A waterborne epoxy resin microcapsule assembly for multiple self-repair of concrete cracks and a preparation method thereof

Abstract

This invention relates to a water-based epoxy resin microcapsule assembly for multiple self-healing of concrete cracks and its preparation method. The microcapsule assembly consists of small-diameter microcapsules formed by coating water-based epoxy resin with high-melting-point polyethylene terephthalate, followed by coating water-based epoxy resin and small-diameter microcapsules with low-melting-point polyoxymethylene. When microcracks first appear in the concrete, the expanding cracks encounter the microcapsule assembly. Under the stress at the crack tip, the outer wall of the microcapsule assembly ruptures, allowing the internal water-based epoxy resin to flow out and diffuse into the concrete crack. There, it reacts with the curing agent mixed in the concrete to repair the crack. Simultaneously, the small-diameter microcapsules also flow out with the water-based epoxy resin and disperse throughout the concrete. When cracks reappear in the concrete, the small-diameter microcapsules at the crack rupture, further repairing the crack. This achieves multiple repairs of concrete cracks, significantly improving the durability of the concrete.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to a water-based epoxy resin microcapsule assembly for multiple self-healing of concrete cracks and its preparation method. Background Technology

[0002] Concrete has become a primary building material due to its low cost, ease of construction, and good durability. However, its brittleness and low tensile strength make it prone to cracking during service, which affects its strength and the safety of the building structure. Furthermore, cracks accelerate the penetration of corrosive substances from the external environment, exacerbating chemical corrosion of the concrete and steel reinforcement, thus reducing the service life of the concrete. In specialized structures such as underground infrastructure, hydroelectric power stations, and nuclear power plants, the use of concrete is increasing, and the requirements for its durability are becoming increasingly stringent.

[0003] To improve the durability of concrete, self-healing concrete is becoming increasingly important. Self-healing concrete refers to concrete that, through its internal self-response mechanism, promptly repairs localized damage or micro-cracks that occur during use, eliminating internal hazards and extending the service life of the concrete. Patent CN112811845A describes an experiment using dimethylthiotoluene diamine as the core material and glyceryl tristearate as the wall material. The preparation method is simple, the microcapsules are spherical with good dispersibility, and the cement-based self-healing material prepared by combining it with epoxy resin microcapsules and ordinary silicate cement achieved a 31% compressive strength repair rate after 28 days of curing at 80% pre-compression, demonstrating a significant self-healing effect. However, because the number of times the microcapsules can repair cracks in the concrete is limited, when cracks reappear at the repaired area, the microcapsules and repair agent in that area have been consumed, limiting its practical application. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a water-based epoxy resin microcapsule assembly for multiple self-repair of concrete cracks and its preparation method, in response to the above-mentioned problems.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] A waterborne epoxy resin microcapsule assembly for multiple self-repairing of concrete cracks is prepared by coating waterborne epoxy resin with polyethylene terephthalate (PET) with a high melting point to form small-particle-size microcapsules, and then coating waterborne epoxy resin with polyoxymethylene (POM) with a low melting point and the small-particle-size microcapsules.

[0007] Furthermore, the raw materials include 30-50 parts by weight of polyoxymethylene, 30-50 parts by weight of polyethylene terephthalate and 40-140 parts by weight of waterborne epoxy resin.

[0008] A method for preparing a water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks includes the following steps:

[0009] Step 1: Heat 30-50 parts by weight of polyethylene terephthalate to 280-300℃ and stir at 300-400 rpm for 30 min; add 20-70 parts by weight of waterborne epoxy resin and continue stirring for 30 min to obtain a polyethylene terephthalate / waterborne epoxy resin mixture.

[0010] Step 2: Stop heating, increase the stirring speed to 1200-1300 rpm, add perfluorotributylamine to the mixture obtained in the previous step, and obtain a suspension of polyethylene terephthalate-coated waterborne epoxy resin microcapsules.

[0011] Step 3: Disperse the suspension with ultrasound for more than 20 min, and dry the microcapsules obtained after filtration and separation to obtain polyethylene terephthalate coated waterborne epoxy resin microcapsules.

[0012] Step 4: Heat 30-50 parts by weight of polyoxymethylene to 200-220℃ and stir at 300-400 rpm for more than 30 minutes; add 20-70 parts by weight of waterborne epoxy resin and the polyethylene terephthalate microcapsules obtained in step 3, and continue stirring for more than 60 minutes.

[0013] Step 5: Stop heating, increase the stirring speed to 1200-1300 rpm, add perfluorotributylamine to the mixture obtained in the previous step, and obtain a suspension containing microcapsule assemblies;

[0014] Step 6: The suspension containing the microcapsule assembly from Step 5 is subjected to ultrasonic dispersion treatment for more than 20 min. The microcapsule assembly obtained after filtration and separation is dried to obtain a water-based epoxy resin microcapsule assembly for multiple self-repair of concrete cracks.

[0015] Furthermore, the polyethylene terephthalate has a melting point of 240-260°C.

[0016] Furthermore, the polyoxymethylene has a melting point of 160-180℃.

[0017] Furthermore, the waterborne epoxy resin is a waterborne polyimide-modified epoxy resin.

[0018] Furthermore, the drying temperature in steps 3 and 6 is 40-60℃.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The microcapsule assembly of the present invention adopts a structure of a large capsule encapsulating a small capsule. The large capsule is composed of a low-melting-point polyoxymethylene coated with waterborne epoxy resin and a small capsule, while the small capsule is made of a high-melting-point polyethylene terephthalate coated with waterborne epoxy resin. In use, the microcapsule assembly prepared according to the present invention can be added to concrete. When microcracks first appear in the concrete, the expanding cracks encounter the microcapsule assembly described in the present invention. Under the stress at the crack tip, the outer wall of the large capsule of the microcapsule assembly ruptures, and the waterborne epoxy resin inside the microcapsule assembly flows out and diffuses into the concrete crack, reacting with the curing agent mixed in the concrete to repair the crack. Simultaneously, the small-diameter microcapsules coated with the outer wall also flow out with the waterborne epoxy resin and disperse in the concrete. When cracks reappear inside the concrete, the small-diameter microcapsules at the crack rupture and repair the crack, thus achieving multiple repairs of the concrete cracks and greatly improving the durability of the concrete.

[0021] (2) The waterborne epoxy resin of the present invention is a waterborne polyimide-modified epoxy resin, which has excellent room temperature fluidity and can undergo a curing reaction with aliphatic amine curing agents at room temperature. In addition, after curing, the waterborne polyimide-modified epoxy resin used in the present invention forms a semi-interpenetrating network compared with the curing of pure epoxy resin, which improves the crosslinking density and high temperature resistance of the material and improves the repair effect of concrete. Attached Figure Description

[0022] Figure 1 The images show the initial repair of cracks in cement concrete with the microcapsule assembly prepared in Example 1, where (a) is the image before repair and (b) is the image after repair.

[0023] Figure 2 Images show the repair of secondary cracks in cement concrete with the microcapsule assembly prepared in Example 1, where (a) is the image before repair and (b) is the image after repair. Detailed Implementation

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] Example 1

[0026] A water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks was prepared by the following method:

[0027] (1) Weigh out 30 parts of polyethylene terephthalate and 70 parts of waterborne epoxy resin according to the required weight of each raw material.

[0028] (2) Add 30 parts of polyethylene terephthalate to a flask, heat to 290°C to melt it completely, and stir at 350 rpm for 30 min.

[0029] (3) Add 70 parts of waterborne epoxy resin to the flask, keep the heating temperature and stirring speed constant, and continue stirring for 30 minutes to make it evenly mixed, so as to obtain a mixture of polyethylene terephthalate and waterborne epoxy resin.

[0030] (4) Stop heating, increase the stirring speed to 1300 rpm, add perfluorotributylamine to the above mixture to obtain a suspension containing polyethylene terephthalate coated waterborne epoxy resin microcapsules;

[0031] (5) The suspension was dispersed by ultrasonic treatment for 20 min, then filtered, and the separated microcapsules were dried in a 60℃ oven for 48 h to obtain polyethylene terephthalate coated waterborne epoxy resin microcapsules (small particle size microcapsules).

[0032] (6) Weigh out 30 parts of polyoxymethylene, 40 parts of waterborne epoxy resin and 30 parts of small particle size microcapsules according to the required weight of each raw material.

[0033] (7) Heat 30 parts of polyoxymethylene to 210°C and stir at 350 rpm for 30 min;

[0034] (8) Add 40 parts of waterborne epoxy resin and 30 parts of small-particle-size microcapsules to the melted polyoxymethylene, keep the heating temperature and stirring speed constant, and continue stirring for 60 minutes to make it evenly mixed.

[0035] (9) Stop heating, increase the stirring speed to 1300 rpm, add perfluorotributylamine to the above mixture to obtain a suspension containing microcapsule assemblies;

[0036] (10) The suspension in (9) was subjected to ultrasonic dispersion for 20 min, and then the microcapsule assembly was separated by filtration. After drying at 60°C for 48 h, the waterborne epoxy resin microcapsule assembly for multiple self-repair of concrete cracks was obtained.

[0037] The average particle size, sealing performance, and micromechanical properties of the water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared above were tested, and the results are listed in Table 1. Table 1 shows that the water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared in this embodiment has a small average particle size, low mass loss rate within 30 days, and good elastic modulus and hardness.

[0038] Table 1. Microcapsule assemblies prepared in Example 1

[0039]

[0040] Self-healing experiments were conducted on cement concrete incorporating the microcapsule assemblies prepared in Example 1:

[0041] 1. Preparation, molding, and curing of self-healing concrete: The microcapsule assembly prepared above was added to concrete (3% of the cement mass) to obtain self-healing concrete. This was poured into a 100mm×100mm×100mm mold and vibrated on a vibrating table until the surface showed signs of slurry. Excess slurry was then removed with a scraper. Immediately after the concrete was formed, a waterproof membrane was covered on the surface. After 24 hours, the mold was removed, and the specimen was moved to a curing room. It was cured for 56 days and then left at room temperature for 14 days.

[0042] 2. Crack Prefabrication and Self-Healing: A splitting crack test is used to induce cracks on the concrete surface, and the initial crack width is measured. After being left at room temperature for 7 days, the crack width is measured again. After the first repair is completed, a second crack prefabrication is performed on the damaged area, and after being left at room temperature for 7 days, the width of this second crack is measured. Figure 1 As shown, after incorporating the water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared in Example 1, cracks as small as 0.25 mm can self-heal. Figure 2 As shown, a secondary crack of 0.21 mm can self-heal.

[0043] Example 2

[0044] A water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks was prepared by the following method:

[0045] The preparation method of the microcapsule assembly is the same as in Example 1, except that:

[0046] (1) Weigh 50 parts of polyethylene terephthalate and 50 parts of waterborne epoxy resin according to the required weight of each raw material to prepare small particle size microcapsules.

[0047] (2) Weigh 40 parts of polyoxymethylene, 40 parts of waterborne epoxy resin and 20 parts of small-diameter microcapsules according to the required weight of each raw material to prepare microcapsule assembly.

[0048] The average particle size, sealing performance, and micromechanical properties of the water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared above were tested, and the results are listed in Table 2. Table 2 shows that the water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared in this embodiment has a small average particle size, low mass loss rate within 30 days, and good elastic modulus and hardness.

[0049] Table 2. Microcapsule assemblies prepared in Example 2

[0050]

[0051] Example 3

[0052] A water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks was prepared by the following method:

[0053] The preparation method of the microcapsule assembly is the same as in Example 1, except that:

[0054] (1) Weigh 40 parts of polyethylene terephthalate and 60 parts of waterborne epoxy resin according to the required weight of each raw material to prepare small particle size microcapsules.

[0055] (2) Weigh 35 parts of polyoxymethylene, 55 parts of waterborne epoxy resin and 10 parts of small-diameter microcapsules according to the required weight of each raw material to prepare microcapsule assembly.

[0056] The average particle size, sealing performance, and micromechanical properties of the water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared above were tested, and the results are listed in Table 3. Table 3 shows that the water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared in this embodiment has a small average particle size, low mass loss rate within 30 days, and good elastic modulus and hardness.

[0057] Table 3. Microcapsule assemblies prepared in Example 3

[0058]

[0059] Example 4

[0060] A water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks was prepared by the following method:

[0061] The preparation method of the microcapsule assembly is the same as in Example 1, except that:

[0062] (1) Weigh out 35 parts of polyethylene terephthalate and 65 parts of waterborne epoxy resin according to the required weight of each raw material to prepare small particle size microcapsules.

[0063] (2) Weigh 50 parts of polyoxymethylene, 35 parts of waterborne epoxy resin and 15 parts of small-diameter microcapsules according to the required weight of each raw material to prepare microcapsule assembly.

[0064] The average particle size, sealing performance, and micromechanical properties of the water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared above were tested, and the results are listed in Table 4. Table 4 shows that the water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared in this embodiment has a small average particle size, low mass loss rate within 30 days, and good elastic modulus and hardness.

[0065] Table 4. Microcapsule assemblies prepared in Example 4

[0066]

[0067] Example 5

[0068] A water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks was prepared by the following method:

[0069] The preparation method of the microcapsule assembly is the same as in Example 1, except that:

[0070] (1) Weigh 45 parts of polyethylene terephthalate and 55 parts of waterborne epoxy resin according to the required weight of each raw material to prepare small particle size microcapsules.

[0071] (2) Weigh 45 parts of polyoxymethylene, 25 parts of waterborne epoxy resin and 30 parts of small-diameter microcapsules according to the required weight of each raw material to prepare microcapsule assembly.

[0072] The average particle size, sealing performance, and micromechanical properties of the waterborne epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared above were tested, and the results are listed in Table 5. Table 5 shows that the waterborne epoxy resin microcapsule assembly for repeated self-healing of concrete cracks prepared in this embodiment has a small average particle size, low mass loss rate within 30 days, and good elastic modulus and hardness.

[0073] Table 5. Microcapsule assemblies prepared in Example 5

[0074]

[0075] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A water-based epoxy resin microcapsule assembly for repeated self-healing of concrete cracks, characterized in that, First, waterborne epoxy resin is coated with polyethylene terephthalate (PET) with a high melting point to form small-particle-size microcapsules. Then, waterborne epoxy resin and small-particle-size microcapsules are coated with polyoxymethylene (POM) with a low melting point to prepare the waterborne epoxy resin microcapsule assembly for multiple self-repair of concrete cracks. The raw materials include 30-50 parts by weight of polyoxymethylene, 30-50 parts by weight of polyethylene terephthalate and 40-140 parts by weight of waterborne epoxy resin. The waterborne epoxy resin is a waterborne polyimide-modified epoxy resin.

2. A method for preparing a water-based epoxy resin microcapsule assembly for repeated self-repair of concrete cracks, characterized in that, Includes the following steps: Step 1: Heat 30-50 parts by weight of polyethylene terephthalate to 280-300℃ and stir at 300-400 rpm for 30 min; add 20-70 parts by weight of waterborne epoxy resin and continue stirring for 30 min to obtain a polyethylene terephthalate / waterborne epoxy resin mixture. Step 2: Stop heating, increase the stirring speed to 1200-1300 rpm, add perfluorotributylamine to the mixture obtained in the previous step, and obtain a suspension of polyethylene terephthalate-coated waterborne epoxy resin microcapsules. Step 3: Disperse the suspension with ultrasound for more than 20 minutes, and dry the microcapsules obtained after filtration and separation to obtain polyethylene terephthalate-coated waterborne epoxy resin microcapsules. Step 4: Heat 30-50 parts by weight of polyoxymethylene to 200-220℃ and stir at 300-400 rpm for more than 30 minutes; add 20-70 parts by weight of waterborne epoxy resin and polyethylene terephthalate obtained in step 3 to coat waterborne epoxy resin microcapsules, and continue stirring for more than 60 minutes. Step 5: Stop heating, increase the stirring speed to 1200-1300 rpm, add perfluorotributylamine to the mixture obtained in the previous step, and obtain a suspension containing microcapsule assemblies; Step 6: Perform ultrasonic dispersion treatment on the suspension containing microcapsule assemblies from Step 5 for more than 20 minutes, and dry the microcapsule assemblies obtained after filtration and separation to obtain water-based epoxy resin microcapsule assemblies for multiple self-repair of concrete cracks.

3. The method for preparing the water-based epoxy resin microcapsule assembly for repeated self-repair of concrete cracks according to claim 2, characterized in that, The polyethylene terephthalate has a melting point of 240-260℃.

4. The method for preparing the water-based epoxy resin microcapsule assembly for repeated self-repair of concrete cracks according to claim 2, characterized in that, The polyoxymethylene has a melting point of 160-180℃.

5. The method for preparing the water-based epoxy resin microcapsule assembly for repeated self-repair of concrete cracks according to claim 2, characterized in that, The waterborne epoxy resin is a waterborne polyimide-modified epoxy resin.

6. The method for preparing the water-based epoxy resin microcapsule assembly for repeated self-repair of concrete cracks according to claim 2, characterized in that, The drying temperature in steps 3 and 6 is 40-60℃.

Images