Restoring silnylon (with links)

This thread may present a good example of where we go wrong with MYOG.  We start for example with Roger’s successful outdoor experience with using Permatex for tent reinforcement patches, and find his experience can be duplicated.  That for me is what they call “QED.”

Instead we dig deeply for every bit of data we can find, and discuss the differences ad nauseam.  At this rate, when do we get a tent built?  My favorite recent examples of this syndrome were the threads comparing strength and durability of silnylon vs silpoly.  With the possible exception of data posted by William Chilton, this became a race to the bottom with data mining.  Even at one point driving a well regarded cottage tent maker to distraction.

I believe Thomas A.  Edison’s approach was to experiment and find out which light emitting filament worked best in practice.  And with that approach, he got quickly to working applications.  Sure, someone eventually came up with a better filament, and today, LED bulbs.  But would that ever happen if Edison were still down in the weeds data mining?  And unlike Edison, we are just MYOGers finding out what works in practice.

With that said, please note that I forgot to mention the silicone patches now marketed by GearAid:  https://www.gearaid.com/products/tenacious-tape-patch-silnylon.

Whether there is now but one tenacious tape that bonds to both sil and PU coated fabrics, or “blends” thereof was not clear to me from the info found online.   It is hard to believe that it is so, not to mention the strength of the bonds, and that the weight of the patches could also be considerable.

With respect to DIY brush-on coatings, my earlier post noted a preference for using durable materials, and replacing  a tent floor if and when needed.  I’ve not seen a compendium of experiences on BPL sufficient sufficient to draw conclusions about thinning silicone in different forms; but from those reported on BPL, doubts led me to simply use better floor materials in the first place.  The argument being that the weight penalty is minimal, and not even that if the floor is one oz/yd2 DCF on many lighter and more expensive DCF products.

Granted that this is not going to get everyone offline and into the workshop doing practical experiments.

This thread may present a good example of where we go wrong with MYOG.
But we have such fun … at little expense. Just electrons.
Otherwise, ROTFLMAO.

My old orange winter tent had a good floor. Light nylon 6,6 fabric, double or triple-coated, made for use on hospital beds, and guaranteed proof against bacterial leakage (ie, a very high HH). Sure, it was a little (little) heavier than the lightest 7D fabric, but it was very reliable.

Cheers

I suggest that the main difference between the Permatx specs and the Wacker specs is the target market.

Certainly. The difference in the target market is also a difference in government regulation. When it comes to the chemical industry, the US is far behind the EU in terms of regulatory oversight and chemical substitution mandates.

The Italian product by Saratoga, for example, is aimed squarely at a consumer market yet the manufacturer provides a wealth of data compared to the poetic metaphors used by Permatex. I’d bet that if Wacker and Saratoga publish these things that it’s not because they think certain users are geekier than others but because EU regulations require it.

Now back to your regularly scheduled program. Would be great if somebody who is knowledgeable were to comment on the difference between neutral-cure and acetoxy-cure silicones in the context of outdoor use.

I THINK …

The acetoxy-cure silicones cure quite fast, which can be an advantage if you want to pack up the tent in the next hour. However, the stuff releases acetic acid, which can be corrosive. It might for instance corrode your tent poles and elbows. It works by absorbing moisture from wherever, so once some moisture has got in then the curing proceeds. So the cartridge sets like a solid ball of rubber (no, not like a rock) within weeks or a month or so.

The neutral cure silicones emit an alcohol while curing, cure more slowly, and may be a bit better outdoors. Maybe. It is also more expensive. The smaller tubes do last a long time if they are carefully capped. But you do not need a lot: a tube would seal several tents if applied carefully.

I am sure there is a lot more to be said, but that is what I know. I use the neutral-cure stuff.

cheers

Thanks, Roger. That’s what I gathered from searching around the net.

I think I’m going to call Wacker in Germany next week and try to see if I can’t speak to somebody with technical expertise to ask them what they recommend. If I find out anything useful, I’ll post back here.

Nothing from Wacker yet, but Fabsil (Granger’s) have confirmed that their solution is a neutral-cure silicone, not an acetoxy one. Their chemist confirms that neutral-cure silicones are better suited to use on outdoor products.

So that would explain why Sam was unhappy with Wacker Elastosil E43, an acetoxy-cure silicone.

If somebody who writes German happens to read this, perhaps it would be worth conveying this information to UL forums in German, where Wacker Elastosil E43 is regularly recommended for seam-sealing. It might not be the best choice, after all.

I’m still interested in hearing from Wacker themselves about which neutral-cure silicone would be best for application to siliconised nylon. My call to Germany was re-routed to their office in France, where my request was promptly ignored. Things are very busy at work this week but when/if I find out anything else, I’ll post back here.

OK, Roger. I give up.  What does “ROTFLMAO” mean?

BTW, will go back to having the fun soon.  Surgeries can really put the kibosh on that for a bit.

Hi Sam

It is old, possibly even from pre-web days when we used ‘news-groups’.

Rolling On The Floor Laughing My Ass Off.

Some degree of amusement and disbelief maybe?

Cheers
PS: get well soon.

Thanks, Roger.  And to my surprise, it was actually on Google.  Nice cartoon.

Anyone know anything about polydimethylsiloxane (PDMS)? It seems to be the most commonly used “silicone oil.” Chinese tent companies have taken to describing their flys as “coated both sides with silicone oil.”

Apparently, they are not the only ones. Westmark described their Ultrasil product similiarly: https://web.archive.org/web/20200315082449/https://westmarkcorp.com/product/30d-nylon-ripstop-ultrasil/

Is PDMS what the mills are coating silnylon with? If so, should we be using it to re-coat silnylon?

PDMS is available. I just ordered this: https://www.amazon.com/gp/product/B00ZM36C98/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

And various supply houses will sell it by the quart in a great variety of viscosities.

Following from the last post…turns out PDMS is “silicone.” Silicone caulk is PDMS plus curing agent, plus additives (silica for durability, other adhesive stuff, etc.).

Doing a little digging, it would be possible to mix up PDMS with a curing agent to the viscosity best suited for brush work. Cost-wish, however, it looks like it would be more expensive than caulk + mineral spirits.

Oh yes, PDMS may be a ‘silicone’, but saying something is a ‘silicone’ is a bit like saying something is a hydrocarbon. There are tens of thousand of each.

If it is an ‘oil’ it is not going to cure to a dry state. Spread the tent out on a wood floor and then try to stand upright on the floor! (Yes, personal experience!)

Needs testing!
Cheers

Roger, yeah, that’s what I thought when I first read about PDMS, but it turns out that when we think of “silicone rubber” it is nearly always cured PDMS. Yeah, there are lots of silicones, and lots of silicone oils, but when we see a tube that says 100% silicone, this means cured PDMS.

In any case, the problem for DIY has always been viscosity. There is nothign wrong with 100% silicone caulk and there is nothing wrong with Permatex Flowable, except for the fact that both are too viscous to paint onto a tent fly. I’m checking with some silicone specialists about the possiblity of getting something like Permatex (PDMS with the curing agent already mixed in, plus maybe some silica for toughness) in lower viscosity.

Stumphges,
I am sure you know how and why I generally use 100% clear silicone caulk and mineral spirits to change viscosity.
Fortunately, unopened caulk keeps for a couple years, however, the most common problem is the curing agent breaking down too soon and never really drying. Some have better shelf lives than others.
Adding more solvent (mineral spirits) is a problem. Even mineral spirits are “wet”, in the sense that they have absorbed enough water to initiate the curing. Keeping it “dry” means that there is none of the pesky water molecules in it, since water acts as a catalyst. While you can make stuff “dry” by adding various chemicals that use up water, the resultant reactions do not lend themselves to strength as they cure. I suspect their problems are: 1) packaging and/or 2) finding a solvent that does NOT allow ANY water to dissolve into it (A nearly impossible task.)

Here is more info (excerpted from here: https://www.askthebuilder.com/caulks/ )
100 percent silicone caulk is made by reducing silica sand into a basic silicone oil polymer. In order to give the caulk body, fillers such as mica (a mineral) and clay are added. These caulks work best when used on non-porous objects such as metals and glass. The silicone oil makes it virtually impossible for paints to adhere to 100 percent silicone caulk. This oil tends to bleed slowly out of the caulk for many years.

100 percent silicone caulks require moisture from the air in order to cure. If you live in a dry climate, you will notice that these caulks take a longer time to dry. As the silicone caulk cures it emits acetic acid, one of the primary ingredients of vinegar. These fumes can irritate your eyes and nose.

100 percent silicone caulks require moisture from the air in order to cure.
Some silicones do require water as a catalyst, while others rely on a solvent to evaporate. The distinction is critical.

The silicones which use water absorb it and start to cure. This typically happens with the stuff you get in cartridges or ‘caulking guns’. The trouble is that once the seal at the tip of the cartridge has been broken, a little bit of water slowly creeps in and the whole cartridge sets into a solid lump of rubber. This may take several months. Cartridges have to be all used up quickly.

The silicones which rely on a solvent are more expensive and usually come in smaller (metal) tubes. They may be labeled as an adhesive rather than as a caulking compound. The glory of this type is that the contents of a 2-year old half-used tube, if well-sealed, will be just as good as when new. I have had tubes last even longer.

Cheers

I had a standard plastic tube of silicone caulk.  After I opened it, and it sat around for a couple years, the silicone in the tube cured into a blob, and there was a liquid that didn’t cure.  I had the end covered with the plastic cap that comes with the tube.  The liquid leaked out a bit through the cap that didn’t quite seal perfectly.

Like Roger just said.

Other times I’ve had tubes last for years.  Check before using by putting a blob out and making sure it cures overnight before using it and ruining some project.

Aside from the general joy of geeking out and overthinking things, all I’m really trying to do is find a neutral cure silicone rubber product that has the right viscosity for re-coating silicone-impregnated fabrics right out of the tube/can. Permatex seems to be a great product with great adhesion to existing coatings – see Roger and Sam’s experiences using it to bond silnylon pieces together.

Permatex is an oxime-cure silicone product with a little silica mixed in, perhaps for toughness. I’m trying to find something just like Permatex but with thickness and viscosity suitable for brushing or spraying onto flys without need for a solvent to thin it.

“the general joy of geeking out and overthinking things”

+1

yeah, getting a container of premixed to the right viscosity makes a lot of sense

Well, continuing to dig around above my pay grade, I found that silicone is very permeable to vapour: https://www.versaperm.com/materials/Silicone%20and%20vapour%20permeability.php

We can file this in the not-quite-completely-useless section.

Stumphges,

That is consistent with the ability of water vapor to penetrate silicone coatings.  Of course it would also apply to silpoly as well as silnylon.  But only the polyester in silpoly is resistant to absorption of moisture.

There may be a solution.  Skytex 27 is a paraglider fabric that is a sub one ounce PU coated ripstop 6.6 nylon from Porcher that is sold by Extrem Textil, as well as some companies in France.  It is not waterproof, but you can’t blow through it either.  The hand, or drape, of the finished fabric is more robust than 7, 10, and 15D silnylons.  Will test some to see how it responds to moisture, not in terms of waterproofness, but rather in terms of whether the fabric holds its shape when wet.  Then will apply a very thin coat of Gear Aid Tent Sure, and test again. If it looks promising will post more info.  Am thinking about a Skytex tent floor that might be superior to one oz DCF.

For silcoated nylon, as mentioned earlier, some of the sil-based sprays do well to rejuvenate tent flies, as I found out with a tent from Wilderness Equipment, an Australian company, a tebt that had endured many lengthy rainstorms.  I’ve never seen a silcoated tent fabric peel, as concerned the OP; rather think the peeling is a product of PU coatings, which can be addressed with Tent Sure and some other PU-based products.

I was doing a section of the GR9 while this thread was revived.

On the Meaningless Geek Front: Stumphges’ comment that Permatex is an oxime-cure silicone further refines the distinction made above between neutral-cure and acetoxy-cure silicones. Oxime-cure is one of the types of neutral-cure formulas (another common one being alkoxy).

And Jerry has requested that S. Seeber test the MVTR of silnylon. Could it turn out that silnylon is a WPB fabric with permanent DWR?!?

WPB?
No. I have never found it at all ‘breathable’.

Cheers

We’re talking about this: https://www.versaperm.com/materials/Silicone%20and%20vapour%20permeability.php

not much use without urethane in the comparison chart, but…

It would seem that oxygen can go through silicone, but that says nothing for water. The oxygen molecule is non-polar, while water is quite polar. As that web site mentions,
The vapour permeability of silicone rubber can very drastically (e.g. by five or six orders of magnitude!) due to several factors, including:
Physical structure
Temperature
Specific gas
The table of permeability is for oxygen, not water. I think we would have noticed if silnylon let a lot of water through.

Cheers