Characterizing the flow of slurries using percolation theory based functions

All polymer slurries that have a high concentration of filler are shear thinning. A new function was found that linearly correlates the power law constant, n, to the concentration of the filler. The behavior of this function suggests that the Newtonian to power-law behavior may be dominated by percolation processes and the area of the filler. A theory is presented that predicts the power law constant, n, as a function of filler cluster formation and the decrease of dissipation due to no velocity gradient in the clusters. This percolation based rheological analysis is then extended to polystyrene melts and highly filled polyethylene resin. Highly filled polymer compounds can present processing challenges, including high screw shaft torque, energy consumption, pressure and melt temperature. A percolation based evaluation of the effects of filler concentration on melt processing is presented using experiments with a batch mixer. It is demonstrated that measurements can be correlated to the theoretical treatment of the rheology as a particulate percolating system. The implications of the increase in viscosity with filler concentration on polymer processing are discussed from a practical engineering perspective. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers