Many materials in the food, chemical, and pharmaceutical industries, from raw materials, additives, and intermediates through to manufactured products, are supplied as relatively free-flowing powders suitable for the manufacturing process or final application. These materials are often stored for extended periods, during which time some powders will gain strength due to particle/particle interactions. This is generally referred to as ‘caking’ and can significantly limit the ability of a powder to pass through the process train without interruption and can detrimentally impact product quality.
Caking occurs through one or more mechanisms – typically, mechanical, chemical, and thermal – with the migration and absorption of water often the most influential. Limiting caking can be achieved by managing environmental conditions to keep materials in an optimal state; by adjusting the operational parameters (typically limiting the time the material is stationary) or by modifying the product formulation.
Through testing and understanding the behavior of each material, it becomes possible to assess and minimize the risk of caking at different points in the process, to maximize and maintain product quality. Powder testing results can inform, for example, decisions about how often the material needs to be tumbled or agitated to keep it in a fit state for subsequent processing, and whether it can maintain its quality if packed in bags, kegs, bulk containers, or tankers.
Regardless of the mechanism, however, determining the precise conditions which minimize the potential for caking requires a comprehensive understanding of the changes in flow properties that occur as a consequence.
Click the link to read or download “Quantifying Powder Caking using the FT4 Powder Rheometer”.