- 學位論文
聚乙烯共乙烯醇/聚偏二氟乙烯複合膜於滲透蒸發與蒸氣滲透之探討
Investigation of EVAL /PVDF composite membrane for pervaporation and vapor permeation
摘要
中文摘要 本研究利用濕式相轉換法製備非對稱聚偏二氟乙烯poly(vinylidene fluoride)基材膜，並利用電漿活化基材膜表面使其親水化提升poly (ethylene-co-vinyl alcohol)/ poly(vinylidene fluoride)，EVAL/PVDF複合膜之界面安定性。研究中將探討交聯劑3-isocyanatopropyltriethoxysilane (ICPTEOS)添加與否對EVAL/PVDF複合膜應用在不同操作方式分離異丙醇水溶液之分離效能及其長期穩定性的影響。 研究中第一部分探討凝聚劑組成變化對基材膜結構變化之影響，並且以氫氣電漿改質PVDF基材膜之表面，藉以改善複合膜界面之密著性，由不同電漿功率及處理時間找出最佳的電漿處理條件。結果發現以水當凝聚劑之PVDF基材膜以150W氫氣電漿處理60秒所製備之純EVAL/PVDF複合膜其蒸氣滲透(vapor permeation)效能最佳，當分離90wt %異丙醇水溶液之透過量達480 g/m2 h，透過水濃度大於99wt%以上，分離效能明顯優於滲透蒸發(透過量為800 g/m2 h，透過水濃度約為86wt%)並且有很好的長時間穩定性，發現經28天後，其分離效能大致維持不變。 第二部份乃利用溶膠-凝膠法製備出聚乙烯共乙烯醇-氧化矽/聚偏二氟乙烯(EVAL-ICPTEOS/PVDF)複合薄膜，由固態的核磁共振儀(solid state-NMR)、傅立葉轉換紅外線光譜儀(FTIR)證明聚乙烯共乙烯醇之氫氧基確實與所添加含矽的交聯劑（ICPTEOS）的異氰酸酯基產生交聯反應，藉由廣角X-ray 繞射發現當ICPTEOS含量增加，其薄膜之網狀結構會將高分子鏈撐開而導致整體薄膜結晶性下降。此外，研究中探討EVAL-ICPTEOS/PVDF複合薄膜中，ICPTEOS的添加量對滲透蒸發分離90 wt%異丙醇水溶液分離效能及其長期穩定性的影響，發現添加10 wt% ICPTEOS所製備出之複合薄膜其透過量約為569 g/m2 h，透過水濃度大於96.8 wt%，且其長期穩定性(long-term stability)可維持36天以上。 結合兩部分的研究，可發現不同的操作模式分離90 wt%異丙醇水溶液時，可以選用不同方法製備的膜。在操作模式為蒸氣滲透時可利用EVAL/PVDF複合薄膜，可得到較高的透過量及透過水濃度並且也有良好的穩定性；而在操作模式為滲透蒸發時則必須選用EVAL-ICPTEOS/PVDF複合薄膜，可得到較佳的分離效能並且也具有較佳的長時間穩定性。
並列摘要
Abstract The present work is proposed to evaluate the potential of using vapor permeation or pervaporation processes and long-term stability to separate isopropanol/water mixtures. The asymmetric membranes of poly (vinylidene fluoride) were prepared by wet phase inversion method with of coagulation medium various compocitions. In addition, poly(ethylene-co-vinyl alcohol) was coated on the porous poly(vinylidene fluoride) membrane to improve the membrane permselectivity. In this study, two kinds of EVAL membranes were prepared by using pure EVAL or blends of 3-isocyanato-prpyltriethoxysilane (ICPTEOS) and EVAL. In first part, the EVAL/PVDF composite membrane with pre-treated plasma effectively prevented interface peeling. Optimum vapor permeation results, the permeation rate of 560 (g/m2‧hr) and 99wt% of water concentration in permeate, were obtained with an EVAL/PVDF composite membrane prepared from the asymmetric PVDF substrate membranes prepared in water coagulation bath, then treated with 150W/60sec plasma treatment condition. Till now, the membrane life of vapor permeation process through the durability test for 90 wt% aqueous isopropanol solution has more than 28 days. In second part, an organic /inorganic hybrid composite membrane were prepared by adding 3-isocyanato-prpyltriethoxysilane (ICPTEOS) in the Poly (ethylene-co-vinyl alcohol) (EVAL) to fabricate EVAL-ICPTEOS/ poly (vinylidene fluoride) (PVDF) composite membrane. The active layer of the EVAL/ICPTEOS/ PVDF composite membrane was prepared by sol-gel method, and the same condition or parameters on the first part for prepared composite membrane. In order to confirm the crosslinking reaction between EVAL and crosslinking agent containing siloxane, the hybrid membrane was characterized by FTIR and Si-NMR. The crystallization of hybrid membrane were characterized by using wide-angle X-ray diffraction (WXRD). The thermal stability and degree of swelling of the EVAL-silica hybrid materials was characterized by TGA and swelling measurement, respectively. Optimum pervaporation performance results, the permeation rate of 569 (g/m2‧hr) and 96.8wt% of water concentration in permeate, were obtained with the EVAL-ICPTEOS/PVDF composite membrane. Till now, the membrane life of pervaporation process through the durability test for 90wt% aqueous isopropanol solution has more than 36 days. The EVAL/ICPTEOS/ PVDF composite membranes effectively improve the pervaporation performance and the long-term stability for the separation of aqueous isopropanol solution.