PEKK vs PEEK: Understanding the Key Differences and Uses

In the aerospace sector, high-performance polymers like PEKK and PEEK play an essential role in achieving lighter weight, greater thermal resistance, and superior mechanical strength. Both materials belong to the polyaryletherketone (PAEK) family, but they exhibit distinct properties that make each suited for different applications. Understanding the nuances between Pekk and Peek can help engineers, designers, and material scientists make more informed decisions.

In this article, we’ll break down the fundamental differences between PEKK and PEEK in terms of performance, manufacturing compatibility, aerospace use cases, and cost considerations.

What Are PEKK and PEEK?

PEKK (Polyetherketoneketone)

PEKK is a semi-crystalline thermoplastic known for its high thermal stability, chemical resistance, and strong mechanical performance. Thanks to its slower crystallization rate and tunable processing conditions, PEKK offers greater flexibility in part manufacturing.

PEEK (Polyetheretherketone)

PEEK, one of the most widely used PAEK materials, is valued for its exceptional mechanical strength, creep resistance, and long-term chemical stability. Peek's processability and performance consistency make it a popular choice for high-heat, high-stress environments.

Key Differences Between PEKK and PEEK

While PEKK (Polyetherketoneketone) and PEEK (Polyetheretherketone) both belong to the high-performance PAEK family of thermoplastics, their material behaviors diverge in ways that significantly affect how they are used in aerospace, industrial, and additive manufacturing settings. For engineers, OEMs, and manufacturers evaluating which polymer to use for a given part or project, it's critical to understand these differences beyond the datasheet — especially when working with advanced 3D printing materials.

Crystallization Rate is one of the most fundamental technical distinctions between the two. PEKK crystallizes more slowly than PEEK, which allows for more tunable processing conditions. This gives PEKK greater versatility during manufacturing, especially when fine-tuning properties such as part strength, shrinkage, and dimensional stability. For aerospace engineers designing mission-critical parts, this tunability can lead to better outcomes in both prototyping and production. Peek, on the other hand, has a faster crystallization rate, which results in a more rigid structure once cooled. While this rigidity provides strength, it also imposes stricter requirements on process control — particularly during high-temperature molding or 3D printing.

When it comes to thermal resistance, both  PEKK and Peek perform admirably, but  PEKK edges ahead with a slightly higher maximum operating temperature of around 260°C, compared to Peek’s 250°C. This small difference becomes substantial in aerospace and defense applications, where prolonged exposure to extreme heat is routine. Components in engine compartments, air ducts, and flame-prone environments demand polymers that not only survive, but perform consistently under thermal stress. In those scenarios,  PEKK's thermal endurance can be the deciding factor.

The mechanical strength of each material depends on how you define strength.  PEKK is often favored for its superior compressive strength, making it ideal for applications that involve pressure, impact, or crushing forces — such as aircraft interior brackets or lightweight manufacturing tools and aids.  PEEK, however, has higher tensile strength, making it more appropriate for structural parts that require resistance to pulling forces. Think of load-bearing housings, clamps, and space vehicle enclosures where long-term tension without deformation is vital. Neither is universally “stronger” than the other — it entirely depends on the force profile of the intended application.

Printability — particularly for additive manufacturing — is where PEKK really shines. Thanks to its slower crystallization and higher flow properties,  PEKK offers better layer adhesion, less warping, and easier print settings. These traits make PEKK a top choice for companies embracing 3D printed production parts, especially in situations where part accuracy and visual quality matter.  PEEK is certainly printable — and American Additive supports PEEK-based projects as well — but its printability demands highly controlled environments, including heated chambers, precise cooling, and specific build plate temperatures. For customers needing to balance print success rates with material performance,  PEKK is often the more forgiving and scalable option.

On the front of chemical resistance, both materials are considered best-in-class. They resist a wide range of aggressive substances including hydrocarbons, acids, bases, and solvents, making them suitable for aerospace fuel systems, chemical processing equipment, and medical sterilization environments. Whether you're developing production-replacement parts for mission-critical platforms or high-touch components that face repeated sterilization, both  PEKK and PEEK provide the necessary resistance. Here, the choice between them comes down to secondary needs like heat, strength, or manufacturability.

One area where  PEKK clearly differentiates itself is Flame, Smoke, and Toxicity (FST) performance. In aerospace, materials must pass rigorous FST standards for cabin interiors and safety-critical components.  PEKK's inherent structure gives it superior flame resistance, extremely low smoke generation, and virtually non-toxic off-gassing. These properties make it a standout material for commercial aviation interiors and other aerospace applications where FST certification is a prerequisite.  PEEK, while still compliant in many use cases, does not match the ultra-low smoke and toxicity profile of  PEKK. When fire safety and passenger health are top priorities,  PEKK becomes the clear frontrunner.

Finally, the topic of cost cannot be ignored.  PEKK tends to be slightly more expensive than  PEEK due to differences in raw material sourcing and processing complexity. While the cost difference is not dramatic, it can influence decisions in large-volume production or budget-constrained programs. For companies manufacturing at scale or optimizing around cost-efficiency in 3D printing, Peek may be more favorable — especially in applications where its tensile strength or chemical resistance is sufficient. However, many clients find that the long-term performance advantages of  PEKK (especially when factoring in reduced part failures, lighter weight, or easier printability) offset its slightly higher price.

In summary, while  PEKK and Peek are often mentioned in the same conversation, their key differences warrant serious consideration.  PEKK is more adaptable in manufacturing, better for 3D printing, and offers superior FST and thermal properties — making it ideal for aerospace interiors, on-demand replacement parts, and additive use cases.  PEEK, meanwhile, excels in long-term mechanical durability and is better suited for high-load applications, high-volume parts, and harsh chemical environments.

Whether you're exploring new designs or refining an existing one, selecting the right high-performance polymer is mission-critical.

Aerospace Applications of PEKK

PEKK is increasingly being used in aerospace applications where weight reduction, heat resistance, and flammability standards are critical. It excels in:

• Brackets, ducts, and interior components requiring FST compliance
• Lightweight structural parts for commercial aircraft
• Parts where reduced warping and high detail resolution are needed in 3D printed aerospace components

Aerospace Applications of Peek

Peek remains a go-to for applications requiring extreme strength and chemical resistance:

• 3D printed production parts
• Components exposed to high pressure and heat in engine compartments
• Insulating components in electrical systems
• Load-bearing structural elements in space systems

PEKK vs PEEK in 3D Printing

For additive manufacturing,  PEKK typically offers better layer adhesion, printability, and reduced warping compared to Peek. This makes Pekk a strong candidate for industrial 3D printing when tight dimensional tolerances and surface finish are essential.

Peek, on the other hand, demands precise control over print environments but can yield parts with exceptional strength when processed correctly.

To explore more about 3D printing materials like Peek, check out our PEEK material guide.

Choosing Between PEKK and PEEK

Ultimately, the choice between PEKK and PEEK depends on the specific performance requirements of your part:

• Choose PEKK if your application demands flame resistance, dimensional accuracy, and superior printability.
• Choose PEEK for legacy use cases where tensile strength, fatigue resistance, and chemical exposure are top concerns.

You can always contact us to talk to a 3D printing expert about which material best fits your aerospace or industrial application.

American Additive Can Help

At American Additive, we specialize in engineering-grade materials like  PEKK and PEEK for critical aerospace and defense applications. When you're designing high-performance production parts or need lightweight rapid prototypes to validte design , our team of experts can guide you in selecting the right polymer and manufacturing process.

Ready to bring your next aerospace innovation to life? Talk to a 3D printing expert today.