MODELING OF ASYMMETRIC MEMBRANE FORMATION .1. CRITIQUE OF EVAPORATION MODELS AND DEVELOPMENT OF A DIFFUSION EQUATION FORMALISM FOR THE QUENCH PERIOD

Date

1986-09-15

Author

Yılmaz, Levent
MCHUGH, AJ

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In this paper a review and critique is presented of the mathematical models which have been developed to describe the mass transfer processes occurring during asymmetric membrane formation in polymeric systems. A principal object is to point out several shortcomings of the modelling efforts which have been primarily confined to a description of the evaporation step. This is followed by a detailed discussion of the general mass transfer problem along with the development of a model based on a pseudobinary diffusion equation formalism, to describe the solvent—nonsolvent exchange process which occurs during quenching. The derivation demonstrates that the pseudobinary approach enables the decoupling of the mixing rule from the diffusion equations, therefore allowing its separate specification without affecting the validity of the transport model. Solution of the model equations allows plotting of concentration profiles directly onto the ternary phase diagram. The discussion shows how such ternary concentration plots can be used to differentiate formation conditions for completely dense morphologies from those of either asymmetric or porous structures. Finally, a special case solution to the mass transfer model is presented to predict concentrations of the nonsolvent and polymer as a function of time and distance in the forming membrane.

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https://hdl.handle.net/11511/48189

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Department of Chemical Engineering, Article