Ultem® (PEI)
The amber engineering plastic specified when a part has to hold strength and stiffness hot, and be flame retardant doing it. Stocked in sheet and rod.
What Ultem is
Polyetherimide with high strength, stiffness, and broad chemical resistance.
Why engineers specify it
Ultem sits between the general engineering plastics and PEEK. It holds strength and stiffness at temperatures that soften acetal or nylon, it is inherently flame retardant, and it costs meaningfully less than PEEK. The usual design conversation is Ultem or PEEK: if the service temperature and the chemistry are inside what Ultem handles, it is the cheaper answer, and PEEK is what you move to when they are not.
Machining Ultem
Ultem machines cleanly but is notch-sensitive and prone to stress cracking, and the cutting fluid matters more than the feeds — the wrong coolant can craze parts that looked perfect leaving the shop. Sharp tooling, generous internal radii and annealing between roughing and finishing are what keep close-tolerance work stable.
Machining Ultem (PEI): stress cracking, tolerances and where it beats PEEKNeed Ultem parts machined to print?
Send us a drawing and we will quote it. Precision plastic machining in Linden, New Jersey since 1968.