DEVELOPMENT OF A PREDICTIVE POWER LAW RELATIONSHIP FOR CONCENTRATED SLURRIES, PART 1: THEORY

摘要

All polymer slurries that have a high concentration of filler are shear thinning. This can include the starting materials for sheet molding compound, polymer based inks, many reactive extrusions systems, and polymer concentrates that are let down in extrusion systems as color concentrates or opacifiers. Several sizes of calcium carbonate were initially investigated because of their extensive use in the polymer industry as fillers. The investigation focused on developing an analytical tool that would lead to understanding and the prediction of the flow characteristics of slurries that have a Newtonian continuous phase but have high enough filler concentration to exhibit shear thinning or power law characteristics. This work's focuses on concentrations where the initial yield behavior is not dominant 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. We present here a theory that predicts the characteristic of the power law constant, n, as a function of filler concentration and is based on observing and modeling the well-known plug formation in the center of a tube as the material flows down the tube. The plug was experimentally shown to be a non-dissipating volume in the flowing slurry. This percolation based rheological analysis was then extended to a highly filled Polyethylene resin.