PAI Torlon: Polyamide-Imide Extreme-Performance Polymer Properties & Processing
Published: 2026-05-27
Polyamide-imide (PAI), commercially known as Solvay Torlon, occupies the performance space between PEEK and polyimide (Vespel)—offering higher strength and temperature resistance than PEEK without the extreme processing difficulty and cost of...
Polyamide-imide (PAI), commercially known as Solvay Torlon, occupies the performance space between PEEK and polyimide (Vespel)—offering higher strength and temperature resistance than PEEK without the extreme processing difficulty and cost of Vespel. PAI delivers the highest tensile strength of any unreinforced thermoplastic (130 MPa for Torlon 4203) and maintains useful mechanical properties to 260°C continuous service. Its exceptional creep resistance, low coefficient of thermal expansion (CTE ~25 ppm/°C), and outstanding wear resistance make it the material of choice for aerospace thrust washers, automotive transmission seals, and semiconductor test sockets.
PAI requires a complex post-cure cycle after molding to achieve full mechanical properties. Green (as-molded) parts must undergo a stepped temperature cure program lasting up to 7 days, progressively heating from 150°C to 260°C in controlled increments. This post-cure drives off residual NMP solvent and completes the imidization reaction—without it, the part will have only 50-60% of its rated strength and will outgas excessively at elevated temperature. Torlon 4301 (PTFE-filled) provides the best wear and friction properties for bearing applications; Torlon 5030 (30% glass fiber) offers maximum stiffness and load-bearing capacity.
Technical Properties
| Density | 1.41 g/cm³ |
|---|---|
| Tensile Strength | 130 MPa (unfilled); 200 MPa (30% GF) |
| Melting Point | N/A (Amorphous, Tg 275°C) |
| Shrinkage Rate | 0.6-0.8% |
| Flexural Modulus | 5.0 GPa |
| Hdt | 278 °C at 1.82 MPa |
| Continuous Service Temp | 260 °C |
Engineering Tool: Shrinkage & Cost Estimator
Calculate part weight, mold cavity dimensions accounting for shrinkage, and material cost — all locally in your browser.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Solvay Torlon 4203 | |
| Torlon 4301 (PTFE-filled) | |
| Torlon 5030 (30% GF) |
Frequently Asked Questions
What is the post-cure requirement for Torlon PAI and why is it critical?
Torlon PAI requires a mandatory post-cure cycle after injection molding—this is not optional. Green parts contain residual N-methyl-2-pyrrolidone (NMP) solvent from the polymerization process and have incomplete imidization. The post-cure program typically runs 5-7 days: ramp from 150°C to 260°C in 5-10°C increments, holding at each step for several hours. Without post-cure: (1) tensile strength is reduced by 40-50%, (2) the part outgasses NMP at elevated temperatures contaminating sensitive environments (semiconductor, aerospace), and (3) dimensional stability is compromised as the part continues to cure in service. Always verify post-cure completion by measuring glass transition temperature—fully cured Torlon reaches Tg 275°C.
How does PAI Torlon compare to PEEK for wear and friction applications?
Torlon 4301 (PTFE-filled) outperforms unfilled PEEK in wear resistance by approximately 3-5× in dry sliding conditions against steel. Its PV limit (pressure × velocity) at 100 fpm is approximately 30,000 psi·fpm versus 15,000 psi·fpm for unfilled PEEK. However, Torlon is 2-3× the raw material cost of PEEK and requires the 7-day post-cure cycle, adding significant lead time. For moderate wear applications below 200°C, bearing-grade PEEK (with PTFE/graphite) is often the more economical choice. Specify Torlon when the combination of high load, continuous temperature above 200°C, and maximum wear life justifies the cost premium.
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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