How to Adapt Die Design to Resin Rheology and Avoid Melt Fracture, 2000 Polymers, Laminations & Coatings Conference Proceedings
Natti S. Rao--In general melt fracture can be defined as a discontinuity in the flow of the melt which can manifest itself as waviness or shark skin on the surface of the extrudate or slip in the die, to mention a few examples of as to how the phenomenon of melt fracture can occur in the practice. By changing the dimensions of a die in such a way that the melt flow takes place in regions of shear where melt fracture cannot occur, it is possible to avoid melt fracture. This paper deals with easily applicable practical methods of die design which show as to how these changes in the die contour can be accomplished in order to eliminate melt fracture. The design procedure is illustrated by means of examples of dies used in pelletizing, blow molding, blown film and extrusion coating processes. This approach can also be applied to assess the performance of an existing die.
How to Adapt Die Design to Resin Rheology and Avoid Melt Fracture, 2000 Polymers, Laminations & Coat
