Discrete Element Modeling (DEM) of Agglomeration of Polymer Particles

The models of particle interaction in colloid systems present a valuable tool for the investigation of the stability of these systems. Our model is based on the Discrete Element Method (DEM) and describes each particle in the dispersion by its position, size, shape and velocity. Behavior of the system is described by various forces acting between the particles and/or between the surrounding fluid and the particle. We employ the DLVO theory, Brownian motion, Hooke's law and the viscous dissipation by Stokes law as the constitutive description of force interactions. The model is capable to simulate trajectories of hundreds of particles in two or three spatial dimensions as well as details of two-particle interactions. The model has been carefully validated to be in agreement with general thermodynamic theories. This means that our model realistically predicts not only mean velocity of colloid particles but also distribution of particle velocities and their mean square displacement consistent with Stokes-Einstein equation. Model results represent dynamics of aggregation of a colloidal system into gel-like network and dynamic evolution of meta-stable colloid dispersion. Thus we are also able to predict stability and dynamic evolution of the colloids with various thermodynamic parameters of the system, e.g., size of dispersed particles, concentration of ions in the surrounding electrolyte, etc. Modeling of particle agglomeration by DEM concept is helpful also in the characterization of morphologies of colloidal agglomerates.