添加劑對聚醚碸薄膜的結構及過濾效能之影響

Abstract

本研究使用不同的溶劑以及添加劑配置高分子鑄膜液，再藉由濕式法製備薄膜，並進一步的研究其薄膜結構以及相關之過濾性質。本研究中所使用的高分子為聚醚碸(Polyethersulfone, PES)以及聚碸(Polysulfone, PSF)，溶劑則選用了DMAc以及2P和將兩者混合的共溶劑，添加劑則選用了雙離子化合物與分子量為8000的聚乙二醇(Polyethylene Glycol, PEG)。 本研究主要從溶劑系統和添加劑的面向來討論。以溶劑系統而言，固定高分子和添加劑濃度之下，溶劑的選擇代表鑄膜液黏度的改變。對於PES而言，DMAc比起2P有更低的黏度，因此在PES/DMAc的成膜階段，質傳較快速的情況能使薄膜中的PES填補質傳交換出的溶劑所留下的空隙，因此PES/DMAc系統的薄膜表面為極緻密的結構；相較之下，PES/2P系統的薄膜表面會形成連通性較佳的海綿狀結構，也因此有較佳的純水通過率。然而雖然PES/2P系統有著良好的純水通過率，但與75%2P的溶劑系統相比，會因純2P系統的海綿層較厚而增加過濾阻力，因此通過率會略低於75%2P系統。 添加劑則同樣在薄膜表面的結構扮演著重要的角色。在成膜階段，添加劑藉由FTIR檢測確認並無殘存於表面，因此在被質傳交換出薄膜之時，便在薄膜表面形成了造孔效應使薄膜表面的連通性增加，因此提升了薄膜的通過率，然而在添加達一定量以上，會使薄膜的表面截留率下降。 而若是未來投入實際應用，薄膜的使用壽命也是值得注意的地方。在本研究中，含有添加劑之系統的薄膜抗汙度有所提升，因此未來希望能找到鑄膜液的最佳比例，以製備出高連通性、適當的海綿層厚度及孔洞尺寸，以獲得理想薄膜。

In this study, we prepared polymer membranes using different solvent compositions and additives to make polymer casting solutions and prepared membranes via wet-phase inversion method in order to conduct the membrane structures and filtration properties. Polymers used were Polyethersulfone (PES) and Polysulfone (PSF). Solvents included DMAc, 2P, and their mixtures, while additives were zwitterionic compounds and polyethylene glycol (PEG) with a molecular weight of 8000. In this study, the solvent system and additives was discussed. For solvent systems, with fixed concentrations of polymer and additives, solvent choice affects the viscosity of the casting solution. For PES, DMAc has lower viscosity than 2P, leading to way faster mass transfer rate during membrane formation. This results in a dense surface in the PES/DMAc system, while PES/2P forms a more porous sponge layer with higher water permeability. However, the pure 2P system, with thicker sponge layers, showed slightly lower flux due to increased filtration resistance compared to the 75% 2P system. Additives also play an important role in the surface structure. During membrane formation, results of FTIR microscopy confirmed that no additives remained on the surface. Instead, they induced a pore-forming effect when mass transfer exchanges occured, increasing membrane surface connectivity and improving water permeability. However, excessive additives reduce the membrane's surface filtration efficiency. For practical applications, the membrane's service life is crucial, and in this study, additives enhance fouling resistance. The goal is to find the optimal casting solution ratio to produce membranes with high connectivity, suitable sponge thickness, and pore size.