Promotion of polysulfone membrane by thermal-mechanical stretching process

Abstract

In this study, the effects of thermal-mechanical stretching process on the morphology and structure of asymmetric polysulfone membranes have been investigated. Phase inversion method was used for preparation of polymeric flat sheet membranes and membrane samples were prepared by composition of 15 % PSf as polymer and 85 % NMP as solvent. Stretching process was used to modify membrane performance by changing its pore size characteristics above the glass transition temperature of the membrane. Taguchi orthogonal array (OA) experimental design methodology with using Qualitek-4 software was applied for designing and also analyzing the results. Stretching temperature, load and load holding time as three effective factors and elongation percentage of membrane as final response were considered. The pore structure and roughness of the stretched and non stretched membranes were investigated by atomic force microscopy (AFM) while the membrane surface structure was characterized using scanning electron microscopy (SEM). Permeation results for pure water feed indicate that modified stretched membrane with 9.53 % elongation has approximately the pure water flux (PWF) about 1.8 times of the non-stretched membrane. Also surface roughness and fouling phenomenon are decreased significantly for this elongation percentage.