A method for preparing a modified polyetherimide-based composite dielectric film

Abstract

A method for preparing a modified polyetherimide-based composite dielectric film, comprising the following steps: step 1, preparing a tannic acid solution, preparing a zinc sulfate heptahydrate solution, and preparing a silicon dioxide dispersion; step 2, preparing a zinc sulfate-silicon dioxide mixed solution, and preparing a core-shell structure filler TA-Zn II @SiO2; Step 3, prepare diamine dispersion; core-shell structure filler TA-Zn II @SiO2 filler is added to the diamine dispersion; step 4, bisphenol A diether dianhydride is added to the diamine dispersion to obtain a polyamic acid colloid; step 5, vacuum-bubbling the polyamic acid colloid, uniformly coating the polyamic acid colloid on a glass plate, removing the solvent in the film in a high-temperature oven, keeping the temperature, and obtaining a modified polyetherimide-based composite dielectric film after cooling; solving the interface mismatch problem between the SiO2 filler and the polyetherimide matrix, significantly reducing the aggregation of carriers at the interface, improving the breakdown strength of the composite dielectric, and effectively enhancing the energy storage performance of the polyetherimide-based dielectric.

Description

Technical Field

[0001] The present invention belongs to the technical field of dielectric energy storage, and in particular relates to a method for preparing a modified polyetherimide-based composite dielectric film. Background Art

[0002] Dielectric capacitors have the characteristics of high power density, low-cost manufacturing, fast charging and discharging, and safety and environmental protection. They are in huge demand in industries such as high-voltage flexible direct current transmission and new energy vehicles. The polymer film capacitors widely used in the current market use biaxially oriented polypropylene (BOPP). However, the operating temperature of BOPP film is relatively low. When the temperature exceeds 105°C, its dielectric loss will increase sharply, resulting in a rapid decrease in charging and discharging efficiency, which cannot meet the performance requirements of electronic equipment in high-temperature environments. In order to ensure its stable operation at high temperatures, an additional cooling system is usually required to maintain the operating temperature of BOPP, which not only increases production costs but also leads to an increase in the size of the equipment. Therefore, it is necessary to develop high-temperature dielectric materials with good thermal stability and excellent energy storage performance at high temperatures.

[0003] Polyetherimide (PEI) is considered a promising high-temperature dielectric material due to its high breakdown strength, excellent heat resistance, simple synthesis process, and easily tunable molecular structure. Through structural design from the microscopic to the mesoscopic level, the introduction of hydroxyl-surface-modified SiO2 nanoparticles improves the dielectric and energy storage properties of the PEI matrix. However, the interfacial mismatch between the nanofiller and the polymer matrix leads to carrier accumulation at the filler-matrix interface, reducing the breakdown field strength and reliability of the composite. Summary of the Invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the object of the present invention is to provide a method for preparing a modified polyetherimide-based composite dielectric film having high energy storage performance.

[0005] To achieve the above object, the present invention adopts the following scheme:

[0006] A method for preparing a modified polyetherimide-based composite dielectric film comprises the following steps:

[0007] Step 1: dissolving 0.02-0.06 g of tannic acid in 25-75 mL of deionized water to prepare a tannic acid solution, dissolving 0.005-0.015 g of zinc sulfate heptahydrate in 25-75 mL of deionized water to prepare a zinc sulfate heptahydrate solution, and dissolving 0.05-0.15 g of hydroxyl-modified silica nanoparticles in 50-150 mL of deionized water to prepare a silica dispersion;

[0008] Step 2: Pour the zinc sulfate heptahydrate solution into the silica dispersion prepared in step 1 and mix evenly to obtain a zinc sulfate silica mixture. Then, add the tannic acid solution into the zinc sulfate silica mixture and mix evenly. Centrifuge and wash the mixture at 12000 rpm for several times, and freeze-dry to prepare a core-shell structure filler TA-Zn. II @SiO2;

[0009] Step 3: 1.5-4.5 g of 4,4'-diaminodiphenyl ether required for polyetherimide is dissolved in 18.3-54.9 mL of N-methyl-2-pyrrolidone solvent to obtain a diamine dispersion; then the core-shell structure filler TA-Zn II Add SiO2 filler into diamine dispersion and stir evenly;

[0010] Step 4, weighing 4.019-12.057 g of bisphenol A diether dianhydride, and adding it to the diamine dispersion in 6 portions to obtain a polyamic acid colloid;

[0011] Step 5: Vacuum the polyamic acid colloid, then evenly coat the polyamic acid colloid on a glass plate with a scraper, and then place it in a high-temperature oven to remove the solvent in the film, keep it warm at 150°C for 1 hour, keep it warm at 200°C for 1 hour, keep it warm at 250°C for 1 hour, and keep it warm at 300°C for 1 hour. After natural cooling, a modified polyetherimide-based composite dielectric film is obtained.

[0012] In the step 1, the concentration of the tannic acid solution is 0.0004-0.0012 mol / L, and the concentration of the zinc sulfate heptahydrate solution is 0.0012-0.0036 mol / L.

[0013] In the step 2, when the tannic acid solution is mixed with the zinc sulfate-silicon dioxide mixture, it is necessary to perform the mixing under ultrasonic conditions, and the ultrasonic time is 8-10s.

[0014] In the step 3, 4,4'-diaminodiphenyl ether is dispersed in the N-methyl-2-pyrrolidone solvent by ultrasonication for 5-15 minutes.

[0015] In step 3, the core-shell structure filler TA-Zn is added II The mass of the SiO2 filler is 0.1%-0.5% of the total mass of 4,4'-diaminodiphenyl ether and bisphenol A diether dianhydride.

[0016] In the step 4, the amounts of bisphenol A diether dianhydride added to the diamine dispersion are 2-6 g, 1-3 g, 0.5-1.5 g, 0.3-0.9 g, 0.1-0.3 g, and 0.119-0.357 g six times, and the stirring time after each addition is 10-20 min, 10-20 min, 10-20 min, 10-20 min, 20-40 min, and 60-120 min, respectively.

[0017] In the step 4, during the addition of bisphenol A diether dianhydride, mechanical stirring is maintained at a low temperature of 0-10° C. and a speed of 3000 rpm.

[0018] In step 5, the temperature and time for removing the solvent from the film are 80-90° C. and 12-18 hours, respectively.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention aims to enhance the energy storage performance of PEI-based composite dielectric films, addressing existing issues with polymer matrices, such as low dielectric constant and high dielectric loss at high temperatures. To alleviate the interfacial mismatch between the nanofiller and the polymer matrix, the invention innovatively employs a tannic acid metal-organic framework as a buffer shell to reduce interfacial incompatibility between the matrix and filler, thereby enhancing the composite's energy storage performance.

[0021] The present invention applies core-shell structure fillers to polyetherimide to obtain a modified polyetherimide-based composite dielectric film with excellent energy storage performance. To address the problems of insufficient dielectric constant of the polymer matrix and insulation failure caused by charge accumulation, the polyetherimide-based dielectric is carefully designed from microscopic to mesoscopic perspectives, and its dielectric properties and high-temperature energy storage capacity are deeply studied. The core of the present invention is to prepare a special core-shell structure filler, that is, on the surface of hydroxyl-modified silica (SiO2) nanoparticles, a tannic acid organic metal framework (TA-Zn) is successfully coated. II ); This TA-Zn II The introduction of @SiO2 core-shell structure filler not only solves the interface mismatch problem between SiO2 filler and polyetherimide matrix, but also significantly reduces the aggregation of carriers at the interface; this series of improvements significantly improves the breakdown strength of the composite medium, thereby effectively enhancing the energy storage performance of polyetherimide-based dielectrics.

[0022] Preparation of core-shell TA-Zn nanoparticles by coating tannic acid metal-organic frameworks on the surface of hydroxyl-modified silica nanoparticles II @SiO2 filler, followed by TA-Zn IIThe introduction of SiO2 filler into the polyetherimide matrix and the introduction of tannic acid metal organic framework alleviated the interface mismatch problem between SiO2 filler and matrix, reduced the aggregation of carriers at the interface, improved the breakdown performance of the composite dielectric, and ultimately effectively improved the energy storage performance of the polyetherimide-based dielectric. II The discharge energy density of the @SiO2 / PEI composite film at 25°C and 150°C was 5.9 J / cm³ and 4.6 J / cm³, respectively, and the energy storage efficiency remained at 85.6% and 83.4%. Compared with pure PEI, the energy storage efficiency increased by 75.1% and 154%, respectively. This proves that the energy storage performance of polymer dielectrics can be improved through interface structure design strategies, providing a new reference direction for the research of energy storage dielectrics. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 TA-Zn II @SiO2 filler preparation flow chart.

[0024] Figure 2 TA-Zn II @Flowchart for preparation of SiO2 / PEI composite film.

[0025] Figure 3 TA-Zn prepared in Example 1, Example 2, Example 3 and Comparative Example 1 II @Weibull distribution of breakdown field strength of SiO2 / PEI composite film and PEI film at 25℃ and 150℃.

[0026] Figure 4 TA-Zn prepared in Example 1, Example 2, Example 3 and Comparative Example 1 II @Energy storage density and energy storage efficiency diagram of SiO2 / PEI composite film and PEI film at 25℃ and 150℃. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Example 1

[0028] A method for preparing a modified polyetherimide-based composite dielectric film comprises the following steps:

[0029] Step 1: dissolving 0.02 g of tannic acid in 25 mL of deionized water to prepare a tannic acid solution, dissolving 0.005 g of zinc sulfate heptahydrate in 25 mL of deionized water to prepare a zinc sulfate solution, and dissolving 0.05 g of hydroxyl-modified silica nanoparticles in 50 mL of deionized water to prepare a silica dispersion;

[0030] The concentration of the tannic acid solution was 0.0004 mol / L, and the concentration of the zinc sulfate heptahydrate solution was 0.0012 mol / L;

[0031] Step 2: Pour the zinc sulfate solution into the silica dispersion and mix evenly to obtain a zinc sulfate silica mixture. Then, add the tannic acid solution into the mixture and mix evenly. The mixing needs to be carried out under ultrasonic conditions, and the ultrasonic time is 8s. The mixture is centrifuged and washed multiple times at a speed of 12000 rpm, and freeze-dried to prepare the core-shell structure filler TA-Zn II @SiO2;

[0032] Step 3: 1.5 g of 4,4'-diaminodiphenyl ether required for polyetherimide was dissolved in 18.3 mL of N-methyl-2-pyrrolidone solvent and ultrasonicated for 5 min to obtain a diamine dispersion; then TA-Zn II @SiO2 filler is added to the diamine dispersion and stirred evenly, and the added TA-Zn II The mass of SiO2 filler is 0.1% of the total mass of 4,4'-diaminodiphenyl ether and bisphenol A diether dianhydride;

[0033] Step 4, weighing 4.019 g of bisphenol A diether dianhydride, adding it to the diamine dispersion in 6 times, maintaining the low temperature of 0° C. and mechanically stirring at a speed of 3000 rpm; the addition amounts were 2 g, 1 g, 0.5 g, 0.3 g, 0.1 g, and 0.119 g, respectively, and the stirring time after each addition was 10 min, 10 min, 10 min, 10 min, 20 min, and 60 min, respectively, to obtain a polyamic acid colloid;

[0034] Step 5: Vacuum the polyamic acid colloid, then evenly coat the polyamic acid colloid on a glass plate with a scraper, and then place it in a high-temperature oven at 80°C to remove the solvent in the film for 12 hours, keep it warm at 150°C for 1 hour, keep it warm at 200°C for 1 hour, keep it warm at 250°C for 1 hour, and keep it warm at 300°C for 1 hour. After natural cooling, a modified polyetherimide-based composite dielectric film is obtained.

[0035] Figure 1 Example 1TA-Zn II @SiO2 filler preparation flow chart.

[0036] Figure 2 Example 1TA-Zn II @Flowchart for preparation of SiO2 / PEI composite film. Example 2

[0037] A method for preparing a modified polyetherimide-based composite dielectric film comprises the following steps:

[0038] Step 1: 0.04 g of tannic acid was dissolved in 50 mL of deionized water to prepare a tannic acid solution, 0.01 g of zinc sulfate heptahydrate was dissolved in 50 mL of deionized water to prepare a zinc sulfate solution, and 0.1 g of hydroxyl-modified silica nanoparticles was dissolved in 100 mL of deionized water to prepare a silica dispersion.

[0039] The concentration of the tannic acid solution was 0.0008 mol / L, and the concentration of the zinc sulfate heptahydrate solution was 0.0024 mol / L;

[0040] Step 2: Pour the zinc sulfate solution into the silica dispersion and mix evenly to obtain a zinc sulfate silica mixture. Then, add the tannic acid solution into the mixture and mix evenly. The mixing needs to be carried out under ultrasonic conditions, and the ultrasonic time is 9s. The mixture is centrifuged and washed multiple times at a speed of 12000 rpm, and freeze-dried to prepare the core-shell structure filler TA-Zn II @SiO2;

[0041] Step 3: 3 g of 4,4'-diaminodiphenyl ether required for polyetherimide was dissolved in 36.6 mL of N-methyl-2-pyrrolidone solvent and ultrasonicated for 10 min to obtain a diamine dispersion; then TA-Zn II @SiO2 filler is added to the diamine dispersion and stirred evenly, and the added TA-Zn II The mass of the SiO2 filler is 0.3% of the total mass of 4,4'-diaminodiphenyl ether and bisphenol A diether dianhydride.

[0042] Step 4, weighing 8.038 g of bisphenol A diether dianhydride, adding it to the diamine dispersion in 6 times, maintaining a low temperature of 5° C. and mechanically stirring at a speed of 3000 rpm; the added amounts were 4 g, 2 g, 1 g, 0.6 g, 0.2 g, and 0.238 g, and the stirring time after each addition was 15 min, 15 min, 15 min, 15 min, 30 min, and 90 min, respectively, to obtain a polyamic acid colloid;

[0043] Step 5: Vacuum the polyamic acid colloid, then evenly coat the polyamic acid colloid on a glass plate with a scraper, and then place it in a high-temperature oven at 85°C to remove the solvent in the film for 16 hours, keep it warm at 150°C for 1 hour, keep it warm at 200°C for 1 hour, keep it warm at 250°C for 1 hour, and keep it warm at 300°C for 1 hour. After natural cooling, a modified polyetherimide-based composite dielectric film is obtained. Example 3

[0044] A method for preparing a modified polyetherimide-based composite dielectric film comprises the following steps:

[0045] Step 1: 0.06 g of tannic acid was dissolved in 75 mL of deionized water to prepare a tannic acid solution, 0.015 g of zinc sulfate heptahydrate was dissolved in 75 mL of deionized water to prepare a zinc sulfate solution, and 0.15 g of hydroxyl-modified silica nanoparticles was dissolved in 150 mL of deionized water to prepare a silica dispersion.

[0046] The concentration of the tannic acid solution was 0.0012 mol / L, and the concentration of the zinc sulfate heptahydrate solution was 0.0036 mol / L;

[0047] Step 2: Pour the zinc sulfate solution into the silica dispersion and mix evenly to obtain a zinc sulfate silica mixture. Then, add the tannic acid solution into the mixture and mix evenly. The mixing needs to be carried out under ultrasonic conditions, and the ultrasonic time is 10s. The mixture is centrifuged and washed multiple times at a speed of 12000 rpm, and freeze-dried to prepare a core-shell structure filler TA-Zn. II @SiO2;

[0048] Step 3: 4.5 g of 4,4'-diaminodiphenyl ether required for polyetherimide was dissolved in 54.9 mL of N-methyl-2-pyrrolidone solvent and ultrasonicated for 15 min to obtain a diamine dispersion; then TA-Zn II @SiO2 filler is added to the diamine dispersion and stirred evenly, and the added TA-Zn II The mass of SiO2 filler is 0.5% of the total mass of 4,4'-diaminodiphenyl ether and bisphenol A diether dianhydride;

[0049] Step 4, weighing 12.057 g of bisphenol A diether dianhydride, adding it to the diamine dispersion in 6 times, maintaining a low temperature of 10° C. and mechanically stirring at 3000 rpm; the added amounts were 6 g, 3 g, 1.5 g, 0.9 g, 0.3 g, and 0.357 g, respectively, and the stirring time after each addition was 20 min, 20 min, 20 min, 20 min, 40 min, and 120 min, respectively, to obtain a polyamic acid colloid;

[0050] Step 5: Vacuum the polyamic acid colloid, then evenly coat the polyamic acid colloid on a glass plate with a scraper, and then place it in a high-temperature oven at 90°C to remove the solvent in the film for 18 hours, keep it warm at 150°C for 1 hour, keep it warm at 200°C for 1 hour, keep it warm at 250°C for 1 hour, and keep it warm at 300°C for 1 hour. After natural cooling, a modified polyetherimide-based composite dielectric film is obtained.

[0051] Comparative Example 1

[0052] No core-shell filler TA-Zn is added during the synthesis of polyetherimide II @SiO 2，Prepare pure polyetherimide comparison sample, the specific steps are as follows:

[0053] Step 1: dissolve 1.5 g of 4,4'-diaminodiphenyl ether in 18.3 mL of N-methyl-2-pyrrolidone solvent and sonicate for 5 minutes to obtain a diamine dispersion;

[0054] Step 2, weighing 4.019 g of bisphenol A diether dianhydride, adding it to the diamine dispersion in 6 times, and maintaining mechanical stirring at a low temperature of 3000 rpm; the addition amounts were 2 g, 1 g, 0.5 g, 0.3 g, 0.1 g, and 0.119 g, respectively, and the stirring time after each addition was 10 min, 10 min, 10 min, 10 min, 20 min, and 60 min, respectively, to obtain a polyamic acid colloid;

[0055] Step 3: vacuum-bubble the polyamic acid colloid, then evenly coat the polyamic acid colloid on a glass plate with a scraper, and then place it in a high-temperature oven at 80°C to remove the solvent in the film for 12 hours, keep it warm at 150°C for 1 hour, keep it warm at 200°C for 1 hour, keep it warm at 250°C for 1 hour, and keep it warm at 300°C for 1 hour, and then cool it naturally to obtain a polyetherimide film.

[0056] Figure 3 TA-Zn prepared in Example 1, Example 2, Example 3 and Comparative Example 1 II @ Weibull distribution of breakdown field strength of SiO2 / PEI composite film and PEI film at 25℃ and 150℃. II After adding SiO2 filler, the breakdown field strength of the composite film is significantly improved compared to pure PEI film at both room temperature and high temperature. Because the SiO2 core layer has high insulation properties and a wide bandgap, and the core-shell structure's layer-by-layer dielectric constant buffering method avoids stress concentration in the material, the design of the SiO2 core layer can effectively improve the breakdown field strength of the composite material. At both 25°C and 150°C, the composite film with the highest breakdown field strength is the 0.3% component, with breakdown field strengths of 619kV / mm and 599kV / mm at room temperature and high temperature, respectively. Compared to the pure PEI film's 507kV / mm at room temperature and 505kV / mm at high temperature, these breakdown field strengths are increased by 22.1% and 18.6%, respectively.

[0057] Figure 4 TA-Zn prepared in Example 1, Example 2, Example 3 and Comparative Example 1 II @ Energy storage density and energy storage efficiency of SiO2 / PEI composite film and PEI film at 25℃ and 150℃. As shown in the figure, when the doping amount is 0.3%, TA-Zn II@SiO2 / PEI composite film has an electric field strength of 5.9J / cm at an electric field strength of 600kV / mm 3 The energy storage density is 100 J / cm2, while its efficiency is maintained at 85.6%, which is 3.37 J / cm2 higher than that of pure PEI film. 3 75.1% higher. Although the 0.1% composite film has 6.2J / cm 3 The energy storage density of the composite film is 3.2 J / cm2 at an electric field strength of 420 kV / mm. 3 The energy storage density of the composite film was 0.3 wt%, and the energy storage efficiency was increased to 87.3%. This result shows that a higher doping content is not conducive to improving the energy storage density of the polymer dielectric. At a high temperature of 150 ° C, the component with the best energy storage performance of the composite film is still 0.3 wt%, which has an energy storage capacity of 4.8 J / cm at an electric field strength of 620 kV / mm. 3 The energy storage density decreased, and the energy storage efficiency dropped to 81.8%. This shows that the energy storage density and energy storage efficiency of polymer dielectrics will decrease with increasing temperature, but the presence of the SiO2 core layer and the tannic acid metal organic framework shell layer improves the energy storage performance of polymer dielectrics.

Claims

1. A method for preparing a modified polyetherimide-based composite dielectric film, characterized in that: The following steps are involved: Step 1: dissolving 0.02-0.06 g of tannic acid in 25-75 mL of deionized water to prepare a tannic acid solution, dissolving 0.005-0.015 g of zinc sulfate heptahydrate in 25-75 mL of deionized water to prepare a zinc sulfate heptahydrate solution, and dissolving 0.05-0.15 g of hydroxyl-modified silica nanoparticles in 50-150 mL of deionized water to prepare a silica dispersion; Step 2: Pour the zinc sulfate solution into the silica dispersion prepared in step 1 and mix evenly to obtain a zinc sulfate silica mixture. Then, add the tannic acid solution into the zinc sulfate silica mixture and mix evenly. Centrifuge and wash the mixture several times at 12000 rpm and freeze-dry to prepare a core-shell structure filler TA-Zn. II @SiO2; Step 3, dissolve 1.5-4.5g of 4,4'-diaminodiphenyl ether in 18.3-54.9mL of N-methyl-2-pyrrolidone solvent to obtain a diamine dispersion; then add the core-shell structure filler TA-Zn II Add SiO2 to the diamine dispersion and stir evenly; Step 4, weighing 4.019-12.057 g of bisphenol A diether dianhydride, and adding it to the diamine dispersion in 6 portions to obtain a polyamic acid colloid; Step 5: Vacuum the polyamic acid colloid to remove bubbles, then use a scraper to evenly coat the polyamic acid colloid on a glass plate, and then place it in a high-temperature oven to remove the solvent in the film, keep it warm at 150°C for 1 hour, keep it warm at 200°C for 1 hour, keep it warm at 250°C for 1 hour, and keep it warm at 300°C for 1 hour. After natural cooling, a modified polyetherimide-based composite dielectric film is obtained.

2. The method for preparing a modified polyetherimide-based composite dielectric film according to claim 1, characterized in that: In the step 1, the concentration of the tannic acid solution is 0.0004-0.0012 mol / L, and the concentration of the zinc sulfate heptahydrate solution is 0.0012-0.0036 mol / L.

3. The method for preparing a modified polyetherimide-based composite dielectric film according to claim 1, characterized in that: In step 2, the tannic acid solution and the zinc sulfate-silica mixture are mixed under ultrasonic conditions for 8-10 seconds.

4. The method for preparing a modified polyetherimide-based composite dielectric film according to claim 1, characterized in that: In the step 3, 4,4'-diaminodiphenyl ether is dispersed in the N-methyl-2-pyrrolidone solvent by ultrasonication for 5-15 minutes.

5. The method for preparing a modified polyetherimide-based composite dielectric film according to claim 1, characterized in that: In step 3, the core-shell filler TA-Zn is added II The mass of @SiO2 is 0.1%-0.5% of the total mass of 4,4'-diaminodiphenyl ether and bisphenol A diether dianhydride.

6. The method for preparing a modified polyetherimide-based composite dielectric film according to claim 1, characterized in that: In the step 4, bisphenol A diether dianhydride is added to the diamine dispersion, and the addition amounts for 6 times are 2-6 g, 1-3 g, 0.5-1.5 g, 0.3-0.9 g, 0.1-0.3 g, and 0.119-0.357 g, respectively. The stirring time after each addition is 10-20 min, 10-20 min, 10-20 min, 10-20 min, 20-40 min, and 60-120 min, respectively.

7. The method for preparing a modified polyetherimide-based composite dielectric film according to claim 1, characterized in that: In the step 4, during the addition of bisphenol A diether dianhydride, the temperature is kept at 0-10° C. and the stirring speed is mechanically controlled at 3000 rpm.

8. The method for preparing a modified polyetherimide-based composite dielectric film according to claim 1, characterized in that: In step 5, the temperature and time for removing the solvent from the film are 80-90° C. and 12-18 h, respectively.

Images