The Fuel Cell Proton Exchange Membranes

In this thesis, we study the properties and development of the proton-exchange membrane and focus on the status and defects of the typical polyperfluorosulfonic acid membrane, of which high cost is the most obstacles for the commerce of the fuel celt. In order to reduce the membrane's cost, we prepared the membrane by simultaneous radiation grafting of styrene onto Teflon-Polytetrafluorethylene films and subsequent sulfonated by the chlorosulfonic acid introducing the activity sulfonic acid grape into the grafting side chains of the polymer films.The simultaneous radiation grafting of styrene onto Polytetrafluorethylene films was studied at room temperature. The effects of grafting conditions, such as the type of solvent, monomer concentration, irradiation dose, dose rate and irradiation time, were investigated. The content of styrene was found to be dependent on the investigated grafting conditions, of which the dose rate and monomer concentration were the major conditions, and the dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be of 0.4286 and 1.1662 orders, respectively. The results indicate that the grafting reaction is competitive and the copolymerization and the graft-copolymerization are existing at the same time. The grafting proceeds by the so-called front mechanism in which the grafting starts at the surface of the films and moves toward the middle of the film by successive diffusion of the styrene through the grafted layers.In the sulfonation reaction, the membrane physic-chemical properties such as swelling behavior, ion exchange capacity, hydration number, shape stability and ionic conductivity were studied as the function of the content of styrene. Thermal as well as chemical stability of the membrane was also investigated. The membrane properties were found to be dependent upon the content of styrene. The membrane physic-chemical properties compare to Nafion 117 except that their chemical stability has to be further improved to make them acceptable for practical use in the proton exchange membrane fuel cell. The proton transport through the membrane follows the "liquid-like" proton conductivity mechanism y and the water balance is important for the working condition of the fuel cell.The membrane prepared by the radiation-induced graft copolymerization will satisfy the requirements of the proton-exchange membrane fuel cell as well as reduce the cost of the fuel cell. We can conclude that this method is successful in synthesis the proton-exchange membrane.