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Views: 0 Author: Site Editor Publish Time: 2026-07-09 Origin: MBH office
Hydrogen fuel cell systems put unusual demands on the plastic components hidden inside them — insulators, seals, manifold parts, and structural brackets all have to survive humid, chemically active environments while holding tight tolerances for years without maintenance. Metal isn't always the answer: it adds weight, can corrode, and often needs additional insulation. That's why engineers increasingly turn to high-performance thermoplastics like PEEK and PEI (Ultem) for precision fuel cell parts.
Both materials show up constantly in fuel cell design discussions, but they aren't interchangeable. This guide breaks down where each one fits, so you can match the material to the part instead of over-specifying (and overpaying) or under-specifying (and risking failure).
Fuel cell stacks operate in a demanding internal environment: humidified hydrogen and air streams, operating temperatures that can climb well above 80°C in some stack designs, and a constant need for electrical isolation between conductive components. Components commonly machined from engineering plastics include:
End plate insulators and separator frames
Manifold and flow-field structural components
Sensor housings and connector strips
Static seals and gaskets for stack sealing
Test fixtures and sockets used in fuel cell R&D and QC
The right plastic needs to combine electrical insulation, dimensional stability under humidity and heat, and resistance to the chemical environment inside the stack — while still being practical to machine to tight tolerances.
Property | PEEK | PEI (Ultem 1000) |
|---|---|---|
Max. continuous service temp | ~250°C | 170°C |
Chemical resistance | Excellent, incl. steam & hot water | Good, resistant to acids & hydrolysis |
Dielectric strength | High | High |
Dimensional stability | Excellent | Excellent, low creep |
Flame retardancy | Inherent | Inherent, UL94 V-0 |
Machinability | Good | Very good |
Relative cost | Higher | Lower |
The short version: PEEK is the choice when the part sees sustained high heat or aggressive chemical exposure, particularly anywhere close to the stack's hottest zones or exposed to steam cycles. PEI is the more cost-effective choice for parts that need strong electrical insulation, stiffness, and flame retardancy but don't need to survive PEEK-level heat — which describes a large share of the structural and insulating parts in a typical stack.
Choose PEEK for:
Components near high-temperature zones of the stack
Parts exposed to repeated steam/hot water cycling
Seals and bushings requiring low friction plus high heat resistance
Choose PEI for:
End plate insulators and separator frames
Connector strips, coil bobbins, and sensor housings
Structural brackets and manifold components where flame retardancy and stiffness matter more than extreme heat resistance
Cost-sensitive projects where PEEK's full temperature range isn't required
If your design has both — some parts need PEEK's headroom, others don't — that split isn't unusual. Most fuel cell OEMs and integrators end up using more than one engineering plastic across a single stack design, rather than specifying one material everywhere.
If you're scoping material options for a fuel cell project, send us your part drawing or application details — we can recommend PEEK, PEI, or a mix of both based on the specific temperature and chemical exposure your components will see.
