Preparation of Porous PVA Membranes
Date Issued
2006
Date
2006
Author(s)
Wu, Szu-Hua
DOI
zh-TW
Abstract
Porous hydrophilic poly (vinyl alcohol) (PVA) membranes were prepared by the phase inversion method. Two kinds of coagulant were used in the present work: sodium chloride aqueous solution and alcohols, including methanol, ethanol, 1-propyl alcohol, 1-butyl alcohol.
Experimental results showed that porous membranes, using NaCl(aq) as coagulant, contracted to form dense structure at the drying stage because of Tg depression resulted from plasticization caused by the remaining water in the membrane before drying. The contraction during drying stage can be presented either by freeze drying or by replacing water with appropriate alcohols, which have lower degree of plasticization.
We have also investigated the possibility of using alcohols as coagulant because of their nonsolvency to PVA to prepared membranes. Analysis of the affinity between polymer and measurement of concentration change during membrane forming provide insight into how the porous structure was formed. For a PVA/H2O/strong nonsolvent system, the high solvent outflux resulted in a of high polymer concentration layer (gel layer), and then turned into a dense skin. On the other hand, for a PVA/H2O/weak nonsolvent system, the influx of coagulant to the cast film dominated, resulting in phase separation near the surface and a porous surface structure.
Subjects
聚乙烯醇
濕式相轉換法
孔洞膜
polyvinyl alcohol
immersion precipitation
porous membrane
Type
thesis
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