TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preparation (Claimed): Preparation of (I) (where the components (a) and (b) are assembled in the desired order) comprises the steps of:(i) providing each of the gasket layers with at least one recess at one or more locations;(ii) partially or totally filling the at least one recess in the first and in the second gasket layer with the second gasket material; and(iii) applying the second gasket material on the front of the first gasket layer and on the back of the second gasket layer, where the steps (ii) and (iii) are performed in such a way that the second gasket material in the at least one recess (11) in the first gasket layer and the second gasket material in the at least one recess (12) in the second gasket layer join the second gasket material on the front of the first gasket layer to the second gasket material on the back of the second gasket layer. Preferred Components: In (I) at least one recess in the first gasket layer is a hole through the first gasket layer and the at least one recess in the second gasket layer is a hole through the second gasket layer. The first gasket material is a polyimide. The thickness of the gasket layers is in the range of 5-1,000 microns. The gasket layers: on (A) each form a frame; and is in contact with at least one of the electrodes. The surfaces of (A) are completely covered by the two electrodes and the gasket layers. The contact area of the electrodes to the gasket layers is provided with fluoropolymer (poly(tetrafluoroethylene-co-hexafluoropropylene)). The two gasket layers: extend beyond (A) and are in flat contact with one another; and are welded to one another. The second gasket material is: a thermoplastically processable material; a fluoropolymer; and in contact with electrically conducting separator plates. (A) comprises polyazoles. (A) is doped with an acid, preferably phosphoric acid (at least 50 wt.%). (A) is obtainable by a method comprising:(i) mixing one or more aromatic tetra amino compounds with one or more aromatic carboxylic acids and/or esters containing at least two acid groups per carboxylic acid monomer, or mixing one or more aromatic and/or heteroaromatic diaminocarboxylic acids in polyphosphoric acid to form a solution and/or dispersion;(ii) applying a layer using the mixture according to step (i) to a support or to an electrode;(iii) heating the sheet-like structure/layer obtainable according to step (ii) under inert gas to temperatures of up to 350degreesC, preferably up to 280degreesC, to form the polyazole polymer; and (iv) treating the membrane formed in step (iii) until it is self-supporting.The degree of doping is 3-50. (A) comprises one or more polymer(s) obtainable by a polymerization of monomers comprising phosphonic acid groups and/or monomers comprising sulfuric acid groups. In (I) at least one of the electrodes is made of a compressible material. The partially or totally filling the at least one recess in the first and/or the second gasket layer with the second gasket material and the application of the second gasket material on the front of the first gasket layer and on the back of the second gasket layer is achieved by thermoplastic processing in the viscoelastic state. The second gasket material is applied on the front of the first gasket layer and on the back of the second gasket layer by the use of an injection moulding process or a compression moulding process.