4 - Properties

Abstract

This chapter discusses the end-use properties as well as the morphology and structure of fluorinated ionomers products, precursor polymers and ionic forms. The Hyflon-Ion polymer may exhibit a superior balance of properties if other aspects of polymer quality, such as EW distribution, molecular weight (MW) distribution, and end group stability, is maintained. The precursor forms are not ionomers and have properties completely different from the ionic forms. The precursor polymers are hydrophobic, non-conducting, inert materials that resemble a highly plasticized TFE copolymer. They are readily melt-fabricable. Extruded films of the Nafion precursor polymer are soft and pliable, and tend to stick to themselves; this is particularly true at low EW. They are easily stretchable at room temperature or slightly elevated temperature with some shrinkage in the transverse direction (TD). The ionic forms are noticeably stiffer than their precursor polymers because of ionic cross-linking. The dominant property of fluorinated ionomers is their ability to absorb large quantities of water or polar organic solvents. Other properties are then very much a function of the polymer's water or solvent content. With increasing water or solvent content the dimensions, conductivity and permeability of the ionomer increases, and the strength and the ability to reject anions decreases. Fluorinated ionomers swell, and in some cases dissolve, in polar solvents. The properties and morphology of these polymers are dominated by this swelling process. In some cases a mixture of solvents is a more effective swelling agent than either component alone.