Impregnation

Here's where I'm seeing "coated": http://www.bearpawtents.com

You are right that there is not much difference *for silicone coatings*. The stuff is put on using a coating process – a doctor blade on each side. But the end result is impregnation. PU coating is done the same way but the PU does not penetrate the fabric: the stuff sits on the surface.

Cheers

From what I have been told "coated" means its only applied on one side were as "impregnated" implies both sides covered.

Roger,
If the process is the same, why does silicone penetrate the fabric and not PU?

Rog and Jace, thanks for the replies!

I emailed the mfr. His response:
—
Silnylon is made by bathing the ripstop as it comes off of the mill. Therefore, the ripstop is coated on both sides and within the weave. There is no difference between the terms silicone coated, double-coated silicone ripstop and impregnated. They are all made the same and they are all the same material. There is no such thing as "single coated silnylon".

Thanks,
John
—

Thats true, there really isn't much of a difference between the two. Its mainly just marketing hype. Essentially all silnylon is coated with an excess amount of liquid silicone and then the excess is scraped off with a knife before curing.

Just a few Coating/Impregnation methods:
roll over knife
roll over gap
dip/immersion
kiss coat
gravure roll
against the roll

Hi Travis

Another reason for calling silnylon 'double-coated' is that people are familiar with the concept of coating. 'Impregnation' might not mean the same thing to some people … :-)

But in answer to your question and to OP about how it is done: not all coating plants actually immerse the fabric. Many do literally scrape a gloop of polymer over the fabric with a huge 'doctor' blade, like a putty knife. Getting this right is tricky, which is why there are 'seconds' for sale.

Now, why does the silicone polymer go into the fabric while PU does not? That is a function of the surface tension between the polymer and the fabric. The silicone polymer is designed to really 'wet' the fabric; the PU polymer usually does not.

Does it matter whether the fabric is 'coated' or immersed? Yes and no. If you are talking about double-coated silnylon, then it does not really matter. But you can also get PU/silicone fabric: silicone coating on one side and going a bit into the fabric, and PU coating on the other side and also going a bit into the fabric. You can only do that by coating.

This sort of fabric (PU/silicone) has a much higher water pressure rating than double-coated silicone: I have tested both and watched what is happening at high pressure under some magnification. Water can actually penetrate the current dry-look silicone coatings: it is slightly porous. But water can not penetrate the PU layer: it is not porous. So if you put the silicone side against the water you can SEE the water penetrate the fabric at pressure. This does not happen when the PU side faces the water.

Unfortunately, it seems that the PU/silicone fabrics are only made in China to order, and an order is hundreds of yards at a time. I have not found anyone selling the fabric by the yard (yet).

Ain't technology wonderful?

Cheers

Roger

You can get it from http://www.extremtextil.de/catalog/Fabrics/coated/Nylon-tent-fabric-silicone-PU-coated-80g-sqm::1162.html in your favourite colour

PS why do posts not accept hyperlinks anymore?

DAD:
"Well, you see, son….when a man sees a woman he likes…he kind of walks over and says…well, he looks over and…ummm…he writes her a letter expressing…well, ummm…"

SON:
"How did you meet mom?"

DAD:
"Well, that's different!"

Yeah, the title of the post was pretty funny when I first saw it!

Fantastic Roger. Thanks much for the explanation.

As for technology? Its the cause of and solution to all of life's problems.

What's the difference between impregnation and coating?

Your aim.

Sorry. Couldn't help it. Mods, feel free to delete!

LOL!

Hi Stuart

80 gsm? Way more than I'll buy. I have samples from Asia which are below 40 gsm, with PU/silicone coating. But they won't talk about anything short of 1000 m.

However
http://www.extremtextil.de/catalog/Fabrics/coated/Ripstop-Nylon-tent-fabric-silicone-PU-coated::1000.html
is more interesting. Hum …

Cheers

What are the advantages of a silicone/PU coating over regular silnylon?

The hydrostatic head appears very similar to
http://www.extremtextil.de/catalog/Fabrics/coated/Ripstop-Nylon-tent-fabric-silicone-coated-50-g-sqm-2nd-choice::1195.html
which is half the price (and which I have already ordered!)

Hi Stuart

> What are the advantages of a silicone/PU coating over regular silnylon?
* you can use ordinary seam-sealing tape on the PU side
* the PU layer is inherently more WP than the silicone layer – see my reply to Travis further up the page. Silicone polymer is actually micro-porous under pressure; PU is not.

Cheers

I've given my TarpTent Moment a silicone re-coat on the outsite top 1/2 of the tent to prevent the dreaded mist-through in a driving rain.

After 2 seasons of use the extra coating shows no signs of coming off. I'm hoping that, even though it was not exactly an inpregnation of the silnylon, it still soaked into the weave enough to have a durable grip. The mix was a thin 5:1 ratio of odorless mineral spirits to GE Silicone caulk.

Anyone ever have re-coated silnylon "delaminate" or peel off?

I recoated bottom of bivy, both inside and outside

I used probably 2:1 dilution

Outside against ground started peeling off after a few trips – I think I won't do this on the against ground side again

Inside againsy my mattress I think is maybe peeling off some after maybe 100 nights, which isn't too bad

I think thinner dilution might work better

I think a rain fly where there is no direct wear would work better

Has anyone tried to re-coat polyurethane coated fabric?

A friend who runs an outdoor program for high school
kids got stuck with several thousand dollars of tarps with a .25 oz urethane coating of poor quality (probably a water based coating rather than
a solvent coating) which wasn't enough
to make the fabric waterproof under the pressure of rain.

Yes, David, I have, with Kenyon and McNett (TentSure) products, but never successfully.
It seems that once the original PU coating begins to degrade, coatings will not help.
I have some 20 year old TNF PU nylon fabric (1.7 oz with coat) that has never degraded, so I guess it is best to start with the best quality available, no matter what fabric/coating you are using. Possibly if your friend's tarps are new, and the thin coating has not begun to degrade, a recoat product might work. It is quite expensive, though, for such a large number of tarps.