Microstructural interpretations on thermo-mechanical relaxation and electrical conductivity of polyamide-12/polypropylene-MWCNT nanocomposites

Ternary-nanocomposites of polyamide 12 (PA-12) and multi-walled carbon nanotubes-embedded-polypropylene (MWCNT-embedded-PP) were fabricated by direct-melt-mixing-route and characterized for their dispersion-nanomorphology and phase-selective micromorphology. The crystallite sizes remained in the range of 8-9 nm and a broadening in loss-tangent peaks shifting towards higher temperatures with MWCNT was observed. The DC electrical conductivity remained dependent on the change in morphology from domain-dispersed (MWCNT-embedded-PP dispersed in PA-12 matrix) in PA-12/PP-MWCNT (70:30) to quasi-co-continuous (MWCNT-embedded-PP forming elongated domains of PP-MWCNT dispersed in PA-12 matrix tending to be near-continuous) in PA-12/PP-MWCNT (60:40). The conceptual feasibility of designing nanocomposites wherein the switch-over in solid-state relaxation behaviour vis-a-vis electrical conductivity is thus found to be controlled by morphology that ensures phase-selective conductive response for functional applications, as in flexible electronics, unlike the ones with rigid and high melting (thermally stiff) polyamides such as polyamide 6 or polyamide 66.