Zirfon (R) is a porous composite separator material composed of a polysulfone matrix and ZrO2 which is present as a powder. The manufacturing is based on the film-casting technique. The separator is very stable in concentrated KOH solutions at elevated temperatures. Even with a high loading of ZrO2 it is possible to produce very flexible separators with attractive mechanical properties. The main challenge for this Zirfon (R) material is to replace the asbestos diaphragms which are presently used in industrial alkaline water electrolysis. Different companies are already testing this separator. Excellent results have been obtained. Another field of interest is related to the use of such a separator in Ni-H-2 batteries both for earth and space applications.