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® PEI fasteners and custom hardware are also available in glass filled grades for greater 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. Instead it has a glass transition temperature which is (Tg) is 217º C (422º F).

The continuous service temperature of 170º C (340º F).


Additionally, the material has high strength and stiffness as well as a high tensile modulus.

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


Ultem® PEI fasteners and custom 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 excelllent electrical properties.

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


Ultem® PEI is naturally flame retardant. The UL ratings are 94 V0, V2, and 5VA.

And it give off very little smoke.


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

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

Ultem® PEI is 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. These include sodium bicarbonate, potassium cyanide, sodium sulfide, and others. Also, PEI shows stress cracking in chlorinated solvents. These include carbon tetrachloride, tetrachloroethylene, and others.

Cell Tower Antennas

Ultem® 2300 set screws have been often used in antennas in cell phone towers in Europe. Because of their strength and the fact that they are microwave clear Ultem® 2300 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. So the clear microwave property of the material ensures the electrons from the particle accelerator will hit the experiment as the scientists intended.

AM/FM Radio Transmitters

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

Medical and Scientific Instruments

Additionally 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

Ultem® PEIcannot withstand continuous radiation. However, in short bursts, this plastic performs well. Thus, MRI machines and other medical equipment are manufactured using Ultem® PEI fasteners and custom parts.

Trays and Containers for the Food Industry

Ultem® 1000 is FDA and USDA-compliant as well as microwave clear. Thus 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 to cook or heat food.

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