Polyetherimide (PEI; branded as Ultem[1]) is an amorphous, amber-to-transparent thermoplastic with characteristics similar to the related plastic PEEK.

When comparing PEI to PEEK, the former is cheaper but has lower impact strength and a tighter temperature range.

[3] Due to its adhesive properties and chemical stability it became a popular bed material for FFF 3D printers.

Polyetherimide is able to resist high temperatures while maintaining stable electrical properties over a wide range of frequencies.

This high strength material offers excellent chemical resistance and ductile properties suitable for various applications, even those involving steam exposure.