Membranes were prepared from a castmg solution of a water-soluble polymer, poly (vmyl pyrrohdone) (PVP), and a membrane forming polymer, poly (ether sulfone), m l-methyl-2-pyrrohdone (NMP) as solvent by immersing them m mixtures of water and NMP It was found that the addltlon of PVP to the ternary system suppresses the formatlon of macrovolds m the sub-layer, while the ultraflltratlon-type top-layer consists of a closely packed layer of nodules Using a model for mass transfer m this quaternary system, it 1s possible to explam the effects of the additive on macrovold formation Strong mdlcatlons are found that the appearance of a nodular structure m the top-layer follows a mechanism of spmodal decomposltlon dunng the very early stages of the lmmerslon step Keywords membrane preparation and structure, theory, thermodynamics, macrovolds, phase-mverslon membranes [ 1,2] In recent, years, Reuvers et al [ 1 ] developed a model for the descrlptlon of mass transfer during the lmmerslon step Two types of de

This paper presents a state of art review on the stability of supported liquid membranes (SLM). The backgrounds of SLM instability phenomena are presented, and various mechanisms for explaining these phenomena are treated in detail. Several suggestions for stability improvement are discussed.

SYNOPSISSodium hypochlorite solutions are used to treat membranes prepared from a polymeric blend containing poly(viny1 pyrrolidone) (PVP) to increase their water permeability. Sodium hypochlorite affects the membrane material in such a way that PVP is selectively removed from the membrane matrix. The mechanism of the reaction between hypochlorite and PVP is investigated by several chemical analysis techniques of the reaction products. Strong indications are found that the reaction involves chain scission of PVP according to a radical mechanism. 0 1995 John Wiley & Sons, Inc.

Over the past years, the equilibrium sorption of gases in polymers has been intensively studied. Mostly, glassy polymers were investigated because of their excellent selective mass transport properties. This work does not focus on the equilibrium sorption but on the kinetics to reach the equilibrium. We developed a new experimental method measuring the sorption‐induced dilation kinetics of a polymer film. Carbon dioxide and glassy, aromatic polyimides were chosen as model systems. Low‐pressure experiments demonstrate that the measured dilation kinetics represent the sorption kinetics. A significant delay between the sorption and dilation kinetics is based on the fact that dilation kinetics occurs simultaneously with the concentration increase in the center of the polymer film. High‐pressure experiments reveal significant differences in dilation kinetics compared to low‐pressure experiments. Generally, three regimes can be distinguished in the dilation kinetics: a first, fast volume increase followed by two much slower regimes of volume increase. The magnitude of fast and slow dilation kinetics strongly depends on the swelling history of the polymer sample. The results of the experiments are analyzed in the light of a model relating the fast dilation kinetics to a reversible “Fickian” dilation and the slower dilation kinetics to an irreversible, relaxational dilation. © 1995 John Wiley & Sons, Inc.

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