Polyetherimide — commercially known as Ultem® (SABIC) — is the material that gets specified once the design requirements have been clarified by failure. It is not the cheapest engineering thermoplastic on the list. It is not the easiest to process. But it occupies a specific performance position — continuous service above 170°C, inherent UL94 V-0 flame retardancy without additives, steam autoclave sterilizability, and dielectric stability that does not degrade with temperature or humidity — that no combination of lower-tier engineering resins can replicate.
This guide explains what PEI plastic actually is, what it genuinely offers, where it has real limitations, and what PEI injection molding demands from tooling, machines, and process discipline.
The Chemistry That Creates PEI's Performance Ceiling
Polyetherimide is an amorphous thermoplastic belonging to the polyimide family, incorporating ether linkages that improve processability relative to fully aromatic polyimides. The repeating unit contains both imide groups — which provide the high-temperature stability and flame retardancy — and ether linkages — which reduce melt viscosity enough to allow conventional injection molding at high temperatures.
This combination is chemically deliberate and performance-consequential. The imide ring structure is thermally stable to temperatures that cause chain scission in polyesters, polyamides, and polycarbonates. The aromatic backbone resists oxidative degradation that degrades aliphatic polymers at elevated temperatures. The ether linkages maintain enough chain flexibility to allow flow at processing temperatures — though “enough flexibility” in PEI terms still means melt temperatures above 340°C.
The glass transition temperature (Tg) of PEI plastic is approximately 217°C — the highest Tg of any commercially injection-moldable amorphous thermoplastic at standard cost levels. This single number has more implications than most material property tables communicate:
- Parts retain mechanical stiffness and dimensional accuracy at continuous operating temperatures where PC, ABS, PA, and PBT have long since softened
- Autoclave sterilization at 134°C presents no thermal challenge — the operating temperature is 83°C below Tg
- Short-term excursions to 200°C do not cause permanent deformation in lightly loaded components
- The processing temperature needed to achieve adequate melt flow — 340–420°C — is a direct consequence of this same thermal stability
Amber transparency is a characteristic the datasheet mentions but engineers sometimes underestimate in its practical implications. PEI’s amorphous structure produces natural amber-colored transparency — not optical-grade clarity, but sufficient to allow visual inspection of part interior geometry, fluid presence in a tube or channel, or assembly alignment — in applications where other high-performance engineering resins are completely opaque.
PEI Plastic Properties: The Numbers and What They Mean in the Real World
Thermal Performance — The Defining Capability
| Propiedad | PEI (Ultem 1000) | PEI GF30 (Ultem 2300) | Unidad |
|---|---|---|---|
| Glass transition temperature | 217 | 217 | °C |
| Heat deflection temperature (1.82 MPa) | 198 | 210 | °C |
| Temperatura de servicio continuo | 170 | 180 | °C |
| Short-term peak temperature | up to 200 | up to 220 | °C |
| UL94 flammability rating | V-0, 5VA | V-0, 5VA | — |
| Limiting oxygen index (LOI) | 47% | — | — |
The HDT of 198°C at 1.82 MPa for unfilled PEI plastic is not merely a high number — it means that under a meaningful mechanical load, the material maintains dimensional stability within 20°C of its Tg. No standard engineering thermoplastic (PA, PBT, PC, ABS, POM) approaches this under equivalent load conditions.
The limiting oxygen index of 47% for PEI means that in air (21% oxygen), the material cannot sustain combustion without an external ignition source. This inherent flame retardancy — achieved without any halogenated or phosphorus-based flame retardant additives — is critical for aerospace and aviation applications where halogen-free flame retardancy is a regulatory requirement, not just a preference.
Propiedades mecánicas
| Propiedad | PEI (Ultem 1000) | PEI GF30 (Ultem 2300) | Unidad |
|---|---|---|---|
| Tensile strength | 105 | 165 | MPa |
| Módulo de flexión | 3,300 | 9,000 | MPa |
| Notch impact strength (Izod) | 50 | 90 | J/m |
| Alargamiento a la rotura | 60 | 3 | % |
| Dureza Rockwell | M109 | M114 | — |
Unfilled PEI plastic is notable for a mechanical property combination that is unusual in high-performance engineering resins: high tensile strength combined with 60% elongation at break. Most high-modulus engineering resins sacrifice ductility for stiffness. Unfilled PEI retains meaningful ductility that allows it to withstand assembly operations, snap-fit deflection, and thermal shock without brittle fracture — while still delivering tensile strength of 105 MPa.
GF30-reinforced PEI approximately triples the flexural modulus to 9,000 MPa — approaching the structural stiffness of aluminum in some loading configurations — at the cost of nearly eliminating elongation (3% at break). For structural brackets, load-bearing housings, and precision-dimensional connectors in high-temperature environments, GF30 PEI plastic is the standard specification. For parts requiring any ductility or that must survive installation impacts, unfilled grades are the appropriate choice.
Propiedades eléctricas
| Propiedad | Valor | Unidad |
|---|---|---|
| Rigidez dieléctrica | 28 – 31 | kV/mm |
| Resistividad volumétrica | 10¹⁵ – 10¹⁷ | Ω-cm |
| Constante dieléctrica (1 MHz) | 3.15 | — |
| Factor de disipación (1 MHz) | 0.0013 | — |
| Arc resistance | 128 | seconds |
The electrical property that distinguishes PEI plastic from lower-tier engineering resins is not the absolute magnitude of any single value but the stability of those values across temperature and humidity ranges. The dielectric constant of 3.15 and dissipation factor of 0.0013 are maintained with minimal variation from room temperature to 200°C and from dry conditions to humid environments.
For radar components, high-frequency antenna substrates, aerospace avionics housings, and precision circuit board connectors operating in variable thermal and humidity environments, this electrical stability is a functional requirement — not a nice-to-have.
Chemical Resistance and ESC: The Limitation That Requires Serious Attention
PEI demonstrates broad chemical resistance across its primary application environments. It resists:
- Automotive fluids: fuels, oils, hydraulic fluids, coolants
- Aqueous solutions: dilute acids, dilute alkalis, salt solutions
- Alcohols and aliphatic hydrocarbons
- Aqueous cleaning agents and most industrial lubricants
However, PEI plastic has a significant chemical vulnerability that must be understood before specification: environmental stress cracking (ESC) in the presence of chlorinated solvents, aromatic hydrocarbons, ketones, and certain concentrated acids under mechanical stress.
ESC in amorphous polymers — including PEI — occurs when a chemical agent that does not dissolve the polymer bulk nonetheless penetrates the surface and reduces the critical stress for crack initiation below the level of residual or applied stress in the part. The result is crazing or brittle fracture at stress levels that would not cause failure in the absence of the chemical.
For PEI plastic, the primary ESC agents to avoid are:
- Chlorinated solvents (methylene chloride, chloroform, trichloroethylene)
- Ketones and esters (acetone, MEK, ethyl acetate)
- Aromatic hydrocarbons (toluene, xylene) at elevated temperature
- Strong alkalis (NaOH, KOH at elevated concentration)
The practical implication: any PEI plastic part that will contact these agents while under stress — from assembly preload, thermal expansion mismatch, or service load — requires either material substitution (consider PEEK, PPS, or PPSU for severe ESC environments) or explicit chemical compatibility testing in the actual service condition before production commitment.
At Dimud, ESC risk evaluation is part of our material selection review process for PEI plastic projects. Chemical exposure mapping is completed at the DFM stage — not discovered during field validation.
PEI Injection Molding: What the High Tg Actually Demands From Your Process
PEI injection molding is categorically different from processing commodity or mid-tier engineering thermoplastics. The same thermal stability that makes the material useful in high-temperature service makes it resistant to the melt flow that injection molding requires. Understanding what this means in practice is the first step toward consistent, defect-free PEI plastic parts.
Equipment Requirements — This Is Not a Standard Machine Application
Not every injection molding machine can process PEI. The requirements are specific:
Barrel and screw temperature capability: Processing temperature for PEI injection molding runs at 340–420°C melt temperature — significantly above the barrel capability of most general-purpose machines rated to 350–380°C maximum. High-performance screw and barrel assemblies rated to 450°C+ are required for reliable PEI processing with adequate thermal headroom.
Screw design: A general-purpose screw with a high compression ratio generates excessive frictional shear heat in the metering zone when processing PEI — pushing local melt temperatures above 430°C, where degradation begins. A low-compression-ratio screw (2.0:1 to 2.5:1) distributes heat input more uniformly and gives the process engineer actual control over melt temperature.
Screw and barrel materials: High-process-temperature amorphous materials like PEI are abrasive to standard tool steel screws when glass fiber-reinforced grades are run. Bimetallic or Xaloy-lined barrels and hardened screws are standard for GF-PEI production.
Nozzle: A positive-shutoff nozzle is recommended to prevent the PEI melt from drooling at high processing temperatures, which would leave a degraded cold slug at the sprue entry and produce dark streaks in the part.
En Dimud, nuestros servicios de moldeo por inyección de plásticos for PEI plastic run on machines specifically configured for high-performance engineering resins — with temperature-verified barrel profiles and documented process qualification records for each grade.
Drying: The Non-Negotiable First Step
PEI plastic absorbs moisture at approximately 0.25% at equilibrium — modest in absolute terms, but catastrophic in effect at processing temperatures above 340°C. Water vaporizes explosively in the barrel, producing:
- Splay marks (silver streaks) on part surfaces — immediately disqualifying for aerospace and medical applications
- Internal voids reducing mechanical strength — not visible without sectioning or CT scanning
- Hydrolytic chain scission — permanently reduces molecular weight, weakening all mechanical properties in the finished part
PEI drying requirements:
- Temperature: 150°C
- Duration: 4 hours minimum (GF grades: up to 6 hours)
- Equipment: Desiccant (dehumidifying) dryer with outlet dew point ≤ −30°C
- Maximum moisture target: ≤ 0.05% by weight
- Post-drying handling: process within 30 minutes; do not return dried material to open containers
The 150°C drying temperature is higher than most engineering resins and requires a dryer capable of operating at this setpoint with adequate airflow. Standard hot-air ovens are insufficient — they cannot deliver the dew point needed to remove internal pellet moisture.
Processing Temperature: The Window Between Flow and Degradation
PEI injection molding melt temperature for standard grades runs at 340–400°C:
| Barrel Zone | Unfilled PEI | PEI GF30 |
|---|---|---|
| Feed zone | 280 – 310°C | 290 – 320°C |
| Compression zone | 320 – 355°C | 330 – 360°C |
| Metering zone | 355 – 390°C | 360 – 400°C |
| Nozzle | 340 – 375°C | 345 – 380°C |
| Mold temperature | 65 – 175°C | 65 – 150°C |
The degradation onset for PEI plastic occurs at approximately 430–450°C — giving a processing window of 40–80°C above the minimum flow temperature before degradation begins. This is a tighter window than most engineering resins and requires barrel temperature control to ±5°C at each zone to reliably stay within it.
Mold temperature for PEI injection molding is notably high — 65–175°C — with most precision applications using 100–150°C. The high mold temperature is required because:
- PEI melt has high viscosity even at 380°C — a cold mold causes premature freeze-off in thin sections before the cavity is filled
- Higher mold temperatures allow more complete stress relaxation during solidification, reducing birefringence and residual stress in precision optical or structural components
- For applications requiring maximum surface quality, mold temperatures above 120°C produce part surface finishes that replicate the cavity finish accurately
High mold temperatures require mold designs with adequate oil-heated cooling circuits capable of maintaining precise temperature setpoints — not standard water-cooled circuits, which cannot reliably hold above 90°C.
Injection Parameters
| Parámetro | Unfilled PEI | PEI GF30 |
|---|---|---|
| Presión de inyección | 100 – 170 MPa | 120 – 200 MPa |
| Presión de mantenimiento | 50 – 80% of injection | 50 – 75% of injection |
| Velocidad de inyección | Medium (profiled) | Medium-slow |
| Contrapresión | 3 – 10 MPa | 3 – 10 MPa |
| Contracción del molde | 0.5 – 0.7% | 0.1 – 0.5% |
PEI melt has significantly higher viscosity than commodity or standard engineering thermoplastics — this is why injection pressure requirements of 100–200 MPa are standard rather than exceptional. Gate sizing must be generous; undersized gates create high local shear rates that generate degradation heat at the gate entry, producing discoloration and mechanical property reduction in the gate area regardless of correct barrel temperature management.
For thin-walled PEI plastic parts (walls < 2 mm), profiled injection speed — accelerating progressively as the melt front moves through the cavity — is required to avoid short shots without the flow mark and jetting defects that result from initial high-speed injection through an open gate.
Mold Design Considerations for PEI Injection Molding
PEI’s low mold shrinkage (0.5–0.7% unfilled, 0.1–0.5% GF grades) enables tight dimensional tolerances — one of the material’s key advantages for precision connector and aerospace component production. Achieving these tolerances in practice requires mold design that accounts for the high processing temperature environment:
Mold steel: H13 hot work tool steel is recommended for PEI injection mold cavities — its elevated-temperature hardness maintains dimensional stability at the 150°C+ mold temperatures used for precision PEI applications. Standard P20 loses hardness at sustained temperatures above 120°C. For GF-PEI plastic grades, cavity inserts in D2 or a PVD-coated H13 grade protect against the abrasive glass fiber content.
Gate design: Edge or tab gates positioned away from cosmetically critical surfaces are preferred. Direct or sprue gating is used for single-cavity tools where maximum packing of thick sections is required. Avoid thin submarine or tunnel gates — the high melt viscosity of PEI generates excessive shear heat through small gates.
Venting: PEI injection molding generates volatile degradation products if any overheating occurs. Mold venting at the flow front extremities, parting lines, and ejector pins must be adequate to prevent gas trapping and burn marks — vent depth 0.025–0.040 mm for standard PEI, not significantly different from other engineering resins.
Runner systems: Cold runner systems with large-diameter, full-round runners (minimum 6 mm diameter) minimize pressure drop and heat loss between machine and cavity. Hot runner systems can be used for PEI injection molding with manifolds and drops designed for temperatures up to 420°C — a requirement that eliminates standard hot runner hardware not designed for high-temperature engineering resins.
Nuestra fabricación de moldes de precisión team at Dimud designs PEI tooling in H13 as standard, with oil-heated mold temperature control and vent placement verified against mold flow simulation results.
PEI Plastic Grades: From General-Purpose to Specialized Performance
Ultem 1000 — The Baseline
Unfilled, general-purpose PEI. Amber transparent. HDT 198°C, tensile strength 105 MPa, elongation 60%, UL94 V-0 and 5VA. The standard grade for medical device components requiring autoclave sterilization, aircraft interior components needing inherent flame retardancy, and electrical insulators requiring stable dielectric properties to 200°C. RoHS compliant. NSF 51 (food equipment) listed in recognized colors.
Ultem 2100, 2200, 2300 — Glass Fiber Reinforced Series
10%, 20%, and 30% glass fiber reinforcement respectively. Progressive increase in flexural modulus (Ultem 2300: ~9,000 MPa), HDT (Ultem 2300: 210°C), and dimensional stability — with corresponding reduction in elongation and impact resistance. GF30 (Ultem 2300) is the standard specification for structural aerospace brackets, high-precision connector housings requiring tight tolerances under thermal cycling, and industrial components under sustained mechanical load at elevated temperatures. Carries UL94 V-0 and 5VA ratings, NSF 51 listing, and WRAS certification in recognized colors.
Ultem 5000 Series — Mineral Reinforced Grades
Mica-filled PEI plastic grades offering isotropic shrinkage (in contrast to the anisotropic shrinkage of GF grades) with improved dimensional stability in flat or symmetrically shaped components. Surface finish is improved over GF grades. Used for precision housings, flat structural panels, and components where the warpage that can occur in GF grades creates dimensional problems. Particularly relevant for large flat parts where GF fiber orientation would produce unacceptable differential shrinkage.
High-Flow PEI Grades
Several commercial grades — including Ultem 1010 and certain Sabic CRS grades — are formulated for improved melt flow at equivalent temperature, enabling thin-wall injection molding of complex geometries that would require excessive pressure with standard viscosity grades. Food-contact compliant Ultem 1010 is also the standard specification for food processing equipment components requiring NSF 51 and FDA compliance with autoclave sterilization capability.
Extem (PEI-SI) — When Standard PEI Is Not Enough
For applications where standard PEI’s 217°C Tg is insufficient — certain semiconductor process equipment, high-temperature industrial tooling, and automotive applications adjacent to high-heat power electronics — SABIC’s Extem grades (polyetherimide-siloxane copolymers) offer Tg values up to 267°C while retaining the injection moldability that distinguishes PEI from fully aromatic polyimides (Vespel, Torlon) that require alternative processing methods.
Where PEI Plastic Is the Specification Engineers Arrive At
Aerospace and Aviation Interiors
FAR 25.853 (Federal Aviation Regulation for aircraft interior flammability) and OSU heat release requirements drive material selection for aircraft cabin interior components — seat components, overhead panels, galley inserts, and ducting. PEI’s inherent UL94 5VA rating, low smoke emission (limiting oxygen index 47%), and halogen-free flame retardancy without additives make it one of the preferred engineering thermoplastics for aviation interior components.
The weight reduction versus metal — PEI at 1.27 g/cm³ versus aluminum at 2.7 g/cm³ — is a secondary benefit that accumulates meaningfully across the many hundreds of plastic components in a modern commercial aircraft interior.
Medical Devices and Sterilizable Equipment
PEI plastic withstands steam autoclave sterilization at 134°C for hundreds of cycles without dimensional change or property degradation — a performance level that PC (which distorts above 130°C under steam conditions), PA (which absorbs moisture during sterilization, changing dimensions), and PBT (whose ester bonds are susceptible to hydrolysis under steam) cannot match.
For reusable surgical instruments, diagnostic equipment housings, dental unit components, and laboratory automation parts requiring repeated steam sterilization, PEI plastic is the standard engineering thermoplastic specification. It also passes gamma radiation and EtO sterilization with acceptable property retention for most medical grades.
Biocompatibility — ISO 10993 evaluated grades are commercially available from SABIC. Medical-grade Ultem with USP Class VI and ISO 10993 compliance is the specification baseline for patient-contact and fluid-contact components in medical devices.
Semiconductor and Electronics Manufacturing Equipment
The combination of high-temperature stability, dielectric consistency, and low outgassing makes PEI plastic a standard material in semiconductor wafer handling equipment, IC test sockets, burn-in board components, and PCB connectors operating in high-temperature test environments.
High-purity grades with controlled ionic contamination levels are specified for applications where metal ion contamination of wafer surfaces during processing is a yield risk.
Automotive High-Temperature Electrical Components
PEI plastic’s HDT of 198–210°C enables it to serve in automotive electrical applications where the proximity to combustion engines, high-power electronics, and exhaust-adjacent thermal environments pushes beyond PA66 GF30’s practical ceiling. Sensor housings on or near engine blocks, high-voltage connector housings in EV battery management systems, and motor resolver housings in traction motor assemblies all represent applications where PEI plastic provides performance that standard engineering resins cannot reliably deliver.
Nuestra automotive injection molding capabilities at Dimud include PEI plastic production for sensor housings and high-temperature connector components serving Tier 1 automotive clients in Europe and North America.
PEI Plastic vs. PEEK: The High-Performance Choice Most Engineers Get Wrong
PEI and PEEK are the two most commercially significant high-performance engineering thermoplastics for injection molding. They are not interchangeable, and the wrong choice in either direction wastes either money (over-specifying PEEK) or performance (under-specifying PEI when PEEK is needed).
| Propiedad | PEI (Ultem 1000) | PEEK (Unfilled) |
|---|---|---|
| Continuous service temp. | 170°C | 250°C |
| Glass transition temperature | 217°C | 143°C (Tg), 343°C (Tm) |
| Tensile strength | 105 MPa | 100 MPa |
| Chemical resistance to chlorinated solvents | Poor — ESC risk | Excelente |
| Chemical resistance to concentrated H₂SO₄ | Limitado | Limitado |
| Inherent flame retardancy (UL94 V-0) | Yes — no additives | Yes — no additives |
| Gamma radiation resistance | Bien | Excelente |
| Material cost (relative) | Lower (1×) | Higher (3–5×) |
| Processing temperature | 340–420°C | 360–400°C |
| Crystalline structure | Amorphous | Semi-crystalline |
Choose PEI plastic when: maximum operating temperature is below 200°C continuous; inherent halogen-free flame retardancy is required; autoclave sterilizability is needed at standard 134°C conditions; dielectric stability across temperature is the primary electrical requirement; or cost is a meaningful constraint between the two materials.
Choose PEEK when: operating temperature continuously exceeds 200°C; the application involves prolonged contact with aggressive organic solvents (especially chlorinated or ketone-family); wear resistance is a primary requirement (PEEK is significantly more wear-resistant); or the part will be subjected to extended gamma radiation exposure in medical/nuclear applications.
The most common incorrect specification is PEEK selected for temperature resistance in an application where PEI would perform identically — at 3–5× lower material cost. If the operating temperature is under 170°C continuous, the default should be PEI unless specific chemical or wear requirements push toward PEEK.
Common Defects in PEI Injection Molding and Their Root Causes
Because PEI plastic is primarily specified for high-performance applications — aerospace, medical, precision electronics — defect tolerance is essentially zero. Understanding the root cause of each defect type is more important in PEI production than in commodity thermoplastic work.
Silver streaks / splay: The most common PEI injection molding defect. Root cause in the vast majority of cases: inadequate drying. PEI moisture content above 0.05% at the time of processing vaporizes in the barrel and produces surface splay. Secondary causes: excessive melt temperature above 430°C causing thermal degradation, or dead zones in the nozzle or runner where PEI stagnates between shots. Solution priority: verify drying protocol and dew point first.
Discoloration / brown or black streaks: Thermal degradation from melt temperature exceeding ~430°C, excessive residence time in the barrel, or stagnation at the nozzle tip. Solution: reduce barrel setpoints by 10°C increments while monitoring fill performance; reduce residence time by adjusting shot size relative to barrel capacity; replace nozzle with positive-shutoff design.
Short shots: Insufficient melt temperature (too low for adequate flow), undersized gates creating excessive pressure drop, or mold temperature too low causing premature freeze-off. Solution: verify melt temperature with pyrometer (do not rely solely on barrel setpoints); check gate dimensions against minimum recommended for wall thickness; increase mold temperature setpoint.
Sink marks: Insufficient holding pressure or time; gate freezing before the cavity is fully packed; thick section geometry creating localized shrinkage demand. Solution: increase holding pressure and time; verify gate size is adequate for packing the thickest section; add overflow wells adjacent to thick sections if gate cannot be relocated.
Weld lines visible on clear or amber-transparent surfaces: Two melt fronts meeting at reduced temperature — mold too cold, injection speed too slow at the convergence point. Solution: increase mold temperature toward 150°C; use profiled injection speed to maintain melt front temperature at convergence point.
Stress whitening / crazing after assembly: Environmental stress cracking from chemical contact combined with assembly stress or press-fit preload. This is not a processing defect — it is a design or material specification issue. Review chemical exposure map and mechanical loading at all contact points; evaluate whether grade change or design modification is required.
Working With Dimud on PEI Plastic Projects
PEI injection molding is a process discipline that most contract manufacturers do not invest in — the equipment requirements, drying demands, and processing window management require specific infrastructure and documented process knowledge that general-purpose injection molding shops do not maintain.
Dimud’s approach to PEI plastic production is built around the three areas where most PEI projects fail:
Drying verification, not assumption: Every PEI production run begins with a documented drying cycle record including dryer temperature, duration, and dew point measurement at the dryer outlet. We do not assume that a correctly set dryer timer equals correctly dried material. The dew point record is the verification, and it is provided to clients as part of our process documentation package.
High-temperature-capable tooling: PEI molds at Dimud are designed and built in H13 tool steel with oil-heated mold temperature control systems capable of stable setpoints to 175°C. This is not standard mold infrastructure — it is a deliberate capability investment for high-performance engineering resin processing. Our rapid tooling service can also deliver PEI-compatible prototype tooling for first article validation before production tooling investment.
DFM focused on ESC risk and assembly design: PEI’s ESC vulnerability is not visible in standard property tables and is not called out in most material datasheets at the practical level engineers need. Our Design for Manufacturability analysis for PEI plastic projects explicitly maps chemical exposure risk, identifies assembly-induced stress concentrations, and reviews gate location relative to areas of residual stress accumulation — before tooling begins.
We work with clients across industries where PEI plastic performance is a genuine requirement: aerospace interior components, medical devices requiring steam sterilization, automotive high-temperature electrical parts, and semiconductor equipment housings. Our operations serve clients in Europe, North America, and the Middle East through integrated mold factory, CNC machining, and production capabilities.
Explore our complete injection molding materials guide to understand where PEI fits within the full spectrum of engineering thermoplastics we process, or contact us directly to discuss your PEI injection molding requirements.
PEI Plastic FAQ
PEI stands for polyetherimide — an amorphous, high-performance engineering thermoplastic in the polyimide family, incorporating ether linkages to improve processability. Ultem is SABIC's commercial brand name for PEI resin, originally developed by GE Plastics in the 1980s. Ultem is the dominant commercial form of PEI for injection molding, available in nearly 100 grades ranging from unfilled transparent amber material to glass- and mineral-reinforced structural compounds.
PEI plastic has a glass transition temperature of 217°C and a heat deflection temperature of 198°C at 1.82 MPa load (unfilled grades). Continuous service temperature is approximately 170°C for unfilled PEI and up to 180°C for GF30 grades. Short-term peak temperatures to 200°C are tolerable in lightly loaded applications. For continuous service above 200°C, Extem (PEI-siloxane copolymer) grades or PEEK are the appropriate specifications.
PEI's high glass transition temperature (217°C) and rigid aromatic backbone require high melt temperatures — 340–420°C — to achieve adequate melt flow for injection molding. This is a direct consequence of the thermal stability that makes PEI useful at high service temperatures. The processing window between minimum flow temperature and thermal degradation onset (~430°C) is approximately 40–80°C, which requires tighter barrel temperature control than most engineering resins.
Yes — PEI plastic is one of the preferred engineering thermoplastics for reusable medical devices requiring steam autoclave sterilization at 121°C or 134°C. Its glass transition temperature of 217°C is 83°C above standard autoclave conditions, meaning the material maintains dimensional stability through hundreds of sterilization cycles without softening or warping. It also supports gamma radiation and EtO (ethylene oxide) sterilization. Always confirm with the specific grade's medical certification documentation for patient-contact applications.
Both are high-performance engineering thermoplastics with high-temperature resistance, flame retardancy, and broad chemical resistance. Key differences: PEI plastic is amorphous with a Tg of 217°C; PEEK is semi-crystalline with a Tm of 343°C and a continuous service temperature to 250°C. PEEK has superior resistance to chlorinated solvents and aggressive chemical environments where PEI risks ESC. PEI plastic has better inherent flame retardancy and lower material cost (typically 3–5× less than PEEK). For applications below 200°C without aggressive solvent exposure, PEI plastic provides equivalent functional performance at significantly lower cost.
ESC in PEI occurs when the material is simultaneously exposed to a chemical agent (particularly chlorinated solvents, ketones, aromatic hydrocarbons, or strong alkalis) and mechanical stress — either from applied loads, residual molding stress, or assembly preload. The chemical penetrates the polymer surface and reduces the critical stress for crack initiation below the actual stress level in the part, producing crazing or brittle fracture. Prevention requires: chemical exposure mapping before material specification; design practices that minimize residual stress (adequate corner radii, uniform wall thickness, appropriate gate location); and material substitution to PEEK or PPS for applications with unavoidable exposure to ESC-inducing agents.
Specific PEI plastic grades are certified for food-contact applications. Ultem 1010, for example, carries NSF 51 (food equipment materials), FDA compliance, and WRAS certification. These grades are used in food processing equipment, beverage dispensing components, and dairy processing machinery where both food-contact compliance and steam sterilization capability are required. Not all PEI plastic grades are food-contact certified — confirm grade-level compliance, not just the polymer family, before specifying for food-contact applications.
