Composite dielectric taking polyetherimide as matrix and preparation method thereof

Abstract

The invention discloses a composite dielectric taking polyetherimide as a matrix and a preparation method of the composite dielectric, the composite dielectric comprises the polyetherimide matrix and inorganic filler, and the inorganic filler comprises barium titanate and boron nitride. The barium titanate and the boron nitride are added into the polyetherimide matrix, so that the prepared composite dielectric is uniform in structure distribution, and the dielectric property, the discharge energy density and the breakdown-resistant field strength are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a composite dielectric based on polyetherimide and its preparation method. Background Technology

[0002] Dielectric capacitors are a new type of energy storage device with high capacitance, power density, and energy density. As a charge storage medium utilizing dielectric materials, they play a crucial role in applications with high transient power requirements, such as power systems for electric vehicles, fast-charging modules in portable electronic devices, and power systems in aerospace vehicles. Compared to ceramic-based dielectric materials, polymer dielectrics offer advantages such as high breakdown strength, low dielectric loss, good flexibility, and ease of processing, making them more suitable for practical production applications.

[0003] However, polymer dielectrics often exhibit low dielectric constants and polarization capabilities, resulting in limited energy density. Furthermore, applications in electric vehicles, aerospace, and oil and gas exploration often require temperatures exceeding 140°C, posing a significant challenge to polymer dielectrics. For some traditional polymer dielectrics, the following two factors may affect their performance: (i) the mobility of molecular chains increases at high temperatures, softening the polymer structure and increasing the risk of electromechanical breakdown; (ii) high temperatures can promote charge injection and bulk excitation, thereby increasing the number and mobility of charge carriers and thus increasing polymer conduction losses. Therefore, finding a material with a high glass transition temperature (Tg) and thermal stability is becoming increasingly important.

[0004] Polyetherimide (PEI) is a high-performance engineering plastic with excellent mechanical properties, thermal stability, and dielectric properties, along with a high glass transition temperature of approximately 237°C, making it widely used in dielectric energy storage. Compared to traditional polyimide (PI), PEI introduces ether bonds without damaging its original main chain structure, retaining excellent mechanical properties, chemical stability, and heat resistance, while also exhibiting better processability and flexibility. However, the low dielectric constant and low breakdown field strength of PEI limit its application in energy storage. Therefore, improving its dielectric constant and breakdown field strength while maintaining low dielectric loss is currently the primary goal. Summary of the Invention

[0005] This invention addresses the technical problem of low dielectric constant and breakdown field strength in existing dielectrics prepared using polyetherimide, and aims to provide a composite dielectric based on polyetherimide and its preparation method.

[0006] The composite dielectric based on polyetherimide of the present invention comprises: a polyetherimide matrix and an inorganic filler, wherein the inorganic filler comprises barium titanate and boron nitride.

[0007] Preferably, the mass ratio of the polyetherimide, the barium titanate, and the boron nitride is 1.0:1.0~4.0:0.2~0.6, and more preferably 1.0:3.0:0.4.

[0008] Another object of the present invention is to provide a method for preparing the aforementioned composite dielectric, comprising:

[0009] Step S1: Add barium titanate and boron nitride inorganic fillers to an organic solvent and stir to disperse them to obtain a filler solution. Then, add polyetherimide matrix to the filler solution at 50℃~70℃ and stir at 50℃~70℃ to obtain a dielectric mixture.

[0010] Step S2: First, apply the dielectric mixture onto the thin film substrate, then rotate the thin film substrate to evenly disperse the dielectric mixture, and then let the thin film substrate with the dispersed dielectric mixture stand at room temperature for pre-curing.

[0011] Step S3, then dry at 60℃~80℃ to remove organic solvent, to obtain composite dielectric.

[0012] Preferably, in step S1, the mass ratio of the polyetherimide, barium titanate, boron nitride, and organic solvent in the dielectric mixture is 1.0:1.0~4.0:0.2~0.6:15.0~18.0, more preferably 1.0:3.0:0.4:16.0; and preferably, the organic solvent is N,N-dimethylformamide.

[0013] Preferably, step S1 specifically involves adding barium titanate and boron nitride inorganic fillers to an organic solvent and stirring and dispersing them at a low speed of 180-220 r / min, preferably 200 r / min, for 1.5 h to obtain a filler solution.

[0014] Preferably, in step S1, after adding the polyetherimide matrix to the filler solution at 50°C~70°C, preferably 60°C, the solution is first stirred at 50°C~70°C, preferably 60°C, at a stirring speed of 8~12 r / s, preferably 10 r / s for 0.5-2 min, preferably 1 min, and then heated at 50°C~70°C, preferably 60°C, at a stirring speed of 18~22 r / s, preferably 20 r / s for 25~40 min, preferably 30 min.

[0015] Preferably, in step S2,

[0016] The thin film substrate is a thin film substrate with a conductive layer or a non-conductive thin film substrate; preferably, the thin film substrate with a conductive layer is an ITO-PET flexible conductive film, and more preferably, the dielectric mixture is applied to the side of the thin film substrate with the conductive layer on the side with the conductive layer;

[0017] Alternatively, the thickness of the thin film substrate is 0.120~0.130 mm, more preferably 0.125 mm.

[0018] Preferably, in step S2, the thin film substrate with the dispersed dielectric mixture is left to stand at room temperature for 0.5-2 hours, preferably 1 hour, for pre-curing.

[0019] Preferably, in step S2, the spin coater speed is set to 400-2000 r / s, preferably 1000 r / s, and the spin coating time is 10-30 s, preferably 20 s.

[0020] Preferably, in step S3, the organic solvent is removed by drying at 60°C to 80°C, preferably 70°C, for 20 to 40 hours, preferably 24 hours, to obtain the composite dielectric.

[0021] The positive and progressive effects of this invention are as follows:

[0022] 1) This invention provides a composite dielectric with a mixed single-layer structure based on polyetherimide (PEI) and doped with inorganic fillers barium titanate (BTO) and boron nitride (BN). The resulting composite dielectric has a uniform structure distribution and significantly improved dielectric properties, discharge energy density, and breakdown field strength compared to commercial polyetherimide. It has application prospects in electronic components, electric vehicles, aerospace and other fields. Its excellent high-temperature stability also increases the feasibility of its application in high-temperature environments.

[0023] 2) Currently, the relative permittivity of commercially available polyetherimide (PEI) at 100Hz is about 3.3, and the theoretical discharge energy density is about 1.32J / cm³. The composite dielectric provided by this invention has a relative permittivity of about 38 at 100Hz and a discharge energy density of 2.3J / cm³, which is 76% higher than the initial theoretical value, while having a high energy storage efficiency of 94.5%. Attached Figure Description

[0024] Figure 1 The graph shows the relative permittivity of the PEI monolayer composite dielectric films with different amounts of BTO added, prepared in Examples 1.1-1.5; where the horizontal axis represents frequency in Hz and the vertical axis represents permittivity.

[0025] Figure 2 The surface microstructure of the PEI monolayer composite dielectric film with 15% BTO added prepared in Example 1.4 is shown in the figure.

[0026] Figure 3 Cross-sectional microstructure of the PEI monolayer composite dielectric film with 15% BTO added prepared in Example 1.4;

[0027] Figure 4 The graph shows the polarization electric field intensity of the PEI monolayer composite dielectric film with 15% BTO and 2% BN prepared in Example 2.3; the horizontal axis represents the electric field intensity in MV / m, and the vertical axis represents the polarization intensity in μC / cm. 2 . Detailed Implementation

[0028] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] Examples 1.1-1.5: Preparation of high dielectric composite dielectric films by adding barium titanate (BTO)

[0030] (1) Weigh 7.5-9.5g of organic solvent N,N-dimethylformamide (DMF) and 0-2g of barium titanate (BTO) using an electronic balance, put them into a beaker and disperse them evenly for 1.5h using a magnetic stirrer at a speed of 200r / min to obtain the filler solution.

[0031] (2) Weigh 0.5g of the matrix polyetherimide (PEI) using an electronic balance, then pour the matrix powder into the filler solution prepared in step (1), stir at 10r / s for 1min at 60℃, and then continue to stir vigorously at 20r / s for 30min at 60℃ to obtain a uniformly dispersed dielectric mixture.

[0032] (3) Cut a 2cm*2cm ITO-PET flexible conductive film substrate with a thickness of 0.125mm. First, apply the dielectric mixture prepared in step (2) to the conductive side of the substrate, and then put it into a spin coater and rotate it at a speed of 2000r / s for 20s so that the dielectric mixture is evenly dispersed on the film substrate.

[0033] (4) Take out the thin film substrate and let it stand at room temperature for 30 minutes. Finally, put the film into an oven at 70°C and dry it for 24 hours to remove the organic solvent N,N-dimethylformamide (DMF) and obtain the composite dielectric film.

[0034] Process parameters for BTO / PEI composite dielectric thin films in Examples 1.1-1.5

[0035] process parameters Example 1.1 Example 1.2 Example 1.3 Example 1.4 Example 1.5 BTO content (g) 0 0.5 1.0 1.5 2.0 DMF content (g) 9.5 9.0 8.5 8.0 7.5

[0036] like Figure 1As shown in the figure, the relative permittivity of the composite dielectric films with different BTO additions prepared in Examples 1.1-1.5 is as follows. As can be seen from the figure, Example 1.4, that is, the PEI composite dielectric with 15% BTO added, has the largest relative permittivity at 100Hz, which is about 38, which is several times higher than the relative permittivity of pure PEI (Example 1.1).

[0037] like Figure 2 The image shows the surface microstructure of the PEI monolayer composite dielectric film with 15% BTO added prepared in Example 1.4. It can be observed that the PEI matrix has a regular shape and is evenly distributed, while the scattered BTO fillers are distributed on its skeleton.

[0038] like Figure 3 The image shown is a cross-sectional microstructure of the PEI monolayer composite dielectric film with 15% BTO added prepared in Example 1.4. Delamination can be observed at the cross-section. In other words, the composite monolayer film prepared on a PET substrate using a spin-coating process with PEI as the substrate exhibits relatively consistent delamination and thickness across the entire cross-section, indicating that the prepared film is relatively stable and uniform.

[0039] Examples 2.1-2.4: Preparation of composite electrolyte films with high breakdown field strength by adding boron nitride (BN)

[0040] (1) Weigh 7.7-8.0g of organic solvent N,N-dimethylformamide (DMF), 1.5g of barium titanate (BTO), and 0-0.3g of boron nitride (BN) using an electronic balance, place them in a beaker, and then disperse them evenly for 1.5h using a magnetic stirrer at a speed of 200r / min.

[0041] (2) The remaining steps are the same as steps (2)(3)(4) in Examples 1.1-1.5. Of course, when spin-coating the dielectric mixture, a non-conductive thin film substrate needs to be selected for coating.

[0042] Process parameters for BN / 15%BTO / PEI composite dielectric thin films in Examples 2.1-2.4

[0043] process parameters Example 2.1 Example 2.2 Example 2.3 Example 2.4 BN content (g) 0 0.1 0.2 0.3 DMF content (g) 8.0 7.9 7.8 7.7

[0044] And such Figure 4 As shown, the polarization electric field strength curve of the PEI monolayer composite dielectric film with 15% BTO and 2% BN prepared in Example 2.3 at room temperature at 10 Hz is reflected. The measured breakdown field strength is 40.3 MV / m.

[0045] As shown in Table 1 below, the breakdown field strength of the single-layer composite dielectric film prepared in Example 2.3 is 48% higher than that of pure PEI (Example 2.1) under the same conditions, and it also has better energy storage performance.

[0046] Table 1. Comparison of dielectric properties in Examples 2.1-2.4

[0047] performance Example 2.1 Example 2.2 Example 2.3 Example 2.4 Relative permittivity (at 100Hz) 38.72 36.18 38.21 38.03 Breakthrough field strength (MV / m) 27.26831 27.54953 40.32405 9.81591 Energy storage density (J / cm3) 1.01968 0.97518 2.33341 0.13254 Energy storage efficiency (%) 95.75394 94.98112 94.50036 87.85018

[0048] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. Those skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention shall be defined by the appended claims.

Claims

1. A composite dielectric based on polyetherimide, characterized in that, The composite dielectric comprises a polyetherimide matrix and an inorganic filler, wherein the inorganic filler comprises barium titanate and boron nitride.

2. The composite dielectric as described in claim 1, characterized in that, The mass ratio of the polyetherimide, barium titanate, and boron nitride is 1.0:1.0~4.0:0.2~0.6, preferably 1.0:3.0:0.

4.

3. A method for preparing the composite dielectric according to claim 1 or 2, characterized in that, The method includes: Step S1: Add barium titanate and boron nitride inorganic fillers to an organic solvent and stir to disperse them to obtain a filler solution. Then, add polyetherimide matrix to the filler solution at 50℃~70℃ and stir at 50℃~70℃ to obtain a dielectric mixture. Step S2: First, apply the dielectric mixture onto the thin film substrate, then rotate the thin film substrate to evenly disperse the dielectric mixture, and then let the thin film substrate with the dispersed dielectric mixture stand at room temperature for pre-curing. Step S3, then dry at 60℃~80℃ to remove organic solvent, to obtain composite dielectric.

4. The method as described in claim 3, characterized in that, In step S1, the mass ratio of the polyetherimide, barium titanate, boron nitride, and organic solvent in the dielectric mixture is 1.0:1.0~4.0:0.2~0.6:15.0~18.0, preferably 1.0:3.0:0.4:16.0; preferably, the organic solvent is N,N-dimethylformamide.

5. The method as described in claim 3, characterized in that, Step S1 specifically involves adding barium titanate and boron nitride inorganic fillers to an organic solvent and stirring and dispersing them at a low speed of 180-220 r / min, preferably 200 r / min, for 1.5 h to obtain a filler solution.

6. The method as described in claim 3, characterized in that, In step S1, after adding the polyetherimide matrix to the filler solution at 50℃~70℃, preferably 60℃, the solution is first stirred at 50℃~70℃, preferably 60℃, at a stirring speed of 8~12r / s, preferably 10r / s for 0.5-2min, preferably 1min, and then heated at 50℃~70℃, preferably 60℃, at a stirring speed of 18~22r / s, preferably 20r / s for 25~40min, preferably 30min.

7. The method as described in claim 3, characterized in that, In step S2, The thin film substrate is a thin film substrate with a conductive layer or a non-conductive thin film substrate; preferably, the thin film substrate with a conductive layer is an ITO-PET flexible conductive film, and more preferably, the dielectric mixture is applied to the side of the thin film substrate with the conductive layer on the side with the conductive layer; Alternatively, the thickness of the thin film substrate is 0.120~0.130 mm, more preferably 0.125 mm.

8. The method as described in claim 3, characterized in that, In step S2, the thin film substrate containing the dispersed dielectric mixture is left to stand at room temperature for 0.5-2 hours, preferably 1 hour, for pre-curing.

9. The method as described in claim 3, characterized in that, In step S2, the spin coater speed is set to 400-2000 r / s, preferably 1000 r / s, and the spin coating time is 10-30 s, preferably 20 s.

10. The method as described in claim 3, characterized in that, In step S3, the organic solvent is removed by drying at 60℃~80℃, preferably 70℃, for 20~40h, preferably 24h, to obtain the composite dielectric.

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