The answer is 42...

Sticky, cohesive powders don’t flow well - or do they? Tip out flour and the lumps of agglomerated powder contrast sharply with the way a non-cohesive powder like sugar goes everywhere when spilled. In general it is true that fine powders are cohesive and don’t flow well, but there are exceptions where the opposite is true. Our recent studies (see below) show that forcing powders along pipes - which works so successfully with water and other fluids - fails with coarse powders, which lock up and resist. However, cohesive powders can be made to flow, rather like toothpaste extruding from a tube.

This reminds us that simplistic assessments of flowability, like ‘good’ or ‘bad’, can mislead. Single number methods used to describe powder flowability, such as angle of repose, Carrs Index or Flow Function derived from shear testing, provide only one window on the subject, one of very many that are actually needed to build a comprehensive picture of powder behaviour. So, how many parameters do we need to describe powder flowability? Temperature and mass require a single number description; a cup of tea may require at least four variants (size, sugar, milk, type of tea); and a complex item such as a person would be too challenging to even consider. Powders may require 20 numbers. Understanding how they relate to the process is the key to matching powder and plant characteristics and achieving efficient processing. Reliance on a single number can be very misleading.

Reg Freeman, Managing Director

Helping hopper design!

Powtech 2008 (29 Sep-2 Oct; Nürnberg, Germany) sees the introduction of a significant new tool for hopper development as we launch the Hopper Design Software package for the FT4 Powder Rheometer. Drawing on the characterization capabilities of this universal powder tester, the new software improves access to well-established hopper design methodologies, speeding up and simplifying compilation and interpretation of the required data. This is also the subject of Tim Freeman’s tutorial at the Exhibitors Forum in Hall 8, on Thursday 2 October at 1300 h. See us for a demo in Hall 6/Stand 6-450 or click here for more information.

Shear faster

Launched at the end of 2007, the 1 ml Shear Cell for the FT4 has proved extremely popular and we will soon be offering even faster and more convenient testing for anyone working with limited sample quantities. Details of an enhanced methodology for the 1 ml Shear Cell will be available on our booth at the American Association of Pharmaceutical Scientists Annual Meeting & Exposition (16-20 Nov; Atlanta; USA), together with information about our new databases for pharmaceutical excipients Visit us on Booth 540.

Join our workshop in Atlanta

Powder Flow and Process Analytical Technology(PAT) tools for implemention of QbD

Monday 17 November 2008 4 - 6pm:
Omni Hotel at CNN Center, Atlanta

Coinciding with the AAPS 2008 Annual Meeting & Exposition

We are delighted to join forces in Atlanta with C-Therm Technologies, to present a workshop at which users of C-Therm effusivity systems and the FT4 Powder Rheometer will discuss their experiences. The event will be valuable for those seeking to better understand different formulation and PAT tools for implementing QbD. The program includes speakers from Pfizer, Covidien and Long Island University.

There is no charge to attend, but numbers are limited and early registration is advised. For provisional programme and registration details visit here.

Extrusion examined

Very cohesive powders can behave more like a fluid when pressurised or subjected to forced flow. Such powders may extrude like toothpaste, whereas normally free flowing powders will resist forced flow. At PSA 2008 (2-4 Sep; Stratford-upon-Avon, UK) Reg Freeman presented the results of work using the FT4 to examine the extrusion, flow in confined spaces and normal stresses generated when powders are sheared. The different extrusion behaviour of cohesive and non-cohesive powders and their ability to switch from ‘good’ to ‘bad’ flowability, was well described by the measured powder properties.

For more details click here to request the paper.

Hints & Tips 4

'Better powder processing’ is the latest in our occasional Hints & Tips series. Correlating processing experience with powder properties is a powerful way of determining which variables critically impact performance. Developing Processability Rankings (PRs) for powders in specific processes supports this approach, and Hints & Tips 4 offers practical advice on how to go about this.

To request your copy click here.

New article on powder metallurgy

At the June 2008 World Congress on Powder Metallurgy & Particulate Materials, Reg Freeman presented the results of studies to investigate the bulk, dynamic flow and shear properties of steel, tungsten, aluminium and ceramics - correlating these with the ability to fill a die. An article which includes some of the data presented is now available.

To request your copy click here.

With a packed conference schedule this year we very much look forward to meeting you at:

30 Sep - 2 Oct 2008

NürnbergMesse GmbH, Nürnberg, Germany
Hall 6, Stand 450

16 - 20 November 2008

Atlanta GA, USA
Booth #540

17 - 19 March 2009

Jacob K. Javits Center
New York NY, USA
Booth 1269

11 - 15 May 2009

Frankfurt, Germany
Hall 5.1, Stand F38