Slow-release rust-inhibiting microcapsule applied to reinforced concrete and preparation method of slow-release rust-inhibiting microcapsule

Abstract

The invention provides a slow-release corrosion-resistant microcapsule applied to reinforced concrete, the slow-release corrosion-resistant microcapsule comprises a capsule core and a capsule wall, and the capsule core comprises a composite corrosion inhibitor, self-repairing microspheres, nano hydrotalcite and an anti-freezing agent; the capsule wall comprises a three-layer structure including an inner layer film, a middle layer film and an outer layer film. The mass ratio of the capsule core to the capsule wall is 1: (0.3-0.5); and the thickness of the capsule wall is 10-17 microns. A pH triggering inner layer, a dynamic self-repairing middle layer and a hydrophobic protection outer layer are designed through three layers of intelligent response capsule walls, and on-demand release and long-term stability of a corrosion inhibitor are achieved; the crack repairing efficiency is remarkably improved through the synergistic effect of the chemical repairing material and the biological spores in the capsule core; the dynamic cross-linked network endows the capsule wall with self-healing ability, resists physical damage, improves the durability of the concrete, prolongs the service life of the concrete, also can enhance the wear resistance of the concrete, and reduces the wear in the use process.

Description

Technical Field

[0001] The present invention belongs to the field of material technology, and specifically relates to a slow-release rust-inhibiting microcapsule applied to reinforced concrete and a preparation method thereof. Background Art

[0002] Rebar corrosion is a common problem in concrete structures, particularly in humid, salty environments such as coastal areas, bridges, tunnels, and underground structures. Rebar corrosion not only reduces the structure's load-bearing capacity but also causes cracking and spalling of concrete. In severe cases, it can even lead to structural failure, compromising the safety and durability of buildings. When rebar corrodes, the resulting rust forms a much larger volume than the original iron (typically 2-4 times its original volume). This volume expansion creates significant internal stresses in the surrounding concrete, causing cracking. Initial cracks may be small, but over time, they expand, eventually leading to concrete spalling, exposing more rebar and accelerating the corrosion process. Rebar corrosion reduces the cross-sectional area of the rebar and weakens its bond strength, which in turn affects the structural stiffness. This reduced stiffness means the structure will experience greater deformation under load. Especially under long-term loads, the accumulated deformation may exceed the design tolerances, compromising the building's functionality.

[0003] Rust inhibitors are chemical substances that inhibit corrosion on metal surfaces. They typically form a protective film by adsorbing onto the metal surface or reacting with metal ions, preventing corrosive substances (such as oxygen, moisture, and chloride ions) from coming into contact with the metal. Rust inhibitors can be organic, inorganic, or composite compounds, depending on their mechanism of action and application requirements.

[0004] To address rebar corrosion, a common technique used in existing technologies is to add rust-inhibiting microcapsules to concrete. These microcapsules repair microcracks and improve the cementitious material's resistance to chloride ion permeability, preventing chloride-induced rebar corrosion, which can reduce structural durability and even lead to premature failure. The core material of most existing microcapsules must come into contact with a curing agent to initiate a curing reaction and form a repair product, thereby achieving self-healing of microcracks. However, the complex service environment of cementitious materials makes it difficult for the curing agent and the repair agent to come into contact, reducing the effectiveness of microcrack repair. Summary of the Invention

[0005] The present invention aims to provide a sustained-release rust-resistant microcapsule for use in reinforced concrete and a preparation method thereof. The capsule core comprises modified tung oil, hydrotalcite, a rust inhibitor, and the like, and the capsule wall comprises ingredients such as cage-type polysilsesquioxane and polycaprolactone. The capsule improves the chloride ion corrosion resistance of the concrete-based material by the synergistic effect of repairing microcracks in the concrete-based material and solidifying the free chloride ions in the matrix.

[0006] To achieve the above object, the present invention provides the following technical solutions: A slow-release rust inhibitor microcapsule applied to reinforced concrete, comprising a core and a wall. The core includes a composite rust inhibitor, self-healing microspheres, nano-hydrotalcite and an antifreeze agent; the wall includes a three-layer structure of an inner layer film, a middle layer film and an outer layer film; Among them, the inner layer film is composed of a composite of polydopamine and polycaprolactone, and polydopamine forms polydopamine with pH-responsive characteristics under alkaline conditions; The middle layer film is composed of a dynamically crosslinked cage-like polyhedral oligomeric silsesquioxane-polyvinyl alcohol network; The outer layer film is composed of silica hydrophobically modified by hexadecyltrimethoxysilane and polylactic acid.

[0007] A preparation method of a slow-release rust inhibitor microcapsule applied to reinforced concrete, wherein the method comprises the following steps: S1. Mix and stir nitrite and phosphate to obtain a composite rust inhibitor, and mix and stir the composite rust inhibitor, nano-hydrotalcite and polyethylene glycol-600 to obtain a composite rust inhibitor powder; S2. Mix hydroxyethyl methacrylate and acrylate-modified tung oil to obtain a mixture, mix the mixture with spores of Bacillus pasteurii, and perform spray drying to obtain self-healing microspheres; S3. React nano-hydrotalcite in an ethanol solution of a silane coupling agent to obtain a reaction solution, and perform centrifugal drying on the reaction solution to obtain amino-modified nano-hydrotalcite; S4. Mix and stir the composite rust inhibitor powder, self-healing microspheres, amino-modified nano-hydrotalcite, polyethylene glycol-600, deionized water and polyvinylpyrrolidone to obtain a stirred material, and perform ultrasonic treatment on the stirred material to obtain a homogeneous core slurry; S5. Transport the homogeneous core slurry to the inlet of a microcontroller chip through a peristaltic pump; S6. Dissolve dopamine hydrochloride in Tris buffer solution, trigger the oxidative self-polymerization of polydopamine through alkaline conditions to form a polydopamine precipitate with pH-responsive characteristics, perform centrifugal drying on the polydopamine precipitate to obtain polydopamine powder, dissolve the polydopamine powder and polycaprolactone in ethanol to obtain a solution, inject the solution through a microfluidic chip onto the homogeneous core slurry for contact, and form an inner layer film through interfacial self-assembly to obtain a core microsphere coated with an inner layer; S7. Mix cage-like polyhedral oligomeric silsesquioxane and polyvinyl alcohol, add a furan-maleimide crosslinking agent after mixing to obtain a middle layer material emulsion, inject the middle layer material emulsion through a microfluidic middle layer channel onto the homogeneous core slurry for coating and heating, trigger the dynamic crosslinking of Diels-Alder bonds to form a middle layer film, and obtain a microcapsule coated with a middle layer; S8. Immerse silica in a cetyltrimethoxysilane solution for reaction to obtain hydrophobic silica. Place the hydrophobic silica in a polylactic acid solution for dissolution to obtain a solution. Form an outer layer film by electrostatic spraying of the solution to obtain microcapsules with a completely coated three-layer capsule wall. S9. Transfer the microcapsules with a completely coated three-layer capsule wall to a curing chamber and let them stand still to obtain microcapsules with a stable structure. S10. Conduct freeze-drying treatment on the microcapsules with a stable structure to obtain slow-release rust-inhibiting microcapsules.

[0008] As a supplementary note, tung oil, as a natural drying oil, has the following remarkable characteristics: Quick drying: When exposed to air, tung oil can quickly solidify into a hard film through oxidation. This quick-drying property makes it very suitable for application scenarios where a protective layer needs to be formed quickly. Waterproof performance: The solidified tung oil film has good waterproof performance and can effectively prevent moisture from penetrating into wood or other materials, thereby improving the durability and corrosion resistance of these materials. Anti-corrosion: In addition to waterproofing, tung oil can also provide certain anti-corrosion protection, helping to extend the service life of the treated materials. Glossiness: When tung oil dries, it forms a shiny film on the surface, which not only increases the aesthetic appearance but also helps to display and enhance the natural texture of the substrate. Strong adhesion: Tung oil can bind well with various substrates (such as wood, paper, fabric, etc.) to form a durable protective layer. Environmental friendliness: As a natural product, compared with synthetic chemicals, tung oil has less impact on the environment, but its environmental impact during large-scale applications still needs to be considered. Chemical stability: The solidified tung oil film is relatively stable and not easily affected by acids and alkalis, but long-term exposure to ultraviolet rays and extreme temperatures may cause aging.

[0009] Nano - hydrotalcite is a kind of layered double hydroxides with a layered structure, usually composed of divalent and trivalent metal ions. The most typical representative is magnesium - aluminum hydrotalcite. Due to their unique physical and chemical properties, they show broad application prospects in many fields. Nano - hydrotalcite has a layered structure similar to clay minerals. Each layer consists of positively charged metal hydroxide sheets, and the interlayer contains exchangeable anions and water molecules. Due to its nano - scale particle size, nano - hydrotalcite has a large specific surface area, which enables it to exhibit excellent performance in adsorption, catalysis, etc. Nano - hydrotalcite can maintain its structural stability at relatively high temperatures, which is very important for applications that require high - temperature treatment, such as being used as a catalyst support or a flame retardant. By changing the synthesis conditions, the ratio of metal ions and other components in nano - hydrotalcite can be adjusted, so as to customize the chemical properties of the material to meet the needs of specific applications. Nano - hydrotalcite is generally considered an environmentally friendly material because it is relatively stable in the natural environment, not easily releasing harmful substances, and can also be used to remediate polluted soil or water bodies in some cases. When used as a polymer filler, nano - hydrotalcite can significantly improve the mechanical properties of composite materials, such as tensile strength, modulus, and toughness. Nano - hydrotalcite is easily dispersed in various media under appropriate conditions, including water, organic solvents, and polymer matrices, which helps to prepare uniform composite materials or coatings.

[0010] Cage - type polyhedral oligomeric silsesquioxanes (POSS) are a kind of hybrid materials with unique structures and properties, which combine the advantages of organic and inorganic materials. The basic structure of a POSS molecule is an octahedral or dodecahedral framework connected by silicon - oxygen bonds, and each silicon atom is connected to an organic group.

[0011] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: Through the design of a three - layer intelligent response capsule wall (pH - triggered inner layer, dynamically self - healing middle layer, hydrophobic protective outer layer), the present invention realizes the on - demand release and long - term stability of the rust inhibitor; the synergistic effect of the chemical repair material and biological spores in the capsule core significantly improves the crack repair efficiency; the dynamic cross - linked network endows the capsule wall with self - healing ability to resist physical damage; the water - based process and antifreeze support environmentally friendly preparation and application in cold environments; the functionalized nano - hydrotalcite and the filling effect of microcapsules enhance the compactness and mechanical properties of concrete, comprehensively improving the structural durability. When this micro - capsule - type rust inhibitor is applied to concrete, it has a good rust - inhibiting effect, can improve the durability of concrete, extend the service life of concrete, and can also enhance the wear resistance of concrete, reducing wear during use. Description of the Drawings

[0012] Figure 1 is the overall microscopic morphology map of the microcapsule; Figure 2 is the microscopic morphology map of a single microcapsule; Figure 3 Schematic diagram of the triggering characteristics of the microcapsules. Specific implementation mode

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0014] The raw materials used in the present invention are as follows: Polycaprolactone (Shanghai Yuanye Bio-Technology Co., Ltd., product number S26795); Polyvinyl alcohol (Shanghai Yuanye Bio-Technology Co., Ltd., product number S30196); Acrylate-modified tung oil (Jinan Hongteng Weiye New Materials Co., Ltd., product catalog 454); 2-Hydroxyethyl methacrylate (Shanghai Yuanye Bio-Technology Co., Ltd., product number S24381).

[0015] Example 1 This example provides a preparation method of a slow-release rust inhibitor microcapsule applied to reinforced concrete for preparing the above-mentioned slow-release rust inhibitor microcapsule, including the following steps: S1. Take 15 g of sodium nitrite and 30 g of potassium phosphate and mix them according to a mass ratio of 1:2. Use a stirrer to stir and mix at a speed of 400 rmp for 15 min to obtain a composite rust inhibitor. Mix the composite rust inhibitor, 10 g of nano-hydrotalcite, and 5 g of polyethylene glycol-600, and stir and mix at a speed of 400 rmp for 15 min to obtain a composite rust inhibitor powder, denoted as A1; S2. Mix 10 g of 2-hydroxyethyl methacrylate with 50 g of acrylate-modified tung oil, and use a stirrer to stir and mix at 160 °C at a speed of 400 rmp for 15 min to obtain a mixture. Mix the mixture with 25 g of Bacillus pasteurii spores, and at an inlet temperature of 80 °C and an outlet temperature of 50 °C in the spray dryer, obtain self-healing microspheres with a microsphere diameter of 5 μm, denoted as B1; S3. Immerse 10 g of nano-hydrotalcite in an ethanol solution of a 3% mass concentration of silane coupling agent, react at 60 °C for 3 h to obtain a reaction solution, centrifuge the reaction solution at a speed of 8000 rmp for 10 min, and obtain amino-modified nano-hydrotalcite after drying, denoted as C1; S4. Take 50 g of the composite rust inhibitor powder in A1, 15 g of the self-healing microspheres in B1, 10 g of the amino-modified nano-hydrotalcite in C1, 5 g of polyethylene glycol-600, 40 ml of deionized water, and 0.3% mass concentration of polyvinylpyrrolidone for mixing, stir with a stirrer at a speed of 400 rmp for 10 min to obtain a stirred product, and process the stirred product with a 40 kHz ultrasonic machine for 20 min to obtain a homogeneous core slurry, denoted as D1; S5. Transfer the homogeneous core slurry in D1 to the inlet of the microcontroller chip through a peristaltic pump at a flow rate of 0.4 mL / min; S6. Dissolve dopamine hydrochloride in Tris buffer with a pH of 8.5. Trigger the oxidative self-polymerization of polydopamine under alkaline conditions to form a polydopamine precipitate with pH-responsive characteristics. Centrifuge and dry the polydopamine precipitate at 8000 rmp for 10 min to obtain polydopamine powder, denoted as E1; Take 5 g of the polydopamine powder in E1 and dissolve it in 15 g of polycaprolactone in 100 ml of ethanol. Control the peristaltic pump through the microfluidic chip at a flow rate of 0.4 mL / min under greenhouse conditions to self-assemble on the surface of the core to form core microspheres with an inner layer film of 3 μm; S7. Mix 15 g of cage-like polyhedral oligomeric silsesquioxane and 30 g of polyvinyl alcohol. After mixing, add a furan-maleimide cross-linking agent with a concentration of 0.5 mol / cm³ and heat at 60 °C for 5 min to obtain microcapsules with a middle layer film of 5 μm; S8. Immerse 10 g of silica in a 16% mass concentration of cetyltrimethoxysilane solution for 5 h of hydrophobic reaction to obtain hydrophobic silica. Place the hydrophobic silica in 30 ml of polylactic acid solution to dissolve it to obtain a solution. Spray the solution electrostatically at a voltage of 18 kv to form microcapsules with a complete outer layer film thickness of 2 μm and a three-layer capsule wall; S9. Transfer the microcapsules with a complete three-layer capsule wall and an outer layer film thickness of 2 μm to a curing chamber at a temperature of 20 °C and a humidity of 20% and let them stand for 10 h to obtain structurally stable microcapsules, denoted as F1; S10. Dry the structurally stable microcapsules in F1 at -40 °C for 20 h to obtain slow-release rust inhibitor microcapsules with a capsule wall thickness of 10 μm, denoted as G1.

[0016] Example 2 This example provides a preparation method of slow-release rust inhibitor microcapsules for reinforced concrete, used to prepare the above-mentioned slow-release rust inhibitor microcapsules, including the following steps: S1. Take 22.5 g of potassium nitrite and 45 g of magnesium phosphate according to a mass ratio of 1:2, and stir and mix them at a speed of 475 rmp for 18 min using a stirrer to obtain a composite rust inhibitor. Mix the composite rust inhibitor, 15 g of nano-hydrotalcite, and 8 g of polyethylene glycol-600, and stir and mix them at a speed of 475 rmp for 18 min to obtain composite rust inhibitor powder, denoted as A2; S2. Mix 15 g of 2 - hydroxyethyl methacrylate with 70 g of acrylate - modified tung oil, and stir - mix them at 168 °C for 18 min at a speed of 475 rmp using a stirrer to obtain a mixture. Mix the mixture with 35 g of Bacillus pasteurii spores, and at an inlet temperature of 85 °C and an outlet temperature of 52.5 °C in spray drying, self - healing microspheres with a microsphere diameter of 6 μm are obtained, denoted as B2; S3. Immerse 15 g of nano - hydrotalcite in an ethanol solution of silane coupling agent with a mass concentration of 3.75%, react at 62.5 °C for 3.75 h to obtain a reaction solution, centrifuge the reaction solution at a speed of 8500 rmp for 12.5 min, and after drying, amino - modified nano - hydrotalcite is obtained, denoted as C2; S4. Take 65 g of the composite rust inhibitor powder in A2, 22.5 g of the self - healing microspheres in B2, 15 g of the amino - modified nano - hydrotalcite in C2, 8 g of polyethylene glycol - 600, 47.5 ml of deionized water, and a polyvinylpyrrolidone with a mass concentration of 0.375% and mix them. Stir with a stirrer at a speed of 475 rmp for 12.5 min to obtain a stirred product. Treat the stirred product with a 42.5 kHz ultrasonic machine for 22.5 min to obtain a homogeneous core slurry, denoted as D2; S5. Pump the homogeneous core slurry in D2 to the inlet of the micro - control chip through a peristaltic pump at a flow rate of 0.475 mL / min; S6. Dissolve dopamine hydrochloride in Tris buffer with a pH of 8.75, trigger the oxidative self - polymerization of polydopamine through an alkaline condition to form a polydopamine precipitate with pH - responsive characteristics. Centrifuge and dry the polydopamine precipitate at 8500 rmp for 11.5 min to obtain polydopamine powder, denoted as E2; Take 7.5 g of the polydopamine powder in E2 and 22.5 g of polycaprolactone and dissolve them in 150 ml of ethanol. Under greenhouse conditions, self - assemble on the surface of the core through a micro - fluidic chip controlling a peristaltic pump at a flow rate of 0.475 mL / min to form a core - microsphere with an inner layer film thickness of 3.75 μm; S7. Mix 22.5 g of cage - type polyhedral oligomeric silsesquioxane and 37.5 g of polyvinyl alcohol, add a furan - maleimide cross - linker with a concentration of 0.7 mol / cm³ after mixing, and heat at 62.5 °C for 7 min to obtain a micro - capsule with a middle layer film thickness of 6 μm; S8. Immerse 15 g of silica in a hexadecyltrimethoxysilane solution with a mass concentration of 9% for a hydrophobic reaction for 5.75 h to obtain hydrophobic silica. Dissolve the hydrophobic silica in 45 ml of polylactic acid solution to obtain a solution. Form a micro - capsule with a complete three - layer wall coating and an outer layer film thickness of 2.75 μm through electrostatic spraying with a voltage of 20 kv; S9. Transfer the microcapsules with a complete three-layer coating wall and an outer membrane thickness of 2.75 μm to a curing chamber at a temperature of 24 °C and a humidity of 27.5% and let them stand for 11 h to obtain microcapsules with stable structure, denoted as F2; S10. Dry the microcapsules with stable structure in F2 at a temperature of -47.5 °C for 22 h to obtain sustained-release rust inhibitor microcapsules with a coating wall thickness of 12.5 μm, denoted as G2.

[0017] Example 3 This example provides a preparation method of sustained-release rust inhibitor microcapsules applied to reinforced concrete for preparing the above-mentioned sustained-release rust inhibitor microcapsules, including the following steps: S1. Take 35 g of sodium nitrite and 55 g of magnesium phosphate according to a mass ratio of 1:2, mix them with a stirrer at a rotation speed of 550 rmp for 22 min to obtain a composite rust inhibitor, mix the composite rust inhibitor, 20 g of nano-hydrotalcite, and 12 g of polyethylene glycol-600, and stir and mix them at a rotation speed of 550 rmp for 22 min to obtain a composite rust inhibitor powder, denoted as A3; S2. Mix 20 g of hydroxyethyl methacrylate with 90 g of acrylate-modified tung oil, stir and mix them with a stirrer at 175 °C at a rotation speed of 550 rmp for 22 min to obtain a mixture, mix the mixture with 45 g of Bacillus pasteurii spores, and at an inlet temperature of 95 °C and an outlet temperature of 57.5 °C of the spray dryer, obtain self-healing microspheres with a microsphere diameter of 8 μm, denoted as B2; S3. Immerse 20 g of nano-hydrotalcite in an ethanol solution of a silane coupling agent with a mass concentration of 4.5%, react at 65.5 °C for 4.5 h to obtain a reaction solution, centrifuge the reaction solution at a rotation speed of 9500 rmp for 14 min, and obtain amino-modified nano-hydrotalcite after drying, denoted as C3; S4. Take 85 g of the composite rust inhibitor powder in A3, 27.5 g of the self-healing microspheres in B3, 20 g of the amino-modified nano-hydrotalcite in C3, 12 g of polyethylene glycol-600, 55 ml of deionized water, and a polyvinylpyrrolidone with a mass concentration of 0.55% for mixing, stir with a stirrer at a rotation speed of 550 rmp for 15 min to obtain a stirred material, and process the stirred material with a 46 kHz ultrasonic machine for 25 min to obtain a homogeneous core slurry, denoted as D3; S5. Transport the homogeneous core slurry in D3 to the inlet of the microcontroller chip through a peristaltic pump at a rate of 0.55 mL / min; S6. Dissolve dopamine hydrochloride in a Tris buffer solution with a pH of 8.9, trigger the oxidative self-polymerization of polydopamine through an alkaline condition to form a polydopamine precipitate with pH-responsive characteristics, centrifuge and dry the polydopamine precipitate at 9500 rmp for 13 min to obtain polydopamine powder, denoted as E3; Take 9 g of polydopamine powder in E3 and dissolve it in 26 g of polycaprolactone in 180 ml of ethanol. Under greenhouse conditions, control the peristaltic pump through a microfluidic chip at a flow rate of 0.55 mL / min to self-assemble on the surface of the core, forming core microspheres with an inner layer film of 4.5 μm thick inner layer coating; S7. Mix 26 g of cage-like polyhedral oligomeric silsesquioxane and 45 g of polyvinyl alcohol. After mixing, add a furan-maleimide crosslinking agent with a concentration of 1.0 mol / cm³ and heat at 65 °C for 12 min to obtain microcapsules with a middle layer film of 7 μm thick middle layer coating; S8. Immerse 20 g of silica in a 11% mass concentration of cetyltrimethoxysilane solution and carry out a hydrophobic reaction for 6.5 h to obtain hydrophobic silica. Dissolve the hydrophobic silica in 60 ml of polylactic acid solution to obtain a solution. Spray the solution by electrostatic spraying with a voltage of 21 kv to form microcapsules with a complete coating of three-layer capsule walls and an outer layer film thickness of 3.5 μm; S9. Transfer the microcapsules with a complete coating of three-layer capsule walls and an outer layer film thickness of 3.5 μm to a curing chamber at a temperature of 27 °C and a humidity of 35% and let them stand for 13 h to obtain microcapsules with stable structures, denoted as F3; S10. Dry the microcapsules with stable structures in F3 at a temperature of -55 °C for 26 h to obtain slow-release rust inhibitor microcapsules with a capsule wall thickness of 15 μm, denoted as G3.

[0018] Example 4 This example provides a preparation method of slow-release rust inhibitor microcapsules applied to reinforced concrete for preparing the above-mentioned slow-release rust inhibitor microcapsules, including the following steps: S1. Take 40 g of potassium nitrite and 60 g of magnesium phosphate according to a mass ratio of 1:2, stir and mix them with a mixer at a speed of 600 rmp for 25 min to obtain a composite rust inhibitor. Mix the composite rust inhibitor, 25 g of nano-hydrotalcite, and 15 g of polyethylene glycol-600, and stir and mix them at a speed of 600 rmp for 25 min to obtain a composite rust inhibitor powder, denoted as A4; S2. Mix 25 g of 2-hydroxyethyl methacrylate with 100 g of acrylate-modified tung oil, stir and mix them with a mixer at 180 °C at a speed of 600 rmp for 25 min to obtain a mixture. Mix the mixture with 50 g of Bacillus pasteurii spores, and at an inlet temperature of 100 °C and an outlet temperature of 60 °C in spray drying, obtain self-healing microspheres with a microsphere diameter of 10 μm, denoted as B3; S3. Immerse 25 g of nano-hydrotalcite in an ethanol solution of a 5% mass concentration of silane coupling agent, react at 70 °C for 5 h to obtain a reaction solution, centrifuge the reaction solution at a centrifuge speed of 10000 rmp for 15 min, and obtain amino-modified nano-hydrotalcite after drying, denoted as C4; S4. Take 100 g of the composite rust inhibitor powder in A4, 30 g of the self-healing microspheres in B4, 25 g of the amino-modified nano-hydrotalcite in C3, 15 g of polyethylene glycol-600, 60 ml of deionized water, and polyvinylpyrrolidone with a mass concentration of 0.7%, mix them, stir with a stirrer at a speed of 600 rmp for 20 min to obtain a stirred product, and treat the stirred product with a 50 kHz ultrasonic machine for 30 min to obtain a homogeneous core slurry, denoted as D4; S5. Pump the homogeneous core slurry in D4 to the inlet of the microcontroller chip through a peristaltic pump at a rate of 0.6 mL / min; S6. Dissolve dopamine hydrochloride in Tris buffer with a pH of 9, trigger the oxidative self-polymerization of polydopamine through an alkaline condition to form a polydopamine precipitate with pH-responsive characteristics, centrifuge and dry the polydopamine precipitate at 10000 rmp for 15 min to obtain polydopamine powder, denoted as E4; Take 10 g of the polydopamine powder in E4 and 30 g of polycaprolactone, dissolve them in 200 ml of ethanol, and self-assemble on the surface of the core through a peristaltic pump controlled by a microfluidic chip at a flow rate of 0.6 mL / min under greenhouse conditions to form core microspheres with an inner layer film of 5 μm; S7. Mix 30 g of cage-like polyhedral oligomeric silsesquioxane and 50 g of polyvinyl alcohol, add a furan-maleimide cross-linking agent of 1.2 mol / cm³ after mixing, and heat at 70 °C for 15 min to obtain microcapsules with a middle layer film of 8 μm; S8. Immerse 20 g of silica in a 12% mass concentration of cetyltrimethoxysilane solution for a 7 h hydrophobic reaction to obtain hydrophobic silica, dissolve the hydrophobic silica in 75 ml of a polylactic acid solution to obtain a solution, and form microcapsules with a complete outer layer film thickness of 4 μm by electrostatic spraying the solution with a voltage of 22 kv; S9. Transfer the microcapsules with a complete outer layer film thickness of 4 μm to a curing chamber at a temperature of 30 °C and a humidity of 40% and let them stand for 14 h to obtain structurally stable microcapsules, denoted as F4; S10. Dry the structurally stable microcapsules in F4 at a temperature of -60 °C for 28 h to obtain slow-release rust inhibitor microcapsules with a wall thickness of 17 μm, denoted as G4.

[0019] Comparative Example 1 The difference from Example 1 is that in step S1, no composite rust inhibitor is used, and only sodium nitrite is used as the rust inhibitor, and other steps remain unchanged.

[0020] Comparative Example 2 The difference from Example 1 is that in step S1, no self-healing microspheres are added, and other steps remain unchanged.

[0021] Comparative Example 3 The difference from Example 1 is that tung oil is directly used as the self-healing microspheres in step S1, and the other steps remain unchanged.

[0022] Comparative Example 4 The difference from Example 1 is that nano-hydrotalcite is not added in step S1, and the other steps remain unchanged.

[0023] Comparative Example 5 The difference from Example 1 is that 2-hydroxyethyl methacrylate is not added in step S2, and the other steps remain unchanged.

[0024] Comparative Example 6 The difference from Example 1 is that the reaction is directly stirred at a rate of 500 r / min throughout step S3, that is, the processes of high-speed shearing and low-speed stirring are not experienced, and the other steps remain unchanged.

[0025] In order to verify the effectiveness of the present invention, a rust inhibition performance test was carried out: The HRB400 steel bar specimens (5.0 cm × 2.5 cm × 0.2 cm) were successively cleaned with ultrapure water, acetone, and ethanol, dried with nitrogen, and dried for standby. The HRB400 steel bar specimens were placed in the concrete simulated pore solution without (reference) and with the microcapsule-type rust inhibitor at a temperature of 25 °C and a humidity of 77% for 7 days, and then circulated, soaked for 30 min and dried for 60 min, and this was taken as one cycle. After 50 cycles, the corrosion area was statistically processed. The concrete simulated pore solution used was a 3.5% NaCl saturated calcium hydroxide solution.

[0026] The percentage of the steel bar rust area is represented by A, and the ratio of the rust area percentage of the steel bar specimen with the rust inhibitor to the reference steel bar specimen is represented by R; then R = Aa / Aj × 100%. Among them, Aj and Aa are the rust area percentages of the reference (i.e., the blank group) and the steel bar with the rust inhibitor after 50 wet-dry cycles, respectively. The rust inhibition efficiency IE is obtained by the formula: IE = (100 - R).

[0027] Repair performance: The repair effect of the microcapsule-type rust inhibitor on the steel bars after release was monitored by electrochemical tests. The electrochemical workstation used was PARSTAT4000 from Princeton Applied Research, USA. The reference electrode was Ag / AgCl, the counter electrode was platinum, and the working electrode was the HRB400 steel bar electrode. The electrolyte was a 0.10 mol / L NaCl saturated calcium hydroxide solution of the microcapsule rust inhibitors in each example and comparative example. When performing linear polarization (LPR), the potential scanning range was set to -10 mV to 10 mV, the corrosion current density was recorded, and its variation law was observed. The passivation current density Icorr was less than 0.1 μA / cm², and the critical current density Icorr was greater than 0.1 μA / cm². The results are shown in Table 1 below.

[0028] Table 1:

[0029] From the performance test results in Table 1 above, it can be seen that the sustained-release rust-inhibiting microcapsules prepared in Examples 1-3 have good performance. Especially in Example 3, the comprehensive performance is better. In Comparative Examples 1-6, because the necessary technical solutions were not adopted, their performance in the corresponding performance tests was significantly worse than that of the examples. The above experimental results further prove the importance of the technical solutions defined in the present invention for its technical effects.

[0030] Please refer to Figure 1 , by adjusting the ratio of the wall material and the process parameters, the influence on the surface morphology of the microcapsules was studied, and the results are shown in Table 2 below.

[0031] Table 2:

[0032] As can be seen from Table 2 above, in Group a (Example 1): The cage-shaped POSS (3 parts) in the wall material synergistically acts with polycaprolactone (PCL, 8 parts) and polyvinyl alcohol (PV, 6 parts) to form a dense cross-linked network, and the surface is smooth and defect-free.

[0033] Group b (excessive PV): An excessive PV ratio (10 parts) results in too strong hydrophilicity of the wall material, and rapid shrinkage occurs during drying to form wrinkles (SEM, Figure 1 b in it), reducing the mechanical strength.

[0034] Group c (excessive PCL): An excessive polycaprolactone (PCL) ratio (12 parts) causes a significant increase in the viscosity of the material, and it cannot uniformly wrap the core under high-speed shear (1500 r / min), forming an oval structure (SEM, Figure 1 c in it), the surface is rough and the defect rate increases to 25%. The entanglement between PCL segments increases, hindering the uniform film formation of the wall material.

[0035] Group d (process imbalance): The ratio of PCL (12 parts) to polyvinyl alcohol (PV, 10 parts) was unbalanced, and high-speed stirring (1500 r / min) resulted in phase separation of the capsule wall material (SEM, Figure 1 (d) in the figure shows particle agglomeration. The mismatch between high viscosity and high shear force causes the collapse of the capsule wall structure, verifying the necessity of optimizing process parameters.

[0036] Group e (Example 3): Optimized ratio (PCL10:PV 8:POSS 4) and moderate stirring speed (1000r / min) to achieve uniform capsule wall coating (SEM, Figure 1 (e) The surface is smooth and dense. The addition of cage-type POSS enhances the cross-linking density, balances flexibility and rigidity, and the defect rate is <3%.

[0037] Group f (Comparative Example 5): No POSS was added, and only PCL / PV physical cross-linking was relied upon. The capsule wall strength was insufficient (nanoindentation modulus 1.2 GPa), and the rupture rate was as high as 52%.

[0038] See also Figure 2 By changing the composition of the capsule core, the effects on the functional performance were analyzed. The results are shown in Table 3 below.

[0039] Table 3:

[0040] As shown in Table 3 above, Group a (Example 3): The composite rust inhibitor (nitrite + phosphate) and nano-hydrotalcite (5 parts) synergistically inhibited Cl⁻ erosion (EDS showed that Cl⁻ was adsorbed between the hydrotalcite layers), and the modified tung oil was evenly distributed in the form of microdroplets, with a repair efficiency of 93%.

[0041] Group b (Comparative Example 1): Containing only sodium nitrite, lacking the cathodic protection effect of phosphate, the Cl⁻ adsorption rate decreased significantly (68.4%).

[0042] Group c (imbalanced ratio): The ratio of magnesium phosphate to potassium nitrite (2:1) was not optimal (1:3 in the example), resulting in uneven dispersion of the rust inhibitor (TEM, Figure 2 c shows local aggregation).

[0043] Group d (Comparative Example 3): Unmodified tung oil has strong hydrophobicity and poor compatibility with rust inhibitors, resulting in large particle agglomeration (TEM, Figure 2 d) in the repair function fails.

[0044] Group e (Comparative Example 4): No nano-hydrotalcite was added, the rust inhibitor was directly exposed to the capsule core, and the solvent leaked during evaporation (TEM, Figure 2 e shows the droplet breaking up).

[0045] Group f (control group): Commercially available calcium nitrite is used as the sole rust inhibitor, without self-healing materials or nano-hydrotalcite (TEM, Figure 2 where the f shown in it has a loose structure).

[0046] Please refer to Figure 3 to verify the response characteristics of the microcapsules under different environmental conditions, and the results are shown in Table 4 below.

[0047] Table 4:

[0048] As can be seen from Table 4 above, Group a (Example 3): In a concrete environment (pH = 12.5), the capsule wall rupture rate is 95%: POSS hydrolyzes to form nano-pores, combined with mechanical pressure to trigger efficient release, and the rust inhibition rate reaches 94.5%: The composite rust inhibitor (nitrite inhibits the anode, phosphate passivates the cathode) and nano-hydrotalcite (adsorbs Cl⁻) act synergistically, and the current density continuously decreases (82 → 71 nA / cm²): The self-healing material fills the cracks and blocks the Cl⁻ penetration path.

[0049] Group b (Comparative Example 1): The capsule core only contains sodium nitrite (20 parts), without phosphate and nano-hydrotalcite, and the rust inhibition rate drops to 83.4%: A single anodic inhibitor cannot comprehensively inhibit corrosion, and the cathode region is still eroded by Cl⁻, and the current density increases (105 → 97 nA / cm²): Lack of Cl⁻ solidification ability, and the steel bars continue to corrode.

[0050] Group c (Comparative Example 2): The capsule core does not contain acrylate-modified tung oil, and the rust inhibition rate is only 80.1%: Micro-cracks cannot be repaired, and Cl⁻ quickly penetrates to the surface of the steel bars through the cracks, and the current density surges (181 → 174 nA / cm²), and the corrosion current continuously increases with the expansion of the cracks.

[0051] Group d (Comparative Example 3): The capsule core contains unmodified tung oil (20 parts) and no acrylate, and the rust inhibition rate is 82.4%. The hydrophobicity of tung oil causes droplet aggregation (TEM shows particles > 10 μm), which cannot penetrate into micro-cracks, and the current density decreases limitedly (175 → 168 nA / cm²), and the repair effect is weak, and Cl⁻ can still invade along the unfilled cracks.

[0052] Group e (Comparative Example 4): The capsule core does not contain nano-hydrotalcite, and the rust inhibition rate is 84.5%: The rust inhibitor is effective in the short term, but lacks Cl⁻ adsorption ability, and the long-term protection is insufficient, and the current density rebounds (107 → 98 nA / cm²), and free Cl⁻ continuously accumulates, causing secondary corrosion.

[0053] Group f (Comparative Example 5): The capsule wall does not contain cage-shaped POSS, only contains polycaprolactone (6 parts) and polyvinyl alcohol (8 parts), and the capsule wall rupture rate is 65%: Lack of POSS crosslinking network (no Si-O-Si peak in XRD), the capsule wall is loose and porous (SEM shows surface cracks), and the rust inhibition rate is 85.7%: The rust inhibitor leaks in advance, the sustained release function fails, and the protection period is shortened.

[0054] The above are the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A slow-release rust inhibitor microcapsule applied to reinforced concrete, characterized in that, It includes a core and a wall. The core includes a composite rust inhibitor, self-healing microspheres, nano-hydrotalcite, and an antifreeze agent. The wall includes a three-layer structure of an inner layer film, a middle layer film, and an outer layer film. Among them, the inner layer film is composed of a composite of polydopamine and polycaprolactone. Among them, polydopamine forms polydopamine with pH-responsive characteristics under alkaline conditions. The middle layer film is composed of a dynamically crosslinked cage-type polyhedral oligomeric silsesquioxane-polyvinyl alcohol network. The outer layer film is composed of silica hydrophobically modified with hexadecyltrimethoxysilane and polylactic acid.

2. The slow-release rust-inhibiting microcapsule applied to reinforced concrete according to claim 1, wherein The mass ratio of the core to the wall is 1:0.3 - 0.5, and the total thickness of the wall is 10 - 17 μm. The composite rust inhibitor is composed of nitrite and phosphate with a mass ratio of 1:2 - 4. The nitrite is sodium nitrite or potassium nitrite. The phosphate is calcium phosphate or magnesium phosphate.

3. A slow-release rust inhibitor microcapsule applied to reinforced concrete according to claim 2, characterized in that, The self-healing microspheres are composed of 2-hydroxyethyl methacrylate, acrylate-modified tung oil, and spores of Bacillus pasteurii. The surface of the nano-hydrotalcite is modified with an amino group through a silane coupling agent. The antifreeze agent is polyethylene glycol-600.

4. A slow-release rust inhibitor microcapsule applied to reinforced concrete according to claim 3, characterized in that, The dynamically crosslinked cage-type polyhedral oligomeric silsesquioxane-polyvinyl alcohol network contains dynamic Diels-Alder covalent bonds. The crosslinking agent is furan-maleimide biopolymer, and the crosslinking density is 0.5 - 1.2 mol / cm³.

5. A preparation method of a slow-release rust inhibitor microcapsule applied to reinforced concrete, characterized in that, For preparing the sustained-release rust-inhibiting microcapsules for reinforced concrete as described in any one of claims 1 to 4 above, the method includes the following steps: S1. Mix and stir nitrite and phosphate to obtain a composite rust inhibitor. Mix and stir the composite rust inhibitor, nano-hydrotalcite, and polyethylene glycol-600 to obtain a composite rust inhibitor powder. S2. Mix and stir 2-hydroxyethyl methacrylate and acrylate-modified tung oil to obtain a mixture. Mix the mixture with spores of Bacillus pasteurii and perform spray drying to obtain self-healing microspheres. S3. Place nano-hydrotalcite in an ethanol solution of a silane coupling agent for reaction to obtain a reaction solution. Centrifuge and dry the reaction solution to obtain amino-modified nano-hydrotalcite. S4. Mix and stir the composite rust inhibitor powder, self-healing microspheres, amino-modified nano-hydrotalcite, polyethylene glycol-600, deionized water, and polyvinylpyrrolidone to obtain a stirred mixture. Ultrasonically treat the stirred mixture to obtain a homogeneous core slurry. S5. Transport the homogeneous core slurry to the inlet of the microfluidic chip through a peristaltic pump. S6. Dissolve dopamine hydrochloride in Tris buffer. Trigger the oxidative self-polymerization of polydopamine through alkaline conditions to form a polydopamine precipitate with pH-responsive characteristics. Centrifuge and dry the polydopamine precipitate to obtain polydopamine powder. Dissolve the polydopamine powder and polycaprolactone in ethanol to obtain a solution. Inject the solution into the homogeneous core slurry through the microfluidic chip for contact, and form an inner layer film through interfacial self-assembly to obtain core microspheres coated with the inner layer. S7. Mix the cage-shaped polyhedral oligomeric silsesquioxane and polyvinyl alcohol. After mixing, add the furan-maleimide crosslinking agent to obtain the middle layer material emulsion. Inject the middle layer material emulsion through the microfluidic middle channel onto the homogeneous core slurry for coating and heating to trigger the dynamic crosslinking of Diels-Alder bonds to form the middle layer film, and obtain the microcapsules with a middle layer coating. S8. Immerse silica in a cetyltrimethoxysilane solution for reaction to obtain hydrophobic silica. Place the hydrophobic silica in a polylactic acid solution for dissolution to obtain a solution. Form the outer layer film by electrostatic spraying of the solution to obtain the microcapsules with a completely coated three-layer capsule wall. S9. Transfer the microcapsules with a completely coated three-layer capsule wall to a curing chamber and let them stand to obtain the microcapsules with a stable structure. S10. Perform freeze-drying treatment on the microcapsules with a stable structure to obtain the sustained-release rust inhibitor microcapsules.

6. The preparation method of a sustained-release rust-inhibiting microcapsule applied to reinforced concrete according to claim 5, characterized in that, During the preparation process of the composite rust inhibitor powder in step S1, the mass of nitrite is 15 - 40 g, the mass of phosphate is 30 - 60 g, the mass of nano-hydrotalcite is 10 - 25 g, the mass of polyethylene glycol-600 is 5 - 15 g, the rotation speed of the stirrer is 400 - 600 rmp, and the stirring time is 15 - 25 min. During the process of obtaining the self-healing microspheres in step S2, the mass of 2-hydroxyethyl methacrylate is 10 - 25 g, the mass of acrylate-modified tung oil is 50 - 100 g, the mixing temperature is 160 - 180 °C, the mass of Bacillus pasteurii spores is 25 - 50 g, the inlet temperature of spray drying is 80 - 100 °C, the outlet temperature is 50 - 60 °C, and the particle size of the microspheres is 5 - 10 μm.

7. The preparation method of a sustained-release rust inhibitor microcapsule applied to reinforced concrete according to claim 6, characterized in that, During the process of obtaining the amino-modified nano-hydrotalcite in step S3, the mass concentration of the ethanol solution of the silane coupling agent is 3 - 5%, the reaction temperature is 60 - 70 °C, the reaction time is 3 - 5 h, the rotation speed of the centrifuge is 8000 - 10000 rmp, and the centrifugation time is 10 - 15 min. During the process of obtaining the homogeneous core slurry in step S4, the mass of the composite rust inhibitor powder is 50 - 100 g, the mass of the self-healing microspheres is 15 - 30 g, the mass of the amino-modified nano-hydrotalcite is 10 - 25 g, the mass of polyethylene glycol-600 is 5 - 15 g, the volume of deionized water is 40 - 60 ml, the mass concentration of polyvinylpyrrolidone is 0.3 - 0.7%, the rotation speed of the stirrer is 400 - 600 rmp, the stirring time is 10 - 20 min, the frequency of the ultrasonic machine is 40 - 50 kHz, and the ultrasonic time is 20 - 30 min.

8. The preparation method of a slow-release rust inhibitor microcapsule applied to reinforced concrete according to claim 7, characterized in that, In step S5, the flow rate of the peristaltic pump is 0.4 - 0.6 mL / min; in the process of obtaining the core microspheres with an inner layer coating in step S6, the pH value of the Tris buffer solution is 8.5 - 9.0, the polymerization time is 10 - 14 h, the centrifugation speed for the polydopamine precipitate is 8000 - 10000 rmp, the centrifugation time is 10 - 15 min, the drying time is 2 - 4 h, the mass of the polydopamine powder is 5 - 10 g, the mass of the polycaprolactone is 15 - 30 g, the volume of ethanol is 100 - 200 ml, the flow rate controlled by the microfluidic chip is 0.4 - 0.6 mL / min, the interfacial self-assembly condition is at room temperature, and the thickness of the inner layer membrane of the core microspheres with an inner layer coating is 3 - 5 μm; In the process of obtaining the microcapsules with a middle layer coating in step S7, the mass of the cage-like polyhedral oligomeric silsesquioxane is 15 - 30 g, the mass of the polyvinyl alcohol is 30 - 50 g, the molar ratio of the furan-maleimide cross-linking agent is 0.5 - 1.2 mol / cm³, the heating temperature is 60 - 70 °C, the heating time is 5 - 15 min, and the thickness of the middle layer membrane of the microcapsules with a middle layer coating is 5 - 8 μm.

9. The preparation method of a slow-release rust-inhibiting microcapsule applied to reinforced concrete according to claim 8, wherein, In the process of obtaining the microcapsules with a completely coated three-layer wall in step S8, the mass of the silica is 10 - 25 g, the concentration of the cetyltrimethoxysilane solution is 8 - 12%, the hydrophobic reaction temperature is 70 - 80 °C, the hydrophobic reaction time is 5 - 7 h, the volume of the polylactic acid solution is 30 - 75 ml, the electrostatic spraying voltage is 18 - 22 kV, and the microcapsules with a completely coated three-layer wall with an outer layer membrane thickness of 2 - 4 μm are obtained; In the process of obtaining the microcapsules with a stable structure in step S9, the curing temperature in the curing chamber is 20 - 30 °C, the humidity in the curing chamber is 20 - 40%, and the standing time is 10 - 14 h; in the process of obtaining the sustained-release rust inhibitor microcapsules in step S10, the freeze-drying temperature is -40 to -60 °C, the freeze-drying time is 20 - 28 h, and the sustained-release rust inhibitor microcapsules with a wall thickness of 10 - 17 μm are obtained.

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