Graphite Sheet Thermal Conductivity Flexibility Bimodal Fillers
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Solution Overview
Problem
Conventional graphite sheets prepared from polyimide films suffer from poor flexibility and thermal conductivity due to brittleness, which is exacerbated by the addition of fillers that create voids and surface roughness, making it difficult to balance thermal conductivity and physical properties.
Innovation Solution
A method involving polyimide films with 2 or more fillers of different average particle diameters, where the fillers are sublimated during carbonizing and graphitizing steps to form voids, achieving a thermal conductivity of at least 1,400 W/m·K, while maintaining flexibility and preventing surface protrusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fillers are added to polyimide films to improve flexibility, then flexibility is improved, but thermal conductivity deteriorates due to void formation
Solution Approach 1:
The invention changes the particle size parameter of fillers by using a bimodal distribution with both fine particles (0.1-1 μm) and coarse particles (1-10 μm). The fine particles fill voids and maintain thermal pathways, while coarse particles provide flexibility. This parameter optimization resolves the contradiction between flexibility and thermal conductivity.
Solution Approach 2:
The invention uses a composite filler system combining two different particle sizes in specific proportions (fine particles: 1-10 wt%, coarse particles: 90-99 wt%). This composite approach allows the fine particles to maintain thermal conductivity by filling voids while coarse particles provide flexibility, simultaneously achieving both desired properties.
2Reliability
If heat treatment is applied during carbonizing and graphitizing steps to achieve high thermal conductivity, then thermal conductivity is improved, but flexibility deteriorates due to brittleness
Solution Approach 1:
The invention optimizes the particle size parameters of fillers to create a bimodal distribution that addresses the brittleness issue. The specific size ranges (fine: 0.1-1 μm, coarse: 1-10 μm) are selected to maintain flexibility even after high-temperature heat treatment during carbonizing and graphitizing steps.
Solution Approach 2:
The fine particles act as intermediaries that bridge the matrix and coarse particles, preventing stress concentration and reducing brittleness during heat treatment. This intermediary role allows the material to maintain flexibility while achieving high thermal conductivity through proper heat treatment.
3Ease of operation
If fillers are added to form voids during carbonizing steps, then flexibility is improved, but manufacturing precision deteriorates due to surface roughness
Solution Approach 1:
The invention carefully selects the particle size parameters, particularly keeping fine particles in the 0.1-1 μm range and limiting their content to 1-10 wt%. This parameter control ensures that fine particles fill voids without creating excessive surface roughness, maintaining both flexibility and surface quality.
Solution Approach 2:
The invention applies local quality by using fine particles specifically to fill internal voids while coarse particles maintain overall structure. The fine particles are strategically positioned in the matrix to improve flexibility without significantly affecting surface roughness, achieving localized functionality.
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 method produces high-performance graphite sheets with enhanced thermal conductivity and flexibility, minimizing defects and processability issues, thereby reducing labor, time, and cost in their preparation.
Implementation Method 1
the fillers may be sublimated at the steps of carbonizing and/or graphitizing, causing to form the voids in the graphite sheet
Data Source
AI summary
The present invention provides a method for preparing a high-performance graphite sheet by imidizing a polyamic acid resulting from a reaction of dianhydride monomer(s) and diamine monomer(s) to obtain a polyimide film; and carbonizing and/or graphitizing the polyimide film to obtain a high-performance graphite sheet, where the polyimide film contains 2 or more fillers having different average particle diameters, and the thermal conductivity of the graphite sheet is at least 1,400 W/m·K. Further, the present invention provides a graphite sheet obtained by the above method.