CN116375016A - Method for preparing high-heat-conductivity polyimide graphite film by chemical imidization of doped graphene - Google Patents

Abstract

The invention discloses a method for preparing a high-heat-conductivity polyimide graphite film by chemical imidization of doped graphene, which comprises the following steps: s1, sequentially adding diamine and dianhydride into a polar solvent A, and fully stirring and dissolving to obtain a polyamic acid resin solution; s2, adding graphene oxide and reinforcing agent into an imidizing reagent, and performing ultrasonic dispersion to obtain graphene oxide dispersion liquid; s3, mixing the polyamic acid resin solution and the graphene oxide dispersion liquid to obtain polyamic acid slurry, and then performing centrifugal defoaming, tape casting and film forming, and performing high-temperature imidization treatment to obtain a composite film; s4, carbonizing the composite film at high temperature, and then cooling to room temperature to obtain a carbonized film; and S5, graphitizing the carbonized film at a high temperature, and then cooling to room temperature to obtain the polyimide graphite film with high heat conductivity. According to the invention, graphene oxide can be uniformly dispersed, the heat conduction performance of the product is improved, and the strength of the product is enhanced on the basis of introducing an enhanced phase to ensure the heat conduction performance.

Description

Method for preparing high thermal conductivity polyimide graphite film by chemical imidization of doped graphene

technical field

The invention belongs to the technical field of thin films, and in particular relates to a method for preparing a high thermal conductivity polyimide graphite film by chemical imidization of doped graphene.

Background technique

The polymer material polyimide (PI) has many advantages such as excellent high and low temperature resistance, good chemical corrosion resistance, outstanding electrical insulation and high dimensional stability, and is widely used in aerospace, electronics and other fields. In order to broaden its application in the fields of high thermal conductivity and high heat dissipation, it is essential to improve the thermal conductivity of polyimide PI resin matrix. Polyimide high thermal conductivity graphite film basically relies on imports. The production of polyimide film in my country mainly adopts thermal imidization film production process. Compared with foreign chemical imidization film production process, the production efficiency is low and the thermal dimensional stability is poor. Low strength and low thermal stability. The precursor PI base film produced by this kind of thermal imidization method is cracked during the high temperature carbonization process, the surface is wrinkled and dull, the thermal conductivity is low, and it is not resistant to folding and cannot meet high thermal conductivity. Film production requirements of graphite film process. Chinese patent CN106853966A joins graphene in strong polar organic solvent to disperse, first adds diamine, then adds dianhydride to reaction polymerization chemical imidization method to make membrane; It is very easy to deoxidize and turn black at high temperature, and it is necessary to avoid contact with reducing substances, and the diamine that is preferentially added is generally reducing, and the reaction between diamine and dianhydride will release a large amount of heat, which will affect the dispersion effect and lead to agglomeration. Reduce thermal conductivity and uniformity.

Contents of the invention

In view of the above-mentioned technical problems, the invention provides a method for preparing high thermal conductivity polyimide graphite film by chemical imidization of doped graphene. The present invention disperses graphene oxide in imidization reagent, and Carboxyl groups and hydroxyl groups on the surface of olefins form hydrogen bonds, which is conducive to the peeling and dispersion of graphene oxide sheets, avoiding agglomeration, and solving the characteristics of graphene oxide that is easy to agglomerate and difficult to disperse, resulting in poor film orientation, resulting in heat conduction in different areas on the surface of the prepared graphite film The problem of large difference in rate; the present invention also enhances its strength on the basis of ensuring thermal conductivity by introducing a reinforcing phase into the graphene oxide slurry.

Technical scheme of the present invention is:

The invention relates to a method for preparing a high thermal conductivity polyimide graphite film by chemical imidization of doped graphene, comprising the following steps:

S1, adding diamine and dianhydride to polar solvent A in sequence, fully stirring and dissolving to obtain a polyamic acid resin solution;

S2, adding the graphene oxide and the reinforcing phase into the imidization reagent, and ultrasonically dispersing to obtain a graphene oxide dispersion;

S3. Mix the polyamic acid resin solution prepared in step S1 with the graphene oxide dispersion prepared in step S2 to obtain a polyamic acid slurry, which is then sequentially subjected to centrifugal defoaming, casting into a film, and subjected to high-temperature imine After chemical treatment, a graphene oxide-doped polyimide composite film is obtained;

S4, carbonizing the graphene oxide-doped polyimide composite film at high temperature, and then lowering it to room temperature to obtain a carbonized film;

S5. Perform high-temperature graphitization on the carbonized film, and then lower it to room temperature to obtain a polyimide graphite film with high thermal conductivity.

Preferably, in step S1, the diamine is a mixture of one or more of diphenyl ether diamine, p-phenylenediamine, 4,4'-benzidine, and 4,4'-diaminobenzophenone ; The dianhydride is a mixture of one or more of pyromellitic dianhydride, diphenyl ether dianhydride, and biphenyl dianhydride; the diamine is in an equimolar ratio to the dianhydride, and the total weight accounts for 15-20% of the total mass of the polyamic acid resin solution.

Preferably, in step S1, the specific operation method of adding the diamine and dianhydride separately is: first add the diamine monomer into the polar solvent A at one time, and after fully dissolving, then add the dianhydride monomer with stirring The reaction was added in portions.

Preferably, in step S2, the imidization reagent is a mixture of acetic anhydride, catalyst and polar solvent B, and the catalyst is one or more of pyridine, picoline, diethylpyridine, and isoquinoline ; Wherein the molar ratio of acetic anhydride/catalyst is 2-5:1, and the sum of the mass of acetic anhydride and catalyst accounts for 20-50% of the total weight of the imidization reagent.

Preferably, in step S2, graphene oxide is graphene oxide prepared by the Humers method. The present invention avoids the phenomenon of graphene oxide deoxidation reduction, agglomeration and aggregation by dispersing graphene oxide in the imidization reagent, and can Keep the graphene oxide dispersed evenly, improve the thermal conductivity of the product and make the heat conduction more uniform.

Preferably, in step S1, the polar solvent A is a polar aprotic solvent, including N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide or dimethylsulfoxide Any one or more of them; in step S2, the polar solvent B used in the imidization reagent is also a polar aprotic solvent, including N-methylpyrrolidone, N, N-dimethylformamide, N, N - any one or more of dimethylacetamide or dimethyl sulfoxide.

Preferably, in step S2, the reinforcing phase is swelling starch ether and its derivatives, lignocellulose and its derivatives, redispersible latex powder, lignosulfonate and its derivatives, nanocellulose and One or more of its derivatives, carbon nanotubes, and carbon fibers are mixed in any proportion; the mass ratio of the reinforcing phase to graphene oxide is (0-50): (50-100).

Preferably, in step S2, the time for ultrasonic dispersion is 60-180 minutes.

Preferably, the content of graphene oxide in the graphene oxide dispersion used in step S3 is 0.1-1% of the solid content of the polyamic acid resin solution.

Preferably, in step S3, after the polyamic acid slurry is prepared, the obtained polyamic acid slurry is degassed by a centrifugal degassing machine, and cast on a glass plate to form a film, and the temperature is raised in stages, at 60- Insulate at 80°C for 20-30min, at 170-190°C for 20-30min, at 300-320°C for 10-20min, and at 400-425°C for 5-10min to obtain graphene oxide doped polyimide Amine composite film.

Preferably, in the S4 step, the specific steps of high-temperature carbonization are as follows: the graphene oxide-doped polyimide composite thin and graphite paper are cross-laminated in the constant temperature interval in the vacuum carbonization furnace, and a certain pressure (10-20g/ cm ² ), then carry out carbonization treatment, keep at 400-500°C for 20-30min, at 600-700°C for 20-30min, at 750-850°C for 20-30min, at 900-1000°C for 20-30min, at 1100-1200°C Keep for 20-30min, then cool down to room temperature naturally to obtain carbonized film.

Preferably, in step S5, the specific steps of high-temperature graphitization are as follows: the carbonized film and graphite paper are cross-laminated and placed in the constant temperature range of the graphitization furnace, and a certain pressure (10-20g/cm ² ) is applied, in an argon atmosphere In the first 1.5-2h, the temperature is raised to 1100-1200°C, then the temperature is raised to 1900-2000°C for 2.5-3h, and then the temperature is raised to 2600-2800°C and kept for 50-60min, and then the temperature is naturally cooled to room temperature to obtain high thermal conductivity. Polyimide graphite film.

The beneficial effects of the present invention are:

(1) The present invention disperses graphene oxide in the imidization reagent. On the one hand, the dehydrating agent acetic anhydride in the imidization reagent forms hydrogen bonds with the carbonyl and hydroxyl hydrogen on the graphene oxide (GO), reducing the amount of graphene oxide. The inter-lamellar combination has a better dispersion effect, and through the combined action of the dehydrating agent and the catalyst in the chemical imidization reagent, the polyamic acid is converted into polyimide, and a film with high orientation is prepared;

(2) In the present invention, the graphene oxide mixed slurry is obtained by introducing a reinforcing phase into the graphene oxide slurry, and the thermal conduction film prepared by doping it into polyimide acid has a better interlayer orientation on the basis of ensuring thermal conductivity. Good, higher strength;

(3) in actual production, ultrasonically disperse graphene oxide in the reaction solvent tank, and equipment technology is difficult to realize, and disperse graphene in the imidization reagent that the present invention proposes, equipment is easy to realize, adapts to large-scale production; The present invention adopts chemical The high thermal conductivity polyimide graphite film prepared by imidization has high production efficiency and superior comprehensive performance. The present invention is closer to the actual industrial production process and has high equipment feasibility.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are exemplary only, and are not intended to limit the scope of the present invention. Also, in the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concept of the present invention.

Example 1

In a nitrogen atmosphere, diamine 19.15g ODA (4,4'-diaminodiphenyl ether) and dianhydride 20.85g PMDA (pyromellitic dianhydride) were added to 168.7mL DMF (N, In N-dimethylformamide), the specific operation formula is: firstly add the diamine ODA monomer into the DMF solution at one time, after fully dissolving, then add the dianhydride PMDA monomer in batches with stirring reaction Adding, stirring and reacting at constant temperature for 5 hours to obtain a polyamic acid resin solution with a solute concentration of 20 wt%.

Graphene oxide was prepared from natural flake graphite by the Hummer method.

A mixture of imidization reagent acetic anhydride-isoquinoline and DMF was prepared (the imidization reagent concentration was 24%, and the molar ratio of acetic anhydride to catalyst was AA:IQ=5:2).

Mix lignocellulose (reinforcing phase) with the prepared graphene oxide (the mass ratio of lignocellulose to graphene oxide is 1:10), add the prepared imidization reagent, and ultrasonically disperse for 2 hours to obtain graphene oxide dispersion liquid.

Add in the above-mentioned graphene oxide dispersion liquid in the polyamic acid resin solution (the add-on of graphene oxide dispersion liquid is 40% of the polyamic acid resin solution quality, wherein the graphene oxide mass content is solidly contained in the polyamic acid resin solution 0.1%), then stir quickly evenly, cast film on a glass plate after centrifugation and defoaming, enter the oven for treatment, keep warm at 80°C for 20min, keep warm at 180°C for 30min, keep warm at 300°C for 20min, and keep warm at 425°C 5min, the graphene oxide doped polyimide composite film was obtained.

The resulting graphene oxide-doped polyimide film and graphite paper are cross-laminated and placed in the constant temperature range of the vacuum carbonization furnace, and a certain pressure (17g/cm ² ) is applied, and then the temperature is programmed to raise the carbonization treatment. The specific temperature rise process is as follows: : Keep at 500°C for 30min, 700°C for 30min, 850°C for 30min, 1000°C for 30min, 1200°C for 30min, then cool down to room temperature naturally to obtain carbonized film;

Lay the carbonized film and graphite paper cross-layered in the constant temperature zone of the graphitization furnace, and apply a certain pressure (20g/cm ² ), and carry out graphitization treatment in an inert gas atmosphere. Then raise the temperature to 2000°C for another 2.5 hours, then raise the temperature to 2600°C for another 2 hours and keep it for 50 minutes, then cool down to room temperature naturally to obtain a polyimide graphite film with high thermal conductivity.

Example 2

The mass content of graphene oxide is 0.3% of the solid content of the polyamic acid resin solution, and other conditions are the same as in Example 1.

Example 3

The mass content of graphene oxide is 0.5% of the solid content of the polyamic acid resin solution, and other conditions are the same as in Example 1.

Example 4

The mass content of graphene oxide is 0.7% of the solid content of the polyamic acid resin solution, and other conditions are the same as in Example 1.

Example 5

The mass content of graphene oxide is 0.9% of the solid content of the polyamic acid resin solution, and other conditions are the same as in Example 1.

Example 6

Prepare imidization reagent acetic anhydride-picoline and DMF mixture (imidization reagent concentration is 24%, acetic anhydride to catalyst molar ratio is AA:AP=5:2), other conditions are the same as Example 1.

Example 7

The reinforcing phase is carbon nanotubes, and other conditions are the same as in Example 1.

Example 8

Lignocellulose (enhanced phase) was mixed with the obtained graphene oxide in a mass ratio of 1:1, and other conditions were the same as in Example 1.

Example 9

Lignocellulose (enhanced phase) was mixed with the obtained graphene oxide at a mass ratio of 1:100, and other conditions were the same as in Example 1.

Comparative example 1

The mass content of graphene oxide is 0.05% of the solid content of the polyamic acid resin solution, and other conditions are the same as in Example 1.

Comparative example 2

The mass content of graphene oxide is 1.2% of the solid content of the polyamic acid resin solution, and other conditions are the same as in Example 1.

Comparative example 3

Graphene oxide was not dispersed in the imidization reagent, but was instead dispersed in 168.7mL DMF for 2h, with a mass content of 0.1% of the solid content of the polyamic acid resin solution, and other conditions were the same as in Example 1.

Comparative example 4

Without reinforcing phase, other conditions are the same as in Example 1.

Comparative example 5

Lignocellulose (enhanced phase) was mixed with the obtained graphene oxide at a mass ratio of 2:1, and other conditions were the same as in Example 1.

The graphite film of embodiment 1-9 and comparative example 1-5 is carried out performance test

(1) Thermal conductivity test method: refer to the relevant regulations of ASTM E 1461.

Laboratory environmental conditions: 23°C±2°C, 50%±5%RH.

The specific test results are shown in Table 1:

Table 1

It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principle of the present invention, and not to limit the present invention. Therefore, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present invention shall fall within the protection scope of the present invention. Furthermore, it is intended that the appended claims of the present invention embrace all changes and modifications that come within the scope and metesques of the appended claims, or equivalents of such scope and metes and bounds.

Claims (10)

1. The method for preparing the high-heat-conductivity polyimide graphite film by chemical imidization of doped graphene is characterized by comprising the following steps of:

s1, sequentially adding diamine and dianhydride into a polar solvent A, and fully stirring and dissolving to obtain a polyamic acid resin solution;

s2, adding graphene oxide and reinforcing agent into an imidizing reagent, and performing ultrasonic dispersion to obtain graphene oxide dispersion liquid;

s3, mixing the polyamic acid resin solution prepared in the step S1 and the graphene oxide dispersion liquid prepared in the step S2 to obtain polyamic acid slurry, sequentially performing centrifugal defoaming and tape casting to form a film, and performing high-temperature imidization treatment to obtain a graphene oxide doped polyimide composite film;

s4, carbonizing the graphene oxide doped polyimide composite film at high temperature, and then cooling to room temperature to obtain a carbonized film;

and S5, graphitizing the carbonized film at a high temperature, and then cooling to room temperature to obtain the polyimide graphite film with high heat conductivity.

2. The method of claim 1, wherein in step S1, the diamine is a mixture of one or more of diphenyl ether diamine, p-phenylene diamine, 4 '-benzidine, 4' -diaminobenzophenone; the dianhydride is one or a mixture of more of pyromellitic dianhydride, diphenyl ether dianhydride and biphenyl dianhydride; the diamine and the dianhydride are in equimolar ratio, and the total weight accounts for 15-20% of the total mass of the polyamic acid resin solution.

3. The method according to claim 1, wherein in step S1, the specific operation mode of adding diamine and dianhydride respectively is: firstly, adding diamine monomer into polar solvent A at one time, after fully dissolving, adding dianhydride monomer in batches along with stirring reaction.

4. The method according to claim 1, wherein in the step S2, the imidizing agent is a mixture of acetic anhydride, a catalyst and a polar solvent B, and the catalyst is one or more of pyridine, picoline, diethylpyridine and isoquinoline; wherein the mole ratio of acetic anhydride/catalyst is 2-5: 1, the sum of the mass of the acetic anhydride and the mass of the catalyst accounts for 20-50% of the total weight of the imidizing agent.

5. The method according to claim 4, wherein in step S1, the polar solvent a is a polar aprotic solvent including any one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, or dimethylsulfoxide; in step S2, the polar solvent B used in the imidizing agent is also a polar aprotic solvent, and comprises any one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide or dimethylsulfoxide.

6. The method according to claim 1, wherein in step S2, the reinforcing phase is one or more of swelling starch ether and its derivatives, lignocellulose and its derivatives, redispersible latex powder, lignosulfonate and its derivatives, nanocellulose and its derivatives, carbon nanotubes, and carbon fibers mixed in any ratio; the mass ratio of the reinforcing phase to the graphene oxide is (0-50): (50-100).

7. The method according to claim 1, wherein the content of graphene oxide in the graphene oxide dispersion liquid used in step S3 is 0.1 to 1% of the solid content weight of the polyamic acid resin solution.

8. The method according to claim 1, wherein in step S3, after the polyamic acid slurry is prepared, the obtained polyamic acid slurry is defoamed by a centrifugal deaerating machine, and then cast on a glass plate to form a film, and the film is prepared by adopting a step heating mode, and then insulating at 60-80 ℃ for 20-30min, 170-190 ℃ for 20-30min, 300-320 ℃ for 10-20min and 400-425 ℃ for 5-10min, so as to obtain the graphene oxide doped polyimide composite film.

9. The method according to claim 1, wherein in step S4, the specific step of high temperature carbonization is as follows: the graphene oxide doped polyimide composite thin and the graphite paper are alternately stacked in a constant temperature interval in a vacuum carbonization furnace, certain pressure is applied, carbonization treatment is carried out, the temperature is kept at 400-500 ℃ for 20-30min, the temperature is kept at 600-700 ℃ for 20-30min, the temperature is kept at 750-850 ℃ for 20-30min, the temperature is kept at 900-1000 ℃ for 20-30min, the temperature is kept at 1100-1200 ℃ for 20-30min, and then natural cooling is carried out to room temperature, so that a carbonized film is obtained.

10. The method according to claim 1, wherein in step S5, the specific step of high temperature graphitization is as follows: and (3) cross-laminating the carbonized film and the graphite paper in a constant temperature interval in a graphitization furnace, applying a certain pressure, heating to 1100-1200 ℃ in an argon atmosphere for 1.5-2h, heating to 1900-2000 ℃ for 2.5-3h, keeping the temperature for 2-2.5h to 2600-2800 ℃ and keeping the temperature for 50-60min, and naturally cooling to room temperature to obtain the polyimide graphite film with high heat conductivity.