Magnetic nanoparticle composite microcapsule, and preparation method therefor and use thereof

Abstract

A magnetic nanoparticle composite microcapsule, and a preparation method therefor and the use thereof. The preparation method comprises: diluting concentrated ammonia water with absolute ethanol in which nano-Fe3O4 is dispersed, stirring same and adding ethyl orthosilicate, centrifuging same, and then performing washing to obtain Fe3O4 / SiO2 particles; dispersing same in anhydrous ethanol, then adding isopropanol containing tetrabutyl titanate, and performing a treatment to obtain Fe3O4 / SiO2 / TiO2 nanoparticles; adding polyurethane TDI prepolymer to the Fe3O4 / SiO2 / TiO2 nanoparticles, adding same to a core material, then dripping an emulsifier, and stirring same to obtain a core material emulsion; and heating same in a water bath, dropwise adding butanediol, and performing heating, stirring and vacuum filtration to obtain a magnetic nanoparticle composite microcapsule. By means of the loading with a core material having a repair function, the prepared magnetic microcapsule can actively repair damage to an insulating material caused by electrical and mechanical stress, thereby improving the reliability of a device.

Description

A magnetic nanoparticle composite microcapsule, its preparation method and application Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a magnetic nanoparticle composite microcapsule, its preparation method, and its application. Background Technology

[0002] Epoxy resins are widely used in high-voltage power equipment and electronic device packaging due to their low manufacturing cost, good mechanical properties, and excellent insulation characteristics. However, during the long-term operation of electrical equipment, epoxy resin insulation materials are subjected to strong electric field stress and mechanical vibration stress, leading to defects such as microcracks and micropores on the surface or inside the material. Especially under strong electric field stress, internal defects can cause local electric field distortion, leading to charge accumulation and partial discharge, ultimately creating dendritic damage channels and causing dielectric insulation failure. Therefore, it is urgent to explore an effective defense method against the electrical and mechanical damage of epoxy resins to extend the service life of insulation materials and ensure the safe operation of power equipment.

[0003] To suppress the development of electrical tree damage, current research largely focuses on improving the insulation performance of epoxy resin materials through nano-modification and doping. By introducing charge traps and particle steric hindrance, the energy required for electrical tree development is consumed while influencing its growth path, thereby increasing energy consumption and growth distance during tree propagation and delaying the aging of insulating materials. However, while nano-modification and doping can improve electrical properties and slow down electrical tree development to some extent, it still has certain limitations. For example, nanoparticles tend to agglomerate in the epoxy resin matrix, causing local stress concentration in the composite material. This not only fails to suppress the initiation and development of electrical trees but also leads to a series of problems such as increased dielectric loss and decreased mechanical properties. The dielectric constant mismatch between inorganic particles and the epoxy resin matrix interface easily leads to interfacial charge accumulation, causing local electric field distortion. Furthermore, inorganic nanoparticle doping cannot suppress mechanical damage to the material.

[0004] Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing magnetic nanoparticle composite microcapsules.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: including,

[0009] Concentrated ammonia was diluted in anhydrous ethanol containing nano-Fe3O4, stirred and tetraethyl orthosilicate was added, centrifuged and filtered and washed to obtain Fe3O4 / SiO2 particles. 2-5 ml of tetraethyl orthosilicate was added for every 1 g of the nano-Fe3O4.

[0010] Fe3O4 / SiO2 particles were dispersed in anhydrous ethanol to obtain Fe3O4 / SiO2-ethanol solution. Isopropanol solution containing tetrabutyl titanate was added to Fe3O4 / SiO2-ethanol solution to form reaction system I. Reaction system I was heated and stirred, and then washed, dried and calcined in sequence to obtain Fe3O4 / SiO2 / TiO2 nanoparticles.

[0011] Polyurethane TDI prepolymer was dissolved in ethyl acetate and stirred, and Fe3O4 / SiO2 / TiO2 nanoparticles were added. The mixture was ultrasonically dispersed to obtain a mixture. A core material was added to the mixture to obtain an oil phase. The core material was composed of an alicyclic epoxy monomer and a cationic photoinitiator.

[0012] An emulsifier was added dropwise to the oil phase and stirred to obtain a core material emulsion. After heating in a water bath, butanediol was added dropwise, and the mixture was heated again and stirred. After vacuum filtration and washing, magnetic nanoparticle composite microcapsules were obtained.

[0013] In a preferred embodiment of the preparation method of the magnetic nanoparticle composite microcapsules of the present invention, the heating temperature of the reaction system I is 60-80°C.

[0014] In a preferred embodiment of the preparation method of the magnetic nanoparticle composite microcapsules of the present invention, the volume ratio of tetraethyl orthosilicate to tetrabutyl titanate is 0.8 to 1.2:1.

[0015] In a preferred embodiment of the preparation method of the magnetic nanoparticle composite microcapsules of the present invention, the drying is performed in a vacuum oven at 50-80°C for 8-10 hours, and the calcination is performed in air at 500-600°C for 1.5-3 hours.

[0016] In a preferred embodiment of the preparation method of the magnetic nanoparticle composite microcapsules of the present invention, the mass ratio of the polyurethane TDI prepolymer to the Fe3O4 / SiO2 / TiO2 nanoparticles is 40 to 90:1.

[0017] In a preferred embodiment of the preparation method of the magnetic nanoparticle composite microcapsules of the present invention, the mass ratio of the core material to Fe3O4 / SiO2 / TiO2 nanoparticles is 80-200:1.

[0018] In a preferred embodiment of the preparation method of the magnetic nanoparticle composite microcapsules of the present invention, the emulsifier is obtained by ultrasonic treatment of a mixture of gum arabic and amphiphilic TiO2 nanoparticles in deionized water.

[0019] In a preferred embodiment of the preparation method of the magnetic nanoparticle composite microcapsules of the present invention, the core material emulsion is heated to a water bath temperature of 50-60°C, and then the temperature is raised to 70-80°C after the water bath.

[0020] Another objective of this invention is to overcome the shortcomings of the prior art and provide a magnetic nanoparticle composite microcapsule.

[0021] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of magnetic nanoparticle composite microcapsules in the preparation of self-healing composite materials.

[0022] Beneficial effects of this invention:

[0023] The magnetic microcapsules prepared in this invention, by loading a repair-functional core material within the microcapsules, enable active repair of damage to insulating materials caused by electromechanical stress, thereby improving the reliability of power equipment. Furthermore, the composite of Fe3O4 / SiO2 / TiO2 particles with the microcapsules imparts magnetism to them. By controlling the magnetic field applied to the microcapsules, their directional movement can be controlled, thus achieving precise repair of insulation damage. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0025] Figure 1 is a schematic diagram of the magnetic microcapsules prepared according to the present invention.

[0026] Figure 2 is a schematic diagram of the relative permittivity of the microcapsules and epoxy resin prepared in Example 1 of the present invention under different doping concentrations.

[0027] Figure 3 is a schematic diagram of the tensile strength of the microcapsules and epoxy resin prepared in Example 1 of the present invention under different doping concentrations.

[0028] Figure 4 is a schematic diagram of the AC breakdown field strength and voltage of the magnetic nanoparticle composite microcapsules prepared in Example 1 of the present invention under the condition of post-damage repair with epoxy resin. Detailed Implementation

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0030] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0031] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0032] The sources of the raw materials used in this invention are shown in Table 1.

[0033] Table 1

[0034] The emulsifier used in this invention is obtained by mixing 2g of gum arabic (GA) and 1g of amphiphilic TiO2 nanoparticles in 60mL of deionized water and then ultrasonically treating the mixture.

[0035] The core material used in this invention is prepared by mixing an alicyclic epoxy monomer (ERL-4221) and a cationic photoinitiator (PI6992) at a mass ratio of 100:6.

[0036] Example 1

[0037] This embodiment provides a method for preparing magnetic nanoparticle composite microcapsules, specifically as follows:

[0038] 1) 4.5 ml of concentrated ammonia was diluted in 40 ml of anhydrous ethanol containing 0.25 g of nano-Fe3O4 particles. The mixture was stirred and 0.8 mL of tetraethyl orthosilicate was added. The mixture was allowed to stand and stirred for 12 h. After centrifugation, the mixture was filtered and washed to obtain Fe3O4 / SiO2 particles.

[0039] 2) Fe3O4 / SiO2 particles were dispersed in 40 ml of anhydrous ethanol to obtain Fe3O4 / SiO2-ethanol solution. 8 ml of isopropanol solution containing 1 ml of tetrabutyl titanate was added to Fe3O4 / SiO2-ethanol solution to form reaction system I. Reaction system I was heated and stirred at 70 °C for 12 h. The reddish-brown precipitate was washed 5 times with deionized water and ethanol and dried in a vacuum oven at 60 °C for 8 h. Then it was calcined in air at 500 °C for 2 h to obtain Fe3O4 / SiO2 / TiO2 nanoparticles.

[0040] 3) 4.5g of polyurethane TDI prepolymer was dissolved in 10mL of ethyl acetate and mechanically stirred at 65℃ for 10min until the prepolymer was completely dissolved. 0.1g of Fe3O4 / SiO2 / TiO2 nanoparticles were added to the mixed solution and ultrasonically dispersed for 3h to obtain a mixed solution. 13.5g of core material was added to the mixed solution to obtain an oil phase. Then, the oil phase was rapidly added dropwise to the emulsifier and mechanically stirred for about 1h to form an O / W (oil-in-water) system to obtain a core material emulsion. The mass ratio of polyurethane TDI prepolymer to Fe3O4 / SiO2 / TiO2 nanoparticles was 45:1, and the mass ratio of core material to Fe3O4 / SiO2 / TiO2 nanoparticles was 135:1.

[0041] 4) The core material emulsion was heated in a water bath at 50°C, and 3.15g of butanediol (BDO) was added dropwise. The temperature was raised to 70°C, and the mixture was mechanically stirred for 1 hour. After vacuum filtration, the mixture was washed with deionized water to obtain magnetic nanoparticle composite microcapsule samples. The samples were then dried in a low-light environment for 12 hours before use.

[0042] The composite microcapsules prepared in Example 1 were doped with epoxy resin at different concentrations. Figure 2 shows a schematic diagram of the relative permittivity of the microcapsules and epoxy resin prepared in Example 1 at different doping concentrations. It can be seen that at a power frequency of 50 Hz, the relative permittivity of the epoxy resin / microcapsule composite material increases slightly with the increase of the doping concentration of the microcapsules. When the doping concentration is below 5 wt%, the epoxy resin / microcapsule composite material basically maintains the excellent dielectric properties of the epoxy base material (the relative permittivity is 4.07, 4.12, and 4.17 when the doping concentration is 0 wt%, 2.5 wt%, and 5 wt%, respectively), and has low dielectric loss.

[0043] Figure 3 is a schematic diagram of the tensile strength of the microcapsules and epoxy resin prepared in Example 1 of the present invention at different doping concentrations. It can be seen that the introduction of microcapsules improves the mechanical properties of the epoxy resin matrix to a certain extent. As the doping concentration of microcapsules increases, the tensile strength of the epoxy resin / microcapsule composite material shows a trend of first increasing and then decreasing. When the doping concentration is 5wt%, the tensile strength reaches a maximum of 38.9MPa. When the doping concentration is 10wt%, the tensile strength of the epoxy resin / microcapsule composite material is still better than that of the pure epoxy resin matrix. Therefore, the doping of a small amount of microcapsules can effectively improve the mechanical properties of the epoxy resin matrix.

[0044] Example 2

[0045] The difference between this embodiment and Embodiment 1 is that the amount of polyurethane TDI prepolymer in step 3) is adjusted to 9g, so that the mass ratio of polyurethane TDI prepolymer to Fe3O4 / SiO2 / TiO2 nanoparticles is 90:1.

[0046] The remaining steps are the same as in Example 1, resulting in the magnetic nanoparticle composite microcapsules of this example.

[0047] Example 3

[0048] The difference between this embodiment and Embodiment 1 is that the amount of polyurethane TDI prepolymer in step 3) is adjusted to 6g, so that the mass ratio of polyurethane TDI prepolymer to Fe3O4 / SiO2 / TiO2 nanoparticles is 60:1.

[0049] Example 4

[0050] The difference between this embodiment and Embodiment 1 is that the amount of core material used in the preparation step of the core material emulsion was adjusted to 18.5g, so that the mass ratio of core material to Fe3O4 / SiO2 / TiO2 nanoparticles is 185:1.

[0051] The remaining steps are the same as in Example 1, resulting in the magnetic nanoparticle composite microcapsules of this example.

[0052] Example 5

[0053] The difference between this embodiment and Embodiment 1 is that the amount of core material used in the preparation step of the core material emulsion was adjusted to 8.5g, so that the mass ratio of core material to Fe3O4 / SiO2 / TiO2 nanoparticles is 85:1.

[0054] The remaining steps are the same as in Example 1, resulting in the magnetic nanoparticle composite microcapsules of this example.

[0055] Comparative Example 1

[0056] Comparative Example 1 provides a microcapsule that does not contain Fe3O4 / SiO2 / TiO2 nanoparticles.

[0057] Comparative Example 2

[0058] Comparative Example 2 is based on Example 1. The difference between Comparative Example 2 and Example 1 is that the amount of polyurethane TDI prepolymer in step 3) was adjusted to 2g, so that the mass ratio of polyurethane TDI prepolymer to Fe3O4 / SiO2 / TiO2 nanoparticles is 20:1.

[0059] Comparative Example 3

[0060] Comparative Example 3 is based on Example 1. The difference between Comparative Example 3 and Example 1 is that the amount of core material in the preparation step of the core material emulsion was adjusted to 30g, so that the mass ratio of core material to Fe3O4 / SiO2 / TiO2 nanoparticles is 300:1.

[0061] Example 6

[0062] This embodiment provides an application of magnetic microcapsules in the preparation of self-healing composite materials, specifically:

[0063] The magnetic nanoparticle composite microcapsules prepared in Examples 1 to 5 were composited with epoxy resin and doped at 5 wt%. Damage to the surface of the epoxy resin / microcapsule composite material was simulated by scalpel scratches. The mechanical properties and self-healing properties were tested and compared with those of Comparative Examples 1 to 3. The results are shown in Tables 1 and 2.

[0064] Table 1

[0065] As shown in Table 1, compared with the tensile strength of pure epoxy resin (the tensile strength of epoxy resin is 34.01 MPa), the introduction of microcapsules can effectively improve the mechanical properties of epoxy resin. This is because the polyurethane segments on the polyurethane shell of the microcapsules will randomly insert into the epoxy resin segments to form a polyurethane / epoxy resin graft polymer. The two produce a positive synergistic enhancement effect, thereby improving the mechanical properties of the epoxy resin / microcapsule composite material.

[0066] Table 2

[0067] Figure 4 is a schematic diagram of the AC breakdown field strength and voltage of the magnetic nanoparticle composite microcapsules and epoxy resin after damage repair in Example 1 of the present invention. As can be seen from Table 2 and Figure 4, the epoxy resin / microcapsule composite material prepared in Example 1 has a breakdown voltage reduction of more than 33% after being scratched. After scratch repair, the insulation strength can be restored to 80% to 90% of the initial state, indicating that the microcapsules effectively repair the damage to the insulation material. When the insulation material is damaged, the microcapsules rupture, causing the core material to flow out. Due to the capillary effect, the damage channel is instantly filled. Under the irradiation of ultraviolet light or natural light, the core material composed of alicyclic epoxy monomers and cationic photoinitiators will undergo photopolymerization reaction and solidify, thereby achieving the repair of the insulation material damage.

[0068] While the epoxy resin / microcapsule composite materials prepared in Examples 2 to 4 have a certain self-healing function, the repair efficiency is low and the insulation strength can only be restored to 70% to 80% of the initial state. The microcapsules prepared in Example 2 are plump spheres, but the outer shell is relatively thick. Under the action of external force, the outer shell of the microcapsules is difficult to break, and the core material enclosed by the outer shell cannot flow out smoothly to effectively repair the damage to the insulating material. The microcapsules prepared in Example 3 have low mechanical strength due to the excessive core material load. During the preparation of epoxy resin / microcapsule composite materials, the microcapsules will break, causing the core material to flow out and solidify prematurely, thus losing the self-repair function. In Example 4, due to the small amount of core material loaded in the microcapsules, the microcapsules are shriveled and cannot effectively repair the defects of the insulating material. In Comparative Example 1, since Fe3O4 / SiO2 / TiO2 nanoparticles were not added during the preparation of the microcapsules, the prepared microcapsules are not magnetic and cannot be directionally moved to the vulnerable parts of the insulating material by magnetic field or other methods. Therefore, their repair efficiency is also relatively low.

[0069] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing magnetic nanoparticle composite microcapsules, characterized in that: include, Concentrated ammonia was diluted in anhydrous ethanol containing nano-Fe3O4, stirred and tetraethyl orthosilicate was added, centrifuged and filtered and washed to obtain Fe3O4 / SiO2 particles. 2-5 ml of tetraethyl orthosilicate was added for every 1 g of the nano-Fe3O4. Fe3O4 / SiO2 particles were dispersed in anhydrous ethanol to obtain Fe3O4 / SiO2-ethanol solution. Isopropanol solution containing tetrabutyl titanate was added to Fe3O4 / SiO2-ethanol solution to form reaction system I. Reaction system I was heated and stirred, and then washed, dried and calcined in sequence to obtain Fe3O4 / SiO2 / TiO2 nanoparticles. Polyurethane TDI prepolymer was dissolved in ethyl acetate and stirred, and Fe3O4 / SiO2 / TiO2 nanoparticles were added. The mixture was ultrasonically dispersed to obtain a mixture. A core material was added to the mixture to obtain an oil phase. The core material was composed of an alicyclic epoxy monomer and a cationic photoinitiator. An emulsifier was added dropwise to the oil phase and stirred to obtain a core material emulsion. After heating in a water bath, butanediol was added dropwise, and the mixture was heated again and stirred. After vacuum filtration and washing, magnetic nanoparticle composite microcapsules were obtained.

2. The method for preparing magnetic nanoparticle composite microcapsules as described in claim 1, characterized in that: The heating temperature of reaction system I is 60–80°C.

3. The method for preparing magnetic nanoparticle composite microcapsules as described in claim 1, characterized in that: The volume ratio of tetraethyl orthosilicate to tetrabutyl titanate is 0.8 to 1.2:

1.

4. The method for preparing magnetic nanoparticle composite microcapsules as described in claim 1, characterized in that: The drying process involves drying in a vacuum oven at 50–80°C for 8–10 hours, and the calcination process involves calcining in air at 500–600°C for 1.5–3 hours.

5. The method for preparing magnetic nanoparticle composite microcapsules as described in claim 1, characterized in that: The mass ratio of the polyurethane TDI prepolymer to Fe3O4 / SiO2 / TiO2 nanoparticles is 40–90:

1.

6. The method for preparing magnetic nanoparticle composite microcapsules as described in claim 1, characterized in that: The mass ratio of the core material to Fe3O4 / SiO2 / TiO2 nanoparticles is 80–200:

1.

7. The method for preparing magnetic nanoparticle composite microcapsules as described in claim 1, characterized in that: The emulsifier is obtained by ultrasonic treatment of a mixture of gum arabic and amphiphilic TiO2 nanoparticles in deionized water.

8. The method for preparing magnetic nanoparticle composite microcapsules as described in claim 1, characterized in that: The core material emulsion is heated in a water bath at a temperature of 50–60°C, and then reheated at a temperature of 70–80°C.

9. Magnetic nanoparticle composite microcapsules prepared by any one of the preparation methods described in claims 1 to 8.

10. The application of the magnetic nanoparticle composite microcapsules as described in claim 9 in the preparation of self-healing composite materials.

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