PEEK and PEI (Ultem): High-Temperature Polymers for Aerospace Automotive

PEEK (Polyether Ether Ketone) and PEI (Polyetherimide), marketed under the Sabic brand name Ultem, are high-performance engineering thermoplastics designed for demanding applications requiring exceptional thermal resistance, chemical resistance, and mechanical strength. Both materials can be processed using FDM 3D printing to produce parts that withstand extreme environments where standard plastics would fail.

PEEK offers one of the highest temperature resistances among commercially available thermoplastics, with a continuous service temperature exceeding 250 degrees Celsius. It also provides excellent chemical resistance to acids, bases, and organic solvents. PEEK parts exhibit low smoke and toxic gas emissions when exposed to fire, making them suitable for aerospace interior applications. The material has excellent wear resistance and low coefficient of friction, ideal for bushings, bearings, and seals.

PEI (Ultem) offers continuous service temperatures up to 200 degrees Celsius with excellent flame resistance and low smoke production. Ultem 9085 is the most common FDM grade, offering good impact strength and dimensional stability. The material is inherently flame retardant and meets aerospace flammability requirements without additives. Ultem provides good chemical resistance to automotive fluids, alcohols, and weak acids while being attacked by strong acids and bases.

Printing PEEK and PEI requires specialized equipment capable of reaching extrusion temperatures above 350 degrees Celsius for PEEK and around 350 to 390 degrees Celsius for Ultem. A heated chamber maintained at temperatures near the glass transition temperature of the material reduces residual stresses and warping. PEEK requires a build plate temperature of approximately 120 degrees Celsius, while Ultem typically prints at 140 to 200 degrees Celsius on the build plate.

Post-processing of PEEK and PEI parts includes removing support structures and any necessary machining to achieve final dimensions. Both materials can be machined using standard metalworking techniques, though tool wear is higher than with aluminum or brass. Annealing after printing can improve crystallinity and dimensional stability but requires controlled heating and cooling to avoid warping. The exceptional properties of these materials justify the additional processing complexity for applications where standard polymers cannot perform.