Two part epoxy static mixer - introducing air bubbles

[esteess]

I want to use a static mixer nozzle to mix hardener with an epoxy resin that both are formerly degassed in separate containers.
The question is that is the mixing in the nozzle going to introduce air into the polymer mix and all degassing process done will become pointless?
It is well known that excessive disturbing degassed mixture can bring air back into the substance (like in the stirring mixing process), however I never came across any information with regards to static mixing process.
Any thoughts?

Stan

 

[btrueblood]

No, I don't think the mixer on its own will introduce any bubbles. Using the cheap mixers that come with some syringe-packed 2 part epoxies, I have never seen same. These do have the advantage of being fully degassed, loaded, matched cylinders and thus give a fairly perfect delivery of the two parts to the face of the mixer.

 

[Compositepro]

Air bubbles might be introduced during the initial fill of the static mixer if it is not done with care. To minimize the possibility of air bubble entrainment, the mixer should be filled from bottom to top and slowly so that the flow front of the resin can flush air out without entrapping bubbles. Once the mixer is filled and flushed there will be no further issues.

One very serious problem I have experienced with two part syringes and static mixers is an air pocket in the syringe itself. It is not unusual for there to be some air in the syringe when you buy it or to get some into the syringe between uses. When you press on the plunger, resin will flow immediately from the syringe chambers with no air pocket. If there is an air pocket, first the pocket will be compressed, with no immediate flow of resin. Then after stopping the plunger, the air pocket will expand and continue to press resin from the one chamber. So, if you see any resin dribbling out after dispensing is done, it indicates a problem that should be immediately corrected. The resin ratios will not be correct. This issue is most serious if you are dispensing drops of resin.

 

[GregLocock]

We used to vacuum degas epoxy after mixing, as it was being used to seal underwater electronics

Cheers

Greg Locock


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