균일한 기공을 가진 polycarbonate track etched membrane의 불소화로 인한 표면특성과 물 투과도의 변화를 조사하였다. 반응온도와 반응시간을 각각 상온과 3분으로 일정하게 유지하면서 질소로 희석된 혼합가스의 불소 농도 및 압력을 변화시켜 멤브레인을 불소화하였다. Field emission scanning electron microscopy(FESEM)을 통해 혼합가스의 절대압력이 1.5 bar 이하이고 불소, 질소 혼합비가 1:30으로 희석되었을 때 멤브레인 표면이 손상되지 않음을 알 수 있었다. 또한, 혼합비 1:30의 혼합가스로 1.5 bar에서 불소화한 멤브레인의 물 투과도는 원래 멤브레인의 2배 가까이 증가하였다. 불소화 압력이 낮으면 표면은 친수성을 띈 반면, 불소화 압력이 증가하면 소수성으로 변하였다. X-ray photoelectron spectroscopy(XPS)를 통해 불소분압이 높아짐에 따라 멤브레인 표면에서 내부로의 불소 침투속도가 증가하는 현상과 불소가 도입된 부분의 산소 함량이 증가한 현상을 볼 수 있었다. 표면이 소수성을 띄는 멤브레인의 물 투과도가 증가한 현상은 기공 표면이 소수성을 띌수록 slip 경계조건에 근접하게 되어 기공을 통한 물 흐름이 원활해졌기 때문으로 해석되었다.

The effect of fluorination on the surface characteristics and water permeability of an isopore polycarbonate track etched membrane was examined. The membrane was fluorinated with gas mixtures containing fluorine and nitrogen of various composition under various pressure at room temperature for 3 minutes. The field emission scanning electron microscopy (FESEM) analysis showed that the shape of the membrane surface was not changed when it was fluorinated with a gas mixture at 1.5 bar which contained a low molar ratio of fluorine to nitrogen such as 1:30. Meanwhile, the membrane fluorinated with a mixture having a F₂ : N₂ ratio of 1:30 at 1.5 bar showed an improved water permeability almost twice higher than that the original membrane had. The membrane surface got to possess more hydrophilicity than the original one when it was mildly fluorinated at low pressure. However, it became hydrophobic when it was further fluorinated under higher pressure. X-ray photoelectron spectroscopy (XPS) analysis revealed that the penetration rate of fluorine into the membrane increased along with the increase of the partial pressure of fluorine and that the inner layer containing fluorine possessed more oxygen than that in the original membrane. The phenomenon that the membrane having hydrophobic surface showed high water permeability was due to the slip boundary condition in the pore surface where water droplets pass through hydrophobic pores more easily with less friction resistance than through hydrophilic pores.

Microfiltration Surface Fluorination Water Permeability Hydrophilicity Hydrophobicity

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