CN114956065B - Amino modified graphene, preparation method thereof, amino modified graphene coating and application - Google Patents

Amino modified graphene, preparation method thereof, amino modified graphene coating and application Download PDF

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CN114956065B
CN114956065B CN202210605350.5A CN202210605350A CN114956065B CN 114956065 B CN114956065 B CN 114956065B CN 202210605350 A CN202210605350 A CN 202210605350A CN 114956065 B CN114956065 B CN 114956065B
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modified graphene
amino
graphene
amino modified
coating
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CN114956065A (en
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蔡金明
陈其赞
郝振亮
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Guangdong Morion Nanotech Co Ltd
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Guangdong Morion Nanotech Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/182—Graphene
    • C01B32/194—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D1/00—Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/08—Anti-corrosive paints
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides amino modified graphene, a preparation method thereof, an amino modified graphene coating and application thereof, and particularly relates to the technical field of corrosion prevention. According to the amino modified graphene, the amino groups and the carboxyl groups are transversely and covalently bridged at the edge of the graphene to form the amino modified graphene, so that the dispersibility of the graphene in a solvent is improved; the amino group containing lone pair electrons can form secondary covalent bonding with carboxyl groups at the edge of the graphene oxide with hydroxyl groups and epoxy groups, so that transverse bridging butt joint is constructed, pi-pi interaction of delocalized pi electrons is enhanced, interaction of upper and lower layers of graphene is enhanced, finally, the amino modified graphene which is longitudinally densely stacked and transversely covalently bridged and stacked layer by layer is obtained, and the thickness of the amino modified graphene which is stacked layer by layer is reduced.

Description

Amino modified graphene, preparation method thereof, amino modified graphene coating and application
Technical Field
The invention relates to the technical field of corrosion prevention, in particular to amino modified graphene, a preparation method thereof, an amino modified graphene coating and application thereof.
Background
Graphene is a very potential corrosion-resistant material, and is attracting wide attention in the corrosion-resistant field. Mainly due to the following characteristics of graphene: the composite material has an ultra-large specific surface area, and can effectively shield external corrosive media; lamellar SP of graphene 2 The hybridization exhibits excellent mechanical and tribological properties. Because the geometric aperture of the six-membered ring of the graphene is only 0.064nm and even smaller than the very small helium Van der Waals diameter (0.28 nm), the single-piece defect-free graphene can effectively shield direct penetration of corrosive media such as water molecules, oxygen and the like.
Graphene is a quasi-two-dimensional structure, can be stacked layer by layer in a coating, effectively prevents diffusion of corrosive media, and can effectively reduce the dissolution rate of a metal substrate when the graphene is used as an anticorrosive coating due to ultra-fast electronic conduction performance. The thickness of the single-layer graphene oxide is larger than that of graphene due to the existence of functional groups such as hydroxyl groups, epoxy groups and the like on the surface of the graphene oxide.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide amino modified graphene so as to relieve the technical problem that the thickness of single-layer graphene oxide is larger than that of graphene due to the existence of functional groups such as hydroxyl groups, epoxy groups and the like on the surface of graphene oxide in the prior art.
In order to solve the technical problems, the invention adopts the following technical scheme:
the first aspect of the invention provides amino modified graphene, wherein amino groups and carboxyl groups are laterally and covalently bridged at the edge of the graphene.
The second aspect of the invention provides a preparation method of the amino modified graphene, which comprises the following steps:
step A: carrying out first spray granulation on the graphene oxide aqueous solution to obtain graphene powder with reserved edge carboxyl groups;
and (B) step (B): adding an amino modifier into the graphene powder preparation solution with the reserved edge carboxyl, and uniformly mixing to obtain a mixed solution;
step C: and carrying out a second spray granulation after carrying out a hydrothermal reaction on the mixed solution to obtain the amino modified graphene.
Alternatively, the temperatures of the first spray granulation and the second spray granulation are each independently 180 ℃ to 250 ℃.
Preferably, in step a, the concentration of the graphene oxide aqueous solution is 0.5wt.% to 1.5wt.%.
Preferably, in the step A, the pH of the graphene oxide aqueous solution is 2-4.
Optionally, the amino modifier comprises 2-6 diaminopyridine.
Preferably, the addition amount of the amino modifier is 0.1wt.% to 20wt.% of the mass of the graphene powder retaining the edge carboxyl groups.
Optionally, in step C, the temperature of the hydrothermal reaction is 60 ℃ to 120 ℃.
Preferably, the hydrothermal reaction time is 0.5h to 3h.
Optionally, in step B, the mixing means comprises ultrasonic mixing.
Preferably, the ultrasonic mixing is carried out for a period of time ranging from 1min to 10min.
The third aspect of the invention provides an amino modified graphene coating, which comprises graphene powder with reserved edge carboxyl groups, the amino modified graphene, a solvent, a dispersing agent and a modifying agent.
The amino-modified graphene is the amino-modified graphene prepared by the preparation method in the first aspect or the second aspect.
The graphene powder with the reserved edge carboxyl is prepared in the step A of the preparation method.
Optionally, the mass ratio of the graphene powder with the reserved edge carboxyl to the amino modified graphene is 1:0.1-1.
Preferably, the solvent includes an organic solvent and an inorganic solvent.
Preferably, the organic solvent comprises NMP and/or DMF.
Preferably, the inorganic solvent comprises deionized water.
Optionally, the dispersant comprises PVP and/or CMC.
Preferably, the modifier comprises PVDF and/or dopamine hydrochloride.
Preferably, the content of the dispersing agent is 0.1% -20%.
Preferably, the content of the modifier is 0.1% -20%.
The fourth aspect of the invention provides application of the amino modified graphene coating in metal corrosion prevention.
Compared with the prior art, the invention has at least the following beneficial effects:
according to the amino modified graphene provided by the invention, the lateral covalent bonding between the carboxyl and the amino at the edge of the graphene oxide is realized through amino modification, and meanwhile, the dispersibility of the graphene in a solvent is improved; the amino group containing lone pair electrons can form secondary covalent bonding with carboxyl groups at the edge of the graphene oxide with hydroxyl groups and epoxy groups, so that transverse bridging butt joint is constructed, pi-pi interaction of delocalized pi electrons is enhanced, interaction of upper and lower layers of graphene is enhanced, finally, the amino modified graphene which is longitudinally densely stacked and transversely covalently bridged and stacked layer by layer is obtained, and the thickness of the amino modified graphene which is stacked layer by layer is reduced.
According to the preparation method of the amino modified graphene, the hydroxyl and epoxy functional groups on the surface of the graphene oxide are removed, so that the interlayer gap between graphene is reduced, and the thickness of the amino modified graphene is reduced. The preparation method has simple process and strong process controllability, and is beneficial to industrialized mass production.
According to the amino modified graphene coating provided by the invention, the lateral bridging of graphene and graphene is realized by utilizing the covalent bonding effect of the isolated amino group of the amino modified graphene and the carboxyl functional group in the graphene with the reserved edge carboxyl, so that a large-area lateral shielding area is obtained. The isolated electron pairs existing in the amino modified graphene can be bonded, so that the dispersibility of the amino modified graphene powder is improved; by adding a trace amount of small molecule adhesive as a modifier, the interlayer binding force of the graphene is further improved, and the anti-corrosion performance of the amino modified graphene coating is improved.
According to the application of the amino modified graphene coating, amino in the amino modified graphene coating can promote passivation of a metal surface layer to form multistage protection through electrons which are not generated by dissolution of a metal substrate; in addition, the lone pair electron pair and delocalized pi electron group contained in the amino form coordination bonds with atoms on the surface of the metal substrate, so that the active sites on the surface of the metal substrate are reduced, the adhesive force between the coating and the metal substrate is enhanced, and the coating with excellent performance is provided for metal corrosion prevention.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a graph of thermal weight of graphene oxide used in example 1;
FIG. 2 is an infrared spectrum of amino-modified graphene obtained in example 1;
FIG. 3 is an infrared spectrum of amino-modified graphene obtained in example 2;
fig. 4 is an infrared spectrum of amino-modified graphene obtained in example 3.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. The components of embodiments of the present invention may be arranged and designed in a wide variety of different configurations.
At present, graphene is usually added into a conventional anti-corrosion system as an auxiliary material, and few anti-corrosion coatings using graphene as a main material or pure graphene are used. The research on the reasonable internal stacking arrangement of the graphene anti-corrosion coating is rare. A "labyrinth" mix has been built in the anticorrosive paint, usually in the form of a small addition, starting from increasing the free penetration path of the corrosive medium and slowing down the penetration rate of the corrosive medium. Graphene oxide is the most desirable layered layer-by-layer stack structure as a filler, but there is also penetration of corrosive media through the interlayer pores.
The first aspect of the invention provides amino modified graphene, wherein amino groups and carboxyl groups are laterally and covalently bridged at the edge of the graphene.
According to the amino modified graphene provided by the invention, the lateral covalent bonding between the carboxyl and the amino at the edge of the graphene oxide is realized through amino modification, and meanwhile, the dispersibility of the graphene in a solvent is improved; the amino group containing lone pair electrons can form secondary covalent bonding with carboxyl groups at the edge of the graphene oxide with hydroxyl groups and epoxy groups, so that transverse bridging butt joint is constructed, pi-pi interaction of delocalized pi electrons is enhanced, interaction of upper and lower layers of graphene is enhanced, finally, the amino modified graphene which is longitudinally densely stacked and transversely covalently bridged and stacked layer by layer is obtained, and the thickness of the amino modified graphene which is stacked layer by layer is reduced.
The second aspect of the invention provides a preparation method of the amino modified graphene, which comprises the following steps:
step A: carrying out first spray granulation on the graphene oxide aqueous solution to obtain graphene powder with reserved edge carboxyl groups;
and (B) step (B): adding an amino modifier into the graphene powder preparation solution with the reserved edge carboxyl, and uniformly mixing to obtain a mixed solution;
step C: and carrying out a second spray granulation after carrying out a hydrothermal reaction on the mixed solution to obtain the amino modified graphene.
According to the preparation method of the amino modified graphene, the hydroxyl and epoxy functional groups on the surface of the graphene oxide are removed, so that the interlayer gap between graphene is reduced, and the thickness of the amino modified graphene is reduced. The preparation method has simple process and strong process controllability, and is beneficial to industrialized mass production.
Graphene oxide (graphene oxide) is an oxide of graphene, and may be represented by english abbreviation GO.
Alternatively, the temperatures of the first spray granulation and the second spray granulation are each independently 180 ℃ to 250 ℃.
The temperature determination of the first and second spray granulation is determined based on the thermogravimetric profile of the graphene oxide used.
Optionally, the amino modifier comprises 2-6 diaminopyridine.
The structural formula of the 2-6 diaminopyridine is shown as the following formula (1).
As can be seen from formula (1), the amino group contains a lone pair electron pair and a delocalized pi electron group, four extra-nuclear electrons exist in the outer orbitals of the nitrogen atom in the amino group, three of the electrons form a covalent bond with H, C atoms, but one electron which does not form a lone pair of the covalent bond exists, and the six-membered ring-like structure shows a delocalized pi bond effect similar to that of a grapheme carbon six-membered ring, so that pi-pi conjugation is facilitated to form pi-pi with grapheme.
Preferably, in step a, the concentration of the graphene oxide aqueous solution is 0.5wt.% to 1.5wt.%
In some embodiments of the invention, the concentration of the graphene oxide aqueous solution is typically, but not limited to, 0.5wt.%, 0.6wt.%, 0.7wt.%, 0.8wt.%, 0.9wt.%, 1.0wt.%, 1.1wt.%, 1.2wt.%, 1.3wt.%, 1.4wt.%, or 1.5wt.%.
Preferably, in the step A, the pH of the graphene oxide aqueous solution is 2-4.
Preferably, the addition amount of the amino modifier is 0.1wt.% to 20wt.% of the mass of the graphene powder retaining the edge carboxyl groups.
When the addition amount of the amino modifier is less than 0.1wt.%, only a small amount of graphene is subjected to amino improvement, and a large amount of non-modified graphene still exists, so that a large-area barrier network is not constructed, and the corrosion resistance is reduced; when the addition amount of the amino modifier is more than 20 wt%, excessive amino modifier can increase the interlayer gap between the graphene and the graphene of the anti-corrosion coating, reduce the compactness and reduce the anti-corrosion performance.
In some embodiments of the present invention, the amino modifier is typically added in an amount of, but not limited to, 0.1wt.%, 0.5wt.%, 1wt.%, 3wt.%, 5wt.%, 7wt.%, 9wt.%, 11wt.%, 13wt.%, 15wt.%, 17wt.%, or 20wt.%.
Optionally, in step C, the temperature of the hydrothermal reaction is 60 ℃ to 120 ℃.
In the hydrothermal reaction, the edge carboxyl of the graphene oxide and one of the amino groups of the 2-6 diaminopyridine undergo a condensation reaction to form a C-N bond and generate a water molecule, and meanwhile, an additional amino group is obtained, so that the condensation reaction with the edge carboxyl of other graphene oxides is facilitated, and a large-area anti-corrosion interface is constructed; in addition, epoxy groups on the surface of the graphite oxide can also generate a hydroxyl group while generating a C-N bond through ring-opening reaction with an amino modifier. Mainly reacts with carboxyl functional groups under hydrothermal conditions at 85 ℃.
In some embodiments of the invention, the temperature of the hydrothermal reaction is typically, but not limited to, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, or 120 ℃.
Preferably, the hydrothermal reaction time is 0.5h to 3h.
In some embodiments of the invention, the time of the hydrothermal reaction is typically, but not limited to, 0.5h, 1h, 1.5h, 2h, 2.5h, or 3h.
Optionally, in step B, the mixing means comprises ultrasonic mixing.
Preferably, the ultrasonic mixing is carried out for a period of time ranging from 1min to 10min.
In some embodiments of the invention, the time of the ultrasonic mixing is typically, but not limited to, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 minutes.
The third aspect of the invention provides an amino modified graphene coating, which comprises graphene powder with reserved edge carboxyl groups, the amino modified graphene, a solvent, a dispersing agent and a modifying agent.
The amino-modified graphene is the amino-modified graphene prepared by the preparation method in the first aspect or the second aspect.
The graphene powder with the reserved edge carboxyl is prepared in the step A of the preparation method.
According to the amino modified graphene coating provided by the invention, the lateral bridging of graphene and graphene is realized by utilizing the covalent bonding effect of the isolated amino group of the amino modified graphene and the carboxyl functional group in the graphene with the reserved edge carboxyl, so that a large-area lateral shielding area is obtained. The isolated electron pairs existing in the amino modified graphene can be bonded, so that the dispersibility of the amino modified graphene powder is improved; by adding a trace amount of small molecule adhesive as a modifier, the interlayer binding force of the graphene is further improved, and the anti-corrosion performance of the amino modified graphene coating is improved.
The labyrinth barrier layer is constructed by adding graphene powder with reserved edge carboxyl and amino modified graphene, and corrosion mediums such as water molecules, oxygen and the like are isolated by utilizing the intrinsic characteristics of the graphene, so that the corrosion resistance is achieved.
Optionally, the mass ratio of the graphene powder with the reserved edge carboxyl to the amino modified graphene is 1:0.1-1.
When the mass ratio of the graphene powder with reserved edge carboxyl groups to the amino modified graphene is greater than or less than 1:0.1, the modified graphene oxide and the graphene with reserved edge carboxyl groups are difficult to achieve bonding matching, and the redundant non-modified graphene or modified graphene is not beneficial to building an ideal anti-corrosion interface.
Preferably, the solvent includes an organic solvent and an inorganic solvent.
Preferably, the organic solvent comprises NMP and/or DMF.
NMP refers to N-methylpyrrolidone, which is an organic substance with chemical formula of C 5 H 9 NO, which is colorless to pale yellow transparent liquid, has slight ammonia smell, is mixed with water in any proportion, is dissolved in various organic solvents such as diethyl ether, acetone, ester, halogenated hydrocarbon, aromatic hydrocarbon and the like, and is almost completely mixed with all solvents.
DMF refers to N, N-dimethylformamide, which is an organic compound with the chemical formula of C 3 H 7 NO, a colorless transparent liquid. Is not only an industrial raw material with extremely wide application, but also an excellent solvent with wide application. Can be mixed with water and most organic solvents except halogenated hydrocarbon at will, and has good dissolving capacity for various organic compounds and inorganic compounds.
Preferably, the inorganic solvent comprises deionized water.
Optionally, the dispersant comprises PVP and/or CMC.
PVP refers to polyvinylpyrrolidone, and is mainly used as an oil dispersant for promoting graphene dispersion and avoiding graphene agglomeration.
CMC refers to carboxymethyl cellulose, which is mainly used as a water-based dispersing agent, carboxyl groups on the CMC enable the surface of graphene to carry negative charges, and an electric double layer is formed on the surface of the graphene, when two graphene particles approach to the mutual penetration of diffusion layers of the two graphene particles, the homopolar charges are mutually repelled, and the graphene particles are forced to be separated, so that the dispersed graphene particles are stable.
Preferably, the modifier comprises PVDF and/or dopamine hydrochloride.
PVDF is polyvinylidene fluoride, a highly non-reactive thermoplastic fluoropolymer. Which can be synthesized by polymerization of 1, 1-difluoroethylene. The amino modified graphene coating is mainly used for adjusting viscosity, and proper viscosity is beneficial to coating construction.
Dopamine hydrochloride is an organic matter and has a chemical formula of C 8 H 12 ClNO 2 White needle crystals or crystalline powder; is easy to dissolve in water, is soluble in methanol and hot 95% ethanol, is soluble in sodium hydroxide solution, and is insoluble in ether, chloroform and benzene; no smell, slightly bitter taste. The dopamine hydrochloride is mainly used for enhancing the interlayer adhesive force of graphene in the amino modified graphene coating, and the graphene coating is prevented from peeling off.
Preferably, the content of the dispersing agent is 0.1% -20%.
Preferably, the content of the modifier is 0.1% -20%.
In some embodiments of the present invention, the dispersant is typically, but not limited to, 0.1%, 1%, 5%, 10%, 15% or 20%; the modifier is typically present in an amount of, but not limited to, 0.1%, 1%, 5%, 10%, 15% or 20%.
The fourth aspect of the invention provides application of the amino modified graphene coating in metal corrosion prevention.
According to the application of the amino modified graphene coating, amino in the amino modified graphene coating can promote passivation of a metal surface layer to form multistage protection through electrons which are not generated by dissolution of a metal substrate; in addition, the lone pair electron pair and delocalized pi electron group contained in the amino form coordination bonds with atoms on the surface of the metal substrate, so that the active sites on the surface of the metal substrate are reduced, the adhesive force between the coating and the metal substrate is enhanced, and the coating with excellent performance is provided for metal corrosion prevention.
When the amino modified graphene coating is used, firstly, heating a metal substrate to 60-100 ℃, spraying the amino modified graphene coating on a workpiece in a spraying manner, and then drying in an oven at 60-100 ℃ for 2-10 hours to obtain the metal workpiece coated with the amino modified graphene anti-corrosion coating.
In some embodiments of the invention, a PVDF coating is sprayed on the amino modified graphene anticorrosive coating, which is favorable for isolating moisture and increasing a multiple protection mechanism, and further improves the anticorrosive performance of the coating.
The PVDF solution has a mass fraction of 0.5% -4% and the solvent is typically but not limited to NMP.
And (3) spraying a second layer on the metal workpiece, and then drying in an oven at 60-100 ℃ for 2-10h.
Some embodiments of the present invention will be described in detail below with reference to examples. The following embodiments and features of the embodiments may be combined with each other without conflict.
Example 1
The embodiment provides amino modified graphene and an amino modified graphene coating, which specifically comprise the following steps:
1) The thermal weight curve of the graphene oxide is tested, as shown in fig. 1, the graphene oxide powder falls off at about 200 ℃ in a mass curve, and the hydroxyl and epoxy groups on the surface of the graphene oxide fall off under the temperature condition by combining with a Raman test. Therefore, the shedding temperature of the hydroxyl groups and the epoxy groups which are easy to shed on the upper surface and the lower surface of the graphene oxide is 200 ℃. And (3) selecting graphene oxide aqueous solution slurry with the PH=2 mass fraction of 1% as a raw material, setting the spraying temperature to 210 ℃, removing hydroxyl groups and epoxy groups which are easy to fall off on the surface of the graphene oxide through spray granulation, retaining carboxyl functional groups with edges difficult to fall off, reducing the thickness of a graphene oxide monolayer, and obtaining graphene powder with edge carboxyl retained.
2) Dissolving the graphene powder with the edge carboxyl reserved in the step 1) in deionized water, stirring and dispersing, selecting 2-6 diaminopyridine as an amino modifier, adding 3% of 2-6 diaminopyridine according to the mass ratio of the powder, and carrying out ultrasonic treatment for 5min to obtain a mixed solution.
3) And carrying out hydrothermal reaction on the mixed solution for 2 hours at the temperature of 85 ℃, removing one-OH from the carboxyl at the edge of the graphene, removing one H ion from one amino group of the 2-6 diaminopyridine, realizing covalent bonding modification of the amino group and the carboxyl, and generating a part of water.
4) And (3) carrying out spray granulation on the solution obtained after the hydrothermal reaction in the step (3) at the temperature of 210 ℃ to obtain the amino modified graphene powder.
5) The graphene powder with reserved edge carboxyl obtained in the step 2) and the amino modified graphene powder obtained in the step 4) are mixed according to the following ratio of 1: mixing with a mass ratio of 0.5, taking NMP as a solvent, PVP as a dispersing agent, dopamine hydrochloride and the like as a micromolecular binder, wherein the addition amount of the PVP dispersing agent is 0.5%, and the addition amount of the dopamine hydrochloride is 0.1%, so as to obtain the amino modified graphene coating with 3% of solid content.
As shown in FIG. 2, the infrared spectrum of GO is 1500cm -1 There is no C-N stretching vibration peak, and a C-N stretching vibration peak appears at 1500cm < -1 > after amino modification, because the amino and carboxyl react in a condensation way, and the-OH group in the carboxyl is replaced to generate the C-N stretching vibration peak.
Example 2
The difference between the amino-modified graphene and the amino-modified graphene coating provided in this embodiment and embodiment 1 is that the hydrothermal temperature in step 3) is 75 ℃, and the solution after the hydrothermal reaction is subjected to infrared spectroscopy, and the result is shown in fig. 3, and the other raw materials and steps are the same as those in embodiment 1, and are not repeated here.
As can be seen from FIG. 3, the infrared spectrum of the sample hydrothermal at 75℃is 1500cm -1 The intensity of C-N stretching vibration peak at the position is reduced. This is mainly due to the reduced amount of C-N covalent bonds formed by the condensation reaction of the amino groups with the carboxyl groups to replace the-OH functions in the carboxyl groups.
Example 3
The present embodiment provides an amino-modified graphene and an amino-modified graphene coating, which are different from embodiment 1 in that the temperature of spray granulation in step 2) and step 4) is 150 ℃, and the obtained amino-modified graphene is subjected to infrared spectrum, and as a result, as shown in fig. 4, the other raw materials and steps are the same as those in embodiment 1, and are not described herein.
As can be seen from FIG. 4, 3339cm representing the hydroxyl-OH and epoxy C-O vibrational peaks of graphene oxide -1 And 1216cm -1 And a strong vibration peak still exists at the position, which indicates that most of hydroxyl groups and epoxy groups on the surface of the graphene oxide do not fall off.
Example 4
The present embodiment provides an amino-modified graphene and an amino-modified graphene coating, which are different from embodiment 1 in that the mass fraction of the graphene oxide aqueous solution in step 1) is 1%, the rest of the raw materials and steps with pH of 4 are the same as embodiment 1, and no further description is given here.
Example 5
The present embodiment provides an amino-modified graphene and an amino-modified graphene coating, which are different from embodiment 1 in that the addition amount of 2-6 diaminopyridine in step 2) is 0.1%, and the other raw materials and steps are the same as those in embodiment 1, and are not described here again.
Example 6
The present embodiment provides an amino-modified graphene and an amino-modified graphene coating, which are different from embodiment 1 in that the addition amount of 2-6 diaminopyridine in step 2) is 20%, and the other raw materials and steps are the same as those in embodiment 1, and are not described here again.
Example 7
This example provides an amino-modified graphene and amino-modified graphene coating, unlike example 1, in step 5) two powders were mixed according to 1: the mass ratio of 0.1 was mixed, and the other raw materials and steps were the same as those of example 1, and will not be described again.
Example 8
This example provides an amino-modified graphene and amino-modified graphene coating, unlike example 1, in step 5) two powders were mixed according to 1:1, and the rest raw materials and steps are the same as those of the embodiment 1, and are not repeated here.
Comparative example 1
The comparative example provides an EP resin anticorrosive paint which comprises phenolic epoxy resin, chlorinated rubber epoxy resin, reactive diluent, titanium pigment, acetylene black, auxiliary agent, epoxy resin curing agent and curing accelerator.
Test example 1
The amino-modified graphene coating obtained in examples 1 to 8 and the EP resin anticorrosive coating obtained in comparative example 1 were subjected to corrosion performance test. The test method is as follows:
step 1: and (3) selecting a 304 stainless steel plate as a substrate, polishing by using fine sand paper, performing ultrasonic alternate cleaning for 3 times by using acetone and absolute ethyl alcohol, and drying at 60 ℃ for later use.
Step 2: and heating the cleaned metal substrate to 80 ℃, directly spraying on the workpiece by using a spray gun spraying mode, and then drying in a 100 ℃ oven for 5 hours to obtain the metal workpiece coated with the coating.
Step 3: and 2, preparing PVDF solution with the mass fraction of 2% by taking NMP as a solvent and PVDF as a solute, spraying a second layer on the metal workpiece coated with the coating obtained in the step 2, and drying in an oven at 80 ℃ for 5 hours to obtain the metal workpiece with the anti-corrosion coating.
Step 4: firstly, two scratches are carved on the surface of a metal workpiece with an anti-corrosion coating in an intersecting way, then salt spray anti-corrosion test is carried out, and salt spray test results of a plurality of groups of samples in 50h, 100h, 200h and 300h are observed.
The test result shows that the EP resin anticorrosive paint provided in the comparative example 1 starts to generate corrosion spots when the salt fog is generated for 50 hours, and gradually diffuses from scratch parts along with the time to generate a large number of corrosion spots; after the 300h salt spray corrosion resistance test is finished, the workpiece obtained in the embodiment 1 has corrosion spots at the positions of scratches and has no corrosion spots at other positions; the work piece obtained in example 2 had some small corrosion spots in the place other than the scratch, in addition to the corrosion spots in the scratch after the salt spray corrosion resistance test was completed.
The workpiece obtained in example 3 has more corrosion spots after 300h test is finished, and corrosion at the chemical mark is serious, mainly due to the fact that hydroxyl and epoxy groups belong to hydrophilic functional groups, copper hydroxyl and epoxy groups can also have a certain moisture absorption effect to generate bonding reaction with amino functional groups of 2-6 diaminopyridine, so that the interlayer gap of graphene is increased, and a corrosion medium can be diffused in a larger transverse gap.
Test example 2
The corrosion performance test was performed on the amino-modified graphene coating obtained in example 1, and the difference from test example 1 is that the metal substrate after cleaning in step 2 was heated to 150 ℃, and the rest steps are the same as those in test example 1, and are not described here again.
The results showed that at 150 ℃ spraying, there was some small blisters on the surface of the coating and the graphene layers were less orderly arranged in lateral stacks, mainly due to swelling and poor self-assembly ability due to evaporation with solvent. The salt spray corrosion resistance test result shows that a large number of corrosion spots appear on the sample of the workpiece obtained in the step 3 after 200 hours, and the corrosion spots are generated uniformly at the large part of bulge positions.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (15)

1. An amino modified graphene is characterized in that an amino group and a carboxyl group are laterally and covalently bridged at the edge of the graphene;
the preparation method of the amino modified graphene comprises the following steps:
step A: carrying out first spray granulation on a graphene oxide aqueous solution with the concentration of 0.5wt.% to 1.5wt.% and the pH of 2 to 4 to obtain graphene powder with reserved edge carboxyl groups;
and (B) step (B): adding 0.1-20 wt.% of amino modifier into the graphene powder preparation solution with the reserved edge carboxyl groups, and uniformly mixing to obtain a mixed solution;
step C: carrying out a second spray granulation after carrying out a hydrothermal reaction on the mixed solution to obtain the amino modified graphene;
the temperature of the first spray granulation and the second spray granulation are each independently 180 ℃ to 250 ℃.
2. The amino modified graphene of claim 1, wherein the amino modifier comprises at least one of 2-6 diaminopyridine, semicarbazide, phenylenediamine, and aniline trimer.
3. The amino modified graphene of claim 1, wherein in step C, the temperature of the hydrothermal reaction is 60 ℃ to 120 ℃;
the hydrothermal reaction time is 0.5h-3h.
4. The amino modified graphene of claim 1, wherein in step B, the means of mixing comprises ultrasonic mixing.
5. The amino modified graphene of claim 1, wherein the time of ultrasonic mixing is 1min-10min.
6. An amino modified graphene coating, which is characterized by comprising the graphene powder with the edge carboxyl reserved, according to claims 1-5, the amino modified graphene according to claim 1, and a solvent, a dispersing agent and a modifying agent.
7. The amino-modified graphene coating according to claim 6, wherein the mass ratio of the graphene powder with the edge carboxyl groups reserved to the amino-modified graphene is 1:0.1-1.
8. The amino modified graphene coating of claim 6, wherein the solvent comprises an organic solvent and an inorganic solvent.
9. The amino modified graphene coating of claim 8, wherein the organic solvent comprises NMP and/or DMF.
10. The amino modified graphene coating of claim 8, wherein the inorganic solvent comprises deionized water.
11. The amino modified graphene coating of claim 6, wherein the dispersant comprises PVP and/or CMC.
12. The amino modified graphene coating of claim 6, wherein the modifier comprises PVDF and/or dopamine hydrochloride.
13. The amino modified graphene coating of claim 6, wherein the dispersant is present in an amount of 0.1% -20%.
14. The amino modified graphene coating of claim 6, wherein the modifier is present in an amount of 0.1% -20%.
15. Use of an amino modified graphene coating according to any one of claims 6-13 for metal corrosion protection.
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