Self-early-warning and self-repairing integrated coating and preparation method

Abstract

The invention discloses a self-early-warning and self-repairing integrated coating, and particularly relates to the field of coatings, the self-early-warning and self-repairing integrated coating comprises a capsule D, a capsule A and a PDMS matrix which are mixed according to the mass ratio of 1: 1: 10; the capsule D is obtained by mixing an electron donor D compound solution, an HDI solution and a continuous phase solution, emulsifying, performing ice bath, preserving heat, filtering, washing and drying, and the electron donor D is a carbazole molecule or a dibenzothiophene molecule; the capsule A is obtained by mixing an electron acceptor A compound solution, an HDI solution and a continuous phase solution, emulsifying, performing ice bath, preserving heat, filtering, washing and drying, and the electron acceptor A is a 1, 2, 4, 5-tetracyanobenzene molecule; the continuous phase solution is a mixed aqueous solution of urea, resorcinol, ammonium chloride and sodium dodecyl benzene sulfonate, the compatibility problem of self-early warning and self-repairing factors is solved, light and color response factors with the characteristics of timeliness, accuracy and universality are developed, timely early warning is achieved when the coating is damaged, misjudgment is not likely to happen, and the self-repairing effect is achieved while self-early warning is conducted.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and more specifically, to a self-warning and self-repairing integrated coating and a preparation method thereof. Background Art

[0002] Organic coatings are an important means of protecting metals from corrosion. However, they are affected by chemical environment, ultraviolet rays, mechanical action, etc., and will produce microscopic defects or macroscopic damage during service. Aging and damage can easily lead to coating failure and loss of protective properties for the metal substrate.

[0003] At present, there are three main strategies for constructing self-warning coatings: one is to add functional factors with light and color transformation properties to the coating matrix material; the second is to modify the functional factors into the coating matrix material structure to prepare intrinsic self-warning coatings; the third is to introduce microcapsule technology, where the functional factors are encapsulated in microcapsule containers and released at the right time to play a role. The warning process of microcapsules is as follows: the cracks in the coating extend to the microcapsules, causing them to rupture, and the warning factors encapsulated in the microcapsules are dispersed to the cracks under capillary action, reacting under specific conditions to produce light and color changes, thereby playing a warning role.

[0004] However, existing research on self-warning coatings faces many problems, such as delayed warning, unclear light and color response, etc., and this field mainly studies self-warning coatings or self-repairing coatings separately, and there are few reports on integrated coatings. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present invention provide a self-warning and self-repairing integrated coating and a preparation method. The technical problem to be solved by the present invention is: to solve the compatibility problem of self-warning and self-repairing factors, to develop light and color response factors with the characteristics of timeliness, accuracy and universality, to achieve timely warning when the coating is damaged and not easy to misjudge, and to achieve self-repairing effect while self-warning.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a self-warning and self-repairing integrated coating based on molecular self-assembly, comprising capsule D, capsule A and PDMS (polydimethylsiloxane) matrix, wherein capsule D, capsule A and PDMS matrix are mixed in a mass ratio of 1:1:10; capsule D is obtained by mixing an electron donor D compound solution, an HDI (hexamethylene diisocyanate) solution and a continuous phase solution, and the mixture is subjected to emulsification, ice bath, heat preservation, filtration, washing and drying, wherein the electron donor D is a carbazole molecule or a dibenzothiophene molecule; capsule A is obtained by mixing an electron acceptor A compound solution, an HDI solution and a continuous phase solution, and the mixture is subjected to emulsification, ice bath, heat preservation, filtration, washing and drying, wherein the electron acceptor A is a 1,2,4,5-tetracyanobenzene molecule; the continuous phase solution comprises a mixed solution of a mixed aqueous solution of urea, resorcinol and ammonium chloride and an aqueous solution of sodium dodecylbenzene sulfonate.

[0007] A method for preparing a self-warning and self-repairing integrated coating comprises the following steps:

[0008] S1. preparing a dispersed phase solution: dissolving the electron donor D and the electron acceptor A in the pretreated HDI solution, respectively, to obtain an HDI solution of the electron donor D and an HDI solution of the electron acceptor A, respectively, as the core material of the microcapsule;

[0009] S2. preparing a continuous phase solution: adding urea, resorcinol and ammonium chloride into deionized water and stirring them thoroughly to obtain a mixed aqueous solution, then adding an aqueous solution of sodium dodecylbenzene sulfonate and adjusting the pH value to obtain a continuous phase solution;

[0010] S3, preparing microcapsules: adding the continuous phase solution to the HDI solution of the electron donor D and the HDI solution of the electron acceptor A respectively, stirring and emulsifying, adjusting the surface tension and then dropping the formaldehyde solution and treating in an ice bath, then stirring and slowly heating to 50-60°C, after the reaction is completed, stopping heating, filtering, washing and drying the product to obtain capsules D and capsules A loaded with electron donors and acceptors respectively;

[0011] S4. Prepare the coating: add capsule D and capsule A into the PDMS matrix, stir and mix, add a curing agent, and obtain the integrated coating after curing.

[0012] In a preferred embodiment, the electron donor D compound and the electron acceptor A compound in step S1 do not need to be accurately calculated in molar ratio, and can be added at will until the solution is saturated. The pretreated HDI solution is obtained by adding 5-10mL of butyl acetate solution to 10-20mL of HDI solution and ultrasonicating for 5-10min. The optimal value of HDI solution is 15mL, and the optimal value of butyl acetate solution is 10mL. At this ratio, the HDI solution and the butyl acetate solution can be fully and effectively mixed, so that not only the concentration of the HDI solution is guaranteed to have no obvious adverse effect on the subsequent microcapsule synthesis and repair effect, but also its solubility to the electron donor D or the electron acceptor A is greatly improved.

[0013] In a preferred embodiment, in step S2, urea, resorcinol and ammonium chloride are mixed in a mass ratio of 20:4:3, and the concentration of urea in the mixed aqueous solution is 0.067 g / mL.

[0014] In a preferred embodiment, in step S2, the mass concentration of the aqueous solution of sodium dodecylbenzene sulfonate is 1.5-2.5wt%, and the optimal value is 2.0wt%. The optimal concentration value can improve the coverage rate of the core material in the subsequent synthesis process.

[0015] In a preferred embodiment, in step S2, the pH is adjusted to 3.5 by using a 0.5 mol / L HCl solution.

[0016] In a preferred embodiment, in step S3, the volume ratio of the dispersed phase solution to the continuous phase solution is 1:7-10, and the optimal value is 1:8. The use of the optimal value can improve the utilization rate of subsequent wall materials while ensuring their hardness.

[0017] In a preferred embodiment, in step S3, the stirring speed is 400-800 rpm.

[0018] In a preferred embodiment, in step S3, the surface tension is adjusted by adding 1 to 2 drops of n-octanol solution. The surface tension adjustment effectively removes a large number of bubbles on the liquid surface, and is beneficial to the mixing of the continuous phase and the dispersed phase, thereby promoting the subsequent synthesis of microcapsules.

[0019] In a preferred embodiment, in step S3, the mass concentration of the formaldehyde solution is 37%, the formaldehyde concentration in the solution after the formaldehyde is added is 0.02-0.05 g / mL, and the optimal value is 0.04 g / mL. The optimal value, i.e., the optimal ratio of the reaction of formaldehyde and urea, can ensure perfect mixing of formaldehyde and urea in the solution during the ice bath process, thereby improving the utilization rate.

[0020] In a preferred embodiment, in step S3, the rate of slowly heating is 0.5-1°C / min, and the optimal value is 1°C / min. The optimal value can save synthesis time while ensuring the regular morphology of the microcapsules, thereby improving experimental efficiency.

[0021] In a preferred embodiment, in step S3, the total time for product ripening after the reaction is completed is about 1-2 hours.

[0022] In a preferred embodiment, in step S3, washing is performed successively with anhydrous ethanol, acetone, and deionized water.

[0023] In a preferred embodiment, in step S4, the mass ratio of PDMS matrix to curing agent is 10:1, the mass ratio of capsule D to capsule A is 1:0.5-2, the total capsule content is 3% w / w-10% w / w, and the optimal value is 5% w / w. The optimal value reduces the excessively high internal porosity of the coating caused by the high content of microcapsules, effectively ensuring the mechanical properties of the coating. In addition, the 5% w / w microcapsule content is sufficient to ensure the self-warning and self-repairing properties of the coating.

[0024] Technical effects and advantages of the present invention:

[0025] 1. Good stability: Both electron donors and electron acceptors are small organic molecules with a wide range of sources, simple and stable structures, and suitable for long-term storage.

[0026] 2. Rapid warning: The self-assembly reaction of electron donors and acceptors is a non-chemical reaction process. When the donors and acceptors meet and combine, they will quickly form a stable electron transfer complex and cause color changes, achieving the purpose of rapid response.

[0027] 3. Obvious changes in light and color: Generally, individual electron donors and electron acceptors are colorless, but after the two form an electron transfer complex, the energy level becomes narrower due to the electron transfer effect between the donor and the acceptor, showing rich fluorescence and color changes visible to the naked eye.

[0028] 4. Rapid repair: The mutually compatible early warning factors and repair factors in the microcapsules will be immediately released when the coating is damaged and react with water vapor in the air to form polyurethane, which plays a role in rapid repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are used to provide further understanding of the technical solutions of the present invention and constitute a part of the present invention. The embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0030] Figure 1 This is the SEM image of the microcapsules prepared in step S3.

[0031] Figure 2 This is a comparison chart of the warning effect after scratching of the self-warning and self-repairing integrated coating prepared with carbazole and 1,2,4,5-tetracyanobenzene as response factors.

[0032] Figure 3 This is a comparison chart of the warning effect after scratches produced by the self-warning and self-repairing integrated coating prepared with dibenzothiophene and 1,2,4,5-tetracyanobenzene as response factors.

[0033] Figure 4 The SEM images of the self-warning and self-repairing integrated coating prepared using carbazole and 1,2,4,5-tetracyanobenzene as response factors are compared to produce scratches. DETAILED DESCRIPTION

[0034] The present invention provides a self-warning and self-repairing integrated coating based on molecular self-assembly, wherein a coating repair agent solution encapsulating an electron donor D and an electron acceptor A is respectively prepared into polyurea-formaldehyde microcapsules D and polyurea-formaldehyde microcapsules A, and the two are uniformly dispersed in an organic resin, thereby constructing an organic coating with both early warning response function and self-repairing function.

[0035] When the coating is not damaged, the electron donor D and the electron acceptor A sealed in capsule D and capsule A respectively are isolated from each other and will not produce color changes due to complexation.

[0036] When the coating is damaged, the solutions of electron donor D molecules and electron acceptor A molecules loaded inside capsule D and capsule A are released respectively. Under the action of electron transfer, obvious color changes occur quickly, achieving the purpose of coating damage warning.

[0037] Specifically, when the coating is damaged and the electron donor D and the electron acceptor A are released, the electron donor D has an electron-donating group, while the electron acceptor A has a strong electron-withdrawing group, and there is an electron donor-acceptor interaction between the two. This interaction makes the D and A molecules have a certain affinity, so that they can recognize and approach each other.

[0038] For example, when the D and A molecules are sufficiently close, electrons are transferred from the highest occupied molecular orbital (HOMO) of the electron donor D (carbazole or dibenzothiophene) to the lowest unoccupied molecular orbital (LUMO) of the electron acceptor A (1,2,4,5-tetracyanobenzene), forming a charge transfer complex. This complex is a complex in which D and A are stabilized by electrostatic interactions and possible π-π stacking. When the complex is formed, the electrons are in an excited state. When these electrons return to the ground state from the excited state, they release energy in the form of photons, resulting in luminescence.

[0039] The HDI solution of electron donor D, D / HDI solution, and the HDI solution of electron acceptor A, A / HDI solution, can not only effectively dissolve electron donor D and electron acceptor A, but also be released immediately as a repair agent when the microcapsules are broken due to coating damage and react with water vapor in the air to form polyurethane, which plays a role in rapid repair and avoids the consequences of metal corrosion caused by untimely manual detection. After self-repair, the microcapsules lose the ability to repair again, but the color warning will not disappear, so it can remind technicians to re-coat to avoid metal corrosion caused by secondary damage to the coating.

[0040] Figure 1 From left to right are polyurea-formaldehyde microcapsules of HDI solution encapsulating donor carbazole, polyurea-formaldehyde microcapsules of HDI solution encapsulating donor dibenzothiophene, and polyurea-formaldehyde microcapsules of HDI solution encapsulating acceptor 1,2,4,5-tetracyanobenzene.

[0041] Figure 2 This is a comparison chart of the warning effect after scratches on the self-warning and self-repairing integrated coating prepared with carbazole and 1,2,4,5-tetracyanobenzene as response factors. From left to right are the undamaged coating picture, the damaged coating light warning picture, and the damaged coating fluorescence warning picture.

[0042] Figure 3 This is a comparison chart of the warning effect after scratches on the self-warning and self-repairing integrated coating prepared with dibenzothiophene and 1,2,4,5-tetracyanobenzene as response factors. From left to right are the undamaged coating picture, the damaged coating light warning picture, and the damaged coating fluorescence warning picture.

[0043] Figure 4 Taking carbazole and 1,2,4,5-tetracyanobenzene as response factors as examples, the prepared self-warning and self-repairing integrated coating produces a comparison chart of the repair effect after scratches. From left to right, they are the SEM images of the damaged epoxy coating without microcapsules after immersion in 3.5% NaCl solution for 48 hours, and the SEM images of the damaged epoxy coating containing 5% w / w microcapsules after immersion in 3.5% NaCl solution for 48 hours.

[0044] Example 1

[0045] The preparation is carried out using the carbazole molecule as D1 and the 1,2,4,5-tetracyanobenzene molecule as A.

[0046] S1. Prepare dispersed phase solution: 10 mL of butyl acetate solution and 15 mL of HDI solution are mixed and ultrasonicated for 5 min to obtain a pretreated HDI solution.

[0047] 500 mg of D1 was dissolved in the pretreated HDI solution and mixed evenly by ultrasonication for 30 min to obtain a dispersed phase solution of D1 (effective load solution).

[0048] 500 mg of A was dissolved in the pretreated HDI solution and mixed evenly by ultrasonication for 30 min to obtain a dispersed phase solution of A (effective load solution).

[0049] S2. Prepare the continuous phase solution: add 10 g urea, 2 g resorcinol, and 1.5 g ammonium chloride into a 500 mL three-necked flask, then add 150 mL deionized water, and stir at a rate of 250 rpm.

[0050] 0.612 g of sodium dodecylbenzene sulfonate was added into 30 mL of deionized water and stirred until completely dissolved to prepare an emulsifier solution.

[0051] Add all the emulsifier solution into the three-necked flask and keep stirring until the drug is completely dissolved.

[0052] Finally, the pH value of the above system was adjusted to 3.5 using a 0.5 mol / L HCl solution by an acidity meter to obtain a continuous phase solution. The second continuous phase solution was prepared in the same way, and the two continuous phase solutions were added to the D / HDI solution and the A / HDI solution respectively.

[0053] S3, preparation of microcapsules: set the stirring speed to 600rpm, add the effective load solution of D1 dropwise to one of the continuous phase solutions to form an O / W emulsion. Keep stirring, emulsify for 1h, take out the three-necked flask, add 1 drop of 1-octanol to adjust the surface tension of the liquid. Add 10mL of formaldehyde solution and ice bath and ultrasonic for 30min. Take out the three-necked flask, continue to maintain the stirring speed at 600rpm, and gradually increase the temperature to 55℃ at a heating rate of 1℃ / min. Wait for 1h before encapsulation is completed, and the polyurea-formaldehyde microcapsules of HDI solution of D1 are obtained.

[0054] The product was immediately taken out and filtered, and the filtered product was repeatedly washed with anhydrous ethanol, acetone, and deionized water to remove the surface HDI residue and excess D1 payload solution.

[0055] The dispersed phase solution (payload solution) of A in S1 and the second continuous phase solution in S2 are used to prepare polyurea-formaldehyde microcapsules of HDI solution of A in the same way through S3, and are cleaned in the same way.

[0056] S4. Preparation of coating:

[0057] 0.4 g of washed D1 / HDI microcapsules and A / HDI microcapsules were weighed and co-doped into 14.5 g of polydimethylsiloxane (PDMS) matrix and mixed evenly.

[0058] Add 1.45 g of curing agent and stir evenly, pour into a petri dish and spread evenly, and place in a 26°C oven to dry for 12 hours.

[0059] Artificial scratches were made, and the time and intensity of the light color at the scratches were examined. The capsule wall at the scratches was damaged, releasing the HDI solution of carbazole and 1,2,4,5-tetracyanobenzene. The two quickly self-assembled into a complex through electron transfer, and the reaction produced a color change. The color change appeared almost instantly, thus achieving a self-warning function. The HDI solution immediately reacted with water vapor in the air to form polyurethane, thereby achieving a self-repair function. The two functions do not affect each other.

[0060] Supplementary explanation: the following is the difference from the existing technology:

[0061] HDI solution is used as a repair agent. Although compared with the patent content of a self-warning coating based on a charge transfer complex and its preparation method (CN116496676B), the core difference is not only reflected in the adjustment of the core material (introduction of HDI solution), but also in the significant optimization of the raw material system and emulsification process. If the emulsifier system based on poly (ethylene-alt-maleic anhydride) in the previous patent is directly used, even if its dosage is adjusted, it is still impossible to prepare a stable emulsion. The reason is:

[0062] 1. Emulsifier compatibility problem: Poly(ethylene-alt-maleic anhydride) has insufficient ability to regulate the interfacial energy between the dispersed phase and the continuous phase of the HDI solution, resulting in the emulsion stability not meeting the standard;

[0063] 2. System compatibility limitations: The polarity characteristics of the HDI solution do not match the chemical structure of the original emulsifier, making it difficult to form a uniform dispersion system;

[0064] 3. Process parameter sensitivity: The volume ratio of the continuous phase to the dispersed phase must be precisely controlled within a specific range (such as the ratio described in this application), otherwise the emulsion will stratify or break due to interfacial tension imbalance.

[0065] Therefore, it can be seen that the key advantages of choosing HDI solution as a repair agent in this application are:

[0066] 1. Optimization of dissolution performance: HDI solution exhibits excellent solubility for electron donor D and electron acceptor A compounds, solving the technical bottleneck of D / A being difficult to dissolve in conventional repair agents (such as epoxy resin); pretreatment of HDI solution with butyl acetate further improves the dissolution efficiency of D / A, and the pretreatment solvent is chemically inert to HDI and the microcapsule synthesis system to avoid interference from side reactions.

[0067] 2. System stability guarantee: There is no chemical repulsion reaction between HDI solution and D / A compound, ensuring that the photochromic response function of charge transfer complexes (CTCs) can be quickly triggered after the repair agent is released; by strictly screening the emulsifier type (such as the specific surfactant of this application) and optimizing the dispersed phase / continuous phase volume ratio, the stability problem of HDI emulsion preparation has been overcome.

[0068] In summary, the core innovation of this application is that through the selection of repair agent (HDI solution), optimization of pretreatment process and reconstruction of emulsification system, the problem of preparation failure caused by poor raw material adaptability and insufficient emulsion stability in the prior art is systematically solved, and finally the efficient preparation and performance improvement of self-warning coating is achieved.

[0069] Working principle of the present invention:

[0070] In view of the problems of the prior art, the present invention provides a method for preparing a self-warning coating with rapid and obvious response, simple structure and wide application range. This project focuses on the electron donor / acceptor (D / A) forming a supramolecular assembly electron transfer complex (CTCs) through electron migration. With the multiple advantages of D / A self-assembly to form CTCs, such as good stability, rapid reactivity, obvious light color change, and no strict requirements for the reaction molar ratio, the D and A molecules are encapsulated with the help of microencapsulation technology to prepare a warning factor with light and color response function, and both D and A can be well dissolved in the commonly used repair agent HDI solution at this stage, so as to construct a new self-warning and self-repairing integrated coating.

[0071] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A self-warning and self-repairing integrated coating, characterized in that: The integrated coating comprises capsule D, capsule A and PDMS matrix, and capsule D, capsule A and PDMS matrix are mixed in a mass ratio of 1:1:10; The capsule D is obtained by mixing an electron donor D compound solution, an HDI solution, and a continuous phase solution, and then emulsifying, ice bathing, heat preservation, filtering, washing, and drying. The electron donor D is a carbazole molecule or a dibenzothiophene molecule. Capsule A is obtained by mixing an electron acceptor A compound solution, an HDI solution, and a continuous phase solution, and then emulsifying, ice bathing, heat preservation, filtering, washing, and drying. The electron acceptor A is a 1,2,4,5-tetracyanobenzene molecule. The continuous phase solution includes a mixed solution of a mixed aqueous solution of urea, resorcinol, and ammonium chloride and an aqueous solution of sodium dodecylbenzene sulfonate.

2. A method for preparing a self-warning and self-repairing integrated coating, characterized in that: The following steps are involved: S1. preparing a dispersed phase solution: dissolving the electron donor D and the electron acceptor A in the pretreated HDI solution, respectively, to obtain an HDI solution of the electron donor D and an HDI solution of the electron acceptor A, respectively, as the core material of the microcapsule; S2. preparing a continuous phase solution: adding urea, resorcinol and ammonium chloride into deionized water and stirring them thoroughly to obtain a mixed aqueous solution, then adding an aqueous solution of sodium dodecylbenzene sulfonate and adjusting the pH value to obtain a continuous phase solution; S3, preparing microcapsules: adding the continuous phase solution to the HDI solution of the electron donor D and the HDI solution of the electron acceptor A respectively, stirring and emulsifying, adjusting the surface tension and then dropping the formaldehyde solution and treating in an ice bath, then stirring and slowly heating to 50-60°C, after the reaction is completed, stopping heating, filtering, washing and drying the product to obtain capsules D and capsules A loaded with electron donors and acceptors respectively; S4. Prepare the coating: add capsule D and capsule A into the PDMS matrix, stir and mix, add a curing agent, and obtain the integrated coating after curing.

3. The method for preparing a self-warning and self-repairing integrated coating according to claim 2, characterized in that: In the step S1, the pre-treated HDI solution is prepared by adding 5-10 mL of butyl acetate solution to 10-20 mL of HDI solution and ultrasonically mixing for 5-10 minutes.

4. The method for preparing a self-warning and self-repairing integrated coating according to claim 2, characterized in that: In step S2, urea, resorcinol and ammonium chloride are mixed in a mass ratio of 20:4:3, and the concentration of urea in the mixed aqueous solution is 0.067 g / mL.

5. The method for preparing a self-warning and self-repairing integrated coating according to claim 2, characterized in that: In step S2, the mass concentration of the aqueous solution of sodium dodecylbenzene sulfonate is 1.5-2.5wt%.

6. A self-warning and self-repairing integrated coating and preparation method according to claim 2, characterized in that: In the step S2, the pH is adjusted to 3.5 by using a 0.5 mol / L HCl solution.

7. The method for preparing a self-warning and self-repairing integrated coating according to claim 2, characterized in that: In the step S3, the volume ratio of the dispersed phase solution to the continuous phase solution is 1:7-10.

8. The method for preparing a self-warning and self-repairing integrated coating according to claim 2, characterized in that: In step S3, the surface tension is adjusted by adding 1 to 2 drops of n-octanol solution.

9. The method for preparing a self-warning and self-repairing integrated coating according to claim 2, characterized in that: In step S3, the mass concentration of the formaldehyde solution is 37%, and the formaldehyde concentration in the solution after the formaldehyde is added dropwise is 0.02-0.05 g / mL.

10. According to the method for preparing a self-warning and self-repairing integrated coating according to claim 2, in the step S4, the mass ratio of the PDMS matrix and the curing agent is 10:1, the mass ratio of capsule D to capsule A is 1:0.5-2, and the total content of the capsules is 3% w / w-10% w / w.

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