阅读说明：本技术 一种低成本聚合物基导热绝缘复合材料及其制备方法 (Low-cost polymer-based heat-conducting and insulating composite material and preparation method thereof ) 是由 李延报 刘宝成 吉泽民 武智胜 于 2020-10-20 设计创作，主要内容包括：本发明涉及一种低成本聚合物基导热绝缘复合材料及其制备方法。以热塑性聚合物为基体、导热粒子和低导热填充粒子为填料,采用溶液混合或熔融共混法将聚合物和填料混合均匀,后热压成型得到聚合物-导热粒子-填充粒子三元导热绝缘复合材料。其优势在于加入廉价的第三相填充粒子,增加了聚合物基体的热导率并使导热粒子在聚合物基体中更易形成导热网络,该结构可降低导热粒子的填充量且能有效增加复合材料的热导率。本发明得到的聚合基复合材料热导率可达8.50W/(m·K)。该复合材料具有热导率高、电绝缘、成本低、制备工艺简单、工艺拓展性强等优点。(The invention relates to a low-cost polymer-based heat-conducting and insulating composite material and a preparation method thereof. The ternary heat-conducting insulating composite material of the polymer, the heat-conducting particles and the filling particles is obtained by taking a thermoplastic polymer as a matrix, taking the heat-conducting particles and the low-heat-conducting filling particles as fillers, uniformly mixing the polymer and the fillers by adopting a solution mixing or melt blending method, and then carrying out hot press molding. The composite material has the advantages that the third-phase filling particles which are low in price are added, the thermal conductivity of the polymer matrix is increased, the heat conducting particles can form a heat conducting network in the polymer matrix more easily, the filling amount of the heat conducting particles can be reduced, and the thermal conductivity of the composite material can be effectively increased. The thermal conductivity of the polymer-based composite material obtained by the invention can reach 8.50W/(m.K). The composite material has the advantages of high thermal conductivity, electric insulation, low cost, simple preparation process, strong process expansibility and the like.)

1. The low-cost polymer-based heat-conducting and insulating composite material is characterized by comprising three components, namely thermoplastic polymer, heat-conducting particles and low-heat-conducting filling particles, wherein the volume content of a polymer matrix in the polymer-based heat-conducting composite material is 10% -65%, the volume content of the heat-conducting particles is 5% -30%, and the volume content of the filling particles is 10% -60%.

2. The low cost polymer-based thermally conductive and insulating composite of claim 1, wherein the thermoplastic polymer is one or more of polystyrene, polyurethane, polyethylene, polyamide, or polypropylene.

3. The low cost polymer-based thermally conductive and insulating composite material according to claim 1, wherein the thermally conductive particles are one or more of boron nitride, silicon carbide, silicon nitride or aluminum nitride, and have a particle size of 1-50 μm.

4. The low cost polymer-based thermally conductive and insulating composite as claimed in claim 1, wherein the low thermal conductive filler particles are one or more of calcium carbonate, talc, silica, alumina or titanium oxide, and have a particle size of 20nm to 50 μm.

5. The method for preparing the low-cost polymer-based heat-conducting and insulating composite material as claimed in claim 1, is characterized in that a solution blending method or a melt blending method is adopted to uniformly mix a polymer and a filler to prepare a composite material prepressing material, and then the polymer-heat-conducting particle-filling particle ternary heat-conducting and insulating composite material is obtained through hot press molding.

6. The method of claim 5, wherein the solution blending process comprises: the heat conducting particles and the filling particles are dispersed uniformly in a solvent by ultrasonic in proportion, then a polymer is added to dissolve to obtain a mixture system, and a precipitation method is adopted to prepare the composite material prepressing material.

7. The method of claim 6, wherein the solvent is one of N, N dimethylformamide, isopropanol, formic acid, or tetrahydrofuran.

8. The method of claim 5, wherein the melt blending process comprises: and respectively and uniformly mixing the polymer, the heat conducting particles and the filling particles by using a two-roll extruder, a double-screw extruder or an internal mixer according to a proportion to obtain the composite material prepressing material.

9. The method of claim 5, wherein the hot press forming method is: adding the prepressing material for preparing the composite material into a metal die, and obtaining the composite material by adopting three-stage hot press molding.

10. The method of claim 9, wherein the three-stage hot pressing comprises: preheating the raw material at 0-5 MPa for 3-10 min, hot-pressing and exhausting at 3-10 MPa for 3-10 min, and hot-pressing and molding at 5-15 MPa for 5-10 min.

Technical Field

The invention belongs to the technical field of functional composite materials, and particularly relates to a low-cost polymer-based heat-conducting and insulating composite material and a preparation method thereof.

Background

The heat accumulation of electronic equipment can seriously reduce the running speed, efficiency and reliability of the equipment, even lead the equipment to burn out and explode. With the further miniaturization, high integration and high performance of electronic devices, the conventional heat dissipation method cannot effectively solve the heat dissipation problem. The heat management material with strong heat dissipation capability, low production cost, simple process and strong industrial expansibility receives wide attention. Polymer-based materials are attracting attention as thermally conductive materials due to their excellent electrical insulation, lightness and ease of processing. However, common polymers typically have low thermal conductivity [ <0.4W/(m · K) ]. Thus, thermally conductive particles (including metal-based, ceramic-based, or carbon-based materials) having high thermal conductivity are added to the polymer matrix to increase its thermal conductivity. The addition of metal or carbon-based materials therein to increase thermal conductivity inevitably increases the electrical conductivity of the composite material, which limits their practical application as electrically insulating electronic packaging materials.

Conventional thermally conductive composites require high volume fractions (>50 vol%) of thermally conductive particles to be filled to achieve high thermal conductivity [ < 5W/(m-K) ] at room temperature. However, the high content of the heat conductive particles leads to poor processability, high density and high cost of the polymer matrix composite. Since thermal energy is primarily transferred through lattice vibrations (phonons) in the insulating material, poor coupling between the filler/filler and/or filler/polymer matrix interfaces can result in significant thermal resistance, caused by phonon scattering. Therefore, since the random distribution of the filler in the matrix results in high interface thermal resistance and poor interface interaction, it is difficult to achieve high thermal conductivity [ >5W/(m · K) ], which requires precise control and design of the composition and structure of the material. In order to significantly increase the thermal conductivity of polymer-based composites, it is an effective approach to construct thermally conductive networks with low percolation thresholds and/or minimized interfacial thermal resistance.

Liqiang (a polypropylene-polyamide heat-conducting composite material, CN107857937) uses dopamine to modify the surface of a glass fiber, and then aluminum nitride particles are attached to the glass fiber to form a modified glass fiber; and adding the modified glass fiber, the heat-conducting filler, the flame retardant and the compatilizer into the polypropylene-polyamide. The mechanical property of the composite material product is enhanced, and the requirement of thermal conductivity is ensured. The method is characterized in that the synergistic effect of the filler is utilized to increase the thermal conductivity of the composite material. Therefore, the preparation of the high-thermal-conductivity and insulating polymer-based composite material by adopting a simple process and low cost is still an important problem to be solved urgently in the field.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a low-cost polymer-based heat-conducting and insulating composite material, and the invention also aims to provide a preparation method of the material.

The technical scheme of the invention is as follows: the ternary heat-conducting insulating composite material of the polymer, the heat-conducting particles and the filling particles is prepared by taking a thermoplastic polymer as a matrix and taking high heat-conducting particles and low heat-conducting filling particles as fillers, uniformly mixing the polymer and the fillers by adopting a solution mixing or melt blending method, and then forming. The composite material has the advantages that the third-phase filling particles which are low in price are added, the thermal conductivity of the polymer matrix is increased, the heat conducting particles can form a heat conducting network in the polymer matrix more easily, the filling amount of the heat conducting particles can be reduced, and the thermal conductivity of the composite material can be effectively increased. The thermal conductivity of the polymer-based composite material obtained by the invention can reach 8.50W/(m.K). The composite material has the advantages of high thermal conductivity, electric insulation, low cost, simple preparation process, strong process expansibility and the like.

The specific technical scheme of the invention is as follows: the low-cost polymer-based heat-conducting and insulating composite material is characterized by comprising three components, namely thermoplastic polymer, heat-conducting particles and low-heat-conducting filling particles, wherein the volume content of a polymer matrix in the polymer-based heat-conducting composite material is 10% -65%, the volume content of the heat-conducting particles is 5% -30%, and the volume content of the filling particles is 10% -60%. The addition of filler particles increases the thermal conductivity of the polymer matrix, and the filler particles make the thermally conductive particles more likely to form a thermally conductive network in the thermoplastic polymer matrix.

Preferably, the thermoplastic polymer is one or more of, but not limited to, polystyrene, polyurethane, polyethylene, polyamide, or polypropylene.

The above-mentioned thermally conductive particles are preferably one or more of, but not limited to, boron nitride, silicon carbide, silicon nitride, or aluminum nitride, and have a particle diameter of 1 to 50 μm.

Preferably, the low thermal conductive filler particles are one or more of calcium carbonate, talcum powder, silicon oxide, aluminum oxide or titanium oxide, and the particle size of the low thermal conductive filler particles is 20nm-50 μm.

The invention also provides a preparation method of the low-cost polymer-based heat-conducting and insulating composite material, which is characterized in that a solution blending method or a melt blending method is adopted to uniformly mix a polymer and a filler to prepare a composite material prepressing material, and then the polymer-heat-conducting particle-filling particle ternary heat-conducting and insulating composite material is obtained through hot press molding.

The solution blending method is preferably as follows: the heat conducting particles and the filling particles are dispersed uniformly in a solvent by ultrasonic in proportion, then a polymer is added to dissolve to obtain a mixture system, and a precipitation method is adopted to prepare the composite material prepressing material.

Preferably, the solvent is, but not limited to, one of N, N dimethylformamide, isopropanol, formic acid, or tetrahydrofuran.

Preferably, the melt blending method is one of a two-roll method, a twin-screw extrusion method or an internal mixer, and the specific method is as follows: and respectively and uniformly mixing the polymer, the heat conducting particles and the filling particles by using a two-roll extruder, a double-screw extruder or an internal mixer according to a proportion to obtain the composite material prepressing material.

Preferably, the hot press molding method is: adding the prepressing material for preparing the composite material into a metal die, and obtaining the composite material by adopting three-stage hot press molding. The preferred three-stage hot pressing method comprises the following steps: preheating the raw material at 0-5 MPa for 3-10 min, hot-pressing and exhausting at 3-10 MPa for 3-10 min, and hot-pressing and molding at 5-15 MPa for 5-10 min.

Has the advantages that:

(1) the polymer-based composite material disclosed by the invention has good heat-conducting property. The invention adds cheap filling particles into the polymer matrix, increases the thermal conductivity of the polymer matrix, and fills a certain amount of filling particles, so that the addition amount of the heat conducting particles is obviously reduced, but the heat conducting particles can be easily contacted with each other to form a heat conducting network. The form (linear or sheet) of the heat conducting particles is selected to increase the interface contact among the heat conducting particles and reduce the interface thermal resistance so as to improve the thermal conductivity of the composite material. The addition amount of the heat conducting particles in the composite material is in the range of 5-30 vol%, when the filling amount of the heat conducting particles is 30 vol%, the heat conductivity of the polymer-based heat conducting composite material can reach 8.50W/(m.K), and the heat conductivity is adjusted in the range of 1.91-8.50W/(m.K) according to different process parameters and composition formulas.

(2) In the preparation of the polymer-based heat-conducting and insulating composite material disclosed by the invention, the price of the filling particles is low (1.0-20 yuan/kg), the sources are wide, and meanwhile, the preparation method is simple and easy to implement, does not need special instruments, can realize large-scale production, is low in cost and has universality.

Detailed Description

The present invention will be described in further detail below with reference to examples. It should be noted that the following examples are only for illustrating the technical solutions of the present invention and are not limiting. Modifications and equivalents of the present invention may be made by those skilled in the art without departing from the spirit and scope of the present invention, and are intended to be included within the scope of the appended claims.

Example 1

Respectively adding 7.19g of flaky boron nitride and 23.19g of calcium carbonate powder into 87mL of N, N-dimethylformamide, ultrasonically dispersing in water bath at normal temperature for 30min, adding 5.34g of polystyrene into the mixed solution at 80 ℃ under stirring, and intensively stirring and mixing until the polystyrene is completely dissolved. The ternary mixed solution was quickly poured into 870mL of deionized water for precipitation. Washing the precipitate with deionized water for three times, and drying at 80 ℃ for 24h to obtain the composite material prepressing material.

Weighing 11.80g of composite material prepressing material according to the size of a mould (sample size phi is 30mm multiplied by 8mm), preheating the raw material for 5min under the pressure of 0MPa at 170 ℃, then pressurizing to 5MPa, exhausting for 5min, and finally hot-pressing for 5min under the pressure of 10MPa to obtain a polymer-based heat-conducting insulating composite material sample.

Example 2

Respectively adding 5.39g of flaky boron nitride and 13.86g of talcum powder into 87mL of N, N-dimethylformamide, ultrasonically dispersing in water bath at normal temperature for 30min, adding 5.34g of polystyrene into the mixed solution at 80 ℃ under stirring, and intensively stirring and mixing until the polystyrene is completely dissolved. The ternary mixed solution was quickly poured into 870mL of deionized water for precipitation. Washing the precipitate with deionized water for three times, and drying at 80 ℃ for 24h to obtain the composite material prepressing material.

Weighing 10.83g of composite material prepressing material according to the size of a mould (sample size phi is 30mm multiplied by 8mm), preheating the raw material for 7min under the condition of 180 ℃ and under the pressure of 1MPa, then pressurizing to 3MPa, exhausting for 3min, and finally hot-pressing for 7min under the pressure of 8MPa to obtain a polymer-based heat-conducting insulating composite material sample.

Example 3

Respectively adding 3.59g of boron nitride and 27.21g of silicon oxide into 87mL of N, N-dimethylformamide, ultrasonically dispersing in a water bath at normal temperature for 30min, adding 5.34g of polystyrene into the mixed solution at 80 ℃ under stirring, and intensively stirring and mixing until the polystyrene is completely dissolved. The ternary mixed solution was quickly poured into 1200mL of deionized water for precipitation. Washing the precipitate with deionized water for three times, and drying at 80 ℃ for 24h to obtain the composite material prepressing material.

Weighing 11.94g of composite material prepressing material according to the size of a mould (sample size phi is 30mm multiplied by 8mm), preheating the raw material for 3min under the pressure of 3MPa at 190 ℃, then pressurizing to 10MPa, exhausting for 10min, and finally hot-pressing for 6min under the pressure of 13MPa to obtain a polymer-based heat-conducting insulating composite material sample.

Example 4

Respectively adding 8.09g of boron nitride and 15.21g of alumina into 87mL of N, N-dimethylformamide, ultrasonically dispersing in water bath at normal temperature for 30min, adding 5.34g of polyurethane into the mixed solution at 80 ℃ under stirring, and intensively stirring and mixing until the polystyrene is completely dissolved. The ternary mixed solution was quickly poured into 1220mL of deionized water for precipitation. Washing the precipitate with deionized water for three times, and drying at 80 ℃ for 24h to obtain the composite material prepressing material.

Weighing 12.61g of composite material prepressing material according to the size of a mould (sample size phi is 30mm multiplied by 8mm), preheating the raw material for 10min under the condition of 170 ℃ and applying 5MPa, then pressurizing to 8MPa, exhausting for 3min, and finally hot-pressing for 5min by adopting the pressure of 15MPa to prepare the polymer-based heat-conducting insulating composite material sample.

Example 5

Respectively adding 6.74g of boron nitride and 19.00g of titanium oxide into 50mL of N, N-dimethylformamide, ultrasonically dispersing in a water bath at normal temperature for 30min, adding 5.34g of polystyrene into the mixed solution at 80 ℃ under stirring, and intensively stirring and mixing until the polystyrene is completely dissolved. The ternary mixed solution was quickly poured into 1310mL of deionized water for precipitation. Washing the precipitate with deionized water for three times, and drying at 80 ℃ for 24h to obtain the composite material prepressing material.

Weighing 13.69g of composite material prepressing material according to the size of a mould (sample size phi is 30mm multiplied by 8mm), preheating the raw material for 4min under the pressure of 1MPa at 190 ℃, then pressurizing to 8MPa, exhausting for 3min, and finally hot-pressing for 8min by adopting the pressure of 12MPa to prepare the polymer-based heat-conducting insulating composite material sample.

Example 6

Respectively adding 8.17g of flaky boron nitride and 18.97g of calcium carbonate powder into 80mL of N, N-dimethylformamide, ultrasonically dispersing in a water bath at normal temperature for 30min, adding 5.6g of polyurethane into the mixed solution at 80 ℃ under stirring, and intensively stirring and mixing until the polyurethane is completely dissolved. The ternary mixed solution was quickly poured into 1310mL of deionized water for precipitation. Washing the precipitate with deionized water for three times, and drying at 80 ℃ for 24h to obtain the composite material prepressing material.

Weighing 11.89g of composite material prepressing material according to the size of a mould (sample size phi is 30mm multiplied by 8mm), preheating the raw material for 6min under the pressure of 4MPa at 190 ℃, then pressurizing to 10MPa, exhausting for 6min, and finally hot-pressing for 6min under the pressure of 10MPa to obtain a polymer-based heat-conducting insulating composite material sample.

Example 7

Heating and rolling 30g of polyethylene by two rollers at 130 ℃, adding 44.61g of flaky boron nitride, 12.78g of linear silicon carbide and 51.89g of silicon oxide mixed particles into the rollers, and rolling for 5 times to obtain the composite material prepressing material.

Weighing 10.02g of composite material prepressing material according to the size of a mould (sample size phi is 30mm multiplied by 8mm), preheating the raw material for 5min under the pressure of 5MPa at 170 ℃, pressurizing to 10MPa, exhausting for 7min, and finally hot-pressing for 7min under the pressure of 13MPa to obtain a polymer-based heat-conducting insulating composite material sample.

Example 8

20g of polyethylene, 29.74g of flaky boron nitride, 9.01g of silicon nitride and 62.26g of alumina mixed particles are added into a torque rheometer and meshed for 30min to prepare the composite material prepressing material.

Weighing 13.06g of composite material prepressing material according to the size of a mould (sample size phi is 30mm multiplied by 8mm), preheating the raw material for 10min under the condition of applying 5MPa at 160 ℃, then pressurizing to 10MPa, exhausting for 8min, and finally hot-pressing for 8min under the pressure of 15MPa to obtain a polymer-based heat-conducting insulating composite material sample.

Comparative example 1

Respectively adding 8.66g of boron nitride and 9.35g of polystyrene into 87mL of tetrahydrofuran, stirring and mixing at 80 ℃, and obtaining a binary mixed solution system after the polystyrene is completely dissolved. The binary mixed solution was quickly poured into 870mL of deionized water for precipitation. Washing the precipitate with deionized water for three times, and drying at 80 ℃ for 24h to obtain the composite material prepressing material.

Weighing 8.01g of composite material prepressing material according to the size of a mould (sample size phi is 30mm multiplied by 8mm), preheating the raw material for 5min under the pressure of 0MPa at 170 ℃, then pressurizing to 5MPa, exhausting for 5min, and finally hot-pressing for 5min under the pressure of 10MPa to obtain a polymer-based heat-conducting insulating composite material sample.

The properties of the polymer-based thermally conductive composite samples obtained as described above, as measured using a HotWireTC3000E thermal conductivity tester, are listed in table 1. As can be seen from Table 1, the thermal conductivity of the polymer-based heat-conducting composite material disclosed by the invention can reach 8.50W/(m.K), and can be adjusted within the range of 1.91-8.50W/(m.K) according to different process parameters and composition formulas.

TABLE 1 composition and thermal conductivity of Polymer-based thermally conductive composite samples