Symmetric membrane
Also known as: homogeneous membrane, isotropic membrane, uniform membrane
Membrane whose structure and pore size are the same across the entire thickness — as opposed to an asymmetric membrane with a dense skin layer over a porous support.
Description
A symmetric (also: homogeneous or isotropic) membrane has the same build across its entire thickness — material density and pore size are constant from the top to the bottom edge. Classic examples are dense hydrophilic polymer or elastomer films (e.g. PU, PES or PTFE films) and some composite foils. In textile use they are often called monolithic membranes: moisture does not pass through micro pores but diffuses outward through the swollen polymer.
The counterpart is the asymmetric membrane used in reverse osmosis, ultrafiltration and many outdoor laminates: here a very thin, dense skin layer forms the actual separation plane while a much thicker porous layer serves as mechanical support. Symmetric membranes are structurally simpler, chemically more homogeneous and easier to reproduce — but often slower and with limited throughput. In apparel, symmetric builds are typical of monolithic rain and wind membranes where no pores can clog.
- Build and pore size constant across the thickness
- Vapour transport by diffusion (monolithic)
- No cloggable micro pores — chemically and mechanically robust
- Counterpart: asymmetric membrane with dense skin + support
Properties
| Build | Homogeneous, constant pore size across the whole thickness |
|---|---|
| Transport mechanism | Diffusion through monolithic polymer |
| Counterpart | Asymmetric membrane (dense skin + support) |
Related product categories
Sources & references
2- Wikipedia: Membrane Wikipedia — Freie Enzyklopädie https://en.wikipedia.org/wiki/Membrane
- Wikipedia: Synthetic membrane Wikipedia — Freie Enzyklopädie https://en.wikipedia.org/wiki/Synthetic_membrane
