Recycling PEEK: extrusion walkthrough from regrind to filament

Our experiences with the recycling of shredded polyether ether ketone (PEEK). Starting with a batch of PEEK regrind, we adjust the extrusion settings for optimal filament quality.

1. General: the study about recycling PEEK

This document shows a detailed explanation of the extrusion process for shredded PEEK. It gives a overview of how we managed to get the right extrusion settings. We also provide information about the cleaning process and we discuss some important things to keep in mind when extruding PEEK with 3devo’s filament maker.

Please note that this document is only an indication on the extrusion process for PEEK, different machines and polymer grades may require different settings.

The Victrex 450G material data sheet recommends a drying period of 3 hours, just to be sure that we removed all the excess moisture we dried the material for 7 hours. The residual moisture content should be < 0.02%.

Table 1 shows some important material properties relevant for extrusion:

Table 1: Relevant properties of shredded PEEK – Victrex 450G.
MaterialVictrex PEEK 450G (shredded)
Melting point (°C)343
Glass transition temperature (°C)143-150
Drying temperature (°C)150
Drying time (h)3-7

2. Cleaning the extruder

It is important to note that PEEK cannot stay in the extruder after extrusion since this will cause impurities that will impact the quality of subsequent production.

It is important that the hopper sensor is turned off and also it is very important to have the extrusion screw rotate continuous.

Before extrusion the machine was cleaned using Devoclean Mid-Temperature, a universal cleaning material. Make sure the hopper sensor is switched off. Extrude with Devoclean Mid-Temperature until you can no longer see any material in the hopper opening.

Only when you no longer see Devoclean Mid-Temperature in the hopper opening, do you add Devoclean High-Temperature, which contains glass fiber specifically for cleaning at high temperatures. Always ensure that the extrusion system continues to run and increase the temperature. Make sure that you keep extruding 5 to 10 minutes longer so you can be sure that Devoclean Mid-Temperature is completely removed. The Devoclean High-Temperature was used to heat the filament maker up to the desired temperature before adding the PEEK to the hopper.

If you no longer see Devoclean High-Temperature in the hopper opening, PEEK is added. Also during this step it is important that the extrusion screw continues to run and is at the required temperature.

When you have finished extruding PEEK, it is important that PEEK is never allowed to cool down in the extrusion system. This means that the steps with Devoclean High-Temperature and Mid-Temperature must be carried out again. Devoclean High-Temperature must also never stay in the extrusion system.

Devoclean Mid-Temperature can stay in the extruder after extrusion has finished. Although HDPE can be used to remove all of the Devoclean Mid-Temperature which will make for a faster start-up the next time the extruder is used.

3. The material

Figure 1 shows the shredded PEEK we used for these tests. We had approximately 200 grams of material to work with, this means we had to change settings quickly to make the most of the amount of product we could work with.

Figure 1: The shredded PEEK.

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