• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.362-367
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• 2023

Recently, research and development of proton exchange membrane fuel cells (PEMFC) membranes are progressing in the direction of thinning to reduce prices and improve performance. Demand for hydrogen-powered vehicles for commercial vehicles is also increasing, and their durability should be five times greater than those for passenger vehicles. Despite the thinning of the membranes, the durability of the membranes must be increased five times, so the improvement of the durability of the membranes has become more important. Since the acceleration durability evaluation time also needs to be shortened, the protocol using oxygen instead of air in the existing protocol was applied to a 10 ㎛ thin membrane to evaluate durability. The accelerated durability test (Open circuit voltage holding) was terminated at 720 hours. If the air-based department of energy (DOE) protocol was used, a lifespan of 450,000 km of driving hours would be expected, with a durability of about 1,500 hours. During the chemical durability evaluation, the active area of the electrode decreased by 51%, suggesting that catalyst degradation had an effect on membrane durability. Reducing the catalyst degradation rate is expected to increase membrane durability.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.517-522
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• 2023

A chemical/mechanical durability test of polymer membrane evaluation method is used in which air and hydrogen are supplied to the proton exchange membrane fuel cell (PEMFC) and wet/dry is repeated in the open circuit voltage (OCV) state. In this protocol, when wet/dry is repeated, voltage increase/decrease is repeated, resulting in electrode degradation. When the membrane durability is excellent, the number of voltage changes increases and the evaluation is terminated due to electrode degradation, which may cause a problem that the original purpose of membrane durability evaluation cannot be performed. In this study, the same protocol as the department of energy (DOE) was used, but oxygen was used instead of air as the cathode gas, and the wet/dry time and flow rate were also increased to increase the chemical/mechanical degradation rate of the membrane, thereby shortening the durability evaluation time of the membrane to improve these problems. The durability test of the Nafion 211 membrane electrode assembly (MEA) was completed after 2,300 cycles by increasing the acceleration by 2.6 times using oxygen instead of air. This protocol also accelerated degradation of the membrane and accelerated degradation of the electrode catalyst, which also had the advantage of simultaneously evaluating the durability of the membrane and the electrode.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.595-604
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• 1992

Carbonate-type polyurethane resins containing anionic moieties were systhesized from NCO-terminated prepolymer method. Membranes were manufactured from the polymer solution and the separation of aqueous ethanol solution was investigated. To enhance the property of urethane resin, carbonate-type polyol(PTMCG) was used. ${\alpha}^{\prime},{\alpha}^{{\prime}{\prime}}$-dimethylolpropionic acid was used as a chain extender to increase the hydrophilicily of the urethane membrane. The ionization of the pendent carboxylic groups in urethane resin was carried out using trimthylamine. To confirm the formation of anionic groups in urethane resin, IR spectra of model compounds were compared with those of urethane resins. It was confirmed that the concentration of hard segment and hydrogen bond contributed to the property of the concentration of hard segment and hydrogen bond contributed to the property of urethane resin in which the mole ratio of chain extender and polyol was from 3:1 to urethane resin in which the mole ratio of chain extender and polyol was from 3:1 to 5:1. The carbonate-type polyurethane containing pendent carboxylic grop(PU) had Tg of around-$25^{\circ}C$ and Tm, $45^{\circ}C$ measured by DSC. Transition temperatures of one containing pendent anionic group(APU) prepared from the ionization of PU shifted to $8{\sim}10^{\circ}C$ lower temperature region than those of PU. Pervaporation membrane was prepared through the casting method. N, N-dimethylformamide (DMF) were used as a solvent and hexamethylene diisocyanate(HMDl) as a crosslinking agent. Swelling degree increased with ethanol concentration in mixure and the control of the swelling degree of the membrane could be achieved by crossliking. The results of pervaporation were as follows : separation factor, 2.3~9.8 ; flux, $27{\sim}79.5g/m^2hr$. Pervaporation separation capacity could be enhanced by reducing the molecular weight of polyol from 2,000 to 1,000.