"Roy Lewallen" wrote in message
...
That would have been polypropylene, widely sold in hardware and DIY
stores. It rots in no time if exposed to UV. Polyester holds up very
well, and nylon is just about as good. (I think most of the rope sold
specifically for antenna use is polyester.) I'd use black rope if I lived
in an area having a lot of direct sunlight and/or one that's at at high
elevation, since this improves its UV resistance, but ordinary nylon or
polyester rope lasts many years at my western Oregon QTH. (Maybe the
moss/algae growth helps.) I like nylon because its stretchiness acts as a
shock absorber, but this would be a disadvantage for some applications.

Roy Lewallen

Polyester (Dacron) rope has the higher ultraviolet resistance. Nylon,
especially if formulated with UV absorbers and anti-oxidants does fairly
well too. If you get acid rain in your area, Nylon will not last nearly as
long.
Polyethylene and polypropylene ropes are rapidly destroyed in sunlight.

The mechanism that protects polyester from ultraviolet in sunlight is an
interesting one. When a short wavelength photon hits the polymer in the
rope, its energy has to go somewhere. Often it just heats the polymer, but
sometimes it breaks the polymer chain. Polyolefin ropes (polypropylene and
polyethylene) have an easily broken polymer backbone. The backbone is much
stronger in polyamides (Nylon). Polyesters, however, have aromatic
(benzene-like) structures in them that absorb the short wavelength UV
radiation and re-emit it as longer wavelength fluorescence. In
polyethylene terephthalate (PET, Dacron) this fluorescence is generally in
the near infrared so it is not visible. In polyethylene naphthalate (PEN),
the fluorescence is in the visible region. This polyester has better
barrier properties for food use and can withstand slightly higher
temperatures than the PET used in most plastic soft drink bottles and food
containers. But the fluorescence is unwanted in most food applications so
quenching agents are added to suppress this property.

Dacron is DuPont's proprietary name for their PET. Usually rope sellers
charge a premium for the name, but polyester fibers as used in ropes are
manufactured by many other companies. Roy is correct about the black rope
lasting longer. Carbon black added to the polyester is an excellent UV
absorber.

73, Barry WA4VZQ

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