How to Turn off the Flame When Doing a High Temperature Purge
This was a first. Watching a company purging PEEK resin. Their process was to execute a purge at temperatures between 800°F and 900°F (426°C and 482°C,) which was what they required to get a complete, clean purge of the barrel and screw.
What I saw was a torch coming out of the nozzle. The combination of high temperature, peek and purging compound turn the nozzle into a flame thrower. Plus, at these high temps, the purging material would come out like water.
This was their normal procedure for purging PEEK with this particular purging compound.
Now, open flame is not something you want in the course of plastics processing. It can create a hazardous situation and puts personnel in unnecessary danger. So we put our technicians to work on a solution for a flame-free, safer purging process.
A successful, flame-free PEEK purge
None of the off-the-shelf purging products were going to be a solution for purging at such high temperatures. So we worked on the chemistry.
We started with a purging compound aptly named Purge-Atory. Recommended for use with gas emitting resins, it is a chemically reactive compound with a SAN resin carrier. Next we tweaked the compound by adding some stabilizers and modifiers. Then the SAN resin was changed to a different grade with a higher melt index.
Next came the testing. Using the same process as before, at the same temperature, but with the new Purge-Atory “High Temp” compound, the processors got the perfect purge without the flame. And resin didn’t turn to a messy, watery consistency.
If you mold with PEEK resin, this is an effective, straight-forward purging process. No special procedures needed.