Rheology, electrical conductivity, and the phase behavior of cocontinuous PA6/ABS blends with MWNT:: Correlating the aspect ratio of MWNT with the percolation threshold

Multiwalled carbon nanotubes (purified, p-MWNT and similar to NH2 functionalized, f-MWWT) were melt-mixed with 50/50 cocontinuous blends of polyamide 6 (PA6) and acrylonitrile-butadiene-styrene in a conical twin-screw microcompounder to obtain conductive polymer blends utilizing the conceptual approach of double-percolation. The state of dispersion of the tubes was assessed using AC electrical conductivity measurements and melt-rheology. The rheological and the electrical percolation threshold was observed to be similar to 1-2 wt % and similar to 3-4 wt %, respectively, for blends with p-MWNT. In case of blends with f-MWNT, the rheological percolation threshold was observed to be higher (2-3 wt %) than p-MWNT but the electrical percolation threshold remained almost same. However, the absolute values were significantly lower than blends with p-MWNT. In addition, significant refinement in the cocontinuous morphology of the blends with increasing concentration of MWNT was observed in both the cases. Further, an attempt was made to understand the underlying concepts in relation to cocontinuous morphologies that how the geometrical percolation threshold which adversely suffered because of the attrition of tubes under prolonged shear contributed further in retaining the rheological percolation threshold. (C) 2008 Wiley Periodicals, Inc.