Check out the C&EN article on the Denver symposium on "PET Recycling: Bridging the Gaps through Innovation." Remaining challenges exist to develop better non-yellowing additives, adhesives that release labels easily and detection methods for sorting plastic waste streams. Recycling PET makes sense from a Life Cycle Analysis, but you can make it even better. And put those bottles in the recycle bin!
David Cornell, Association of Postconsumer Plastic Recyclers, adds more details on the kinds of challenges they need chemists to solve:
1. Estimation of melt flow rate, or index, with no contact and in under 0.05 seconds. This is needed to identify extrusion-grade vs. injection-grade polyolefins in the environment of auto-sorting machines.
2. Creation of a relatively stiff, high shrink in the transverse direction polyolefin film for making shrink labels. The shrink ratio needs to be at least 45%, better 60%. The need is to have a float-in-water label that is efficiently applied and attractive and economical.
3. Identification of ultraviolet light inhibiting agents that protect product in clear PET plastic such that the PET containing the UVI additive can be melted and remelted without causing the PET to yellow or haze.
4. Identification of adhesives, particularly pressure sensitive adhesives, that preferentially attach to polyolefin labels and detach from PET bottles. The adhesives need to detach from PET is caustic water baths of 80C.
5. Identify water soluble adhesives that once released into hot caustic water, do not re-deposit onto PET flakes
6. Creation of machinery that allows for the sorting of either packaging items or flakes of packaging into 4 or more streams at up to 2000 lbs/hour/stream and do so with at least 99% accuracy and do so inexpensively
7. Identify low cost means of raising the melt flow index, post polymerization, for HDPE and lowering the melt flow index, post polymerization, for polypropylene.
Feel free to send your ideas to Dave@plasticsrecycling.org