A study on the effect of nano-ZnO on rheological and dynamic mechanical properties of polypropylene: Experiments and models

Three polypropylene (PP)/zinc oxide nanocomposites containing 5, 10 and 15 wt.% nanoparticles were prepared through melt-blending. Compression molded samples for dynamic mechanical and morphological studies were prepared. The nano-ZnO particles were observed to be dispersed uniformly, but with a different level of coalescence, by means of scanning electron microscopy (SEM). The plots of experimental and theoretical storage moduli values at 20 °C for various loadings of nanoparticles by wt.% Showed that the Einstein model had better agreement with experimental values while the Guth model deviated the most. Dynamic rheometry using a parallel plate rheometer showed that the rheological moduli of the nanocomposites increased with increase in nanofiller concentration; however this increase was greater in the high frequency region. There was an increase in complex viscosity of the nanocomposites with increasing the nanofiller concentration. Moreover, the rheological behavior of nanocomposites is more sensitive to nanoparticle concentration at low frequencies. All of the models used for prediction of melt viscosity underestimated the viscosity of nanocomposites, but the Einstein equation was the nearest to experimental values.