Bryan Martin wrote:
Polypropylene rope is often simply called "poly rope" and sold as such,
so some might think the "poly" is short for polyester. Polypropylene
rope is cheap and light (it floats on water) but it doesn't tolerate
direct sunlight for long.



Depending on how you define "for long", neither will polyester. Unless
specifically treated with UV blockers, three weeks is a long time for
polyester. If treated with the UV blockers, "long" may run into months
(maybe).