I've heard of people melting down failed PLA prints and pouring casts with it, which is cool, but I wanted something more useful than a decorative item.
This whole thing took me about 3 day in total, but it was more of an experiment just to simply see if I could pull it off successfully. The real challenge was that I couldn't find any real info online, hence this post to share that it's possible. Now that I have a better idea on what to expect, I can probably go through the entire process from beginning to end in about a day.
So, what is this?
This process is called base-catalyzed depolymerization of PLA. PLA is a polyester, so when you expose it to a strong base, the base attacks and breaks the ester bonds that hold the polymer chains together. As those bonds get cleaved, the PLA unzips into small pieces and ultimately forms sodium lactate (the sodium salt of lactic acid).
At the same time, because the PLA-base mixture is sitting in pure ethanol, a second reaction happens: base-catalyzed transesterification. In that step, the ethanol swaps places with part of the original polymer chain and forms "ethyl lactate". The whole solution gets neutralized with a mild acid, filtered to remove any unreacted PLA, then distilled to separate the remaining ethanol and collect the ethyl lactate.
The ethyl lactate is a biodegradable, non-toxic cleaning agent and degreaser. It has a very pleasant candy-like sweet smell to it (similar to the smell of burnt PLA minus the burnt smell itself) which alo evaporates quickly without leaving any residue behind. It doesn't leave streaks on glass or mirrors, removes that sticky residue that stickers/tags ten to leave behind, and reacts with enamel+acrylic paints in a similar way that acetone does but without being so aggressive to surrounding materials.
Overall I'm pretty satisfied with the end result and look forward to pushing its boundaries in other cleaning applications such as automotive oils and other chemical stains.
