The invention provides a polymeric composition for use in making membranes which are relatively impervious to liquid water, but which are relatively pervious to water vapour. The composition comprises a mixture or blend of a thermoplastic elastomeric base material and a modifying agent. The modifying agent reduces the stickiness or tackiness of the base material. The modifying agent forms 5-40% by mass of the mixture, while the base material forms 60-95% by mass of the mixture.
