Novel radiation grafted membranes based on fluorinated polymers for Proton Exchange Membrane Fuel Cell applications.
Sahl Sadeghi
Material Science Engineering, MSc. Thesis, 2016
Thesis Jury
Assoc.Prof. Dr. Selmiye Alkan Gursel, Assoc.Prof. Dr. Gozde Ince, Assis.Prof. Dr. Oktay Demircan, Assis.Prof. Dr. Fevzi Cebeci
Date & Time: August 9th, 2016 – 14:00 PM Place: FENS G032
Keywords : Nanomedicine, nanoparticle-based gene therapy, microRNA, cancer
Abstract
The cost of proton exchange membrane (PEM) fuel cell is one of the obstacles on the path of utilizing the sustainable hydrogen renewable energy. In this paper a facile method for preparing poly(vinylidene fluoride) (PVDF)-g-poly(styrene sulfonate acid) (PSSA) membranes by radiation induced graft polymerization is reported. Sodium styrene sulfonate (SSS) monomer used for grafting of SSS from PVDF powder in aqueous dimethyl sulfoxide (DMSO) solution, and precipitated after synthesis. Later on, the resulted PVDF-g-PSSS graft copolymer membranes were prepared by vapor induced phase separation (VIPS) technique at 60% relative humidity (RH), and dried under vacuum at high temperature to achieve PVDF-g-PSSA proton conducting nano-porous membranes. PVDF-g-PSSA membranes were characterized by their proton conductivity, water up-take, mechanical and thermal properties, and it was found that these membranes are promising in terms of ionic conductivity and mechanical tensile strength compared to Nafion® NR-211.
Additionally, new cross-linked proton exchange membrane containing doped phosphoric acid (PA) was prepared by radiation induced grafting of 4-vinylpyridine (4-VP) and divinylbenzene (DVB) mixtures at various concentrations from poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by acid doping. The effect of grafting parameters such as DVB concentration on the degree of grafting was investigated. The properties of the obtained membranes were evaluated using for mechanical properties, ionic conductivity, and fuel cell performance. Of all samples, the cross-linked membrane obtained from grafting a mixture of 4-VP with 1 vol% DVB having a graft level of 50% exhibited proton conductivity as high as 75 mS/cm under 50% relative humidity (RH) at 120 °C. The mechanical properties of the crosslinked membranes were significantly improved compared to the non-crosslinked counterpart.