The Formation Mechanism of Microporous Symmetric or Asymmetric Membranes

The Formation Mechanism of Microporous Symmetric or Asymmetric Membranes. The original recipes and subsequent modifications for preparing asymmetric membranes are deeply rooted in empiricism. Detailed descriptions of membrane preparation techniques are given in the literature.2 30 Only after extensive use of the scanning electron microscope, which provided the necessary structural information, was it possible to rationalize the various parameters for membrane preparation processes. At first, the asymmetric structure was obtained mainly in membranes made from cellulose acetate. But later it became ap- 

Phase inversion membranes can be prepared from any polymer mixture which forms, under certain conditions of temperature and composition, a homogeneous solution and separates at a different temperature or composition into two phases. A further condition, however, is that both phases are continuous. If the liquid phase is discontinuous, a closed-cell foam structure will be obtained and if the solid phase is discontinuous, a polymer powder will be obtained instead of a rigid structure. 

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