PEEK (Polyether Ether Ketone) and PEI (Polyetherimide, often known by Sabic's Ultem trade name) are the high-performance polymer family — the materials that survive environments where ordinary engineering thermoplastics give up.
They're also the most expensive, the most demanding to print, and the most over-specified materials in the FDM world. Used appropriately, they're irreplaceable. Used because they sound impressive, they're a waste of money.
The Property Profile
Continuous service temperature 200-260 °C (PEEK), 170-200 °C (PEI). Tensile strength 90-110 MPa unfilled, 130-180 MPa for carbon-filled grades. Excellent chemical resistance to most industrial fluids. Inherently flame-retardant (V-0 rated without additives). Excellent fatigue performance.
These properties put PEEK and PEI in the top tier of engineering polymers. They're the materials of choice when nothing less will do.
When PEEK or PEI Is the Right Answer
High-temperature applications: components near hot exhausts, around engines, in autoclave-sterilised medical equipment, in aerospace hot-section accessories. Applications above PA-CF's 130-160 °C envelope.
Aggressive chemical environments: oil and gas, certain pharmaceutical applications, chemically harsh manufacturing processes. Resistance to fuels, hydraulic fluids, common industrial solvents and many acids and alkalis is excellent.
Aerospace and defence applications requiring inherent flame retardancy, low smoke and toxicity (LST), and high-strength performance. PEEK and PEI both meet many aerospace material specifications without additives.
High-temperature service (>150 °C continuous)
Aggressive chemical exposure
Aerospace flame and smoke requirements
Sterilisable medical applications
Demanding fatigue applications
When They're Not the Right Answer
When the application would be perfectly served by PA-CF or PA-GF at one-fifth the cost. Most industrial brackets, jigs, fixtures and tooling don't need PEEK's envelope and won't benefit from paying for it.
When the supplier doesn't have the equipment to print them properly. PEEK requires print chamber temperatures of 130-180 °C, nozzle temperatures of 380-430 °C, and controlled cool-down profiles. Most FDM machines simply can't reach these temperatures. Printing PEEK on a machine that can't deliver the conditions produces parts that look like PEEK but lack PEEK properties.
Print and Post-Process Considerations
PEEK and PEI both benefit dramatically from controlled annealing post-print. Properly annealed PEEK can approach datasheet values; as-printed PEEK typically sits 30-40% below. The annealing recipe is part of the production specification, not an optional extra.
Both materials are notoriously moisture-sensitive. Filament must be stored dry and dried before printing. Wet PEEK prints with foaming, voids and dramatically reduced mechanical properties.
Working with Global3D
We support Australian customers with high-performance polymer printing on suitably equipped machines, with the controlled annealing and inspection that the materials demand. Talk to us about whether PEEK or PEI is genuinely the right material for your application.