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donmilne

How weatherproof is PLA

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I read that PLA is biodegradeable - a statement that makes me want to shop for a roll of ABS. But, before I go too far overboard... does anybody have numbers on how well PLA stands up to weather: rain, cold, strong sunlight etc?

Of course, I happily make things out of wood, which is also a biodegradable material, which also has a tendency to warp, shrink or swell if not protected. You would typically protect wood by regularly painting it - ideally with an oil based paint.

How well can PLA be expected to hold up in outdoor applications?

 

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Well, since making outdoor lights, I can tell you some things, I found out....

Not all pla's are sunlight resistant, after some months they might turn pale.

Don't use black or dark coloured pla, even in the sparse dutch sunlight it gets to hot and becomes soft.

Moisture gets in between the layers, so turns green after a while.

What works for me is to put your product in a varnish? Colourless paint for a day.

Regards Kees

 

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I made a printed plant support tag last season. It's like a little stick with a ring you stick in the soil to hold the bean plants up.

Anyways, after a season of gardening being in the soil with sun/rain/wateriing/soil it still kept it's shape and function but it was substantially more brittle. I'd be surprised if it would survive 2 seasons.

 

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I have an outdoor electric car charging station with a gray PLA printed knob on it. It's been out in the rain and snow since September 2013, so 5 months. No weathering visible yet. It is used/touched approximately 3 times per day on average.

I've heard that ABS loses color also in UV light.

 

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I had PLA in the garden soil coming out after 2 years basically unchanged.

On the other hand, PLA warps over time... if you have a load bearing part, it will deflect/bend, no matter the temp (unless it is permanently freezing). I guess a knob thing will to quite well outdoors, but a hook will not. ABS will see surface degradation from UV, but will hold it's structural integrity much longer. If you apply a thin layer of clear, UV filtering varnish, it'll last forever...

 

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Hmm. I didn't expect that PLA would sag over time - it doesn't seem to go with being brittle. Thanks for that tip.

I'm also surprised that ABS might fade, I know that external switch boxes etc are often made of ABS so I guess I assumed all ABS is like that. Is there a specific clear UV coating that is recommended?

 

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I'm interested in this topic because i plan to make some outdoor stuff.

I found this topic showing how a printed PLA object behaves in nasty conditions:

http://www.protoparadigm.com/blog/2013/06/weathering-of-3d-printed-pla-objects/

I'm wondering if applying paint or some kind of varnish would change this... i have no experience sadly, during my internet search i found some stuff talking about dipping in Epoxy?

This is interesting too:

http://iepas.net/using-pla-for-long-term-outdoor-applications/

 

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I find the first article a bit anecdotal, and I wonder if the low quality of the prints accelerated their degradation: all that dirt and moisture being trapped in the "grain".

The second article however I find very interesting. It seems to be saying that the claimed biodegradability of PLA is largely hype. I can believe that the colored dye might get bleached relatively quickly if not protected from UV, but it would be interesting to know what the effect is on mechanical aspects: brittleness etc. I'm especially interested in objects that are not buried in the ground! :)

 

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From what i've read it seems that the main problem for PLA is heat. If exposed to the sun a black object might begin to 'melt' and loose its form. Other than that the biodegradability of PLA won't occur in natural conditions.

I wasn't able to find many informations about this. My guess is white PLA should behave good outdoor.

 

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I agree, especially if you spray some lacquer on the outside for added UV protection.

Actually, bells ringing in my head... a lot of outdoor ABS objects are gray (e.g. IP5x box), while indoor objects are white. Doesn't the gray signify a UV resistance treatment? I'm thinking that it might be useful to stick to existing standards - and know what the treatment is! :)

 

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even if the Tg of PLA is 65C, there are many occasions outdoors where material gets close to or over that temp. There was even an anecdotal post about PLA parts sagging over tome (which is what I was referring to as "loadbearing").

PLA does biodegrade, but only under certain conditions, Keegan documented it quite well: https://groups.google.com/forum/?fromgroups=#!searchin/ultimaker/hydrolysis/ultimaker/8s1bq_9LsRM/DxLchSNlAD8J

In regards to UV protection, commercial ABS for extrusion molding has UV filtering additives already mixed in... I would assume our ABS filament doesn't have any/much of that, since it wasn't parts of the specs. any art supply store has lots of UV protecting varnishes, just get one you like, and follow the instructions... if you pick one that contains acetone, it will create the best surface bond with ABS imaginable :-)

 

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