Characterization of polymer blends PES/SPSf and PES/SPEEK for direct methanol fuel cells

Existing polymer electrolyte membranes (PEMs) applied for hydrogen fuel cells are frequently not suitable for direct methanol fuel cells due to the high methanol permeability. Therefore, new materials are required and in order to avoid laborious fuel cell experiments with a so-called membrane–electrode assembly (MEA) proper characterization methods are needed which can be used as a first estimate. Various methods have been selected, such as swelling measurements, ion-exchange capacity (IEC), electrical resistance, permselectivity, sorption isotherms and methanol permeability which give information on the conductive properties and methanol permeability properties of the materials. These methods have been applied on blends of polyethersulfone (PES)/sulfonated polysulfone (SPSf) and PES/sulfonated polyetheretherketone (SPEEK) in which the composition has been changed to obtain defined properties. Based on the results, it can be concluded that the methods can be used as a first estimate to select proper materials for direct methanol fuel cell applications