Restoring a shelter with a degraded PU coating

[Nick Gatel]

This came up in another thread, so I am starting a new thread to avoid hijacking the other one.

In that thread I stated this about my Chouinard Pyramid,

These are PU coated nylon, so waterproofing is a bit of a task, as you need to remove the PU coating first. I need to re-do mine, a job for this fall.

Greg Mihalik asked,

Just curious – What dissolves PU but not nylon?

I am not a fabric expert, so if I present anything about fabrics that is incorrect you have been forewarned :-)

I have successfully restored a few Polyurethane (PU) coated nylon shelters over the years. Years ago most shelters and tarps were PU coated ripstop nylon. Today there are still PU nylon  shelters from a lot of the larger tent manufacturers, however a lot of the “UL” tents from the likes of Sierra Designs, MSR, etc. are starting to use silnylon or a PU/Sil nylon.

So how do you know if you PU coating is bad? First, it might be leaking. Or you may see the PU coating actually peeling. But usually when the PU starts to degrade the fabric starts to get sticky when it is folded up and stored and/or it starts to smell bad. The smell is unique. The closest thing I can compare it to is vomit.

To restore the fabric you will need to remove all of the PU coating, which is applied to the inside of the fabric. I don’t know of any chemical that will remove the PU without damaging the nylon. So we need to wash the coating off.

One thing you should NEVER do is put your shelter in a washing machine, whether it is PU coated or silnylon. There is on exception to this rule: if you want to remove the PU coating, the washing machine is your friend. Here is what I do.

• Machine wash it with dish soap, such as Dawn.
• Machine wash it again with WooLite.
• If all the coating is not removed, a soft nylon brush with dish soap and water should finish the job. Be gentle!
• Run it through the washer again without any soap.
• Hang dry it.

Disclaimer: Do this at your own risk. If for some reason the shelter is damaged by the washing machine I am not liable, not responsible, and I probably do not exist.

Once the shelter is completely dry, you will need to coat the inside of the fabric. Years ago I made my own mixture, but McNett’s Gear Aid Tent Sure Polyurethane Sealant is a better way to go. Follow the instructions.

Some shelters you may need to apply it in sections, with the shelter spread on top of a large table. With my pyramid I can just set it up in the backyard inside-out and apply the Tent Sure.

Now you need to let it dry for several days.

Lastly, apply a thin layer of talcum powder before you store the shelter.

 

 

 

[David Thomas]

While I agree that putting a shelter in a washing machine is always a risk because:

• the physical stresses (especially in a top-loader) can tear seams,
• pockets of water get trapped making for heavy and unbalanced loads, and
• detergent, especially, delaminates the PU coating.

If, however, you WANT to remove the coating, and especially if you have a front-loading machine (or go to the laundromat and use their front-loader), then I’d suggest a modern detergent like TIDE versus milder options like Dawn or Woolite.  The nylon on its own is very resistant to almost everything (except DEET) and will take hot-water washes, lots of detergent and hot dryers just fine.  I’ve got 100% nylon articles I’ve been doing that with for 35 years now.

OTOH, the lovely thing about a washer is that it does all that agitating so you don’t have to.  If the only reason to put a shelter in the washer is to delaminate the coating, then use a modern detergent in a trash can.  No physical stresses and you can let it soak for hours, stirring occasionally with 2×4 or canoe paddle.

[DAN-Y/FANCEE FEEST]

Do you think a heavy coating of talcum powder would impregnate the pu coating to a point of eliminating the odor and stickiness?

[Nick Gatel]

Dan,

My experience is once the PU starts to peel off, get sticky, or smell there is nothing that will stop it. Others may have had luck with some method, but I haven’t heard of one.

Years ago many of us used PU coated nylon tarps. These were pretty inexpensive compared to a tent and much more likely to have a problem. Wasn’t unusual for me to have a problem in a year or two. I have a 30+ year old Sierra Designs Clip Flashlight and a same vintage Sierra Designs Super Flash and the original PU coating is still good. Have to store them completely dry and best in a cool environment. Mine have always been stored in the garage, which isn’t a cool environment in the desert. Also UV exposure accelerates the degradation. I normally keep my shelters in my pack unless it is going to rain or snow, which prolongs the life.

I rarely use my Chouinard anymore, usually once a year for fun. I should probably get rid of it, but renewing it will be a fun project for my blog. I’m a pack rat and have a lot of gear I bought decades ago.

[Rodney Ackerman]

So glad to see the information in this thread. My SD Mondo 5 fly was replaced (not a new one) by the mfr at no cost to me a number of years ago because of the tacky undercoating issue ( and yep, yukky vomit smell). I had been storing it in the attic of garage. Oops! Definitely very hot in Michigan summers.

Since then I have stored the replacement in the “cool,dry” environment as suggested. However, this fly is now getting sticky and smelly. So much for the environment as being the only factor in the cause of degradation. I suppose it could be that it was already beginning to deteriorate prior to me receiving it.

Nevertheless I will be using the suggestions here to restore it as it is a great 5 person “grandkids” tent.

Thanks guys for this information. Always appreciate it when I find relative solutions while browsing around the site.

Rod

 

[Anonymous]

Perhaps I am missing something, but if your tent, fly, or what not has degrading, delaminating PU, and you take off the coating to reapply more…why the hey Zeus would you apply a crappy PU product to it instead of silicone?   If you use a crappy PU type product, will just happen again and probably in the nearer future (meaning it likely won’t last near as long as the manufacturer applied, previous coating).

Well applied, right blend of silicone to spirits is pretty durable, and easier/quicker/more efficient to re-coat, because it doesn’t delaminate like PU. It just gradually wears off, but as long as there is some still bonded to the fibers, then you just reapply more later.  There is no work in trying to wash the rest of it off in order to reapply more.

So yes, I vote for turning your once PU coated tent into a silicone coated tent. : )

[Buck Nelson]

I’d like to add that enough DEET will dissolve almost all synthetics, except for nylon. Nylon is not dissolved by DEET, although coatings or any other synthetics which are part of the nylon material might be.

[Franco Darioli]

from Rodney :
“Since then I have stored the replacement in the “cool,dry” environment as suggested. However, this fly is now getting sticky and smelly”

There is a line of thought that it can be caused by the material not off gassing so the gas is doing the damage. This should be more obvious on the inner parts of a tightly stored tent.

[Edward John M]

What gas would that be Franco?

Loose is what I have always tried to do but I have lost a couple of tents to this stinky delamination over the decades. Storing the fly and the inner separately may help and I only just thought of that but taking apart integral pitch tents can be a PITA sometimes

[Franco Darioli]

What gas ?

Apparently  isocyanates but I am only passing on a theory.

[Rodney Ackerman]

Could not say if the inner most places are worse than others, but there are definitely places with greater stickiness. Maybe that is true.

This seems to be a common issue. Could it be the nature of the beast and is inevitable? Mine is over 20 years old. Perhaps it is just at the end of its life and is in need of being restored?

Having just looked at OsHA site and seeing this…maybe I should pitch it instead! Lol

“Isocyanates are compounds containing the isocyanate group (-NCO). They react with compounds containing alcohol (hydroxyl) groups to produce polyurethane polymers, which are components of polyurethane foams, thermoplastic elastomers, spandex fibers, and polyurethane paints. Isocyanates are the raw materials that make up all polyurethane products. Jobs that may involve exposure to isocyanates include painting, foam-blowing, and the manufacture of many Polyurethane products, such as chemicals, polyurethane foam, insulation materials, surface coatings, car seats, furniture, foam mattresses, under-carpet padding, packaging materials, shoes, laminated fabrics, polyurethane rubber, and adhesives, and during the thermal degradation of polyurethane products

Health effects of isocyanate exposure include irritation of skin and mucous membranes, chest tightness, and difficult breathing. Isocyanates include compounds classified as potential human carcinogens and known to cause cancer in animals. The main effects of hazardous exposures are occupational asthma and other lung problems, as well as irritation of the eyes, nose, throat, and skin.”

I know…probably have to breathe it for years on end for these symptoms. This site did not show the MSDS and I am not going there.

Not sure when I might get to restoration, as there is no imminent need and thus my motivation is low.

[Roger Caffin]

The whole PU thing is complicated, and I am not 100% sure I understand it fully. However, this is my understanding.

The first PU was a water-based coating, which was polymerised on the fabric. You had to get the polymerisation just right for the coating to last a long time. Unfortunately, not all coating plants managed this. Their coatings lasted for a few years (enough for the warranty), then water crept back in and degraded the result.

Since then the chemists have come up with a different form of PU: thermoplastic PU or TPU. Normally this is hard and is used to make things like phone cases. However, it seems that a very thin layer can be bonded to fabric to make a waterproof coating. As far as I know, TPU does not degrade the way the older PU did.

By-products can include isocyanates as the material starts with or contained a diisocyante. What this means for safety is not something I have researched.

Silicones are safer.

Cheers

[Nick Gatel]

Almost three years after starting this thread, I finally restored my Chouinard Pyramid PU coating. So far, so good . . .

http://popupbackpacker.com/resurrection-my-chouinard-pyramid-rises-from-the-dead/

 

[Elliott Wolin]

Smelly PU can often be de-smelled with Mirazyme.  This has worked many times for me, but not always, not sure why.

[Roger Caffin]

@Nick

Amazing stuff. Patagonia are to be praised for their work.

Cheers

[R]

Thank you for posting!  I didn’t know this was possible.  I have a Sierra Designs Tiros 2, in great shape, save for the fact that it’s gone all sticky on the inside.  No cracking or peeling yet, but definitely on it’s way…

 

[Nick Gatel]

Amazing stuff. Patagonia are to be praised for their work.

Roger, I really, really like Patagonia gear and the company. Been using it since the ’70s, which was easy since they are based in California. Not to mention Yvon Chouinard, who is the sole owner of Patagonia, has done so much good work outside of his company, how he responsibly runs the company, and how he treats employees. All this good stuff and he was able to become a billionaire.

Patagonia has truly been a pioneer in outdoor clothing, and their history is really interesting. I wrote this post a while back, which reviews much of Patagonia’s history and influence on the outdoor industry. You might find it interesting, Understanding Layers Using by Patagonia Clothing as a Guide. Probably not to your standards or Nisley’s since you guys are scientists and I’m just a guy who has to figure out what works for me by experience. What’s the saying, something like, “If you learn by your mistakes, I must be a genius.”

[Nick Gatel]

Thank you for posting!  I didn’t know this was possible.  I have a Sierra Designs Tiros 2, in great shape, save for the fact that it’s gone all sticky on the inside.  No cracking or peeling yet, but definitely on it’s way…

So far I’m thrilled. But how long will it last?

Years ago I recoated a couple flat tarps used as shelters, and the nylon wore out before the new coating did, but I treated them hard, sometimes folding them for use as groundsheets. But most people today aren’t interested in this, they just buy a new, lighter, and “improved” product.

Over the years I had a few things crack and peel. But the sticky problem seems to be when the two coated surfaces are stored in contact with each other. Storing a tent wet or damp will cause this, but I have always dried damp gear before storing it. I have two really old Sierra Design tents — one of the original Flashlights from the ’70s and an ’80s Super Flash — both of the rainfalls are still in good condition and both were purchased prior to the Chouinard.

[R]

Nick,

Any reason you stuck with PU instead of switching to silicone?

Would the Permatex Flowable silicone work for this, or would that still need to be diluted?

[Nick Gatel]

Any reason you stuck with PU instead of switching to silicone?

I thought about this. From my research, and I’m no expert, PU fabrics are coated on the inside of the material. SilNylon is actually impregnated with silicone on both sides. In both instances, it seems to me, the waterproofing saturates the material on a microscopic level, especially since nylon is hygroscopic.

My thought on this is that while I could remove the coating of PU on the fabric, it would be unlikely all of it would be removed down in side the material. Since silicone wouldn’t adhere well to PU, I had my doubts. Plus I would probably have needed to silicone both sides, instead of renewing he PU on one side of the material.

Am I right or wrong? Who knows? J

ust seemed simpler to go with the PU. The PU is a thin milky white material that spreads easy with a brush, Actually it is the consistency of milk and much easier than the silicone/mineral spirits concoctions I have used in the past.

[R]

Makes sense – thanks.

[Mark Ries]

Bringing back old thread. Years back I used a product to recoat a tent called Kenyon recoat 3. I used it on a eureka timber lite . I used it according to directions it went well and looked good dried. The next rain we used it in kept us dry but another rain after that we packed the tent up wet as it was still raining in the morning when we got to our location that night and set up the tent the coating had turned back to white liquid goo lucky for us there were shelters also and we used one that night and left tent up to dry which it did. I’m kinda wondering if Nick or anybody else has had that experience when recoating a tent

[Roger Caffin]

It is water-based. Get it wet for too long (12 hrs?) and it will revert to that milky-white goo as you called it. It may even then wash off.

This is characteristic of all of the older ‘PU’ coatings: they will degrade when wet. The stuff is no longer a realistic option for outdoors use, and has been superceded by ‘TPU’ which is a very different thing and works. But I don’t think you can recoat TPU at home.

New tent I think.

Cheers

[Mark Ries]

Thanks Roger. It didn’t take 12+ hrs, more like 7-8. So can I assume then that the McNett Gear-aid tent sure polyurethane sealant that Nick used would have the same problems?

[Mark Ries]

I guess maybe it might have taken 12+ hrs cause we had an all night rain before packing up in the morning wet then 6-7 hrs to the next campsite

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