1. Temperature Resistance: The Deciding Factor
The primary differentiator between PEEK and Vespel® is their thermal ceiling. Aerospace environments often involve extreme heat where standard plastics would simply melt.
- PEEK: A high-performance thermoplastic with a continuous service temperature of up to 480°F (250°C). It maintains its mechanical properties well near its melting point.
- Vespel®: A polyimide that does not “melt.” It can operate continuously at temperatures up to 550°F (288°C) and withstand excursions up to 900°F. For jet engine environments, Vespel® is often the only viable choice.
2. Wear and Friction Performance
If your part involves constant movement, such as a seal, bushing, or bearing, friction is your enemy.
Vespel® is legendary for its extremely low wear rate and ability to operate without lubrication, even in a vacuum. While PEEK has excellent wear resistance—especially when reinforced, such as our PEEK-GF30 (Glass-Filled)—it may gall or seize under high-pressure velocity (PV) limits where Vespel® thrives.
3. Chemical Resistance and Outgassing
Both materials are highly resistant to aerospace fluids (fuels, solvents, and lubricants). However, for space applications, outgassing is a critical metric. Vespel® has a long history of success in NASA missions due to its extremely low outgassing, ensuring that sensitive optical equipment remains uncontaminated.
4. Cost and Producibility
Efficiency in the supply chain is vital. Here is where the materials differ in terms of “manufacturability”:
- PEEK: Generally more cost-effective and available in more forms. Cylex Plastics offers Unfilled PEEK Rods, PEEK Tubes, and even PEEK Film for lightweight shielding.
- Vespel®: A premium material with a higher price point. It is typically reserved for components where no other material can survive. We provide Vespel® PI Sheets & Rods for these mission-critical needs.
Summary Comparison Table
| Feature | PEEK | Vespel® (PI) |
|---|---|---|
| Max Service Temp | 480°F (250°C) | 550°F+ (288°C+) |
| Lubrication Required | Low | Self-Lubricating |
| Machinability | Excellent | Good (Brittle) |
| Common Use | Brackets, Valve Seats | Engine Seals, Bushings |
Which Should You Choose?
Choose PEEK if you need a high-strength, lightweight material that offers excellent chemical resistance at a lower cost for temperatures under 480°F. If you need even more precision in small parts, consider our Small Diameter PEEK Rods.
Choose Vespel® if your application involves extreme heat (above 500°F), requires high wear resistance without lubrication, or must operate in the vacuum of space.
Expert Advice from Cylex Plastics
Not sure which grade is right for your aerospace project? Our team at Cylex Plastics is here to help you navigate our full range of Plastic Materials to find the perfect fit.
