Correlation between spinning temperature, membrane morphology, and performance of Psf/PVP/NMP/Water hollow fiber membrane forming system

Asymmetric polysulfone (Psf)/polyvinylpyrrolidone (PVP) hollow fiber membranes were fabricated via dry-wet spinning process in a custom made apparatus with controlled spinneret and spinning lines temperature. This study investigated the effect of isothermal spinning temperatures on morphology, performance, and their relationship. The hollow fibers prepared at isothermal conditions provide greater control over morphology and performance. Thickness of skin at inner side varied with spinning temperature, while morphology at outer cross-section and surface remained same. Three different layers of skin were observed by high-resolution SEM and nodular skin topography by AFM. The viscosity of dope solution was tremendously varied with temperature, which in turn dictates the precipitation rate. Precipitation rate was found to be the controlling parameter for skin thickness. Skin thickness varied from 7.04 to 2.44 μm, as temperature of spinning was changed from 15 to 40°C. The membrane performance was studied by pure water permeability and solute rejection by gel permeation chromatography. Pure water flux increased from 17 to 30 mL/(m² h mmHg) and NMWCO from 13,000 Da to 25,000 Da, with increase in spinning temperature, thereby demonstrating the control of spinning temperature on morphology and membrane performance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012