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The backstory: I'm installing a pigeon net in my home. Because of the shape of the opening I'm installing the net in and the material on the sides it's difficult to anchor the net using the normal means but I can print clips that will hold the net in place.

The clips will be outside and will be exposed to the weather and direct sunlight, the weather here is relatively hot (up to 30C) with a lot of sun most of the year and rain in the winter.

I only have PLA, ABS and PETG available, anything else will take too long to arrive.

I don't care about the parts changing color and mostly I don't care about them deforming a little bit - only about breaking.

If the parts have to be replaced after a year I'm ok with it, less then that will be annoying, longer will be better.

So, under those conditions, which of the 3 materials is more durable?

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Ok, I tried all 3 materials.

PLA failed after less then one day, I believe it deformed from the constant pressure and fell out (I didn't find the part but I didn't really search for it, there's some tall grass below the window)

ABS lasted about a year, it fell strait down and I found the part, it looks ok if probably deformed by just a few mm so it doesn't pressure fit anymore.

PETG still going strong as I write this

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    $\begingroup$ PLA is not ice to desappear in one day, I have parts printed two years ago an still is working in good shape. Also "nice" testing if you loose one testing part and don't try to find it, what kind of proof is that? $\endgroup$ – Fernando Baltazar Jul 14 '18 at 22:34
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    $\begingroup$ @FernandoBaltazar - those parts are pressure-fit on the outside of a ledge on the 3rd floor and hold a tight pigeon net, the most likely failure mode is that the part deforms just enough to not hold the ledge any more and is then shot into the street below by the tension of the net. it makes sense PLA does not work for this specific case because it involves constant pressure and PLA is known for deforming under pressure, the direct sun and heat probably doesn't help - this isn't proof that PLA isn't good for outdoor use but it does show PLA doesn't work for my specific use $\endgroup$ – Nir Jul 18 '18 at 5:18
  • $\begingroup$ Well, all depends on kind of testing and robustness of the parts involved. I have parts as supports for antenna for repetiers directly to sun exposed with no shadow during the whole day. Of course some parts need to be for stronger material like ABS and some polycarbonates, but as a hobbie we will use the material available on the market. $\endgroup$ – Fernando Baltazar Jul 18 '18 at 16:54
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    $\begingroup$ @Blossoming_Flower - Both ABS and PETG are completely solid at any outdoor temperature anywhere on earth, so the Tg temperature is kind of irrelevant here. I used cheap Chinese "natural" PETG (also, natural ABS from the same supplier) $\endgroup$ – Nir Dec 13 '18 at 6:41
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    $\begingroup$ @Nir then any clue why the ABS deformed and the PETG didn't? $\endgroup$ – timetofly Dec 13 '18 at 19:54
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PLA would be a non-starter for outdoor use as it's biodegradable and can breakdown in sunlight. Albeit slowly, but won't be useful for long term project.

ABS would be a good choice for longevity, as it can last in outdoor situations for quite a while. Its glass transition temperature is above 100 degrees celsius so it'll last in most climates. As for strength ABS is one of the better choices out there, also it's slightly softer than PLA meaning it will flex before breaking, PLA is much more likely to shatter. ABS is well known for warping while printing though. Not a huge problem though, if you're used to printing with it.

PETG not a bad choice either. It has a glass transition temperature around 80-90°C. So if you're building in a hot place with direct sunlight with some reflection, you could have deformation issues, though not that likely. It is stronger than ABS and it's also easier to print (less warping issues). PETG is also supposedly 'food safe' meaning if the outdoor animals start pecking at it, it'll probably not kill them... I wouldn't recommend trying to taste it though. Finally PETG is a bit closer to PLA in terms of brittleness so it may shatter before flexing. ABS is less brittle than PETG.

If it were me I'd go with ABS despite its issues with warping while printing. If you're newer to printing, then probably better to go with PETG.

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    $\begingroup$ I do not think PLA is more susceptible to breaking down from sunlight than any other plastic. Biodegradation of PLA will not take place if it's only sitting outside - you need a carefully controlled commercial composting facility to get it to do anything. $\endgroup$ – Tom van der Zanden May 2 '17 at 16:16
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    $\begingroup$ According to this article: emerginginvestigators.org/2013/11/… Degradation of PLA is significantly increased with exposure to UV light. $\endgroup$ – Diesel May 2 '17 at 16:44
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    $\begingroup$ They were specifically trying to get PLA to degrade. According to that article "The specific type of light used in this experiment is UVC [...] UVC light is not commonly found in sunlight because the ozone layer of the atmosphere absorbs most UVC light.". $\endgroup$ – Tom van der Zanden May 2 '17 at 19:02
  • $\begingroup$ Another benefit of ABS: if you vaporsmooth the surface. This does prevent moisture from creeping in through the layer boundries. $\endgroup$ – Trish Jul 15 '18 at 8:56
  • $\begingroup$ Prints over time do handle well: youtube.com/watch?v=qqNfa_zExRU $\endgroup$ – Trish Sep 14 '18 at 13:28
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I might be late to the party, but I have a suggestion. Why not use ASA filament, it's the kind of plastic used in car cup holders, lawn rakes and sprinkler heads, it is both heat and cold resistant, as well as solar stable and weatherproof. As far as printing with it it is similar to printing in ABS as far as I am aware, I might be wrong though. I personally am surprised how often this kind of question pops up and literally No One mentions ASA filament. I think I might buy some because I like the idea of printing something that can be left outside.

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    $\begingroup$ ASA needs a print temperature of 250+ °C, which most printers with lined hotends can't reach without destroying the liner. Some ASA filament (3DXMax) even wants 270-290 °C. Heated bed is mandatory and ask for 80 to 110 °C. It also is best printed in an enclosure, which all are facts that make it a nieche product. It's fumes from the printing from printing also are likely to be toxic (research pending), and is one of those notorious hard to print filaments as it has severe layer adhesion problems and answers to those with splitting. $\endgroup$ – Trish Apr 5 '19 at 4:57
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    $\begingroup$ In addition to what @Trish said, ASA is also relatively hard to get (unless you live in amazon-prime-free-shipping-land, sometimes referred to as the USA), I don't know of any filament supplier in my entire country that sells ASA $\endgroup$ – Nir Apr 8 '19 at 13:08
  • $\begingroup$ I wouldn't be so quick to dismiss this suggestion. I didn't know about ASA, yet I have an enclosed, air filtered printer with a 300ºC+ extruder w/ heated bed. Looking it up, dozens of choices available next day on Amazon Prime for me - I live in Scotland. $\endgroup$ – Rab Jan 28 at 17:37
  • $\begingroup$ I've been using ASA and I'm pretty happy with it. Agreed that you need some high temps, I think I have to print at 270 which is the absolute tops of what my printer does, and bed, and enclosed, and mind the fumes, but if you happen to have that tech, it's easier to print than either PETG or ABS. Few colors. Supply in the USA is easy, multiple vendors, don't need amazon to get it. $\endgroup$ – Brian Bulkowski Jun 3 at 17:22
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We use PLA in an outdoor environment, non-direct sunlight. PLA seems to be just as strong as day one. It has been about six months now.

Of course, you must seal coat to protect from moisture.

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    $\begingroup$ I have some PLA parts outside since about 18 months now with no protection whatsoever. Except for some discoloration the parts are as strong as the first day. Of course the climate of your region plays a role in this too. I'm in Belgium, not in Arizona! $\endgroup$ – ON5MF Jurgen Jul 18 '18 at 6:13
  • $\begingroup$ I'm in California, 30 degrees Fahrenheit up to 110. $\endgroup$ – Rob Jul 23 '18 at 1:55
  • $\begingroup$ Good watch in this regard: youtube.com/watch?v=qqNfa_zExRU $\endgroup$ – Trish Sep 14 '18 at 13:29
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What colour was your PLA? PLA will soften around 60C and a dark colour will easily get hotter than that in direct sun on a 30C day. Clear PLA seems to have much, much better temperature resistance, but any sort of PETG will kick it's butt in that regard.

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