Polyetherimide (PEI) supplier: high-heat, inherently flame-retardant grades
Amber-transparent, inherently flame-retardant and strong to 170°C+, PEI covers much of the high-heat range at a lower price than PEEK, with aircraft-interior FST credentials. It is amorphous: its continuous-use rating is about 170°C versus roughly 240–260°C for PEEK, and its chemical resistance is narrower.
One gaylord to a truckload · A polymer chemist reviews every quote · Every prime lot from our suppliers ships with a COA
Updated October 2026
Request a Quote- Impact strength
- Moderate
- Heat (HDT)
- ~190-210°C
- Clarity
- Transparent amber
At a glance
- Form
- Pellets and stock shapes
- Order size
- One gaylord to a truckload
- Grades
- Unfilled transparent grades · Glass-filled (10-40%) · Aircraft FST-compliant grades
- Paperwork
- Supplier COA on every prime lot
- Ships to
- U.S. and Canada
- Sourcing
- Matched to your spec
The short answer
PEI is the choice for high heat, stiffness, tight tolerances, and flame and smoke performance without added flame retardant, at a lower cost than PEEK. It suits parts that run up to about 170°C continuous and stay away from chlorinated solvents and strong bases. The usual problem is moisture: PEI molded wet loses molecular weight for good, and splay is only the visible sign.
Grades we source
Tap a grade to add it to your quote request.
About Polyetherimide (PEI)
PEI combines high strength and stiffness, tight dimensional stability, inherent flame retardance with low smoke, and repeat steam-sterilizability. It is the standard for aircraft interiors, high-heat electrical parts, and reusable medical components (non-implant).
Common applications
- Aircraft interior components
- High-heat connectors and sockets
- Sterilizable trays and instrument parts
- Microwave and food-service ware
- Metal replacement under the hood
Typical properties
| Impact strength | Moderate |
|---|---|
| Heat (HDT) | ~190-210°C |
| Clarity | Transparent amber |
| Chemical resistance | Good vs. acids, salts, alcohols and aliphatic hydrocarbons; attacked by strong bases; crazes in chlorinated solvents |
| Relative cost | High |
Property ranges are general guidance and vary by grade and supplier; a polymer chemist confirms the exact spec against the data sheet and certificate of analysis for your application.
Which grade to ask for
Choose by flow, glass level and the paperwork the part needs.
| Grade type | Use it for | Watch out for |
|---|---|---|
| Unfilled, standard flow | Transparent amber parts, electrical parts, sterilizable components | Notch-sensitive (notched Izod about 50–60 J/m), so keep sharp inside corners out of the design |
| Unfilled, high flow | Thin walls, long flow lengths, connectors and sockets | Lower viscosity can mean less stress-crack margin; check against the chemicals the part will see |
| Glass-filled (10–40%) | Brackets, metal replacement under the hood, high-heat electrical parts | Opaque; abrasive to screws and gates; still close to isotropic in shrinkage |
| Aircraft interior (FST) grades | Cabin panels, ducts, clips, seating parts | Flammability, heat release and smoke data apply to the exact grade and color |
| Food-contact and reusable-ware grades | Food-service trays, microwave ware, reusable lids | Strong alkaline detergents attack PEI; check your wash chemistry |
| Healthcare grades | Sterilization trays, instrument handles, device parts | Steam cycle life varies widely by grade; ask for cycle data and biocompatibility data |
Typical starting points. Grades vary, so confirm on the data sheet for the exact grade.
Processing notes
- Drying. Required. Dry at 150°C / 302°F for 4–6 h to 0.02% moisture. Published guidance caps cumulative drying at 24 h, so do not leave PEI in a hot dryer over a weekend and then run it. See the drying chart for other resins.
- Melt temperature. 350–410°C / 662–770°F. Keep barrel residence short, about 2–5 minutes, and size the press so the shot uses a reasonable share of the barrel.
- Mold temperature. 135–180°C / 275–356°F, with oil or electric heating. The hotter end lowers molded-in stress, which matters for parts that see cleaners or solvents.
- Shrinkage. Unfilled about 0.5–0.7%, and genuinely isotropic. With 30% glass about 0.20–0.40% in both directions. PEI shrinks roughly half as much as PEEK, so a PEEK tool runs PEI parts oversize.
- Regrind. Up to about 25% same-grade regrind, dried like virgin, is a common starting point; confirm it with part testing. For UL-listed parts, the UL 746D allowance is up to 25% in-house regrind of the same grade. FST and medical programs may allow less or none.
- Most common defect. Splay and bubbles from wet resin. The part may look acceptable and still be brittle, because water at melt temperature shortens the polymer chains. Stress cracking near solvents is the second most common complaint and usually traces to a cold mold or sharp corners.
What to put on the purchase order
- Grade, glass level and flow class. Standard or high flow, and the glass percentage. A high-flow grade is not a drop-in for a standard-flow grade on a crack-sensitive part.
- Melt flow and test condition. Copy both from the data sheet so the COA value can be compared directly.
- Color. Natural transparent amber or an opaque color. For FST and UL work the color is part of the tested material, so a color change can need new data.
- Flame documents. UL recognition is grade-specific and color-specific. Check the grade’s listing on UL Product iQ for flame class at your wall thickness and for RTI.
- Aircraft interiors. Ask for the grade’s documented test data to 14 CFR 25.853 and its Appendix F as your program requires: vertical burn for interior materials, and heat release and smoke density for large interior panels on transport aircraft. Add lot traceability.
- Food or medical. Ask for the producer’s FDA letter for the exact grade, or biocompatibility data for healthcare grades.
- COA values to check. Melt flow, and glass content (ash) for filled grades.
When to consider something else
- If the part sees chlorinated solvents, strong bases or continuous heat above about 170°C, look at PEEK: PEEK vs. PEI.
- If you need the most steam cycles and higher impact strength, look at PPSU.
- If the part can be opaque and needs broad chemical resistance at lower cost, look at glass-filled PPS.
- If you need a transparent amber sulfone for long hot-water service, compare PES.
- If the part is a halogen-free flame-retardant housing that runs cooler, see best plastic for electrical housings.
Common questions
Does PEI need to be dried?
Yes. Dry it at 150°C (302°F) for 4–6 hours to 0.02% moisture. Water at melt temperature breaks the polymer chains, so wet PEI makes brittle parts even when the surface looks fine. Published guidance caps total drying at 24 hours.
What is the difference between PEI and PEEK?
PEI is amorphous, transparent amber and inherently flame retardant, with a higher unfilled heat deflection (about 200°C) and low, even shrinkage. PEEK is semi-crystalline, with a higher long-term temperature limit (about 240–260°C), better chemical, wear and fatigue resistance, and a much higher cost.
Is PEI food safe?
Some PEI grades are made for food-contact and reusable food-service use, but compliance depends on the exact grade and color. Ask for the producer’s FDA letter for that grade. Check your detergent too, because strong alkaline cleaners attack PEI.
Is PEI flame retardant?
PEI is inherently flame resistant with low smoke, and many grades reach UL 94 V-0 without added flame retardant. UL recognition is grade-specific and color-specific, and it applies at a stated thickness. Check the grade’s listing on UL Product iQ.
Tell us the Polyetherimide (PEI) grade you run now
A polymer chemist reviews every request, then matches your grade or finds a qualified equivalent and prices it.
What to send for an accurate quote
- The grade name, from any supplier, or a data sheet
- Color (natural, black or a custom match)
- Fill type and percentage, if any
- Melt flow, if you know it
- Quantity for this order and what you use in a year
- Ship-to city and state or province
Send us the PEI grade and glass level
Send the PEI grade, fill level and volume; a polymer chemist reviews it and you get a quote on that grade or a qualified equivalent.
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