Co‐extrusion of unfilled and TiO₂‐filled polyethylene: Influence of viscosity and die cross‐section on interface shape

Abstract

Abstract An experimental study of the co‐extrusion of polyethylene and TiO 2 ‐filled polyethylene through capillary and rectangular cross‐section dies has been carried out. The influence of viscosity ratio, cross‐section type, die length and duration of flow has been studied. Low viscosity melts will encapsulate high viscosity melts during flow through cylindrical and rectangular dies. Low viscosity unfilled melts can encapsulate higher viscosity filled melts and low vicosity filled melts can encapsulate higher viscosity unfilled melts. However, the rate and extent of encapsulation seems to be greater for the former case. This may be due to differences in the viscosity‐shear stress behavior of the filled and unfilled melts. In rectangular dies, the extent of encapsulation for any pair is greater when the interface is initially perpendicular to the shorter cross‐section dimension. The results are consistent with the idea that encapsulation primarily depends upon the ratio of die length to initial interface length.