Factors influencing structure formation and polypropylene prepared by twin-screw extrusion (2)

Comparison of the viscosity ratio effect on phase size between twin screw extruder and an internal mixing chamber indicated a significantly coarser dispersed phase in the latter case at high viscosity ratio. At a lower viscosity ratio the phase size and size distribution were identical in the two processing environments. The minor-phase morphology in the centre of the extruded strand was not found to be highly sensitive to the screw speed and the volumetric flow rate. This indicates that the minor phase in these blends is not highly dependent on the shear stress and energy imposed on the material before the die. The above results are contrasted with previous detailed studies carried out in an internal mixing chamber.