The June 1 piece about degradable additives in PET [NAPCOR says degradables won't hold up under scrutiny, Page 1] brought back memories.
I used to work for what once was the world's largest polyester producer, in the same group that obtained the first FDA non-objection letter and introduced the first soft drink bottle containing recycled content. We made the cover of Discover magazine for that accomplishment. Also, I authored a book chapter on polyester recycling. Hopefully, my credentials pass muster for what I am about to write.
In general, degradables in PET is probably a bad idea so many things can go wrong.
Since the sellers of the degradable additive have not provided supporting evidence of their claims (per your article), then they bear a high burden of proof that their additive won't damage some aspect of polyester reclaiming, recycling, or products made therefrom.
Further, the additive supplier is not qualified to say the additive is compatible. This is for the polyester, PET bottle and recycle industries to decide. These industries have worked together to make PET the most successfully recycled plastic of all, most notably in demanding sectors like food contact.
The polyethylene industry experimented with degradables in the early 1990s. The prototype film had poor mechanical properties, so they thickened the gauge with more virgin polymer to offset the degradable additive, starch.
Useless when wet, the film required a prohibitively expensive modification to PE's polymer chemistry and went nowhere commercially.
What good is it if PET has to add more polymer or modify the feedstock recipe to compensate for a new and improved version of yesteryear's starch?
The current trend of lightweighting bottles could stall out. Or maybe it weakens some strapping when that load of bricks or lumber is shifting on a forklift, or makes carpets wear out faster.
What if the additives, even in small quantities, became harmful contaminants in the post-consumer stream?
Also, consider the reclaimers that convert the raw scrap into feedable form. I remember buying a truckload of what I thought was pure polyester felt scrap, only to find it had a small amount of nylon in a couple of gaylords. The operators in the condux building emptied out, once that nylon started offgassing.
Has anyone tested this degradable additive to see what happens in a polyester condux machine, grinder or pelletizer?
I have known the people at NAPCOR since its inception. As an early recycler, my group worked with their first president, and their current staff deserves high marks for knowledge and competence. They get my support for waving a flag of caution.
It is easy to claim that a degradable additive is compatible with the many different ways polyester is recycled. Let's see the proof.