CN115322648B - Modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint and preparation method thereof - Google Patents
Modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint and preparation method thereof Download PDFInfo
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- 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
- C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
- C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
- C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
- C08G59/62—Alcohols or phenols
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- 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
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- 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
- C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
- C09D7/40—Additives
- C09D7/60—Additives non-macromolecular
- C09D7/61—Additives non-macromolecular inorganic
- C09D7/62—Additives non-macromolecular inorganic modified by treatment with other compounds
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Abstract
The invention belongs to the technical field of functional materials, and discloses a modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint and a preparation method thereof. According to the invention, epoxy vegetable oil and natural polyphenol are respectively dissolved in ethanol, mixed after complete dissolution, then modified graphene is dispersed in ethanol, and uniformly dispersed suspension is obtained by ultrasonic treatment, three components are fully fused under magnetic stirring, and a finished coating liquid can be obtained after solvent is removed by rotary evaporation. The crosslinking capacity of each component can be successfully enhanced by modifying the graphene oxide, the problem that conventional fillers are easy to settle is effectively solved, and the stability of the product is improved. The formula of the coating adopts renewable bio-based raw materials, has simple components, does not release pollutants when in use, is easy to degrade and update when in service life, is environment-friendly, and has dominant significance for green industrial innovation of the epoxy anticorrosive coating.
Description
Technical Field
The invention belongs to the technical field of functional materials, and particularly relates to a modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint and a preparation method thereof.
Background
The penetration of the sustainable development concept at present promotes the transformation of the chemical industry, and the coating industry under the background also implements an innovative production standard, and the traditional petroleum-based coating is gradually replaced by a novel coating added with modified vegetable oil due to the limitation of volatile organic solvents and bisphenol A resin. Epoxy resins are widely used in paint because of their good protective properties and durability, so the environmental protection production mode of epoxy resins and the application of renewable raw materials have certain guiding significance for the development of paint products.
Among various renewable raw materials, epoxy-modified vegetable oils have attracted great attention in the scientific and industrial fields, and are ideal renewable substitutes for petroleum-based epoxy resins, but their inherent characteristics such as poor mechanical strength have made it impossible to achieve the hardness and strength required for practical production. Therefore, the natural polyphenol similar to bisphenol A in structure is used as a curing agent to be matched with the epoxy vegetable oil to generate hyperbranched aromatic and alicyclic polyester according to the rich active phenolic hydroxyl terminal, so that a highly crosslinked network is formed, and the effects of hardness, toughness and economy are achieved.
In order to endow epoxy resin with wider application value, nano filler is often introduced into the field of functional materials. Based on the requirement of corrosion resistance, graphene oxide is often selected in the industry because of excellent electron blocking capability and dispersion effect on impact stress. However, the graphene oxide has poor compatibility when directly added into an epoxy resin-based paint.
The present invention is therefore directed to modifying graphene oxide while introducing the above-mentioned emerging epoxy-phenol resin system into the market, thereby leading the coating industry to shift to clean production.
Disclosure of Invention
In order to overcome the defects and shortcomings of the prior art, the primary purpose of the invention is to provide the modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint. The stable metal protective coating is obtained by introducing modified graphene into a bio-based epoxy-phenol formula system, and experiments prove that the metal protective coating has good metal affinity and corrosion resistance after a heat curing process.
The invention further aims to provide a preparation method of the modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint.
The invention also aims to provide application of the modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint.
The aim of the invention is achieved by the following scheme:
the modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint comprises the following raw materials in percentage by mass: 65-85% of epoxy vegetable oil, 15-35% of natural polyphenol and 0.025-0.4% of modified graphene. The epoxy vegetable oil is used as a resin matrix, the natural polyphenol is used as a curing agent, and the modified graphene is used as an anti-corrosion functional filler.
The epoxy vegetable oil is at least one of epoxy soybean oil, epoxy castor oil, epoxy linseed oil and epoxy tung oil;
the natural polyphenol is at least one of tannic acid, quercetin, urushiol and gallic acid.
Preferably, the epoxy vegetable oil and the natural polyphenol are used in an amount such that the molar ratio of epoxy groups to phenolic hydroxyl groups is 1:1-1:2.
The modified graphene is histidine grafted acid reduced graphene oxide, and the modified graphene is added into a coating to prepare nano particles.
The modified graphene is prepared by the following method:
(1) Dispersing graphene oxide in a solvent, adding 1-ethyl-3- (3- (dimethylamino) propyl) carbodiimide, and fully stirring and uniformly mixing to prepare uniform suspension;
(2) Dissolving histidine in a solvent, wherein the solvent is the same as that in the step (1), and then fully mixing the histidine with the suspension in the step (1), and stirring the mixture at room temperature for reaction;
(3) And (3) regulating the pH value of the mixed solution obtained in the step (2) to 8-10, adding a reducing agent into the mixed solution, heating and stirring the mixed solution to react, and purifying the mixed solution after the reaction is finished to obtain the modified graphene.
The mass ratio of raw materials graphene oxide, 1-ethyl-3- (3- (dimethylamino) propyl) carbodiimide, histidine and reducing agent used in the steps (1) - (3) is 3:1:1:20-5:1:1:60;
the solvent in the step (1) is one of N, N-dimethylformamide, N-dimethylacetamide, N-dimethylpropionamide, N-diethylformamide and N, N-diethylacetamide.
The graphene oxide in the step (1) is prepared by using a practically improved Hummers method, and the specific preparation process is as follows: adding 1 part by mass of sodium nitrate into 40-50 parts by volume of concentrated sulfuric acid to react with 2 parts by mass of graphite powder, stirring for 20-50 minutes under ice bath condition, adding 5-10 parts by mass of potassium permanganate for a small amount for multiple times within 1 hour, carrying out ice bath reaction for 2 hours, heating to 25-40 ℃ to react for 30 minutes, dropwise adding 50-70 parts by volume of water, stirring for 30 minutes in 98 ℃ by oil bath, adding 70-160 parts by volume of 60 ℃ warm water at room temperature for 1 hour, adding 7-10 parts by volume of 30% hydrogen peroxide, standing overnight, discarding supernatant, centrifuging for 5-15 minutes at 10000 revolutions, washing for 3 times by 5% hydrochloric acid, washing for 3 times by deionized water, and obtaining self-made graphene oxide after freeze drying, wherein when 1 part by volume is 1 milliliter, the corresponding 1 part by mass is 1 gram.
The reaction time of stirring at room temperature in the step (2) is 24 hours or longer.
The reducing agent in the step (3) is a natural biological base reducing agent, preferably at least one of tannic acid, ascorbic acid, glutathione, gallic acid and chitosan.
The reaction is carried out by heating and stirring in the step (3) and is carried out by heating to 60-80 ℃ and stirring for 5-8 hours.
And (3) purifying, namely naturally cooling to room temperature after the reaction is finished, centrifugally separating, washing with absolute ethyl alcohol, washing with water, and finally freeze-drying to obtain the histidine grafted acid reduced graphene oxide.
According to the invention, the graphene is subjected to surface modification, and the reactive groups are added to the surface of the graphene to promote interface combination between the graphene and a matrix, so that the sedimentation phenomenon of the graphene in the coating is effectively improved. Meanwhile, the natural polyphenol has chelating ability with iron, can provide good adhesion force between the system and a metal substrate besides the function of a corrosion inhibitor, so that the system has remarkable advantages in the aspect of metal protection.
The preparation method of the modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint comprises the following steps: respectively dissolving the epoxy vegetable oil and the natural polyphenol in absolute ethyl alcohol according to the formula amount by adopting a solvent blending method, and then uniformly mixing and stirring the two solutions to obtain a solution 1; and (3) weighing the formula amount of modified graphene, dispersing the modified graphene in absolute ethyl alcohol, carrying out ultrasonic preparation on the modified graphene to prepare nano particles, mixing the nano particles with the solution 1, stirring and uniformly mixing the nano particles, and carrying out rotary evaporation to remove the ethanol to obtain the coating liquid doped with the modified graphene.
The epoxy vegetable oil and the natural polyphenol are respectively dissolved in absolute ethyl alcohol according to the formula amount, preferably are respectively dissolved in absolute ethyl alcohol with the volume of one time; the weighed amount of modified graphene is preferably dispersed in the absolute ethyl alcohol with the volume twice that of the modified graphene.
The modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint is applied to rust protection of metal instruments in ships, mechanical parts, highway facilities and the like which are easy to be exposed in humid environments, antibacterial of perishable materials such as wood and the like and waterproof toughening of paper models. Among them, the antibacterial is preferably against staphylococcus aureus or against escherichia coli.
The application method of the modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint comprises the following steps: preheating the coating liquid at 40-60 ℃ to reduce the viscosity, coating the coating liquid on a metal substrate by using a coating machine, wherein the thickness is 100-500 microns, drying in vacuum to remove bubbles, and curing for 2 hours at 120-150 ℃ and 5 hours after curing at 180-200 ℃ under vacuum conditions to obtain the epoxy resin anti-corrosion coating.
The invention selects bio-based materials produced in a large scale in an industrialized way, explores the application possibility of the pure bio-based coating, and adds modified graphene nano particles purposefully to enhance the anti-corrosion performance of the pure bio-based coating. In order to increase the dispersibility and the stability of the coating, firstly, practice and improvement are carried out on graphene oxide prepared by a Hummers method, and the nano sheet with higher stripping degree is obtained; then, histidine is grafted at the edge of the nano-sheet to enable the lamellar structure to be more stable, meanwhile, the histidine has the function of a curing accelerator, so that the nano-sheet can react with a resin substrate to form stable chemical crosslinking in the curing process, and the nano-sheet can also play the role of a corrosion inhibitor when in use; finally, reducing by using a bio-based reducing agent to obtain histidine grafted acid reduced graphene oxide, wherein the reduced surface groups of the sheet layer not only enhance the electron shielding effect, but also increase the hydrophobicity of the sheet layer, so that the compatibility with an oil phase and a solvent is increased.
Compared with the prior art, the invention has the following advantages:
the invention adopts renewable resources vegetable oil and natural polyphenol as raw materials to prepare the pure bio-based epoxy resin which is used as the main body of the anticorrosive paint. The bio-based epoxy resin is used for the anti-corrosion coating, and has practical production and application values. This is not only to cope with international restrictions on bisphenol a resins and volatile organic solvents, but also to meet the concept of sustainable development. The pure bio-based epoxy resin is easy to decompose under the strong alkaline condition, and the product is nontoxic and harmless, and truly has the characteristics of environmental friendliness, degradability, easy updating and the like. The natural polyphenol has antibacterial property, so that the paint product is not easy to deteriorate in the storage process, the addition of a chemical antibacterial agent can be omitted, and the ecological affinity is stronger.
The modification of graphene oxide enables histidine to play a dual role in a coating liquid system, namely, a curing accelerator, a corrosion inhibitor and a nano filler are fused, so that particles can participate in a curing reaction and provide a protection function. Promoting the reaction, reducing the thermosetting temperature, and the enhanced resin performance can achieve the efficacy which is even stronger than that of the abiotic imidazole-based accelerator; the grafted and modified graphene lamellar structure is more stable, and the problem that graphene is easy to sink in a traditional coating system is solved. Meanwhile, the graphene with good dispersion can effectively reduce the generation of micropores in a coating matrix and prevent corrosive ions from penetrating, and electrons cannot be captured by oxygen because the oxidation process of metal only occurs on the surface and mass transfer is limited by the coating, so that the oxidation reaction of the metal matrix is inhibited, and the metal matrix has excellent corrosion resistance. The histidine molecule helps to increase the dispersibility and the applicable range of the histidine molecule, and provides the feasibility of application in the aspect of anticorrosive paint for the epoxy resin of the pure bio-based component.
The amount of the added modified graphene can reach 0.4% of the total system, the dispersion is good, compared with the unmodified graphene oxide coating added with 0.05% for the same storage time, the modified graphene oxide coating can also show better stability (see figure 1), and the modified graphene oxide coating can be stored for one year with less sedimentation.
Drawings
FIG. 1 is a comparison of the stability of the coating solutions of comparative example 2 and example 4 after half a month of storage. Wherein (a) is the preparation beginning and (b) is after standing for half a month. (a) And (b) the left bottle represents the coating liquid in comparative example 2, and the right bottle represents the coating liquid in example 4.
FIG. 2 is a Nyquist plot of a coating obtained by electrochemical EIS testing after 1 month of immersion in a 3.5wt% sodium chloride solution, where (a) is the initial stage of immersion and (b) is 1 month of immersion.
FIG. 3 is a DMA curve of storage modulus (E') and tan delta as a function of temperature after curing of the coating, wherein the heating rate is 5℃per minute.
FIG. 4 is a graph showing the antibacterial properties of the coating liquid, wherein (a) represents Staphylococcus aureus, (b) represents Escherichia coli, the upper medium in (a) and (b) are blank controls, the coating liquid of example 4 is mixed in the left medium, and the coating liquid of comparative example 1 is mixed in the right medium.
Fig. 5 is a graph showing the difference in immersion effect in water between the uncoated and coated paper boat models.
FIG. 6 is a graph of a chemical immersion experiment of a paint chip. (a) is the initial soaking period, and (b) is after soaking for 3 days. (a) And (b) the solvent in the left three culture dishes is 10% hydrochloric acid, and the solvent in the right three culture dishes is 10% sodium hydroxide; (a) And (b) the original chips added to the three rows of dishes from top to bottom were the coating chips prepared in comparative example 1, example 3, and example 4.
FIG. 7 is a graph showing the viscosity of various coating liquids as a function of shear rate.
Fig. 8 is an infrared characterization diagram of graphene particles before and after modification in example 1.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The reagents used in the examples are commercially available as usual unless otherwise specified.
Example 1
The modified graphene is prepared by taking graphite powder as a raw material, and the specific operation flow is as follows:
to 48 ml of concentrated sulfuric acid, 1 g of sodium nitrate was added to react with 2 g of graphite powder, and the mixture was stirred in an ice bath at a temperature below 4℃for 30 minutes. Adding 8 g of potassium permanganate for a small amount for a plurality of times within 1 hour, keeping ice bath, continuing stirring for 2 hours, heating to 35 ℃ for reaction for 30 minutes, slowly adding 63 ml of deionized water, transferring to oil bath, stirring for 30 minutes at 98 ℃, adding 100 ml of warm water at 60 ℃ within 1 hour at room temperature, adding 8 ml of 30% hydrogen peroxide, standing overnight, discarding the supernatant, centrifuging for 5 minutes at 10000 revolutions, taking precipitate, washing for 3 times with 5% hydrochloric acid, washing for 3 times with deionized water, and freeze-drying to obtain self-made graphene oxide.
0.4 g of graphene oxide is taken and dissolved in 120 ml of N, N-dimethylformamide, and after ultrasonic treatment is carried out for 2 hours, 0.1 g of 1-ethyl-3- (3- (dimethylamino) propyl) carbodiimide is added, and the mixture is fully and uniformly mixed for 15 minutes to prepare uniform suspension. 0.1 g histidine was dissolved in 50 ml N, N-dimethylformamide, and the mixture was thoroughly mixed with the above suspension, followed by stirring at room temperature for 24 hours. The pH of the mixture was adjusted to 10 with ammonia, 4 g of tannic acid was added thereto, and the reaction was carried out with magnetic stirring at 80℃for 6 hours. And cooling, centrifuging at 10000 r for 10 min, taking precipitate, washing with absolute ethanol for 3 times, washing with deionized water for 3 times, and freeze-drying to obtain histidine grafted acid reduced graphene oxide.
Example 2
The preparation and the use of the modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint comprise the following specific operation procedures:
16 g of epoxidized soybean oil and 4 g of tannic acid are respectively dissolved in 10 ml of absolute ethyl alcohol, and then the two solutions are mixed and stirred uniformly. 0.01 g of modified graphene is weighed and dispersed in 10 ml of absolute ethyl alcohol, the absolute ethyl alcohol is mixed with an ethanol solution of a resin substrate after ultrasonic treatment for 30 minutes, magnetic stirring is carried out for 30 minutes, and then ethanol is removed after reduced pressure evaporation for 30 minutes at 50 ℃, so that coating liquid doped with 0.05% of modified graphene can be obtained.
After the surface coating of the tinplate is ground and polished by sand paper, the coating liquid preheated at 50 ℃ is dripped, and the coating liquid is coated by a 100-micrometer coater. Air bubbles are removed by vacuum treatment at 50 ℃ for 30 minutes, and the mixture is cured for 5 hours at 180 ℃ after being pre-cured for 2 hours at 120 ℃. And (3) after cooling, repeatedly coating a layer of coating by using a 100-micrometer coater, and solidifying for 7 hours to obtain the metal protective coating with excellent corrosion resistance.
Example 3
The preparation and the use of the modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint comprise the following specific operation procedures:
16 g of epoxidized soybean oil and 4 g of tannic acid are respectively dissolved in 10 ml of absolute ethyl alcohol, and then the two solutions are mixed and stirred uniformly. 0.04 g of modified graphene is weighed and dispersed in 10 ml of absolute ethyl alcohol, the absolute ethyl alcohol is mixed with an ethanol solution of a resin substrate after ultrasonic treatment for 30 minutes, magnetic stirring is carried out for 30 minutes, and then ethanol is removed after reduced pressure evaporation for 30 minutes at 50 ℃, so that coating liquid doped with 0.2% of modified graphene can be obtained.
After the surface coating of the tinplate is ground and polished by sand paper, the coating liquid preheated at 50 ℃ is dripped, and the coating liquid is coated by a 100-micrometer coater. Air bubbles are removed by vacuum treatment at 50 ℃ for 30 minutes, and the mixture is cured for 5 hours at 180 ℃ after being pre-cured for 2 hours at 120 ℃. And (3) after cooling, repeatedly coating a layer of coating by using a 100-micrometer coater, and solidifying for 7 hours to obtain the metal protective coating with excellent corrosion resistance.
Example 4
The preparation and the use of the modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint comprise the following specific operation procedures:
16 g of epoxidized soybean oil and 4 g of tannic acid are respectively dissolved in 10 ml of absolute ethyl alcohol, and then the two solutions are mixed and stirred uniformly. 0.08 g of modified graphene is weighed and dispersed in 20 ml of absolute ethyl alcohol, the absolute ethyl alcohol is mixed with an ethanol solution of a resin substrate after ultrasonic treatment for 30 minutes, magnetic stirring is carried out for 30 minutes, and then ethanol is removed after reduced pressure evaporation for 30 minutes at 50 ℃, so that coating liquid doped with 0.4% of modified graphene can be obtained.
After the surface coating of the tinplate is ground and polished by sand paper, the coating liquid preheated at 50 ℃ is dripped, and the coating liquid is coated by a 100-micrometer coater. Air bubbles are removed by vacuum treatment at 50 ℃ for 30 minutes, and the mixture is cured for 5 hours at 180 ℃ after being pre-cured for 2 hours at 120 ℃. And (3) after cooling, repeatedly coating a layer of coating by using a 100-micrometer coater, and solidifying for 7 hours to obtain the metal protective coating with excellent corrosion resistance.
Example 5
The preparation and the use of the modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint comprise the following specific operation procedures:
15 g of epoxy castor oil is taken to be dissolved in 10 ml of absolute ethyl alcohol, 5 g of quercetin is taken to be heated and dissolved in 20 ml of absolute ethyl alcohol, and then the two solutions are mixed and stirred uniformly. 0.01 g of modified graphene is weighed and dispersed in 10 ml of absolute ethyl alcohol, the absolute ethyl alcohol is mixed with an ethanol solution of a resin substrate after ultrasonic treatment for 30 minutes, magnetic stirring is carried out for 30 minutes, and then ethanol is removed after reduced pressure evaporation for 30 minutes at 50 ℃, so that coating liquid doped with 0.05% of modified graphene can be obtained.
After the surface coating of the tinplate is ground and polished by sand paper, the coating liquid preheated at 50 ℃ is dripped, and the coating liquid is coated by a 100-micrometer coater. And (3) carrying out vacuum treatment at 50 ℃ for 30 minutes to remove bubbles, regulating the temperature to 150 ℃ for pre-curing for 2 hours, and then carrying out post-curing at 200 ℃ for 5 hours to obtain the compact anti-corrosion coating.
Comparative example 1
The preparation and the use of the blank (without adding particles) bio-based epoxy-phenol system resin coating are as follows:
16 g of epoxidized soybean oil and 4 g of tannic acid are respectively dissolved in 10 ml of absolute ethyl alcohol, and then the two solutions are mixed and stirred uniformly. And then evaporating under reduced pressure at 50 ℃ for 30 minutes to remove ethanol, and collecting and obtaining blank coating liquid.
After the surface coating of the tinplate is ground and polished by sand paper, the coating liquid preheated at 50 ℃ is dripped, and the coating liquid is coated by a 100-micrometer coater. Air bubbles are removed by vacuum treatment at 50 ℃ for 30 minutes, and the mixture is cured for 5 hours at 180 ℃ after being pre-cured for 2 hours at 120 ℃. And (5) after cooling, repeatedly coating a layer of coating by using a 100-micrometer coater, and solidifying for 7 hours to obtain the blank coating with balanced toughness and hardness.
Comparative example 2
The preparation and the application of the graphene oxide doped bio-based epoxy-phenol system resin anticorrosive paint comprise the following specific operation procedures:
16 g of epoxidized soybean oil and 4 g of tannic acid are respectively dissolved in 10 ml of absolute ethyl alcohol, and then the two solutions are mixed and stirred uniformly. 0.01 g of self-made graphene oxide (namely, the graphene oxide prepared in the embodiment 1) is weighed and dispersed in 10 ml of absolute ethyl alcohol, the absolute ethyl alcohol is mixed with an ethanol solution of a resin base material after ultrasonic treatment for 30 minutes, magnetic stirring is carried out for 30 minutes, then the ethanol is removed after reduced pressure evaporation for 30 minutes at 50 ℃, and then a coating liquid doped with 0.05% of graphene oxide can be obtained.
Performance evaluation
1. Corrosion resistance
Polarization and ac impedance spectroscopy tests were performed on a CHI-660E electrochemical workstation using a conventional three electrode cell. First, a 3.5wt% aqueous sodium chloride solution was prepared at room temperature as a corrosion medium, with a tin-plated electrode having an exposed area of 1 square centimeter as a working electrode, a saturated silver/silver chloride electrode as a reference electrode, and a platinum sheet having an exposed area of 1 square centimeter as a counter electrode, respectively. The polarization curve was plotted at a scan rate of 0.01 volts per second over the open circuit potential range of-0.3 to +0.3 volts to determine the corrosion potential and corrosion current density. Using the same three electrode cell, the nyquist curve was obtained by EIS testing at a sinusoidal amplitude of 20 millivolts over a frequency range of 100 khz to 0.01 hz. The Nyquist curve mainly reflects the change rule of the resistance value of the anti-corrosion coating along with time, the radius of the curve can directly reflect the impedance of the coating, and the larger the resistance value is, the better the protection effect of the coating on the metal surface is. The nyquist plot obtained by electrochemical EIS testing after 1 month immersion in 3.5wt% sodium chloride solution is shown in fig. 2, which shows that the coating still exhibits a resistance value on the order of e+9 after 1 month immersion, and examples 2, 3, 4 are significantly stronger than comparative example 1, i.e. demonstrate the effectiveness of the present invention.
2. Thermal mechanical Properties
The coating film was cut into a 20 mm x 10 mm rectangle by dynamic thermo-mechanical analysis at-30 to 170℃and at a heating rate of 5℃per minute to give the storage modulus (E') and tan delta values of the heat cured film. The storage modulus plot in FIG. 3 shows that both the comparative example and the example show a "Z" shape with a distinct glassy to rubbery transition region and a tan delta peak temperature representing the glass transition temperature of the cured coating film. The amount of the added particles can influence the crosslinking density of the system by calculating the formula of the crosslinking density, namely the modified graphene participates in the curing reaction, and stable dispersibility is realized in the system by chemical crosslinking, which is consistent with the expected result.
3. Antibacterial property
The staphylococcus aureus ATCC29213 and the escherichia coli ATCC25922 are used as indication strains, the coating liquid is added into the solid beef extract peptone culture medium, as shown in figure 4, no strain grows on the surface of the solid beef extract peptone culture medium after the solid beef extract peptone culture medium is cultured for 3 days after the solid beef extract peptone culture medium is coated with the coating liquid, and the freshness of the solid beef extract peptone culture medium during the storage period of the solid beef extract peptone culture medium is ensured.
4. Water barrier property
The preheated coating of example 3 was dipped with a brush and brushed on the surface of the paper boat, and after 7 hours of heat curing (curing conditions are the same as in example 3), the paper boat model with the coating was obtained by natural cooling. The effect of soaking a paper boat model with or without a coating in water is shown in fig. 5, which shows that the paper boat after the coating prepared in example 3 is applied can remain floating on the water surface for half a month to longer, and the uncoated paper boat has absorbed water and settled within 1 day.
5. Degradability of
The coating pieces cut in comparative example 1, example 3 and example 4 are immersed in 10% hydrochloric acid and sodium hydroxide solution for 3 days respectively, as shown in fig. 6, the coating pieces in the hydrochloric acid solution are intact, the coating pieces in the sodium hydroxide solution are obviously degraded, and when the coating is damaged or reaches the use time limit, the coating can be updated by brushing alkali liquor, so that the characteristic of easy degradation and update is reflected.
6. Structural characterization
FIG. 7 is a graph showing the viscosity of various coating liquids as a function of shear rate. Comparative example 2 showed shear thinning at a shear rate of around 100 revolutions, due to rearrangement of particles with high speed movement, indicating that graphene oxide was physically dispersed in the coating, whereas examples 2, 3, 4 began to decrease in viscosity at a shear rate of around 1000 revolutions, consistent with comparative example 1 where no particles were added, indicating that the modified graphene was stable chemical cross-linking in the coating.
Fig. 8 is an infrared characterization diagram of graphene particles before and after modification in example 1. In the figure, the appearance of an amide bond peak proves that histidine is successfully grafted on the surface of the graphene oxide, and the shrinkage or even disappearance of an oxygen-containing group peak proves that the modified graphene oxide is successfully reduced.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (10)
1. The modified graphene doped bio-based epoxy-phenol system resin anticorrosive paint is characterized by comprising the following raw materials in percentage by mass: 65% -85% of epoxy vegetable oil, 15% -35% of natural polyphenol and 0.025% -0.4% of modified graphene, wherein the modified graphene is histidine grafted acid reduced graphene oxide; the sum of the mass percentages of the raw materials is 100%;
the modified graphene is prepared by the following method:
(1) Dispersing graphene oxide in a solvent, adding 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride, and fully stirring and uniformly mixing to prepare uniform suspension;
(2) Dissolving histidine in a solvent, wherein the solvent is the same as that in the step (1), and then fully mixing the histidine with the suspension in the step (1), and stirring the mixture at room temperature for reaction;
(3) Adjusting the pH value of the mixed solution obtained in the step (2) to 8-10, adding a reducing agent into the mixed solution, heating and stirring the mixed solution to react, and purifying the mixed solution after the reaction is finished to obtain modified graphene;
the graphene oxide in the step (1) is prepared by improving the Hummers method, and the specific preparation process is as follows: adding 1 part by mass of sodium nitrate into 40-50 parts by volume of concentrated sulfuric acid to react with 2 parts by mass of graphite powder, stirring for 20-50 minutes under ice bath condition, adding 5-10 parts by mass of potassium permanganate for a small amount for multiple times within 1 hour, carrying out ice bath reaction for 2 hours, heating to 25-40 ℃ to react for 30 minutes, dropwise adding 50-70 parts by volume of water, stirring for 30 minutes in 98 ℃ by oil bath, adding 70-160 parts by volume of 60 ℃ warm water at room temperature for 1 hour, adding 7-10 parts by volume of 30% hydrogen peroxide, standing overnight, discarding supernatant, centrifuging for 5-15 minutes at 10000 revolutions, washing for 3 times by 5% hydrochloric acid, washing for 3 times by deionized water, and obtaining self-made graphene oxide after freeze drying, wherein when 1 part by volume is 1 milliliter, the corresponding 1 part by mass is 1 gram.
2. The modified graphene-doped biobased epoxy-phenol system resin anticorrosive paint according to claim 1, characterized in that:
the epoxy vegetable oil is at least one of epoxy soybean oil, epoxy castor oil, epoxy linseed oil and epoxy tung oil;
the natural polyphenol is at least one of tannic acid, quercetin, urushiol and gallic acid.
3. The modified graphene-doped biobased epoxy-phenol system resin anticorrosive paint according to claim 1, characterized in that:
the mass ratio of raw materials graphene oxide, 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride, histidine and reducing agent used in the steps (1) - (3) is 3:1:1:20-5:1:1:60.
4. The modified graphene-doped biobased epoxy-phenol system resin anticorrosive paint according to claim 1, characterized in that:
the solvent in the step (1) is one of N, N-dimethylformamide, N-dimethylacetamide, N-dimethylpropionamide, N-diethylformamide and N, N-diethylacetamide.
5. The modified graphene-doped biobased epoxy-phenol system resin anticorrosive paint according to claim 1, characterized in that:
the stirring reaction time at room temperature in the step (2) is more than 24 hours;
the reaction is carried out by heating and stirring in the step (3) and is carried out by heating to 60-80 ℃ and stirring for 5-8 hours.
6. The modified graphene-doped biobased epoxy-phenol system resin anticorrosive paint according to claim 1, characterized in that:
the reducing agent in the step (3) is a natural bio-based reducing agent.
7. The modified graphene-doped biobased epoxy-phenol system resin anticorrosive paint according to claim 6, characterized in that:
the reducing agent in the step (3) is at least one of tannic acid, ascorbic acid, glutathione, gallic acid and chitosan.
8. A method for preparing the modified graphene-doped biobased epoxy-phenol system resin anticorrosive paint according to any one of claims 1 to 7, characterized by comprising the following steps: respectively dissolving epoxy vegetable oil and natural polyphenol in absolute ethyl alcohol according to formula amount by adopting a solvent blending method, and then uniformly mixing and stirring the two solutions to obtain a solution 1; and (3) weighing the formula amount of modified graphene, dispersing the modified graphene in absolute ethyl alcohol, carrying out ultrasonic preparation on the modified graphene to prepare nano particles, mixing the nano particles with the solution 1, stirring and uniformly mixing the nano particles, and carrying out rotary evaporation to remove the ethanol to obtain the coating liquid doped with the modified graphene.
9. Use of the modified graphene-doped biobased epoxy-phenol system resin anticorrosive paint according to any one of claims 1-7 in rust protection of metal instruments, wood antibiosis and waterproof toughening of paper models.
10. A method of using the modified graphene-doped biobased epoxy-phenol system resin anticorrosive paint according to any one of claims 1 to 7, characterized by comprising the steps of:
preheating the coating liquid to reduce the viscosity, coating the coating liquid on a metal substrate by using a coating machine, drying in vacuum to remove bubbles, and keeping the vacuum condition for pre-curing for 2 hours at 120-150 ℃ and post-curing for 5 hours at 180-200 ℃ to obtain the epoxy resin anti-corrosion coating.
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