By the Numbers: Crushing It – How Bad is Thermal Degradation in Synthetic Insulation?
Sep 28, 2021 at 9:00 am #3728321
Companion forum thread to: By the Numbers: Crushing It – How Bad is Thermal Degradation in Synthetic Insulation?
In part two of this investigation, we see what happens when you crush insulation beneath a stack of concrete pavers – again and again.Sep 28, 2021 at 10:43 am #3728329Jeff McWilliamsBPL Member
I wonder if the following technique may more closely approximate putting into a stuff sack:
Drop garment or sample under test into a lexan/plexiglass tube or hollow cylinder. The diameter of the tube would be chosen to approximate the amount of folding, crumpling, and/or “squashing” that happens when one shoves a bunch of clothes into a compression stuff sack and then tightens down the webbing straps to form a dense “ball” that a backpacker typically drops into their backpack.
Use a piston with a round plate having the same diameter as the inner diameter of the tube to “squash” the test piece to a specified force, then raise the piston. The compress and release times per cycle, and number of cycles are TBD.Sep 28, 2021 at 11:08 am #3728332
Thanks for reading. I am now doing a second round of testing on the same samples, as described in the article. After that, I expect to do a 3rd round of testing along the lines you suggest.Oct 3, 2021 at 1:02 pm #3728734Tim HawthorneBPL Member
Excellent article! I agree that the “bending forces” caused by stuffing synthetics into small stuff sacks causes additional degradation to synthetic insulation fibers. The bending forces tend to break the fibers, especially older fibers, and that reduces the loft and probably air entrapment. I have some 40 to 50 year old synthetics that have never been stuffed that still have good loft.Oct 3, 2021 at 2:29 pm #3728739Eric BlumensaadtBPL Member
@danepackerLocale: Mojave Desert
The US Army Nautick Labs tests also agree with these tests. That’s why theArmy chose Climashield.Oct 3, 2021 at 4:29 pm #3728752Roger CaffinBPL Member
@rcaffinLocale: Wollemi & Kosciusko NPs, Europe
Real Testing: wonderful stuff. Thank you.
But I would like to query two figures in this quote from the article:
Based on these sources, I assumed an average weight of 202 pounds (92 kg) and an average skin surface of about 25 square feet (2.3 square meters).
An average American male weighs 202 lb? That is 50% heavier than me. Are all walkers this heavy? I do wonder. Perhaps that figure includes a large number of couch potatoes?
I do not think it is of much use quoting the average skin surface of about 25 square feet as that is for the whole skin surface: front, back and sides, all around arms and legs. That is far more than the frontal cross-section, which is closer to what rests on a sleeping bag when we sleep. Even so, those concrete slabs sure flattened the stuff.
I wonder whether a lot of the degradation might come from ‘grinding’ the stuff: moving around on it while lying on it. Or from having a pack squash it against your back. Testing that might be difficult.
Your observation that the performance of these synthetics has improved is much appreciated. I know they started off rather poor, but that was 20 – 30 years ago. Have you asked the companies about this? It might be interesting to see if you could get a reply from the TECHNICAL people (NOT the marketing arm).
CheersOct 3, 2021 at 5:20 pm #3728753
I share your concern about the average male data, as well as the simple method I used to calculate the pressure to use. I am guessing that most people who go backpacking weigh less than the average US male. Clearly, my approach is an over simplification, but I needed some frame of reference to proceed from. I can think of reasons why my number could be too low or too high. However, since I tested with 1x to 4x that weight, I think the results are still reasonable.
I did not use the 25 square foot figure. I used less than half of that (10 square feet) for skin surface.
I am now continuing the test along the lines described at the end of the paper. I would not be surprised after another 9 or 12 crushes, nothing will change. Next, I will use a different approach that will cause the fibers to bend as they would when stuffed. I am afraid I can’t test “grinding”, but hopefully, the 3rd round of testing will shine some greater light on the subject.
I can’t help wonder if the salts and oils that ooze out of a person in a sleeping bag impact the resilience of synthetic insulation. I have an old Arcteryx Atom AR Hoody. I cut it open so I could observe the Coreloft insulation within. What I found was a solid mass. Kind of looks like crumpled paper that you pull from your pocket after it goes through the washer and dryer. I only use that jacket around town when it is not cold, so it works for that. Even if this could be a mechanism, who knows how the industry might have changed the chemicals applied to the polyester to prevent such deterioration.
What I do know is that every time I pull the insulation samples from the pavers, they seem to get fully puffed up in a few minutes and I have to admit, I am impressed with what seems to be a successful manipulation of the properties of polyester fibers.
My experience in trying to contact these companies is that they don’t respond. I have been unable to even find anyone at Primaloft or Climashield with whom to discuss my findings. If anyone has any contacts in those companies, please PM me and I will see if they will talk to me.Oct 3, 2021 at 5:43 pm #3728754Roger CaffinBPL Member
@rcaffinLocale: Wollemi & Kosciusko NPs, Europe
since I tested with 1x to 4x that weight, I think the results are still reasonable.
But I suspect using a figure of 5 squ feet might be closer to reality. 2 sqft for torso, 2 sqft for both legs, 1 sqft for arms – which often are not even on the material.
We (Sue & I) have some BPL Cocoon jackets from at least 14 years ago. They are still fairly good. They are stored between trips on coat hangers. OK, I have been considering replacing them with something using a modern synthetic, but I have not yet done so.
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