Fig. 1 displays the relationship between tensile stress and strain
of the PP/G1 composites. It can be seen that the values of the tensile
strain at break decreases with increasing the GNPs weight fraction.
Fig. 2 presents the relationship between tensile stress and strain for
the PP/G2 composites. When the GNPs weight fraction is smaller
than 0.3 wt.%, the values of the tensile strain at break are only
slightly lower than that of the unfilled PP; while when the GNPs
weight fraction is more than 0.3 wt.%, the values of the tensile
strain at break significantly decrease with increasing the GNPs
weight fraction. Fig. 3 illustrates the relationship between tensile
stress and strain for the PP/G3 composites. Similar to the results