Cross-Linked Polyaryl Blend Membranes for Polymer Electrolyte Fuel Cells

The preparation and characterization of different types of proton-conducting polymer blend membranes are presented in this paper. The investigations arc focused on the determination of the thermal stability of the membranes, because thermal stability is one of the important parameters or the application of the membranes in polymer electrolyte fuel cells. In addition to the thermal stability, chemical stability, proton conductivity and mechanical strength are required. The characterization of the membranes was performed by thermogravimetry (TGA), a combined TGA and FTIR analysis where infrared spectroscopy is used for the determination or decomposition products, and experiments on the dependence of W ater uptake (swelling) of the membranes on temperature. Ionically cross-linked membranes have been investigated. The TGA-FTIR coupling experiments showed clearly, that the decomposition of the membranes starts at approximate to 230 degrees C. and that in some cases the principal membrane component which is Sulfonated polyaryletherketone splits off SO(2) at slightly lower temperature in the membrane than in the pure substance. Most of the other polymeric components of the blend membranes were slightly more stable in the membrane than in the pure form. The ionically cross-linked membranes were tested in direct methanol fuel cells as well as in a H(2)/air fuel cell and exhibit a performance which compares favorably with standard membranes.