Influence of coagulant temperature and on-line drawing on the mechanical properties and permeation performance of cellulose acetate hollow fibers

Cellulose acetate (CA) ultrafiltration hollow fibers were prepared via the dry-wet spinning technique. In the spinning process, the coagulant temperature was varied, and hence the on-line draw ratio was affected. The results revealed that the maximal draw ratio increased with the increase of coagulant temperature up to 55 degrees C and then leveled off. The inner diameters, outer diameters and thickness of the hollow fiber decreased with the increase of the draw ratio. The tensile properties of the resulting hollow fibers were measured, and the breaking tensile stress increased with the increase of draw ratio. When the coagulant temperature was increased from 25 to 70 degrees C, the porosity increased, the pore size was slightly enlarged in the outer skin, the hydraulic permeability increased, and the percentage of retention R decreased. In summary, by increasing the coagulant temperature, the maximal draw ratio can be increased, and hence the mass transfer properties and the other properties of drawn CA hollow fiber can be varied.