Capacitor Film Cast Raw Sheet Beta-Form Control
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Solution Overview
Problem
Current capacitor films face challenges in achieving high voltage resistance, processing suitability, and high electric capacity due to the trade-off between surface roughness and crystallinity, which affects extensibility and film thickness.
Innovation Solution
A cast raw sheet for capacitor films is developed using a polypropylene resin with a weight average molecular weight of 100,000 to 500,000, a molecular weight distribution of 7 or more, and containing 97% isotactic components, with a β-form proportion of 1% to 20%, produced through slurry polymerization and sequential extraction, allowing for balanced stereoregularity and extensibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the surface is roughened by forming β-form to improve processing suitability, then the processing suitability for winding elements is improved, but the voltage resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the β-form content within 1-20% range and molecular weight distribution (Mw/Mn) of 7 or more. This optimization allows the surface to have sufficient roughness for processing suitability while limiting excessive roughness that would harm voltage resistance, thereby resolving the contradiction between ease of operation and reliability
Solution Approach 2:
The patent applies local quality by creating fine unevenness specifically on the film surface through controlled β-form generation, while maintaining the bulk material's high crystallinity and stereoregularity. This localized surface modification improves processing suitability without compromising the overall voltage resistance of the film
2Reliability
If the crystallinity is increased to improve voltage resistance, then the voltage resistance is improved, but the extensibility deteriorates
Solution Approach 1:
The patent resolves this contradiction by optimizing the molecular weight distribution parameter (Mw/Mn ≥ 7) and controlling β-form content (1-20%). These parameter changes enable the material to achieve both high crystallinity for voltage resistance and sufficient extensibility for manufacturing, as the broad molecular weight distribution provides chain flexibility while high stereoregularity ensures crystallinity
3Quantity of substance
If the film thickness is reduced to improve electric capacity, then the electric capacity is improved, but the mechanical strength deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the molecular weight (100,000-500,000) and molecular weight distribution (Mw/Mn ≥ 7). These parameters enable the production of extremely thin films with maintained mechanical strength, as the broad molecular weight distribution provides chain entanglement and flexibility even at reduced thickness, supporting both high electric capacity and mechanical integrity
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 capacitor film with high voltage resistance, excellent processing suitability, and high electric capacity, enabling the production of extremely thin films suitable for capacitors while maintaining mechanical strength and surface roughness.
Implementation Method 1
When a molten polypropylene resin is crystallized within a particular temperature range, the β-form is generated. When this β-form is drawn at the vicinity of the melting point thereof, a spherulite of β-form transfers to a spherulite of α-form with a density different from that of β-form. The density-difference between these crystal forms generates fine unevenness on the film surface.
Implementation Method 2
When this β-form is drawn at the vicinity of the melting point thereof, a spherulite of β-form transfers to a spherulite of α-form with a density different from that of β-form.
Data Source
AI summary
A cast raw sheet for a capacitor film, prepared by heating and melting a polypropylene resin and extruding the resin from a T-die, wherein the polypropylene resin has: a weight average molecular weight, determined by gel permeation chromatography, of 100,000 or more and 500,000 or less; and a molecular weight distribution Mw/Mn of 7 or more, the resin contains 97% by mass or more of an isotactic component that is an extraction residue obtained by sequential extraction, and the cast raw sheet contains a β-form in a proportion of 1% or more and less than 20%, the proportion being determined by X-ray diffraction intensity.