Poly(vinylidene fluoride) (PVDF) membranes were prepared via hybrid process of the thermally induced phase separation (TIPS) and the non-solvent induced phase separation (NIPS) from the dope solution system of polymer/diluent/solvent. Various coagulants were tested such as water, glycerol, ethanol. N-methyl-2-pyrrolidone (NMP) or dibutyl phthalate (DBP) was added to nonsolvent as a solvent or a diluent, respectively, to control the phase separation rate and affinity with dope solution. It was examined that changes of phase separation behavior induced by coagulants affected the surface structure and properties of the membranes. Real time phase separation mechanism studies were conducted by using optical microscope system and were compared with the structures of the flat sheet membranes. Hollow fiber membranes were prepared by using a melt spinning apparatus, and it was confirmed that change of inner coagulant affected the inner surface structure of the hollow fiber membranes. It was proved that permeation characteristics were enhanced while maintaining the mechnical strength and rejection performance.

고분자/희석제/용매 시스템에서 열유도 상분리(TIPS)/비용매유도 상분리(NIPS) 혼합공정으로 poly(vinylidene fluoride)(PVDF) 막을 제조하였다. Water, glycerol, ethanol 등 다양한 비용매를 내부 응고액으로 사용하였다. 또한 비용매에 용매인 N-methyl-2-pyrrolidone(NMP)나 희석제인 dibutyl phthalate(DBP)를 첨가하여 상 분리 속도 및 dope 용액과의 친화도를 조절하였다. 내부 응고액에 따른 상분리 거동의 변화가 표면구조 및 물성에 영향을 미치는 것을 확인하였다. 광학현미경을 이용하여 계면에서의 상분리 거동을 실시간으로 확인하였고 그 결과를 실제 평막형태로 제조된 막의 구조와 비교하였다. 용융방사 장치를 사용하여 실제 중공사막을 제조하였고 내부 응고액의 변화에 따른 중공사막 내부 표면구조의 변화를 확인하였고 기계적 강도 및 제거율을 유지하면서 투과도가 향상됨을 확인하였다.

Keywords: poly(vinylidene fluoride), thermally induced phase separation, non-solvent induced phase separation, coagulant, hollow fiber membrane