1. The graphene conductive coating is characterized by comprising an aqueous acrylic emulsion and reduced graphene oxide;

the reduced graphene oxide accounts for 5-10% of the mass of the aqueous acrylic emulsion;

the reduced graphene oxide comprises the following reduced graphene oxide with different particle size distribution ranges in parts by weight: 10-15 parts of reduced graphene oxide with the particle size distribution range of 5-10nm, 30-50 parts of reduced graphene oxide with the particle size distribution range of 30-100nm and 20-40 parts of reduced graphene oxide with the particle size distribution range of 200-400 nm;

the reduced graphene oxide is obtained by reducing graphene oxide with ascorbic acid.

2. The graphene conductive coating as claimed in claim 1, wherein a C-N chemical bond is formed at a defect in the molecular structure of the reduced graphene oxide.

3. The graphene conductive coating according to claim 2, wherein the reduced graphene oxide is a lamellar structure, and two adjacent lamellar structures are bonded through the C-N chemical bond.

4. The graphene conductive coating according to claim 1, wherein the reduced graphene oxide is of a lamellar structure, and gelatin is sandwiched between two adjacent lamellar structures.

5. The graphene conductive coating according to claim 1, wherein the gelatin has an isoelectric point of 6.0-6.5, and the graphene conductive coating has a pH of 7.0-7.5.

6. A preparation method of a graphene conductive coating is characterized by comprising the following specific preparation steps:

according to the weight portion, 80-120 portions of aqueous acrylic emulsion, 60-80 portions of water, 2-3 portions of wetting dispersant, 1-3 portions of defoaming agent, 0.5-1.0 portion of preservative and reduced graphene oxide with the mass of 5-10% of the aqueous acrylic emulsion are taken in sequence;

the reduced graphene oxide comprises the following reduced graphene oxide with different particle size distribution ranges in parts by weight: 10-15 parts of reduced graphene oxide with the particle size distribution range of 5-10nm, 30-50 parts of reduced graphene oxide with the particle size distribution range of 30-100nm and 20-40 parts of reduced graphene oxide with the particle size distribution range of 200-400 nm;

the reduced graphene oxide is obtained by reducing graphene oxide with ascorbic acid;

dispersing reduced graphene oxide in water, adding the aqueous acrylic emulsion, the wetting dispersant, the defoaming agent and the preservative, continuously dispersing uniformly, and discharging to obtain the graphene conductive coating.

7. The preparation method of the graphene conductive coating according to claim 6, wherein the specific preparation steps further comprise:

preparing reduced graphene oxide: the method comprises the following steps of (1) mixing graphene oxide and melamine according to a mass ratio of 10: 1-20: 1, after mixing and ball milling, carrying out high-temperature and high-pressure reaction at the temperature of 800-; and reducing the obtained pretreated graphene oxide by using an ascorbic acid solution to obtain reduced graphene oxide.

8. The preparation method of the graphene conductive coating according to claim 6, wherein the specific preparation steps further comprise: gelatin is sandwiched between the reduced graphene oxide layers.

Background

The coating conductivity of the electrical property coating can reach 10^-10The grade of S/cm meets the basic requirements of electrical performance materials, can lead out accumulated static charges and conduct current, and is widely applied to the fields of electronics, aerospace, petrochemical engineering pipelines and the like. The conductivity of electrical coatings depends to a large extent on the conductive materials introduced, and the development of new conductive materials has become a focus of attention. Since graphene has been successfully produced by anderley hom and constatin norworth schoft, it has been receiving much attention from researchers. The graphene oxide is used as an oxide of graphene, and the excellent electronic conductivity, mechanical property, aging resistance and other properties of the graphene are still maintained after the graphene oxide is reduced. The graphene and the derivatives thereof are introduced into the polymer, so that the electrical property of the polymer can be effectively improved.

Graphene can be prepared by a number of methods, including ball milling, micromechanical exfoliation, gas-liquid phase exfoliation, redox, and the like. The good electrical properties can be verified by many methods, such as testing the graphene powder directly, or testing the graphene powder after preparing the graphene powder into a film in the form of polyelectrolyte. However, the degree of improvement of the electrical properties of the coating by the graphene is influenced by the dispersion degree, the particle size, the addition amount and other factors of the graphene and the oxide thereof. According to literature reports, the more graphene or graphene oxide in a certain range, the smaller the particle size and the more uniform the dispersion, the better the electrical property of the coating; the disadvantages are that the adhesion, toughness and stability of the coating are reduced.

The first conductive materials used in electrical coatings were metals, silver and copper, which have been widely used to date. Common conductive materials are also carbon-based materials, such as graphene, carbon fibers, carbon black, graphite fibers, carbon nanotubes, and the like. The theoretical resistivity of the graphene is smaller than that of silver and copper, so that the graphene has great application potential.

Disclosure of Invention

The invention aims to overcome the defects that the dispersibility of graphene and the stability of a coating cannot be considered when the graphene is added in the conventional conductive coating, and provides a graphene conductive coating and a preparation method thereof.

The invention aims to provide a graphene conductive coating.

The invention also aims to provide a preparation method of the graphene conductive coating.

The above purpose of the invention is realized by the following technical scheme:

a graphene conductive coating comprises an aqueous acrylic emulsion and reduced graphene oxide;

the reduced graphene oxide accounts for 5-10% of the mass of the aqueous acrylic emulsion;

the reduced graphene oxide comprises the following reduced graphene oxide with different particle size distribution ranges in parts by weight: 10-15 parts of reduced graphene oxide with the particle size distribution range of 5-10nm, 30-50 parts of reduced graphene oxide with the particle size distribution range of 30-100nm and 20-40 parts of reduced graphene oxide with the particle size distribution range of 200-400 nm;

the reduced graphene oxide is obtained by reducing graphene oxide with ascorbic acid.

According to the technical scheme, the reduced graphene oxide with different particle size distribution ranges is adopted, firstly, the reduced graphene oxide with different particle sizes can be filled with particles with small particle sizes in gaps among particles with large particle sizes in the using process of a product, so that a continuous conductive network is formed, the product performance is sufficiently ensured, and thus, the completeness of the conductive network is ensured without adding more graphene; more importantly, in the process of preparing and storing the product, after small-particle graphene is dispersed, the small-particle graphene can be stably dispersed in a graphene lamellar structure with relatively larger particles, so that excessive agglomeration of small particles can be avoided, and the single-lamellar structure of the small-particle graphene can be used as a conductive connector between adjacent lamellar layers of large-particle graphene, so that the transmission of electrons between the adjacent graphene lamellar layers is possible.

Furthermore, C-N chemical bonds are formed at the defects in the molecular structure of the reduced graphene oxide.

Further, the reduced graphene oxide is of a lamellar structure, and two adjacent lamellar structures are combined through the C-N chemical bond.

The defects in the graphene molecular structure are repaired by utilizing the C-N chemical bonds, and meanwhile, the defects are used as binding sites in the repairing process (the physicochemical properties of the defects are more active and are more likely to react), so that the C-N chemical bonds are formed in the adjacent graphene lamellar structures.

Further, the reduced graphene oxide is of a lamellar structure, and gelatin is clamped between two adjacent lamellar structures.

Further, the gelatin is gelatin with an isoelectric point of 6.0-6.5, and the pH value of the graphene conductive coating is 7.0-7.5.

Gelatin molecules with specific isoelectric points are clamped between graphene layers, and the pH value of the coating deviates from the isoelectric points of the gelatin, so that amino groups in a gelatin molecular structure are protonated, and the molecular chains expand due to mutual repulsion of like charges in the molecular structure, and therefore, the dispersed graphene lamellar structure can be well fixed, and the storage stability of a product is prevented from being reduced due to the distance change of the graphene lamellar structure.

A preparation method of a graphene conductive coating comprises the following specific preparation steps:

according to the weight portion, 80-120 portions of aqueous acrylic emulsion, 60-80 portions of water, 2-3 portions of wetting dispersant, 1-3 portions of defoaming agent, 0.5-1.0 portion of preservative and reduced graphene oxide with the mass of 5-10% of the aqueous acrylic emulsion are taken in sequence;

the reduced graphene oxide comprises the following reduced graphene oxide with different particle size distribution ranges in parts by weight: 10-15 parts of reduced graphene oxide with the particle size distribution range of 5-10nm, 30-50 parts of reduced graphene oxide with the particle size distribution range of 30-100nm and 20-40 parts of reduced graphene oxide with the particle size distribution range of 200-400 nm;

the reduced graphene oxide is obtained by reducing graphene oxide with ascorbic acid;

dispersing reduced graphene oxide in water, adding the aqueous acrylic emulsion, the wetting dispersant, the defoaming agent and the preservative, continuously dispersing uniformly, and discharging to obtain the graphene conductive coating.

Further, the specific preparation steps further comprise:

preparing reduced graphene oxide: the method comprises the following steps of (1) mixing graphene oxide and melamine according to a mass ratio of 10: 1-20: 1, after mixing and ball milling, carrying out high-temperature and high-pressure reaction at the temperature of 800-; and reducing the obtained pretreated graphene oxide by using an ascorbic acid solution to obtain reduced graphene oxide.

Further, the specific preparation steps further comprise: gelatin is sandwiched between the reduced graphene oxide layers.

Detailed Description

The present invention is further illustrated by the following specific examples, which are not intended to limit the invention in any way. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Unless otherwise indicated, reagents and materials used in the following examples are commercially available.

Example 1

The method comprises the following steps of (1) mixing graphene oxide and melamine according to a mass ratio of 10: 1, adding the mixture into a ball milling tank, and mixing the materials according to a ball material mass ratio of 20: 1 adding ball milling beads, carrying out ball milling mixing for 36 hours at the rotating speed of 500r/min, discharging to obtain a ball milling material, transferring the ball milling material into a high-pressure furnace, carrying out high-temperature high-pressure reaction for 8 hours at the temperature of 800 ℃ and the pressure of 5.0MPa under the condition of nitrogen atmosphere, cooling, and discharging to obtain pretreated graphene oxide;

mixing the pretreated graphene oxide with an ascorbic acid solution with the mass fraction of 5%, carrying out reduction reaction for 3 hours at the rotating speed of 300r/min, filtering, washing and drying to obtain reduced graphene oxide;

reducing graphene oxide and a gelatin solution with the mass fraction of 3% according to the mass ratio of 1: 5, after mixing, carrying out ultrasonic dispersion for 30min under the condition that the ultrasonic frequency is 60kHz, carrying out suction filtration, collecting a filter cake, transferring the obtained filter cake into a drying oven, and drying the filter cake to constant weight under the condition that the temperature is 85 ℃ to obtain the reduced graphene oxide with the gelatin in between; the gelatin is gelatin with isoelectric point of 6.0;

screening the reduced graphene oxide with the gelatin in the clamping way step by step to obtain the following raw materials with different particle size distribution ranges in parts by weight: 10 parts of reduced graphene oxide with the particle size distribution range of 5-10nm, 30 parts of reduced graphene oxide with the particle size distribution range of 30-100nm and 20 parts of reduced graphene oxide with the particle size distribution range of 200-400 nm; uniformly mixing the materials by using a stirrer to obtain a compound graphene raw material;

according to the weight parts, 80 parts of water-based acrylic emulsion with the solid content of 35%, 60 parts of water, 2 parts of wetting dispersant OT75, 1 part of defoamer polydimethylsiloxane, 0.5 part of preservative David Hill-75 and a compound graphene raw material with the mass of the water-based acrylic emulsion of 5% are taken in sequence;

dispersing reduced graphene oxide in water, adding aqueous acrylic emulsion with the solid content of 30%, wetting dispersant OT75, defoamer polydimethylsiloxane and preservative Davweihui-75, continuously dispersing uniformly, adjusting the pH value to 7.0, and discharging to obtain the graphene conductive coating.

Example 2

The method comprises the following steps of (1) mixing graphene oxide and melamine according to a mass ratio of 15: 1, adding the mixture into a ball milling tank, and mixing the materials according to a ball material mass ratio of 25: 1 adding ball milling beads, performing ball milling and mixing for 56 hours at the rotating speed of 560r/min, discharging to obtain a ball milling material, transferring the ball milling material into a high-pressure furnace, performing high-temperature and high-pressure reaction for 10 hours at the temperature of 1000 ℃ and the pressure of 8.0MPa in the nitrogen atmosphere, cooling, and discharging to obtain pretreated graphene oxide;

mixing the pretreated graphene oxide with an ascorbic acid solution with the mass fraction of 6%, carrying out reduction reaction for 3.5 hours at the rotating speed of 400r/min, filtering, washing and drying to obtain reduced graphene oxide;

reducing graphene oxide and a gelatin solution with the mass fraction of 4% according to the mass ratio of 1: 8, mixing, performing ultrasonic dispersion for 40min under the ultrasonic frequency of 80kHz, performing suction filtration, collecting a filter cake, transferring the obtained filter cake into a drying oven, and drying at the temperature of 88 ℃ to constant weight to obtain the reduced graphene oxide with the gelatin; the gelatin is gelatin with isoelectric point of 6.2;

screening the reduced graphene oxide with the gelatin in the clamping way step by step to obtain the following raw materials with different particle size distribution ranges in parts by weight: 12 parts of reduced graphene oxide with the particle size distribution range of 8-10nm, 50 parts of reduced graphene oxide with the particle size distribution range of 50-100nm and 30 parts of reduced graphene oxide with the particle size distribution range of 300-400 nm; uniformly mixing the materials by using a stirrer to obtain a compound graphene raw material;

according to the weight parts, 100 parts of water-based acrylic emulsion with the solid content of 35%, 70 parts of water, 2.5 parts of wetting dispersant OT75, 2 parts of defoamer polydimethylsiloxane, 0.6 part of preservative Daoweishil-75 and a compound graphene raw material accounting for 8% of the mass of the water-based acrylic emulsion are taken in sequence;

dispersing reduced graphene oxide in water, adding 35% of water-based acrylic emulsion, wetting dispersant OT75, defoamer polydimethylsiloxane and preservative Davweichi-75, continuously dispersing uniformly, adjusting pH to 7.2, and discharging to obtain the graphene conductive coating.

Example 3

The preparation method comprises the following steps of (1) mixing graphene oxide and melamine according to a mass ratio of 20: 1, adding the mixture into a ball milling tank, and mixing the materials according to a ball material mass ratio of 30: 1 adding ball milling beads, carrying out ball milling mixing for 72 hours at the rotating speed of 600r/min, discharging to obtain a ball milling material, transferring the ball milling material into a high-pressure furnace, carrying out high-temperature high-pressure reaction for 12 hours at the temperature of 1200 ℃ and the pressure of 10.0MPa in the nitrogen atmosphere, cooling, and discharging to obtain pretreated graphene oxide;

mixing the pretreated graphene oxide with 10% ascorbic acid solution by mass, carrying out reduction reaction for 4 hours at the rotating speed of 500r/min, filtering, washing and drying to obtain reduced graphene oxide;

reducing graphene oxide and a gelatin solution with the mass fraction of 5% according to the mass ratio of 1: 10, performing ultrasonic dispersion for 50min under the condition that the ultrasonic frequency is 120kHz, performing suction filtration, collecting a filter cake, transferring the obtained filter cake into a drying oven, and drying the filter cake to constant weight under the condition that the temperature is 90 ℃ to obtain the reduced graphene oxide with the gelatin in between; the gelatin is gelatin with isoelectric point of 6.5;

screening the reduced graphene oxide with the gelatin in the clamping way step by step to obtain the following raw materials with different particle size distribution ranges in parts by weight: 15 parts of reduced graphene oxide with the particle size distribution range of 7-10nm, 50 parts of reduced graphene oxide with the particle size distribution range of 60-100nm and 40 parts of reduced graphene oxide with the particle size distribution range of 280-400 nm; uniformly mixing the materials by using a stirrer to obtain a compound graphene raw material;

according to the weight parts, 120 parts of water-based acrylic emulsion with the solid content of 40%, 80 parts of water, 3 parts of wetting dispersant OT75, 3 parts of defoamer polydimethylsiloxane, 1.0 part of preservative David Hill-75 and a compound graphene raw material accounting for 10% of the mass of the water-based acrylic emulsion are taken in sequence;

dispersing reduced graphene oxide in water, adding 40% of aqueous acrylic emulsion, wetting dispersant OT75, defoamer polydimethylsiloxane and preservative Davweichi-75, continuously dispersing uniformly, adjusting pH to 7.5, and discharging to obtain the graphene conductive coating.

Example 4

This example differs from example 1 in that: gelatin with isoelectric point of 7.0 is selected, and the rest conditions are kept unchanged.

Example 5

This example differs from example 1 in that: melamine was not added and the remaining conditions were kept unchanged.

Comparative example 1

The method comprises the following steps of (1) mixing graphene oxide and melamine according to a mass ratio of 10: 1, adding the mixture into a ball milling tank, and mixing the materials according to a ball material mass ratio of 20: 1 adding ball milling beads, carrying out ball milling mixing for 36 hours at the rotating speed of 500r/min, discharging to obtain a ball milling material, transferring the ball milling material into a high-pressure furnace, carrying out high-temperature high-pressure reaction for 8 hours at the temperature of 800 ℃ and the pressure of 5.0MPa under the condition of nitrogen atmosphere, cooling, and discharging to obtain pretreated graphene oxide;

mixing the pretreated graphene oxide with an ascorbic acid solution with the mass fraction of 5%, carrying out reduction reaction for 3 hours at the rotating speed of 300r/min, filtering, washing and drying to obtain reduced graphene oxide;

reducing graphene oxide and a gelatin solution with the mass fraction of 3% according to the mass ratio of 1: 5, after mixing, carrying out ultrasonic dispersion for 30min under the condition that the ultrasonic frequency is 60kHz, carrying out suction filtration, collecting a filter cake, transferring the obtained filter cake into a drying oven, and drying the filter cake to constant weight under the condition that the temperature is 85 ℃ to obtain the reduced graphene oxide with the gelatin in between; the gelatin is gelatin with isoelectric point of 6.0;

screening the reduced graphene oxide with the gelatin in the clamping way step by step to obtain the reduced graphene oxide with the particle size distribution range of 5-10 nm;

according to the weight portion, 80 portions of water-based acrylic emulsion with the solid content of 35 percent, 60 portions of water, 2 portions of wetting dispersant OT75, 1 portion of defoamer polydimethylsiloxane, 0.5 portion of preservative Daoweishil-75 and 5 percent of reduced graphene oxide with the particle size distribution range of 5-10nm by mass of the water-based acrylic emulsion are taken in sequence;

firstly, dispersing reduced graphene oxide with the particle size distribution range of 5-10nm in water, then adding aqueous acrylic emulsion with the solid content of 30%, wetting dispersant OT75, defoaming agent polydimethylsiloxane and preservative Davihil-75, continuously dispersing uniformly, adjusting the pH value to 7.0, and discharging to obtain the graphene conductive coating.

The products obtained in examples 1 to 5 and comparative example 1 were subjected to performance tests, and the specific test methods and test results were as follows:

the products of the above examples and comparative examples were placed in an environment at a temperature of 55 ℃ for 35 days, and the product performance was tested before and after placement:

thermal storage stability: observing whether the product sinks and is agglomerated before and after being stored;

and (3) conductivity test:

the coating is sprayed on a PET plate which is cleaned in advance and is 250mm multiplied by 400mm, the PET plate is dried at room temperature, copper foils which are 250mm multiplied by 5mm are pasted on two sides of a coating film, in order to reduce errors, 3 parallel sample plates are made for each coating sample, and the thickness of a dry film of each sample plate is controlled to be 80-85 mu m.

The resistance was measured with a VICTOR VC890+ digital multimeter, and the average value was taken, and the resistivity of the sample was calculated from the formula ρ ═ Rs · (a × d/l).

In the formula: rs-the average value of the resistance of the product, Ω;

a, the thickness of a coating film is cm; d, the width of the sample plate is cm; l length of the panel, cm.

Table 1: product Performance test results (before Heat storage)

	Stability in thermal storage	Resistivity (omega cm)
			Example 1	Without agglomeration and bottom sinking	0.042
Example 2	Without agglomeration and bottom sinking	0.044
			Example 3	Without agglomeration and bottom sinking	0.041
Example 4	Without agglomeration and bottom sinking	0.062
			Example 5	Without agglomeration and bottom sinking	0.058
Comparative example 1	Without agglomeration and bottom sinking	0.092

Table 2: product Performance test results (after 35 days of Heat storage)

	Stability in thermal storage	Resistivity (omega cm)
			Example 1	Without agglomeration and bottom sinking	0.055
Example 2	Without agglomeration and bottom sinking	0.056
			Example 3	Without agglomeration and bottom sinking	0.053
Example 4	Without agglomeration and bottom sinking	0.078
			Example 5	Without agglomeration and bottom sinking	0.077
Comparative example 1	Partially sinking bottom	2.866

As can be seen from the test results in tables 1 and 2, the product obtained by the method has excellent conductivity and good storage stability.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.