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

Abstract

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.

Effect of silica nanoparticles on physical, mechanical, and wear properties of natural fiber reinforced polymer composites

“…[6][7][8] To relinquish the gap between the polymer composite services to the requirements of the application, utilization of nanoparticles for developing polymer nanocomposites is now being set forward. [9] Polymer nanocomposites are the composites produced by the combination of polymer matrix with the dispersion of nanoparticles. [10] It has been found that the inclusion of nanoparticles enhances various properties of polymer composite, such as superior toughness and mechanical strength, excellent electrical and thermal properties, outstanding flame retardancy, and a more significant barrier to moisture and gases.…”

Carbon nanotubes interaction with amorphous and semi‐crystalline domains of polypropylene in melt‐mixed composites: Influence of multiwall carbon nanotubes agglomerate and their modifications

“…Earlier we have observed a higher average agglomerate size corresponding to D‐MWCNTs as compared to N‐MWCNTs from optical microscopic analysis. [ 24 ] The higher L/D ratio (~270 for D‐MWCNTs as compared to ~158 for N‐MWCNTs) [ 14 ] leads to higher extent of agglomeration in D‐MWCNTs. Further, N‐MWCNTs show higher value of specific surface area as compared to D‐MWCNTs due to less compact agglomerate structure associated with N‐MWCNTs, which involve higher fraction of individualized nanotubes.…”

“…The increase in temperature corresponds to T onset and T final values in PP/MWCNTs is due to the kinetic barrier imposed by nanotubes, which delays the degradation process of PP. Further, as the concentration of the nanotubes exceeds the electrical percolation threshold, [ 14 ] the action of MWCNTs on delaying the thermal degradation of PP is much more evident from the respective T onset and T final corresponding to PP/MWCNTs composites. Moreover, these values along with residual weight data also suggest that PP chains engage in interfacial interaction with “individualized” MWCNT, thus forming a thicker “interphase.” The influence of N‐MWCNTs is higher as compared to D‐MWCNTs in the formation of thicker “interphase,” which is due to the presence of higher fraction of “individualized” N‐MWCNTs in the respective composites.…”

“…Further, dispersion of MWCNTs in PP matrix primarily depends on the extent of “agglomeration” associated with the MWCNTs type, interfacial interaction between PP and MWCNTs and the parameters used in processing. [ 5,14 ] The influence of “agglomeration” in the as‐synthesized MWCNTs has also been explored extensively on the dispersion state of MWCNTs in PP/MWCNTs composites. [ 14 ] The surface free energy difference between PP and MWCNTs is higher as compared to polar polymers, hence it dictates the dominance of “MWCNTs‐MWCNTs” interaction as compared to “polymer‐MWCNTs” interaction in PP/MWCNTs composites.…”

“…[ 5,14 ] The influence of “agglomeration” in the as‐synthesized MWCNTs has also been explored extensively on the dispersion state of MWCNTs in PP/MWCNTs composites. [ 14 ] The surface free energy difference between PP and MWCNTs is higher as compared to polar polymers, hence it dictates the dominance of “MWCNTs‐MWCNTs” interaction as compared to “polymer‐MWCNTs” interaction in PP/MWCNTs composites. This hypothesis has also been validated via extensive morphological investigation reported by various research groups, wherein “micro” and “nano‐sized” MWCNTs agglomerates are observed via optical and transmission electron microscopy (TEM).…”