Properties of Torlon® PAI

Torlon® PAI combines the exceptional performance of thermoset polyimides with the melt-processing advantage of thermoplastics. In addition to wear-resistance, toughness, and high strength at elevated temperatures, Torlon® PAI resins exhibit greater compressive strength and higher impact resistance than most advanced engineering plastics. High creep resistance and an extremely low coefficient of linear thermal expansion (CLTE) provide excellent dimensional stability.

High-Temperature Wear Resistance 

Wear-resistant grades of Torlon® PAI offer tailored combinations of mechanical and tribological properties, along with excellent chemical resistance and high thermal stability. This accounts for Torlon® PAI’s broad acceptance in replacing metal over a wide range of temperature and PV conditions, even when lubrication is marginal or non-existent. Specially formulated grades can perform in lubricated environments at exceptionally high pressures and velocities (PV).

Discover all Torlon® PAI grades

Wear performance and stiffness stability at elevated temperatures

Torlon® 4275 demonstrates excellent wear resistance and stable mechanical performance under combined load, friction and temperature conditions, making it suitable for continuous-duty applications.

Under lubricated conditions (Dexron 3 ATF, 500K PV), Torlon® 4275 exhibits very low wear over extended operation, with measured wear depths of approximately 3.4–3.7 microns over more than 100 hours. During operation, the material maintains a stable temperature range of approximately 100–130°C, indicating controlled frictional behaviour and consistent performance.

Torlon® 4275 also retains high mechanical stiffness across a wide temperature range, maintaining its torsional modulus significantly longer than comparable high-performance polymers. A marked reduction in stiffness occurs only at approximately 270–300°C, confirming its suitability for applications requiring mechanical integrity at elevated temperatures.

Performance characteristics:

• Stable wear performance over time
• Controlled thermal behaviour during operation
• Strong stiffness retention at elevated temperatures
• Delayed mechanical degradation compared to alternative materials

High Strength at Elevated Temperature

Torlon® PAI offers unmatched strength at elevated temperatures, exhibiting greater strength at 200°C (400°F) than other advanced engineering resins at room temperature. High-strength grades are used to manufacture precision components used in repetitive-use, load-bearing operations. Glass-fiber and carbon-fiber-filled grades add strength and stiffness at high temperature, with the added benefit of low creep, excellent fatigue resistance, and enhanced thermal expansion properties. 

Strength-to-weight performance and thermal expansion characteristics

Torlon® PAI combines high mechanical strength with low material density, enabling components that deliver strong performance while reducing overall system weight.

Torlon® PAI grades such as 4203L and 5030 provide high specific tensile strength, exceeding that of several commonly used metal alloys, including aluminium grades. This makes them suitable for applications where weight reduction is critical without compromising structural integrity.

At the same time, Torlon® PAI exhibits a higher coefficient of linear thermal expansion (CLTE) than metals such as aluminium and steel, but within a controlled and predictable range. This allows engineers to account for thermal expansion in design while benefiting from the material’s dimensional stability and consistent behaviour under temperature variation.

Mechanical strength and toughness of Torlon® PAI

Torlon® PAI exhibits high mechanical strength and stiffness, combined with strong performance under compressive load and impact conditions. This makes it suitable for precision components operating under repetitive stress, load and mechanical shock.

Torlon® 4203L demonstrates high flexural strength and modulus, exceeding those of comparable high-performance polymers such as polyimides (PI) and thermoplastic polyimides (TPI). This indicates strong resistance to deformation under load and reliable structural performance in demanding applications.

In compression, Torlon® PAI also delivers significantly higher strength than comparable neat plastics, supporting its use in components subjected to continuous load or contact stress.

In terms of toughness, Torlon® grades provide strong impact resistance, with 4203L showing particularly high values compared to other advanced polymers such as PEEK and PI. This combination of strength and toughness allows Torlon® PAI to maintain performance even in applications involving mechanical shock or repeated loading cycles.

Chemical Resistance

Torlon® PAI is virtually unaffected by aliphatic and aromatic hydrocarbons, chlorinated and fluorinated hydrocarbons, and most acids at moderate temperatures. The polymer, however, may be attacked by saturated steam, strong bases, and some high-temperature acid systems. Proper post-cure of Torlon® PAI parts is necessary to achieve optimal chemical resistance.

Like other high-temperature engineering resins and composites, Torlon® PAI parts absorb water, but the rate is slow and parts can be rapidly restored to original dimensions and properties by drying.

Of particular interest to aerospace and automotive engineers is the ability of a polymer to maintain its properties after exposure to commonly used fluids. Total immersion tests show Torlon® PAI is not affected by aircraft hydraulic fluid at low temperatures or by common lubricating fluids and turbine oil, even under stress at elevated temperatures.