雙凝聚槽成膜系統對聚(乙烯共乙烯醇)薄膜結構的影響

Effect of dual-coagulation bath method membrane formation system on the morphology of poly(ethylene-co-vinyl alcohol)membrane

黃收智(Shou-Chih Huang)

指導教授 ： ARRAY(0xc1a1e34)

中原大學/工學院/化學工程研究所/碩士(2009年)

https://doi.org/10.6840/cycu200901094

摘要

論文主要目的是探討以雙凝聚劑(第一凝聚劑為乙醇，第二凝聚劑為水)誘導相分離法，製備具雙連續(bicontinuous)結構之對稱性Poly (ethylene-co-vinyl alcohol) (EVAL)薄膜。同時釐清形成雙連續結構之成膜機制。
將鑄膜液( EVAL / N-methyl-2-pyrrolidinone (NMP))刮於玻璃板後，立即浸入乙醇槽中，於控制溶劑與非溶劑交換後，將薄膜以冷凍萃取法固化結構，以便觀察薄膜結構於乙醇槽中的演變。發現浸泡於乙醇槽中5分鐘，薄膜會由短時間得到的緻密結構轉變為此時的雙連續結構。即使再增加浸泡於乙醇槽的時間，薄膜結構也不在有明顯的成長，猜測可能因EVAL為結晶性高分子，於成膜過程中會誘發結晶現象形成膠化(gel)，造成黏度大幅提升使得合併成長現象被抑制，其雙連續結構得以維持。
將於乙醇槽中所生成之膠化態薄膜再浸入第二凝聚槽-水槽中時，由於水與NMP、乙醇之間的親合性極佳，因此水易於NMP和乙醇快速的進行交換，而固化結構且維持雙連續結構型態之薄膜。
第一槽之醇類種類改變時，藉著不同醇類、EVAL高分子和溶劑之間親合性的差異造成質傳速率不同，可以對薄膜達到結構控制之目的。將以雙凝聚槽系統製備之EVAL薄膜進行親疏水性的的接觸角測試，發現由於薄膜表面同時具有奈米與微米級的孔洞結構，使得水的接觸角可由原來的65o提升至120°，大幅增加了薄膜的疏水性。

關鍵字

聚(乙烯共乙烯醇) ； 雙凝聚槽 ； 雙連續結構

並列摘要

The main purpose of this study was preparation of Poly (ethylene-co-vinyl alcohol) (EVAL) membranes with bi-continuous structure by dual-coagulation method and investigated the membrane formation mechanism at the same time
The casting solution (EVAL / N-methyl-2-pyrrolidinone(NMP) solution) cast on glass plate and immersed into ethanol bath quickly. After a period of time, liquid nitrogen was used to freeze the casting membranes immediately and low temperature ethanol bath was used to exchange solvent slowly to make sure the structure formation in the first ethanol bath without any destruction. The results showed that the bi-continuous structure was formed when the casting solution immersed into the ethanol bath for 5min. The reason should be that EVAL polymer crystallization induced the physical gel to suppress structure coarsening in ethanol bath. Using the second bath, water bath, was an easy way to exchange solvent and nonsolvent to vitrify the casting membrane.
The morphologyof EVAL membranes can be controlled by using different first coagulation bath due to affinity different between alcohol, EVAL and NMP. The hydrophobicity of membrane surface was increased from 65o to 120o, because the nano-scale and micro-scale pores were formed.

並列關鍵字

bi-continuous structure ； poly(ethylene-co-vinyl alcohol) ； dual-coagulation bath

參考文獻

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