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I'm interested in 3d printed reaction chambers, but can't find any good information on chemical resistances of PLA, just vague claims that it "might not be" "because it's biodegradable" or that it depends on additives (likely true, but it would be nice to know if there's hope of finding PLA without problematic additives if the PLA itself is okay). Is there any published research or even anecdotes (which could suggest it's worth spending effort to investigate further) on this topic?

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  • $\begingroup$ You could test HCl resistance by squirting out some clorox into a small glass and dip a failed print in. Other acids may be hard to come by using common household chemicals. $\endgroup$ Apr 11 '19 at 17:55
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    $\begingroup$ actually, this calls for a lab test... I would suggest to design some kind of sample piece (like, a small tray with a diameter 2mm cylindrical cavity, 1.5mm material to the sides, 1mm bottom, 2mm cavity depth, and some 40mm to clamp the sample holder to a bench) and print some dozens of them using identical g-code. mark the sample holders with the concentration and acid used on the holder part. Next is adding one drop of each tested acid to each sample holder and have it sit there for 24 hours. $\endgroup$
    – Trish
    Apr 11 '19 at 19:13
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    $\begingroup$ You could do accelerated testing by putting PLA in hot HCL solution. It might have a chance with HCL. It wouldn't have much chance with HNO3 or H2SO4. Chlorinated plastics are usually stable. Don't use Clorox, Muriatic acid is HCL. $\endgroup$
    – Perry Webb
    Apr 11 '19 at 21:41
  • $\begingroup$ @LuxClaridge: As Perry noted, Clorox is not HCl. "Muriatic acid" is indeed the easy ordinary-consumer-available source of HCl. $\endgroup$ Apr 11 '19 at 22:50
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    $\begingroup$ Interesting question. Web research only led to anecdotes that PLA is not terribly resistant to HCL but I couldn't find anything definitive. PLA is a polyester, so data on polyester may give some guidance. engineeringtoolbox.com/chemical-resistance-polyester-d_784.html This report is on other plastics, but it gives good background on chemical resistance and factors that affect it such as temperature and mechanical stress. plasticpipe.org/pdf/… $\endgroup$
    – T. M.
    Apr 13 '19 at 0:34
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As @T. M. notes in his comment, there are many good charts of chemical compatibility with various agents. Very few (I found none) include information about PLA. By all means, use search engines to find some information.

But, no data source is as true to your specific needs as is testing your candidate materials with your agents.

As a first test put the agent in a tall thin jar or test tube. Use a few test filaments so that the ends are dipping into the agent. Check for signs of dissolution, swelling, softening, or any relevant change in the material's characteristics. Examine the candidate filaments right away, then after minutes, then hours, and if any material survives, perhaps in days.

Print test objects. Test them with your agent. Try until you find something that works.

The online material compatibility tables will help you eliminate materials before testing them. If it says a material is incompatible, it probably is incompatible. If rated as highly compatible, it should be tested because the formulation of a filament may not match the material tested for the compatibility tables. If you are running out of options, try the intermediate compatibility plastics.

Bottom line, use the online information to help direct your search, but you should do your own tests.

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The paper Chemical Compatibility of Fused Filament Fabrication-based 3-D Printed Components with Solutions Commonly Used in Semiconductor Wet Processing, found by user R Kiselev in the comments on another question, has results for this, and finds (this is summarized; details in paper) that PLA has fairly good resistance to HCl at 37%. It did not fare as well against other acids or solvents except IPA.

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