Rheological behavior of concentrated suspensions as affected by the dynamics of the mixing process

Development of an epoxy based intumescent system comprising of nanoclays blended with appropriate formulating agents

“…This mechanism that is valid for suspensions with noncolloidal particles, i.e., break-down of the particle agglomerates with increasing specific energy input, is thus expected to give rise to decreases in dynamic properties with increasing specific energy input, which were indeed observed during the dispersion of non-colloidal graphite particles into polymeric matrices [30,31]. However, as indicated in Figs.…”

“…With the nanoclays the motion of polymer For conventional mixtures of non-colloidal particles incorporated into a polymer melt the process of structuring and the resulting changes in the rheological behavior (i.e., in the total absence of intercalation and exfoliation) are very different. Kalyon and coworkers have shown, that for non-colloidal graphite particles, which were initially agglomerated, the increase of the mixing time and the associated increase of the specific energy input progressively lead to the break-down of the particle agglomerates and the encapsulation of the particles by the binder [30][31][32]. With such non-colloidal particle agglomerates prior to dispersion there is significant void space between the ultimate particles of the agglomerates.…”

“…This void space contributes to the volume fraction of the solid phase. As the agglomerates are broken down during the dispersion process of suspensions with non-colloidal particles, the void space in between the ultimate particles becomes progressively occupied by the binder and consequently the yield stress and the shear viscosity as well as the elasticity of the suspension, decrease [30,31].…”

“…A typical relationship between the shear viscosity of a suspension, Á s , and the shear viscosity of the binder of the suspension, Á b , at the same shear rate would be given by [30,36]: Thus, at constant , changes in the relative viscosity of the suspension, i.e., Á s /Á b , would be associated with changes in the maximum packing fraction, max . It appears that there is a significant difference in the magnitude of complex viscosity values of Formulations #3c (containing nanoclays) versus Formulations #1 and #2, in spite of constant (Fig.…”

A Review of Dynamic Models of Hot-Melt Extrusion

“…Various studies were dedicated to the evolution of material characteristics, such as the viscosity, melt density, size and shape distribution of the particle clusters, electrical properties and evidenced complex dependencies with respect to the degree of mixing, the quantity of air into the extruded compound, etc. [25][26][27][28][29][30][31][32][33]. For some extruded materials, analytical studies do not allow one to obtain an accurate representation of the rheological properties, and in-line measurements from an actual extrusion device are required [34].…”