Scientists in Japan develop plastic that dissolves in seawater within hours
reuters.com
reuters.com
> Aida said the new material is as strong as petroleum-based plastics but breaks down into its original components when exposed to salt. Those components can then be further processed by naturally occurring bacteria, thereby avoiding generating microplastics that can harm aquatic life and enter the food chain.
It seems like the rate at which this naturally occurring bacteria consume the components is pretty important in determining whether there will be microplastics in the ocean long enough to impact sea life. The quoted conclusion seems overly optimistic.
> In the initial tests, one of the monomers was a common food additive called sodium hexametaphosphate and the other was any of several guanidinium ion-based monomers.
hexametaphosphate: https://en.wikipedia.org/wiki/Sodium_hexametaphosphate
> SHMP hydrolyzes in aqueous solution, particularly under acidic conditions and/or heat, ...
Those phosphate bounds are weak, and break in water. I don't expect problems.
guanidinium: https://en.wikipedia.org/wiki/Guanidine
> It is found in urine predominantly in patients experiencing renal failure.
> Recent studies suggest that guanidinium is produced by bacteria as a toxic byproduct. To alleviate the toxicity of guanidinium, bacteria have developed a class of transporters known as guanidinium exporters or Gdx proteins to expel the extra amounts of this ion to the outside of the cell.
It's too far from my area, but it looks like similar to urea thst is used to dump excess of nitrogen in pee. It looks like guanidinium is produced naturally and dumped by some bacteria and probably other bacteria use it because nitrogen is difficult to get.