The ePTFE is a kind of microporous membrane formed from polytetrafluoroethylene by extrusion.
It is found that the surface of the PTFE membrane is full of fibrillary micropores, and there are as many as 9 billion micropores per square inch. The cross-section is a kind of network structure, and the three-dimensional structure of the pore has very complex structures, such as network connection, hole inlay, channel bending. The diameter of the water vapor molecule is 0.0004µm, while the diameter of mist with the smallest diameter in rainwater is 20µm. the diameter of the drizzle is as high as 400µm, the pore diameter of polytetrafluoroethylene varies from 0.1µm to 0.5µm. As we can see, the pore diameter of the expanded PTFE membrane is between water vapor and rainwater, so it is the top waterproof and breathable material. The composite fabric is made of expanded polytetrafluoroethylene film (ePTFE) and polyester fiber by a special process.
PTFE is stronger. You can see and feel the difference in the material, and unlike ePTFE, it will not break down when it's touched. Since ePTFE material is touch-sensitive, it often requires support. As a result, many expanded PTFE films used in protective vents are laminated to fabric to minimize damage.