtaining the pre-dispersed boron nitride powder, it can undergo porousization and fluorination reactions more uniformly in subsequent steps. The cavitation effect generated by high-frequency ultrasound helps to disperse and break up the aggregates of boron nitride powder. Absolute ethanol or isopropanol can dissolve or carry away trace organic impurities, reduce the surface tension, making it easier for boron nitride powder to disperse. Vacuum drying at 100-120 °C can effectively remove the solvent and moisture, resulting in a more stable and consistent powder state for subsequent processing.

[0020] S1.2. Heat it up to 350 - 400 °C by introducing a dilute oxygen stream, keep it warm for 1 - 2 h, cool it, place it in a mixed acid solution, soak for 30 min, filter, wash, and dry to obtain pretreated boron nitride. The dilute oxygen stream includes oxygen and nitrogen, and the volume ratio of oxygen to nitrogen is 1:(9 - 10). The mixed acid solution includes sulfuric acid and hydrofluoric acid.

[0021] Introduce a dilute oxygen stream at 350 - 400 °C to cause a small amount of oxidation or defects on the surface or between layers of boron nitride, providing an entry point for subsequent porous formation or etching. Soak it in the mixed acid to remove part of the oxide layer and impurities, and at the same time generate micropores or defect structures between the boron nitride layers or at the grain boundaries. The oxidation and acid etching processes can expose more hydroxyl groups or defect sites on the surface of boron nitride, laying a foundation for subsequent fluorinated plasma etching. At a dilute oxygen stream and medium temperature, boron nitride is locally oxidized to form boron - oxygen bonds, nitrogen - oxygen bonds, etc., generating soluble oxides. The mixed acid can etch the oxide layer or microcrack sites, further increasing the specific surface area and porosity. Through the dual means of oxidation and etching, surface defects and microporous structures are introduced, facilitating the entry of subsequent fluorine atoms or silane coupling agents.

[0022] S1.3. Place the pretreated boron nitride in a plasma etching system, adjust the ambient pressure to 8 - 10 Pa, introduce a fluorine - containing gas with a flow rate of 10 - 50 sccm, set the radio - frequency power of the plasma etching system to 100 - 300 W, carry out the etching reaction for 10 - 30 min, heat up to 100 - 150 °C and dry to obtain fluorinated porous boron nitride wafers. The fluorine - containing gas includes at least one of carbon tetrafluoride, trifluoromethane, and sulfur hexafluoride.

[0023] Under the action of plasma, the vulnerable parts on the surface of boron nitride are further etched to form a porous structure, and at the same time, fluorine atoms are introduced on the surface or between layers. Fluorine elements can reduce the polarization degree of the material, making the subsequent composite materials have smaller dielectric losses at high frequencies. The boron nitride matrix itself has high - temperature tolerance, and moderate etching and fluorination will not seriously damage its crystal skeleton, still retaining excellent heat - resistant characteristics. Driven by the radio - frequency power, charged particles bombard the surface of boron nitride, etching the defect sites or the positions with weak inter - layer bonding to form holes; after the fluorine - containing gas dissociates, it combines with the active sites on the surface of boron nitride to form B−F, N−F, etc. bonds; finally, gently dry at 100 - 150 °C to remove adsorbed gases and residual products, obtaining stable fluorinated porous boron nitride wafers.

[0024] S1.4. Add the fluorinated porous boron nitride wafers to the surface - modifying solution and stir at a stirring speed of 100 - 150 rpm for 30 min to obtain modified fluorinated porous boron nitride wafers, where the mass ratio of the fluorinated porous boron nitride wafers to the surface - modifying solution is 1:(5 - 10).

[0025] The surface modification solution contains a fluorinated intermediate, a silane reagent, and a low-molecular surfactant, which can form a silane layer or a fluoroalkyl segment on the surface of the fluorinated porous boron nitride wafer, enhancing the affinity for the silicone rubber matrix. The low-molecular surfactant and the silane coupling agent act synergistically to reduce the secondary agglomeration of the fluorinated porous boron nitride wafers, maintain a good dispersion of the lamellae or particles, endow the fluorinated porous boron nitride wafers with better chemical compatibility, facilitate stable and uniform dispersion in the silicone rubber, and play the functions of heat conduction, low dielectric constant, and heat resistance. The silane reagent (such as 3-chloropropyltriethoxysilane, triethoxychlorosilane, etc.) can hydrolyze and condense on the surface of the fluorinated porous boron nitride wafer to form interfacial bonds such as Si−O−BN; the fluorinated intermediate introduces hydrophobic and low-dielectric properties to it. During the stirring process, the dispersant / surfactant is adsorbed on the surface of the lamellae to construct a stable dispersion system. After modification, the surface energy of the fluorinated porous boron nitride wafer decreases, the electrostatic or intermolecular attraction weakens, and it is more likely to maintain dispersion during the subsequent mixing of the silicone rubber matrix.

[0026] S1.5. Add indium-titanium alloy particles to the surface modification solution and stir at a stirring speed of 80 - 120 rpm, heat up to 40 °C, and stir for 30 min to obtain modified indium-titanium alloy particles, where the mass ratio of indium-titanium alloy particles to the surface modification solution is 1:(3 - 8).

[0027] Similar to the previous step, the silane reagent reacts with the oxide layer or metal hydroxyl groups present on the surface of the indium-titanium alloy to form a strong chemical bonding layer. By controlling the stirring speed and temperature, while ensuring the dispersion effect, the morphology of the metal particles / fibers is avoided from being damaged. After the surface is coated with fluorosilane, it can prevent the particles from being oxidized and corroded at high temperatures or during subsequent curing, and enhance the synergistic strengthening performance with the matrix. There is often a layer of metal oxide or passivation film on the surface of indium-titanium alloy particles. Through silane coupling, a bridge bond formed between metal−oxygen−silicon can be formed. The fluorine-based segment reduces the surface energy of the particles, improves the dispersibility and anti-oxidation ability in the silicone rubber matrix. Heating to 40 °C can accelerate the solvent evaporation and chemical bonding process, but the temperature should not be too high to avoid triggering local side reactions or damaging the alloy microstructure.

[0028] Indium-titanium alloy particles are used as the metal reinforcing component in the composite material because after indium (In) and titanium (Ti) form an alloy, they have high strength and high temperature resistance, and can maintain stable mechanical properties in an environment of 200 - 300 °C and above. When added to the silicone rubber matrix as particles or microfibers, it can significantly improve the tensile strength, tear strength, and creep resistance of the material, preventing the cable sheath or insulation layer from deforming due to plastic flow at high temperatures. Both indium and titanium have relatively excellent antioxidant properties. Titanium can form a dense oxide film at high temperatures, and indium alloys can also maintain good antioxidant properties within a certain temperature range. Compared with common iron-nickel-based metals, indium-titanium alloys are more resistant to oxidation and corrosion in the cable usage environment, ensuring the long life and stability of the material. After surface modification, the interface between indium-titanium alloy particles and the silicone rubber matrix is more firmly bonded. During high-temperature cross-linking or two-stage curing, it is not easy to fail or fall off, giving full play to the metal reinforcement effect. In the overall composite formula, fluorinated porous boron nitride wafers mainly bring low dielectric and high thermal conductivity characteristics, while indium-titanium alloy particles play the role of high-temperature mechanical strengthening. The two complement each other, providing multi-dimensional performance improvement for cable materials.

[0029] S1.6. Respectively heat the modified fluorinated porous boron nitride wafers and modified indium-titanium alloy particles to 70 - 90 °C, dry for 1 - 2 h, then heat to 120 - 150 °C, and keep warm for 30 min.

[0030] Drying in the first stage (70 - 90 °C) can remove residual solvents, and keeping warm in the second stage (120 - 150 °C) enables further condensation or cross-linking of the silane coupling agent, forming a stable modified layer on the surface of the particles / lamellae. After this heat treatment, the chemical bonding between the modified layer and the substrate surface is more firm, not easily decomposed or fallen off at high temperatures. The low-molecular surfactant and the silane part basically complete the reaction, reducing organic volatiles or side reactions during mixing, and ensuring excellent interfacial characteristics in the high-temperature silicone rubber matrix.

[0031] First, remove solvents at low temperature, and then strengthen silane condensation at medium temperature. This temperature control method can effectively avoid the decomposition or local sintering of the interface agent caused by high temperature at one time. At 120 - 150 °C, the alkoxy groups on the silane molecules or react more deeply with the surface hydroxyl groups to form a dense heat-resistant surface layer. By curing the modified layer at high temperature, the tendency of moisture absorption or agglomeration during storage and transportation can be reduced.

[0032] S2. Heat the polysiloxane matrix to the molten state, first add the modified fluorinated porous boron nitride wafers for mixing, and then add the modified indium-titanium alloy particles for mixing. The mixing temperature is controlled at 80 - 100 °C, and the mixing time is 10 - 15 min to obtain a silicone rubber composite.

[0033] Step S2 includes: S2.1. Heat the silicone matrix to 80 - 100°C, stir at a speed of 50 - 80 rpm, add a dispersion aid, an antioxidant, and an anti-sticking agent, and stir until the viscosity of the silicone matrix reaches a preset viscosity to obtain a molten silicone matrix; the silicone matrix includes at least one of polydimethylsiloxane, polymethylphenylsiloxane, and multi-component copolymeric polysiloxane. The multi-component copolymeric polysiloxane includes at least two of silane hydrogen groups, vinyl groups, and benzene ring groups. The dispersion aid includes at least one of polyether molecular dispersants, polyester polymer dispersants, and silicone-modified dispersants. The antioxidant includes at least one of hindered phenol antioxidants, hindered amine antioxidants, phosphite antioxidants, and phosphate antioxidants. The anti-sticking agent includes at least one of stearic acid, zinc stearate, erucamide, polydimethylsiloxane oil, silicone release agent, polyethylene wax, microcrystalline wax, and montan wax.

[0034] In the temperature range of 80 - 100°C, the silicone matrix changes from a highly viscoelastic state to a flowable molten state, which is conducive to the uniform dispersion of subsequent fillers. The dispersion aid, antioxidant, anti-sticking agent, etc. are added at this time, so that they can be fully dissolved, wetted or dispersed when the matrix viscosity is still relatively low, improving the overall process stability. The dispersion aid can reduce the polymer viscosity at the molecular level and enhance the wettability of the filler surface, making it easier for the modified fluorinated porous boron nitride crystals and indium-titanium alloy particles to be uniformly dispersed subsequently. The antioxidant can inhibit the oxidative degradation of the silicone matrix and additives during high-temperature or long-term processing, maintaining the material properties. The anti-sticking agent can reduce the adhesion of the molten polymer to the equipment wall and the screw, facilitating continuous mixing and subsequent molding. By controlling the stirring speed (50 - 80 rpm) and the dosage of the dispersion aid, the flow viscosity of the matrix can be precisely adjusted to an appropriate range, creating an appropriate shear environment for the next-step filler dispersion, ensuring effective dispersion while preventing excessive shear.

[0035] In the range of 80 - 100°C, the molecular chain segments obtain sufficient freedom of movement without undergoing high-temperature degradation. The polar / non-polar segments of the dispersion aid can interact with both the matrix and the filler, thereby reducing the surface tension and enhancing the wetting at the microscopic level. The combined action of a slight temperature increase and appropriate shear makes the distribution of silicone chain segments more uniform. The viscosity can be judged by real-time torque or fluidity testing, and when it reaches the preset value, stop or proceed to the next step. In one embodiment, the preset viscosity can be 2000 - 20000 cP.

[0036] In some embodiments, the silicone matrix is further modified, and the modification method is as follows: Hydrosilylation reaction: An addition reaction is carried out between a polysiloxane containing a silicon - hydrogen group and a functional organic compound containing an unsaturated bond (such as C = C or C≡C) in the presence of a platinum catalyst. For example, a polysiloxane matrix containing a silicon - hydrogen group is reacted with a monomer with an arylethynyl group (C≡C–Ar) under platinum - catalyzed conditions to form a Si–C bond, firmly grafting the arylethynyl group onto the silicone backbone.

[0037] Copolymerization reaction: Introducing functional monomers during the polymerization process is also a method to directly embed various functional groups into the polysiloxane backbone. For example, a silane monomer with an arylethynyl function can be copolymerized with other silane monomers (such as dimethylsilane monomers). Through the Grignard reaction or other silicon chemical reactions, a polysiloxane matrix with randomly or sequentially distributed functional side groups can be obtained. The Grignard reaction generates an alkylmagnesium halide, i.e., a Grignard reagent, by reacting a halide with metallic magnesium in anhydrous diethyl ether or tetrahydrofuran. As a nucleophile, the Grignard reagent can undergo an addition reaction with carbonyl compounds such as aldehydes, ketones, and carboxylic acids to form new carbon - carbon bonds. One is a dimethylsilane monomer, and the other is a silane monomer with an arylethynyl function. Through appropriate cross - linkers and catalysts, a copolymerization reaction is carried out under dry conditions to obtain a polysiloxane matrix that is both flexible and has an arylethynyl function.

[0038] By adopting various modification methods such as hydrosilylation, copolymerization, and the Grignard reaction, arylethynyl or other unsaturated functional groups are introduced into the polysiloxane matrix. This multi - path modification method enables the polysiloxane matrix to not only have excellent flexibility and insulation properties but also form a network structure with a high degree of cross - linking and stronger heat resistance during high - temperature curing.

[0039] S2.2: Add the modified fluorinated porous boron nitride wafers to the molten polysiloxane matrix, increase the rotation speed to 100 - 150 rpm, and maintain it at 80 - 100 °C for 3 - 5 min.

[0040] First, increasing the stirring speed to 100 - 150 rpm is beneficial to fully disperse and mix the modified fluorinated porous boron nitride wafers into the matrix. The short - time high - shear of 3 - 5 minutes can quickly overcome the aggregation force between the filler particles and reduce secondary agglomeration. The surface of the modified fluorinated porous boron nitride wafers already has a fluorination modification and a silane coupling layer (as described in step S1). At this time, it is compatible or bonded with the dispersing aids / silicon groups in the polysiloxane matrix, and can microscopically construct a stable filler - matrix interface, improving the dielectric stability, insulation property, and heat dissipation performance of the subsequent materials in a high - temperature environment.

[0041] In the range of 80 - 100 °C, most silicone rubber matrices have not yet entered the high-temperature rapid curing stage, allowing sufficient time for the dispersion of modified fluorinated porous boron nitride wafer layers, avoiding premature vulcanization of local rubber compounds and affecting subsequent processing. The modified fluorinated porous boron nitride wafers originally have a low surface energy (due to fluorination treatment) and are more likely to depolymerize into wafer layers under high shear in the matrix, forming wafer layer skeletons or heat conduction channels. The silyl groups carried on the surface of the modified fluorinated porous boron nitride wafers can form Si−O−Si or other weak chemical / physical bonds with the matrix, improving the filler-matrix adhesion. The modified fluorinated porous boron nitride wafers themselves have high thermal conductivity and high temperature resistance. If the dispersion process can be uniform at this time, a heat conduction network can be established in the final material and the overall dielectric constant can be reduced.

[0042] S2.3. Then add modified indium-titanium alloy particles, reduce the rotation speed to 80 - 100 rpm, continue stirring for 5 - 10 min, and maintain the temperature at 80 - 100 °C to obtain a silicone composite. Continuously detect the viscosity of the system. If the viscosity exceeds the preset viscosity, the temperature can be moderately increased to 100 - 110 °C, but avoid exceeding 120 °C to prevent premature cross-linking of the silicone components.

[0043] Reducing the rotation speed from 100 - 150 rpm to 80 - 100 rpm can provide sufficient dispersing force without significantly damaging the morphology of metal microfibers or particles, protecting their reinforcing skeleton function. The medium shear time of 5 - 10 minutes can further evenly distribute the indium-titanium particles in the matrix-modified fluorinated porous boron nitride wafer mixture system. The modified indium-titanium alloy particles and the already well-dispersed modified fluorinated porous boron nitride wafers synergistically provide mechanical reinforcement for the matrix, enhancing the tensile, tear, creep resistance, and high-temperature oxidation resistance; By adding the modified fluorinated porous boron nitride wafers first and then the modified indium-titanium alloy particles, adverse factors such as mutual interference and agglomeration between the fillers are reduced, enabling the modified fluorinated porous boron nitride wafers and the modified indium-titanium alloy particles to each perform their functions and embed into the silicone matrix.

[0044] The surface of the indium-titanium alloy has been modified by fluorosilane and will basically not decompose or be severely oxidized at this temperature; finally, a silicone composite with moderate fluidity and high dispersion is obtained, providing good operability for subsequent molding, extrusion, or secondary curing processes.

[0045] First, high-shear disperse and modify the fluorinated porous boron nitride wafers, and then medium-shear disperse and modify the indium-titanium alloy particles to avoid agglomeration caused by the simultaneous entry of multiple fillers at once and prevent the modified indium-titanium alloy particles from being broken or agglomerated under excessive shear. The modified fluorinated porous boron nitride wafers mainly bring low dielectric and high thermal conductivity characteristics, while the modified indium-titanium alloy particles improve the tensile strength, creep resistance, and heat resistance and oxidation resistance. Both form good interfacial bonding with the matrix, reducing cohesive defects. Continuously maintaining the temperature at 80 - 100 °C is beneficial for the additives to maintain their activity and prevent the matrix from curing prematurely, achieving good dispersion uniformity.

[0046] S3. Wrap the silica gel composite around the outer surface of the cable core, heat it to 150 - 160 °C and hold for 20 - 30 min, then raise the temperature to 220 - 230 °C and hold for 2 - 4 h to obtain the high-temperature resistant silicone rubber cable material.

[0047] Step S3 includes: S3.1. Put the silica gel composite into an extruder and coat it on the outer surface of the cable core.

[0048] Using an extruder to extrude the pre-mixed silica gel composite and continuously coat it on the outer surface of the cable core can ensure the thickness and uniformity of the sheath layer, and it is not easy to have areas with material shortage or excessive thickness. In the previous step (S2), the silica gel composite has not undergone large-scale cross-linking and is in a plastic state, which is convenient for extrusion molding. After extrusion, the sheath closely adheres to the contour of the cable core, seamlessly fits, and lays the foundation for subsequent hot pressing and curing. Immediately coating the cable core can prevent it from being damaged by the outside world during subsequent processing or in a high-temperature environment, and at the same time, it can also more directly cooperate with the curing step to make the sheath and the core wire form a firm shape synchronously. Conducted at normal temperature or medium temperature, the silica gel composite maintains appropriate fluidity due to the action of dispersion additives, anti-sticking agents, etc., and forms a uniform outer layer during extrusion; this step can be connected to the subsequent hot pressing equipment, and the material enters the hot pressing / curing area in a plastic state, reducing the energy consumption and internal stress caused by cooling and reheating.

[0049] S3.2. Raise the temperature to 150 - 160 °C and hold for 20 - 30 min, and apply a hot pressing pressure of 5 - 15 MPa.

[0050] Maintain at a temperature of 150 - 160°C for 20 - 30 minutes, and partial cross-linking begins to occur inside the silicone rubber. The sheath gradually transforms from a plastic state to a cured state with a certain elasticity. This stage can initially shape the sheath and make it fit the surface contour of the cable core, preventing collapse or deformation. Applying a hot press of 5 - 15 MPa can tightly compact the sheath material, expel residual air bubbles and microvoids, reduce internal defects in the finished product, improve the mechanical properties and insulation properties of the material, and is also beneficial for the dimensional stability of the sheath at high temperatures later. During primary curing, hot pressing in a relatively mild temperature range helps to relieve the shear stress and microstructural defects inside the composite material, laying a good foundation for reducing cracking or deformation during subsequent secondary curing at a higher temperature (220 - 230°C).

[0051] Better densification is achieved through external pressure. Especially in the composite system of indium-titanium alloy particles and modified fluorinated porous boron nitride wafers, it can make the filler distribution uniform and bond firmly with the matrix. At this temperature and for a certain period of time, any residual small molecules or gases can be gradually released and discharged through the surface or interface of the sheath.

[0052] S3.3. After hot pressing, slowly raise the temperature to 220 - 230°C, maintain for 2 - 4 h, and then slowly cool down to room temperature at a rate of 1 - 2°C / min to obtain a high-temperature resistant silicone rubber cable material.

[0053] Further raise the temperature to 220 - 230°C and maintain for 2 - 4 hours to allow the functional groups that have not fully reacted inside to continue cross-linking, improving the mechanical stability and thermal aging life of the material in a high-temperature environment. This high-temperature range can completely complete the cross-linking or aryl chemical bond reaction, enabling the silicone rubber to have a higher glass transition temperature or a higher upper limit of use temperature. Slow cooling at a rate of 1 - 2°C / min can avoid excessive thermal stress caused by too large a temperature difference between the inside and outside of the sheath, prevent microcracks or bubbles. Through slow cooling after long-term high-temperature heat preservation, the internal stress of the material can be fully relaxed, and a more complete and low internal stress insulating sheath can be obtained. After being treated at this high-temperature stage, the cable material can withstand a short-term temperature impact of 250 - 300°C or even higher and maintain good insulation, dielectric, and mechanical properties.

[0054] After mild primary curing and then high-temperature long-term heat preservation, ensure that the polysiloxane matrix network forms a more compact three-dimensional structure, and the interfacial bonding between the filler and the matrix is also stronger. In this temperature range, if a small amount of oxygen enters, the antioxidant plays a protective role in the material, maintaining the polysiloxane backbone and metal particles from being over-oxidized. Slow cooling can cause the molecular chain segments and filler framework to gradually contract with the decrease in temperature and release stress, minimizing the risk of deformation or cracking of the product to the greatest extent.

[0055] The elastic modulus of the high-temperature resistant silicone rubber cable material obtained by final curing (Pa or MPa) is controlled by the parameters of various components, and the control equation is: Among them, is the overall enhancement scale factor (Pa or MPa). The value of k needs to be determined by fitting through multiple repeated experiments and can be between 100 MPa and 1000 MPa. The specific value reflects the overall strengthening ability of the composite system. is used to convert the non-linear contributions of the functional monomer and the filler into actual modulus values. Multiple repeated experiments are to set different parameters of fluorinated porous boron nitride wafers, indium-titanium alloy particles, and silicone matrix, with other environmental conditions being the same. After conducting the experiments, the obtained data is processed by fitting to estimate k, which is an empirical parameter summarized by the experimental operator. is the molar fraction of the functional monomer (dimensionless), representing the molar fraction of functional groups on the silicone matrix, such as the molar fractions of silicon hydride groups, vinyl groups, and benzene ring groups relative to the silicone matrix. is 0.05 - 0.3. is a sensitive parameter (dimensionless) reflecting the cross-linking effect caused by the functional monomer. is between 1 and 10. The larger the value, the more saturated the cross-linking reaction tends to be at a lower p value. and are the volume fractions (dimensionless) of the modified fluorinated porous boron nitride wafers and the modified indium-titanium alloy particles. is a parameter (dimensionless) for the enhancement effect of the modified fluorinated porous boron nitride wafers. is a parameter (dimensionless) for the enhancement effect of the modified indium-titanium alloy particles. is the basic enhancement constant, which can be between 0.5 and 2.0. Prepare several groups of specimens with different volume fractions and different enhancement particle sizes, and obtain the strength (or other mechanical indexes) of each group of specimens through systematic mechanical tests. Then use the established model to regress or fit these data to obtain a set of model parameters that can best represent the system, including . is the reference particle size. is 1 μm. and are the average particle sizes of the modified fluorinated porous boron nitride wafers and the modified indium-titanium alloy particles respectively. In one embodiment, is 100 nm - 1 μm, is 1 - 10 μm.

[0056] This coupled form of multiple particle volume fraction + characteristic size + enhancement coefficient can reflect the synergistic strengthening of different reinforcing phases in the composite material in a unified expression. This model can accurately reflect the mechanical behavior of the composite material and has guiding significance for predicting the elastic modulus of the finally obtained high-temperature resistant silicone rubber cable material based on the parameters of the actual filler and silicone matrix.

[0057] The present invention provides a high-temperature resistant silicone rubber cable material, which is made by a preparation method of a high-temperature resistant silicone rubber cable material. The high-temperature resistant silicone rubber cable material includes fluorinated porous boron nitride wafers, indium-titanium alloy particles, and a silicone matrix; wherein, The fluorinated porous boron nitride wafers are used to improve the heat resistance of the high-temperature resistant silicone rubber cable material, enhance the insulation performance of the high-temperature resistant silicone rubber cable material and its chemical inertness at high temperatures; The indium-titanium alloy particles are used to form a framework to improve the tensile strength and heat resistance of the high-temperature resistant silicone rubber cable material; The silicone matrix serves as an elastic component to provide the processability and insulation performance of the high-temperature resistant silicone rubber cable material.

[0058] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a high temperature resistant silicone rubber cable material, characterized in that the steps include: S1, immersing the fluorinated porous boron nitrogen wafer and the indium titanium alloy particles in a surface modification solution in an inert atmosphere, stirring for 30 minutes, and drying to obtain modified fluorinated porous boron nitrogen wafer and modified indium titanium alloy particles, wherein the surface modification solution comprises a fluorinated intermediate, a silane reagent and a low molecular surfactant; S2, heating the polysilicone matrix to a molten state, first adding the modified fluorinated porous boron nitrogen crystals for mixing, and then adding the modified indium titanium alloy particles for mixing, the mixing temperature is controlled at 80-100° C., the mixing time is 10-15 min, to obtain a silicone rubber composite; S3. Wrap the silica gel composite material on the outer surface of the cable core, heat it to 150-160°C and keep it for 20-30 minutes, then heat it to 220-230°C and keep it for 2-4 hours to obtain a high temperature resistant silicone rubber cable material.

2. The method for preparing a high temperature resistant silicone rubber cable material according to claim 1, characterized in that: In step S1, the fluorinated intermediate includes at least one of 2,2,3,3-tetrafluoro-1,4-butanediol, 3,3,4,4,5,5-hexafluoro-1,6-hexanediol, and 3,3,3-trifluoropropanol, the silane reagent includes at least one of 3-chloropropyltriethoxysilane, triethoxychlorosilane, and tri(methoxy)silane, and the low molecular surfactant includes at least one of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and sorbitan monooleate.

3. The method for preparing a high temperature resistant silicone rubber cable material according to claim 1 or 2, characterized in that: Step S1 includes: S1.

1. Place the boron nitride powder in anhydrous ethanol or isopropanol for ultrasonic dispersion at a power of 200-400W for 10-20min, then heat to 100-120℃ and vacuum dry for 2h; S1.2, introduce a dilute oxygen flow and heat to 350-400°C, keep warm for 1-2 hours, cool and place in a mixed acid solution, soak for 30 minutes, filter, wash and dry to obtain pretreated boron nitride; S1.3, placing the pretreated boron nitride in a plasma etching system, adjusting the ambient pressure to 8-10 Pa, introducing a fluorine-containing gas with a gas flow rate of 10-50 sccm, setting the radio frequency power of the plasma etching system to 100-300 W, etching for 10-30 min, heating to 100-150 ° C and drying to obtain a fluorinated porous boron nitride wafer; S1.4, adding the fluorinated porous boron nitrogen wafer into the surface modification solution and stirring at a stirring speed of 100-150 rpm for 30 min to obtain a modified fluorinated porous boron nitrogen wafer, wherein the mass ratio of the fluorinated porous boron nitrogen wafer to the surface modification solution is 1:(5-10); S1.5, adding indium titanium alloy particles to the surface modification solution and stirring at a stirring speed of 80-120 rpm, heating to 40°C, and stirring for 30 min to obtain modified indium titanium alloy particles, wherein the mass ratio of the indium titanium alloy particles to the surface modification solution is 1:(3-8); S1.

6. Raise the temperature of the modified fluorinated porous boron nitrogen wafer and the modified indium titanium alloy particles to 70-90°C, dry for 1-2 hours, and then raise the temperature to 120-150°C and keep warm for 30 minutes.

4. The method for preparing a high temperature resistant silicone rubber cable material according to claim 3, characterized in that: In step S1.2, the diluted oxygen gas flow includes oxygen and nitrogen, the volume ratio of oxygen to nitrogen is 1:(9-10), and the mixed acid solution includes sulfuric acid and hydrofluoric acid; In step S1.3, the fluorine-containing gas includes at least one of carbon tetrafluoride, trifluoromethane, and sulfur hexafluoride.

5. The method for preparing a high temperature resistant silicone rubber cable material according to claim 1, characterized in that: Step S2 includes: S2.1, heating the polysilicone matrix to 80-100°C, stirring at a stirring speed of 50-80 rpm, adding a dispersing aid, an antioxidant and an anti-sticking agent, and stirring until the viscosity of the polysilicone matrix reaches a preset viscosity, thereby obtaining a molten polysilicone matrix; S2.2, adding the modified fluorinated porous boron nitrogen wafer into the molten polysilicone matrix, increasing the rotation speed to 100-150 rpm, and maintaining at 80-100° C. for 3-5 min; S2.3, add the modified indium titanium alloy particles, reduce the rotation speed to 80-100 rpm, continue stirring for 5-10 minutes, maintain the temperature at 80-100° C., and obtain a silica gel composite.

6. The method for preparing a high temperature resistant silicone rubber cable material according to claim 5, characterized in that: In step S2.1, the polysilicone matrix includes at least one of polydimethylsiloxane, polymethylphenylsiloxane, and a multi-polymer polysiloxane, the multi-polymer polysiloxane includes at least two of a silicon hydrogen group, a vinyl group, and a benzene ring group, the dispersing aid includes at least one of a polyether type molecular dispersant, a polyester type polymer dispersant, and a silicone modified dispersant, the antioxidant includes at least one of a hindered phenol antioxidant, a hindered amine antioxidant, a phosphite antioxidant, and a phosphate antioxidant, and the anti-sticking agent includes at least one of stearic acid, zinc stearate, erucamide, polydimethylsiloxane oil, a silicone release agent, polyethylene wax, microcrystalline wax, and montan wax.

7. The method for preparing a high temperature resistant silicone rubber cable material according to claim 1, characterized in that: Step S3 includes: S3.1, putting the silica gel composite into an extruder and coating the outer surface of the cable core; S3.2, raise the temperature to 150~160℃ and maintain for 20~30min, and apply hot pressing pressure of 5~15MPa; S3.

3. After hot pressing is completed, slowly heat up to 220~230℃, maintain for 2~4h, and slowly cool down to room temperature at a rate of 1~2℃ / min to obtain high temperature resistant silicone rubber cable material.

8. A high temperature resistant silicone rubber cable material, characterized in that: It is made by the preparation method of a high temperature resistant silicone rubber cable material according to any one of claims 1 to 7, wherein the high temperature resistant silicone rubber cable material comprises a fluorinated porous boron nitrogen wafer, indium titanium alloy particles and a polysilicone matrix; wherein, The fluorinated porous boron nitrogen wafer is used to improve the heat resistance of the high temperature resistant silicone rubber cable material, and improve the insulation and chemical inertness of the high temperature resistant silicone rubber cable material at high temperatures; The indium-titanium alloy particles are used to form a skeleton to improve the tensile strength and heat resistance of the high-temperature resistant silicone rubber cable material; The polysilicone matrix as an elastic component provides the high temperature resistant silicone rubber cable material with processability and insulation.

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