Polymer Engineering Center > Research > Die Lines and Die Lip Build-up in Plastics Extrusion

Die lines are annoying striations on plastic film, sheet or pipe surfaces. They not only damage extrudate aesthetics, but also compromise product properties. This research project has identified distinct die line mechanisms and affecting factors. Current work focuses on fluid mechanics and polymer rheology in the die line formation and on exploring ways to suppress these striations. Die lip build-up is an accumulation of undesired materials around the die orifice in plastics extrusion. It destroys extrudate quality, and causes the line to be shut down for cleaning. It has been experimentally proved that flaring (diverging) die orifice can dramatically reduce the build-up. Viscoelasticity of molten plastics has been found to be responsible for this reduction and a die design scheme resulting from this research can be employed for maximal suppression. A student performs a rheological test of an anisotropic polymer inorganic composite sample