CN114410222B - Modified hexagonal boron nitride and epoxy organic silicon resin coating material and preparation method thereof - Google Patents

Abstract

The invention discloses a modified hexagonal boron nitride and epoxy organic silicon resin coating material and a preparation method thereof, and relates to the technical field of anticorrosive materials. The modified hexagonal boron nitride has the structure that polydopamine is coated outside the hexagonal boron nitride, and nano zinc oxide is grafted on the surface of the polydopamine. According to the invention, the hexagonal boron nitride is subjected to surface functionalization treatment, the hexagonal boron nitride is coated by polydopamine, the distribution of the hexagonal boron nitride in resin is improved, and meanwhile, the interfacial compatibility of the hexagonal boron nitride and the resin is further improved by grafting nano zinc oxide by utilizing active groups on the surface of the polydopamine. The modified hexagonal boron nitride has good dispersibility in polymer materials, and the application field of the hexagonal boron nitride is further expanded.

Description

Modified hexagonal boron nitride and epoxy organic silicon resin coating material and preparation method thereof

Technical Field

The invention relates to the technical field of anticorrosive materials, in particular to a modified hexagonal boron nitride and epoxy organic silicon resin coating material and a preparation method thereof.

Background

The corrosion and protection of equipment in the marine environment are technical problems faced by naval of various countries in the world and are also main problems of equipment guarantee. The shipboard aircraft is in service in a marine environment, not only is corroded by marine atmosphere, seawater and continuous dry/wet alternate circulation, but also is corroded by ship combustion waste gas, shipboard aircraft engine waste gas and the like, and a high-acidity wet liquid film with the pH value of 2.4-4.0 is formed by the waste gas and marine salt fog, so that the service life of the shipboard aircraft is greatly shortened. The corrosion phenomenon in the marine environment seriously affects the equipment performance and equipment management work, directly or indirectly reduces the safety and reliability of equipment, the coating protection is generally adopted due to simple construction, convenient maintenance, low cost and wide adaptability, and is the most main technical means for corrosion prevention of carrier-based aircrafts, and more than 70 percent of the corrosion protection work of carrier-based flight equipment is finished by coating anticorrosive paint.

The two-dimensional material has unique structure and peculiar mechanical, thermal, electrical, optical and other properties, overcomes the defects of the traditional inorganic filler to a certain extent, and provides a new idea for researching and developing novel anticorrosive paint. The impermeability and chemical stability of the two-dimensional material are beneficial to converting the 'nano barrier effect' into the 'labyrinth effect' on the organic coating structure, so that the permeation path of corrosive media is prolonged, and the method has great application potential. Hexagonal boron nitride (h-BN), also known as "white graphene", has received wide attention from researchers due to its high thermal conductivity, high insulating properties and chemical inertness, and compared to graphene, hexagonal boron nitride is non-conductive and does not undergo galvanic corrosion in a 3.5% sodium chloride solution in cooperation with a metal matrix, thus exhibiting great application potential in the field of corrosion protection. However, due to the high specific surface area of hexagonal boron nitride and the strong van der waals force between layers, h-BN is easily agglomerated in the polymer material, and the compatibility at the filler-resin interface is poor, so that covalent bond method or non-covalent bond method modification is often required on the surface of nano hexagonal boron nitride to improve the dispersibility and agglomeration phenomenon in the resin.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a modified hexagonal boron nitride and epoxy organic silicon resin coating material with good dispersibility and interface compatibility in a polymer material and a preparation method thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the modified hexagonal boron nitride is characterized in that polydopamine is coated outside the hexagonal boron nitride (h-BN), and nano zinc oxide is grafted on the surface of the polydopamine.

The polydopamine can generate self-polymerization reaction under certain conditions, and can be coated on the surfaces of various solid materials to improve the compatibility of the functional solid materials and resin. In addition, the nano zinc oxide is grafted outside the polydopamine-coated hexagonal boron nitride, so that the nano zinc oxide can be connected with epoxy organic silicon resin through an oxirane bond, chemical bonding between the resin and the filler is realized, and the interface compatibility between the filler and the resin is enhanced.

In addition, the invention also discloses a preparation method of the modified hexagonal boron nitride, which comprises the following steps:

(1) Dispersing hexagonal boron nitride in a Tirs buffer solution with the pH value of 8.0-8.5 to obtain a dispersion liquid;

(2) Adding dopamine hydrochloride into the dispersion liquid for full reaction;

(3) Filtering, washing and drying the reacted solution to obtain polydopamine-coated hexagonal boron nitride (PDA-BN);

(4) And (3) adding the product prepared in the step (3) into a mixed solution of zinc salt and hexamethylenetetramine, performing ultrasonic dispersion, performing hydrothermal reaction, filtering, washing and drying to obtain the modified hexagonal boron nitride (PDA-BN @ ZnO).

According to the invention, the polydopamine-coated hexagonal boron nitride is prepared through the self-polymerization reaction of polydopamine, and then the hydrothermal reaction is carried out to graft the nano zinc oxide. The hexagonal boron nitride has a remarkable shielding effect, can prolong the propagation path of a corrosive medium in a resin material, and greatly improves the corrosion resistance of the epoxy organic silicon resin. The following formula is the principle of improving the interface compatibility of nano zinc oxide:

preferably, after the step (3) is finished, putting the polydopamine-coated hexagonal boron nitride into a magnesium chloride solution, stirring, filtering and drying.

The significance of stirring the hexagonal boron nitride coated by the polydopamine in the magnesium chloride solution is that magnesium ions and zinc ions have similar ionic radii, the polydopamine can react with the magnesium ions to form a metal ion chelate, so that nucleation sites on the polydopamine are fully opened, and the nano zinc oxide generated by the hydrothermal reaction can fully cover the surface of the polydopamine.

More preferably, the concentration of magnesium chloride in the magnesium chloride solution is 0.05-0.2 mol/L, and the stirring time is 10-15 h.

Preferably, in the process of preparing polydopamine-coated hexagonal boron nitride, the mass ratio of the hexagonal boron nitride to dopamine hydrochloride is 1 (0.4-0.6), the concentration of the dopamine hydrochloride in a buffer solution is 0.6-1.2 mg/mL, and the reaction temperature is 50-70 ℃. When the proportion and the concentration of the raw materials meet the above limits, the polymerization of dopamine is more facilitated.

Preferably, in the process of grafting the nano zinc oxide, the zinc salt is zinc nitrate and/or zinc nitrate hexahydrate, and when the zinc salt is zinc nitrate hexahydrate, the mass ratio of the zinc salt to the polydopamine-coated hexagonal boron nitride is 1: (2.5-3.0). In the mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine, the mass ratio of zinc nitrate hexahydrate, hexamethylenetetramine and water = (0.6-0.8): (0.3-0.4): (80-90), wherein the reaction temperature in the step (4) is 80-100 ℃. When the proportion of the raw materials meets the above limit, nano zinc oxide can be uniformly grafted on the surface of the polydopamine-coated hexagonal boron nitride.

Meanwhile, the invention also discloses an epoxy organic silicon resin coating material which contains the modified hexagonal boron nitride. The preparation method of the epoxy organic silicon resin coating material comprises the following steps:

(1) Dissolving modified hexagonal boron nitride in a diluent, and performing ultrasonic dispersion to obtain a dispersion liquid;

(2) Adding epoxy organic silicon resin into the dispersion liquid, and uniformly mixing to obtain a mixed liquid;

(3) Adding a silane coupling agent into the mixed solution, uniformly stirring and curing;

(4) And coating the cured product, and drying to obtain the epoxy organic silicon resin coating material.

Preferably, the epoxy silicone resin is

An EF resin; the diluent is butyl acetate; the silane coupling agent is 3-aminopropyl triethoxysilane. The silane coupling agent and the filler have interaction, the resin needs to be matched with the curing agent, and when the types of the components meet the above limits, the prepared epoxy organic silicon resin coating can be ensured to have higher crosslinking density.

Preferably, the coating manner is spin coating or spray coating.

Compared with the prior art, the invention has the beneficial effects that: according to the invention, the polydopamine is used for coating the hexagonal boron nitride, and the nano zinc oxide is grafted, so that the dispersibility of the hexagonal boron nitride in a resin material is improved, the interface compatibility between the hexagonal boron nitride filler and the resin is improved, and the corrosion resistance of the epoxy organic silicon resin coating is greatly improved. In addition, the introduction of the nano zinc oxide also endows the coating with certain antibacterial and uvioresistant performances; in addition, dopamine and the like are green and environment-friendly products, and the products cannot pollute the natural environment in the preparation and use processes.

Drawings

FIG. 1 is a schematic diagram of the preparation process of the epoxy silicone resin coating material of the present invention;

FIG. 2 is an electron micrograph of dispersed hexagonal boron nitride, intermediate polydopamine coated hexagonal boron nitride, and final product modified hexagonal boron nitride during preparation of example 1;

fig. 3 is a graph showing the effect of dispersing hexagonal boron nitride dispersed during the preparation of example 1, intermediate polydopamine coated hexagonal boron nitride, and final product modified hexagonal boron nitride in butyl acetate.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments.

Example 1

In an embodiment of the modified hexagonal boron nitride of the present invention, a preparation method of the modified hexagonal boron nitride of the present embodiment is as follows:

(1) Preparing a Tris buffer solution with the pH value of 8.5;

(2) Adding 2 parts of hexagonal boron nitride into 97.2 parts of Tris buffer solution for ultrasonic dispersion to obtain a dispersion solution;

(3) Adding 0.8 part of dopamine hydrochloride into the dispersion, and placing the dispersion in a water bath kettle at 60 ℃ for full reaction for 24 hours;

(4) Carrying out suction filtration, washing and drying on the reacted solution to obtain polydopamine-coated hexagonal boron nitride;

(5) Adding 2 parts of polydopamine-coated hexagonal boron nitride into a mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine, ultrasonically dispersing for 10min, then placing the mixture in a water bath, reacting for 2.5h at 90 ℃, and performing suction filtration, washing and drying to obtain modified hexagonal boron nitride; the mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine comprises the following components: 0.8 part of zinc nitrate hexahydrate, 0.38 part of hexamethylenetetramine and 90 parts of deionized water.

Example 2

In an embodiment of the modified hexagonal boron nitride according to the present invention, the only difference between this embodiment and embodiment 1 is that after step (4) is completed, the polydopamine-coated hexagonal boron nitride is put into an aqueous magnesium chloride solution with a magnesium chloride concentration of 0.1mol/L, stirred for 12 hours, filtered and dried.

Example 3

An example of modified hexagonal boron nitride according to the present invention differs from example 1 in that: in the step (3), the weight part of dopamine hydrochloride is 1.2 parts; in the step (5), 0.72 part by weight of zinc nitrate hexahydrate, 0.34 part by weight of hexamethylenetetramine, and 80 parts by weight of deionized water.

Example 4

An embodiment of the modified hexagonal boron nitride of the present invention is different from embodiment 1 in that, in step (3), the part by weight of dopamine hydrochloride is 1 part; in the step (5), 0.67 part by weight of zinc nitrate hexahydrate, 0.32 part by weight of hexamethylenetetramine, and 85 parts by weight of deionized water.

Examples 5 to 8

In the examples of the epoxy organic silicon resin coating material of the invention, examples 5 to 8 respectively contain the modified hexagonal boron nitride described in examples 1 to 4; the preparation method of examples 5 to 8 is shown in FIG. 1, and specifically as follows:

(1) Ultrasonically cleaning a 2024 aluminum alloy sheet with the thickness of 5 × 3.5 × 0.2cm by using ethanol, cleaning for 10min to remove impurities such as grease, dust and the like on the surface of the sheet, and drying at 80 ℃;

(2) Taking 3 parts of modified hexagonal boron nitride and 68 parts of modified hexagonal boron nitride

EF epoxy silicone resin and 17 parts of aminopropyltriethoxysilane (Texaco AMEO) are added into 12 parts of butyl acetate, uniformly dispersed epoxy silicone resin coating is obtained through ultrasonic and mechanical stirring, then the coating is coated on the surface of pretreated metal through a spin coating method, and the epoxy silicone resin coating is obtained after the coating is rotated at a high speed of 100rpm for 8s and then cured for 12 hours at room temperature.

Comparative example 1

An epoxy silicone resin coating that differs from example 5 in that it does not contain modified hexagonal boron nitride and in that the butyl acetate is 15 parts by weight.

Comparative example 2

An epoxy silicone resin coating that differs from example 5 in that modified hexagonal boron nitride is replaced with hexagonal boron nitride.

Comparative example 3

An epoxy silicone resin coating that differs from example 5 in that modified hexagonal boron nitride is replaced with polydopamine-coated hexagonal boron nitride.

The coating prepared above was soaked in 3.5wt% nacl solution for 30 days and tested for low frequency impedance modulus, the test results are shown in table 1:

TABLE 1

As can be seen from Table 1, the addition of hexagonal boron nitride to the resin can increase the corrosion resistance of the coating to a certain extent, and the low-frequency impedance modulus is increased by two orders of magnitude due to better compatibility of the filler and the resin after modification by polydopamine. Compared with the modified hexagonal boron nitride grafted with the nano zinc oxide, the corrosion resistance of the coating is further improved; in addition, the test results show that the performance of the modified hexagonal boron nitride prepared by stirring the polydopamine-coated hexagonal boron nitride in magnesium chloride is obviously superior to that of the untreated modified hexagonal boron nitride.

The glass transition temperature of the above coating was tested and the test results are shown in table 2:

TABLE 2

The higher the glass transition temperature, the higher the crosslinking density of the composite material, and correspondingly, the higher the compactness of the composite material, the tighter the combination of the filler and the resin. The test results show that the modified boron nitride prepared by the method of the invention is used as the filler, the coating prepared by mixing the modified boron nitride with the resin has the highest crosslinking density, and the compatibility between the filler and the resin is better.

FIG. 2 is an electron micrograph of h-BN dispersed during the preparation of example 1, intermediate PDA-BN formed, final PDA-BN @ ZnO; in FIGS. (a, b), the unmodified h-BN exhibits a platelet morphology, indicating successful exfoliation of the h-BN; in graphs (c, d), the modified PDA-BN showed a rough, uneven surface, indicating that the polydopamine coating has been successfully modified on the h-BN surface, and that the polydopamine also easily binds h-BN with similar particle size during the formation of the surface coating due to the properties of the polydopamine bioadhesive, which explains why the observed phenomenon of increased particle size of h-BN compared to that before modification after modification of the polydopamine coating; the graphs (e, f) are electron micrographs of PDA-BN @ ZnO, compared with the graphs (c, d), particulate matters are obviously generated on the surface of the material, which is attributed to the successful grafting of the nano zinc oxide on the surface of the material, and the nano zinc oxide also presents different forms, the nano zinc oxide particles in the graph (e) are mainly spherical, and the rod-shaped nano zinc oxide product is found in the graph (f), which is attributed to the reaction temperature, wherein the zinc oxide product is mainly spherical when the reaction temperature is less than 90 ℃, the dendritic zinc oxide when the reaction temperature is more than 110 ℃, and the reaction temperature is between the two when the material is synthesized, so the generated zinc oxide presents two different forms.

FIG. 3 is a graph showing the effect of dispersing hexagonal boron nitride dispersed during the preparation of example 1, intermediate polydopamine coated hexagonal boron nitride, and final product modified boron nitride (from left to right) in butyl acetate; as can be seen from the figure, even though stirring and ultrasonic dispersion are carried out, h-BN is difficult to be uniformly dispersed in butyl acetate, and remarkable sedimentation phenomenon occurs, while PDA-BN and PDA-BN @ ZnO can be well dispersed. After standing for 4 hours, the PDA-BN also has a remarkable sedimentation phenomenon, and the PDA-BN @ ZnO still shows a better dispersion state. Therefore, the dispersibility of h-BN can be obviously improved by the PDA coating in the butyl acetate solvent, and the dispersibility of the raw material is further improved after the ZnO is grafted on the surface.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims (6)

1. The modified hexagonal boron nitride is characterized in that the modified hexagonal boron nitride has a structure that polydopamine is coated outside the hexagonal boron nitride, and nano zinc oxide is grafted on the surface of the polydopamine;

the preparation method of the modified hexagonal boron nitride comprises the following steps:

(1) Dispersing hexagonal boron nitride in a buffer solution with the pH value of 8.0-8.5 to obtain a dispersion liquid;

(2) Adding dopamine hydrochloride into the dispersion liquid for full reaction;

(3) Filtering, washing and drying the reacted solution to obtain polydopamine-coated hexagonal boron nitride;

(4) Adding the product prepared in the step (3) into a mixed solution of zinc salt and hexamethylenetetramine, performing ultrasonic dispersion, fully reacting at 80-100 ℃, filtering, washing and drying to obtain the modified hexagonal boron nitride;

in the step (4), the zinc salt is zinc nitrate and/or zinc nitrate hexahydrate; when the zinc salt is zinc nitrate hexahydrate, the mass ratio of the zinc salt to the polydopamine-coated hexagonal boron nitride is 1: (2.5 to 3.0); in the mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine, the mass ratio of zinc nitrate hexahydrate, hexamethylenetetramine and water = (0.6 to 0.8): (0.3-0.4): (80-90).

2. The modified hexagonal boron nitride according to claim 1, wherein after the end of step (3), the polydopamine-coated hexagonal boron nitride is placed in a magnesium chloride solution to be stirred, filtered and dried.

3. The modified hexagonal boron nitride according to claim 2, wherein the concentration of magnesium chloride in the magnesium chloride solution is 0.05 to 0.2mol/L, and the stirring time is 10 to 15h.

4. The modified hexagonal boron nitride according to claim 1, wherein the mass ratio of the hexagonal boron nitride to the dopamine hydrochloride is 1 (0.4 to 0.6).

5. An epoxy silicone resin coating material, characterized by comprising the modified hexagonal boron nitride of any one of claims 1~4, a diluent, an epoxy silicone resin, a silane coupling agent.

6. A method for preparing the epoxy silicone resin coating material according to claim 5, characterized by comprising the steps of:

(1) Dissolving modified hexagonal boron nitride in a diluent, and performing ultrasonic dispersion to obtain a dispersion liquid;

(2) Adding epoxy organic silicon resin into the dispersion liquid, and uniformly mixing to obtain a mixed liquid;

(3) Adding a silane coupling agent into the mixed solution, uniformly stirring and curing;

(4) And coating the cured product, and drying to obtain the epoxy organic silicon resin coating material.

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