Fuel Cell Separator Composition for Wet Heat Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fuel cell separators face challenges with wet heat resistance, contact resistance stability, and thickness accuracy, leading to decreased performance and stability in sustained power generation due to water absorption and poor heat resistance in existing technologies.
Innovation Solution
A fuel cell separator composition comprising graphite powder and a biphenyl novolak-type epoxy resin with specific properties, including a preferred mean particle size and specific surface area, along with a phenolic resin curing agent and imidazole curing accelerator, is molded to achieve excellent wet heat resistance and maintain contact resistance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a phenolic resin with hexamine curing agent is used to achieve low water uptake, then saturation water uptake is reduced to 0.4-0.6%, but the separator experiences swelling, cracking, and breakage due to non-uniform extension, and ammonium ions dissolve out during operation leading to decreased performance
Solution Approach 1:
The patent changes the chemical composition parameters of the curing agent system, replacing hexamine with a combination of phenolic resin and imidazole compound. This parameter change eliminates the formation of ammonium ions while maintaining low water uptake, resolving the contradiction between water resistance and long-term stability.
Solution Approach 2:
The imidazole compound acts as an intermediary catalyst that enables efficient curing of the phenolic resin without forming harmful ammonium ions. This intermediary substance provides the benefits of low water uptake while avoiding the harmful effects of hexamine decomposition, thus resolving the stability issue.
2Length of stationary object
If ortho-cresol novolak-type epoxy resin is used as the main ingredient of the binder resin, then the separator can be molded with reduced thickness, but water uptake increases leading to decreased performance and failure
Solution Approach 1:
The patent changes the chemical structure parameter of the epoxy resin from ortho-cresol novolak-type to phenolic resin with specific molecular weight and dispersity. This parameter change maintains the ability to mold thin separators while significantly reducing water uptake, resolving the contradiction between thickness reduction and water resistance.
3Quantity of substance
If high-molecular-weight resins are selected to achieve low water uptake in biphenyl novolak-type epoxy resins, then water uptake is reduced, but the resin has high melt viscosity resulting in poor flowability, large thickness variation, and high initial contact resistance
Solution Approach 1:
The patent optimizes the molecular weight parameter to a specific range (450-1,500) and controls dispersity (Mw/Mn) to be 2.0 or less. This precise parameter control achieves low water uptake while maintaining appropriate melt viscosity for good flowability and thickness uniformity, resolving the contradiction between water resistance and manufacturing precision.
Solution Approach 2:
The patent uses a moderate molecular weight range rather than extremely high molecular weight, achieving sufficient water resistance while avoiding the excessive viscosity problems. This partial action approach balances water uptake reduction with maintainability of good flowability and thickness accuracy.
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 fuel cell separator exhibits high resistance to wet heat, maintaining stable power generation efficiency over a long period with minimal change in contact resistance and low water uptake, ensuring consistent electrical conductivity and mechanical strength.
Implementation Method 1
a curing accelerator, and a phenolic resin curing agent... imidazole compound... accelerates the curing reaction
Implementation Method 2
a phenolic resin curing agent... curing reaction... crosslink density
Implementation Method 3
low water uptake... wet heat resistance... hydrophobic properties
Data Source
AI summary
Provided is a fuel cell separator obtained by molding a composition that contains an epoxy resin and a graphite powder, wherein: the epoxy resin contains a main resin, a curing agent, and a curing accelerator; the main resin contains a biphenyl novolak-type epoxy resin having an ICI viscosity of 0.03-0.12 Pa·s at 150°C; and the curing agent is a novolak-type phenol resin having a weight-average molecular weight of 420-1,500 and a dispersion degree of 2.0 or less.