Nafion溶液成膜的物理性質與形態學研究

Physical Properties and Morphology of Nafion Membranes Prepared from Various Solutions

黃振宏(Cheng-Hung Huang)

指導教授 ： 林秀麗

元智大學/工程學院/化學工程與材料科學學系/碩士(2003年)

摘要

Nafion質子交換膜是目前使用於燃料電池最普遍的膜材。本論文
使用DuPont公司生產Nafion溶液分別以醇/水溶液及DMF溶液置換後，在室溫及120℃下揮發成膜。室溫下揮發的薄膜，薄膜性質是易脆的無法完整從培養皿中取出其機械性質差﹔用DMF置換DuPont公司Nafion溶液中醇/水溶液在高溫下揮發成膜，有較好的機械性質，經水膨潤後外型是柔軟、有彈性、有凝聚性的。薄膜溶劑含量測定數據顯示，室溫揮發形成的薄膜溶劑含量明顯高於在高溫下揮發形成的薄膜，室溫成膜後加熱annealing時間越久產生的物理交聯越多且結晶度越大，膜材越不容易被水膨潤，水含量也較低，薄膜膨潤過程中溫度也會影響其含水率。DSC熱分析數據顯示，加熱annealing處理可促進Nafion分子產生規則排列形成很大的結晶區，且隨著加熱annealing時間增加，其結晶區熔解吸熱也越大。以AC-impedance量測得到的導電度，我們可看到導電度隨著膜材加熱的時間增加而降低。在WAXD分析數據顯示，結晶度隨著加熱時間增加而增加，且Nafion膜以水膨潤後會使結晶度稍微下降。以SAXS研究Nafion薄膜的微結構：隨著加熱annealing時間增加，屬於主鏈氟碳化合物產生部份結晶的長區間間距增加，ionic cluster的長區間間距卻隨著加熱annealing時間增加而減小，用水膨潤後溼膜ionic cluster的長區間間距明顯大於乾膜。分析Nafion膜內的結晶粒子及離子聚集區可能是介於lamellae及球體﹙spherulite﹚結構之間。

關鍵字

Nafion薄膜 ； 小角度X-光散射 ； 廣角X-光散射

並列摘要

Nafion ion exchange membrane is widely used as membrane of polymer electrolyte membrane fuel cell (PEMFC). In this thesis, we prepare Nafion solutions by replacing solvents of Nafion solutions with methanol/H2O, ethanol/H2O, propanol/H2O, and DMF (N,N-dimethyl formamide) solvents.The Nafion/alcohol/ H2O solutions were evaporated at room temperature to prepare Nafion membranes, which were brittle and had poor mechanical properties. However, these membranes crystallized after annealing at 120℃. The Nafion/DMF solutions were evaporated at 120℃ to prepare membranes. DSC and WAXD data revealed that the degree of crystallinity of Nafion membrane increased with increasing annealing time, which leaded to decreases in the degree of swelling of membrane in water and the ionic conductivity as annealing time increased. SAXS data showed that the long spacing of crystalline domain increased and the long spacing of ionic cluster decreased with increasing annealing time. The long spacing of ionic cluster increased after the membrane were swelled with water.

並列關鍵字

Nafion membrane ； Small angle X-ray scattering ； Wide angle X-ray scattering

參考文獻

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