Fuel Cell Adhesive Sheet for High-Heat MEA Peripheral Sealing
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Solution Overview
Problem
Existing sealing materials for fuel cells face challenges in maintaining high sealing performance in high-temperature and high-humidity environments, require complex adhesion processes, and are prone to adhesion failures such as floating, peeling, and voids.
Innovation Solution
A thermosetting adhesive sheet for fuel cells composed of a polyurethane resin with reactive functional groups and a cross-linking agent, having specific physical properties such as a gel fraction of 60% or higher, storage elastic modulus between 5.0×10^4 Pa and 1.0×10^8 Pa, and a glass transition temperature between −10° C. and 100° C., allowing for room-temperature storage and adhesion without curing treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hot-melt adhesive is used for sealing, then adhesion can be achieved, but high-temperature pressing is required which causes thermal damage to MEA and increases operation time
Solution Approach 1:
The patent changes the temperature parameter from high-temperature hot-melt adhesive (requiring high-temperature pressing) to room-temperature curable adhesive composition. The adhesive composition contains a polyurethane resin with reactive functional groups that cure at room temperature, eliminating the need for high-temperature pressing and preventing thermal damage to the MEA while maintaining effective adhesion.
2Ease of operation
If adhesive sheet is stored at room temperature, then handling is simplified, but adhesion performance degrades in high-temperature and high-humidity environment
Solution Approach 1:
The patent applies preliminary action by pre-forming the adhesive sheet at room temperature with controlled gel fraction (30-80 mass %) and specific storage elastic modulus range. This preliminary preparation ensures the adhesive remains stable during storage and handling while maintaining the capability to achieve reliable adhesion even in high-temperature and high-humidity environments, eliminating the need for low-temperature storage.
3Strength
If curing treatment process is performed after adhesion, then adhesion strength is improved, but operation time increases and process complexity increases
Solution Approach 1:
The patent merges the adhesion and curing processes into a single step. The adhesive composition is applied to the MEA and simultaneously adheres and cures at room temperature without requiring separate curing treatment. This integration eliminates additional operation time and process complexity while achieving sufficient adhesion strength for sealing the fuel cell.
4Reliability
If gel fraction is increased to improve adhesion stability, then storage elastic modulus increases, but adhesion flexibility decreases
Solution Approach 1:
The patent optimizes the gel fraction parameter to a specific range (30-80 mass %) and controls the storage elastic modulus to be within 10³ to 10⁸ Pa at 25°C. This parameter optimization balances adhesion stability and flexibility, ensuring the adhesive remains stable during storage and handling while maintaining sufficient flexibility for effective adhesion to the MEA surface.
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 adhesive sheet provides excellent storage stability, prevents adhesion failures, and maintains adhesiveness in high-temperature and high-humidity conditions, facilitating easy handling and operation.
Implementation Method 1
containing a cured product of an adhesive composition containing a polyurethane resin having a reactive functional group and a cross-linking agent
Implementation Method 2
a storage elastic modulus at 100° C. (G′100) of 5.0×104 Pa or higher and 1.0×108 Pa or lower; and a decreasing rate of a storage elastic modulus at 120° C. (G′120) to the storage elastic modulus at 100° C. (G′100) of 0.5 or less
Data Source
AI summary
A thermosetting adhesive sheet 10 for sealing the periphery of a membrane electrode assembly, which is composed of a solid polymer electrolyte membrane and electrodes placed on both sides of the solid polymer electrolyte membrane contains an adhesive layer 14. The adhesive layer 14 is formed of a cured product of an adhesive composition containing a polyurethane resin having a reactive functional group and a cross-linking agent, where the adhesive layer 14 has a gel fraction of 60 mass % or higher, a storage elastic modulus at 100° C. (G′100) of 5.0×104 Pa or higher and 1.0×108 Pa or lower, and a decreasing rate of a storage elastic modulus at 120° C. (G′120) to the storage elastic modulus at 100° C. (G′100) of 0.5 or less.