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Plastics and acetone

A project log for 3D Printing Post-Processing

Considerations and improving on 3D print post-processing techniques

BadgerBadgerMushroomBadgerBadgerMushroom 06/21/2015 at 13:490 Comments

Now that it's weekend, starting with some of the basics. I tried to read a lot on what materials acetone would affect and how, but that wasn't so easy to find, and I figured why not try it out. So in the picture on the gallery I have a line-up of some plastics to try, lined up on a 3D printing glass (with a black background).

On the upper row there's first some shaving from a typical water canister, high-density polyethylene PE-HD (2), then a piece of electric wire outer insulation - these are made from a few different materials, I'm not sure what this is but it's very similar to the ultrasonic mister's, and finally a piece of PLA printing filament for a 3D printer. On the middle, there's a piece of ABS plastic for control, we (or at least I) pretty much already know how acetone behaves with ABS, but it's good to have it for comparison to the others.

And on the lower row there's a piece of polyethylene PE from a water bottle cap, piece of transparent water bottle polyethylene terephthalate PET (1) and finally a cutting from small transparent plastic grocery bag, possibly some kind of polyethylene as well. The plastic bottle and transparent plastic bag have been set to the side of the glass plate for reference, in the before-pic.

Next it would be a good idea to consult materials data sheet for Acetone, if not consulted before. This stuff is basically your basic nail polish removed, except whereas nail polish removed is usually well below 50% proof (or even acetone-free), here we're working with industrial 100% proof acetone. And instead of a small bottle, there could be quite a lot of it... Though I have what I need in a smaller, airtight glass container, and opened windows at both ends of the room to cross-ventilate.

Even so, after the experiment and barely even smelling any acetone, I started feeling little light-headed, and not in a good way, so open goes the patio door. I guess it's a "Do as I say, not as I do" though, I would consider doing this in industrial fume hood, outside or with one plastic sample at time. And with that, commence mad scientists mode!

The experiment involved using a polyprophylene straw, seen in the after-image, which I already knew to be acetone-proof, to move about half a milliliter of 100% acetone on each sample. Then let it evaporate, taking about 5 minutes, and add a second half milliliter to see prolonged effect. The image for after-experiment was taken at 5 minutes after second application, or 10 minutes application total. (This was 7 samples, as the amounts could have been little over half milliliter, I'd consider that evaporating one centiliter in 10 minutes, so a wide container in room temperature could easily evaporate a desiliter in hour, a full liter or quarter gallon in a day!)

In the after-picture one can see the ABS sample melting, or dissolving as the technical term goes though one might be excused for using the more descriptive term here. The plastic wire insulation looks mostly unaffected, but on the glass plate around it looks to be an oily substance, and pressing with the polyprophylene straw it appears much softer than originally. This doesn't bode well for submerging the whole ultrasonic mister. The 3D printer PLA sample has maintained integrity, but it has the largest amount of residue (though this is white on black, so highly visible) on the glass. Using PLA to 3D-print pieces and fittings for the apparatus would then require at least care.

The other samples, however, look mostly unaffected, with the clear thin plastic bag even showing no residue around it. I believe this shows that, contrary to what one might expect, plastic could well be used for the acetone polishing apparatus, thus simplifying construction and reducing fragmentation worry on the off-chance of explosion (It will, however, not be fire-proof!). What's more, using a plastic bag like the one shown in the before-picture could improve durability, re-usability and cleanup immensely.

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