Moisture has a major influence on the flow characteristics of bulk materials, and of powders in particular. Environmentally acquired moisture can have positive and negative effects. Powders stored in humid environments can take on unwanted surface moisture, which can hinder flow as well as alter material properties. However, environmental moisture can also be of benefit, for instance by providing a conductive path to dissipate electrostatic charge or acting as a lubricant to improve flowability.
The question thus becomes, “How much moisture will my powder take up, and, more importantly, how will this moisture uptake impact my process and products?” A comprehensive understanding of the properties of a powder enables formulators, plant designers, operators and quality departments to make an informed assessment of potential process interruptions on product quality due to changes in humidity. Once the characteristics of a powder have been established, the sensitivity to humidity can be investigated with confidence.
This article discusses the impact of exposing powders to increasing humidity by evaluating changes in powder flow characteristics. It covers how changes in humidity affect a powder’s moisture content, and predicting a powder’s response to changes in humidity. It also presents examples of applications in which humidity and moisture are detrimental, as well as applications in which they are beneficial.