Polydopamine enhanced vertical graphene oxide flame-retardant material and preparation method thereof

Abstract

The invention relates to a polydopamine enhanced vertical graphene oxide flame-retardant material and a preparation method thereof, in particular to a method for preparing a vertical graphene oxide flame-retardant material with enhanced mechanical properties by adding dopamine and polyamide acid ammonium salt into a graphene oxide solution and adopting a freeze drying technology. According to the method, the mechanical strength and the flame retardant property of the vertical graphene oxide are remarkably improved by utilizing the adhesion and the cross-linking capacity of dopamine and combining a unique structure formed in the freeze drying process, and the application of the vertical graphene oxide in the field of high-performance materials is expanded.

Description

Technical Field

[0001] The present invention relates to a polydopamine-enhanced vertically aligned graphene oxide flame retardant material and a preparation method thereof, belonging to the technical field of graphene. Background Art

[0002] Currently, commonly used commercial foam thermal insulation materials (such as polyurethane and expanded polystyrene) are widely used due to their advantages of low density, low cost, and low thermal conductivity. However, their high flammability severely limits their application in the field of flame retardancy. Graphene, as an emerging carbon nanomaterial, has a special two-dimensional interlayer structure and a high specific surface area, which not only enhances the thermal stability of materials but also significantly improves the flame retardant performance through dual mechanisms of physical barrier and chemical flame retardancy. Researchers have developed various graphene composite flame retardant coating materials. In particular, graphene aerogels (or foams) prepared by three-dimensional assembly technology are noteworthy. This material can significantly enhance the flame retardancy of substrates such as polymer foams with a small amount of addition, becoming an important development direction for environmentally friendly flame retardant materials. However, existing graphene aerogels still have technical bottlenecks such as insufficient mechanical strength and limited room for improvement in flame retardant performance.

[0003] Polydopamine contains many active functional groups. Functional groups such as amino and phenolic hydroxyl groups in its molecular structure endow it with the ability to undergo chemical reactions with other materials to form compounds with flame retardant properties. Inspired by the mussel structure, through a specific synthesis method, vertically aligned polydopamine / graphene oxide foams with a two-dimensional sheet vertical structure assembled from polydopamine-modified graphene oxide can significantly improve the mechanical and thermal stability as well as the flame retardant performance of graphene. This material not only has excellent flame retardant performance but may also perform well in mechanics, thermotics, etc., providing new ideas and methods for the research and application of flame retardant materials. However, there is currently no report on polydopamine-modified vertically aligned graphene oxide flame retardant materials. Summary of the Invention

[0004] Aiming at the problems of poor mechanical strength, poor flame retardant performance, and difficult application of existing vertically aligned graphene oxide flame retardant materials themselves, the present invention provides a polydopamine-enhanced vertically aligned graphene oxide flame retardant material and a preparation method thereof.

[0005] The present invention prepares a vertically aligned porous structure by modifying graphene oxide with polydopamine and combining a directional freezing technique, significantly improving the mechanical strength and flame retardant performance of the material.

[0006] The present invention is implemented by the following technical solutions:

[0007] A preparation method of a polydopamine-enhanced vertically aligned graphene oxide flame retardant material, comprising the following steps:

[0008] (1) Prepare a polyamic acid ammonium salt solution;

[0009] (2) Mix the graphene oxide solution with the dopamine-Tris buffer solution for reaction to obtain a graphene oxide solution modified with polydopamine.

[0010] (3) Mix the solutions of steps (1) and (2) to enable the self-polymerization of dopamine on the surface of graphene oxide to achieve the purpose of enhancement. After directional freezing and freeze-drying, a polydopamine-enhanced vertical graphene oxide flame retardant material is obtained.

[0011] Preferably according to the present invention, in step (1), the preparation of the polyamic acid ammonium salt solution is specifically as follows:

[0012] Add polyamic acid solid to water, then add triethylamine, and stir and mix evenly to form a polyamic acid ammonium salt solution.

[0013] Preferably according to the present invention, in step (2), the solid content of the graphene oxide solution is 0.1%-6%.

[0014] Preferably according to the present invention, in step (2), the pH value of the dopamine-Tris buffer solution is 8-12.

[0015] Preferably according to the present invention, in step (2), the mixing reaction is carried out under stirring conditions for 20-26 h.

[0016] Preferably according to the present invention, in step (3), the mass ratio of dopamine in the dopamine-Tris buffer solution, graphene oxide in the graphene oxide solution, and polyamic acid ammonium salt in the polyamic acid ammonium salt solution is (0.05-20):1:1, based on the mass of the solid.

[0017] Preferably according to the present invention, in step (3), the directional freezing uses liquid nitrogen or semiconductor temperature control technology.

[0018] Preferably according to the present invention, in step (3), the freeze-drying is carried out according to the existing technology.

[0019] A polydopamine-enhanced vertical graphene oxide flame retardant material is prepared by the above method.

[0020] Application of the above-mentioned polydopamine-enhanced vertical graphene oxide flame retardant material in flame retardant plastics, rubbers or fire-fighting fabrics.

[0021] Technical features and advantages of the present invention:

[0022] 1. The preparation method of the present invention forms a vertically arranged structure of polydopamine-enhanced graphene oxide, thereby improving the disadvantage of poor mechanical strength of vertical graphene oxide and opening up new application fields for it.

[0023] 2. Compared with the prior art, the present invention uses polydopamine to enhance graphene oxide, strengthening the strength of the graphene oxide sheets, hoping to improve the disadvantage of poor mechanical strength of the vertical graphene oxide flame retardant material, making its application range wider. Description of the Drawings

[0024] Figure 1 : SEM image of the polydopamine-modified graphene oxide material, showing a vertically aligned structure.

[0025] Figure 2 : Physical diagram of the flame retardant material and comparison of combustion tests. Detailed Description of the Invention

[0026] In order to more clearly illustrate the technical solution of the present invention, the following will be further described in conjunction with each embodiment.

[0027] It should be understood that the implementation of the present invention is not limited to the following embodiments, and any formal modification and / or change made to the present invention will fall within the protection scope of the present invention. In the following embodiments, unless otherwise specified, the equipment and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following embodiments are conventional methods in the art unless otherwise specified.

[0028] Example 1:

[0029] A preparation method of a dopamine-enhanced vertical graphene oxide flame retardant material, the steps are as follows:

[0030] (a) Prepare a polyamic acid ammonium salt solution:

[0031] Add a certain amount of polyamic acid solid to water, and then add a certain proportion of triethylamine, stir and mix evenly to form a polyamic acid ammonium salt solution.

[0032] (b) Prepare a polydopamine-enhanced vertical graphene oxide flame retardant material:

[0033] Mix the dopamine solution with a pH of 8-12, the graphene oxide solution, and the polyamic acid ammonium salt solution evenly, with the solid mass ratio being (1:1:1), and perform directional freezing and freeze-drying to finally obtain a polydopamine-enhanced vertical graphene oxide flame retardant material.

[0034] Example 2

[0035] The preparation method is the same as that described in Example 1, except that:

[0036] In step b, the solid mass ratio of the dopamine solution, the graphene oxide solution, and the polyamic acid ammonium salt solution is 0.05:1:1.

[0037] Example 3

[0038] The preparation method is the same as that in Example 1, except that:

[0039] In step b, the solid mass ratio of the dopamine solution, the graphene oxide solution, and the polyamic acid ammonium salt solution is 20:1:1.

[0040] Comparative Example 1

[0041] The preparation method is the same as that in Example 1, except that:

[0042] The dopamine solution was not added in step b.

[0043] Comparative Example 2

[0044] The preparation method is the same as that in Example 1, except that dopamine and polyamic acid ammonium salt were not added in step b.

[0045] Experimental Example

[0046] Flame retardancy test. Standard samples were cut from the vertically aligned graphene oxide flame retardant materials prepared in the examples and comparative examples, and their flame retardancy was tested with an open flame. The test standards are shown in Table 1, and the test results are shown in Table 2.

[0047] Table 1 uses the UL94-V combustion method to judge the flame retardancy of the prepared products.

[0048] UL94-V Flame Retardancy Judgment Conditions V-0 V-1 V-2 Afterflame Time of a Single Specimen (s) ≤10 ≤30 ≤30 Total Afterflame Time of a Group of Specimens under Any Conditioning (s) ≤50 ≤250 ≤250 Time of (Afterflame + Afterglow) of a Single Specimen after the Second Flame Application (s) ≤60 ≤30 ≤60 Whether the Afterflame or Afterglow Spreads to the Fixture No No No No Whether the Flame Particles or Drippings Ignite the Cotton Pad No No No Yes

[0049] Table 2 Flame retardancy grade performance test data of different samples

[0050]

[0051] From the test results of Examples 1-3 in Table 2, it can be seen that the addition of dopamine is beneficial to enhancing the mechanical properties of the vertically aligned graphene material and maintaining a good vertical structure. Compared with the comparative examples, it can effectively prevent oxygen from entering and slow down the combustion rate. After combustion, the product forms a carbon layer, which can isolate the spread of the flame, further slow down the combustion, and effectively inhibit the heat transfer to the other side.

[0052] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a polydopamine-enhanced vertical graphene oxide flame retardant material, comprising the following steps: (1) preparing a polyamic acid ammonium salt solution; (2) mixing the graphene oxide solution with a dopamine-Tris buffer solution to obtain a polydopamine-modified graphene oxide solution; (3) mixing the solutions of step (1) and (2) to allow dopamine to self-polymerize on the surface of graphene oxide to achieve the purpose of reinforcement, and obtaining a polydopamine-reinforced vertical graphene oxide flame retardant material through directional freezing and freeze drying.

2. The preparation method according to claim 1, characterized in that: In step (1), the preparation of the polyamic acid ammonium salt solution is specifically as follows: Add polyamic acid solid into water, then add triethylamine, stir and mix evenly to form a polyamic acid ammonium salt solution.

3. The preparation method according to claim 1, characterized in that: In step (2), the solid content of the graphene oxide solution is 0.1%-6%.

4. The preparation method according to claim 1, characterized in that: In step (2), the pH value of the dopamine-Tris buffer solution is 8-12.

5. The preparation method according to claim 1, characterized in that: In step (2), the mixed reaction is carried out under stirring for 20-26 hours.

6. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of dopamine in the dopamine-Tris buffer solution, graphene oxide in the graphene oxide solution, and polyamic acid ammonium salt in the polyamic acid ammonium salt solution is (0.05-20):1:1, based on the mass of the solid.

7. The preparation method according to claim 1, characterized in that: In step (3), the directional freezing adopts liquid nitrogen or semiconductor temperature control technology.

8. A polydopamine-enhanced vertical graphene oxide flame retardant material, prepared by the method according to any one of claims 1 to 7.

9. Use of the polydopamine-enhanced vertical graphene oxide flame retardant material according to claim 8 in flame retardant plastics, rubbers or fire-fighting fabrics.

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