Microstructures in phase-inversion membranes. Part 1. Formation of macrovoids

Abstract

A new mechanism for the formation of macrovolds m phase-mverslon membranes IS proposed It 1s based on the observed difference m type of demlxmg of a thm film of a polymer solution when immersed m a nonsolvent bath delayed or instantaneous demlxmg The explanation for macrovold formation assumes local condltlons of delayed demlxmg m front of a certain layer of nuclei already formed, due to a change m mterfaclal composltlons at the advancing coagulation front, as compared to the ongnal composltlon at the interface film-bath Effects of vanatlons m membrane formation condltlons which can be calculated using the model of diffusive mass transport m thm films of polymeric solutions m combmatlon with phase separation m phase-mverslon membranes, completely support the mechanism as proposed

Fabrication of novel poly(m-phenylene isophthalamide) hollow fiber nanofiltration membrane for effective removal of trace amount perfluorooctane sulfonate from water

“…That is due to that the dope solution and bore fluid (water) are co-extruded through the spinneret, and the diffusion exchange between the solvent and non-solvent is instantaneous that results in a highly unstable dope solution so that a rapid demixing process occurs. Such condition favors the formation of cellular-like macrovoid structures [40]. In the transition layer, located in the middle of the membrane, spongy-like structure is formed due to the delayed phase transition process.…”

L’Etat des Ressources En Eau au Maghreb En 2009

“…La formation de ces différentes structures morphologiques a été attribuée par de nombreux auteurs à la séparation de phase lors de la coagulation (Reuvers et al, 1987 ;Smolders et al, 1992 Par ailleurs, l'aptitude de ces membranes à retenir des cations laisse à supposer qu'au cours de la coagulation, les molécules d'eau qui pénètrent dans la matrice de la membrane attirent les groupes carboxyliques, provoquant ainsi une orientation préférentielle de ces groupes vers le centre des structures poreuses. Par conséquent, les groupes carboxyliques sont préférentiellement distribués à l'interface des pores et sur les surfaces membranaires.…”

Phase Diagram and Membrane Desalination

“…It was found that with asymmetric membranes, the porosity increases with the increase of the immersion bath temperature [47]. Raising the temperature increases mutual diffusivities between the nonsolvent (as water) and the solvent (as DMF) in the casting solution during demixing process.…”