The investigation of irregular inner skin morphology of hollow fiber membranes at high-speed spinning and the solutions to overcome it

The increase in bore fluid flow rate can effectively eliminate the deformation. The addition of the solvent to the bore fluid can also eliminate the deformation when 70 wt.% NMP/water was used as bore fluid. No inner layer deformation was observed when dope and bore flow rates were increased up to 4 and 3 ml/min, respectively. However, the first three approaches may have negative side effects. The fourth approach gives us the most promising results. Even after increasing take-up speed up to 470% from its original take-up speed, the resultant fibers show no irregular formation at inner layer morphology and no changes in their inner and outer diameter. Thus, it can be said that by utilizing this approach, more flexible and easy control over fibers can be achieved.