Differential scanning calorimetry and thermogravimetric analysis investigation of the thermal properties and degradation of some radiation‐grafted films and membranes

Abstract

The influence of irradiation and grafting on the crystallinity of three base polymers has been investigated with differential scanning calorimetry. Grafting has the largest effect on the base polymer crystallinity and results in a reduction of the crystallinity. The thermal degradation of the base polymers and grafted films has been investigated with thermogravimetric analysis. The extent of the fluorination of the base polymer, the irradiation method, and the graft level all influence the thermal degradation and its activation energy. It is proposed that the variation of the chain lengths of the grafted polystyrene chains is actually a primary underlying factor responsible for the influence of these various parameters on the degradation process. The first results of a comparative thermal analysis of some fuel‐cell membranes are also presented, and the promise and shortcomings of this method are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2612–2624, 2004

A novel approach to prepare proton exchange membranes from fluoropolymer powder by pre-irradiation induced graft polymerization

“…As shown in Fig. 5, pristine PVDF has a single endothermic peak at 169.3 • C. After 15 kGy ␥-ray irradiation, the melting peak of PVDF slightly increased to 170.5 • C, meanwhile, the enthalpy and the degree of crystallinity (X c ) increased, which is consistent with previous reports [28].…”

Ion track grafting: A way of producing low-cost and highly proton conductive membranes for fuel cell applications

“…Many other type of membranes have already been tested: (i) non-fluorinated membranes [4]: sulfonated copolymers of polystyrene-polybutadiene, polyethersulfone, polyphenylenesulfone [5,6], polyetherketone [4,[7][8][9], polyarylene ethers [10], polyimides [11,12], polybenzimidazole [8,[13][14][15], polyacrylates [16][17][18], oxadiazole-based polymers [19] and (ii) fluorinated membranes: trifluoroethylene (TFE) copolymers and many radiografted polystyrene or styrene derivatives onto fluorinated polymer such as ethylene tetrafluoethylene (ETFE) or PVDF [20][21][22][23][24][25][26][27][28][29]. Some of these new polymers are promising but the two main problems are a lower conductivity and stability in oxidizing conditions compared to Nafion ® shortening the life time in fuel cell conditions [30][31][32][33].…”

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

“…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). Therefore the fluctuations in IEC measurements may be disproportionately affected by the deterioration of the radical sites in the amorphous regions of the ETFE film.…”