CN113861480B - Multilayer composite barrier film based on reduced graphene oxide and preparation method and application - Google Patents

Abstract

The invention relates to a multi-layer composite barrier film based on reduced graphene oxide and a preparation method and application thereof. The PEI/GO mixed solution is configured; the conditions are controlled so that PEI reduces GO to RGO; excess PEI is removed by suction filtration; Dissolved in a solvent; a layer-by-layer RGO/PEI composite film with a multi-layer brick wall structure was prepared on the substrate using a layer-by-layer sol-gel method. In the film preparation process of the present invention, PEI acts as both a reducing agent and a matrix: reduced graphene oxide, as the matrix of the composite membrane, and excess PEI is removed by suction filtration during the preparation process, so the hydrophilic PEI in the composite membrane The content was effectively reduced, and a high-performance multilayer composite barrier film based on reduced graphene oxide with low PEI content was prepared.

Description

Multilayer composite barrier film based on reduced graphene oxide, preparation method and application

technical field

The invention belongs to the technical field of packaging films, and in particular relates to a multilayer composite barrier film based on reduced graphene oxide, its preparation method and application.

Background technique

Active gases (such as oxygen) and water vapor in nature are not conducive to the long-term storage of commodities, such as: they will cause food corruption, damage microelectronic devices, and reduce the life and stability of metal devices. Therefore, the design of new high-performance packaging films has been a research hotspot for many years. For general inorganic barrier films, most of them have excellent intrinsic barrier properties, but they are often prone to penetrating pinholes or internal defects after bending or stretching. For most polymer barrier films, their flexibility is stronger, their mechanical properties are better, and their intrinsic barrier properties are excellent, but their microstructure and barrier properties are sensitive to the external environment, and are prone to structural deterioration over time. changes and reduction in performance. In recent years, composite films of two-dimensional inorganic nanosheets/polymers have attracted widespread attention. Most of the composite films have a thickness in the range of tens of nanometers to tens of microns. Provides extremely high gas barrier properties. Through the preparation method of layer-by-layer assembly, the electrostatic interaction makes the nanosheets tend to be deposited flat in the film, thus forming a compact multi-layer brick-wall structure: the nanosheets are used as bricks, and the polymer matrix is mortar. . When gas molecules migrate inside the film, they tend to avoid the nanosheets with strong barrier properties and permeate through more tortuous paths, which greatly enhances the gas barrier properties of the film. Among various nanosheets, graphene (or reduced graphene oxide) is one of the most preferred choices, because it has a very high specific surface area and excellent mechanical properties, strong hydrophobicity and can completely block most gases molecular. So far, scientists have discovered a series of graphene/polymer composite barrier films with super gas barrier properties.

Among them, the reduced graphene oxide/polyethyleneimine (RGO/PEI) composite film is one with outstanding performance. The RGO/PEI composite film prepared by layer-by-layer self-assembly technology has a multi-layer structure, and the PEI molecular chain plays a strong binding role on the RGO sheet. Gas barrier rate is a very popular research object at present. However, due to the hydrophilicity of the polymer material, the film will absorb water when exposed to the air, causing plasticization of the film and rearrangement of the internal microstructure, thereby increasing the air permeability of the film and reducing the service life. Therefore, in the process of film preparation, the content of hydrophobic RGO should be increased and the content of hydrophilic polymer materials should be reduced. However, the composition of composite materials has a great influence on its performance, and there is a strong interaction between them, which is a very complicated research content.

The technical solution of the prior art 1, the layer-by-layer deposition of the pulling method, such as the preparation of an A/B composite multilayer barrier film, one of A and B is graphene oxide, and the other is a polymer matrix material: First, select a substrate (such as polyethylene terephthalate (PET)), and perform conventional chemical treatment, corona treatment and cleaning on the substrate to make the substrate have a high affinity for the deposition material. Prepare solution A and solution B, and adjust the pH value so that solution A and solution B present different acidity and alkalinity. The different acidity and alkalinity are for the strong interaction between A and B materials during layer-by-layer deposition, which can be closely combined.

The specific film-forming steps are as follows: immerse the substrate in solution A for a period of time, take out the substrate and clean and dry (part of the solute needs to be annealed to stabilize the structure), at this time a layer of A film is deposited on the substrate; immerse the substrate in B solution for a period of time, take out the substrate, clean and dry (part of the solute needs to be annealed to stabilize the structure), at this time a layer of A film and a layer of B film are deposited on the substrate; repeat the above two steps until the preset number of film layers. Finally, a composite multilayer film of A/B is deposited on the substrate. When the thickness of a single layer is preset reasonably, the film usually has a brick wall structure.

Disadvantages of this technique:

1. The solute must be stably dispersed in the solvent, so graphene oxide with high surface activity should be used. However, the hydrophilicity of graphene oxide is not conducive to gas barrier, and it contains defects, a large number of oxygen-containing groups, and its structural stability is not as good as that of graphene or reduced graphene oxide.

2. The single preparation process of the film is soaking in solution A-cleaning-soaking in solution B-cleaning. The steps are complicated, the preparation time is long, and the preparation cost is high.

3. Film formation is affected by many aspects, such as: PH value, soaking time, solution concentration, solute activity, etc. The control conditions are complicated and the research is difficult.

In the prior art, the layer-by-layer deposition of the scraping method, that is, the layer-by-layer sol-gel method, such as the preparation of an A/B composite multilayer barrier film, one of A and B is graphene oxide, and the other is a polymer matrix material: first select the lining Substrate (such as polyethylene terephthalate (PET)), the substrate is subjected to conventional chemical treatment, corona treatment and cleaning, so that the substrate has a high affinity for the deposition material. Make up a solution of A and a solution of B.

The specific film forming steps are as follows: Use a scraper to evenly apply a layer of A solution on the substrate, wait for the solution to evaporate and self-assemble into a film (part of the solute needs to be annealed to stabilize the structure), and a layer of A film is deposited on the substrate ; Use a scraper to evenly apply a layer of B solution on the substrate, wait for the solution to evaporate and self-assemble into a film (part of the solute needs to be annealed to stabilize the structure), and a layer of A film and a layer of B film are deposited on the substrate; Repeat the above two steps until the preset number of film layers is reached. Finally, a composite multilayer film of A/B is deposited on the substrate. When the thickness of a single layer is preset reasonably, the film usually has a brick wall structure.

Or directly configure the AB mixed solution, and then use the layer-by-layer sol-gel method to prepare the A/B composite multilayer film. That is: use a scraper to evenly apply a layer of AB mixed solution on the substrate, wait for the solution to evaporate and self-assemble into a film (part of the solute needs to be annealed to stabilize the structure), and a layer of A/B composite film is deposited on the substrate; Repeat the above steps until the preset number of film layers is reached. Finally, a composite multilayer film of A/B is deposited on the substrate. When the thickness of a single layer is preset reasonably, the film usually has a brick wall structure.

Disadvantages of this technology: the solute must be stably dispersed in the solvent, so graphene oxide with high surface activity is used. However, the hydrophilicity of graphene oxide is not conducive to gas barrier, and it contains defects, a large number of oxygen-containing groups, and its structural stability is not as good as that of graphene or reduced graphene oxide.

In the prior art suction filtration membrane-forming method, a solution of A and a solution of B are first prepared, one of A and B is graphene oxide, and the other is a polymer matrix material. Mix solution A and solution B as required, and then use a material with very small pores as a filter membrane (such as cellulose acetate filter cloth) to suction filter the mixed solution of A and B. An A/B composite thin film was deposited on the filter membrane.

Select a substrate (such as polyethylene terephthalate (PET)), and perform conventional chemical treatment, corona treatment and cleaning on the substrate to make the substrate have a high affinity for the deposition material. The A/B composite film left on the filter membrane is transferred to the substrate, that is, the A/B composite multilayer film coated on the substrate is prepared.

Disadvantages of this technology: After the film is formed by suction filtration, the film is deposited on the filter cloth. In the later stage, the film needs to be transferred from the filter cloth to the substrate. The film is very thin, the transfer is difficult, and the transfer process is prone to defects.

Contents of the invention

The present invention proposes a multilayer composite barrier film based on reduced graphene oxide and its preparation method and application. In the process of film preparation, graphene oxide is reduced, and finally a kind of film coated on the substrate based on reduced graphite oxide is prepared. High-performance multi-layer composite barrier film with vinyl, low polymer matrix content.

The specific technical solutions are:

The preparation method of the multilayer composite barrier film based on reduced graphene oxide comprises the following steps:

Configure PEI/GO mixed solution;

Control conditions make PEI reduce GO to RGO;

Suction filtration to remove excess PEI;

PEI/RGO mixture redissolved in solvent;

A layer of RGO/PEI composite film with multilayer brick wall structure was prepared on the substrate by layer-by-layer sol-gel method.

specific:

S1. Select and perform conventional chemical treatment, corona treatment and cleaning on the thin film substrate, so that the substrate has a high affinity for the deposition material;

S2. Add a certain amount of graphene oxide powder into deionized water, ultrasonic and stir to disperse the graphene oxide powder and convert it into a single-layer structure; that is, a single-layer graphene oxide GO solution is prepared;

S3. Add a certain concentration of polyethyleneimine PEI solution to the GO solution, stir to mix evenly;

S4. The mixed solution was placed at 80°C and stirred for several hours; PEI was used as a reducing agent to reduce or partially reduce GO to reduced graphene oxide RGO; at the same time, some PEI molecules were adsorbed on the surface of RGO by chemical modification or physical adsorption;

S5. Use a filter cloth with smaller pores to filter the mixed solution after the reaction; leave the mixture of RGO and PEI on the filter cloth;

S6. Use warm water to continue suction filtration, clean the RGO and PEI mixture on the filter cloth, and remove excess PEI molecules;

S7. Scrape off the mixture of RGO and PEI on the filter cloth, sonicate and stir to make it redissolve and disperse in deionized water, and configure a new RGO/PEI mixed solution;

S8. Place the pre-treated film substrate horizontally and fix it;

S9. Take out a certain amount of mixed solution according to the concentration of the RGO/PEI mixed solution; the mixed solution taken out should be enough to form a composite film with a thickness less than the maximum diameter of RGO on the substrate;

S10. Apply the mixed solution taken out evenly on the substrate with an applicator or a scraper, and let it stand to form a film; the film forming process controls conditions such as temperature, humidity, and blast as required;

S11. Obtain a RGO/PEI composite film coated on the substrate;

S12. Steps S9-11 are repeated, and the amount of each mixed solution should be equal;

S13. After repeating for a certain number of times, a layer of RGO/PEI composite film with a multi-layer structure (brick wall structure) deposited on the substrate is obtained.

The multilayer composite barrier film based on reduced graphene oxide obtained in the present invention can be used as a packaging material, especially a packaging material for food.

In the film preparation process of the present invention, PEI is simultaneously used as a reducing agent and a matrix: reduced graphene oxide, as a matrix (mortar structure) of a composite film. And excess PEI is removed by suction filtration in the preparation process, so the content of hydrophilic PEI in the composite film has been effectively reduced (PEI is needed and very important, but too much PEI causes the film to absorb water, which is not conducive to Its barrier properties), prepared a high-performance multilayer composite barrier film based on reduced graphene oxide, low PEI content.

Description of drawings

Fig. 1 is the RGO/PEI-0.05 composite film that embodiment 1 prepares;

Fig. 2 is the RGO/PEI-0.1 composite film that embodiment 2 prepares;

Figure 3 is the RGO/PEI-0.3 composite film prepared in Example 3.

Detailed ways

The specific technical solutions of the present invention are described in conjunction with the examples.

Example 1

Take a 10cm×10cm PET with a thickness of 35μm as the substrate, wash it with deionized water and methanol, and do corona treatment to improve its affinity. Mix a certain amount of graphene oxide powder (outer diameter 0.5-3μm, <3 layers) with deionized water, use 10w ultrasonic treatment for 10 minutes, supplemented by stirring, and configure to a concentration of 100mL and a concentration of 0.1mg mL ^-1 monolayer graphene oxide (GO) aqueous solution. Add 100 mL of polyethyleneimine (PEI) solution with a concentration of 0.05 mg mL ^-1 to the GO aqueous solution, and stir to make the mixture uniform. The mixed solution was placed under the condition of 80°C and stirred for 3 hours, and the color of the solution changed from brown to black, that is, the reduction of graphene oxide was realized. Using cellulose acetate filter paper with pores of 0.2 μm, the mixed solution after the reaction was suction-filtered, and washed with warm water several times. The mixture of RGO and PEI on the filter cloth was scraped off, ultrasonically treated and stirred to re-dissolve and disperse in deionized water to prepare a mixed solution of RGO/PEI with a total solute content of 0.5 wt%. Place the pre-treated film substrate horizontally and fix it. Take out 1mL of the mixed solution, spread the taken out mixed solution evenly on the substrate with a spreader or a spatula, and let it stand at 60°C to form a film. A total of 20 times of smearing of the mixed solution and static film formation were carried out, and finally a layer of RGO/PEI-0.05 composite film with a multi-layer brick wall structure was coated on the substrate, as shown in Figure 1.

According to the analysis test, after the PET substrate is coated with RGO/PEI-0.05 composite film, its gas permeability is reduced from 54.86cm ³ m ^-2 day ^-1 atm ^-1 to 0.94cm ³ m ^-2 day ^-1 atm ^-1 . The coating exhibits extremely efficient gas barrier properties.

Example 2

Take a 10cm×10cm PET with a thickness of 35μm as the substrate, wash it with deionized water and methanol, and do corona treatment to improve its affinity. Mix a certain amount of graphene oxide powder (outer diameter 0.5-3μm, <3 layers) with deionized water, use 10w ultrasonic treatment for 10 minutes, supplemented by stirring, and configure to a concentration of 100mL and a concentration of 0.1mg mL ^-1 monolayer graphene oxide (GO) aqueous solution. Add 100 mL of polyethyleneimine (PEI) solution with a concentration of 0.1 mg mL ^-1 to the GO aqueous solution, and stir to make the mixture uniform. The mixed solution was placed under the condition of 80°C and stirred for 3 hours, and the color of the solution changed from brown to black, that is, the reduction of graphene oxide was realized. Using cellulose acetate filter paper with pores of 0.2 μm, the mixed solution after the reaction was suction-filtered, and washed with warm water several times. The mixture of RGO and PEI on the filter cloth was scraped off, ultrasonically treated and stirred to re-dissolve and disperse in deionized water to prepare a mixed solution of RGO/PEI with a total solute content of 0.5 wt%. Place the pre-treated film substrate horizontally and fix it. Take out 1mL of the mixed solution, spread the taken out mixed solution evenly on the substrate with a spreader or a spatula, and let it stand at 60°C to form a film. A total of 20 times of smearing of the mixed solution and static film formation were carried out, and finally a layer of RGO/PEI-0.1 composite film with a multi-layer brick wall structure was coated on the substrate, as shown in Figure 2.

According to the analysis test, after the PET substrate is coated with RGO/PEI-0.1 composite film, its gas permeability is reduced from 54.86cm ³ m ^-2 day ^-1 atm ^-1 to 0.25cm ³ m ^-2 day ^-1 atm ^-1 . The coating exhibits extremely efficient gas barrier properties.

Example 3

Take a 10cm×10cm PET with a thickness of 35μm as the substrate, wash it with deionized water and methanol, and do corona treatment to improve its affinity. Mix a certain amount of graphene oxide powder (outer diameter 0.5-3μm, <3 layers) with deionized water, use 10w ultrasonic treatment for 10 minutes, supplemented by stirring, and configure to a concentration of 100mL and a concentration of 0.1mg mL ^-1 monolayer graphene oxide (GO) aqueous solution. Add 100 mL of polyethyleneimine (PEI) solution with a concentration of 0.3 mg mL ^-1 to the GO aqueous solution, and stir to make the mixture uniform. The mixed solution was placed under the condition of 80°C and stirred for 3 hours, and the color of the solution changed from brown to black, that is, the reduction of graphene oxide was realized. Using cellulose acetate filter paper with pores of 0.2 μm, the mixed solution after the reaction was suction-filtered, and washed with warm water several times. The mixture of RGO and PEI on the filter cloth was scraped off, ultrasonically treated and stirred to re-dissolve and disperse in deionized water to prepare a mixed solution of RGO/PEI with a total solute content of 0.5 wt%. Place the pre-treated film substrate horizontally and fix it. Take out 1mL of the mixed solution, spread the taken out mixed solution evenly on the substrate with a spreader or a spatula, and let it stand at 60°C to form a film. A total of 20 times of smearing of the mixed solution and static film formation were carried out, and finally a layer of RGO/PEI-0.3 composite film with a multi-layer brick wall structure was coated on the substrate, as shown in Figure 3.

According to the analysis test, the gas permeability of PET substrate was reduced from 54.86cm ³ m ^-2 day ^-1 atm ^-1 to 0.17cm ³ m ^-2 day ^-1 atm ^-1 after coating RGO/PEI-0.3 composite film. The coating exhibits extremely efficient gas barrier properties.

Claims (6)

1. The preparation method of the multilayer composite barrier film based on the reduced graphene oxide is characterized by comprising the following steps:

preparing a PEI/GO mixed solution;

controlling conditions to reduce GO to RGO by PEI;

filtering to remove redundant PEI;

re-dissolving the PEI/RGO mixture in a solvent;

preparing a layer of RGO/PEI composite film with a multilayer brick wall structure on a substrate by using a layer-by-layer sol-gel method.

2. The method of preparing a reduced graphene oxide based multilayer composite barrier film according to claim 1, comprising the steps of:

s1, selecting and carrying out conventional chemical treatment, corona treatment and cleaning on a thin film substrate to ensure that the substrate has high affinity to a deposition material;

s2, adding a certain amount of graphene oxide powder into deionized water, and performing ultrasonic stirring to disperse the graphene oxide powder and convert the graphene oxide powder into a single-layer structure, namely preparing a single-layer graphene oxide GO solution;

s3, adding a polyethyleneimine PEI solution with a certain concentration into the GO solution, and stirring to uniformly mix;

s4, stirring the mixed solution at 80 ℃; PEI is used as a reducing agent to reduce or partially reduce GO into reduced graphene oxide RGO; meanwhile, part of PEI molecules are adsorbed on the RGO surface in a chemical modification or physical adsorption mode;

s5, filtering the reacted mixed solution by using filter cloth, and leaving a mixture of RGO and PEI on the filter cloth;

s6, continuously performing suction filtration by using warm water, cleaning the mixture of RGO and PEI on the filter cloth, and removing redundant PEI molecules;

s7, scraping the mixture of RGO and PEI on the filter cloth, ultrasonically treating, stirring, dissolving again in deionized water, and dispersing in deionized water to prepare a new RGO/PEI mixed solution;

s8, horizontally placing and fixing the film substrate which is well pretreated;

s9, taking out a certain amount of mixed solution according to the concentration of the RGO/PEI mixed solution; the mixed solution taken out is enough to form a composite film with the thickness smaller than the maximum diameter of the RGO on the substrate;

s10, uniformly coating the taken mixed solution on a substrate by using a coater or a scraper, and standing to form a film; controlling conditions according to requirements in the film forming process;

s11, obtaining an RGO/PEI composite film coated on a substrate;

s12, repeating the steps S9-11;

and S13, repeating for a certain number of times to obtain an RGO/PEI composite film which has a multilayer brick wall structure and is deposited on the substrate.

3. The method for preparing the multilayer composite barrier film based on the reduced graphene oxide according to claim 2, wherein the film forming process of S10 is carried out under the conditions of temperature, humidity and air blowing as required.

4. The method for preparing the multilayer composite barrier film based on the reduced graphene oxide according to claim 2, wherein in the step S12, the film forming process of S10 is carried out in such a manner that the taking amount of each mixed solution is equal when the steps S9-11 are repeated.

5. Multilayer composite barrier film based on reduced graphene oxide, characterized in that it is obtained according to the preparation process of any one of claims 1 to 4.

6. Use of a multilayer composite barrier film based on reduced graphene oxide according to claim 5 as a packaging material.

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