ePTFE at a glance
- Full name
- Expanded polytetrafluoroethylene
- Used in
- Gore-Tex, eVent, and others
- Mechanism
- Microporous, hydrophobic
How the film is made
PTFE is the polymer sold as Teflon. Stretch a thin sheet of it rapidly and it doesn't tear, it fibrillates into a lattice of nodes and fibrils with enormous numbers of tiny voids between them. Those voids are the pores, and they're what makes the film work.
Why it works
The resulting membrane is hydrophobic, so liquid water is repelled at the pore openings while vapour molecules pass through freely. It's also extremely thin and mechanically fragile, which is why it's always laminated to a face fabric and usually protected on the inside as well.
How it compares with polyurethane
ePTFE holds up better than polyurethane against contamination in most conditions, which matters because body oils, sunscreen and detergent can block a membrane's pores. It's also the reason older waterproof gear is caught up in the PFAS conversation: PTFE is a fluoropolymer, and the industry's move to ePE membranes and PFC-free finishes is a response to that.
What this means when you're choosing
- Whether a shell names its membrane at all, since unnamed usually means polyurethane
- How the membrane is protected, because body oils are what clog ePTFE
- Wash instructions, which for these fabrics are maintenance rather than optional
The common mistake
Washing it with ordinary detergent
Detergent residue is surfactant, and surfactant left in the fabric attracts water rather than shedding it. Use a technical cleaner, rinse twice, and tumble dry warm to reactivate the DWR. Fabric softener is the worst thing you can put near one.
Common questions
Is ePTFE the same as Gore-Tex?
Gore-Tex was built on ePTFE and is the best-known example, but it isn't the only one. eVent and several other membranes use ePTFE too, and newer Gore-Tex products use an ePE membrane instead.
Can an ePTFE membrane get clogged?
Yes. Body oils, sunscreen, insect repellent and detergent residue can all block pores, which is why breathability improves after a proper wash. Many ePTFE laminates add a protective layer specifically to slow this.