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Concerning the microstructure of dry‐RO membranes
Author(s) -
Kesting R. E.
Publication year - 1973
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1973.070170610
Subject(s) - membrane , microstructure , materials science , paracrystalline , substructure , transmission electron microscopy , chemical engineering , cellulose acetate , lamellar structure , porosity , scanning electron microscope , composite material , crystallography , chemistry , nanotechnology , biochemistry , structural engineering , engineering
The microstructure of cellulose acetate reverse osmosis membranes which have been prepared by the Kesting dry process has been elucidated with the aid of scanning and transmission electron microscopy. The dry‐RO membranes consist of three layers: skin, transition layer, and substructure. The gel morphology of each of these layers originates in its sol precursors within the nascent membrane which manage to survive the sol → gel transition intact. The dense skin layer is composed of aggregates of tiny, slightly ellipsoidal nodules which are believed to be paracrystalline in nature. Immediately beneath the skin lies the transition layer, a narrow band of intermediate density consisting of widely separated closed cells. Below the latter lies the porous substructure which is composed of micrometer‐sized, open‐celled voids. Because of the size of their substructural voids, dry‐RO membranes are able to reversibly undergo wet–dry cycling without densification and loss of permeability.