PEKK (Polyetherketoneketone)

PEKK (polyetherketoneketone) belongs to the same polyaryletherketone (PAEK) family as PEEK. For most grades the glass transition is about 155–165 °C, above the 143 °C of PEEK, and the polymer combines excellent resistance to fuels, oils, hydraulic fluids and most solvents with inherent flame resistance and low smoke and heat release. Its distinctive feature is adjustable crystallization: by changing the ratio of terephthalic to isophthalic units in the polymer chain, producers offer grades that range from slow-crystallizing, nearly amorphous types to fast-crystallizing ones with a higher melting point.

Choose PEKK for printed parts that must work beyond the limits of PEI or in fuels, oils and solvents, and where PEEK is difficult to print with good layer bonding: aerospace and space brackets, ducts and covers, and high-temperature tooling. It is among the most expensive FDM materials, and like every printed high-performance polymer it is weaker across the layers. On Uretyco, PEKK is offered through partners with high-temperature FDM printers; grade, feasibility and lead time are confirmed during quote and order review.

Mechanical and physical properties

FDM printing PEKK

PEKK is printed on high-temperature FDM systems with heated build chambers, at nozzle temperatures well above 300 °C. Slow-crystallizing grades stay largely amorphous while the next layer is deposited, which helps layers fuse and reduces warping compared with PEEK. Faster-crystallizing and carbon-filled grades give higher stiffness and heat resistance but are more demanding to print. Design and ordering points:

• Orientation: across-layer strength is often 30–50% lower than in-plane strength. Keep main loads, clips and bosses in the layer plane, and state a fixed orientation in the order notes.
• Crystallinity and annealing: some grades are printed largely amorphous and annealed afterwards. Annealing raises stiffness above Tg and chemical resistance, but parts shrink slightly and can distort, so state whether it is required and allow for it on critical dimensions.
• Walls and features: plan walls of at least about 1.0–1.5 mm and avoid very thin pins and ribs; fine detail is limited by the bead width of industrial nozzles.
• Supports and cosmetic faces: surfaces more than about 45° from vertical need supports, usually a breakaway material. Mark faces that must stay clean and avoid supports inside closed channels.
• Holes and threads: drill or ream fit-critical holes after printing and use threaded inserts; printed threads suit low loads only.

Tolerances and surface

Without a drawing tolerance, FDM parts on Uretyco follow the default of ±0.5 mm or ±0.5%, whichever is greater; actual results vary with orientation, part size, supports and post-processing, and tighter values on well-supported features need a drawing and acceptance in the quote. Annealing adds shrinkage and possible distortion, so leave machining allowance on bores, sealing faces and datums that must be accurate, and mark them on a drawing. Surfaces show layer lines; natural grades are tan to amber and filled grades black. Final values are confirmed in the quote and order review.

Finishing options

PEKK parts are usually used as printed, with critical features machined afterwards. Like PEEK, PEKK is difficult to paint or bond without surface activation.

Cost and lead-time drivers

PEKK filament is among the most expensive FDM materials, and only a limited number of high-temperature printers can process it, so material, machine time and availability drive the price. The main levers:

• Grade: unfilled, carbon-filled and electrostatic-dissipative (ESD) grades differ in price and availability; name the grade so that it can be confirmed in the quote.
• Build volume and supports: large solid parts mean long builds; reduce supports through orientation and use sparse fill where stiffness allows.
• Annealing and post-machining: each adds a step and time, so specify them only where the application needs them.
• Documents: material certificates, lot traceability and a certificate of conformance are opt-in and can extend the lead time. Request them at quote time, especially for aerospace projects.

PEKK vs. other high-performance polymers

PEKK earns its price in printed parts that need PAEK-level chemical and flame resistance with better layer bonding than PEEK. If the part stays below about 150 °C and the chemical exposure is moderate, PEI is the established and less expensive FDM choice. For machined or molded parts, PEEK is the more widely available PAEK.

When not to choose PEKK

Typical applications

• Aerospace and space brackets, clips, ducts and covers exposed to fuels, hydraulic fluids or flame requirements.
• Low-outgassing parts for vacuum and space hardware, in grades tested to ASTM E595.
• Electrostatic-dissipative fixtures and housings (ESD grades) for electronics handling and fuel-system parts.
• High-temperature jigs, fixtures and tooling that must withstand solvents and cleaning agents.
• Prototypes and spare parts for oil, gas and chemical processing.

Specifying PEKK on Uretyco

1. 1
   Upload STL, 3MF or STEP

   STEP is preferred when features will be machined; add a 2D drawing for tolerances, threads and inserts.

2. 2
   Select PEKK and the grade

   Unfilled, carbon-filled or ESD: name the grade or the required properties so that availability is confirmed in the quote.

3. 3
   Describe the environment

   State the service temperature, loads, fluids and any flame, smoke, toxicity or outgassing requirement.

4. 4
   Define orientation, annealing and finishing

   Note the main load direction, cosmetic faces, whether annealing is required and which faces are machined afterwards.

5. 5
   Request documents and review the quote

   Ask for certified material, traceability or a certificate of conformance at quote time; feasibility and lead time are confirmed in the quote and order review.

FAQ

PEKK or PEEK for printed parts?

For FDM, PEKK is often the more practical PAEK: slower crystallization gives better layer bonding and less warping, and the higher Tg helps parts that remain amorphous. PEEK is more widely available, usually somewhat less expensive and the standard for machined and molded parts. If the part will be machined or molded, start with PEEK; if it must be printed, compare both in the quote.

Do printed PEKK parts need annealing?

It depends on the grade and the requirement. Parts from slow-crystallizing grades are largely amorphous as printed: tough and dimensionally predictable, but they lose stiffness near Tg. Annealing crystallizes them, which raises stiffness at high temperature and chemical resistance, at the cost of slight shrinkage and a risk of distortion. State the service temperature so that the right grade and post-processing can be chosen.

Is PEKK also available for laser sintering or machining?

PEKK powders are processed by laser sintering on specialized high-temperature powder-bed systems, mainly for qualified aerospace parts. This is a separate process with its own material data and qualification, not a variant of FDM. PEKK stock shapes for machining also exist but are far less common than PEEK. Both routes are reviewed case by case during quoting.

Is PEKK suitable for aircraft and space applications?

PEKK is inherently flame-retardant with low smoke and heat release, and some filaments come with outgassing data to ASTM E595, which is why it is used in aerospace and space hardware. Material data are a starting point: compliance of a specific part depends on grade, wall thickness, finish and test method, and is shown through your own qualification.

Related resources

• PEEKThe more widely available PAEK, also for CNC and molding.
• PEI (ULTEM)Lower-cost FDM choice for flame-rated parts.
• PPSChemical-resistant alternative at lower cost.
• 3D PrintingTechnologies, files and cost drivers.
• Certificates & Inspection ReportsMaterial certificates, conformance and inspection documents.
• Material Selection GuideStart from the requirement, not the material name.