Polypropylene film with enhanced energy storage properties, method, application and film capacitor

Abstract

The present invention relates to a polypropylene film, method, application, and film capacitor with enhanced energy storage properties. The technical features are: preparing an ammonium persulfate aqueous solution; fully soaking a polypropylene film with the ammonium persulfate aqueous solution, securing the polypropylene film with two glass plates, and irradiating the film under an ultraviolet lamp; removing the ultraviolet-irradiated polypropylene film, rinsing, heating, and drying the film to obtain a polypropylene film with surface hydroxyl groups modified; and placing the hydroxyl-modified polypropylene film in a silane coupling agent solution for chemical grafting to obtain a polypropylene film with enhanced energy storage properties. The present invention utilizes ultraviolet irradiation and solution chemical reaction methods to graft polar groups, optimizing the deep trap density and energy level on the film surface, improving the film's insulation and energy storage properties, and having the advantages of significant improvement, ease of operation, and low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of film capacitors and relates to the energy storage characteristics of film capacitors, in particular to a polypropylene film with enhanced energy storage characteristics, a method, an application and a film capacitor. Background Art

[0002] In recent years, the rapid development of technologies such as new energy vehicles, electromagnetic weapons, oil extraction, and wind power generation has led to increasingly stringent requirements for high-energy storage capacitors, which are no longer met by existing capacitors. Polypropylene film, the most widely used commercially, offers exceptionally high breakdown strength, extremely low dielectric loss, and low cost, making it the optimal choice for developing next-generation high-performance capacitors. However, its relatively low energy storage density limits its further application. Improving the energy storage characteristics of film capacitors is a pressing issue. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a polypropylene film, method, application and film capacitor with enhanced energy storage properties. By ultraviolet irradiation and chemical reaction to graft polar groups, the interface structure between the polypropylene film and the electrode is improved, the deep trap distribution and energy level are optimized, and the energy storage performance of the polypropylene film is improved.

[0004] The present invention solves the existing technical problems by adopting the following technical solutions:

[0005] In a first aspect, the present invention provides a method for enhancing the energy storage properties of a polypropylene film, comprising the following steps:

[0006] Step 1, preparing an aqueous solution of ammonium persulfate;

[0007] Step 2: Fully soak the polypropylene film with an aqueous solution of ammonium persulfate, fix the polypropylene film with two glass plates, and place it under an ultraviolet lamp for irradiation;

[0008] Step 3, taking out the polypropylene film after ultraviolet light irradiation, washing, heating, and drying to obtain a polypropylene film with surface hydroxyl groups modified;

[0009] Step 4: placing the hydroxyl-modified polypropylene film into a silane coupling agent solution for chemical grafting reaction, and obtaining a polypropylene film with enhanced energy storage properties after washing and drying.

[0010] Furthermore, the mass fraction of ammonium persulfate in the ammonium persulfate aqueous solution is 20% to 40%.

[0011] Furthermore, the preparation method of the ammonium persulfate aqueous solution is: at room temperature, using a magnetic stirrer to uniformly mix ammonium persulfate and deionized water to obtain the ammonium persulfate aqueous solution.

[0012] Furthermore, the irradiation time under the ultraviolet lamp in step 2 is 15 to 90 seconds.

[0013] Furthermore, the method for rinsing the polypropylene film in step 3 is: rinsing with deionized water, and the method for heating is: placing the polypropylene film in a 40-60° C. water bath and heating it for 15-25 hours.

[0014] Furthermore, the silane coupling agent solution adopts KH560 ethanol aqueous solution, wherein the concentration of KH560 is 5wt% to 15wt%, and the volume ratio of ethanol to deionized water is (8.5 to 9.5): (0.5 to 1.5).

[0015] Furthermore, the temperature of the chemical grafting reaction in step 4 is 50-70°C.

[0016] Furthermore, the thickness of the polypropylene film is 3 to 25 microns.

[0017] In a second aspect, the present invention further provides a polypropylene film with enhanced energy storage properties, comprising a polypropylene film body and a modified functional group, wherein the modified functional group is an epoxy silane group.

[0018] In a third aspect, the present invention further provides an application of a polypropylene film with enhanced energy storage properties prepared according to the method for enhancing the energy storage properties of a polypropylene film described in the first aspect above, or an application of a polypropylene film with enhanced energy storage properties described in the second aspect above.

[0019] In a third aspect, the present invention also provides a polypropylene film capacitor, wherein the polypropylene film of the polypropylene film capacitor is a polypropylene film with enhanced energy storage characteristics prepared according to the method for enhancing the energy storage characteristics of the polypropylene film described in the first aspect above, or a polypropylene film with enhanced energy storage characteristics described in the second aspect above.

[0020] The advantages and positive effects of the present invention are:

[0021] The present invention adopts ultraviolet irradiation and solution chemical reaction methods to graft polar groups, and grafts a highly polar and long-branched silane coupling agent on the surface of the polypropylene film, thereby providing more deep traps to capture injected charges, thereby suppressing the injection of electrode charges. In addition, by improving the interface structure between the polypropylene film and the electrode, the distribution and energy level of the deep traps are optimized, and the insulation and energy storage properties of the film are improved. The invention has the characteristics of obvious improvement effect, simple operation and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a comparison chart of the changes in the composition elements of the polypropylene film before and after the use of the present invention;

[0023] Figure 2This is a comparison chart of the discharge energy density of the polypropylene film before and after using the present invention;

[0024] Figure 3 This is a schematic diagram of the reaction of polypropylene grafting KH560;

[0025] Figure 4 This is the molecular structure diagram of polypropylene grafted KH560. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0027] Example 1

[0028] This invention proposes a method for enhancing the energy storage properties of polypropylene film. The method involves grafting hydroxyl groups via ultraviolet irradiation and then grafting a silane coupling agent, KH560, via a chemical reaction. This increases the polarity and breakdown strength of the polypropylene film, effectively regulating the charge injection process of the polypropylene film, and thereby improving the film's energy storage performance. The specific method includes the following steps:

[0029] Step 1: Use a magnetic stirrer to uniformly mix ammonium persulfate and deionized water to prepare an ammonium persulfate aqueous solution, wherein the ammonium persulfate content in the ammonium sulfate aqueous solution is 40 wt % and the mixture is carried out at room temperature.

[0030] Step 2: Drop an aqueous solution of ammonium persulfate onto a polypropylene film having a thickness of 15 μm, sandwich the polypropylene film between two quartz glass plates, and place the film under an ultraviolet lamp for irradiation.

[0031] This step is implemented as follows: A polypropylene film is placed on a clean quartz glass plate, which is larger than the polypropylene film. An aqueous ammonium persulfate solution is dripped onto the polypropylene film. Then, a similar quartz glass plate is pressed against the polypropylene film, applying pressure to fully infiltrate the ammonium persulfate solution into the polypropylene and squeeze out any air between the polypropylene film and the glass plate. This creates a three-layer combination of quartz glass plate / polypropylene film / quartz glass plate. This combination is then exposed to ultraviolet light for 75 seconds.

[0032] Step 3: Take out the polypropylene film after UV irradiation and rinse it with deionized water; place the polypropylene film in a 50° C. water bath and heat it for 20 hours, and then dry it to obtain a polypropylene film with surface hydroxyl modified.

[0033] Step 4: placing the hydroxyl-modified polypropylene film into a silane coupling agent solution for chemical grafting reaction.

[0034] In this embodiment, the silane coupling agent solution uses KH560 ethanol aqueous solution, wherein the concentration of KH560 is 10wt%, the volume ratio of ethanol to deionized water is 9:1, the reaction temperature is 60°C, and after washing and drying with ethanol, a high energy storage density polypropylene film is finally obtained. Figure 3 Figure 3 is a schematic diagram of the polypropylene grafting KH560 reaction. The specific process is as follows: First, the polypropylene molecular chain forms an oxide film under the action of a strong oxidant. Secondly, hydroxyl (-OH) groups are grafted through a hydrolysis reaction. Then, the KH560 molecules themselves undergo a hydrolysis reaction to obtain Si-OH groups, which then react with the -OH groups on the polypropylene surface to form a polypropylene grafted KH560 structure.

[0035] Example 2

[0036] This invention proposes a method for enhancing the energy storage properties of polypropylene film. The method involves grafting hydroxyl groups via ultraviolet irradiation and then grafting a silane coupling agent, KH560, via a chemical reaction. This increases the polarity and breakdown strength of the polypropylene film, effectively regulating the charge injection process of the polypropylene film, and thereby improving the film's energy storage performance. The specific method includes the following steps:

[0037] Step 1: Use a magnetic stirrer to uniformly mix ammonium persulfate and deionized water to prepare an ammonium persulfate aqueous solution, wherein the ammonium persulfate content in the ammonium sulfate aqueous solution is 30 wt % and the mixture is carried out at room temperature.

[0038] Step 2: Drop an aqueous solution of ammonium persulfate onto a polypropylene film having a thickness of 10 μm, sandwich the polypropylene film between two quartz glass plates, and place the film under an ultraviolet lamp for irradiation.

[0039] This step is implemented as follows: A polypropylene film is placed on a clean quartz glass plate, which is larger than the polypropylene film. An aqueous ammonium persulfate solution is dripped onto the polypropylene film. Then, a similar quartz glass plate is pressed against the polypropylene film, applying pressure to fully infiltrate the ammonium persulfate solution into the polypropylene and squeeze out any air between the polypropylene film and the glass plate. This creates a three-layer combination of quartz glass plate / polypropylene film / quartz glass plate. This combination is then exposed to ultraviolet light for 60 seconds.

[0040] Step 3: Take out the polypropylene film after UV irradiation and rinse it with deionized water; place the polypropylene film in a 45° C. water bath and heat it for 18 hours, and then dry it to obtain a polypropylene film with surface hydroxyl modified.

[0041] Step 4: placing the hydroxyl-modified polypropylene film into a silane coupling agent solution for chemical grafting reaction.

[0042] In this embodiment, the silane coupling agent solution uses KH560 ethanol aqueous solution, wherein the concentration of KH560 is 5wt%, the volume ratio of ethanol to deionized water is 8.5:1.5, the reaction temperature is 50°C, and after washing and drying with ethanol, a high energy storage density polypropylene film is finally obtained.

[0043] Example 3

[0044] The present invention also provides a polypropylene film with enhanced energy storage properties, which is prepared using the above method. The polypropylene film with enhanced energy storage properties comprises a polypropylene film body and a modified functional group, wherein the modified functional group is an epoxy silane group. Figure 4 This is the molecular structure diagram of polypropylene grafted with KH560, where KH560 is grafted onto the tertiary carbon of the polypropylene molecular chain.

[0045] Example 4

[0046] The present invention also proposes an application method of a polypropylene film with enhanced energy storage properties. The polypropylene film is applied to a polypropylene film capacitor. The polypropylene film of the polypropylene film capacitor adopts the polypropylene film with enhanced energy storage properties.

[0047] The present invention successfully grafts a highly polar and long-branched silane coupling agent onto the surface of a polypropylene film through ultraviolet irradiation and solution chemical reaction, thereby optimizing the interfacial structure of the polypropylene film and providing more deep traps to capture injected charges, thereby improving the energy storage performance of the polypropylene film. Figure 1 The graph shows the changes in the composition elements of the polypropylene film before and after modification. It can be seen that the oxygen content of the modified film increases and new silicon elements appear, which indicates that the silane coupling agent KH560 has been successfully grafted onto the polypropylene film. Figure 2 The figure shows the change in discharge energy density of polypropylene film before and after modification. The square symbol represents the change in discharge energy density of polypropylene film before modification. Its discharge energy density at the maximum electric field of 700kV / mm is 4.76J / cm 3 After modification, the maximum withstand electric field of the film increased to 800kV / mm, and the discharge energy density also increased to 6.23J / cm 3 As can be seen from the above comparison diagram, the insulation performance and energy storage performance of the polypropylene film modified by the present invention are significantly improved.

[0048] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific embodiments. Any other embodiments derived by those skilled in the art based on the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims

1. A polypropylene film capacitor with enhanced energy storage characteristics, characterized in that: The polypropylene film with enhanced energy storage properties is prepared according to the following method: Step 1, preparing an aqueous solution of ammonium persulfate; Step 2: Fully soak the polypropylene film with an aqueous solution of ammonium persulfate, fix the polypropylene film with two glass plates, and place it under an ultraviolet lamp for irradiation; Step 3, taking out the polypropylene film after ultraviolet light irradiation, washing, heating, and drying to obtain a polypropylene film with surface hydroxyl groups modified; Step 4: placing the hydroxyl-modified polypropylene film into a silane coupling agent solution for chemical grafting reaction to obtain a polypropylene film with enhanced energy storage properties, wherein the silane coupling agent solution is a KH560 ethanol aqueous solution.

2. The polypropylene film capacitor with enhanced energy storage characteristics according to claim 1, characterized in that: The mass fraction of ammonium persulfate in the ammonium persulfate aqueous solution is 20% to 40%.

3. The polypropylene film capacitor with enhanced energy storage characteristics according to claim 2, characterized in that: The preparation method of the ammonium persulfate aqueous solution comprises: uniformly mixing ammonium persulfate and deionized water using a magnetic stirrer at room temperature to obtain the ammonium persulfate aqueous solution.

4. The polypropylene film capacitor with enhanced energy storage characteristics according to claim 1, characterized in that: The irradiation time under the ultraviolet lamp in step 2 is 15 to 90 seconds.

5. The polypropylene film capacitor with enhanced energy storage characteristics according to claim 1, characterized in that: The method for washing the polypropylene film in step 3 is: washing with deionized water; the method for heating is: placing the polypropylene film in a water bath at 40-60° C. and heating for 15-25 hours.

6. The polypropylene film capacitor with enhanced energy storage characteristics according to claim 1, characterized in that: The concentration of KH560 in the KH560 ethanol aqueous solution is 5wt% to 15wt%, and the volume ratio of ethanol to deionized water is (8.5 to 9.5): (0.5 to 1.5).

7. The polypropylene film capacitor with enhanced energy storage characteristics according to claim 1, characterized in that: The temperature of the chemical grafting reaction in step 4 is 50-70°C.

8. The polypropylene film capacitor with enhanced energy storage characteristics according to any one of claims 2 to 7, characterized in that: The thickness of the polypropylene film is 3 to 25 microns.

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