The effect of Bisphenol A vs Bisphenol F on the performance of polysulfone membranes

Abstract

Microfiltration is widely used in water filtration to remove large particles, suspended solids, and bacteria. This study explores the properties and performance of polysulfone membranes synthesized with Bisphenol A (pBPA) and Bisphenol F (pBPF) at two molecular weights (20 & 40 kDa). The relationship between water permeance and the viscosity of polymer solutions used for membrane fabrication is explored through solution rheology and permeability tests. Thermal properties, analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), show that pBPF undergoes a two-step degradation process, while pBPA degrades in a single step. Both classes of polymer maintain a high thermal stability up to 450 °C with glass transition temperatures between 160 -190 °C. The Young's modulus increases with molecular weight and polymer casting solution concentration, as indicated by stress-strain curves, with similar trends in strength across membranes cast at similar concentrations. Deionized (DI) water permeance decreases logarithmically with membrane thickness, polymer concentration in the membrane solution, and viscosity. Across all polymers at equivalent casting concentrations, comparable DI water permeance is observed. Swelling studies with 1,4-butanediol (BDO) and 1butanol (BtOH) showed significant increases in membrane volume compared to water. pBPA membranes exhibited a marked decrease in BtOH permeance and all membranes displayed reduced permeance for BDO. These findings provided insights into the various ways processing conditions can influence the properties and potential utility of polysulfone membranes for microfiltration processes.