본 연구에서는 PEO [poly(ethylene oxide)]/EVA [poly(ethylene-co-vinyl acetate)]에 MWCNT (multi-walled carbon nanotube)-COOH 1, 2, 3, 5 wt% 첨가하여 PEO/EVA/MWCNT-COOH 복합막을 제조하였다. 그리고 복합막에 대해 30 ℃, 4~8 bar의 압력에서 N₂, O₂, CO₂의 기체투과 성질을 조사하였다. 각 PEO/EVA/MWCNT-COOH 복합막들에서 CO₂의 투과도는 압력 증가에 따라 증가하였고, N₂와 O₂는 압력에 거의 변화를 받지 않았다. 그리고 MWCNT-COOH 함량이 증가하면서 CO₂ 투과도가 증가하다가 2 wt% MWCNT-COOH 함량이상에서 감소하였는데 2 wt% MWCNT-COOH 복합막은 8 bar에서 CO₂/N₂ 선택도 77.8과 CO₂ 투과도 84 barrer를 나타내었다. 높은 CO₂/N₂ 선택도와 CO₂ 투과도는 사극자 CO₂와 PEO 내의 극성 에테르기, EVA의 극성 에스터기와 함께 MWCNT 표면의 -COOH기 간의 높은 친화력 때문이다.

In this study, polyethylene oxide (PEO)/polyethylene-co-vinyl acetate (EVA)/multi-walled carbon nanotube (MWCNT)-COOH composite membranes were prepared by adding 1, 2, 3, and 5 wt% of MWCNT-COOH to PEO/EVA respectively. The gas permeation properties of N₂, O₂ and CO₂ at 30 ℃ and 4~8 bar pressure were investigated. In each PEO/EVA/ MWCNT-COOH composite membranes, the permeability of CO₂ increased with increasing the pressure, but the permeability of N₂ and O₂ were independent of the feeding pressure. As the MWCNT-COOH content increased, the CO₂ permeability increased and then decreased above 2 wt% MWCNT-COOH content. The 2 wt% MWCNT-COOH composite membrane exhibited a CO₂/N₂ selectivity of 77.8 and a CO₂ permeability of 84 barrer at 8 bar. The high CO₂/N₂ selectivity and CO₂ permeability were due to the high affinity between the quadrupolar CO₂, polar ether groups of PEO, and the polar ester groups of EVA. Additionally, the strong affinity between CO₂ and the -COOH groups on the MWCNT surface contributed to the high permeability of CO₂.