Swirling Diffused Air Flow and Its Effect on Helical Fiber Motion in Swirl-Die Melt Blowing

In melt blowing, high-velocity air impinges upon a polymer stream and attenuates it into micro-fibrous materials. The structure of the melt-blown die controls the airflow field and determines the process of fiber formation. This work focused on exploring the air swirling diffusion in a particular swirl-die melt blowing. The air swirling diffusion was analyzed by measuring the lateral velocity (vr), and the lateral twisting velocity (vs) by using single- and dual-wire probe hot-wire anemometer. Results showed that the vr had a diffusion boundary, while the distribution of the vs located out of the diffusion boundary of vr. The fiber paths in the swirl-die melt blowing, which was captured by high-speed camera, showed that the cone angle of the fiber path was consistent with the cone angle of vr-diffusion boundary. However, most of the twisting velocity (vs) located out of the region of fiber path, resulting in that the fiber helical motion was initiated just at a critical z-position, rather than in the region further away from the die. This work shows that energy-wasting of vs exists during swirl-die melt blowing, and a more optimized structure of this kind of die should be found.