Improved durability of diaphragm for higher temperature electrolysis

A process or method for obtaining a diaphragm, the process comprising the steps of;

• i) providing a casted diaphragm piece comprising a polymeric binder,
• ii) functionalizing the polymeric binder, wherein the resulting functionalisation enables crosslinking,
• iii) optionally rinsing the resulting functionalized diaphragm from step ii) with a solvent,
• iv) further processing the diaphragm piece comprising
• a) drying the rinsed functionalized diaphragm from step iii), at about 20° C. to about 80° C. and during a period from about 12 h to about 48 h, or until the diaphragm is essentially free of solvent and adding a cross-linking agent in the diaphragm matrix after drying the functionalised diaphragm, or
• b) displacing the solvent with a cross-linking agent in the diaphragm matrix, wherein the cross-linking agent is a di-alcohol, such as e.g. ethylene glycol or propylene glycol, or a tri-alcohol such as e.g. glycerol,
• v) crosslinking the dried diaphragm resulting from step iv), at about 180° C. to about 240° C. during a period of about 12 h to about 48 h,
• vi) after completion of the crosslinking from step v) the diaphragm is rinsed in solvent and optionally post treated.