On the formation of macrovoids in PMMA membranes
Resource
Journal of Membrane Science 155 (1): 31-43
Journal
Journal of Membrane Science
Journal Volume
155
Journal Issue
1
Pages
31-43
Date Issued
1999
Date
1999
Author(s)
Abstract
In this work, the formation of macrovoids in two membrane formation systems was investigated. The polymer and the coagulant used in these two systems were the same: PMMA and water, but the solvents used to dissolve PMMA were different - NMP for one system (system A) and acetone/Tween 80 solution for the other (system B). According to SEM and AFM analyses, it was found that, although the macrostructures of the membranes fabricated by systems A and B are similar, the microstructures are different. On the basis of optical observation of the growth of macrovoids, it is proposed that the difference in the microstructure can be explained by the difference in the growth mechanism of macrovoids: the growth of macrovoids is by convection for system A and by diffusion for system B. The difference in the growth mechanism of macrovoids can also account for some other differences between systems A and B: system B is more sensitive to the casting thickness than system A, and the addition of salt in the coagulation bath can effectively inhibit the growth of macrovoids in system B but not in system A. Copyright (C) 1999 Elsevier Science B.V. In this work, the formation of macrovoids in two membrane formation systems was investigated. The polymer and the coagulant used in these two systems were the same: PMMA and water, but the solvents used to dissolve PMMA were different - NMP for one system (system A) and acetone/Tween 80 solution for the other (system B). According to SEM and AFM analyses, it was found that, although the macrostructures of the membranes fabricated by systems A and B are similar, the microstructures are different. On the basis of optical observation of the growth of macrovoids, it is proposed that the difference in the microstructure can be explained by the difference in the growth mechanism of macrovoids: the growth of macrovoids is by convection for system A and by diffusion for system B. The difference in the growth mechanism of macrovoids can also account for some other differences between systems A and B: system B is more sensitive to the casting thickness than system A, and the addition of salt in the coagulation bath can effectively inhibit the growth of macrovoids in system B but not in system.
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journal article
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