CN115232443A - Method for preparing heat-conducting composite material from graphene and polymer - Google Patents
Method for preparing heat-conducting composite material from graphene and polymer Download PDFInfo
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- CN115232443A CN115232443A CN202210988981.XA CN202210988981A CN115232443A CN 115232443 A CN115232443 A CN 115232443A CN 202210988981 A CN202210988981 A CN 202210988981A CN 115232443 A CN115232443 A CN 115232443A
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
Abstract
The scheme discloses a method for preparing a heat-conducting composite material from graphene and a polymer, which is to fill graphene sheet material particles coated with wax into a resin material by adopting a melt blending method to prepare the heat-conducting composite material. According to the method, the graphene sheets are wrapped by the wax to serve as the heat-conducting filler of the resin matrix, so that the problem of dispersion of graphene in the resin is solved, and the filling amount of the graphene in the resin is increased; and the high shearing strength of the double-screw extruder promotes the full fusion of the resin and the graphene, and a large-area heat conduction passage is formed, so that the heat conductivity of the composite material is improved.
Description
Technical Field
The invention relates to the technical field of heat conduction materials, in particular to a method for preparing a heat conduction composite material by using graphene and a polymer.
Background
With the development of electronic device equipment toward large capacity, high power density, and small and light weight, a large amount of heat is inevitably generated and accumulated by the design of small volume and high power, so that the temperature of the device is increased, the performance of the electronic device equipment is reduced, even the service life is shortened, and potential safety hazards are brought. In order to improve the heat dissipation problem of electronic devices, the graphene composite material with high heat conduction efficiency is receiving more and more attention from researchers.
The polymer has the advantages of light weight, strong corrosion resistance, excellent mechanical strength, processability, low cost and the like, has strong plasticity, can meet the heat conduction requirements of electronic devices with different shapes, and thus becomes the preferable base material for preparing the heat conduction composite material, but the polymer has low heat conductivity. A highly thermally conductive filler is generally selected to be compounded therewith to improve thermal conductivity. Due to the unique two-dimensional lamellar structure, high aspect ratio, excellent mechanical strength and high-efficiency electric heat transmission performance of graphene, a great deal of research is initiated by taking graphene as a filler of a polymer.
At present, methods for compounding graphene and polymers generally include a solution method, an in-situ method, a blending method and the like. The solution method is to uniformly disperse graphene in a low-viscosity resin solution, and then to prepare a composite material of graphene and a polymer through solvent volatilization, although graphene can be well dispersed in a resin through an organic solvent, the problems of difficulty in removing the organic solvent, environmental pollution, difficulty in recycling and the like exist, and the solution method is not suitable for large-scale industrial production. The in-situ method is to add graphene powder into a low-viscosity polymer reaction monomer, and introduce graphene when synthesizing a high molecular polymer, but the in-situ method has the defects of complex process, high cost, difficulty in regulating and controlling high molecules and the like, and is not popularized on a large scale. Among them, the blending method is the most common method because of its simple operation process, green environmental protection, and wide applicability. However, graphene has a large specific surface area and pi-pi noncovalent bond interaction exists between sheets, so that graphene is difficult to be uniformly dispersed in resin with high viscosity. Most of the graphene sheets exist in the matrix in the form of clusters, so that the graphene sheets do not form a communicated heat conduction network in the matrix, and polymer chains covering the graphene sheets hinder phonon vibration propagation, thereby reducing the thermal conductivity of the graphene and polymer composite material.
Disclosure of Invention
One object of the present disclosure is to provide a method for preparing a thermal conductive composite material from graphene and a polymer, which can improve dispersion of graphene in a high-viscosity resin, increase a filling amount of graphene, and form a connected graphene thermal conductive network, so that thermal conductivity of the thermal conductive composite material prepared from graphene and the polymer is greatly increased, thereby improving application of the thermal conductive composite material in heat dissipation of an electronic device.
In order to achieve the purpose, the scheme is as follows:
a method for preparing a heat-conducting composite material from graphene and a polymer comprises the step of filling graphene sheet material particles coated with wax into a resin material by adopting a melt blending method to prepare the heat-conducting composite material.
Preferably, the graphene sheet material particles coated with the wax are prepared by the following steps:
uniformly mixing the graphene sheet material with wax;
melting the wax, and cooling to form the wax wrapped on the surface of the graphene sheet;
and crushing to form graphene sheet material particles coated with wax.
Preferably, the graphene sheets and the wax are mixed according to the mass ratio of 1; preferably, the graphene sheets and the wax are mixed according to the mass ratio of 1.
Preferably, the graphene sheet and the wax are mixed in a mixer for a time period of 10 to 60min.
Preferably, the graphene sheet comprises 1 to 30 layers of graphene, preferably 1 to 10 layers of graphene.
Preferably, the graphene sheet has a sheet diameter of 5 to 50 μm, and preferably, the sheet diameter is 10 to 30 μm.
Preferably, the wax is one or more of polyethylene wax, polypropylene wax and polyamide wax.
Preferably, the particle size of the graphene sheet material particles coated with the wax is 1 to 500 μm, and preferably, the particle size is 50 to 100 μm.
Preferably, the wax is melted at a temperature of 90 to 150 ℃.
Preferably, the preparation of the heat-conducting composite material by filling the graphene sheet particles wrapped with the wax in the resin material by using a melt blending method comprises the following steps:
1. fully mixing the raw materials by a double-motion mixer according to the following mass percentage,
10-50% of graphene sheet particles coated with wax, 30-50% of resin, 10-30% of curing agent, 0.05-1.2% of flatting agent, 0.2-1% of defoaming agent and 5-10% of additive;
2. injecting the mixed raw materials into a double-screw extruder through an injection machine, and performing melt extrusion, wherein the rotating speed of a screw is 0-350 r/min, the preferred rotating speed of the screw is 100-200 r/min, the temperature of a machine barrel is 90-200 ℃, and the preferred temperature of the machine barrel is 110-150 ℃;
3. obtaining the heat-conducting composite material by adopting a thermosetting molding mode, wherein the baking temperature is 100-200 ℃, and the baking time is 5-180 minutes;
wherein the resin is one or more of epoxy resin, acrylic resin, polyurethane, polyester and phenolic resin;
the mixing time is 5 to 60min, preferably 10 to 30min, more preferably 15min.
The beneficial effect of this scheme as follows:
according to the preparation method, the graphene sheets wrapped by the wax are used as the heat-conducting filler of the resin matrix, so that the problem of dispersion of graphene in the resin is solved, and the filling amount of the graphene in the resin is increased; and the high shearing strength of the double-screw extruder promotes the full fusion of the resin and the graphene, and a large-area heat conduction passage is formed, so that the heat conductivity of the composite material is improved.
Detailed Description
Embodiments of the present solution are described in further detail below. It is clear that the described embodiments are only a part of the embodiments of the solution, and not an exhaustive list of all embodiments. It should be noted that, in the present embodiment, the features of the embodiment may be combined with each other without conflict.
Based on the problem that graphene is difficult to disperse uniformly in resin with high viscosity when graphene and polymer are used for preparing the heat-conducting composite material, the inventor of the application provides a method for preparing the heat-conducting composite material by using graphene sheets and polymer, the method can improve the dispersion of graphene in the resin with high viscosity, improve the filling amount of graphene, and form a communicated graphene heat-conducting network, so that the heat conductivity of the heat-conducting composite material prepared by using graphene and polymer is greatly improved, and the application of the heat-conducting composite material in electronic devices is improved.
The application provides that when a heat-conducting composite material is prepared from graphene and a polymer, a melt blending method which is simple in process and capable of realizing large-scale production is selected, in order to improve the dispersion problem of the graphene in molten resin and increase effective graphene filling amount, the graphene sheet material is modified by wax, then the wax is melted at high temperature, the melted wax uniformly wraps the graphene sheet material and then is crushed at low temperature, and particles of the graphene sheet material wrapped by the wax are prepared. Due to the existence of a wax interface, the graphene sheets are prevented from agglomerating when being mechanically mixed with resin, the graphene and the resin are fully fused under the action of high-strength shearing force of a double-screw extruder, and meanwhile, wax is melted into the molten resin, so that the viscosity of the resin can be reduced, the dispersion of the graphene in the resin is promoted, the filling amount of the graphene is increased, the wax can be melted into fluid under the action of the double-screw extruder, the graphene sheets wrapped by the wax are released, and the graphene sheets are connected with the sheets to form a communicated heat conducting network; thereby obtaining the heat-conducting composite material with more excellent heat-conducting property.
The present application will be described below with reference to specific examples.
Example 1
The preparation method of the heat-conducting composite material by using the graphene and the polymer comprises the following steps:
1. adding a graphene sheet material (GR) and WAX (WAX) into a double-motion mixer according to the mass ratio of 1; 2. putting the GR-WAX precursor at the temperature of 100-120 ℃, melting WAX at high temperature to cover the surface of a graphene sheet layer, mixing the melted WAX with graphene to present a molten state, then tabletting through a tablet machine, and communicating the metal surface of the tablet machine with a water circulation cooling device to ensure that the molten WAX and graphene mixture can be pressed into a sheet shape and simultaneously cooled into a solid, so that the formed sheet is beneficial to the uniform distribution of the graphene in the WAX and is convenient for crushing;
3. putting the slices into a pulverizer to be pulverized, and then sieving the pulverized slices by a sieve of 100-200 meshes to obtain small particles (GR-WAX) formed by coating the graphene sheets with WAX;
4. according to the total amount of the mixed materials, 40wt.% of GR-WAX powder, 44wt.% of bisphenol A epoxy resin E-12 and 10 wt.% of polyamide resin curing agent 650,0.5wt.% of polyacrylate flatting agent BYK-LPX 22737 adsorbed by silicon dioxide, and 0.5wt.% of mica powder with defoaming CERAFLOUR 961 and 5wt.% are added into a double-motion mixer, and all the raw materials are mixed in the mixer for 20min to obtain a mixed material with the GR filling amount of 10%; 5. putting the mixture into a charging barrel of a double-screw extruder, and mixing and extruding the mixture by the double-screw extruder; the rotating speed of the screw is 100-200 r/min, and the temperature is 110-150 ℃;
6. thermosetting molding to obtain the heat-conducting composite material of graphene and resin, wherein the thermosetting temperature is 100-200 ℃, and the thermosetting time is 5-180 min.
Example 2
Different from the embodiment 1, the mass ratio of GR to WAX in the step 1 is 3; the GR filler in the mixture obtained in step 4 was 15%, and the remaining preparation steps and conditions were the same as in example 1.
Example 3
Different from the embodiment 1, the mass ratio of GR to WAX in the step 1 is 1; the GR filler in the mixture obtained in the step 4 is 20%, and the other preparation steps and conditions are the same as those in the example 1.
Comparative example 1
Unlike example 1, the raw materials used for mixing were not GR-WAX powder but Graphene (GR) powder, except for including steps 1 to 3 in example 1. The preparation steps and conditions in comparative example 1 were the same as in step 4, step 5 and step 6 of example 1, and the filling amount of graphene in the obtained composite material was 10%.
Comparative example 2
Unlike comparative example 1, the raw material for mixing did not contain graphene, and the prepared composite material was not filled with graphene, and the prepared composite material was a pure resin material. The preparation procedure and conditions in comparative example 2 were the same as in comparative example 1.
The thermal conductivity of the thermally conductive composites prepared in examples 1 to 3 and comparative examples 1 to 2 was tested, and the results are shown in table 1.
TABLE 1
From table 1, the filling amount of graphene in the composite material prepared by the method can reach 10-20%, and the thermal conductivity of the thermal conductive composite material prepared from graphene and polymer is increased along with the increase of the filling amount; in example 3, when the filling amount of graphene in the polymer resin reaches 20%, the thermal conductivity can reach 2.84W/(m · K).
In comparative example 1 in which no coating treatment with wax was performed, when the amount of graphene filled in the polymer resin reached 10%, the thermal conductivity was the highest and 0.96W/(m · K), and when the amount of filling exceeded 10%, the thermal conductivity decreased with the increase in the amount of filling. This may be due to non-uniform dispersion and agglomeration of the graphene. When the filling amount of the graphene in the polymer resin reaches 20%, the extrusion material of the extruder is in a bean curd residue shape, and the original mechanical property of the resin is lost.
It can be seen from comparison between example 3 and comparative examples 1 and 2 that, while mechanical properties are ensured, the thermal conductivity of the thermal conductive composite material prepared by the method is increased by 11.3 times compared with the thermal conductivity of the thermal conductive material of comparative example 2 in which graphene is not filled in the polymer, and the thermal conductivity is increased by 1.96 times compared with the thermal conductivity of the composite material of comparative example 1 in which graphene without wax is filled in the polymer.
It should be understood that the above-described embodiments of the present invention are examples for clearly illustrating the invention, and are not to be construed as limiting the embodiments of the present invention, and it will be obvious to those skilled in the art that various changes and modifications can be made on the basis of the above description, and it is not intended to exhaust all embodiments, and obvious changes and modifications can be made on the basis of the technical solutions of the present invention.
Claims (10)
1. The method for preparing the heat-conducting composite material from the graphene and the polymer is characterized by comprising the step of filling graphene sheet material particles coated with wax into a resin material by adopting a melt blending method to prepare the heat-conducting composite material.
2. The method of claim 1, wherein the graphene sheet particles encapsulating the wax are prepared by:
uniformly mixing the graphene sheet material with wax;
melting the wax, and cooling to form the wax wrapped on the surface of the graphene sheet;
and crushing to form graphene sheet material particles coated with wax.
3. The method of claim 2, wherein the graphene sheets and the wax are mixed in a mass ratio of 1; preferably, the graphene sheet and the wax are mixed in a mass ratio of 1.
4. The method of claim 2, wherein the graphene sheets and the wax are mixed in the mixer for a time period of 10 to 60 minutes.
5. The method of claim 2, wherein the graphene sheet comprises 1 to 30 layers of graphene, preferably 1 to 10 layers of graphene.
6. The method of claim 2, wherein the graphene sheets have a sheet size of 5 to 50 μm, preferably 10 to 30 μm.
7. The method of claim 2, wherein the wax is one or more of a polyethylene wax, a polypropylene wax, and a polyamide wax.
8. The method according to claim 2, wherein the particle size of the graphene sheet particles encapsulating the wax is 1 to 500 μm, preferably 50 to 100 μm.
9. A method according to claim 2, characterized in that the wax melting temperature is 90-150 ℃.
10. The method of claim 1, wherein the step of filling the graphene sheet material particles wrapped with the wax in the resin material by melt blending to obtain the heat-conducting composite material specifically comprises the following steps:
1. fully mixing the raw materials by using a double-motion mixer according to the following mass percentage,
10-50% of graphene sheet particles coated with wax, 30-50% of resin, 10-30% of curing agent, 0.05-1.2% of flatting agent, 0.2-1% of defoaming agent and 5-10% of additive;
2. injecting the mixed raw materials into a double-screw extruder through an injection machine, and performing melt extrusion, wherein the rotating speed of a screw is 0-350 r/min, preferably 100-200 r/min, the temperature of a machine barrel is 90-200 ℃, and preferably the temperature of the machine barrel is 110-150 ℃;
3. obtaining the heat-conducting composite material by adopting a thermosetting molding mode, wherein the baking temperature is 100-200 ℃, and the baking time is 5-180 minutes;
wherein the resin is one or more of epoxy resin, acrylic resin, polyurethane, polyester and phenolic resin;
the mixing time is 5 to 60min, preferably 10 to 30min, more preferably 15min.
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