Spray agglomeration of polymer particles: Influence of spray parameters on shape factors

This work systematically investigates the influence of spray parameters on the shape factor descriptors and the fractal dimensions of polymer agglomerates produced by fluidised bed spray agglomeration. Polystyrene primary-particles with sizes <100 mu m (Geldart C/A) are used to investigate the shape formation during the agglomeration process with regard to the spray-parameters, i.e., volume flows of the atomization gas and the binder liquid. As binding agent, a solution of polymethyl-methacrylate in acetone is used. Analysis of the ag-glomerates is carried out using scanning electron microscopy and laser diffraction. Development of agglomerate -size and the distributions of the shape factors circularity, roundness and compactness are monitored by image analysis and correlated with the spray parameters. The calculation of the fractal dimensions with regard to the Sauter mean diameter using the box counting method is performed and compared with the shape factors, resulting in two complementary methods to describe the shape of agglomerates.