以非溶劑誘導相轉移法製備多孔型薄膜

Preparation of porous membranes via non-solvent induced phase inversion method

陳勝昌(Sheng-Chang Chen)

指導教授 ： 鄭廖平

淡江大學/工學院/化學工程與材料工程學系碩士班/碩士(2013年)

https://doi.org/10.6846/TKU.2013.00842

摘要

本研究首先利用非溶劑誘導法製備水/丁醇/甲酸/尼龍66四成份系統的多孔型尼龍66薄膜。水，對於尼龍66薄膜是強非溶劑，它可以增加製膜液中的晶核密度，當使用丁醇作為軟性沉澱槽時，液液相分離已充分的被壓制。當在製膜液中逐漸的添加水的含量時，藉由觀察薄膜的形態可發現成核密度明顯的增加。當製膜液含少量的水時(<2.5%)，薄膜的截面形態呈現巨型球晶，高含水量(>7.5%)的製膜液則呈現互相交織的軸晶和互相連通孔洞的對稱型雙連續薄膜。水通量和抗張強度的測量結果和薄膜的形態、孔隙度和孔洞尺寸有關。此外，藉由XRD、FTIR-ATR和DSC等儀器分析，得薄膜為a-type結晶且結晶度大約38%，並由DSC的測量得知薄膜的熔點為~265℃。本研究接著利用溼式相轉換法製作PVDF薄膜，並探討於製膜液中添加界面活性劑吐溫20對所形成薄膜的物性及其超過濾效率的影響。我們利用FESEM觀察薄膜的上、下表面和截面的形態，發現隨著吐溫20添加量的增加，截面的手指狀巨孔結構越趨於明顯，球晶顆粒也由束狀變為樹枝狀，且上表面孔洞也逐漸增加。我們也用拉力試驗量測薄膜的抗張強度機械性質。而吐溫20在薄膜的殘留量則由接觸角測試、FTIR-ATR、NMR、XPS等加以分析，並得知界面活性劑幾乎已被完全移除。由薄膜的水通量和超過濾實驗可知薄膜具有相當高的通量和良好的選擇率。最後，本研究利用溼紡法和乾噴溼紡法製備毛細管薄膜，並探討在製膜液中添加吐溫20對薄膜特性的影響。我們利用SEM攝影觀察毛細管薄膜內外表面和截面的結構和形態，發現毛細管薄膜隨著界面活性劑的添加，薄膜表面逐漸產生孔洞，巨孔結構越趨於明顯，且球晶形態從束狀轉為樹枝狀，並藉由拉力試驗得知薄膜的機械強度隨著添加界面活性劑而下降。製膜液的穩態黏度，由流變儀來測定，發現黏度隨著界面活性劑而增加。最後，我們用FTIR-ATR、接觸角測試和NMR分析吐溫20在毛細管薄膜的殘留量，結果顯示，經過仔細清洗後，吐溫20在薄膜中的殘留量僅約0.3%。

關鍵字

尼龍66 ； 聚偏二氟乙烯 ； 恆溫浸漬沉澱法 ； 多孔型薄膜 ； 毛細管薄膜 ； 成孔劑

並列摘要

Microporous Nylon-66 membranes were prepared by non-solvent induced phase separation (NIPS) from the Water/1-Butanol/Formic acid/Nylon66 quaternary system. Water, as a strong non-solvent for Nylon-66, was employed to enhance polymer crystal nucleation in the casting dope, while 1-butanol was adopted as a soft coagulant whereby liquid-liquid demixing mechanism can be sufficiently suppressed. By gradually increasing the water content in the dope, the effect of nucleation density on the morphology of the membrane was clearly manifested. While low water content (<2.5%) dopes resulted in membranes consisting of large full spherulites, high water content (>7.5%) dopes gave rise to symmetric bi-continuous membranes composed of small interlocked, stick-like crystallites intertwining with continuous channels of micropores. Water permeation flux and tensile strength of the membranes were measured and correlated with the porosity, pore size, and membrane morphology. In addition, X-ray diffraction (XRD) and Fourier Transform Infrared-Attenuated total reflection (FTIR-ATR) analyses indicate that the membranes contained a-type crystals with a crystallinity of ~38 %, consistent with that determined from Differential Scanning Calorimetry (DSC). The later method also showed that all membranes have a similar crystal melting behavior with Tm ~265 oC.
PVDF membranes are prepared via immersion precipitation method. The effects of Tween20 additive in casting dope on the membrane structure and ultra-filtration performance have been studied subsequently. We used field emission scanning electron microscope (FESEM) to observe the morphologies of the membrane cross-section, top and bottom surfaces. The results indicated that the structure of the crystalline particles changed from sheaf-like to stick-like shape and that the finger-like macrovoids and the nano-pore on the top surface became more obvious as the amount added Tween20 increases. Also, we utilized tensile strength measurements to determine the mechanical property of membranes. The residual Tween20 in the membrane was analyzed by contact angle measurement, Fourier Transform Infrared-Attenuated total reflection (FTIR-ATR), Nuclear Magnetic Resonance (NMR) and X-ray Photoelectron Spectrometer (XPS), and we found that the surfactant has almost been removed completely. The water flux and ultra-filtration experiments showed that the membranes exhibit both relatively high permeability and selectivity.
At last, capillary membranes were fabricated by both the wet spinning and dry-jet wet spinning methods. The issues of Tween20 additive in casting dope and air gap have been investigated. We used scanning electron microscope (SEM) to observe the morphologies of cross-section, external and inner surface of the formed capillary membranes. The results showed that pore size and porosity of the external and inner surface increased, the shell side and lumen side of macrovoid structure was enhanced, and the structure of spherulite changed from sheaf-like to stick-like with increasing the amount of surfactant in the casting dope. The mechanical property and the viscosity under different shear rate were determined by tensile strength and rheometeic measurements we found that the viscosity of casting dope increased and tensile strength of membranes decreased with increasing the surfactant in the casting dope. Furthermore, the results of Fourier Transform Infrared-Attenuated total reflection (FTIR-ATR), contact angle measurement and Nuclear Magnetic Resonance (NMR) revealed that the residual quantity of Tween20 in the capillary membranes is only about 0.3% after a series of washing steps.

並列關鍵字

Nylon66 ； poly(vinylidene fluoride) ； Isothermal immersion precipitation method ； Porous membrane ； Capillary membrane ； Pore former

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