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°C as compared to 200, 220, and 240°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.