Corona resistant polyimide-polyperfluoroalkylalkene film and method of making

Abstract

This application relates to the technical field of polymer insulating materials, specifically disclosing a corona-resistant polyimide-perfluoroethylene propylene film and its preparation method. The film comprises a polyimide base film and an interface treatment layer, a gradient transition layer, and a functional protective layer sequentially disposed on the polyimide base film. The interface treatment layer is formed by curing an interface treatment slurry. The gradient transition layer comprises the following raw materials in parts by weight: 100 parts of perfluoroethylene propylene dispersion, 30-50 parts of interface treatment slurry, 3-8 parts of leveling agent, 5-10 parts of nanofiller, and 0.5-1.5 parts of latent curing agent. The functional protective layer comprises the following raw materials in parts by weight: 100 parts of perfluoroethylene propylene dispersion, 2-5 parts of hydrophobic fumed silica, 1-3 parts of leveling agent, and 0.1-0.5 parts of antioxidant. This application can improve the interfacial delamination resistance of the polyimide-perfluoroethylene propylene composite film under long-term cyclic stress.

Description

Technical Field

[0001] This invention relates to the technical field of polymer insulating materials, and in particular to a corona-resistant polyimide-perfluoroethylene propylene film and its preparation method. Background Technology

[0002] With the rapid development of modern power electronics technology towards higher frequencies, higher power densities, and miniaturization, the performance requirements for electrical equipment insulation materials are becoming increasingly stringent. Especially in variable frequency motors, new energy vehicle drive systems, and aerospace and deep-sea special equipment, insulation materials need to withstand the strong partial discharge effects, high temperatures, and complex mechanical stresses caused by high-frequency pulse voltages over long periods. Polyimide (PI) film, due to its excellent high-temperature resistance, superior mechanical properties, high insulation strength, and good chemical stability, is currently one of the preferred materials for high-performance motor insulation. However, pure polyimide materials have inherent limitations in resisting partial discharges induced by high-frequency pulse voltages. Fluorinated ethylene propylene (FEP), as a fully fluorinated thermoplastic material, possesses excellent dielectric properties, extremely low dielectric loss, outstanding chemical resistance, and inherently high corona resistance. Combining FEP with PI to construct composite films can theoretically complement each other's advantages, resulting in materials with superior overall performance.

[0003] In related technologies, a corona-resistant polyimide-perfluoroethylene propylene composite film is disclosed, which is composed of a polyimide film layer and a perfluoroethylene propylene layer disposed on the surface of the polyimide film layer. The perfluoroethylene propylene layer is obtained by curing a perfluoroethylene propylene composite liquid. The perfluoroethylene propylene composite liquid is prepared from the following raw materials in parts by weight: 60-80 parts of perfluoroethylene propylene dispersion, 8-20 parts of filler, 3-8 parts of leveling agent, and 5-15 parts of maleic anhydride-acrylamide copolymer. The leveling agent is composed of glycidyl methacrylate and fluorocarbon surfactant in a ratio of (0.3-0.5):1.

[0004] Regarding the aforementioned technologies, although the copolymer enhances the initial adhesion, the thermal expansion coefficients of PI and FEP differ significantly. Under temperature cycling caused by motor start-up and shutdown, load changes, and high-frequency vibration caused by electromagnetic force, the interface will be subjected to alternating shear stress. Under long-term cyclic stress, the interface may fatigue crack, eventually leading to interlayer delamination. Summary of the Invention

[0005] To improve the interfacial delamination resistance of polyimide-perfluoroethylene propylene composite films under long-term cyclic stress, this application provides a corona-resistant polyimide-perfluoroethylene propylene film and its preparation method.

[0006] In a first aspect, this application provides a corona-resistant polyimide-perfluoroethylene propylene film, which adopts the following technical solution: A corona-resistant polyimide-perfluoroethylene propylene film comprises a polyimide base film and an interface treatment layer, a gradient transition layer, and a functional protective layer sequentially disposed on the polyimide base film. The interface treatment layer is formed by curing an interface treatment slurry. The gradient transition layer comprises the following raw materials in parts by weight: 100 parts of perfluoroethylene propylene dispersion, 30-50 parts of interface treatment slurry, 3-8 parts of leveling agent, 5-10 parts of nanofiller, and 0.5-1.5 parts of latent curing agent. The functional protective layer comprises the following raw materials in parts by weight: 100 parts of perfluoroethylene propylene dispersion, 2-5 parts of hydrophobic fumed silica, 1-3 parts of leveling agent, and 0.1-0.5 parts of antioxidant.

[0007] In one specific implementation, the interface treatment slurry comprises the following raw materials in parts by weight: 100 parts of fluorinated polysiloxane elastomer prepolymer, 15-25 parts of nanofiller, 1-2 parts of photoinitiator, and 200-300 parts of fluorinated solvent.

[0008] In one specific implementation, the solid content of the poly(perfluoroethylene) propylene dispersion is 55-65%.

[0009] Secondly, this application provides a method for preparing a corona-resistant polyimide-perfluoroethylene propylene film, which adopts the following technical solution: A method for preparing a corona-resistant polyimide-perfluoroethylene propylene film includes the following steps: S1. The polyimide film is subjected to argon plasma treatment and argon ion beam irradiation to obtain a polyimide-based film; S2. A portion of the interface treatment slurry is coated on the surface of the polyimide-based film and cured under ultraviolet light under nitrogen protection to form a chemical anchoring layer. Another portion of the interface treatment slurry is deposited on the surface of the chemical anchoring layer by electrostatic spraying and cured at 75-85℃ to form a stress dissipation layer. The chemical anchoring layer and the stress dissipation layer together form the interface treatment layer. S3. According to the ratio of the gradient transition layer, mix the polytetrafluoroethylene propylene dispersion, leveling agent, nanofiller, interface treatment slurry and latent curing agent evenly, apply it to the surface of the stress dissipation layer, and level it at 58-64℃ for 2-4 minutes to form a gradient transition wet film. S4. According to the ratio of the functional protective layer, the polytetrafluoroethylene propylene dispersion, hydrophobic fumed silica, leveling agent and antioxidant are mixed evenly and coated on the surface of the gradient transition layer to form a functional protective wet film. S5. The composite film structure prepared in S4 is heat-treated at 100-120℃ for 2-3 min, then heated to 180-200℃ and heat-treated under nitrogen protection for 1.5-2.5 min, then heated to 300-320℃ and heat-treated under nitrogen protection for 1-2 min, then cooled to 110-125℃ and held at that temperature under nitrogen protection for 1-2 min, and then allowed to cool naturally to room temperature. Surface corona treatment is then performed to obtain a corona-resistant polyimide-perfluoroethylene propylene film.

[0010] In one specific feasible implementation, in step S1, the polyimide film has a thickness of 25-50 μm, is treated with argon plasma of 200 W for 30-60 s, and then treated with 100 eV energy and 0.5 mA / cm². 2 Irradiation with an argon ion beam for 110-130 s yields a polyimide-based film.

[0011] In one specific implementation, in step S2, electrostatic spray deposition is performed under conditions of 15 kV voltage, 1.5-2.5 mL / h flow rate, and 60°C substrate temperature.

[0012] In one specific feasible implementation, in step S5, surface corona treatment is performed at a power of 1.5kW and a speed of 9-11m / min.

[0013] In one specific feasible embodiment, the fluorinated polysiloxane elastomer prepolymer is prepared according to the following steps: Under nitrogen protection, terminal hydrogen-based polydimethylsiloxane and anhydrous toluene were mixed and heated to 110-115℃, then distilled and the distillate was collected. The mixture was cooled to 80-85℃, chloroplatinic acid catalyst was added, and 2-carbonyl-tetrahydrofuran-3-hydroxy-methacrylate was added dropwise. After the addition was completed, the temperature was raised to 90-95℃ and the reaction was maintained for 3.5-4.5 hours. The mixture was then cooled to 60-65℃, activated carbon was added, and the mixture was decolorized and adsorbed for 20-30 minutes. The mixture was filtered, and the toluene was removed by rotary evaporation of the filtrate to obtain the F-PDMS reaction solution. Hydroxyl-terminated perfluoropolyether, anhydrous toluene, hexamethylene diisocyanate, and dibutyltin dilaurate catalyst were mixed, heated to 50-55℃, and reacted for 2.5-3 hours to obtain isocyanate-terminated PFPE. Isocyanate-terminated PFPE was added to the F-PDMS reaction solution, followed by the addition of dibutyltin dilaurate catalyst. The temperature was raised to 80-85℃ and the reaction was maintained for 5.5-6 hours to obtain a copolymerization reaction solution. The copolymerization reaction solution was washed sequentially with NaHCO3 aqueous solution and deionized water until neutral. After drying with anhydrous MgSO4, the solution was filtered, and the solvent was removed by rotary evaporation of the filtrate to obtain the PFPE-PDMS block copolymer. PFPE-PDMS block, anhydrous THF, and 1,3-bis(maleamide)propane were mixed, and dibutyltin dilaurate catalyst was added. The mixture was heated to 65-70°C under nitrogen protection and kept at this temperature for 7.5-8 hours. A 50% methanol aqueous solution was added dropwise, and the mixture was allowed to stand to precipitate. The precipitate was then filtered, washed, and dried to obtain an elastic solid. The elastic solid was dissolved in anhydrous dioxane, and trimethylsilanol and o-methylhydroquinone were added. Under nitrogen protection, the mixture was heated to 90-95°C and kept at that temperature for 11-12 hours. The temperature was then lowered to 40-50°C, and 2-carbonyl-tetrahydrofuran-3-hydroxy-methacrylate and an antioxidant were added. After mixing thoroughly, the mixture was filtered, and the solvent was removed by rotary evaporation of the filtrate to obtain a fluorinated polysiloxane elastomer prepolymer.

[0014] In summary, this application has the following beneficial effects: 1. This application improves the interfacial delamination resistance of polyimide-perfluoroethylene propylene composite films under long-term cyclic stress by using a defined raw material ratio and a structural design of a polyimide-based film and an interface treatment layer, a gradient transition layer, and a functional protective layer sequentially disposed on the polyimide-based film.

[0015] 2. In this application, the solid content of the poly(perfluoroethylene propylene) dispersion is preferably 55-65%, which can further improve the interfacial peeling resistance of the polyimide-poly(perfluoroethylene propylene) composite film under long-term cyclic stress.

[0016] 3. In this application, a polyimide film with a thickness of 25-50 μm is preferably used, which is treated with argon plasma of 200W for 30-60 seconds, followed by treatment with 100eV energy and 0.5mA / cm². 2 Argon ion beam irradiation for 110-130s can further improve the interfacial peeling resistance of polyimide-perfluoroethylene propylene composite films under long-term cyclic stress. Detailed Implementation

[0017] Unless otherwise specified, all raw materials used in this application were commercially available. Nano-graphene oxide, 0.5-3 μm in diameter, was purchased from Zhongke Leiming (Beijing) Technology Co., Ltd. Photoinitiator, model BASFIRGACURE907. Hydrogen-terminated polydimethylsiloxane, CAS No. 70900-21-9, active ingredient content 99%. Chloroplatinic acid catalyst, CAS No. 18497-13-7, was purchased from Wuhan Jiyesheng Chemical Co., Ltd. 2-Carbonyl-tetrahydrofuran-3-hydroxy-methacrylate, CAS No. 195000-66-9, was purchased from Wuhan Woxuan Technology Co., Ltd. Hydroxyl-terminated perfluoropolyether, molecular weight 500-10000, was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd. Hexamethylene diisocyanate, CAS No. 822-06-0, model HT-100. Dibutyltin dilaurate catalyst, CAS No. 77-58-8, was purchased from Shandong Yunxin New Material Technology Co., Ltd. 1,3-Bis(maleamide)propane, CAS No. 28537-69-1. Trimethylsilyl alcohol, CAS No. 1066-40-6. o-Methylhydroquinone, model SH-164932. BHT antioxidant is Bayer antioxidant 2246. Perfluoroethylene propylene dispersion was purchased from Dongguan Caihua Plastics Technology Co., Ltd. Leveling agent is Evonik TEGORad 2100 solvent-based leveling agent. Latent curing agent, model QXA101. Hydrophobic fumed silica, model HB-152. Antioxidant is antioxidant 1010.

[0018] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0019] Example Example 1

[0020] This embodiment provides a corona-resistant polyimide-perfluoroethylene propylene film, comprising a polyimide base film and an interface treatment layer, a gradient transition layer, and a functional protective layer sequentially disposed on the polyimide base film.

[0021] The interface treatment layer is a layer formed by the curing of the interface treatment slurry.

[0022] The interface treatment slurry includes the following raw materials: 100 kg of fluorinated polysiloxane elastomer prepolymer, 20 kg of nano-graphene oxide, 1.5 kg of photoinitiator, and 250 kg of perfluorohexane.

[0023] Fluorinated polysiloxane elastomer prepolymers are prepared according to the following steps: Under nitrogen protection, 100 g of hydrogen-terminated polydimethylsiloxane and 200 mL of anhydrous toluene were mixed and heated to 110 °C. After distillation to remove water, the distillate was collected. The mixture was cooled to 80 °C, and chloroplatinic acid catalyst was added. Then, 21.8 g of 2-carbonyl-tetrahydrofuran-3-hydroxy-methacrylate was added dropwise. After the addition was complete, the temperature was raised to 90 °C and maintained for 4.5 h. The mixture was then cooled to 60 °C, and activated carbon was added for decolorization and adsorption for 30 minutes. The mixture was filtered, and the toluene was removed by rotary evaporation of the filtrate to obtain the F-PDMS reaction solution.

[0024] 100g of hydroxyl-terminated perfluoropolyether, 150mL of anhydrous toluene, 8.4g of hexamethylene diisocyanate, and 0.1g of dibutyltin dilaurate catalyst were mixed, heated to 50℃, and reacted for 3 hours to obtain isocyanate-terminated PFPE.

[0025] Isocyanate-terminated PFPE was added to the F-PDMS reaction solution, followed by 0.1 g of dibutyltin dilaurate catalyst. The mixture was heated to 80°C and reacted for 6 hours to obtain the copolymerization solution. A 5% (w / w) concentration of... The copolymerization solution was washed sequentially with aqueous solution and deionized water until neutral, and then rinsed with anhydrous water. After drying, the mixture was filtered, and the solvent was removed by rotary evaporation of the filtrate to obtain the PFPE-PDMS block.

[0026] 100g of PFPE-PDMS block, 150mL of anhydrous THF, and 7.2g of 1,3-bis(maleamide)propane were mixed, and 0.1g of dibutyltin dilaurate catalyst was added. The mixture was heated to 65℃ under nitrogen protection and kept at this temperature for 8 hours. Ten times the volume of 50% methanol aqueous solution was added dropwise, and the mixture was allowed to stand to precipitate. The precipitate was then filtered, washed, and dried to obtain an elastic solid.

[0027] The elastic solid was dissolved in 200 mL of anhydrous dioxane, and 12.5 g of trimethylsilanol and 100 ppm of o-methylhydroquinone were added. Under nitrogen protection, the mixture was heated to 90 °C and reacted for 12 hours. The temperature was then lowered to 50 °C, and 12 g of 2-carbonyl-tetrahydrofuran-3-hydroxy-methacrylate and 0.1 g of BHT antioxidant were added. After mixing thoroughly, the mixture was filtered, and the solvent was removed by rotary evaporation of the filtrate to obtain a fluorinated polysiloxane elastomer prepolymer.

[0028] The gradient transition layer comprises the following raw materials: 100 kg of poly(fluoroethylene propylene) dispersion with a solid content of 60%, 40 kg of interface treatment slurry, 5.5 kg of leveling agent, 7.5 kg of nano-graphene oxide, and 1 kg of latent curing agent.

[0029] The functional protective layer comprises the following raw materials: 100 kg of poly(fluoroethylene propylene) dispersion with a solid content of 60%, 3.5 kg of hydrophobic fumed silica, 2 kg of leveling agent, and 0.3 kg of antioxidant.

[0030] This embodiment also provides a method for preparing a corona-resistant polyimide-perfluoroethylene propylene film, comprising the following steps: A 40 μm thick polyimide film was treated with 200 W argon plasma for 45 s, followed by treatment with 100 eV energy and 0.5 mA / cm² plasma. 2 Irradiation with an argon ion beam for 120 s yielded a polyimide-based film with a rough surface.

[0031] The interface treatment slurry is coated on the surface of a polyimide-based film with a wet film thickness of 5 μm. It is then cured under nitrogen protection and 365 nm ultraviolet light to form a chemical anchoring layer. The interface treatment slurry is then electrostatically sprayed onto the surface of the chemical anchoring layer at a voltage of 15 kV, a flow rate of 2 mL / h, and a substrate temperature of 60 °C. The temperature is then raised to 80 °C and cured for 10 minutes to form a stress dissipation layer. The chemical anchoring layer and the stress dissipation layer together form the interface treatment layer.

[0032] S3. According to the ratio of the gradient transition layer, mix the 60% solid content polytetrafluoroethylene propylene dispersion, leveling agent, nano-graphene oxide, interface treatment slurry, and latent curing agent evenly, and coat it on the surface of the stress dissipation layer. The wet film thickness is 15μm. Level it at 60℃ for 3 minutes to form a gradient transition wet film.

[0033] According to the formula of the functional protective layer, a 60% solid content polytetrafluoroethylene propylene dispersion, hydrophobic fumed silica, leveling agent and antioxidant are mixed evenly and coated on the surface of the gradient transition layer, with a wet film thickness of 8μm, to form a functional protective wet film.

[0034] S5. The composite film structure prepared in step S4 is heat-treated at 110℃ for 2.5 min, heated to 190℃, heat-treated under nitrogen protection for 2 min, heated to 310℃, heat-treated under nitrogen protection for 1.5 min, cooled to 120℃, annealed under nitrogen protection for 1.5 min, and naturally cooled to room temperature. Then, it is subjected to surface corona treatment at a power of 1.5 kW and a speed of 10 m / min to obtain a corona-resistant polyimide-perfluoroethylene propylene film. Example 2

[0035] The only difference between this embodiment and Embodiment 1 is that the gradient transition layer includes the following raw materials: 100 kg of polytetrafluoroethylene propylene dispersion, 30 kg of interface treatment slurry, 3 kg of leveling agent, 5 kg of nano-graphene oxide, and 0.5 kg of latent curing agent. Example 3

[0036] The only difference between this embodiment and Embodiment 1 is that the gradient transition layer includes the following raw materials: 100 kg of polytetrafluoroethylene propylene dispersion, 50 kg of interface treatment slurry, 8 kg of leveling agent, 10 kg of nano-graphene oxide, and 1.5 kg of latent curing agent. Example 4

[0037] The only difference between this embodiment and Embodiment 1 is that the functional protective layer includes the following raw materials: 100 kg of polytetrafluoroethylene propylene dispersion, 2 kg of hydrophobic fumed silica, 1 kg of leveling agent, and 0.1 kg of antioxidant. Example 5

[0038] The only difference between this embodiment and Embodiment 1 is that the functional protective layer includes the following raw materials: 100 kg of poly(fluoroethylene propylene) dispersion, 5 kg of hydrophobic fumed silica, 3 kg of leveling agent, and 0.5 kg of antioxidant. Example 6

[0039] The only difference between this embodiment and Embodiment 1 is that the interface treatment slurry includes the following raw materials: 100 kg of fluorinated polysiloxane elastomer prepolymer, 15 kg of nano-graphene oxide, 1 kg of photoinitiator, and 200 kg of perfluorohexane. Example 7

[0040] The only difference between this embodiment and Embodiment 1 is that the interface treatment slurry includes the following raw materials: 100 kg of fluorinated polysiloxane elastomer prepolymer, 25 kg of nano-graphene oxide, 2 kg of photoinitiator, and 300 kg of perfluorohexane. Example 8

[0041] The only difference between this embodiment and Embodiment 1 is that a polytetrafluoroethylene propylene dispersion with a solid content of 50% is used instead of a polytetrafluoroethylene propylene dispersion with a solid content of 60%. Example 9

[0042] The only difference between this embodiment and Embodiment 1 is that a polytetrafluoroethylene propylene dispersion with a solid content of 55% is used instead of a polytetrafluoroethylene propylene dispersion with a solid content of 60%. Example 10

[0043] The only difference between this embodiment and Embodiment 1 is that a polytetrafluoroethylene propylene dispersion with a solid content of 65% is used instead of a polytetrafluoroethylene propylene dispersion with a solid content of 60%. Example 11

[0044] The only difference between this embodiment and Embodiment 1 is that a polytetrafluoroethylene propylene dispersion with a solid content of 70% is used instead of a polytetrafluoroethylene propylene dispersion with a solid content of 60%. Example 12

[0045] The only difference between this embodiment and Example 1 is that the fluorinated polysiloxane elastomer prepolymer is prepared according to the following steps: Under nitrogen protection, 100 g of hydrogen-terminated polydimethylsiloxane and 200 mL of anhydrous toluene were mixed and heated to 115 °C. After distillation to remove water, the distillate was collected. The mixture was cooled to 85 °C, and chloroplatinic acid catalyst was added. Then, 21.8 g of 2-carbonyl-tetrahydrofuran-3-hydroxy-methacrylate was added dropwise. After the addition was complete, the temperature was raised to 95 °C and maintained for 3.5 h. The mixture was then cooled to 65 °C, and activated carbon was added for decolorization and adsorption for 20 minutes. The mixture was filtered, and the toluene was removed by rotary evaporation of the filtrate to obtain the F-PDMS reaction solution.

[0046] 100g of hydroxyl-terminated perfluoropolyether, 150mL of anhydrous toluene, 8.4g of hexamethylene diisocyanate, and 0.1g of dibutyltin dilaurate catalyst were mixed, heated to 55℃, and reacted for 2.5 hours to obtain isocyanate-terminated PFPE.

[0047] Isocyanate-terminated PFPE was added to the F-PDMS reaction solution, followed by 0.1 g of dibutyltin dilaurate catalyst. The mixture was heated to 85°C and maintained at this temperature for 5.5 hours to obtain the copolymerization solution. A 5% (w / w) concentration of... The copolymerization solution was washed sequentially with aqueous solution and deionized water until neutral, and then rinsed with anhydrous water. After drying, the mixture was filtered, and the solvent was removed by rotary evaporation of the filtrate to obtain the PFPE-PDMS block.

[0048] 100g of PFPE-PDMS block, 150mL of anhydrous THF, and 7.2g of 1,3-bis(maleamide)propane were mixed, and 0.1g of dibutyltin dilaurate catalyst was added. The mixture was heated to 70℃ under nitrogen protection and kept at this temperature for 7.5 hours. Ten times the volume of 50% methanol aqueous solution was added dropwise, and the mixture was allowed to stand to precipitate. The precipitate was then filtered, washed, and dried to obtain an elastic solid.

[0049] The elastic solid was dissolved in 200 mL of anhydrous dioxane, and 12.5 g of trimethylsilanol and 100 ppm of o-methylhydroquinone were added. Under nitrogen protection, the mixture was heated to 95 °C and kept at that temperature for 11 hours. The temperature was then lowered to 40 °C, and 12 g of 2-carbonyl-tetrahydrofuran-3-hydroxy-methacrylate and 0.1 g of BHT antioxidant were added. After mixing thoroughly, the mixture was filtered, and the solvent was removed by rotary evaporation of the filtrate to obtain a fluorinated polysiloxane elastomer prepolymer. Example 13

[0050] The only difference between this embodiment and Embodiment 1 is that, in step S1, a 20 μm thick polyimide film is treated with 200 W argon plasma for 25 s, followed by treatment with 100 eV energy and 0.5 mA / cm².2 Irradiation with an argon ion beam for 100 s yielded a polyimide-based film with a rough surface. Example 14

[0051] The only difference between this embodiment and Embodiment 1 is that, in step S1, the 25μm thick polyimide film is treated with 200W argon plasma for 30s, followed by treatment with 100eV energy and 0.5mA / cm² plasma. 2 Irradiation with an argon ion beam for 110 s yielded a polyimide-based film with a rough surface. Example 15

[0052] The only difference between this embodiment and Embodiment 1 is that, in step S1, a 50 μm thick polyimide film is treated with 200 W argon plasma for 60 s, followed by treatment with 100 eV energy and 0.5 mA / cm². 2 Irradiation with an argon ion beam for 130 s yielded a polyimide-based film with a rough surface. Example 16

[0053] The only difference between this embodiment and Embodiment 1 is that, in step S1, a 60 μm thick polyimide film is treated with 200 W argon plasma for 70 s, followed by treatment with 100 eV energy and 0.5 mA / cm². 2 Irradiation with an argon ion beam for 140 s yielded a polyimide-based film with a rough surface. Example 17

[0054] The only difference between this embodiment and Embodiment 1 is that the interface treatment slurry is electrostatically sprayed onto the surface of the chemical anchoring layer under conditions of 15kV voltage, 1mL / h flow rate, and 60℃ substrate temperature, and then heated to 80℃ and cured for 10 minutes to form a stress dissipation layer. Example 18

[0055] The only difference between this embodiment and Embodiment 1 is that the interface treatment slurry is electrostatically sprayed onto the surface of the chemical anchoring layer under conditions of 15kV voltage, 1.5mL / h flow rate, and 60℃ substrate temperature, and then heated to 80℃ and cured for 10 minutes to form a stress dissipation layer. Example 19

[0056] The only difference between this embodiment and Embodiment 1 is that the interface treatment slurry is electrostatically sprayed onto the surface of the chemical anchoring layer under conditions of 15kV voltage, 2.5mL / h flow rate, and 60℃ substrate temperature, and then heated to 80℃ and cured for 10 minutes to form a stress dissipation layer. Example 20

[0057] The only difference between this embodiment and Embodiment 1 is that the interface treatment slurry is electrostatically sprayed onto the surface of the chemical anchoring layer under conditions of 15kV voltage, 3mL / h flow rate, and 60℃ substrate temperature, and then heated to 80℃ and cured for 10 minutes to form a stress dissipation layer. Example 21

[0058] The only difference between this embodiment and Embodiment 1 is that the surface corona treatment is performed under the conditions of 1.5kW power and 8m / min speed. Example 22

[0059] The only difference between this embodiment and Embodiment 1 is that the surface corona treatment is performed under the conditions of 1.5kW power and 9m / min speed. Example 23

[0060] The only difference between this embodiment and Embodiment 1 is that surface corona treatment is performed under the conditions of 1.5kW power and 11m / min speed. Example 24

[0061] The only difference between this embodiment and Embodiment 1 is that surface corona treatment is performed under the conditions of 1.5kW power and 12m / min speed. Example 25

[0062] The only difference between this embodiment and Embodiment 1 is that the preparation method of the corona-resistant polyimide-perfluoroethylene propylene film includes the following steps: A 40 μm thick polyimide film was treated with 200 W argon plasma for 45 s, followed by treatment with 100 eV energy and 0.5 mA / cm² plasma. 2 Irradiation with an argon ion beam for 120 s yielded a polyimide-based film with a rough surface.

[0063] The interface treatment slurry is coated on the surface of a polyimide-based film with a wet film thickness of 5 μm. It is then cured under nitrogen protection and 365 nm ultraviolet light to form a chemical anchoring layer. The interface treatment slurry is then electrostatically sprayed onto the surface of the chemical anchoring layer at a voltage of 15 kV, a flow rate of 2 mL / h, and a substrate temperature of 60 °C. The temperature is then raised to 75 °C and cured for 10 minutes to form a stress dissipation layer. The chemical anchoring layer and the stress dissipation layer together form the interface treatment layer.

[0064] According to the ratio of the gradient transition layer, a 60% solid content polytetrafluoroethylene propylene dispersion, leveling agent, nano-graphene oxide, interface treatment slurry, and latent curing agent are mixed evenly and coated on the surface of the stress dissipation layer. The wet film thickness is 15μm. Leveling is performed at 58℃ for 2 minutes to form a gradient transition wet film.

[0065] According to the formula of the functional protective layer, a 60% solid content polytetrafluoroethylene propylene dispersion, hydrophobic fumed silica, leveling agent and antioxidant are mixed evenly and coated on the surface of the gradient transition layer, with a wet film thickness of 8μm, to form a functional protective wet film.

[0066] S5. The composite film structure prepared in step S4 is heat-treated at 100℃ for 3 min, heated to 180℃, heat-treated under nitrogen protection for 2.5 min, heated to 300℃, heat-treated under nitrogen protection for 2 min, cooled to 110℃, annealed under nitrogen protection for 2 min, and naturally cooled to room temperature. Then, it is subjected to surface corona treatment at a power of 1.5kW and a speed of 10m / min to obtain a corona-resistant polyimide-perfluoroethylene propylene film. Example 26

[0067] The only difference between this embodiment and Embodiment 1 is that the preparation method of the corona-resistant polyimide-perfluoroethylene propylene film includes the following steps: A 40 μm thick polyimide film was treated with 200 W argon plasma for 45 s, followed by treatment with 100 eV energy and 0.5 mA / cm² plasma. 2 Irradiation with an argon ion beam for 120 s yielded a polyimide-based film with a rough surface.

[0068] The interface treatment slurry is coated on the surface of a polyimide-based film with a wet film thickness of 5 μm. It is then cured under nitrogen protection and 365 nm ultraviolet light to form a chemical anchoring layer. The interface treatment slurry is then electrostatically sprayed onto the surface of the chemical anchoring layer at a voltage of 15 kV, a flow rate of 2 mL / h, and a substrate temperature of 60 °C. The temperature is then raised to 85 °C and cured for 10 minutes to form a stress dissipation layer. The chemical anchoring layer and the stress dissipation layer together form the interface treatment layer.

[0069] According to the ratio of the gradient transition layer, a 60% solid content polytetrafluoroethylene propylene dispersion, leveling agent, nano-graphene oxide, interface treatment slurry, and latent curing agent are mixed evenly and coated on the surface of the stress dissipation layer. The wet film thickness is 15μm. The mixture is leveled at 64℃ for 4 minutes to form a gradient transition wet film.

[0070] According to the formula of the functional protective layer, a 60% solid content polytetrafluoroethylene propylene dispersion, hydrophobic fumed silica, leveling agent and antioxidant are mixed evenly and coated on the surface of the gradient transition layer, with a wet film thickness of 8μm, to form a functional protective wet film.

[0071] S5. The composite film structure prepared in step S4 is heat-treated at 120℃ for 2 min, heated to 200℃, heat-treated under nitrogen protection for 1.5 min, heated to 320℃, heat-treated under nitrogen protection for 1 min, cooled to 125℃, annealed under nitrogen protection for 1 min, and naturally cooled to room temperature. Then, it is subjected to surface corona treatment at a power of 1.5kW and a speed of 10m / min to obtain a corona-resistant polyimide-perfluoroethylene propylene film.

[0072] Comparative Example Comparative Example 1 The only difference between this comparative example and Example 1 is that the corona-resistant polyimide-perfluoroethylene propylene film does not include an interface treatment layer.

[0073] Comparative Example 2 The only difference between this comparative example and Example 1 is that the corona-resistant polyimide-perfluoroethylene propylene film does not include a gradient transition layer.

[0074] Comparative Example 3 The only difference between this comparative example and Example 1 is that the corona-resistant polyimide-perfluoroethylene propylene film does not include a functional protective layer.

[0075] Comparative Example 4 The only difference between this comparative example and Example 1 is that, in the raw materials of the gradient transition layer, an equal amount of polytetrafluoroethylene propylene dispersion is used to replace the interface treatment slurry.

[0076] Comparative Example 5 The only difference between this comparative example and Example 1 is that, in the raw materials of the gradient transition layer, an equal amount of polytetrafluoroethylene propylene dispersion is used to replace the leveling agent.

[0077] Comparative Example 6 The only difference between this comparative example and Example 1 is that, in the raw materials of the gradient transition layer, an equal amount of poly(fluoroethylene propylene) dispersion is used to replace the nano-graphene oxide.

[0078] Comparative Example 7 The only difference between this comparative example and Example 1 is that, in the raw materials of the functional protective layer, an equal amount of polytetrafluoroethylene propylene dispersion is used to replace the hydrophobic fumed silica.

[0079] Comparative Example 8 The only difference between this comparative example and Example 1 is that, in the raw materials of the functional protective layer, an equal amount of polytetrafluoroethylene propylene dispersion is used to replace the leveling agent.

[0080] Performance testing The following performance tests were conducted on Examples 1-26 and Comparative Examples 1-8: According to ASTM D903-18, "Standard Test Method for Adhesive Strength, Peel or Tear Strength," the initial static peel strength of the corona-resistant polyimide-perfluoroethylene propylene films in each example and comparative example was tested. The corona-resistant polyimide-perfluoroethylene propylene films were heat-treated at 85°C and 85%RH for 12 hours, then allowed to stand at room temperature for 12 hours, and cyclically treated for 500 cycles. The static peel strength of the corona-resistant polyimide-perfluoroethylene propylene films after long-term cyclic treatment was then tested. The test results are shown in Table 1.

[0081] Table 1 Combining Example 1 and Comparative Examples 1-8 with Table 1, it can be seen that compared with Example 1, the initial static peel strength of Comparative Examples 1-8 is significantly smaller. Moreover, the difference between the initial static peel strength and the static peel strength after heat treatment is larger. This indicates that the raw material ratio and preparation method of Example 1 can improve the interfacial peel resistance of polyimide-perfluoroethylene propylene composite film under long-term cyclic stress.

[0082] In the fluorinated polysiloxane elastomer prepolymer, the maleimide groups form chemical bonds with the amino and carboxyl groups on the PI surface after plasma / ion beam activation. The furan groups form a dynamic covalent network during curing. The perfluoropolyether segments in the elastomer are highly compatible with the fluorocarbon backbone of the FEP, achieving molecular-level miscibility. The polysiloxane segments provide flexibility, while the fluorocarbon segments provide affinity with the FEP. During preparation, ion beam irradiation creates a roughness of 20-50 nm on the PI surface. The elastomer slurry fills these nano-pits, and the porous, sponge-like stress-dissipating layer formed by electrostatic spraying provides mechanical anchoring points for the upper gradient transition layer. In the gradient transition layer, the elastomer and FEP form an interpenetrating network, eliminating clear phase interfaces. Chemical bonds provide a high-strength basic bond, while the interpenetrating network provides additional mechanical bonding points and stress distribution points. This combination requires overcoming both chemical bond energy and mechanical interlocking energy during exfoliation. The interface treatment layer, acting as a primary stress buffer layer, features a porous structure formed by electrostatic spraying that allows for compressible deformation and absorbs strain energy. The low glass transition temperature of the polysiloxane segments ensures wide-temperature-range flexibility. The gradient transition layer avoids stress concentration caused by abrupt modulus changes, achieving a continuous transition of the coefficient of thermal expansion through a compositional gradient. When subjected to thermomechanical stress, the stress is gradually transferred and dissipated within the modulus gradient layer, preventing concentration at a single interface and significantly reducing peak interfacial stress. Nanofillers enhance the matrix's mechanical properties while optimizing stress transmission and distribution in the interfacial region; the interface morphology design ensures the filler functions effectively in the interfacial region. Staged curing allows for controlled formation of each layer according to the design, ensuring optimal bonding between interfaces and ultimately achieving the designed gradient structure and performance. Therefore, this application constructs an actively adaptable and long-term stable interfacial system, transforming interlayer delamination into a cohesive performance problem solvable through the material's inherent properties, resulting in a significant improvement in anti-delamination performance.

[0083] As can be seen from Examples 1-26 and Table 1, the raw material ratios and preparation methods within the range of Examples 1-26 can all improve the interfacial delamination resistance of polyimide-perfluoroethylene propylene composite films under long-term cyclic stress.

[0084] Comparison of the test data from various embodiments shows that the preferred method is to use a polytetrafluoroethylene propylene dispersion with a solid content of 55-65% and a polyimide film thickness of 25-50 μm, followed by argon plasma treatment with a power of 200W for 30-60 seconds, and then treatment with a beam density of 0.5 mA / cm² at an energy of 100 eV. 2 Argon ion beam irradiation for 110-130 s, electrostatic spray deposition at 15 kV, flow rate of 1.5-2.5 mL / h, and substrate temperature of 60 °C, followed by surface corona treatment at 1.5 kW power and 9-11 m / min speed can further improve the interfacial peel resistance of polyimide-perfluoroethylene propylene composite films under long-term cyclic stress.

[0085] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A corona-resistant polyimide-perfluoroethylene propylene film, characterized in that, The material comprises a polyimide-based film and an interface treatment layer, a gradient transition layer, and a functional protective layer sequentially disposed on the polyimide-based film. The interface treatment layer is formed by curing an interface treatment slurry. The gradient transition layer comprises the following raw materials in parts by weight: 100 parts of perfluoroethylene propylene dispersion, 30-50 parts of interface treatment slurry, 3-8 parts of leveling agent, 5-10 parts of nanofiller, and 0.5-1.5 parts of latent curing agent. The functional protective layer comprises the following raw materials in parts by weight: 100 parts of perfluoroethylene propylene dispersion, 2-5 parts of hydrophobic fumed silica, 1-3 parts of leveling agent, and 0.1-0.5 parts of antioxidant.

2. The corona-resistant polyimide-perfluoroethylene propylene film according to claim 1, characterized in that, The interface treatment slurry comprises the following raw materials in parts by weight: 100 parts of fluorinated polysiloxane elastomer prepolymer, 15-25 parts of nanofiller, 1-2 parts of photoinitiator, and 200-300 parts of fluorinated solvent.

3. The corona-resistant polyimide-perfluoroethylene propylene film according to claim 2, characterized in that, The fluorinated polysiloxane elastomer prepolymer was prepared according to the following steps: Under nitrogen protection, terminal hydrogen-based polydimethylsiloxane and anhydrous toluene were mixed and heated to 110-115℃, then distilled and the distillate was collected. The mixture was cooled to 80-85℃, chloroplatinic acid catalyst was added, and 2-carbonyl-tetrahydrofuran-3-hydroxy-methacrylate was added dropwise. After the addition was completed, the temperature was raised to 90-95℃ and the reaction was maintained for 3.5-4.5 hours. The mixture was then cooled to 60-65℃, activated carbon was added, and the mixture was decolorized and adsorbed for 20-30 minutes. The mixture was filtered, and the toluene was removed by rotary evaporation of the filtrate to obtain the F-PDMS reaction solution. Hydroxyl-terminated perfluoropolyether, anhydrous toluene, hexamethylene diisocyanate, and dibutyltin dilaurate catalyst were mixed, heated to 50-55℃, and reacted for 2.5-3 hours to obtain isocyanate-terminated PFPE. Isocyanate-terminated PFPE was added to the F-PDMS reaction solution, followed by the addition of dibutyltin dilaurate catalyst. The mixture was heated to 80-85°C and maintained at this temperature for 5.5-6 hours to obtain the copolymerization reaction solution. The copolymerization solution was washed sequentially with aqueous solution and deionized water until neutral, and then rinsed with anhydrous water. After drying, the mixture was filtered, and the solvent was removed by rotary evaporation of the filtrate to obtain the PFPE-PDMS block compound. PFPE-PDMS block, anhydrous THF, and 1,3-bis(maleamide)propane were mixed, and dibutyltin dilaurate catalyst was added. The mixture was heated to 65-70°C under nitrogen protection and kept at this temperature for 7.5-8 hours. A 50% methanol aqueous solution was added dropwise, and the mixture was allowed to stand to precipitate. The precipitate was then filtered, washed, and dried to obtain an elastic solid. The elastic solid was dissolved in anhydrous dioxane, and trimethylsilanol and o-methylhydroquinone were added. Under nitrogen protection, the mixture was heated to 90-95°C and kept at that temperature for 11-12 hours. The temperature was then lowered to 40-50°C, and 2-carbonyl-tetrahydrofuran-3-hydroxy-methacrylate and an antioxidant were added. After mixing thoroughly, the mixture was filtered, and the solvent was removed by rotary evaporation of the filtrate to obtain a fluorinated polysiloxane elastomer prepolymer.

4. The corona-resistant polyimide-perfluoroethylene propylene film according to claim 1, characterized in that, The solid content of the poly(fluoroethylene) propylene dispersion is 55-65%.

5. A method for preparing a corona-resistant polyimide-perfluoroethylene propylene film according to any one of claims 1-4, characterized in that, Includes the following steps: S1. The polyimide film is subjected to argon plasma treatment and argon ion beam irradiation to obtain a polyimide-based film; S2. A portion of the interface treatment slurry is coated on the surface of the polyimide-based film and cured under ultraviolet light under nitrogen protection to form a chemical anchoring layer. Another portion of the interface treatment slurry is deposited on the surface of the chemical anchoring layer by electrostatic spraying and cured at 75-85℃ to form a stress dissipation layer. The chemical anchoring layer and the stress dissipation layer together form the interface treatment layer. S3. According to the ratio of the gradient transition layer, mix the polytetrafluoroethylene propylene dispersion, leveling agent, nanofiller, interface treatment slurry and latent curing agent evenly, apply it to the surface of the stress dissipation layer, and level it at 58-64℃ for 2-4 minutes to form a gradient transition wet film. S4. According to the ratio of the functional protective layer, the polytetrafluoroethylene propylene dispersion, hydrophobic fumed silica, leveling agent and antioxidant are mixed evenly and coated on the surface of the gradient transition layer to form a functional protective wet film. S5. The composite film structure prepared in S4 is heat-treated at 100-120℃ for 2-3 min, then heated to 180-200℃ and heat-treated under nitrogen protection for 1.5-2.5 min, then heated to 300-320℃ and heat-treated under nitrogen protection for 1-2 min, then cooled to 110-125℃ and held at that temperature under nitrogen protection for 1-2 min, and then allowed to cool naturally to room temperature. Surface corona treatment is then performed to obtain a corona-resistant polyimide-perfluoroethylene propylene film.

6. The method for preparing the corona-resistant polyimide-perfluoroethylene propylene film according to claim 5, characterized in that, In step S1, the polyimide film has a thickness of 25-50 μm, is treated with argon plasma of 200 W for 30-60 s, and then treated with 100 eV energy and 0.5 mA / cm². 2 Irradiation with an argon ion beam for 110-130 s yields a polyimide-based film.

7. The method for preparing the corona-resistant polyimide-perfluoroethylene propylene film according to claim 5, characterized in that, In step S2, electrostatic spray deposition is performed under the conditions of 15kV voltage, 1.5-2.5mL / h flow rate, and 60℃ substrate temperature.

8. The method for preparing the corona-resistant polyimide-perfluoroethylene propylene film according to claim 5, characterized in that, In step S5, surface corona treatment is performed at a power of 1.5kW and a speed of 9-11m / min.

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