Perfluorinated radiation grafting

Radiation-grafted PEMs based on perfluorinated substrates (32) have been developed by Rouilly et al., who used FEP as the base polymer... 

The RAI Research Corporation also offers a range of battery separators under the name of Permion (JL). These membranes are made by radiation grafting of a suitably active group onto an inert base film. The active groups include weak acids such as acrylic and substituted acrylic acid and stronger acidic groups such as sulfonated styrene. The base film can be Teflon R, polyethylene or polypropylene. They are thus not strictly perfluorinated membranes as is Nafion, but in chemical inertness and in many physical properties such as electrical conductivity and ion flux are useful as separators in batteries. 

Most of the commonly used membranes used in DMFC exhibit acceptable performance stability after thousands of hours under steady-state operation, including perfluorinated sulfonic acid, PTFE-co-HFP radiation-grafted poly- styrenes, and sPAE [85]. However, membrane durability results under unsteady-state operation are stUl scarce. Siroma et al. [114] have shown that a significant fraction of Nation dissolved after 1 week of DMFC operation with methanol solution. 

The only way to apply chemically bonded thin perfluorosulfonic acid layer onto the surface of an inert support is to graft perfluorinated functional monomers onto perfluorinated polymers. Some features of radiation-induced graft copolymerization of PFAVESF onto fluoropolymers were investigated. The studies showed that neither irradiation of a fluoropolymer-PFAVESF mixture (direct grafting) or interaction of PFAVESF with previously irradiated fluoropolymers (preirradiation grafting) yielded the grafted copolymers. It was assumed that this is connected with the low activity of PFAVE in radical polymerization. A special method has been developed for the synthesis of grafted copolymer. Previously irradiated fluoropolymer powders were used to prevent waste of PFAVESF. 

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