High-temperature-resistant poly (4-methyl-1-pentene) dielectric film with synergistically improved insulating strength and dielectric property as well as preparation method and application of high-temperature-resistant poly (4-methyl-1-pentene) dielectric film

Abstract

The invention discloses a high-temperature-resistant poly (4-methyl-1-pentene) dielectric film with synergistically improved insulating strength and dielectric property and a preparation method and application thereof, and belongs to the field of preparation processes of polymer energy storage dielectric materials. The invention aims to solve the problems that the existing polymer energy storage material is low in energy storage density at high temperature, and the dielectric property and the insulating strength cannot be improved at the same time. The invention provides a method for preparing a norbornene dianhydride grafted poly (4-methyl-1-pentene) film by a two-step method by using poly (4-methyl-1-pentene) particles, norbornene dianhydride and dicumyl peroxide and combining a solution suspension technology with a melt casting extrusion technology and a one-way stretching traction technology. The high-temperature-resistant poly (4-methyl-1-pentene)-based dielectric film prepared by the invention has excellent breakdown strength and dielectric property, and the discharge energy density is as high as 5.92 J / cm < 3 > when the charge-discharge efficiency is greater than or equal to 90% at 150 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of preparation process of polymer energy storage media materials. Background Technology

[0002] Electrostatic capacitors play a crucial role in new energy vehicles and high-voltage direct current transmission systems based on voltage source converters due to their excellent charge-discharge rates and superior power density. Polymer dielectrics exhibit excellent insulation properties and self-healing characteristics, making them the preferred material for commercial film capacitors. However, actual operating conditions involve coupling of multiple stress fields, including electrical and thermal fields, which severely degrades the insulation performance and energy storage characteristics of dielectric films, limiting the application of film capacitors in harsh environments. Taking commercial biaxially oriented polypropylene (BOPP) film as an example, BOPP has a long-term service temperature below 105℃, but the hot spots generated by temperature rise in the power systems of new energy vehicles can reach as high as 150℃, failing to meet the requirements of miniaturization, system integration, and higher reliability in power equipment.

[0003] Poly(4-methyl-1-pentene), a commercial nonpolar polyolefin with a structure similar to polypropylene (PP), exhibits superior thermal stability and can be mass-produced into films via melt extrusion. However, as a nonpolar linear polymer, the coupling effect between dielectric constant and breakdown strength limits further improvement in energy storage density. Grafting maleic anhydride (MAH) is currently the main method to improve the dielectric constant of olefin polymers. Although MAH grafting can effectively improve the polarization strength of the polymer, the near-planar anhydride structure cannot provide sufficient free volume for dipole orientation polarization, and dielectric relaxation leads to a significant increase in polarization loss of the material. As Li Junlu et al. stated in "Grafting Process and High-Temperature Energy Storage Characteristics of Melt-Grafted Polypropylene Films" (Insulating Materials, 2025, 58(04):1-8.), MAH grafting leads to a sharp increase in the loss tangent of the material at high frequencies. In addition, the energy storage characteristics of polymer dielectrics are closely related to the grafting reaction mode. As described by Chen Qian et al. in "Research Progress and Application of Maleic Anhydride-Grafted Polypropylene" (China Plastics, 2025, 39(03):102-108.), the melt grafting method, due to its high reaction temperature, easily leads to the destruction and cross-linking of the polymer molecular structure. The polymer molecular backbone breaks and degrades at high temperatures, reducing the molecular weight of the material and severely deteriorating its insulation strength and mechanical properties. Furthermore, the free radicals generated by molecular chain breakage also increase the dielectric loss of the material. Therefore, the development and industrial production of polymer energy storage materials are of great significance. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that existing polymer energy storage materials have low energy storage density at high temperatures and cannot simultaneously improve dielectric properties and insulation strength. The invention provides a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistic improvement of insulation strength and dielectric properties, as well as its preparation method and application.

[0005] This invention aims to promote the synergistic improvement of dielectric properties and insulation strength of polymer energy storage materials, so as to improve the problem of low energy storage density of polymer energy storage materials at high temperatures. It also aims to prepare norbornene-grafted poly(4-methyl-1-pentene) energy storage dielectric films on a large scale by combining melt casting extrusion and uniaxial stretching.

[0006] This invention uses poly(4-methyl-1-pentene) particles, norbornene, and dicumyl peroxide to provide a two-step method for preparing norbornene-grafted poly(4-methyl-1-pentene) films by combining solution suspension technology with melt casting extrusion and uniaxial stretching technology.

[0007] After norbornene is grafted with poly(4-methyl-1-pentene) particles, deep traps that capture charges can be introduced to suppress charge injection and long-range transport, thereby obtaining excellent high-temperature insulation properties. The polar acyl groups in norbornene help to improve the orientation polarization and dielectric response of the energy storage medium. The synergistic improvement in breakdown strength and relative permittivity gives the energy storage medium of norbornene grafted with poly(4-methyl-1-pentene) excellent high-temperature energy storage performance.

[0008] A high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistically improved insulation strength and dielectric properties is disclosed, exhibiting a glass transition temperature of 234.07℃~235.13℃; a dielectric constant of 2.19~2.33 at 150℃; a breakdown strength of 678.9MV / m~796.6MV / m; and a discharge energy density of 4.23 J / cm². 3 ~5.92 J / cm 3 The charge / discharge efficiency is ≥90%.

[0009] A method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric thin film with synergistically improved insulation strength and dielectric properties is specifically carried out according to the following steps:

[0010] 1. Weigh out poly(4-methyl-1-pentene) particles, dicumyl peroxide, and norbornyl anhydride; place dicumyl peroxide and norbornyl anhydride in a sealed glass bottle;

[0011] 2. Add organic solvent to the sealed glass bottle from step 1, stir to dissolve, and obtain a mixed solution;

[0012] 3. Pour the mixed solution into the poly(4-methyl-1-pentene) weighed in step 1, so that the mixed solution fully wets the surface of the poly(4-methyl-1-pentene) particles, and obtain poly(4-methyl-1-pentene) with wetted surface.

[0013] IV. Place the surface-wetted poly(4-methyl-1-pentene) in an oven and dry it for a period of time to obtain the treated poly(4-methyl-1-pentene) particles.

[0014] 5. The treated poly(4-methyl-1-pentene) particles are fed into the hopper. The torque rheometer is set with twin screw speed, heating zone temperature and die head extrusion temperature. The treated poly(4-methyl-1-pentene) particles are heated by the torque rheometer to become molten, and the grafted polymer is obtained.

[0015] 6. The molten grafted polymer is drawn from the die head onto the quench roller, so that the melt adheres tightly to the quench roller. The quench roller temperature is set, and the film is cast, stretched, and rolled into a roll. This process produces a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistically improved insulation strength and dielectric properties.

[0016] A high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistically improved insulation strength and dielectric properties is used to prepare polymer film capacitors.

[0017] This invention has significant advantages over existing technologies:

[0018] 1. This invention avoids the disadvantages of traditional melt grafting processes, such as difficulty in control and numerous by-products. It adopts a solution suspension technology combined with torque rheometer and unidirectional stretching technology. Solvent-assisted grafting allows the resin particle surface to fully contact the grafted monomer and undergo pre-reaction, avoiding the thermal decomposition of the grafted monomer and resin material during the high-temperature process of melt extrusion. The preparation process is continuous and uniform, enabling large-scale roll-to-roll preparation and is well compatible with the actual industrial production of capacitor films.

[0019] 2. The high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistic improvement in insulation strength and dielectric properties prepared by this invention has an increased glass transition temperature and enhanced high-temperature stability due to the presence of norbornene-grafted poly(4-methyl-1-pentene) dielectric film material.

[0020] 3. The acyl group in the grafted monomer norbornene used in this invention can significantly improve the deep trap energy level of the energy storage medium, effectively suppress charge injection and transport at high temperatures, and significantly improve the insulation performance and energy storage efficiency of the material.

[0021] 4. This invention grafts norbornene anhydride with a spatial three-dimensional structure, which increases the free volume near the acyl group while introducing the polar acyl group. This allows the material to be rapidly oriented and polarized under the action of an electric field and reduces dielectric relaxation. The modified polymer maintains low dielectric loss while significantly improving the relative dielectric constant.

[0022] 5. The high-temperature resistant poly(4-methyl-1-pentene) dielectric film (norbornene-grafted poly(4-methyl-1-pentene) dielectric film material) prepared by this invention exhibits significantly enhanced high-temperature energy storage characteristics due to the synergistic improvement in insulation strength and dielectric properties, resulting in excellent high-temperature capacitance characteristics; at 150℃ and with a charge / discharge efficiency ≥90%, the energy storage density reaches as high as 5.92 J / cm³. 3 . Attached Figure Description

[0023] Figure 1 The chemical structural formulas of the matrix poly(4-methyl-1-pentene), the grafted monomer norbornene, the grafting initiator dicumyl peroxide, and the reaction formula of norbornene grafted poly(4-methyl-1-pentene) are used in this invention.

[0024] Figure 2 This is a schematic diagram of the orbital energy levels of the energy storage medium film prepared by norbornitic anhydride grafted with poly(4-methyl-1-pentene) in Example 1 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared by the control example.

[0025] Figure 3 The XRD patterns of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium films prepared in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example are shown.

[0026] Figure 4 Fourier transform infrared spectra of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium films prepared in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example.

[0027] Figure 5 The DSC curves of the energy storage medium films prepared by norbornene grafted poly(4-methyl-1-pentene) in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example are shown.

[0028] Figure 6 The dielectric spectrum of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium film prepared in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example at 150°C.

[0029] Figure 7 The norbornene-grafted poly(4-methyl-1-pentene) energy storage dielectric films prepared in Examples 1 and 2, and the pure poly(4-methyl-1-pentene) energy storage dielectric film prepared in the control example, were compared at 10... 3 Diothermal spectrum at Hz;

[0030] Figure 8 The image shows the Weibull breakdown strength distribution at 150°C of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium films prepared in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example.

[0031] Figure 9 The energy storage characteristics of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium films prepared in Examples 1 and 2, and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example, at 150°C, are shown as a function of electric field strength. Detailed Implementation

[0032] Specific Implementation Method 1: This implementation method provides a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistically improved insulation strength and dielectric properties. The glass transition temperature is 234.07℃~235.13℃; the dielectric constant at 150℃ is 2.19~2.33; the breakdown strength is 678.9MV / m~796.6MV / m; and the discharge energy density is 4.23 J / cm². 3 ~5.92 J / cm 3 The charge / discharge efficiency is ≥90%.

[0033] Specific Implementation Method Two: This implementation method is a method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistic improvement in insulation strength and dielectric properties, specifically completed according to the following steps:

[0034] 1. Weigh out poly(4-methyl-1-pentene) particles, dicumyl peroxide, and norbornyl anhydride; place dicumyl peroxide and norbornyl anhydride in a sealed glass bottle;

[0035] 2. Add organic solvent to the sealed glass bottle from step 1, stir to dissolve, and obtain a mixed solution;

[0036] 3. Pour the mixed solution into the poly(4-methyl-1-pentene) weighed in step 1, so that the mixed solution fully wets the surface of the poly(4-methyl-1-pentene) particles, and obtain poly(4-methyl-1-pentene) with wetted surface.

[0037] IV. Place the surface-wetted poly(4-methyl-1-pentene) in an oven and dry it for a period of time to obtain the treated poly(4-methyl-1-pentene) particles.

[0038] 5. The treated poly(4-methyl-1-pentene) particles are fed into the hopper. The torque rheometer is set with twin screw speed, heating zone temperature and die head extrusion temperature. The treated poly(4-methyl-1-pentene) particles are heated by the torque rheometer to become molten, and the grafted polymer is obtained.

[0039] 6. The molten grafted polymer is drawn from the die head onto the quench roller, so that the melt adheres tightly to the quench roller. The quench roller temperature is set, and the film is cast, stretched, and rolled into a roll. This process produces a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistically improved insulation strength and dielectric properties.

[0040] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the mass ratio of poly(4-methyl-1-pentene) particles, dicumyl peroxide, and norbornene anhydride in step 1 is 100:0.05:(0.5~1). The other steps are the same as in Specific Implementation Method 1 or 2.

[0041] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the organic solvent in step two is anhydrous ethanol; the mass ratio of the poly(4-methyl-1-pentene) particles to the volume of the organic solvent in step one is 100g:(5mL~20mL); the stirring and dissolving temperature in step two is 60℃, and the stirring and dissolving time is 6h. Other steps are the same as in Specific Implementation Methods One to Three.

[0042] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the soaking time in step three is 10-12 hours. The other steps are the same as in Specific Implementation Methods One to Four.

[0043] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the drying temperature in step four is 60°C. The other steps are the same as in Specific Implementation Methods One to Five.

[0044] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the drying time in step four is 12-15 hours. The other steps are the same as in Specific Implementation Methods One to Six.

[0045] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One through Seven in that: the rotational speed of the twin-screw in the torque rheometer described in step five is 60 r / min, the heating temperatures of heating zones 1 through 6 are 250℃, 250℃, 260℃, 260℃, 270℃, and 270℃ respectively, and the extrusion temperature at the die head is 270℃. Other steps are the same as in Specific Implementation Methods One through Seven.

[0046] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that: one side of the molten grafted polymer described in step six is ​​cooled by a quench roller, while the other side is allowed to cool naturally. The quench roller is drawn and stretched into a film at a temperature of 215°C and then wound into a roll, thus preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistically improved insulation strength and dielectric properties. Other steps are the same as in Specific Implementation Methods One through Eight.

[0047] Specific Implementation Method 10: This implementation method is a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistic improvement in insulation strength and dielectric properties, used to prepare polymer film capacitors.

[0048] The beneficial effects of the present invention are verified using the following embodiments:

[0049] Example 1: A method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistic improvement in insulation strength and dielectric properties, specifically comprising the following steps:

[0050] 1. Weigh out poly(4-methyl-1-pentene) particles, dicumyl peroxide, and norbornyl anhydride; place dicumyl peroxide and norbornyl anhydride in a sealed glass bottle;

[0051] The mass ratio of poly(4-methyl-1-pentene) particles, dicumyl peroxide, and norbornene anhydride in step one is 100:0.05:0.5;

[0052] 2. Add organic solvent to the sealed glass bottle from step 1, stir to dissolve, and obtain a mixed solution;

[0053] The stirring and dissolving temperature in step two is 60°C, and the stirring and dissolving time is 6 hours.

[0054] The organic solvent mentioned in step two is anhydrous ethanol;

[0055] The mass ratio of the poly(4-methyl-1-pentene) particles to the volume ratio of the organic solvent in step one is 100 g: 10 mL.

[0056] 3. Pour the mixed solution into the poly(4-methyl-1-pentene) weighed in step 1, and let the mixed solution fully wet the surface of the poly(4-methyl-1-pentene) particles for 12 hours to obtain poly(4-methyl-1-pentene) with a wetted surface.

[0057] 4. The surface-wetted poly(4-methyl-1-pentene) was placed in an oven at 60°C and dried for 12 hours to obtain the treated poly(4-methyl-1-pentene) particles.

[0058] 5. The treated poly(4-methyl-1-pentene) particles are fed into the hopper. The torque rheometer is set with twin screw speed, heating zone temperature and die head extrusion temperature. The treated poly(4-methyl-1-pentene) particles are heated by the torque rheometer to become molten, and the grafted polymer is obtained.

[0059] The torque rheometer twin screw mentioned in step five rotates at 60 r / min, and the heating temperatures of heating zones 1 to 6 are 250℃, 250℃, 260℃, 260℃, 270℃ and 270℃ respectively, and the extrusion temperature of the die head is 270℃.

[0060] 6. Using a copper scraper, the molten grafted polymer is drawn from the die head onto the quench roller, so that the melt adheres tightly to the quench roller. The quench roller temperature is set to 215℃. One side of the grafted polymer is cooled by the quench roller temperature, while the other side is cooled naturally. The polymer is cast, stretched, and rolled into a film at the quench roller temperature of 215℃, thus obtaining a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistic improvement in insulation strength and dielectric properties.

[0061] Example 2: The difference between this example and Example 1 is that the mass ratio of poly(4-methyl-1-pentene) particles, dicumyl peroxide, and norbornene anhydride in step one is 100:0.05:1. All other steps and parameters are the same as in Example 1.

[0062] Comparative example: The preparation method of pure poly(4-methyl-1-pentene) energy storage dielectric thin film is carried out according to the following steps:

[0063] 1. Add poly(4-methyl-1-pentene) particles into the hopper, set the twin-screw speed, heating zone temperature and die head extrusion temperature of the torque rheometer, and the poly(4-methyl-1-pentene) particles are heated by the torque rheometer to become molten, thus obtaining molten poly(4-methyl-1-pentene);

[0064] The torque rheometer twin screw in step one has a rotational speed of 60 r / min, and the heating temperatures of heating zones 1 to 6 are 250℃, 250℃, 260℃, 260℃, 270℃ and 270℃ respectively. The extrusion temperature of the die head is 270℃.

[0065] 2. Using a copper doctor blade, molten poly(4-methyl-1-pentene) is drawn from the die head onto a quench roller, so that the melt adheres tightly to the quench roller. The quench roller temperature is set to 215°C. One side of the grafted polymer is cooled by the quench roller temperature, while the other side is cooled naturally. The polymer is cast, stretched, and wound into a film at a quench roller temperature of 215°C, thus obtaining a pure poly(4-methyl-1-pentene) energy storage medium film.

[0066] The poly(4-methyl-1-pentene) films prepared in the comparative example and Examples 1 and 2 were characterized in structure and analyzed in performance:

[0067] Figure 2 This is a schematic diagram of the orbital energy levels of the energy storage medium film prepared by norbornitic anhydride grafted with poly(4-methyl-1-pentene) in Example 1 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared by the control example.

[0068] Depend on Figure 2 It can be seen that the HOMO level of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium prepared by the two-step method is -7.41 eV, the LUMO level is -0.88 eV, and the band gap is 6.53 eV. In contrast, the HOMO level of the pure poly(4-methyl-1-pentene) energy storage medium prepared in the control example is -7.44 eV, the LUMO level is 1.74 eV, and the band gap is 9.18 eV. Compared with the pure poly(4-methyl-1-pentene) energy storage medium film, the LUMO level of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium is reduced by 2.62 eV. This indicates that the grafted capacitor film material prepared in the examples exhibits higher electron affinity, and the energy level difference between the grafted and ungrafted segments can introduce deep traps to capture charges, suppressing charge injection and transport at high temperatures and improving its insulation performance.

[0069] Figure 3 The XRD patterns of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium films prepared in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example are shown.

[0070] Depend on Figure 3 It can be seen that the poly(4-methyl-1-pentene) dielectric films prepared in the control example and Examples 1 and 2 are all semi-crystalline polymers, and the grafting reaction did not change the crystal structure of poly(4-methyl-1-pentene).

[0071] Figure 4 Fourier transform infrared spectra of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium films prepared in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example.

[0072] Depend on Figure 4 It can be seen that the poly(4-methyl-1-pentene) dielectric films prepared in Examples 1 and 2 have a dielectric strength of 1500 cm⁻¹. -1 ~1700cm -1 The presence of a C=O stretching vibration peak in the interval, which is absent in the control example, proves the successful grafting of norbornyl anhydride.

[0073] Figure 5 The DSC curves of the energy storage medium films prepared by norbornene grafted poly(4-methyl-1-pentene) in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example are shown.

[0074] Figure 5 It can be seen that the glass transition temperatures of the poly(4-methyl-1-pentene) dielectric films prepared in the control example and Examples 1 and 2 are 233.08℃, 234.07℃ and 235.13℃, respectively. Examples 1 and 2, after grafting norbornene anhydride, show an increased glass transition temperature and improved high temperature resistance.

[0075] Figure 6 The dielectric spectrum of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium film prepared in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example at 150°C.

[0076] Figure 6 The poly(4-methyl-1-pentene) dielectric films prepared in the comparative example and Examples 1 and 2 are shown to be resistant to oxidation at 150°C and 10 °C. 3 The relative permittivity at Hz was 1.85, 2.19, and 2.33, respectively. The polar acyl group introduced in the examples effectively enhanced the dielectric response of the energy storage medium, and this enhancement further increased with increasing grafting content. Simultaneously, the spatial stereochemistry of norbornene provided sufficient free volume for the orientation polarization of the dipoles, reducing dielectric relaxation.

[0077] Figure 7 The norbornene-grafted poly(4-methyl-1-pentene) energy storage dielectric films prepared in Examples 1 and 2, and the pure poly(4-methyl-1-pentene) energy storage dielectric film prepared in the control example, were compared at 10... 3 Diothermal spectrum at Hz;

[0078] Depend on Figure 7It can be seen that the energy storage media prepared in Examples 1 and 2 maintain certain dielectric stability within the test range of 25℃ to 150℃, and the dielectric loss values ​​are all less than 0.003. A peak in dielectric loss occurs at 50℃, which is due to the increased thermal motion of polymer molecular chains caused by higher temperature, leading to enhanced dipole orientation polarization. Since orientation polarization has a certain hysteresis, the loss tangent increases. Higher temperatures reduce the hysteresis and energy loss during polarization, thus decreasing the loss tangent.

[0079] Figure 8 The image shows the Weibull breakdown strength distribution at 150°C of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium films prepared in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example.

[0080] Depend on Figure 8 It can be seen that, thanks to the energy level difference between the norbornadipic anhydride-modified segments and the ungrafted segments, the deep trapping energy level of the dielectric film is significantly improved. This is beneficial for hindering charge injection and long-range migration under high-temperature conditions, thus enhancing the high-temperature insulation performance of the dielectric films in the examples. The characteristic breakdown field strengths of the norbornadipic anhydride-grafted poly(4-methyl-1-pentene) energy storage dielectric films prepared in Examples 1 and 2 at 150°C are 796.6 MV / m and 678.9 MV / m, respectively, which are much higher than the breakdown field strength of 467.4 MV / m of the control example. This is mainly because the norbornadipic anhydride improves the deep trapping energy level of the polymer, while the three-dimensional structure effectively hinders charge migration along the chain, suppresses conduction losses at high temperatures, and enhances insulation performance. In addition, the shape factor of the energy storage dielectric films prepared in Examples 1 and 2 is better than that of the control example, indicating that they have good high-temperature insulation stability.

[0081] Figure 9 The energy storage characteristics of the norbornene-grafted poly(4-methyl-1-pentene) energy storage medium films prepared in Examples 1 and 2 and the pure poly(4-methyl-1-pentene) energy storage medium film prepared in the control example at 150°C are shown as a function of electric field strength.

[0082] Depend on Figure 9 It can be seen that, due to the synergistic improvement in insulation strength and dielectric properties, the norbornene-grafted poly(4-methyl-1-pentene) energy storage dielectric films prepared in Examples 1 and 2 exhibit superior high-temperature energy storage characteristics compared to pure poly(4-methyl-1-pentene) energy storage dielectric films. At 150°C and with a charge / discharge efficiency ≥90%, the discharge energy densities of the energy storage dielectrics prepared in Examples 1 and 2 are 5.92 J / cm², respectively. 3 and 4.23 J / cm 3Under the same conditions, the discharge energy density of pure poly(4-methyl-1-pentene) energy storage medium is only 1.84 J / cm². 3 .

[0083] In summary, the poly(4-methyl-1-pentene) energy storage medium with high breakdown strength prepared by the two-step method of this invention exhibits excellent high-temperature energy storage performance. By grafting norbornene anhydride, the polar acyl groups significantly improve the polarization intensity and relative permittivity of the energy storage medium. Furthermore, through band structure modulation, the energy level difference between the norbornene-modified and ungrafted molecular chains can act as a deep trap for capturing charges, significantly suppressing charge injection and long-range migration at high temperatures, reducing conduction losses, and improving high-temperature breakdown strength. Benefiting from the synergistic improvement in dielectric properties and insulation strength, the energy storage media prepared in Examples 1 and 2 both exhibit excellent high-temperature energy storage characteristics. At 150°C and with a charge / discharge efficiency ≥90%, Example 1 has a discharge energy density 3.22 times that of the control example; Example 2 has a discharge energy density 2.30 times that of the control example. The preparation process of this invention adopts a two-step method, namely, solution suspension technology combined with torque rheometer and unidirectional stretching equipment. The preparation process is directly compatible with the "roll-to-roll" production process of industrial capacitor films. This invention provides a promising application example for the molecular structure design of polymer dielectrics and further verifies the application prospects of poly(4-methyl-1-pentene) film capacitors under extreme conditions.

Claims

1. A high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistically improved insulation strength and dielectric properties, characterized in that... The dielectric thin film has a glass transition temperature of 234.07℃ to 235.13℃; a dielectric constant of 2.19 to 2.33 at 150℃; a breakdown strength of 678.9 MV / m to 796.6 MV / m; and a discharge energy density of 4.23 J / cm². 3 ~5.92 J / cm 3 The charge / discharge efficiency is ≥90%.

2. The method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric thin film with synergistic improvement in insulation strength and dielectric properties as described in claim 1, characterized in that... The preparation method is specifically carried out according to the following steps:

1. Weigh out poly(4-methyl-1-pentene) particles, dicumyl peroxide, and norbornyl anhydride; place dicumyl peroxide and norbornyl anhydride in a sealed glass bottle; 2. Add organic solvent to the sealed glass bottle from step 1, stir to dissolve, and obtain a mixed solution; 3. Pour the mixed solution into the poly(4-methyl-1-pentene) weighed in step 1, so that the mixed solution fully wets the surface of the poly(4-methyl-1-pentene) particles, and obtain poly(4-methyl-1-pentene) with wetted surface. IV. Place the surface-wetted poly(4-methyl-1-pentene) in an oven and dry it for a period of time to obtain the treated poly(4-methyl-1-pentene) particles.

5. The treated poly(4-methyl-1-pentene) particles are fed into the hopper. The torque rheometer is set with twin screw speed, heating zone temperature and die head extrusion temperature. The treated poly(4-methyl-1-pentene) particles are heated by the torque rheometer to become molten, and the grafted polymer is obtained.

6. The molten grafted polymer is drawn from the die head onto the quench roller, so that the melt adheres tightly to the quench roller. The quench roller temperature is set, and the film is cast, stretched, and rolled into a roll. This process produces a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistically improved insulation strength and dielectric properties.

3. The method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric thin film with synergistic improvement in insulation strength and dielectric properties according to claim 2, characterized in that... The mass ratio of poly(4-methyl-1-pentene) particles, dicumyl peroxide, and norbornene anhydride in step one is 100:0.05:(0.5~1).

4. The method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric thin film with synergistic improvement in insulation strength and dielectric properties according to claim 2, characterized in that... The organic solvent mentioned in step two is anhydrous ethanol; the mass ratio of the poly(4-methyl-1-pentene) particles to the volume ratio of the organic solvent mentioned in step one is 100g:(5mL~20mL); the stirring and dissolving temperature mentioned in step two is 60℃, and the stirring and dissolving time is 6h.

5. The method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric thin film with synergistic improvement in insulation strength and dielectric properties according to claim 2, characterized in that... The soaking time described in step three is 10 to 12 hours.

6. The method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric thin film with synergistic improvement in insulation strength and dielectric properties according to claim 2, characterized in that... The drying temperature described in step four is 60°C.

7. The method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric thin film with synergistic improvement in insulation strength and dielectric properties according to claim 2, characterized in that... The drying time described in step four is 12 to 15 hours.

8. The method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric thin film with synergistic improvement in insulation strength and dielectric properties according to claim 2, characterized in that... In step five, the torque rheometer twin screw rotates at 60 r / min, and the heating temperatures of heating zones 1 to 6 are 250℃, 250℃, 260℃, 260℃, 270℃ and 270℃ respectively. The extrusion temperature of the die head is 270℃.

9. The method for preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric thin film with synergistic improvement in insulation strength and dielectric properties according to claim 2, characterized in that... In step six, one side of the molten grafted polymer is cooled by a quenching roller, while the other side is cooled naturally. The quenching roller is stretched into a film at a temperature of 215°C and then rolled up, thus preparing a high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistically improved insulation strength and dielectric properties.

10. The application of the high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistic improvement in insulation strength and dielectric properties as described in claim 1, characterized in that... A high-temperature resistant poly(4-methyl-1-pentene) dielectric film with synergistically improved insulation strength and dielectric properties is used to prepare polymer film capacitors.

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