Blends of Polypropylene and Ethylene Octene Comonomer with Conducting Fillers: Influence of State of Dispersion of Conducting Fillers on Electrical Conductivity

Blends of polypropylene/ethylene octene comonomer (PP/EOC) with conducting fillers viz., carbon black (CB) and multiwall carbon nanotubes (MWNT) were prepared using melt mixing technique with varying filler concentration and blend compositions. Thermo gravimetric analysis studies indicated that presence of filler enhanced the thermal stability of PP/EOC blends. Morphological analysis revealed the formation of matrix-dispersed droplet and co-continuous type of morphology depending on the blend compositions. Significant reduction in droplet size and finer ligament thickness in co-continuous structure were observed in the blends with filler due to compatibilization action. Fillers were found to be aggregated in the EOC phase irrespective of blends compositions and could be related to the affinity of the fillers toward EOC phase. The electrical conductivity of PP/EOC blends with CB and MWNT was found to be highest for 80/20 composition and decreased as EOC content increased. The percolation threshold of CB was between 10 and 15 wt% for the 80/20 and 70/30 blends whereas it was 15-20 wt% for blends with EOC content higher than 30 wt%. The percolation threshold was 2-3 wt% MWNT for PP/EOC blends. This was attributed to the aggregated filler network preferentially in the EOC phase. The melt-rheological behavior of PP/EOC blends was significantly influenced in presence of both the fillers. POLYM. ENG. SCI., 49:1502-1510, 2009. (C) 2009 Society of Plastics Engineers