Dynamic and steady state flow of polypropylene/mica systems

Six compositions containing commercial polypropylene, PP, and monodispersed, untreated phlogopite mica were prepared. Their rheological properties were determined at 180°C in dynamic and capillary flows. The results are discussed in terms of strain‐induced orientation of mica flakes. Two critical volume fractions were found to affect the flow: ψ c defined as a concentration of flakes overlap and ψ m as a concentration of maximum packing of freely sedimenting particles. At ψ > ψ c yield stress and at ψ > ψ m non‐linearity in dynamic response were observed.