Polyetherimide (PEI), commonly referred to by brand name Ultem®, is an amorphous thermoplastic polymer that offers a combination of desirable mechanical and thermal characteristics. Due to its robustness and versatility, it is used in demanding engineering applications spanning various industries, including aerospace, automotive, electronics, medical technology, and food processing. However, working with an experienced partner is key to ensure your finished parts meet specifications.

Advantages of PEI For Demanding Applications

PEI is used across industries because it combines thermal, mechanical, and chemical properties that are hard to match.

High Heat Resistance – PEI has a high glass transition temperature, making it stable in continuous-use temperatures up to about 340°F (170°C) without deformation. This is especially valuable in aerospace, automotive, and electronics where thermal stability is critical.
Dimensional Stability – It maintains its shape and size under mechanical stress and thermal cycling. Its low coefficient of thermal expansion makes it ideal for tight-tolerance parts.
Strength and Stiffness – PEI offers high tensile and flexural strength. It is rigid even at elevated temperatures, making it a good choice for structural components.
Flame Resistance – It has inherent flame retardancy without needing additives. It typically meets UL 94 V-0 ratings, making it safe for electrical and aerospace applications.
Electrical Insulation – PEI has excellent dielectric properties and is widely used in electrical and electronic components that require insulation under thermal and mechanical loads.
Chemical Resistance – It resists many chemicals, including hydrocarbons, alcohols, and acids. This makes it suitable for environments where chemical exposure is a concern.
Creep Resistance – PEI resists deformation even under prolonged mechanical stress, especially at high temperatures.
Sterilization Compatibility – It’s widely used in medical applications because it can withstand repeated autoclave sterilization without degrading.
Transparency (Optional) – Some grades of PEI are optically transparent in thin sections, which is useful for sight glasses, diagnostic equipment, and other applications where visual inspection is needed.

Challenges Working With PEI

While PEI brings many advantages to injection molded or machined components, product engineers must take care to work with a plastic fabricator with expertise and experience working with this specialized material. By choosing a knowledgeable fabricator, designers can help ensure that the final product meets the desired specifications and performance standards.

Proper handling and processing are crucial, as PEI requires specific conditions to achieve optimal results. PEI is hygroscopic, meaning it absorbs moisture from the air. It can absorb up to 0.25–0.5% water by weight at saturation in standard atmospheric conditions. Even 0.1% moisture can cause problems during molding, leading to splay, bubbles, or loss of mechanical strength because the water vaporizes at PEI processing temps, 644–750°F (~340–400°C). Fabricators need to thoroughly dry the material to prevent moisture-related issues during molding.

When injection molding, the high melt temperature also necessitates specialized high-temperature equipment. PEI has a narrow processing window, which requires precise control over temperature. Overheating can degrade the material, and underheating causes poor flow and incomplete fills. Experience and expertise in handling PEI’s unique challenges can significantly influence the quality and performance of the final product.

PEI can be machined to tight tolerances with minimal warping or internal stress (especially annealed stock), making it a good choice for precision components like gears, valves, and insulators. However, PEI’s high rigidity and abrasiveness, especially with filled grades (glass or carbon), wear down tools faster. Thermal buildup during machining must be managed to avoid melting or distortion in the component. Additionally, filled grades can be brittle, so extra care is required for sharp corners or thin features.

Ensinger TECAPEI™ Grades

Ensinger’s PEI plastic material offering is extruded in sheet and rod shapes using Ultem and is known by the trade name TECAPEI. There are several grades available:

TECAPEI unfilled is equivalent to Ultem® 1000 series. TECAPEI natural unreinforced PEI is suitable for contact with foods. It is also available in black. Both provide exceptional mechanical, thermal, and electrical properties without the inclusion of fillers.

TECAPEI™ EF natural is another unreinforced PIE; however, it is 100 percent bio-based, providing a sustainable alternative to traditional PEI. The bioplastic provides mechanical strength and rigidity comparable to traditional PEI, featuring exceptional hydrolysis resistance and dimensional stability.

TECAPEI™ GF30 Nat is equivalent to Ultem®2300 Series. It is a 30% glass-filled PEI that combines the inherent qualities of PEI with the reinforcing power of glass fibers. It exhibits high rigidity, exceptional mechanical strength, excellent dimensional stability, and good resistance to high-energy radiation. These properties make 30% glass fiber-reinforced PEI suitable for parts subjected to high static loads in elevated temperature conditions over extended periods.

Your Partner for PEI Injection Molding or Machining

Working with PEI requires precision, the right equipment, and experience handling high-temperature engineering plastics. At Ensinger, we manufacture TECAPEI™ using Ultem® resin and support our customers with deep technical knowledge of PEI’s processing requirements. Whether you need tight-tolerance machined parts or complex injection-molded components, our team can help you select the right grade, optimize performance, and avoid common pitfalls in processing that can lead to poor quality parts.

Ultem^® is a registered trademark of the Saudi Basic Industries Corporation (SABIC)

Polyetherimide for High-Performance Applications: Why Processing Expertise Matters