BOPP Film Composition for Higher Capacitor Breakdown Strength
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Solution Overview
Problem
Current biaxially oriented polypropylene (BOPP) films for capacitors lack improved electrical properties and long-term stability, particularly in high-throughput applications, with dielectric breakdown field strength being a critical but not well-understood parameter due to stochastic behavior and variability in testing methods.
Innovation Solution
A biaxially oriented polypropylene film comprising a polypropylene composition with a high isotactic polypropylene resin and a polymeric α-nucleating agent, optimized with a specific weight percentage range and melt flow rate, providing a dielectric breakdown field strength of at least 595 kV/mm, achieved through a continuous biaxial orientation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If biaxially oriented polypropylene films are made thinner to meet market demands for smaller capacitors, then capacitance density improves, but dielectric breakdown field strength becomes more difficult to maintain
Solution Approach 1:
The patent changes the chemical composition parameters of the polypropylene resin, specifically using high isotacticity polypropylene (isotactic pentad fraction ≥93%) with controlled melt flow rate (0.4-10 g/10 min) to achieve superior dielectric breakdown field strength in thinner films
Solution Approach 2:
The patent creates a composite material system by combining high isotacticity polypropylene with specific additives including antioxidants (e.g., Irganox 1010, Irganox 1330) and processing aids, resulting in a film composition that maintains high dielectric strength at reduced thickness
2Temperature
If high isotactic polypropylene resin is used to improve heat resistance and crystallinity, then operating temperature capability improves, but processing difficulty increases
Solution Approach 1:
The patent carefully controls the melt flow rate parameter within 0.4-10 g/10 min to balance crystallinity (for heat resistance) and processability, and uses specific isotacticity ranges (93-98%) to optimize both thermal properties and manufacturing ease
Solution Approach 2:
The patent introduces processing aids and lubricants as intermediary substances to facilitate the processing of high isotacticity polypropylene, enabling easier manufacturing while maintaining the high crystallinity and heat resistance properties
3Reliability
If numerous individual breakdown measurements are performed to account for stochastic behavior, then measurement reliability improves, but testing time and complexity increase
Solution Approach 1:
The patent performs preliminary optimization of film composition and processing parameters to achieve consistent, high-performance material, thereby reducing the number of measurements needed to establish reliable breakdown characteristics
Solution Approach 2:
The patent replaces extensive mechanical testing with a optimized measurement protocol using standardized electrode geometries and controlled testing conditions, reducing testing time while maintaining statistical reliability through proper sample preparation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The film exhibits enhanced dielectric breakdown field strength and stability, as evidenced by a two-parameter Weibull distribution, enabling improved performance in capacitor applications under extreme conditions.
Implementation Method 1
a polymeric α-nucleating agent
Implementation Method 2
the high isotacticity is the high heat resistance of the final film, relating to the high crystallinity
Implementation Method 3
biaxially oriented polypropylene film
Data Source
AI summary
The present invention is directed to a biaxially oriented polypropylene (BOPP) film with improved breakdown strength and to a capacitor comprising an insulation film comprising a layer of the biaxially oriented polypropylene film of the present invention. The present invention is further directed to a process for producing a biaxially oriented polypropylene film. Finally, the present invention is further directed to the use of a biaxially oriented polypropylene film of the present invention as layer of an insulation film of a capacitor. The BOPP film comprises a polypropylene composition, wherein the polypropylene composition comprises a high isotactic homopolymer of propylene and a polymeric α-nucleating agent. The BOPP film has a dielectric breakdown field strength Eb63.2 of at least 595 kV/mm. The process for producing a biaxially oriented polypropylene film comprises the steps of extruding a polypropylene composition to a flat film and orienting the flat film simultaneously in the machine direction and in the transverse direction.