PLA chemical resistances? Especially HCl, other acids
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?
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.
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.
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.
@LuxClaridge: As Perry noted, Clorox is not HCl. "Muriatic acid" is indeed the easy ordinary-consumer-available source of HCl.
Woops, totally blanked there. It was The Works toilet bowl cleaner that I was what I should have said.
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. https://www.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. https://plasticpipe.org/pdf/tr-19_thermoplastic_pipe_for_transport_of_chemical.pdf
Found another article: http://www.fastenercomponents.com/news/acid-resistant-pla/ That lists the best acid resistant plastics. None that I've searched so far are 3D printable. Also found more material that indicated PLA is likely to be less acid resistant than polyester (usually that means PET if not specified) I think this is one of those cases where 3D printing isn't the right solution. Hot high concentration acid solutions are the worst, and maybe with cooler low concentration you would be fine. If you do some testing, please update.
This might be of use, from Chemistry.SE: How to dissolve PLA (polylactic acid)?. Doesn't mention HCl though, unfortunately, but does mention bio-degradability. TBH, you would be better off asking this question on Chemistry.SE, which is a shame as, if you did, you'd have to delete the question on this site, as you can't x-post.
@Greenonline: Why is cross-posting not acceptable? Last I checked it was fine as long as the question was separately on-topic for both SE sites, but maybe something has changed or this policy is specific to either 3dp or chem SE?
Read Can I cross post my question from one site to another? and in particular Is cross-posting a question on multiple Stack Exchange sites permitted if the question is on-topic for each site? and this answer. So *no*... would be the answer, 99.9% of the time :-) Do you want me to migrate it?
@Greenonline: If you think it would get more relevant eyes on chem SE, please do. It's not getting any here, anyway.
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.