Resin Data
PEI
Polieterimida (Ultem)
PEI·High Performance·Amorphous
PEI (Polyetherimide) is the "mid-range PEEK": amorphous, amber transparent, and with one of the highest continuous-use temperatures of any transparent thermoplastic —Tg of 217°C, HDT of 200°C unreinforced, continuous use at 170°C. The dominant world brand is Ultem —developed by GE Plastics in 1982, today part of SABIC Specialties— with nearly 100 grades available. Solvay has Extem as the high-end variant, and bio-based alternatives are emerging.
Its great strength is the unique amorphous combination: characteristic amber transparency, inherent FST (Flame/Smoke/Toxicity) meeting FAR 25.853 without halogenated additives, USP Class VI and ISO 10993 for medical, chemical resistance to dilute acids, hydrocarbons, alcohols, and exceptional dimensional stability (shrinkage 0.5-0.7%, isotropic). Cost sits between PEEK above ($50-100/kg) and PSU below: $25-50/kg for Ultem 1000, up to $80/kg for specialty aerospace grades.
Flagship applications: aerospace interiors (ceiling panels, ducting, seats, in-flight entertainment panels —Ultem 2300 with 30% GF saves 15% weight vs aluminum), sterilizable medical devices (autoclavable surgical instruments, hundreds of cycles), 5G connectors (dielectric stability up to GHz), domestic oven and microwave parts, high-temp flex PCBs. Are you running Ultem or PEI? Share your experience in the comments.
The ranges shown in these data tables were compiled by the MVPS team from various parameter sheets and literature, integrating the lower and upper limits for each material type.
This information must be carefully reviewed when developing injection molding processes. Final ranges and processing tolerances are the responsibility of the engineer in charge.
These ranges are not recommended for developing specific process tolerances. MVPS always recommends requesting and consulting the supplier's data sheet.
General Properties
| Chemical Structure | Amorphous |
| Specific Gravity (Density) | 1.28:1 |
| L/D Ratio | 18 – 24 |
| Compression Ratio | 2 – 3 |
| Tonnage Factor | 4.63 – 6.18kN/cm² |
| Thermal Diffusivity | 0.1432mm²/s |
| Max Shear Rate | 40,0001/s |
| Shrinkage | 0.6 – 0.8% |
| Regrind | ⚠ Caution |
| Heat Deflection (HDT) @ 1.82 MPa | 191°C |
| Glass Transition (Tg) @ 10°C/min | 217°C |
| Vicat Softening @ 50N | 220°C |
Drying
| Drying Temperature | 149 – 160°C |
| Drying Time | 3 – 6h |
| Recommended Moisture | 0.02% |
| Recommended Dryer Type | Desiccant |
| Dew Point | -40°C |
Temperatures
| Melt | 338 – 416°C |
| Nozzle | 343 – 399°C |
| Front | 343 – 399°C |
| Middle | 338 – 399°C |
| Rear | 332 – 399°C |
| Demolding | 85 – 185°C |
| Mold (Cooling) | 68 – 174°C |
| Feed Throat | 35 – 79°C |
Processing
| Back Pressure | 3.4 – 6.9bar |
| Screw Speed | 10 – 100RPM |
| Injection Speed | High |
| Barrel Occupancy | 40 – 60% |
| Injection Pressure | 700 – 1,500Pbar |
| Holding Pressure | 175 – 1,200Pbar |
| Cushion | 6.4 – 12.7mm |
Mold
| Runner Diameter | 3.05 – 6.1mm |
| Gate Diameter | 0.76 – 1.52mm |
| Gate Area | 0.46 – 1.82mm² |
| Wall Thickness | 0.51 – 3.81mm |
Venting
| Depth (Vent Depth) | 0.0203 – 0.0508mm |
| Land (Vent Land) | 0.508 – 1.52mm |
| Width (Vent / Clearance) | 3.81 – 12.7mm |
| Relief (Relief Channel) | 0.2032 – 0.4064mm |
Frequently asked questions
**PEI** (Polyetherimide) is an aromatic amorphous thermoplastic with a chemical structure alternating **ether groups** (-O-) and **imide groups** (cyclic N-CO-N rings). The imide rings are what give it the characteristic **amber translucent color** —they absorb visible light in the blue-violet range. The rigid backbone gives it: **Tg 217°C** (the highest among transparent amorphous commercials), **HDT 200°C** unfilled, **continuous use 170°C**, **inherent V-0**, **broad chemical resistance**. It's one of the few amorphous plastics approaching PEEK in temperature.
- **Ultem 1000**: standard, amber transparent, general balance — the most used.
- **Ultem 1010**: variant with slightly higher Tg and better thermal performance, **industrial FDM 3D print favorite**.
- **Ultem 2300**: 30% glass fiber, opaque, **aerospace stiffness** (seats, panels).
- **Ultem 9085**: **aerospace-specific FDM grade** (3D printing), meets FAR 25.853 + FAA, listed for in-flight interior components.
- **Ultem 9075/9080**: FST-optimized for aircraft air ducts.
- **Solvay Extem**: high-performance variant with Tg up to 267°C, higher cost.
For non-FDM processes (injection, machining, extrusion), the most used are 1000, 1010, and 2300.
- **Drying**: 150°C × 4 h in desiccant dryer with dew point <-30°C. Reinforced: 6 h. Final moisture <0.02% mandatory (otherwise bubbles, streaks, low properties).
- **Melt**: 350-410°C (standard Ultem 1000: 380-400°C; aerospace 9085: 400-420°C).
- **Mold**: **135-180°C mandatory** —if you mold with cold tool (<120°C) the part has high residual stress and may crack spontaneously months later.
- **Residence**: <10-15 min. PEI is thermally stable but pigments can color-shift sustained >382°C.
- **Injection speed**: medium-high. Shear thinning aids filling.
It meets **FAR 25.853** (Federal Aviation Regulation) **without halogenated additives**:
- **Flame**: inherent V-0, doesn't propagate flame.
- **Smoke**: extremely low smoke emission during combustion —critical in aircraft evacuation.
- **Toxicity**: combustion gases classified as low in HCN, HCl, CO compared to other FR plastics.
- **Heat release rate**: low OSU heat release (<65 kW/m²·min, required by FAR 25.853 Appendix F Part IV).
Result: **an Ultem ceiling panel, divider, air duct, or seat meets FAA and EASA regulations** without post-mold treatment. **15% lighter than aluminum**, no corrosion issues.
**Yes, exceptional**. Many Ultem grades meet:
- **USP Class VI** (United States Pharmacopeia, chronic implant toxicity tests).
- **ISO 10993** (biocompatibility for medical devices).
- **Repeated sterilization without degradation**: gamma, EtO, 134°C steam autoclave —hundreds of cycles.
Applications: **reusable surgical instruments** (scalpel handles, retractors, modular kits), **sterilization trays** replacing steel, **dental devices**, **in-vitro analyzer components** chemically sterilized. For permanent implants, **PEEK** is still preferred for its bone-matching modulus, but PEI dominates **reusable**.
**Shrinkage 0.5-0.7%, isotropic**, one of the most predictable of high-performance plastics. Reasons:
- It's **amorphous** (no crystallization) → no crystalline directionality.
- **No significant post-mold shrinkage** if process was correct (no residual stress).
With 30% GF (Ultem 2300): shrinkage drops to 0.2-0.5%, but mild **anisotropy appears** from fiber orientation. Predictability is key for parts like **fine-pitch connectors** or **transparent optical components** where micron tolerances matter.
- **PEEK** ([Polyether Ether Ketone](/en/desktop/datos-de-resina/peek)) **wins on**: max continuous temperature (260°C vs 170°C), universal chemical resistance, fatigue resistance, biocompatibility for **permanent implants**. It's semi-crystalline.
- **PEI/Ultem wins on**: cost (50-70% cheaper), **amber transparency**, easier processing (amorphous, no crystallinity control needed), **better inherent FST** for aerospace interiors, **dimensional stability** (no post-shrinkage).
**2026 rule**: for aerospace interiors, reusable medical, or high-temp transparent components → **PEI Ultem**. For structural aerospace, implantable medical, oil & gas downhole → **PEEK**.
**Yes, well for an amorphous**, but with specific limitations:
- **Resists**: dilute acids (H₂SO₄ 10%, HCl), dilute bases, alcohols (ethanol, isopropanol), aliphatic hydrocarbons, lubricating oils, fuels (Jet A, gasoline), hot water and steam.
- **Doesn't resist**: **chlorinated solvents** (methylene chloride, chloroform —they dissolve it), **ketones** (acetone, MEK), **concentrated bases** (50% NaOH hot), amines, hydrazine.
**Critical design topic**: PEI is susceptible to **stress-cracking in solvents** when there's residual mold stress. That's why hot mold (135-180°C) and post-mold annealing are important for parts that will see solvents in service.
**Yes, mechanically** —can be recycled post-industrial up to 25-50% regrind without significant loss. **It's thermally stable**, withstands multiple extruder passes. **Limitations**: for medical and structural aerospace, regrind isn't allowed for traceability. For industrial applications (electrical insulators, technical parts) 25%+ regrind is accepted. The **chemical complexity** of the PEI backbone makes chemical recycling (depolymerization) less practical than for simple polyesters like PET.
**Bubbles and silver streaks from insufficient drying moisture**. PEI is **hygroscopic** —can absorb 0.25% moisture in ambient air in 24h. If you process with moisture >0.02%, **defects guaranteed**. Symptoms: silver streaks, microbubbles, **color shift** (darker or milky). Cure: 150°C × 4-6h drying mandatory without shortcuts, desiccant dryer with dew point <-30°C, **don't open bags more than 1 hour before loading**. Second common issue: **stress-cracking in service** when part has residual mold stress + solvent contact —solution is hot mold (160°C+) and/or 1-2h annealing at Tg+10°C.
Sources
- SABIC Specialties — Ultem Resin Family· SABIC Specialties
- Pexco — Why Ultem Excels in Aerospace, Medical, and Semiconductor Applications· Pexco
- Curbell Plastics — Ultem PEI Material Guide· Curbell Plastics
- Genesis Medical Plastics — Ultem PEI Properties in Medical Devices· Genesis Medical Plastics
- Polyetherimide (Wikipedia)· Wikipedia