Preparation method and application of modified graphene

Abstract

The invention belongs to the field of graphene, and particularly relates to a preparation method and application of modified graphene, the method comprises the following steps: (1) mixing a modifier, graphite and water to obtain a pretreated graphite dispersion liquid; and (2) stripping and modifying the graphite dispersion liquid pretreated in the step (1) to obtain a modified graphene dispersion liquid, and the modifier is TPE-PNIPAM. The modified graphene is prepared by taking graphite as a raw material, water as a dispersion medium and TPE-PNIPAM as a stripping auxiliary agent and a modifier through a micro-jet homogenizer one-step method, the preparation process is simple and efficient, the process is green and safe, meanwhile, the number of layers of the prepared modified graphene is small, the thickness of the modified graphene is about 0.93 nm, the modified graphene is about 2-3 layers, the defects are low, and the preparation method is suitable for industrial production. The water-soluble polyurethane has good dispersibility in water, and has good dispersibility and storage stability in a resin matrix.

Description

Technical Field

[0001] The present invention belongs to the field of graphene, and particularly relates to a preparation method and application of modified graphene. Background Art

[0002] Graphene is a two-dimensional sheet formed by stacking sp 2 hybridized carbon atom layers. Due to its good shielding and impermeability, it can effectively block corrosive media such as oxygen, water, and chlorides, and plays an important role in the corrosion protection of metals and other aspects.

[0003] Currently, most graphene preparation methods have complex processes, involving multiple cumbersome processes such as pretreatment, long-time reaction, modification, and drying, and even require harsh conditions such as strong acids and strong oxidants. As a new type of graphite exfoliation technology, the microjet method generally has the problem of low exfoliation efficiency due to the weak conjugate action between the existing exfoliating aids and graphene.

[0004] Although graphene has excellent optical, electrical, and mechanical properties, etc., its surface lacks active functional groups, and there is a strong π-π stacking effect between the sheets, which is extremely prone to agglomeration. Therefore, it is crucial to improve the dispersion stability of graphene in the polymer matrix. Currently, the modification methods of graphene two-dimensional materials are mainly divided into two categories, namely covalent bond modification and non-covalent bond modification. Covalent bond modification is to modify by covalently connecting new functional groups at highly active sites such as the edges or defects of graphene two-dimensional materials. Non-covalent bond modification is to modify graphene two-dimensional materials by means of π-π stacking interaction, ionic bond, hydrogen bond, etc. Among them, the π-π stacking interaction is the most common and effective way of non-covalent modification of graphene two-dimensional materials. The highly conjugated structure of graphene two-dimensional materials itself is prone to π-π interaction with other conjugated structures or small molecules and polymers containing aromatic rings. This modification process does not destroy the intrinsic structure of graphene two-dimensional materials and retains its physical and chemical properties.

[0005] In summary, efficiently and greenly preparing low-defect and few-layer graphene and realizing its uniform dispersion in the polymer matrix are the keys to fully exerting the excellent properties of graphene and promoting its large-scale application. Summary of the Invention

[0006] To improve the deficiencies of the existing technology, the present invention provides a preparation method and application of modified graphene. By using a modifier, π-π interaction is formed between graphene and the modifier to obtain modified graphene with better dispersion.

[0007] In the first aspect, the present invention provides a preparation method of modified graphene, including the following steps:

[0008] (1) Mix the modifier, graphite, and water to obtain a pretreated graphite dispersion;

[0009] (2) Subject the pretreated graphite dispersion obtained in step (1) to exfoliation and modification to obtain a modified graphene dispersion. The modifier is TPE-PNIPAM; TPE-PNIPAM has the following structural formula:

[0010]

[0011] According to an embodiment of the present invention, in the pretreated graphite dispersion in step (1), the concentration of the modifier is 0.1 - 10 mg / mL, for example, 0.1 - 5 mg / mL, or 1 - 15 mg / mL, or 5 - 10 mg / mL. Exemplarily, it is 1 mg / mL, 2 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL, 8 mg / mL, 10 mg / mL.

[0012] According to an embodiment of the present invention, in step (1), in the pretreated graphite dispersion, the concentration of the graphite is 1 - 50 mg / mL, for example, 5 - 20 mg / mL, or 15 - 45 mg / mL. Exemplarily, it is 1 mg / mL, 3 mg / mL, 5 mg / mL, 6 mg / mL, 8 mg / mL, 10 mg / mL, 12 mg / mL, 14 mg / mL, 15 mg / mL, 17 mg / mL, 18 mg / mL, 20 mg / mL, 30 mg / mL, 35 mg / mL, 40 mg / mL, 50 mg / mL.

[0013] According to an embodiment of the present invention, step (1) specifically includes the following steps: Add graphite to water, then add the modifier, and use a high-shear dispersion emulsifier to shear and disperse to obtain a pretreated graphite dispersion.

[0014] According to an embodiment of the present invention, the time for shearing and dispersing using a high-shear dispersion emulsifier is between 1 - 60 min, for example, 10 - 60 min. Exemplarily, it is 15 min, 30 min, 45 min; the rotation speed of the high-shear dispersion emulsifier is 100 - 15000 rpm, for example, 200 - 12000 rpm. Exemplarily, it is 1000 rpm, 2000 rpm, 10000 rpm.

[0015] According to an embodiment of the present invention, step (1) specifically includes the following steps: Add graphite to water, then add the modifier, and then perform ultrasonic treatment to obtain a pretreated graphite dispersion.

[0016] According to an embodiment of the present invention, the time for ultrasonic treatment is 1 - 10 min; the power for ultrasonic treatment is 100 - 200 W.

[0017] According to an embodiment of the present invention, step (1) specifically includes the following steps: adding graphite into water, then adding a modifier, and stirring to obtain a pretreated graphite dispersion.

[0018] According to an embodiment of the present invention, in step (2), the peeling and modification are carried out using a microfluidic homogenizer.

[0019] According to an embodiment of the present invention, step (2) specifically includes the following steps: adding the pretreated graphite dispersion into a microfluidic homogenizer for peeling and modification to obtain a modified graphene dispersion.

[0020] According to an embodiment of the present invention, in step (2), the process of peeling and modifying the pretreated graphite dispersion in the microfluidic homogenizer includes the following steps: circulating the pretreated graphite dispersion through a 100 - 400 μm (exemplarily 200 μm, 250 μm, 300 μm, or 400 μm) nozzle for 3 - 8 times (exemplarily 3 times, 5 times, or 8 times), and the pressure is 5000 - 20000 psi (exemplarily 5000 psi, 10000 psi, or 15000 psi).

[0021] According to an embodiment of the present invention, the modified graphene is obtained by peeling a graphite dispersion of graphite, a modifier, and water.

[0022] According to an embodiment of the present invention, the graphite is selected from at least one of natural flake graphite, expanded graphite, graphite powder, etc. Further, the form of the graphite is powder, for example, the mesh number of the graphite powder is from 100 mesh to 5000 mesh.

[0023] In a second aspect, the present invention provides a modified graphene prepared by the above method, and the modified graphene has substantially the same Figure 3 scanning electron microscope, transmission electron microscope, and atomic force microscope images as shown.

[0024] According to an embodiment of the present invention, the modified graphene has substantially the same Figure 2 Raman spectrum as shown.

[0025] According to an embodiment of the present invention, the modified graphene has substantially the same Figure 4 infrared spectrum as shown.

[0026] According to an embodiment of the present invention, the modified graphene has substantially the same Figure 5 ultraviolet spectrum as shown.

[0027] According to an embodiment of the present invention, the modified graphene has substantially the same Figure 6 fluorescence spectrum as shown.

[0028] According to an embodiment of the present invention, the modified graphene has an elemental analysis diagram substantially as Figure 7 shown.

[0029] According to an embodiment of the present invention, the thickness of the modified graphene is less than or equal to 0.4 nm, for example, 0.34 nm.

[0030] According to an embodiment of the present invention, the thickness of the modified graphene is 2 to 5 layers of graphene, for example, 2 to 3 layers of graphene.

[0031] According to an embodiment of the present invention, the solubility of the modified graphene in water is greater than or equal to 3 mg / mL (calculated based on the graphite content), and preferably the solubility of the modified graphene in water is greater than or equal to 5 mg / mL.

[0032] In a third aspect, the present invention provides an application of the above-mentioned modified graphene in an anticorrosive coating.

[0033] In a fourth aspect, the present invention provides an anticorrosive coating, which comprises the above-mentioned modified graphene, a photoinitiator, an epoxy resin and a solvent.

[0034] According to an embodiment of the present invention, the photoinitiator is selected from cationic photoinitiators, and the cationic photoinitiator is selected from one of aryl diazonium salts, diaryliodonium salts, triarylsulfonium salts, arylferrocene salts, and an example is diphenyl-(4-phenylthio)phenylsulfonium hexafluoroantimonate (CAS No.: 71449-78-0).

[0035] According to an embodiment of the present invention, the epoxy resin is selected from one or more of bisphenol A epoxy resins, hydrogenated bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, glycidyl ether epoxy resins, alicyclic epoxy resins, silicone-modified epoxy resins, polyurethane epoxy resins, and examples are bisphenol A epoxy resins and hydrogenated bisphenol A epoxy resins.

[0036] According to an embodiment of the present invention, the mass ratio of the epoxy resin to the photoinitiator is (10 to 50):1, preferably (15 - 30):1, for example, 25:1.

[0037] According to an embodiment of the present invention, the mass ratio of the modified graphene to the epoxy resin is 1:(50 to 300), preferably 1:(100 to 200), for example, 1:100, 1:200.

[0038] According to an embodiment of the present invention, the solvent is selected from one or more of tetrahydrofuran, ethanol, and water, for example, water.

[0039] According to an embodiment of the present invention, in the anticorrosive coating, the concentration of the modified graphene is 0.5% - 1%.

[0040] According to an embodiment of the present invention, in the anticorrosive coating, the concentration of epoxy resin is 95.2% - 95.67%.

[0041] According to an embodiment of the present invention, in the anticorrosive coating, the concentration of photoinitiator is 3.8% - 3.83%.

[0042] Beneficial effects

[0043] (1) In the present invention, graphite is used as the raw material, water is used as the dispersion medium, and TPE-PNIPAM is used as the exfoliation aid and modifier. Modified graphene is prepared by a one-step method using a microfluidic homogenizer. The preparation process is simple and efficient, the process is green and safe. At the same time, the prepared modified graphene has fewer layers, the thickness of the modified graphene is about 0.93 nm, which is about 2 - 3 layers of graphene, with low defects, good dispersion in water, and good dispersion and storage stability in the resin matrix.

[0044] (2) The present invention uses TPE-PNIPAM containing four benzene ring units as the exfoliation aid, which is extremely easy to form π-π interactions with graphene, thereby promoting the efficient exfoliation of graphene. Good exfoliation can be achieved with fewer nozzle cycles (3 - 8 times), reducing the exfoliation difficulty.

[0045] (3) The modified graphene dispersion prepared in the present invention shows negative charge, and a cationic photoinitiator is used. Phase transfer is achieved through charge interaction, and finally, the uniform dispersion of the modified graphene dispersion in epoxy resin is realized, better exerting the shielding performance of the modified graphene. Description of the drawings

[0046] Figure 1 Digital photos of the modified graphene TPG, the comparative graphite sheet G, and the comparative modified graphene CA-G aqueous dispersions prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0047] Figure 2 Raman spectra of the modified graphene TPG prepared in Example 1 and the comparative graphite sheet G prepared in Comparative Example 1.

[0048] Figure 3 Scanning electron microscope, transmission electron microscope, and atomic force microscope images of the modified graphene TPG prepared in Example 1 and the comparative graphite sheet G prepared in Comparative Example 1.

[0049] Figure 4 Infrared spectra of the modified graphene TPG prepared in Example 1, the comparative graphite sheet G prepared in Comparative Example 1, and the modifier TPE-PNIPAM.

[0050] Figure 5UV spectra of modifier TPE-PNIPAM and modified graphene TPG in Example 1.

[0051] Figure 6 Fluorescence spectra of modifier TPE-PNIPAM and modified graphene TPG in Example 1.

[0052] Figure 7 Elemental analysis diagrams of modified graphene TPG prepared in Example 1, comparative graphite sheet G prepared in Comparative Example 1, and modifier TPE-PNIPAM.

[0053] Figure 8 Digital photos of the graphene / epoxy resin mixture TPG / EP obtained by mixing modified graphene TPG prepared in Example 1 with epoxy resin at different times.

[0054] Figure 9 Potentiodynamic polarization curves of the anti-corrosion coatings prepared in Examples 4, 5, 6, and 7 after 10 days of immersion.

[0055] Figure 10 Cross-sectional SEM images of the anti-corrosion coatings prepared in Examples 4 - 7, where Figure 10 (a) corresponds to Example 4, Figure 10 (b) corresponds to Example 5, Figure 10 (c) corresponds to Example 6, Figure 10 (d) corresponds to Example 7.

[0056] Figure 11 Results of the salt spray corrosion test of the anti-corrosion coatings prepared in Examples 4 - 7; where Figure 11 (a) corresponds to Example 4, Figure 11 (b) corresponds to Example 5, Figure 11 (c) corresponds to Example 6, Figure 11 (d) corresponds to Example 7. Detailed Description of the Preferred Embodiments

[0057] The following will further elaborate on the modified graphene of the present invention, its preparation method, and applications in conjunction with specific examples. It should be understood that the following examples are only for illustrative and explanatory purposes of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0058] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

[0059] Graphite powder (1200 mesh) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Epoxy resin (EP, E51) was purchased from China National Bluestar (Group) Co., Ltd. The cationic photoinitiator was purchased from Nantong Xinaxi New Materials Co., Ltd., China. The modifier TPE-PNIPAM was synthesized according to the known method in the literature. Q235 steel plates were used as the coating substrates, provided by BGD Precision Instruments (Guangzhou) Co., Ltd. Before use, they were polished with 200-mesh sandpaper, then cleaned with ethanol and dried for later use.

[0060] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

[0061] Example 1

[0062] (1) First, 0.1 g of TPE-PNIPAM (tetraphenylethylene-poly(N-isopropylacrylamide)) was added to 100 g of deionized water and stirred evenly. Then, 0.5 g of graphite powder was added and stirred thoroughly to prepare a pretreated graphite aqueous dispersion. In the dispersion, the concentration of graphite powder was 5 mg / mL, and the concentration of TPE-PNIPAM was 1 mg / mL.

[0063] (2) The above-mentioned graphite aqueous dispersion was added to a microfluidic homogenizer and circulated 5 times through a 400-μm nozzle at 20000 psi. The whole process took about 10 min to obtain a modified graphene dispersion TPG.

[0064] The appearance photo of the modified graphene dispersion is as Figure 1 shown. After the modified graphene dispersion was left standing for 24 h, the modified graphene dispersion was still evenly dispersed without obvious agglomeration. The modified graphene prepared in this example showed good dispersibility and stability in the dispersion.

[0065] Example 2

[0066] (1) First, 0.05 g of TPE-PNIPAM (tetraphenylethylene-poly(N-isopropylacrylamide)) was added to 100 g of deionized water and stirred evenly. Then, 0.5 g of graphite powder was added and stirred thoroughly to prepare a pretreated graphite aqueous dispersion. In the dispersion, the concentration of graphite powder was 5 mg / mL, and the concentration of TPE-PNIPAM was 0.5 mg / mL.

[0067] (2) The above-mentioned graphite aqueous dispersion was added to a microfluidic homogenizer and circulated 5 times through a 400-μm nozzle at 20000 psi. The whole process took about 10 min to obtain a modified graphene dispersion TPG.

[0068] Example 3

[0069] (1) First, add 0.15 g of TPE-PNIPAM (tetraphenylethylene-poly(N-isopropylacrylamide)) to 100 g of deionized water, stir evenly, and then add 0.5 g of graphite powder and stir thoroughly to prepare a pretreated graphite aqueous dispersion. In the dispersion, the concentration of graphite powder is 5 mg / mL, and the concentration of TPE-PNIPAM is 1.5 mg / mL;

[0070] (2) Add the above graphite aqueous dispersion to a microfluidic homogenizer, and circulate it 5 times through a 400-μm nozzle at 20000 psi. The whole process takes about 10 min; a modified graphene dispersion TPG is obtained.

[0071] Comparative Example 1

[0072] (1) Add 0.5 g of graphite powder to 100 g of deionized water, stir evenly to prepare a pretreated graphite aqueous dispersion, and the concentration of graphite powder is 5 mg / mL;

[0073] (2) Add the above graphite aqueous dispersion to a microfluidic homogenizer, and circulate it 5 times through a 400-μm nozzle at 20000 psi. The whole process takes about 10 min to obtain a graphite dispersion G (comparative graphite flakes).

[0074] The preparation method of Comparative Example 1 is the same as that of Example 1, except that: in step (1) of Example 1, a modifier TPE-PNIPAM was added, and no modifier was used in this comparative example.

[0075] Comparative Example 2

[0076] (1) First, add 0.1 g of CA (calcein) to 100 g of deionized water, stir evenly, and then add 0.5 g of graphite powder and stir thoroughly to prepare a pretreated graphite aqueous dispersion. In the dispersion, the concentration of graphite powder is 5 mg / mL, and the concentration of CA is 1 mg / mL;

[0077] (2) Add the above graphite aqueous dispersion to a microfluidic homogenizer, and circulate it 5 times through a 400-μm nozzle at 20000 psi to obtain a comparative modified graphene dispersion CA-G. The whole process takes about 10 min;

[0078] The appearance photo of the comparative modified graphene dispersion CA-G is as Figure 1 (c) shown. After the comparative modified graphene dispersion is left standing for 24 h, the dispersion is relatively uniform, but there is a certain degree of agglomeration and sedimentation.

[0079] The digital photos of the modified graphene dispersion TPG obtained in Example 1 and the graphite dispersion G obtained in Comparative Example 1 are as Figure 1 (a), Figure 1In Figure (b), on the left is the comparative graphite sheet, i.e., the modified graphite dispersion G prepared in Comparative Example 1, and on the right is the modified graphene, i.e., the modified graphene dispersion TPG prepared in Example 1. As can be seen from the figure, at 0 h, both the graphite dispersion G and the modified graphene dispersion TPG are uniformly dispersed in the aqueous solution; after 24 h, the modified graphite dispersion G shows obvious stratification, and a large number of graphite sheets agglomerate and settle at the bottom layer of the solution, unable to form an effective dispersion, while the modified graphene dispersion TPG can be stably dispersed in the aqueous solution for a long time without obvious agglomeration. The modified graphene shows good dispersibility and stability in the dispersion.

[0080] The Raman spectrum of the modified graphene dispersion TPG is as Figure 2 shown. The D peak, G peak, and 2D peak are the Raman characteristics of graphene. The D peak represents the defects in the carbon atom lattice, and the G peak represents the in-plane stretching vibration of sp 2 hybridized carbon atoms. Therefore, the intensity ratio (I D / I G ) of the D peak and G peak can be used to evaluate the defect degree of graphene. As Figure 2 shown, the I D / I G value of the modified graphene TPG decreases from 0.24 (G) to 0.02 (TPG), indicating that the graphene prepared with TPE-PNIPAM as the modifier has fewer surface defects. In addition, the number of graphene layers can be inferred from the shape of the 2D peak. The 2D peak of single-layer graphene is a sharp peak. The fewer the number of graphene layers, the sharper the shape of the 2D peak. It can be observed from the figure that the 2D peak of TPG is sharper, indicating that the number of graphite layers in TPG is fewer.

[0081] See Figure 3 shown for the SEM, TEM, and AFM images of the graphite sheets (hereinafter referred to as G flakes) in the graphite dispersion G and the modified graphene (hereinafter referred to as TPG flakes) in the modified graphene dispersion TPG. In the figure, a is the SEM image of the G flakes in Comparative Example 1, b is the SEM image of the TPG flakes in Example 1, c is the TEM image of the G flakes in Comparative Example 1, d is the TEM image of the TPG flakes in Example 1, and e is the AFM image and height profile curve of the modified TPG flakes in Example 1.

[0082] From Figure 3It can be clearly observed that the G flakes are closely arranged, with large sizes and few edges, while the sizes of the TPG flakes are significantly reduced. The above scanning electron microscope images indicate that the modifier TPE-PNIPAM can reduce the size of graphene flakes. Transmission electron microscopy can directly observe the number of graphene layers. As can be seen from the figure, the number of layers of the TPG flakes is significantly less than that of the G flakes, showing the typical few-layer characteristics of graphene, which proves that TPE-PNIPAM helps to assist in the exfoliation of few-layer graphene; AFM is one of the most direct methods to quantify the degree of graphene exfoliation. Figure 3 The AFM images and height profile curves in e show that the thickness of TPG is about 0.93 nm. Since the thickness of a single layer of graphene is about 0.34 nm, it is calculated that the modified graphene TPG flakes are about 2 - 3 layers, which further proves that the TPE-PMIPAM-assisted microjet process is an effective method for separating few-layer graphene.

[0083] Figure 4 The FTIR spectra of the G flakes, TPE-PNIPAM, and TPG flakes are shown. As shown in the figure, there are no obvious characteristic peaks in the G flakes, indicating that the surface of the G flakes prepared by microjet does not contain oxygen-containing functional groups; the spectrum of the TPG flakes is similar to that of TPE-PNIPAM, indicating that the surface of the TPG flakes contains TPE-PNIPAM. The characteristic peaks of the TPG flakes mainly come from the modifier. However, the characteristic peaks of the TPG flakes, such as the N-H stretching vibration (3300 cm -1 ) and the benzene ring stretching vibration peaks (1650 cm -1 and 1550 cm -1 ), are significantly blue-shifted to 3290 cm -1 , 1639 cm -1 and 1535 cm -1 , indicating the interaction between graphene and TPE-PNIPAM. It is speculated that the reason is that the benzene ring in the modifier TPE-PNIPAM forms a π-π interaction with graphene.

[0084] The experimental results were further verified by UV-vis. As Figure 5 shown, the UV-vis absorption spectra of the G flakes and TPG flakes dispersed in aqueous solution were compared. Due to the π-π* transition of the C=C bond, TPE-PNIPAM has an absorption peak at 223 nm. When the modifier TPE-PNIPAM is adsorbed on the surface of graphene, this absorption peak is blue-shifted to 220 nm, indicating the strong π-π interaction between TPE-PNIPAM and graphene. At the same time, due to the strong influence of the π-π interaction, the fluorescence intensity of TPE-PNIPAM is significantly reduced.

[0085] As Figure 6As shown, after the modifier TPE-PNIPAM is excited by an absorption wavelength of 365 nm, it exhibits a characteristic fluorescence peak at 472 nm. This absorption peak blue-shifts to 463 nm in the TPG thin film, and at the same time, the peak intensity decreases significantly, indicating that the fluorescence emission of the modifier TPE-PNIPAM occurs in the TPG thin film. This phenomenon suggests that there is an electron energy transfer between TPE-PNIPAM and graphene.

[0086] The chemical compositions of the G thin film and the TPG thin film were analyzed by XPS. In Figure 7 , C atoms and O atoms were detected in the G thin film. In the TPG thin film, in addition to C atoms and O atoms, an additional N atomic peak was found. This comes from the amide group in TPE-PNIPAM, indicating that the TPG surface contains the modifier TPE-PNIPAM. This is consistent with the results of the infrared test.

[0087] Figure 8 Shows digital photos of the modified graphene / epoxy resin mixture (TPG 1％ / EP) after being placed for different times. After being placed for 48 h, there is no obvious change in TPG 1％ / EP. TPG can still be stably dispersed in the epoxy resin, and there is no agglomeration sedimentation or delamination of the graphite flakes. This further indicates that the TPG / EP has excellent storage stability.

[0088] Example 4

[0089] (1) 50 mL of the modified graphene dispersion liquid TPG in Example 1 was mixed with a mixture of 57.5 g of bisphenol A epoxy resin and 2.3 g of diphenyl-(4-phenylthio)phenylsulfonium hexafluoroantimonate (wherein the mass ratio of the modified graphene to the A-type epoxy resin mixture is 25:1, abbreviated as the bisphenol A epoxy resin mixture). After standing and phase separation, the water was removed to obtain a modified graphene / epoxy resin mixture, where the mass fraction of the modified graphene is 0.5%.

[0090] (2) First, a layer of bisphenol A epoxy resin mixture was coated on the surface of the steel sheet by a spin coater at 2500 rpm, and UV light curing was carried out while spin coating. Subsequently, the modified graphene / epoxy resin mixture was coated at 1500 rpm and cured by light.

[0091] (3) Step (2) was repeated 1 time to obtain a B-TPG 0.5％ / EP anticorrosive coating.

[0092] The potentiodynamic polarization curve of the coating prepared in this example is as Figure 9 shown. After the B-TPG 0.5％ / EP anticorrosive coating was soaked for 10 days, the corrosion potential E corr was -0.66 V, and the corrosion current Icorr is 2.81×10 -9 Acm -2 。Still has good anti-corrosion protection effect.

[0093] Example 5

[0094] (1) First, add 0.1 g of TPE-PNIPAM to 100 g of deionized water, stir evenly, and then add 0.5 g of graphite powder and stir well to prepare a pretreated graphite aqueous dispersion. The concentration of graphite powder is 5 mg / mL, and the concentration of TPE-PNIPAM is 1 mg / mL.

[0095] (2) Add the above graphite aqueous dispersion to a microfluidic homogenizer and circulate it 5 times through a 400 μm nozzle at 20000 psi. The whole process takes about 10 min to obtain a modified graphene dispersion.

[0096] (3) Mix 100 ml of the modified graphene dispersion with a mixture of 57.5 g of bisphenol A epoxy resin and 2.3 g of diphenyl-(4-phenylthio)phenylsulfonium hexafluoroantimonate (the mass ratio of the modified graphene to the bisphenol A epoxy resin mixture is 25:1), let it stand and phase-separate, and remove the water to obtain a modified graphene / epoxy resin mixture, where the mass fraction of the modified graphene is 1%.

[0097] (4) First, coat a layer of type A epoxy resin mixture on the steel sheet surface with a spin coater at 2500 rpm, perform UV light curing while spin coating, and then coat the graphene / epoxy resin mixture at 1500 rpm and perform light curing.

[0098] (5) Repeat step (4) once to obtain a B-TPG 1％ / EP anti-corrosion coating.

[0099] The potentiodynamic polarization curve of the coating prepared in this example is as Figure 9 shown. After 10 days of immersion, the corrosion potential E 1％ of the B-TPG corr / EP anti-corrosion coating is -0.49 V, and the corrosion current I corr is 1.04×10 -10 Acm -2 。It means that the coating is corroded more slightly during the immersion period, and the anti-corrosion protection effect is excellent.

[0100] Example 6

[0101] (1) Mix a mixture of 57.5 g of bisphenol A epoxy resin and 2.3 g of diphenyl-(4-phenylthio)phenylsulfonium hexafluoroantimonate, let it stand and phase-separate, and remove the water to obtain an epoxy resin mixture.

[0102] (2) Coating the surface of the steel sheet with a bisphenol A epoxy resin mixture at 2500 rpm using a spin coater and performing photocuring, with UV photocuring carried out during the spin coating process.

[0103] (3) Repeat step (2) four times to obtain an EP anti-corrosion coating.

[0104] The potentiodynamic polarization curve of the coating prepared in this example is as Figure 9 shown. After 10 days of immersion, the corrosion potential E corr is -0.78 V, and the corrosion current I corr is 4.57×10 -6 A / cm -2 . This means that the coating has suffered severe corrosion during the immersion period.

[0105] Example 7

[0106] (1) First, add 0.1 g of TPE-PNIPAM to 100 g of deionized water, stir evenly, and then add 0.5 g of graphite powder and stir well to prepare a pretreated graphite aqueous dispersion. The concentration of the graphite powder is 50 mg / mL, and the concentration of TPE-PNIPAM is 1 mg / mL.

[0107] (2) Add the above graphite aqueous dispersion to a microfluidic homogenizer and circulate it 5 times through a 400 μm nozzle at 20000 psi. The whole process takes about 10 min to obtain a modified graphene dispersion n.

[0108] (3) Mix 100 ml of the modified graphene aqueous dispersion with a mixture of 57.5 g of bisphenol A epoxy resin and 2.3 g of diphenyl-(4-phenylthio)phenylsulfonium hexafluoroantimonate (the mass ratio of modified graphene to the mixture is 25:1), let it stand and phase-separate, and remove the water to obtain a modified graphene / epoxy resin mixture, where the mass fraction of the modified graphene is 1%.

[0109] (4) Coating the surface of the steel sheet with the graphene / bisphenol A epoxy resin mixture at 1500 rpm using a spin coater and performing photocuring, with UV photocuring carried out during the spin coating process.

[0110] (5) Repeat step (4) four times to obtain a TPG 1％ / EP anti-corrosion coating.

[0111] The potentiodynamic polarization curve of the prepared coating is as Figure 9 shown. After 10 days of immersion, the corrosion potential E corr is -0.73 V, and the corrosion current I corr is 7.68×10 -7 A / cm -2, are all less than the EP coating, indicating TPG 1％ The graphene in the / EP anti-corrosion coating can provide an excellent protection barrier for the metal. However, both the corrosion potential and the corrosion current are higher than those of the coatings prepared in Example 4 and Example 5, which means that the coating has been corroded to a certain extent during the immersion period.

[0112] Figure 10 are the cross-sectional SEM images of the coatings prepared in Example 4, Example 5, Example 6, and Example 7. It can be seen from Figure 10 that the thickness of these four coatings is about 80 μm. Compared with Figure 10 the EP coating (Example 6) in c, the fracture surface of the coating with modified graphene TPG added is rougher. The cracks show non-linear expansion and do not penetrate the entire cross-section. This is because graphene blocks the crack propagation and dissipates a large amount of energy. The epoxy coating shows a typical brittle fracture mode, and the cracks are groove-shaped and penetrate the entire cross-section of the coating. Moreover, Figure 10 the TPG 1％ / EP coating (Example 7) and Figure 10 the bionic coating B-TPG 0.5％ / EP (Example 4) in a and Figure 10 the B-TPG 1％ / EP (Example 5) in b also have great differences in cross-sectional morphology. We observed that the graphene nanosheets in the TPG 1％ / EP coating fill the entire cross-section. In the coatings prepared in Example 4 and Example 5, the pure epoxy resin layer is used as an insulating layer to avoid direct contact between graphene and the metal substrate, and the modified graphene nanosheets are evenly dispersed in the epoxy resin mixture.

[0113] The coatings in Example 4-7 were subjected to corrosion resistance tests. The corrosion resistance of the damaged coatings was analyzed by salt spray tests. The salt spray tests were carried out using a salt spray tester. A 5.0 wt% NaCl solution was continuously sprayed on the samples at 35 °C, and the sample tilt angle was 20°. The test results are as Figure 11 shown. Among them, (a) corresponds to the coating of Example 4, (b) corresponds to the coating of Example 5, (c) corresponds to the coating of Example 6, and (d) corresponds to the coating of Example 7: After 7 days, a large amount of blue-black rust substances appeared at the scratched area of the EP coating, and with the extension of the test time, the corrosion area gradually increased, and the rust substances spread inward along the scratched area. At the same time, a relatively large area of blue-black corrosion substances also appeared at the scratched area of the TPG 1％ / EP coating. However, the composite coatings B-TPG 0.5％ / EP and B-TPG 1％Only a few very small corrosion pits appear in the / EP, and there is no obvious expansion in the subsequent corrosion area. The reason lies in the high affinity between the modified graphene and the epoxy resin, and the large number of well-dispersed graphene in the tight stacked structure that extends the path for corrosive substances to enter.

[0114] The specific implementation manners of the present invention have been exemplarily described above through embodiments. However, the protection scope of the present invention is not limited to the above exemplary implementation manners. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A preparation method of modified graphene, characterized in that, The method includes the following steps: (1) Mix a modifier, graphite, and water to obtain a pretreated graphite dispersion; (2) Subject the pretreated graphite dispersion in step (1) to exfoliation and modification to obtain a modified graphene dispersion. The modifier is TPE-PNIPAM; the TPE-PNIPAM has the following structural formula:

2. The preparation method of the modified graphene according to claim 1, wherein, In the pretreated graphite dispersion in step (1), the concentration of the modifier is 0.1 - 10 mg / mL; the concentration of the graphite is 1 - 50 mg / mL.

3. The preparation method of the modified graphene according to claim 1, characterized in that Step (1) is selected from one of the following steps: Add graphite to water, then add the modifier, and use a high-shear dispersion emulsifier to shear and disperse to obtain a pretreated graphite dispersion; Or, add graphite to water, then add the modifier, and then perform ultrasonic treatment to obtain a pretreated graphite dispersion; Or, add graphite to water, then add the modifier, and stir to obtain a pretreated graphite dispersion.

4. The preparation method of the modified graphene according to any one of claims 1-3, characterized in that, Step (2) specifically includes the following steps: Add the pretreated graphite dispersion to a microfluidic homogenizer for exfoliation and modification to obtain a modified graphene dispersion. Preferably, in step (2), the process of exfoliation and modification of the pretreated graphite dispersion in the microfluidic homogenizer includes the following steps: Circulate the pretreated graphite dispersion through a 100 - 400 μm nozzle 3 - 8 times, with a pressure of 5000 - 20000 psi.

5. The preparation method of the modified graphene according to any one of claims 1-3, characterized in that, The graphite is selected from at least one of natural flake graphite, expanded graphite, graphite powder, etc.

6. A modified graphene prepared by the method according to any one of claims 1-5, characterized in that, The modified graphene has scanning electron microscope, transmission electron microscope, and atomic force microscope images as shown in Figure 3.

7. A modified graphene prepared by the method according to any one of claims 1-5, characterized in that, The thickness of the modified graphene is less than or equal to 0.4 nm; the thickness of the modified graphene is 2 - 5 layers of graphene. Preferably, calculated by the graphite content, the solubility of the modified graphene in water is greater than or equal to 3 mg / mL.

8. Application of the modified graphene prepared by the method according to any one of claims 1 - 5 and the modified graphene according to claim 6 or 7 in an anticorrosive coating.

9. An anticorrosive coating, characterized in that, The anticorrosive coating includes a photoinitiator, an epoxy resin, a solvent, the modified graphene prepared by the method according to any one of claims 1 - 5, and the modified graphene according to claim 6 or 7. Preferably, the photoinitiator is selected from cationic photoinitiators, and the cationic photoinitiator is selected from one of aryl diazonium salts, diaryliodonium salts, triarylsulfonium salts, and arylferrocene salts. Preferably, the epoxy resin is selected from one or more of bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, glycidyl ether type epoxy resins, alicyclic epoxy resins, organosilicon-modified epoxy resins, and polyurethane epoxy resins.

10. The anticorrosive coating according to claim 9, characterized in that, The mass ratio of the epoxy resin to the photoinitiator is (10 - 50):1, and the mass ratio of the modified graphene to the epoxy resin is 1:(50 - 300). Preferably, in the anticorrosive coating, the concentration of the modified graphene is 0.5% - 1%, the concentration of the epoxy resin is 95.2% - 95.67%, and the concentration of the photoinitiator is 3.8% - 3.83%.

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