Behavior of Fine Particle Agglomerates in a Newtonian Molten Polymer Under a Shear Flow

The dispersing behavior of a particle agglomerate in a mixture consisting of spherical fine particles and a molten polymer was investigated with the application of shear in a cone–plate apparatus. After attaining a constant agglomerated state by applying a small shear, the shear rate was changed to a set value and kept constant over a certain time. Viscosity measurement during shear application and analysis of particle agglomeration in a solidified mixture were conducted. In a dispersing process, agglomerates were broken up to a steady dispersed state corresponding to the shear rate applied and the average number of agglomerated particles could be well correlated by a deformation of the mixture in each particle volume fraction. The viscosity of the mixture with a particle loading of 0.15 had a good relationship with the agglomerated number independent of shear rate; thus, the viscosity of suspension may help in the understanding of the dispersing behavior. However, the concentrated mixture could not achieve a complete dispersion and the viscosity was significantly affected by the time response of the agglomerated structure to shear application, although a dynamic rheological measurement of mixtures with different particle loadings provided much the same result.