Self-repairing polystyrene / azobenzene insulating film, preparation method and application thereof

Abstract

The application discloses a self-repairing polystyrene / azobenzene insulating film and a preparation method and application thereof, and relates to the technical field of insulating films.The polystyrene / azobenzene insulating film is prepared by reacting monomer styrene, an initiator and monomer azobenzene.The polystyrene / azobenzene film prepared by the application has excellent self-repairing performance, can repair mechanical damage and electrical damage under the conditions of ultraviolet light and heating, has a low dielectric constant and good insulating performance, and thus has a good application prospect in the fields of power electronics and insulating equipment.

Description

Technical Field

[0001] This invention relates to the field of insulating film technology, specifically to a self-healing polystyrene / azobenzene insulating film, its preparation method, and its application. Background Technology

[0002] Due to the long-term effects of electrical, thermal, and mechanical stresses, the insulating materials in power equipment and power electronic devices inevitably develop defects or damage of varying degrees. This severely affects their electrical and mechanical properties, shortens their service life, and poses a significant challenge to their safety. Therefore, the self-healing properties of materials have received widespread attention from academia and industry in recent years and have become a research hotspot in the field of insulating materials.

[0003] Existing self-healing methods include: adding hydrogen-bonded self-healing materials to an insulating polymer matrix [Bian WC et al. Polylmers, 2017, 9(9): 431.], achieving self-healing through localized high-temperature melting and reshaping using superparamagnetic nanoparticles [Yang Y et al. Nat Nanotechnol, 2019, 14(2): 151-155.], and adding microcapsules containing a repair solution to achieve self-healing [Gao L et al. Matter, 2020, 2(2): 451-463.]. However, current self-healing methods share common drawbacks, including demanding repair conditions and high repair costs. Therefore, researching more convenient self-healing methods has significant engineering practical value.

[0004] Azobenzene is a typical small organic molecule system. Its molecular structure contains a non-rotating nitrogen-nitrogen double bond, resulting in two isomers: cis and trans. The trans isomer can transform into the cis isomer under ultraviolet light irradiation, while the cis isomer can reversibly transform into the trans isomer under heating or visible light irradiation. These two isomers have different glass transition temperatures and melting temperatures, thus azobenzene compounds may achieve reversible transitions between solid and gel states under relatively low external stimuli, showing broad application prospects in the field of self-healing materials. Summary of the Invention

[0005] The purpose of this invention is to provide a self-healing polystyrene / azobenzene insulating film, its preparation method, and its applications, in order to address the shortcomings of existing technologies and research. The polystyrene / azobenzene insulating film prepared by this invention exhibits excellent self-healing properties, capable of repairing mechanical and electrical damage under both ultraviolet light and heating conditions. Furthermore, it possesses a low dielectric constant and good insulation properties, thus showing promising application prospects in the fields of power electronics and insulation equipment.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a self-healing polystyrene / azobenzene insulating film includes the following steps: S1. Cuprous bromide and 4,4'-dinonyl-2,2'-bipyridine are added to the reaction vessel and stirred thoroughly to allow them to coordinate and obtain reaction solvent A; S2. Add the monomer styrene and the brominated initiator containing azide groups into the reaction vessel, freeze the reaction system with liquid nitrogen, and pre-treat it by evacuation. S3. After reacting in an oil bath, remove the reaction system. S4. After stopping the reaction, the sample was purified by passing it through a neutral alumina column, then the solution was concentrated, the precipitate was filtered and vacuum dried to obtain the macromolecular initiator PS-Br. S5. Add cuprous bromide, 4,4'-dinonyl-2,2'-bipyridine, copper powder and solvent toluene to a new reaction vessel and stir thoroughly to allow them to coordinate and obtain reaction solvent B; S6. The macromolecular initiator PS-Br and the methacrylate monomer containing an azobenzene side group were added to a reaction vessel. The reaction system was frozen with liquid nitrogen, evacuated, purged with nitrogen, and then frozen again. This pretreatment was repeated three times. The reaction system was then placed in an oil bath and removed. After the reaction was stopped, the sample was purified by a neutral alumina column, the solution was concentrated, the precipitate was filtered, and then vacuum dried to obtain a yellow powder, PS-Br. b -PAzM; S7, Powder yellow PS- b -PAzM is melted into a film using a flat vulcanizing machine to form a self-healing polystyrene / azobenzene insulating film.

[0007] A further improvement of the present invention is that the mass ratio of cuprous bromide to 4,4'-dinonyl-2,2'-bipyridine in S1 is 1:(3.2-3.8).

[0008] A further improvement of the present invention is that the pretreatment described in S2 is performed by freezing with liquid nitrogen, evacuating, filling with nitrogen, and freezing again, repeated three times; the volume ratio of the monomer styrene to the brominated initiator containing azide groups is (500-750):1.

[0009] A further improvement of the present invention is that the oil bath temperature in S3 is 90-110℃ and the reaction time is 24-28 hours.

[0010] A further improvement of the present invention is that, after the reaction is stopped in step S4, tetrahydrofuran is used for dissolution, tetrahydrofuran is used as the mobile phase for reaction, and then anhydrous ethanol is used for precipitation; the particle size of the neutral alumina column is 200-300 mesh; and the vacuum drying time is 48-60 h.

[0011] A further improvement of the present invention is that the mass ratio of cuprous bromide, 4,4'-dinonyl-2,2'-bipyridine to copper powder in S5 is (2.1-2.3):(12.5-12.8):1.

[0012] A further improvement of the present invention is that the mass ratio of the macromolecular initiator PS-Br to the methacrylate monomer containing the azobenzene side group in S6 is 2.2:(1-1.2). The melt film formation process described in S7 involves preheating the flat vulcanizing machine for 5-10 minutes at a temperature of 150-200°C, followed by formal pressing for 10-15 minutes with ventilation in between, and finally cooling for 10-15 minutes to obtain the film.

[0013] A self-healing polystyrene / azobenzene insulating film, prepared by the aforementioned method, has the following molecular structure:

[0014] In the molecular structure formula, x and y exhibit different values ​​depending on the different mass ratios of styrene, cuprous bromide, and azobenzene selected during the preparation process.

[0015] An application of a self-healing polystyrene / azobenzene insulating film, wherein the polystyrene / azobenzene insulating film self-heals itself by heating after being subjected to mechanical damage, corona damage, or electrical tree damage; The heating conditions are heating in a constant temperature hot table or oven at 90-110℃ for 45-60 minutes. Alternatively, the polystyrene / azobenzene insulating film can self-repair by ultraviolet light after being subjected to mechanical damage, corona damage, or electrical tree damage. The ultraviolet light irradiation conditions are a power of 300-400 mW·cm. -2 Irradiate under ultraviolet light for 45-60 minutes.

[0016] Application of a self-healing polystyrene / azobenzene insulating film in the fields of power electronics and insulation equipment.

[0017] The present invention has at least the following beneficial technical effects: This invention provides a self-healing polystyrene / azobenzene insulating film. By introducing azobenzene containing a large number of non-rotatable nitrogen-nitrogen double bonds, reversible transformation between trans and cis isomers is achieved under different light irradiation conditions. Through the reduction of the glass transition temperature and melting temperature of the cis and trans isomers before and after ultraviolet irradiation, the material can be converted into a liquid or semi-liquid molten state under ultraviolet light, thus achieving ultraviolet light self-healing. At the same time, due to the low glass transition temperature of azobenzene and the thermoplasticity of polystyrene, heating self-healing is achieved, and the film's low dielectric properties and good insulation properties are effectively guaranteed.

[0018] This invention provides a method for preparing a self-healing polystyrene / azobenzene insulating film. The film obtained by the polymerization reaction of styrene and monomer azobenzene has both insulating and self-healing properties. Based on different needs, its mass ratio can be adjusted within a certain range to obtain better insulation performance or better self-healing performance.

[0019] This invention provides an application of a self-healing polystyrene / azobenzene insulating film. The heating self-healing method makes it possible to reuse the material, thus enabling multiple recycling, repair, and reuse of waste materials. Ultraviolet irradiation is easier to implement and less expensive. The non-contact repair method makes it possible to repair electrical devices without interruption. Therefore, it has good application prospects in the fields of power electronics and insulation equipment. Attached Figure Description

[0020] Figure 1 The 1H NMR spectrum of the macromolecular initiator (PS-Br) is shown.

[0021] Figure 2 For self-healing polystyrene / azobenzene insulation material (PS- b The proton NMR spectrum of -PAzM.

[0022] Figure 3 For self-healing polystyrene / azobenzene insulation material (PS- b Differential scanning calorimetry (DSC) of PAzM.

[0023] Figure 4 For polystyrene (PS) and self-healing polystyrene / azobenzene insulation materials (PS- b Infrared spectrum of -PAzM.

[0024] Figure 5 The relative permittivity diagram for self-healing polystyrene / azobenzene insulating films.

[0025] Figure 6This is a comparison image of the self-healing polystyrene / azobenzene insulating film before and after heating for self-healing in Example 7 of the present invention; wherein... Figure 6 (a) Before repair, Figure 6 (b) is after repair.

[0026] Figure 7 This is a comparison image of the self-healing polystyrene / azobenzene insulating film before and after ultraviolet light self-healing in Example 9 of the present invention; wherein... Figure 7 (a) Before repair, Figure 7 (b) is after repair.

[0027] Figure 8 This is a schematic diagram illustrating two self-healing mechanisms of the self-healing polystyrene / azobenzene insulating film of the present invention. Detailed Implementation

[0028] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] This invention provides a self-healing polystyrene / azobenzene insulating film, the molecular structure of which is shown below:

[0030] In the molecular structure formula, x and y have different values ​​depending on the different mass ratios of styrene, cuprous bromide, and azobenzene selected during the preparation process.

[0031] Example 1: Preparation of a self-healing polystyrene / azobenzene insulating film S1. Add cuprous bromide and 4,4'-dinonyl-2,2'-bipyridine (DNBPY) to the reaction vessel and stir thoroughly to allow them to coordinate and obtain the reaction solvent.

[0032] Specifically, the mass of cuprous bromide and 4,4'-dinonyl-2,2'-bipyridine (DNBPY) in S1 is 50 mg and 190 mg, respectively.

[0033] S2. Add the monomer styrene and the brominated initiator containing azide groups into the reaction vessel, freeze the reaction system with liquid nitrogen, and perform pretreatment by evacuation.

[0034] Specifically, the pretreatment described in S2 involves freezing with liquid nitrogen, evacuating, filling with nitrogen, and freezing again, which needs to be repeated three times; the volumes of the monomer styrene and the brominated initiator containing azide groups are 10 mL and 20 µL, respectively.

[0035] S3. Place the reaction system in an oil bath and react for a certain period of time before removing it.

[0036] Specifically, the oil bath temperature in S3 is 110°C, and the reaction time is 24 hours.

[0037] S4. After the reaction is stopped, the sample is purified by passing it through a neutral alumina column, then the solution is concentrated, the precipitate is filtered and then vacuum dried to obtain the macromolecular initiator PS-Br.

[0038] Specifically, after the reaction is stopped as described in S4, the product needs to be dissolved in tetrahydrofuran and reacted using tetrahydrofuran as the mobile phase, followed by precipitation with anhydrous ethanol; the neutral alumina column has a particle size of 200 mesh; and the vacuum drying time is 48 hours.

[0039] S5. Add cuprous bromide, 4,4'-dinonyl-2,2'-bipyridine (DNBPY), copper powder and solvent toluene into a new reaction vessel, and stir thoroughly to allow them to coordinate and obtain the reaction solvent.

[0040] Specifically, the masses of cuprous bromide, 4,4'-dinonyl-2,2'-bipyridine (DNBPY), and copper powder in S5 are 12.6 mg, 75 mg, and 6 mg, respectively.

[0041] S6. The macromolecular initiator PS-Br and the methacrylate monomer containing an azobenzene side group were added to a reaction vessel. The reaction system was frozen with liquid nitrogen, evacuated, purged with nitrogen, and then frozen again. This pretreatment was repeated three times. The reaction system was then placed in an oil bath and removed. After the reaction was stopped, the sample was purified by a neutral alumina column, the solution was concentrated, the precipitate was filtered, and then vacuum dried to obtain a yellow powder, PS-Br. b -PAzM.

[0042] Specifically, the macromolecular initiator PS-Br and the methacrylate monomer containing azobenzene side groups in S6 have masses of 396 mg and 180 mg, respectively.

[0043] S7. Powder PS- b -PAzM is melted into a film using a flat vulcanizing machine to form a self-healing polystyrene / azobenzene insulating film.

[0044] Specifically, the melt film formation process described in S7 requires preheating the flat vulcanizing machine for 5 minutes at a temperature of 150°C, followed by formal pressing for 15 minutes, with ventilation required in between, and finally cooling for 10 minutes to obtain the film.

[0045] The proton NMR spectrum of the macromolecular initiator (PS-Br) is as follows: Figure 1 As shown; self-healing polystyrene / azobenzene insulation material (PS- b The proton NMR spectrum of -PAzM is as follows: Figure 2 As shown, differential scanning calorimetry (DSC) is as follows: Figure 3 As shown.

[0046] The self-healing polystyrene / azobenzene insulating film prepared by this invention has a low dielectric constant and good insulation properties, thus showing promising application prospects in the fields of power electronics and insulation equipment. Polystyrene (PS) and self-healing polystyrene / azobenzene insulating materials (PS- b The infrared spectrum of -PAzM is as follows Figure 4 As shown; the relative permittivity of the self-healing polystyrene / azobenzene insulating film is as follows: Figure 5 As shown.

[0047] Example 2: Preparation of a self-healing polystyrene / azobenzene insulating film Similar to the method used in Example 1, only some changes were made. Specifically, the pressing temperature described in S7 of Example 1 was changed to 200°C, and the actual pressing time was changed to 10 minutes. Finally, a self-healing polystyrene / azobenzene insulating film was also obtained.

[0048] Example 3: Preparation of a self-healing polystyrene / azobenzene insulating film Similar to the method used in Example 1, only some changes were made. Specifically, the particle size of the neutral alumina column described in S4 of Example 1 was changed to 300 mesh. Finally, a self-healing polystyrene / azobenzene insulating film was also obtained.

[0049] Example 4: Preparation of a self-healing polystyrene / azobenzene insulating film Similar to the method used in Example 1, only some changes were made. Specifically, the particle size of the neutral alumina column described in S4 of Example 1 was changed to 300 mesh; the tableting temperature described in S7 of Example 1 was changed to 200°C, and the formal tableting time was changed to 10 minutes. Finally, a self-healing polystyrene / azobenzene insulating film was also obtained.

[0050] Example 5: Preparation of a self-healing polystyrene / azobenzene insulating film Similar to the method used in Example 1, with only minor modifications. Specifically, the mass of 4,4'-dinonyl-2,2'-bipyridine in S1 of Example 1 was changed to 160 mg; the volume of styrene monomer in S2 of Example 1 was changed to 15 mL; the oil bath temperature in S3 of Example 1 was changed to 90°C and the reaction time to 28 hours; and the vacuum drying time in S4 of Example 1 was changed to 60 hours. Finally, a self-healing polystyrene / azobenzene insulating film was obtained.

[0051] Example 6: Preparation of a self-healing polystyrene / azobenzene insulating film Similar to the method used in Example 1, only some modifications were made. Specifically, the mass of cuprous bromide and 4,4'-dinonyl-2,2'-bipyridine described in S5 of Example 1 was changed to 13.8 mg and 76.8 mg, respectively; the mass of the methacrylate monomer containing the azobenzene side group described in S6 of Example 1 was changed to 216 mg; and the preheating time described in S7 of Example 1 was changed to 10 minutes and the cooling time to 15 minutes. Finally, a self-healing polystyrene / azobenzene insulating film was also obtained.

[0052] Example 7: Heating self-healing of self-healing polystyrene / azobenzene insulating film The self-healing properties of the polystyrene / azobenzene insulating film prepared in Example 1 were tested by cutting a piece of the film and creating a scratch with a needle tip. The scratch was then examined under an optical microscope. Figure 6 As shown on the left, after heating on a constant-temperature hot stage at 90°C for 60 minutes, the results were observed using an optical microscope in the same location. Figure 6 As shown on the right, the scratches are clearly repaired by comparing the images. This demonstrates that the self-healing polystyrene / azobenzene insulating film prepared in this invention possesses excellent heat-induced self-healing properties, providing a possibility for the reuse of the material.

[0053] Example 8: Heating self-healing of self-healing polystyrene / azobenzene insulating film Similar to the method used in Example 7, only some modifications were made. Specifically, the temperature of the isothermal heating stage in Example 7 was changed to 110°C, and the heating time was 45 minutes. The scratches were still completely repaired, thus demonstrating that the self-healing polystyrene / azobenzene insulating film prepared by this invention possesses excellent heat-induced self-healing properties, providing the possibility for material reuse.

[0054] Example 9: UV self-healing of self-healing polystyrene / azobenzene insulating film To test the UV self-healing properties of the self-healing polystyrene / azobenzene insulating film prepared in Example 1, a piece of the film was cut off, and a scratch was made with a needle tip. The results were observed under an optical microscope. Figure 7 As shown on the left, then at a power of 300mW·cm -2 After irradiation under a UV lamp for 60 minutes, the images were observed under an optical microscope at the same location, and the results were as follows. Figure 7 As shown on the right, a comparison of the images clearly shows that the scratches are much shallower.

[0055] Example 10: UV self-healing of self-healing polystyrene / azobenzene insulating film Similar to the method used in Example 9, only some modifications were made. Specifically, the power of the ultraviolet lamp in Example 9 was changed to 400 mW·cm⁻¹. -2 The irradiation time was 45 minutes. Finally, the scratches were also repaired, thus demonstrating that the self-healing polystyrene / azobenzene insulating film prepared by this invention possesses strong ultraviolet light self-healing properties, and the non-contact repair method has broad development prospects.

[0056] at last Figure 8 Two self-healing mechanisms of the self-healing polystyrene / azobenzene insulating film of the present invention are demonstrated.

[0057] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to strictly limit the present invention. Therefore, it should be noted that any modifications and improvements made to the present invention by those skilled in the art without departing from the design concept described herein should be considered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a self-healing polystyrene / azobenzene insulating film, characterized in that, Includes the following steps: S1. Cuprous bromide and 4,4'-dinonyl-2,2'-bipyridine are added to the reaction vessel and stirred thoroughly to allow them to coordinate and obtain reaction solvent A; S2. Add the monomer styrene and the brominated initiator containing azide groups into the reaction vessel, freeze the reaction system with liquid nitrogen, and pre-treat it by evacuation. S3. After reacting in an oil bath, remove the reaction system. S4. After stopping the reaction, the sample was purified by passing it through a neutral alumina column, then the solution was concentrated, the precipitate was filtered and vacuum dried to obtain the macromolecular initiator PS-Br. S5. Add cuprous bromide, 4,4'-dinonyl-2,2'-bipyridine, copper powder and solvent toluene to a new reaction vessel and stir thoroughly to allow them to coordinate and obtain reaction solvent B; S6. The macromolecular initiator PS-Br and the methacrylate monomer containing an azobenzene side group were added to a reaction vessel. The reaction system was frozen with liquid nitrogen, evacuated, purged with nitrogen, and then frozen again. This pretreatment was repeated three times. The reaction system was then placed in an oil bath and removed. After the reaction was stopped, the sample was purified by a neutral alumina column, the solution was concentrated, the precipitate was filtered, and then vacuum dried to obtain a yellow powder, PS-Br. b -PAzM; S7, Powder yellow PS- b -PAzM is melted into a film using a flat vulcanizing machine to form a self-healing polystyrene / azobenzene insulating film.

2. The method for preparing a self-healing polystyrene / azobenzene insulating film according to claim 1, characterized in that, The mass ratio of cuprous bromide to 4,4'-dinonyl-2,2'-bipyridine in S1 is 1:(3.2-3.8).

3. The method for preparing a self-healing polystyrene / azobenzene insulating film according to claim 1, characterized in that, The pretreatment described in S2 involves freezing with liquid nitrogen, evacuating, filling with nitrogen, and freezing again, repeated three times; the volume ratio of the monomer styrene to the brominated initiator containing azide groups is (500-750):

1.

4. The method for preparing a self-healing polystyrene / azobenzene insulating film according to claim 1, characterized in that, The oil bath temperature described in S3 is 90-110℃, and the reaction time is 24-28 hours.

5. The method for preparing a self-healing polystyrene / azobenzene insulating film according to claim 1, characterized in that, After the reaction is stopped as described in S4, tetrahydrofuran is used for dissolution, and the reaction is carried out using tetrahydrofuran as the mobile phase, followed by precipitation with anhydrous ethanol; the particle size of the neutral alumina column is 200-300 mesh; the vacuum drying time is 48-60 h.

6. The method for preparing a self-healing polystyrene / azobenzene insulating film according to claim 1, characterized in that, The mass ratio of cuprous bromide, 4,4'-dinonyl-2,2'-bipyridine to copper powder in S5 is (2.1-2.3):(12.5-12.8):

1.

7. The method for preparing a self-healing polystyrene / azobenzene insulating film according to claim 1, characterized in that, The mass ratio of the macromolecular initiator PS-Br to the methacrylate monomer containing an azobenzene side group in S6 is 2.2:(1-1.2). The melt film formation process described in S7 involves preheating the flat vulcanizing machine for 5-10 minutes at a temperature of 150-200°C, followed by formal pressing for 10-15 minutes with ventilation in between, and finally cooling for 10-15 minutes to obtain the film.

8. A self-healing polystyrene / azobenzene insulating film, characterized in that, The molecular structure is prepared by any one of claims 1 to 7 and is shown below: In the molecular structure formula, x and y exhibit different values ​​depending on the different mass ratios of styrene, cuprous bromide, and azobenzene selected during the preparation process.

9. The application of the self-healing polystyrene / azobenzene insulating film according to claim 8, characterized in that, The polystyrene / azobenzene insulating film can self-repair by heating after being subjected to mechanical damage, corona damage, or electrical tree damage. The heating conditions are heating in a constant temperature hot table or oven at 90-110℃ for 45-60 minutes. Alternatively, the polystyrene / azobenzene insulating film can self-repair by ultraviolet light after being subjected to mechanical damage, corona damage, or electrical tree damage. The ultraviolet light irradiation conditions are a power of 300-400 mW·cm. -2 Irradiate under ultraviolet light for 45-60 minutes.

10. The application of the self-healing polystyrene / azobenzene insulating film according to claim 8 in the field of power electronics and insulation equipment.

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