Thermoplastic
PEI (Ultem)
Amber, transparent, flame retardant, and stable to 170 °C.
Published values for unfilled grades at 23 °C unless stated. Confirm against the supplier datasheet for the grade you specify.
What it is
PEI is an amorphous polymer with inherent flame retardance and very low smoke emission, which is why it dominates aircraft interiors. It holds dimensional stability to 170 °C and is transparent in an amber tint.
Being amorphous rather than semi-crystalline, it machines and molds more predictably than PEEK and costs substantially less, at the price of lower chemical and wear resistance.
Where it is used
- Aircraft interior panels, ducting, and fittings
- Sterilizable medical trays and instrument handles
- Electrical insulators and connectors at high temperature
- Semiconductor test fixtures
- Printed high-temperature prototypes and tooling
Processing notes
Dry 4–6 hours at 150 °C. Melt 340–400 °C, mold 140–175 °C.
It is a stiff-flowing material; expect high injection pressure and design generous gates and runners.
Susceptible to stress cracking from partially halogenated solvents. Check cleaning and assembly chemicals before release.
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Design notes
Use generous radii; amorphous high-temperature polymers concentrate molded-in stress at corners.
Anneal parts that will see high service temperature, to relieve molding stress before it relieves itself as warp.
Specify the UL file and rating explicitly if the flame performance is a requirement rather than a bonus.
Grades and variants
- Ultem 1000, unfilled general purpose
- Ultem 2300 to 30 % glass filled
- Ultem 9085, the standard aerospace printing grade
- Medical grades with ISO 10993 documentation
- Aerospace grades certified to FAR 25.853
Specifying this material?
Send your CAD and target volumes. We come back with a price, a lead time, and any material or design notes that would reduce either.