Effects of direct sunlight on 3D prints

[Jason]

I've recently helped my university get it's first ever 3D printer (Replicator), and one of the professors has been putting all of the objects I have printed into a glass display case, which is subject to direct sunlight for half the day (next to an east facing window). I'm a little bit concerned about the effect it might have on the prints over time, but I'm not exactly sure what is happening physically.

I remember hearing that with certain kinds of plastics, UV radiation can weaken the chemical bonds or mess with the structure of the plastic in some way, making it turn yellow and become very brittle over time. I'm not sure how correct that is, but can anyone help shed some light (-_-) on what happens when sunlight hits ABS / PLA for too long?

My personal discomfort doesn't have as much weight as an objective scientific understanding, so I'd like to be able to explain WHY it's just not a good idea! Thanks!

[Ward Elder]

I hear that Lego is made from ABS and at Disney it is permanently outside with some sitting in the lake!  (a large dragon serpent).  It all looked pretty good (and cool) to me.

 

Thank you,

 

 

Ward M. Elder

ElderSoft

42 Appleton St.

Winnipeg, MB

R2G1K5

(204) 791-7754   (Cell)

 

wa...@eldersoft.ca

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[Adan Akerman]

I wonder if they use standard-issue Lego for such things. They may do special runs with UV stabilizers that might otherwise hurt their chances of passing child safety testing for leachables/extractables. They also, almost certainly, replace the models frequently. 

I have old Lego bricks that show sun bleaching. Not too sure about our filament, though.

[Bill Culverhouse]

I have an ABS printed mailbox handle that has been outside in direct sun since January and shows no signs of
spitting or noticeable fading.

-b

[Sean Tu]

Jason, from where every you are reading this, stop and take a look around the room at all the plastic things that around you that you that have been sitting in the sun over the years that you've never been worried about. Why start now?

FYI, there is a photo oxidation reaction that does take place, and does change the polymer, but the process is slow (or else we would just put the plastic in the sun to degrade and solve the whole landfill problem.) There are 6 to 10 steps that I've forgotten long ago. If your really curious and doing this for a university find an organic chem prof and have him explain it to you.

[hellphish]

Jason, you aren't wrong. There are additives that affect the color of
plastic over time. The best example I can think of is the SNES where
the additives used to increase flame retardedness caused the case to
yellow more quickly. Here is a short article
http://www.vintagecomputing.com/index.php/archives/189

[Matt Minuti]

IIRC, if it's behind glass, a lot of the UV won't get through. Especially through window glass, then display glass.

If it's going to be in direct sunlight, it might be worth doing it in black. Most black dyes absorb UV instead of allowing the plastic to absorb it.