Composite liquid fluororubber as well as preparation method and application thereof

Abstract

The invention relates to the technical field of liquid fluororubber, in particular to composite liquid fluororubber as well as a preparation method and application thereof, and the composite liquid fluororubber comprises the following components: graphene oxide and functional end group modified liquid fluororubber, the end group of the functional end group modified liquid fluorine rubber must contain unsaturated double bonds. The composite liquid fluorine rubber can be cured through ultraviolet irradiation and is more environmentally friendly, the cured fluorine rubber has good tensile property, flame retardant property, high temperature resistance and wear resistance, and the dispersity of all components in the composite liquid fluorine rubber is good.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid fluororubbers, and particularly to a composite liquid fluororubber, a preparation method thereof, and an application thereof. Background Art

[0002] The molecular weight of solid fluororubbers is generally above 100,000, and it relies on high-temperature compression molding or extrusion molding processes, which gradually exposes three bottlenecks in new industrial scenarios: First, the forming accuracy is difficult to break through the millimeter-level limit and cannot meet the nanometer-level tolerances required for semiconductor equipment seals; second, it is impossible to achieve complex flow channel structures with a wall thickness of less than 0.5 mm, which restricts the lightweight design of the new energy battery sealing system; third, the traditional vulcanization process needs to be carried out above 150 °C, generating phenolic volatiles, which does not meet the increasingly strict environmental protection standards. Taking new energy vehicles as an example, the sealing of their power battery packs not only needs to be stable in the electrolyte environment for a long time, but also maintains a low long-term penetration rate. These requirements directly gave rise to the innovation of the material system.

[0003] As a representative of special polymer materials, liquid fluororubbers are a high-end branch formed by optimizing the molecular structure and innovating the processing technology on the basis of traditional fluororubbers. Its technological development process is closely related to the demand upgrade of the industrial field for sealing materials under extreme working conditions. Since the industrialization of traditional fluororubbers in the 1950s, relying on the C-F bonds formed by the strong electronegativity of fluorine atoms in the main chain, they have shown significant advantages in properties such as high temperature resistance and chemical corrosion resistance, and have gradually become the core sealing materials in fields such as aerospace and automotive manufacturing. However, with the increasing demand for material processing accuracy and complex shapes in emerging industries such as semiconductor manufacturing and new energy batteries, traditional solid fluororubbers have shown limitations in microstructural forming and thin-walled part processing, which directly gave rise to the technological innovation of liquid fluororubbers.

[0004] A large number of studies on the preparation process of liquid fluororubbers have been carried out by predecessors. For example: CN106146857B discloses a "preparation method of a toughened modified epoxy resin system with carboxyl-terminated liquid fluororubber", which is prepared by using carboxyl-terminated liquid fluororubber and epoxy resin as raw materials. The obtained fluororubber has a good toughening effect, and its tensile strength and elongation at break are relatively high.

[0005] Another example is that CN111925529B discloses a "POSS-modified silane-terminated liquid fluororubber, adhesive and preparation method". After pre-treating the hydroxyl-terminated liquid fluororubber to remove water, it is placed in a reaction kettle, isocyanate and a catalyst are added, and then a polyhedral oligomeric silsesquioxane with a hydroxyl functionality of not less than 2 dissolved in a solvent is added to continue the reaction. Subsequently, a silane coupling agent is added to the system for end-capping, and the solvent is removed to obtain the modified liquid fluororubber. This modified liquid fluororubber has excellent mechanical properties and oil resistance, and is safer and more environmentally friendly.

[0006] However, liquid fluororubber is a high-molecular fluoropolymer, and its flame retardancy still has room for improvement. Therefore, it is urgent to develop a liquid fluororubber with good flame retardancy and good tensile properties after curing. Summary of the Invention

[0007] The main object of the present invention is to provide a composite liquid fluororubber and a preparation method thereof. The liquid fluororubber can be cured by ultraviolet light irradiation, which is more environmentally friendly. The cured fluororubber has good tensile properties, flame retardancy, high temperature resistance and wear resistance, and the components in the composite liquid fluororubber have good dispersibility.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] On the one hand, the present invention provides a composite liquid fluororubber, comprising the following components: graphene oxide and functional end-group modified liquid fluororubber; the end-group of the functional end-group modified liquid fluororubber must contain an unsaturated double bond.

[0010] In some embodiments, the mass ratio of the graphene oxide to the functional end-group modified liquid fluororubber is (0.05 - 0.25):1.

[0011] Preferably, the mass ratio of the graphene oxide to the functional end-group modified liquid fluororubber is 0.15:1.

[0012] In some embodiments, the number average molecular weight of the functional end-group modified liquid fluororubber is 5000 - 8000.

[0013] In some embodiments, the preparation method of the functional end-group modified liquid fluororubber comprises the following steps:

[0014] S1. Mix and dissolve liquid carboxyl-terminated fluororubber with a first solvent, add pyridine and thionyl chloride, heat to 60 - 70 °C and stir for 5 - 7 h, evaporate the solvent under reduced pressure, wash, and obtain acyl chloride-terminated liquid fluororubber for standby;

[0015] S2. At -5 - 0 °C, mix cyanuric chloride with a second solvent, add 3-methyl-3-buten-1-ol and an acid-binding agent thereto, control the temperature at 0 - 5 °C and stir constantly for 2 - 4 h, filter, extract, concentrate under reduced pressure, and then perform column chromatography to obtain the compound shown in Formula I

[0016]

[0017] S3. Mix the compound shown in Formula I in Step S2 with 1,3-propanediamine and add a third solvent, cool to -10 - -5 °C, add an acid-binding agent and stir constantly for 1 - 3 h, filter, extract, concentrate under reduced pressure, and then perform column chromatography to obtain the compound shown in Formula II

[0018]

[0019] S4. Mix the compound shown in Formula II in Step S3 with the terminal acyl chloride group liquid fluororubber in Step S1, add a first solvent and an acid-binding agent, stir at a constant temperature at room temperature for 10 to 14 h, then add 3-triethoxysilyl-1-propylamine, continue stirring for 1 to 3 h, filter after the reaction ends, add petroleum ether to the filtrate until no precipitate is produced, and filter to obtain the functional end-group modified liquid fluororubber.

[0020] Liquid terminal carboxyl fluororubber is one of the commonly used fluororubbers at present. It has good oil resistance and high temperature resistance. However, when the liquid terminal carboxyl fluororubber is made into a sealant, its use in some specific environments is restricted to a certain extent, and it often needs to be compounded with other additives (such as: silica, titanium dioxide, and graphene, etc.). These inorganic materials are prone to agglomeration in the liquid fluororubber, which affects the performance of the final sealant.

[0021] The functional end-group modified liquid fluororubber of the present application first reacts the liquid terminal carboxyl fluororubber with thionyl chloride to convert the carboxyl group at the end group into an acyl chloride group, improving the reaction activity. Subsequently, cyanuric chloride, 3-methyl-3-buten-1-ol, and 1,3-propanediamine are used as the main raw materials to synthesize the compound shown in Formula II. The compound shown in Formula II caps the liquid fluororubber through the reaction of the amino group in the compound shown in Formula II with the terminal acyl chloride group liquid fluororubber. Then, 3-triethoxysilyl-1-propylamine is added to react to obtain the functional end-group modified liquid fluororubber. The functional end-group modified liquid fluororubber prepared by this method has good ultraviolet cross-linking curing performance, avoids the addition of isocyanates and reduces the harm to construction workers. At the same time, the functional end-group modified liquid fluororubber also has certain flame retardant properties and certain tensile properties after cross-linking. In addition, graphene oxide can be more evenly dispersed in the functional end-group modified liquid fluororubber of the present application, avoiding the agglomeration effect. The reason may be: on the one hand, the functional end-group modified liquid fluororubber contains an unsaturated double bond structure in its end group, which can cross-link itself under ultraviolet light irradiation and thus cure. Due to the increase in cross-linking density, the mechanical properties of the cured liquid fluororubber are improved; on the other hand, the functional end-group modified liquid fluororubber contains a large amount of N and Si elements in its end group, and the two improve the flame retardant performance of the composite liquid fluororubber through different flame retardant mechanisms; on the third hand, by finally introducing 3-triethoxysilyl-1-propylamine in the present application, the end group of the functional end-group modified liquid fluororubber can be given a large amount of siloxane structure, which can form hydrogen bonds with graphene oxide, thereby preventing the phenomenon of self-agglomeration of graphene oxide and improving the performance of the composite liquid fluororubber after curing.

[0022] In some embodiments, in step S2, the molar ratio of cyanuric chloride to 3-methyl-3-buten-1-ol is 1:(1 to 1.2).

[0023] Preferably, in step S2, the molar ratio of cyanuric chloride to 3-methyl-3-buten-1-ol is 1:1.1.

[0024] In some embodiments, in step S3, the molar ratio of the compound shown in formula I to 1,3-propanediamine is 1:(1 to 1.2).

[0025] Preferably, in step S3, the molar ratio of the compound shown in formula I to 1,3-propanediamine is 1:1.1.

[0026] In some embodiments, in step S4, the mass ratio of the compound shown in formula II to the terminal acyl chloride group-containing liquid fluororubber is (0.1 to 0.5):1.

[0027] Preferably, in step S4, the mass ratio of the compound shown in formula II to the terminal acyl chloride group-containing liquid fluororubber is 0.3:1.

[0028] In some embodiments, the molar ratio of the compound shown in formula II to 3-triethoxysilyl-1-propylamine is 1:(1 to 1.3).

[0029] Preferably, the molar ratio of the compound shown in formula II to 3-triethoxysilyl-1-propylamine is 1:1.2.

[0030] In some embodiments, the first solvent is any one of tetrahydrofuran, acetone, and N,N-dimethylformamide.

[0031] In some embodiments, the second solvent is acetone or acetonitrile.

[0032] In some embodiments, the third solvent is any one of dichloromethane, chloroform, and tetrahydrofuran.

[0033] In some embodiments, the acid-binding agent is any one of sodium bicarbonate, potassium bicarbonate, sodium carbonate, and potassium carbonate.

[0034] On the other hand, the present invention provides a method for preparing a composite liquid fluororubber, comprising the following steps: mixing and stirring the functional end-group modified liquid fluororubber and graphene oxide at room temperature to disperse them, thus obtaining the composite liquid fluororubber.

[0035] On yet another aspect, the present invention provides an application of the composite liquid fluororubber in a sealant.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The composite liquid fluororubber of the present invention is prepared by mixing graphene oxide and functional end-group modified liquid fluororubber. The composite liquid fluororubber can be cured under ultraviolet light irradiation. The curing process is green and environmentally friendly, avoiding the addition of isocyanates. In addition, the cured composite liquid fluororubber has certain flame retardancy, tensile properties, high temperature resistance and wear resistance.

[0038] (2) For the functional end-group modified liquid fluororubber of the present invention, first, the liquid carboxyl-terminated fluororubber reacts with thionyl dichloride to convert the carboxyl group at the end group into an acyl chloride group, improving the reaction activity. Subsequently, cyanuric chloride, 3-methyl-3-buten-1-ol, and 1,3-propanediamine are used as the main raw materials to synthesize the compound shown in Formula II. The amine group in the compound shown in Formula II reacts with the terminal acyl chloride group liquid fluororubber to cap the liquid fluororubber with the compound shown in Formula II. Subsequently, 3-triethoxysilyl-1-propylamine is added to react to obtain the functional end-group modified liquid fluororubber. The functional end-group modified liquid fluororubber prepared by this method also has certain flame retardancy and certain tensile properties after crosslinking. In addition, graphene oxide can be more uniformly dispersed in the functional end-group modified liquid fluororubber of the present application, avoiding the agglomeration effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 1H NMR spectrum of the compound shown in Formula I in Preparation Example 1;

[0040] Figure 2 1H NMR spectrum of the compound shown in Formula II in Preparation Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0041] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation manners of the present invention.

[0042] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0043] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. Various improvements and changes can be made to the specific embodiments of the description of this invention without departing from the scope or spirit of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description and examples of this application are merely exemplary.

[0044] It should be noted that operations such as "drying", "filtration", "stirring", etc. described in this invention are routine operations for those skilled in the art and can be selected according to actual operations.

[0045] The liquid carboxyl-terminated fluororubber is prepared by the company's own technology (specific reference: CN105968247B), with a viscosity of 30 Pa·s; the graphene oxide is purchased from Jiangxi Shuobang New Material Technology Co., Ltd.

[0046] Preparation Example 1

[0047] A preparation method of a functional end-group modified liquid fluororubber includes the following steps:

[0048] S1. Mix and dissolve 10 g of liquid carboxyl-terminated fluororubber with 100 mL of tetrahydrofuran, add 3 g of pyridine and 5 g of thionyl chloride, raise the temperature to 65 °C and stir for 6 h, evaporate the solvent under reduced pressure, wash, and obtain acyl chloride-terminated liquid fluororubber for standby;

[0049] S2. At -3 °C, mix 3 g of cyanuric chloride and 35 mL of acetone, add 1.55 g of 3-methyl-3-buten-1-ol and 2 g of sodium bicarbonate thereto, control the temperature at 3 °C and stir constantly for 3 h, filter, extract, concentrate under reduced pressure, and then perform column chromatography to obtain the compound shown in Formula I. The reference nuclear magnetic resonance hydrogen spectrum is Figure 1

[0050]

[0051] S3. Mix 3 g of the compound shown in Formula I in step S2 with 1 g of 1,3-propanediamine, add 38 mL of dichloromethane, cool to -7 °C, add 1.6 g of sodium bicarbonate, stir constantly for 2 h, filter, extract, concentrate under reduced pressure, and then perform column chromatography to obtain the compound shown in Formula II. The reference nuclear magnetic resonance hydrogen spectrum is Figure 2

[0052]

[0053] S4. Mix 3 g of the compound shown in Formula II in Step S3 with 10 g of the terminal acyl chloride group-containing liquid fluororubber in Step S1, add 150 mL of tetrahydrofuran and 1.4 g of sodium bicarbonate, stir at a constant temperature at room temperature for 12 h, then add 3 g of 3-triethoxysilyl-1-propylamine, continue stirring for 2 h, filter after the reaction ends, add petroleum ether to the filtrate until no precipitate is produced, and filter to obtain the functional end-group modified liquid fluororubber.

[0054] Preparation Example 2

[0055] A preparation method of a functional end-group modified liquid fluororubber, comprising the following steps:

[0056] S1. Mix 10 g of liquid carboxyl-terminated fluororubber with 100 mL of tetrahydrofuran and dissolve, add 3 g of pyridine and 5 g of thionyl chloride, raise the temperature to 65 °C and stir for 6 h, evaporate the solvent under reduced pressure, wash, and obtain the terminal acyl chloride group-containing liquid fluororubber for standby;

[0057] S2. At -3 °C, mix 3 g of cyanuric chloride and 35 mL of acetone, add 2.8 g of 3-methyl-3-buten-1-ol and 4 g of sodium bicarbonate thereto, control the temperature at 3 °C and stir at a constant temperature for 3 h, filter, extract, concentrate under reduced pressure, and then pass through column chromatography to obtain the compound shown in Formula III

[0058]

[0059] S3. Mix 3 g of the compound shown in Formula I in Step S2 with 1 g of 1,3-propanediamine, add 38 mL of dichloromethane, cool to -7 °C, add 1.6 g of sodium bicarbonate, stir at a constant temperature for 2 h, filter, extract, concentrate under reduced pressure, and then pass through column chromatography to obtain the compound shown in Formula IV

[0060]

[0061] S4. Mix 3 g of the compound shown in Formula IV in Step S3 with 10 g of the terminal acyl chloride group-containing liquid fluororubber in Step S1, add 150 mL of tetrahydrofuran and 1.4 g of sodium bicarbonate, stir at a constant temperature at room temperature for 12 h, filter after the reaction ends, add petroleum ether to the filtrate until no precipitate is produced, and filter to obtain the functional end-group modified liquid fluororubber.

[0062] Preparation Example 3

[0063] A preparation method of a functional end-group modified liquid fluororubber, comprising the following steps:

[0064] S1. Mix 10 g of liquid carboxyl-terminated fluororubber with 100 mL of tetrahydrofuran and dissolve, add 3 g of pyridine and 5 g of thionyl chloride, raise the temperature to 65 °C and stir for 6 h, evaporate the solvent under reduced pressure, wash, and obtain the terminal acyl chloride group-containing liquid fluororubber for standby;

[0065] S2. At -3°C, mix 3 g of cyanuric chloride with 1.2 g of 1,3-propanediamine, add them to 38 mL of dichloromethane, cool to -7°C, add 1.6 g of sodium bicarbonate, stir at a constant temperature for 2 h, filter, extract, concentrate under reduced pressure, and then perform column chromatography to obtain the compound shown in Formula V.

[0066]

[0067] S3. Mix 3 g of the compound shown in Formula V obtained in Step S2 with 10 g of the terminal acyl chloride group-containing liquid fluororubber obtained in Step S1, add them to 150 mL of tetrahydrofuran and 1.4 g of sodium bicarbonate, stir at a constant temperature at room temperature for 12 h, then add 6 g of 3-triethoxysilyl-1-propylamine, continue to stir for 2 h. After the reaction is completed, filter. Add petroleum ether to the filtrate until no precipitate is produced, and then filter to obtain the functional end-group modified liquid fluororubber.

[0068] Preparation Example 4

[0069] A preparation method of a functional end-group modified liquid fluororubber, comprising the following steps:

[0070] S1. Dissolve 10 g of liquid carboxyl-terminated fluororubber in 100 mL of tetrahydrofuran, add 3 g of pyridine and 5 g of thionyl chloride, heat to 65°C and stir for 6 h, evaporate the solvent under reduced pressure, wash, and obtain the terminal acyl chloride group-containing liquid fluororubber for standby.

[0071] S2. At -3°C, mix 3 g of 3,5-dichloroaniline with 35 mL of chloroform, add 1.75 g of 3-methyl-3-buten-1-ol and 2.3 g of sodium bicarbonate thereto, control the temperature at 3°C and stir at a constant temperature for 3 h, filter, extract, concentrate under reduced pressure, and then perform column chromatography to obtain the compound shown in Formula VI.

[0072]

[0073] S3. Mix 3 g of the compound shown in Formula II obtained in Step S3 with 10 g of the terminal acyl chloride group-containing liquid fluororubber obtained in Step S1, add them to 150 mL of tetrahydrofuran and 1.4 g of sodium bicarbonate, stir at a constant temperature at room temperature for 12 h, then add 3 g of 3-triethoxysilyl-1-propylamine, continue to stir for 2 h. After the reaction is completed, filter. Add petroleum ether to the filtrate until no precipitate is produced, and then filter to obtain the functional end-group modified liquid fluororubber.

[0074] Example 1

[0075] A composite liquid fluororubber, comprising graphene oxide and a functional end-group modified liquid fluororubber with a mass ratio of 0.15:1.

[0076] Among them, the functional end-group modified liquid fluororubber is prepared from Preparation Example 1, and its number-average molecular weight is 5367.

[0077] The preparation method of the composite liquid fluororubber includes the following steps: mixing and stirring the functional end-group modified liquid fluororubber and graphene oxide at room temperature to disperse them, thus obtaining the composite liquid fluororubber.

[0078] Example 2

[0079] A composite liquid fluororubber includes graphene oxide and functional end-group modified liquid fluororubber with a mass ratio of 0.05:1.

[0080] Among them, the functional end-group modified liquid fluororubber is prepared from Preparation Example 1, and its number-average molecular weight is 5683.

[0081] The preparation method of the composite liquid fluororubber includes the following steps: mixing and stirring the functional end-group modified liquid fluororubber and graphene oxide at room temperature to disperse them, thus obtaining the composite liquid fluororubber.

[0082] Example 3

[0083] A composite liquid fluororubber includes graphene oxide and functional end-group modified liquid fluororubber with a mass ratio of 0.25:1.

[0084] Among them, the functional end-group modified liquid fluororubber is prepared from Preparation Example 1, and its number-average molecular weight is 6154.

[0085] The preparation method of the composite liquid fluororubber includes the following steps: mixing and stirring the functional end-group modified liquid fluororubber and graphene oxide at room temperature to disperse them, thus obtaining the composite liquid fluororubber.

[0086] Example 4

[0087] A composite liquid fluororubber and its preparation method, the specific implementation manner is the same as that of Example 1, the difference is that the functional end-group modified liquid fluororubber is prepared from Preparation Example 2.

[0088] Example 5

[0089] A composite liquid fluororubber and its preparation method, the specific implementation manner is the same as that of Example 1, the difference is that the functional end-group modified liquid fluororubber is prepared from Preparation Example 4.

[0090] Example 6

[0091] A composite liquid fluororubber and its preparation method, the specific implementation manner is the same as that of Example 1, the difference is that the number-average molecular weight of the functional end-group modified liquid fluororubber is 8897.

[0092] Comparative Example 1

[0093] A composite liquid fluororubber and its preparation method. The specific implementation manner is the same as that of Example 1, except that the functional end-group modified liquid fluororubber is prepared by Preparation Example 3.

[0094] Comparative Example 2

[0095] A composite liquid fluororubber and its preparation method. The specific implementation manner is the same as that of Example 1, except that an equal mass of liquid carboxyl-terminated fluororubber is used instead of the functional end-group modified liquid fluororubber.

[0096] Performance test:

[0097] (1) Tensile property: The composite liquid fluororubbers of Examples 1 to 6 and Comparative Example 1 were cured by ultraviolet light (wavelength 400 nm) for 10 min to obtain specimens with a thickness of 4 mm. The composite liquid fluororubber of Comparative Example 2 was mixed with HDI at a mass ratio of 1:0.05 and cured at 80 °C for 4 h to obtain specimens with a thickness of 4 mm, and then tested according to the GB / T 528-2009 standard;

[0098] (2) Flame retardant property: Tested according to the UL94-2017 standard;

[0099] (3) Dispersibility: Observe whether sedimentation occurs after standing at room temperature for 30 days.

[0100] The composite liquid fluororubbers of each example and comparative example were tested according to the above method, and the results are shown in Table 1.

[0101] Table 1

[0102]

[0103] According to the data in Table 1, it can be seen that the composite liquid fluororubber prepared in Examples 1 to 3 has high tensile strength, good flame retardant performance, uniform dispersion of each component, and good stability; compared with Example 1, in Example 4, due to the change in the molar ratio of cyanuric chloride and 3-methyl-3-buten-1-ol, the dispersibility of the functional end-group modified liquid fluororubber and graphene oxide becomes poor, and there is no Si element in it, so the effect of synergistic flame retardancy of multiple elements cannot be formed; in Example 5, due to the use of 3,5-dichloroaniline instead of cyanuric chloride, the flame retardant performance of the composite liquid fluororubber decreases; in Example 6, due to the change in the number-average molecular weight of the functional end-group modified liquid fluororubber, the viscosity of the composite liquid fluororubber increases and the fluidity decreases, and graphene oxide cannot be effectively dispersed, resulting in turbidity of the system and agglomeration of graphene oxide; in Comparative Example 1, since the functional end-group modified liquid fluororubber does not contain double bonds, on the one hand, the composite liquid fluororubber cannot be cured by ultraviolet light curing, but instead uses the conventional isocyanate method for curing, and the tensile strength decreases after curing; in Comparative Example 2, due to the use of liquid carboxyl-terminated fluororubber instead of the functional end-group modified liquid fluororubber, the dispersibility of graphene oxide in it becomes poor, and the tensile performance and flame retardant performance of the composite liquid fluororubber both decrease.

[0104] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A composite liquid fluororubber, characterized in that It comprises the following components: graphene oxide and functional end-group modified liquid fluororubber; the end group of the functional end-group modified liquid fluororubber must contain an unsaturated double bond.

2. The composite liquid fluororubber according to claim 1, wherein The mass ratio of the graphene oxide to the functional end-group modified liquid fluororubber is (0.05 - 0.25):

1.

3. The composite liquid fluororubber according to claim 1, characterized in that, The number-average molecular weight of the functional end-group modified liquid fluororubber is 5000 - 8000.

4. The composite liquid fluororubber according to claim 1, characterized in that, The preparation method of the functional end-group modified liquid fluororubber comprises the following steps: S1. Mix and dissolve the liquid carboxyl-terminated fluororubber with a first solvent, add pyridine and thionyl chloride, heat to 60 - 70 °C and stir for 5 - 7 h, evaporate the solvent under reduced pressure, wash, and obtain the acyl chloride-terminated liquid fluororubber for standby. S2. At -5 - 0 °C, mix cyanuric chloride and a second solvent, add 3-methyl-3-buten-1-ol and an acid-binding agent thereto, control the temperature at 0 - 5 °C and stir at a constant temperature for 2 - 4 h, filter, extract, concentrate under reduced pressure, and then perform column chromatography to obtain the compound shown in Formula I. S3. Mix the compound shown in Formula I in Step S2 with 1,3-propanediamine and add a third solvent, cool to -10 - -5 °C, add an acid-binding agent and stir at a constant temperature for 1 - 3 h, filter, extract, concentrate under reduced pressure, and then perform column chromatography to obtain the compound shown in Formula II. S4. Mix the compound shown in Formula II in Step S3 with the acyl chloride-terminated liquid fluororubber in Step S1, add a first solvent and an acid-binding agent, stir at a constant temperature at room temperature for 10 - 14 h, then add 3-triethoxysilyl-1-propylamine, continue to stir for 1 - 3 h, after the reaction ends, filter, add petroleum ether to the filtrate until no precipitate is produced, and filter to obtain the functional end-group modified liquid fluororubber.

5. The composite liquid fluororubber according to claim 4, characterized in that, In Step S2, the molar ratio of the cyanuric chloride to the 3-methyl-3-buten-1-ol is 1:(1 - 1.2).

6. The composite liquid fluororubber according to claim 4, wherein In Step S3, the molar ratio of the compound shown in Formula I to the 1,3-propanediamine is 1:(1 - 1.2).

7. The composite liquid fluororubber according to claim 4, characterized in that, In Step S4, the mass ratio of the compound shown in Formula II to the acyl chloride-terminated liquid fluororubber is (0.1 - 0.5):

1.

8. The composite liquid fluororubber according to claim 4, wherein In Step S4, the molar ratio of the compound shown in Formula II to the 3-triethoxysilyl-1-propylamine is 1:(1 - 1.3).

9. A method for preparing the composite liquid fluororubber according to any one of claims 1 to 8, characterized in that, It comprises the following steps: Mix and stir the functional end-group modified liquid fluororubber and the graphene oxide at room temperature to disperse them, and thus obtain the composite liquid fluororubber.

10. The application of the composite liquid fluororubber according to any one of claims 1 - 8 in a sealant.

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