A common question when it comes to polyurethane tubing, is the difference between the two polyurethanes: ester-based and ether-based.
For the chemists in the crowd, ether has two carbons bonded to an oxygen atom. Ester however has a double oxygen bond with a carbon atom.
Practically speaking, there’s a trade-off to be made by the user. The ester-based resin handles oil slightly better but it degrades quickly when introduced to moisture. The ether-based resin handles oil slightly less well, and handles water very well. In fact, ether-based polyurethane is an excellent choice for water applications.
To me, the ether-based resin is an easy choice. The ester though is a little cheaper and is the material you often see in inexpensive imported tubing. In fact, if you see polyurethane tubing for sale at a discount house and are marveling at the low price, you’re most certainly looking at ester-based material. You won’t be able to tell the difference until it gets wet.