Polyetherimide Film Surface Roughness for Capacitor Slidability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current dielectric films for film capacitors face challenges with heat resistance, slidability, and voltage proof, particularly in high-temperature applications like hybrid cars, where existing resins like PP, PET, PPS, and PEN have limitations in heat resistance, dielectric breakdown voltage, and dielectric loss, and amorphous PEI films lack ductility for biaxial stretching.
Innovation Solution
A method for manufacturing a film with a thermoplastic resin composition, including a polyetherimide resin, using a T-die extrusion process with a cooling roll having a specific rough surface pattern to enhance heat resistance, slidability, and voltage proof, by transferring a uniformly aligned pattern of minute bosses or dents onto the film surface, optimizing surface roughness and dynamic friction coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thermoplastic resin film is used for film capacitors, then heat resistance and dielectric properties are improved, but slidability deteriorates causing manufacturing troubles
Solution Approach 1:
The invention applies a roughening treatment only to the surface layer of the film while maintaining the bulk properties of the thermoplastic resin. This creates a dual-layer structure where the surface has enhanced slidability through controlled roughness (Ra: 0.03-0.5 μm) while the interior maintains the heat resistance and dielectric properties of the original thermoplastic resin composition.
Solution Approach 2:
The invention creates a composite structure by combining a thermoplastic resin base material with a surface layer having specific roughness characteristics. The surface layer is formed by dispersing inorganic particles or applying a coating that creates the desired roughness profile, resulting in a composite material that exhibits both improved slidability and retained thermal properties.
2Ease of operation
If the film surface is roughened to improve slidability, then manufacturing operation is improved, but dielectric breakdown voltage deteriorates
Solution Approach 1:
The invention precisely controls the surface roughness parameters, specifically maintaining Ra within 0.03-0.5 μm and Rz within 0.06-1.0 μm. This parameter optimization ensures that the surface is rough enough to provide slidability during manufacturing but not so rough as to create defects that would compromise dielectric breakdown voltage. The controlled roughness prevents excessive stress concentration while maintaining operational ease.
3Temperature
If amorphous PEI resin is used to achieve high heat resistance, then temperature resistance is improved, but ductility deteriorates preventing biaxial stretching
Solution Approach 1:
The invention applies a roughening treatment only to the surface layer of the film while maintaining the bulk properties of the thermoplastic resin. This creates a dual-layer structure where the surface has enhanced slidability through controlled roughness (Ra: 0.03-0.5 μm) while the interior maintains the heat resistance and dielectric properties of the original thermoplastic resin composition.
Solution Approach 2:
The invention creates a composite structure by combining a thermoplastic resin base material with a surface layer having specific roughness characteristics. The surface layer is formed by dispersing inorganic particles or applying a coating that creates the desired roughness profile, resulting in a composite material that exhibits both improved slidability and retained thermal properties.
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 solution results in a film with improved heat resistance, enhanced productivity, and high voltage proof, addressing the limitations of existing films by achieving excellent slidability and dielectric breakdown voltage, suitable for high-temperature applications without the need for biaxial stretching.
Implementation Method 1
pinching and cooling the film between a pressure roll and a cooling roll having a rough surface, thereby transferring a uniformly aligned pattern of a plurality of minute bosses or dents onto a surface of the film
Implementation Method 2
melting and extruding the forming material to a film through a T-die
Data Source
AI summary
A film for film capacitors having a thickness of 10 microns or less, is manufactured by the successive steps of: mixing and preparing a forming material composed of a thermoplastic resin composition; melting and extruding the forming material to a film through a T-die; pinching and cooling the film between a pressure roll and a cooling roll having a rough surface for forming a rough surface to the film, wherein the rough surface of the cooling roll has (σ/Ra) of 0.2 or less, and the rough surface of the film has (σ/Ra) of 0.2 or less, where (Ra) is an arithmetic average roughness defined by a method specified in JIS B 0601 2001, and (σ) is a standard deviation; and rolling up the cooled film onto a winding tube in a winding unit.