Highly-insulating all-organic composite dielectric material, and preparation method therefor and use thereof

Abstract

The present invention belongs to the technical field of dielectric capacitors. Disclosed are a highly-insulating all-organic composite dielectric material, and a preparation method therefor and the use thereof. In the present invention, polyvinylidene fluoride (PVDF) is taken as a substrate, and is first treated with KOH to remove hydrogen fluoride and then treated with H2SO4 to achieve hydroxylation, thereby preparing a molecularly-modified hydroxyl-functionalized PVDF dielectric film by means of the two-step treatment method; and by means of a hydrogen bond formed between hydroxyl and fluorine, the dielectric loss of the dielectric film is reduced, and the insulation performance of the dielectric film is improved. Specifically, the film has relatively high insulating strength (-617.18 MV / m) and relatively low dielectric loss, indicating that the film can stably operate under high electric field intensity. In addition, the preparation process provided by the present invention is simple in terms of flow, is environmentally friendly and pollution-free, and can be promoted and implemented.

Description

A high-insulation all-organic composite dielectric material and its preparation method and application Technical Field

[0001] The invention relates to a high-insulation all-organic composite dielectric material and a preparation method and application thereof, belonging to the technical field of dielectric capacitors. Background Art

[0002] Dielectric capacitors, due to their unique advantages of high power density, are widely used in fast-charging and discharging applications such as high-power pulse power supplies, hybrid vehicles, and electromagnetic weapons. Polymer capacitors, in particular, have attracted widespread attention due to their ease of processing, excellent stability, high breakdown strength, and wide capacitance range. As the application of polymer capacitors expands, the requirements for dielectric breakdown performance are becoming increasingly stringent. This necessitates the development of a series of polymer capacitors with high dielectric breakdown performance.

[0003] Polyvinylidene fluoride (PVDF), a common functional material, possesses high mechanical properties and dielectric constant, but its low withstand voltage limits its application. To improve the breakdown performance of polymers, doping with fillers with wide band gaps is a common approach. However, the complex doping process and unstable behavior severely restrict the development of dielectric capacitors. Modifying the polymer molecular chain can effectively circumvent these problems. Therefore, it is essential to provide a highly insulating, all-organic composite dielectric material based on molecular modification.

[0004] Summary of the Invention

[0005] In order to solve the problem of poor withstand voltage performance of existing film capacitors, the present invention provides a high-insulation all-organic composite dielectric material and a preparation method and application thereof.

[0006] The technical solution of the present invention:

[0007] One of the purposes of the present invention is to provide a method for preparing a high-insulation all-organic composite dielectric material, the method comprising the following steps:

[0008] (1) Defluorination of PVDF using alkali;

[0009] (2) A hydroxylation treatment is performed using an acid to obtain a molecularly modified hydroxyl-functionalized PVDF dielectric material.

[0010] Further defined, (1) specifically comprises: adding PVDF powder to an alkaline solution, magnetically stirring, ultrasonically treating with methanol, and then repeatedly centrifuging and washing until the pH value is 7.1 to 7.6, and then drying, grinding and sieving in sequence.

[0011] It is further defined that the alkaline solution is a KOH solution with a concentration of 5 to 7 wt %; and the volume mass ratio of the KOH solution to the PVDF is 10 mL:1 g.

[0012] Further defined, (2) specifically comprises: adding the PVDF powder after alkaline treatment to an acid solution, heating at 80°C for 12 hours, ultrasonically treating with methanol, and then repeatedly centrifuging and washing until the pH value reaches 7.1 to 7.6.

[0013] It is further defined that the acid solution is concentrated sulfuric acid with a concentration of 98 wt %; the volume mass ratio of concentrated sulfuric acid to PVDF powder after alkaline treatment is 10 mL:2 g.

[0014] It is further defined that the ultrasonic treatment time is 25 to 35 minutes, the centrifugal washing speed is 600 to 800 r / min, and the time is 5 to 8 minutes.

[0015] A second object of the present invention is to provide a high-insulation all-organic composite dielectric material obtained by the above preparation method.

[0016] A third object of the present invention is to provide an application of the above-mentioned high-insulation all-organic composite dielectric material for preparing a high-insulation all-organic composite dielectric film.

[0017] It is further defined that the preparation method of the high-insulation all-organic composite dielectric film is: dissolving the high-insulation all-organic composite dielectric material in N,N-dimethylacetamide to obtain a casting glue, vacuum degassing treatment, scraping and coating it on a glass plate to form a film, irradiating it with an infrared radiation lamp, and then drying, peeling and drying to obtain a high-insulation all-organic composite dielectric film.

[0018] A fourth object of the present invention is to provide an application of the above-mentioned high-insulation all-organic composite dielectric film, specifically for the preparation of dielectric capacitors. Beneficial effects:

[0019] The present invention is based on polyvinylidene fluoride (PVDF), first carries out alkali treatment to remove fluorine (-F), then carries out acid treatment to achieve the purpose of further hydroxylation (-OH), and finally realizes the defluorination hydroxyl treatment of PVDF, utilizes hydroxyl group and residual fluorine to form hydrogen bond, makes the mechanical properties and Young's modulus of medium be enhanced, and breakdown strength is effectively improved. At the same time, the hydrogen bond formed in the defluorination hydroxyl process can limit dipole steering, thereby reducing dielectric constant and dielectric loss. And hydrogen bond can effectively hinder the movement of carriers inside polymer, improve the resistance of medium, reduce conductivity. Compared with the prior art, the present invention also has the following advantages:

[0020] (1) After the present invention defluorinates hydroxyl groups in PVDF, the relative intensity of the weakly polar α phase in PVDF gradually decreases, while the relative intensity of the corresponding polar β phase gradually increases, significantly reducing dielectric loss and improving insulation performance. The material exhibits low dielectric loss under high electric fields and good insulation performance, enabling stable operation under high electric fields.

[0021] (2) The all-organic composite medium prepared by the molecular modification method provided by the present invention has excellent insulation and energy storage properties, and the film quality is uniform and stable. The synthetic process involved is simple, environmentally friendly and pollution-free, and the equipment is low-cost, suitable for large-scale production, and has very broad research value and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a comparison of X-ray diffraction patterns of high-insulation all-organic composite dielectric films prepared in different embodiments;

[0023] FIG2 is a comparison of infrared spectra of high-insulation all-organic composite dielectric films prepared in different embodiments;

[0024] FIG3 is a Weibull distribution diagram of the breakdown field strength of high-insulation all-organic composite dielectric films prepared in different embodiments;

[0025] FIG4 is a comparison diagram of the dielectric properties of high-insulation all-organic composite dielectric films prepared in different embodiments. DETAILED DESCRIPTION

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0027] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0028] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0029] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0030] Example 1:

[0031] Step 1: Magnetic stirring of PVDF powder in a 6% KOH solution (ratio of KOH solution to PVDF powder: 10 ml: 1 g) was performed for 30 minutes. The mixture was ultrasonicated and centrifuged seven times using methanol for 330 minutes at a centrifuge speed of 600 rpm for 6 minutes. The pH value was measured to be 7.3. The PVDF powder was then dried, ground, and filtered through a sieve.

[0032] Step 2: The PVDF powder treated with alkaline conditions in Step 1 was subjected to acidic conditions. The PVDF was added to 98% concentrated sulfuric acid at a ratio of 10 ml of concentrated sulfuric acid to 2 g of PVDF and heated at 80°C for 12 hours. Seven cycles of sonication and centrifugation were performed using methanol for 30 minutes at a centrifuge speed of 800 rpm for 6 minutes. The pH value was measured at 7.3. The powder was then dried, ground, and filtered through a sieve.

[0033] Step 3: The treated PVDF is dissolved in N,N-dimethylacetamide to obtain a casting glue, vacuum degassing treatment, and film coating is performed on a glass plate. The film is irradiated with infrared light. After the coating is completed, the infrared radiation lamp power is 1000W for 10 seconds. After drying, peeling and drying, a high-insulation all-organic flexible composite dielectric is obtained, which is named "30-minute alkaline treatment".

[0034] Example 2:

[0035] The difference between this embodiment and embodiment 1 is that the PVDF powder is magnetically stirred in the KOH solution for 60 minutes, and the rest of the operation process and parameter settings are the same as those in embodiment 1, and are named "60-minute alkaline treatment".

[0036] The specific operation process is as follows:

[0037] Step 1: Magnetic stirring of PVDF powder in a 6% KOH solution (ratio of KOH solution to PVDF powder: 10 ml: 1 g) was performed for 30 minutes. The mixture was ultrasonicated and centrifuged seven times using methanol for 30 minutes at 600 rpm for 6 minutes. The pH value was measured to be 7.3. The PVDF powder was then dried, ground, and filtered through a sieve.

[0038] Step 2: The PVDF powder treated with alkaline conditions in Step 1 was subjected to acidic conditions. The PVDF was added to 98% concentrated sulfuric acid at a ratio of 10 ml of concentrated sulfuric acid to 2 g of PVDF and heated at 80°C for 12 hours. Six cycles of sonication and centrifugation were performed using methanol for 30 minutes at a centrifuge speed of 800 rpm for 6 minutes. The pH value was measured at 7.3. The powder was then dried, ground, and filtered through a sieve.

[0039] Step 3: The treated PVDF is dissolved in N,N-dimethylacetamide to obtain a casting glue, vacuum degassing treatment, and film coating is performed on a glass plate. The film is irradiated with infrared light. After the coating is completed, the infrared radiation lamp power is 1000W for 6 seconds. After drying, peeling and drying, a high-insulation all-organic flexible composite dielectric is obtained, which is named "60-minute alkaline treatment".

[0040] Example 3:

[0041] The difference between this embodiment and embodiment 1 is that the PVDF powder is magnetically stirred in the KOH solution for 90 minutes, and the rest of the operation process and parameter settings are the same as those in embodiment 1, and are named "90 minutes alkaline treatment".

[0042] The specific operation process is as follows:

[0043] Step 1: Magnetic stirring of PVDF powder in a 6% KOH solution (ratio of KOH solution to PVDF powder: 10 ml: 1 g) was performed for 30 minutes. Six cycles of methanol sonication and centrifugation were performed, each lasting 30 minutes at 600 rpm for 6 minutes. The pH value was measured to be 7.3. The PVDF powder was then dried, ground, and filtered through a sieve.

[0044] Step 2: The PVDF powder treated with alkaline conditions in Step 1 was subjected to acidic conditions. The PVDF was added to 98% concentrated sulfuric acid at a ratio of 10 ml of concentrated sulfuric acid to 2 g of PVDF and heated at 80°C for 12 hours. Six cycles of sonication and centrifugation were performed using methanol for 30 minutes at a centrifuge speed of 800 rpm for 6 minutes. The pH value was measured at 7.3. The powder was then dried, ground, and filtered through a sieve.

[0045] Step 3: The treated PVDF is dissolved in N,N-dimethylacetamide to obtain a casting glue, vacuum degassing treatment, and film coating is performed on a glass plate. The film is irradiated with infrared light. After the coating is completed, the infrared radiation lamp power is 1000W for 10 seconds. After drying, peeling and drying, a high-insulation all-organic flexible composite dielectric is obtained, which is named "90-minute alkaline treatment".

[0046] Comparative Example 1:

[0047] The difference between this comparative example and Example 1 is that step 1 treatment is not performed, and the remaining operation process and parameter settings are the same as those in Example 1, and it is named "acidic condition treatment only".

[0048] The specific operation process is as follows:

[0049] Step 1: Treat PVDF powder with acidic conditions by adding 98% concentrated sulfuric acid (10 ml:2 g) and heating at 80°C for 12 hours. Ultrasonication and centrifugation were repeated six times using methanol for 30 minutes, centrifuged at 800 rpm for 6 minutes, and the pH was measured at 7.3. Dry, grind, and filter through a sieve.

[0050] Step 2: The treated PVDF is dissolved in N,N-dimethylacetamide to obtain a casting glue, vacuum degassing treatment is carried out, and a film is formed on a glass plate by scraping. After the coating is completed, infrared radiation is irradiated with a lamp tube power of 1000W for 10 seconds. After drying, peeling and drying, a high-insulation all-organic flexible composite dielectric is obtained, which is named "acidic condition only treatment".

[0051] Comparative Example 2:

[0052] The difference between this comparative example and Example 1 is that step 2 treatment is not performed, and the remaining operation process and parameter settings are the same as those in Example 1, and it is named "alkaline condition treatment only".

[0053] The specific operation process is as follows:

[0054] Step 1: First, magnetically stir PVDF powder in a 6% KOH solution for 60 minutes. The ratio of KOH solution to PVDF powder is 10ml:1g. Sonicate and centrifuge the solution six times using methanol for 30 minutes at a centrifuge speed of 600 rpm for 6 minutes. The pH value is tested to be 7.5. Dry and grind the PVDF powder, then filter it through a sieve.

[0055] Step 3: The treated PVDF is dissolved in N,N-dimethylacetamide to obtain a casting glue, vacuum degassing treatment is performed, and a film is formed on a glass plate by scraping. After the coating is completed, infrared radiation is irradiated with a lamp tube power of 1000W for 10 seconds. After drying, peeling and drying, a high-insulation all-organic flexible composite dielectric is obtained, which is named "alkaline condition only treatment".

[0056] Comparative Example 3:

[0057] The difference between this comparative example and Example 1 is that step 1 and step 2 were not performed, and the remaining operation process and parameter settings were the same as those in Example 1, and the comparative example was named "PVDF".

[0058] The specific operation process is as follows:

[0059] PVDF powder is dissolved in N,N-dimethylacetamide to obtain a casting glue, which is then vacuum degassed and coated on a glass plate to form a film. After coating, infrared radiation is irradiated with a lamp tube power of 1000W for 10 seconds. After drying, peeling and drying, a high-insulation, fully organic, flexible composite dielectric is obtained, named "PVDF".

[0060] Effect example:

[0061] (1) XRD tests were performed on the PVDF membranes treated with alkaline conditions for 30 minutes, 60 minutes, 90 minutes, acidic conditions only, alkaline conditions only, and PVDF membranes obtained in Examples 1 to 3 and Comparative Examples 3, respectively. The results are shown in FIG1 . The characteristic diffraction peaks of the α-phase, β-phase, and γ-phase of the PVDF material can be clearly observed. As the alkaline treatment time increases, the α-phase of PVDF weakens and the β-phase strengthens.

[0062] (2) The 30-minute alkaline treatment PVDF membrane, 60-minute alkaline treatment PVDF membrane, 90-minute alkaline treatment PVDF membrane, acidic treatment only, alkaline treatment only, and PVDF membrane obtained in Examples 1 to 3 and Comparative Examples 3 were subjected to infrared spectroscopy tests. The results are shown in FIG2 . At 1550-1650 cm -1 The absorption band corresponding to the double bond and hydroxyl group is 3300-3500 cm -1 . And at 1700cm -1 , 2500cm -1 The corresponding peak near the bottom is the hydrogen bond between F and H. It can be observed that the peak changes after acid-base treatment, and the hydrogen bond peak corresponding to the 60-minute alkaline treatment is the strongest.

[0063] (3) Breakdown tests were performed on the PVDF membranes obtained in Examples 1 to 3 and Comparative Examples 1 to 3, which were treated with alkaline conditions for 30 minutes, 60 minutes, 90 minutes, acidic conditions only, alkaline conditions only, and PVDF membranes, respectively. The results are shown in Figure 3. As the alkaline treatment time increases, the hydrogen bonds formed between the hydroxyl groups and the fluorine enhance the breakdown field strength of the medium. This increases from 480 MV / m for PVDF to 620 MV / m for 60 minutes of alkaline treatment. However, the breakdown strength of PVDF treated with either acidic or alkaline conditions alone decreases sharply, all below 350 MV / m.

[0064] (4) Dielectric spectrum tests were performed on the PVDF membranes obtained in Examples 1 to 3 and Comparative Examples 1 to 3, which were treated with alkaline conditions for 30 minutes, 60 minutes, 90 minutes, only treated with acidic conditions, only treated with alkaline conditions, and PVDF membranes. The results are shown in Figure 4. As the alkaline treatment time increases, the hydrogen bonds formed between the hydroxyl groups and the fluorine limit the dipole rotation, so that the dielectric constant and dielectric loss of the medium are reduced. The dielectric constant decreases from 9.84 for PVDF to 8.45 for 60 minutes of alkaline treatment, and the dielectric loss decreases from 0.05 for PVDF to 0.0324 for 60 minutes of alkaline treatment. For PVDF treated with only acidic or alkaline conditions, the dielectric constant is 9.05 and 9.29, and the dielectric loss is 0.0806 and 0.1, which are both increased compared to the dielectric constant and dielectric loss of the 60-minute alkaline treatment.

[0065] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing a high-insulation all-organic composite dielectric material, characterized in that: include: (1) Defluorination treatment of PVDF using alkali; (2) A hydroxylation treatment is performed using an acid to obtain a molecularly modified hydroxyl-functionalized PVDF dielectric material.

2. The preparation method according to claim 1, characterized in that: (1) Specifically, PVDF powder is added to an alkaline solution, magnetically stirred, ultrasonically treated with methanol, and then repeatedly centrifuged and washed until the pH value is 7.1 to 7.6, and then dried, ground and sieved in sequence.

3. The preparation method according to claim 2, characterized in that: The alkaline solution is a KOH solution with a concentration of 5-7 wt %; the volume mass ratio of the KOH solution to the PVDF is 10 mL:1 g.

4. The preparation method according to claim 1, characterized in that: (2) Specifically, the PVDF powder treated with alkali was added to an acid solution, heated at 80°C for 12 h, ultrasonically treated with methanol, and then repeatedly centrifuged and washed until the pH value was 7.1 to 7.

6.

5. The preparation method according to claim 4, characterized in that: The acid solution is concentrated sulfuric acid with a concentration of 98 wt %; the volume mass ratio of the concentrated sulfuric acid to the PVDF powder treated with alkali is 10 mL:2 g.

6. The preparation method according to claim 2 or 5, characterized in that: The ultrasonic treatment time is 25 to 35 minutes, the centrifugal washing speed is 600 to 800 r / min, and the time is 5 to 8 minutes.

7. A high-insulation all-organic composite dielectric material, characterized in that: The material is a molecularly modified hydroxyl-functionalized PVDF dielectric material prepared by the methods described in claims 1 to 8.

8. A method for preparing a high-insulation all-organic composite dielectric film, characterized in that: After coating the high-insulation all-organic composite dielectric material according to claim 9, the film is irradiated with infrared light, and then dried, peeled and dried to obtain a high-insulation all-organic composite dielectric film.

9. A high-insulation all-organic composite dielectric film obtained by the preparation method according to claim 8.

10. An application of the high-insulation all-organic composite dielectric film according to claim 9, characterized in that: Used in the preparation of dielectric capacitors.

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