CN110776745A - Preparation method of thermal interface material - Google Patents
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Abstract
The invention discloses a preparation method of a thermal interface material, wherein the optimal proportion of heat-conducting filler is determined by the solvent filling amount in a heat-conducting particle pile masonry, the heat-conducting filler is subjected to surface pretreatment and ball milling and is fully and uniformly mixed, the heat-conducting filler, silicone rubber resin, a catalyst, an inhibitor, silicone oil and a cross-linking agent are fully and uniformly mixed in an internal mixer to obtain silicone rubber compound, and the silicone rubber compound is subjected to high-temperature die pressing and secondary vulcanization to obtain the high-heat-conductivity low-hardness insulating silicone rubber thermal interface material with the heat conductivity coefficient of 2-10W/m.K and the Shore A hardness of 20-30. According to the invention, through determining a proper heat-conducting filler proportion, carrying out surface treatment and ball milling dispersion on the heat-conducting filler uniformly, an effective heat-conducting network is formed in the silicon rubber matrix, so that the heat-conducting silicon rubber with high heat conductivity coefficient, low hardness, good insulating property and stable performance is obtained.
Description
Technical Field
The invention relates to a preparation method of a thermal interface material, in particular to a preparation method of a high-thermal-conductivity low-hardness insulation silicone rubber thermal interface material, and belongs to the technical field of heat conduction materials.
Background
With the development of electronic devices toward high power and miniaturization, the requirement for the thermal conductivity of the thermal conductive material is higher and higher. As is well known, electronic and electrical products generate heat during operation, and if the electronic devices cannot effectively dissipate heat, the working reliability of the electronic and electrical products is reduced, the service life is shortened, the power is reduced, and even potential safety hazards are brought. In order to solve the problem, in the conventional method, a heat conduction gasket and the like prepared from heat conduction materials are added on the contact surface of the electronic component and the radiator, so that the electronic component and the radiator are in gapless contact. Therefore, the good heat conduction material has the advantages of high heat conduction coefficient, low hardness, good flexibility, good aging resistance, good cold and hot circulation stability, simple construction, low cost and the like.
At present, interface heat conduction materials used in the market are heat conduction resin, heat conduction adhesive, heat conduction rubber and the like. The heat conducting material is generally prepared by compounding a high molecular material, inorganic salts or oils and heat conducting fillers. Among them, the heat conductive filler is usually an inorganic filler such as boron nitride, aluminum nitride, silicon carbide, zinc oxide, magnesium oxide, or aluminum oxide, a metal conductive filler such as copper, aluminum, silver, or tin, or a carbon-based filler such as carbon fiber, carbon nanotube, graphite, graphene, or carbon black. Unlike general rubber which uses C-C bond as main chain structure, silicone rubber uses silicon-oxygen bond as main chain, and the particularity of its structure also determines its advantages such as high and low temperature resistance (-50-250 ℃), good elasticity, high air permeability, high voltage resistance and radiation resistance (Journal of nuclear materials,2015,464: 210-) -215. Therefore, the high-thermal-conductivity insulating material with excellent performance, which is prepared by compounding the silicone rubber resin serving as a thermal conductive matrix and the high-thermal-conductivity filler, has important significance and value.
It is well known that heat is transferred mainly by three means, thermal conduction, thermal convection and thermal radiation. For thermally conductive silicone rubber, heat is transferred primarily by thermal conduction. However, the internal heat conduction channel of the currently adopted heat conduction silicone rubber is insufficient, so that the heat conduction performance of the silicone pad is poor, and the application range of the silicone pad is limited. Numerous researches show that the condition that the heat-conducting silicone rubber has good heat-conducting performance is that more heat-conducting network chains are formed between the heat-conducting filler particles and the silicone rubber matrix, so that the heat-conducting channel is ensured to be smooth. The thermal conductivity of the silicone rubber filled with the heat-conducting filler with too large particle size is higher than that of the silicone rubber filled with the heat-conducting filler with small particle size under the same filling amount. It is to be noted that too large or too small particles of the heat conductive filler affect the continuity of the heat conductive network, too large particles affect the chains of the surrounding heat conductive network, too small particles affect the continuity of the heat conductive network, and the smaller the particle size of the particles, the larger the specific surface area thereof, the more serious the agglomeration of the particles, and the less dense the packing becomes. Therefore, the larger or smaller particle size of the particles does not take advantage of the improvement in the thermal conductivity of the thermally conductive silicone rubber. In addition to the particle size of the thermally conductive filler, the loading of the thermally conductive filler determines to a large extent the thermal conductivity of the composite material, and in general, the greater the loading, the denser the thermally conductive network formed between the thermally conductive fillers, and the higher the thermal conductivity of the material (chemical engineering and equipment, 2014, 6: 25-28). However, the increase in the amount of the heat conductive filler increases the viscosity of the silicone rubber, deteriorates the processability, and even makes it impossible to process the silicone rubber. For example, Zhongsu et Al (specialty rubber products, 2007, 28 (5): 19-21) filled silicone rubber with three Al2O3 types of different particle sizes, the thermal conductivity can reach 1.23W/(m.K), which is larger than the thermal conductivity of single particle size filling. Chinese patent 201310205354.5 discloses a preparation method of a heat-conducting insulating silicone rubber thermal interface material, wherein heat-conducting fillers with different particle sizes are blended with silicone rubber, and the heat-conducting insulating silicone rubber with a heat conductivity coefficient of 0.8-2.5W/(m.K) is obtained through mould pressing. In addition, the higher the thermal conductivity of the filler, the higher the thermal conductivity of the filled composite material, at the same volume or mass fraction of the filler.
At present, binary or ternary fillers are mostly compounded in documents or patents to obtain the heat-conducting insulating silicone rubber. For example, in "design of highly filled heat conductive silicone rubber composite system and study of influence law", jintianpeng et Al (great university of chemical, beijing, 2013) prepared 3 μm and 24 μm Al2O3 in a mass ratio of 2:1, a silicone rubber composite system with a thermal conductivity of 2.34W/(m · K) was prepared. Chinese patent 201010223158.7 discloses a method for preparing heat-conducting silicone rubber, wherein 1250 mesh, 3000 mesh and 7000 mesh aluminum oxide are mixed and added into silicone rubber to prepare silicone rubber with heat conductivity coefficient larger than 3W/(m.K). The chinese invention patent 201711123056.6 discloses a preparation method of a high thermal conductivity composite silica gel gasket, which realizes reasonable distribution of alumina particles in a silica gel matrix and improvement of the thermal conductivity of the alumina particles by screening spherical alumina particles, and finally improves the thermal conductivity of a silicone rubber gasket to more than 6.0W. It is worth noting that at present, the compounding proportion of the heat conduction particles with different particle diameters is mostly obtained by a trial and error method, and the experiment workload is huge, and the time and the labor are consumed.
Disclosure of Invention
The invention aims to solve the defects of the prior art, and provides a preparation method of a heat-conducting silicone rubber thermal interface material, which is high in heat conductivity coefficient, good in stability and convenient to prepare, aiming at the problem of large workload caused by trial and error method of compounding traditional heat-conducting particles. The preparation method starts from the contact mode between filler particles, the compatibility between the particles and a matrix, and the space arrangement and dispersion condition of the particles in the matrix, determines the optimal proportion of the heat-conducting filler according to the filling amount of the solvent in the heat-conducting particle pile masonry, compounds the heat-conducting filler particles with different particle sizes and different types, further promotes the contact between the filler particles in a ball milling mode, and disperses in the silicon rubber resin matrix to form an effective heat-conducting passage, thereby realizing the preparation of the heat-conducting silicon rubber with high heat-conducting coefficient.
The technical scheme adopted by the invention is as follows:
a method for preparing a thermal interface material comprises the following steps:
the selection of the material of S1 is carried out,
selecting the following components in parts by mass: 10-80 parts of silicon rubber base material, 20-90 parts of heat conducting filler, 0.5-8 parts of surface treating agent, 0.2-6 parts of silicone oil, 0.1-2.5 parts of cross-linking agent, 0.01-2 parts of catalyst and 0.01-1 part of inhibitor,
the heat-conducting filler is compounded by heat-conducting materials with different particle sizes and different densities, and the volume fraction of the filler in the stacked body of the heat-conducting filler is
The stacking density of the stacked masonry is rho
st，
ρ
st≤4g/cm
3；
S2 heat-conducting filler treatment,
coating and modifying the surface of the heat-conducting filler by using a surface treating agent, and then performing ball milling operation to obtain the fine-grinding heat-conducting filler;
the S3 internal mixer is used for mixing,
adding the fine-grinding heat-conducting filler, the silicon rubber base material, the silicon oil, the cross-linking agent, the catalyst and the inhibitor into an internal mixer for uniform mixing to prepare silicon rubber compound;
s4, vulcanization molding is carried out,
and preheating the silicon rubber compound, and then placing the preheated silicon rubber compound into a mold cavity for mold pressing vulcanization molding.
Preferably, the silicone rubber substrate is one or more of methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber, ethylene-terminated liquid silicone rubber and polyvinyl liquid silicone rubber.
Preferably, the cross-linking agent is one or more of di-tert-butyl peroxide, benzoyl peroxide, dicumyl peroxide, 2, 4-dichlorobenzoyl peroxide, 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane and tert-butyl perbenzoate.
Preferably, the catalyst is a platinum catalyst.
Preferably, the inhibitor is one or more of hexamethylcyclotrisilazane, diphenylsilanediol and methylphenyldiethoxysilane.
Preferably, the heat conducting filler is at least two of aluminum oxide, boron nitride, aluminum nitride, silicon carbide and zinc oxide.
Preferably, the step S1 of compounding the heat conductive material includes the following steps,
s01, proportioning and cleaning the filler,
selecting at least two heat-conducting fillers with the particle size of 0.1-500 mu m according to the expected volume fraction of the fillers and the stacking density of the stacked masonry, adding a low-boiling-point solvent, performing centrifugal oscillation, and drying to constant weight;
the impregnation of the S02 filler is carried out,
putting the dried heat-conducting filler into a centrifuge tube, adding a filling mixed solvent, performing centrifugal treatment on the mixture of a polar solvent and a non-polar solvent according to the mass ratio of 1:2 or 2:3, sucking supernatant liquid in the centrifuge tube by absorbent cotton, sucking residual solvent on the surface of a heat-conducting filler accumulation body by using filter paper, weighing and recording;
the determination of the content of the voids of S03,
W
st＝1-W
s(2)
in the formula, w
sIs filled with mixed solventAmount, w
stIs the mass of the filler, w
sAnd w
stAll can be obtained by experimental measurement.
W
sIs the mass fraction of the mixed solvent, W
stIs the mass fraction of the filler pile masonry,
is the volume fraction of filler in the packing, p
stFor packing the packing material to pile up the packing density, rho
sIs the density of the mixed solvent,. rho
fIt is the density of the filler that is,
according to
And ρ
stAnd (6) judging.
Preferably, the polar solvent is one or more of methanol, ethanol, acetone, tetrahydrofuran, dimethyl sulfoxide and N, N-dimethylformamide,
the nonpolar solvent is one or more of chloroform, benzene, cyclohexane, carbon disulfide and petroleum ether
The invention has the following beneficial effects:
by determining a proper proportion of the heat-conducting filler, performing surface treatment and ball milling dispersion on the heat-conducting filler uniformly, an effective heat-conducting network is formed in the silicone rubber matrix, and thus the heat-conducting silicone rubber with high heat conductivity coefficient, low hardness, good insulating property and stable performance is obtained. The high-thermal-conductivity low-hardness insulation silicone rubber thermal interface material prepared by the invention has the advantages of excellent heat conductivity, excellent processing and forming performance, simple production process, high production efficiency and the like, can be widely applied to the fields of electronic and electric appliances, aerospace, war industry, automobiles, high-power LEDs and the like, and has wide market application prospect.
Drawings
FIG. 1 is a schematic structural view of an SEM photograph of high thermal conductivity and low hardness silicone rubber prepared by the preparation method of the thermal interface material of the present invention.
Detailed Description
The invention provides a preparation method of a thermal interface material. The technical solution of the present invention is described in detail below with reference to the accompanying drawings so that it can be more easily understood and appreciated.
A method for preparing a thermal interface material comprises the following steps:
selecting materials according to the following parts by weight: 10-80 parts of silicon rubber base material, 20-90 parts of heat conducting filler, 0.5-8 parts of surface treating agent, 0.2-6 parts of silicone oil, 0.1-2.5 parts of cross-linking agent, 0.01-2 parts of catalyst and 0.01-1 part of inhibitor,
wherein the heat-conducting filler is compounded by heat-conducting materials with different particle sizes and different densities, and the volume fraction of the filler in the stacked body of the heat-conducting filler is
The stacking density of the stacked masonry is rho
st，
ρ
st≤4g/cm
3。
And (3) treating the heat-conducting filler, namely coating and modifying the surface of the heat-conducting filler by using a surface treating agent, and then performing ball milling operation to obtain the fine-grinding heat-conducting filler. The ball milling speed is 50-800 r/min, and the ball milling time is 10-150 min.
And (2) mixing by using an internal mixer, namely adding the fine-grinding heat-conducting filler, the silicone rubber base material, the silicone oil, the cross-linking agent, the catalyst and the inhibitor into the internal mixer for uniform mixing to prepare the silicone rubber compound, wherein the rotating speed of the internal mixer is 30-100 rpm, and the internal mixing time is 5-20 min.
And (4) vulcanization molding, namely preheating the silicon rubber compound, and then placing the preheated silicon rubber compound into a mold cavity for mold pressing vulcanization molding. Specifically, the silicone rubber compound is placed in a vacuum oven for treatment for 20-60 min, then placed in a mold cavity preheated to 100-140 ℃, after mold closing, the mold is placed on a flat vulcanizing machine for vulcanization, the vulcanization pressure is 5-10 MPa, the vulcanization time is 5-20 min, and the mold pressing method is adopted for vulcanization molding. And after the first-stage vulcanization molding, placing the grinding tool cooled to room temperature in a blast oven for secondary vulcanization, wherein the vulcanization temperature is 200 ℃, the vulcanization time is 1-2 h, and after the grinding tool is naturally cooled to room temperature, taking out the grinding tool to obtain the high-heat-conductivity low-hardness insulating silicon rubber. The heat conductivity coefficient of the heat-conducting silicon rubber composite material is 2-10W/m.K.
In the scheme, the silicon rubber base material is one or a combination of more of methyl vinyl silicon rubber, methyl phenyl vinyl silicon rubber, ethylene-terminated liquid silicon rubber and polyvinyl liquid silicon rubber. The cross-linking agent is one or more of di-tert-butyl peroxide, benzoyl peroxide, dicumyl peroxide, 2, 4-dichlorobenzoyl peroxide, 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane and tert-butyl perbenzoate. The catalyst is a platinum catalyst. The inhibitor is one or more of hexamethylcyclotrisilazane, diphenylsilanediol and methyl phenyl diethoxysilane. The heat conducting filler is at least two of aluminum oxide, boron nitride, aluminum nitride, silicon carbide and zinc oxide. The surface treating agent is one or more of A151, KH550, KH560 or KH 570.
The compounding of the heat conduction material comprises the following steps:
the method comprises the following steps of proportioning and cleaning fillers, selecting at least two heat-conducting fillers with the particle size of 0.1-500 mu m according to the expected volume fraction of the fillers and the stacking density of the stacked masonry, adding a low-boiling-point solvent, performing centrifugal oscillation, and drying to constant weight;
soaking the filler, putting the dried heat-conducting filler into a centrifuge tube, adding a filling mixed solvent, performing centrifugal treatment by using a mixture of a polar solvent and a non-polar solvent according to a mass ratio of 1:2 or 2:3, sucking supernatant liquid in the centrifuge tube by using absorbent cotton, sucking the residual solvent on the surface of a heat-conducting filler accumulation body by using filter paper, weighing and recording;
the determination of the content of the voids,
W
st＝1-W
s(2)
in the formula, w
sAs a filling amount of the mixed solvent, w
stIs the mass of the filler, W
sIs the mass fraction of the mixed solvent, W
stIs the mass fraction of the filler pile masonry,
is the volume fraction of filler in the packing, p
stFor packing the packing material to pile up the packing density, rho
sIs the density of the mixed solvent,. rho
fIs the density of the filler according to
And ρ
stAnd (6) judging.
The particle size of the large-particle-size heat-conducting filler is 70-500 mu m, and the particle size of the small-particle-size heat-conducting filler is 0.1-10 mu m. Wherein, the proportion of the heat-conducting fillers with different particle diameters and different types is determined according to the measurement result of the solvent filling amount in the reactor masonry.
The polar solvent is one or more of methanol, ethanol, acetone, tetrahydrofuran, dimethyl sulfoxide and N, N-dimethylformamide, and the nonpolar solvent is one or more of chloroform, benzene, cyclohexane, carbon disulfide and petroleum ether.
Example 1
The heat-conducting silicone rubber comprises the following components in parts by weight: silicon rubber base material: 80 parts of heat-conducting filler: 80 parts of a surface treating agent: 1.0 part, silicone oil: 0.5 part of cross-linking agent: 1.0 part of catalyst: 0.05 part of inhibitor: 0.02 part.
According to the measurement result of the solvent filling amount in the reactor masonry, the best mass ratio of the heat-conducting filler is determined as follows: alumina (particle size 75 μm): alumina (particle size 3 μm): aluminum nitride (particle size 10 μm): 2:4:1. Preparing a surface treating agent A151 into a solution, and respectively performing surface treatment on heat-conducting fillers with different scales under the treatment condition of 60 ℃ and performing electromagnetic stirring for 2 hours; after the treatment, filtering, drying and crushing are carried out, and various heat-conducting fillers with good surface treatment can be obtained. Secondly, the heat-conducting filler is fully and uniformly mixed by adopting a ball milling method. Wherein the ball milling speed is 200r/min, and the ball milling time is 100 min; then, 80 parts of heat-conducting filler, 80 parts of methyl vinyl silicone rubber, 1.0 part of silicone oil, 1.0 part of 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane, 0.05 part of platinum catalyst and 0.02 part of diphenylsilanediol are added into an internal mixer to be internally mixed until the mixture is uniformly mixed, and the silicone rubber compound filled with the heat-conducting filler is obtained. Then, the uniformly stirred silicone rubber compound is placed in a vacuum oven for treatment for 0.5h, so that air bubbles mixed in the silicone rubber compound are completely extracted. Weighing a certain amount of silicon rubber compound (the quality is based on the thickness required by a sample) and placing the silicon rubber compound into a die cavity preheated to 100 ℃, after die assembly, placing the die on a flat vulcanizing machine for vulcanization, wherein the vulcanization pressure is 5MPa, and the vulcanization time is 20 min. And finally, after the first-stage vulcanization molding, placing the grinding tool cooled to room temperature in a blast oven for secondary vulcanization, wherein the vulcanization temperature is 200 ℃, the vulcanization time is 1h, and after the grinding tool is naturally cooled to room temperature, taking out the grinding tool to obtain the high-thermal-conductivity low-hardness insulating silicon rubber. The heat conductivity coefficient of the heat-conducting silicon rubber composite material is 6.3W/m.K.
Example 2
The heat-conducting silicone rubber comprises the following components in parts by weight: silicon rubber matrix: 60 parts of heat-conducting filler: 80 parts of a surface treating agent: 1.0 part, silicone oil: 0.3 part of cross-linking agent: 1.5 parts of catalyst: 0.0 part of inhibitor: 0.01 part.
Firstly, according to the measurement result of the solvent filling amount in the reactor masonry, the optimal mass ratio of the heat-conducting filler is determined as follows: alumina (particle size 40 μm): aluminum nitride (particle size 6 μm): boron nitride (particle size 3 μm): 1: 3: 2.5. preparing a surface treating agent KH560 into a solution, and respectively performing surface treatment on heat-conducting fillers with different scales under the treatment condition of 60 ℃ and magnetically stirring for 2 hours; after the treatment, filtering, drying and crushing are carried out, and various heat-conducting fillers with good surface treatment can be obtained. Secondly, the heat-conducting filler is fully and uniformly mixed by adopting a ball milling method. Wherein the ball milling speed is 400r/min, and the ball milling time is 30 min; then, 80 parts of heat-conducting filler, 60 parts of ethylene-terminated liquid silicone rubber, 0.3 part of polyvinyl silicone oil, 1.5 parts of 2, 4-dichlorobenzoyl peroxide, 0.02 part of platinum catalyst and 0.01 part of methyl phenyl diethoxy silane are added into an internal mixer to be mixed uniformly, and the silicone rubber compound filled with the heat-conducting filler is obtained. Then, the uniformly stirred silicone rubber compound is placed in a vacuum oven for treatment for 0.5h, so that air bubbles mixed in the silicone rubber compound are completely extracted. Weighing a certain amount of silicon rubber compound (the quality is based on the thickness required by a sample) and putting the silicon rubber compound into a die cavity preheated to 120 ℃, after die assembly, putting the die on a flat vulcanizing machine for vulcanization, wherein the vulcanization pressure is 3MPa, and the vulcanization time is 15 min. And finally, after the first-stage vulcanization molding, placing the grinding tool cooled to room temperature in a blast oven for secondary vulcanization, wherein the vulcanization temperature is 200 ℃, the vulcanization time is 1h, and after the grinding tool is naturally cooled to room temperature, taking out the grinding tool to obtain the high-thermal-conductivity low-hardness insulating silicon rubber. The heat conductivity coefficient of the heat-conducting silicon rubber composite material is 4.6W/m.K.
Example 3
The heat-conducting silicone rubber comprises the following components in parts by weight: silicon rubber matrix: 75 parts of heat-conducting filler: 80 parts of a surface treating agent: 1.0 part, silicone oil: 3 parts of a crosslinking agent: 2.0 parts of catalyst: 1.0 part of inhibitor: 0.05 part.
Firstly, according to the measurement result of the solvent filling amount in the reactor masonry, the optimal mass ratio of the heat-conducting filler is determined as follows: alumina (particle size 75 μm): zinc oxide (particle size 100 nm): boron nitride (particle size 10 μm): 2.5: 1.2: 1.0. preparing a surface treating agent KH550 into a solution, and respectively performing surface treatment on heat-conducting fillers with different scales under the treatment condition of 60 ℃ and magnetically stirring for 2 hours; after the treatment, filtering, drying and crushing are carried out, and various heat-conducting fillers with good surface treatment can be obtained. Secondly, the heat-conducting filler is fully and uniformly mixed by adopting a ball milling method. Wherein the ball milling speed is 500r/min, and the ball milling time is 10 min; then, 75 parts of heat-conducting filler, 80 parts of methyl phenyl vinyl silicone rubber, 3 parts of vinyl-terminated silicone oil, 2.0 parts of dicumyl peroxide, 1 part of platinum catalyst and 0.05 part of diphenylsilanediol are added into an internal mixer to be internally mixed until the mixture is uniformly mixed, and the silicon rubber compound filled with the heat-conducting filler is obtained. Then, the uniformly stirred silicone rubber compound is placed in a vacuum oven for treatment for 0.5h, so that air bubbles mixed in the silicone rubber compound are completely extracted. Weighing a certain amount of silicon rubber compound (the quality is based on the thickness required by a sample) and placing the silicon rubber compound into a die cavity preheated to 140 ℃, after die assembly, placing the die on a flat vulcanizing machine for vulcanization, wherein the vulcanization pressure is 5MPa, and the vulcanization time is 10 min. And finally, after the first-stage vulcanization molding, placing the grinding tool cooled to room temperature in a blast oven for secondary vulcanization, wherein the vulcanization temperature is 200 ℃, the vulcanization time is 1h, and after the grinding tool is naturally cooled to room temperature, taking out the grinding tool to obtain the high-thermal-conductivity low-hardness insulating silicon rubber. The heat conductivity coefficient of the heat-conducting silicon rubber composite material is 8.5W/m.K.
Example 4
The heat-conducting silicone rubber comprises the following components in parts by weight: silicon rubber matrix: 80 parts of heat-conducting filler: 65 parts of a surface treating agent: 1.0 part, silicone oil: 6 parts of a crosslinking agent: 1.0 part of catalyst: 0.05 part of inhibitor: 0.02 part.
Firstly, according to the measurement result of the solvent filling amount in the reactor masonry, the optimal mass ratio of the heat-conducting filler is determined as follows: boron nitride (particle size 25 μm): aluminum nitride (particle size 10 μm): 3.2: 1.4. preparing a surface treating agent KH550 into a solution, and respectively performing surface treatment on heat-conducting fillers with different scales under the treatment condition of 60 ℃ and magnetically stirring for 2 hours; after the treatment, filtering, drying and crushing are carried out, and various heat-conducting fillers with good surface treatment can be obtained. Secondly, the heat-conducting filler is fully and uniformly mixed by adopting a ball milling method. Wherein the ball milling speed is 350r/min, and the ball milling time is 25 min; then, 65 parts of heat-conducting filler, 80 parts of methyl vinyl silicone rubber, 6 parts of polyvinyl silicone oil, 1.0 part of 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane, 0.05 part of platinum catalyst and 0.02 part of hexamethylcyclotrisilazane are added into an internal mixer to be internally mixed until the mixture is uniformly mixed, and the silicone rubber compound filled with the heat-conducting filler is obtained. Then, the uniformly stirred silicone rubber compound is placed in a vacuum oven for treatment for 0.5h, so that air bubbles mixed in the silicone rubber compound are completely extracted. Weighing a certain amount of silicon rubber compound (the quality is based on the thickness required by a sample) and putting the silicon rubber compound into a die cavity preheated to 120 ℃, after die assembly, putting the die on a flat vulcanizing machine for vulcanization, wherein the vulcanization pressure is 10MPa, and the vulcanization time is 20 min. And finally, after the first-stage vulcanization molding, placing the grinding tool cooled to room temperature in a blast oven for secondary vulcanization, wherein the vulcanization temperature is 200 ℃, the vulcanization time is 2 hours, and after the grinding tool is naturally cooled to room temperature, taking out the grinding tool to obtain the high-thermal-conductivity low-hardness insulating silicon rubber. The heat conductivity coefficient of the heat-conducting silicon rubber composite material is 7.9W/m.K.
Fig. 1 shows an SEM photograph of the high thermal conductive low hardness silicone rubber: (a) example 1 magnification 115 times); (b) example 2 (50 x magnification); (c) example 3 (500 x magnification); (d) example 4 (5000 x magnification).
Table 1 properties of high thermal conductivity low hardness silicone rubber.
Through the above description, it can be found that the preparation method of the thermal interface material of the present invention determines a proper proportion of the heat conductive filler, performs surface treatment and ball milling dispersion on the heat conductive filler uniformly, so as to form an effective heat conductive network in the silicone rubber matrix, thereby obtaining the heat conductive silicone rubber with high heat conductivity coefficient, low hardness, good insulating property and stable performance. The high-thermal-conductivity low-hardness insulation silicone rubber thermal interface material prepared by the invention has the advantages of excellent heat conductivity, excellent processing and forming performance, simple production process, high production efficiency and the like, can be widely applied to the fields of electronic and electric appliances, aerospace, war industry, automobiles, high-power LEDs and the like, and has wide market application prospect.
The technical solutions of the present invention are fully described above, it should be noted that the specific embodiments of the present invention are not limited by the above description, and all technical solutions formed by equivalent or equivalent changes in structure, method, or function according to the spirit of the present invention by those skilled in the art are within the scope of the present invention.
Claims (8)
1. A preparation method of a thermal interface material is characterized by comprising the following steps:
the selection of the material of S1 is carried out,
selecting the following components in parts by mass: 10-80 parts of silicon rubber base material, 20-90 parts of heat conducting filler, 0.5-8 parts of surface treating agent, 0.2-6 parts of silicone oil, 0.1-2.5 parts of cross-linking agent, 0.01-2 parts of catalyst and 0.01-1 part of inhibitor,
the heat-conducting filler is compounded by heat-conducting materials with different particle sizes and different densities, and the volume fraction of the filler in the stacked body of the heat-conducting filler is
The stacking density of the stacked masonry is rho
st，
ρ
st≤4g/cm
3；
S2 heat-conducting filler treatment,
coating and modifying the surface of the heat-conducting filler by using a surface treating agent, and then performing ball milling operation to obtain the fine-grinding heat-conducting filler;
the S3 internal mixer is used for mixing,
adding the fine-grinding heat-conducting filler, the silicon rubber base material, the silicon oil, the cross-linking agent, the catalyst and the inhibitor into an internal mixer for uniform mixing to prepare silicon rubber compound;
s4, vulcanization molding is carried out,
and preheating the silicon rubber compound, and then placing the preheated silicon rubber compound into a mold cavity for mold pressing vulcanization molding.
2. The method of claim 1, wherein the step of preparing a thermal interface material comprises:
the silicon rubber base material is one or a combination of more of methyl vinyl silicon rubber, methyl phenyl vinyl silicon rubber, ethylene-terminated liquid silicon rubber and polyvinyl liquid silicon rubber.
3. The method of claim 1, wherein the step of preparing a thermal interface material comprises:
the cross-linking agent is one or a combination of more of di-tert-butyl peroxide, benzoyl peroxide, dicumyl peroxide, 2, 4-dichlorobenzoyl peroxide, 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane and tert-butyl perbenzoate.
4. The method of claim 1, wherein the step of preparing a thermal interface material comprises:
the catalyst is a platinum catalyst.
5. The method of claim 1, wherein the step of preparing a thermal interface material comprises:
the inhibitor is one or more of hexamethylcyclotrisilazane, diphenyl silanediol and methyl phenyl diethoxysilane.
6. The method of claim 1, wherein the step of preparing a thermal interface material comprises:
the heat-conducting filler is at least two combinations of aluminum oxide, boron nitride, aluminum nitride, silicon carbide and zinc oxide.
7. The method of claim 1, wherein the step of preparing a thermal interface material comprises:
the compounding of the heat conductive material in the step S1 comprises the following steps,
s01, proportioning and cleaning the filler,
selecting at least two heat-conducting fillers with the particle size of 0.1-500 mu m according to the expected volume fraction of the fillers and the stacking density of the stacked masonry, adding a low-boiling-point solvent, performing centrifugal oscillation, and drying to constant weight;
the impregnation of the S02 filler is carried out,
putting the dried heat-conducting filler into a centrifuge tube, adding a filling mixed solvent, performing centrifugal treatment on the mixture of a polar solvent and a non-polar solvent according to the mass ratio of 1:2 or 2:3, sucking supernatant liquid in the centrifuge tube by absorbent cotton, sucking residual solvent on the surface of a heat-conducting filler accumulation body by using filter paper, weighing and recording;
the determination of the content of the voids of S03,
W
st＝1-W
s(2)
in the formula, w
sAs a filling amount of the mixed solvent, w
stIs the mass of the filler, W
sIs the mass fraction of the mixed solvent, W
stIs the mass fraction of the filler pile masonry,
is the volume fraction of filler in the packing, p
stFor packing the packing material to pile up the packing density, rho
sIs the density of the mixed solvent,. rho
fIt is the density of the filler that is,
according to
And ρ
stAnd (6) judging.
8. The method of claim 7, wherein the step of preparing a thermal interface material comprises:
the polar solvent is one or the combination of more of methanol, ethanol, acetone, tetrahydrofuran, dimethyl sulfoxide and N, N-dimethylformamide,
the nonpolar solvent is one or more of chloroform, benzene, cyclohexane, carbon disulfide and petroleum ether.
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Application publication date: 20200211 |