Chemical Polymer Separation (PLA, ABS, HIPS, and PETG)

AI Thread Summary
The discussion revolves around isolating different polymers—PLA, ABS, HIPS, and PETG—from a granular mixture. The user seeks a non-toxic, cost-effective solution with a tolerable smell to separate PLA and PETG, considering their similar densities of approximately 1.27g/ml. They propose using a weighted solution around 1.2g/ml and mention previous attempts with glycerin in water, which were unsuccessful due to air bubble formation. A potential solution discussed is calcium chloride, although its effectiveness remains uncertain. The user successfully separated ABS from HIPS using a 50/50 mix of acetic acid and water but is unsure how to isolate PETG from PLA. Suggestions include using surfactants to manage effective density issues, with plain soap recommended as a starting point. The user plans to wash the plastic before separation to minimize contaminants and does not expect to refresh the flotation medium frequently.
not_a_chemist
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Good day all!

I've got a granular mixture of PLA, ABS, HIPS, and PETG with a particle size of about a quarter inch, and I'm trying to isolate each polymer from the mix. PLA and PETG have densities of about 1.27g/ml, and ABS and HIPS have densities of around 1.06g/ml. I think a weighted solution of about 1.2g/ml would do nicely to separate the PLA/PETG, but I'm not sure what the best solvent/solute would be. I've already tried glycerin in water, and air bubbles tend to nucleate on the surface of the plastic, reducing the effective density and defeating the purpose. I'd like to use something that's non-toxic, cheap, and with a tolerable smell. Tall order?

I think calcium chloride might do the trick, but I'm not entirely sure.

I found a way to separate the ABS from the HIPS (50/50 volumetric mix of acetic acid and water), but I'm completely at a loss for how to isolate PETG from PLA. Any thoughts?

Thank you all very much!
 
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not_a_chemist said:
and with a tolerable smell. Tall order?
"Tolerable smell" over how long a time? You're essentially washing things, which brings surfactants https://en.wikipedia.org/wiki/Surfactant , for control of your "effective density" problem, but those are going to be an extra rinse step. How often do you anticipate refresh/replacement of your flotation medium?
 
I'll be working with the solution for about forty five minutes, but probably only once a week. Surfactants sound like a good idea, are there any that would be the best to try? I don't have access to as large of a stock as I would like, so it would have to be special ordered.

I don't anticipate refreshing/replacing the solution very often. The plastic will be washed prior to being separated, and I don't imagine much dirt/adhesives or other contaminates will make it in.

Thank you!
 
not_a_chemist said:
washed prior to being separated,
Should go a long way toward controlling "smell."
not_a_chemist said:
best to try?
Plain soap, and work your way to more expensive?
 
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