High-mod fibers and aging, UV-degradation etc.

[Tree Access]

Aloha!
I found information (or at least mentioning) on the Buzz about flex-fatigue here and there, but not really a thread to sum up info about physical properties of modern high-modulus fibers as Dyneema, Technora, Vectran, PBO etc., and especially information about aging and UV degradation.

So maybe this thread can shine a light on this broad topic.
Since this stuff is used a lot in high-performance yachting and they spend an incredible amount of money on this sport there must be a lot of data about!
And it also gets used in a lot of other industries and surely in ones I do not even no about...
Who sorted out the information already, what are your experiences?
Do you have interesting documents about it?
Stuff like:
http://www.sciencedirect.com/science/article/pii/S0273117705005454
http://onlinelibrary.wiley.com/doi/10.1002/app.35132/abstract

 

[Tree Access]

My main point at the moment is the use of Technora and Vectran for life support rather then friction hitches, may it be for friction savers, redirect-(or any kind of-)slings, stem anchors, whatever.

How do they hold on when exposed to our work-environment?
Personally I am quite confident to use them, but more info would be fine nonetheless.

How long to use a vectran frictionsaver f.e.?
Do you have any rules of thumb?

 

[knudeNoggin]

[ QUOTE ]
Aloha!
I found information (or at least mentioning) on the Buzz about flex-fatigue here and there, but not really a thread to sum up info about physical properties of modern high-modulus fibers as Dyneema, Technora, Vectran, PBO etc., and especially information about aging and UV degradation.


[/ QUOTE ]

Thanks for those two URLinks.

It's frustrating to try to learn about such qualities,
in that one can find some seemingly well-informed
blanket statements that HMPE (Spectra & Dyneema)
is unaffected by UV radiation, but see marketed cordage
boasting of UV coatings to protect it, and of some
test results (on rockclimbing slings) that suggest
that it suffers UV more than even nylon (!?). Huh?!

[ QUOTE ]
The results indicate that exposing high strength fibers in continuous yarn form to UV led to serious loss in strength of the fibers except for Spectra® fibers.

[/ QUOTE ]

This is such a statement, from one of your URLinks.
(I'll surmise that the other three materials were PBO,
Vectran, & Kevlar (of some variety --like Spectra &
Dyneema, which isn't always noted), and that Dyneema
can be assumed to have the same qualities as Spectra.)

IIRC, some studies of thick towing lines used by tugs
made of HMPE showed some slight increase of strength
from moderate usage --presumably from an evening
of load-bearing among fibres--, and not much UV
degradation; but then UV affects primarily surface fibres
and these lines have much below the surface.

Again, some tests of climbing slings showed greater
apparent degradation --from what, is a guess-- than
those of traditional nylon. These would be dog-leg
slings pulled from "sport climbs" and replaced. Kolin
Powick of Black Diamond Equipment Ltd. has done some
testing of replaced slings.

In many cases, though, these hi-strength materials are
used <u>in the core</u> of lines and not at the surface,
so aren't so directly exposed to UV. I believe, though,
that some canyoneering lines have brought Technora
to the mantle/sheath, sometimes in mixture w/polyester?

Among rockclimbers, understandably, there has grown
an awareness that the once-vaunted higher strength (per
size &amp; weight) of such materials comes with a too-high
price of higher impact forces on dynamic loading. In
sailing, though, there should be continued use &amp; need,
in part in standing rigging replacing wire, and also in
sails, so that might be the best place to seek information
re UV effects (taking care to understand how such effects
were defended --by sheathing, by some coating treatment?).


*kN*

 

[Tree Access]

In the meantime I've heard from companys working with Technora and Kevlar, UV Degradation is not a big problem, or at least self abrasion is the much bigger one.
But no still data for all this.
UV is a problem vor Vectran and especially for PBO (which is the strongest, most static and most expensive of all them). But thats irrelevant for Tree Climbers, I know.