収束ゾーンでのライフ: Life in the Convergence Zone

One year ago I put three test objects left over from another experiment – two PLA, one PHA – outside in a flower pot mostly-buried, just the ends sticking out into daylight to see how they would do. They were placed outside with full exposure to weather and about half-day exposure to sun, sunrise to midday.

On October 27th, I brought them inside! I posted about it live on Mastodon, with a lot of photos if you’re into that sort of report. But to summarise!

The white PLA remained largely unchanged. This was mostly as expected; we don’t get very hot here, and it wasn’t a particularly hot summer but has been a dry year by our standards. Similarly, the control piece of wood showed very little tendency towards compost, and mostly changed colour more than anything else.

The 20% wood-filled PLA was much more strongly affected, though I think more by the sun than being buried. In particular, the sun-exposed areas showed lots of fading and felt a little brittle in comparison. Also, while I didn’t notice it during the retrieval, there was a little bit of layer compression in those areas. The buried areas showed less change.

The 20% wood-filled PHA was the most affected, with substantially more layer compression on the sun-exposed portion of the piece. But also, it was the only filament to show self-composting breakdown! This is rather in line with my expectations, and meets the advertised property of being more easily compostable than PLA.

It was also interesting that the PHA showed very little bleaching in the sun exposed portion but much more so from underground, the opposite of the PLA test piece.

So while this wasn’t intended as a composting test – and shouldn’t be taken as one – it does show that at our latitude (near the 49th parallel) and our climate, PLA is indeed hardy outdoors, and PHA… isn’t nearly as much so. A substantial portion of that is definitely water and soil-contact related, as opposed to simple sunlight; the 20% wood-infill PHA in some ways did better in the sun than the 20% wood-filled PLA, a surprising result. But the layer distortion was significant.

I’ve had plenty of objects in both materials survive unchanged indoors over the same time period, so I’m not seeing anything to worry about on that front.

I rather want to stage this test again with pure PHA (no wood infill) to see how they compare, but I haven’t had time to set it up yet. If things calm down, though, I’ll give it a go – and of course post about it here. ^_^

Posted via Solarbird{y|z|yz}, Collected.