A Study of Manufacturing Methods for PEEK/HA

Polyether ether ketone (PEEK) possesses many characteristics which make it a promising material for orthopedics. It is a biocompatible, non-toxic, radiolucent, and corrosion resistant material with incredible toughness, rigidity, and an elastic modulus similar to bone. Despite its many favorable qualities, pure PEEK’s biological inertness has hindered its immediate use in orthopedics. One method of combating this drawback involves supplementing PEEK with a compound like Hydroxyapatite (HA), which greatly increases PEEK’s osteogenic capabilities and introduces the possibility of using the composite material to 3D print bone scaffolds and implants. The only difficulty with utilizing PEEK/HA is the elaborate process required to manufacture it. This research explores three methods for producing PEEK/HA composite material in order to promote its usage in 3D printing orthopedic implants.

Hello, my name is Elijah Pointer. My research this summer was a study of manufacturing methods for PEEK/HA under Dr. Bagheri.

In this video, I will first explain what PEEK/HA is and why it is significant. Next, I will describe the filament extrusion process and different manufacturing methods of the material. Lastly, I will provide my results and troubles I encountered, as well as future improvements and next steps for this area of research.

PEEK stands for polyether ether ketone. It is a high performance polymer with characteristics such as biocompatibility, non-toxicity, radiolucency, toughness, rigidity, and a bone-like elastic modulus. One of its few drawbacks is its inherent biological inertness, which hinders its more widespread usage in a field like orthopedics, which would greatly benefit from its qualities. However, supplementing it with an additive such as hydroxyapatite, or HA for short, reduces this inertness and opens up the possibilities of 3D printing bone scaffolds and implants with PEEK/HA material.

To use PEEK/HA material in 3D prints, the composite material is often made into pellets and drawn into filament using an extruder such as this one. Pellets are dropped into the funnel, where an auger pushes them further into the barrel where they are melted down and pushed out of the nozzle as a thin filament.

The first manufacturing method I employed was dry mixing. This method involves mixing the PEEK pellets with HA powder two to three times at 3000 rpm for 30 seconds. I would then extrude the pellets into filament.

The second method, re-extrusion, is really just an extension of dry mixing. Basically, I would create the dry mixed filament but then cut it into pellet sized pieces and run them through the extruder one to two more times to better mix the composite material.

In situ was the final method I employed. Unlike dry mixing, the in situ method chemically forms PEEK/HA in one go. This is the most complex and time consuming of the three. It involves adding various compounds into a heated mixture and gradually increasing the temperature until the solution is formed. It is then poured out into a tray and broken into extrudable pieces.

As you can see in the top left, I struggled to obtain a good sample of in situ material. The window between liquidation and burning of the materials was incredibly small. Additionally, the in situ material I was able to produce hardly shared any of PEEK’s strength or toughness. As a result, I did not get to extrude with this method.

Right beneath it is the re-extruded material which I cut back into pellets. Compared to the dry mixed material to the right of it, it appeared to brown over time likely due to constant exposure to the extruder’s heat. Overall, however, it still retained most of its strength and toughness, but with a lower quality texture from unintended exposure to moisture between extrusions.

Some future improvements and next steps for future research include vacuum storing all material and filament to maintain texture quality, possibly revising or optimizing the in situ method to avoid burnt and brittle material, and eventually 3D printing scaffold samples, such as the one on the left, with the PEEK/HA filament.

Thank you.