Owen wrote:
. . .
Polypropylene is also resistant to mild acids (and alkalis), but it is
a slippery (greasy) rope that doesn't hold knots or splices as readily
as natural fibre ropes.

Polypropylene deteriorates rapidly from the UV in sunlight. Here in
western Oregon it'll last a couple of years before seriously weakening,
but in Denver (mile high and lots of sun) it turns to little more than
powder in about six months.

Roy Lewallen, W7EL

I have used rayon for years .....in fact I put rayon between the posts that
held my grape vines ....went by the old QTH yesterday and the grapes were
still up after almost 20 years .....

73 all de Tom Popovic KI3R