添加劑對polysulfone非對稱性薄膜型態與滲透蒸發之影響---平板膜與管狀膜

Effect of additives on the morphology and pervaporation performance of asymmetric polysulfone membranes---Flat and tubular

蔡惠安(Hui-An Tsai)

指導教授 ： 賴君義

中原大學/工學院/化學工程研究所/博士(2002年)

https://doi.org/10.6840/cycu200200044

摘要

本論文係於製備非對稱性PSf平板膜與管狀膜時，於PSf/NMP鑄膜液中導入添加劑，包括非溶劑型添加劑（界面活性劑）或溶劑型添加劑（DGDE），探討添加劑對薄膜的結構型態、成膜機制、機械性質與分離效能的影響。此外，研究中針對具LCST-type相分離機制之PSf/DGDE /Alcohol（高分子/溶劑/凝聚劑）系統，深入探討成膜溫度與醇類凝聚劑對結構型態之影響。

研究結果發現：在PSf/NMP/H2O的平板膜成膜系統中，添加疏水性界面活性劑Span-80或提高薄膜成膜溫度時，會抑制巨型孔洞之形成且會形成皮層，應用在滲透蒸發（pervaporation）分離乙醇水溶液時透過率下降但對水選擇比增加。由滲透實驗結果顯示添加Span-80會使凝聚劑水分子是以diffusion之方式進入膜內，因而降低溶劑與非溶劑間之交換速率。在機械性質方面，添加疏水性界面活性劑會使薄膜斷裂伸度、斷裂強度與楊氏係數同時增加，此現象迥異於一般高分子材料的機械性質。

在管狀膜的製備方面，除了紡絲液中Span-80添加會影響膜的結構型態與分離效能外，管狀膜的紡製條件也會影響。當紡製時氣距長度增加，分子鏈排列順向度（orientation）提高，管狀膜的結構會較緻密，因此斷裂強度增加，應用在滲透揮發（vapor permeation）分離乙醇水溶液時對水的選擇比增加。芯液中溶劑NMP含量增加時，管狀膜之內表面結構較具多孔性，使滲透揮發透過率因而提升。

此外，研究中發現溶劑型添加劑DGDE之添加亦會抑制PSf非對稱性平板膜與管狀膜之巨型孔洞，隨著DGDE添加量的增加，管狀膜應用在滲透蒸發分離乙醇水溶液時其分離效能之趨勢與前述添加非溶劑型界面活性劑（Span-80）系統類似，透過率降低而對水選擇比則提高。

研究中也利用具LCST-type相分離機制的PSf/DGDE/ Alcohol成膜系統製備出一新穎的三明治薄膜結構型態，該結構包含上層多孔性lacy-like結構，中間為緻密層，下層則為多孔性的海綿狀結構。當成膜溫度降低或醇類凝聚劑之碳數增加時，三明治構造中之緻密層厚度會增加。

關鍵字

添加劑 ； 滲透蒸發 ； 平板膜 ； 管狀膜 ； 薄膜

並列摘要

In this work, the effects of additives i.e., nonsolvent type additive（surfactant）and solvent type additive（DGDE）on the morphology, mechanical property and separation performance of the asymmetric polysulfone flat and tubular membranes were investigated. In addition, the effects of the membrane formation temperature and the kinds of coagulation media on the membrane morphology for the PSf/DGDE/Alcohol membrane formation system with a low critical solution temperature（LCST）phenomenon were also investigated.

The results revealed that the addition of nonsolvent type surfactant（Span-80）in the casting solution and/or increasing the formation temperature can suppress the macrovoids in polymeric membrane. Thus, the exchange rate between the solvent and nonsolvent during the membrane formation process decreases resulting in an asymmetric PSf membrane with a dense skin layer observed. The perselectivity of water increases and the permeation rate decreases for the pervaporation separation of aqueous alcohol solution. In addition, compared with the general polymeric materials, a special mechanical property was observed, i.e., the tensile strength and elongation at break and Young’s modulus increases with the concentration of Span-80 in the casting solution increases.

In the preparation of PSf tubular membrane, the addition of Span-80 in dope solution and variation of spinning conditions such as air gap and bore liquid composition can also affect the morphology and the separation performance of the vapor permeation of aqueous ethanol solution. The tubular membrane structure was more compact and oriented as increases the air gap distance, resulting in the increasing of tensile strength at break and separation factor of vapor permeation of aqueous ethanol solution. The porous inner skin layer can be obtained by means of increases the NMP content in the bore liquid, resulting in the increasing of permeation rate. In addition, the morphology and separation performance of PSf asymmetric flat and tubular membrane can also be affected by adding solvent type additive（DGDE）in polymer solution. The macrovoids of PSf asymmetric flat and tubular membrane were suppressed by adding DGDE in the PSf/NMP casting solution. . The permeation rate decreased while separation factor increased with increasing the DGDE content in the PSf/NMP casting solution. Similar results were obtained in the system of addition nonsolvent type surfactant in the casting solution.

Furthermore, novel membrane morphology, sandwich structure was prepared by using the LCST-type PSf/DGDE/Alcohol membrane formation system. The PSf/DGDE polymer solution showed LCST-type phase separation mechanism, the transmittance of polymer solution decreases with increasing temperature. The sandwich structure composed of a lacy-like top porous layer, a dense middle layer and sponge-like bottom porous layer. The sandwich structure was facilitated to prepare in the case of lower temperature or higher molar volume of alcohol coagulant.

並列關鍵字

Additive ； Membrane ； Pervaporation ； Flat membrane ； Tubular membrane

參考文獻

26. 黃冠勛，探討添加劑對巨型孔洞形成之影響，中原大學化工系碩士論文（2001）

10. 黃冠勛，探討添加劑對巨型孔洞形成之影響，中原大學化工系碩士論文（2001）

1. M. H. V. Mulder, Basic Principles of Membrane Technology, Kluwer Academic Publishers, The Netherlands, 1996.

2. S. Loeb, S. Sourirajan, Sea water demineralization by means of an osmotic membrane, Adv. Chem. Ser., 38 (1962) 117.

5. P. Vandeweerdt and H. Berghmans, Temperature-concentration behavior of solution polydisperse, atactic poly ( methyl methacrylate ) and its influence on the formation of amorphous, microporous membranes, Macromolecules, 24(1991) 3547.