@moira
It's very cool to read. Thanks for your patience and sharing.
I have a PLA printed Honda logo that's been hanging on my motorcycle for 6 years and still looks brand new. I expected more degradation. @bart
@moira I'm curious where this test was done and how severe the weather (UV/temp/direct sun/ECT) was. Where I live, I made some pla planter signs for the garden and they didn't last one summer. The PETG ones I made are going on their 4th with no signs of deterioration other than one that got broken
@tristan North of Seattle, full sun exposure half the day (and in summer we have like 18 hour days at peak), you can check our historical temperatures and weather for the whole year I think at places like ambientweather and weatherunderground if you like.
@tristan but mostly we don't get the UV hammer you do places like Hawai'i because the sun is mostly at a lower to much lower angle than with places further south. Goes through a lot more atmosphere.
It was not a hot summer, which arguably was a bit disappointing from this test standpoint. Regardless, the PLA held up fine, as expected. I’ve seen oil-plastics do much worse - including the flowerpot I used which faded quite a bit!
oh dang look - #PHA is showing some self-composting breakdown as it dries!
this is more along the lines of my expectations; #PLA and PHA do both biodegrade but PHA is (reportedly) better at it. I think we’re seeing that here, particularly since it’s mostly in the buried portion!
@JoshuaACNewman Mostly what I was wondering about was how much more quickly PHA would degrade than PLA in a full-exposure environment where I live. Given that both PHA and PLA get their carbon from plants, which in turn get it from the air, via carbon-dioxide extraction, I’m not actually interested in trying to break either down more quickly - as medium-term carbon stores, I think we should be thinking about how to break them down less quickly and maybe stacking up bricks of it in abandoned coal mines or something.
@JoshuaACNewman Well, that's the trick, isn't it? Figuring out carbon-neutral ways to produce stuff in general, then applying that to PLA, then storing it in a way that makes it take a very, very long time to break down. Making very-low-density coal, effectively.
I'm not saying I KNOW THE WAY!! or something, it's just a thought I toy with. It - or more likely something higher density, see also your carbon fibres, and in some fiction I've written literally artificially-produced diamond sheets - is probably one of the many ways we'll have to use to get out of this mess.
@JoshuaACNewman The difference being, of course, that we already have a lot of infrastructure around making plastic. We don't have that for diamond, coal, and so forth.
@moira And plastic remains an amazing material. Its degradation over time into "useless plastic" without becoming "dirt" is really a problem though.
Diamond takes a lot of energy (heat and pressure), which probably has a positive carbon footprint. If you can do it with solar, it's another matter.
But getting old plastic back to being good plastic seems to be the challenge. As always, it's a matter of pushing the molecules uphill. That energy has to come from somewhere.
It’s interesting that the #PHA shows very little bleaching in the sun exposed portion but much more so from underground, the opposite of the #PLA, despite the layer compression. Neat!
Oh wow I forgot! Here’s the bit of softwood I put into the dirt at the same time! It seems almost as unaffected as the white PLA. No really, it’s taking longer to dry but otherwise it feels the same on both ends.
The wood control really shows very little decomposition so do not mistake this for a composting experiment, it’s more of an outdoor durability experiment.
A flower pot can tell us a lot but isn’t a perfect setting. A real compost heap that got up to temperature would be a very interesting comparison. Also just in-ground with soil critters.
@linux_mclinuxface PHA is definitely not good for soil contact or a year exposed to direct sunlight. (At a point that's about as sunny as our location gets anyway.)
@linux_mclinuxface I only use plant-sourced plastics, so PHA and PLA are of more interest to me. I've had some success using PLA outdoors. (My air quality sensor is sitting on a custom PLA mounting rack right now, in a relatively shaded area. It should be fine indefinitely.)
I might be willing to use PETG if I ever set up one of those 2-litre-bottle-to-thread recycling systems, though.
But mostly, I want my prints to get their carbon from the atmosphere (via plants), not from the ground.
I want to stress this is not temperature directly; these objects are reused from a glass point verification test, #PHA holds its shape to much higher temperatures than #PLA.
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