Effects of extrusion conditions on die-swell behavior of polypropylene/diatomite composite melts

Die-swell is an important parameter for characterization of elastic properties during extrusion of polymeric melts, and the degree of swell is usually expressed by die-swell ratio (B). The swell ratio for polypropylene composites filled with diatomite with different particle sizes (volume fraction of 10%) was measured by means of a melt flow rate instrument to investigate the effects of die geometry and extrusion conditions on the die-swell behavior of the composite melts with temperature varying from 210 to 230 °C and load varying from 5 to 12.5 kg. The results showed that B of the composites increased nonlinearly with increase of shear stress and shear rate, while it decreased linearly with rise of temperature. When load and temperature were constant, B increased nonlinearly with increase of the die diameter, whereas it reduced nonlinearly with increase of the die length/diameter ratio.