Two-Part Thermal Interface Composition With Non-Abrasive High Filler Loading
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Solution Overview
Problem
Current thermal interface materials for electric vehicles face challenges such as insufficient thermal conductivity, difficulty in production, poor shelf stability, high costs, and the use of abrasive fillers that can damage equipment, while also requiring high filler content and the ability to flow at room temperature to fill gaps effectively.
Innovation Solution
A two-part thermal interface material composition featuring a prepolymer with blocked isocyanate groups and a polyamine component, with 50% or more thermally conductive fillers like aluminum hydroxide, which reacts at room temperature to form a high-conductivity, low-viscosity material that is shelf-stable and non-abrasive, and has a specific gravity of 2.5 or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high filler content (50% or more) is used to achieve high thermal conductivity, then thermal conductivity is improved, but viscosity increases making it difficult to flow and fill gaps at room temperature
Solution Approach 1:
The patent changes the chemical parameters of the matrix phase by using a two-part reactive composition that remains liquid at room temperature. The key parameter change is the use of low molecular weight components (e.g., caprolactone with MW 114, 1,6-hexanediol with MW 118) that maintain fluidity despite high filler content (50-90 wt%). The composition stays liquid until curing, enabling gap filling, then transforms to a solid with high thermal conductivity.
Solution Approach 2:
The patent creates a composite material system combining thermally conductive fillers (aluminum hydroxide, aluminum oxide, boron nitride, etc.) with a reactive oligomeric composition. This composite structure allows the filler particles to be suspended in the liquid matrix at high concentrations while maintaining flowability, and after curing forms a solid composite with enhanced thermal conductivity properties.
2Temperature
If two-part reactive compositions are used to achieve high thermal conductivity and gap filling, then thermal conductivity and flowability are improved, but shelf stability deteriorates due to premature reaction
Solution Approach 1:
The patent divides the composition into two separate parts that are stored independently: Part A containing the oligomeric composition with blocked isocyanate groups, and Part B containing the carbamate-reactive compound. This segmentation prevents premature reaction between the components, maintaining shelf stability, while allowing the user to mix them before application to achieve the desired thermal conductivity and flow properties.
Solution Approach 2:
The patent uses a blocking compound as an intermediary to temporarily mask the reactivity of the isocyanate groups. The blocking compound (e.g., phenol, carboxylic acid) forms a stable carbamate block that prevents premature reaction with the polyamine, allowing shelf-stable storage. Upon mixing Part A and Part B, the blocking is reversed and the reactive carbamate groups become available for crosslinking.
3Temperature
If conventional fillers are used to achieve thermal conductivity, then thermal performance is improved, but equipment damage occurs due to abrasive properties
Solution Approach 1:
The patent changes the physical parameter of filler hardness by selecting soft, non-abrasive fillers such as aluminum hydroxide (Mohs hardness ~3), aluminum oxide (Mohs hardness ~9 but used in controlled forms), and boron nitride. These fillers provide adequate thermal conductivity (aluminum hydroxide: 30 W/mK, boron nitride: 290 W/mK) without the aggressive abrasiveness of traditional fillers like aluminum powder or ceramic beads, thereby protecting processing equipment.
Solution Approach 2:
The patent employs aluminum hydroxide as a preferred filler that decomposes at relatively low temperatures (around 200°C) to release water and leave behind aluminum oxide. This 'short-living' filler provides thermal conductivity during processing and then transforms in situ, avoiding the need for durable, expensive, or highly abrasive permanent fillers while still achieving the thermal management objective.
4Quantity of substance
If high filler content is used to reduce material cost, then raw material cost is reduced, but manufacturing complexity increases due to mixing and processing difficulties
Solution Approach 1:
The patent changes the rheological parameters of the composition by using low-viscosity oligomeric components and controlling the molecular weight and functionality of the reactors. This allows high filler content (50-90 wt%) to be incorporated while maintaining a pourable, easy-to-mix liquid state during manufacturing and application, eliminating the need for complex high-shear mixing equipment or specialized processing procedures.
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 achieves high thermal conductivity (up to 3.0 W/mK), excellent shelf stability, and cost-effectiveness, while avoiding the use of abrasive fillers, ensuring efficient heat transfer and ease of application in electric vehicle battery thermal management systems.
Implementation Method 1
a first part comprising at least a prepolymer including two or more carbamate groups, wherein the prepolymer is formed by blocking one or more of the isocyanate groups of an aromatic polyisocyanate prepolymer with a phenol group of a blocking compound; and a second part comprising at least one or more polyamine compounds capable of a reaction with the prepolymer
Implementation Method 2
50 weight percent or more of one or more thermally conductive fillers, based on the total weight of the two-part composition
Data Source
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Figure 3
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AI summary
The teachings herein relate to new compositions for thermal interface materials that provide improved thermal conductivity without requiring filler materials that are expensive or abrasive. The improved thermal conductivity is achieved using a combination of increased filler loading, selection of a filler having a broad particle size distribution, and selection of filler that is non-abrasive. The thermal interface material preferably has a specific gravity of about 4.0 or less, about 3.0 or less, about 2.5 or less, or about 2.4 or less. The thermal interface material may be a two-part composition. In order to achieve maximum thermal conductivity, each part preferably includes a liquid matrix material and dispersed filler. Upon mixing, the first and second parts may react to increase this viscosity (e.g., by polymerizing and/or cross-linking). The first part preferably includes a carbamate-containing compound that reacts with a carbamate-reactive compound, which is preferably in the second component. The first part preferably is substantially or entirely free of isocyanate containing compounds, as these compounds may reduce the shelf life stability of the composition. The carbamate-reactive compound preferably is a polyamine, including two or more spaced apart amine groups. The first part, the second part, or both, preferably includes a catalyst for accelerating the reaction between the carbamate-containing compound and the carbamate-reactive compound.