CN111320967A - High-thermal-conductivity silicone sealant modified by multilevel-structure filler and preparation method thereof - Google Patents
High-thermal-conductivity silicone sealant modified by multilevel-structure filler and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J183/00—Adhesives based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Adhesives based on derivatives of such polymers
- C09J183/04—Polysiloxanes
- C09J183/08—Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen, and oxygen
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
- C09J11/02—Non-macromolecular additives
- C09J11/04—Non-macromolecular additives inorganic
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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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- 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
- C08K2201/00—Specific properties of additives
- C08K2201/011—Nanostructured additives
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Abstract
The invention discloses a high-thermal-conductivity silicone sealant modified by a multi-level structural filler, which is prepared by taking alkoxy-terminated polysiloxane as a base adhesive, taking polypropylene fibers, polypropylene particles and BN nanoparticles as composite thermal-conductivity fillers, adding nano calcium carbonate, a cross-linking agent and a catalyst, and stirring and kneading; the alkoxy end-capped polysiloxane is prepared by mixing a siloxane monomer with a mixed solution of modified phosphazene and sodium ethoxide at normal temperature and then taking methyltrimethoxysilane as an end-capping agent; the preparation method of the modified phosphazene comprises the following steps: the linear phosphazene with low polymerization degree and hydrofluoric acid are mixed and reacted at 150 ℃. The invention also discloses a preparation method of the high-thermal-conductivity silicone sealant. The silicone sealant disclosed by the invention not only solves the problems of viscosity peak and curing failure, but also has high peel strength and bonding strength and excellent heat-conducting property.
Description
The technical field is as follows:
the invention relates to the field of organosilicon sealants, in particular to a high-thermal-conductivity silicone sealant modified by a multilevel-structure filler and a preparation method thereof.
Background art:
the organic silicon rubber is a high molecular elastomer insulating material with inorganic and organic properties, and has the properties of inorganic and organic materials, such as high and low temperature resistance, oxidation resistance, radiation resistance, good dielectric property, flame retardancy, hydrophobicity, demoulding, small temperature viscosity coefficient, no toxicity, no odor, physiological inertia and the like. Through modification, the organic silicon polymer can also be prepared into materials with excellent performance, such as flame retardance, electric conduction, heat conduction, optical activity, separation membranes and the like, and the application range of the organic silicon polymer is extended to various fields of national defense, science and technology, national economy and even daily life of people. Silicone rubbers can be classified into 3 types according to their vulcanization mechanism: the organic peroxide initiates free radical crosslinking type, polycondensation reaction type and addition reaction type. The room temperature vulcanized silicone rubber is a novel organic silicon elastomer, and the most remarkable characteristic of the product is that the product can be cured without heating and pressurizing at room temperature except the excellent electrical property, chemical inertness, high and low temperature resistance, aging resistance, flame retardance, water vapor resistance and the like of the common high temperature vulcanized silicone rubber, does not absorb or release heat during curing, has small shrinkage rate after curing, has good cohesiveness to various materials such as metal, glass, ceramics and concrete, and is extremely convenient to use.
The dealcoholized room temperature vulcanized silicone sealant has the characteristics of excellent weather resistance, no corrosion of micromolecular alcohol removed during vulcanization on a base material, no environmental pollution and the like, and has been widely applied to the fields of buildings, electronics, electrics, aerospace, automobile industry and the like.
The invention content is as follows:
the invention aims to solve the technical problem of providing a high-thermal-conductivity silicone sealant modified by a multilevel-structure filler aiming at the defects of the prior art, and on one hand, the self-made modified phosphazene is used as a catalyst in the preparation of alkoxy-terminated polymethylsiloxane, so that the problem that the silicone sealant prepared by taking titanate as the catalyst in the prior art is easy to cure and lose efficacy is solved. On the other hand, the BN nano-sheet is wound and coated on the surfaces of the polypropylene particles and the polypropylene fibers to prepare the composite filler, and the BN nano-sheet forms a long-distance oriented high-heat-conduction path on the surface of the polypropylene fibers, so that the heat-conduction performance of the sealant is improved, and the mechanical property of the sealant is also improved. The invention also discloses a preparation method of the high-thermal-conductivity silicone sealant. The preparation method has the advantages of simple process and low cost, and the prepared sealant not only eliminates the problems of viscosity peak and curing failure, but also has high peel strength and bonding strength and excellent heat-conducting property.
In order to better solve the technical problems, the invention adopts the following technical scheme:
a high heat conduction silicone sealant with multilevel structure filler modification is prepared by taking alkoxy-terminated polysiloxane as a base adhesive, taking polypropylene fiber, polypropylene particles and BN nanoparticles as composite heat conduction fillers, adding nano calcium carbonate, a cross-linking agent and a catalyst, and stirring and kneading;
the alkoxy end-capped polysiloxane is prepared by mixing a siloxane monomer with a mixed solution of modified phosphazene and sodium ethoxide at normal temperature and then taking methyltrimethoxysilane as an end-capping agent;
the preparation method of the modified phosphazene comprises the following steps: the linear phosphazene with low polymerization degree and hydrofluoric acid are mixed and reacted at 150 ℃.
Preferably, in the above technical solution, the molar ratio of the linear phosphazene to the hydrofluoric acid is 1: (4.5-5.5), wherein the reaction time of the linear phosphazene and hydrofluoric acid is 2.5-5.5 h.
Preferably, the preparation method of the mixed solution of the modified phosphazene and the sodium ethoxide comprises the following steps: firstly, stirring and mixing sodium hydroxide, deionized water and absolute ethyl alcohol uniformly at normal temperature according to the mass ratio of 1:2:2, and then adding modified phosphazene and stirring and mixing to obtain the modified phosphazene; the mass concentration of the modified phosphazene and sodium ethoxide mixed solution is 1-5%.
In order to solve the technical problems, the invention also provides a preparation method of the multilevel-structure filler modified high-thermal-conductivity silicone sealant, which comprises the following steps:
(1) mixing siloxane monomers with a mixed solution of modified phosphazene and sodium ethoxide at normal temperature, uniformly stirring, removing air bubbles and moisture in vacuum, stirring at 30-50 ℃, adding methyltrimethoxysilane and octamethylcyclotetrasiloxane, quickly stirring, keeping the vacuum to remove methanol generated in a reaction system, stirring and mixing for 25-35 min, and adding a terminator to terminate the reaction to obtain alkoxy end-blocked polysiloxane;
(2) mixing polypropylene fibers, polypropylene particles and VAE705, stirring at 20000-23000 rpm for 2-4 min, adding BN nanoparticles, continuously stirring and mixing for 2-4 min, and drying the mixed material at 80 ℃ for 10-12 h to obtain the composite heat-conducting filler;
(3) adding the prepared alkoxy-terminated polysiloxane, the composite heat-conducting filler and the nano calcium carbonate into a kneading machine, stirring and mixing for 1-2 h at 100-120 ℃, then adding the cross-linking agent, stirring and mixing for 30min, finally sequentially adding the silane coupling agent and the catalyst, and continuously stirring and mixing for 10-15 min to obtain the high-heat-conducting silicone sealant.
Preferably, in the step (1), when the siloxane monomer is mixed with the mixed solution of the modified phosphazene and the sodium ethoxide at normal temperature, the dosage of the modified phosphazene and the sodium ethoxide is 5-25 ppm, and when the siloxane monomer is mixed with the mixed solution of the modified phosphazene and the sodium ethoxide, the mixed solution of the modified phosphazene and the sodium ethoxide is firstly diluted by 100 times in advance.
Preferably, in the step (1), the mass ratio of the siloxane monomer, the methyltrimethoxysilane and the octamethylcyclotetrasiloxane is 100: (1.5-2.5): (0.35-0.55).
Preferably, in the step (1), the terminator is one of hexamethyldisilazane, phosphorous acid, sodium phosphite, and trioctylamine.
Preferably, in the step (2), the mass ratio of the polypropylene fibers, the polypropylene particles, the VAE705 and the BN nanosheets is 3: (5-6): (2-2.5): 3.
preferably, in the step (3), the amounts of the components in parts by weight are as follows: 100 parts of alkoxy-terminated polysiloxane, 4-9 parts of composite heat-conducting filler, 8-12 parts of nano calcium carbonate, 3-7 parts of cross-linking agent, 1-4 parts of silane coupling agent and 1-3 parts of catalyst.
Preferably, in the step (3), the crosslinking agent is one of methyl tributyl ketoxime silane and vinyl tributyl ketoxime silane; the catalyst is one of an organic tin catalyst and dibutyltin dilaurate.
Due to the adoption of the technical scheme, the invention has the following beneficial effects:
the traditional alkoxy-terminated polysiloxane is usually prepared by taking titanate as a catalyst, the method is high in cost, and the prepared target product cannot completely solve the problems of high viscosity and curing failure. In order to solve the problems, the alkoxy-terminated polysiloxane is prepared by taking the self-made modified phosphazene as the catalyst, the method is simple to operate, and the prepared target product not only eliminates the problems of high viscosity peak and curing failure, but also has high peel strength and bonding strength.
The BN nanosheet has good heat-conducting property, but has poor compatibility with a polymer matrix, a good heat-conducting network cannot be formed when the BN nanosheet is added into the polymer material matrix as a heat-conducting filler, and the mechanical property of the polymer matrix is easily seriously influenced due to the agglomeration of the BN nanosheet. Therefore, the polypropylene particles, the polypropylene fibers and the VAE705 emulsion are mixed and stirred, the VAE705 emulsion is used as an adhesive to cover the surfaces of the polypropylene particles and the polypropylene fibers, and then the mixture is mixed with the BN nanosheet, so that the BN nanosheet is uniformly covered on the surfaces of the polypropylene particles and the polypropylene fibers; the addition of the polypropylene fiber can improve the contact area of adjacent BN nano sheets, thereby obviously reducing the interface thermal resistance and improving the heat-conducting property of the sealant. And the polypropylene fiber and the polypropylene particle are compounded with each other, so that the continuity of a continuous phase can be improved, the gaps of the continuous phase can be reduced, and the mechanical property of the sealant can be further improved.
The specific implementation mode is as follows:
the present invention is further illustrated by the following examples, which are provided for the purpose of illustration only and are not intended to be limiting.
Example 1
A preparation method of a high-thermal-conductivity silicone sealant modified by a multilevel-structure filler comprises the following steps:
(1) mixing the linear and hydrofluoric acid with low degree of polymerization in a molar ratio of 1: 4.5, mixing and reacting for 2.5h at 150 ℃ to prepare modified phosphazene; stirring and mixing sodium hydroxide, deionized water and absolute ethyl alcohol uniformly at normal temperature according to the mass ratio of 1:2:2, and then adding modified phosphazene and stirring and mixing to obtain the modified phosphazene; the mass concentration of the modified phosphazene and sodium ethoxide mixed solution is 1%; mixing and stirring 100 parts by weight of siloxane monomer with the mixed solution of the modified phosphazene and sodium ethoxide at normal temperature uniformly, wherein the dosage of the modified phosphazene and the sodium ethoxide is 5 ppm; removing air bubbles and moisture in vacuum, stirring at 50 ℃, adding 1.5 parts of methyltrimethoxysilane and 0.35 part of octamethylcyclotetrasiloxane, quickly stirring, keeping the methanol generated in the vacuum removal reaction system, stirring and mixing for 25min, adding hexamethyldisilazane to terminate the reaction, and preparing alkoxy-terminated polysiloxane;
(2) mixing 3 parts of polypropylene fiber, 5 parts of polypropylene particles and 2 parts of VAE705 in parts by weight, stirring at a high speed of 20000rpm for 2min, adding 3 parts of BN nanoparticles, continuously stirring and mixing for 2min, and drying the mixed material at 80 ℃ for 10h to obtain the composite heat-conducting filler;
(3) adding 100 parts by weight of the prepared alkoxy-terminated polysiloxane, 4 parts by weight of composite heat-conducting filler and 8 parts by weight of nano calcium carbonate into a kneader, stirring and mixing for 1 hour at 100 ℃, then adding 3 parts by weight of cross-linking agent, stirring and mixing for 30min, finally sequentially adding 1 part by weight of silane coupling agent and 1 part by weight of catalyst, and continuously stirring and mixing for 10min to obtain the high-heat-conductivity silicone sealant.
Example 2
A preparation method of a high-thermal-conductivity silicone sealant modified by a multilevel-structure filler comprises the following steps:
(1) mixing the linear and hydrofluoric acid with low degree of polymerization in a molar ratio of 1: 5.5, mixing and reacting for 5.5 hours at 150 ℃ to prepare modified phosphazene; stirring and mixing sodium hydroxide, deionized water and absolute ethyl alcohol uniformly at normal temperature according to the mass ratio of 1:2:2, and then adding modified phosphazene and stirring and mixing to obtain the modified phosphazene; the mass concentration of the modified phosphazene and sodium ethoxide mixed solution is 5%; mixing and stirring 100 parts by weight of siloxane monomer with a mixed solution of modified phosphazene and sodium ethoxide at normal temperature, wherein the dosage of the modified phosphazene and the sodium ethoxide is 25 ppm; removing air bubbles and moisture in vacuum, stirring at 50 ℃, adding 2.5 parts of methyltrimethoxysilane and 0.55 part of octamethylcyclotetrasiloxane, stirring rapidly, keeping the vacuum to remove the methanol generated in the reaction system, stirring and mixing for 35min, adding phosphorous acid to stop the reaction, and preparing the alkoxy-terminated polysiloxane;
(2) mixing 3 parts of polypropylene fiber, 6 parts of polypropylene particles and 2.5 parts of VAE705 in parts by weight, stirring at 23000rpm for 4min at a high speed, adding 3 parts of BN nanoparticles, continuously stirring and mixing for 4min, and drying the mixed material at 80 ℃ for 12h to obtain the composite heat-conducting filler;
(3) adding 100 parts by weight of the prepared alkoxy-terminated polysiloxane, 9 parts by weight of composite heat-conducting filler and 12 parts by weight of nano calcium carbonate into a kneader, stirring and mixing for 2 hours at 120 ℃, then adding 7 parts by weight of cross-linking agent, stirring and mixing for 30 minutes, finally sequentially adding 4 parts by weight of silane coupling agent and 3 parts by weight of catalyst, and continuously stirring and mixing for 15 minutes to obtain the high-heat-conductivity silicone sealant.
Example 3
A preparation method of a high-thermal-conductivity silicone sealant modified by a multilevel-structure filler comprises the following steps:
(1) mixing the linear and hydrofluoric acid with low degree of polymerization in a molar ratio of 1: 5, mixing and reacting for 3 hours at 150 ℃ to prepare modified phosphazene; stirring and mixing sodium hydroxide, deionized water and absolute ethyl alcohol uniformly at normal temperature according to the mass ratio of 1:2:2, and then adding modified phosphazene and stirring and mixing to obtain the modified phosphazene; the mass concentration of the modified phosphazene and sodium ethoxide mixed solution is 2%; mixing and stirring 100 parts by weight of siloxane monomer with the mixed solution of the modified phosphazene and sodium ethoxide at normal temperature uniformly, wherein the dosage of the modified phosphazene and the sodium ethoxide is 10 ppm; removing air bubbles and moisture in vacuum, stirring at 45 ℃, adding 1.5 parts of methyltrimethoxysilane and 0.4 part of octamethylcyclotetrasiloxane, stirring rapidly, keeping the vacuum to remove the methanol generated in the reaction system, stirring and mixing for 30min, adding sodium phosphite to terminate the reaction, and preparing alkoxy-terminated polysiloxane;
(2) mixing 3 parts of polypropylene fiber, 5 parts of polypropylene particles and 2 parts of VAE705 in parts by weight, stirring at a high speed of 21000rpm for 3min, adding 3 parts of BN nanoparticles, continuously stirring and mixing for 3min, and drying the mixed material at 80 ℃ for 11h to obtain the composite heat-conducting filler;
(3) adding 100 parts by weight of the prepared alkoxy-terminated polysiloxane, 5 parts by weight of composite heat-conducting filler and 9 parts by weight of nano calcium carbonate into a kneader, stirring and mixing for 1 hour at 110 ℃, then adding 4 parts by weight of cross-linking agent, stirring and mixing for 30min, finally sequentially adding 2 parts by weight of silane coupling agent and 2 parts by weight of catalyst, and continuously stirring and mixing for 12min to obtain the high-heat-conductivity silicone sealant.
Example 4
A preparation method of a high-thermal-conductivity silicone sealant modified by a multilevel-structure filler comprises the following steps:
(1) mixing the linear and hydrofluoric acid with low degree of polymerization in a molar ratio of 1: 5, mixing and reacting for 3.5 hours at 150 ℃ to prepare modified phosphazene; stirring and mixing sodium hydroxide, deionized water and absolute ethyl alcohol uniformly at normal temperature according to the mass ratio of 1:2:2, and then adding modified phosphazene and stirring and mixing to obtain the modified phosphazene; the mass concentration of the modified phosphazene and sodium ethoxide mixed solution is 3%; mixing and stirring 100 parts by weight of siloxane monomer with a mixed solution of modified phosphazene and sodium ethoxide at normal temperature, wherein the use amount of the modified phosphazene and the sodium ethoxide is 15 ppm; removing air bubbles and moisture in vacuum, stirring at 50 ℃, adding 2 parts of methyltrimethoxysilane and 0.45 part of octamethylcyclotetrasiloxane, quickly stirring, keeping the methanol generated in the vacuum removal reaction system, stirring and mixing for 30min, adding hexamethyldisilazane, phosphorous acid, sodium phosphite and trioctylamine to terminate the reaction, and preparing alkoxy-terminated polysiloxane;
(2) mixing 3 parts of polypropylene fiber, 6 parts of polypropylene particles and 2 parts of VAE705 in parts by weight, stirring at 22000rpm for 4min at a high speed, adding 3 parts of BN nanoparticles, continuously stirring and mixing for 4min, and drying the mixed material at 80 ℃ for 10h to obtain the composite heat-conducting filler;
(3) adding 100 parts by weight of the prepared alkoxy-terminated polysiloxane, 6 parts by weight of composite heat-conducting filler and 10 parts by weight of nano calcium carbonate into a kneader, stirring and mixing for 1h at 120 ℃, then adding 5 parts by weight of cross-linking agent, stirring and mixing for 30min, finally sequentially adding 3 parts by weight of silane coupling agent and 2 parts by weight of catalyst, and continuously stirring and mixing for 10min to obtain the high-heat-conductivity silicone sealant.
Example 5
A preparation method of a high-thermal-conductivity silicone sealant modified by a multilevel-structure filler comprises the following steps:
(1) mixing the linear and hydrofluoric acid with low degree of polymerization in a molar ratio of 1: 5, mixing and reacting for 4.5 hours at 150 ℃ to prepare modified phosphazene; stirring and mixing sodium hydroxide, deionized water and absolute ethyl alcohol uniformly at normal temperature according to the mass ratio of 1:2:2, and then adding modified phosphazene and stirring and mixing to obtain the modified phosphazene; the mass concentration of the modified phosphazene and sodium ethoxide mixed solution is 4%; mixing and stirring 100 parts by weight of siloxane monomer with a mixed solution of modified phosphazene and sodium ethoxide at normal temperature, wherein the dosage of the modified phosphazene and the sodium ethoxide is 20 ppm; removing air bubbles and moisture in vacuum, stirring at 50 ℃, adding 2 parts of methyltrimethoxysilane and 0.45 part of octamethylcyclotetrasiloxane, stirring rapidly, keeping the methanol generated in the vacuum removal reaction system, stirring and mixing for 30min, adding trioctylamine to terminate the reaction, and obtaining the alkoxy-terminated polysiloxane;
(2) mixing 3 parts of polypropylene fiber, 5.5 parts of polypropylene particles and 2 parts of VAE705 in parts by weight, stirring at a high speed of 20000rpm for 4min, adding 3 parts of BN nanoparticles, continuously stirring and mixing for 4min, and drying the mixed material at 80 ℃ for 10h to obtain the composite heat-conducting filler;
(3) adding 100 parts by weight of the prepared alkoxy-terminated polysiloxane, 7 parts by weight of composite heat-conducting filler and 10 parts by weight of nano calcium carbonate into a kneader, stirring and mixing for 1 hour at 100 ℃, then adding 6 parts by weight of cross-linking agent, stirring and mixing for 30min, finally sequentially adding 3 parts by weight of silane coupling agent and 1 part by weight of catalyst, and continuously stirring and mixing for 10min to obtain the high-heat-conductivity silicone sealant.
Example 6
A preparation method of a high-thermal-conductivity silicone sealant modified by a multilevel-structure filler comprises the following steps:
(1) mixing the linear and hydrofluoric acid with low degree of polymerization in a molar ratio of 1: (4, mixing and reacting at 150 ℃ for 5 hours to obtain modified phosphazene, stirring and mixing sodium hydroxide, deionized water and absolute ethyl alcohol uniformly at normal temperature according to the mass ratio of 1:2:2, adding the modified phosphazene and sodium ethoxide, stirring and mixing to obtain a mixed solution of the modified phosphazene and the sodium ethoxide, wherein the mass concentration of the mixed solution of the modified phosphazene and the sodium ethoxide is 4 percent, mixing and stirring 100 parts of siloxane monomer with the mixed solution of the modified phosphazene and the sodium ethoxide uniformly at normal temperature by weight, the using amount of the modified phosphazene and the sodium ethoxide is 20ppm, removing bubbles and moisture in vacuum, stirring at 50 ℃, adding 2 parts of methyltrimethoxysilane and 0.45 part of octamethylcyclotetrasiloxane, stirring rapidly, keeping methanol generated in a vacuum removal reaction system, stirring and mixing for 30 minutes, and adding hexamethyldisilazane to terminate the reaction to obtain alkoxy-terminated polysiloxane;
(2) mixing 3 parts of polypropylene fiber, 5.5 parts of polypropylene particles and 5 parts of VAE705 in parts by weight, stirring at a high speed of 22000rpm for 3min, adding 3 parts of BN nanoparticles, continuously stirring and mixing for 3min, and drying the mixed material at 80 ℃ for 12h to obtain the composite heat-conducting filler;
(3) adding 100 parts by weight of the prepared alkoxy-terminated polysiloxane, 8 parts by weight of composite heat-conducting filler and 11 parts by weight of nano calcium carbonate into a kneader, stirring and mixing for 2 hours at 120 ℃, then adding 6.5 parts by weight of cross-linking agent, stirring and mixing for 30 minutes, finally sequentially adding 3.5 parts by weight of silane coupling agent and 3 parts by weight of catalyst, and continuously stirring and mixing for 15 minutes to obtain the high-heat-conductivity silicone sealant.
And testing the performance of the prepared high-thermal-conductivity silicone sealant.
(1) Shear strength; performing aluminum sheet to aluminum sheet according to GB/T7124 + 2008 standard;
(2) tensile strength and elongation at break; according to the GB/T528-1998 standard, the sample is dumbbell type II, and the stretching speed is 500 mm/min;
(3) hardness; the Shore A hardness is measured according to the GB/T531.1-2008 standard.
(4) Thermal conductivity; the thermal conductivity was measured using a thermal conductivity meter, model DRL-III, Hunan Tan instruments and meters, Inc.
The test results are shown in table 1; wherein, the comparative example is the silicone sealant without adding the composite heat-conducting filler.
TABLE 1
The test result particles show that the heat-conducting property and the mechanical property of the sealant added with the self-made composite heat-conducting filler are effectively improved.
Although specific embodiments of the invention have been described, many other forms and modifications of the invention will be apparent to those skilled in the art. It is to be understood that the appended claims and this invention generally cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.
Claims (10)
1. A high heat conduction silicone sealant modified by a filler with a multilevel structure is characterized in that alkoxy-terminated polysiloxane is used as a base adhesive, polypropylene fibers, polypropylene particles and BN nanoparticles are used as composite heat conduction fillers, and nano calcium carbonate, a cross-linking agent and a catalyst are added for stirring and kneading to prepare the silicone sealant;
the alkoxy end-capped polysiloxane is prepared by mixing a siloxane monomer with a mixed solution of modified phosphazene and sodium ethoxide at normal temperature and then taking methyltrimethoxysilane as an end-capping agent;
the preparation method of the modified phosphazene comprises the following steps: the linear phosphazene with low polymerization degree and hydrofluoric acid are mixed and reacted at 150 ℃.
2. The sealant of claim 1, wherein the molar ratio of the linear phosphazene to the hydrofluoric acid is 1: (4.5-5.5), wherein the reaction time of the linear phosphazene and hydrofluoric acid is 2.5-5.5 h.
3. The multilevel-structure filler modified high-thermal-conductivity silicone sealant as claimed in claim 1, wherein the preparation method of the modified phosphazene and sodium ethoxide mixed solution is as follows: firstly, stirring and mixing sodium hydroxide, deionized water and absolute ethyl alcohol uniformly at normal temperature according to the mass ratio of 1:2:2, and then adding modified phosphazene and stirring and mixing to obtain the modified phosphazene; the mass concentration of the modified phosphazene and sodium ethoxide mixed solution is 1-5%.
4. The preparation method of the multilevel structural filler modified high thermal conductivity silicone sealant according to any one of claims 1 to 3, characterized by comprising the following steps:
(1) mixing siloxane monomers with a mixed solution of modified phosphazene and sodium ethoxide at normal temperature, uniformly stirring, removing air bubbles and moisture in vacuum, stirring at 30-50 ℃, adding methyltrimethoxysilane and octamethylcyclotetrasiloxane, quickly stirring, keeping the vacuum to remove methanol generated in a reaction system, stirring and mixing for 25-35 min, and adding a terminator to terminate the reaction to obtain alkoxy end-blocked polysiloxane;
(2) mixing polypropylene fibers, polypropylene particles and VAE705, stirring at 20000-23000 rpm for 2-4 min, adding BN nanoparticles, continuously stirring and mixing for 2-4 min, and drying the mixed material at 80 ℃ for 10-12 h to obtain the composite heat-conducting filler;
(3) adding the prepared alkoxy-terminated polysiloxane, the composite heat-conducting filler and the nano calcium carbonate into a kneading machine, stirring and mixing for 1-2 h at 100-120 ℃, then adding the cross-linking agent, stirring and mixing for 30min, finally sequentially adding the silane coupling agent and the catalyst, and continuously stirring and mixing for 10-15 min to obtain the high-heat-conducting silicone sealant.
5. The preparation method of the multilevel-structure filler modified high-thermal-conductivity silicone sealant according to claim 4, wherein in the step (1), when the siloxane monomer is mixed with the mixed solution of the modified phosphazene and the sodium ethoxide at normal temperature, the dosage of the modified phosphazene and the sodium ethoxide is 5-25 ppm, and when the siloxane monomer is mixed, the mixed solution of the modified phosphazene and the sodium ethoxide is firstly diluted by 100 times in advance.
6. The preparation method of the multilevel-structure filler modified high-thermal-conductivity silicone sealant as claimed in claim 4, wherein in the step (1), the mass ratio of the siloxane monomer, the methyltrimethoxysilane and the octamethylcyclotetrasiloxane is 100: (1.5-2.5): (0.35-0.55).
7. The method for preparing the multilevel-structure filler modified high thermal conductivity silicone sealant according to claim 4, wherein in the step (1), the terminating agent is one of hexamethyldisilazane, phosphorous acid, sodium phosphite, and trioctylamine.
8. The preparation method of the multilevel-structure filler-modified high-thermal-conductivity silicone sealant according to claim 4, wherein in the step (2), the mass ratio of the polypropylene fibers, the polypropylene particles, the VAE705 and the BN nanosheets is 3: (5-6): (2-2.5): 3.
9. the preparation method of the multilevel-structure filler modified high-thermal-conductivity silicone sealant as claimed in claim 4, wherein in the step (3), the amounts of the components are respectively as follows in parts by weight: 100 parts of alkoxy-terminated polysiloxane, 4-9 parts of composite heat-conducting filler, 8-12 parts of nano calcium carbonate, 3-7 parts of cross-linking agent, 1-4 parts of silane coupling agent and 1-3 parts of catalyst.
10. The preparation method of the filler-modified high-thermal-conductivity silicone sealant with the multilevel structure according to claim 4, wherein in the step (3), the crosslinking agent is one of methyl tributyl ketoxime silane and vinyl tributyl ketoxime silane; the catalyst is one of an organic tin catalyst and dibutyltin dilaurate.
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| CN202010206233.2A Pending CN111320967A (en) | 2020-03-23 | 2020-03-23 | High-thermal-conductivity silicone sealant modified by multilevel-structure filler and preparation method thereof |
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