本研究結合熱與非溶劑誘導兩種相分離法製備聚乙烯乙烯醇薄膜，在水/二甲亞砜/聚乙烯乙烯醇成膜系統之相圖中選擇適當的製膜液與沉澱槽組成，利用兩者之溶劑、非溶劑比例相同的特點，讓沉澱槽濃度保持恆定可重複使用(稱為reusable bath)，並藉由改變沉澱槽組成以及沉澱槽溫度，探討其對薄膜結構之影響。隨著沉澱槽中DMSO溶劑增加至70%，薄膜上表面開始出現孔洞，截面部分則由胞孔型結構轉變為顆粒狀結構。當沉澱槽溫度上昇至45度時，薄膜結構鬆散而脆弱；而下降至5oC時，薄膜較紮實，孔隙也較小。上表面均為多孔型表面，截面則為顆粒狀結構。由DSC、XRD測量，得知各薄膜之結晶度約在20~30%之間。水通量則以reusable bath製備之薄膜通量最大，過濾藍色葡聚醣測試則以5度製備之薄膜阻隔效果最佳。接著我們在系統中摻入添加劑(PVP、Tween20)製備中空纖維薄膜，探討不同比例添加劑對於薄膜結構之影響。當摻入PVP時，內表面有孔洞分布在表面上，外表面僅少量小孔洞存在，截面皆有手指型巨孔的產生，水通量以摻入7.5%PVP之薄膜其通量最大，玻尿酸過濾則以未摻入PVP之薄膜其阻隔效果較佳；當摻入Tween20，內表面均有孔洞分布，其中T-5孔洞極少，T-10孔洞最多，而外表面屬於緻密層，截面也均有手指型巨孔產生，水通量以摻入15%Tween20之薄膜其通量最大，而玻尿酸過濾則以摻入5%之薄膜阻隔效果較佳。 In this study, we combine thermal and non-solvent induced phase inversion method to prepare EVOH membranes from the water/DMSO/EVOH system. In the phase diagram, we found a dope composition whose solvent and non-solvent ratio was equal to that in the precipitation bath. The composition of the bath could maintain constant by itself offer the precipitation process; we call the bath “reusable bath.” By changing the composition and temperature of the bath, we investigated their effects on the membranes structure. With the increase of DMSO concentration to 70% in the bath, pores began to form on the top surface of the membrane, while cross section evolved from cellular to particulate morphology. When the bath temperature was raised to 45oC, the formed membrane were loosely packed and fragile. At 5oC, the membrane was tightly packed, and the pores were smaller. The top surface was porous and the cross section demonstrated a particulate structure. XRD and DSC analyses indicated that the membranes had crystallinity of 20~30%. Pure water flux experiments showed that the membrane prepared from the reusable bath exhibited the highest permeation flux and filtration tests showed that the membrane prepared from 5oC reusable bath exhibited the highest rejection. We prepared EVOH hollow fibers with additives PVP and Tween20 to investigate their effects of the membrane structures. Using PVP, both the inner and external surfaces of the membrane were porous; however, the pore in the external surface were smaller. All membranes had cross section consisting of finger-like macrovoids. In the case of adding Tween20 in the dope, the inner surface was porous. The pore density was smallest for 5% addition, and largest for 10% addition. The external surface of all membranes were dense and nonporous. Water flux experiments showed that adding 7.5% PVP and 15% Tween20 gave rise to membranes with highest permeation fluxes in respective series, and hyaluronic acid filtration experiments showed that membranes with no PVP addition and 5% Tween20 addition exhibited highest rejection.
