Composite Multilayer Seal for PEM Fuel Cell Bipolar Plates
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Solution Overview
Problem
Existing sealing solutions for PEM fuel cells, such as silicone-based elastomers, are inadequate for high-temperature applications due to deterioration and permeation issues, and fluoroelastomers lack sufficient compliance for sealing bipolar plates without causing stress, while traditional die-cut or molded gaskets lead to misalignment and leakage.
Innovation Solution
A composite seal with a multiple layer elastomeric construction, featuring a low-durometer elastomer compliant layer coated or encapsulated with a fluoroelastomer or fluoropolymer protective layer, applied directly to fuel cell components to provide chemical and thermal resistance, compressive compliance, and minimize leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicone-based elastomers are used for sealing, then ease of manufacture and low cost are achieved, but chemical resistance and thermal stability deteriorate at high temperatures
Solution Approach 1:
The patent employs a composite sealing structure consisting of a silicone-based elastomer layer combined with a fluoroelastomer or fluoropolymer coating. The silicone layer provides ease of manufacture and compliance, while the fluoroelastomer/fluoropolymer layer contributes chemical resistance and thermal stability, thereby resolving the contradiction between ease of manufacture and chemical resistance.
2Reliability
If fluoroelastomer is used for sealing, then chemical resistance and thermal stability are improved, but compressive compliance deteriorates due to high durometer values
Solution Approach 1:
The patent combines a soft silicone-based elastomer layer (providing compressive compliance) with a fluoroelastomer or fluoropolymer coating (providing chemical resistance and thermal stability). This composite structure allows the sealing system to achieve both compliance and chemical resistance simultaneously.
Solution Approach 2:
The fluoroelastomer/fluoropolymer coating is applied as a thin layer on the surface of the silicone elastomer, providing localized chemical resistance and thermal stability where needed, while the bulk silicone material maintains compressive compliance for effective sealing.
3Ease of manufacture
If traditional die-cut or molded gaskets are used, then ease of manufacture is achieved, but sealing precision deteriorates due to misalignment and leakage
Solution Approach 1:
The composite seal integrates the silicone elastomer layer and fluoroelastomer/fluoropolymer coating into a unified structure that combines the manufacturing advantages of molded gaskets with the sealing precision of custom-fitted seals, reducing misalignment and leakage.
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 composite seal offers improved durability, chemical resistance, and compressive compliance, reducing leakage and stress on fuel cell components, while maintaining a thin profile and adaptability for various fuel cell designs, enhancing the overall sealing performance and reliability.
Implementation Method 1
their use in high temperature fuel cell applications is problematic due to their vulnerability to deterioration over time and subsequent interaction with a fluorene constituent, as well as the high pH values, commonly associated within a fuel cell environment
Implementation Method 2
Fluoro materials, however, generally do not possess durometer values less than 55 Shore A, which presents an additional problem with respect to providing the necessary compliance for sealing anode and cathode bipolar plates to an adjoining MEA without resulting in undue stress on components of the fuel cell assembly
Implementation Method 3
it is desirable to provide an improved sealing solution, said sealing solution providing the necessary chemical and thermal resistance properties, as well as the necessary compressive compliance properties, needed for use in both low and high temperature yielding fuel cell applications
Implementation Method 4
its use in low temperature fuel cell applications has the potential for long term permeation of low molecular weight gases and materials through the silicone body due to its inherently porous molecular structure
Data Source
AI summary
A composite seal having a multilayer elastomeric construction and method for constructing the same is provided. More specifically, the present invention provides a composite seal comprised of a low-durometer elastomer compliant layer coated with, or alternatively encapsulated by, a thin protective layer for securely sealing a bipolar plate and a membrane electrode assembly of a fuel cell. The elastomer compliant layer is preferably a silicone constituent and the thin coat protective layer is preferably a fluoroelastomer or fluoropolymer constituent suitable for bonding to the elastomer compliant layer. The foregoing layers constructing the composite seal are preferably deposited directly onto the aforementioned fuel cell components along a predetermined periphery. The resulting composite seal is thin in construction, resistive to undesired chemical and thermal reactions and provides the necessary compressive compliance without undue stress on the fuel cell assembly.