Shear‐stimulated formation of multi‐wall carbon nanotube networks in polymer melts

We report on shear‐induced nanotube network formation in multi‐wall nanotubes/polycarbonate (MWNT/PC) composite melts which was directly monitored by the time‐resolved DC‐conductivity measurements during steady shear. A small steady shear applied for 1 h to a non‐conductive composite with initially well‐dispersed nanotubes was found to induce the insulator‐to‐conductor transition resulting in a conductivity increase by about six orders of magnitude. Similar composite melt annealed without steady shear demonstrates much slower process of the network formation what can be attributed to an agglomeration of attractively interacting nanotubes in polymer melts. The rheologic properties were also measured for shear‐stimulated agglomeration. Unexpected difference between the electrical and mechanical networks in MWNT/PC composites was found. For the modeling of the network formation a shear‐dependent kinetic equation for the nanotube agglomeration was coupled with empirical formula for insulator‐to‐conductor transition. magnified image Electric DC‐conductivity and shear modulus (G′ and G″) of MWNT/PC melt (230 °C) measured simultaneously during shear‐stimulated network formation.