Instrumented Indentation on Intercalated Clay Reinforced Polypropylene Nanocomposites

Instrumented indentation techniques were employed to investigate the local stiffness in comparison to the global stiffness in organomodified clay filled maleated polypropylene (MAPP). The morphology of composites was observed under transmission electron microscopy. Both highly intercalated and well exfoliated clay structures were observed in clay filled MAPP system. As a result, the region where indentation load was applied could be considered as the local composite system. Instrumented indentation was performed on three distinct positions: (a) clay intercalated and congregated region supported by MAPP matrix; (b) aggregate-MAPP boundary; and (c) the MAPP alone. The clay aggregated region generally showed higher stiffness as compared to the MAPP matrix. And, the relative increase in indentation stiffness is substantially higher than the relative increase in tensile and compressive stiffnesses. Good linear correlation obtained between the changes in global and local indentation stiffness suggests plausible future application of nanoindentation technique in predicting the mechanical properties of the composite bulk. Furthermore, the highly intercalated morphology clearly provides a local and highly confined nanocomposite system similar to natural materials with optimum stiffening potential