In the present study, polypropylene/nanoclay (PP/NC) and polypropylene/nano-calcium carbonate (PP/CC) nanocomposites with different weight percentages of filler were prepared using a twin-screw extruder. The effects of nanoparticles content on the nanocomposite were studied using the hardness measured under the applied loads in the range of 10-100 gf. It was observed that the microhardness increases with an increase in the nanofiller weight percentage. The hardness reaches its maximum for 1 wt% and 3 wt% for PP/NC and PP/CC, respectively. The results of the present study are evaluated by analytical methods proposed by Marsh and Tabor. For this purpose, mechanical properties of PP nanocomposites were obtained by uniaxial tensile and compression tests. The results were incorporated in Tabor and Marsh formula. According to the analytical methods, the results obtained from compression test were more accurate than those obtained from tensile test. In addition, variation of H/Y ratio (H and Y are microhardness and yield stress, respectively) versus the filler content under different applied loads was obtained. Finally, the Marsh model is modified in this work. The modified model proves more accurate in prediction of microhardness and H/Y ratio of PP nanocomposite at different applied loadings. The new proposed model correlates the yield stress, elastic modulus, and the applied load to microhardness. © 2016 Author(s).
