A practical guide to selecting PEI ULTEM™ and PAI Torlon® for electrically insulating and mechanically loaded components in defence and other critical systems.
Introduction
Defence and security systems place unusual demands on materials. Equipment has to work reliably through vibration, temperature extremes and long service intervals, often close to sensitive electronics. At the same time, components are needed in small quantities, design revisions are frequent, and procurement expects documented traceability.
These conditions favour high-performance thermoplastics machined from stock shapes. Machining needs no injection-moulding tooling, so prototypes, replacement parts and small series can be produced directly from sheet or rod, to the current drawing revision.
Within one critical assembly, two very different jobs typically have to be covered: electrical insulation and mechanically loaded wear performance. This is why two materials appear together so often in this field. PEI ULTEM™ handles the electrical and thermal side, PAI Torlon® handles the mechanical and tribological side. This guide explains how to choose between them.
Requirements in Defence and Critical Systems
A typical requirement profile combines several factors: continuous vibration, wide temperature ranges, sensitive electronic and optical subsystems, long maintenance-free intervals, electrical insulation in some positions, mechanical load and wear in others, documented material traceability, and small production quantities per variant. Injection moulding is rarely economical at these volumes, so machining from stock shapes is usually the appropriate manufacturing route.
PEI ULTEM™ for Electrical and Thermal Requirements
PEI (polyetherimide), widely known under the trade name ULTEM™, is an amorphous high-performance thermoplastic. Its combination of very good dielectric properties, inherent flame resistance and low smoke emission makes it a standard choice for electrical insulators, connector bodies and sensor carriers.
Key characteristics for this application field:
- Very good dielectric properties and electrical insulation
- Inherent flame resistance and low smoke emission
- Continuous operating temperature of approximately 170 °C
- Good dimensional stability and low weight
- Semi-transparent appearance, machinable to tight tolerances
PEI is available as sheets and rods and machines cleanly to precise insulating components. Note that PEI covers electrical and thermal duties; it is not the material for highly loaded wear positions. That is where PAI takes over.
PAI Torlon® for Mechanical and Tribological Requirements
PAI (polyamide-imide), known under the trade name Torlon®, offers outstanding strength and stiffness among melt-processable thermoplastics. Depending on grade and load profile, PAI Torlon® remains usable under demanding conditions up to approximately 260 °C.
Typical positions are bushings, bearing elements, actuator components and guide systems, machined from rod stock. Tribologically modified PAI Torlon® grades are designed for low-lubrication operation. The suitability of a grade for a specific bearing application is always assessed against the actual load profile, including load, speed, temperature and counterface.
PEI or PAI: Selecting the Correct Material
| Criterion | PEI ULTEM™ | PAI Torlon® |
|---|---|---|
| Primary function | Electrical insulation, thermal stability | Mechanical strength, wear performance |
| Electrical insulation | Very good | Secondary consideration |
| Mechanical loading | Moderate | High |
| Wear performance | Not the primary strength | Very good with tribological grades |
| Continuous operating temperature | Approx. 170 °C | Up to approx. 260 °C, grade-dependent |
| Typical components | Insulators, connector bodies, sensor carriers | Bushings, bearing elements, actuator parts |
| Available stock shapes | Sheets and rods | Stock shapes on request |
| Typical quantities | Single parts to small series | Single parts to small series |
If the component insulates, carries electronics or sits close to sensors: PEI. If the component slides, bears load or wears: PAI. Many critical assemblies need both, machined from the respective stock shape.
Typical Machined Components
Electrical insulators, connector bodies, sensor carriers, electro-optical mounts, bushings, bearing elements, guide elements, structural supports, spacers, prototypes, replacement parts and small-series components.
Available Stock Shapes and CNC Machining
PEI is available as sheets and rods, cut to size or machined into finished parts. PAI Torlon® stock shapes are available on request through the technical team. CNC machining covers prototypes, single parts and small series, produced without moulding tools and to the current drawing revision.
Why Source Through Plastix Factory?
Plastix Factory connects material selection, availability information, technical documentation and ordering in one digital platform. Stock shapes and cut-to-size pieces can be configured and ordered online, and CNC-machined finished parts are accessible through the same route. The platform is backed by the manufacturing experience of COMCO EPP in semi-finished products and CNC-machined plastic parts. Special materials and PAI Torlon® requirements are handled by the technical team.
Summary
PEI ULTEM™ and PAI Torlon® cover two different functions within defence and critical assemblies: PEI for electrical insulation and thermal stability, PAI for mechanical load and wear. Both are machined from stock shapes, which makes small quantities, frequent revisions and traceable small-series production economical.
Check Availability and Order Online
Special grades, PAI stock shapes and CNC-machined finished parts can be submitted to the technical team for review.
ULTEM™ is a trademark of SABIC. Torlon® is a registered trademark of Syensqo.