Waterproof Breathable Rain Jacket Construction…

I have been wondering about the same thing.  This is a complicated subject.

I think everyone uses nylon.  In order for WPB to work, the outer surface has to be hydrophobic.  So they treat it with fluoridated chemicals.  That makes it hydrophobic for a while, but it wets out after a while.  Then it becomes less breathable so the inner surface of the WPB gets wet.

As an aside, I wish people would test to see how long it takes to wet out, how much rain,…  It seems like tests are more with the initial fabric that is only briefly exposed to rain.

There’s something about Neoshell fabric that makes it better.  I made a rain jacket with it.  Nylon with, I believe, a fluoridated DWR.  I can walk around in the rain for hours and it maintains DWR.  The inner surface doesn’t get wet.  I need to test this more though.  You would think in western Oregon I’d have sufficient opportunity to test.

I made a jacket from RSBTR generic WPB fabric.  I like it because it’s lighter.  But then it also got ripped.  It wets out in the rain after about an hour, then the inside surface gets wet.  Stuff in my inside pockets, and my shirt get wet.  They don’t make it anymore.  I have had similar experience with other generic WPB fabrics.

I just made a jacket from Powershield pro ultralight but haven’t tested it yet.  I think it will be the same as the Neoshell.  You can get both of those from Discovery Fabrics in Vancouver B.C.  They were friendly with me over the phone, even though I was from the U.S.  They said they were exempt from tariffs because they originally bought it from the U.S.

A complication is the fluoridated DWR treatments, is they are harmful to the people that manufacture them, and to the wearer, and to wildlife.  They used to have C8, but that has been discontinued.  Then C6 which is probably also discontinued.  Then C0 which I think they currently use but may be discontinuing also.  Maybe they have some other chemical they’re using.  Maybe these fluoridated chemicals aren’t actually that bad, possible to manufacture without polluting .  This is all very confusing and opaque, at least to me.

Polyester is naturally more hydrophobic than nylon.  It’s not as strong as nylon, but not that much, not really an issue.  But then they treat the polyester so some fabric is hydrophobic and some is hydrophilic.  I don’t know if the treatment is fluoridated.  I don’t know if it wets out in the rain after a while.  Any polyester fabric I’ve used wets out.

Polypropylene is naturally very hydrophobic.  You don’t need to treat it with DWR.  I don’t think it wets out in the rain at all.  It’s weaker and melts at a lower temperature than nylon and polyester.  I don’t think this would be an issue, you might have to have slightly higher denier fabric.

I’ve made gaiters with polypropylene fabric.  They do not wet out when I walk for hours in wet brush.  The only problem is the only fabric I see is very low denier spun bonded fabric that rips when it brushes against a stick.

So, I wish that they made WPB fabric with polypropylene fabric on the outside instead of nylon or polyester.  Then they wouldn’t have to treat with DWR that doesn’t work very well.

One problem I see with that is polypropylene is generic.  Manufacturers couldn’t patent it.  If someone made a better WPB, others would immediately copy and the product would become generic so the price they could charge would be limited.  Better to come up with some cool named new DWR treatment.  That doesn’t work very well.

Another thing would be if people came out with polypropylene woven fabric with several deniers, like 15 or 20 and 200.  Then I could make my gaiters that would work.  I think that would be straightforward to produce such fabric.  The only woven fabric I’ve found is from Mood fabric.  It’s intended for upholstery.  I think it’s very heavy but they don’t say.  And it doesn’t look very strong.  Lot’s of spun bonded polypropylene fabric available in different weights – at my local fabric store and on amazon.

I made a shirt with the spun bonded polypropylene fabric.  I need to test in the rain.  I think water would bead off the outer surface, but if it was hit with rain drops, water would go through.  That’s why you need a WPB membrane.

One other complication is that if you have too much insulation, then you start sweating.  If you have a jacket and a base layer and you’re exercising vigorously at a temperature greater than maybe 40 or 50 F, that’s too much so you’ll sweat.  Even if the WPB was working perfectly.

It’s easy to confuse sweating from too much insulation with WPB failure.

There are a few 100% polyester jackets out there. (OR Strotoburst, MH Stretch Ozonic & Trailverse, Patagonia Boulder Fork & Triolet to name a few…) But you’re correct, in that there is a lot of opacity regarding materials & information. I was reading something yesterday where the phrase “There’s money in the mystery” was oft repeated, and that is certainly the case with waterproof-breathables.

I guess I’m wondering if Polyester outer layers are superior against wetting out, vs. the more common Nylon-outer jackets.

Just a few assumptions for clarity’s sake too…

– Discussing jacket materials, without regard to layering underneath. (The wearer is responsible for that.)

– It’s 2026 where forever chemicals are banned, so it’s probably best to focus on “right now” options, and not worry about now-banned, or obsolete tech & materials.

– Mechanical ventilation is important regardless of material, and thus, let’s assume pit-zips are a given…

I don’t think polyester has superior DWR, but I haven’t seem any test results about this.  They just test the fabric in it’s initial state and don’t look at how many hours it takes to wet out.  If anyone has such data it would be interesting.

I think C0 is what they currently use.  Not as good as C6 and C8 but good enough.  Maybe it’s more susceptible to dirt so you have to wash it more often.  Maybe you have to re-treat it more often.

The thing about the inner layers is that it confuses things.  People may think the WPB is failing when actually it’s just too much insulation.  Even just a base layer and jacket may be too much.  In that case making a better WPB is largely futile.  You could just remove your jacket and let your base layer and you get wet, and then dry off when you get to shelter.  I need to try my polypropylene shirt in the rain.

My opinion about ventilation is a bit off a lot of people.  When I’ve tried pit zips they didn’t seem to do much.  What does work is to unzip the front of the jacket.  That much ventilation is somewhat effective.  It also reduces insulation so it helps with that.  But not so good if the rain is blowing from the front of you.

Richard Nisley once posted some data showing Nylon has 4.5% regain (moisture retention), polyester 0.4%.  So when the DWR does fail, nylon will wet out faster, absorb more water, be heavier for it and take longer to dry, all else equal.  But they rarely are.  Material thickness and construction will matter as well in these areas so a polyester of one construction could wet out faster and be heavier than a nylon of a different construction.

This also doesn’t mean DWR will fail earlier in nylon.  I think a more important factor is whether the DWR adheres better to one material type and construction or not.  A quick online search result said DWR adheres better to nylon than polyester.

Insectshield applies permanent (durable) permethrin treatment to synthetic fabrics through a proprietary process where the application acts more like a dye than a “paint”.   It would be a nice step forward if a safe DWR could be formulated that behaved the same way.

I think a more important factor is whether the DWR adheres better to one material type and construction or not.  A quick online search result said DWR adheres better to nylon than polyester.

Oh, now there’s an interesting angle that I hadn’t thought of! The DWR bonding to the nylon fibers better than Polyester, or vice-versa.

Polypropylene seems more promising than polyester for rain gear, but we have to rely on the manufacturers to make fabric appropriate for our uses, which they currently do not. Perhaps in the future.

This isn’t the first time polypropylene has been considered. Frogg Toggs uses polypropylene (sometimes combined with polyethylene, depending on the product) which traces back to 3m Propore in the past (with DriDucks in between the two, time-wise). Frogg Toggs is actually pretty close to what we want: If only it could be a little bit more breathable…

The problem is that there are so many factors involved that I don’t know where to start. Even for myself there are too many unknows, let alone that I can explain it all to someone else.