Relationship of Rheological Study with Morphological Characteristics of Multicomponent (Talc and Calcium Carbonate) Filled Polypropylene Hybrid Composites

Polypropylene (PP) copolymer reinforced with talc, CaCO3, or multicomponent fillers (a combination of talc and CaCO3) were compounded in a Brabender Plasti-Corder (R) internal mixer. These compounds then experienced an extrusion process by means of a capillary rheometer. The rheological and morphological (SEM) properties of the extrudate were analyzed to investigate the effect of shear stress, filler type, and temperature. The rheological studies revealed that the incorporation of multicomponent fillers has increased the melt viscosity. However, different ratio of filler type demonstrates no significant effect. It is also shown that the system appears pseudoplastic over one range of shear rates but dilatant over another. The presence of filler seems to have a pronounced influence on dilatant flow in filled PP. Observation on SEM analysis at high shear stress showed that large CaCO3 agglomerates are seen to be randomly dispersed whereas talc particles are more uniformly distributed and oriented to flow direction, suggesting better mixing.