LAUSR

This study revealed, a thorough investigation of coagulation residence time effects on the morphology, crystallinity, mechanical properties and oxygen (O2), nitrogen (N2) gas transport behaviour of asymmetric membranes prepared through PVA/water/THF ternary system using non-solvent induced phase separation method. For this purpose PVA asymmetric membranes were fabricated at different coagulation residence of 3–24 h and then evaluated using various analytical techniques. The scanning electron microscopy was utilised to observe membrane morphologies to determine the membrane matrix structure, pore size distribution and bi-layer thickness ratio. X-ray diffraction was employed to examine the crystallinity of membranes. The variation in overall porosity and mechanical characteristics were investigated through gravimetric based analysis and universal testing machine respectively. Whereas, O2 and N2 gas transport behaviour of asymmetric membranes was recorded using gas permeation testing unit. The results showed that different sponge type, interconnected porous membranes, having thin durable dense layer morphology were obtained by varying residence time of coagulation process at constant temperature and concentration. A shorter residence time favoured the formation of single chain porous network having small pores size (1–2 μm) with porosity of 56.31% and thicker dense layer, having low O2 gas permeation rate and high mechanical characteristics such as tensile strength and elongation at break. However, a long residence time in coagulation bath facilitated the formation of double chain more porous network having pores size distribution between 2 and 3 μm with porosity of 75.52% and thinner dense layer, having high O2 gas permeation rate. The tensile strength of membranes is high in-spite of higher porosity and lower thickness of dense layer.