Synthesis and Characterization of Bromine-containing Polybenzimidazole Copolymers for High-temperature Proton Exchange Membrane Fuel Cells

• Main Authors: Yi-Hsin Lan, 藍翊心
• Other Authors: Jyh-Chien Chen
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/80937979883518080463

碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 102 === To start with, an novel dicarboxylic acid containing bromine as side group and ether linkage was synthesized from the bromination of 4,4’-oxybis(benzoic acid). Next, a bromine-containing polybenzimidazole was synthesized from 2,2’-dibromo-4,4’-oxybis(benzoic acid)(1) and 3,3’-diaminobenzidine. In addition, a series of poly(aryl ether benzimidazole) copolymers bearing different m-phenylene /p-phenylene linkage contents were synthesized by condensation polymerization in polyphosphoric acid (PPA) by varying the feed ratio of isophthalic acid/ terephthalic acid to 2,2’-dibromo-4,4’-oxybis(benzoic acid)(1). Finally, the characterization of the pristine polymer and the other copolymers were discussed. The inherent viscosities of PBI-1~PBI-7 between 0.60~1.58, and they have good thermal stabilities. The 10% weight loss temperature of the polymers were between 459~514℃, and the results show char yield at 800 ℃ were in the range of 55~71%. On the other hand, the synthesized PBIs samples except PBI-7 present good solubility in polar aprotic solvents. They are easy to form the transparent, flexible and tough films by solution casting due to introduction of side groups. It was found that these membranes show good oxidative stabilities. The residual weight of these samples were 67~91% after immersing the membrane samples in 68 ℃ hot 3% H2O2 aqueous solution containing 4 ppm Fe2+ before the membranes were broken. The acid doping levels of PBI-1~PBI-6 were between 7.1~14.4. PBI-1~PBI-6 have a conductivity between 0.58~1.67 S/cm at 160℃. The maximum power densities could reach 140 to 290 mW/cm2. The single cell test exhibits a open circuit voltage of 0.36~0.45 V. The PBI membranes with high proton conductivities show potential application as the high temperature proton exchange membrane in fuel cell.