So, then....
Which flexible filament should be used when making a flexible cup to drink from?
Are any "food-safe"? (Just thinking here of all of those water bottles that are now labeled as "BHA/PBA free")

Quote Originally Posted by pyrophreek View Post
In regards to why TPU is not recommended for long term immersion in water, a better understanding of the polymer chemistry is needed.

From Wikipedia:


What this means is that when you submerge the TPU in water, water molecules (which are polar) will slowly intercolate into the polar "crystals", and serve as lubricant between chains. This will cause the TPU to become swollen, and cause a loss of the elastic recovery response. How much of an effect this is depends on the exact chemistry of the specific TPU formulation, as they vary greatly.