4mo ago

Should I distill IPA (isopropanol alcohol) at home for 3D-printing?

TL;DR No.

What you should do:

buy fresh IPA. It is approx. $5/L. As such a 2L washing bin is approx. $10 + 10L waste disposal. In the broader picture of total costs and production value, this is manageable (resin cost, machine depreciation, PPE/gloves, ...)!
use two or three stages of washing
fill the washing containers with as little as necessary to get it done
periodically expose the liquid to sunlight and let the particles settle down. Separate the "clean" liquid from the sump (you might add special chemicals to speed up this process).
if the first stage needs replacement: 1.) responsible disposal of the liquid in compliance with local regulation 2.) move the liquids around: (the third stage is the new fresh liquid, the second is the prior third stage and the second washing station is now the first "dirty" stage).
check for alternative chemicals that can be used with your particular resin

If you use water-washable resin: IT IS A DANGEROUS LIQUID! Dispose of dirty water responsibly as chemical waste.

Long answer:

To answer that, let's first look at what isopropanol (IPA) is: Its formal name is propan-2-ol and its CAS number is 67-63-0.

As a starting point, check a database like GESTIS (German) and NOT wikipedia: https://gestis.dguv.de/data?name=011190

At the top of the page we see that it has GHS-02 and GHS-07 warning labels. Looking further, it is a colourless liquid with a flash point of 12°C and an ignition point of 425°C. The explosive range is 2-13.4% vol. The signal word is DANGER.

Scrolling down:

The substance forms explosive peroxides.

What does this mean?

There is no mechanism mentioned, but generally, if you expose these chemicals to sunlight they will react over time to form a peroxide, which is much more reactive and can explode at high concentrations (there are exceptions to this rule, but most of them go boom).

This means for distillation:

avoid "old" IPA if possible
check for peroxides (if necessary, treat the peroxides before distillation)
don't distill dry (leave some liquid in the sump to avoid high concentrations of peroxides)

As I believe this shouldn't be done at home I won't tell you how it can be safely done (if this isn't enough to deter you: read scientific literature/books describing how it shall be done).

Instead, focus further on what advice is out there on the internet/YouTube:

A water distiller is made for water and water isn't flammable and doesn't form explosive atmospheres. In other words they are unsafe for Isopropanol or Ethanol.
Do you think a 2kg fire extinguisher is enough? Are you truly capable of thinking rationally when there is a fire or would you panic like most people?
Don't even consider doing it indoors or in a garage.
Don't work with large volumes. In a laboratory with proper fumehoods and equipment, there might be limits like 500mL batch sizes.
If somebody isn't wearing eye protection or heating large amounts of liquid without stirring question his qualification to talk about this topic. Being an influencer or posting online, like this post, doesn't require any formal qualification as such even the big YouTubers/influencers post horrendous content that is dangerous or misleading.

13 comments

I sort of feel bad about raining on the parade of the person distilling isopropanol in his garage earlier, but it really is dangerous.
But most of us chemists also need to be reminded of it. To the point that someone had to write a paper whose entire point is “don’t distill isopropanol”.
- You can't blame him.
  Our education system doesn't train us on this. After high school, you might never heard IPA before or know what peroxide are. You don't even know enough to understand how to read these hazards/datasheets (assuming you know that these documents even exist).
  From a technical standpoint it looks easy: heat it up, let it condense, done.
  It is all over social media for a while now. Further suggesting it is good practice/safe to the viewer.
  Most people never experience what power even a small volume of 1L of alcohol vapor can have. They also never experienced that they would fall in shock if it goes wrong. Unable to do anything for a minute or two. Recently did the math on a 30L IPA vapor tank to smooth "large" Polymaker Polysmooth prints (just the energy set free in an explosion). This was the moment I looked for alternative options as it was a scary number asking for serious engineering to keep it safe.
  In my opinion resin manufacturers are to blame too. Downplaying the hazards of resin 3D-printing. In the previous paragraph, I mentioned how the education system doesn't prepare us and as such also the influencer/reviewer might not know. Even assuming best intentions they echo/amplify the message that resin printing is safe.
  Providing a recent example how misinformation spreads involving an influencer I won't name and Prusa's response: https://old.reddit.com/r/prusa3d/comments/1ekn24x/are_cf_filled_filaments_dangerous_prusament_lab/
  Toxicology is rocket science. Understanding (understanding isn't the same as accepting without questioning) what somebody says without being an expert is (near) impossible and even between experts there is often a discussion on what the results mean/what action shall be taken.
  I don't question the results Prusa published but I highly disagree with the message:
  TLDR - our Prusament filaments with carbon fibers and prints made of them are safe The National Institute of Public Health used two methods of measurement. The skin irritation (image 1) and cytotoxicity (image 2) tests involved 30 volunteers (aged between 29 and 70 years) wearing prints made of PCCF and PA11CF materials taped to their skin. The measurement results showed that none of the volunteers had the slightest irritation even after more than 72 hours of wearing the print on their skin. [...]
  If you would test with loose asbestos fibers the test would likely also pass and I hope we all agree that asbestos is dangerous. So right from the start, we have an oversimplification (average Joe isn't interested in 5 pages of what was measured. He is looking for simple answers) or Mr. Prusa wasn't aware of the context of these results (context is critical for toxicology!).
  What I believe has happened here: Prusa Research did the responsible and tested if their workplace conditions are safe for the employees. This means this data is likely specific to factory conditions and production steps. What then happened is that this unnamed influencer posted a sensational video and Prusa took this data and posted it as a response completely out of context.
  As most people probably trust Prusa Research they now likely feel like it is certain that Carbon fiber-filled materials (in every application) are safe while the actual truth is nobody knows a good answer at the moment.
  The next step is people printing parts like bushing out of these filaments. Bushings more or less grind themself which means we now might have fine carbon fiber dust and damaged fibres which might be a health risk (again: nobody knows exactly if there is a safe level and what this would be for these composite filaments).>
  
  Shit just even for filament printing, there's some solvents that get thrown around online that yeah, you really shouldn't use in a home setting, it's really easy to get things like MEK, which work, but starting to get into nasty territory for stuff that will dissolve filament.
  Most people do not have adequate ppe or ventilation to deal with chemicals at home, or a fire cabinet, or even know how to find an SDS.
  Semi related, lithium batteries are straight up terrifying, primary cells more than rechargeables, but same idea, I honestly hope no one ever gets to experience an actual full on cell failure, I avoided them thankfully but heard stories of just how much energy is released in even one C or D sized cell going.
  On the composite filaments, abrasive filament sure sounds like a great thing to make wear surfaces out of! There's a list if things that idk if I'd print, and that'd be up there, ots oil bronze bushings are like, a buck, maybe 2? And they'll last a hell of a lot longer.
- Don't feel bad, if they listen you've likely saved their life.

I use an old Britta filter with some cheese cloth to filter my old IPA. Pour in the old nasty stuff, let it sit for a day, pretty clean reusable IPA comes out the other end.

13 comments