Manipulating the morphology of PA6/POE blends using graphene to achieve balanced electrical and mechanical properties

Abstract

We investigate the effect of graphene localization on the morphology and properties of Polyamide 6 (PA6)/Polyolefin elastomer (POE) blends. Two systems with different compositions were studied: (i) 60/40 (a composition near phase inversion) and (ii) 80/20 (a highly asymmetric composition). In this study, we demonstrate that the migration behavior of graphene is strongly dependent on its dispersion state, which is determined by mixing order. We show that the neat 60/40 (PA6/POE) blend has an unstable co-continuous morphology which breaks up over time during annealing to a droplet-matrix morphology with POE being the continuous phase. The addition of 3 wt% graphene leads to co-continuous morphologies independent of mixing order. In the case of 80/20 systems, preparation of nanocomposites with a POE master batch resulted in elongated POE dispersed domains which becomes a co-continuous morphology at higher level of graphene content (1.5 wt%). However, we observed a decrease in the continuity of the POE phase in the nanocomposite containing 3%wt of graphene due to a reduction of coalescence. Our rheological and electrical measurements revealed that the graphene formed a stronger percolated structure in 80/20 blend containing 3 wt% of graphene in comparison to 60/40/3 nanocomposites, which resulted in lower electrical resistivity. The electrical percolation threshold in this system is 0.66 wt% which demonstrates that using graphene to induce co-continuity in a highly asymmetric composition is a promising approach to design electrically conductive blends with a very low percolation threshold.