Cycloolefin copolymer-furil composite dielectric film and preparation method thereof

Abstract

The invention discloses a preparation method of a cycloolefin copolymer-furil composite dielectric film, and belongs to the technical field of film capacitors. Small organic molecule furil is doped into a cycloolefin copolymer to prepare a cycloolefin copolymer composite dielectric film, interface defects are avoided through molecular-level uniform dispersion, and the breakdown strength and the performance stability of a composite dielectric are improved. The furil forms a deep trap for binding carriers by virtue of the LUMO energy level lower than that of the cycloolefin copolymer, so that the energy storage efficiency is improved. The prepared composite dielectric medium is excellent in performance, and the maximum discharge energy density is increased to 4.46 J / cm < 3 > at 150 DEG C when the energy storage efficiency is greater than 90%.

Description

Technical Field

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

[0002] Energy storage thin film dielectrics have excellent energy storage performance and stability, and show good application prospects in high-voltage DC transmission converters, photovoltaic inverters, wind power inverters, and new energy vehicle inverters. With the development of miniaturization and integration of modern power equipment, it is required that the energy storage dielectric still maintains excellent energy storage performance in high-temperature environments. Cycloolefin copolymers have better heat resistance than commercial biaxially oriented polypropylene and lower dielectric losses than aromatic polymers with high Tg, and are a good polymer matrix, but have a small dielectric constant and a low maximum discharge energy density. Therefore, it is necessary to study the improvement of the discharge energy density of cycloolefin copolymers. Researchers have improved the dielectric constant of composite dielectrics and reduced the losses of polymers by introducing inorganic nano-fillers into the polymer matrix, thereby improving the energy storage performance. However, the inorganic nano-fillers have large differences in intrinsic properties from the polymer matrix and are prone to agglomeration, reducing the performance of the composite material; the multi-layer structure of the composite dielectric can combine the advantages of different polymers and is a widely used method. The constructed interfacial region can limit the transport process of carriers, thereby achieving performance improvement, but due to the incomplete compatibility of different polymers, there are often a large number of defects at the interface, thus 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.

[0003] Therefore, there is an urgent need to develop a preparation method for cycloolefin copolymer composite dielectric films that is simple in process and has high energy storage efficiency in high-temperature environments. Summary of the Invention

[0004] Aiming at the problems existing in the existing composite dielectric films, the present invention proposes a cycloolefin copolymer-furoyl hydrazone composite dielectric film and a preparation method thereof.

[0005] One of the purposes of the present invention is to provide a preparation method for a cycloolefin copolymer-furoyl hydrazone composite dielectric film, comprising the following steps: Dissolve the cycloolefin copolymer and furoyl hydrazone in an organic solvent to obtain a composite solution; apply the composite solution on a substrate and obtain a cycloolefin copolymer-furoyl hydrazone composite dielectric film after drying treatment; wherein, the mass percentage of furoyl hydrazone in the cycloolefin copolymer composite dielectric film is 0.05-0.2%.

[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, the cycloolefin copolymer and furoin are dissolved in an organic solvent to obtain a composite solution, which includes adding the cycloolefin copolymer and furoin to the organic solvent and stirring at a speed of 100 to 300 r / min at 100 to 120 °C until completely dissolved to obtain the composite solution.

[0009] Preferably, the thickness of the cycloolefin copolymer composite dielectric film is 10 to 14 μm.

[0010] Preferably, it needs to be left standing for 10 to 15 hours before the drying treatment.

[0011] Preferably, the drying treatment includes heating at 120 to 180 °C for 5 to 7 hours in a vacuum state.

[0012] The second object of the present invention is to provide a cycloolefin copolymer-furoin composite dielectric film prepared by the preparation method as described above.

[0013] The beneficial effects of the present invention: In the present invention, a cycloolefin copolymer composite dielectric film is prepared by introducing furoin into the cycloolefin copolymer, improving the energy storage efficiency and performance stability of the cycloolefin copolymer composite dielectric film. Incorporating the organic small molecule furoin into the cycloolefin copolymer to prepare a cycloolefin copolymer composite dielectric film, avoiding interface defects through molecular-level uniform dispersion, and enhancing the breakdown strength and performance stability of the composite dielectric. Furoin forms deep traps for bound carriers with its LUMO energy level lower than that of the cycloolefin copolymer, enhancing the energy storage efficiency. The prepared composite dielectric has excellent performance. At 150 °C, when the energy storage efficiency is greater than 90%, the maximum discharge energy density is increased to 4.46 J / cm 3 . Description of the Drawings

[0014] Figure 1 is the ultraviolet photoelectron spectrum of the cycloolefin copolymer; Figure 2 is the ultraviolet-visible absorption spectrum of the cycloolefin copolymer; Figure 3 is the ultraviolet photoelectron spectrum of furoin; Figure 4is the ultraviolet-visible absorption spectrum of furoin Figure 5 is the Weibull distribution probability plot of the breakdown voltage of cycloolefin copolymer and composite dielectric doped with 0.1 wt% furoin at 150 °C Figure 6 is the energy storage characteristic diagram of cycloolefin copolymer and composite dielectric doped with 0.1 wt% furoin at 150 °C Specific embodiments

[0015] According to the first aspect of the present invention, there is provided a method for preparing a cycloolefin copolymer-furoin composite dielectric film, comprising the following steps: Dissolve cycloolefin copolymer and furoin in an organic solvent to obtain a composite solution; apply the composite solution on a substrate and obtain a cycloolefin copolymer composite dielectric film after drying treatment; Among them, the mass percentage of furoin in the cycloolefin copolymer-furoin composite dielectric film is 0.05-0.2%.

[0016] In the present invention, furoin can be completely dissolved in xylene solvent, and molecular-level uniform dispersion is achieved through solution blending, avoiding the performance degradation caused by easy agglomeration of inorganic nanofillers due to large differences in properties from the polymer matrix; there is no need to construct a multi-layer structure, avoiding interface defects caused by poor compatibility between different polymers, thereby reducing the carrier leakage path, avoiding partial discharge and energy loss caused by filler agglomeration or interface defects, and improving the energy storage efficiency; the uniform microstructure reduces the weak points in the film, avoiding electrical breakdown caused by agglomerates or interface defects, improving the uniformity of the breakdown field strength, and further improving the film quality stability; the mass percentage of furoin in the cycloolefin copolymer composite dielectric film being 0.05-0.2% ensures the uniform dispersion of furoin in the cycloolefin copolymer.

[0017] As Figure 1 and Figure 2 shown, the secondary electron cutoff energy (Ecutoff) of the cycloolefin copolymer is 16.27 eV, the minimum photoelectron binding energy (EHOMO) of the dielectric is 4.78 eV, and the band gap (Eg) is 5.30 eV. After calculation, the highest occupied molecular orbital (HOMO) energy level of the cycloolefin copolymer is -9.355 Ev, and the lowest unoccupied molecular orbital (LUMO) energy level is -3.98 eV. As Figure 3 and Figure 4As shown, the secondary electron cutoff energy (Ecutoff) of furoin is 16.06 eV, the minimum photoelectron binding energy (EHOMO) of the dielectric is 2.95 eV, the band gap (Eg) is 2.94 eV. After calculation, the highest occupied molecular orbital (HOMO) energy level of furoin is -8.33 eV, and the lowest unoccupied molecular orbital (LUMO) energy level is -5.39 eV; The lowest unoccupied molecular orbital (LUMO) energy level of furoin is -5.39 eV, which is significantly lower than the LUMO energy level of -3.98 eV of the cycloolefin copolymer. The low energy level forms shallow trap sites, captures carriers and inhibits their migration, reduces leakage current, and improves energy storage efficiency.

[0018] In the present invention, without complex copolymerization reactions or multi-layer assembly, the uniform dispersion of furoin can be achieved only by dissolution-stirring-coating. The process has strong controllability, avoiding batch differences caused by cumbersome traditional processes, ensuring the uniformity of film thickness and composition, and thus improving performance stability.

[0019] 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 is in the range of about 65% - 82%, and the glass transition temperature range is 78~178°C.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] In a preferred embodiment of the present invention, the cycloolefin copolymer and furoyl hydrazide are dissolved in an organic solvent to obtain a composite solution, including adding the cycloolefin copolymer and furoyl hydrazide 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 composite solution.

[0024] In the present invention, long-term stirring combined with a rotation speed of 150-250 r / min promotes the uniform dispersion of small molecule impurities, and at the same time discharges the dissolved air to avoid the formation of pore defects after the film is dried. When it is lower than 150 r / min, the solution turbulence is insufficient, and furoyl hydrazide 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 and reduce the molecular weight.

[0025] In a preferred embodiment of the present invention, the thickness of the cycloolefin copolymer composite dielectric film is 10-14 μm.

[0026] 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 to balance the thickness control accuracy of the industrial coating process and the high-field application requirements.

[0027] In a preferred embodiment of the present invention, it is necessary to stand for 10-15 hours before the drying treatment.

[0028] 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 furoyl hydrazide molecules from disordered dispersion to a thermodynamically stable state and uniform distribution. Samples without standing may cause local aggregation of furoyl hydrazide due to the rapid volatilization of the solvent. 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 to avoid the formation of film defects after coating.

[0029] In a preferred embodiment of the present invention, the drying treatment includes heating at 120-180 °C for 5-7 hours in a vacuum state.

[0030] In the present invention, the vacuum environment reduces the boiling point of the solvent, and 120-180 °C ensures the complete volatilization of the solvent. 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 causes oxidative degradation of the cycloolefin copolymer. The vacuum environment can also avoid the rupture 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.

[0031] According to the second aspect of the present invention, a cycloolefin copolymer-furoyl hydrazide composite dielectric film prepared by the preparation method as described above is provided.

[0032] Examples A preparation method of a cycloolefin copolymer-furoin diacyl composite dielectric film comprises the following steps: Put 1.1988 g of cycloolefin copolymer and 0.0012 g of furoin diacyl into 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 until completely dissolved, then evenly apply the solution on a silicon wafer, let it stand at room temperature for 12 h, and then heat it in a vacuum oven at 120 - 180 °C under vacuum for 6 h to obtain a composite dielectric film with a thickness of 10 - 14 μm.

[0033] Dissolve 1.2 g of 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 apply it on a silicon wafer to prepare a blank control group.

[0034] Figure 5 It is the Weibull distribution probability diagram of the breakdown voltage of the cycloolefin copolymer and the composite dielectric doped with 0.1 wt% of furoin diacyl at 150 °C. The breakdown strength of the composite dielectric at a cumulative failure probability of 63.2% is increased from 506.5 MV / m to 577.5 MV / m. Figure 6 It is the energy storage characteristics of the cycloolefin copolymer and the composite dielectric doped with 0.1 wt% of furoin diacyl at 150 °C. When the energy storage efficiency is above 90%, the maximum discharge energy density of the composite dielectric is increased from 3.03 J / cm 3 to 4.46 J / cm 3 .

Claims

1. A method for preparing a cycloolefin copolymer-furoin composite dielectric film, characterized in that, Comprising the following steps: Dissolve the cycloolefin copolymer and furoin in an organic solvent to obtain a composite solution; apply the composite solution onto a substrate, and after drying treatment, obtain a cycloolefin copolymer-furoin composite dielectric film; Among them, the mass percentage of furoin in the cycloolefin copolymer composite dielectric film is 0.05-0.2%.

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 ratio of norbornene is in the range of 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, The step of dissolving the cycloolefin copolymer and furoin in an organic solvent to obtain a composite 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 a composite solution.

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

6. The preparation method according to claim 1, characterized in that, It is necessary to stand for 10-15 hours before the drying treatment.

7. The preparation method according to claim 6, characterized in that, The drying treatment includes heating at 120-180 °C for 5-7 hours under a vacuum state.

8. A cycloolefin copolymer-furoin composite dielectric film prepared by the preparation method according to any one of claims 1-7.

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