Improved electrical conductivity of polymer/carbon black composites by simultaneous dispersion and interaction-induced network assembly

A versatile networking method is reported for conductive polymer/carbon black (CB) composites on the basis of simultaneous dispersion and interaction-induced network assembly during melt compounding via addition of a very small amount (about 1 wt%) of secondary polymer that has stronger interaction with CB than the matrix polymer. Four different systems including polyamide 6 (PA6)-modified polycarbonate (PC)/CB, thermoplastic polyurethane (TPU)-modified polyoxymethylene (POM)/CB, PA6-modified POM/CB and TPU-modified polypropylene (PP)/CB composites were investigated to demonstrate the feasibility of the method. 1 wt% secondary polymer can effectively induce assembly of CB particles, forming higher-structure loosely-packed agglomerates. Even with 0.3 wt% secondary polymer, the percolation threshold could decrease by 30%. The mechanism for the hierarchical morphology of filler arrangement is proposed on the basis of preferential wetting and infiltration of CB by secondary polymer and the assembly of dispersed CB aggregates around/in the small droplets of secondary polymer. The reduced inter-agglomerate tunnelling distance and enhanced secondary electric field are proposed as the mechanisms for improved electrical conductivity.