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Granular Materials

Granular materials are able to flow similar to liquids, but are composed of solid particles. They are important to many industries including pharmaceuticals, construction and food. Processes dealing with granular materials often occur over varying timescales, from long storage or transportation times to powder compaction, which occurs in the blink of an eye. Issues including processing history and storage conditions have an effect on the properties of the particles leading to changes in how granular systems respond to external stimuli.

Research into granular materials within the MML group contains good variety. Flow and adhesion properties of toner and carrier particles in a printer are of interest. This binary system requires particle interactions to allow for the fine toner particles to adhere to the bulkier carrier particles for deposition on the printed paper, whilst allowing carrier particles to be reused and preventing toner particles from forming clumps. The ring shear testing technique was used to investigate the flow properties of both model and real toner-carrier particle systems.

Pharmaceutical powders are also a current research area, especially when compacted to form tablets. The use of computational modelling and compaction simulators to investigate tablet production is of current interest. Computational simulations using quantum theory and molecular dynamics allow for investigations into the material properties of the powder. The discrete element method and the finite element method, in conjunction with the Drucker-Prager cap model can simulate entire pharmaceutical powder systems. Some of the work was conducted with the Pfizer Institute for Pharmaceutical Materials Science, with several members belonging to both the Pfizer Institute and the MML group.

[1] Kojima, T. and Elliott, J.A. "Incipient flow properties of two-component fine powder systems and their relationships with bulk density and particle contacts", Powder Tech., 228, 359-370 (2012). link

[2] Han, L.H., Elliott, J.A., Bentham, A.C., Mills, A., Amidon, G. and Hancock, B.C. "A Modified Drucker-Prager Cap Model for Die Compaction Simulation of Pharmaceutical Powders", Int. J. Solids Struct., 45, 3088-3106 (2008). link

People specializing in this area

Academic Staff

Prof James Elliott, MA (Cantab) CPhys MInstPhys

I am directing projects on the compaction and flow of pharmaceutical powders for tablet manufacture, and also binary mixtures of toners for electrophotographic applications.

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