CN114605658A - Preparation method of polyimide-based modified graphene heat-conducting composite material - Google Patents

Abstract

The invention discloses a preparation method of a polyimide-based modified graphene heat-conducting composite material, which comprises the following steps: firstly, obtaining Graphene Nanosheets (GNS) by an electrochemical graphite stripping method; then, carrying out Diels-Alder reaction on maleimide and GNS to obtain maleimide modified graphene heat-conducting filler (M @ GNS); and finally, preparing a maleimide @ graphene/polyimide composite material (marked as M @ GNS/PI) with polyimide as a matrix and M @ GNS as a filler by an in-situ polymerization method and a chemical imine method. The method can connect the carboxyl-terminated PAA (polyamide acid) with the functionalized graphene through a C-N-C bond, so that the compatibility of the graphene and a matrix is enhanced, and the heat-conducting property of the polyimide composite material is obviously improved under the filling of low-content filler.

Description

A kind of preparation method of polyimide-based modified graphene thermally conductive composite material

technical field

The invention relates to the technical field of thermally conductive polymer composite materials, in particular to a polyimide-based modified graphene thermally conductive composite material.

Background technique

With the advent of the 5G era, modern electronic technology is rapidly developing in the direction of miniaturization, high integration and multi-functionality. Serious heat dissipation problems greatly threaten the reliability and life of high-tech equipment. Polymer-based polymers are widely used in microelectronic packaging and other fields due to their light weight, easy processing, excellent mechanical properties and electrical insulation properties. However, their applications are limited due to their low thermal conductivity. It is necessary to improve the thermal conductivity of composites by introducing fillers, regulating interfacial thermal resistance and constructing thermal conduction paths.

At present, thermal conductive fillers such as graphene, carbon nanotubes, boron nitride nanosheets, and carbon fibers have become the main force for regulating the thermal conductivity of composite materials due to their inherent advantages in superconductivity and thermal channels. The modification of thermally conductive fillers is an effective means to control the interface thermal resistance between fillers and substrates and between fillers. The modification of thermally conductive fillers is divided into covalent bond modification and non-covalent bond modification. Covalent bond modification has the advantages of various methods and stable product properties. Recently, the construction of thermal conduction pathways by constructing covalent bonds between fillers and matrices has been gradually studied. By modifying the surface structure of the filler, while improving the dispersion of the filler, it also promotes the effective transmission of phonons between the filler and the matrix, thereby improving the thermal conductivity of the composite material.

SUMMARY OF THE INVENTION

Based on the problems existing in the above-mentioned prior art, the present invention provides a preparation method of a polyimide-based modified graphene thermally conductive composite material, aiming at improving the thermal conductivity of the composite material.

The present invention adopts following technical scheme for realizing purpose:

A preparation method of a polyimide-based modified graphene thermally conductive composite material is characterized in that: first, graphene nanosheets are obtained by an electrochemical exfoliation graphite method, which is denoted as GNS; then maleimide and GNS are passed through Diels. -Alder reaction to obtain maleimide-modified graphene thermal conductive filler, denoted as M@GNS; finally, polyimide as matrix and M@GNS as filler were prepared by in-situ polymerization and chemical imide method The maleimide@graphene/polyimide composite was denoted as M@GNS/PI. Specifically include the following steps:

Step 1. Preparation of GNS

Using graphite foil as anode, platinum foil as cathode, 0.1-0.12mol/L ammonium sulfate aqueous solution as electrolyte, stripping voltage of 15-15.3V constant voltage, electrochemical stripping of graphite foil, washing and drying by suction filtration After, get GNS;

Step 2. Synthesis of M@GNS

Dissolve 45-50 mg maleimide in 40-50 mL N,N dimethylformamide, add 10-15 mg GNS to the solution, sonicate for 50-60 min, and then heat in an oil bath at 115-120 °C for 14- 16h, then irradiated under ultraviolet light for 10-15min; after cooling to room temperature, the obtained suspension was filtered through a polytetrafluoroethylene disc membrane, and then washed with 60-75mL ethanol vacuum filtration to remove unreacted maleimide ; Finally, the filter cake was collected and vacuum-dried at room temperature to obtain M@GNS;

Step 3. Synthesis of M@GNS/PAA/PI

Under nitrogen atmosphere, add 0.5940～0.5950g 4,4-diaminodiphenylmethane (MDA) and 8.5～9.5mL N,N dimethylformamide to the three-necked flask and dissolve, add M@GNS and sonicate for 50 ~60min, stir in ice water bath for 5 ~ 10min, then add 0.9000 ~ 0.9010g 3,3'-4,4'-biphenyltetracarboxylic dianhydride (BPDA) and molecular sieve, stir in ice water bath for 15 ~ 20min, to obtain M@GNS/PAA solution; then add 0.15-0.2 mL triethylamine and 0.08-0.1 mL pyridine to obtain M@GNS/PAA/PI solution;

Step 4. Synthesis of M@GNS/PI

The obtained M@GNS/PAA/PI solution was cast on a clean glass substrate, coated with a doctor blade, and dried at 60-70 °C for 1-1.5 h; finally, M@GNS/PAA/PI was prepared by gradient thermal imidization. @GNS/PI thermally conductive composites.

Further, the procedure of the gradient thermal imidization in step 4 is: firstly heating at 120°C for 1 hour, then heating at 200°C for 1 hour, and finally heating at 250°C for 1 hour.

Further, in step 3, the amount of M@GNS added accounts for 0-15wt% of the total mass of 4,4-diaminodiphenylmethane and 3,3'-4,4'-biphenyltetracarboxylic dianhydride.

The invention also discloses the M@GNS/PI composite material obtained by the above preparation method.

The beneficial effects of the present invention are embodied in:

1. The present invention constructs a heat transfer path between graphene and polyimide through covalent bonds inside the composite material, benefiting from the effect of the C-N-C bond formed between the functionalized substance maleimide and polyimide, The heat transfer performance between graphene and the substrate is greatly enhanced. At the same time, the covalent bond formed between maleimide and graphene also effectively improves the dispersibility of the filler and improves the overall thermal conductivity of the composite material.

2. The method of the present invention can connect the carboxyl-terminated PAA (polyamic acid) and the functionalized graphene through C-N-C bonds, so as to enhance the compatibility between graphene and the matrix, so as to achieve a significant increase in the polymerization under low-content filler filling. Thermal conductivity of imide composites.

Description of drawings

Fig. 1 is the reaction mechanism diagram of functionalized graphene of the present invention and polyamic acid, wherein (a) is the reaction mechanism diagram with polyamic acid after maleimide-modified graphene, (b) is the polyamic acid part The process of imidization to polyimide;

Fig. 2 is the SEM image of the GNS and M@GNS obtained in Example 1 of the present invention, wherein (a) is GNS and (b) is M@GNS;

FIG. 3 is a graph of the thermal conductivity of the composite materials obtained in each embodiment of the present invention and a comparative example.

Detailed ways

The embodiments of the present invention are described in detail below. This embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation manner and a specific operation process, but the protection scope of the present invention is not limited to the following implementation. example.

Example 1

In this example, 5wt% M@GNS/PI composite material was prepared according to the following steps

Step 1. Preparation of GNS

Using graphite foil as anode, platinum foil as cathode, 0.1 mol/L ammonium sulfate aqueous solution as electrolyte, stripping voltage of 15V constant voltage, electrochemical stripping of graphite foil, washing and drying by suction filtration to obtain GNS.

Step 2. Synthesis of M@GNS

Dissolve 45mg maleimide in 40mL N,N dimethylformamide, add 10mg GNS to the solution, sonicate for 50min, then heat in an oil bath at 120°C for 16h, and then irradiate under ultraviolet light for 13min; cool to room temperature Then, the resulting suspension was filtered through a polytetrafluoroethylene disc membrane (0.1 μm pore size, 50 mm in diameter), and then washed with 75 mL of ethanol by vacuum filtration to remove any unreacted maleimide; finally, the filter cake was collected and Vacuum dried at room temperature to obtain M@GNS.

Step 3. Synthesis of M@GNS/PAA/PI

Under nitrogen atmosphere, 0.5948g of 4,4-diaminodiphenylmethane and 9mL of N,N dimethylformamide were added to the three-necked flask and dissolved, according to the mass fraction of 5wt% (accounting for 4,4-diaminodiphenylmethane). phenylmethane and 5 wt% of the total mass of 3,3'-4,4'-biphenyltetracarboxylic dianhydride) were added to M@GNS and sonicated for 50 min, stirred for 5 min in an ice-water bath, and then added 0.9003 g of 3,3'-4 ,4'-biphenyltetracarboxylic dianhydride and molecular sieves were stirred in an ice-water bath for 15 min to obtain a M@GNS/PAA solution with a certain viscosity; then 0.2 mL of triethylamine and 0.1 mL of pyridine were added to obtain a M@GNS/PAA solution with a certain viscosity @GNS/PAA/PI solution.

Step 4. Synthesis of M@GNS/PI

The obtained M@GNS/PAA/PI solution was cast on a clean glass substrate, coated with a doctor blade, and dried at 60 °C for 1.5 h; Heating at 200 °C for 1 h, and finally heating at 250 °C for 1 h), the M@GNS/PI thermally conductive composite film was obtained.

Example 2

In this example, a 10wt% M@GNS/PI composite material was prepared in the same way as in Example 1, except that in step 3, M@GNS was added at a mass fraction of 10wt%.

Example 3

In this example, a 15wt% M@GNS/PI composite material was prepared by the same method as Example 1, except that in step 3, M@GNS was added at a mass fraction of 15wt%.

Comparative Example 1

In this comparative example, a 5wt% GNS/PI composite was prepared as follows:

Step 1. Preparation of GNS

Using graphite foil as anode, platinum foil as cathode, 0.1 mol/L ammonium sulfate aqueous solution as electrolyte, stripping voltage of 15V constant voltage, electrochemical stripping of graphite foil, washing and drying by suction filtration to obtain GNS.

Step 2. Preparation of GNS/PI composites

Under nitrogen atmosphere, 0.5948g of 4,4-diaminodiphenylmethane and 9mL of N,N dimethylformamide were added to the three-necked flask and dissolved, according to the mass fraction of 5wt% (accounting for 4,4-diaminodiphenylmethane). phenylmethane and 5wt% of the total mass of 3,3'-4,4'-biphenyltetracarboxylic dianhydride) were added to GNS and sonicated for 100min, stirred for 5min under an ice-water bath, and then added 0.9003g of 3,3'-4,4 '-Biphenyltetracarboxylic dianhydride and molecular sieves were stirred in an ice-water bath for 15 min to obtain M@GNS/PAA solution with a certain viscosity; then 0.2 mL of triethylamine and 0.1 mL of pyridine were added to obtain GNS/PAA with a certain viscosity /PI solution.

Step 3. Synthesis of GNS/PI

The resulting GNS/PAA/PI solution was cast on a clean glass substrate, coated with a doctor blade, and dried at 60 °C for 1.5 h; finally, by gradient thermal imidization (first at 120 °C for 1 h, then at 200 °C for 1.5 h). ℃ heating for 1 h, and finally heating at 250 ℃ for 1 h) to obtain the GNS/PI thermally conductive composite film.

Comparative Example 2

In this comparative example, a 10wt% GNS/PI composite material was prepared in the same way as in Comparative Example 1, except that in step 2, the mass fraction of 10wt% (accounting for 4,4-diaminodiphenylmethane and 3,3'-4, 10wt% of the total mass of 4'-biphenyltetracarboxylic dianhydride) was added to GNS.

Comparative Example 3

In this comparative example, a 15wt% GNS/PI composite material was prepared in the same way as in Comparative Example 1, except that in step 2, the mass fraction of 15wt% (accounting for 4,4-diaminodiphenylmethane and 3,3'-4, 15wt% of the total mass of 4'-biphenyltetracarboxylic dianhydride) was added to GNS.

Figure 1 shows the reaction mechanism of maleimide-modified graphene and polyamic acid. It can be seen from the figure that the N-H group in maleimide, the functionalized substance of M@GNS, can be obtained by chemical imine method. It reacts with carboxyl-terminated polyamic acid (PAA), and bridges between maleimide and the carboxyl group at the end of polyamic acid (PAA) through a C-N-C bond. At the same time, the interior of polyamic acid (PAA) will undergo partial imidization to generate PAA/PI.

Figure 2 shows the SEM images before and after maleimide modification of graphene. From the figure, it can be seen that the surface of GNS before modification is relatively smooth, and there are small organic particles on the surface of graphene after modification, which indicates that through maleimide A covalent bond was formed with graphene, and maleimide was successfully attached to the surface of graphene.

Figure 3 shows the thermal conductivity test results of each embodiment and the comparative example. It can be seen from the figure that as the filler content increases, the thermal conductivity of the composite material tends to increase. This is because the higher the filler content, the denser the thermal conduction path, and Under the same filler, the thermal conductivity of M@GNS/PI composites is higher than that of GNS/PI composites, which indicates that the effect of the C-N-C bond formed between the functionalized substance maleimide and polyimide greatly enhances the Heat transfer properties of graphene and substrate. At the same time, the covalent bond formed between maleimide and graphene also effectively improved the dispersibility of the filler and improved the overall thermal conductivity of the composite material.

The above are only exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention. within.

Claims (5)

1. a preparation method of polyimide-based modified graphene thermally conductive composite material, is characterized in that: at first obtain graphene nanosheet by electrochemical peeling graphite method, be denoted as GNS; Then by maleimide and GNS Through Diels-Alder reaction, maleimide-modified graphene thermal conductive filler was obtained, denoted as M@GNS; finally, polyimide as matrix and M@GNS were prepared by in-situ polymerization and chemical imide method. is the maleimide@graphene/polyimide composite with filler, denoted as M@GNS/PI. 2. preparation method according to claim 1, is characterized in that, comprises the steps: Step 1. Preparation of GNS Using graphite foil as anode, platinum foil as cathode, 0.1-0.12mol/L ammonium sulfate aqueous solution as electrolyte, stripping voltage of 15-15.3V constant voltage, electrochemical stripping of graphite foil, washing and drying by suction filtration After, get GNS; Step 2. Synthesis of M@GNS Dissolve 45-50 mg maleimide in 40-50 mL N,N dimethylformamide, add 10-15 mg GNS to the solution, ultrasonicate for 50-60 min, and then heat in an oil bath at 115-120 °C for 14-16 h, Irradiate under ultraviolet light for 10-15 min; after cooling to room temperature, the obtained suspension is filtered through a polytetrafluoroethylene disc membrane, and then washed with 60-75 mL of ethanol by vacuum filtration to remove unreacted maleimide; finally , the filter cake was collected and dried under vacuum at room temperature to obtain M@GNS; Step 3. Synthesis of M@GNS/PAA/PI Under nitrogen atmosphere, add 0.5940～0.5950g 4,4-diaminodiphenylmethane and 8.5～9.5mL N,N dimethylformamide to the three-necked flask and dissolve it, add M@GNS and ultrasonicate for 50～60min, place in ice Stir in a water bath for 5-10 min, then add 0.9000-0.9010 g of 3,3'-4,4'-biphenyltetracarboxylic dianhydride and molecular sieves, and stir in an ice-water bath for 15-20 min to obtain M@GNS/PAA solution; then Add 0.15-0.2 mL of triethylamine and 0.08-0.1 mL of pyridine to obtain M@GNS/PAA/PI solution; Step 4. Synthesis of M@GNS/PI The obtained M@GNS/PAA/PI solution was cast on a clean glass substrate, coated with a doctor blade, and dried at 60-70 °C for 1-1.5 h; finally, M@GNS/PAA/PI was prepared by gradient thermal imidization. @GNS/PI thermally conductive composites. 3. The preparation method according to claim 2, characterized in that: the procedure of gradient thermal imidization in step 4 is: firstly heating at 120°C for 1 hour, then heating at 200°C for 1 hour, and finally heating at 250°C for 1 hour . 4. preparation method according to claim 2 is characterized in that: in step 3, the addition of M@GNS accounts for 4,4-diaminodiphenylmethane and 3,3'-4,4'-biphenyltetrakis 0-15wt% of the total mass of formic dianhydride. 5. An M@GNS/PI composite material obtained by the preparation method according to any one of claims 1 to 4.

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