Does heat alone degrade climbing gear?

Help me figure this out, my wife and I are arguing about this subject.

Can heat alone degrade climbing gear? The kind of heat you can expect to find by leaving your gear in the trunk of a car in the summer in the desert.

From my understanding, it's primarily UV radiation that degrades our gear. She seems to think that the heat, UV or not, will degrade the gear (ropes, slings, harnesses, nylon, dyneema, etc, etc - any softgoods).

Obviously extreme heat, to the point of melting, would degrade the gear - I agree. But I'm not sure you'd see that kind of heat in this situation. Obviously the trunk of a car in the summer in the desert is going to get pretty hot, but I would think the gear would need to be in direct sun for the damage to occur. I could be wrong.

I guess as an example, if we left our softgoods in the trunk of a car in the summer in the desert for a week, would they still be good to go or would we need to be concerned? That's the crux of our argument.

Thanks for any feedback or advice.

A hot car has the potential to degrade the adhesives used in climbing shoes.

Last time I dug up some values for heat degradation of Nylon:

https://www.mountainproject.com/forum/topic/118791533/storing-rope-in-heat#ForumMessage-126394069

From my perspective neither of you are correct. What degrades soft gear is usage. Normal exposure to UV radiation, oxidation, acid rain, heat, etc. has little impact on soft gear compared to usage over the course of its life span. Myself and others have shown this to be true. In my case we did laboratory experiments to asses the affect of acid rain and UV on climbing ropes. 

Andrew R wrote:

A hot car has the potential to degrade the adhesives used in climbing shoes.

This. I wouldn't worry about nylon or dyneema gear as much, as it's realistically not that much of an issue. As poster above states, over time in extreme conditions, degradation might occur on those as well. 

But for all your other gear, especially anything with leather and/or glue, leaving it an extremely hot car can degrade it. Couple of hours, maybe not so much. But let's say leaving your rock climbing shoes in the trunk of your car while going summer alpine climbing for a week? Maybe not such a great idea. A friend of mine did this once, he found that the shoes shrunk a size.  

The seatbelts in your car are still good, right?

People who live out of their vans also don’t have a problem, though their vans tend to be better insulated, and they take steps to not park in the sun, and to use window shades whenever possible…

Bottom line, I wouldn’t worry about rope, slings, etc that were left in a car trunk for a week. But I would still take steps to avoid it, if possible, because it seems like it would be easy to avoid it?

Victor Machtel wrote:

This. I wouldn't worry about nylon or dyneema gear as much, as it's realistically not that much of an issue. As poster above states, over time in extreme conditions, degradation might occur on those as well. 

But for all your other gear, especially anything with leather and/or glue, leaving it an extremely hot car can degrade it. Couple of hours, maybe not so much. But let's say leaving your rock climbing shoes in the trunk of your car while going summer alpine climbing for a week? Maybe not such a great idea. A friend of mine did this once, he found that the shoes shrunk a size.  

Definitely true for the shoes. I was living out of my car on the road last year for six months, and multiple pairs of resoled climbing shoes started delaminating super quickly after being in the hot car for a long time. Slings and rope didn’t have any noticeable issues over the same period of time. I think reflective window shades would help, and putting stuff in my black roof box probably made things worse.

I couldn't find the video quickly, but HowNot2 broke two pieces of webbing? nylon sling? of the same age but different storage conditions: one that lived in the bottom of a closet was fine, one that lived in an attic (and was thus subject to many temperature swings) was weaker and made weird sounds

Edit, found it: https://m.youtube.com/shorts/2SZXaJlQoH4

I think there is a bolt failure in Turkey that was attributed to having the bonding agent in the trunk for a few days before bolt installation.

And chocolate melts easily; it's one of the ten essentials you should always have in case of emergency...

dave custer wrote:

I think there is a bolt failure in Turkey that was attributed to having the bonding agent in the trunk for a few days before bolt installation.

And chocolate melts easily; it's one of the ten essentials you should always have in case of emergency...

Completely agree that chocolate is a 10 essential, actually find that Ten are Essential.

If a Bond agent failed in Turkey they should've bolted earlier.

Nylons can degrade in a car... 

dave custer wrote:

I think there is a bolt failure in Turkey that was attributed to having the bonding agent in the trunk for a few days before bolt installation.

And chocolate melts easily; it's one of the ten essentials you should always have in case of emergency...

This is why I carry my chocolate in M&M form, nestled amongst shock-absorbing peanuts and raisins.

Short answer:
Yes, heat of a trunk in summer in death valley will degrade soft goods... but probably not enough to matter, for our uses with the safety margins we have built in, unless very well over the recommended replacement life of the item anyways.

Long answer:
* UV is real rough on our soft goods. Nylon doesn't take it well. Polyester takes it better. Dyneema takes it best. UV inhibitors are a thing and can help. Dark colors fare better. Sometimes extremely cheap webbing doesn't have inhibitors in them, like super cheap backpacks, and you will find the straps disintegrate after a couple summers.
* Heat does degrade polymers, but the heats we are talking about, the rates that it is damaging them are long enough to probably not worry about. Comparing nylon slings left in the dark of a cool closet vs. the dark of a hot trunk in death valley for like 20 years, for sure the heat exposed ones would be weaker... how much weaker? Who knows. Probably still stronger than the 14kN rating of a typical good size cam, I'd imagine.
* The recommended replacement intervals are assuming storage in the dark and only reasonable UV exposure when actually used... if you need something out in the UV constantly, you need to pretty considerably derate the replacement interval.
* Strength is not the full story. We depend on the dynamic properties of our climbing ropes. Those properties probably also degrade with prolonged chronic heat... again, you would probably want to retire your rope due to age and accumulated fuzz or core shots far before it really became an issue.

Seatbelts are almost always polyester. Higher UV resistance, abrasion resistance, lower water absorption, etc... 22-27kN single strand. Their width is far more for comfort than actually needing that much strength.

Just replace your soft goods reasonably close to the recommended date.