Pre‐Irradiation Grafting of Styrene/Divinylbenzene onto Poly(tetrafluoroethylene‐co‐hexafluoropropylene) from Non‐Solvents

Abstract

Pre-irradiation grafting of styrene/divinylbenzene (DVB) onto poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films was studied with respect to the influence of solvent. Particularly favorable grafting conditions with long radical lifetimes and reasonably high polymerization rates were achieved with solvents that are precipitants for the newly formed polystyrene, e.g., low-molecular-mass alcohols like i PrOH, AcOH, their mixtures with H 2 O, and H 2 O/surfactant systems. Using one of these solvents significantly extended the range of accessible graft levels, and a specific degree of grafting was obtained at a much lower monomer concentration and irradiation dose than with grafting in a good solvent such as toluene. As practical consequences, the monomer was used more efficiently, and the radiation damage of the perfluorinated base material was reduced with the result of improved mechanical properties of the grafted films.

Polyethylene-based radiation grafted anion-exchange membranes for alkaline fuel cells

“…Methanol is selected as solvent as being an effective medium for grafting of VBC onto PE because it acts as a non-solvent for grafted polymer (PE-g-PVBC), resulting in restricted chain mobility, hence increased radical lifetime and, consequently, enhanced grafting kinetics [29]. The DG increased more rapidly with increasing monomer concentration up to 50% and thereafter, only a slight increase with increased concentration was observed up to 80%, with DG falling slightly at 100% monomer concentration as illustrated in Fig.…”

Suitability of some fluoropolymers used as base films for preparation of polymer electrolyte fuel cell membranes

“…Binary monomers of styrene/divinylbenzene (DVB) have been widely used as the graft components. Other monomers, such as styrene derivatives and acrylic monomers, have also been investigated [5][6][7][8][9][10]. The base film in the membrane functions as a hydrophobic host that constrains the membrane swelling in water and provides mechanical strength and dimensional stability.…”

“…This allows the possibility to apply a high irradiation dose for membrane preparation without affecting their inherent mechanical property. The FEP-based fuel cell membranes have been systematically investigated by Paul Scherrer Institute (PSI, Switzerland) for about 20 years [10,[15][16][17][18][19]. The current-voltage performances of fuel cells containing such membranes favorably compare for those cells containing Nafion membranes under the same operating conditions.…”

An empirical study into the effect of long term storage (−36±2°C) of electron-beamed ETFE on the properties of radiation-grafted alkaline anion-exchange membranes

“…Previous research has shown that grafting of irradiated fluoropolymer films proceeds by the grafting front mechanism. The grafting is initiated first at the surface of the film; these regions become swollen by solvent and provide access to deeper reaction sites within the film for additional monomer polymerisation (Brack et al, 2000;Rager, 2003). However, crystallite regions of the film remain practically unaltered during the grafting process, meaning grafting predominately takes place in the amorphous regions (Brack et al, 2004;Walsby et al, 2001).…”