Packed audience for seminar
UK. The recent Powder Flow 2009 seminar played to a packed house at the Royal Society of Chemistry in London. Organised by The Formulation Science and Technology Group (FSTG) of the Royal Society of Chemistry in partnership with Freeman Technology and in association with Dechema, the organisation behind the Achema exhibition in Germany, the purpose of the event was to provide an up-to-date picture of powder flow measurement as a way of better understanding powder interactions and structure.
   In the words of Dr Philippe Rogueda, chairman of the organising committee, powder flow science is currently at a very exciting stage, attracting much interest. Existing at the frontier between solid colloid science, physical chemistry, chemical engineering and physics, it is an area in need of further research to be fully understood. There is a need to be able to measure interparticle forces in new ways to be able to account for them on the macroscopic level, he said.
  Opening the proceedings, Dr Rogueda stressed the importance of further research, saying that delegates should focus their collective thoughts on what is being measured when using alternative powder characterisation techniques, what the results mean and how best they can applied.
  Throughout the day leading experts presented their work on measuring and understanding powder flow, with a particular look at powder rheology as a tool to explain particulate behaviour in phenomenon such as fluidisation, aerosolisation and handling solid particulate matter. Powder flow theory and visualisation using laser technology were covered and the latest techniques for assessing powder flowability were also outlined.
  The plenary lecture, given by Prof Antonio Castellanos , University of Seville, covered the fluidisation of micro and nanoparticles which is proving to be a promising technique for many emerging industrial applications. Work at Seville has extended pioneering work carried out by Prof Derek Geldart in predicting the fluidisation attributes of cohesive powders. Incidentally, the event saw the surprise attendance of Prof Geldart, one of the founding fathers of fluidisation technology. 
  Prof Mojtaba Ghadiri, Leeds University, explained some of the work that is trying to address problems faced by drug manufacturers in predicting the flow of small quantities of powder, where unsufficient material is available for testing or where there is a need to test powder flowability at low levels of stress. Leeds is in the process of developing an indentation method which meets both these criteria with results analysed by Discrete Element Modelling (DEM). 
  Prof Dietmar Schulze, University of Braunschweig, concentrated on the age old problem of getting powder to move out of storage and the need to critically determine a powder's yield limit by using appropriate shear testers to help determine flow characteristics. The RST-XS, a computer controlled ring shear tester able to complete automated test procedures, has been developed by Prof Schulze.
  Prof Fernando Muzzio, University of Rutgers, examined the relationship between electrostatics and cohesion and discussed a number of methods available for characterising powder flow properties. Results are related to electrical properties like impedance, acquired charge, and dielectrophoretically induced powder adhesion and show a surprising degree of correlation to powder flow properties. 
  Prof Robert Price, University of Bath, looked into fluidisation and dispersion characteristics of cohesive powder systems, with emphasis on pharmaceutical powder formulations, and drug inhalation powders in particular. Excipients, used as the carrier for active ingredients in a medication, influence the entrainment and deaggregation behaviour of formulations, and their characterisation and manipulation is critical in optimising drug delivery performance. He showed how fluidisation of a carrier based formulation depends on the cohesivity of the blend structure, what effect drag force and particle-particle and particle-wall collisions have on the active, and the way in which modelling in conjunction with measurement of powder reactivity to an air flow provides a means of investigating process control and understanding formulations.
Dr Seamus Murphy, Oxford Lasers, outlined the capabilities of laser imaging techniques, one application of which is used to size particles in high velocity metal spraying processes.
Tim Freeman, Freeman Technology, outlined the possibilities for dynamic characterisation methods which can deal with complex powder behaviour or situations where flow properties are likely to change depending on the conditions imposed. Using dynamic techniques, of the kind offered by Freeman Technology, it is possible to simulate a range of conditions and measure powder response, replicating conditions that might be experienced in practice. The advantage is that a database of flow properties can be built up to enhance process understanding.
  The event also had a number of poster abstracts from: GlaxoSmithKline Research & Development Limited; Capsugel; Fraunhofer IKTS; Teijin Aramid GmbH; University of Birmingham; University of Bath; and University of Greenwich. Exhibitors and sponsors included: University of Greenwich; Scientific and Medical Products Ltd; Freeman Technology; Capsugel; Dantec Dynamics; Malvern; SAY Group Ltd; and Friesland Campina.
• For more information on the Formulation Science and Technology Group activities please log on to: www.formulation.org.uk