Conductive sealant and aircraft fuel tank

Abstract

The invention relates to the technical field of high polymer material sealants, in particular to a conductive sealant and an aircraft fuel tank. The conductive sealant comprises a base paste and a vulcanizing paste, wherein the mass ratio of the base paste to the vulcanizing paste is (100-200): 1; the base paste is prepared from 100 parts by weight of polytrifluoropropyl methyl siloxane, 1 to 8 parts by weight of MXene, 100 to 250 parts by weight of conductive filler, 5 to 65 parts by weight of reinforcing filler, 1 to 8 parts by weight of heat-resistant agent, 0.2 to 3 parts by weight of catalyst and 1 to 5 parts by weight of methyl fluorosilicone oil; the vulcanization paste comprises 10 parts by weight of hydrogen-containing silicone oil and 5-15 parts by weight of white carbon black. The conductive sealant provided by the invention is small in density, has the advantages of good conductive uniformity, good high temperature resistance and excellent medium resistance, and is especially suitable for being used in an aircraft fuel tank.

Description

Technical Field

[0001] This invention relates to the field of polymer sealant technology, and particularly to a conductive sealant and an aircraft fuel tank. Background Technology

[0002] During flight, the fuel inside the fuel tank is constantly vibrating. The sloshing of the fuel itself and the relative movement between the fuel and the internal structure of the tank can lead to the generation and accumulation of static charge. Once the static charge accumulates to a certain level, the high-energy spark generated by its discharge could potentially ignite the fuel in the tank, causing a deflagration accident. To promptly remove static charge, conductive sealants can be used inside the fuel tank.

[0003] Conductive sealants are special polymer composite materials that combine conductivity and sealing functions. They are typically made with rubber (such as silicone rubber and polysulfide rubber) or resin (such as epoxy resin) as the matrix, incorporating conductive fillers (such as silver powder, copper powder, and silver-plated particles). However, existing conductive sealants generally suffer from high density and uneven conductivity. Moreover, silicone rubber has insufficient resistance to media such as fuel oil, while polysulfide rubber and resin have limited operating temperature ranges and are not resistant to high temperatures. None of them can simultaneously meet the requirements of high-temperature resistance and resistance to various media.

[0004] Therefore, there is an urgent need to provide a conductive sealant that has low density and combines advantages such as good electrical uniformity, good high temperature resistance, and excellent resistance to media. Summary of the Invention

[0005] To address the problems of high density and difficulty in simultaneously achieving good conductivity uniformity, high temperature resistance, and excellent media resistance in existing conductive sealants, this invention provides a conductive sealant and an aircraft fuel tank. The conductive sealant provided in this invention, by adjusting the amounts of components in the base paste and the curing paste, uses polytrifluoropropylmethylsiloxane as the raw rubber in the base paste, adding MXene and methyl fluorosilicone oil, and adds silica to the curing paste. The synergistic effect of these components reduces the density of the conductive sealant while simultaneously enabling it to possess uniform conductivity, good high temperature resistance, and excellent media resistance.

[0006] To address the aforementioned problems, a first aspect of the present invention provides a conductive sealant; wherein the conductive sealant comprises a base paste and a vulcanizing paste, and the mass ratio of the base paste to the vulcanizing paste is 100-200:1;

[0007] The base paste comprises 100 parts by weight of polytrifluoropropylmethylsiloxane, 1-8 parts by weight of MXene, 100-250 parts by weight of conductive filler, 5-65 parts by weight of reinforcing filler, 1-8 parts by weight of heat resistant agent, 0.2-3 parts by weight of catalyst and 1-5 parts by weight of methyl fluorosilicone oil.

[0008] The vulcanizing paste comprises 10 parts by weight of hydrogen-containing silicone oil and 5-15 parts by weight of silica.

[0009] A second aspect of the present invention provides an aircraft fuel tank comprising the conductive sealant described in the first aspect of the present invention.

[0010] Compared with the prior art, the present invention has the following beneficial technical effects:

[0011] 1) The conductive sealant provided in this invention, by adjusting the amount of base paste and vulcanizing paste, uses polytrifluoropropylmethylsiloxane as raw rubber in the base paste, adds MXene and methyl fluorosilicone oil, and adds silica in the vulcanizing paste. The components work synergistically to reduce the density of the conductive sealant while significantly improving its conductivity uniformity and high temperature resistance (e.g., it can withstand a high temperature of 200°C), and enhancing its resistance to media. This allows the conductive sealant to have uniform conductivity, good high temperature resistance, and excellent resistance to media.

[0012] 2) The conductive sealant provided by this invention has a simple preparation method, good comprehensive performance, and high vulcanization activity at room temperature. It is especially suitable for parts in the aerospace field where there is a need for conductivity and sealing, such as the fuel tank of an aircraft.

[0013] 3) The conductive sealant provided by this invention achieves room temperature curing of the conductive sealant via a dehydrogenation condensation route. The high trifluoropropyl content in polytrifluoropropylmethylsiloxane significantly improves the conductive sealant's resistance to media. Compared to other curing mechanisms, the small molecule products during curing of dehydrogenation-type sealants are easily released, resulting in a higher heat resistance rating than alcohol-type conductive fluorosilicone sealants, making them suitable for industrial application. Detailed Implementation

[0014] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this invention are intended to cover non-exclusive inclusion.

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] A first aspect of the present invention provides a conductive sealant, wherein the conductive sealant comprises a base paste and a vulcanizing paste; wherein the mass ratio of the base paste to the vulcanizing paste is 100-200:1;

[0017] The base paste comprises 100 parts by weight of polytrifluoropropylmethylsiloxane, 1-8 parts by weight of MXene, 100-250 parts by weight of conductive filler, 5-65 parts by weight of reinforcing filler, 1-8 parts by weight of heat resistant agent, 0.2-3 parts by weight of catalyst and 1-5 parts by weight of methyl fluorosilicone oil.

[0018] The vulcanizing paste comprises 10 parts by weight of hydrogen-containing silicone oil and 5-15 parts by weight of silica.

[0019] In this invention, the inventors discovered through research that by adjusting the amounts of base paste and vulcanizing paste in the raw materials for preparing the conductive sealant, using polytrifluoropropylmethylsiloxane as raw rubber in the base paste, and adding MXene and methyl fluorosilicone oil, and adding silica in the vulcanizing paste, the synergistic effect of each component can significantly improve the conductivity uniformity and high-temperature resistance (e.g., resistant to 200°C) of the conductive sealant while reducing its density, and enhance its resistance to media, thus enabling the conductive sealant to possess uniform conductivity, good high-temperature resistance, and excellent resistance to media.

[0020] In one embodiment of the present invention, the mass ratio of the base paste to the vulcanizing paste is 120-150:1. Specifically, in this invention, when the mass ratio of the base paste to the vulcanizing paste is 120-150:1, the conductive sealant exhibits better high-temperature resistance, retaining good tensile strength and elongation at break even after high-temperature treatment at 200°C.

[0021] In one embodiment of the present invention, the base paste comprises 100 parts by weight of polytrifluoropropylmethylsiloxane, 3-6 parts by weight of MXene, 150-180 parts by weight of conductive filler, 20-50 parts by weight of reinforcing filler, 3-5 parts by weight of heat resistant agent, 0.5-2.5 parts by weight of catalyst, and 2-4 parts by weight of methyl fluorosilicone oil. In this invention, when the content of the above components in the base paste is within the aforementioned defined range, the conductive sealant has a lower density and better conductivity uniformity, high-temperature resistance, and media resistance.

[0022] In one embodiment of the present invention, the viscosity of the polytrifluoropropylmethylsiloxane at 23°C is 5 Pa·s-82 Pa·s, preferably 20 Pa·s-50 Pa·s.

[0023] In this invention, polytrifluoropropylmethylsiloxane can be synthesized according to known methods or commercially available products can be used directly. Adjusting the viscosity of polytrifluoropropylmethylsiloxane helps improve the mixing effect of the base paste and the curing paste, thereby further improving the conductivity uniformity, high-temperature resistance, and media resistance of the conductive sealant.

[0024] In one embodiment of the present invention, the MXene is a two-dimensional MXene nanosheet, preferably, the MXene is Ti3C2T. x MXene powder.

[0025] In this invention, MXene is a general term for two-dimensional transition metal carbides and carbonitrides, with the chemical formula M. n+1 X n T x In this formula, M represents an early transition metal element, such as titanium or vanadium; X represents carbon and / or nitrogen; T represents functional groups on the material surface, such as -OH or -F; and n ranges from 1 to 4. MXene can synergistically construct a conductive network with conductive fillers. On the one hand, it can improve the conductivity of the conductive sealant while reducing the amount of conductive filler used, thus helping to reduce the density of the conductive sealant. On the other hand, it can significantly improve the conductivity uniformity of the conductive sealant, avoiding localized non-conductive phenomena.

[0026] In one embodiment of the present invention, the conductive filler includes one or more of silver powder, silver-plated aluminum powder, silver-plated nickel powder, silver-plated copper powder, copper powder, conductive carbon black, and carbon nanotubes; preferably, it includes one or more of silane coupling agent modified silver powder, silver-plated aluminum powder, silver-plated nickel powder, silver-plated copper powder, copper powder, conductive carbon black, and carbon nanotubes.

[0027] In this invention, the conductive filler is a conventional conductive powder in the art. To further improve the compatibility of the conductive filler with MXene and polytrifluoropropylmethylsiloxane, a silane coupling agent can be used to modify the conductive filler: the conductive filler is added to an aqueous solution of ethanol and stirred, and the silane coupling agent is added during stirring. The mixture is then reacted at 60-70°C for 3-5 hours, followed by cooling, filtration, and drying to obtain the modified conductive filler. The silane coupling agent includes γ-glycidoxypropyltrimethoxysilane and / or γ-aminopropyltriethoxysilane; the mass ratio of the silane coupling agent to the conductive filler is 1:480-520. Conductive fillers modified with silane coupling agents can interact with functional groups such as -OH and -F on the surface of two-dimensional MXene nanosheets, or be directly adsorbed onto the two-dimensional MXene nanosheets. This helps to effectively improve the conductivity and conductivity uniformity of conductive sealants, reduce the amount of conductive filler used, and lower the density of conductive sealants. As a result, conductive sealants not only have high conductivity and low density, but also have more uniform conductivity, better high temperature resistance, and better resistance to media.

[0028] In one embodiment of the present invention, the particle size of the silver powder, silver-plated aluminum powder, silver-plated nickel powder, silver-plated copper powder, and copper powder is 5-15 μm; the particle size of the conductive carbon black is 10-40 μm; and the diameter of the carbon nanotube is 5-15 nm and the length is 5-25 μm.

[0029] In one embodiment of the present invention, the reinforcing filler includes one or more of silica (e.g., fumed silica and / or precipitated silica), carbon black, light calcium carbonate, and titanium dioxide.

[0030] In one embodiment of the present invention, the heat-resistant agent comprises ferric oxide and / or cerium oxide. For example, it may be ferric oxide alone, or cerium oxide alone, or ferric oxide and cerium oxide in any mass ratio; wherein the mass ratio of ferric oxide to cerium oxide may be 0.8-1.2:1.

[0031] In one embodiment of the present invention, the catalyst comprises one or more of dibutyltin diacetate, dibutyltin dilaurate, and di(ethylhexanoate)dibutyltin. In this invention, the catalyst exhibits high catalytic activity, enabling deep vulcanization of the conductive sealant at room temperature.

[0032] In one embodiment of the present invention, the viscosity of the methyl fluorosilicone oil at 23°C is 0.1 Pa·s-1 Pa·s, preferably 0.4 Pa·s-0.6 Pa·s.

[0033] In this invention, methyl fluorosilicone oil is a commercially available product. Adding methyl fluorosilicone oil to the base paste helps adjust the viscosity, facilitates subsequent mixing of the base paste and the curing paste, and further improves the conductivity uniformity, high-temperature resistance, and media resistance of the conductive sealant, thereby enhancing the overall performance of the conductive sealant.

[0034] In one embodiment of the present invention, the vulcanizing paste comprises 10 parts by weight of hydrogen-containing silicone oil and 8-12 parts by weight of silica.

[0035] In this invention, the inventors discovered through research that adding a small amount of silica to the vulcanizing paste can adjust the viscosity of the vulcanizing paste, which helps to improve the process performance of the vulcanizing paste, thereby improving the mixing effect of the base paste and the vulcanizing paste, and further improving the conductivity uniformity, high temperature resistance and media resistance of the conductive sealant.

[0036] In one embodiment of the present invention, the hydrogen content in the hydrogen-containing silicone oil is 1.2-1.55 wt%, preferably 1.4-1.55 wt%.

[0037] In this invention, by controlling the hydrogen content in the hydrogen-containing silicone oil, the crosslinking density of polytrifluoropropylmethylsiloxane and the hydrogen-containing silicone oil can be increased, which helps to further improve the high-temperature resistance of the conductive sealant.

[0038] A second aspect of the present invention provides an aircraft fuel tank comprising the conductive sealant described in the first aspect of the present invention.

[0039] The conductive sealant of this invention has high vulcanization activity at room temperature, low density, and high conductivity. It combines the advantages of good conductivity uniformity, good high temperature resistance, and excellent resistance to media. It is especially suitable for parts in the aerospace field where there is a need for conductivity and sealing, such as aircraft fuel tanks.

[0040] The present invention will now be described in detail with reference to specific embodiments thereof, but it should be understood that the scope of protection of the present invention is not limited to the embodiments.

[0041] The viscosity of polytrifluoropropylmethylsiloxane and methylfluorosilicone oil at 23°C was measured using a rotational viscometer, and the hydrogen content in hydrogen-containing silicone oil was measured by titration.

[0042] Example 1

[0043] Weigh 180 parts by weight of silver-plated aluminum powder (average particle size of 5-15 μm), add it to 95% ethanol aqueous solution and stir. During the process, add 0.36 parts of silane coupling agent γ-glycidoxypropyltrimethoxysilane and react at 65℃ for 4 hours. Then cool, filter and dry to obtain modified silver-plated aluminum powder.

[0044] Weigh each component of the base paste according to the weight proportions in Table 1, then add them to a three-roll mill and mix evenly to obtain the base paste; weigh each component of the vulcanizing paste according to the weight proportions in Table 1, then add them to a high-speed mixer and mix evenly to obtain the vulcanizing paste; mix the base paste and the vulcanizing paste according to the mass ratios in Table 1 and carry out the vulcanization reaction at room temperature to obtain the conductive sealant.

[0045] Table 1

[0046]

[0047] Example 2

[0048] Weigh 150 parts by weight of silver-plated copper powder (average particle size of 5-15 μm), add it to 95% ethanol aqueous solution and stir. During the process, add 0.3 parts of silane coupling agent γ-glycidoxypropyltrimethoxysilane and react at 70℃ for 3 hours. Then cool, filter and dry to obtain modified silver-plated copper powder.

[0049] Weigh each component of the base paste according to the weight proportions in Table 2, then add them to a three-roll mill and mix evenly to obtain the base paste; weigh each component of the vulcanizing paste according to the weight proportions in Table 2, then add them to a high-speed mixer and mix evenly to obtain the vulcanizing paste; mix the base paste and the vulcanizing paste according to the mass ratios in Table 2 and carry out the vulcanization reaction at room temperature to obtain the conductive sealant.

[0050] Table 2

[0051]

[0052] Example 3

[0053] Weigh 3 parts by weight of conductive carbon black (average particle size 10-40 μm) and 160 parts by weight of silver powder (average particle size 5-15 μm), add them to 95% ethanol aqueous solution and stir. During the process, add 0.33 parts by weight of silane coupling agent γ-aminopropyltriethoxysilane and react at 60℃ for 4 h. Then cool, filter and dry to obtain modified conductive carbon black and modified silver powder.

[0054] Weigh each component of the base paste according to the weight proportions in Table 3, then add them to a three-roll mill and mix evenly to obtain the base paste; weigh each component of the vulcanizing paste according to the weight proportions in Table 3, then add them to a high-speed mixer and mix evenly to obtain the vulcanizing paste; mix the base paste and the vulcanizing paste according to the mass ratios in Table 3 and carry out the vulcanization reaction at room temperature to obtain the conductive sealant.

[0055] Table 3

[0056]

[0057] Example 4

[0058] Same as Example 3, except that the hydrogen content in the hydrogen-containing silicone oil is 0.75 wt%.

[0059] Comparative Example 1

[0060] Similar to Example 1, except that the amount of modified silver-plated aluminum powder added is 250 parts, and MXene is omitted from the base paste.

[0061] Comparative Example 2

[0062] Same as Example 1, except that MXene is omitted from the base paste.

[0063] Comparative Example 3

[0064] Similar to Example 3, except that polytrifluoropropylmethylsiloxane is replaced in equal amounts with copolymerized hydroxyl-terminated liquid fluorosilicone raw material F50 (i.e., a copolymer of repeating units of trifluoropropylmethylsiloxane and dimethylsiloxane in a molar ratio of 1:1).

[0065] Test Example 1

[0066] The density, conductivity, and high-temperature resistance of the conductive sealants in Examples 1-4 and Comparative Examples 1-3 were tested, and the test results are shown in Table 4.

[0067] The density test method is GB / T 533-2008; the tensile strength and elongation at break test methods are GB / T 528-2009.

[0068] The volume resistivity of the conductive sealant was tested using a four-probe tester. The conductive sealant was made into a 6cm x 6cm film, evenly divided into 9 regions. One point was selected within each region, and the volume resistivity of each point was measured using the four-probe tester. When the volume resistivity test result exceeded the upper limit of the four-probe tester's testing range (i.e., excessive resistance), it indicated that the test point was not conductive. The average value of the test data from the conductive test points was used as the test result. If any non-conductive points were found, there was no need to calculate the volume resistivity of the film. The lower the volume resistivity, the better the conductivity of the conductive sealant.

[0069] The heat resistance treatment method involves placing the sample at 200℃ for 24 hours. The smaller the change in tensile strength and elongation at break before and after the heat resistance treatment, the better the high-temperature resistance of the conductive sealant.

[0070] Table 4

[0071]

[0072] Note: "-" in the table indicates that no test was performed.

[0073] As shown in Table 4, compared with Example 4, the conductive sealant prepared using hydrogen-containing silicone oil with a relatively high hydrogen content in Example 3 exhibited significantly smaller changes in tensile strength and elongation at break after heat treatment. This indicates that increasing the hydrogen content in the hydrogen-containing silicone oil helps improve the high-temperature resistance of the conductive sealant. This may be because, in the conductive sealant of the present invention, increasing the hydrogen content in the hydrogen-containing silicone oil helps increase the crosslinking density of the conductive sealant, and increased crosslinking density helps improve the high-temperature resistance of the conductive sealant. Therefore, the high-temperature resistance of Example 3 is superior to that of Example 4.

[0074] By comparing Example 1 and Comparative Example 1, it can be seen that, under the premise of similar volume resistivity, the density of the conductive sealant in Example 1 is significantly lower. This is because a small amount of MXene is added to Example 1. MXene can form a conductive network with the conductive filler. Therefore, the conductive sealant in Example 1 can still have a lower volume resistivity, i.e., higher conductivity, while reducing the amount of conductive filler used.

[0075] The conductive sealant in Comparative Example 2 exhibited localized non-conductivity during conductivity testing. Compared to Example 1, Comparative Example 2 did not contain MXene. A comparison of Example 1 and Comparative Example 2 shows that the addition of a small amount of MXene can significantly improve the conductivity uniformity of the conductive sealant. This is because MXene can form a conductive network with conductive fillers, promoting the formation of more conductive pathways, thus resulting in a more uniform and superior conductivity of the prepared conductive sealant.

[0076] Test Example 2

[0077] The media resistance of the conductive sealants in Examples 1-4 and Comparative Examples 1-3 was tested, and the test results are shown in Table 5. The media resistance test method was as follows: the conductive sealant to be tested was immersed in 95# aviation gasoline at 60°C for 7 days, then removed and observed to see if the conductive sealant became sticky.

[0078] Table 5

[0079]

[0080]

[0081] Table 5 shows that the conductive sealant prepared in Comparative Example 3 exhibited significant volume expansion after the media resistance test. This indicates that using polytrifluoropropylmethylsiloxane as the raw material in the base paste can significantly improve the media resistance of the conductive sealant.

[0082] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A conductive sealant, characterized in that, The conductive sealant comprises a base paste and a vulcanizing paste, wherein the mass ratio of the base paste to the vulcanizing paste is 100-200:1; The base paste comprises 100 parts by weight of polytrifluoropropylmethylsiloxane, 1-8 parts by weight of MXene, 100-250 parts by weight of conductive filler, 5-65 parts by weight of reinforcing filler, 1-8 parts by weight of heat resistant agent, 0.2-3 parts by weight of catalyst and 1-5 parts by weight of methyl fluorosilicone oil. The vulcanizing paste comprises 10 parts by weight of hydrogen-containing silicone oil and 5-15 parts by weight of silica.

2. The conductive sealant according to claim 1, wherein, The mass ratio of the base paste to the vulcanizing paste is 120-150:

1.

3. The conductive sealant according to claim 1 or 2, wherein, The base paste comprises 100 parts by weight of polytrifluoropropylmethylsiloxane, 3-6 parts by weight of MXene, 150-180 parts by weight of conductive filler, 20-50 parts by weight of reinforcing filler, 3-5 parts by weight of heat resistant agent, 0.5-2.5 parts by weight of catalyst and 2-4 parts by weight of methyl fluorosilicone oil.

4. The conductive sealant according to any one of claims 1-3, wherein, The viscosity of the polytrifluoropropylmethylsiloxane at 23°C is 5 Pa·s-82 Pa·s, preferably 20 Pa·s-50 Pa·s.

5. The conductive sealant according to any one of claims 1-4, wherein, The MXene is Ti3C2T x MXene powder.

6. The conductive sealant according to any one of claims 1-5, wherein, The conductive filler includes one or more of the following: silver powder, silver-plated aluminum powder, silver-plated nickel powder, silver-plated copper powder, copper powder, conductive carbon black, and carbon nanotubes; preferably, it includes one or more of the following: silver powder modified with silane coupling agent, silver-plated aluminum powder, silver-plated nickel powder, silver-plated copper powder, copper powder, conductive carbon black, and carbon nanotubes. Preferably, the reinforcing filler includes one or more of silica, carbon black, light calcium carbonate, and titanium dioxide; Preferably, the heat-resistant agent comprises ferric oxide and / or cerium oxide; Preferably, the catalyst comprises one or more of dibutyltin diacetate, dibutyltin dilaurate, and dibutyltin di(ethylhexanoate).

7. The conductive sealant according to any one of claims 1-6, wherein, The viscosity of the methyl fluorosilicone oil at 23°C is 0.1 Pa·s-1 Pa·s, preferably 0.4 Pa·s-0.6 Pa·s.

8. The conductive sealant according to any one of claims 1-7, wherein, The vulcanizing paste comprises 10 parts by weight of hydrogen-containing silicone oil and 8-12 parts by weight of silica.

9. The conductive sealant according to any one of claims 1-8, wherein, The hydrogen content in the hydrogen-containing silicone oil is 1.2-1.55 wt%, preferably 1.4-1.55 wt%.

10. An aircraft fuel tank, characterized in that, Includes the conductive sealant according to any one of claims 1-9.

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