Glass bead‐filled polypropylene part I: Rheological and mechanical properties

Five glass bead‐filled polypropylene composites were rheologically characterized at 240°C using two rotational rheometers to obtain low shear‐rate data and a capillary rheometer to obtain high shear‐rate data. Both steady and dynamic properties were measured at low shear rates. Each composite was also injection molded into tensile and flexural test bars for a mechanical properties profile at 25°C. The tensile modulus was determined from a simple extensional deformation whereas the flexural modulus was determined from a three‐point‐bend test. The relative shear viscosity and relative loss modulus are different nonlinear functions of the volume fraction of beads at a constant shear rate, while the relative storage modulus appears to be a linear function of bead fraction. The relative viscosity decreases with increasing shear rate and the zero shear‐rate data are in very good agreement with the Guth‐Gold equation. The relative tensile modulus and relative flexural modulus are each linear functions of bead fraction over the entire range of filler concentration, 0‐29 vol percent. From these data it is concluded that a simple correspondence between slow viscous flow and small strain elasticity does not exist for these composites.