A link to the preprint. I'll do the actual math on how many transitions/second it works out to later and edit.
I've had an eye on this for like a decade, so I'm hyped.
Edit:
So, because of the structure of the crystal the atoms are in, it actually has 5 resonances. These were expected, although a couple other weak ones showed up as well. They give a what I understand to be a projected undisturbed value of 2,020,407,384,335.(2) KHz.
Then a possible redefinition of the second could be "The time taken for 2,020,407,384,335,200 peaks of the radiation produced by the first nuclear isomerism of an unperturbed ^229^Th nucleus to pass a fixed point in space."
Not very well. Those long molecules break down into shorter segments every time they're recycled, which makes for an inferior and eventually useless product. Some plastics are also thermoset and can't ever be melted again, and some are just hard to recycle for other reasons and get picked out and landfilled. The whole idea of plastics recycling is basically greenwashing on a massive scale; the industry put a lot of money into promoting it to avoid scrutiny.
That being said, they're also permanent in the good way. Plastics don't biodegrade or erode. If you bury a plastic pipe in the ground, it may well still be there and intact in a million years. Anything natural will rot long before that, common metals will corrode, and concrete usually has metal rebar that pulls it apart as it corrodes. Plastic is also lightweight, which ceramics (stone-like materials) and metals are not, while still being strong under tension like metals.
Sunlight does slowly break down many plastics, but only into ever-smaller particles, which is where the microplastics in OP come from.