A study was made on the rheological properties of alumina-polypropylene mixture system. The effects of solid volume concentration on mixing and flow properties were investigated at a variety of concentrations.
The torque after the mixing time of 1h at 453K increased with increasing solid concentration from 0% to 60%, but fell off when the concentration became as high as 70%. SEM photographs indicated that this decrease of torque corresponded to the transition of particle packing structure from the capillary state to the funicular one. The apparent viscosity of the mixture was measured by a capillary type viscosimeter in the temperature range of 436K to 453K. The effect of capillary dimension on viscosity was examined by using six kinds of dies with the same radius of 0.5mm but different lengths varying 0.5mm to 15mm. The end correction obtained at a constant shear rate of 103s-1 decreased from ten to nearly zero with increasing concentration from 0% to 70%. Also, the higher the measured temperature, the smaller the end correction became. The true viscosity, calculated by using the above values of end correction, tended to increase rapidly beyond the concentration of 40%. This increase in viscosity was, however, relatively small compared with the theoretically expected value.
