| Summary: | 碩士 === 南台科技大學 === 化學工程與材枓工程系 === 98 === The main objective of this study is to develop a proton exchange membrane with good conductivity, electrode compatibility and methanol resistance. The main works of this study include the synthesis and identification of sulfonated polyfluoroethersulfone,the preparation of proton exchange membrane, the fabrication of membrane electrode assembly (MEA) and the determination of the optimum degree of sulfonation and condition of MEA fabrication.
Firstly, the synthesis experiment were conducted by condensation polymerization of hydroquinone 2-potassium sulfonate(HPS), hexafluoro-bisphenol A(6F-BPA) and 4-fluorophenyl sulfone(4-FPS). The yield and average molecular weight were investigated under various operational parameters, including monomer selection,reaction temperature, reaction time and the purge of nitrogen, to explore their effect on the polymerization reaction and find out the optimum reaction condition.
The results showed that the maximum yield,48.04％, was obtained under the conditions of HPS/6F-BPA/4-FPS feeding ratio of 3/2/5, synthesis temperature of 160℃ and reaction time of 6hrs. The weight average molecular weights, determined by GPC, ranged from 24100 to 32400 with respect to variant degree of sulfonation. When the HPS mole ratio in the feed was raised, the degree of sulfonation of copolymer increased and then the proton conductivity、methanol permeability and hydrophilic property was also enhanced. The proton conductivity was raised to 0.06 S/cm at 80% degree of sulfonation. The contact angle of polymer membranes was varied from 82.97 to 58.91 with respect to 40 to 80％ of degree of sulfonation. In addition, after acidification, the water absorbability of polymer membrane increased, but the thermal stability analysed by DSC and TGA was decreased.
Secondly, the copolymer were used to produce proton exchange membranes and then the MEAs were also fabricated by hot press forming the membrane with electrode at temperature of 130℃. Pt/C was coated on the membrane directly to fabricate a MEA for PEMFC operation. A single cell test was carried out using H2/air as the fuel and oxidant. A current density of 400mAcm-2 was obtained at 130℃ hot press temperature and 80% degree of sulfonation.
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