Comparison of instabilities in horizontal and vertical coextrusion.

摘要

Multilayer coextrusion was used to produce extruded trims having up to several thousand alternating horizontal or vertical layers. This work studied and compared the different instabilities that occur during coextrusion of films having horizontal and vertical layer orientations. This study demonstrated that wave instabilities, which are very prominent in films having layers with horizontal orientation, are non-existent for films having vertical lavers extruded with same materials and processing conditions. This behavior may be due to the orientation of the lavers with respect to the direct of flow. Scatter instabilities occurred with greater numbers of horizontal layers, but not with vertical layers. The scattering-related mixing of the layers created a drastic reduction in width and an increase in thickness of the sheet with horizontal layers. Both horizontally and vertically layered sheet showed curving of the layer interfaces. This curving was severe in sheet with vertical layers and led to encapsulation of the vertically-layered structure by one of the materials.