Polyetheretherketone, alias PEEK
Polyetheretherketone, or PEEK as it is
popularly known, is a semi-crystalline thermoplastic widely used in engineering applications. It is undoubtedly a popular choice for seals, but why? The secret lies in special properties that set it apart from other engineering plastics.
Why is Polyetheretherketone PEEK a Popular Choice for Seals? (5 Top Reasons)
1) Strength Properties:
PEEK is often considered the first choice polymer for high-performance applications because of its excellent strength and hardness properties. It has low density, giving it a high strength-to-weight ratio and making it ideal for aerospace applications where every ounce counts.
2) High Temperature Applications:
PEEK can retain its flexural and tensile properties at very high continuous service temperatures (482 F or more), and is ideal for steam and high pressure water environments. Even at such high temperatures it remains dimensionally stable. It also exhibits resistance to thermal fatigue: PEEK seals can be heated, cooled, and reheated repeatedly without degradation. PEEK is also flame retardant, and even when exposed to flames it emits low smoke and low toxic gas emission.
3) Chemical Resistance:
Polyetheretherketone PEEK has good chemical resistance to dilute acids, hydrocarbons, greases and oils, alkalis, and alcohols. The only solvents that severely attack PEEK are concentrated nitric acid and sulfuric acid. It performs very well in salt water environments. Another added benefit is that PEEK exhibits low water absorption rates, which can affect the dimensional stability of seals. Unlike most plastics, PEEK is considered one of the best plastics for vacuum applications because of its relatively low outgassing characteristics.
PEEK has excellent abrasion resistance and provides a low friction, hard surface that is very resistant to wear. One of the benefits of PEEK is that it is not hard enough to damage metal surfaces it contacts. This can be vital in applications in rotary shaft seals and piston rings.
There are a variety of ways to modify the properties of PEEK using fillers such as fiberglass, carbon, graphite, polyimide, and PTFE. A 30% glass or carbon filler is commonly used to increase flexural strength and dimensional stability, while reducing creep. Combining PEEK with 5% PTFE creates a self-lubricating surface without reducing strength. Adding polyimide can increase the range of temperatures at which PEEK can retain its strength.
Polyetheretherketone PEEK has a reputation as being the first choice for many high performance seal applications because of its strength properties, reliable performance in high temperature applications, chemical and wear resistance, and the variety of fillers than can significantly enhance its already outstanding properties.
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