Journal of Materials Science, Vol.29, No.11, 2931-2938, 1994
Steady and Oscillatory Flows of Silicon-Polypropylene Ceramic Compounds
The rheological properties of a ceramic moulding compound, silicon powder with a polypropylene binder system, were studied using a Rheometrics mechanical spectrometer RMS-800 and an Instron capillary rheometer. The study included steady simple shear flow, transient start-up shear flow, stress relaxation upon cessation of steady shear flow, stress relaxation after a sudden shear displacement, and dynamic oscillatory shear flow. Yield behaviour was observed in both steady-shear and dynamic measurements. The empirical Cox-Merz rule which is usually applicable to polymer melts and solutions was found to be invalid for this material. The modified Cox-Merz rule, in which the apparent viscosity versus shear rate is equal to the complex viscosity versus the shear-rate amplitude in the highly non-linear region, was found to be valid for this material system. A series of anomalous phenomena were also observed during the shear-flow experiments including work hardening in the very-low-shear-rate region, stress oscillation in the high-shear-rate region, and stress relaxation followed by substantial stress growth in the stress-relaxation measurements.