STEADY AND OSCILLATORY FLOWS OF SILICON-POLYPROPYLENE CERAMIC COMPOUNDS

The rheological properties of a ceramic moulding compound, silicon pow der with a polypropylene binder system, were studied using a Rheometri cs 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 r elaxation after a sudden shear displacement, and dynamic oscillatory s hear flow. Yield behaviour was observed in both steady-shear and dynam ic measurements. The empirical Cox-Merz rule which is usually applicab le to polymer melts and solutions was found to be invalid for this mat erial. The modified Cox-Merz rule, in which the apparent viscosity ver sus 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 observ ed during the shear-flow experiments including work hardening in the v ery-low-shear-rate region, stress oscillation in the high-shear-rate r egion, and stress relaxation followed by substantial stress growth in the stress-relaxation measurements.