Melt Rheological Properties of Silver-Powder-Filled Polypropylene Composites

The melt rheological properties of titanate coupling-agent-treated particulate silver powder (varying from 0 to 5.6 vol% of Ag) were investigated. The effect of filler concentration on shear stress, shear rate, melt viscosity, and melt elasticity parameters were determined by using a piston-type capillary rheometer. The study shows that the materials follow a power law in viscous behavior over the entire range of shear rates and temperatures investigated. The melt viscosity decreases with filler content up to 4.1% and increases with a further increase in filler content. Interestingly, the viscosity of the composition was lower than that of unfilled polypropylene. The melt elasticity decreases with an increase in Ag content in the composites up to 4.1%; beyond that, it increases. The effect of temperature on the viscoelastic properties of filled polypropylene was also investigated.