Nano-indentation as a tool for evaluating the rheological threshold in polymer composites

Abstract

We investigated the variation of nano-mechanical properties of Poly (propylene) (PP)/Carbon Black (CB) composite using nano-indentation and evaluated rheological threshold of the composites. PP/CB composites were prepared by melt-mixing process with varying CB content (0–20 wt %) using a micro-compounder. The rheological threshold of the composites was calculated using well known rheometer technique by power law relation. We also employed nano-indentation technique as an additional novel tool for evaluating rheological threshold in PP/CB composites. Rheological and nano-indentation measurements were correlated to assess the rheological threshold in PP/CB composites. The modulus of elasticity of PP/CB composites was increased from 0.8 GPa to 1.4 GPa with 20 wt % CB loading. There was a minor enhancement in the tensile strength of PP/CB composites with increase in CB content and the elongation at yield was decreased due to the brittleness imparted by CB. The thermal stability of PP/CB system also improved with CB content as the decomposition temperature was shifted from 450 °C to 500 °C.