[jkqwzsoo]

Thinking about it for a minute, I’m not sure why we need fluoropolymers for waterproof technical fabrics. Unless I’m very much mistaken, PDMS rubber, polypropylene, polyethylene, and other materials provide similar levels of water resistance, without requiring the use of fluorine-containing compounds. Most explanations I read for Gor-Tex-type materials using PTFE (e.g., [0]) reference the hydrophobicity of the material, which is (IMO) similar to explaining why cars are powered by rockets because rockets are very fast. Cars are, of course, not typically powered by rockets because it is not necessary.

PDMS rubber, polypropylene, polyethylene, and PTFE all have very high water contact angles (a measure of the strength of interaction of water and the surface) and low water uptake [1]. I work with a stretched polypropylene film (Celgard — a material that is often used as a support/spacer material in Li-ion batteries) and it’s extremely hydrophobic. I used a piece of this film to build a bubble trap ([2]), for example (bubble traps typically use PTFE membranes…). It is not optimized for water resistance, so it does wet eventually, but it’s pretty good for “not trying”. Surfaces coated with PDMS (or glass coated with short PDMS chains — i.e., silanized glass [3]) are extremely hydrophobic.

The only time I personally use PTFE (or PFA, MFA, FEP, or ETFE) is when I need materials to be resistant (including both resistance to chemical degradation as well as swelling) to strong organic solvents (like NMP, THF, etc.) or strong acids and bases (like piranha, aqua regia, or a nitrating solution). These conditions are unlikely to be encountered while cycling.

This all said, I’m not an expert on the design of Gor-Tex type materials. However, I assume it is highly related to the pore structure of the materials to prevent liquid water intrusion (the same as for membranes designed for membrane distillation). Given the similar hydrophobicity of these materials, it seems like it should be possible to produce similar results with PP, PE, etc. And this is all before introducing the ability of nanomaterials and nanopatterning (perhaps transferred with imprint lithography [4]) to produce metastable ultrahydrophobicity [5] on the surface of materials.

[0] https://www.sungodtech.com/how-much-do-you-know-about-ptfe-w..., https://outdoorguru.com/how-to-en/how-does-waterproof-and-br... [1] https://www.accudynetest.com/polytable_03.html, https://omnexus.specialchem.com/polymer-properties/propertie... [2] https://static.wixstatic.com/media/ec0ae9_aacc723ea77d46619d... [3] https://en.wikipedia.org/wiki/Silanization [4] https://pubs.acs.org/doi/10.1021/acsomega.8b03138 [5] https://en.wikipedia.org/wiki/Wetting#Cassie–Baxter_model

[qbasic_forever]

There are polypropylene waterproof fabrics, particularly Frogg Toggs brand gear is popular in the ultralight world: https://www.froggtoggsraingear.com/technology.shtm

They're good jackets in my experience--truly waterproof and breathable like goretex, and very inexpensive. They are very very fragile though and easily rip or tear open from any sharp objects, like getting poked with a branch. As I understand it's basically like tyvek house wrap material but made into a more flexible material for clothes. Goretex stuff is more durable in my experience.

[exmadscientist]

As the article says (see also this comment https://news.ycombinator.com/item?id=33856967 ), that's exactly the direction they're planning to head. Given that their PE membrane isn't on the market yet, there must be some R&D issue or other, but that's life in R&D.

[twic]

PTFE also repels oil. That means that the holes in the face fabric and the pores in the membrane don't get clogged up with oil from the wearer's body. Do those other polymers have that property? I honestly have no idea how significant this is compared to the hydrophobicity though.

[snowwrestler]

The PTFE in GoreTex is expanded (ePTFE) and while it chemically does not bind to oil, oil can mechanically clog the pores. For decades GoreTex has had a layer of polyurethane on top of the ePTFE to prevent this.