What's going on with Acetone and ABS chemically?

[rm446]

In 3D printing it is a well known trick to use Acetone to smooth/dissolve prints made from ABS plastic. Most articles call acetone a "solvent" of ABS but after some experimentation with PLA plastic and THF "solvent" I get the feeling "solvent" may be too vague a term.

The main observable difference is Acetone seems to turn ABS into a slurry. This slurry can be used as a glue or a filler because once it dries you're left with acetone plastic in the same shape as the slurry. THF on the other hand just seems to destroy PLA plastic. No slurry is produced, the plastic is just eaten away.

My hypothesis is the THF must be breaking down the polymer chain of PLA, thus permanently destroying it. I'm guessing Acetone must be doing something different to ABS, as the plastic doesn't seem to get destroyed.

Does anyone know definitively what's going on between ABS and Acetone chemically?

Thank!

 

[Navin A S]

Acetone is known to act as a plasticizer for ABS, meaning it helps to make the plastic softer and more pliable. This is due to the fact that Acetone is a polar solvent and can interact with the polar groups present in the ABS polymer chain. Acetone will penetrate the ABS polymer chain and act as a plasticizer, causing it to swell and soften. The result is a slurry-like mixture that can be used as a glue or filler. In contrast, THF is a non-polar solvent and therefore cannot interact with the polar groups in the PLA polymer chain. As a result, it breaks down the PLA polymer chain, which leads to it being permanently destroyed.