Fluorinated silicone rubber capable of being vitrified and preparation method thereof

Abstract

The invention discloses ceramic fluorinated silicone rubber and a preparation method thereof. The ceramizable fluorosilicone rubber comprises the following raw materials in parts by weight: 100 parts of fluorosilicone raw rubber, 10-30 parts of fumed silica, 4-8 parts of a structure control agent, 10-20 parts of an organic-inorganic compound fire-resistant filler, 4-10 parts of reinforced fibers, 20-30 parts of a carbon-based ceramic additive and 1-2 parts of a vulcanizing agent. The preparation method comprises the following steps: S1, adding the fluorosilicone raw rubber into a kneading machine, and then adding the fumed silica and the structure control agent to start mixing; s2, adding an organic-inorganic compound refractory filler, reinforced fibers and a carbon-based ceramic additive into the mixed material obtained after mixing in the step S1, and continuously mixing; s3, carrying out vacuum treatment on the material mixed in the S2, cooling the material to room temperature, adding a vulcanizing agent into a double-roller open mill, and uniformly mixing; and S4, performing tabletting vulcanization on the material mixed in the step S3 on a plate vulcanizing machine, and then performing secondary vulcanization in a drying oven to obtain the ceramization fluorinated silicone rubber.

Description

Technical Field

[0001] The invention relates to the technical field of organic silicon fireproof materials, and in particular to a ceramicizable fluorosilicone rubber and a preparation method thereof. Background Art

[0002] Methyl vinyl trifluoropropyl silicone rubber (FMVQ) has high and low temperature resistance, low dielectric properties given by its main chain Si-O-Si structure and side chain trifluoropropyl (-CH 2 CH 2 CF 3 ) brings excellent solvent resistance, hydrophobicity and oleophobicity, and is widely used in high-end fields such as aerospace sealing, military electronic packaging and industrial oil-resistant pipelines.

[0003] However, fluorosilicone rubber faces severe challenges in applications involving flammable media such as aviation fuel systems or high-temperature oxidative environments: its thermal decomposition temperature is low, and the fluorine-containing free radicals produced by thermal decomposition will accelerate the degradation of the material. Although traditional flame retardant modification technology (such as adding inorganic hydroxides) can improve the limiting oxygen index, the amount added is large, resulting in significant degradation of the material's mechanical properties and loss of oil resistance. At the same time, because fluorosilicone rubber has an essential shortcoming in fire resistance, the composite material structure will be destroyed after encountering open flames and high-temperature environments, and it will be unable to further hinder the spread of flames.

[0004] Ceramicization is an important method to improve the fire resistance of fluorosilicone rubber. However, the ceramicization temperature of traditional ceramic fillers is significantly higher than the thermal decomposition starting temperature of fluorosilicone rubber. The material is pyrolyzed and destroyed before forming an effective ceramic layer, and the structural integrity cannot be maintained. In addition, the pores generated by the decomposition of the matrix at high temperature will further weaken the density of the ceramic layer.

[0005] Although the introduction of methyl vinyl silicone rubber into fluorosilicone rubber using the traditional blending system can partially improve the high temperature resistance of the composite material, thereby facilitating the ceramicization process, the solvent resistance of the composite material is greatly reduced. At the same time, the difference between the two rubbers will lead to a decrease in the mechanical properties of the composite material.

[0006] Therefore, how to develop new composite materials with both high fire resistance and flame retardancy while retaining the intrinsic properties of fluorosilicone rubber has become a key research direction to break through the bottleneck of fluorosilicone rubber fire safety.

[0007] Chinese patent application CN119177025A discloses a highly oil-resistant and fire-resistant silicone rubber material and its preparation method, which is composed of a methyl vinyl trifluoropropyl silicone rubber and a non-fluorinated silicone rubber composite base material (100 parts) and functional additives, including: a flux containing a silicon-oxygen compound (1-10 parts), a bismuth-molybdenum-doped magnesium-cobalt-nickel-copper-zinc oxide catalyst (1-5 parts), a structural control agent (2-8 parts), a flame retardant (10-50 parts), and a refractory filler (20-80 parts), which synergistically improves the fire resistance, oil resistance and flame retardancy of the material. This patented technology uses a homemade flux and a structural control agent to make the filler evenly dispersed in the composite material; by compounding fluorosilicone rubber with non-fluorinated silicone rubber, flame retardancy and oil resistance are achieved; and by using a bismuth-molybdenum-doped magnesium-cobalt-nickel-copper-zinc oxide catalyst, the organic-inorganic conversion of the composite material is promoted. Summary of the invention

[0008] The present invention provides a ceramicizable fluorosilicone rubber and a preparation method thereof, which can solve the following problems: 1) when the ceramicizing temperature of conventional ceramic fillers is low, the ceramic body structure is loose and the strength is low; 2) the temperature required for ceramicizing by conventional ceramicizing technology is much higher than the decomposition temperature of fluorosilicone rubber, and the ceramicizing rate does not match the decomposition rate of fluorosilicone rubber.

[0009] The present invention obtains a fluorosilicone rubber material having excellent fireproof, flame retardant and oil-resistant properties under the synergistic effect of fluorosilicone raw rubber, carbon-based ceramic additives, organic-inorganic composite refractory filler and reinforcing fiber.

[0010] [1] A ceramicizable fluorosilicone rubber, comprising the following raw materials in parts by weight: 100 parts of fluorosilicone raw rubber, 10 to 30 parts (e.g., 22 parts, 23 parts, 25 parts, 26 parts, etc.) of fumed silica, 4 to 8 parts (e.g., 6 parts, 7 parts, etc.) of a structure control agent, 10 to 20 parts (e.g., 13 parts, 15 parts, 16 parts, etc.) of an organic-inorganic composite refractory filler, 4 to 10 parts (e.g., 5 parts, 6 parts, 7 parts, 9 parts, etc.) of reinforcing fibers, 20 to 30 parts (e.g., 23 parts, 24 parts, 25 parts, 26 parts, etc.) of a carbon-based ceramic additive, and 1 to 2 parts (e.g., 1.2 parts, 1.5 parts, etc.) of a vulcanizing agent;

[0011] The organic-inorganic composite refractory filler is a mixture of organic zirconium and a low-melting-point flux, wherein the mass ratio of the organic zirconium to the low-melting-point flux is 1:3-5, such as 1:4, etc.; the low-melting-point flux is one or more of zinc borate, boron oxide, and a low-melting-point glass powder with a melting temperature of 320-500°C;

[0012] The reinforcing fiber is a mixture of a first fiber and a second fiber, wherein the aspect ratio of the first fiber is 50 to 100:1, such as 80:1, etc., the aspect ratio of the second fiber is 101 to 300:1, such as 200:1, 250:1, etc., and the mass ratio of the first fiber to the second fiber is 1:1 to 2, such as 1:1.5, etc.;

[0013] The carbon-based ceramic additive is a mixture of mesophase asphalt, nano iron oxide and expanded graphite modified by a silane coupling agent, and the preparation method thereof comprises the following steps:

[0014] (1) soaking the mesophase asphalt in a toluene solvent, washing it, and drying it;

[0015] (2) mixing the mesophase pitch obtained in step (1) and nano-iron oxide in a mass ratio of 1:0.01 to 0.05 (e.g., 1:0.02, 1:0.03, 1:0.04, etc.) and uniformly dispersing them in anhydrous ethanol by ultrasonication, and then removing the ethanol to obtain a mixture;

[0016] (3) heating the mixture obtained in step (2) to 200-300° C. (e.g., 210° C., 240° C., 250° C., etc.) and keeping the temperature for 1-2 h (e.g., 1.5 h, etc.) for pre-oxidation treatment;

[0017] (4) mixing the pre-oxidation product of step (3) with expanded graphite in a mass ratio of 1:0.5 to 2 (e.g., 1:0.8, 1:1, 1:1.2, etc.) to obtain a carbon-based ceramic additive precursor;

[0018] (5) Mixing the carbon-based ceramic additive precursor and the silane coupling agent mixed liquid in a mass ratio of 1:0.03 to 0.05 (e.g., 1:0.04, etc.), separating the solid from the liquid, and drying the solid to obtain the carbon-based ceramic additive.

[0019] The organic-inorganic composite refractory filler used in the system of the present invention is a mixture of organic zirconium and a low-melting point flux. The organic zirconium can decompose to generate zirconium oxide at a temperature above 200°C, which is evenly dispersed in the matrix to form a physical barrier, inhibiting heat transfer, catalyzing the carbonization of the rubber matrix and delaying thermal decomposition. The low-melting point flux melts at a relatively low temperature, forms a continuous glass phase with the zirconium oxide particles, fills the pores of the carbon layer, and improves the density. Different from the traditional direct addition of zirconium oxide filler, the organic components of organic zirconium can be better dispersed in fluorosilicone rubber, thereby avoiding the direct addition of zirconium oxide to induce agglomeration and increase brittleness. At the same time, the zirconium ions generated by the organic zirconium during the high-temperature decomposition process are more active and can participate in the ceramicization reaction more quickly, and the ligands in the decomposition process can adsorb free radicals, thereby inhibiting the decomposition rate of fluorosilicone rubber at high temperatures.

[0020] The reinforcing fibers used in the system of the present invention are a mixture of a first fiber and a second fiber, wherein short fibers with an aspect ratio of 50 to 100:1 are evenly dispersed, and local cracks are suppressed by bridging, thereby improving the initial crack resistance of the material. Fibers with an aspect ratio of 101 to 300:1 span multiple ceramic sintered units to form a cross-scale support skeleton. With this aspect ratio combination, the fibers can effectively transfer stress and avoid the entanglement problem caused by too many long fibers. It not only improves the bending strength, but also catalyzes the carbonization reaction to further increase the residual carbon rate, thereby blocking oxygen diffusion and improving the fire resistance of the composite material.

[0021] After high-temperature carbonization, the mesophase asphalt forms a highly graphitized carbon layer with a high residual carbon rate. The formed nano-scale flakes can be embedded in the silicone rubber matrix to enhance the interfacial bonding force. At the same time, the carbon layer and the silicone rubber ceramic layer form a "carbon-ceramic" composite structure, which has both antioxidant and thermal shock resistance. However, because the mesophase asphalt contains light aromatics or low molecular weight components that are not completely polycondensed, it is prone to gasification during the high-temperature carbonization process, which in turn causes the carbon layer structure to rupture. The present invention uses a toluene immersion process to selectively dissolve and remove some light components, thereby effectively reducing the risk of structural rupture. In addition, there are interfacial compatibility defects between the mesophase asphalt and the fluorosilicone rubber matrix, which may lead to uneven dispersion, thereby having a negative impact on the mechanical properties and fire resistance of the material. The introduction of oxygen-containing functional groups (such as -OH, -COOH, etc.) through pre-oxidation treatment and the use of silane coupling agents for surface modification can significantly enhance its chemical bonding with fluorosilicone rubber. At the same time, under high temperature conditions, the aromatic molecules of the mesophase asphalt undergo dehydrogenation condensation reactions to form a three-dimensional cross-linked network structure, which not only improves the thermal stability of the material, but also promotes the early start of the carbonization process, thereby quickly building a dense protective layer at the beginning of the flame attack. It is worth noting that the introduction of nano-iron oxide can catalyze the dehydrogenation and cross-linking reactions, significantly reducing the carbonization starting temperature.

[0022] The structure of expanded graphite has a strong physical adsorption effect on non-polar oil media, and this adsorption behavior may cause the oil resistance of fluorosilicone rubber to decrease. Surface modification with silane coupling agent can construct a Si-OC covalent bond bridging layer on the graphite surface to solve the phase separation problem between graphite and rubber while maintaining the oil resistance of perfluorosilicone rubber. Modified expanded graphite can effectively fill the pores of the ceramic layer through high-temperature expansion, and cooperate with the continuous carbon skeleton formed by asphalt carbonization to build a three-dimensional support network.

[0023] The ceramicizable fluorosilicone rubber, the fluorosilicone raw rubber may include methyl vinyl trifluoropropyl silicone rubber. Further, the vinyl content of the methyl vinyl trifluoropropyl silicone rubber may be 0.1 mol% to 3.0 mol%, such as 0.3 mol%, 0.4 mol%, etc.

[0024] The molecular weight of the ceramicizable fluorosilicone rubber can be 600,000 to 1.3 million g / mol, such as 900,000 g / mol, 1 million g / mol, 1.2 million g / mol, etc.

[0025] In some preferred examples, the ceramicizable fluorosilicone rubber, the fumed silica includes hydrophobic fumed silica. In the ceramicizable fluorosilicone rubber system of the present invention, the molecular structure of the fluorosilicone rubber itself has strong hydrophobicity, and the hydroxyl group of the hydrophilic silica easily absorbs water, forming a hydrogen bond network during mixing, resulting in filler agglomeration, thereby affecting the processing performance and final physical properties of the fluorosilicone rubber. The surface of the hydrophobic silica has strong hydrophobicity, good compatibility with fluorosilicone rubber, and can provide better dispersibility and mechanical properties. Therefore, it is preferred to use hydrophobic fumed silica as a reinforcing filler.

[0026] The ceramicizable fluorosilicone rubber and the fumed silica may have a specific surface area of ​​150 to 400 m 2 / g, for example 200m 2 / g, 230m 2 / g, 250m 2 / g, etc.

[0027] The ceramicizable fluorosilicone rubber, the structure control agent may include one or more of hydroxy fluorosilicone oil, hexamethyldisilazane, tetramethyldivinyldisilazane. Further, the viscosity of the hydroxy fluorosilicone oil at 25°C may be 90 to 150 mPa·s, such as 100 mPa·s.

[0028] The ceramicizable fluorosilicone rubber, the organic zirconium may include at least one of zirconium acetylacetonate and tetrakis(triethanolamine)zirconate.

[0029] In the ceramicizable fluorosilicone rubber, the first fiber and the second fiber can be independently one or more combinations of carbon fiber, basalt fiber and quartz fiber.

[0030] The ceramicizable fluorosilicone rubber may have a mesophase asphalt mesophase content of 100%.

[0031] The ceramicizable fluorosilicone rubber, the size of the nano iron oxide can be 20 to 500 nm, such as 50 nm, 100 nm, etc.

[0032] In some preferred examples, the particle size of the expanded graphite in the ceramicizable fluorosilicone rubber is 1000-1500 mesh, such as 1340 mesh. Expanded graphite is made of natural flake graphite, and the retained graphite layered crystal characteristics can be used as a template to guide the transformation of the intermediate phase asphalt molecules to an ordered graphite structure. However, there are dispersibility problems in the fluorosilicone rubber matrix, which may lead to the attenuation of the mechanical properties and fire resistance of the material. Under high temperature conditions, the volume of expanded graphite expands dramatically (the expansion multiple can reach 100-400 times), and this drastic volume change will destroy the continuous phase structure formed during the ceramicization process. By preferably selecting particles with smaller particle sizes, the expansion multiple can be limited, and the densification degree of the ablation interface can be significantly improved.

[0033] The ceramicizable fluorosilicone rubber, the silane coupling agent may include at least one of KH-550, KH-560, KH-570, and vinyltrimethoxysilane.

[0034] In the method for preparing the carbon-based ceramic additive, in step (1), the soaking time may be 5 to 8 days, such as 6 days, 7 days, etc.

[0035] In the method for preparing the carbon-based ceramic additive, in step (2), the ultrasonic time can be 30 to 60 minutes, such as 40 minutes, 50 minutes, etc.

[0036] In the method for preparing the carbon-based ceramic additive, in step (3), the atmosphere of the pre-oxidation treatment may be air.

[0037] In the method for preparing the carbon-based ceramic additive, in step (3), the heating rate can be 1 to 3° C. / min, for example, 2° C. / min.

[0038] In some embodiments, in the method for preparing the carbon-based ceramic additive, in step (4), the particle size of the pre-oxidation product mixed with the expanded graphite is ≤10 μm.

[0039] In the method for preparing the carbon-based ceramic additive, in step (5), the solvent of the silane coupling agent mixture can be ethanol and water. Further, the volume ratio of ethanol to water can be 9 to 19:1, such as 14:1.

[0040] In the method for preparing the carbon-based ceramic additive, in step (5), the mass concentration of the silane coupling agent in the silane coupling agent mixed solution can be 3% to 5%, such as 4%.

[0041] The ceramicizable fluorosilicone rubber, the vulcanizing agent may include one or more of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, diisopropylbenzene peroxide, and di-tert-butyl peroxide.

[0042] [2] The method for preparing a ceramicizable fluorosilicone rubber according to [1] comprises the steps of:

[0043] S1, adding fluorosilicone raw rubber into a kneader, and then adding fumed silica and a structure control agent to start mixing;

[0044] S2, adding an organic-inorganic composite refractory filler, reinforcing fiber and a carbon-based ceramic additive to the mixed material after step S1 and continuing to mix;

[0045] S3, vacuum treating the material mixed in step S2, and then adding a vulcanizing agent on a double-roll mill to mix evenly after the material is cooled to room temperature;

[0046] S4, vulcanizing the material mixed in step S3 on a flat vulcanizer, and then performing secondary vulcanization in an oven to obtain the ceramicizable fluorosilicone rubber.

[0047] In step S1, the mixing temperature may be 50-60°C, and the mixing time may be 40-60 minutes.

[0048] In step S2, the mixing temperature may be 50-60°C, and the mixing time may be 40-60 minutes.

[0049] In step S3, the vacuum treatment temperature may be 140 to 150°C, the vacuum degree may be -0.04 to -0.07 MPa, and the vacuum treatment time may be 60 to 120 min.

[0050] In step S4, the temperature of the vulcanizing press for tabletting can be 170-185° C., the time can be 10-20 min, and the pressure can be 10-15 MPa.

[0051] In step S4, the secondary vulcanization temperature may be 190-200° C., and the time may be 60-120 min.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. The ceramicizable fluorosilicone rubber of the present invention fully retains the intrinsic oil resistance and solvent resistance of fluorosilicone rubber, and successfully realizes the preparation of ceramicizable fluorosilicone rubber with both excellent solvent resistance and high-strength fire resistance by introducing innovative components.

[0054] 2. The present invention innovatively uses mesophase asphalt and expanded graphite to construct a composite carbon-based ceramic additive, wherein the pre-oxidized asphalt can form a highly graphitized carbon layer when heated, and the modified expanded graphite can effectively fill the pores of the ceramic layer through the high-temperature expansion effect, thereby significantly improving the residual carbon rate of the ceramic layer and significantly optimizing the high-temperature structural stability of the ceramic layer.

[0055] 3. The present invention uses an organic-inorganic composite refractory filler and, through the synergistic effect of organic zirconium and a low-melting-point flux, achieves uniform dispersion of the filler and introduces zirconium elements at a relatively low temperature, thereby improving the strength of the ceramic layer.

[0056] 4. The present invention avoids the problem of fiber material agglomeration in the material by compositely using the first fiber and the second fiber with different aspect ratios, constructs a three-dimensional support skeleton in the material, and thus improves the mechanical strength of the composite material before and after ceramicization. DETAILED DESCRIPTION

[0057] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. The operating methods in the following examples where no specific conditions are indicated are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0058] In the following examples, unless otherwise specified, the unit of molecular weight is g / mol, parts are parts by weight, and the mesophase content of the mesophase asphalt is 100%.

[0059] Embodiment 1:

[0060] Preparation of ceramicizable fluorosilicone rubber:

[0061] The invention comprises the following raw materials in parts by weight: 100 parts of fluorosilicone raw rubber, 25 parts of fumed silica, 6 parts of structure control agent, 15 parts of organic-inorganic composite refractory filler, 7 parts of reinforcing fiber, 25 parts of carbon-based ceramic additive and 1.5 parts of vulcanizing agent.

[0062] The fluorosilicone rubber is methyl vinyl trifluoropropyl silicone rubber with a vinyl content of 0.4 mol% and a molecular weight of 900,000. The fumed silica is hydrophobic with a specific surface area of ​​200 m 2 / g. The structure control agent is hydroxy fluorosilicone oil with a viscosity (25°C) of 150mPa·s. The organic-inorganic composite refractory filler is a mixture of 3 parts of zirconium acetylacetonate and 12 parts of zinc borate. The reinforcing fiber is a mixture of 3 parts of carbon fiber with an aspect ratio of 100:1 and 4 parts of carbon fiber with an aspect ratio of 200:1. The vulcanizing agent is 1.5 parts of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane. The preparation steps of the carbon-based ceramic additive include:

[0063] (1) Soak the mesophase asphalt in toluene solvent for 5 days, take it out and wash it with anhydrous ethanol and deionized water for 3-5 times to remove residual solvent and impurities, and dry it at 60°C to constant weight.

[0064] (2) Mix the dried mesophase asphalt with 100 nm nano-iron oxide in a mass ratio of 1:0.04, add anhydrous ethanol as a dispersion medium, perform ultrasonic dispersion treatment for 50 min, and dry and remove the ethanol to obtain a mixture.

[0065] (3) The mixture was pre-oxidized in air by heating to 240°C at a rate of 2°C / min and maintaining the temperature for 1 h.

[0066] (4) The pre-oxidation product is mechanically ground to obtain a powder with a particle size of ≤10 μm, and the powder is mixed with 1000 mesh expanded graphite in a mass ratio of 1:1 to obtain a carbon-based ceramic additive precursor.

[0067] (5) A 3 wt % KH-550 ethanol / water (volume ratio 9 / 1) mixed solution was prepared, and the carbon-based ceramic additive precursor and the KH-550 mixed solution were mixed in a mass ratio of 1:1, stirred for 1 h, and centrifuged to obtain a carbon-based ceramic additive.

[0068] The steps for preparing ceramic fluorosilicone rubber include:

[0069] S1, adding fluorosilicone raw rubber into a kneader, and then adding fumed silica and a structure control agent to start mixing;

[0070] S2, adding organic-inorganic composite refractory filler, reinforcing fiber, and carbon-based ceramic additive to the mixed material after S1 and continuing to mix;

[0071] S3, vacuum treating the mixed material in S2, and then adding a vulcanizing agent on a double-roll mill to mix the mixed material evenly after the material is cooled to room temperature;

[0072] S4, vulcanizing the material mixed in S3 on a flat vulcanizer, and then performing secondary vulcanization in an oven to obtain a ceramic fluorosilicone rubber.

[0073] The mixing temperature in S1 was 50°C and the mixing time was 40 min.

[0074] The mixing temperature in S2 was 50°C and the mixing time was 40 min.

[0075] The vacuum treatment temperature in S3 is 140°C, the vacuum degree is -0.05MPa, and the vacuum treatment time is 120min.

[0076] The temperature of the flat vulcanizer in S4 is 175°C, the time is 15 minutes, and the pressure is 13MPa; the secondary vulcanization temperature is 200°C, and the time is 80 minutes.

[0077] Embodiment 2:

[0078] Preparation of ceramicizable fluorosilicone rubber:

[0079] The invention comprises the following raw materials in parts by weight: 100 parts of fluorosilicone raw rubber, 23 parts of fumed silica, 7 parts of a structure control agent, 15 parts of an organic-inorganic composite refractory filler, 5 parts of reinforcing fibers, 23 parts of a carbon-based ceramic additive, and 1 part of a vulcanizing agent.

[0080] The fluorosilicone rubber is methyl vinyl trifluoropropyl silicone rubber with a vinyl content of 0.3 mol% and a molecular weight of 1 million. The fumed silica is hydrophobic with a specific surface area of ​​230 m 2 / g. The structure control agent is hydroxy fluorosilicone oil with a viscosity (25°C) of 100mPa·s. The organic-inorganic composite refractory filler is a mixture of 3.5 parts of zirconium acetylacetonate and 11.5 parts of low-melting glass powder with a melting temperature of 350°C. The reinforcing fiber is a mixture of 2 parts of carbon fiber with an aspect ratio of 80:1 and 3 parts of carbon fiber with an aspect ratio of 250:1. The vulcanizing agent is 1 part of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane. The preparation steps of the carbon-based ceramic additive include:

[0081] (1) The mesophase asphalt was immersed in a toluene solvent for 6 days, and then washed with anhydrous ethanol and deionized water for 3-5 times to remove the residual solvent and impurities, and dried at 60° C. to constant weight.

[0082] (2) Mix the dried mesophase asphalt and 50 nm nano-iron oxide in a mass ratio of 1:0.03, add anhydrous ethanol as a dispersion medium, perform ultrasonic dispersion treatment for 40 min, and dry to remove the ethanol to obtain a mixture.

[0083] (3) The mixture was pre-oxidized in air by heating to 250°C at a rate of 2°C / min and maintaining the temperature for 1 h.

[0084] (4) The pre-oxidation product is mechanically ground to obtain a powder with a particle size of ≤10 μm, and the powder is mixed with 1000 mesh expanded graphite at a ratio of 1:1.2 to obtain a carbon-based ceramic additive precursor.

[0085] (5) A 4 wt % KH-550 ethanol / water (volume ratio 14 / 1) mixed solution was prepared, and the carbon-based ceramic additive precursor and the KH-550 mixed solution were mixed in a mass ratio of 1:1, stirred for 1 h, and centrifuged to obtain a carbon-based ceramic additive.

[0086] The steps for preparing ceramic fluorosilicone rubber include:

[0087] S1, adding fluorosilicone raw rubber into a kneader, and then adding fumed silica and a structure control agent to start mixing;

[0088] S2, adding organic-inorganic composite refractory filler, reinforcing fiber, and carbon-based ceramic additive to the mixed material after S1 and continuing to mix;

[0089] S3, vacuum treating the mixed material in S2, and then adding a vulcanizing agent on a double-roll mill to mix the mixed material evenly after the material is cooled to room temperature;

[0090] S4, vulcanizing the material mixed in S3 on a flat vulcanizer, and then performing secondary vulcanization in an oven to obtain a ceramic fluorosilicone rubber.

[0091] The mixing temperature in S1 was 60°C and the mixing time was 50 min.

[0092] The mixing temperature in S2 was 60° C. and the mixing time was 50 min.

[0093] The vacuum treatment temperature in S3 is 145°C, the vacuum degree is -0.05MPa, and the vacuum treatment time is 100min.

[0094] The temperature of the flat vulcanizer in S4 is 170°C, the time is 15 minutes, and the pressure is 10MPa; the secondary vulcanization temperature is 190°C, and the time is 110 minutes.

[0095] Embodiment 3:

[0096] Preparation of ceramicizable fluorosilicone rubber:

[0097] The invention comprises the following raw materials in parts by weight: 100 parts of fluorosilicone raw rubber, 26 parts of fumed silica, 7 parts of a structure control agent, 13 parts of an organic-inorganic composite refractory filler, 6 parts of reinforcing fibers, 26 parts of a carbon-based ceramic additive, and 1.2 parts of a vulcanizing agent.

[0098] The fluorosilicone rubber is methyl vinyl trifluoropropyl silicone rubber with a vinyl content of 0.3 mol% and a molecular weight of 1.2 million. The fumed silica is hydrophobic with a specific surface area of ​​200 m 2 / g. The structure control agent is hydroxy fluorosilicone oil with a viscosity (25°C) of 90 mPa·s. The organic-inorganic composite refractory filler is a mixture of 3 parts of tetrakis(triethanolamine) zirconate and 10 parts of boron oxide. The reinforcing fiber is a mixture of 2 parts of basalt fiber with an aspect ratio of 50:1 and 4 parts of basalt fiber with an aspect ratio of 200:1. The vulcanizing agent is 1.2 parts of diisopropylbenzene peroxide. The preparation steps of the carbon-based ceramic additive include:

[0099] (1) The mesophase asphalt is immersed in a toluene solvent for 7 days, taken out and washed with anhydrous ethanol and deionized water for 3-5 times to remove residual solvent and impurities, and dried at 60°C to constant weight.

[0100] (2) Mix the dried mesophase asphalt with 100 nm nano-iron oxide in a mass ratio of 1:0.02, add anhydrous ethanol as a dispersion medium, perform ultrasonic dispersion treatment for 40 minutes, and dry and remove the ethanol to obtain a mixture.

[0101] (3) The mixture was pre-oxidized in air: the temperature was raised to 210°C at a rate of 2°C / min and maintained at this temperature for 1.5 h.

[0102] (4) The pre-oxidation product is mechanically ground to obtain a powder with a particle size of ≤10 μm, and the powder is mixed with 1340 mesh expanded graphite at a ratio of 1:0.8 to obtain a carbon-based ceramic additive precursor.

[0103] (5) A 3 wt % KH-560 ethanol / water (volume ratio 9 / 1) mixed solution was prepared, and the carbon-based ceramic additive precursor and the KH-560 mixed solution were mixed in a mass ratio of 1:1, stirred for 1.5 h, and centrifuged to obtain a carbon-based ceramic additive.

[0104] The steps for preparing ceramic fluorosilicone rubber include:

[0105] S1, adding fluorosilicone raw rubber into a kneader, and then adding fumed silica and a structure control agent to start mixing;

[0106] S2, adding organic-inorganic composite refractory filler, reinforcing fiber, and carbon-based ceramic additive to the mixed material after S1 and continuing to mix;

[0107] S3, vacuum treating the mixed material in S2, and then adding a vulcanizing agent on a double-roll mill to mix the mixed material evenly after the material is cooled to room temperature;

[0108] S4, vulcanizing the material mixed in S3 on a flat vulcanizer, and then performing secondary vulcanization in an oven to obtain a ceramic fluorosilicone rubber.

[0109] The mixing temperature in S1 was 55°C and the mixing time was 50 min.

[0110] The mixing temperature in S2 was 55°C and the mixing time was 50 min.

[0111] The vacuum treatment temperature in S3 is 145°C, the vacuum degree is -0.055MPa, and the vacuum treatment time is 120min.

[0112] The temperature of the flat vulcanizer in S4 is 180°C, the time is 11 minutes, and the pressure is 12 MPa; the secondary vulcanization temperature is 200°C, and the time is 100 minutes.

[0113] Embodiment 4:

[0114] Preparation of ceramicizable fluorosilicone rubber:

[0115] The invention comprises the following raw materials in parts by weight: 100 parts of fluorosilicone raw rubber, 22 parts of fumed silica, 6 parts of a structure control agent, 16 parts of an organic-inorganic composite refractory filler, 9 parts of reinforcing fibers, 24 parts of a carbon-based ceramic additive, and 1.5 parts of a vulcanizing agent.

[0116] The fluorosilicone rubber is methyl vinyl trifluoropropyl silicone rubber with a vinyl content of 0.4 mol% and a molecular weight of 1 million. The fumed silica is hydrophobic with a specific surface area of ​​250m 2 / g. The structure control agent is hexamethyldisilazane. The organic-inorganic composite refractory filler is a mixture of 4 parts of tetrakis(triethanolamine)zirconate and 12 parts of zinc borate. The reinforcing fiber is a mixture of 4 parts of quartz fiber with an aspect ratio of 50:1 and 5 parts of quartz fiber with an aspect ratio of 300:1. The vulcanizing agent is 1.5 parts of diisopropylbenzene peroxide. The preparation steps of the carbon-based ceramic additive include:

[0117] (1) The mesophase asphalt is immersed in a toluene solvent for 7 days, taken out and washed with anhydrous ethanol and deionized water for 3-5 times to remove residual solvent and impurities, and dried at 60°C to constant weight.

[0118] (2) Mix the dried mesophase asphalt with 100 nm nano-iron oxide in a mass ratio of 1:0.02, add anhydrous ethanol as a dispersion medium, perform ultrasonic dispersion for 30 minutes, and dry to remove the ethanol to obtain a mixture.

[0119] (3) The mixture was pre-oxidized in air by heating to 250°C at a rate of 2°C / min and maintaining the temperature for 1 h.

[0120] (4) The pre-oxidation product is mechanically ground to obtain a powder with a particle size of ≤10 μm, and the powder is mixed with 1000 mesh expanded graphite in a ratio of 1:1 to obtain a carbon-based ceramic additive precursor.

[0121] (5) A 3 wt % KH-570 ethanol / water (volume ratio 19 / 1) mixed solution was prepared, and the carbon-based ceramic additive precursor and the KH-570 mixed solution were mixed in a mass ratio of 1:1, stirred for 1.5 h, and centrifuged to obtain a carbon-based ceramic additive.

[0122] The steps for preparing ceramic fluorosilicone rubber include:

[0123] S1, adding fluorosilicone raw rubber into a kneader, and then adding fumed silica and a structure control agent to start mixing;

[0124] S2, adding organic-inorganic composite refractory filler, reinforcing fiber, and carbon-based ceramic additive to the mixed material after S1 and continuing to mix;

[0125] S3, vacuum treating the mixed material in S2, and then adding a vulcanizing agent on a double-roll mill to mix the mixed material evenly after the material is cooled to room temperature;

[0126] S4, vulcanizing the material mixed in S3 on a flat vulcanizer, and then performing secondary vulcanization in an oven to obtain a ceramic fluorosilicone rubber.

[0127] The mixing temperature in S1 was 50°C and the mixing time was 50 min.

[0128] The mixing temperature in S2 was 50°C and the mixing time was 50 min.

[0129] The vacuum treatment temperature in S3 is 140°C, the vacuum degree is -0.06MPa, and the vacuum treatment time is 110min.

[0130] The temperature of the flat vulcanizer in S4 is 180°C, the time is 12 minutes, and the pressure is 12 MPa; the secondary vulcanization temperature is 195°C, and the time is 120 minutes.

[0131] Comparative Example 1:

[0132] The difference between Comparative Example 1 and Example 1 is that an equal mass of traditional ceramic filler wollastonite is used in this comparative example to replace the carbon-based ceramic additive, and the rest is the same as Example 1.

[0133] Comparative Example 2:

[0134] The only difference between Comparative Example 2 and Example 2 is that the carbon-based ceramic additive used in this comparative example has not been pre-oxidized and modified, that is, step (3) and step (5) are missing, and the mixture obtained in step (2) is mechanically ground to obtain a powder with a particle size of ≤10 μm, which is mixed with 1000 mesh expanded graphite in a ratio of 1:1 to obtain a carbon-based ceramic additive. The rest is the same as Example 2.

[0135] Comparative Example 3:

[0136] The difference between Comparative Example 3 and Example 3 is that an equal mass of boron oxide is used to replace the organic-inorganic composite refractory filler in this comparative example, and the rest is the same as Example 3.

[0137] Comparative Example 4:

[0138] The only difference between Comparative Example 4 and Example 4 is that all the reinforcing fibers in this comparative example are quartz fibers with an aspect ratio of 50:1, and the rest is the same as Example 4.

[0139] Comparative Example 5:

[0140] The only difference between Comparative Example 5 and Example 4 is that all the reinforcing fibers in this comparative example are quartz fibers with an aspect ratio of 300:1, and the rest are the same as Example 4.

[0141] Performance inspection test:

[0142] The performance tests of composite materials were carried out with reference to national standards, among which: the hardness test standard is GB / T10807-2006; the apparent density test standard is GB / T 6343-2009; the flame retardant performance test standard is GB / T 10707-2008; the ceramic body bending strength test standard is GB / T 6569-2006: the test sample size is 80mm×5mm×5mm, the sample is placed in a tube furnace for ablation, the heating rate is 10℃ / min, and the sample is taken out after ablation at 650℃ for 1h to test the bending strength; the tensile stress-strain performance test standard is GB / T 528-2009; the oil resistance test standard is GB / T1690-2010, the test sample size is 25mm×25mm×2mm, the sample is placed in No. 1 standard oil for immersion for 14 days, and the size change is tested. The ablation test sample has a length × width of 10 mm × 10 mm and a thickness of 4 mm, and is ablated under a butane flame at 1300°C for 30 min.

[0143] The performance test results of the fluorosilicone rubber provided in the above embodiments and comparative examples are shown in the following table.

[0144]

[0145] Comparison between Example 1 and Comparative Example 1 shows that the use of wollastonite instead of carbon-based ceramic additives leads to a significant decrease in the mechanical properties of fluorosilicone rubber. At the same time, because wollastonite can only participate in the ceramicization reaction at a higher temperature, it cannot quickly form a ceramic layer, which leads to cracking of the ceramic layer during the ablation process. Traditional fillers require a higher ceramicization temperature, and the low-temperature carbonization function of carbon-based ceramic additives is irreplaceable.

[0146] Comparison between Comparative Example 2 and Example 2 shows that the carbon-based ceramic additive can significantly improve the fire resistance of the ceramicizable fluorosilicone rubber after pre-oxidation and modification. Asphalt and expanded graphite that have not been pre-oxidized and modified have poor compatibility with fluorosilicone rubber, which easily leads to filler agglomeration, so the mechanical properties of fluorosilicone rubber are greatly reduced. On the other hand, the initial carbonization temperature of the unpre-oxidized mesophase asphalt is relatively high, and a continuous carbon skeleton cannot be formed quickly, and the part ablated by the flame cannot be quickly protected, thus causing the ceramic layer to crack during the ablation process. The unmodified carbon-based additive leads to a decrease in performance, and pre-oxidation and silane modification are necessary conditions for low-temperature carbonization and interface strengthening.

[0147] Comparison between Example 3 and Example 3 shows that although there is no cracking during the ablation process when only low melting point flux is added, its strength is significantly reduced. This is because although the low melting point flux can melt to form a liquid phase to fill the gaps formed in the ceramic layer, the lack of carbonization of zirconium ions, physical barrier effect of zirconium oxide and free radical adsorption of ligands makes it impossible to effectively inhibit the thermal decomposition of fluorosilicone rubber at above 200°C, thus resulting in a decrease in the strength of the ceramic layer. Organic-inorganic composite refractory fillers are the key to ensuring the thermal stability of fluorosilicone rubber in the early stage of a fire.

[0148] Comparison between Comparative Example 4 and Example 4 shows that the bending strength of the ceramic decreases when only quartz fibers with an aspect ratio of 50:1 are used. This is because although fibers with a small aspect ratio can be evenly dispersed and inhibit local cracks through "micro-region bridging", they are not strong enough as a whole when attacked by flames and cannot form a continuous reinforcement skeleton in the ceramic layer, resulting in a decrease in the strength of the ceramic layer.

[0149] Comparison between Example 5 and Example 4 shows that the mechanical properties of the composite material are greatly reduced when only quartz fibers with an aspect ratio of 300:1 are used. This is because when too many long fibers are added, they are difficult to disperse evenly in the composite material, and the entanglement and accumulation of the fibers easily cause stress concentration in some areas of the material, thereby greatly reducing the mechanical properties. Therefore, reinforcing fibers with different aspect ratios are the key to constructing a three-dimensional support skeleton to achieve a mechanical-fireproof synergistic effect.

[0150] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A ceramicizable fluorosilicone rubber, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of fluorosilicone rubber, 10 to 30 parts of fumed silica, 4 to 8 parts of a structure control agent, 10 to 20 parts of an organic-inorganic composite refractory filler, 4 to 10 parts of reinforcing fibers, 20 to 30 parts of a carbon-based ceramic additive, and 1 to 2 parts of a vulcanizing agent; The organic-inorganic composite refractory filler is a mixture of organic zirconium and a low-melting-point flux, wherein the mass ratio of the organic zirconium to the low-melting-point flux is 1:3-5; the low-melting-point flux is one or more of zinc borate, boron oxide, and a low-melting-point glass powder having a melting temperature of 320-500°C; The reinforcing fiber is a mixture of a first fiber and a second fiber, wherein the aspect ratio of the first fiber is 50 to 100:1, the aspect ratio of the second fiber is 101 to 300:1, and the mass ratio of the first fiber to the second fiber is 1:1 to 2; The carbon-based ceramic additive is a mixture of mesophase asphalt, nano iron oxide and expanded graphite modified by a silane coupling agent, and the preparation method thereof comprises the following steps: (1) soaking the mesophase asphalt in a toluene solvent, washing it, and drying it; (2) mixing the mesophase pitch obtained in step (1) and nano-iron oxide in a mass ratio of 1:0.01 to 0.05 and uniformly dispersing them in anhydrous ethanol by ultrasonication, and then removing the ethanol to obtain a mixture; (3) heating the mixture obtained in step (2) to 200-300° C. and keeping the temperature for 1-2 hours for pre-oxidation treatment; (4) mixing the pre-oxidation product of step (3) with expanded graphite in a mass ratio of 1:0.5 to 2 to obtain a carbon-based ceramic additive precursor; (5) Mixing the carbon-based ceramic additive precursor and the silane coupling agent mixed liquid in a mass ratio of 1:0.03-0.05, separating the solid from the liquid, and drying the solid to obtain the carbon-based ceramic additive.

2. The ceramicizable fluorosilicone rubber according to claim 1, characterized in that: The fluorosilicone rubber includes methyl vinyl trifluoropropyl silicone rubber; The vinyl content of the methyl vinyl trifluoropropyl silicone rubber is 0.1 mol% to 3.0 mol%; The molecular weight of the fluorosilicone raw rubber is 600,000 to 1.3 million g / mol.

3. The ceramicizable fluorosilicone rubber according to claim 1, characterized in that: The fumed silica includes hydrophobic fumed silica; The specific surface area of ​​the fumed silica is 150 to 400 m 2 / g.

4. The ceramicizable fluorosilicone rubber according to claim 1, characterized in that: The structure control agent includes one or more of hydroxy fluorosilicone oil, hexamethyldisilazane, and tetramethyldivinyldisilazane; The hydroxy fluorosilicone oil has a viscosity of 90 to 150 mPa·s at 25°C.

5. The ceramicizable fluorosilicone rubber according to claim 1, characterized in that: The organic zirconium comprises at least one of zirconium acetylacetonate and tetrakis(triethanolamine)zirconate.

6. The ceramicizable fluorosilicone rubber according to claim 1, characterized in that: The first fiber and the second fiber are independently selected from the group consisting of carbon fiber, basalt fiber, and quartz fiber, or a combination thereof.

7. The ceramicizable fluorosilicone rubber according to claim 1, characterized in that: The mesophase asphalt has a mesophase content of 100%; The size of the nano iron oxide is 20 to 500 nm; The particle size of the expanded graphite is 1000-1500 mesh; The silane coupling agent includes at least one of KH-550, KH-560, KH-570 and vinyl trimethoxy silane; In the preparation method of the carbon-based ceramic additive: In step (1), the soaking time is 5 to 8 days; In step (2), the ultrasonic treatment time is 30 to 60 minutes; In step (3), the atmosphere of the pre-oxidation treatment is air, and the heating rate is 1 to 3°C / min; In step (4), the particle size of the pre-oxidation product mixed with the expanded graphite is ≤10 μm; In step (5), the solvent of the silane coupling agent mixed solution is ethanol and water, and the volume ratio of ethanol to water is 9 to 19:1, and the mass concentration of the silane coupling agent in the silane coupling agent mixed solution is 3% to 5%.

8. The ceramicizable fluorosilicone rubber according to claim 1, characterized in that: The vulcanizing agent includes one or more of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, diisopropylbenzene peroxide, and di-tert-butyl peroxide.

9. The method for preparing a ceramicizable fluorosilicone rubber according to any one of claims 1 to 8, characterized in that: Includes steps: S1, adding fluorosilicone raw rubber into a kneader, and then adding fumed silica and a structure control agent to start mixing; S2, adding an organic-inorganic composite refractory filler, reinforcing fiber and a carbon-based ceramic additive to the mixed material after step S1 and continuing to mix; S3, vacuum treating the material mixed in step S2, and then adding a vulcanizing agent on a double-roll mill to mix evenly after the material is cooled to room temperature; S4, vulcanizing the material mixed in step S3 on a flat vulcanizer, and then performing secondary vulcanization in an oven to obtain the ceramicizable fluorosilicone rubber.

10. The method for preparing ceramic fluorosilicone rubber according to claim 9, characterized in that: In step S1, the mixing temperature is 50-60° C. and the mixing time is 40-60 min; In step S2, the mixing temperature is 50-60° C. and the mixing time is 40-60 min; In step S3, the vacuum treatment temperature is 140 to 150° C., the vacuum degree is -0.04 to -0.07 MPa, and the vacuum treatment time is 60 to 120 min; In step S4, the temperature of the vulcanization of the flat vulcanizing machine is 170-185° C., the time is 10-20 min, the pressure is 10-15 MPa, and the secondary vulcanization temperature is 190-200° C., and the time is 60-120 min.

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