(424b) Particle Heteroaggregation: Analysis by a Property Discrete Population Balance Model

In important technical processes (crystallization, polymerization, coating processes) heteroaggregation between unlike particles plays a decisive role. If the particle species are of different size and zeta potential, formation of morphologically different heteroaggregates (clusters) can be observed. The cluster composition is influenced by adjusting the mixing ratio of the particle species. By using fluorescently labeled particles in a binary particle mixture of polystyrene (PS, 2μm) and melamine formaldehyde particles (MF-RhB, 366nm, labeled with Rhodamine-B) it is possible to analyze the heteroaggregation process by flow cytometry, which provides a multidimensional resolution of cluster composition [1]. The dynamics of the cluster formation process and the tuning of cluster composition via the particle mixing ratio by means of discrete bivariate population balance simulations are presented. The two internal coordinates represent the particle species and characterize the cluster composition. The property space is semi-heuristically reduced to the physically relevant coordinates for improved computational handling [2]. Aggregation rates are determined by two different kernel concepts, which are based on deterministic models under consideration of Brownian motion and DLVO theory. The kernel for ?patchy-particles' accounts for the heterogeneous surface structure of aggregated clusters [3], while a ?charge-balance' kernel calculates the interaction potential between two clusters on the basis of a mean electrostatic charge [2]. A comparison with experimental data shows the applicability of both concepts. To improve the deterministic prediction of aggregation kinetics and consolidate the multi-scale approach, interaction potentials will be measured by atomic force microscopy and compared with DLVO models. References: [1] S. Rollié, K. Sundmacher; Langmuir, 2008, 24, 13348. [2] S. Rollié, H. Briesen, K. Sundmacher, J. Colloid Interface Sci., 2009, doi:10.1016/ j.jcis.2009.04.031, in press. [3] A. Moncho-Jorda, G. Odriozola, M. Tirado-Miranda, A. Schmitt, R. Hidalgo- Álvarez; Phys. Rev. E, 2003, 011404.