SYNERGIC EFFECT OF TWO INORGANIC FILLERS ON THE MECHANICAL AND THERMAL PROPERTIES OF HYBRID POLYPROPYLENE COMPOSITES

Inorganic fillers such as CaCO3 and clays are widely used as fillers to improve the mechanical and physical properties of polypropylene (PP). With the aim of improving simultaneously the stiffness and yield stress of PP, hybrid nanocomposites comprising PP/CaCO3/clay (montmorillonite) were prepared and their thermal and mechanical properties were investigated and compared with those of PP/CaCO3 and PP/clay composites. Morphological characterizations of the composites were performed by SEM and XRD analyses. The results showed exfoliated clay in the hybrid composite with a much higher degree than in PP/clay composite. Increase in modulus and yield stress and better thermal stability was attained for hybrid composites as a result of the clay exfoliation. The toughening effect of two different types of CaCO3 particles was also observed in hybrid composites, where an effective enhancement of the mechanical and thermal properties were achieved depending on the origin, specific area, particle and pore size of the CaCO3 used.