Dielectric energy storage material, preparation method and application thereof

Abstract

The application belongs to the field of organic polymer dielectric materials, and specifically discloses a dielectric energy storage material, a preparation method and application thereof.The dielectric energy storage material comprises the following components in parts by weight: polypropylene grafted polyetherimide 5-35 parts, and polypropylene 70-90 parts.The polypropylene grafted polyetherimide is added to the polypropylene matrix, and the polypropylene grafted polyetherimide can significantly improve the dielectric constant and the breakdown field strength of the material, thereby providing technical support for improving the energy storage density and reliability of the capacitor.

Description

Technical Field

[0001] The present invention belongs to the field of polymer dielectric materials, and in particular relates to a dielectric energy storage material and a preparation method and application thereof. Background Art

[0002] Polypropylene (PP) films are widely used in capacitors due to their high electrical strength, excellent self-healing properties, and low losses. However, current PP films have low dielectric constants and weak breakdown field strengths, resulting in low energy storage density and reliability in dielectric film capacitors. To enhance the dielectric properties of PP, physical methods can be used to disperse dielectric fillers within a PP matrix, creating PP nanocomposite dielectric materials. However, this physical mixing method generally requires nanoscale dielectric fillers, which are prone to agglomeration. Furthermore, the interfacial compatibility between the nanofillers and the PP matrix is ​​poor, leading to internal heterogeneity within the material system and decreased mechanical properties. Furthermore, ensuring uniform dispersion of the nanofillers within the PP matrix requires complex preparation and processing methods, further increasing production costs and limiting the large-scale production and use of these PP nanocomposite dielectric materials. The development of a PP material with high dielectric energy storage properties is a highly practical and pressing issue. Summary of the Invention

[0003] In response to the problems of low dielectric constant and low breakdown field strength of polypropylene-based dielectric energy storage materials involved in the above-mentioned prior art, the present invention will provide a dielectric energy storage material and its preparation method and application.

[0004] To achieve the above objectives, the following technical solutions are specifically included:

[0005] In one aspect, the present invention provides a dielectric energy storage material comprising the following components in parts by weight: 5-35 parts of polypropylene grafted polyetherimide and 70-90 parts of polypropylene.

[0006] Polyetherimide (PEI) has excellent high-temperature resistance and dielectric properties. The present invention chemically grafts it onto polypropylene (PP), introduces functional side chains into the PP main chain, and forms polypropylene-grafted polyetherimide (PP-g-PEI). PP-g-PEI and PP are then compounded to form a dielectric energy storage material. This not only significantly improves the dielectric constant and breakdown field strength of the material, but also enhances the polarity and interfacial compatibility of PP, improving the uniformity of the system. This avoids the poor compatibility of conventional fillers and PP physically blended together, and can further improve the energy storage density and efficiency of polypropylene-based dielectric energy storage film capacitors.

[0007] The type of polypropylene of the present invention is not particularly limited, and conventional dielectric polypropylene can achieve the purpose of the present invention. Preferably, the polypropylene has a melt flow rate of 0.5-20 g / 10 min, more preferably 1-5 g / 10 min, as measured at 230°C and 2.16 kg according to ISO 1133.

[0008] Preferably, in the dielectric energy storage material, the mass percentage of the polypropylene grafted polyetherimide is 10-30%.

[0009] Further preferably, in the dielectric energy storage material, the mass percentage of the polypropylene grafted polyetherimide is 10-20%.

[0010] Within a certain range, as the PP-g-PEI content in the dielectric energy storage material increases, the dielectric constant gradually increases and the breakdown field strength gradually decreases. At the above-mentioned mass percentage of polypropylene grafted polyetherimide, the dielectric energy storage material can simultaneously maintain a relatively high dielectric constant and breakdown field strength, laying the foundation for further improving the energy storage density and energy storage efficiency of polypropylene dielectric energy storage film capacitors.

[0011] In another aspect, the present invention provides a method for preparing the dielectric energy storage material, comprising the following steps:

[0012] (1) m-phenylenediamine and 4,4'-(4,4'-isopropyldiphenyloxy) diphthalic anhydride react in a solvent to obtain polyetherimide;

[0013] (2) in the presence of an interface agent, the polyetherimide and PP-g-MAH react to obtain polypropylene grafted polyetherimide;

[0014] (3) Polypropylene and the polypropylene grafted polyetherimide are mixed, melted, hot-pressed and cooled to obtain the dielectric energy storage material.

[0015] In the preparation method of the present invention, PP grafted PEI (PP-g-PEI) is prepared by a solid phase method based on polypropylene grafted maleic anhydride (PP-g-MAH). The chemical structure of the PP-g-PEI is as follows:

[0016]

[0017] Where m and n are the degree of polymerization.

[0018] Preferably, in step (1), the mass ratio of m-phenylenediamine to 4,4'-(4,4'-isopropyldiphenoxy)diphthalic anhydride is (10-30):(50-80).

[0019] Preferably, in step (1), the solvent comprises dimethylacetamide (DMAC), the reaction time is 24-48 hours, and the reaction is carried out under stirring conditions and under the protection of an inert gas.

[0020] Preferably, in step (1), the concentration of m-phenylenediamine in the solvent is 10-20 wt.%.

[0021] Preferably, in step (2), the mass ratio of the polyetherimide to PP-g-MAH is (20-40):(5-20).

[0022] Preferably, in step (2), the solvent includes xylene, the reaction time is 2-5 hours, the reaction temperature is 80-100° C., and the reaction is carried out under stirring conditions and inert gas protection.

[0023] Preferably, in step (2), the mass ratio of the interfacial agent, polyetherimide and PP-g-MAH is interfacial agent:polyetherimide:PP-g-MAH=(200-300):(10-30):(20-40).

[0024] Preferably, in step (2), the mass percentage of MAH in the PP-g-MAH is 1-11%, more preferably 4-10%.

[0025] Preferably, in step (2), the melt mass flow rate of the PP-g-MAH measured at 230° C. and 2.16 kg according to ISO 1133 is 0.5-10 g / 10 min.

[0026] Preferably, in step (3), the melting temperature is 190-220° C., and the melting time is 5-10 min.

[0027] Preferably, in step (3), the hot pressing pressure is 5-20 kPa, and the hot pressing time is 5-40 min.

[0028] In addition, the present invention also provides an application of the dielectric energy storage material in preparing a capacitor.

[0029] Preferably, the dielectric energy storage material has a frequency range of 0.1 Hz to 10 6 The dielectric constant is 2.35-2.6 at Hz.

[0030] Preferably, the dielectric energy storage material has a breakdown field strength of 200-450 kV / mm at 25° C., more preferably 300-400 kV / mm.

[0031] The dielectric energy storage material of the present invention has a high dielectric constant and breakdown field strength. Using it as a material for preparing a capacitor can further improve the dielectric energy storage characteristics of the capacitor, such as further improving the energy storage density and reliability of the capacitor.

[0032] Compared with the existing technology, the present invention has the following beneficial effects: the present invention adds polypropylene grafted polyetherimide to the polypropylene matrix, and the polypropylene grafted polyetherimide can significantly improve the dielectric constant and breakdown field strength of the material, providing technical support for improving the energy storage density and reliability of the capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart for the synthesis of polypropylene grafted polyimide (PP-g-PEI), wherein m and n involved in the chemical structures of PEI, PP-g-MAH, and PP-g-PEI are their respective degrees of polymerization.

[0034] Figure 2 Spectra of the dielectric energy storage materials of Examples 1-3 and Comparative Examples 1-2.

[0035] Figure 3 Graph showing the DC breakdown test results of the dielectric energy storage materials of Examples 1-3 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0036] To better illustrate the objectives, technical solutions, and advantages of the present invention, the present invention will be further described below with reference to specific examples. The experimental methods used in the examples and / or comparative examples are conventional methods unless otherwise specified; the materials and reagents used are commercially available unless otherwise specified.

[0037] Polypropylene: Borealis, HC-300BF, melt flow rate of 3.3 g / 10 min at 230° C. and 2.16 kg according to ISO 1133.

[0038] PP-g-MAH: SK General Chemical, South Korea, brand 18722, melt mass flow rate tested at 230°C, 2.16 kg according to ISO 1133: 7.0 g / 10 min.

[0039] Example 1

[0040] A method for preparing a dielectric energy storage material comprises the following steps:

[0041] (1) In the presence of DMAC solvent, 15 parts by weight of m-phenylenediamine (the concentration of m-phenylenediamine in the solvent is 15 wt.%) and 65 parts by weight of 4,4'-(4,4'-isopropyldiphenoxy) diphthalic anhydride were added, and nitrogen was introduced to expel air from the system. Under nitrogen protection and stirring, the reaction was carried out for 28 hours to obtain polyetherimide;

[0042] (2) 30 parts by weight of polyetherimide and 250 parts by weight of xylene as an interfacial agent were added to 15 parts by weight of PP-g-MAH in sequence, and nitrogen was introduced; the mixture was then placed in a 90°C heat-collecting constant temperature heating magnetic stirrer in an oil bath for 3 hours to react. After the oil bath reaction, the graft copolymer was filtered and rinsed with methanol to remove excess interfacial agent and DMAC solvent. The rinsed graft copolymer was placed in a 60°C vacuum drying oven for 1 hour to remove excess methanol. Finally, polypropylene grafted polyetherimide was obtained, and the synthetic route thereof is as shown in the attached figure. Figure 1 As shown;

[0043] (3) 90 wt.% polypropylene and 10 wt.% polypropylene grafted polyetherimide were mixed in a blender at a blending temperature of 190-200°C, a blending speed of 5-15 rpm, and a blending time of 10-30 min; then transferred to a twin-screw extruder, melted at 200°C for 5 min, and finally, hot pressed in a flat-plate vulcanizer at pressures of 5 kPa, 10 kPa, 15 kPa, and 20 kPa for 5 to 10 minutes, followed by water cooling for 6 to 10 minutes (the device was water-cooled), and cold pressed to room temperature to obtain a dielectric energy storage material film sample with a thickness of 80-100 μm.

[0044] Example 2

[0045] Compared with Example 1, this embodiment differs in that, in step (3), this embodiment uses 80 wt.% polypropylene and 20 wt.% polypropylene grafted polyetherimide to mix in a blender, and the rest is the same.

[0046] Example 3

[0047] The difference between this embodiment and embodiment 1 is that in step (3), this embodiment uses 70 wt.% polypropylene and 30 wt.% polypropylene grafted polyetherimide to mix in a blender, and the rest is the same.

[0048] Comparative Example 1

[0049] This comparative example uses pure polypropylene raw material, commercially available product Borealis HC-300BF, which is melted at 180-200°C for 5 minutes, then hot-pressed under stepped pressure on a flat vulcanizer for several times, and cold-pressed to room temperature to obtain the desired film.

[0050] Comparative Example 2

[0051] In this comparative example, 90 wt.% polypropylene and 10 wt.% PP-g-MAH were mixed in a blender at a blending temperature of 190-200°C, a blending speed of 5-15 rpm, and a blending time of 10-30 min; then transferred to a twin-screw extruder, melted at 180-200°C for 5 min, and finally, hot pressed under stepped pressure on a flat vulcanizer for a certain period of time, and cold pressed to room temperature to obtain a dielectric energy storage material film sample.

[0052] Performance testing:

[0053] (1) Circular gold electrodes with diameters of 22 mm and 25 mm were sputtered on the upper and lower surfaces of the films obtained in the above embodiment and comparative example respectively by an ion sputtering instrument. Then, the spectrum of the films at room temperature was measured by a broadband dielectric impedance meter. The results are shown in FIG. Figure 2 shown.

[0054] (2) The films prepared in the above examples and comparative examples were placed in a voltage tester for DC breakdown testing. The two breakdown electrodes used in the test were both spherical copper electrodes with a diameter of 25 mm, and the test voltage rise rate was 1 kV / s. Each sample film was measured 10 times to ensure the comparability of the results, and the breakdown results were analyzed using the Weibull function. The results are shown in Figure 2. Figure 3 shown.

[0055] Depend on Figure 2 It can be seen that the dielectric energy storage film materials in Examples 1-3 of the present invention have a high 6 Hz, the dielectric constant is 2.35-2.6. At a frequency of 100 Hz, the dielectric constant of the film of Comparative Example 1 is 2.28, the dielectric constant of the film of Comparative Example 2 is 2.41, and the dielectric constants of the films of Examples 1-3 are 2.46, 2.49, and 2.51, respectively. Compared with pure PP and the composite system of PP-g-MAH and PP, the dielectric energy storage material obtained by compounding PP and PP-g-PEI of the present invention has a significantly improved dielectric constant; at the same time, as the content of PP-g-PEI added to the system increases, the dielectric constant of the obtained dielectric energy storage material continues to rise.

[0056] Depend on Figure 3It can be seen that at 25°C, the characteristic breakdown field strength of Example 1 is 398.53 kV / mm, while the characteristic breakdown field strength of Comparative Example 1 is 334.88 kV / mm. Compared with Comparative Example 1, the breakdown field strength of the film of Example 1 is increased by 19.0%. It can be seen that the dielectric energy storage material obtained by compounding PP and PP-g-PEI of the present invention has a significantly improved breakdown field strength than that of pure PP. It can be seen that the introduction of PEI in PP-g-PEI can introduce deeper traps into the polypropylene matrix. These deep traps can capture more carriers, thereby inhibiting the transfer of charge and improving the breakdown field strength of the material. In addition, the inventors of the present invention found that within a certain range, as the content of PP-g-PEI in the dielectric energy storage material increases, the thickness of the material's lamellae will be significantly reduced, that is, more imperfect thin lamellae will be formed, and these thin lamellae will lead to an increase in structural defects in the internal crystalline region. These defects become electric field concentration points, causing electric field distortion and increasing the risk of electrical breakdown. Therefore, a trade-off needs to be made between the introduction of deep traps (increasing the breakdown field strength) and the crystallization ability of the material (the solution of the present invention is embodied in reducing the breakdown field strength) to achieve the ultimate goal of increasing the breakdown field strength. Therefore, in the dielectric energy storage material of the present invention, the mass percentage of PP-g-PEI is preferably 10-20%.

[0057] The dielectric energy storage properties of a material are closely related to its breakdown field strength and dielectric constant. The dielectric energy storage material obtained by compounding PP with PP-g-PEI in this invention has a higher dielectric constant and breakdown field strength than similar products, and exhibits excellent dielectric energy storage properties.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A dielectric energy storage material, characterized in that The dielectric energy storage material comprises the following components in parts by weight: 5-35 parts of polypropylene grafted polyetherimide and 70-90 parts of polypropylene; in the dielectric energy storage material, the mass percentage of the polypropylene grafted polyetherimide is 10-20%; The preparation method of the polypropylene grafted polyetherimide comprises the following steps: (1) In a solvent, m-phenylenediamine and 4,4'-(4,4'-isopropyldiphenyloxy) diphthalic anhydride react to obtain polyetherimide; (2) In the presence of xylene, the polyetherimide and PP-g-MAH react to obtain polypropylene grafted polyetherimide.

2. The dielectric energy storage material according to claim 1, wherein The polypropylene has a melt mass flow rate of 0.5-20 g / 10 min when tested at 230° C. and 2.16 kg according to ISO 1133.

3. A method for preparing the dielectric energy storage material according to claim 1 or 2, characterized in that: The steps include: (1) In a solvent, m-phenylenediamine and 4,4'-(4,4'-isopropyldiphenyloxy) diphthalic anhydride react to obtain polyetherimide; (2) reacting the polyetherimide with PP-g-MAH in the presence of xylene to obtain polypropylene grafted polyetherimide; (3) Polypropylene and the polypropylene grafted polyetherimide are mixed, melted, hot-pressed and cooled to obtain the dielectric energy storage material.

4. The method for preparing a dielectric energy storage material according to claim 3, wherein: In step (1), the mass ratio of m-phenylenediamine to 4,4'-(4,4'-isopropyldiphenyloxy)diphthalic anhydride is (10-30):(50-80).

5. The method for preparing a dielectric energy storage material according to claim 3, wherein: In step (1), the solvent includes dimethylacetamide, the reaction time is 24-48 hours, and the reaction is carried out under stirring conditions and inert gas protection.

6. The method for preparing a dielectric energy storage material according to claim 3, wherein: In step (2), the mass ratio of the polyetherimide to PP-g-MAH is (20-40): (5-20).

7. The method for preparing a dielectric energy storage material according to claim 3, wherein: In step (2), the reaction time is 2-5 hours, the reaction temperature is 80-100° C., and the reaction is carried out under stirring conditions and inert gas protection.

8. The method for preparing a dielectric energy storage material according to claim 3, wherein: In step (3), the melting temperature is 180-200°C.

9. Use of the dielectric energy storage material according to claim 1 or 2 in preparing a capacitor.

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