Rheological and thermodynamic behaviour of PSf/ZnO: Effect of zinc oxide

Abstract

The synthesis of zinc oxide nanoparticle normally involves zinc precursor and reduction during the preparation. To improve the dispersion of nanoparticle, the ZnO synthesis is the most promising option since the particles can stabilize in dope solution. However, the process of ZnO synthesis required the addition of polar precursor and reduction agents which are expected to influence the rheological and phase inversion properties of membrane dope solution. It is worth to mention that the rheological properties and phase inversion behaviour of the dope solutions play a critical role in determining the membrane morphology and separation performance. The PSf/ZnO dope solution was prepared via in-situ synthesis using three different precursors and reducing agents. The concentration was varied from 0 wt. %, 1 wt.% and 2 wt.% before dissolving in N-Methyl-2-pyrrolidone (NMP) as it will completely dissolved together. Three different precursors used were Zinc Chloride, Zinc Nitrate and Zinc Acetate while Sodium Borohydride, Hydrazine Hydrate and Urea are three different reduction agents. The thermal stability of the dope solutions was analyzed using cloud test measurement and the rheological properties were measured using viscometer toward the viscosity of the dope solution. Thermodynamic stability analysis denotes that the hydrazine hydrate has the lowest non-solvent percentage which is 3.30 %. Meanwhile, zinc nitrate with hydrazine hydrate have the lowest non-solvent percentage which is 1.59 %. This also shows that the zinc nitrate with urea binodal line nearly to the solvent/polymer axis which might resulted on faster demixing rate and miscibility gap become shorter. The viscosity results of urea as reducing agent in dope solution is highest as compared with two other reducing agents. Thus, as the concentration of zinc oxide increases, the viscosity and thermodynamic instability of the solution increased at the room temperature.