Synthesis of Moderate Water-Uptake and Low Methanol Permeable Polymer Electrolyte Membrane from Functionalized Polyisoprene Impregnated Carbon Nanotubes

摘要

The study of the synthesis of polymer electrolyte membrane exhibiting moderate water uptake and low methanol permeation for fuel cell application using functionalized polyisoprene impregnated with carbon nanotubes (CNTs) was carried out. The functionalization of the polymer with chlorosulphonic acid of different initial concentrations of 0.0013, 0.001, 0.0017, and 0.0023 mol/L at the minimum time of 1hr produced ion exchange capacities (IEC) of 1.22, 1.92, 2.74, and 4.92 mmol/g, respectively, and at the maximum sulphonation time of 18hrs the IEC were 7.74, 8.78, 11.10, and 16.93 mmol/g, respectively. Their corresponding degrees of sulphonation (DS) for 1hr were 3.53, 5.55, 7.91, and 14.21%, respectively, and while at 18hrs their corresponding DS were 22.35, 25.37, 32.04, and 48.88%, respectively, which implies that IEC and DS are directly proportional to the concentration of acid used and reaction time. Result also showed that synthesized membrane without carbon nanotubes absorbed so much of it weight in water; 31.34 and 73.97% of its weight in both 1 day and 6 days for membrane with 48.88% DS. Whereas the membrane that was impregnated with CNTs of the same DS exhibited a lesser absorption of 23.23 and 53.23% of its weight in both 1 day and 6 days, thereby reducing the high water uptake of the membrane that would have affected it negatively by 1.3 fold. Apart from the conductivity of the synthesized membrane witnessing an increase by 1 order with the membrane impregnated with CNTs from 10sup-3/sup S/cm to 10sup-2/sup S/cm, it was also found out that the methanol crossover was lower than that of commercial Nafion, where membrane impregnated with CNTs had methanol crossover improvement with a difference of 0.48 Mol/L over its counterpart without CNTs as a result of the presence of CNTs.