Torlon PAI vs Ultem PEI: Complete Engineering Comparison (2026) — Temperature, Strength, Cost

Which Material Should You Choose?Choose Torlon PAI (Polyamide-imide) if:Extreme-temperature structural applications above 200°Chighest strength and creep resistancesemiconductor and aerospace componentsChoose Ultem PEI (Polyetherimide)...

Torlon PAI and Ultem PEI are both high-temperature amorphous thermoplastics, but they occupy very different performance tiers. Torlon is the highest-strength, highest-temperature melt-processable thermoplastic available — with a Tg of 280°C and tensile strength of 152 MPa — while Ultem PEI offers a more accessible combination of high temperature performance (Tg 217°C), inherent flame retardancy, and significantly lower cost. The choice between them is driven by whether the application demands Torlon's extreme capability or whether Ultem's more practical profile suffices.

Property Comparison

Glass Transition Temperature (Tg): Torlon: 280°C / Ultem: 217°C. Torlon's Tg is 63°C higher — this directly translates to a dramatically higher continuous service temperature and HDT. Continuous Service Temperature: Torlon: 260°C / Ultem: 170°C. This 90°C gap is the most significant differentiator — applications above 170°C that require amorphous polymer properties (isotropic shrinkage, transparency, low creep) can only use Torlon. HDT at 1.82 MPa: Torlon: 280°C / Ultem: 201°C. Torlon maintains structural stiffness 80°C higher under load. Tensile Strength (unfilled): Torlon: 152 MPa / Ultem: 105 MPa. Torlon is 45% stronger at room temperature, and the gap widens at elevated temperatures — at 200°C, Torlon retains ~80% of its room-temperature strength while Ultem retains only ~40%. Impact Toughness: Torlon: Notched Izod 4.5 kJ/m² / Ultem: Notched Izod 3.5 kJ/m². Torlon is moderately tougher, but both are significantly less tough than PEEK (5.5 kJ/m²). Neither is recommended for high-impact applications. Creep Resistance: Torlon has the lowest creep of any thermoplastic at 200-260°C — it is specified for thrust bearings and wear components specifically because it does not deform under sustained load at extreme temperatures. Ultem shows measurable creep above 150°C under load. Chemical Resistance: Torlon offers broader chemical resistance than Ultem, particularly to automotive and aerospace fluids (Skydrol hydraulic fluid, jet fuel, synthetic oils). Ultem is resistant to alcohols and hydrocarbons but is attacked by ketones, chlorinated solvents, and strong bases. Flame Retardance: Both achieve UL94 V-0 inherently — Torlon at 0.25mm, Ultem at 0.40mm. Neither requires halogenated or phosphorus-based flame retardant additives. Processing: This is where the practical gap is largest. Ultem processes at 350-400°C melt / 120-150°C mold — achievable on standard high-temperature injection molding machines with pressurized water or oil-heated molds. Torlon requires 340-370°C melt / 200-260°C mold AND a mandatory multi-day post-cure oven cycle (5-7 days of staged heating to 260°C) to achieve full mechanical properties. Without this cure cycle, Torlon parts have 30-40% lower strength and catastrophic wear resistance. Torlon also releases water as a condensation byproduct during molding, requiring vented molds. Cost: Torlon: $80-120/kg resin / Ultem: $30-80/kg resin. Torlon is approximately 2-3× more expensive, and the total piece-part cost differential is even larger when factoring in the mandatory cure cycle (oven equipment, energy, 5-7 day lead time per batch, and quality control of cure completion).

Decision Matrix

Choose Torlon When: (1) Service temperature exceeds 180°C continuous — semiconductor wafer handling at 250-300°C, aerospace bearings and seals in engine compartments, downhole wireline tools; (2) The lowest possible creep at 200-260°C is required — thrust washers, precision wear components, valve seats; (3) The highest tensile strength of any thermoplastic is needed — structural brackets and fasteners in extreme environments; (4) The application requires resistance to aggressive aerospace/automotive fluids at elevated temperature; (5) The production volume is low enough that the cure cycle's 5-7 day lead time is acceptable, or parts are machined from cured Torlon stock shapes. Choose Ultem When: (1) Service temperature is below 170°C — this covers the vast majority of high-temperature amorphous polymer applications; (2) Cost is a significant factor — Ultem is 2-3× less expensive with much simpler processing; (3) The part requires inherent V-0 flame retardance for electrical/electronic applications (connectors, insulators, housings); (4) The part will be autoclave-sterilized for medical device applications — Ultem withstands standard 134°C autoclave cycles; (5) The part requires transparency or translucency — both are amber-transparent, but Ultem is more readily available in optical grades; (6) High-volume production where Torlon's cure cycle makes just-in-time manufacturing impractical.

Comparison at a Glance

Equivalents & Cross-References

Related Diagnostics & Materials

References & Industry Standards

• ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
• UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
• MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
• ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org