Construction of Ternary Phase Diagram and Membrane Morphology Evaluation for Polyamide/Formic acid/Water System

In this article, the ternary phase diagram in polyamide-6 (PA6)/Formic acid (FA)/Water system was constructed by experimental measurement. The determination of binodal curve was measured according to titration of the PA6 polymer solution with water as a non-solvent until the onset of turbidity. Also, the phase separation process of the prepared membranes structures system was investigated. The morphology of PA6 membrane has been formed during phase separation, which is dependent on the phase inversion, and the equilibrium ternary phase diagram system, that is a good tool for understanding and controlling the morphology of the membrane structure. According to the constructed ternary phase diagram of PA6/FA//Water system, a large amount of water (26-39 wt% water) was needed to achieve liquid–liquid phase separation in that ternary system.