ANY plastic without UV stabilizers will degrade in sunlight over time. The
thing about these two is that they're thick, and they're basically opaque.
As such, the sun only degrades the outer molecular layers of the PE, whether
it be HDPE or UHMWPE, but you probably won't notice much, if any difference.
The outer surface may get chalky over the years, but that's about it. PVCs
or "vinyls" will degrade both through loss of plasticizers (which make them
soft) AND UV degradation. When you get that sticky stuff on the outside of
PVC dinks or fenders, that's the plasticizers coming out... they're pretty
much shot at that point.
You have to worry about UV resistance much more in thin pieces of clear
plastics, like acrylic which will "craze" or isinglass, which will degrade,
lose it's plasticizers and turn yellow. You can add uv inhibitors like
nickel compounds or benzophenones, but of course that adds to the
cost/price. The most severe use for this is clear greenhouse film, which is
maybe 4-6 mils thick and is expected to stand up to sunlight for as long as
possible.
The best UV stabilizer is carbon black. It's degraded about as far as it can
go, and is very opaque, which limits the UV exposure of the plastic to the
very outer layer(s) of the synthetic. That's why I only use black
docklines... they will last longer than any other color.
Anyway, any of the thick poly materials should be fine for what you're
talking about. I'd avoid anything made of PVC however.
Keith
__
Why is it that if you tell someone there are 6.3 trillion stars in the
universe they will believe it,
but if you tell them that your teak has wet varnish they have to touch it?
----- Original Message -----
From: "Jim McCorison" jim@starfishmarine.com
I'm not a plastics expert either, but I do know that starboard holds up
fine in UV and UHMW degrades in UV. Talk to your local plastics shop.
Here is an interested FAQ in UHMW http://www.crownplastics.com/FAQ.htm
ANY plastic without UV stabilizers will degrade in sunlight over time. The
thing about these two is that they're thick, and they're basically opaque.
As such, the sun only degrades the outer molecular layers of the PE, whether
it be HDPE or UHMWPE, but you probably won't notice much, if any difference.
The outer surface may get chalky over the years, but that's about it. PVCs
or "vinyls" will degrade both through loss of plasticizers (which make them
soft) AND UV degradation. When you get that sticky stuff on the outside of
PVC dinks or fenders, that's the plasticizers coming out... they're pretty
much shot at that point.
You have to worry about UV resistance much more in thin pieces of clear
plastics, like acrylic which will "craze" or isinglass, which will degrade,
lose it's plasticizers and turn yellow. You can add uv inhibitors like
nickel compounds or benzophenones, but of course that adds to the
cost/price. The most severe use for this is clear greenhouse film, which is
maybe 4-6 mils thick and is expected to stand up to sunlight for as long as
possible.
The best UV stabilizer is carbon black. It's degraded about as far as it can
go, and is very opaque, which limits the UV exposure of the plastic to the
very outer layer(s) of the synthetic. That's why I only use black
docklines... they will last longer than any other color.
Anyway, any of the thick poly materials should be fine for what you're
talking about. I'd avoid anything made of PVC however.
Keith
__
Why is it that if you tell someone there are 6.3 trillion stars in the
universe they will believe it,
but if you tell them that your teak has wet varnish they have to touch it?
----- Original Message -----
From: "Jim McCorison" <jim@starfishmarine.com>
>
> I'm not a plastics expert either, but I do know that starboard holds up
> fine in UV and UHMW degrades in UV. Talk to your local plastics shop.
>
> Here is an interested FAQ in UHMW http://www.crownplastics.com/FAQ.htm
>
