Graphene oxide / polyurethane laminated composite film and preparation method thereof

Abstract

The invention relates to the technical field of membranes, and particularly discloses a graphene oxide / polyurethane laminated composite membrane and a preparation method thereof. The polyurethane layer is arranged between the graphene oxide layers, and a strong interface bonding effect is formed between graphene oxide and polyurethane, so that the strength of the composite film is improved. The polyurethane layer is soft and rich in elasticity, the interface layer can well transmit stress and the polyurethane layer deforms due to strong interface bonding force when the polyurethane layer is subjected to external force, so that the toughness and the swelling resistance of the composite film are improved, the service life of the composite film under the water soaking condition is prolonged, and meanwhile, due to the design of the multi-layer structure, the service life of the composite film is prolonged. The influence of the polyurethane layer on the moisture permeability of the composite film is reduced. The composite film does not destroy the layered structure of the graphene oxide film, does not change the interlamellar spacing, and does not have any influence on the functions of the graphene oxide, and the preparation method is simple and easy to operate, has few influence factors, and is easy for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of membranes, and specifically discloses a graphene oxide / polyurethane laminated composite membrane and a preparation method thereof. Technical Background

[0002] Graphene is a sp 2 A single-atom-layer two-dimensional material with a hexagonal honeycomb structure composed of hybrid carbon atoms, it has excellent mechanical properties, chemical stability and a large specific surface area. Graphene oxide is its derivative, with a large number of oxygen-containing functional groups on the surface, such as hydroxyl, carboxyl, epoxy, etc., which make it have good hydrophilicity and adjustable chemical properties. Studies have shown that submicron-thick membranes made of graphene oxide are completely impermeable to liquids, vapors and gases (including helium), but these membranes allow water to penetrate unimpeded (water passes through the membrane at least 10 faster than helium). 10 times). This is because graphene oxide membranes have unique two-dimensional interlayer channels, which allow water molecules to pass quickly, while other substances are blocked by size screening effect and Donnan effect. Due to this characteristic, graphene oxide membranes have great application prospects in water treatment, seawater desalination, membrane separation and chemical protection. However, self-supporting graphene oxide membranes have poor mechanical properties, are easy to break, and swell in water environments. These defects limit the development of graphene oxide in practical applications.

[0003] In recent years, there have been a lot of studies on the mechanical properties and swelling properties of graphene oxide membranes, mainly through cross-linking, intercalation, gelation and confinement to enhance the mechanical properties and anti-swelling properties of graphene oxide membranes. However, most of the methods are complicated and difficult to prepare on a large scale.

[0004] Therefore, it is necessary to develop a method for preparing enhanced and toughened graphene oxide / polyurethane composite membranes to overcome the technical difficulties of poor mechanical strength of self-supporting graphene oxide membranes and difficulty in large-scale production in practical applications. Summary of the invention

[0005] The technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a graphene oxide / polyurethane laminated composite film and a preparation method thereof, which specifically comprises the following steps:

[0007] S1 Preparation of graphene oxide dispersion: dissolving graphene oxide in deionized water to make the graphene oxide concentration be 0.1-100 g / L, and then vacuum bubbling to prepare a uniform and stable graphene oxide dispersion;

[0008] The graphene oxide has an oxygen content of 30-50%, a sheet size of 0.5-20 μm, and a sheet number of 1-10 layers;

[0009] Preparation of S2 polyurethane solution: taking a solvent-based polyurethane and fully dispersing it in a corresponding solvent to prepare a uniform and stable polyurethane solution with a concentration of 0.01-10 g / L;

[0010] S3 layer-by-layer method to prepare graphene oxide / polyurethane laminated composite film:

[0011] S3-1: preparing a graphene oxide film by blade coating, spin coating, spray coating or casting of a graphene oxide dispersion, and making the film thickness be 2-10 μm, so as to obtain a graphene oxide layer; the graphene oxide sheets in the film have a microscopic sheet stacking structure and are stacked neatly;

[0012] S3-2: After the graphene oxide layer is completely dried, a polyurethane solution is applied on the graphene oxide layer by a method of scraping, spin coating, spraying or casting to obtain a layer of polyurethane; the thickness of the polyurethane layer is 50-5000 nm, and there are island-like structures on the surface;

[0013] S3-3: After the polyurethane layer is completely dried, steps S3-1 and S3-2 are repeated several times according to the required number of layers, so that the graphene oxide layers and the polyurethane layers are alternately stacked and a layer of polyurethane is sandwiched between the two graphene oxide layers, thereby obtaining a graphene oxide / polyurethane laminated composite film.

[0014] Preferably, the polyurethane solution is kept uniformly dispersed by ultrasound.

[0015] Preferably, the polyurethane is waterborne polyurethane dispersed in deionized water.

[0016] Preferably, when the graphene oxide layer and the polyurethane layer are prepared by a scraping method, the scraper scale is set to 1 mm and the scraping speed is set to 10 mm / s.

[0017] Preferably, the graphene oxide layer and the polyurethane layer are dried at 60° C. to form a film.

[0018] In a second aspect, the present invention provides a graphene oxide / polyurethane laminate composite film prepared by the method described in the first aspect.

[0019] Preferably, the graphene oxide / polyurethane laminated composite film has an outermost layer of a graphene oxide layer, and a layer of polyurethane is sandwiched between every two layers of graphene oxide.

[0020] In a third aspect, the present invention provides an application of the graphene oxide / polyurethane laminated composite membrane described in the second aspect as a separation membrane or a protective membrane.

[0021] Preferably, the graphene oxide / polyurethane laminated composite membrane is used as a seawater desalination membrane, a waterproof and breathable membrane, a chemical protection membrane or a water treatment filtration membrane.

[0022] The concept of the present invention is:

[0023] The present invention forms a covalent cross-linking effect by arranging a polyurethane layer between graphene oxide layers, utilizing the free isocyanate groups in the polyurethane to react with the hydroxyl functional groups on the surface of the graphene oxide sheet; a large number of oxygen-containing and nitrogen-containing functional groups in the polyurethane and the graphene oxide can generate abundant hydrogen bonds; and a large number of island-like rough structures are formed on the surface of the low-concentration polyurethane solution during the film-forming process, and the polyurethane and the graphene oxide are closely attached to generate a mechanical interlocking structure at the interface, and under the synergistic effect of the three interfacial bonding forces, a strong interfacial bonding effect is formed between the graphene oxide and the polyurethane, thereby improving the strength of the composite film. The polyurethane layer is soft and elastic, and when subjected to external force, due to the strong interfacial bonding force, the interface layer can well transmit stress, and the polyurethane layer is deformed, thereby improving the toughness of the composite film.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention enhances the anti-swelling performance of the composite film, prolongs the service life of the composite film under water immersion conditions, and at the same time, due to the design of the multilayer structure, reduces the influence of the polyurethane layer on the moisture permeability of the composite film. The composite film does not destroy the layered structure of the graphene oxide film, does not change the interlamellar spacing, has no influence on the function of the graphene oxide itself, and can be used in combination with other methods for enhancing the mechanical properties of graphene oxide, such as polymer modification, surface functional group modification, and ion intercalation. The preparation method provided by the present invention is simple and easy to operate, has few influencing factors, and is easy to be mass-produced industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of the graphene oxide / polyurethane composite film prepared by the present invention;

[0027] Figure 2 This is a cross-sectional electron micrograph of the graphene oxide / polyurethane composite film prepared in Example 1;

[0028] Figure 3 : is the stress-strain curve of graphene oxide and the graphene oxide / polyurethane composite film prepared in Example 1;

[0029] Figure 4 XRD spectra of graphene oxide and the graphene oxide / polyurethane composite film prepared in Example 1 in a wetted state. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0032] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0033] Example 1

[0034] Preparation of graphene oxide layer: Take 1g of graphene oxide with an oxygen content of 48%, an average lateral size of the flakes of about 4μm, and 1-4 flakes, ultrasonically disperse it in 1L of deionized water, and then vacuum bubble it to prepare a uniform and stable graphene oxide aqueous solution with a concentration of 1mg / mL; use a coater to scrape the solution into a film with a scraper scale of 1mm and a scraping speed of 10mm / s, and then dry it at 60℃ to form a film.

[0035] Preparation of polyurethane layer: Take 1 mL of 35% aqueous polyurethane and ultrasonically disperse it in 34 mL of deionized water to prepare a uniform and stable polyurethane solution with a concentration of 10 mg / mL; use a coater to scrape the solution on the above-mentioned graphene oxide film with a scraper scale of 1 mm and a scraping speed of 10 mm / s, and then dry it at 60°C to form a film.

[0036] Layer-by-layer method: First, prepare a layer of graphene oxide. After it is completely dried to form a film, prepare a layer of polyurethane on the graphene oxide layer. After it is completely dried to form a film, prepare a layer of graphene oxide on the polyurethane layer. The graphene oxide layer and the polyurethane layer are alternately stacked, and a layer of polyurethane is sandwiched between the two layers of graphene oxide. Repeat the above steps until a graphene oxide / polyurethane composite film with a total of 5 layers is obtained. The schematic diagram of the composite film is shown in the figure. Figure 1 .

[0037] The cross section of the graphene oxide / polyurethane composite film prepared in Example 1 was observed by scanning electron microscopy. The test results are as follows: Figure 2 As shown. Figure 2 It can be seen from the electron microscope image that the cross-section of the composite film clearly presents a five-layer structure, with a layer of polyurethane sandwiched between every two layers of graphene oxide, and the layered stacking structure of graphene oxide is intact and is not affected by the polyurethane layer.

[0038] Performance Testing

[0039] The tensile strength test was performed on the graphene oxide film prepared under the same conditions as the graphene oxide used in Example 1, and the graphene oxide film prepared under the same conditions, and the test conditions were: sample width 6 mm; length 10 mm; tensile rate 1 mm / min. The test results are shown in FIG. Figure 3 As shown in the figure, the strength and toughness of the graphene oxide / polyurethane composite film are significantly higher than those of the graphene oxide film. The fracture stress increased by 107% from 60MPa of the graphene oxide film to 124MPa of the composite film. The elongation at break also increased by 74% from 1.9% of the graphene oxide to 3.3% of the composite film.

[0040] The graphene oxide / polyurethane film and graphene oxide film prepared in Example 1 were placed in water and fully soaked, then taken out and the surface moisture was wiped dry, and XRD test was performed in a wet state. Figure 4 As shown in the figure, the composite film still has a strong and sharp peak at 10.8° in the wet state, indicating that the layered structure of graphene oxide is intact and has not been destroyed by water swelling. The layered structure of graphene oxide almost disappears, indicating that the composite film has good anti-swelling properties.

Claims

1. A method for preparing a graphene oxide / polyurethane laminated composite film, characterized in that: The specific steps include: S1 Preparation of graphene oxide dispersion: dissolving graphene oxide in deionized water to make the graphene oxide concentration be 0.1-100 g / L, and then vacuum bubbling to prepare a uniform and stable graphene oxide dispersion; The graphene oxide sheet has a size of 0.5-20 μm and a number of 1-10 layers; Preparation of S2 polyurethane solution: taking a solvent-based polyurethane and fully dispersing it in a corresponding solvent to prepare a uniform and stable polyurethane solution with a concentration of 0.01-10 g / L; S3 layer-by-layer method to prepare graphene oxide / polyurethane laminated composite film: S3-1: preparing a graphene oxide film by blade coating, spin coating, spray coating or casting of a graphene oxide dispersion, and making the film thickness be 2-10 μm, so as to obtain a graphene oxide layer; the graphene oxide sheets in the film have a microscopic sheet stacking structure and are stacked neatly; S3-2: After the graphene oxide layer is completely dried, a polyurethane solution is applied on the graphene oxide layer by a method of scraping, spin coating, spraying or casting to obtain a layer of polyurethane; the thickness of the polyurethane layer is 50-5000 nm, and there are island-like structures on the surface; S3-3: After the polyurethane layer is completely dried, steps S3-1 and S3-2 are repeated several times according to the required number of layers, so that the graphene oxide layers and the polyurethane layers are alternately stacked and a layer of polyurethane is sandwiched between the two graphene oxide layers, thereby obtaining a graphene oxide / polyurethane laminated composite film.

2. The method for preparing the graphene oxide / polyurethane laminated composite film according to claim 1, characterized in that: The polyurethane solution was kept uniformly dispersed by ultrasound.

3. The method for preparing the graphene oxide / polyurethane laminated composite film according to claim 1, characterized in that: The polyurethane is water-based polyurethane and is dispersed in deionized water.

4. The method for preparing the graphene oxide / polyurethane laminated composite film according to claim 1, characterized in that: When the graphene oxide layer and the polyurethane layer are prepared by the scraper coating method, the scraper scale is set to 1 mm.

5. The method for preparing the graphene oxide / polyurethane laminated composite film according to claim 4, characterized in that: When the graphene oxide layer and the polyurethane layer were prepared by the scraping method, the scraping speed was 10 mm / s.

6. The method for preparing the graphene oxide / polyurethane laminated composite film according to claim 1, characterized in that: The graphene oxide layer and the polyurethane layer are dried at 60° C. to form a film.

7. A graphene oxide / polyurethane laminate composite film, prepared by the method described in any one of claims 1 to 6.

8. The graphene oxide / polyurethane laminated composite film according to claim 7, characterized in that: The outermost layer of the graphene oxide / polyurethane laminated composite film is a graphene oxide layer, and a layer of polyurethane is sandwiched between every two layers of graphene oxide.

9. Use of the graphene oxide / polyurethane laminated composite membrane according to claim 7 or 8 as a separation membrane or a protective membrane.

10. The use of the graphene oxide / polyurethane laminated composite membrane as a separation membrane or a protective membrane according to claim 9, characterized in that: The graphene oxide / polyurethane laminated composite membrane is used as a seawater desalination membrane, a waterproof and breathable membrane, a chemical protection membrane or a water treatment filtration membrane.

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