On the Toughness Response of iPP and sPP/MWNT Nanocomposites

Abstract

Nanocomposites based in polypropylene (both syndiotactic and isotactic) and multiwall carbon nanotubes (MWNTs) directly blended in the melt via micro-extrusion, were studied. The aim was to determine the role of MWNTs, on the creation of the plastic zone and crack propagation in double-cracked tensile specimens. Essential work of fracture toughness testing was performed on these nanocomposites. In all cases, the effect of MWNT weight fraction on the above properties was extensively studied. Data obtained have shown a non-linear relationship of almost all properties with MWNTs content.

Scanning electron microscopy revealed that a micro crack/craze bridging mechanism can be detected in polymer matrix/ MWNT nanocomposites. This mechanism was observed in the fibrillated areas of the specimens' fractured surfaces. The results obtained showed a promising role of the nanotubes as tougheners for future nanocomposites' applications. Ductile-to-brittle transition was confirmed for MWNT contents above 1 wt%.