CN115109361B - High-temperature-resistant gasket based on tetrafluoroethylene and preparation method thereof - Google Patents
High-temperature-resistant gasket based on tetrafluoroethylene and preparation method thereof Download PDFInfo
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- CN115109361B CN115109361B CN202210786330.2A CN202210786330A CN115109361B CN 115109361 B CN115109361 B CN 115109361B CN 202210786330 A CN202210786330 A CN 202210786330A CN 115109361 B CN115109361 B CN 115109361B
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
- C08L27/02—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L27/12—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C08L27/18—Homopolymers or copolymers or tetrafluoroethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/38—Boron-containing compounds
- C08K2003/382—Boron-containing compounds and nitrogen
- C08K2003/385—Binary compounds of nitrogen with boron
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention relates to a high-temperature-resistant gasket based on tetrafluoroethylene and a preparation method thereof, and belongs to the technical field of high polymer materials. The tetrafluoroethylene-based high-temperature-resistant gasket comprises the following raw materials: polytetrafluoroethylene resin powder, hyperbranched polyimide powder and modified boron nitride powder. The hyperbranched polyimide powder is double bond terminated hyperbranched polyimide, has good compatibility with polytetrafluoroethylene, and the terminated double bond can be crosslinked with the double bond in the polytetrafluoroethylene, and is matched with the hyperbranched structure to promote the formation of an interpenetrating network structure in the gasket material, and the compression-resistant creep property and rebound resilience of the compression-resistant gasket; the modified boron nitride powder is a molecular chain with a modifier grafted on the surface, namely, the modified boron nitride powder contains a siloxane chain, a polyacrylate chain and double bonds, so that a uniform and stable heat conducting net is formed in the obtained gasket, and the heat conductivity of the gasket is improved.
Description
Technical Field
The invention belongs to the technical field of high polymer materials, and particularly relates to a tetrafluoroethylene-based high-temperature-resistant gasket and a preparation method thereof.
Background
Polytetrafluoroethylene has high chemical stability, excellent high and low temperature resistance, outstanding non-tackiness, good lubricity, extremely strong insulation resistance, aging resistance, extremely small water absorption and the like, and is widely applied to the fields of chemistry, industry, medicine and the like. However, the conventional polytetrafluoroethylene gasket product has the defects of low heat conductivity, poor compressive creep resistance and poor rebound resilience, and has poor dimensional stability when subjected to long-term action and cyclic action of load, thereby severely restricting the development of the gasket product. Therefore, the improvement of the thermal conductivity, the compression creep resistance and the rebound resilience of the polytetrafluoroethylene is always the focus of research on polytetrafluoroethylene materials.
The modified polytetrafluoroethylene sealing gasket comprises suspended polytetrafluoroethylene resin, molybdenum disulfide, carbon fiber, polyphenylene sulfide and alumina, and polytetrafluoroethylene is filled and modified by adopting reinforcing filler to improve creep relaxation resistance of the polytetrafluoroethylene sealing gasket, so that the defect of pure polytetrafluoroethylene is improved and overcome. However, the compatibility between the reinforcing filler and the polytetrafluoroethylene base material in the patent is poor, and the processing difficulty of the modified polytetrafluoroethylene sealing gasket is increased.
Therefore, the invention provides a tetrafluoroethylene-based high-temperature-resistant gasket and a preparation method thereof.
Disclosure of Invention
The invention aims to provide a high-temperature-resistant gasket based on tetrafluoroethylene and a preparation method thereof, which are used for solving the problems of low heat conductivity, poor compression creep resistance and poor rebound resilience of the traditional polytetrafluoroethylene gasket.
The aim of the invention can be achieved by the following technical scheme:
a tetrafluoroethylene-based high-temperature-resistant gasket comprises the following raw materials in parts by weight: 15-25 parts of polytetrafluoroethylene resin powder, 4-9.5 parts of hyperbranched polyimide powder and 1-2.7 parts of modified boron nitride powder.
Further, the hyperbranched polyimide powder comprises the following steps:
a1, uniformly mixing 1, 6-hexamethylenediamine and N-methylpyrrolidone, then slowly dropwise adding an N-methylpyrrolidone solution of trimellitic anhydride under the protection of nitrogen at 60-70 ℃, continuously stirring for reaction for 2-3 hours after complete dropwise adding, then adding toluene, heating to 140-150 ℃, carrying out reflux dehydration reaction for 6 hours, evaporating the toluene, cooling, pouring into cold water for precipitation, and then washing, recrystallizing and drying to obtain the imide dicarboxylic acid, wherein the molar ratio of the 1, 6-hexamethylenediamine to the trimellitic anhydride is 1:2;
a2, mixing pentaerythritol, anhydrous aluminum chloride and ethyl acetate, heating to 60 ℃ under the protection of nitrogen, slowly dropwise adding 3-chloropropyl trimethoxysilane, stirring for 20-30min after adding, heating to reflux, maintaining reflux reaction for 3-5h, filtering, and performing reduced pressure rotary evaporation to obtain grafted siloxane triol, wherein the molar ratio of the pentaerythritol to the 3-chloropropyl trimethoxysilane is 1:0.85-0.98;
the reaction is carried out by utilizing the substitution reaction of hydroxyl in pentaerythritol and chlorine in 3-chloropropyl trimethoxysilane to obtain grafted siloxane triol;
a3, uniformly mixing the imide dicarboxylic acid, the grafted siloxane triol, the p-toluenesulfonic acid and the dimethylacetamide, controlling the temperature of a reaction system to be 90-100 ℃ by using condensed water, stirring until no water is generated, reducing the temperature to 60 ℃ for reduced pressure rotary evaporation, adding tetrahydrofuran solution containing methacrylic acid and p-toluenesulfonic acid, heating to reflux, reacting for 2-3 hours, stopping the reaction, reducing the temperature to 30 ℃ for reduced pressure rotary evaporation, and ball milling the obtained product to obtain hyperbranched polyimide powder, wherein the mass ratio of the imide dicarboxylic acid to the grafted siloxane triol to the methacrylic acid is 11:18:7.2-7.5, the mass of the first added p-toluenesulfonic acid is 1-3% of the total mass of the imide dicarboxylic acid and the grafted siloxane triol, and the mass of the second added p-toluenesulfonic acid is 5-7% of the mass of methacrylic acid.
In the reaction, firstly, the condensation polymerization reaction of the imide dicarboxylic acid and the grafted siloxane triol is utilized to obtain hyperbranched polyimide, the hydroxyl is blocked by controlling the quality of the imide dicarboxylic acid and the grafted siloxane triol, and then the carboxyl of the blocked hydroxyl and methacrylic acid is utilized to react to obtain hyperbranched polyimide powder, so that the hyperbranched polyimide powder is a double bond blocked hyperbranched polyimide, has the characteristics of low viscosity, large steric hindrance effect and easy processing, and meanwhile, the monomer imide dicarboxylic acid is obtained by reacting 1, 6-hexamethylenediamine with trimellitic anhydride and consists of long soft alkyl chains, benzene rings and rigid groups of imide rings, and has the toughening effect.
Further, the modified boron nitride powder comprises the following steps:
adding silicon nitride powder into ethyl acetate solution, performing ultrasonic dispersion for 15-25min, heating to 70-75 ℃ under stirring, controlling the temperature to be 70-75 ℃ by using condensed water, adding a modifier and triethylamine, introducing nitrogen for protection, stirring for reaction for 3-4h, cooling to room temperature, performing suction filtration, drying, and performing ball milling to obtain modified boron nitride powder, wherein the dosage ratio of the silicon nitride powder to the ethyl acetate solution to the modifier to the triethylamine is 1g:15-29mL:0.2-0.5g:0.05-0.1g.
In the reaction, epoxy groups in the modifier react with hydroxyl groups on the surface of the silicon nitride powder to enable the surface of the silicon nitride powder to be grafted with molecular chains of the modifier, namely, the silicon chain, polyacrylate chain and double bond are contained, the silicon chain is utilized to enable the modified boron nitride powder to have good dispersibility in a collective material, the polyacrylate chain is utilized to enable the modified boron nitride powder to have good cohesiveness, the double bond is utilized to enable the modified boron nitride powder to have reactivity, and the modified boron nitride powder and polytetrafluoroethylene resin are subjected to reactive crosslinking.
Further, the modifier is formed by mixing butyl acrylate, glycidyl methacrylate and KH-570 according to the mass ratio of 10:5-8:1-3 in an organic solvent, and carrying out polymerization reaction under the action of an initiator and a chain transfer agent at 55-80 ℃.
Further, the specific preparation method of the modifier comprises the following steps:
under the protection of nitrogen, heating ethyl acetate to 50-80 ℃, slowly dropwise adding an ethyl acetate solution in which butyl acrylate, glycidyl methacrylate, KH-570, an initiator AIBN and a chain transfer agent dodecyl mercaptan are dissolved, heating, refluxing and preserving heat for 1-2h after the dropwise adding is completed, adding the initiator AIBN, stirring for 1-1.5h, stopping the reaction, reducing the pressure and steaming at 40 ℃ to obtain a modifier, wherein the total adding mass of the initiator AIBN is 1-3% of the total mass of butyl acrylate, glycidyl methacrylate and KH-570, the adding mass of the initiator AIBN is two thirds of the total adding mass of the initiator AIBN for the first time, and the adding mass of the chain transfer agent dodecyl mercaptan is 6% of the total mass of butyl acrylate, glycidyl methacrylate and KH-570.
The preparation method of the tetrafluoroethylene-based high-temperature-resistant gasket comprises the following steps:
uniformly stirring polytetrafluoroethylene resin powder, hyperbranched polyimide powder and modified boron nitride powder to obtain mixed powder, pouring the mixed powder into a mold, exhausting, cold-pressing to form, sintering to obtain a crude product, trimming and polishing the crude product to obtain a tetrafluoroethylene-based high-temperature-resistant gasket, wherein the stirring speed is 2000-2500r/min; cold pressing conditions: the pressure is 20-40MPa, and the pressure maintaining time is 10-15min; sintering conditions: the temperature rising rate is 40-60 ℃/h, the sintering temperature is 360-370 ℃, and the sintering time is 3-4h.
The invention has the beneficial effects that:
in order to solve the problems in the background art, hyperbranched polyimide powder and modified boron nitride powder are introduced into polytetrafluoroethylene base material, and the high-temperature-resistant gasket with good thermal conductivity, compression creep resistance and rebound resilience is obtained. The mechanism is explained as follows:
the hyperbranched polyimide powder is double-bond-terminated hyperbranched polyimide, has low viscosity, contains a large amount of siloxane in the molecular structure, and has good compatibility with polytetrafluoroethylene; secondly, monomer imide dicarboxylic acid forming the catalyst is obtained by reacting 1, 6-hexamethylenediamine and trimellitic anhydride, and consists of a long soft alkyl chain, a benzene ring and a rigid group of an imide ring, so that the catalyst has the characteristics of an elastomer and has a toughening effect; thirdly, holes in the hyperbranched molecular structure are helpful for the material to absorb impact energy generated when impacted, and further play a role in toughening; fourthly, the end-capped double bond can be crosslinked with the double bond in polytetrafluoroethylene, and the hyperbranched structure is matched with the end-capped double bond to promote the formation of an interpenetrating network structure in the gasket material, so that the toughness of the gasket is further improved (compared with the crosslinking of a linear molecular chain, the crosslinking of the hyperbranched structure has the characteristics of higher steric hindrance, no excessive crosslinking, sacrifice of the elasticity of the material, so that the material is too hard and has moderate crosslinking degree, so that the material has the characteristics of elasticity and hardness; therefore, the introduction of the hyperbranched polyimide powder solves the problems of poor compressive creep resistance and poor rebound resilience of the polytetrafluoroethylene gasket;
the modified boron nitride powder is a molecular chain with a modifier grafted on the surface, namely, the modified boron nitride powder contains a siloxane chain, a polyacrylate chain and double bonds, and the siloxane chain is utilized to ensure that the modified boron nitride powder has good dispersibility in a matrix material, so that a uniform heat conduction network is formed in the obtained gasket; the softness and cohesiveness of polyacrylate chains are utilized to endow the modified boron nitride powder with good cohesiveness, so that polytetrafluoroethylene powder, hyperbranched polyimide powder and modified boron nitride powder in the gasket form a compact sheet body in the tabletting process, and the processing performance of the gasket is improved; the double bond is utilized to endow the modified boron nitride powder with reactivity, so that the modified boron nitride powder is connected into an interpenetrating network in a matrix material, and the stability of a heat conducting network in a gasket is improved;
in conclusion, the tetrafluoroethylene-based high-temperature-resistant gasket obtained by the invention has good heat conductivity, compression creep resistance and rebound resilience.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
Preparation of hyperbranched polyimide powder:
a1, uniformly mixing 0.1mol of 1, 6-hexamethylenediamine and 50mL of N-methylpyrrolidone, then slowly dropwise adding 70mL of N-methylpyrrolidone solution containing 0.2mol of trimellitic anhydride at 60 ℃ under the protection of nitrogen, continuously stirring for reaction for 3 hours after the dropwise addition is completed, then adding 100mL of toluene, heating to 140 ℃, carrying out reflux dehydration reaction for 6 hours, distilling off the toluene, cooling, pouring into cold water for precipitation, and washing, recrystallizing and drying to obtain the imide dicarboxylic acid;
a2, mixing 0.1mol of pentaerythritol, 0.1mol of anhydrous aluminum chloride and 60mL of ethyl acetate, heating to 60 ℃ under the protection of nitrogen, slowly dropwise adding 0.85mol of 3-chloropropyl trimethoxysilane, stirring for 20min after the addition, heating to reflux, maintaining reflux reaction for 3h, filtering, and performing reduced pressure rotary evaporation to obtain grafted siloxane triol;
a3, uniformly mixing 11g of imide dicarboxylic acid, 18g of grafted siloxane triol, 0.3g of p-toluenesulfonic acid and 60mL of dimethylacetamide, controlling the temperature of a reaction system to be 90 ℃ by using condensed water, stirring until no water is generated, reducing the temperature to 60 ℃ for rotary evaporation under reduced pressure, adding a tetrahydrofuran solution containing 7.2g of methacrylic acid and 0.36g of p-toluenesulfonic acid, heating to reflux, reacting for 2 hours, stopping the reaction, reducing the temperature to 30 ℃ for rotary evaporation under reduced pressure, and ball-milling the obtained product to obtain hyperbranched polyimide powder.
Example 2
Preparation of hyperbranched polyimide powder:
a1, uniformly mixing 0.1mol of 1, 6-hexamethylenediamine and 50mL of N-methylpyrrolidone, then slowly dropwise adding 70mL of N-methylpyrrolidone solution containing 0.2mol of trimellitic anhydride at 70 ℃ under the protection of nitrogen, continuously stirring for reacting for 2 hours after the dropwise adding is completed, then adding 100mL of toluene, heating to 150 ℃, carrying out reflux dehydration reaction for 6 hours, distilling off the toluene, cooling, pouring into cold water for precipitation, and washing, recrystallizing and drying to obtain the imide dicarboxylic acid;
a2, mixing 0.1mol of pentaerythritol, 0.1mol of anhydrous aluminum chloride and 60mL of ethyl acetate, heating to 60 ℃ under the protection of nitrogen, slowly dropwise adding 0.98mol of 3-chloropropyl trimethoxysilane, stirring for 30min after the addition, heating to reflux, maintaining reflux reaction for 5h, filtering, and performing reduced pressure rotary evaporation to obtain grafted siloxane triol;
a3, uniformly mixing 11g of imide dicarboxylic acid, 18g of grafted siloxane triol, 0.6g of p-toluenesulfonic acid and 60mL of dimethylacetamide, controlling the temperature of a reaction system to be 100 ℃ by using condensed water, stirring until no water is generated, reducing the temperature to 60 ℃ for rotary evaporation under reduced pressure, adding a tetrahydrofuran solution containing 7.5g of methacrylic acid and 0.37g of p-toluenesulfonic acid, heating to reflux, reacting for 3 hours, stopping the reaction, reducing the temperature to 30 ℃ for rotary evaporation under reduced pressure, and ball-milling the obtained product to obtain hyperbranched polyimide powder.
Example 3
Preparing modified boron nitride powder:
adding 10g of silicon nitride powder into 150mL of ethyl acetate solution, performing ultrasonic dispersion for 15min, heating to 70 ℃ under stirring (the temperature is kept at 70 ℃ by using condensed water), adding 2g of modifier and 0.5g of triethylamine, introducing nitrogen for protection, stirring for reacting for 4h, cooling to room temperature, performing suction filtration, drying and ball milling to obtain modified boron nitride powder;
the specific preparation method of the modifier comprises the following steps:
under the protection of nitrogen, heating ethyl acetate to 50 ℃, slowly dropwise adding an ethyl acetate solution in which 10g of butyl acrylate, 5g of glycidyl methacrylate, 1gKH-570, 0.11g of initiator AIBN and 0.96g of chain transfer agent dodecyl mercaptan are dissolved, heating, refluxing and preserving heat for reaction for 2 hours after the dropwise adding is completed, then adding 0.05g of initiator AIBN, stirring for 1 hour, stopping the reaction, and reducing the temperature to 40 ℃ for rotary evaporation under reduced pressure to obtain the modifier.
Example 4
Preparing modified boron nitride powder:
adding 10g of silicon nitride powder into 290mL of ethyl acetate solution, performing ultrasonic dispersion for 25min, heating to 75 ℃ under stirring (controlling the temperature to be 75 ℃ with condensed water), adding 0.5g of modifier and 0.1g of triethylamine, introducing nitrogen for protection, stirring for reaction for 3h, cooling to room temperature, performing suction filtration, drying and ball milling to obtain modified boron nitride powder;
the specific preparation method of the modifier comprises the following steps:
under the protection of nitrogen, heating ethyl acetate to 80 ℃, slowly dropwise adding an ethyl acetate solution in which 10g of butyl acrylate, 8g of glycidyl methacrylate, 3gKH-570, 0.14g of initiator AIBN and 1.26g of chain transfer agent dodecyl mercaptan are dissolved, heating, refluxing and preserving heat for reaction for 1h, then adding 0.07g of initiator AIBN, stirring for 1h, stopping the reaction, and reducing the pressure to 40 ℃ for rotary evaporation to obtain the modifier.
Example 5
A preparation method of a high-temperature-resistant gasket based on tetrafluoroethylene comprises the following steps:
step one, the raw materials with the following weight portions are included: 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 two, uniformly stirring and mixing polytetrafluoroethylene resin powder, hyperbranched polyimide powder and modified boron nitride powder to obtain mixed powder, pouring the mixed powder into a mold, exhausting, cold-pressing and molding, sintering to obtain a crude product, trimming and polishing the crude product 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, and the pressure maintaining time is 10min; sintering conditions: the temperature rising rate is 40 ℃/h, the sintering temperature is 360-370 ℃, and the sintering time is 3h.
Example 6
A preparation method of a high-temperature-resistant gasket based on tetrafluoroethylene comprises the following steps:
step one, the raw materials with the following weight portions are included: 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 two, uniformly stirring and mixing polytetrafluoroethylene resin powder, hyperbranched polyimide powder and modified boron nitride powder to obtain mixed powder, pouring the mixed powder into a mold, exhausting, cold-pressing and molding, sintering to obtain a crude product, trimming and polishing the crude product to obtain a high-temperature-resistant gasket based on tetrafluoroethylene, wherein the stirring speed is 2000-2500r/min; cold pressing conditions: the pressure is 40MPa, and the pressure maintaining time is 15min; sintering conditions: the temperature rising rate is 60 ℃/h, the sintering temperature is 360-370 ℃, and the sintering time is 4h.
Example 7
A preparation method of a high-temperature-resistant gasket based on tetrafluoroethylene comprises the following steps:
step one, the raw materials with the following weight portions are included: 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 two, uniformly stirring and mixing polytetrafluoroethylene resin powder, hyperbranched polyimide powder and modified boron nitride powder to obtain mixed powder, pouring the mixed powder into a mold, exhausting, cold-pressing and molding, sintering to obtain a crude product, trimming and polishing the crude product to obtain a high-temperature-resistant gasket based on tetrafluoroethylene, wherein the stirring speed is 2000-2500r/min; cold pressing conditions: the pressure is 40MPa, and the pressure maintaining time is 15min; sintering conditions: the temperature rising rate is 60 ℃/h, the sintering temperature is 360-370 ℃, and the sintering time is 4h.
Comparative example 1
A preparation method of a high-temperature-resistant gasket based on tetrafluoroethylene comprises the following steps: compared with example 5, the hyperbranched polyimide powder is replaced by an equivalent of the hyperbranched polyimide powder prepared by the following steps, and the rest are the same;
a1, uniformly mixing 0.1mol of 1, 6-hexamethylenediamine and 50mL of N-methylpyrrolidone, then slowly dropwise adding 70mL of N-methylpyrrolidone solution containing 0.2mol of trimellitic anhydride at 60 ℃ under the protection of nitrogen, continuously stirring for reacting for 2 hours after the dropwise adding is completed, then adding 100mL of toluene, heating to 140 ℃, carrying out reflux dehydration for 6 hours, distilling off the toluene, cooling, pouring into cold water for precipitation, and washing, recrystallizing and drying to obtain the imide dicarboxylic acid;
a2, uniformly mixing 11g of imide dicarboxylic acid, 18g of propylene triol, 0.29g of p-toluenesulfonic acid and 60mL of dimethylacetamide, controlling the temperature of a reaction system to be 90 ℃ by using condensed water, stirring until no water is generated, reducing the temperature to 60 ℃ for rotary evaporation under reduced pressure, adding a tetrahydrofuran solution containing 7.2g of methacrylic acid and 0.36g of p-toluenesulfonic acid, heating to reflux, reacting for 2 hours, stopping the reaction, reducing the temperature to 30 ℃ for rotary evaporation under reduced pressure, and ball-milling the obtained product to obtain hyperbranched polyimide powder.
Comparative example 2
A preparation method of a high-temperature-resistant gasket based on tetrafluoroethylene comprises the following steps: compared with example 6, the modified boron nitride powder was replaced with an equal amount of silicon nitride powder, and the remainder was 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: with reference to ASTM D638, the specimen is a type V specimen specified in the standard, and the stretching speed is 20mm/min;
compression resilience: reference is made to ASTM F36 test;
creep relaxation test: reference ASTM F38-B test;
thermal conductivity coefficient: reference is made to ASTM D5470 test;
the test data are shown in Table 1.
TABLE 1
As can be seen from the data in Table 1, the gaskets obtained in examples 5-7 were superior in thermal conductivity, compressive resilience, and creep relaxation resistance to the gaskets obtained in comparative examples 1-2.
In the description of the present specification, the descriptions of the terms "one embodiment," "example," "specific example," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. 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 foregoing is merely illustrative and explanatory of the invention, as various modifications and additions may be made to the particular embodiments described, or in a similar manner, by those skilled in the art, without departing from the scope of the invention or exceeding the scope of the invention as defined in the claims.
Claims (7)
1. A high temperature resistant gasket based on tetrafluoroethylene, its characterized in that: the material comprises the following raw materials in parts by weight: 15-25 parts of polytetrafluoroethylene resin powder, 4-9.5 parts of hyperbranched polyimide powder and 1-2.7 parts of modified boron nitride powder;
the hyperbranched polyimide powder is prepared by the following steps:
uniformly mixing 1, 6-hexamethylenediamine and N-methylpyrrolidone, then slowly dropwise adding an N-methylpyrrolidone solution of trimellitic anhydride under the protection of nitrogen at 60-70 ℃, continuously stirring for reaction for 2-3 hours after complete dropwise adding, then adding toluene, heating to 140-150 ℃, carrying out reflux dehydration reaction for 6 hours, distilling off the toluene, cooling, pouring into cold water for precipitation, and washing, recrystallizing and drying to obtain the imide dicarboxylic acid, wherein the molar ratio of the 1, 6-hexamethylenediamine to the trimellitic anhydride is 1:2;
uniformly mixing imide dicarboxylic acid, grafted siloxane triol, p-toluenesulfonic acid and dimethylacetamide, controlling the temperature of a reaction system to be 90-100 ℃ by using condensed water, stirring until no water is generated, cooling, decompressing and steaming, adding tetrahydrofuran solution containing methacrylic acid and p-toluenesulfonic acid, heating to reflux, reacting for 2-3 hours, stopping the reaction, cooling, decompressing and steaming, and ball-milling to obtain hyperbranched polyimide powder;
the grafted siloxane triol is prepared by the following steps:
mixing pentaerythritol, anhydrous aluminum chloride and ethyl acetate, heating to 60-65 ℃ under the protection of nitrogen, slowly dropwise adding 3-chloropropyl trimethoxyl silane, stirring for 20-30min after the addition, heating to reflux, maintaining reflux reaction for 3-5h, filtering, and performing reduced pressure rotary evaporation to obtain grafted siloxane triol;
the modified boron nitride powder is prepared by the following steps:
adding silicon nitride powder into ethyl acetate solution, performing ultrasonic dispersion for 15-25min, heating to 70-75 ℃ under stirring, adding a modifier and triethylamine, introducing nitrogen for protection, stirring for reaction for 3-4h, cooling to room temperature, performing suction filtration, drying, and performing ball milling to obtain modified boron nitride powder.
2. A tetrafluoroethylene-based high temperature resistant gasket according to claim 1, wherein: the mass ratio of the imide dicarboxylic acid to the grafted siloxane triol to the methacrylic acid is 11:18:7.2-7.5, the mass of the p-toluenesulfonic acid added for the first time is 1-3% of the total mass of the imide dicarboxylic acid and the grafted siloxane triol, and the mass of the p-toluenesulfonic acid added for the second time is 5-7% of the mass of the methacrylic acid.
3. A tetrafluoroethylene-based high temperature resistant gasket according to claim 1, wherein: the molar ratio of the pentaerythritol to the 3-chloropropyl trimethoxysilane is 1:0.85-0.98.
4. A tetrafluoroethylene-based high temperature resistant gasket according to claim 1, wherein: the dosage ratio of the silicon nitride powder to the ethyl acetate solution to the modifier to the triethylamine is 1g to 15-29mL to 0.2-0.5g to 0.05-0.1g.
5. A tetrafluoroethylene-based high temperature resistant gasket according to claim 1, wherein: the modifier is formed by mixing butyl acrylate, glycidyl methacrylate and KH-570 according to the mass ratio of 10:5-8:1-3 in an organic solvent and performing polymerization reaction under the action of an initiator and a chain transfer agent.
6. A tetrafluoroethylene-based high temperature resistant gasket according to claim 5, wherein: the temperature of the polymerization reaction is 55-80 ℃.
7. The method for preparing the tetrafluoroethylene-based high temperature resistant gasket according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:
stirring and mixing polytetrafluoroethylene resin powder, hyperbranched polyimide powder and modified boron nitride powder uniformly to obtain mixed powder, pouring the mixed powder into a mold, exhausting, cold-pressing and molding, sintering to obtain a crude product, trimming and polishing the crude product to obtain the high-temperature-resistant gasket based on tetrafluoroethylene.
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| US5955568A (en) * | 1996-04-22 | 1999-09-21 | Korea Research Institute Of Chemical Technology | Process for preparing polyamideimide resins by direct polymerization |
| AU2004241111B2 (en) * | 2003-05-15 | 2010-05-27 | Dsm Ip Assets B.V | Manufacture and use of implantable reticulated elastomeric matrices |
| KR20090087515A (en) * | 2005-02-01 | 2009-08-17 | 국립대학법인 나고야공업대학 | Siloxane-modified hyperbranched polyimide |
| US8236906B2 (en) * | 2006-03-22 | 2012-08-07 | Hitachi Chemical Company, Ltd. | Polyamide-imide resin, process for production of polyamide resin, and curable resin composition |
| CN102136327B (en) * | 2010-01-25 | 2012-12-26 | 3M创新有限公司 | Heat-conduction insulation spacer |
| CN102942757A (en) * | 2012-11-05 | 2013-02-27 | 中国矿业大学 | Polytetrafluoroethylene composite friction material and preparation method thereof |
| CN113512262B (en) * | 2021-04-20 | 2022-05-20 | 西安交通大学 | High-speed blending modified PTFE (polytetrafluoroethylene) based multi-component composite filler and preparation method thereof |
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