Lithium-doped residue-driven self-repairing and self-warning dual-function microcapsule, paint, coating and preparation method

Abstract

The application provides a lithium-doped residue-driven self-repairing and self-warning dual-function microcapsule, a coating, a coating layer and a preparation method, and belongs to the technical field of intelligent coatings.The problem to be solved by the application is to develop an intelligent coating with dual functions of initial damage self-repairing and secondary damage self-warning.The microcapsule is prepared by using a Pickering emulsion template method, taking lithium residue particles (LS) as a colloidal stabilizer, emulsifying a mixed solution of a self-healing agent, K3[Fe(CN)6] and CTAB droplets, and taking urea-formaldehyde resin as a wall material.The epoxy resin ab glue is mixed according to the specification ratio, the microcapsule is added, then a defoaming agent is added and stirred and mixed, and then ultrasonic dispersion is performed, so that the coating is obtained.The coating can trigger the warning function after the self-repairing performance is triggered to fail for the first time and reaches a certain threshold, so as to further warn the subsequent repair work, realize the phased response of self-repairing and self-warning, and effectively improve the service life and safety of the metal equipment and save a large amount of cost consumption.

Description

Technical Field

[0001] This invention belongs to the field of intelligent coating technology, specifically relating to a lithium slag-doped self-healing and self-early warning dual-function microcapsule and its preparation method; it also designs a lithium slag-doped self-healing and self-early warning dual-function microcapsule coating and a preparation method for the coating. Background Technology

[0002] Metallic materials play an irreplaceable role in industry, marine engineering, and infrastructure construction; however, their limited protection in harsh environments such as humidity, salt spray, and acids and alkalis has long constrained equipment lifespan and safety. In March 2016, the National Association of Corrosion Engineers (NACE), a leading international organization in the corrosion field, released its latest corrosion survey results based on the IMPACT global corrosion survey project: the global cost of corrosion was estimated at $2.5 trillion. In response, the rapid development of self-healing coatings can provide new ideas for the field of metal protection.

[0003] However, the self-healing capabilities of existing self-healing coatings are often limited in the number of repairs they can perform. Once the healing agent is released, the original coating site is often unusable for repairing subsequent damage. This can easily lead to safety hazards and significant resource waste. To avoid such problems, many scholars have conducted extensive research on the early warning function of self-healing coatings. However, current self-healing-early warning coatings often trigger both self-healing and early warning functions at the initial stage of damage, and the overlapping and interference of the warning colors results in significant resource waste. Therefore, developing an intelligent coating with both initial damage self-healing and secondary damage early warning functions has important practical significance and application value. Summary of the Invention

[0004] The problem to be solved by this invention is to develop a smart coating with dual functions of self-repair of initial damage and self-early warning of secondary damage. It proposes a lithium slag-doped self-repair-early warning dual-function microcapsule and coating, as well as a preparation method.

[0005] This invention aims to prepare highly efficient encapsulated microcapsules of HMDI / K3[Fe(CN)6] bifunctional components using a Pickering emulsion template strategy, and further develop a novel smart coating. The coating of this invention not only achieves a staged response with both self-healing and self-early warning functions, but also demonstrates a novel strategy for protecting against metal corrosion.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a lithium slag-driven self-healing and self-early warning dual-function microcapsule. The microcapsule is prepared and synthesized using the Pickering emulsion template method, with lithium slag particles (LS) as colloidal stabilizers, emulsifying self-healing agents, K3[Fe(CN)6] and hexadecyltrimethylammonium bromide (CTAB) mixed droplets, and urea-formaldehyde (UF) resin as the wall material.

[0007] The microcapsules are prepared as follows: Control of S1 and LS surface contact angle: LS, deionized water and trimethylchlorosilane (TMCS) were placed in a magnetic stirrer and mixed at room temperature. The product was filtered and dried to obtain modified LS for subsequent use. S2. Preparation of prepolymer: Urea and formaldehyde solutions were mixed in a flask at room temperature, and triethanolamine was added dropwise to adjust the pH. After reacting for a period of time, a mixture of urea-formaldehyde resin prepolymers was obtained for subsequent use. S3, Microcapsule Formation Stage: The self-healing agent, K3[Fe(CN)6], CTAB, deionized water and LS were added to a three-necked flask and stirred in a water bath. After reacting for a period of time, the prepolymer was slowly poured into the three-necked flask, and ammonium chloride solution was added dropwise to adjust the pH. Then resorcinol was added to the mixture. After reacting for a period of time, the product was filtered, washed and dried multiple times to finally obtain microcapsules.

[0008] This invention also provides a method for preparing the lithium slag-driven self-healing and self-early warning dual-function microcapsule coating: epoxy resin AB glue is mixed according to specified ratios to obtain a mixed glue. Microcapsules are added to the mixed glue in different proportions, followed by the addition of an antifoaming agent, stirring, and then ultrasonic dispersion to ensure sufficient uniform dispersion of the microcapsules and reduce the influence of air bubbles.

[0009] Furthermore, the self-healing agent is 4,4'-dicyclohexylmethane diisocyanate (HMDI), linseed oil, tung oil, or castor oil.

[0010] Furthermore, in step S1, LS, TMCS and deionized water are weighed and mixed according to the mass ratio of LS, TMCS and deionized water (1-1.3): (0.5-0.8): 100.

[0011] Furthermore, the magnetic stirrer provides 200 rpm to 500 rpm at room temperature for 0.5 h to 3.0 h of stirring.

[0012] Further, in step S2, urea and formaldehyde solution (with a mass concentration of 37%) are weighed at a mass ratio of 1:(1.8-2.5); the pH value is adjusted to 8.5-9.5; the reaction temperature is 60 ℃-80 ℃, and the reaction is carried out at 600-800 r / min for 1-2 h.

[0013] Further, in step S3, the self-healing agent, K3[Fe(CN)6], CTAB, deionized water, and LS are weighed in a mass ratio of 5-15:0.2-1:0.01-0.1:300-500:0.5-2.5 and mixed in a three-necked flask. The mixture is then placed in a water bath and stirred for 0.5-1.5 hours. The stirring speed is maintained at 900-1500 rpm and the temperature at 40-80 ℃. The prepolymer is slowly poured into the three-necked flask and stirred for 0.5-1.5 hours. An appropriate amount of 10 wt% ammonium chloride solution is added dropwise, ensuring that the pH value of the solution is adjusted to 4-5 within 30 minutes, and the stirring speed is adjusted to 300-800 rpm. Resorcinol is weighed at 6 wt.% of the prepolymer and added to the mixture, and the reaction is carried out for 1-3 hours.

[0014] Furthermore, during the coating preparation process, microcapsules are added at 0.01 wt.%-30 wt.% of the epoxy resin mixture; the particle size of the microcapsules is selected to be ≤500 μm; defoamer is added at 0.1 wt.%-5 wt.% of the epoxy resin mixture; and the ultrasonic dispersion time is 30-90 min.

[0015] Furthermore, the prepared coating is applied to have dual functions: self-repair of primary damage and self-early warning of secondary damage after coating.

[0016] Furthermore, when the microcapsule dosage reaches 0.01 wt.%-30 wt.% of the epoxy resin mixture during coating preparation, warning pixels (R:25, G:0, B:152) can be displayed after the same location of the coating is damaged multiple times. The prerequisite for these warning pixels to be converted into acoustic signals, light and color signals, and graphic signals is that the following conditions must be met: , in, T a The threshold for converting warning pixels into multiple warning signals. T p To identify the warning pixel values ​​within the area, R p To identify the total pixel value within the region.

[0017] Furthermore, the particle properties of LS are: contact angle of 70-110° and median particle size of 0.50-1.5 μm.

[0018] The present invention also provides a method for preparing a self-healing and self-early warning dual-function coating driven by lithium slag, specifically by scraping the coating prepared by any of the above methods onto the surface of a substrate and allowing it to air dry naturally to obtain the coating.

[0019] The two-step response mechanism of the self-healing and self-early warning function of the tandem-triggered smart coating of the present invention is as follows: Figure 5As shown, when the coating suffers its first physical damage, the microcapsules rupture, releasing a mixed core material of HMDI and K3[Fe(CN)6. Under capillary action, the core material quickly fills the cracks, and the isocyanate, after release, reacts chemically with moisture in the air to form a cured film, thus protecting the internal substrate. The reaction process is shown in formulas (1) and (2). Regarding the early warning function response, although scholars such as Liu, Li, Ji, and Wu have coupled the self-healing and self-early warning functions of the coating, they all assume that the early warning substance plays a role simultaneously during the self-healing function response, resulting in the defect that the dual function is triggered upon the first damage. This will greatly reduce the functional service life of the coating and cause a large waste of resources. In contrast, the two-step response of self-healing and self-early warning functions can effectively avoid this problem. Specifically, since the reaction between isocyanate and water molecules is irreversible, the same location will no longer have the self-healing function after multiple damages. Once the cured film is further damaged, the internal K3[Fe(CN)6 and the iron substrate will be exposed to air. K3[Fe(CN)6 will then promptly chelate the Fe generated in the early stages of corrosion on the iron substrate. 2+ The formation of Thunberg's blue precipitate results in a significant visual warning effect. [Fe(CN)6]³⁻ and Fe²⁺ are bonded by ionic and coordinate bonds. Fe²⁺ serves as the central metal, and some CN⁻ ligands may rearrange to form binuclear or polynuclear complexes. The specific process is shown in formula (3).

[0020] OCN-R-NCO + H2O→ H2N-R-NH2 + CO2 (1) H2N-R-NH2 + OCN-R-NCO→-R-NHCONH-R- NHCONH-R- (2) 3Fe 2+ + 2[Fe(CN)6] 3- →Fe3[Fe(CN)6]2↓ (3) The beneficial effects of this invention: The preparation method of the lithium slag-doped self-healing and self-early warning dual-function microcapsule coating described in this invention overcomes the limitation of poor coupling between the self-healing and self-early warning functions of traditional protective coatings. The prepared intelligent coating can trigger an early warning function after its self-healing performance fails for the first time, reaching a certain threshold to further alert subsequent repair work. This achieves a phased response of self-healing and self-early warning, effectively improving the service life and safety of metal equipment and saving significant costs.

[0021] This invention discloses a method for preparing a lithium-doped slag-driven self-healing and self-early warning dual-functional microcapsule coating, which solves the problem of color interference in the early warning of existing self-healing and self-early warning coatings. Currently, commonly used colorimetric agents for early warning include rhodamine, 1,10-phenanthroline, o-phenanthroline, phenolphthalein, cresol red, and thymol blue. The colorimetric values ​​provided by these substances largely overlap with the brownish-red pixels (λmax=550-600 nm) of metal corrosion, greatly weakening the early warning performance. This invention utilizes a deep blue Prussian blue (λmax=680-720 nm) generated by the specific combination of K3[Fe(CN)6] and Fe²⁺, which can effectively avoid color gamut interference (overlap rate <5%).

[0022] The preparation method of a lithium-doped slag-driven self-healing and self-early warning dual-function microcapsule coating described in this invention provides a new technical approach for the construction industry, promoting the transformation and upgrading of traditional coatings towards high performance and multi-functionality. Its successful application will drive the development of related industrial chains, promote the integration of new materials, new energy, and intelligent technologies, and inject new impetus into the technological innovation and sustainable development of the construction industry. Attached Figure Description

[0023] Figure 1 This is a microscopic morphology diagram of the microcapsules; Figure 2 This is the color rendering diagram of the intelligent coating described in this invention; Figure 3 These are the microcapsules prepared in Example 1; Figure 4 These are the microcapsules prepared in Example 2; Figure 5 It is a two-step response mechanism that triggers the self-healing and self-early warning function of the smart coating in series; Figure 6 The graph shows the corrosion changes of the coating when the amount of microcapsules is different; Figure 7 These are surface images and pixel-extracted images of the microcapsule-doped coating after corrosion for different number of days. Detailed Implementation Example 1:

[0024] 1. Control of LS surface contact angle: Lithium slag with an initial hydrophobic angle of 54±3° (0.5±1 μm) was used for neutral modification. Ten parts of lithium slag were mixed with 0.03 parts of TMCS in 100 g of deionized water, and then stirred in a water bath for 45 min. The temperature was maintained at 40 ℃, and the stirring speed was adjusted to 400 rpm. After washing and drying, neutral lithium slag particles with a hydrophobic angle of 90±3° were obtained for subsequent use.

[0025] 2. Preparation of prepolymer: Weigh 8 parts urea and 17 parts formaldehyde solution into a flask, then add an appropriate amount of triethanolamine to adjust the pH to 9. Fix the flask containing the mixed solution in a water bath stirrer. React at 70℃ and 650 r / min for 1 h to obtain a urea-formaldehyde resin prepolymer mixture for subsequent use.

[0026] 3. Microcapsule formation stage: 10 parts HMDI, 2 parts K3[Fe(CN)6], and 0.1 parts hexadecyltrimethylammonium bromide were added to 5 parts deionized water and stirred for 0.5 h at a temperature of 40 °C. Then, the mixture, along with 1 part of a mixture of modified lithium slag and cellulose nanoparticles (mass ratio 9:1), was poured into a three-necked flask containing 400 parts deionized water and stirred in a water bath for 50 min at a speed of 1200 rpm and a temperature of 50 °C. The prepolymer was then slowly poured into the three-necked flask and stirred for 0.5 h. A suitable amount of 10 wt% ammonium chloride solution was added dropwise, ensuring the pH of the solution was adjusted to 3-3.5 within 30 min, while simultaneously adjusting the stirring speed to 600 rpm. 1.5 parts resorcinol were added to the mixture, and the reaction was allowed to proceed for 1.5 h. Finally, the product was filtered, washed, and dried multiple times to obtain microcapsules.

[0027] 4. Coating preparation: Epoxy resin AB glue is mixed in a 3:1 ratio to obtain a mixed glue. 1.5 parts of microcapsules are added to 10 parts of the mixed glue, followed by 0.1 parts of defoamer. After stirring and mixing, the mixture is ultrasonically dispersed to ensure that the microcapsules are sufficiently and evenly dispersed and to reduce the impact of air bubbles.

[0028] Example 2: Steps 1, 2, and 4 remain the same as in Example 1.

[0029] Microcapsule formation stage: 10 parts HMDI, 2 parts K3[Fe(CN)6], and 0.1 parts hexadecyltrimethylammonium bromide were added to 5 parts deionized water and stirred for 0.5 h at a temperature of 40 °C. Then, the mixture, along with 0.5 parts of a mixture of modified lithium slag and cellulose nanoparticles (mass ratio 9:1), was poured into a three-necked flask containing 400 parts deionized water and stirred in a water bath for 50 min at a speed of 1200 rpm and a temperature of 50 °C. The prepolymer was then slowly poured into the three-necked flask and stirred for 0.5 h. A suitable amount of 10 wt% ammonium chloride solution was added dropwise, ensuring the pH of the solution was adjusted to 3-3.5 within 30 min, while simultaneously adjusting the stirring speed to 600 rpm. 1.5 parts resorcinol were added to the mixture, and the reaction was allowed to proceed for 1.5 h. Finally, the product was filtered, washed, and dried multiple times to obtain microcapsules.

[0030] The above-mentioned coating is scraped onto the surface of the iron sheet and allowed to air dry naturally to obtain a coating layer.

[0031] Self-repair-self-warning function phased triggering experiment: (1) After the first damage, the coating triggered the self-repair effect, but did not trigger the color warning. Corrosion images of coatings after immersion for 13 days when microcapsule dosages are 0, 5, 10, 15, and 20 wt.% are shown. Figure 6 The corrosion diagrams of the immersed samples for different days (1, 4, 7, 10, 13d) are shown. The microcapsule dosages are 0 wt.% (b-(1-5)) and 15 wt.% (c-(1-5)).

[0032] (2) After repeated damage, the coating's self-healing effect fails, triggering a color warning. Surface images and pixel extraction images of the microcapsule-doped coating after etching for different days are shown below. Figure 7 As shown. (Note: a, d, c, d refer to physical images s when the microcapsule dosage is 14 wt.%, 16 wt.%, 18 wt.%, 20 wt.%, respectively; e, f, g, h refer to the corresponding pixel extraction images; 1, 2, 3, 4 refer to the soaking days).

[0033] exist Figure 6 A small amount of blue substance was observed in (a-5), but this phenomenon was not observed on the surface of other control group samples. This is attributed to insufficient microcapsule doping, which reduces the ability to react with Fe. 2+ The contacted K3[Fe(CN)6] content decreases sharply, thus failing to provide a significant visual warning. It is worth noting that while excessive microcapsule doping can... The sample contained a high amount of K3[Fe(CN)6], but exhibited a strong self-healing ability for the cracks, thus preventing Fe from being released. 2+ The formation of [a substance] inhibits color change. Therefore, to test the self-warning performance of the sample, samples with appropriate microcapsule content (14 wt%, 16 wt%, 18 wt%, 20 wt%) should be selected for the experiment. Furthermore, since the color developer K3[Fe(CN)6] reacts with the Fe produced in the early stages of iron corrosion... 2+ Complexation produces a blue precipitate, therefore the testing period for colorimetric early warning performance should be relatively short (1d, 2d, 3d, 4d). To systematically study the self-early warning response behavior of microcapsules initially applied to coatings, pixel extraction and analysis were performed on the blue precipitate at the crack. Figure 7 Experimental data show that after 4 days of soaking, the proportion of dark blue pixels (R:25, G:0, B:152) on the sample surface is positively correlated with the microcapsule doping amount. Among them, the sample with a doping amount of 20 wt.% has the largest proportion of dark blue pixels (6.83%).

Claims

1. A lithium slag-doped, self-healing, and self-early warning dual-function microcapsule, characterized in that, The microcapsules were prepared and synthesized using the Pickering emulsion template method, with lithium slag particles as colloidal stabilizers, self-healing agents, K3[Fe(CN)6] and hexadecyltrimethylammonium bromide (CTAB) mixed droplets, and urea-formaldehyde UF resin as the wall material. Includes the following steps: S1. Lithium slag particles, deionized water and trimethylchlorosilane (TMCS) are mixed, magnetically stirred at room temperature, filtered, and dried to obtain modified lithium slag particles. S2. Mix urea and formaldehyde until homogeneous at room temperature, add triethanolamine to adjust the pH value, and stir the mixture at 60 ℃-80 ℃ for a period of time to obtain a prepolymer mixture. S3, 1 part of a mixture of modified lithium slag particles and cellulose nanoparticles at a mass ratio of 9:1, added self-healing agent, K3[Fe(CN)6], CTAB, deionized water, modified lithium slag particles and cellulose nanoparticles to a three-necked flask and stirred in a water bath. After reacting for a period of time, the prepolymer mixture was slowly poured in and stirred. Ammonium chloride solution was added dropwise to adjust the pH value. Then resorcinol was added to the mixture. After reacting for a period of time, the product was filtered, washed and dried multiple times to finally obtain microcapsules. S4. When the microcapsule dosage reaches 0.01wt.%-30wt.% of the epoxy resin mixture, warning pixels (R:25, G:0, B:152) can be displayed after the same location of the coating is damaged multiple times. The warning pixels can be converted into acoustic signals, light and color signals, and graphic signals, provided that the following conditions are met: ； in, T a The threshold for converting warning pixels into multiple warning signals. T p To identify the warning pixel values ​​within the area, R p To identify the total pixel value within the region; When the coating suffers its first physical damage, the microcapsules rupture and release a mixed core material of HMDI and K3[Fe(CN)6]. Under the action of capillary force, the core material quickly fills the cracks. At the same time, after the isocyanate is released, -N=C=O reacts chemically with moisture in the air to form a cured film, thereby achieving the effect of protecting the internal substrate. The reaction process is shown in formulas (1) and (2). In terms of early warning function response, since the reaction between isocyanate and water molecules is irreversible, the same location will no longer have the self-repair function after being damaged multiple times. After the cured film is further damaged, the internal K3[Fe(CN)6] and the iron sheet substrate will be exposed to the air. K3[Fe(CN)6] will promptly chelate the Fe generated by the iron sheet in the early stage of corrosion. 2+ It forms Teng's blue precipitate, thus achieving a significant visual warning effect; OCN-R-NCO + H2O→ H2N-R-NH2 + CO2 (1) H2N-R-NH2 + OCN-R-NCO→-R-NHCONH-R- NHCONH-R- (2); The contact angle of lithium slag particles is 70°-110°; The self-healing agent is 4,4'-dicyclohexylmethane diisocyanate (HMDI).

2. The lithium slag-driven self-healing and self-early warning dual-function microcapsule according to claim 1, characterized in that, The median particle size of lithium slag particles is 0.50 μm-1.5 μm.

3. The lithium-doped slag-driven self-healing and self-early warning dual-function microcapsule according to claim 1, characterized in that, In S1, lithium slag particles, TMCS and deionized water are mixed in a mass ratio of (1-1.3):(0.5-0.8):100; the mixture is then magnetically stirred at 200-500 rpm for 0.5-3.0 h.

4. The lithium-doped slag-driven self-healing and self-early warning dual-function microcapsule according to claim 1, characterized in that, In S2, urea and formaldehyde are mixed at a mass ratio of 1:(1.8-2.5); the pH value is adjusted to 8.5-9.5; and the mixture is stirred at 600 r / min-800 r / min for 1-2 h at a temperature of 60 ℃-80 ℃.

5. The lithium-doped slag-driven self-healing and self-early warning dual-function microcapsule according to claim 1, characterized in that, In step S3, the self-healing agent, K3[Fe(CN)6], CTAB, deionized water, and modified lithium slag particles are mixed in a mass ratio of (5-15):(0.2-1):(0.01-0.1):(300-500):(0.5-2.5). The mixture is stirred in a water bath at a temperature of 40 ℃-80 ℃ and a speed of 900 rpm-1500 rpm for 0.5-1.5 hours. The stirring is continued for another 0.5-1.5 hours. The concentration of the ammonium chloride solution is 10 wt%. The pH of the solution is adjusted to 4-5 within 30 minutes, and the speed is adjusted to 300-800 rpm. Resorcinol is weighed at 6 wt.% of the prepolymer and added to the mixture. The reaction is carried out for 1-3 hours.

6. A method for preparing a lithium slag-driven self-healing and self-early warning dual-functional coating comprising the lithium slag-driven self-healing and self-early warning dual-functional microcapsules as described in claim 1, characterized in that, Includes the following steps: Epoxy resin AB glue is mixed in a 3:1 ratio to obtain epoxy resin mixed glue. Microcapsules are added, followed by the addition of defoamer and stirring. The mixture is then ultrasonically dispersed to obtain the coating.

7. The preparation method of a lithium-doped slag-driven self-healing and self-early warning dual-function microcapsule coating according to claim 6, characterized in that, The microcapsule dosage is 0.01 wt.%-30 wt.% of the epoxy resin mixture; the particle size of the selected microcapsules is ≤500 μm; defoamer is added at 0.1-5 wt.% of the epoxy resin mixture; the ultrasonic dispersion time is 30 min-90 min.

8. A method for preparing a lithium-doped slag-driven self-healing and self-early warning dual-functional coating, characterized in that, The coating prepared by the method of claim 6 or 7 is scraped onto the surface of the substrate and allowed to air dry naturally to obtain the coating.

Images