Melt Processing and Properties of Polyamide 6/Graphene Nanoplatelet Composites

Abstract

In this paper, the processing and characterization of Polyamide 6 (PA6) / graphite nanoplatelets (GNPs) composites is reported. PA6/GNPs composites were prepared by melt-mixing using an industrial, co-rotating, intermeshing, twin-screw extruder. A bespoke screw configuration was used that was designed in-house to enhance nanoparticle dispersion into a polymer matrix. The effects of GNPs type (xGnP® M-5 and xGnP® C-500), GNPs content, and extruder screw speed on the bulk properties of the PA6/GNPs nanocomposites were investigated. Results show a considerable improvement in the thermal and mechanical properties of PA6/GNPs composites, as compared with the unfilled PA6 polymer. An increase in crystallinity (%Xc) with increasing GNPs content, and a change in shape of the crystallization exotherms (broadening) and melting endotherms, both suggest a change in the crystal type and perfection. An increase in tensile modulus of as much as 376% and 412% was observed for PA6/M-5 xGnP® and PA6/C-500 xGnP® composites, respectively, at filler contents of 20wt%. The enhancement of Young’s modulus and yield stress can be attributed to the reinforcing effect of GNPs and their uniform dispersion in the PA6 matrix. The rheological response of the composite resembles that of a ‘pseudo-solid’, rather than a molten liquid, and analysis of the rheological data indicates that a percolation threshold was reached at GNPs contents of between 10– 15wt%. The electrical conductivity of the composite also increased with increasing GNPs content, with an addition of 15wt% GNPs resulting in a 6 order-of-magnitude increase in conductivity. The electrical percolation thresholds of all composites were between 10–15wt%.