PLA is a very common plastic used for 3D printing. I have been trying to find off-the-shelf products to dissolve PLA both for just cleaning it off hardware and for removing it if the PLA is used as support material.
My first goal is to find an easy way to remove PLA from nozzles, barrels and so on so they can be assembled cold without fighting with PLA residues. Please remember that we are considering two processes:
A: How to remove PLA from metal parts.
B: Dissolving PLA and leaving ABS untouched.
As for safety,should be reasonably safe when removing PLA by putting the small metal pieces in a glass jar with the chemical and cover with a lid and afterwards fishing out the pieces with tweezers or tongs .
When removing large amount of PLA support structures it will be much more critical to have a safe liquid since normally there will be relatively big objects to treat.
- Boiling water for about 10 minutes then soaking for 24 hours: No obvious change.
- Denatured alcohol soaking for 24 hours: No obvious change.
- Acetone soaking for 24 hours: The PLA swelled up and has a rubbery feel and it split apart into several pieces. The splitting happened after a couple of hours. It was not dissolved (clear liquid).
- MEK= Methyl Ethyl Ketone soaking for 24 hours: Slight swelling, a rubbery feel and partial split length wise. It was not dissolved (clear liquid).
- TriChloroEthane soaking for 24 hours: Slight swelling, a rubbery feel and partial split length wise. It was not dissolved (clear liquid).
- PVC cleaner: Oatley #30782 soaking for 24 hours: Slight swelling, a rubbery feel and partial split length wise. It was not dissolved (clear liquid).
- Weld-On #5: It is a solvent for extruded Acrylic made by IPS corporation. It completely dissolved the PLA in a couple of hours and I ended up with a red liquid. (My PLA sample was red). More Weld-on notes below.
- Miller-Stephenson’s MS-111 Stripping Agent. It dissolved the PLA in an hour or two. That chemical is very nasty, it will even dissolve cured epoxy. It was only allowed to be shipped by ground and it was packaged like those Russian dolls inside each other: I think there were 6 boxes inside each other with padding in-between. One intermediate container was a metal can and inside it another box and finally the glass bottle.
- Draino Crystals. It is a lye-based drain cleaner. No effect after 12 hours.
- Kleen Strip premium sprayable stripper: It is a paint remover containing Methylene Chloride. It is listed as sprayable and comes with a sprayer but is still like a sticky paint remover but thinner. It dissolved the PLA in a couple of hours but is messy and sticky and leaves a residue that has to be scrubbed off.
I bought the Weld-on #5 solvent several years ago and today I am having trouble finding it. On internet I see a #5 cement but that is presumably a thick version and not suitable. Here is a link to what I have: http://www.coloradoplastics.com/wholesale/products/ips-weld-on-adhesives/ips-weld-on-5/
The Weld-on #5 has been discontinued and I have to find and test the replacement. Weld-on recommended #4 but I have not tested it. Here are some details:
Weld-on #5 contains: Methylene Chloride(75-09-02), Glacial Acetic Acid (64-19-7), Methyl Methacrylate Monomer (80-62-6)
Weld-on #4 contains: Methylene Chloride(75-09-02), Methyl Acetate (79-20-9), Methyl Methacrylate Monomer (80-62-6)
I have no idea if the difference is significant, all I know is that #5 works extremely well.
Here is an link to a commercial product in Germany:
3DSystems has a very useful video on Youtube about how to use caustic soda (Sodium Hydroxide) to dissolve PLA used for support. 217 grams is added to 3 liter water used at 60C for 3 hours in an ultrasonic cleaner. 217g in 3 liter is equal to 72.3g in 1 liter equal 1.8 Molar strength.
The listed cost of the ultrasonic is ridiculous pricing. A few days ago I bought a high-power 6l industrial ultrasonic cleaner for $279.
My old one died after about 20 years of service. As soon as it arrives I will of course test it for PLA removal.
The Ultrasonic cleaner arrived, more testing:
This time I tested several different plastic types and varying strength Sodium Hydroxide.
1.0 Molar: 40g per liter water
1.8 Molar: 72g per liter water (same as the video)
3 Molar: 120g per liter water
6 Molar: 240g per liter water
Plastic: Red and White samples of PLA, ABS, Polycarbonate (Lexan) and Nylon-66
After 5 hours in the ultrasonic tank @ 60°C there was no visual effect on the different plastics except the PLA. Amount of dissolved PLA after drying the residue:
1 Molar: 13%
1.8 Molar: 42%
3 Molar: 88%
6 Molar: 56%
Five hours is much longer time than the video but dissolving thin scaffolding will be a lot faster than the solid 2.9mm filament so the estimate of three hours sounds reasonable. The big surprise was that the stronger mixture was worse so it looks like 3-4 Molar is a good value.