CN115663221A - High-strength composite flexible graphite plate and preparation method thereof - Google Patents

Abstract

The invention relates to a high-strength composite flexible graphite plate and a preparation method thereof, wherein the method comprises the following steps: pretreatment of the flexible graphite material: dipping the flexible graphite material in the group treatment solution, and cleaning and drying the flexible graphite material after dipping to obtain a pretreated flexible graphite plate; compounding high molecular monomers: and (3) dipping the high-molecular monomer solution, and then curing and crosslinking the high-molecular monomer to obtain the high-strength composite flexible graphite plate. The radicalization treatment solution comprises an oxidizing agent, a nitriding agent or a borating agent. Compared with the prior art, the method has the advantages that the flexible graphite material is pretreated, and a certain group structure is formed at the defect position of the graphite material. Furthermore, in the process of impregnating and even polymerizing with a polymer resin monomer, the bonding strength between the polymer resin material and the flexible graphite is improved by utilizing the hydrogen bond effect formed by the group formed at the defect part of the graphite material and the polymer resin, and finally the strength of the composite material is realized.

Description

A kind of high-strength composite flexible graphite plate and preparation method thereof

technical field

The invention relates to the field of fuel cell materials, in particular to a high-strength composite flexible graphite plate and a preparation method thereof.

Background technique

Flexible graphite is a material discovered in modern times and processed from natural graphite. It is widely used due to its important properties such as porosity, softness, and interlocking molding without adhesives. However, its poor airtightness and strength limit the scope of application. Therefore, the vacuum impregnation method is often used to fill the pores of flexible graphite with resin monomers or dissolved polymer resins, and further polymerize or desolventize to provide strength and sealing for composite materials. At present, composite flexible graphite materials are widely used in fuel cell bipolar plates, heat transfer in corrosive environments, and electrical and thermal conduction of special electronic devices. And it is considered by the fuel cell industry to be the material most likely to achieve the goal of low-cost bipolar plates.

In the current technology, polymer resin monomers or dissolved polymer materials are generally used as an impregnating solution to impregnate the flexible graphite plate through vacuum impregnation. In order to shorten the immersion time, it is generally necessary to use a lower viscosity immersion solution. This also means that it is difficult to use polymers with complex structures and high crosslinking degrees, which limits the strength of flexible graphite composites. Currently, there is no better solution to this problem.

Contents of the invention

The object of the present invention is to provide a high-strength composite flexible graphite plate and a preparation method thereof in order to overcome at least one of the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

The inventors have learned that the resin-impregnated flexible graphite plate is a composite material with light weight, high thermal conductivity, high electrical conductivity and high air tightness. Therefore, it is also considered to be the best solution for the cost reduction of fuel cell bipolar plates. However, because the solidified polymer material that can provide a high-strength support skeleton for the composite material often has a higher viscosity in a monomer state or a dissolved state, it is difficult to impregnate into flexible graphite. Therefore, the strength of the composite flexible graphite graphite sheet is generally very low. In many applications such as water-cooled heat exchange and fuel cell bipolar plates, the demand for material strength is gradually increasing. The present invention immerses the oxide into the flexible graphite plate through the impregnation method, further controls the oxidation degree of the flexible graphite by controlling the type and concentration of the oxide and the reaction time, and after further drying, the liquid resin is immersed into the flexible graphite through the method of vacuum impregnation. plate, and complete curing. In the method, the oxidized groups of the flexible graphite are used to form hydrogen bonds with the subsequent impregnated resin. Due to the complex and large contact of the two materials, the strength of the composite material is improved, and the specific scheme is as follows:

A high-strength composite flexible graphite plate and a preparation method thereof, the method comprising the following steps:

Pretreatment of flexible graphite material: impregnate the flexible graphite material with the group treatment solution, after the impregnation is completed, wash and dry to obtain the pretreated flexible graphite plate;

Polymer monomer compounding: impregnate the polymer monomer solution, and then cure and crosslink the polymer monomer to obtain a high-strength composite flexible graphite plate.

Further, the radicalization treatment solution includes an oxidizing agent, a nitriding agent or a boronating agent.

Further, the oxidizing agent includes potassium permanganate, concentrated sulfuric acid, concentrated nitric acid or Fenton's reagent, and the concentration of the oxidizing agent is 5-10mol/L.

Further, the oxidizing agent is Fenton's reagent with pH=3-5, wherein the mass concentration of H ₂ O ₂ is 0-30wt%, and zero is not taken.

Further, the nitriding agent includes urea, and the concentration of the nitriding agent is 0.1-10 g/ml; the boronating agent includes boric acid, and the concentration of the borating agent is 0.1-10 g/ml.

Further, during pretreatment, the steps of cleaning and drying are as follows: after dipping, firstly dry at 70-100°C, then heat under an inert atmosphere, and then wash and dry to obtain a pretreated flexible graphite plate.

Further, the heating temperature under the inert atmosphere is 200-500° C., and the heating time is not less than 1 hour. The main purpose is to remove nitriding or borating agents.

Further, the flexible graphite material includes flexible graphite plate or worm graphite.

Further, the polymer monomer includes acrylic monomer, modified acrylic monomer or epoxy resin, and the curing method includes heating curing or curing by adding an initiator, and the initiator includes an azo initiator.

A high-strength composite flexible graphite plate prepared by the above method, the mass ratio of flexible graphite material to polymer monomer in the composite flexible graphite plate is (0.8-1.2):1.

Compared with the prior art, the present invention has the following advantages:

(1) The present invention forms a certain group structure at the defects of the graphite material by pretreating the flexible graphite material. Further, during the impregnation and even polymerization process with the polymer resin monomer, the hydrogen bond between the group formed at the defect of the graphite material and the polymer resin is used to improve the bonding strength between the polymer resin material and the flexible graphite, and finally realize the strength of the composite material;

(2) The expanded graphite after group pretreatment in the present invention can greatly improve the flexural strength of the composite material without changing its bulk density conditions and immersion operation conditions, and the electrical and thermal conductivity of the new composite material obtained No significant changes will occur.

Description of drawings

Fig. 1 is _H2O in embodiment ₁ Mass concentration and sheet material flexural strength relation figure;

FIG. 2 is a graph showing the relationship between the mass concentration of H ₂ O ₂ and the conductivity of the sheet in Example 1.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and the detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

A high-strength composite flexible graphite plate and a preparation method thereof, the method comprising the following steps:

1. Put the flexible graphite material into the reaction kettle, and immerse the radicalization treatment solution into the flexible graphite material by vacuuming; the radicalization treatment solution includes an oxidizing agent, a nitriding agent or a boronizing agent. The oxidizing agent includes potassium permanganate, concentrated sulfuric acid, concentrated nitric acid or Fenton's reagent, and the concentration of the oxidizing agent is 5-10mol/L. The oxidizing agent is Fenton's reagent with pH=3-5, wherein the mass concentration of H ₂ O ₂ is 0-10wt%, and 0 is not taken. The nitriding agent includes urea, and the concentration of the nitriding agent is 0.1-10 g/ml; the boronating agent includes boric acid, and the concentration of the boronizing agent is 0.1-10 g/ml. Flexible graphite materials include flexible graphite sheets or worm graphite;

2. After the reaction between the group treatment solution and the flexible graphite is completed, the pretreated flexible graphite plate can be obtained again through the steps of cleaning and drying; The drying step is as follows: after impregnating, firstly drying, then heating under an inert atmosphere, and then cleaning and drying to obtain a pretreated flexible graphite plate. The heating temperature under an inert atmosphere is 200-500°C, and the time is not less than 1h;

3. Further put the pretreated flexible graphite plate into the reaction kettle, once again immerse the polymer monomer or dissolved substance into the flexible graphite material by vacuum impregnation method, and clean its surface by wiping, cleaning and other methods; Monomers include acrylics, modified acrylic monomers, or epoxies;

4. By increasing the temperature of the above materials, the resin is induced to solidify or the solution is dehydrated to complete the crosslinking of the polymer resin. The initiator includes an azo initiator, and the mass ratio of the flexible graphite material to the polymer monomer in the composite flexible graphite plate obtained is For (0.8-1.2):1.

[Plate Oxidation Method] The specific operation process is: place the pressed flexible graphite light plate in a vacuum reactor with an absolute pressure of 5-200Pa, and after the internal and external gas pressures of the expanded graphite are balanced, then use vacuum to pump in potassium permanganate or concentrated Sulfuric acid or concentrated nitric acid or Fenton’s reagent has a high oxidizing solution, and the oxidizing solution is immersed over the bare plate material, and the vacuum is released to allow the oxidizing solution to soak into the material, and the oxidation is completed. Further, the oxidized material was washed with deionized water, and dried in a vacuum oven at 70-100° C. for 12 hours.

Put the dried material in a vacuum reactor with an absolute pressure of 50-500Pa. After the vacuum pressure is stable, pump in the spare liquid resin monomer and possible initiators to cover the light board material, release the vacuum and possibly increase the reaction The gas pressure above the resin liquid in the kettle, for example, to 1MPa. After being stabilized, the flexible graphite material is taken out; the surface resin is removed by cleaning, and the resin material is cured by a method such as raising the temperature to initiate polymerization. The resin monomer used refers to such as acrylic and modified acrylic monomers, and the initiator is such as azo initiator, etc.; or epoxy resin alcohol solution, etc.

[Plate nitriding method] The specific operation process is as follows: place the pressed flexible graphite light plate in a vacuum reactor with an absolute pressure of 5-200Pa, balance the gas pressure inside and outside the expanded graphite, and then use vacuum to draw in a concentration of 0.1-10g /ml of urea solution, and immerse over light plate material. Release the vacuum to immerse the urea solution into the material, maintain normal pressure or increase the ambient pressure to achieve internal and external equilibrium as soon as possible. And dry at 80°C for 1-24 hours, and then place in a high-temperature furnace with nitrogen atmosphere at 200-500°C for more than 1 hour. Finally, the treated material was washed with deionized water and dried in a vacuum oven at 70-100° C. for 12 hours.

Put the dried material in a vacuum reactor with an absolute pressure of 50-500Pa. After the vacuum pressure is stable, pump in the spare liquid resin monomer and possible initiators to cover the light board material, release the vacuum and possibly increase the reaction The gas pressure above the resin liquid in the kettle, for example, to 1MPa. After being stabilized, the flexible graphite material is taken out; the surface resin is removed by cleaning, and the resin material is cured by a method such as raising the temperature to initiate polymerization. The resin monomer used refers to such as acrylic and modified acrylic monomers, and the initiator is such as azo initiator, etc.; or epoxy resin alcohol solution, etc.

[Powder Oxidation Method] Put the raw materials of flexible graphite plate and worm graphite in a vacuum reactor with an absolute pressure of 5-200Pa, and after the gas pressure inside and outside the expanded graphite is balanced, use vacuum to pump high manganese with a concentration of 5-10mol/L Potassium nitrate or concentrated sulfuric acid or concentrated nitric acid with high oxidizing solution, and stir well to make the two fully mixed. Release the vacuum to allow the oxidizing solution to soak into the material until the oxidation is complete. Further, the oxidized material was washed with deionized water, and dried in a vacuum oven at 70-100° C. for 12 hours.

The above-mentioned worm graphite powder is extruded one or more times to form a flexible graphite plate, and the molding may be completed through a mold. It is further placed in a vacuum reactor to complete the resin impregnation and synthesis process.

【Plate boridation method】

Replace urea in plate nitriding method with boric acid.

Example 1

The pressed flexible graphite light plate is placed in a vacuum reactor with an absolute pressure of 5-200Pa, and after the gas pressure inside and outside the expanded graphite is balanced, the oxidant is sucked in by vacuum, specifically Fenton’s reagent with pH=3-5, wherein H The mass concentration of ₂ O ₂ is 0-10wt%, the oxidant solution is immersed over the light plate material, the vacuum is released to allow the oxidant solution to immerse into the material, and the oxidation is completed. Further, the oxidized material was washed with deionized water, and dried in a vacuum oven at 70-100° C. for 12 hours.

Put the dried material in a vacuum reactor with an absolute pressure of 50-500Pa. After the vacuum pressure is stable, pump in the spare liquid resin monomer and possible initiators to cover the light board material, release the vacuum and possibly increase the reaction The gas pressure above the resin liquid in the kettle, for example, to 1MPa. After being stabilized, the flexible graphite material is taken out; the surface resin is removed by cleaning, and the resin material is cured by initiating polymerization. The resin monomer used is an acrylic monomer, the initiator is an azo initiator, and the mass ratio of the flexible graphite material to the polymer monomer in the obtained composite flexible graphite plate is 1:1.

Fig. _{1 is H in embodiment 1 The mass concentration of O 2 and} the relationship diagram of sheet material flexural strength, Fig. 2 is the relationship diagram of H in embodiment 1 The mass concentration of O ₂ and sheet material conductivity, the _expanded graphite after modification is due to Oxidation free radicals, such as carbonyl, carboxyl, etc., can form hydrogen bonds with the resin polymers that enter and polymerize later, thus improving the binding force of the two phases, thereby improving the strength of the composite material. Although both experiments and literature have shown that highly oxidized graphene oxide does not have conductive properties, the process adopted in the present invention is a vacuum impregnation process, and the internal lamellar structure of flexible graphite does not occur, or slightly changes. The conductive network formed by the inner sheets of flexible graphite has not been destroyed. Therefore, according to the test results, the macroscopic conductive properties of flexible graphite have not changed greatly.

Example 2

Place the pressed flexible graphite light plate in a vacuum reactor with an absolute pressure of 5-200Pa, and after the gas pressure inside and outside the expanded graphite is balanced, use a vacuum to draw in a urea solution with a concentration of 0.1-10g/ml, and immerse it over the light plate material . Release the vacuum to immerse the urea solution into the material, maintain normal pressure or increase the ambient pressure to achieve internal and external equilibrium as soon as possible. And dry at 80°C for 1-24 hours, and then place in a high-temperature furnace with nitrogen atmosphere at 200-500°C for more than 1 hour. Finally, the oxidized material was washed with deionized water, and dried in a vacuum oven at 70-100° C. for 12 hours.

Put the dried material in a vacuum reactor with an absolute pressure of 50-500Pa. After the vacuum pressure is stable, pump in the spare liquid resin monomer and possible initiators to cover the light board material, release the vacuum and possibly increase the reaction The gas pressure above the resin liquid in the kettle, for example, to 1MPa. After being stabilized, the flexible graphite material is taken out; the surface resin is removed by cleaning, and the resin material is cured by a method such as raising the temperature to initiate polymerization. The resin monomer used is an acrylic monomer, the initiator is an azo initiator, and the mass ratio of the flexible graphite material to the polymer monomer in the obtained composite flexible graphite plate is 1:1.

Example 3

Place the raw materials of flexible graphite plate and worm graphite in a vacuum reaction kettle with an absolute pressure of 5-200Pa, and after the gas pressure inside and outside the expanded graphite is balanced, use a vacuum to pump in potassium permanganate or concentrated sulfuric acid with a concentration of 5-10mol/L Or concentrated nitric acid and other highly oxidizing solutions, and fully stir to make the two fully mixed. Release the vacuum to allow the oxidizing solution to soak into the material until the oxidation is complete. Further, the oxidized material was washed with deionized water, and dried in a vacuum oven at 70-100° C. for 12 hours.

The above-mentioned worm graphite powder is extruded one or more times to form a flexible graphite plate, and the molding may be completed through a mold. It is further placed in a vacuum reactor to complete the resin impregnation and synthesis process. The resin monomer used is an acrylic monomer, the initiator is an azo initiator, and the mass ratio of the flexible graphite material to the polymer monomer in the obtained composite flexible graphite plate is 1:1.

Example 4

The urea in embodiment 2 is replaced by boric acid. Boronation and nitriding are similar to oxidation, and both can form free radicals with the defects or edges of worms in flexible graphite, forming -NH, or -N, or -B and other similar groups. Since the groups formed by nitrogen and boron have polar characteristics, it is also easy to form a hydrogen bond structure with the resin. At the same time, the polarity of the group will be more conducive to the conduction of the original expanded graphite, making it have good electrical conductivity after nitriding or boronizing.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention to other forms. Any skilled person who is familiar with this profession may use the technical content disclosed above to change or modify the equivalent of equivalent changes. Example. However, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims (10)

1. a preparation method of high-strength composite flexible graphite plate, is characterized in that, the method may further comprise the steps: Pretreatment of flexible graphite material: impregnate the flexible graphite material with the group treatment solution, after the impregnation is completed, wash and dry to obtain the pretreated flexible graphite plate; Polymer monomer compounding: impregnate the polymer monomer solution, and then cure and crosslink the polymer monomer to obtain a high-strength composite flexible graphite plate. 2. The preparation method of a kind of high-strength composite flexible graphite plate according to claim 1, characterized in that, the radicalization treatment solution comprises an oxidizing agent, a nitriding agent or a boronating agent. 3. the preparation method of a kind of high-strength composite flexible graphite plate according to claim 1 is characterized in that, described oxidizing agent comprises potassium permanganate, the vitriol oil, concentrated nitric acid or Fenton's reagent, and the concentration of oxidizing agent is 5 -10mol/L. 4. the preparation method of a kind of high _- strength composite flexible graphite plate according to claim 3 is characterized in that, described oxidizing agent is the Fenton's reagent of pH=3-5, and wherein H ₂ O The mass concentration of 0 -30wt%, not 0. 5. the preparation method of a kind of high strength composite flexible graphite plate according to claim 1 is characterized in that, described nitriding agent comprises urea, and the concentration of nitriding agent is 0.1-10g/ml; Described boron The borating agent includes boric acid, and the concentration of the borating agent is 0.1-10 g/ml. 6. The preparation method of a kind of high-strength composite flexible graphite plate according to claim 5 is characterized in that, during pretreatment, the steps of cleaning and drying are: after dipping, first carry out drying at 70-100 ° C, and then After heating under an inert atmosphere, then after cleaning and drying, a pretreated flexible graphite plate is obtained. 7 . The method for preparing a high-strength composite flexible graphite plate according to claim 6 , wherein the heating temperature in the inert atmosphere is 200-500° C. and the heating time is not less than 1 hour. 8. A method for preparing a high-strength composite flexible graphite plate according to claim 1, wherein said flexible graphite material comprises flexible graphite plate or worm graphite. 9. the preparation method of a kind of high-strength composite flexible graphite plate according to claim 1, is characterized in that, described polymer monomer comprises acrylic acid, modified acrylic monomer or epoxy resin, and the mode of curing Including curing by heating or adding an initiator, and the initiator includes an azo initiator. 10. A high-strength composite flexible graphite plate prepared by the method described in any one of claims 1-9, characterized in that, the mass ratio of flexible graphite material and macromolecular monomer in the composite flexible graphite plate is (0.8- 1.2):1.

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