The influence of melt-mixing process conditions on electrical conductivity of polypropylene/multiwall carbon nanotubes composites

The influence of melt-mixing parameters on the development of network-like structure of multiwall carbon nanotubes (MWNTs) in injection-molded polypropylene (PP)/MWNTs composites was assessed through AC electrical conductivity measurements. A higher melt-mixing temperature (260 degrees C as compared to 200, 220, and 240 degrees C) at a fixed rotational speed of the screws (150 rpm) and at a fixed mixing time (15 min) has yielded maximum improvement in electrical conductivity in PP/MWNTs composites of 3 wt % MWNTs content. Next to higher melt-mixing temperature, a variation in the melt-mixing time has also led to a variation in electrical conductivity of the composites. Raman spectroscopic analysis revealed an increase in the ratio of intensity due to G-band over that of D-band (IG/ID) of the MWNTs in the skin region as compared to the core region of the injection-molded composites irrespective of the melt-mixing conditions. Microscopic observations could not provide much insight into the variation of MWNTs network-like structure in various PP/MWNTs composites. An attempt has been made to understand the variation of network-like structure of MWNTs in PP/MWNTs composites as a function of melt-mixing parameters through electrical conductivity measurements, Raman spectroscopic analysis, and morphological investigations. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013