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I'm reading the UIAA standard for climbing ropes, which is supplemented by the EN 892 norm (which I can't provide a link to, since this would be piracy). I'm sort of confused about the fact that, even though they do test the ropes for abrasion, humidity and high fall factor effects, nothing is mentioned about temperature. After a quick search I found some evidences (like this or this one) for believing that the properties of nylon can change drastically within a temperature range in which climbing ropes are usually used. EN 892 mentions storage conditions for the ropes before testing, and those conditions include a drying period of 24h in temperatures as high as 50ºC, but the tests themselves are carried on in the very mild temperature of 23ºC. No tests in colder/warmer conditions are mentioned in either texts.

I'm unable to be worried because I'm sure such a blooper wouldn't happen after so much technology has been applied to mountaineering. I think I'm missing something and I'd be happy if someone could provide me a reference that guarantees that ropes have their temperature-dependent phenomena catalogued.

  • While I really would love to see an answer to this, I believe the definition of an ambient temperature range for using climbing rope is not part of any of the relevant bodies of standard. (I also believe that the range in which the human body is able to climb is narrow enough, that there is some room at the upper end) But it's really hard to prove a negative... this is a (now much shortened) comment, because I realized its not an answer, just an opinion.... – knitti May 30 '17 at 20:11
  • @knitti Then it really worries me. I've seen climbing ropes being used in temperatures as low as to -40ºC (like in the Asgard Project) and as high as 50ºC (like some friends of mine in South Africa). That's approximately a 100ºC window. According to what I've read regarding the properties of nylon, I cannot help going into an alert mode: it does matter a lot. =/ – QuantumBrick May 30 '17 at 20:16
  • The size of the window isn't the problem. The problem would be the upper bound, as one would suspect the material lose some tensile strength. My material-science-fu is weak, so I can't really comment on the relevancy of the papers on nylon strength which are available on the net. However my gut says, there is some weakening, perhaps as much as 20% in the vincinty of 50°C. BUT standard testing also tests with 80kg, and I'm much heavier: what do I do? In doubt err on the side of safety and use stronger rope... – knitti May 30 '17 at 20:40
  • I've no background in engineering either, but as a physicist I understand that elasticity is an entropic phenomenon: it only occurs due to the increase in entropy that the polymer's moving molecules in a chain create; i.e, is it disorder dependent. High temperatures maximize disorder, which might turn a catch softer and make the rope jump to critical regime (increase elasticity until there's no more elasticity); low temperatures might turn a catch stiffer and break the rope (decreased elasticity until the rope is almost static). I'm sure of this, but I want to know how much it matters. – QuantumBrick May 30 '17 at 20:46
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    To anyone still interested in these matters, I sent numerous emails to rope companies and I'm receiving replies. I don't know how this community's etiquette works in regard to answering your own question, but I am inclined to answer it in a few days. The conclusions are rather serious. – QuantumBrick Jun 7 '17 at 20:15
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As EN norms are not publicly available and quite costly, I can't confirm for sure that there is no temperature testing - but from what I hear there is none. If anyone can authoritatively confirm or deny this, please write a comment.

The first impulse is to look into fire-fighting resources. Problem there: Their requirement far exceed what a climber is interested in. According to this blog entry the NFPA "Standard on Life Safety Rope and Equipment for Emergency Services" requires rope to withstand a load of 300lbs for 45s at 600degC and 5min at 400degC.

One resource of which the relevant part is available through google books is Dynamic Behavior of Materials, Volume 1. They made tests on a Nylon kernmantle rope with 9mm diameter. Unfortunately, it is again in the context of fire-fighting, meaning a rope fulfilling NFPA1983 was used. However it is Nylon as well, so the temperature properties should be the same/similar.

Static tests were done at room temperature, 100degC and 200 degC. The observed changes in breaking strength (static) relative to room temperature were:

100degC: 84%
200degC: 60%

At the same time the stiffness also decreased a lot:

100degC: 83%
200degC: 39%

Subsequent discussions on dynamic behaviour were again in the context of a firefighter escaping, so no actual falls discussed. However the important point is still brought up:

This reduction in stiffness can be beneficial when the rope is subjected to dynamic loading as long as these dynamic forces do not exceed the reduced strength of the rope.

Lower stiffness means lower peak forces during a fall, it has the same effect as dynamic belaying. These data suggests that the stiffness reduction is even greater than the reduction of breaking strength. So apparently this is simply not an issue for the upper range of temperatures where climbing ropes are used.

  • Nice find! The language in the article suggests they're using static ropes, so wouldn't trust the actual values above, but they should be good for a ballpark estimation. – knitti Jun 1 '17 at 11:36
  • NFPA1983 requires that static elongation under 10% of breaking load must be between 1% and 10%. For climbing ropes the static elongation with 80kg (+-3% of the breaking strength) cannot exceed 10%. Static ropes cannot exceed 5% elongation under 150kg of load). So yes, this seems to be (more) static rope than a climbing rope. Which also makes sense, as it is mostly used for escaping a building. Also I consciously omitted actual values and only gave relative ones because it is not the same ropes. But it's the same material, so relative changes with temperature should be almost the same. – imsodin Jun 1 '17 at 12:19
  • @imsodin unfortunately I don't agree. What provides elasticity to a climbing rope is not the material, but the way the material is wrapped. Climbing ropes are not [only] elastic because they're made of nylon, but because the core is wrapped in a twisted pattern that unfolds when weighted. A proof that this pattern is responsible for almost all elasticity is the fact that static and dynamic ropes are built from the same materials. This means that your answer, although precise for static ropes, does not help with the dynamic case, because the properties that provide elasticity to a dynamic – QuantumBrick Jun 1 '17 at 12:26
  • rope change with temperature more significantly than the nylon itself. Nylon has a melting point of more than 250ºC, but I believe (I infer, I'm not sure - if I were I'd post an answer) that the elastic properties of the webbing are lost before the nylon is affected. That is what worries me the most. (Your answer is nevertheless very interesting, don't get me wrong!) – QuantumBrick Jun 1 '17 at 12:28
  • @QuantumBrick Our comments just crossed, lets move this to chat :D – imsodin Jun 1 '17 at 12:29
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As I said in the comments, I believe my findings deserve an answer on their own. These matters are urgent and I'm a little troubled by what I've found.

I've sent emails to three major rope manufacturers (Petzl, Beal, Mammut). Only Mammut cared to even write me an answer - which made me feel lonely and friendless. But anyway, I don't think there would be any major difference between all answers I would receive.

Remember I asked for clarification about topics that are not contained in either EN 892 or the UIAA standard.

Regarding UV Exposure

Mammut clarified this point in a way that makes sense to me. We should not be worried about UV damage to the rope because the sheath, which is approximately 1mm thick, breaks the UV before it hits the core. This is true for all modern ropes, and some of them actually exaggerate: Sterling's Marathon Pro has a double sheath, which I believe makes this rope's half-life sort of infinite.

Regarding Temperature Range

Mammut says warm temperatures are not a major concern and that they have tested this internally. At this point I sent another email saying that testing stuff internally doesn't convince me unless some statistics are shown to me. Mammut said that they couldn't sent me any statistics, and that they tested the ropes both for the standard temperature (23ºC) and an extreme temperature (50ºC). They say the outcome was the same. I don't believe it. I think there are significant changes in elasticity - but I do believe it's not dangerous to climb in the heat, it only wears your rope significantly more and might turn the catch stiffer if you regularly take whippers in the heat (my opinion).

Regarding low temperatures, my hint was correct: it might not be safe to climb in extremely low temperatures. According to Mammut, cold temperatures might shrink the rope in up to 10% of its length - this makes the catch stiffer. I don't think it would be stiff enough to hurt someone or to break the rope, but I do think taking a factor 2 fall on a frozen rope is not at all a good idea. A major problem about climbing in low temperatures has to to with the heat generated in the impact melting the ice and the rope becoming wet.

Regarding Wet Ropes

This is where the problem is real. According to Mammut, I should not be worried about my rope unless it is wet. Some home-made studies address both the problem of water and dirt on ropes. I also remember having read (I won't look for this reference right now, but I think it was UIAA itself) that climbing ropes might lose up to 80% of their resistances if wet. The combination of water and dirt might be specially dangerous. Mammut said that they have a very strict method for building dry ropes because water is so dangerous - and that sort of makes me wonder why the hell people still build ropes with non-dry treatment.


Conclusion: don't worry about the UV, and unless you're climbing in an icy environment with a non-dry rope, don't worry too much about low temperatures - but keep in mind your rope might be much shorter. Don't take factor 2 whippers (ever, if possible), since in extreme cold they might really hurt or break you up. High temperatures are not dangerous, but your rope will wear out faster climbing in them. Also, high temperatures might come together with high humidity, which is the only thing you should be really worried about.

Curiosity of the day: manufacturers like Mammut do take a seat in the meetings that decide changes in norms and standards. This means they can do something about what's missing in them, if they want. I'm inclined to say that if they are not insisting on including these things in the norms, it's a little because they don't matter much and a little because no one wants to spend more money doing more tests - even if they would clarify a lot.

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