Sulfonated polysulfone (sPSU) was considered as an alternative material for low-temperature proton exchange membrane fuel cell. The possibility of manufacturing sPSU films by a continuous extrusion process is examined. The use of a plasticizer (polyethyleneglycol, PEG) is essential to decrease the glass transition temperature of the material in order to make it processable in the melt state. However, the acidic character of sPSU induces significant degradation of the sPSU/PEG mixtures even at low temperatures (120 degrees C), necessitating the use of high amounts of PEG to perform the extrusion of sPSU film. In these experiments, 30-40% of plasticizer had to be used to successfully produce a film, but a high level of porosity was produced in the membrane after removing the PEG. Although porosity significantly improves the proton conductivity of the membranes, in a fuel cell, the fuel crossover also increases as a result. (c) 2006 Wiley Periodicals, Inc.