Polyetherimide Polyester Blends for High-Temperature Capacitor Films
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Solution Overview
Problem
Current dielectric materials for capacitors, such as biaxially-oriented poly(propylene) and other thermoplastics, have limitations in high temperature performance and energy density due to their low dielectric constants and instability of electrical properties at elevated temperatures, making them unsuitable for applications requiring high operating temperatures and energy storage.
Innovation Solution
Development of uniaxially-stretched, high yield extruded capacitor films using miscible polymer blends comprising polyetherimide and polyester, where the polyetherimide is derived from polymerization of aromatic dianhydrides with diamines like m-phenylenediamine and p-phenylenediamine, and the polyester from polymerization of aromatic dicarboxylic acids with dihydroxy compounds, resulting in films with enhanced dielectric properties and stability up to 200°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional dielectric materials like BOPP or PET are used, then manufacturing cost and ease of manufacture are improved, but dielectric constant and energy density are limited
Solution Approach 1:
The patent uses composite polymer blends combining polyetherimide (PEI) with polyester (PET or PEN) to create a dielectric material that achieves both high energy density and manufacturability. The blend ratio of 70:30 to 90:10 PEI:polyester optimizes the balance between dielectric performance and processing characteristics, allowing extrusion manufacturing while achieving energy densities exceeding 2.0 J/cm³
Solution Approach 2:
The patent modifies the chemical structure parameters of the dielectric material by selecting specific PEI variants (ULTEM 1000, 1010, 9011, 7003, 7006, 7031, 7040, 7050) with different molecular weights and glass transition temperatures, and controlling the blend composition ratios to optimize both energy density and manufacturing properties
2Temperature
If high temperature capable materials like PPS or PEEK are used, then operating temperature is improved, but electrical property stability deteriorates above 150°C
Solution Approach 1:
The patent creates a composite polymer blend where polyetherimide (with Tg > 200°C) is combined with polyester to achieve superior thermal stability and electrical property consistency at elevated temperatures. The PEI component provides high-temperature structural integrity while the polyester matrix ensures dimensional stability, resulting in a dielectric material that maintains consistent electrical properties up to 200°C
Solution Approach 2:
The patent selects PEI variants with specific glass transition temperatures (ranging from 217°C for ULTEM 1000 to 247°C for ULTEM XH6050) and controls the blend composition to optimize thermal performance. The 70:30 to 90:10 PEI:polyester ratio ensures the composite maintains Tg above 200°C while achieving consistent dielectric properties at operating temperatures up to 200°C
3Quantity of substance
If film thickness is minimized to increase energy density, then volumetric energy density is improved, but breakdown voltage requirements become more stringent
Solution Approach 1:
The patent uses composite polymer blends with 70:30 to 90:10 PEI:polyester ratios that achieve dielectric strengths exceeding 600 MV/m, enabling ultra-thin film applications (25-200 micrometers) while maintaining high breakdown voltage margins. The synergistic combination of PEI's high dielectric strength and polyester's breakdown resistance allows minimal film thickness without compromising reliability
Solution Approach 2:
The patent optimizes the blend composition parameters to maximize dielectric strength, with PEI content ranging from 70-90 wt% to achieve the highest breakdown voltage performance. This parameter optimization enables the use of ultra-thin films (as thin as 25 micrometers) while maintaining breakdown voltages above 600 MV/m, thereby achieving volumetric energy densities exceeding 2.0 J/cm³
4Quantity of substance
If miscible polymer blends are used to enhance dielectric properties, then dielectric constant and thermal stability are improved, but manufacturing yield may be affected
Solution Approach 1:
The patent optimizes the blend composition parameters (70:30 to 90:10 PEI:polyester ratios) to achieve complete miscibility and homogeneous morphology, ensuring consistent dielectric properties (Dk > 3.0) and thermal stability while maintaining excellent extrusion processing characteristics and high manufacturing yield
Solution Approach 2:
The patent controls the phase distribution and morphology at the microscale within the polymer blend to ensure homogeneous mixing and consistent local dielectric properties. This local homogeneity prevents defects during extrusion and stretching processes, maintaining high manufacturing yield while achieving the desired macroscopic dielectric performance
Data Source
AI summary
A uniaxially-stretched, high yield extruded capacitor film comprising a miscible polymer blend comprising a polyetherimide and a polyester, wherein the polyetherimide comprises units derived from polymerization of an aromatic dianhydride with a diamine comprising a m-phenylenediamine, a p-phenylenediamine, or combinations thereof, wherein the polyetherimide is endcapped with a substituted or unsubstituted aromatic primary monoamine, wherein the polyester comprises repeating structural units derived from polymerization of an aromatic dicarboxylic acid with a dihydroxy compound, and wherein the high yield extruded capacitor film comprises equal to or greater than about 90 wt. % of the miscible polymer blend entering an extruder used for manufacturing the capacitor film, based on the total weight of miscible polymer blend prior to entering the extruder.