عنوان مقاله [English]
This paper reviews current knowledge about the rheology of highly filled polymers, focusing on hard fillers. Understanding the rheological properties would help for assist the formulation and processing of such polymeric materials. When solid particles are incorporated in a fluid, they affect the rheological behavior of the system via changes in the flow field. Nowadays rheology of suspensions, especially concentrated suspensions, is of great importance due to their wide uses in various fields such as composite, petrochemical and food industries. The main factors affecting the rheological behavior of these composites are discussed, such as maximum packing fraction, percolation threshold and the size distribution of the fillers. The size distribution of the fillers facilitates higher filling levels and decreases the melt mixture viscosity for a specified content of fillers. The limitations and flow instabilities of highly filled polymers often lead to non-linear rheological behavior such as wall slip, polymer-filler separation, swelling and surface instabilities phenomena. Following, mathematical models predicting the maximum packing fraction, which is one of the most important rheological parameters of highly filled composites, is presented. The viscosity-containing equations also discussed as a function of the filler content for unimodal, bimodal and multimodal highly filled suspensions.