Ultem® PEI is a semi-transparent high-temperature plastic. It is used to make custom parts as well as fasteners such as screws, hex nuts, washers, threaded studs, and spacers. It can be both molded and machined. Ultem® hardware is also available in glass-filled grades for enhanced strength and stiffness. (Glass-filled grades are opaque.) Ultem® 1000 is the natural grade, and Ultem® 2300 is the glass-filled grade.

Ultem® PEI Properties:



Ultem® PEI has no actual melting point but rather a glass transition temperature which is (Tg) is 217º C (422º F).

Continuous service temperature of 170º C (340º F).


Also, the material has extremely high strength and stiffness as well as high tensile modulus.

Retains 85% of its tensile strength after 10,000 hours in boiling water and 100% after 2,000 cycles in a steam autoclave at 270º C (518ºF).


Ultem® PEI parts perform well in hot water and steam.

The material is hydrophobic. Therefore, it does not absorb water.

Chemical Resistance

Broad chemical resistance up to high temperatures. Tolerates alcohols, acids, hydrocarbons, and others.

Electrical Properties

Ultem® PEI has outstanding electrical properties.

It has the highest dielectric (insulating) strengths of any commercially available thermoplastic material. The dielectric constant is also stable.


It is naturally flame retardant with UL ratings of 94 V0, V2, and 5VA.

And it give off very little smoke.


The 1000 grade which does not contain fibers is FDA-compliant and USDA-approved.

It is less expensive than other materials in its class, such as PEEK and PES.

RoHS Compliant.

It is microwave clear.

It is an amorphous plastic. Therefore, it has a molecular structure that lacks a continuous repeating form.

PEI is naturally UV resistant.


However, it will not stand up to alkali salts such as sodium bicarbonate, potassium cyanide, sodium sulfide, and others. Also, PEI shows stress cracking in chlorinated solvents, which include carbon tetrachloride, tetrachloroethylene, and others.


Ultem® 2300 flanged hex nuts are used to hold the sound tiles of submarines to the hull of the vessel as it is microwave clear. Therefore, sonar does not detect the hex nuts. Also, it is also fire retardant, and in the case of a fire, the parts have extremely low smoke emissions. Thus the lives of the crew are not endangered.

Cell Tower Antennas

Ultem® 2300 set screws have been used extensively in antennas in cell phone towers in Europe. Because of their strength and the fact that they are microwave clear it is well suited to this application.

Particle Accelerators

In a particle accelerator in England, Ultem® 2300 set screws have been used to insulate two sheets of metal from each other in an experiment. The clear microwave property of the material ensures the electrons from the particle accelerator will hit the experiment apparatus as the scientists intended.

AM/FM Radio Transmitters

Ultem® 1000 custom parts and fasteners are used to make these transmitters because the parts are microwave clear.

Medical and Scientific Instruments

Ultem® 1000 is used for sterilization purposes in the medical industry. Since the parts can withstand repeated cycles in a steam autoclave Ultem PEI is well-suited to this application. As mentioned above, Ultem® will retain 100% of its tensile strength after 2,000 cycles in a steam autoclave at 270º C (518º F).

MRI Machines

PEI cannot withstand continuous radiation. However, in short bursts, this plastic performs well. Thus, MRI machines and other medical equipment are manufactured using Ultem® PEI custom parts and fasteners.

Trays and Containers for the Food Industry

Ultem® 1000 is FDA and USDA-compliant as well as microwave clear. Trays and containers are not affected by microwave cooking units. Therefore with a continuous service temperature of 170º C (340º F), this material is well suited for cooking and heating food.

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