CN111087817A - PDMS-based graphene heat-conducting composite material and preparation method and application thereof - Google Patents
PDMS-based graphene heat-conducting composite material and preparation method and application thereof Download PDFInfo
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- CN111087817A CN111087817A CN201911257312.XA CN201911257312A CN111087817A CN 111087817 A CN111087817 A CN 111087817A CN 201911257312 A CN201911257312 A CN 201911257312A CN 111087817 A CN111087817 A CN 111087817A
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Abstract
The invention relates to the technical field of thermal interface materials, in particular to a PDMS-based graphene heat-conducting composite material and a preparation method and application thereof. The PDMS-based graphene heat-conducting composite material provided by the invention comprises polydimethylsiloxane and non-covalent modified graphene; the non-covalent modified graphene is hyperbranched polyethylene copolymer modified graphene with terminal branched chain grafted polysilsesquioxane. According to the invention, the hyperbranched polyethylene copolymer of which the terminal branched chain is grafted with polysilsesquioxane is adopted to carry out non-covalent modification on graphene, so that the dispersion stability of the graphene in chloroform or tetrahydrofuran is improved; by introducing a silica structure on the surface of the graphene through the modification, the compatibility of the graphene and polydimethylsiloxane can be obviously improved, and the heat-conducting property of the flexible heat-conducting composite material is further improved; the thermal conductivity coefficient of the PDMS-based graphene thermal conductive composite material can reach 0.9W/(m.K).
Description
Technical Field
The invention relates to the technical field of thermal interface materials, in particular to a PDMS-based graphene heat-conducting composite material and a preparation method and application thereof.
Background
In recent years, with the rapid development of the field of microelectronics, miniaturization and integration have gradually become the current development trend. However, the miniaturized and integrated electronic device generates much heat during the use process, thereby affecting the use performance of the electronic product and reducing the service life of the electronic product. Therefore, thermal interface composite materials with better thermal conductivity have become a hot spot for research. The traditional polymer has a low thermal conductivity coefficient (0.15-0.20W/(m.K)), and the thermal conductivity of the traditional polymer can be remarkably improved by adding some high-thermal-conductivity fillers. Graphene is a carbon atom in sp2The honeycomb two-dimensional crystal structure carbon nano material formed by close packing of the hybrid system becomes the best candidate of the heat-conducting filler due to the high heat conductivity coefficient (5000W/(m.K)).
However, poor compatibility of the graphene filler with flexible PDMS significantly affects the curing process and performance of the composite material. The common method for improving the compatibility of the graphene filler and the PDMS matrix is to prepare graphene oxide and covalently graft molecules such as a silane coupling agent on the surface of the graphene oxide to improve the compatibility of the graphene oxide and the PDMS matrix. However, covalent modification of graphene oxide destroys the intrinsic structure of the graphene surface, and reduces the thermal conductivity of the graphene filler.
Disclosure of Invention
The invention aims to provide a PDMS-based graphene heat-conducting composite material and a preparation method and application thereof. The PDMS-based graphene heat-conducting composite material provided by the invention has excellent heat-conducting property.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a PDMS-based graphene heat-conducting composite material, which comprises polydimethylsiloxane and non-covalent modified graphene;
the non-covalent modified graphene is hyperbranched polyethylene copolymer of which the tail end is grafted with polysilsesquioxane, and is non-covalently modified and modified.
Preferably, the mass ratio of the non-covalent modified graphene to the polydimethylsiloxane is (0.5-4.0): (96.0-99.5).
Preferably, the thickness of the PDMS-based graphene heat-conducting composite material is 0.5-1.0 mm.
The invention also provides a preparation method of the PDMS-based graphene heat-conducting composite material, which comprises the following steps:
and mixing the non-covalent modified graphene chloroform solution with polydimethylsiloxane, removing the solvent, and curing to obtain the PDMS-based graphene heat-conducting composite material.
Preferably, the mixture obtained by mixing also comprises curing agents, wherein the curing agents are Sylgard184A and Sylgard 184B;
the mass ratio of Sylgard184A to Sylgard184B is (5-12): 1.
preferably, the curing temperature is 75-85 ℃, and the curing time is 3-5 h.
Preferably, the preparation method of the non-covalent modified graphene comprises the following steps:
in the ethylene atmosphere, mixing acryloyl isobutyl polysilsesquioxane, palladium-diimine and dichloromethane, and carrying out copolymerization grafting reaction to obtain a hyperbranched polyethylene copolymer of the terminal branched chain grafted polysilsesquioxane;
mixing the hyperbranched polyethylene copolymer with the terminal branched chain grafted with the polysilsesquioxane, graphite and chloroform, and performing ultrasonic treatment to obtain the non-covalent modified graphene.
Preferably, the pressure of the ethylene is 0.8-1.2 atm;
the dosage ratio of the acryloyl isobutyl polysilsesquioxane to the palladium-diimine to the dichloromethane is (45-55) g: (1.8-2.2) g: (480-520) mL;
the temperature of the copolymerization grafting reaction is 20-30 ℃, and the time of the copolymerization grafting reaction is 20-30 h.
Preferably, the using amount ratio of the graphite to the hyperbranched polyethylene copolymer of the terminal branched chain grafted polysilsesquioxane to the chloroform is (8-12) mg: (3.5-4.5) mg: 1 mL;
the frequency of the ultrasonic wave is 60-300W, and the time of the ultrasonic wave is 40-50 h.
The invention also provides the application of the PDMS-based graphene heat-conducting composite material in the technical scheme or the PDMS-based graphene heat-conducting composite material prepared by the preparation method in the technical scheme in the field of thermal interface materials.
The invention provides a PDMS-based graphene heat-conducting composite material, which comprises polydimethylsiloxane and non-covalent modified graphene; the non-covalent modified graphene is hyperbranched polyethylene copolymer of which the tail end is grafted with polysilsesquioxane, and is non-covalently modified and modified. According to the invention, the hyperbranched polyethylene copolymer of which the terminal branched chain is grafted with polysilsesquioxane is adopted to carry out non-covalent modification on graphene, so that the dispersion stability of the graphene in chloroform or tetrahydrofuran is improved, and meanwhile, a silica structure is introduced to the surface of the graphene through the modification, so that the compatibility of the graphene and polydimethylsiloxane can be obviously improved, and the heat-conducting property of the flexible heat-conducting composite material is further improved; according to the description of the embodiment, the thermal conductivity coefficient of the PDMS-based graphene thermal conductive composite material can reach 0.9W/(m.K) at most.
Drawings
FIG. 1 is a schematic diagram of a process for preparing a hyperbranched polyethylene copolymer having a terminal-branched POSS grafted thereon;
FIG. 2 is a schematic diagram of graphene obtained by ultrasonic exfoliation of graphite in chloroform solution according to the present invention;
FIG. 3 is a schematic diagram of a process for preparing non-covalently modified graphene;
FIG. 4 is a diagram of a material object of the PDMS-based graphene thermal conductive composite material prepared in comparative example 1 and examples 1 to 7;
fig. 5 is an SEM image of the PDMS-based graphene thermal conductive composite prepared in example 1;
fig. 6 shows the thermal conductivity of the PDMS-based graphene thermal conductive composite material prepared in examples 1 to 7.
Detailed Description
The invention provides a PDMS-based graphene heat-conducting composite material, which comprises polydimethylsiloxane and non-covalent modified graphene;
the non-covalent modified graphene is hyperbranched polyethylene copolymer of which the tail end is grafted with polysilsesquioxane, and is non-covalently modified and modified.
In the invention, the mass ratio of the non-covalent modified graphene to the Polydimethylsiloxane (PDMS) is preferably (0.5-4.0): (96.0 to 99.5), more preferably (1.0 to 3.0): (97.0 to 99.0), most preferably (1.5 to 2.5): (97.5-98.5).
In the invention, the thickness of the PDMS-based graphene heat-conducting composite material is preferably 0.5-1.0 mm, more preferably 0.6-0.9 mm, and most preferably 0.65 mm.
The invention also provides a preparation method of the PDMS-based graphene heat-conducting composite material, which comprises the following steps:
and mixing the non-covalent modified graphene chloroform solution with polydimethylsiloxane, removing the solvent, and curing to obtain the PDMS-based graphene heat-conducting composite material.
In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.
In the invention, the concentration of the chloroform solution of the non-covalent modified graphene is preferably 0.2-2.0 mg/mL, more preferably 0.5-1.5 mg/mL, and most preferably 1.0 mg/mL; the preparation method of the non-covalent modification modified graphene in the chloroform solution of the non-covalent modification modified graphene preferably comprises the following steps:
mixing acryloyl isobutyl polysilsesquioxane (acryloyl isobutyl POSS), palladium-diimine and dichloromethane in ethylene atmosphere, and carrying out copolymerization grafting reaction to obtain a hyperbranched polyethylene copolymer of the terminal branched chain grafted polysilsesquioxane;
mixing the hyperbranched polyethylene copolymer with the terminal branched chain grafted with the polysilsesquioxane, graphite and chloroform, and performing ultrasonic treatment to obtain the non-covalent modified graphene.
In the invention, acryloyl isobutyl polysilsesquioxane, palladium-diimine and dichloromethane are mixed in ethylene atmosphere to carry out copolymerization grafting reaction, thus obtaining the hyperbranched polyethylene copolymer of the end branched chain grafted polysilsesquioxane. In the present invention, polysilsesquioxane is abbreviated as POSS; the pressure of the ethylene is preferably 0.8 to 1.2atm, more preferably 0.9 to 1.1atm, and most preferably 1.0 atm. In the invention, the dosage ratio of the acryloyl isobutyl POSS, the palladium-diimine and the dichloromethane is preferably (45-55) g: (1.8-2.2) g: (480-520) mL, more preferably (48-52) g: (1.9-2.1) g: (490-510) mL, most preferably (45-55) g: (1.8-2.2) g: (490-510) mL.
In the present invention, the specific process of mixing acryloyl isobutyl POSS, palladium-diimine and methylene chloride preferably comprises the steps of:
mixing acryloyl isobutyl POSS with 4/5 volume of dichloromethane, and stirring for 10min until the mixture is fully dissolved to obtain a solution of the acryloyl isobutyl POSS;
mixing palladium-diimine with 1/5 volumes of dichloromethane until fully dissolved to obtain a catalyst solution;
mixing the solution of the acryloyl isobutyl POSS and the solution of the catalyst.
In the present invention, the copolymerization grafting reaction is preferably carried out under stirring, and the stirring is not particularly limited, and may be carried out by a process well known to those skilled in the art; the temperature of the copolymerization grafting reaction is preferably 20-30 ℃, more preferably 22-28 ℃, and most preferably 25 ℃; the time of the copolymerization grafting reaction is preferably 20-30 h, more preferably 22-28 h, and most preferably 24-26 h.
After the copolymerization grafting reaction is finished, the invention preferably carries out post-treatment on the obtained reaction system, wherein the post-treatment is preferably as follows: 1) pouring the reaction system into methanol (the volume ratio of the methanol to the dichloromethane is preferably 4:1) to terminate the reaction, dissolving the obtained polymerization product into toluene (the volume ratio of the toluene to the dichloromethane is preferably 4:25), adding methanol (the volume ratio of the methanol to the dichloromethane is preferably 12:5) to precipitate the polymerization product, repeating the dissolving and precipitating processes for 3 times to fully remove the incompletely reacted acryloyl isobutyl ester POSS; 2): dissolving the polymer treated in the step 1) in tetrahydrofuran (the volume ratio of the tetrahydrofuran to toluene is preferably 3:4), respectively adding 10 drops of hydrogen peroxide and hydrochloric acid, stirring for 30min, adding 80mL of methanol to precipitate the polymer, repeating the steps for 3 times, and performing vacuum drying at 60 ℃ for 24h to obtain a colorless and transparent hyperbranched polyethylene copolymer (marked as HBPE @ POSS) with the terminal branched chain grafted POSS (a preparation process schematic diagram is shown in FIG. 1).
After the hyperbranched polyethylene copolymer of the terminal branched chain grafted polysilsesquioxane is obtained, the hyperbranched polyethylene copolymer of the terminal branched chain grafted polysilsesquioxane, graphite and chloroform are mixed and subjected to ultrasonic treatment to obtain the non-covalent modified and modified graphene (the specific process is shown in fig. 2). In the invention, the graphite is preferably graphite powder, and the invention has no special requirement on the particle size of the graphite powder; in the invention, the use amount ratio of the graphite, the hyperbranched polyethylene copolymer with the terminal branched chain grafted with POSS and chloroform is preferably (8-12) mg: (3.5-4.5) mg: 1mL, more preferably (9-11) mg: (3.8-4.2) mg: 1mL, most preferably 10 mg: 4 mg: 1 mL. The mixing is not particularly limited in the present invention, and may be carried out by a mixing process known to those skilled in the art. In the invention, the frequency of the ultrasonic wave is preferably 60-300W, more preferably 120-240W, and most preferably 180W; the ultrasonic time is preferably 40-50 h, more preferably 42-48 h, and most preferably 48 h; the sonication is preferably carried out under closed conditions. In the invention, in the ultrasonic process, while the graphite is stripped, a silica structure is introduced into the surface of the stripped graphene by the hyperbranched polyethylene copolymer with the terminal branched chain grafted with POSS, so that the non-covalent modification of the surface of the graphene is realized, and the compatibility of the graphene and PDMS is further promoted.
After the ultrasonic treatment is finished, the obtained suspension is preferably subjected to centrifugal treatment, and supernatant liquid is collected to remove the graphite which is not successfully stripped. In the present invention, the rate of the centrifugation is preferably 4000rpm, and the time of the centrifugation is preferably 45 min. In the invention, the supernatant is the crude product of the non-covalent modified graphene chloroform solution; the concentration of the supernatant is preferably 0.10-0.20 mg/mL, and more preferably 0.13 mg/mL.
After the supernatant is obtained, the invention preferably carries out vacuum filtration on the supernatant through a PVDF filter membrane with the aperture of 0.22 mu m to remove free polymers in the supernatant; the vacuum filtration is not particularly limited in the present invention, and may be carried out by a process known to those skilled in the art. After vacuum filtration is finished, the non-covalent modified graphene on the filter membrane is preferably mixed with chloroform, and the chloroform solution of the non-covalent modified graphene is obtained through ultrasonic dispersion.
In the present invention, the mixing process of the chloroform solution of the non-covalently modified graphene and PDMS preferably further comprises a curing agent, preferably Sylgard184A and Sylgard 184B; the mass ratio of Sylgard184A to Sylgard184B is preferably (5-12) to 1, more preferably (8-10): 1, most preferably 10: 1.
In the present invention, the process of mixing and curing the chloroform solution of the non-covalently modified graphene, the curing agent and the PDMS is preferably: mixing Sylgard184A and a chloroform solution of non-covalent modified graphene and PDMS, and continuously stirring for 1h at room temperature until the mixture is uniformly mixed to obtain a mixed solution; drying the obtained mixed solution at 80 deg.C for 30min to remove chloroform solvent; then adding Sylgard184B, stirring in ice water bath for 10min, pouring into a mold for curing (PTFE mold is preferred in the invention), vacuumizing for 1h to remove bubbles, and curing (the specific process is shown in FIG. 3).
In the invention, the mass ratio of the curing agent to the PDMS is preferably (5-12): 1, more preferably 10: 1.
In the invention, the curing temperature is preferably 75-85 ℃, more preferably 80 ℃, and the curing time is preferably 3-5 h, more preferably 4 h.
The invention also provides the application of the PDMS-based graphene heat-conducting composite material in the technical scheme or the PDMS-based graphene heat-conducting composite material prepared by the preparation method in the technical scheme in the field of thermal interface materials.
The PDMS-based graphene thermal conductive composite material, the preparation method and the application thereof provided by the present invention are described in detail with reference to the following embodiments, but they should not be construed as limiting the scope of the present invention.
Example 1
Mixing 5g of acryloyl isobutyl POSS with 40mL of anhydrous dichloromethane in an ethylene atmosphere (25 ℃,1atm), and stirring for 10min until the mixture is uniformly dissolved to obtain an acryloyl isobutyl POSS solution;
dissolving 200mg of Pd-diimine in 10mL of anhydrous dichloromethane to obtain a catalyst solution, adding the catalyst solution into an acryloyl isobutyl POSS solution, carrying out copolymerization grafting reaction for 24h, pouring a product system obtained after the reaction into 200mL of methanol to terminate the reaction, dissolving the obtained polymerization product in 8mL of toluene, adding 120mL of methanol to precipitate the polymerization product, repeating the dissolving and precipitating processes for 3 times, and fully removing the completely unreacted acryloyl isobutyl POSS to obtain a treated polymer;
dissolving the treated polymer in 6mL of tetrahydrofuran, respectively adding 10 drops of hydrogen peroxide and hydrochloric acid, stirring for 30min, adding 80mL of methanol to precipitate the polymer, repeating the steps for 3 times, and performing vacuum drying at 60 ℃ for 24h to obtain a colorless and transparent hyperbranched polyethylene copolymer (marked as HBPE @ POSS) with the terminal branched chain grafted POSS;
mixing 800g of graphite powder, 320mg of HBPE @ POSS and 80mL of chloroform, performing ultrasonic treatment for 48h (200W) under a closed condition, after the ultrasonic treatment is finished, performing centrifugal treatment (4000rpm, 45min) on the obtained suspension, and collecting supernatant to remove the graphite which is not successfully stripped;
passing the supernatant through a PVDF filter membrane with the aperture of 0.22 mu m, and carrying out vacuum filtration to remove free polymers in the supernatant; mixing the non-covalent modified graphene on the filter membrane with chloroform to obtain a chloroform solution (with the concentration of 0.86mg/mL) of the non-covalent modified graphene;
mixing 0.6g of Sylgard184A, 3.9mL of chloroform solution of non-covalently modified graphene and PDMS, stirring at room temperature for 1h until uniform mixing, drying at 80 ℃ for 30min to remove chloroform, adding 0.06g of Sylgard184B, stirring in an ice water bath for 10min, pouring into a PTFE mold, vacuumizing for 1h to remove bubbles, and curing (80 ℃ and 4h) to obtain a PDMS-based graphene thermal conductive composite material in a disc shape with a diameter of 25.4mm and a thickness of 0.65mm (the mass percentage of the non-covalently modified graphene in the PDMS-based graphene thermal conductive composite material is 0.5%).
Example 2
Preparation of chloroform solution of non-covalently modified graphene reference example 1;
mixing 0.6g of Sylgard184A, 7.8mL of chloroform solution of non-covalently modified graphene and PDMS, stirring at room temperature for 1h until uniform mixing, drying at 80 ℃ for 30min to remove chloroform, adding 0.06g of Sylgard184B, stirring in an ice water bath for 10min, pouring into a PTFE mold, vacuumizing for 1h to remove bubbles, and curing (80 ℃ and 4h) to obtain a PDMS-based graphene thermal conductive composite material in a disc shape with a diameter of 25.4mm and a thickness of 0.65mm (the mass percentage of the non-covalently modified graphene in the PDMS-based graphene thermal conductive composite material is 1.0%).
Example 3
Preparation of chloroform solution of non-covalently modified graphene reference example 1;
mixing 0.6g of Sylgard184A, 11.7mL of chloroform solution of non-covalently modified graphene and PDMS, stirring at room temperature for 1h until uniform mixing, drying at 80 ℃ for 30min to remove chloroform, adding 0.06g of Sylgard184B, stirring in an ice water bath for 10min, pouring into a PTFE mold, vacuumizing for 1h to remove bubbles, and curing (80 ℃ and 4h) to obtain a PDMS-based graphene thermal conductive composite material in a disc shape with a diameter of 25.4mm and a thickness of 0.65mm (the mass percentage of the non-covalently modified graphene in the PDMS-based graphene thermal conductive composite material is 1.5%).
Example 4
Preparation of chloroform solution of non-covalently modified graphene reference example 1;
mixing 0.6g of Sylgard184A, 15.7mL of chloroform solution of non-covalently modified graphene and PDMS, stirring at room temperature for 1h until uniform mixing, drying at 80 ℃ for 30min to remove chloroform, adding 0.06g of Sylgard184B, stirring in an ice water bath for 10min, pouring into a PTFE mold, vacuumizing for 1h to remove bubbles, and curing (80 ℃ and 4h) to obtain a PDMS-based graphene thermal conductive composite material in a disc shape with a diameter of 25.4mm and a thickness of 0.65mm (the mass percentage of the non-covalently modified graphene in the PDMS-based graphene thermal conductive composite material is 2.0%).
Example 5
Preparation of chloroform solution of non-covalently modified graphene reference example 1;
0.6g of Sylgard184A, 19.7mL of chloroform solution of non-covalently modified graphene and PDMS were mixed, stirred at room temperature for 1h until uniform mixing, dried at 80 ℃ for 30min to remove chloroform, then 0.06g of Sylgard184B was added, stirred in an ice water bath for 10min, poured into a PTFE mold, evacuated for 1h to remove air bubbles, and cured (80 ℃,4h) to obtain a PDMS-based graphene thermal conductive composite material in the form of a disc with a diameter of 25.4mm and a thickness of 0.65mm (the mass percentage of the non-covalently modified graphene in the PDMS-based graphene thermal conductive composite material is 2.5%).
Example 6
Preparation of chloroform solution of non-covalently modified graphene reference example 1;
mixing 0.6g of Sylgard184A, 23.7mL of chloroform solution of non-covalently modified graphene and PDMS, stirring at room temperature for 1h until uniform mixing, drying at 80 ℃ for 30min to remove chloroform, adding 0.06g of Sylgard184B, stirring in an ice water bath for 10min, pouring into a PTFE mold, vacuumizing for 1h to remove bubbles, and curing (80 ℃ and 4h) to obtain a PDMS-based graphene thermal conductive composite material in a disc shape with a diameter of 25.4mm and a thickness of 0.65mm (the mass percentage of the non-covalently modified graphene in the PDMS-based graphene thermal conductive composite material is 3.0%).
Example 7
Preparation of chloroform solution of non-covalently modified graphene reference example 1;
mixing 0.6g of Sylgard184A, 32.0mL of chloroform solution of non-covalently modified graphene and PDMS, stirring at room temperature for 1h until uniform mixing, drying at 80 ℃ for 30min to remove chloroform, adding 0.06g of Sylgard184B, stirring in an ice water bath for 10min, pouring into a PTFE mold, vacuumizing for 1h to remove bubbles, and curing (80 ℃ and 4h) to obtain a PDMS-based graphene thermal conductive composite material in a disc shape with a diameter of 25.4mm and a thickness of 0.65mm (the mass percentage of the non-covalently modified graphene in the PDMS-based graphene thermal conductive composite material is 4.0%).
Comparative example 1
0.6g of Sylgard184A and PDMS were mixed, stirred at room temperature for 1h until uniform mixing, dried at 80 ℃ for 30min, then 0.06g of Sylgard184B was added, stirred in an ice water bath for 10min, poured into a PTFE mold, evacuated for 1h to remove air bubbles, and cured (80 ℃ C., 4h) to give a thermally conductive composite material in the form of a disc with a diameter of 25.4mm and a thickness of 0.65 mm.
Test example
FIG. 4 is a diagram of a material object of the PDMS-based graphene thermal conductive composite material prepared in comparative example 1 and examples 1 to 7; the PDMS-based graphene thermal conductive composite material described in comparative example 1 and examples 1 to 7 is sequentially arranged from top to bottom from left to right, and it can be seen from the figure that no graphene filler is added in comparative example 1, and the obtained film is colorless and transparent. In examples 1 to 7, the graphene filler is added, and the obtained composite film is in a black opaque state, which indicates that the uniform composite film material is successfully prepared.
SEM tests are carried out on the PDMS-based graphene heat-conducting composite materials prepared in the comparative example 1 and the examples 1 to 7, and the test results are shown in FIG. 5, wherein a to h respectively correspond to SEM images of the PDMS-based graphene heat-conducting composite materials prepared in the comparative example 1 and the examples 1 to 7 in sequence, as can be seen from FIG. 5, no graphene filler is seen in the SEM image of the comparative example 1, the graphene filler is observed in the SEM images of the examples 1 to 7, and the graphene filler is uniformly dispersed in a polymer matrix and does not agglomerate; and with the increase of the graphene filler, the heat conduction network in the polymer matrix is built more and more perfectly.
According to a calculation formula of the thermal conductivity coefficient: obtaining the thermal conductivity coefficient of the PDMS-based graphene thermal conductive composite material prepared in comparative example 1 and examples 1-7 by multiplying the thermal conductivity coefficient by the thermal diffusivity and the specific heat capacity by the density; wherein, a laser method is adopted to measure the thermal diffusion coefficient, wherein the laser thermal conductivity meter measures that the diameter of the sample is 25.4mm and the thickness is less than or equal to 1mm, and a layer of uniform graphite is sprayed on the surface of the sample before the test; testing the specific heat capacity by adopting differential scanning calorimetry;
as shown in fig. 6, it can be seen from fig. 6 that the thermal conductivity of the composite material is greatly improved as the content of the graphene filler is increased. When the mass fraction of the graphene filler is increased from 0 wt% (comparative example 1) to 4.0 wt%, the thermal conductivity is increased from 0.2W/(mK) to 0.9W/(mK), which is a 350% increase over pure PDMS thermal conductivity.
From the above embodiments, it can be seen that the hyperbranched polyethylene copolymer with the non-covalent modified graphene as the terminal branched chain grafted with POSS is used for carrying out non-covalent modification on the graphene, so that the dispersion stability of the graphene in chloroform or tetrahydrofuran is improved, and meanwhile, a silica structure is introduced on the surface of the graphene through the modification, so that the compatibility of the graphene and PDMS can be remarkably improved, and the heat conductivity of the PDMS-based graphene heat-conducting composite material is improved; according to the description of the embodiment, the thermal conductivity coefficient of the PDMS-based graphene thermal conductive composite material can reach 0.9W/(m.K) at most.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. The PDMS-based graphene heat-conducting composite material is characterized by comprising polydimethylsiloxane and non-covalent modified graphene;
the non-covalent modified graphene is hyperbranched polyethylene copolymer of which the tail end is grafted with polysilsesquioxane, and is non-covalently modified and modified.
2. The PDMS-based graphene thermal conductive composite according to claim 1, wherein a mass ratio of the non-covalently modified graphene to the polydimethylsiloxane is (0.5-4.0): (96.0-99.5).
3. The PDMS-based graphene thermal conductive composite according to claim 1 or claim 2, wherein the PDMS-based graphene thermal conductive composite has a thickness of 0.5 to 1.0 mm.
4. The preparation method of the PDMS-based graphene thermal conductive composite according to any one of claims 1 to 3, comprising the steps of:
and mixing the non-covalent modified graphene chloroform solution with polydimethylsiloxane, removing the solvent, and curing to obtain the PDMS-based graphene heat-conducting composite material.
5. The method of claim 4, wherein the mixture further comprises a curing agent selected from the group consisting of Sylgard184A and Sylgard 184B;
the mass ratio of Sylgard184A to Sylgard184B is (5-12): 1.
6. The method according to claim 4, wherein the curing temperature is 75 to 85 ℃ and the curing time is 3 to 5 hours.
7. The method according to claim 4, wherein the method for preparing the non-covalently modified graphene comprises the following steps:
in the ethylene atmosphere, mixing acryloyl isobutyl polysilsesquioxane, palladium-diimine and dichloromethane, and carrying out copolymerization grafting reaction to obtain a hyperbranched polyethylene copolymer of the terminal branched chain grafted polysilsesquioxane;
mixing the hyperbranched polyethylene copolymer with the terminal branched chain grafted with the polysilsesquioxane, graphite and chloroform, and performing ultrasonic treatment to obtain the non-covalent modified graphene.
8. The method according to claim 7, wherein the pressure of the ethylene atmosphere is 0.8 to 1.2 atm;
the dosage ratio of the acryloyl isobutyl polysilsesquioxane to the palladium-diimine to the dichloromethane is (45-55) g: (1.8-2.2) g: (480-520) mL;
the temperature of the copolymerization grafting reaction is 20-30 ℃, and the time of the copolymerization grafting reaction is 20-30 h.
9. The preparation method according to claim 7, wherein the amount ratio of the graphite to the hyperbranched polyethylene copolymer of the terminal branched-chain grafted polysilsesquioxane and chloroform is (8-12) mg: (3.5-4.5) mg: 1 mL;
the frequency of the ultrasonic wave is 60-300W, and the time of the ultrasonic wave is 40-50 h.
10. The use of the PDMS-based graphene thermal composite according to any one of claims 1 to 3 or the PDMS-based graphene thermal composite prepared by the preparation method according to any one of claims 4 to 9 in the field of thermal interface materials.
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