Effect of particle shape on the mixing of powders.

Mixtures were prepared containing 200 g of 600 microns lactose and 0.5 g of 3 microns calcium carbonate of different particle shapes using a Y cone mixer. Measurements were made of the time required to achieve the acceptable standard deviation of mixing sigma A and of the segregation that occurred on subsequently vibrating the mixtures. The time taken to achieve sigma A increased with the irregularity of the particles of both components and the mixtures containing irregular particles segregated less on vibration.