In this brief article, we will cover Powder stickiness measurement and methodologies. Powder stickiness occurs when powder particles absorb water vapor at certain temperatures, transforming from free-flowing to cohesive or sticky states. This stickiness can disrupt various stages, from dosing and storage to production. For example, sticky powders may clog spray-drying equipment, and in storage, they often form clumps in big bags or hoppers, resulting in poor flow and dosing performance.
Accurately measuring and predicting powder stickiness presents a challenge. Adhesive and cohesive forces between particles depend on numerous factors, including particle size, shape, porosity, surface characteristics, and the material’s chemical makeup. Each variable contributes differently to powder behavior, especially as humidity and temperature shift, complicating stickiness assessments.
Powder stickiness measurement and methodologies
Predicting and measuring powder stickiness is crucial for avoiding storage, dosing, and production issues. Since each powder reacts differently to humidity and temperature shifts, assessing stickiness becomes complex. The interdependence of temperature and humidity adds to this challenge, requiring specialized equipment and expertise for reliable analysis.
Two primary methods for measuring stickiness include:
Water Vapor Adsorption Isotherms: This method analyzes how powders interact with water vapor at various humidity levels (0-95%) and temperatures. By applying the Guggenheim, Anderson, and De Boer (GAB) model, we often determine the “stickiness point” from the isotherm at each temperature. However, pinpointing this threshold can be challenging. Although many studies use this method, Delft Solids Solutions has developed an advanced approach to enhance stickiness measurement accuracy.
Dynamic Vapor Sorption (DVS): This technique exposes powders to controlled humidity and measures the resulting weight changes as they absorb moisture. By evaluating these changes, DVS provides insights into a powder’s stickiness tendency under different conditions. This method is particularly valuable for powders with complex moisture absorption behaviors.
Using these methods, industries can better understand and manage powder stickiness, improving handling and processing efficiency.
Powder Rheometry for Real-Time Stickiness Measurement
Our modified powder rheometer enables real-time stickiness measurement, offering a direct way to detect shifts in cohesiveness and friction within the powder bed during fluidization. By observing how particle cohesion changes with temperature and humidity, we can precisely identify the stickiness threshold. This real-time approach has a clear advantage over the indirect vapor adsorption method, which doesn’t directly measure flow changes.
Data collected at each temperature supports the construction of a stickiness diagram, similar to a modified Mollier diagram. This diagram helps us predict and distinguish between sticky and non-sticky conditions. This predictive tool enhances troubleshooting and refines product development.
