Thermally Conductive Gap Filler Composition With Low Viscosity
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Solution Overview
Problem
Current curable polyurethane compositions used as gap fillers in electronic and battery applications have poor heat conductivity and are not suitable for high heat dissipation, requiring high levels of heat-conductive fillers that increase viscosity and storage stability issues, and are not compatible with electrodeposition coating processes.
Innovation Solution
A two-component moisture-curable composition with a filler selected from aluminium oxide, aluminium hydroxide, boron nitride, and others, combined with a polymer containing isocyanate or alkoxysilane groups, achieving high thermal conductivity without the need for drying fillers or dispersing agents, and compatibility with e-coat processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high levels of heat-conductive fillers are added to polyurethane compositions, then thermal conductivity is improved, but viscosity increases and storage stability deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the polyurethane system by using specific isocyanate indices and NCO/OH ratios (2.0-4.0) to optimize the balance between thermal conductivity and viscosity. By controlling the isocyanate index within this range and using polymers with specific OH numbers, the formulation achieves high thermal conductivity without excessive viscosity increase.
Solution Approach 2:
The patent creates a composite material system combining polyurethane polymers with heat-conductive fillers (such as aluminum oxide, aluminum nitride, or boron nitride). The composite formulation uses carefully selected filler types and surface treatments to achieve high thermal conductivity (≥2 W/mK) while maintaining manageable viscosity through optimized polymer-filler interactions.
2Temperature
If high levels of heat-conductive fillers are added to polyurethane compositions, then thermal conductivity is improved, but storage stability worsens
Solution Approach 1:
The patent controls the isocyanate index within the range of 2.0-4.0 and maintains specific NCO/OH ratios to prevent premature curing during storage. By optimizing these chemical parameters and selecting polymers with appropriate OH numbers (10-50 mg KOH/g), the formulation achieves high thermal conductivity while maintaining long-term storage stability without filler drying requirements.
Solution Approach 2:
The patent eliminates the need for filler drying processes by optimizing the polyurethane formulation to be tolerant of moisture-containing fillers. This approach replaces complex filler preparation steps with a more robust formulation that accepts fillers as-is, improving both storage stability and manufacturing simplicity.
3Temperature
If silicone-based compositions are used for heat dissipation, then thermal conductivity is improved, but compatibility with e-coat processes deteriorates
Solution Approach 1:
The patent extracts the problematic silicone components from the formulation and replaces them with polyurethane polymers. This substitution removes the source of e-coat interference (silicone migration and deposition) while maintaining heat dissipation functionality through carefully selected polyurethane-based heat-conductive fillers and polymer matrices.
Solution Approach 2:
The patent uses polyurethane polymers as an intermediary material that bridges the requirements for thermal conductivity and e-coat compatibility. The polyurethane system acts as a mediator between the heat-conductive fillers and the e-coat process, providing a compatible matrix that does not interfere with electrodeposition while still achieving the required thermal performance (≥2 W/mK).
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 composition exhibits high thermal conductivity (at least 2 W/mK) with low viscosity, ensuring effective heat dissipation and storage stability, while being compatible with e-coat processes, thus addressing the limitations of existing technologies.
Implementation Method 1
Polyurethane compositions which crosslink and cure via the reaction of isocyanate groups with hydroxyl or amino groups
Implementation Method 2
involving hydrolysis and condensation of the alkoxysilane groups
Implementation Method 3
involving hydrolysis and condensation of the alkoxysilane groups
Implementation Method 4
a high heat conductivity, since batteries and electronics generate significant amounts of heat which must be dissipated efficiently
Data Source
AI summary
A two-component moisture-curable composition, especially suitable as thermally conductive gap filler, in particular with flame-retardant properties. It is thus highly suitable for use in e-mobility battery bonding or electronic equipment.