Already for a very long time chrysotile asbestos is used as the separator material for alkaline water electrolysis. However, for known health risk reasons and quality drop back of the asbestos raw materials, the asbestos separator is being abandoned, nevertheless the fact that the alternatives are very scarce and still show some drawbacks. Problems of these alternatives are related to their chemical stability in strong alkaline medium at high temperature (above 80°C), and to their limited wettability. Some 15 years ago we developed the ZIRFON^® composite separator which showed very high potential by solving the afore mentioned problems of the alternatives. Nevertheless, for certain applications, this ZIRFON^® separator suffered from limited mechanical strength, and only limited industrial use.

Hence, two years ago Vito started developing the new-ZIRFON^® separator which should completely overcome the mentioned drawbacks. For obtaining this target the new-ZIRFON^® was reinforced with a fabric (PP, ETFE or PEEK), and a fabrication method needed to be developed which enabled continuous fabrication. The latter target was realized by completely reviewing and adapting both the manufacturing process, and the dope formulation. Mid 2006 a collaboration was set up with Agfa as a technological and commercial partner. Within this collaboration a pilot line (50 cm width) for vertical separator casting was constructed. With this pilot several reinforced new-ZIRFON^® separator variants were developed in three thicknesses (250, 550 and 950 µm), and two temperature stability ranges (90°C and 120°C). Their characterization learned that these new-ZIRFON^® separator variants were all hydrophilic and thus wettable in strong alkaline solutions within seconds, have low ionic resistance (2.2 W.cm in 6M KOH at 70°C, or 0.13 W.cm² for the 550µm version), enable working at high current densities (10 kA/m²), do not show dimensional changes, have symmetric surface pore structure, and a total porosity in between 50 and 55%. Moreover, as a result of the new manufacturing process, these New-ZIRFON^® separators have a double skinlayer with identical pores at both sides of it (mean value 0.08 µm) offering a double safety for preventing mixing of gases . Their bubble point is above 7 bar. To conclude it has been shown that the new manufacturing process is feasible at 50 cm width, and that the new-ZIRFON^® separator forms a very interesting alternative for the chrysotile asbestos.

In the paper all characterization results will be shown together with SEM photographs, as well as the future planning for scale up and commercialisation.

Keywords: new-ZIRFON^®, separator, electrochemistry, water electrolysis, hydrogen