CN113441374A

CN113441374A - Preparation method of porous-structure super-hydrophobic surface with self-repairability

Info

Publication number: CN113441374A
Application number: CN202110665404.2A
Authority: CN
Inventors: 冯晓明; 孙鹏飞; 田桂中; 张小伟; 张耀升; 李凤芹
Original assignee: Jiangsu University of Science and Technology
Current assignee: Jiangsu University of Science and Technology
Priority date: 2021-06-16
Filing date: 2021-06-16
Publication date: 2021-09-28
Anticipated expiration: 2041-06-16
Also published as: CN113441374B

Abstract

The invention discloses a preparation method of a porous structure super-hydrophobic surface with self-repairability, which comprises the following preparation steps: (1) mixing an organic silicon compound and a curing agent, coating the mixture on a metal substrate with a pretreated surface, performing precuring to form an organic silicon coating, uniformly spraying a pore-forming agent on the organic silicon coating, and drying, curing and forming; (2) placing the cured and molded metal substrate into deionized water, and stirring to dissolve a pore-forming agent on the surface of the substrate to form an organic silicon surface with a porous structure; (3) and (3) burning the organosilicon surface of the porous structure to obtain the super-hydrophobic surface. According to the invention, the three-dimensional hierarchical structure is prepared on the surface of the metal substrate through the organic silicon compound and the pore-forming agent, the obtained super-hydrophobic surface has excellent mechanical robustness, and the super-hydrophobic surface can be recovered after being directly burned by flame after being seriously damaged, so that the self-repairability is realized.

Description

Preparation method of porous-structure super-hydrophobic surface with self-repairability

Technical Field

The invention belongs to a preparation method of a super-hydrophobic surface, and particularly relates to a preparation method of a porous super-hydrophobic surface with self-healing property.

Background

The super-hydrophobic surface has received extensive attention because of its excellent anti-icing, antifouling, drag reduction's performance, and the super-hydrophobic surface of commonly used possesses excellent contact angle and roll angle, nevertheless through physical wear and chemical corrosion, the micro-nano structure on surface will suffer destruction to the super hydrophobicity has been lost. Therefore, poor mechanical robustness is the fundamental reason why superhydrophobic surfaces are difficult to be applied in industrial production on a large scale, and how to prepare superhydrophobic surfaces with excellent mechanical robustness is an existing problem to be solved urgently.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a preparation method of a super-hydrophobic surface which has excellent mechanical robustness and can be self-repaired.

The technical scheme is as follows: the invention discloses a preparation method of a porous structure super-hydrophobic surface with self-repairability, which comprises the following preparation steps:

(1) mixing an organic silicon compound and a curing agent, coating the mixture on a metal substrate with a pretreated surface, performing precuring to form an organic silicon coating, uniformly spraying a pore-forming agent on the organic silicon coating, and drying, curing and forming;

(2) placing the cured and molded metal substrate into deionized water, and stirring to dissolve a pore-forming agent on the surface of the substrate to form an organic silicon surface with a porous structure;

(3) and (3) burning the organosilicon surface of the porous structure to obtain the super-hydrophobic surface.

In the above scheme, in the burning process of the organosilicon compound, the Si element contained in the organosilicon compound is oxidized to generate SiO₂The particles are adhered to the surface of the substrate material to form a rough structure, and the surface energy of the organic silicon compound is further reduced under high-temperature treatment, so that the surface of the burned organic silicon compound has super-hydrophobic property under the combined action of the particles and the organic silicon compound. In addition, under the action of the pore-forming agent, a compact and continuous pore-shaped structure is formed on the surface of the organic silicon compound, the organic silicon surface positioned in the pores in the firing treatment also has super-hydrophobic property, and under the condition that the whole external part of the super-hydrophobic surface is damaged, the inside of the pore-shaped structure is not influenced by the external environment, so that the abraded surface still has super-hydrophobic property.

Further, in the step (1), the mass ratio of the organic silicon compound to the curing agent is 8-12: 1. wherein the organic silicon compound comprises any one of silicon resin, silicon oil or liquid silicon rubber, the viscosity is controlled to be more than 1000cps, and the organic silicon compound can not be cured due to too low viscosity. Preferred silicones include polydimethylsiloxane, cyclomethicone, aminosiloxane, polymethylphenylsiloxane, and the like. The curing agent is a substance containing active hydroxyl groups which can be conventionally used for curing and molding, and can be correspondingly selected according to the selection of the organic silicon compound.

Further, in the step (1), the pore-forming agent is water-soluble inorganic metal salt, specifically including sodium salt, nitrate, potassium salt, ammonium salt and the like, and the pore-forming agent needs to be easily soluble in water, so that the pore-forming agent can be completely removed in the subsequent stirring and dissolving process, and a porous structure formed on the surface is a key for realizing the surface superhydrophobicity performance. The average particle size of the pore-forming agent is 20-40 meshes, so that the average pore size of surface pore-forming can be controlled. The porous structure is a honeycomb three-dimensional porous structure, pores in the porous structure are continuously distributed, and the pore diameter of the porous structure is 50-500 mu m.

Further, in the step (1), the thickness of the organic silicon coating is 1-3 mm. An excessively thick coating can completely wrap the pore-forming agent particles and prevent the particles from dissolving, and an excessively thin coating can prevent the sample piece from being subjected to self-repairing treatment after being excessively worn.

Further, in the step (1), the metal substrate includes any one of copper, stainless steel or aluminum. Wherein, the metal substrate needs to be pretreated to ensure the coating of the surface organic silicon coating, and the pretreatment specifically comprises the following steps: the method comprises the steps of firstly placing a metal substrate in an oil removing agent, then cleaning to remove oil stains on the surface of the metal substrate, then placing the metal substrate in dilute hydrochloric acid for activation treatment, and finally placing the metal substrate in a drying oven for drying. The organic silicon compound can be coated by adopting a spraying method, the distance between a spray gun and the metal substrate is 20-30 cm, and the pressure of an air compressor is 4-5 Mpa.

Further, in the step (2), the stirring speed is 300-500 r/min, and the stirring time is 1-3 h.

Further, in the step (3), the burning treatment specifically refers to burning the surface of the organic silicon by using a flame thrower, wherein the tip of the flame thrower contacts the surface of the organic silicon, and the burning treatment time is 5-8 min.

The principle of the invention is as follows: SiO generated in the combustion process of Si in the organic silicon compound adopted by the invention₂The reduced surface energy of the particles and of the high temperature treatment is responsible for the superhydrophobicity of the surface. The prepared surface is a three-dimensional porous structure with honeycomb-like layers by dissolving the organic silicon compound and the pore-forming agent, and the subsequent burning treatment further ensures that the surface in the hole also has super-hydrophobicity, so that the surface can still keep the super-hydrophobicity after the surface is worn, and the super-hydrophobicity of the worn surface can be endowed again by the burning treatment, thereby realizing the self-repairing effect of the surface.

Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: (1) the super-hydrophobic surface prepared by the method has excellent mechanical robustness, still has a rolling angle less than 5 degrees after being polished by 1000-mesh sand paper and impacted by water flow, the surface rolling angle is only reduced by 2 degrees, and the water contact angle is still more than 150 degrees; (2) the preparation method is simple and convenient, and the used equipment is common equipment in industrial production and can be used for industrial large-scale production; when the surface is seriously abraded, the super-hydrophobicity can be restored only by directly burning the surface by a flame thrower, the treatment process is greatly simplified, and the method has wide prospect in industrial application.

Drawings

FIG. 1 is a schematic view of the porous structure of the superhydrophobic surface prepared in example 1;

FIG. 2 is an initial contact angle test of a superhydrophobic surface of example 1;

FIG. 3 shows the contact angle test of example 1 after robustness test;

FIG. 4 is a microscope image of example 1 after robustness testing;

FIG. 5 is a contact angle of a sample before the surface of PDMS is burned;

FIG. 6 is a contact angle of a sample after the surface of PDMS is burned;

fig. 7 is a bouncing experimental test of the superhydrophobic surface and the bare copper plate in examples 1, 2, and 3.

Detailed Description

The technical solution of the present invention is further described in detail with reference to the accompanying drawings and examples.

In the following embodiments, in order to verify whether the prepared superhydrophobic surface has good mechanical robustness, robustness tests are divided into a sand paper dragging friction experiment and a water flow impact experiment. And observing the surface before robustness testing and the surface after testing through a microscope, comparing the surface appearances of the surface before robustness testing and the surface after robustness testing, and verifying that the surface after friction still has a similar surface structure with the surface before friction, thereby verifying the self-repairability of the prepared super-hydrophobic surface.

Example 1

A preparation method of a super-hydrophobic surface with a self-repairable porous structure comprises the following steps:

step 1): putting 99.9% of 30mm by 40mm by 5mm red copper sample pieces into a metal degreasing agent for 30min, then cleaning the red copper sample pieces by using plasma water, then putting the red copper sample pieces into a constant-temperature drying box at 70 ℃ for standing for 30min, then putting the dried metal substrate into 10 wt.% HCl for activating for 20min, and putting the dried metal substrate into the constant-temperature drying box at 70 ℃ for 30min after cleaning by using the plasma water;

step 2): mixing PDMS and a curing agent according to a mass ratio of 10:1, stirring for 10min at room temperature, uniformly coating on a treated metal substrate to form a 2mm PDMS coating surface, then placing the PDMS coating surface in a 70 ℃ drying oven for 10min, then uniformly spraying 10g of anhydrous sodium sulfate particles with an average particle size of 20 meshes on the surface of the precured PDMS coating by using a particle spraying machine, and then continuously placing in a 70 ℃ constant temperature drying oven for 1 h. Placing the dried metal substrate into a beaker filled with plasma water, placing the beaker on a magnetic stirrer with the temperature of 40 ℃ and the rotating speed of 400r/min for 1h, stirring the sodium sulfate particles on the surface of PDMS by the magnetic stirrer, and dissolving the sodium sulfate particles in the water to leave irregular continuous holes of 50-200 microns on the surface;

step 3): and (3) placing the metal substrate with the PDMS coating of the multilayer hole structure under a flame thrower for burning for 5min, wherein the height of the flame thrower is 10cm away from the surface of the sample. The burned metal substrate surface presents a milky three-dimensional hierarchical structure, and a super-hydrophobic surface with a self-repairing porous structure is obtained.

Referring to the appearance of the superhydrophobic surface porous structure of fig. 1, it can be seen that the surface forms a honeycomb three-dimensional reticular porous structure after treatment, which illustrates that the porous structure can be prepared by the action of the pore-forming agent, thereby laying a foundation for the self-repair of the superhydrophobic performance of the surface.

Referring to fig. 2 and 3, the initial surface contact angle and the robustness-tested surface contact angle are shown, respectively; in fig. 2, due to the modification of the PDMS with the micro-nano rough hierarchical structure and the low surface energy, the initial surface rolling angle is 3 °, the water contact angle is 157 °, and the super-hydrophobicity is excellent; in fig. 3, after being polished by 1000-mesh sand paper and after being impacted by water flow of 2m/s, the rolling angle of the surface is 5 degrees, the water contact angle is 151 degrees, and the prepared surface is proved to have excellent mechanical robustness; the surface morphology in fig. 4 shows that the superhydrophobic surface after the robustness test still retains a continuous three-dimensional porous structure, and further proves that the surface after the robustness test still has superhydrophobicity.

In order to verify the influence of the burning treatment on the hydrophobic property of the surface organic silicon compound, water contact angle tests are respectively carried out on the completely coated and cured PDMS surface and the burning treated PDMS surface, referring to FIGS. 5 and 6, the contact angle of the PDMS surface before the burning treatment is 123 degrees, and the contact angle of the PDMS surface after the burning treatment is 153 degrees, so that the surface energy of the organic silicon compound can be changed through the burning treatment, and the super-hydrophobic property is achieved.

Example 2

step 1): placing a stainless steel sample of 30mm by 40mm by 5mm into a metal degreasing agent for 30min, then cleaning by using plasma water, then placing the stainless steel sample into a constant-temperature drying box at 70 ℃ for standing for 30min, then placing the dried metal substrate into 10 wt.% of HCl for activating for 20min, and placing the stainless steel sample into the constant-temperature drying box at 70 ℃ for 30min after cleaning by using the plasma water;

step 2): mixing the silicone oil with the viscosity of 1500cps and a curing agent according to the mass ratio of 12:1, stirring for 10min at room temperature, uniformly coating on a treated metal substrate to form a 2mm coating surface, then placing the coating surface in a drying oven at 80 ℃ for 10min, then uniformly spraying 10g of anhydrous sodium metasilicate particles with the average particle size of 30 meshes on the surface of the pre-cured silicone oil coating by using a particle spraying machine, and then continuously placing the coating surface in a constant-temperature drying oven at 80 ℃ for 2 h. Putting the dried metal substrate into a beaker filled with plasma water, placing the beaker on a magnetic stirrer with the temperature of 40 ℃ and the rotating speed set to be 300r/min for 3 hours, stirring and treating anhydrous sodium metasilicate particles on the surface of the silicon oil by the magnetic stirrer, dissolving the anhydrous sodium metasilicate particles in water, and leaving irregular continuous holes of 200-400 microns on the surface;

step 3): and (3) placing the metal substrate with the silicone oil coating with the multi-layer hole structure under a flame thrower for burning treatment for 8min, wherein the height of the flame thrower is 10cm away from the surface of the sample. The burned metal substrate surface presents a milky three-dimensional hierarchical structure, and a super-hydrophobic surface with a self-repairing porous structure is obtained.

Performance detection

TABLE 1

In order to verify that the adopted preparation method has universality and repeatability. In the experiment, 4 samples were prepared by the preparation method in example 2, and the initial contact angle measurement and the contact angle measurement after the mechanical robustness test were performed, respectively. As can be seen from Table 1, the initial contact angles of the five prepared samples are all 150-160 degrees, and the samples still have super-hydrophobicity after robustness testing.

Example 3

step 1): putting an aluminum sample piece of 30mm by 40mm by 5mm into a metal degreasing agent for 30min, then cleaning the aluminum sample piece by using plasma water, then putting the aluminum sample piece into a constant-temperature drying box of 70 ℃ for standing for 30min, then putting the dried metal substrate into 10 wt.% of HCl for activating for 20min, and after cleaning the aluminum sample piece by using the plasma water, putting the aluminum sample piece into the constant-temperature drying box of 70 ℃ for 30 min;

step 2): mixing liquid silicon rubber and a curing agent according to a mass ratio of 8:1, stirring for 10min at room temperature, uniformly coating on a treated metal substrate to form a 2mm coating surface, then placing the coating surface in a drying box at 100 ℃ for 10min, then uniformly spraying 10g of anhydrous sodium metasilicate particles with the average particle size of 40 meshes on the surface of the pre-cured silicone oil coating by using a particle spraying machine, and then continuously placing the coating surface in a constant-temperature drying box at 100 ℃ for 2 h. Putting the dried metal substrate into a beaker filled with plasma water, placing the beaker on a magnetic stirrer with the temperature of 40 ℃ and the rotating speed set to be 500r/min for 2 hours, stirring the anhydrous sodium metasilicate particles on the surface of the coating by the magnetic stirrer, dissolving the anhydrous sodium metasilicate particles into water, and leaving irregular continuous holes of 300-500 microns on the surface;

step 3): the metal substrate with the liquid silicon rubber coating of the multi-layer hole structure is placed under a flame thrower to be burnt for 6min, and the height of the flame thrower is 10cm away from the surface of the sample. The burned metal substrate surface presents a milky three-dimensional hierarchical structure, and a super-hydrophobic surface with a self-repairing porous structure is obtained.

Performance detection

TABLE 2

In order to verify that the adopted preparation method has universality and repeatability. In the experiment, 4 samples were prepared by the preparation method in example 3, and the initial contact angle measurement and the contact angle measurement after the mechanical robustness test were performed, respectively. As can be seen from Table 2, the initial contact angles of the five prepared samples are all 150-160 degrees, and the samples still have super-hydrophobicity after robustness testing.

The surfaces of examples 1-3 were tested in a bouncing test, and the results are shown in Table 3 below.

Table 3 test results of the superhydrophobic surface bounce tests of examples 1-3

As shown in Table 3 and FIG. 7, bounce experiments were performed at room temperature of 20 ℃ and humidity of 45-55%, so as to ensure environmental uniformity, and the drop height of the set drops was 100mm, so as to ensure that the potential energy of the drops falling was uniform. The energy transfer of the droplets was estimated by comparing the maximum diffusion diameter (dmax) of the droplets when they landed on the surface, and since the PDMS coated sample had a lower surface energy, more energy was transferred to kinetic energy, and it was seen from the table that the droplet diffusion diameter of the PDMS coated sample reached a maximum of 82.10 mm. In addition, since the bare substrate sample does not have superhydrophobicity, the droplets cannot form a bounce, the minimum contact diameter of the droplets with the surface is not 0(dmin ≠ 0), while the other three sets of samples have superhydrophobic coatings, the droplets can completely leave the surface, so the minimum contact area of the droplets with the surface is 0(dmin ═ 0). t represents the time taken for the water drop to complete the whole process of diffusion, contraction and bounce. Shorter time taken for the whole process may indicate lower surface energy, the shortest time taken for the PDMS sample is 15.1ms, and higher height of the water drop bouncing to the highest point indicates lower surface adhesion, which may prove better hydrophobicity of the surface. The data in the table show that the spring height of the PDMS coating sample is 90mm, and the results show that the PDMS coating of example 1 has lower surface energy.

Example 4

4 sets of parallel tests were designed, the basic procedure was the same as in example 1, except that the average particle diameters of the anhydrous sodium sulfate particles were 10 mesh, 30 mesh, 40 mesh and 50 mesh, and the prepared superhydrophobic surfaces were respectively subjected to performance testing, and the results obtained are shown in table 4 below.

Table 4 example 4 test results of superhydrophobic surface properties

As can be seen from table 4, the particle diameters of the pore-forming agent (anhydrous sodium sulfate) used had a small influence on the initial contact angles, and the average initial contact angles were all 150 ° to 160 °. But the particle size of the particles has a large influence on the contact angle after the mechanical robustness test. The contact angle of the sample pieces with the grain diameters of 10 meshes and 50 meshes is obviously reduced after robustness testing, and the abrasion resistance is greatly reduced. The analysis reason may be that the sample with the particle size of 10 meshes produces a small pore structure and an unobvious hierarchical structure, so that the surface abrasion is more serious after a robustness experiment. The hole structure generated by the sample piece with the particle size of 50 meshes is large, and after a robustness experiment, the local pore size is large, so that liquid drops are in contact with the inside of the pore size, and the contact angle is obviously reduced. Therefore, the pore-forming agent is selected, and the sample piece with the grain diameter of 20 meshes to 40 meshes has better mechanical robustness.

Example 5

4 sets of parallel tests were designed, the basic procedure was the same as in example 1, except that the thickness of the PDMS coating, specifically 0.5mm, 1mm, 3mm and 4mm, and the prepared superhydrophobic surface was respectively subjected to performance testing, and the obtained results are shown in Table 5 below.

Table 5 example 4 test results of superhydrophobic surface properties

As can be seen from Table 5, the initial contact angles were less affected by the use of coatings of different thicknesses, and the average initial contact angles were all 150 to 160 °. But coatings of different thicknesses have a greater effect on the contact angle after the second mechanical robustness test after repair. The contact angle of a sample piece with the coating thickness of 0.5mm is obviously reduced after the secondary robustness test. The analytical reasons may be that after severe wear of the excessively thin coating thickness, a part of the substrate remains exposed after repair due to the excessively thin coating. From the results of the robustness experiments, too thin a coating may result in failure to recover superhydrophobicity after repair. From experimental results, the coating with the coating thickness of 2mm still has super-hydrophobicity after being repaired even after 10 times of robustness tests, and the practical application requirements are met. However, an excessively thick coating is unnecessary, the appearance is affected by the excessively thick coating, the organic salt is not dissolved easily, and when the coating is 3mm, the organic salt is deposited at the bottom of the coating and cannot be dissolved completely, so that the coating thickness should be controlled to be 1-3 mm.

Example 6

The basic procedure was the same as in example 1, except that a superhydrophobic surface was directly prepared without using a pore-forming agent, and the performance of the prepared superhydrophobic surface was tested, and the results obtained were as shown in table 6 below.

Table 6 example 6 test results of superhydrophobic surface properties

As can be seen from table 6, the initial contact angle of the sample without using the porogen is lower than that of the sample using the porogen, because the three-dimensional hierarchical structure cannot be formed on the surface of the sample without the porogen, and the coarse hierarchical structure can increase the contact angle of the surface of the sample. After robustness testing, the samples without the pore former lost hydrophobicity after abrasion.

Example 7

The basic procedure was the same as in example 1, except that an insoluble inorganic metal salt was sprayed on the surface of the coating to prepare a superhydrophobic surface, and the results obtained were as shown in table 7 below.

Table 7 example 7 test results of superhydrophobic surface properties

As can be seen from table 7, the use of the easily soluble inorganic salt and the hardly soluble inorganic salt had no effect on the initial contact angle of the sample, but the contact angle after the robustness test using the hardly soluble inorganic salt was greatly reduced. Since a large amount of the sparingly soluble inorganic salt remains in the coating layer and a part of the inorganic salt is exposed to the surface of the sample after abrasion, the contact angle of the sample is significantly reduced after the inorganic salt is brought into contact with the water droplet.

Claims

1. A preparation method of a porous structure super-hydrophobic surface with self-repairability is characterized by comprising the following preparation steps:

2. The method for preparing a superhydrophobic surface with a porous structure having self-repairability according to claim 1, wherein: in the step (1), the mass ratio of the organic silicon compound to the curing agent is 8-12: 1.

3. the method for preparing a superhydrophobic surface with a porous structure having self-repairability according to claim 2, wherein: the organic silicon compound comprises any one of silicone resin, silicone oil or liquid silicone rubber.

4. The method for preparing a superhydrophobic surface with a porous structure having self-repairability according to claim 1, wherein: in the step (1), the pore-forming agent is water-soluble inorganic metal salt, and the average particle size of the pore-forming agent is 20-40 meshes.

5. The method for preparing a superhydrophobic surface with a porous structure having self-repairability according to claim 1, wherein: in the step (1), the thickness of the organic silicon coating is 1-3 mm.

6. The method for preparing a superhydrophobic surface with a porous structure having self-repairability according to claim 1, wherein: in the step (1), the metal substrate includes any one of copper, stainless steel or aluminum.

7. The method for preparing a superhydrophobic surface with a porous structure having self-repairability according to claim 1, wherein: in the step (1), the pretreatment specifically comprises: the method comprises the steps of firstly placing a metal substrate in an oil removing agent, then cleaning to remove oil stains on the surface of the metal substrate, then placing the metal substrate in dilute hydrochloric acid for activation treatment, and finally placing the metal substrate in a drying oven for drying.

8. The method for preparing a superhydrophobic surface with a porous structure having self-repairability according to claim 1, wherein: in the step (2), the porous structure is a honeycomb three-dimensional porous structure, pores in the porous structure are continuously distributed, and the pore diameter of the porous structure is 50-500 mu m.

9. The method for preparing a superhydrophobic surface with a porous structure having self-repairability according to claim 1, wherein: in the step (2), the stirring speed is 300-500 r/min, and the stirring time is 1-3 h.

10. The method for preparing a superhydrophobic surface with a porous structure having self-repairability according to claim 1, wherein: in the step (3), the burning treatment specifically refers to burning the surface of the organic silicon by using a flame thrower, wherein the tip of the flame thrower is in contact with the surface of the organic silicon, and the burning treatment time is 5-8 min.