Graphene-based anticorrosive paint and preparation method thereof

Abstract

The invention discloses a graphene-based anticorrosive coating and a preparation method thereof, and relates to the technical field of coatings. When the graphene-based anti-corrosion coating is prepared, dimethyl dimethoxy silane, functionalized dimethoxy siloxane and 3-aminopropyl dimethoxy methylsilane are subjected to a reaction, and a functionalized siloxane oligomer is prepared; castor oil and epoxy chloropropane are subjected to a reaction, and modified castor oil is prepared; the preparation method comprises the following steps: carrying out hydrothermal reaction on graphene oxide and cerous nitrate to prepare pre-modified graphene; reacting sodium lignin sulfonate, formaldehyde and tetraethylenepentamine, and coating the pre-modified graphene with the sodium lignin sulfonate, the formaldehyde and the tetraethylenepentamine to prepare modified graphene; and uniformly mixing epoxy resin, the modified castor oil, the functionalized siloxane oligomer, the modified graphene, isophorone diamine and acetone to prepare the graphene-based anticorrosive coating. The graphene-based anticorrosive paint prepared by the invention has excellent flame retardance, corrosion resistance and self-repairing performance.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically to a graphene-based anti-corrosion coating and a preparation method thereof. Background Art

[0002] Corrosion, as a common phenomenon, widely exists in industrial production and daily life, involving many fields such as infrastructure transportation, energy equipment, manufacturing, and public utilities. The economic losses caused by corrosion every year are extremely huge, and the problems caused by metal corrosion cannot be underestimated. Metal corrosion refers to the phenomenon that metal materials are damaged by chemical or electrochemical reactions with the surrounding media (seawater, atmosphere, acids, alkalis, etc.) under physical, mechanical, or biological factors. Currently, there are mainly four common metal anti-corrosion technologies, namely designing corrosion-resistant alloys, electrochemical protection, inhibitor protection, and organic coating protection. Among them, the organic coating technology has been widely used in the anti-corrosion field due to its characteristics such as simple preparation, low cost, and outstanding effects.

[0003] However, during the curing and use processes of organic coatings, defects such as micropores and cracks are likely to occur. Corrosive media such as H2O, O2, and Cl - penetrate through the defects to the metal substrate, accelerating the corrosion of the damaged parts, thus greatly shortening the service life of the coating. Therefore, the development of self-healing anti-corrosion coating technology is particularly important. After the surface of the coating is damaged, the damaged part can achieve self-repair through physical or chemical changes, extending the service life of the coating and greatly reducing the cost of metal anti-corrosion. Summary of the Invention

[0004] The purpose of the present invention is to provide a graphene-based anti-corrosion coating and a preparation method thereof to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A graphene-based anti-corrosion coating is prepared by reacting dimethyldimethoxysilane, functionalized dimethoxysiloxane, and 3-aminopropyldimethoxymethylsilane to obtain a functionalized siloxane oligomer; reacting sodium lignosulfonate, formaldehyde, and tetraethylenepentamine and coating them on pre-modified graphene to obtain modified graphene; and uniformly mixing epoxy resin, modified castor oil, functionalized siloxane oligomer, modified graphene, isophorone diamine, and acetone.

[0007] The functionalized dimethoxysiloxane is prepared by reacting 3-glycidoxypropyl dimethoxymethylsilane and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxide.

[0008] The modified castor oil is prepared by reacting castor oil and epichlorohydrin.

[0009] The pre-modified graphene is prepared by hydrothermal reaction of graphene oxide and cerium nitrate.

[0010] A preparation method of a graphene-based anti-corrosion coating, the preparation method of the graphene-based anti-corrosion coating comprising the following preparation steps:

[0011] (1) Mix dimethyldimethoxysilane, functionalized dimethoxysiloxane, and 3-aminopropyldimethoxymethylsilane evenly according to a molar ratio of 1:(0.5 - 0.6):(0.3 - 0.4), then add barium hydroxide in an amount of 0.03 - 0.05 times the mass of dimethyldimethoxysilane, and under nitrogen protection, stir and react at 78 - 82 °C and 200 - 300 r / min for 5 - 6 h, and under vacuum conditions, dry at 56 - 60 °C for 4 - 6 h to obtain a functionalized siloxane oligomer;

[0012] (2) Mix castor oil, epichlorohydrin, and toluene evenly, stir at 30 - 40 °C and 200 - 300 r / min for 20 - 30 min, add triethylamine in an amount of 0.03 - 0.05 times the mass of castor oil, raise the temperature to 55 - 65 °C, continue to stir for 3 - 4 h, wash with a mixture of toluene and deionized water in equal volume for 3 - 5 times, take the organic phase, place it in a drying oven, and dry at 50 - 60 °C for 7 - 8 h under vacuum conditions to obtain modified castor oil;

[0013] (3) Mix pre-modified graphene, sodium lignosulfonate, and deionized water evenly, add tetraethylenepentamine in an amount of 2 - 2.2 times the mass of sodium lignosulfonate, add an aqueous formaldehyde solution in an amount of 0.8 - 1 times the mass of sodium lignosulfonate, stir and react at 88 - 92 °C and 200 - 300 r / min for 7 - 8 h, filter, wash with anhydrous ethanol and deionized water 3 - 5 times each, and dry at 60 - 70 °C for 8 - 9 h under vacuum conditions to obtain modified graphene;

[0014] (4) Weigh 24 - 26 parts of epoxy resin, 18 - 20 parts of modified castor oil, 10 - 12 parts of functionalized siloxane oligomer, 2 - 3 parts of modified graphene, 6 - 8 parts of isophorone diamine, and 20 - 22 parts of acetone by mass; mix epoxy resin, modified castor oil, functionalized siloxane oligomer, modified graphene, isophorone diamine, and acetone evenly to obtain a graphene-based anti-corrosion coating.

[0015] As an optimization, the preparation method of the functionalized dimethoxysiloxane in step (1) is as follows: Add 3-glycidoxypropyl dimethoxymethylsilane and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxide in a molar ratio of 1:1 to tetrahydrofuran which is 8 to 10 times the mass of 3-glycidoxypropyl dimethoxymethylsilane. Stir and react at 58 to 62 °C and 200 to 300 r / min for 3 to 4 h, and under vacuum conditions, dry at 58 to 62 °C for 7 to 8 h to obtain the functionalized dimethoxysiloxane.

[0016] As an optimization, the mass ratio of the castor oil, epichlorohydrin, and toluene in step (2) is 1:(0.4 to 0.6):(8 to 10).

[0017] As an optimization, the preparation method of the pre-modified graphene in step (3) is as follows: Mix cerium nitrate, polyvinylpyrrolidone, deionized water, and absolute ethanol evenly, stir at 10 to 30 °C and 200 to 300 r / min for 50 to 60 min, add graphene oxide which is 4 to 5 times the mass of cerium nitrate, continue to stir for 2 to 3 h, place it in a high-pressure reactor, stir and react at 118 to 122 °C and 200 to 300 r / min for 22 to 24 h, filter, wash 3 to 5 times each with absolute ethanol and deionized water, and under vacuum conditions, dry at 70 to 80 °C for 8 to 9 h to obtain the pre-modified graphene.

[0018] As an optimization, the model of the polyvinylpyrrolidone is PVP-K30.

[0019] As an optimization, the mass ratio of the cerium nitrate, polyvinylpyrrolidone, deionized water, and absolute ethanol is 1:(1.2 to 1.4):(90 to 100):(260 to 280).

[0020] As an optimization, the mass ratio of the pre-modified graphene, sodium lignosulfonate, and deionized water in step (3) is 1:(3 to 4):(200 to 220).

[0021] As an optimization, the mass fraction of the formaldehyde aqueous solution in step (3) is 37%.

[0022] As an optimization, the model of the epoxy resin in step (4) is E51.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0024] When preparing the graphene-based anticorrosive coating of the present invention, 3-glycidoxypropyl dimethoxymethylsilane and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxide are reacted to obtain functionalized dimethoxysiloxane; dimethyldimethoxysilane, functionalized dimethoxysiloxane, and 3-aminopropyldimethoxymethylsilane are reacted to obtain functionalized siloxane oligomer; castor oil and epichlorohydrin are reacted to obtain modified castor oil; graphene oxide and cerium nitrate are hydrothermally reacted to obtain pre-modified graphene; sodium lignosulfonate, formaldehyde, and tetraethylenepentamine are reacted and coated on the pre-modified graphene to obtain modified graphene; epoxy resin, modified castor oil, functionalized siloxane oligomer, modified graphene, isophorone diamine, and acetone are mixed evenly to obtain the graphene-based anticorrosive coating.

[0025] First, 3-glycidoxypropyl dimethoxymethylsilane and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxide are reacted to obtain functionalized dimethoxysiloxane; dimethyldimethoxysilane, functionalized dimethoxysiloxane, and 3-aminopropyldimethoxymethylsilane are reacted to obtain functionalized siloxane oligomer; amino groups and nitroxyl radicals are introduced on the side chains of the functionalized siloxane oligomer molecules, and the nitroxyl radicals react with the carbon-carbon double bonds on the modified castor oil to form alkoxyamine bonds; the alkoxyamine bond is a thermally reversible bond, which can be broken again at high temperature to generate growing chain active radicals and nitroxyl stable radicals. When the system temperature returns to room temperature, the growing chain active radicals and nitroxyl stable radicals combine to form alkoxyamine bonds again. Introducing this kind of alkoxyamine bond with thermally reversible reaction characteristics into the graphene-based anticorrosive coating can, after the coating is damaged, break and recombine the alkoxyamine bonds by heating, realize the repair of the graphene-based anticorrosive coating, and endow the graphene-based anticorrosive coating with self-healing performance. The reaction mechanism is as follows:

[0026] The amino groups introduced on the siloxane oligomer can react with epoxy groups, participate in the curing process of the coating, introduce Si-O-Si in the coating, and improve the flame retardant performance of the graphene-based anticorrosive coating.

[0027] Secondly, modified castor oil is prepared by reacting castor oil with epichlorohydrin; epoxy groups are introduced onto the modified castor oil, enabling the modified castor oil to participate in the curing process of the coating. The carbon-carbon double bonds on the castor oil can react with the nitroxyl radicals on the functionalized siloxane oligomer to form alkoxyamine bonds. Alkoxyamine bonds are thermally reversible bonds that can break again at high temperatures to generate growing chain active radicals and nitroxyl stable radicals. When the system temperature returns to room temperature, the growing chain active radicals and nitroxyl stable radicals combine to form alkoxyamine bonds again. Introducing such alkoxyamine bonds with thermally reversible reaction characteristics into the graphene-based anti-corrosion coating can, after the coating is damaged, break and reorganize the alkoxyamine bonds by heating, achieving the repair of the graphene-based anti-corrosion coating and endowing the graphene-based anti-corrosion coating with self-healing properties.

[0028] Finally, pre-modified graphene is prepared by hydrothermal reaction of graphene oxide with cerium nitrate, and cerium oxide is loaded onto the pre-modified graphene. When the corrosive medium penetrates into the coating, the free cerium ions generated by cerium oxide combine with OH - to form insoluble oxides and deposit on the metal surface, hindering the redox reaction in the precipitation area and inhibiting the cathodic reaction rate, thereby improving the corrosion resistance of the coating; lignosulfonate, formaldehyde, and tetraethylenepentamine are reacted and coated onto the pre-modified graphene to obtain modified graphene; the sulfonyl groups and phenolic hydroxyl groups contained in lignosulfonate, as well as the amino groups contained in tetraethylenepentamine, can complex with the surface of the metal substrate, enhancing the adhesion between the coating and the metal substrate, and playing a good barrier and anti-corrosion role. Specific embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] The epoxy resin used in the examples and comparative examples is of the E51 type.

[0031] Example 1:

[0032] A preparation method of a graphene-based anti-corrosion coating, the preparation method of the graphene-based anti-corrosion coating includes the following preparation steps:

[0033] (1) 3-Glycidoxypropyl dimethoxymethylsilane and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxide were added to tetrahydrofuran which was 8 times the mass of 3-glycidoxypropyl dimethoxymethylsilane at a molar ratio of 1:1, and stirred at 58 °C and 200 r / min for 4 h. Under vacuum conditions, it was dried at 58 °C for 8 h to obtain functionalized dimethoxysiloxane; Dimethyldimethoxysilane, functionalized dimethoxysiloxane, and 3-aminopropyldimethoxymethylsilane were mixed evenly at a molar ratio of 1:0.5:0.3, and then barium hydroxide which was 0.03 times the mass of dimethyldimethoxysilane was added. Under nitrogen protection, it was stirred at 78 °C and 200 r / min for 6 h. Under vacuum conditions, it was dried at 56 °C for 6 h to obtain functionalized siloxane oligomer;

[0034] (2) Castor oil, epichlorohydrin, and toluene were mixed evenly at a mass ratio of 1:0.4:8, stirred at 30 °C and 200 r / min for 30 min, triethylamine which was 0.03 times the mass of castor oil was added, heated to 55 °C, and continued to stir for 4 h. It was washed 3 times with a mixture of toluene and deionized water in equal volume. The organic phase was taken and placed in a drying oven, and dried at 50 °C under vacuum conditions for 8 h to obtain modified castor oil;

[0035] (3) Cerium nitrate, polyvinylpyrrolidone, deionized water, and absolute ethanol were mixed evenly at a mass ratio of 1:1.2:90:260, stirred at 10 °C and 200 r / min for 60 min, graphene oxide which was 4 times the mass of cerium nitrate was added, and continued to stir for 3 h. It was placed in a high-pressure reactor, stirred at 118 °C and 200 r / min for 24 h, filtered, and washed 3 times with absolute ethanol and deionized water respectively. Under vacuum conditions, it was dried at 70 °C for 9 h to obtain pre-modified graphene; Pre-modified graphene, sodium lignosulfonate, and deionized water were mixed evenly at a mass ratio of 1:3:200, tetraethylenepentamine which was 2 times the mass of sodium lignosulfonate was added, and an aqueous formaldehyde solution with a mass fraction of 37% which was 0.8 times the mass of sodium lignosulfonate was added. It was stirred at 88 °C and 200 r / min for 8 h, filtered, and washed 3 times with absolute ethanol and deionized water respectively. Under vacuum conditions, it was dried at 60 °C for 9 h to obtain modified graphene;

[0036] (4) By mass fraction, 24 parts of epoxy resin, 18 parts of modified castor oil, 10 parts of functionalized siloxane oligomer, 2 parts of modified graphene, 6 parts of isophorone diamine, and 20 parts of acetone were weighed; Epoxy resin, modified castor oil, functionalized siloxane oligomer, modified graphene, isophorone diamine, and acetone were mixed evenly to obtain graphene-based anticorrosive coating.

[0037] Example 2:

[0038] A preparation method of a graphene-based anti-corrosion coating, the preparation method of the graphene-based anti-corrosion coating comprising the following preparation steps:

[0039] (1) 3-Glycidoxypropyl dimethoxymethylsilane and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxide are added to tetrahydrofuran which is 9 times the mass of 3-glycidoxypropyl dimethoxymethylsilane at a molar ratio of 1:1, and stirred and reacted at 60 °C and 250 r / min for 3.5 h. Under vacuum conditions, it is dried at 60 °C for 7.5 h to obtain functionalized dimethoxysiloxane; Dimethyldimethoxysilane, functionalized dimethoxysiloxane, and 3-aminopropyldimethoxymethylsilane are mixed evenly at a molar ratio of 1:0.55:0.35, and then barium hydroxide which is 0.04 times the mass of dimethyldimethoxysilane is added. Under nitrogen protection, it is stirred and reacted at 80 °C and 250 r / min for 5.5 h. Under vacuum conditions, it is dried at 58 °C for 5 h to obtain a functionalized siloxane oligomer;

[0040] (2) Castor oil, epichlorohydrin, and toluene are mixed evenly at a mass ratio of 1:0.5:9, stirred at 35 °C and 250 r / min for 25 min, triethylamine which is 0.04 times the mass of castor oil is added, the temperature is raised to 60 °C, and stirring is continued for 3.5 h. It is washed 4 times with a mixture of toluene and deionized water in equal volume. The organic phase is taken and placed in a drying oven. Under vacuum conditions, it is dried at 55 °C for 7.5 h to obtain modified castor oil;

[0041] (3) Cerium nitrate, polyvinylpyrrolidone, deionized water, and absolute ethanol are mixed evenly at a mass ratio of 1:1.3:95:270, stirred at 20 °C and 250 r / min for 55 min, graphene oxide which is 4.5 times the mass of cerium nitrate is added, and stirring is continued for 2.5 h. It is placed in a high-pressure reaction kettle and stirred and reacted at 120 °C and 250 r / min for 23 h. It is filtered and washed 4 times with absolute ethanol and deionized water respectively. Under vacuum conditions, it is dried at 75 °C for 8.5 h to obtain pre-modified graphene; The pre-modified graphene, sodium lignosulfonate, and deionized water are mixed evenly at a mass ratio of 1:3.5:210, tetraethylenepentamine which is 2.1 times the mass of sodium lignosulfonate is added, and an aqueous formaldehyde solution with a mass fraction of 37% which is 0.9 times the mass of sodium lignosulfonate is added. It is stirred and reacted at 90 °C and 250 r / min for 7.5 h. It is filtered and washed 4 times with absolute ethanol and deionized water respectively. Under vacuum conditions, it is dried at 65 °C for 8.5 h to obtain modified graphene;

[0042] (4) By mass parts, weigh 25 parts of epoxy resin, 19 parts of modified castor oil, 11 parts of functionalized siloxane oligomer, 2.5 parts of modified graphene, 7 parts of isophorone diamine, and 21 parts of acetone; mix epoxy resin, modified castor oil, functionalized siloxane oligomer, modified graphene, isophorone diamine, and acetone evenly to obtain graphene-based anti-corrosion coating.

[0043] Example 3:

[0044] A preparation method of graphene-based anti-corrosion coating, the preparation method of the graphene-based anti-corrosion coating includes the following preparation steps:

[0045] (1) Add 3-glycidoxypropyl dimethoxymethylsilane and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxide in a molar ratio of 1:1 to tetrahydrofuran which is 10 times the mass of 3-glycidoxypropyl dimethoxymethylsilane, stir and react at 62 °C and 300 r / min for 3 h, and dry at 62 °C for 7 h under vacuum conditions to obtain functionalized dimethoxysilane; mix dimethyldimethoxysilane, functionalized dimethoxysilane, and 3-aminopropyldimethoxymethylsilane evenly in a molar ratio of 1:0.6:0.4, then add barium hydroxide which is 0.05 times the mass of dimethyldimethoxysilane, stir and react at 82 °C and 300 r / min for 5 h under nitrogen protection, and dry at 60 °C for 4 h under vacuum conditions to obtain functionalized siloxane oligomer;

[0046] (2) Mix castor oil, epichlorohydrin, and toluene evenly in a mass ratio of 1:0.6:10, stir at 40 °C and 300 r / min for 20 min, add triethylamine which is 0.05 times the mass of castor oil, raise the temperature to 65 °C, continue to stir for 3 h, wash 5 times with a mixture of toluene and deionized water in equal volume, take the organic phase, place it in an oven, and dry at 60 °C for 7 h under vacuum conditions to obtain modified castor oil;

[0047] (3) Mix cerium nitrate, polyvinylpyrrolidone, deionized water, and absolute ethanol evenly at a mass ratio of 1:1.4:100:280, stir at 30 °C and 300 r / min for 50 min, add graphene oxide five times the mass of cerium nitrate, continue stirring for 2 h, place it in a high-pressure reactor, stir and react at 122 °C and 300 r / min for 22 h, filter, wash five times with absolute ethanol and deionized water respectively, and dry at 80 °C for 8 h under vacuum conditions to obtain pre-modified graphene; Mix pre-modified graphene, sodium lignosulfonate, and deionized water evenly at a mass ratio of 1:4:220, add tetraethylenepentamine 2.2 times the mass of sodium lignosulfonate, add an aqueous formaldehyde solution with a mass fraction of 37% 1 time the mass of sodium lignosulfonate, stir and react at 92 °C and 300 r / min for 7 h, filter, wash five times with absolute ethanol and deionized water respectively, and dry at 70 °C for 8 h under vacuum conditions to obtain modified graphene;

[0048] (4) By mass, weigh 26 parts of epoxy resin, 20 parts of modified castor oil, 12 parts of functionalized siloxane oligomer, 3 parts of modified graphene, 8 parts of isophorone diamine, and 22 parts of acetone; Mix epoxy resin, modified castor oil, functionalized siloxane oligomer, modified graphene, isophorone diamine, and acetone evenly to obtain a graphene-based anticorrosive coating.

[0049] Comparative Example 1:

[0050] The preparation method of the graphene-based anticorrosive coating in Comparative Example 1 is different from that in Example 2 in step (1). Modify step (1) as follows: Mix dimethyldimethoxysilane and 3-aminopropyldimethoxymethylsilane evenly at a molar ratio of 1.55:0.35, then add barium hydroxide 0.04 times the mass of dimethyldimethoxysilane, stir and react at 80 °C and 250 r / min for 5.5 h under nitrogen protection, and dry at 58 °C for 5 h under vacuum conditions to obtain a functionalized siloxane oligomer. The remaining steps are the same as in Example 2.

[0051] Comparative Example 2:

[0052] The preparation method of the graphene-based anticorrosive coating in Comparative Example 2 is different from that in Example 2 in that step (1) is not carried out. Modify step (4) as follows: By mass, weigh 25 parts of epoxy resin, 19 parts of modified castor oil, 2.5 parts of modified graphene, 18 parts of isophorone diamine, and 21 parts of acetone; Mix epoxy resin, modified castor oil, modified graphene, isophorone diamine, and acetone evenly to obtain a graphene-based anticorrosive coating. The remaining steps are the same as in Example 2.

[0053] Comparative Example 3:

[0054] The preparation method of the graphene-based anti-corrosion coating in Comparative Example 3 is different from that in Example 2 in that step (2) is not carried out, and step (4) is modified as follows: by mass, 44 parts of epoxy resin, 11 parts of functionalized siloxane oligomer, 2.5 parts of modified graphene, 7 parts of isophorone diamine, and 21 parts of acetone are weighed; the epoxy resin, functionalized siloxane oligomer, modified graphene, isophorone diamine, and acetone are mixed evenly to obtain the graphene-based anti-corrosion coating. The remaining steps are the same as those in Example 2.

[0055] Comparative Example 4:

[0056] The preparation method of the graphene-based anti-corrosion coating in Comparative Example 4 is different from that in Example 2 only in step (3), and step (3) is modified as follows: cerium nitrate, polyvinylpyrrolidone, deionized water, and absolute ethanol are mixed evenly according to a mass ratio of 1:1.3:95:270, stirred at 20 °C and 250 r / min for 55 min, graphene oxide 4.5 times the mass of cerium nitrate is added, and stirring is continued for 2.5 h. Then it is placed in a high-pressure reactor, stirred and reacted at 120 °C and 250 r / min for 23 h, filtered, washed 4 times each with absolute ethanol and deionized water, and dried at 75 °C for 8.5 h under vacuum conditions to obtain modified graphene. The remaining steps are the same as those in Example 2.

[0057] Comparative Example 5:

[0058] The preparation method of the graphene-based anti-corrosion coating in Comparative Example 5 is different from that in Example 2 only in step (3), and step (3) is modified as follows: graphene oxide, sodium lignosulfonate, and deionized water are mixed evenly according to a mass ratio of 1:3.5:210, tetraethylenepentamine 2.1 times the mass of sodium lignosulfonate is added, and an aqueous formaldehyde solution with a mass fraction of 37% 0.9 times the mass of sodium lignosulfonate is added. Stirring reaction is carried out at 90 °C and 250 r / min for 7.5 h, filtered, washed 4 times each with absolute ethanol and deionized water, and dried at 65 °C for 8.5 h under vacuum conditions to obtain modified graphene.

[0059] Test Example 1

[0060] Test of self-healing performance

[0061] Test method: Pour the examples and comparative examples into a polytetrafluoroethylene mold, keep warm at 150 °C for 20 min, cool down to 60 °C, keep warm for 30 min, cool down to room temperature, stand for 10 h, demold and take out, prepare standard specimens according to GB / T1040-92, test their tensile strength M, draw a crack with a length of 20 mm and a depth of 3 mm in the middle of the standard specimen, keep warm at 125 °C for 20 min, cool to room temperature, stand for 5 h to obtain the repaired specimen, test its tensile strength N, and calculate the self-healing rate of the examples and comparative examples; self-healing rate = (N / M) × 100%. The results are shown in Table 1.

[0062] Table 1

[0063] Self-repair rate (%) Self-repair rate (%) Example 1 94.67 Comparative Example 1 71.33 Example 2 95.18 Comparative Example 2 70.58 Example 3 95.04 Comparative Example 3 69.24 Comparative Example 4 94.38 Comparative Example 5 94.51

[0064] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-5 in Table 1, it can be found that the graphene-based anti-corrosion coating prepared by the present invention has good self-healing performance.

[0065] By comparison, the self-healing rates of Examples 1-3 are greater than those of Comparative Examples 1-2, indicating that 3-glycidoxypropyl dimethoxymethylsilane and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxide are reacted to prepare functionalized dimethoxysiloxane; dimethyldimethoxysilane, functionalized dimethoxysiloxane, and 3-aminopropyldimethoxymethylsilane are reacted to prepare functionalized siloxane oligomers; nitroxyl radicals are introduced on the side chains of the functionalized siloxane oligomer molecules, and the nitroxyl radicals react with the carbon-carbon double bonds on the modified castor oil to form alkoxyamine bonds; alkoxyamine bonds are a kind of thermally reversible bonds, which can be broken again at high temperature to generate growing chain active radicals and nitroxyl stable radicals. When the system temperature returns to room temperature, the growing chain active radicals and nitroxyl stable radicals combine to form alkoxyamine bonds again. Introducing such alkoxyamine bonds with thermally reversible reaction characteristics into the graphene-based anti-corrosion coating can break and reorganize the alkoxyamine bonds by heating after the coating is damaged, realizing the repair of the graphene-based anti-corrosion coating and endowing the graphene-based anti-corrosion coating with self-healing performance.

[0066] By comparison, the self-healing rates of Examples 1-3 are greater than that of Comparative Example 3, indicating that castor oil and epichlorohydrin are reacted to prepare modified castor oil; epoxy groups are introduced onto the modified castor oil so that the modified castor oil can participate in the curing process of the coating, and the carbon-carbon double bonds on the castor oil can react with the nitroxyl radicals on the functionalized siloxane oligomer to form alkoxyamine bonds. Alkoxyamine bonds are a kind of thermally reversible bonds, which can be broken again at high temperature to generate growing chain active radicals and nitroxyl stable radicals. When the system temperature returns to room temperature, the growing chain active radicals and nitroxyl stable radicals combine to form alkoxyamine bonds again. Introducing such alkoxyamine bonds with thermally reversible reaction characteristics into the graphene-based anti-corrosion coating can break and reorganize the alkoxyamine bonds by heating after the coating is damaged, realizing the repair of the graphene-based anti-corrosion coating and endowing the graphene-based anti-corrosion coating with self-healing performance.

[0067] Test Example 2

[0068] Testing of anti-corrosion performance

[0069] Test method: Test according to the standard of GB / T1771. Evenly coat the examples and comparative examples on the tinplate, keep warm at 150 °C for 20 min, cool down to 60 °C, keep warm for 30 min, cool down to room temperature, stand still for 10 h, start the salt spray test chamber and add an aqueous solution of sodium chloride with a mass fraction of 5% into the chamber. After 24 h, take out the test panel from the salt spray test chamber, wash it with clear water, and check and record the corrosion, rusting and damage conditions. The results are shown in Table 2.

[0070] Table 2

[0071] Neutral salt spray resistance Neutral salt spray resistance Example 1 No abnormality in the paint film Comparative Example 1 No abnormality in the paint film Example 2 No abnormality in the paint film Comparative Example 2 No abnormality in the paint film Example 3 No abnormality in the paint film Comparative Example 3 No abnormality in the paint film Comparative Example 4 Blistering and cracking of the paint film Comparative Example 5 Blistering and cracking of the paint film

[0072] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-5 in Table 2, it can be found that the graphene-based anti-corrosion coating prepared by the present invention has good anti-corrosion performance.

[0073] By comparison, the paint films of Examples 1-3 are intact, while the paint film of Comparative Example 4 shows blistering and cracking phenomena, indicating that lignosulfonate, formaldehyde and tetraethylenepentamine are reacted and coated on pre-modified graphene to obtain modified graphene; the sulfonyl group and phenolic hydroxyl group contained in lignosulfonate, and the amino group contained in tetraethylenepentamine can complex with the surface of the metal substrate, enhance the adhesion ability between the coating and the metal substrate, and play a good barrier and anti-corrosion role.

[0074] By comparison, the paint films of Examples 1-3 are intact, while the paint film of Comparative Example 5 shows blistering and cracking phenomena, indicating that pre-modified graphene is prepared by the hydrothermal reaction of graphene oxide and cerium nitrate, and cerium oxide is loaded on the pre-modified graphene. When the corrosive medium penetrates into the coating, the free cerium ions generated by cerium oxide combine with OH - to form an insoluble oxide and deposit on the metal surface, hindering the redox reaction in the precipitation area and inhibiting the cathodic reaction rate, thereby improving the corrosion resistance of the coating.

[0075] Test Example 3

[0076] Test of flame retardant performance

[0077] Test method: Pour the examples and comparative examples into a polytetrafluoroethylene mold, keep warm at 150 °C for 20 min, cool down to 60 °C, keep warm for 30 min, cool down to room temperature, stand still for 10 h, demold and take out, and prepare the examples and comparative examples into standard specimens according to GB / T2048 to test the limiting oxygen index of the examples and comparative examples. The results are shown in Table 3.

[0078] Table 3

[0079] Limiting oxygen index (%) Limiting oxygen index (%) Example 1 29.89 Comparative Example 1 29.71 Example 2 30.04 Comparative Example 2 23.68 Example 3 29.95 Comparative Example 3 29.47 Comparative Example 4 29.62 Comparative Example 5 29.38

[0080] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 5 in Table 3, it can be found that the graphene-based anti-corrosion coating prepared by the present invention has good flame retardancy performance.

[0081] By comparison, the limiting oxygen index of Examples 1 to 3 is greater than that of Comparative Example 2, indicating that dimethyldimethoxysilane, functionalized dimethoxysiloxane, and 3-aminopropyldimethoxymethylsilane are reacted to prepare a functionalized siloxane oligomer; an amino group is introduced on the side chain of the functionalized siloxane oligomer molecule, and the amino group introduced on the functionalized siloxane oligomer can react with the epoxy group, enabling it to participate in the curing process of the coating, introducing Si-O-Si bonds in the coating, and improving the flame retardancy performance of the graphene-based anti-corrosion coating.

[0082] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and does not limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A graphene-based anticorrosion coating, characterized in that: The graphene-based anticorrosive coating is prepared by reacting dimethyldimethoxysilane, functionalized dimethoxysiloxane, and 3-aminopropyldimethoxymethylsilane to obtain functionalized siloxane oligomers; reacting sodium lignin sulfonate, formaldehyde, and tetraethylenepentamine and coating pre-modified graphene to obtain modified graphene; and uniformly mixing epoxy resin, modified castor oil, functionalized siloxane oligomers, modified graphene, isophoronediamine, and acetone to obtain the coating. The functionalized dimethoxysiloxane is prepared by reacting 3-glycidyloxypropyl dimethoxymethylsilane and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxide; The modified castor oil is prepared by reacting castor oil and epichlorohydrin; The pre-modified graphene is prepared by hydrothermal reaction of graphene oxide and cerium nitrate.

2. A method for preparing a graphene-based anticorrosive coating, characterized in that: The preparation method of the graphene-based anti-corrosion coating comprises the following preparation steps: (1) Dimethyldimethoxysilane, functionalized dimethoxysiloxane, and 3-aminopropyldimethoxymethylsilane are mixed uniformly in a molar ratio of 1:(0.5-0.6):(0.3-0.4), and then 0.03-0.05 times the mass of dimethyldimethoxysilane is added with barium hydroxide, and the mixture is stirred at 78-82° C. and 200-300 r / min for 5-6 hours under nitrogen protection, and dried at 56-60° C. for 4-6 hours under vacuum conditions to obtain a functionalized siloxane oligomer; (2) Castor oil, epichlorohydrin and toluene are mixed uniformly, stirred at 30-40° C. and 200-300 r / min for 20-30 min, triethylamine in an amount of 0.03-0.05 times the mass of castor oil is added, the temperature is raised to 55-65° C., stirring is continued for 3-4 h, and the mixture is washed 3-5 times with an equal volume of toluene and deionized water, the organic phase is taken, placed in a drying oven, and dried at 50-60° C. under vacuum conditions for 7-8 h to obtain modified castor oil; (3) The pre-modified graphene, sodium lignin sulfonate and deionized water are mixed uniformly, tetraethylene pentamine in an amount of 2 to 2.2 times the mass of the sodium lignin sulfonate is added, and a formaldehyde aqueous solution in an amount of 0.8 to 1 times the mass of the sodium lignin sulfonate is added, and the mixture is stirred at 88 to 92° C. and 200 to 300 r / min for 7 to 8 hours, filtered, washed with anhydrous ethanol and deionized water for 3 to 5 times respectively, and dried at 60 to 70° C. under vacuum conditions for 8 to 9 hours to obtain modified graphene; (4) Weigh 24-26 parts of epoxy resin, 18-20 parts of modified castor oil, 10-12 parts of functionalized siloxane oligomer, 2-3 parts of modified graphene, 6-8 parts of isophorone diamine, and 20-22 parts of acetone by mass; mix the epoxy resin, modified castor oil, functionalized siloxane oligomer, modified graphene, isophorone diamine, and acetone uniformly to prepare a graphene-based anticorrosion coating.

3. The method for preparing a graphene-based anticorrosive coating according to claim 2, characterized in that: The preparation method of the functionalized dimethoxysiloxane in step (1) is as follows: 3-glycidyloxypropyl dimethoxymethylsilane and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxide are added in a molar ratio of 1:1 to tetrahydrofuran (8 to 10 times the mass of 3-glycidyloxypropyl dimethoxymethylsilane), and the mixture is stirred at 58 to 62° C. and 200 to 300 r / min for 3 to 4 hours, and dried at 58 to 62° C. under vacuum conditions for 7 to 8 hours to obtain the functionalized dimethoxysiloxane.

4. The method for preparing a graphene-based anticorrosive coating according to claim 2, characterized in that: The mass ratio of castor oil, epichlorohydrin and toluene in step (2) is 1:(0.4-0.6):(8-10).

5. The method for preparing a graphene-based anticorrosive coating according to claim 2, characterized in that: The preparation method of the pre-modified graphene in step (3) is as follows: cerium nitrate, polyvinyl pyrrolidone, deionized water and anhydrous ethanol are uniformly mixed, stirred at 10-30° C. and 200-300 r / min for 50-60 min, graphene oxide with a mass of 4-5 times that of cerium nitrate is added, stirring is continued for 2-3 h, placed in a high-pressure reactor, stirred at 118-122° C. and 200-300 r / min for 22-24 h, filtered, washed with anhydrous ethanol and deionized water for 3-5 times respectively, and dried at 70-80° C. under vacuum conditions for 8-9 h to obtain pre-modified graphene.

6. The method for preparing a graphene-based anticorrosive coating according to claim 5, characterized in that The model of the polyvinyl pyrrolidone is PVP-K30.

7. The method for preparing a graphene-based anticorrosive coating according to claim 5, characterized in that: The mass ratio of the cerium nitrate, polyvinyl pyrrolidone, deionized water and anhydrous ethanol is 1:(1.2-1.4):(90-100):(260-280).

8. The method for preparing a graphene-based anticorrosive coating according to claim 2, characterized in that: The mass ratio of the pre-modified graphene, sodium lignin sulfonate and deionized water in step (3) is 1:(3-4):(200-220).

9. The method for preparing a graphene-based anticorrosive coating according to claim 2, characterized in that: The mass fraction of the formaldehyde aqueous solution in step (3) is 37%.

10. The method for preparing a graphene-based anticorrosive coating according to claim 2, characterized in that: The model of the epoxy resin in step (4) is E51.

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