2 research outputs found
Formation of Fractal-like Structure in Organoclay-Based Polypropylene Nanocomposites
We present the structural features
of organoclay dispersions in
polypropylene melts investigated by shear rheology. Scaling behavior
of the nanocomposites linear viscoelastic properties based on apparent
yield stress and critical strain measurements enables to assess the
fractal dimension <i>d</i><sub>f</sub> of the network formed
by clay particles within the matrix. The network structure induces
a thixotropic behavior which manifests by solid-like behavior accentuation
over time under quiescent conditions and sensitivity to large deformation
shear flow. Formation kinetics of the fractal-like network structure
at rest is discussed through linear and nonlinear rheological investigations.
A two-step process is observed for clay network reorganization over
annealing time, with pronounced transition around 10<sup>4</sup> s.
These phenomena, which picture a nonequilibrium state where interparticle
attractions favor disorientation of the platelets and network growth,
are strongly coupled to the dispersion state of the organoclay within
the polymeric matrix
Aggregation and Separation in Ternary Particle/Oil/Water Systems with Fully Wettable Particles
We report that a variety of ternary
particle/liquid/liquid mixtures
heavily aggregate or separate completely if (1) the particles are
fully or almost fully wetted by one fluid, and (2) if the wetting
fluid volume fraction is comparable to the particle volume fraction.
Aggregation and separation do not happen if the particles are partially
wetted by both fluids, in which case Pickering emulsions appear at
all compositions. Rheological and geometric criteria for aggregation
are proposed and compared with a state diagram of a ternary system
composed of oil, water, and hydrophilic glass particles. Analogies
are drawn to wet granulation and spherical agglomeration, two particle
processing operations in which wetting phenomena are important