Interesting stuff. I landed a consulting contract for Continental PET Technologies in the mid 90s to upgrade their preform process to accept more recycle without disturbing the inner oxygen barrier for Heinz Ketchup bottle three layer process.
We were able to increase the recycle barrier by nearly 40% using a additive from BASF. Huge bonus after completion 2 months earlier the projected. They kept me busy for a few more years until I got burned out.
Being Dinsdale, of course I could have told you what those were...
An old friend used to use them for stash containers... and didn't tell me what "object you see every day in a different form" it was for quite a while.