Influence of carbon nanotube type and novel modification on dispersion, melt-rheology and electrical conductivity of polypropylene/carbon nanotube composites

Melt-mixing was employed to prepare multiwall carbon nanotubes (MWCNTs) based polypropylene (PP) composites, wherein MWCNTs vary in "agglomerate" size and also in terms of "agglomerate" structure. Morphological analysis revealed MWCNTs-D type exhibits bigger "agglomerate" size with compact "agglomerate" structure with respect to MWCNTs-N type, that show smaller "agglomerate" size with porous "agglomerate" structure in the corresponding PP/MWCNTs composites. Melt-rheological analysis showed a rheological percolation threshold of 2 to 3 wt% in PP/MWCNTs-N composites, whereas PP/MWCNTs-D composites exhibited a rheological percolation of 3 to 4 wt% of MWCNTs. AC electrical conductivity measurements exhibited an electrical percolation threshold of 0.5 to 1 wt% of MWCNTs-N, whereas MWCNTs-D type depicts an electrical percolation threshold of 2 to 3 wt% of MWCNTs in the respective composites. Further, an unique dispersant; Li salt of 6-aminohexanoic acid (Li-AHA) was utilized to "deagglomerate" MWCNTs. Moreover, PP-g-MA was also utilized in combination with Li-AHA encapsulated MWCNTs in the corresponding composites. An extensive morphological, rheological, and electrical conductivity measurements suggested the influence of Li-AHA encapsulated MWCNTs and PP-g-MA on the transformation of MWCNTs "agglomerate" into "individualized" and smaller MWCNTs "agglomerate" in PP/MWCNTs composites.