Cycloolefin copolymer composite dielectric film and preparation method thereof

Abstract

The invention discloses a cycloolefin copolymer composite dielectric film and a preparation method thereof, and belongs to the technical field of film capacitors. The cycloolefin copolymer composite dielectric film is prepared by grafting furil onto a cycloolefin copolymer molecular chain, and compared with a method of directly doping furil into a cycloolefin copolymer, a trap with a deeper energy level is introduced at a furil grafting site, so that the energy storage performance of a composite dielectric is improved. The prepared composite dielectric medium is excellent in performance, and the discharge energy density reaches 5.46 J / cm < 3 > when the energy storage efficiency is greater than 95% at 150 DEG C.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film capacitors, and particularly relates to a cycloolefin copolymer composite dielectric film and a preparation method thereof. Background Art

[0002] Polymer-based thin film capacitors have broad development prospects in the fields of new energy vehicle drive, ultra-high voltage flexible DC transmission, and high-energy pulsed power supplies due to their large discharge energy density, fast charge and discharge speed, excellent insulation and self-healing characteristics. However, with the continuous development of electrical equipment towards higher voltage resistance, larger capacity, smaller size, and integration, higher requirements are imposed on the operating temperature and discharge density of thin film capacitors. The energy storage performance of polymer-based thin film capacitors deteriorates rapidly in high-temperature environments, so it is necessary to conduct research on this problem.

[0003] Researchers have improved the dielectric constant of composite dielectrics and reduced the loss of polymers by introducing inorganic nano-fillers into the polymer matrix, thereby enhancing the energy storage performance. However, the large difference in the intrinsic properties between inorganic nano-fillers and the polymer matrix makes them prone to agglomeration, reducing the performance of the composite material. The multi-layer structure of composite dielectrics can combine the advantages of different polymers and is a widely used method. The constructed interfacial region can restrict the carrier transport process, thereby achieving performance improvement. However, due to the incomplete compatibility of different polymers, a large number of defects often exist at the interface, reducing the energy storage performance. By copolymerization reaction, molecular chain segments with functional groups are embedded into the polymer molecular chain, which can effectively improve the energy storage performance, but the polymerization process is relatively cumbersome. Therefore, there is an urgent need to develop a preparation method for cycloolefin copolymer composite dielectric films with simple process, high energy storage efficiency, and stable performance in high-temperature environments. Summary of the Invention

[0004] Aiming at the problems existing in the existing composite dielectric films, the present invention provides a cycloolefin copolymer composite dielectric and a preparation method thereof.

[0005] One of the purposes of the present invention is to provide a preparation method for a cycloolefin copolymer composite dielectric film, comprising the following steps: S1. Dissolve a cycloolefin copolymer and furoin in an organic solvent to obtain a first solution; S2. Add an initiator to the first solution and react to obtain a second solution; S3. Apply the second solution on a substrate and perform a drying treatment to obtain a cycloolefin copolymer composite dielectric film; Wherein, the mass percentage of furoin in the cycloolefin copolymer composite dielectric film is 0.05 - 2%, and the mass percentage of the initiator is 0.02 - 0.03%.

[0006] Preferably, the cycloolefin copolymer is polymerized from ethylene and norbornene, including Topas 8007, Topas 5013, Topas 6013, Topas 6015 or Topas 6017, where the norbornene content ranges from about 65% to 82%, and the glass transition temperature ranges from 78 to 178 °C.

[0007] Preferably, the organic solvent includes one or a combination of more of xylene, toluene, dichloromethane, chloroform, tetrachloroethane or cyclohexane.

[0008] Preferably, dissolving the cycloolefin copolymer and furoin in the organic solvent in S1 to obtain the first solution includes adding the cycloolefin copolymer and furoin to the organic solvent, and stirring at a rotation speed of 100 - 300 r / min at 100 - 120 °C until completely dissolved to obtain the first solution.

[0009] Preferably, the initiator includes one or more of dicumyl peroxide, benzoyl peroxide, di - tert - butyl peroxide, tert - butyl cumyl peroxide or 2,5 - dimethyl - 2,5 - bis(tert - butylperoxy)hexane.

[0010] Preferably, the temperature of the reaction in S2 is 90 - 130 °C, the reaction time is 20 - 24 hours, and the stirring rotation speed is 150 - 250 r / min.

[0011] Preferably, the thickness of the cycloolefin copolymer composite dielectric film is 10 - 14 μm.

[0012] Preferably, it needs to be static for 10 - 15 hours before the drying treatment.

[0013] Preferably, the drying treatment includes heating at 120 - 180 °C for 5 - 7 hours in a vacuum state.

[0014] The second object of the present invention is to provide a cycloolefin copolymer composite dielectric film prepared by the preparation method as described above.

[0015] The beneficial effects of the present invention: The present invention prepares a cycloolefin copolymer composite dielectric film by introducing furoin into the cycloolefin copolymer. Compared with directly incorporating furoin into the cycloolefin copolymer, deeper - level traps are introduced at the grafting sites of furoin, improving the energy storage performance of the composite dielectric. The prepared composite dielectric has excellent performance. At 150 °C, when the energy storage efficiency is 95%, the discharge energy density reaches 5.46 J / cm 3 . Description of the Drawings

[0016] Figure 1 is the cycloolefin copolymer, furoin and cycloolefin copolymer - based composite dielectric COC - F 0.05, COC-F 0.1 , COC-F 0.15 , COC-F 0.2 X-ray diffraction patterns of Figure 2 are the nuclear magnetic resonance hydrogen spectra of nuclear magnetic resonance sample 1, nuclear magnetic resonance sample 2, and COC-F 0.1 ; Figure 3 is the Weibull distribution probability plot of the breakdown voltage of COC-F0.05, COC-F0.1, COC-F0.15, COC-F0.2 composite dielectrics and cycloolefin copolymer films at 150 °C; Figure 4 is COC-F 0.05 , COC-F 0.1 , COC-F 0.15 , COC-F 0.2 energy storage characteristics of composite dielectrics and cycloolefin copolymer films; Figure 5 is the energy storage characteristics of COC-F 0.05 , COC-F 0.1 , COC-F 0.15 , COC-F 0.2 energy storage characteristics of composite dielectrics and cycloolefin copolymer films; Figure 6 is the charge-discharge cycle test result of COC-F 0.15 composite dielectric. Detailed implementation method

[0017] According to the first aspect of the present invention, a method for preparing a cycloolefin copolymer composite dielectric film is provided, including the following steps: S1. Dissolve cycloolefin copolymer and furoin bis(4-methylbenzoate) in an organic solvent to obtain a first solution; S2. Add an initiator to the first solution and react to obtain a second solution; S3. Apply the second solution on a substrate and obtain a cycloolefin copolymer composite dielectric film after drying; wherein, the mass percentage of furoin bis(4-methylbenzoate) in the cycloolefin copolymer composite dielectric film is 0.05-2%, and the mass percentage of the initiator is 0.02-0.03%.

[0018] In the present invention, furoin is introduced into a cycloolefin copolymer to prepare a cycloolefin copolymer composite dielectric film, which improves the energy storage efficiency and performance stability of the cycloolefin copolymer composite dielectric film. Compared with directly incorporating furoin into the cycloolefin copolymer, deeper energy level traps are introduced at the grafting sites of furoin, enhancing the energy storage performance of the composite dielectric and thus improving the performance stability. The mass percentage of furoin in the cycloolefin copolymer composite dielectric film is 0.05 - 2%, and the mass percentage of the initiator is 0.02 - 0.03% to ensure that furoin is grafted onto the cycloolefin copolymer.

[0019] In the present invention, the grafting reaction is initiated by dicumyl peroxide, and furoin is covalently bonded to the polymer chain through chemical bonds, forming deeper energy level traps at the grafting sites, further restricting the movement of charge carriers, enhancing the energy storage efficiency, and increasing the breakdown field strength.

[0020] In the present invention, without complex copolymerization reactions or multilayer assemblies, the uniform dispersion and grafting of furoin can be achieved only through dissolution - stirring - coating. The process has strong controllability, avoiding batch differences caused by cumbersome traditional processes, ensuring the uniformity of the film thickness and composition, and thus improving the performance stability.

[0021] In a preferred embodiment of the present invention, the cycloolefin copolymer is polymerized from ethylene and norbornene, including Topas 8007, Topas5013, Topas6013, Topas6015 or Topas6017, where the content ratio of norbornene ranges from about 65% - 82%, and the glass transition temperature ranges from 78 to 178 °C.

[0022] In the present invention, the cycloolefin copolymer is, for example, Topas 8007, Topas5013, Topas6013, Topas6015, Topas6017, Topas 8007 and Topas5013, Topas5013 and Topas6013, Topas6013 and Topas6015, Topas6015 and Topas6017, or, Topas 8007, Topas5013 and Topas6013.

[0023] In a preferred embodiment of the present invention, the organic solvent includes one or a combination of more of xylene, toluene, dichloromethane, chloroform, tetrachloroethane or cyclohexane.

[0024] In the present invention, the organic solvent is, for example, xylene, toluene, dichloromethane, chloroform, tetrachloroethane, cyclohexane, xylene and toluene, dichloromethane and chloroform, xylene and chloroform, xylene and tetrachloroethane, chloroform and tetrachloroethane, xylene, toluene and dichloromethane, xylene, toluene and tetrachloroethane, or, xylene, dichloromethane and chloroform.

[0025] In a preferred embodiment of the present invention, in S1, dissolving the cycloolefin copolymer and furoin bis(benzoylformate) in an organic solvent to obtain the first solution includes adding the cycloolefin copolymer and furoin bis(benzoylformate) to the organic solvent, and stirring at a rotation speed of 100-300 r / min at 100-120 °C until completely dissolved to obtain the first solution.

[0026] In a preferred embodiment of the present invention, the initiator includes one or more of diisopropylbenzene peroxide, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl isopropylbenzene peroxide, or 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0027] In the present invention, the initiator includes diisopropylbenzene peroxide, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl isopropylbenzene peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, diisopropylbenzene oxide, and benzoyl peroxide, benzoyl peroxide and di-tert-butyl peroxide, tert-butyl isopropylbenzene peroxide and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, tert-butyl isopropylbenzene peroxide and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, or diisopropylbenzene peroxide, benzoyl peroxide and di-tert-butyl peroxide.

[0028] In a preferred embodiment of the present invention, the temperature of the reaction in S2 is 90-130 °C, the reaction time is 20-24 hours, and the stirring rotation speed is 150-250 r / min.

[0029] In the present invention, the half-life temperature of diisopropylbenzene peroxide is 101 °C (10 hours), and 90-130 °C is its high-efficiency decomposition range, which can not only ensure the continuous generation of free radicals and maintain the grafting reaction rate, but also avoid the rapid volatilization of the solvent caused by high temperature. The chain segments of the cycloolefin copolymer are active in this temperature range, which is conducive to the approach of furoin bis(benzoylformate) molecules to the double bond sites of the main chain, increasing the probability of grafting reaction. In the initial stage of the solution grafting reaction, the free radical concentration rises rapidly within 0-12 hours, and the grafting rate increases linearly; it enters a plateau stage from 12-20 hours, and the grafting sites are basically saturated after 24 hours. Exceeding 24 hours may cause the grafted furoin bis(benzoylformate) to desorb due to long-term high temperature, reducing the deep trap density. Long-term stirring combined with a rotation speed of 150-250 r / min promotes the uniform dispersion of unreacted small molecule impurities and discharges the dissolved air at the same time, avoiding the formation of pore defects after the film is dried. When the rotation speed is lower than 150 r / min, the solution turbulence is insufficient, and furoin bis(benzoylformate) may be locally enriched, resulting in the risk of agglomeration; when it is higher than 250 r / min, the mechanical shear force may damage the molecular chain of the cycloolefin copolymer, reducing the molecular weight. Uniform stirring ensures that the temperature of the reaction system is consistent, avoiding uneven decomposition of the initiator caused by local overheating, such as too high temperature near the reactor wall, resulting in local overgrafting and forming regions with uneven dielectric properties.

[0030] In a preferred embodiment of the present invention, the thickness of the cycloolefin copolymer composite dielectric film is 10-14 μm.

[0031] In the present invention, the thinner the film, the lower the statistical probability of internal defects such as impurities and pores, and the higher the breakdown field strength. The present invention selects 10-14 μm, balancing the thickness control accuracy of the industrial coating process and the high-field application requirements.

[0032] In a preferred embodiment of the present invention, it is necessary to stand still for 10-15 hours before drying treatment.

[0033] In the present invention, during the standing process, the xylene solvent slowly volatilizes, and the molecular chains of the cycloolefin copolymer are rearranged through Brownian motion, promoting the migration of the furoin molecules from disordered dispersion to a thermodynamically stable state, and gradually forming grafted chemical bonds. Samples without standing may cause local aggregation of furoin due to rapid solvent volatilization. The tiny bubbles introduced by stirring float up and are discharged during standing, and at the same time, the undissolved solid impurities settle to the bottom of the container, avoiding the formation of film defects after coating.

[0034] In a preferred embodiment of the present invention, the drying treatment includes heating at 120-180 °C for 5-7 hours under a vacuum state.

[0035] In the present invention, the vacuum environment reduces the boiling point of the solvent, and 120-180 °C ensures complete volatilization of the solvent. At the same time, the high temperature promotes the further initiation of the grafting reaction by the fragments of the initiator that have not fully reacted, improving the deep trap density. The 5-7 hour drying time balances the solvent removal efficiency and the risk of thermal aging of the material. Insufficient time results in solvent residue, and too long time leads to oxidative degradation of the cycloolefin copolymer. The vacuum environment can also avoid the breakage of polymer chains caused by the intervention of oxygen, ensuring the structural stability of the film during long-term use at a high temperature of 150 °C.

[0036] In the present invention, 0.05-2% of furoin and 0.02-0.03% of the initiator ensure that furoin is grafted onto the cycloolefin copolymer. The reaction at 90-130 °C and stirring at 250 r / min achieve molecular-level dispersion, without agglomeration and interface defects. The 10-14 μm thickness increases the breakdown field strength to 651.2 MV / m, and the shape factor reaches 24.49 after removing defects by vacuum drying. When the energy storage efficiency ≥ 95%, the energy density reaches 5.46 J / cm 3 . The 20-24 hour reaction cycle, 10-15 hour standing, and industrial-level drying conditions are suitable for a thousand-ton cycloolefin copolymer film production line, and the performance fluctuation between batches is ≤ 3%. This preparation method deeply couples the chemical grafting mechanism with the physical processing technology through precise parameter design, providing an industrially applicable high-performance dielectric material solution for energy storage devices in high-temperature and high-field environments.

[0037] According to the second aspect of the present invention, there is provided a cycloolefin copolymer composite dielectric film prepared by the preparation method as described above.

[0038] Examples The preparation method of the cycloolefin copolymer composite dielectric film comprises the following steps: Put the cycloolefin copolymer and furoin in 10 ml of xylene, stir with a magnetic stirrer at a heating temperature of 110 °C and a rotation speed of 200 r / min for 2 h until dissolved, then add diisopropylbenzene peroxide and continue stirring for 22 h to cause the grafting reaction of furoin. Then evenly coat the solution on a silicon wafer, let it stand at room temperature for 12 h, and then heat it in a vacuum oven at 150 °C for 6 h under vacuum to obtain a composite dielectric film with a thickness of 10 - 14 μm; wherein the total content of the cycloolefin copolymer, furoin and diisopropylbenzene peroxide is kept at 1.2 g, and the mass percentage of the initiator is 0.025%. Composite dielectric films with furoin contents of 0.05 wt%, 0.1 wt%, 0.15 wt% and 0.2 wt% in the cycloolefin copolymer composite dielectric film are respectively prepared, and are named COC-F 0.05 、COC-F 0.1 、COC-F 0.15 、COC-F 0.2 。

[0039] Figure 1 are the cycloolefin copolymer, furoin and the cycloolefin copolymer-based composite dielectric COC-F 0.05 、COC-F 0.1 、COC-F 0.15 、COC-F 0.2 's X-ray diffraction patterns. It can be seen from the figure that furoin has obvious crystallization peaks and is a typical crystal structure; the cycloolefin copolymer and the composite dielectric have only one amorphous diffraction peak with a diffraction angle between 10° - 25°, indicating that the grafting of furoin does not change the crystallinity of the cycloolefin copolymer.

[0040] Dissolve 1.2 g of the cycloolefin copolymer in 10 ml of xylene, stir with a magnetic stirrer at a heating temperature of 110 °C and a rotation speed of 200 r / min for 24 h, and then evenly coat it on a silicon wafer to prepare a blank control group; blend the cycloolefin copolymer and furoin, the total amount of the cycloolefin copolymer and furoin is 12 g, and the mass of furoin is 0.1 wt% of the total amount of the cycloolefin copolymer and furoin, and stir for 24 h to prepare nuclear magnetic sample 1; Blend the cycloolefin copolymer and diisopropylbenzene peroxide, the total amount of the cycloolefin copolymer and diisopropylbenzene peroxide is 12 g, and diisopropylbenzene peroxide is 0.025 wt% of the cycloolefin copolymer and diisopropylbenzene peroxide, and blend and stir for 24 h respectively, and stir for 24 h to prepare nuclear magnetic sample 2.

[0041] Figure 2 The proton nuclear magnetic resonance spectra of nuclear magnetic resonance sample 1, nuclear magnetic resonance sample 2, and COC-F are shown 0.1 ; when both furoin and dicumyl peroxide are incorporated, characteristic peaks that do not appear when either of them is incorporated alone appear, indicating that furoin has been successfully grafted onto the molecular chain of the cycloolefin copolymer.

[0042] Figure 3 The prepared COC-F is shown 0.05 、COC-F 0.1 、COC-F 0.15 、COC-F 0.2 The Weibull distribution probability plot of the breakdown voltage of the composite dielectric of COC-F 0.15 、COC-F 0.05 、COC-F 0.1 、COC-F 0.15 、COC-F 0.2 and the cycloolefin copolymer film at 150 °C. When testing, a DC voltage with a boosting rate of 100 V / s was used, and the maximum voltage applied by the testing equipment was 20,000 V; it can be seen from the figure that the breakdown field strength of the cycloolefin copolymer is 506.5 MV / m, and the shape factor is 16.92; the breakdown field strength of COC-F

[0043] As Figure 4 and Figure 5 shown, the energy storage characteristics of the composite dielectric of COC-F 0.05 、COC-F 0.1 、COC-F 0.15 、COC-F 0.2 and the cycloolefin copolymer film are shown. Before testing, the method of vacuum evaporation was used to evaporate aluminum electrodes with a diameter of 3 mm on the film sample, the signal period was 0.1 s, and the test temperature was 150 °C. When the energy storage efficiency of the cycloolefin copolymer film is not less than 95%, the maximum discharge energy density is 3.03 J / cm 3 This performance is better than that of most current polymer matrices; after grafting and blending furoin, the energy storage performance of the composite dielectric has been significantly improved. Among them, the composite dielectric with a total of 0.15 wt% furoin has a discharge energy density of 5.46 J / cm 3 when the energy storage efficiency is not less than 95%, which is a 74.6% increase compared to the cycloolefin copolymer.

[0044] Figure 6 The COC-F is shown 0.15Charge-discharge cycle test of the composite dielectric; the test temperature is 150 °C and the applied electric field strength is 200 MV / m; during the 5000 charge-discharge cycle tests, the composite dielectric always maintains an almost 100% charge-discharge efficiency and a stable discharge energy density, indicating that the prepared composite dielectric film sample has stable performance and is suitable for long-term applications.

Claims

1. A method for preparing a cycloolefin copolymer composite dielectric film, characterized in that, It includes the following steps: S1. Dissolve the cycloolefin copolymer and furoin diacyl in an organic solvent to obtain a first solution; S2. Add an initiator to the first solution and react to obtain a second solution; S3. Coat the second solution on a substrate and perform a drying treatment to obtain a cycloolefin copolymer composite dielectric film; Among them, the mass percentage of furoin diacyl in the cycloolefin copolymer composite dielectric film is 0.05-2%, and the mass percentage of the initiator is 0.02-0.03%.

2. The preparation method according to claim 1, characterized in that, The cycloolefin copolymer is polymerized from ethylene and norbornene, including Topas 8007, Topas5013, Topas6013, Topas6015 or Topas6017, wherein the content range of norbornene is about 65%-82%, and the glass transition temperature range is 78-178 °C.

3. The preparation method according to claim 1, characterized in that, The organic solvent includes one or a combination of more of xylene, toluene, dichloromethane, chloroform, tetrachloroethane or cyclohexane.

4. The preparation method according to claim 1, wherein In S1, the step of dissolving the cycloolefin copolymer and furoin diacyl in an organic solvent to obtain a first solution includes adding the cycloolefin copolymer and furoin diacyl to the organic solvent, and stirring at a rotation speed of 100-300 r / min at 100-120 °C until completely dissolved to obtain a first solution.

5. The preparation method according to claim 1, characterized in that, The initiator includes one or more of diisopropyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl cumyl peroxide or 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

6. The preparation method according to claim 5, characterized in that, In S2, the reaction temperature is 90-130 °C, the reaction time is 20-24 hours, and the stirring rotation speed is 150-250 r / min.

7. The preparation method according to claim 1, characterized in that, The thickness of the cycloolefin copolymer composite dielectric film is 10-14 μm.

8. The preparation method according to claim 7, characterized in that, It is necessary to stand still for 10-15 hours before the drying treatment.

9. The preparation method according to claim 8, characterized in that, The drying treatment includes heating at 120-180 °C for 5-7 hours in a vacuum state.

10. A cycloolefin copolymer composite dielectric film prepared by the preparation method according to any one of claims 1-9.

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