| Summary: | 碩士 === 中原大學 === 化學工程學系 === 87 === 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 and acetone+ 18 vol% Tween 80 solution for the other. According to SEM and AFM analyses, it was found that, although the macrostructures of the membranes fabricated by systems PMMA/NMP and PMMA/acetone+ 18 vol% Tween-80 are similar, the microstructures are different. On basis of the 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 PMMA/NMP/water and by diffusion for PMMA/acetone+ 18 vol% Tween-80/water. The difference in the growth mechanism of macrovoids can also account for some other differences between systems PMMA/NMP/water and PMMA/acetone+ 18 vol% Tween-80/water: is more sensitive to the casting thickness than PMMA/NMP/water, and the addition of salt in the coagulation bath can effectively inhibit the growth of macrovoids in PMMA/acetone+ 18 vol% Tween-80/water but not in PMMA/NMP/water.
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