阅读说明：本技术 一种芳香二胺改性氧化石墨烯环氧树脂涂料的制备方法 (Preparation method of aromatic diamine modified graphene oxide epoxy resin coating ) 是由 瞿建刚 刘薇薇 李瑶 陈豪杰 曹力文 赵颖 于 2021-09-30 设计创作，主要内容包括：本发明提供了一种芳香二胺改性氧化石墨烯环氧树脂涂料的制备方法,属于金属表面防腐技术领域。其技术方案为：包括以下步骤：步骤一、芳香二胺改性氧化石墨烯粉末的制备；步骤二、复合环氧涂料的制备。本发明的有益效果为：本发明该方法工艺简单,制备的涂料耐腐蚀性大大提高,同时涂料整体的硬度、附着力和柔韧性都有所提升。(The invention provides a preparation method of an aromatic diamine modified graphene oxide epoxy resin coating, and belongs to the technical field of metal surface corrosion prevention. The technical scheme is as follows: the method comprises the following steps: step one, preparing aromatic diamine modified graphene oxide powder; and step two, preparing the composite epoxy coating. The invention has the beneficial effects that: the method has simple process, the corrosion resistance of the prepared coating is greatly improved, and the integral hardness, adhesive force and flexibility of the coating are improved.)

1. The preparation method of the aromatic diamine modified graphene oxide epoxy resin coating is characterized by comprising the following steps:

step one, preparing aromatic diamine modified graphene oxide powder: preparing small-piece graphene oxide by an improved Hummers method, preparing 1-5 mg/mL graphene oxide aqueous dispersion, adding aromatic diamine into the graphene oxide aqueous dispersion, adjusting the pH value of the solution to 10-11, reacting for 5-6 h at 70-80 ℃, washing a reaction product for multiple times by deionized water after the reaction is finished until colorless transparent residual liquid is obtained, finally, ultrasonically dispersing the product uniformly, and performing vacuum freeze drying to obtain aromatic diamine modified graphene oxide powder;

step two, preparing the composite epoxy coating: weighing aromatic diamine modified graphene oxide powder, ultrasonically dispersing the aromatic diamine modified graphene oxide powder in deionized water to obtain an aromatic diamine modified graphene oxide aqueous dispersion, and mixing an emulsion, the aromatic diamine modified graphene oxide aqueous dispersion and color paste according to a mass ratio of 6: 10: 1, mixing, and mechanically stirring for 24 hours to obtain an aromatic diamine modified graphene oxide epoxy resin coating;

in the first step, the improved Hummers method is that under the ice bath condition, 6g of graphite is added into a beaker containing 500mL of concentrated sulfuric acid, 30g of potassium permanganate is slowly added under magnetic stirring, after stirring in the ice bath for 6 hours, stirring is continuously carried out for 48 hours at normal temperature, 500mL of deionized water is slowly added under the ice bath condition, after stirring is carried out for 24 hours, 50mL of hydrogen peroxide is added, when the reaction solution becomes bright yellow, 50mL of 5% hydrochloric acid solution is added, and finally, deionized water is used for multiple times for washing until the pH value of the suspension is neutral, and then, the suspension is frozen and dried.

2. The method for preparing an aromatic diamine-modified graphene oxide epoxy resin coating according to claim 1, wherein in the first step, the size of the platelet graphene oxide is less than 5 μm.

3. The method for preparing an aromatic diamine-modified graphene oxide epoxy resin coating according to claim 1, wherein in the first step, the aromatic diamine is one of p-phenylenediamine, o-phenylenediamine and m-phenylenediamine.

4. The method for preparing the aromatic diamine-modified graphene oxide epoxy resin coating according to claim 1, wherein in the first step, the mass ratio of the graphene oxide to the aromatic diamine is 1: 2-1: 6.

5. the method for preparing the aromatic diamine modified graphene oxide epoxy resin coating according to claim 1, wherein in the first step, NH is selected when the pH value of the solution is adjusted₃·H₂Adjusting the pH value of the mixture to 10-11.

6. The method of preparing an aromatic diamine-modified graphene oxide epoxy resin coating according to claim 1, wherein in the second step, the mass of the aromatic diamine-modified graphene oxide in the aqueous dispersion of aromatic diamine-modified graphene oxide accounts for 0.1 to 0.2 wt% of the aromatic diamine-modified graphene oxide epoxy resin coating.

7. The method for preparing the aromatic diamine modified graphene oxide epoxy resin coating according to claim 1, wherein in the second step, the emulsion has a solid content of 35%, and the emulsion comprises the following components in percentage by mass:

8. the preparation method of the aromatic diamine modified graphene oxide epoxy resin coating according to claim 1, wherein in the second step, the color paste solid content is 44%, and the color paste formula comprises the following components in percentage by mass:

Technical Field

The invention relates to the technical field of metal surface corrosion prevention, in particular to a preparation method of an aromatic diamine modified graphene oxide epoxy resin coating.

Background

The economic loss caused by metal corrosion accounts for about 3% -5% of global GDP every year, and meanwhile, the metal corrosion can reduce the mechanical properties such as strength, plasticity, toughness and the like of the material, further destroy the geometric shape and even cause catastrophic damage to an engineering structure. Therefore, the improvement of the corrosion resistance of the metal material is an important work to be solved urgently.

The organic coating can be used as a barrier coating to reduce the contact between the metal substrate and corrosive substances. At present, the organic coating is in a wide variety, such as epoxy resin, polyurethane, polyphenylene sulfide, chlorinated polyether resin and the like. Among them, epoxy resins are widely used because of their high adhesion, thermal stability, mechanical properties and chemical resistance. In addition, most of the existing epoxy resins adopt safe, low-cost and environment-friendly water as a solvent, so that the cost is reduced, and the harm of a large amount of volatile organic compounds to human and the environment is avoided. However, the conventional coating cannot meet the corrosion prevention requirement of the current market because the epoxy coating contains pores and holes and is exposed to corrosive media for a long time, so that the corrosion prevention durability of the coating is reduced.

The graphene oxide has the advantages of chemical inertia, oxidation resistance, mechanical strength and the like, and has wide application prospect in the field of anticorrosive coatings. Patent 202110479814.8 discloses a graphene-based marine anticorrosive coating and a preparation method thereof, wherein the graphene-based filler is one or more of single-layer graphene, multi-layer graphene and graphene oxide, and the specific surface area and interlayer van der waals force of the graphene-based filler are large, which easily causes partial agglomeration in the coating, and cannot block holes in the coating, thereby failing to achieve the expected anticorrosive effect.

The surface of the graphene oxide contains a large number of oxygen-containing functional groups such as hydroxyl, epoxy, carboxyl and the like, and the functional groups can be used as active sites, so that various possibilities are provided for modification of the graphene oxide. After the graphene oxide is modified, the graphene oxide is dispersed into the epoxy coating, so that on one hand, a corrosive medium can be blocked to a certain extent, and on the other hand, the path through which the corrosive medium passes can be prolonged, and the corrosion resistance of the coating is improved. Patent numbers: 202110017159.4 discloses a preparation method of polyaniline modified graphene oxide/hydroxylated boron nitride composite epoxy coating, but nitrogen protection is needed in the synthesis step, and the preparation cost is high. Patent numbers: 202110462208.5 discloses a functional nano zinc oxide/graphene reinforced waterborne epoxy resin composite coating, but the synthesis reaction needs to be carried out in 10 wt% ethanol water solution, and the temperature needs to be kept at 70 ℃ for 2h, so that the large-scale production is difficult to realize.

The aromatic diamines are mainly: o-phenylenediamine, m-phenylenediamine and p-phenylenediamine, all of which have benzene rings and diamine structures. Two amine groups on the molecule can be utilized to bond with an epoxy group of the graphene oxide, and the steric hindrance effect can effectively improve the agglomeration problem of the graphene oxide. Patent numbers: 202010834362.6 discloses a method for preparing poly-p-phenylenediamine-graphene modified epoxy resin anticorrosive paint, wherein p-phenylenediamine is attached to the surface of graphene by pi-pi interaction, but the stability of non-covalent bonds is weak, so that the structural stability of non-covalent modified graphene oxide is poor.

How to solve the above technical problems is the subject of the present invention.

Disclosure of Invention

The invention aims to provide a preparation method of an aromatic diamine modified graphene oxide epoxy resin coating, which is simple in process, the corrosion resistance of the prepared coating is greatly improved, and the overall hardness, adhesive force and flexibility of the coating are improved.

In order to achieve the purpose, the invention adopts the following technical scheme: a preparation method of an aromatic diamine modified graphene oxide epoxy resin coating comprises the following steps:

step one, preparing aromatic diamine modified graphene oxide powder: preparing small-piece graphene oxide by an improved Hummers method, preparing 1-5 mg/mL graphene oxide aqueous dispersion, adding aromatic diamine into the graphene oxide aqueous dispersion, adjusting the pH value of the solution to 10-11, reacting for 5-6 h at 70-80 ℃, washing a reaction product for multiple times by deionized water after the reaction is finished until colorless transparent residual liquid is obtained, finally, ultrasonically dispersing the product uniformly, and performing vacuum freeze drying to obtain aromatic diamine modified graphene oxide powder;

step two, preparing the composite epoxy coating: weighing aromatic diamine modified graphene oxide powder, ultrasonically dispersing the aromatic diamine modified graphene oxide powder in deionized water to obtain an aromatic diamine modified graphene oxide aqueous dispersion, and mixing an emulsion, the aromatic diamine modified graphene oxide aqueous dispersion and color paste according to a mass ratio of 6: 10: 1, mixing, and mechanically stirring for 24 hours to obtain an aromatic diamine modified graphene oxide epoxy resin coating;

in the first step, the improved Hummers method is that under the ice bath condition, 6g of graphite is added into a beaker containing 500mL of concentrated sulfuric acid, 30g of potassium permanganate is slowly added under magnetic stirring, after stirring in the ice bath for 6 hours, stirring is continuously carried out for 48 hours at normal temperature, 500mL of deionized water is slowly added under the ice bath condition, after stirring is carried out for 24 hours, 50mL of hydrogen peroxide is added, when the reaction solution becomes bright yellow, 50mL of 5% hydrochloric acid solution is added, and finally, deionized water is used for multiple times for washing until the pH value of the suspension is neutral, and then, the suspension is frozen and dried.

According to a further optimized scheme of the preparation method of the aromatic diamine modified graphene oxide epoxy resin coating, in the first step, the size of the small-piece graphene oxide is less than 5 micrometers.

According to a further optimized scheme of the preparation method of the aromatic diamine modified graphene oxide epoxy resin coating, in the step one, the aromatic diamine is one of p-phenylenediamine, o-phenylenediamine and m-phenylenediamine.

According to a further optimized scheme of the preparation method of the aromatic diamine modified graphene oxide epoxy resin coating, in the first step, the mass ratio of graphene oxide to aromatic diamine is 1: 2-1: 6.

the aromatic diamine modified graphene oxide provided by the inventionIn the first step, NH is selected when the pH value of the solution is adjusted₃·H₂Adjusting the pH value of the mixture to 10-11.

In the second step, in the aqueous dispersion of aromatic diamine-modified graphene oxide, the mass of the aromatic diamine-modified graphene oxide accounts for 0.1-0.2 wt% of the aromatic diamine-modified graphene oxide epoxy resin coating.

In the second step, the emulsion solid content is 35%, and the emulsion comprises the following components in percentage by mass:

in the second step, the color paste solid content is 44%, and the color paste formula comprises the following components in percentage by mass:

compared with the prior art, the invention has the beneficial effects that:

(1) the aromatic diamine modified graphene oxide epoxy resin coating prepared by the method disclosed by the invention has corrosion resistance, and the overall hardness, adhesive force and flexibility of the coating are improved.

(2) Compared with the prior patent, the method fully utilizes the advantages of chemical inertness, impermeability and the like of graphene oxide, solves the problem of agglomeration of graphene oxide in the epoxy coating, and utilizes two amino groups in aromatic diamine to carry out covalent modification on graphene oxide, so that the aromatic diamine modified graphene oxide can be uniformly dispersed in epoxy resin.

(3) The method does not increase equipment in the preparation of the coating, has low cost, and only needs aromatic diamine, graphene oxide and NH in the process of preparing the aromatic diamine modified graphene oxide₃·H₂And O, the experimental operation is simple, and the industrial production is convenient.

Drawings

FIG. 1 is an SEM image of a paint film prepared from the 0.15 wt% p-phenylenediamine-modified graphene oxide epoxy resin coating.

FIG. 2 is an SEM image of a paint film prepared from the 0.2 wt% o-phenylenediamine-modified graphene oxide epoxy resin coating.

FIG. 3 is an SEM image of a paint film prepared from the 0.16 wt% m-phenylenediamine-modified graphene oxide epoxy resin coating of the present invention.

FIG. 4 is an SEM image of a paint film prepared from the epoxy resin coating of the present invention.

Detailed Description

The following examples further illustrate the present invention but are not to be construed as limiting the invention. Modifications or substitutions to methods, procedures, or conditions of the invention may be made without departing from the spirit and scope of the invention. The experimental methods and reagents of the formulations not specified in the examples are in accordance with the conventional conditions in the art.

Example 1

Referring to fig. 1 to 4, the present invention provides a technical solution for preparing p-phenylenediamine-modified graphene oxide powder: preparing small-piece graphene oxide by an improved Hummers method, and preparing 1mg/mL graphene oxide aqueous dispersion. 1.014g of p-phenylenediamine was added to 200mL of an aqueous graphene oxide dispersion, the pH of the solution was adjusted to 11, and the reaction was carried out at 70 ℃ for 6 hours. After the reaction is finished, washing the reaction product for many times by deionized water until colorless transparent residual liquid is obtained. And finally, ultrasonically dispersing the product uniformly, and carrying out vacuum freeze drying to obtain the p-phenylenediamine modified graphene oxide powder.

Preparing the composite epoxy coating: 1.275g of p-phenylenediamine-modified graphene oxide powder was weighed and ultrasonically dispersed in 498.725g of deionized water to obtain an aqueous p-phenylenediamine-modified graphene oxide dispersion. And sequentially mixing 300g of emulsion, 500g of p-phenylenediamine modified graphene oxide aqueous dispersion and 50g of color paste, and mechanically stirring for 24 hours to obtain the p-phenylenediamine modified graphene oxide epoxy resin coating.

Preparation of a paint film: electroplating the composite epoxy resin coating on a silane sample plate under the conditions that the voltage is 190V, the temperature is 32 ℃ and the time is 60s, and baking for 20min at 190 ℃ to obtain a paint film with the thickness of 20 +/-1 mu m.

Example 2:

preparing o-phenylenediamine modified graphene oxide powder: preparing small-piece graphene oxide by an improved Hummers method, and preparing 1mg/mL graphene oxide aqueous dispersion. 0.5576g of o-phenylenediamine was added to 200mL of the aqueous graphene oxide dispersion, the pH of the solution was adjusted to 10, and the reaction was carried out at 65 ℃ for 6 hours. After the reaction is finished, washing the reaction product for many times by deionized water until colorless transparent residual liquid is obtained. And finally, ultrasonically dispersing the product uniformly, and performing vacuum freeze drying to obtain o-phenylenediamine modified graphene oxide powder.

Preparing the composite epoxy coating: 1.7g of o-phenylenediamine-modified graphene oxide powder was weighed and ultrasonically dispersed in 498.3g of deionized water to obtain an o-phenylenediamine-modified graphene oxide aqueous dispersion. And sequentially mixing 300g of emulsion, 500g of o-phenylenediamine modified graphene oxide aqueous dispersion and 50g of color paste, and mechanically stirring for 24 hours to obtain the o-phenylenediamine modified graphene oxide epoxy resin coating.

Preparation of a paint film: electroplating the composite epoxy resin coating on a silane sample plate under the conditions that the voltage is 190V, the temperature is 32 ℃ and the time is 60s, and baking for 20min at 190 ℃ to obtain a paint film with the thickness of 20 +/-1 mu m.

Example 3:

preparing m-phenylenediamine modified graphene oxide powder: preparing small-piece graphene oxide by an improved Hummers method, and preparing 1mg/mL graphene oxide aqueous dispersion. 0.5068g of m-phenylenediamine was added to 200mL of an aqueous graphene oxide dispersion, the pH of the solution was adjusted to 11, and the reaction was carried out at 70 ℃ for 6 hours. After the reaction is finished, washing the reaction product for many times by deionized water until colorless transparent residual liquid is obtained. And finally, ultrasonically dispersing the product uniformly, and carrying out vacuum freeze drying to obtain m-phenylenediamine modified graphene oxide powder.

Preparing the composite epoxy coating: 1.36g of m-phenylenediamine-modified graphene oxide powder was weighed and ultrasonically dispersed in 498.64g of deionized water to obtain an m-phenylenediamine-modified graphene oxide aqueous dispersion. And sequentially mixing 300g of emulsion, 500g of m-phenylenediamine modified graphene oxide aqueous dispersion and 50g of color paste, and mechanically stirring for 24 hours to obtain the m-phenylenediamine modified graphene oxide epoxy resin coating.

Preparation of a paint film: electroplating the composite epoxy resin coating on a silane sample plate under the conditions that the voltage is 190V, the temperature is 32 ℃ and the time is 60s, and baking for 20min at 190 ℃ to obtain a paint film with the thickness of 20 +/-1 mu m.

Comparative example:

preparation of epoxy coating: and sequentially mixing 300g of emulsion, 500g of deionized water and 50g of color paste, and mechanically stirring for 24 hours to obtain the epoxy resin coating.

Preparation of a paint film: electroplating the epoxy resin coating on a silane sample plate under the conditions that the voltage is 190V, the temperature is 32 ℃ and the time is 60s, and baking for 20min at 190 ℃ to obtain a paint film with the thickness of 20 +/-1 mu m.

The paint film was subjected to the index test as follows:

the salt spray resistance performance test refers to GB/T12967.3-2008 & lt & ltaluminum and aluminum alloy anodic oxidation film detection method part 3: copper accelerated acetate spray test (CASS test).

The flexibility test is referred to GB/T1731-1993 paint film flexibility determination.

The adhesion test is described in GB/T9286 1998 test for the marking of paint and varnish films.

The hardness test refers to GB/T6739-2006 determination of paint film hardness by a color paint and varnish pencil method.

TABLE 1 salt spray resistance, flexibility, adhesion and hardness testing of the paint films

As can be seen from the table, the salt spray resistance of the examples is not greatly different, and the width of the cross, the bubbles at the cross and the edge rusts are basically consistent when the test is carried out for 240h, wherein the width of the cross is smaller when the test is carried out for 96h and 168h in the example 2. Comparative example salt spray resistance at 48h was not very different from the examples. But as time goes on, the width of the cross becomes larger, finally 4.0mm, and a large amount of bubbles appear at the cross and dense rusty spots appear at the edge. The reason for this is probably because the example adds the aromatic diamine modified graphene oxide capable of being uniformly dispersed in the epoxy resin, and in the curing process of the epoxy resin, the graphene oxide itself has anti-permeability and can be used as a passivation layer to protect the metal from oxidation and corrosion, so the salt spray resistance of the example is greatly improved compared with the comparative example.

The paint films in the examples in the table have greatly improved flexibility and adhesion, but the hardness is not obviously improved. Examples the amino group in the aromatic diamine provides a positive charge and in addition the aromatic diamine can also act as a reducing agent to convert graphene oxide to hydrophobic reduced graphene oxide, helping to eliminate inevitable defects and voids during the curing process, better binding with metals. Therefore, the flexibility and adhesion in the examples were improved as compared with the comparative examples.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any local variations in the formulation and process thereof should be considered within the scope of the present invention.