Coating of bi-component microcapsules encapsulating liquid diamines and isocyanates and use thereof

Abstract

The present application belongs to the field of paint, and relates to a kind of encapsulated liquid diamine and isocyanate two-component microcapsule paint and its application, wherein two-component microcapsule paint comprises paint matrix, and two-component microcapsule system formed by diamine microcapsule and diisocyanate microcapsule;Wherein, the diamine microcapsule is prepared by emulsifying and dispersing liquid diamine in n-heptane, dropping into the aqueous solution containing isocyanate, and preparing diamine microcapsule by water-in-oil interfacial polymerization method.The present application solves the encapsulation of diamine microcapsule, and develops diisocyanate microcapsule, innovatively proposes two-microcapsule system, uses and diisocyanate microcapsule to form two-microcapsule system, and is applied to self-healing material.This two-microcapsule system makes the paint forming coating have excellent self-healing ability, and the durability and self-repairing ability of coating are greatly improved, has good durability and corrosion resistance, and is suitable for industrial scale production application.

Description

Technical Field

[0001] This invention belongs to the field of coatings and relates to a dual microcapsule system coating product with automatic repair and healing function, which can meet the self-repair and healing requirements of coatings in various scenarios and is suitable for coatings used in aerospace, automotive and chemical industries. Background Technology

[0002] Coatings often suffer wear and cracking under prolonged use or in extreme environments, leading to performance degradation and shortened lifespan. Self-healing coating technology, drawing inspiration from biological self-healing capabilities, can repair itself after being stimulated, significantly improving material durability and reliability, extending material lifespan, and reducing maintenance costs. It holds great potential for enhancing the structural integrity and safety of coatings.

[0003] Currently, self-healing materials are mainly divided into two categories: intrinsic and embedded. Intrinsic self-healing materials achieve self-repair through reversible chemical reactions within the material (such as covalent bonds, hydrogen bonds, and metal coordination). Embedded self-healing materials include liquid-core fiber type and microcapsule type. Compared with liquid-core fiber self-healing systems, microcapsule technology and its composite technology with matrix materials have been industrialized. In addition, from the perspectives of identifying microcracks and ease of encapsulation, microcapsules show higher application value as containers for repair agents.

[0004] When cracks appear in a material, the propagation of the cracks within the matrix leads to the rupture of the microcapsules. This allows the repair agent to flow to the crack via capillary action, where it undergoes a polymerization reaction under the action of a catalyst, thereby repairing the crack. Therefore, microcapsule repair agents have the advantages of high efficiency, controllability, and minimal interference with the properties of the material itself.

[0005] However, the remediation effect of microcapsules is often limited by the encapsulation stability of microcapsule reagents and the reaction rate of remediation agents, and often suffers from problems and challenges such as low encapsulation efficiency of remediation agents, slow remediation rate and poor remediation control. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by providing a coating that encapsulates a binary microcapsule of liquid diamine and isocyanate, enabling the coating to self-heal and providing better weather resistance and corrosion resistance.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] A coating for encapsulating binary microcapsules of liquid diamine and isocyanate, comprising a coating matrix and a binary microcapsule system consisting of diamine microcapsules and diisocyanate microcapsules.

[0009] The diamine microcapsules are prepared by emulsifying and dispersing liquid diamine in n-heptane, then dropping it into an aqueous solution containing isocyanate, and finally using an oil-in-water interfacial polymerization method.

[0010] This invention solves the problem of encapsulating diamine microcapsules. Utilizing the immiscibility of n-heptane and diamine, an emulsion containing diamine is prepared using an emulsifier. Diamine microcapsules are then produced via water-in-oil interfacial polymerization. These diamine microcapsules and diisocyanate microcapsules are combined to form a dual-microcapsule system, which is applied to self-healing materials. This dual-microcapsule system endows the coating with excellent self-healing capabilities, significantly improving the coating's durability and self-repairing ability, resulting in good durability and corrosion resistance. Compared to traditional diamine microcapsules, the diamine microcapsules of this invention exhibit better stability, maintaining good stability over a long period and better utilizing the long-term self-repairing and self-healing effects of the dual-microcapsule system. Most importantly, the diamine microcapsules of this invention are based on interfacial polymerization, making them suitable for industrial-scale microcapsule production.

[0011] Liquid diamine and isoflurane diisocyanate (IPDI) form a binary microcapsule system, with each component stored separately within a microcapsule, exhibiting good flowability and chemical stability. However, as a self-healing binary microcapsule system, it reacts rapidly upon contact to form and solidify polyurethane, without releasing non-condensable gases. It possesses excellent chemical stability, high elasticity, and corrosion resistance, effectively preventing the propagation of secondary cracks.

[0012] Therefore, the two-component microcapsule system (dual MCs system) of this invention excels in improving the overall performance of industrial coatings, meeting the durability and corrosion resistance requirements of coatings used in industries including aerospace, automotive, and chemical, and has great potential for further application. Coatings using this dual microcapsule system, when applied to the field of self-healing materials, have the advantages of rapid self-repair reaction and good repair effect.

[0013] Furthermore, the diamine microcapsules are prepared by the following method:

[0014] S101. Dissolve the diamine and the first emulsifier in n-heptane, mix them evenly, and prepare a diamine emulsion.

[0015] Isophorone diisocyanate was dissolved in water to prepare an isophorone diisocyanate solution;

[0016] S102. The diamine emulsion is dropped into the isophorone diisocyanate solution and stirred continuously for 1-5 hours to promote the curing of the spherical structure.

[0017] S103, washing, filtering and drying, to obtain diamine microcapsules.

[0018] This invention solves the problem of encapsulating diamine microcapsules by using a water-in-oil interfacial polymerization method. Interfacial polymerization forms microcapsules with a polyurea shell and a liquid diamine core. The reaction of diamine emulsion droplets with isophorone diisocyanate forms a robust polyurea shell, completing the encapsulation and yielding diamine microcapsules with good stability. The microcapsule yield is high, showing potential for industrial production.

[0019] Furthermore, the diamine is at least one of ethylenediamine (EDA), 1,4-cyclohexanediamine (HMDA), and m-phenylenediamine (MXDA).

[0020] Further, the diamine emulsion is added dropwise to the isophorone diisocyanate solution at a rate of 1 to 2 drops every 1 to 2 seconds.

[0021] Preferably, the first emulsifier is Span 80 and / or sodium dodecylbenzene sulfonate. More preferably, the first emulsifier is sodium dodecylbenzene sulfonate.

[0022] The inventors tried various typical anionic, nonionic, and cationic emulsifiers for emulsification treatment and found that the diamine emulsion formed when sodium dodecylbenzenesulfonate was used as the emulsifier had the best effect.

[0023] Preferably, the drop rate is maintained at 1-2 drops per 1-2 seconds, for example, one drop per second. Most preferably, the drop rate is one drop per second.

[0024] Preferably, the drying process is carried out at room temperature.

[0025] Preferably, the drying temperature does not exceed 40°C, more preferably not more than 35°C, even more preferably not more than 30°C, and even more preferably not more than 25°C.

[0026] Furthermore, the diisocyanate microcapsules are prepared by the following method:

[0027] S201. Dissolve isophorone diisocyanate and the second emulsifier in water, mix well, and prepare an isocyanate emulsion.

[0028] Dissolve polyetheramine, diethylenetriamine, or ethylenediamine in water to prepare a diamine solution.

[0029] S202. The isocyanate emulsion is added dropwise to the diamine solution, and the mixture is stirred for 2 hours to solidify the microcapsule shell.

[0030] S203, filtration, washing with deionized water, drying, to obtain diisocyanate microcapsules.

[0031] Water was used as the dispersed phase, and an emulsion was formed with the assistance of a second emulsifier. The oil-in-water emulsion was added dropwise to an aqueous solution containing diamine. After a certain curing time, isocyanate microcapsules were successfully obtained through washing, filtration and drying.

[0032] Preferably, the isocyanate emulsion is added dropwise to the diamine solution at a rate of 1-2 drops per 1-2 seconds to form microcapsules. The mixture is stirred for 2 hours to solidify the microcapsule shells, taking care to avoid agglomeration. After filtration, the microcapsule is washed with deionized water and dried at room temperature to obtain microcapsule powder. Most preferably, the dropping rate is 1 drop per second.

[0033] Preferably, the amount of the second emulsifier is 0.5 to 5 wt%.

[0034] Preferably, the second emulsifier is Tween 80.

[0035] Preferably, the amount of Tween 80 used is 1 wt% of the solvent water. Attached image description:

[0036] Figure 1 These are scanning electron microscope images and size distributions of different diamine microcapsules. Among them, (a, d) correspond to MCs-EDA, (b, e) correspond to MCs-HMDA, and (c, f) correspond to MCs-MXDA.

[0037] Figure 2 This is a compositional analysis of diamine microcapsules. (a) is a TEM image of the MCs-EDA and a magnified view of the shell structure. (b) is a photograph of different microcapsules. (c) is an infrared spectral image of different microcapsules. (d) is an infrared spectral image of the core and shell materials and the MCs-EDA. (e) is the core content of different microcapsules.

[0038] Figure 3 This section describes the thermal characterization of diamine microcapsules. (a, b) TGA and DSC curves of the core, shell material, and MCsEDA. (c, d, e) TG-DSC curves of MCsEDA, MCsHMDA, and MCsMXDA. (f) DSC curves of different diamine microcapsules.

[0039] Figure 4 The images show scanning electron microscopy and size distribution of different IPDI microcapsules. Among them, (a, d) are MCs-IPDI microcapsules (EDA), (b, e) are MCs-IPDI microcapsules (DETA), and (c, f) are MCs-IPDI microcapsules (D230).

[0040] Figure 5This is a compositional analysis of IPDI microcapsules. The images include: (a) TEM images of MCs-IPDI(EDA) microcapsules, (b) MCs-IPDI(DETA) microcapsules, and (c) MCs-IPDI(D230) microcapsules; (d) core content of MCs-IPDI microcapsules; (e) infrared spectra of the core and shell materials and MCs-IPDI(DETA) microcapsules; and (f) infrared spectra of different MCs-IPDI microcapsules.

[0041] Figure 6 This section describes the thermal characterization of IPDI microcapsules. (a, b, c) show the TGA and DSC curves for three different IPDI microcapsules: MCs-IPDI(EDA), MCs-IPDI(DETA), and MCs-IPDI(D230). (d) shows the TGA curves for the core, shell, and isocyanate microcapsule MCs-IPDI(DETA). (e) shows the TGA curves for the three isocyanate microcapsules. (f) shows the DSC curves for the three isocyanate microcapsules.

[0042] Figure 7 These are OM images of scratched coatings. Among them, (a) is a scratched image of epoxy resin. (b) is a scratched image of PU-F520. (c) is a worn image of epoxy resin. (d) is a worn image of PU-F520. (e) shows the mechanism of crack repair.

[0043] Figure 8 This demonstrates the corrosion resistance of the dual MCs system. (a) is a photograph of the coating. (b) is a schematic diagram of the salt water corrosion resistance test of the Mazda slab coating. Detailed Implementation

[0044] To more clearly describe the inventive objectives, technical solutions, and advantages of the specific embodiments of this invention, the solutions in the specific embodiments will be described in detail below with reference to the accompanying drawings. The specific technical solutions involved in the following specific embodiments are merely for the purpose of clearly and completely describing the innovative technical solutions of this invention. They are only a part of the specific implementation methods that this invention can adopt, not all embodiments, and should not be construed as limiting the innovative solutions of this invention. Any solution that adopts the same inventive concept as this invention should be included within the protection scope of this invention. For those skilled in the art, when understanding the solutions described in the specific embodiments of this invention, conventional technical manuals in the field can be consulted. Furthermore, appropriate understanding or adjustments can be made to the use of technical terms to deduce the same or similar technical solutions without creative effort.

[0045] The ethylenediamine, sodium dodecylbenzenesulfonate, and Tween 80 used in the following examples were purchased from Chengdu Kelong Chemical Co., Ltd.; 1,4-cyclohexanediamine and m-phenylenediamine were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; and diethylenetriamine, polyetheramine D230, isophorone diisocyanate, etc., were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. The resin materials used in the examples—epoxy resin, aspartic polyurea resin F520, and polystyrene resin—were purchased from Shanghai Migazhan Adhesive Products Co., Ltd. and Shenzhen Feiyang Junyan New Materials Co., Ltd., respectively.

[0046] Example 1: Synthesis of Diamine Microcapsules

[0047] Taking the preparation process of microcapsules with ethylenediamine as the core material as an example, diamine microcapsules (ethylenediamine microcapsules, MCs-EDA) are prepared.

[0048] First, 1 mL of ethylenediamine was mixed with 10 mL of n-heptane, and 1 wt.% (relative to n-heptane) of sodium dodecylbenzenesulfonate was added as an emulsifier to prepare a diamine emulsion.

[0049] Then, the diamine emulsion was slowly dropped into 30 mL of an aqueous solution of isophorone diisocyanate with a concentration of 0.25 mol / L, the dropping rate was maintained at one drop per second, and the mixture was stirred continuously for 2 hours to promote the curing of the spherical structure.

[0050] Finally, the mixture was washed, filtered, and dried at room temperature to obtain ethylenediamine microcapsules.

[0051] 1,4-cyclohexanediamine (HMDA) and m-phenylenediamine (MXDA) were separately prepared into solutions with n-heptane in the same volume ratio of ethylenediamine and n-heptane (containing 1 wt% sodium dodecylbenzenesulfonate emulsifier). Then, using the same interfacial polymerization method, diamine microcapsules with 1,4-cyclohexanediamine and m-phenylenediamine as core materials were prepared by dropwise addition to an aqueous solution of isophorone diisocyanate. The three types of diamine microcapsules were named MCs-EDA (ethylenediamine microcapsules), MCs-HMDA (1,4-cyclohexanediamine microcapsules), and MCs-MXDA (m-phenylenediamine microcapsules), respectively.

[0052] Comparative Example 1: Synthesis of Diamine Microcapsules

[0053] Ethylenediamine microcapsules were prepared by mixing 1 mL of ethylenediamine with 10 mL of n-heptane and adding 1 wt.% (relative to n-heptane) sodium dodecylbenzenesulfonate as an emulsifier to form a diamine emulsion. Isophorone diisocyanate was dissolved in water to prepare an aqueous solution of isophorone diisocyanate (IPDI) with a concentration of 0.25 mol / L. Following conventional interfacial polymerization methods, the initiator (IPDI aqueous solution) was added dropwise to the emulsion system (diamine emulsion) at the same dropping rate as in Example 1, 1 drop per second. After the addition was complete, the mixture was stirred continuously for 2 hours to promote the solidification of the spherical structure. Finally, the microcapsules were washed, filtered, and dried at room temperature to obtain ethylenediamine microcapsules.

[0054] This comparative example used a traditional interfacial polymerization method, in which isocyanate was dripped into a pre-emulsified diamine emulsion. Although a certain amount of microcapsules could be generated, the added isophorone diisocyanate solution caused the diamine emulsion to break down and clump together, resulting in a low microcapsule yield, less than 20% of the yield in Example 1. Furthermore, the contents of the resulting diamine microcapsules were relatively small, less than 1 / 3 of those in Example 1 (calculated based on the proportion of microcapsule contents).

[0055] Synthesis of 2-Diamine Microcapsules

[0056] The diamine microcapsules were prepared according to the method in Example 1. Taking ethylenediamine microcapsules as an example, 1 mL of ethylenediamine was mixed with 10 mL of n-heptane, and 1 wt.% (relative to n-heptane) of sodium dodecylbenzenesulfonate was added as an emulsifier to prepare a diamine emulsion.

[0057] The diamine emulsion was slowly added dropwise to a 0.25 mol / L isophorone diisocyanate aqueous solution at a slightly faster rate than in Example 1, maintained at 4-5 drops per second, and stirred continuously for 2 hours to promote the solidification of the spherical structure. Finally, the mixture was washed, filtered, and dried at room temperature to obtain ethylenediamine microcapsules. Due to the relatively fast dropping rate of the diamine emulsion, some aggregation of the diamine microcapsules occurred, with some microcapsules adhering together, which is not conducive to dispersion in coatings. Therefore, the dropping rate of the diamine emulsion should not be too fast, preferably controlled at 1-2 drops per 1-2 seconds.

[0058] Example 2: Synthesis of Isocyanate Microcapsules (IPDI Microcapsules)

[0059] The synthesis of isocyanates into microcapsules is similar to that of diamine microcapsules, utilizing an oil-in-water system. Deionized water is used as the aqueous phase, and Tween 80 is used as an emulsifier to synthesize IPDI microcapsules. Taking isophorone diisocyanate microcapsules as an example, the specific synthesis method is as follows.

[0060] First, add 6g of isophorone diisocyanate to 30mL of water to form an IPDI emulsion; add 1wt% Tween 80 to the water. Dissolve 6g of diamine in 30mL of deionized water to prepare a diamine solution.

[0061] Then, the IPDI emulsion is added to the solution at a rate of 1 drop per second to form microcapsules. The mixture is stirred for 2 hours to solidify the microcapsule shells, taking care not to form agglomerates.

[0062] Finally, the microcapsules were filtered, washed with deionized water, and dried at room temperature for 48 hours to obtain microcapsule powder.

[0063] The corresponding microcapsules contain isophorone diisocyanate as the content, and the isocyanate reacts with different diamines to form the microcapsule shell. Then, using different diamine raw materials, namely ethylenediamine (EDA), diethylenetriamine (DETA), and polyetheramine D230 (PEAD230), three types of isocyanate microcapsules were synthesized and named MCs-IPDI(EDA), MCs-IPDI(DETA), and MCs-IPDI(PEAD230).

[0064] Example 3: Preparation of epoxy resin self-healing coating

[0065] Preparation of self-healing epoxy resin: The MCs-EDA (ethylenediamine microcapsules), MCs-HMDA (1,4-cyclohexanediamine microcapsules), and MCs-MXDA (m-phenylenediamine microcapsules) microcapsules prepared in Example 1, and the MCs-IPDI (EDA), MCs-IPDI (DETA), and MCs-IPDI (PEAD230) microcapsules prepared in Example 2, were mixed with isocyanate microcapsules at a weight ratio of 1:1 to form a binary microcapsule system, which served as a dopant. The selected product was a methylbenzene epoxy resin. TM The epoxy resin used in the adhesive is composed of epichlorohydrin and bisphenol A (or other polyols; bisphenol A is used in this embodiment). According to the epoxy resin instructions, components A and B are mixed in a 1:1 mass ratio, and 10 wt% of a dopant (i.e., the dopant of the binary microcapsule system composed of the aforementioned diamine microcapsules and isocyanate microcapsules in equal proportions) is added to prepare a self-healing epoxy resin.

[0066] The self-healing epoxy resin is poured into a polytetrafluoroethylene mold for molding, vacuum degassing, and room temperature curing to ensure that the microcapsules can be evenly distributed in the resin, thereby improving the performance of the self-healing coating and obtaining an epoxy resin self-healing coating.

[0067] The aforementioned diamine microcapsules and isocyanate microcapsules can also be mixed in a 1:1 molar ratio, primarily using their combined effect to repair cracks. Ideally, the content ratio of the two should be roughly equal; however, in practical applications, the ratio can be adjusted appropriately based on the content of the microcapsule contents.

[0068] Example 4: Preparation of self-healing coating of aspartic polyurea

[0069] Preparation of self-healing aspartic polyurea resin: Similar to Example 3, the dopant was prepared by mixing the amine component and the isocyanate component in a 1:1 molar ratio. The amine component was F520 produced by Shenzhen Feiyang Junyan Co., Ltd., and the isocyanate component was IPDI prepolymer. The two components were mixed in a 1:1 molar ratio to ensure the uniformity of the reaction and the consistency of the product. As in Example 3, 10 wt% of the dopant (the two microcapsules prepared in Examples 1 and 2, with a weight ratio of 1:1, can be adjusted with reference to Example 3) was added to obtain the self-healing aspartic polyurea resin.

[0070] Self-healing aspartic polyurea resin was poured into a polytetrafluoroethylene mold for molding, vacuum degassing, and room temperature curing to ensure that the microcapsules could be uniformly distributed in the resin, thereby improving the performance of the self-healing coating and obtaining an aspartic polyurea resin self-healing coating, which is ready for testing.

[0071] Example 5: Particle size and structure characterization of diamine microcapsules

[0072] Using an optical microscope (OM, model BX51), The surface morphology of the microcapsules was observed, and the size analysis of the microcapsules was obtained from analyzing a dataset of 200 measurements. The diamine microcapsules MCs-EDA, MCs-HMDA, and MCs-MXDA (microcapsule contents: ethylenediamine, 1,4-cyclohexanediamine, and m-phenylenediamine, respectively) prepared in Example 1 were subjected to surface morphology characterization.

[0073] The results of scanning electron microscopy (SEM) are as follows: Figure 1As shown in Figure a, the microcapsules all exhibited good morphology and uniform particle size distribution, with no flocculent matter. The average particle size of MCs-EDA was 0.22 μm, with a variance (σ²) of 0.0026221. For MCs-HMDA, the average particle size was 0.28 μm, with a variance (σ²) of 0.007417. The average particle size of MCs-MXDA was 0.34 μm, with a variance (σ²) of 0.012483. The differences in particle size may be related to the chemical properties of the different diamines. Particle size analysis of the microcapsules was performed using Nano Measure software on 100 samples selected from the captured SEM images. The droplet size of the diamine emulsion determined by optical microscopy was consistent with the SEM results, indicating good consistency in the particle size of the microcapsules.

[0074] It is noteworthy that as the average particle size increases, the dispersion of particle size (i.e., variance σ²) also tends to increase, possibly due to the non-uniformity of the shear force exerted by the stir bar during emulsification. At the center of turbulence, the droplets experience more intense emulsification, resulting in smaller particle sizes; while at the outer edge of turbulence, the smaller shear force leads to relatively larger particle sizes. This effect becomes more pronounced with increasing average particle size, thus increasing the dispersion of the particle size distribution.

[0075] The ethylenediamine microcapsules prepared in Comparative Example 2 exhibited significant agglomeration due to the rapid droplet addition of materials. This hindered the uniform mixing of the binary system microcapsules and impeded their dispersion in the coating for effective function. Therefore, the diamine microcapsules of Comparative Example 1 were not subsequently analyzed.

[0076] Furthermore, scanning electron microscopy was used to determine the core-shell structure of the microcapsules.

[0077] Standard photographs of three types of diamine microcapsules are shown below. Figure 2 As shown in b.

[0078] Further observation of the MCs-EDA microcapsules was conducted using transmission electron microscopy (TEM) to characterize their internal structure. The experimental method was as follows: MCs-EDA microcapsule samples were coated onto aluminum sheets, dried in a vacuum oven, and sputtered with gold to enhance conductivity. The core-shell structure was verified using scanning electron microscopy (SEM), and the size distribution of the microcapsules was investigated. The surface morphology of the microcapsules was also observed using a SEM (Quantum 200ESEM, FEI).

[0079] The results are as follows Figure 2As shown in Figure a, the TEM image of the MCs-EDA microcapsules clearly reveals the core-shell structure of the microcapsules. A magnified view shows a clear boundary and significant contrast between the core and shell. The measured microcapsule size is approximately 350 nm, consistent with the results of SEM and particle size analysis. The TEM image confirms a microcapsule wall thickness of approximately 70 nm, and this uniform wall thickness ensures the stability and functionality of the microcapsules. The TEM image shows a uniform and dense shell structure without obvious defects or voids, indicating effective quality control of the shell.

[0080] Based on the combined observations of SEM and TEM, the following conclusions can be drawn: all three types of diamine microcapsules possess a well-defined core-shell structure, ensuring the encapsulation of liquid diamine and the formation of the shell layer. Furthermore, the microcapsules exhibit uniform particle size and wall thickness, and the preparation process is stable and controllable, guaranteeing their subsequent uniform dispersion and stable performance in the resin material.

[0081] Example 6: Infrared spectroscopy characterization of the core-shell structure of diamine microcapsules

[0082] To further verify the chemical composition and internal structure of the microcapsules, the chemical composition of the microcapsules was characterized using infrared spectroscopy, as follows: Infrared spectroscopy (IR) was used to analyze microcapsules synthesized from different liquid diamines.

[0083] The results are as follows Figure 2 As shown in Figure c, a comparison of the infrared spectra of the three microcapsules (MCs-EDA, MCs-HMDA, and MCs-MXDA) reveals typical chemical functional group peaks at 3300 cm⁻¹. -1 (3447-3186cm -1 The double peak observed at ) is the stretching vibration peak of NH, proving that the liquid diamine was successfully embedded in the microcapsule. Secondly, at 2900 cm⁻¹ -1 (3008-2794cm -1 The peak at ) corresponds to the stretching vibration of CH, and its low position is related to the hydrogen bonds between the urea groups in the polyurea shell. Furthermore, at 1617 cm⁻¹... -1 and 1551cm -1 The double peaks at 2259 cm⁻¹ represent the absorption peaks of C=O and CN, respectively. The low peak positions indicate that these are absorption peaks due to the C=O vibration of the amide, confirming the formation of amide and urea bonds in the microcapsule shell. Furthermore, MCs-HMDA and MCs-MXDA show absorption peaks at 2259 cm⁻¹. -1 A small peak appeared at the point, which is a characteristic peak of free NCO groups (isocyanate groups), indicating that the microcapsules contain unreacted isocyanate groups.

[0084] To verify the shell structure of the microcapsules and the encapsulation of the core material, the infrared spectra of the shell material, core material, and microcapsules were compared. The results are as follows: Figure 2As shown in d, it can be seen that it is located at 2259cm. -1 The absorption peak of the isocyanate group disappears in the infrared spectrum of the microcapsule, indicating that isophorone diisocyanate (IPDI) and liquid diamine successfully reacted in the interfacial polymerization method to form a dense shell. Meanwhile, at 1617 cm⁻¹... -1 The presence of the amide functional group further confirms the occurrence of this reaction, consistent with the core-shell structure observed by TEM.

[0085] In summary, infrared spectroscopy analysis confirmed the chemical composition and internal structure of the microcapsules, indicating that the liquid diamine was successfully encapsulated in a dense shell formed by the reaction of isophorone diisocyanate and liquid diamine.

[0086] Example 7: Determination of the content of the core material of diamine microcapsules

[0087] The core material content of microcapsules is measured using a titration method. This involves dissolving the shell layer with an organic solvent to release the encapsulated core material, allowing the free amine groups to react with hydrochloric acid. The diamine content is calculated by recording the volume of hydrochloric acid solution consumed. Specifically, the core material content of the diamine microcapsules is determined according to standard ATSM D2074-2007. The microcapsules are demulsified with ethylene glycol to dissolve the internal core material. Three drops of bromophenol blue indicator are added, and titration is performed with a hydrochloric acid-isopropanol standard solution to the endpoint. The core material content of the diamine microcapsules is expressed as a mass percentage and calculated using the following formula:

[0088]

[0089] Where c HCl V is the concentration of the hydrochloric acid standard solution (standardized with anhydrous sodium carbonate), V is the volume of the HCl standard solution digested, M is the relative molecular mass of the diamine used in the sample, and m is the mass of the sample.

[0090] The results are as follows Figure 2 As shown in Figure e. The titration results show the diamine content of the several diamine microcapsules prepared in Example 1: ethylenediamine microcapsules ( Figure 2 The ethylenediamine content in the MCsEDA of e is approximately 13.29 wt%, and the 1,4-cyclohexanediamine microcapsules ( Figure 2 The 1,4-cyclohexanediamine content in the MCsHMDA of the middle e was 37.36 wt%, and the m-phenylenediamine microcapsules ( Figure 2 The content of m-xylenediamine in MCsMXDA is approximately 39.69 wt%.

[0091] Example 8: Detection of diamine microcapsules by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)

[0092] To further verify the successful encapsulation of liquid diamine within microcapsules and to investigate its thermal stability, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were employed for testing. The experimental methods are as follows:

[0093] The performance of the microcapsules and the activity of the core material were characterized using TGA. The sample prepared in Example 1 was tested on a TG-DSC synchronous analyzer under nitrogen atmosphere protection, with the temperature increased from 0°C to 800°C at a rate of 10°C / min.

[0094] The thermogravimetric analysis (TGA) and differential thermal scanning calorimetry (DSC) results for the core material, shell material, and microcapsules encapsulating ethylenediamine microcapsules are as follows: Figure 3 As shown. Thermogravimetric analysis and differential scanning calorimetry analysis were performed on MCs-EDA, MCs-HMDA, and MCs-MXDA synthesized from three different diamines, and the curves were compared. Figure 3 As shown in Figure a, the thermogravimetric analysis (TGA) curve revealed a mass loss of approximately 13.3 wt% corresponding to the first TGA plateau in MCs-EDA, corresponding to the encapsulated core material (ethylenediamine). This is consistent with the core material content calculated independently by titration, indicating that the microcapsules successfully encapsulated ethylenediamine. The microcapsule shell maintained its integrity during the thermogravimetric analysis until the core material was completely released. Notably, the loss temperature lagged behind that of the pure core material or shell at higher temperatures, indicating a significant improvement in the thermal stability of the ethylenediamine core material encapsulated in the microcapsules. This sustained-release effect not only helps protect the core material from the direct effects of high-temperature environments but also helps control the release rate of the core material at specific temperatures, thereby extending its service life and effectiveness. Furthermore, the polymerized shell material has an extremely high decomposition temperature, meaning that even under high-temperature conditions, the microcapsule shell can maintain its structural integrity, preventing premature leakage or loss of the internal core material. This excellent thermal stability ensures the reliability and durability of the microcapsules in high-temperature applications.

[0095] like Figure 3As shown in Figure b, by comparing the results of the differential scanning calorimetry (DSC) curve and the thermogravimetric analysis (TGA) curve, a significant endothermic peak was observed in the DSC curve at approximately 120°C. This is attributed to the release of small molecules, particularly the liquid evaporation of the core material, ethylenediamine. Since this endothermic peak is similar to that of pure ethylenediamine, this indicates that ethylenediamine has been successfully encapsulated within the microcapsules. This finding is consistent with the TGA results, further confirming the successful preparation of the microcapsules. For the microcapsule MCs-EDA, the endothermic peaks observed at 250°C and 351°C correspond to the DSC curves of the shell. These two endothermic peaks coincide with the two mass loss plateaus in the TGA curve, corresponding to the two reactions during the decomposition of polyurea resin. The results of the TGA and DSC curves further demonstrate the successful encapsulation of EDA and explain the excellent thermal stability and sustained-release effect of the microcapsules.

[0096] like Figure 3 As shown in Figures c, d, and e, each of the three microcapsules (MCs-EDA, MCs-HMDA, and MCs-MXDA) exhibits three endothermic peaks, which correspond to the three weight loss plateaus in the TGA curves. These endothermic peaks are due to the endothermic reaction of the liquid diamine due to the evaporation of small molecules and the endothermic reaction of the shell. Correspondingly, the mass losses in the TGA curves are 13.3 wt% for MCs-EDA, 15.2 wt% for MCs-HMDA, and 15.3 wt% for MCs-MXDA. These results are largely consistent with the preliminary results of titration statistics; the difference is due to the chemical changes that occur during microcapsule encapsulation. During encapsulation, the diamine molecules react with the isocyanate material, forming not only a dense shell but also short-chain or diamine-terminated long-chain polymers. These polymers still exhibit some reactivity in the titration analysis, leading to higher titration results. These polymers may have high thermal stability during TGA analysis and decompose at higher temperatures, resulting in lower mass losses at lower temperatures. Since the terminal amino group retains its reactivity in the self-healing reaction, we will rely on the titration results to perform calculations for subsequent microencapsulation doping experiments to ensure accurate measurement of the diamine content in the microcapsules.

[0097] exist Figure 3 As shown in Figure f, the DSC curves of different diamine microcapsules reveal a significant shift in the endothermic peak near 105℃. This shift is due to the differences in boiling points among the three different diamines. Specifically, ethylenediamine has a boiling point of 116-117.3℃, 1,4-cyclohexanediamine has a boiling point of 199.4℃, and m-xylenediamine has a boiling point of 247℃. This difference in boiling points is reflected in both the DSC and TGA curves. The DSC curves show that the position of the first peak increases with increasing boiling point.

[0098] In summary, thermogravimetric analysis and differential scanning calorimetry (DSC) provided a deeper understanding of the internal structure of the microcapsules and the changes in their thermal properties with different core materials. The results showed that the three microcapsules successfully encapsulated liquid diamine with excellent thermal stability. Given the volatility and low cost of ethylenediamine, its encapsulation has practical significance; therefore, MCsEDA will be further investigated.

[0099] Example 9 Synthesis of Diamine Microcapsules

[0100] 5 ml of ethylenediamine (EDA, HMDA, or MXDA, see Table 1) was mixed with 30 ml of solvent (n-heptane, diethyl ether, dimethyl silicone oil, see Table 1), and a first emulsifier (see Table 1) of 1 wt.% (relative to the solvent, such as n-heptane) was added to prepare a diamine emulsion. This diamine emulsion was then slowly added dropwise to an aqueous solution containing 1.5 mol / L isophorone diisocyanate at a rate maintained at one drop per second, with continuous stirring for 2 hours to promote the solidification of the spherical structure. Finally, the mixture was washed, filtered, and dried at room temperature to obtain ethylenediamine microcapsules.

[0101] The particle size structure of the diamine microcapsules was characterized according to the method in Example 5. The particle size and wall thickness of different diamine microcapsules were measured, as shown in the table below.

[0102] Table 1. Particle size and wall thickness of diamine microcapsules

[0103]

[0104]

[0105] The above-mentioned case of synthesizing and preparing diamine microcapsules mainly compares the effects of different emulsifiers in preparing diamine microcapsules. The results show that the combination of n-heptane and sodium dodecylbenzenesulfonate with Span 80 has a better effect, especially the emulsification effect of n-heptane and sodium dodecylbenzenesulfonate, which can effectively store diamine in liquid form in the microcapsules.

[0106] Example 10 Morphology characterization of isocyanate microcapsules

[0107] Three isocyanate microcapsules, MCs-IPDI(EDA), MCs-IPDI(DETA), and MCs-IPDI(PEAD230), were prepared by reacting IPDI prepared in Example 2 with three different diamines (ethylenediamine, diethylenetriamine, and polyetheramine D230). The results were observed by scanning electron microscopy (SEM). Figure 4 As shown in a, b, and c.

[0108] Electron microscopy analysis showed that isocyanate microcapsules with a regular spherical structure and good dispersibility were successfully synthesized via interfacial polymerization, without severe adhesion. Specifically, MCs-IPDI (D230) synthesized from IPDI and polyetheramine D230 exhibited the best morphology, followed by MCs-IPDI (DETA) synthesized from IPDI and diethylenetriamine. MCs-IPDI (EDA) synthesized from IPDI and ethylenediamine showed wrinkles on the surface and some adhesion. This difference may be due to the different chemical properties of the three diamine curing agents. Ethylenediamine has a higher basicity, which may affect the surface morphology of the microcapsules during the reaction. Simultaneously, due to the shortest chain length of ethylenediamine, the polymerization on the microcapsule surface may not be dense enough, making it prone to breakage. Diethylenetriamine, as a tri-chain diamine, can increase the cross-linking degree of polyurea on the microcapsule surface, forming a dense shell. However, due to its rapid reaction rate, some polyurea impurities may be generated, which was also observed in SEM observations. Polyetheramine D230, due to its longer chain length, forms a denser shell compared to the other two diamines. However, because of its relatively low reactivity, it requires a longer reaction time to achieve the desired curing effect.

[0109] Then, particle size analysis was performed on the three MCs-IPDIs, and the results are as follows: Figure 4 As shown in d, e, and f, all three microcapsules exhibit clear core-shell structures. While the EDA-formed MCs-IPDI (EDA) shows some adhesion, its core-shell boundary remains distinct. The core-shell structures of MCs-IPDI (DETA) and MCs-IPDI (D230) are even clearer, indicating that all three microcapsules can successfully encapsulate isophorone diisocyanate (IPDI). Specifically, the average particle size of MCs-IPDI (EDA) is 1.689 μm, with a variance (σ²) of 0.5663; the average particle size of MCs-IPDI (DETA) is 0.9322 μm, with a variance (σ²) of 0.2303; and the average particle size of MCs-IPDI (D230) is 1.7134 μm, with a variance (σ²) of 0.6702. Because DETA reacts quickly, it can solidify rapidly when the droplets are small, resulting in a more pronounced small particle size distribution compared to the other two diamines used as curing agents.

[0110] The core content of isocyanate microcapsules was determined with reference to the method for determining the isocyanate group content in polyurethane prepolymers. The content of isocyanate groups (NCO%) was used as the standard. The specific test method is as follows.

[0111] The core content of isocyanate microcapsules was calculated by titration using the di-n-butylamine-anhydrous toluene method, specifically referring to standard HG2409-1992. The core material in the microcapsules was dissolved in ethylene glycol, and 25 mL of anhydrous toluene was added to an Erlenmeyer flask. The mixture was shaken until completely dissolved, and then 25 mL of di-n-butylamine-anhydrous toluene solution was added. The mixture was mixed thoroughly and reacted for 15 min. 100 mL of isopropanol was added, and 4–6 drops of bromophenol blue indicator were added. The solution was titrated to the endpoint with standard hydrochloric acid solution.

[0112] The content of isocyanate groups is expressed as a mass percentage and is calculated using the following formula:

[0113]

[0114] Where V0 is the volume of HCl standard solution consumed by the blank sample, V is the volume of HCl standard solution consumed by the sample, and C HCl denoted as , where is the concentration of the hydrochloric acid standard solution (calibrated using anhydrous sodium carbonate), and m is the sample mass.

[0115] The results showed that the NCO% content of the three microcapsules was 1.021 wt% for MCs-IPDI (EDA), 10.046 wt% for MCs-IPDI (DETA), and 5.409 wt% for MCs-IPDI (D230). Because DETA has a higher reaction rate and can rapidly block isophorone diisocyanate, the corresponding microcapsules have a relatively higher NCO content.

[0116] Example 11 Chemical composition analysis of isocyanate microcapsules

[0117] Further observations were conducted using transmission electron microscopy (TEM) on the MCs-IPDI microcapsules prepared in Example 2. The MCs-IPDI microcapsule samples were coated onto aluminum sheets, dried in a vacuum oven, and sputtered with gold to enhance conductivity. The core-shell structure was verified using scanning electron microscopy (SEM), and the size distribution of the microcapsules was studied. The surface morphology was observed using an SEM (Quantum 200 ESEM, FEI). The results are as follows: Figure 5 As shown in Figures a, b, and c, TEM images of three isocyanate microcapsules were obtained: (a) MCs-IPDI(EDA), (b) MCs-IPDI(DETA), and (c) MCs-IPDI(D230). The core-shell structure of the IPDI microcapsules is clearly visible, indicating good encapsulation. Although MCs-IPDI(EDA) shows some degree of aggregation, the core-shell boundary remains distinct. The core-shell structures of MCs-IPDI(DETA) and MCs-IPDI(D230) are even more pronounced, demonstrating successful IPDI encapsulation.

[0118] Determination of the core content of isocyanate microcapsules

[0119] Referring to the diamine microcapsule titration test method in Example 7, the isocyanate group content in the polyurethane prepolymer was titrated. The isocyanate group content (wt%) was used as an indicator in the titration reaction, and the results are as follows: Figure 5 As shown in Figure d, the results indicate that the isocyanate percentages of the three microcapsules—MCs-IPDI(EDA), MCs-IPDI(DETA), and MCs-IPDI(D230)—are 1.02%, 10.05%, and 5.41%, respectively. The faster the DETA reaction rate, the higher the isocyanate content, and the faster the reaction and encapsulation with IPDI.

[0120] The infrared spectra of the isocyanate microcapsules' core material, shell material, and MCs-IPDI(DETA) were compared, and the results are as follows: Figure 5 As shown in Figure e, the characteristic peaks of isophorone diisocyanate (IPDI) are clearly observed in MCs-IPDI(DETA) within the wavenumber range of the isocyanate NCO characteristic peaks, indicating that the microcapsules prepared by interfacial polymerization successfully encapsulate IPDI. Additionally, the 3000–3500 cm⁻¹... -1 The broad peak at that location may be attributed to the amide functional groups and hydrogen bonds formed.

[0121] The properties of three MCs-IPDI compounds were analyzed using in-depth infrared spectroscopy (IR). Infrared spectra such as... Figure 5 As shown in f, at 2256cm -1 Corresponding to the characteristic peak of isocyanate (NCO), MCs-IPDI (EDA) shows almost no obvious peak at this position, which may indicate a low isocyanate content in this compound or that the NCO group in the structure is affected to some extent. In contrast, MCs-IPDI (DETA) and MCs-IPDI (D230) show a peak at 2256 cm⁻¹. -1 Significant peaks were observed at all locations, indicating the presence of isocyanate in the MCs-IPDI microcapsules. Notably, the peak intensity of MCs-IPDI (D230) was lower than that of MCs-IPDI (DETA). These observations are consistent with previous titration results, further emphasizing the consistency and reliability of the experimental data.

[0122] Thermal performance analysis of IPDI microcapsules

[0123] The thermal stability of isocyanate microcapsules was characterized using methods similar to TGA and DSC analysis for diamine microcapsules. Results are as follows: Figure 6As shown in Figure 1, the thermogravimetric analysis (TGA) curves of IPDI microcapsules (MCs-IPDI(EDA), MCs-IPDI(DETA), and MCs-IPDI(D230)) show only one weight loss plateau, and correspondingly, the differential thermal scanning (DSC) curves also show only one endothermic peak. Increasing the isocyanate encapsulation content leads to an increase in the slope of the TGA weight loss curve. This is because the pyrolysis temperature of isophorone diisocyanate after microencapsulation overlaps with that of the shell, resulting in more IPDI occupying a larger space within the microcapsule. Therefore, as the temperature rises, more IPDI and the shell material decompose simultaneously, leading to a faster weight loss rate and an increased slope of the weight loss curve. The overlap of the two endothermic peaks at similar temperatures can also be observed in the DSC curves.

[0124] like Figure 6 Figure d shows the TGA curves of the core, shell, and isocyanate microcapsules MCs-IPDI(DETA). Figure 6 As shown in Figures e and f, the thermal stability of the microcapsules was analyzed based on TGA and DSC data. The thermogravimetric curves of microencapsulated MCs-IPDI(EDA), MCs-IPDI(DETA), and MCs-IPDI(D230) showed only one weight loss plateau. In contrast, the differential thermal scanning curve (DSC) also showed only one endothermic peak. Furthermore, the slope of the TGA weight loss curve increased with the increase of isocyanate encapsulation amount.

[0125] This may be because the pyrolysis temperature of isophorone diisocyanate after microencapsulation overlaps with that of the shell, resulting in more IPDI occupying a larger space inside the microcapsule. Therefore, as the temperature increases, more IPDI and the shell material decompose simultaneously, leading to a faster weight loss rate and an increased slope of the weight loss curve. Consequently, the overlap of the two endothermic peaks at similar temperatures can be observed in the DSC curve.

[0126] Example 12 Self-healing performance test of binary microcapsule system resin

[0127] To evaluate the self-healing properties of resins doped with binary microcapsule systems, mechanical property tests were used to characterize the impact of microcapsule doping on self-healing performance. Specifically, scratch and abrasion tests were conducted, and the experimental methods were as follows: the resins of the binary microcapsule systems prepared in Examples 3 and 4 were coated to form a coating, simulating potential damage that might be encountered in actual use, and scratch simulations and abrasion tests of different types and depths were performed.

[0128] Scratch test: A hard metal strip or sandpaper is used to scratch or rub the resin coating surface on a 1 square centimeter surface to simulate natural scratch damage and surface abrasion damage. After the scratches and abrasions are formed, they are photographed and recorded using an optical microscope. The samples are then left to stand for 2-10 days to allow for self-healing and repair. Afterward, they are photographed again using an optical microscope, and the changes in abrasion damage on the resin surface are compared.

[0129] In the scratch test, the scratch depth and scratch damage rate were kept consistent for all samples to control variables and ensure reliable experimental results. Optical microscopy (OM) images of the scratch-treated samples are shown below. Figure 7 As shown. Among them, epoxy resin scratches are as follows: Figure 7 As shown in a1 and a2, a2 ​​represents the morphology of the scratch after 48 hours of rest. The PU-F520 scratch is shown below. Figure 7 As shown in b1 and b2, b2 represents the morphology of the scratch after 48 hours of rest. The wear on the epoxy resin coating surface is as follows... Figure 7 As shown in C1 and C2, C2 is the morphology and magnified view of the worn surface after 48 hours of rest. The wear of the PU-F520 resin coating surface is as follows... Figure 7 As shown in d1 and d2, d2 is the morphology and magnified view of the worn surface after 48 hours of rest.

[0130] The mechanism of crack repair is as follows Figure 7 As shown in e.

[0131] By observing and analyzing the scratched areas, it can be seen that the resin of the binary microcapsule system of the present invention has good repair capabilities. The coating self-heals after 48 hours, and the epoxy resin doped with microcapsules reduces the scratch width from approximately 0.32 mm to 0.25 mm. Figure 7 As shown in Figure a.

[0132] The self-healing rate is calculated as follows: η=(l0-l) / l0×100%.

[0133] Where η is the self-healing efficiency, l0 is the initial width of the scratch, and l is the final width of the scratch.

[0134] Therefore, epoxy resin coatings incorporating a binary microcapsule system achieve a self-healing efficiency of approximately 21.8%. The self-healing efficiency of PU-F520 resin was calculated using the same method, achieving approximately 33.3%.

[0135] As can be seen, the originally continuous and distinct strip-shaped scratches became discontinuous after self-healing, with both the width and depth of the scratches significantly reduced, and some scratches even almost completely disappearing. This indicates that after scratch and abrasion damage, the self-healing agent within the microcapsules was successfully released and effectively repaired the resin surface. As a key component of the self-healing system, the binary microcapsule system rapidly responds to abrasion damage to the resin surface, filling the voids in the scratches. With the curing and stabilization of the self-healing agent, the morphology of the scratches is significantly improved, and the continuity and smoothness of the resin surface are effectively restored, effectively improving the resin's abrasion resistance and durability, and better meeting the needs of long-term applications in complex environments.

[0136] Example 13: Corrosion Resistance Test of Binary Microcapsule System Resin

[0137] To more comprehensively evaluate the self-healing properties and durability of resins doped with binary microcapsule systems under different environmental conditions, a salt water immersion experiment was conducted. The salt water immersion experiment simulates the corrosion and aging problems that the resin may encounter in real-world applications (such as seawater immersion). By observing and analyzing the surface characteristics of the resin after salt water immersion, the resin's corrosion resistance and anti-aging properties can be understood.

[0138] The specific experimental method is as follows: On a 4cm*2.5cm tinplate sheet, epoxy resin without microcapsules, epoxy resin with microcapsules (prepared in Example 3), PU-F520 resin without microcapsules, and PU-F520 resin with microcapsules (prepared in Example 4) were coated respectively. The coating area was 2.5cm*2cm. Each group of resins contained three samples: one as a control, and another with a crisscross scratch treatment on the surface. Then, as... Figure 8 As shown in Figure b, the samples were immersed in 10 wt% sodium chloride saline solution to observe and compare the corrosion resistance of each group of resins on tinplate sheets, especially the corrosion phenomenon after scratch treatment.

[0139] Experimental results are as follows Figure 8 As shown in Figure a, the epoxy resin coating without microcapsules showed obvious corrosion and yellowing after 10 days, while the epoxy resin coating with microcapsules maintained a consistent color and showed no obvious rust. Similarly, PU-F520 resin treated with the same method showed obvious rust at the edges of the undoped coating and slight yellowing, while the resin coating with microcapsules exhibited stronger corrosion resistance, almost no change in surface color, and even a self-healing effect on scratches.

[0140] The results showed that the microcapsule-doped resin system exhibited significantly improved corrosion resistance. This is likely because the microcapsule incorporation introduced an additional protective layer into the resin system, effectively isolating it from corrosive media in the external environment, such as moisture, oxygen, and salt, thereby reducing the risk of resin corrosion. Secondly, the microcapsules could promptly release self-healing agents to repair minor damage to the resin surface. This self-healing mechanism helps restore the integrity and continuity of the resin surface, filling potential corrosion channels or defects during the damage repair process, further enhancing the resin's corrosion resistance.

[0141] Furthermore, the incorporation of microcapsules can improve the physical and chemical properties of the resin system, such as increasing its density, reducing porosity, and enhancing its resistance to chemical corrosion. These improvements contribute to enhancing the overall durability of the resin, making it more resistant to harsh environments.

[0142] Example 14: Binary Microcapsule System Resin Corrosion Protection

[0143] Preparation of self-healing epoxy resin: The diamine microcapsules prepared in Example 1 and the isocyanate microcapsules prepared in Example 2 were mixed in a molar ratio of 1:1 to prepare a binary microcapsule system as a dopant. The selected material was a methyl methacrylate (MCMA) resin. TM The epoxy resin used in the adhesive is composed of epichlorohydrin and bisphenol A (or other polyols; bisphenol A is used in this example). Following the epoxy resin instructions, components A and B are mixed in a 1:1 mass ratio, and 10 wt% dopant is added to prepare a self-healing epoxy resin. The self-healing epoxy resin is poured into a polytetrafluoroethylene mold for molding, vacuum degassing, and room temperature curing. This ensures that the microcapsules are uniformly distributed in the resin, thereby improving the performance of the self-healing coating and obtaining a self-healing epoxy resin coating.

[0144] The specific selection of the two types of microcapsules is shown in Table 2 below. Correspondingly, various dual-microcapsule coating products were prepared and tested. Specifically, the self-healing performance of the resin was tested according to the method in Example 12, and the self-healing rate was calculated using the following formula:

[0145] η = (l0 - l) / l0 × 100%

[0146] The self-healing rate of the coating after film formation was examined. Referring to the resin corrosion resistance test in Example 13, the corrosion resistance on the tinplate sheets was compared, and the results are shown in the table below.

[0147] Table 2 Comparison of corrosion resistance of coatings with different doping levels in dual-microcapsule systems

[0148]

[0149]

[0150] *The epoxy resin microcapsules were synthesized according to existing literature methods, “Zhang Xiaoxing, 2018, Research on Microcapsules for Insulating Epoxy Resin Self-Healing System”, and the amount of coating incorporated was 10wt%.

[0151] **The corrosion resistance of the above-mentioned reference example 12 was evaluated. The corrosion resistance effect in example 12 was marked as "++++". For every 20% reduction in corrosion amount, the "+" mark was added, and for every 20% increase in corrosion amount, the "+" mark was removed. The corrosion area was calculated compared to the conventional test group that did not use microcapsules in example 12.

[0152] ***The above self-healing rate evaluation is compared with the results of Example 13. In Example 13, a self-healing rate of 20±5% is marked as "++", a self-healing rate of 30±5% is marked as "+++", and a self-healing rate greater than 0 and less than 10% is marked as "+".

[0153] As shown in Table 2, the experimental results indicate that the dopants prepared by mixing various microcapsules from Examples 1 and 2 of this invention in a 1:1 ratio and applying them to resin can significantly improve the continuity of the film layer, effectively self-heal scratches and other damage, and significantly enhance the corrosion resistance of metallic materials. Traditional epoxy resin microcapsules exhibit poor corrosion resistance and self-healing properties, falling short of the repair capabilities of binary microcapsules. This is because the liquid contents of binary microcapsules can rapidly flow and combine at crack / scratch sites, achieving faster and stronger healing and repair, thus sealing and protecting the metal beneath the coating.

Claims

1. A coating for encapsulating binary microcapsules of liquid diamine and isocyanate, characterized in that, It includes a coating matrix, as well as a binary microcapsule system consisting of diamine microcapsules and isophorone diisocyanate microcapsules; The diamine microcapsules are prepared by emulsifying and dispersing liquid diamine in n-heptane, then dropping it into an aqueous solution containing isophorone diisocyanate, and finally by water-in-oil interfacial polymerization. The diamine is at least one of ethylenediamine, 1,4-cyclohexanediamine, and m-phenylenediamine.

2. The coating for encapsulating binary microcapsules of liquid diamine and isocyanate according to claim 1, characterized in that, The diamine microcapsules were prepared by the following method: S101. Dissolve the diamine and the first emulsifier in n-heptane, mix them evenly, and prepare a diamine emulsion. Isophorone diisocyanate was dissolved in water to prepare an aqueous solution of isophorone diisocyanate; S102. The diamine emulsion is dropped into the aqueous solution of isophorone diisocyanate and stirred continuously for 1-5 hours to promote the curing of the spherical structure. S103, washing, filtering and drying, to obtain diamine microcapsules.

3. The coating for encapsulating binary microcapsules of liquid diamine and isocyanate according to claim 2, characterized in that, The first emulsifier is sodium dodecylbenzenesulfonate.

4. The coating for encapsulating binary microcapsules of liquid diamine and isocyanate according to claim 2, characterized in that, The drying process is carried out at room temperature.

5. The coating for encapsulating binary microcapsules of liquid diamine and isocyanate according to claim 4, characterized in that, The drying temperature should not exceed 40℃.

6. The coating for encapsulating binary microcapsules of liquid diamine and isocyanate according to claim 5, characterized in that, The drying temperature should not exceed 35℃.

7. The coating for encapsulating binary microcapsules of liquid diamine and isocyanate according to claim 6, characterized in that, The drying temperature should not exceed 30℃.

8. The coating for encapsulating binary microcapsules of liquid diamine and isocyanate according to claim 7, characterized in that, The drying temperature should not exceed 25℃.

9. The coating for encapsulating binary microcapsules of liquid diamine and isocyanate according to claim 1, characterized in that, The isophorone diisocyanate microcapsules were prepared by the following method: S201. Dissolve isophorone diisocyanate and the second emulsifier in water, mix them evenly, and prepare isophorone diisocyanate emulsion. Dissolve polyetheramine, diethylenetriamine, or ethylenediamine in water to prepare a diamine solution; S202. The isophorone diisocyanate emulsion is added dropwise to the diamine solution, and the mixture is stirred for 2 hours to solidify the microcapsule shell. S203, filtration, washing with deionized water, drying, to obtain isophorone diisocyanate microcapsules.

10. The coating for encapsulating binary microcapsules of liquid diamine and isocyanate according to claim 9, characterized in that, Isophorone diisocyanate emulsion was added dropwise to a diamine solution at a rate of 1-2 drops every 1-2 seconds to form microcapsules, and the mixture was stirred for 2 hours to solidify the microcapsule shell.

11. The coating for encapsulating binary microcapsules of liquid diamine and isocyanate according to claim 9, characterized in that, The second emulsifier is Tween 80.

12. The application of the coating of the binary microcapsules encapsulating liquid diamine and isocyanate as described in any one of claims 1-11 in the manufacture of self-healing coatings.

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