CN115109361A - A kind of high temperature resistant gasket based on tetrafluoroethylene and preparation method thereof - Google Patents

Abstract

The invention relates to a high temperature resistant gasket based on tetrafluoroethylene and a preparation method thereof, belonging to the technical field of polymer materials. The tetrafluoroethylene-based high temperature resistant gasket includes the following raw materials: polytetrafluoroethylene resin powder, hyperbranched polyimide powder and modified boron nitride powder. The hyperbranched polyimide powder is a double bond-terminated hyperbranched polyimide, which has good compatibility with polytetrafluoroethylene, and the end-capped double bond can occur with the double bond in polytetrafluoroethylene. Cross-linking, combined with its hyperbranched structure, promotes the formation of an interpenetrating network structure in the gasket material, and the compression creep resistance and resilience of the compression gasket; the modified boron nitride powder is surface-grafted with modifiers The molecular chain of the obtained gasket, namely, contains siloxane chain, polyacrylate chain and double bond, so that a uniform and stable heat conduction network is formed in the obtained gasket, and the thermal conductivity of the gasket is improved.

Description

A kind of high temperature resistant gasket based on tetrafluoroethylene and preparation method thereof

technical field

The invention belongs to the technical field of polymer materials, and in particular relates to a high temperature resistant gasket based on tetrafluoroethylene and a preparation method thereof.

Background technique

PTFE has high chemical stability, excellent high and low temperature resistance, outstanding non-stickiness, good lubricity, strong insulation resistance, aging resistance, minimal water absorption, etc. It is widely used In the fields of chemistry, industry, medicine, etc. However, ordinary PTFE gasket products have the disadvantages of low thermal conductivity, poor compression creep resistance, and poor resilience. When subjected to long-term load and cyclic action, the dimensional stability is poor, which seriously restricts its performance. develop. Therefore, improving the thermal conductivity, compressive creep resistance, and resilience of PTFE has always been the focus of PTFE material research.

For example, Chinese patent CN202111166144.0 discloses a method for making modified polytetrafluoroethylene sealing gasket and the sealing gasket, wherein the modified polytetrafluoroethylene sealing gasket includes suspended polytetrafluoroethylene resin, molybdenum disulfide, carbon fiber, polytetrafluoroethylene Phenyl sulfide and alumina are used to fill and modify polytetrafluoroethylene with reinforcing fillers to improve the creep relaxation resistance of polytetrafluoroethylene gaskets, thereby improving and overcoming the defects of pure polytetrafluoroethylene. However, the compatibility between the reinforcing filler and the polytetrafluoroethylene material in this patent is poor, which increases the processing difficulty of the modified polytetrafluoroethylene sealing gasket.

Therefore, the present invention provides a high temperature resistant gasket based on tetrafluoroethylene and a preparation method thereof.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a high temperature resistant gasket based on tetrafluoroethylene and a preparation method thereof, so as to solve the problems of low thermal conductivity, poor compression creep resistance and poor resilience of the existing polytetrafluoroethylene gasket.

The object of the present invention can be realized through the following technical solutions:

A high temperature resistant gasket based on tetrafluoroethylene, comprising the following raw materials in parts by weight: 15-25 parts of polytetrafluoroethylene resin powder, 4-9.5 parts of hyperbranched polyimide powder, 1-10 parts of modified boron nitride powder 2.7 servings.

Further, described hyperbranched polyimide powder comprises the following steps to make:

A1. After mixing 1,6-hexanediamine and N-methylpyrrolidone evenly, then under nitrogen protection, at 60-70°C, slowly add the N-methylpyrrolidone solution of trimellitic anhydride dropwise. After the dropwise addition is complete, continue to stir the reaction 2-3h, then add toluene, heat up to 140-150℃, dehydrate under reflux for 6h, steam out toluene, cool, pour into cold water for precipitation, wash with water, recrystallize, and dry to obtain imide dicarboxylic acid, Wherein, the molar ratio of 1,6-hexanediamine and trimellitic anhydride is 1:2;

A2. After mixing pentaerythritol, anhydrous aluminum chloride and ethyl acetate, under nitrogen protection, heat to 60°C, then slowly add 3-chloropropyltrimethoxysilane dropwise, after adding, stir for 20-30min, and finally Heating to reflux, maintaining the reflux reaction for 3-5h, filtering, and rotary-evaporating under reduced pressure to obtain the grafted siloxane triol, wherein the molar ratio of pentaerythritol and 3-chloropropyltrimethoxysilane is 1:0.85- 0.98;

In above-mentioned reaction, utilize the substitution reaction of hydroxyl in pentaerythritol and chlorine in 3-chloropropyltrimethoxysilane to obtain grafted siloxane triol;

A3. Mix imide dicarboxylic acid, grafted siloxane triol, p-toluenesulfonic acid and dimethylacetamide evenly, then use condensed water to control the temperature of the reaction system to 90-100 ° C, and stir until anhydrous Generated, reduced to 60°C under reduced pressure and rotary-evaporated, added tetrahydrofuran solution containing methacrylic acid and p-toluenesulfonic acid, heated to reflux, and reacted for 2-3 hours, stopped the reaction, reduced to 30°C under reduced pressure and rotary-evaporated, and the resultant was ball-milled , to obtain hyperbranched polyimide powder, wherein the mass ratio of imide dicarboxylic acid, grafted siloxane triol, and methacrylic acid is 11:18:7.2-7.5. The mass is 1-3% of the total mass of imide dicarboxylic acid and grafted siloxane triol, and the mass of p-toluenesulfonic acid added again is 5-7% of the mass of methacrylic acid.

In the above-mentioned reaction, the condensation polymerization of imide dicarboxylic acid and grafted siloxane triol was used first to obtain hyperbranched polyimide, and the hyperbranched polyimide was obtained by using imine dicarboxylic acid, grafted siloxane triol The control of the quality of the alcohol makes the hydroxyl end capped, and then the capped hydroxyl group reacts with the carboxyl group of methacrylic acid to obtain hyperbranched polyimide powder. It can be seen that the hyperbranched polyimide powder is a double bond end capped hyperbranched Polyimide has the characteristics of low viscosity, large steric hindrance effect and easy processing. At the same time, its monomer imide dicarboxylic acid is obtained by the reaction of 1,6-hexanediamine and trimellitic anhydride. The chain is composed of rigid groups of benzene ring and imide ring, which has a toughening effect.

Further, the modified boron nitride powder comprises the following steps:

Add the silicon nitride powder to the ethyl acetate solution, and ultrasonically disperse it for 15-25min, then heat to 70-75°C under stirring (and control the temperature with condensed water to maintain it at 70-75°C), then add modifier and Triethylamine, nitrogen protection, stirring and reacting for 3-4 hours, cooling to room temperature, suction filtration, drying, and ball milling to obtain modified boron nitride powder, among which, silicon nitride powder, ethyl acetate solution, modifier , the dosage ratio of triethylamine is 1g:15-29mL:0.2-0.5g:0.05-0.1g.

In the above reaction, the epoxy group in the modifier is used to react with the hydroxyl group on the surface of the silicon nitride powder, so that the molecular chain of the modifier is grafted on the surface of the silicon nitride powder, that is, containing siloxane chain, polymer Acrylate chain and double bond, the use of siloxane chain to make the modified boron nitride powder good dispersibility in the collective material, the use of polyacrylate chain to give the modified boron nitride powder good adhesion, the use of double bond The modified boron nitride powder is given reactivity, so that the modified boron nitride powder and the polytetrafluoroethylene resin are reversely cross-linked.

Further, the modifier is that butyl acrylate, glycidyl methacrylate and KH-570 are mixed in an organic solvent according to a mass ratio of 10:5-8:1-3 under the action of an initiator and a chain transfer agent. Formed by polymerization at 55-80°C.

Further, the concrete preparation method of described modifier comprises the following steps:

Under nitrogen protection, the ethyl acetate was heated to 50-80°C, and then butyl acrylate, glycidyl methacrylate, KH-570, initiator AIBN and chain transfer agent dodecyl sulfide were slowly added dropwise. The ethyl acetate solution of alcohol is added dropwise, heated and refluxed for 1-2 hours, then the initiator AIBN is added, stirred for 1-1.5 hours, the reaction is stopped, the reaction is stopped, and the reaction is reduced to 40 °C under reduced pressure and rotary evaporation to obtain a modifier, which is used to initiate The total mass of AIBN added is 1-3% of the total mass of butyl acrylate, glycidyl methacrylate and KH-570, and the mass of AIBN added for the first time is two-thirds of the mass of total initiator AIBN added, The added mass of chain transfer agent dodecyl mercaptan is 6% of the total mass of butyl acrylate, glycidyl methacrylate and KH-570.

The preparation method of the high temperature resistant gasket based on tetrafluoroethylene comprises the following steps:

After the polytetrafluoroethylene resin powder, hyperbranched polyimide powder and modified boron nitride powder are stirred and mixed uniformly, the mixed powder is obtained, and the mixed powder is poured into the mold, and is formed by exhausting and cold pressing. After sintering again, a crude product is obtained, and the crude product is trimmed and polished to obtain a high temperature resistant gasket based on tetrafluoroethylene, wherein the stirring speed is 2000-2500r/min; cold pressing conditions: the pressure is 20-40MPa, and the pressure holding time is 10-15min; sintering conditions: the heating rate is 40-60°C/h, the sintering temperature is 360-370°C, and the sintering time is 3-4h.

Beneficial effects of the present invention:

In order to solve the problems mentioned in the background art, the present invention introduces hyperbranched polyimide powder and modified boron nitride powder into the polytetrafluoroethylene material to obtain good thermal conductivity, good compression creep resistance and recovery. High temperature resistant gasket with good elasticity. The mechanism is explained as follows:

The hyperbranched polyimide powder is a double bond-terminated hyperbranched polyimide with low viscosity. First, its molecular structure contains a large amount of siloxane, which gives it good compatibility with polytetrafluoroethylene. Compatibility; Second, the monomer imide dicarboxylic acid that constitutes it is obtained by the reaction of 1,6-hexanediamine and trimellitic anhydride, which is composed of long soft alkyl chains and rigid groups of benzene rings and imide rings. It has the characteristics of an elastomer and has a toughening effect; thirdly, the holes in its hyperbranched molecular structure help the material absorb the impact energy generated when it is impacted, and further play a toughening role; fourthly, its sealing The double bond at the end can be cross-linked with the double bond in PTFE, and with its hyperbranched structure, it promotes the formation of an interpenetrating network structure in the gasket material and further improves the toughness of the gasket (the cross-linked phase of this hyperbranched structure). Compared with the cross-linking of linear molecular chains, because of its large steric hindrance, it will not cross-link excessively, sacrificing the elasticity of the material, so that the material is extremely hard and has the characteristics of moderate cross-linking, making the material both elasticity and hardness. Therefore, the introduction of hyperbranched polyimide powder solves the problems of poor compressive creep resistance and poor resilience of PTFE gaskets;

The modified boron nitride powder is a molecular chain with a modifier grafted on the surface, that is, it contains a siloxane chain, a polyacrylate chain and a double bond. The siloxane chain is used to make the modified boron nitride powder in the matrix material. The good dispersibility in the material promotes the formation of a uniform thermal network in the obtained gasket; the flexibility and adhesion of the polyacrylate chain are used to give the modified boron nitride powder good adhesion, so that the polytetrafluoroethylene in the gasket is The vinyl fluoride powder, hyperbranched polyimide powder and modified boron nitride powder form a compact body during the tableting process, which improves the processing performance of the gasket; the reactivity of the modified boron nitride powder is given by the double bond, so that the The modified boron nitride powder is inserted into the interpenetrating network in the matrix material to improve the stability of the heat conduction network in the gasket;

To sum up, the tetrafluoroethylene-based high temperature gasket obtained by the present invention has good thermal conductivity, compression creep resistance and resilience.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

Preparation of hyperbranched polyimide powder:

A1. After mixing 0.1mol 1,6-hexanediamine and 50mL N-methylpyrrolidone evenly, then under nitrogen protection, at 60°C, slowly add 70mL N-methylpyrrolidone solution containing 0.2mol trimellitic anhydride dropwise, and add dropwise completely After that, continue stirring for 3 hours, then add 100 mL of toluene, heat up to 140°C, dehydrate under reflux for 6 hours, steam out toluene, cool, pour into cold water for precipitation, wash with water, recrystallize, and dry to obtain imide dicarboxylate acid;

A2. After mixing 0.1mol pentaerythritol, 0.1mol anhydrous aluminum chloride and 60mL ethyl acetate, under nitrogen protection, heat to 60°C, then slowly add 0.85mol 3-chloropropyltrimethoxysilane dropwise, after adding , stirred for 20min, finally heated to reflux, and maintained the reflux reaction for 3h, filtered, and rotary-evaporated under reduced pressure to obtain the grafted siloxane triol;

A3. Mix 11g of imide dicarboxylic acid, 18g of grafted siloxane triol, 0.3g of p-toluenesulfonic acid and 60mL of dimethylacetamide evenly, then use condensed water to control the temperature of the reaction system to be 90°C, stir Until no water was produced, it was reduced to 60°C under reduced pressure and rotary-evaporated, and a tetrahydrofuran solution containing 7.2g of methacrylic acid and 0.36g of p-toluenesulfonic acid was added, heated to reflux, and reacted for 2h, the reaction was stopped, and the reaction was reduced to 30°C under reduced pressure and rotated. Steam, and the resultant is ball-milled to obtain hyperbranched polyimide powder.

Example 2

Preparation of hyperbranched polyimide powder:

A1. After mixing 0.1mol 1,6-hexanediamine and 50mL N-methylpyrrolidone evenly, then under nitrogen protection, at 70°C, slowly add 70mL N-methylpyrrolidone solution containing 0.2mol trimellitic anhydride dropwise, and add dropwise completely Then, continue stirring for 2 hours, then add 100 mL of toluene, raise the temperature to 150°C, perform reflux dehydration reaction for 6 hours, evaporate the toluene, cool, pour into cold water for precipitation, wash with water, recrystallize, and dry to obtain imide dicarboxylate acid;

A2. After mixing 0.1mol pentaerythritol, 0.1mol anhydrous aluminum chloride and 60mL ethyl acetate, under nitrogen protection, heat to 60°C, then slowly add 0.98mol 3-chloropropyltrimethoxysilane dropwise, after adding , stirred for 30min, finally heated to reflux, and maintained the reflux reaction for 5h, filtered, and rotary-evaporated under reduced pressure to obtain the grafted siloxane triol;

A3. Mix 11 g of imide dicarboxylic acid, 18 g of grafted siloxane triol, 0.6 g of p-toluenesulfonic acid and 60 mL of dimethylacetamide, and then use condensed water to control the temperature of the reaction system to be 100 ° C, stir Until no water was produced, it was reduced to 60°C under reduced pressure and rotary evaporated, and a tetrahydrofuran solution containing 7.5g of methacrylic acid and 0.37g of p-toluenesulfonic acid was added, heated to reflux, and reacted for 3h, the reaction was stopped, and the reaction was stopped and reduced to 30°C under reduced pressure and rotated. Steam, and the resultant is ball-milled to obtain hyperbranched polyimide powder.

Example 3

Preparation of modified boron nitride powder:

Add 10g of silicon nitride powder to 150mL of ethyl acetate solution, and ultrasonically disperse for 15min, then heat to 70°C under stirring (and use condensed water to control the temperature to maintain at 70°C), then add 2g of modifier and 0.5g of trisulfite. Ethylamine was protected by nitrogen, and stirred for 4 hours, cooled to room temperature, suction filtered, dried, and ball-milled to obtain modified boron nitride powder;

The specific preparation method of the modifier comprises the following steps:

Under nitrogen protection, the ethyl acetate was heated to 50°C, and then 10g of butyl acrylate, 5g of glycidyl methacrylate, 1g of KH-570, 0.11g of initiator AIBN and 0.96g of chain transfer agent were slowly added dropwise. The ethyl acetate solution of dialkyl mercaptan was added dropwise, heated and refluxed for 2 hours, then added with 0.05g of AIBN as an initiator, stirred for 1 hour, stopped the reaction, reduced to 40°C under reduced pressure and rotary evaporated to obtain the modifier.

Example 4

Preparation of modified boron nitride powder:

Add 10g of silicon nitride powder to 290mL of ethyl acetate solution, and ultrasonically disperse it for 25min, then heat to 75°C under stirring (and control the temperature to maintain at 75°C with condensed water), then add 0.5g modifier and 0.1g Triethylamine, nitrogen protection, and stirring reaction for 3h, cooled to room temperature, suction filtration, drying, ball milling, to obtain modified boron nitride powder;

The specific preparation method of the modifier comprises the following steps:

Under nitrogen protection, the ethyl acetate was heated to 80°C, and then 10g of butyl acrylate, 8g of glycidyl methacrylate, 3g of KH-570, 0.14g of initiator AIBN and 1.26g of chain transfer agent were slowly added dropwise. The ethyl acetate solution of dialkyl mercaptan was added dropwise, heated under reflux for 1 hour, and then added 0.07 g of AIBN as an initiator, stirred for 1 hour, stopped the reaction, and then reduced to 40°C under reduced pressure and rotary evaporation to obtain the modifier.

Example 5

A preparation method of a high temperature resistant gasket based on tetrafluoroethylene:

Step 1, including the following raw materials by weight: 15 parts of polytetrafluoroethylene resin powder, 4 parts of hyperbranched polyimide powder prepared in Example 1, and 1 part of modified boron nitride powder prepared in Example 3;

Step 2: After stirring and mixing the polytetrafluoroethylene resin powder, the hyperbranched polyimide powder and the modified boron nitride powder uniformly, a mixed powder is obtained. Press molding, and then sintering to obtain a crude product, which is trimmed and polished to obtain a high temperature resistant gasket based on tetrafluoroethylene, wherein the stirring speed is 2000-2500r/min; cold pressing conditions: the pressure is 20MPa, the pressure holding time 10min; sintering conditions: the heating rate is 40°C/h, the sintering temperature is 360-370°C, and the sintering time is 3h.

Example 6

A preparation method of a high temperature resistant gasket based on tetrafluoroethylene:

Step 1, including the following raw materials by weight: 20 parts of polytetrafluoroethylene resin powder, 7 parts of hyperbranched polyimide powder prepared in Example 2, and 1.5 parts of modified boron nitride powder prepared in Example 4;

Step 2: After stirring and mixing the polytetrafluoroethylene resin powder, the hyperbranched polyimide powder and the modified boron nitride powder uniformly, a mixed powder is obtained. Press molding, and then sintering to obtain crude products. The crude products are trimmed and polished to obtain high temperature resistant gaskets based on tetrafluoroethylene, wherein the stirring speed is 2000-2500r/min; cold pressing conditions: pressure is 40MPa, pressure holding time 15min; sintering conditions: the heating rate is 60°C/h, the sintering temperature is 360-370°C, and the sintering time is 4h.

Example 7

A preparation method of a high temperature resistant gasket based on tetrafluoroethylene:

Step 1, including the following raw materials by weight: 25 parts of polytetrafluoroethylene resin powder, 9.5 parts of hyperbranched polyimide powder prepared in Example 1, and 2.7 parts of modified boron nitride powder prepared in Example 3;

Step 2: After stirring and mixing the polytetrafluoroethylene resin powder, the hyperbranched polyimide powder and the modified boron nitride powder uniformly, a mixed powder is obtained. Press molding, and then sintering to obtain crude products. The crude products are trimmed and polished to obtain high temperature resistant gaskets based on tetrafluoroethylene, wherein the stirring speed is 2000-2500r/min; cold pressing conditions: pressure is 40MPa, pressure holding time 15min; sintering conditions: the heating rate is 60°C/h, the sintering temperature is 360-370°C, and the sintering time is 4h.

Comparative Example 1

A preparation method of a tetrafluoroethylene-based high temperature gasket: compared with Example 5, the hyperbranched polyimide powder was replaced with the hyperbranched polyimide powder prepared by the following steps of equal parts, and the remaining same;

A1. After mixing 0.1mol 1,6-hexanediamine and 50mL N-methylpyrrolidone evenly, then under nitrogen protection, at 60°C, slowly add 70mL N-methylpyrrolidone solution containing 0.2mol trimellitic anhydride dropwise, and add dropwise completely After the reaction was continued for 2 hours, 100 mL of toluene was added, the temperature was raised to 140 °C, and the dehydration reaction was performed under reflux for 6 hours. The toluene was evaporated, cooled, poured into cold water for precipitation, washed with water, recrystallized, and dried to obtain imide dicarboxylate. acid;

A2. Mix 11g of imide dicarboxylic acid, 18g of glycerol, 0.29g of p-toluenesulfonic acid and 60mL of dimethylacetamide evenly, then use condensed water to control the temperature of the reaction system to be 90°C, and stir until no water is produced. , reduced to 60 ℃ under reduced pressure rotary evaporation, added a tetrahydrofuran solution containing 7.2 g methacrylic acid and 0.36 g p-toluenesulfonic acid, heated to reflux, and reacted for 2 h, stopped the reaction, reduced to 30 ℃ under reduced pressure rotary evaporation, the resultant Ball milling to obtain hyperbranched polyimide powder.

Comparative Example 2

A preparation method of a high temperature resistant gasket based on tetrafluoroethylene: compared with Example 6, the modified boron nitride powder was replaced with an equal amount of silicon nitride powder, and the rest were the same.

Example 8

The gaskets obtained in Examples 5-7 and Comparative Examples 1-2 were subjected to the following performance tests:

Tensile properties: refer to ASTM D638 test, the sample is the V-type sample specified in the standard, and the tensile speed is 20mm/min;

Compression resilience: refer to ASTM F36 test;

Creep relaxation test: refer to ASTM F38-B test;

Thermal conductivity: refer to ASTM D5470 test;

The above test data are shown in Table 1.

Table 1

It can be seen from the data in Table 1 that the thermal conductivity, compressive resilience, and creep relaxation resistance of the gaskets obtained in Examples 5-7 are better than those obtained in Comparative Examples 1-2.

In the description of the specification, description with reference to the terms "one embodiment," "example," "specific example," etc. means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one of the present invention examples or examples. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above contents are only examples and descriptions of the present invention, and those skilled in the art can make various modifications or supplements to the described specific embodiments or replace them in similar ways, as long as they do not deviate from the invention or exceed the present rights The scope defined by the claims shall all belong to the protection scope of the present invention.

Claims (9)

1. a high temperature resistant gasket based on tetrafluoroethylene, is characterized in that: comprise the raw material of following parts by weight: 15-25 parts of polytetrafluoroethylene resin powder, 4-9.5 parts of hyperbranched polyimide powder, modified 1-2.7 parts of boron nitride powder; Described hyperbranched polyimide powder comprises the following steps to make: Mix imide dicarboxylic acid, grafted siloxane triol, p-toluenesulfonic acid and dimethylacetamide evenly, then use condensed water to control the temperature of the reaction system to be 90-100 ° C, stir until no water is produced, Rotary evaporation under reduced pressure, adding tetrahydrofuran solution containing methacrylic acid and p-toluenesulfonic acid, heating to reflux, and reacting for 2-3 hours, stopping the reaction, cooling under reduced pressure, rotary evaporation, and ball milling to obtain hyperbranched polyimide powder. 2. a kind of high temperature resistant gasket based on tetrafluoroethylene according to claim 1, is characterized in that: the mass ratio of described imide dicarboxylic acid, grafted siloxane triol, methacrylic acid is 11:18:7.2-7.5, the mass of p-toluenesulfonic acid added for the first time is 1-3% of the total mass of imide dicarboxylic acid and grafted siloxane triol, and the mass of p-toluenesulfonic acid added again is methyl benzene. 5-7% of the mass of the base acrylic acid. 3. a kind of high temperature resistant gasket based on tetrafluoroethylene according to claim 1 is characterized in that: described grafted siloxane triol comprises the following steps to make: After mixing pentaerythritol, anhydrous aluminum chloride and ethyl acetate, under nitrogen protection, heat to 60-65 ℃, then slowly add 3-chloropropyltrimethoxysilane dropwise, after adding, stir for 20-30min, and finally Heating to reflux, maintaining the reflux reaction for 3-5h, filtering, and rotary-evaporating under reduced pressure to obtain the grafted siloxane triol. 4 . The tetrafluoroethylene-based high temperature gasket according to claim 3 , wherein the molar ratio of the pentaerythritol and 3-chloropropyltrimethoxysilane is 1:0.85-0.98. 5 . 5. A tetrafluoroethylene-based high temperature gasket according to claim 1, wherein the modified boron nitride powder comprises the following steps: Add the silicon nitride powder to the ethyl acetate solution, and ultrasonically disperse it for 15-25min, then heat to 70-75°C under stirring, then add the modifier and triethylamine, pass nitrogen protection, and stir to react for 3- 4h, cooled to room temperature, suction filtered, dried, and ball-milled to obtain modified boron nitride powder. 6. a kind of high temperature resistant gasket based on tetrafluoroethylene according to claim 5, is characterized in that: the consumption ratio of described silicon nitride powder, ethyl acetate solution, modifier, triethylamine is 1g : 15-29mL: 0.2-0.5g: 0.05-0.1g. 7. a kind of high temperature resistant gasket based on tetrafluoroethylene according to claim 5, is characterized in that: described modifier is butyl acrylate, glycidyl methacrylate and KH-570 according to mass ratio 10 :5-8:1-3 is mixed in organic solvent and formed by polymerization reaction under the action of initiator and chain transfer agent. 8 . The high temperature resistant gasket based on tetrafluoroethylene according to claim 7 , wherein the temperature of the polymerization reaction is 55-80° C. 9 . 9. the preparation method of a kind of high temperature resistant gasket based on tetrafluoroethylene according to claim 1, is characterized in that: comprise the following steps: After the polytetrafluoroethylene resin powder, hyperbranched polyimide powder and modified boron nitride powder are stirred and mixed uniformly, the mixed powder is obtained, and the mixed powder is poured into the mold, and is formed by exhausting and cold pressing. After sintering again, a crude product is obtained, and the crude product is trimmed and polished to obtain a high temperature resistant gasket based on tetrafluoroethylene.