Investigation of shear stress effect within a spinneret on flux, separation and thermomechanical properties of hollow fiber ultrafiltration membranes

The development of high performance P84 co-polyimide hollow fibers for pervaporation dehydration of isopropanol

“…This may be ascribed to enhanced molecular orientation of polymer chains at hollow fiber surface and increased wall thickness at high shear rates. Similar phenomena were observed for gas separation membranes and UF membranes (Cao et al, 2004;Qin et al, 2000).…”

“…On the other hand, fibers spun with an air gap distance of 5 mm exhibit the largest wall thickness which is due to the die-swell effect. Highly viscous random-coil polymer solution tends to relax the shear-induced orientation by exhibiting expansion in the transverse direction (to the spinning direction) after passing through an annulus straight spinneret (Qin et al, 2000;Qin and Chung, 2004). Fig.…”

Dual-layer P84/polyethersulfone hollow fibers for pervaporation dehydration of isopropanol

“…For the wet-spun hollow fibers (ID: A-1, A-13), the flux decreases 34% and separation factor increases 14% when the outer-layer dope flow rate was increased from 0.1 to 0.2 ml/min. The enhanced separation factor/selectivity may be attributed to shear induced better polymer chain packing at a higher outer-layer dope flow rate because shear rate is proportional to flow rate at the outer annulus wall of a spinneret [25]. On the other hand, the flux/permeance is sacrificed due to a higher substructure resistance at the outer selective layer.…”

Power‐law polymer solution flow in a converging annular spinneret: Analytical approximation and numerical computation

“…Aptel et al 13 found that increasing the dope extrusion rate could reduce the permeability. Chung et al [14][15][16] have also investigated the effect of the shear stress and shear rate within the spinneret on the morphology and properties of the hollow fiber membranes. Their results revealed that the fibers had a lower permeability due to the greater molecular orientation but a higher selectivity with increasing shear rates.…”