RHEOLOGY OF MIXED POWDER PLASTISOLS

Plastisols of fine iron and hardmetal powders, mixed with binder systems based upon polystyrene and polyethylene, have been formulated from which basic rheological data have been obtained. These data indicate that the plastisols with powder volume loadings up to Approximately 80% will flow satisfactorily under injection moulding conditions. Viscosity levels were found to reduce with increasing shear rate, though a critical level of shear rate may be reached beyond which dilatant flow behaviour tends to occur. This effect is considered to be due to the dissociation of the binder system from the powder surfaces at extremes of shear rate for specific plastisol formulations.