The Influence of a Titanate Coupling Agent on the Rheological Properties of PP/CaCO₃

The present work deals with the study of the rheological properties of polypropylene/calcium carbonate composites treated with a titanate coupling agent. The study focused on the examination of the flow behavior of the material under different conditions of shear rate and temperature. A more pronounced pseudoplastic behavior was observed for the filled material than for neat polypropylene. It was also found that the power law index increases slightly with increasing temperature and increased concentration of the coupling agent; but decreases with the amount of filler and shear rate. On the other hand, the viscosity increased with increased amount of the filler, especially at low shear rates, but showed a substantial reduction with increased temperature and concentration of the coupling agent. The activation energy, too, was found to decrease with shear rate and concentration of the titanate agent, confirming, hence, the lubricating action of this coupling agent. Finally, through the shift factor that was calculated for both the viscosity and the shear stress functions, the flow master curves superposed for all the materials that were studied.