When it comes to ultra-high performance thermoplastic polymers, few can compete with PEKK (polyether-ketone-ketone). A member of the PAEK family, PEKK resins can be customised and fine-tuned to produce grades with a range of melt temperatures and crystallisation rates.
This results in a material that can be 3d printed in an amorphous state and post processed to a semi-crystalline state. PEKK offers outstanding performance across multiple categories:
Constant use temperature resistance of >250°C – short term up to 300°C
Remarkably high stiffness, impact resistance and strength
Inherently flame retardant
Chemically resistant to virtually all organic and inorganic substances
Good insulating properties
So, with all of these outstanding characteristics, where’s the catch? Well, it requires careful processing and a 3d printer capable of printing at elevated temperatures, in both nozzle and chamber.
Also, it’s not exactly cheap. Depending on supplier and grade, prices can be upwards of €800/kg. But then, nor should it be cheap. Cost and value do not mean the same thing. Ultra-high-performance resins should be valued as precious materials and used only where situations call for their exceptional properties.
At Fabriworks we have found an innovative solution to both cost and sustainability when using PEKK. A couple of years ago, we successfully recycled some Arkema Kepstan® PEKK regrind material through our 3devo desktop extruder to produce high quality 1.75mm filament.
The process starts with pre-drying the regrind material for eight hours at 120°C to reduce moisture to a minimum. As the processing temperature window for PEKK is between 340°-360°C the extruder needs to be brought up to temperature using two separate purge compounds. The first, low-temp, compound sees the temperature rise to 280°C before switching to the second, high-temp, compound at 300°C. Running this second compound, we bring the temperature up to PEKK processing temps of ~360°C.
Once the flow of PEKK has flushed all purge compound from the barrel and the parameters have been fine tuned for a consistent flow, the filament can be spooled.
But, just like the ramp up… the ramp down and cleaning of the extruder must be carefully managed, and transitions from one material to the next need to correspond with the overlap temperature range of each of the purge compounds.
This recyclability of PEKK is super interesting and valuable in its own right, but being able to extrude our own filament also means we can buy pellets in bulk (typically min. 25kgs). Even when you build-in time spent extruding, and the small quantity of purge material used, this represents a significant saving over buying filament. Plus, the experience gained in extruding is hugely valuable when it comes to printing with PEKK. More on that to come!
