Simulation on structural optimization of spinneret for hollow fiber membrane fabricated by dry-jet wet spinning
In the process of fabricating hollow fiber membranes by dry jet wet spinning,spinneret as one of the key compo-nents,its dimension and internal geometry have an important effect on the orientation of polymer molecular chains and the final membrane morphology.Optimizing the spinneret structure is helpful to improve the spinnability of membrane filaments and product quality.A three-dimensional spinneret flow channel model was established and the effects of flow channel structure parameters such as the length of straight channel,annulus-gap dimension and flow angle of conical channel on the shear flow in the spinneret,die swell at the outlet of spinneret and the elongational flow in the air gap were investigated by numerical simulation.The simulation results show that the pressure and pressure drop of the dope solution flowing through the inlet of the spinneret forming hole increase with the increase of the length of straight channel,and decrease with the increase of the annulus-gap dimension and flow angle of conical channel,and the longer the straight channel,the more conducive to the full development of the solution flow.Compared with the length of straight channel,the annulus-gap dimension and the flow angle of conical channel have a more significant effect on die swelling behavior of the solution.With the increase of annulus-gap dimension and flow angle,the die swelling phenomenon decreas-es.The length of straight channel and flow angle of conical channel have no obvious effect on the outer diameter profile of the primary fiber in the air gap.The orientation and strength of the membrane filament can be increased,and the flow stability in the spin-ning process can be improved when the length of straight channel and annulus-gap dimension are increased and the conical channel spinneret is used.The optimized structure of the spinneret is as follows:the length of straight channel is 1.1 mm,the annulus-gap dimension is 0.11 mm(that is,the ratio of length to gap is about 10),and the conical flow angle is greater than 30°.
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