Preparation method and application of intelligent magnetic targeting hyperbranched polyurethane self-healing microcapsule

Abstract

The application discloses a preparation method and application of intelligent magnetic target super-branched polyurethane self-healing microcapsules, and comprises photosensitive microcapsules and epoxy resin which can be magnetically targeted, wherein Fe3O4@SiO2 nanoparticles of the microcapsule shell layer provide the microcapsules with the effect of targeted movement. In order to prevent the photosensitive resin inside the microcapsules from curing in advance, the shell layer is further modified by TiO2 / g-C3N4 to effectively shield the external visible light and ultraviolet light. For the damage of the base material to the electrical tree in the use process, after the electrical tree breaks the microcapsules, the core material in the capsules enters the damage channel through the siphon effect, and the in-situ electrochromic effect is good for repairing the electrical tree damage. The composite material system realizes the self-repairing of mechanical and electrical tree damage of the dielectric packaging material after long-term use, improves the service life of the material, and effectively avoids potential safety hazards in the later period.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microcapsule self-healing material preparation, and particularly relates to a preparation method and application of intelligent magnetic targeting hyperbranched polyurethane self-healing microcapsules. BACKGROUND

[0002] In addition to the inherent advantages of light weight and low cost, solid insulating dielectric materials such as epoxy resin, polyurethane, and polyethylene also have high electrical breakdown strength and low dielectric loss, and are widely used in the electronic and battery packaging industries. However, during use, such polymers are inevitably subjected to electrical tree damage due to long-term electrical and thermal stress. Electrical trees are a phenomenon of high polymer insulation failure caused by electrical breakdown, which is often difficult to detect and repair in time. Intelligent microcapsule self-healing materials can automatically detect and repair minor internal damage, avoiding accidents and saving resources. However, the high viscosity and poor flowability of epoxy resin result in slow repair speed of epoxy resin microcapsules, and even effective repair is difficult to achieve. Therefore, it is urgent to explore an effective defense method for the electrical tree damage problem of epoxy resin to improve the service life of insulating materials and ensure the safe operation of power equipment. SUMMARY

[0003] To solve the existing problems, the application provides a preparation method and application of intelligent magnetic targeting hyperbranched polyurethane self-healing microcapsules, which realizes targeted distribution of light-induced self-repair, and improves the service life and safety of insulating materials.

[0004] To achieve the above application purposes, the technical solutions adopted by the application are as follows:

[0005] A preparation method of intelligent magnetic targeting hyperbranched polyurethane self-healing microcapsules, which comprises the following steps:

[0006] S1: preparing Fe3O4@SiO2 magnetic particles.

[0007] S2: preparing a TiO2 / g-C3N4 composite light shielding agent: uniformly stirring g-C3N4 and TiO2, pouring into a crucible, calcining in a muffle furnace, grinding after cooling, and obtaining the prepared TiO2 / g-C3N4 composite material for preventing premature curing of the core material.

[0008] S3: mixing urea and formaldehyde solution, stirring and dissolving, adjusting the pH to 8-10, and reacting at 65-75 DEG C for 1-1.2 hours to obtain a urea-formaldehyde resin prepolymer;

[0009] S4 The photosensitive epoxy resin E-51, hyperbranched polyurethane, diphenyl-(4-phenylthio) phenyl sulfonium hexafluoroantimonate (photoinitiator 6976), hydroxycyclohexyl phenyl ketone (photoinitiator 184L) of the photosensitive system are mixed, ultrasonic stirring is uniform, and a healing agent is obtained. The healing agent is poured into a dispersion liquid containing sodium dodecylbenzenesulfonate, polyvinyl alcohol and TiO2 / g-C3N4, emulsified by using a high-speed homogenizer to form an O / W system, and a core material emulsion is obtained;

[0010] S5 The system of S3 and S4 is poured into a four-necked flask, stirred at 45-70°C for 15 min to make the mixture uniform, Fe3O4@SiO2 magnetic particles are added and stirred for 15 min, ammonium chloride is added to adjust the pH to 3-5, and after the system is stable, the curing agent resorcinol is added, constant temperature reaction is carried out for 4 h, and after filtration, washing and drying, the photosensitive resin microcapsules capable of magnetic targeting distribution are finally prepared.

[0011] In some exemplary specific embodiments of the present application, the preparation method of Fe3O4@SiO2 magnetic particles is as follows:

[0012] (1) Fe3O4 is prepared by high-temperature thermal decomposition: iron chloride hexahydrate, sodium acetate and sodium citrate are added to a beaker with ethanol and ethylene glycol and stirred for 30 min. It is added to a reaction kettle with a polytetrafluoroethylene lining, the temperature is set to 200°C, and the reaction is carried out for 10 h. After cooling to room temperature, the nanoparticles are collected with a magnet and washed repeatedly with ethanol and water to obtain Fe3O4 magnetic nanoparticles.

[0013] (2) The Fe3O4 magnetic nanoparticles are dispersed in an ethanol solution, ammonia water is added, and stirred for about 30 min; 8 mL of tetraethyl orthosilicate is added to 100 mL of ethanol, stirred uniformly, and then slowly dropped, and the reaction is carried out at 36°C for 6 h. After filtration and washing, Fe3O4@SiO2 magnetic particles are obtained.

[0014] In step (1), the mass-volume ratio of ethanol, ethylene glycol, iron chloride hexahydrate, trisodium citrate dihydrate and sodium acetate is (15-30) mL:(45-60) mL:(1-3) g:(1-3) g:(3-6) g;

[0015] Preferably, in step (1), the mass-volume ratio of ethanol, ethylene glycol, iron chloride hexahydrate, trisodium citrate dihydrate and sodium acetate is (15-30) mL:(45-55) mL:(2-3) g:(1-3) g:(3-6) g.

[0016] In step (2), the mass-volume ratio of nano-Fe3O4 particles, concentrated ammonia water, anhydrous ethanol and tetraethyl orthosilicate is (1-6) g:(130-240) g:(90-110) g:(1-10) g;

[0017] Preferably, the volume ratio of nano-Fe3O4 particles, concentrated ammonia water, anhydrous ethanol and tetraethyl orthosilicate is (1-3) g:(130-160) g:(90-100) g:(3-8) g.

[0018] In some exemplary embodiments of the present application, g-C3N4 is prepared by direct thermal polymerization: a certain amount of melamine is weighed into a crucible, placed in a muffle furnace for calcination, and after cooling, ground to obtain light yellow g-C3N4.

[0019] Preferably, the mass of melamine is about 10-12g, the temperature is 450-460℃, and the time is 4.2-4.5h.

[0020] Preferably, the mass of melamine is about 10-12g, the temperature is 450-460℃, and the time is 4.2-4.5h.

[0021] In the technical scheme of the present application, the mass ratio of g-C3N4 to TiO2 in S2 is 3-5:1, the temperature is 450-500℃, and the time is 4.5-5h, which is used to prevent the premature curing of the photosensitive core material.

[0022] Preferably, the mass ratio of g-C3N4 to TiO2 is 4-5:1, the temperature is 450-460℃, and the time is 4.5-4.8h.

[0023] In the technical scheme of the present application, preferably, the mass ratio of urea to formaldehyde in S3 is 1:2-2.5, the pH is 8-9, the temperature is 70-72℃, and the time is 1-1.2h.

[0024] In the technical scheme of the present application, the mass ratio of epoxy resin E-51, hyperbranched polyurethane, photoinitiator 6976, photoinitiator 184L in S4 is 5-7:5-7:0.2-0.4:0.2-0.4, and the ultrasonic dispersion time is 15-30min. The amount of emulsifier sodium dodecyl sulfonate is 4-6% of the total mass of epoxy resin E-51 and hyperbranched polyurethane, the amount of dispersant polyvinyl alcohol is 8-10% of the total mass of epoxy resin E-51 and hyperbranched polyurethane, and the amount of TiO2 / g-C3N4 is 4-6% of the total mass of epoxy resin E-51 and hyperbranched polyurethane.

[0025] In the technical scheme of the present application, in the preparation process of S5 microcapsules, the reaction temperature is 50-60℃, the reaction time is 4-5h, and the mass ratio of Fe3O4@SiO2, urea-formaldehyde resin prepolymer and healing agent is 3-6:5-15:10-15.

[0026] Preferably, the reaction temperature is 50-60 DEG C, the reaction time is 4-5h, and the mass ratio of Fe3O4@SiO2, urea-formaldehyde resin prepolymer and healing agent core material is 3-5:6-12:10-13. After stirring for 15 min at 50 DEG C, Fe3O4@SiO2 magnetic particles are added and stirred for 15 min, ammonium chloride is added to adjust the pH to about 4, the curing agent resorcinol is added after the system is stable, and constant temperature reaction is carried out for 4h. After filtration, washing and drying, the photosensitive resin microcapsules capable of magnetic targeting distribution are finally obtained.

[0027] The present application has the advantages of:

[0028] 1) The intelligent magnetic targeting hyperbranched polyurethane self-healing microcapsule prepared by the present application realizes the targeted distribution of the microcapsule by modifying the microcapsule shell layer with Fe3O4@SiO2. The mixed system of TiO2 / g-C3N4 has good shielding effect on visible light and ultraviolet light, which can effectively prevent the premature curing of the healing agent in the microcapsule, and effectively prolong the service life of the microcapsule.

[0029] 2) The intelligent magnetic targeting self-healing resin microcapsule prepared by the present application adopts a mixed system of epoxy resin and hyperbranched polyurethane. Epoxy resin has low cost and is a commonly used photosensitive resin, but its viscosity is high and its flowability is poor. Hyperbranched polyurethane has unique properties due to its highly branched molecular structure, such as low viscosity, high solubility and fast photo-curing response. Compared with previous studies, the mixed healing agent system as the core material has better flowability and lower viscosity. When the microcapsule is broken due to external electric stress or mechanical stress, the healing agent can quickly fill the cracks under the action of siphon, and on the other hand, the production cost is effectively controlled. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is the directional movement photo of the magnetic responsive microcapsule prepared in Example 3 of the present application under no magnetic field (A) and external magnetic field (B), Figure 1 (C) is the magnetic performance curve of the magnetic particles;

[0031] Figure 2 is the Fourier infrared spectrum of the self-healing resin microcapsule in the present application;

[0032] Figure 3 is the SEM image of the magnetic targeting self-healing resin microcapsule in the present application;

[0033] Figure 4 is the TEM image of the magnetic targeting self-healing resin microcapsule in the present application;

[0034] Figure 5 is the performance comparison chart of the shell UV absorbance in the present application;

[0035] Figure 6 A self-repairing process diagram of application example 1;

[0036] Figure 7 A self-repairing process diagram of application example 2. DETAILED DESCRIPTION

[0037] The application will be further described in the following specific examples, so that those skilled in the art can better understand and implement the application.

[0038] The raw materials and reagents used in the application are commercially available unless otherwise specified.

[0039] TiO2Changzhou Fengshu Chemical Co., Ltd., FA-18s.

[0040] Epoxy resin e-51 Nantong Star, E-51, viscosity 15000 mpa.s.

[0041] Hyperbranched polyurethane RJ544 Guangzhou Yousu Three Technology Co., Ltd., RJ544, viscosity 500-2500 mpa.

[0042] The g-C3N4 used in the following specific examples of the application is prepared by direct thermal polymerization. The specific preparation method is as follows: 10g of melamine is weighed into a crucible, placed in a muffle furnace, calcined at 500℃ for 4.5h, cooled to room temperature, and then taken out to prepare light yellow g-C3N4. Example 1

[0043] A preparation method of an intelligent magnetic targeting hyperbranched polyurethane self-healing microcapsule generally includes three steps, which are preparation of nano magnetic particles Fe3O4@SiO2, preparation of light shielding agent, and preparation of magnetic targeting microcapsule.

[0044] (1) Preparation of Fe3O4@SiO2

[0045] 1) Preparation of Fe3O4 magnetic nanoparticles: 1.5g of FeCl3·6H2O, 3.65g of NaAc, 1.5g of Na3CA, 15mL of EG and 45mL of DEG are added into a beaker and stirred for 30min. Add to the reaction kettle containing polytetrafluoroethylene lining, set the temperature to 200℃, and react for 10h. After cooling to room temperature, collect the nanoparticles with a magnet, and wash repeatedly with EtoH and H2O to obtain Fe3O4 magnetic nanoparticles.

[0046] 2) Preparation of Fe3O4@SiO2: 3g of Fe3O4 magnetic nanoparticles were dispersed in a mixed solution of ethanol, 12.35 mL of NH3·H2O was added, and stirred for about 30 min; 8 mL of TEOS was added to 100 mL of ethanol, stirred uniformly, then slowly dropped, and reacted at 36°C for 6h. After filtration and washing, Fe3O4@SiO2 magnetic particle dispersion was obtained.

[0047] (2) Preparation of light shielding agent

[0048] g-C3N4 / TiO2 was prepared by calcination method, g-C3N4 and TiO2 were poured into the crucible at a ratio of 5:1, put into the muffle furnace, calcined at 450°C for 4.5h, cooled and taken out, ground to prepare g-C3N4 / TiO2 composite light shielding agent.

[0049] (3) Preparation of intelligent magnetic targeting self-healing resin microcapsule

[0050] 1) 2g of urea and 4.58g of formaldehyde solution were weighed, the pH was adjusted to about 8-9 with triethanolamine, and the reaction was carried out at 70°C for 1h to prepare a urea-formaldehyde (UF) prepolymer solution.

[0051] 2) 1g of polyvinyl alcohol was added to 100mL of water, heated to dissolve, cooled, and then 0.48g of sodium dodecyl sulfonate and 0.5g of g-C3N4 / TiO2 composite light shielding agent were added and stirred until uniform. 6g of epoxy resin e-51, 6g of hyperbranched polyurethane, 0.24g of photoinitiator 6976, and 0.24g of photoinitiator 184L were weighed and added with stirring, and ultrasonic stirring was carried out for 30min to prepare a composite system healing agent. The healing agent was moved to a high-speed homogenizer shear machine and emulsified at 4000r / min for 15min, which was the emulsification stage of the healing agent, forming an O / W emulsion.

[0052] 3) The prepared UF prepolymer and healing agent system were moved to a three-necked flask, 0.5g of ammonium chloride and 0.2g of resorcinol were added, the temperature was adjusted to 50°C, and the reaction was carried out for 30min, then 3.2g of Fe3O4@SiO2 and 0.3g of resorcinol were added, and the reaction was carried out at 50°C for 3.5h, finally the product was filtered and washed with ethanol and water, and dried at room temperature for 48h to obtain a magnetic light-induced microcapsule. Example 2

[0053] (1) Preparation of Fe3O4@SiO2:

[0054] 1) Preparation of Fe3O4 magnetic nanoparticles: 2 g of FeCl3·6H2O, 5.3 g of NaAc, 2 g of Na3CA, 15 mL of LEG and 45 mL of DEG were added to a beaker and stirred for 30 min. It was added to a reaction kettle with a polytetrafluoroethylene liner, the temperature was set to 200°C, and the reaction was carried out for 10 h. After cooling to room temperature, the nanoparticles were collected with a magnet and repeatedly washed with EtoH and H2O to obtain Fe3O4 magnetic nanoparticles.

[0055] 2) Preparation of Fe3O4@SiO2: 3 g of Fe3O4 magnetic nanoparticles prepared according to the operation of Example 1 were taken to prepare Fe3O4@SiO2 magnetic particle dispersion.

[0056] (2) Preparation of light shielding agent

[0057] g-C3N4 / TiO2 was prepared by calcination method. g-C3N4 and TiO2 were poured into a crucible in a ratio of 4:1 and placed in a muffle furnace, calcined at 450°C for 4.5 hours, and then taken out after cooling and ground to prepare g-C3N4 / TiO2 composite light shielding agent.

[0058] (3) Preparation of intelligent magnetic targeting self-healing resin microcapsules

[0059] 1) 3 g of urea and 6.75 g of formaldehyde solution were weighed and the pH was adjusted to about 8-9 with triethanolamine, and the reaction was carried out at 70°C for 1 h to prepare a urea-formaldehyde (UF) prepolymer solution.

[0060] 2) The preparation method of the O / W emulsion of the healing agent is the same as that of Example 1.

[0061] 3) The prepared UF prepolymer and healing agent system were moved to a three-necked flask, 0.5 g of ammonium chloride and 0.2 g of resorcinol were added, the temperature was adjusted to 50°C, and the reaction was carried out for 30 min, then 4.2 g of Fe3O4@SiO2 and 0.3 g of resorcinol were added, and the reaction was carried out at 50°C for 3.5 h. Finally, the product was filtered and washed with ethanol and water, and dried at room temperature for 48 h to obtain light-induced microcapsules with magnetism. Example 3

[0062] (1) Preparation of Fe3O4@SiO2

[0063] 1) Preparation of Fe3O4 magnetic nanoparticles: 2 g of FeCl3·6H2O, 4.2 g of NaAc, 2 g of Na3CA, 15 mL of LEG and 45 mL of DEG were added to a beaker and stirred for 30 min. It was added to a reaction kettle with a polytetrafluoroethylene liner, the temperature was set to 200°C, and the reaction was carried out for 10 h. After cooling to room temperature, the nanoparticles were collected with a magnet and repeatedly washed with EtoH and H2O to obtain Fe3O4 magnetic nanoparticles.

[0064] 2) Preparation of Fe3O4@SiO2: 3 g of Fe3O4 magnetic nanoparticles prepared according to the procedure of Example 1 were used to prepare a dispersion of Fe3O4@SiO2 magnetic particles.

[0065] (2) Preparation of light shielding agent

[0066] The g-C3N4 / TiO2 was prepared by calcination method. g-C3N4 and TiO2 were poured into a crucible in a ratio of 3:1 and placed in a muffle furnace, calcined at 450°C for 4.5 hours, and after cooling, ground to obtain g-C3N4 / TiO2 composite light shielding agent.

[0067] (3) Preparation of intelligent magnetic targeting self-healing resin microcapsules

[0068] 1) 3.5 g of urea and 7.25 g of formaldehyde solution were weighed and the pH was adjusted to about 8-9 with triethanolamine, and the reaction was carried out at 70°C for 1 h to prepare a urea-formaldehyde (UF) prepolymer solution.

[0069] 2) The preparation method of the emulsion of the healing agent O / W is the same as that of Example 1.

[0070] 3) The prepared UF prepolymer and healing agent system were moved to a three-necked flask, 0.5 g of ammonium chloride and 0.2 g of resorcinol were added, the temperature was adjusted to 50°C, and the reaction was carried out for 30 min, then 4.2 g of Fe3O4@SiO2 was added and the reaction was carried out at 50°C for 3.5 h, finally the product was filtered and washed with ethanol and water, and dried at room temperature for 48 h to obtain light-induced microcapsules with magnetism. Comparative Example 1

[0071] A method for preparing an intelligent magnetic targeting epoxy resin self-healing microcapsule

[0072] (1) Preparation of Fe3O4@SiO2: same as Example 1;

[0073] (2) Preparation of g-C3N4 / TiO2: same as Example 1;

[0074] (3) Preparation of intelligent magnetic targeting self-healing resin microcapsules

[0075] 1) 2 g of urea and 4.58 g of formaldehyde solution were weighed and the pH was adjusted to about 8-9 with triethanolamine, and the reaction was carried out at 70°C for 1 h to prepare a urea-formaldehyde (UF) prepolymer solution.

[0076] 2) In 100 mL of water, add 1 g of polyvinyl alcohol, heat to dissolve, cool, and then add 0.48 g of sodium dodecyl sulfonate and 0.5 g of g-C3N4 / TiO2 composite light shielding agent and stir until uniform. Weigh 12 g of epoxy resin e-51, 0.48 g of photoinitiator 6976, and add under stirring, ultrasonic stirring for 30 min to prepare a healing agent for the composite system. Move the healing agent to a high-speed homogenizer shear machine and emulsify at 4000 r / min for 15 min. This stage is the emulsification stage of the healing agent, forming an O / W emulsion.

[0077] 3) Move the prepared UF prepolymer and healing agent system to a three-necked flask, add 0.5 g of ammonium chloride and 0.2 g of resorcinol, and adjust the temperature to 50°C for 30 min. Add 3.2 g of Fe3O4@SiO2 and 0.3 g of resorcinol, and then react at 50°C for 3.5 h. Finally, filter and wash the product with ethanol and water, and dry at room temperature for 48 h to obtain a magnetic light-initiated microcapsule. Comparative Example 2

[0078] The preparation method of the TiO2-containing intelligent magnetic targeting hyperbranched polyurethane self-healing microcapsule is the same as that of Example 1, except that TiO2 is used instead of g-C3N4 / TiO2.

[0079] Application Example 1

[0080] Mix the epoxy resin with the curing agent, add about 4% of Example 1, stir uniformly and degas, and add to a transparent mold. Add two extremely fine probes as electrodes in each sample, and place at room temperature for about 24 h until the entire resin composite system is completely cured, for further pressure breakdown healing experiments.

[0081] Application Example 2

[0082] Mix the epoxy resin with the curing agent, add about 4% of Comparative Example 1, stir uniformly and degas, and add to a transparent mold. Add two extremely fine probes as electrodes in each sample, and place at room temperature for about 24 h until the entire resin composite system is completely cured, for further pressure breakdown healing experiments.

[0083] Figure 1 is the intelligent magnetic targeting microcapsule prepared in Example 3, Figure 1 A is a photo without a magnetic field, and the microcapsules are mostly distributed at the bottom of the bottle, with a brown color; Figure 1 B is a photo under a high-strength magnet, and the photo shows that under the action of the right magnet, the microcapsules are mostly adsorbed on the right side, and the right side (close to the magnet) in the bottle presents a dark opaque color, while the other parts are colorless and opaque. Figure 1C represents the hysteresis loop diagram of the magnetic particles. As shown in the diagram, the saturation magnetization of the prepared microcapsules is 61.17 emu / g, exhibiting excellent paramagnetic properties. Therefore, we can achieve the directional distribution of microcapsules in vulnerable areas such as the interior or exterior of materials.

[0084] like Figure 2 Curves a, b, and c correspond to the infrared curves of the composite resin healing agent microcapsules, epoxy resin E-51, and hyperbranched polyurethane, respectively, at 3400 cm⁻¹. -1 The left and right positions correspond to the vibrational absorption peaks of -OH and -NH-, respectively. By comparison, the absorption peak signal of curve a at this point is significantly lower than that of curve b. This is because curve c does not contain -OH. 2970~2870 cm⁻¹ -1 The absorption at this point corresponds to the CH vibration of alkyl groups. The a curve shows an absorption at 1700 cm⁻¹. -1 The vibrational absorption peak of the ester group in -NHCOO- corresponds to curve c, while curve b does not have a corresponding vibrational absorption peak. (1610 cm⁻¹) -1 The point is a tensile vibration at C=O, 1510cm -1 The characteristic peaks at 1485 cm⁻¹ and 1485 cm⁻¹ are both absorption peaks generated by the skeletal vibration of the benzene ring, while the peak at 914 cm⁻¹ is an absorption peak generated by the tensile vibration of C=O. -1 and 832cm -1 The peak at point a represents the stretching vibration of the epoxy ring. By comparing curve a with curves b and c, we have demonstrated the successful synthesis of microcapsules containing the composite healing agent.

[0085] like Figure 3 As shown in Figure 4, the microcapsules are spherical, indicating good emulsification and dispersion during the experiment, and the size is relatively uniform, with the spheres measuring 100-150 μm. Figure 4 TEM analysis showed that the microcapsules had coatings at their edges and a distinct core-shell structure, which proves the successful synthesis of the microcapsules.

[0086] To test the light-shielding performance of the shells, this invention selected equal masses of Example 1 (i.e., samples containing g-C3N4 / -TiO2 composite material) and Comparative Example 2 (pure TiO2 material samples). The shells were effectively broken through meticulous grinding. Subsequently, anhydrous ethanol was used as a solvent to wash and filter the broken samples multiple times to thoroughly remove residual healing agent from the capsules. To ensure optimal removal, this washing and filtering step was repeated 2 to 3 times. Finally, g-C3N4 / -TiO2 and TiO2 microcapsule shells were obtained after drying, and their absorbance was measured using ultraviolet-visible spectroscopy. Figure 5 It can be seen that the g-C3N4 / -TiO2 shell structure has significantly better light absorption performance than the TiO2 shell in the 200-400nm range.

[0087] like Figure 6 The diagram shows the repair process of electrical tree damage in Application Example 1. The arrows indicate the appearance, growth, generation, and repair of the electrical tree. It can be seen that most of the damaged parts have been well filled and covered, with an area of ​​more than 90%. Figure 7 The arrows indicate the processes of appearance, growth, formation, and repair of electrical trees. The figure shows the repair in application example 2. Due to the poor flowability of epoxy resin, the damaged part was not well repaired after 48 hours. The reason may be that the healing agent that flowed out solidified, preventing the repair agent inside the microcapsule from flowing out completely. From the above, we can prove that the composite healing agent is significantly better than the comparative example.

[0088] The above embodiments are for illustrative purposes only and are not intended to limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A smart magnetically targeted hyperbranched polyurethane self-healing microcapsule, characterized in that, The wall material of the intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsule is urea-formaldehyde resin containing Fe3O4@SiO2 magnetic particles, and the core material includes a TiO2 / g-C3N4 composite light shielding agent and a healing agent composed of epoxy resin, hyperbranched polyurethane and curing agent.

2. The preparation method of the intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsules according to claim 1, characterized in that, Includes the following steps: S1 preparation of Fe3O4@SiO2 magnetic particles; S2 Preparation of TiO2 / g-C3N4 composite light shielding agent: After g-C3N4 and TiO2 are stirred evenly, they are poured into a crucible, calcined in a muffle furnace, cooled and then ground to obtain TiO2 / g-C3N4 composite material, which is used to prevent the core material from curing prematurely; S3 mixes urea and formaldehyde solution, stirs to dissolve, adjusts pH to 8-10, and reacts at 65-75℃ for 1-1.2h to obtain urea-formaldehyde resin prepolymer; S4 mixes photosensitive epoxy resin E-51, hyperbranched polyurethane, diphenyl-(4-phenylthio)phenylsulfonium hexafluoroantimonate, and hydroxycyclohexylphenyl ketone, and ultrasonically stirs them to obtain a healing agent; the healing agent is poured into a dispersion containing sodium dodecylbenzenesulfonate, polyvinyl alcohol, and TiO2 / g-C3N4, and emulsified using a high-speed homogenizer to form an O / W system, thus obtaining a core material emulsion; S5 involves mixing the urea-formaldehyde resin prepolymer of S3 and the core material emulsion of S4 at 45-70°C, adding Fe3O4@SiO2 magnetic particles and mixing evenly, then adding ammonium chloride to adjust the pH to 3-5. After the system stabilizes, resorcinol is added and the reaction is carried out at a constant temperature. The reaction product is then filtered, washed and dried to obtain intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsules.

3. The method for preparing the intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsules according to claim 2, characterized in that, In step S2, the mass ratio of g-C3N4 to TiO2 is 3~5:1, the temperature is 450~500℃, and the time is 4.5~5h.

4. The method for preparing the intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsules according to claim 2, characterized in that, The mass ratio of S3 urea to formaldehyde is 1:2~2.

5.

5. The method for preparing the intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsules according to claim 2, characterized in that, In step S4, the mass ratio of epoxy resin E-51, hyperbranched polyurethane, diphenyl-(4-phenylthio)phenylsulfonium hexafluoroantimonate, and hydroxycyclohexylphenyl ketone is 5~7:5~7:0.2~0.4:0.2~0.

4.

6. The method for preparing the intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsules according to claim 2, characterized in that, In step S4, the amount of sodium dodecylbenzenesulfonate is 4-6% of the total mass of epoxy resin E-51 and hyperbranched polyurethane, the amount of polyvinyl alcohol is 8-10% of the total mass of epoxy resin E-51 and hyperbranched polyurethane, and the amount of TiO2 / g-C3N4 is 4-6% of the total mass of epoxy resin E-51 and hyperbranched polyurethane.

7. The method for preparing intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsules according to claim 2, characterized in that, In step S5, the mass ratio of Fe3O4@SiO2, urea-formaldehyde resin prepolymer, and healing agent is 3~5:6~12:10~13.

8. The method for preparing intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsules according to claim 2, characterized in that, In step S5, the reaction temperature is 50~60℃ and the reaction time is 4~5h.

9. An insulating dielectric material, characterized in that, It includes the intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsules as described in claim 1.

10. The insulating dielectric material according to claim 9, characterized in that, In the insulating dielectric material, the amount of the intelligent magnetically targeted hyperbranched polyurethane self-healing microcapsules added is 2~10 wt.

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