Dyneema/Spectra webbing lifetime?

[trumpetsailor]

How long do the modern variants of high strength fibers retain ~90% of their rated strength, when kept unused in a cool, dry, and dark location?

 

I've spent a few hours searching the web and have found few empirical breaking strengths with anything approaching reasonable statistics. It looks like the manufacturers would prefer that webbing be turned over every 1-2 years. I'm, in principle, a big fan of the lightweight runners and slings that are now available, but I worry about aging. I tend to do, at most, a few alpine climbs with a very light rack and a few roped-up trips on glaciers each year, so I'd like to get 4-5 safe years out of my investments.

 

I'm considering expanding my rack somewhat and some gear, like Tri-cams and sewn runners, comes with the choice between nylon and Spectra/Dyneema. Which is going to give the safest (and lightest) bang for the buck between now and 2015?

 

Thanks!

[hemp22]

I can't give you a direct answer to your question about maintaining 90% of strength - but I'd say that if you're only doing a few climbs & glacier trips a year, then you shouldn't have any issue with skinny dyneema slings wearing out.

 

the dyneema slings do wear out more quickly than nylon - but that seems to be primarily from abrasion that's seen with heavy usage. So, if you were using them every weekend, you'd probably want to look at replacing them after 2-3 years. But only a few trips a year isn't going to wear them out quickly.

 

Also, 90% of the original strength is still like 20kN, which is still overkill. For alpine & glacier, you'd probably have to lose > 50% of the strength of the sling before the sling becomes the weak link (instead of your placement).

[chris]

The crux of the matter is UV damage - dyneema/spectra material ages faster than nylon due to sunlight. For a recreational user like yourself, consider replacing dyneema slings every three years, and nylon slings every five.

[tradhead]

Chris,

 

I could be wrong, but it is my understanding that polyethelene/Spectra fibers have significantly better UV resistance than nylon. See the graph in this article from Wikipedia:

 

http://en.wikipedia.org/wiki/Sailcloth

 

Note that the graph shows UV resistance, so a higher value equates to better performance.

 

My biggest concern with using Spectra slings is that it has much greater specific stiffness than nylon and essentially no permanent stretch at failure. This equates to less energy storage and way less energy absorbtion capacity than nylon, so Spectra slings can generate dangerously high loads if shockloaded with minimal or no rope in the system. This is an issue for anchor material and potentially slings on the first piece after the anchor. I believe that several companies including DMM have studied this issue of late.

 

If I'm using a spectra sling as the primary anchor material, I always try to incorporate the rope independently for redundancy in case the anchor gets shock loaded for some reason. Just my 2 cents, YMMV.

[trumpetsailor]

Great information, it's a useful supplement to things I'm reading elsewhere. As hemp22 suspected, I'm hardly wedded to a "90%" number. Thank you!

[Maxtrax]

The crux of the matter is UV damage - dyneema/spectra material ages faster than nylon due to sunlight. For a recreational user like yourself, consider replacing dyneema slings every three years, and nylon slings every five.

 

Incorrect, UHMWPE (Dyneema/Spectra are trade names) has significantly higher UV resistance and abrasion/wear resistance than Nylon. Personally I replace my Dyneema slings when they start fuzzing out/fraying (typically every 4-5 years) or if they get a permanent kink in them similar to a coreshot in a rope.

 

Regarding long-term storage with no use, nylon naturally degrades over time, enough that most manufacturers recommend retiring any lead ropes 10 years after date of manufacture or 5 years after purchase, whichever comes first. UHMWPE also degrades over time but I believe at a much slower rate, though I can't find my reference right now without being on a school computer.

 

 

Edited to clarify/add:

 

The above refers strictly to a direct comparison of the fibers/yarns. Dyneema is often quoted as being 10x as strong as steel but the second half of the statement is ommited. Dyneema has a 10x higher tensile strength than steel when you compare equal masses of the materials - not if you compare a skinny climbing sling to a large girder or I-beam. The same principle applies when comparing climbing slings.

 

Functionally, Dyneema slings may appear to have lower wear resistance than nylon and/or age quicker than nylon slings. This is simply because there is significantly less material in the Dyneema slings than the nylon slings currently on the market. Typically when people compare climbing slings they are looking at 1" (25.4mm) or 11/16" (17.5mm) nylon vs. 8mm or 10mm Dyneema. That is comparing apples to oranges (or at least pears). For a better comparison, one should really consider 1/2" (12.7mm) nylon vs. 8mm Dyneema as both have roughly equivalent masses per length (a shoulder length sling out of either has a mass of 18gm +/- 1gm).

Edited September 11, 2010 by Maxtrax

[tugboat]

Matrax is right.... Spectra has a higher UV index vs Nylon. This is backed up by suppliers specs, my own use over a 10 year period. My own pulltesting of ten year old samples vs nylon. And its dramatically witnessed within the sailing community...where they are seeing ten year use in harsh Uv conditions and still sustaining extreme loading.

 

As reargds "shelf life" of Spectra....After ten years of use i am finding 90% plus strength both in fabric and webbing samples that i personally pull test with digital data aquisition thru a digital load cell. I test spectra that has been exposed to all differnet conditions over different age periods.

[tugboat]

PS...one thing to remember with spectra slings is that while the webbing may be pure spectra (usaully not), the stitching is generally Nylon. This then becomes your weak link if exposure is the issue. Spectra thread may be used but is not that common (for several reasons). Spectra webs for climbing are generally a blend of Nylon and Spectra to balance out the good and bad properties of pure spectra fiber....eg; lower heat resistance, lower stretch, decreased ability for weft in spectra to hold its structure under load due to its "teflon" like nature. Nylon fabric and thread hold there grip better due to there higher friction coefficient...and provide more stretch and durability to the sling.

[jfs1978]

Matrax is right.... Spectra has a higher UV index vs Nylon. This is backed up by suppliers specs, my own use over a 10 year period. My own pulltesting of ten year old samples vs nylon. And its dramatically witnessed within the sailing community...where they are seeing ten year use in harsh Uv conditions and still sustaining extreme loading.

 

As reargds "shelf life" of Spectra....After ten years of use i am finding 90% plus strength both in fabric and webbing samples that i personally pull test with digital data aquisition thru a digital load cell. I test spectra that has been exposed to all differnet conditions over different age periods.

Tugboat, that's interesting. I've had 5-year old Mammut 8mm slings pull tested after 4-5 years of moderate use and they reliably failed at 50-60% in multiple tests. I believe this has been noted by others as well.

 

note: of course 50% is still 11kn-ish...

[hemp22]

for skinny dyneema climbing slings, i think the conventional wisdom is that the significant strength loss over time is more likely due to abrasion and knotting/bending.

[Friedrich]

I found this independent research paper testing various "high strength" cordages in various ways on another forum awhile ago. Good hard data.

http://www.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf'>http://www.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf

 

Their testing is more extreme than real-world conditions, but so are the standard UIAA tests. Scroll down to the last chart, it's pretty interesting. From what they found, the performance of spectra cordage degrades quickly under repeated knotting/bending. Nylon does not.

No info on Dyneema since this study pre-dates the introduction of that material. Sun-fading and exposure to salt water was not part of their testing.

 

Their main page has more studies along with some good stuff about multiplcation of forces, etc.

http://www.xmission.com/~tmoyer/testing/

 

Hope this is a helpful addition to the discussion.

[jfs1978]

for skinny dyneema climbing slings, i think the conventional wisdom is that the significant strength loss over time is more likely due to abrasion and knotting/bending.

Yes that's true. Tugboats data seemed to contradict this.

[snoboy]

From what they found, the performance of spectra cordage degrades quickly under repeated knotting/bending. Nylon does not.

No info on Dyneema since this study pre-dates the introduction of that material. Sun-fading and exposure to salt water was not part of their testing.

 

Spectra = Dyneema = UHMWPE at least as far as I know, and my quick google search supports.

[tugboat]

Dyneema = netherlands name for spectra

 

Spectra = North America name for UHMWPE. (liscenced to Honeywell by DSM if i recall correctley)

 

"Dyneema" is often mislabelled as the Nylon/spectra blended slings we see from companies like Mammut, onsight, etc...

 

As regards jfs1978 test results.... i don't question your results; as, after 15 years of testing all different materials and scenarios i have found that there many variables involved that can effect differnet outcomes. Sometimes these variables are obvious, sometimes not. For example...my own test were on pure shuttle loomed, critical use, spectra 1 inch wide webbing, bartacked with pure spectra nylon thread. I then pull over minimum 9mm pins. Now, while these slings may have seen much environmental exposure, they were not "climbing" use slings and so may not have see the flexural exposure that your mammut's did. The Mammut slings will be a Nylon/spectra blend with Nylon bartacking (so product is not entirely spectra fiber)....this could possibly account for the loss vs pure spectra., given that the nylon is more prone to uv damage and etc...

 

Yes,...i too have come across the data that reflects flexuaral degradation. Most of my products have not seen repetitive bending and flexing....so i should have qualified my results on that note (my apologies).

 

Some studies have found that newer genrations of Spectra have less of a flex fatigue problem vs older spectra generations...

And they have also found that initial loss in strength occurs at a certain rate, and then the loss decreases exponentially.

 

I recentley set my shop back up, and put my pull testing facility back in action....so i will do some more testing and research into this area. I will sew up some pure spectra from old stock and new stock, using both old and new nylon thread. And i will bust some old slings i have kicking around.

 

Ill post my results when i get done. And i'll video them and upload to you tube.

 

 

 

 

Edited March 6, 2011 by tugboat

[Chad_A]

Please do, interesting to hear input.

[tugboat]

Yes....looking back on my post...i did say "exposed to all different conditions". I do believe my statment is too broad as i am primarily referring to pure spectra exposed to the elements and workplace. While my products see lots of use in their respective industry...they are not neccessarily treated in the same manner as a climber's gear may be treated over years. And all my spectra is sewn with spectra thread vs the flex fatigue of knotting...and the 'pinch point' issue of knotting.

 

So my statements should have been qualified...

 

As pure Spectra slings are not a good choice for climbing (and not available as far as i have seen), i have not tested pure spectra slings exposed to the climbing environment; so jfs1978's mammut sling tests are not directley comparable to my tests (diff envrons and materials)...

 

The most exposed and repetivley used pure spectra i have heard of is in the sailing industry.... but this is not my industry so actual info is second hand here...

 

I will carry out some tests on ten year old, highly weather exposed pure spectra sewn slings in the next week and post the results so we can get to the bottom of this.

 

 

 

 

Edited March 6, 2011 by tugboat

[tugboat]

jfs1978....note the condtions of your pull test setup,...so we are not increasing our test variables as well. For example; did you pull over 9mm pins or larger or smaller? Also...for the most accurate results one should pull test identical new slings on your own equipment and then repeat after the usage timeframe vs relying on the manufacturers tag specs... (= much more controlled study)

 

Also of note....in my opinion the slings attaching chocks, quickdraws etc dont offer enough elasticity to change the fall factor. But as soon as you get into one foot plus legth nylon slings, the elsasticity dramatically shows itself on the test bed. Note the ballistic Nylon in my pics stretching vs the all spectra harness pics being pulled.

Edited March 6, 2011 by tugboat

[tugboat]

http://www.dyneema.com/en_US/public/dyneema/downloads/DYNPR068E1006_Antifouling_Micanti.pdf

[tugboat]

pics

Edited March 6, 2011 by tugboat

[tugboat]

Edited March 6, 2011 by tugboat

[tugboat]

the dyneema slings do wear out more quickly than nylon - but that seems to be primarily from abrasion that's seen with heavy usage. So, if you were using them every weekend, you'd probably want to look at replacing them after 2-3 years. But only a few trips a year isn't going to wear them out quickly.

 

Actually from the manufacturers actual abrasion resistance is higher than Nylon. However, Spectra, being very slippery, tends to catch on things easily....eg the thin fibers 'catch' on rock crystals and pull thru the nylon. Nylon locks upon itself better in the warp and weft....and thus are less likley to have strands pull. So in that way its a mute point...real world vs the lab...

[jfs1978]

Tugboat thanks for your work and posting the info! Cool stuff. To be honest, I am mainly interested in this kind of thing from an academic standpoint. I have yet to see anything that really gives me serious pause with regard to the gear on my own rack. Like I said...it's interesting.

 

Sorry but I don't know any specs on the rig. Only that it was at a climbing mfr. we all know and use and done as a favor to satisfy my own curiosity.

[tugboat]

jfs1978, no problem...its academic and practical for me too. Since i need to know the academics to get my product and knowledge correct for the customer. I guess the main reason i piped up on the spectra life issue is that the question has been popping up in my industry. I now have product returning to me that is 8-10 years old. It's entirely made of spectra fibers, and people are replacing them with new harnesses. IN exchange i get to bust the old ones. I've been finding full to over 90% strength much of the time (not all the time) But ten years ago i built things way overkill (read; liability).

 

As the years have past and advanced materials and engineering have progressed.....manufacturers have found that they can pass "standards" using less and less material. THis, while still strong, leads to "life" or "durability" issue. In a way that's how i see the thin "ultra tape" (nylon/spectra) blend sewn slings climber's are using: you can decrese the size and weight of the product and meet specs.....but at what longterm cost?

 

Rock and Ice did an interesting arcticle that might apply here:

 

http://rockandice.com/articles/how-to-climb/article/494-busted

 

Also the reason i mentioned "before and after" tests....is that i have found, on occasion, that some slings, and several harnesses, dont meet there rated UIAA specs when bought brand new.... this can be for several reasons....that i wont go into here (it doesnt mean they are unsafe). So if you don't have a real world average before the test, the "after" number is based on someone elses #'s. its all academic at this point. The stuff is so over kill...

 

In all my testing, climbing and building the number one thing i have learned is inspect your equipment regularly and leave at least 3-4 inch tails extruding from any "joint" eg tighed water knot, double passed buckle etc.... without this tail your putting yourself in danger.

 

F

 

 

Edited March 6, 2011 by tugboat

[tugboat]

For those interested, i have started a Blog on Stunt harness manufacturing (as this is my area of expertise). Since i came from a climbing background and then transitioned into film work.... the Blog will have applicable material to climbing sewing theory and practice.

 

 

The Blog is just in its infancy. But i will try to work and ad to it everyday for this interested in following. This blog is presented as educational/information source, rather than a promotion of my company.

 

http://stuntharness.blogspot.com/

[tugboat]

Well....time to eat some crow. While in the past i have found well used and exposed spectra to maintain significant strength (up to 90% in specific cases....not climbing); todays tests show definite loss of strength when exposed to severe, year round conditions (snow,rain,sun). I tracked down some 3-5 year exposed pure spectra and tacked some slings for testing and compared to new spectra. I only did a couple of tests. But i found that in general that the highly weather exposed spectra was 65-70 percent the strength of the new spectra sling. I also recordered the knot slipping potential of a hand tied spectra sling for anyone interested.

 

Furthermore, what is interesting as regards spectra shelf life, is what i found looking back at the brand new spectra breaking strength as compared to today's "new" spectra sling comparison sample. The "new" spectra sling material from today was taken of the roll from a batch that i stored in good condions from eight years ago. Looking back at test samples from that eight years, i found there was no change in sling strength (at least when pulled over an 8mm pins (UiAA calls for 10mm) at all. In 2003 i measured samples breaking at 5450 pounds, and today at 5500lbs over the same shackles.

 

here's links to the videos:

 

 

[video:youtube]

[video:youtube]

 

 

 

Edited July 5, 2011 by tugboat