Ultem (PEI) FAQ: Grades, Properties & Machining

Ultem is SABIC's trade name for polyetherimide (PEI), a high-performance amorphous thermoplastic that combines excellent mechanical properties, inherent flame resistance, and broad chemical resistance at a price well below PEEK. It is widely specified for aerospace components, medical device parts, semiconductor equipment, and food-processing tooling. This FAQ addresses the most common questions engineers ask when evaluating or sourcing Ultem.

What is the difference between Ultem 1000, 2300, and 2200?

These are the three most commonly stocked Ultem grades in sheet and rod form. Ultem 1000 is the unfilled base resin—amber-translucent, isotropic, and the standard benchmark for PEI mechanical and thermal properties (tensile strength ~15,200 psi, HDT ~392°F/200°C). Ultem 2300 adds 30% short glass fiber reinforcement, raising tensile strength to ~24,500 psi and increasing stiffness significantly while lowering thermal expansion; it is opaque and used where dimensional stability and load-bearing are critical. Ultem 2200 incorporates 20% glass fiber, offering an intermediate combination of strength and toughness. For applications requiring isotropy and machinability, specify 1000. For high-load structural parts, 2300. See the full Ultem grades guide for a complete property table comparison.

Is Ultem autoclavable?

Yes. Ultem 1000 and most unfilled PEI grades withstand repeated steam autoclave sterilization at 134°C (273°F) per standard hospital autoclave cycles (Gravity and Pre-Vacuum). The material retains its mechanical properties and dimensional stability through hundreds of cycles when properly dried before processing. This makes Ultem a preferred choice for reusable surgical instrument handles, trays, and fixturing that must withstand repeated steam sterilization without distortion or degradation. Glass-filled Ultem grades (2200, 2300) also survive autoclaving but may show slight surface darkening over many cycles. For comparison, standard polycarbonate degrades after as few as 10–20 autoclave cycles. See the Ultem applications guide for medical sterilization case studies.

Does Ultem meet FDA and USP Class VI requirements?

Ultem 1000 in its natural (amber) form is certified compliant with FDA 21 CFR 177.1655 (polyetherimide resins) for food-contact applications and meets USP Class VI biological reactivity testing, which is the standard for plastics in indirect medical device contact. It is also compliant with EU Regulation 10/2011 for plastic food contact materials. Note that compliance applies to the base unfilled resin; glass-filled grades and grades with colorants require separate confirmation. Always request a Certificate of Conformance (CoC) or compliance letter from your supplier when traceability is required. The Ultem FDA guide covers the full regulatory landscape, including 3-A Dairy, NSF, and EU food-contact frameworks.

What are Ultem's aerospace flammability ratings?

Ultem's inherent flame resistance is one of its defining characteristics. It achieves UL 94 V-0 at 0.032″ thickness (unfilled resin), a limiting oxygen index (LOI) of approximately 47%, and produces relatively low smoke and toxic gas emission during combustion. For aerospace interior applications, Ultem meets the FAR 25.853 requirements for heat release (OSU 65/65), smoke density (NBS), and flammability that govern commercial aircraft cabin components. These properties are achieved without halogenated flame-retardant additives, which simplifies RoHS compliance. Ultem is routinely found in aircraft seat components, overhead bin brackets, galley parts, and structural panels. Compare to PEEK aerospace performance for applications requiring even higher service temperatures.

Are glass-filled Ultem grades harder to machine?

Glass-filled grades (Ultem 2200, 2300) are significantly more abrasive than unfilled Ultem 1000. Expect 3–5× faster tool wear when machining 30% GF compared to natural PEI. Use polycrystalline diamond (PCD) or ceramic inserts for production runs; tungsten carbide (C-2 grade) for prototype quantities. Cutting speeds should be reduced 20–30% versus unfilled PEI, and feed rates optimized to minimize glass fiber pullout at the surface. Thin-wall features in GF grades are prone to delamination if cutting forces are excessive. Dimensional tolerances tighter than ±0.002″ require careful thermal management; GF grades have lower thermal expansion than unfilled PEI, which is an advantage in precision work. The Ultem machining guide provides detailed feeds, speeds, and tooling recommendations.

How do you machine unfilled Ultem 1000?

Unfilled Ultem 1000 machines similarly to a hard acrylic or polysulfone—clean chip formation, good surface finish achievable, moderate tool wear. Use sharp carbide or HSS tooling with positive rake angles. Cutting speeds of 400–700 SFPM for turning; milling at moderate chip loads. PEI is sensitive to elevated cutting temperatures—overheating causes surface discoloration (darkening of the amber color) and possible subsurface stress cracking. Use compressed air or water-soluble coolant for heat control; avoid cutting oils that may wick into surface voids. Pre-dry stock before close-tolerance machining (moisture absorption causes dimensional variation). Tapping: 65% thread engagement with spiral-flute taps. Full parameters are in the Ultem machining guide.

How does Ultem cost compare to PEEK?

Ultem (PEI) is typically 30–60% less expensive than natural PEEK in equivalent sizes and forms, making it the first high-performance thermoplastic to evaluate when PEEK's price is a barrier. Ultem 1000 rod and sheet typically runs $20–$45 per pound depending on size; natural PEEK runs $50–$120 per pound. The cost advantage narrows for smaller sizes and specialty grades. Ultem 2300 (glass-filled) is priced between unfilled Ultem and natural PEEK. If your application requires operation above 480°F (250°C), chemical resistance to strong aromatic solvents, or semicrystalline structure (for fatigue and chemical resistance), PEEK may be necessary despite the premium. The Ultem vs PEEK comparison provides a structured decision guide.

What colors does Ultem come in?

Ultem 1000 (unfilled) is amber-translucent in its natural state—this distinctive color is intrinsic to the PEI polymer backbone and is one of the material's recognizable characteristics. Opaque black Ultem is available in some grades (particularly in sheet form) using carbon-black colorant. Glass-filled grades (2200, 2300) are an opaque tan or light gray due to the glass fiber content. Custom colors are not commonly available in stocked sheet and rod; if a specific color is required, painting post-machining or selecting a different material base is more practical. The amber color of Ultem 1000 is often an advantage in applications where part inspection or light transmission is helpful. Review stocked options at the Ultem product page.

Is Ultem steam-stable?

Ultem is hydrolytically stable and retains good mechanical properties after prolonged exposure to hot water and steam within its service temperature range. At typical autoclave conditions (134°C / 273°F), Ultem 1000 shows minimal property degradation over hundreds of cycles. However, at sustained temperatures above 150°C (302°F) in the presence of pressurized steam (superheated or high-pressure autoclave), some grades can show surface dulling and marginal strength reduction over long service. For high-pressure steam applications (above 150 psi steam, 170°C+), evaluate PVDF or PEEK for their superior hydrolytic stability at higher temperatures. The Ultem properties datasheet lists water absorption and hydrolytic stability data.

What are typical lead times for Ultem sheet and rod?

Ultem 1000 in natural and black, in common rod diameters (0.25″–6.0″) and sheet thicknesses (0.125″–3.0″), is typically stocked for same-day or next-day shipment. Ultem 2300 (30% GF) in standard rod and sheet is widely stocked but may have slightly longer lead times. Less common sizes, large-diameter rod (>6.0″), thick plate (>3.0″), and Ultem 2200 may require 2–4 weeks. Specialty grades (Ultem with FDA-specific CoC, low-outgassing Ultem for vacuum service) add documentation lead time. For critical schedule items, confirm stock availability at the Ultem line card before finalizing the order.

What is Ultem's continuous use temperature?

Ultem 1000 has a continuous use temperature of approximately 340°F (170°C) with a heat deflection temperature (HDT) under 264 psi of 392°F (200°C). This places it well above polycarbonate (~270°F continuous), polysulfone (~300°F continuous), and most other amorphous engineering thermoplastics, but below PEEK (~480°F continuous) and Torlon PAI (~500°F+). Glass-filled grades have similar continuous use ratings. For applications at 350°F–480°F, PEEK is the natural next step. For applications above 480°F, Torlon (PAI) or Vespel (polyimide) should be evaluated. Temperature data for comparison is in the Ultem properties guide.

Is Ultem suitable for semiconductor and vacuum applications?

Ultem is used in semiconductor equipment for wafer handling components, test sockets, and structural parts in clean-room environments. It offers low outgassing, no halogen content, good dimensional stability, and resistance to many process chemicals including dilute acids and bases. Low-outgassing grades tested per NASA ASTM E595 are available for vacuum applications. Ultem is generally not suitable for exposure to concentrated sulfuric acid, chlorinated solvents, or strong alkalis at elevated temperatures. For aggressive semiconductor chemical environments (HF, hot H2SO4, NMP), PEEK or PVDF are required. See the Ultem applications guide for semiconductor case studies.

More related guides

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