Rheological, crystallization and electrical characterization of bi-filler nanocomposites of polypropylene, carbon nanotube and carbon black under quiescent and shear conditions

In the present research, the effect of shear on the crystallization behavior of polypropylene (PP) nanocomposites loaded with carbon nanotube (CNT) and carbon black (CB) has been evaluated. Rheological properties, crystallization under shear, and electrical conductivity under shear of the bi-filler PP/CNT/CB nanocomposites have been evaluated and compared with those of the mono-filler PP/CNT and PP/CB nanocomposites. According to the rheological analyses, in the comparison between mono-filler and bi-filler nanocomposites with the same filler content, the storage modulus, complex viscosity, non-terminal behavior, and solid-like behavior of the bi-filler nanocomposites were higher than those of the mono-filler nanocomposites. Whereas, the storage modulus and complex viscosity of the bi-filler nanocomposites with half filler content were intermediate of the mono-filler nanocomposites. The zero viscosity of the bi-filler nanocomposite with the same filler content was about 6 times that of the mono-filler nanocomposites. Whereas, the zero viscosity values of the bi-filler nanocomposites with half filler content were 1.1-3.4 times those of the CB-loaded and 0.3-0.9 those of the CNT-loaded nanocomposites. According to the non-isothermal crystallization test, in the comparison between mono-filler and bi-filler nanocomposites with the same filler content, the crystallization temperature (T c ) of the bi-filler nanocomposites was 2.7 °C–3.5 °C higher than that of the mono-filler nanocomposites. Whereas, the T c of the bi-filler nanocomposites with half filler content were 1.4 °C–3.7 °C higher than those of the CB-loaded and 0.8 °C–1.5 °C lower than those of the CNT-loaded nanocomposites. According to the isothermal crystallization test, applying shear and increasing the shear rate and time accelerated the crystallization of the mono-filler and bi-filler nanocomposites, however to different extents. Under shear, the crystallization rate of mono-filler and bi-filler nanocomposites increased by 2 and 5 times, respectively. Electrical conductivity measurement revealed that shearing reduced the conductivity of the mono-filler and bi-filler nanocomposites by 120 and 200 times, respectively.