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I can't seem to find any reliable answer to this question. My understanding was always that PETG should be solvent-resistant, including to acetone, but parts printed from the various "PETG" filaments I have range from utterly falling apart (layer delaminations, outright ripping under tension) to deformation and smoothing of corners when soaked in acetone. Parts printed in actual PET are unaffected, as expected.

Is this an expected consequence of the modification to PET that produces PETG, or is it a sign that lots of filament vendors are deceptive and shipping some weird garbage and calling it "PETG"?

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    $\begingroup$ Yeah many people have has this problem, this should help a lot reddit.com/r/3Dprinting/comments/p8c85d/…. $\endgroup$
    – F.Ahmed
    Sep 10, 2022 at 0:40
  • $\begingroup$ @F.Ahmed: Could you expand that into an answer? $\endgroup$ Sep 10, 2022 at 1:27
  • $\begingroup$ It depends on the brand, and yes it does seem some manufacturers are selling fake PETG , or adding some other material to it $\endgroup$
    – F.Ahmed
    Sep 10, 2022 at 9:25
  • $\begingroup$ Any cubic filament and ICE filaments seem to be unaffected and are cheap on Amazon $\endgroup$
    – F.Ahmed
    Sep 10, 2022 at 9:27

2 Answers 2

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I have tried to use PETG grid to hold my ABS models above the acetone for vapor smoothing. Specifically, I have used Prusament PETG in the Prusa Orange colors.

After a few hours acetone turned orange, and grid turned soft and gooey. Can't tell if all PETG will be affected, but this one sure is.

Element below was flat and stiff. Photo of the crate

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To my understanding all PETG is vulnerable to different solvents to a certain degree. Despite PET being resistant to acids of many kinds, hence why it is used in plastic bottles and plastic-ware, this does not transfer over.

Nearly all filaments are incapable of handling the stronger kinds of acids, and although I cannot speak for the manufacturers on Amazon, poor quality will inexorably aggravate the thermoplastic more-so.

If it's any consolation, most/any filaments available are not remarkably chemically stable, least of all against organic solvents.

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    $\begingroup$ Do you have a source for why PETG would be affected by solvents where PET is not? $\endgroup$ Oct 1, 2022 at 1:59
  • $\begingroup$ Sadly, no. The only sources I can find state that PET is chemically stable, or that PETG is not. You, good sir, have pushed my casual research abilities to the limit! $\endgroup$ Oct 1, 2022 at 2:19

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