Polyimide Film for Graphite Sheet Using Sublimable Filler
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Solution Overview
Problem
High-thickness graphite sheets with excellent surface quality and thermal conductivity are difficult to produce due to sublimation gas generation during carbonization and graphitization, leading to damage of the graphite structure and low yield.
Innovation Solution
A polyimide film with a thickness of 100 μm or larger, incorporating a sublimable inorganic filler, is formed using a method involving a polyamic acid solution, imidizing agent, and dehydrating agent, followed by heat treatment, to facilitate gas exhaustion and improve structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high-thickness polyimide film (100 μm or more) is used to manufacture high-thickness graphite sheet, then the heat capacity and thermal energy storage capability are improved, but the surface quality deteriorates and graphite structure becomes damaged due to sublimation gas generation
Solution Approach 1:
The patent extracts the harmful sublimation gas from the interior of the polyimide film by introducing a sublimable inorganic filler that preferentially sublimes and creates pathways for gas escape. This removes the harmful factor (sublimation gas) that causes surface damage while preserving the desired high thickness.
Solution Approach 2:
The sublimable inorganic filler acts as an intermediary substance between the polyimide matrix and the sublimation gas. It facilitates gas exhaustion by creating channels and reducing pressure buildup, thereby protecting the graphite structure from damage while allowing high-thickness film formation.
2Device complexity
If carbonization and graphitization are performed simultaneously on surface layer and inside the polyimide film, then the manufacturing process is simplified, but the graphite structure is damaged due to large amount of sublimation gas generated from inside
Solution Approach 1:
The sublimable inorganic filler is introduced into the polyimide film before carbonization and graphitization. This preliminary action creates gas escape pathways and reduces internal pressure during the subsequent simultaneous carbonization and graphitization process, preventing graphite structure damage while maintaining process simplicity.
Solution Approach 2:
The patent converts the harmful effect of sublimation gas into a beneficial process by using the sublimable inorganic filler to create controlled gas escape channels. The sublimation process itself is harnessed to prevent pressure buildup and protect the graphite structure, turning a harmful phenomenon into a protective mechanism.
3Quantity of substance
If a high-thickness polyimide film is used to achieve high-thickness graphite sheet, then the heat capacity is improved, but the yield decreases due to damage of graphite structure from sublimation gas pressure
Solution Approach 1:
The harmful sublimation gas is extracted from the interior by the sublimable inorganic filler, which creates escape pathways and reduces pressure buildup. This prevents graphite structure damage and increases the yield of high-quality high-thickness graphite sheets.
Solution Approach 2:
The patent changes the physical and chemical parameters of the polyimide film by incorporating the sublimable inorganic filler. This modification alters the thermal decomposition behavior and pressure distribution during carbonization and graphitization, enabling high-thickness film production with improved yield.
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 approach results in a high-thickness graphite sheet with enhanced surface quality and thermal conductivity, characterized by a 1%-weight-loss thermal decomposition temperature of 480°C or lower and an L* value of 40 or higher, achieving improved thermal diffusivity and reduced surface projections.
Implementation Method 1
the sublimable inorganic filler may be included in an amount in a range of 0.15 parts to 0.25 parts by weight per 100 parts by weight of the polyimide film
Implementation Method 2
a 1%-weight-loss thermal decomposition temperature of 480° C. or lower being measured by thermogravimetric analysis (TGA)
Implementation Method 3
forming the polyimide film by performing a heat treatment on the gel film
Data Source
AI summary
Disclosed are a polyimide film for a graphite sheet, the polyimide film having a thickness of 100 μm or larger and a 1%-weight-loss thermal decomposition temperature of 480° C. or lower and/or an L* value of 40 or higher being measured with a colorimeter, a method of forming the same polyimide film, and a graphite sheet manufactured using the same polyimide film.