The structural changes of cellulose acetate membranes with the variation of acetone evaporation time and the gas permeation characteristics of He, N₂ and O₂ for those membranes were examined. The dried cellulose acetate membrane by isopropanol exchange treatment represented asymmetric structure which consists of a skin layer and a support layer. By changing the solvent evaporation time, the thickness of the membrane skin layer increased for the first 2 minutes, and then decreased gradually. The gas permeation rate depended on the thickness of skin layer and it was in the order of He>N₂O₂2. The permeation mechanism appears to be the combination of Knudsen flow and viscous flow. The effect of Knudsen flow was increased with acetone evaporation time. At 9 minutes of evaporation time, α_He/N2 was about 1.90.

본 연구에서는 용매증발시간을 변화시켜 제조한 i-PrOH 치환 건조된 cellulose acetate 막에서 용매증발시간에 따른 막의 구조변화 및 기체(He, N₂, O₂)의 투과성능을 평가하였다. i-PrOH 치환 건조된 cellulose acetate 막구조는 비대칭구조를 나타내었으며 용매증발시간 2분을 전후하여 skin층의 두께는 증가하다가 감소하였다. 기체투과속도는 skin층의 두께변화에 따라 크게 의존하였고, 투과계수의 크기는 He>N₂ O₂ 순으로 나타났다. 한편 기체투과기구는 Knudsen flow와 viscous flow의 혼합형태를 나타내었으며, 증발시간이 커질수록 Knudsen flow의 영향이 증가하였다. 증발시간 9분일때 α_He/N2는 1.9이었다.

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