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ParzivalR
Posts: 9
Joined: Mon Apr 20, 2020 3:44 pm

PLA and Acetone? Doubt about it.

Wed Apr 22, 2020 7:53 pm

Hi Everyone!

When I started my adventures with 3D printers in 2015 I printed all the time with ABS. More than once, with the intention of post-processing with acetone steam to polish it. It wasn't until a year ago that I started using PLA and PETG.
According to a lot of content on the internet, PLA does not suffer (or almost does not suffer) effects when having contact with acetone. I am a consumer of Printalot filament (I am Argentine, and they are nationally produced, very good).
Big was my surprise when discovering that acetone discolors and melts the PLA produced by them. In contrast, Createbot brand filament (of Chinese origin) does not show any visile change. For this reason I decided to contact Printalot, to which they replied that they use pure PLA to produce their rolls and that is why it becomes rubbery. In my case, I print it correctly between 220 ° and 225 ° (celcius) at a speed between 85 and 100mm / s and the bed between 60 ° and 65 °.

What do you know or think about it? Greetings to all! :D ;)

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dkightley
Posts: 2244
Joined: Tue Mar 10, 2015 4:09 pm

Re: PLA and Acetone? Doubt about it.

Wed Apr 22, 2020 8:50 pm

Acetone will soften PLA. very slightly...but it will not do to PLA what it does to ABS...i.e. dissolve it quickly so it liquifies sufficiently to self-smooth the surface, and then harden off as the acetone evaporates.

And as far as I am aware, there are no other generally available "solvents" that will do so. Exposing PLA to Dichloromethane vapour will soften it to a lesser degree...but the part will take something like 24 hours to lose the flexibility that it gets having been exposed to the vapour.

Neither have I heard of much success using a naked flame/blowtorch to do the same. The only method I've heard of any success is covering with paint or varnish...in a sufficiently thick layer to fill the extrusion lines.
Doug Kightley
Volunteer at the National Tramway Museum http://www.tramway.co.uk
Railway modeller and webmaster at http://www.talkingtgauge.net

arhi
Posts: 447
Joined: Thu Oct 06, 2016 5:13 pm

Re: PLA and Acetone? Doubt about it.

Wed Apr 22, 2020 9:57 pm

Depending on the additives PLA will get "crumbly", get "soft", get "rotten" from ACETONE and similar solvents.

Smoothing PLA surface, I tried everything, from MEK to Dichloromethane and while most of those super poisonous solvents will allow you to chemically weld PLA (using Dichloromethane to glue / chem-weld PLA to PLA is stronger than any glue I tried, never managed to break the bond, always break PLA part first) and no solvents work, the only thing that works is elbow greese :( ... sand, start "rough" with 400 to 600 depending on the quality of your print, move up to 2000, make sure to do it slowly and with water so you don't melt the plastic, then filler, then sanding 1000-2000+water, then primer, 2000 sanding, and finally acrylic or polyurethane paint (few coats with water sanding in between) ... you can get parts that look injection molded :)
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ParzivalR
Posts: 9
Joined: Mon Apr 20, 2020 3:44 pm

Re: PLA and Acetone? Doubt about it.

Thu Apr 23, 2020 11:20 am

Thanks very much for the answers :D

In my case, acetone does not soften the PLA, but renders the part structurally and aesthetically unusable. I am attaching two photos so you can observe the effects of a small bathroom.
WhatsApp Image 2020-04-23 at 12.07.10.jpeg
WhatsApp Image 2020-04-23 at 12.07.10 (1).jpeg
I was planning to use sand abrasion as seen in this Thingiverse post (https://www.thingiverse.com/thing:3666116) and then post-processing with paint or varnish as tell me. I have seen some good results.

Image

At first, when noticing such degradation of the PLA Printalot with acetone and the need to increase the extrusion temperature to 220° to avoid extrusion problems (the classic TOC TOC), I distrusted that it really was PLA. Now I know that PLA and acetone should be kept away from each other :? :lol:

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