- 學位論文
聚四氟乙烯膜之電漿改質及其滲透蒸發與黏著性質研究
Study on the plasma modified PTFE membranes for pervaporation and adhesion properties enhancement
摘要
本論文主要利用電漿及臭氧處理程序進行鐵氟龍（polytetrafluoroethylene, PTFE）薄膜表面之改質。針對PTFE薄膜表面進行分子設計，及親水化處理，以提升其應用於滲透蒸發（pervaporation, PV）與蒸氣滲透(vapor permeation, VP)脫水程序中，分離有機水溶液之效能及表面對銅箔之黏著強度。 研究中先藉由氫氣電漿進行緻密形之PTFE（skiving PTFE, s-PTFE）薄膜表面改質，同時配合光學放射光譜儀（Optical Emission Spectroscopy, OES）進行電漿性質之診斷，以探討電漿改質s-PTFE之反應機構。由於電漿活性物種可藉由擴散及對流方式運動而充滿整個反應器，因此不論將s-PTFE膜材置放於電極區上游或下游端，皆能有改質之效果。研究中發現將s-PTFE膜材置於距RF電極端10公分遠之位置，其表面親水化程度最高。相較於單一次氫氣電漿處理，以重複多次之氫氣電漿處理可以在s-PTFE膜上形成一較穩定且親水之表面。然而，由於s-PTFE之高分子鏈本身熱運動，致使即使經過重複電漿處理之s-PTFE膜表面，仍有疏水性回復之現象。 為了降低改質親水化後膜材表面之疏水性回復現象，可以在PTFE表面導入較長之親水鏈段，使得親水之高分子鏈不易遷移至膜材內部，而可長期的保持其改質後之親水性。針對多孔性之expanded PTFE（e-PTFE）薄膜，分別利用乙炔/氮氣混合氣體電漿聚合法，及電漿誘導後接枝聚合法導入acrylamide（e-PTFE-g-PAAm）進行改質，可以有效提升其表面親水性，其表面對水接觸角由109.7o降至34.1o。親水化後膜表面之疏水性回復現象可有效抑制，經三年老化測試仍保持在36.9o。 對於緻密形之s-PTFE薄膜，研究中以近年新發展之電漿改質方式：電漿誘導固態聚合（Solid State Polymerization）改質薄膜程序，改質緻密形之s-PTFE薄膜。此法改質s-PTFE薄膜，不但步驟較為簡單，且可以有效提昇膜材表面的親水性，並且具有減緩老化現象之效果。 本研究首先發展出結合電漿及臭氧處理改質PTFE薄膜。利用氫氣電漿處理可以有效的在s-PTFE薄膜表面進行氫化（hydrogenation）及去氟化（defluorination）反應，而將C-H團基導入至s-PTFE表面。利用在s-PTFE表面所生成的C-H團基，做為臭氧處理的受體，以臭氧將其反應成為過氧化基。即可利用易於控制分子構形之自由基轉移聚合法（atom transfer radical polymerization, ATRP）於s-PTFE表面進行分子設計，並於s-PTFE膜表面導入苯乙烯磺酸鈉鹽(sodium 4-styrenesulfonate，NaSS)分子鏈，經質子化後成s-PTFE-g-PSSA膜，由於s-PTFE基材膜良好之穩定性及改質層優異之選擇性，所以在長期操作58天下能夠維持其滲透蒸發之分離效能。以s-PTFE-g-PSSA薄膜滲透蒸發分離90 wt%異丙醇水溶液，其透過量為355 g/m2.hr而透過水濃度可高達99.9 wt%。 利用不同接枝改質方法，可在s-PTFE表面建構出不同glycidyl methacrylate（GMA）分子鏈之構形。研究中顯示，膜材表面之分子構形及化學組成，均對其與銅箔之黏著強度造成影響。表面接枝GMA之s-PTFE薄膜（s-PTFE-g-PGMA），可藉由開環試劑與環氧樹脂反應後，提升薄膜表面對銅箔之黏著強度。薄膜表面與銅箔之剝離強度（180o）可由未改質前之0.2 N/cm，提升至5.8 N/cm。（s-PTFE-g-PGMA以ethylenediamine開環）
並列摘要
In this work, plasma and ozone treatment processes were applied to modify the PTFE membrane surface. Hydrophilic modification and molecular design on the surface of PTFE membrane was carried out to improve the dehydration performance of the pervaporation and vapor permeation of organic aqueous solution, and the adhesion strength between the PTFE membrane and copper foil. Hydrogen plasma treatment was applied to modify the skiving PTFE (s-PTFE) membrane surface accompany with in-situ diagnose by OES to investigate the mechanism of modification. Regardless of placing s-PTFE membrane on the position of downstream or upstream of the electrode region, the diffusion and convection transport of the active species in the plasma, resulting in the s-PTFE membrane surface can be modified. It was found that optimal position for the surface hydrophilicity enhancement of plasma-treated s-PTFE is at the remote distance of 10 cm from the electrode. Compared with the one time H2 plasma treatment, a more stable and more hydrophilic s-PTFE membrane surface can be created by a repeated hydrogen plasma treatment. However, a small hydrophobic recovery phenomenon appeared due to the thermal motion of the PTFE polymer chain even after repeatedly plasma treated. The hydrophobic recovery phenomenon can be suppressed by introducing longer hydrophilic polymer chains onto the PTFE membrane surface. Thus, the hydrophilic polymer chain is difficult to migrate into the bulk layer; resulting in the hydrophilicity of PTFE membrane surface can be remained. For the porous e-PTFE membranes, both acetylene/nitrogen gas mixture plasma and plasma-induced acrylamide monomer (e-PTFE-g-PAAm) post grafting polymerization method were carried out to improve the surface hydrophilicity of the e-PTFE membrane and to prevent the hydrophobic recovery phenomenon. The contact angle decreases from 109.7oof the e-PTFE membrane to 34.1o of e-PTFE-g-PAAM membrane. For the durability test of the surface contact angle increased from 34.1o to 36.9o for 3 years. For the dense s-PTFE membrane, “Plasma induced Solid-State Polymerization” a new developed method in recently years was carried out. The method is simple but effectively improve the surface hydrophilicity of the s-PTFE membrane and suppress the surface hydrophobic recovery effect. At last, a novel PTFE membrane modification by hydrogen plasma combined with ozone treatment was developed. C-H groups were introduced into the s-PTFE membrane surface through defluorination and hydrogenation reactions under hydrogen plasma treatment. The C-H groups then served as ozone accessible sites to form peroxide groups under ozone treatment. Molecular design on s-PTFE surface was carried out by grafting polymerization by atom transfer radical polymerization which is easy to control the molecular architecture initiating from the peroxide groups, and introduce sodium 4-styrenesulfonate (NaSS) molecular chains onto the s-PTFE membrane (s-PTFE-g-PNaSS) which was further protonized to form s-PTFE-g-PSSA membrane. The modified s-PTFE-g-PSSA membrane was very stable for long-term operation of pervaporation dehydration process attribute to the excellent stability of s-PTFE membrane. The PTFE-g-PSSA membrane was very stable for 58 days operation of pervaporation dehydration process of 90 wt% aqueous IPA solution at 25 oC, and the permeation flux and high water concentration in permeate of 355 g/m2.hr and 99.9 wt% was obtained respectively. Different grafting method utilized to build GMA macromolecular architecture on s-PTFE surface. It was found that both the architecture and chemical composition on the s-PTFE surface influence on the adhesion strength with copper metal. The adhesion between epoxy resin and metals could be further improved by reacting with curing agents. Compared with the unmodified s-PTFE membrane, the 180o peel strength between s-PTFE membrane and Cu foil increases from 0.2 N/cm of the s-PTFE membrane to 5.8 N/cm of the s-PTFE-g-PGMA membrane by reacting with ethylenediamine.