Cementitious material surface biomimetic hydrophobic coating and method of making same

Abstract

The application discloses a kind of cement-based material surface biomimetic hydrophobic coating, including 0.1-0.6 parts of organic matter containing catechol group, 0.2-3 parts of dodecylamine, 17-75 parts of tris buffer solution, 13-69 parts of anhydrous ethanol, 0.1-0.5 parts of hydrogen peroxide, 0.1-1 parts of deposition aid;Coating surface microstructure is plate block and small spherical shape.The application also discloses the preparation method of the cement-based material surface biomimetic hydrophobic coating, including the following steps: mixing dopamine, dodecylamine, tris buffer solution and anhydrous ethanol, and loading into the middle part of atomization device container for spraying deposition solution;CuSO4 and H2O2 are divided and loaded into the container on both sides of atomization device;Each face of cement test block is sprayed, dried, and cyclically sprayed-dried;Surface is washed, and naturally dried.The application prepares biomimetic hydrophobic coating on cement-based material surface by one-step co-deposition method, and the prepared coating has the characteristics of good hydrophobicity and uniform deposition.

Description

Technical Field

[0001] The invention relates to a hydrophobic coating and a preparation method thereof, in particular to a bionic hydrophobic coating on the surface of a cement-based material and a preparation method thereof. Background Art

[0002] Cement-based materials contain numerous tiny pores on and within their surfaces, making them extremely susceptible to water and ion penetration and erosion. These pores then undergo complex chemical reactions with various hydration products, causing structural damage and deteriorating mechanical properties. In recent years, biomimetics have advanced, and numerous biomimetic organic coatings have been designed. However, organic protective materials are not well compatible with inorganic cement matrices, while organic coatings struggle to establish strong adhesion to wet surfaces. Hydrophobic coatings, in particular, are difficult to apply directly to wet, hydrophilic cement surfaces; the surface must first be dried before application. Consequently, conventional hydrophobic coatings, when applied to cement-based surfaces, particularly wet ones, suffer from reduced mechanical properties and poor water resistance. Mussels, in humid marine environments, can use their filopodia to form strong adhesion to various substrates. The catechol functional groups in their adhesive proteins are key to achieving this strong adhesion. Inspired by this, dopamine, a compound with catechol functional groups, has been extensively studied. Lee et al. proposed a method in which a thin film substrate is immersed in an aqueous solution of dopamine, and a PDA coating attached to the surface of the substrate is formed by the self-polymerization of dopamine. In previous studies, the preparation of dopamine hydrophobic coatings usually involves the deposition of a PDA coating and a subsequent secondary hydrophobic modification process of the coating. For example, Cao et al. immersed a brass substrate in an aqueous solution of dopamine, prepared a PDA coating on its surface, and then modified it with perfluorodecanethiol (PFDT) to obtain a hydrophobic surface. The corrosion resistance of the hydrophobically modified brass substrate was also significantly improved. However, these methods require multiple depositions on the substrate surface to generate a PDA coating with hydrophobic properties.

[0003] The Chinese patent application number 201910847215.X discloses a concrete anti-corrosion coating and a preparation method thereof. It requires the adhesion of three layers of coating, namely, an induction layer, a mineralization layer, and a low surface energy layer, on the concrete surface in sequence to achieve hydrophobic and anti-corrosion properties. The process is cumbersome and highly correlated. If an evenly attached induction layer is not formed, it cannot provide sufficient templates and carriers for the subsequent mineralization process, thereby reducing the overall functionality of the coating; and multi-layer coating can easily lead to an excessively thick coating, reducing the concrete's own bearing capacity. The Chinese patent application number 202210801843.6 discloses a super-amphiphobic and super-weather-resistant silicone protective coating and a preparation method thereof, which needs to be carried out under heating conditions.

[0004] In general, the existing methods for preparing hydrophobic coatings for concrete have complicated operating steps, complex raw material components, harsh experimental conditions, strong requirements for surface dryness, poor practical applicability, and difficult to control deposition uniformity. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a bionic hydrophobic coating on the surface of cement-based materials with good hydrophobicity and uniform deposition. Another purpose of the present invention is to provide a simple and convenient method for preparing a bionic hydrophobic coating on the surface of cement-based materials that can protect against moisture.

[0006] Technical solution: The bionic hydrophobic coating on the surface of a cement-based material described in the present invention includes 0.1 to 0.6 parts of an organic matter containing a catechol group, 0.2 to 3 parts of dodecylamine, 17 to 75 parts of a tris buffer solution, 13 to 69 parts of anhydrous ethanol, 0.1 to 0.5 parts of hydrogen peroxide, and 0.1 to 1 part of a deposition aid; the surface microstructure of the coating is plate-shaped and spherical.

[0007] Furthermore, the deposition aid is one or more of a copper ion solution, a magnesium ion solution, an iron ion solution and a calcium ion solution, preferably a copper sulfate solution.

[0008] Furthermore, the organic matter containing catechol groups is any one of dopamine, phenolic acid, and tannic acid, preferably dopamine. Furthermore, the surface microstructure of the coating is controlled by adjusting the ratio of tris buffer solution and anhydrous ethanol, the ratio of dopamine and dodecylamine, and different types of deposition aids. For example, when the volume ratio of tris buffer solution to ethanol is lower than 1:3, the PDA derivatives are mostly scattered small spheres; when the ratio is higher than 5:1, they are mostly plate-like, and the coverage is low, and the deposition thickness is too low, resulting in reduced hydrophobicity of the coating. When the amount of dodecylamine is continuously increased, the number of scattered small spherical PDA derivatives increases, and the blocky PDA derivatives gradually decrease. When the metal salt ion Cu is added 2+ , Fe 3+ , Ca 2+ Afterwards, the coverage and density of the PDA coating on the concrete surface were improved, and the PDA derivatives tended to have agglomerated and blocky structures, thereby improving the hydrophobicity of the hydrophobic coating in terms of macroscopic performance.

[0009] The method for preparing a biomimetic hydrophobic coating on the surface of a cement-based material according to the present invention comprises the following steps:

[0010] (1) An organic compound containing a catechol group, dodecylamine, a tris buffer solution, and anhydrous ethanol are uniformly mixed and placed in the middle portion of a container of an atomizer for spraying a deposition solution;

[0011] (2) Adding a deposition aid and hydrogen peroxide solution to the containers on both sides of the atomizing device;

[0012] (3) spraying each surface of the cement test block and then drying it in air, repeating the spraying-drying process;

[0013] (4) After spraying, the surface is rinsed and allowed to dry naturally to obtain a bionic hydrophobic coating on the surface of the cement-based material.

[0014] Furthermore, in step (1), the volume ratio of tris buffer solution to anhydrous ethanol is 1:3 to 5:1, and the mass ratio of dopamine to dodecylamine is 1:1 to 30. Preferably, the volume ratio of tris buffer solution to anhydrous ethanol is 3:1, and the mass ratio of dopamine to dodecylamine is 1:1.

[0015] Furthermore, in step (2), the concentration of the deposition aid is 2-3 g / L, and the concentration of the hydrogen peroxide is 0.1-0.2 g / L.

[0016] Furthermore, in step (3), the spraying distance is 5 to 10 cm, the drying time is 10 to 15 minutes, and the atomizing nozzle is always kept perpendicular to the cement test block during spraying. The cycle is 6 to 8 times.

[0017] Furthermore, in step (4), the rinsing is performed by alternately rinsing with deionized water and anhydrous ethanol, and the natural drying time is 24 to 30 hours.

[0018] Preparation principle: Mimicking the adhesion mechanism of marine organisms such as mussels, the two components are an aqueous solution and an ethanol solution. The aqueous solution contains dopamine, hydrogen peroxide, and a deposition aid. Dopamine has a catechol structure and contains a large number of benzene rings and phenolic hydroxyl groups. The benzene rings are tightly bound to each other through π-π interactions, enhancing cohesion. The phenolic hydroxyl groups form hydrogen bonds with the substrate surface to achieve adhesion. Hydrogen peroxide can oxidize the phenolic hydroxyl groups to quinones. At the same time, the presence of the deposition aid provides metal-DOPA interaction, enhancing the mechanical strength of adhesion. The ethanol solution contains the hydrophobic molecule dodecylamine. Dodecylamine is a low-free-energy substance that gives the PDA coating its hydrophobic properties.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0020] 1. A biomimetic hydrophobic coating was prepared on the surface of cement-based materials using a one-step co-deposition method. The solution composition conditions for the preparation were successfully optimized. The prepared coating has good hydrophobicity and uniform deposition.

[0021] 2. A highly hydrophobic effect can be achieved by directly spraying on a wet surface. The operation is simpler and more convenient, and it is also highly feasible in practical applications. It can be used for hydrophobic protection of cement-based material surfaces in seawater environments, hydraulic environments, and humid environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the atomizing device of the present invention;

[0023] Figure 2 Surface contact angle data of the coating deposited at different ratios of tris buffer solution to ethanol in Example 4;

[0024] Figure 3 Surface contact angle data of the coatings deposited at different dopamine / dodecylamine ratios in Example 5;

[0025] Figure 4 The surface contact angle data of the coating deposited at different ratios within the optimal dopamine / dodecylamine ratio range in Example 5;

[0026] Figure 5 The scanning electron microscope images of the cross-section of the coating prepared by different preparation methods are shown in Figure 1, where a is without dodecylamine, b is dip coating, and c is spray coating.

[0027] Figure 6 The scanning electron microscope images of the cross section of the coating prepared by the dipping method of different metal salt ions in Example 4, where a is Cu 2+ , b is Mg 2+ , c is Fe 3+ , d is Ca 2+ ;

[0028] Figure 7 Surface contact angle data of the coating prepared by the metal salt ion dip coating method in Example 4. DETAILED DESCRIPTION

[0029] In the following examples, the pH value of the tris-HCl buffer solution is preferably 8-9, and the density is 1.05 g / cm 3 The density of anhydrous ethanol is 0.786g / cm 3 The relative molecular mass of dopamine is 153.18. The relative molecular mass of dodecylamine is 185.35. The molar mass of copper sulfate is 160 g / mol.

[0030] like Figure 1 The atomizing device used when spraying the deposition solution includes three chambers. The middle chamber is used to load the solution mixed in step (1), and the chambers on both sides are used to place the deposition aid and hydrogen peroxide respectively. The three chambers are connected to the nozzle through pipelines.

[0031] Example 1

[0032] A method for preparing a biomimetic hydrophobic coating on the surface of a cement-based material comprises the following steps:

[0033] (1) 0.6 parts of tannic acid, 0.6 parts of dodecylamine, 17 parts of tris buffer solution and 69 parts of anhydrous ethanol were uniformly mixed and loaded into the middle part of the atomizer container of the spray deposition solution; the volume ratio of tris buffer solution to anhydrous ethanol was 1:3, and the mass ratio of tannic acid to dodecylamine was 1:1.

[0034] (2) 0.5 parts of 2 g / L deposition aid calcium sulfate solution and 0.1 parts of 0.1 g / L hydrogen peroxide solution were added to the containers on both sides of the atomizing device.

[0035] (3) Spray each surface of the wet cement test block. During spraying, always keep the atomizing nozzle at a right angle to the test block and maintain a distance of 5 cm. Spray each surface of the cement test block for 10 seconds. Then dry in air for 10 minutes. Repeat the spray-drying process 6 times.

[0036] (4) After spraying, the surface of the cement specimen was repeatedly rinsed with deionized water and anhydrous ethanol and dried naturally for 24 hours to obtain a bionic hydrophobic coating on the surface of the cement-based material. The microstructure of the coating surface was plate-like and spherical.

[0037] The calcium sulfate solution in this embodiment can be replaced by any one of copper sulfate solution, magnesium sulfate solution or iron sulfate solution.

[0038] Example 2

[0039] A method for preparing a biomimetic hydrophobic coating on the surface of a cement-based material comprises the following steps:

[0040] (1) 0.1 parts of phenolic acid, 3 parts of dodecylamine, 75 parts of tris buffer solution and 13 parts of anhydrous ethanol were uniformly mixed and loaded into the middle part of the atomizer container of the spray deposition solution; the volume ratio of tris buffer solution to anhydrous ethanol was 5:1, and the mass ratio of phenolic acid to dodecylamine was 1:30.

[0041] (2) 1 part of 3 g / L magnesium sulfate solution as a deposition aid and 0.5 parts of 0.2 g / L hydrogen peroxide solution were added to the containers on both sides of the atomizing device.

[0042] (3) Spray each surface of the wet cement test block. During spraying, always keep the atomizing nozzle at a right angle to the test block and maintain a distance of 10 cm. Spray each surface of the cement test block for 10 seconds. Then dry in air for 15 minutes. Repeat the spray-drying process 8 times.

[0043] (4) After spraying, the surface of the cement specimen was repeatedly rinsed with deionized water and anhydrous ethanol and dried naturally for 30 hours to obtain a bionic hydrophobic coating on the surface of the cement-based material. The microstructure of the coating surface was plate-like and spherical.

[0044] Example 3

[0045] A method for preparing a biomimetic hydrophobic coating on the surface of a cement-based material comprises the following steps:

[0046] (1) 0.2 parts of dopamine, 0.2 parts of dodecylamine, 68 parts of tris buffer solution and 20 parts of anhydrous ethanol were uniformly mixed and loaded into the middle part of the atomizer container of the spray deposition solution; the volume ratio of tris buffer solution and anhydrous ethanol was 3:1, and the mass ratio of dopamine and dodecylamine was 1:1.

[0047] (2) 0.1 part of 2.5 g / L copper sulfate solution as a deposition aid and 0.2 part of 0.15 g / L hydrogen peroxide solution were added to the containers on both sides of the atomizing device.

[0048] (3) Spray each surface of the wet cement test block. During spraying, always keep the atomizing nozzle at a right angle to the test block and maintain a distance of 7 cm. Spray each surface of the cement test block for 10 seconds. Then dry in air for 13 minutes. Repeat the spray-drying process 7 times.

[0049] (4) After spraying, the surface of the cement specimen was repeatedly rinsed with deionized water and anhydrous ethanol and dried naturally for 27 h to obtain a bionic hydrophobic coating on the surface of the cement-based material. The microstructure of the coating surface was plate-like and spherical.

[0050] Example 4

[0051] This example aims to determine the optimal volume ratio of tris buffer solution and ethanol.

[0052] A method for preparing a biomimetic hydrophobic coating on the surface of a cement-based material comprises the following steps:

[0053] (1) 0.2 parts of dopamine, 0.2 parts of dodecylamine, 17-75 (17, 26, 44, 60, 68, 72, 75) parts of tris buffer solution and 13-69 (69, 60, 43, 27, 20, 16, 13) parts of anhydrous ethanol were uniformly mixed and loaded into the middle part of the atomizer container of the spray deposition solution; the volume ratio of tris buffer solution and anhydrous ethanol was controlled to be 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, respectively, and the mass ratio of dopamine and dodecylamine was 1:1.

[0054] (2) 0.2 parts of 2.4 g / L copper sulfate solution as a deposition aid and 0.2 parts of 0.196 g / L hydrogen peroxide solution were added to the containers on both sides of the atomizing device.

[0055] (3) Spray each surface of the wet cement test block. During spraying, always keep the atomizing nozzle at a right angle to the test block and maintain a distance of 8 cm. Spray each surface of the cement test block for 10 seconds. Then dry in air for 10 minutes. Repeat the spray-drying process 6 times.

[0056] (4) After spraying, the surface of the cement specimen was repeatedly rinsed with deionized water and anhydrous ethanol and dried naturally for 24 hours to obtain a bionic hydrophobic coating on the surface of the cement-based material. The microstructure of the coating surface was plate-like and spherical.

[0057] The instrument measures the contact angle of the coating prepared at different volume ratios of tris buffer solution and ethanol. Figure 2 As shown, when the volume ratio of tris buffer solution to ethanol is 3:1, the best hydrophobic effect is shown, CA = 138° ± 3°.

[0058] Example 5

[0059] This example aims to determine the optimal volume ratio of dopamine and laurylamine.

[0060] The remaining steps of this embodiment are the same as those of embodiment 4, with the only difference being that the mass ratio of dopamine to dodecylamine is controlled to be 1:1, 1:5, 1:10, 1:15, 1:20, and 1:30, respectively. The contact angles of the coatings prepared at different dopamine / dodecylamine ratios were measured to narrow the ratio range. Figure 3 As shown, the optimal ratio range is 1:1.

[0061] Then, the refinement intervals were 1:0.5, 1:2, 1:3, and 1:4, and the contact angles were measured, e.g. Figure 4 As shown, the optimal dopamine / dodecylamine ratio was 1:1, with a CA of 143° ± 4°.

[0062] Comparative Example 1

[0063] The remaining steps of this comparative example are the same as those of Example 3, with the only difference being that dodecylamine is not added in step (1).

[0064] Comparative Example 2

[0065] The remaining steps of this comparative example are the same as those in Example 3, with the only difference being that steps (2) to (4) are replaced by: immersing the pre-dried cement test block in the deposition solution, placing it on an oscillator, and oscillating it at a speed of 140 r / min for 1 h. After the oscillation is completed, taking it out, repeatedly rinsing it with deionized water and anhydrous ethanol, and drying it at room temperature for 24 h to complete the preparation of the hydrophobic coating.

[0066] like Figure 5 As shown, scanning electron microscopy reveals that the coatings prepared by the spray coating method (Example 3) and the dip coating method (Comparative Example 2) have similar thicknesses, but the spray coating is deposited more densely and compactly, which helps improve the durability of the hydrophobic coating itself. The coating prepared by deposition without the addition of dodecylamine (Comparative Example 1) has mostly scattered small globules of PDA derivatives on its surface, resulting in low coating coverage. However, the PDA coating prepared by co-deposition of dopamine and dodecylamine (Example 3) is more dense, which helps improve the coating's hydrophobic properties.

[0067] Example 6

[0068] This example aims to explore the effects of metal salt ions on the deposition performance and hydrophobicity of biomimetic hydrophobic coatings on cement-based surfaces.

[0069] The remaining steps of this embodiment are the same as those of Example 4, with the only difference being that the deposition aid copper sulfate solution is replaced with copper chloride (CuCl2), magnesium chloride (MgCl2), ferric chloride (FeCl3), and calcium chloride (CaCl2) of the same concentration to prepare four different deposition solutions.

[0070] The surfaces of the coatings prepared by the four metal salt ion dipping methods were observed using a scanning electron microscope. Figure 6 As shown, Cu is added to the deposition solution 2+ The surface of the prepared coating is covered with a large number of block-shaped PDA derivatives, and small spherical PDA derivatives are scattered among them. Figure 7 As shown in the surface contact angle data of the coating, it can be seen that the addition of Cu 2+ The contact angle obtained by the deposition solution is the largest, indicating that Cu 2+ It is still an advantageous deposition aid.

[0071] In addition, the surface microstructure of the coating is controlled by adjusting the ratio of tris buffer solution and anhydrous ethanol, the ratio of dopamine and dodecylamine, and different types of deposition aids. For example, when the volume ratio of tris buffer solution to ethanol is lower than 1:3, the PDA derivatives are mostly scattered small spheres; when the ratio is higher than 5:1, they are mostly plate-like, and the coverage is low, and the deposition thickness is too low, resulting in reduced hydrophobicity of the coating. When the amount of dodecylamine increases, the number of scattered small spherical PDA derivatives increases, and the blocky PDA derivatives gradually decrease. When the metal salt ion Cu is added, the PDA derivatives are mostly scattered small spheres ... 2+ , Fe 3+ , Ca 2+ Afterwards, the coverage and density of the PDA coating on the concrete surface were improved, and the PDA derivatives tended to have agglomerated and blocky structures, thereby improving the hydrophobicity of the hydrophobic coating in terms of macroscopic performance.

[0072] Among the above embodiments, embodiment 3 is the best embodiment.

Claims

1. A method for preparing a bionic hydrophobic coating on the surface of a cement-based material, characterized in that: The following steps are involved: (1) The organic matter containing catechol groups, dodecylamine, tris buffer solution and anhydrous ethanol are uniformly mixed and placed in the middle part of the atomizer container for spraying the deposition solution; (2) Add the deposition aid and hydrogen peroxide solution into the containers on both sides of the atomizing device; (3) Spray each surface of the cement test block and then dry it in air, repeating the spray-drying process; (4) After spraying, rinse the surface and allow it to dry naturally to obtain a bionic hydrophobic coating on the surface of the cement-based material; The bionic hydrophobic coating on the surface of the cement-based material comprises 0.1-0.6 parts of an organic substance containing a catechol group, 0.2-3 parts of dodecylamine, 17-75 parts of a tris buffer solution, 13-69 parts of anhydrous ethanol, 0.1-0.5 parts of hydrogen peroxide, and 0.1-1 parts of a deposition aid; the surface microstructure of the coating is plate-like and spherical; In the step (3), the spraying distance is 5 to 10 cm, the drying time is 10 to 15 minutes, and the atomizing nozzle is always kept vertical to the cement test block during spraying; the cycle is 6 to 8 times; The organic compound containing catechol groups is any one of dopamine, phenolic aldehyde, and tannic acid; In the step (1), the volume ratio of the tris buffer solution to anhydrous ethanol is 1:1-5:1, and the mass ratio of the organic matter containing a catechol group to dodecylamine is 1:1-30.

2. The method for preparing a biomimetic hydrophobic coating on a cement-based material surface according to claim 1, wherein: The deposition aid is one or more of a copper ion solution, a magnesium ion solution, an iron ion solution and a calcium ion solution.

3. The method for preparing a biomimetic hydrophobic coating on a cement-based material surface according to claim 1, wherein: In the step (2), the concentration of the deposition aid is 2-3 g / L, and the concentration of the hydrogen peroxide is 0.1-0.2 g / L.

4. The method for preparing a biomimetic hydrophobic coating on a cement-based material surface according to claim 1, wherein: In the step (4), the washing is performed by alternately washing with deionized water and anhydrous ethanol.

5. The method for preparing a biomimetic hydrophobic coating on a cement-based material surface according to claim 1, wherein: In the step (4), the natural drying time is 24 to 30 hours.

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