Response release type microcapsule for cement-based material impermeability and preparation method thereof

Abstract

The invention discloses a response release type microcapsule for cement-based material impermeability and a preparation method of the response release type microcapsule, and belongs to the technical field of civil engineering materials. The response release type microcapsule comprises a capsule core and a capsule wall, the capsule core comprises the following components: a hydrophobic organic phase change material, an emulsifier and water; the capsule wall comprises the following components: a macromolecular prepolymer, a response material and water. The core material is subjected to microencapsulation packaging, an external response mechanism is introduced, and controllable release of the core material is realized while adverse effects of the core material on hydration and mechanical properties of the cement-based material are reduced, so that the anti-permeability performance of the cement-based material is directionally improved, optimization of a pore structure of the cement-based material and collaborative improvement of the anti-permeability performance are realized, and the anti-permeability performance of the cement-based material is improved. The problems that an existing method for improving the impermeability of the cement-based material interferes with the normal hydration process of cement, adverse effects are generated on mechanical properties, and applicability is poor are solved.

Description

Technical Field

[0001] This invention relates to the field of civil engineering materials technology, specifically to a responsive release microcapsule for impermeability of cement-based materials and its preparation method. Background Technology

[0002] High-altitude regions, influenced by their unique geographical environment, typically exhibit climatic characteristics such as low air pressure and low humidity. Under these conditions, the evaporation rate of moisture within cement-based materials is significantly accelerated, and the cement hydration reaction is easily inhibited. This leads to the formation of interconnected pores and microcracks within the material, reducing its overall density and impermeability. Simultaneously, the deteriorated pore structure provides favorable conditions for the migration of corrosive media such as chloride ions, increasing the risk of steel reinforcement corrosion and adversely affecting the long-term service performance of engineering structures. Therefore, improving the impermeability of cement-based materials in the low-pressure, low-humidity environment of high-altitude regions has become an important research direction for ensuring the durability and safety of engineering structures.

[0003] Existing research often focuses on improving the impermeability of cementitious materials by reducing their porosity or introducing hydrophobic components. For example, Chinese patent application CN110156405B proposes a method for improving the impermeability of high-altitude concrete by adding paraffin emulsion. However, the direct introduction of hydrophobic materials in this type of method interferes with the normal hydration process of cement to some extent, thus adversely affecting the mechanical properties of cementitious materials. Its applicability still needs further optimization. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a responsive release microcapsule for cement-based materials to improve impermeability and its preparation method. By microencapsulating the core material and introducing an external response mechanism, the core material's adverse effects on the hydration and mechanical properties of cement-based materials are reduced, while the core material is released in a controlled manner. This results in a targeted improvement in the impermeability of cement-based materials, thus solving the problems of existing methods for improving the impermeability of cement-based materials interfering with the normal hydration process of cement, adversely affecting mechanical properties, and having poor applicability.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a responsive release microcapsule for waterproofing cement-based materials, comprising a core and a wall. The core comprises the following components: a hydrophobic organic phase change material, an emulsifier, and water; The capsule wall comprises the following components: a polymeric prepolymer, a responsive material, and water.

[0006] The beneficial effects of this invention are as follows: By introducing a responsive material with microwave absorption characteristics into the raw materials for preparing the capsule wall, a composite wall material system with both structural and external field response functions is constructed. The responsive material is distributed continuously or semi-continuously on the surface of the wall material during the polymerization of the polymer prepolymer, ensuring the structural stability of the microcapsules under conventional curing conditions. Under external microwave radiation, the responsive material in the wall material selectively absorbs microwave energy and converts it into heat energy, forming a localized temperature rise region. Due to the difference in thermophysical properties between the wall material matrix and the responsive material, the localized temperature rise induces thermal stress concentration within the wall material, leading to localized softening or the formation of micro-fracture channels, while the overall structure of the microcapsule remains stable. Under the synergistic effect of localized instability and thermal action, the hydrophobic organic phase change material in the microcapsule core is heated above its phase change temperature and liquefied, released outward through the microchannels formed by the wall material. After release, the phase change material flows and spreads within the interconnected pores and microcracks of the cementitious material, and then solidifies upon cooling, forming a continuous and dense hydrophobic sealing structure, thereby blocking the migration channels of corrosive media such as moisture and chloride ions. Furthermore, the overall temperature rise generated during microwave radiation helps promote the cement hydration reaction, achieving optimized pore structure and synergistic improvement in impermeability of the cementitious material without affecting early hydration and mechanical properties.

[0007] Furthermore, the core comprises the following components by weight: 5-15 parts of hydrophobic organic phase change material, 0.5-1.5 parts of emulsifier, and 85-95 parts of deionized water; The capsule wall comprises the following components by weight: 2-15 parts of polymer prepolymer, 1-5 parts of responsive material, and 4-30 parts of deionized water.

[0008] Furthermore, hydrophobic organic phase change materials include eicosane and / or lauric acid.

[0009] Furthermore, the emulsifier is a compound emulsification system composed of anionic and nonionic emulsifiers. The anionic emulsifier includes at least one of phosphate ester surfactants and fatty alcohol polyoxyethylene sulfate; the nonionic emulsifier includes at least one of polyether-modified silicone and fatty alcohol polyoxyethylene ether.

[0010] Furthermore, the polymeric prepolymer includes a mixture of etherified melamine-formaldehyde resin and polyvinyl alcohol.

[0011] Furthermore, the responsive materials include nano-silicon carbide and / or nano-carbon black.

[0012] Furthermore, the mass ratio of the hydrophobic organic phase change material in the core to the polymer prepolymer in the core wall is 4:1 to 1:1.

[0013] A second aspect of the present invention provides a method for preparing the above-mentioned responsive release microcapsules for waterproofing cement-based materials, comprising the following steps: S1. After melting the hydrophobic organic phase change material, it is mixed with an emulsifier and deionized water and sheared to emulsify, thus obtaining an emulsified core material solution. S2. Mix and stir the polymer prepolymer, responsive material and deionized water to obtain a wall material solution; S3. First, add the wall material solution obtained in S2 dropwise to the emulsified core material solution obtained in S1. Then, adjust the pH to promote the polymerization reaction. Next, adjust the pH again to terminate the reaction. Finally, wash, filter and dry to obtain responsive release microcapsules.

[0014] The beneficial effects of this invention are: the preparation method of this invention is simple, the conditions are mild, the efficiency is high, it is suitable for large-scale and industrial production, and it has broad application prospects and practical value.

[0015] Furthermore, the melting temperature in S1 is 60-65℃; the shearing speed is 1000-2000 rpm, and the time is 20-30 min.

[0016] Furthermore, the mixing speed in S2 is 500-600 rpm, and the time is 20-30 min.

[0017] Furthermore, the dripping time in S3 is 30-35 minutes, and the dripping process is carried out with stirring at a speed of 400-500 rpm.

[0018] Furthermore, in S3, the pH is adjusted to 3-4 using an acidic regulator; The polymerization reaction is carried out at a temperature of 65-80℃ for 90-120 minutes. The pH was then adjusted again to 7-8 using an alkaline adjuster.

[0019] Furthermore, the stirring speed during the polymerization reaction is 400-600 rpm.

[0020] Furthermore, the acid regulator includes at least one of citric acid monohydrate, acetic acid, and hydrochloric acid.

[0021] Furthermore, the alkalinity regulator includes NaOH solution.

[0022] Furthermore, the mass concentration of the NaOH solution is 10 wt.%.

[0023] A third aspect of the present invention provides the application of the above-mentioned responsive release microcapsules for impermeability of cement-based materials in the optimization of pore structure and improvement of impermeability of cement-based materials.

[0024] A fourth aspect of the present invention provides a method for optimizing the pore structure and improving the impermeability of a cement-based material, comprising the following steps: incorporating the above-mentioned cement-based impermeable responsive release microcapsules into the cement-based material for curing, and then subjecting it to microwave irradiation to complete the optimization of the pore structure and improvement of the impermeability of the cement-based material.

[0025] The beneficial effects of this invention are as follows: By incorporating responsive release microcapsules into cement-based materials and subjecting them to microwave radiation, this invention can achieve synergistic improvement in the pore structure and impermeability of cement-based materials, avoiding the adverse effects of hydrophobic organic phase change materials on the cement hydration reaction and mechanical properties during the mixing and curing stages. This results in greater controllability, practicality, and applicability.

[0026] Furthermore, the microwave radiation has a power of 500-1000W, a frequency of 2-3 GHz, and a duration of 60-90 s.

[0027] Preferably, the microwave radiation has a power of 700 W, a frequency of 2.45 GHz, and a duration of 60-90 s.

[0028] The present invention has the following beneficial effects: 1. This invention effectively avoids the adverse effects of hydrophobic organic phase change materials on cement hydration reaction and mechanical properties during mixing and curing by microencapsulating them, thereby improving the compatibility of cement-based material systems.

[0029] 2. This invention introduces a responsive material with microwave absorption properties into the microcapsule wall material, causing the microcapsules to become locally unstable under external microwave excitation and realize the directional release of the core material, thereby improving the pore structure and enhancing the impermeability of cement-based materials as needed during their service life.

[0030] 3. This invention achieves controllable enhancement of the impermeability of cement-based materials through a synergistic method of external field response triggering, core material release, and pore sealing, making it suitable for adverse service environments such as high altitudes and low air pressure. Attached Figure Description

[0031] Figure 1 The images show the external morphology and microstructure of the responsive release microcapsules prepared in Example 1. Figure 2 The figures show the contact angle characterization of Comparative Examples 1-3 and Example 1 in the test examples, where (a) is Comparative Example 1, (b) is Comparative Example 2, (c) is Comparative Example 3, and (d) is Example 1. Detailed Implementation

[0032] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0033] Example 1: A responsive release microcapsule for impermeability of cement-based materials, comprising a core and a wall; The core comprises the following components by weight: 8 parts eicosane, 1 part emulsifier (a mixture of dodecyl phosphate, a phosphate ester surfactant, and polyether-modified silicone BYK-348 in a mass ratio of 4:3), and 91 parts deionized water; The capsule wall comprises the following components by weight: 8 parts of a mixture of etherified melamine-formaldehyde resin (Hunan Xuetian Fine Chemical Co., Ltd.) and polyvinyl alcohol (Shanghai Maclean Biochemical Technology Co., Ltd.) (etherified melamine-formaldehyde resin and polyvinyl alcohol are mixed at a mass ratio of 97:3), 3 parts of nano-silicon carbide, and 16 parts of deionized water. In this embodiment, the mass ratio of the hydrophobic organic phase change material in the core to the polymer prepolymer in the shell is 2:1.

[0034] The preparation method of the above-mentioned responsive release microcapsules for impermeability of cement-based materials includes the following steps: S1. Eicosane is heated and melted in a 60°C water bath. Then, the melted eicosane, emulsifier and deionized water are mixed and sheared at 1500 rpm for 25 min to obtain an emulsified core material solution. S2. Mix the mixture of etherified melamine formaldehyde resin and polyvinyl alcohol, nano-silicon carbide and deionized water in a magnetic stirrer at 550 rpm for 25 min to obtain a wall material solution. S3. Slowly add the wall material solution obtained in S2 to the emulsified core material solution obtained in S1, control the adding time to 32 min, and stir thoroughly in a magnetic stirrer at a speed of 450 rpm. S4. After the addition is complete, first raise the reaction temperature to 70℃, and adjust the pH to 3.5 with hydrochloric acid. Adjust the magnetic stirring speed to 300 rpm and react for 105 min. Then add 10 wt.% sodium hydroxide solution to adjust the pH to 7.5, terminate the reaction, cool to room temperature, filter, wash, and finally dry in a 50℃ oven to constant weight to obtain responsive release microcapsules for cement-based materials' impermeability (the appearance and microstructure of the microcapsules are shown in the figure). Figure 1 (As shown).

[0035] A method for preparing cement-based materials based on responsive release microcapsules for impermeability control includes the following steps: (1) Weigh an appropriate amount of silicate cement and water according to a water-cement ratio of 0.4, and 3% of the mass of silicate cement as responsive release microcapsules; (2) After thoroughly mixing the responsive release microcapsules and water, add silicate cement, stir, mold, and cure; (3) After curing for 3 days, the composite cement-based material was microwave irradiated for 60 seconds using a microwave transmitter (power: 700 W, frequency: 2.45 GHz) and then cured for 28 days to obtain a cement-based material test block with impermeability.

[0036] Example 2: A responsive release microcapsule for impermeability of cement-based materials, comprising a core and a wall; The core comprises the following components by weight: 6 parts eicosane, 0.7 parts emulsifier (a mixture of dodecyl phosphate surfactant and polyether-modified silicone BYK-348 in a 1:1 mass ratio) and 93.3 parts deionized water; The capsule wall comprises the following components by weight: 4 parts of a mixture of etherified melamine-formaldehyde resin and polyvinyl alcohol (the etherified melamine-formaldehyde resin and polyvinyl alcohol are mixed at a mass ratio of 99:1), 2 parts of nano-silicon carbide, and 8 parts of deionized water. In this embodiment, the mass ratio of the hydrophobic organic phase change material in the core to the polymer prepolymer in the shell is 4:1.

[0037] The preparation method of the above-mentioned responsive release microcapsules for impermeability of cement-based materials includes the following steps: The preparation method of the responsive release microcapsules for impermeability of cement-based materials in this embodiment is the same as in Example 1.

[0038] A method for preparing cement-based materials based on responsive release microcapsules for impermeability control includes the following steps: The method for preparing cement-based materials in this embodiment is the same as in Embodiment 1, except that the amount of responsive release microcapsules incorporated is 5 wt.% relative to the mass of silicate cement.

[0039] Example 3: A responsive release microcapsule for impermeability of cement-based materials, comprising a core and a wall; The core comprises the following components by weight: 9 parts eicosane, 1.1 parts emulsifier (a mixture of dodecyl phosphate surfactant and polyether-modified silicone BYK-348 in a mass ratio of 3:2), and 89.9 parts deionized water; The capsule wall comprises the following components by weight: 6 parts of a mixture of etherified melamine formaldehyde resin and polyvinyl alcohol (the etherified melamine formaldehyde resin and polyvinyl alcohol are mixed at a mass ratio of 95:5), 4 parts of nano-silicon carbide, and 12 parts of deionized water. In this embodiment, the mass ratio of the hydrophobic organic phase change material in the core to the polymer prepolymer in the shell is 4:3.

[0040] The preparation method of the above-mentioned responsive release microcapsules for impermeability of cement-based materials includes the following steps: The preparation method of the responsive release microcapsules for impermeability of cement-based materials in this embodiment is the same as in Example 1.

[0041] A method for preparing cement-based materials based on responsive release microcapsules for impermeability control includes the following steps: The method for preparing cement-based materials in this embodiment is the same as in Embodiment 1, except that the amount of responsive release microcapsules incorporated is 4 wt.% relative to the mass of silicate cement.

[0042] Example 4: A responsive release microcapsule for impermeability of cement-based materials, comprising a core and a wall; The core comprises the following components by weight: 12 parts eicosane, 1.5 parts emulsifier (a mixture of dodecyl phosphate surfactant and polyether-modified silicone BYK-348 in a mass ratio of 2:1), and 86.5 parts deionized water; The capsule wall comprises the following components by weight: 6 parts of a mixture of etherified melamine formaldehyde resin and polyvinyl alcohol (the etherified melamine formaldehyde resin and polyvinyl alcohol are mixed at a mass ratio of 93:7), 5 parts of nano-silicon carbide, and 12 parts of deionized water. In this embodiment, the mass ratio of the hydrophobic organic phase change material in the core to the polymer prepolymer in the shell is 1:1.

[0043] The preparation method of the above-mentioned responsive release microcapsules for impermeability of cement-based materials includes the following steps: The preparation method of the responsive release microcapsules for impermeability of cement-based materials in this embodiment is the same as in Example 1.

[0044] A method for preparing cement-based materials based on responsive release microcapsules for impermeability control includes the following steps: The method for preparing cement-based materials in this embodiment is the same as in Embodiment 1, except that the amount of responsive release microcapsules incorporated is 1 wt.% relative to the mass of silicate cement.

[0045] Comparative Example 1: A method for preparing cement-based materials includes the following steps: In this comparative example, the preparation of the cement-based material does not incorporate responsive release microcapsules, and the remaining steps are the same as in Example 1.

[0046] Comparative Example 2: A method for preparing cement-based materials, wherein the comparative example does not involve the preparation of responsive release microcapsules, but instead directly applies the raw material of the capsule core to the preparation of cement-based materials, specifically including the following steps: (1) Eicosane was heated and melted in a water bath at 60°C. Then, the melted eicosane, emulsifier and deionized water were mixed and sheared at 1500 rpm for 25 min to obtain an emulsified core material solution. (2) Weigh an appropriate amount of silicate cement and water according to a water-cement ratio of 0.127, and an emulsified core material solution of 30% relative to the mass of silicate cement; (3) After thoroughly mixing the emulsified core material solution and water, add silicate cement, stir, mold, and cure; (3) After curing for 3 days, the composite cement-based material was microwave irradiated for 70 seconds using a microwave transmitter (power: 700 W, frequency: 2.45 GHz) and then cured for 28 days to obtain cement-based material test blocks.

[0047] Comparative Example 3: A microcapsule for waterproofing cement-based materials includes a core and a wall. The core comprises the following components by weight: 8 parts eicosane, 1 part emulsifier (a mixture of dodecyl phosphate, a phosphate ester surfactant, and polyether-modified silicone BYK-348 in a mass ratio of 4:3), and 91 parts deionized water; The capsule wall comprises the following components by weight: 8 parts of a mixture of etherified melamine-formaldehyde resin and polyvinyl alcohol (same as in Example 1) and 16 parts of deionized water; In this embodiment, the mass ratio of the hydrophobic organic phase change material in the core to the polymer prepolymer in the shell is 2:1.

[0048] The preparation method of the above-mentioned responsive release microcapsules for impermeability of cement-based materials includes the following steps: The preparation method of the responsive release microcapsules for cement-based materials in this embodiment is the same as that in Example 1, except that the wall material solution does not contain the responsive material nano-silicon carbide.

[0049] A method for preparing cement-based materials based on responsive release microcapsules for impermeability control includes the following steps: The method for preparing cement-based materials in this embodiment is the same as in Embodiment 1, except that the amount of responsive release microcapsules incorporated is 3 wt.% relative to the mass of silicate cement.

[0050] Experimental example: The cement-based materials prepared in Examples 1-4 and Comparative Examples 1-3 were tested according to GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete" and GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The impermeability of the cement-based materials was evaluated by water absorption rate and contact angle, and their 28-day strength was tested.

[0051] The experimental results are shown in Table 1 and Figure 2 As shown.

[0052] Table 1 Performance Characterization

[0053] The results show that the cement-based materials prepared in Examples 1-4 of this invention simultaneously possess high compressive strength, low water absorption, and high contact angle. Compared with ordinary cement-based material systems (Comparative Example 1), the water absorption is reduced by 60%-80%. Furthermore, this invention avoids the significant reduction in compressive strength that occurs when hydrophobic organic phase change materials are directly applied to cement-based material preparation, as seen in Comparative Example 2. A comparison with Comparative Example 3 reveals that this invention, by adding responsive materials, achieves the liquefaction and release of hydrophobic organic phase change materials through microwave radiation without destabilizing the microcapsule structure. This optimizes the pore structure of the cement-based material and synergistically improves its impermeability. Compared to Comparative Example 3, the cement-based materials in Examples 1-4 of this invention exhibit significantly reduced water absorption and a significantly increased contact angle.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A responsive release microcapsule for waterproofing cement-based materials, characterized in that, Including the core and the wall; The core comprises the following components: a hydrophobic organic phase change material, an emulsifier, and water; The capsule wall comprises the following components: a polymeric prepolymer, a responsive material, and water.

2. The responsive release microcapsule for waterproofing cement-based materials according to claim 1, characterized in that, The core comprises the following components by weight: 5-15 parts of hydrophobic organic phase change material, 0.5-1.5 parts of emulsifier, and 85-95 parts of deionized water; The capsule wall comprises the following components by weight: 2-15 parts of polymer prepolymer, 1-5 parts of responsive material, and 4-30 parts of deionized water.

3. The responsive release microcapsules for impermeability of cement-based materials according to claim 1 or 2, characterized in that, The hydrophobic organic phase change material includes eicosane and / or lauric acid; The emulsifier is a compound emulsification system composed of anionic and nonionic emulsifiers. The anionic emulsifier includes at least one of phosphate ester surfactants and fatty alcohol polyoxyethylene sulfate. The nonionic emulsifier includes at least one of polyether-modified silicone and fatty alcohol polyoxyethylene ether.

4. The responsive release microcapsules for waterproofing cement-based materials according to claim 1 or 2, characterized in that, The polymer prepolymer is a mixture of etherified melamine-formaldehyde resin and polyvinyl alcohol; The responsive material includes nano-silicon carbide and / or nano-carbon black.

5. The release-type microcapsule for cement-based impermeability according to claim 1 or 2, characterized in that, The mass ratio of the hydrophobic organic phase change material in the core to the polymer prepolymer in the core wall is 4:1 to 1:

1.

6. The method for preparing the responsive release microcapsules for waterproofing cement-based materials according to any one of claims 1-5, characterized in that, Includes the following steps: S1. After melting the hydrophobic organic phase change material, it is mixed with an emulsifier and deionized water and sheared to emulsify, thus obtaining an emulsified core material solution. S2. Mix and stir the polymer prepolymer, responsive material and deionized water to obtain a wall material solution; S3. First, add the wall material solution obtained in S2 dropwise to the emulsified core material solution obtained in S1. Then, adjust the pH to promote the polymerization reaction. Next, adjust the pH again to terminate the reaction. Finally, wash, filter and dry to obtain responsive release microcapsules.

7. The method for preparing responsive release microcapsules for waterproofing cement-based materials according to claim 6, characterized in that, In step S3, the pH is adjusted to 3-4 using an acidic regulator. The polymerization reaction is carried out at a temperature of 65-80℃ for 90-120 minutes. The pH was then adjusted again to 7-8 using an alkaline adjuster.

8. The application of the responsive release microcapsules for impermeability of cement-based materials as described in any one of claims 1-5 in the optimization of pore structure and improvement of impermeability of cement-based materials.

9. A method for optimizing the pore structure and improving the impermeability of cement-based materials, characterized in that, The method includes the following steps: incorporating the responsive release microcapsules for cement-based impermeability as described in any one of claims 1-5 into cement-based materials for curing, followed by microwave irradiation to optimize the pore structure and improve the impermeability of the cement-based materials.

10. The method for optimizing the pore structure and improving the impermeability of cement-based materials according to claim 9, characterized in that, The microwave radiation has a power of 500-1000 W, a frequency of 2-3 GHz, and a duration of 60-90 s.

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