CN110524922B - Preparation method of heat-conducting silicone rubber composite material - Google Patents
Preparation method of heat-conducting silicone rubber composite material Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
- B29C43/22—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of indefinite length
- B29C43/24—Calendering
- B29C43/245—Adjusting calender parameters, e.g. bank quantity
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Abstract
The invention discloses a preparation method of a heat-conducting silicone rubber composite material. The preparation method comprises mixing water and layered heat-conducting filler, ultrasonically dispersing, adding vinyl silicone oil, heating and stirring to evaporate water to obtain pre-dispersion; mixing silicon rubber, a reinforcing agent, a pre-dispersion agent and a vulcanizing agent by a rubber kneading machine to obtain a rubber compound, rolling the rubber compound into a sheet by a rubber rolling mill, pre-vulcanizing by hot air, then stretching and drawing to thin the film, stretching and orienting, rolling the thin film into a cylinder, slicing the cylinder along the direction vertical to the axis of the cylinder, and vulcanizing and shaping. The film has high thermal conductivity because the heat-conducting filler is oriented along the thickness direction of the film. The thermal conductivity range of the silicone rubber composite material is 4-14W/(m.k), the thermal conductivity can be adjusted by changing the technological parameters and the traction elongation of a calender, and the preparation process of the composite material is simple in process and environment-friendly.
Description
Technical Field
The invention relates to the field of preparation of heat-conducting silicon rubber composite materials, in particular to a preparation method for realizing different orientation degrees of a layered heat-conducting filler in a silicon rubber matrix through a rubber calender so that the silicon rubber composite material obtains high heat conductivity and adjustable heat conductivity.
Background
With the development of electronic components towards miniaturization and integration, the demand for high thermal conductive materials is more and more urgent. The traditional metal-based heat conduction material has the defects of high density, difficult processing and no elasticity although the heat conductivity is high. The heat-conducting polymer material has the advantages of low density, easy processing, variable shape and the like. The heat-conducting filler for the polymer comprises alumina, boron nitride, metal powder (copper powder, silver powder and the like) and carbon-based filler (graphite, carbon nano tubes and the like). The existing research shows that in order to realize high thermal conductivity of the heat-conducting polymer material, the method of increasing the dosage of the heat-conducting filler is usually adopted, but the method usually causes the obvious reduction of the mechanical property of the material.
In addition, the orientation of the filler can enable the heat-conducting high polymer material to obtain higher heat conductivity. For example, the Chinese patent CN106867094A reports that the heat conductivity of the prepared heat-conducting composite material in the orientation direction is improved by pressing the rubber composite material into sheets by using an open mill and then overlapping the sheets compared with the conventional direct mixing method. However, for open mill processing, the rubber material roll-passing time is short, the roll speed, the speed ratio, the roll distance and the roll temperature are difficult to adjust, the orientation of the heat-conducting filler is insufficient, the orientation degree is difficult to control, and therefore the heat conductivity of the heat-conducting material has a remarkable improvement space.
Disclosure of Invention
The invention aims to overcome the defects of the prior technical scheme and provide a method for preparing a high-thermal-conductivity silicone rubber composite material by rolling through a rubber rolling mill.
In order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows:
a preparation method of a heat-conducting silicon rubber composite material comprises the following steps:
(1) mixing the layered heat-conducting filler with water, ultrasonically dispersing and stripping the heat-conducting filler, then adding vinyl silicone oil, uniformly mixing and stirring, and heating to evaporate water to obtain a vinyl silicone oil pre-dispersion of the layered heat-conducting filler; the layered heat-conducting filler is one or a mixture of hexagonal boron nitride, aluminum nitride, layered graphite and graphene;
(2) mixing the silicon rubber, the reinforcing agent and the vinyl silicone oil pre-dispersion of the heat-conducting filler in a rubber kneading machine, adding a vulcanizing agent, and uniformly mixing to prepare rubber compound;
(3) calendering the rubber compound by using a rubber calender to obtain a thin rubber sheet, heating for prevulcanization, drawing and stretching, controlling the elongation rate to be 50% -100%, and rolling to obtain a rubber cylinder; the temperature of the calendering rollers is 50-80 ℃, the speed ratio is 1.1-1.3, and the roller distance between two adjacent rollers is 0.5-2.0 mm;
(4) cutting the rubber cylinder into rubber sheets along the direction vertical to the axis of the cylinder, controlling the thickness to be 1-10 mm, and vulcanizing and shaping at low pressure;
the heat-conducting silicon rubber composite material comprises the following raw materials in parts by mass: 100 parts of silicone rubber, 40-200 parts of layered heat-conducting filler, 10-50 parts of vinyl silicone oil, 10-40 parts of reinforcing agent and 1-5 parts of vulcanizing agent.
In order to further achieve the object of the present invention, preferably, the silicone rubber is one or a mixture of two or more of dimethyl silicone rubber, methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber.
Preferably, the power of the ultrasound is 300-600W, and the ultrasound time is 2-4 h.
Preferably, the reinforcing agent is one or a mixture of precipitated silica and fumed silica.
Preferably, the vulcanizing agent is one or a mixture of 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide, dicumyl peroxide and dibenzoyl peroxide.
Preferably, the viscosity of the vinyl silicone oil is 100 to 500 mPas.
Preferably, the rubber calender adopts a 3-roller calender or a 4-roller calender, and the roller arrangement adopts an I-type, S-type or type arrangement mode.
Preferably, in the step (3), the heating and pre-vulcanizing is to heat the thin film in a hot drying tunnel at 180-200 ℃, and the heating time is 1-3 min.
Preferably, in the step (4), the vulcanization pressure of the cut thin film is 0.5-2.0 MPa, the heating temperature is 160-190 ℃, and the vulcanization time is 5-20 min.
Preferably, in the step (1), the layered heat-conducting filler and the water are mixed according to a mass ratio of 1: 2-1: 4; the stirring speed for uniformly mixing and stirring is 100-300 r/min, and the stirring time is 30-60 min; the heating temperature for heating and evaporating water is 100-150 ℃.
The film after the rolling is precured to ensure that the film does not break in the process of traction and stretching.
The main principle of the invention is that the calendering effect of a calender is utilized, when the silicone rubber mixture added with the layered heat-conducting filler passes through a gradually narrowed roller gap of the calender, the filler generates obvious orientation behavior along the calendering direction, namely, the oriented arrangement of the layered filler is generated along the calendering direction, and the smaller the roller distance is, the higher the orientation degree of the filler is. And the calendered thin film is drawn and stretched, so that the silicon rubber molecular chain can be stretched and oriented, the film is further thinned, and the heat-conducting filler can generate higher orientation degree. When the rolled sheet is rolled into a cylinder, the heat conductive filler forms a plurality of heat conductive paths along the axial direction of the cylinder (i.e., perpendicular to the rolling direction), and thus the thermal conductivity along the axial direction of the cylinder is higher. The cylinder is cut into films with the thickness of 1-10 mm along the direction perpendicular to the axis, and the application requirements of the heat conducting sheets with different thicknesses are mainly met.
For the conventional open mill to realize the filler orientation mode, the orientation degree of the heat-conducting filler cannot be controlled and adjusted because the speed ratio, the roller temperature and the like of a roller of the open mill are difficult to adjust, the heat conductivity of the mixture is low and difficult to adjust and control, and in addition, the mechanical property of the silicone rubber sheet is poor. Compared with the existing method for realizing the orientation of the heat-conducting filler by adopting a rubber open mill, the method adopts the calender to carry out calendering orientation on the silicon rubber mixture, and can adjust the orientation degree of the heat-conducting filler in the silicon rubber mixture in a larger range by adjusting the roll distance, the speed ratio and the roll temperature of the calender, thereby obtaining the silicon rubber sheet with high heat conductivity and high mechanical property on the basis of not increasing the using amount of the heat-conducting filler.
Compared with the prior art, the invention has the outstanding advantages that:
(1) the rubber calender is adopted to replace a rubber open mill, so that the technological parameters such as roll spacing, speed ratio, roll temperature and the like can be continuously adjusted, the number of the rollers and the arrangement mode of the rollers can be properly adjusted to obtain the heat-conducting silicone rubber composite materials with different orientation degrees, and the heat conductivity of the silicone rubber composite materials can be adjusted in a larger range only by changing the calendering technological parameters under the condition of not changing the using amount of the heat-conducting filler;
(2) after the layered heat-conducting filler is ultrasonically stripped, the specific surface area of the layered heat-conducting filler is remarkably increased, and after the vinyl silicone oil pre-dispersion of the heat-conducting filler is prepared, the heat-conducting filler is more uniformly dispersed in a silicone rubber matrix, so that the heat conductivity of the silicone rubber composite material is remarkably improved;
(3) the whole preparation process does not need any organic solvent, has no VOC emission, is green and environment-friendly, has simple process flow, and is easy to realize continuous production.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clear, the method of the present invention is described below by way of specific embodiments, which are only used for explaining the present invention and are not meant to be limiting.
The tensile strength of the silicone rubber sheet was measured in accordance with GB/T528-2009. The thermal conductivity of the silicone rubber sheet is measured by a laser flash method (refer to national standard GB/T22588-:
λ＝α×Cp×ρ (1)
in the formula:
λ -thermal conductivity, in W/(m.K);
alpha-thermal diffusion coefficient in m2/s；
CpSpecific heatThe unit is J/(kg. K);
rho-density in kg/m3。
Example 1:
the heat-conducting silicon rubber composite material comprises the following raw materials in parts by weight:
methyl vinyl silicone rubber 100 parts
Hexagonal boron nitride 100 parts
25 parts of vinyl silicone oil
Precipitated white carbon black 25 parts
2 parts of 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide
A preparation method of a heat-conducting silicon rubber composite material comprises the following steps:
(1) mixing hexagonal boron nitride and water according to the mass ratio of 1:3, carrying out ultrasonic dispersion with the power of 600W for 4h to strip the hexagonal boron nitride, then adding vinyl silicone oil with the viscosity of 300mPa & s, heating, mixing and stirring at the stirring speed of 300r/min for 60min at the heating temperature of 150 ℃ to completely evaporate water to obtain a vinyl silicone oil pre-dispersion of the hexagonal boron nitride;
(2) mixing methyl vinyl silicone rubber, precipitated white carbon black and vinyl silicone oil pre-dispersion of hexagonal boron nitride in a rubber kneading machine, then adding 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide, and uniformly mixing to prepare rubber compound;
(3) calendering the mixed rubber by a three-roller I-type calender at the roller temperature of 50 ℃, the roller spacing of 2.0mm and the speed ratio of 1.1 to obtain a rubber sheet, heating the rubber sheet by a hot drying channel at the temperature of 180 ℃ for 2min to pre-vulcanize the rubber sheet, then drawing and stretching the rubber sheet with the elongation of 50%, and rolling the rubber sheet to obtain a rubber cylinder;
(4) cutting the rubber cylinder along the direction vertical to the axis of the cylinder to obtain a rubber sheet with the thickness of 2mm, and then carrying out low-pressure vulcanization at the vulcanization temperature of 160 ℃, the vulcanization pressure of 0.5MPa and the vulcanization time of 20 min.
The thermal conductivity of the obtained silicone rubber composite material in the thickness direction is 4.1W/(m.K), and the tensile strength is 5.1 MPa.
Example 2:
the heat-conducting silicon rubber composite material comprises the following raw materials in parts by weight:
methyl vinyl silicone rubber 100 parts
Hexagonal boron nitride 100 parts
25 parts of vinyl silicone oil
Precipitated white carbon black 25 parts
2 parts of 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide
A preparation method of a heat-conducting silicon rubber composite material comprises the following steps:
(1) mixing hexagonal boron nitride and water according to the mass ratio of 1:3, carrying out ultrasonic dispersion with the power of 600W for 4h to strip the hexagonal boron nitride, then adding vinyl silicone oil with the viscosity of 100mPa & s, heating, mixing and stirring at the stirring speed of 300r/min for 60min at the heating temperature of 150 ℃ to completely evaporate water to obtain a vinyl silicone oil pre-dispersion of the hexagonal boron nitride;
(2) mixing methyl vinyl silicone rubber, precipitated white carbon black and vinyl silicone oil pre-dispersion of hexagonal boron nitride in a rubber kneading machine, adding a vulcanizing agent 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide, and uniformly mixing to prepare a rubber compound;
(3) calendering the rubber compound by using a four-roll calender, wherein the roll temperature is 80 ℃, the roll spacing is 0.5mm, the speed ratio is 1.3, a rubber sheet is obtained, the rubber sheet is heated by a hot drying channel at the temperature of 180 ℃ for 2min to be pre-vulcanized, and then the rubber sheet is drawn and stretched, the elongation is 50%, and the rubber cylinder is obtained by rolling;
(4) cutting the rubber cylinder along the direction vertical to the axis of the cylinder to obtain a rubber sheet with the thickness of 2mm, and then carrying out low-pressure vulcanization at the vulcanization temperature of 160 ℃, the vulcanization pressure of 0.5MPa and the vulcanization time of 20 min.
The thermal conductivity of the obtained silicone rubber composite material in the thickness direction is 6.5W/(m.K), and the tensile strength is 5.3 MPa.
Example 3:
the heat-conducting silicon rubber composite material comprises the following raw materials in parts by weight:
methyl vinyl silicone rubber 100 parts
200 parts of hexagonal boron nitride
30 portions of fumed silica
50 parts of vinyl silicone oil
5 parts of 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide
A preparation method of a heat-conducting silicon rubber composite material comprises the following steps:
(1) mixing hexagonal boron nitride and water according to a mass ratio of 1:4, carrying out ultrasonic dispersion with the power of 600W for 3h to strip the hexagonal boron nitride, then adding vinyl silicone oil with the viscosity of 100mPa & s, mixing and stirring at the stirring speed of 300r/min for 40min, heating at the temperature of 130 ℃, and completely evaporating water to obtain a vinyl silicone oil pre-dispersion of the hexagonal boron nitride;
(2) uniformly mixing methyl vinyl silicone rubber, fumed silica and a vinyl silicone oil pre-dispersion of boron nitride in a rubber kneading machine, and finally adding 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide to prepare a rubber compound;
(3) calendering the rubber compound by using a four-roller I-type calender, wherein the roller temperature is 80 ℃, the roller spacing is 1.0mm, the speed ratio is 1.3, a rubber sheet is obtained, the rubber sheet is heated by a hot drying channel at the temperature of 200 ℃ for 1min to be pre-vulcanized and shaped, and then the rubber sheet is drawn and stretched, the elongation is 100%, and the rubber cylinder is obtained by rolling;
(4) cutting the rubber cylinder along the direction vertical to the axis of the cylinder to obtain a rubber sheet with the thickness of 3mm, and then carrying out low-pressure vulcanization at the vulcanization temperature of 180 ℃, the vulcanization pressure of 1.0MPa and the vulcanization time of 10 min.
The thermal conductivity of the obtained silicone rubber composite material in the thickness direction is 10.6W/(m.K), and the tensile strength is 4.2 MPa.
Example 4:
the heat-conducting silicon rubber composite material comprises the following raw materials in parts by weight:
methyl vinyl silicone rubber 100 parts
180 parts of layered graphite
20 portions of fumed silica
Vinyl silicone oil 30 parts
Dicumyl peroxide 1.5 parts
A preparation method of a heat-conducting silicon rubber composite material comprises the following steps:
(1) mixing the laminar graphite and water according to a mass ratio of 1:3, performing ultrasonic dispersion with the power of 500W for 3 hours to peel the laminar graphite, then adding vinyl silicone oil with the viscosity of 500mPa & s, mixing and stirring at the stirring speed of 300r/min for 50min, heating at the temperature of 150 ℃, and completely evaporating water to obtain a vinyl silicone oil pre-dispersion of the laminar graphite;
(2) mixing methyl vinyl silicone rubber, fumed silica and vinyl silicone oil pre-dispersion of layered graphite in a rubber kneading machine, then adding a vulcanizing agent dicumyl peroxide, and uniformly mixing to prepare a rubber compound;
(3) calendering the rubber compound by using a four-roller I-type calender, wherein the roller temperature is 80 ℃, the roller spacing is 1.2mm, the speed ratio is 1.3, so as to obtain a thin rubber sheet, heating the thin rubber sheet by a hot drying channel at the temperature of 180 ℃ for 2min to pre-vulcanize and shape the thin rubber sheet, then drawing and stretching the thin rubber sheet, and rolling the thin rubber sheet to obtain a rubber cylinder, wherein the elongation of the thin rubber sheet is 100%;
(4) cutting the rubber cylinder along the direction vertical to the axis of the cylinder to obtain a rubber sheet with the thickness of 3mm, and then carrying out low-pressure vulcanization at the vulcanization temperature of 200 ℃, the vulcanization pressure of 0.5MPa and the vulcanization time of 5 min.
The thermal conductivity of the obtained silicone rubber composite material in the thickness direction is 8.1W/(m.K), and the tensile strength is 4.5 MPa.
Example 5:
the heat-conducting silicon rubber composite material comprises the following raw materials in parts by weight:
methyl phenyl vinyl silicone rubber 100 parts
40 parts of graphene
20 portions of fumed silica
10 parts of vinyl silicone oil
Dicumyl peroxide 1 part
A preparation method of a heat-conducting silicon rubber composite material comprises the following steps:
(1) mixing graphene and water according to a mass ratio of 1:4, performing ultrasonic dispersion with the power of 600W for 2 hours to strip the graphene, then adding vinyl silicone oil with the viscosity of 100mPa & s, mixing and stirring at the stirring speed of 200r/min for 30min, heating at the temperature of 150 ℃, and completely evaporating water to obtain a vinyl silicone oil pre-dispersion of the graphene;
(2) mixing methyl phenyl vinyl silicone rubber, fumed silica and vinyl silicone oil pre-dispersion of graphene in a rubber kneading machine, then adding a vulcanizing agent dicumyl peroxide, and uniformly mixing to prepare rubber compound;
(3) calendering the rubber compound by using a four-roller I-type calender, wherein the roller temperature is 60 ℃, the roller spacing is 1.0mm, the speed ratio is 1.3, so as to obtain a rubber sheet, heating the rubber sheet by a hot drying channel at the temperature of 200 ℃ for 1min to pre-vulcanize and shape the rubber sheet, then drawing and stretching the rubber sheet, and rolling the rubber sheet to obtain a rubber cylinder, wherein the elongation of the rubber sheet is 100%;
(4) cutting the rubber cylinder along the direction vertical to the axis of the cylinder to obtain a rubber sheet with the thickness of 2mm, and then carrying out low-pressure vulcanization at the vulcanization temperature of 180 ℃, the vulcanization pressure of 1.0MPa and the vulcanization time of 10 min.
The thermal conductivity of the obtained silicone rubber composite material in the thickness direction was 7.9W/(m.K), and the tensile strength was 5.7 MPa.
Example 6:
the heat-conducting silicon rubber composite material comprises the following raw materials in parts by weight:
methyl phenyl vinyl silicone rubber 100 parts
80 parts of graphene
10 portions of fumed silica
Vinyl silicone oil 20 parts
Dicumyl peroxide 5 parts
A preparation method of a heat-conducting silicon rubber composite material comprises the following steps:
(1) mixing graphene and water according to a mass ratio of 1:3, performing ultrasonic dispersion with the power of 600W for 4 hours to strip the graphene, then adding vinyl silicone oil with the viscosity of 100mPa & s, mixing and stirring at the stirring speed of 300r/min for 60min, heating at the temperature of 150 ℃, and completely evaporating water to obtain a vinyl silicone oil pre-dispersion of the graphene;
(2) mixing methyl phenyl vinyl silicone rubber, fumed silica and vinyl silicone oil pre-dispersion of graphene in a rubber kneading machine, then adding a vulcanizing agent dicumyl peroxide, and uniformly mixing to prepare a rubber compound;
(3) calendering the rubber compound by using a four-roller S-shaped calender, wherein the roller temperature is 80 ℃, the roller spacing is 1.0mm, the speed ratio is 1.2, so as to obtain a rubber sheet, heating the rubber sheet by a hot drying channel at the temperature of 200 ℃ for 1min to pre-vulcanize and shape the rubber sheet, then drawing and stretching the rubber sheet, and the elongation is 100%, and rolling the rubber sheet to obtain a rubber cylinder;
(4) cutting the rubber cylinder along the direction vertical to the axis of the cylinder to obtain a rubber sheet with the thickness of 2mm, and then carrying out low-pressure vulcanization at the vulcanization temperature of 190 ℃ under the vulcanization pressure of 1.0MPa for 5 min.
The thermal conductivity of the obtained silicone rubber composite material in the thickness direction was 13.7W/(m.K), and the tensile strength was 5.9 MPa.
Example 7:
the heat-conducting silicon rubber composite material comprises the following raw materials in parts by weight:
methyl phenyl vinyl silicone rubber 100 parts
Aluminum nitride 150 parts
20 portions of fumed silica
Vinyl silicone oil 30 parts
Dicumyl peroxide 3 parts
A preparation method of a heat-conducting silicon rubber composite material comprises the following steps:
(1) mixing aluminum nitride and water according to the mass ratio of 1:3, performing ultrasonic dispersion with the power of 600W for 4 hours to strip the aluminum nitride, then adding vinyl silicone oil with the viscosity of 500mPa & s, mixing and stirring at the stirring speed of 200r/min for 60min, heating at the temperature of 150 ℃, and completely evaporating water to obtain a vinyl silicone oil pre-dispersion of the aluminum nitride;
(2) uniformly mixing methyl vinyl silicone rubber, fumed silica and vinyl silicone oil pre-dispersion of aluminum nitride in a rubber kneading machine, and finally adding a vulcanizing agent dicumyl peroxide to prepare a rubber compound;
(3) calendering the rubber compound by using a four-roll calender, wherein the roll temperature is 60 ℃, the roll spacing is 1.0mm, and the speed ratio is 1.2 to obtain a thin rubber sheet, heating the thin rubber sheet by a hot drying channel at the temperature of 200 ℃ for 1min to pre-vulcanize and shape the thin rubber sheet, then drawing and stretching the thin rubber sheet, wherein the elongation is 100%, and rolling the thin rubber sheet to obtain a rubber cylinder;
(4) cutting the rubber cylinder along the direction vertical to the axis of the cylinder to obtain a 2mm rubber sheet, and then carrying out low-pressure vulcanization at the vulcanization temperature of 190 ℃ under the vulcanization pressure of 1.5MPa for 5 min.
The thermal conductivity of the obtained silicone rubber composite material in the thickness direction is 7.5W/(m.K), and the tensile strength is 4.0 MPa.
Comparative example:
the heat-conducting silicon rubber composite material comprises the following raw materials in parts by weight:
methyl vinyl silicone rubber 100 parts
200 parts of hexagonal boron nitride
30 portions of fumed silica
40 parts of vinyl silicone oil
5 parts of 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide
A preparation method of a heat-conducting silicon rubber composite material comprises the following steps: uniformly mixing methyl vinyl silicone rubber, fumed silica, hexagonal boron nitride and vinyl silicone oil in a rubber kneading machine, and finally adding a vulcanizing agent 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide to prepare a rubber compound; and (3) discharging the sheets by using an open mill, wherein the roll temperature is 50 ℃, the roll spacing is 1.0mm, the speed ratio is 1.3, and then carrying out pressure vulcanization, wherein the vulcanization temperature is 170 ℃, the vulcanization pressure is 13.0MPa, and the vulcanization time is 15 min.
The thermal conductivity of the obtained silicone rubber composite material in the thickness direction is 2.7W/(m.K), and the tensile strength is 2.1 MPa.
Compared with the comparative example, in examples 1 to 7, the silicone rubber composite material prepared by using the rubber calender has the lowest thermal conductivity of 4.1W/(m · K), which is 52% higher than that in the comparative example, and the lowest tensile strength (4.0MPa) of the silicone rubber vulcanized sheet is 90% higher than that in the comparative example, which indicates that the thermal conductivity and mechanical properties of the silicone rubber composite material prepared by the calendering process method can be significantly improved compared with the sheet outlet method of the open mill, the thermal conductivity of the silicone rubber composite material can be adjusted in a larger range along with the change of calendering process parameters on the premise of not increasing the amount of the heat-conducting filler, the roll temperature is increased in a certain range, the speed ratio is increased, the roll distance is reduced, the thermal conductivity of the silicone rubber composite material is correspondingly improved, and in addition, after the sheet is precured, the rubber molecular chains are also subjected to tensile orientation by traction and stretching, thereby further improving the thermal conductivity of the composite material. Therefore, compared with the prior art, the regulation and control method is completely different, and the silicon rubber composite material can be used as a flexible heat conduction material which simultaneously meets high heat conductivity and high tensile strength and is used for heat conduction packaging of equipment and devices such as electronics, electrical appliances, communication, mobile phones and the like.
It will be understood by those skilled in the art that the present invention is not limited to the embodiments disclosed, but is capable of numerous changes and modifications without departing from the spirit and scope of the invention, and that various changes, modifications, substitutions, combinations and simplifications may be made without departing from the spirit and scope of the invention in its broadest form and are therefore intended to be covered by the present invention.
Claims (9)
1. A preparation method of a heat-conducting silicon rubber composite material is characterized by comprising the following steps:
(1) mixing the layered heat-conducting filler with water, ultrasonically dispersing and stripping the heat-conducting filler, then adding vinyl silicone oil, uniformly mixing and stirring, and heating to evaporate water to obtain a vinyl silicone oil pre-dispersion of the layered heat-conducting filler; the layered heat-conducting filler is one or a mixture of hexagonal boron nitride, aluminum nitride, layered graphite and graphene;
(2) mixing the silicon rubber, the reinforcing agent and the vinyl silicone oil pre-dispersion of the heat-conducting filler in a rubber kneading machine, adding a vulcanizing agent, and uniformly mixing to prepare rubber compound;
(3) calendering the rubber compound by using a rubber calender to obtain a thin rubber sheet, heating for prevulcanization, drawing and stretching, controlling the elongation rate to be 50-100%, and rolling to obtain a rubber cylinder; the temperature of the calendering rollers is 50-80 ℃, the speed ratio is 1.1-1.3, and the roller distance between two adjacent rollers is 0.5-2.0 mm; the heating and pre-vulcanizing step is to heat the thin film in a hot drying tunnel at 180-200 ℃, wherein the heating time is 1-3 min;
(4) cutting the rubber cylinder into rubber sheets along the direction vertical to the axis of the cylinder, controlling the thickness to be 1-10 mm, and vulcanizing and shaping at low pressure;
the heat-conducting silicon rubber composite material comprises the following raw materials in parts by mass: 100 parts of silicone rubber, 40-200 parts of layered heat-conducting filler, 10-50 parts of vinyl silicone oil, 10-40 parts of reinforcing agent and 1-5 parts of vulcanizing agent.
2. The method for preparing the heat-conductive silicone rubber composite material according to claim 1, characterized in that: the silicon rubber is one or a mixture of dimethyl silicon rubber, methyl vinyl silicon rubber and methyl phenyl vinyl silicon rubber.
3. The method for preparing the heat-conductive silicone rubber composite material according to claim 1, characterized in that: the power of the ultrasound is 300-600W, and the ultrasound time is 2-4 h.
4. The method for preparing the heat-conductive silicone rubber composite material according to claim 1, characterized in that: the reinforcing agent is one or a mixture of more of precipitated white carbon black and gas-phase white carbon black.
5. The method for preparing the heat-conductive silicone rubber composite material according to claim 1, characterized in that: the vulcanizing agent is one or a mixture of 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide, dicumyl peroxide and dibenzoyl peroxide.
6. The method for preparing the heat-conductive silicone rubber composite material according to claim 1, characterized in that: the viscosity of the vinyl silicone oil is 100-500 mPas.
7. The method for preparing the heat-conductive silicone rubber composite material according to claim 1, characterized in that: the rubber calender adopts a 3-roller calender or a 4-roller calender, and the rollers are arranged in an I-type, S-type or type arrangement mode.
8. The method for preparing the heat-conductive silicone rubber composite material according to claim 1, characterized in that: in the step (4), the vulcanizing pressure is 0.5-2.0 MPa, the heating temperature is 160-190 ℃, and the vulcanizing time is 5-20 min.
9. The method for preparing the heat-conductive silicone rubber composite material according to claim 1, characterized in that: in the step (1), the layered heat-conducting filler and water are mixed according to a mass ratio of 1: 2-1: 4; the stirring speed for uniformly mixing and stirring is 100-300 r/min, and the stirring time is 30-60 min; the heating temperature for heating and evaporating water is 100-150 ℃.
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