Torlon (PAI) vs. PEEK: Selecting the Polymer for Extreme Mechanical and Thermal Demands
Torlon vs. PEEK: The Two Highest-Performance Thermoplastics
Torlon (Polyamide-imide, PAI) and PEEK (Polyetheretherketone) are the two highest-performing thermoplastics available for engineering applications. Both operate in extreme thermal and mechanical environments, but they are not interchangeable — their strengths diverge sharply. Torlon offers the highest mechanical strength of any thermoplastic. PEEK offers superior chemical resistance, processability, and toughness.
This comparison references data from ASTM International standards and manufacturer technical data from Solvay (Torlon) and Victrex (PEEK).
Mechanical Performance
Torlon is the strongest unfilled thermoplastic available:
| Property | Torlon 4203 (unfilled) | PEEK (unfilled) |
|---|---|---|
| Tensile Strength (MPa) | 190 | 100 |
| Flexural Strength (MPa) | 250 | 170 |
| Flexural Modulus (GPa) | 5.0 | 3.6 |
| Compressive Strength (MPa) | 270 | 130 |
| Hardness (Rockwell E) | 86 | 78 |
Torlon's tensile strength (190 MPa) is nearly double PEEK's, and its compressive strength (270 MPa) is more than double. For pure mechanical loading — especially compressive — Torlon dominates.
Thermal Performance
Both materials are exceptional at high temperature, but Torlon's Tg (275°C) is significantly higher than PEEK's Tg (143°C). Torlon maintains mechanical properties at temperatures where PEEK has softened. However, PEEK's crystalline melting point (343°C) allows it to be processed by standard injection molding, while Torlon requires specialized high-temperature processing equipment.
Chemical Resistance
PEEK is significantly more chemically resistant than Torlon. Torlon is attacked by strong bases and some polar solvents, while PEEK resists virtually everything except concentrated sulfuric acid and halogens at high temperature. For chemical processing applications, PEEK is the clear choice.
Processing
This is where the trade-off is most dramatic:
- PEEK: Melt processable by injection molding (343°C melt). Standard equipment with high-temperature capability. Re-grind and reprocess possible.
- Torlon: Requires specialized compression molding or high-temperature injection molding (350-380°C melt + 650-700°F mold temperature). Cannot be reprocessed. Significantly higher processing cost.
Recommendations
- Aerospace structural components (high load, high temp): Torlon — unmatched strength-to-weight at temperature
- Downhole oil & gas: PEEK — chemical resistance + adequate strength + processable
- High-load bearings and wear surfaces: Torlon 4301 (filled) — lowest wear rate of any thermoplastic
- Medical implants: PEEK — biocompatibility certification + sterilizable + processable
- Precision gears (unlubricated): Torlon 4301 — superior PV capability and dimensional stability
- High-volume production: PEEK — standard processing, lower per-part cost
References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- ISO. ISO 1043 — Plastics — Symbols and Abbreviated Terms. iso.org
- National Institute of Standards and Technology (NIST). Polymer Properties Database. nist.gov
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb — Material Property Data. matweb.com