Study on the melt flow behavior of glass bead filled polypropylene

Glass beads were mixed into isotactic polypropylene by single and twin-screw extruders and the effect of glass bead content, bead size and preparation route on the melt flow properties of the composites were evaluated by melt flow rate (MFR), capillary rheometer and torque rheometer tests. The results indicated that the filler content and processing route showed greater effect than bead size. The apparent viscosity (η) of the materials first increased with the addition of glass beads and then decreased with increasing glass bead content, but η did not show great variation with the bead sizes studied. The viscosity of the composites prepared by single screw extruder was higher than that prepared by twin-screw extruder. In the torque rheology test, the maximum torque (Tmax) increased with the increase of filler content, then reduced at quite high filler content, while the equilibrium torque (Te) and the energy consumption shown by the integrated area (A) of the torque vs time curves presented a roughly increasing trend. With filler particle size increasing, the Te and the A values first increased and then reached an equilibrium value. Te and the A values of the composites prepared by single screw extruder were significantly larger than those of the composites prepared by twin-screw extruder.