Experimental evaluation of the effect of particle properties on the segregation of ternary powder mixtures

Abstract

Segregation of components, especially the low content level of a highly active substance, has serious deleterious effects on powder formulation. This study investigates the effect of particle properties, particularly size, shape, density and cohesion, on the segregation of laundry detergent powders. Tetraacetylethylenediamine (TAED) particles, spray-dried synthetic detergent powder referred to as Blown Powder (BP) and Enzyme Placebo Granules (EP granules) are used as a model formulation. The segregation of components is evaluated using image processing of the photographic records taken from the front face of a two-dimensional heap of powders. Coefficient of variation concept is considered as segregation index. It is shown that EP granules, the component used as low-level ingredient (< 2 wt%) in the ternary mixture, are prone to extensive segregation due to their higher density as compared to BP and TAED particles. Desired properties for segregation minimisation of EP granules have been further investigated. It is found that the segregation of EP granules can be reduced noticeably by applying a thin layer of a sticky liquid on them before mixing with the rest of powders with full particle size distribution of the components. Polyethylene glycol has been used for this purpose. Addition of 2.5 wt% gives an optimum level to reduce the segregation of EP granules without compromising the flowability of the mixture as well as EP granules themselves.