CN108774447B

CN108774447B - Preparation method of carbon-silver microsphere/epoxy resin super-hydrophobic coating

Info

Publication number: CN108774447B
Application number: CN201810578424.4A
Authority: CN
Inventors: 赵美云; 吴阳; 赵新泽; 田森; 习森明; 彭文昱
Original assignee: China Three Gorges University CTGU
Current assignee: China Three Gorges University CTGU
Priority date: 2018-06-05
Filing date: 2018-06-05
Publication date: 2020-06-16
Anticipated expiration: 2038-06-05
Also published as: CN108774447A

Abstract

The invention belongs to the technical field of preparation of super-hydrophobic materials, and particularly relates to a preparation method of a carbon-silver microsphere/epoxy resin super-hydrophobic coating. The method comprises the steps of preparation of flower-shaped carbon-silver microspheres, low surface energy modification, combination of super-hydrophobic powder and a substrate and the like. The finishing angle of various substrates coated with the super-hydrophobic powder to water is more than 150 degrees, and the rolling angle is less than 10 degrees. Moreover, the combined super-hydrophobic substrate has strong abrasion resistance, self-cleaning property, stain resistance, high temperature resistance and chemical stability. Meanwhile, the surface of the composite material can be repaired by screening, spraying or dip coating again even if the surface is damaged forcibly. The preparation method disclosed by the invention is simple in preparation process, easy in raw material obtaining, non-toxic, environment-friendly, low in cost, strong in stability, suitable for large-area preparation and application, and suitable for the fields of industrial pipeline transportation with extremely severe working environment, the preparation of an oil-water separation metal net and the like.

Description

Preparation method of carbon-silver microsphere/epoxy resin super-hydrophobic coating

Technical Field

The invention belongs to the technical field of super-hydrophobic coating preparation, and particularly relates to a preparation method of a carbon-silver microsphere/epoxy resin super-hydrophobic coating, which can be used for preparing a super-hydrophobic coating with strong wear resistance, self-cleaning property, stain resistance and chemical stability.

Background

The super-hydrophobic phenomenon exists widely in nature, such as lotus leaf surface, butterfly wing, water strider leg, etc. A superhydrophobic surface generally refers to a surface having a material surface with an ending angle greater than 150 ° and a rolling angle less than 10 ° with respect to water. Superhydrophobic surfaces have many unique and superior properties: the characteristics of hydrophobicity, self-cleaning property, corrosion resistance, anti-icing property, anti-fog property and the like enable the paint to have huge application prospect in a plurality of fields.

The super-hydrophobic powder has better storage, transportation and selectivity, and can be combined on various living goods or instrument and equipment by different methods. The multifunctional water-saving cleaning agent can be applied to the surfaces of automobiles, airplanes, spacecrafts and high-rise buildings, when water falls on the surfaces, the water can be quickly discharged, a large amount of dust on the surfaces can be taken away, the cleaning times are reduced, the cleaning cost can be reduced, and the high-altitude operation can be avoided. On the other hand, the powder is black and has high thermal stability, so the powder can be coated on panels of solar energy and the like, can absorb a large amount of heat, can protect the surface from the influence of corrosive environments such as acid rain and the like, and can quickly drain water to prevent rain, fog and dew from falling on the surface in winter and being frozen to influence the work of the solar energy panel.

Disclosure of Invention

The invention aims to provide a preparation method of a carbon-silver microsphere/epoxy resin super-hydrophobic coating, provides a simple, convenient and universal method for preparing a super-hydrophobic coating in a large area, and solves the problems of high production cost, weak mechanical strength, strong substrate tolerance, single preparation method and the like of super-hydrophobicity. The super-hydrophobic powder sample with the three-dimensional multilevel structure can be directly screened and sprinkled on various substrates adhered with double-sided adhesive or epoxy resin adhesives. The modified surface has stable hydrophobicity, the finishing angle of the modified surface to water is larger than 150 degrees, the rolling angle is smaller than 10 degrees, and the modified surface has strong mechanical property, chemical property, thermal stability, self-cleaning property and anti-fouling property.

In order to realize the purpose of the invention, the invention adopts the following technical scheme to realize:

1. a preparation method of a carbon-silver microsphere/epoxy resin super-hydrophobic coating comprises the following steps:

a, preparing flower-shaped carbon-silver microspheres: adding a silver-containing compound into a mixed solution of water and ethanol, stirring to form a transparent solution, then dropwise adding ammonia water into the transparent solution to adjust the pH value, then dropwise adding a dopamine aqueous solution, magnetically stirring, after the reaction is finished, carrying out suction filtration, continuously washing with ethanol and deionized water, and then carrying out freeze drying to form a dopamine/silver polymer; finally calcining in a muffle furnace, and cleaning with ethanol to obtain flower-shaped carbon-silver microspheres;

b, low surface energy modification: b, dispersing the flower-like carbon-silver microspheres prepared in the step A in a n-hexyl mixed alkane solution containing a fluorine modifier, magnetically stirring, and then filtering, washing with n-hexane and drying to obtain modified super-hydrophobic powder;

c, preparing the surface of the super-hydrophobic coating: firstly, dissolving epoxy resin and a curing agent into N, N-dimethylformamide, then adding polyvinylidene fluoride-hexafluoropropylene copolymer particles, violently stirring to obtain a mixed solution, soaking a cleaned substrate in the mixed solution for 5-10 min, taking out and drying at room temperature for 3-5 min, then uniformly scattering the super-hydrophobic powder prepared in the step B on the surface of the substrate, and drying to form the super-hydrophobic coating.

Preferably, the silver-containing compound of step a is silver nitrate. Silver ions in the silver nitrate can be well chelated with a phthalic acid group in the dopamine to influence the appearance of the surface of the carbon particle and increase the surface area.

Preferably, the concentration of the silver nitrate added into the mixed solution of water and ethanol in the step A is 0.06-0.08 mol/L, and the volume ratio of the ethanol to the water in the mixed solution of the water and the ethanol in the step A is 1/3-1/2.

Because the ethanol and the water are completely fused, the generation of precipitate caused by the reaction of hydroxide ions and silver ions in the silver nitrate can be prevented to a certain extent when the ammonia water is dripped.

Preferably, the concentration of the silver nitrate added into the mixed solution of water and ethanol in the step A is 0.06-0.08 mol/L, and the volume ratio of the ethanol to the water in the mixed solution of the water and the ethanol in the step A is 1: 2-3. The dopamine aqueous solution with a proper concentration can ensure that silver ions in silver nitrate and o-phenylephrine groups in dopamine are completely chelated, and carbon/silver microspheres with relatively smooth surfaces are prevented from being generated due to insufficient concentration of silver nitrate.

Preferably, the pH value of the ammonia water in the step A is adjusted to 8-9, the magnetic stirring temperature in the step A is 15-30 ℃, and the stirring time is 10-12 hours. The alkaline environment with the pH value of 8-9 is more favorable for chelating reaction, the reaction time is prolonged as much as possible, the reaction can be more thorough, and more carbon/silver microspheres are generated.

Preferably, the step A is carried out by suction filtration, continuously washed by ethanol and deionized water, and then placed in a refrigerator with the temperature of minus 20-25 ℃ for freezing for 20-24 hours to be completely dried, so as to form a dopamine/silver polymer; and finally calcining the microspheres in a sealed muffle furnace at 450-500 ℃ for 2-3 h, and cleaning the microspheres with ethanol to obtain the flower-shaped carbon-silver microspheres. The surface appearance can be controlled by adopting low-temperature freeze drying, which is beneficial to the formation of a flower-shaped structure; the dopamine/silver polymer with no form can be converted into flower-like carbon-silver microspheres by high-temperature calcination at 450-500 ℃.

Preferably, the fluorine-containing modifier in the step B is perfluorooctyl triethoxysilane, and the volume concentration of the perfluorooctyl triethoxy silicon in the n-hexane mixed solution is 0.5-1%. The modification time can be shortened by increasing the concentration of the perfluorooctyl triethoxysilane by a proper amount, and the fluorine-containing modifier can be self-assembled on the surface of the carbon/silver microsphere and can be combined with the surface more firmly.

Preferably, the volume ratio of the epoxy resin, the curing agent and the N, N-dimethylformamide in the step C is 3: 1: 40-50, wherein the mass concentration of the polyvinylidene fluoride-hexafluoropropylene copolymer is as follows: 0.02-0.03 g/mL. Because the epoxy resin is a hydrophilic substance and the polyvinylidene fluoride-hexafluoropropylene copolymer is a hydrophobic substance, the polyvinylidene fluoride-hexafluoropropylene copolymer with a certain concentration is added, so that the hydrophobicity of the binder can be increased, and the bonding strength of the coating can be increased.

Preferably, the substrate comprises glass or cotton cloth or stainless steel mesh or paper or aluminium sheet or otherwise. The different substrate materials are chosen here to demonstrate that the coating can be used universally with a wide variety of substrate materials and is highly versatile.

Preferably, in the step C, the super-hydrophobic powder prepared in the step B may be directly adhered to the surface of the substrate by a double-sided adhesive tape or a sprayed liquid adhesive, and the super-hydrophobic coating may be formed after drying. In order to demonstrate the strong applicability of such coatings, it is possible here to apply them to different substrates by means of simple bonding methods.

The invention has the beneficial effects that:

1. the process is simple, the raw materials are easy to obtain, and the cost is low;

2. the prepared flower-shaped carbon-silver microspheres have the grain size of about 1 mu m, have a flower-shaped multi-stage structure, and have stable super-hydrophobicity after being modified by a fluorine-containing modifier;

3. the super-hydrophobic powder is not influenced by the surface appearance and the performance of a substrate, has strong universality, has substrate independence and is suitable for various substrates;

4. the surface of the prepared material has super-hydrophobicity, self-cleaning property and anti-fouling property, the finishing angle of water is more than 150 degrees, and the rolling angle is less than 10 degrees;

5. high mechanical strength, high adhesion and long service life. The coating was placed on 400# sandpaper and subjected to 200g of gravity, and the surface was strongly superhydrophobic even after 200 rubbing cycles (one cycle of 10cm forward and 10cm back). In addition, the coating still has strong super-hydrophobicity after being placed in a natural environment (wind, sun and rain) for 6 months.

6. Has strong chemical stability and thermal stability.

Description of the drawings:

FIG. 1: scanning electron micrographs of the flower-like superhydrophobic carbon-silver microsphere particles obtained in example 1;

FIG. 2: the finishing angle and the rolling angle of the flower-shaped super-hydrophobic carbon-silver microsphere coating obtained in example 1;

FIG. 3: hydrophobic pattern of the flower-like super-hydrophobic carbon-silver microsphere coating obtained in example 2 after rubbing;

FIG. 4: the hydrophobicity change chart of the flower-shaped super-hydrophobic carbon-silver microsphere coating obtained in the example 2 after acid-base soaking;

FIG. 5: thermal decomposition curve of the flower-like super-hydrophobic carbon-silver microsphere coating obtained in example 3;

FIG. 6: oil-water separation diagram of the flower-like super-hydrophobic carbon-silver microsphere coating obtained in example 4.

Detailed Description

The technical solution of the present invention is further illustrated by the following examples.

Example 1

(1) Preparing flower-shaped carbon-silver microsphere particles:

1.25 g of silver nitrate was dissolved in a mixed solution of 80 mL of water and 40 mL of ethanol, and a certain amount of ammonia (0.02M) was added dropwise thereto under magnetic stirring to adjust the pH to about 8.5. To the system, 50 mL of 20 mg/mL dopamine hydrochloride solution was added dropwise and the reaction was continued for 12 h. After the reaction is finished, the mixture is filtered by suction and is frozen in a refrigerator at the temperature of minus 25 ℃ for 24 hours. And then calcining the mixture for 3 hours in a sealed muffle furnace at the temperature of 450 ℃ to obtain a black powdery product, thereby completing the preparation of the flower-shaped carbon-silver microsphere particles.

(2) Low surface energy modification:

and C, adding the carbon-silver microsphere powder product prepared in the step A into 50 ml of perfluorooctyl triethoxysilane normal hexane solution with the concentration of 0.5%, and stirring to disperse the mixture. After reacting for 20 min, obtaining modified white powder through centrifugation, n-hexane washing and drying processes. Finally, the modified powder sample was dried in an oven at 80 ℃ for 2 h to obtain a superhydrophobic powder. The scanning electron microscope picture of the modified carbon-silver microsphere particle is shown in fig. 1.

(3) Preparing a coating:

dissolving 4 mL of epoxy resin and a curing agent (volume ratio is 3: 1) in 40 mL of N, N-dimethylformamide, adding 1 g of polyvinylidene fluoride-hexafluoropropylene copolymer, and continuously stirring to completely dissolve the polyvinylidene fluoride-hexafluoropropylene copolymer; and (3) soaking the cleaned substrate in the solution for 10 min, taking out, drying in the air for 3 min, uniformly spreading the powder on the surface, and drying to obtain different super-hydrophobic samples. A water end angle and roll angle picture of the resulting coating is shown in fig. 2. As shown in FIG. 1, a large number of carbon-silver microspheres with the diameter of 1-5 μm are distributed on the surface of the coating, and the nano-scale folds on the surface of the microspheres are distributed on the surface of the microspheres like petals. The contact angle of the coating, as measured in FIG. 2, was 157. + -. 0.75 ℃ and the sliding angle was 4.5. + -. 0.5 ℃.

Example 2:

(1) preparing flower-shaped carbon-silver microsphere particles:

(2) Low surface energy modification:

and C, adding the carbon-silver microsphere powder product prepared in the step A into 50 ml of perfluorooctyl triethoxysilane normal hexane solution with the concentration of 0.5%, and stirring to disperse the mixture. After reacting for 20 min, obtaining modified white powder through centrifugation, n-hexane washing and drying processes. Finally, the modified powder sample was dried in an oven at 80 ℃ for 2 h to obtain a superhydrophobic powder.

(3) Preparing a coating:

dissolving 4 mL of epoxy resin and a curing agent (volume ratio is 3: 1) in 40 mL of N, N-dimethylformamide, adding 1 g of polyvinylidene fluoride-hexafluoropropylene copolymer, and continuously stirring to completely dissolve the polyvinylidene fluoride-hexafluoropropylene copolymer; and (3) soaking the cleaned substrate in the solution for 10 min, taking out, drying in the air for 3 min, uniformly spreading the powder on the surface, and drying to obtain different super-hydrophobic samples. The poor hydrophobic coating prepared had very strong mechanical and chemical stability, and fig. 3 is a hydrophobic photograph of a glass coating rubbed for 50 cycles (one round for 10cm each back and forth with a 400 grit sandpaper load of 200 g) and 200 rounds. FIG. 4 is a graph of end angle changes of a glass coating immersed in an acid-base salt solution for different times. As can be seen from fig. 3, even if the rubbing is performed for 200 cycles, the liquid drop can still maintain a spherical shape on the coating surface, and the contact angle is still larger than 150 °. As can be seen from fig. 4, even if the coating was immersed in 2M hydrochloric acid solution for 120 min, the contact angle was still greater than 150 °; for alkaline solutions and salt solutions, the soaking time exceeded 180 min and the surface contact angle varied over 6 °, indicating that the coating had good chemical stability.

Example 3:

(1) preparing flower-shaped carbon-silver microsphere particles:

(2) Low surface energy modification:

and C, adding the carbon-silver microsphere powder product prepared in the step A into 50 ml of a n-hexane solution of perfluorooctyl triethoxysilane with the concentration of 0.5%, and stirring to disperse the carbon-silver microsphere powder product. After reacting for 20 min, obtaining modified white powder through centrifugation, n-hexane washing and drying processes. Finally, the modified powder sample was dried in an oven at 80 ℃ for 2 h to obtain a superhydrophobic powder.

(3) Preparing a coating:

and adhering double-sided adhesive tape on a clean glass substrate material, then spreading the prepared super-hydrophobic powder on the double-sided adhesive tape, and drying at room temperature to obtain the super-hydrophobic glass surface. The surface has high thermal stability. Fig. 5 is a thermal decomposition curve thereof. As can be seen from FIG. 5, the thermal decomposition temperature of the coating is in the range of 200-582 ℃, and even if the temperature is as high as 403 ℃, the thermal decomposition amount is only 25%, which indicates that the coating has strong thermal stability.

Example 4:

(1) preparing flower-shaped carbon-silver microsphere particles:

(2) Low surface energy modification:

(3) Preparing a super-hydrophobic coating:

spraying a layer of liquid glue on a clean PU sponge substrate material, then scattering the prepared super-hydrophobic powder on the sponge substrate sprayed with the glue, and airing at room temperature to obtain the super-hydrophobic sponge. The sponge has strong oleophylic and super-hydrophobic properties, so that the sponge can be applied to oil-water separation. As can be seen from fig. 6, when the superhydrophobic sponge was inserted into water, it was found that the sponge was not wetted; but as soon as the sponge contacts the dyed heavy oil (dichloroethane) at the bottom of the beaker, the oil is completely absorbed by the sponge, indicating that the super-hydrophobic sponge has good oil-water separation effect.

The above description is provided for further details of the present invention with reference to specific examples, which should not be construed as limiting the scope of the present invention, but it should be understood that those skilled in the art can make several simple substitutions without departing from the spirit of the present invention.

Claims

b, low surface energy modification: b, dispersing the flower-like carbon-silver microspheres prepared in the step A in a normal hexane solution containing a fluorine modifier, magnetically stirring, and then filtering, washing with normal hexane, and drying to obtain modified super-hydrophobic powder;

c, preparing the surface of the super-hydrophobic coating: firstly, dissolving epoxy resin and a curing agent into N, N-dimethylformamide, then adding polyvinylidene fluoride-hexafluoropropylene copolymer particles, violently stirring to obtain a mixed solution, soaking a cleaned substrate into the mixed solution for 5-10 min, taking out, drying at room temperature for 3-5 min, then uniformly scattering the super-hydrophobic powder prepared in the step B on the surface of the substrate, and drying to form a super-hydrophobic coating;

and C, epoxy resin, a curing agent and N, N-dimethylformamide in a volume ratio of 3: 1: 40-50, wherein the mass concentration of the polyvinylidene fluoride-hexafluoropropylene copolymer in the mixed solution is as follows: 0.02-0.03 g/mL.

2. The method for preparing the carbon-silver microsphere/epoxy resin super-hydrophobic coating according to claim 1, wherein the method comprises the following steps: the silver-containing compound in the step A is silver nitrate.

3. The method for preparing the carbon-silver microsphere/epoxy resin super-hydrophobic coating according to claim 2, characterized in that: the concentration of the silver nitrate added into the mixed solution of the water and the ethanol in the step A is 0.06-0.08 mol/L, and the volume ratio of the ethanol to the water in the mixed solution of the water and the ethanol in the step A is 1: 2-3.

4. The method for preparing the carbon-silver microsphere/epoxy resin super-hydrophobic coating according to claim 2, characterized in that: the concentration of the dopamine aqueous solution in the step A is 15-25 mg/mL, and the volume ratio of the dopamine aqueous solution to the silver nitrate solution in the step A is 1/3-1/2.

5. The method for preparing the carbon-silver microsphere/epoxy resin super-hydrophobic coating according to claim 1, wherein the method comprises the following steps: and (B) adjusting the pH value of the ammonia water in the step (A) to 8-9, wherein the magnetic stirring temperature in the step (A) is 15-30 ℃, and the stirring time is 10-12 h.

6. The method for preparing the carbon-silver microsphere/epoxy resin super-hydrophobic coating according to claim 1, wherein the method comprises the following steps: step A, performing suction filtration, continuously washing with ethanol and deionized water, and then placing in a refrigerator at the temperature of-20-25 ℃ for freezing for 20-24 hours to completely dry the product to form a dopamine/silver polymer; and finally calcining the microspheres in a sealed muffle furnace at 450-500 ℃ for 2-3 h, and cleaning the microspheres with ethanol to obtain the flower-shaped carbon-silver microspheres.

7. The method for preparing the carbon-silver microsphere/epoxy resin super-hydrophobic coating according to claim 1, wherein the method comprises the following steps: and the fluorine-containing modifier in the step B is perfluorooctyl triethoxysilane, and the volume concentration of the perfluorooctyl triethoxysilane in the normal hexane mixed solution is 0.5-1%.

8. The method for preparing the carbon-silver microsphere/epoxy resin super-hydrophobic coating according to claim 1, wherein the method comprises the following steps: the substrate comprises glass or cotton cloth or stainless steel mesh or paper or aluminum sheet.

9. The method for preparing the carbon-silver microsphere/epoxy resin super-hydrophobic coating according to claim 1, wherein the method comprises the following steps: in the step C, the super-hydrophobic powder prepared in the step B can be directly adhered to the surface of the substrate through double-sided adhesive tape or sprayed liquid adhesive, and the super-hydrophobic coating can be formed after drying.